High-Energy-Density Cathode Material Achieved by Upgrading Low-Voltage Li₃V₂O₅ via Ni Doping

High-energy-density lithium-ion batteries have great need for cathode materials with exceptional specific discharge capacity. Li₃V₂O₅ shows great potential because of its high capacity (e.g., 266 mA h g^-1 at 0.1 A g^-1). However, its low-lying voltage plateau (∼0.6 V vs Li⁺/Li) restricts its use exclusively to anode applications. This work presents for the first time the development of Li₃V₂O₅ as a high-energy-density cathode material through Ni doping. Structural analysis reveals that Ni-doped Li₃V₂O₅ forms a cation-disordered rock-salt phase with a uniform distribution of Ni. Introducing 1 mol % Ni (denoted as LVON2) prolongs the V-based plateau (∼2.5 V) and results in an additional discharge capacity of 35 mA h g^-1. In particular, a plateau ascribed to Ni²⁺/Ni³⁺ redox reaction emerges at ∼3.5 V, contributing an extra discharge capacity of 42 mA h g^-1. Consequently, LVON2 achieves high specific discharge capacities of 270.8 mA h g^-1 at 50 mA g^-1 and 339.4 mA h g^-1 at 20 mA g^-1 (corresponding to an energy density of 837 W h kg^-1), surpassing the pristine Li₃V₂O₅ and many latest cathode materials. Density functional theory calculation shows that Ni preferentially occupies the empty tetragonal sites in Li₃V₂O₅, leading to a larger off-center displacement of the neighboring LiO₆ octahedra and the expansion of unit cell volume. This structural manipulation improves the electrochemical dynamics of Li₃V₂O₅ with a better rate capability (143.3 mA h g^-1 for LVON2 vs 94.1 mA h g^-1 for the pristine sample at 1000 mA g^-1) and a decreased charge-transfer resistance (159.2 Ω for LVON2 vs 278.6 Ω for the pristine sample). Differential scanning calorimetry and finite element analysis also reveal the enhanced thermal stability of Ni-doped Li₃V₂O₅ at both material and full battery levels. This advancement lays a solid foundation for the development of Li₃V₂O₅-based cathode materials for high-energy-density lithium-ion batteries.