Acid Induced Conversion towards Robust and Lithiophilic Interface for Li-Li7La3Zr2O12 Solid-State Battery

Solid-state lithium batteries (SSBs) promise high energy and power densities as well as enhanced safety owing to the use of Li metal and nonflammable solid-state electrolytes. Particularly, cubic garnet–type Ta-substituted Li7La3Zr2O12 (LLZTO) is prominent for high ionic conductivity and stable nature against Li metal. However, poor interfacial contact of Li/LLZO interface is an emerging obstacle for demanding applications. Herein, to tackle this problem, a novel and facile strategy is demonstrated using H3PO4 to react with the Li2CO3/LiOH passivation layer of the LLZTO surface to form a uniform Li3PO4 modification layer. The Li3PO4 layer not only promotes the interfacial wettability by reducing the significant difference of surface energy, but also produces a robust solid electrolyte interphase (SEI) to inhibit lithium dendrite penetration. The symmetric cell exhibits a dramatically reduced interfacial resistance of 7.0 Ohm∙cm2 and an ultrastable galvanostatic cycling, over 1600 hours at 0.1 mA cm-2 and over 450 hours at 0.5 mA cm-2. Besides, hybrid solid-state full cells matching with different cathodes also display excellent electrochemical performances. LiFePO4 exhibits a stable cycling (~150 mAh g-1) and good rate performance. Especially for S cathode, coulombic efficiencies remain higher than 99% during 200 cycles. Ternary NCM523 cathode also confirms the anodic interfacial stability up to high voltage (4.5V). Therefore this facial strategy provides a stepping stone for future applications of solid-state Li-ion and Li-S batteries.