Coated High-Ni Cathode Particles for Stable Lithium-Ion Cycling
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Solution Overview
Problem
Conventional nickel-based lithium transition metal oxide positive electrode active materials in lithium secondary batteries face issues with thermal stability, life shortening due to side reactions, and increased resistance during charging/discharging, particularly when formed as secondary particles from agglomerated primary micro particles.
Innovation Solution
A nickel-based lithium transition metal oxide positive electrode active material is developed in the form of secondary particles formed by agglomeration of primary macro particles with a lithium-metal oxide coating layer, specifically LiaNi1-x-yCoxM1yM2wO2, where M1 includes metals like Mn or Al, and M2 includes Ba, Ca, Zr, Ti, Mg, Ta, Nb, or Mo, with a low-temperature phase LixCoO2 coating, which reduces the need for a washing process and enhances structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional nickel-based lithium transition metal oxide is formed as secondary particles from agglomerated primary micro particles, then the particle strength is low and specific surface area is large, but this causes severe particle cracking during rolling process, large amount of gas production during cell operation, and low stability
Solution Approach 1:
The patent divides the particle structure into hierarchical levels: secondary particles are formed by agglomeration of primary macro particles (0.1-3 μm), which themselves are composed of smaller crystallites. This segmentation allows the outer secondary particle structure to provide mechanical strength while the inner primary macro particles maintain adequate surface area for electrochemical reactions, preventing particle cracking during rolling
Solution Approach 2:
The patent changes the particle size parameters by forming primary macro particles with D50 of 0.1-3 μm (larger than conventional micro particles) and secondary particles with D50 of 1-15 μm. This parameter change reduces the specific surface area to volume ratio, minimizing surface-related side reactions and improving particle strength while maintaining electrochemical performance
2Quantity of substance
If high-Ni lithium transition metal oxide with high nickel content is used to ensure high capacity, then the capacity is high, but the chemical stability is reduced due to structural problems and thermal stability is difficult to ensure
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core contains high-Ni lithium transition metal oxide (LiaNi1-x-yCoxM1yM2wO2 with x+y≥0.8) for high capacity, while the outer shell consists of lithium-metal oxide coating layer for stability. This allows different regions of the particle to have different compositions optimized for their specific functions
Solution Approach 2:
The patent creates a composite material structure combining high-Ni lithium transition metal oxide core with lithium-metal oxide shell. The core provides high capacity through high nickel content (x+y≥0.8), while the shell provides chemical and thermal stability, protecting the unstable high-Ni core from degradation during cycling
3Object-generated harmful factors
If washing process is applied to reduce lithium impurities on the surface, then the gas generation is reduced, but the life is shortened by surface damage of the positive electrode active material particles
Solution Approach 1:
The patent converts the harmful effect of lithium impurities into a beneficial feature by using them as a foundation for the coating layer. The lithium impurities on the particle surface serve as nucleation sites for forming the lithium-metal oxide coating layer, which then protects the particle surface. This eliminates the need for washing processes that would damage the particles while still reducing gas generation
Solution Approach 2:
The patent performs preliminary action by forming the lithium-metal oxide coating layer before electrode fabrication. This pre-formed coating layer protects the particle surface from damage during subsequent processing steps like rolling and electrode formation, while also preventing lithium impurity-related gas generation during cell operation
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 solution improves the life characteristics and reduces resistance during charging/discharging of lithium secondary batteries by maintaining chemical and thermal stability, while minimizing surface damage and gas generation, thereby extending the battery's lifespan and performance.
Implementation Method 1
a coating layer of a lithium-metal oxide on a surface of the secondary particle, wherein the lithium-metal oxide is a low-temperature phase LixCoO2
Data Source
AI summary
The present disclosure discloses a positive electrode active material for a lithium secondary battery comprising a secondary particle having an average particle size (D50) of 1 to 15 μm, formed by agglomeration of at least two primary macro particles having an average particle size (D50) of 0.1 to 3 μm; and a coating layer of a lithium-metal oxide on a surface of the secondary particle, wherein the primary macro particles are represented by LiaNi1-x-yCoxM1yM2wO2 (1.0≤a≤1.5, 0≤x≤0.2, 0≤y≤0.2, 0≤w≤0.1, 0≤x+y≤0.2, M1 includes at least one metal of Mn or Al, and M2 includes at least one metal selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb and Mo), and wherein the lithium-metal oxide is a low-temperature phase LixCoO2(0<x≤1) having at least one of a spinel structure (Fd-3m) or a disordered rock-salt structure (Fm-3m).