Optimization of the Li₃BO₃ Glass Interlayer for Garnet-Based All-Solid-State Lithium–Metal Batteries

Abstract

Lithium (Li)-dendrite penetration and poor interfacial wetting between Li-metal anode and the solid electrolyte are two major potential drawbacks concerning the long-term performance of garnet-based solid-state Li-metal batteries (SSLBs). To address these problems, the amorphous Li 3 BO 3 (LBO) glass interlayer in between Li anode and the solid electrolyte was demonstrated as a promising solution. However, this approach requires a thorough optimization to achieve effective performance and safety improvements in SSLBs. In this work, systematic design of experiments revealed optimal synthesis parameters stepwise to obtain a thin and uniform LBO interlayer in between Li 6.4 La 3 Zr 1.6 Ta 0.6 O 12 (LLZT) solid electrolyte and Li anode by using a screen-printing technique. The investigated synthesis parameters included LBO slurry compositions, heating rates, heating temperatures, heating times, and cooling rates. As a result, a pinhole-free LBO glass layer with ∼5 μm thickness could be coated onto LLZT pellets. The resulting LBO interlayer enhanced Limetal wetting and increased the interfacial conductivity from 1.32 × 10 −4 (from LBO-free) to 1.06 × 10 −3 S/cm. Electrochemical characterization of symmetrical cells revealed positive roles of the LBO interlayer such as (i) reducing interfacial impedance and offering uniform current flow across interfaces, (ii) preventing Li-dendrite penetration, and (iii) increasing the critical current density (CCD) and cycle life of SSLBs.

Grain boundary modification of Li₃PO₄ and Li₃BO₃ in garnet-type solid electrolyte for suppressing Li dendrite growth

“…30) In this study, Li 3 PO 4 (LPO) and Li 3 BO 3 (LBO) which with moderate ionic conductivity and low melting points were introduced into the grain boundary of LGLZ. LPO and LBO are used as a sintering aid of LLZ and its related materials, 31),32) interfacial layer, 33) and passivation layer 34) between LLZ and Li metal. The sintering and electrochemical properties of grain boundary modified LLGZ by the co-sintering were examined.…”