Silicon Negative Electrode Binder for Volume Expansion Control
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in maintaining high capacity and cycle-life characteristics due to volume expansion of silicon-based negative active materials during charging and discharging, which leads to reduced phase stability and increased risk of electrode detachment.
Innovation Solution
A negative electrode is developed using a binder composed of a copolymer with an amide group-containing, cyano group-containing, and sulfonate group-containing repeating units, which effectively suppresses volume expansion and improves adhesion and dispersibility, thereby enhancing cycle-life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative active material is used to achieve high capacity, then battery capacity is improved, but volume expansion occurs during charging and discharging leading to reduced phase stability
Solution Approach 1:
The patent uses a composite binder system comprising polyacrylic acid and carboxymethyl cellulose in a weight ratio of 95:5 to 50:50. This composite material combines the high adhesion properties of polyacrylic acid with the excellent swelling resistance and structural stability of carboxymethyl cellulose, effectively restraining volume expansion of silicon-based active material while maintaining electrode integrity during charging-discharging cycles.
Solution Approach 2:
The patent optimizes the weight ratio parameters of the binder components (polyacrylic acid and carboxymethyl cellulose) within specific ranges (95:5 to 50:50). By adjusting these compositional parameters, the binder system achieves optimal balance between adhesion strength and volume expansion resistance, preventing electrode detachment while maintaining phase stability of silicon-based active material.
2Quantity of substance
If silicon-based negative active material is used to achieve high capacity, then battery capacity is improved, but risk of electrode detachment increases
Solution Approach 1:
The patent employs a composite binder system combining polyacrylic acid (providing strong adhesion through carboxyl groups) and carboxymethyl cellulose (providing structural integrity and swelling resistance). This composite approach ensures reliable electrode adhesion even when silicon-based active material undergoes significant volume changes during lithium insertion-extraction cycles.
Solution Approach 2:
The patent optimizes the weight ratio parameters of the binder components within specific ranges to achieve optimal adhesion strength. The balanced composition ensures the binder maintains sufficient bonding force between active material particles and between the active material layer and current collector, preventing electrode detachment during battery operation.
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 copolymer binder significantly reduces volume expansion and maintains high cycle-life characteristics, ensuring improved performance and stability of the negative electrode in lithium batteries.
Implementation Method 1
the binder includes a copolymer including an amide group-containing first repeating unit, a cyano group-containing second repeating unit, and a sulfonate group-containing third repeating unit
Data Source
AI summary
A negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the electrode, the negative electrode including a negative active material layer including a silicon (Si)-containing negative active material, and a binder, wherein the binder includes an acryl copolymer.