Achieving Both High Ionic Conductivity and High Interfacial Stability with the Li_2+xC_1–xB_xO₃ Solid-State Electrolyte: Design from Theoretical Calculations

A crystalline solid electrolyte interphase Li₂CO₃ material with a large band gap shows promise toward next-generation all-solid-state lithium batteries (ASSLBs). However, the inferior ionic diffusivity restricts such structures to a real battery setup. Herein, based on density functional theory calculation and Python materials genomics, we theoretically develop the chemistry and local structural motifs to build a mixed boron–carbon framework Li_2+xC_1–xB_xO₃ (LCBO). We examine the electrochemical and chemical stabilities of LCBO-electrode interfaces by analyzing the thermodynamics of formation of interfacial phases. Interestingly, the LCBO material is automatically protected from further decomposition through the self-generated resistive interphase (Li₂CO₃ and Li₃BO₃), which gives a wide range of operating potential. LCBO shows high interfacial stability with LiCoO₂, LiMnO₂, and LiMn₂O₄. More importantly, the theoretical Li-ion migration barrier of LCBO (x = 0.375) is approximately 0.23 ± 0.02 eV through a cooperative migration mechanism. Therefore, the LCBO material combines high Li-ion diffusivity with good interfacial stability, which makes it a promising solid-state electrolyte material for ASSLBs.