Dissolution of manganese from the LiMn2O4 cathode material has been shown to be another significant barrier in high-voltage lithium ion batteries, since it links surface redox instability, electrolyte breakdown, dissolution of transition metals, and ensuing interphase instability. Current post mortem methods based on simple chemical assays give accurate estimates of total manganese but do not provide details about the start of dissolution, redistribution of the released Mn2+ species within the electrolyte, and the effect of the electrolyte chemistry on the voltage window where dissolution occurs. In this paper, a voltage-gated electrolyte-resolved reconstruction technique is proposed, which considers the proton magnetic resonance imaging data as electrolyte-based manganese inventory information. It includes concentration calibration from the image intensity, assignment of concentration change to specific voltages, spatial segmentation of the electrolyte into three compartments close to the cathode, central region, and anode side, and calculation of inventory descriptors accounting for spatial concentration versus molar inventories. The analysis of the proton magnetic resonance imaging data obtained for LiMn2O4 cells containing 1 M LiPF6 EC:DMC liquid electrolyte, LiPF6 EC:DMC gel electrolyte, and 1 M LiTFSI methyl-3-cyanopropanoate electrolyte reveals the appearance of manganese release gate at 4.1 V, an increased rate of manganese dissolution in the high voltage regime beyond 4.7 V, and the map-based maximal concentration of Mn2+ in the gel electrolyte region of 36 µmol L−1. Reconstruction of regional manganese inventories results in the values of 8.42×10−10, 6.51×10−10, and 8.45×10−10 mol for cathode, middle, and anode electrolyte regions, leading to the total first cycle value of 2.34×10−9 mol. Despite having a smaller local concentration, the anode side compartment has a similar molar inventory because of larger electrolyte volume in this region, proving that concentration gradient does not correlate with degradation potential. Suppression of charge window intensity rise in the cyanester-LiTFSI electrolyte suggests that the latter prevents voltage-gate manganese dissolution process instead of lowering the final dissolved manganese concentration.
