Nitrogen-Doped Lithium Lanthanum Titanate Nanofiber-Polymer Composite Electrolytes for All-Solid-State Lithium Batteries
Journal of the Electrochemical Society
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 Li 3x La 2/3 − x TiO 3 (LLTO) nanofibers by heat treatment in the ammoniacontaining 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
... ure 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. Nitrogendoped 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 × 10 −4 S•cm −1 at room temperature and an electrochemical stability window of up to 4.9 V vs Li|Li + . The all-solid-state Li metal|composite electrolyte|LiFePO 4 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.