Si-Based Battery Negative Electrode Binder Network
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing nonaqueous electrolyte secondary batteries face issues with electrode conduction path breakage, separation of the active material layer, and peeling between the current collector and the active material layer due to volume changes, leading to unsatisfactory lifetime characteristics. Additionally, crosslinked polyacrylic acid binders fail to adequately cover the Si-based active material surface, resulting in electrolyte solution decomposition and reduced battery retention.
Innovation Solution
A negative electrode agent comprising a binder with a crosslinked high molecular weight polycarboxylic acid salt and a non-crosslinked low molecular weight polycarboxylic acid, forming an interpenetrating polymer network to enhance durability and prevent SEI breakage, while ensuring adequate coverage and stability during charge and discharge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If crosslinked polyacrylic acid is used as a binder to improve electrode structure stability, then the electrode structure becomes more resistant to breakage, but the coverage rate on Si-based active material surface decreases leading to electrolyte decomposition
Solution Approach 1:
The invention uses a composite binder system combining polyacrylic acid (PAA) and carboxymethyl cellulose (CMC) in a specific ratio (PAA:CMC = 1:4 to 1:10). This composite approach leverages the strength-providing capability of crosslinked PAA while using CMC to ensure adequate surface coverage and electrolyte stability, thus resolving the contradiction between structural stability and reliability
Solution Approach 2:
The invention optimizes the molecular weight of PAA to be 1,000,000 to 5,000,000 and controls the crosslinking degree within specific ranges (0.1-3.0 mol% crosslinking agent relative to carboxyl groups). These parameter optimizations ensure that the binder provides sufficient structural support without excessive crosslinking that would reduce surface coverage, thereby maintaining both strength and reliability
2Strength
If high molecular weight polymer is used to improve durability against volume expansion, then the binder strength increases, but the manufacturing complexity and crosslinking control difficulty increase
Solution Approach 1:
The invention specifies precise parameter ranges: PAA molecular weight of 1,000,000 to 5,000,000 and crosslinking agent amount of 0.1 to 3.0 mol% relative to carboxyl groups. These optimized parameters enable effective crosslinking without excessive complexity, balancing binder strength with manufacturability
Solution Approach 2:
The invention introduces CMC as an intermediary component that works synergistically with crosslinked PAA. CMC provides additional binding functionality and helps manage the crosslinking process, reducing the complexity associated with high molecular weight polymer crosslinking while maintaining durability
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 solution provides a negative electrode with improved durability and lifetime characteristics by suppressing internal stress and SEI formation, maintaining battery performance and capacity retention over repeated charge cycles.
Implementation Method 1
the binder comprises a first water-soluble linear polymer and a second water-soluble linear polymer, the water-soluble polymers contained in the binder contain a carboxyl group, the first water-soluble polymer having been crosslinked... the first water-soluble polymer is a polycarboxylic acid salt
Implementation Method 2
the first water-soluble polymer having been crosslinked
Implementation Method 3
the water-soluble polymers contained in the binder contain a carboxyl group
Data Source
Figure 1~2
AI summary
The invention provides a negative electrode for nonaqueous electrolyte secondary batteries, which has excellent lifetime characteristics, a negative electrode agent for nonaqueous electrolyte secondary batteries, which is used therefor, and a nonaqueous electrolyte secondary battery provided with the negative electrode. The negative electrode agent for nonaqueous electrolyte secondary batteries related to the present invention comprises, at least, an active material and a binder wherein the binder contains a first water-soluble polymer of linear polycarboxylate and a second water-soluble polymer of linear polycarboxylic acid. The first water-soluble polymer has a crosslinked structure of high molecular weight, and the second water-soluble polymer has a low molecular weight.