2-噻吩甲腈在高电压锂离子电池中的应用

摘要

为了改善锂离子电池在高电压下的电化学性能，以2-噻吩甲腈作为一种新型的电解液添加剂，采用线性扫描伏安法(LSV)研究其对1 mol/L LiPF6/EC+EMC(EC与EMC质量分数之比为1：2)电解液电化学窗口的影响。通过扫描电镜(SEM)、X线光电子能谱(XPS)、傅里叶红外光谱(IR)、充放电测试、循环伏安(CV)和交流阻抗(EIS)对含不同电解液的锂离子电池循环前后的正极材料表面及其电化学性能进行表征。研究结果表明：2-噻吩甲腈能优先于电解液溶剂发生氧化分解反应并在正极表面形成致密的导电聚合物膜；添加质量分数为0.1%2-噻吩甲腈的钴酸锂电池在3.0~4.5 V以0.5C倍率循环100次后容量保持率高达91.99%，在5C倍率下放电比容量为152.8 mA·h·g−1；与电解液中未添加2-噻吩甲腈的电池相比，其循环后电荷转移阻抗的增加被抑制，在高电压下表现出较好的循环和倍率性能。%In order to improve the high-voltage performance of lithium-ion batteries, 2-Thiophenecarbonitrile as a novel additive was evaluated in commercial electrolyte. The influence of 2-Thiophenecarbonitrile on electrochemical window of commercial electrolyte was detected by linear sweep voltammetry (LSV). The surface chemistry and electrochemical behaviors of cathodes were investigated using scanning electron microscope(SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometer (IR), charge-discharge test and cyclic before the decomposition of solvents and electrochemical impedance spectroscopy (EIS). The results indicate that 2-Thiophenecarbonitrile can be oxidized in preference to solvents and form a conducting polymer film on the surface of cathodes. With 0.1% (mass fraction) 2-Thiophenecarbonitrile in electrolyte, the capacity retention of LiCoO2 battery keeps 91.99% after 100 cycles in the voltage of 3.0 V to 4.5 V, and the specific discharge capacity at high rate (5C) reaches 152.8 mA·h·g−1. Compared with cells without additive in electrolyte, the increase of charge transfer resistance is restrained and the electrochemical properties under high voltage operation are improved significantly.