As the world transitions toward cleaner, renewable sources of energy, lithium-ion batteries have become increasingly important. These batteries do everything from power electric vehicles to store the electricity generated by solar arrays and wind farms. 

However, figuring out what to do with batteries that have outlived their usefulness has become a growing challenge. 

Researchers in China believe they have identified a solution. By injecting battery cells with an electrolyte solution that contains lithium ions, they restored the usefulness of spent batteries, allowing them to hold nearly as much charge as a new battery, according to Scientific American.

The researchers compared the process to providing a sick human with intravenous fluids. 

"If we can give an injection to a sick person to help them recover, why can't we have a magic potion for drained batteries, too?" asked Yue Gao, a chemist at Fudan University in Shanghai, per Scientific American.

A lithium-ion battery typically is considered "dead" when it can't hold 80% of its original charge, which typically takes 8-10 years or 2,000 charges. Sometimes such batteries can be given new lives in different applications that require lower energy output, such as providing storage for solar-generated electricity.

Often, however, spent batteries are ground into "black mass" that then can be harvested for reusable materials such as lithium and graphite, according to Scientific American.

By injecting spent battery cells with the lithium-ion electrolyte fluid, the researchers were able to restore batteries to 96% capacity, the study found. These batteries remained operational for as long as six times the typical lifetime of a lithium-ion battery, or about 12,000 charge-discharge cycles. 

As EVs and renewable energy become more prevalent, the number of spent lithium-ion batteries is expected to skyrocket. As a result, figuring out how to properly dispose of — and recycle — these batteries has become a top priority. 

"The demand for lithium-ion batteries, especially for EVs, is rapidly increasing," according to a report by the U.N. Development Programme. "By 2030, global demand is projected to reach 4,700 gigawatt-hours with over 80% driven by the EV sector. 

"By 2040, the volume of end-of-life lithium-ion batteries is expected to reach 20,500 kilotons, emphasizing the need for effective waste management strategies."

Therefore, extending the life of and properly disposing of lithium-ion batteries will be key to the success of any cleaner-energy future. 

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"The team's work is revolutionary because it provides a new idea to reuse end-of-life batteries," said Jiangong Zhu of Shanghai's Tongji University, who was not involved in the study, per Scientific American.

However, with battery-replenishing technology still early in its development, the researchers have acknowledged that several hurdles remain to be overcome. For example, the study only tested the lithium-ion injections on a single-cell battery; large batteries, such as those in EVs, can contain hundreds or even thousands of cells.

Still, the team envisions a future wherein battery-rejuvenation stations are widely available, allowing EV drivers to periodically restore their lithium-ion batteries. With lithium-ion batteries accounting for as much as 40% of the cost of a new EV, the ability to restore spent batteries could save consumers considerable amounts of money, as well.

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