Renewable energy storage and conversion are critical to addressing the challenges of climate change and enabling the green transition. Because of their proven advantages, such as high energy density, low self-discharge rate, long cycle life, and lightweight, conventional lithium-ion batteries are regarded as the most convenient and efficient devices for short-term energy storage in the market today.

Conventional lithium-ion batteries are a proven and ubiquitous technology that uses a solid, porous separator soaked in an organic liquid electrolyte to shuttle charges between electrodes for energy conversion and storage. These electrolyte solutions provide high conductivity and excellent electrode surface wetting. However, liquid electrolytes based on highly volatile and flammable organic solvents also have some well-established drawbacks, including low ion selectivity, poor long-term stability, and, most importantly, safety issues. Solid-state lithium batteries replace the electrolyte-soaked separator with an ionically conductive solid, thereby eliminating the liquid electrolyte altogether. In comparison, all-solid-state lithium batteries mitigate the persistent issues posed by conventional liquid electrolytes, particularly safety and long-term electrochemical and thermal stabilities. In doing so, solid-state batteries also provide improved energy & power densities via combination with high-capacity, high-voltage electrode materials, and reduced need for packaging and state-of-charge monitoring circuits, thereby improving capacity and charging speeds while potentially reducing production costs.

Figure 1 – Conventional and solid state batteries.

Because of these advantages, a rapidly growing trend of research into solid-state electrolytes (SSEs) for use in lithium batteries has emerged in recent years. SSEs that have received a lot of attention can be divided into two categories: inorganic ceramic electrolytes and organic polymeric electrolytes. The former is commonly based on oxides and sulfides, with sulfide-based electrolytes like Li2S–P2S5 and Li2S–P2S5–MSx exhibiting significantly high ionic conductivities at room temperature as well as good mechanical strength and flexibility. However, they have some disadvantages, such as low oxidation stability, sensitivity to H2O, and poor compatibility with cathode materials. Because of their high conductivity and stability, oxide-based solid electrolytes such as garnet Li7La3Zr2O12 (LLZO), perovskite Li3.3La0.56TiO3 (LLTO), NASICON (lithium superionic conductor) LiTi2(PO4)3, and LISICON (sodium superionic conductor) Li14Zn(GeO4)4 are widely studied. On the other hand, ceramics have a rigid nature, and the corresponding electrolytes are challenging to process.

Solid-state batteries have great potential in a wide variety of industries, including automotive, grid energy storage, consumer electronics, industrial, and aerospace. The adoption of solid-state batteries is based on value addition, where the value of their improved performance is deemed to be worth the cost of investing in new manufacturing processes and upscaling of potentially costly solid electrolyte materials. As such, premium markets such as EV and consumer electronics are the most likely to push deployment of this technology forward, where the superior performance of solid-state batteries can justify an additional price premium on the final product. Grid storage may follow in the future, but is unlikely to be a first mover for large-scale deployment due to price sensitivity compared to other grid storage technologies such as natural gas.

Figure 2 – An example of a solid-state battery pouch cell.

According to industry estimates, electric vehicles will account for 10–12 percent of overall automotive sales by 2030. Several factors push EV adoption, including favorable policies in Europe, China, and India; product advances by key OEMs such as Honda and Volkswagen; and battery technological advancements. One of the key motivators for the adoption of electric vehicles is technological breakthroughs in batteries to improve vehicle performance and consumer range anxiety by offering EV products with long-lasting, fast-charging batteries at their core. The cost of Li-ion batteries fell to $137 per kWh in 2020, with 100 kWh expected to be the tipping point at which EV will reach cost parity with internal combustion. To continue decreasing battery costs towards this tipping point, either technology should develop to have a higher energy density for the same price, or material and production costs must fall over time. While moving to low-cost electrode materials such as lithium iron phosphate and low cobalt/high nickel formulations can help on the materials front, cost-effective manufacturing of solid-state batteries can improve help achieve this tipping point from an energy density and charge speed perspective.

Figure 3 – Electrical car with solid-state batteries

As a result, major material firms, OEMs, and research institutes are boosting their investments in solid-state battery R&D. OEMs are working closely with many players in the battery manufacturing arena to guarantee that solid-state batteries are commercialized quickly and at low cost. As a result, more than 100 players are involved in the technology’s development at the material, battery pack, and vehicle levels. As slot-die coating is already an industry standard technique for electrode coating in conventional LIB’s, developing slot-die based manufacturing of solid-state battery devices can support cost-effective manufacturing of this new technology by leveraging well-established production process knowledge and hardware. At FOM technologies, we are enabling major battery players to develop new solid-state batteries structures and materials accelerating the market adoption of this technology.