School of Chemistry, South China Normal University, Guangzhou 510006, China.
National and Local Joint Engineering Research Center of MPTES in High Energy and Safety LIBs, Engineering Research Center of MTEES (Ministry of Education), and Key Lab. of ETESPG(GHEI), South China Normal University, Guangzhou 510006, China.
J Phys Chem Lett. 2021 May 13;12(18):4327-4338. doi: 10.1021/acs.jpclett.1c00803. Epub 2021 Apr 30.
Nickel-rich oxide/graphite cells under high voltage operation provide high energy density but present short cycle life because of the parasitic electrolyte decomposition reactions. In this work, we report a novel electrolyte additive, N,O-bis(trimehylsilyl)-trifluoroacetamide (NOB), which enables nickel-rich oxide/graphite cells to operate stably under high voltage. When evaluated in a nickel-rich oxide-based full cell, LiNiCoMnO (NCM523)/graphite using a carbonate electrolyte, 1 wt % NOB provides the cell with capacity retention improved from 38% to 73% after 100 cycles at 1C under 4.5 V. It is found that NOB is able to eliminate hydrogen fluoride in the electrolyte. The radicals resulting from the interaction of NOB with the fluoride ion can be preferentially oxidized on the cathode compared with the electrolyte solvents, with its reaction products constructing N-containing interphases simultaneously on the cathode and anode, which suppress the parasitic electrolyte decomposition reactions, leading to the significantly improved cycle stability of nickel-rich oxide/graphite cells under high voltage.
在高压操作下，富镍氧化物/石墨电池提供高能量密度，但由于寄生电解质分解反应，其循环寿命较短。在这项工作中，我们报告了一种新型电解质添加剂，N,O-双（三甲基甲硅烷基）-三氟乙酰胺（NOB），它使富镍氧化物/石墨电池能够在高压下稳定运行。在使用碳酸盐电解质的基于富镍氧化物的全电池中进行评估时，在 4.5 V 下以 1C 的倍率循环 100 次后，1wt%NOB 可将电池的容量保持率从 38%提高到 73%。研究发现，NOB 能够消除电解质中的氟化氢。NOB 与氟离子相互作用产生的自由基可以优先在阴极上被氧化，而不是电解质溶剂，其反应产物同时在阴极和阳极上构建含 N 的界面，从而抑制寄生电解质分解反应，显著提高了富镍氧化物/石墨电池在高压下的循环稳定性。
