Positive Electrode Protective Layer for Battery Short-Circuit Prevention
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Solution Overview
Problem
Existing nonaqueous electrolyte secondary batteries face issues with low-resistance internal short-circuits due to foreign matter contamination and heat generation from nail sticking, which are not adequately addressed by existing insulating layers, particularly when large foreign matter is involved or during abnormal conditions like nail sticking.
Innovation Solution
A positive electrode with a protective layer composed mainly of inorganic particles, an electro-conductive material, and a binding material is applied to the current collector, covering the area where the positive electrode mixture layer is disposed and extending to exposed portions, providing a hard barrier that prevents redox reactions and maintains electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin insulating layer made of only binder resin is formed on the exposed portion of the positive electrode current collector, then the structure is simple and manufacturing is easy, but the effect of preventing internal short-circuit due to foreign matter contamination is insufficient
Solution Approach 1:
The insulating layer is formed as a composite material containing inorganic particles (such as aluminum oxide, titanium oxide, or silicon oxide) dispersed in a binder resin matrix. This composite structure provides both mechanical integrity from the binder and enhanced insulating properties and foreign matter resistance from the inorganic particles, effectively preventing internal short-circuits while maintaining a manageable layer structure.
Solution Approach 2:
The insulating layer is applied specifically to the exposed portion of the positive electrode current collector where foreign matter contamination and short-circuit risks are most likely to occur, rather than covering the entire current collector surface. This localized application provides targeted protection where it is most needed while minimizing unnecessary material usage and maintaining electrical conductivity in the active electrode regions.
2Object-generated harmful factors
If only a binder resin-based insulating layer is used, then the manufacturing process is simple, but the ability to suppress heat generation during abnormal conditions like nail sticking is insufficient
Solution Approach 1:
The insulating layer incorporates inorganic particles with high thermal stability and electrical resistivity into the binder resin matrix. These inorganic particles create additional resistance pathways that suppress current flow during abnormal conditions such as nail sticking, thereby reducing heat generation. The composite structure achieves enhanced safety performance while using a straightforward coating process that does not significantly complicate manufacturing.
3Speed
If the positive electrode is made smaller than the negative electrode to ensure smooth lithium ion movement, then ion transport is improved, but the exposed portion of the current collector increases the risk of foreign matter entering and causing short-circuit
Solution Approach 1:
The insulating layer is applied specifically to the exposed portion of the positive electrode current collector that faces the negative electrode, providing targeted protection against foreign matter contamination in the high-risk area. This localized insulation allows the positive electrode to maintain its smaller dimensions for optimal lithium ion transport while adding protective functionality only where the exposed current collector creates short-circuit risks.
Solution Approach 2:
The insulating layer acts as an intermediary barrier between the exposed positive electrode current collector and the negative electrode, preventing direct contact that would occur if foreign matter were to enter the gap. This intermediary layer maintains the necessary electrode spacing and provides electrical insulation, allowing the electrode design to prioritize ion transport efficiency while mitigating the increased contamination risk from the exposed current collector surface.
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 suppresses low-resistance internal short-circuits and reduces heat generation during abnormal conditions, such as nail sticking, while maintaining good battery characteristics and safety without deteriorating current collecting properties.
Implementation Method 1
a protective layer disposed between the positive electrode current collector and the positive electrode mixture layer... The protective layer contains inorganic particles, an electro-conductive material, and a binding material
Implementation Method 2
The protective layer contains inorganic particles... and is mainly composed of the inorganic particles... providing a hard barrier that prevents redox reactions
Implementation Method 3
The protective layer contains inorganic particles, an electro-conductive material, and a binding material... maintains electrical conductivity
Implementation Method 4
The protective layer contains inorganic particles, an electro-conductive material, and a binding material... is mainly composed of the inorganic particles
Data Source
AI summary
The positive electrode as an embodiment includes a positive electrode current collector mainly composed of aluminum, a positive electrode mixture layer containing a lithium-containing transition metal oxide and disposed above the positive electrode current collector, and a protective layer disposed between the positive electrode current collector and the positive electrode mixture layer. The protective layer contains inorganic particles, an electro-conductive material, and a binding material; is mainly composed of the inorganic particles; and is disposed on the positive electrode current collector to cover the positive electrode current collector in approximately the entire area where the positive electrode mixture layer is disposed and at least a part of the exposed portion of the positive electrode current collector where the positive electrode mixture layer is not disposed on the surface of the positive electrode current collector.