Rechargeable Magnesium Batteries (MRB), where high capacity Mg metal is used as the anode material, are promising candidates for next generation batteries due to their energy density, safety and cost. However, the lack of efficient cathode materials hinders their development.
Like their lithium-ion counterparts, transition metal oxides are the basic cathode materials in BRMs. However, the slow diffusion of Mg ions inside the oxides poses a serious problem. To overcome this, some researchers have explored sulfur-based materials. But sulfur-based cathodes for MRBs have serious limitations: low electronic conductivity, slow diffusion of Mg into solid Mg-S compounds, and dissolubility of polysulfides in electrolytes, resulting in low flow capacity and poor flowability. cyclability.
Now, a research team that included Dr Shimokawa from Tohoku University and Professor Ichitsubo has developed liquid sulfur / sulphide composite cathodes enabling high throughput magnesium batteries. Their article was published in the Journal of Materials Chemistry A.
Liquid sulfur / sulfide composite materials can be made spontaneously by electrochemical oxidation of metal sulfides, such as iron sulfide, in an ionic liquid electrolyte at 150. The composite material has shown high performance in terms of capacity, potential, strength. cyclability and throughput capacity.
The researchers achieved a discharge capacity of about 900 mAh / g at a high current density of 1246 mA / g based on the mass of active sulfur. In addition, they found that the discharge potential was improved by using out of equilibrium sulfur formed by rapid charging processes.
This material allowed stable cathodic performance at 150 for more than 50 cycles. Such high cyclability could be attributed to the following: high structural reversibility of the active material in liquid state, low solubility of polysulfides in ionic liquid electrolyte, and high utilization rate of sulfur due to its adhesion to conductive sulfide particles that form a morphology during the synthesis of composite materials.
Despite the progress of researchers, several problems remain. “We need electrolytes compatible with the cathode and anode materials, because the ionic liquid used in this work passive the Mg metal anode,” Shimokawa said. “In the future, it is important to develop new electrochemically stable electrolytes to make MRBs more practical for widespread use.”
Although MRBs are still in the development stage, the research team hopes their work will provide a new way to use liquid sulfur as high throughput cathode materials for MRBs. “This would stimulate the improvement of sulfur-based materials to achieve next-generation high performance batteries,” added Shimokawa.
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