Maximal Utilization of a High-Loading Cathode in Li-O2 Batteries: A Double Oxygen Supply System.

To realize the potential high capacity of lithium-oxygen (Li-O2) batteries, a double oxygen supply system for cells with high-loading cathodes is devised in this study. High-loading thick electrodes can achieve exceptionally high capacities, but this promise has been plagued by partial utilization of thick electrodes in Li-O2 cells due to the kinetic limitation imposed by oxygen transport. The proposed double oxygen supply system provides oxygen gas to the cathode not only from the cathode opening but also from the separator side to ensure sufficient oxygen supply to the whole high-loading electrode. Subsequently, the entire region of the high-loading cathode is rendered active, resulting in a uniform vertical distribution of discharge products. The maximum utilization of the high-loading electrodes is, thus, achieved, along with a remarkably increased capacity, low overpotential, and cycle life. By this strategy, CNT cathodes can be cycled with a capacity of 5 mAh cm-2, without using any additional catalyst.

Direct Observation of Carboxymethyl Cellulose and Styrene-Butadiene Rubber Binder Distribution in Practical Graphite Anodes for Li-Ion Batteries.

Despite the important role of carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) binders in graphite electrodes for Li-ion batteries, the direct analysis of these binders remains challenging, particularly at very low concentrations as in practical graphite anodes. In this paper, we report the systematic investigation of the physiochemical behavior of the CMC and SBR binders and direct observations of their distributions in practical graphite electrodes. The key to this unprecedented capability is combining the advantages of several analytic techniques, including laser-ablation laser-induced break-down spectroscopy, time of flight secondary ion mass spectrometry, and a surface and interfacial cutting analysis system. By correlating the vertical distribution with the adsorption behaviors of the CMC, our study reveals that the CMC migration toward the surface during the drying process depends on the degree of cross-linked binder-graphite network generation, which is determined by the surface property of graphite and CMC materials. The suggested analytical techniques enable the independent tracing of CMC and SBR, disclosing the different vertical distribution of SBR from that of the CMC binder in our practical graphite anodes. This achievement provides additional opportunity to analyze the correlation between the binder distribution and mechanical properties of the electrodes.