Ultrathin Li6.75La3Zr1.75Ta0.25O12-Based Composite Solid Electrolytes Laminated on Anode and Cathode Surfaces for Anode-free Lithium Metal Batteries

The low ionic conductivity, thermal stability and incompatibility of pellet-like solid-state electrolytes lead to low cycling performance in anode-free lithium metal batteries. Herein, we report an effective and feasible composite solid electrolyte-designing approach using the garnet (Li6.75La3Zr1.75Ta0.25O12, LLZTO)–polymer composite electrolyte (LLZTO/PEO-CPE) laminated on both the anode and cathode surfaces with an ultrathin thickness of 7–10 μm by spin coating method. It is found that the LLZTO/PEO-CPE exhibits a high ionic conductivity of about 4.76 × 10–4 S/cm at room temperature, excellent thermal stability, and good compatibility. Moreover, it simplifies the preparation of solid electrolytes and reduces the interfacial and grain boundary resistances for ion transfer. The use of both anode and cathode laminating enables dendrite-free lithium plating on copper with a high average coulombic efficiency and cycling stability of 98.8 and 41.2%, respectively, after the 65 cycles at 0.2 mA/cm2 and 55 °C in an anode-free battery. This work provides a new design of solid-state electrolytes (SSEs) to achieve safe and dendrite-free anode-free batteries.