Positive Electrode Active Material Particle Size Distribution
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high volumetric density, thermal stability, and reduced contact resistance due to the use of active materials with different particle diameters, which complicates manufacturing and affects battery performance.
Innovation Solution
A positive electrode active material is developed by mixing small-diameter (0.5 µm to 1 µm) and large-diameter (5 µm to 20 µm) active materials in a specific weight ratio (7+x:3-x) along with a conductive material and a collector with an uneven structure to enhance packing density and output density, while improving thermal stability and electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If two different types and particle sizes of active materials are mixed to improve volumetric density, then packing density improves, but contact resistance increases
Solution Approach 1:
The patent optimizes the particle size parameters by defining specific ranges: small particles with average diameter 0.3-1.0 µm and large particles with average diameter 3-20 µm. It also optimizes the weight ratio parameter to 70-90% small particles and 10-30% large particles, achieving both high packing density and acceptable contact resistance through parameter optimization
Solution Approach 2:
The patent creates a composite particle system combining two different particle sizes of the same active material (lithium cobalt oxide). This composite structure allows small particles to fill voids between large particles, improving volumetric density while maintaining sufficient contact pathways for electrical conductivity
2Quantity of substance
If active material particle diameter is reduced below 1 µm to improve packing density, then volumetric density improves, but contact resistance greatly increases
Solution Approach 1:
The patent merges two particle size groups (small particles 0.3-1.0 µm and large particles 3-20 µm) into a single mixed system. The small particles fill the interstices between large particles, and the combination creates a synergistic effect where the small particles provide density while the large particles maintain conductive networks
Solution Approach 2:
The patent specifies that small particles should have average diameter 0.3-1.0 µm (not below 1 µm alone) and large particles 3-20 µm, with a weight ratio of 70-90% small to 10-30% large. This parameter combination optimizes both packing density and contact resistance
3Reliability
If complex coating techniques are applied to improve battery characteristics, then thermal stability and performance improve, but manufacturing complexity increases
Solution Approach 1:
The patent extracts the coating step entirely from the manufacturing process. Instead of applying coating layers to active material particles, it uses the active material particles themselves in a optimized size distribution, eliminating the complex coating process while achieving high thermal stability through the inherent properties of lithium cobalt oxide
Solution Approach 2:
The active material particles serve their own function of improving battery characteristics through their size distribution and packing arrangement, without requiring external coating layers or additional protective structures
Data Source
Figure 1
AI summary
Provided is a positive electrode active material. The positive electrode active material includes: a small-diameter active material having an average particle diameter of about 0.5 µm and a maximum particle diameter of less than about 1 µm; and a large-diameter active material having an average particle diameter of about 5 µm to about 20 µm and a maximum particle diameter of less than about 100 µm.