Unlocking long-term cycling of ultrahigh‑nickel NCM cathodes at high voltage by boron-induced lattice stabilization

High‑nickel LiNi_0.90Co_0.05Mn_0.05O₂ (NCM9055), endowed with exceptional energy density, has emerged as one of the core cathode candidates for lithium-ion batteries in electric vehicles, portable electronic devices, and stationary energy storage systems. However, under high charging voltage conditions, severe cationic mixing and the reduction of Ni²⁺ migration energy barriers can induce irreversible phase transformation from the layered structure to a defective rock-salt phase. This degradation pathway critically compromises the structural integrity and electrochemical reversibility of the material. In this work, B³⁺ was successfully incorporated into the lattice via solid-state sintering, forming strong BO covalent bonds with oxygen ions. These bonds raise the migration energy barrier for Ni²⁺ and anchor lattice oxygen, synergistically suppressing cation disorder and oxygen release. Additionally, the introduced boron creates a "riveting effect" within the crystal lattice, enhancing mechanical stability during electrochemical cycling. As a result, the modified material demonstrates markedly enhanced electrochemical performance when doped with boron at a molar ratio of 1% (relative to Ni + Co + Mn). At 1C with a high charging cutoff voltage of 4.5 V, it retains 77.58% of its capacity after 500 cycles, substantially outperforming the unmodified cathode (61.12%). Superior durability is also observed at the high rate of 5C over 700 cycles. This work demonstrates that boron-induced lattice stabilization constitutes a promising and mechanistically grounded strategy for developing next-generation, structurally robust, high-voltage ultra-high‑nickel cathode materials.