Positive Electrode with Dielectric Particles for Battery Resistance
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Solution Overview
Problem
Lithium-ion secondary batteries face issues with dielectric particle aggregation leading to increased cell resistance and reduced durability due to insufficient contact between dielectric particles and the electrolytic solution, causing corrosion and decomposition.
Innovation Solution
A positive electrode with a peak pore diameter smaller than or equal to the median diameter of dielectric particles, containing 0.1% to 2% by mass dielectric particles with high relative permittivity, and a bimodal particle size distribution of the active material to enhance contact and stability, reducing cell resistance and improving durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dielectric particles with particle sizes of 200 nm or less are used to increase dielectric polarization, then the dissociation degree of supporting salt in electrolytic solution increases, but the particles aggregate causing reduction in contact rate with electrolytic solution and increase in cell resistance
Solution Approach 1:
The patent changes the particle size parameter of dielectric particles from 200 nm or less to 0.2 μm to 2 μm (200 nm to 2000 nm). This parameter change prevents aggregation while maintaining sufficient dielectric polarization effectiveness, thereby reducing cell resistance while preserving the beneficial effects on electrolytic solution dissociation.
Solution Approach 2:
The patent specifies that dielectric particles should be distributed throughout the positive electrode active material layer with controlled local concentration. This ensures adequate contact between particles and electrolytic solution in local regions while maintaining overall polarization effectiveness, preventing both aggregation and insufficient contact.
2Reliability
If dielectric particles are used in large amounts to enhance electrolytic solution stability and acid trapping, then electrode corrosion and solution decomposition are prevented, but particle aggregation occurs reducing contact rate and increasing cell resistance
Solution Approach 1:
The patent optimizes the particle size parameter to 0.2 μm to 2 μm, which allows using sufficient amounts of dielectric particles for electrolytic solution stabilization and acid trapping without causing aggregation. This particle size range maintains both stability enhancement and low cell resistance.
Solution Approach 2:
The patent creates a composite structure where dielectric particles are dispersed within the positive electrode active material layer. This composite approach allows the dielectric particles to perform multiple functions (acid trapping, solution stabilization) while the active material matrix prevents aggregation and maintains good contact with electrolytic solution.
3Area of stationary object
If smaller particle sizes are used to increase surface area and contact with electrolytic solution, then dielectric polarization effectiveness increases, but aggregation occurs reducing the beneficial effects
Solution Approach 1:
The patent selects an optimal particle size range of 0.2 μm to 2 μm that balances surface area availability with dispersion stability. This size range provides sufficient surface area for dielectric polarization while being large enough to resist aggregation, maintaining stable dispersion in the electrode structure.
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 lower cell resistance and higher durability of lithium-ion secondary batteries by increasing dielectric polarization and acid trapping, preventing corrosion and decomposition, and maintaining high energy density.
Implementation Method 1
the dielectric polarization of the dielectric particles will be insufficiently effective in increasing the dissociation degree of the supporting salt in the electrolytic solution
Implementation Method 2
dielectric particles having a relative permittivity of 20 or more
Implementation Method 3
the dielectric particles will be insufficiently effective in trapping a small amount of an acid in the electrolytic solution
Data Source
AI summary
Provided is a positive electrode including: a positive electrode current collector; and a positive electrode material mixture layer, the positive electrode material mixture layer including a positive electrode active material and dielectric particles, the positive electrode having a peak pore diameter smaller than or equal to the median diameter of the dielectric particles. Also provided is an electricity storage device including: the positive electrode; a negative electrode; and an electrolytic solution.