Community Research and Development Information Service - CORDIS

FP7

BACCARA Report Summary

Project ID: 608491
Funded under: FP7-ENERGY
Country: France

Final Report Summary - BACCARA (Battery and superCapacitor ChARActerization and testing)

Executive Summary:

Energy storage devices have been available for decades. Today, as high energy and eco-friendly systems with longer lifetimes and safer performances are needed, future emerging technologies are actively foreseen. They are expected to be grounded on new concepts and the integration of advanced materials with enhanced capabilities. Hence, basic research must be intensively conducted on the properties of new promising materials in order to provide a fundamental understanding of their behavior in the course of device aging and cycling.

The performances of lithium ion batteries and supercapacitors are governed by complex, intricated reaction mechanisms and processes which develop over an extended range of length- and time-scales. In fact, interactions at the electrode-electrolyte surface largely determine the system capacity and cyclability. This is intensified by going nano, because a significantly increased surface of the active materials is exposed to the ion-conducting electrolyte. However, molecular-level details on the structure, composition, and evolution during cycling of the interfacial regions are often lacking. Therefore, the role of interfaces remains mostly unpredictable as well as their dependence on the dynamic interactions between the main constituents.

In this context, the Baccara project concentrated its efforts during 3 years to investigate the fading mechanism in nanoSilicon-based Lithium ion batteries and graphene-based supercapacitors.

■ The project developed a multi-probe technical platform for in-depth multi-scale characterizations of the electrolyte/electrode interfaces in these systems, especially with regard to their evolution during cycling.
Coupling electrochemical testing to advanced in situ/operando investigations is one key enabling methodology to elucidate the degradation phenomena in electrodes for energy storage.

■ The physical, chemical and electro-chemical properties of the negative nanoelectrodes were quantified by systematically coupling electrochemical testing to the large panel of cutting-edge spectroscopy, scattering and imaging techniques available, including NMR, XPS, TOF-SIMS, STEM-EELS, Raman, FTIR, Synchrotron X-rays Reflectivity and Diffraction.
The fading mechanism in Silicon-based LiB full cell was elucidated.
The origin of the capacity decay on cycling Silicon LiB full cells (vs NMC) configuration using classical carbonates electrolytes was studied. Detailed interpretation of the species and components mapping at nm scale was performed. It was assessed that the inorganic part of the Solid Electrolyte Interphase mostly develops during the early stage of cycling, while the degradation of the organic solvents of the electrolyte continuously occurs upon cycling. For extended cycling, all lithium ions available for cycling are consumed because of parasitic reactions and trapped either in an intermediate part of the SEI or in the electrolyte.

■ Ex situ and real-time insights were gained into the degradation mechanisms and interfacial main features at atomic, molecular and nano-scales.
New insights into the Solid Electrolyte Interphase (SEI) formed on Silicon were gained.
Operando characterization techniques were implemented on Synchrotron beam line (ESRF), TEM, FTIR and Raman. The dynamical behavior of Si-based anodes was revealed, providing unprecedented real-time diagnosis of the SEI formation and growth, the lithiathion/delithiation mechanisms and their impact on the morphological/structural evolution of the nanoSi.
The formation and evolution of the SEI was monitored during the first battery cycles by operando Synchrotron X-ray Reflectivity and its dependence on the nature of the electrolyte was investigated. In the case of benchmark carbonate electrolytes, it was found that a two-layers interfacial region is formed, with subsequent continuous breathing of the SEI. In contrast, it was shown that a reduced SEI forms with pure IL. An intermediate behavior was evidenced with mixtures. In complement, operando Synchrotron X-ray Diffraction evidenced that the pressure exerted from the “breathing” amorphized shell (Si or LixSi) onto the continuously shrinking crystalline Si core is responsible for electrochemically-driven variations of the internal stress, providing hints for the limitations of Li incorporation in Silicon NPs anodes.
In-situ ATR-FTIR spectroelectrochemical analysis revealed that the SEI is mostly formed during the first delithiation. The influence of the electrode morphology and active material loading density on the electrode capacity was further quantified by Raman.
The I(G)/I(D) ratio of the raman signal of graphen in SC electrodes was monitored operando during long cycling to follow the dynamical disorder evolution of stockpiled graphene platelets.

■ The systems were tested in full cell configuration at the lab scale and on demonstrator /prototypes by industrial partners. Safety tests were also performed for both LIB and SC prototype cells.

■ Ultimately, the project could establish a system approach to design tailored interfaces/interphases, with potential application for safer and more efficient energy storage systems.
The better understanding of the fading mechanism allowed the consortium to propose and test solutions to improve the battery
Improvement solutions for safer Si-based LiB were proposed and explored.
A set of solutions to improve the interface aging was proposed, including optimization of the electrodes formulation using PAMA as dispersant, oligomer coating on Si particles, or modified electrolyte formulations by using specially designed ionic liquid (IL) based electrolytes. The latter was examined in details and appeared to be a promising strategy. Mixtures of carbonates and ionic liquid electrolytes were successfully tested and a better cyclability was obtained in full cell. It was shown also that mixtures of IL + traditional electrolytes improve the safety of cells.

■ New types of specific active materials for supercapacitors were developed and tested.
● Anthraquinone (AQ) molecules were grafted on a graphene substrate to promote the overall capacitance via a supplementary faradaic contribution. Performing supercapacitor pouch cells were fabricated by coupling the AQ grafted graphene electrode with a homemade micro/meso porous carbon. A very good behavior of the AQ grafted graphene electrodes upon ageing was obtained. Yet, the redox activity of Anthraquinone takes place both in acidic and basic aqueous media, which drastically limits the maximum potential of SC cells (ESW=0,9V). In these conditions, despite the very good capacitances of the AQ grafted graphene electrodes, the specific energy of the SC cells was too limited to be really competitive versus the current commercial organic electrolyte based-SC cells. Optimized cylinder cells of 4000F were achieved and displayed a specific energy of 1Wh/kg.

● Water-based electrode formulations using a homemade porous carbon as active material coupled with the graphene as a conductive filler were tested and developed. As expected, low amounts of graphene turned out to be definitely fairly easy to disperse in the water-based electrode formulations. This allowed to obtain well dispersed graphene particles in the final carbon electrode, promoting the electronic percolation with the selected porous carbon. Some substantial gains on the electrical conductivity (20%) and on the capacitance (10%) were observed for electrodes made of 90% of the selected porous carbon.

■ Expertise and know-how on materials design and cells testing.
Knowledge on electrolyte formulation and purification has been gained during the project and will result in new products available in the industrial portfolio.
Knowledge on the Methodology of Safety Testing (including procedures, Set-up, evaluation, conclusions) has been gained and will be used to provide R&D services on Safety related issues of Energy storage devices.

Baccara results provided inputs to help and guide the development of future, higher energy and eco-friendly energy storage systems with longer lifetimes and safer performances.
Further research is essential to anticipate the upcoming challenges and provide optimization-based approaches that will be required to make them available in the coming years for the market. These results could feed in the reflections on future discussions in the framework of H2020.

Project Context and Objectives:

A Publishable brochure of the baccara objectives, challenges and key results has been written and add to this report in annex.
The main elements of the context and objectives of the project are put here, please refer to the brochure for more complementary information

Efficient intermittent renewable power sources and eco-friendly energy-saving technologies are foreseen to realize the transition towards a fossil fuels-free economy.
In the perspective of a carbon-free electricity chain, electrochemical devices for energy storage, as lithium ion batteries (LiB) and supercapacitors (SCs), are key ingredients. Although they have already penetrated the automotive, domestic and portable markets, the widespread customer-attractive release of industrial products available at reasonable costs for reasonable duration times is still a true challenge for the 21st century.

Basic and applied research are needed to establish the criteria for the rational design of advanced electrodes and electrolytes for use in next-generation devices. Efforts are worldwide focused on the design of high performance active materials, as Silicon for LiBs or Graphene for SCs. These promising materials must be stable, easily-processed, possibly recyclable, low cost, based on non-rare natural resources, and compatible with other system components.

A key challenge is to control and tailor the electrode-electrolyte interfaces which primarily pilot the performances of the devices.

The long-term stability of electrochemical energy storage devices is critical for their use in practical applications, e.g. in electric vehicles for instance. Ultimate control and optimization of the system lifetime requires in general to clarify the ageing mechanisms and identify mitigation solutions. The BACCARA project was launched to address these issues in modern energy storage systems, e.g. LiB based on Silicon nanopowders as anode and Ucaps using graphene as active material.

The project workflow was deployed along two main periods to fulfil a two-fold objective:

• Goal 1 / Period 1 : Understanding of Ageing
■ Extensive physical, chemical and electrochemical characterizations of LiBs and Ucaps to gain in-depth knowledge on basic ageing mechanisms, with particular emphasis on interfaces and interphases evolution during electrodes cycling.
■ Setting, testing and operation of a multi-probe characterization techniques platform for multi-scale (post-mortem and operando) surface and bulk analysis.
■ Integrated approach/methodology to quantify the degradation during calendar ageing and cycling in full-cells, at both lab (swagelock) and industrial prototype scales (including safety tests).

• Goal 2 / Period 2 : Improvement of Interfaces
■ Design high quality tailored interfaces for batteries and supercapacitors with enhanced performances.
■ Propose solutions for improving lifetimes, capacity and safety performance, to be scaled up for industrial testing in pouch cells.

LiB are everywhere in our daily life (cells, labtops, etc). In fact, the LiB market was driven during the last decade by the information technologies development. In the near future, the market expansion for LiBs is anticipated to be driven, and possibly boosted, by the development of electrical vehicles. To fit with the demand in high power storage in transportation, batteries will be coupled with supercapacitors. In fact, when combined with Ucaps, Lithium-ion batteries not only do perform better, but their lifetime is extended.

Supercapacitors (also called ultracapacitors) are electrical storage systems capable to deliver high power (roughly 10 KW/kg i.e. 1 to 2 orders of magnitudes higher than batteries) during a high number of cycles (up to 1,000,000 cycles). Electrostatic forces are at the origin of the storage via the formation of a capacitive double layer at the electrode/electrolyte interface, which explains such a behaviour in terms of fast kinetics and ageing. Supercapacitors are particularly interesting for specific transient applications that require short time constants and high life time. As such, they will play a key role as future emerging energy storage technology in particular in the transportation sector (example: stop&start hybridation system in cars). The major limit of supercapacitors remains their specific energy: limited to 7-8Wh/kg for the best commercial systems.

Baccara addressed fundamental challenges related to the optimisation of both LiBs and SCs technologies. The project defined a strategy to tackle the main hurdles related to the use of Silicon-based and graphene-based active materials, as they were faced by academic and industrial players worldwide at the beginning of the project.

● Si-based LiB market. The use of Silicon-based anodes could constitute a breakthrough for next-generation batteries. Accordingly, the global silicon-based anode battery market was valued at USD 96.5 Million in 2015 and is expected to grow at a CAGR of 43.4% between 2016 and 2022. North America accounted for the largest share of the silicon anode battery market in 2015, while the Asian-Pacific market is expected to grow at the highest CAGR. The European market stands in between those two trends. However, the growth of the market in the coming years is expected to be restrained by major difficulties related to the intrinsic mechanism for Lithium insertion into Silicon leading to a continuous solid electrolyte interface (SEI) formation and lithium irreversible consumption.

● Graphene-based Ucaps market. The supercapacitor market is estimated to be valued at USD 568.2 million in 2015 and expected to reach USD 2,181.2 Million by 2022 at a CAGR of 20.7 % between 2016 and 2022. One major restraint to the growth of the supercapacitor market is the high cost of active materials. Some of the recently developed supercapacitors use highly conductive materials such as graphene, which is attractive because of its high theoretical double layer capacitance but is more expensive than activated carbon.

BACCARA’s challenge for LiBs
BACCARA addressed the challenge of gaining applicable knowledge on the SEI composition, morphology and ageing during Si-based battery cycling. The ultimate goal was to define criteria and potential solutions to control the SEI structure, e.g. to optimize the balance between layer thickness (piloting the irreversible consumption of Li), stability and composition in order to promote Lithium diffusion and electronic accessibility. With this purpose, novel nanoscale materials, e.g. Silicon Nanopowders, were chosen and different types of electrolytes were investigated to evaluate their impact on the interfacial properties. Silicon nanopowders were selected as anode LiB active material because they are already available at industrial level in Europe. Because of their large exchange specific area, the SEI is stabilized with respect to bulk and can be more easily studied. Ionic liquids and different IL/carbonate Mixtures were investigated and tested in half and full cell configurations.
BACCARA’s challenge for SCs
The possibility of using modified graphene to enhance the performance of supercapacitors was evaluated within Baccara to provide guidelines for the design of high performance SCs, e.g. high specific energy (Wh/kg) and excellent stability with ageing. Modified graphene, namely grafted graphene electrodes was chosen as electrode active material in acidic aqueous electrolyte. An AQ grafted graphene negative electrode was coupled with a tailored positive electrode (homemade carbon) to promote the performances of the overall system. Knowledge on the stability upon long lasting cycling was accumulated using systematic cycling of pouch cells and analysis of the components every 20000 cycles.

Project Results:

A Publishable brochure of the baccara objectives, challenges and key results has been written and add to this report in annex.
The main elements of the S & T results/foregrounds of the project are put here, please refer to the brochure for more complementary information

The BACCARA project concentrated its efforts during 3 years to investigate the fading mechanism in nanoSilicon-based Lithium ion batteries and graphene-based supercapacitors. It has reached its objectives in developing in-depth understanding of the interfaces behavior which primarily pilot the performances of the LIB and Supercapacitor devices and engaged basic research activities to evaluate and test new routes to improve performances at the lab and prototype scale devices.

■ A panel of advanced experimental multiprobe characterisation techniques was set up and linked with dedicated transfer modules to provide relevant multiscale characterization for LiB and SC.

■ The fading mechanism in Silicon-based LiB full cell was elucidated.
The origin of the capacity decay on cycling Silicon LiB full cells (vs NMC) configuration using classical carbonates electrolytes was studied. It was assessed that the inorganic part of the Solid Electrolyte Interphase mostly develops during the early stage of cycling, while the degradation of the organic solvents of the electrolyte continuously occurs upon cycling. For extended cycling, all lithium ions available for cycling are consumed because of parasitic reactions and trapped either in an intermediate part of the SEI or in the electrolyte.

■ New insights into the Solid Electrolyte Interphase (SEI) formed on Silicon and the Nanoparticles behavior were gained.
Operando characterization techniques were implemented on Synchrotron beam line (ESRF), TEM, FTIR and Raman. The dynamical behavior of Si-based anodes was revealed, providing unprecedented real-time diagnosis of the SEI formation and growth, the lithiathion/delithiation mechanisms and their impact on the morphological/structural evolution of the nanoSi.

Let’s emphasise that coupling electrochemical testing to advanced in situ/operando investigations is one key enabling methodology to elucidate the degradation phenomena in electrodes for energy storage.

■ Improvement solutions for safer Si-based LiB were proposed and explored.
A set of solutions to control and improve the interface aging was proposed, including optimization of the electrodes formulation using PAMA as dispersant, oligomer coating on Si particles, or modified electrolyte formulations by using specially designed ionic liquid (IL) based electrolytes. The latter was examined in details and appeared to be a promising strategy. Mixtures of carbonates and ionic liquid electrolytes were successfully tested and a better cyclability was obtained in full cell. It was shown also that mixtures of IL + traditional electrolytes improve the safety of cells.

■ New types of specific active materials for supercapacitors were developed and evaluated.
● Anthraquinone (AQ) molecules were grafted on a graphene substrate to promote the overall capacitance via a supplementary faradaic contribution. Performing supercapacitor pouch cells were fabricated by coupling the AQ grafted graphene electrode with a homemade micro/meso porous carbon. A very good behavior of the AQ grafted graphene electrodes upon ageing was obtained. In these conditions, despite the very good capacitances of the AQ grafted graphene electrodes, the specific energy of the SC cells was too limited to be really competitive versus the current commercial organic electrolyte based-SC cells. Optimized cylinder cells of 4000F were achieved and displayed a specific energy of 1Wh/kg.

● Water-based electrode formulations using a homemade porous carbon as active material coupled with the graphene as a conductive filler were tested and developed. As expected, low amounts of graphene turned out to be definitely fairly easy to disperse in the water-based electrode formulations. This allowed to obtain well dispersed graphene particles in the final carbon electrode, promoting the electronic percolation with the selected porous carbon. Some substantial gains on the electrical conductivity (20%) and on the capacitance (10%) were observed for electrodes made of 90% of the selected porous carbon.

The BACCARA project is positioned within an industrial work flow towards demonstrator cells that can help building a commercial product in the future:
Expertise and know-how on materials design and cells testing
• Knowledge on electrolyte formulation and purification has been gained during the project and will result in new products available in the industrial portfolio.
• Knowledge on the Methodology of Safety Testing (including procedures, Set-up, evaluation, conclusions) has been gained and will be used to provide R&D services on Safety related issues of Energy storage devices.
• The use of graphene as conductive additive in carbon based electrodes turned out to be very satisfactory. Such an improvement could favorably impact the behavior of upcoming supercapacitor cells. Of course, the question of cost must be carefully examined: graphene should yield a substantial increase of the electrode performances to meet specific requirements which are hardly attainable with usual low-cost materials.

Baccara results provided inputs to help and guide the development of future, higher energy and eco-friendly energy storage systems with longer lifetimes and safer performances.

Potential Impact:
A special delivrable has been built dedicated to exploitation plan of the project key results for all the partners. Please refer to the deliverable for more detail
- Baccara consortium has developed during three years fundamental understanding of fading mechanism of LIB and SC electrodes and was able to propose new solutions for improving the systems.
- These results are of importance and will help to carry on research for a deeper understanding and to design optimized solutions for development of new systems that could find place on market in a near future.
- Industrial partners gain also knowledge in tailoring materials, cell prototyping and safety tests. These results are available for them to improve their market products or future one’s.

Baccara consortium had during the 3 years of the project the wish to share and disseminate as much as possible its results.
- An advisory board was built to discuss results with outside experts and help the consortium to define the goad road map for improvement.
- Links with the Hi-C project were created and a common Workshop was organized allowing the gathering of a large community on experts of the LIB and SC communities to discuss the results and proposed new ideas.
- Part of the results on the fundamental expertise developed during the project were published or will be soon for the latest.
- These results were presented and discussed in international and national conferences of characterization and electrochemical communities, during the duration of the project and will still be in the next months.

Baccara results provided inputs to help and guide the development of future, higher energy and eco-friendly energy storage systems with longer lifetimes and safer performances.
Further research is essential to anticipate the upcoming challenges and provide optimization-based approaches that will be required to make them available in the coming years for the market. These results could feed in the reflections on future discussions in the framework of H2020.

In a dedicated delivrable ( DEL6.3) the consortium made a deep analysis of the main results of the project and their exploitation for each partner. In this document, each KER is described in details in a specific part, where the context is summarized and the results are explained, the exploitation plan of each partner is tackled and finally coupled with quantified risk analysis.

Here are the 10 Key Exploitation Results ( KERs) of the Baccara project:
- New knowledge on the formation and evolution of SEI in Si anodes for Li-ion batteries with classical carbonate electrolytes..
- New knowledge on the mechanic stability of silicon particles under prolonged cycling
- New concepts for safer Li-ion batteries (mixtures of electrolytes)
- New Expertise on electrolyte formulation, synthesis and purification
- Progress in using graphene aqueous formulations for Ucaps
- Knowledge on Ucap (grafted) graphene electrodes stability under prolonged cycling
- Expertise on safety of Lithium Ion Cells
- New tools, methods and technical platform for LiB electrodes characterization
- Operando techniques for real-time characterization of energy storage devices
- Training, Visibility, Attractiveness and Networking

List of Websites:
http://project-baccara.eu/

List of contacts
Commissariat à l’Energie Atomique et aux Energies Alternatives (CEA) – Grenoble, France
Dr. Pascale BAYLE-GUILLEMAUD pascale.bayle-guillemaud@cea.fr
Dr. Sandrine LYONNARD sandrine.lyonnard@cea.fr

Centre National de la Recherche Scientifique, (CNRS – IMN) – Nantes, France
Dr. Dominique Guyomard dominique.guyomard@cnrs-imn.fr
Dr. Philippe Moreau philippe.moreau@cnrs-imn.fr

Technion – Israel Institute of Technology – Haifa, Israel
Prof. Yair Ein-Eli eineli@technion.ac.il
Dr. Alexander Kraytsberg alexkra@mt.technion.ac.il

Hutchinson GmbH – Mannheim, Germany
Dr. David Ayme-Perrot david.ayme-perrot@cdr.hutchinson.fr
Michael Mussler michael.mussler@hutchinson.de

Varta Micro Innovation GmbH (VMI) – Graz, Austria
Dipl.-Ing. Dr. Stefan Koller s.koller@vartamicroinnovation.com
Dipl.-Ing. Dr. Harald Kren h.kren@vartamicroinnovation.com

Ionic Liquids Technologies GmbH (IOLITEC) – Heilbronn, Germany
Dr. Boyan Iliev iliev@iolitec.de

Contact

Jerome Planes, (Contracts administrative manager)
Tel.: +33 4 38 78 31 64
Fax: +33 4 38 78 5153
E-mail
Record Number: 199813 / Last updated on: 2017-06-21
Follow us on: RSS Facebook Twitter YouTube Managed by the EU Publications Office Top