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"... Faster dendrite growth was associated with lower stress levels in a commonly used battery electrolyte material. Using a new technique that allowed them to directly measure the stress around growing dendrites, the researchers found cracks formed at stress levels as low as 25 percent of what would be expected under mechanical stress alone.
The experiments ... instead revealed another culprit: chemical reactions caused by high electrical currents that weaken the electrolyte and make it more susceptible to dendrite growth. Researchers had previously proposed that such reactions cause dendrite growth, but the new study provides the first experimental data on the interplay between chemical and mechanical stress in dendrite formation. ..."
From the abstract:
"Charging rates, cycling performance and safety of solid-state batteries using metal negative electrodes are often limited by dendrites, 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, we directly measure stresses around growing dendrites in garnet Li6.6La3Zr1.6Ta0.4O12, a highly stable solid electrolyte.
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."
Electrochemical corrosion accompanies dendrite growth in solid electrolytes (no public access)
Researchers used a new visualization technique to measure stress in a battery material as a dendrite crack grows. This video shows two different rates of charging, with brighter colors corresponding to higher stress. A bowtie-shaped pattern can be seen at the crack tip. Less stress is required to break the material under fast-charging conditions.
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