Lithium Composite Oxide Interface Design for Stable High-Capacity Cathodes
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Solution Overview
Problem
Current lithium secondary batteries face challenges in achieving stability and electrical characteristics due to issues like cation mixing, structural instability, and side reactions in positive electrode materials.
Innovation Solution
A lithium composite oxide is developed with primary and secondary particles, where niobium-containing oxides are present at the interface between primary particles and the surface of secondary particles, enhancing lithium ion diffusion and stabilizing the crystal structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Ni content in positive electrode active material is increased to achieve high capacity characteristics, then discharge capacity is improved, but structural instability occurs due to Li/Ni cation mixing
Solution Approach 1:
The patent applies local quality by introducing a concentration gradient of Ni content within particles, where the surface region has lower Ni content (reducing cation mixing and improving stability) while the inner region maintains high Ni content (providing high capacity). This spatial variation in composition resolves the contradiction between capacity and stability.
Solution Approach 2:
The patent creates a composite structure with two distinct regions: a surface region with lower Ni content and an inner region with high Ni content. This composite approach allows the material to simultaneously exhibit the stability characteristics of low-Ni regions and the high capacity characteristics of high-Ni regions.
2Quantity of substance
If Li/Ni cation mixing is intensified to achieve high capacity, then discharge capacity increases, but Li by-products are generated causing gelation and gas generation
Solution Approach 1:
The patent reduces Li by-product generation by creating a surface region with lower Ni content, which minimizes cation mixing at the particle surface where electrolyte contact occurs. This local compositional adjustment prevents the formation of harmful Li by-products while preserving high capacity in the inner region.
3Quantity of substance
If Ni-rich positive electrode active materials are used to achieve high capacity, then discharge capacity is improved, but rate characteristics deteriorate
Solution Approach 1:
The patent improves rate characteristics by creating a surface region with lower Ni content and higher conductivity, which facilitates fast ion transport. The inner region maintains high Ni content for capacity. This spatial differentiation allows the material to exhibit both high capacity and good rate characteristics.
4Quantity of substance
If Ni-rich positive electrode active materials are used to achieve high capacity, then discharge capacity is improved, but stability at high temperature deteriorates
Solution Approach 1:
The patent enhances high-temperature stability by concentrating high Ni content in the inner region while maintaining a surface region with lower Ni content that is more resistant to thermal degradation. This spatial distribution allows the material to maintain both high capacity and thermal stability.
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 lithium composite oxide improves the stability and electrical characteristics of the positive electrode material, reducing side reactions and maintaining performance even at high temperatures.
Implementation Method 1
primary particles enabling lithium intercalation and deintercalation
Implementation Method 2
materials enabling reversible intercalation/deintercalation of lithium ions
Implementation Method 3
there is a niobium (Nb)-containing oxide in at least a part of a region selected from the interface between the primary particles and the surface of the secondary particle
Implementation Method 4
improving the stability of a crystal structure
Implementation Method 5
by inhibiting interfacial side reactions in the lithium composite oxide
Data Source
AI summary
The present invention relates to a lithium composite oxide having improved stability and electrical characteristics as a positive electrode material by inhibiting an interfacial side reaction in the lithium composite oxide and improving the stability of a crystal structure and ion conductivity, and a lithium secondary battery including the same.