In Situ Synthesis and Dual Functionalization of Nano Silicon Enabled by a Semisolid Lithium Rechargeable Flow Battery

Nanosized silicon has attracted considerable attentions as a new-generation anode material for lithium-ion batteries (LIBs) due to its exceptional theoretical capacity and reasonable cyclic stability. However, serious side reactions often take place at the nanosized silicon/electrolyte interface in LIBs, where critical electrochemical properties such as initial Coulombic efficiency (ICE) are compromised. On the basis of this feature, a new method is developed to synthesize nanosilicon-based particles in a facile, scalable way, which are endowed with the function of prelithiation and storage stability in air. A semisolid lithium rechargeable flow battery (SSFB) technology is used for the first time to convert the micrometer-sized silicon raw material into an amorphous-nanosilicon-based material (ANSBM), as a result of the pulverization process induced by the repeated lithiation/delithiation cycles. The particle size is successfully reduced from 1-4 μm to around 30 nm after cycles in the flow battery. Bulk functionalization of the nano silicon is introduced by the unbalanced lithiation/delithiation cyclic process, which endows ANSBM with a unique prelithiation capability universally applicable to different anode systems such as nanosized Si, SiO, and graphite, as evidenced by the significantly improved ICEs. Superior air stability (10% relative humidity) is exhibited by ANSBM due to surface functionalization by the stable interfacial layer encapsulated by electron-conductive carbon. The outcome of this work provides a promising way to synthesize dual-functionalized nano silicon with good electrochemical performance in terms of improved capacity and increased initial Coulombic efficiency when it is composited with other typical anode materials.