Prospective life-cycle assessment of an argyrodite type solid-state battery

Examensarbete för masterexamen
Heydorn, Zackarias
Hjortsberg, Sofie
Rechargeable battery technologies are used in a variety of applications, and recently the use in electric vehicles and grid storage have received a lot of attention. This is largely because an electrified car fleet and improved grid­ storage capacity (to offset the variable nature of renewable electricity production) are envisioned to reduce greenhouse gas emission. Today's dominant battery technology, the lithium-ion battery (LIB), is associated with safety issues, such as aggressive fires caused by thermal runaway. Furthermore, it is also associated with sustainability issues, such as leakage of toxic substances, energy intensive production and its content of critical and/or geochemically scarce materials, e.g. lithium, nickel, and cobalt. Solid-state batteries (SSEs) are a novel battery technology utilizing solid instead ofliquid electrolytes, which is the dominant design today. SSE cells are expected to become a future competitor to LIB cells due to potential for increased energy densities, higher safety and cyclability. In this work, the SSE literature was first reviewed to find a SSE cell with promising performance that has not been previously studied from an environmental life-cycle perspective. The battery cell chosen was an anode-free argyrodite-type SSE, which uses a silver-carbon nanoparticle layer to promote an even lithium plating when charged. To identify environmental hotspots and benchmark the life-cycle environmental impacts of this battery cell at a point in time when it has reached scaled up production, a prospective life cycle assessment (LCA) with a cradle­ to-gate scope was performed. The functional unit was defined as 1 kWh of theoretical storage capacity produced and the prospective LCA focused on climate change and mineral resource depletion impacts. The prospective LCA concluded that the studied battery would perform comparably to LIBs when it comes to climate change, but that was dependent on the type of electricity source, heating, and cooling production assumed for the background system. An identified hotspot was the production of carbon nanofibers. Furthermore, the study showed that the short-term mineral scarcity performed similar in comparison with LIEs. The battery did, however, perform considerably worse regarding long-term mineral resource scarcity due to its silver content. This indicates that the battery might be unfit for large scale manufacturing unless the silver used in the separator layer can be reliably recycled or substituted. This was tested in a sensitivity analysis, where it was shown that replacing the silver with magnesium would reduce the long-term mineral resource depletion impact with 69%, the short-term mineral resource depletion impact with 29'X, and the climate change impact with 14%.
Solid state battery, prospective life cycle assesment, solid electrolyte, argyrodite, climate change, mineral resource depletion
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