China makes breakthrough in battery tech with rechargeable Ca-O2 batteries

Chinese scientists have developed a calcium–oxygen battery that is rechargeable for 700 cycles at room temperature, an article published in Nature on Wednesday said.

This innovative power source uses calcium as the anode and aligned carbon nanotube (CNT) sheet as the air cathode with a calcium-based solution as electrolyte.

Why is it a big deal?

The calcium-oxygen battery harnesses the chemical reactions made between metallic calcium, oxygen, and an electrolyte to store and release energy. Calcium is a rich divalent metal on the planet, making it an accessible and cost-effective material for battery technology. Additionally, calcium-oxygen batteries have the highest theoretical energy density among batteries based on metallic calcium, providing the potential for high energy storage. 

This kind of battery offers the potential for high energy density at a low cost. However, it has a poor electrochemical reversibility at room temperature. Meaning, scientists need to find the suitable electrolytes at room temperature and manage discharge products for practical implementation.

The Chinese team found an ionic liquid-based electrolyte that enables both reversible ion movement  – charging and discharging – and improved kinetics. This electrolyte makes the battery rechargeable at room temperature with impressive performance – being charged and discharged over 700 times in prototype tests.

The team also proved the batteries are flexible and capable of being integrated into the growing wearable tech industry.

(Cover: Screenshot of the article published on Nature on February 7, 2024.)