Private Sector - Organisations
Funding: European Space Agency - Lithium Cells for Space Exploration (2014-2015)
Main Contractor: Micro and Nano-Technology Laboratory , DUTH
Subcontractor(s): Centre for Research and Technology-Hellas
Scientific Coordinator: Filippos Farmakis, Assistant Professor
Technical Objectives and Requirements
Li-ion batteries are one of the most successful stories in modern electrochemistry. These batteries, which became a commercial reality about 2 decades ago, are dominating the markets with increasingly wider applications, including space applications. Present challenges specifically for space applications are to increase their specific energy density (Wh/kg) and improve their low temperature performance in order to meet the demanding requirements of space missions and man-portable applications.
A specific design target is future Landers and surface probes or package missions, to be launched in 2018, (e.g. Lunar Lander) or beyond. Moon surface environment was the reference frame for this ESA TRP Activity. Outside temperatures for a lander on the Lunar surface without illumination can reach as low as -173o C. While a lander’s thermal control subsystem will ensure sensitive components such as the battery do not see such low extremes of temperature, having a battery which can operate at low temperatures relative to currently qualified technologies can drastically decrease the energy demand for heating and so increase the duration for which the lander can survive in darkness, with the goal to survive until the next Lunar day. The potentially long (up to 14 days) darkness periods which a Lunar surface mission can experience drive the need for high energy density Lithium-ion battery technology in order to successfully complete such a mission with as much payload as possible.
The objective of this Project was to develop, manufacture and evaluate Lithium‐ion prototype cells with a target specific energy of 200 Wh/Kg or more at BoL, capable of operating under low temperature conditions (as low as -40o C).
The procedure for reaching this objective was based on:
- Review of the existing state-of-the-art electrochemical systems and cells technologies and selection of the most promising electrochemical couple(s) and electrolytes(s)
- Development of advanced anode materials and testing of three-electrode cells based on the most promising materials
- Development of prototype cells and evaluation under cycling tests
The Lithium ion prototype cells that would develop were required to be in compliant with the following Specific Requirements:
- R1. Specific Energy density at C/10 and 100%DoD at +20oC equal or higher to 200 Wh/kg at BoL and 160 Wh/kg at EoL
- R2. Capacity of ≥1 Ah
- R3. Operation temperature between -40o C and +20o C for charge and discharge
- R4. Self‐discharge less than 5% per day at 20o C.
- R5. Capability to deliver <80 % of capacity at +20o C when cycled at -40o C (C/15 charge and C/10 discharge rate) at 100% DoD
- R6. At least 100 cycles at cycling regime defined by previous requirement
Currently, the state-of-the-art space qualified batteries by European manufactures can reach up to 155 Wh/kg (at C/2) at 25 oC (i.e. VES180 by SAFT ) and provide satisfactory performance in cycling only down to 0 oC. Below 0 oC the charging of these Li-ion batteries is the main limitation.
Results of the Project
During the Project, ≥1 Ah silicon-based high energy density prototype cells, following components characterization and optimization, were designed, developed, manufactured and tested under room and sub-zero temperature conditions down to -40oC.
The developed and tested prototype cells exhibited energy density of around 208 Wh/Kg at room temperature under C/10 charge-discharge rate. Moreover, the prototype cells could retain and deliver more than 75% of their capacity at room temperature upon cycling at -40 oC, demonstrating an energy density of 140 Wh/kg.
Researchers involved (from DUTH)
Filippos Farmakis, Assistant Professor, Electrical Engineering Department @DUTH /Scientific Coordinator
Kostas Elmasides, Assistant Professor, Environmental Engineering Department@DUTH
Nikolaos Georgoulas, Professor and Director of MNT Lab, Electrical Engineering Department @DUTH
Ioannis Karafyllides, Professor, Electrical Engineering Department@DUTH
Kyriakos Eneveis, Electrical Engineer, DUTH graduate