Bilayer-graphene-coated Si nanoparticles as advanced anodes for high-rate lithium-ion batteries

Journal Pre-proof Bilayer-graphene-coated Si nanoparticles as advanced anodes for high-rate lithiumion batteries Xuli Ding, Yanjie Wang PII:

S0013-4686(19)31846-8

DOI:

https://doi.org/10.1016/j.electacta.2019.134975

Reference:

EA 134975

To appear in:

Electrochimica Acta

Received Date: 31 March 2019 Revised Date:

29 September 2019

Accepted Date: 29 September 2019

Please cite this article as: X. Ding, Y. Wang, Bilayer-graphene-coated Si nanoparticles as advanced anodes for high-rate lithium-ion batteries, Electrochimica Acta (2019), doi: https://doi.org/10.1016/ j.electacta.2019.134975. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.

Bilayer-Graphene-Coated Si Nanoparticles As Advanced Anodes For High-Rate LithiumIon Batteries Xuli Ding,a* Yanjie Wangb a

Department of Physics, School of Science, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu

212003, P. R. China b

School of Material Science and Engineering, Tongji University, Shanghai 201804, P. R. China

Abstract Silicon is a promising anode material for the next-generation of high-specific-energy lithium-ion batteries (LIBs), but commercial silicon still has difficulty in gaining both high rate capability and long cycle life for practical application due to poor electrical conductivity and an unstable solid electrolyte interface. Here, a simple electrode with bilayer-graphene-coated Si nanoparticles embedded in a porous current collector is adopted and exceptional electrochemical performance is obtained in lithium-ions batteries. A possible mechanism is analyzed from the insight provided from the conductivity balance between electrons and ions. Used as binder-free and additive-free anodes, the Si composite displays good rate capacity (up to 50 A g-1) and cycling stability (3000 cycles with ~89% capacity retention). Coupled with a possible physical insight, economical and feasible fabrication process, the electrode designs developed are likely to stimulate more opportunities for the next-generation high-specific-energy LIBs with enhanced power. It is further demonstrated that even in a full-cell electrochemical test, it is stable for 260 cycles and 87% capacity retention is achieved. Keywords: Silicon; Anode; Bilayer-graphene; High-rate; Lithium-ion battery. 1. Introduction The ever-increasing demand of mobile electronic commodities, advanced communication facilities and electric/hybrid vehicles, has stimulated the fast development of lithium-ion batteries (LIBs) towards higher rate capability, longer cycle life, and higher energy/power density.1-3 High specific capacity materials with good conductivity are the key to further improvements in the electrochemical performance of LIBs.4-6 Among numerous candidates, Si is regarded as a competitive candidate for the next-generation

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LIBs owing to its high specific capacity (3579 mAh g-1 at room temperature, Li3.75Si), low work potential (~0.2 V versus Li/Li+) and abundance on the earth (~27%).7-12 Despite the distinct advantages, key issues faced by the Si anodes are still the instability of the solid electrolyte interphase (SEI) and low Coulombic efficiency (CE) caused by large volume expansion/extraction during repeated lithiation/de-lithiation processes and slow charge-transfer kinetics due to the inherent poor electrical conductivity of the semiconductor Si (Eg ~1.1eV),13-20 which results in limited rate capacity and cycling life that fall short for practical applications. Hence, rational designs of structure to stimulate higher rate capability and longer cycle life for the Si-based anode are intensively required. In recent years, extensive efforts have been devoted to exploit new construction for Si anodes with improved electrochemical performance.21-34 Among these, not only the Si-Cu hybrid 29, 32 but also the Si-carbon composite 30, 33, 34 can promote a high rate capacity at high current densities. Others like double-walled Si nanotubes

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can provide a specific

capacity of 600 mAh g-1 at current density of 24 Ag-1. Therefore these desirable results should trigger new efforts to push the development of the Si-based LIBs towards higher capability. Although new designs of Si-based composite anodes have been recently developed,35-44 the battery performance of LIBs still needs to be improved, especially considering the applications expanding to electric vehicles and utility grids. A strategy to improve the electronic conductivity of Si-based anodes with high ions access and complete electrode use is still highly anticipated for high-rate and long-cycle LIBs. Inspired by the merit of ultrafast lithium diffusion in bilayer graphene 45 and other superior properties of graphene,46-48 in this work, Si nanoparticles are coated with bilayer graphene (BGra) that is synthesized via the thermal evaporation deposition assisted CVD method, and then deposited on the Ni foam by a simple layer-by-layer assembly strategy. The fabricated electrodes are used as binder-free and additivefree anodes in LIBs, which exhibit competitive rate capability up to 50 A g-1and long cycling stability. The material designs make full use of the merits of the composite materials from Si, bilayer graphene and metal foam. These composites can provide high capacity with enhanced ions access, reaching naturally good rate capacity and cycling life, as well as high columbic efficiencies required for full-cell operation. In consequence, several long-standing puzzles with Si-based electrodes could be solved: unstable SEI and

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inner poor electric conductivity. Without using of any conductive additives and binders, the fabricated electrodes have achieved stable cycling in half- and full-cell operation. The possible physical insight for the enhanced electrode performance is also proposed and analyzed which may bring new insights in the LIBs development. 2. Experimental Section 2.1 Materials Fabrication. Preparation of Si@Cu and Si@BGra The commercial Cu powder (Aladdin) was heated continuously up to 1100oC to generate Cu vaporization, and the evaporated Cu atoms are condensed quickly on the surface of Si nanoparticles in the double-temperature-zone vacuum chamber. The obtained Si-Cu composite was denoted as Si@Cu. Then, the chemical vapor deposition (CVD) process was carried out again at 1000 oC for 30 min under hydrogen and argon as carrier gases, with a CH4, H2, Ar mixed ratio of 10sccm, 20 sccm, and 100 sccm, respectively, to growth bilayer graphene on the surface of Cu. The process parameters can be adjusted according to varied requirements. After growth, the tube furnace is cooled down to room temperature under Ar and H2 gas protection. The Si@BGra was obtained after cleaning in diluted nitric acid and deionized water (Here, we use Si@BGra to tab the Si-Graphene composite in our work, ). Fabrication of Ni-foam supported Si@BGra composite (Si@BGra/Ni): The Si@BGra nanoparticles were loaded onto the Ni foam (Lifeixin, Shenzhen, 60~80% porosity) via dropping in a layer-by-layer fashion using ethanol. The mass loading of the Si@BGra is adjusted in the range of 1~3mg cm-2. After ethanol evaporation a binder-free and additive-free anode was obtained and assembled into the battery. 2.2 Electrochemical measurements Cell assembly and electrochemical testing: Electrochemical experiments are performed using CR2032type coin cells with a Celgard 2300 membrane as the separator and lithium-foil as counter electrode. The electrolyte consisted of 1M LiPF6 in the mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) (1:1 in volume ratio). The working electrode consisted of 100% Si@BGra without the conducting agent (such as Super P) and binder. The cells were assembled in an argon-filled glove box with oxygen

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and water content of less than 2 ppm. The electrochemical impedance spectra (EIS) in the frequency range varied from 0.1 Hz to 1MHz were recorded using a DH7000 workstation. The electrochemical performance was evaluated on a LAND battery test system (Wuhan Kingnuo Electronics Co., Ltd., China) at 25oC. The cut-off voltage was 0.005 V versus Li/Li+ for discharge and 1.6 V versus Li/Li+ for charge. The specific capacity was calculated based on the weight of Si@BGra. Lithium iron phosphate (LFP) was used as the cathode for the full cell assembly and the test battery was cycled between 2.0-3.6 V. The cathode mixture consisted of LFP: Super P: PVP (8:1:1). The areal capacity of the LFP cathode (~8mm diameter) tested with Li metal as the counter electrode is ~3.9 mAh cm-2 at a current density of 0.3 mA cm-2. The mass loading of the Si@Gra was 1.1 mg cm-2 in a full-cell configuration, gaining an areal capacity of ~4.5 mAh cm-2 at a current density of 0.3 mA cm-2, giving a Negative/Positive (N/P) capacity ratio of ~1.15. 2.3 Material characterization Structure and morphology characterization: The morphologies of the Si@BGra and Si@BGra/Ni were observed by transmission electron microscopy (TEM, JEOL JEM-2100) and field emission scanning electron microscopy (SEM, FEI Nova NanoSEM 45). Raman spectra was recorded at an operating power level of 2 mW on a confocal Raman spectrometer (Thermfisher, US) using a 532 nm excitation laser with spot size of 0.7 um. Raman mapping was also performed for the G band (~1580 cm-1) and 2D band (~2700 cm-1). The X-ray power diffraction (XRD) is also carried out on an X’Pert PRO diffractometer (PANalytical B.V., Holland) with high-intensity Cu Ka1 irradiation (λ = 1.5406 Å). The thermogravimeter-differential thermal analysis (TG-DTA) was also done to analyze the corresponding graphene level in the composites by the thermogravimetric analysis instrument (Linseis L75VS, Germany) in the set temperature range. 3. Results and Discussion A schematic illustration of the fabrication process for Si@BGra/Ni is depicted in Figure 1. The first step of the fabrication process was to form Si@Cu composite via the thermal vaporization and condensation of Cu powder. Then, double-layer graphene was grown on the surface of the Cu catalyst via the low pressure

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CVD. Next, the as-prepared Si@Cu@BGra was cleaned by diluted nitric acid and deionized water to remove Cu. Then, the Si@BGra ethanol ultrasonic solution was dripped onto the Ni skeleton via layerby-layer assembly. Finally, the Si@BGra/Ni was dried and used as the anode to assemble batteries. More details about the fabrication process are provided in the supporting information (Fig. S1). The morphology of the prepared composite was characterized by SEM, which shows that the Si@BGra nanoparticles are uniformly dispersed on the nickel skeleton. Figure 2(d-f) are the HRTEM images for the bare Si nanoparticles, Si@BGra, and the fringe strips, separately. As shown, the

Figure 1. Schematic illustration of the preparation process for the Si@BGra and Si@BGra/Ni. The yellow represents a Si nanoparticle, the orange is the Cu powder, the gray is the bi-layer graphene and the green is the nickel foam. bare Si surface is smooth (Fig.2d) and the Si@BGra (Fig.2e) are covered with yarn-like graphene. The edges of the synthesized graphene in Figure 2(f) show two stripes and four in the overlapping area that is of typical character for the bilayer graphene. Raman spectroscopy is also a powerful tool to identify the layer number of graphene. As shown in the inset of Figure 2(g), the relative intensity of G to 2D peak is close to 1, which is a criteria for the bilayer graphene. The G band (Fig. 2h) and 2D band (Fig. 2i) mapping reveal good uniformity of the synthesized bilayer graphene. More information varied from

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element mapping to TG analysis, can be found in the supporting Fig.S2~Fig.S5. From the statistical results given by the Raman mapping, the percentage of the bilayer graphene in the synthesized samples is ~80%, and the ~20% residue is attributed to multilayer graphene (3~10 layers), the statistical results for the percent of graphene with varied layer numbers are shown in supporting Fig.S13. (a)

(c)

(b)

10 um

50 um

(e)

(d)

0.2 um

(f)

Si

BGra (f) 20 nm

(h)

(g)

BGra

5 nm

(i)

BGra

G band

2D band

Figure 2. (a-c) SEM images of the Si@BGra/Ni at different magnifications, (a-c) HRTEM images of the bare Si nanoparticles (d), Bilayer-graphene-coated Si nanoparticles (e), and the strips at the edges of bilayer graphene (f). (g) Raman spectra for the Si@BGra (g) inset is the result in the wavenumber range of 1000~3000 cm-1, Raman mapping results for the G band (h), and 2D band (i) for the bilayer graphene, the color scale is identical for figures 2(h) and 2(i).

The fabricated Si@BGra/Ni anode exhibited an unexpected electrochemical performance. Figure 3(a) shows the cyclic voltammograms (CV) of the first five cycles of the Si@BGra/Ni electrode in the

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potential window between 0V and 2V versus Li+/Li. As seen, two cathodic peaks at 0.72 V and 0.10V in the first cycle are assigned to the formation of the solid electrolyte interphase (SEI) and LixSi4 alloy, respectively.43-45, 49 On the inverse process, two broad and apparent anodic peaks at 0.33V and 0.53V are ascribed to the phase transition from LixSi alloy to Si substance.49, 50 The CVs with different sequences overlap well with each other except the first one, which indicates good reversibility of the fabricated electrode and it outperformed than the traditional foil-based electrode (compared in Fig. S6). (a)

(c)

(b)

(d)

Figure 3. (a) Cyclic voltammogram (CV) curve for the Si@BGra/Ni. (b) Electrochemical impedance spectra for the Si@BGra/Ni and Si@BGra anode before and after 1000 cycles (including fitting datas). (c) Rate capability of the Si@BGra/Ni at the current densities varied from 1.0 A g-1 to 50 A g-1. (d) Cycling capability of the Si@BGra/Ni at a current density of 20.0 A g-1 for 3500 cycles.

The electrochemical impedance spectra (EIS) is already confirmed a powerful tool for exploring the kinetic process and mechanism of the electrochemical reactions.54,55 The EIS before cycling and after several hundred and even thousands of cycles are plotted in Figure 3(b). In addition, the fitted data is also shown in the supporting Fig.S14 for more information. It is seen that the EIS are composed of one or two

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linked semicircles in the high to medium frequencies and a sloped line at low frequency. The equivalent circuit for the EIS is shown in the inset of Fig. 3(b), in which, the Rc is the total resistance of the cell, which is a combined resistance of electrodes, electrolyte and separator.51, 52 Rs and Cs are the resistance and capacitance of the SEI on the electrode surfaces, which corresponds to the semicircle at high frequencies, while the Rct and Cdl are charge-transfer resistance and corresponding double-layer capacitance that correspond to the semicircle at medium frequencies.51,

52, 54, 55

W is the Warburg

impedance related to the diffusion resistance of lithium ions at the electrode-electrolyte interfaces that correspond to the sloped line at low frequency. 54, 55 It is shown that in the Nyquist pattern, that the Rct for Si@Bra is much higher than that of Si@BGra/Ni, and the semicircle at medium frequency cannot even be formed in the spectra for Si@BGra. In addition, the Rct for the Si@BGra/Ni increases gradually with the increase of the cycle numbers, while the arc representing Rc even disappears as the cycles reach 1000 cycles (indicated in Fig. 3b). It is important to note that good rate capability is realized in the Si@BGra/Ni electrode in Figure 3(c). When the current densities are increased from 1.0 to 5.0, 10.0, 20.0, 30.0, 40.0 and 50.0 A g-1, the electrode shows good capacity retention, as the specific capacity changes from 3100 to 2500, 2000, 1200, 800, 500, and 400 mA h g-1, respectively. In contrast to previous cycles, the specific capacity can recover again even after four repetitive sequences while the current densities are returned from 50.0 to 1.0 Ag-1. Given that, the good rate capability of the Si@BGra/Ni electrode can be attributed to the following features: i) The 3D interconnected framework serves as an electron highway and accommodates the Si@BGra particles; ii) The BGra coating layer acts as a flexible protective layer to facilitate the thin and stable SEI formation; iii) The rigid skeleton supported Si particles overcome the issue of active materials peeling when a foil-based current collector is used; iv) The porous structure enhances the contact area between charged particles and electrolyte and improves the Li-ion transfer. As a consequence, the utilization rate of the active materials is greatly improved and the high specific capacity is obtained correspondingly. Beyond this, in the lithiation-delithiation process, the Si@BGra nanoparticles stay firmly on the Ni skeleton instead of migrating despite there being no binder. In light of this fact, it is tentatively speculated that the Si particles (~50 nm) do not shift in the discharge-charge

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process because the Li+ ion (~2 Å) is too small to move the Si particle due to a relative volume rate of Li+/Si=10-7, disregarding the anisotropy of the polycrystalline Si. Additionally, the fabricated anode exhibits not only superior rate capability but also ultra-long cycling stability. Figure 3(d) shows the cycle behavior of the Si@BGra/Ni anode at a current density of 20.0 A g-1. It is cycled at 1.0 A g-1for the initial 20 cycles and the specific capacity achieved is around 3200 mA h g-1. After that, as current density is increased to 20.0 A g-1, a specific capacity of 1008 mA h g-1 can be sustained for the following 3000 cycles, with a rapid increase of the CE from the initial 81.9% to 99.7% in few cycles, and then up to 99.9%~100% in the subsequent cycling. The loading mass of the Si@BGra on the foam Ni is chosen in three groups 0.5 mg cm-2, 1.0 mg cm-2, and 2.0 mg cm-2, which are further compared in Fig. S7 and the corresponding results are also shown in Fig. S8. The mass loading for all the samples described here is ~1.0 mg cm-2. The discharge-charge curves for different sequences are illustrated in Figure 4(a). As revealed, the first discharge curve displays a long flat lithiation plateau at ~0.1V, which is caused by the alloying of LixSi and and a two-phase process taking place during the first lithiation of (crystalline or amorphous) silicon.49-53, 56, 57Afterwards, the lithiation and delithiation curves varied from cycles 2nd to 1000th and exhibited the typical character of amorphous Si with a steep swell rather than a plateau. It should be noted that the Si anode is reported to have a discharge threshold at ~ 0.06 V; if potential falls any lower than that Si will undergo a severe volume expansion resulting in pulverization or peeling from the collector. However, the Si@BGra/Ni here exhibited good reversibility and stability even when the anode was discharged to 0.005V. Since each pair of discharge-charge curves shows similar characteristics without obvious variation or polarization in Figure 4(b), small mechanical stresses may be generated during the process of insertion and de-insertion of lithium ions,58, 59 which is different from that in most cases.

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(a)

(c)

(b)

(d)

Figure 4. (a) Discharge-charge curves: (a) at cycle number of 1st, 2nd, 100th, 300th, 500th, and 1000th at a dischargecharge rate of 10.0 A g-1, with the first discharge-charge rate being 1.0 A g-1. (b) at current densities of 1.0, 5.0, 10.0, 20.0, 30.0, 40.0 and 50.0 A g-1. (c) Cycle properties at current densities of 3.0 A g-1, 5.0 A g-1, 7.0 A g-1 for the original 1000 cycles. (d) Full-cell cycles of the Si@BGra/Ni anode paired with a lithium iron phosphate (LiFePO4) cathode. The Coulombic efficiency (CE) is plotted in the blue color in the second y-axis.

Figure 4 (c) shows the comparison of cycle performance for the Si@BGra/Ni anodes at different current densities for the original 1000 cycles. From the figure, the specific capacity decreases with increasing current densities, but the capacity is retained after 1000 cycles and is nearly similar for different samples. It is deduced that the loss rate for each cycle is nearly the same at varied current densities, which indicates the structural stability of the fabricated anode. Up to now, despite the improvement of electrochemical performance of the Si-based anodes are reached, but only to a limited extent.29-34 Here, the Si@BGra/Ni anode is developed with a special electrode design to address the issues mentioned in virtue of multiple functions. A full-cell battery with the lithium iron phosphate as the cathode is constructed and the cycling

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performance is shown in Figure 4(d). The fabricated electrode exhibits stable cycling with 90% capacity retention after 260 cycles at a current density of 1.5 mA cm-2 and areal capacity of 3.5 mAh cm-2. The voltage profiles at different cycles do not exhibit many differences, indicating that both negative and positive electrodes are stable with continuous cycling. This unexpected full-cell stability is ascribed to the designed structure specifically the anode fabrication that consists of flexible graphene and an electronic connection. The combined electrical and mechanical properties of the graphene and metal foam allow for use the optimal properties of the Si-Graphene composite materials for the next-generation high-specificenergy LIBs. The morphology evolution of the Si@BGra/Ni electrode after 500 cycles (Fig.5a-b) and 3500 cycles (Fig.5c-d) are compared in Figure 5. As seen from the measured results, the Si particles exhibit significant changes as compared to their initial state (before cycling), but these changes are much less dramatic than those usually recorded on standard composite electrodes after extensive cycling. It is indicated that the distribution of the Si particles on the Ni foam is consistent, even after 3500 cycles, and (a)

(b)

1 um

100 um

(d)

(c)

100 um

1 um

Figure 5. SEM image comparison for the disassembled Si@BGra/Ni half-cell batteries after 500 cycles (a, b) and 3500 cycles (c, d). All the discharge-charge rates are 10 A g-1.

the particles are still coagulated. Si nanoparticles have not fractured even after several thousands of cycles (Figure 5d), which are different from our previous reports.28,

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After such long cycling, the

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Si@BGra particles still maintain a good configuration on the Ni skeleton, despite the active silicon particles showing some changes as compared to the particles without cycling. From the cycled results, it can be concluded that the Si nanoparticles display strong endurance on the foam. In the electrode design, the balance between the electron mobility and lithium ion mobility is critical to maintain good electrochemical activity. In the electrode with a foam-based current collector, the effective conductivity or diffusion rate of the transport charges can be expressed in the following formula according to Fick’s first law of diffusion60 J=-D.dc(x)⁄dx, in which D is the diffusion coefficient and c(x) is the mass concentration. Under the same mass concentration gradient, the rate of transport is governed by the diffusivity. First, electrolyte is the best phase for ion conduction in the studied system (the diffusion coefficient is much larger in the liquid phase than in the solid phase). The active particles are not assembled as a relatively thick solid composite on the current collector. They are arranged as a porous structure active medium/current collector interpenetrated with the electrolyte located within the pores (as indicated in Fig. 6b). Therefore, Li ions can access to the active medium by travelling in the liquid phase only, benefiting from a high diffusivity all along their transport to the active medium. In addition, as also sketched in Figure 6 (a) and (b), the contact area between the active materials and electrolyte is not a traditional single face-face contact but a multiple face-face contact. This increased contact area favors an easier and more effective charge transfer between electrolyte and the active material. Therefore, as compared to standard composite electrodes, the easier access of Li ions to the active material provided by the porous structure of the foam and the larger exchange surface between the electrolyte and the active material result in a lowering of the charge-transfer impedance. In addition, it should be noted that the effect of van der Waals interactions between bilayer-graphene might be important for the fabrication of binder-free electrodes. Based on the factors mentioned above, the interactions will promote the effective reaction between the active materials and lithium ions. This will improve the utilization rate of active materials that is beneficial for improving the rate and cycle capability, because the incomplete electrode use results in the capacity loss and low rate capacity.

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(a)

Electrolyte

(b) Ni foam

carbon

Si particles

black

Electrolyte

Si particles

Figure 6. Schematic illustration: (a) Conventional metal current collector and electrode active materials, (b) Ni foam supported active Si particles.

At the same time, a similar experiment was carried out on the copper foam, but the results were not as ideal as expected. When the current density was increased to 50 Ag-1 the specific capacity had already fallen to zero in the Si@BGra/Cu anode, although the conductivity of Cu is higher than that of Ni (supporting Fig. S12). The poor stability of Si@BGra/Cu compared with Si@BGra/Ni may be caused by the partial oxidation during the electrochemical reaction process that leaves Cu more easily etched as compared to Ni especially in the defects region. This is possibly due to the different industrial preparation technologies used for Cu and Ni foams which generate different porosity and pore sizes, however, the explicit mechanism is still not very clear and more research is needed. It is speculated that such a fabricated structure (Si@BGra/Ni) just right reaches the ideal balance between the conductivity of electrons and lithium ions, which ensures the desired electrochemical performance. The design combined the advantages of highly conducing Ni and Gra, as well as high capacity Si, is responsible for the high rate capability and cycling stability of the fabricated electrode. More importantly, bilayer graphene acts as a thin protective layer avoiding the direct exposure of Si in the electrolyte and facilitates the thin and stable SEI formation, which is a key issue for the long-life Si-based anodes. Additionally, such assembled anode can avoid the peeling of Si active particles from the current collector. In addition, it should be

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noted that such fabrication could eliminate the use of binders and conductive additives, which is beneficial for decreasing the cost of integral battery fabrication. 4. Conclusions High-quality bilayer graphene on the Si nanoparticles is synthesized by CVD method with the aid of thermal vaporization and condensing Cu powder. The fabricated Si@BGra/Ni electrode can deliver a high capacity of ~2500 mAh g-1 at 3.0 A g-1 and 85% capacity retention after 1000 cycles, which can also deliver a capacity of 800 mAh g-1 at a higher current density of 20.0 A g-1, and sustain stable 3000 cycles without obvious capacity decay. Importantly, a good rate of 50 A g-1 with capacity ~400 mA h g-1 is obtained. Possible physical insight for the good electrochemical performance in such fabricated electrode is analyzed. The results suggest that the Si@BGra/Ni electrode is an attractive candidate for the low-cost high-specific-energy next-generation LIBs. ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website. Notes The authors declare no competing financial interest. Acknowledge The authors gratefully acknowledge the financial support by the National Natural Science Foundation of China (Grant No. 11604245, 11874282), and Scientific Research Foundation Project (1052931707) from Jiangsu University of Science and Technology

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Declaration of interests ☐ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.