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Vol. 19 (2027)

Anionic Bottom-Up Flux Orchestrated via Hard Carbon Surface Chemistry for Stable Sodium-Ion Batteries

https://doi.org/10.1007/s40820-026-02339-w
Peiyao Wang
Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, People’s Republic of China
Shendong Xu
School of Carbon Neutrality Science and Engineering, Anhui University of Science and Technology, Hefei 231131, People’s Republic of China
Siya Wang
Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, People’s Republic of China
Xiaoyu Cui
Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, People’s Republic of China
Jin Bai
Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, People’s Republic of China
Yuping Sun
Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, People’s Republic of China
Xuebin Zhu
Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, People’s Republic of China
Bangchuan Zhao
Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, People’s Republic of China
Shulei Chou
Institute for Carbon Neutralization Technology, College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035, People’s Republic of China
Xingqiao Wu
Institute for Carbon Neutralization Technology, College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035, People’s Republic of China

Corresponding Author: Xingqiao Wu

xingqiaowu@wzu.edu.cn

Nano-Micro Letters, Vol. 19 (2027), Article Number: 43

Abstract

Hard carbon anodes for sodium-ion batteries suffer from unstable solid-electrolyte interphase formation, leading to low initial Coulombic efficiency and poor cycle stability. Herein, we demonstrate a molecular-level surface design that actively orchestrates an anionic bottom-up flux from the electrolyte bulk to the hard carbon interface. By engineering a synergistic pair of pyridinic-N and carbonyl groups on the carbon surface, we create a functional-differentiation microenvironment where pyridinic-N selectively anchors PF6− anions, while the cooperative carbonyl repels solvent molecules. This dual functionality establishes a sustained concentration gradient that drives a continuous reverse flux of anions toward the interface, fundamentally redirecting the electrolyte decomposition pathway from solvent-dominated to anion-preferential. The tailored surface lowers the PF6− decomposition barrier by over 70%, yielding a thin, inorganic-rich solid-electrolyte interphase dominated by NaF and Na2O. The optimized anode achieves 91.9% Coulombic efficiency with high reversible capacity of 368.2 mAh g−1, and 96.5% capacity retention after 5,000 cycles. A pouch cell assembled with NFPP cathode achieves an energy density of 239.1 Wh kg−1 and stable operation over 500 cycles, demonstrating strong practical potential. This work establishes active surface-guided anionic transport as a powerful strategy for interphase engineering in advanced sodium-ion batteries.


Highlights:
1 A cooperative pair of pyridinic-N and carbonyl groups creates a trap-and-repel microenvironment that actively programs interfacial reactions.
2 The functional differentiation drives a sustained bottom-up anionic flux, steering decomposition toward an anion-derived pathway.
3 The resulting inorganic-rich solid-electrolyte interphase enables 91.9% initial Coulombic efficiency and 96.5% capacity retention over 5,000 cycles.

Keywords

Hard carbon Sodium-ion battery Interphase engineering Bottom-up anionic flux Inorganic-rich SEI
Wang, Peiyao, Shendong Xu, Siya Wang, Xiaoyu Cui, Jin Bai, Yuping Sun, Xuebin Zhu, Bangchuan Zhao, Shulei Chou, and Xingqiao Wu. 2026. “Anionic Bottom-Up Flux Orchestrated via Hard Carbon Surface Chemistry for Stable Sodium-Ion Batteries”. Nano-Micro Letters 19 (September):43. https://doi.org/10.1007/s40820-026-02339-w.
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