Polyimide Binder for Lithium Battery Conversion Anodes

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Solution Overview

Problem

Lithium secondary batteries using transition metal compounds as active materials face challenges with low charge/discharge reversibility and durability due to significant electrode expansion/contraction, leading to increased irreversible capacity and reduced cycle characteristics.

Innovation Solution

A lithium secondary battery design incorporating a metal compound active material, such as iron oxide, with a polyimide-base resin binder that stores and releases lithium ions through conversion reactions, which enhances the electrode's mechanical strength and stability, suppressing volume changes and granular growth of simple metals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If transition metal compounds are used as active materials to achieve high capacity through conversion reactions, then charge/discharge capacity is improved, but charge/discharge reversibility and cycle characteristics deteriorate due to large electrode expansion/contraction

Engineering Contradiction:

Improvecharge/discharge capacityVSAvoidcharge/discharge reversibility and cycle characteristics

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies this principle by using a gel polymer electrolyte that can flexibly accommodate the large volume changes of transition metal compounds during conversion reactions. The gel polymer electrolyte acts as a flexible medium that maintains ionic conductivity while adapting to electrode expansion and contraction, thereby preserving charge/discharge reversibility and improving cycle characteristics.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent employs composite materials by combining transition metal compounds with conductive materials and incorporating them into a gel polymer electrolyte system. This composite structure maintains the high capacity benefits of transition metal compounds while the conductive material network and gel polymer matrix provide structural stability and ionic conductivity, reducing the harmful effects of volume expansion/contraction.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If transition metal compounds undergo conversion reactions to achieve high capacity, then charge/discharge capacity is improved, but irreversible capacity increases due to disruption of Li+ ion conducting path

Engineering Contradiction:

Improvecharge/discharge capacityVSAvoidirreversible capacity

Core Design Contradiction:

Quantity of substanceVSLoss of energy

Solution Approach 1:

The gel polymer electrolyte provides a flexible, continuous ionic conducting path that can accommodate electrode volume changes without disrupting Li+ ion transport. This maintains reversible capacity while allowing the use of high-capacity transition metal compounds.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The gel polymer electrolyte acts as an intermediary medium between the transition metal compound active material and the current collector, maintaining continuous ionic conductivity despite electrode expansion/contraction. This mediator prevents disruption of the Li+ ion conducting path, reducing irreversible capacity loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Quantity of substance

If simple metal grows granularly through electrode reactions to achieve high capacity, then charge/discharge capacity is improved, but durability decreases due to increased irreversible capacity

Engineering Contradiction:

Improvecharge/discharge capacityVSAvoiddurability

Core Design Contradiction:

Quantity of substanceVSDuration of action of stationary object

Solution Approach 1:

The gel polymer electrolyte provides a flexible constraint that limits excessive granular growth of simple metals during electrode reactions. This maintains capacity while improving durability by preventing uncontrolled metal aggregation that would increase irreversible capacity.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The gel polymer electrolyte serves as an intermediary that mediates between the simple metal particles and the surrounding environment, providing a stable matrix that prevents uncontrolled granular growth and maintains structural integrity over extended cycling.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 battery achieves high capacity and improved durability by maintaining the conductive network and structural integrity during charge/discharge cycles, resulting in superior cycle characteristics and extended battery life.

Implementation Method 1

the active material of at least one of a positive electrode and a negative electrode has a metal compound which stores and releases lithium ions through conversion reactions

Methodology Applied

Scientific EffectConversion reaction: Redox Reactions

Implementation Method 2

Methodology Applied

Scientific EffectMechanical reinforcement:

Data Source

PatentUS9276256B2Lithium secondary battery and method of manufacturing same

Publication Date: 2016.03.01 TOYOTA JIDOSHA KK

AI summary

A lithium secondary battery provided by this invention has electrodes and configured in a structure in which active material layers, including active materials and binders, are held by collectors. The active material of at least one of the positive electrode and the negative electrode of the electrodes is formed from a metal compound which stores and releases lithium ions through conversion reactions. The lithium secondary battery includes a polyimide-base resin as a binder.