Dry Electrode Calendering for Crack-Resistant Battery Sheets
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Solution Overview
Problem
The manufacturing process of lithium secondary battery electrodes often results in defective surfaces due to uneven solvent evaporation, leading to pinholes, cracks, and variations in composition, and existing dry methods lack sufficient tensile strength, necessitating a method to improve electrode quality and tensile strength without a drying process.
Innovation Solution
A dry electrode sheet manufacturing method using a calendering process with a composition of electrode active materials and binders, where the dry electrode composition is passed through multiple rolls with controlled intervals and rotational speeds to achieve the desired compression ratio and fiberization of the binder, eliminating the need for a drying process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If a drying operation is performed to remove solvent from the electrode mixture layer, then the solvent is evaporated to form the electrode, but pinholes or cracks are formed in the electrode mixture layer resulting in defective electrode surfaces
Solution Approach 1:
The invention extracts and eliminates the drying operation entirely from the manufacturing process. By using a dry electrode mixture without solvent, the harmful evaporation process is removed, preventing pinhole and crack formation while still achieving the necessary solvent removal function through alternative means (no solvent present)
Solution Approach 2:
The invention changes the fundamental parameter of the electrode mixture from wet (solvent-based) to dry (solvent-free). This parameter change eliminates the evaporation process and its associated defects, transforming the manufacturing approach from conventional slurry coating to dry powder metallurgy-like processing
2Loss of substance
If a drying operation is performed to remove solvent, then the electrode is formed, but uneven drying occurs causing particle floating and composition variation in the electrode mixture layer
Solution Approach 1:
The invention extracts the solvent from the electrode mixture formulation, eliminating the drying operation and its associated uneven evaporation problems. Without solvent present, there is no evaporation process to cause particle floating or composition variation
Solution Approach 2:
The invention fundamentally changes the electrode mixture from a wet slurry requiring evaporation to a dry powder mixture. This parameter change eliminates the evaporation mechanism that causes composition non-uniformity, ensuring consistent electrode properties throughout
3Productivity
If a dry method is used to manufacture the electrode without solvent, then the drying operation is omitted, but cracks are generated on the electrode surface due to insufficient tensile strength
Solution Approach 1:
The invention uses composite materials with specific focus on optimized binder formulations and particle size distributions. The binder acts as a binding agent that provides tensile strength to the dry electrode mixture, preventing crack formation while maintaining the solvent-free advantage
Solution Approach 2:
The invention optimizes parameters such as binder content, particle size distribution, and compression conditions to achieve sufficient tensile strength in the dry electrode. By carefully controlling these parameters, the electrode gains enough mechanical strength to prevent cracking during handling and assembly
4Ease of manufacture
If conventional dry method is used without binder optimization, then the manufacturing process is simplified, but the electrode lacks sufficient tensile strength and generates cracks
Solution Approach 1:
The invention employs optimized composite material formulations with specific binder types and concentrations. The binder composition is carefully selected to provide maximum binding strength while maintaining process simplicity, creating a robust dry electrode structure
Solution Approach 2:
The invention optimizes critical parameters including binder content percentage, particle size distribution ratios, and compression pressure levels. These parameter optimizations ensure sufficient tensile strength is achieved without complicating the manufacturing process
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 enhances the tensile strength of the dry electrode sheet, prevents cracking, and simplifies the manufacturing process, resulting in improved electrode quality and reduced equipment costs by eliminating the drying step.
Implementation Method 1
a calendering operation of preparing an dry electrode sheet by passing the dry electrode composition through a calender roll including three or more rolls... The first interval W1 and the second interval W2 have a compression rate of 0.10 or more and 0.65 or less
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A method of manufacturing a dry electrode sheet for a secondary battery includes providing a dry electrode composition comprising an electrode active material and a binder, a calendering operation of preparing an electrode sheet by passing the dry electrode composition through a calender roll including three or more rolls. The calendering operation includes a first electrode sheet manufacturing operation of manufacturing a first electrode sheet by injecting the dry electrode composition between two adjacent rolls spaced apart from each other by a first interval W1, and an electrode sheet manufacturing operation of manufacturing a dry electrode sheet by inserting the first electrode sheet between two adjacent rolls spaced apart from each other by a second interval W2. The first interval W1 and the second interval W2 have a compression rate of 0.10 or more and 0.65 or less, represented by the equation (1) compression rate = (W1-W2)/W1.