2, Tohoku University, Katahira, , Japan
3, Argonne National Laboratory, Lemont, Illinois, United States
4, Brookhaven National Laboratory, Upton, New York, United States
Silicon with its ~10 times theoretical Li capacity compared with carbon-based electrodes, becomes one of the most promising alternative anode materials in lithium-ion batteries. However, its application is challenging due to the more than 400% volume expansion during lithiation, and the subsequent volume reduction during de-lithiation. Nanostructured Si materials have been studied to accommodate the volume change and to mitigate the issues, including Si nanowires, Si nanotubes and nano-porous Si. Here we investigate a novel form of nano-porous Si structure prepared by a liquid metal de-alloying method. The nanopores effectively prevent electrode cracking and therefore ensure long-term durability and stable performance within batteries. However, morphological changes and degradation of the Si nanoporous electrode during charging and discharging are still not fully understood, which limit utilizing this novel electrode with its full capacity. We apply synchrotron-based x-ray nano-tomography to quantify the three-dimensional morphological changes of the nanoprous Si anodes under different cycling conditions. We quantify the evolution of the electrode thickness and the material density distribution within the electrode as a function of electrochemical cycling. The delamination process, the morphological evolution and the degradation of the batteries will be discussed.