连续硅基杂化隔膜涂层对锂离子电池性能的影响

Influence of Continuous Si-based Hybrid Coating Separator on Lithium Ion Battery Performance

通过卷对卷连续常压等离子体增强化学气相沉积(atmospheric pressure plasma enhanced chemical vapor deposition,AP-PECVD)法,对锂离子电池聚乙烯(PE)隔膜进行涂层,制备了硅基杂化纳米颗粒涂层隔膜。通过衰减全反射傅里叶变换红外光谱仪(ATR-FTIR)、扫描电子显微镜(SEM)和光学接触角测量仪对不同功率密度下涂层隔膜的物化性能进行表征,组装了LiFePO4/Li扣式电池并对其电化学性能进行测试,研究了100次循环后隔膜的表面特性。结果表明:纳米颗粒涂层隔膜含有-COOH、-OH、Si-O-Si、Si-OH等极性亲水基团,可显著降低电解液的接触角,提高润湿性;涂层隔膜的欧姆阻抗(Rs)和电荷迁移阻抗(Rct)显著降低,电导率增加。不同功率密度下的涂层隔膜能显著提高隔膜的物化性能和电池的电化学性能,但涂层隔膜的性能和功率密度之间并不呈正相关的关系,0.83 W/cm2功率密度下的涂层隔膜展示出更优的物化性能和电化学性。1C倍率100次循环后,未处理隔膜和涂层隔膜表面的孔隙都有一定程度的减小且Rs有所增加,但相对未处理的PE,涂层隔膜的颗粒与隔膜表面结合较好,孔径的减小和Rct的增加较少。

This paper used a roll-to-roll continuous atmospheric pressure plasma enhanced chemical vapor deposition(AP-PECVD)method to deposit the Si-based hybrid nanoparticle on the polyethylene(PE)separator surface at different power densities.The coated PE separators were analyzed by attenuated total reflection Fourier transform infrared spectroscopy(ATR-FTIR),scanning electron microscopy(SEM)and optical contact angle measuring device.The LiFePO4/Li button batteries were assembled with the pristine and coated PE separators to characterize their electrochemical properties.The results indicate that the separator surface has been coated by hybrid nanoparticles and the polar hydrophilic groups are introduced,such as-COOH,-OH,Si-O-Si and Si-OH,which can significantly reduce the PE separator contact angle for electrolyte and improve the wetting property.The ohmic impedance(Rs)and the charge transfer impedance(Rct)of the coated separators have been significantly reduced,and the conductivity has been increased.The coated separators at different power densities can significantly improve their physicochemical properties and the electrochemical performance of the assembled batteries.However,there is no linear correlation between the coated separator performance and the power densities.The coated separator at 0.83 W/cm2 power density exhibits better physicochemical and electrochemical performance.After 100 charge-discharge cycles at 1 C,the pore size has been decreased,and the value of Rshas been increased for both pristine PE separator and coated separator.Compared to the pristine PE,the particles of coated separator combine well with its surface,and there are less decrease of pore size and increase of Rct.