In-situ synthesis of vanadium pentoxide nanofibre/exfoliated graphene nanohybrid and its supercapacitor applications

Choudhury, Arup,Bonso, Jeliza S.,Wunch, Melissa,Yang, Kap Seung,Ferraris, John P.,Yang, Duck J. Elsevier 2015 Journal of Power Sources Vol.287 No.-

<P><B>Abstract</B></P> <P>A novel nanohybrid material composed of vanadium pentoxide nanofibres (VNFs) and exfoliated graphene were prepared by <I>in-situ</I> growth of VNFs onto graphene nanosheets, and explicated as electrode material for supercapacitor applications. The existence of non-covalent interactions between VNFs and graphene surfaces was confirmed by Raman and Fourier transform infrared (FTIR) spectroscopes. Morphological analysis of the nanohybrid revealed that the VNF layer uniformly grown on the graphene surfaces, producing high specific surface area and good electronic or ionic conducing path. High crystalline structure with small d-spacing of the VNFs on graphene was observed in X-ray diffraction (XRD) analysis. Compared to pristine VNF, the VNF/graphene nanohybrid exhibited higher specific capacitance of 218 F g<SUP>−1</SUP> at current density of 1 A g<SUP>−1</SUP>, higher energy density of 22 Wh kg<SUP>−1</SUP> and power density of 3594 W kg<SUP>−1</SUP>. Asymmetric supercapacitor devices were prepared using the Spectracarb 2225 activated carbon cloth and VNF/graphene nanohybrid as positive and negative electrode, respectively. The asymmetric device exhibited capacitance of 279 F g<SUP>−1</SUP> at 1 A g<SUP>−1</SUP>, energy density of 37.2 Wh kg<SUP>−1</SUP> and power density of 3743 W kg<SUP>−1</SUP>, which are comparable and or superior to reported asymmetric devices consisting of carbon material and metal oxide as electrode components.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Preparation of novel nanohybrid by <I>in-situ</I> growth of V<SUB>2</SUB>O<SUB>5</SUB> nanofibres on graphene. </LI> <LI> Electrochemical characterizations of the nanohybrid for supercapacitor application. </LI> <LI> Maximum capacitance observed for asymmetric devices. </LI> <LI> Energy density of asymmetric devices was 69% higher than that of symmetric device. </LI> </UL> </P>

Electrochemical energy storage performance of carbon nanofiber electrodes derived from 6FDA-durene

Jung, Kyung-Hye,Panapitiya, Nimanka,Ferraris, John P IOP 2018 Nanotechnology Vol.29 No.27

<P>Carbon nanofibers (CNFs) are promising electrode materials for electrochemical double layer capacitors due to their high porosity and electrical conductivity. CNFs were prepared by electrospinning and subsequent thermal treatment of a new precursor polymer, 6FDA-durene, without the addition of pore generating agents. The conversion of precursor nanofibers into CNFs was confirmed using Raman spectroscopy. CNFs were activated and annealed, and nitrogen adsorption/desorption measurements were conducted to determine surface area and porosity. These activated/annealed CNFs were used as binderless electrodes in coin cells with an ionic liquid electrolyte. The devices displayed a specific capacitance of 128 F g<SUP>−1</SUP>, an energy density of 63.4 Wh kg<SUP>−1</SUP> (at 1 A g<SUP>−1</SUP>), and a power density of 11.0 KW kg<SUP>−1</SUP> (at 7 A g<SUP>−1</SUP>).</P>

Preparation of porous carbon nanofibers derived from PBI/PLLA for supercapacitor electrodes

Jung, Kyung-Hye,Ferraris, John P IOP 2016 Nanotechnology Vol.27 No.42

<P>Porous carbon nanofibers were prepared by electrospinning blend solutions of polybenzimidazole/poly-L-lactic acid (PBI/PLLA) and carbonization. During thermal treatment, PLLA was decomposed, resulting in the creation of pores in the carbon nanofibers. From SEM images, it is shown that carbon nanofibers had diameters in the range of 100–200 nm. The conversion of PBI to carbon was confirmed by Raman spectroscopy, and the surface area and pore volume of carbon nanofibers were determined using nitrogen adsorption/desorption analyses. To investigate electrochemical performances, coin-type cells were assembled using free-standing carbon nanofiber electrodes and ionic liquid electrolyte. cyclic voltammetry studies show that the PBI/PLLA-derived porous carbon nanofiber electrodes have higher capacitance due to lower electrochemical impedance compared to carbon nanofiber electrode from PBI only. These porous carbon nanofibers were activated using ammonia for further porosity improvement and annealed to remove the surface functional groups to better match the polarity of electrode and electrolyte. Ragone plots, correlating energy density with power density calculated from galvanostatic charge–discharge curves, reveal that activation/annealing further improves energy and power densities.</P>

Kinetic Stability of Bulk LiNiO₂ and Surface Degradation by Oxygen Evolution in LiNiO₂ -Based Cathode Materials

Kong, Fantai,Liang, Chaoping,Wang, Luhua,Zheng, Yongping,Perananthan, Sahila,Longo, Roberto C.,Ferraris, John P.,Kim, Moon,Cho, Kyeongjae Wiley (John WileySons) 2019 ADVANCED ENERGY MATERIALS Vol.9 No.2

Fabrication of carbon nanofiber electrodes using poly(acrylonitrile‑co‑vinylimidazole) and their energy storage performance

정경혜,김소정,손예지,John P. Ferraris 한국탄소학회 2019 Carbon Letters Vol.29 No.2

For electrodes in electrochemical double-layer capacitors, carbon nanofibers (CNFs) were prepared by thermal treatment of precursor polymer nanofibers, fabricated by electrospinning. Poly(acrylonitrile-co-vinylimidazole) (PAV) was employed as a precursor polymer of carbon nanofibers due to the effective cyclization of PAV polymer chains during thermal treatment compared to a typical precursor, polyacrylonitrile (PAN). PAV solutions with different comonomer compositions were prepared and electrospun to produce precursor nanofibers. Surface images obtained from scanning electron microscopy showed that their nanofibrous structure was well preserved after carbonization. It was also confirmed that electrospun PAV nanofibers were successfully converted to carbon nanofibers after the carbonization step by Raman spectroscopy. Carbon nanofiber electrodes derived from PAV showed higher specific capacitances and energy/power densities than those from PAN, which was tested by coin-type cells. It was also shown that PAV with an acrylonitrile/vinylimidazole composition of 83:17 is most promising for the carbon nanofiber precursor exhibiting a specific capacitance of 114 F/g. Their energy and power density are 70.1 Wh/kg at 1 A/g and 9.5 W/kg at 6 A/g, respectively. In addition, pouch cells were assembled to load the higher amount of electrode materials in the cells, and a box-like cyclic voltammetry was obtained with high capacitances.

에너지 저장 장치용 탄소 나노 섬유의 새로운 전구체 고분자

정경혜 ( Kyung Hye Jung ),존페라리스 ( John P. Ferraris ) 대구가톨릭대학교 자연과학연구소 2015 자연과학연구논문집 Vol.13 No.1

슈퍼커패시터는 에너지 저장 장치의 하나로 높은 파워 밀도와 짧은 충전 시간, 긴 수명을 가지지만, 에너지 밀도가 낮다는 단점이 있다. 탄소 나노 섬유를 슈퍼커패시터의 전극으로 사용하여 에너지 밀도를 높일 수 있다. 탄소 나노 섬유는 주로 전구체 고분자를 전기 방사하여 제작한 나노 섬유를 탄소화라는 열처리를 통해 만든다. 본 연구는 기존의 전형적인 전구체 고분자인 polyacrylonitrile (PAN)를 대체할 수 있는 전구체로 poly(acrylonitrile-co-vinylimidazole)을 소개한다. 이 고분자는 성공적으로 전기방사가 가능하고 1000℃의 탄소화 단계 후에도 나노 섬유 구조를 유지하였다. 또한 기존의 PAN으로 제작한 전극에 비해 높은 전기용량, 에너지 밀도, 파워 밀도를 보였다. 그리고 acrylonitrile과 vinylimidazole의 비율을 다양화한 결과 75:25에서 가장 훌륭한 에너지 저장 특성을 보였다. Supercapacitors fill a unique niche in terms of energy storage because they have high power density and long cyclability but low energy density. Carbon nanofibers are good candidate for supercapacitor electrode materials to improve their energy density. Typically, carbon nanofiber electrodes are prepared by thermal treatments of precursor polymer nanofibers, fabricated by electro spinning. This study introduces poly(acrylonitrile-co-vinylimidazole) as a noble precursor polymer of carbon nanofiber electrode. The polymer solutions were successfully electrospun, and their nanofibrous structure was well preserved after the carbonization step at 1000°C. The carbon nanofibers derived from poly(acrylonitrile-co-vinylimidazole) showed superior specific capacitances, and energy and power densities compared to those from polyacrylonitrile. It is also shown that the copolymer with a feed rate of 75:25 (acrylonitrile:vinylimidazole) is most promising for the carbon nanofiber precursor exhibiting high energy storage performance.

Fabrication of carbon nanofiber electrodes using poly(acrylonitrile‑co‑vinylimidazole) and their energy storage performance

Kyung‑Hye Jung,So Jeong Kim,Ye Ji Son,John P. Ferraris 한국탄소학회 2019 Carbon Letters Vol.29 No.2

For electrodes in electrochemical double-layer capacitors, carbon nanofibers (CNFs) were prepared by thermal treatment of precursor polymer nanofibers, fabricated by electrospinning. Poly(acrylonitrile-co-vinylimidazole) (PAV) was employed as a precursor polymer of carbon nanofibers due to the effective cyclization of PAV polymer chains during thermal treatment compared to a typical precursor, polyacrylonitrile (PAN). PAV solutions with different comonomer compositions were prepared and electrospun to produce precursor nanofibers. Surface images obtained from scanning electron microscopy showed that their nanofibrous structure was well preserved after carbonization. It was also confirmed that electrospun PAV nanofibers were successfully converted to carbon nanofibers after the carbonization step by Raman spectroscopy. Carbon nanofiber electrodes derived from PAV showed higher specific capacitances and energy/power densities than those from PAN, which was tested by coin-type cells. It was also shown that PAV with an acrylonitrile/vinylimidazole composition of 83:17 is most promising for the carbon nanofiber precursor exhibiting a specific capacitance of 114 F/g. Their energy and power density are 70.1 Wh/kg at 1 A/g and 9.5 W/kg at 6 A/g, respectively. In addition, pouch cells were assembled to load the higher amount of electrode materials in the cells, and a box-like cyclic voltammetry was obtained with high capacitances.

Electrochemical Properties of Activated Polyacrylonitrile/pitch Carbon Fibers Produced Using Electrospinning

Kim, Bo-Hye,Bui, Nhu-Ngoc,Yang, Kap-Seung,dela Cruz, Marilou E.,Ferraris, John P. Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.9

The electrospinnability of pitch was improved by blending in a solution of polyacrylonitrile (PAN) resulting in the reduction of the average fiber diameter from 2000 to 750 nm. Activated carbon fibers (ACFs) derived by stabilization, carbonization and steam activation at 700, 800, and 900 ${^{\circ}C}$ of the PAN/pitch electrospun fibers for 60 min were investigated as electrodes for supercapacitors. The Brunauer, Emmett, Teller (BET) specific surface area ranged from 732 to 1877 $m^2g^{-1}$ and the specific capacitance from 75.5 to 143.5 $Fg^{-1}$, depending on the activation conditions. Electrodes from the electrospun web activated at 900 ${^{\circ}C}$ exhibited a particularly quick response showing a high frequency of 5.5 Hz at a phase angle of ‒$45^o$ of the impedance spectroscopy.

Electrochemical Properties of Activated Polyacrylonitrile/pitch Carbon Fibers Produced Using Electrospinning

Bo-Hye Kim,Nhu-Ngoc Bui,Kap-Seung Yang,Marilou E. dela Cruz,John P. Ferraris 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.9

The electrospinnability of pitch was improved by blending in a solution of polyacrylonitrile (PAN) resulting in the reduction of the average fiber diameter from 2000 to 750 nm. Activated carbon fibers (ACFs) derived by stabilization, carbonization and steam activation at 700, 800, and 900 °C of the PAN/pitch electrospun fibers for 60 min were investigated as electrodes for supercapacitors. The Brunauer, Emmett, Teller (BET) specific surface area ranged from 732 to 1877 m2g-1 and the specific capacitance from 75.5 to 143.5 Fg-1, depending on the activation conditions. Electrodes from the electrospun web activated at 900 °C exhibited a particularly quick response showing a high frequency of 5.5 Hz at a phase angle of ‒45° of the impedance spectroscopy.