R. Vasant Kumar

High energy density lithium batteries : materials, engineering, applications

What are Batteries? Quantities Characterizing Batteries I. PRIMARY BATTERIES The Early Batteries The Zn/C cell: Lechlanche and Gassner Type, Current Zinc/Carbon Cells Alkaline Batteries Button Batteries: HgO Cells, Zn/AgO2 Cells, Zn/air Cells Li Primary Batteries: Li/SOCl2 Cells, Li/SO2 Cells Oxyride Batteries Damage in Primary Batteries Conclusions II SECONDARY BATTERIES Overview of Secondary Batteries: Lead-Acid Cells, Ni/Cd Cells, Secondary Li-ion Cells Cathodes: Introduction, Structural Changes, Next-Generation Materials, Size Effects Anodes for Li-Ion Batteries: Introduction, Instabilities during Electrochemical Cycling, Nanostructures Anodes, Other Materials Theoretical Analysis for Li-Ion Batteries: Introduction, Fracture Mechanism Analysis, Cahns Gradient Thermodynamics, Design Criteria Conclusions and Future Outlook

Synthesis of semiconducting polymer microparticles as solid ionophore with abundant complexing sites for long-life Pb(II) sensors.

Intrinsically electrically semiconducting microparticles of semiladder poly(m-phenylenediamine-co-2-hydroxy-5-sulfonic aniline) structures containing abundant functional groups, like -NH-, -N=, -NH2, -OH, -SO3H as complexation sites, were efficiently synthesized by chemical oxidative copolymerization of m-phenylenediamine and 2-hydroxy-5-sulfonic aniline. The obtained copolymers were found to be nonporous spherical microparticles that were able to achieve greater π-conjugated structure, smaller particle aggregate size, and stronger interaction with Pb(II) ions than poly(m-phenylenediamine) containing only -NH-, -N=, and -NH2. A potentiometric Pb(II) sensor was fabricated on the basis of the copolymer microparticles as a crucial solid ionophore component within plasticized PVC. The sensor exhibited a Nernstian response to Pb(II) ions over a wide concentration range, together with a fast response, a wide pH range capability, a long lifetime of up to 5 months, and good selectivity over a wide variety of other ions and redox species. The process for synthesizing the microparticles and fabricating the Pb(II)-sensor can be facilely scaled-up for use in the straightforward long-term online monitoring of Pb(II) ions in heavily polluted wastewaters. This study develops an understanding of the facile synthesis of conducting microparticles bearing many functional groups and their structures governing the potentiometric susceptibility toward interaction between Pb(II) ions and the microparticles for fabricating robust long-lived Pb(II)-sensor, signifying the potential suitability of such novel materials for inexpensive sensitive detection of Pb(II) ions.

Preparation and characterization of nano-structured lead oxide from spent lead acid battery paste.

As part of contribution for developing a green recycling process of spent lead acid battery, a nanostructural lead oxide was prepared under the present investigation in low temperature calcination of lead citrate powder. The lead citrate, the precursor for preparation of this lead oxide, was synthesized through leaching of spent lead acid battery paste in citric acid solution. Both lead citrate and oxide products were characterized by means of thermogravimetric-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and scanning electron microscope (SEM). The results showed that the lead citrate was sheet-shape crystal of Pb(C(6)H(6)O(7)) · H(2)O. When the citrate was calcined in N(2) gas, β-PbO in the orthorhombic phase was the main product containing small amount of Pb and C and it formed as spherical particles of 50-60 nm in diameter. On combusting the citrate in air at 370°C (for 20 min), a mixture of orthorhombic β-PbO, tetragonal α-PbO and Pb with the particle size of 100-200 nm was obtained, with β-PbO as the major product. The property of the nanostructural lead oxide was investigated by electrochemical technique, such as cyclic voltammetry (CV). The CV measurements presented the electrochemical redox potentials, with reversibility and cycle stability over 15 cycles.

Leaching of spent lead acid battery paste components by sodium citrate and acetic acid

A sustainable method, with minimal pollution and low energy cost in comparison with the conventional smelting methods, is proposed for treating components of spent lead-acid battery pastes in aqueous organic acid(s). In this study, PbO, PbO2, and PbSO4, the three major components in a spent lead paste, were individually reacted with a mixture of aqueous sodium citrate and acetic acid solution. Pure lead citrate precursor of Pb3(C6H5O7)2 · 3H2O is the only product crystallized in each leaching experiment. Conditions were optimized for individual lead compounds which were then used as the basis for leaching real industrial spent paste. In this work, efficient leaching process is achieved and raw material cost is reduced by using aqueous sodium citrate and acetic acid, instead of aqueous sodium citrate and citric acid as reported in a pioneering hydrometallurgical method earlier. Acetic acid is not only cheaper than citric acid but is also more effective in aiding dissolution of the lead compounds thus speeding up the leaching process in comparison with citric acid. Lead citrate is readily crystallized from the aqueous solution due to its low solubility and can be combusted to directly produce leady oxide as a precursor for making new battery pastes.

Graphene-wrapped sulfur/metal organic framework-derived microporous carbon composite for lithium sulfur batteries

A three-dimensional hierarchical sandwich-type graphene sheet-sulfur/carbon (GS-S/CZIF8-D) composite for use in a cathode for a lithium sulfur (Li-S) battery has been prepared by an ultrasonic method. The microporous carbon host was prepared by a one-step pyrolysis of Zeolitic Imidazolate Framework-8 (ZIF-8), a typical zinc-containing metal organic framework (MOF), which offers a tunable porous structure into which electro-active sulfur can be diffused. The thin graphene sheet, wrapped around the sulfur/zeolitic imidazolate framework-8 derived carbon (S/CZIF8-D) composite, has excellent electrical conductivity and mechanical flexibility, thus facilitating rapid electron transport and accommodating the changes in volume of the sulfur electrode. Compared with the S/CZIF8-D sample, Li-S batteries with the GS-S/CZIF8-D composite cathode showed enhanced capacity, improved electrochemical stability, and relatively high columbic efficiency by taking advantage of the synergistic effects of the microporous carbon ...

Construction of sandwich-type hybrid structures by anchoring mesoporous ZnMn2O4 nanofoams on reduced graphene oxide with highly enhanced capability

We have developed a sandwich-type hybrid nanostructure by anchoring foam-like zinc manganate (ZnMn2O4) on reduced graphene oxide (rGO) (rGO/ZnMn2O4 NFs) via a trisodium citrate (TSC) assisted solution reaction followed by a post-calcination treatment. The interconnected sheet-like ZnMn2O4 subunits have assembled into mesoporous nanofoams on rGO sheets with the beneficial help of TSC. When cycled at a current density of 180 mA g−1, the hybrid rGO/ZnMn2O4 NF anodes present a high discharge capacity of 945 mA h g−1 even after 150 cycles with long cycle durability and good rate capability. Such highly enhanced electrochemical performance is ascribed to the sandwich-type hierarchical foam structure effectively promoting the ion/charge transport whilst buffering volume variations upon continuous discharge/charge cycling. These results indicate that a porous anode scaffold with conductive connections is a promising structural design for rechargeable batteries with superior reversible lithium storage capability.

Rational Design of NiCoO2@SnO2 Heterostructure Attached on Amorphous Carbon Nanotubes with Improved Lithium Storage Properties

It still remains very challenging to design proper heterostructures to enhance the electrochemical performance of transition metal oxide-based anode materials for lithium-ion batteries. Here, we synthesized the NiCoO2 nanosheets@SnO2 layer heterostructure supported by amorphous carbon nanotubes (ACNTs) which is derived from polymeric nanotubes (PNTs) by a stepwise method. The inner SnO2 layer not only provides a considerable capacity contribution but also produces the extra Li2O to promote the charge process of NiCoO2 and thus results in a rising cycling performance. Combining with the contribution of ACNTs backbone and ultrathin NiCoO2 nanosheets, the specific capacities of these one-dimensional nanostructures show an interesting gradually increasing trend even after 100 cycles at 400 mA g(-1) with a final result of 1166 mAh g(-1). This approach can be an efficient general strategy for the preparation of mixed-metal-oxide one-dimensional nanostructures and this innovative design of hybrid electrode materials provides a promising approach for batteries with improved electrochemical performance.

Enhancement of diffusion kinetics in porous MoN nanorods-based counter electrode in a dye-sensitized solar cell

Developing low-cost materials to replace platinum as a counter electrode in dye-sensitized solar cells (DSSCs) is very important towards commercialization of DSSCs. For replacing platinum, it is found that transition metal nitrides are promising candidates to efficiently catalyze the reduction of triiodide ions in DSSCs. However, mass transport limitations in the metal nitride electrode are one of the problems that require solutions. Herein, we show enhancement of diffusion kinetics for the active electrochemical process on the counter electrode of DSSCs with MoN fabricated into a porous nanorod morphology. A thin film composed of porous MoN nanorods on a metallic Ti foil substrate has been prepared for the first time by nitridation of a nanowire-like precursor of Mo3O10(C6H8N)2·2H2O, which was prepared hydrothermally by reacting ammonium heptamolybdate and aniline. The diameter and the length of the MoN nanorods are in the range of 40–100 nm and 0.5–2 μm, respectively. Compared with a MoN electrode composed of sphere-like nanoparticles typically with a diameter from 50 to 100 nm, the porous MoN nanorod counter electrode provides a higher electrochemical performance in DSSCs. The corresponding DSSC shows an energy conversion efficiency of 7.29%, which is superior to the 6.48% of the device using the MoN electrode with sphere-like particles. Even more significantly, this value is comparable with the conversion efficiency of 7.42% that was achieved using the conventional precious metal-based Pt-FTO (fluorine-doped tin oxide) electrode in a DSSC. These exciting results, which are comparable to those obtained by precious metal electro-catalysis, are attributed to enhancement of diffusion kinetics of the MoN counter electrode as a result of favorable morphology. The electrochemical impedance spectra (EIS) demonstrate that the diffusion resistance in the case of the porous MoN nanorod electrode is much smaller than that in the MoN nanoparticle electrode due to a larger porosity and interconnected channels for electrolyte in the porous nanorod-structured electrode. The results are helpful for developing highly efficient and low-cost electrodes through the understanding of the kinetics of the porous MoN nanorod counter electrode.

Cylindrical Fresnel lenses based on carbon nanotube forests

The forests of carbon nanotubes have been termed as the darkest man-made materials. Such materials exhibit near-perfect optical absorption (reflectance ∼ 0.045%) due to low reflectance and nanoscale surface roughness. We have demonstrated the utilization of these perfectly absorbing forests to produce binary amplitude cylindrical Fresnel lenses. The opaque Fresnel zones are defined by the dark nanotube forests and these lenses display efficient focusing performance at optical wavelengths. Lensing performance was analyzed both computationally and experimentally with good agreement. Such nanostructure based lenses have many potential applications in devices like photovoltaic solar cells.

Automated Analysis of Carbon in Powdered Geological and Environmental Samples by Raman Spectroscopy

Raman spectroscopy can be used to assess the structure of naturally occurring carbonaceous materials (CM), which exist in a wide range of crystal structures. The sources of these geological and environmental materials include rocks, soils, river sediments, and marine sediment cores, all of which can contain carbonaceous material ranging from highly crystalline graphite to amorphous-like organic compounds. In order to fully characterize a geological sample and its intrinsic heterogeneity, several spectra must be collected and analyzed in a precise and repeatable manner. Here, we describe a suitable processing and analysis technique. We show that short-period ball-mill grinding does not introduce structural changes to semi-graphitized material and allows for easy collection of Raman spectra from the resulting powder. Two automated peak-fitting procedures are defined that allow for rapid processing of large datasets. For very disordered CM, Lorentzian profiles are fitted to five characteristic peaks, for highly graphitized material, three Voigt profiles are fitted. Peak area ratios and peak width measurements are used to classify each spectrum and allow easy comparison between samples. By applying this technique to samples collected in Taiwan after Typhoon Morakot, sources of carbon to offshore sediments have been identified. Carbon eroded from different areas of Taiwan can be seen mixed and deposited in the offshore flood sediments, and both graphite and amorphous-like carbon have been recycled from terrestrial to marine deposits. The practicality of this application illustrates the potential for this technique to be deployed to sediment-sourcing problems in a wide range of geological settings.