线面碳包覆的LiMn_(0.6)Fe_(0.4)PO_(4)复配低钴NCM的电化学性能研究

Study on Electro-Chemical Properties of LiMn_(0.6)Fe_(0.4)PO_(4)Coated by Linear-Surface Dimension Carbon Mixed with Low-Cobalt NCM

锂离子电池LiFePO_(4)的能量密度改进已迅速接近极限,为了提高能量密度,降低瓦时成本,满足消费者续航需求,需要开发一种低成本,高能量密度的材料,LiMnPO_(4)既具有LiFePO_(4)的长循环能力,又具有LiMnPO_(4)的高电压平台特点,可以很好地结合LiMnPO_(4)和LiFePO_(4)的优点。磷酸锰铁锂理论容量与磷酸铁锂相同,为172mAh/g,但是它相对于Li+/Li的电极电势为4.1V,远高于磷酸铁锂的3.2V,其能量密度将比磷酸铁锂提高15%。但是LiMn_(0.6)Fe_(0.4)PO_(4)因为Mn溶出导致循环性能恶化,以及导电性差,低温性能恶化严重,为了改善循环以及低温性能需要对LiMn_(0.6)Fe_(0.4)PO_(4)进行改性。通过线状CNT混面状石墨烯包覆磷酸锰铁锂,并且将其与NCM低钴三元材料复配达到长循环,低温容量保留率高,无双电压平台的优异的电化学性能。

The lithium-ion battery LiFePO_(4) has approached the limit energy-density.To increase the energy density,reduce the cost of battery and meet the needs of consumers,a low-cost,high-energy-density material needs to be developed.LiMn_(0.6)Fe_(0.4)PO_(4)has both the long-cycle capability of LiFePO_(4) and the high-voltage platform characteristics of LiMnPO_(4),which can well combine the advantages of LiMnPO_(4) and LiFePO_(4).The theoretical capacity of lithium both are 172 mAh/g,but the electrode potential of LiMnPO_(4) relative to Li+/Li is 4.1 V,which is much higher than 3.2V of LiFePO_(4),and its energy density is 15%higher than that of LiFePO_(4).However,LiMn_(0.6)Fe_(0.4)PO_(4)has poor cycling performance because of Mn Dissolution,and its conductivity is low,and the low-temperature performance is deteriorated seriously.In order to improve the cycling and low-temperature performance,it is necessary to modify LiMn_(0.6)Fe_(0.4)PO_(4).In this paper,LiMn_(0.6)Fe_(0.4)PO_(4)is coated by linear-surface dimension carbon,and mixed with NCM of low-cobalt to achieve long cycle,high low-temperature capacity retention,without double-voltage platform of excellent electro-chemical performance.