Polydopamine-induced nano-coating layer for high stability of nickel-rich cathode in secondary batteries

High-Ni layered-oxide cathodes are the most prospective cathode materials for next-generation Li-ion batteries (LIBs) in electric vehicles (EVs) owing to their high specific capacity. However, High-Ni layered-oxide cathode materials exhibit inferior cyclability and low thermal stability owing to the side reaction between Ni⁴⁺ and the electrolytes. To solve these surface-related problems, we proposed a strategy for forming LiNbO₃ (LNO)—with outstanding thermal stability and ionic conductivity—on a Ni-rich layered-oxide surface using polydopamine (PDA). The PDA formed on the transition metal hydroxide surface has copious catechol OH groups, which attract the Nb ions in the solution to form a LNO coating layer during the calcination process. The LiNi_0.8Co_0.1Mn_0.1O₂ (pristine LNCM) electrode experiences enormous degradation when cycled after being subjected to severe conditions—such as a full charge and a 60°C storage test—but the LiNbO₃-coated LNCM (LNO-LNCM) electrode exhibits particularly stable cycling performance. Furthermore, differential scanning calorimetry (DSC) results exhibited that the LNO coating notably ameliorated the thermal stability of the cathode material. As a result, our experimental results suggest that the development of cathode materials that can withstand greatly oxidized states and high-temperature environments is achievable.