Positive Electrode Coating to Minimize Residual Lithium

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Solution Overview

Problem

Lithium secondary batteries face limitations due to poor thermal stability and high cost associated with existing methods for preparing positive electrode active materials, which result in reduced capacity, output, and lifetime, primarily due to residual lithium by-products and inefficient coating processes.

Innovation Solution

A method involving the use of a washing solution with a chelate anion to form a lithium chelate compound coating on lithium transition metal oxides, followed by heat treatment to create a Li-M-O solid solution coating, which minimizes residual lithium and enhances conductivity, thereby reducing process steps and improving battery performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a two-step process of washing and coating with inorganic oxide is used, then lithium by-products are minimized, but manufacturing cost increases and coating uniformity is poor

Engineering Contradiction:

Improveminimization of lithium by-productsVSAvoidmanufacturing cost and process complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent combines the washing step and coating step into a single integrated process. The washing solution contains both washing agents and coating precursors, allowing simultaneous removal of lithium by-products and formation of coating layers on the positive electrode active material surface, thereby eliminating the need for separate washing and coating processes

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The washing solution serves multiple functions simultaneously: it washes away lithium by-products, provides coating precursors for forming protective layers, and acts as a medium for uniform distribution of coating materials. This multi-functional approach replaces the conventional two-step process with a single versatile solution

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If inorganic oxide powder coating is used, then lithium by-products are reduced, but coating uniformity is low and thick coating layers form only on secondary particle surfaces

Engineering Contradiction:

Improvereduction of lithium by-productsVSAvoidcoating uniformity and thickness control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent enables different coating characteristics on different scales: uniform thin coating layers on primary particle surfaces through the washing solution approach, while maintaining thicker protective layers on secondary particle surfaces where needed. This local differentiation optimizes both uniformity and protective functionality

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The washing solution acts as an intermediary medium that delivers coating precursors uniformly to particle surfaces. The solution-based approach allows precise control of coating thickness and composition, replacing the inconsistent powder coating method with a controllable liquid-phase deposition process

Inventive Principle:

Principle #24Intermediary (Mediator)

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 approach effectively minimizes residual lithium, enhances lithium ion and electrical conductivity, and reduces internal resistance, leading to improved capacity, output, and lifetime of lithium secondary batteries.

Implementation Method 1

a second step of preparing a lithium transition metal oxide having a coating layer including a lithium chelate compound formed thereon by washing the sintered product using a washing solution, in which a coating layer precursor including a chelate anion is included

Methodology Applied

Scientific EffectChelation:

Implementation Method 2

a third step of preparing a lithium transition metal oxide having a coating layer including a lithium (Li)-M-O solid solution formed thereon by performing a heat treatment on the lithium transition metal oxide having the coating layer including the lithium chelate compound formed thereon

Methodology Applied

Scientific EffectHeat treatment: Heat Treatment

Data Source

PatentUS20230278887A1Positive Electrode Active Material and Method of Preparing the Same

Publication Date: 2023.09.07 LG CHEM LTD

AI summary

A method of preparing a positive electrode active material; includes a first step of preparing a sintered product by mixing a positive electrode active material precursor and a lithium-containing raw material and sintering the mixture, a second step of preparing a lithium transition metal oxide having a coating layer including a lithium chelate compound formed thereon by washing the sintered product using a washing solution, in which a coating layer precursor including a chelate anion is included, and drying the sintered product, and a third step of preparing a lithium transition metal oxide having a coating layer including a Li-M-O solid solution formed thereon by performing a heat treatment on the lithium transition metal oxide having the coating layer including the lithium chelate compound formed thereon.