葡萄糖作碳源时碳包覆量对LiFePO_(4)及其锂电池性能的影响

Effect of carbon-coated amount on performances of FePO_(4)and its lithium battery under glucose as carbon source

首先,以Li_(2)CO_(3),NH_(4)H_(2)PO_(4),Fe(NO_(3))_(3)·9H_(2)O,葡萄糖、无水乙醇为原料,采用溶胶凝胶法合成FePO_(4)前驱体,再采用碳热还原法制备了碳包覆的LiFePO_(4)(简称为LFP/C);然后,考察了葡萄糖作为碳源时碳包覆量对LFP/C相纯度、粒径、形貌等的影响,并评价了LFP/C作为正极的锂离子电池的电化学性能。结果表明:当碳包覆量过少或过多时,均不利于LFP/C的高温成型过程,在Fe∶Li∶C(摩尔比)为1.00∶1.02∶0.15时,制得的LFP/C-2纯度更高、分散性更好、颗粒更均匀;以LFP/C-2作为正极制作的锂离子电池,在0.2 C充放电倍率下的初始充放电比容量分别为152.20,132.73 m Ah/g,首次充放电效率达91.20%,并且在10.0 C充放电倍率下的充放电比容量能保持在94.70 m Ah/g。

Firstly,FePO_(4)precursor was synthesized by sol-gel method with Li_(2)CO_(3),NH_(4)H_(2)PO_(4),Fe(NO_(3))_(3)·9 H_(2)O,glucose and anhydrous ethanol as raw materials,and then carbon-coated lithium iron phosphate(hereinafter referred to as LFP/C)was prepared by carbothermal reduction method.Then the effects of the amount of glucose as a carbon source on the phase purity and particle size and morphology of LFP/C were investigated.The electrochemical performance of lithium-ion batteries with LFP/C as positive electrode was evaluated.The results showed that when the carbon-coated amount was too little or too much,it was not favorable for the high-temperature forming process on LFP/C.When the molar ratio of Fe∶Li∶C at 1.00∶1.02∶0.15,the LFP/C-2 obtained had higher purity,better dispersibility,and more uniform particles.The lithium-ion battery,which made from LFP/C-2 as the positive electrode,had the initial specific capacity of charge-discharge at 152.20,132.73 mAh/g on the premise of 0.2 C-rate(referred to the ratio of current to nominal capacitance of a battery when it was charged and discharged.),respectively,and the initial charge-discharge efficiency was up to 91.20%.Meanwhile,the specific capacity of charge-discharge could be maintained at 94.70 mAh/g at 10.0 C-rate.