Constructing a Multifunctional Interlayer toward Ultra‐High Critical Current Density for Garnet‐Based Solid‐State Lithium Batteries

Abstract All‐solid‐state lithium batteries (ASSLBs), exhibiting great advantages of high energy density and safety, are proposed to be the next generation energy storage system. However, the successful commercialization of garnet‐based ASSLBs is hindered by the poor contact between solid‐state electrolytes (Li 6.25 Ga 0.25 La 3 Zr 2 O 12 , LGLZO) and lithium anode, as well as low critical current density (CCD). Herein, an indium tin oxide (ITO) layer is prepared on LGLZO by ultrasonic spraying technique, where ITO reacts with molten lithium to form a composite interlayer, consisting of Li 13 In 3 , Li 2 O, and LiInSn. Experiments and density functional theory calculations demonstrate that such a unique interlayer plays a multifunctional role in achieving simultaneously better interface wettability, uniform Li deposition, and dendrite suppression at Li/LGLZO interface. Consequently, the CCD of ITO‐treated symmetric cell is increased to a record‐high value of 12.05 mA cm −2 at room temperature, which is expected to promote practical application of ASSLBs. Moreover, the Li/ITO@LGLZO/Li cell exhibits a low interfacial resistance of only 5.9 Ω cm 2 and performs stable electrochemical operations for over 2000 h at 2 mA cm −2 . The Li/ITO@LGLZO/LiFePO 4 full cell also delivers superior electrochemical performances, demonstrating the efficiency of the ITO layer.