Laminated Secondary Battery Electrode Structure Against Curling and Warping
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Solution Overview
Problem
Secondary batteries with laminated structures, particularly those featuring a single-sided positive electrode plate, are prone to curling and warping, leading to separator shrinkage, short circuits, interface black spots, and lithium precipitation, which affect safety and cycling performance.
Innovation Solution
The secondary battery design includes a single-sided positive electrode plate with a first and second positive electrode material layer, where the mass percentage difference of binders (Y2-Y1) between these layers is controlled within 0<Y2-Y1≤1.7, along with specific ranges for binder and conductive agent percentages, densities, and thicknesses to enhance adhesion force and prevent curling and warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single-sided positive electrode plate is used to increase energy density, then energy density is improved, but the electrode plate is prone to curling and separator shrinkage causing short circuits
Solution Approach 1:
The positive electrode plate is segmented into two distinct layers: a first positive electrode material layer and a second positive electrode material layer. This segmentation allows each layer to serve different functions - the first layer provides structural support and electrical connection, while the second layer optimizes for adhesion to the separator, thereby preventing curling and short circuits while maintaining high energy density
Solution Approach 2:
Different regions of the positive electrode plate are given different properties through the two-layer structure. The first layer has properties optimized for electrical conductivity and structural integrity, while the second layer has properties specifically optimized for adhesion to the separator. This local differentiation of properties prevents the electrode plate from curling and maintains reliability
2Quantity of substance
If a single-sided positive electrode plate is used to increase energy density, then energy density is improved, but the electrode plate is prone to warping during cycling
Solution Approach 1:
The positive electrode plate is divided into two layers with the second layer specifically designed to counteract warping forces during cycling. This segmentation allows the structure to maintain stability while preserving the high energy density benefits of the single-sided design
Solution Approach 2:
The mass percentage of binder in the second positive electrode material layer is specifically controlled to be higher than in the first layer (Y2 > Y1 with 0 < Y2-Y1 ≤ 1.7). This parameter change in binder content enhances adhesion and prevents warping during cycling while maintaining energy density
3Strength
If binder content is increased to improve adhesion force, then adhesion force is improved, but energy density decreases due to binder providing no capacity
Solution Approach 1:
The positive electrode plate is segmented into two layers, allowing the binder content to be optimized differently in each layer. The second layer has higher binder content specifically for adhesion to the separator, while the first layer maintains lower binder content for higher energy density. This segmentation resolves the contradiction by localizing the binder's function
Solution Approach 2:
Different binder percentages are applied to different layers of the positive electrode plate. The second layer has locally increased binder content (Y2 > Y1) specifically where adhesion to the separator is needed, while the first layer maintains lower binder content for energy density. This local quality differentiation resolves the contradiction between adhesion and energy density
Data Source
AI summary
An electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate; and the positive electrode plate, the negative electrode plate, and the separator are stacked. An outermost electrode plate of the electrode assembly is a single-sided positive electrode plate. The single-sided positive electrode plate includes a positive electrode current collector, a first positive electrode material layer, and a second positive electrode material layer stacked sequentially. The first positive electrode material layer is located between the positive electrode current collector and the second positive electrode material layer. The second positive electrode material layer is adjacent to the separator. The first positive electrode material layer includes a first positive electrode active substance, a first binder, and a first conductive agent.