Single-Particle Cathode Coating to Prevent Slurry Gelation
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Solution Overview
Problem
High nickel positive electrode active materials face issues such as structural collapse, increased resistance, and slurry gelation due to lithium byproducts, leading to degraded performance in lithium secondary batteries.
Innovation Solution
A positive electrode active material with a lithium composite transition metal oxide in a single particle form, coated with a first discontinuous island and continuous layer, featuring a boron and cobalt concentration gradient, reduces surface reactions and slurry gelation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a single particle type nickel-based positive electrode active material is prepared at high sintering temperature, then particle structural stability is improved, but phase change to Fm-3m rock-salt structure occurs causing increased resistance and decreased energy density
Solution Approach 1:
The patent optimizes the sintering temperature parameter to a specific range (700-900°C) that maintains particle structural stability while preventing phase change to the harmful Fm-3m rock-salt structure. This parameter optimization resolves the contradiction by finding the optimal temperature window where structural stability is achieved without excessive NiO formation.
Solution Approach 2:
The patent creates a composite positive electrode active material containing both the desired R-3m layered structure and controlled amounts of NiO phase. By designing this composite structure with specific phase ratios and distributions, the patent achieves structural stability while managing the harmful effects of NiO to minimize resistance increase.
2Reliability
If lithium byproduct on surface reacts with external substances during slurry preparation, then coating formation occurs, but slurry gelation happens making uniform application difficult
Solution Approach 1:
The patent performs preliminary surface treatment of the positive electrode active material particles before slurry preparation. By pre-modifying the particle surfaces with specific coatings or treatments, the patent prevents excessive reactions with slurry components that would cause gelation, while still achieving the desired protective coating formation.
Solution Approach 2:
The patent introduces intermediary substances or surface modifications that mediate between the lithium byproduct on particle surfaces and external substances in the slurry. These intermediaries control the reaction to form beneficial coatings while preventing the harmful gelation effect, maintaining slurry uniformity and applicability.
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
Improves capacity, resistance, and life characteristics by minimizing particle cracking and slurry gelation, enhancing dispersibility and sphericity.
Implementation Method 1
a coating portion formed on a surface of the lithium composite transition metal oxide, wherein the coating portion includes a first coating portion; and a second coating portion
Implementation Method 2
the first coating portion has a concentration gradient in which an amount of boron (B) decreases and an amount of cobalt (Co) increases from a surface thereof toward a center of a positive electrode active material particle
Data Source
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AI summary
The present invention relates to a positive electrode active material including a lithium composite transition metal oxide in a form of a single particle; and a coating portion formed on a surface of the lithium composite transition metal oxide, wherein the coating portion includes a first coating portion; and a second coating portion, wherein the first coating portion is in a form of a discontinuously formed island, and the second coating portion is in a form of a continuously formed coating layer, wherein the first coating portion has a concentration gradient in which an amount of boron (B) decreases and an amount of cobalt (Co) increases from a surface thereof toward a center of a positive electrode active material particle, and the amount of the boron (B) among total metals excluding lithium in the positive electrode active material is in a range of 0.1 mol% to 1.25 mol%, and a positive electrode and a lithium secondary battery which include the same.