Today, state of the art lithium batteries are based on liquid electrolytes, due to their high ionic conductivity at room temperature. However, these batteries still exhibit shortcomings related to safety, durability and complexity of manufacturing or maintenance. For these reasons, all-solid-state lithium-metal batteries, employing solid electrolytes, have gained attention in recent decades due to their enhanced safety, chemical stability, and thermal stability [1,2].  Among solid electrolytes, ceramic ones offer superior chemical and thermal stability, resistance against dendrite growth, superior mechanical properties and wide electrochemical window. Despite their potential, their full deployment is still hindered by their performances and interfacial detrimental interactions with the electrodes [3,4]. 
Apart of the efforts of the scientific community at materials level, attention needs to be placed also at processing level. In this regard our group is exploring disruptive manufacturing processes for ceramic electrolytes and cathodes: 3D printing and ultra-fast high temperature sintering (UHS), in order to approach next generation of full ceramic devices. 
In the present study NASICON-type Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) electrolytes were printed by stereolithography (SLA) in complex geometries difficult or sometimes impossible to produce with conventional ceramic forming techniques. Despite its benefits, only a limited number of studies have utilized 3D printing in the production of full ceramic electrolytes [5,6].  SLA is a promising method that allows the fabrication of intricate shapes with high resolution [7]. Here we present the development of SLA processes to produce LAGP full-ceramic electrolytes exploring two different geometrical approaches: the conventional flat electrolyte and a corrugated one which offer an increased interfacial area with electrodes thus leading to a reduced area specific resistance with the same projected area respect to its flat counterpart. Self standing LAGP structures were printed, debinded and sintered. Crack-free LAGP electrolytes with flat and corrugated geometries were succesfully produced  with high densification (>80%), and uniform shrinkage in all directions. Those electrolytes demonstrated to have conductivities in good agreement with LAGP manufactured with conventional techniques (10⁻⁵-10⁻⁴ S/cm) and no detrimental reactions or degradation due to the debinding step were detected. Furthermore simmetrical cells Li/LAGP/Li flat and corrugated were tested in plating/stripping galvanostatic tests up to 200h. 
The printed electrolytes were also coupled with Co-free LiFePO₄ (LFP) cathodes printed by robocasting and attached by conventional thermal treatments (600ºC, 4h, N₂ atmosphere). Even if 3D printing of LFP cathodes by robocasting has been reported in literature before it was limited to Li-ion batteries (employing liquid electrolytes) [8]. Our approach will potentially open doors to a full-printed, full-phosphate ASSB.
Simultaneously, we are developing UHS for the same electrolyte and cathode materials. UHS was introduced in 2020 as a sintering technique able to densify ceramics in seconds, with the promise of significantly decreasing both the production times and energy usage respect to conventional time-consuming and energy hungry thermal processes [9]. This method also aims to mitigate degradation phenomena and minimize lithium losses [9-11]. Results on UHS of the raw materials and printed pieces will be presented. LAGP was sintered by UHS in less than 2 minutes reaching very high densification (88%) and ionic conductivities comparable with the ones obtained by conventional sintering (10⁻⁴ S/cm). Furthermore, LFP was successfully attached on LAGP electrolytes by this technique avoiding detrimental interfacial interactions. Finally, UHS was successfully applied to 3D printed LAGP electrolytes lowering the times needed for debinding and sintering from days to minutes.
In conclusion, we believe that the combination of 3D printing (performances enhanced by design) and UHS (limitation of Li losses and degradation phenomena) will pave the way to the next generation of Co-free full-phosphate batteries with complex geometries.