Wenrui Wei,Yulong Zheng,Minghua Huang,Jing Shi,Lei Li,Zhicheng Shi,Shuai Liu,Huanlei Wang
Designing carbon anodes with rich heteroatoms and dilated graphitic interlayer spacing via a one-step synthesis process plays a vital role in accelerating the practical application of potassium ion batteries, but it is still a big challenge. Herein, P-doped S-rich mesoporous carbon (PSMC) is prepared by direct phosphate-assisted carbonization of carrageenan, and it exhibits excellent potassium storage capacity (449 mA h g−1 at 0.1 A g−1), superior rate performance (233 mA h g−1 at 2 A g−1) and long-term stability (97.3% capacity retention after 1000 cycles), due to the high sulfur doping (16.48 wt%) and the coexistence of ordered and disordered regions in the structure. Ex situ characterization, GITT and theoretical calculations reveal that the promotion of covalent sulfur can effectively increase the adsorption of K+ and enhance the K+ reaction kinetics. The proposed one-step synthesis strategy demonstrates the precise use of the composition in biomass, enabling large-scale production of high-performance anodes for K+ storage.
S doping is an effective strategy to improve the potassium-ion storage performance of carbon-based materials. However, due to the large atomic radius of S and poor thermal stability, it is challenging to synthesize carbon materials with high sulfur content by solid-phase transformation. In this work, we designed a multi-cavity structure that can confine the molten S during heat treatment and make it fully react, then achieving high S doping (7.6 at. %). As we known, S doping can also effectively increase the active sites of carbon materials to obtain higher capacity. In addition, through different ex/in-situ characterizations and DFT calculations , we confirmed that the S atoms can effectively expand the interlayer spacing of carbon, which facilitates the intercalation/deintercalation reaction of K + , thereby significantly improving the rate performance. Therefore, benefiting from the effect of S-doping, the sample exhibits high reversible specific capacity (401.0 mAh g −1 at 0.1 A/g) and rate performance (167.2 mAh g −1 at 5 A/g). The as-assembled K + hybrid capacitor delivers both high energy density and power density (138.5 W h kg −1 and 7692.5 W kg −1 , respectively). This work provides a new approach to design S content carbon-based materials for high performance K + storage.
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