Secondary Battery Positive Electrode Core Hardness Gradient
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Secondary batteries with winding-type electrode assemblies experience electrode plate deformation and elongation during charge-discharge cycles, leading to increased short-circuit risks due to reduced distance between positive and negative electrodes.
Innovation Solution
The positive electrode core is designed with a first region having a 0.2% proof stress of 50 N/mm² or less and a second region with a proof stress greater than 50 N/mm², dispersing stress and suppressing deformation and elongation by varying the hardness of the core regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a soft positive electrode core is used to reduce electrode plate deformation, then electrode plate deformation is improved, but electrode plate elongation occurs in the width direction
Solution Approach 1:
The positive electrode core is designed with different hardness values in different regions: a first region with hardness of 40 HV or less and a second region with hardness greater than 40 HV. This local quality differentiation allows the softer first region to absorb stress and prevent deformation while the harder second region maintains overall structural integrity and prevents excessive elongation in the width direction.
Solution Approach 2:
The positive electrode core is divided into multiple regions with different mechanical properties - a first region (softer) and a second region (harder). This segmentation allows each region to perform its specific function: the softer first region handles stress concentration to prevent deformation, while the harder second region provides structural support to limit elongation.
2Length of moving object
If the positive electrode core elongates in the width direction, then the distance between positive and negative electrodes decreases, but this increases short-circuit risk
Solution Approach 1:
The harder second region with hardness greater than 40 HV provides structural rigidity that constrains the overall elongation of the positive electrode core in the width direction, thereby maintaining adequate spacing between electrodes and reducing short-circuit risk, while the softer first region handles local stress.
3Ease of manufacture
If a uniform hardness positive electrode core is used, then manufacturing is simpler, but it cannot simultaneously suppress both electrode plate deformation and elongation
Solution Approach 1:
The patent implements local quality differentiation in the positive electrode core by creating regions with different hardness values (first region: ≤40 HV, second region: >40 HV). This allows the core to exhibit different mechanical responses in different areas, simultaneously suppressing both electrode plate deformation and elongation, with manufacturing methods such as differential rolling or annealing processes.
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 design effectively suppresses electrode plate deformation and elongation, reducing the risk of short-circuits and maintaining battery performance.
Implementation Method 1
the positive electrode core has a first region at a winding-start end and a second region which is a region other than the first region, a 0.2% proof stress of the positive electrode core in the first region is less than or equal to 50 N/mm²
Implementation Method 2
a 0.2% proof stress of the positive electrode core in the first region is less than or equal to 50 N/mm²
Data Source
Figure 1
Figure 2
AI summary
Provided is a secondary battery capable of suppressing electrode plate deformation and electrode plate elongation caused by charging and discharging. This secondary battery has an electrode body in which a negative electrode and a positive electrode, which has a belt-like positive electrode core body (30) and a positive electrode mixture layer provided on the positive electrode core body (30), are wound with a separator therebetween. The secondary battery is characterized in that: the positive electrode core body (30) has a first region (32) which is a winding start end part and a second region (34) which is a region other than the first region (32); the 0.2% yield strength of the positive electrode core body in the first region (32) is 50 N/mm2 or less; and the 0.2% yield strength of the positive electrode core body in the second region (34) is greater than 50 N/mm2.