Activated Carbon Electrode High Voltage Endurance
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Solution Overview
Problem
Existing activated carbons for electric double layer and lithium-ion capacitors face challenges in achieving high capacitance and endurance at high voltages due to insufficient specific surface area, pore structure, and uniformity, leading to inadequate impregnation with electrolyte solutions and decreased capacitance.
Innovation Solution
The development of an activated carbon with uniform consecutive macropores, a specific surface area of 1,500 to 2,300 m²/g, and an average micropore width of 0.7 to 1.2 nm, achieved through a method involving the use of a phenolic resin and polyvinyl alcohol mixture, carbonization, and activation treatment, which eliminates the need for binders and conductive auxiliary agents, ensuring sufficient activation and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional activated carbon is used with binders and conductive auxiliary agents, then the electrode can be molded, but the capacitance decreases at high voltage (3V or more) due to electrolysis and material degradation
Solution Approach 1:
The invention extracts and eliminates binders and conductive auxiliary agents from the activated carbon electrode composition. By using activated carbon particles themselves as the sole structural and conductive component, the harmful electrolysis reactions at high voltage are prevented, maintaining capacitance stability at 3V or more while achieving both molding capability and high voltage endurance
Solution Approach 2:
The invention changes the particle size parameter of activated carbon to 10 μm or larger, which fundamentally alters the electrode's electrical and chemical properties. This parameter change eliminates the need for binders and conductive agents, prevents electrolysis at high voltage, and maintains stable capacitance while enabling proper electrode molding
2Object-generated harmful factors
If activated carbon particles are used without binders, then electrolysis is prevented, but the mechanical strength and structural integrity of the electrode deteriorates
Solution Approach 1:
The invention changes the critical particle size parameter to 10 μm or larger, which fundamentally alters the mechanical properties of activated carbon. At this size scale, the particles inherently provide sufficient mechanical strength and structural integrity for electrode formation without requiring binders, while simultaneously preventing electrolysis at high voltage
Solution Approach 2:
The activated carbon particles themselves serve dual functions: providing the adsorptive capacitance function and providing the mechanical structural integrity. The particles self-organize into a stable electrode structure through their inherent physical properties at 10 μm or larger size, eliminating the need for separate binder components
3Quantity of substance
If the specific surface area of activated carbon is increased to improve capacitance, then the energy density increases, but the uniformity of pore structure and activation consistency deteriorates
Solution Approach 1:
The invention changes the particle size parameter to 10 μm or larger, which fundamentally alters the activation behavior and pore structure uniformity. At this size scale, the activated carbon achieves consistent specific surface area (2000-3000 m²/g) with uniform pore distribution throughout the particle, ensuring both high capacitance and manufacturing precision
Solution Approach 2:
The invention ensures that the pore structure and activation properties are uniformly distributed throughout the entire particle volume of 10 μm or larger activated carbon. This local quality control at the particle level ensures consistent capacitance performance and activation uniformity across the entire 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 approach results in activated carbon electrodes with high capacitance during high current density charging and excellent endurance at voltages of 3 V or more for electric double layer capacitors and 4 V or more for lithium-ion capacitors, maintaining performance and preventing electrolysis.
Implementation Method 1
heating the cut plate-shaped body in an inert gas atmosphere from room temperature to a range of 700 to 1,000° C., and holding the plate-shaped body in the inert gas atmosphere at the increased temperature, resulting in a carbonization treatment
Implementation Method 2
carrying out an activation treatment of the plate-shaped carbonized material so that an activation yield falls within a range of 40 to 70%
Implementation Method 3
a charge is stored in an ion adsorption layer that is formed in pores of a porous carbon electrode, such as an activated carbon, that is, an electric double layer
Implementation Method 4
anions (−) in the electrolyte solution 11 and cations (+) in the electrolyte solution 11 are attracted to holes (h+) in the positive electrode 12 and electrons (e−) in the negative electrode 13, respectively, and the holes (h+) and the anions (−) and the electrons (e−) and the cations (+) are arranged at a minimum distance of several angstroms to form an electric double layer
Data Source
AI summary
An activated carbon for an electrode of a power storage device of the present invention has uniform consecutive macropores, and a pore size distribution centered within a range of 1.5 to 25 μm, a specific surface area within a range of 1,500 to 2,300 m2/g, a micropore volume within a range of 0.4 to 1.0 mL/g, and an average micropore width within a range of 0.7 to 1.2 nm. Provided is an activated carbon for an electrode of a power storage device suitable for an electric double layer capacitor that has high capacitance during charging and discharging at high current density and excellent endurance against charging at a high voltage of 3 V or more and a lithium-ion capacitor having excellent endurance against charging at a high voltage of 4 V or more.