Carbon Black Coating for Battery Capacity Retention

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Solution Overview

Problem

Nonaqueous electrolytic solution secondary batteries, such as lithium ion batteries, face a decrease in battery capacity due to the reaction between carbon black and the electrolytic solution in the negative electrode active material layer, leading to reduced durability and high-rate characteristics.

Innovation Solution

A coating film made of a lithium transition metal composite oxide with lithium ion conductivity is formed on the surface of carbon black in the negative electrode active material layer, suppressing the decomposition of the electrolytic solution and preventing the growth of a passivation film, thereby maintaining high-rate and cycle characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If carbon black with high DBP absorption amount is added to improve high-rate characteristic, then lithium ion diffusion is improved, but battery capacity decreases due to reaction between carbon black and electrolytic solution

Engineering Contradiction:

Improvelithium ion diffusion rateVSAvoidbattery capacity retention

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

A coating film made of lithium transition metal composite oxide is introduced as an intermediary layer between the carbon black and the electrolytic solution. This coating film mediates the interaction by allowing lithium ion diffusion while preventing direct harmful reactions between carbon black and electrolyte, thus resolving the contradiction between improving diffusion rate and maintaining capacity retention.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The surface properties of carbon black are modified by coating it with lithium transition metal composite oxide. This changes the chemical and physical parameters of the carbon black surface, making it less reactive with the electrolytic solution while maintaining its conductivity and lithium ion diffusion capabilities.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If carbon black is added to increase electrolytic solution retention, then high-rate characteristic is improved, but passivation film grows on negative electrode surface causing capacity decrease

Engineering Contradiction:

Improveelectrolytic solution retentionVSAvoidcycle characteristic

Core Design Contradiction:

Quantity of substanceVSDuration of action of moving object

Solution Approach 1:

The coating film acts as an intermediary that prevents direct contact between carbon black and electrolytic solution, thereby preventing passivation film formation while still allowing the carbon black to perform its function of retaining electrolytic solution and enhancing high-rate characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The coating film is applied in advance to carbon black particles before they are incorporated into the negative electrode. This preliminary protective action prevents the subsequent formation of harmful passivation films during battery cycling, thus preserving cycle characteristic.

Inventive Principle:

Principle #9Preliminary anti-action

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 solution effectively inhibits capacity decrease during repeated charging and discharging, ensuring both high-rate and cycle characteristics are maintained, enhancing the battery's durability and performance.

Implementation Method 1

a coating film made of a lithium transition metal composite oxide having lithium ion conductivity is formed on at least part of a surface of the carbon black

Methodology Applied

Scientific EffectLithium ion conductivity: Conduction (electrical)

Data Source

PatentUS9979015B2Nonaqueous electrolytic solution secondary battery

Publication Date: 2018.05.22 TOYOTA JIDOSHA KK

AI summary

The present teaching provides a nonaqueous electrolytic solution secondary battery in which both a satisfactory high-rate characteristic and a high cycle characteristic (prevention of decrease in capacity) are realized. The nonaqueous electrolytic solution secondary battery of the present teaching includes a positive electrode provided with a positive electrode active material layer, a negative electrode provided with a negative electrode active material layer, and a nonaqueous electrolytic solution. The negative electrode active material layer includes a negative electrode active material and carbon black. A coating film made of a lithium transition metal composite oxide having lithium ion conductivity is formed on at least part of a surface of the carbon black.