In operando X-ray diffraction strain measurement in Ni₃Sn₂ – Coated inverse opal nanoscaffold anodes for Li-ion batteries

Volume changes associated with the (de)lithiation of a nanostructured Ni₃Sn₂ coated nickel inverse opal scaffold anode create mismatch stresses and strains between the Ni₃Sn₂ anode material and its mechanically supporting Ni scaffold. Using in operando synchrotron x-ray diffraction measurements, elastic strains in the Ni scaffold are determined during cyclic (dis)charging of the Ni₃Sn₂ anode. These strains are characterized using both the center position of the Ni diffraction peaks, to quantify the average strain, and the peak breadth, which describes the distribution of strain in the measured volume. Upon lithiation (half-cell discharging) or delithiation (half-cell charging), compressive strains and peak breadth linearly increase or decrease, respectively, with charge. The evolution of the average strains and peak breadths suggests that some irreversible plastic deformation and/or delamination occurs during cycling, which can result in capacity fade in the anode. The strain behavior associated with cycling of the Ni₃Sn₂ anode is similar to that observed in recent studies on a Ni inverse-opal supported amorphous Si anode and demonstrates that the (de)lithiation-induced deformation and damage mechanisms are likely equivalent in both anodes, even though the magnitude of mismatch strain in the Ni₃Sn₂ is lower due to the lower (de)lithiation-induced contraction/expansion.