In-situ constructing 3D graphdiyne as all-carbon binder for high-performance silicon anode

Author’s Accepted Manuscript In-Situ Constructing 3D Graphdiyne as All-Carbon Binder for High-Performance Silicon Anode Liang Li, Zicheng Zuo, Hong Shang, Fan Wang, Yuliang Li www.elsevier.com/locate/nanoenergy

PII: DOI: Reference:

S2211-2855(18)30601-3 https://doi.org/10.1016/j.nanoen.2018.08.039 NANOEN2969

To appear in: Nano Energy Received date: 25 May 2018 Revised date: 17 August 2018 Accepted date: 18 August 2018 Cite this article as: Liang Li, Zicheng Zuo, Hong Shang, Fan Wang and Yuliang Li, In-Situ Constructing 3D Graphdiyne as All-Carbon Binder for HighPerformance Silicon Anode, Nano Energy, https://doi.org/10.1016/j.nanoen.2018.08.039 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. 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.

In-Situ Constructing 3D Graphdiyne as AllCarbon Binder for High-Performance Silicon Anode

Liang Li a,b, Zicheng Zuo a*, Hong Shang, Fan Wang a,b, Yuliang Li a,b*

a

Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Research/Education

Center for Excellence in Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China b

University of Chinese Academy of Sciences, Beijing 100049, P. R. China

[email protected] [email protected]

*

Corresponding authors.

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Abstract

The main issue of Si anode is the large volume variations during alloying/dealloying processes, which severely causes the disintegration in the pre-designed conductive and mechanical networks and the interfacial contact between the current collector and Si particles; moreover, it can hardly be overcome economically. Here, the growth methodology of ultrathin graphdiyne nanosheets is scalably developed for in-situ constructing the 3D all-carbon conductive and mechanical networks and firstly enhancing the interfacial contact between current collector and Si anode via chemical bonding. Seamlessly hold by the ultrathin graphdiyne nanosheets, the disintegrations of the silicon anodes in the conductive networks and the interfacial contact are effectively retarded; as a result, the silicon electrode shows impressive enhancements in term of the capacity (2300 mA h g –1), and long-term stability for high-energydensity battery (1343 W h l–1). Such method shows great promises for realizing the commerciallevel applications of Si anode.

Graphical Abstract

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The construction of all-carbon binder for the Si anode is successfully realized by an in-situ growth strategy of graphdiyne nanosheets, which effectively avoids the disintegrations in the mechanical and conductive networks of the electrode and firstly improves the interfacial contact with the current collector through chemical bonding.

Keywords: graphdiyne, silicon anode, 2D material, lithium-ion battery, all-carbon binder

1. Introduction Slimming lithium-ion batteries (LIBs) while simultaneously increasing their energydensity will be necessary to satisfy the huge demand from the fast-paced developments in the portable electronics and low-emission vehicles [1-3]. As an important component of commercial LIBs, the graphite, has reached a specific capacity close to its theoretical value of 372 mA h g –1 , leaving less room for further improvements in both volumetric and mass-energy density. Because it is abundant and has a much higher theoretical specific capacity (4200 mA h g–1) and lower working potential [4-6] than many well-studied oxides, sulfides, and other materials [7-11], silicon has been considered for many years as promising anode candidate that could increase the energy-density of LIBs. Unfortunately, silicon electrodes suffer from large variations in volume (>300%) during alloying/dealloying processes, resulting in severe pulverization and disintegration of the conductive networks and the solid electrolyte interphase (SEI) [4, 12-14], leading to dramatic increases in contact impedance and remarkably shorter lifetimes. Thus, there remain many intractable challenges inhibiting the realization of silicon anodes for commercialized LIBs.

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Nowadays, rationally combining with carbon materials while introducing suitable voids was thought to be an efficient strategy for overcoming the problems of conductivity and interfacial instability associated with large volume expansion of silicon materials [15-19]. In these methods, which take advantage of the carbon material for both its structural stability and conductivity, the silicon nanomaterials are commonly encapsulated in a carbon nanoshells through various expensive high-temperature pathways. Alternatively, various nonconductive polymers have been introduced for their ability to strengthen the interactions between the silicon particles and the current collector, and firm the conductive networks through the enhanced van der Waals interactions, hydrogen bonds, as well as covalent bonds, for substituting the conventional polymer binders [e.g., poly(vinylidene difluoride)] [5, 14, 20-23]. Inevitably, both the electronic and ionic conductivities on the electrodes will be severely cut down by the large amount of nonconductive polymers. Although some progresses have been achieved, approaches that can integrate the advantages of abovementioned methods, while being possible to scale up, have not yet been developed. Inspired by the in-situ growth of graphdiyne (GDY) nanosheets on copper foil [24-29], we suspected that the highly stable and conductive two-dimensional (2D) all-carbon nanosheets featuring three-dimensional (3D) accessible channels for Li+ ions [30-32] might also be capable of firmly grasping silicon particles on the copper current collector during the in situ growth process. If so, the GDY nanosheets might also strengthen silicon anodes in terms of both their mechanical and electronic properties. Realization of the in-situ decoration of GDY nanosheets on silicon particles could potentially have several positive effects: (i) 3D all-carbon conductive and mechanical networks could be constructed in situ, seamlessly coating the silicon particles for improved electron transfer and alleviating the structural degradation caused by huge volumetric

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changes; (ii) growth of GDY nanosheets might strengthen the interaction between the silicon particles and the current collector and minimize contact impedance during cycling; (iii) the method would be easy to scale up. In this study, we used such an approach to prepare a highperformance silicon anode (2300 mA h g–1), which would be readily scalable for assembling a LIB with high energy density (1343 W h l–1). 2. Experimental methods Precursor preparation Tetrabutylammonium

fluoride,

hexabromobenzene,

anhydrous

zinc

chloride,

and

ethynyltrimethylsilane were obtained from J&K Scientific and used without further treatment. Toluene and tetrahydrofuran were redistilled from Na crumbs under an Ar flow. The synthesis of hexakis[(trimethylsilyl)ethynyl]benzene and its deprotection to give HEB were performed according to our previously reported method [24]. HEB was solubilized in diethyl ether (1 mg mL–1) and stored in a refrigerator for the following in situ growth reaction. Si electrode preparation: SiNPs having a diameter of 30 nm were purchased from Aladdin. The slurry for scalable preparation of the electrode contained 95% SiNPs and 5% PVDF, which were mixed well overnight in 1-methyl-2-pyrrolidinone. The resulting slurry was loaded uniformly onto the copper foil using a wet film preparation equipment and then dried at 60 °C in a vacuum oven. For comparison, a control sample, named SuperP-Si, was prepared by coating a slurry comprising 70% SiNPs, 20 SuperP carbon black, and 10% PVDF onto copper foil and drying under the same conditions. The as-prepared electrodes were stored at 120 °C in a vacuum oven overnight prior to their application. In situ growth of GDY nanosheets

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The as-prepared electrodes (12 cm  7 cm) were immersed in a solution of HEB (5–15 mg) and pyridine (2 mL) in CH2Cl2 (40 mL) in a glass vessel. The growth of the GDY nanosheets was performed at room temperature for 2 day. The electrodes were then washed three times with EtOH to remove any residues and dried in a vacuum oven. Subsequently, the electrodes were thermally treated in a tube furnace at 180 °C for 2 h in the presence of N2 gas. The as-treated samples were used as electrodes for assembling the half-cells and full cells for the electrochemical measurments. To control the thickness of the GDY on the SiNPs, the amount of HEB in the reaction was varied from 5 (GDY-Si1) to 10 (GDY-Si2) to 15 mg (GDY-Si3). NCA cathode The LiNi0.8Co0.15Al0.05O2 cathode material was bought from Hefei Kejing Materials Technology. A slurry containing NCA (90%), SuperP carbon black (5%), and PTFE (5%), was stirred overnight and then coated on aluminum foil. The as-obtained NCA cathode was dried at 90 °C and then stored at 120 °C in a vacuum oven overnight, prior to its application. Characterization The morphologies of the as-prepared samples were examined using field emission scanning electron microscopy (FESEM, Hitachi S-4800) and TEM (JEM-2100F). Raman spectra were recorded using an NT-MDT NTEGRA Spectra system, with excitation from an Ar laser at 473 nm. XPS was performed using an ESCALab250Xi apparatus. XRD was performed using an Empyrean diffractometer and Cu K radiation, with an output power of 1.6 kW at a voltage of 40 kV. Electrochemical testing

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The thermally treated (GDY-Si) and control samples were cut into small pieces (diameter: 1 cm) for testing in coin cells. For LIB anode testing, the electrolyte was 1 M LiPF6 in ethylene carbonate and dimethyl carbonate (EC/DMC, 1:1, v/v), the separator was a Celgard 2300 membrane, and the counter electrode was lithium foil. Cyclic voltammograms at various sweeping rates and electrochemical impedance spectra were recorded using a CHI 660 D apparatus; EIS was performed using a sinusoidal signal with an amplitude of 10 mV over frequencies in the range from 100 kHz to 0.1 Hz. Galvanostatic charge/discharge curves at various rates and long-term stabilities were measured using a LAND battery testing system. For the GDY-Si//NCA full cell, the as-prepared anode and cathode were cut and assembled into a square electrode (2  2 cm). 3. Result and discussion

Scheme 1. a–c) Schematic representation of the preparation of a silicon anode seamlessly coated in situ by GDY nanosheets. d) Schematic representation of 3D GDY

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frameworks that seamlessly support and strongly bind silicon nanoparticles (SiNPs) on the current collector. e, f) Photographs of a large-scale silicon anode before and after in situ coating of GDY nanosheets. g) Photograph of a double-sided silicon anode prepared using this method. Copper foil is used prevailingly as the current collector in the anodes of commercial LIBs. Coincidentally, the growth of GDY can be catalyzed by copper foil in solution under mild conditions, suggesting an obvious path for preparing promising silicon anodes. Prior the in situ growth of GDY nanosheets, we prepared a silicon electrode by coating a slurry containing welldispersed SiNPs (95%) onto copper foil and then drying at 60 C (Scheme 1a, 1b). This procedure is commonly adopted in the production of commercial LIBs; it can easily be scaled up while guaranteeing the uniform loading of electrode materials (Scheme 1e). After the solvent had been removed, the large-scale silicon anode was used for in situ catalysis of the growth of GDY nanosheets on the electrode in a reaction solution at room temperature. Scheme 1c and 1d presents a possible 3D structure for the resulting assembly of GDY nanosheets, SiNPs, and current collector. Schemes 1e and 1f reveal the variation in the appearance of the silicon anode before and after the seamless 3D coating of GDY nanosheets. We also used this method to readily grow GDY nanosheets on double-sided electrodes (Scheme 1g), which could be applied in commercial batteries.

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Fig 1. a) Typical XRD patterns and b) Raman spectra of a silicon anode after in situ seamless coating of 3D GDY nanosheets. c) XPS spectra and d) corresponding elemental contents of electrodes before and after coating with different amounts of GDY nanosheets. We used X-ray diffraction (XRD) to characterize the as-prepared silicon anodes. After in situ growth of the GDY nanosheets, the XRD patterns revealed the coexistence of SiNPs, elemental Cu, and GDY nanosheets; the absence of any impurities confirmed the cleanliness of this method. The Raman spectrum in Fig. 1b displays the typical characteristic peaks of GDY nanosheets and SiNPs. The sharp peak at 2168 cm–1 is indicative of the formation of the diyne linkages in the GDY framework, suggesting the successful preparation of GDY nanosheets on the silicon anode. The seamless growth of GDY nanosheets on the SiNPs changed the surface elemental composition, as observed using X-ray photoelectron spectroscopy (XPS). Figs. 1c and 1d reveal the changes in the characteristic Si 2p, C 1s, F 1s, and Cu 2p signals; the intensity of the peaks of Si 2p and F 1s gradually decreased upon seamless coating of the GDY nanosheets

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on the electrodes, while those of C 1s and Cu 2p, originating from the GDY nanosheets, increased. Thus, the content of GDY nanosheets on the SiNPs could be controlled readily through this mild method. The negligible intensities of the Si 2p and F 1s signals for sample GDY-Si3 indicate that the SiNPs could be covered well after in situ growth of the GDY nanosheets.

Fig 2. SEM images of silicon anodes after coating with different amounts of GDY nanosheets. a, b) GDY-Si1; c, d) GDY-Si2; e, f) GDY-Si3; g, h) cross-sectional images of GDYSi2; i) cross-sectional image of SuperP-Si. Figure 2 and (Fig. S1) present SEM images of the silicon anodes before and after in situ coating of GDY nanosheets. In the absence of the GDY nanosheets, the SiNPs were loading in an incompact manner on the electrode, leaving many voids (Fig. S2). The smooth morphologies of the SiNPs and their isolation indicated that the network of SuperP-Si was poorly continuous— a fragile arrangement considering the large volume changes that would occur during the alloying

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and dealloying processes. Nevertheless, this morphology with many voids favored the subsequent in situ growth of GDY nanosheets, because the GDY growth was initiated by and closely associated with the underlying copper foil, thereby improving the contact impedance. In addition, the consecutive voids on the electrode supplied enough room for the seamless coating of GDY nanosheets, in-situ constructing a 3D conductive and mechanical network, and alleviating the system of volumetric expansion during the alloying processes. After in situ growth of GDY, the GDY nanosheets appeared to be bound strongly on the SiNPs, forming a rugged surface (Fig. 2a), quite different from that of the bare SiNPs (Fig. S1 and S3). The wrinkles on the SiNPs indicated that the GDY had an obvious 2D morphology. More importantly, in-situ growth allowed the formation of a very good 3D all-carbon network composed of GDY nanosheets cross-linked together through covalent bonds. Planted on the Cu substrate and grown three-dimensionally in the voids, we expected such a structure to provide high mechanical strength to relieve the passive effect of dramatic volume changes, more so than novel polymer binders and inorganic coating layers

[13, 20, 33]

. Increasing the amount of hexaethynylbenzene

(HEB) in the reaction mixture increased the size of the GDY nanosheets (Figs. 2c and 2e), with the voids on the electrodes becoming perfectly filled with GDY nanosheets, forming an integrated electrode. The transparency of the GDY nanosheets on the SiNPs indicated their ultrathin nature (Fig. 2f); indeed, the thickness of the nanosheets was approximately 3 nm, much thinner than many reported in the literatures [25, 34]. The growth of the GDY nanosheets was initiated by the bottom copper substrate; therefore, the silicon should have stronger contact with the substrate than that in the SuperP-Si sample (Fig. S4). A typical cross-section image of GDYSi2 reveals (Fig. 2g) remarkably enhanced contact between the silicon anode and the substrate, compared with that in SuperP-Si (Fig. 2i), suggesting improved charge transfer in the battery.

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Furthermore, the growth of GDY nanosheets in the electrode voids provided support to the SiNPs, preventing their exfoliation from the conductive network.

Fig 3. a) Low- and b, c) high-resolution TEM images of GDY-coated SiNPs (GDY-Si2). d–f) Corresponding elemental distribution information of the selected region in a); Highresolution TEM images of g) a GDY nanosheet and h) copper nanoparticles embedded in a GDY framework. We used transmission electron microscopy (TEM) to characterize the interaction between the SiNPs and the GDY nanosheets (Figure 3 and Fig. S5). The large-scale image in Fig. 3a reveals that the 2D GDY nanosheets, similar to other 2D nanomaterials,[16, 17] that bound

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effectively to the SiNPs, forming a strong integrate. From the high-resolution images in Figs. 3b and 3c, we can distinguish well-defined patterns representing the lamellar structure of the GDY with an interlayer distance of 0.365 nm [25, 35] and the SiNPs. Importantly, the GDY nanosheets were bound close to the SiNPs along their surface profile, implying a strong interaction between them. We expected such intimate contact between the GDY nanosheets and the SiNPs would greatly minimize the impedance for the migration of both electrons and Li+ ions. The thickness of this GDY layer is about 3 nm, consistent with its ultrathin property in the SEM testing. Furthermore, taking advantage of the high mechanical strength of the all-carbon GDY, the 3D Li+-accessible GDY shell on the silicon particles would potentially efficiently retard the structural pulverization of the silicon. Figs. 3d–f (Fig. S6-S8) depict the distribution of the corresponding elements, clearly delineating the spherical SiNPs embedded well in the GDY framework. The copper atoms in the GDY framework originated from the Cu substrate catalyzing the growth of the GDY. The high-resolution image in Fig. 3g reveals the existence of nanopores on the ultrathin GDY nanosheets, possible channels for cross-plane transfer of Li+ ions. Meanwhile, the copper nanoparticles embedded in the GDY nanosheets (Fig. 3h) would presumably assist in improving the electronic conductivity of the electrode during electrochemical applications.

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Fig 4. Electrochemical performance of as-prepared silicon anodes under various conditions. a) CV curves (first three cycles) of GDY-Si3. b) Charge/discharge curves of GDYSi3 at various current densities. c) Variations in specific capacity of GDY-Si anodes at various current densities. d) Long-term stability of GDY-Si and Super P-Si anodes at a charge/discharge rate of 1 A g–1. e) EIS variations of GDY-Si anode before and after long-term cycling test. f) Comparison of performance with some other reported materials. The tight binding of the SiNPs to the current collector and the 3D conductive network constructed by the GDY nanosheets both favored the use of such electrodes of LIBs. Thus, we used a half-cell testing system to examine their potential application as LIB anodes. The cyclic voltammograms of GDY-Si3 in Figure 4a reveal the typical activation process of the silicon anodes in the first three cycles; the stable cathodic curves after the first cycle indicate the

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formation of a stable SEI in the first cycle. The galvanostatic charge/discharge curves of GDYSi3 (Fig. 4b) reveal the electrochemical behavior of the GDY-modified silicon anode, which exhibited low polarization even under a high current rate of 4 A g–1. The as-obtained anode had a high coulombic efficiency (CE) of 75%, suitable for the assembly of full cells. This CE appeared to be mainly inherited from the SiNPs (Fig. S9). After activation, the GDY-Si anodes would presumably have a high reversible capacity [36] for storing Li ions, and it is improved as the content of GDY nanosheets increased. The highest specific capacity of 2307 mA h g–1 could be reversibly achieved from the well-supported GDY-Si3 sample; this value is comparable with those of costly graphene-coated SiNPs and carbon-protected silicon nanowires [17, 37]. The electrode of GDY-Si3, which had the highest content of GDY, had the best conductive network and least large voids; therefore, it delivered the best rate performance with a capacity of 1490 mA h g–1 at 2 A g–1 and 1152 mA h g–1 at 4 A g–1. After being operated at the high rate of 4 A g–1, the electrode can still retain a high capacity of 1770 mA h g–1 at 1 A g–1, showing good reversibility. We also tested the long-term stability of the GDY-Si samples at a current density of 1 A g–1. The introduction of the GDY nanosheets on the silicon anode definitely enhanced the performance. In a control experiment, the performance of the SuperP-Si electrode (70% Si; 20% SuperP carbon; 10% PVDF) exhibited a sharp decline in capacity even when operated under a low current density of 0.2 A g–1, with no capacity retention after 30 cycles. In contrast, after 200 cycles at 1 A g–1, the GDY-supported silicon anodes of GDY-Si1, GDY-Si2, and GDY-Si3 retained robust capacities, as high as 448, 632, and 1250 mA h g–1, respectively. Simultaneously, great improvements were also realized in the long-term CEs at high current density, in contrast to the fluctuant CE of SuperP-Si electrode. Indeed, the CE of the SuperP-Si electrode varied widely during the cycling tests, on account to an unstable SEI caused by the huge volume changes

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during the alloying/dealloying processes. After in-situ intertwining of the GDY nanosheets, the silicon anodes exhibited stable and high CEs, because the 3D GDY network inhibits the electrode fracture that would otherwise produce new sites for the formation of the SEI, leading to a low CEs. Fig. 4e displays the impedance of GDY-Si3. According to the EIS, it demonstrates that the activation process was necessary to lower the electrochemical impedance. The electron transfer process improved after long-term cycling, while the impedance was slightly lower, in contrast to the behavior reported for silicon electrodes [6]. The slight decrease in impedance is consistent with the seamless coating of GDY nanosheets on the SiNPs, which can stabilize the conductive network and the SEI on the electrode. The performance of the silicon anodes constructed using this method is as good as, or better than, that of some other well-studied materials [9, 15, 17, 38-45] (Fig. 4f), suggesting great potential for their application within nextgeneration high-energy-density LIBs.

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Fig 5. a–c) SEM images of the GDY-Si3 anode after long-term cycling tests. d) Largescale TEM image revealing the 3D continuity of the GDY-Si anode after cycling. e) Elemental distribution of the selected area in d). f, g) Schematic representations of f) the interaction of the 3D seamless GDY with the SiNPs and the current collector and g) a possible mechanism for the protecting effect of the seamless GDY nanosheets on the silicon anode after the dramatic change in volume. We characterized the electrode after cycling to explore the reasons behind the highperformance Li+ ion storage. The thickness of the electrode increased by about 80% relative to that before cycling (Fig. 5a); that is the indication that the volumetric increase was greater than 80%. The large volumetirc increase is attributed by the high content of Si NPs on the electrode. In addition, the electrode became much denser, suggesting that the voids in the electrode helped

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to retard the volumetric changes [15, 16, 37, 46]. The electrode remained firmly anchored on the Cu foil without any obvious cracks on the bottom, even though its thickness had increased so dramatically. The magnified cross-sectional image in Fig. 5b reveals that the swollen and pulverized SiNPs remained firmly embedded in the GDY network, leaving no apparent voids in the bulk of the electrode. Moreover, the electrode was flat, without any notable fractures on its surface (Fig. 5c), reaffirming the good mechanical strength of the GDY network against to the high stress and strain caused by the large variations in volume [4, 47, 48]. The corresponding TEM image in Fig. 5d confirmed that the GDY nanosheets maintained their effective 3D network that held the SiNPs tightly. Because of the volume expansion, the pulverized SiNPs were more widely dispersed in the conductive GDY network. The remarkably wide distribution of silicon atoms in the carbon framework is evidence for a high content of active silicon on this electrode, further highlighting the practicality of this in situ method. Figs. 5f and 5g present schematic representations of the possible interactions among the elements in the electrode. As illustrated, the 3D transfer model of Li+ ions in the GDY framework has an innate advantage— barrier-free channels for Li+ ion migration—over systems containing only sp2-hybridized carbon atoms; in addition, the seamless GDY shell on the particles prevents pulverization of the SiNPs and, thereby, the electrode does not exhibit any accompanying decrease in conductivity.

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Fig 6. a) Photographs of an as-assembled GDY-Si//NCA full cell (2  2 cm) powering three sets of LED lights. b) Charge/discharge curves of the GDY-Si//NCA full cell at a current density of 0.1 A g–1 (based on the mass loading of Si anode). c) Long-term stability of the GDYSi//NCA full cell at a current density of 0.5 A g–1 (based on the mass loading of Si anode). To further demonstrate the superior performance of silicon electrodes fabricated using this method, we paired an as-prepared electrode having a size of 2  2 cm with a commercial LiNi0.8Co0.15Al0.05O2 (NCA) cathode (Fig. S10) to assemble the full cell (Figure 6a). After charging, we used this cell as a power source for lighting a homemade device containing 26 LEDs, delivering a stable energy output. Measurements of the charging/discharging performance of this cell provided an areal capacity reaching 1.06 mA h cm–2. This full cell displayed a good cycle performance, with great promise for further improvements. Because the average voltage of the full cell was approximately 3.42 V, the volumetric energy density (1343 W h L–1) and mass energy density (417 W h kg–1), calculated based on the thickness [6 m (anode) + 21 m (cathode)] and weight [0.6 mg cm–2 (anode) + 8.1 mg cm–2 (cathode)] of the electrode, were significantly higher than those of many previously reported [49], suggesting great potential for use in high-energy-density LIBs.

Conclusion In summary, the growth methodology of ultrathin GDY nanosheets under mild conditions can be used to solve what have previously seemed intractable problems resulting from severe volumetric changes of silicon anodes. Using the in-situ growth strategy established herein, ultrathin GDY nanosheets can be firmly coated onto SiNPs, constructing 3D all-carbon

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conductive and mechanical networks that improve electron migration and retard structural degradation during the alloying/dealloying processes; in addition, the in-situ growth of GDY nanosheets initiated by the bottom Cu foil strengthens the contact between the silicon particles and the Cu current collector, a situation that is difficult to achieve using prevailing electrode preparation methods. Furthermore, and most importantly, this simple method is definitely scalable and suitable for practical applications. When integrated with GDY, silicon anodes exhibit remarkable improvements in long-term stability. We suspect that the use of this method will also improve the performance of other types of potential electrode materials.

Acknowledgement This work was supported by the National Nature Science Foundation of China (21790050,21790051), and the National Key Research and Development Project of China(2016YFA0200104) and the Key Program of the Chinese Academy of Sciences (QYZDYSSW-SLH015).

Notes The authors declare no competing financial interest.

Appendix A. Supporting information. Supporting information associated with this article can be found in the online version at XXXX.

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SEM images of the bare Si anode loading on the the Cu foil; Cross-sectional SEM image of as-loaded SiNPs on the Cu foil; Cross-sectional SEM image of GDY-Si3 on the Cu foil; TEM images of the SiNPs using in the work; TEM images of GDY-Si1; Elemental distribution information of the selected region; Electrochemical performance of Si and NCA electrode.

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Highlights   

A scalable method for constructing all-carbon binder of ultrathin graphdiyne is firstly established for solving the volumetric problems of Si anode economically; The 3D conductive and mechanical networks of graphdiyne nanosheets can be robustly constructed in the Si electrode, simultaneously increasing the interfacial contact with the current collector, and improving the electron and ion transfer; The sp carbon-rich framework of graphdiyne shows great superiorities for seamlessly protecting the Si anode, better than sp2 carbons; as a result, the modified Si anode can deliver a reliable capacity (2300 mA h g–1) for storing the Li ions, and achieves an energy density up to 1343 W h l–1 (417 W h kg–1).

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