固体电解质包覆LiMn_2O_4正极材料的合成及表征

Synthesis and Characterization of Li_(1.3)Al_(0.3)Ti_(1.7)(PO_4)_3-coated LiMn_2O_4

采用湿化学法制备Li1.3Al0.3Ti1.7(PO4)3包覆LiMn2O4。采用X射线衍射、扫描电镜、恒电流充放电等技术对合成产物进行物相、形貌和电化学分析。结果表明:Li1.3Al0.3Ti1.7(PO4)3包覆LiMn2O4与LiMn2O4有相似的X射线衍射结果,且包覆后的LiMn2O4循环伏安峰电流和电荷转移阻抗变化不大。室温及55℃,以0.2 C充放电倍率循环40次时,Li1.3Al0.3Ti1.7(PO4)3包覆LiMn2O4的容量保持率分别为98.2%和93.7%,未包覆的LiMn2O4的容量保持率分别为85.4%和79.1%。当以2 C倍率室温充放电循环时,Li1.3Al0.3Ti1.7(PO4)3包覆LiMn2O4的容量保持率比未包覆的LiMn2O4高8%;55℃充放电循环时,Li1.3Al0.3Ti1.7(PO4)3包覆LiMn2O4的容量保持率比未包覆的LiMn2O4高11.1%。

Li1.3Al0.3Ti1.7（PO4）3-coated LiMn2O4 was prepared by the wet chemical route.The phase,surface morphology,and the electrochemical properties of the prepared powders were characterized by X-ray diffraction,scanning electron micrograph,and galvanostatic charge-discharge experiments.Li1.3Al0.3Ti1.7（PO4）3-coated LiMn2O4 has the similar X-ray diffraction patterns,cyclic voltammograms,and charge-transfer resistance as LiMn2O4.The two powders show the similar values of lithium-ion diffusion coefficient.When cycled at room temperature and 55 ℃ for 40 times at the charge-discharge rate of 0.2 C,Li1.3Al0.3Ti1.7（PO4）3-coated LiMn2O4 shows the capacity retention of 98.2% and 93.7%,respectively,which are considerably higher than the values of 85.4% and 79.1% for the uncoated one.Both the capacity retention differences between LATP-coated LiMn2O4 and LiMn2O4 cycling at room temperature and 55 ℃ become larger with the increase of the charge-discharge rate.When the charge-discharge reaches 2 C,the capacity retention of LATP-coated LiMn2O4 becomes 8% higher than the uncoated LiMn2O4 for the room temperature cycling,and it becomes 11.1% higher than the latter when cycled at 55 ℃.