Flexible Positive Electrode Binder for Volume-Shrinkage Stability
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Solution Overview
Problem
The performance of lithium-ion batteries is compromised due to the shrinkage of layered transition metal oxides in positive electrode plates, leading to a failure in the electrical connection between the active material and the conductive agent, as the binder separates and tears under volume change.
Innovation Solution
A flexible binder is used to bind the layered transition metal oxide and conductive agent, allowing the binder to deform and maintain electrical connections despite volume changes, using materials like polyethylene-based and polyisocyanate-based binders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional binder is used to bind the layered transition metal oxide and conductive agent, then the electrode structure is maintained during battery operation, but the binder tears and separates due to volume shrinkage of the active material, causing loss of electrical connection
Solution Approach 1:
The patent changes the physical and chemical parameters of the binder by introducing a cross-linked gel polymer matrix with specific gel content (5-50 wt%). This cross-linked network structure provides both mechanical strength and flexibility, allowing the binder to maintain integrity while accommodating volume changes of the active material during charge-discharge cycles.
Solution Approach 2:
The patent creates a composite binder system combining gel polymer electrolyte with cross-linking agents to form a gel polymer network. This composite structure integrates the flexibility of gel polymer with the structural stability of cross-linked networks, enabling the binder to simultaneously maintain electrical connection and resist tearing under volume stress.
2Quantity of substance
If the layered transition metal oxide is used as positive electrode active material, then high energy density is achieved, but the volume of the active material greatly shrinks during battery use, resulting in enlarged gap between active material and binder
Solution Approach 1:
The patent applies beforehand cushioning by creating a cross-linked gel polymer network structure in advance that can accommodate future volume changes. The gel network acts as a cushioning matrix that maintains contact between active material particles and conductive agents even when volume shrinkage occurs during battery operation.
Solution Approach 2:
The patent introduces dynamics by using a gel polymer electrolyte with cross-linked network that can dynamically adapt its structure during battery operation. The gel network can flexibly adjust to volume changes of the active material while maintaining structural integrity and electrical connection throughout charge-discharge cycles.
3Strength
If the binder is made rigid to maintain structural integrity, then the electrode structure is stable, but the binder cannot deform to adapt to volume changes of the active material, causing separation and binding failure
Solution Approach 1:
The patent uses a gel polymer electrolyte with cross-linked network that functions as a flexible binding matrix. This gel network provides both structural integrity and flexibility, allowing it to deform with volume changes while maintaining the electrode structure and electrical connections between active material and conductive agents.
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 flexible binder maintains electrical connections, reducing the impact of volume changes on battery performance and enhancing the battery's cycle stability, energy density, and safety.
Implementation Method 1
The flexible binder has good stretchability. When the volume of the layered transition metal oxide shrinks and the layered transition metal oxide tears the binder, the flexible binder deforms, to adapt to the volume shrinking of the layered transition metal oxide and maintain an electrical connection between the layered transition metal oxide and the conductive agent
Implementation Method 2
A —NH2 group and a C═O group in PVP-PEI form a dynamic hydrogen bond network, so that PVP-PEI has a good self-healing property and a certain degree of stretchability
Implementation Method 3
The PMDOPA includes abundant O-diphenol functional groups, so that PMDOPA has a good binding property and better flexibility
Data Source
AI summary
A positive electrode plate and a preparation method therefor, a battery cell, a battery, and an electric device are described. The positive electrode plate includes: an active material layer, where the active material layer includes a first active material, a conductive agent, and a binder. The first active material includes a layered transition metal oxide, and the binder includes a flexible binder, configured to bind the first active material and the conductive agent. Performance of a battery including the positive electrode plate is improved.