  As one of the most promising next-generation energy storage device, lithium
metal batteries have been extensively investigated. However, the poor safety
issue and undesired lithium dendrites growth hinder the development of lithium
metal batteries. The application of solid state electrolytes has attracted
increasing attention as they can solve the safety issue and partly inhibit the
growth of lithium dendrites. Polyethylene oxide (PEO)-based electrolytes are
very promising due to their enhanced safety and excellent flexibility. However,
PEO-based electrolytes suffer from low ionic conductivity at room temperature
and can't effectively inhibit lithium dendrites at high temperature due to the
intrinsic semi-crystalline properties and poor mechanical strength. In this
work, a novel coral-like Li6.25Al0.25La3Zr2O12 (LALZO) is synthesized to use as
an active ceramic filler in PEO. The PEO with LALZO coral (PLC) exhibits
increased ionic conductivity and mechanical strength, which leads to the
uniform deposition/stripping of lithium metal. The Li symmetric cells with PLC
cycle for 1500 h without short circuit at 50 centidegree. The assembled
LiFePO4/PLC/Li batteries display excellent cycling stability at both 60 and 50
centidegree. This work reveals that the electrochemical properties of organic
and inorganic composite electrolyte can be effectively improved by tuning the
microstructure of the filler, such as the coral-like LALZO architecture.
