Reconstruction of R 3¯ m Disordered Phase Homogenizing Li + Distribution Toward Mitigating H2‐H3 Phase Transition in LiNi 0.95 Co 0.02 Mn 0.03 O 2

ABSTRACT Electro‐chemo‐mechanical coupling failure severely deteriorates the cycling performance of LiNi 0.95 Co 0.02 Mn 0.03 O 2 (NCM95), which results from the inhomogeneous lithium‐ion distribution at high charge states, coupled with lattice mismatch in drastic phase transformation. To mitigate this challenge, in this work, an in‐situ R m‑type disordered phase was induced by interfacial lithium and oxygen vacancies, exhibiting excellent dynamic lattice matching with the underlying layered framework of NCM95. Crucially, differing from the previously reported inert NiO rock salt, the optimal disordered phase possesses redox activity and undergoes thermodynamically driven delithiation reconstruction process. The reconstructed disordered phase homogenizes the lithium‐ion distribution and mitigates deep delithiation along with drastic H2‐H3 phase transition to promote structural integrity of NCM95. Concurrently, the electrode/electrolyte interface is stabilized by lowering the nickel oxidation state and inhibiting gradual defect formation within the layered lattice. As a result of the structural stability effect, the modified NCM95 exhibits a capacity retention of 99% after 100 cycles at 50 mA g −1 , 80% after 400 cycles at 250 mA g −1 , and 83% after 900 cycles in all‐solid‐state battery system. This work clarifies the “double‐edged” nature of cation disorder and provides a structurally stable, lattice‐matched interface design scheme for ultrahigh nickel content layered cathodes.