Polyanion-assisted ionic-electronic conductive agents designed for high density Si-based anodes

Abstract

Graphite-silicon (GS) composite electrodes have been actively studied due to the practical aspects as anodes for lithium ion batteries. Unfortunately, the amount of loaded Si in the GS composite electrode is required to be limited to avoid catastrophic issues arising from the volume change of Si anodes. To keep pace with the research trend and enhance the energy density of lithium ion batteries, it is inevitable to increase the density of GS composite electrodes in the cell. However, the permeability of organic electrolyte is typically deteriorated as the electrode gets denser. In addition, some relevant issues associated with the cell resistance and electrode utilization seriously aggravate the cell performance. In this study, a capillary-inspired conductive agent (CCA) is employed as an electron/ion dual-conductive agent to address the above-mentioned challenges of high-density GS composite electrodes. Unlike conventional carbon blacks, the CCA is capable of providing an efficient conductive pathway for electrons and improving the electrolyte impregnation property due to the hydrophilic nature of polyanion polymer. Even when a trace amount of CCA (around 2 wt %) is introduced in the electrode composition, high-density GS composite electrodes show significant improvements in capacity retention (85% after 150 cycles) and Coulombic efficiency (99.9%).