Hierarchical urchin-shaped α-MnO2 on graphene-coated carbon microfibers: a binder-free electrode for rechargeable aqueous Na–air battery

Khan, Ziyauddin,Park, Seungyoung,Hwang, Soo Min,Yang, Juchan,Lee, Youngsu,Song, Hyun-Kon,Kim, Youngsik,Ko, Hyunhyub Nature Publishing Group 2016 NPG Asia Materials Vol.8 No.-

<P>With the increasing demand of cost-effective and high-energy devices, sodium-air (Na-air) batteries have attracted immense interest due to the natural abundance of sodium in contrast to lithium. In particular, an aqueous Na-air battery has fundamental advantage over non-aqueous batteries due to the formation of highly water-soluble discharge product, which improve the overall performance of the system in terms of energy density, cyclic stability and round-trip efficiency. Despite these advantages, the rechargeability of aqueous Na-air batteries has not yet been demonstrated when using non-precious metal catalysts. In this work, we rationally synthesized a binder-free and robust electrode by directly growing urchin-shaped MnO2 nanowires on porous reduced graphene oxide-coated carbon microfiber (MGC) mats and fabricated an aqueous Na-air cell using the MGC as an air electrode to demonstrate the rechargeability of an aqueous Na-air battery. The fabricated aqueous Na-air cell exhibited excellent rechargeability and rate capability with a low overpotential gap (0.7 V) and high round-trip efficiency (81%). We believe that our approach opens a new avenue for synthesizing robust and binder-free electrodes that can be utilized to build not only metal-air batteries but also other energy systems such as supercapacitors, metal-ion batteries and fuel cells.</P>

Binary N,S-doped carbon nanospheres from bio-inspired artificial melanosomes: A route to efficient air electrodes for seawater batteries

Khan, Ziyauddin,Park, Sung O,Yang, Juchan,Park, Seungyoung,Shanker, Ravi,Song, Hyun-Kon,Kim, Youngsik,Kwak, Sang Kyu,Ko, Hyunhyub The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.47

<P>Cost-effective and environmentally friendly seawater-electrolyte-based batteries exhibit high energy density and demonstrate immense potential for use in future energy storage devices; however, lack of high-performance negative and positive electrodes significantly challenges their practical applications. In this study, N-doped and N,S-doped carbon nanospheres (referred to as NCSs and NSCSs, respectively) are synthesized <I>via</I> the pyrolysis of melanosomes, which is a bio-inspired polymer. Electrocatalytic activity measurements reveal the bifunctionality of the prepared catalysts. NSCSs exhibit a distinctively higher performance than NCSs when used as an air electrode in seawater batteries under ambient conditions (referred to as static mode hereafter). Further, due to the introduction of air flow into the seawater electrolyte (referred to as flow mode hereafter), NSCSs exhibit an improved cell discharge potential. The high performance of the cell is attributed to the high surface area, bifunctional electrocatalytic activity, generation of new active sites, improvement of spin density in NSCSs, and continuous flow of air to the electrolyte. The cell in the flow mode exhibits an overpotential gap of 0.56 V, a round-trip efficiency of 84%, a maximum power density of 203 mW g<SUP>−1</SUP>, and an outstanding cycling stability up to 100 cycles. The developed synthetic method provides an effective, scalable approach for doping binary or ternary atoms into the carbon host matrix, which can motivate further experimental and theoretical studies of electrode materials in various energy storage devices. In addition, the concept and results obtained by the introduction of air flow into the electrolyte can lead to the improvement of cell performance in terms of electrical energy efficiency, which can be exploited in various metal-air batteries.</P>

Urchin shaped MnO₂ nanowires for Rechargeable Aqueous Sodium-air Battery

Ziyauddin Khan,Seungyoung Park,Soo Min Hwang,Juchan Yang,Youngsu Lee,Hyunkon Song,Youngsik Kim,Hyunhyub Ko 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Three-dimensional SnS₂ nanopetals for hybrid sodium-air batteries

Khan, Ziyauddin,Parveen, Nazish,Ansari, Sajid Ali,Senthilkumar, S.T.,Park, Seungyoung,Kim, Youngsik,Cho, Moo Hwan,Ko, Hyunhyub Elsevier 2017 ELECTROCHIMICA ACTA Vol.257 No.-

<P><B>Abstract</B></P> <P>Na-air batteries are regarded as a potential alternate to Li-air batteries due to the abundant sodium source and high theoretical energy density. However, non-aqueous Na-air battery suffers from the electrode polarization owing to the formation of insoluble discharge product, which severely limits its cyclability and performance. Herein, a high performance hybrid Na-air cell is demonstrated using a dual electrolyte (mixed aqueous and non-aqueous electrolyte) system and three dimensionally (3D) grown tin sulfide (SnS<SUB>2</SUB>) nanopetals based air electrode. 3D SnS<SUB>2</SUB> nanopetals are synthesized by a facile solvothermal method and used as an air electrode material for hybrid Na-air battery. The vertically-grown and self-assembled ultra-thin nanosheets of 3D SnS<SUB>2</SUB> nanopetals provide exposed active sites for the efficient air and electrolyte diffusion to air electrodes, resulting in high performance hybrid Na-air cell. The fabricated hybrid Na-air cell displays low overpotential gap (0.52V), high round trip efficiency (83%), high power density (300mWg<SUP>−1</SUP>) and good rechargeability up to 40 cycles. The proposed 3D SnS<SUB>2</SUB> nanopetals as air electrodes can provide a robust platform for the future development of Na-air batteries and other energy storage devices.</P>

Highly porous graphitic carbon and Ni₂P₂O₇ for a high performance aqueous hybrid supercapacitor

Senthilkumar, Baskar,Khan, Ziyauddin,Park, Seungyoung,Kim, Kyoungho,Ko, Hyunhyub,Kim, Youngsik The Royal Society of Chemistry 2015 Journal of Materials Chemistry A Vol.3 No.43

<▼1><P>A high energy hybrid capacitor fabricated from highly porous graphitic carbon and novel electrode material Ni2P2O7 delivers a maximum energy density of 65 W h kg<SUP>−1</SUP> at a power density of 800 W kg<SUP>−1</SUP>, good rate capability and cycling stability in an aqueous Na-ion based electrolyte.</P></▼1><▼2><P>An aqueous Na-ion based hybrid capacitor has been successfully developed by using highly porous graphitic carbon (HPGC) derived from waste writing paper and a new electrode material as a negative and positive electrode, respectively. HPGC was prepared <I>via</I> hydrothermal carbonization and subsequent KOH activation of waste writing paper which showed a highly porous stacked sheet-like morphology with an exceptionally high BET specific surface area (1254 m<SUP>2</SUP> g<SUP>−1</SUP>). HPGC exhibited typical electrical double layer capacitor (EDLC) behavior with a high specific capacitance of 384 F g<SUP>−1</SUP> and good negative working potential (−1.0 V) in an aqueous electrolyte. On the other hand, Ni2P2O7 was synthesized by a simple co-precipitation technique and tested as a cathode material which delivered a maximum specific capacitance of 1893 F g<SUP>−1</SUP> at 2 A g<SUP>−1</SUP> current density. The fabricated HPGC‖Ni2P2O7 hybrid device displayed excellent cyclic stability up to 2000 cycles and delivered a maximum energy density of 65 W h kg<SUP>−1</SUP> at 800 W kg<SUP>−1</SUP> power density in a Na-ion based aqueous electrolyte.</P></▼2>

Feasibility of using hollow double walled Mn₂O₃ nanocubes for hybrid Na-air battery

Parveen, Nazish,Khan, Ziyauddin,Ansari, Sajid Ali,Park, Seungyoung,Senthilkumar, S.T.,Kim, Youngsik,Ko, Hyunhyub,Cho, Moo Hwan Elsevier 2019 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.360 No.-

<P><B>Abstract</B></P> <P>Synthesis of the strongly anisotropic materials, such as highly porous hollow double walled cubes are considered excellent approach to maximize the diffusion of electrolytes. Herein, hollow doubled walled (HDW) Mn<SUB>2</SUB>O<SUB>3</SUB> nanocubes (NCs) were synthesized by facile hydrothermal method followed by calcination method. The growth of nanocubes were studied by performing hydrothermal reaction at different times ranging from 3 to 9 h. Thereafter, the feasibility of prepared HDW NCs as air cathode in hybrid Na-air battery was systematically investigated. Among all, the sample prepared by 9 h hydrothermal treatment showed superior performance than 3 and 6 h samples. The fabricated hybrid Na-air cell using HDW Mn<SUB>2</SUB>O<SUB>3</SUB> NCs displayed 330 mV overpotential gap and 90% electrical energy efficiency at 5 mA g<SUP>−1</SUP> current density, maximum of 0.2 W g<SUP>−1</SUP> power density and good cyclic stability up to 75 cycles which is attributed to the highly porous nature of material that allows efficient diffusion of electrolyte ions and oxygen from air. Thus, present investigation suggests that HDW Mn<SUB>2</SUB>O<SUB>3</SUB> NCs can be a potential air cathode and can be utilized in other metal-air battery systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hollow doubled walled Mn<SUB>2</SUB>O<SUB>3</SUB> nanocubes were synthesized by hydrothermal method. </LI> <LI> Its feasibility as air cathode for hybrid Na-air battery was analyzed. </LI> <LI> The cell displayed 330 mV overpotential gap and maximum of 0.2 W g<SUP>−1</SUP> power density. </LI> <LI> It also displayed 90% energy efficiency with good cyclic stability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Hollow double walled Mn<SUB>2</SUB>O<SUB>3</SUB> nanocubes were synthesized and its feasibility for hybrid Na-air battery was systematically studied.</P> <P>[DISPLAY OMISSION]</P>

Rechargeable Na/Ni batteries based on the Ni(OH)₂/NiOOH redox couple with high energy density and good cycling performance

Park, Seungyoung,Khan, Ziyauddin,Shin, Tae Joo,Kim, Youngsik,Ko, Hyunhyub The Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.4

<P>Rechargeable battery systems that use Na-based anodes as alternatives to Li-ion batteries are highly desirable for grid-scale energy storage systems owing to the high abundance and low cost of Na. Furthermore, aqueous Na batteries are advantageous considering the cost, safety and cycle life. However, the limited energy density is still a critical issue for Na-based batteries. Here, we demonstrate a high performance rechargeable battery using dual electrolytes based on a Na metal anode and a redox couple of hierarchical NiCoAl-layered double hydroxide (NiCoAl-LDH) nanosheets on a carbon microfiber electrode with high energy storage capacity. In this design, the wide potential range of the Na metal anode and the high capacity of hierarchical NiCoAl-LDH nanosheets on a carbon microfiber cathode enable a rechargeable Na/Ni battery with excellent energy storage performance. For stable operation in a hybrid system using non-aqueous and aqueous electrolytes, an alkali-ion solid electrolyte (NASICON, Na3Zr2Si2PO12) is used for the separation of electrolytes. The Na/Ni battery exhibits a stable operating voltage of ∼3.1 V during discharge which outperforms the low cell voltage (∼1.23 V) of an aqueous rechargeable battery, a high capacity of ∼350 mA h g<SUP>−1</SUP>, and a resulting high energy density of ∼1085 W h kg<SUP>−1</SUP>. With the combination of a solid-state redox couple as the cathode and a metallic sodium anode, our study demonstrates the high potential of Na based batteries for high energy EES systems.</P>

Recent development on carbon based heterostructures for their applications in energy and environment: A review

Theerthagiri Jayaraman,Arun Prasad Murthy,Venugopal Elakkiya,Sivaraman Chandrasekaran,Palaniyandy Nithyadharseni,Ziyauddin Khan,Raja Arumugam Senthil,Ravishanker,Mitty Raghavender,Parasuraman Kuppusam 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.64 No.-

Nanostructured carbon based materials with unique and tunable properties make them to be utilized forvarious applications in different forms especially for energy and environmental applications. Carbon is adistinctive chemical element which has superior properties such as porous structure, low cost, resistanceto basic and acidic conditions, easy accessibility, low density, good recycling properties, more abundantand ability to combine with other chemical elements in different ways. In this review, we have criticallyassessed the recent developments in carbon based heterostructures for their applications in energy andenvironment. Special consideration has been paid on the applications in dye-sensitized solar cells,hydrogen evolution reaction, oxygen evolution reaction, Li-ion battery, supercapacitor, photocatalysis forthe degradation of organic pollutants, electrochemical/bio sensors and biomedical applications. Finally,the challenges and future developments of carbon based heterostructures for applications in energy andenvironment are also outlined.

Cross-Aligned Silver Nanowire Transparent Electrodes for Flexible and Force-Sensitive Mechanochromic Touch Screens

조승세,고현협,강세원,박종화,이영수,Ashish Pandya,Ravi Shanker,Ziyauddin Khan,Stephen L. Craig 한국고분자학회 2018 한국고분자학회 학술대회 연구논문 초록집 Vol.43 No.1

Large-Area Cross-Aligned Silver Nanowire Electrodes for Flexible, Transparent, and Force-Sensitive Mechanochromic Touch Screens

Cho, Seungse,Kang, Saewon,Pandya, Ashish,Shanker, Ravi,Khan, Ziyauddin,Lee, Youngsu,Park, Jonghwa,Craig, Stephen L.,Ko, Hyunhyub American Chemical Society 2017 ACS NANO Vol.11 No.4

<P>Silver nanowire (AgNW) networks are considered to be promising structures for use as flexible transparent electrodes for various optoelectronic devices. One important application of AgNW transparent electrodes is the flexible touch screens. However, the performances of flexible touch screens are still limited by the large surface roughness and low electrical to optical conductivity ratio of random network AgNW electrodes. In addition, although the perception of writing force on the touch screen enables a variety of different functions, the current technology still relies on the complicated capacitive force touch sensors. This paper demonstrates a simple and high-throughput bar-coating assembly technique for the fabrication of large area (>20 x 20 cm(2)), highly cross-aligned AgNW networks for transparent electrodes with the sheet resistance of 21.0 Omega sq(-1) at 95.0% of optical transmittance, which compares favorably with that of random AgNW networks (sheet resistance of 21.0 Omega sq(-1) at 90.4% of optical transmittance). As a proof of concept demonstration, we fabricate flexible, transparent, and force-sensitive touch screens using cross-aligned AgNW electrodes integrated with mechanochromic spiropyran-polydirnethylsiloxane composite film. Our force-sensitive touch screens enable the precise monitoring of dynamic writings, tracing and drawing of underneath pictures, and perception of handwriting patterns with locally different writing forces. The suggested technique provides a robust and Powerful platform for the controllable assembly of nanowires beyond the scale of conventional fabrication techniques, which can find diverse applications in multifunctional flexible electronic and optoelectronic devices.</P>