Negative Electrode Binder Design for Battery Adhesion and Resistance
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Solution Overview
Problem
Current binders for secondary batteries, such as PVDF and SBR, compromise battery performance due to insufficient adhesion and flexibility, leading to increased resistance and reduced capacity and lifespan, especially when used with materials like natural graphite or metal-based active materials.
Innovation Solution
A negative electrode design featuring a first layer with styrene-butadiene-based rubber and a second layer with (meth)acrylate-based polymer, optimized for adhesion and resistance characteristics, reduces binder content while enhancing adhesion between the current collector and active material and cohesion between active materials, thereby decreasing electrode resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PVDF binder is used to achieve good miscibility with graphite material, then adhesion between current collector and active material is improved, but battery capacity and efficiency deteriorate due to polymer fibers covering active material
Solution Approach 1:
The patent changes the chemical composition parameters of the binder from PVDF to a copolymer containing carboxylic acid groups (such as polyacrylic acid, polyacrylamide, or their crosslinked products). This parameter change allows the binder to maintain strong adhesion through chemical bonding while reducing the covering effect on active material, thereby improving battery capacity and efficiency.
Solution Approach 2:
The patent uses a composite binder system consisting of copolymer molecules with carboxylic acid groups that can form crosslinked networks. This composite structure provides both strong adhesion through chemical bonding and sufficient flexibility, resolving the contradiction between adhesion strength and battery performance.
2Strength
If PVDF binder is used to fabricate electrode plate, then adhesion is improved, but cycle characteristic deteriorates due to insufficient flexibility causing bond breakage during charging and discharging
Solution Approach 1:
The patent changes the physical and chemical parameters of the binder by using copolymers with carboxylic acid groups that exhibit viscoelastic properties. These materials provide both strong adhesion and sufficient flexibility to accommodate expansion and contraction during charging and discharging, preventing bond breakage and improving cycle characteristics.
Solution Approach 2:
The patent employs a binder system with flexible molecular chains that can deform elastically during battery operation. The copolymer structure with carboxylic acid groups forms a flexible network that maintains adhesion while accommodating volume changes, thereby improving duration of action and cycle life.
3Reliability
If SBR binder is used to increase battery capacity, then capacity is improved, but adhesion between current collector and active material is insufficient despite elasticity providing adhesion durability
Solution Approach 1:
The patent changes the chemical functionality of the binder by introducing carboxylic acid groups in the copolymer structure. This parameter change enables strong chemical bonding between the binder and both the current collector and active material, achieving sufficient adhesion while maintaining the capacity benefits of reduced binder content.
Solution Approach 2:
The copolymer with carboxylic acid groups acts as an intermediary that forms strong chemical bonds with both the current collector and active material. This mediator function ensures sufficient adhesion strength while allowing for reduced binder content to achieve high battery capacity.
4Reliability
If binder content is reduced to satisfy high capacity and high output, then capacity and output are improved, but adhesion with current collector is reduced increasing probability of cutting or deintercalation
Solution Approach 1:
The patent changes the chemical composition of the binder to copolymers with carboxylic acid groups that provide high adhesion strength per unit mass. This parameter change allows for reduced binder content while maintaining sufficient adhesion, thereby achieving high capacity and output without compromising structural integrity.
Solution Approach 2:
The patent uses a flexible copolymer binder system that can maintain strong adhesion even at low concentrations. The molecular structure provides sufficient bonding strength to prevent cutting and deintercalation while allowing for reduced binder content to achieve high capacity and output.
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
This configuration significantly improves battery capacity and lifespan by maintaining strong adhesion and cohesion even with reduced binder content, leading to enhanced performance and reduced resistance in the electrode.
Implementation Method 1
adhesion between a negative electrode current collector and an active material
Implementation Method 2
cohesion between active materials
Data Source
AI summary
The present invention provides a negative electrode for a secondary battery, the negative electrode including a negative electrode current collector, a first negative electrode active material layer located on the negative electrode current collector, and a second negative electrode active material layer located on the first negative electrode active material layer, such that resistance in the electrode is decreased due to an increase in adhesion between the negative electrode current collector and the active material and cohesion between the active materials, thereby significantly improving capacity and lifespan characteristics of a battery, a method of fabricating the same, and a secondary battery including the same.