Stabilized Lithium-Ion Electrodes Using Trace Water Additives
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Solution Overview
Problem
Lithium-ion batteries, particularly those with manganese spinel and olivine electrodes, face significant degradation issues due to manganese ion instability and dissolution in organic electrolytes, leading to capacity loss and impedance rise, especially at elevated temperatures, which hampers their adoption in electric and hybrid vehicles.
Innovation Solution
The development of non-aqueous electrolytes containing electrode stabilizing additives such as substituted or unsubstituted hydrocarbons with oxygen atoms and aryl, alkenyl, or alkynyl groups, which form passivating films on electrodes to prevent manganese and iron ion dissolution, thereby enhancing the stability and performance of lithium-ion batteries across a broad temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LiPF6-based organic electrolytes are used in manganese spinel and olivine batteries, then the batteries can operate with initial high capacity, but the batteries suffer from severe capacity fading and impedance rise due to manganese and iron ion dissolution, especially at elevated temperatures
Solution Approach 1:
The patent introduces trace amounts of water (0.01-5% by weight) as an intermediary substance in the electrolyte composition. This small amount of water acts as a mediator that suppresses the dissolution of manganese and iron ions from the electrode materials into the organic electrolyte, thereby preventing capacity fading and extending battery calendar life without significantly compromising initial capacity
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte by incorporating trace water along with specific additives (vinylene carbonate 0.1-5%, fluoroethylene carbonate 0.1-5%, and LiPF6 0.1-1.0 M). This parameter change transforms the electrolyte's interaction with the electrode surfaces, reducing ion dissolution and improving long-term stability
2Ease of manufacture
If manganese spinel electrodes are used to reduce cost and improve power, then the batteries become more economical and safer, but the batteries exhibit poor capacity retention due to manganese ion instability and dissolution in organic electrolytes
Solution Approach 1:
Trace water serves as an intermediary that stabilizes manganese ions in the spinel electrode structure by suppressing their dissolution into the electrolyte. This allows the use of cost-effective manganese spinel materials while achieving acceptable capacity retention through the mediating effect of water on the electrode-electrolyte interface
Solution Approach 2:
The patent uses trace amounts of water, a cheap and readily available substance, to achieve a protective effect against manganese dissolution. This inexpensive additive compensates for the inherent instability of manganese spinel, making the overall battery system more cost-effective despite the reliability challenges of manganese-based cathodes
3Power
If batteries are operated at elevated temperatures above 40-50°C to improve power delivery, then the power output increases, but the electrochemical degradation accelerates due to manganese ion dissolution and electrolyte instability
Solution Approach 1:
The electrolyte composition with trace water and specific additives (vinylene carbonate and fluoroethylene carbonate) provides beforehand cushioning against thermal degradation. This pre-configured stable chemical environment cushions the electrode materials from harsh conditions at elevated temperatures, suppressing manganese and iron ion dissolution even when the battery operates above 40-50°C
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 these electrolytes results in lithium-ion batteries with improved specific power, energy, and extended calendar and cycle life, with minimal power or capacity loss, effectively addressing the degradation issues faced by manganese spinel and olivine-based batteries.
Implementation Method 1
additives such as substituted or unsubstituted hydrocarbons with oxygen atoms and aryl, alkenyl, or alkynyl groups, which form passivating films on electrodes to prevent manganese and iron ion dissolution
Implementation Method 2
Lithium-ion batteries utilize carbon anodes, lithiated transition metal oxide cathodes, and an organic-based solvent electrolyte with a dissolved conducting salt such as lithium hexafluorophosphate (LiPF6)
Implementation Method 3
The Mn2+ ions that are formed dissolve in the LiPF6-containing organic electrolyte
Implementation Method 4
the dissolved manganese ions diffuse through the electrolyte to the graphite anode
Implementation Method 5
where they are likely reduced to manganese metal and deposited on the anode surface
Data Source
AI summary
The present invention relates to non-aqueous electrolytes having electrode stabilizing additives, stabilized electrodes, and electrochemical devices containing the same. Thus the present invention provides electrolytes containing an alkali metal salt, a polar aprotic solvent, and an electrode stabilizing additive. In certain electrolytes, the alkali metal salt is a bis(chelato)borate and the additives include substituted or unsubstituted linear, branched or cyclic hydrocarbons comprising at least one oxygen atom and at least one aryl, alkenyl or alkynyl group. In other electrolytes, the additives include a substituted aryl compound or a substituted or unsubstituted heteroaryl compound wherein the additive comprises at least one oxygen atom. There are also provided methods of making the electrolytes and batteries employing the electrolytes. The invention also provides for electrode materials. Cathodes of the present invention may be further stabilized by surface coating the particles of the spinel or olivine with a material that can neutralize acid or otherwise lessen or prevent leaching of the manganese or iron ions. In some embodiments the coating is polymeric and in other embodiments the coating is a metal oxide such as ZrO2, TiO2, ZnO, WO3, Al2O3, MgO, SiO2, SnO2 AlPO4, Al(OH)3, a mixture of any two or more thereof.