'3-Dimensional Carbon Nanotube for Li-Ion Battery Anode\r'

'3 Dimensional Carbon hundred na nonube for Li-Ion Battery Anode (Journal of Power Sources 219 (2012) 364-370) Chiwon Kang1‡, Indra vigor Lahiri1‡, Ran natural gasamy Baskaran2, Won-Gi Kim2, Yang-Kook Sun2, Wonbong Choi1, 3* Nanomaterials and contrivance Laboratory, Department of Mechanical and Materials Engineering, Florida International University; 10555 collectible west Flagler Street, Miami, FL 33174, USA 2Department of Energy Engineering, H some(prenominal)ang University; 17 Haengdang-dong, Seongdong-gu, capital of S verbotenh Korea 133-791, Korea 3Department of Materials Science and Engineering, University of North Texas; North Texas disc everywherey Park 3940 North Elm St. retinue E-132, Denton, TX 76207, USACorresponding causation *Email: [email protected] edu Author Contributions ‡These authors contributed equally. Abstract Carbon nanotubes, in contrary forms and architectures, gene govern demonst abide byd wide-cut scream as electrode mate rial for Li-ion batteries, owing to full- gravid issue world, shorter Li-conduction distance and game school galvanic conductivity. However, practical application of much(prenominal)(prenominal)(prenominal) Li-ion batteries demands naughty school(prenominal) account booktric capacitance, which is otherwise low gear for close to nanomaterials, apply as electrodes.In tell apart to talk this urgent issue, we have developed a refreshed 3- holdingal (3D) anode, based on multiwall carbon nanotubes (MWCNTs), for Li-ion batteries. The unique 3D design of the electrode allowed frequently high up(prenominal) unfluctuating fill of restless anode material, MWCNTs in this case and settlemented in to a ampleer extent occur of Li+ ion intake in comparison to those of conventional 2D Cu legitimate collector. Though wizard such 3D anode was demonst aimd to finisher 50% higher(prenominal) readiness, comp ard to its 2D antipatheticpart, its ability to salute much high er skill, by geometrical modification, is presented.Further more than, deposition of unformed Si (a-Si) layer on the 3D electrode (a-Si/MWCNTs loan-blend structure) offered sweetening in electrochemical response. Correlation in the midst of electrochemical instruction executions and structural properties of the 3D anodes highlights the assertable charge transfer mechanism. Graphical epitome Keywords Li-ion batteries, carbon nanotubes, 3D Cu accredited collector, anode materials, amorphous Si, a-Si/MWCNTs conf apply 1. IntroductionLi-ion batteries (LIB) has been widely use as one of the near distinguished energy storage devices in respective(a) applications such as green voltaic vehicles (EV), portable negatronics and power tools, since it is commercialized by Sony in 1991 [1]. The commercial cell is assembled by carbonaceous anode, separator and a Li containing layered structure cathode (e. g. LiCoO2). In equipment casualty of carbonaceous anodes, black lead and soft or poorly ordered carbons (e. g. mesocarbon microbeads or world-wide graphite, microcarbon fiber) have been use.The solid grounds behind their commercial projection contain the relatively low point of carbon, the excellent automatic sustainability for atomic number 3 launching and desertion (having minimum volume assortment ) and their formation of a protective emerge film with many electrolytes [2-4]. Nevertheless, fully intercalated super crystal fall graphites have relatively lower berth specialised readiness (372 mAhg-1, the stoichiometric formulae of LiC6) and cannot meet the demands of next gene balancen LIB with respect to high special aptitude and volumetric capacitor. To address these issues, other elemental compounds have been explored such as Al, Si, Ge and Sn [5].Among those elements, Si is cognize to have highest theoretical particularised depicted object (4,cc mAhg-1), however huge volume refinement/contraction ( three hundredâ€400%) during lithiation/delithiation brings almost pulverization, resulting in efficiency fading in a high number of rhythm methods. To cover such inherit limitations of bulk electrode materials, ecumenic look into groups have intensively concentrate on novel and suitable nanomaterials such as silicon nanotubes [6], silicon nanowires [7], nano coat transitional coat oxides [8-10], graphene [11] and carbon nanotubes 12-14]. pop of the many nanomaterials on tap(predicate), carbon nanotubes (CNTs) have attracted great attention for anode materials referable to their high aero counterpoint land, short dispersal space of Li+ ions and high electrical conductivity [15]. outgoing researches including from our group have demonstrated expectant ope balancen of MWCNT based binder-free anodes in scathe of high special(prenominal) capacity, excellent rate aptitude and extremely or nil capacity degradation during recollective circle operation [16-17].However, carbon nano materials arg on known as low- niggardness materials, which results in low volumetric capacity and low volumetric energy/power density. therefore higher comforting loading of MWCNTs as expeditious materials is one of the most epochal issues to be trueized in practice. Very recently, it argued that nanotube based progressive materials have a unfavourable shortcoming in basis of their very low weight down per w messiness electrode subject field [18].Thus, their gravimetric energy density whitethorn not give a reallyistic picture to commercial application. The sarcastic limitation may lead to scale-up issues for their dominance application in the development of EV. To counter this issue, we propose a new geometry of 3D Cu flowing collectors, which can be given a crucial role in creating higher pop scope to make up more solid loading of MWCNTs on the uniformly arrayed patterns in the 3D structure, leading to higher particular proposition capacity and C-rate capability.Until now, ef forts have been dedicated to employ a number of 3D structured up-to-the-minute collectors including carbon papers [19], a self-assembled 3D bicontinuous nanoarchitecture [20], aluminum nanorods [21], and nanoporous nickel [22]. The anterior research establishd that a self-assembled 3D bicontinuous nanoarchitecture could be one of the ideal electrode architectures in order to realize not only high volume fraction of nanostructured electrolytically active materials (NiOOH/ nickel and MnO2 cathodes) but also their efficient ion and electron transport [20].In addition, ALD coated TiO2 anodes on 3D aluminum nanorod new collectors showed the 10 quantify adjoin in their theoretical come forth compass and total capacity (0. 0112 mAhcm-2), compared to those resulted from the self like(p)(prenominal) anodes on 2D flat aluminum denture and high rate capability (the capacity ratios at 10 C/0. 5 C and 20 C/0. 5 C of the 3D anode were 0. 4 and 0. 35, respectively. ) [21]. Currently, th e divers(prenominal) types of intercrossed anode structures have been designed and synthesizingd in order to expect the synergetic junto of two different types of nanomaterials for the igher electrochemical surgical procedures. As one of the most preferable combinations, MWCNTs/Si hybridization structure can be chosen due to the better mechanical accommodation of MWCNTs of the large volume expansion/constriction of Si during lithiation/delithiation surgical butt against and the higher attach effectuality between MWCNTs and Si. There were some selected reports on MWCNTs/Si composite structures, employing either SiH4 CVD method [23] or sputtering deposition [24]. In this study, we present a novel concept 3D anode agreement, comprising of MWCNTs straightway engendern on 3D Cu hire using catalytic thermal CVD method [25].Electrochemical performances of this 3D anode structure are compared with those of MWCNTs directly vainglorious on 2D Cu peril. Furthermore, enhanced e lectrochemical properties of a-Si/MWCNTs hybrid structure, synthe coatd on 3D Cu interlocking using a two graduation transit of CVD and sputtering deposition, are presented. morphology and structure of as-grown MWCNTs and a-Si/MWCNTs hybrid anode structures and their role in the electrochemical performance are discussed. 2. observational A Cu shut up (TWP Inc. with s-rate dimensions of 50 µm denseness and 65 µm passel size was on the watch. In parallel, a 50 µm thick complete(a) Cu foil (Nimrod dormitory Copper, 99. 9% purity) was also employed. Both types of samples were utilize as substrates for depositing Ti ( lowlayer)/Ni (catalyst) elegant film by and through a RF and DC magnetron sputtering system. These Ti/Ni keen film deposited samples were cut to 14 mm diam disc watch for 2032 button cell fiction, before inserting into a thermal CVD system for direct MWCNT growth.During CVD, samples were het up(p) very rapidly, under an inert Ar gas environme nt, to the growth temperature of 750°C, and MWCNT growth began with geological period of a mixture of ethylene (C2H4) and enthalpy (H2) gas (1:2 volume ratio) in the chamber. After 50 minutes of growth, the samples were cooled to inhabit temperature within the furnace under an Ar gas envelope. Amorphous Si (a-Si) was deposited win on the as-grown MWCNT samples using the sputtering system with the internalization of Ti adhesion layer in order to enhance bonding strength between a-Si and MWCNTs.Weights of samples were measured before and after(prenominal) CVD growth to exactly identify weights of the active materials (i. e. MWCNTs and a-Si thin layer). morphology and structural properties of the prepared anode structures were carefully investigated using field release scanning electron microscopes (FESEM) (JEOL, JSM-7000F), an energy disseminative spectroscope (EDS) (Thermo Electron Corporation, NORAN System SIX), a Raman spectrometer (Ar+ laser with ? = 514 nm, 33 mW power) and a field emission transmission electron microscope (FETEM) (FEI, TECHNAI F20).Electrochemical performance for these anodic materials was conducted in a typical coin cell (half cell). The cells were assembled in a CR2032 press. The complete cell assembly was carried out in an argon glovebox under extremely low levels of oxygen and humidity ( some(prenominal) undividedly <0. 1 ppm). A pure Li (purity, 99. 9%) metal foil (150 µm thickness) was used as two the lineament electrode and counter electrode, while the MWCNTs on 3D Cu involvement, the MWCNTs on 2D Cu foil and the a-Si/MWCNTs composite on 3D Cu web were used as the working electrodes.All the coin cells employed a solution 1. 0 M LiPF6 in EC-DEC (ethylene carbonate : diethyl carbonate, 1:1 in volume ratio) as the electrolyte and a typical polypropylene-polyethylene material (Celgard 3401) as the separator. The charge- deplete tests of the cells were performed in TOSCAT 3100U multichannel battery testing unit, at a continual temperature of 30°C, in galvanostatic (constant menses density) mode. The cells were rhythm method of birth controld in the potential drop range 3. 0 †0. 01 V, recording a current value in each 10 mV step, at a slow rate (0. C) during the initial formation process and at various C-rates in the following cycles. 3. Results and watchword 3. 1. Theoretical unhurriedness of the clear airfield of 3D Cu lock away The decide to introduce 3D Cu manoeuvre as current collector was to annex in emerge domain of a function for the growth of MWCNTs, thus leading to more amount of Li+ intake into them, as compared to 2D Cu foil. 3D Cu interlock was an interlaced structure of numerous Cu wires ( vermiform process A. class 1(a) and solve 1(b). ).Simple geometrical exemplar was followed to calculate the total surface area of this 3D structure, since the calculation of the actual surface area of the assembled 3D Cu operate was very difficult. For easier calculati on, the cylindrical Cu wires were simplify to rectangular wires of equivalent surface area, creating a cuboid array (Appendix A. discover 1(c). ). In this study, MWCNTs were synthesized on the teetotum and lateral surface areas of the 3D Cu appointment only, thusly only these areas were con sidered for calculation. aim 1(a) was a schematic moot of an anode plenty built up of 4 layers of MWCNTs on 3D Cu mesh.As a real example, we implemented an anode stack system using 9 individual MWCNTs on 3D Cu mesh, in which MWCNTs were coated over the entire area of the Cu meshes as illustrated in code 1(b). The assembled anodes were physically bonded by adhesion agitate between the involved MWCNTs. This phenomenon may be thought of as macrocosm in some way analogous to â€Å"velcro” effect of scales on wool fibers [26]. A simple geometrical relationship was established to calculate the total surface area of 3D Cu mesh and 2D Cu foil (no hole).Variation of the surface ratio of 3D Cu mesh to 2D Cu foil as a pop off of the thickness (T) and the size of holes (L) of 3D Cu mesh is presented in Figure 1(c) (The detail calculation procedure is shown in the Appendix A. ). Surface area diversity magnitude with the thickness of the structure, though its relation with hole size was not straight beforehand owing to contribution from a quick-frozen Cu wire diameter. It may be recalled here that the present study used a Cu mesh with its dimension 50 µm thickness and 65 µm hole size, which showed surface area improvement (almost 60%) as compared to 2D Cu foil.Empirically, the amount weight of MWCNTs on 3D Cu mesh was 4. 37 mg for a cell with 14 mm diameter and 50 µm thickness dimension, which represented solid loading increase by 400%. Thus, it was imbed that the theoretical calculation was inconsistent with the data-based results since it did not include the influence of aver parameters on the properties of MWCNTs such as their diameters, lengths and densities during the CVD growth. From an anode system assembled using 9 individual MWCNTs on 3D Cu mesh (The size of a cell is 15 mm diameter and 50 µm thickness. , the amount maximum loading amount and packing density of MWCNTs were higher than 50 mg and 0. 248 g/cm3, respectively. The weight of sonsy anodes proportionally increase with the number of individual one, which is in a good agreement with the calculation results. 3. 2. Morphology and structural properties of MWCNTs and a-Si/MWCNTs on 3D Cu mesh Unique 3D structure of the proposed anode is expected to influence the electrochemical performance. Structural characterization, involving SEM and Raman spectroscopic analysis, has been conducted on these 3D anodes (See Figure 2. . As presented in Figure 2(a), MWCNTs were homogeneously and densely grown over the whole top and lateral Cu mesh area. In addition, the high exaggeration SEM image showed the randomly entangled MWCNTs with their length approximately 30 µm and diameter in the range of 200 †300 nm (See Figure 2(b)). Compared to the 2D Cu foil, the surface areas of the Cu wires surrounding the hole spaces could be available sites for the MWCNT growth, which is structural reward of the 3D Cu mesh to increase the weight of the MWCNTs as active materials.In Figure 2(c), the sketch of the cross section bring in of MWCNTs grown on a whiz Cu wire exhibited the densely grown larger diameter MWCNTs on the top surface area and relatively little diameter MWCNTs on the lateral side area. Along with the structural characteristic, the interfacial concord between active material and current collector importantly influences the electrochemical performance of the anode system. It is highlighted that the soused bonding between MWCNTs and Cu making it affirmable to directly grow MWCNTs on Cu mainly originate in from TiC underlayer [16, 27].The TiC underlayer was formed by the reaction of Ti thin film sputter deposited onto 3D Cu mesh with carbo n trumpeter gas at high temperature about 750°C during CVD processing. High ratio of ID/IG ( somewhat 1) in Raman spectra (Figure 2(d)) of the MWCNT structure also developed high defacement density in the structure. It is inform that the MWCNTs containing more defects showed the better electrochemical performance since the higher straw man of defects provided with more available sites for Li+ ion intakes into the MWCNTs structure and shortened the public exposure length of Li+ ion [28-29].MWCNTs possessing more defects, generated by mechanical breakage and chemical etching, resulted in an increase in specific capacity compared to untreated MWCNTs. In the case of a-Si/MWCNTs hybrid structure, the broad intensity peak more or less 480 cm-1 (in Raman spectra) showed amorphous Si [30]. It was subsequently affirm from the EDS analysis in the linearly selected area across the SEM image as shown in discover 2(d) that Si was deposited on the some portion of the surface of the MW CNTs. The line profile denoting Si K distinguishably appeared, demonstrating the presence of a-Si deposited layer. . 3. Electrochemical performances of the MWCNTs based anode systems 3. 3. 1. Charge/ rout out capacities Electrochemical performance tests were conducted on these anode structures and the results were presented in Figure 3. First charge- dangle curves for all the anode systems were presented in Figure 3(a). The button cells were charged/dismissed in a galvanostatic mode between 0. 01 and 3 V, at C-rate of 0. 1 C (specific current 38 mAg-1) determined by theoretical specific capacity of graphite (372 mAhg-1).In the case of MWCNTs on 3D Cu mesh electrodes, several samples with different solid loading of MWCNTs were measured under the same condition and showed sightly chuck out capacity 474 mAhg-1, LiC4. 7. In Figure 3(a), all the bagging curves exhibited a plateau in the potentiality range 0. 75 †0. 9 V. such plateau was found in most graphite or CNT based anode s and cauline from the decomposition of electrolyte and the formation of solid electrolyte interphase (SEI) on the carbonaceous anode materials [3, 31].Based on the very identical first kindle curves of the MWCNTs and the a-Si/MWCNTs electrodes, it was implied that the MWCNTs mainly controlled the electrochemical properties in both anode structures since the major weight (above 99% weight ratio) of the structure came from the MWCNTs. However, the do of a-Si incorporation on the electrochemical performance were investigated by the first charge curves of the both anodes. The total specific charge capacities of the MWCNTs and the a-Si/MWCNTs electrodes were 299 mAhg-1 and 345 mAhg-1 (almost 16% improvement), respectively.In addition, the Coulombic efficiency of the a-Si/MWCNTs 67% was higher by around 4% than that of the MWCNTs 63%. The relatively higher irreversible capacity at the first charge-discharge cycle is considered a critical limitation of carbonaceous anode materials and the capacity qualifying may be mainly associated with solid electrolyte interphase (SEI) formation or a aeonian alloy formation [31]. Another possible reason involved the insertion of lithium ions into defect sites (e. g. microcavities) residing in the MWCNTs and their entangled structures [32].Li ions inserted into the defect regions at the first discharge process might be trapped and could not be completely extracted during the charge process. lithium oxide formation at higher voltage could also be another reason for the initial capacity loss [33]. However, Figure 3(a) showed that most Li insertion process proceeded mostly below 1. 5V (versus Li/Li+) so that the possibility of charge using up due to lithium oxide formation may be excluded, in the present case. It may be mentioned here that the higher determine from the a-Si/MWCNTs indicated the a-Si thin layer could play a role in maintaining the stability f SEI formation [17]. On the contrary, the first discharge curves of all the specimens of the MWCNTs on 2D Cu foil represented the ordinary specific discharge capacity 323 mAhg-1, LiC6. 9. The average capacity value was more than 3 multiplication lower than that of our previous result [16]. It was speculated that the significant difference was due to different morphology of MWCNTs (average diameter 80 nm, which was sheer than that of the current MWCNTs). At higher growth temperature, the size of the catalytic Ni islands became larger on account of their more facile diffusion [34].With respect to major electrochemically active sites being on and near the surface of MWCNTs [16], the thicker MWCNTs have less active surface area per mass available for participating in electrochemical reaction as compared to the thinner MWCNTs, thereby resulting in the lower specific capacity. During the initial cycle, the MWCNTs on 3D Cu mesh offered 47% higher average specific capacity compared to that of the MWCNTs on 2D Cu foil. It may be historied here that this sp ecific capacity sweetener is close to surface area sweetening 60% also.Compared to the MWCNTs on 3D Cu anodes, the a-Si deposited MWCNT anodes offered the higher average specific discharge capacity 517 mAhg-1, LiC4. 3. This enhancement could be cerebrate to the presence of a-Si thin layer with its high specific capacity on the MWCNTs. It was observe that the weight of the deposited a-Si was lower than 1% of that of the MWCNTs; therefore, the a-Si thin layer did not have any major contribution except subtle increase in the overall specific capacity of the anode, unlike the previous results from Si nanotubes [6] and Si nanowires [7]. . 3. 2. pass stability Cycling stability tests are essential to prove electrochemical performance of the anodes at long make pass operation in the real application. Figure 3(b) illustrates a comparison of the pass stabilities obtained from the three different kinds of anode systems up to 50 cycles at 1 C-rate (current density 372 mAg-1). In the cas e of the MWCNTs on 3D Cu mesh electrode, the reversible capacity meagrely increase from 226 mAhg-1 at first cycle to 258 mAhg-1 at 39th cycle and and thence gradually faded to 254 mAhg-1 until 50th cycles.Such a trend of increase in capacity over the whole cycles is inconsistent with previous results from the constant capacity of MWCNT [16-17]. It was speculated that the continuous charge-discharge process led to create more surface area on the densely entangled MWCNT network structure. We also investigated whether such an energizing process was due to more defects in the structures of MWCNTs induced by the charge-discharge process. According to the SEM images presented in Figure 4(a) and (b), it was not evident that consummate(a) defects or structural damages appeared in the both 150 cycled and just one discharged anode systems.HRTEM images revealed that for both the anode systems, the structural lawfulness of graphene layers still remained with the shallow amorphous second pha se region on the surround of the MWCNTs as shown in Figure 4(c) and (d). In addition, it was pointed out that there was no appreciable volume variation during lithiation and delithiation. No open evidence of diameter change was discover between the as-grown MWCNTs and the MWCNTs subjected to 150 charge-discharge cycles (Figure 2(b) and 4(a)). This observation is in agreement with small volume change of graphitic carbon upon lithium insertion and decline (typically LiC6, around 12%) [35].In the same manner, it was sustain that the specific capacity of the a-Si/MWCNTs on 3D Cu was gradually increased. Along with the electrochemical activation process of MWCNTs, the result could reveal the effect of capacity improvement with to boot incorporated a-Si to take more Li+ ion intakes (almost 10% enhancement of the reversible capacity). Furthermore, the Si-C bonding at the interface between a-Si and MWCNTs was strong enough to avoid peeling off of the a-Si layer during the cycling test. It was highlighted that MWCNTs and a-Si/MWCNTs grown on 3D Cu mesh showed good cycling stability without severe capacity degradation.However, for the MWCNTs on 2D Cu foil, the average reversible capacity 163 mAhg-1 was kept constant until the number of 50 cycles. It should be famed that the larger reversible capacity of the 3D MWCNTs was presumably due to their large surface area to accommodate more Li+ ion intercalation. In terms of the reversibility of charge-discharge process, the Coulombic efficiency of the MWCNTs on 3D Cu mesh was more than 98% after the initial 4 cycles at 1. 0 C-rate and then increased to 99% after 22 cycles tally to the result shown in Figure 3(c).Such reversibility was ascribed to the decent supply of Li+ ions from Li metal foil used as the reference electrode and counter electrode in the button cell. 3. 3. 3. array capability Rate capability tests are also crucial to prove electrochemical performance of the anodes at higher charge-discharge rate operat ion. Figure 3(d) showed the rate capability of the proposed anodes. The discharge capacity of the MWCNTs on 3D Cu mesh was almost constant around 300 mAhg-1 until reaching 1 C-rate (372 mAg-1) and then decreased to 283 mAhg-1 at 3 C-rate (1,116 mAg-1) and further to 250 mAhg-1 at 5 C-rate (1,860 mAg-1).It may be highlighted that discharge capacity dismissly increased with C-rate from 0. 1 C to 1 C and the phenomenon could be attributed to the electrochemical activation process of MWCNTs during cycling as mentioned above. At higher C-rates (e. g. 3 C and 5 C), Li+ ions were inserted and extracted into and from the only surface regions of the forest-like MWCNTs structure due to the limitation of diffusion length of Li+ ions. Another interesting observation was slight increase in specific capacity from 283 mAhg-1 at 1st cycle to 320 mAhg-1 at 22nd cycle at the same 0. 1 C (38 mAg-1) rate.It was again corroborate that higher number of cycles during C-rate tests could be a reason to ef fectively carry out electrochemical activation process in the MWCNT structures. On the contrary, the MWCNTs on 2D Cu foil electrode showed a typical staircase type decreasing capacity fashion till the tested limit of 5 C-rate. The direct comparison revealed the higher C-rate capability of the MWCNTs on 3D Cu mesh electrode, as compared to the MWCNTs on 2D Cu foil. In particular, at 5 C, the average specific discharge capacity of the MWCNTs on 3D Cu mesh was 249 mAhg-1 (14% increase), whereas that of the MWCNTs on 2D Cu foil was 218 mAhg-1.The result could be strongly associated with the higher surface area for Li+ ion intercalation due to approximately 4 time higher solid loading of MWCNTs on 3D Cu mesh. Furthermore, the higher C-rate capability is significantly attributed to the strong bonding and the lower electric resistance between Cu and MWCNTs, through TiC interface layer [36-37]. Moreover, at 5 C, the average capacity of the a-Si/MWCNTs on 3D Cu mesh electrode was 334 mAhg -1 (34% enhancement), while that of the MWCNTs on 3D Cu mesh was 249 mAhg-1. In addition, the average capacity ratios at 5 C/0. C of the MWCNTs on 3D Cu mesh and the MWCNTs on 2D Cu foil were 0. 86 and 0. 8, respectively, whereas the ratio of the a-Si/MWCNTs on 3D Cu mesh was around 0. 93. According to the better performances, it was proven that a-Si thin layer coating on MWCNTs could play an important role in the enhancement of C-rate capability. 4. Conclusion A novel 3D MWCNTs on Cu current collectors as an anode of LIB was developed. The 3D anodes showed higher specific capacity, cycling stability and C-rate efficiency as compared to those of the MWCNTs on 2D Cu foil anodes.The better performances of the 3D anodes were attributed to the higher average solid loading of MWCNTs, which was 4 times higher than that of the 2D anodes. Addition of the a-Si onto the 3D MWCNTs/Cu showed the further enhancement of electrochemical properties. Acknowledgment Authors thank N. Ricks and Y. Liu for Nano fabrication speediness and FESEM characterization, S. Saxena for allowing to use the Raman facility and J. Hwang and R. Banerjee for HRTEM characterization. It is grateful that J. Kim and D. Kim who provided us with the schematic diagrams.This research was, in part, back up by WCU (World Class University) program through the Korea Science and Engineering Foundation funded by the Ministry of Education, Science and Technology (R31-2008-000-10092) and AFOSR Grant (FA9550-09-1-0544). Appendix A. Supplementary data List of figure captions Figure 1. (a) A schematic mock up of an anode stack assembled using 4 total of converted uniform stacking cuboid arrays from the geometry of a real 3D Cu mesh (The bottom right gusset shows a unit cell of the cuboid arrays. , (b) SEM images exhibiting a cross-section perpendicular to the anode system stacked by 9 individual MWCNTs on 3D Cu mesh and extremely entangled structures of MWCNTs, (c) The surface area and its increment of the 3D C u mesh and the 2D Cu foil and the average real weight of MWCNTs as a function of different thickness and hole sizes (The inset illustrates a unit cell of the 3D Cu mesh with its dimension. ). Figure 2. Morphology and structure of the proposed anode systems. a) A plane glance of SEM image showing the MWCNTs covered on the 3D Cu mesh, (b) The threadlike let on structures of MWCNTs on the 3D Cu mesh with their diameter in the range of 200 †300 nm, (c) Schematic diagram (not to scale) of the geometry of the MWCNTs grown on the 3D Cu mesh and the a-Si deposited MWCNTs structure on the 3D Cu mesh, (d) EDS elemental analysis of the a-Si/MWCNTs hybrid structure in the linearly selected area across the SEM image, (e) Raman spectroscopic response indicating high defect density of MWCNTs according to ID/IG ratio around 1 and the amorphous Si peak at around 480 cm-1 in the a-Si/MWCNTs. Figure 3.Electrochemical performance of the anode structures of as-grown MWCNTs on 3D Cu mesh, MWCNTs o n 2D Cu foil and a-Si/MWCNTs core-shell composite on 3D Cu mesh. 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