Solid-state electrochemical energy storage

Sodium ceramic batteries operating at high temperatures

Principal investigators: Elisa Mercadelli, Alessandra Sanson

Involved personnel: Angela Gondolini, Nicola Sangiorgi, Alex Sangiorgi

ZEBRA batteries (Zero Emission Battery Research Activities), due to their high energy and power density, are one of the best solutions to the actual energy demand for stationary application (energy backup for data center) and for sustainable mobility with electric and hybrid cars.

These systems are based on nickel-sodium chloride cells operating at high temperatures (about 270°C-350 °C), enclosed in a thermal container and uses a ceramic β”-alumina tube as solid electrolyte.

The ceramic process needed to produce the electrolytic compartment has a key role to enhance and adapt the batteries performances to the specific requirements for stationary regime applications. Each minimal composition or process deviation strongly influences the final properties of the device.

For this porpouse ISTEC mainly deals with the ad-hoc study of the productive process, from the powders synthesis to their forming and sintering needed to obtain β”-alumina membranes with suitable mechanical strength and  morphological-structural characteristics.

The research is deeply focused onto the analysis of the materials sintering behavior, on the study of reactive sintering processes and how the thermal treatments could influence the chemical-structural properties of the material. The optimization of the entire ceramic process aims to the production of a full density material with chemical-microstructural properties suitable for high efficiency batteries.

ISTEC is actually able to produce, via die pressing, electrolytic membranes of the pure β”-alumina or reinforced through the addition of a YSZ-based secondary phase, with diameter up to 50 mm, thickness < 2 mm and density values higher than 98%. Nevertheless tape casting and screen printing are considered as alternative production methods to reduce the membrane thickness and increase at the same time its size in order to implement the cell efficiency and its energy density.

Finally, the research activity is devoted to the study of all-solid-state Na+ rechargeable ceramic batteries that have been considered the next-generation energy storage devices. The elimination of liquid parts from the device is in fact a key factor to increase its safety and durability.

Equipment and processes

β”-alumina materials, used to realize electrolytic membranes for ceramic batteries, are produced at ISTEC by conventional solid state synthesis. The synthesis conditions and the precursors nature are carefully chosen to produce powders with the desired phase and morphology suitable for the subsequent shaping processes.

The powders are then:

• die-pressed or tape casted to obtain planar electrolytes,
• isostatically pressed or slip casted to produce tubes.

The as-obtained green products are finally thermally treated at high temperatures to be properly consolidated.

At each processing step the materials are characterized by:

• x-ray diffractometry to follow the phase evolution
• thermal/dilatometric analyses to either evaluate the thermal cycle necessary for the formation of the desired crystallographic phase and the sintering behavior
• density measurements to determine the eventual residual porosity,
• morphological-microstructural analysis via electronic scanning microscopy to evaluate the powders morphology and the microstructures of the sintered materials,
• 4-point bending and biaxial flexure tests (ring on ring) to evaluate the mechanical strength of the produced membranes.

Main partners

• Istituto di Tecnologie  Avanzate per l’Energia “Nicola giordano” (CNR-ITAE)

Projects

• RdS

Publications

• E. Mercadelli, A.S. Aricò, A. Gondolini, S. Siracusano, M. Ferraro, V. Antonucci, A. Sanson “Influence of powders thermal activation process on the production of planar β-alumina ceramic membranes” Journal of Alloys and Compounds 696 (2017) 1080-1089.