Capacitor Electrode Production via Controlled Solvent Drying and Calendering
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Solution Overview
Problem
Conventional electrodes for electric double layer capacitors face challenges in achieving smaller and lighter designs while maintaining sufficient performance, due to insufficient physical adhesiveness and internal resistance, and limitations in thickness for mechanical strength.
Innovation Solution
A method involving the formation of an undercoat layer with electrically conductive particles and a binder on a current collector, followed by a carbon-based electrode layer, with both layers undergoing drying and calendering treatment to achieve a high-density electrode layer, where the solvent content is set within a specific range of 5 to 35% by weight before calendering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the electrode layer is made thinner to reduce electrode size and weight, then the energy density per unit volume improves, but the mechanical strength becomes insufficient
Solution Approach 1:
The electrode structure is divided into multiple functional layers: a support layer providing mechanical strength and an active material layer containing the carbon particles and binder for electrochemical function. This segmentation allows the support layer to bear the mechanical load while the active material layer can be made thin for high energy density.
Solution Approach 2:
A binder is introduced as an intermediary material that adheres the carbon particles to each other and to the support layer. This binder creates a cohesive structure that maintains mechanical integrity even when the active material layer is made thin, resolving the contradiction between thickness reduction and strength maintenance.
2Ease of manufacture
If conventional vapor deposition or bonding methods are used to attach the current collector to activated carbon, then the manufacturing process is simple, but the physical adhesiveness is insufficient and internal resistance decreases inadequately
Solution Approach 1:
The electrode uses a composite structure combining a support layer (current collector) with an active material layer containing carbon particles and binder. This composite approach provides both strong adhesion and low internal resistance, improving upon simple vapor deposition or bonding methods while maintaining manufacturing feasibility.
3Reliability
If an intermediate layer of carbon black and binder is used to bond the electrode layer to the current collector, then the adhesiveness improves and contact resistance decreases, but the electrode layer thickness cannot be reduced further due to mechanical strength requirements
Solution Approach 1:
The electrode is segmented into a support layer and an active material layer, where the support layer serves as both the current collector and the bonding substrate. This eliminates the need for a separate intermediate layer, as the support layer itself provides the mechanical strength and bonding function, allowing the active material layer to be made thinner.
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 a thinner, lighter electrode with improved adhesive properties and reduced internal resistance, enabling higher energy density per unit volume and capacity in electric double layer capacitors.
Implementation Method 1
drying the electrode coating layer to set an amount of a solvent remaining in the whole of the layer formed on the current collector
Implementation Method 2
subjecting the electrode coating layer after the drying to calendering treatment
Data Source
AI summary
The present invention provides a method of producing an electrode for an electric double layer capacitor, which yields the electrode with an electrode layer having a higher density by calendering treatment. A method of producing an electrode for a capacitor, which comprises at least a current collector and an electrode layer on the current collector, the method comprising the steps of: applying an electrode layer coating material which comprises at least a carbon material, a binder and a solvent, onto the current collector to form an electrode coating layer; drying the electrode coating layer on the current collector to set the amount of the solvent remaining in the electrode coating layer within a range of 5 to 35% by weight of the layer; and subjecting the electrode coating layer after the drying to calendering treatment to yield an electrode layer.