Electrolyte solvation structure manipulation enables safe and stable aqueous sodium ion batteries

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 8; no. 28; pp. 1419 - 14197
• Main Authors: Ao, Huaisheng, Chen, Chunyuan, Hou, Zhiguo, Cai, Wenlong, Liu, Mengke, Jin, Yueang, Zhang, Xin, Zhu, Yongchun, Qian, Yitai
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 21.07.2020
• Subjects: Additives; Aqueous electrolytes; Batteries; Dimethylformamide; Electric potential; electric potential difference; Electrochemistry; Electrolytes; Energy storage; guidelines; Inorganic salts; Ion currents; Nickel; Operating temperature; Performance degradation; Pigments; Safety; Sheaths; Sodium; Sodium carbonate; Sodium-ion batteries; Solid electrolytes; Solvation; solvents; Stability; temperature; Urea; Voltage
• ISSN: 2050-7488; 2050-7496; 2050-7496
• DOI: 10.1039/d0ta04800c

Aqueous sodium ion batteries (ASIBs) have been limited by their poor electrochemical stability. The use of highly concentrated aqueous electrolytes is considered as an efficient strategy that increases the voltage window and improves the cycling stability. However, their cost and safety are still subjects of serious concern for practical applications. In this work, we show that a new multi-component aqueous electrolyte (MCAE) could widen the voltage window to 2.8 V with the formation of a composite solvent sheath and promote the generation of a uniform solid electrolyte interface (SEI) layer consisting of complexes with inorganic salt Na 2 CO 3 and other organic components, which significantly inhibits the side reaction. Thus, this MCAE guaranteed good electrochemical stability of Na 3 V 2 (PO 4 ) 3 and NaTi 2 (PO 4 ) 3 , which suffer from severe performance degradation in aqueous electrolytes. Simultaneously, this MCAE exhibits high safety, a wide operating temperature range (−50 °C to 50 °C) and high ionic conductivity because of urea and N , N -dimethylformamide (DMF) additives. In addition, a nickel-based Prussian blue analog (NiHCF)/NaTi 2 (PO 4 ) 3 sodium-ion full battery using such a MCAE delivers 80% capacity retention after 2000 cycles at 2C rate. Moreover, our work provides important guidelines to investigate safe, environmentally friendly and high-stability ASIBs for large-scale energy storage. A multi-component aqueous electrolyte with a composite solvent sheath can widen the voltage window to 2.8 V and inhibit side reactions. A solid electrolyte interface layer containing Na 2 CO 3 and organic compounds suppresses the reaction of water with the discharged anode.