Urea-Based Ionic Liquid Electrolytes for Aluminum-Ion Batteries
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Solution Overview
Problem
Aluminum-ion batteries face challenges such as high costs due to expensive organic cations, deposition issues from anionic species, extreme hygroscopicity of ionic liquids leading to side reactions, and corrosion of metal substrates, which affect coulombic efficiency and cycle life.
Innovation Solution
Development of improved ionic liquid electrolytes using mixtures of aluminum chloride (AlCl3) and organic compounds like urea or acetamide, along with corrosion-resistant current collectors and hydrophilic polymer binders, to facilitate cost-effective, scalable, and stable aluminum-ion batteries with enhanced energy density and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ionic liquids with organic cations are used as electrolytes, then the battery can operate, but the cost is high
Solution Approach 1:
The patent replaces expensive conventional ionic liquid cations (imidazolium, pyridinium, ammonium) with inexpensive urea molecules. Urea is a cheap, readily available compound that forms stable ionic liquids with AlCl3, dramatically reducing electrolyte cost while maintaining functional performance
Solution Approach 2:
The patent changes the chemical composition parameters of the ionic liquid by using specific AlCl3:urea molar ratios (1.1 to 1.7, preferably 1.2 to 1.5). This parameter optimization ensures the formation of the desired [AlCl2(urea)n]+ cations while maintaining liquid state and electrochemical performance at low cost
2Productivity
If anionic species are used for aluminum deposition, then the battery can charge, but deposition issues occur affecting coulombic efficiency
Solution Approach 1:
The patent inverts the conventional approach by using cationic [AlCl2(urea)n]+ species instead of anionic species for aluminum deposition. This inversion enables reversible aluminum plating/stripping at the anode with high coulombic efficiency (95-99%), solving the deposition issues associated with anionic mechanisms
Solution Approach 2:
The patent optimizes the AlCl3:urea molar ratio to ensure sufficient AlCl3 content (at least 1.1:1 ratio) to form the cationic [AlCl2(urea)n]+ species. This parameter control is critical for achieving the desired cationic deposition mechanism and high coulombic efficiency
3Ease of operation
If conventional ionic liquids are used, then the battery can operate, but extreme hygroscopicity leads to side reactions
Solution Approach 1:
The patent replaces hygroscopic conventional ionic liquids with urea-based ionic liquids that have significantly reduced moisture sensitivity. Urea's molecular structure and bonding characteristics result in lower hygroscopicity, reducing water uptake and subsequent harmful side reactions while maintaining operational functionality
4Ease of manufacture
If metal substrates are used as current collectors, then the battery can be manufactured, but corrosion occurs reducing cycle life
Solution Approach 1:
The patent employs composite current collector structures, specifically carbon-based materials (carbon fiber paper, carbon cloth, graphite fiber) or metal substrates with protective carbon coatings. These composite structures provide both electrical conductivity and corrosion resistance in the AlCl3-based ionic liquid environment, enabling long cycle life while maintaining manufacturability
5Ease of manufacture
If AlCl3 and urea are mixed to form ionic liquid, then cost is reduced, but residual water and HCl require removal
Solution Approach 1:
The patent implements preliminary purification steps during electrolyte preparation, including vacuum treatment and heating to remove residual water and HCl formed during AlCl3 and urea mixing. This preliminary action ensures high purity electrolyte before battery assembly, addressing the contamination issue while maintaining the cost benefits of urea-based formulation
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 use of urea-based ionic liquid electrolytes increases theoretical energy density, maintains high coulombic efficiency across varying charge rates, and extends battery operation temperature range, while corrosion-resistant current collectors ensure long cycle life and flexibility for wearable devices.
Implementation Method 1
AlCl3 undergoes asymmetric cleavage to form a tetrachloroaluminate anion (AlCl4-) and an aluminum chloride cation (AlCl2+) in which a ligand is datively bonded to (or associated through coordination via sharing of lone pair electrons) the AlCl2+ cation
Implementation Method 2
an aluminum chloride cation (AlCl2+) in which a ligand is datively bonded to (or associated through coordination via sharing of lone pair electrons) the AlCl2+ cation
Implementation Method 3
associated through coordination via sharing of lone pair electrons
Implementation Method 4
adding aluminum in the ionic liquid, and subjecting the ionic liquid to vacuum for 0.2 h to 24 h to remove residual water, hydrochloric acid or organic impurities
Implementation Method 5
including a cationic electroactive species for aluminum deposition during charging
Implementation Method 6
Due to the high natural abundance and three electron redox properties of aluminum
Data Source
Figure 1~2B
Figure 4A
Figure 4B~4C
AI summary
A metal -ion battery includes: 1) an anode including a metal; 2) a cathode; and 3) an ionic liquid electrolyte disposed between the anode and the cathode, wherein the ionic liquid electrolyte corresponds to a mixture of a metal halide and an organic compound.