Tuning Li nucleation and growth via oxygen vacancy-enriched 3D flexible self-supporting protection layer of P-Mn3O4−x for advanced lithium-sulfur batteries

Abstract

Lithium sulfur batteries have attracted much attention due to their high theoretical specific energy and environmental friendliness. However, the practical application is severely plagued by the cycling life issues resulting from the uncontrollable generation and growth of Li dendrites. Herein, an innovative 3D flexible self-supporting Li anode protection layer of P-Mn3O4−x is constructed via a facile solvothermal method followed by an annealing process. Benefiting from the rich oxygen vacancies coupled with the 3D flexible self-supporting skeleton, abundant lithiophilic sites and high ionic conductivity are obtained, which succeed in guiding Li+ homogeneous adsorption and redistribution, accelerating Li+ diffusion rate, inducing Li+ uniform deposition and nucleation. DFT calculations and experimental results conclusively demonstrate such a protection mechanism. Meanwhile, the effective anchoring and catalytic nature of polar P-Mn3O4−x can also be applied as an immobilization-diffusion-conversion host to improve polysulfides redox. Taking advantage of these merits, super-stable functions for Li symmetric cell matched with P-Mn3O4−x layer are achieved, which exhibits an ultralong lifespan of >5000 h with an ultralow overpotential of 20 mV, far lower than that of bare Li symmetric cell (overpotential of 800 mV only after 250 h) at high current densities of 5 mA cm−2 and high plating/stripping capacity of 10 mA h cm−2. Even in Li|P-Mn3O4−x||S full cell at 1 C, a high initial discharge specific capacity of 843.1 mA h g−1 is still delivered with ultralow capacity fading rate of 0.07% per cycle after 250 cycles, further confirming the synergistic regulation of P-Mn3O4−x for Li nucleation behavior. This work illustrates a sufficient guarantee of 3D protection layer coupled with oxygen vacancies in guiding Li diffusion and nucleation behavior and provides new guidance for promoting the development of advanced Li-S batteries.