Sulfur-Crosslinked Anode Binder for Peel Strength and Low Swelling
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Solution Overview
Problem
Non-aqueous secondary battery negative electrodes face challenges with weak adhesion to current collectors and swelling due to expansion and contraction of active materials, leading to poor cycle characteristics and increased risk of electrode structure collapse.
Innovation Solution
A binder composition with a particulate binder having a cross-linked structure through sulfur bonding is used, which exhibits low sedimentation upon centrifugation and includes an aliphatic conjugated diene monomer unit, enhancing peel strength and inhibiting swelling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional binder composition is used, then the negative electrode mixed material layer can be formed on the current collector, but the peel strength is insufficient and the electrode structure becomes unstable during cycling
Solution Approach 1:
The patent uses a composite binder system comprising both a conventional binder (e.g., polyvinylidene fluoride) and a novel binder with cross-linked structure through sulfur bonding. This composite binder composition synergistically combines the advantages of both binders to achieve both strong adhesion (peel strength) and structural stability during cycling, resolving the contradiction between initial bonding strength and long-term reliability.
Solution Approach 2:
The patent modifies the binder composition by introducing specific components with cross-linked structures through sulfur bonding and controlling the sediment amount after centrifugation. These parameter changes in the binder's chemical structure and physical properties enable simultaneous improvement of both peel strength and cycle characteristics, transforming the binder's performance to satisfy both requirements.
2Duration of action of moving object
If the negative electrode active material undergoes expansion and contraction during charging and discharging, then the battery can be repeatedly charged and discharged, but the electrode plate structure collapses and the negative electrode swells
Solution Approach 1:
The patent employs a binder composition with cross-linked structure through sulfur bonding that provides preemptive structural support to the negative electrode. This binder acts as a cushioning framework before electrode structure collapse can occur, maintaining electrode integrity during the expansion and contraction cycles of the active material, thus preventing swelling while enabling repeated charging and discharging.
3Strength
If the binder composition has high adhesion to ensure strong bonding, then the peel strength improves, but the cycle characteristics may deteriorate due to binder rigidity
Solution Approach 1:
The patent carefully controls the sediment amount after centrifugation of the binder composition and adjusts the cross-linking density through sulfur bonding. These parameter optimizations ensure the binder maintains appropriate flexibility and adhesion balance, achieving strong initial bonding while preserving the ability to accommodate volume changes during cycling, thus extending cycle life without sacrificing peel strength.
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 binder composition achieves excellent peel strength and cycle characteristics by improving adhesion and flexibility, reducing the likelihood of electrode swelling and maintaining battery performance over cycles.
Implementation Method 1
the particulate binder has a cross-linked structure through bonding via sulfur
Implementation Method 2
an amount of sediment obtained upon centrifugation of the binder composition for a non-aqueous secondary battery negative electrode at a rotation speed of 110,000 rpm
Data Source
AI summary
Provided is a binder composition for a non-aqueous secondary battery negative electrode with which it is possible to form a negative electrode having excellent peel strength and low tendency to swell after cycling and a secondary battery having excellent cycle characteristics. The binder composition contains a particulate binder and a dispersion medium. The particulate binder has a cross-linked structure through bonding via sulfur. The amount of sediment obtained upon centrifugation of the binder composition at a rotation speed of 110,000 rpm is less than 5.0 parts by mass when the amount of all solid content contained in the binder composition is taken to be 100 parts by mass.