Positive Electrode Plate Coating Layout to Prevent Battery Overdischarge
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Solution Overview
Problem
Lithium-ion secondary batteries face issues with overdischarge and rapid performance fading due to gelation during stirring when nanoscale lithium iron phosphate or lithium manganese iron phosphate is mixed with layered transition metal oxides, leading to equilibrium potential differences and solid-phase concentration polarization.
Innovation Solution
The olivine-structured phosphate compound is divided into small-grained and large-grained parts, with the small-grained part applied on both sides of the current collector as a coating layer and the large-grained part mixed with layered transition metal oxide, forming a second coating layer to prevent gelation and improve charge-discharge capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If nanoscale lithium iron phosphate or lithium manganese iron phosphate is directly mixed with layered transition metal oxide, then the charge-discharge capabilities are improved, but gelation occurs during stirring and performance fades rapidly
Solution Approach 1:
The patent divides the olivine-structured phosphate compound into two distinct particle size ranges: small particles (0.5-2 μm) applied separately on both sides of the current collector, and large particles (>2 μm) mixed with layered transition metal oxide. This segmentation prevents gelation during stirring while maintaining high charge-discharge capabilities, as the small particles provide rapid reaction kinetics without causing aggregation issues that plague nanoscale materials.
Solution Approach 2:
The patent applies different particle sizes of olivine-structured phosphate compound to different locations and functions within the electrode structure. Small particles are applied on both sides of the current collector to provide stable foundation and prevent gelation, while large particles are mixed with layered transition metal oxide in the second coating layer to maximize charge-discharge capabilities. This local differentiation optimizes both stability and performance.
2Power
If small-grained olivine-structured phosphate compound is mixed with layered transition metal oxide, then the kinetic performance is improved, but solid-phase concentration polarization increases causing overdischarge
Solution Approach 1:
The patent segments the olivine-structured phosphate compound into small and large particle sizes and assigns them different functions. Small particles (0.5-2 μm) are applied separately on both sides of the current collector to provide low solid-phase concentration polarization and prevent overdischarge. Large particles are mixed with layered transition metal oxide to provide high kinetic performance. This functional segmentation resolves the contradiction between kinetic performance and overdischarge suppression.
Solution Approach 2:
The patent extracts the small-grained olivine-structured phosphate compound from the mixture with layered transition metal oxide and applies it separately on both sides of the current collector. This extraction allows the small particles to发挥 their low solid-phase concentration polarization advantage without being contaminated by the high polarization effect of layered transition metal oxide, thereby preventing overdischarge while maintaining kinetic performance.
3Reliability
If olivine-structured phosphate compound is divided into small-grained and large-grained parts and applied in separate layers, then gelation is prevented and cycle stability is enhanced, but the device structure becomes more complex
Solution Approach 1:
The patent divides the olivine-structured phosphate compound into small and large particle sizes and applies them in two separate coating layers. This segmentation prevents gelation during stirring and enhances cycle stability by optimizing the functional distribution of different particle sizes. The increased structural complexity is justified by the significant improvement in reliability and performance stability.
Solution Approach 2:
The patent applies the small-grained olivine-structured phosphate compound on both sides of the current collector first, before mixing the large-grained part with layered transition metal oxide. This preliminary action creates a stable foundation that prevents gelation during subsequent mixing and application of the second coating layer, simplifying the overall manufacturing process despite the two-layer structure.
Data Source
AI summary
This application provides a positive electrode plate, a lithium-ion secondary battery, a battery module, a battery pack, and an electrical device. The positive electrode plate of this application includes: a current collector, a first coating layer applied on both sides of the current collector, and a second coating layer applied on a surface of the first coating layer. The first coating layer contains a small-grained olivine-structured phosphate compound, and a particle diameter of the small-grained olivine-structured phosphate compound is 0.5 to 2 μm. The second coating layer contains: a large-grained olivine-structured phosphate compound and a layered transition metal oxide; or a large-grained olivine-structured phosphate compound and a pure layered transition metal oxide. A particle diameter of the large-grained olivine-structured phosphate compound is larger than a particle diameter of the small-grained olivine-structured phosphate compound.