Li-Ion Electrode Coating With Insulating Layer Boundary Control
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Solution Overview
Problem
The existing methods for manufacturing non-aqueous electrolyte secondary batteries require separate facilities for coating and drying the positive electrode active material layer and the insulating layer, leading to increased manufacturing costs and potential intermixing of pastes at the boundary, which can worsen the battery's input-output current characteristics.
Innovation Solution
The technique of simultaneous coating and drying of a positive electrode paste containing active material particles and an insulating paste with an inorganic filler is employed, where the pastes are applied and dried together, forming an intermixed portion that adjusts the intruding width to optimize the battery's performance by controlling the weight ratios of binders and fillers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate facilities are used for coating and drying the positive electrode active material layer and the insulating layer, then the coating quality can be controlled, but the manufacturing cost increases
Solution Approach 1:
The patent combines the coating and drying processes for both the positive electrode active material layer and the insulating layer into a single integrated facility. This merging eliminates the need for separate coating and drying facilities, reducing manufacturing costs while maintaining coating quality through optimized process design that handles both layers simultaneously.
2Productivity
If the positive electrode paste and insulating paste are applied at the same time, then the manufacturing process is simplified, but the pastes may intermix at the boundary portion worsening input-output current characteristics
Solution Approach 1:
The patent applies different paste formulations with locally optimized properties to different regions. The insulating paste contains inorganic filler particles and binder in specific ratios that create a paste with different flow characteristics compared to the positive electrode paste. This local differentiation in paste composition prevents intermixing at the boundary while allowing simultaneous application, maintaining both productivity and reliability.
Solution Approach 2:
The patent changes key parameters of the insulating paste, specifically the weight ratio of binder to inorganic filler (set between 0.05 and 0.5), and the mean particle size of inorganic filler (1 μm to 10 μm). These parameter adjustments create a paste with controlled viscosity and flow properties that prevent intermixing with the positive electrode paste during simultaneous coating, thereby maintaining good input-output current characteristics.
Data Source
AI summary
A lithium-ion secondary battery includes an inorganic filler having a mean particle size of 1 μm to 10 μm. A ratio A/B is 14 to 28, where A is a weight ratio of a second binder and the inorganic filler (i.e., second binder/inorganic filler) in an insulating layer, and B is a weight ratio of a first binder and positive electrode active material particles (i.e., first binder/positive electrode active material particles) in a positive electrode active material layer.