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

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.