Al-W Coated Cathode Active Material for High-Voltage Li Diffusion
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Solution Overview
Problem
Lithium composite transition metal oxides in the form of single particles face challenges with high lithium diffusion resistance, non-uniform ion movement, and rapid performance degradation at high voltages and temperatures due to rock salt phase formation and structural instability.
Innovation Solution
A positive electrode active material is developed with a lithium composite transition metal oxide in the form of single or pseudo-single particles, coated with aluminum (Al) and tungsten (W), where the nickel content and BET specific surface area are optimized within specific ranges to enhance particle strength and stability, thereby improving high-temperature and high-voltage performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a lithium composite transition metal oxide in the form of a single particle is used, then particle strength is improved and particle breakage is reduced, but lithium diffusion resistance increases due to fewer interfaces between primary particles
Solution Approach 1:
The single particle is segmented into multiple primary particles (nodules) that are sintered together to form a composite structure. This segmentation creates internal interfaces that serve as lithium ion diffusion paths, improving lithium mobility while maintaining the overall single-particle structure for high strength and low breakage.
2Object-generated harmful factors
If a lithium composite transition metal oxide in the form of a single particle is used, then gas generation is reduced, but lifespan properties degrade due to crystal structure deformation from non-uniform lithium-ion movement
Solution Approach 1:
The particle is divided into multiple small primary particles (10-50 nm) that are sintered together. This segmentation enables uniform lithium ion movement across the particle structure, preventing crystal structure deformation and extending lifespan, while the overall single-particle morphology reduces gas generation.
Solution Approach 2:
Different regions of the particle have different structures: the core consists of sintered primary particles with internal interfaces for uniform ion movement, while the outer surface maintains a compact single-particle structure to minimize gas generation and electrolyte contact.
3Power
If the voltage is increased to exceed 4.35V, then battery capacity is improved, but side reactions with electrolyte become severe and transition metal ions are eluted
Solution Approach 1:
A coating layer is introduced as an intermediary between the lithium composite transition metal oxide and the electrolyte. This coating layer prevents direct contact and harmful side reactions at high voltages above 4.35V, while allowing the high-voltage operation to maintain battery capacity.
Data Source
AI summary
A positive electrode active material includes a lithium composite transition metal oxide in the form of a single particle composed of one single nodule and/or in the form of a pseudo-single particle, which is a composite of 30 or less nodules, and a coating layer formed on the surface of the lithium composite transition metal oxide particle. The coating layer contains aluminum (Al) and tungsten (W). The positive electrode active material satisfies Equation 1 below:45≤X×X′≤56 [Equation 1]wherein, X is the content of nickel among all metals except for lithium in the lithium composite transition metal oxide (unit: mol %), and X′ is the BET specific surface area of the positive electrode active material (unit: m2/g).