腈基功能化有机硅基电解液在4.4V钴酸锂/石墨锂离子电池中的性能研究

Nitrile group functionalized organosilicon compound as electrolytes for 4.4 V LiCoO_2/graphite full cell

研究了3-丙基腈-甲氧基乙氧基-二甲基硅烷(SN1)作为电解液共溶剂对高电压钴酸锂/石墨全电池电化学性能的影响.在商业烷基碳酸酯电解液里掺入30%SN1(体积分数),钴酸锂/石墨全电池在4.4 V截止电压下仍表现出良好的循环稳定性和倍率性能:以0.5 C充放电,首次放电比容量为154 mA h/g,循环150周后,容量保持率为92.9%;当放电倍率增加到1和1.5 C时,放电容量分别为143和133 mA h/g.电化学阻抗谱、扫描电镜和傅里叶红外光谱的结果表明,耐高电压腈基功能化有机硅化合物的引入有效抑制了共溶剂电解液在正极材料表面的分解,压制了循环过程中电极极化的增长,为电极/电解液界面的Li+扩散和电荷转移提供了有利的动力学条件.

Dimethyl-2-methoxylethoxyl-3-nitrilepropylsilane （SN1） is miscible with the commercial carbonate electrolyte and used as co-solvent to form hybrid electrolyte with a content up to 30 vol%. By using such hybrid electrolyte, the LiCoOJgraphite full cell exhibits good cyclic stability and rate capability at an upper cutoff voltage of 4.4 V, showing an initial specific capacity of 154 mA h/g and 92.9% capacity retention after 150 cycles at 0.5 C rate. When the rate is increased to 1 and 1.5 C, the cell still retains a specific capacity of 143 and 133 mA h/g, respectively. The results of scanning electron microscopy, fourier transform infrared and electrochemical impedance spectroscopy show that SN1 as a co-solvent reduces the decomposition of the electrolyte and suppresses the polarization growth of the cell over cycling which facilitates Li＋ diffusion and electron transportation at electrode/ electrolyte interface.