Conditioned Carbon Electrodes for Wide Temperature Capacitors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current electrolyte solutions for electrochemical devices face challenges in achieving high temperature performance without high vapor pressure and maintaining low temperature functionality, especially in capacitors and lithium batteries, where solvents used for low temperature performance often limit high voltage operation and stability.
Innovation Solution
The use of a solvent system comprising 20-100% by weight of symmetrical and unsymmetrical carbonates, combined with conductive salts like lithium or quaternary ammonium salts, which are heat-treated and used with activated carbon electrodes to reduce internal resistance and enhance low temperature and high temperature performance, achieving a stable operating voltage of 4V and wide liquidus range from -70°C to >150°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If volatile solvents like acetonitrile, THF, or low molecular weight esters are used to achieve low temperature performance, then low temperature freezing point is reduced, but high temperature vapor pressure increases
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte solvent system by using specific ratios of cyclic carbonates (ethylene carbonate, propylene carbonate) combined with linear carbonates (dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate) to achieve both low freezing point and low vapor pressure, eliminating the need for volatile solvents
Solution Approach 2:
The patent employs a composite solvent system combining multiple carbonate components (cyclic and linear) with specific physical and chemical properties that complement each other, creating a synergistic electrolyte solution that simultaneously achieves low temperature fluidity and high temperature stability with low vapor pressure
2Temperature
If organic carbonate mixtures are used to achieve low temperature performance, then freezing point is reduced, but operating voltage is limited to about 3V
Solution Approach 1:
The patent optimizes the concentration ratios of different carbonate components in the electrolyte solution to change the electrochemical window and interfacial properties, enabling stable operation at higher voltages (up to 4V) while maintaining low temperature performance
Solution Approach 2:
The patent modifies the local chemical environment at the electrode-electrolyte interface through the specific carbonate composition, creating favorable conditions for high voltage operation while the bulk solvent composition maintains low freezing point
3Quantity of substance
If activated carbon electrodes are used to increase surface area, then energy storage capacity is improved, but internal resistance increases due to oxygen-containing functional groups
Solution Approach 1:
The patent applies preliminary heat treatment to the activated carbon electrodes before use, which removes oxygen-containing functional groups and stabilizes the carbon structure in advance, thereby reducing internal resistance and improving electrochemical performance before the electrodes are put into service
Solution Approach 2:
The patent converts the harmful effect of oxygen-containing functional groups (which cause high internal resistance and voltage limitations) into a benefit by applying heat treatment that selectively removes these groups, thereby improving the overall performance and stability of the electrode material
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
This solution provides improved energy density, reduced internal resistance, and stable performance across a wide temperature range, enabling efficient operation of ultra capacitors and lithium ion batteries with high power density and long lifetime.
Implementation Method 1
an electrolyte solution which comprises a conductive salt such as a lithium salt or a quaternary ammonium salt
Implementation Method 2
these carbons are 'activated' in a second step using steam or catalyzed with KOH, NaOH and/or carbon dioxide and KOH to increase the surface area
Data Source
AI summary
There is provided an improvement for capacitors having activated carbon electrodes by the use of an electrolyte solution containing a carbonate of the formula RO(C═O)OR1 and a conductive salt such as a lithium salt or a quaternary ammonium salt at a concentration of from 0.6 to 3 mol/l.