Cathode Active Material Composite Structure for Battery Stability

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Solution Overview

Problem

Conventional lithium manganese composite oxides used in electric vehicle batteries suffer from manganese elution at high temperatures and high currents, leading to battery deterioration and limited capacity, while attempts to improve stability through post-treatment increase costs and do not effectively address structural variations.

Innovation Solution

A cathode active material with the composition wLi2MO3 * xLiM'O2 * yLiM"2O4 * zLi3PO4, where 0<w<1, 0<x<1, 0<y<0.1, 0<z<0.1, and w+x+y+z=1, incorporating transition metals like Mn, Ni, and Co, with Li3PO4 added in the precursor stage to enhance ion conductivity and prevent structural collapse.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If lithium manganese composite oxide is used as cathode active material, then cost is reduced and stability at high voltage is improved, but manganese elution occurs at high temperatures and high currents causing battery deterioration

Engineering Contradiction:

Improvestability at high voltageVSAvoidmanganese elution

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent uses a composite cathode active material with spinel structure LiMn2O4 containing lithium nickel composite oxide or lithium cobalt composite oxide dispersed in the spinel matrix. This composite structure provides both the cost advantage and high voltage stability of lithium manganese composite oxide while the dispersed lithium nickel/cobalt composite oxide particles prevent manganese elution at high temperatures and currents, resolving the contradiction between stability and harmful elution.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If lithium manganese composite oxide is used, then capacity per unit weight is limited, but high energy density is required for electric vehicle applications

Engineering Contradiction:

Improvecapacity per unit weightVSAvoidenergy density

Core Design Contradiction:

Quantity of substanceVSUse of energy by moving object

Solution Approach 1:

The composite structure combines lithium manganese composite oxide (spinel structure) with lithium nickel composite oxide or lithium cobalt composite oxide. The lithium nickel/cobalt composite oxide components contribute higher capacity per unit weight, while the lithium manganese spinel matrix provides structural stability. This composite approach achieves both high energy density and practical stability required for electric vehicle applications.

Inventive Principle:

Principle #40Composite materials

3Quantity of substance

If layered structure cathode active material containing Li2MnO3 is used, then capacity increases after activation, but structural variation occurs causing conversion to spinel structure and loose contact between domains

Engineering Contradiction:

ImprovecapacityVSAvoidstructural stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent performs preliminary action by dispersing lithium nickel composite oxide or lithium cobalt composite oxide particles within the spinel structure LiMn2O4 matrix before battery operation. This pre-established composite structure prevents the detrimental structural variation and spinel conversion that occur in layered Li2MnO3 materials after activation, while still allowing capacity increase through controlled mechanisms. The dispersed particles maintain domain contact and structural integrity.

Inventive Principle:

Principle #10Preliminary 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 cathode active material exhibits increased capacity and superior rate characteristics by minimizing structural variations and maintaining stability, even after activation, thereby improving battery performance and extending lifespan.

Implementation Method 1

with Li3PO4 added in the precursor stage to enhance ion conductivity and prevent structural collapse

Methodology Applied

Scientific EffectIon conductivity: Conduction (electrical)

Implementation Method 2

cathode active material for secondary batteries that exhibits a high capacity and superior stability at a high voltage

Methodology Applied

Scientific EffectElectrochemical reaction: Redox Reactions

Data Source

PatentEP2613384B1Cathode active material for secondary battery

Publication Date: 2018.05.23 LG CHEM LTD

AI summary

Disclosed is a cathode active material represented by the following Formula 1, the cathode active material being in the form of a solid solution or a composite, and a secondary battery including the cathode active material. wLi2MO3*xLiM'O2*yLiM"2O4*zLi3PO4 (1) wherein 0<w<1, 0<x<1, 0<y<0.3, 0<z<0.1 and w+x+y+z=1 are satisfied, M is at least one element selected from first or second period transition metals having a mean oxidation number of +4, M' is at least one element selected from first or second period transition metals having a mean oxidation number of +3, and M" is at least one element selected from first to fourth period transition metals having a combination of mean oxidation numbers of +3 and +4.