Controlling of Dispersion State of Particles in Slurry and Electrochemical Properties of Electrodes

Abstract

The electrode materials which exhibit high capacity have attracted much attention because the capacity of the materials directly commits to the energy density of LIBs and driving miles of EVs. So that, many researchers devote their efforts to find new electrode materials with high capacity such as lithium excess layered oxide, Ni-rich materials and silicon. Electrode manufacturing process, generally consists of (1) preparing slurry, (2) coating the slurry on current collector, (3) drying, (4) pressing steps, is another important issue to achieve LIBs with high energy density.Compared with numerous reports described with the electrode material development, however, only the limited numbers of papers related to the electrode construction process have been published [1-5]. To shed light the relationship between the electrode construction process and the battery performance is an essential research for obtaining the best performance from electrode materials and assembled LIB cells.In the present study, we focused our attention on the slurry preparation step among above-mentioned four steps. The slurry preparation is the first step in the electrode construction process, and we recognize the dispersion state of particles achieved during slurry preparation greatly influences the battery performance.Three different preparation processes were applied to achieve the different dispersion state of particles in slurries, and thus obtained slurries are characterized by rheological measurement. It is found that dispersion process with highly loaded slurry or under high shear flow reduces elastic moduli and that their combination achieved the most dispersed state of the particles among the slurries investigated. X-ray computed tomography unveiled that the electrodes manufactured from these slurries contain the aggregates and the size of aggregates in the electrodes was reduced with the decrease in elastic moduli of slurry. At the discharge current density of 10 mA g–1, these electrodes exhibited 140 mAh g–1 of discharge capacities. At 1000 mA g–1, the electrode prepared from highly loaded slurry maintained 80% of the capacity that obtained at the current density of 10 mA g–1. The capacity of the electrode prepared from the slurry under highly loaded and high shear flow, on the other hand, dropped below 10%, indicated that the electrode from the most dispersed slurry has the worst rate performance.[Ref.]1) K. M. Kim et al., J. Power Sources, 83, 108 (1999).2) E. Ligneel et al., J. Electrochem. Soc., 154, A235 (2007).3) G.-W. Lee et al., J. Power Sources, 195, 6049 (2010).4) B. Bitsch et al., J. Power Sources, 265, 81 (2014).5) S. Lim et al., J. Power Sources, 299, 221 (2015).