Sumitomo Chemical targets 2028 for halide solid electrolyte mass production

Sumitomo Chemical has not disclosed conductivity data for the halide electrolyte pictured here, developed with Kyoto University and Tottori University

(Image courtesy of Sumitomo Chemical)

Sumitomo Chemical plans to begin mass production of a halide-based solid electrolyte for EV batteries in fiscal 2028, multiple reports indicate. Its research relationship with Kyoto University and Tottori University dates back to at least 2020. The company has not published conductivity data or a capacity target, so its performance claims remain company-stated rather than independently verified.

The performance case behind Sumitomo’s halide electrolyte

Sumitomo positions the new material as an alternative to sulphide and oxide electrolytes. Separately, competing manufacturers are already working toward solid-state battery commercialisation in the same 2027 to 2028 window, using distinct chemistries.

Sulphide-based electrolytes are widely regarded as the benchmark for ionic conductivity in solid-state batteries, a property that governs how fast a cell charges and discharges. Manufacturing them typically requires tightly controlled humidity, adding cost to production lines. That’s general industry context, not a comparison Sumitomo has made against its own data.

Sumitomo says its halide-based material, built around chlorine and other elements, is designed to achieve comparable performance. No specific conductivity figures have been published, so the claim stands as the company’s own characterisation. Sumitomo says battery manufacturers could partially reuse existing lithium-ion production equipment and settings, a claim the company has not independently verified with public data.

A research partnership with a longer history than this announcement

Sumitomo Chemical’s ties with Kyoto University and Tottori University did not begin with this month’s reports. Kyoto University and Sumitomo Chemical agreed to joint research on solid-type battery materials in 2020, and the three parties jointly developed a soft solid-type battery material in 2022, reaching roughly 230 watt-hours per kilogram without requiring external pressure.

That 2022 material is a different specific output from the halide-based electrolyte in the current reports. The current evidence confirms an ongoing research relationship between the three parties, not that this halide electrolyte descends from the 2022 work. The two announcements are related through that partnership, not confirmed as the same development line.

Where this timeline sits against Toyota and Nissan’s solid-state battery plans

Toyota’s own newsroom confirms it aims to commercialise all-solid-state batteries with Idemitsu Kosan in 2027 or 2028, using a sulfide-based solid electrolyte. That work is separate from Toyota’s cathode material partnership with Sumitomo Metal Mining. Sumitomo Metal Mining is a different company from Sumitomo Chemical, despite the shared name. Nissan’s own newsroom confirms it is targeting solid-state battery commercialisation for fiscal 2028, having reached required performance benchmarks in full-size prototypes.

Sumitomo Chemical’s fiscal 2028 target for the halide electrolyte sits in that same window. This is an editorial observation rather than a claim from any single source: three Japanese manufacturers are now pursuing three distinct solid-state battery chemistries on overlapping timelines, and none has yet published the independent data that would let readers compare them directly.

Sumitomo Chemical has not disclosed conductivity data, production capacity, or named customers for the halide electrolyte. Those gaps, more than the fiscal 2028 date, will determine whether the material becomes a genuine alternative to the chemistries Toyota, Idemitsu, and Nissan have already committed to on a similar timeline.

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