High-performance lithium metal batteries enabled by a nano-sized garnet solid-state electrolyte modified separator

Lithium metal batteries, as one of high-energy-density batteries, have become the hot spot for numerous researchers. However, serious safety problems caused by lithium dendrites need to be urgently addressed. In this work, we introduce nano-sized garnet solid-state electrolyte Li6.75La3Zr1.75Ta0.25O12 (LLZTO) to fabricate a high-safety thin composite solid electrolyte membrane (20 μm) that is simple in process and facile in preparation conditions. The thin composite solid electrolyte film has better wrinkle resistance than ordinary polyethylene (PE) films and can guide the uniform deposition of lithium ions and suppress the growth of lithium dendrites. The thermal stability of the PE separator modified by double-coated nano-sized LLZTO is enhanced, which exhibits only 30 % shrinking percentage at 140 °C in comparison with 90 % of ordinary PE. The lithium symmetric cell with the nano-sized garnet solid-state electrolyte modified separator is relatively stable after 1000 h cycling at the current density of 1 mA cm−2. More importantly, after adding the adaptable electrolyte, the lithium metal battery assembled with modified separator can be maintained for 150 cycles (0.2C) stably with a high cathode active material loading of NCM811 (18 mg cm−2), and can maintain above 95 % Coulombic efficiency on average. Our work provides a pathway for the preparation of superior thermal stability and high safety garnet-based composite membranes towards lithium metal batteries.