Over-lithiated Spinel Cathode Material for High Energy Density

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Solution Overview

Problem

Current high-energy cathode materials, such as over-lithiated layered oxides, suffer from irreversible capacity loss, gas generation, poor rate capability, and voltage suppression due to structural changes, limiting their practical use in lithium-ion batteries.

Innovation Solution

Development of a novel active material comprising lithium, manganese, nickel, and oxygen, represented by compounds like LixMn1.5−aNi0.5−bO4−w, which is characterized by specific X-ray diffraction patterns and synthesized through heat treatment of over-lithiated spinel materials, enhancing energy density and stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If over-lithiated layered oxides are used to increase energy density, then theoretical gravimetric energy density is improved (up to 1110 Wh/kg), but irreversible capacity loss increases (up to 30%), gas generation occurs, rate capability deteriorates, and voltage suppression happens due to structure change

Engineering Contradiction:

Improvetheoretical gravimetric energy densityVSAvoidirreversible capacity loss

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The invention changes the crystal structure parameter from layered oxide to spinel structure, while maintaining over-lithiation (x > 1.0 in LixMO2). This structural parameter change fundamentally alters the material's electrochemical behavior, eliminating the harmful effects of over-lithiated layered oxides while preserving high energy density. The spinel structure provides better structural stability during lithium insertion/extraction cycles.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite material system combining over-lithiated spinel structure with specific cation compositions (Mn, Ni, and optionally other transition metals). This composite approach at the atomic level optimizes both capacity and stability, achieving high energy density without the severe degradation issues of conventional over-lithiated layered oxides.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If additional lithium is added to LiM2O4 to obtain Li2M2O4, then theoretical gravimetric energy density is improved (about 1087 Wh/kg), but discharge voltage decreases to below three volts which is too low for practical use

Engineering Contradiction:

Improvetheoretical gravimetric energy densityVSAvoiddischarge voltage

Core Design Contradiction:

Use of energy by moving objectVSPower

Solution Approach 1:

The invention changes the structural parameter from spinel Li2M2O4 to over-lithiated spinel LixMO2 (x > 1.0), which fundamentally alters the electrochemical potential characteristics. The over-lithiated spinel structure maintains higher discharge voltages (above 3 volts) compared to Li2M2O4, making it practically usable while achieving comparable or higher energy density through optimized lithium content and cation composition.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If conventional LiMn2O4 spinel material is used, then structural stability is maintained, but theoretical gravimetric energy density is limited (about 492 Wh/kg)

Engineering Contradiction:

Improvestructural stabilityVSAvoidtheoretical gravimetric energy density

Core Design Contradiction:

Stability of the object's compositionVSUse of energy by moving object

Solution Approach 1:

The invention changes the lithium content parameter from stoichiometric (x=1.0 in LiMn2O4) to over-lithiated (x > 1.0 in LixMO2). This parameter change increases the theoretical gravimetric energy density from 492 Wh/kg to above 1000 Wh/kg while the spinel structure maintains structural stability through its inherent framework and cation distribution.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite material system with optimized cation composition (Mn, Ni, and optionally other transition metals in the spinel structure) that synergistically enhances both energy density and structural stability. The multi-element composition allows for tailored electronic and structural properties that exceed conventional single-metal spinels.

Inventive Principle:

Principle #40Composite materials

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 novel material demonstrates improved specific capacity, rate capability, and cycle life, with an energy density comparable to next-generation cathode materials, maintaining higher voltage stability and reducing irreversible capacity loss.

Implementation Method 1

synthesized through heat treatment of over-lithiated spinel materials

Methodology Applied

Scientific EffectHeat treatment: Heat Treatment

Implementation Method 2

characterized by a powder X-ray diffraction pattern substantially the same as the X-ray powder diffraction pattern

Methodology Applied

Scientific EffectX-ray diffraction: Bragg Diffraction

Data Source

PatentUS9123959B2High energy cathode material

Publication Date: 2015.09.01 WILDCAT DISCOVERY TECHNOLOGIES INC

AI summary

A composition for use in a battery electrode comprising a compound including lithium, manganese, nickel, and oxygen. The composition is characterized by a powder X-ray diffraction pattern having peaks including 18.6±0.2, 35.0±0.2, 36.4±0.2, 37.7±0.2, 42.1±0.2, and 44.5±0.2 degrees 2θ as measured using Cu Kα radiation.