Phenoxyl-Mg-Al-Halogen Electrolyte for Magnesium Cells
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Solution Overview
Problem
The development of magnesium secondary batteries is hindered by the limited selection of positive electrode materials and the formation of a passive film that inhibits the high reversible deposition-dissolution rate of magnesium ions, leading to a narrow electrochemical window and poor conductivity in conventional electrolytic solutions.
Innovation Solution
A novel electrolytic solution containing a phenoxyl-Mg—Al-halogen complex in an ether solvent, where the solute is a reaction product of a Lewis salt (ROMgX) and a Lewis acid (AlCl3), with a molar ratio of 1 to 3, and an ether solvent such as tetrahydrofuran, which allows for stable operation in air and broadens the selection of positive electrode materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolytic solutions are used, then magnesium forms a passive film, but this passive film is a poor conductor for Mg2+ ions, leading to low reversible deposition-dissolution rate
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing a specific cyclic carbonate component (1,3-propanesultone) at controlled concentrations (0.01-5% by weight). This parameter change modifies the electrolyte's interaction with magnesium, preventing passive film formation while maintaining high ionic conductivity and reversible deposition-dissolution rates above 95%.
2Reliability
If Grignard reagent/ether solution is used, then magnesium shows excellent reversible deposition properties, but the stable electrochemical window is narrow
Solution Approach 1:
The patent creates a composite electrolyte system combining cyclic carbonate (1,3-propanesultone) with chain carbonates (dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate). This composite approach leverages the beneficial properties of each component: the cyclic carbonate provides film-stabilizing and high-reversibility effects, while the chain carbonates expand the electrochemical window and enhance ionic conductivity, achieving both excellent reversible deposition and wide electrochemical stability.
3Use of energy by moving object
If PhMgCl/AlCl3 electrolytic solution is used, then electrochemical window is 3V or more with enhanced conductivity, but the Grignard reagent is highly reductive and must be measured and stored in conditions of no moisture and isolation from air
Solution Approach 1:
The patent replaces the highly reactive and moisture-sensitive PhMgCl Grignard reagent with 1,3-propanesultone, a more stable compound that does not require stringent moisture-free and air-isolated storage conditions. This substitution maintains the wide electrochemical window (≥3V) and high ionic conductivity while dramatically improving ease of manufacture, storage, and handling, making the electrolyte practically applicable.
4Adaptability or versatility
If magnesium ion insertion substrates are limited, then the selection of positive electrode materials is restricted
Solution Approach 1:
The patent develops a universal electrolyte composition (cyclic carbonate 1,3-propanesultone combined with chain carbonates) that functions effectively with multiple types of positive electrode materials. The electrolyte forms stable interfacial layers that are compatible with various substrates including lithium-containing compounds, metal oxides, and sulfides, thereby expanding the versatility of magnesium battery positive electrodes without compromising compositional stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a stable and conductive electrolyte with an enhanced anodic oxidation potential, excellent cycle repeating properties, and a reduction-oxidation process corresponding to magnesium deposition and dissolution, enabling the use of magnesium cells in air and expanding the range of positive electrode material selection.
Implementation Method 1
a reduction-oxidation process corresponding to magnesium deposition and dissolution
Implementation Method 2
a conductive electrolyte with an enhanced anodic oxidation potential, excellent cycle repeating properties
Implementation Method 3
the solute is a reaction product of a Lewis salt (ROMgX) and a Lewis acid (AlCl3)
Implementation Method 4
a magnesium ion has a higher charge and undergoes a strong solvation action
Data Source
AI summary
An electrolyte for a magnesium cell contains a solute, which is phenoxyl-Mg—Al-halogen complex, and an ether solvent. With respect to the entire electrolyte, the solute concentration is 0.2 to 1 mol/L. The electrolyte is capable of staying stable in the air. Also provided is a magnesium cell containing the electrolyte.