Stability and Formation of the Li₃PS₄/Li, Li₃PS₄/Li₂S, and Li₂S/Li Interfaces: A Theoretical Study

Abstract

Solid electrolytes have shown superior behavior and many advantages over liquid electrolytes, including simplicity in battery design. However, some chemical and structural instability problems arise when solid electrolytes form a direct interface with the negative Li-metal electrode. In particular, it was recognized that the interface between the β-Li 3 PS 4 crystal and lithium anode is quite unstable and tends to promote structural defects that inhibit the correct functioning of the device. As a possible way out of this problem, we propose a material, Li 2 S, as a passivating coating for the Li/β-Li 3 PS 4 interface. We investigated the mutual affinity between Li/Li 2 S and Li 2 S/β-Li 3 PS 4 interfaces by DFT methods and investigated the structural stability through the adhesion energy and mechanical stress. Furthermore, a topological analysis of the electron density identified preferential paths for the migration of Li ions.

A computational study of the negative LiIn modified anode and its interaction with β-Li3PS4 solid–electrolyte for battery applications

“…Thus, the adhesion energies presented in Table 2 for the LiIn/LPS interfaces all indicate a good adhesion between LiIn and LPS at the anode/solid–electrolyte interface, despite the absence of any major reconstruction of the interfaces. When compared to our previous investigation of the Li-metal/LPS interface, 6 which presents adhesion energy over one order of magnitude larger, an interesting correlation can be drawn with the reported experimental characteristics of the two anodes and their computed bulk properties. The very large E adh of the Li-metal/LPS interface is due to the reduction of P 5+ to P −3 , which causes a dramatic reconstruction of the interface, creating a mixed layer of Li 2 S and Li 3 P between the two surfaces, which contrasts with the relatively minor rearrangement presented here for all LiIn/LPS interfaces.…”

“…The simulations were conducted by applying the density functional theory (DFT) with PBE0 hybrid functional 15,16 and all-electron basis sets 6-11 17 contracted to [1s,2sp], 8-6311-1 contracted to [1s,4sp,1d], 18 8-521-1 to [1s,3sp,1d], 19 and 9-763111-631 20 to [1s,6sp,3d], for Li, S, P, and In atoms, respectively. Such combination of functional and basis sets for Li, S, and P provided accurate results in our previous works on similar systems; 5,6 In basis set has been successfully used for In alloys and In sulfide studies. 20–22 All the calculations were performed using the most recent version of the CRYSTAL program.…”

“…3(a)–(d). When compared to Δ E values for Li/LPS interfaces, with a corresponding value of about 0.9 eV, 6 this descriptor suggests that a higher thermodynamic barrier to LPS reduction is present in LiIn surfaces, though this effect is far less present when the outermost layer of the LiIn surface consists of Li atoms.…”

“…In our previous ASSLBs computational investigations, 5,6 we performed a detailed analysis of the Li 3 PS 4 (LPS) solid electrolyte and its interface with Li-metal. These studies confirmed the promising potential of LPS as a solid electrolyte and provided insights into the morphology of electrolyte microparticles.…”