钠电池电解液的溶剂种类有哪些？

What types of solvents are used in electrolytes for sodium-ion batteries?

商用钠离子电解液溶剂分为碳酸酯、醚类、羧酸酯三大体系，量产电芯以多元碳酸混合溶剂为主，三类溶剂性能、适用场景差异明显。第一类碳酸酯溶剂，分为环状与链状，环状 EC、PC 介电常数极高，解离钠盐能力强，充放电时辅助负极生成均匀稳定 SEI 膜；链状 DMC、EMC、DEC 粘度极低，低温流动性优异，提升快充性能，行业通用 EC EMC D 三元复配体系，平衡成膜与低温表现，适配绝大多数储能、低速动力量产电池。第二类醚类溶剂包含 DME、TEGDME，粘度极低，-40℃超低温容量保持率出色，充放电极化小，但电化学窗口窄，高压工况易分解，仅用于特种低温设备研发，无法量产高压大容量电芯。第三类羧酸酯凝固点极低，低温性能优秀、原料成本低廉，但高温下极易发生氧化分解，通常仅作为少量辅助溶剂添加，改善户外低温设备放电能力。醚与羧酸酯均无法单独做主溶剂，仅能和碳酸酯复配改性，目前市面全部规模化钠电池储能、动力产品均采用碳酸酯混合溶剂体系，技术成熟、安全可控，适配普鲁士蓝、聚阴离子、层状氧化物全正极路线。

Commercial sodium electrolyte solvents are divided into three categories: carbonates, ethers and carboxylates. Mass-produced cells mainly adopt mixed carbonate solvents with distinct performance and applicable scenarios for each type. The first category, carbonates, are split into cyclic and linear types. Cyclic EC and PC feature high dielectric constants with strong sodium salt dissociation capacity and assist the formation of uniform stable SEI films on anodes during cycling. Linear DMC, EMC and DEC have ultra-low viscosity and excellent low-temperature fluidity to boost fast-charging performance. The universal industrial ternary blend of EC EMC balances film-forming and low-temperature performance for most mass-produced energy storage and low-power sodium-ion cells. The second category, ethers including DME and TEGDME, have ultra-low viscosity, outstanding capacity retention at -40℃ and minor polarization, yet suffer narrow electrochemical windows and easy decomposition under high voltage. They are only applied in R&D of special low-temperature equipment instead of mass production of high-voltage large-capacity cells. The third category, carboxylates, have ultra-low freezing points, favorable low-temperature performance and low raw material costs, but are prone to oxidative decomposition at high temperatures, so they are only added in small amounts as auxiliary solvents to improve discharge performance of outdoor low-temperature equipment. Neither ethers nor carboxylates can be used as main solvents independently and can only be blended with carbonates for modification. All commercial mass-produced sodium-ion energy storage and power cells adopt mixed carbonate solvents with mature, controllable safety, compatible with Prussian blue, polyanion and layered oxide cathode systems.