Polyacrylonitrile Binder for Metallic Anode Batteries
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Solution Overview
Problem
Lithium secondary batteries using metallic anode active materials face rapid capacity reduction and shortened cycle life due to volume changes during charge/discharge, as conventional binders fail to maintain adequate adhesion and cohesion, leading to separation from current collectors and electrode deformation.
Innovation Solution
A polyacrylonitrile-based electrode binder with a cohesion force of at least 0.98 N/cm and adhesion force ranging from 0.00098 N/mm to 0.689 N/mm is used, which effectively inhibits separation of the anode active material from the current collector and reduces electrode deformation, thereby improving the battery's lifetime and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional binders (PVdF, SBR) are used for metallic anode active materials, then the binder is easy to manufacture and apply, but the adhesion and cohesion forces are insufficient, causing separation from current collector and internal cracks during charge/discharge
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by using polyacrylonitrile with specific molecular weight (100,000 to 1,000,000) and specific gravity (1.15 to 1.20), which provides optimal adhesion force (0.05 to 0.70 N/mm) and cohesion force (1.0 to 5.0 N/cm) for metallic anode materials, resolving the insufficient binding strength issue while maintaining cycle life
Solution Approach 2:
The patent creates a composite structure where polyacrylonitrile binder combines with metallic anode active materials through specific adhesion mechanisms, forming a stable composite that maintains structural integrity during volume changes, thereby improving both strength and reliability simultaneously
2Stability of the object's composition
If PI (poly imide) with high adhesion force is used, then the crack within electrode is reduced, but the cohesion force between binder and current collector is very strong, causing electrode deformation and current collector extension or wrinkling
Solution Approach 1:
The patent adjusts the adhesion force parameter to an optimal range (0.05 to 0.70 N/mm) using polyacrylonitrile, which is sufficient to prevent internal cracks but controlled enough to avoid excessive binding to the current collector, thus preventing electrode deformation while maintaining crack resistance
Solution Approach 2:
The patent applies partial adhesion force - enough to bind active material particles together and prevent cracks, but not excessive to cause deformation, achieving the right balance through specific binder selection and parameter control
3Quantity of substance
If metallic materials (silicon, tin) are used as anode active materials to increase capacity, then the battery capacity is improved, but the volume change during charge/discharge causes separation from current collector and rapid capacity reduction
Solution Approach 1:
The patent changes the binder properties to match the high volume expansion requirements of metallic anode materials, using polyacrylonitrile with specific mechanical properties that can accommodate large volume changes while maintaining adhesion, enabling high capacity materials to function reliably over many cycles
Solution Approach 2:
The polyacrylonitrile binder acts as an intermediary between the metallic anode active material and the current collector, absorbing volume changes and maintaining the connection, thereby enabling the use of high-capacity metallic materials without suffering from separation issues
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 polyacrylonitrile binder enhances the adhesion and cohesion forces, reducing cracks and thickness expansion, thus improving the battery's cycle life and capacity retention, while also simplifying the fabrication process by avoiding high-temperature heat treatment.
Implementation Method 1
a polymer whose cohesion force with a metal(loid) electrode active material is equal to or more than 0.98 N/cm (100gf/cm), and adhesion force with an electrode current collector ranges from 0.00098 N/mm (0.1gf/mm) to 0.689 N/mm (70gf/mm)
Implementation Method 2
a polymer whose cohesion force with a metal(loid) electrode active material is equal to or more than 0.98 N/cm (100gf/cm)
Data Source
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AI summary
Disclosed is an electrode binder for a secondary battery, an electrode including the electrode binder, and the secondary battery. The disclosed electrode binder for the secondary battery includes a polymer whose cohesion force with a metal(loid) electrode active material is equal to or more than 100gf/cm, and adhesion force with an electrode current collector ranges from 0.1gf/mm to 70gf/mm, the metal(loid) electrode active material being capable of reversibly storing and discharging lithium, wherein the polymer includes at least one kind selected from the group including polyamide imide, polyamide, polyacrylonitrile, polyacrylic acid and polyvinyl alcohol.