A research team in China has developed a new type of electrolyte for high-energy Li-ion batteries with a self-purifying feature that opens a promising approach for electrolyte engineering for next-generation high-energy Li-ion batteries. A paper on their work is published in the RSC journal Energy & Environmental Science.
Conventional LiPF6/carbonate electrolyte is burdened with poor oxidative stability and reactive decomposition products (HF, PF5, POF3, etc.). This results in less-stable electrode/electrolyte interphases, which thereby promotes the dissolution of transition metal ions, accelerates constant decomposition of electrolyte solvent, and results in the degradation of LIBs.
The researchers, from Zhejiang University, Beijing National Laboratory for Condensed Matter Physics, and Qingdao Institute of Bioenergy and Bioprocess Technology, developed a 1.6 M lithium bis(fluorosulfonyl)imide (LiFSI) in (2-cyanoethyl) triethoxysilane (TEOSCN) electrolyte with a self-purifying feature.
TEOSCN molecules in electrolyte can effectively eliminate the reactive pernicious species, while the anions of FSI-dominate the interphase components with low-resistance on both graphite and Ni-rich NMC cathode although at an essentially low concentration. This self-purifying electrolyte system enables long-term cycling of MCMB||NMC811 full-cells for 1000 cycles with an ultra-high capacity retention of 91% at 25 °C and for 500 cycles with a retention of 81% at 60 °C.
Even in extreme cases, i.e., exposed in the air for 1 h, this electrolyte can still allow stable charge-discharge cycling of MCMB||NMC811 full-cells without degradation, which can largely simplify the manufacturing processes of LIBs. The ‘self-purifying-plus-passivation’ strategy opens a promising frontier for the electrolyte engineering towards next-generation high-energy LIBs.
Electrochemical performance of Li||NMC811 half-cells using different electrolytes. (a) Cycling performance of Li||NMC811 half-cells using different electrolytes under 1 C charge and 2 C discharge between 2.8 V to 4.3 V. Voltage profiles of Li||NMC811 half-cells using LiFSI-TEOSCN (b), BE + 2% VC (c) and BE (d) electrolytes between 2.8 V to 4.3 V. Lu et al.
Di Lu, Xincheng Lei, Suting Weng, Ruhong Li, Jiedong Li, Ling Lv, Haikuo Zhang, Yiqiang Huang, Junbo Zhang, Shuoqing Zhang, Liwu Fan, Xuefeng Wang, Lixin Chen, Guanglei Cui, Dong Su and Xiulin Fan (2022) “Self-purifying electrolyte enables high energy Li ion batteries” Energy & Environmental Science doi: 10.1039/D2EE00483F