Cathode Active Material Coating for Battery Capacity and Cycle Retention
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving improved initial discharge capacities and cycle retention rates as their application fields expand.
Innovation Solution
A positive electrode active material for lithium secondary batteries is developed, comprising Li, Ni, and an element X with a specific coating on lithium metal composite oxide particles, where the coating contains elements like Al, Ti, Nb, Zr, P, B, Mg, Ba, Si, Sn, or W, with precise abundance and distribution measured by X-ray photoelectron spectroscopy and scanning electron microscope-energy dispersive X-ray spectroscopy, ensuring optimal surface composition and structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating layer containing tungsten is applied on the surface of lithium-nickel composite oxide particles, then the initial discharge capacities and cycle retention rates are improved, but the manufacturing precision and surface composition control become more complex
Solution Approach 1:
The patent applies parameter changes by precisely controlling the atomic ratio of element X to lithium (Xat/Liat) within a specific range (0.05 to 0.50) and controlling the standard deviation of element X distribution (σx) to be 15.0 or less. These quantitative parameter specifications enable systematic optimization of the coating composition to achieve both improved cycle retention rates and controlled surface composition, resolving the technical contradiction between reliability and manufacturing precision.
Solution Approach 2:
The patent applies local quality by focusing the coating modification specifically on the surface region of the lithium metal composite oxide particles rather than the bulk material. The coating layer is designed to contain element X with controlled abundance and distribution specifically at the particle surfaces, creating localized compositional differences that improve electrochemical performance while maintaining control over the overall material properties.
2Quantity of substance
If the coating contains element X with high abundance near the surface, then the initial discharge capacity increases, but the uniformity of element X distribution across particles decreases
Solution Approach 1:
The patent resolves this contradiction by establishing an optimal parameter range for the atomic ratio Xat/Liat (0.05 to 0.50) and setting a maximum standard deviation σx ≤ 15.0. This quantitative control ensures that sufficient element X is present at the surface to enhance initial discharge capacity while maintaining uniform distribution across particles, preventing both deficiency and excessive variability.
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 significantly enhances the initial discharge capacities and cycle retention rates of lithium secondary batteries, providing better performance and longevity.
Implementation Method 1
containing particles including a coating on a surface of a lithium metal composite oxide, in which the coating contains the element X
Implementation Method 2
Xat is an abundance of the element X near the surface of the particle, which is measured by X-ray photoelectron spectroscopy
Implementation Method 3
σx is a standard deviation calculated from the abundances of the element X near the surfaces of a plurality of the particles, which is measured by scanning electron microscope-energy dispersive X-ray spectroscopy
Implementation Method 4
In the X-ray diffraction measurement using CuKα rays, two diffraction peaks are present within a range of 2θ＝38.5±1°
Data Source
AI summary
A positive electrode active material for a lithium secondary battery, containing at least Li, Ni, and an element X, containing particles including a coating on a surface of a lithium metal composite oxide, in which the coating contains the element X, the element X is one or more elements selected from the group consisting of Al, Ti, Nb, Zr, P, B, Mg, Ba, Si, Sn, and W, and a formula (1) and a formula (2) are satisfied.0.20≤Xat/Liat (1)σX≤13.0 (2)