It is conventionally difficult to measure lithium ion concentrations inside commercially standard battery cell configurations using X-rays because the weak signals of lithium cannot be distinguished from the strong signals of other heavy transition metal elements that are present in batteries. Here, we show a novel operando correlative imaging technique of X-ray Compton scattering-computed tomography (XCS-CT) that maps lithium ion concentration distributions and 3D electrode microstructural changes and lithium dendrite growth inside batteries during charging and discharging. The XCS-CT imaging is complemented by time-of-flight secondary ion mass spectrometry (ToF-SIMS) and cryo-plasma focused ion beam (cryo-PFIB) to study effects of pressure inside batteries on lithium chemical distributions and physical structures. We also show the effects of super-resolution convolutional neural network (SRCNN) model that improve image resolution while maintaining a relatively large field-of-view for microstructural quantification.

Using the insights uncovered by characterisation, we develop two advanced processing methods to make electrode microstructure that speeds up lithium ion diffusion, one is directional ice templating for making electrodes with vertical pores for lithium ion batteries with liquid electrolyte, and the other is directional freezing and polymerisation for fabricating cathodes with vertical columns of cathode material and solid polymer electrolyte for solid-state lithium metal batteries. The method directly incorporates the solid polymer electrolyte in the electrode structure within a single process.