(Invited) Solid State Batteries: Energy Density, Cycle- and Manufacturability

Abstract

Conventional Li-ion batteries (LIBs) are close to practical limits in energy density and cost. The major disadvantage of LIBs is the presence of a flammable electrolyte and a porous separator, which makes them hazardous and restrict the choice of electroactive materials. Solid state batteries (SSBs) could be potentially safer and more energy dense if dendrite-free Li anode is used. The Advanced Research Projects Agency (ARPA-E), which funds high risk, high reward transformational research to reduce energy related emissions, reduce imports of energy from foreign sources, improve energy efficiency, and ensure US technological lead in advanced energy technologies, focuses on the development and scale up of membrane component for solid state batteries as well as full cells with high energy density. According the Integration and Optimization of Novel Ion-Conducting Solids (IONICS) program, a thin (≤20 μm) solid state (ceramic or polymer) electrolyte has to demonstrate ASR ≤5 Ohm-cm2 with high current density and movable areal capacity in Li metal cells. Several major risks for SSBs with Li metal anode have been identified: 1) low electrolyte conductivity, 2) incompatibility of solid membrane with Li metal, 3) anode volume change, 4) dendrite formation, and 5) non-uniform Li plating/segregation, and mitigation strategies will be examined. These issues are related mainly to cyclability, while the cell architecture (e.g. thickness, porosity, non-active materials) defines the energy density and affects its manufacturability, which remains mostly uncharted territory for solid state batteries. Recent advances and trends in the development of novel approaches to materials for solid state batteries, their design and manufacturing of large format full solid electrolyte cells with different cathodes that is being funded by ARPA-E via RANGE, IONICS and OPEN 2018 programs will be discussed.