Decline of fossil fuels and combat against the greenhouse effect are inescapable challenges that require the implementation of new storage systems with high energy density, high power and high cyclability. Our research activity consists in :
- the optimisation of Li-ion battery systems and
- the development of alternative innovative energy storage systems.
Our know-how is centred on synthesis, electrode formulation and electrochemical characterisation. State-of-the-art in situ and operando techniques (XRD, Mössbauer spectroscopy…) are continuously developed and employed to get deeper insight into the electrochemical mechanisms and their failure.
Integration of Li-ion batteries specifically adapted to the storage of renewable energy, e.g. photovoltaic energy, in isolated sites as well as in smart grids is also being developed (collaboration Institut Electronique du Sud).
Some specific activities in these fields can be highlighted:
1) Conversion type electrode materials, which provide very high energy, lie at the heart of our research. They still suffer from serious problems, such as low Coulombic efficiency, high polarisation, poor cycle life (volume expansion) and limited rate capability that still prevent their commercial viability. To overcome these limitations, activities are oriented at:
in-depth investigation of the electrochemical mechanisms in the bulk as well as at the electrolyte/electrode interface (ANR ICARES (2011-2014), NEWMAST (2014-2017)
optimisation of the electrode by nanostructuring, formulation (binder/conductive additive) as well as by composite preparation (e.g. confinement in porous matrix ) (RS2E, bilateral collaboration with Bar-Ilan University, Israel)
These actions, which aim to address the last issues impeding commercial reality, are strengthened by strong collaboration with industrial partners and national centres or agencies such as SAFT, TOTAL, CNES, Saint-Gobain, ADEME, etc.
2) Known lithium-rich resources are relatively limited and their availability is uncertain in the long term. Sodium-based batteries could be a viable substitute for lithium in large-scale systems because of the widespread abundance and low cost. A wide research effort (RS2E, ANR DESCARTES (2014-2017)) is dedicated to finding new efficient negative electrodes for alternative Na-ion batteries. Our recent results show that outstanding performances (capacity and cycle life) are provided by intermetallic compounds in Na-ion batteries which could be realistic negative electrode candidates for future rechargeable batteries.
These performances are correlated to unexpected scientific oddness, which opens a fascinating fundamental new field. Moreover, increased activity is currently centred on 2 electrons systems such as Mg and Ca.
3) Specific characterisation techniques are at the heart of the research presented above: at the microscopic level, phenomena are systematically analysed using Mössbauer spectrometry, X-ray diffraction and X-ray absorption spectroscopy, coupled to ab initio calculations. Operando approaches are relentlessly developed to follow in detail the behaviour of battery materials during operation.