PVP分散剂对高倍率LiFePO_4锂离子蓄电池性能作用

Effects of PVP dispersant on electrochemical performance of high rate Li-ion cells with LiFePO_4 cathode

采用粒度分析、流变分析、扫描电子显微镜法（SEM）等技术研究了PVP分散剂添加量对LiFePO4正极浆料粒度分布及流变性的影响规律。通过配方优化，制作高倍率放电18650型LiFePO4锂离子电池，并对其循环及倍率等性能进行了对比研究。结果表明，随着PVP加入量的提高，浆料的黏度呈现下降的趋势，浆料的粒度则先减小后增大，PVP加入量在0.4%～0.8%时，可达到最优的浆料分散效果。用PVP含量0.6%的LiFePO4正极浆料制作容量为1.1 Ah的18650电池表现出优异的高倍率放电及循环性能，在1.5 A充10 A放的条件下，900次循环后容量保持率高达90%以上，优于未使用PVP分散剂的传统磷酸铁锂电池；30 A高倍率放电容量可达到标称容量的94.6%。

The particle size analysis, rheological analysis and SEM observation were applied to study the effects of PVP dispersant content on particle size distribution and rheologic behavior of LiFePO4 slurry. 18650 Li-ion cells with LiFePO4 cathode were fabricated through formula optimization, and cycle and rate performances of the cells were evaluated and compared to the cellwithout PVP. The results show that the slurry viscosity decreases with the increase of PVP content, and the particle size of slurry declines firstly then rises. The best PVP amount is 0.4%～0.8%. The LiFePO4 cathode with 0.6%PVP was used to prepare 1.1 Ah 18650 Li-ion cells, having perfect high rate discharge and cycle performances. More than 90%of capacity retention after charging at 1.5 A and discharging at 10 A is achieved after 900 cycles for the cellwith PVP, which is superior to traditional one. The capacity retention is 94.6%even at 30 A discharge rate for the cellwith PVP.