Electrochemical corrosion accompanies dendrite growth in solid electrolytes.

Fincher, Cole D; Gilgenbach, Colin; Roach, Christian; Osmundsen, Rachel; Penn, Aubrey; Thouless, Michael D; Carter, W Craig; Sheldon, Brian W et al. · Nature · 2026

biomechanical · Level V

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Abstract

Charging rates, cycling performance and safety of solid-state batteries using metal negative electrodes are often limited by dendrites<sup>1-3</sup>, the growth of which depends on coupling between electrochemical and mechanical driving forces. Previously, it has been assumed that dendrites propagate when plating-induced stresses reach the fracture stress of the solid electrolyte. Here we show that dendrites can propagate at far lower stresses. Using operando birefringence microscopy<sup>4</sup>, we directly measure stresses around growing dendrites in garnet Li<sub>6.6</sub>La<sub>3</sub>Zr<sub>1.6</sub>Ta<sub>0.4</sub>O<sub>12</sub>, a highly stable solid electrolyte<sup>5-7</sup>. Plating-induced stresses are present throughout growth and approach the mechanical fracture stress for the slowest-growing dendrites. As current densities and dendrite velocities increase, the stresses accompanying dendrite growth surprisingly decrease, with dendrite propagation occurring at stresses up to 75% lower than under mechanical load alone. Cryogenic scanning transmission electron microscopy (STEM) of dendrites propagated at high current reveals electrolyte decomposition to new phases, associated with which is a net molar volume contraction. The electrochemically induced mode of embrittlement may be mitigated through understanding and control of the nature of phase transitions accompanying instability.