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See detailResorcinol-Formaldehyde Carbon Xerogels as Lithium-Ion Battery Anodes: Synthesis, Grinding, Coating on current collector and Electrochemical characterization
Piedboeuf, Marie-Laure ULg; Léonard, Alexandre ULg; Pirard, Jean-Paul ULg et al

Poster (2014, July 17)

Rechargeable lithium-ion batteries show great advantages over traditional batteries and are extensively used for consumer electronic devices due to their high energy density and long cycle life. However ... [more ▼]

Rechargeable lithium-ion batteries show great advantages over traditional batteries and are extensively used for consumer electronic devices due to their high energy density and long cycle life. However, the improvement of performance of current lithium-ion batteries requires the optimization of the materials used (electrolyte and electrodes). Therefore, tremendous efforts have been dedicated to exploring new materials with high capacity, excellent cycling performance, low cost and high safety features [1-4]. As an example, carbon xerogels are promising candidates in the development of new high performance C-based anode materials for Li-ion batteries, since such carbonaceous materials show very small changes of volume during the charge/discharge process, providing an improved cycle life. Nevertheless, hard carbons also exhibit quite high irreversible capacity losses due to their intrinsic high microporosity and, compared to graphite, a poor rate performance related to slow diffusion of Li in the internal structure [5-6]. To reduce these disadvantages, the structural and textural characteristics need to be carefully controlled. Also, due to the different morphology of these materials compared to graphite, the deposition of carbon xerogels on current collectors needs to be studied in detail. In this work, porous carbon xerogels were synthetized from Resorcinol-Formaldehyde mixtures by adjusting the pH of the solution in order to obtain different mesopore sizes. Monoliths of carbon xerogels were obtained after drying of the polymer gel and pyrolysis [7]. Mercury intrusion porosimetry and nitrogen adsorption techniques (BET) was used to characterize the pore texture of the carbon xerogels. These monoliths were ground to particles around 10 µm for all the samples. The resulting powders were then mixed with a binder and a solvent to form slurries and then cast on copper foil using a bar coater. After evaporation of the solvent, the resulting coatings were analyzed using scanning electron microscopy (SEM) for the morphology and their thickness was monitored by profilometry. The resulting electrodes were subjected to electrochemical characterization. Since the particle sizes and the method of coating was the same for all the samples, it was possible to evaluate selectively the influence of the textural and structural parameters of the different carbon materials on their performances. Electrochemical characterizations were performed using charge-discharge galvanostatic curves and cyclic voltammetry in Li/C half cells between 0.005 and 1.5 V vs. Li+/Li. References 1) Goodenough J.B., Kim Y. J. Power Sources 2011; 196(16): 6688-6694. 2) Bruce P.G. Solid State Ionics 2008; 179: 752-760. 3) Armand M., Tarascon J.-M., Nature 2008; 451: 652-657. 4) Scrosati B., Garche J., J. Power Sources 2010 ; 195 : 2419-2430. 5) Yuan X., Chao Y.-J., Ma Z.-F., Deng X., Electrochemistry Communications 2007 ; 9 : 2591-2595. 6) Zanto E.J., Ritter J.A., Popov B.N., Proceedings - Electrochemical Society 1999; 98-16: 71-8. 7) Job N., Théry A., Pirard R., Marien J., Kocon L., Rouzaud J., Béguin F., Pirard J. Carbon 2005; 43: 2481-2494. [less ▲]

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See detailInfluence du broyage mécanique sur la taille et les paramètres texturaux de particules de xérogels de carbone
Piedboeuf, Marie-Laure ULg; Léonard, Alexandre ULg; Traina, Karl et al

Conference (2014, May 15)

Les xérogels de carbone sont des candidats prometteurs pour une utilisation dans de nombreux domaines tels que le stockage de l’énergie électrochimique (anodes pour batteries Li-ion ou supercondensateurs ... [more ▼]

Les xérogels de carbone sont des candidats prometteurs pour une utilisation dans de nombreux domaines tels que le stockage de l’énergie électrochimique (anodes pour batteries Li-ion ou supercondensateurs), l’adsorption ou en tant que supports de catalyseurs (dont les électrocatalyseurs de pile à combustible PEM, par exemple) [1]. En plus de leur grande pureté, un des avantages principaux des xérogels de carbone est de pouvoir contrôler leur texture poreuse notamment via les conditions de synthèse [2, 3]. Ce sont les étapes de séchage et de pyrolyse qui permettent de moduler la texture finale des matériaux obtenus. Après vieillissement, les mélanges aqueux résorcinol-formaldéhyde mènent à des gels polymères susceptibles d’être convertis en polymères secs après séchage sous vide et, in fine, en xérogels de carbone après pyrolyse sous atmosphère inerte. Au cours de ces étapes, les produits obtenus restent cependant sous forme monolithique. Dans le cadre des applications pré-citées (catalyse, stockage électrochimique ou adsorption), il est néanmoins nécessaire de réduire les pièces monolithiques en particules de dimensions appropriées pour l’application cible. Dans ce cas, une étape clé est de pouvoir contrôler leur taille finale. Le comportement à l’attrition de matériaux présentant différentes textures poreuses a été étudié en détail. Les broyages ont été effectués dans un broyeur planétaire en conditions sèche ou humide sur des gels polymères secs ainsi que sur des xérogels de carbone obtenus après pyrolyse à 800°C. La granulométrie laser à diffraction lumineuse ainsi que la microscopie électronique à balayage ont été utilisées afin d’évaluer la distribution des tailles particulaires de la poudre broyée. Les résultats indiquent que la texture poreuse des matériaux, leur nature (polymère ou carbone) et leur dureté sont des facteurs significatifs qui influencent fortement les mécanismes de comminution/fragmentation lors du broyage, en particulier si l’on considère les xérogels de carbone. En effet, il apparait que le broyage par voie sèche de polymères secs (avant pyrolyse) semble être la manière la plus efficace pour obtenir une distribution de taille de particules homogène pour toutes les textures poreuses étudiées. Dans les conditions de broyage employées, il est possible d’obtenir des particules carbonées présentant une distribution de taille de particules centrée sur 10 µm, avec rétention de la texture mésoporeuse. Les résultats de cette recherche montrent également la possibilité d’utiliser la porosimétrie à intrusion de mercure en tant qu’outil pour évaluer simultanément la taille des mésopores ainsi que la taille des particules de matériaux broyés. 1. Yuan, X., Y.-J. Chao, Z.-F. Ma and X. Deng, Electrochemistry Communications, 9(10), 2591-2595 (2007). 2. Job, N., R. Pirard, J. Marien and J.-P. Pirard, Carbon, 42(3): p. 619-628 (2004). 3. Scherdel, C., R. Gayer and G. Reichenauer, J Porous Mater, 19(3): p. 351-360 (2012).  [less ▲]

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See detailRapid aqueous synthesis of ordered mesoporous carbons: Investigation of synthesis variables and application as anode materials for Li-ion batteries
Léonard, Alexandre ULg; Gommes, Cédric ULg; Piedboeuf, Marie-Laure ULg et al

in Microporousand Mesoporous Materials (2014), 195

Ordered mesoporous carbons (OMC) were synthesized via a direct templating pathway by a synthesis route that features short duration, moderate temperature and aqueous media. Resorcinol was used as carbon ... [more ▼]

Ordered mesoporous carbons (OMC) were synthesized via a direct templating pathway by a synthesis route that features short duration, moderate temperature and aqueous media. Resorcinol was used as carbon precursor and hexamethylenetetramine as a source of formaldehyde and ammonia to respectively cross-link the framework and regulate the pH. The temperature of the heat treatment leading to the formation of the solid polymer was shown to have a strong influence on the structural and textural parameters. In particular, moderate temperatures led to the coexistence of differently-sized entangled hexagonal mesostructures, whereas the higher temperatures led to a sharp decrease in the mesopore volume. The performance of these materials as anode materials for Li-ion batteries has been investigated in detail. Although these OMC show reversible capacities similar to those reported for hard carbons, their long-term cycling remains very stable for over 100 cycles of charge/discharge. The optimization of the reported short preparation pathway offers new possibilities regarding the application of ordered mesoporous carbons in various fields, such as energy storage, sorption and heterogeneous catalysis [less ▲]

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See detailResorcinol-Formaldehyde Carbon Xerogels as Anode Material for Lithium-Ion Battery: Synthesis, Grinding and Coating on Current Collector
Piedboeuf, Marie-Laure ULg; Léonard, Alexandre ULg; Pirard, Jean-Paul ULg et al

Poster (2013, September 24)

Rechargeable lithium-ion batteries show great advantages over traditional batteries and are extensively used for consumer electronic devices due to their high energy density and long cycle life. However ... [more ▼]

Rechargeable lithium-ion batteries show great advantages over traditional batteries and are extensively used for consumer electronic devices due to their high energy density and long cycle life. However, the improvement of performance of current lithium-ion batteries requires the optimization of the materials used (electrolyte and electrodes). Therefore, tremendous efforts have been dedicated to exploring new materials with high capacity, excellent cycling performance, low cost and high safety features [1-3]. As an example, carbon xerogels are promising candidates in the development of new high performance C-based anode materials for Li-ion batteries, since such carbonaceous materials show very small changes of volume during the charge/discharge process, providing a long cycle life. Nevertheless, hard carbons also exhibit quite high irreversible capacity losses due to their intrinsic high microporosity [4]. To overcome these disadvantages, the structural and textural characteristics need to be carefully controlled. Also, due to the different morphology of these materials compared to graphite, the deposition of carbon xerogels on current collectors needs to be studied in detail. In this work, porous carbon xerogels have been synthesized from Resorcinol-Formaldehyde mixtures by adjusting the pH of the solution in order to obtain different mesopore sizes. Monoliths of carbon xerogels are obtained after drying of the polymer gel and pyrolysis [5]. These monoliths have been ground by two different methods and particle size distributions were measured by granulometry. Mercury intrusion porosimetry and nitrogen adsorption techniques (BET) have been used to characterize the pore texture of the monolithic and the powder materials. Different conditions have been used for the mixing of carbon xerogels with a binder and a solvent to form slurries. The latter have been cast on a copper foil using bar coating with different openings. After evaporation of the solvent, the resulting coatings were analyzed using scanning electron microscopy (SEM) for the morphology and their thickness was monitored by profilometry. First results indicate that the method of grinding has no influence on the final particle size distribution of the powder. The structural features of the carbon xerogels is well preserved for particles down to one micrometer. Nevertheless, a study of grinding duration shows that additional particles with sizes close to that of the porosity of the carbon appear. As a consequence, the grinding conditions were chosen so as to obtain a compromise between particles small enough to realize a coating on a current collector and particles large enough to maintain the carbon gel structural characteristics. References 1) Goodenough J.B., Kim Y. J. Power Sources 2011; 196(16): 6688-6694. 2) Bruce P.G. Solid State Ionics 2008; 179: 752-760. 3) Cairns A. J., Albertus P. Ann. Rev. Chem. Biomol. Eng. 2010; 1: 299-320. 4) Tran T., Yebka B., Song X., Nazri G., Kinoshita K., Curtis D. J. Power Sources 2000; 85: 269-278. 5) Job N., Théry A., Pirard R., Marien J., Kocon L., Rouzaud J., Béguin F., Pirard J. Carbon 2005; 43: 2481-2494. [less ▲]

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See detailXérogels de carbone à base de résorcinol-formaldéhyde en tant que matériaux d’anode pour batterie Li-ion; Synthèse et broyage avec contrôle de la granulométrie
Piedboeuf, Marie-Laure ULg; Léonard, Alexandre ULg; Pirard, Jean-Paul ULg et al

Conference (2013, May)

Xérogels de carbone à base de résorcinol-formaldéhyde en tant que matériaux d’anode pour batteries Li-ion : synthèse et broyage avec contrôle de la granulométrie Les xérogels de carbone sont des candidats ... [more ▼]

Xérogels de carbone à base de résorcinol-formaldéhyde en tant que matériaux d’anode pour batteries Li-ion : synthèse et broyage avec contrôle de la granulométrie Les xérogels de carbone sont des candidats prometteurs en tant que matériaux d’anodes de batterie Li-ion étant donné que leur faible variation de volume lors des cycles de charge-décharge devrait conduire à une durée de vie plus élevée. Néanmoins, du fait de leur morphologie fort différente de celle du graphite, tout un travail de mise au point du dépôt sur collecteur de courant se doit d’être effectué. Une partie de cette étude consiste à contrôler la granulométrie des particules issues du processus de broyage préalable à la préparation d’une encre. Dans ce travail, quatre xérogels de carbone de textures différentes ont été synthétisés et deux méthodes de broyage ont été utilisées pour réduire la taille des monolithes obtenus après synthèse. Les premiers résultats indiquent que la méthode de broyage n’a pas d’influence sur la distribution de la taille des particules et la structure des matériaux est bien conservée pour des particules de taille allant jusqu’au micromètre. [less ▲]

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See detailResorcinol-formaldehyde carbon xerogels as lithium-ion battery anode materials: influence of porosity on capacity and cycling behaviour
Piedboeuf, Marie-Laure ULg; Léonard, Alexandre ULg; Khomenko, Volodymyr et al

Poster (2012, July 05)

Carbon xerogels are promising candidates in the development of new high performance C-based anode materials for Li-ion batteries. Indeed, their specific capacities widely exceed that of conventional ... [more ▼]

Carbon xerogels are promising candidates in the development of new high performance C-based anode materials for Li-ion batteries. Indeed, their specific capacities widely exceed that of conventional graphitic structures, and they can be intercalated/deintercalated in a low-cost electrolyte based on propylene carbonate (PC), which has an excellent conductivity at low temperatures. In addition, such carbonaceous materials show very small changes of volume during the charge/discharge, providing a long cycle life of such an anode. Nevertheless, hard carbons also exhibit quite high irreversible capacity losses due to their intrinsic high microporosity and, compared to graphite, a poor rate performance related to slow diffusion of Li in the internal structure[1]. To reduce these disadvantages, the structural and textural characteristics need to be carefully controlled. Porous carbon xerogels can easily be prepared from resorcinol-formaldehyde aqueous mixtures, which are polymerized, dried and pyrolysed. The porosity of these xerogels is mainly governed by the pH of the precursor solution as well as by the drying procedure. Globally, these materials are composed of microporous nodules delimiting meso- or macroporous voids, the size of which is adjusted via the synthesis pH. Too a high microporosity can induce considerable irreversible capacity losses and too small mesopores may hinder the proper chemical diffusion of lithium ions within a bulk electrode material. The latter is often a rate-limiting step and optimized transport pathways could be provided by creating large mesopores or even macropores within the microporous carbon [3]. Here we report on the preliminary electrochemical characterization of porous carbon xerogels prepared by vacuum drying procedure. By adjusting the pH of the precursor solution, the materials obtained develop low to high values of specific surface areas and exhibit homogeneous pore sizes that range from several microns to several nanometers. The electrochemical performance of these materials as electrode compounds was tested by galvanostatic charge-discharge of 16-mm disc electrodes assembled in CR2016 coin cells or of 13-mm disc electrodes in home-made Swagelok-type cells. The first results show that all the samples show quite a high irreversible capacity during the first cycle; this irreversible capacity is proportional to the specific surface area. Its value nevertheless remains quite low for the low-surface area macroporous sample. The latter also shows the best reversible capacity after the second cycle, with values approaching that of commonly used graphite. For example, when cycled at a rate of C/20 for 10 cycles, this sample showed a capacity of 320 mAh/g; the value was kept at 200 mAh/g when increasing the rate up to C/5. The long-term cycling performance was investigated by cycling the anodes at C/20 and C/5. Again, the macroporous sample behaves best, with superior capacity retention and invariable discharge capacity of ~175 mAh/g after more than 100 cycles. The electrochemical properties of carbon xerogels was evaluated in the conditions which are used typically for graphite (cycles in the potentials range from 0.003 to 1.5 V vs. Li+/Li). A higher reversible capacity of 400 mAh/g could be obtained for the macroporous sample using a discharge with plating of Li as described in [4], but this method could not be accepted in the case of Lithium-ion batteries. These first results show that carbon xerogels are very promising candidates as anode materials for Li batteries, providing the textural characteristics are carefully controlled. The ongoing work is dealing with the establishment of possible relationships between textural features and electrochemical performance in order to shed light on the requirements that will dictate the best synthesis procedures. References: [1] T. Tran, B. Yebka, X. Song, G. Nazri, K. Kinoshita and D. Curtis, J. Power Sources, 85, 269, 2000. [2] N. Job, A. Théry, R. Pirard, J. Marien, L. Kocon, J.-N. Rouzaud, F. Béguin and J.-P. Pirard, Carbon 43, 2481, 2005. [3] F. Cheng, Z. Tao, J. Liang, and J. Chen, Chem. Mater., 20, 667, 2008. [4] W. Xing, J. S. Xue, J.R. Dahn, J. Electrochem. Soc, 143, 3046, 1996. [less ▲]

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See detailResorcinol-formaldehyde carbon xerogels as lithium-ion battery anode materials: influence of porosity on capacity and cycling behaviour
Léonard, Alexandre ULg; Piedboeuf, Marie-Laure ULg; Khomenko, Volodymyr et al

in Fagadar-Cosma, Eugenia (Ed.) Insights into novel solid materials, their recyclability and integration into Li polymer batteries for EVs. Future research directions in this field.:Book of abstracts (2012, July)

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See detailResorcinol-formaldehyde carbon xerogels as lithium-ion battery anode materials: influence of porosity on capacity and cycling behaviour
Léonard, Alexandre ULg; Piedboeuf, Marie-Laure ULg; Khomenko, Volodymyr et al

in Proceedings of the International Carbon Conference 2012 (2012)

Detailed reference viewed: 103 (16 ULg)