'Anode-free' Li metal batteries constitute a promising candidate for next-generation electrochemical energy storage devices. However, currently technologies suffer from rapid capacity loss due to uneven Li deposition and dissolution, resulting in continous electrolyte decomposition, loss of chunks of electrically isolated Li as 'dead Li' and also creating significant safety risks through the formation of short circuits.[1] A further issue is self-discharge after Li is plated onto anodic current collectors during charging. This occurs through two routes - reaction of Li metal with the electrolyte, and electrochemical galvanic corrosion where electroylte reduction happens via current collector, and Li is converted to Li+ - both pathways result in significant reduction in capacity if charged 'anode-free' batteries are left to rest. Prior work has established this phenomina as a result of differences in the SEI formation kinetics on Cu and plated Li metal,[1] and shown that the rate of corrosion may be altered through application of stable interphase coatings.[2] The current work utilises an approach combining Electrochemical Impedance Spectroscopy (EIS) with operando 7Li NMR to establih differences in corrosion behaviour and interphase evolution with different Li plating amounts. Assignment of features in the EIS Distribution of Relaxation Times profiles are made to cathodic interphase processes, and separate features are observed for Cu and Li interphase charge transfer. Interphasial capacitance values are extracted from EIS data through are recently developed general phase element analysis, providing information about charge transfer kinetics at Cu and Li interphases. SEM imaging is utilised to correlate observed differences in Li metal signal intensity in operando 7Li NMR with changes in plated Li morphology and the interphasial evolution tracked via EIS analysis. The developed workflow allows deconvolution of interphase evolution of Cu and Li using a simple experimental set up. This allows a deeper understanding of the exact mecahnisms for Li metal corrosion under different plated Li loadings, with higher loadings almost entirely initially suprresing Cu interphase evolution. The same methods are then applied to study novel developed inorganic-organic polymer coated 'anode-free' batteries - incooperating multi-strength polymeric cross-linking approaches to produce extreme elastomeric properties - showing improved corrosion resistance and interphase stability. This work highlights the potential application of polymer coatings to enable high performance 'anode-free' batteries and their ability to reduce self-discharge through Li corrosion.