Rolled Supercapacitor Electrode Using Oriented Graphite Flakes
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Solution Overview
Problem
Current supercapacitors face challenges with low volumetric capacitances and energy densities due to limitations in electrode thickness, active material mass loading, and porosity, particularly with graphene-based electrodes which are brittle and have low tap densities, making it difficult to produce thick, highly porous electrodes that maintain high capacitance and energy storage efficiency.
Innovation Solution
The development of a rolled supercapacitor using exfoliated or expanded graphite flakes oriented parallel to the electrode plane, with a process that includes thermal exfoliation and mechanical shearing to create graphite worms or expanded graphite, which are then activated and used in a laminar structure with thin electrolyte layers to achieve high specific surface areas and densities, allowing for thicker, more robust electrodes with improved porosity and accessibility to electrolytes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional activated carbon electrodes are used to achieve high surface area, then specific capacitance is improved, but volumetric capacitance and energy density deteriorate due to low tap density and inability to produce thick electrodes
Solution Approach 1:
The patent changes the physical state and morphology of graphite material from conventional particles to exfoliated/expanded flake structures with specific orientation. This parameter change enables both high surface area for capacitance and high tap density for volumetric energy density, resolving the contradiction between specific and volumetric capacitance
Solution Approach 2:
The patent transitions from three-dimensional random particle packing to two-dimensional oriented flake structures. This dimensional change allows flakes to be stacked parallel to the electrode plane, maximizing surface area utilization while achieving high mass loading and thick electrode construction, thereby improving both specific and volumetric capacitance
2Quantity of substance
If electrode thickness is increased to improve energy density, then volumetric energy density is improved, but porosity and electrolyte accessibility deteriorate
Solution Approach 1:
The patent uses two-dimensional oriented flake structures that can be stacked to form thick electrodes while maintaining porosity. The parallel orientation of flakes creates inter-flake spaces that serve as electrolyte access channels, allowing thick electrodes to maintain both high energy density and adequate porosity
Solution Approach 2:
The patent creates a porous structure through the oriented stacking of exfoliated graphite flakes. The inter-flake spaces form a controlled porosity that allows electrolyte penetration even in thick electrodes, resolving the contradiction between electrode thickness and porosity maintenance
3Measurement precision
If graphene-based electrodes are used to achieve high surface area, then specific capacitance is improved, but mechanical strength and ease of manufacture deteriorate due to brittleness and low tap density
Solution Approach 1:
The patent uses composite structures formed by oriented stacking of exfoliated graphite flakes to create mechanically robust electrodes. The layered composite structure provides both high surface area for capacitance and mechanical strength, eliminating the brittleness issue of conventional graphene-based electrodes
Solution Approach 2:
The patent changes the morphology from conventional graphene particles to oriented exfoliated flake structures. This parameter change in shape and arrangement provides mechanical integrity while maintaining high surface area, resolving the contradiction between specific capacitance and mechanical strength
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 enables the production of supercapacitors with significantly higher volumetric capacitances and energy densities, overcoming the limitations of conventional methods by achieving higher active material mass loadings and tap densities, resulting in more efficient energy storage and power delivery.
Implementation Method 1
thermal exfoliation and mechanical shearing to create graphite worms or expanded graphite
Implementation Method 2
thermal exfoliation and mechanical shearing to create graphite worms or expanded graphite
Implementation Method 3
storing energy in the diffuse double layer. This double layer, created naturally at a solid-electrolyte interface when voltage is imposed
Implementation Method 4
storing energy in the diffuse double layer. This double layer, created naturally at a solid-electrolyte interface when voltage is imposed, has a thickness of only about 1 nm
Data Source
AI summary
Provided is rolled supercapacitor comprising an anode, a cathode, a porous separator, and an electrolyte, wherein the anode contains a wound anode roll of an anode active material having an anode roll length, width, and thickness and the anode active material contains flakes of graphite worms or expanded graphite that are oriented substantially parallel to the plane defined by the anode roll length and width; and/or the cathode contains a wound cathode roll of a cathode active material having a cathode roll length, width, and thickness, wherein the cathode active material contains flakes of graphite worms or expanded graphite that are oriented substantially parallel to the plane defined by the cathode roll length and width; and wherein the anode roll width and/or the cathode roll width is substantially perpendicular to the separator.