Lithium Transition Metal Composite Oxide Porosity Control

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Solution Overview

Problem

Conventional lithium excess type positive active materials for nonaqueous electrolyte secondary batteries exhibit low energy efficiency and discharge capacity due to high charge-discharge hysteresis and porosity issues, which affect the battery's ability to maintain a stable crystal structure and efficient lithium ion transport.

Innovation Solution

A lithium transition metal composite oxide with a specific molar ratio of Li/Me between 1.05 and 1.4 and porosity ranging from 5 to 15%, synthesized using a method that involves mixing a lithium compound with a transition metal hydroxide precursor and firing at 750 to 1000°C, to achieve an α-NaFeO2 structure and optimal porosity for improved energy efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the porosity of the positive active material is increased to improve energy efficiency and discharge capacity, then the charge-discharge hysteresis is reduced, but the structural stability deteriorates

Engineering Contradiction:

Improvecharge-discharge hysteresisVSAvoidcrystal structure stability

Core Design Contradiction:

Loss of energyVSStability of the object's composition

Solution Approach 1:

The patent applies parameter changes by precisely controlling the porosity within the range of 5-15% and the Li/Me ratio within 1.05-1.40. These specific parameter ranges optimize the balance between energy efficiency (reduced hysteresis) and structural stability, allowing the material to exhibit both low charge-discharge hysteresis and maintained crystal structure integrity during cycling

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite materials by creating a lithium excess type positive active material with specific composition (Li1+αMe1−αO2) that combines lithium oxide with transition metal oxides. This composite structure enables the material to achieve both low hysteresis through controlled porosity and structural stability through the specific stoichiometric ratio and crystal phase composition

Inventive Principle:

Principle #40Composite materials

2Loss of energy

If the Li/Me ratio is increased to improve discharge capacity, then the energy efficiency is improved, but the risk of structure change to spinel type increases

Engineering Contradiction:

Improveenergy efficiencyVSAvoidcharge-discharge cycle performance

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent applies parameter changes by optimizing the Li/Me ratio within the specific range of 1.05-1.40 and the Mn/Me ratio within 0.20-0.55. These controlled parameter changes enable the material to achieve high energy efficiency while preventing the detrimental phase transformation to spinel structure, thereby maintaining reliable charge-discharge cycle performance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs feedback control in the synthesis process by adjusting the Li/Me ratio and porosity based on the desired balance between energy efficiency and cycle stability. The specific compositional parameters are determined through feedback from performance data, ensuring that the material achieves optimal energy efficiency without compromising structural reliability during cycling

Inventive Principle:

Principle #23Feedback

3Productivity

If the porosity is increased to improve lithium ion transport, then the discharge capacity is improved, but the manufacturing precision becomes more difficult to control

Engineering Contradiction:

Improvedischarge capacityVSAvoidporosity control

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by establishing the porosity within the narrow range of 5-15% and the Li/Me ratio within 1.05-1.40. These precisely controlled parameters enable the material to achieve improved discharge capacity through enhanced lithium ion transport while maintaining manufacturing precision and reproducibility in the synthesis process

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 excess type positive active material with enhanced energy efficiency and discharge capacity, reducing charge-discharge hysteresis and improving the battery's overall performance by controlling porosity and crystal structure.

Implementation Method 1

mixing a lithium compound with a transition metal hydroxide precursor and firing at 750 to 1000°C to prepare the lithium transition metal composite oxide

Methodology Applied

Scientific EffectSolid-state reaction:

Implementation Method 2

to achieve an α-NaFeO2 structure

Methodology Applied

Scientific EffectCrystallization: Crystallisation

Implementation Method 3

a positive active material capable of absorbing and releasing lithium ions

Methodology Applied

Scientific EffectIon intercalation:

Data Source

PatentUS20230078256A1Positive active material for nonaqueous electrolyte secondary battery, method of producing positive active material for nonaqueous electrolyte secondary battery, positive electrode for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery

Publication Date: 2023.03.16 GS YUASA INT LTD

AI summary

Disclosed is a positive active material for a nonaqueous electrolyte secondary battery containing a lithium transition metal composite oxide, in which the lithium transition metal composite oxide has an α-NaFeO2 structure, a molar ratio Li/Me of Li and a transition metal (Me) of 1.05≤Li/Me≤1.4, and a porosity of 5 to 15%.