Characteristics and structural change of layered polysilane (Si6H6) anode for lithium ion batteries

Layered polysilane (Si6H6) has a graphite-like structure with higher capacity than crystalline silicon. The rate of increase of the thickness of a layered polysilane electrode after 10 charge–discharge cycles was smaller than that for a Si powder electrode, although the layered polysilane electrode has higher capacity. The structural changes of electrochemically lithiated and delithiated layered polysilane at room temperature were studied using scanning electron microscopy, X-ray diffraction and Raman spectroscopy. Layered polysilane became amorphous by insertion of lithium to 0 V, whereas insertion of lithium into crystalline silicon produces Li15Si4. Layered polysilane maintained an amorphous state during lithium insertion and deinsertion, whereas silicon changed between Li15Si4 and amorphous LixSi, which explains the smaller volume change of a layered polysilane electrode compared with a Si powder electrode.