Ultra‐Fine Nano‐Mg(OH)₂ Electrodeposited in Flexible Confined Space and its Enhancement of the Performance of LiFePO₄ Lithium‐Ion Batteries

Abstract

To improve the Li‐ion diffusion and extreme‐environment performance of LiFePO4 (LFP) lithium‐ion batteries, a composite cathode material is fabricated using ultra‐fine nano‐Mg(OH)2 (MH). First, a flexible confined space is designed in the local area of the cathode surface, through the transition of charged xanthan gum polymer molecules under electric field force and the self‐assembly of the xanthan gum network. Then, the 20 nm nano‐Mg(OH)2 is prepared through cathodic electrodeposition within the local flexible confined space, and subsequent in situ surface modification as it traverses the xanthan gum network under gravity. LFP‐MH significantly changes the density and homogeneity of the cathode electrolyte interphase film and improves the electrolyte affinity. The Li||LFP‐MH half‐cell demonstrates excellent rate capability (110 mAh g−1 at 5 C) and long‐term cycle performance (116.6 mAh g−1 at 1 C after 1000 cycles), and maintains over 100 mAh g−1 after 150 cycles at 60 °C, as well as no structural collapse of the cathode material after 400 cycles at 5 V high cut‐off voltage. The cell also shows an obvious decrease in inner resistance after 100 cycles (99.53/133.12 Ω). This work provides a significant advancement toward LiFePO4 lithium‐ion batteries with excellent electrochemical performance and tolerance to extreme‐environment.