Silicon-based lithium-ion battery anodes and their application in solid-state batteries

Silicon is one of the most common elements on Earth and is widely used in microelectronics. Also, it is well known as the most promising anode material for lithium-ion batteries due to its high theoretical specific capacity. However, silicon-based anodes are far from successful implementation because of the inherent disadvantages, such as mechanical degradation, absence of electric conductivity, and short cycling life. A comprehensive review of the lithium-ion battery anodes based on silicon is presented and discussed in terms of successful approaches leading to more durable silicon-based nanocomposite architectures that can potentially overcome the existing limitations of the silicon-based anodes. Besides silicon itself as active material, other anode components, such as polymer binders and electrically conductive carbon phases, play significant roles in the silicon-based electrode stability and the overall lithium-ion battery performance. Different types of binders are discussed in terms of their ionic, electronic, and the overall electric conductivity, and ability to minimize detrimental effects of mechanical deterioration of silicon during the repeated lithiation–delithiation cycles. To maintain electrical conductivity within the anode, especially during delithiation, carbon-based conductive phases are introduced as common additives. However, the advantages of the silicon-carbon nanocomposites are diminished by significant specific capacity loss due to the low capacity of the carbon phase. Thus, carbon-free silicon-based anodes are discussed as an important approach for the development of silicon-based anodes. The balance between the ionic and electronic conductivity in the lithium-ion battery anodes is emphasized with regard to the anode electrochemical performance. In comparison to silicon, its low-dimensional allotrope silicene can also be used in lithium-ion batteries. Its potential advantages and theoretically predicted properties favorable for lithium-ion battery anodes are known and are emphasized in terms of electric conductivity, morphology, synthesis conditions, and lithium-ion transport mechanisms fundamentally different from those of silicon. In terms of solid-state batteries, the first successful example of a solid-state battery with silicon anode is discussed in terms of its advantages and disadvantages.