Cobalt-Free LiNiO₂ with a Selenium Coating as a High-Energy Layered Cathode Material for Lithium-Ion Batteries

Considering the high cost of cobalt, cobalt-free lithium nickel oxide (LiNiO₂), which has an extremely high theoretical specific capacity, has become attractive. However, its application is hampered by continuous irreversible phase changes, unstable interfaces, and particle pulverization. Herein, an ≈35 nm-thick selenium (Se) coating is applied to modify LiNiO₂ using a combination of solid-phase mixing and low-temperature sintering. After 300 cycles, the selenium-coated LiNiO₂ (Se-LNO) cathode exhibits unusually high capacity retention of 82.09% at a charge cutoff voltage of 4.3 V. Furthermore, the coating modification improves the rate performance of the cathode materials, which exhibit considerable specific capacities of 168.7 and 149.6 mAh g^-1 at current densities of 2 and 5 C, respectively. The significantly enhanced electrochemical performance can be attributed to the ability of the Se coating to enhance the structural stability of the cathode materials by suppressing phase transitions, stabilizing the interface, enhancing the kinetic behavior of the electrode, and reducing particle pulverization. According to the findings of this study, manipulating the Se coating in cathodes may provide a viable path for lower-cost and higher-energy-density Co-free lithium-ion batteries.