Operando Building of a Superior Interface Hybrid Film Enables Chemomechanically Durable Co-Free Ni-Rich Cathodes

The Co-free Ni-rich layered cathodes become pivotal to reduce cost and increase benefit toward next-generation Li-ion batteries yet raise a major challenge for their extremely fragile cathode-electrolyte interface (CEI) film. Herein, we report the in situ construction of the Si/B-enriched organic-inorganic hybrid CEI films on LiNi_0.9Mn_0.1O₂ (NM91) with the assistance of tris(trimethylsilyl) borate (TMSB) additive. The hybrid film exhibits superior Young's modulus, mechanical strength, and ductility, which greatly dissipate the microstrain of Co-free Ni-rich cathodes under various states of charge with high structural integrity. Furthermore, the surface oxygen anions have been significantly stabilized by bonding with the Si and B ions of TMSB with high safety. These merits enable a durable Co-free Ni-rich layered cathode with 96.9% and 87.7% capacity retentions (versus 72.7% and 70.2% of NM91) at a high rate of 5C and a high-temperature of 55 °C after 100 cycles. In a pouch-type full cell, 88.8% of initial capacity is still maintained after cycling at 1C for 500 times, greatly expediting the development and application of Co-free Ni-rich layered cathodes.