Water-Based Cathode Slurry with Fluorine Polymer Coating
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Solution Overview
Problem
The challenge in developing a water-based coating technology for lithium ion battery positive electrodes is the difficulty in achieving complete and stable surface protection due to the reactivity of cathode materials with water, leading to poor adhesion and increased direct current resistance (DCR), which affects cycle stability and capacity retention.
Innovation Solution
A water-based lithium ion battery cathode slurry comprising a conductive agent and a fluorine-containing polymer binder, with a double shell coating structure including a thin LiF inner layer and a hydrophobic outer polymer layer, enhances water stability and reduces ion exchange, thereby improving adhesion and DCR performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a water-based coating process is used for cathode preparation, then environmental safety and cost are improved, but surface protection stability and adhesion deteriorate due to cathode material reactivity with water
Solution Approach 1:
The cathode material surface is pre-coated with a protective layer before water-based slurry application. This preliminary protective coating prevents direct contact between water and the reactive cathode material surface, eliminating the harmful reaction while maintaining the benefits of water-based processing.
Solution Approach 2:
An intermediary protective coating layer is introduced between the water-based slurry and the cathode material. This intermediary layer acts as a barrier that prevents harmful interactions while allowing the binding function to occur, thus resolving the contradiction between using water-based processes and maintaining surface protection stability.
2Object-affected harmful factors
If a water-based coating process is used for cathode preparation, then environmental safety and cost are improved, but direct current resistance increases affecting cycle stability
Solution Approach 1:
The cathode material surface is pre-coated with a protective layer before water-based slurry application. This preliminary protective coating prevents direct contact between water and the reactive cathode material surface, eliminating the harmful reaction while maintaining the benefits of water-based processing.
Solution Approach 2:
An intermediary protective coating layer is introduced between the water-based slurry and the cathode material. This intermediary layer acts as a barrier that prevents harmful interactions while allowing the binding function to occur, thus resolving the contradiction between using water-based processes and maintaining surface protection stability.
3Reliability
If traditional NMP-based slurry is used, then coating quality and binding performance are improved, but flammability and environmental toxicity worsen
Solution Approach 1:
The solvent parameter is changed from organic NMP to water. This fundamental parameter change eliminates flammability and toxicity issues while maintaining the slurry's functional properties through careful formulation of the water-based system with appropriate binders and additives.
Solution Approach 2:
The patent replaces expensive and hazardous NMP solvent with cheap and safe water. Although water-based slurries present formulation challenges, the substitution achieves the goal of eliminating flammability and toxicity while reducing cost, accepting that new formulation approaches are needed.
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 proposed solution effectively reduces DCR, enhances cycle stability, and maintains capacity retention, making it suitable for automotive applications where high pulse power and long battery life are required.
Implementation Method 1
the primary particles comprising a coating layer comprising a polymer, the coating layer being hydrophobic
Implementation Method 2
enhances water stability and reduces ion exchange
Data Source
Figure 1.1~1.2
Figure 1.3~1.4
Figure 1.5~1.6
AI summary
A water-based lithium ion battery cathode slurry comprising a cathode active material comprising a lithium transition metal oxide powder wherein the lithium transition metal oxide powder consists of agglomerates of primary particles, the primary particles comprising a coating layer comprising a polymer is proposed. The polymer is preferably a fluorine-containing polymer comprising at least 50 wt% of fluorine. The coating layer preferably comprises a first inner and a second outer coating layer, the second outer layer comprising the fluorine-containing polymer, and the first inner layer consisting of a reaction product of the fluorine-containing polymer and the surface of the primary particles. The reaction product preferably comprises LiF.