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European Magnesium Interactive Battery Community

Periodic Reporting for period 2 - E-MAGIC (European Magnesium Interactive Battery Community)

Reporting period: 2020-07-01 to 2021-12-31

E-MAGIC is a four-year (2019-2022) FET Proactive project focused on Rechargeable Magnesium Batteries (RMB) and 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 RMB 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 and Mg-S 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 environmentally 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. 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 development of the project (M1-M36) the project’s activities have been dedicated to:
(i) Computational methods to speed up new materials screening process, support the development of novel material concepts and fundamental understanding of battery chemistries
(ii) Development of new methodologies for selecting and processing optimal Mg-alloys anodes.
(ii) Most suitable electrolyte system to enhance the reversible capacity through reducing the formation of surface inert films and minimize corrosion processes
(iii) Development and optimization of different cathode materials nanostructure, architecture and functionality under RMB electrolyte solutions.
(iv) Scale up of promising novel cathode materials.
(v) Manufacture and testing of RMB pouch cells with reference materials
(vi) Manufacturing process to integrate the reference and advanced materials into a battery cell prototype to assess and validate the technology.
(v) 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 investigated.
• Thin AZ31 Mg alloy foils have been used as anodes for RMB
• 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.
• Synthesis and optimization of the non-corrosive magnesium borate (Mg[B(hfip)4]2) electrolytes.
• Ethers and glyme solvents like DME are important for the field of Mg batteries since they allow reversible behavior of Mg anodes.
• Battery test using CP cathode with borate electrolyte shows a good cycling stability, demonstrating a good compatibility between CP and non-corrosive borate electrolyte.
• Several cathode materials have been tested, with the most promising results for FeFe(CN)6, VS4 and 14PAQ.
• The design of S-cathodes with high reversible capacity and cycling stability has been supported by DFT calculations.
• Mg-S cells 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.
• Functional separator and hybrid sulfur cathode materials were fabricated with Chevrel phase additive. The Mg-S cells were tested with the new functional separators, sulfur cathodes with active material loading of ~1mg cm-2, 0.3 M Mg[B(hfip)4]2/DME as electrolyte and Mg metal anode.
• RMB pouch cells have been assembled and tested using reference materials. An optimized reference system was reached in pouch cell level that matches the established coin cell electrochemical response demonstrating an energy density of 20-25 Wh/kg. Throughout the test of nearly 500 cycles, the coulombic efficiencies improved close to 100% and it had a capacity retention of 80% at the end, which is considered an industrial standard for battery health and safety.
• Some pouch cells have been manufactured using the new developed ultrathin AZ31 alloy anode and are currently under testing.
• It has been proposed a step-by-step component replacement strategy of laboratory-validated aluminum current collector, Mg[B(hfip)4]2 /DME electrolyte, VS4 cathode and AZ31 magnesium alloy anode to reach a competitive, high-energy density, advanced RMB chemistry.
• An environmental profile of future RMB has been generated, deducing its environmental performance from Li-ion available information
Amongst several findings some of them can be pointed out as beyond SoA outcomes which pave the upcoming scientific and practical advances in Mg-ion batteries:
• The development of automated computational tools to accelerate the discovery of novel materials to be used as intercalation electrodes.
• Chevrel Phase does not intercalate Mg in Cl-free solutions at room temperature. E-MAGIC 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.
• In E-MAGIC, the Mg[B(hfip)4]2) / glyme based electrolyte composition was optimized by means of the glyme solvent and the addition of new additives. These electrolyte improvements have reduced the Mg plating/stripping overpotential and allowed enhanced Mg cycling performance.
• The new boron-based electrolyte system has allowed the development of three promising cathode materials where the anionic redox chemistry was activated, enabling multielectron transfer in insertion cathodes for high energy multivalent batteries
• VS4 was taken as a model material for reversible two-electron redox reaction with synergetic cationic-anionic contribution, which has been verified in RMB.
• The promising cathodic material developed is PAQ/Ketjenblack based composites which has been demonstrated towards high energy and long-lifespan RMB when the new boron-based electrolyte is used.
• The combination of the Mg anode with S using materials with high specific capacity.
• The feasibility of processing ultrathin Mg anodes by using the AZ31 Mg alloy has been demonstrated.
• The first RMB prototype has been manufactured, achieving 30Wh/kg for more than 500 cycles.
Magnesium batteries constitute a promising alternative amongst non-Li energy storage systems