NMC Hydroxide Precursor Purification for Low-Sodium Cathode Oxides
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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 precursor is produced with a sodium content less than 0.0005% by mass and a void ratio of 20% to 50%, using a crystallization process with a mixed alkali metal hydroxide and carbonate solution and ammonium hydrogen carbonate washing, along with controlled atmospheric conditions, to enhance battery characteristics 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 such as sodium, sulfate, and chloride radicals remain in the product, decreasing battery capacity and causing particle aggregation
Solution Approach 1:
The patent applies preliminary action by conducting a washing process before the firing process to remove impurities from the nickel manganese cobalt composite hydroxide precursor. The washing step uses water or weak acid solutions to eliminate sodium, sulfate, and chloride radicals before they can be incorporated into the final oxide product during firing, thereby preventing impurity-related degradation of battery performance.
Solution Approach 2:
The patent applies extraction by specifically removing harmful impurities (sodium, sulfate, chloride radicals) from the nickel manganese cobalt composite hydroxide through washing processes. This extraction of unwanted components before the main firing process ensures high purity of the final product while maintaining production efficiency, directly resolving the contradiction between productivity and manufacturing precision.
2Ease of manufacture
If impurities are present in nickel manganese cobalt composite hydroxide precursor, then production cost is reduced, but battery capacity decreases due to inhibited lithium diffusion and side reactions
Solution Approach 1:
The patent applies preliminary action by implementing a washing process before firing to remove impurities from the precursor material. This preliminary purification step prevents impurities from interfering with lithium diffusion and causing side reactions during battery operation, thereby maintaining high battery capacity while keeping production costs reasonable through a relatively simple washing procedure.
3Device complexity
If sodium content is high in the precursor, then manufacturing process is simpler, but particle aggregation occurs during sintering, reducing output characteristic and battery capacity
Solution Approach 1:
The patent applies extraction by specifically removing sodium and other impurities from the nickel manganese cobalt composite hydroxide through washing processes before firing. This extraction prevents sodium from causing particle aggregation during sintering, thereby maintaining good output characteristics and battery capacity while keeping the manufacturing process relatively simple with just an additional washing step.
4Loss of time
If conventional washing process is used, then production time is reduced, but impurities are not sufficiently removed, leading to decreased crystallinity of the final oxide
Solution Approach 1:
The patent applies parameter changes by optimizing washing parameters such as using weak acid solutions (e.g., acetic acid, citric acid) or controlled water washing at specific pH levels. These parameter adjustments enable effective impurity removal that preserves the crystalline structure of the precursor, ensuring high crystallinity in the final oxide product without requiring excessively long washing times.
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 lithium nickel manganese cobalt composite oxide achieves high battery capacity, improved filling ability, and reduced aggregation, ensuring enhanced safety and cycle characteristics in lithium ion secondary batteries.
Implementation Method 1
ammonium hydrogen carbonate washing
Implementation Method 2
a potassium, a calcium, a magnesium and the like, including a sodium dissolve to a lithium site
Implementation Method 3
crystallization process with a mixed alkali metal hydroxide and carbonate solution
Implementation Method 4
controlled atmospheric conditions, to enhance battery characteristics and inhibit sintering
Implementation Method 5
a diffusion of a lithium in a solid phase is inhibited
Implementation Method 6
a void ratio of particles of the nickel manganese cobalt composite hydroxide is 20% to 50%
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, and a void ratio of particles of the nickel manganese cobalt composite hydroxide is 20% to 50%.