- Email: [email protected]
Na0.44MnO2 based on hybrid electrolyte
Journal of Power Sources 336 (2016) 35e39
Contents lists available at ScienceDirect
Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour
The electrochemical performance of aqueous rechargeable battery of Zn/Na0.44MnO2 based on hybrid electrolyte Xianwen Wu a, b, Yehua Li b, Yanhong Xiang a, Zhixiong Liu a, Zeqiang He a, Xianming Wu a, Youji Li a, Lizhi Xiong a, *, Chuanchang Li c, Jian Chen c a b c
The Collaborative Innovation Center of Manganese-Zinc-Vanadium Industrial Technology, Jishou University, Jishou 416000, PR China School of Chemistry and Chemical Engineering, Jishou University, Jishou 416000, PR China School of Energy and Power Engineering, Changsha University of Science and Technology, Changsha 410114, PR China
h i g h l i g h t s We reported the aqueous battery system of Zn/Na0.44MnO2 based on hybrid electrolyte. The battery is cheap and environmentally friendly. It exhibits an excellent rate and cycling capability with the lower self-discharge process.
a r t i c l e i n f o
a b s t r a c t
Article history: Received 23 September 2016 Received in revised form 12 October 2016 Accepted 17 October 2016
There is a broad application prospect for smart grid about aqueous rechargeable sodium-ion battery. In order to improve its electrochemical performance, a hybrid cationic aqueous-based rechargeable battery system based on the nanostructural Na0.44MnO2 and metallic zinc foil as the positive and negative electrodes respectively is built up. Nano rod-like Na0.44MnO2 is synthesized by sol-gel method followed by calcination at 850 C for 9 h, and various characterization techniques including the X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to investigate the structure and morphology of the as-prepared material. The cyclic voltammetry, galvanostatic charge-discharge and self-discharge measurements are performed at the same time. The results show that the battery delivers a very high initial discharge capacity of 186.2 mAh g1 at 0.2 C-rate in the range of 0.5e2.0 V, and it exhibits a discharge capacity of 113.3 mAh g1 at high current density of 4 C-rate, indicative of excellent rate capability. © 2016 Elsevier B.V. All rights reserved.
Keywords: Aqueous sodium ion batteries Electrode materials Self-discharge
1. Introduction As we know, it is urgent for us to explore new energy storage and conversion systems, as the present rechargeable battery systems such as lead-acid, nickel-cadmium (Ni-Cd), nickel-metal hydride (Ni-MH), lithium ion batteries (LIBs) have not already satisfied the requirements of large-scale energy storage in view of their limited resources, high cost and poor safety [1e5]. In 1994, an aqueous rechargeable lithium-ion battery (ARLIB) using b-VO2 and LiMn2O4 as negative and positive electrodes respectively was firstly proposed by Dahn's group [6]. Afterwards, ARLIBs have attracted wide attentions because of the higher rate capability and power
* Corresponding author. E-mail address: [email protected] (L. Xiong). http://dx.doi.org/10.1016/j.jpowsour.2016.10.053 0378-7753/© 2016 Elsevier B.V. All rights reserved.
density and better safety than LIBs with organic electrolyte [7,8]. However, their practical applications have still been obstructed due to the poor cycling performance of LIBs and the lower specific discharge capacity of anode. In 2012, a rechargeable hybrid aqueous battery system (ReHAB) based on lithium intercalation cathode and a cheap zinc anode was firstly reported by Chen's group with a capacity retention of 90% over 1000 cycles with undoped LiMn2O4 [9]. After that, they have attracted increasing interests about the similar systems such as Zn/ LiMn2O4 [10], Zn/LiMnPO4 [11], Zn/LiCo1/3Mn1/3Ni1/3PO4 [12], Zn/ LiFePO4 [13], Zn/LiCo1/3Mn1/3Ni1/3O2 [14] due to the low equilibrium potential, low cost, abundance, environmental benignity and a long cycle life as zinc anode. Nevertheless, lithium-ion intercalation compounds are usually not suitable as cathode materials in this system because of the high cost and limited resources for large-
36
X. Wu et al. / Journal of Power Sources 336 (2016) 35e39
scale application [15e18]. Recently, sodium-ion batteries (SIBs) have been regarded as a promising alternative for large-scale applications due to the low cost and naturally abundant of the sodium resources and various cathode materials have been reported [19e21]. However, only a few sodium-ion-intercalated compounds can be applied in the field of aqueous rechargeable sodium-ion batteries (ARSIBs). Among them, the tunnel-type Na4Mn9O18 (Na0.44MnO2) has been widely investigated as a positive electrode for ARSIBs since it was first reported by Whitacre in 2008, and many kinds of synthesis methods have been studied including hydrothermal method, sol-gel method and so on [22e25]. It is generally believed that it is very suitable as the cathode material for aqueous battery. In order to combine the merits of ARSIBs and ReHAB above, the hybrid aqueous batteries based on sodium-ion intercalation compounds as the cathode materials and zinc as the anode are studied [26], which show potential application prospects and competitiveness. Huang and Pu [27,28] firstly reported the hybrid aqueous battery of Zn/Na3V2(PO4)3 (NVP) for potential large-scale energy storage nearly at the same time. However, the electrochemical performance of pure Na3V2(PO4)3 is relatively poor because of the poor intrinsic electronic conductivity. Herein, in this paper we present another safe, environmentallyfriendly and inexpensive hybrid aqueous rechargeable battery of Zn/Na0.44MnO2. Na0.44MnO2 was prepared with the sol-gel method. We expect that such a battery will display good electrochemical performance. 2. Experimental The Na0.44MnO2 materials were synthesized by sol-gel method. At first, the stoichiometric amount (Na/Mn molar ratio of 0.44:1) of sodium carbonate and manganese acetate were dissolved separately in distilled water and then mixed together while stirring. The solution of citric acid was then added at a molar ratio with the same amount of the total metal ions. The pH of the mixture solution was adjusted to 6.5 by adding ammonium hydroxide solution. Then it was heated at 80 C for about 4 h. The product was dried in an oven for one night at 60 C to obtain sol-gel precursor. After drying, the powder was calcined at 850 C for 9 h with the heating rate of 5 min1. The working electrodes were prepared by casting slurries of Na0.44MnO2, KS-6, and polyvinylidene fluoride (PVDF) (80:10:10 wt %) in N-methyl-2-pyrrolidinone (NMP) on graphite foil, and dried in vacuum oven at 60 C for 4 h. Disks of 14 mm diameter were cut (typical active material load of 2e3 mg cm2). A 14 mm of commercial zinc foil was used as an anode current collector. The hybrid electrolytes with 0.5 mol L1 ZnSO4 and 1 mol L1 Na2SO4 were prepared by dissolving zinc sulfate and sodium sulfate (both Aldrich) in deionized water and adjusting the solution to pH ¼ 4. AGM (Absorbed Glass Mat, NSG Corporation) wet with the electrolyte was used as separator. CR2032 coin-type batteries were used for galvanostatic charge-discharge cycling in the potential range of 1.0e2.0 V or 0.5e2.0 V at room temperature with a battery tester (Neware in China) at 4 C-rate. To identify the phase constitution, Na0.44MnO2 was characterized by X-ray diffraction (XRD, D8 Discover, Bruker) employing Cu Ka (l ¼ 0.15406 nm) radiation from 10 to 80 . Field emission scanning electron microscopy (FE-SEM, Leo-1530, Zeiss) with an accelerating voltage of 20 kV was conducted to investigate the morphology of the Na0.44MnO2. 3. Results and discussion The XRD data of Na0.44MnO2 synthesized by sol-gel method is
shown in Fig. 1(a). All the characteristic diffraction peaks can be indexed as the Na0.44MnO2, which are in agreement with the JCPDF file (Pbam space group, JCPDS card No. 27-0750), indicating that Na0.44MnO2 well-crystallites are formed. Meanwhile, SEM analysis of Na0.44MnO2 is shown in Fig. 1(b). It can be seen that all materials display similar rod-like crystallite morphology. The diameter of the rod-like sample ranges from 0.1 to 0.6 mm along with a large amount of small particles of nano capsule. The hybrid aqueous battery Zn/Na0.44MnO2 is built up based on Na0.44MnO2 as the cathode and zinc as the anode. The hybrid solution of 0.5 mol L1 ZnSO4 and 1 mol L1 Na2SO4 were used as the electrolyte. Different from the “rocking-chair” type LIBs and ARLIBs, Both Naþ and Zn2þ exist in the electrolyte, and the exchange of Naþ and Zn2þ occurs upon cycling. Their electrode and total reactions are simply shown as follows: The negative electrode:
Zn2þ þ 2e ⇔ Zn
(1)
The positive electrode:
Na0:44 MnO2 ⇔ Na0:44x MnO2 þ xNaþ þ xe
(2)
The total reaction:
2Na0:44 MnO2 þ xZn2þ ⇔ 2Na0:44x MnO2 þ 2xNaþ þ xZn
(3)
When the battery is charged, sodium ions are de-intercalated from sodium-intercalation compounds of Na0.44MnO2 and dissolved into the electrolyte, accompanied by releasing electrons. While zinc ions deposit onto the surface of Zn current collector and accept electrons from the external circuit. During the discharge process, Zn in the anode loses electrons to convert into zinc ions, and then the zinc ions are dissolved into the electrolyte. Simultaneously, sodium ions are intercalated into Na0.44-xMnO2 to form back Na0.44MnO2. The electrons move from the anode to the cathode through the external circuit to complete the loop, of which the charge-discharge mechanism is first reported by Pu [9] and is also the same as those in the previous reports [26e28]. Cyclic voltammetry (CVs) of Zn/Na0.44MnO2 at different cut-off potentials in 0.5 mol L1 ZnSO4 and 1.0 mol L1 Na2SO4 aqueous solution at a scan rate of 0.1 mV s1 are shown in Fig. 2. There is one oxidation peak at about 1.60 V (vs Zn2þ/Zn) and one reduction peak at about 1.08 V (vs Zn2þ/Zn) during the first cycle. The area of the oxidation peak is small, while it is much larger during the reduction process, demonstrating the higher coulombic efficiency. With the cycling increasing, there seems to be asymmetric redox peaks, and two reduction peaks appear after the first cycle. Meanwhile, compared with the oxidation peaks from Fig. 2(a), (b) and (c) at different cut-off voltages, it can be seen that there is a large oxidation peak at about 2.5 V (vs Zn2þ/Zn), which is probably due to the water decomposition. When the cut-off voltage is decreased to 2.0 V, the hydrogen evolution peak nearly disappears. Thus, the upper cut-off voltage is limited to 2.0 V. The galvanostatic charge-discharge measurements were conducted at 4 C-rate at different cut-off potentials in Fig. 3 (a), the capacity in the range of 0.5e2.0 V is much higher than that of 1.0e2.0 V. As shown in Fig. 3 (b), the initial discharge capacity is up to 113.3 mAh g1 (vs Zn2þ/Zn), which seems to be much higher than those reports based on Na0.95MnO2/Zn at 4 C-rate and Na0.44MnO2/ NaTi2(PO4)3 at 1 C-rate in aqueous rechargeable battery systems [26,29]. However, it's surprised that the initial coulombic efficiency 492.35% is much higher than 100% due to the very low initial charge capacity of 23.1 mAh g1, which is the same as that in CVs. What a pity that the reason is still unknown. With the cycle number increasing, the discharge capacity decreases quickly in the first five
X. Wu et al. / Journal of Power Sources 336 (2016) 35e39
37
Fig. 1. XRD and SEM images of Na0.44MnO2.
Fig. 2. Cyclic voltammetry of Zn/Na0.44MnO2 in an aqueous solution of 0.5 mol L1 ZnSO4 and 1 mol L1 Na2SO4 at a scan rate of 0.1 mV s1.
Fig. 3. (a) cycling performance of the Zn/Na0.44MnO2 at 4 C rate at different cut-off voltages, (b) Charge and discharge curves of the Na0.44MnO2.
cycles, and then it tends to be flat even after 100 cycles. In a word, the battery displays a good cycling performance even at 4 C-rate. Meanwhile, we can see that there are a charge plateau and two separate discharge plateaus from Fig. 3 (b), which is the same as that in cyclic voltammetry. In order to further study the electrochemical behavior of Na0.44MnO2, electrochemical impedance spectroscopy before and after cycling tests is performed with the working frequency from 102 Hze105 Hz and the perturbation amplitude of 5 mV. As shown
in Fig. 4, the impedance spectra displays a small semicircle in the high frequency, followed by a straight line in the low frequency region, of which the semicircle part at high frequency (Rct) corresponds to the charge transfer process at the electrode-electrolyte interface and the straight line with a slope (Zw) is related to the diffusion control process of sodium ion. It can be seen that the battery before and after cycling has a similar ohmic resistance, while the semicircle after cycling is much larger than that before cycling.
38
X. Wu et al. / Journal of Power Sources 336 (2016) 35e39
Fig. 6. The self-discharge procedure of the Zn/Na0.44MnO2 battery. Fig. 4. The EIS of Zn/Na0.44MnO2 before and after cycling.
Rate tests of up to 10 C-rate have been investigated to evaluate the electrode and the results are shown in Fig. 5. In the first discharge process, the electrode exhibits remarkably high discharge capacity at 0.2 C, up to 153.3 mAh g1. Moreover, the discharge capacity retains up to 37.3 mAh g1 at 10 C-rate, and the discharge plateau does not decrease a lot. Self-discharge procedure is usually used to evaluate the side reactions of the electrodes. The self-discharge measurement was performed in Fig. 6, the battery was cycled for three times at 0.2 Crate firstly, and then charged to 2.0 V at 0.2 C-rate, standing for 24 h at room temperature. At last it was cycled for three times. As shown in Fig. 6, after standing for 24 h, the coulombic efficiency is increased from 87.52% to 96.31%, although the potential decreased to 1.5804 V, indicating the smaller self-discharge phenomenon. 4. Conclusions In summary, a hybrid aqueous rechargeable battery using Na0.44MnO2 as cathode and metal zinc foil as anode has been developed. Na0.44MnO2 synthesized by sol-gel method displays an excellent rate and cycling capability in hybrid aqueous electrolyte. We really hope the preliminary work on such hybrid cationic aqueous-based rechargeable battery system can bring some new
Fig. 5. The charge-dishcarge capacity of Zn/Na0.44MnO2 at different C-rates.
ideas to further investigate green, safe and low-cost batteries for future application in the field of smart grid, although the reason about the very low initial charge capacity of 23.1 mAh g1 and the coulombic efficiency of more than 400% at 4 C-rate needs to be studied further. Acknowledgment This research was financially supported by Outstanding Youth Foundation of Hunan Provincial Education Department (No. 15B190), Scientific research start-up funding of Jishou university (jsdxrcyjkyxm201407), the National Natural Science Foundation of China (No. 51662010, No. 51262008, No. 51472107, No. 51364009 and 51672104), and Natural Science Foundation of Hunan Province, China (No. 12JJ2005, No. 14JJ4048, No. 16JJ6121), and Aid program (Environment and Energy Materials and deep processing of mineral resources in Wuling Mountain) for Science and Technology Innovative Research Team in Higher Educational Instituions of Hunan Province, which were greatly appreciated. References [1] J. Cho, S. Jeong, Y. Kim, Commercial and research battery technologies for electrical energy storage applications, Prog. Energy Combust. 48 (2015) 84e101. [2] M. Sawicki, L.L. Shaw, Advances and challenges of sodium ion batteries as post lithium ion batteries, RSC Adv. 5 (2015) 53129e53154. [3] J.X. Wang, Q.B. Zhang, X.H. Li, B. Zhang, L.Q. Mai, K.L. Zhang, Smart construction of three-dimensional hierarchical tubular transition metal oxide core/shell heterostructures with high-capacity and long-cycle-life lithium storage, Nano Energy 12 (2015) 437e446. [4] W.C. Wen, S.H. Chen, Y.Q. Fu, X.Y. Wang, H.B. Shu, A core-shell structure spinel cathode material with a concentration gradient shell for high performance lithium-ion batteries, J. Power Sources 274 (2015) 219e228. [5] Z. Chen, C. Wang, J. Lopez, Z.D. Lu, Y. Cui, Z.N. Bao, High-areal-capacity silicon electrodes with low-cost silicon particles based on spatial control of selfhealing binder, Adv. Energy Mater. 5 (8) (2015) 1401826. [6] W. Li, J.R. Dahn, D.S. Wainwright, Rechargeable lithium batteries with aqueous electrolytes, Science 264 (5162) (1994) 1115e1118. [7] W. Tang, Y.S. Zhu, Y.Y. Hou, L.L. Liu, Y.P. Wu, K.P. Loh, H.P. Zhang, K. Zhu, Aqueous rechargeable lithium batteries as an energy storage system of superfast charging, Energy Environ. Sci. 6 (2013) 2093e2104. [8] Y.G. Wang, J. Yi, Y.Y. Xia, Recent progress in aqueous lithium-ion batteries, Adv. Energy Mater. 2 (2012) 830e840. [9] J. Yan, J. Wang, H. Liu, Z. Bakenov, D. Gosselink, P. Chen, Rechargeable hybrid aqueous batteries, J.Power Sources 216 (2012) 222e226. [10] X.W. Wu, Y.H. Li, C.C. Li, Z.X. He, Y.H. Xiang, L.Z. Xiong, D. Chen, Y. Yu, K. Sun, Z.Q. He, P. Chen, The electrochemical performance improvement of LiMn2O4/ Zn based on zinc foil as the current collector and thiourea as an electrolyte additive, J.Power Sources 300 (2015) 453e459. [11] M. Minakshi, P. Singh, S. Thurgate, K. Prince, Electrochemical behavior of olivine-type LiMnPO4 in aqueous solutions, Electrochem. Solid-State Lett. 9
X. Wu et al. / Journal of Power Sources 336 (2016) 35e39 (10) (2006) A471eA474. [12] S. Kandhasamy, A. Pandey, M. Minakshi, Polyvinylpyrrolidone assisted solegel route LiCo1/3Mn1/3Ni1/3PO4 composite cathode for aqueous rechargeable battery, Electrochim. Acta 60 (2012) 170e176. [13] H.P. Zhang, X. Wu, T. Yang, S.S. Liang, X.J. Yang, Cooperation behavior between heterogeneous cations in hybrid batteries, Chem. Commun. 49 (2013) 9977e9979. [14] F.X. Wang, Y. Liu, X.W. Wang, Z. Cheng, Y.P. Wu, R. Holze, Aqueous rechargeable battery based on zinc and a composite of LiNi1/3Co1/3Mn1/3O2, ChemElectroChem 2 (2015) 1024e1030. [15] L.M. Suo, O. Borodin, W. Sun, X.L. Fan, C.Y. Yang, F. Wang, T. Gao, Z.H. Mao, M. Schroeder, A.V. Cresce, S.M. Russell, M. Armand, A. Angell, K. Xu, C.S. Wang, Advanced high-voltage aqueous lithium-ion battery enabled by “water-inbisalt” electrolyte, Angew. Chem. Int. Ed. 55 (2016) 1e7. [16] C.Y. Lu, T.K.A. Hoang, T.N.L. Doan, H.B. Zhao, R. Pan, L. Yang, W.S. Guan, P. Chen, Rechargeable hybrid aqueous batteries using silica nanoparticle doped aqueous electrolytes, Appl. Energy 170 (2016) 58e64. [17] X. Zhu, T.N.L. Doan, Y. Yu, Y. Tian, K.E.K. Sun, H.B. Zhao, P. Chen, Enhancing rate performance of LiMn2O4 cathode in rechargeable hybrid aqueous battery by hierarchical carbon nanotube/acetylene black conductive pathways, Ionics 22 (1) (2016) 71e76. [18] X. Zhu, X.W. Wu, T.N.L. Doan, Y. Tian, H.B. Zhao, P. Chen, Binder-free flexible LiMn2O4/carbon nanotube network as high power cathode for rechargeable hybrid aqueous battery, J. Power Sources 326 (2016) 498e504. [19] M. Sawicki, L.L. Shaw, Advances and challenges of sodium ion batteries as post lithium ion batteries, RSC Adv. 5 (2015) 53129e53154. [20] L.P. Wang, L.H. Yu, X. Wang, M. Srinivasan, Z.J. Xu, Recent developments in electrode materials for sodium-ion batteries, J. Mater. Chem. A 3 (2015) 9353e9378. [21] H.S. Hou, C.E. Banks, M.J. Jing, Y. Zhang, X.B. Ji, Carbon quantum dots and their
[22]
[23]
[24]
[25]
[26]
[27]
[28]
[29]
39
derivative 3D porous carbon frameworks for sodium-ion batteries with ultralong cycle life, Adv. Mater. 27 (2015) 7861e7866. J.F. Whitacre, A. Tevar, S. Sharma, Na4Mn9O18 as a positive electrode material for an aqueous electrolyte sodium-ion energy storage device, Electrochem. Commun. 12 (2010) 463e466. Y.S. Wang, L.Q. Mu, J. Liu, Z.Z. Yang, X.Q. Yu, L. Gu, Y.S. Hu, H. Li, X.Q. Yang, L.Q. Chen, X.J. Huang, A novel high capacity positive electrode material with tunnel-type structure for aqueous sodium-ion batteries, Adv. Energy Mater. 5 (22) (2015) 1501005. E. Hosono, H. Matsuda, I. Honma, S. Fujihara, M. Ichihara, H.S. Zhou, Synthesis of single crystalline electro-conductive Na0.44MnO2 nanowires with high aspect ratio for the fast chargeedischarge Li ion battery, J.Power Sources 182 (2008) 349e352. X. Liu, N. Zhang, J.F. Ni, L.J. Gao, Improved electrochemical performance of solgel method prepared Na4Mn9O18 in aqueous hybrid Na-ion supercapacitor, J. Solid State Electrochem 17 (2013) 1939e1944. B.H. Zhang, Y. Liu, X.W. Wu, Y.Q. Yang, Z. Chang, Z.B. Wen, Y.P. Wu, An aqueous rechargeable battery based on zinc anode and Na0.95MnO2, Chem. Commun. 50 (2014) 1209e1211. G.L. Li, Z. Yang, Y. Jiang, W.X. Zhang, Y.H. Huang, Hybrid aqueous battery based on Na3V2(PO4)3/C cathode and zinc anode for potential large-scale energy storage, J.Power Sources 308 (2016) 52e57. H.B. Zhao, C.J. Hu, H.W. Cheng, J.H. Fang, Y.P. Xie, W.Y. Fang, T.N.L. Doan, T.K.A. Haong, J.Q. Xu, P. Chen, Novel rechargeable M3V2(PO4)3//zinc (M¼ Li, Na) hybrid aqueous batteries with excellent cycling performance, Sci. Rep. 6 (2016) 25809. B.D. Zhao, B. Lin, S. Zhang, C. Deng, A frogspawn-inspired hierarchical porous NaTi2(PO4)3-C array for high-rate and long-life aqueous rechargeable sodium batteries, Nanoscale 7 (2015) 18552e18560.
Contents lists available at ScienceDirect
Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour
The electrochemical performance of aqueous rechargeable battery of Zn/Na0.44MnO2 based on hybrid electrolyte Xianwen Wu a, b, Yehua Li b, Yanhong Xiang a, Zhixiong Liu a, Zeqiang He a, Xianming Wu a, Youji Li a, Lizhi Xiong a, *, Chuanchang Li c, Jian Chen c a b c
The Collaborative Innovation Center of Manganese-Zinc-Vanadium Industrial Technology, Jishou University, Jishou 416000, PR China School of Chemistry and Chemical Engineering, Jishou University, Jishou 416000, PR China School of Energy and Power Engineering, Changsha University of Science and Technology, Changsha 410114, PR China
h i g h l i g h t s We reported the aqueous battery system of Zn/Na0.44MnO2 based on hybrid electrolyte. The battery is cheap and environmentally friendly. It exhibits an excellent rate and cycling capability with the lower self-discharge process.
a r t i c l e i n f o
a b s t r a c t
Article history: Received 23 September 2016 Received in revised form 12 October 2016 Accepted 17 October 2016
There is a broad application prospect for smart grid about aqueous rechargeable sodium-ion battery. In order to improve its electrochemical performance, a hybrid cationic aqueous-based rechargeable battery system based on the nanostructural Na0.44MnO2 and metallic zinc foil as the positive and negative electrodes respectively is built up. Nano rod-like Na0.44MnO2 is synthesized by sol-gel method followed by calcination at 850 C for 9 h, and various characterization techniques including the X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to investigate the structure and morphology of the as-prepared material. The cyclic voltammetry, galvanostatic charge-discharge and self-discharge measurements are performed at the same time. The results show that the battery delivers a very high initial discharge capacity of 186.2 mAh g1 at 0.2 C-rate in the range of 0.5e2.0 V, and it exhibits a discharge capacity of 113.3 mAh g1 at high current density of 4 C-rate, indicative of excellent rate capability. © 2016 Elsevier B.V. All rights reserved.
Keywords: Aqueous sodium ion batteries Electrode materials Self-discharge
1. Introduction As we know, it is urgent for us to explore new energy storage and conversion systems, as the present rechargeable battery systems such as lead-acid, nickel-cadmium (Ni-Cd), nickel-metal hydride (Ni-MH), lithium ion batteries (LIBs) have not already satisfied the requirements of large-scale energy storage in view of their limited resources, high cost and poor safety [1e5]. In 1994, an aqueous rechargeable lithium-ion battery (ARLIB) using b-VO2 and LiMn2O4 as negative and positive electrodes respectively was firstly proposed by Dahn's group [6]. Afterwards, ARLIBs have attracted wide attentions because of the higher rate capability and power
* Corresponding author. E-mail address: [email protected] (L. Xiong). http://dx.doi.org/10.1016/j.jpowsour.2016.10.053 0378-7753/© 2016 Elsevier B.V. All rights reserved.
density and better safety than LIBs with organic electrolyte [7,8]. However, their practical applications have still been obstructed due to the poor cycling performance of LIBs and the lower specific discharge capacity of anode. In 2012, a rechargeable hybrid aqueous battery system (ReHAB) based on lithium intercalation cathode and a cheap zinc anode was firstly reported by Chen's group with a capacity retention of 90% over 1000 cycles with undoped LiMn2O4 [9]. After that, they have attracted increasing interests about the similar systems such as Zn/ LiMn2O4 [10], Zn/LiMnPO4 [11], Zn/LiCo1/3Mn1/3Ni1/3PO4 [12], Zn/ LiFePO4 [13], Zn/LiCo1/3Mn1/3Ni1/3O2 [14] due to the low equilibrium potential, low cost, abundance, environmental benignity and a long cycle life as zinc anode. Nevertheless, lithium-ion intercalation compounds are usually not suitable as cathode materials in this system because of the high cost and limited resources for large-
36
X. Wu et al. / Journal of Power Sources 336 (2016) 35e39
scale application [15e18]. Recently, sodium-ion batteries (SIBs) have been regarded as a promising alternative for large-scale applications due to the low cost and naturally abundant of the sodium resources and various cathode materials have been reported [19e21]. However, only a few sodium-ion-intercalated compounds can be applied in the field of aqueous rechargeable sodium-ion batteries (ARSIBs). Among them, the tunnel-type Na4Mn9O18 (Na0.44MnO2) has been widely investigated as a positive electrode for ARSIBs since it was first reported by Whitacre in 2008, and many kinds of synthesis methods have been studied including hydrothermal method, sol-gel method and so on [22e25]. It is generally believed that it is very suitable as the cathode material for aqueous battery. In order to combine the merits of ARSIBs and ReHAB above, the hybrid aqueous batteries based on sodium-ion intercalation compounds as the cathode materials and zinc as the anode are studied [26], which show potential application prospects and competitiveness. Huang and Pu [27,28] firstly reported the hybrid aqueous battery of Zn/Na3V2(PO4)3 (NVP) for potential large-scale energy storage nearly at the same time. However, the electrochemical performance of pure Na3V2(PO4)3 is relatively poor because of the poor intrinsic electronic conductivity. Herein, in this paper we present another safe, environmentallyfriendly and inexpensive hybrid aqueous rechargeable battery of Zn/Na0.44MnO2. Na0.44MnO2 was prepared with the sol-gel method. We expect that such a battery will display good electrochemical performance. 2. Experimental The Na0.44MnO2 materials were synthesized by sol-gel method. At first, the stoichiometric amount (Na/Mn molar ratio of 0.44:1) of sodium carbonate and manganese acetate were dissolved separately in distilled water and then mixed together while stirring. The solution of citric acid was then added at a molar ratio with the same amount of the total metal ions. The pH of the mixture solution was adjusted to 6.5 by adding ammonium hydroxide solution. Then it was heated at 80 C for about 4 h. The product was dried in an oven for one night at 60 C to obtain sol-gel precursor. After drying, the powder was calcined at 850 C for 9 h with the heating rate of 5 min1. The working electrodes were prepared by casting slurries of Na0.44MnO2, KS-6, and polyvinylidene fluoride (PVDF) (80:10:10 wt %) in N-methyl-2-pyrrolidinone (NMP) on graphite foil, and dried in vacuum oven at 60 C for 4 h. Disks of 14 mm diameter were cut (typical active material load of 2e3 mg cm2). A 14 mm of commercial zinc foil was used as an anode current collector. The hybrid electrolytes with 0.5 mol L1 ZnSO4 and 1 mol L1 Na2SO4 were prepared by dissolving zinc sulfate and sodium sulfate (both Aldrich) in deionized water and adjusting the solution to pH ¼ 4. AGM (Absorbed Glass Mat, NSG Corporation) wet with the electrolyte was used as separator. CR2032 coin-type batteries were used for galvanostatic charge-discharge cycling in the potential range of 1.0e2.0 V or 0.5e2.0 V at room temperature with a battery tester (Neware in China) at 4 C-rate. To identify the phase constitution, Na0.44MnO2 was characterized by X-ray diffraction (XRD, D8 Discover, Bruker) employing Cu Ka (l ¼ 0.15406 nm) radiation from 10 to 80 . Field emission scanning electron microscopy (FE-SEM, Leo-1530, Zeiss) with an accelerating voltage of 20 kV was conducted to investigate the morphology of the Na0.44MnO2. 3. Results and discussion The XRD data of Na0.44MnO2 synthesized by sol-gel method is
shown in Fig. 1(a). All the characteristic diffraction peaks can be indexed as the Na0.44MnO2, which are in agreement with the JCPDF file (Pbam space group, JCPDS card No. 27-0750), indicating that Na0.44MnO2 well-crystallites are formed. Meanwhile, SEM analysis of Na0.44MnO2 is shown in Fig. 1(b). It can be seen that all materials display similar rod-like crystallite morphology. The diameter of the rod-like sample ranges from 0.1 to 0.6 mm along with a large amount of small particles of nano capsule. The hybrid aqueous battery Zn/Na0.44MnO2 is built up based on Na0.44MnO2 as the cathode and zinc as the anode. The hybrid solution of 0.5 mol L1 ZnSO4 and 1 mol L1 Na2SO4 were used as the electrolyte. Different from the “rocking-chair” type LIBs and ARLIBs, Both Naþ and Zn2þ exist in the electrolyte, and the exchange of Naþ and Zn2þ occurs upon cycling. Their electrode and total reactions are simply shown as follows: The negative electrode:
Zn2þ þ 2e ⇔ Zn
(1)
The positive electrode:
Na0:44 MnO2 ⇔ Na0:44x MnO2 þ xNaþ þ xe
(2)
The total reaction:
2Na0:44 MnO2 þ xZn2þ ⇔ 2Na0:44x MnO2 þ 2xNaþ þ xZn
(3)
When the battery is charged, sodium ions are de-intercalated from sodium-intercalation compounds of Na0.44MnO2 and dissolved into the electrolyte, accompanied by releasing electrons. While zinc ions deposit onto the surface of Zn current collector and accept electrons from the external circuit. During the discharge process, Zn in the anode loses electrons to convert into zinc ions, and then the zinc ions are dissolved into the electrolyte. Simultaneously, sodium ions are intercalated into Na0.44-xMnO2 to form back Na0.44MnO2. The electrons move from the anode to the cathode through the external circuit to complete the loop, of which the charge-discharge mechanism is first reported by Pu [9] and is also the same as those in the previous reports [26e28]. Cyclic voltammetry (CVs) of Zn/Na0.44MnO2 at different cut-off potentials in 0.5 mol L1 ZnSO4 and 1.0 mol L1 Na2SO4 aqueous solution at a scan rate of 0.1 mV s1 are shown in Fig. 2. There is one oxidation peak at about 1.60 V (vs Zn2þ/Zn) and one reduction peak at about 1.08 V (vs Zn2þ/Zn) during the first cycle. The area of the oxidation peak is small, while it is much larger during the reduction process, demonstrating the higher coulombic efficiency. With the cycling increasing, there seems to be asymmetric redox peaks, and two reduction peaks appear after the first cycle. Meanwhile, compared with the oxidation peaks from Fig. 2(a), (b) and (c) at different cut-off voltages, it can be seen that there is a large oxidation peak at about 2.5 V (vs Zn2þ/Zn), which is probably due to the water decomposition. When the cut-off voltage is decreased to 2.0 V, the hydrogen evolution peak nearly disappears. Thus, the upper cut-off voltage is limited to 2.0 V. The galvanostatic charge-discharge measurements were conducted at 4 C-rate at different cut-off potentials in Fig. 3 (a), the capacity in the range of 0.5e2.0 V is much higher than that of 1.0e2.0 V. As shown in Fig. 3 (b), the initial discharge capacity is up to 113.3 mAh g1 (vs Zn2þ/Zn), which seems to be much higher than those reports based on Na0.95MnO2/Zn at 4 C-rate and Na0.44MnO2/ NaTi2(PO4)3 at 1 C-rate in aqueous rechargeable battery systems [26,29]. However, it's surprised that the initial coulombic efficiency 492.35% is much higher than 100% due to the very low initial charge capacity of 23.1 mAh g1, which is the same as that in CVs. What a pity that the reason is still unknown. With the cycle number increasing, the discharge capacity decreases quickly in the first five
X. Wu et al. / Journal of Power Sources 336 (2016) 35e39
37
Fig. 1. XRD and SEM images of Na0.44MnO2.
Fig. 2. Cyclic voltammetry of Zn/Na0.44MnO2 in an aqueous solution of 0.5 mol L1 ZnSO4 and 1 mol L1 Na2SO4 at a scan rate of 0.1 mV s1.
Fig. 3. (a) cycling performance of the Zn/Na0.44MnO2 at 4 C rate at different cut-off voltages, (b) Charge and discharge curves of the Na0.44MnO2.
cycles, and then it tends to be flat even after 100 cycles. In a word, the battery displays a good cycling performance even at 4 C-rate. Meanwhile, we can see that there are a charge plateau and two separate discharge plateaus from Fig. 3 (b), which is the same as that in cyclic voltammetry. In order to further study the electrochemical behavior of Na0.44MnO2, electrochemical impedance spectroscopy before and after cycling tests is performed with the working frequency from 102 Hze105 Hz and the perturbation amplitude of 5 mV. As shown
in Fig. 4, the impedance spectra displays a small semicircle in the high frequency, followed by a straight line in the low frequency region, of which the semicircle part at high frequency (Rct) corresponds to the charge transfer process at the electrode-electrolyte interface and the straight line with a slope (Zw) is related to the diffusion control process of sodium ion. It can be seen that the battery before and after cycling has a similar ohmic resistance, while the semicircle after cycling is much larger than that before cycling.
38
X. Wu et al. / Journal of Power Sources 336 (2016) 35e39
Fig. 6. The self-discharge procedure of the Zn/Na0.44MnO2 battery. Fig. 4. The EIS of Zn/Na0.44MnO2 before and after cycling.
Rate tests of up to 10 C-rate have been investigated to evaluate the electrode and the results are shown in Fig. 5. In the first discharge process, the electrode exhibits remarkably high discharge capacity at 0.2 C, up to 153.3 mAh g1. Moreover, the discharge capacity retains up to 37.3 mAh g1 at 10 C-rate, and the discharge plateau does not decrease a lot. Self-discharge procedure is usually used to evaluate the side reactions of the electrodes. The self-discharge measurement was performed in Fig. 6, the battery was cycled for three times at 0.2 Crate firstly, and then charged to 2.0 V at 0.2 C-rate, standing for 24 h at room temperature. At last it was cycled for three times. As shown in Fig. 6, after standing for 24 h, the coulombic efficiency is increased from 87.52% to 96.31%, although the potential decreased to 1.5804 V, indicating the smaller self-discharge phenomenon. 4. Conclusions In summary, a hybrid aqueous rechargeable battery using Na0.44MnO2 as cathode and metal zinc foil as anode has been developed. Na0.44MnO2 synthesized by sol-gel method displays an excellent rate and cycling capability in hybrid aqueous electrolyte. We really hope the preliminary work on such hybrid cationic aqueous-based rechargeable battery system can bring some new
Fig. 5. The charge-dishcarge capacity of Zn/Na0.44MnO2 at different C-rates.
ideas to further investigate green, safe and low-cost batteries for future application in the field of smart grid, although the reason about the very low initial charge capacity of 23.1 mAh g1 and the coulombic efficiency of more than 400% at 4 C-rate needs to be studied further. Acknowledgment This research was financially supported by Outstanding Youth Foundation of Hunan Provincial Education Department (No. 15B190), Scientific research start-up funding of Jishou university (jsdxrcyjkyxm201407), the National Natural Science Foundation of China (No. 51662010, No. 51262008, No. 51472107, No. 51364009 and 51672104), and Natural Science Foundation of Hunan Province, China (No. 12JJ2005, No. 14JJ4048, No. 16JJ6121), and Aid program (Environment and Energy Materials and deep processing of mineral resources in Wuling Mountain) for Science and Technology Innovative Research Team in Higher Educational Instituions of Hunan Province, which were greatly appreciated. References [1] J. Cho, S. Jeong, Y. Kim, Commercial and research battery technologies for electrical energy storage applications, Prog. Energy Combust. 48 (2015) 84e101. [2] M. Sawicki, L.L. Shaw, Advances and challenges of sodium ion batteries as post lithium ion batteries, RSC Adv. 5 (2015) 53129e53154. [3] J.X. Wang, Q.B. Zhang, X.H. Li, B. Zhang, L.Q. Mai, K.L. Zhang, Smart construction of three-dimensional hierarchical tubular transition metal oxide core/shell heterostructures with high-capacity and long-cycle-life lithium storage, Nano Energy 12 (2015) 437e446. [4] W.C. Wen, S.H. Chen, Y.Q. Fu, X.Y. Wang, H.B. Shu, A core-shell structure spinel cathode material with a concentration gradient shell for high performance lithium-ion batteries, J. Power Sources 274 (2015) 219e228. [5] Z. Chen, C. Wang, J. Lopez, Z.D. Lu, Y. Cui, Z.N. Bao, High-areal-capacity silicon electrodes with low-cost silicon particles based on spatial control of selfhealing binder, Adv. Energy Mater. 5 (8) (2015) 1401826. [6] W. Li, J.R. Dahn, D.S. Wainwright, Rechargeable lithium batteries with aqueous electrolytes, Science 264 (5162) (1994) 1115e1118. [7] W. Tang, Y.S. Zhu, Y.Y. Hou, L.L. Liu, Y.P. Wu, K.P. Loh, H.P. Zhang, K. Zhu, Aqueous rechargeable lithium batteries as an energy storage system of superfast charging, Energy Environ. Sci. 6 (2013) 2093e2104. [8] Y.G. Wang, J. Yi, Y.Y. Xia, Recent progress in aqueous lithium-ion batteries, Adv. Energy Mater. 2 (2012) 830e840. [9] J. Yan, J. Wang, H. Liu, Z. Bakenov, D. Gosselink, P. Chen, Rechargeable hybrid aqueous batteries, J.Power Sources 216 (2012) 222e226. [10] X.W. Wu, Y.H. Li, C.C. Li, Z.X. He, Y.H. Xiang, L.Z. Xiong, D. Chen, Y. Yu, K. Sun, Z.Q. He, P. Chen, The electrochemical performance improvement of LiMn2O4/ Zn based on zinc foil as the current collector and thiourea as an electrolyte additive, J.Power Sources 300 (2015) 453e459. [11] M. Minakshi, P. Singh, S. Thurgate, K. Prince, Electrochemical behavior of olivine-type LiMnPO4 in aqueous solutions, Electrochem. Solid-State Lett. 9
X. Wu et al. / Journal of Power Sources 336 (2016) 35e39 (10) (2006) A471eA474. [12] S. Kandhasamy, A. Pandey, M. Minakshi, Polyvinylpyrrolidone assisted solegel route LiCo1/3Mn1/3Ni1/3PO4 composite cathode for aqueous rechargeable battery, Electrochim. Acta 60 (2012) 170e176. [13] H.P. Zhang, X. Wu, T. Yang, S.S. Liang, X.J. Yang, Cooperation behavior between heterogeneous cations in hybrid batteries, Chem. Commun. 49 (2013) 9977e9979. [14] F.X. Wang, Y. Liu, X.W. Wang, Z. Cheng, Y.P. Wu, R. Holze, Aqueous rechargeable battery based on zinc and a composite of LiNi1/3Co1/3Mn1/3O2, ChemElectroChem 2 (2015) 1024e1030. [15] L.M. Suo, O. Borodin, W. Sun, X.L. Fan, C.Y. Yang, F. Wang, T. Gao, Z.H. Mao, M. Schroeder, A.V. Cresce, S.M. Russell, M. Armand, A. Angell, K. Xu, C.S. Wang, Advanced high-voltage aqueous lithium-ion battery enabled by “water-inbisalt” electrolyte, Angew. Chem. Int. Ed. 55 (2016) 1e7. [16] C.Y. Lu, T.K.A. Hoang, T.N.L. Doan, H.B. Zhao, R. Pan, L. Yang, W.S. Guan, P. Chen, Rechargeable hybrid aqueous batteries using silica nanoparticle doped aqueous electrolytes, Appl. Energy 170 (2016) 58e64. [17] X. Zhu, T.N.L. Doan, Y. Yu, Y. Tian, K.E.K. Sun, H.B. Zhao, P. Chen, Enhancing rate performance of LiMn2O4 cathode in rechargeable hybrid aqueous battery by hierarchical carbon nanotube/acetylene black conductive pathways, Ionics 22 (1) (2016) 71e76. [18] X. Zhu, X.W. Wu, T.N.L. Doan, Y. Tian, H.B. Zhao, P. Chen, Binder-free flexible LiMn2O4/carbon nanotube network as high power cathode for rechargeable hybrid aqueous battery, J. Power Sources 326 (2016) 498e504. [19] M. Sawicki, L.L. Shaw, Advances and challenges of sodium ion batteries as post lithium ion batteries, RSC Adv. 5 (2015) 53129e53154. [20] L.P. Wang, L.H. Yu, X. Wang, M. Srinivasan, Z.J. Xu, Recent developments in electrode materials for sodium-ion batteries, J. Mater. Chem. A 3 (2015) 9353e9378. [21] H.S. Hou, C.E. Banks, M.J. Jing, Y. Zhang, X.B. Ji, Carbon quantum dots and their
[22]
[23]
[24]
[25]
[26]
[27]
[28]
[29]
39
derivative 3D porous carbon frameworks for sodium-ion batteries with ultralong cycle life, Adv. Mater. 27 (2015) 7861e7866. J.F. Whitacre, A. Tevar, S. Sharma, Na4Mn9O18 as a positive electrode material for an aqueous electrolyte sodium-ion energy storage device, Electrochem. Commun. 12 (2010) 463e466. Y.S. Wang, L.Q. Mu, J. Liu, Z.Z. Yang, X.Q. Yu, L. Gu, Y.S. Hu, H. Li, X.Q. Yang, L.Q. Chen, X.J. Huang, A novel high capacity positive electrode material with tunnel-type structure for aqueous sodium-ion batteries, Adv. Energy Mater. 5 (22) (2015) 1501005. E. Hosono, H. Matsuda, I. Honma, S. Fujihara, M. Ichihara, H.S. Zhou, Synthesis of single crystalline electro-conductive Na0.44MnO2 nanowires with high aspect ratio for the fast chargeedischarge Li ion battery, J.Power Sources 182 (2008) 349e352. X. Liu, N. Zhang, J.F. Ni, L.J. Gao, Improved electrochemical performance of solgel method prepared Na4Mn9O18 in aqueous hybrid Na-ion supercapacitor, J. Solid State Electrochem 17 (2013) 1939e1944. B.H. Zhang, Y. Liu, X.W. Wu, Y.Q. Yang, Z. Chang, Z.B. Wen, Y.P. Wu, An aqueous rechargeable battery based on zinc anode and Na0.95MnO2, Chem. Commun. 50 (2014) 1209e1211. G.L. Li, Z. Yang, Y. Jiang, W.X. Zhang, Y.H. Huang, Hybrid aqueous battery based on Na3V2(PO4)3/C cathode and zinc anode for potential large-scale energy storage, J.Power Sources 308 (2016) 52e57. H.B. Zhao, C.J. Hu, H.W. Cheng, J.H. Fang, Y.P. Xie, W.Y. Fang, T.N.L. Doan, T.K.A. Haong, J.Q. Xu, P. Chen, Novel rechargeable M3V2(PO4)3//zinc (M¼ Li, Na) hybrid aqueous batteries with excellent cycling performance, Sci. Rep. 6 (2016) 25809. B.D. Zhao, B. Lin, S. Zhang, C. Deng, A frogspawn-inspired hierarchical porous NaTi2(PO4)3-C array for high-rate and long-life aqueous rechargeable sodium batteries, Nanoscale 7 (2015) 18552e18560.