Enhancement of Ionic Transport at the Interface of LLZTO by Using Lithium Borohydride Ammoniates

Abstract Garnetbased all‐solid‐state electrolytes are promising because of their wide electrochemical window and high ionic conductivity. However, the preparation process for garnet‐based solid‐state electrolytes is complex, requiring a high sintering temperature (>1050 °C) and a long sintering time (>10 h), which results in poor contact with the electrode. In this work, hydride coating modification can effectively improve the interface contact of oxide particles and enhance the ability of ion conduction. Hence, a series of composite electrolytes Li_6.4La₃Zr_1.4Ta_0.6O₁₂‐xwt%Li(NH₃)_0.2BH₄ (LLZTO‐xwt%LNB, 0≤x≤30) is synthesized at Room temperature (RT), in which hydrides uniformly coat and fill in the pores of LLZTO to provide lithium‐ion transport channels. At 30 °C, the conductivity of LLZTO‐10wt%Li(NH₃)_0.2BH₄ (LLZTO‐10wt%LNB, 2.3 × 10⁻⁴ S cm⁻¹) is four orders higher than pristine untreated LLZTO (8.7 × 10⁻⁸ S cm⁻¹), and two orders higher than pristine Li(NH₃)_0.2BH₄ (1.3 × 10⁻⁶ S cm⁻¹). The critical current density reaches up to 3 mA cm⁻², demonstrating excellent stability against lithium. These strategies positively impact the development and application of solid‐state electrolytes.