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

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.