Targeting Acceleration of the Rate-Determining Step in Sulfur Redox and Dendrite-Free Lithium: Heterointerface and Electron Structural Engineering.

Abstract

Currently, most catalysts for lithium-sulfur batteries suffer from some shortcomings, including restricted active sites and poor catalytic kinetics. Herein, we developed an advanced catalyst of V-MXene@octahedral porous carbon (MX@OPC), which features a "built-in interfacial electric field" (BIEF) and "dual-functional catalytic active sites" (DCASs), to target the accelerated rate-determining step in polysulfide redox kinetics and dendrite-free lithium behaviors. The well-designed heterointerface forms the BIEF due to the differences in work function and charge distribution, contributing to enhanced interfacial electron transfer and low lithium-ion diffusion barriers. The DCASs with superior Li₂S₄ desorption efficiently catalyze the conversion from Li₂S₄ to Li₂S₂ by the distribution of relaxation times (DRT) analysis and density functional theory (DFT) calculations. The V-MXene exhibits strong lithophilicity, which facilitates uniform nucleation and dendrite-free growth of lithium. As a result, a battery with MX@OPC delivers a capacity fade rate per cycle as low as 0.017% over 1200 cycles at 2 C. Furthermore, MX@OPC renders a Li||Li symmetric cell to maintain a stable overpotential of 16 mV over 2500 h. This work provides inspiring insights into directed catalysis and generation of BIEF toward accelerating the rate-determining-step in sulfur redox and dendrite-free lithium deposition in Li-S batteries.