Positive Electrode Material with Bimodal Particles for Dense Li-Ion Cathodes
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Solution Overview
Problem
Lithium-rich manganese-based oxides, while offering high capacity, suffer from low rate characteristics and reduced electrode density due to high BET specific surface area, leading to issues in electrode processability and particle breakage during rolling.
Innovation Solution
A positive electrode material comprising lithium-rich manganese-based oxide and small particle lithium transition metal oxide in the form of single or pseudo-single particles, with controlled D50 values, is used to enhance electrode density and durability, incorporating a bimodal particle size distribution to improve packing and reduce slurry viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the primary particles are made smaller to increase the BET specific surface area, then the rate characteristics are improved, but the rolling density of the positive electrode is lowered
Solution Approach 1:
The invention divides the positive electrode active material into two distinct particle size segments: small primary particles (0.5-5 μm) for high rate characteristics and large secondary particles (5-20 μm) for high rolling density. This segmentation allows each particle size to fulfill its specific function optimally without compromising the other property.
Solution Approach 2:
The invention creates a composite particle structure where small primary particles are aggregated to form larger secondary particles. This composite structure combines the advantages of both size scales: the small primary particles provide high surface area for fast lithium ion diffusion, while the larger secondary particle structure maintains high packing density in the electrode.
2Reliability
If a metal oxide coating is applied to enhance surface stability, then the electrode density is improved, but the rate characteristics are further lowered
Solution Approach 1:
The invention changes the particle size parameter (using larger secondary particles with D50 of 5-20 μm) to reduce the total specific surface area, thereby minimizing the negative impact of metal oxide coating on rate characteristics while still achieving sufficient surface stability for electrode density improvement.
Data Source
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AI summary
The present disclosure relates to a positive electrode material for a lithium secondary battery comprising: a first positive electrode active material containing lithium-rich manganese-based oxide; and a second positive electrode active material having one or more particles in the form of a single particle consisting of one nodule or a pseudo-single particle that is a composite of 30 or fewer nodules, and containing lithium transition metal oxide, wherein the first positive electrode active material has a D50 of 8 µm or more, and has a larger value than the D50 of the second positive electrode active material, and to a positive electrode slurry, positive electrode and lithium secondary battery comprising the positive electrode material.