Lithium Transition Metal Composite Oxide Surface Layer for Gas Suppression
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries, such as lithium ion batteries, face challenges in reducing gas generation during high-temperature storage, which affects their volume stability and performance, as existing technologies like JP 2002-075367A, JP 2000-315502A, and JP 2009-146739A are insufficient in achieving the required reduction in gas generation.
Innovation Solution
A positive electrode active material with core particles of lithium transition metal composite oxide, represented by LiaNi1−x−yCoxM1yM2O2, where M1 includes Mn or Al and M2 includes Zr, Ta, or Mo, with a surface layer containing boron, tungsten, and oxygen, formed through heat-treating core particles with boron oxide or its compounds and tungsten oxide, reducing gas generation and improving output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a lithium transition metal composite oxide is used as a positive electrode active material, then high charge-discharge capacity is achieved, but gas generation increases during high-temperature storage
Solution Approach 1:
The patent applies local quality by creating a surface layer with specific composition (containing W, Mo, Nb, or Ta) on the positive electrode active material particles. This surface layer has different chemical properties than the bulk material, providing localized protection against gas-generating reactions while preserving the high-capacity bulk composition. The surface layer acts as a barrier that selectively prevents harmful interactions at the particle surface during high-temperature storage.
Solution Approach 2:
The patent employs composite materials by combining the lithium transition metal composite oxide core with a surface layer containing specific elements (W, Mo, Nb, or Ta). This composite structure integrates the high capacity benefits of the lithium transition metal oxide with the thermal stability and gas-suppression properties of the surface layer elements, resolving the contradiction between capacity and gas generation.
2Reliability
If cobalt is used as a constituent component of raw material for lithium cobalt oxide, then high performance is achieved, but costs increase and supply anxiety arises due to scarce resources
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the positive electrode active material. Specifically, it uses lithium transition metal composite oxides where transition metals other than cobalt (such as Ni, Co, Mn combinations with specific ratios) are employed, and incorporates surface layer elements (W, Mo, Nb, Ta). This compositional parameter adjustment maintains electrochemical performance while reducing dependence on scarce cobalt resources.
3Reliability
If existing coating treatments are applied to lithium transition metal composite oxide, then some improvements are achieved, but gas generation during high-temperature storage is not sufficiently reduced
Solution Approach 1:
The patent applies parameter changes by specifically selecting and controlling the composition of the surface layer, containing elements W, Mo, Nb, or Ta at defined concentration ranges. This precise compositional parameter optimization provides superior gas suppression during high-temperature storage compared to conventional coating treatments, while maintaining high initial charge-discharge capacity and heat 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 proposed solution effectively reduces gas generation during high-temperature storage and enhances the output characteristics of nonaqueous electrolyte secondary batteries, making them suitable for severe operating environments and applications like electric vehicles.
Implementation Method 1
a surface layer located on a surface of the core particles, and the surface layer comprising boron, tungsten and oxygen; wherein the surface layer is obtained by heat-treating the core particles
Data Source
AI summary
The present invention provides a positive electrode active material for non-aqueous electrolyte secondary battery comprising:core particles comprising a lithium transition metal composite oxide represented by the general formula:LiaNi1−x−yCoxM1yM2zO2 wherein 1.00≤a≤1.50, 0.00≤x≤0.50, 0.00≤y≤0.50, 0.00≤z≤0.02, 0.00≤x+y≤0.70, M1 is at least one element selected from the group consisting of Mn and Al, M2 is at least one element selected from the group consisting of Zr, Ta, Nb and Mo, anda surface layer located on a surface of the core particles, the surface layer comprising lithium, boron, tungsten and oxygen.