A breathable inorganic–organic interface for fabricating a crack-free nickel-rich cathode with long-term stability

Abstract

Nickel (Ni)-rich layered oxide cathodes are essential energy materials for high-energy-density lithium-ion batteries owing to their high theoretical capacity. However, they are prone to serious structural collapse and an unstable cathode electrolyte interphase (CEI). Herein, we report a facile and novel hybrid organic–inorganic polyurea (HPU) coating to modify the surface of the LiNi_0.94Co_0.05Mn_0.01O₂ (Ni94) cathode via molecular layer deposition (MLD). Serving as a robust protective barrier, the HPU coating effectively suppresses cathode–electrolyte side reactions and promotes the formation of an ultra-thin CEI. Simultaneously, the mechanically stable and ‘breathable’ HPU coating maintains the integrity of cathode particles during charge/discharge without inducing serious cracking. Moreover, the stabilized CEI prevents further crack-induced interphase degradation and near-surface phase transformation, suppressing the variation in the chemical state and local environment of Ni. As a result, the surface-modified cathode can maintain 94.9% of its initial capacity in 200 cycles. This work highlights the importance of interphase engineering and outlines a new pathway towards forming a high-energy and stable Ni-rich layered cathode.