Multi-dimensional conductive carbon conglomeration as conductive additives for tailoring graphite/silicon alloy anodes in lithium ion batteries

To satisfy the ever-increasing demand for high-capacity and fast-charging anodes in lithium-ion batteries, the use of Si-based materials has been regarded as the most promising strategy because of their distinct lithiation capacities and kinetics. However, Si-based anodes are vulnerable to particle pulverization during repeated charge-discharge cycles, which causes the electrical isolation of Si particles. This study proposes a novel strategy to prevent the electrical isolation of micro Si alloy-based electrodes by employing multi-dimensional carbon conglomeration as a conductive additive. A multi-dimensional carbon conglomeration containing N-doped reduced graphene oxide and carbon black (NrGO/CB) was fabricated by a scalable dry method without using solvents through a mechano-fusion process. NrGO/CB functions as a valid electron transfer mechanism by activating new types of electron transfer pathways within the carbon particles through cross-linked sp³–sp² hybrid covalent bonds. Unlike the typical sp³-hydridized system, the presence of conjugated π bonds next to the sp³-hydridized carbon causes the electrons to be delocalized at the sp³-hydridized carbon, thereby significantly enhancing electron mobility of NrGO/CB. Furthermore, the addition of a small amount of graphite functions as an initiative to integrate multi-dimensional NrGO/CB with the Si alloy particles, thereby extending the electron transfer network across the entire electrode scale. Accordingly, Si alloy anodes integrated with NrGO/CB and graphite demonstrated electrochemical performances with exceptional initial Coulombic efficiency (90.26 %) and cycling stability (101.9 % after 100 cycles at 0.1 C) compared to those of conventional carbon additives.