Humidity Sensors and Micro-supercapacitors Based on Carbon/Agarose Gel Composite Fibers

구형준,김성곤,Paul V. Braun 한국고분자학회 2017 한국고분자학회 학술대회 연구논문 초록집 Vol.42 No.2

Fabrication of 50 to 1000 nm Monodisperse ZnS Colloids

채원식,Ryan J. Kershner,Paul V. Braun 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.1

Monodisperse ZnS colloidal particles with precisely specified diameters over a broad size range were synthesized by controlled aggregation. Sub-10nm ZnS seed crystals were first nucleated at ambient temperature and then grown at an elevated temperature, which produced large polydisperse colloidal particles. Subsequent rapid thermal quenching and heating processes induced a number of secondary nucleations in addition to growing the large polydisperse microparticles which were finally removed by centrifugation and discarded at the completion of the reaction. The secondary nuclei were then aggregated further at elevated temperatures, resulting in colloidal particles which exhibited a nearly monodisperse size distribution. Particle diameters were controlled over a wide size range from 50 nm to 1 μm. Mie simulations of the experiment extinction spectra determined that the volume fraction of the ZnS is 0.66 in an aggregated colloidal particle and the colloidal particle effective refractive index is approximately 2.0 at 590 nm in water. The surface of the colloidal particles was subsequently coated with silica to produce ZnS@silica core-shell particles.

Flexible Binder-Free CuS/Polydopamine-Coated Carbon Cloth for High Voltage Supercapacitors

Yang, MinHo,Choi, Jaewon,Kim, Sung-Kon,Braun, Paul V. Wiley (John WileySons) 2018 Energy technology Vol.6 No.9

Fabrication of 50 to 1000 nm Monodisperse ZnS Colloids

Chae, Weon-Sik,Kershner, Ryan J.,Braun, Paul V. Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.1

Monodisperse ZnS colloidal particles with precisely specified diameters over a broad size range were synthesized by controlled aggregation. Sub-10nm ZnS seed crystals were first nucleated at ambient temperature and then grown at an elevated temperature, which produced large polydisperse colloidal particles. Subsequent rapid thermal quenching and heating processes induced a number of secondary nucleations in addition to growing the large polydisperse microparticles which were finally removed by centrifugation and discarded at the completion of the reaction. The secondary nuclei were then aggregated further at elevated temperatures, resulting in colloidal particles which exhibited a nearly monodisperse size distribution. Particle diameters were controlled over a wide size range from 50 nm to 1 μm. Mie simulations of the experiment extinction spectra determined that the volume fraction of the ZnS is 0.66 in an aggregated colloidal particle and the colloidal particle effective refractive index is approximately 2.0 at 590 nm in water. The surface of the colloidal particles was subsequently coated with silica to produce ZnS@silica core-shell particles.

In Operando Strain Measurement of Bicontinuous Silicon-Coated Nickel Inverse Opal Anodes for Li-Ion Batteries

Glazer, Matthew P. B.,Cho, Jiung,Almer, Jonathan,Okasinski, John,Braun, Paul V.,Dunand, David C. Wiley Blackwell (John Wiley Sons) 2015 ADVANCED ENERGY MATERIALS Vol.5 No.14

Flexible and Wearable Fiber Microsupercapacitors Based on Carbon Nanotube–Agarose Gel Composite Electrodes

Kim, Sung-Kon,Koo, Hyung-Jun,Liu, Jinyun,Braun, Paul V. American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.23

<P>Fiber electrodes provide interesting opportunities for energy storage by providing both mechanical flexibility and the opportunity to impart multifunctionality to fabrics. We show here carbon nanotube (CNT)-embedded agarose gel composite fiber electrodes, with a diameter of 120 mu m, consisting of 60 wt % CNTs that can serve as the basis for flexible and wearable fiber microsupercapacitors (mSCs). Via an extrusion process, CNT bundles are induced to align in an agarose filament matrix. Due to the shear alignment of the CNT bundles, the dehydrated filaments have an electrical conductivity as high as 8.3 S cm(-1) .The composite fiber electrodes are mechanically stable, enabling formation of twisted two-ply fiber mSCs integrated with a solid electrolyte. The fiber mSC shows a high capacitance (similar to 1.2 F cm(-3)), good rate retention (similar to 90%) at discharge current densities ranging from 5.1 to 38 mA cm(-3), long cycle life under repeated charging/discharging (10% fade after 10 000 cycles) and good performance after at least 1000 cycles of deformation) with a radius of curvature of 12.3 mm (90 degrees bend). After being coated with a thin layer of poly(dimethylsiloxane), the fiber mSCs could be cycled over 10 000 times under water. Impedance studies indicate that the superior performance is due to the high electrical conductivity along the aligned CNTs and the large electrode surface area that is accessible through the ion-conducting agarose.</P>

Extremely Durable, Flexible Supercapacitors with Greatly Improved Performance at High Temperatures

Kim, Sung-Kon,Kim, Hae Jin,Lee, Jong-Chan,Braun, Paul V.,Park, Ho Seok American Chemical Society 2015 ACS NANO Vol.9 No.8

<P>The reliability and durability of energy storage devices are as important as their essential characteristics (<I>e.g.</I>, energy and power density) for stable power output and long lifespan and thus much more crucial under harsh conditions. However, energy storage under extreme conditions is still a big challenge because of unavoidable performance decays and the inevitable damage of components. Here, we report high-temperature operating, flexible supercapacitors (f-SCs) that can provide reliable power output and extreme durability under severe electrochemical, mechanical, and thermal conditions. The outstanding capacitive features (<I>e.g.</I>, ∼40% enhancement of the rate capability and a maximum capacitances of 170 F g<SUP>–1</SUP> and 18.7 mF cm<SUP>–2</SUP> at 160 °C) are attributed to facilitated ion transport at elevated temperatures. Under high-temperature operation and/or a flexibility test in both static and dynamic modes at elevated temperatures >100 °C, the f-SCs showed extreme long-term stability of 100000 cycles (>93% of initial capacitance value) and mechanical durability after hundreds of bending cycles (at bend angles of 60–180°). Even at 120 °C, the versatile design of tandem serial and parallel f-SCs was demonstrated to provide both desirable energy and power requirements at high temperatures.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2015/ancac3.2015.9.issue-8/acsnano.5b03732/production/images/medium/nn-2015-037329_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn5b03732'>ACS Electronic Supporting Info</A></P>

Enhanced cycle stability of polypyrrole-derived nitrogen-doped carbon-coated tin oxide hollow nanofibers for lithium battery anodes

Pham-Cong, De,Park, Jung Soo,Kim, Jae Hyun,Kim, Jinwoo,Braun, Paul V.,Choi, Jun Hee,Kim, Su Jae,Jeong, Se Young,Cho, Chae Ryong Elsevier 2017 Carbon Vol.111 No.-

<P>SnO2 hollow nanofibers (SnO2 hNFs) are prepared through electrospinning and annealing processes. The polypyrrole layers coated onto the surface of the SnO2 hNFs are annealed in a nitrogen atmosphere. The nitrogen-doped carbon-coated SnO2 hNFs (SnO2/NC hNFs) are composed of SnO2 hNFs with a wall thickness of 60-80 nm and a nitrogen-doped carbon layer similar to 10 nm thick. The nitrogen content in the carbon layer is approximately 7.95%. Owing to the nitrogen-doped carbon shell layers, the specific reversible capacity of SnO2/NC hNFs at a current density of 0.2 A g(-1) after 100 cycles is 1648 mAh g(-1) which is 427% higher than that of (386 mAh g(-1)) SnO2 hNFs. This strategy may open new avenues for the design of other composite architectures as electrode materials in order to achieve high-performance lithium ion batteries. (C) 2016 Elsevier Ltd. All rights reserved.</P>

Effect of Ordered Intermediate Porosity on Ion Transport in Hierarchically Nanoporous Electrodes

Chae, Weon-Sik,Gough, Dara Van,Ham, Sung-Kyoung,Robinson, David B.,Braun, Paul V. American Chemical Society 2012 ACS APPLIED MATERIALS & INTERFACES Vol.4 No.8

<P>The high surface area of nanoporous electrodes makes them promising for use in electrochemical double-layer supercapacitors, desalination and pollution remediation, and drug delivery applications. When designed well and operating near their peak power, their charging rates are limited by ion transport through their long, narrow pores. This can be alleviated by creating pores of intermediate diameter that penetrate the electrode. We have fabricated electrodes featuring these by creating colloidal crystal-templated opals of nanoporous gold formed by dealloying. The resulting electrodes contain a bimodal pore-size distribution, with large pores on the order of several 100 nm and small pores on the order of 10 nm. Electrochemical impedance spectrometry shows that porous gold opals sacrifice some capacitance, but possess a lower internal resistance, when compared to a porous gold electrode with only the smaller-diameter pores. The architectural flexibility of this approach provides a greater ability to design a balance between power density and energy density.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2012/aamick.2012.4.issue-8/am300798j/production/images/medium/am-2012-00798j_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am300798j'>ACS Electronic Supporting Info</A></P>

<i>In operando</i> X-ray diffraction strain measurement in Ni₃Sn₂ – Coated inverse opal nanoscaffold anodes for Li-ion batteries

Glazer, Matthew P.B.,Wang, Junjie,Cho, Jiung,Almer, Jonathan D.,Okasinski, John S.,Braun, Paul V.,Dunand, David C. Elsevier 2017 Journal of Power Sources Vol.367 No.-

<P><B>Abstract</B></P> <P>Volume changes associated with the (de)lithiation of a nanostructured Ni<SUB>3</SUB>Sn<SUB>2</SUB> coated nickel inverse opal scaffold anode create mismatch stresses and strains between the Ni<SUB>3</SUB>Sn<SUB>2</SUB> anode material and its mechanically supporting Ni scaffold. Using <I>in operando</I> synchrotron x-ray diffraction measurements, elastic strains in the Ni scaffold are determined during cyclic (dis)charging of the Ni<SUB>3</SUB>Sn<SUB>2</SUB> anode. These strains are characterized using both the center position of the Ni diffraction peaks, to quantify the average strain, and the peak breadth, which describes the distribution of strain in the measured volume. Upon lithiation (half-cell discharging) or delithiation (half-cell charging), compressive strains and peak breadth linearly increase or decrease, respectively, with charge. The evolution of the average strains and peak breadths suggests that some irreversible plastic deformation and/or delamination occurs during cycling, which can result in capacity fade in the anode. The strain behavior associated with cycling of the Ni<SUB>3</SUB>Sn<SUB>2</SUB> anode is similar to that observed in recent studies on a Ni inverse-opal supported amorphous Si anode and demonstrates that the (de)lithiation-induced deformation and damage mechanisms are likely equivalent in both anodes, even though the magnitude of mismatch strain in the Ni<SUB>3</SUB>Sn<SUB>2</SUB> is lower due to the lower (de)lithiation-induced contraction/expansion.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Lithiation-induced strains quantified in a Ni<SUB>3</SUB>Sn<SUB>2</SUB> inverse opal anode <I>in operando</I>. </LI> <LI> Lithiation induces compressive average strains in Ni inverse opal scaffold. </LI> <LI> Ni inverse opal scaffold strain distribution reversibly broadens upon lithiation. </LI> <LI> Three measured volumes show similar cyclic strain averages and distributions. </LI> <LI> Ni<SUB>3</SUB>Sn<SUB>2</SUB> measured cyclic strains are similar to prior Si inverse opal anode studies. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>