This is set to the hottest year on record since measurements began and there’s an urgent need for the world’s automakers to perfect carbon-neutral or carbon-negative solutions like synthetic fuel and hydrogen, but also solid-state batteries. As the 2027 Euro 7 emissions deadline approaches, carmakers are focusing their collective minds on developing solid-state batteries. Almost 50 patents related to solid-state technology have been filed over the past couple of months by the world’s leading carmakers, each bringing a unique approach to a particular challenge associated with the concept.
Honda: Solid-State Roadmap Promises Greater Durability and Range
The Japanese carmaker has filed 17 patents related to solid-state batteries in the past few weeks. Their collective aim to enhance the performance, durability, safety, and manufacturability, focusing on addressing key challenges that have limited the commercial adoption of solid-state batteries.
Together, these patents offer a comprehensive roadmap toward building solid-state batteries that are not only more efficient and energy-dense but also safer, easier to manufacture, and more structurally sound, making them a promising option for future electric vehicles and energy storage applications.
Overall, these innovations could help EVs become more competitive with internal combustion vehicles by delivering improved range, safety, durability, and convenience, accelerating the transition to electric transportation.
Several patents center around improving homogeneity, bonding strength, and cyclability in solid-state batteries, which enhances both energy efficiency and battery lifespan.
These improvements target better integration between the electrolyte and electrode layers, resulting in more stable cycling and reduced degradation over time.
Another major theme across the patents is manufacturing process improvements. A trio of patents propose methods for producing solid electrolyte sheets with greater safety and mass productivity, using techniques to minimize surface roughness, wrinkles, and bubbles, which contribute to more reliable and efficient batteries.
Structural innovations to ensure safe operation and reduce risks of failure are also addressed. To that end, one patent aims to prevent short circuits by optimizing layer arrangements and insulating materials.
To boost energy efficiency and durability, Honda aims to improve energy density by optimizing surface pressure distribution in battery modules, while another patent seeks to enhance energy flow and minimize localized stress within the battery.
Finally, we found patents that focus on electrolyte conductivity and metal ion management. One such patent enhances ion conductivity and crack resistance by improving electrolyte sheet strength, while another targets better control over metal ion deposition, ensuring that lithium remains stable on solid electrolyte surfaces, which is crucial for consistent energy output and longevity.
BMW: Optimizing High-Performance Cell Structures
On the verge of debuting its Neue Klasse architecture, BMW has filed seven patents in recent weeks that concentrate on optimizing structural integrity, pressure management, and high-density cell designs to improve battery efficiency and reliability, making them suitable for high-performance applications.
Among them are solutions for winding stacks of the solid electrolyte sheets used to make solid-state batteries into cylindrical cell shapes. This winding design helps maximize energy density by efficiently using space within the cell. Such a configuration is beneficial for creating a compact yet high-capacity battery, ideal for the space constraints and high power demands of electric vehicles.
The automaker has also considered developing new anode materials for an all-solid-state battery in order to prevent anode expansion under charging. This prolonged stability means that high charge and discharge rates can be achieved without undue stress on the cell. As a result, battery performance can be maintained while reducing risks associated with material displacement or cracking.
Similarly, another patent describes a device that applies a carefully calculated amount of pressure to the electrochemical electrode arrangement while maintaining the form stability of the housing; in other words, it applies pressure to prevent delamination of internal layers without deforming the cell housing. This setup ensures that the battery’s internal structure remains stable under pressure changes, improving battery life and cycle stability. By controlling pressure effectively, BMW aims to enhance durability and minimize degradation—critical for extending the lifespan of EV batteries under high-demand conditions.
Similarly, another interesting idea is that of a battery with a layered structure. This structure would include a current collector made of an elastic and conductive material. The precise makeup of this material and the design of a “pressure-applying mechanism” – a defined force-to-displacement function – would help to balance pressure changes within the battery, common under high charging and discharging events.
There are also more complex solutions mentioned, like producing active material particles. These active materials would have cavities within them that would be filled with electrolyte particles. These active materials could be responsive to temperature or pressure changes, helping to maintain the stability of power delivery in extreme conditions.
Finally, BMW has filed a patent for a system of manufacturing a layered battery consistently and efficiently, using one calendar module (a system that operates on specific timing) to apply an electrode layer to a carrier foil and another calendar module to apply the electrolyte layer to the electrode layer. This approach aims to create thin, well-bonded layers, reducing internal resistance and enhancing energy density. This process also aids in achieving a compact, multi-layered cell structure, ideal for high-performance applications where energy and space efficiency are paramount.
Stellantis & Mercedes-Benz: Compact, High-Density Battery Designs
The Stellantis group’s vision of the future muscle car is all-electric. Like BMW, it needs to find ways of making batteries efficiently, so it has developed a compression housing for solid-state battery modules that keeps the solid electrolyte and electrodes closely packed together under high pressure. This prevent the risk of delamination during charge and discharge and promotes better energy density, contributing to battery longevity and reliability in electric vehicles.
Mercedes has filed a similar patent with the aim of enhancing battery life and performance.
The German carmaker has also designed a phosphorous-free solid electrolyte with a cubic Argyrodite (an uncommon silver germanium sulphide material) structure that boasts superior electrochemical properties, which could improve a battery’s long-term stability.
General Motors: Enhancing Battery Resilience and Output
GM’s contribution is to create a battery with a silicon base. This base includes an elastomeric (polymer-based) layer to absorb stress from the battery’s silicon anode material that significantly expands during charging. Unlike the ideas filed by Stellantis and BMW, this patent allows a certain amount of deformation. However, the silicon base is meant to push the anode back into its original shape and position once charging is complete and the material is no longer stressed. This stress-relieving feature is critical for avoiding electrode cracking, thereby enhancing both battery durability and efficiency.
Hyundai: Scalable Solid-State Battery Tech
We’re not surprised to see Hyundai keeping pace with BMW, filing seven solid-state battery patents that reflect a comprehensive approach to achieving a high-performance, scalable solid-state battery technology well-suited for the next generation of electric vehicles.
One suggests a dry method of manufacturing electrodes for secondary lithium batteries to avoid the exposure of all-solid-state batteries to polar solvents, which can significantly break down the chemical structures of the battery and compromise its stability and safety. By using this technique, Hyundai is improving manufacturing efficiency, reducing costs, and mitigating environmental impact by eliminating the need for solvent drying and recovery steps.
The Seoul-based automaker has also proposed a new structure for an anode active layer that improves the power performance of an all-solid-state battery by using two different kinds of binders and adjusting the amount of solid electrolyte in each layer to suit. This means the battery can always operate at its peak, even when exposed to extreme temperatures, charge/discharge rates, or other vulnerabilities of traditional liquid-state batteries. Such a design helps to increase energy density and improve performance under high-power conditions, a key requirement for EVs demanding rapid charging and discharging cycles.
Other ideas include a negative electrode with a rubber-based binder, which improves manufacturing efficiency and performance versus regular binders. The rubber-based binder allows for a more resilient electrode layer that can withstand mechanical stresses during cycling, which is essential for long-term battery stability and performance.
Hyundai has also looked at the cathode with respect to a dry manufacturing process that uses a fibrous binder to improve energy density and overcome issues with traditional wet manufacturing. By using a fibrous binder and a dry process, Hyundai is creating a cathode that can support higher power outputs and reduce internal resistance, which is critical for the high energy demands of EVs.
In another patent, Hyundai has designed a battery with a core layer with a solid electrolyte with a large average particle diameter, and a surface layer with a second electrolyte with a small average particle diameter. Hyundai says this can improve water stability and reduce interfacial resistance. This helps maintain the integrity and performance of the battery over long-term use and in diverse environmental conditions.
Lastly, Hyundai proposes another means of fusing layers together by applying pressure to the battery while simultaneously applying an electrical current. This creates a plasma between the electrode layers and the solid electrolyte layer, preventing delamination. Hyundai’s plasma-assisted pressurization method aims to improve cycle stability and boost overall performance in EV applications.
Nissan: Improving Battery Efficiency
Nissan is in dire straits at present, with its CEO taking half-pay and restructuring the business in a bid to stay afloat. It’s even asking for help from Mitsubishi, which may explain why it has filed only one patent related to solid-state batteries.
The focus is on manufacturing a battery electrode that features an active material, a solid electrolyte, a fibrous conductivity aid, and polytetrafluoroethylene, a synthetic polymer discovered in 1938 (by American chemist Roy Flunkett) that is exceptionally resistant to high temperatures. These features contribute to more consistent power output and lower internal resistance, essential for battery efficiency.
Toyota: Maximizing Performance and Safety
Toyota has filed a series of patents in the last few weeks that reveal a broad strategy for solid-state batteries, emphasizing electrolyte innovation, safety mechanisms, and manufacturing techniques designed to maximize both performance and safety.
In regards to improving battery performance, one patent describes a method for producing sulfide-based solid electrolytes with high ionic conductivity. Toyota’s method includes reducing hydrogen sulfide generation, which improves safety by minimizing toxic gas release during cell operation. This improved electrolyte stability not only enhances safety but also supports higher power densities by allowing for more robust ionic transfer within the battery.
Like Mercedes and Stellantis, Toyota also ponders increasing pressure on a solid-state battery. Toyota’s system dynamically adjusts pressure within the solid-state battery to maintain internal connections and temporarily restore performance during stressful conditions, aiding in extended battery life.
Another critical Toyota design detects internal short circuits and switches the battery from charging to discharging to prevent critical failures, enhancing safety in solid-state batteries.
Toyota has also been working on improving the electrical conductivity of silicon-based anodes, known for their high energy density but significant volume expansion issues. By reducing oxygen content in silicon particles and using smaller electrolyte particles, Toyota has improved conductivity and reduced volume expansion issues in silicon-based anodes, enhancing the battery’s cycle life and efficiency.
Toyota also considers vehicle-related impacts on battery longevity, as seen in a patent that includes a mechanism to suppress charging and discharging during impacts to protect the battery. By temporarily halting activity during impacts, Toyota aims to extend the lifespan and operational reliability of solid-state batteries in real-world automotive environments.
Toyota has patented a positive electrode design where active material particles are coated with a film containing phosphorus, boron, and oxygen, with optional lithium or sodium.
A protective coating on Toyota’s positive electrode stabilizes the interface with the electrolyte, reduces degradation, and supports efficient ion transfer which is crucial for maintaining capacity over extended use.
Ford: Simplifying Battery Manufacturing
Finally, the Blue Oval has proposed an idea of simplified manufacturing of solid-state batteries that sees electrode and separator layers directly printed onto each other, eliminating traditional binders and solvents. This method could significantly reduce production time and cost while ensuring high material purity, contributing to an efficient and scalable production process.
Solid-State Batteries: Driving the Next EV Revolution Toward Efficiency and Sustainability
The world’s automakers are converging on similar paths in their race to develop solid-state batteries, focusing on improving battery stability, efficiency, and reducing production costs. Each major player—BMW, Toyota, Hyundai, and others—brings unique contributions to the table, from winding solid electrolyte sheets into cells and experimenting with advanced materials to designing anodes and cathodes that optimize ion flow and incorporating compression systems that maintain cohesion within the layers. These efforts reflect a broader industry shift, indicating that solid-state batteries are on the verge of becoming a reality. However, questions remain about their long-term performance and whether different approaches might achieve similar efficiencies, as the industry is still uncovering the full potential of this technology.
Beyond just advancing battery performance, automakers are beginning to address the critical need for sustainable materials, with an emphasis on using less lithium and other resources more effectively. As solid-state batteries edge closer to commercial viability, recycling and reusing these materials will be essential, and we can expect more patents and innovations in this area in the coming years. Once the optimal recipe for these batteries is achieved, automakers will have a transformative technology in their hands, capable of reshaping the EV market, reducing environmental impact, and providing consumers with cleaner, safer, and more efficient transportation.
