NMC Composite Hydroxide Purification to Prevent Cathode Particle Aggregation
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Solution Overview
Problem
Existing lithium nickel manganese cobalt composite oxides used as positive electrode materials in lithium ion secondary batteries suffer from impurities such as sodium, sulfate, and chloride radicals, which decrease battery capacity, inhibit lithium diffusion, and cause particle aggregation, leading to reduced output and safety issues.
Innovation Solution
A nickel manganese cobalt composite hydroxide is produced with a sodium content less than 0.0005% by mass, using a crystallization process with an alkaline carbonate solution and a non-oxidizing atmosphere, followed by washing with ammonium hydrogen carbonate, to enhance specific surface area and inhibit sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional mixing and firing process is used to produce lithium nickel manganese cobalt composite oxide, then production efficiency is improved, but impurities (sodium, sulfate, chloride) deteriorate reaction with lithium and decrease crystallinity
Solution Approach 1:
The patent applies preliminary action by conducting a washing process before the firing step to remove impurities (sodium, sulfate, chloride) from the nickel manganese cobalt composite hydroxide precursor. This preliminary purification ensures that when the material is subsequently fired and mixed with lithium compound, the crystallinity is not deteriorated by impurity-induced side reactions, thus resolving the contradiction between production efficiency and manufacturing precision.
2Quantity of substance
If impurities are present in nickel manganese cobalt composite hydroxide, then raw material availability is improved, but battery capacity decreases due to inhibited lithium diffusion
Solution Approach 1:
The patent applies the extraction principle by removing impurities (sodium, sulfate, chloride) from the nickel manganese cobalt composite hydroxide through a washing process using purified water. This extraction of harmful substances eliminates their negative impact on lithium diffusion and battery capacity, while maintaining the availability of the composite hydroxide as a raw material for subsequent lithium compound formation.
3Ease of manufacture
If impurities such as sodium are present in the composite hydroxide, then production cost is reduced, but particle aggregation occurs and output characteristic deteriorates
Solution Approach 1:
The patent converts the harmful effect of impurities into a beneficial process by using the washing step to remove sodium and other impurities that would otherwise cause particle aggregation during firing. By eliminating these harmful substances before the firing process, the patent prevents aggregation and maintains excellent output characteristics, while the washing process itself is a simple, low-cost operation.
4Reliability
If excessive lithium is accumulated at negative electrode to compensate for irreversible capacity, then battery capacity is maintained, but safety problems occur
Solution Approach 1:
The patent applies extraction by removing impurities (sodium, sulfate, chloride) from the nickel manganese cobalt composite hydroxide through washing. This eliminates the source of irreversible capacity loss, preventing excessive lithium accumulation at the negative electrode and thereby resolving the safety problems associated with compensating for such losses.
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 composite hydroxide and oxide materials improve battery capacity, filling ability, and inhibit particle aggregation, resulting in enhanced cycle characteristics and safety.
Implementation Method 1
a crystallization process with an alkaline carbonate solution and a non-oxidizing atmosphere
Implementation Method 2
followed by washing with ammonium hydrogen carbonate
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.