Low-valent cation substitution engineering regulates Li₂S durable electrodeposition in practical lithium-sulfur batteries

Abstract

Rational electrocatalyst design is an effective approach to accelerate Li₂S deposition kinetics and suppress polysulfide shuttling in Li-S batteries. Increasing the sulfur loading and cathode area is crucial to inspect their effectiveness in practical applications. However, concentrated polysulfide intermediates remain a great challenge to the cycling performance. Herein, to fast consume polysulfide intermediates, we provide a novel design strategy based on low-valent cation substitution to build highly active catalytic surfaces with massive active sites. As a proof of concept, a trimetallic perovskite oxide LaCu₀.₅Co₀.₅O₃₋ₓ (LCCO) electrocatalyst is constructed via low-valent Cu²⁺ substitution. This induces lattice self-adaptation and considerable oxygen vacancy, shifting the d-band center toward the Fermi level. Notably, the fast Li₂S deposition rate but slow Li₂S diffusion rate induces 3D electrodeposition of dense Li₂S nanoparticles, homogenizing the electric field for continuous Li₂S deposition. Consequently, Li-S batteries with LCCO-functionalized separator exhibit a high areal capacity of 5.92 mAh cm⁻² at a current density of 0.5 mA cm⁻² under a high sulfur loading (7.54 mg cm⁻²) and lean electrolyte (7 μL mg⁻¹). Furthermore, high-loading large-size pouch cells (64 cm²) with a capacity of 1024 mAh g⁻¹ at 10 mA show stable cycling. This study highlights the low-valent cation substitution strategy to modulate d-electrons for practical electrocatalysts in Li-S batteries.