The BMW Group has integrated large-format solid-state battery cells from partner Solid Power into a test vehicle, a BMW i7. The aim is to test how the solid-state cells behave in everyday road operation.
BMW and Solid Power have been working together on solid-state batteries for years. The partnership dates back to 2016. Things turned serious three years ago when both sides signed a technology transfer agreement. One direct result is the testing of solid-state cells in a BMW test car.
The solid power cells with their sulphide-based electrolyte are fully integrated into a battery pack, which the BMW Group hopes will provide further essential findings in the test programme in the coming months. In particular, the partners want to investigate the management of cell expansion. Both partners are also focusing on how the operating pressure can be controlled and how the temperature boundary conditions can be adjusted.
BMW doesn’t provide much more detail but states that the concept battery integrated in the test vehicle “combines proven Gen5 construction principles (prismatic cells in modules) with new, innovative module concepts for integrating ASSB cells from Solid Power.”
Gen5 refers to the prismatic cells currently installed in modules in BMW electric cars. These are not yet the future round cells of the new class, which the company labels Gen6. The test car is a modified i7, the new electric flagship BMW presented in April 2022.
Higher energy density
BMW and Solid Power see a higher energy density than current battery technologies as one of the solid-state battery’s major advantages. The Munich-based company emphasises that although the innovative cells are being developed and manufactured by Solid Power, this is being done in close collaboration with experts from the BMW Group.
The partners see the potential, but there will be no rapid series production: “Further development steps are required to implement ASSB technology in a competitive overall storage system,” says the press release.
Martin Schuster, Vice President of Battery Cells and Cell Modules at the BMW Group, commented: “Our BMW i7 ASSB test vehicle on the road is a perfect example of the BMW Group’s technology-open mindset. We are continuously advancing the development of new battery cell technologies and expanding our know-how with valuable partners such as Solid Power.”
President and Chief Executive Officer of Solid Power, John Van Scoter, responded: “Solid Power is extremely proud that our partnership with BMW has resulted in the first demonstration of truly all-solid-state battery cells in a vehicle. We believe in the promise of ASSBs and continue to drive innovation of our sulfide electrolyte to support that future for EVs.”
Qualification process
Solid Power produced and delivered the first A-samples of the solid-state cells to BMW at the end of 2023. This delivery marked the start of the formal automotive qualification process. BMW wanted to install the cells in a demonstration vehicle before the middle of the current decade, and this has been achieved.
At the same time, BMW is setting up a prototype line for solid-state battery cells based on the solid-power designs at its Cell Manufacturing Competence Centre in Parsdorf near Munich. This is made possible by a research and development license granted to BMW by the US company.
University of Colorado spin-off
Solid Power was founded in 2011 as a spin-off from the University of Colorado. Today, the company is one of the world’s most promising developers of solid-state battery cells. In the summer of 2022, the U.S. company announced that it had completed the installation of its pilot production line and could now supply cells for qualification tests to its investors and customers.
In addition to BMW, SK On and Ford are among the most prominent partners. The pilot line will automatically produce all-solid-state battery cells using the company’s sulphide-based solid electrolyte material. At full capacity, the pilot line is expected to be able to make around 15,000 cells per year. Series production is scheduled to start later.
The company uses conventional NMC cathodes, so production does not have to be switched. In combination with a silicon anode and a solid electrolyte, Solid Power wants to build a cell with a gravimetric energy density of 390 Wh/kg. If a lithium metal anode is used instead of the silicon anode, the cell (still with an NCM-811 cathode) achieves an energy density of 440 Wh/kg.
“The cooperation with Solid Power underlines the BMW Group’s battery strategy: to further develop innovative battery technologies on equal footing with leading industry partners. This strategically strong position in the value chain ensures the BMW Group access to all new and innovative battery cell research worldwide,” concludes the BMW press release.
