To increase electrode cycling performance in lithium batteries, most researchers generally play on the active material optimization. In this paper, it is shown that there is also a need for fundamental studies in the field of nonactive components of the composite electrode. Optimization of the environment of Li 1.2 V 3 O 8 active material within the composite electrode leads to a roomtemperature cycling capacity of 280 mAh/g instead of 180 mAh/g with Bellcore-type electrode. Well performing composite electrode was achieved with efficient electronic conduction network, good carbon black/Li 1.2 V 3 O 8 interface, and total collection of active material grains. The key role of the homogeneous and efficient carbon black ͑CB͒ distribution, due to good interactions between pre-plastifed polyethylene oxide binder and CB, and optimized PEO/CB ratio, has been determined.Polymers are mostly studied for their application as the electrolyte solvent of lithium batteries, 1 rather than for their application as the binder of composite electrodes. As a result, for composite electrodes in liquid or gelled electrolyte, the binder used is almost always Poly͑tetrafluoro ethylene͒ ͑PTFE͒ or poly͑vinylidene fluoride͒ ͑PVdF͒ based polymers. However, remarkable improvement resulted from the use of a copolymer of vinylidene fluoride with hexafluoropropylene ͑PVdF-HFP͒ in both electrolyte and composite electrode, which lead to the well-known LiPLIon technology. 2 Few recent papers give examples of composite electrodes made with other polymers. 3-6 The main goals were to achieve a higher liquid electrolyte uptake by selecting less crystalline polymers, thus leading to larger ionic conductivity, or to decrease capacity fading with chemically more stable polymers. In fact, little is known on the exact role of the polymer binder on composite electrode performance and we think there is a need for fundamental researches on model systems.This study focuses on the polymeric binder used for lithium trivanadate (Li 1.2 V 3 O 8 ) based composite electrodes, and its influence on the battery performance. Li 1.2 V 3 O 8 that offers a theoretical capacity of 360 mAh/g was investigated as a very promising positive electrode material during the past two decades. 7-10 However, the experimental capacity generally remains much lower than the theoretical value. It is actually of only 180 mAh/g with Bellcore-type composite electrode. 2 Li 1.2 V 3 O 8 is thus a material of choice to investigate the influence of the binder on the composite electrode capacity.In this paper, the Li insertion and cycling behaviors of a given Li 1.2 V 3 O 8 compound are studied in the same experimental conditions when varying only the polymeric binder of the composite electrode. These data are compared to that obtained with Bellcore-type electrode, considered as a reference.
ExperimentalA home-synthesized Li 1.2 V 3 O 8 ͑at 580°C 11 ͒ was used as the active material, and carbon black ͑Super-P, noted CB͒ as a conductive agent. The binders were pure polyethylene oxide ͑PEO͒, plastifie...
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