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Nano Energy

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Low temperature, atmospheric pressure for synthesis of a new carbon Ene-yne and application in Li storage

Zhiyu Jiaa, Zicheng Zuoa, Yuanping Yia, Huibiao Liua,c, Dan Lib, Yongjun Lia,c, Yuliang Lia,c,⁎

a Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences,Beijing 100190, PR Chinab Department of Chemistry, Shantou University, Shantou 515063, PR Chinac University of Chinese Academy of Sciences, Beijing 100049, PR China

A R T I C L E I N F O

Keywords:Carbon Ene-yneSolvent-phaseAlkadiyneConductivityLi storage

A B S T R A C T

Carbon Ene-yne (CEY), a novel two-dimensional full carbon material, was synthesized from tetraethynylethene.Compared with the traditional preparation method of carbon materials, CEY was synthesized by chemicalmethod in solvent-phase under mild condition (low temperature, atmospheric pressure). Diyne of CEY wereconnected through vinyl groups which is help for π-electron transition, thus this new material exhibits excellentelectronic property. Small band gap of 0.05 eV was predicted for CEY, and high conductivity of CEY film is up to1.4×10−2 S/m which facilitates its application in electronic devices. Lithium-ion batteries featuring CEY-basedelectrode exhibit excellent electrochemical performance, including high specific capacities, outstanding rateperformances, and a long cycle lives. We obtained a much high and reversible capacities of up to 410 mA h/geven after a long-term cycling at a high current density of 748 mA/g. Additionally, prepared by our mild solvent-phase chemical method, CEY might be a new star as a versatile materials for many electrochemical applications.

1. Introduction

Carbon allotropes are unique and very versatile elements capable offorming different architectures at the nanoscale, such as fullerene [1],carbon nanotube [2], graphene [3]. As new form of non-natural carbonallotropes related to graphite/graphene, sp hybrid allotrope and sp-sp2

hybrid allotrope have already been subjected of interest for theiroutstanding structures and electronic properties. Carbyne, a linear,one dimensional chain of sp-hybrid carbon atoms, has already receivedgreat attention in the past twenty years, because of its extreme metallicbehaviors, room temperature superconductivity, intriguing nonlinearoptical properties, high hydrogen storage capability [4–10], and third-order nonlinear optical properties [11]. In 1972, carbyne materialsincorporating up to 16 conjugated C≡C units were first synthesized byWalton and co-workers [12]. Since then, many theoretical investiga-tions demonstrate that such a linear carbyne should have a higherstrength, elastic modulus and stiffness than any known carbonallotropes, including diamond, carbon nanotube and graphene.However, the practical applications of linear carbyne is intensivelyobstructed by the synthesis method, which can only inefficientlyproduce carbyne with a low polymerization degree (less than 22), notenough for further utilizations. Computational studies have indicated

that acetylenic chains can be used to connect benzene rings flexibly andform various hybrid structure, such as graphyne (GP), a planar sheetwith 6-C hexagon connected by acetylenic chain (–C≡C–) is stable [13].Recently, numerous monomeric and oligomeric compounds have beensuccessfully synthesized, supporting early theoretical predictions onthe stability of sp-sp2 hybrid structure [14–16]. Via these aforemen-tioned predictions, we innovatively applied a benzene ring for increas-ing the stability of the long-chain carbyne, and extending its 2-dimensional continuity; thus, we first successfully prepared the large-scale graphdiyne (GDY) film through an in situ cross-coupling reactionon Cu foil from hexaethynylbenzene by solvent-phase reaction [17–19].Graphdiyne characterized with high π-conjugated, uniformly distrib-uted pores, and tunable electronic properties [20–23]. It has possibleapplications as gas separation membranes [24–26], catalysis [27],energy storage materials [28–30], and anode materials in batteries[31,32]. Up to now, the graphdiyne films from solvent-phase reactionhave reached an outstanding film conductivity (2.5×10−4 S/m) close tothe normal inorganic semiconductor, such as ZnO [33]. In view ofexcellent properties and applications of graphdiyne from experimentaland theoretical investigations, any other sp-sp2 hybrid carbon allotropeis being explored.

Here, a novel two-dimensional full carbon material was designed

http://dx.doi.org/10.1016/j.nanoen.2017.01.049Received 14 December 2016; Received in revised form 13 January 2017; Accepted 23 January 2017

⁎ Corresponding author at: Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences,Beijing 100190, PR China.

E-mail addresses: zuozic@iccas.ac.cn (Z. Zuo), liyj@iccas.ac.cn (Y. Li), ylli@iccas.ac.cn (Y. Li).

Nano Energy 33 (2017) 343–349

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MARK

and synthesized from tetraethynylethene by solvent-phase reaction(Fig. 1). The material is composed of ene and yne, so we named it asCarbon Ene-yne (CEY). Theoretical study suggests that this kind ofCEY materials is promising semiconductor materials for electronicapplication [34]. Herein, via in situ cross-coupling reaction in solution,this novel CEY film with a high conductivity up to (1.4×10−2 S/m) isfirstly synthesized in large scale. The perethynylated derivative C40+8iso-Pr3Si is the first known representatives of the expanded radialene[11]. We supposed C40 is the smallest unit of network structure, whichcould simplify the DFT calculations. Further theoretical prediction andexperimental test of this CEY material prove its wonderful electronicproperties. Since the yne-riched materials might offer more positionsfor lithium-ion storage, as-prepared CEY delivers a high specificcapacity for lithium storage up to (1326 mA h/g), about triple of thecommercial graphite. On account of the well expanded two-dimen-sional (2D) continuity in the CEY, such thin film anode without anyconductive additives benefits for the insertion/desertion of Li+ andcharge transfer process. Long-term testing demonstrates that CEYshows a robust reversibility (410 mA h/g) even under a high currentdensity (748 mA/g), indicating its promising applications in Li+

batteries anode materials.

2. Experimental section

2.1. Synthesis of CEY film

Tetrakis(trimethylsilylethynyl)ethane (27 mg) was added to metha-nol (10 mL), and then excessive K2CO3 was added to above solution for15 min. The reaction was test by TLC, the starting substrate wasdisappeared at this point. Water (5 mL) was used to quench thisreaction, n-pentane (10 mL) was added to the reaction system. Themixture was washed with saturated aqueous NaHCO3 and brine, thenevaporated to dryness. Because tetraethynylethene (TEE) is modestlystable in solvent at room temperature, the solvent was evaporatedunder vacuum at 0 °C, and then pyridine (20 mL) was added undernitrogen atmosphere at 0 °C. The primrose yellow solution will be usedfor next step.

Copper foil was washed with 4 M hydrochloric acid (HCl) (100 mL),sonicated for 3 min, washed with water and ethanol, sonicated for3 min, washed twice with acetone, and dried under nitrogen (N2).Several (10) pieces of copper foil (2×2 cm2) and pyridine (100 mL) wascharged in a three-neck flask (250 mL); the mixture was heated at100 °C under N2 for 1 h. The above primrose yellow solution wastransferred to a N2-protected constant addition funnel, and addeddropwise into the mixture containing pyridine (100 mL) and the piecesof copper foil at 100 °C; this addition process lasted for 3 h. Afteraddition of TEE, the reaction mixture was maintained at 100 °C for 3days. Upon completion of the reaction, the pyridine was evaporatedunder reduced pressure. A black film was obtained on the copper foil.We get the sample CEY-1 (0.1 mg/cm2). The thickness of CEY film is1 µm.

When 13.5 mg and 5.4 mg Tetrakis(trimethylsilylethynyl)ethanewere used, respectively, sample CEY-2 and CEY-3 were prepared.The thickness of them are 500 nm and 200 nm, respectively.

2.2. Density functional theory (DFT) calculations

All the geometric structures are optimized by density functionaltheory (DFT) at the B3LYP/6-31 G (d, p) level. Based on the optimizedgeometries, the binding energies (ΔG) were then corrected by the basisset superposition error (BSSE).

2.3. Materials characterizations

The X-ray photoelectron spectroscopy (XPS) measurements wereperformed on the Thermo Scientific ESCALab 250Xi using 200 Wmonochromated Al Kα radiation. The banding energies obtained in theXPS analysis were corrected with reference to C1s (284.8 eV). X-raypowder diffraction (XRD) data were collected using a Japan Rigaku D/max-2500 rotation anode x-ray diffractometer equipped with graohite-monochromatized Cu Kα radiation (λ=1.54178 Å). The work functionswere measured by UV photoelectron spectroscopy (UPS; GammadataVUV 5050) using a He II discharge lamp (hν, 21.22 eV). The workfunction was determined using the secondary-electron cutoff (Ecutoff)of the UPS using nickel as a reference. The position of the Fermi levelwas calibrated by measuring the Fermi edge of nickel. Raman spectrawere taken on a Renishaw-2000 Raman spectrometer at resolution of2 cm−1 by using the 514.5 nm line of an Argon ion laser as theexcitation source. Scanning electron microscope (SEM) measurementswere performed on a Hitachi Model S-4800 field emission scanningelectron microscope. The TEM and HRTEM measurements wereperformed on a JEM-2100F electron microscopy with an acceleratingvoltage of 200 kV.

2.4. Electrochemical measurements

We use a typical Li-ion battery to estimate the Li storage capacity ofCEY. Electrochemical experiments were performed using 2032 coin-type cells. We cut the CEY films grown on the copper foil into piecesand used them directly as working electrodes without the addition ofany binders. A pure Li foil was used as the counter electrode. Thecounter electrode was separated from the working electrode by aCelgard 2500 polymeric separator. The electrolyte comprised a solutionof 1 M LiPF6 in ethylene carbonate (EC) and dimethyl carbonate(DMC) (1:1, v/v). We assembled the cells in an argon-filled glove boxin which the concentrations of moisture and oxygen were below 1 ppm.

3. Result and discussion

The optimized geometry and band structures of CEY were obtainedfrom DFT calculations [35,36]. The CEY sheet structure is shown inFig. 1b, where the unit cell is drawn in red line. The a- and b-axes of the

Fig. 1. Schematic of large-scale CEY synthesis. (I) Synthesis of CEY. (II) Photograph of large-scale CEY film.

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cell are orthogonal to each other and their optimized lattice parametersare 11.289 and 9.679 Å, respectively. Periodic first-principles calcula-tions were carried out with Vienna Ab-initio Package (VASP) within thegeneralized gradient approximation. The exchange-correlation functionof Perdew-Burke-Ernzerhof and the projector-augmented wave meth-ods were used. The plane wave basis cutoff energy was set to 400 eV.The Brillouin zone was sampled with an 11×11×1 Monkhorst-Pack k-point grid (Fig. 2a). For Brillouin Zone integration, the Gaussiansmearing method with a 0.05 eV width was applied for smearing. Theconvergence criterion of total energy was set to 10−5 eV for theelectronic self-consistent cycle. Both atomic positions and cell para-meters were allowed to relax. From the band structures (Fig. 2b), CEYmaterials are predicted to be semiconductor, in which the smallestband gap has a value of 0.05 eV at the Γ-point, which can be a usefulfeature for employing the CEY as semiconducting channels in FETs.

The characteristic of CEY was investigated by spectroscopic tech-niques firstly. Fig. 3a shows a solid state 13C NMR spectrum of CEYpowder. The spectrum shows two groups of resonances: one at

130.55 ppm and one at 60.98 ppm. The broad peak at 130.55 ppm isfrom sp2 hybridized carbons. The sp-hybrid carbon's signals span abroad range with a median value of 60.98 ppm, which is different fromthe typical chemical shift of alkyne (65–90 ppm). Refer to π cloud ofthe carbon-carbon triple bond, this could be ascribed to the electron-density of conjugative effect. The more electron-density gained thesystem, the greater the observed chemical shift fails to predict what weobserve. As reported by Tykwinski [6,8], 13C NMR signals of carbyne(broad signal centered at 63.7 ppm) is smaller than the theoreticalchemical shift. When the number of carbyne unit increase, the chemicalshift goes smaller. These findings strongly support the assertion thatthe obtained CEY should possess a polyyne-link structure.

X-ray photoelectron spectroscopy (XPS) was used for furthercharacterize the CEY films and confirm unambiguously that these filmsare composed of only elemental carbon. The XPS survey scan shown inFig. S1 demonstrates only the peaks associated with CEY. The XPS C 1sspectrum in Fig. 3b shows peak at 284.8 eV which can be deconvolutedinto four subpeaks, corresponding to sp2 (C=C) at binding energy of

Fig. 2. (A) Schematic of the Carbon Ene-yne in this study. (B) The corresponding calculated band structure.

Fig. 3. (a) Solid 13C NMR of CEY powder. (b) XPS spectra of CEY films for C 1s. (c) Raman spectra of CEY films on position (A), (B), (C). (d) UPS spectra of CEY film.

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284.4 eV, sp (C≡C) at 285.0 eV, C–O at 286.0 eV, and C=O at 287.8 eV,respectively [17]. The presence of elemental O derivatives from theadsorption of air in the pores of networks and small amounts ofoxygen-containing functionalities. The area ratio of sp/sp2 is close to 4,which confirms the chemical composition of diyne groups and vinylmoiety in as-prepared CEY.

Raman spectroscopy was used to evaluate the quality and uni-formity of CEY film on the surface of silicon pellet. We analysed theRaman character at three different positions (A) (B) (C), as shown inFig. 3c. All the Raman spectra of CEY film at these positions exhibitthree characteristic peaks: 1473.0 cm−1, 1572.0 cm−1, 1915.1 cm−1,2183.2 cm−1. CEY exhibit a weak D line at 1473 cm−1, corresponding toa breathing mode or k-point photos of A1g symmetry, and a relativelystrong G line at 1572.0 cm−1, which should be assigned to the in-planebond-stretching motion of pairs of Csp2 atoms (the first order scatteringof the E2g photons), which is red shift comparing to the G band ofgraphite (1575.0 cm−1) [37]. The peaks at 1915.1 cm−1 and2183.2 cm−1 can be attributed to the vibration of conjugated diynelinks (–C≡C–C≡C–) [17,38].

To explore the direct redox reaction property of CEY, Ecutoff valuewas measured with ultraviolet photoelectron spectra (UPS) (Fig. 3d).The work functions (Փ) was thus calculated with the equation [39,40],Փ=hv−EFemi−Ecutoff, where hv, EFemi and Ecutoff are the bondingenergy of excitation light (21.22 eV), the Fermi level edge (0 eV in thiscase), and the inelastic secondary electron cutoff measured in Fig. 3d,respectively. The work functions of 4. 52eV was obtained. The reduc-tion potential was obtained from the equation [41–43], Փ/e=E(vs SHE)

+4.44 V, where Փ is the work functions, E is the reduction potentialversus standard hydrogen electrode (SHE). The reduction potential ofCEY was estimated to be about 0.08 V vs SHE, which is lower thanthose of other kinds of carbon allotropes such as carbon nanotubes(+0.50 V vs SHE) and graphene oxides (+0.48 V vs SCE) [44],suggesting CEY is the excellent reducing agent among all the carbonmaterials for electroless deposition of metals.

We use scanning electron microscopy (SEM) and transmissionelectron microscope (TEM) to investigate the typical morphology ofCEY films. Fig. 4a shows a scanning electron microscope (SEM) image

of CEY film (CEY-1) on a copper substrate, which indicates the film isuniform and compact. The thickness of the CEY is approximately 1 µm.As we shown in the Supporting information, we can control thethickness of film at the different chemical conditions. The typicalatomic force microscopy (AFM) images were used for further evaluat-ing the thicknesses of these CEY films (Fig. 4d, e, f). The thicknessesare 1 µm, 500 nm, 200 nm respectively. Fig. 4b shows a TEM image ofthe typical CEY (CEY-1), and a multilayer film can be observed. High-resolution TEM (HRTEM) characterization and corresponding se-lected-area electron diffraction (SAED) patterns reveal the high crystal-linity of CEY in certain areas (Fig. 4c), the layer-by-layer structurecould be clearly observed, and the interlayer spacing is 0.45 nm, whichis obviously larger than that of graphite (0.335 nm); the expandedinterlayer spacing in CEY might accelerate the Li+ transportationamong the planar nanosheets which could promote the rate perfor-mance in the application of lithium-ion storage. Same results were goton CEY-2 and CEY-3 films. The HRTEM images of CEY-2 and CEY-3films can be found in the Supporting information Fig. S2a and b. Theinterlayer spacing of CEY-2 and CEY-3 is also 0.45 nm.

I –V curves of CEY films were measured for determining theconductivity according to Formula 1:

rκ = dIdL/π dV2 (1)

dI and dV are the difference of electrical current and electric potentialduring the linear region, dL is the thickness of different nanostructures,the Pt-coated tip radius ( < 25 nm).

When the bias voltage was applied from −2 to +2 V, the filmsexhibit the standard ohm curves (Fig. 5b). Via the calculation, it issurprisingly found that the conductivities of CEY-1, CEY-2 and CEY-3are high up to 1.4×10−2 S/m, 1.6×10−2 S/m and 1.1×10−2 S/m,respectively. The similar conductivity of CEY films with differentthickness means that the conductivity of the thin films is reproducibleand reliable. Moreover, this high conductivity matches well with theDFT calculations, which is close to the normal inorganic semiconduc-tor, as nanophase ZnO exhibiting conductivity from 2×10−4 to2×10−2 S/m at 450–600 °C [31].

Our previous experimental and theoretical investigations have

Fig. 4. (a) The SEM image of CEY film (CEY-1) on the surface of copper foil. (b) The TEM image of CEY film (CEY-1). (c) HRTEM image of CEY film (CEY-1), related SAED patterns arein corresponding insets. The AFM image of CEY films (d) 1 µm (CEY-1); (e) 500 nm (CEY-2); (f) 200 nm (CEY-3) (the thickness datas of film were inserted into the AFM images).

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already demonstrated that the alkyne-rich feature of graphdiyne isuseful for its high-capacity Li+ storage. Therefore, CEY, whose ynecontent is higher than graphdiyne, might be a new promising materialsfor Li+ storage. Due to its excellent conductivity, large-scale prepara-tion, two-dimensional feature as well as alkyne rich structure, CEY-1(1 µm) is evaluated by a typical 2032 coin-type half-cell system. We cutthe CEY-1 grown on the copper foil into pieces and used them directlyas working electrodes without any additions of polymer binder andconductive agent; this is a yearning strategy to maximize the volu-metric/mass energy density of a practical battery (Fig. 5a). Ourprepared Li-ion batteries incorporating CEY-1 electrode exhibit ex-cellent electrochemical performance. Galvanostatic charge-dischargecycling is used to study capacity variations at different currentdensities, and understand charge-discharge profiles and coulombicefficiency. The voltage range used in the Galvanostatic cycling graphs ofthe first two cycles were between 0.005 and 3.0 V vs. Li with a currentrate of 37.4 mA/g (Fig. 5c). During the first discharge cycle, the voltagedrops sharply from the open-circuit voltage (OCV) of about 2.8 V toabout 1.3 V corresponding to the beginning of the Li+ ions insertioninto the CEY film. The discharge profile mainly consists of a voltageplateau at about 0.7 V. At about 0.1 V, the voltage drops with a gentlesloping profile. This sloping portion covers a capacity of about1823 mA h/g. The overall capacity at the end of the first deep dischargeis 2563 mA h/g. However, the initial coulombic efficiency is 51.7%,because of the activation process for forming a stable solid electrolyteinterphase (SEI) on the CEY film electrodes during the first dischargestep. Cyclic voltammetry (CV) is used to complement galvanostaticcycling tests by analyzing conversion reaction as well as redoxpotentials. CV was carried out at a scan rate of 0.1 mV/s. The voltagerange used was 0–3 V for 1–2 cycles. Lithium was used as the counterelectrode. The cyclic voltammetry curve in Fig. 5d was resulted fromboth CEY film and its copper substrate. The peaks observed in CV(Fig. 5d) closely resemble galvanostatic discharge-charge profiles

(Fig. 5c). The first cycle cathodic scan shows a continuous reductionin potential from the OCV of about 1.3 V, 0.7 V, 0.1 V, which is verysimilar to the first discharge-cycle profile during galvanostatic cycling.This is indicative of the partial reduction of CEY-1 film on copper andalso corresponds to the beginning of Li+ ions insertion into thenanoporous structure of CEY. A highly efficient Li-ion battery requiresits electrode materials to possess at least two qualities: (1) a highcapacity for Li storage and (2) sufficient space for Li diffusion. Theunique structure of CEY features a large number of nanoscale, whichhas great number of Li storage sites and favors the absorption/desorption and diffusion of Li ions, both in-plane and out-of-plane.This could be the reason why the CV curve has two pairs of cathodic/anodic peaks. Whilst, SEI layer might make the first cycle CV curveirreversibly. Fig. 5e displays the rate performance of CEY-1, we couldstill observe reversible capacities of 1015, 820, 693 and 361 mAh/g athigh current densities of 74.8 mA/g, 187 mA/g, 374 mA/g and748 mA/g respectively. After 120 cycles, the half-cell battery stillexhibits excellent reversibility and rate performance, and we couldstill observe reversible capacities of 970, 750, 650 and 410 mA h/g athigh current densities of 74.8 mA/g, 187 mA/g, 374 mA/g and748 mA/g respectively (Fig. 5f). We ascribe the excellent rate capacitiesand superior cycle stabilities to the high conductivity and chemicalstability of CEY film. From electrochemical impedance spectra of theCEY-1 before and after cycling (Fig. 5g), it reveals that the contact andcharge-transfer resistances of the CEY electrode demonstrate that suchfilm electrode is intensively grown copper foil and stabilizes the charge-transfer process during the long-term cycling performance.

After 120 cycles, we investigated the morphological variationcausing by the reiterative Li+ insertion/desertion processes under ahigh current density. The SEM image in Fig. 6a show a CEY-1 filmunder the state of unstorage Li+(discharge state), which is similar withthe primary film. The film is uniform and compact. We examined themorphology of CEY-1 film under the state of full Li+ charge state

Fig. 5. (a) Representation of a CEY-based battery. (b) Typical I-V curve of CEY film at the different thickness (a-1 µm, b-500 nm and c-200 nm). Performance of CEY film in a Li-ion halfcell. (c) Galvanostatic charge/discharge profile of a CEY film electrode at a current density of 37.4 mA/g, recorded between 5 mV and 3 V. (d) Cyclic voltammetry curves of the CEY filmbased electrode with copper substrate, recorded at a scan rate of 0.1 mV/s. (e) Rate performance of CEY film at 37.4 mA/g, 74.8 mA/g, 187 mA/g, 374 mA/g and 748 mA/g; (f) After 120cycles, rate performance of CEY film at 37.4 mA/g, 74.8 mA/g, 187 mA/g, 374 mA/g and 748 mA/g. (g) Nyquist plots of a CEY film based electrode before and after 120 cycles at acurrent density of 748 mA/g.

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(Fig. 6b). Some small particles have been generated on the filmelectrode, causing by the formation of stable solid electrolyte inter-phase (SEI) on the primary structure of CEY. From the SEM image ofthe large area morphology, the integrality of CEY-1 indicates that thecontinuity is maintained during the whole long-term charge/dischargeprocess. In addition, the CEY-1 electrode still sticks on the coppersubstrate firmly. Thus, all the above observations in the electrode aftercycling further support that the negligible variation in the charge-transfer resistance is obligatory. For deeply understanding the layer-like structure stability of CEY after the long-time cycling under a highLi+ transfer, the electrode is characterized by HRTEM. The well-defined layer-like feature in Fig. 6c, d indicates that the alkyne-richframework is ultra-robust during the electrochemical reaction. Thelayer-by-layer structure still could be clearly observed, and the inter-layer spacing is 0.45 nm. From Fig. 6e, we can observe the solidelectrolyte interphase (SEI) layer. Raman spectrum was also used toanalyse the mechanism of Li+ storage. Fig. 6f show the Ramanspectrum of CEY-1 film at unstorage Li and storage Li states, we canobserve the signal of –C≡C–C≡C– at 1915.1 cm−1 and 2183.2 cm−1 atunstorage Li+ state (Charge state). When Li+ insert into the CEY at thedischarge state, the signal of alkadiyne decreased. Refer to themechanism of Li+ storage in graphdiyne, this could be ascribed to (i)lithium insertion within the “cavities” in the material [45,46], (ii)lithium binding absorbed on each side of the carbon sheet [47], (iii)lithium binding on the so called “covalent” site [48]. When the Li+ wasstored, lithium transfers its 2 s electrons to the carbon host. Owing tothe high conjugate structure of CEY, the electrons of lithium wouldmigrate on the carbon host. This could decrease the signal ofconjugated diene links (–C≡C–C≡C–) in Raman spectrum.

4. Conclusion

We designed and synthesized a novel two dimensional full-carbonmaterials (Carbon Ene-yne) by conjugating diyne with vinyl groups bysolvent-phase reaction. Theoretically, such well-defined structure con-tains 80% sp-hybrid carbon in its framework, showing a much largeconjugation degree. Small band gap of 0.05 eV was predicted and

proved based on the CEY, which facilitates its application in photo-electronic devices. Its application in storing the Li+ ions in batterydemonstrates that the CEY film is a promising anode, which can delivera high reversible specific capacity up to 1326 mA h/g, triple than that ofcommercial graphite. The enlarged structure parameter and highconjugation degree offers the film electrode exciting rate performanceand long-time stability. Moreover, Carbon Ene-yne film mildly grownon the substrates may shield light on some other green applications,such as electronics, optoelectronics, energy storages, package, andcatalysts.

Acknowledgements

We thank all the members of Yuliang Li laboratory. This work wassupported by the National Key Research and Development Project ofChina (2016YFA0200104), the Key Program of the Chinese Academy ofScience (QYZDY-SSW-SLH015).

Appendix A. Supporting material

Supplementary data associated with this article can be found in theonline version at doi:10.1016/j.nanoen.2017.01.049.

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