Core-Shell Cathode Precursor for Lithium Battery Stability
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Solution Overview
Problem
High nickel-based lithium oxide cathode active materials in lithium secondary batteries suffer from structural and chemical instability, leading to reduced battery capacity and lifespan due to side reactions with the electrolyte, and existing solutions do not adequately address both stability and capacity properties.
Innovation Solution
A cathode active material precursor with a core-shell structure is developed, where a first transition metal composite hydroxide core is coated with a second transition metal composite hydroxide shell containing doping metals from Group 4 to 12, such as W, Nb, or Mo, to enhance structural stability and control particle size distribution, preventing excessive fine or coarse powder formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel-based lithium oxide is used as cathode active material to secure high capacity, then battery capacity is improved, but structural and chemical stability deteriorates leading to reduced lifespan
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core contains high nickel content (0.8-0.95) for high capacity, while the shell contains doping metals (Group 4-12) to provide structural stability. This spatial differentiation allows each region to fulfill its specific function: the core provides capacity while the shell provides stability, resolving the contradiction between high capacity and structural stability.
Solution Approach 2:
The patent uses composite materials by combining high nickel-based lithium oxide with doping metals from Group 4-12 (such as W, Nb, Mo, Ta) to form a composite cathode active material. The doping metals are incorporated into the crystal structure at specific sites, creating a composite material that maintains the high capacity characteristics of high nickel oxide while gaining the structural stability provided by the doping metals, thus resolving the contradiction between capacity and stability.
2Quantity of substance
If high nickel content is increased to improve capacity, then battery capacity is improved, but side reactions with electrolyte increase causing capacity degradation
Solution Approach 1:
The patent applies local quality by concentrating the high nickel content in the core region where it provides capacity, while placing the doping metals in the shell region that interfaces with the electrolyte. This spatial separation ensures that the region most prone to side reactions with the electrolyte (the surface/shell) contains stabilizing doping metals rather than reactive high nickel content, thus reducing harmful side reactions while maintaining high capacity.
Solution Approach 2:
The doping metals in the shell act as intermediaries between the high nickel core and the electrolyte. They provide a protective interface that reduces direct contact and harmful interactions between the reactive high nickel material and the electrolyte, thereby mitigating side reactions and capacity degradation while allowing the high nickel core to maintain its capacity-providing function.
3Reliability
If uniform doping is applied throughout the material to improve stability, then structural stability is improved, but capacity properties deteriorate
Solution Approach 1:
The patent applies local quality by distributing doping metals non-uniformly throughout the material - specifically concentrating them in the shell region (0.05-0.20 μm thickness) while keeping the core region (0.5-2.0 μm diameter) rich in high nickel content. This localized doping strategy ensures that stability-providing doping metals are present where needed (at the surface for structural integrity and electrolyte interface), while capacity-providing high nickel material remains dominant in the core volume, thus achieving both stability and capacity properties.
Data Source
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AI summary
A cathode active material precursor for a lithium secondary battery is provided according to embodiments of the present invention. The cathode active material precursor for a lithium secondary battery includes a core including a first transition metal composite hydroxide, and a shell which is formed on the core and includes a second transition metal composite hydroxide in which the first transition metal composite hydroxide is doped with a doping metal including at least one of Group 4 to Group 12 metals, wherein the cathode active material precursor has a particle size distribution degree of 0.8 to 1.6 defined by Equation 1. Thereby, it is possible to suppress capacity degradation of the secondary battery due to doping while improving the structural stability of the cathode active material precursor.