Single-Crystal Cathode Active Material for Crack-Stable Li Batteries
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Solution Overview
Problem
Lithium secondary batteries face issues with mechanical and chemical stability, particularly at high temperatures, due to cracks in lithium metal oxide particles during the manufacturing process and intercalation/deintercalation, leading to reduced lifespan and discharge capacity.
Innovation Solution
A cathode for lithium secondary batteries is developed with lithium metal oxide particles having a single-particle shape and single-crystalline or poly-crystalline structure, where the average crystal size is controlled within specific ranges to enhance mechanical and chemical stability, and a method involving multiple calcination cycles is used to prepare the cathode active material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium metal oxide particles with secondary particle shape and polycrystalline structure are used, then manufacturing process is simpler, but cracks occur during pressing and intercalation/deintercalation leading to reduced stability and lifespan
Solution Approach 1:
The patent changes the crystallographic parameters by transitioning from polycrystalline to single-crystalline structure, and controls crystal size within 0.3-2.0 μm range. This parameter change eliminates grain boundaries that cause cracking while maintaining manufacturability through controlled synthesis methods
Solution Approach 2:
The patent creates a composite structure where single-crystalline lithium metal oxide particles are coated with protective layers (such as lithium phosphate or other stable compounds). This composite approach enhances mechanical and chemical stability without significantly increasing structural complexity
2Strength
If single-particle shape particles are used, then crack resistance improves, but manufacturing precision requirements increase due to specific crystal size and structure control
Solution Approach 1:
The patent establishes specific parameter ranges for crystal size (0.3-2.0 μm) and employs controlled calcination processes with precise temperature and time parameters. These parameter specifications enable reproduction of single-crystalline structures with desired properties while maintaining manufacturing feasibility
Solution Approach 2:
The patent employs preliminary calcination treatments and precursor preparation steps that pre-form the crystal structure before final particle formation. This preliminary action ensures single-crystalline structure development and size control are achieved during manufacturing rather than requiring post-processing
3Strength
If larger crystal sizes are used, then mechanical stability improves, but discharge capacity and power properties deteriorate
Solution Approach 1:
The patent optimizes crystal size within the specific range of 0.3-2.0 μm, balancing mechanical stability and electrochemical performance. This parameter optimization ensures sufficient crystal size for stability while maintaining small enough dimensions for adequate lithium ion diffusion and electrical conductivity
Solution Approach 2:
The patent employs partial crystallization control where not all regions of the particle are fully crystallized, or uses slightly smaller crystal sizes than the theoretical maximum for stability. This partial approach prevents excessive crystal growth that would harm power properties while achieving sufficient mechanical stability
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 provides improved mechanical and chemical stability, maintaining high discharge capacity and power properties while extending the battery's lifespan and enhancing high-temperature performance.
Implementation Method 1
a first calcination of the mixture is performed at a first temperature. A second calcination of a product from the first calcination is performed at a second temperature lower than the first temperature.
Data Source
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AI summary
A cathode (100) for a lithium secondary battery includes a cathode current collector, and a cathode active material layer (110) satisfying a specific formula formed on the cathode current collector (105). The cathode active material layer (110) includes lithium metal oxide particles that have a single-particle shape, and a single-crystalline structure or a poly-crystalline structure including two or more single crystals. A lithium secondary battery including the cathode (100), and a method of preparing a cathode active material are also provided.