腈基功能化有机硅电解液添加剂对LiFePO4电池低温性能的影响

合成了一种腈基功能化有机硅化合物3-氰乙基-二乙氧基-甲基硅烷(DESCN), 并对其化学结构和电化学窗口进行了表征. 采用恒流充放电、 扫描电子显微镜(SEM)、 X射线光电子能谱(XPS)及电化学阻抗谱(EIS)等方法研究了DESCN添加剂对LiFePO₄电池低温性能的影响. 结果表明, DESCN化合物能够在电极表面参与形成更薄、 更均匀且致密的固体电解质界面(SEI)膜, 抑制电解液副反应的发生, 减小界面膜阻抗, 有利于低温下电极/电解液界面的Li⁺扩散和电荷转移, 从而提高LiFePO₄电池的低温性能.

Effect of Nitrile Group Functionalized Organosilicon as Electrolyte Additive on Low-temperature Performance of LiFePO4 Battery†

A nitrile group functionalized organosilicon compound, 3-(diethoxy-methyl-silanyl)-propionitrile(DESCN) was synthesized and its chemical structure and electrochemical window were characterized. The effects of DESCN on the low-temperature performance of LiFePO₄ cell were investigated by charge-discharge cycling test, scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS) and electrochemical impedance spectroscopy(EIS) and so on. It is revealed that adding 2%DESCN could improve the low-temperature performance of LiFePO₄ cell. At -20 ℃, the cell exhibits a high discharge capacity of 73 mA·h/g and are stable after 50 cycles. DESCN involved in the formation of stable solid electrolyte interface(SEI) film to inhibit electrolyte decomposition and decrease the battery resistance, which facilitate Li⁺ diffusion and electron transportation at electrode/electrolyte interface at low-temperature.