Role of Crystal Symmetry in the Reversibility of Stacking-Sequence Changes in Layered Intercalation Electrodes.

The performance of many technologies, such as Li- and Na-ion batteries as well as some two-dimensional (2D) electronics, is dependent upon the reversibility of stacking-sequence-change phase transformations. However, the mechanisms by which such transformations lead to degradation are not well understood. This study explores lattice-invariant shear as a source of irreversibility in stacking-sequence changes, and through an analysis of crystal symmetry shows that common electrode materials (graphitic carbon, layered oxides, and layered sulfides) are generally susceptible to lattice-invariant shear. The resulting irreversible changes to microstructure upon cycling ("electrochemical creep") could contribute to the degradation of the electrode and capacity fade.