Lithium Composite Oxide Core-Shell Structure for Battery Safety
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Solution Overview
Problem
Lithium secondary batteries using lithium-containing composite oxides as cathode active materials face challenges in achieving high volume capacity density, safety, cyclic properties, and low temperature characteristics, with existing solutions not fully satisfying these requirements.
Innovation Solution
A process for producing lithium-containing composite oxides represented by the formula LipNxMyOzFa, involving the firing of a mixture containing lithium, N (Co, Mn, Ni) and M (Al, alkaline earth metals) sources, with optional fluorine, and subsequent treatment with Zr or Ti-containing solutions to achieve high surface concentration of these elements, stabilizing the structure and enhancing properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LiCoO2 is used as cathode active material to achieve high voltage (4V) and high energy density, then voltage and energy density are improved, but volume capacity density and safety are insufficient
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the interior maintains high-Co content for energy density while the surface has modified composition (with Al, Ti, Zr, or Nb additions) for safety and stability. This spatial differentiation of material properties resolves the contradiction between energy density and safety.
Solution Approach 2:
The patent uses composite materials by combining LiCoO2 with other metal oxides (LiAlO3, LiTiO3, LiZrO3, or LiNbO3) to create a composite cathode material. This composite approach allows simultaneous achievement of high energy density from LiCoO2 and improved safety/stability from the composite phases.
2Reliability
If particle size of LiCoO2 is controlled to improve coating properties and cyclic properties, then cyclic properties are improved, but volume capacity density is not fully satisfactory
Solution Approach 1:
The patent applies parameter changes by precisely controlling particle size within 5-20 μm and adjusting the ratio of fine to coarse particles (0.2-2.0 by volume). It also modifies the crystal structure through chemical composition control (Co content 70-90 mol%) to optimize both cyclic properties and volume capacity density simultaneously.
3Reliability
If Co atoms are replaced with W, Mn, Ta, Ti or Nb to improve cyclic properties, then cyclic properties are improved, but volume capacity density and weight capacity density are not fully satisfactory
Solution Approach 1:
The patent applies local quality by concentrating the dopant elements (Ti, Zr, Nb, or Al) at the particle surface through the core-shell structure, while maintaining high-Co content in the interior. This surface-localized modification improves cyclic properties without significantly reducing volume capacity density.
Solution Approach 2:
The patent optimizes the dopant concentration at specific ranges (0.1-5.0 mol% for Ti, Zr, or Nb; 0.1-10.0 mol% for Al) and controls particle size parameters to achieve the balance between cyclic properties and volume capacity density, rather than using broad Co replacement ranges.
4Reliability
If hexagonal LiCoO2 with specific lattice constants is used to improve cyclic properties, then cyclic properties are improved, but volume capacity density and weight capacity density remain insufficient
Solution Approach 1:
The patent applies parameter changes by controlling the c-axis lattice constant to 14.04-14.06 Å (a narrow range) and optimizing particle size to 5-20 μm with specific volume distribution. These precise parameter controls achieve both improved cyclic properties and satisfactory volume capacity 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 resulting lithium-containing composite oxides exhibit improved volume capacity density, safety, cyclic durability, and low temperature characteristics, making them suitable for high-performance lithium secondary batteries.
Implementation Method 1
firing of a mixture containing lithium, N (Co, Mn, Ni) and M (Al, alkaline earth metals) sources, with optional fluorine
Implementation Method 2
firing of a mixture containing lithium, N (Co, Mn, Ni) and M (Al, alkaline earth metals) sources, with optional fluorine
Implementation Method 3
subsequent treatment with Zr or Ti-containing solutions to achieve high surface concentration of these elements
Data Source
AI summary
To provide a process for producing a lithium-containing composite oxide for a positive electrode of a lithium secondary battery, which has a large volume capacity density, high safety, excellent durability for charge and discharge cycles and excellent low temperature characteristics.