Li-Ion Cathode Binder Composition to Prevent Slurry Gelation
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Solution Overview
Problem
The use of chlorine-containing polyvinylidene fluoride-based polymers as binders in lithium ion secondary batteries leads to gelation of the electrode mixture slurry, affecting the productivity and performance of the battery, and results in deteriorated aging efficiency and battery life characteristics compared to chlorine-free polymers.
Innovation Solution
A lithium ion secondary battery with a positive electrode mixture layer containing a layered lithium-nickel composite oxide, LiOH, Li2CO3, and a chlorine-containing polyvinylidene fluoride-based polymer, where the content of LiOH and Li2CO3 is between 0.1-2.1 weight % each, and the total content is 0.2-4.2 weight %, and the chlorine content is between 30 μg/g and 120 μg/g, to prevent gelation and improve battery life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a chlorine-containing polyvinylidene fluoride-based polymer is used as a binder to prevent gelation of the electrode mixture slurry, then the gelation problem is solved, but the aging efficiency and battery life characteristics deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by incorporating specific amounts of LiOH (0.1-5 wt%) and Li2CO3 (0.1-5 wt%) into the chlorine-containing polyvinylidene fluoride-based polymer system. This parameter modification allows the binder to maintain its ability to prevent slurry gelation while improving adhesion to the positive electrode active material, thereby enhancing battery life characteristics without sacrificing ease of manufacture
Solution Approach 2:
The patent creates a composite binder system by combining chlorine-containing polyvinylidene fluoride-based polymer with LiOH and Li2CO3. This composite material approach leverages the gelation-preventing properties of the chlorine-containing polymer while the LiOH and Li2CO3 components improve interfacial adhesion and electrochemical stability, resolving the contradiction between ease of manufacture and reliability
2Strength
If a poly(vinylidene fluoride)-based polymer is used as a binder, then the binder provides good adhesion, but the electrode mixture slurry gels due to cross-linking between polyene structures
Solution Approach 1:
The patent extracts or introduces specific inorganic components (LiOH and Li2CO3) into the binder system to counteract the harmful cross-linking effects. These extracted/added components serve to inhibit the formation of gel structures while preserving the beneficial adhesive properties of the polyvinylidene fluoride-based polymer, thus maintaining both strength and ease of manufacture
Solution Approach 2:
LiOH and Li2CO3 act as intermediary substances between the polyvinylidene fluoride-based polymer and the electrode mixture components. These intermediaries prevent direct harmful interactions that lead to gelation while maintaining the adhesive function of the binder, resolving the contradiction between strength and ease of manufacture
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 effectively prevents gelation of the electrode mixture slurry and enhances the life characteristics of the lithium ion secondary battery by optimizing the content of chlorine-containing polyvinylidene fluoride-based polymers, resulting in improved battery performance and longevity.
Implementation Method 1
the electrode mixture slurry tends to gel. For this reason, it becomes difficult to apply the electrode mixture slurry to a current collector... it is possible to suppress the gelation of the electrode mixture slurry in a manufacturing process
Data Source
AI summary
A purpose of the present invention is to provide a lithium ion secondary battery having more improved life characteristics while suppressing gelation of an electrode mixture slurry in a manufacturing process. The lithium ion secondary battery according to the present invention comprises a positive electrode having a positive electrode mixture layer comprising a layered lithium-nickel composite oxide in which a proportion of nickel in metals other than lithium is 80 mol % or more; LiOH; Li2CO3; and a chlorine-containing polyvinylidene fluoride-based polymer, wherein a content of LiOH in the positive electrode mixture layer and a content of Li2CO3 in the positive electrode mixture layer are each 0.1 weight % or more and 2.1 weight % or less, a total content of LiOH and Li2CO3 in the positive electrode mixture layer is 0.2 weight % or more and 4.2 weight % or less, and a content of chlorine in the positive electrode mixture layer is 30 μg/g or more and 120 μg/g or less.