Polymer-induced solid–electrolyte interphase on hard carbon enabling 5C fast-charging practical sodium-ion pouch cell
Yongrong Sun, Junjie Du, Tianze Shi, Daxian Zuo, Jiaming Tian, Chengrong Xu, Bo Peng, Jie Yang, Sheng Xu, Yiwen Liu, Yu Shi, Haoshen Zhou, Shaohua Guo
Abstract
ABSTRACT Achieving <15 min fast-charging technology for long-life sodium-ion batteries (SIBs) remains a formidable challenge, primarily due to parasitic reactions and unstable solid–electrolyte interphase (SEI) at the hard carbon (HC) interface. Here we develop a universal polymer-induced SEI strategy that enables an Ah-level SIB pouch cell to achieve <10 min fast-charging capability. We design a <4.0 nm functionalized polymer molecular layer, polyethylenesulfonyl fluoride (PESF), coated on the HC surface (PolyHC) to minimize electrolyte decomposition. The PESF with the –SO2F group attached has a powerful polar feature, which simultaneously induces an anion enriched at the PolyHC interface and tailors extra F atoms, contributing to the architecture of a ∼5.0 nm stable SEI that hybridizes polymer and NaF. This SEI with a resilient polymer skeleton permanently holds the generated inorganic component, enabling long-term structural stability during fast charging. The assembled 1.2 Ah pouch cell, paired with NaNi1/3Fe1/3Mn1/3O2 cathode and PolyHC anode, displays exceptional fast-charging capability and durability. This method is compatible with various HCs, offering a novel perspective for modulating the HC interface chemistry.