Hyundai files U.S. patent application to use copper in solid-state batteries

Hyundai secures U.S. patent

Hyundai has officially filed a U.S. patent that introduces a novel use of copper in sulfide-based solid-state batteries, addressing long-standing challenges with conductivity and cost. Traditionally, copper has been avoided in these designs because sulfides are highly corrosive and cause rapid degradation.

Automakers have instead relied on nickel or stainless steel, but both are significantly more expensive and less conductive. This development signals Hyundai’s intent to improve battery efficiency while reducing production costs.

Protective coating on copper

Hyundai’s patent explains that the company has engineered a protective coating designed to make copper survive in the harsh environment of sulfide electrolytes. This protective layer reduces corrosion, improves adhesion between materials, and extends the usable life of the copper component.

By shielding copper from chemical attack, the coating ensures the material retains its superior conductivity throughout battery use. This innovation enables copper to operate reliably across many charging and discharging cycles.

Six-layer battery structure

The patent outlines a six-layer stack—copper anode current collector → protective coating → anode → sulfide electrolyte → cathode → terminal collector—to keep copper stable against the sulfide electrolyte.

Reports note that the layering allows each section to reinforce the overall performance while safeguarding weak points. Hyundai’s design demonstrates a practical way of incorporating copper without sacrificing durability.

Why copper matters

Copper is highly valued because it offers superior electrical conductivity compared to stainless steel or nickel, making it more efficient in transferring energy. According to Carbuzz, recent commodity pricing shows copper typically trades well below nickel, supporting a potential materials-cost advantage for copper-based designs.

Copper is already an essential component in today’s lithium-ion batteries, where it plays a critical role in performance. Bringing it back into solid-state battery designs could provide both technical and financial advantages.

Problems with other metals

Until now, sulfide-based solid-state batteries have used nickel alloys or stainless steel as alternatives to copper, despite their shortcomings. While these materials offer strong resistance to corrosive sulfides, they introduce trade-offs by reducing electrical conductivity.

Lower conductivity results in slower charging speeds, reduced efficiency, and increased production costs for automakers. Hyundai’s copper solution is designed to address these weaknesses directly, restoring conductivity without compromising durability.

Cost savings with copper

Copper’s affordability provides a significant financial advantage when compared with alternatives like nickel or stainless steel in large-scale battery production. Market data indicates copper prices average between $8,000 and $9,000 per ton, while nickel costs between $20,000 and $25,000 per ton.

This substantial difference translates into lower overall material costs for battery manufacturers. For electric vehicles, that reduction could help bring down sticker prices and encourage broader consumer adoption.

Benefits for EVs

Solid-state batteries already promise key advantages such as greater energy density, faster charging speeds, and safer operation compared to conventional lithium-ion cells. Hyundai’s copper design adds another dimension by lowering material costs and increasing durability, which extends battery life.

Fewer replacements over a vehicle’s lifetime would reduce total ownership costs for consumers. EV drivers could enjoy longer driving ranges, reduced charging times, and improved overall value.

Pilot production plans

In early 2025, Hyundai confirmed the launch of a pilot production line for solid-state batteries at its Uiwang Research Institute in South Korea. This facility represents a critical step between laboratory research and large-scale commercialization.

The pilot line allows Hyundai to refine production techniques and validate new materials like copper under real-world conditions. Such a move underscores the company’s determination to push solid-state technology closer to market readiness.

Partnerships and research

Hyundai has built a multi-track development strategy by collaborating with leading battery companies and academic institutions. It is working with SES AI and Factorial Energy on next-generation battery technologies, while also engaging Seoul National University in research efforts.

The company has filed multiple solid-state battery patents in the United States to secure its innovations. These partnerships improve Hyundai’s chances of overcoming technical barriers and achieving faster commercialization.

Improved durability

According to Hyundai’s filings, the protective coating on copper enhances adhesion between the current collector and the anode. This improvement reduces the likelihood of structural separation during repeated charge and discharge cycles.

The coating also minimizes sulfide corrosion, which has been the primary obstacle to copper use in solid-state cells. As a result, batteries could maintain performance for longer periods before experiencing noticeable degradation.

Faster charging potential

One of the biggest consumer benefits of solid-state batteries is their ability to charge more quickly than conventional lithium-ion packs. By using copper, conductivity is improved, which allows electrons to move more efficiently through the system.

Industry reports project that charging times for solid-state batteries could potentially be reduced from over 30 minutes to under 15 minutes, depending on further development and commercialization. This development would make EV charging more convenient and competitive with traditional refueling times.

Energy density gains

Hyundai’s copper-based approach may also enable significant improvements in energy density compared with today’s lithium-ion cells. Analysts project that, if conductivity gains are realized, solid-state batteries could potentially exceed energy densities of 500 Wh/kg, compared to the typical 250–300 Wh/kg for conventional lithium-ion cells.

Higher density means more power can be stored in smaller, lighter battery packs. For consumers, this translates to longer driving ranges without adding unnecessary vehicle weight.

Industry competition

Hyundai is not the only automaker pursuing solid-state battery breakthroughs, as companies like Toyota, BMW, Volkswagen, and Nissan are also investing heavily in research. Each competitor is exploring different methods, ranging from entirely new chemistries to unique structural designs.

Hyundai’s approach, however, focuses on enhancing proven designs with copper to balance performance, cost, and durability. This practical path may give Hyundai an advantage in reaching the market sooner.

Industry challenges remain

Despite promising advances, serious technical and commercial hurdles remain before solid-state batteries can reach mass production. Hyundai must demonstrate that its copper coating can withstand thousands of cycles without degrading.

At the same time, scaling manufacturing requires exact processes and significant capital investment. Analysts caution that widespread commercialization is still several years away, even with Hyundai’s progress.

Why do Hyundai EVs charge more slowly at Tesla Superchargers? Does it change your view on using them?

Market impact of copper use

Industry analysts suggest Hyundai’s copper patent could significantly reshape the economics of battery manufacturing. Lower material costs would reduce EV production expenses and potentially make electric cars more affordable for mainstream buyers.

Increased reliance on copper could also shift global demand patterns and influence raw material supply chains. This development highlights how material choices directly affect both technology adoption and broader market dynamics.

Want to see how far Hyundai can push the limits? Hyundai unveils upgraded Ioniq 6 with top local driving range.

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This slideshow was made with AI assistance and human editing.