Dual sulfur-doped sites boost potassium storage in carbon nanosheets derived from low-cost sulfonate

As a new energy storage system, K-ion batteries (KIBs) have the advantages of low price and competitive high energy density. However, due to the large radius of K+, in the process of intercalation/deintercalation, the traditional carbon anode materials usually display insufficient cycle life and poor rate performance in KIBs. In this work, inexpensive and widely-sourced sodium p-toluenesulfonate (CH3C6H4SO3Na) is used as raw material to synthesize dual sulfur-doped carbon nanosheets (DS-CN) by a simple one-step carbonization method. The nanosheets possess an enlarged interlayer distance (4.25 angstrom) which allows large K+ to intercalate. C-S bonds and the embedded ultrafine sulfate provide active sites to enhance capacity and accelerate kinetics. Moreover, a high S/O ratio would reduce the irreversible reactions caused by oxygen functional groups. The high reversible specific capacity (331.9 mA h g(-1) at 50 mA g(-1)), good rate performance (165.3 mA h g(-1) at 1000 mA g(-1)) and long cycle stability (0.011% capacity decay per cycle) are attributed to the multiple synergistic effects of enlarged layer spacing, reaction between C-S bonds and K+, as well as more active -C-SO2- bonds, as confirmed by ex-situ XPS and electrochemical analysis. Our work shows a feasible and effective way to develop low-cost, high-performance carbon anode materials for KIBs.

Automated summary

This study successfully synthesized dual sulfur-doped carbon nanosheets using inexpensive and widely-sourced raw materials, which exhibited excellent performance in K-ion batteries, including high reversible specific capacity, good rate performance, and long cycle stability. The results demonstrate the feasibility and effectiveness of developing low-cost, high-performance carbon anode materials for KIBs.