High-rate sodium metal batteries enabled by trifluormethylfullerene
Pengju Li, Xiaobo Huang, Zhipeng Jiang, Han Zhang, Pengwei Yu， Xing Lu* and Jia Xie*
Nano Res., 2022. https://doi.org/10.1007/s12274-022-4349-8
ABSTRACT
Sodium metal is a promising anode for sodium batteries due to its high theoretical capacity and low cost. However, the serious Na dendrite growth and low Coulombic efficiency, especially at high current densities/cycling capacities, severely limit the application of sodium metal anodes. Herein, trifluoromethylfullerene, C60(CF3)6, is designed as an electrolyte additive to enable the high-rate cycling of sodium metal anodes with high Coulombic efficiency. The CF3 groups contribute to the formation of stable NaF-rich solid electrolyte interface layer, while C60 cages induce the uniform distribution of sodium ions and promote the formation of smooth and compact morphology. Thus, Na||Cu cell with C60(CF3)6 can be cycled at 2 mA cm−2 and 10 mAh cm−2 over 180 cycles with an average Coulombic efficiency of 99.9%, and Na||Na cell can be cycled at 10 mA cm−2 over 600 cycles. Furthermore, Na||NaV2(PO4)3@C full cell exhibits high capacity retention of 84% over 2000 cycles at 20 C (~3 mA cm−2).
摘要
钠金属因其具有理论容量高、成本低等优点，被认为是一种很有前途的钠电池负极材料。然而，在高电流/容量密度下，严重的钠枝晶生长和低库仑效率，严重限制了钠金属负极的应用。本工作通过合理的分子结构设计，合成了三氟甲基富勒烯C60(CF3)6添加剂。作为一种新型的含氟电解液添加剂，C60(CF3)6不仅增强了钠离子在电解液中的迁移能力，而且促进形成富含NaF的SEI层，诱导钠的均匀沉积。在2 mA cm−2/10 mAh cm−2条件下，含有C60(CF3)6的Na||Cu电池可循环超过180圈，平均库伦效率高达99.9%。同时，含有C60(CF3)6的Na||Na对称电池在10 mA cm−2下可稳定循环超过600圈，表现出优异的循环稳定性。此外，含有C60(CF3)6的Na||Na3V2(PO3)4@C全电池在20C（3 mA cm−2）下循环2000圈后容量保持率仍高达84%，具有较大的实际应用价值。这种以富勒烯衍生物为添加剂的思路不仅拓展了富勒烯材料的应用范围，而且为高倍率钠金属电池的开发提供了一种可行的方案。
