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The City University of Hong Kong has developed a flexible antifreeze water zinc-manganese battery that can be used in the field of flexible electronic devices.

2019-03-29 来源:亚科官网
With the rapid development of flexible portable and wearable electronic devices, flexible water-based batteries have become the main research object of developing flexible energy storage devices due to their advantages of safety, non-toxicity, stable performance, high specific capacity and simple fabrication. Recently, Professor Zhi Chunyi from the City University of Hong Kong has prepared a flexible water-based zinc-manganese battery that can work in a low temperature environment of -20 °C by modifying the hydrogel electrolyte, which can be used in the field of flexible electronic devices.
Preparation method of Antifreeze battery
Referring to the traditional antifreeze battery, there are mainly two preparation methods. One is to use an ultra-high concentration of acid, alkali, and salt electrolyte to reduce the freezing point, but once such a high concentration of electrolyte leaks, it will cause corrosion and pollution. Another method is to use an ionic liquid as an electrolyte, which can effectively avoid the problem of freezing of the electrolyte at a low temperature. Unfortunately, the ionic liquid itself has the disadvantages of being flammable and toxic, and generally requires strict preparation of the battery. Complex production and packaging processes, but there are still huge security risks.
None of the above methods are suitable for preparing a flexible wearable antifreeze battery. The ideal antifreeze electrolyte should have the following characteristics: (i) low freezing point; (ii) non-toxic and harmless; (ii) good ionic conductivity at low temperatures; and (iv) flexibility and mechanical stability at low temperatures. Therefore, designing a highly efficient antifreeze hydrogel polymer electrolyte is of great significance for the development of flexible water-based batteries operating in low temperature environments.
Flexible antifreeze battery
In addition, the new chargeable and dischargeable zinc-manganese battery generally uses a neutral and non-corrosive zinc salt as the electrolyte, which is not only simple to manufacture, low in cost, but also safe, non-toxic, and high in capacity, effectively avoiding the risk of burning and explosive, which is a better choice for the preparation of flexible hydrogel-based energy storage. Therefore, in order to realize the flexible antifreeze battery, Professor Zhi Chunyi first designed an oil-water double crosslinked hydrogel based on ethylene glycol/polyacrylamide, which exhibits low freezing point and high ion conductivity. High salt tolerance and strong mechanical stability (~900% stretchable), the ether group introduced in the hydrogel matrix can form strong hydrogen bonds with free water molecules, which can effectively reduce the freezing point of the hydrogel. And maintaining a high conductivity ion rate; then applying it as a zinc ion battery polymer type electrolyte to prepare a flexible antifreeze water system zinc manganese battery. At the same time, in terms of battery assembly, they used a highly conductive carbon nanotube textile as the current collector of the electrode, and coated the hydrothermally synthesized manganese dioxide nanorod/carbon nanotube composite material on the surface as a flexible positive electrode, and a flexible negative electrode. Then, a nickel-copper alloy cloth is used as a current collector, and zinc is prepared by electrodepositing zinc on the surface thereof. The assembled flexible water-based zinc-manganese battery can still maintain a discharge capacity of 146 mA•h•g-1 at -20 °C, and the capacity retention rate is 72.54% of the initial capacity after 600 cycles.
Ordinary hydrogels will freeze and become brittle at -20 °C, which will not only stop the power supply of the battery, but also lose flexibility. In contrast, thanks to the flexible electrode and hydrogel design, the flexible antifreeze battery remains below freezing point. It exhibits excellent flexibility and can withstand extreme conditions such as repeated bending, heavy material pressure, hammering and ice water immersion at low temperatures, showing good mechanical stability and safety.
As for the application, the team first put the flexible antifreeze water zinc-manganese battery into the water, and then refrigerated to seal the battery into the ice cube. The "ice battery" can still supply power to the electronic watch stably, and then increase the output voltage after connecting in series. After that, the antifreeze battery can stably supply energy for LED lights, smart watches and cold light sheets, and exhibits broad application prospects for flexible electronic devices operating in a low temperature environment.
Edited by Suzhou Yacoo Science Co., Ltd.