High Solid Content Slurry Coating for Battery Electrodes
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Solution Overview
Problem
The existing methods for preparing secondary battery electrodes are complex and inefficient, leading to nonuniform electrode coating layers and decreased adhesion between the electrode and current collector due to solvent evaporation and high-temperature pressing processes, which can cause damage to the current collector.
Innovation Solution
A method involving the preparation of a slurry with a high solid content (70-90 wt %) that is simultaneously coated and pressed onto a current collector using a rolling apparatus, eliminating the need for a separate drying process and reducing the risk of damage to the current collector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a liquid slurry with low solid content (30-60 wt%) is used for coating, then the coating process can be easily performed, but the solvent evaporation during drying causes nonuniform material distribution and decreased adhesion between electrode and current collector
Solution Approach 1:
The patent changes the key parameter of solid content from 30-60 wt% to 70-90 wt%, transforming the slurry from liquid to paste form. This parameter change eliminates the need for drying processes that cause nonuniform material distribution and adhesion problems, while the paste's high viscosity enables direct coating onto current collectors without requiring complex drying tunnels.
2Reliability
If a separate drying process is conducted after coating, then the solvent can be removed, but the process complexity increases and production time is extended
Solution Approach 1:
The patent extracts and eliminates the separate drying process from the electrode manufacturing sequence. By using high solid content paste (70-90 wt%), the solvent content is minimized, allowing the paste to be directly coated and pressed without requiring a dedicated drying tunnel, thus simplifying the overall process while still achieving adequate solvent removal.
Solution Approach 2:
The patent merges the coating and pressing operations into a single integrated step. The high solid content paste is directly coated onto the current collector and immediately pressed to form the electrode layer, combining what were previously separate coating-drying-pressing steps into a more efficient one-step process.
3Productivity
If high-temperature pressing is applied to decrease coating layer thickness, then the capacity density increases, but damage such as wrinkles or curling occurs in the current collector
Solution Approach 1:
The patent changes the pressing parameters by using moderate pressure and temperature conditions rather than high-temperature pressing. The high solid content paste (70-90 wt%) maintains its shape and adhesion under milder pressing conditions, achieving the desired thickness reduction and capacity density increase without causing wrinkles or curling in the current collector.
4Reliability
If a complicated transfer process is used to move slurry from storage mixer to head tank, then the slurry can be properly stored, but the manufacturing complexity increases
Solution Approach 1:
The patent extracts and eliminates the complicated transfer process involving storage mixers and head tanks. The high solid content paste can be directly handled and coated without requiring complex transfer systems, as its high viscosity prevents settling and maintains stability during direct coating operations.
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 results in a more convenient and efficient electrode preparation process with uniform material dispersion and minimized solvent evaporation, enhancing adhesion and reducing damage to the current collector, thereby improving the overall quality of the electrode coating layer.
Implementation Method 1
passing the current collector through a rolling apparatus together with the slurry in the form of a paste to simultaneously press it while forming an electrode coating layer on the current collector
Implementation Method 2
a solvent is evaporated during the drying process after coating, thus influencing the arrangement of solid contents to form a coating layer of a nonuniform distribution
Data Source
AI summary
The present invention provides a method for preparing an electrode for a secondary battery, including the steps of: (i) mixing and kneading an active material, a binder, and a conductive material together with a solvent to prepare a slurry in the form of a paste having a solid content of 70 to 90 wt %; (ii) positioning the slurry in the form of a paste on a current collector; and (iii) passing the current collector through a rolling apparatus together with the slurry in the form of a paste to simultaneously press it while forming an electrode coating layer on the current collector.