Jiyong Eom

Structural enhancement of Na3V2(PO4)3/C composite cathode materials by pillar ion doping for high power and long cycle life sodium-ion batteries

Structurally stabilized Na3V2(PO4)3/C composite cathode materials with excellent electrochemical performance can be obtained by incorporating functional pillar ions into the structure. As pillar ions, K-ions have a larger ionic radius compared to Na-ions, and play an important role in enlarging the Na-ion diffusion pathway and in increasing the lattice volume by elongating the c-axis, thereby improving the rate performance. Furthermore, since the incorporated K-ions rarely participate in the electrochemical extraction/insertion reactions, they can stabilize the Na3V2(PO4)3 structure by suppressing significant lattice volume changes or structural distortion, even in a wide range of voltage windows accompanying multiple transitions of V ions and phase distortions. We investigated how the K-ion doping level affected the crystal structure and electrochemical properties of Na3V2(PO4)3 cathode materials for Na-ion batteries.

Fabrication of Graphene Embedded LiFePO4 Using a Catalyst Assisted Self Assembly Method as a Cathode Material for High Power Lithium-Ion Batteries

We have designed a unique microstructure of graphene embedded LiFePO4 by a catalyst assisted self assembly method as a cathode material for high power lithium-ion batteries. The stable amide bonds between LiFePO4 and graphene were formed by the catalyst assisted self assembly. High conductive graphene provides a fast electron transfer path, and many pores inside the structure facilitate the lithium-ion diffusion. The graphene embedded LiFePO4 fabricated by the novel method shows enhanced cycling performance and rate-capability compared with that of carbon coated LiFePO4 as a cathode material for high power lithium-ion batteries.

Preparation of single-walled carbon nanotube/silicon composites and their lithium storage properties.

Single-walled carbon nanotube (SWCNT)/silicon composites were produced from the purified SWCNTs and Si powder by high-energy ball-milling and then electrochemically inserted with Li using Li/(SWCNT/Si) cells. The highest reversible capacity and lowest irreversible capacity of the SWCNT/Si composites were measured to be 1845 and 474 mAh g(-1) after ball-milling for 60 min, respectively. During the charge/discharge process, most of the Li ions were inserted into the SWCNT/Si composites by alloying with Si particles below 0.2 V and extracted from the SWCNT/Si composites by dealloying with Si particles around 0.5 V. The enhanced capacity and cycle performance of the SWCNT/Si composites produced by high-energy ball-milling were due primarily to the fact that SWCNTs provided a flexible conductive matrix, which compensated for the dimensional changes of Si particles during Li insertion and avoided loosening of the interparticle contacts during the crumbling of Si particles. The ball-milling contributed to a decrease in the particle size of SWCNTs and Si particles and to an increase in the electrical contact between SWCNTs and Si particles in the SWCNT/Si composites.

Black titanium oxide nanoarray electrodes for high rate Li-ion microbatteries

Black TiO2−x nanotube arrays, which are synthesized by an electrochemical method and subsequent thermal conversion in a hydrogen atmosphere, are employed as binder-free, free-standing electrodes for high rate Li-ion microbatteries. Excellent cyclability and superior rate capability are achieved by an oxygen-deficient structure of TiO2 with increased electronic conductivity and the formation of metallic titanium hydride phases on the substrate.

China's Building Energy Use: A Long-Term Perspective based on a Detailed Assessment

We present here a detailed, service-based model of Chinas building energy use, nested in the GCAM (Global Change Assessment Model) integrated assessment framework. Using the model, we explore long-term pathways of Chinas building energy use and identify opportunities of reducing greenhouse gas emissions. The inclusion of a structural model of building energy demands within an integrated assessment framework represents a major methodological advance. It allows for a structural understanding of the drivers of building energy consumption while simultaneously considering the other human and natural system interactions that influence changes in the global energy system and climate. We also explore a range of different scenarios to gain insights into how Chinas building sector might evolve and what the implications might be for improved building energy technology and carbon policies. The analysis suggests that Chinas building energy growth will not wane anytime soon, although technology improvement will put downward pressure on this growth. Also, regardless of the scenarios represented, the growth will involve the continued, rapid electrification of the buildings sector throughout the century, and this transition will be accelerated by the implementation of carbon policy.

Scenarios of global municipal water-use demand projections over the 21st century

Abstract Three future projections of global municipal water use are established: business-as usual (BAU), low technological improvement (Low Tech), and high technological improvement (High Tech). A global municipal water demand model is constructed using global water-use statistics at the country scale, calibrated to the base year of 2005, and simulated to the end of the 21st century. Since the constructed water demand model hinges on socio-economic variables (population, income), water price, and end-use technology and efficiency improvement rates, projections of those input variables are adopted to characterize the uncertainty in future water demand estimates. The water demand model is linked to the Global Change Assessment Model (GCAM), a global change integrated assessment model. Under the reference (BAU) scenario, the global total water withdrawal increases from 466 km3 year−1 in 2005 to 1098 km3 year−1 in 2100, while withdrawals in the High and Low Tech scenarios are 437 and 2000 km3 year−1, respectively. Editor Z.W. Kundzewicz; Associate editor D. Gerten Citation Hejazi, M., Edmonds, J., Chaturvedi, V., Davies, E., and Eom, J.Y., 2013. Scenarios of global municipal water use demand projections over the 21st century. Hydrological Sciences Journal, 58 (3), 519–538

Tailoring Crystal Structure and Morphology of LiFePO4/C Cathode Materials Synthesized by Heterogeneous Growth on Nanostructured LiFePO4 Seed Crystals

Porous and coarse (5-10 μm) LiFePO₄/C composites with excellent electrochemical performance were synthesized by a growth technology using nanostructured (100-200 nm) LiFePO₄ as seed crystals for the 2nd crystallization process. The porous and coarse LiFePO₄/C presented a high initial discharge capacity (∼155 mA h g⁻¹ at 0.1 C), superior rate-capability (∼100 mA h g⁻¹ at 5 C, ∼65 % of the discharge capacity at 0.1 C), and excellent cycling performance (∼131 mA h g⁻¹, ∼98 % of its initial discharge capacity after 100 cycles at 1 C). The improvement in the rate-capability of the LiFePO₄/C was attributed to the high reaction area resulted from the pore tunnels formed inside LiFePO₄ particles and short Li-ion diffusion length. The improved cycling performance of the LiFePO₄/C resulted from the enhanced structural stability against Li-deficient LiFePO₄ phase formation after cycling by the expansion of the 1D Li-ion diffusion channel in the LiFePO₄ crystal structure.

Shareholder Incentives for Utility-Delivered Energy Efficiency Programs in California

Energy efficiency is increasingly being recognized as a resource warranting aggressive public investment. The State of California has committed an unprecedented sum of

Fabrication of tin-cobalt/carbon composite electrodes by electrodeposition using cationic surfactant for lithium-ion batteries

2.2 billion in ratepayer funds to utility-based energy efficiency programs from 2006 through 2008; the State finalized in 2007 the determination of the shared-savings incentive mechanism for the 2006-2008 programs and beyond. This study seeks to examine whether the adopted incentive mechanism would ensure an efficient delivery of the programs, and what reforms, if any, could be proposed to meet this end. I develop a game theory model for the implementation of the programs, in which a regulator adopts an energy savings target and a shared-savings incentive mechanism before a utility firm proposes program funding, gets the proposal authorized, and begins to manage the programs. The study reveals that each utility firm requires a certain minimum level of incentive rate, in order for the mechanism to encourage the firm to achieve the adopted energy savings target, eventually bringing non-negative bill savings to its customers. It also reveals that a higher-than-minimum incentive rate can achieve not only a greater net social benefit but also greater bill savings for customers. Model-based analysis of California energy efficiency programs suggests that a higher-than-adopted incentive rate is warranted and that social efficiency would be improved by customizing incentive mechanisms for individual utilities and updating them on a regular basis.

Modularity and technological change : A primer and synthesis

Sn-Co alloy and Sn-Co/C composite are fabricated on the nodule-type Cu substrate by co-electrodeposition process using the pulse current in the pyrophosphate bath, and then their cycling performances are examined. To modify the surface property of carbon (acetylene black) particles and improve the dispersion of agglomerated carbon particles, CTAB (Cetrimonium bromide (C16H33)N(CH3)3Br) as a cationic surfactant is added into the electrodeposition bath.10.1007/s13391-016-6077-2 By addition of the CTAB, the amount of the carbon content in the Sn-Co/C composite is increased, and also the carbon particles are uniformly distributed in the Sn-Co electrodeposit. The Sn0.6Co0.4 alloy and (Sn0.6Co0.4)0.71/C0.29 composite are obtained after annealing as the final products. The (Sn0.6Co0.4)0.71/C0.29 composite anode exhibits better the capacity retention than the Sn0.6Co0.4 alloy anode due primarily to the role of the well-dispersed carbon particles as the second buffer phase and electrical conductive path in the Sn-Co/C composite during cycling.