Single-Particle NMC Cathode Structure for High-Nickel Stability
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Solution Overview
Problem
Conventional lithium nickel cobalt manganese oxide positive electrode active materials face issues with particle breakage, structural collapse, and reduced thermal stability due to high nickel content, leading to increased degradation and safety concerns in lithium secondary batteries.
Innovation Solution
A method of preparing a single particle type lithium nickel-based oxide with a nickel content of 90 mol% or more, utilizing a precursor with a specific BET/D50 ratio of 0.5 to 2, sintered at 800°C to 900°C, and coated with elements like cobalt to enhance thermal stability and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel content (90 mol% or more) is used in the positive electrode active material, then high capacity is achieved, but thermal stability deteriorates due to increased side reactions with electrolyte solution
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core region contains high nickel content (90 mol% or more) for high capacity, while the outer shell region has reduced nickel content and increased cobalt content for enhanced thermal stability. This spatial differentiation of composition allows simultaneous optimization of capacity and safety properties in different regions of the same particle.
Solution Approach 2:
The patent employs composite materials by combining multiple transition metal oxides (nickel oxide, cobalt oxide, manganese oxide) in a graded composition within a single particle. The composite structure transitions from high-nickel core to lower-nickel shell, creating a material that exhibits both high capacity characteristics and improved thermal stability that neither component could achieve alone.
2Ease of manufacture
If secondary particle structure with aggregated primary particles is used, then manufacturing is easier, but particle breakage and cracking occur during rolling and charge-discharge processes
Solution Approach 1:
The patent applies segmentation by designing a single particle that contains multiple nodules (3-30 units) internally, where each nodule is a distinct crystalline domain. These nodules are strongly bonded at their interfaces, creating a segmented yet integrated structure that maintains particle integrity during mechanical processing and electrochemical cycling while allowing internal stress distribution.
Solution Approach 2:
The patent implements the nested doll principle by embedding multiple nodules within a single particle boundary, where smaller crystalline domains (nodules) are contained within the larger particle structure. This hierarchical nesting allows the particle to maintain structural integrity while accommodating volume changes during lithium insertion/extraction through nodule-level deformation.
3Quantity of substance
If high nickel content is used, then capacity increases, but structural stability deteriorates leading to particle breakage and cracks
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core region contains high nickel content (90 mol% or more) for high capacity, while the outer shell region has reduced nickel content and increased cobalt content for enhanced thermal stability. This spatial differentiation of composition allows simultaneous optimization of capacity and safety properties in different regions of the same particle.
Solution Approach 2:
The patent implements beforehand cushioning by introducing a protective shell layer around the high-nickel core, where the lower-nickel, higher-cobalt shell acts as a buffer that prevents structural collapse and particle breakage during electrochemical cycling. This shell cushioning effect protects the brittle high-nickel core from mechanical failure while allowing it to deliver high capacity.
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 achieves high capacity and thermal stability, reducing side reactions and gas generation, enabling excellent high-temperature and high-voltage charging performance in lithium secondary batteries.
Implementation Method 1
sintering the mixture
Data Source
Figure 1
Figure 2
AI summary
The present invention relates to a positive electrode active material, which includes a single particle type lithium nickel-based oxide including nickel, cobalt and manganese, having an amount of nickel among total metals excluding lithium of 90 mol% or more, and including 1 to 30 nodules, wherein D50 is in a range of 5 µm to 7um, and a maximum value of heat flow, which is measured with a differential scanning calorimeter (DSC) while a coin-half cell prepared by using the positive electrode active material is charged to 4.25 V and then heated from room temperature to 380°C at a heating rate of 10°C/min, is 15.0 W/g or less, and a preparation method thereof.