Dual-Layer Battery Electrode 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 poses a significant safety hazard and limits their application.
Innovation Solution
A battery design featuring a positive electrode plate with a dual-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 by using a high content of fluorinated polyolefin and/or chlorinated polyolefin polymer material, along with a conductive material, to enhance nail penetration safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-layer positive electrode structure 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 active material layer is divided into two distinct layers: an upper layer containing the main positive active material for electrochemical performance, and a lower layer containing polymer material and conductive material for safety functions. This segmentation allows each layer to specialize in its function, with the lower layer masking metal burrs to prevent internal short circuits during nail penetration, while the upper layer maintains electrical performance.
Solution Approach 2:
The lower layer acts as an intermediary safety barrier between the metal current collector (with potential metal burrs) and the upper positive active material layer. This intermediate layer masks the harmful metal burrs, preventing direct contact and internal short circuits, while still allowing the electrode to function normally during operation.
2Reliability
If the underlying positive active material layer uses high content of polymer material for safety coating function, then the nail penetration safety is improved, but the electrical conductivity may be reduced
Solution Approach 1:
The lower layer is formulated as a composite material containing both polymer material (for safety coating and masking function) and conductive material (for maintaining electrical conductivity). This composite structure ensures that the safety function is not compromised by the insulating nature of polymer materials, as the conductive material compensates for the conductivity loss while the polymer provides the protective masking effect.
3Reliability
If a dual-layer positive active material structure is implemented, then the nail penetration safety is significantly improved, but the manufacturing process complexity increases
Solution Approach 1:
The manufacturing process is segmented into two coating steps: first applying the upper positive active material layer containing the main electrochemical active material, then applying the lower layer containing polymer material and conductive material. This sequential coating approach, while adding a step, uses standard coating equipment and processes, making the implementation feasible without requiring entirely new manufacturing technologies.
Solution Approach 2:
The lower layer serves multiple functions simultaneously: it acts as a safety coating to mask metal burrs, provides a barrier layer for thermal management, and maintains electrical conductivity through the incorporated conductive material. This multi-functionality reduces the need for additional separate components or processes, thereby limiting the increase in manufacturing complexity.
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 dual-layer structure significantly improves nail penetration safety by preventing internal short circuits and thermal runaway, while also maintaining excellent electrical properties and processability, thereby enhancing the overall safety and performance of lithium-ion batteries.
Implementation Method 1
the at least two layers of the positive active material are respectively formed on the current collector and they are usually tightly bonded together
Implementation Method 2
the DC resistance growth rate of the battery at 130°C is no less than 100%, wherein the first polymer material comprises fluorinated polyolefin and/or chlorinated polyolefin polymer material
Data Source
Figure 1
AI summary
This application relates to a battery comprising a positive electrode plate, a separator, a negative electrode plate and an electrolyte, wherein the positive electrode plate comprises a positive electrode current collector (10) and at least two layers of positive active material coated on at least one surface of the positive electrode current collector (10), and wherein the underlying positive active material layer (12) in contact with the positive electrode current collector (10) comprises a first positive active material, a first polymer material and a first 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, and the viscosity at normal temperature of the electrolyte is ≤4cp.