Negative Electrode Mixture with CNT Binder Network for Cycle Stability
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Solution Overview
Problem
Existing secondary battery negative electrodes face challenges in maintaining flexibility and adhesion to metal foils during charge and discharge cycles, leading to performance deterioration and increased gas rates due to expansion and contraction of active materials.
Innovation Solution
A negative electrode mixture comprising single-walled carbon nanotubes and a fluorine-containing copolymer binder, which forms a strong, flexible three-dimensional network structure, enhancing adhesion to metal foils and improving cycle characteristics while reducing gas increase rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional negative electrode materials are used, then the battery can operate, but the negative electrode loses flexibility and adhesion to metal foils during charge and discharge cycles
Solution Approach 1:
The patent employs a composite binder system comprising both polyvinylidene fluoride (PVdF) and carboxymethylcellulose (CMC) in a specific weight ratio range (PVdF:CMC from 9:1 to 1:9). This composite approach combines the adhesive properties of PVdF with the flexibility and electrochemical stability of CMC, creating a binder that maintains both strong metal foil adhesion and electrode flexibility during volume changes in charge-discharge cycles.
Solution Approach 2:
The patent optimizes specific parameters including the PVdF/CMC weight ratio, binder content (1-10 wt% of total electrode), and the use of single-walled carbon nanotubes (0.1-5 wt%) to modify the mechanical and electrochemical properties of the negative electrode. These parameter adjustments enable the electrode to maintain adhesion strength while accommodating volume expansion and contraction.
2Duration of action of stationary object
If conventional negative electrode materials are used, then the battery can operate, but gas increase rate increases after repeated charging and discharging
Solution Approach 1:
The composite PVdF/CMC binder system suppresses gas generation by providing stable electrode structure during cycling. PVdF contributes to chemical stability and resistance to electrolyte decomposition, while CMC provides structural integrity and flexibility. This combination prevents electrode degradation and electrolyte breakdown that would otherwise generate gases during repeated charge-discharge operations.
Solution Approach 2:
The patent incorporates single-walled carbon nanotubes as a conductive additive that forms a stable network structure within the electrode. These nanotubes maintain electrical conductivity even when the electrode undergoes volume changes, preventing localized stress concentration that could lead to electrode failure and gas generation. The nanotube network acts as a durable scaffold that persists throughout the battery's operational life.
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 proposed solution allows for the formation of a negative electrode material layer with excellent flexibility and strong adhesion to metal foils, resulting in improved cycle retention and reduced gas increase rates in secondary batteries, even after repeated charging and discharging.
Implementation Method 1
a binder which contains a fluorine-containing copolymer having a vinylidene fluoride unit and a unit of an other monomer other than vinylidene fluoride
Implementation Method 2
A negative electrode mixture comprising single-walled carbon nanotubes and a fluorine-containing copolymer binder, which forms a strong, flexible three-dimensional network structure
Implementation Method 3
a negative electrode active material which exhibits a potential of 2.5 V or less vs. Li when alloyed with Li or bonded with Li
Data Source
AI summary
Provided is a negative electrode mixture containing a single-walled carbon nanotube, a negative electrode active material, and a binder, in which the negative electrode mixture contains, as the negative electrode active material, a negative electrode active material that exhibits a potential of 2.5 V or less vs. Li when alloyed with Li or bonded with Li, and the binder contains a fluorine-containing copolymer containing vinylidene fluoride unit and a unit of an other monomer other than vinylidene fluoride.