Porous Cathode Active Material with Bimodal Particle Packing
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Solution Overview
Problem
Current positive electrode active materials in secondary batteries face challenges in balancing power performance and mechanical strength, limiting their suitability for new-generation electrochemical systems.
Innovation Solution
A positive electrode active material with secondary particles formed through aggregation of primary particles, featuring a bimodal particle size distribution and pores, which facilitates three-dimensional lithium ion transfer paths and supports different particle sizes for enhanced mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the particle size of positive electrode active material is reduced to improve power performance, then the mechanical strength deteriorates
Solution Approach 1:
The positive electrode active material is divided into primary particles (0.5-5 μm) that aggregate to form secondary particles (5-20 μm). This segmentation allows the smaller primary particles to provide short lithium ion transfer paths for high power performance, while the aggregation into larger secondary particles maintains mechanical strength and structural integrity during battery operation.
2Length of moving object
If the particle size is reduced to shorten lithium ion transfer paths, then the compacted density deteriorates
Solution Approach 1:
The invention introduces a bimodal particle size distribution with two distinct size ranges (primary particles 0.5-5 μm and secondary particles 5-20 μm). This dimensional differentiation in particle sizes allows small particles to fill voids between larger particles, optimizing both lithium ion transfer path length and compacted density simultaneously.
3Ease of manufacture
If uniform particle size is used to simplify manufacturing, then the mechanical strength and power performance deteriorate
Solution Approach 1:
The invention applies different particle size qualities to different functional requirements: smaller primary particles (0.5-5 μm) for high power performance and short ion paths, and larger secondary particles (5-20 μm) for mechanical strength. This local quality differentiation through bimodal distribution optimizes both performance aspects while maintaining manufacturing feasibility through controlled aggregation.
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 bimodal particle size distribution and pores improve the power performance, mechanical strength, and energy density of the battery by shortening lithium ion transfer paths and enhancing the compacted density of the positive electrode sheet.
Implementation Method 1
shortening a solid-phase mass transfer path of lithium ions
Implementation Method 2
improving the compacted density of the positive electrode sheet
Data Source
AI summary
Provided in the present application are a positive electrode active material, a positive electrode sheet, a secondary battery, and an electric device. The positive electrode active material is present in a form of secondary particles formed through aggregation of primary particles. At least some of the secondary particles have pores. A particle size distribution diagram of the positive electrode active material that is measured by using a laser diffraction method is of a bimodal shape. A difference between a peak position of a second peak and a peak position of a first peak is 1 μm to 13 μm.