Cathode Slurry Composition to Prevent Electrode Layer Collapse
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Solution Overview
Problem
The challenge in increasing the capacity of non-aqueous electrolytic solution secondary batteries lies in the collapse of the positive electrode active material layer due to the use of low-viscosity solvents, which decreases fluidity and ion conductivity, limiting battery performance.
Innovation Solution
A manufacturing method that involves applying a slurry containing a high content of positive electrode active material with a solvent having a vapor pressure of 4.0 kPa or more, limited to less than 1.0% by mass, and ensuring a contact angle of 45° or less with the separator, to maintain fluidity and prevent collapse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the content of positive electrode active material in the slurry is increased to improve battery capacity, then the energy density increases, but the fluidity of the slurry decreases causing the coating film to collapse
Solution Approach 1:
The patent changes the chemical composition parameters of the non-aqueous solvent by specifying that it must not contain solvents with a vapor pressure of 4.0 kPa or more at 25°C. This parameter control prevents the coating film from collapsing while maintaining high active material content (75% by mass or more) in the slurry, thus resolving the contradiction between increasing capacity and maintaining fluidity.
2Stability of the object's composition
If low-viscosity solvent is added to improve slurry fluidity, then the coating film can be formed, but the solvent volatilizes during formation causing the coating film to partially collapse
Solution Approach 1:
The patent applies parameter change by controlling the vapor pressure parameter of the non-aqueous solvent to be less than 4.0 kPa at 25°C. This prevents excessive volatilization during coating film formation, maintaining both fluidity for proper coating application and reliability for preventing collapse during the formation process.
Solution Approach 2:
The patent uses a specific non-aqueous solvent as an intermediary substance that mediates between the need for fluidity (to enable coating) and the need for stability (to prevent collapse). The solvent with controlled vapor pressure acts as a stable intermediary that does not rapidly evaporate, unlike conventional low-viscosity solvents.
3Quantity of substance
If the content of positive electrode active material is increased to 75% by mass or more, then the energy density increases, but the slurry properties become close to powder state reducing ion conductivity
Solution Approach 1:
The patent changes the parameter of non-aqueous solvent composition to exclude high vapor pressure solvents, which maintains the slurry in a proper state even at 75% or more active material content. This prevents the slurry from becoming too powder-like, thereby maintaining ion conductivity while achieving high energy density.
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
This method allows for the formation of a positive electrode active material layer with high active material content and improved fluidity, enhancing battery performance by preventing collapse and maintaining ion conductivity.
Implementation Method 1
the slurry for forming a positive electrode, containing a positive electrode active material at a content of 75% by mass or more
Implementation Method 2
adding a solvent having a vapor pressure of 4.0 kPa or more to the slurry-like positive electrode active material layer
Implementation Method 3
ensuring a contact angle of 45° or less with the separator
Data Source
AI summary
Provided are a method for manufacturing a non-aqueous electrolytic solution secondary battery in which a positive electrode collector, a positive electrode active material layer, a separator, a negative electrode active material layer, and a negative electrode collector are laminated in this order, the method including applying a slurry for forming a positive electrode onto the positive electrode collector to form a slurry-like positive electrode active material layer, and adding a solvent having a vapor pressure of 4.0 kPa or more to the slurry-like positive electrode active material layer, the slurry for forming a positive electrode, containing a positive electrode active material at a content of 75% by mass or more, a conductive auxiliary agent, an electrolyte, and a non-aqueous solvent (I) in which a content of the solvent having a vapor pressure of 4.0 kPa or more is less than 1.0% by mass; and a non-aqueous electrolytic solution secondary battery which can be obtained by the manufacturing method.