Positive Electrode Conductive Material Volatile Component

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Solution Overview

Problem

Nonaqueous electrolyte secondary batteries face challenges in achieving high energy density while maintaining durability, particularly when the positive electrode's action potential is increased, leading to deteriorated input and output characteristics due to low electron conductivity and increased resistance caused by the inclusion of inorganic phosphate compounds.

Innovation Solution

Incorporating a conductive material with a high volatile component content into the positive electrode active material layer, along with an inorganic phosphate compound, to enhance electron conductivity and suppress capacity deterioration, thereby improving durability and input/output characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an inorganic phosphate compound is added to the positive electrode to improve durability and prevent transition metal elution, then the durability is improved, but the electron conductivity decreases and resistance increases, leading to deteriorated input and output characteristics

Engineering Contradiction:

ImprovedurabilityVSAvoidinput and output characteristics

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent combines inorganic phosphate compound particles with conductive material particles to form a composite positive electrode active material layer. This composite structure allows the inorganic phosphate compound to provide durability and prevent transition metal elution, while the conductive material compensates for the low electron conductivity, thereby maintaining satisfactory input and output characteristics.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If the action potential of the positive electrode is increased to improve energy density, then the energy density is improved, but the durability deteriorates significantly due to increased resistance and capacity deterioration

Engineering Contradiction:

Improveenergy densityVSAvoiddurability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent uses a composite of inorganic phosphate compound and conductive material in the positive electrode active material layer. This composite structure enables the battery to operate at high action potentials (4.3 V or higher vs. lithium metal) for improved energy density, while the inorganic phosphate compound prevents transition metal elution and the conductive material maintains electron conductivity, thereby preserving durability.

Inventive Principle:

Principle #40Composite materials

3Power

If a conductive material with high volatile component content is used to improve electron conductivity, then the electron conductivity is improved, but electrochemical side reactions occur and capacity deterioration increases

Engineering Contradiction:

Improveelectron conductivityVSAvoidcapacity deterioration

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent utilizes the volatile component in the conductive material, which would normally cause harmful electrochemical side reactions, and converts it into a beneficial effect. The volatile component reacts to form a coating on the surface of the inorganic phosphate compound particles, which improves electron conductivity while the inorganic phosphate compound suppresses capacity deterioration, thereby transforming a potential harm into a benefit.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 combination of high-volatility conductive materials and inorganic phosphate compounds in the positive electrode active material layer reduces resistance and maintains high durability, achieving satisfactory input and output characteristics even at higher action potentials.

Implementation Method 1

an inorganic phosphate compound (b) having ion conductivity

Methodology Applied

Scientific EffectIon conductivity: Conduction (electrical)

Implementation Method 2

the electron conductivity of the positive electrode can be improved

Methodology Applied

Scientific EffectElectron conductivity: Conduction (electrical)

Implementation Method 3

the volatile component contained in the conductive material is likely to cause an electrochemical side reaction to occur

Methodology Applied

Scientific EffectElectrochemical side reaction: Redox Reactions

Data Source

PatentUS10361435B2Nonaqueous electrolyte secondary battery

Publication Date: 2019.07.23 TOYOTA JIDOSHA KK

AI summary

Provided is a nonaqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a nonaqueous electrolytic solution. The positive electrode includes a positive electrode current collector and a positive electrode active material layer that is formed on the positive electrode current collector. The positive electrode active material layer contains a positive electrode active material, an inorganic phosphate compound having ion conductivity, and a conductive material. The volatile component content in the conductive material is at least 0.15 mass % when measured according to JIS K 6221 (1982).