Covalent Coating of Micro‐Sized Silicon With Dynamically Bonded Graphene Layers Toward Stably Cycled Lithium Storage

Abstract

State-of-the-art carbon coatings are sought to protect high-capacity silicon anodes, which suffer from low conductivity, large volume change and fast degradation. However, this approach falls short when handling physical-electrical disconnections between carbon shells and silicon microparticulate (SiMP) with drastic size variations. Here, a strategy of covalent coating is developed to establish a robust encapsulation structure. The obtained covalent Si-C bonds enable an effectively dynamic connection between the electrochemically deforming SiMP and the sliding graphene layers, preventing the evolution of gaps between SiMP and the carbon shell and maintaining persistent electrical connections as well as mechanical toughness. As a result of high structure reversibility, the cycling stability of thick SiMP anodes is greatly improved, up to a high areal capacity of 5.6 mAh cm −2 and volumetric capacity of 2564 mAh cm −3 . This interface bonding effect demonstrates the great potential for suppressing deformation involved degradation of high-capacity materials through coating strategies.

Advanced Micro/Nanostructure Silicon-Based Anode Materials for High-Energy Lithium-Ion Batteries: From Liquid- to Solid-State Batteries

“…This volumetric oscillation engenders a susceptibility to fracture, further exacerbated by anisotropic expansion�a phenomenon arising from the volume shift during lithiation, rendering micron particles intrinsically susceptible to breakage under substantial stresses. 53 Additionally, due to their larger particle size, micro/nano structure Si anodes materials grapple with constrained charge transfer kinetics, culminating in diminished fast charge/discharge capability�reflecting a concern that warrants contemplation. 54 Within this mosaic of endeavors, the epoch of Si/carbon composites emerges as a harbinger of promise, poised to steer industrial applications to new heights.…”

“…Foremost among these is the pronounced volume variation witnessed by micron Si during the lithiation/delithiation process, a departure from the more manageable behavior exhibited by nano Si. This volumetric oscillation engenders a susceptibility to fracture, further exacerbated by anisotropic expansiona phenomenon arising from the volume shift during lithiation, rendering micron particles intrinsically susceptible to breakage under substantial stresses . Additionally, due to their larger particle size, micro/nano structure Si anodes materials grapple with constrained charge transfer kinetics, culminating in diminished fast charge/discharge capabilityreflecting a concern that warrants contemplation .…”

High-Rate SiO Lithium-Ion Battery Anode Enabled by Rationally Interfacial Hybrid Encapsulation Engineering

“…For example, an in situ graphene-coated SiO anode, which manifested reinforced cycling performance (∼70% capacity retention after 500 cycles), has recently been reported . Further studies confirmed that strong covalent Si–O–C or Si–C chemical bonding at the interface can maintain permanent electrical connection and mechanical toughness, thus enhancing cycling stability. , Yet, the coupled e – /Li + transport in the graphene layer is low, resulting in a limited improvement in rate capability. , …”

“…40 Further studies confirmed that strong covalent Si−O−C or Si−C chemical bonding at the interface can maintain permanent electrical connection and mechanical toughness, thus enhancing cycling stability. 39,41 Yet, the coupled e − /Li + transport in the graphene layer is low, resulting in a limited improvement in rate capability. 42,43 (3) Tailoring of Li + diffusion by combining a second coating layer (Figure 1b).…”

Micrometer-scale single crystalline particles of niobium titanium oxide enabling an Ah-level pouch cell with superior fast-charging capability

“…22–24 Despite the exciting progress in achieving fast charge/discharge properties at the material level, nanostructures of the as-fabricated TiNb 2 O 7 would cause low compaction density of the electrode and serious parasitic reactions with the electrolyte due to the high accessible surface area. 25,26 Practical fast charging should be achieved at high mass loading and compaction density of the electrode with respect to the consideration of high energy density demand of batteries, which causes the contradiction between particle size and reaction kinetics in common knowledge. To date, fundamental understanding of the electrochemical reaction and structural stability of the MSC-TiNb 2 O 7 and investigation of the possibility for fast-charging applications are lacking.…”