Lithium-Ion Battery Electrode Sheet Granulation Pressing
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Solution Overview
Problem
The manufacturing methods for lithium-ion secondary battery electrode sheets using granulated particles often result in insufficient peel strength, even when pressing conditions are set similarly to those used with mixture pastes, due to differences in the bonding mechanisms and particle configurations.
Innovation Solution
A method involving the preparation of granulated particles with active material particles and a binder, followed by feeding, leveling, and pressing these particles onto a current collector, where the ratio of the layer thickness to the mean particle size (t/D50) is set below 1 to ensure high peel strength and uniform weight distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If granulated particles are used to form the active material layer, then the drying step can be eliminated and manufacturing cost reduced, but the peel strength of the active material layer becomes insufficient
Solution Approach 1:
The invention changes the particle size parameter of the granulated particles to a specific range (0.5 μm to 5 μm, with D50 of 1 μm to 3 μm) to optimize both the elimination of the drying step and the achievement of sufficient peel strength. This parameter optimization allows the particles to pack densely and bond effectively without requiring thermal drying.
Solution Approach 2:
The invention applies a binder solution to the current collector before feeding the granulated particles. This preliminary action ensures that the particles are immediately bonded to the collector upon contact, achieving sufficient peel strength without requiring a subsequent drying step to evaporate solvents.
2Device complexity
If the same pressing conditions are used for granulated particles as for mixture paste, then the process is simplified, but the peel strength remains insufficient
Solution Approach 1:
The invention optimizes the pressing pressure parameter to a specific range (0.1 MPa to 10 MPa, preferably 0.5 MPa to 5 MPa) to achieve sufficient peel strength for granulated particles. This differs from mixture paste processing and represents a parameter change specifically tailored to granulated particle characteristics.
Solution Approach 2:
The invention applies a binder solution locally to the current collector surface before particle feeding. This creates a localized bonding zone that enhances peel strength at the particle-collector interface without requiring global process changes or increased pressing pressure throughout the entire system.
3Manufacturing precision
If the particle size of granulated particles is reduced to improve layer uniformity, then weight distribution becomes more uniform, but the peel strength may be affected
Solution Approach 1:
The invention identifies an optimal particle size range (0.5 μm to 5 μm, D50 of 1 μm to 3 μm) that simultaneously achieves uniform weight distribution and sufficient peel strength. Particles that are too small fail to provide adequate mechanical interlocking, while particles that are too large create uneven distribution. The specified range optimizes both characteristics.
Solution Approach 2:
The invention uses a composite structure consisting of granulated particles (containing active material) combined with a binder material. This composite approach allows the particles to maintain their size for uniformity while the binder provides the adhesive bonding necessary for peel strength, resolving the contradiction between particle size and bonding performance.
Data Source
AI summary
A method of manufacturing a lithium-ion secondary battery electrode sheet proposed herein includes the step of pressing granulated particles (13a), wherein the ratio (t/D50) is less than 1, where D50 is the mean particle size of the granulated particles (13a) and t is the thickness of a layer (14) of active material particles (13a1) after pressing.