What are the approaches to improve low-temperature performance of sodium-ion batteries?

低温衰减核心是电解液粘度上升、钠离子迁移阻力增大、SEI 阻抗升高，优化分为电解液、电极、电芯热管理三大主线。一电解液低温改性：低凝固点醚、羧酸酯复配溶剂，降低低温粘度；添加低温导电助剂，提升 - 20℃~-40℃离子电导率；搭配低温专用成膜添加剂，避免低温下 SEI 增厚抬升内阻。二电极材料优化：正极纳米化缩短钠离子扩散距离，减小低温极化；硬碳调控孔径，拓宽低温钠传输通道；电极薄涂布工艺，缩短离子迁移路径，降低低温压降。三 PACK 配套热管理：低温加热膜集成，环境低于 0℃自动预热至安全充电区间；水冷 / 风冷全域均温，缩小模组电芯温差。四极片工艺微调：降低压实密度预留充足微孔，低温电解液充分浸润；采用薄隔膜、低阻抗导电剂减小低温回路阻抗。此外系统层面优化充电策略，低温下降低充电电流，抑制负极金属钠析出，杜绝短路隐患。材料、电解液、温控、充电策略协同优化，可使 - 20℃容量保持率从 75% 提升至 88% 以上，完美适配北方户储、户外农机、极地储能等低温场景。

Low-temperature fading mainly originates from rising electrolyte viscosity, increased sodium migration resistance and higher SEI impedance. Optimizations include three main lines: electrolytes, electrodes and PACK thermal management. 1. Low-temperature electrolyte modification: Blend low-freezing ether and carboxylate solvents to cut viscosity; add low-temperature conductive additives to lift ionic conductivity at -20℃~-40℃; match dedicated film formers to avoid thickened SEI and high resistance under cold conditions. 2. Electrode optimization: Nanocrystallized cathodes shorten sodium diffusion distance to reduce low-temperature polarization; adjust hard carbon pore sizes to widen ion channels; thin electrode coating shortens migration paths and mitigates voltage drop. 3. PACK thermal management integration: Built heating films auto-preheat to safe charging temperature below 0℃; water/air cooling equalizes temperature across modules. 4. Electrode tuning: Lower compaction density to reserve micropores for full cold electrolyte infiltration; adopt thin separators and low-impedance conductive agents to cut loop resistance. Optimize charging algorithms at system level by reducing low-temperature current to suppress sodium precipitation and short-circuit risks. Synergy of materials, electrolyte, temperature control and charging strategies lifts capacity retention at -20℃ from 75% to over 88%, fully fitting northern household storage, farm machinery and polar energy storage.