Development of Silicon Polymer Electrodes with a Hybrid Polymer Electrolyte for All-Solid-State Lithium-Ion Batteries

The development of solid-state lithium-ion batteries is a promising step to meet the increasing demand for safe batteries with a high energy density. In this work, silicon electrodes containing an organic/inorganic hybrid polymer electrolyte (HPE) are reported. Depending on the conducting salt and the inclusion of an ionic liquid (IL), the HPE exhibits an ionic conductivity between 0.24 ± 0.11 mS cm-1 and 0.94 ± 0.07 mS cm-1 at 60 °C. The achievable capacity in Si/HPE/Li cells depends strongly on the C-rate and the areal capacity of the electrodes, as well as on the electrolyte and electrode composition. Among the cells tested, those with an HPE containing lithium bis(fluorosulfonyl)imide (LiFSI) and no IL exhibit the highest capacity retention and average coulombic efficiency. The use of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and/or the addition of an IL enables higher electrode loadings, however at the expense of capacity retention. Si electrodes with a higher Si content show an improved cell performance compared to those with less Si. A combination of electrodes containing 75 wt% silicon with an HPE with LiFSI and IL reaches a high capacity of approx. 1500 mA h gSi-1 at 0.1 C with a capacity retention of 74% after 100 cycles.