Synergistic Anionic Vacancy and Heteroatom Doping in High-Entropy MXenes for Efficient Polysulfide Electrocatalysis in Lean-Electrolyte Lithium−Sulfur Batteries

Lithium−sulfur batteries (LSBs) hold great promise for next-generation energy storage, yet their practical application is hindered by the polysulfide shuttle effect and sluggish redox kinetics, especially under lean-electrolyte conditions. While high-entropy MXenes (HE-MX) exhibit promising electrocatalytic potential for addressing these issues, their performance is compromised by nanosheet restacking and an unfavorable electronic structure. Herein, we propose a synergistic dual-defect engineering strategy to address these limitations. A three-dimensional (3D) network consisting of P-doped, anion-vacancy-rich TiVCrMoC 3 T x HE-MX integrated with carbon nanotubes (P-HE-MX@C) is constructed as a multifunctional separator coating for LSBs. Comprehensive experimental analyses and density functional theory calculations reveal that the co-introduction of P-dopants and anionic vacancies upshifts the d -band center of HE-MX, optimizing polysulfide adsorption, substantially reducing the energy barriers for Li 2 S nucleation/decomposition, and accelerating Li + diffusion. This multifunctional electrocatalytic enhancement markedly expedites overall sulfur redox kinetics. Consequently, the cell employing the P-HE-MX@C modified separator achieves a low-capacity decay rate of 0.048% per cycle over 900 cycles at 1.0 C. Even under a high sulfur loading (5.69 mg cm −2 ) and a lean electrolyte (4.53 μL mg −1 ), the cell still delivers a high areal capacity of 5.67 mAh cm −2 at 0.1 C after 100 cycles. Additionally, the pouch cell with high sulfur loading maintains an ultrahigh capacity of 1.92 Ah over 20 cycles. This work establishes a fundamental design principle for the synergistic electronic engineering of high-entropy electrocatalysts, facilitating the development of high-energy, long-lifespan energy storage systems.