Nickel-Rich Cathode Oxide Adhesion for Thermal and Cycle Stability
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Solution Overview
Problem
Existing positive electrode active materials for lithium ion batteries, such as Li(Ni, Co, Al)O2 and Li(Ni, Co, Mn)O2, face issues with thermal stability and cycle characteristics due to inefficient surface modification with elements like Zr, W, and Nb, leading to poor adherence and independent particle formation, which affects battery performance.
Innovation Solution
A positive electrode active material composition of LiaNibCOcMndMeOf, where 1.0≤a≤1.05, 0.8≤b≤0.9, b+c+d+e=1, 1.8≤f≤2.2, and 0.0025≤e/(b+c+d+e)≤0.016, with M being Zr, Ta, or W, is developed, ensuring oxide adherence through a wet process mixing and firing method to improve cycle characteristics and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface modification with elements like Zr, W, and Nb is performed by kneading oxides simultaneously with lithium source in a dry process, then the positive electrode active material can be produced, but the different elements do not adhere efficiently to the precursor surface, resulting in independent particles that do not improve battery characteristics
Solution Approach 1:
The patent uses a slurry as an intermediary medium to facilitate the uniform distribution and adherence of different element oxides (Zr, W, Nb) to the precursor surface. The slurry contains the oxides dispersed in a liquid carrier, allowing them to be evenly distributed and adhere to the precursor before drying and firing, thereby eliminating independent particles and improving battery characteristics.
Solution Approach 2:
The patent changes the physical state of the mixing process from dry to wet (using slurry), and controls the particle size of the different element oxides to 10 μm or less. These parameter changes enable efficient adherence of the oxides to the precursor surface, preventing formation of independent particles and ensuring uniform distribution throughout the positive electrode active material.
2Use of energy by moving object
If high Ni ratio materials like Li(Ni, Co, Al)O2 and Li(Ni, Co, Mn)O2 are used to increase energy density, then the energy consumption and cruising distance problems are addressed, but thermal stability and cycle characteristics deteriorate
Solution Approach 1:
The patent creates a composite material structure where different element oxides (Zr, W, Nb) are incorporated into the high Ni ratio positive electrode active material matrix. This composite structure maintains the high energy density of the nickel-rich material while the dispersed oxide particles provide thermal stability and improve cycle characteristics by suppressing degradation reactions.
Solution Approach 2:
The patent applies local quality modification by distributing different element oxides throughout the positive electrode active material at specific concentrations (0.0025≤e/(b+c+d+e)≤0.016). These localized modifications of the material composition provide thermal stability and improved cycle characteristics while maintaining the overall high energy density of the nickel-rich material.
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 enhanced battery characteristics by ensuring efficient adherence of oxides to the surface of positive electrode active material particles, improving cycle and thermal stability, and maintaining discharge capacity, as demonstrated by WDX mapping analysis and battery performance metrics.
Implementation Method 1
WDX mapping analysis of positive electrode active material particles in a field of view of 50 μm×50 μm by FE-EPMA indicates that an oxide of M adheres to surfaces of the positive electrode active material particles
Implementation Method 2
mixing at least one selected from an oxide of Zr, an oxide of Ta and an oxide of W, which has a 50% cumulative volume particle size D50 of 1 μm or less, with the precursor of the positive electrode active material for lithium ion batteries in a wet process
Implementation Method 3
mixing the mixture with a lithium source in a dry process and firing it at 700° C. or more for 4 hours or more
Data Source
AI summary
A positive electrode active material for lithium ion batteries, the positive electrode active material being represented by a composition shown in the following formula (1):LiaNibCOcMndMeOf (1)in which formula (1), 1.0≤a≤1.05, 0.8≤b≤0.9, b+c+d+e=1, 1.8≤f≤2.2, 0.0025≤e/(b+c+d+e)≤0.016, and M is at least one selected from Zr, Ta and W;wherein WDX mapping analysis of positive electrode active material particles in a field of view of 50 μm×50 μm by FE-EPMA indicates that an oxide of the M adheres to surfaces of the positive electrode active material particles, and the oxide of the M is not present as independent particles that do not adhere to the surfaces of the positive electrode active material particles.