The Lab Battery Hit 824 Wh/kg. Turning It Into a Car You Can Buy Is the Hard Part.

The battery industry's holy grail isn't hard to describe: a cell that holds far more energy, never catches fire, and costs about the same as what goes into cars today. A Beijing company named WeLion New Energy thinks it's getting close — though by its own account, the finish line is still measured in years, not months.

Why semi-solid-state matters

Today's lithium-ion batteries rely on a flammable liquid electrolyte to shuttle ions between electrodes — the same liquid behind the fire risk that has dogged EVs, phones, and grid installations. Fully solid-state cells swap that liquid for a solid material, which would boost both energy density and safety, but they remain brutally difficult to manufacture at scale.

WeLion has taken the middle path: semi-solid-state cells with a part-liquid, part-solid electrolyte. It's a compromise, but a productive one. According to MIT Technology Review's profile, the company's 2023 battery pack — built with Shanghai EV-maker Nio — reached an energy density of 360 watt-hours per kilogram, against roughly 200 wh/kg for a typical lithium-ion pack today. That translated to a claimed range of more than 1,000 kilometers. The catch: only about 200 of those packs were ever made, because production was expensive. WeLion says Nio is still using them.

More recently, the company's engineers tested a semi-solid-state cell that hit a reported 824 wh/kg — more than triple the density of a standard lithium-ion battery, per the report.

The caveats

Lab results are not products. WeLion declined to share key details about the 2025 prototype — how many charge cycles it survives, how capacity degrades over its lifetime — and the company says commercialization is far off. It also acknowledges a blunt cost problem: its semi-solid-state batteries cost more than conventional lithium-ion cells from giants like CATL, which have scale WeLion can't yet match.

The company's near-term roadmap reflects that reality. Per the profile, WeLion plans a drone battery at 410 wh/kg before the end of this year and its first all-solid-state car battery — rated 400 wh/kg — in 2027. This month, two inland cargo ships running on its batteries are scheduled to launch in Huzhou, each carrying battery packs near 4,000 kilowatt-hours, enough for 250 kilometers of sailing, the company says.

Why it matters beyond cars

MIT Technology Review flags the decarbonization math: transportation accounts for roughly 10% of China's carbon emissions, and emissions from vessels moving goods along the country's inland waterways are projected to grow about 25% this decade, reaching 18.7 million metric tons by 2030. Electric ships on WeLion-powered routes would eat directly into that.

The company currently runs 11 gigawatt-hours of annual manufacturing capacity across four Chinese plants, with two more facilities — another 18 GWh combined — under construction. Scaling up semi-solid-state production cheaply enough to compete in a crowded battery market remains, as the report puts it, WeLion's defining challenge.

Written by the BidAsk Newsroom. Based on reporting from the sources below.