All-Solid State Rechargeable Batteries: Manufacturing of Composite Cathodes

Abstract

All-solid-state batteries have great potential for both improvement of cell safety and increase of energy density. Safety improvements are obviously attained by removing the flammable liquid electrolyte. For the energy density, values up to 400Wh/kg are often claimed. Results of theoretical calculations reveal that specific energies beyond 400 Wh/kg and energy densities of more than 1200 Wh/L can be reached with all solid state Li-ion cells. Great challenges remain in manufacturing of the components and the cell stack. All-solid battery cells as presented here typically consist of a lithium metal anode, a thin all-solid separator and a composite cathode. While the Lithium metal anode and the separator can probably be single-phase, the composite cathode requires a much more complex structure to ensure both good electrical and ionic conductivity. In addition, the contact resistance at the components’ interfaces needs to be minimized. Such cathodes ideally consist of evenly dispersed particles in solid electrolyte, with no remaining porosity. In this work, a practical approach for manufacturing of all-solid composite cathodes is presented. The impact of different compositions and manufacturing technologies on the electrode structure and conductivity is shown. Composite cathodes comprising active material, polymer based electrolytes and conductive agents are manufactured by dry mixing, hot pressing and extrusion, respectively. SEM and TGA-DSC analysis reveal the structure of the resulting electrodes. Results of density and porosity measurements are also shown. Ionic and electrical conductivities are measured as well. In conclusion, the impact of composition and processing on the quality of all-solid state composite cathodes is shown and discussed in this work. Recommendations towards improved manufacturing routes are derived. Figure 1