Nonaqueous Battery Electrodes With Carbon Nanotubes for Expansion Stability
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries with high active material density are susceptible to expansion and contraction during charging and discharging, leading to loss of electrical conductivity, impaired electrolyte flowability, and reduced durability.
Innovation Solution
Incorporating negative-electrode-side and positive-electrode-side carbon nanotubes into the electrode mixture layers, while using a negative electrode active material with a high capacity density, such as a Si-containing material, to achieve an expansion rate of 10% or more during charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the electrode is compressed with high pressure to increase active material density, then the capacity density is improved, but the electrical conductivity is lost due to damage to electrically conductive paths
Solution Approach 1:
The patent uses a composite structure consisting of active material particles embedded in a porous conductive matrix. This matrix maintains electrical conductivity even when compressed, while allowing high active material density. The conductive matrix acts as a flexible network that preserves conductive paths under compression stress.
Solution Approach 2:
The patent employs a porous conductive matrix that maintains void spaces even under compression. These pores allow the conductive network to remain intact while accommodating high active material loading. The porous structure prevents complete collapse of conductive paths during high-pressure compression.
2Quantity of substance
If the electrode is compressed with high pressure to increase active material density, then the capacity density is improved, but the flowability or liquid permeability of nonaqueous electrolyte is impaired
Solution Approach 1:
The porous conductive matrix maintains open pores that allow electrolyte flow even when the electrode is highly compressed. The pore size and connectivity are controlled to ensure adequate electrolyte permeability while maximizing active material density within the compressed structure.
3Stability of the object's composition
If VGCFs are contained in the electrode to reduce expansion and contraction influence, then the structural stability is improved, but the electrode is hardly compressed and active material density cannot be highly increased
Solution Approach 1:
The patent replaces rigid VGCFs with a flexible conductive matrix composite that provides structural stability without excessive rigidity. This matrix allows the electrode to be compressed to high densities while maintaining conductive paths and accommodating volume changes during charging/discharging cycles.
4Quantity of substance
If the negative electrode expands and contracts greatly during charging and discharging, then the capacity density is improved, but the amount of nonaqueous electrolyte in the positive electrode is reduced and cycle characteristics degrade
Solution Approach 1:
The porous conductive matrix in both electrodes acts as a buffer that accommodates volume changes during charging/discharging. The porous structure maintains electrolyte reservoir capacity and ensures continuous electrolyte availability, preventing electrolyte depletion in the positive electrode even when the negative electrode undergoes large expansion/contraction cycles.
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 configuration enhances the battery's capacity and maintains cycle characteristics by improving electrical conductivity and electrolyte flowability, while allowing for higher active material density without compromising durability.
Implementation Method 1
the negative electrode mixture layer includes a negative electrode active material capable of absorbing and releasing lithium ions, and negative-electrode-side carbon nanotubes, the positive electrode mixture layer includes a positive electrode active material capable of absorbing and releasing lithium ions, and positive-electrode-side carbon nanotubes
Implementation Method 2
the negative electrode mixture layer includes a negative electrode active material capable of absorbing and releasing lithium ions
Implementation Method 3
the positive electrode mixture layer includes a positive electrode active material capable of absorbing and releasing lithium ions
Data Source
AI summary
A nonaqueous electrolyte secondary battery includes a positive electrode, a negative electrode, and a nonaqueous electrolyte. The positive electrode includes a positive electrode current collector, and a positive electrode mixture layer supported on the positive electrode current collector. The negative electrode includes a negative electrode current collector, and a negative electrode mixture layer supported on the negative electrode current collector. The negative electrode mixture layer includes a negative electrode active material capable of absorbing and releasing lithium ions, and negative-electrode-side carbon nanotubes. The positive electrode mixture layer includes a positive electrode active material capable of absorbing and releasing lithium ions, and positive-electrode-side carbon nanotubes. The expansion rate during charging of the negative electrode is 10% or more.