Double Sintering of Lithium Deficient NMC Precursor

Solution Overview

Problem

The production of high Ni-excess lithium-nickel-manganese-cobalt oxide (NMC) cathode materials for large-scale lithium-ion batteries faces challenges in achieving low soluble base content and high throughput while maintaining safety and cycle stability, due to issues with thermodynamic stability, reaction kinetics, and heat transfer limitations in existing sintering methods.

Innovation Solution

A double sintering method using a lithium deficient intermediate product, where the first sintering is conducted in a rotary furnace at 650-850°C to produce a lithium deficient precursor, followed by a second sintering at 800-1000°C to achieve the final composition, optimizing the Li:M stoichiometry and reducing soluble base content, and optionally incorporating surface coatings for enhanced stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If high Ni-excess NMC is produced using conventional sintering methods, then energy density increases, but soluble base content increases and cycle stability deteriorates

Engineering Contradiction:

Improveenergy densityVSAvoidcycle stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The sintering process is divided into two separate stages: first sintering at 650-850°C to form a lithium-deficient intermediate product, then second sintering at 800-1000°C to achieve final composition. This segmentation allows optimization of each stage for different purposes, resolving the contradiction between energy density and cycle stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first sintering stage performs preliminary formation of the cathode material structure with controlled lithium content, creating a lithium-deficient intermediate product. This preliminary action enables better control of reaction kinetics and reduces soluble base formation before the final sintering stage, improving cycle stability while maintaining high energy density.

Inventive Principle:

Principle #10Preliminary action

2Use of energy by moving object

If high Ni-excess NMC is produced using conventional sintering methods, then energy density increases, but soluble base content increases

Engineering Contradiction:

Improveenergy densityVSAvoidsoluble base content

Core Design Contradiction:

Use of energy by moving objectVSLoss of substance

Solution Approach 1:

The sintering process is divided into two separate stages: first sintering at 650-850°C to form a lithium-deficient intermediate product, then second sintering at 800-1000°C to achieve final composition. This segmentation allows optimization of each stage for different purposes, resolving the contradiction between energy density and cycle stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the lithium-to-metal ratio parameter during sintering, first using a lithium-deficient composition (ratio < 1) in the first sintering stage, then adjusting to the target composition in the second stage. This parameter change optimizes reaction kinetics and reduces soluble base formation while maintaining high energy density.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If sintering temperature is increased to improve reaction kinetics, then manufacturing efficiency increases, but heat transfer limitations worsen

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoidheat transfer limitations

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

The sintering process is divided into two separate stages: first sintering at 650-850°C to form a lithium-deficient intermediate product, then second sintering at 800-1000°C to achieve final composition. This segmentation allows optimization of each stage for different purposes, resolving the contradiction between energy density and cycle stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the lithium-to-metal ratio parameter during sintering, first using a lithium-deficient composition (ratio < 1) in the first sintering stage, then adjusting to the target composition in the second stage. This parameter change optimizes reaction kinetics and reduces soluble base formation while maintaining high energy density.

Inventive Principle:

Principle #35Parameter changes

4Use of energy by moving object

If lithium stoichiometry is optimized for high capacity, then energy density increases, but thermodynamic stability decreases

Engineering Contradiction:

Improveenergy densityVSAvoidthermodynamic stability

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The first sintering stage performs preliminary formation of the cathode material structure with controlled lithium content, creating a lithium-deficient intermediate product. This preliminary action enables better control of reaction kinetics and reduces soluble base formation before the final sintering stage, improving cycle stability while maintaining high energy density.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the lithium-to-metal ratio parameter during sintering, first using a lithium-deficient composition (ratio < 1) in the first sintering stage, then adjusting to the target composition in the second stage. This parameter change optimizes reaction kinetics and reduces soluble base formation while maintaining high energy density.

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

This method enables the production of high Ni-excess NMC with low soluble base content and improved cycle stability, increasing throughput and reducing manufacturing costs, while ensuring safety by minimizing oxygen stoichiometry and enhancing electrochemical performance.

Implementation Method 1

the first sintering is conducted in a rotary furnace at 650-850°C to produce a lithium deficient precursor

Methodology Applied

Scientific EffectThermal energy transfer: Conduction (thermal)

Implementation Method 2

followed by a second sintering at 800-1000°C to achieve the final composition

Methodology Applied

Scientific EffectThermal energy transfer: Conduction (thermal)

Implementation Method 3

A double sintering method using a lithium deficient intermediate product

Methodology Applied

Scientific EffectSintering: Sintering

Data Source

PatentUS11114662B2Precursor and method for preparing Ni based cathode material for rechargeable lithium ion batteries

Publication Date: 2021.09.07 UMICORE(BE)

AI summary

A crystalline precursor compound for manufacturing a lithium transition metal based oxide powder usable as an active positive electrode material in lithium-ion batteries, the precursor having a general formula Li1−a((Niz(Ni1/2 Mn1/2)yCox)1−k Ak)1+aO2, wherein x+y+z=1, 0.1≤x≤0.4, 0.25≤z≤0.52, A is a dopant, 0≤k≤0.1, and 0.03≤a≤0.35, wherein the precursor has a crystalline size L expressed in nm, with 15≤L≤36. Also a method is described for manufacturing a positive electrode material having a general formula Li1+a′M′1−a−O2, with M′=(Niz(Ni1/2 Mn1/2)yCOx)1−k Ak, wherein x+y+z=1.0.1≤x≤0.4, 0.25≤z≤0.52, A is a dopant, 0≤k≤0.1, and 0.01≤a′≤0.10, by sintering the lithium deficient precursor powder mixed with either one of LiOH, LiOH.H2O, in an oxidizing atmosphere at a temperature between 800 and 1000° C., for a time between 6 and 36 hrs.