今天花费了许多研发，试图使锂离子细胞更安全。有些化学本质上比其他化学更安全。例如，铁磷酸锂（LFP）细胞使用化学稳定的LFP，它不会表现出金属氧化物锂离子细胞所经历的能量热失控。
但是，处理和处理单元格时必须始终要小心。测试细胞时，测试的目标可能是在压力条件下（例如温度极端或高电荷/排放速率）评估细胞性能。在这种压力测试期间，必须注意监测热失控的开始的迹象，然后继续采取适当的措施。
什么是热失控？
First, what is thermal runaway? Thermal runaway in a cell occurs when the cell internal temperature gets high enough to ignite the electrolyte, which is an organic liquid. Once the electrolyte is ignited, the oxide material in the cathode will break down and release oxygen. Now, in the damaged cell you have fuel (liquid organic electrolyte) and oxygen (from the oxides in the cathode)—ingredients for a fire that can generate its own oxygen, making it extremely difficult to extinguish（见图）。
For thermal runaway to start, enough heat must be generated in the cell to ignite the electrolyte. Normally, this happens because of damaged separator material. The thin poly-plastic material can be damaged by improper manufacturing or being punctured by metallic dendrite growth.
If the separator is punctured by a dendrite, the dendrite shorts the electrodes together. Current can freely flow as the anode and cathode come in contact through a short circuit where the damaged separator no longer keeps them apart. As current flows, heat is generated in the internal short and thermal runaway begins. More heat means more separator damage as the separator melts. More damage means more internal shorts, and more shorts mean more heat. Eventually, this heat can grow to the point where it ignites the electrolyte. The heat also causes the breakdown of the oxides in the cathode, which releases oxygen to feed the fire of the burning electrolyte.
结束热失控
安全系统可以安装在实验室或制造业中，基本上可以在何处进行热失控的启动。安全系统包括气体/氧气剥夺和水。更常见的气体系统包括二氧化碳，氩气或氮。
有了这些系统，想法是用不含氧气的气体淹没该区域，因此使任何东西都难以燃烧。问题是，由于受损的细胞会产生自己的氧气，因此这些系统不会熄灭电池火。气体系统可能会防止火力传播到附近的易燃材料（电线，架子，塑料存储容器等）。
Water, on the other hand, works differently. Instead of trying to deny oxygen to the fire, water is applied to the cell to drop the cell temperature. The goal is to remove the heat to ensure electrolyte doesn’t burn as fuel and further oxygen isn’t released. Of course, a side benefit of water is that it will also stop nearby materials from burning. So, water is commonly used, even though it creates quite a mess as it’s sprayed onto a burning test setup.
防止热失控
管理热失控的最佳方法是防止其启动。
首先，应使用高质量的材料和精心控制的组装过程制造细胞，以避免分离器缺陷。确保对电极和分离器的正确比对将防止堆栈边缘（在小袋细胞中）或果冻（在棱柱形和圆柱形细胞中）周围的短裤。
在充电或放电,它是至关重要的nsure that cells aren’t overcharged or over-discharged, which can cause plating and internal shorts. By continuously monitoring cell open-circuit voltage, this will ensure cells remain within their safe operating range. By continuously monitoring the amp-hours of energy put into the cell, it will ensure too much charge isn’t pushed into the cell, which will cause overcharging.
这些电气极限很容易通过正确设计的电池测试设备来管理，如果电池测试设备检测到不正确的电参数，可以立即停止充电或排放。这样的参数包括电压太高，电压太低，泵入电池的能量过多（放大器小时）或损坏的导线，这可能会导致测量误差，从而掩盖了对过度充电或过度充电的准确检测。有关预防细胞过度充电的其他信息，请查看文章“防止过度充电锂离子细胞。”
Also during charging or discharging, cell temperature should be monitored. It’s to be expected that cell temperatures will rise during high-rate charging and discharging. When these high-rate charge/discharge steps are applied during elevated environmental temperature, it may be difficult to detect that the cell is getting too hot until it’s too late. Setting a proper thermal threshold would allow an alarm signal to be tripped and appropriate action taken before the onset of thermal runaway.
一旦绊倒热极限，适当的动作应包括立即终止所有电活动；即，立即停止充电或排出细胞。即使在施加电流停止后，电池的温度也应继续受到监测。如果温度继续升高，则应立即将细胞移至水箱中以冷却细胞。或者，可以激活洒水装置以降低细胞以降低温度。
这些动作将使细胞热量保持足够低，以防止分离器熔化，电解质点火和从阴极的氧化物涂层中释放出氧气。
鲍勃·佐洛（Bob Zollo）是电池测试的解决方案架构师，电子工业解决方案组，Keysight Technologies。
