WeLion New Energy and its semi-solid-state batteries

Most batteries today, including those in smartphones and electric vehicles, use lithium-ion technology, which relies on a liquid electrolyte to help lithium ions move between the battery’s electrodes during charging and discharging. While effective, this liquid is flammable, posing a fire hazard. Additionally, lithium-ion batteries have a limited energy density, meaning they can only store a certain amount of energy per kilogram of battery weight. This restricts how far electric vehicles can travel on a single charge. For example, today’s average lithium-ion battery pack in electric vehicles stores about 200 watt-hours per kilogram (wh/kg), which translates to a typical range of around 400 to 500 kilometers (250 to 310 miles) per charge.

Solid-state batteries replace the liquid electrolyte with a solid material, which can improve safety by eliminating the fire risk and potentially increase energy density. However, fully solid-state batteries are extremely difficult to manufacture at scale. WeLion New Energy, a Chinese company founded in 2016 and headquartered in Beijing, focuses instead on semi-solid-state batteries. These batteries use an electrolyte that is part liquid and part solid, offering a balance between manufacturability and performance. The company’s cofounders include Chen Liquan, a scientist at the Chinese Academy of Sciences who led China’s first all-solid-state battery development in 1988.

In 2023, WeLion partnered with Nio, a Shanghai-based electric vehicle (EV) manufacturer known for its battery-swapping technology, to release a semi-solid-state battery pack. This pack achieved an energy density of 360 wh/kg, significantly higher than the 200 wh/kg average for lithium-ion packs. This translated to a range of over 1,000 kilometers (621 miles) per charge. However, only about 200 of these battery packs were produced due to their high cost. Despite this, Nio continues to use them in its vehicles. WeLion has also applied its battery technology to power cargo ships and ferries through a subsidiary, demonstrating its versatility beyond passenger vehicles.

In 2025, WeLion’s engineers achieved a major milestone by developing a semi-solid-state battery with an energy density of 824 wh/kg during laboratory testing. This is more than three times the energy density of standard lithium-ion batteries available today. Such high energy density could enable electric vehicles to travel much farther on a single charge or allow smaller batteries to power larger vehicles. However, the article notes that laboratory results do not always translate directly to real-world performance, and details about the battery’s durability, such as how many charge cycles it can endure or how its capacity degrades over time, remain unclear.

China is the world’s largest emitter of carbon dioxide, with its transportation sector contributing around 10% of the country’s total emissions. Switching more vehicles to electric power could help reduce these emissions. Additionally, the carbon dioxide emissions from ships transporting goods along China’s waterways are projected to grow by about 25% this decade, reaching 18.7 million metric tons by 2030. Batteries that power electric ships could play a key role in reducing emissions in this sector, as they offer a cleaner alternative to diesel engines. WeLion is developing batteries specifically for this purpose, including two inland cargo ships expected to launch in October 2026 in Huzhou, eastern China.

Despite its progress, WeLion faces significant challenges in scaling up production of its semi-solid-state batteries and competing on cost. The company acknowledges that its batteries are currently more expensive than conventional lithium-ion batteries produced by larger competitors like CATL, a leading Chinese battery manufacturer. Another challenge is translating laboratory success into reliable commercial products. For example, while WeLion’s 2025 prototype showed high energy density, the article does not provide details on its lifespan or performance over repeated use. The company has not disclosed how many times the battery can be charged and discharged or how its capacity degrades over time, which are critical factors for real-world adoption.