Dendrite-growth resistance in solid state electrolytes

Abstract

We address dendrite growth resistance in solid electrolytes in all-solid-state Li-ion batteries. First,

we introduce a dendrite-growth model in the electrical, ionic-flow, temperature, and stress fields

in the solid-state electrolyte. The model analysis shows that the applied electrode potential

generates field singularities at the dendrite/crack tip, driven by electrochemical ion-deposition

pressure and the thermal-conductivity jump at the dendrite/electrolyte interface. An extended J-

integral is introduced to characterize the stress and temperature-gradient singularities and

associated driving forces of the dendrite/crack tip in the heat-generating medium. These

singularities are then used to construct universal threshold-current-density diagrams of

dendrite/crack growth in solid electrolytes. From the universal diagram, the resistance to

dendrite/crack growth is defined. This resistance depends on the dendrite/crack length, film

thickness, and the properties of the electrochemically active solid-state electrolyte. These

properties include ion conductivity, thermal conductivity, thermal expansion coefficient, elastic

moduli, and toughness against dendrite/crack growth. The analyses show that the driving force

from thermal stresses induced by Joule heating of the ionic current in the electrolyte is particularly

significant for short dendrite/crack structures. The polarity of the temperature gradient in the

electrolyte is found to be a primary factor in determining the threshold current density for short-

dendrite/crack growth. The analysis offers methods for testing the dendrite/crack toughness of the

electrochemically active solid-state electrolyte. It also guides the design of battery-cell packing

sequences to maximize resistance to dendrite/crack formation and growth along the cooling path.