Thermally treated caffeine doped active carbon (Caffeine-Norit) is studied as a catalyst for the ... more Thermally treated caffeine doped active carbon (Caffeine-Norit) is studied as a catalyst for the oxygen reduction reaction (ORR) with application in metal-air systems and neutral aqueous electrolytes. Catalytic activity is characterized by polarization curves and Tafel plots and the results are compared with 5% Platinum (5% Pt-Norit) and 4% Silver (4% Ag-Norit) catalysts. The Tafel slopes of all three catalysts are the same, the activity of Ag-Norit being somewhat smaller then both Caffeine-Norit and Pt-Norit. The polarization curves are also comparable, especially in the low current density region. The increase of overpotential for the Caffeine-Norit at current density higher than 50 mA cm-2 is due to accumulation of H2O2 in the catalyst layer. This was demonstrated by using a simple method for detection of peroxides in neutral electrolytes based on indigo carmine indicator.
Surface characterization of Ir-based Ti- and Sn-containing electrodes of nominal composition, Ir0... more Surface characterization of Ir-based Ti- and Sn-containing electrodes of nominal composition, Ir03Ti(07)SnO2 (0 x 0.7), was performed ex situ by scanning electron microscopy and energy—dispersive x-ray and n situ by open—circuit potential measurements and cyclic voltammetry. Despite the use of SnCl2 as precursor, energy-dispersive x-ray results showed the real composition to be very distinct from nominal due to SnCl4 volatilization during the calcination step in
In contrast to lead-acid battery cells in lithium-ion battery LiFePo4 in serial connection can no... more In contrast to lead-acid battery cells in lithium-ion battery LiFePo4 in serial connection can not be balanced with each other during the loading process. This is because the current stops flowing when the cell is full. This means that LiFePO4 packs require management system (BMS}, because the proper electrical and thermal control of a lithiumion traction battery consisting of many cells, divided into several modules, is imperative. During operation, voltage, and temperature variations in the cells may result in an electrical imbalance of the cell to the cell and cause a decline in the capacity of the entire set of cells of the battery by approximately 25%. In this work is presented and analyzed by the authors developed management system (BMS) of traction modular lithium-ion battery. This system shall keep under review, control and balance the battery balancing battery, based on current accurate measurements of cell voltage and active equalization parameters. KЕYWORDS: EV-electric v...
Lithium-air batteries have recently received attention due to their high theoretical specific cap... more Lithium-air batteries have recently received attention due to their high theoretical specific capacity, which is much higher than that of existing lithium-ion batteries. This work aims to study the gas-diffusion electrode behavior in various non-aqueous electrolytes, potential candidates for use in lithium-air battery, and also its work in a semi cell against lithium metal electrode. Gas-diffusion electrode was prepared with two catalysts – pyrolyzed CoTMPP and Active Carbon Co/Ni tested in a standard 2032 button cell. The slow cycling voltammetry (CV) of CoTMPP electrode shows irreversible O2 reaction instead of Co/Ni electrode where the capacity of oxygen evolution reaction is about 3 times less than of the oxygen reduction reaction. Nevertheless, the obtained reversibility at slow CV, the galvanostatic cycling tests at 1 mA shows irreversibility of the process most probably to the very high polarization at that current.
... Titre du document / Document title. POTASSIUM BRONZES AS ACTIVE MATERIAL FOR LI-ION BATTERIES... more ... Titre du document / Document title. POTASSIUM BRONZES AS ACTIVE MATERIAL FOR LI-ION BATTERIES. Auteur(s) / Author(s). ALEKSANDROVA Albena ; UZUNOV Ivan ;BANOV Branimir ; MOMCHILOV Anton ; Revue / Journal Title. ...
The excellent results were obtained with LiV3O8 treated by water as a cathode material for rechar... more The excellent results were obtained with LiV3O8 treated by water as a cathode material for rechargeable lithium cells [1]. West at al. [2] performed parallel study on KV3O8 and K3V5O13. They found that insertion of a considerable amount of lithium ions might occur in the structure of KV3O8 but using low current rate. In contrast to LiV3O8, which is the only existing phase in the equilibrium phase diagram between V2O5 and LiVO3 [3], four different phases K3V5O14, KV3O8, K2V8O21 and KV5O13 are distinguished in the phase diagram between V2O5 and KVO3 [3]. The electrochemical behavior of those four phases was studied in [4] and it was established a very good performance of the two poor of potassium phases. On the basis of the fact that the structure of the potassium vanadates is layered as the LiV3O8 one, the same preliminary treatment by water [1] was applied to those compounds.
The rate of lithium ion insertion in different types of manganese dioxide, depending on their pre... more The rate of lithium ion insertion in different types of manganese dioxide, depending on their pretreatment temperature, was investigated. To obtain maximum utilization at heavy discharge drains, the optimum thermal pretreatment temperature for different chemical ...
163 Lithium ion batteries: active electrode materials based on manganese dioxide K. Banov, D. Iva... more 163 Lithium ion batteries: active electrode materials based on manganese dioxide K. Banov, D. Ivanova, L. Fachikov, V. Kotev, T. Stankulov, B. Banov 1,3 1 Institute of Electrochemistry and Energy Systems, IEES, 1, Acad. G. Bonchev str., bl. 10, 1113 Sofia University of Chemical Technology and Metallurgy – UCTM, bul. “Kl. Ohridski” 8, 1756 Sofia 3 European Polytechnical University – EPU, 23, “St. St. Cyril and Methodius” str., 2300 Pernik 4 Institute of Mechanics, IM, 1, Acad. G. Bonchev str., bl. 4, 1113 Sofia
This work aims at a comparative study on positive electrodes used in advanced rechargeable lithiu... more This work aims at a comparative study on positive electrodes used in advanced rechargeable lithium batteries. The relationship between structural and electrochemical properties is examined with materials currently studied as lithium intercalation compounds for their potential use in Li-ion batteries. Three types of transition-metal oxides are considered, namely, MnO 2 , LiMn 2 O 4 and LiNi 1-y M y O 2 compounds in their various frameworks. Based on the correlation between structural stability and capacity retention of host lattices, the various methods to improve the cycle life of the Li-ion cell are discussed.
New Trends in Intercalation Compounds for Energy Storage, 2002
ABSTRACT The production of 3C products in electronics information and communication has now been ... more ABSTRACT The production of 3C products in electronics information and communication has now been oriented toward wireless and portable electronic devices. Therefore the high performance components of the product are designed to be “lighter, thinner, short, smaller”. For this reason urgent demand exist for secondary batteries that are more compact, lighter and higher energy density. The second big market of lithium batteries will be the electrical bikes and electrical cars. The battery industry requires the integration of various technologies in the field of chemistry, material science, knowhow, etc. The continuous development on the theoretical side and furthermore a long period of experience in R&D groups are also needed. The market demands products to be lighter, reliable, with higher electric power capacity and improved safety design. The commercially available rechargeable lithium batteries refers to the Li-Ion battery which uses carbon powder as negative active electrode material and lithiated metallic oxides as cobaltate and nickelate for positive active electrode material. For the moment only LiCoO2 (lithium cobaltate) as positive electrode material occupies the market. However, the cost of LiCoO2 material is so high that it would take up too much of the battery cost and besides, its specific energy density is not the highest, therefore, it may be replaced by the concurrent LiNiO2. The price of LiNiO2 material is less expensive with the highest specific gravimetric capacity, but it is difficult for synthesis and treatment. Both materials are not environmentally friendly.
NATO Science for Peace and Security Series B: Physics and Biophysics, 2009
Si/C composites have been employed in an attempt to overcome the problems of Si-based negative Li... more Si/C composites have been employed in an attempt to overcome the problems of Si-based negative Li-ion electrodes. The composites were produced by coating, followed by a two-step solid state reaction. Electrodes were prepared therefrom by spreading on a Cu foil. The materials were characterized by SEM and XRD. The Si phase in the composite shows an enhanced crystalline structure compared
New Trends in Intercalation Compounds for Energy Storage, 2002
ABSTRACT The manganese spinel is one of the most investigated materials for lithium-ion batteries... more ABSTRACT The manganese spinel is one of the most investigated materials for lithium-ion batteries because of its relatively low cost, high working voltage and environmental benignity. There are several different methods for manganese spinel obtaining, namely: solid-state reaction, melt-impregnation, the Pechini process, emulsion-drying method and sol-gel method [1-3]. The starting capacity and cyclability of the obtained material depend on the starting compounds and synthesis conditions. The particle size of the cathode materials obtained by the mentioned above methods varies from a hundredth nanometres to about ten microns. These materials manifest electrochemical activity after heating at temperatures above 450°C (capacity from 45 mAh/g at 450°C to 115-120 mAh/g at 800°C are obtained) [4-6].
New Trends in Intercalation Compounds for Energy Storage, 2002
ABSTRACT The particle size of the active cathode materials for lithium ion batteries plays an imp... more ABSTRACT The particle size of the active cathode materials for lithium ion batteries plays an important role for the electrochemical behaviour of the cell [1-5]. Two main technological principles are in the basis of proposed method of synthesis of active electrode materials with controlled particle size: a convective drying in liquid agent followed by firing in gas media. Varying the parameters responsible for the obtained particles size, as volume of drops and concentration of starting solution, it can be synthesised homogeneous electrode materials with controlled grain size ranged form 1.5 μm to 50 nm.
Thermally treated caffeine doped active carbon (Caffeine-Norit) is studied as a catalyst for the ... more Thermally treated caffeine doped active carbon (Caffeine-Norit) is studied as a catalyst for the oxygen reduction reaction (ORR) with application in metal-air systems and neutral aqueous electrolytes. Catalytic activity is characterized by polarization curves and Tafel plots and the results are compared with 5% Platinum (5% Pt-Norit) and 4% Silver (4% Ag-Norit) catalysts. The Tafel slopes of all three catalysts are the same, the activity of Ag-Norit being somewhat smaller then both Caffeine-Norit and Pt-Norit. The polarization curves are also comparable, especially in the low current density region. The increase of overpotential for the Caffeine-Norit at current density higher than 50 mA cm-2 is due to accumulation of H2O2 in the catalyst layer. This was demonstrated by using a simple method for detection of peroxides in neutral electrolytes based on indigo carmine indicator.
Surface characterization of Ir-based Ti- and Sn-containing electrodes of nominal composition, Ir0... more Surface characterization of Ir-based Ti- and Sn-containing electrodes of nominal composition, Ir03Ti(07)SnO2 (0 x 0.7), was performed ex situ by scanning electron microscopy and energy—dispersive x-ray and n situ by open—circuit potential measurements and cyclic voltammetry. Despite the use of SnCl2 as precursor, energy-dispersive x-ray results showed the real composition to be very distinct from nominal due to SnCl4 volatilization during the calcination step in
In contrast to lead-acid battery cells in lithium-ion battery LiFePo4 in serial connection can no... more In contrast to lead-acid battery cells in lithium-ion battery LiFePo4 in serial connection can not be balanced with each other during the loading process. This is because the current stops flowing when the cell is full. This means that LiFePO4 packs require management system (BMS}, because the proper electrical and thermal control of a lithiumion traction battery consisting of many cells, divided into several modules, is imperative. During operation, voltage, and temperature variations in the cells may result in an electrical imbalance of the cell to the cell and cause a decline in the capacity of the entire set of cells of the battery by approximately 25%. In this work is presented and analyzed by the authors developed management system (BMS) of traction modular lithium-ion battery. This system shall keep under review, control and balance the battery balancing battery, based on current accurate measurements of cell voltage and active equalization parameters. KЕYWORDS: EV-electric v...
Lithium-air batteries have recently received attention due to their high theoretical specific cap... more Lithium-air batteries have recently received attention due to their high theoretical specific capacity, which is much higher than that of existing lithium-ion batteries. This work aims to study the gas-diffusion electrode behavior in various non-aqueous electrolytes, potential candidates for use in lithium-air battery, and also its work in a semi cell against lithium metal electrode. Gas-diffusion electrode was prepared with two catalysts – pyrolyzed CoTMPP and Active Carbon Co/Ni tested in a standard 2032 button cell. The slow cycling voltammetry (CV) of CoTMPP electrode shows irreversible O2 reaction instead of Co/Ni electrode where the capacity of oxygen evolution reaction is about 3 times less than of the oxygen reduction reaction. Nevertheless, the obtained reversibility at slow CV, the galvanostatic cycling tests at 1 mA shows irreversibility of the process most probably to the very high polarization at that current.
... Titre du document / Document title. POTASSIUM BRONZES AS ACTIVE MATERIAL FOR LI-ION BATTERIES... more ... Titre du document / Document title. POTASSIUM BRONZES AS ACTIVE MATERIAL FOR LI-ION BATTERIES. Auteur(s) / Author(s). ALEKSANDROVA Albena ; UZUNOV Ivan ;BANOV Branimir ; MOMCHILOV Anton ; Revue / Journal Title. ...
The excellent results were obtained with LiV3O8 treated by water as a cathode material for rechar... more The excellent results were obtained with LiV3O8 treated by water as a cathode material for rechargeable lithium cells [1]. West at al. [2] performed parallel study on KV3O8 and K3V5O13. They found that insertion of a considerable amount of lithium ions might occur in the structure of KV3O8 but using low current rate. In contrast to LiV3O8, which is the only existing phase in the equilibrium phase diagram between V2O5 and LiVO3 [3], four different phases K3V5O14, KV3O8, K2V8O21 and KV5O13 are distinguished in the phase diagram between V2O5 and KVO3 [3]. The electrochemical behavior of those four phases was studied in [4] and it was established a very good performance of the two poor of potassium phases. On the basis of the fact that the structure of the potassium vanadates is layered as the LiV3O8 one, the same preliminary treatment by water [1] was applied to those compounds.
The rate of lithium ion insertion in different types of manganese dioxide, depending on their pre... more The rate of lithium ion insertion in different types of manganese dioxide, depending on their pretreatment temperature, was investigated. To obtain maximum utilization at heavy discharge drains, the optimum thermal pretreatment temperature for different chemical ...
163 Lithium ion batteries: active electrode materials based on manganese dioxide K. Banov, D. Iva... more 163 Lithium ion batteries: active electrode materials based on manganese dioxide K. Banov, D. Ivanova, L. Fachikov, V. Kotev, T. Stankulov, B. Banov 1,3 1 Institute of Electrochemistry and Energy Systems, IEES, 1, Acad. G. Bonchev str., bl. 10, 1113 Sofia University of Chemical Technology and Metallurgy – UCTM, bul. “Kl. Ohridski” 8, 1756 Sofia 3 European Polytechnical University – EPU, 23, “St. St. Cyril and Methodius” str., 2300 Pernik 4 Institute of Mechanics, IM, 1, Acad. G. Bonchev str., bl. 4, 1113 Sofia
This work aims at a comparative study on positive electrodes used in advanced rechargeable lithiu... more This work aims at a comparative study on positive electrodes used in advanced rechargeable lithium batteries. The relationship between structural and electrochemical properties is examined with materials currently studied as lithium intercalation compounds for their potential use in Li-ion batteries. Three types of transition-metal oxides are considered, namely, MnO 2 , LiMn 2 O 4 and LiNi 1-y M y O 2 compounds in their various frameworks. Based on the correlation between structural stability and capacity retention of host lattices, the various methods to improve the cycle life of the Li-ion cell are discussed.
New Trends in Intercalation Compounds for Energy Storage, 2002
ABSTRACT The production of 3C products in electronics information and communication has now been ... more ABSTRACT The production of 3C products in electronics information and communication has now been oriented toward wireless and portable electronic devices. Therefore the high performance components of the product are designed to be “lighter, thinner, short, smaller”. For this reason urgent demand exist for secondary batteries that are more compact, lighter and higher energy density. The second big market of lithium batteries will be the electrical bikes and electrical cars. The battery industry requires the integration of various technologies in the field of chemistry, material science, knowhow, etc. The continuous development on the theoretical side and furthermore a long period of experience in R&D groups are also needed. The market demands products to be lighter, reliable, with higher electric power capacity and improved safety design. The commercially available rechargeable lithium batteries refers to the Li-Ion battery which uses carbon powder as negative active electrode material and lithiated metallic oxides as cobaltate and nickelate for positive active electrode material. For the moment only LiCoO2 (lithium cobaltate) as positive electrode material occupies the market. However, the cost of LiCoO2 material is so high that it would take up too much of the battery cost and besides, its specific energy density is not the highest, therefore, it may be replaced by the concurrent LiNiO2. The price of LiNiO2 material is less expensive with the highest specific gravimetric capacity, but it is difficult for synthesis and treatment. Both materials are not environmentally friendly.
NATO Science for Peace and Security Series B: Physics and Biophysics, 2009
Si/C composites have been employed in an attempt to overcome the problems of Si-based negative Li... more Si/C composites have been employed in an attempt to overcome the problems of Si-based negative Li-ion electrodes. The composites were produced by coating, followed by a two-step solid state reaction. Electrodes were prepared therefrom by spreading on a Cu foil. The materials were characterized by SEM and XRD. The Si phase in the composite shows an enhanced crystalline structure compared
New Trends in Intercalation Compounds for Energy Storage, 2002
ABSTRACT The manganese spinel is one of the most investigated materials for lithium-ion batteries... more ABSTRACT The manganese spinel is one of the most investigated materials for lithium-ion batteries because of its relatively low cost, high working voltage and environmental benignity. There are several different methods for manganese spinel obtaining, namely: solid-state reaction, melt-impregnation, the Pechini process, emulsion-drying method and sol-gel method [1-3]. The starting capacity and cyclability of the obtained material depend on the starting compounds and synthesis conditions. The particle size of the cathode materials obtained by the mentioned above methods varies from a hundredth nanometres to about ten microns. These materials manifest electrochemical activity after heating at temperatures above 450°C (capacity from 45 mAh/g at 450°C to 115-120 mAh/g at 800°C are obtained) [4-6].
New Trends in Intercalation Compounds for Energy Storage, 2002
ABSTRACT The particle size of the active cathode materials for lithium ion batteries plays an imp... more ABSTRACT The particle size of the active cathode materials for lithium ion batteries plays an important role for the electrochemical behaviour of the cell [1-5]. Two main technological principles are in the basis of proposed method of synthesis of active electrode materials with controlled particle size: a convective drying in liquid agent followed by firing in gas media. Varying the parameters responsible for the obtained particles size, as volume of drops and concentration of starting solution, it can be synthesised homogeneous electrode materials with controlled grain size ranged form 1.5 μm to 50 nm.
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