Battery Electrode Sheet Coating for Solvent-Free Isolation
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Solution Overview
Problem
The existing electrode sheet manufacturing process for battery cells involves a wet process using N-Methyl-pyrrolidone, which poses health and environmental risks, and requires multiple drying steps, increasing the risk of cell short circuits and reducing energy density due to the close proximity of electrodes.
Innovation Solution
An intermediate current collector with a conductive carbon primer coating free of active material, coated with a dry lamination process using a polymer binder, and an active layer applied without solvents, reducing the need for drying steps and enhancing safety by eliminating solvent interactions with active materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a wet process using NMP is used to apply both active material and ceramic layer simultaneously, then the manufacturing process is simplified, but health and environmental risks increase and multiple drying steps are required
Solution Approach 1:
The patent divides the coating process into two separate stages: first applying the ceramic layer with NMP binder, then applying the active material layer with PVDF binder. This segmentation allows each layer to be optimized independently, eliminating the need for simultaneous application while reducing overall solvent exposure risks.
Solution Approach 2:
The patent changes the binder material from NMP to PVDF for the active material layer, and applies the active material after the ceramic layer is already in place. This parameter change eliminates the need for NMP drying steps while maintaining manufacturing simplicity.
2Quantity of substance
If electrodes are placed very close to each other to increase energy density, then space optimization is achieved, but the risk of cell short circuit increases
Solution Approach 1:
The patent applies the ceramic layer and isolation coatings on the current collector edges before applying the active material. This preliminary action ensures that protective isolation barriers are in place before the electrodes are positioned close together, preventing short circuits while maintaining high energy density.
Solution Approach 2:
The patent introduces a ceramic layer as an intermediary protective barrier between the active material and the current collector edges. This ceramic layer acts as a physical separator that prevents direct contact between electrodes while allowing the electrodes to be positioned close together for high energy density.
3Reliability
If multiple drying steps are implemented to remove NMP solvent, then complete solvent removal is achieved, but the manufacturing process complexity and time increase
Solution Approach 1:
The patent changes the binder from NMP to PVDF, which has different evaporation characteristics. PVDF allows for reduced drying steps while still achieving complete solvent removal, thereby reducing manufacturing time without compromising reliability.
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 approach minimizes drying steps, enhances safety by preventing solvent exposure, and maintains high conductivity and adhesion between the active material and current collector, while reducing the risk of cell short circuits and improving energy density.
Implementation Method 1
a current collector to conduct the electric current to the terminals of the cell
Implementation Method 2
an electrically isolating coating applied in the longitudinal direction on the metallic substrate foil on both edges of (each of) the conductive carbon primer coating(s)
Implementation Method 3
The conductive carbon primer coating comprises conductive carbon and a polymer binder; The active layer comprises active material and a polymer binder
Data Source
Figure 1
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AI summary
The intermediate current collector (6) comprises: - a metallic substrate conductive foil (12) extending in a longitudinal direction (L); - at least one conductive carbon primer coating (14) covering at least partially the metallic substrate foil (12) in the longitudinal direction (L); and - an electrically isolating coating (16) applied in the longitudinal direction (L) on the metallic substrate foil (12) on both edges of the conductive carbon primer coating (14), the isolation coatings (16) framing the conductive carbon primer coating (14) in a transversal direction (T) perpendicular to the longitudinal direction (L). The conductive carbon primer coating (14) is free of any active material.