过充保护添加剂1,2-二甲氧基-4-硝基苯和1,4-二甲氧基-2-硝基苯在锂离子电池中的应用

在锂离子电池电解液1 mol·L^-1 LiPF₆/(碳酸乙烯酯(EC)+碳酸二乙酯(DEC)+碳酸甲乙酯(EMC) (1:1:1,体积比))中分别添加1,2-二甲氧基-4-硝基苯(DMNB1)和1,4-二甲氧基-2-硝基苯(DMNB2)作为防过充添加剂.采用循环伏安(CV)、恒流充放电、过充测试、电化学阻抗谱(EIS)、扫描电子显微镜(SEM)等手段研究了DMNB1和DMNB2 的防过充效果, 以及添加剂与LiNi_1/3Co_1/3Mn_1/3O₂材料的相容性. 结果表明: DMNB1 和DMNB2 的氧化电位都在4.3 V (vs Li/Li⁺)以上, 且均能显著提高电池的过充保护性能. 100%过充和5 V截止电压过充测试表明, DMNB1 的防过充性能优于DMNB2. 采用基础电解液、添加0.1 mol·L^-1 DMNB1 和添加0.1 mol·L^-1DMNB2 电解液的LiNi_1/3Co_1/3Mn_1/3O₂/Li 电池, 0.2C 倍率下循环100 次, 容量保持率分别为98.4%、95.9%和68.1%. 证明硝基在添加剂苯环上的取代位置和其电化学性能之间有着密切联系.

Application of 1,2-Dimethoxy-4-nitro-benzene and 1,4-Dimethoxy- 2-nitro-benzene as Overcharge Protection Additives in Lithium-Ion Batteries

1,2-Dimethoxy-4-nitro-benzene (DMNB1) and 1,4-dimethoxy-2-nitro-benzene (DMNB2) were selected as new redox shuttle additives for overcharge protection in lithium-ion batteries. The base electrolyte is 1 mol·L^-1 LiPF₆/(ethylene carbonate (EC)+diethyl carbonate (DEC)+ethyl-methyl carbonate (EMC) (1:1:1, by volume)). Cyclic voltammetry (CV), charge-discharge cycle performance, overcharge tests, electrochemical impedance spectra (EIS), and scanning electron microscopy (SEM) were used to investigate the electrochemical performances of DMNB1 and DMNB2. The overcharge protection of DMNB1 and DMNB2 on lithium-ion batteries and the compatibility of both additives with the LiNi_1/3CoMn_1/3O₂ electrode have been studied. The results show that the working potentials of the both additives are above 4.3 V (vs Li/Li⁺), and thus are suitable for overcharge protection in lithium-ion batteries. Lithium-ion batteries with DMNB1 and DMNB2 have an improved overcharging tolerance. DMNB1 shows better overcharge protective performance, in the 100% overcharge and 5 V cutoff voltage tests, than DMNB2. After 100 cycles at 0.2C rate, the capacity retention rates of the LiNi_1/3Co_1/3Mn_1/3O₂/Li cells with the base electrolyte and the electrolyte with DMNB1 and DMNB2 are 98.4%, 95.9%, and 68.1%, respectively. The electrochemical properties and the location of the nitro-group on the benzene of the overcharge protection additives are closely linked.