Polyrotaxane Electrode Binder for Battery Cycle Stability
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Solution Overview
Problem
Existing non-aqueous secondary battery binders fail to improve the cycle characteristics of batteries, leading to reduced performance and lifespan due to insufficient adhesion and conformability with electrode active material expansion and contraction.
Innovation Solution
A non-aqueous secondary battery binder polymer is developed, comprising a first structural unit from a non-ionic compound with one ethylenically unsaturated bond, a second structural unit from a compound with a carboxy group and one ethylenically unsaturated bond, and a third structural unit from a polyrotaxane with a cyclic framework and stopper groups, enhancing adhesion and conformability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binders are used in non-aqueous secondary batteries, then the battery can be manufactured with standard materials, but the cycle characteristics and adhesion performance are insufficient
Solution Approach 1:
The binder polymer is designed as a composite material containing three distinct structural units: (a1) non-ionic compound units providing adhesion, (a2) carboxy group-containing units providing conformability, and (a3) polyrotaxane units providing expansion/contraction resistance. This composite structure at the molecular level enables simultaneous achievement of strong adhesion and excellent cycle characteristics.
Solution Approach 2:
Different structural units within the binder polymer perform specialized functions: the non-ionic compound units (a1) specifically provide adhesion to electrode active materials, the carboxy group units (a2) provide conformability to expansion/contraction, and the polyrotaxane units (a3) provide mechanical strength. This local specialization of functions within the single binder material resolves the contradiction between adhesion and cycle characteristics.
2Strength
If the binder maintains strong adhesion to electrode active materials, then electrode integrity is improved, but flexibility to accommodate expansion and contraction is reduced
Solution Approach 1:
The binder polymer incorporates different structural units with specialized local functions: non-ionic compound units (a1) provide strong adhesion to electrode active materials, while carboxy group-containing units (a2) provide conformability to expansion and contraction movements. This functional differentiation within the single polymer enables simultaneous achievement of both strong adhesion and flexibility.
Solution Approach 2:
The carboxy group-containing structural units (a2) can change their physical state and flexibility in response to moisture content changes during battery operation, allowing the binder to adapt its conformability parameter dynamically while maintaining adhesion through the non-ionic units (a1).
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 polymer significantly improves the cycle characteristics of non-aqueous secondary batteries by maintaining adhesion between electrode active materials and the current collector, even under conditions of expansion and contraction, resulting in enhanced battery performance and lifespan.
Implementation Method 1
a third structural unit derived from a polyrotaxane including a cyclic molecule having a cyclic framework to which a group containing an ethylenically unsaturated bond is bonded and a chain molecule that passes through an opening of the cyclic molecule
Data Source
Figure 1~2
AI summary
A non-aqueous secondary battery binder polymer including a first structural unit derived from a monomer (a1), a second structural unit derived from a monomer (a2), and a third structural unit derived from a monomer (a3), wherein the monomer (a1) is a non-ionic 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 monomer (a3) is a polyrotaxane including a cyclic molecule having a cyclic framework to which a group containing an ethylenically unsaturated bond is bonded and a chain molecule that passes through an openings of the cyclic molecule and has stopper groups at both ends.