【摘要】 为进一步提高高镍三元放电比容量,将充电截止电压从4.3 V提高到4.5/4.7 V,放电比容量可从200 m Ah g^-1提高到230 m Ah g^-1,这对提高能量密度是非常有利的,但同时会导致界面稳定性进一步降低.本文在商业电解液(1 mol L^-1 LiPF₆/EC:DEC=1:1,体积比)基础上,加入双添加剂二氟草酸硼酸锂（LiDFOB）和三甲基硅基磷酸酯（TMSP）,一方面形成富含F, B, Si等元素的无机组分界面膜增加高电压下界面稳定性;另一方面, TMSP中的Si-O键具有清除电解液中高腐蚀性HF的作用,以此增加电解液的稳定性.在成膜和除HF的双重作用下,抑制了4.5/4.7 V高截止电压下的界面反应、过渡金属溶出、表面相变及产气.组装的LiNi_0.8Co_0.1Mn_0.1O₂/Li电池在4.5 V下具有800圈的循环寿命,在4.7 V下具有500圈的循环寿命.更多还原

【Abstract】 The LiNi_0.8Co_0.1Mn_0.1O₂ （Ni-rich NCM） cathode materials suffer from electrochemical performance degradation upon cycling due to detrimental cathode interface reactions and irreversible surface phase transition when operating at a high voltage（≥4.5 V）. Herein, a traditional carbonate electrolyte with lithium difluoro（oxalato）borate（Li DFOB） and tris（trimethylsilyl）phosphate（TMSP） as dual additives that can preferentially oxidize and decompose to form a stable F, B and Si-rich cathode-electrolyte interphase（CEI） that effectively inhibits continual electrolyte decomposition, transition metal dissolves, surface phase transition and gas generation. In addition, TMSP also removes trace H₂O/HF in the electrolyte to increase the electrolyte stability. Owing to the synergistic effect of Li DFOB and TMSP, the Li/LiNi_0.8Co₀.1)Mn_0.1O₂half cells exhibit the capacity retention 76.3% after 500 cycles at a super high voltage of 4.7 V, the graphite/LiNi_0.8Co_0.1Mn_0.1O₂ full cells exhibit high capacity retention of 82.8% after 500 cycles at 4.5 V, and Li/LiNi_0.8Co_0.1Mn_0.1O₂ pouch cells exhibit high capacity retention 94% after 200 cycles at 4.5 V. This work is expected to provide an effective electrolyte optimizing strategy compatible with high energy density lithium-ion battery manufacturing systems.更多还原