Influence of dislocations on ionic conductivity and dendrite formation in solid electrolytes

Abstract

In order to study the recently proposed strategy to tailor the electrical property of ceramics by the introduction of dislocations, numerical calculations are performed on the influence of parallel straight dislocations on ionic conductivity and dendrite formation in single-crystal solid electrolytes. If the diameter of a dislocation pipe is more than root(2) times larger than the distance between neighboring dislocations, the ionic current density is nearly uniform on the electrode and the dendrite formation would be avoided. Furthermore, under the condition, the mean ionic conductivity is higher than that without dislocations by several orders of magnitude. It may be practically possible to increase the ionic conductivity by several orders of magnitude without dendrite formation by introducing appropriate dislocations because the required dislocation density in the order of 1017 m-2 has already been reported experimentally although the reports were not for metal oxides.

Theoretical upper limit of dislocation density in slightly-ductile single-crystal ceramics

“…Indeed, Wang et al [35] experimentally reported the dislocation density as high as 10 18 m −2 in single-crystal ceramics (alumina) by high-temperature laser shock peening in 2021. Accordingly, the theoretically predicted increase in ionic conductivity by 6 or 7 orders of magnitude without dendrite formation by introducing parallel straight dislocations into single-crystal solid electrolytes with the dislocation density higher than about 10 17 m −2 may be practically possible [24]. Although the numerical curves in figures 2 and 4 are shifted to higher or lower dislocation densities for ceramics with higher or lower compressive strength, respectively, the qualitative conclusion is unaffected.…”

“…With regard to diffusion coefficient of ions which is proportional to ionic conductivity in solid electrolyte, it is several orders of magnitude higher along dislocations compared to that in the bulk solid [3,[24][25][26][27]. Accordingly, it is expected that ionic conductivity increases considerably by introducing appropriate dislocations in solid electrolyte [3-5, 20, 24].…”

“…Accordingly, it is expected that ionic conductivity increases considerably by introducing appropriate dislocations in solid electrolyte [3-5, 20, 24]. Recently, the authors [24] have theoretically shown that the ionic conductivity could be increased by 6 or 7 orders of magnitude without dendrite formation by introducing parallel straight dislocations into single-crystal solid electrolytes with the dislocation density higher than about 10 17 m −2 . The dislocation density higher than 10 17 m − 2 has not yet been experimentally reported for ceramics except for one case although such the high dislocation densities have been experimentally reported for metals, metalloids, and biomaterials several times [10,[20][21][22][23][28][29][30][31][32].…”

Merits and Demerits of Machine Learning of Ferroelectric, Flexoelectric, and Electrolytic Properties of Ceramic Materials

“…For each straight dislocation, a dislocation pipe is considered along which ionic conductivity is significantly higher than that in the bulk because the concentration of vacancies is considerably higher [59][60][61][62]. The typical diameter of a dislocation pipe is denoted by 𝛿, and the distance between neighboring dislocations is denoted by 𝑑 which is given by Equation ( 31) [57]:…”

“…Under the condition of all-dislocation-ceramics, the ionic current density is spatially uniform and the mean ionic conductivity could be seven orders of magnitude larger than that in the bulk (Figure 17) [57]. Below the critical dislocation density, on the other hand, dendrite formation may be inevitable because the ionic current is concentrated along dislocations (Figure 17) [57]. Recently, it has been suggested that the introduction of dislocations is useful for improving the functional, electrical and mechanical properties of ceramics, which is called dislocation engineering [62][63][64][65][177][178][179][180].…”