Nanoscale inhomogeneities build up in electrode particles during cycling, and decrease the reversibility of the battery reactions . Both the irreversible structural damage in individual electrode particles, for example the fracturing of Si negative electrodes , and the formation of electrochemically inactive species, for example the formation of the solid-electrolyte interphase (SEI) , lead to the irreversible loss of active materials and depletion of the usable lithium inventory and electrolyte . Resolving the three dimensional (3D) spatial distribution of heterogeneous degradation at the single electrode particle level with nanometer resolution can shed light into battery degradation pathways and their reaction kinetics, leading to the development of new materials and strategies for improved battery performance.