Orderly meso-perforated spherical and apple-shaped 3D carbon microstructures for high-energy supercapacitors and high-capacity Li-ion battery anodes

Mhamane, Dattakumar,Kim, Myeong-Seong,Park, Byung-Hoon,Choi, Hun-Seok,Kim, Young Hwan,Aravindan, Vanchiappan,Phadkule, Ajitkumar,Kim, Kwang-Bum The Royal Society of Chemistry 2018 Journal of materials chemistry. A, Materials for e Vol.6 No.15

<P>The Stöber synthesis, which is composed of two steps of the formation of RF resin spheres in presence of an NH3catalyst and the carbonization of RF resin spheres under an inert atmosphere, is a well-known approach to the preparation of carbon spheres (CSs). We herein modified the first step of the Stöber procedure to introduce morphological and physicochemical changes to CSs. Two different fully perforated 3D carbon-based micromaterials were prepared, namely spherical meso-perforated carbon (SSMPC) and apple-shaped meso-perforated carbon (ASMPC). In the preparation of these materials, we adopted colloidal silica-mediated spray drying method followed by carbonization and silica removal. High specific surface areas and pore volumes were achieved for both ASMPC (1141 m<SUP>2</SUP>g<SUP>−1</SUP>and 3.2 cm<SUP>3</SUP>g<SUP>−1</SUP>) and SSMPC (1050 m<SUP>2</SUP>g<SUP>−1</SUP>and 2.1 cm<SUP>3</SUP>g<SUP>−1</SUP>). We then evaluated the charge storage properties in organic media from supercapacitor (SC) as well as Li-ion battery (LIB) perspectives. An ASMPC-based symmetric SC was capable of delivering a specific capacitance and energy density of 260 F g<SUP>−1</SUP>and 75.56 W h kg<SUP>−1</SUP>, respectively, in addition to an excellent cyclability of 30 000 cycles. In the LIB, ASMPC exhibited a maximum capacity of 1698 mA h g<SUP>−1</SUP>after 175 cycles at 200 mA g<SUP>−1</SUP>. We systematically elaborated that inaccessible interior sites of the 3D CSs could become accessible through the introduction of meso-perforations on the periphery and in the interior. We expected that the 3D shape and meso-perforations were responsible for the exceptional performance of CSs in SCs and LIBs.</P>

Rusted iron wire waste into high performance anode (α-Fe₂O₃) for Li-ion batteries: an efficient waste management approach

Mhamane, Dattakumar,Kim, Hyun-Kyung,Aravindan, Vanchiappan,Roh, Kwang Chul,Srinivasan, Madhavi,Kim, Kwang-Bum The Royal Society of Chemistry 2016 GREEN CHEMISTRY Vol.18 No.5

<P>Superior Li-storage properties are reported for interconnected alpha-Fe2O3 derived from iron based wires collected from waste i.e. building supplies or scrap. An interconnected morphology is acquired without the addition of any surfactant or shape controlling agent. We also explore the possibility of employing such a material as a potential low cost conversion type anode for the fabrication of Li-ion cells with a LiMn2O4 cathode. Remarkably, alpha-Fe2O3 displayed a capacity of similar to 1119 mA h g(-1) at a current density of 0.05 A g(-1) in a half-cell configuration. Good cyclability is also noted, for example alpha-Fe2O3 delivered similar to 800 mA h g(-1) after 215 cycles at a current density of 0.2 A g(-1). The irreversible capacity loss of the alpha-Fe2O3 anode has been effectively circumvented by an electrochemical pre-lithiation process and the anode is eventually paired with the eco-friendly cathode, LiMn2O4. The full-cell, LiMn2O4/alpha-Fe2O3 delivered the initial reversible capacity of similar to 737 mA h g(-1) with similar to 78% retention after 40 cycles. This efficient waste management system with a gram scale synthesis procedure for alpha-Fe2O3 nanoparticles indeed paved the way for developing high performance Li-ion power packs for high energy requirements.</P>

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>

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.

Synthesis of LiFePO4/graphene microspheres while avoiding restacking of graphene sheet’s for high-rate lithium-ion batteries

김명성,이건우,이석우,정준희,Dattakumar Mhamane,노광철,김광범 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.52 No.-

LiFePO4/graphene microspheres are synthesized while avoiding the restacking of graphene sheets using aspray-drying process and a subsequent heat treatment. To determine an optimal condition for preventingthe restacking of graphene sheets in the composites, we control the weight ratio of LiFePO4 to rGO. Whenthe amount of rGO in the composite exceeds a specific amount, the rGO sheets are spontaneouslyrestacked. The restacked rGO sheets impede the Li ion movement, which is leading to the deterioration ofthe electrochemical performance at high C-rates. The microspheres synthesized exhibit a high specificcapacity, excellent rate capability, and good cycling stability.

Bulk metal-derived metal oxide nanoparticles on oxidized carbon surface

Kim, Hyun-Kyung,Aravindan, Vanchiappan,Mhamane, Dattakumar,Yoon, Seung-Beom,Park, Sang-Hoon,Nazarian-Samani, Masoud,Han, Joong Tark,Park, Ho Seok,Roh, Kwang Chul,Kim, Kwang-Bum Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.752 No.-

<P><B>Abstract</B></P> <P>Nano-sized metal oxides have gained widespread interest because of their multifarious applications in catalysis, energy storage, semiconductors, and nanomedicine. Though many viable solution-based techniques for the preparation of nanoparticles (NPs) have been reported, meeting efficiency and scalability requirements remains challenging. Here, we demonstrate the generalized and facile method to yield metal oxide NPs that exploit bulk metal particulates. Based on a galvanic reaction, the interface between bulk metal powder and oxidized carbonaceous material transforms metals in to oxide/hydroxide NPs on the carbonaceous surface, owing to the resulting potential difference. This preparation procedure uses a solution-based synthesis technique, which is relatively straightforward, eco-friendly, scalable, inexpensive, and can be easily executed for a variety of metals; for instance, we demonstrated this approach for Zn, Ni, Co, Sn and Cu.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A simple method for producing metal oxide nanoparticle composites is described. </LI> <LI> Readily available bulk metals were converted to metal oxide nanoparticle composites. </LI> <LI> The resulting composites were tested as electrode materials in supercapacitors. </LI> <LI> This method can be used for a variety of metals. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Synthesis of LiFePO₄/graphene microspheres while avoiding restacking of graphene sheet’s for high-rate lithium-ion batteries

Kim, Myeong-Seong,Lee, Geon-Woo,Lee, Suk-Woo,Jeong, Jun Hui,Mhamane, Dattakumar,Roh, Kwang Chul,Kim, Kwang-Bum Elsevier 2017 Journal of industrial and engineering chemistry Vol.52 No.-

<P><B>Abstract</B></P> <P>LiFePO<SUB>4</SUB>/graphene microspheres are synthesized while avoiding the restacking of graphene sheets using a spray-drying process and a subsequent heat treatment. To determine an optimal condition for preventing the restacking of graphene sheets in the composites, we control the weight ratio of LiFePO<SUB>4</SUB> to rGO. When the amount of rGO in the composite exceeds a specific amount, the rGO sheets are spontaneously restacked. The restacked rGO sheets impede the Li ion movement, which is leading to the deterioration of the electrochemical performance at high C-rates. The microspheres synthesized exhibit a high specific capacity, excellent rate capability, and good cycling stability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> LFP/graphene composite was synthesized while avoiding graphene sheets restacking. </LI> <LI> Degree of graphene sheets restacking affected the rate capability of the composites. </LI> <LI> Restacked graphene sheets blocked Li ion movement in the electrode. </LI> <LI> LFP/graphene composite exhibited improved rate capability and cyclability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>To fully exploit the properties of graphene as an electrode material for energy storage devices, it is important to prevent the restacking of graphene sheets. In this study, three-dimensional (3D) micro-spherical LiFePO<SUB>4</SUB>/graphene composites were synthesized while avoiding the restacking of graphene sheets using a scalable, facile, and simple spray-drying process and a subsequent heat treatment. In this system, the LiFePO<SUB>4</SUB> nanoparticles acted not only as the active material but also as the spacer between the graphene sheets. To determine an optimal condition for preventing the restacking of graphene sheets in the composites, we controlled the weight ratio of LiFePO<SUB>4</SUB> to graphene. During this process, the degree of restacking of graphene sheets in the composites had a significant effect on their morphology and electrochemical properties. The 3D LiFePO<SUB>4</SUB>/graphene microspheres were micrometer-sized spherical assemblies with 100nm-sized LiFePO<SUB>4</SUB> nanoparticles and graphene sheets. The microspheres exhibited a high specific capacity of 163mAhg<SUP>−1</SUP> at 0.1 C-rate, excellent rate capability (65% of the initial discharge capacity (0.1 C-rate) at 30 C-rate), and good cycling stability (81.6% capacity retention after 1000 cycles).</P> <P>[DISPLAY OMISSION]</P>