Tuning Porous Carbon into Hard Carbon via an S<sub>N</sub>2 Reaction for Enhanced Sodium Storage.

Zhang, Yan; Zheng, Biao; Fu, Qingfeng; Duan, Yan; Hu, Aiping; Zhong, Wenbin; Liu, Jilei · Nano Lett · 2026

basic_science · Level V

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Abstract

Porous carbon (PC) is widely used in energy storage devices such as supercapacitors due to its high surface area and abundant ion-accessible pores. However, its excessive open porosity in sodium-ion batteries (SIBs) leads to severe side reactions and low initial Coulombic efficiency. Regulating pore structures to transform PC into hard carbon (HC) with rich closed-pores is essential for improving sodium storage performance. Here, we report a direct microstructural conversion of PC into high-performance HC anodes for SIBs via the upcycling of polytetrafluoroethylene (PTFE) waste. Assisted by Brønsted-basic NH<sub>3</sub>, the ultrastrong C-F bonds in PTFE are efficiently cleaved, inducing <i>in situ</i> carbon deposition that transforms open pores into a closed-pore structure with curved graphitic domains. The optimized YPT-1200 electrode achieves a high reversible capacity of 370.3 mAh g<sup>-1</sup> with satisfactory initial Coulombic efficiency of 78.0% as well as impressive cycling stability (83.4% capacity retention over 300 cycles at 0.5C).