Oxidized Graphite Electrode Active Material for High Capacitance
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Solution Overview
Problem
Conventional alkaline activation methods for producing active carbon for electrochemical double layer capacitors (EDLCs) result in electrodes with low capacitance per volume and poor charge/discharge cycle characteristics due to expansion and cracking from electrolyte intercalation, along with increased manufacturing costs and equipment corrosion.
Innovation Solution
A method involving pre-treating carbon materials through heat treatment, followed by oxidation with specific oxidants and subsequent reduction, to form an oxidized graphite structure with increased interlayer distance, enhancing capacitance per volume and reducing electrode expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If active carbon with large specific surface area is used to form more electrochemical double layers, then specific capacitance per mass increases, but electrode density decreases, limiting specific capacitance per volume
Solution Approach 1:
The invention changes the structural parameters of carbon materials by controlling interlayer distance through oxidation and heat treatment processes. By adjusting the interlayer distance to 0.34-0.5 nm, the invention achieves optimal balance between specific surface area and electrode density, thereby improving both specific capacitance per mass and specific capacitance per volume simultaneously
2Quantity of substance
If alkaline activation method is used to increase capacitance per volume, then interlayer distance increases and capacitance improves, but electrode expansion and cracking occur due to repeated intercalation and deintercalation
Solution Approach 1:
The invention performs preliminary oxidation and heat treatment on carbon materials before they are used as electrode active material. This preliminary action creates a stable graphite-like structure with controlled interlayer distance, which prevents subsequent expansion and cracking during repeated charge/discharge cycles, thereby improving reliability while maintaining high capacitance per volume
3Ease of manufacture
If conventional alkaline activation is used to produce active carbon, then manufacturing process is established, but equipment corrosion and increased manufacturing costs occur
Solution Approach 1:
The invention uses strong oxidants such as nitric acid, sulfuric acid, or phosphoric acid to oxidize carbon materials at elevated temperatures (300-2000°C). This oxidation process creates a graphite-like structure with increased interlayer distance without requiring alkaline activation, thereby eliminating equipment corrosion issues while maintaining ease of manufacture through a simplified process
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 method significantly increases capacitance per volume, reduces electrode expansion, and simplifies the production process, resulting in improved durability and lower internal resistance for EDLCs, making them suitable for high-performance energy storage devices.
Implementation Method 1
pre-treating a carbon material through heat treatment
Implementation Method 2
oxidizing the pre-treated carbon material using an oxidant
Data Source
AI summary
An active material of the present invention has fine pores formed in the interlayer of a carbon material capable of exhibiting electrochemical double layer capacitance. The fine pores are formed by forming an oxidized graphite structure combined with oxygen in the interlayer of a part or whole of the carbon material containing soft carbon and then removing a part or whole of oxygen in the interlayer. A method for producing an energy storage active material for use in an electrochemical double layer capacitor comprises pre-treating a carbon material through heat treatment and oxidizing the pre-treated carbon material using an oxidant. The method further comprises reducing the oxidized carbon material through heat treatment. The interlayer distances of an active material for respective steps, measured by a powder X-ray diffraction method, are 0.33˜0.36 nm in the pre-treatment step, 0.5˜2.1 nm in the oxidation step, and 0.34˜0.5 nm in the reduction step.