Compared with traditional lithium-ion systems, solid-state batteries could achieve significantly higher energy density, improved safety and long calendar lifetime. Apart from searching for new electrolyte compositions with high ionic-conductivity, the primary challenge in the development of custom-shaped solid-state batteries is building variable solid-state architectures by forward-thinking fabrication methods. 3D printing is considered as the most advanced method for the fabrication of advanced batteries. However, solid electrolytes remain a bottleneck in the all-printed batteries and, hitherto, has not been systematically investigated.

In our research, an attempt has been made to address the issue of 3D printing of polymer and composite electrolytes and to compare their conductivity with that of the electrolytes prepared by standard casting procedure. The influence of relative content of polymers on the ease of extrusion and printing processes was evaluated. We focused on understanding the multifaceted interrelation between the composition, properties, pathways for ionic-conduction and interfacial phenomena induced by the printing process.

We have found that in all-solid PLA-PEO-LiTFSI printed-electrolytes, the conductivity plots obey the Arrhenius temperature dependence. The bulk conductivity is 8×10^-5 S/cm and the grain-boundary conductivity is 1.5×10^-4S/cm for silica-containing electrolytes at 120°C. It is suggested that the coordination mechanism of the lithium cation by the oxygen of the PLA chain is similar to that of PEO, and local relaxation motions of PLA chain segments promote lithium-ion hopping between oxygens of adjacent CH-O groups.

Quasi-solid polymer electrolytes were obtained by the infusion of ionic liquid Pyr14TFSI with dissolved LiTFSI salt. The measurements of diffusion coefficients by PGSE-NMR suggest that the Li⁺ ions are mainly coordinated by the PEO segments in the polymer blend. Increase of the PEO content in quasi-solid electrolytes at the expense of PLA polymer, leads to more than one order of magnitude improvement of bulk conductivity of quasi-solid electrolytes, approaching 0.2mS cm⁻¹ at 60 °C.