Nitrogen-Doped Lithium Lanthanum Titanate Nanofiber-Polymer Composite Electrolytes for All-Solid-State Lithium Batteries

Currently cation doping is common for improving ionic conductivity of metal oxide-based lithium-ion conductors. In this work, anions (nitrogen ions) have been doped to perovskite Li3xLa2/3 - xTiO3 (LLTO) nanofibers by heat treatment in the ammonia-containing atmosphere, and substituted for oxygen anions partially in the perovskite structure. Density-functional theory (DFT) calculation results reveal that nitrogen doping weakens the bonding of Li ions on the A sites in perovskite ABO(3) structure and allows for larger lattice distortion, reducing the activation energy for Li-ion hopping in both the forward and backward jumping directions. Experimental results have also confirmed that nitrogen doping has improved ionic conductivity of LLTO. Nitrogen-doped LLTO nanofibers have been incorporated with a poly (vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) polymer to form a solid-state composite electrolyte, which exhibits ionic conductivity of 3.8 x 10(-4) S center dot cm(-1) at room temperature and an electrochemical stability window of up to 4.9 V vs Li divide Li+. The all-solid-state Li metal divide composite electrolyte divide LiFePO4 lithium batteries, which employ nitrogen-doped LLTO nanofibers, show better rate capability and cycling stability at room temperature than the counterparts with pristine LLTO nanofibers.

Automated summary

The study focused on improving the ionic conductivity of LLTO by nitrogen doping and successfully preparing a solid-state composite electrolyte. The electrochemical performance tests demonstrated that the nitrogen-doped composite electrolyte exhibited good ionic conductivity and cycling stability at room temperature.