Interfacial potential regulation by spinel heterostructure to mitigate oxygen evolution in Lithium-Rich materials

Abstract

Lithium-rich Layered Oxides (LLO), characterized by their high theoretical capacity, have been identified as a key contender in the realm of lithium-ion batteries. Nevertheless, the structural degradation and voltage decay issues have impeded the commercialization of this material. In this study, a urea phosphate pyrolysis-induced modification combined with multiple synergistic modifications has been introduced for lithium-rich materials, achieving high electrochemical activity retention. During the thermal decomposition of urea phosphate, PO₄^3-, NH₃ and CO₂ are released, which can induce Li/O vacancies in lithium-rich materials and the transformation of the surface layered structure to spinel structure. Various in-situ tests demonstrate that the electrical conductivity and structural stability of the material have been improved. After 500 cycles at 1C, the capacity retention rate reached 82.9 %, with a voltage attenuation of only 0.91 mV/cycle. Theoretical calculations indicate a diminished overlap between the TM 3d and O 2p orbitals within the heterostructure, as well as an elevated oxygen vacancy formation energy. The inhibition of oxygen evolution from the LLO material by Li₄Mn₅O₁₂ is elucidated from the perspective of the reverse electric field generated by the potential difference at the interface. This study proposes a rational design strategy that advances the mechanistic understanding of LLO material modification.