Bimodal NCM Cathode Material for Dense, Crack-Resistant Electrodes
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Solution Overview
Problem
Lithium nickel-cobalt-manganese oxides used in lithium secondary batteries face challenges with low roll-pressing density, energy density, and high-temperature stability, leading to issues such as electrode cracking and reduced lifespan.
Innovation Solution
A positive electrode material comprising a bimodal particle size distribution of lithium composite transition metal oxides with a nickel content of 80% or greater, specifically a combination of large and small diameter particles with a 3 μm or greater difference in average particle diameter, enhancing roll-pressing density and energy density while improving high-temperature lifespan properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If an electrode is roll-pressed hard to increase the roll-pressing density, then the roll-pressing density is improved, but the current collector breaks and the positive electrode material cracks
Solution Approach 1:
The patent employs small particles as a cushioning phase that fills voids between large particles before roll-pressing. This pre-positioning of smaller particles creates a more uniform stress distribution during electrode fabrication, preventing stress concentration that would otherwise cause cracking of the current collector or electrode material.
2Quantity of substance
If a lithium nickel-cobalt-manganese oxide having a high content of Ni is used to increase capacity properties, then the reversible capacity is improved, but the structural stability is reduced at high temperatures, so that electrochemical performance such as high-temperature lifespan is deteriorated
Solution Approach 1:
The patent changes the particle size parameter to resolve the stability-capacity contradiction. By controlling particle size rather than compositional ratios, the patent achieves high capacity through increased nickel content while maintaining stability through the physical structure of bimodal particle distribution, which provides thermal management and structural support.
Data Source
Figure 1
AI summary
A positive electrode material including a first positive electrode active material represented by Formula 1 and a second positive electrode active material represented by Formula 2, a positive electrode including the same, and a lithium secondary battery including the positive electrode are provided. The positive electrode material has a bimodal particle size distribution including large diameter particles and small diameter particles, and the difference in average particle diameter (D50) between the large diameter particles and the small diameter particles is 3 µm or greater.