Magnetic Field‐induced Disordered Phase of Spinel Oxides for High Battery Performance
Shuwei Sun, Xiaoning Li, Chu Zhang, Xuefeng Wang, Jianli Wang, Chin‐Wei Wang, Zhichuan J. Xu, Zhenxiang Cheng, Ying Bai
Abstract
Abstract The disordered phase of spinel LiMn 1.5 Ni 0.5 O 4 (LNMO) is more appealing as high‐voltage cathode due to its superior electrochemical performance compared to its ordered counterpart. Various methods are developed to induce a phase transition. However, the resulting materials often suffer from capacity degradation due to the adverse influence of accompanying Mn 3+ ions. This study presents the utilization of local magnetic fields generated by a magnetic Fe 3 O 4 shell to induce a disordered phase transition in LNMO at lower temperature, transitioning it from an order state without significantly increasing the Mn 3+ content. The pivotal role played by the local magnetic fields is evidenced through comparisons with samples with nonmagnetic Al 2 O 3 shell, samples subjected to sole heat treatment, and samples heat‐treated within magnetic fields. The key finding is that magnetic fields can initiate a radical pair mechanism, enabling the induction of order‐disorder phase transition even at lower temperatures. The disordered spinal LNMO with a magnetic Fe 3 O 4 shell exhibits excellent cycling stability and kinetic properties in electrochemical characterization as a result. This innovation not only unravels the intricate interplay between the disordered phase and Mn 3+ content in the cathode spinel but also pioneers the use of magnetic field effects for manipulating material phases.