Imaging in-operando LiCoO2 nanocrystallites with Bragg coherent X-ray diffraction

Abstract

Although the LiCoO2 (LCO) cathode material has been widely used in commercial lithium ion batteries (LIB) and shows high stability, LIB’s improvements have several challenges that still need to be overcome. In this paper, we have studied the in-operando structural properties of LCO within battery cells using Bragg Coherent X-ray Diffraction Imaging to identify ways to optimise the LCO batteries’ cycling. We have successfully reconstructed the X-ray scattering phase variation (a fingerprint of atomic displacement) within a  ≈ (1.6 × 1.4 × 1.3) μm3 LCO nanocrystal across a charge/discharge cycle. Reconstructions indicate strained domains forming, expanding, and fragmenting near the surface of the nanocrystal during charging, with a determined maximum relative lattice displacements of 0.467 Å. While discharging, all domains replicate in reverse the effects observed from the charging states, but with a lower maximum relative lattice displacements of 0.226 Å. These findings show the inefficiency-increasing domain dynamics within LCO lattices during cycling. Although lithium cobalt(III) oxide (LCO) is a widely used and highly stable lithium-ion battery material, several challenges still need to be overcome. Here, the authors use in-operando Bragg Coherent X-ray Diffraction Imaging to visualize the structural properties of LCO in battery cells and identify inefficiency-increasing domain dynamics during cycling.