Lithium-Rich Cathode Material Crystal Structure Control
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Solution Overview
Problem
Lithium rich cathode active materials for lithium ion secondary batteries suffer from a decrease in discharge capacity during repeated charge and discharge cycles, failing to maintain high performance.
Innovation Solution
A cathode active material comprising a lithium-containing composite oxide with a specific chemical formula, aLi(Li1/3Mn2/3)O2.(1−a)LiMO2, where M includes Ni and Mn, and a controlled X-ray diffraction pattern integral breadth of the (110) plane, is used to enhance discharge capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium rich cathode active material is used to increase discharge capacity, then discharge capacity is improved, but discharge capacity decreases during repeated charge and discharge cycles
Solution Approach 1:
The patent changes the crystal structure parameters by controlling the integral breadth of the (110) plane peak in the C2/m phase to be at most 1.25 degrees. This parameter control optimizes the lattice structure to accommodate lithium ion insertion/extraction while maintaining structural stability during repeated cycles, thereby preserving discharge capacity.
Solution Approach 2:
The patent employs a composite oxide material with dual-phase structure (C2/m and R-3m space groups) where the specific combination and proportion of phases creates a synergistic effect. The C2/m phase provides high capacity while the R-3m phase contributes to structural stability, and their composite structure prevents capacity fade during cycling.
2Quantity of substance
If lithium rich cathode active material composition is used to achieve high discharge capacity, then discharge capacity is improved, but structural stability during cycling deteriorates
Solution Approach 1:
The patent precisely controls the integral breadth parameter of the (110) plane diffraction peak to be at most 1.25 degrees, which corresponds to optimal crystal lattice ordering and domain size. This parameter optimization ensures the crystal structure maintains its integrity during lithium ion insertion and extraction, preventing structural degradation while preserving high discharge capacity.
Solution Approach 2:
The patent creates local structural optimization within the crystal lattice by ensuring the C2/m phase has specific diffraction characteristics (integral breadth ≤1.25°), which indicates well-ordered local atomic arrangements. This local structural quality in the active material domains provides stable pathways for lithium ion transport while maintaining overall structural stability during cycling.
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 results in a lithium ion secondary battery with high discharge capacity and minimal capacity decrease during charge and discharge cycles, improving cycle characteristics.
Implementation Method 1
in an X-ray diffraction pattern, the integral breadth of a peak of (110) plane assigned to a crystal structure with space group C2/m is at most 1.25 deg
Data Source
AI summary
To provide a cathode active material capable of obtaining a lithium ion secondary battery which has a high discharge capacity and of which a decrease of the discharge capacity when a charge and discharge cycle is repeatedly carried out is suppressed, a positive electrode for a lithium ion secondary battery, and a lithium ion secondary battery. A cathode active material comprising a lithium-containing composite oxide represented by the formula aLi(Li1/3Mn2/3)O2.(1−a)LiMO2 (wherein M is an element containing at least Ni and Mn, and 0<a<1), wherein in an X-ray diffraction pattern, the integral breadth of a peak of (110) plane assigned to a crystal structure with space group C2/m is at most 1.25 deg.