Silicon–Carbon Nanocomposite Semi-Solid Negolyte and Its Application in Redox Flow Batteries

Abstract

Nonaqueous redox flow battery (RFB) is a promising technology to improve the energy density of RFBs for both stationary grid energy storage and electric vehicle applications. Despite tremendous advancement made in high-capacity flow posolyte, lithium metal has been dominantly exploited as a nonflowable counter electrode in reported lithium-based RFBs to date due to the lack of efficient and high-capacity flow negolyte. Here, we report a silicon–carbon nanocomposite semi-solid negolyte, achieving a high reversible capacity (>1200 mAh g–1) and stable cycle life (>100 cycles). A facile process of incipient wetness impregnation followed by polymerization/carbonization is developed to synthesize monodispersed Si–C nanocomposite with ultrathin graphitic carbon coating. Exploiting Si–C nanocomposite as the negolyte effectively suppresses the volume change of Si particles and enhances the electrical conductivity of the negolyte. Coupling with highly concentrated LiI (5.0 M), we demonstrate the first lithium metal-free Si-based negolyte in a full all-flow cell configuration with a stable cycle life (>60 cycles), high Coulombic efficiency (>90%), and the highest full cell voltage (3.0 V) reported for Li metal-free RFBs. Our successful demonstration of lithium metal-free all-flow battery highlights the promising potential of Si-based negolyte to replace lithium metal for high-energy-density RFBs.

Recent progress in organic redox flow batteries: Active materials, electrolytes and membranes

“…18 ). Thereafter, many other insoluble Li-ion based active species (sulfur [158,167,168] , polysulfide [10,169] , silicon [170,171] , LFP [172,173] , LTO [174] etc.) have been demonstrated as the semisolid suspensions in non-aqueous based RFBs.…”

Silicon Anodes for High‐Performance Storage Devices: Structural Design, Material Compounding, Advances in Electrolytes and Binders

“…The silicon‐graphite composite anode was synthesized by Mechanofusion process, two‐step ball milling and a facile incipient wetness impregnation method. As a result, superior cycle ability and rate capability were achieved, compared to conventional Si anode . Graphene is also one of the main materials for silicon‐carbon composite.…”

Interphases in Electroactive Suspension Systems: Where Chemistry Meets Mesoscale Physics

“…The added challenge is that rather than forming a clearer picture of underlying mechanisms, these studies appear to provide phenomenological explanations based on conflicting assumptions. For instance, silicon and carbon based slurries are shown to maintain both good and bad inter‐particle contact under cycling . The contribution of interface between current collector and slurry towards electrical resistance is shown to be both significant and insignificant .…”

“…SSRFBs based on different material systems were demonstrated in subsequent studies by various research groups: (i) a full‐cell based on carbon coated LiTi 2 (PO 4 ) 3 and LiFePO 4 with KB in aqueous electrolyte; (ii) a half‐cell with LiFePO 4 with KB in commercial LP30 (EC:DMC) electrolyte; (iii) a half‐cell with silicon with KB in LP30 and EC:DEC; and (iv) a full‐cell with P2‐type Na x Ni 0.22 Co 0.11 Mn 0.66 O 2 and NaTi 2 (PO 4 ) 3 in EC:DMC:NaPF 6 (0.5 M) . These studies are proof of the great potential SSRFBs have in terms of utilizing a variety of active materials, conductive additives, and electrolytes.…”