Computational study of ${\mathrm{Li}}_3{\mathrm{BO}}_3$ and ${\mathrm{Li}}_3{\mathrm{BN}}_2$ II: Stability analysis of pure phases and of model interfaces with Li anodes

Journal Article · 17 August 2021 · Physical Review Materials

DOI: https://doi.org/10.1103/physrevmaterials.5.085403 · OSTI ID:1826065

Li, Yan  ^[1]; Hood, Zachary D.  ^[2]; Holzwarth, N. W.  ^[1]

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1. Wake Forest Univ., Winston-Salem, NC (United States)
2. Argonne National Lab. (ANL), Argonne, IL (United States)

Both ${\mathrm{Li}}_3{\mathrm{BO}}_3$ and ${\mathrm{Li}}_3{\mathrm{BN}}_2$ materials have promising properties for use in all solid-state batteries and other technologies dependent on electrolytes with significant ionic conductivity. As the second of a two-part study, the structural properties of ${\mathrm{Li}}_3{\mathrm{BO}}_3$ and three reported phases of ${\mathrm{Li}}_3{\mathrm{BN}}_2$ are investigated using first-principles modeling techniques. For alpha- ${\mathrm{Li}}_3{\mathrm{BN}}_2$, the tetragonal P4₂/mnm structure reported in the literature is found to be unstable as evidenced by imaginary phonon modes near the M point of its Brillouin zone. Our simulations within the harmonic approximation suggest that the real α phase has the orthorhombic space group symmetry Pmmn formed with twice as many formula units and tiny adjustments of the equivalent lattice parameters and fractional coordinates. Extending the analysis of the Pmmn α- ${\mathrm{Li}}_3{\mathrm{BN}}_2$ structure to the quasiharmonic approximation improves the agreement between the room-temperature x-ray pattern reported in the literature and the corresponding simulation results. In anticipation of the use of the monoclinic phases of ${\mathrm{Li}}_3{\mathrm{BO}}_3$ and ${\mathrm{Li}}_3{\mathrm{BN}}_2$ in Li ion conducting applications, chemical stability is investigated in terms of free-energy differences of possible decomposition and Li reaction processes, finding encouraging results. As further investigations of ${\mathrm{Li}}_3{\mathrm{BO}}_3$ and β- ${\mathrm{Li}}_3{\mathrm{BN}}_2$ as electrolyte or coating materials, particularly for use with Li metal anodes, idealized electrolyte/Li interfaces were investigated in terms of their geometric, energetic, and electronic properties. The results find the electrolyte/Li interfaces to be quite favorable, perhaps comparable to the pioneering LiPON/Li system.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Laboratory Directed Research and Development (LDRD) Program
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1826065
• Journal Information: Physical Review Materials, Journal Name: Physical Review Materials Journal Issue: 8 Vol. 5; ISSN 2475-9953
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English