Superior Cycling Stability in Zinc-Ion Batteries with Ca2+-Induced Cathode-Electrolyte Interface and Phytic Acid: Experimental Validation of Theoretical Predictions

Abstract

This study investigates the impact of Ca²⁺ and phytic acid (PA) pre-insertion on the performance of vanadium oxide (V₆O₁₃) as a cathode material for aqueous zinc-ion batteries. Ab initio molecular dynamics (AIMD) simulations reveal that the diffusion coefficient of Ca²⁺ is higher than that of Zn²⁺, leading to the preferential extraction of Ca²⁺. The extracted Ca²⁺ readily forms a dense cathode-electrolyte interphase (CEI) with SO₄²⁻ on the electrode surface, effectively mitigating electrode dissolution. Furthermore, density functional theory (DFT) calculations indicate that the incorporation of Ca²⁺ lowers the diffusion energy barrier for Zn²⁺, facilitating its diffusion. Additionally, PA insertion stabilizes the interlayer spacing of V₆O₁₃, and its strong chelating ability stabilizes the structure by preventing collapse during cycling. Experimental validation through a one-step solvothermal method confirms these theoretical predictions. The CaVO-PA composite exhibits excellent cycling stability, with a capacity retention rate increasing from 60% to 102% after 3000 cycles at 10 A g⁻¹. Even at 20 A g⁻¹, it delivers a specific capacity of 170.2 mAh g⁻¹ with stable Coulombic efficiency. After 10 000 cycles, the capacity shows no significant degradation, demonstrating superior cycling stability and high current tolerance, thereby confirming the effectiveness of the CEI and PA in enhancing electrochemical performance.