高电压钴酸锂的氧化锌低温包覆改性研究

Study on Low Temperature ZnO Coating of High Voltage LiCoO_(2) Cathode

制备高电压钴酸锂是目前锂离子电池正极材料的研究热点之一,但随着充电截止电压的升高,会加剧电极表面副反应的发生及钴酸锂结构的衰退,从而降低其电化学性能。表面包覆是改善上述问题的有效有段,本文采用湿化学法对钴酸锂材料进行了氧化锌包覆,研究了煅烧温度对包覆层特性及钴酸锂电化学性能的影响。结果表明,在煅烧温度达到450℃时包覆前驱体乙酸锌完全分解为氧化锌包覆层,且对钴酸锂本身晶体结构没有产生明显影响,随着煅烧温度的升高,包覆层结晶颗粒变大。氧化锌包覆后钴酸锂循环性能明显改善,LCO-Z450样品在3~4.5V电压区间充放电循环40周后容量保持率达89.8%,而相同条件下未包覆的钴酸锂样品只有72.1%。

The preparation of high-voltage LiCoO_(2) is one of the research hotspots of cathode materials for lithium-ion batteries at present.However,with the increase of charging cut-off voltage,the occurrence of side reactions on the electrode surface and the decline of the structure of LiCoO_(2) will be aggravated,which will reduce its electrochemical performance.Surface coating is an effective way to improve the above problems.In this paper,ZnO coating of LiCoO_(2) was carried out by wet chemical method,and the influence of calcination temperature on the characteristics of the coating and the electrochemical properties of LiCoO_(2) was studied.The results show that when the calcination temperature reaches 450 ℃,the coated precursor zinc acetate is completely decomposed into zinc oxide,and has no obvious effect on the crystal structure of LiCoO_(2).With the increase of calcination temperature,the crystalline particles of the coating become larger.The cycle performance of LiCoO_(2) coated with ZnO was significantly improved.The capacity retention rate of LCO-Z450 samples after 40 cycles in the voltage range of 3~4.5 V was 89.8 %,while that of uncoated LiCoO_(2) samples under the same conditions was only 72.1 %.