Corresponding Author

Xing-De Xiang(xiangxingde@nefu.edu.cn)


Aqueous sodium-ion batteries show promising application in fields of large-scale storage of intermittent renewable energies owing to the earth-abundant sodium resources and incombustible aqueous electrolytes. Primary factors determining whether they can be commercially utilized are low cost and long lifetime. Among current electrode materials, NASICON-type NaTi2(PO4)3 arouses wide interests as an anode material for aqueous sodium-ion batteries as it offers a high specific capacity, fast Na-transport ability and reasonable working potential, however, suffering from insufficient cycling performance caused by severe dissolution of active materials in traditional aqueous electrolytes. In this work, a functional sulfate electrolyte (2 mol·L-1 Na2SO4 + 0.3 mol·L-1 MgSO4) was designed by coupling concentrated Na2SO4 salt and functional MgSO4 additive to enhance the cycling stability of NaTi2(PO4)3/C material. Experimental results from cyclic voltammetry and galvanostatic measurements suggest that the electrolyte can improve electrochemical reversibility and cycling performance of NaTi2(PO4)3/C material relative to traditional electrolyte (1 mol·L-1 Na2SO4). In specific, the material harvested a reversible capacity of 93.4 mAh·g-1 and impressive capacity retention of 96.5% at the specific current of 100 mA·g-1 in the functional sulfate electrolyte, but exhibited a reversible capacity of 88.6 mAh·g-1 and much lower capacity retention of 72.1% in the traditional electrolyte. In order to explore intrinsic causes of the performance improvement, structural properties of the material before and after cycling were comparatively investigated by using X-ray diffraction and X-ray photon spectroscopy. It is found that the material showed excellent structural stability and formation of protective Mg-containing interfacial layer during cycling in the functional sulfate electrolyte. Both the raised electrolyte-salt concentration and functional MgSO4 additive should be responsible for the enhanced structural stability. The high electrolyte-salt concentration could decrease electrochemical activity and widen electrochemical stability window of electrolyte solvents, while the MgSO4 additive could timely capture the hydroxyl group resulting from water-solvent decomposition to prevent the alkalization of aqueous electrolytes and spontaneously form protective Mg(OH)2 interfaces. As a result, the electrolyte could suppress the dissolution of active NaTi2(PO4)3, thus, resulting in the enhanced structural stability and cycling performance. With an aim to further exhibit the feasibility for practical application, full aqueous sodium-ion batteries were assembled by coupling Na2Ni[Fe(CN)6] cathode, functional sulfate electrolyte and NaTi2(PO4)3/C anode. Charge/discharge tests show that the battery could deliver a working voltage of 1.3 V and a reversible capacity of 84.2 mAh·g-1 (calculated as the mass of active anode material) at the current of 100 mA·g-1, achieving a specific energy of about 110 Wh·kg-1. After being continuously charging and discharging for 500 cycles at the current of 500 mA·g-1, it achieved high capacity retention of 80%. The results in this work suggest that designing functional additive-containing sulfate electrolytes is an effective strategy to fabricate low-cost, long-lifetime aqueous sodium-ion batteries.

Graphical Abstract


aqueous sodium-ion batteries, anode material, sulfate electrolyte, structural stability, cycling performance

Publication Date


Online Available Date


Revised Date


Received Date



[1] Liu SY(刘双), Shao L Y(邵涟漪), Zhang X J(张雪静), Tao Z J(陶占军), Chen J(陈军). Advances in electrode materials for aqueous rechargeable sodium-ion batteries[J]. Acta Phys. Chim. Sin.(物理化学学报), 2018, 34(6): 581-597.

[2] Cao Y(曹翊), Wang Y G(王永刚), Wang Q(王青), Zhang Z Y(张兆勇), Che Y(车勇), Xia Y Y(夏永姚), Dai X(戴翔). Development of aqueous sodium ion battery[J]. Energy Storage Sci. Tech.(储能科学与技术), 2016, 5: 317-323.

[3] Guo Z W, Zhao Y, Ding Y X, Dong X L, Chen L, Cao J Y, Wang C C, Xia Y Y, Peng H S, Wang Y G. Multi-functional flexible aqueous sodium-ion batteries with high safety[J]. Chem, 2017, 3(2): 348-362.
doi: 10.1016/j.chempr.2017.05.004 URL

[4] Liu Y C(刘永畅), Chen C C(陈程成), Zhang N(张宁), Tao Z L(陶占良), Chen J(陈军). Research and application of key materials for sodium ion batteries[J]. J. Electrochem.(电化学), 2016, 22(5): 437-452.

[5] Zhang F, Li W F, Xiang X D, Sun M L. Highly stable Na-storage performance of Na0.5Mn0.5Ti0.5O2 microrods as cathode for aqueous sodium-ion batteries[J]. J. Electroanal. Chem., 2017, 802: 22-26.
doi: 10.1016/j.jelechem.2017.08.042 URL

[6] Wang Y S, Mu L Q, Liu J, Yang Z Z, Yu X Q, Gu L, Hu Y S, Li H, Yang X Q, Chen L Q, Huang X J. A novel high capacity positive electrode material with tunnel-type structure for aqueous sodium-ion batteries[J]. Adv. Energy Mater., 2015, 5(22): 1501005.
doi: 10.1002/aenm.201501005 URL

[7] Zhang X Q, Hou Z G, Li X N, Liang J W, Zhu Y C, Qian Y T. Na birnessite with high capacity and long cycle life for rechargeable aqueous sodium-ion battery cathode electrodes[J]. J. Mater. Chem. A, 2016, 4(3): 856-860.
doi: 10.1039/C5TA08857G URL

[8] Lin X H(林兴灏), Chi X W(迟晓伟), Liu Y(刘宇), Yang J H(杨建华). Na3+xV2-xMgx(PO4)3 cathode preparation and its application in aqueous sodium-ion batteries[J]. Chin. J. Power Sources(电源技术), 2019, 43: 1821-1824.

[9] Liu S, Wang L B, Liu J, Zhou M, Nian Q S, Feng Y Z, Tao Z L, Shao L Y. Na3V2(PO4)2F3-SWCNT: a high voltage cathode for non-aqueous and aqueous sodium-ion batteries[J]. J. Mater. Chem. A, 2019, 7(1): 248-256.
doi: 10.1039/C8TA09194C URL

[10] Lei P, Wang Y, Zhang F, Wan X, Xiang X D. Carbon-coated Na2.2V1.2Ti0.8(PO4)3 cathode with excellent cycling performance for aqueous sodium-ion batteries[J]. ChemElectroChem, 2018, 5(17): 2482-2487.
doi: 10.1002/celc.v5.17 URL

[11] Fernadez-Ropero A J, Zarrabeitia M, Reynaud M, Rojo T, Casas-Cabanas M. Toward safe and sustainable batteries: Na4Fe3(PO4)2P2O7 as a low cost cathode for rechargeable aqueous Na-ion batteries[J]. J. Phys. Chem. C, 2018, 122(1): 133-142.
doi: 10.1021/acs.jpcc.7b09803 URL

[12] Li Y(李勇), He W X(何玮鑫), Zheng X Y(郑芯月), Yu S L(于胜兰), Li H T(李海同), Li H Y(黎弘毅), Zhang R(张蓉), Wang Y(王雨). Prussian blue cathode materials for aqueous sodium-ion batteries: Preparation and electrochemical performance[J]. J. Inorg. Mater.(无机材料学报), 2019, 34(4): 365-372.
doi: 10.15541/jim20180272

[13] Wang W L(王武练), Zhang J(张军), Wang Q S(王秋实), Chen L(陈亮), Wang Z P(王兆平). High-quality Fe4[Fe(CN)6]3 nanocubes: Synjournal and electrochemical performance as cathode material for aqueous sodium-ion battery[J]. J. Inorg. Mater.(无机材料学报), 2019, 34(12): 1301-1308.
doi: 10.15541/jim20190076

[14] Luo D X, Lei P, Tian G R, Huang Y X, Ren X F, Xiang X D. Insight into electrochemical properties and reaction mechanism of a cobalt-rich Prussian Blue analogue cathode in a NaSO3CF3 electrolyte for aqueous sodium-ion batteries[J]. J. Phys. Chem. C, 2020, 124(11): 5958-5965.
doi: 10.1021/acs.jpcc.9b11758 URL

[15] Cai D P, Yang X H, Qu B H, Wang T H. Comparison of the electrochemical performance of iron hexacyanoferrate with high and low quality as cathode materials for aqueous sodium-ion batteries[J]. Chem. Commun., 2017, 53(50): 6780-6783.
doi: 10.1039/C7CC02516E URL

[16] Zhang Q C, Man P, He B, Li C W, Li Q L, Pan Z H, Wang Z X, Yang J, Wang Z, Zhou Z Y, Lu X H, Niu Z Q, Yao Y G, Wei L. Binder-free NaTi2(PO4)3 anodes for high-performance coaxial-fiber aqueous rechargeable sodium-ion batteries[J]. Nano Energy, 2020, 67: 104212.
doi: 10.1016/j.nanoen.2019.104212 URL

[17] Qiu Y G, Yu Y H, Xu J, Liu Y, Ou M Y, Sun S X, Wei P, Deng Z, Xu Y, Fang C, Li Q, Han J T, Huang Y H. Redox potential regulation toward suppressing hydrogen evolution in aqueous sodium-ion batteries: Na1.5Ti1.5Fe0.5(PO4)3[J]. J. Mater. Chem. A, 2019, 7(43): 24953-24963.
doi: 10.1039/C9TA08829F URL

[18] Lei P, Liu K, Wan X, Luo D X, Xiang X D. Ultrafast Na intercalation chemistry of Na2Ti3/2Mn1/2(PO4)3 nanodots planted in a carbon matrix as a low cost anode for aqueous sodium-ion batteries[J]. Chem. Commun., 2019, 55(4): 509-512.
doi: 10.1039/C8CC07668E URL

[19] Gu T T, Zhou M, Liu M Y, Wang K L, Cheng S J, Jiang K. A polyimide MWCNTs composite as high capacity anode for aqueous SIBs[J]. RSC Adv., 2016, 6: 53319-53323.
doi: 10.1039/C6RA09075C URL

[20] Deng W W, Shen Y F, Qian J F, Yang H X. A polyimide anode with high capacity and superior cyclability for aqueous Na-ion batteries[J]. Chem. Commun., 2015, 51(24): 5097-5099.
doi: 10.1039/C5CC00073D URL

[21] Wu M G, Ni W, Hu J, Ma J M. NASICON-structured NaTi2(PO4)3 for sustainable energy storage[J]. Nano-Micro Lett., 2019, 11(1): 44.
doi: 10.1007/s40820-019-0273-1 URL

[22] Zheng W T, Lei P, Luo D X, Huang Y X, Tian G R, Xiang X D. Understanding the effect of structural compositions on electrochemical properties of titanium-based polyanionic compounds for superior sodium storage[J]. Solid State Ionics, 2020, 345: 115194.
doi: 10.1016/j.ssi.2019.115194 URL

[23] Malchik F, Shpigel N, Levi M D, Penki T R, Gavriel B, Bergman G, Turgeman M, Aurbach D, Gogotsi Y. MXene conductive binder for improving performance of sodium-ion anodes in water-in-salt electrolyte[J]. Nano Energy, 2021, 79: 105433.
doi: 10.1016/j.nanoen.2020.105433 URL

[24] Mohamed A I, Whitacre J F. Capacity fade of NaTi2(PO4)3 in aqueous electrolyte solutions: Relating pH increases to long term stability[J]. Electrochim. Acta, 2017, 235: 730-739.
doi: 10.1016/j.electacta.2017.03.106 URL

[25] Zhan X W, Shirpour M. Evolution of solid/aqueous interface in aqueous sodium-ion batteries[J]. Chem. Commun., 2017, 53(1): 204-207.
doi: 10.1039/C6CC08901A URL

[26] Luo D X, Lei P, Huang Y X, Tian G R, Xiang X D. Improved electrochemical performance of graphene-integrated NaTi2(PO4)3/C anode in high-concentration electrolyte for aqueous sodium-ion batteries[J]. J. Electroanal. Chem., 2019, 838: 66-72.
doi: 10.1016/j.jelechem.2019.02.057 URL

[27] Lei P, Li S J, Luo D X, Huang Y X, Tian G R, Xiang X D. Fabricating a carbon-encapsulated NaTi2(PO4)3 framework as a robust anode material for aqueous sodium-ion batteries[J]. J. Electroanal. Chem., 2019, 847: 113180.
doi: 10.1016/j.jelechem.2019.05.062 URL

[28] Li X N, Zhu X B, Liang J W, Hou Z G, Wang Y, Lin N, Zhu Y C, Qian Y T. Graphene-supported NaTi2(PO4)3 as a high rate anode material for aqueous sodium ion batteries[J]. J. Electrochem. Soc., 2014, 161(6): A1181-A1187.
doi: 10.1149/2.0081409jes URL

[29] Zhang F, Li W F, Xiang X D, Sun M L. Nanocrystal-assembled porous Na3MgTi(PO4)3 aggregates as highly stable anode for aqueous sodium-ion batteries[J]. Chem. Eur. J., 2017, 23(52): 12944-12948.
doi: 10.1002/chem.v23.52 URL

[30] Gao H C, Goodenough J B. An aqueous symmetric sodium-ion battery with NASICON-structured Na3MnTi(PO4)3[J]. Angew. Chem. Int. Ed., 2016, 55(41): 12768-12772.
doi: 10.1002/anie.201606508 URL

[31] Wang H B, Zhang T R, Chen C, Ling M, Lin Z, Zhang S Q, Pan F, Liang C D. High-performance aqueous symmetric sodium-ion battery using NASICON-structured Na2VTi(PO4)3[J]. Nano Res., 2017, 11(1): 490-498.
doi: 10.1007/s12274-017-1657-5 URL

[32] Suo L M, Borodin O, Wang Y S, Rong X H, Sun W, Fan X L, Xu S Y, Schroeder M A, Cresce A V, Wang F, Yang C Y, Hu Y S, Xu K, Wang C S. “Water-in-salt” electrolyte makes aqueous sodium-ion battery safe, green, and long-lasting[J]. Adv. Energy Mater., 2017, 7(21): 1701189.
doi: 10.1002/aenm.v7.21 URL

[33] Zhang H, Jeong S, Qin B, Carvalho D V, Buchholz D, Passerini S. Towards high-performance aqueous sodium-ion batteries: Stabilizing the solid/liquid interface for NASICON-type Na2VTi(PO4)3 using concentrated electro-lytes[J]. ChemSusChem, 2018, 11(8): 1382-1389.
doi: 10.1002/cssc.v11.8 URL

[34] Kuhnel R S, Reber D, Battaglia C. A high-voltage aqueous electrolyte for sodium-ion batteries[J]. ACS Energy Lett., 2017, 2(9): 2005-2006.
doi: 10.1021/acsenergylett.7b00623 URL

[35] Mao W T, Zhang S J, Cao F P, Pan J L, Ding Y M, Ma C, Li M L, Hou Z G, Bao K Y T, Qian Y T. Synjournal of NaTi2(PO4)3@C microspheres by an in situ process and their electrochemical properties[J]. J. Alloys Compd., 2020, 842: 155300.
doi: 10.1016/j.jallcom.2020.155300 URL

[36] Zhao Y Y, Wei Z X, Pang Q, Wei Y J, Cai Y M, Fu Q, Du F, Sarapulova A, Ehrenberg H, Liu B B, Chen G. NASICON-type Mg0.5Ti2(PO4)3 negative electrode material exhibits different electrochemical energy storage mechanisms in Na-ion and Li-ion batteries[J]. ACS Appl. Mater. Interfaces, 2017, 9(5): 4709-4718.
doi: 10.1021/acsami.6b14196 URL



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.