Cyclic voltammetry experiments (CV,

Cyclic voltammetry experiments (CV, Fig. 4b) show lithiation and
delithiation peaks at potentials typical of the reaction of Si21. An
activation process occurred over the first few cycles, as indicated
by the increase of the CV peak intensity and a decrease of the charge
transfer resistance measured by impedance spectroscopy (Supplementary
Fig. S10). To study the electrode morphology after activation,
the cell was disassembled after 60 cycles to observe the nano-Siwith SEM. The nano-Si still showed high porosity, but the initial
nanoparticles evolved into nanoporous frameworks (Supplementary
Fig. S11b–c). Two processes could have happened during activation