Adaptively-generated multivalent active sites suppress destructive phase transition in high-nickel layered oxide cathodes

Abstract

Phase stability of high-nickel layered materials is crucial for enhancing the cyclic performance of lithium-ion batteries. The successive phase transition, accompanied by lattice contraction and stretching in high-nickel cathodes, results in continuous accumulation of lattice strain and structural destruction. Here, we propose a novel approach of adaptively-generated multivalent transition metal disordering to inhibit the destructive phase transitions in layered materials. To demonstrate feasibility, we design a binary high-nickel cathode material, LiNi_0.85Fe_0.15O₂(LNF8515), which utilizes the variable valence of Fe to prevent the successive phase transition through charge delocalization. Effective regulation of the redox mechanism of transition metals through potentiostatic control is essential to mitigate significant continuous phase changes resulting from polarization. In LNF8515, the absence of Li⁺/Ni²⁺ anti-site defects enables the material to achieve an initial capacity of 217.8 mAh g⁻¹. LNF8515 does not undergo continuous phase transition, resulting in improved cycling stability and reduced strain. In-situ XRD, grazing incident wide angle X-ray scattering and first-principles studies indicate that adaptively-generated multivalence of Fe²⁺, Fe³⁺, and Fe⁴⁺ prevent charge localization, suppressing the continuum phase transition. This study paves a new avenue to improve the cyclic stability of high-nickel oxide cathodes.