Silica-assisted bottom-up synthesis of graphene-like high surface area carbon for highly efficient ultracapacitor and Li-ion hybrid capacitor applications

Mhamane, D.,Aravindan, V.,Kim, M. S.,Kim, H. K.,Roh, K.,Ruan, D.,Lee, S.,Srinivasan, M.,Kim, K. B. Royal Society of Chemistry 2016 Journal of Materials Chemistry A Vol.4 No.15

<P>We report a facile bottom-up approach for the synthesis of pure and macro-sized (> 500 nm) graphene-like carbon by precisely employing sp(2) carbon rich 1,2,4,5-benzene tetracarboxylic acid (BTCA) as a precursor. We also addressed the features, such as high specific surface area (SSA) and sp(2) hybridized carbon content, of the BTCA-derived carbon (BTCADC) over conventional top-down processed reduced graphene oxide (RGO). For instance, a two fold enhancement in SSA (960 m(2) g(-1)) and C : O atomic ratio (similar to 19) was noted for BTCADC when compared to RGO (SSA: 402 m(2) g(-1) and C : O ratio similar to 10). The SSA of BTCADC was further extended to 2673 m(2) g(-1) via a chemical activation process (A-BTCADC) along with a high pore volume (2.15 cm(3) g(-1)). Furthermore, we attempted to explain the unsolved issue of carbon layer stacking (pi-pi stacking) in RGO by precisely adopting a bottom-up approach. From an application point of view, we explored the possibility of using such carbonaceous materials as promising electrodes for both symmetric and Li-ion hybrid supercapacitor configurations in an organic medium. The A-BTCADC based symmetric cell in a 1 M tetraethylammonium tetrafluoroborate (TEA.BF4) in acetonitrile (ACN) electrolyte displayed a specific capacitance (C-sp) of 225 F g(-1) (at 0.5 A g(-1)) with a stable cycling profile of up to 10 000 cycles (at 10 A g(-1)) between 0 and 3 V. This bottom-up approach opens new avenues to extend graphene-based science and technology to the next level.</P>

Ultrathin Polyimide Coating for a Spinel LiNi_0.5Mn_1.5O₄ Cathode and Its Superior Lithium Storage Properties under Elevated Temperature Conditions

Kim, M. C.,Kim, S. H.,Aravindan, V.,Kim, W. S.,Lee, S. Y.,Lee, Y. S. The Electrochemical Society 2013 Journal of the Electrochemical Society Vol.160 No.8

<P>In this study, we present the influence of polyimide (PI) coating concentration on the electrochemical properties of high voltage, spinel phase LiNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB> cathodes, particularly under elevated temperature conditions. First, the adipic acid-mediated sol-gel technique was employed to synthesize sub-micron sized LiNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB> particles, where Mn was in the 4+ state. Thermal polymerization was used to produce the PI coating from polyamic acid. The presence of the PI layer was confirmed by transmission electron microscopy and Fourier-transform infrared analyzes. All test cells delivered good cycleability under ambient temperature conditions, irrespective of the PI coating concentration, with a prominent plateau at 4.7 V vs. Li, whereas all test cells experienced the poorest electrochemical behavior under elevated temperature conditions except 0.3 wt.% PI. The 0.3 wt.% PI coated LiNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB> phase delivered excellent cycleability with capacity retention of > 90% at 55°C. Poor compatibility and severe reactivity toward the electrolyte solution resulted in the poorest performance which was clearly evidenced by the scanning electron microscopy analysis and supported well by impedance studies after galvanostatic cycling.</P>

Realizing the Performance of LiCoPO₄Cathodes by Fe Substitution with Off-Stoichiometry

Yang, S. M. G.,Aravindan, V.,Cho, W. I.,Chang, D. R.,Kim, H. S.,Lee, Y. S. The Electrochemical Society 2012 Journal of the Electrochemical Society Vol.159 No.7

Prediction of flexural behaviour of RC beams strengthened with ultra high performance fiber reinforced concrete

Ramachandra Murthy A,M. Aravindan,P. Ganesh 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.3

This paper predicts the flexural behaviour of reinforced concrete (RC) beams strengthened with a precast strip of ultra-high performance fiber-reinforced concrete (UHPFRC). In the first phase, ultimate load capacity of preloaded and strengthened RC beams by UHPFRC was predicted by using various analytical models available in the literature. RC beams were preloaded under static loading approximately to 70%, 80% and 90% of ultimate load of control beams. The models such as modified Kaar and sectional analysis predicted the ultimate load in close agreement to the corresponding experimental observations. In the second phase, the famous fatigue life models such as Papakonstantinou model and Ferrier model were employed to predict the number of cycles to failure and the corresponding deflection. The models were used to predict the life of the (i) strengthened RC beams after subjecting them to different pre-loadings (70%, 80% and 90% of ultimate load) under static loading and (ii) strengthened RC beams after subjecting them to different preloading cycles under fatigue loading. In both the cases precast UHPFRC strip of 10 mm thickness is attached on the tension face. It is found that both the models predicted the number of cycles to failure and the corresponding deflection very close to the experimental values. It can be concluded that the models are found to be robust and reliable for cement based strengthening systems also. Further, the Wang model which is based on Palmgren-Miner’s rule is employed to predict the no. of cycles to failure and it is found that the predicted values are in very good agreement with the corresponding experimental observations.

Prediction of flexural behaviour of RC beams strengthened with ultra high performance fiber reinforced concrete

Murthy A, Ramachandra,Aravindan, M.,Ganesh, P. Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.3

This paper predicts the flexural behaviour of reinforced concrete (RC) beams strengthened with a precast strip of ultra-high performance fiber-reinforced concrete (UHPFRC). In the first phase, ultimate load capacity of preloaded and strengthened RC beams by UHPFRC was predicted by using various analytical models available in the literature. RC beams were preloaded under static loading approximately to 70%, 80% and 90% of ultimate load of control beams. The models such as modified Kaar and sectional analysis predicted the ultimate load in close agreement to the corresponding experimental observations. In the second phase, the famous fatigue life models such as Papakonstantinou model and Ferrier model were employed to predict the number of cycles to failure and the corresponding deflection. The models were used to predict the life of the (i) strengthened RC beams after subjecting them to different pre-loadings (70%, 80% and 90% of ultimate load) under static loading and (ii) strengthened RC beams after subjecting them to different preloading cycles under fatigue loading. In both the cases precast UHPFRC strip of 10 mm thickness is attached on the tension face. It is found that both the models predicted the number of cycles to failure and the corresponding deflection very close to the experimental values. It can be concluded that the models are found to be robust and reliable for cement based strengthening systems also. Further, the Wang model which is based on Palmgren-Miner's rule is employed to predict the no. of cycles to failure and it is found that the predicted values are in very good agreement with the corresponding experimental observations.

Synthesis and optimization of NASICON-type Li3V2(PO4)3 by adipic acid-mediated solid-state approach

Son, J. N.,Kim, S. H.,Kim, M. C.,Kim, K. J.,Aravindan, V.,Cho, W. I.,Lee, Y. S. Springer-Verlag 2013 Journal of applied electrochemistry Vol.43 No.6

TiO₂-reduced graphene oxide nanocomposites by microwave-assisted forced hydrolysis as excellent insertion anode for Li-ion battery and capacitor

Kim, H.K.,Mhamane, D.,Kim, M.S.,Roh, H.K.,Aravindan, V.,Madhavi, S.,Roh, K.C.,Kim, K.B. Elsevier Sequoia 2016 Journal of Power Sources Vol.327 No.-

TiO<SUB>2</SUB>-reduced graphene oxide (rGO) nanocomposite (TiO<SUB>2</SUB>-rGO) is fabricated by microwave-assisted forced hydrolysis and examined as prospective electrode for energy storage applications, especially in Li-ion battery (LIB) and Li-ion capacitor (LIC). First, the uniformly distributed nanoscopic TiO<SUB>2</SUB> particulates (~3 nm) over rGO nanosheets is evaluated as anode in half-cell assembly to ascertain the Li-insertion behavior and found that ~0.68 mol Li (~227 mAh g<SUP>-1</SUP>) is reversible. Then, ''rocking-chair'' type LIB is fabricated with spinel LiMn<SUB>2</SUB>O<SUB>4</SUB> cathode, and the LiMn<SUB>2</SUB>O<SUB>4</SUB>/TiO<SUB>2</SUB>-rGO assembly exhibits high capacity (~120 mAh g<SUP>-1</SUP> at 0.1 C rate), good rate capability (~53 mAh g<SUP>-1</SUP> at 1 C rate), and excellent cycleability (~90% initial reversible capacity after 1000 cycle) as well. Similarly, the LIC is also constructed with activated carbon cathode, and such configuration delivered a maximum energy density of ~50 Wh kg<SUP>-1</SUP> with ~82% retention after 4000 cycles. The synergistic effect of both rGO and anatase nanoparticles provides excellent energy efficiency and battery performance in different kind of Li-ion based energy storage devices.

LiFePO₄ modified Li_1.02(Co_0.9Fe_0.1)_0.98PO₄ cathodes with improved lithium storage properties

Jang, I. C.,Son, C. G.,Yang, S. M. G.,Lee, J. W.,Cho, A. R.,Aravindan, V.,Park, G. J.,Kang, K. S.,Kim, W. S.,Cho, W. I.,Lee, Y. S. Royal Society of Chemistry 2011 Journal of materials chemistry Vol.21 No.18

<P>LiCoPO<SUB>4</SUB> and Li<SUB>1.02</SUB>(Co<SUB>0.9</SUB>Fe<SUB>0.1</SUB>)<SUB>0.98</SUB>PO<SUB>4</SUB> were prepared by conventional solid state reactions. The surface modification of Li<SUB>1.02</SUB>(Co<SUB>0.9</SUB>Fe<SUB>0.1</SUB>)<SUB>0.98</SUB>PO<SUB>4</SUB> particulates by LiFePO<SUB>4</SUB> was successfully carried out by a dry coating procedure. TEM analysis confirmed the presence of a LiFePO<SUB>4</SUB> coating layer of about 20 nm on the surface of the Li<SUB>1.02</SUB>(Co<SUB>0.9</SUB>Fe<SUB>0.1</SUB>)<SUB>0.98</SUB>PO<SUB>4</SUB> particles. All three cells delivered high initial discharge capacities of 122, 130 and 128 mA h g<SUP>−1</SUP> for LiCoPO<SUB>4</SUB>, Li<SUB>1.02</SUB>(Co<SUB>0.9</SUB>Fe<SUB>0.1</SUB>)<SUB>0.98</SUB>PO<SUB>4</SUB>, and LiFePO<SUB>4</SUB> modified Li<SUB>1.02</SUB>(Co<SUB>0.9</SUB>Fe<SUB>0.1</SUB>)<SUB>0.98</SUB>PO<SUB>4</SUB>, respectively. However, these cells presented quite different cycle retention rates after 20 cycles, 21, 22 and 70% for LiCoPO<SUB>4</SUB>, Li<SUB>1.02</SUB>(Co<SUB>0.9</SUB>Fe<SUB>0.1</SUB>)<SUB>0.98</SUB>PO<SUB>4</SUB>, and LiFePO<SUB>4</SUB> modified Li<SUB>1.02</SUB>(Co<SUB>0.9</SUB>Fe<SUB>0.1</SUB>)<SUB>0.98</SUB>PO<SUB>4</SUB>, respectively. The improved cycle retention of the LiFePO<SUB>4</SUB>-modified Li<SUB>1.02</SUB>(Co<SUB>0.9</SUB>Fe<SUB>0.1</SUB>)<SUB>0.98</SUB>PO<SUB>4</SUB> resulted from its reduced reactivity towards the electrolyte and the effective prevention of resistive layer formation on the LiCoPO<SUB>4</SUB> surface during high voltage cycling.</P> <P>Graphic Abstract</P><P>LiFePO<SUB>4</SUB> modified Li<SUB>1.02</SUB>(Co<SUB>0.9</SUB>Fe<SUB>0.1</SUB>)<SUB>0.98</SUB>PO<SUB>4</SUB> cathodes resulted in improved cyclability, which is due to reduced reactivity towards electrolytes. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1jm10574d'> </P>