Electrolyte Design with Dual –CN Groups Containing Additives to Enable High-Voltage Na3V2(PO4)2F3‑Based Sodium-Ion Batteries

• Published in: Journal of the American Chemical Society Vol. 146; no. 18; pp. 12519 - 12529
• Main Authors: Jiang, Mingqin, Li, Tianyu, Qiu, Yanling, Hou, Xin, Lin, Hongzhen, Zheng, Qiong, Li, Xianfeng
• Format: Journal Article
• Language: English
• Published: American Chemical Society 08-05-2024
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.4c00702

Na3V2(PO4)2F3 is recognized as a promising cathode for high energy density sodium-ion batteries due to its high average potential of ∼3.95 V (vs Na/Na+). A high-voltage-resistant electrolyte is of high importance due to the long duration of 4.2 V (vs Na/Na+) when improving cyclability. Herein, a targeted electrolyte containing additives with two –CN groups like succinonitrile has been designed. In this design, one –CN group is accessible to the solvation sheath and enables the other –CN in dinitrile being exposed and subsequently squeezed into the electric double layer. Then, the squeezed –CN group is prone to a preferential adsorption on the electrode surface prior to the exposed –CH2/–CH3 in Na+-solvent and oxidized to construct a stable and electrically insulating interface enriched CN–/NCO–/Na3N. The Na3V2(PO4)2F3-based sodium-ion batteries within a high-voltage of 2–4.3 V (vs Na/Na+) can accordingly achieve an excellent cycling stability (e.g., 95.07% reversible capacity at 1 C for 1,5-dicyanopentane and 98.4% at 2 C and 93.0% reversible capacity at 5 C for succinonitrile after 1000 cycles). This work proposes a new way to design high-voltage electrolytes for high energy density sodium-ion batteries.