Negative Electrode Mixture Layer Orientation Control
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face challenges in maintaining cycle life and preventing battery swelling due to deformation during charge/discharge cycles, especially when using deformable materials like laminate films, and existing techniques do not adequately address these issues.
Innovation Solution
A negative electrode for nonaqueous electrolyte secondary batteries is designed with a mixture layer containing graphite active material particles and a binder, with a specific density and particle size distribution, and a controlled degree of orientation to enhance input characteristics and reduce swelling, achieved by adjusting the rolling pressure and particle size distribution of the negative electrode mixture layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the packing density of active material is increased by raising the rolling pressure during electrode manufacture, then the energy density of the battery is improved, but the degree of orientation of graphite particles increases causing reduced input characteristics and cycle life
Solution Approach 1:
The patent changes the particle size distribution parameter of graphite particles (specifically controlling the proportion of particles with diameter 0.7mm or more to 30-70%) to resolve the contradiction. This parameter change allows achieving high packing density without excessive orientation, thereby improving both energy density and input characteristics simultaneously
Solution Approach 2:
The patent uses a composite approach by combining graphite particles with specific size distribution characteristics. The mixed particle size composition creates a more efficient packing structure that reduces orientation effects while maximizing energy density, effectively resolving the technical contradiction through material composition optimization
2Quantity of substance
If the rolling pressure is raised to increase packing density, then the energy density is improved, but the graphite particles are deformed or cleaved further increasing orientation and reducing cycle life
Solution Approach 1:
The patent changes the particle size distribution parameter (controlling particles with diameter 0.7mm or more to 30-70%) to reduce deformation and cleavage during rolling. This parameter optimization allows achieving high packing density while minimizing particle damage, thereby improving both energy density and cycle life
3Quantity of substance
If the degree of orientation of graphite particles is increased, then the packing density is improved, but lithium ions are unlikely to be stored in graphite particles reducing input characteristics
Solution Approach 1:
The patent optimizes the particle size distribution parameter (particles with diameter 0.7mm or more at 30-70%) to control the degree of orientation during rolling. This parameter control achieves high packing density while maintaining sufficient edge plane exposure for lithium ion storage, resolving the contradiction between packing density and input characteristics
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
The solution results in a high-capacity battery with improved cycle life and reduced swelling after repeated charge/discharge cycles, maintaining performance and capacity retention even under high-temperature conditions.
Implementation Method 1
raising the rolling pressure during the manufacture of electrodes
Implementation Method 2
lithium ions are intercalated between layers from edge planes of graphite crystals
Implementation Method 3
the diffraction intensity ratio (002)/(110) determined by the X-ray diffraction of the negative electrode
Data Source
AI summary
A negative electrode for nonaqueous electrolyte secondary batteries includes a negative electrode core member and a negative electrode mixture layer attached to the negative electrode core member, wherein the negative electrode mixture layer contains negative electrode active material particles with a graphite structure and a binder, the mixture density of the negative electrode mixture layer is 1.5 g/cm3 to 1.8 g/cm3, the ratio I(002)/I(110) of the diffraction intensity I(002) of the (002) plane to the diffraction intensity I(110) of the (110) plane satisfies 60≦I(002)/I(110)≦120 as determined by measuring the negative electrode mixture layer by an X-ray diffraction method, the amount of particles with a size of 1 μm to 10 μm in the particle size distribution of a crushed product of the negative electrode mixture layer is 12% to 25% by volume.