Lithium-reinforced polyoxometalate as effective catalytic interlayer for high-sulfur-loading and long-life lithium-sulfur batteries

Abstract

Lithium-sulfur (Li-S) batteries have garnered significant attention as the promising next-generation energy storage devices due to the ultrahigh theoretical energy density. However, the inherent problems including shuttle effect and sluggish kinetics obstruct their practical application. Herein, lithiation polyoxometalates material Li₃PW₁₂O₄₀ (LPW) is proposed with not only the electron activity of H₃PW₁₂O₄₀ (HPW), but also the promoted lithium ion (Li⁺) conductivity and polysulfide reactions catalysis. The theoretical calculations and experimental validation demonstrate that the replacement of H⁺ with Li⁺ in HPW has resulted in unique structural characteristics concerning suitable adsorption and catalytic configurations, and high lithium transference number (t_Li+ = 0.84). Therefore, LPW as a separator functional coating effectively suppresses the shuttle effect in Li-S batteries and enhances overall Li⁺ conduction reaction kinetics. The Li-S battery with the LPW-based modified separator achieves an initial discharge capacity of 1510.2 mAh g⁻¹ and maintaining a reversible capacity of 710.9 mAh g⁻¹ after 400 cycles at 0.5 C. Remarkably, even with a low E/S ratio of 3.0 g_electrolyte g_sulfur⁻¹ and a high sulfur loading of 8.0 mg cm⁻², the batteries deliver a high energy density of 379 Wh kg⁻¹ in a 2.4 Ah pouch cell. This study underscores a novel approach for the design of polyoxometalate-based composite materials, thereby broadening their potential applications.