Solid-state batteries: where the field actually stands
The best demonstrated cell reaches 410 Wh/kg against 250 for conventional Li-ion — but conventional packs cost $115/kWh, and solid-state has to ride that curve down. No solid-state cell is in a series-production vehicle yet.
Solid-state batteries carry four metrics and 8 milestones here. It is a field defined less by whether the chemistry works than by whether it can get cheap enough to matter.
Energy density is the frontier number because it sets range and weight. QuantumScape's QSE-5 lithium-metal cell leads at 410 Wh/kg (about 844 Wh/L) as a sample cell. Samsung SDI's sulfide all-solid cells, Toyota's sulfide target for 2027–28 and CATL's EV solid-state roadmap all sit around 400 Wh/kg, with CATL's announced 'condensed' semi-solid cell rated near 500. Conventional NMC lithium-ion tops out around 250–300. Read the fine print the tracker attaches to each figure: lab and sample cells beat production cells, and every number here is labelled by stage.
Fast charge is the second promise, and it is the one to hold most loosely. Toyota claims a 10-minute 10→80% charge, Samsung SDI targets 12 minutes, QuantumScape's QSE-5 does 15 minutes at 4C, against roughly 30 for a typical EV pack. But the best conventional LFP fast-chargers already approach 10 minutes, so this metric is read as a claim or target until verified in production packs rather than as a settled advantage.
The metric that governs the field is cost. The volume-weighted average lithium-ion pack price was $115/kWh in 2024, down from a $150 average in 2022. Below roughly $100/kWh, EVs approach price parity with combustion. Solid-state cells start far above that line and must ride it down — which is why a 40% density advantage does not automatically translate into a market. Research output is heavy at about 7,632 papers a year, well ahead of most fields on this tracker, which is what a chemistry problem looks like before it becomes a manufacturing problem.
Progress has been steady and unspectacular. Samsung SDI began running a dedicated sulfide pilot line in 2023, the first major maker to move from lab to pilot production. QuantumScape shipped QSE-5 B-samples to automotive customers for qualification in 2024, a step from prototype toward a product. CATL announced its ~500 Wh/kg condensed cell in 2023, initially aimed at aviation.
2026 brought validation rather than production. Honda R&D signed a multi-year joint research agreement with QuantumScape after completing a hands-on technology evaluation — a second major automaker alongside VW's PowerCo, though both sides stress development and manufacturing scale-up rather than commercial production. ProLogium agreed to a $3.8B SPAC merger, billing itself as the only company able to publicly demonstrate a solid-state mass-production line; it opened a GWh-class gigafactory in Taoyuan in 2024, has shipped over 800,000 cells, and is building a Dunkirk plant backed by roughly €1.4B in French subsidies. Toyota and Idemitsu continue scaling sulfide electrolyte production, the supply step that gates a 2027–28 launch.
Two milestones remain locked: first solid-state cells in series-production vehicles, targeted around 2027 by Toyota and Samsung SDI, and solid-state at automotive scale and cost around 2030. Both are still ahead.