High-Nickel NCMA Precursor Wet Synthesis for Uniform Particle Growth
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Solution Overview
Problem
Conventional methods for producing high-nickel NCMA quaternary cathode materials face issues with uneven particle size, inconsistent morphology, and high content of Na and S, leading to poor electrochemical performance and safety concerns in lithium-ion batteries due to defects in traditional feeding and washing processes.
Innovation Solution
A wet synthesis method involving a dual feeding mode in two reactors to control particle growth and a mixed washing solution of sodium carbonate and sodium hydroxide to reduce Na and S content, ensuring uniform particle distribution and improved structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional upper feeding method with single liquid feed pipe is used, then the process is simple, but material mixing is uneven and local supersaturation occurs leading to high pH and large numbers of crystal nuclei
Solution Approach 1:
The single liquid feed pipe is segmented into multiple feed pipes arranged in an array. Each feed pipe delivers precipitating agent to different locations in the reactor, ensuring uniform distribution and preventing local supersaturation. This segmentation transforms a simple but problematic single-point feeding system into a multi-point feeding system that maintains simplicity while achieving uniform particle size distribution.
Solution Approach 2:
The feeding system transitions from one-dimensional single-point feeding to two-dimensional array distribution. Multiple feed pipes are arranged in a specific geometric pattern within the reactor, creating a spatial distribution network that ensures uniform reagent delivery across the reaction zone, thereby preventing localized high concentration zones and improving particle size consistency.
2Reliability
If ammonia is used as complexing agent, then reaction rate is controlled and pH fluctuates in small range, but Al3+ precipitates faster leading to formation of many small particles
Solution Approach 1:
Aluminum salt is pre-mixed with ammonia water before being introduced into the reactor. This preliminary complexation ensures that aluminum ions are already bound to ammonia molecules, controlling their precipitation rate and preventing the formation of excessive fine particles. The pre-complexation action synchronizes the precipitation behavior of different metal ions, leading to more uniform particle size distribution.
Solution Approach 2:
Ammonia acts as an intermediary complexing agent that temporarily binds metal ions before precipitation. By forming ammine complexes with aluminum and other metal ions, ammonia mediates the precipitation process, controlling the release and deposition of metal hydroxides. This intermediary role of ammonia ensures synchronized precipitation of all metal ions, preventing aluminum from precipitating too rapidly.
3Loss of substance
If NaOH washing solution with high concentration is used, then SO42− elution is improved, but Al(OH)3 dissolves causing main content deviation and morphology change
Solution Approach 1:
The washing process uses a controlled concentration of NaOH solution (0.5-2.0 mol/L) rather than high concentration. This parameter optimization allows sufficient sulfate ion removal through ion exchange while preventing the dissolution of Al(OH)3. The moderate NaOH concentration creates an optimal balance between removing harmful sulfate ions and preserving the aluminum content and particle morphology.
Solution Approach 2:
The washing process is performed continuously with multiple washing steps using the optimized NaOH concentration. This continuous washing action ensures thorough sulfate removal while maintaining stable product composition and morphology throughout the washing sequence, preventing both under-washing and over-washing effects.
4Use of energy by stationary object
If sintering temperature is kept ≤800° C., then energy consumption is reduced, but SO42− cannot be completely decomposed
Solution Approach 1:
The washing step with NaOH solution is performed before sintering to pre-remove sulfate ions from the precursor. This preliminary sulfate removal reduces the sulfate burden that would otherwise require high sintering temperatures for decomposition. By addressing sulfate removal in advance at lower temperatures, the subsequent sintering can be performed at ≤800°C while still achieving low final sulfate content.
Solution Approach 2:
The sulfate removal process continues through both the washing stage (chemical removal) and sintering stage (thermal decomposition). This continuous sulfate elimination approach ensures that sulfate ions are progressively removed through multiple mechanisms, achieving complete decomposition and removal at moderate sintering temperatures without requiring excessive energy input.
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 method produces high-nickel NCMA quaternary precursors with uniform particle size and improved sphericity, reducing Na and S content below 50 ppm and 800 ppm respectively, enhancing structural stability, cycle life, and electrochemical performance of lithium-ion batteries.
Implementation Method 1
Using ammonia as the complexing agent, NH3·H2O can be complexed with Ni2+ and CO2+ so that the reaction rate is controlled to allow the pH to fluctuate in a small range during the reaction
Implementation Method 2
the traditional washing process of NCM ternary precursors utilizes NaOH as the washing solution, which can be reacted with ammonium sulfate double salt crystals and damage the structure of the double salt, causing the release of sulfate ions
Implementation Method 3
synthesizing solid tiny crystal nuclei of the NCMA quaternary precursor in a first reactor, and prompting the solid tiny crystal nuclei of the quaternary precursor to continuously grow to a certain particle size in a second reactor
Implementation Method 4
a wet synthesis method of high-nickel NCMA quaternary precursor involves synthesizing solid tiny crystal nuclei
Data Source
AI summary
In the technical field of lithium ion batteries, disclosed is a wet synthesis method of a high-nickel NCMA quaternary precursor. The method includes synthesizing solid tiny crystal nuclei of the NCMA quaternary precursor in a first reactor, and prompting the crystal nuclei of the quaternary precursor to grow to a certain particle size in a second reactor, wherein in the first reactor, an upper feeding mode is used to continuously produce the solid tiny crystal nuclei of the NCMA quaternary precursor. In the second reactor, an upper-and-lower dual feeding mode is used to prompt the continuous growth of the solid tiny crystal nuclei of the NCMA quaternary precursor. During a washing process, the NCMA quaternary precursor is washed with a mixed alkali solution of sodium carbonate and sodium hydroxide at certain concentration, so that Na can be reduced below 50 ppm and sulfur can be reduced below 800 ppm.