Experimental Visualization of Commercial Lithium Ion Battery Cathodes: Distinguishing Between the Microstructure Components Using Atomic Force Microscopy

Abstract

The integration of lithium-ion batteries (LIB) into transportation through the implementation of hybrid and electric vehicles is driving fundamental research into improving their performance and lifetime. The rapid production of new electric vehicles by several popular brands also raises the question of how much material will eventually need to be reused or recycled. With a combination of an enhanced fundamental analysis of commercially utilized electrodes with fundamental chemical knowledge, answers to the scientific material challenges of lithium ion batteries will aid in not only the implementation of battery powered electrical transport but also the development of end of life recycling processes. Here, using quantitative nanomechanical and conductive atomic force microscopy, which are nondestructive and rapid techniques, the different components of the composite electrode are unveiled at the nanoscale, identifying the mechanism by which the active material binds together and how the conductive network is formed. Changes in the polymer binder network are observed in an aged cell and are shown to affect the mechanical integrity of the electrode structure, which can lead to the failure of the electrode. The links between nanomechanical and macro-mechanical properties were evaluated using a scratch test and optical microscopy to show that the mechanical integrity of the aged cell was weaker than that of the untouched cell.