Lithium-ion batteries (LIBs) have some serious safety problems, such as lithium dendrite formation during charging/discharging cycles that may cause internal short-circuiting, fires, and even explosions. A new double-scale in situ experimental setup, which can record all phenomena during the electrochemical testing, was developed. Lithium dendrite growth behavior of commercial LIBs during small-current-density charging at room temperature was observed in situ. The formation, growth, and dissolution of lithium dendrites, and dead lithium residue were all observed and recorded using this new experimental test system. A detailed model of lithium electrodeposition and dissolution processes was proposed. The electrode structures were determined by X-ray diffraction (XRD). The surface morphologies were examined by scanning electron microscopy (SEM). The texture and surface morphology of the graphite active layer affected lithium dendrite initiation as well as its growth processes.

Measurements of mechanical properties of copper current collector foils were performed using three techniques: a standard microtensile testing machine equipped with a laser sensor, dynamic mechanical analysis (DMA), and nanoindentation. For electrolytic copper (E-Cu) foils, we find elastic moduli of approximately 70 GPa, and for rolled copper (R-Cu) foils, we find elastic moduli of approximately 50 GPa.