Lithium hectorite clay as the ionic conductor in LiCoO2 cathodes

Cathodes based on LiCoO2 that contain various lithium-conducting species (lithium hectorite, lithium Laponite, and lithium-exchanged Nafion) are studied in conjunction with lithium metal anodes and composite electrolytes based upon lithium hectorite clays as the charge carrier. Performance is compared to that of cells with a standard liquid electrolyte (i.e., LiPF6 +1:1 w/w ethylene carbonate:ethyl methyl carbonate). Effects on cathode capacity are examined for these variables: hot-press force used in construction of the porous cathode, carbon type (graphite vs. carbon black), and clay particle size. AC impedance spectroscopy is used to probe the cells and equivalent circuits are used to model the physical processes that occur. Cathodes containing 4 wt% lithium hectorite +3 wt% lithium-exchanged Nafion +3 wt% carbon black exhibit discharge capacities approximately 90 mAh/g LiCoO2 compared to that observed in a standard cell of 110 mAh/g LiCoO2. These clay-containing cathodes are potentially attractive for use in single-ion conducting lithium-ion batteries designed for high discharge applications.