Lithium-ion batteries used in smartphones and other devices are susceptible to catching fire and even exploding if they begin to overheat, but a material inspired by the hydrogels found in nappies and contact lenses could reduce the risk.
The batteries used in many modern technologies each contain one or more lithium-ion cells, which can collectively generate a large amount of power. But the batteries are relatively fragile, and if one or more cells become damaged they can trigger a chain reaction that releases a battery鈥檚 power dramatically and dangerously in a process called 鈥渢hermal runaway鈥�. There have been incidents involving electric cars, smartphones and 聽catching fire due to faulty batteries.
Prior to thermal runaway it is preferential for each of the lithium-ion cells within a battery to conduct heat with its neighbours, helping to cool down any that may be approaching thermal runaway. But once the situation reaches a certain tipping point it would be desirable to instead isolate the dangerously hot cell so that its rising heat doesn鈥檛 jeopardise other cells.
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at Tsinghua University in Beijing and his colleagues have created a material that can be used to wrap individual cells and conducts heat well to maintain thermal equilibrium. At a certain temperature 鈥� which can be tweaked to suit different batteries 鈥� water trapped in the material evaporates and leaves a skeleton that instead insulates the cells from each other to prevent the situation worsening. The material is a hydrogel impregnated with tiny ceramic particles that can be formed into any shape to suit different battery designs.
Materials like aerogels have been used in the past to isolate cells in batteries, but they are permanent insulators and are expensive to manufacture. The researchers say that the new hydrogel material is cheap to make, and that they are already working with industry to add it to the safety features of new batteries.
Wu says that the problem of thermal runaway is a vital safety issue to solve. 鈥淲e鈥檙e very interested in the situation over battery safety, and considering that electric vehicles are growing so fast the problem is very, very important and immediate,鈥� he says. 鈥淚n mainland China we鈥檝e had at least 7000 cases of batteries catching on fire in accidents in only one year and it is rising dramatically. And, considering that in a global market this number can be doubled or even much more, this situation is very serious.鈥�
ACS Nano
