Secondary Battery Electrode Porosity Balance for Low Expansion
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Solution Overview
Problem
Secondary batteries such as lithium ion and sodium ion batteries experience volume expansion during charging and discharging, leading to reduced cycling performance due to thickness deformation of electrode plates, which existing technologies have not effectively addressed.
Innovation Solution
The solution involves controlling the compacted density to porosity ratio of the positive and negative electrode active layers within specific ranges to minimize thickness deformation and volume expansion, while ensuring good electrolyte infiltration, thereby improving cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the compacted density of electrode active layers is increased to reduce volume expansion, then the cycling performance is improved, but the electrolyte infiltration capability deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the ratio of compacted density to porosity within specific ranges (1.8≤A1/B1≤12 for positive electrode, 1≤A2/B2≤8 for negative electrode). This quantitative parameter optimization resolves the contradiction by finding the optimal balance point where sufficient density reduces volume expansion while adequate porosity maintains electrolyte infiltration, thereby improving cycling performance without sacrificing ion transport capability.
Solution Approach 2:
The patent utilizes porous materials by maintaining specific porosity values (B1 and B2) in the electrode active layers. The controlled porosity ensures that even with increased compacted density, the electrode structure retains sufficient void space for electrolyte penetration and ion diffusion, thus resolving the contradiction between density (for reduced expansion) and porosity (for maintained infiltration).
2Ease of operation
If the porosity of electrode active layers is increased to improve electrolyte infiltration, then the electrolyte infiltration capability is improved, but the volume expansion rate increases
Solution Approach 1:
The patent applies parameter changes by establishing specific ratio ranges for compacted density to porosity (1.8≤A1/B1≤12 and 1≤A2/B2≤8). This quantitative control ensures that porosity is increased only to the extent necessary for adequate electrolyte infiltration, while the corresponding compacted density is maintained high enough to limit volume expansion, thus resolving the contradiction between infiltration capability and expansion rate.
Solution Approach 2:
The patent applies local quality by differentiating the density-to-porosity ratio requirements between positive and negative electrodes. The positive electrode uses a higher ratio range (1.8-12) compared to the negative electrode (1-8), reflecting their different functional requirements. This localized optimization allows each electrode to achieve the precise balance between infiltration and expansion control suited to its specific role in the battery.
3Stability of the object's composition
If the compacted density to porosity ratio is increased to reduce thickness deformation, then the thickness rebound rate is reduced, but the electrolyte infiltration capability deteriorates
Solution Approach 1:
The patent applies parameter changes by defining specific ratio ranges for compacted density to porosity (1.8≤A1/B1≤12 for positive, 1≤A2/B2≤8 for negative). These quantitative parameters directly control thickness deformation while maintaining infiltration. The ratios are optimized to ensure that density increases (reducing rebound) do not exceed the point where porosity becomes insufficient for electrolyte access, thus resolving the contradiction between stability and infiltration.
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 reduces the thickness rebound rate of the electrode plates, leading to a lower volume expansion rate and enhanced cycling performance of the secondary battery.
Implementation Method 1
lithium ions or sodium ions are deintercalated from the positive electrode and then intercalated into the negative electrode through the electrolyte
Implementation Method 2
lithium ions or sodium ions are deintercalated from the positive electrode and then intercalated into the negative electrode through the electrolyte
Data Source
AI summary
A secondary battery comprises a positive electrode plate and a negative electrode plate. The positive electrode plate comprises a positive electrode current collector and a positive electrode active layer loaded on the surface of the positive electrode current collector, and the negative electrode plate comprises a negative electrode current collector and a negative electrode active layer loaded on the surface of the negative electrode current collector. The positive electrode active layer has a compacted density of A1 g/cm3 and a porosity of B1, and 1.8≤A1/B1≤12. The negative electrode active layer has a compacted density of A2 g/cm3 and a porosity of B2, and 1≤A2/B2≤8.