Composite Cathode Active Material Suppressing Additional Phases
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Solution Overview
Problem
Conventional cathode active materials for lithium batteries have limited electrical capacity and discharge life due to the formation of additional phases during the preparation process, which deteriorates their initial capacity and lifespan.
Innovation Solution
A method involving the controlled mixing of a transition metal source and a reducing agent to prepare a composite cathode active material precursor, followed by calcination with a lithium source, where the reducing agent is supplied in limited amounts to suppress the formation of additional phases, resulting in a lithium transition metal oxide with enhanced discharge capacity and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cathode active materials are used, then the battery can operate, but the electrical capacity and discharge life are limited due to formation of additional phases during preparation
Solution Approach 1:
A coating layer is formed on the surface of the cathode active material particles before they are assembled into electrodes. This preliminary protective action prevents the formation of harmful additional phases during subsequent high-temperature calcination and battery operation, thereby extending discharge life while maintaining electrical capacity.
Solution Approach 2:
A coating layer comprising at least one of an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of a coating element is introduced as an intermediary between the cathode active material and the environment. This coating layer acts as a protective barrier that prevents degradation and formation of additional phases during preparation and operation.
2Manufacturing precision
If the cathode active material is prepared without coating, then the preparation process is simple, but the initial capacity and lifespan deteriorate due to additional phase formation
Solution Approach 1:
The preparation method utilizes parameter changes during calcination - specifically, the coating layer is formed in-situ during the high-temperature calcination process (700-1000°C) by controlling the decomposition of precursor compounds. This approach achieves precise coating thickness and composition control through temperature and time parameters without requiring separate coating equipment.
3Duration of action of stationary object
If a coating layer is applied to protect the cathode active material, then discharge life improves, but the preparation process becomes more complex
Solution Approach 1:
The coating layer formation process is merged with the existing calcination process. The coating precursors are mixed with the cathode active material before calcination, and the coating layer is formed in-situ during the same high-temperature treatment used to synthesize the cathode material itself. This combines two processes into one, avoiding additional manufacturing steps.
Solution Approach 2:
The coating layer is formed through self-service mechanisms during calcination. The coating precursors decompose and react autonomously at the calcination temperature to form the protective coating layer without requiring external intervention or separate coating equipment. The system uses its own thermal energy to create the protective layer.
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 approach leads to a composite cathode active material with improved initial discharge capacity, high rate characteristics, and extended lifespan, characterized by secondary particles with a specific surface area of 3.0 m2/g or greater and an average particle diameter of 5 μm or less, formed by binding primary plate-shaped particles.
Implementation Method 1
mixing a transition metal source and a reducing agent to prepare a composite cathode active material precursor
Implementation Method 2
mixing and calcining the composite cathode active material precursor and a lithium source to prepare a lithium transition metal oxide
Data Source
AI summary
Provided are a method of preparing a cathode active material, a composite cathode active material, and a cathode and a lithium battery containing the composite cathode active material. The method includes mixing a transition metal source and a reducing agent to prepare a cathode active material precursor; and mixing and calcining the cathode active material precursor to prepare a lithium transition metal oxide, wherein a supplied amount of the reducing agent is about 0.003 mole/hr or less with respect to 1 mole/hr of a supplied amount of the transition metal source.