Ultrahigh nickel cathode with microstructural refinement and intergranular coating for high-energy Li-ion batteries

Abstract

Ultrahigh nickel oxides (Ni content > 90%) hold great promise for high-performance cathodes for the future generation of lithium-ion batteries (LIBs). However, these cathode materials cause problems such as harmful parasitic reactions at the cathode/electrolyte interface, degradation of the layered structure, and the creation of microcracks. Herein, a microstructural refinement and intergranular coating strategy is proposed to engineer ultrahigh nickel cathode LiNi_0.96Co_0.03Mn_0.01O₂ (NCM). The W-doping-induced fine-grained microstructure not only endows NCM with excellent mechanical properties but also promotes infiltration of the fluoride-containing coating along the grain boundaries inside the secondary particles, thereby forming intergranular coatings. This combined fine-grained microstructure and intergranular coating strategy reduces the formation of microcracks and suppresses the additional parasitic electrolyte reactions caused by them, thereby inhibiting the degradation of the layered phase. Consequently, the modified NCM cathode achieved exceptional electrochemical properties, especially delivering a high initial capacity of 230.8 mA h g⁻¹ (0.1 C) and a capacity retention exceeding 96% after 100 cycles at 0.5 C in half cells. After 500 cycles in full cells, the capacity retention increases by 21.2% compared with NCM. This strategy mitigates multiple degradation mechanisms in Ni-rich cathodes and provides a generalized strategy for developing advanced ultrahigh-nickel cathodes for industrial application.