钠电池 CEI 膜的作用是什么？

What are the functions of CEI films in sodium-ion batteries?

CEI 四大核心作用稳定正极电化学体系，提升循环与安全性能。第一隔绝副反应，致密膜分开正极晶体与电解液，抑制高压下电解液持续氧化，减少电芯产气鼓包、降低电解液消耗速度。第二抑制金属溶出，包裹正极骨架缓解晶格畸变，阻挡钒、锰、铁等离子溶解进入电解液，避免迁移至负极破坏 SE 膜。第三优化离子传导，合格 CE 通透钠离子，不会大幅抬升正极界面阻抗，防止充放电极化、超温。第四拓宽电压窗口，稳定 CE 支撑更高充电电压，充分释放正极理论容量，提升电芯能量密度。若 CE 疏松易破损，电解液持续损耗，内阻快速上涨、容量加速衰减，储能、动力电池使用寿命会大幅缩短。

CEI has four core functions to stabilize cathode electrochemistry and improve cycle and safety performance. First, it isolates side reactions: dense films separate cathode crystals from electrolytes, restrain continuous electrolyte oxidation under high voltage, reduce cell gas swelling and slow electrolyte consumption. Second, it suppresses metal dissolution: the film wraps cathode skeletons to ease lattice distortion and block dissolved vanadium, manganese and iron ions from migrating to anodes and damaging SEI. Third, it optimizes ion conduction: qualified CEI permits sodium penetration without sharply raising cathode interfacial impedance, avoiding polarization and overheating during cycling. Fourth, it widens voltage windows; stable CEI supports higher charging voltages to fully release cathode theoretical capacity and boost cell energy density. Loose fragile CEI causes continuous electrolyte loss, rapid resistance growth and accelerated capacity fading, greatly shortening the service life of energy storage and power batteries.