Lithium heterogeneities in cylinder-type Li-ion batteries – fatigue induced by cycling

Integrity and uniformity are crucial factors for stable, safe, robust and well-predicted operation of Li-ion batteries. The uniformity of lithium distribution in the graphite anode in fully charged state was studied by a combination of spatially-resolved time-of-flight neutron diffraction, powder diffraction using synchrotron radiation and electrochemical measurements. Studies were carried out on a series of NCA|C Li-ion cells of 18650-type with various cycle numbers. Experimentally obtained lithium distribution under in operando and ex situ conditions have been found in fair agreement and revealed a non-uniform character of lithiation in the graphite anode in charged state, where the degree of heterogeneity increases with the number of cycles.