Lithium-Ion Capacitor Electrolyte for Wide-Temperature Stability
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Solution Overview
Problem
Lithium-ion capacitors using plane foils as positive current collectors face issues such as electrode material peeling, deterioration at high temperatures, and increased resistance at low temperatures, limiting their performance and stability.
Innovation Solution
A lithium-ion capacitor design featuring a positive electrode with a plain foil current collector, a positive electrode mixture layer doped with anions, and an electrolyte containing specific lithium salts (fluorine-containing inorganic acid and acid imide) to maintain stability and reduce resistance across temperature ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a plane foil is used as a positive current collector, then the structure is simple and manufacturing is easier, but the positive electrode active material layer easily peels off and deterioration is remarkable
Solution Approach 1:
The invention changes the surface properties of the plane foil by forming an oxide film through anodization or chemical oxidation, transforming the inert metal surface into a surface with oxygen-containing functional groups that can chemically bond with the electrode active material, thereby preventing peeling while maintaining the simple plane foil structure
Solution Approach 2:
The invention creates a composite structure where the plane foil is covered with an oxide film layer that serves as an intermediate bonding layer between the metal substrate and the electrode active material, combining the electrical conductivity of the metal with the bonding capability of the oxide surface
2Ease of manufacture
If a plane foil is used as a positive current collector, then manufacturing is simpler, but gas generation becomes remarkable at high temperatures
Solution Approach 1:
The invention changes the chemical composition of the current collector surface by forming an oxide film that contains oxygen-containing functional groups, which react with or adsorb decomposition products at high temperatures, thereby suppressing gas generation while maintaining the simple plane foil manufacturing process
3Power
If conventional electrolyte composition is used, then initial conductivity is achieved, but resistance increases at low temperatures and high temperatures cause deterioration
Solution Approach 1:
The invention uses a composite electrolyte system combining two different lithium salts (LiPF6 and LiBF4) in specific proportions, where LiPF6 provides high ionic conductivity at room temperature and LiBF4 provides thermal stability and low-temperature performance, achieving broad temperature range reliability while maintaining good conductivity
Solution Approach 2:
The invention optimizes the concentration ratio of the two lithium salts in the electrolyte, specifically setting LiPF6 to 1-30 mmol/L and LiBF4 to 27-59 mmol/L in a 1:1 vol/vol mixture of cyclic carbonate and chain carbonate, thereby tuning the electrolyte's ionic conductivity, viscosity, and temperature stability to achieve balanced performance across wide temperature ranges
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 design ensures the lithium-ion capacitor remains stable at high temperatures and maintains low resistance at low temperatures, enhancing its durability and performance.
Implementation Method 1
The positive electrode mixture layer contains a positive electrode active material reversibly doped with an anion
Implementation Method 2
The negative electrode mixture layer contains a negative electrode active material reversibly doped with a lithium ion
Implementation Method 3
an electrolyte having lithium ion conductivity
Data Source
AI summary
In a lithium-ion capacitor, the positive electrode includes a positive current collector and a positive electrode mixture layer. The positive electrode mixture layer contains a positive electrode active material. An electrostatic capacity of the positive current collector is less than or equal to 20 μF/cm2. The negative electrode includes a negative current collector and a negative electrode mixture layer. The negative electrode mixture layer contains a negative electrode active material. The electrolyte contains a first lithium salt and a second lithium salt. The first lithium salt is a lithium salt of a fluorine-containing inorganic acid, and the second lithium salt is a lithium salt of a fluorine-containing acid imide. A proportion of a molar concentration of the first lithium salt in a total molar concentration of the first lithium salt and the second lithium salt in the electrolyte is more than 0% and less than or equal to 35%.