Calcium-ion batteries (CIBs) promise to solve the limitations of current lithium-ion technology. Unlike lithium, which experiences shortages due to high demand, calcium is abundant. It can also provide an electrochemical window comparable to that of lithium. 

However, CIBs have been held back by physical limitations, specifically the difficulty of maintaining stable performance over many charge cycles and the slow movement of ions through the battery. 

In a paper published in Advanced Science, researchers at the Hong Kong University of Science and Technology, in collaboration with Shanghai Jiao Tong University, detailed how they overcame these barriers using quasi-solid-state electrolytes (QSSEs).

The team, led by Prof. Yoonseob Kim of the Department of Chemical and Biological Engineering, designed redox-active covalent organic frameworks (COFs) rich in carbonyl groups. These frameworks act as highways for calcium ions.

Experimental data showed that Ca²⁺ transports quickly through the ordered pores of the COFs. At room temperature, the system achieved a Ca²⁺ transport capability of more than 0.53 and an ionic conductivity of 0.46 mS cm⁻¹.

When tested in a full-cell configuration, the technology demonstrated durability and power. The battery reached a reversible specific capacity of 155.9 mAh g–1 and proved it could last through long-term use, retaining over 74.6% of its capacity after 1,000 cycles at 1 A g–1. 

These metrics suggest that CIBs could eventually compete with current commercial batteries in fields ranging from electric vehicles to large-scale renewable energy grids.

HKUST Prof. Kim said:

"Our research highlights the transformative potential of calcium-ion batteries as a sustainable alternative to lithium-ion technology. By leveraging the unique properties of redox covalent organic frameworks, we have taken a significant step towards realizing high-performance energy storage solutions that can meet the demands of a greener future."

Read the full article here to learn more about the new calcium-ion battery technology.

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