Battery Pack Thermal Runaway Prevention via Immersed Coolant and Barrier Liquid
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Solution Overview
Problem
Lithium-ion battery packs face safety issues due to uncontrolled thermal runaway, where heat generated can lead to neighboring cells overheating and potential fire or explosion, with existing solutions like silicone oil not effectively preventing further propagation of heat during thermal events.
Innovation Solution
A battery pack design that partially immerses a battery module in a coolant with a vaporization starting temperature between 70°C and 200°C, covered by a barrier liquid, which is immiscible and non-volatile below 200°C, to absorb and dissipate heat rapidly during thermal runaway, preventing propagation and reducing fire risk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If silicone oil is used to immerse the battery pack to isolate air and reduce fire possibility, then fire risk is reduced, but the heat generated during thermal runaway heats up the silicone oil to above 200°C, causing it to become a heat source that accelerates thermal runaway propagation
Solution Approach 1:
The patent changes the key parameter of the insulating liquid from high flash point (silicone oil above 200°C) to low flash point (fuel below 100°C). This parameter change transforms the liquid's behavior during thermal runaway: instead of becoming a heat source that accelerates propagation, the low flash point fuel vaporizes first, creating a protective vapor layer that isolates the battery cells from external oxygen and slows down thermal runaway propagation.
Solution Approach 2:
The patent converts the potentially harmful low flash point characteristic into a beneficial protective mechanism. The low flash point fuel, when exposed to thermal runaway heat, vaporizes and forms a protective atmosphere around the battery cells. This vapor layer acts as a physical barrier that prevents external oxygen from reaching the cells, thereby converting what could be a fire hazard into a protective measure that slows thermal runaway propagation.
2Reliability
If a coolant with low vaporization temperature is used to absorb heat during thermal runaway, then thermal runaway propagation is delayed, but the coolant may evaporate too quickly under normal operating conditions, leading to loss of coolant
Solution Approach 1:
The patent introduces a second liquid (high flash point insulating liquid) as an intermediary substance that forms a protective layer over the low flash point fuel. This intermediary layer acts as a barrier that prevents the fuel from direct contact with air, thereby preventing premature evaporation during normal operation. During thermal runaway, when temperature exceeds the fuel's flash point, the fuel vaporizes to provide protective vapor atmosphere, while the insulating liquid layer continues to provide physical containment.
Solution Approach 2:
The patent creates different functional zones within the liquid system: the low flash point fuel provides thermal protection through controlled vaporization at high temperatures, while the high flash point insulating liquid provides physical containment and prevents premature evaporation at normal temperatures. Each liquid performs its specific function in its optimal temperature range, achieving both thermal runaway prevention and coolant retention.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The described solution effectively delays or prevents thermal runaway propagation by using the high vaporization latent heat of the coolant and the sealing properties of the barrier liquid, maintaining the battery pack at a lower temperature and reducing the risk of fire, while also providing a flame-retardant and insulating environment.
Implementation Method 1
the heat generated by the battery pack is conducted to the battery box through the coolant
Implementation Method 2
the coolant is vaporized rapidly, and the generated heat in the thermal runaway is taken away by using the high vaporization latent heat
Implementation Method 3
the generated heat in the thermal runaway is taken away by using the high vaporization latent heat
Implementation Method 4
The density of the barrier liquid is less than the density of the coolant, and the barrier liquid and the coolant are immiscible. The barrier liquid is suspended above the coolant
Data Source
AI summary
A battery pack relating to the field of batteries includes a battery module, a coolant and a battery box. The battery module and the coolant are disposed in the battery box. The battery module is at least partially immersed in the coolant. A sealing layer containing a barrier liquid is covered on the coolant. The heat generated by the battery cell which occurs thermal runaway is taken away rapidly by using the vaporization latent heat of the coolant, to thereby avoid heat accumulation and prevent propagation of thermal runaway among battery cells, thereby protecting the safety of the battery pack.