Among the alkaline earth metal elements, calcium has the advantages of low polarization, standard electrode potential close to that of lithium, ion of +2 valence (the number of charges is twice that of lithium ion), abundant reserves, and low cost. Therefore, calcium-ion batteries have the potential to become efficient and low-cost energy storage batteries.
In 2016, researchers developed a new type of calcium ion liquid battery. Although its working voltage is not high (<1V), it shows good cycle stability at high temperature (550-700℃). Although the researchers did not find the reversible redox reaction of calcium ions at room temperature, they found that calcium ions in carbonate electrolytes can undergo reversible deposition reaction on the surface of the calcium negative electrode at 75-100 °C, and can cycle at 100 °C. 30+ weeks. However, in order to make calcium ion batteries practical, the operating temperature must be lowered to room temperature. It is necessary to find positive and negative electrode materials that can realize reversible calcium ion insertion/extraction and improve their electrochemical performance, including room temperature cycle characteristics, rate characteristics and Working voltage (currently < 2V).
The researchers proposed a new type of calcium ion battery, which uses tin foil as the negative electrode to undergo reversible alloying reaction with calcium ions, and adopts the integrated design of active material and current collector; and uses graphite as the positive electrode to realize the reversible intercalation/deintercalation of anions. Reaction; a carbonate-based solvent dissolved in calcium hexafluorophosphate and having 5V high voltage resistance characteristics is used as the electrolyte. The calcium ion battery has excellent electrochemical performance, the average discharge medium voltage is as high as 4.45V, and the capacity retention rate after 350 cycles at room temperature is greater than 95%.