LiNiMnCoO2 Cathode Coating for High-Temperature Stability

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Solution Overview

Problem

Lithium nickel-based cathode active materials for batteries face issues such as rapid phase transition, gas generation, chemical instability, and high production costs, which limit their application due to structural instability and impurity-related problems, affecting charge-discharge performance and safety.

Innovation Solution

A cathode active material composed of lithium nickel-manganese-cobalt oxide with a nickel content of at least 40% is coated with an ion-conductive solid compound, enhancing high temperature stability and electrical conductivity while forming a stable interface with the electrolyte to prevent ignition and explosion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If LiNiO2 oxide is produced by conventional process with excessive Li source and oxygen atmosphere, then high discharge capacity is achieved, but crystal structure becomes expanded and unstable causing serious deterioration of cycle properties

Engineering Contradiction:

Improvedischarge capacityVSAvoidcycle properties

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent changes the chemical composition parameters by introducing a specific doping formula LiNi1-x-yMnxCoyO2 where Mn and Co are added in controlled amounts. This compositional parameter change stabilizes the crystal structure while maintaining high discharge capacity, resolving the contradiction between capacity and cycle stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite cathode material by doping Mn and Co into the LiNiO2 structure. This composite approach combines the high capacity of Ni-based materials with the structural stability provided by Mn and Co, achieving both high discharge capacity and improved cycle properties.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If LiNiO2 particle has secondary particle structure formed by aggregation of primary particles, then production is facilitated, but area in contact with electrolyte is increased causing excessive gas generation and decreased high temperature stability

Engineering Contradiction:

Improveproduction facilitationVSAvoidgas generation and high temperature stability

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent applies a protective coating layer specifically on the surface of the secondary particles. This local modification maintains the easy manufacturability of secondary particle structures while the coating layer reduces harmful surface reactions that cause gas generation and high temperature instability.

Inventive Principle:

Principle #3Local quality

3Ease of operation

If LiNiO2 oxide is exposed to air and moisture, then processing is simplified, but chemical-resistance at surface is drastically decreased causing NMP-PVDF slurry polymerization and gellation

Engineering Contradiction:

Improveprocessing simplicityVSAvoidchemical-resistance

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent performs preliminary surface treatment during the synthesis process by conducting heat treatment in a controlled atmosphere and forming a stable surface phase. This preliminary action protects the material from subsequent exposure to air and moisture, preventing slurry polymerization and gellation while maintaining processing simplicity.

Inventive Principle:

Principle #10Preliminary action

4Reliability

If LiCoO2 is used as cathode active material, then excellent cycle properties are achieved, but cost increases due to scarcity of cobalt and safety is reduced

Engineering Contradiction:

Improvecycle propertiesVSAvoidproduction cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the metal composition parameters by reducing Co content and increasing Ni content in the LiNi1-x-yMnxCoyO2 formula. This parameter change lowers material cost while the controlled addition of Mn and Co maintains cycle properties, resolving the contradiction between cost and reliability.

Inventive Principle:

Principle #35Parameter changes

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 provides a lithium nickel-manganese-cobalt oxide cathode active material with improved high temperature stability and high capacity without deteriorating electrical conductivity, ensuring safety and performance in lithium secondary batteries.

Implementation Method 1

coated with an ion-conductive solid compound at a surface thereof

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Data Source

PatentUS9118075B2Cathode active material for lithium secondary battery

Publication Date: 2015.08.25 LG ENERGY SOLUTION LTD

AI summary

Disclosed herein is a cathode active material based on lithium nickel-manganese-cobalt oxide represented by Formula 1, wherein the lithium nickel-manganese-cobalt oxide has nickel content of at least 40% among overall transition metals and is coated with an ion-conductive solid compound at a surface thereof. A lithium secondary battery having the disclosed cathode active material has advantages of not deteriorating electrical conductivity while maintaining high temperature stability, so as to efficiently provide high charge capacity.