Positive electrode plate and electrochemical device
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion batteries face safety hazards due to internal short circuits, which existing modifications to incorporate PTC materials into the electrode active material layer or as a separate safety coating either compromise electrochemical performance or fail to improve safety effectively, particularly during nail penetration and high-temperature conditions.
Innovation Solution
A positive electrode plate design featuring a current collector, a positive active material layer, and a safety coating with a polymer matrix comprising fluorinated polyolefin and/or chlorinated polyolefin, a conductive material, and an inorganic filler, where the polymer matrix includes two types of polymers with differing solubility in oil solvents, and the inorganic filler stabilizes the coating and enhances response speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PTC materials are 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 functional layers: a current collector, a safety coating layer containing PTC materials, and an active material layer. This segmentation allows the PTC materials to provide safety functions without directly interfering with the electrochemical performance of the active materials, resolving the contradiction between safety improvement and electrochemical performance maintenance.
Solution Approach 2:
The patent introduces a binder material as an intermediary between the PTC materials and the active material layer. The binder prevents direct contact between PTC materials and active materials, thereby preventing the PTC materials from adversely affecting electrochemical performance while still enabling the PTC materials to provide safety protection through their positive temperature coefficient characteristics.
2Reliability
If a separate PTC material layer is placed between the current collector and active material layer, then safety effect is achieved, but the PTC material layer is dissolved by solvent during coating
Solution Approach 1:
The binder serves as an intermediary that protects the PTC materials from direct contact with the solvent in the active material slurry. This prevents dissolution of the PTC material layer while maintaining its safety functionality, and also provides mechanical support to prevent squeezing during compaction.
Solution Approach 2:
The patent creates a composite safety coating layer comprising PTC materials, binder, and conductive materials. This composite structure enhances the stability of the PTC material layer by providing a matrix that resists solvent penetration and mechanical deformation, while maintaining the PTC effect for safety protection.
3Reliability
If PTC material layer is used, then safety performance is improved, but internal resistance increases excessively
Solution Approach 1:
The patent optimizes the composition parameters of the safety coating layer, including the ratio of PTC materials to binder and conductive materials. By carefully controlling these parameters, the patent achieves a balance where the PTC materials provide adequate safety protection while the conductive materials and binder maintain acceptable electrical conductivity, preventing excessive internal resistance increase.
Solution Approach 2:
The composite structure of the safety coating layer, combining PTC materials with conductive materials and binder, creates a balanced system where the conductive components compensate for the resistance increase from PTC materials, maintaining overall electrical performance while providing safety protection.
4Reliability
If PTC materials are incorporated into the electrode structure, then safety during nail penetration is improved, but cracking occurs in the coating
Solution Approach 1:
The binder in the composite safety coating layer provides mechanical strength and flexibility, creating a cohesive matrix that prevents cracking during nail penetration testing. This allows the PTC materials to provide safety protection while the binder maintains the structural integrity of the coating under mechanical stress.
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 preventing internal short circuits and maintaining electrochemical integrity during nail penetration and high temperatures, while reducing the risk of cracking and excessive internal resistance growth.
Implementation Method 1
the solvent (such as NMP) in the slurry would dissolve the PTC material of the PTC layer
Implementation Method 2
the solvent (such as NMP) in the slurry would dissolve the PTC material of the PTC layer
Implementation Method 3
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
Data Source
AI summary
The present invention relates to a positive electrode plate and an electrochemical device. The positive electrode plate comprises a current collector, a positive active material layer and a safety coating disposed between the current collector and the positive active material layer, wherein the safety coating comprises a polymer matrix, a conductive material and an inorganic filler, wherein the polymer matrix comprises at least two types of polymer materials, and the first type of polymer material is fluorinated polyolefin and/or chlorinated polyolefin, and the solubility of the second type of polymer material in oil solvent is smaller than the solubility of the first type of polymer material; and the weight percentage of the first type of polymer material relative to the total weight of the polymer matrix, the conductive material and the inorganic filler is 17.5% or more. The positive electrode plate improves high temperature safety of electrochemical device.