One of the types of batteries commonly used in electric vehicles is lithium-ion batteries, but due to collisions or other impacts on the car will cause the lithium-ion batteries to ignite or explode, and the shocks will cause internal short circuits in the electrodes. Due to "thermal runaway", small fires Will spread to the entire battery and other parts of the car.
Dr. Yu Zhu, Associate Professor of Polymer Science at the University of Akron, said: "Although everyone has made great efforts in battery thermal management, the recent accidents of fire and explosion of electric vehicle batteries are still worrying the public. In most In some cases, the battery will only catch fire if it is abnormally affected by external shocks or impacts. "
Dr. Yu Zhu worked with his team to improve the safety of lithium-ion batteries by creating a "shear thickening" electrolyte (a substance that becomes thicker under impact).
The electrolyte is placed between the positive electrode and the negative electrode, so that the positive electrode and the negative electrode can resist the impact, so that in any collision accident, the battery will not cause fire or explosion. Under normal circumstances, the new electrolyte will remain soft.
Dr. Yu Zhu said: "The positive and negative electrodes of lithium-ion batteries in electric vehicles are separated by a very soft film and a liquid electrolyte. It is still a very challenging task to replace only the liquid electrolyte with a solid electrolyte because The electrolytes are all porous and require liquid to fill the pores. Therefore, under normal circumstances, we still use electrolytes similar to liquids, but under impact, the liquid electrolyte can enhance its mechanical strength, so we developed shear Thicken the electrolyte. "
You can think of this electrolyte as a mixture of water and flour. When you slowly mix the flour and water with your hands, you will feel a trace of resistance. However, if you increase the stirring speed, you will obviously feel a lot of resistance. In fact, the bowling ball can bounce back on the surface formed by water and flour, and the surface composed of water and flour behaves like a solid under impact.
A liquid with this characteristic is called a dilatant and is a non-Newtonian fluid. If the electrolyte is also a kind of swell, it can prevent the battery from short-circuiting when it is subjected to external shocks. However, making a shear-thickening electrolyte can be much more difficult than mixing flour and water, because the composition of the electrolyte is very complex, containing different ions, solvents, and various additives.
Zhu said that in the preliminary study, we showed a modified low-cost glass fiber that can produce shear-thickening electrolytes, which are compatible with commercial lithium-ion batteries and exhibit very good impact resistance. Compared with traditional liquid electrolytes, such shear thickening electrolytes will not significantly reduce the performance of lithium-ion batteries.
When impacted, the electrolyte will immediately become a solid, and due to the shear thickening effect, it will generate more force to resist external impact. This solution can be used as a supplement to the external thermal management system of the battery pack, because the external thermal management system of the battery pack is often unable to cope with the sudden external shock of the battery.
In addition, Zhu said that this research can not only improve the safety of lithium-ion batteries, especially the safety of lithium-ion batteries used in electric vehicles, but also be used for other purposes, such as bulletproof energy storage devices.
The start of the shield machine refers to a series of work in which the shield machine is driven from the tunnel door to the undisturbed soil section by using the temporarily assembled pipe segments, Reaction Frame and other equipment of the working shaft. Reinforcement of the starting end, installation of shield machine, starting bracket, assembly of shield machine, installation of reaction frame, shield machine system debugging.
Starting Frame,Shield Launching Frame,Shield Starting Base Structure,Starting Base Frame
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