Solid-state electrolytes with fast lithium conduction are the core of the all-solid-state Li-battery technology. By substituting the organic electrolyte with a piece of non-flammable ceramic material, we can achieve better safety, higher specific capacity, and a higher energy density. To date, the major bottleneck for this technology is the slow Li diffusion in the solid-state electrolyte and the interfacial incompatibility between the electrolyte and electrodes. To resolve these issues, several families of fast ionic conductors have been developed. Understanding Li diffusion in these materials is essential to the development of novel family fast ionic conductors. To this end, atomistic modeling provides us with a unique tool to obtain comprehensive information on atom motion, which is difficult to access with experimental techniques. In this talk, we showcase our group’s atomistic simulations regarding a novel family of superionic conductors, Li-rich antiperovskites (LiRAPs)

LiRAPs are a promising family of solid electrolytes, which exhibit ionic conductivities above 1 mS/cm at room temperature, among the highest reported values to date. Here, we report on the defect chemistry and the associated lithium transport in Li₃OCl, a prototypical LiRAP, using DFT calculations and classical MD simulations [1]. We studied these materials’ phase, interfacial, and voltage stability [2,3] with DFT, showing good agreement with experiments, further proposing low-dimensional superionic antiperovskites [3]. In addition, the interfacial properties were studied for both protonated and fluorinated materials [4]. Analogous simulations were also carried out for Na-rich antiperovskites [5].

Acknowledgments

Support from the Research Grants Council of Hong Kong is gratefully acknowledged.

References

[1] Z Lu, C Chen, ZM Baiyee, X Chen, C Niu, F Ciucci. Defect chemistry and lithium transport in Li3OCl antiperovskite superionic conductors. Physical Chemistry Chemical Physics 17 (48), 32547-32555 (2015)

[2] Z Lu, F Ciucci. Antiperovskite cathodes for lithium batteries. Journal of Material Chemistry A, 6, 5185-5192 (2018)

[3] Z Lu, J Liu, F Ciucci. Superionic conduction in low-dimensional-networked antiperovskites. Energy Storage Materials, 28, 146-152 (2020)

[4] M Effat, J Liu, Z Lu, TH Wan, and F Ciucci. Stability, elastic properties, and the Li transport mechanism of the protonated and fluorinated antiperovskite lithium conductors. ACS Applied Materials and Interfaces, 12, 49, 55011-55022 (2020)

[5] TH Wan, Z Lu, F Ciucci. A first principle study of the phase stability, ion transport and substitution strategy for highly ionic conductive sodium antiperovskite as a solid electrolyte for sodium ion batteries. Journal of Power Sources, 390, 61-70 (2018)