A Li⁺ and PANI co-intercalation strategy for hydrated V₂O₅ to enhance zinc ion storage performance

Layered vanadium-based oxides are regarded as promising cathode materials for zinc-ion batteries (ZIBs) due to their open-framework crystal structure and high theoretical specific capacity. However, the sluggish Zn²⁺ diffusion and poor structural stability limit their wide application in ZIBs. Herein, a new strategy is proposed to introduce metal ions and conjugated conductive polymers into layered hydrated V₂O₅ as a cathode material for ZIBs. For demonstration, Li⁺ and polyaniline (PANI) are co-intercalated into hydrated V₂O₅ (LPVO) resulting in an enlarged spacing of 14.4 Å. A ZIB with this LPVO cathode exhibits a capacity of 377 mA h g⁻¹ at a current density of 0.1 A g⁻¹, which is higher than that of a single Li⁺ pre-intercalated hydrated V₂O₅ (LVO) or PANI pre-intercalated host (PVO). Besides, a long-term cycling stability (94% capacity retention after 800 cycles at 5 A g⁻¹) is achieved. The synergistic effect of pre-intercalated Li⁺ and PANI in LPVO originates from the weak electrostatic interactions between Zn²⁺ and the host O²⁻. Density functional theory (DFT) calculation results clearly show that LPVO possesses the lowest binding energy of 1.67 eV for Zn²⁺ insertion into the host (2.41 eV for LVO, 1.84 eV for PVO), indicating favorable reaction kinetics in LPVO, which is also confirmed by the fastest Zn²⁺ diffusion coefficient of LPVO among the three samples. The enlarged lattice space and stabilized host structure also improve the cycling performance. Our study elucidates the advantages of co-intercalated alien species in the host and provides a facile strategy to obtain high performance ZIBs.