Cathode Active Material Composition to Minimize Particle Cracking
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Solution Overview
Problem
Rechargeable lithium batteries face issues with cracks during charging and discharging due to particle size mismatch, leading to gas generation, electrolyte depletion, and reduced safety and performance.
Innovation Solution
A positive electrode active material comprising a first lithium nickel-cobalt-aluminum-based composite oxide with radially oriented primary particles and a second lithium nickel-cobalt-aluminum-manganese-based composite oxide, prepared through co-firing with a lithium raw material, enhances lithium diffusion and structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel-based positive electrode active materials are used to increase capacity, then battery capacity is improved, but cracks occur inside particles during charging and discharging, leading to gas generation and reduced safety
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core contains high-nickel content (LiNi0.9Co0.05Al0.05O2) for high capacity, while the outer shell contains low-nickel content (LiNi0.8Co0.1Mn0.1O2) for structural stability. This gradient composition allows different regions of the particle to have different properties optimized for their specific functions.
Solution Approach 2:
The patent uses composite materials by combining two different lithium nickel-based composite oxides with different compositions and properties. The core-shell structure integrates high-nickel material for capacity with low-nickel material for stability, creating a composite positive electrode active material that achieves both high capacity and structural integrity during cycling.
2Use of energy by moving object
If large and small particles of different particle sizes are mixed to increase energy density, then energy density is improved, but cracks occur inside particles during long-term cycling, causing electrolyte depletion and reduced performance
Solution Approach 1:
The patent segments the positive electrode active material into two distinct particle size ranges: large particles (5 μm to 20 μm) providing high energy density and small particles (3 μm to 8 μm) with core-shell structure providing structural stability. This segmentation allows each particle type to fulfill different functional requirements while working together in the electrode.
Solution Approach 2:
The patent applies local quality by creating a core-shell structure where the inner core contains high-nickel content (LiNi0.9Co0.05Al0.05O2) for high capacity, while the outer shell contains low-nickel content (LiNi0.8Co0.1Mn0.1O2) for structural stability. This gradient composition allows different regions of the particle to have different properties optimized for their specific functions.
3Quantity of substance
If cracks occur inside particles during charging and discharging, then capacity is temporarily maintained, but side reactions with electrolyte solution cause gas generation and electrolyte depletion, reducing safety and performance
Solution Approach 1:
The patent applies beforehand cushioning by pre-coating the high-nickel core particles with a low-nickel shell material before electrode assembly. This protective shell is formed in advance to prevent cracks and side reactions during subsequent charging and discharging cycles, cushioning the high-nickel core from harmful electrolyte contact.
Solution Approach 2:
The patent converts the inherent structural weakness of high-nickel materials (prone to cracking) into a benefit by using the low-nickel shell material to deliberately control and manage the particle structure. The shell acts as a protective layer that prevents uncontrolled cracking and harmful side reactions, turning a potential failure mode into a protective mechanism.
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 material achieves high capacity, high initial charge and discharge efficiency, and excellent cycle-life characteristics by minimizing particle cracking and optimizing composition distribution.
Implementation Method 1
enhances lithium diffusion and structural stability
Implementation Method 2
performing heat treatment
Data Source
Figure 1(A)~1(C)
Figure 2
Figure 3
AI summary
Disclosed are a positive electrode active material for a rechargeable lithium battery, a preparation method thereof and a rechargeable lithium battery, the positive electrode active material for a rechargeable lithium battery including a first positive electrode active material in a form of secondary particles including a lithium nickel-cobalt-aluminum-based composite oxide and formed by agglomerating a plurality of primary particles, wherein at least a portion of the primary particles is oriented radially; and a second positive electrode active material in a form of secondary particles including a lithium nickel-cobalt-aluminum-manganese-based composite oxide, and formed by agglomerating a plurality of primary particles, wherein an average particle diameter of secondary particles of the first positive electrode active material is larger than an average particle diameter of the secondary particles of the second positive electrode active material.