Fabrication of organometallic halide perovskite electrochemical supercapacitors utilizing quasi-solid-state electrolytes for energy storage devices

Journal Pre-proof Fabrication of organometallic halide perovskite electrochemical supercapacitors utilizing quasi-solid-state electrolytes for energy storage devices Idris Popoola, Mohammed Gondal, Luqman Oloore, AbdulJelili Popoola, Jwaher AlGhamdi PII:

S0013-4686(19)32408-9

DOI:

https://doi.org/10.1016/j.electacta.2019.135536

Reference:

EA 135536

To appear in:

Electrochimica Acta

Received Date: 3 September 2019 Revised Date:

21 November 2019

Accepted Date: 15 December 2019

Please cite this article as: I. Popoola, M. Gondal, L. Oloore, A. Popoola, J. AlGhamdi, Fabrication of organometallic halide perovskite electrochemical supercapacitors utilizing quasi-solid-state electrolytes for energy storage devices, Electrochimica Acta (2020), doi: https://doi.org/10.1016/ j.electacta.2019.135536. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.

Fabrication of Organometallic Halide Perovskite Electrochemical Supercapacitors utilizing Quasi-Solid-State Electrolytes for Energy Storage Devices a,b Idris Popoola , Mohammed Gondala,b*, Luqman Oloorea,b, AbdulJelili Popoolaa,b and Jwaher AlGhamdic a

Laser Research Group, Physics Department, King Fahd University of Petroleum and Minerals, P.O. Box 5047, Dhahran 31261, Saudi Arabia. b King Abdullah Center for Atomic and Renewable Energy (KACARE), King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia. c Department of Chemistry, College of Science, Imam Abdulrahman Bin Faisal University, Dammam 31113, Saudi Arabia

Fabrication of Organometallic Halide Perovskite Electrochemical Supercapacitors utilizing Quasi-Solid-State Electrolytes for Energy Storage Devices Idris Popoolaa,b, Mohammed Gondala,b*, Luqman Oloorea,b, AbdulJelili Popoolaa,b and Jwaher AlGhamdic a

Laser Research Group, Physics Department, King Fahd University of Petroleum and Minerals, P.O. Box 5047, Dhahran 31261, Saudi Arabia.

b

K.A.CARE Energy Research & Innovation Center at King Fahd University of Petroleum and Minerals, P.O. Box 5047, Dhahran 31261, Saudi Arabia

c

Department of Chemistry, College of Science, Imam Abdulrahman Bin Faisal University, Dammam 31113, Saudi Arabia

*Corresponding author. E-mail address: [email protected] (M.A. Gondal), Telephone: +96613-8602351/8603274;

1

Abstract Organometallic halide perovskite materials have gained enormous interest in energy conversion and various optoelectronics applications. These unique materials possess great ionic response. Hence, their suitability for energy storage device applications needs to be explored. We fabricated for the first time all-solid-state perovskite electrochemical supercapacitors with high areal capacitance, fast charge-discharge rate, high power density and superior cyclability. We investigated electrochemical energy storage performance of two different quasi-solid-state electrolytes sandwiched between two symmetric perovskite electrodes. We recorded highest areal capacitance of 21.50 µF/cm2 which is 3.65 times greater than areal capacitance recorded by similar perovskite electrochemical capacitors utilizing liquid-state electrolytes. High power density of 5.05 W/cm2 was achieved. Electrochemical impedance spectroscopy (EIS) was used to study the ionic transport mechanism and properties of our fabricated devices. The Nyquist plots exhibit linear characteristic across low and high frequency ranges, indicating excellent electrolytes diffusion into the perovskite electrodes and confirming ideal supercapacitor behavior of these devices. All devices exhibit short relaxation time with device having least relaxation time of 251.19 µs indicative of fast discharge properties of fabricated devices. Our devices show excellent cyclability with device retaining 98.34% of its initial capacitance after 1000 cycles. Keywords: Perovskite, Supercapacitors, Quasi-solid-state electrolytes, Power density, Cyclability, Energy storage.

2

1. Introduction Energy generation from renewable energy sources may not be easily integrated into the grid due to their intermittent nature. Hence, it is pertinent to have energy storage devices that store the energy from renewable energy sources at their peak availability and utilizes the stored energy at their downtime. Novel energy storage devices with enhanced performance and low cost are also highly desirable to fulfil the growing demand of electric vehicles and intermittent renewable energies. Batteries and supercapacitors are major energy storage devices that are capable of maintaining uninterrupted energy supply from renewable energy sources. Unlike batteries, supercapacitors do not suffer from limited cycle life and poor charge-discharge rates occasioned by electrochemical redox reactions [1]. Supercapacitors, also referred as electrochemical capacitors, utilize either electrochemical double layer mechanism or pseudo-capacitance rapid surface redox reaction at the electrode/electrolyte interface to store energy [1]. Due to the rapid charge-discharge rates as compared to batteries, high power density and their long cycle life, supercapacitors

exhibit

complementarity potential to batteries or could ultimately replace them in several energy harvesting and storage applications [1,2]. Supercapacitors as on-demand energy storage devices have found wide ranging applications, including in electric vehicles, pulse power system, digital communication instruments, integration into energy conversion and various electronic devices [1– 4]. Supercapacitors have received great research attentions with many groups working to develop new electrode materials, electrolytes and architectures to improving the charge-discharge rate, capacity, cycle lifetime, energy density and power density [5–8].

Supercapacitors architectures are broadly categorized into symmetric and asymmetric supercapacitors.

Typical

supercapacitors

architecture

consists

of

electrode/electrolyte/separator/electrolyte/electrode structure [9]. Several electrode materials have been investigated for the improvement of capacitive storage potential of supercapacitors. Common 3

supercapacitors electrode materials include carbon, carbon nanotubes (CNTs), carbon nanofibers (CNFs), activated carbon, graphene, graphene quantum dots, MnO2, RuO2 and IrO2 [4,10–14]. Polymer electrode materials such as polypyrrole and polyaniline have equally been reported for supercapacitors [1,15].

Organometallic halide materials with the structure ABX3 have been found to possess dual electronic-ionic conduction property [2,16]. The dual electronic-ionic conduction property exhibited by this class of materials make them promising candidates for energy storage applications. were employed as electrode for electrochemical capacitive cells. Zhou et al. first investigated the ionic conduction of methyl ammonium lead triiodide (MAPbI3) in a symmetric electrochemical capacitor (EC) [16]. The study concluded that the formation of ions and their transport processes in perovskites EC device are mainly initiated by free charge carriers and could as well be dependent on the interface. They recorded low overall specific capacitance of the perovskite EC devices and suggest possible improvement by optimizing the properties of the electrolyte. Sequel to Zhou et al.’s work, Pious et al. fabricated a lead-free zero-dimensional methylammonium bismuth iodide (CH3NH3)3Bi2I9 perovskite electrochemical double layer capacitor (EDLC) on carbon cloth [2]. A 5.5 mF/cm2 total areal capacitance was achieved. The electrochemical impedance spectroscopy (EIS) measurement revealed low resistance to the charge transport which is good for the device performance. The reported devices utilized butanol with methyl ammonium iodide (MAI) as electrolyte. The butanol was found to cause gradual degradation of the perovskite electrode [16].

Liquid electrolyte has a drawback of drying up faster and consequently reduces the usage lifetime of the perovskite EC device. Hence, gel and polymer quasi-solid-state electrolytes have gained prominence as substitute for liquid electrolytes for the fabrication of solid-state supercapacitors. Quasi-solid-state electrolytes have equally found applications in batteries and dye-sensitized solar

4

cells (DSSCs) [17–21]. Among commonly utilized solid-state electrolytes electrochemical supercapacitors are DI water/polyvinyl alcohol (PVA)/KOH, DI water/PVA/H3PO4 [13]. Wang et al. developed a quasi-solid-state electrolyte by immersing polyacrylamide gel (PAM-G) matrix in 6 M KOH aqueous solution for 60 hours. The fabricated electric double layer supercapacitor utilizing the PAM-G electrolyte recorded a specific capacitance of 196 F·g-1 at a charge-discharge current density of 1 A·g-1 and a 98% capacitance retention after 5000 cycles at 1 A·g-1[22]. A PVANa2SO4 quasi-solid-state electrolyte was reported by Cheng et al. for the fabrication of asymmetric MoS2/MWCNT and PANI/MWCNT composite electrodes supercapacitors. The asymmetric supercapacitors recorded a highest specific capacitance of 138.1 F.g-1 at 1 A.g-1, a maximum energy density of 15.09 Wh.kg-1 and a peak power density of 2217.95 W.kg-1 [23]. However, water-based electrolytes are not suitable for perovskite electrochemical cells as the perovskite electrodes would be fast degraded by the moisture content of the electrolytes. Hence, the need for synthesizing of non-aqueous solid-state electrolytes that would lead to improve performance of organometallichalide-based perovskite electrochemical supercapacitors.

In this work, we synthesized two different novel quasi-solid-state electrolytes that were used in the fabrication of perovskite electrochemical supercapacitors for the investigation of energy storage potential of halide-based perovskite materials. The potential of the electrolytes to act as both electrolyte materials and separators were investigated for the first time. One-step and two-step solution processed perovskite fabrication methods were employed to fabricate the perovskite active electrodes. The performance of the perovskite electrodes fabricated by the two fabrication techniques were studied and their morphologies were found to play important role in the electrochemical energy storage performance of the perovskite electrochemical supercapacitors.

5

2. Materials and Method 2.1 Materials Lead (II) iodide PbI2 (99.9%, Sigma Aldrich), methyl ammonium iodide (MAI 99%, Sigma Aldrich), poly vinyl alcohol (PVA, Fluker AG), chlorobenzene (anhydrous 99.8%, Sigma Aldrich), potassium hydroxide (KOH) pellets (85%, Sigma Aldrich), fluorine-doped tin oxide (FTO) glass (15 Ω sq-1, Solaronix), anhydrous N,N-dimethylformamide (DMF, 98.8%, Sigma-Aldrich), 2propanol (99.5%, Sigma Aldrich), acetone (99.5%, Gainland Chemical Company), ethanol (99.8%, Sigma Aldrich) and Fisherbrand™ qualitative grade plain filter paper circles - P8 Grade. 2.2 Electrolyte preparation To prepare the quasi-solid-state electrolytes, the first electrolyte codenamed CHLPVAKOH was prepared as follows. 10 mL of chlorobenzene were taken from its stock and transferred into a vial. 1 g of PVA was measured using a digital balance and added to the chlorobenzene in the vial. The mixture of the chlorobenzene and PVA was vigorous stirred and heated at 90 oC until a clear transparent solution was achieved and was allowed to cool to room temperature. 0.8 g KOH were added to the clear solution and further stirred rigorously at 90 oC until the added KOH completely dissolved. The second electrolyte codenamed CHLPVAKOHMAI was prepared by similar method with the addition of 30 mg of MAI after the full dissolution of KOH in the chlorobenzene-PVA solution. 2.3 Perovskite active layers preparation The entire chemicals were utilized as purchased with no further treatment. The one-step solution processed active MAPbI3 perovskite precursor material was synthesized by dissolving 406 mg of PbI2 and 140 mg of CH3NH3I in 1 mL of DMF solvent. The mixture was stirred at 70 oC for 8 h. The as-prepared perovskite precursor solution was then filtered through a 0.45 µm polytetrafluoroethylene (PTFE) filter and stored in glove-box filled with nitrogen before use. To prepared the two-step solution processed active MAPbI3 perovskite precursors, PbI2 was dissolved 6

in DMF at a concentration of 460 mg/mL and stirred for 8 h at a temperature of 70 oC. The PbI2 solution was filtered by 0.45 µm PTFE filter. The second precursor for the two-step solution processed perovskite was prepared by dissolving 10 mg of CH3NH3I in 1 mL of 2-propanol with no stirring or heating required. 2.4 Device fabrication 2.4.1 Fabrication of one-Step solution processed perovskite electrochemical supercapacitors FTO glasses were sequentially cleaned in sonicator with soap, deionized (DI) water, acetone and ethanol for 30 min per cleaning process. After the cleaning with ethanol, the FTO glasses were heated at 100 oC to remove residual organic solvent. 50 µl of the as-prepared one-step solution processed perovskite precursor solution were deposited on the precleaned FTO glass and spincoated at 3000 rpm for 30 s. The deposited perovskite precursor film was allowed to dry at ambient temperature for 5 min and subsequently annealed at 110 oC for 25 min. The temperature of the hot plate was then allowed to cool to 30 oC and the perovskite active electrode was removed. A symmetric perovskite electrochemical supercapacitor was then coupled with a sandwiched electrolyte between two perovskite active electrodes with the aid of binder clips. 2.4.2 Fabrication of two-step solution processed perovskite electrochemical supercapacitors 50 µl of the as-prepared PbI3 solution were dropped on the precleaned FTO glass and spin-coated at 3000 rpm for 30 s. The deposited PbI3 film was allowed to dry at ambient temperature for 5 min and subsequently annealed at 110 oC for 25 min. The temperature of the hot plate was then allowed to cool to 30 oC. 50 µl of CH3NH3I solution were then spin-coated on the PbI2 film and annealed at 110 oC for 25 min also before it was allowed to cool to 30 oC. The fabricated two-step solution processed perovskite electrodes were used in symmetric perovskite electrochemical supercapacitor containing electrolyte between them and held together by binder clips. 2.5 Material characterization

7

The morphology of the fabricated electrodes was studied using Lyra TESCAN field emission scanning electron microscopy (FESEM) equipped with an accelerating voltage of 5 kV. The infrared spectra of the prepared electrolytes were recorded in the range of 4000 – 600 cm-1 using Nicolet iS50FT-IR (ATR-mode) spectrophotometer 2.6 Electrochemical characterization The cyclic voltammetry (CV) measurement of the devices was carried out on Autolab PG302N equipped with NOVA 2.1 software by a two-electrode system. The operating potential for the CV measurement ranges between 0 V to 0.6 V. The electrochemical impedance spectroscopy (EIS) measurement of the devices was conducted using the same equipment. The operating frequencies of the EIS measurement ranges from 0.1 Hz to 100 kHz at a voltage scan rate of 10 mV/s. Linear sweep voltammetry (LSV) was performed on the as-synthesized quasi-solid-state electrolytes using FTO/electrolyte/FTO configuration at a sweep rate of 0.1 V s-1 for voltage range between 0 V and 3 V. The capacitance of the devices was estimated from the CV plot using equation (1) given as 2Vo

C=

∫

v

| i | dt

0

2Vo

(1)

where i is the current (µA), Vo is the maximum voltage (V), v is the scan rate (mV/s) and dt is the differential time (s) of the CV plot. The areal capacitance is given in equation (2), Cs =

C Π

(2)

where Π is the surface area (cm2) of the active electrode. The real and imaginary capacitance as a function of frequency is given in equation (3) and (4), respectively as:

8

C'= −

C"=

Z" 2π f Z

2

(3)

Z' 2π f Z

2

(4)

where C' is the real capacitance (µF), C" is the imaginary capacitance (µF), Z' is the real impedance (Ω), Z" is the imaginary impedance (Ω), Z is the resultant complex impedance (Ω) [as given in equation (5)] and f is the frequency. Z=

( ( Z ')

2

+ ( Z ") 2

)

(5)

The energy density (ED) and power density (PD) of the devices were derived from equations (6) and (7) [7,24,25]: ED =

C ( ∆V )

2

7200 ∏

(6)

Vo 2 PD = 4(ESR) ∏

(7)

3. Results and Discussion 3.1 ATR-FTIR spectral characterization of CHLPVAKOH and CHLPVAKOHMAI electrolytes Chlorobenzene-PVA mixture was allowed to turn clear under vigorous stirring and heating at 90 oC temperature before the addition of KOH. The colorless solution soon started to turn brownish as the KOH dissolved in the solution and then blackish as the KOH totally dissolved under same vigorous stirring and heating temperature. The solution was kept for five days to allow steady evaporation of the excess solvent until a suitable viscous solution was obtained. FTIR spectroscopy was used to investigate the interactions among the constituent materials of the electrolytes. The FTIR spectra for CHLPVAKOH electrolyte, pure chlorobenzene, pure PVA and pure KOH are depicted in Figure 1a. The peaks assignment of the FTIR spectra of all samples were

9

done using John Coates interpretation of infrared spectra [26]. For pure chlorobenzene the frequency at 997 cm-1 is assigned to strong C=C bending mode while the frequencies 704 cm-1, 679 cm-1 and 604 cm-1 are assigned to C=Cl stretching modes. The frequencies at 3356 cm-1, 3311 cm-1, 3308 cm-1, 3265 cm-1 and 3250 cm-1 are assigned to strong broad -OH stretching of intermolecularly bonded alcohol for pure PVA. Also, the frequencies 2940 cm-1, 2923 cm-1 and 2909 cm-1 are assigned to weak broad -OH intermolecularly bonded alcohol in the pure PVA. The peaks at 1428 cm-1, 1375 cm-1 and 1330 cm-1 are assigned to medium -OH bending mode for the PVA. Strong C=O stretching secondary alcohol mode is noted at frequency 1027 cm-1 for pure PVA. The peak at 3265 cm-1 corresponding to the strong stretching frequency of -OH of pure PVA shifted to about 3266 cm-1 in the CHLPVAKOH complex. The frequency 2923 cm-1 due to the weak -OH stretching shifted to 2930 cm-1 in the complex. The -OH medium bending frequency 1428 cm-1 of pure PVA shifted to 1403 cm-1 in the CHLPVAKOH electrolyte complex. The C=Cl stretching frequency 704 cm-1 of pure chlorobenzene shifted to 738 cm-1 in the CHLPVAKOH complex. The absorption of peaks of chlorobenzene (1579, 1474, 1443, 1119 and 1085 cm-1) and KOH (1635, 1451, 1049, 877 and 676 cm-1) were absent in the CHLPVAKOH electrolyte complex. Furthermore, the CHLPVAKOH electrolyte complex exhibited some new peaks at 2162 cm-1, 2151 cm-1, 1984 cm-1, 1149 cm-1, 1101 cm-1 and 822 cm-1. The changes in the existing peaks and the formation of new peaks in the CHLPVAKOH FTIR spectra established the complexation of the constituent electrolyte materials.

The FTIR spectra of the CHLPVAKOHMAI electrolyte which in addition to CHLPVAKOH complex contains MAI are shown in Figure 1b. For pure MAI the frequency at 3447 cm-1 is assigned to strong N-H stretching, while the frequency 3093 cm-1 is assigned to weak =C-H stretching. The frequencies 1480 cm-1 and 1403 cm-1 are assigned to C-H bending of the methyl group, while the peak at 1250 cm-1 is assigned to medium C-N stretching. The MAI peak at 3446

10

cm-1 and PVA peak at 3315 cm-1 are seen to merge into a broader peak at 3381 cm-1 of the CHLPVAKOHMAI electrolyte complex. Similarly, the MAI peak at 3087 cm-1 and PVA peak at 2918 cm-1 are supposed to have merged into a narrower 2923 cm-1 peak of the CHLPVAKOHMAI complex. The absorption peaks at 1608 cm-1 (MAI) and 1727 cm-1 (PVA) are seen to merge into peak 1571 cm-1 of CHLPVAKOHMAI complex. The MAI characteristic peak is seen repeated in the CHLPVAKOHMAI electrolyte complex. The PVA frequency 1425 cm-1 is shifted to 1438 cm-1 in the CHLPVAKOHMAI electrolyte. MAI (1392 cm-1), PVA (1244 and 1022 cm-1) and chlorobenzene (704, 675, 459 and 421 cm-1) frequencies are shifted to 1404 cm-1, 1074 cm-1, 1026 cm-1, 703 cm-1, 680 cm-1, 463 cm-1 and 419 cm-1, respectively. The MAI peak at 912 cm-1 and PVA peak at 933 cm-1 are not found in CHLPVAKOHMAI electrolyte complex. A new peak at 733 cm-1 is found in CHLPVAKOHMAI complex. The changes in the existing peaks and the formation of new peaks in the FTIR spectra of the CHLPVAKOHMAI electrolyte confirmed the complexation of the constituent electrolyte materials.

Figure 1 (c-d) shows the Nyquist plots of the as-synthesized quasi-solid-state electrolytes obtained from the EIS measurement using two-electrode system by sandwiching the respective electrolytes in between two FTO conducting glasses. The ionic conductivities of the as-synthesized quasi-solidstate electrolytes were calculated from the Nyquist plots by the equation σ = (t/(Rb * A)), where σ is the ionic conductivity, t is the electrolyte thickness, Rb is the bulk electrolyte resistance and A is the electrolyte contact area. The CHLPVAKOH and CHLPVAKOHMAI electrolytes recorded ionic conductivities of 1.3 × 10-3 S cm-1 and 3.4 × 10-3 S cm-1, respectively. Likewise, linear sweep voltammetry (LSV) was conducted to investigate the electrochemical stability of the quasi-solidstate electrolytes at 0.1 V s-1 sweep rate. The electrolytes exhibit stable voltage windows between 0 V and 1.21 V (Figure S1).

11

3.2 One-step processed perovskite electrochemical supercapacitors 3.2.1 Fabrication and morphological characterization of one-step processed perovskite active electrodes In the fabrication of the perovskite electrochemical supercapacitors, one-step solution processing technique was first used for the fabrication of the active perovskite electrodes. A 50 µL precursor of as-prepared MAPbI3 in DMF was spin-coated on an exposed area of 0.9 cm2 of precleaned fluorinedoped tin oxide (FTO) glass at 3000 rpm for 30 s at a ramp rate of 500 rpm. The as spin-coated electrodes were heated at 110 oC for 25 min and subsequently allowed to cool to room temperature afterward. Eight perovskite active electrodes were fabricated using the above described procedure. The perovskite active electrodes were used to fabricate four different symmetric perovskite electrochemical supercapacitors codenamed PES01, PES02, PES03 and PES04. Figure 2a shows the fabrication process of the perovskite electrochemical supercapacitors. PES01 consists of two symmetric perovskite active electrodes with CHLPVAKOH electrolyte sandwiched between them with no distinct separator material. The electrolyte was spin-coated on each perovskite active electrodes at 3000 rpm for 45 s at a ramp rate of 500 rpm to form the sandwiched perovskite electrochemical supercapacitor device coupled with the aid of binder clips. PES02 is similar to PES01; however, it utilizes CHLPVAKOHMAI electrolyte. The perovskite electrochemical supercapacitors PES01 and PES02 were fabricated and coupled to investigate the potential of the as-synthesized electrolytes to perform the dual functions of electrolyte materials and separators. For the fabrication of PES03 and PES04 devices, pre-cut filter papers were soaked for 2 h in CHLPVAKOH and CHLPVAKOHMAI electrolytes, respectively. The electrolyte-soaked filter papers were carefully placed in between the symmetric perovskite active electrodes for PES03 and PES04 devices, respectively. The filter paper serves as separator for the PES03 and PES04 devices.

12

The typical morphology of the one-step processed perovskite active electrodes is investigated by SEM. The morphology (Figure 2 b-c) shows ribbon-like MAPbI3 of the perovskite active electrodes that are well distributed on the FTO substrate.

3.2.2 Electrochemical characterizations of one-step processed perovskite electrochemical supercapacitors To investigate the electrochemical energy storage performance of the fabricated perovskite electrochemical supercapacitors, electrochemical measurements were conducted for all the devices. Cyclic voltammetry (CV) was conducted at different scan rates ranging from 50 mV/s, 100 mV/s. 200 mV/s to 500 mV/s at a potential voltage running between 0 V to 0.6 V. All devices show rectangular CV behavior across the different scan rates with a linear increase in current as a function of scan rate as evident in Figure 3. The rectangular CV behavior and the linear current increase with respect to scan rate establish the ideal capacitive performance of the devices which also indicate high power output potential and very fast discharge process over the entire surface of the electrodes owing to fast electrolyte diffusion and fast charge transport [1,7,27–30]. The PES01 device attained a maximum current of 0.55 µA at a scan rate of 500 mV/s, while the PES02 device reached a peak current of 1.19 µA at the same scan rate, which is more than double that recorded by PES01. The higher peak current attained by PES02 as compared to PES01 is ascribed to the ionic transport properties of the MAI added to its electrolyte [2,16]. PES03 device utilizing CHLPVAKOH electrolyte with filter paper separator attained a maximum current value 3.51 µA at a scan rate of 500 mV/s. PES04 consisting of CHLPVAKOHMAI electrolyte and filter paper separator on the other hand recorded a peak current value of 0.94 µA at a scan rate of 500 mV/s, which is 3.74 times less than that recorded by PES03 device. It could be said that the separator helped in the enhancement of the supercapacitor performance of PES03; however, the same could not be said of PES04 device. The relatively low current value of PES04 device, despite its electrolyte containing MAI, could be due to the difficulty of the ionic migration of the MAI in the 13

CHLPVAKOHMAI electrolyte bulk through the filter paper separator [31–34], as we believe MAI is the main ionic transport material in this electrolyte as earlier demonstrated in PES02 device. Figure S2 shows the areal capacitance obtained at different scan rates for all the different devices. The areal capacitance was calculated with device geometric area of 0.9 cm2. The areal capacitance of PES01 device as a function of scan rate (Figure S2a) shows a highest areal capacitance value of 3.88 µF/cm2 at scan rate of 50 mV/s and 81.70% of this capacitance was retained at 500 mV/s scan rate. The PES02 device (Figure S2b) recorded an areal capacitance of 8.32 µF/cm2 at the scan rate of 50 mV/s and the capacitance retention at 500 mV/s scan rate is 85.46%. We noted that the areal capacitance value of the PES02 device is also more than twice that of PES01 device, consistent with their peak currents behavior and confirming the enhanced capacitive energy storage performance of CHLPVAKOHMAI electrolyte in the absence of distinct separator. Hence, we are able to show that both CHLPVAKOH and CHLPVAKOHMAI electrolytes could perform the dual roles of electrolyte material and separator, simultaneously. Figure S2 recorded a maximum areal capacitance of 21.50 µF/cm2 at 50 mV/s scan rate for PES03 device and retaining 98.82% of this capacitance at a higher scan rate of 500 mV/s. PES04 device (Figure S2d) on the other hand achieved an areal capacitance value of 9.16 µF/cm2 at the scan rate of 50 mV/s and could only retain 47.38% of this capacitance at 500 mV/s scan rate.

To further examine the electrochemical performance of the various PES devices, electrochemical impedance spectroscopy (EIS) was performed at the AC voltage amplitude of 10 mV in the frequency range from 100 kHz to 0.1 Hz. The Nyquist plots of the PES devices are shown in Figure 4. At high frequency region of the imaginary and real impedance axes of the Nyquist plots, all devices exhibit no semicircle indicative of the very small charge transfer resistance supplied by PES devices utilizing the as-synthesized quasi-solid-state electrolytes [1,35]. All the PES devices also show straight lines Nyquist plots at low frequency, thereby manifesting ideal electric-double-layer 14

capacitor (EDLC) properties [1,24,36]. The straight lines exhibited at both the low and high frequency regions of the Nyquist plots of the PES devices confirmed the absence of faradaic reaction between the electrolyte/electrode interface. Hence, no pseudo-capacitance behavior was observed in the PES devices rather they exhibited ideal EDLC properties. PES01, PES03 and PES04 devices Nyquist plots straight lines are nearly parallel to the imaginary impedance axis at the low frequency region establishing the ideal capacitive charging-discharging mechanism of the perovskite electrodes [1]. Meanwhile, PES02 device shows a Nyquist plot straight line that is completely parallel to the imaginary impedance axis at both low and high frequency regions. The equivalent circuit diagram used in the fitting the Nyquist plots is shown as an inset in Figure 4b. The equivalent series resistance (ESR), which is ascribed to the ionic conductivity between the electrolyte and the perovskite electrodes, is obtained from the real impedance axis intercept of the Nyquist plot [1,2,8,37]. The ESR values of approximately 18.71 Ω, 0.02 Ω, 55.22 Ω and 504.39 Ω were obtained for PES01, PES02, PES03 and PES04 devices, respectively. The lower ESR values got for all the PES devices result from the large electrolyte-penetrable active surface area provided by the MAPbI3 perovskite electrodes [2]. PES02 device particularly recorded a very low ESR value of 0.02 Ω owing to the enhanced ionic mobility provided by MA+ and I- in the CHLPVAKOHMAI electrolyte [2,16]. On the other hand, PES04 device despite utilizing same electrolyte (CHLPVAKOHMAI) as PES02, has a relatively high ESR value as compared with other devices. The ESR value for PES04 device as posited earlier is as a result of the difficulty in the MA+ and Iions migration within the filter paper separator [33]. In the same vain, it is noticed that PES01 device (without separator) recorded a lower ESR as against that recorded by PES03 device (with separator) owing to ease of ions migration in the absence of separator.

The frequency dependence of the phase angle of the PES devices is shown in Figure S3 to get additional information about the capacitive energy storage performance of the PES devices. For an 15

excellent capacitive performance, the phase angle of the PES devices is expected to be closer to 90o [1,7,8,38]. While PES01 device phase angle in closer to 90o at the low frequency region (Figure S3a), PES02 device phase angle reaches 90o (Figure S3b). PES01 device attained a phase angle of ~ 85o at approximately 16 Hz. The phase angle of 90o recorded by PES02 device is consistent with the vertical line shown by its Nyquist plot, thus manifesting ideal capacitive performance. However, phase angles of PES03 (Figure S3c) and PES04 (Figure S3d) devices show deviation from 90o with maximum recorded phase angles of 79o and 62o, respectively. The deviation is again ascribed to presence of the filter paper separator in the PES03 and PES04 devices. Figure 5 shows the plot of the real (red) and imaginary (blue) capacitances of the PES devices obtained from the EIS measurement as a function of frequency. The real capacitance C′ of PES01 device increases from 0.17 µF at 10 kHz to 7.06 µF at 0.1 Hz (Figure 5a), while PES02 device C′ increases from 281.45 µF at 10 kHz to 1964.60 at 0.1 Hz (Figure 5b). Similarly, PES03 device C′ increases from 0.04 µF at 10 kHz to 7.08 µF at 0.1 Hz (Figure 5c) with PES04 device showing increment in C′ from 0.01 µF to 2.40 µF as the frequency decreases from 10 kHz to 0.1 Hz (Figure 5d). It is observed that the C′ increased as the frequency decreased and became less frequency dependent for PES02 device. The non-frequency dependent behavior exhibited by the PES02 device is attributed to the MAPbI3 electrode structure and interface between the perovskite electrode and the CHLPVAKOHMAI electrolyte [7,39,40]. The relaxation time constant (τo), which corresponds to the inverse of the characteristic frequency (fo) at which the imaginary capacitance C″ manifests a peak, is the minimum time required to discharge all the energy in the PES devices with an efficiency of greater than 50% [1,7,41–43]. The relaxation time constants (τo = 1/ fo) recorded for PES01, PES02, PES03 and PES04 devices are 501.18 µs, 251.19 µs, 1.00 ms and 1.25 ms, respectively.

16

To illustrate the overall performance of the PES devices, the Ragone plot is shown in Figure 6a. The maximum energy density of 0.78 nWh/cm2 and power density of 5.34 mW/cm2 were estimated for PES01 device, while PES02 device recorded the highest energy density and power density of 1.67 nWh/cm2 and 5045.00 mW/cm2, respectively. PES03 device recorded the maximum energy density of 4.30 nWh/cm2 and power density of 1.81 mW/cm2, whereas PES04 device possessed the peak energy density of 1.83 nWh/cm2 and power density of 0.20 mW/cm2. It is noted that the very small ESR value recorded by PES02 device is responsible for the very high power density attained by it [4]. Meanwhile, PES03 device showed the highest energy density value as compared to other devices due to the high capacitance value it achieved. The charge-discharge cycle stability of the PES devices was investigated by CV at a scan rate of 100 mV/s. Figure 6 (b-e) shows the normalized capacitances of the PES devices against cycle number. PES01 device (Figure 6b) retained 93.32% of its initial capacitance value after 1000 charge-discharge cycles. PES02 device (Figure 6c) has a 93.47% capacitance retention value after 1000 cycles. Devices PES03 and PES04 (Figure 6 d-e) were found to retain 73.29% and 82.82% of their initial capacitances after 1000 cycles, respectively.

3.3 Two-step processed perovskite electrochemical supercapacitors 3.3.1 Fabrication and morphological characterization of two-Step processed perovskite active electrodes The electrochemical supercapacitor performance of two-step solution processed perovskite active electrodes utilizing the as-prepared quasi-solid-state electrolytes were equally studied. A 50 µl precursor of as-prepared PbI2 in DMF was spin-coated on an exposed area of 0.9 cm2 of precleaned fluorine-doped tin oxide (FTO) glass at 3000 rpm for 45 s at a ramp rate of 500 rpm. The as spincoated PbI3 perovskite precursor were heated at 110 oC for 25 min and subsequently allowed to cool to room temperature afterward. To complete the perovskite active electrode, 50 µl MAI in 2propanol were spin-coated at 3000 rpm for 45 s at a ramp rate of 500 rpm on the as-prepared PbI3 17

film. The yellowish PbI3 film immediately turned brownish on reacting with the MAI precursor solution [44–48]. The electrode was transferred to an hot plate and heated at 110 oC for 25 min. The two-step solution processed technique was used to fabricate eight perovskite active electrodes. The perovskite active electrodes were then used to fabricate another four different symmetric perovskite electrochemical supercapacitors codenamed PES05, PES06, PES07 and PES08. PES05, PES06, PES07 and PES08 devices mirror those of PES01, PES02, PES03 and PES04 devices, respectively, with the only difference being the method employed to fabricate their perovskite active electrodes. The morphology (Figure 7 a-b) shows well distributed but tightly packed MAPbI3 structure as compared with the morphology of the one-step solution processed MAPbI3 perovskite active electrodes (Figure 2 b-c) [44–46,48–53].

3.3.2

Electrochemical

characterizations

two-step

processed

perovskite

electrochemical

supercapacitors To investigate the electrochemical energy storage performance of the two-step solution processed fabricated PES devices, electrochemical measurements were carried out. CV was conducted at different scan rates ranging from 50 mV/s to 500 mV/s at a potential voltage running between 0 V to 0.6 V. PES05 and PES06 devices showed almost perfect rectangular CV behavior across the different scan rates with a linear increase in current as a function of scan rate as shown in Figure 7 (c-d). PES07 device showed a less rectangular CV behavior at very high scan rate of 500 mV/s (Figure 7e). PES08 device on the contrary manifested poor rectangular CV properties at all the chosen scan rates (Figure 7f).

The device PES05 reached a maximum current of 1.30 µA at a scan rate of 500 mV/s, while the device PES06 attained a peak current of 1.27 µA at the same scan rate, which is almost equal that recorded by PES05. The nearly equal highest currents attained by both PES05 and PES06 is a departure from that of their mirror PES01 and PES02 devices, respectively. The PES06 device, 18

recording a slightly lower maximum current of 1.27 µA as compared to PES05, can be ascribed to the poor ionic transport properties of the MAI of the CHLPVAKOHMAI electrolyte within twostep solution processed perovskite electrode/electrolyte interface. The dense morphology of the two-step solution processed perovskite electrodes does not allow for fast ion migration within the perovskite electrode/electrolyte interface. The presence of filter paper separator within the PES07 and PES08 devices further worsen the performance of the current responses as function of the scan rates, with PES07 and PES08 reaching a maximum current density of 0.70 µA and 0.12 µA both at scan rate of 50 mV/s, respectively.

Figure S4 shows the areal capacitance found at different scan rates for the two-step solution processed PES devices. The areal capacitance as a function of scan rate of PES05 device (Figure S4a) demonstrates an areal capacitance value of 8.06 µF/cm2 at scan rate of 50 mV/s and 101.74% of this capacitance was retained at 500 mV/s scan rate. The PES06 device (Figure S4b) achieved an areal capacitance of 7.27 µF/cm2 at the scan rate of 50 mV/s and the capacitance retention of 101.24% at 500 mV/s scan rate was recorded. The areal capacitance values of PES06 device are lower compared to those of PES05 device at similar scan rates. Further establishing the poor performance of CHLPVAKOHMAI electrolyte in two-step solution processed PES device owing to the inadequate penetration of the electrolyte into the perovskite electrodes. Figure S4c recorded a highest areal capacitance of 6.15 µF/cm2 at 50 mV/s scan rate for device PES07 and retained 59.84% of this capacitance at a higher scan rate of 500 mV/s. Meanwhile, PES08 device (Figure S4d) retained only 26.86% at scan rate of 500 mV/s of the initial areal capacitance value of 1.86 µF/cm2 at the scan rate of 50 mV/s.

The Nyquist plots of the PES devices obtained from the EIS measurements carried out at the AC amplitude voltage of 10 mV in the frequency range of 100 kHz to 0.1 Hz are shown in Figure 8. 19

The devices show straight lines Nyquist plots at both high and low frequency regions of the imaginary and real impedance axes of the Nyquist plots. The straight lines Nyquist plots exhibited by PES05, PES06, PES07 and PES08 devices confirmed the ideal capacitive charging-discharging mechanism of the two-step solution processed perovskite electrodes [1]. Similar equivalent circuit diagram shown in the inset of Figure 4b was used to fit the Nyquist plots. The ESR values of approximately 19.28 Ω, 25.27 Ω, 384.18 Ω and 954.50 Ω were obtained for devices PES05, PES06, PES07 and PES08, respectively. The ESR values obtained for the two-step solution processed PES devices are higher than those got for their respective one-step solution processed mirrored PES devices. These result from the small electrolyte-accessible active surface area provided by the twostep solution processed MAPbI3 perovskite electrodes. PES08 device particularly recorded a high ESR value of 954.50 Ω owing to the diminished ionic mobility of the MA+ and I- in the CHLPVAKOHMAI electrolyte within the densely packed MAPbI3 perovskite electrodes and further worsen by the presence of the filter paper separator.

The frequency dependence of the phase angle of the two-step solution processed PES devices is shown in Figure S5. While PES05 and PES06 devices exhibit phase angles that are closer to 90o at the low frequency region, PES07 and PES08 devices phase angle deviate farther from 90o reaching maximum phase angles of 70o and 75o, respectively. These deviations are equally ascribed to presence of the filter paper separator. The capacitances of the PES05, PES06, PES07 and PES08 devices as function of frequencies are demonstrated in Figure S6. The wine color plot represents the real capacitances, while the olive color plot depicts the imaginary capacitances of the PES devices. The real capacitance C′ of PES05 device increases from 0.17 µF at 10 kHz to 602 µF at 0.1 Hz, while PES06 device C′ increases from 0.21 µF at 10 kHz to 4.52 µF at 0.1 Hz. Likewise, PES07 device C′ increases from 2.09E-5 µF at 10 kHz to 0.76 µF at 0.1 Hz with PES08 device showing increment in C′ from 8.60E-4 µF to 1.84 µF as the frequency decreases from 10 kHz to 0.1 20

Hz. The real capacitance C′ increased as the frequency decreased. The relaxation time constants (τo) obtained from the corresponding frequency of imaginary capacitance peak are 501.18 µs, 317.60 µs, 3.98 ms and 4.88 ms for PES05, PES06, PES07 and PES08, respectively. . The Ragone plot of the two-step solution processed PES devices is shown in Figure 9a. The maximum energy density of 1.66 nWh/cm2 and power density of 5.19 mW/cm2 were estimated for PES05 device, while PES06 device recorded the highest energy density and power density of 1.47 nWh/cm2 and 3.96 mW/cm2, respectively. PES07 device recorded the maximum energy density of 1.23 nWh/cm2 and power density of 0.26 mW/cm2, whereas PES08 device possessed the peak energy density of 0.37 nWh/cm2 and power density of 0.11 mW/cm2. The normalized capacitances of the two-step solution processed PES devices against cycle number is shown in Figure 9 (b-e) to examine the charge-discharge cycle stability. PES05 device (Figure 9b) retained 95.51% of its initial capacitance value after 1000 charge-discharge cycles. PES06 device (Figure 9c) has a 98.27% capacitance retention value after 1000 cycles. Devices PES07 and PES08 (Figure 9 d-e) were however found to retain 72.95% and 62.37% of their initial capacitances after 1000 cycles, respectively.

4. Conclusions In summary, to the best of our knowledge, we fabricated for the first time, perovskite electrochemical supercapacitors utilizing quasi-solid-state electrolytes. We developed and investigated the electrochemical energy storage performance of two different quasi-solid-state electrolytes sandwiched between two symmetric perovskite electrodes. We found that MAI is the main ionic transport material in the CHLPVAKOHMAI electrolyte. The potential of the assynthesized electrolytes to perform the dual functions of electrolyte materials and separators were investigated. We recorded highest areal capacitance of 21.50 µF/cm2 which is 3.65 times greater 21

than areal capacitance recorded by similar perovskite electrochemical capacitors utilizing liquidstate electrolytes. A very high power density of 5.05 W/cm2 was achieved. Electrochemical impedance spectroscopy (EIS) was used to study the ionic transport mechanism and properties of the as-fabricated devices. All devices exhibited short relaxation time to with device recording the shortest relaxation time of 251.19 µs, indicative of the fast discharge properties of the as-fabricated devices. Two methods were used to fabricate the perovskite active electrodes. One-step solution processed MAPbI3 perovskite electrode morphology revealed a loosely connected ribbon-like MAPbI3 structures that allow for adequate interpenetration of the electrolyte thus leading to rapid ions transport at the perovskite electrode/electrolyte interface. The closely packed morphological structure of the two-step solution processed MAPbI3 perovskite electrodes does not allow for fast ion migration within the perovskite electrode/electrolyte interface. The devices show excellent cyclability with device retaining 98.34% of its initial capacitance value after 1000 cycle.

Supporting Information Supplementary information is included, also available from the authors.

Acknowledgements The authors acknowledge the funding support provided by the King Abdullah City for Atomic and Renewable Energy (K.A.CARE) through project KACARE182-GSGP-07 and KACARE182-RFP02. The authors are thankful to King Fahd University of Petroleum & Minerals (KFUPM), Dhahran, Saudi Arabia.

Competing Interest The authors declare no conflict of interest.

Reference [1]

W. Liu, Y. Feng, X. Yan, J. Chen, Q. Xue, Superior Micro‐Supercapacitors Based on Graphene Quantum

Dots. Adv. Funct. Mater., 23 (2013) pp. 4111-4122

doi:10.1002/adfm.201203771 22

.

[2]

J.K. Pious, M.L. Lekshmi, C. Muthu, R.B. Rakhi, V.C. Nair, Zero-Dimensional Methylammonium Bismuth Iodide-Based Lead-Free Perovskite Capacitor, ACS Omega, 2 9 (2017) pp. 5798–5802, doi:10.1021/acsomega.7b00973.

[3]

Y. Gao, Y.S. Zhou, W. Xiong, L.J. Jiang, P. Thirugnanam, X. Huang, M.M. Wang, L. Jiang, Y.F. Lu, Transparent , flexible , and solid-state supercapacitors based on graphene electrodes based on graphene electrodes, APL Materials 1, (2013) pp. 012101; doi:10.1063/1.4808242

[4]

R. Yuksel, Z. Sarioba, A. Cirpan, P. Hiralal, H.E. Unalan, Transparent and Flexible Supercapacitors with Single Walled Carbon Nanotube Thin Film Electrodes, ACS Appl. Mater. Interfaces, 6 17 (2014), pp. 15434–15439, doi:10.1021/am504021u.

[5]

C. Romanitan, P. Varasteanu, I. Mihalache, D. Culita, S. Somacescu, R. Pascu, E. Tanasa, S.A. V Eremia, A. Boldeiu, M. Simion, A. Radoi, M. Kusko, High-performance solid state supercapacitors assembling graphene interconnected networks in porous silicon electrode by electrochemical methods using, Sci. Rep.

8 (2018) pp. 1–14. doi:10.1038/s41598-018-

28049-x. [6]

K. Shi, K.P. Giapis, Scalable Fabrication of Supercapacitors by Nozzle-Free Electrospinning, ACS Appl. Energy Mater., 1 2 (2018) pp. 296–300, doi:10.1021/acsaem.7b00227.

[7]

K. Lee, H. Lee, Y. Shin, Y. Yoon, D. Kim, H. Lee, Nano Energy Highly transparent and fl exible supercapacitors using graphene-graphene quantum dots chelate, Nano Energy. 26 (2016) pp. 746–754, doi:10.1016/j.nanoen.2016.06.030.

[8]

M.F. El-kady, R.B. Kaner, Scalable fabrication of high-power graphene microsupercapacitors for flexible and on-chip energy storage, Nat. Commun. 4 (2013) pp. 1475– 1479, doi:10.1038/ncomms2446.

[9]

N. Liu, Y. Gao, Recent Progress in Micro-Supercapacitors with In-Plane Interdigital Electrode Architecture, Small, 13, (2017) pp. 1701989, doi:10.1002/smll.201701989.

[10]

Q. Chen, H. Zhou, Z. Hong, S. Luo, H. Duan, H. Wang, Y. Liu, G. Li, Y. Yang, Planar

23

Heterojunction Perovskite Solar Cells via Vapor-Assisted Solution Process, J. Am. Chem. Soc., 136 2 (2014), pp. 622–625. doi:10.1021/ja411509g. [11]

E. Edri, S. Kirmayer, S. Mukhopadhyay, K. Gartsman, G. Hodes, D. Cahen, Elucidating the charge carrier separation and working mechanism of CH3NH3PbI(3-x)Cl(x) perovskite solar cells., Nat. Commun. 5 (2014) pp. 3461. doi:10.1038/ncomms4461.

[12]

T. Baikie, Y. Fang, J.M. Kadro, M. Schreyer, F. Wei, S.G. Mhaisalkar, M. Gratzel, T.J. White, Synthesis and crystal chemistry of the hybrid perovskite (CH3NH3)PbI3 for solidstate sensitised solar cell applications, J. Mater. Chem. A. 1 (2013) pp. 5628. doi:10.1039/c3ta10518k.

[13]

J. Li, V. Mishukova, All-solid-state micro-supercapacitors based on inkjet printed graphene electrodes, Appl. Phys. Lett. 109, (2016) pp. 123901, doi:10.1063/1.4962728.

[14]

X. Yan, Z. Tai, Q. Xue, Nanoscale Fabrication of carbon nanofiber – polyaniline composite flexible paper for supercapacitor, Nanoscale 3 (2011) pp. 212-216, doi:10.1039/c0nr00470g.

[15]

Z. Li, H. Zhang, Q. Liu, L. Sun, L. Stanciu, J. Xie, Fabrication of High-Surface-Area Graphene / Polyaniline Nanocomposites and Their Application in Supercapacitors, ACS Appl. Mater. Interfaces, 5 7 (2013) pp. 2685–2691. doi:10.1021/am4001634.

[16]

S. Zhou, L. Li, H. Yu, J. Chen, C. Wong, N. Zhao, Thin Film Electrochemical Capacitors Based on Organolead Triiodide Perovskite, Adv. Electron. Mater., 2 (2016) pp. 1600114. doi:10.1002/aelm.201600114.

[17]

S.Z. Zhang, X.L. Wang, X.H. Xia, Z.J. Yao, Y.J. Xu, D.H. Wang, D. Xie, J.B. Wu, D. Gu, J.P. Tu, Smart construction of intimate interface between solid polymer electrolyte and 3Darray electrode for quasi-solid-state lithium ion batteries, J. of Power Sources 434 (2019). doi:10.1016/j.jpowsour.2019.226726.

[18]

A. Sacco, F. Bella, D. La Pierre, M. Castellino, S. Bianco, R. Bongiovanni, C. Fabrizio, Electrodes/Electrolyte Interfaces in the Presence of a Surface‐Modified Photopolymer

24

Electrolyte: Application in Dye‐Sensitized Solar Cells. ChemPhysChem, 16 (2015) 960969. doi:10.1002/cphc.201402891.

[19] F. Bella, A. Lamberti, A. Sacco, S. Bianco, A. Chiodoni, R. Bongiovanni, Novel electrode and electrolyte membranes : Towards fl exible dye-sensitized solar cell combining vertically aligned TiO 2 nanotube array and light-cured polymer network, J. Memb. Sci. 470 (2014) 125–131. doi:10.1016/j.memsci.2014.07.020. [20]

F. Bella, M. Imperiyka, A. Ahmad, Photochemically produced quasi-linear copolymers for stable and efficient electrolytes in dye-sensitized solar cells. Journal of Photochemistry and Photobiology

A:

Chemistry,

289,

(2014)

73-80.

https://doi.org/10.1016/j.jphotochem.2014.05.018 [21]

F. Bella, E. Daniela, S. Bianco, R. Bongiovanni, Photo-polymerization of acrylic / methacrylic gel – polymer electrolyte membranes for dye-sensitized solar cells, Chem. Eng. J. 225 (2013) 873–879. doi:10.1016/j.cej.2013.04.057.

[22]

D. Wang, L. Yu, B. He, L. Wang, A high-performance carbon-carbon ( C / C ) Quasi-SolidState

Supercapacitor

with

Conducting

Gel

Electrolyte,

International

journal

of

electrochemical science 13 (2018) 2530–2543. doi:10.20964/2018.03.73. [23]

B. Cheng, R. Cheng, F. Tan, X. Liu, J. Huo, G. Yue, Highly Efficient Quasi-Solid-State Asymmetric Supercapacitors Based on MoS 2 / MWCNT and PANI / MWCNT Composite Electrodes, Nanoscale Research Letters 14:66 (2019 doi:10.1186/s11671-019-2902-5) .

[24]

Y. Yoon, K. Lee, C. Baik, H. Yoo, M. Min, Y. Park, S.M. Lee, H. Lee, Anti-Solvent Derived Non-Stacked Reduced Graphene Oxide for High Performance Supercapacitors, Adv. Mater.,

25 (2013) pp. 4437-4444. doi:10.1002/adma.201301230. [25]

J. Lin, C. Zhang, Z. Yan, Y. Zhu, Z. Peng, R.H. Hauge, D. Natelson, J.M. Tour, 3 ‐ Dimensional Graphene Carbon Nanotube Carpet-Based Microsupercapacitors with High Electrochemical Performance, Nano Lett., 13 1 (2013) pp. 72–78.

25

[26]

J. Coates, Interpretation of Infrared Spectra , A Practical Approach, iEncyclopedia of Analytical Chemistry R.A. Meyers (Ed.) (2000) pp. 10815–10837, John Wiley & Sons Ltd, Chichester.

[27]

X. Lu, M. Yu, G. Wang, Y. Tong and Y. Li, Flexible solid-state supercapacitors: design, fabrication

and

applications

Energy,

Environ.

7

Sci.,

(2014)

pp.

2160-2181

doi:10.1039/c4ee00960f. [28]

Y. Fu, X. Cai, H. Wu, Z. Lv, S. Hou, M. Peng, X. Yu, Fiber Supercapacitors Utilizing Pen Ink for Flexible / Wearable Energy Storage, Adv. Mater., 24 (2012) pp. 5713-5718. doi:10.1002/adma.201202930.

[29]

P. Mandake, P.B. Karandikar, Effect of Separator Thickness Variation for Supercapacitor with

Polyethylene

Separator

Material,

IJSRSET

2

(2016)

pp.

967–971,

doi:10.32628/IJSRSET1622232 [30]

S. Xian-Zhong, Z. Xiong, H. Bo, M. Yan-Wei, Effects of Separator on the Electrochemical Performance of Electrical Double-Layer Capacitor and Hybrid Battery-Supercapacitor, Acta Phys. -Chim. Sin. 30 (2014) pp. 485–491. doi:10.3866/PKU.WHXB201401131.

[31]

P. Mandake, P.B. Karandikar,

Significance of Separator Thickness for Supercapacitor,

IJRASET 4 (2016) pp. 214–218. [32]

N.S.M. Nor, M. Deraman, R. Omar, E. Taer, R. Farma, N.H. Basri, B.N.M. Dolah, Nanoporous separators for supercapacitor using activated carbon monolith electrode from oil palm

empty fruit

bunches,

AIP

Conference Proceedings 1586,

(2014) pp. 68,

doi:10.1063/1.4866732. [33]

V. Vijayakumar, B. Anothumakkool, T,

Nair, V. Badiger, S. Kurungot, Aqueous gel

polymer electrolyte prepared using a UV-assisted in situ polymerization strategy, J. Mater. Chem. A 5 (2017) pp. 8461–8476 . doi:10.1039/C7TA01514C. [34]

M.D. Stoller, S. Park, Y. Zhu, J. An, R.S. Ruoff, Graphene-Based Ultracapacitors, Nano

26

Lett., 8 10 (2008) pp. 3498–3502, doi: 10.1021/nl802558y [35]

Y. Wang, Z. Shi, Y. Huang, Y. Ma, C. Wang, M. Chen, Y. Chen, Supercapacitor Devices Based on Graphene Materials, J. Phys. Chem. C, 113 30 (2009), pp. 13103–13107. doi: 10.1021/jp902214f, .

[36]

Y. Yoon, K. Lee, S. Kwon, S. Seo, H. Yoo, S. Kim, Y. Shin, Y. Park, D. Kim, J. Choi, H. Lee, Vertical Alignments of Graphene Sheets Spatially and Densely Piled for Fast Ion Di ff usion in Compact Supercapacitors, ACS Nano 8 5 (2014) pp. 4580–4590. doi: 10.1021/nn500150

[37]

K. Sheng, Y. Sun, C. Li, W. Yuan, G. Shi, Ultrahigh-rate supercapacitors based on eletrochemically reduced graphene oxide for ac line-filtering, Sci. Re.p 2 (2012) pp. 3–7. doi:10.1038/srep00247.

[38]

P. Taberna, P. Simon and J. Fauvarque J.E. Soc, P. A-a, Electrochemical Characteristics and Impedance Spectroscopy Studies of Carbon-Carbon Supercapacitors, J. Electrochem. Soc. 3, (2003) pp. A292-A300. doi:10.1149/1.1543948.

[39]

W. Si, C. Yan, Y. Chen, O.G. Schmidt, On chip, all solid-state and flexible microsupercapacitors with high performance based on MnOx/Au multilayers Energy Environ. Sci.,

6, (2013) pp. 3218-3223 . doi:10.1039/c3ee41286e. [40]

D. Pech, M. Brunet, H. Durou, P. Huang, V. Mochalin, Y. Gogotsi, P. Taberna, P. Simon, Ultrahigh-power micrometre-sized supercapacitors based on onion-like carbon, Nature Nanotechnology 5 (2010) pp. 651–654. doi:10.1038/nnano.2010.162.

[41]

P.W. Ruch, D. Cericola, A. Foelske, R. Kötz, A. Wokaun, Electrochimica Acta A comparison of the aging of electrochemical double layer capacitors with acetonitrile and propylene carbonate-based electrolytes at elevated voltages, Electrochim. Acta. 55 (2010) pp. 2352–2357. doi:10.1016/j.electacta.2009.11.098.

[42]

M. Beidaghi, C. Wang, Micro-Supercapacitors Based on Interdigital Electrodes of Reduced

27

Graphene Oxide and Carbon Nanotube Composites with Ultra high Power Handling Performance, Adv. Funct. Mater., 22 (2012) pp. 4501-4510. doi:10.1002/adfm.201201292. [43]

D. Bi, A.M. El-zohry, A. Hagfeldt, G. Boschloo, Improved Morphology Control Using a Modified Two-Step Method for Efficient Perovskite Solar Cells, ACS Appl. Mater. Interfaces, 6 21 (2014) pp. 18751–18757, doi: 10.1021/am504320h

[44]

M. Gratzel, Sequential deposition as a route to high-performance perovskite-sensitized solar cells, Nature 499 (2013) pp. 4–8. doi:10.1038/nature12340.

[45]

L. Chen, K. Lee, W. Wu, C. Hsu, Z. Tseng, X.H. Sun, Effect of Different CH3NH3PbI3 Morphologies on Photovoltaic Properties of Perovskite Solar Cells, Nanoscale Research Letters 13 (2018) pp. 140. doi:10.1186/s11671-018-2556-8

[46]

T. Zhang, M. Yang, Y. Zhao, K. Zhu, Controllable Sequential Deposition of Planar CH3NH3PbI3 Perovskite Films via Adjustable Volume Expansion, Nano Lett., 15 6 (2015) pp. 3959–3963. doi:10.1021/acs.nanolett.5b00843.

[47]

H. Ko, J. Lee and N. Park, 15.76% efficiency perovskite solar cells prepared under high relative humidity: importance of PbI2 morphology in two-step deposition of CH3NH3PbI3 J. Mater. Chem. A, 3, (2015) pp. 8808-8815. doi:10.1039/C5TA00658A.

[48]

L. Zheng, D. Zhang, Y. Ma, Z. Lu, Z. Chen, Morphology control of the perovskite fi lms for efficient solar cells, Dalton Trans.,44, (2015) pp. 10582-10593. doi:10.1039/c4dt03869j.

[49]

Y. XuLifeng, Z. ShiSongtao, L. XuJunyan, X. DongHuijue, W.Yanhong L. Li, Q. Meng, Efficient Hybrid Mesoscopic Solar Cells with Morphology-Controlled CH 3 NH 3 PbI 3-x Cl x Derived from Two-Step Spin Coating Method, ACS Appl. Mater. Interfaces, 7 4, (2015) pp. 2242–2248. doi:10.1021/am5057807.

[50]

D. Liu, L. Wu, C. Li, S. Ren, J. Zhang, W. Li, L. Feng, Controlling CH3NH3PbI3–xClx Film Morphology with Two-Step Annealing Method for Efficient Hybrid Perovskite Solar Cells, ACS Appl. Mater. Interfaces, 7 30 (2015) pp. 16330–16337. doi: 10.1021/acsami.5b03324,

28

[51]

A. Ip, L. Quan, M. Adachi, J. Mcdowell, J. Xu, D. Kim, H. Edward, D. Kim, E. Sargent, A two-step route to planar perovskite cells exhibiting reduced hysteresis A two-step route to planar perovskite cells exhibiting reduced hysteresis, Appl. Phys. Lett. 106, (2015) pp. 143902. doi:10.1063/1.4917238.

[52]

S. Chen, L. Lei, S. Yang, Y. Liu, and Z. Wang, Characterizations of Perovskite Obtained from Two- Step Deposition on Mesoporous Titania, ACS Appl. Mater. Interfaces, 7 46, (2015) pp. 25770–25776. doi:10.1021/acsami.5b07511.

[53]

J. Yan, Q. Wang, T. Wei, Z. Fan, Recent Advances in Design and Fabrication of Electrochemical Supercapacitors with High Energy Densities, Adv. Energy Mater., 4 (2014) pp. 1300816. doi:10.1002/aenm.201300816.

29

Figures

Figure 1

30

Figure 2

31

Figure 3

32

Figure 4

33

Figure 5

34

Figure 6

35

Figure 7

36

Figure 8

37

Figure 9

38

Legends Figure 1: ATR-FTIR spectra of a) CHLPVAKOH electrolyte and its pure constituent materials. b) CHLPVAKOHMAI and its pure constituent materials. c) Nyquist plot of the CHLPVAKOH quasisolid-state electrolyte. d) Nyquist plot of the CHLPVAKOHMAI quasi-solid-state electrolyte. Figure 2: a) Schematic of fabrication procedure of perovskite electrochemical supercapacitors showing sequential steps of spin coating MAPbI3 precursor solution on precleaned FTO glass, followed by annealing at 110 oC and subsequent sandwiching of the as-prepared electrolyte (with/without separator) in between the as-fabricated perovskite active electrodes. b) SEM image of one-step solution processed fabricated perovskite active electrode at 5 µm showing ribbon-like perovskite films. c) SEM image of one-step solution processed fabricated perovskite active electrode at 20 µm showing uniform dispersion of the ribbon-like perovskite films. Figure 3: a) Cyclic voltammetry (CV) curves at the different scan rate of PES01 one-step fabricated perovskite active electrode utilizing CHLPVAKOH electrolyte without separator. b) CV curves at the different scan rate of PES02 one-step fabricated perovskite active electrode utilizing CHLPVAKOHMAI electrolyte without separator. c) CV curves at the different scan rate of PES03 one-step fabricated perovskite active electrode utilizing CHLPVAKOH electrolyte with separator. d) CV curves at the different scan rate of PES04 one-step fabricated perovskite active electrode utilizing CHLPVAKOHMAI electrolyte with separator. Figure 4: a) Electrochemical impedance spectroscopy (EIS) Nyquist plots of device PES01 onestep fabricated perovskite active electrode utilizing CHLPVAKOH electrolyte without separator. b) EIS Nyquist plots of device PES02 one-step fabricated perovskite active electrode utilizing CHLPVAKOHMAI electrolyte without separator [inset: equivalent circuit diagram used in fitting the Nyquist curves]. c) EIS Nyquist plots of device PES03 one-step fabricated perovskite active electrode utilizing CHLPVAKOH electrolyte with separator. d) EIS Nyquist plots of device PES04 one-step fabricated perovskite active electrode utilizing CHLPVAKOHMAI electrolyte with separator. Figure 5: a) Evolution of real (C`, red plot) and imaginary (C”, blue plot) capacitances with frequency for device PES01 one-step fabricated perovskite active electrode utilizing CHLPVAKOH electrolyte without separator. b) Evolution of real (C`, red plot) and imaginary (C”, blue plot) capacitances with frequency for device PES02 one-step fabricated perovskite active electrode utilizing CHLPVAKOHMAI electrolyte without separator. c) Evolution of real (C`, red plot) and imaginary (C”, blue plot) capacitances with frequency for device PES03 one-step fabricated perovskite active electrode utilizing CHLPVAKOH electrolyte with separator. d) Evolution of real (C`, red plot) and imaginary (C”, blue plot) capacitances with frequency for device PES04 one-step fabricated perovskite active electrode utilizing CHLPVAKOHMAI electrolyte with separator. Figure 6: a) Ragone plot showing power density vs energy density of devices PES01, PES02, PES03 and PES04. b) Cyclic stability showing normalized capacitance versus cycle number of 1000 at scan rate of 100 mV/s for devices PES01 one-step fabricated perovskite active electrode utilizing CHLPVAKOH electrolyte without separator. c) Cyclic stability showing normalized capacitance versus cycle number of 1000 at scan rate of 100 mV/s for devices PES01 one-step fabricated perovskite active electrode utilizing CHLPVAKOHMAI electrolyte without separator. d) Cyclic stability showing normalized capacitance versus cycle number of 1000 at scan rate of 100 mV/s for devices PES03 one-step fabricated perovskite active electrode utilizing CHLPVAKOH electrolyte with separator. e) Cyclic stability showing normalized capacitance versus cycle number 39

of 1000 at scan rate of 100 mV/s for devices PES04 one-step fabricated perovskite active electrode utilizing CHLPVAKOHMAI electrolyte with separator.

Figure 7: a) SEM image of two-step solution processed fabricated perovskite active electrode at 5 µm showing ribbon-like perovskite films. b) SEM image of two-step solution processed fabricated perovskite active electrode at 20 µm showing uniform dispersion of the ribbon-like perovskite films. c) Cyclic voltammetry (CV) curves at the different scan rate of PES05 one-step fabricated perovskite active electrode utilizing CHLPVAKOH electrolyte without separator. d) CV curves at the different scan rate of PES06 one-step fabricated perovskite active electrode utilizing CHLPVAKOHMAI electrolyte without separator. e) CV curves at the different scan rate of PES07 one-step fabricated perovskite active electrode utilizing CHLPVAKOH electrolyte with separator. f) CV curves at the different scan rate of PES08 one-step fabricated perovskite active electrode utilizing CHLPVAKOHMAI electrolyte with separator.

Figure 8: a) EIS Nyquist plots of device PES05 one-step fabricated perovskite active electrode utilizing CHLPVAKOH electrolyte without separator. b) EIS Nyquist plots of device PES06 onestep fabricated perovskite active electrode utilizing CHLPVAKOHMAI electrolyte without separator. c) EIS Nyquist plots of device PES07 one-step fabricated perovskite active electrode utilizing CHLPVAKOH electrolyte with separator. d) EIS Nyquist plots of device PES08 one-step fabricated perovskite active electrode utilizing CHLPVAKOHMAI electrolyte with separator. Figure 9: a) Ragone plot showing power density vs energy density of devices PES05, PES06, PES07 and PES08. b) Cyclic stability showing normalized capacitance versus cycle number of 1000 at scan rate of 100 mV/s for devices PES05 one-step fabricated perovskite active electrode utilizing CHLPVAKOH electrolyte without separator. c) Cyclic stability showing normalized capacitance versus cycle number of 1000 at scan rate of 100 mV/s for devices PES06 one-step fabricated perovskite active electrode utilizing CHLPVAKOHMAI electrolyte without separator. d) Cyclic stability showing normalized capacitance versus cycle number of 1000 at scan rate of 100 mV/s for devices PES07 one-step fabricated perovskite active electrode utilizing CHLPVAKOH electrolyte with separator. e) Cyclic stability showing normalized capacitance versus cycle number of 1000 at scan rate of 100 mV/s for devices PES08 one-step fabricated perovskite active electrode utilizing CHLPVAKOHMAI electrolyte with separator.

40

Author Contributions

Idris Popoola and Mohammed Gondal contributed in the design of concept, experimental procedure, analysis of results and discussion, outlined and reviewed the manuscript. Idris Popoola, Luqman Oloore, AbdulJelili Popoola and Jwaher AlGhamdi performed the experiments, collected data, and also contributed in drafting the manuscript.

Declaration of Interest Statement The authors declare no competing interests and all authors are aware of the submission and agree to its publication in Food Chemistry.