CNF-CMC Anode Slurry for Thermal Wrinkle-Resistant Drying
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Solution Overview
Problem
The manufacturing process of lithium secondary batteries faces defects due to thermal wrinkling of the anode current collector during the drying process, which leads to cracks in the electrode.
Innovation Solution
An anode slurry composition is developed, comprising an anode active material, a conductive material, and two or more types of cellulose-based binders, specifically carboxymethyl cellulose (CMC) and cellulose nanofibrils (CNF), with a weight ratio of CNF to CMC ranging from 0.05 to 3.00, which minimizes thermal wrinkling by suppressing thermal expansion of the current collector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the drying temperature is increased to improve drying efficiency, then the drying speed is improved, but thermal wrinkling of the current collector occurs leading to electrode cracks
Solution Approach 1:
The invention changes the chemical composition parameters of the binder system by incorporating cellulose nanofibrils (CNF) with specific aspect ratios (length/width > 10) alongside carboxymethyl cellulose (CMC). This compositional parameter change modifies the thermal expansion characteristics of the electrode, allowing it to withstand higher drying temperatures without causing current collector wrinkling, thus enabling faster drying while maintaining electrode integrity.
Solution Approach 2:
The invention uses a composite binder system combining cellulose nanofibrils (CNF) and carboxymethyl cellulose (CMC) in specific weight ratios (CNF: 0.1-5.0 wt%, CMC: 0.5-2.0 wt%). This composite material approach creates a synergistic effect where the nanofibrils provide structural reinforcement and control thermal expansion, while the CMC provides binding functionality, allowing the electrode to withstand thermal stress during high-temperature drying processes.
2Quantity of substance
If thinner current collector foil is used to increase energy density, then the energy density is improved, but the foil is more susceptible to thermal expansion and wrinkling
Solution Approach 1:
The invention changes the mechanical and thermal parameters of the electrode composite by incorporating cellulose nanofibrils with high aspect ratios. This modification enhances the overall structural rigidity and thermal stability of the electrode, compensating for the reduced mechanical strength inherent in thinner current collector foils, thereby preventing wrinkling while maintaining high energy density.
Solution Approach 2:
The invention employs a composite binder system with cellulose nanofibrils (CNF) and carboxymethyl cellulose (CMC) that creates a reinforced electrode structure. The nanofibrils act as structural reinforcement elements within the binder matrix, providing enhanced mechanical strength and thermal stability to thin current collector foils, enabling them to resist thermal expansion and wrinkling during the drying 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
The use of the anode slurry composition effectively reduces the occurrence of thermal wrinkles, enhancing the productivity of electrodes and increasing the energy density of the manufactured batteries.
Implementation Method 1
the electrode temperature rises to the temperature of the drying furnace at the end of the drying process, causing the foil to thermally expand while the electrode fails to withstand this expansion
Data Source
AI summary
An anode slurry composition includes: an anode active material; a conductive material; and two or more types of cellulose-based binders. The cellulose-based binders include carboxymethyl cellulose (CMC) and cellulose nanofibrils (CNF), and the weight ratio of the cellulose nanofibrils (CNF) to the carboxymethyl cellulose (CMC) in the cellulose-based binders (CNF/CMC) is in the range of about 0.05 to 3.00.