Abstract: Given the energy demands of the electromobility market, the energy density and safety of lithium batteries (LBs) need to be improved, whereas its cost needs to be decreased. For the enhanced performance and decreased cost, more suitable electrode and electrolyte materials should be developed based on the improved understanding of the degradation mechanisms and structure–performance correlation in the LB system. Thus, various in situ characterization technologies have been developed during the past decades, providing abundant guidelines on the design of electrode and electrolyte materials. Here we first review the progress of in situ characterization of LBs and emphasize the feature of the multi-model coupling of different characterization techniques. Then, we systematically discuss how in situ characterization technologies reveal the electrochemical processes and fundamental mechanisms of different electrode systems based on representative electrode materials and electrolyte components. Finally, we discuss the current challenges, future opportunities, and possible directions to promote in situ characterization technologies for further improvement of the battery performance.