碳酸丙烯酯含量对中间相炭微球负极材料电化学性能的影响

Effect of propylene carbonate content on the electrochemical performance of mesocarbon microbeads as negative electrode

碳酸丙烯酯(PC)溶剂具有极低的熔点和较高的介电常数,因此作为锂离子电池电解液溶剂,可以有效提高锂离子电池的低温性能。但由于PC易与锂离子在石墨负极表面发生共嵌入而破坏石墨结构,从而导致电池性能急剧变差。以结构稳定的中间相炭微球为负极,利用循环伏安、充放电循环测试和交流阻抗测试方法,研究了不同PC溶剂含量电解液对中间相炭微球电化学性能的影响。结果表明,中间相炭微球结构稳定,当PC含量增加到40%时仍未发生共嵌入现象。同时,随着PC含量的增加,中间相炭微球的循环性能逐步衰减。而PC含量为10%时,中间相炭微球具有最佳的循环性能,其与在不含PC溶剂的电解液中的循环性能相比,没有明显变化,循环100次后的放电比容量为207.1 m A·h/g,容量保持率为57.5%。

Propylene carbonate(PC)with many advantages over other organic carbonates such as low melting point and high dielectric constant can be applied in electrolyte as solvent to improve the low temperature performance of lithium ion batteries effectively.However,PC can easily decompose on graphite electrode surface and cointercalate into graphite electrode with lithium ions,leading to poor cycle performance.In this paper,cyclic voltammetry(CV),galvanostatic charge-discharge and electrochemical impedance spectroscopy(EIS)tests were used to systematically analyze the effects of electrolyte with different PC contents on electrochemical performance of mesocarbon microbeads(MCMB).The results showed that MCMB has stable structure and no cointercalation reaction happened in MCMB even as the content of PC was increased to 40%.Meanwhile,with the increase of PC content,the cycle performance of MCMB is decayed gradually.In particular,the discharge specific capacity of battery with 10%PC solvent is 207.1 mA·h/g after 100 cycles with a capacity retention of 57.5%,showing the best electrochemical performance,which is almost similar with that of battery without PC solvent.