Polyrotaxane Composite Binder Particles for Battery Electrode Cycling
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Solution Overview
Problem
Conventional binders for non-aqueous secondary batteries fail to maintain sufficient binding between electrode active materials and the current collector due to insufficient toughness and conformity, leading to decreased discharge capacity and cycle characteristics.
Innovation Solution
Composite particles comprising a copolymer and polyrotaxane, where the polyrotaxane has a cyclic molecule with a chain molecule and stopper groups, are used to form a binder that can withstand the expansion and contraction of electrode active materials, maintaining adhesion over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional binders are used in non-aqueous secondary batteries, then the electrode structure is simple and easy to manufacture, but the binding strength between electrode active materials and current collector is insufficient
Solution Approach 1:
The invention uses a composite binder system comprising polyrotaxane and copolymer particles. The polyrotaxane provides toughness and elasticity to withstand expansion/contraction, while the copolymer particles contribute to adhesion and binding strength. This composite structure resolves the contradiction by combining materials with complementary properties to achieve both high binding strength and structural complexity.
Solution Approach 2:
The invention modifies the binder properties by controlling the glass transition temperature (Tg) of the copolymer particles to be 30°C or lower, and by adjusting the content of specific structural units (15-70 mass% styrene, 10-40 mass% ethylenically unsaturated carboxylic acid ester). These parameter changes enable the binder to maintain flexibility and adhesion at operating temperatures, improving binding strength without excessive structural complexity.
2Reliability
If binders with higher toughness are used to withstand expansion and contraction, then cycle characteristics improve, but the binder composition becomes more complex
Solution Approach 1:
The composite binder system combines polyrotaxane (providing toughness and elasticity) with copolymer particles (providing adhesion and structural stability). This combination allows the binder to withstand repeated expansion and contraction of electrode materials during charging/discharging cycles, significantly improving cycle characteristics while maintaining a manageable composition through defined component ratios.
Solution Approach 2:
The polyrotaxane component forms a flexible matrix that can accommodate the volume changes of electrode active materials during charge-discharge cycles. The flexible structure of polyrotaxane, with its cyclic molecules threaded on linear chains, provides elastic deformation capability that maintains binder integrity over many cycles, improving reliability without requiring overly complex compositions.
3Reliability
If the binder has sufficient adhesion to maintain binding over time, then cycle characteristics improve, but the manufacturing process becomes more difficult
Solution Approach 1:
The copolymer particles are pre-synthesized with controlled glass transition temperature and specific structural unit composition before being incorporated into the binder system. This preliminary preparation ensures that the particles possess the necessary adhesion properties and flexibility in advance, simplifying the final binder manufacturing process while guaranteeing long-term adhesion performance and cycle characteristics.
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 composite particles enhance the binding properties between electrode active materials and the current collector, resulting in non-aqueous secondary batteries with improved cycle characteristics.
Implementation Method 1
the polyrotaxane has a cyclic molecule with a cyclic skeleton and a chain molecule passing through an opening of the cyclic molecule and having stopper groups at both ends
Implementation Method 2
maintaining adhesion over time
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The composite particle includes a copolymer and a polyrotaxane, the copolymer having a first structural unit derived from a monomer (al) and a second structural unit derived from a monomer (a2), the monomer (a1) is a nonionic compound having only one ethylenically unsaturated bond, the monomer (a2) is a compound having a carboxy group and only one ethylenically unsaturated bond, and the polyrotaxane has a cyclic molecule having a cyclic skeleton and a chain molecule that penetrates an opening of the cyclic molecule and has stopper groups at both ends, and does not contain an ethylenically unsaturated bond.