Lithium Composite Oxide C2/m Crystal Structure for Battery Stability
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Solution Overview
Problem
Conventional lithium-ion batteries with lithium composite oxides having a crystal structure belonging to the space group R-3m suffer from insufficient cation mixing, leading to unstable crystal structures and reduced capacity and cycle characteristics due to excessive oxygen desorption during charging.
Innovation Solution
A positive-electrode active material with a lithium composite oxide having a crystal structure belonging to the space group C2/m, incorporating elements like F, Cl, N, or S, which stabilizes the structure by promoting cation-anion interaction and increasing cation mixing, thereby enhancing lithium diffusibility and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium composite oxide with R-3m crystal structure is used, then capacity can be increased, but crystal structure stability deteriorates due to insufficient cation mixing and excessive oxygen desorption
Solution Approach 1:
The patent changes the crystal structure parameter from R-3m space group to C2/m space group by controlling the integrated intensity ratio I(001)/I(131) to be 0.05 or less. This parameter change fundamentally alters the cation mixing characteristics and oxygen desorption behavior, achieving both high capacity and structural stability simultaneously
Solution Approach 2:
The patent creates a composite material system with specific elemental composition (Li, Mn, Co, Ni, O) arranged in a C2/m crystal structure. The specific ratio of elements and their spatial arrangement in the C2/m structure produces synergistic effects that enhance both capacity and stability compared to conventional R-3m structures
2Reliability
If cation mixing is increased to stabilize crystal structure, then discharge capacity and operating voltage improve, but manufacturing precision requirements increase due to specific XRD pattern control
Solution Approach 1:
The patent establishes a feedback mechanism where the XRD pattern (specifically I(001)/I(131) ratio) serves as a quantitative indicator of cation mixing degree. By measuring this ratio and adjusting synthesis parameters accordingly, manufacturers can control the crystal structure to achieve desired performance with predictable outcomes
Solution Approach 2:
The patent transforms the complex multi-parameter synthesis control into a single critical parameter control: the integrated intensity ratio I(001)/I(131). By focusing on this one parameter, the manufacturing process becomes more manageable while ensuring consistent high performance
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 composite oxide with a C2/m structure and specific integrated intensity ratios improves the discharge capacity, operating voltage, and cycle characteristics by maintaining a stable crystal structure even during extensive lithium deintercalation, resulting in higher-capacity batteries with better performance.
Implementation Method 1
stabilizes the structure by promoting cation-anion interaction
Implementation Method 2
an X-ray diffraction (XRD) pattern of the lithium composite oxide comprises a first peak within the first range of 44 degrees to 46 degrees of a diffraction angle 2θ and a second peak within the second range of 18 degrees to 20 degrees of the diffraction angle 2θ
Data Source
AI summary
A positive-electrode active material contains a lithium composite oxide containing at least one selected from the group consisting of F, Cl, N, and S. The crystal structure of the lithium composite oxide belongs to a space group C2/m. An XRD pattern of the lithium composite oxide comprises a first peak within the first range of 44 degrees to 46 degrees of a diffraction angle 2θ and a second peak within the second range of 18 degrees to 20 degrees of the diffraction angle 2θ. The ratio of the second integrated intensity of the second peak to the first integrated intensity of the first peak is within a range of 0.05 to 0.90.