Achieving directional zinc ion transport in a belt-like orderly arranged vanadium dioxide cathode material

Abstract

Developing stable, high-capacity cathodes for zinc-ion batteries represents a key step toward accelerating their commercialization. However, the considerably enlarged ion radius of hydrated Zn²⁺ induces sluggish reaction kinetics and poor structural durability of the cathode materials. Herein, we propose to achieve directional Zn²⁺ transport and shorten Zn²⁺ diffusion pathways by fabricating belt-like orderly arranged VO₂ (B-VO₂). Relative to conventional VO₂ (C-VO₂) with inherently sluggish ion transport dynamics, the prepared B-VO₂ exhibits favorable rapid Zn²⁺ diffusion along the c-axis within the (110) crystallographic plane, with its diffusion coefficient ranging from 10⁻⁸ to 10⁻¹⁰ cm² s⁻¹, which is 2 orders of magnitude higher than that of C-VO₂ (10⁻¹⁰ to 10⁻¹² cm² s⁻¹). The assembled aqueous zinc-ion batteries deliver an impressive initial specific capacity (357.6 mAh g⁻¹ at 0.2 A g⁻¹), with 86.1% capacity retention after 4000 cycles at 5 A g⁻¹, which is significantly superior to the cycling performance of C-VO₂ (52.6% capacity retention after 1500 cycles at 5 A g⁻¹). The pouch cell delivers a high initial discharge capacity of 193.8 mAh g⁻¹ at 1 A g⁻¹ and retains 90.1% of its initial capacity after 100 stable cycles. The results demonstrate that regulating the structural arrangement of vanadium-based cathode materials is an effective strategy to boost ion transport kinetics for high-performance aqueous zinc-ion batteries.