No abstract

Boosting reversible solid‐liquid phase transformation from lithium polysulfides to Li2S and suppressing the shuttling of lithium polysulfides from the cathode to the lithium anode are critical challenges in lithium‐sulfur batteries. Here, sulfiphilic single atomic cobalt implanted in lithiophilic heteroatoms‐dopped carbon (SACo@HC) matrix with a CoN3S structure for high‐performance lithium‐sulfur batteries is reported. Density functional theory calculation and in situ experiments demonstrate that the optimal CoN3S structure in SACo@HC can effectively improve the adsorption and redox conversion efficiency of lithium polysulfides. Consequently, the S‐SACo@HC composite with sulfur loading of 80 wt% delivers a high capacity of 1425.1 mAh g−1 at 0.05 C and outstanding rate performance with 745.9 mAh g−1 at 4 C. Furthermore, a capacity of 680.8 mAh g−1 at 0.5 C with a low electrolyte/sulfur ratio (6 µL mg−1) can be achieved even after 300 cycles. With the harsh conditions of lean electrolyte (E/S = 4 µL mg−1) and high sulfur loading (5.4 mg cm−2), a superior area capacity of 5.8 mAh cm−2 can be obtained. This work contributes to building a profound understanding of the adsorption and interface engineering of lithium polysulfides and provides ideas to tackle the long‐standing polysulfide shuttle problem of lithium‐sulfur batteries.

Potassium‐ion batteries (PIBs) have been regarded as a competitive alternative for lithium‐ion batteries, owing to the natural abundance, low cost, and similar rocking‐chair working mechanism of potassium element. However, it is challenging to simultaneously prepare suitable potassium ion anode materials of low voltage plateau, high capacity, and long cycle life. In this work, onion‐like soft carbon (OLSC) of high heteroatom content is prepared by using solvent‐sensitive self‐assembly properties of asphaltene molecules. The OLSC electrode exhibits a low voltage plateau because of a high degree of graphitization. Meanwhile, it possesses excellent cycling stability and rate capability due to the high stability of the onion‐like structure and fast transport of potassium ions, the latter of which is caused by heteroatom‐induced expanded interlayers as found by first‐principle calculations. Compared with existing carbon materials, the OLSC synthesized in this study exhibits a high reversible capacity of 466 mAh g–1 at 20 mA g–1, a reversible capacity of 222 mAh g–1 and capacity retention of 95% after 1600 cycles at 1 A g–1. This work connects the nanostructure of carbon materials and electrochemical performance and provides new insights in improving carbon‐based anodes for PIBs.