Hyundai Motor has filed a patent application in the United States for a method that allows copper to be used inside sulphide-based solid-state batteries, a development aimed at improving efficiency and reducing material costs.
The filing describes the use of a protective coating applied to a copper anode current collector, making it resistant to sulphide corrosion. The design stacks copper with a coating layer, anode, sulphide electrolyte, cathode, and terminal collector, enabling copper to retain its conductivity and structural stability through repeated charging cycles.
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The approach could make copper viable again in solid-state batteries, where nickel or stainless steel are typically used to withstand the corrosive properties of sulphides. Copper’s higher conductivity and lower cost compared with these alternatives could enhance both performance and affordability of next-generation cells.
According to the filing, the buffer layer includes a carbon sheet structure, potentially with vertically aligned carbon nanotubes, integrated with lithiophilic metals such as silver, gold or aluminium. This buffer is designed with a porous structure to help maintain stability, suppress lithium deposition at the edges of the anode and support uniform cycling.
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Solid-state batteries replace liquid electrolytes with solid materials, enabling higher energy density, faster charging and improved safety. Despite their promise, widespread adoption has been limited by challenges with cost and durability. The potential reintroduction of copper could lower production costs while improving stability in demanding EV applications.
Hyundai has been advancing its solid-state battery programme through multiple avenues, including partnerships with SES AI, Factorial Energy and Seoul National University. In January, the company announced plans for a pilot production line at its Uiwang Research Institute, while also continuing to pursue patent filings in the United States related to solid-state technology.
