Cold sintering of LATP- and LiFePO4-based cathodes for Li-ion solid-state batteries
WAETZIG K. 1, VINNICHENKO M. 1, BEAUPAIN J. 1, AUER H. 1, ZAPP N. 1, KUSNEZOFF M. 1
1 Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Dresden, Germany
All solid-state batteries (ASSB) working at ambient temperature are very promising but simultaneously most challenging approach for electrochemical storage devices. Especially oxide / phosphate electrolytes offer unique opportunities for in air manufacturing, intrinsic safety, and high energy density. Among ceramic electrolyte Li1.3Al0.3Ti1.7(PO4)3 (LATP) is providing a high Li-ion conductivity of 1 x 10-3 S/cm after sintering at temperatures > 1000 °C . Therefore, this solid electrolyte is a promising candidate as Li-ion conductor in composite cathodes, which are composed of a Li-ion conductive material and an active material for Li storage and electronic conductivity. In case of conventional sintering, the active material is reacting with the LATP electrolyte by forming electrochemically inactive phases . To avoid this undesirable reaction during preparation of composite cathodes, the sintering temperature has to be reduced extremely. For pure LATP electrolyte, the addition of sintering aids and the cold sintering were successfully demonstrated for the reduction of sintering temperatures [3,4] along with achieving relative densities >90% of the theoretical value.
In this study, the preparation of thin composite cathodes (< 100 µm) of LATP with active material LiFePO4 by tape casting is presented. For densification of these cathodes, cold sintering is developed as process with reduced sintering temperatures. Finally, the cathodes are characterized by electron microscopy (microstructure), X-ray diffraction (phase analysis) and electrochemical measurement in coin cells with polymer separator.
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