Boron Nitride Enhanced Garnet-Type (Li_6.25Al_0.25La₃Zr₂O₁₂) Ceramic Electrolyte for an All-Solid-State Lithium-Ion Battery

Solid-state electrolytes (SSEs) are expected to improve not only the safety but also the energy density of lithium-ion batteries, especially referring to the application of most promising Li metal anode which encounters deleterious dendritic growth. The key challenge for the SSEs is the pursuit of higher ionic conductivity, higher mechanical strength, and better chemical and electrochemical stability. Herein, for the first time, hexagonal boron nitride (BN) is employed as the effective additive for garnet-type Li_6.25Al_0.25La₃Zr₂O₁₂ (LALZO) SSE during sintering, which induces comprehensively improved properties. Compared with the LALZO electrolyte without BN, a small percentage of 1 wt % BN added to the LALZO electrolyte exhibits 30 times higher ionic conductivity (6.21 × 10^–5 S cm^–1), 6.6 times higher surface hardness (∼0.5 GPa), and 6.3 times higher reduced modulus (5.6 GPa), much improved chemical stability against air (anti-Li₂CO₃), and electrochemical stability during lithium stripping/plating at different current densities. As a result, the all-solid-state lithium-ion battery composed of lithium metal anode and LiCoO₂ cathode with the 1 wt % BN enhanced LALZO electrolyte delivers a discharge capacity of 120 mA h g^–1 and a much higher capacity retention (67% vs 33%) after 50 cycles at a rate of 0.1C than that without BN addition. This BN enhanced garnet-type ceramic electrolyte may provide a facile and efficient approach to further promote the solid-state electrolyte for next-generation high performance energy storage devices.