异丙醇协助Al_2O_3包覆LiMn_2O_4合成及高温电化学性能研究

Synthesis and Electrochemical Performance of Isopropyl Alchol( IPA) Assisted Al_2O_3 Coated LiMn_2O_4 at Elevated Temperature

采用溶胶凝胶法,以硫酸铝、异丙醇（IPA）为原料对Li Mn2O4进行包覆。合成了含2%（质量分数）Al2O3表面包覆的Li Mn2O4电极材料。利用场发射扫描电镜（FESEM）对制备材料的形貌进行表征。结果显示,异丙醇协助包覆后材料表面呈现均匀分布的Al2O3颗粒。在55℃,3.0－4.5 V,1C充放电测试表明,IPA协助包覆可以显著提高Li Mn2O4正极材料高温下的循环稳定性。以异丙醇协助的Al2O3包覆Li Mn2O4材料作为正极,100次循环容量保持率为87.3%,而未加异丙醇包覆后的Li Mn2O4材料100次循环容量保持率为82.2%,未经过包覆的材料只有74.1%。不同倍率恒流充放电测试结果表明,异丙醇协助包覆能够改善Li Mn2O4的倍率性能,在5C和10C的放电倍率下的放电比容量分别达到了102.1和91.0 m Ah·g^-1。通过电感耦合等离子体质谱仪（ICP）测试样品在电解液中Mn的溶解浓度。结果显示,高温（55℃）储存20 d后,异丙醇协助包覆的Li Mn2O4材料中Mn在电解液中的浓度仅为58.7×10^-6,远远低于未加异丙醇包覆的和未经过包覆的。

A series of spinel Li Mn2O4 coated with 2% Al2O3 were synthesized by Al2（ SO4）3and isopropyl alcohol（ IPA） assisted sol-gel process. The morphologies of the as-prepared materials were characterized by field emission scanning electron microscopy（ FESEM）. The results showed that Al2O3 particles uniformly distributed on the surface of the spinel Li Mn2O4 prepared by IPA assisted process. Galvanostatic charge-discharge test indicated that the IPA-assisted coating could significantly improve the cycle stability of spinel Li Mn2O4 at elevated temperature. The capacity retention of the Al2O3-IPA-coated Li Mn2O4 as cathode material was 87. 3% after100 cycles（ condition： 3. 0 － 4. 5 V,1C,55 ℃）,Which was considerably higher than the value of 82. 2% for the coated Li Mn2O4 prepared without IPA assisted process and 74. 1% for the uncoated one. Tests with different discharge rates showed that the Al2O3-IPA-coated Li Mn2O4 produced excellent rate capability： 102. 1 m Ah·g- 1at 5C and 91. 0 m Ah·g^- 1at 10 C. After the storage at 55 ℃for 20 d,the Mn dissolution from the spinel samples was tested by inductive coupled plasma emission spectrometer（ ICP）. The solubility of Mn for Al2O3-IPA-coated Li Mn2O4 was only 58. 71 × 10^- 6,which was much lower than that for the ones without IPA assisted process and uncoated.