NMC Hydroxide Precursor Purification for Low-Sodium Cathode Particles
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Solution Overview
Problem
Existing lithium nickel manganese cobalt composite oxides used in secondary batteries suffer from impurities such as sodium, sulfate, and chloride radicals, which degrade battery performance by inhibiting lithium diffusion, reducing capacity, and causing particle aggregation, leading to decreased output and safety issues.
Innovation Solution
A method for producing nickel manganese cobalt composite hydroxide as a precursor, involving a crystallization process with an alkaline carbonate solution and a washing step using ammonium hydrogen carbonate, effectively reduces impurity levels, particularly sodium, to less than 0.0005% by mass, and controls particle size and structure to enhance battery characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional production methods are used to manufacture lithium nickel manganese cobalt composite oxide, then production cost and process simplicity are maintained, but impurities such as sodium, sulfate, and chloride radicals remain in the product, causing harmful effects on battery performance
Solution Approach 1:
The patent applies preliminary action by performing a washing treatment on the nickel manganese cobalt composite hydroxide precursor before the firing process. This washing step removes impurities such as sodium, sulfate, and chloride radicals from the precursor material, preventing them from being incorporated into the final lithium nickel manganese cobalt composite oxide product. By addressing impurity removal in advance, the patent ensures high battery performance without requiring complex post-processing or sacrificing production simplicity.
2Manufacturing precision
If impurities are not removed from the nickel manganese cobalt composite hydroxide precursor, then production process complexity is minimized, but the crystallinity of the lithium nickel manganese cobalt composite oxide decreases due to side reactions induced by impurities
Solution Approach 1:
The patent performs the washing treatment as a preliminary step before firing, removing impurities that would otherwise cause side reactions during the high-temperature synthesis process. This preliminary purification ensures that the lithium nickel manganese cobalt composite oxide forms with high crystallinity and proper layered structure, while the washing process itself is simple and does not significantly increase production process complexity.
3Quantity of substance
If impurities are present in the lithium nickel manganese cobalt composite oxide, then production cost is reduced, but lithium diffusion in the solid phase is inhibited, decreasing battery capacity
Solution Approach 1:
The patent removes impurities from the nickel manganese cobalt composite hydroxide precursor through washing before the firing process. This preliminary removal prevents impurities from being present in the final lithium nickel manganese cobalt composite oxide product, thereby ensuring that lithium diffusion in the solid phase is not inhibited and battery capacity is maximized. The washing step is simple and does not significantly increase production cost.
4Power
If impurities such as sodium are not removed from the precursor, then production process simplicity is maintained, but particles of lithium nickel manganese cobalt composite oxide aggregate by sintering, deteriorating reactivity and output characteristic
Solution Approach 1:
The patent performs a washing treatment on the nickel manganese cobalt composite hydroxide precursor before firing to remove impurities such as sodium. This preliminary removal prevents particle aggregation by sintering during the high-temperature synthesis process, ensuring that the final product maintains good reactivity and output characteristics. The washing step is simple and does not significantly increase production process complexity.
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 resulting nickel manganese cobalt composite hydroxide and lithium nickel manganese cobalt composite oxide exhibit improved battery capacity, reduced aggregation, and enhanced safety, with sodium content minimized, leading to higher energy density and stability in lithium ion secondary batteries.
Implementation Method 1
a crystallization process with an alkaline carbonate solution
Implementation Method 2
a washing step using ammonium hydrogen carbonate, effectively reduces impurity levels
Data Source
AI summary
A nickel manganese cobalt composite hydroxide, which is a precursor of a positive electrode active material, and which is composed of secondary particles to which primary particles containing a nickel, a manganese, and a cobalt are aggregated, or composed of the primary particles and the secondary particles, wherein a sodium content contained in the nickel manganese cobalt composite hydroxide is less than 0.0005% by mass. Also, a ratio of an average particle size of a lithium nickel manganese cobalt composite oxide divided by an average particle size of the nickel manganese cobalt composite hydroxide, which is a precursor, is 0.95 to 1.05, and further, when observing 100 or more particles of the lithium nickel manganese cobalt composite oxide selected randomly by a scanning electron microscope, a number that an aggregation of secondary particles is observed is 5% or less with respect to a total number of observed secondary particles.