Sodium-ion batteries can be made using copper sulfide

Researchers from the Korea Advanced Institute of Science and Technology (KAIST) have developed a new strategy for extending sodium-ion batteries’ cyclability, using copper sulfide as the electrode material.

Published in the journal Advanced Science, their strategy has led to high-performance conversion reactions and is expected to advance the commercialisation of sodium-ion batteries as they emerge as an alternative to lithium-ion batteries.

Commercial lithium-ion batteries use intercalation-type materials, such as graphite, to serve as anode (negative electrode) materials that store and release lithium ions between planes of carbon atoms. But graphite anodes have not been viable for high-capacity sodium storage due to their insufficient spacing between the carbon atom layers to accommodate sodium ions. Conversion and alloying reaction-type materials have thus been explored to meet higher capacity in the anode part; however, those materials generally undergo large volume expansions and abrupt crystallographic changes, which lead to severe capacity degradation.

Led by Professor Jong Min Yuk, the KAIST researchers confirmed that semi-coherent phase interfaces and grain boundaries in conversion reactions play key roles in enabling pulverisation-tolerant conversion reactions and capacity recovery, respectively. They also uncovered a stable sodium storage mechanism using copper sulfide, an electrode material that is pulverisation-tolerant and induces capacity recovery.

While most conversion and alloying reaction-type battery materials experience severe capacity degradation, copper sulfides underwent a gradual crystallographic change to make the semi-coherent interfaces, which eventually prevented the pulverisation of particles. Based on this mechanism, the team found that copper sulfide exhibits a high capacity and high cycling stability regardless of its size and morphology.

Their findings suggest that when employing copper sulfide, sodium-ion batteries will have a lifetime of more than five years with one charge per a day. Furthermore, copper sulfide is cost-competitive as it is composed of abundant natural materials such as copper and sulfur — unlike lithium-ion batteries, which use lithium and cobalt.

“Employing copper sulfide can advance sodium-ion batteries, which could contribute to the development of low-cost energy storage systems and address the micro-dust issue,” Prof Yuk said.

Image caption: Professor Jong Min Yuk and his two PhD candidates.

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