Positive Electrode Active Material for High-Temperature Stability

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Solution Overview

Problem

Lithium-nickel composite oxides used in lithium secondary batteries face challenges with high-temperature stability and side reactions with electrolyte solutions, leading to potential battery swelling and safety issues, such as explosion or ignition, due to their poor structural integrity and high surface area.

Innovation Solution

A positive electrode active material with secondary particles having a grain boundary density of 0.5 or less and lithium ion diffusion pathways aligned in the same direction, reducing the specific surface area and grain boundaries, thereby enhancing thermal stability and minimizing side reactions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If lithium-nickel composite oxide is used as positive electrode active material, then reversible capacity is improved (approximately 200 mAh/g), but high-temperature stability deteriorates due to poor crystal structure stability and high surface area

Engineering Contradiction:

Improvereversible capacityVSAvoidhigh-temperature stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The positive electrode active material is divided into secondary particles composed of multiple primary particles. This segmentation reduces the specific surface area of the material while maintaining the high reversible capacity characteristics of lithium-nickel composite oxide, thereby improving high-temperature stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses composite secondary particles formed by aggregating multiple primary particles of lithium-nickel composite oxide. This composite structure combines the high capacity benefits of lithium-nickel oxide with improved thermal stability through reduced surface area and modified particle morphology.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If lithium-nickel composite oxide with high surface area is used, then reversible capacity is improved, but side reaction with electrolyte solution increases leading to gas generation and battery swelling

Engineering Contradiction:

Improvereversible capacityVSAvoidgas generation from side reaction

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

By segmenting the material into secondary particles with controlled grain boundary density (0.3 to 0.5), the specific surface area is reduced, which decreases the contact area between the positive electrode active material and electrolyte solution, thereby reducing side reactions and gas generation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention creates local quality differences by forming secondary particles with specific grain boundary densities. This local structural optimization reduces the reactive surface area while maintaining the bulk material's high capacity characteristics, minimizing harmful side reactions.

Inventive Principle:

Principle #3Local quality

3Use of energy by moving object

If lithium-nickel composite oxide is used to achieve high capacity, then energy density is improved, but safety deteriorates due to decomposition under external pressure and potential rupture or ignition

Engineering Contradiction:

Improveenergy densityVSAvoidsafety under pressure

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The segmentation into secondary particles with controlled grain boundary density provides a more stable structural framework that can better withstand external pressure during charging, preventing decomposition and maintaining safety while preserving high energy density.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The specific secondary particle structure with grain boundary density of 0.3 to 0.5 acts as a preventive measure, cushioning against the harmful effects of external pressure before decomposition can occur, thereby preventing safety incidents while maintaining high capacity.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 improves high-temperature stability and reduces gas generation, maintaining reversible capacity while ensuring safety by minimizing side reactions and maintaining structural integrity under high-pressure conditions.

Implementation Method 1

a primary particle, which is a lithium-based composite oxide having lithium ion diffusion pathways in the same direction as the major axis

Methodology Applied

Scientific EffectIon diffusion: Diffusion

Data Source

PatentUS11990616B2Positive electrode active material for lithium secondary battery and lithium secondary battery including the same

Publication Date: 2024.05.21 ECOPRO BM CO LTD

AI summary

The present invention relates to a positive electrode active material for a lithium secondary battery and a lithium secondary battery including the same. The positive electrode active material according to the present invention reduces the specific surface area and grain boundary of a secondary particle in which a side reaction with an electrolyte solution occurs to improve the high-temperature stability of the positive electrode active material and reduce gas generation caused by the positive electrode active material.