In this paper, to improve the elevated temperature performance of spinel LiMn2O4 as cathode materials, the cation/anion co-doping and surface modification together were adopted. The SiO2 coated Li1.02Co0.1Mn1.9O4−xSx spinels were synthesized by the solid-state reaction method and Sol-gel coating process. The samples are characterized by XRD, SEM, galvanostatic charge-discharge. The results show that the Li1.02Co0.1Mn1.9O3.98S0.02 exhibits the best initial discharge capacity of 122mAh/g, and capacity retention rate gets to 92% after 100 cycles at room temperature (25 °C). The substitution of Co and S for Mn and O in LiMn2O4 can enhance the crystal structure stability and overcomes the Jahn-Teller distortion, but cannot resolve the elevated temperature cycling issue of the spinel cathode materials. The capacity loss of Li1.02Co0.1Mn1.9O3.98S0.02 without SiO2 coating gets to 38% after 50 cycles, whereas the 2.0wt.% SiO2-coated Li1.02Co0.1Mn1.9O3.98S0.02 cathode material has only 5.0% capacity loss after 50 cycles at elevated temperature (55°C). It indicates that nano SiO2 coating could suppress Mn dissolution in the electrolyte during cycles. So combining cation/anion co-doping and surface modification is best way to improve the elevated temperature cycling performance of spinel LiMn2O4 as cathode materials.
Performance of Manganese and Antimony co-doping Tin Dioxide Anodes Prepared at Different Temperatures