Positive Electrode Binder Composition for Paste Stability and Peel Strength

The patent changes the chemical composition parameters of the binder by incorporating specific ratios of polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN), controlling the nitrile group content within 1-10 mmol/g, and adjusting the polymer molecular weight and distribution. These parameter changes enable simultaneous optimization of paste stability, peel strength, and output characteristics that conventional single-component binders cannot achieve.

The patent uses a composite binder system combining PVDF and PAN polymers in specific ratios, creating a multi-component material that leverages the complementary properties of each component. PVDF provides mechanical strength and adhesion, while PAN contributes nitrile groups for lithium ion interaction and electrochemical activity. This composite approach resolves the contradiction by integrating multiple functions into a single binder system.

The patent designs the binder composition to perform multiple functions simultaneously: PVDF provides strong adhesion to the current collector and mechanical integrity (peel strength), while PAN with its nitrile groups contributes to electrochemical activity and lithium ion transport (output characteristics). The binder also maintains paste stability during mixing and coating processes. This multi-functional design resolves the contradiction by making the binder system capable of achieving multiple performance goals at once.

The patent optimizes specific parameters including the PVDF/PAN ratio, nitrile group content (1-10 mmol/g), and polymer molecular weight distribution to achieve the desired balance. By precisely controlling these parameters, the binder composition can provide sufficient peel strength while maintaining good output characteristics, preventing the trade-off between these two properties.

The composite PVDF-PAN binder system resolves this contradiction by dividing functional responsibilities: PVDF provides mechanical stability and paste consistency, while PAN contributes electrochemical activity for output characteristics. The synergistic interaction between the two polymers allows the system to achieve good output performance without sacrificing paste stability.

The patent controls the nitrile group content within 1-10 mmol/g and adjusts the PVDF/PAN ratio to optimize the balance between electrochemical activity and mechanical stability. This parameter control ensures that the binder provides sufficient output characteristics while maintaining paste stability during processing and electrode formation.