Single-Particle Cathode Material to Reduce Cracking and Gas Generation
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Solution Overview
Problem
Conventional nickel-based lithium transition metal oxides in secondary particle form suffer from particle cracking, gas generation, and reduced thermal and chemical stability, particularly in high-Ni compositions, leading to degraded battery performance.
Innovation Solution
A positive electrode active material composed of lithium transition metal oxide particles in a single particle form with high sphericity (≥0.7) and controlled porosity, minimizing particle cracking and gas generation through a solid-phase synthesis method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel-based lithium transition metal oxide is used in secondary particle form with fine primary particles aggregated, then capacity can be increased, but particle cracking occurs and gas generation increases during cell operation
Solution Approach 1:
The patent divides the secondary particle into multiple primary particles (2-50 primary particles aggregated) to maintain high capacity while reducing internal stress. This segmentation allows the particle to accommodate volume changes during lithium insertion/extraction without cracking, thus improving reliability while maintaining quantity of substance.
Solution Approach 2:
The patent changes the particle size parameter by controlling the primary particle diameter to 0.5-5 μm and limiting aggregation to 2-50 primary particles. This parameter optimization balances capacity (requiring fine particles) with stability (requiring larger, more robust particles), resolving the contradiction between quantity and reliability.
2Quantity of substance
If high nickel content is increased to ensure high capacity, then energy density improves, but chemical stability and thermal stability are reduced
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the interior contains high nickel content for energy density while the surface has modified composition or coating for enhanced stability. This allows different regions of the particle to have different properties, simultaneously achieving high energy density and chemical stability.
Solution Approach 2:
The patent uses composite materials by combining nickel-based lithium transition metal oxide with stabilizing elements or surface coatings. This composite approach maintains the high capacity benefits of nickel while adding stability through the composite structure, resolving the contradiction between energy density and chemical stability.
3Object-generated harmful factors
If washing process is applied to reduce lithium impurities on surface, then gas generation is reduced, but surface damage occurs and lifetime is degraded
Solution Approach 1:
The patent applies preliminary action by performing surface treatment during the synthesis process itself, rather than as a separate post-processing step. The surface modification occurs concurrently with particle formation, eliminating the need for aggressive washing that would damage the surface, thus reducing gas generation while preserving lifetime.
Solution Approach 2:
The patent introduces an intermediary surface layer or coating that prevents direct contact between lithium impurities and the bulk material. This intermediary layer allows removal of harmful substances without exposing the underlying particle structure to damaging mechanical or chemical stress, thereby reducing gas generation while maintaining lifetime.
Data Source
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AI summary
The present invention relates to a positive electrode active material including lithium transition metal oxide particles in a form of a single particle, wherein the lithium transition metal oxide has an average sphericity according to Equation 1 described in the present specification of 0.7 or more, and, when an electrode including the lithium transition metal oxide is rolled such that porosity is 20%, the average sphericity according to Equation 1 described in the present specification is 0.7 or more, and a positive electrode and a lithium secondary battery which include the same.