Amorphous-Coated High-Nickel Cathode Material Against Cracks and Gelation
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Solution Overview
Problem
High nickel positive electrode active materials face issues such as microcracks leading to structural collapse, increased resistance due to NiO phase change, and slurry gelation from lithium byproducts, which degrade performance and energy density.
Innovation Solution
A positive electrode active material with a lithium composite transition metal oxide core coated by an amorphous lithium compound, featuring a discontinuous island-like first coating and continuous layer-like second coating, incorporating boron and cobalt, reduces lithium ion dissolution 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 applies parameter changes by controlling the sintering temperature to be 700°C or lower, which prevents the phase change to Fm-3m rock-salt structure while still achieving particle structural stability. This temperature parameter optimization resolves the contradiction between structural stability and resistance increase.
Solution Approach 2:
The patent uses composite materials by forming a core-shell structure where the core is nickel-based positive electrode active material and the shell is an amorphous lithium compound coating layer. This composite structure maintains structural stability while preventing harmful phase changes and reducing resistance.
2Quantity of substance
If lithium byproduct is present on the surface of positive electrode active material, then capacity characteristics are improved, but slurry gelation occurs making uniform application difficult
Solution Approach 1:
The patent introduces an amorphous lithium compound as an intermediary substance that coats the surface of the positive electrode active material. This intermediary layer moderates the interaction between lithium byproduct and the slurry components, preventing gelation while preserving the beneficial effects of lithium byproduct on capacity characteristics.
3Quantity of substance
If co-precipitation is used to prepare high nickel positive electrode active material, then capacity characteristics are improved, but microcracks form causing structural collapse and decreased life characteristics
Solution Approach 1:
The patent applies a thin film coating of amorphous lithium compound on the surface of the high nickel positive electrode active material. This flexible protective shell prevents microcrack formation and propagation, maintaining structural integrity and improving life characteristics while preserving the high nickel content for capacity characteristics.
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 enhances stability, reduces resistance, and improves dispersibility, leading to improved capacity, life, and energy density while preventing slurry gelation.
Implementation Method 1
forming an amorphous lithium compound on a surface of the positive electrode active material to reduce a lithium byproduct
Implementation Method 2
prevent the performance degradation of the positive electrode active material and the gelation of the slurry by introducing an additional process during the preparation of the positive electrode active material to suppress a reaction of the Li byproduct present on the surface
Data Source
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AI summary
The present invention relates to a positive electrode active material capable of improving performance of a lithium secondary battery, wherein it 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 which is formed on the lithium composite transition metal oxide and includes an amorphous lithium compound, 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 and the second coating portion each independently include boron (B) and cobalt (Co), and optionally include at least one coating element selected from the group consisting of Co, Al, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, La, and Hf, and a positive electrode and a lithium secondary battery which include the same.