Towards co-sintering of oxide-based inorganic solid-state batteries. Understanding and overcoming the temperature barriers

Resumen

All inorganic solid-state batteries (SSBs) are considered the batteries of the future because of their superior energy density and safety. Their commercialization is in its infancy since further understanding of the materials and processing aspects is still required. Here we propose an oxide-based SSB model comprising NMC+LATP+carbon composite cathode, LATP solid electrolyte, and Li metal anode able to potentially convey an energy density of 300 Wh/kg and 700 Wh/l. A review of existing processing techniques of the selected materials indicates the necessity of very high densification temperatures to assure sufficient ionic conductivity and mechanical stability. The electrode and electrolyte need to be co-densified to avoid interfacial contact resistance, but the components of the composite cathode react at these elevated temperatures. In this work, the composite cathode thermal compatibility is first studied to determine the tolerance of the system under temperature, considering also the heating atmosphere and the decomposition reaction mechanism. In a second step, mitigation strategies to overcome the threshold limits identified have been examined, such as the selection of the carbon conducting additive and the impact of other additives. On the other hand, the realization that the threshold temperature is much lower than the conventional processing temperature requires the exploration of alternative low-temperature densification techniques. Hence a high-pressure low-temperature (HPLT) technique has been identified and initially investigated for oxide-based ceramic solid electrolyte densification. Our results show that this technique enables a significant reduction of the processing temperature and time compared to conventional sintering. Finally, preliminary investigations indicate that with further exploration of the HPLT technique, the realization of the proposed SSB model should be possible, resulting in significant gains of processing consumed energy.