Revolutionizing Energy Storage: How Old EV Batteries Can Fulfill China’s Energy Demands

Used electric vehicle (EV) batteries have the potential to fulfill two-thirds of China’s grid storage requirements by storing energy when renewable sources are plentiful and delivering power during peak demand periods.

During times when the wind isn’t blowing and the sun isn’t shining, the generation of renewable energy may decline, risking supply shortages, particularly during peak demand times in the mornings and evenings, as well as in winter. Typically, natural gas and coal plants compensate for this gap. Countries like China, the USA, the UK, and Australia are constructing large-scale battery-based grid storage solutions to harness renewable energy for later use.

As electric vehicle adoption rises, experts like Ma Ruifei from Tsinghua University argue that repurposed EV batteries can be integrated into the power grid, accelerating the transition to a carbon-neutral power system more affordably. Their research indicates that used batteries could meet 67% of China’s power grid storage needs by 2050, while simultaneously reducing costs by 2.5%.

EV batteries naturally degrade over time with repeated charging and discharging cycles and are often discarded once they reach about 80% of their original capacity. Although this degradation impacts the vehicle’s range and acceleration, it has minimal effect on grid storage applications, where multiple batteries are charged and discharged over extended periods.

“It still retains ample power, and when utilized for storage, its degradation is relatively slow,” says Gil Lacy from Teesside University, UK.

“Materials that are costly to mine and process for batteries should not be wasted when the cells still have 80% usable capacity,” asserts Rhodri Jarvis from University College London. “There’s significant interest in utilizing second-life battery packs, not only for cost reduction but also for enhancing sustainability.”

In a related study, researchers have drawn differing conclusions regarding whether energy storage using used batteries is more cost-effective than new lithium-ion batteries, whose prices are steadily decreasing.

However, with the increasing popularity of electric vehicles, used batteries may become a more economical option. Over 17 million electric vehicles are set to be sold in 2024, accounting for about 20% of global car sales, with nearly two-thirds being purchased in China.

The study projects that in a scenario where various battery chemistries are procured across China and utilized at 40% of their original capacity, second-life grid storage will grow significantly after 2030, as the demand for new batteries stabilizes. By 2050, total capacity is anticipated to reach 2 trillion watts.

In a contrasting scenario that relies solely on new batteries and pumped hydro storage (where water is pumped into a reservoir and released to drive turbines), the total capacity would only reach about half of this figure.

Second-life battery storage remains largely untested; however, US startup Redwood Materials has implemented a 63-megawatt-hour project using 10-year-old car batteries to power a data center in Nevada. The company claims its system is priced under $150 per kilowatt-hour and can deliver power for over 24 hours, exceeding the capabilities of new lithium-ion batteries.

Nonetheless, sorting and grouping used batteries by similar capacity levels is essential. If not, the management system must bypass individual batteries; otherwise, the group will cease to charge once the weakest battery reaches capacity.

Furthermore, damaged batteries need to be identified, and every several hundred cells must be equipped with temperature and voltage sensors. Overheating can result in significant fire hazards.

“The risks are obviously elevated, so ensuring safety, isolation, balance, and implementing robust risk-reduction measures is crucial,” Lacey emphasizes.