With the continued explosion of Samsung's Note7 cell phone explosion, mobile phone hardware security issues have also aroused public concern. “Why does the explosion of electric vehicles and mobile phones happen? Because of the characteristics of lithium-ion batteries, it has a certain safety risk.†Recently, Zhang Ning, a doctoral student at the School of Chemistry of Nankai University, designed a new cathode material and electrolyte for “water zinc ion†batteries. The performance, safety, and stability of zinc-ion batteries have been greatly improved and improved. Related scientific research results have been published in the American Chemical Journal, a leading journal in materials and chemistry. The result is now patented.
Zhang Ning introduced that lithium-ion batteries have been widely used in people's production and life. However, due to lithium ions shuttled between the positive and negative electrodes, it is easy to form acicular metallic lithium on the surface of the negative electrode, namely "Lithium dendrites", thus piercing the diaphragm. The internal short circuit, together with the use of flammable organic electrolytes, greatly reduces the safety of lithium batteries. In addition, the lack of lithium resources and uneven distribution (mainly concentrated in South America), so that lithium-ion battery prices continue to rise, which is not conducive to its application in the field of large-scale energy storage. However, zinc resources are rich and cheap. At the same time, there are no flammable or explosive hazards in the aqueous electrolyte. Its characteristics are suitable for large-scale energy storage systems, such as smart grids. Therefore, Zhang Ning will be targeted for water-based zinc-ion batteries.
The battery system is generally composed of a positive electrode, a negative electrode, and an electrolyte. Zhang Ning and his team used the low temperature solution method to successfully synthesize a cation-defective ZnMn2O4 as a positive electrode, and for the first time used a high-concentration large-scale anion electrolyte, zinc trifluoromethanesulfonate (Zn) for the first time. (CF3SO3)2). Due to the unique structure and electrolyte characteristics of the positive electrode material, the cycle stability of the zinc ion battery is greatly improved. After 500 cycles, the capacity retention rate is as high as 94%, the Coulomb efficiency is 100%, and rapid charging and energy “zero waste†are realized.
The use of zinc ion batteries can not only improve battery performance, safety and stability, but also reduce costs. It is understood that the current market price of metal zinc is about two US dollars per kilogram, while the metal lithium price is about 300 US dollars per kilogram; from the annual output point of view, annual output of metal zinc is about 5 million tons, while the annual output of metallic lithium is only about 4 Ten thousand tons. Zinc resources are cheap and readily available, and are more suitable for large-scale use in production practices.
However, this water-based zinc ion battery still has certain problems. Zhang Ning frankly stated that this battery cathode material has a low energy density, which is about half that of lithium-ion battery cathode materials. Therefore, it is currently more suitable for large-scale energy storage systems. Not suitable for mobile phones and other portable electronic devices. "Future work can focus on developing high-voltage, high-capacity cathode materials to increase the energy density of the battery," said Zhang Ning. (Reporter Hu Chunyan)
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