Lithium-Nickel Composite Oxide Core-Shell Design for Battery Capacity and Thermal Stability
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Solution Overview
Problem
Current lithium-nickel composite oxides for non-aqueous electrolyte secondary batteries face challenges in achieving high capacity and output while maintaining thermal stability, as replacing nickel with other elements either reduces capacity or complicates synthesis due to cation mixing, and existing washing processes do not adequately address these requirements.
Innovation Solution
A lithium-nickel composite oxide with a specific composition (LibNi1-x-yCoxMyO2) is developed, where M is Al, Ti, Mn, or W, and the c-axis length is optimized to 14.185 angstroms, with controlled porosity and occupancy, allowing for improved thermal stability and ion release/insertion, and a process involving calcining and water washing is used to produce the active material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel content in lithium-nickel composite oxide is increased to achieve high capacity, then charge and discharge capacity is improved, but thermal stability deteriorates
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core region contains high nickel content (0.8-0.95) for high capacity, while the outer shell region contains lower nickel content (0.6-0.8) for thermal stability. This spatial differentiation of composition allows simultaneous optimization of both capacity and thermal stability properties in different regions of the same particle.
Solution Approach 2:
The patent uses composite materials by combining nickel-rich and nickel-poor regions within a single composite oxide structure (LiNi1-x-yCoxMyO2). The composite nature allows the material to exhibit both high capacity characteristics from the nickel-rich core and thermal stability from the nickel-poor shell, resolving the contradiction between these two properties.
2Stability of the object's composition
If nickel is replaced with other elements to improve thermal stability, then thermal stability is improved, but charge and discharge capacity is reduced
Solution Approach 1:
The patent applies local quality by concentrating the nickel substitution elements (Co and Mn) in the outer shell region rather than uniformly distributing them throughout the particle. This localized substitution maintains thermal stability where needed (at the surface) while preserving high nickel content and capacity in the inner core region.
Solution Approach 2:
The patent changes the spatial distribution parameter of nickel substitution, creating a gradient from high nickel content in the core to lower nickel content in the shell. This parameter change allows the material to achieve both high capacity (from core nickel) and thermal stability (from shell substitution) simultaneously.
3Stability of the object's composition
If conventional washing process is used to improve thermal stability, then thermal stability is improved, but manufacturing complexity increases and capacity is reduced
Solution Approach 1:
The patent applies preliminary action by incorporating the thermal stability function directly into the material synthesis step itself, rather than requiring a separate post-synthesis washing treatment. The controlled atmospheric calcination process simultaneously achieves capacity retention and thermal stability improvement, eliminating the need for additional manufacturing steps.
Solution Approach 2:
The patent extracts the thermal stability enhancement function from the separate washing process and integrates it into the calcination process. By controlling the calcination atmosphere and parameters, the material achieves inherent thermal stability without requiring extraction of excess lithium or other post-treatments.
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 enables a non-aqueous electrolyte secondary battery with high capacity, high output, and improved safety by enhancing crystallinity and reducing cation mixing, while maintaining thermal stability and facilitating lithium ion transfer.
Implementation Method 1
calcining the resulting mixture
Implementation Method 2
the lithium nickel oxide has a crystal structure
Implementation Method 3
washing with water after calcining
Data Source
AI summary
The purpose of the present invention is to provide a positive-electrode active material for non-aqueous electrolyte secondary batteries that is capable of achieving both a high capacity and a high output. This positive-electrode active material contains a lithium-nickel composite oxide represented by the general formula: LibNi1-x-yCoxMyO2 wherein M represents at least one element selected from Al, Ti, Mn and W, b is 0.95≤b≤1.03, x is 0<x≤0.15, y is 0<y≤0.07, and x and y is x+y≤0.16, wherein c-axis length of the lithium-nickel composite oxide is 14.185 angstrom or greater as determined by a Rietveld analysis of X-ray diffraction.