Anode Adhesion Layer for Secondary Battery Expansion Control

Solution Overview

Problem

Secondary batteries utilizing gel electrolytes face challenges in balancing the suppression of anode active material expansion and shrinkage with maintaining adhesibility to the separator, as physically-tough polymer binders either fail to adhere well due to low swelling or lose mechanical strength when swollen.

Innovation Solution

Incorporating an adhesion layer between the anode and electrolyte layer, using a third polymer compound with polar groups and the same polymer chain as the electrolyte layer, which enhances adhesibility and mechanical strength, thereby suppressing active material expansion and shrinkage while improving adhesion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a physically-tough polymer compound such as polyimide is used as a binder to suppress expansion and shrinkage of the active material, then the mechanical strength is improved, but the adhesibility of the anode with respect to the separator is lowered

Engineering Contradiction:

Improvemechanical strength of binderVSAvoidadhesibility of anode to separator

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The binder is constructed as a composite material comprising two distinct polymer compounds: a first polymer compound (physically-tough polymer like polyimide) that provides mechanical strength to suppress active material expansion, and a second polymer compound (swollen polymer like polyacrylonitrile) that provides adhesibility to the separator. This composite binder structure resolves the contradiction by combining materials with complementary properties.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The binder exhibits local quality differentiation through its dual-polymer composition, where different regions or phases of the binder perform different functions: the first polymer compound primarily provides structural support and expansion suppression, while the second polymer compound primarily provides adhesion to the separator. This functional differentiation within the binder resolves the contradiction between strength and adhesibility.

Inventive Principle:

Principle #3Local quality

2Reliability

If another polymer compound that is easily swollen with respect to the solvent is used as a binder to improve adhesibility, then the adhesibility is improved, but the physical strength of the whole binder is lowered

Engineering Contradiction:

Improveadhesibility of anode to separatorVSAvoidmechanical strength of binder

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The binder is constructed as a composite material comprising two distinct polymer compounds: a first polymer compound (physically-tough polymer like polyimide) that provides mechanical strength to suppress active material expansion, and a second polymer compound (swollen polymer like polyacrylonitrile) that provides adhesibility to the separator. This composite binder structure resolves the contradiction by combining materials with complementary properties.

Inventive Principle:

Principle #40Composite materials

3Reliability

If a gel electrolyte is used to prevent liquid leakage and improve adhesibility, then the adhesibility of anode to separator is improved, but the active material is easily expanded and shrunk during charge and discharge

Engineering Contradiction:

Improveadhesibility of anode to separatorVSAvoidexpansion and shrinkage of active material

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The binder is constructed as a composite material comprising two distinct polymer compounds: a first polymer compound (physically-tough polymer like polyimide) that provides mechanical strength to suppress active material expansion, and a second polymer compound (swollen polymer like polyacrylonitrile) that provides adhesibility to the separator. This composite binder structure resolves the contradiction by combining materials with complementary properties.

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

This configuration effectively balances the suppression of active material expansion and shrinkage with improved adhesibility to the separator, leading to enhanced cycle characteristics and reduced peeling of the anode from the electrolyte layer.

Implementation Method 1

the adhesion layer includes a third polymer compound, the third polymer compound includes a polar group and a polymer chain same as the polymer chain of the second polymer compound

Methodology Applied

Scientific EffectPolar group interaction:

Implementation Method 2

the third polymer compound includes a polar group and a polymer chain same as the polymer chain of the second polymer compound

Methodology Applied

Scientific EffectPolymer chain compatibility:

Implementation Method 3

In the gel electrolyte, an electrolytic solution is held by a polymer compound, and therefore, liquid leakage is prevented

Methodology Applied

Scientific EffectGel structure: Gel

Implementation Method 4

The electrolytic solution contains a solvent and an electrolyte salt

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Data Source

PatentUS10826038B2Secondary battery, battery pack, and electric vehicle

Publication Date: 2020.11.03 MURATA MFG CO LTD

AI summary

A secondary battery includes: a cathode and an anode opposed to each other with a separator in between; an electrolyte layer provided between the anode and the separator; and an adhesion layer provided between the anode and the electrolyte layer, wherein the anode includes an active material and a first polymer compound, the electrolyte layer includes an electrolytic solution and a second polymer compound, the adhesion layer includes a third polymer compound, the first polymer compound includes a polar group, the second polymer compound includes a polymer chain, and the third polymer compound includes a polar group and a polymer chain same as the polymer chain of the second polymer compound.