Relay-Type Catalysis by a Dual-Metal Single-Atom System in a Waste Biomass Derivative Host for High-Rate and Durable Li–S Batteries

An environmental-friendly and sustainable carbon-based host is one of the most competitive strategies for achieving high loading and practicality of Li-S batteries. However, the polysulfide conversion reaction kinetics is still limited by the nonuniform or monofunctional catalyst configuration in the carbon host. In this work, we propose a catalysis mode based on "relay-type" co-operation by adjacent dual-metal single atoms for high-rate and durable Li-S batteries. A discarded sericin fabric-derived porous N-doped carbon with a stacked schistose structure is prepared as the high-loading sulfur (84 wt %) host by a facile ionothermal method, which further enables the uniform anchoring of Fe/Co dual-metal single atoms. This multifunctional host enables superior lithiophilic-sulfiphilic and electrocatalytic capabilities contributed by the "relay-type" single-atom modulation effects on different conversion stages of liquid polysulfides and solid Li₂S₂/Li₂S, leading to the suppression of the "shuttle effect", alleviation of nucleation and decomposition barriers of Li₂S_x, and acceleration of polysulfide conversion kinetics. The corresponding Li-S batteries exhibit a high specific capacity of 1399.0 mA h g^-1, high-rate performance up to 10 C, and excellent cycling stability over 1000 cycles. They can also endure the high sulfur loading of 8.5 mg cm^-2 and the lean electrolyte condition and yield an areal capacity as high as 8.6 mA h cm^-2. This work evidentially demonstrates the potential of waste biomass reutilization coupled with the design of a single-atom system for practical Li-S batteries with high energy density.