Thermal relaxation of lithium dendrites

The average lengths (lambda) over bar of lithium dendrites produced by charging symmetric Li-0 batteries at various temperatures are matched by Monte Carlo computations dealing both with Li+ transport in the electrolyte and thermal relaxation of Li-0 electrodeposits. We found that experimental (lambda) over bar (T) variations cannot be solely accounted by the temperature dependence of Li+ mobility in the solvent but require the involvement of competitive Li-atom transport from metastable dendrite tips to smoother domains over Delta E-R(double dagger) similar to 20 kJ mol(-1) barriers. A transition state theory analysis of Li-atom diffusion in solids yields a negative entropy of activation for the relaxation process: Delta S-R(double dagger) approximate to -46 J mol(-1) K-1 that is consistent with the transformation of amorphous into crystalline Li-0 electrodeposits. Significantly, our Delta E-R(double dagger) similar to 20 kJ mol(-1) value compares favorably with the activation barriers recently derived from DFT calculations for self-diffusion on Li-0(001) and (111) crystal surfaces. Our findings suggest a key role for the mobility of interfacial Li-atoms in determining the morphology of dendrites at temperatures above the onset of surface reconstruction: T-SR approximate to 0.65 T-MB (T-MB = 453 K: the melting point of bulk Li-0).