Polyamide Binder Composition for Silicon Anode Expansion Control
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Solution Overview
Problem
Commercial lithium-ion batteries based on graphite negative electrodes have reached their theoretical limit, and silicon-based electrodes suffer from volume expansion and contraction during charging and discharging, leading to mechanical and electrical performance degradation.
Innovation Solution
A polyamide polymer binder with a specific mole ratio of repeating structural units A to B, formed by reacting diamine and polyamine with dibasic acid anhydride, is used to inhibit volume expansion while maintaining flexibility, featuring a balanced hardness and softness, and is precipitated using an ether solvent for large-scale production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If aromatic polymer binders with strong π-π bonding interactions are used, then tensile strength to resist volume expansion is improved, but the binder becomes inelastic and loses flexibility
Solution Approach 1:
The patent applies local quality by creating a block copolymer structure where aromatic units (providing strength through π-π stacking) and aliphatic units (providing flexibility) are distributed in specific blocks rather than uniformly mixed. This allows different regions of the polymer to exhibit different properties - the aromatic blocks provide local strength to resist silicon expansion while the aliphatic blocks provide local flexibility, and the overall polymer chain integrates both functions.
2Strength
If polymer cross-linking is increased to resist volume expansion, then structural strength is improved, but the binder becomes too rigid to function as a bonding agent
Solution Approach 1:
The patent applies parameter changes by precisely controlling the ratio of aromatic to aliphatic units in the block copolymer structure. By adjusting this compositional parameter, the patent optimizes the balance between cross-linking density (which provides expansion resistance) and chain flexibility (which enables bonding). The specific block structure allows sufficient cross-linking for strength while maintaining the flexibility needed for bonding functionality.
3Adaptability or versatility
If small interaction forces are used for cross-linking, then flexibility is maintained, but the backbone strength becomes too low to resist silicon particle expansion
Solution Approach 1:
The patent applies composite materials by creating a block copolymer that combines aromatic units (which form strong π-π stacking interactions) with aliphatic units (which provide flexibility). This composite structure at the molecular level allows the binder to simultaneously achieve high backbone strength from the aromatic blocks and maintained flexibility from the aliphatic blocks, resolving the contradiction between these two properties.
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 effectively suppresses silicon particle expansion, retains electrode connectivity, and enhances electrical performance by forming a strong bond with silicon particles, improving cycle performance and adhesion force.
Implementation Method 1
the binder of the present disclosure includes a polyamide polymer, in which the repeating structural unit B serves as a hard segment in the polyamide polymer backbone, the relatively flexible repeating structural unit A serves as a soft segment in the polyamide polymer backbone
Implementation Method 2
the aromatic polymers have a rigid and organized polymer backbone structure characterized by strong π-π bonding interactions between the polymers
Implementation Method 3
adding ether solvent, collecting precipitate to obtain the binder
Data Source
AI summary
A binder, including a polyamide polymer containing repeating structural units A shown in formula (I) and repeating structural units B shown in formula (II), in which R1 is an aryl group not containing amide groups and amino groups, R2 includes an aryl group containing at least one amide groups or at least one amino groups, and a mole ratio of the repeating structural units A to the repeating structural units B is (2:1) to (6:1).