Optimized 4-V Spinel Cathode Material with High Energy Density for Li-Ion Cells Operating at 60 °C



Spinel cathodes comprising 16-μm, AlPO4-coated Li1.09Mn1.83Al0.08O4 with a high energy density of 1.2 W h cm-3 are synthesized via a conventional solid-state reaction using MnO2 and Li2CO3 at 770 °C for 10 h and using a solution-based coating method in bulk scale (>20 kg). The cathodes are coated by aluminum phosphate at a thickness of <10 nm. The coated cathodes exhibit a first discharge capacity of 108 mA·h g-1 and a coulombic efficiency of >99.8%, and their capacity retention is 78% after 200 cycles at a 0.5C rate in a Li-ion cell under 60 °C. More importantly, a Li-ion cell containing the coated cathode does not exhibit a swelling problem after 200 cycles at 60 °C. Transmission and scanning electron microscopy suggest that the uniformly distributed AlPO4 coating and the possible formation of a solid solution phase along the surface play key roles in enhancing the electrochemical performance of the LiMn2O4 spinel at 60 °C.