An interlayer with low solubility for lithium enhances tolerance to dendrite growth in solid state electrolytes

All solid state Li-ion batteries employing metallic lithium as an anode offer higher energy densities while also being safer than conventional liquid electrolyte based Li-ion batteries. However, the growth of tiny filaments of lithium (dendrites) across the solid state electrolyte layer leads to premature shorting of cells and limits their practical viability. The microscopic mechanisms that lead to lithium dendrite growth in solid state cells are still unclear. Using garnet based lithium ion conductor as a model solid state electrolyte, we show that interfacial void growth during lithium dissolution precedes dendrite nucleation and growth. Using a simple electrostatic model, we show that current density at the edges of the voids could be amplified by as much as four orders of magnitude making the cells highly susceptible to dendrite growth after void formation. We propose the use of metallic interlayers with low solubility and high nucleation overpotential for lithium to delay void growth. These interlayers increase dendrite growth tolerance in solid state electrolytes without the undue necessity for high stack pressures.