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Graphene composite plastic film as current collector for aluminum-graphite batteries
Materials Letters 254 (2019) 436–439
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/mlblue
Graphene composite plastic film as current collector for aluminum-graphite batteries Yu Wang a,b, Fangyu Gan b, Kanghua Chen a,b,⇑ a b
Powder Metallurgy Research Institute, Central South University, Changsha 410083, China State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China
a r t i c l e
i n f o
Article history: Received 20 April 2019 Received in revised form 25 May 2019 Accepted 25 June 2019 Available online 26 June 2019 Keywords: Aluminum-ion batteries Current collector Energy storage and conversion Carbon materials
a b s t r a c t The use of rare metals as current collectors in aluminum-ion batteries is an urgent problem to be solved, so there are significant interests in the development of light-weight and high-efficiency materials as current collector. Herein, we report a polyvinyl-alcohol/graphene composite film as current collector in aluminum-ion batteries which synthesized by a simple solution method. The film containing 20 wt% graphene demonstrates high electrical conductivity up to 164Scm 1 with 30 lm in thicknesses and 2.8 mg cm 2 in areal density. According to the electrochemical measurements, a reversible capacity of 89 mAh g 1 is obtained at a rate of 1C in aluminum-graphite battery. Ó 2019 Published by Elsevier B.V.
1. Introduction Aluminum-ion batteries (AIBs) exhibit high theoretical volumetric capacity of 8040 mAh cm 3 and are considered a promising source of power supply due to the abundance and non-toxicity of aluminum metal [1–3]. Remarkably, Dai and their colleagues assembled an aluminum-ion battery using the original natural graphite flakes as the cathode, with a discharge capacity of 110 mAh g 1 (at 0.9 C) and more than 6000 cycles [4]. However, the above-mentioned researches use the rare metal (tantalum, nickel and molybdenum) and expensive carbon paper as current collector due to the unique corrosion resistance presented in aluminum ionic liquid [5,6]. This would restrict the industrialization of AIBs due to the natural resources scarcity and high cost and low productivity of carbon paper. Consequently, developing a fruitful in earth resources and low-cost current collector is highly desired [7]. Here, we mainly discuss the feasibility of a highly conductive and lightweight poly(vinyl alcohol)/graphene (PVA/GNP) conductive composite film used as a current collector in aluminumgraphite batteries. PVA/GNP composite in the form of film is prepared by simple solution processing which graphene dispersed into the PVA matrix referenced to the literature [8]. The stability of the composite film in aluminum ionic liquid was confirmed. ⇑ Corresponding author at: Powder Metallurgy Research Institute, Central South University, Changsha 410083, China. E-mail address: [email protected] (K. Chen). https://doi.org/10.1016/j.matlet.2019.06.082 0167-577X/Ó 2019 Published by Elsevier B.V.
Simultaneously, explored whether it meets the electrical and mechanical properties as a current collector is quite necessary. The electrochemical performance has also been further verified while graphite cathode based PVA/GNP current collector and aluminum foil anode in a low-cost room temperature ionic liquid electrolyte mixed triethylamine hydrochloride (Et3CHCl) with AlCl3 [9]. 2. Experiment High conductivity graphene aqueous solution and poly(vinyl alcohol) powered (Mw = 180000) were used for preparing PVA/ GNP composite film while the process was referred to the literature [8]. Active materials for the cathode and anode were graphite and aluminum foil with a thickness of 20 lm (both current collector and electrode), respectively. The electrode was fabricated by preparing a slurry containing active materials graphite, carbon black powder, and binder PVDF with a weight ratio of 8:1:1 in NMP. The slurry was coated on the PVA/GNP composite film by the doctor blade technique. All electrodes were placed in a vacuum oven and dried over-night at 80 °C before being assembled in soft case cells in an argon-filled glove box. The separator was a porous glass fiber paper. The electrolyte is ionic liquid in a mixture of AlCl3/Et3CHCl (1.7:1 m/m). A DMR-1C sheet resistance apparatus was employed to investigate the composite film resistance and calculate its conductivity according to the formula R = q l/(l w) = q/w and j = 1/q (R represents sheet resistance, O; q represents resistivity, O cm; l represents width and length of a square, and w
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Y. Wang et al. / Materials Letters 254 (2019) 436–439
represents thickness of film, respectively, cm; j represents conductivity, S cm 1) [10] An average of 10 specimens from composite film were measured to obtain the conductivity j. The structure of the film was observed using a scanning electron microscope model QUANTA-200. The mechanical properties of the composite film were determined using a universal testing machine model MTS810. Charge-discharge tests were carried out using a Land battery test system (Wuhan Land-CT2001A, China) which the range of voltages is 0–2.4 V. The cyclic voltammetry (CV) results were collected using a CHI606 workstation. The scan rate of the CV test was 1 mVs 1. 3. Results and discussion Owing to the high corrosive of AlCl3 ionic liquids on most metals (except tantalum, nickel and molybdenum), it is necessary to investigate the stability of PVA/GNP composite film in AlCl3/Et3CHCl ionic liquid electrolyte. PVA/GNP composite film was directly added to weighing bottles containing prepared ionic liquid in a mixture of AlCl3/Et3CHCl and allowed to stand for 7200 h. As shown in Fig. 1(a), it can be discovered that there was no obvious reaction while the film is insoluble in the ionic liquid and can maintain integrity. We further verified whether the AlCl3/Et3CHCl ionic liquid changed after soaking the composite film. Fig. 1(b) shows the Raman spectra of the electrolyte before and after soaking the PVA/GNP composite film. Two peaks at 311 cm 1 and 347 cm 1 were detected, which is assigned to the Al-Cl terminal stretching frequencies in AlCl4 anions and Al2Cl7 anions. The Raman spectra of the electrolyte after and before soaking the composite film is the same [9], which confirms the stability of the composite film in the ion liquid. When PVA/GNP composite film was used as a current collector, the areal density of GNP in composite film about 0.56 mg cm 2. Compared to the graphite active material 5 mg cm 2, graphene
mainly provides electronic. The below CV curve of the graphitePVA/GNP electrodes can prove that no side electrochemical reaction and redox reactions only occurs at the graphite/electrolyte interface. Therefore, GNP mainly provides electronic and does not affect the stability of the composite film as current collector. The electrical conductivity of the PVA/GNP composite film mainly needs to meet two characteristics: providing electrical transport to the active material and supporting the active material. Therefore, to investigate whether it meets the electrical properties as a current collector is essential. The resistivity and conductivity of the composite film is shown in Fig. 2(a) and (b). It can be found that the conductivity is as high as 164S cm 1 at an ultrahigh content of GNP, for example, 20% by weight. Moreover, the composite film is much lighter about 2.8 mg cm 2 in areal density compared that of molybdenum sheet (about 16 mg cm 2), which would greatly reduce the weight of the battery and meet the requirements of the actual application of the battery. Surface morphology of the PVA/GNP composite film was shown in the Fig. 2(c). It reveals that GNP particles are well dispersed and no significant cluster or agglomerates was found in PVA matrix. The graphene overlaps each other to form a good conductive path. The insert image in Fig. 2(c) shows that the composite film is sufficiently smooth, strong and flexible as a current collector. The mechanical property of the PVA/GNP composite film was shown in the Table 1. Compared with the pure PVA film, the tensile stress of the PVA/GNP composite film increased by about 33.26% and the elongation at break gradually decreases. However, the tensile strength of graphite-PVA/GNP electrode is relatively lower (8.33 MPa), compared to the other electrodes [11], while still acceptable. Therefore, this composite film would be sufficiently formidable and flexible for applications as a current collector. The electrochemistry property of the PVA/GNP composite film as current collector in aluminum-ion battery was verified. Fig. 3 (a) shows the CV curves of the Al-graphite battery based on PVA/
before
after
Fig. 1. (a) Comparison of weighing bottles with AlCl3/Et3CHCl ionic liquids to which were added in PVA/GNP composite film. (b) Raman spectra of electrolyte before and after soaking the PVA/GNP composite film.
Fig. 2. (a) and (b) Resistivity and conductivity of the PVA/GNP composite film. (c) SEM micrographs of fractured surfaces of PVA/GNP composite film.
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Table 1 Tensile properties of the films. Sample
Tensile strain (%)
Tensile stress (MPa)
Pure PVA PVA/GNP composite film Electrode based on PVA/GNP
180.34 79 6.93
18.34 19.42 8.33
GNP composite film as current collector (graphite-PVA/GNP electrode). Two-well defined reduction peaks are noted at 1.5 (a’ peak) and 2.0 V (b’ peak). Accordingly, the oxidation peaks are found at 1.8 V (a peak) and 2.1 V (b peak), respectively. The CV curve of the graphite-PVA/GNP electrodes shows no side electrochemical reaction associated with it referenced in the literature [3]. Therefore, the observed redox reactions only occur at the graphite/electrolyte interface. Fig. 3(b–d) shows the charge/discharge
performance of graphite-PVA/GNP electrodes between 0 and 2.4 V in the electrolyte of AlCl3/Et3CHCl at a rate of 1C. Noting that the electrode delivered a discharge capacity (87 mAh g 1) based on the weight of graphite and gradually stabilize the average voltage at 1.75 V. The cycle stability and rate performance of the electrode were also shown good performance, which shows no decrease in the capacity of the graphite-PVA/GNP electrode. This suggests that the PVA/GNP composite film as a current collector is a promising candidate current collector for AIB. 4. Conclusion In conclusion, we have successfully prepared and demonstrate a high electrical conductivity and lightweight PVA/GNP composites film as current collector in aluminum-ion batteries. The composite film has a highly stability in aluminum ionic liquids. In addition,
Fig. 3. (a) CV profile of graphite-PVA/GNP electrodes at a scan rate of 1 mV s 1. (b) Galvanostatic voltage profiles of electrodes at the fifth cycle (rate = 1 C). (c) Rate performances and cycling performances of the graphite-PVA/GNP electrodes. (d) Average voltage of the graphite-PVA/GNP electrodes at 1 C. (e) Long cycling performances of the graphite-PVA/GNP electrodes.
Y. Wang et al. / Materials Letters 254 (2019) 436–439
weight of the PVA/GNP composite film (2.8 mg cm 2) is much lighter than a molybdenum sheet (about 16 mg cm 2), leading to reduce the weight of the battery in AIBs. Based on PVA/GNP composite film as a current collector, a capacity of 89 mAh g 1 at a rate of 1 C with an average voltage 1.75 V is achieved in Al-graphite battery. It demonstrates that PVA/GNP composite film can be utilized effectively as current collector within the AIBs for the largescale potential applications.
Acknowledgments This work was supported by National Key Research and Development Program of China (No. 2016YFB0300801), Major Research Equipment Development Projects of National Natural Science Foundation of China (No. 51327902).
References [1] M.C. Lin, M. Gong, B. Lu, et al., An ultrafast rechargeable aluminium-ion battery, Sci. Found. China 520 (4) (2015) 19–20.
439
[2] P. Bhauriyal, A. Mahata, B. Pathak, The staging mechanism of AlCl4 intercalation in a graphite electrode for an aluminium-ion battery, PCCP 19 (11) (2017) 7980. [3] H. Jiao, C. Wang, J. Tu, et al., A rechargeable Al-ion battery: Al/molten AlCl3urea/graphite, Chem. Commun. 53 (15) (2017) 2331–2334. [4] D.Y. Wang, C.Y. Wei, M.C. Lin, et al., Advanced rechargeable aluminium ion battery with a high-quality natural graphite cathode, Nat. Commun. 8 (2017) 14283. [5] H. Chen, C. Chen, Y. Liu, et al., High-quality graphene microflower design for high-performance Li–S and Al-ion batteries, Adv. Energy Mater. 7 (17) (2017). [6] M. Angell, C.J. Pan, Y. Rong, et al., High coulombic efficiency aluminum-ion battery using an AlCl3-urea ionic liquid analog electrolyte, Proc. Natl. Acad. Sci. U.S.A. (2017) 834. [7] S. Yehezkel, M. Auinat, N. Sezin, et al., Bundled and densified carbon nanotubes (CNT) fabrics as flexible ultra-light weight Li-ion battery anode current collectors, J. Power Sources 312 (2016) 109–115. [8] X. Yang, L. Li, S. Shang, et al., Synthesis and characterization of layer-aligned poly(vinyl alcohol)/graphene nanocomposites, Polymer 51 (15) (2010) 3431– 3435. [9] H. Xu et al., Low-cost AlCl3/Et3NHCl electrolyte for high-performance aluminum-ion battery, Energy Storage Mater. (2018). [10] S.H. Deng, Y. Wang, X. Yang, The study of electrochemical synthesis, properties and composite mechanism of PANI/PVA and PANI/PVA/Ag composite films, Pigm. Resin Technol. 47 (1) (2018) 00–01. [11] H. Lu, J. Hagberg, G. Lindbergh, et al., Li4Ti5O12, flexible, lightweight electrodes based on cellulose nanofibrils as binder and carbon fibers as current collectors for Li-ion batteries, Nano Energy 39 (2017) 140–150.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/mlblue
Graphene composite plastic film as current collector for aluminum-graphite batteries Yu Wang a,b, Fangyu Gan b, Kanghua Chen a,b,⇑ a b
Powder Metallurgy Research Institute, Central South University, Changsha 410083, China State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China
a r t i c l e
i n f o
Article history: Received 20 April 2019 Received in revised form 25 May 2019 Accepted 25 June 2019 Available online 26 June 2019 Keywords: Aluminum-ion batteries Current collector Energy storage and conversion Carbon materials
a b s t r a c t The use of rare metals as current collectors in aluminum-ion batteries is an urgent problem to be solved, so there are significant interests in the development of light-weight and high-efficiency materials as current collector. Herein, we report a polyvinyl-alcohol/graphene composite film as current collector in aluminum-ion batteries which synthesized by a simple solution method. The film containing 20 wt% graphene demonstrates high electrical conductivity up to 164Scm 1 with 30 lm in thicknesses and 2.8 mg cm 2 in areal density. According to the electrochemical measurements, a reversible capacity of 89 mAh g 1 is obtained at a rate of 1C in aluminum-graphite battery. Ó 2019 Published by Elsevier B.V.
1. Introduction Aluminum-ion batteries (AIBs) exhibit high theoretical volumetric capacity of 8040 mAh cm 3 and are considered a promising source of power supply due to the abundance and non-toxicity of aluminum metal [1–3]. Remarkably, Dai and their colleagues assembled an aluminum-ion battery using the original natural graphite flakes as the cathode, with a discharge capacity of 110 mAh g 1 (at 0.9 C) and more than 6000 cycles [4]. However, the above-mentioned researches use the rare metal (tantalum, nickel and molybdenum) and expensive carbon paper as current collector due to the unique corrosion resistance presented in aluminum ionic liquid [5,6]. This would restrict the industrialization of AIBs due to the natural resources scarcity and high cost and low productivity of carbon paper. Consequently, developing a fruitful in earth resources and low-cost current collector is highly desired [7]. Here, we mainly discuss the feasibility of a highly conductive and lightweight poly(vinyl alcohol)/graphene (PVA/GNP) conductive composite film used as a current collector in aluminumgraphite batteries. PVA/GNP composite in the form of film is prepared by simple solution processing which graphene dispersed into the PVA matrix referenced to the literature [8]. The stability of the composite film in aluminum ionic liquid was confirmed. ⇑ Corresponding author at: Powder Metallurgy Research Institute, Central South University, Changsha 410083, China. E-mail address: [email protected] (K. Chen). https://doi.org/10.1016/j.matlet.2019.06.082 0167-577X/Ó 2019 Published by Elsevier B.V.
Simultaneously, explored whether it meets the electrical and mechanical properties as a current collector is quite necessary. The electrochemical performance has also been further verified while graphite cathode based PVA/GNP current collector and aluminum foil anode in a low-cost room temperature ionic liquid electrolyte mixed triethylamine hydrochloride (Et3CHCl) with AlCl3 [9]. 2. Experiment High conductivity graphene aqueous solution and poly(vinyl alcohol) powered (Mw = 180000) were used for preparing PVA/ GNP composite film while the process was referred to the literature [8]. Active materials for the cathode and anode were graphite and aluminum foil with a thickness of 20 lm (both current collector and electrode), respectively. The electrode was fabricated by preparing a slurry containing active materials graphite, carbon black powder, and binder PVDF with a weight ratio of 8:1:1 in NMP. The slurry was coated on the PVA/GNP composite film by the doctor blade technique. All electrodes were placed in a vacuum oven and dried over-night at 80 °C before being assembled in soft case cells in an argon-filled glove box. The separator was a porous glass fiber paper. The electrolyte is ionic liquid in a mixture of AlCl3/Et3CHCl (1.7:1 m/m). A DMR-1C sheet resistance apparatus was employed to investigate the composite film resistance and calculate its conductivity according to the formula R = q l/(l w) = q/w and j = 1/q (R represents sheet resistance, O; q represents resistivity, O cm; l represents width and length of a square, and w
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Y. Wang et al. / Materials Letters 254 (2019) 436–439
represents thickness of film, respectively, cm; j represents conductivity, S cm 1) [10] An average of 10 specimens from composite film were measured to obtain the conductivity j. The structure of the film was observed using a scanning electron microscope model QUANTA-200. The mechanical properties of the composite film were determined using a universal testing machine model MTS810. Charge-discharge tests were carried out using a Land battery test system (Wuhan Land-CT2001A, China) which the range of voltages is 0–2.4 V. The cyclic voltammetry (CV) results were collected using a CHI606 workstation. The scan rate of the CV test was 1 mVs 1. 3. Results and discussion Owing to the high corrosive of AlCl3 ionic liquids on most metals (except tantalum, nickel and molybdenum), it is necessary to investigate the stability of PVA/GNP composite film in AlCl3/Et3CHCl ionic liquid electrolyte. PVA/GNP composite film was directly added to weighing bottles containing prepared ionic liquid in a mixture of AlCl3/Et3CHCl and allowed to stand for 7200 h. As shown in Fig. 1(a), it can be discovered that there was no obvious reaction while the film is insoluble in the ionic liquid and can maintain integrity. We further verified whether the AlCl3/Et3CHCl ionic liquid changed after soaking the composite film. Fig. 1(b) shows the Raman spectra of the electrolyte before and after soaking the PVA/GNP composite film. Two peaks at 311 cm 1 and 347 cm 1 were detected, which is assigned to the Al-Cl terminal stretching frequencies in AlCl4 anions and Al2Cl7 anions. The Raman spectra of the electrolyte after and before soaking the composite film is the same [9], which confirms the stability of the composite film in the ion liquid. When PVA/GNP composite film was used as a current collector, the areal density of GNP in composite film about 0.56 mg cm 2. Compared to the graphite active material 5 mg cm 2, graphene
mainly provides electronic. The below CV curve of the graphitePVA/GNP electrodes can prove that no side electrochemical reaction and redox reactions only occurs at the graphite/electrolyte interface. Therefore, GNP mainly provides electronic and does not affect the stability of the composite film as current collector. The electrical conductivity of the PVA/GNP composite film mainly needs to meet two characteristics: providing electrical transport to the active material and supporting the active material. Therefore, to investigate whether it meets the electrical properties as a current collector is essential. The resistivity and conductivity of the composite film is shown in Fig. 2(a) and (b). It can be found that the conductivity is as high as 164S cm 1 at an ultrahigh content of GNP, for example, 20% by weight. Moreover, the composite film is much lighter about 2.8 mg cm 2 in areal density compared that of molybdenum sheet (about 16 mg cm 2), which would greatly reduce the weight of the battery and meet the requirements of the actual application of the battery. Surface morphology of the PVA/GNP composite film was shown in the Fig. 2(c). It reveals that GNP particles are well dispersed and no significant cluster or agglomerates was found in PVA matrix. The graphene overlaps each other to form a good conductive path. The insert image in Fig. 2(c) shows that the composite film is sufficiently smooth, strong and flexible as a current collector. The mechanical property of the PVA/GNP composite film was shown in the Table 1. Compared with the pure PVA film, the tensile stress of the PVA/GNP composite film increased by about 33.26% and the elongation at break gradually decreases. However, the tensile strength of graphite-PVA/GNP electrode is relatively lower (8.33 MPa), compared to the other electrodes [11], while still acceptable. Therefore, this composite film would be sufficiently formidable and flexible for applications as a current collector. The electrochemistry property of the PVA/GNP composite film as current collector in aluminum-ion battery was verified. Fig. 3 (a) shows the CV curves of the Al-graphite battery based on PVA/
before
after
Fig. 1. (a) Comparison of weighing bottles with AlCl3/Et3CHCl ionic liquids to which were added in PVA/GNP composite film. (b) Raman spectra of electrolyte before and after soaking the PVA/GNP composite film.
Fig. 2. (a) and (b) Resistivity and conductivity of the PVA/GNP composite film. (c) SEM micrographs of fractured surfaces of PVA/GNP composite film.
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Table 1 Tensile properties of the films. Sample
Tensile strain (%)
Tensile stress (MPa)
Pure PVA PVA/GNP composite film Electrode based on PVA/GNP
180.34 79 6.93
18.34 19.42 8.33
GNP composite film as current collector (graphite-PVA/GNP electrode). Two-well defined reduction peaks are noted at 1.5 (a’ peak) and 2.0 V (b’ peak). Accordingly, the oxidation peaks are found at 1.8 V (a peak) and 2.1 V (b peak), respectively. The CV curve of the graphite-PVA/GNP electrodes shows no side electrochemical reaction associated with it referenced in the literature [3]. Therefore, the observed redox reactions only occur at the graphite/electrolyte interface. Fig. 3(b–d) shows the charge/discharge
performance of graphite-PVA/GNP electrodes between 0 and 2.4 V in the electrolyte of AlCl3/Et3CHCl at a rate of 1C. Noting that the electrode delivered a discharge capacity (87 mAh g 1) based on the weight of graphite and gradually stabilize the average voltage at 1.75 V. The cycle stability and rate performance of the electrode were also shown good performance, which shows no decrease in the capacity of the graphite-PVA/GNP electrode. This suggests that the PVA/GNP composite film as a current collector is a promising candidate current collector for AIB. 4. Conclusion In conclusion, we have successfully prepared and demonstrate a high electrical conductivity and lightweight PVA/GNP composites film as current collector in aluminum-ion batteries. The composite film has a highly stability in aluminum ionic liquids. In addition,
Fig. 3. (a) CV profile of graphite-PVA/GNP electrodes at a scan rate of 1 mV s 1. (b) Galvanostatic voltage profiles of electrodes at the fifth cycle (rate = 1 C). (c) Rate performances and cycling performances of the graphite-PVA/GNP electrodes. (d) Average voltage of the graphite-PVA/GNP electrodes at 1 C. (e) Long cycling performances of the graphite-PVA/GNP electrodes.
Y. Wang et al. / Materials Letters 254 (2019) 436–439
weight of the PVA/GNP composite film (2.8 mg cm 2) is much lighter than a molybdenum sheet (about 16 mg cm 2), leading to reduce the weight of the battery in AIBs. Based on PVA/GNP composite film as a current collector, a capacity of 89 mAh g 1 at a rate of 1 C with an average voltage 1.75 V is achieved in Al-graphite battery. It demonstrates that PVA/GNP composite film can be utilized effectively as current collector within the AIBs for the largescale potential applications.
Acknowledgments This work was supported by National Key Research and Development Program of China (No. 2016YFB0300801), Major Research Equipment Development Projects of National Natural Science Foundation of China (No. 51327902).
References [1] M.C. Lin, M. Gong, B. Lu, et al., An ultrafast rechargeable aluminium-ion battery, Sci. Found. China 520 (4) (2015) 19–20.
439
[2] P. Bhauriyal, A. Mahata, B. Pathak, The staging mechanism of AlCl4 intercalation in a graphite electrode for an aluminium-ion battery, PCCP 19 (11) (2017) 7980. [3] H. Jiao, C. Wang, J. Tu, et al., A rechargeable Al-ion battery: Al/molten AlCl3urea/graphite, Chem. Commun. 53 (15) (2017) 2331–2334. [4] D.Y. Wang, C.Y. Wei, M.C. Lin, et al., Advanced rechargeable aluminium ion battery with a high-quality natural graphite cathode, Nat. Commun. 8 (2017) 14283. [5] H. Chen, C. Chen, Y. Liu, et al., High-quality graphene microflower design for high-performance Li–S and Al-ion batteries, Adv. Energy Mater. 7 (17) (2017). [6] M. Angell, C.J. Pan, Y. Rong, et al., High coulombic efficiency aluminum-ion battery using an AlCl3-urea ionic liquid analog electrolyte, Proc. Natl. Acad. Sci. U.S.A. (2017) 834. [7] S. Yehezkel, M. Auinat, N. Sezin, et al., Bundled and densified carbon nanotubes (CNT) fabrics as flexible ultra-light weight Li-ion battery anode current collectors, J. Power Sources 312 (2016) 109–115. [8] X. Yang, L. Li, S. Shang, et al., Synthesis and characterization of layer-aligned poly(vinyl alcohol)/graphene nanocomposites, Polymer 51 (15) (2010) 3431– 3435. [9] H. Xu et al., Low-cost AlCl3/Et3NHCl electrolyte for high-performance aluminum-ion battery, Energy Storage Mater. (2018). [10] S.H. Deng, Y. Wang, X. Yang, The study of electrochemical synthesis, properties and composite mechanism of PANI/PVA and PANI/PVA/Ag composite films, Pigm. Resin Technol. 47 (1) (2018) 00–01. [11] H. Lu, J. Hagberg, G. Lindbergh, et al., Li4Ti5O12, flexible, lightweight electrodes based on cellulose nanofibrils as binder and carbon fibers as current collectors for Li-ion batteries, Nano Energy 39 (2017) 140–150.