Activated Carbon Electrode for Power-Storage Device
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Solution Overview
Problem
Existing activated carbons for power-storage devices, such as electric double layer capacitors and lithium ion capacitors, face challenges in achieving high volumetric capacitance, durability at high voltages, and uniform activation due to insufficient specific surface area, macropore distribution, and binder or conductive auxiliary agent usage.
Innovation Solution
The development of activated carbon with uniform consecutive macropores of 0.01 to 5 μm, a specific surface area of 1500 to 2700 m2/g, and a bulk density of 0.49 to 1.0 g/cm3, produced through a method involving a phenolic resin and polyvinyl alcohol mixture, pore-forming agents, and cross-linking agents, followed by carbonization and activation in an inert gas atmosphere, eliminating the need for binders or conductive materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional activated carbon particles with diameter of 1 to 10 μm are molded into sheet shape using binder and conductive auxiliary agent, then electrode manufacturing is simplified, but volumetric capacitance and high-voltage durability are reduced due to contact interface defects and insufficient specific surface area
Solution Approach 1:
The invention extracts and eliminates the binder and conductive auxiliary agent from the electrode structure, using only activated carbon particles. This removes the harmful contact interfaces between particles that cause capacitance decline and reduce high-voltage durability, while maintaining ease of manufacture through simplified material composition
Solution Approach 2:
The invention changes the particle size parameter to 10 μm or larger, which reduces the number of particle contacts and interfaces compared to conventional 1-10 μm particles. This parameter change decreases the total contact interface area, reducing capacitance decline and improving high-voltage durability while maintaining manufacturability
2Use of energy by moving object
If charging voltage is increased to 3V or more to improve energy density, then energy storage capacity increases, but electrolysis occurs between electrodes and electrolyte causing capacitance reduction and degradation
Solution Approach 1:
The invention changes the particle size parameter to 10 μm or larger, which modifies the electrode's interaction with the electrolyte. This reduces electrolysis reactions at high voltages, enabling stable operation at 3V or more while improving energy density, thereby resolving the contradiction between energy storage capacity and capacitance stability
3Quantity of substance
If specific surface area is increased to improve capacitance, then energy storage capacity increases, but manufacturing complexity and activation uniformity become problematic
Solution Approach 1:
The invention changes the particle size to 10 μm or larger, which provides sufficient specific surface area for high capacitance while maintaining uniform activation throughout the particle. This size parameter ensures that the activation process can penetrate and uniformly treat the entire particle, avoiding the non-uniform activation problems associated with smaller particles or complex structures
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 volumetric capacitance, improved durability at high voltages (3V or more for electric double layer capacitors and 4V or more for lithium ion capacitors), and enhanced activation yield, enabling efficient electrolyte infiltration and charge/discharge performance.
Implementation Method 1
capability of charging and discharging at a high rate, (2) high reversibility of charging and discharging cycles, (3) longer cycle life, and (4) environmentally friendly property due to no use of heavy metal in an electrode or an electrolyte. These characteristics are associated with no use of heavy metal in an electric double layer capacitor, operation by ion's physical adsorption and desorption
Implementation Method 2
operation by ion's physical adsorption and desorption
Data Source
AI summary
First, the present invention involves adding a curing catalyst to a phenolic resin, polyvinyl alcohol, a pore-forming agent, and a cross-linking agent, and mixing, casting, heating, and drying the same. Next, the plate-shaped porous phenolic resin obtained thereby which has uniform consecutive macropores having an average pore diameter in the range of 3 to 35 μm and formed in a three-dimensional network pattern is immersed with an organic solvent. Thereafter, this block is extracted and pressure is applied thereto. It is possible to obtain plate-shaped activated carbon for use in an electrode of a power-storage device by carbonizing and activating a block which has undergone this procedure by keeping the same at an increased temperature.