China's 120°C Test Will Define the World's 'Solid-State' Batteries

A 120°C furnace is about to become the world's gatekeeper for what can be labeled a "solid-state" battery, the next-generation cell that swaps a conventional lithium-ion pack's flammable liquid electrolyte for a solid one and promises higher energy density and safer operation.

On 21 August 2026, China's State Administration for Market Regulation (SAMR) said a Chinese-led proposal had been approved as a new work item at the International Electrotechnical Commission (IEC), the first international standards project in the solid-state battery field (news.metal.com). The proposal, titled "Application guide, test items and conditions for solid-state batteries for secondary lithium-ion batteries for electric vehicle propulsion," lands less than two months after China's own national solid-state standard took effect in July 2026.

The rule China is exporting is a single mechanical test. The Chinese national standard, which the IEC draft is built on, requires a cell to survive six hours at 120°C and lose no more than 0.5% of its mass (chinaevhome.com). Chinese validation data cited by SMM showed true all-solid-state samples under that 0.5% threshold, while mixed solid-liquid cells measured 1.68% to 10.33%, well outside the definition. Semi-solid chemistries, the kind several Chinese OEMs are scaling first, are explicitly excluded by the test.

That gate is more than a chemistry debate. It decides which factories, supply chains, and patent positions are eligible for the next battery cycle, and it is being placed at the center of a global drafting room: experts from France, Japan, and South Korea are participating alongside Chinese experts, per the SAMR announcement (news.metal.com).

What changes from here is the process, not the verdict. An IEC work item is the formal start of rule-writing, not a finalized standard. The proposal now moves through committee drafts, committee drafts for vote, and final draft international standard stages before publication, a multi-year track during which any participating national body can submit technical comments or competing definitions (scmp.com). The "China writes the rulebook" line in the wire headlines is therefore best read as "China wrote the first draft and is running the drafting meetings."

China's leverage to do that is recent and concrete. Chinese entities published 6,312 all-solid-state battery patents in 2025, roughly 44% of the global total, surpassing Japan's 3,331, according to figures cited by academician Ouyang Minggao. By March 2026, Chinese applicants held about 34% of more than 38,000 cumulative solid-state patents (evsays.com). On the standards side, the Chinese national standard took effect in July 2026, giving Chinese engineers a working template to bring to Geneva rather than an abstract proposal.

Japan and South Korea are not out of the game. Both countries retain strong core patents, particularly Toyota, with roughly 1,800 patent families around sulfide electrolytes, the chemistry most Chinese SSB roadmaps also depend on (evsays.com). During the comment period, that patent base gives Tokyo and Seoul real leverage to argue for sulfide-friendly test conditions or carve-outs, even if the procedural pen sits in Beijing.

The cost gap explains why the test is politically charged. Current solid-state cells are estimated to cost five to ten times conventional lithium-ion batteries, according to SMM-cited industry views (news.metal.com). A definition that excludes a cheaper semi-solid cell from "solid-state" labeling is a definition that protects the price premium of true all-solid-state designs, and the suppliers who reach them first. Ouyang Minggao's roadmap puts the first commercial generation at 200 to 300 Wh/kg graphite or low-silicon sulfide cells through 2027, 400 Wh/kg high-silicon sulfide by 2030, and 500 Wh/kg lithium-anode chemistry around 2035 (evsays.com). Mass production, he has said, is three to five years away.

The Chinese companies lining up to be measured against the gate are not running the same race. CATL is focused on the sulfide route, with a lab prototype above 500 Wh/kg, a small-scale pilot in 2027, and large-scale vehicle deployment after 2030. BYD disclosed six SSB patents in August 2026 and plans small-volume vehicle testing in 2027 with mass commercialization around 2030. Dongfeng has completed a 0.2 GWh pilot line and is targeting 50,000 SSB-equipped vehicle deliveries by 2027; FAW Hongqi completed an all-solid-state pack prototype in January 2026, with mass production deployment targeted at the end of 2027 (chinaevhome.com). The market forecaster EVTank projects global solid-state battery shipments of 607.2 GWh by 2030, up from 8.0 GWh in 2025, a compound annual growth rate of more than 130% (chinaevhome.com).

The watch item is whether the 120°C test survives the comment period intact, whether Japan and South Korea use the standards body's final-draft window to push sulfide-friendly revisions, and whether European and U.S. automakers, neither of which has a domestic cell champion of comparable scale, sign on to a definition their suppliers will have to meet. The furnace is on. The chemistry inside it is still being negotiated.