Developing a Double Protection Strategy for High-Performance Spinel LiNi_0.5Mn_1.5O₄ Cathodes

LiNi_0.5Mn_1.5O₄ is a promising cathode material with high-voltage and three-dimensional lithium-ion transport channels. Rapid capacity degradation due to HF corrosion has been a great challenge hindering the application of high-voltage cathode materials. Herein, a double protection strategy for high-performance LiNi_0.5Mn_1.5O₄ cathodes has been designed using Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) with both high ionic conductivity and high surface basicity as the modifier of the poly(vinylidene fluoride) (PVDF) binder and the HF scavenger. It has been demonstrated that the modified PVDF binder possesses a higher Li⁺ diffusion coefficient than incipient PVDF, resulting in better overall electrochemical properties. Meanwhile, the result of first-principles calculations revealed that the reaction between HF and LLZTO has higher chemical reactivity than that between HF and LiNi_0.5Mn_1.5O₄. The scanning electron microscopy images further confirmed that the insoluble byproducts produced by HF corrosion deposit on the surface of LLZTO particles only because of the high chemical reactivity between HF and LLZTO, while the LNMO particles are well preserved. The modified LNMO-LLZTO cathode presents better cycling stability (even at elevated temperature) and rate capability than the LNMO cathode. This work provides a novel design strategy for high-performance lithium-ion batteries.