Boron-Coated Positive Electrode Material for Thermal Stability
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Solution Overview
Problem
Existing secondary batteries face challenges in achieving enhanced battery characteristics, such as improved thermal stability, cyclability, and output characteristics, due to limitations in the configuration and properties of their positive electrode active materials.
Innovation Solution
A positive electrode active material for secondary batteries is developed, comprising a layered rock-salt lithium-nickel composite oxide with a specific crystallite size and specific surface area, and a boron compound covering its surface. This configuration enhances the material's properties and battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a lithium composite oxide with lithium borate on surface is used to improve thermal stability, then thermal stability is improved, but battery characteristics such as cyclability and output may deteriorate
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the center part contains lithium-nickel composite oxide with specific crystal structure, and the covering part contains lithium borate compound. This allows different regions to have different functions: the core provides high capacity while the shell provides thermal stability and surface protection, resolving the contradiction between thermal stability and cyclability.
Solution Approach 2:
The patent uses composite materials by combining lithium-nickel composite oxide (center part) with lithium borate compound (covering part) to create a composite positive electrode active material. This composite structure integrates the high capacity characteristics of lithium-nickel oxide with the thermal stability and surface protection properties of lithium borate, simultaneously improving both thermal stability and cyclability.
2Duration of action of moving object
If the crystallite size is increased to improve capacity retention, then capacity retention is improved, but specific surface area decreases which may affect reaction kinetics
Solution Approach 1:
The patent applies parameter changes by precisely controlling the crystallite size of the (104) plane within 30-80 nm range and adjusting the specific surface area to 0.3-1.5 m²/g. This optimization balances the benefits of larger crystallites (better capacity retention) with the advantages of adequate surface area (maintained reaction kinetics), resolving the contradiction between these two parameters.
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 proposed positive electrode active material achieves desirable and enhanced battery characteristics, including improved capacity retention, reduced gas generation, and enhanced energy density, thereby addressing the limitations of existing technologies.
Implementation Method 1
The covering part covers a surface of the center part and includes a boron compound
Implementation Method 2
The crystallite size is calculated by X-ray diffractometry and Scherrer equation
Implementation Method 3
The crystallite size is calculated by X-ray diffractometry and Scherrer equation
Implementation Method 4
The specific surface area is measured by Brunauer-Emmett-Teller specific surface area measurement method
Implementation Method 5
The first element concentration ratio is calculated on the basis of a C1s spectrum and an O1s spectrum measured by X-ray photoelectron spectroscopy
Data Source
AI summary
A positive electrode active material for a secondary battery includes a center part and a covering part. The center part includes a layered rock-salt lithium-nickel composite oxide. The covering part covers a surface of the center part and includes a boron compound. The positive electrode active material has a crystallite size of a (104) plane that is greater than or equal to 40.0 nm and less than or equal to 74.5 nm. The crystallite size is calculated by X-ray diffractometry and Scherrer equation. The positive electrode active material has a specific surface area that satisfies a condition represented by −0.0160×Z+1.72≤A≤−0.0324×Z+2.94 where Z is the crystallite size (nm), and A is the specific surface area (m2/g). The specific surface area is measured by BET specific surface area measurement method.