Unraveling the Atomic-Level Manipulation Mechanism of Li2S Redox Kinetics via Electron-Donor Doping for Designing High-Volumetric-Energy-Density, Lean-Electrolyte Lithium–Sulfur Batteries

Designing dense thick sulfur cathodes to gain high-volumetric/areal-capacity lithium–sulfur batteries (LSBs) in lean electrolytes is extremely desired. Nevertheless, the severe Li 2 S clogging and unclear mechanism seriously hinder its development. Herein, an integrated strategy is developed to manipulate Li 2 S redox kinetics of CoP/MXene catalyst via electron-donor Cu doping. Meanwhile a dense S/Cu 0.1 Co 0.9 P/MXene cathode (density = 1.95 g cm −3 ) is constructed, which presents a large volumetric capacity of 1664 Ah L −1 (routine electrolyte) and a high areal capacity of ≈8.3 mAh cm −2 (lean electrolyte of 5.0 µL mg s −1 ) at 0.1 C. Systematical thermodynamics, kinetics, and theoretical simulation confirm that electron-donor Cu doping induces the charge accumulation of Co atoms to form more chemical bonding with polysulfides, whereas weakens Co  S bonding energy and generates abundant lattice vacancies and active sites to facilitate the diffusion and catalysis of polysulfides/Li 2 S on electrocatalyst surface, thereby decreasing the diffusion energy barrier and activation energy of Li 2 S nucleation and dissolution, boosting Li 2 S redox kinetics, and inhibiting shuttling in the dense thick sulfur cathode. This work deeply understands the atomic-level manipulation mechanism of Li 2 S redox kinetics and provides dependable principles for designing high-volumetric-energy-density, lean-electrolyte LSBs through integrating bidirectional electro-catalysts with manipulated Li 2 S redox and dense-sulfur engineering.