什么是钠电池的溶剂？

What are solvents for sodium-ion battery electrolytes?

电解液溶剂占电解液总质量 80% 以上，是电解液基础主体，核心功能是溶解钠盐溶质、分散各类功能添加剂，搭建钠离子迁移的液态通道，电解液的粘度、凝固点、电化学窗口、成膜性能全部由溶剂体系决定。溶剂本身不导电，也不参与电极储钠电化学反应，两大核心基础特性为高介电常数与低粘度：高介电常数可以充分解离钠盐，释放游离钠离子；低粘度能够降低离子移动阻力，保障高低温环境下充放电顺畅。钠电池溶剂必须满足四大硬性标准：宽电化学稳定窗口，充放电过程不易氧化还原；耐高低温，低温不易凝固、高温不易分解；低可燃性，降低热失控燃烧风险；化学惰性，不与钠盐、正负极材料发生副反应。行业主流采用多元混合溶剂配方，单一溶剂很难同时兼顾全部性能。溶剂复配方案是电解液厂商核心研发方向，针对北方低温储能、大功率叉车、长时工商业储能等不同场景调整配比，分别侧重低温流动性、高温稳定性、SEI 成膜能力，直接决定电池快充能力、循环寿命与安全上限。

Electrolyte solvents account for over 80% of the total electrolyte mass and serve as the fundamental matrix of electrolytes. Their core functions include dissolving sodium salt solutes, dispersing various functional additives and forming liquid channels for sodium ion migration. The viscosity, freezing point, electrochemical window and film-forming performance of electrolytes are all determined by solvent systems. Solvents are non-conductive and do not participate in sodium storage electrode reactions. They possess two key intrinsic properties: high dielectric constant to fully dissociate sodium salts and release free sodium ions, and low viscosity to reduce ion migration resistance and ensure smooth charging and discharging under high and low temperatures. Sodium battery solvents must meet four rigid standards: wide electrochemical stability window to resist oxidation and reduction during cycling, wide temperature tolerance without solidification at low temperature or decomposition at high temperature, low flammability to mitigate thermal runaway risks, and chemical inertness to avoid side reactions with sodium salts and electrode materials. The industry mainly adopts mixed multi-solvent formulas, as single solvents can hardly balance all performance indicators. Solvent blending schemes are the core R&D focus of electrolyte manufacturers. Formulas are adjusted for scenarios such as northern low-temperature energy storage, high-power forklifts and long-duration industrial & commercial energy storage, prioritizing low-temperature fluidity, high-temperature stability and SEI film-forming capacity respectively, which directly determine the fast-charging capability, cycle life and safety limit of batteries.