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MONOLITHIC BATTERIES FOR SPACESHIP APPLICATIONS

Periodic Reporting for period 1 - MONBASA (MONOLITHIC BATTERIES FOR SPACESHIP APPLICATIONS)

Reporting period: 2016-06-01 to 2018-05-31

Worldwide nanosatellite launches are increasing year after year for a growing set of applications and services, from earth observation to telecommunication. One of the crucial components of small satellites for improving and widening their performance and applications are energy storage systems. In this sense, MONBASA project aims at the development of a full thin-film solid-state Li-ion battery which can represent a step forward in terms of weight, volume, safety and performance with respect to the present Li-ion battery technology mainly based on standard liquid electrolyte. This approach should overcome operational problems and safety hazards under space-like conditions that characterise currently available solutions and affects small satellite performance in particular. One of the novelties of the project relies on the use of physical vapour deposition techniques for the fabrication of the cells, which are processing technologies used for other satellite components. The following specific project objectives have been set:
- An improved electrochemical performance of current solid state batteries based on high voltage cathodes and ceramic solid electrolytes with ionic conductivities much higher than commercial solid electrolytes.
- A full analysis of physical and chemical properties of the most relevant battery interface performed with the most advanced surface and interface analysis tools.
- Study of full cell integration with MEMS device (a crucial technology for sensors and actuators in most advanced satellites)
- The validated space applicability of the novel energy storage solution
During MONBASA project, most of the effort was devoted to tune processing methods for thin film battery components. Although the functional thin film all solid state full cell was not obtained, remarkable results were achieved with hybrid cells using thin film electrodes and liquid electrolyte. Different deposition parameters were explored to obtain the high voltage cathode with best performances (Fig. 1). Very high specific capacities were obtained: 85% of the maximum theoretical value. In addition, the high cathode showed an outstanding cycle life keeping more than 80% of its initial capacity during more than 2030 cycles; even if cycled at rather high current rates, e.g. full charge or discharge in 1 hour. As a reference, commercial cathodes of the same material can deliver the same performance only during 150 cycles (Fig. 2).
For the ceramic electrolyte, three different fabrication routes were explored. The difficulties to obtain a functional cell pushed the consortium to explore new materials and processing methods such as transition metal accommodation layers and glassy electrolytes.
Concerning the anode, metallic Li was selected as starting material. High quality and high purity Li metal films have been obtained and tested with reference commercial solid electrolytes. The thin film Li anodes have shown an outstanding performance reducing the operating temperature of the solid electrolyte from 70 ºC to 45ºC (Fig. 3).
Different accommodation interlayers between cell components were also explored in order to guarantee higher stability during cycling.
For battery testing under space-like conditions, a device was specifically designed in the framework of the project (Fig. 4). The device was used to test some thin film cells assembled with liquid electrolyte which were compared with conventional cells. The cycling was carried out at different temperatures and under vacuum, the thin film cells with liquid electrolyte performed better than the conventional ones.
In addition, in the framework of the project three events were organized: an open ethic training given by Dr. Lluis Montoliu, an open seminar titled “Space Technologies for non-space actors” delivered by Nanospace’s CEO at M18 meeting and the final „Workshop on space batteries“ held within The Battery Show Europe 2018 in Hannover at M24. The first two events were recorded and spread through the MONBASA web page. On top of this, a brouchure was published and social network profiles were regularly fed with the most interesting news, results and relevant information to MONBASA project. Finally two Policy Briefs are in place and will be distributed in the following months.
The most representative results are those related to the positive electrode which outperforms current commercial electrodes with the same active material and the thin film Li metal anodes. In view of these results the consortium is in the process of filing one joint patent application with great interest in the subsequent exploitation. The fabrication protocol, including the electrolyte and negative electrode and encapsulation with the resulting full cell is another result which the consortium will try to file a patent for. The commercialisation of the testing device will be evaluated.
Fig 2. Outstanding thin film cathode
Fig 3. Cycling of Li/Li symmetrical cells at different temperatures
Fig 4. Space like conditions testing device
Fig 1. High voltage battery with thin film electrodes