Negative Electrode Plasticizer and Binder for Lithium Battery Stability
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in maintaining stable negative electrodes and enhancing ionic conductivity, which affects their rate-capability and overall performance.
Innovation Solution
A negative electrode composition including a current collector, a negative active material layer with a polyhydric alcohol plasticizer having 2 to 5 OH groups, and an aqueous linear polymer binder, such as cellulose-based or acrylate-based compounds, is used to improve ionic conductivity and maintain a stable structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binders are used in the negative electrode, then the electrode structure may be simple and easy to manufacture, but the ionic conductivity is insufficient and the electrode stability deteriorates
Solution Approach 1:
The patent uses a composite binder system comprising both carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) in a specific weight ratio range (CMC: 0.1-5 wt%, SBR: 0.1-5 wt%). This composite approach combines the advantages of CMC (providing structural stability and adhesion) with SBR (providing flexibility and ionic conductivity), thereby achieving both electrode stability and good electrochemical performance without excessive complexity
Solution Approach 2:
The patent optimizes the weight ratio parameters of the binder components to achieve the desired balance between stability and conductivity. By controlling the CMC content at 0.1-5 wt% and SBR content at 0.1-5 wt%, the patent finds the optimal parameter range that provides sufficient ionic conductivity while maintaining structural integrity and adhesion to the current collector
2Speed
If the negative electrode is designed for high rate-capability, then the charging and discharging speed improves, but the ionic conductivity must be increased which may affect electrode stability
Solution Approach 1:
The patent adjusts the binder composition parameters to enhance ionic conductivity for high-rate applications. By incorporating SBR (0.1-5 wt%) alongside CMC, the patent creates a binder system with optimized ion transport properties that enables fast charging and discharging while preserving electrode structural stability through the synergistic effect of both polymers
Solution Approach 2:
The composite binder system of CMC and SBR provides dual functionality: CMC ensures structural stability and adhesion, while SBR enhances ionic conductivity for high-rate performance. This composite approach allows the electrode to achieve excellent rate-capability without compromising stability, as each component compensates for the limitations of the other
3Strength
If the binder content is increased to improve adhesion, then the adhesion to current collector improves, but the ionic conductivity may be reduced due to excessive binder
Solution Approach 1:
The patent precisely controls the binder content parameters, limiting CMC to 0.1-5 wt% and SBR to 0.1-5 wt% of the total electrode weight. This parameter optimization ensures sufficient adhesion strength while preventing excessive binder accumulation that would block ion transport pathways. The low but optimized concentrations maintain both mechanical adhesion and ionic conductivity
Solution Approach 2:
The composite binder system allows for reduced overall binder content while maintaining adhesion through the synergistic interaction between CMC and SBR. The CMC provides strong adhesion to the current collector, while SBR contributes to ionic conductivity, enabling the patent to achieve both good adhesion and high ionic conductivity with minimal binder content (total 0.2-10 wt%)
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 solution enhances ionic conductivity and reduces resistance, leading to improved high-rate charging and discharging characteristics of the negative electrode, while maintaining adhesion to the current collector.
Implementation Method 1
increases ionic conductivity in the negative electrode
Implementation Method 2
reduces resistance
Implementation Method 3
maintaining adhesion to the current collector
Data Source
AI summary
A negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same are provided. The negative electrode for a rechargeable lithium battery includes a current collector and a negative active material layer on the current collector, wherein the negative active material layer comprises a negative active material, a binder, and a polyhydric alcohol plasticizer having 2 to 5 OH groups per molecule of the polyhydric alcohol plasticizer, and the binder is an aqueous linear polymer binder including a cellulose-based compound, an acrylate-based compound, or a combination thereof.