Schematic model demonstrating grain boundaries and phase interfaces formations for copper sulfide anodes used in sodium ion batteries (Image source: KAIST)

The world keeps looking for cheaper, safer, longer lasting, and more powerful alternatives to lithium ion batteries. Commercial lithium ion batteries have been around since 1991 and have found applications powering everything from personal electronics, to electric vehicles (EVs), to electric power grids.

Sodium ion batteries have shown some promise—sodium ions replace the lithium ions as charge carriers inside the battery during charging and discharging. Sodium is significantly more available and cheaper than lithium. Sodium ion batteries could also be safer—they can be completely drained of their charge during shipping or storage, while lithium ion batteries need to maintain about 30% of their charge providing energy that could ignite a fire if the batteries are somehow damaged.

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.

To build viable sodium ion batteries, a search is on for materials that can achieve higher capacity in the anode. Most such materials unfortunately have large volume expansions and abrupt crystallographic changes when incorporating sodium ions, which lead to severe capacity degradation.

A team at the Korea Advanced Institute of Science and Technology (KAIST) has described in a news release their work using copper sulfide as an anode storage medium for sodium ion batteries. Professor Jong Min Yuk’s team confirmed the stable sodium storage mechanism using copper sulfide that is pulverized and that induces capacity recovery. According to the news release, “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. Even better, copper sulfide, composed of abundant natural materials such as copper and sulfur, has better cost competitiveness than lithium ion batteries, which use lithium and cobalt.”

According to Yuk, “Sodium ion batteries 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.”

As with so many battery research results, the replacement of lithium ion batteries with commercial sodium ion batteries does not seem like it will happen any time soon, despite the optimism of the Korean team. But progress is continuing and the incentive to improve upon lithium ion batteries is increasing almost daily as a move to further electrification of the transportation system and battery storage for the electric grid reaches primetime.

Senior Editor Kevin Clemens has been writing about energy, automotive, and transportation topics for more than 30 years. He has masters degrees in Materials Engineering and Environmental Education and a doctorate degree in Mechanical Engineering, specializing in aerodynamics. He has set several world land speed records on electric motorcycles that he built in his workshop.

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