Enhanced Electrochemical Performance and Thermal Stability of ZrO₂- and rGO–ZrO₂-Coated Li[Ni_0.8Co_0.1Mn_0.1]O₂ Cathode Material for Li-Ion Batteries

LiNi0.8Co0.1Mn0.1O2 (NCM811) has been considered as a promising cathode for Li-ion batteries (LIBs) due to its high electrochemical capacity and low cost; however, poor cycling stability is one of the main restricting factors in industrial applications of the NCM811 cathode material. Notably, the capacity fading and low structural stability of NCM811 are intensified at elevated temperatures. ZrO2- and composite rGO–ZrO2-coated NCM811 were fabricated by a facile wet chemical method and evaluated at 25 and 55 °C to overcome these impediments. The ZrO2 coating provides superior cycling and thermal stability and perfectly protects the cathode active material from deleterious side reactions, and HF attacks by suppressing the direct contact of NCM811 particles and electrolytes. Despite these advantages, the discharge capacity of the ZrO2-coated cathode material (166.3, 187.7 mAh g–1) is slightly lower than that of the pristine cathode (171.7, 193.0 mAh g–1) due to the insulative nature of ZrO2 NPs, after one cycle at ambient and elevated temperatures. The first cycle discharge capacity increased to 185.9 and 206.7 mAh g–1 at 25 and 55 °C, respectively, with the rGO–ZrO2-coated cathode material. The capacity retention reached 92.4 and 83.3%, showing high capacities of 171.8 and 172.3 mAh g–1 at 1C after 100 cycles at 25 and 55 °C, whereas the pristine cathode material exhibited low retention values of 72.4 and 54.5% with discharge capacities of 124.3 and 105.2 mAh g–1 under the same conditions, respectively. The incorporation of rGO into the coating can make up for the ZrO2 coating imperfection and, at the same time, can enhance the ion/electron conductivity of the electrode by providing a conductive network on the surface of the cathode material. In light of the fact that ZrO2- and composite rGO–ZrO2-coated NCM811 cathode materials exhibit superior performance; they can pave the way for industrial applications of high-energy-density lithium-ion batteries.