Layered Lithium-Nickel Cathode Surface Chemistry for Thermal Stability
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Solution Overview
Problem
Existing secondary batteries have not achieved sufficient battery characteristics, particularly in terms of thermal stability and energy density, despite efforts to improve them.
Innovation Solution
A positive electrode for a secondary battery is designed with a lithium-nickel composite oxide of layered rock-salt type, where the atomic concentration ratios of Al to Ni are carefully controlled through X-ray photoelectron spectroscopy, and a film formed on the surface to stabilize the crystal structure and prevent decomposition of the electrolytic solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a layer including LiAlO2 is provided on the surface of lithium-transition-metal composite oxide particles to improve thermal stability, then thermal stability is improved, but the battery characteristic is still insufficient
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of Al atoms within the lithium-nickel composite oxide particles. The Al concentration is highest at the surface (ratio X: 0.05≤X≤0.50) and decreases toward the interior (ratio Y: 0.01≤Y≤0.08), with the surface-to-interior concentration ratio Z satisfying 1.20≤Z≤2.52. This localized variation in Al concentration optimizes both thermal stability at the surface and overall battery performance throughout the particle structure.
Solution Approach 2:
The patent employs parameter changes by precisely controlling the Al concentration ratios (X, Y, and Z) within the lithium-nickel composite oxide. By adjusting these concentration parameters to specific ranges, the patent achieves optimal balance between thermal stability and battery characteristics, including discharge capacity retention and resistance to gas generation.
2Quantity of substance
If high nickel content is used in lithium-nickel composite oxide to increase energy density, then energy density is improved, but discharge capacity decreases and gas is generated
Solution Approach 1:
The patent applies local quality by concentrating Al atoms preferentially at the surface region of lithium-nickel composite oxide particles. The surface Al concentration ratio X (0.05≤X≤0.50) is significantly higher than the interior ratio Y (0.01≤Y≤0.08), creating a protective surface layer that stabilizes high-nickel content material and prevents gas generation while maintaining high energy density.
Solution Approach 2:
The patent uses composite materials by combining lithium-nickel composite oxide with controlled Al doping. The composite structure features Al atoms distributed in a solid solution state with specific concentration gradients, creating a material that combines the high energy density of lithium-nickel oxide with the stabilizing effect of Al, thereby preventing capacity fade and gas generation.
3Object-generated harmful factors
If Al concentration is increased uniformly throughout lithium-nickel composite oxide to prevent gas generation, then gas generation is reduced, but energy density decreases
Solution Approach 1:
The patent applies local quality by creating a non-uniform Al concentration distribution within the lithium-nickel composite oxide particles. The surface region has higher Al concentration (ratio X: 0.05≤X≤0.50) to prevent gas generation and improve stability, while the interior maintains lower Al concentration (ratio Y: 0.01≤Y≤0.08) to preserve energy density and electrochemical activity.
Solution Approach 2:
The patent employs parameter changes by optimizing the Al concentration ratios at different locations. The surface-to-interior concentration ratio Z (1.20≤Z≤2.52) is controlled to achieve the right balance: sufficient Al at the surface to prevent gas generation while maintaining overall low Al content to preserve energy density.
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 design achieves superior battery characteristics by preventing discharge capacity decrease, gas generation, and swelling, while maintaining high energy density and stable lithium-ion insertion and extraction.
Implementation Method 1
a film formed on the surface to stabilize the crystal structure and prevent decomposition of the electrolytic solution
Implementation Method 2
According to an analysis of the positive electrode active material layer performed at a surface of the positive electrode active material layer by X-ray photoelectron spectroscopy
Data Source
AI summary
A secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes a positive electrode active material layer. The positive electrode active material layer includes a lithium-nickel composite oxide of a layered rock-salt type.