过充保护添加剂氰基功能化2, 5-二叔丁基对苯二酚的合成及其在锂离子电池中的应用

设计合成了单氰基功能化的2, 5-二叔丁基-1-（β-氰基乙氧基）-4-甲氧基苯（RS-MCN）和双氰基功能化的2, 5-二叔丁基-1, 4-（β-氰基乙氧基）苯（RS-DCN），并用作氧化还原过充添加剂开展了其在锂离子电子中的应用研究。通过丙烯氰和2, 5-二叔丁基对苯二酚的迈克尔加成反应可高效合成RS-MCN和RS-DCN，氰乙基取代后的过充保护添加剂分子的可逆氧化还原电位分别为4.02、4.08 V（vs Li/Li⁺）；并且单氰基取代的RS-MCN在商业碳酸酯电解液1 mol·L^-1 LiPF6/EC+DEC+EMC（1：1：1,体积比）中的溶解度可高达0.3 mol·L^-1。RSMCN和RS-DCN对LiFePO₄/Li电池的过充保护性能和电极相容性也进行了深入的研究，实验结果表明：RSMCN具有更好的过充保护性能和电极相容性，其5 V截止电压过充保护时间可超过1200 h，100%过充保护大于90周循环；0.3 mol·L^-1 RS-MCN的添加能使100%过充的LiFePO₄/Li电池在2.5C倍率条件下正常循环，其放电比容量达153.5 mAh·g^-1。此外，RS-MCN的添加对LiFePO₄/Li电池在2.5-3.8 V条件下的循环性能有明显改善，添加有RS-MCN的电池在60周的循环后容量保持率高达94.4%，而商业电解液的电池在60周循环后的容量保持率降至84.3%。因此，氰基功能化RS-MCN是一类具有潜在应用前景的过充保护添加剂。

Nitrile-Modified 2, 5-Di-tert-butyl-hydroquinones as Redox Shuttle Overcharge Additives for Lithium-Ion Batteries

Nitrile-modified 2, 5-di-tert-butyl-hydroquinones were synthesized and investigated as redox shuttle overcharge additives for LiFePO₄/Li cells. The cyanoethylation reaction was utilized to synthesize the target molecules 2, 5-di-tert-butyl-1, 4-di(β-cyanoethoxyl)benzene (RS-DCN) and 2, 5-di-tert-butyl-1-(β-cyanoethoxyl)-4-methoxybenzene (RS-MCN) in high efficiency from 2, 5-di-tert-butyl-hydroquinone and acrylonitrile. The solubility, cyclic voltammetric measurements, 5 V overcharge test, 100% overcharge test, high rate performance under 100% overcharge conditions, and cycle performance under normal conditions were studied in detail for the electrolyte with the addition of RS-DCN or RS-MCN. The RS-MCN compounds with the asymmetric structure delivered better solubility (with max. 0.3 mol·L^-1 in 1.0 mol·L^-1 LiPF6/EC+DEC+EMC, 1 : 1 : 1, in vol.), higher overcharge protection life (over 1200 h for the 5 V overcharge test), and excellent rate performance under 100% overcharge conditions (specific discharge capacity reached 153.5 mAh·g^-1 at 2.5C). The addition of RS-MCN also improved the cycling performance of the LiFePO₄/Li cell under the charge-discharge voltage range of 2.5-3.8 V.