Gradient Porosity Electrode for High Energy Density
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Solution Overview
Problem
Increasing the thickness of the active material-containing layer in lithium-ion secondary batteries to enhance energy density leads to reduced electrolyte permeability, as the distance between the active material and the current collector increases, making it difficult for the electrolyte to penetrate effectively, thereby affecting charge-discharge characteristics.
Innovation Solution
The active material-containing layer is formed with a specific porosity gradient, where the porosity near the surface is higher than near the current collector, ensuring high porosity and permeability, even after compression, allowing diethyl carbonate to permeate at a rate of 0.1 g/(cm2·min or higher, by controlling the average porosity in segments of the layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of the active material-containing layer is increased to enhance energy density, then the energy density is improved, but the electrolyte permeability deteriorates
Solution Approach 1:
The patent applies local quality by creating a non-uniform porosity distribution within the active material-containing layer. Specifically, the porosity is designed to be higher in the lower portion (near the current collector) and lower in the upper portion (surface), forming a gradient structure. This localized variation in porosity allows the lower portion to maintain high electrolyte permeability despite the overall increased thickness, while the upper portion can have higher active material density for energy density improvement.
2Quantity of substance
If the thickness of the active material-containing layer is increased, then the energy density is improved, but the charge-discharge characteristics deteriorate
Solution Approach 1:
The patent creates a gradient porosity structure where the lower portion has higher porosity to ensure rapid electrolyte access and ion transport near the current collector, while the upper portion has lower porosity to maximize active material content. This local differentiation resolves the contradiction by ensuring that the regions most critical for charge-discharge performance (near the current collector) maintain optimal permeability, while other regions contribute to energy density.
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 maintains high electrolyte permeability in the active material-containing layer, even with increased thickness, enhancing the battery's performance and productivity by ensuring smooth lithium ion movement and dispersion.
Implementation Method 1
diethyl carbonate permeates the active material-containing layer at a rate of 0.1 g/(cm2·min) or higher
Data Source
AI summary
The electrode of the present invention includes a current collector and an active material-containing layer formed on one side or both sides of the current collector. The active material-containing layer has a thickness of 20 to 200 μm per one side of the current collector, and diethyl carbonate permeates the active material-containing layer at a rate of 0.1 g/(cm2·min) or higher. Further, the method for producing an electrode of the present invention includes the steps of: forming an electrode precursor by forming an active material-containing layer on one side or both sides of a current collector; and compressing the electrode precursor. In the electrode precursor forming step, the active material-containing layer is formed such that the active material-containing layer has a higher porosity in a portion close to the current collector then in other portions.