Lithium Composite Oxide Cathode High Voltage Cycle Life
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Solution Overview
Problem
Lithium ion secondary batteries using existing lithium-containing composite oxides with Ni, Co, and Mn suffer from insufficient cycle characteristics when charged at high voltages due to the lack of durability improvement in the interior composite oxide, despite surface modifications.
Innovation Solution
A lithium-containing composite oxide with a specific formula (LiaNibCocMndMeO2) and structural characteristics, including a layered rock salt crystal structure with space group R-3m, is developed, which enhances the durability against high voltage charging by optimizing the ratio of integrated intensities in X-ray diffraction patterns and crystallite size, thereby improving cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the lithium ion secondary battery is charged at a high voltage of at least 4.5 V vs Li+/Li to increase energy density, then the energy density is improved, but the cycle characteristics become insufficient due to poor durability of the interior lithium-containing composite oxide
Solution Approach 1:
The patent applies local quality by creating a surface layer with high manganese content (manganese portion) that has different properties from the interior. This surface layer with specific composition ratio (Ni:Co:Mn = b2:c2:d2 where b2+c2+d2=1 and 0<d2<1) provides localized protection against high voltage charging, improving cycle characteristics while maintaining high energy density capability
Solution Approach 2:
The patent uses composite materials by combining lithium-containing composite oxide with specific crystal structure (space group R-3m) and a surface layer containing high manganese portion. The composite structure integrates the high voltage charging capability of the interior oxide with the protective surface layer, achieving both high energy density and good cycle characteristics
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 lithium-containing composite oxide achieves favorable cycle characteristics and high discharge capacity even when charged at high voltages, leading to a more stable lithium ion secondary battery performance.
Implementation Method 1
in an X-ray diffraction pattern obtained by reflection X-ray diffraction employing Cu-Kα rays, the ratio (I104/I110) of the integrated intensity (I104) of a peak of (104) plane assigned to a crystal structure with space group R-3m to the integrated intensity (I110) of a peak of (110) plane assigned to a crystal structure with space group R-3m is at least 4.20
Data Source
AI summary
To provide a lithium-containing composite oxide, a cathode active material and a positive electrode for a lithium ion secondary battery, with which a lithium ion secondary battery having favorable cycle characteristics even when charged at a high voltage can be obtained; and a lithium ion secondary battery having favorable cycle characteristics even when charged at a high voltage. A lithium-containing composite oxide which is represented by LiaNibCocMndMeO2 wherein M is Mg, Ca, Al, Ti, V, Nb, Mo, W or Zr, a+b+c+d+e=2, “a” is from 1.01 to 1.10, b is from 0.30 to 0.95, c is from 0 to 0.35, d is from 0 to 0.35, and e is from 0 to 0.05, wherein in an X-ray diffraction pattern obtained by reflection X-ray diffraction employing Cu-Kα rays, the ratio (I104/I110) of the integrated intensity (I104) of a peak of (104) plane to the integrated intensity (I110) of a peak of (110) plane is at least 4.20.