Homogeneity of lithium distribution in cylinder-type Li-ion batteries

TL;DR

This study uses neutron diffraction, X-ray tomography, and electrochemical analysis to reveal non-uniform lithium distribution in 18650-type Li-ion batteries, highlighting the influence of cell geometry and electrode connections.

Contribution

It provides the first in situ, spatially-resolved analysis of lithium distribution in commercial Li-ion batteries under real operating conditions.

Findings

Lithium distribution in graphite anodes is non-homogeneous.

Deviations occur both radially and axially within the cell.

Cell geometry and electrode connections influence lithium homogeneity.

Abstract

Spatially-resolved neutron powder diffraction with gauge volume 2x2x20 mm3 has been applied to probe the lithium concentration in the graphite anode of different Li-ion cells of 18650-type in situ in charged state. Structural studies performed in combination with electrochemical measurements and X-ray computed tomography under real cell operating conditions unambiguously revealed non-homogeneity of lithium distribution in the graphite anode. Deviations from a homogeneous behaviour have been found in both radial and axial directions of 18650-type cells and were discussed in the frame of cell geometry and electrical connection of electrodes, which might play a crucial role in the homogeneity of the lithium distribution in the active materials within each electrode.