3-Dimensional Carbon Nanotube for Li-Ion Battery Anode

3 Dimensional coulomb Nanotube for Li-Ion Battery Anode (Journal of Power Sources 219 (2012) 364-370) Chiwon Kang1, Indranil Lahiri1, Ran accelerator pedalamy Baskaran2, Won-Gi Kim2, Yang-Kook Sun2, Wonbong Choi1, 3* Nanomaterials and wind Laboratory, Department of Mechanical and Materials Engineering, Florida International University 10555 West Flagler Street, Miami, FL 33174, USA 2Department of Energy Engineering, Hanyang University 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea 3Department of Materials Science and Engineering, University of northern Texas North Texas Discovery Park 3940 North Elm St. Suite E-132, Denton, TX 76207, USACorresponding Author *Email emailprotected edu Author Contributions These authors contributed equally. Abstract Carbon nanotubes, in different forms and architectures, extradite demonstrated good promise as electrode material for Li-ion batteries, owing to large start area, victimizeer Li-conduction distance and high galvanic conductivit y. However, practical cover of such(prenominal) Li-ion batteries demands high volumetric cognitive content, which is otherwisewise miserable for to the highest degree nanomaterials, use as electrodes.In order to address this urgent issue, we scram developed a novel 3-dimensional (3D) anode, found on multiwall snow nanotubes (MWCNTs), for Li-ion batteries. The grotesque 3D design of the electrode al first geared much higher real loading of quick anode material, MWCNTs in this case and resulted in more amount of Li+ ion aspiration in comparison to those of conventional 2D Cu current collector. though one such 3D anode was demonstrated to offer 50% higher expertness, compared to its 2D counterpart, its ability to deliver much higher capacity, by geometric modification, is presented.Furthermore, deposition of amorphous Si (a-Si) layer on the 3D electrode (a-Si/MWCNTs crossbred structure) offered enhancement in electrochemical response. Correlation between electrochemical performances and geomorphologic properties of the 3D anodes highlights the possible charge transfer mechanism. Graphical abstract Keywords Li-ion batteries, cytosine nanotubes, 3D Cu current collector, anode materials, amorphous Si, a-Si/MWCNTs composite 1. IntroductionLi-ion batteries (LIB) has been widely used as one of the most important capacity storage devices in diverse applications such as green electric vehicles (EV), portable electronics and procedure tools, since it is commercialized by Sony in 1991 1. The commercial cell is assembled by carboniferous anode, separator and a Li containing layered structure cathode (e. g. LiCoO2). In call of carbonaceous anodes, graphite and soft or poorly ordered carbons (e. g. mesocarbon microbeads or spherical graphite, microcarbon fiber) have been employed.The reasons behind their commercial prominence contain the comparatively low cost of carbon, the excellent mechanical sustainability for lithium insertion and desertion (having minimum volume change ) and their formation of a protective surface hire with many electrolytes 2-4. Nevertheless, fully intercalated highly crystalline graphites have relatively lower specific capacity (372 mAhg-1, the stoichiometric formulae of LiC6) and cannot meet the demands of next genesis LIB with respect to high specific capacity and volumetric capacity. To address these issues, other elemental compounds have been explored such as Al, Si, Ge and Sn 5.Among those elements, Si is known to have highest theoretical specific capacity (4,200 mAhg-1), however abundant volume expansion/contraction (300400%) during lithiation/delithiation brings about pulverization, resulting in capacity fading in a high number of cycles. To overcome such inherit limitations of bulk electrode materials, worldwide research groups have intensively focus on novel and suitable nanomaterials such as ti nanotubes 6, silicon nanowires 7, nano sized transitional metal oxides 8-10, graphene 11 and carb on nanotubes 12-14. Out of the many nanomaterials available, carbon nanotubes (CNTs) have attracted great attention for anode materials due to their high surface area, short diffusion length of Li+ ions and high electrical conductivity 15. noncurrent researches including from our group have demonstrated outstanding performance of MWCNT based binder-free anodes in equipment casualty of high specific capacity, excellent rate capability and exceedingly or nil capacity degradation during long cycle mental process 16-17.However, carbon nano materials are known as low-density materials, which results in low volumetric capacity and low volumetric energy/power density. indeed higher solid loading of MWCNTs as active materials is one of the most significant issues to be take a leakd in practice. Very recently, it argued that nanotube based active materials have a critical shortcoming in terms of their very low weight per unit electrode area 18.Thus, their gravimetric energy density may not give a realistic sketch to commercial application. The critical limitation may lead to scale-up issues for their potential application in the development of EV. To counter this issue, we propose a new geometry of 3D Cu current collectors, which can play a crucial role in creating higher surface area to accommodate more solid loading of MWCNTs on the uniformly arrayed patterns in the 3D structure, leadership to higher specific capacity and C-rate capability.Until now, efforts have been dedicated to employ a number of 3D structured current collectors including carbon papers 19, a self-assembled 3D bicontinuous nanoarchitecture 20, aluminum nanorods 21, and nanoporous nickel 22. The previous research proved 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 note and MnO2 cathodes) but also their efficient ion a nd electron transport 20.In addition, ALD coated TiO2 anodes on 3D aluminum nanorod current collectors showed the 10 times increase in their theoretical area and total capacity (0. 0112 mAhcm-2), compared to those resulted from the same anodes on 2D flat aluminum plate 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, the diverse types of cross anode structures have been designed and synthesized in order to expect the synergetic combination of 2 different types of nanomaterials for the igher electrochemical performances. As one of the most preferable combinations, MWCNTs/Si hybridization structure can be chosen due to the expose mechanical accommodation of MWCNTs of the large volume expansion/constriction of Si during lithiation/delithiation process and the higher bonding expertness between MWCNTs and Si. There were close to selected reports on MWCNTs/Si composite structures, employi ng either SiH4 CVD method 23 or spatter deposition 24. In this study, we present a novel concept 3D anode organisation, comprising of MWCNTs instantly grown on 3D Cu mesh victimisation catalytic thermal CVD method 25.Electrochemical performances of this 3D anode structure are compared with those of MWCNTs directly grown on 2D Cu foil. Furthermore, enhanced electrochemical properties of a-Si/MWCNTs hybrid structure, synthesized on 3D Cu mesh using a 2 step process 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 saucerussed. 2. Experimental A Cu mesh (TWP Inc. with average dimensions of 50 m thickness and 65 m hole size was prepared. In parallel, a 50 m thick pure Cu foil (Nimrod Hall Copper, 99. 9% purity) was also employed. Both types of samples were used as substrates for depositing Ti (underlayer)/Ni (catalyst) thin film through a RF and DC magnetron sputtering system. These Ti/Ni thin film deposited samples were cut to 14 mm diameter disc shape for 2032 button cell assembly, before inserting into a thermal CVD system for direct MWCNT growth.During CVD, samples were heated very rapidly, under an inert Ar gas environment, to the growth temperature of 750C, and MWCNT growth began with flow of a mixture of ethylene (C2H4) and enthalpy (H2) gas (12 volume ratio) in the chamber. After 50 proceedings of growth, the samples were cooled to room temperature within the furnace under an Ar gas envelope. Amorphous Si (a-Si) was deposited further on the as-grown MWCNT samples using the sputtering system with the incorporation of Ti adhesion layer in order to enhance bonding strength between a-Si and MWCNTs.Weights of samples were measured before and after CVD growth to exactly attain weights of the active materials (i. e. MWCNTs and a-Si thin layer). Morphology and structural properties of the prepared anode structures were c arefully investigated using field emission scanning electron microscopes (FESEM) (JEOL, JSM-7000F), an energy dispersive prism 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 tell apart cell assembly was carried out in an argon glovebox under exceedingly low levels of oxygen and humidity (both individually