Lithium-sulphur batteries with a high theoretical energy density are regarded as promising energy storage devices for electric vehicles and large-scale electricity storage. However, the low active material utilization, low sulphur loading and poor cycling stability restrict their practical applications. Herein, we present an effective strategy to obtain Li/polysulphide batteries with high-energy density and long-cyclic life using three-dimensional nitrogen/sulphur codoped graphene sponge electrodes. The nitrogen/sulphur codoped graphene sponge electrode provides enough space for a high sulphur loading, facilitates fast charge transfer and better immobilization of polysulphide ions. The hetero-doped nitrogen/sulphur sites are demonstrated to show strong binding energy and be capable of anchoring polysulphides based on first-principles calculations. As a result, a high specific capacity of 1,200 mAh g-1 at 0.2C rate, a high-rate capacity of 430 mAh g-1 at 2C rate and excellent cycling stability for 500 cycles with ∼0.078% capacity decay per cycle are achieved.
Bibliographical noteFunding Information:
This work was funded in part by the Advanced Research Projects Agency-Energy (ARPA-E), US Department of Energy, under Award Number DE-AR0000377. G.S.H. also gratefully acknowledges the Robert A. Welch foundation (F-1535) for partial financial support of the computational work and the Texas Advanced Computing Center (TACC) for providing HPC resources.
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