Cathode Active Material Microstructure for Output and Strength
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Solution Overview
Problem
Existing positive electrode active materials for lithium ion secondary batteries, particularly those with hollow or multilayer structures, suffer from inadequate output characteristics and mechanical strength, which can be compromised during manufacturing processes.
Innovation Solution
A positive electrode active material composed of lithium transition metal-containing composite oxide particles with a specific composition and structure, including a layered rock salt type crystal structure, secondary particles formed from primary particles with controlled size and distribution, and a network of communication holes and internal space sections, enhancing mechanical strength and reaction area with electrolytes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a hollow structure or multilayer structure with space sections is formed in the positive electrode active material, then the reaction area with electrolyte increases and output characteristics improve, but the mechanical strength decreases and particles may collapse during manufacturing
Solution Approach 1:
The patent applies local quality by creating a heterogeneous particle structure where the outer shell has different properties than the interior. Specifically, the particles have a dense outer shell structure that provides mechanical strength and resistance to collapse during manufacturing, while the interior contains space sections and communication holes that increase electrolyte contact area and improve output characteristics. This local differentiation allows simultaneous optimization of both mechanical strength and power output.
2Area of stationary object
If particles with small particle size are used, then the specific surface area increases and reaction area with electrolyte is secured, but the positive electrode resistance may increase due to thin positive electrode formation
Solution Approach 1:
The patent employs porous materials by incorporating communication holes and space sections within the particle structure. These internal porous features increase the effective surface area available for electrolyte interaction without requiring a reduction in overall particle size. The communication holes provide pathways for electrolyte penetration deep into the particle interior, maintaining low resistance while the controlled porosity prevents excessive thinning of the positive electrode structure.
3Reliability
If particles with narrow particle size distribution are used, then the voltage applied to particles in electrode becomes uniform and selective degradation is suppressed, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies segmentation by controlling the particle size distribution through a two-stage process: first forming nuclei with a specific size range, then allowing controlled growth to achieve the target distribution. This segmented approach to particle formation enables precise control over the final particle size distribution, ensuring uniform voltage application across all particles in the electrode while suppressing selective degradation of fine particles during cycling.
Data Source
AI summary
The positive electrode active material is capable of reducing positive electrode resistance, exhibiting better output characteristics, and having high mechanical strength when the positive electrode active material is used in a lithium ion secondary battery. Secondary particles have a d50 of 3.0 to 7.0 μm, a BET specific surface area of 2.0 to 5.0 m2/g, a tap density of 1.0 to 2.0 g/cm3, and an oil absorption amount of 30 to 60 ml/100 g. In each of a plurality of primary particles having a primary particle size of 0.1 to 1.0 μm, a coefficient of variation of the concentration of an additive element M is 1.5 or less. The volume of a linking section between the primary particles per primary particle, obtained from the total volume of the linking section and the number of primary particles constituting the secondary particles, is 5×105 to 9×107 nm3.