Positive Electrode Sheet Resistance Layer for Slower Lithium Release
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Solution Overview
Problem
Lithium-ion secondary batteries have a limited cycle life, with capacity decaying to 80% of its initial value after approximately 800 to 900 charge and discharge cycles, necessitating improvements in surface coatings and conductive material content to enhance service life, but existing methods are costly and technically challenging.
Innovation Solution
A positive electrode sheet for secondary batteries is designed with a current collector, a resistance layer, and a positive electrode active material layer, where the resistance layer has a higher resistance than the active material layer, and is strategically positioned to control lithium ion release, ensuring power performance while extending battery life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the cycle life of lithium-ion secondary batteries is extended by improving surface coating and increasing conductive material content, then service life is improved, but manufacturing cost and technical complexity increase significantly
Solution Approach 1:
The positive electrode sheet is segmented into multiple functional layers: a current collector, a positive electrode active material layer, and a resistance layer. This segmentation allows each layer to perform its specific function - the active material layer provides lithium ion storage while the resistance layer controls release kinetics, achieving extended cycle life without requiring complex surface coatings or high conductive material content throughout the entire electrode structure
Solution Approach 2:
The resistance layer is applied locally on specific regions of the current collector rather than uniformly throughout the entire electrode. This local quality approach allows precise control over lithium ion release in specific areas, extending battery service life while minimizing the amount of additional materials needed and reducing manufacturing complexity compared to global modifications
2Duration of action of stationary object
If a resistance layer is added to control lithium ion release, then cycle life is extended, but device structure becomes more complex
Solution Approach 1:
The resistance layer serves multiple functions simultaneously: it controls lithium ion release kinetics to extend cycle life, maintains power performance through optimized resistance values (0.1-10 Ω·cm²), and provides a straightforward structural addition that integrates easily with existing electrode manufacturing processes. This multi-functionality reduces the need for multiple separate components or complex surface treatment processes
Solution Approach 2:
The positive electrode sheet is constructed as a composite structure combining the current collector, positive electrode active material layer, and resistance layer. This composite material approach allows each component to contribute its specific properties - the active material provides capacity while the resistance layer modulates ion transport - achieving extended cycle life through a relatively simple layered composite structure rather than complex modifications to existing materials
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 effectively slows down lithium ion deintercalation, retains lithium during charging, and gradually releases it during battery aging, resulting in increased cycle life and maintained capacity, with the battery capacity initially increasing and then decreasing, thereby prolonging the service life.
Implementation Method 1
a resistance layer... a resistance of the resistance layer is greater than a resistance of the positive electrode active material layer... by controlling the release of lithium ions, it is realized that the capacity decay of the battery is slowed down
Implementation Method 2
the deintercalated speed of active lithium ions in partial regions of the positive electrode sheet is slowed down, so that part of lithium is retained in the regions
Data Source
AI summary
A positive electrode sheet includes a current collector including a coating region and a non-coating region, a resistance layer disposed on the current collector and including a conductive agent, a first binder, and a first positive electrode active material, and a positive electrode active material layer including a second positive electrode active material, a conductive agent, and a second binder. A resistance of the resistance layer is greater than a resistance of the positive electrode active material layer. In a cross section of the positive electrode sheet, a projection of at least a part of the positive electrode active material layer on the current collector and a projection of the resistance layer on the current collector do not overlap. A polarization parameter P of the positive electrode sheet is in a range of 0.4-65.0 and equals ((1−S)/S)·(R1/R2).