Redesign of Li2MP2O7 (M = Fe or Mn) by Tuning the Li Diffusion in Rechargeable Battery Electrodes

Defects in crystals such as antisites generally lead to the deterioration of the ionic conductivity of solid-state ionic conductors. Herein, using first-principles calculations, we demonstrate that the Li diffusion in Li 2 MP 2 O 7 (M = Fe or Mn), a promising battery material, is sensitively affected by the presence of Li/M antisites; however, unexpectedly, the antisites significantly promote Li diffusion. The calculations reveal that the presence of antisites reduces the barrier of Li hopping and opens new paths for Li diffusion in the Li 2 MP 2 O 7 crystal. In our experimental verification, we succeeded in synthesizing crystalline Li 2 MnP 2 O 7 with varying Li/Mn antisite contents and demonstrated that the inclusion of antisites results in improved power capability with faster Li diffusion for Li-ion battery electrodes. We believe that this unexpected finding of increasing the ionic c…