Graphite Negative Electrode Layer for Uniform Expansion Control
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Solution Overview
Problem
Graphite-based negative active materials in energy storage devices experience significant expansion and contraction during charge-discharge cycles, leading to degradation of the electrode and separator, which affects the performance of the device.
Innovation Solution
The use of solid graphite particles with an aspect ratio of 1 to 5 and a uniform density in the negative active material layer, applied without pressing, allows for uniform expansion and reduced stress, maintaining a high packing ratio and suppressing non-uniform expansion of the negative electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If graphite is used as negative active material to increase energy density, then energy density is improved, but electrode expansion during charge-discharge degrades device performance
Solution Approach 1:
The patent changes the physical parameters of graphite particles by controlling their aspect ratio to fall within 1.05 to 1.30 and spherical shape, which modifies how the graphite expands and contracts during charge-discharge cycles. This parameter optimization allows graphite to maintain high energy density while reducing harmful expansion effects on the electrode structure
Solution Approach 2:
The patent creates a composite structure by combining graphite particles with specific aspect ratios and spherical shapes with the electrode matrix. This composite approach allows the graphite to contribute high energy density while the controlled morphology and structure mitigate expansion issues, resolving the contradiction between energy density and reliability
2Quantity of substance
If graphite particles with high aspect ratio are used, then volumetric energy density is improved, but non-uniform expansion occurs during initial charge
Solution Approach 1:
The patent optimizes the aspect ratio parameter of graphite particles to a specific range (1.05 to 1.30) and controls their spherical shape. This parameter optimization ensures that the particles achieve high volumetric energy density while maintaining uniform expansion characteristics during initial charge, preventing the non-uniform expansion that would occur with particles outside this range
3Quantity of substance
If negative active material layer is pressed to increase density, then packing ratio is improved, but expansion during initial charge increases
Solution Approach 1:
The patent changes the particle morphology parameters (aspect ratio and spherical shape) of the graphite to fall within specific ranges. This parameter optimization allows the material to achieve high packing ratio through particle arrangement and density without requiring excessive pressing, thereby reducing the overall expansion volume during initial charge while maintaining efficient space utilization
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 enhances the suppressive effect on the expansion of the negative electrode during initial charge, maintaining the integrity and performance of the energy storage device by preventing non-uniform expansion and improving charge-discharge efficiency.
Implementation Method 1
graphite expands and contracts significantly during charge-discharge
Implementation Method 2
maintaining a high packing ratio and suppressing non-uniform expansion of the negative electrode
Data Source
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AI summary
An aspect of the present invention is an energy storage device including an electrode assembly that has a negative electrode and a positive electrode, where the negative electrode contains a negative electrode substrate and a negative active material, and has a negative active material layer disposed in an unpressed shape along at least one surface of the negative electrode substrate, the negative active material includes solid graphite particles as a main component, and the solid graphite particles have an aspect ratio of 1 or more and 5 or less.