Polyamic Acid Electrode Binder for Silicon Anode Cycle Stability
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Solution Overview
Problem
Existing electrode binders for lithium ion secondary batteries with active materials that undergo large volume changes, such as silicon or tin, suffer from poor cycle characteristics due to layer destruction and interface peeling, leading to deteriorated battery performance.
Innovation Solution
A polyamic acid-based electrode binder resin composition is developed, using specific tetracarboxylic dianhydrides and diamines to create a water-soluble polyimide that improves adhesion and stability, combined with water-soluble polymers like polyacrylic acid, enhancing the cycle characteristics of the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a general-purpose binder such as polyvinylidene fluoride or a rubber-based resin is used for the electrode containing silicon or tin active materials, then the electrode can be manufactured with standard materials, but the active material layer is destroyed or the interface between the current collector and the active material layer is peeled off due to large volume change during charge/discharge, leading to deteriorated cycle characteristics
Solution Approach 1:
The invention changes the chemical composition parameters of the binder by incorporating specific functional groups (carboxyl, hydroxyl, or amine groups) that can form coordination bonds with silicon or tin atoms. This chemical parameter change enables the binder to adapt to the large volume changes of the active material during charge/discharge cycles, maintaining adhesion and preventing layer destruction or interface peeling, thus improving cycle characteristics while remaining manufacturable
Solution Approach 2:
The invention creates a composite binder system by combining polyvinylidene fluoride or rubber-based resin with water-soluble polymers containing specific functional groups (carboxymethyl cellulose, polyacrylic acid, polyvinyl alcohol, or polyvinylpyrrolidone). This composite structure allows the binder to simultaneously provide mechanical strength and chemical adhesion to the active material, resolving the contradiction between ease of manufacture and cycle characteristics
2Reliability
If aromatic polyimide is used as an electrode binder, then excellent adhesion and stability are achieved, but the poor solubility in organic solvents requires high-temperature heating (350°C) for dehydration and ring-closure to form the electrode layer, increasing manufacturing complexity and energy consumption
Solution Approach 1:
The invention changes the solvent parameter from organic solvents to water, enabling the polyamic acid precursor to dissolve readily without requiring high-temperature processing. The use of water as a solvent simplifies the manufacturing process while maintaining the excellent adhesion and stability properties of polyimide-based binders through the formation of coordination bonds with the active material
Solution Approach 2:
The invention performs the binding action in advance by using polyamic acid that already contains the necessary functional groups (carboxyl, hydroxyl, or amine groups) in its structure. This preliminary preparation allows the binder to form coordination bonds with the active material during the simplified water-based processing, eliminating the need for high-temperature dehydration and ring-closure steps while still achieving excellent adhesion and stability
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 polyamic acid-based binder composition significantly improves the cycle characteristics of lithium ion secondary batteries by maintaining adhesion and stability during charge/discharge cycles, resulting in higher capacity retention and initial charge/discharge efficiency.
Implementation Method 1
it has gradually come to light by experimentation that a binder containing a specific functional group such as a carboxyl group, a hydroxyl group, or an amine group, forms a coordination bond with a specific active material
Implementation Method 2
Patent Document 2 describes a polyimide binder obtained from an aqueous polyamic acid solution containing imidazoles
Data Source
AI summary
Disclosed is an electrode binder resin composition containing a polyamic acid, a water-soluble polymer other than the polyamic acid, and a solvent. The use of the electrode binder resin composition improves cyclic characteristics.