Coated NCM Cathode Particles With Pore Control for High-Voltage Stability
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Solution Overview
Problem
Lithium composite transition metal oxide particles in the form of single or quasi-single particles exhibit low lithium mobility, leading to reduced battery capacity and poor output characteristics, and undergo increased side reactions and degradation at high voltages and temperatures.
Innovation Solution
A positive electrode active material comprising lithium composite transition metal oxide particles with a specific pore distribution and a coating layer, formulated to enhance particle strength, suppress electrolyte interactions, and improve high-temperature stability, characterized by a pore ratio (P2/P1) of 1.0 ≤ P2/P1 ≤ 4.0, with a nickel content of 50-80 mol% and a coating layer containing Al and W.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If lithium composite transition metal oxide particles are formed as single particles with larger primary particles, then particle strength is improved and breakage is reduced, but lithium mobility decreases due to reduced interfacial area, resulting in low battery capacity and poor output characteristics
Solution Approach 1:
The invention divides the single particle into multiple primary particles (2-50 primary particles) that are sintered together to form a secondary particle structure. This segmentation increases the interfacial area between primary particles, providing more diffusion paths for lithium ions and improving lithium mobility, while maintaining the overall particle strength through the sintered structure.
Solution Approach 2:
The invention employs a nested structure where multiple primary particles are embedded within a secondary particle matrix. The primary particles are arranged in a nested configuration that maximizes interfacial contact area while maintaining structural integrity, allowing lithium ions to diffuse through multiple interfaces within the secondary particle.
2Productivity
If NCM-based lithium composite transition metal oxides are operated at high voltage of 4.35 V or more to achieve high capacity, then battery capacity is improved, but side reactions with electrolyte increase and performance degradation accelerates
Solution Approach 1:
The invention introduces an intermediary coating layer comprising aluminum oxide and tungsten oxide on the surface of the lithium composite transition metal oxide particles. This coating layer acts as a mediator that reduces direct contact between the high-voltage active material and the electrolyte, suppressing side reactions and performance degradation while allowing the battery to operate at high voltage (4.35 V or more) for high capacity.
3Object-affected harmful factors
If single particle form is used to reduce contact area with electrolyte and suppress side reactions, then gas generation is reduced and lifespan is improved, but interfacial area for lithium ion diffusion is reduced
Solution Approach 1:
The invention segments the particle into multiple primary particles (2-50 primary particles) within each secondary particle. This segmentation creates numerous internal interfaces that serve as diffusion paths for lithium ions, increasing the effective interfacial area for lithium ion diffusion while the outer coating layer continues to suppress harmful side reactions with the electrolyte.
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 active material exhibits improved initial efficiency, rate characteristics, and high-temperature lifespan due to reduced particle breakage, suppressed gas generation, and enhanced durability through uniform coating distribution.
Implementation Method 1
a coating layer which is formed on a surface of the lithium composite transition metal oxide particles
Implementation Method 2
active materials enabling intercalation/deintercalation of lithium ions
Data Source
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AI summary
A positive electrode active material according to the present invention is a positive electrode active material including lithium composite transition metal oxide particles having a nickel content of 50 mol% to 80 mol% among all metals excluding lithium and having the form of a single particle formed of one single nodule, or a quasi-single particle, a composite of up to 30 nodules, and a coating layer formed on a surface of the lithium composite transition metal oxide particles, wherein the positive electrode active material satisfies Equation 1 below. 1.0≤P2/P1≤4.0 In Equation 1 above, P1 is a total volume of pores having a pore diameter greater than 40 A in the positive electrode active material, and P2 is a total volume of pores having a pore diameter of 40 Å or less in the positive electrode active material.