干法制备LiFePO_(4)厚电极的电化学性能

Electrochemical performance of LiFePO_(4)thick electrodes prepared by dry method

为实现更高的能量密度,探究利用干法工艺制备厚电极的电化学性能。通过构建点-线-面三维导电网络,采用干法电极制备工艺,制备138μm、217μm和303μm厚(面密度分别为26.7 mg/cm^(2)、35.0 mg/cm^(2)和47.9 mg/cm^(2))的磷酸铁锂(LiFePO_(4))厚电极。以0.10 C在2.50~4.25 V充放电,电极的可逆比容量分别为157.5 mAh/g、158.7 mAh/g和153.2 mAh/g,接近30μm厚(面密度为1.0 mg/cm^(2))对比电池的158.1 mAh/g。在不同电流下进行50次循环,仅0.50 C和1.00 C倍率下循环的容量受厚度影响。以0.50 C循环时,循环曲线出现“跳水”现象,且发生时间随着厚度的增加而提前,主要是因为厚电极在较大电流下充电时,在负极表面沉积大量高比表面金属锂,导致电池内的电解液干涸。

To achieve higher energy density,the electrochemical performance of thick electrodes prepared by dry process was explored.Lithium iron phosphate(LiFePO_(4))thick electrodes with thickness of 138μm,217μm and 303μm(area density was respectively 26.7 mg/cm^(2),35.0 mg/cm^(2) and 47.9 mg/cm^(2))were prepared by constructing point-line-surface three-dimensional conductive network and using a solvent-free electrode preparation process.When charged and discharged at 0.10 C in 2.50-4.25 V,the specific discharge capacity of the thick electrodes was respectively 157.5 mAh/g,158.7 mAh/g and 153.2 mAh/g,similar to 158.1 mAh/g of the compared electrode with thickness of 30μm and an area density of 1.0 mg/cm^(2).After 50 cycles at different currents,only the capacity of the cycle at rates of 0.50 C and 1.00 C was affected by the thickness.When cycled at 0.50 C,the cycle curves appeared"jumping"phenomenon,the occurrence time was advanced with the increase of thickness.The main reason was that when the thick electrode was charged at a large current,a large amount of high specific surface metal lithium was deposited on the surface of anode,resulting in the drying of the electrolyte in the battery.