Toward Large-Scale Production of Solid-State Batteries: Manufacturing Process Analysis and Cost Assessment for the Composite Cathode
Authors: Voss Philipp , Atik Jaschar , Krätzig Oliver , Leker Jens , Lux Simon 
Published: February 2024

In 2022 the lithium-ion battery (LIB) price has increased for the first time since its commercialization while LIBs are approaching their physicochemical energy limits.1,2 Therefore, next-generation or post LIB concepts are being intensively researched, solid-state batteries (SSBs) being evaluated to be among the most promising.3 While companies are already announcing ambitious large-scale production plans for SSBs, academic SSB research is still mainly confined to the laboratory-scale.4 The number of studies regarding SSB material scale-up, large-scale manufacturing or cost calculations is very limited.

This work aims to address some of the named research gaps and reduce the knowledge gap between academia and industry. Particularly, the scaled cathode production and its cost assessment for sulfidic and oxidic SSBs are regarded. Therefor, suitable materials and processing pathways for giga-scale production of the composite cathode were ascertained by aggregating the data from a literature review, a patent analysis and expert interviews. Further, the cathode production cost was calculated by adapting the cost model of Duffner et al. (2021).5

Regarding the processing of sulfide-based SSB cathodes a wet and a dry production route is being distinguished . The wet route contains the identical process steps, as already established in LIB production, hence a quick adoption and rapid scale-up is feasible, which is expressed in the technology readiness level (TRL) of 6, the highest of all observed processes. However, challenges regarding densification and solvent compatibility must be solved beforehand. The dry route omits solvent compatibility problems. Next to equivalent challenges with densification, the scale-up of the newly implemented steps ‘dry mixing’ and ‘dry coating’ is currently limiting the large-scale potential, which is reflected in a lower TRL of 4. The scale-up of the oxidic SSB cathode production is still in its infancy (TRL 4), associated with limited processing know-how. The overall process chain will be similar to LIB production, but with the addition of a final co-sintering step, which is also the biggest barrier toward scale-up. Sintering process innovations are evaluated as promising by experts and could potentially enable low-cost, high throughput processing, but are still far from industrial scale.

Cost calculations revealed that in the basic scenario, assuming a giga-scale production with state-of-the-art materials (cathode active material: NMC811, catholyte: Li6PS5Cl/Li7La3Zr2O12) while considering ascertained challenges, both SSB electrodes show significantly higher production cost than the LIB equivalent. Particularly, oxide-based cathodes show about three times the production cost of LIB cathodes (Figure 1a). By overcoming material and process challenges significant cost reductions are possible as simulated in an optimized future scenario (Figure 1b). The cost difference of LIB and oxidic SSB cathodes reduces to 16% and the dry process for sulfide-based cathodes even results in cost parity (~ 44 $ kWh1), showing the potential for cost competitiveness. The biggest drivers towards cost reduction are the increase of the cathode active material share and decreased prices of the solid electrolyte. On the process-level especially optimized mixing and drying for the sulfide-based cathode and a reduction of the sintering temperature below 500 °C for the oxide-based cathode lead to significant cost reductions.

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Figure 1