Silicon (Si) is a promising anode material for lithium-ion batteries but has long been suffering from low conductivity, drastic volume change, poor cycling performance, etc. Adding SiO, Al, etc. to form Si-based binary composite films can improve some properties but have to give up others. Here, we prepared a ternary Si-SiO-Al composite film anode by adding SiO and Al together into Si using magnetron sputtering. This film has an extraordinary combination of conductivity, specific capacity, cycling stability, rate performance, etc., when compared with its binary and unary counterparts. While both SiO and Al can separately mitigate anode cracking resulting from the huge volume expansion during the lithiation/delithiation cycling process, the synergetic effect of adding SiO and Al together to form a ternary composite film can produce much better results. This film maintains an island structure that can efficiently buffer the volume expansion during the cycling process, giving rise to superior cycling performance and excellent rate performance. In addition, the cosputtered Al improves the electrical conductivity of the anode at the same time. This unique combination of anode properties, together with the low cost, suggests that the Si-SiO-Al composite film has the potential to be commercialized as a binder-free anode for lithium-ion batteries. This work also provides an efficient means to modulate the anode properties with more degrees of freedom.
Keywords: Si anode; cycling stability; lithium-ion batteries; rate performance; ternary composite film.