Electrical storage has a key role to play in the energy transition. Not only to bridge the period between generation and consumption of renewable electric energy, but also to improve electricity transmission, extensive research is being carried out for better, safer and more efficient battery technologies. In addition to new materials and technologies for batteries, we are also looking for solutions to optimise existing battery technologies. The ultimate aim is to extend their range, lifetime and performance, and increase the charge rate without sacrificing safety.
Lieve De Doncker
New materials for batteries
The ever increasing integration of renewable energy sources, which vary by nature and difficult to predict, requires a highly flexible electrical energy system. One option to provide this flexibility is the introduction of energy storage in the electricity grid. Storage can smoothen the intermittent electricity production and improve matching demand and supply. Electrical energy storage technologies are also essential in making transport and industrial activities more sustainable. For individual consumers, it means they can store their locally produced energy for later use, instead of delivering it back to the grid.
The EnergyVille battery research covers the whole value chain from basic material research, over cell architectures and new battery concepts to battery management and system integration. For next generation Li-ion batteries, we focus on solid-state batteries. In our small pilot line with dry room we develop also upscale processes to demonstrate up to Amp-hour pouch cells. The materials, processing and upscaling tasks are supported with strong modelling activities and advanced characterization expertise. In addition, we already look into more exploratory chemistries for beyond 2030.
What battery materials are investigated within EnergyVille?
- Electrode materials: Besides direct production of beyond state-of-the-art material compositions and morphologies, also surface modifications of electrode powders such as the synthesis of core-shell materials are offered. Characterization and optimization of the physical, chemical, and electrochemical properties of electrode materials with focus on in-operando methods, provides fundamental understanding which constitutes a pivotal advantage in further advancement and optimization.
- Solid electrolytes: We have the facilities and expertise to synthesize and characterize solid-electrolyte materials. Our research and development on solid nanocomposite electrolytes is unique in the world, showing record high ion conductivities. In our interface lab, we have patterning and thin-film deposition capabilities for the electrical and electrochemical characterization of individual interfaces and to measure interface ion conductivities in at different oxide/electrolyte interfaces.
- Dense high-capacity electrodes: A key differentiator of our solid-state cell technology is that the solid electrolyte is fabricated from a liquid precursor. This allows it to be easily introduced into dense porous electrodes by its liquid form where it is solidified once in place. From a technological point, only slight modifications are needed to existing toolsets for (wet) Li-ion batteries, a development which is also carried out in our upscale pouch cell pilot line. From a performance point of view, it enables high volumetric capacity as dense solid-state electrodes with high ratio of active material are now possible. The monolithic nature of the solid nanocomposite electrolyte also ensures complete contact between the active material and electrolyte as is the case in current day cells with liquid electrolytes.
- Functional buffer layers: The introduction of high voltage positive electrodes (“5V materials”) is hindered by lack of electrolytes with sufficiently large electrochemical window. In our cell integration work, ultra-thin buffer layers are applied to isolate the ionic conductors from the electronic conductors. Basic material research on the so-called dual conductor materials will pave the way to ultra-dense electrodes with fast charging characteristics.
- Lithium metal anodes: Lithium metal anodes have been the holy grail of rechargeable Li-ion batteries since their invention in the mid-20th century. The general belief is that the solid-state battery technology will finally make lithium metal anodes reality. The solid electrolyte offers a mechanical barrier against lithium dendrites, however many more issues need to be resolved first. One advantage of the porous graphite electrodes was their high electrochemically active surface area which assures a low local current density. Going to a planar lithium foil anode implies large current densities which are not helping for control of morphology and dendrite formation. Hence, micro-structuring of the lithium anodes is proposed. Chemical stability against lithium is a problem still for solid electrolytes. Proper buffer layers need to be developed. Finally, de-plating of lithium against a rigid solid electrolytes mains the formation of large voids and thus loss of contact. Several approaches are being evaluated in our lab, and a combination of two or more are likely to bring a technologically viable solution.
Modelling, characterization and testing of batteries and battery materials
In-depth characterization of the cell performance and its constituents (e.g., cathode, anode, electrolyte, and separator) is a crucial step in order to assess the maturity of a new component or cell architecture. Moreover, longevity of batteries needs to be ensured for many thousands of cycles by the so-called ‘accelerated aging tests’ for applications in electric vehicle and stationary storage. Energy and power rating, thermal behaviour, and life-time are the most important technical signatures of a given battery. Advanced characterization (i.e., electrochemical, chemical, physical) methods available in EnergyVille enable a comprehensive investigation of the battery behaviour. The experimental data are further interpreted with the aid of physics-based models in order to unequivocally and quantitatively interpret the results and to predict the battery behaviour beyond the timeframe of experiments (lifetime simulation).
New battery cell architectures
Electrochemical cells are the building blocks of battery modules and packs and define to a large extent the energy-storage characteristics of a given battery design. Novel cell structures are essential to address the ever-increasing demand for lighter and safer batteries with higher power/storage capabilities. In this regard, R&D is required to decrease the contribution of the inactive components (e.g., current collectors, conductive additives, separator, electrolyte, binder, packaging, etc.) in the overall mass/volume of the cell. The advanced processing and pouch-line infrastructure in EnergyVille aims to accelerate the R&D activities towards new electrolytes and electrodes where high loading of active-mass and high electronic/ionic conductivities are coupled to push the performance limits of the state-of-the-art (i.e., lithium-ion) batteries and to realize next generation (e.g., solid-state, Na-ion, lithium-sulfur, metal-air, etc.,) cell chemistries.
Exploratory cell concepts
Together with the exploration of new materials and cell architectures, we are exploring novel concepts for battery cells. In this out-of-the-box approach, we step away from conventional powder based composite batteries and look for new and improved ways to tackle requirements for future applications. For example, flexible and thin form factor will be needed for flexible electronics, integrated small form batteries will be needed to power the internet of things. Nanostructured current collector and thin-film materials are potential concepts which we explore. Also existing concepts such as metal-air and lithium-sulfur batteries will need out-of-the-box innovation to tackle some of the many remaining practical issues. Also here, novel nanoengineered concepts are being explored.
New battery concepts
The development of new battery cell technologies and architectures goes hand in hand with the search for new concepts for battery modules and their integration within the total battery pack, rack and trays. The main driver for this research path is of course to look for the optimal configuration which preserves the performance of the battery technology, taking into account not only electrical but also thermal aspects. Aside from this, the proposed modules should be stackable, having standardized connections to battery electrical and optional thermal management systems, contributing to flexible solutions which have a place in a circular economy model by their applicability in multiple first and second life applications. To support this activity EnergyVille is relying on its expertise on battery materials and cell behavior in different applications and environmental conditions.
Battery management systems
EnergyVille has developed an optimised Battery and Ultracapacitor Management System. A Battery Management System makes sure that the battery is always operated in safe conditions and in an energy efficient way. The BMS monitors the components in a battery and contains a battery model which can estimate the energy contents (State of Charge) by using measured cell voltages, current and temperature. This allows us to understand how batteries age and degrade. In addition to testing we also do physical modelling of batteries where we can study heat effects, which have a big impact on battery degradation. By better monitoring and controlling the battery we extend its life cycle without compromising on safety, ultimately creating a lower cost per produced kWh.
Battery integration support
Based on its expertise on storage technologies and in particular on batteries, EnergyVille is offering services to objectively check the feasibility of a battery solution for a given application with specific conditions. The right selection of technology and the dimensioning thereof can be proposed together with insights on the connection to the total energy system and the related requirements and standards. In this scope EnergyVille is also developing advanced technologies for a more optimal integration serving both the needs of the end-user and the grid connected to it. For the operational phase, EnergyVille is supporting energy management systems by providing more detailed battery information (e.g. ageing effect of service delivery) based on which more intelligent decisions can be made.
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