钠电池的焊接工艺有哪些要求？

What are the requirements for the welding process of sodium-ion batteries?

钠电池焊接涵盖电芯极耳焊、模组汇流排串并联焊两大环节，直接决定模组导电可靠性与安全阈值，五大硬性规范必须落地执行。第一焊点牢固无虚焊、假焊，焊接拉力需达标，长期充放电循环与运输振动下焊点不得脱落，避免模组断路停机故障；第二焊点平整无毛刺、无熔融炸点，焊接时杜绝铝箔金属碎屑产生，防止碎屑落入电芯内部刺穿隔膜诱发微短路，同时不能烧穿极耳、隔膜与封装铝塑膜；第三焊接温度精准闭环管控，瞬时高温不可传导至电芯本体，否则会破坏内部 SEI/CEI 膜、加速电解液分解，造成电芯热衰减；第四低阻抗设计，焊点厚度、熔深统一，减少回路电压压降，降低模组整体发热，提升能量转换效率；第五全模组焊点一致性，统一激光 / 超声焊接参数，各焊点温升、阻抗差值控制在极小区间，杜绝局部热点。量产主流采用超声波焊适配薄铝极耳，大容量模组选用激光焊提升熔接强度，焊接完成后同步配套绝缘覆膜、绝缘电阻复检，双重拦截焊接缺陷模组流入 PACK 工序。

Welding of sodium-ion batteries includes tab welding of single cells and series-parallel welding of module busbars, which directly determine the conductive reliability and safety threshold of modules, with five rigid specifications to be fully implemented. First, welding points shall be firm without cold solder or false welding, and the welding tension must reach the standard. Welding points shall not fall off during long-term charge-discharge cycles and transportation vibration to avoid module circuit break and shutdown failures. Second, welding points shall be flat without burrs or molten splashes. Aluminum metal scraps shall not be generated during welding to prevent scraps from falling into cells, piercing separators and inducing micro-short circuits, and tabs, separators and packaging aluminum plastic films cannot be burnt through. Third, welding temperature shall be precisely closed-loop controlled. Instant high temperature shall not be transmitted to cell bodies, otherwise the internal SEI/CEI films will be damaged, electrolyte decomposition accelerated and cell thermal decay triggered. Fourth, low impedance design with unified welding point thickness and penetration depth reduces circuit voltage drop, lowers overall module heat generation and improves energy conversion efficiency. Fifth, consistent welding points for the whole module with unified laser or ultrasonic welding parameters, and the temperature rise and impedance difference of each welding point are controlled within a tiny range to eliminate local hot spots. Ultrasonic welding is mainstream for thin aluminum tabs in mass production, while laser welding is adopted for large-capacity modules to enhance fusion strength. After welding, insulating film covering and insulation resistance re-inspection are carried out simultaneously to double intercept modules with welding defects before PACK procedures.