Solid-State Batteries: What Still Has to Work?
A solid-state battery prototype can make an impressive journey. What still has to work before the battery becomes a dependable product for everyday electric cars?
This video explains ions and electrons, liquid and solid electrolytes, hybrid cells and lithium-metal anodes. It follows the evidence from the 2011 LGPS milestone through laboratory charging and endurance results, BMW and Mercedes vehicle tests, Honda production engineering and Idemitsu material scale-up.
Charging conditions, calendar ageing, pack pressure, factory yield and delivered cost all matter. QuantumScape QSE-5 uses a solid ceramic separator with liquid catholyte; Toyota and Idemitsu’s 2027–2028 ambition remains a target. The October 2026 PowerBlock announcement concerns a data-centre reference design.
Company results are attributed, unknown conditions remain unknown, and the closing checklist asks what would demonstrate repeatable customer readiness. Sources and publication dates are documented in the accompanying fact sheet.
Educational documentary. Not financial or investment advice.
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Sources and credits
Photo credits (Wikimedia Commons)
- Stuttgart panorama, 15 April 2009; geographic context only, label capture date: Thomas Wolf (Der Wolf im Wald), CC0 - https://commons.wikimedia.org/wiki/File%3APanorama_Stuttgart.jpg
- Denmark–Sweden Öresund bridge roadway, 16 August 2011; geographic context only, label capture date: Ypsilon from Finland, CC0 - https://commons.wikimedia.org/wiki/File%3AOresund_bridge_2011.jpg
- Malmö Central Station area, 13 June 2024; destination context only, label capture date: Jin Zan, CC0 - https://commons.wikimedia.org/wiki/File%3AMalm%C3%B6_C_och_domstolsbyggnad%2C_Malm%C3%B6%2C_13062024.jpg
- Munich, Theatinerkirche exterior, 2 February 2024; city context only, label capture date: Wilfredor, CC0 - https://commons.wikimedia.org/wiki/File%3AExterior_of_Theatinerkirche%2C_Munich.jpg
Primary sources
- S1 — Noriaki Kamaya, Kenji Homma, Yuichiro Yamakawa and colleagues, A lithium superionic conductor, Nature Materials, 31 July 2011. https://www.nature.com/articles/nmat3066; https://doi.org/10.1038/nmat3066. Abstract opened: conductivity and room-temperature condition confirmed. Subscription full text was not needed for this narrowly used figure.
- S2 — Xia Hu, Zhijia Zhang and colleagues, External-pressure–electrochemistry coupling in solid-state lithium metal batteries, Nature Reviews Materials, 2 April 2024. https://www.nature.com/articles/s41578-024-00669-y?error=cookies_not_supported. Initial DOI request failed; publisher abstract reached on retry. Fabrication/stack distinction and pressure effects confirmed. No fabricated quantitative pressure recommendation.
- S3 — Elif Pınar Alsaç, Douglas Lars Nelson and colleagues, Characterizing Electrode Materials and Interfaces in Solid-State Batteries, Chemical Reviews, online 4 February 2025. https://doi.org/10.1021/acs.chemrev.4c00584; https://pubmed.ncbi.nlm.nih.gov/39903474/; https://pmc.ncbi.nlm.nih.gov/articles/PMC11869192/. ACS returned 403; the authors' abstract and open paper were reached through PubMed/PMC. Author name corrected during checking. Contact loss, interphase reactions and lithium-growth discussion checked; no numerical claim from this paper used.
- S4 — Volkswagen Group / PowerCo, PowerCo confirms results: QuantumScape's solid-state cell passes first endurance test, 3 January 2024. https://www.volkswagen-group.com/en/press-releases/powerco-confirms-results-quantumscapes-solid-state-cell-passes-first-endurance-test-18031.; release is not independent fleet data.
- S5 — QuantumScape, Releases Next-Generation Solid-State Battery Separator Equipment, Cobra, 5 December 2024. https://ir.quantumscape.com/news-releases/news-release-details/quantumscape-releases-next-generation-solid-state-battery.
- S6 — BMW Group, BMW Group and Solid Power are testing all-solid-state battery cells in a BMW i7, 20 May 2025. https://www.press.bmwgroup.com/usa/article/detail/T0450262EN_US/bmw-group-and-solid-power-are-testing-all-solid-state-battery-cells-in-a-bmw-i7.
- S7 — Mercedes-Benz, Long-distance test successfully completed: EQS with solid-state battery covers 749 miles on a single charge, 9 September 2025. https://media.mbusa.com/news/long-distance-test-successfully-completed-eqs-with-solid-state-battery-covers-749-miles-on-a-single-charge. Source's production enthusiasm is not adopted as proof of fleet readiness.
- S8 — Idemitsu Kosan, Final Investment Decision and Construction Start for Large Pilot Facility for Solid Electrolytes, 29 January 2026. https://www.idemitsu.com/jp/news/2025/260129_en.pdf. PDF pp. 1–2 checked: decision, construction, Chiba location and 2027–2028 target confirmed.
- S9 — Honda, Honda Unveils Demonstration Production Line for All-Solid-State Batteries Located in Sakura City, Tochigi Prefecture, Japan, 21 November 2024. https://hondanews.com/en-US/releases/honda-unveils-demonstration-production-line-for-all-solid-state-batteries-located-in-sakura-city-tochigi-prefecture-japan. Line description checked: 27,400 m² total floor area, planned January start, roll pressing and cost/process verification. Plans retain future/attributed language.
- S10 — QuantumScape, 2025 Form 10-K, filed 25 February 2026. https://ir.quantumscape.com/static-files/26bac171-b3b6-425d-8b9e-bf2c7d0d4040. Glossary and pp. 8–10 checked for ceramic separator, liquid catholyte and scale-up consistency risks. Liquid catholyte confirmation prevents mislabelling as all-solid-state.
- S11 — QuantumScape, Q4 2025 shareholder letter, 11 February 2026. https://ir.quantumscape.com/static-files/298db199-d53c-4b90-bf9e-e1fd2a5df11a. Pages 2–3 checked for inauguration and line purpose; licensing partners' gigawatt-hour scale remains an objective.
- S12 — QuantumScape, QuantumScape Announces QS PowerBlock for In-Rack Energy Storage in AI Data Centers, 8 October 2026. https://www.quantumscape.com/quantumscape-announces-qs-powerblock-for-in-rack-energy-storage-in-ai-data-centers/. Final limitation paragraph checked: controlled prototype tests and modelling; no vehicle-readiness inference.
- S13 — Idemitsu Kosan, A pole-raising ceremony was held for the construction of Large pilot facility solid electrolytes, 20 May 2026. https://www.idemitsu.com/en/news/index.html; https://www.idemitsu.com/jp/news/2026/260520.pdf. Release-list entry and original Japanese PDF opened on 13 October 2026. The release date is 20 May; ceremony took place 13 May.
- S14 — US Department of Energy Office of Science, DOE Explains...Batteries, undated explanatory page. https://www.energy.gov/science/doe-explainsbatteries. Chemical energy, ions inside/electrons outside and reversible-cycle explanation. Supporting general mechanism only; no dated product claim.
- S15 — DOE/EPRI, 2013 Electricity Storage Handbook in Collaboration with NRECA, July 2013, lithium-ion section. https://www.energy.gov/sites/prod/files/2013/08/f2/ElecStorageHndbk2013.pdf. Ion-conducting/electron-blocking separator mechanism; no historical market-size forecast adopted.
Not regulated financial advice.