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European Magnesium Interactive Battery Community

Periodic Reporting for period 1 - E-MAGIC (European Magnesium Interactive Battery Community)

Reporting period: 2019-01-01 to 2020-06-30

E-MAGIC is a four year (2019-2022) FET Proactive project that sought for a practical Rechargeable Magnesium Batteries (RMB) as a cutting-edge high-risk / high-reward research and innovation that aims at demonstrating a new technological paradigm within the scope of disruptive micro-energy and storage technologies.

The potential to use metallic Mg anodes in rechargeable batteries brings important advantages in terms of energy density, cost and safety. The RMB constitutes an example of such promising alternative amongst non-Li energy storage systems. Nevertheless, Mg-batteries must be effectively rechargeable to be sustainable and cost-effective. E-MAGIC consortium focuses on developing both Mg-ion (insertion) and Mg-S (conversion) technologies to address the potential of RMB. However, the emerging reversible insertion or conversion Mg-based batteries have its own limitations preventing them from having a significant impact.

E-MAGIC's strategies include the use of computational studies to set a basis to identify potential materials. Combining theoretical with experimental approaches E-MAGIC intents to achieve one of its main objectives: Develop a disruptive scientific and technical approach for new generation high energy density and environmental friendly RMB.

In this context, E-MAGIC claims to provide novel and innovative solutions focusing on:
1. Building up a rational design of materials and structures on the basis of computational approaches at different length scales
2. Explore alternative anode processing based on Mg-alloys, Mg-surface protective films, and structured Mg-metal-surface
3. Development of electrolyte systems with extended practical stable voltage windows
4. Improve the cathode nanostructure, architecture and functionality under RMB electrolyte solutions
5. Promote the evolution of a RMB by simulating its performance integrated into a hybrid micro energy storage system

The E-MAGIC technical objectives are supported along the project life by the other main objective: Reinforcement of the European magnesium community. This community currently gathers some the highest qualified European chemists, physicists, computer scientists, applied mathematicians, environmental and energy management engineers. Thus, E-MAGIC intends to contribute to reduce the barriers for increased penetration rate of distributed and/or intermittent renewable energy sources since the development of this type of batteries will increase the stability and reduce the cost for hybrid (energy) storage solutions
During the current reporting period (M1-M18) the project’s activities have been dedicated to the development of

(i) computational methods to speed up new materials screening process, support the development of novel material concepts and fundamental understanding of battery chemistries
(ii) most suitable electrolyte system to enhance the reversible capacity through reducing the formation of surface inert films and minimize corrosion processes
(iii) manufacturing process to integrate the reference and advanced materials into a battery cell prototype to assess and validate the technology
(iv) an environmental profile of future RMB

The main work performed up to day by E-MAGIC consortium can be summarized as:

• Most suitable metal anode systems have been theoretically investigated in order to identify binary alloying elements which reduce the stacking fault energies on alloying.
• Development and validation of a continuum model to predict the ideal electrolyte concentration.
• Computational models and experimental approaches have supported the solvent optimization of non-corrosive borate-based electrolytes.
• Ethers in general and glyme solvents like dimethoxyethane (DME) in particular are very important for the field of Mg batteries since they allow reversible behavior of Mg anodes. However, the intercalation process of Mg cations in V2O5 electrodes is affected strongly by the formation of stable solvation shell with DME.
• The intercalation process of Mg ions into Mo6S8 Chevrel Phase (CP) electrodes occurs at higher potential in all phenyl complex (APC) solutions than in Mg imide/chloride/DME (ICD) solutions. For practical applications the choice of electrolyte solution may have a great impact on the cells’ energy density, even upon using identical electrodes.
• At RT, CP possesses poor electrochemical activity in Cl-free solutions. To promote the intercalation process is suggested a chemical or electrochemical pretreatment of the CP cathode.
• Battery test using CP cathode with borate electrolyte shows a good cycling stability, demonstrating a good compatibility between CP and non-corrosive borate electrolyte.
• By changing the solvent from DME to diglyme (G2), better electrolytic properties of the borate electrolyte in terms of plating/stripping over-potentials has been demonstrated.
• It has established a computational workflow that autonomously calculates descriptors for founding in database materials as cathode.
• Several alternative cathodes have been proposed and tested, with the most promising results so far for Prussian green (FeFe(CN)6), vanadium tetrasulfide (VS4) and polyanthraquinone-based organic cathode (14PAQ). The organic cathode 14PAQ enabled more than 500 discharge/charge cycles at 1C with an initial capacity about 300 mAh.g−1.
• The design of S-cathodes with high reversible capacity and cycling stability has been supported by DFT calculations. The interaction energies between Mg-polysulfides and various metal sulfides and oxides have been investigated. The results have been considered for designing advanced sulfur and hybrid sulfur cathodes.
• Mg-S cells with sulfur composite based on nitrogen doped graphene-multiwall carbon nanotube have been discharged/charged for 50 cycles at C/50 in borate-based electrolyte. Reversible redox reaction of sulfur with borate electrolyte in Mg-based batteries was confirmed (in-situ Raman measurements).
• It was manufactured the first intercalation (90 mAh.g−1) and conversion (400 mAh.g−1) pouch cell prototypes. Performance is similar to those results found with coin cells, but a fast capacity fading was observed. Nevertheless, these results are the basis for further optimization of the manufacturing process and degradation studies in order to demonstrate a suitable RMB.
Amongst several findings two of them can be pointed out as beyond state-of-the-art outcomes which pave the upcoming scientific and practical advances in Mg-ion batteries:

1. The development of automated computational tools to accelerate the discovery of novel materials to be used as intercalation electrodes. The workflow is continuously developed and may be accessed at https://gitlab.com/asc‐dtu/workflows/ion‐insertion‐battery‐workflow

2. Chevrel Phase MgxMo6S8, the main benchmarking Mg intercalation compound, does not intercalate Mg in Cl-free solutions at room temperature (RT). E-MAGIC project reveals that Cl-based species have a critical role in the electrochemical processes of intercalation of Mg ions. This finding may open a hatch for the future development of practical RMBs.

At the time being of delivering this report, E-MAGIC consortium expected to combine theoretical and experimental approaches to provide solutions to overcome the current limitations of Mg-based batteries. This aim will be an add value to reinforce the competences of the European battery industry.