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Heat Shield

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Germany

Due to the growing energy density of battery systems in Electric Vehicle, the developers of lithium ion batteries must satisfy ever higher safety requirements. It is especially crucial to keep a single damaged cell from overheating the entire battery module. The goal is greater range without the battery growing in size and weight. If neighboring healthy cells also heat up due to the heat buildup, a chain reaction can result that, in the worst case, could lead the entire battery system to explode.
Heat shields between individual cells are designed so that the heat from a damaged cell remains insulated until it can be drained away. The heat shield has three key characteristics: 
1. Heat resistant: The shield itself consists of a heat resistant material, a silicone-based elastomer 
2. Outstanding heat insulation: It slows the heat transfer between the cells with a waffle-like structure – tiny pockets of air provide outstanding heat insulation. 
3. Minimum loss of energy density: The shield is very thin, with a maximum thickness of just 1 mm. The loss of the existing energy density due to the shield’s use is hardly noticeable.
The procedure for development of the heat shield involves mounting samples of the heat shield on a surface heated to 600° C and recording the temperature on its rear side with thermocouples. Series of tests have shown that temperatures significantly under 200°C occur on the rear side after 30 seconds. This will adequately protect a neighboring cell against the destruction of cathode material or the separator. The exact boundary values admittedly depend on a multitude of specific parameters such as the chemistry and geometry of the battery cells. Consideration has been given to the heat shield’s mounting. Since the air pockets adhere well to the smooth metallic surface of a prismatic cell (a suction effect) an individual shield can be precisely position. It would even be possible to expand the function of the heat shield with additional development steps. If this flexible formed part were extended over the top of the cell, it could enclose and seal the rupture disc located there. In case of overpressure in the battery cell, the rupture disc ensures that the resulting partially toxic gases escape in a controlled way. 

Benefits:
• It drains away heat from damaged cell efficiently.
• It increases battery efficiency.
• Safety is increased significantly with use of it.
• It could enclose and seal rupture disc over top of the cell.

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