battery | What you need to know about solid state batteries

Range, performance and safety: Solid state batteries promise improvements in important parameters, but are still in the early stages of development. All you need to know about solid state battery at a glance.

Existing lithium-ion batteries (LIB) are based on liquid electrolytes and are currently used in many mobile and stationary applications. However, their improvement potential is getting smaller and smaller as technology advances. Experts predict that liquid electrolyte LIBs will slowly reach their limits in the next decade. On the other hand, solid state batteries with solid electrolytes promise improvements in several important performance parameters. They are currently under development and could be put on the market in the coming years.

Against this background, the Fraunhofer Institute for Systems Research and Innovation (ISI) has developed a roadmap for solid-state batteries that critically evaluates research findings and compares the development potential of solid-state batteries with existing lithium-ion batteries for the following batteries. Decade. The roadmap shows: Solid-state batteries have a lot of potential, but they have to prove their commercial viability in the next five years. In our Q&A, we present the exact results of the Fraunhofer Roadmap as well as everything worth knowing about the solid state battery.

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What are solid state batteries?

A battery containing a solid-state electrolyte is called a solid-state battery (SSB), as Springer author Martin Doppelbauer explains in the Energy Storage chapter (page 158f) of the book Fundamentals of Electrical Mobility. This is not a new type of battery, but a different type of lithium-ion battery. “Solid electrolytes provide ionic conductivity in a solid that is not liquid,” Doppelbauer says. Solid state batteries, also known as solid state batteries, are the next generation of rechargeable batteries.

What are the advantages of solid state batteries?

According to the Fraunhofer researchers, the roadmap results show that solid-state batteries must achieve significant performance improvements over the latest liquid electrolyte LIBs in order to achieve relevant market shares. Important performance parameters are energy density, safety, service life, costs and the ability to fast charge.

  • Solid state batteries have the potential to be classic LIBs in terms of energy density It must be bypassed, especially since it made it possible to use lithium metal anodes. “Solid-state batteries have the ability to increase energy density beyond the limits of conventional lithium-ion cells to up to 1,200 W/L and over 400 W/kg,” says Markus Schaefer CTO at Mercedes-Benz in an interview as an important part of our strategy “from ATZextra 2021 – Electric mobility on the road to success.
  • In addition, apply to them Safety High even at the cellular level because it does not contain flammable liquids.
  • to her life span Even LIBs can bypass a liquid electrolyte, but technical challenges such as volume changes during charging or discharging still have to be overcome.
  • The Costs According to the scientists, solid-state batteries should be much higher at the start of their market launch compared to current LIBs, in part due to lower production volumes.
  • The Fast charging capability of solid-state batteries are currently limited by the typically low ionic conductivity of solid electrolytes, but their design can be adapted specifically for this purpose.

In general, according to Fraunhofer researchers, it should be noted that improving one performance parameter often comes at the expense of another, and batteries can be designed according to specific requirements and applications.

What materials are considered for solid state battery components?

Anode active substances (am): According to the Fraunhofer researchers, lithium (Li) and silicon (Si) are promising. Lithium metal anodes promise the highest energy density, but processing technologies have not yet been established in large-scale production. Although Si-based anodes have declared themselves as the technology of choice for the next generation of LIB, compared to Li-metal anodes, a lower energy density is typically achieved in SSB.

cathode active material (Cathode active materials – CAM): nickel-rich layered oxides (NMC, NCA), lithium iron phosphate (LFP), and in the long run, possibly also sulfur or high-voltage materials. According to the researchers, the highest energy density in SSB cells is currently achieved through the use of NMC/NCA layer oxides. LFP materials are of interest due to their low cost and high stability.

What SE material groups are there?

The main component of solid state batteries is the solid electrolyte (SE). According to the Fraunhofer roadmap, there are currently three promising groups of renewable energy materials, namely oxide electrolytes, sulfide electrolytes and polymer electrolytes.

  • oxide ions It is generally said to have high mechanical and chemical stability, but requires high-temperature production steps during processing (sintering), is brittle, and has a relatively poor ionic conductivity.
  • Sulfide electrolytes (also called thiophosphate electrolytes) is mechanically softer and more flexible than SE oxide and therefore easier to process (in addition, no sintering process is required). The disadvantages of the material system are the limited availability, which is currently limited to the research scope, and the limited chemical compatibility with high-voltage Li-metal and CAM.
  • Polymer electrolytes According to the roadmap, this is the most established material system among all SEs, which is also reflected in the availability of materials and production technology. According to the researchers, limited ionic conductivities at room temperature, poor chemical compatibility with high voltage CAM, and low limited current density due to the ionic conductivity mechanism present challenges on the way to broader market implementation.

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Where are solid state batteries mainly used?

According to the roadmap, the automotive market as a whole should have the greatest potential of solid-state batteries and become their main field of application in the medium to long term. The automotive market is likely to be the first area of ​​application of oxidized solid state batteries – presumably around 2028. Given the high initial costs, it is envisaged that solid state batteries will initially be used in the upper market segments. In the long term, the effects of expansion could help the technology open up more areas of application, such as trucks and stationary storage systems or, after 2035, also in passenger aviation.

According to the roadmap, solid-state batteries based on sulfide electrolytes can be used initially in the consumer sector and there in laptops, smartphones or power tools, since the requirements and test methods are less stringent here.

What obstacles do solid state batteries still have to overcome?

Dr. Thomas Schmaltz, who coordinated the research work on the roadmap at Fraunhofer ISI, identifies three main challenges:

  • Since it is currently not expected that any solid-state battery concept will ultimately have the best performance, parallel development of different approaches and therefore higher investments is necessary.
  • Solid-state batteries will be in constant competition with liquid electrolyte lithium-ion batteries and, due to their initially high costs, will have to make significant performance improvements, indicating that the initial applications will be more in the premium segment.
  • Private and public funding that goes beyond purely research funding is necessary in order to catch up with European actors compared to Asian and American actors – specifically in patenting, product development, production technologies, pilot production, as well as emerging and industrial activities. If successful, Europe could play a leading role in developing solid-state battery technologies in the future.

How is the market developing?

The first production of solid-state batteries is already in place, as explained by Springer author Doppelbauer in the aforementioned book chapter (page 159). Large-scale market entry is expected by mid-2020. The Fraunhofer roadmap predicts that solid-state battery production, which is currently still less than 2 GWh globally and is based on polymer SSB, could increase sharply between 2025 and 2030 – When solid state batteries based on oxide and sulfide electrolytes are introduced to the market. Production capacity is estimated at 15-55 GWh in 2030 and 40-120 GWh in 2035, which is about 1-2% of the then emerging LIB market. Thus, liquid electrolyte LIBs will dominate the market for the foreseeable future.

Japanese automaker Nissan expects the cost of solid-state batteries to drop to $75 per kilowatt-hour by fiscal year 2028, and up to $65 per kilowatt-hour in the next step. As a result, the cost of electric cars is comparable to the cost of gasoline-powered vehicles. In 2028, Nissan wants to launch an electric car with self-developed solid batteries. For this purpose, the first production line will be built at the main plant in Yokohama in fiscal year 2024. What this should look like and what materials and manufacturing process are required in a recently submitted prototype system for armored solid-state batteries are investigated.

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