Positive Electrode Plate Safety Coating for Battery Short Circuit Protection
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Solution Overview
Problem
Lithium ion batteries face safety hazards due to internal short circuits, which existing PTC material modifications fail to adequately address, affecting both safety and electrochemical performance.
Innovation Solution
A positive electrode plate design featuring a current collector with a safety coating, a difficultly soluble layer, and a positive active material layer, where the safety coating includes a polymer matrix, conductive material, and inorganic filler, and the difficultly soluble layer comprises a binder and conductive agent with specific solubility properties to enhance stability and response speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PTC material is added to the electrode active material layer, then safety performance is improved, but electrochemical performance deteriorates
Solution Approach 1:
The patent divides the electrode structure into distinct layers: a current collector, a PTC safety coating layer, and a positive active material layer. This segmentation allows the PTC material to provide safety functions without interfering with the electrochemical performance of the active material, as the PTC layer acts as a separate protective barrier rather than a mixed component.
Solution Approach 2:
The patent introduces an intermediate protective layer between the PTC safety coating and the positive active material layer. This intermediate layer prevents direct contact and interaction between the PTC material and the active material, eliminating the harmful effect of PTC material on electrochemical performance while maintaining the safety protection function.
2Reliability
If a separate PTC material layer is placed between the current collector and electrode active material layer, then safety effect is achieved, but the solvent in slurry dissolves the PTC material and destroys its effect
Solution Approach 1:
The patent introduces an intermediate protective layer between the PTC safety coating and the positive active material layer. This intermediate layer acts as a barrier that prevents the solvent (such as NMP) in the active material slurry from dissolving the PTC material, thereby maintaining the structural integrity and functional stability of the PTC layer.
Solution Approach 2:
The patent employs a composite structure consisting of multiple layers with different material properties: the PTC safety coating layer, the intermediate protective layer, and the positive active material layer. This composite structure combines the safety benefits of PTC material with the chemical stability provided by the intermediate layer that is resistant to solvent dissolution.
3Reliability
If PTC material layer is used, then safety performance is improved, but during compacting the layer is squeezed to the edge and active material contacts current collector directly
Solution Approach 1:
The patent creates a composite multi-layer structure where the PTC safety coating layer is combined with the positive active material layer through an intermediate protective layer. This composite structure provides better mechanical stability during the compacting process, preventing the PTC layer from being squeezed to the edges and maintaining proper layer alignment and separation.
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 design significantly improves safety and electrical performance by stabilizing the safety coating, preventing direct contact between layers, and enhancing the PTC effect, thereby reducing the risk of internal short circuits and maintaining electrochemical performance.
Implementation Method 1
A PTC (Positive Temperature Coefficient) material is a positive temperature coefficient heat sensitive material, which has the characteristic that its resistivity increases with increasing temperature. When the temperature exceeds a certain temperature, the resistivity of the PTC material increases rapidly stepwise.
Data Source
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AI summary
This application relates to a positive electrode plate and an electrochemical device. The positive electrode plate includes a current collector, a safety coating, a difficultly soluble layer and a positive active material layer, wherein the safety coating, the difficultly soluble layer and the positive active material layer are successively disposed on the current collector; wherein the safety coating includes a polymer matrix, a conductive material and an inorganic filler; wherein the difficultly soluble layer includes a binder and a conductive agent, and wherein the binder of the difficultly soluble layer has a solubility in an oil solvent smaller than the solubility of the polymer matrix of the safety coating in such oil solvent. When the electrochemical device (such as a capacitor, a primary battery, or a secondary battery) is in a high temperature condition or an internal short circuit occurs, the positive electrode plate can quickly disconnect the circuit, thereby improving the high temperature safety of the electrochemical device.