Multi-Element Synergistic Doping Enables Cooperative Structural Stabilization of Ultra-High-Nickel Cathodes

Ultrahigh-nickel layered oxide cathodes (LiNi_xCo_yMn_1–x–yO₂, NCM, Ni ≥ 90%) are promising for high-energy-density lithium-ion batteries (LIBs) but suffer from severe structural instability. The H2–H3 phase transition induces lattice strain and cracking, while Li⁺/Ni²⁺ mixing impedes Li⁺ transport, causing rapid degradation. Herein, a ternary synergistic modification strategy based on multielement codoping is proposed, in which B³⁺, Ti⁴⁺, and Al³⁺ are simultaneously introduced into an ultrahigh-nickel NCM cathodes. B³⁺ preferentially occupies tetrahedral interstitial sites within the oxygen framework, alleviating phase-transition-induced stress accumulation, suppressing microcrack generation, and facilitating Li⁺ migration. In contrast, Ti⁴⁺ and Al³⁺ mainly reside at transition-metal sites, where they stabilize the local TM-O coordination environment and reduce Li⁺/Ni²⁺ mixing, thereby maintaining the structural integrity of the layered framework. Benefiting from these synergistic effects, the codoped cathode delivers a high initial discharge capacity of 222.72 mAh g^–1, retains 90.1% capacity after 200 cycles at 1C, and maintains 182 mAh g^–1 at 5C. This work establishes a rational and scalable design paradigm for ultrahigh-nickel NCM cathodes.