LiNi0.8Co0.15Al0.05O2 cathodes exhibiting improved capacity retention and thermal stability due to a lithium iron phosphate coating

Nickel-rich layered cathode materials for lithium ion batteries, e.g., LiNi0.8Co0.15Al0.05O2, have garnered considerable academic and industrial research interests, due to their higher specific energy and lower cost than the widely commercialized LiCoO2. To be more widely deployed in electric vehicles, Ni-rich cathodes with further improved thermal stability and energy densities need to be developed. Herein, we use an industrially viable fusion mixing method to apply LiFePO4 nanoparticles as a coating on LiNi0.8Co0.15Al0.05O2. The LiFePO4 coating helps to reduce the formation of cathode-electrolyte interface layer and the extent of cation mixing in LiNi0.8Co0.15Al0.05O2, which lowers electrochemical polarizations and charge transfer impedance. Compared to pristine LiNi0.8Co0.15Al0.05O2, the LiNi0.8Co0.15Al0.05O2-LiFePO4 composite in a full pouch cell exhibits a higher reversible capacity of 210 mAh.g(-1) and capacity retention (>95% after 100 cycles) when it is charged up to 4.5 V. In situ calorimetric measurements show that the temperature rise in LiNi0.8Co0.15Al0.05O2- LiFePO4 pouch cells at higher rates (>C/2) is lower than in pristine LiNi0.8Co0.15Al0.05O2, by 10 degrees C. The coating strategy in this work can be applied to other nickel-rich and Li-rich cathodes. (C) 2019 Elsevier Ltd. All rights reserved.