High-power and long-life aqueous potassium 2000mah 18650 battery developed successfully

Recently, Jiang Liwei, a doctoral student at the Institute of Physics, Chinese Academy of Sciences/Key Laboratory of Clean Energy, Beijing National Research Center for Condensed Matter Physics, under the guidance of researcher Hu Yongsheng and associate researcher Lu Yaxiang, used manganese-rich potassium-based Prussian blue with iron partially replacing manganese as the positive electrode, organic dye perylene brilliant purple red 29 (PTCDI) as the negative electrode, and 22 mol/L potassium trifluoromethanesulfonate aqueous solution as the electrolyte, and successfully constructed an aqueous potassium ion 2000mah 18650 battery. The research results were recently published in Nature-Energy.

Aqueous alkali metal ion batteries have become one of the emerging candidate systems for grid energy storage due to their inherent safety. However, due to the dissolution of many electrode materials in water and the narrow voltage window of traditional aqueous electrolytes, the choice of electrode materials in aqueous batteries is greatly limited.

For the positive electrode, the manganese-rich potassium-based Prussian blue material has become the first choice for the positive electrode material of aqueous potassium ion batteries because it is stable in water and has the advantages of high voltage and high capacity. However, it has serious dissolution problems when circulating in low-salt concentration electrolytes. The researchers found that after using a high-salt concentration 22mol/L potassium trifluoromethanesulfonate aqueous electrolyte, the dissolution of the electrode was greatly reduced, but the voltage and cycle attenuation phenomenon still existed. The study further found that by partially replacing manganese with iron, the material dissolution can be reduced and the cycle performance can be greatly improved. Through further optimization, the new battery positive electrode material has almost no voltage and capacity attenuation in the first 40 cycles.

Because there are very few negative electrode materials that can be used for aqueous potassium ion batteries, this study used the organic dye PTCDI as the negative electrode for the first time, and found that PTCDI has a high potassium storage capacity and good rate performance in 22mol/L potassium trifluoromethanesulfonate electrolyte. The relevant electrolyte not only has a wide voltage window and high conductivity, but also because there is little free water in the high salt concentration electrolyte, it can inhibit the dissolution of the positive and negative electrode materials, so that the 2000mah 18650 battery has the characteristics of high voltage, wide temperature range, high power, and long life.

The assembled aqueous potassium ion 2000mah 18650 battery can operate in the voltage range of 0V~2.6V, with a theoretical energy density of 80Wh/kg and a life of more than 2000 times (retention rate of 73%). The researchers also assembled an aqueous potassium ion soft pack battery and demonstrated the good low rate and high and low temperature performance of the soft pack battery.

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