Operando neutron reflectometry of of a crystalline silicon anode protected by an artificial SEI during lithiation/delithiation– The role of

Silicon electrodes for Li-batteries have a ten times higher gravimetric energy density than current electrodes. The major drawback is the big capacity fading associated with the volume expansion(~300%) and the continious growth of the solid-electrolyte-interphase(SEI) layerwhile consuming electrolyte and active material. It was shown that artificial SEI-layer may suppress the SEI-formation. However, if the native silicon oxide (SiOx) layer was not removed before the artificial SEI layer deposition, it will be still present as buried interface. Since the removal of this native silicon oxide layer is time-consuming and expensive. It is therefore important to understand the influence of this layer. Neutron reflectometry is an excellent tool for this investigation because of the high scattering length density contrast of silicon and lithium as well as the high sensitivity to thin layers.