An effective strategy to enhance the electrochemical performance of LiNi0.6Mn0.2Co0.2O2: Optimizing a Li diffusion pathway via magnetic alignment of single-crystal cathode material under an ordinary 0.4-T magnetic field

Abstract

A strategy to enhance the electrochemical performance of a single-crystal LiNixMnyCozO2 (NCM) electrode is proposed herein based on a preferred orientation of a Li diffusion pathway along the working direction under an ordinary 0.4-T magnetic field. Hexagonal NCM622 single crystals can be aligned along their crystallographic c-axis parallel to the applied magnetic field because the crystal has an easy magnetization axis along the c-axis. The horizontal magnetic field–oriented NCM622 cathode (HMFC) shows inhibited polarization and increased lithium-ion conductivity. The suppressed polarization promotes cyclability, increasing the specific capacity from 157.93 to 168.75 mAhg−1 after the 100th cycle at 0.5 C. Furthermore, the increased diffusion coefficient (from 3.06 × 10−10 cm2s−1 to 7.12 × 10−10 cm2s−1) causes substantial improvement in the rate performance, achieving a high specific capacity of 130.77 mAhg−1 at 10 C, while the electrode without magnetic treatment achieves a specific capacity of only 115.88 mAhg−1. Owing to such a superior electrochemical performance, the HMFC electrodes show high potential for lithium-ion batteries in the EV industry. Decreasing the magnetic field from 6 to 0.4 T for cathode alignment facilitates the applicability of the proposed strategy to production lines of battery plants using commercially available permanent magnets because a magnetic field of 0.4 T is easily achievable.