Polyrotaxane Binder Polymer for Battery Electrode Adhesion

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Solution Overview

Problem

Existing non-aqueous secondary battery binders fail to maintain adequate adhesion between electrode active materials and current collectors due to insufficient conformability, leading to reduced cycle characteristics and discharge capacity as the electrodes expand and contract during charging and discharging.

Innovation Solution

A non-aqueous secondary battery binder polymer is developed, comprising structural units derived from a non-ionic compound with one ethylenically unsaturated bond, a compound with a carboxy group and one ethylenically unsaturated bond, and a polyrotaxane with a cyclic molecule and a chain molecule having stopper groups, which provides conformability and maintains adhesion through a pulley effect and air spring mechanism.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional binders are used in non-aqueous secondary batteries, then the battery can be manufactured with standard materials, but the adhesion between electrode active materials and current collectors deteriorates during charging and discharging cycles

Engineering Contradiction:

Improvecycle characteristicsVSAvoidadhesion between electrode active materials and current collector

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The binder polymer incorporates a polyrotaxane structure with movable cyclic molecules that can dynamically adjust their position along the chain molecule axis. This dynamic structure allows the binder to conform to the expansion and contraction of electrode active materials during charging and discharging, maintaining adhesion strength throughout battery cycles. The cyclic molecules act like pulleys that can move freely, providing mechanical flexibility to accommodate volume changes.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the glass transition temperature parameter of the binder polymer to 30°C or lower, which enhances the flexibility and conformability of the binder at operating temperatures. This parameter change allows the binder to remain soft and adaptable during battery cycling, preventing adhesion loss while maintaining structural integrity. The low Tg ensures the binder stays in a rubbery state that can deform with electrode expansion/contraction.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the binder polymer has high conformability to accommodate electrode expansion and contraction, then cycle characteristics improve, but the structural complexity of the binder increases

Engineering Contradiction:

Improvecycle characteristicsVSAvoidbinder structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The binder polymer utilizes a polyrotaxane structure where cyclic molecules are threaded onto a chain molecule, creating a nested configuration. The cyclic molecules (such as cyclodextrins) are nested within the polymer chain structure, allowing them to move independently while being constrained by the chain. This nested architecture provides complex functionality (conformability through cyclic movement) without requiring entirely separate components, thus managing structural complexity efficiently.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The binder is formulated as a composite polymer containing multiple structural units: polyrotaxane units for conformability, and additional functional units for adhesion and stability. This composite approach combines different molecular functionalities within a single binder material, achieving high cycle characteristics through the synergistic effect of the polyrotaxane's mechanical flexibility and the other units' bonding capabilities, rather than using multiple separate binder materials.

Inventive Principle:

Principle #40Composite materials

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 enhances the adhesion between electrode active materials and current collectors, preventing peeling and maintaining cycle characteristics, thus improving the performance of non-aqueous secondary batteries.

Implementation Method 1

provides conformability and maintains adhesion through a pulley effect and air spring mechanism

Methodology Applied

Scientific EffectPulley effect: Pulley

Implementation Method 2

provides conformability and maintains adhesion through a pulley effect and air spring mechanism

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS20260038836A1Non-aqueous secondary battery binder polymer, non-aqueous secondary battery binder composition, and non-aqueous secondary battery electrode

Publication Date: 2026.02.05 RESONAC CORP

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.