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.

用于锂离子电池（Li-batteries）的硅电极，其重量能量密度是现有商用电极的十倍。其主要缺陷在于伴随约300%体积膨胀的严重容量衰减，以及固体电解质界面（solid-electrolyte-interphase, SEI）层的持续生长，该过程会消耗电解液与活性物质。已有研究证实，人工SEI层可抑制SEI的生成。但若在人工SEI层沉积前未去除天然氧化硅（SiOx）层，该层仍会以埋藏界面的形式留存于体系中。由于去除该天然氧化硅层既耗时且成本高昂，因此厘清该氧化硅层的影响至关重要。中子反射法（Neutron Reflectometry）正是开展此类研究的理想工具，其优势在于硅与锂具备极高的散射长度密度对比度，且该方法对薄层结构拥有极高的检测灵敏度。