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

Spinel cathodes comprising 16‐μm, AlPO 4 ‐coated Li 1.09 Mn 1.83 Al 0.08 O 4 with a high energy density of 1.2 W h cm ‐3 are synthesized via a conventional solid‐state reaction using MnO 2 and Li 2 CO 3 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 0.5 C 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 AlPO 4 coating and the possible formation of a solid solution phase along the surface play key roles in enhancing the electrochemical performance of the LiMn 2 O 4 spinel at 60 °C.