Two-Layer Positive Electrode Plate for Nail Penetration Safety
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Solution Overview
Problem
Lithium-ion batteries are prone to fires and explosions due to internal short circuits caused by nail penetration, which limits their safety and application.
Innovation Solution
A battery design featuring a positive electrode plate with a two-layer structure, where the underlying positive active material layer acts as a binder and PTC safety coating, effectively masking metal burrs and preventing internal short circuits, comprising a first polymer material like fluorinated polyolefin and/or chlorinated polyolefin, and a second layer with a higher conductive material content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-layer positive electrode plate is used, then the manufacturing process is simple, but the nail penetration safety is poor due to metal burrs causing internal short circuits
Solution Approach 1:
The positive electrode plate is divided into two distinct layers: an upper positive active material layer containing conductive material for electrical performance, and a lower polymer material layer for safety protection. This segmentation allows each layer to specialize in its function, with the lower layer acting as a safety barrier against metal burrs during nail penetration events.
Solution Approach 2:
The lower polymer material layer serves as an intermediary safety barrier between the current collector and the external environment. When nail penetration occurs, this layer prevents direct contact between metal burrs and the current collector, thereby avoiding internal short circuits while still allowing the upper layer to maintain electrical conductivity.
2Reliability
If the underlying positive active material layer contains high polymer material content for safety, then the PTC effect is enhanced, but the electrical conductivity may be reduced
Solution Approach 1:
Different regions of the positive electrode plate have different material compositions optimized for their specific functions. The lower layer has high polymer material content (30-80 wt%) to maximize PTC effect and thermal safety, while the upper layer has higher conductive material content to ensure electrical conductivity. This local quality differentiation resolves the contradiction between safety and conductivity.
Solution Approach 2:
The positive electrode plate uses a composite structure with two distinct material compositions. The lower layer combines polymer material with positive active material in specific ratios to achieve both PTC safety effects and basic conductivity, while the upper layer compensates for conductivity requirements. This composite approach allows the system to achieve both thermal safety and electrical performance.
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 battery exhibits improved nail penetration safety and electrical properties, with the underlying positive active material layer effectively wrapping metal burrs and exhibiting a positive temperature coefficient effect to prevent thermal runaway.
Implementation Method 1
the first polymer material comprises fluorinated polyolefin and/or chlorinated polyolefin polymer material
Data Source
AI summary
This application relates to a battery comprising a positive electrode plate, a separator, and a negative electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and at least two layers of positive active material coated on at least one surface of the positive electrode current collector, and wherein an underlying positive active material layer in contact with the positive electrode current collector comprises a first positive active material, a first polymer material and a first conductive material; and wherein an upper positive active material layer in contact with the underlying positive active material layer and away from the positive electrode current collector comprises a second positive active material, a second polymer material and a second conductive material, and the first polymer material comprises fluorinated polyolefin and/or chlorinated polyolefin polymer material. The battery has good safety and improved electrical properties.