Thermosensitive Coating for Battery Safety
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Solution Overview
Problem
Current positive temperature coefficient (PTC) coating layers in batteries suffer from high internal resistance, reduced cycling performance, and poor PTC effect, necessitating a solution to enhance battery safety and performance.
Innovation Solution
A thermosensitive coating layer with electrical conductivity is introduced, comprising thermosensitive polymer microspheres that melt at a specific temperature to form continuous electron blocking layers, reducing internal resistance and preventing thermal runaway, while maintaining compatibility with solvents and active materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PTC coating layer is provided inside the battery to improve safety, then thermal runaway prevention is enhanced, but internal resistance increases and cycling performance deteriorates
Solution Approach 1:
The patent changes the physical and chemical parameters of the coating layer by using thermosensitive polymer microspheres that undergo phase transition at specific temperatures. This allows the coating to remain conductive at normal operating temperatures (maintaining low internal resistance) while becoming insulating at thermal runaway temperatures (providing safety protection). The specific parameters changed include the glass transition temperature of the polymer and the conductivity state of the coating layer.
Solution Approach 2:
The coating layer transitions from a static conductive structure to a dynamic structure that changes its properties in response to temperature variations. The thermosensitive polymer microspheres dynamically adjust the coating's conductivity based on thermal conditions, being conductive during normal use and insulating during thermal runaway, thus resolving the contradiction between maintaining low resistance and providing safety protection.
2Reliability
If a PTC coating layer is provided to prevent thermal runaway, then battery safety is improved, but cycling performance is reduced
Solution Approach 1:
The patent utilizes parameter changes in the thermosensitive polymer to achieve temperature-dependent functionality. The coating maintains favorable electrical and mechanical parameters during normal cycling operations, preserving cycling performance, while activating protective functions only when thermal runaway conditions are detected, thus maintaining both long duration and high reliability.
3Reliability
If a thermosensitive coating layer is introduced to achieve thermal blockage, then safety during thermal runaway is enhanced, but internal resistance may increase
Solution Approach 1:
The patent employs phase transitions of thermosensitive polymer microspheres as the core mechanism. These microspheres undergo a phase change from a conductive state at low temperatures to an insulating state at high temperatures, enabling the coating to provide thermal blockage only when necessary. This phase transition approach allows the system to achieve safety functionality without permanently increasing internal resistance.
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 achieves low resistance, good cycling performance, and effective thermal blockage during thermal runaway, enhancing battery safety and energy density without adverse effects in normal use environments.
Implementation Method 1
thermosensitive polymer microspheres in the thermosensitive coating layer melt to form a plurality of continuous electron blocking layers
Implementation Method 2
When a thermosensitive temperature is reached, thermosensitive polymer microspheres in the thermosensitive coating layer melt to form a plurality of continuous electron blocking layers
Implementation Method 3
The thermosensitive coating layer has electrical conductivity and provides a high-temperature blockage
Implementation Method 4
the composite fusion layer is provided between the thermosensitive coating layer and the positive electrode active material layer
Data Source
AI summary
Disclosed are a positive electrode plate and a battery including the positive electrode plate. The positive electrode plate includes a positive electrode current collector, at least one thermosensitive coating layer, at least one composite fusion layer, and at least one positive electrode active material layer. The thermosensitive coating layer has electrical conductivity at room temperature, and has advantages of increasing a contact area between the active material and the current collector, effectively reducing battery polarization, and the like. When a temperature of the positive electrode plate during use reaches a thermosensitive temperature and higher, thermosensitive polymer microspheres melt to form at least one continuous electron blocking layer, therefore forming a current blockage, and an internal blockage is formed inside the battery, thereby preventing further thermal runaway of a secondary battery, and improving safety performance of the secondary battery.