Ultrafast Knock-Off Li⁺ Diffusion and Subtle Structural Evolution of Li₅V₃O₈ Anode in Lithium-Ion Batteries

Li₅V₃O₈, a lithiation product derived from the LiV₃O₈ cathode, has emerged as a promising intercalation-type anode material, boasting a theoretical capacity of 256 mA h g^-1. Through a comprehensive combination of experimental and theoretical approaches, we demonstrate its capability to intercalate a substantial amount of Li⁺ at extremely high rates. Experimental findings reveal that Li₅V₃O₈ exhibits outstanding high-rate capability (with a specific capacity of 152 mA h g^-1, 60% of the theoretical capacity at 40 C) and exceptional cyclability (with a capacity retention of 80% after 11,000 cycles at 20 C). The structural changes in Li₅V₃O₈ during the lithiation/delithiation cycles are subtle and reversible. First-principles calculations highlight a knock-off mechanism in Li⁺ diffusion within Li₅V₃O₈, with an estimated energy barrier ranging from 0.16 to 0.38 eV, considerably lower than that of a direct hopping mechanism (0.62-1.44 eV). These ultrafast ion diffusion properties are attributed to interlock interactions among interstitial tetrahedral Li⁺ and neighboring octahedral lattice Li⁺, facilitating long-distance and chain-like Li⁺ diffusion. This study not only introduces an influential vanadium-based anode material with practical implications for fast-charging lithium-ion batteries but also provides fundamental insights into solid state Li⁺ diffusion kinetics.