Silicon Anode Slurry Binder Composition for Crack-Resistant Electrodes
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Solution Overview
Problem
Negative electrodes with silicon-containing active materials in rechargeable batteries face issues such as expansion, reduced electronic conductivity, and cracking during the coating and drying processes, leading to capacity deterioration and poor cycle characteristics.
Innovation Solution
A negative electrode slurry is developed, comprising a silicon-containing active material, a binder with a particulate dispersed body and an acrylic acid-acrylonitrile-based copolymer, and a solvent. The binder's composition, including a water-soluble polymer with a specific copolymer ratio, helps in suppressing electrode expansion and reducing cracking during processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a silicon-containing active material is used to increase capacity, then the battery capacity is improved, but the electrode expands and contracts violently during charge and discharge
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by using a copolymer containing both acrylic acid units and acrylonitrile units in specific ratios. This compositional parameter change allows the binder to simultaneously provide strong adhesion and flexibility, accommodating the volume changes of silicon-containing active materials during charge-discharge cycles while maintaining electrode structural stability.
Solution Approach 2:
The patent employs a composite binder system consisting of multiple components: a copolymer containing acrylic acid and acrylonitrile units, and optionally other polymers such as carboxymethyl cellulose or styrene-butadiene rubber. This composite material approach combines the advantages of different polymer components to achieve both strong binding and flexibility, resolving the contradiction between capacity improvement and volume stability.
2Quantity of substance
If the negative electrode thickness is increased to greater than or equal to about 3.5 mAh/cm2, then the battery capacity is improved, but cracks occur in the negative electrode during coating and drying processes
Solution Approach 1:
The patent modifies the binder composition parameters to include a copolymer with specific ratios of acrylic acid and acrylonitrile units, which changes the rheological and mechanical properties of the electrode slurry. This parameter change improves the slurry's coating characteristics and drying behavior, preventing crack formation even in thick electrodes with area capacity of 3.5 mAh/cm2 or greater.
3Stability of the object's composition
If an acrylic acid-based polymer with relatively high hardness is used as a binder to suppress expansion, then the electrode expansion is reduced, but cracks occur during coating and drying processes
Solution Approach 1:
The patent creates a composite binder material consisting of a copolymer with both acrylic acid units (providing hardness and expansion control) and acrylonitrile units (providing flexibility and crack resistance). This composite approach combines the beneficial properties of different polymer components, achieving both expansion suppression and crack prevention during coating and drying processes.
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 suppresses the expansion of negative electrodes, reduces cracking during the coating and drying processes, and improves the cycle maintenance rate of rechargeable batteries, leading to enhanced performance and longevity.
Implementation Method 1
the binder includes a particulate dispersed body and a water-soluble polymer including a copolymer including an acrylic acid-based monomer and an acrylonitrile-based monomer
Implementation Method 2
a binder for binding the negative active material
Implementation Method 3
a solvent for dispersing the negative active material and the binder in the negative electrode slurry
Implementation Method 4
cracks may occur in the negative electrode during coating and drying processes of the negative electrode slurry
Data Source
AI summary
A negative electrode slurry includes a negative active material including a first active material in an amount of greater than or equal to about 5 wt % and less than or equal to about 100 wt %, a binder for binding the negative active material, and a solvent for dispersing the negative active material and the binder in the negative electrode slurry, wherein the first active material contains silicon atoms in an amount of greater than or equal to about 20 wt % and less than or equal to about 100 wt %, the binder includes a particulate dispersed body and a water-soluble polymer containing an acrylic acid-acrylonitrile-based copolymer, and when a sum of an amount of the negative active material and an amount of the binder is 100 wt %, an amount of the water-soluble polymer is greater than or equal to about 0.5 wt % and less than or equal to about 2 wt %.