EUROLIS (project No. 314515) is a collaborative small or medium scale focused research project funded by European Union and coordinated by the National Institute of Chemistry, Ljubljana, Slovenia.
The project has started on 1st of October 2012 and it will run for 4 years. The aim of the project is development of an advanced and sustainable lithium sulphur (Li-S) battery for automotive use. Intense collaboration between 7 research organizations (universities and research institutes) and 4 industrial partners (3 large enterprises and 1 SME) will enable a fast progress from understanding to optimisation of Li-S cells. The potential commercial use of Li-S cell will be tested within three generations of Li-S batteries.
The project includes basic research on various levels which will help understand the mechanisms governing the Li-S cell in different electrochemical environments. The applied part of research will focus on optimisation and integration of materials into 18650 cells and cell testing for their appropriateness in the automotive applications.
Li-ion batteries become a reality in the future vehicles, although they do not fulfil completely the demands of consumers. In this respect batteries with higher energy density are required. Lithium technology utilizing sulphur as a cathode is one of the optimal choices since it offers the possibility of achieving high-energy, long-life storage batteries with a potential low price. At present, the practical use is faced with two major problems: (i) a low intrinsic conductivity of sulphur and polysulphides and (ii) loss of active materials due to solubility of the intermediate products in the commonly used electrolytes. The low intrinsic conductivity can be overcome using improved electronic wiring. The occurrence of soluble polysulphides is reflected as a loss of the active material during the cycling and additionally soluble polysulphides are responsible for overcharging problem which lowers the energy efficiency. With an aim to have stable capacity retention with a good cycling efficiency it is important to find a suitable electrochemical environment for the lithium sulphur batteries. Possible approaches are using polysulphide reservoirs with modified surfaces in the highly mesoporous conductive matrix. Proposed system with high surface area should enable weak adsorption of polysulphides intermediates allowing reversible desorption. This way a full utilization of the active material without significant losses can be obtained. In order to understand the influence of surface area and surface modification, including interactions between electrolyte and sulphur based cathode composite we need to have a reliable characterization techniques. In this respect different electrochemical, spectroscopic and physical characterization (in-situ or ex-situ) techniques can provide us valuable informations about the possible mechanism which can be used in planning of substrates for sulphur in the Li-S batteries.
The RTD work can be divided into three phases:
- Active components preparation
- Analytical work and measurements
- Prototype assembling and testing
Project work packages:
WP1 Project administrative and financial management
The work package represents continuous efforts to carry out the financial and administrative coordination by controlling information flow & communication.
WP2 System definition
In this work package the technical coordination activities and system integration activities take place. This WP contains the coordination of the system selection and integration into prototype with final testing procedure according to the defined standards.
WP3 Cathode composite
Objectives of the work package have been broken down into well-defined parameters which will be studied during project duration. For instance, parameters like a) influence of the materials and the composite morphology; b) impact of the type of substrate and its surface properties, c) ratio between sulphur and substrate and d) thickness and loading will be determined within this WP.
WP4 Electrolytes and separators: Formulation and Modelling
WP5 Analytical tools
The objective of this work package is the use of different in situ and ex situ analytical tools for analysis of Li-S batteries at different stages of charge and discharge with the aim to understand the Li-S battery electrochemical properties. Within this work the following analytical tools will be used: XPS, different spectroscopic techniques and electrochemical techniques.
WP6 Benchmarking of other Li-S technologies
In this work package we will be benchmarking alternative Li-S technologies, like a combination of lithiated silicon as anode and sulphur as cathode. Additionally, we will test the performance of a flow battery using catholyte as an alternative technology. Finally, an all solid state sulphur battery based on a ceramic separator will be developed and tested.
WP7 Integration, scale up, testing, life cycle assessment and benchmarking
The objective of this work package is the integration of cathode composite and electrolytes developed in WP3 and WP4 into prototype cells. The performance and safety behaviour of each generation will be separately assessed and compared with the Li-ion technology. A full life cycle assessment (LCA) will be performed.
Extending the range of electric vehicles
An EU-funded project is working on developing three generations of lithium–sulphur (Li–S) battery prototypes. Overcoming the main obstacles that cut the Li–S battery life short should pave the way for promising applications in the automotive industry.
The possibility of achieving high-energy, long-life storage batteries has tremendous scientific and technological significance. An example is the Li–S cell that offers higher energy density compared with conventional Li-ion cells at a low cost. Despite significant advances, there are major challenges regarding its wide-scale implementation. These include sulphur's low intrinsic conductivity as well as undesirable molecules stemming from cathode disintegration — called polysulphides — that dissolve into the battery electrolyte liquid.
In the EU-funded project 'Advanced European lithium sulphur cells for automotive applications' (http://www.eurolis.eu/ (EUROLIS)), researchers are seeking to stabilise Li–S cathodes by using polysulphide reservoirs with modified surfaces. The proposed system with a high surface area should enable weak adsorption of polysulphide intermediates and also reversible desorption. The active material is therefore fully utilised.
To further understand the impact of the surface area and the interactions between electrolyte and sulphur-based cathode composites, reliable characterisation techniques are required. EUROLIS has developed a number of different in situ and ex situ tools for analysing Li–S batteries at different stages of discharge and charge. This has helped further understand the electrochemical properties of the Li–S battery. EUROLIS used these to effectively monitor polysulphide formation and diffusion or migration in different parts of the Li–S battery.
Ultraviolet-visible spectroscopy and the four-electrode modified Swagelok cells could find use in quantitatively determining polysulphides in the separator in addition to distinguishing different polysulphide types. Another spectroscopic tool — sulphur K-edge X-ray absorption spectroscopy — has enabled partners to qualitatively and quantitatively determine polysulphides in the composite cathode.
The electrode composition has been defined to maximise sulphur loading on the positive electrode. Separators, lithium and electrolyte filling were adapted to prepare 12 prototype cells in a standard configuration. Other activities involved benchmarking alternative Li–S technologies. Focus has been placed on solid-state or polymer batteries since both can efficiently prevent polysulphide migration.
EUROLIS activities are significantly contributing to developing know-how regarding Li–S battery production. Dissemination activities include the project website, publications in peer-reviewed scientific journals and conference attendances.