钠电池热失控的触发因素有哪些？

What are the triggering factors of thermal runaway for sodium-ion batteries?

钠电池热失控分为四大类核心触发因素，覆盖电气滥用、机械损伤、热滥用、电芯原生制造缺陷，四类诱因可单独作用，也会叠加加速热失控进程。第一类电气滥用，也是现场最常见诱因，包含持续过充、深度过放、内外短路、大电流过载。过充时正极钠离子过度脱嵌，晶格坍塌释放大量热量，电解液氧化分解产生可燃气体；正负极直接短路瞬间产生超大焦耳热，短时间抬升电芯温度突破临界值；长期大电流充放电持续累积焦耳热，缓慢推高基底温度，埋下热失控隐患。第二类机械滥用，外力造成电芯物理破损，涵盖针刺、重物挤压、剧烈冲击跌落、极片毛刺刺破隔膜。隔膜破损后正负极直接接触形成内部微短路，局部集中放热，逐步扩散至整个电芯，储能电站搬运、车辆颠簸、叉车撞击均会诱发该类故障。第三类热滥用，电芯长期处于超温环境，包含储能舱通风失效、夏季密闭暴晒、周边起火烘烤、散热系统故障。环境持续 45℃以上高温会加速电解液副反应，降低材料热分解临界温度，轻微电气扰动即可触发链式放热反应。第四类电芯出厂原生缺陷，生产环节管控不足遗留隐患，包含极片超长毛刺、隔膜孔洞、电解液杂质、封装密封不严、化成分容筛选漏检。此类电芯正常使用初期无明显异常，长期循环后局部副反应持续累积，自发出现局部升温，最终演化成热失控。除此之外，电池包 PACK 设计缺陷，如汇流排接触不良、线束过热、电芯排布过密散热通道堵塞，会放大以上四类诱因的升温效应，大幅提升热失控发生概率。

Thermal runaway of sodium-ion batteries has four major categories of triggering factors: electrical abuse, mechanical damage, thermal abuse and inherent cell manufacturing defects, which act alone or jointly to accelerate runaway. First, electrical abuse, the most frequent on-site trigger, includes continuous overcharge, deep over-discharge, internal/external short circuit and high-current overload. Overcharge causes excessive sodium deintercalation and cathode lattice collapse to release heat and flammable gas. Direct positive-negative short circuit generates instantaneous massive Joule heat to cross critical temperature; long-term high-current operation accumulates residual heat gradually. Second, mechanical abuse refers to physical cell damage from needle puncture, heavy squeeze, violent impact and burr piercing of separators. Broken separators create micro short circuits with localized concentrated heat spreading across cells, often triggered by storage transportation vibration or vehicle collision. Third, thermal abuse means prolonged high-temperature exposure, such as failed cabin ventilation, sealed summer exposure, adjacent fire and broken cooling systems. Constant temperature above 45℃ accelerates electrolyte side reactions and lowers thermal decomposition thresholds, enabling runaway from minor electrical disturbances. Fourth, inherent factory defects from loose production control: overlong electrode burrs, separator holes, electrolyte impurities, poor sealing and unqualified screening during formation & grading. Such cells show no early abnormalities but accumulate local heat after long cycles to trigger spontaneous runaway. Additionally, flawed PACK design including poor busbar contact, overheated wiring and dense cell layout blocking heat dissipation amplifies temperature risks and raises runaway probability.