Silicon Anode Binder Composition for Volume Expansion Control
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Solution Overview
Problem
Silicon-based active materials in negative electrodes of lithium secondary batteries face challenges due to volume expansion during charge/discharge cycles, leading to reduced lifespan and energy density.
Innovation Solution
A negative electrode with a silicon-based active material and a binder composition that includes an aqueous binder and a rubber-based binder in a specific weight ratio (82:18 to 88:12), which minimizes volume expansion and enhances lifespan and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a silicon-based active material is used in the negative electrode, then the capacity and energy density are significantly improved, but the volume expansion during charge/discharge causes deterioration in lifespan properties
Solution Approach 1:
The patent changes the chemical composition parameters of the binder system by incorporating specific aqueous binders (polyacrylic acid, polyvinyl alcohol) in optimized weight ratios (5-20 wt% of total binder). This parameter optimization allows the binder to effectively accommodate silicon's volume expansion while maintaining electrode integrity, thus resolving the contradiction between high capacity and lifespan reliability
Solution Approach 2:
The patent creates a composite binder system combining multiple binder types (aqueous binder + polyvinylidene fluoride + carboxymethyl cellulose) with complementary properties. The aqueous binder provides flexibility for volume expansion, while the other binders provide structural stability, together enabling both high capacity utilization and improved lifespan properties
2Use of energy by moving object
If a silicon-based active material is used to achieve high energy density, then the energy density is improved, but the volume expansion problem limits its universal application
Solution Approach 1:
The patent optimizes the weight ratio parameters of the binder components, specifically setting the aqueous binder content at 5-20 wt% of total binder and polyvinylidene fluoride at 70-85 wt%. These parameter adjustments create a binder system that effectively manages silicon's volume expansion, enabling universal application of silicon-based negative electrodes while maintaining high energy density
3Weight of moving object
If the negative electrode is made thinner to reduce weight, then the weight is reduced, but the mechanical strength and structural integrity may be compromised
Solution Approach 1:
The patent changes the binder composition parameters by incorporating aqueous binders with high binding strength (polyacrylic acid, polyvinyl alcohol) in optimized amounts. These binders provide superior adhesion and mechanical reinforcement, enabling the use of thinner negative electrodes while maintaining sufficient mechanical strength and structural integrity
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 proposed solution effectively minimizes volume expansion of silicon-based active materials, thereby improving the lifespan and energy density of lithium secondary batteries while enabling the production of thin-film electrodes.
Implementation Method 1
a negative electrode binder, wherein the negative electrode binder includes an aqueous binder and a rubber-based binder in a weight ratio of 82:18 to 88:12
Data Source
AI summary
The present invention relates to a negative electrode including a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, wherein the negative electrode active material layer includes a silicon-based active material and a negative electrode binder, wherein the negative electrode binder includes an aqueous binder and a rubber-based binder in a weight ratio of 82:18 to 88:12, and the aqueous binder includes at least one selected from the group consisting of polyvinyl alcohol, polyacrylic acid, polyethylene glycol, polyacrylonitrile, and polyacryl amide.