Página 1 dos resultados de 21 itens digitais encontrados em 0.013 segundos

Capacitance effects superimposed on redox processes in molecular-cluster batteries: a synergic route to high-capacity energy storage

Wang, Heng; Zeng, Zhaoyang; Kawasaki, Naoya; Eckert, Hellmut; Yoshikawa, Hirofumi; Awaga, Kunio
Fonte: Wiley-VCH Verlag; Weinheim Publicador: Wiley-VCH Verlag; Weinheim
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
177.78918%
Rechargeable molecular-cluster batteries (MCBs) based on the manganese cluster complex [Mn12O12- (CH3CH2C(CH3)2COO)16(H2O)4] ([Mn12]) that exhibited a capacity of approximately 200 Ahkg-1 in the battery voltage range of 4.0 to 2.0 V were developed. In these batteries, the capacity of approximately 100 Ahkg-1 in the range of 4.0-3.0 V is caused by a chemical reduction from [Mn12]0 to [Mn12]8-, whereas the other half in the range of 3.0-2.0 V cannot be explained by a redox change of the Mn ions. We performed the cyclic voltammetry (CV) and 7Li solid-state NMR measurements on the Mn12-MCBs to investigate the origin of the capacity below 3.0 V. Pseudo-rectangular-shaped CV curves in the range of 3.0-2.0 V demonstrate the presence of an electrical double-layer (EDL) capacitance in Mn12-MCBs, which corresponds to approximately 100 Ahkg-1. 7Li NMR studies suggest that Li ions form an EDL with electrons in carbon black electrodes in the capacitance voltage range. The capacitance effects are not formed by the single-carbon electrodes alone, but appear only in the mixture of Mn12 and the carbon black electrodes. This type of coexistence of capacitance effects and redox reaction in one electrochemical cell is quite unusual and can serve as a new working principle for high-performance energy-storage devices.; MEXT; DFG

Physical and electrochemical properties of synthesized carbon nanotubes [CNTs] on a metal substrate by thermal chemical vapor deposition

Gwon, Yong Hwan; Ha, Jong Keun; Cho, Kwon Koo; Kim, Hye Sung
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 05/01/2012 EN
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177.78918%
Multi-walled carbon nanotubes were synthesized on a Ni/Au/Ti substrate using a thermal chemical vapor deposition process. A Ni layer was used as a catalyst, and an Au layer was applied as a barrier in order to prevent diffusion between Ni and Ti within the substrate during the growth of carbon nanotubes. The results showed that vertically aligned multi-walled carbon nanotubes could be uniformly grown on the Ti substrate (i.e., metal substrate), thus indicating that the Au buffer layer effectively prevented interdiffusion of the catalyst and metal substrate. Synthesized carbon nanotubes on the Ti substrate have the diameter of about 80 to 120 nm and the length of about 5 to 10 μm. The Ti substrate, with carbon nanotubes, was prepared as an electrode for a lithium rechargeable battery, and its electrochemical properties were investigated. In a Li/CNT cell with carbon nanotubes on a 60-nm Au buffer layer, the first discharge capacity and discharge capacity after the 50th cycle were 210 and 80 μAh/cm2, respectively.

In Situ Ambient Pressure X-ray Photoelectron Spectroscopy Studies of Lithium-Oxygen Redox Reactions

Lu, Yi-Chun; Crumlin, Ethan J.; Veith, Gabriel M.; Harding, Jonathon R.; Mutoro, Eva; Baggetto, Loïc; Dudney, Nancy J.; Liu, Zhi; Shao-Horn, Yang
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 08/10/2012 EN
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192.8718%
The lack of fundamental understanding of the oxygen reduction and oxygen evolution in nonaqueous electrolytes significantly hinders the development of rechargeable lithium-air batteries. Here we employ a solid-state Li4+xTi5O12/LiPON/LixV2O5 cell and examine in situ the chemistry of Li-O2 reaction products on LixV2O5 as a function of applied voltage under ultra high vacuum (UHV) and at 500 mtorr of oxygen pressure using ambient pressure X-ray photoelectron spectroscopy (APXPS). Under UHV, lithium intercalated into LixV2O5 while molecular oxygen was reduced to form lithium peroxide on LixV2O5 in the presence of oxygen upon discharge. Interestingly, the oxidation of Li2O2 began at much lower overpotentials (~240 mV) than the charge overpotentials of conventional Li-O2 cells with aprotic electrolytes (~1000 mV). Our study provides the first evidence of reversible lithium peroxide formation and decomposition in situ on an oxide surface using a solid-state cell, and new insights into the reaction mechanism of Li-O2 chemistry.

Design and Testing of a Percutaneously Implantable Fetal Pacemaker

Loeb, Gerald E.; Zhou, Li; Zheng, Kaihui; Nicholson, Adriana; Peck, Raymond A.; Krishnan, Anjana; Silka, Michael; Pruetz, Jay; Chmait, Ramen; Bar-Cohen, Yaniv
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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382.3381%
We are developing a cardiac pacemaker with a small, cylindrical shape that permits percutaneous implantation into a fetus to treat complete heart block and consequent hydrops fetalis, which can otherwise be fatal. The device uses off-the-shelf components including a rechargeable lithium cell and a highly efficient relaxation oscillator encapsulated in epoxy and glass. A corkscrew electrode made from activated iridium can be screwed into the myocardium, followed by release of the pacemaker and a short, flexible lead entirely within the chest of the fetus to avoid dislodgement from fetal movement. Acute tests in adult rabbits demonstrated the range of electrical parameters required for successful pacing and the feasibility of successfully implanting the device percutaneously under ultrasonic imaging guidance. The lithium cell can be recharged inductively as needed, as indicated by a small decline in the pulsing rate.

Charging-free electrochemical system for harvesting low-grade thermal energy

Yang, Yuan; Lee, Seok Woo; Ghasemi, Hadi; Loomis, James; Li, Xiaobo; Kraemer, Daniel; Zheng, Guangyuan; Cui, Yi; Chen, Gang
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
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377.78918%
Tremendous low-grade heat is stored in industrial processes and the environment. Efficient and low-cost utilization of the low-grade heat is critical to imminent energy and environmental challenges. Here, a rechargeable electrochemical cell (battery) is used to harvest such thermal energy because its voltage changes significantly with temperature. Moreover, by carefully tuning the composition of electrodes, the charging process is purely powered by thermal energy and no electricity is required to charge it. A high heat-to-electricity conversion efficiency of 2.0% can be reached when it is operated between 20 and 60 °C. Such charging-free characteristic may have potential application for harvesting low-grade heat from the environment, especially in remote areas.

Percutaneously Inject able Fetal Pacemaker: Electrodes, Mechanical Design and Implantation*

Zhou, Li; Chmait, Ramen; Bar-Cohen, Yaniv; Peck, Raymond A.; Loeb, Gerald E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
Relevância na Pesquisa
377.78918%
We are developing a self-contained cardiac pacemaker with a small, cylindrical shape (~3×20mm) that permits it to be implanted percutaneously into a fetus to treat complete heart block and consequent hydrops fetalis, which is otherwise fatal. The device uses off-the-shelf components including a rechargeable lithium cell and a highly efficient relaxation oscillator encapsulated in epoxy and glass. A corkscrew electrode made from activated iridium can be screwed into the myocardium, followed by release of the pacemaker and a short, flexible lead entirely within the chest of the fetus to avoid dislodgement from fetal movement. The feasibility of implanting the device percutaneously under ultrasonic imaging guidance was demonstrated in acute adult rabbit experiments.

From lithium to sodium: cell chemistry of room temperature sodium–air and sodium–sulfur batteries

Adelhelm, Philipp; Hartmann, Pascal; Bender, Conrad L; Busche, Martin; Eufinger, Christine; Janek, Juergen
Fonte: Beilstein-Institut Publicador: Beilstein-Institut
Tipo: Artigo de Revista Científica
Publicado em 23/04/2015 EN
Relevância na Pesquisa
299.94246%
Research devoted to room temperature lithium–sulfur (Li/S8) and lithium–oxygen (Li/O2) batteries has significantly increased over the past ten years. The race to develop such cell systems is mainly motivated by the very high theoretical energy density and the abundance of sulfur and oxygen. The cell chemistry, however, is complex, and progress toward practical device development remains hampered by some fundamental key issues, which are currently being tackled by numerous approaches. Quite surprisingly, not much is known about the analogous sodium-based battery systems, although the already commercialized, high-temperature Na/S8 and Na/NiCl2 batteries suggest that a rechargeable battery based on sodium is feasible on a large scale. Moreover, the natural abundance of sodium is an attractive benefit for the development of batteries based on low cost components. This review provides a summary of the state-of-the-art knowledge on lithium–sulfur and lithium–oxygen batteries and a direct comparison with the analogous sodium systems. The general properties, major benefits and challenges, recent strategies for performance improvements and general guidelines for further development are summarized and critically discussed. In general...

Simple synthesis of highly catalytic carbon-free MnCo2O4@Ni as an oxygen electrode for rechargeable Li–O2 batteries with long-term stability

Kalubarme, Ramchandra S.; Jadhav, Harsharaj S.; Ngo, Duc Tung; Park, Ga-Eun; Fisher, John G.; Choi, Yun-Il; Ryu, Won-Hee; Park, Chan-Jin
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 21/08/2015 EN
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514.31887%
An effective integrated design with a free standing and carbon-free architecture of spinel MnCo2O4 oxide prepared using facile and cost effective hydrothermal method as the oxygen electrode for the Li–O2 battery, is introduced to avoid the parasitic reactions of carbon and binder with discharge products and reaction intermediates, respectively. The highly porous structure of the electrode allows the electrolyte and oxygen to diffuse effectively into the catalytically active sites and hence improve the cell performance. The amorphous Li2O2 will then precipitate and decompose on the surface of free-standing catalyst nanorods. Electrochemical examination demonstrates that the free-standing electrode without carbon support gives the highest specific capacity and the minimum capacity fading among the rechargeable Li–O2 batteries tested. The Li-O2 cell has demonstrated a cyclability of 119 cycles while maintaining a moderate specific capacity of 1000 mAh g−1. Furthermore, the synergistic effect of the fast kinetics of electron transport provided by the free-standing structure and the high electro-catalytic activity of the spinel oxide enables excellent performance of the oxygen electrode for Li-O2 cells.

Ionomer-Liquid Electrolyte Hybrid Ionic Conductor for High Cycling Stability of Lithium Metal Electrodes

Song, Jongchan; Lee, Hongkyung; Choo, Min-Ju; Park, Jung-Ki; Kim, Hee-Tak
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 28/09/2015 EN
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196.70828%
The inhomogeneous Li electrodeposition of lithium metal electrode has been a major impediment to the realization of rechargeable lithium metal batteries. Although single ion conducting ionomers can induce more homogeneous Li electrodeposition by preventing Li+ depletion at Li surface, currently available materials do not allow room-temperature operation due to their low room temperature conductivities. In the paper, we report that a highly conductive ionomer/liquid electrolyte hybrid layer tightly laminated on Li metal electrode can realize stable Li electrodeposition at high current densities up to 10 mA cm−2 and permit room-temperature operation of corresponding Li metal batteries with low polarizations. The hybrid layer is fabricated by laminating few micron-thick Nafion layer on Li metal electrode followed by soaking 1 M LiPF6 EC/DEC (1/1) electrolyte. The Li/Li symmetric cell with the hybrid layer stably operates at a high current density of 10 mA cm−2 for more than 2000 h, which corresponds to more than five-fold enhancement compared with bare Li metal electrode. Also, the prototype Li/LiCoO2 battery with the hybrid layer offers cycling stability more than 350 cycles. These results demonstrate that the hybrid strategy successfully combines the advantages of bi-ionic liquid electrolyte (fast Li+ transport) and single ionic ionomer (prevention of Li+ depletion).

Electrode-Electrolyte Interfaces in Solid Polymer Lithium Batteries

Hu, Qichao
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation
EN_US
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312.5199%
This thesis studies the performance of solid polymer lithium batteries from room temperature to elevated temperatures using mainly electrochemical techniques, with emphasis on the bulk properties of the polymer electrolyte and the electrode-electrolyte interfaces. Its contributions include: 1) Demonstrated the relationship between polymer segmental motion and ionic conductivity indeed has a Vogel-Tammann-Fulcher (VTF) dependence, and improved the conductivity of the graft copolymer electrolyte (GCE) by almost an order of magnitude by changing the ion-conducting block from poly(oxyethylene) methacrylate (POEM) to a block with a lower glass transition temperature ((T_g)) poly(oxyethylene) acrylate (POEA). 2) Identified the rate-limiting step in the battery occurs at the cathode-electrolyte interface using both full cell and symmetric cell electrochemical impedance spectroscopy (EIS), improved the battery rate capability by using the GCE as both the electrolyte and the cathode binder to reduce the resistance at the cathode-electrolyte interface, and used TEM and SEM to visualize the polymer-particle interface (full cells with (LiFePO_4) as the cathode active material and lithium metal as the anode were assembled and tested). 3) Applied the solid polymer battery to oil and gas drilling application...

In-situ and ex-situ observations of lithium de-intercalation from LiCoO₂ : atomic force microscopy and transmission electron microscopy studies

Clémençon, Anne
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 108 p.; 4865449 bytes; 4871579 bytes; application/pdf; application/pdf
ENG
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177.78918%
Lithium cobalt dioxide is the most commonly used material for positive electrodes in lithium rechargeable batteries. During lithium de-intercalation from this material, ... undergoes a number of phase transitions, which have been studied by bulk techniques and first-principles calculations. The objective of this work was to examine the effect of charge and discharge on individual LiC₀O₂ crystals. Atomic Force Microscopy and Transmission Electron Microscopy were used to observe the effects of lithium ion de-intercalation from ... in individual crystals. This work was the first study to use in-situ Atomic Force Microscopy to probe the dynamic evolution of ... crystal morphology as lithium ions are de-intercalated from the material. The overall crystal morphology did not seem to evolve very much during the first charge and discharge cycle however evidence was found for expansion and contraction of crystal steps during cycling. The evolution of layer spacing was quantified from AFM data and was found to be in agreement with X-ray diffraction studies by other researchers. Furthermore, rounded bumps were observed on the surface of most of the crystals, and it is speculated that these bumps are Li₂CO₃ impurities, formed on the surface of LiC₀O₂ after storage in air. Lastly...

Structural and electrochemical properties of Li-Ni-Co oxides synthesized by wet chemistry via a succinic-acid-assisted technique

Castro García, Socorro; Julien, C.; Señarís Rodríguez, María Antonia
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
590.55117%
Lithiated metal oxides LiCo1−yNiyO2 were synthesized by a sol–gel method using succinic acid as chelating agent. Microcrystalline materials were formed by calcination in oxygen at 800°C. The physicochemical properties of the powders (crystallinity, lattice constants, size grain) has been investigated in the compositional range 0≤y≤1. Structural studies show that a layered single phase was obtained. The local cationic environment has been studied by Raman and FTIR spectroscopy. The changes in the vibrational spectra are well related to those observed by X-ray diffraction. It is shown that the lithium predominant layers are preserved in the entire range of substitution. Pelletized LiCo1−yNiyO2 powders (0.2≤y≤1.0) were tested in Li//LiCo1−yNiyO2 cells by galvanostatic titration. These cells have an initial capacity of 140 mAh/g in the voltage range 2.8–4.2 V and show attractive charge–discharge profiles upon cycling.

Layered LiNi0.5Co0.5O2 cathode materials grown by soft-chemistry via various solution methods

Julien, C.; Letranchant, C.; Rangan, S.; Lemal, M.; Ziolkiewicz, S.; Castro García, Socorro; El-Farh, L.; Benkaddour, M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
602.41125%
The lithiated nickel–cobalt oxide LiNi0.5Co0.5O2 used as cathode material was grown at low-temperature using different aqueous solution methods. The wet chemistry involved the mixture of metal salts (acetates or nitrates) with various carboxylic acid-based aqueous solutions. Physicochemical and electrochemical properties of LiNi0.5Co0.5O2 products calcined at 400–600°C were extensively investigated. The four methods used involved complexing agents such as either citric, oxalic, aminoacetic (glycine), or succinic acid in aqueous medium which functioned as a fuel, decomposed the metal complexes at low temperature, and yielded the free impurity LiNi0.5Co0.5O2 compounds. Thermal (TG–DTA) analyses and XRD data show that powders grown with a layered structure ( space group) have been obtained at temperatures below 400°C by the acidification reaction of the aqueous solutions. The local structure of synthesized products was characterized by Fourier transform infrared (FTIR) spectroscopy. The electrochemical properties of the synthesized products were evaluated in rechargeable Li cells using a non-aqueous organic electrolyte (1 M LiClO4 in propylene carbonate, PC). The LiNi0.5Co0.5O2 positive electrodes fired at 600°C exhibited good cycling behavior.

Porous Perovskite LaNiO3 Nanocubes as Cathode Catalysts for Li-O2 Batteries with Low Charge Potential

Zhang, Jian; Zhao, Yubao; Zhao, Xiao; Liu, Zhaolin; Chen, Wei
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 08/08/2014 EN
Relevância na Pesquisa
393.15086%
Developing efficient catalyst for oxygen evolution reaction (OER) is essential for rechargeable Li-O2 battery. In our present work, porous LaNiO3 nanocubes were employed as electrocatalyst in Li-O2 battery cell. The as-prepared battery showed excellent charging performance with significantly reduced overpotential (3.40 V). The synergistic effect of porous structure, large specific surface area and high electrocatalytic activity of porous LaNiO3 nanocubes ensured the Li-O2 battery with enchanced capacity and good cycle stability. Furthermore, it was found that the lithium anode corrosion and cathode passivation were responsible for the capacity fading of Li-O2 battery. Our results indicated that porous LaNiO3 nanocubes represent a promising cathode catalyst for Li-O2 battery.

Re-building Daniell Cell with a Li-ion exchange Film

Dong, Xiaoli; Wang, Yonggang; Xia, Yongyao
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 05/11/2014 EN
Relevância na Pesquisa
291.6336%
Daniell cell (i.e. Zn-Cu battery) is widely used in chemistry curricula to illustrate how batteries work, although it has been supplanted in the late 19th century by more modern battery designs because of Cu2+-crossover-induced self-discharge and un-rechargeable characteristic. Herein, it is re-built by using a ceramic Li-ion exchange film to separate Cu and Zn electrodes for preventing Cu2+-crossover between two electrodes. The re-built Zn-Cu battery can be cycled for 150 times without capacity attenuation and self-discharge, and displays a theoretical energy density of 68.3 Wh kg−1. It is more important that both electrodes of the battery are renewable, reusable, low toxicity and environmentally friendly. Owing to these advantages mentioned above, the re-built Daniell cell can be considered as a promising and green stationary power source for large-scale energy storage.

Flexible lithium–oxygen battery based on a recoverable cathode

Liu, Qing-Chao; Xu, Ji-Jing; Xu, Dan; Zhang, Xin-Bo
Fonte: Nature Pub. Group Publicador: Nature Pub. Group
Tipo: Artigo de Revista Científica
Publicado em 03/08/2015 EN
Relevância na Pesquisa
190.55117%
Although flexible power sources are crucial for the realization next-generation flexible electronics, their application in such devices is hindered by their low theoretical energy density. Rechargeable lithium–oxygen (Li–O2) batteries can provide extremely high specific energies, while the conventional Li–O2 battery is bulky, inflexible and limited by the absence of effective components and an adjustable cell configuration. Here we show that a flexible Li–O2 battery can be fabricated using unique TiO2 nanowire arrays grown onto carbon textiles (NAs/CT) as a free-standing cathode and that superior electrochemical performances can be obtained even under stringent bending and twisting conditions. Furthermore, the TiO2 NAs/CT cathode features excellent recoverability, which significantly extends the cycle life of the Li–O2 battery and lowers its life cycle cost.

A lithium-ion battery based on a graphene nanoflakes ink anode and a lithium iron phosphate cathode

Hassoun, Jusef; Bonaccorso, Francesco; Agostini, Marco; Angelucci, Marco; Betti, Maria Grazia; Cingolani, Roberto; Gemmi, Mauro; Mariani, Carlo; Panero, Stefania; Pellegrini, Vittorio; Scrosati, Bruno
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 10/03/2014
Relevância na Pesquisa
184.70193%
Li-ion rechargeable batteries have enabled the wireless revolution transforming global communication. Future challenges, however, demands distributed energy supply at a level that is not feasible with the current energy-storage technology. New materials, capable of providing higher energy density are needed. Here we report a new class of lithium-ion batteries based on a graphene ink anode and a lithium iron phosphate cathode. By carefully balancing the cell composition and suppressing the initial irreversible capacity of the anode, we demonstrate an optimal battery performance in terms of specific capacity, i.e. 165 mAhg-1, estimated energy density of about 190 Whkg-1 and life, with a stable operation for over 80 charge-discharge cycles. We link these unique properties to the graphene nanoflake anode displaying crystalline order and high uptake of lithium at the edges, as well as to its structural and morphological optimization in relation to the overall battery composition. Our approach, compatible with any printing technologies, is cheap and scalable and opens up new opportunities for the development of high-capacity Li-ion batteries.; Comment: 17 pages, 10 figures

Charge transport in lithium peroxide: Relevance for rechargeable metal-air batteries

Radin, Maxwell D.; Siegel, Donald J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 13/05/2013
Relevância na Pesquisa
288.3229%
The mechanisms and efficiency of charge transport in lithium peroxide (Li2O2) are key factors in understanding the performance of non-aqueous Li-air batteries. Towards revealing these mechanisms, here we use first-principles calculations to predict the concentrations and mobilities of charge carriers and intrinsic defects in Li2O2 as a function of cell voltage. Our calculations reveal that changes in the charge state of O2 dimers controls the defect chemistry and conductivity of Li2O2. Negative lithium vacancies (missing Li+) and small hole polarons are identified as the dominant charge carriers. The electronic conductivity associated with polaron hopping (5 x 10-20 S/cm) is comparable to the ionic conductivity arising from the migration of Li-ions (4 x 10-19 S/cm), suggesting that charge transport in Li2O2 occurs through a mixture of ionic and polaronic contributions. These data indicate that the bulk regions of crystalline Li2O2 are insulating, with appreciable charge transport occurring only at moderately high charging potentials that drive partial delithiation. The implications of limited charge transport on discharge and recharge mechanisms are discussed, and a two-stage charging process linking charge transport, discharge product morphology...

Toward a Lithium−“Air” Battery: The Effect of CO_2 on the Chemistry of a Lithium−Oxygen Cell

Lim, Hyung-Kyu; Lim, Hee-Dae; Park, Kyu-Young; Seo, Dong-Hwa; Gwon, Hyeokjo; Hong, Jihyun; Goddard, William A., III; Kim, Hyungjun; Kang, Kisuk
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 03/07/2013
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419.77977%
Lithium–oxygen chemistry offers the highest energy density for a rechargeable system as a “lithium–air battery”. Most studies of lithium–air batteries have focused on demonstrating battery operations in pure oxygen conditions; such a battery should technically be described as a “lithium–dioxygen battery”. Consequently, the next step for the lithium–“air” battery is to understand how the reaction chemistry is affected by the constituents of ambient air. Among the components of air, CO_2 is of particular interest because of its high solubility in organic solvents and it can react actively with O_2–•, which is the key intermediate species in Li–O_2 battery reactions. In this work, we investigated the reaction mechanisms in the Li–O_2/CO_2 cell under various electrolyte conditions using quantum mechanical simulations combined with experimental verification. Our most important finding is that the subtle balance among various reaction pathways influencing the potential energy surfaces can be modified by the electrolyte solvation effect. Thus, a low dielectric electrolyte tends to primarily form Li_2O_2, while a high dielectric electrolyte is effective in electrochemically activating CO_2, yielding only Li_2CO_3. Most surprisingly...

EIS diagnostics of aged Li-ion batteries

Plancha, Maria João; Luz, Paulo P. da; Rangel, C. M.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 ENG
Relevância na Pesquisa
388.3229%
High-power batteries with long cycling life and adequate storage behaviour are needed as energy sources devices for (hybrid) electric vehicles and lithium-ion rechargeable cells are the most promising candidates. In this work, Li-ion cells with a nominal capacity of 10 Ah were studied. Electrochemical impedance spectroscopy (EIS) was used for studying the cycling ageing effect on discharge capacity fade. EIS measurements were conducted in a galvanostatic mode, by means of a Solartron Electrochemical Interface 1286 and a Solartron FRA 1250 controlled by Zplot from Scribner Associates. Scanning frequency ranged from 600 Hz to 0.005 Hz and the ac amplitude was set to 100 mA. An equivalent circuit complex non-linear least squares fitting procedure was used for spectra analyses. Cell charge transfer and film resistances were estimated at several cycle life stages and its evolution on cycle number was analysed. Capacity losses were estimated after 300, 600 and 1200 cycles at C/1 discharge rate and were found to be 5.8, 7.5 and 16.8% of the initial capacity, respectively. EIS data revealed that the major factor responsible for the observed capacity fade was the cell’s charge transfer resistance (Rct) increase following the opposite tendency of the discharge capacity values with cycle number. Very little change can be attributed to film resistances as a result of ageing by cycling. The SEI layer thickness appeared to increase from 0 to 300 cycles remaining almost constant up to 1200 cycles. The effect of a high storage temperature on the performance of the sealed commercial batteries was evaluated by means of discharge capacity measurements and impedance behaviour. The thermal ageing conditions were applied over time and the results were interpreted taking into account the cell’s state of charge (SOC). Before storage at 45 oC...