Lithium-Rich Layered Oxide Cathode with Phase Gradient
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Solution Overview
Problem
Current lithium-ion battery cathode materials have low specific capacity, limiting the energy density of lithium-ion batteries, and existing materials are costly and environmentally unfriendly.
Innovation Solution
A lithium-rich layered oxide material with a phase structure gradient is synthesized using a coprecipitation-solid phase synthesis method, featuring a core-shell structure of xLi2MnO3.(1−x)LiTMO2 and yLi2MnO3.(1−y)LiTMO2, where the monoclinic Li2MnO3 structural unit is gradually reduced from the center to the surface, and the rhombohedral LiTMO2 structure is gradually increased, enhancing discharge capacity and cyclic stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional cathode materials (layered lithium cobalt oxide, lithium nickelate oxide, etc.) are used, then the battery can operate reliably, but the specific capacity remains below 200 mAh/g, limiting energy density improvement
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the surface layer has different composition and properties than the core. The surface layer is enriched with Li2MnO3 phase to improve stability, while the core maintains higher capacity characteristics, thus achieving both high specific capacity and structural stability simultaneously
Solution Approach 2:
The patent uses composite materials by combining Li2MnO3 and LiTMO2 phases in a core-shell configuration. This composite structure leverages the stability of Li2MnO3 on the surface and the high capacity of LiTMO2 in the core, resolving the contradiction between reliability and specific capacity
2Quantity of substance
If lithium-rich manganese-based cathode material is used to achieve high specific capacity (300-350 mAh/g), then energy density can reach 1000 Wh/Kg, but the material structure becomes complex requiring precise phase composition control
Solution Approach 1:
The patent segments the cathode material into distinct core and shell regions with different phase compositions. The core contains LiTMO2-rich phase for high capacity, while the shell contains Li2MnO3-rich phase for stability. This segmentation simplifies the overall structure control by dividing the complex phase composition into manageable regions with clear functional assignments
Solution Approach 2:
The patent employs parameter changes by controlling the molar ratio of Li2MnO3 to LiTMO2 in different regions of the cathode material. By adjusting this compositional parameter in the core-shell structure, the material achieves optimal balance between capacity and stability without requiring complex multi-phase compositions throughout the entire structure
3Quantity of substance
If Li2MnO3 is used to stabilize material structure and provide extra capacity at high voltage, then specific discharge capacity reaches 300-350 mAh/g, but the preparation process requires precise control of synthesis conditions
Solution Approach 1:
The patent applies preliminary action by pre-forming the core-shell structure with appropriate phase distribution before final sintering. The coprecipitation step creates a precursor with the desired core-shell morphology and phase composition, which then guides the final material formation during sintering, reducing the complexity of synthesizing the exact final structure directly
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-rich layered oxide material achieves a high discharge capacity greater than 250 mA/g at 25° C., improving cyclic stability and safety while being cost-effective and environmentally friendly, with a simple and controllable preparation process suitable for large-scale industrialization.
Implementation Method 1
A method for making a lithium-rich layered oxide material with a phase structure gradient is disclosed, the method being a coprecipitation-solid phase synthesis method
Data Source
AI summary
A lithium-rich layered oxide material with a phase structure gradient and method for making the same are disclosed, used as cathode material for lithium ion battery. The invention has the following technical features: the spherical granule-shaped lithium-rich layered oxide material contains two types of structural units whose ratio gradually changes from the center to the surface of the spherical granule, wherein the monoclinic Li2MnO3 structural unit is gradually reduced, and the rhombohedral LiTMO2 structural unit is gradually increased from the center to the surface of the spherical granule. By controlling the ratio of the monoclinic Li2MnO3 structural unit versus the rhombohedral LiTMO2 structural unit along from the center to the surface the spherical granule, the performance of the Lithium-rich layered oxide materials as cathode for lithium ion battery, such as cyclic stability, specific discharge capacity, safety and other properties, is improved. The preparation process is simple and easy to control, the cost of raw materials is low and the environment is friendly. It can be industrialized on a large scale and has a good prospect of application.