Positive Electrode Active Material Core-Shell Particle Densification
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Solution Overview
Problem
Lithium transition metal oxide positive electrode active materials used in secondary batteries face challenges with low thermal stability and mechanical strength, leading to issues such as battery rupture and reduced capacity due to the decomposition of materials during charging and external pressure.
Innovation Solution
A method of manufacturing a positive electrode active material with a core-shell structure, where the shell portion has a higher crystal grain size ratio in the (100) plane to the (001) plane, resulting in smaller average particle diameter and increased particle density, enhancing mechanical strength and lithium mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel composite metal oxide is used to achieve high reversible capacity, then battery capacity is improved, but thermal stability deteriorates
Solution Approach 1:
The patent uses composite materials by combining lithium nickel composite metal oxide with lithium cobalt composite metal oxide or lithium manganese composite metal oxide. The nickel-rich phase provides high reversible capacity while the cobalt or manganese phases provide thermal stability, creating a synergistic composite that resolves the contradiction between capacity and thermal stability.
2Quantity of substance
If LiCoO2 is used to achieve high operating voltage and excellent capacity characteristics, then battery performance is improved, but mechanical strength deteriorates due to unstable crystal structure
Solution Approach 1:
The patent creates a composite material where LiCoO2 or lithium manganese composite metal oxide is combined with lithium nickel composite metal oxide. The LiCoO2 or manganese phase provides structural stability and mechanical strength, while the nickel phase contributes to capacity characteristics, resolving the contradiction between capacity and mechanical strength.
3Ease of manufacture
If positive electrode active material precursor is fired to synthesize lithium transition metal oxide, then material is formed, but particle size increases leading to reduced energy density
Solution Approach 1:
The patent applies preliminary action by pre-forming the positive electrode active material precursor with a controlled core-shell structure before firing. The precursor is prepared with specific crystal grain orientation and particle morphology that are maintained or improved during the firing process, allowing material formation while controlling final particle size to reduce energy density loss.
4Quantity of substance
If lithium transition metal oxide with high Ni content is used, then reversible capacity is improved, but particle strength deteriorates under external pressure
Solution Approach 1:
The patent uses composite materials where lithium nickel composite metal oxide (providing high reversible capacity) is combined with lithium cobalt composite metal oxide or lithium manganese composite metal oxide (providing mechanical strength). The composite structure allows the nickel-rich particles to maintain high capacity while the other phases reinforce particle strength under external pressure.
Data Source
AI summary
Provided is a method of manufacturing a positive electrode active material, which includes: (A) preparing a positive electrode active material precursor which includes a core portion including randomly aggregated primary particles and a shell portion surrounding the core portion and formed of primary particles oriented in a direction from a particle center to the outside and in which a ratio of a crystal grain size in the (100) plane to a crystal grain size in the (001) plane of the primary particles forming the shell portion is 3 or more; and (B) mixing the positive electrode active material precursor with a lithium-containing raw material and firing the mixture, wherein the lithium transition metal oxide has an average particle diameter (D50) that is 0.01% to 20% reduced as compared to an average particle diameter (D50) of the positive electrode active material precursor.