Assembly of Si@Void@Graphene Anodes for Lithium‐Ion Batteries: In Situ Enveloping of Nickel‐Coated Silicon Particles with Graphene

Abstract

In this report, a yolk‐shell‐structured Si/graphene (Si/GR) material has been designed and successfully fabricated as an anode for lithium‐ion batteries (LIBs). With this approach, Si@Ni composite particles were fabricated by electroless deposition of a nickel template directly on silicon; then, three‐dimensional (3D) graphene layers were grown in situ around the composite particles to obtain a Si@Ni@GR structure. After removing the nickel interlayer, some voids were generated between the silicon particles and the graphene layers, thus forming a Si@void@GR structure. The coexistence of voids and the graphene layer may provide a synergistic effect. The voids may reserve space for silicon particles during volume expansion and buffer the mechanical pressure of the graphene layer. Meanwhile, the graphene cover may enhance lithium‐ion transport efficiency and electron transport rate, thereby improving the electrical conductivity of the anode. The well‐coated layers can also prevent the Si particles from being directly exposed to electrolyte, which can promote the formation of a stable SEI film and reduce the irreversible consumption of Li+. Therefore, such unique yolk‐shell structures offer the resultant Si@void@GR electrode a high reversible discharge capacity (1595 mAh g−1 after 100 cycles at a current density of 500 mA g−1) and the capacity to deliver a discharge capacity of 990 mAh g−1 even at a high current density of 4.8 A g−1.

Controlling Void Space in Crumpled Graphene‐Encapsulated Silicon Anodes using Sacrificial Polystyrene Nanoparticles

“…VCrGO@Si-1 retained around 80.6 % of the initial capacity after 200 cycles while VCrGO@Si-0 only retained 61.3 %. At a higher active material loading of 2.4 mg cm À 2 , VCrGO@Si-1 displayed a high areal capacity of 2.26 mAh cm À 2 , which only dropped by < 20 % after [20,23,24,26,33,[50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68] 145 cycles. Based on the calculation for the capacity contributed by pure silicon (94.3 %) at 1 A g À 1 , the carefully tuned reserved void space of VCrGO@Si-1 can effectively buffer the volume change of Si NPs in the core, without introducing excess volume, improving overall performance.…”

“…Figure 7. Areal capacity retention of recent works reporting Si/C based anode [20,23,24,26,33,[50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68]. …”

The influence of contact engineering on silicon‐based anode for li‐ion batteries

“…involved electrochemical deposition to coat nickel template on the surface of clusters of Si nanoparticles, then graphene was formed in situ through the catalysis of Ni on triethylene glycol, and Ni template was removed by HF solution to get Si@void@GR composite (Figure 8A). [ 126 ] TEM images showed that several Si nanoparticles were surrounded by a complete graphene layer with void around (Figure 8B). Compared with bare Si, Si@void@GR showed significantly improved cycle and rate performance (Figure 8C).…”

“…C, Rate capabilities of Si and Si@void@GR at current densities ranging from 0.5 to 4.8 Ag –1 . [ 126 ] Copyright 2019, Wiley‐VCH. D, TEM image of the SiNPs@C PS composite with schematic inset.…”

Preparation of graphene-like carbon attached porous silicon anode by magnesiothermic and nickel-catalyzed reduction reactions

“…Ni catalyst was etched away by FeCl 3 aqueous solution and was thought as a sacrificial layer for providing void space for Si microparticles expansion within the graphene cage. Zhao et al [28] designed a yolk-shell-structured Si/ graphene material as an anode for lithiumion batteries, which showed a high reversible discharge capacity of 1595 mAh g −1 after 100 cycles at a current density of 500 mA g −1 and 990 mAh g −1 at a higher current density of 4.8 A g −1 . Herein, lithium-ion transport efficiency and electron transport rate may be enhanced by the graphene cover, causing the improvement of the anodic electrical conductivity.…”