Silicon Anode Binder Composition for CNT Contact Stability
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Solution Overview
Problem
The insufficient contact between carbon nanotubes (CNTs) and silicon-containing materials in negative electrodes of non-aqueous electrolyte secondary batteries leads to poor cycle characteristics due to hydrophobicity of CNTs and hydrophilicity of polyacrylic acid (salt) binders, resulting in inadequate conductive paths and bonding.
Innovation Solution
Incorporating an acrylic polymer with both hydrophilic and hydrophobic structural units, including carboxyl groups, which enhances bonding between CNTs and silicon-containing materials, forming efficient conductive paths and improving adhesion to the current collector, thereby maintaining close contact during charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyacrylic acid (salt) is used as a binder to enhance bonding property, then bonding to silicon-containing material is improved, but bonding to carbon nanotubes is insufficient due to hydrophilicity of the binder and hydrophobicity of CNTs
Solution Approach 1:
The patent uses a binder containing both hydrophilic and hydrophobic groups to create a composite binding system. The hydrophilic groups (carboxyl, hydroxyl) bond with silicon-containing materials while hydrophobic groups (alkyl chains) bond with carbon nanotubes, resolving the contradiction between bonding to different materials with opposite surface properties.
Solution Approach 2:
The patent modifies the binder's chemical structure by incorporating both hydrophilic and hydrophobic functional groups. This changes the binder's surface interaction parameters, enabling it to interact effectively with both hydrophilic silicon-containing materials and hydrophobic carbon nanotubes simultaneously.
2Reliability
If carbon nanotubes are included in the negative electrode mixture to increase conductivity, then conductive paths are formed, but contact points with silicon-containing material are insufficient due to hydrophobicity of CNTs
Solution Approach 1:
The binder acts as an intermediary substance between carbon nanotubes and silicon-containing materials. It mediates the interaction by providing hydrophobic groups that contact CNTs and hydrophilic groups that contact silicon-containing materials, enabling effective conductive path formation through the silicon-containing material particles.
Solution Approach 2:
The dual-nature binder creates a composite interface that bridges the hydrophobic CNTs and hydrophilic silicon-containing materials, enabling sufficient contact points and effective conductive path formation without requiring modification of the CNTs themselves.
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 approach significantly improves the cycle characteristics of non-aqueous electrolyte secondary batteries by maintaining conductive paths and enhancing lithium ion conductivity and reducing resistance, leading to higher capacity and stability.
Implementation Method 1
CNTs have hydrophobicity, and the contact points between the CNTs and the Si-containing material may not be sufficiently formed
Implementation Method 2
polyacrylic acid (salt) has hydrophilicity, and does not exhibit a sufficient bonding to the hydrophobic CNTs
Implementation Method 3
the binder includes an acrylic polymer, and the polymer includes a hydrophilic structural unit having a carboxyl group, and a hydrophobic structural unit
Implementation Method 4
a negative electrode active material capable of electrochemically absorbing and releasing lithium ions
Data Source
AI summary
A negative electrode for a non-aqueous electrolyte secondary battery includes a negative electrode mixture including a negative electrode active material capable of electrochemically absorbing and releasing lithium ions, carbon nanotubes, and a binder. The negative electrode active material includes a silicon-containing material, and the binder includes an acrylic polymer. The polymer includes a hydrophilic structural unit having a carboxyl group, and a hydrophobic structural unit.