BMW is moving closer to a practical solid-state battery, filing two groundbreaking patents with the European Patent Office. The automaker’s innovative battery design uses a special winding technique that creates uniform internal pressure distribution without requiring external compression mechanisms. Additionally, the cell uniquely expands upon initial charging, eliminating gaps between the winding and housing to guarantee stable mechanical pressure and reliable electrical contact. This is a critical step toward bringing safer, more efficient solid-state batteries to mainstream electric vehicles.
Beyond Lithium-Ion: The Perks of Going Solid
As electric vehicles (EVs) become mainstream, traditional liquid-electrolyte batteries face limitations that solid-state technology could overcome. Solid-state batteries use a solid electrolyte medium – typically a ceramic – but require external pressure from the cell housing to press it against the windings to ensure reliable contact. Vehicle and battery makers are experimenting with ideas to achieve this economically.
Solid-state batteries have several advantages:
- Higher energy density
- Higher possible voltages
- Better cycling performance
- Lower fire risk
- More stable electrolyte interface formation
BMW’s Breakthrough: Pressure Without Compression
BMW’s first patent outlines a novel winding method that layers electrodes, solid electrolyte, and isolation materials around a central axis. The result? A cylindrical cell that maintains uniform internal pressure—without relying on bulky external compression mechanisms.
But pressure alone isn’t enough. The second patent addresses a critical challenge: the gap between the winding and the housing. BMW’s solution? A winding that expands during its initial charge cycle, pressing evenly against the housing to ensure firm contact and stable performance. Achieving this effect requires precise material choices and a tightly controlled winding process—an engineering feat that could move solid-state batteries from concept to commercial reality.
The Race to Scale: BMW’s Solid-State Gamble
BMW says its patent is unique thanks to a unique winding technique that creates uniform internal pressure without external force, and a clever material configuration that causes the cell layers to expand during initial use. This expansion fills the housing, locking everything into stable, reliable contact.
Of course, a patent isn’t a product. The real challenge lies in scaling this breakthrough for mass production. If BMW can pull it off, this could be the solid-state breakthrough the EV world has been chasing for years.
