Silicon Anode Binder IPN Structure for Volume Expansion Control

Solution Overview

Problem

Silicon-based negative active materials in lithium rechargeable batteries undergo significant volume expansion during charge and discharge cycles, leading to deteriorated charge and discharge characteristics and cycle-life characteristics.

Innovation Solution

A binder composition with an interpenetrating polymer network (IPN) structure, comprising a cyclic polymer and polyacrylamide, is used to control volume expansion, improve adherence, and enhance stability with respect to the electrolyte, including an alkali metal ion and a phosphorus-based compound, and optionally polyalkylene glycol.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If Si-based negative active material is used to achieve high charge capacity, then energy density is improved, but volume expansion occurs during charge and discharge cycles leading to deteriorated charge and discharge characteristics and cycle-life characteristics

Engineering Contradiction:

Improvecharge capacityVSAvoidcycle-life characteristics

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The binder composition is designed to accommodate and cushion the volume expansion of Si-based active material before it causes damage. The IPN structure with dual polymer networks provides a compliant matrix that absorbs expansion stress, preventing electrode disintegration and maintaining cycle-life characteristics while preserving high charge capacity.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The invention uses a composite binder system comprising two different polymers with complementary properties. One polymer provides adhesion to the active material, while the other provides flexibility to accommodate volume expansion. This composite approach allows the binder to simultaneously maintain structural integrity and absorb expansion stress, resolving the contradiction between capacity and reliability.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If Si-based negative active material is used to achieve high charge capacity, then energy density is improved, but charge and discharge characteristics are deteriorated due to volume expansion

Engineering Contradiction:

Improvecharge capacityVSAvoidcharge and discharge characteristics

Core Design Contradiction:

Quantity of substanceVSEase of operation

Solution Approach 1:

The binder composition is designed to accommodate and cushion the volume expansion of Si-based active material before it causes damage. The IPN structure with dual polymer networks provides a compliant matrix that absorbs expansion stress, preventing electrode disintegration and maintaining cycle-life characteristics while preserving high charge capacity.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The invention changes the physical and chemical parameters of the binder system by using two polymers with different glass transition temperatures, crosslinking densities, and mechanical properties. This allows the binder to exhibit both rigidity for structural support and flexibility for expansion accommodation, thereby improving charge and discharge characteristics while maintaining high capacity.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If conventional binder composition is used, then manufacturing is simple, but volume expansion of active material cannot be effectively controlled

Engineering Contradiction:

Improvebinder composition preparationVSAvoidvolume expansion control

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The invention uses a composite binder system comprising two different polymers with complementary properties. One polymer provides adhesion to the active material, while the other provides flexibility to accommodate volume expansion. This composite approach allows the binder to simultaneously maintain structural integrity and absorb expansion stress, resolving the contradiction between capacity and reliability.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS9768448B2Binder composition for rechargeable lithium battery, method of preparing same, electrode for rechargeable lithium battery and rechargeable lithium battery including same

Publication Date: 2017.09.19 SAMSUNG SDI CO LTD

AI summary

A binder composition for a rechargeable lithium battery includes: an interpenetrating polymer network (IPN) structure including a cyclic polymer including a structural unit represented by Chemical Formula 1 or a structural unit represented by Chemical Formula 2, and polyacrylamide. A method of preparing the same, and an electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same are also disclosed.In Chemical Formulae 1 and 2, R1 to R3, R11 to R16, and n and m are the same as defined in the detailed description.