Positive Electrode Layer Structure for Balanced Li-Ion Deintercalation
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Solution Overview
Problem
Existing lithium batteries face challenges in achieving balanced conductivity across different regions of the positive electrode plate, leading to lithium ion deintercalation imbalances that affect cycling and rate performance.
Innovation Solution
A positive electrode plate design with a first film layer containing lithium transition metal phosphate and carbon coating, and a second film layer containing lithium transition metal oxide and a conductive agent, with a controlled resistivity difference of 10-200 Ω·cm, to improve conductivity and reduce lithium ion deintercalation imbalances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a positive electrode plate with uniform composition is used, then manufacturing is simple, but conductivity is uneven across different regions leading to lithium ion deintercalation imbalance
Solution Approach 1:
The positive electrode plate is segmented into multiple film layers (first film layer with lithium transition metal phosphate and carbon coating, second film layer with lithium transition metal oxide and conductive agent) with different compositions and conductivity characteristics. This segmentation allows each layer to contribute differently to overall conductivity, achieving balanced lithium ion deintercalation across the electrode while maintaining a manageable structural complexity through systematic layering.
Solution Approach 2:
Different regions of the positive electrode plate are assigned different local qualities through the multi-layer structure. The first film layer provides high conductivity in regions where lithium transition metal phosphate is used, while the second film layer provides complementary conductivity where lithium transition metal oxide is present. This local quality differentiation ensures uniform lithium ion deintercalation rates across the entire electrode surface.
2Productivity
If conductive agent is added to improve conductivity, then rate performance improves, but internal resistance increases due to excessive resistivity difference between film layers
Solution Approach 1:
The resistivity difference between the first and second film layers is precisely controlled within the range of 10-200 Ω·cm by adjusting the composition and thickness of each layer. This parameter control allows the conductive agent in the second film layer to enhance overall conductivity and improve rate performance, while the controlled resistivity difference prevents excessive internal resistance that would harm cycling performance.
Solution Approach 2:
The positive electrode plate uses a composite multi-layer structure where the first film layer (lithium transition metal phosphate with carbon coating) and second film layer (lithium transition metal oxide with conductive agent) are combined. This composite structure leverages the complementary conductivity characteristics of different materials, allowing the conductive agent to boost rate performance while the overall composite structure maintains balanced internal resistance for good cycling performance.
3Reliability
If carbon coating is applied on lithium transition metal phosphate, then conductivity of first film layer improves, but resistivity difference with second film layer becomes excessive
Solution Approach 1:
The carbon coating thickness and composition in the first film layer are optimized to provide sufficient conductivity enhancement for lithium transition metal phosphate, while the resistivity difference with the second film layer containing conductive agent is controlled within 10-200 Ω·cm. This parameter optimization ensures that the carbon coating improves conductivity balance without creating excessive resistivity differences that would limit lithium ion deintercalation rate.
Solution Approach 2:
The conductive agent in the second film layer acts as an intermediary that bridges the conductivity gap between the carbon-coated lithium transition metal phosphate in the first layer and the lithium transition metal oxide. This intermediary conductive agent ensures that the carbon coating's conductivity enhancement does not create excessive resistivity differences, maintaining both conductivity balance and high lithium ion deintercalation rates.
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 design enhances the cycling and rate performance of lithium batteries by balancing conductivity across film layers, reducing internal resistance and lithium ion imbalances, while maintaining energy density.
Implementation Method 1
The conductive agent added to the second film layer with a large resistivity value may reduce the overall resistivity of the second film layer and improve conductivity of the second film layer
Implementation Method 2
the first film layer includes a lithium transition metal phosphate and a carbon coating applied on at least part of the surface of the lithium transition metal phosphate
Implementation Method 3
reduce the lithium ion deintercalation imbalance caused by the excessive resistivity difference between the first film layer and the second film layer
Data Source
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AI summary
Embodiments of the present application provide a positive electrode plate, a secondary battery and an electrical apparatus. The positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, where the positive electrode film layer includes a first film layer and a second film layer in a thickness direction of the positive electrode plate; the first film layer includes a lithium transition metal phosphate and a carbon coating applied on at least part of the surface of the lithium transition metal phosphate, and the second film layer includes a lithium transition metal oxide and a conductive agent; and a resistivity difference between the second film layer and the first film layer is 10-200 Ω·cm. The technical solutions of the present application may improve the cycling and rate performance of the battery.