什么是钠电池电解液的添加剂？

What are additives for electrolytes of sodium-ion batteries?

电解液添加剂是添加量仅 0.1%~5% 的精细功能性化学品，不会改变溶剂、钠盐基础理化特性，针对性弥补电解液、电极界面各类性能短板，是电解液企业核心技术壁垒。基础钠盐   溶剂配方同质化严重，不同厂商电解液循环、低温、安全性能差距完全依靠添加剂配方区分。按照核心作用分为五大品类：成膜添加剂是最主流品类，充放电时优先在电极表面反应，构建均匀致密 SEI/CEI 钝化膜，大幅降低首次不可逆容量；阻燃添加剂提升电解液闪点，抑制热失控链式放热反应；低温添加剂降低体系凝固点与粘度，拓宽低温放电区间；除水除酸添加剂中和电解液微量水分、酸性杂质，抑制钠盐水解产气；高压稳定添加剂提升电解液氧化耐受能力，适配高电压层状氧化物正极。单种添加剂作用单一，高端长循环储能电解液通常复配 3 至 5 种添加剂协同起效，兼顾界面稳定、低温放电、防火防胀气多重需求，少量添加即可大幅延长电池循环寿命，显著提升全场景使用稳定性。

Electrolyte additives are fine functional chemicals with a dosage ranging only from 0.1% to 5%. They do not alter the basic physical and chemical properties of solvents and sodium salts, but targetedly compensate various performance defects of electrolytes and electrode interfaces, forming the core technical barrier of electrolyte manufacturers. Basic formulas consisting of sodium salts and solvents are highly homogeneous, and differences in cycling, low-temperature and safety performance between manufacturers entirely depend on additive formulas. Additives are categorized into five core types by function. Film-forming additives, the most widely used category, preferentially react on electrode surfaces during cycling to form uniform compact SEI/CEI passivation films and drastically reduce initial irreversible capacity. Flame retardant additives raise electrolyte flash points and restrain chain exothermic reactions of thermal runaway. Low-temperature additives lower the freezing point and viscosity of the system to widen low-temperature discharge windows. Water and acid scavengers neutralize trace moisture and acidic impurities in electrolytes and inhibit sodium salt hydrolysis and gas generation. High-voltage stabilizing additives improve electrolyte oxidation resistance for high-voltage layered oxide cathodes. A single additive only delivers limited effects, so high-end long-cycle energy storage electrolytes usually blend 3 to 5 additives for synergistic effects, balancing interface stability, low-temperature discharge, fire prevention and anti-gassing requirements. A tiny dosage can greatly extend battery cycle life and remarkably improve stability across all application scenarios.