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

Abstract

Designing dense thick sulfur cathodes to gain high-volumetric/areal-capacity lithium–sulfur batteries (LSBs) in lean electrolytes is extremely desired. Nevertheless, the severe Li2S clogging and unclear mechanism seriously hinder its development. Herein, an integrated strategy is developed to manipulate Li2S redox kinetics of CoP/MXene catalyst via electron-donor Cu doping. Meanwhile a dense S/Cu0.1Co0.9P/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 mgs−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/Li2S on electrocatalyst surface, thereby decreasing the diffusion energy barrier and activation energy of Li2S nucleation and dissolution, boosting Li2S redox kinetics, and inhibiting shuttling in the dense thick sulfur cathode. This work deeply understands the atomic-level manipulation mechanism of Li2S redox kinetics and provides dependable principles for designing high-volumetric-energy-density, lean-electrolyte LSBs through integrating bidirectional electro-catalysts with manipulated Li2S redox and dense-sulfur engineering.