Hard carbon (HC) is a promising anode material in developing sodium-ion batteries (SIBs). However, due to diminished ion diffusion kinetics, low initial coulombic efficiency (ICE) and continuous electrolyte decomposition, HC-based SIBs have led to sluggish rate capability and specific capacity. Herein, we utilised a polymer with dense functional groups containing carboxylic acid in its side chains as a binder that demonstrates ion transport, defect passivation and better mechanical stability. The consecutive polar functional groups provide ion transfer channels and enhanced adhesion to electrode components. The poly(hydroxycarbonylmethylene) (PFA) binder for the HC electrode achieved the highest ICE of 80.8% and a specific capacity of 288 mA h g⁻¹ and 254 mA h g⁻¹ at 30 mA g⁻¹ and 60 mA g⁻¹, respectively, which are superior to those for HC electrodes containing PAA and PVDF binders. Anodic half-cells containing the PFA binder showed high capacity retention of 85.4% (250 cycles) and 91.6% (200 cycles) at current densities of 60 mA g⁻¹ and 30 mA g⁻¹ respectively. In addition, the presence of dense polar groups boosted the diffusion kinetics and lowered the Na⁺ activation energy. XPS and SEM studies further verified that the dense functional groups influence the formation of a thin, stable and inorganic-rich solid–electrolyte interface and crack-free electrodes. Therefore, polymers with dense functional groups will help in the early adoption of SIBs in the market.

中文翻译：

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用于高性能硬碳阳极钠离子电池的水溶性稠密功能化聚（羟基羰基亚甲基）粘合剂

硬碳（HC）是开发钠离子电池（SIB）时很有前景的负极材料。然而，由于离子扩散动力学减弱、初始库仑效率（ICE）低和电解质持续分解，HC基SIB导致倍率性能和比容量低下。在此，我们利用侧链含有羧酸的致密官能团的聚合物作为粘合剂，具有离子传输、缺陷钝化和更好的机械稳定性。连续的极性官能团提供离子传输通道并增强对电极组件的粘附力。用于HC电极的聚（羟基羰基亚甲基）（PFA）粘合剂在30 mA g ^-1和60 mA g ^-1下实现了最高80.8%的ICE和288 mA hg ^-1和254 mA hg ^-1的比容量。 ，优于含有 PAA 和 PVDF 粘合剂的 HC 电极。含有PFA粘合剂的阳极半电池在60 mA g ^-1和30 mA g ^-1的电流密度下分别表现出85.4%（250个循环）和91.6%（200个循环）的高容量保持率。此外，致密极性基团的存在增强了扩散动力学并降低了Na ⁺活化能。 XPS 和 SEM 研究进一步证实，致密的官能团会影响薄、稳定且富含无机物的固体电解质界面和无裂纹电极的形成。因此，具有密集官能团的聚合物将有助于SIB在市场上的早期采用。