Activating Transition-Metal Oxides through In Situ Regulation of Lower Hubbard Band for Catalytic Conversion of Lithium Polysulfides

Abstract

Catalytic conversion of lithium polysulfides (LiPSs) is regarded as an effective avenue to tackle the shuttle effect of lithium–sulfur (Li–S) batteries, especially based upon transition-metal oxides (TMOs). However, the activity origin and corresponding mechanistic insights into such catalytic systems remain elusive. Herein, an activated state associated with the lower Hubbard band (LHB) transition is proposed to elucidate the origin of activity of TMOs by taking Mn₃O₄ as a model electrocatalyst. Specifically, the broadening of LHB width, the upshift of LHB position, and the orbital rearrangement of LHB, triggered by the in situ substitution of the O atoms in Mn₃O₄ with the S atoms of LiPSs under working conditions, synergistically enable fast electron transfer and modulate the adsorption capability to a moderate level. Benefiting from these advantages, the Mn₃O₄ electrocatalyst is converted from the torpid state to the activated state for expediting LiPS conversion. Eventually, the Li–S batteries assembled with Mn₃O₄ deliver excellent rate performance over 6 C and outstanding cycling stability over 1000 cycles. Moreover, an Ah-scale pouch cell is constructed and delivers a notable energy density of 388.1 W h kg^–1. Our work offers a promising pathway based on the regulation of LHB for designing high-performance electrocatalysts for Li–S systems and beyond.