Constructing Stable Li6.4La3Zr1.4Ta0.6O12|Li Interface by Buffer Layer of Li4(BH4)3I/BN with High Ionic Conductivity and Critical Current Density

Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) solid electrolyte, renowned for its high ionic conductivity and robust safety profile at room-temperature, holds tremendous promise for diverse applications. However, it faces significant challenges, including high interface impedance with lithium and a propensity for lithium dendrite formation. To address these issues, a novel Li 4 (BH 4 ) 3 I/2(d-BN) (LBHIbn) composite buffer layer — exhibiting high ionic conductivity and critical current density — is introduced at the LLZTO|Li interface. Theoretical calculations reveal that LBHIbn, serving as a protective layer of LLZTO, possesses a lower interface energy (0.366 J m −2 ) against lithium metal compared to LiBH 4 (0.434 J m −2 ). Consequently, at 30 °C, the interface impedance of the LLZTO | LBHIbn | Li system is significantly reduced to 4 Ω cm −2 . Simultaneously, the critical current density increases from 0.93 mA cm −2 of LLZTO | Li to 5.29 mA cm −2 (for LLZTO-LBHIbn | Li) with stable lithium-ion plating/stripping cycling demonstrated over 1000 h. Unlike conventional metal-based buffer layers that suffer from limited ionic conductivity, LBHIbn uniquely integrates high ionic conductivity (4.0 × 10−⁴ S cm −1 ) with superior electronic insulation (1.9 × 10−⁹ S cm −1 ), achieving simultaneous reduction of interfacial resistance (4Ω cm 2 at 30 °C) and effective suppression of lithium dendrite growth. This study demonstrates that the LBHIbn interface treatment effectively mitigates the interfacial issues between the LLZTO electrolyte and lithium anode, thereby expanding the potential applicability of hydride and oxide electrolyte materials in all-solid-state batteries