Layered Positive Electrode Material with SO2 Sintering for Low Residual Alkali
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Solution Overview
Problem
Layered positive electrode materials in lithium-ion batteries face issues with high surface residual alkali and pH values, leading to gelation during homogenization, which complicates the production process, causes lithium loss, and pollutes water resources, necessitating a more efficient method to reduce residual alkali and enhance conductivity.
Innovation Solution
A preparation method involving primary and secondary sintering of nickel-cobalt-manganese hydroxide with a lithium source in specific atmospheres and conditions, where sulfur dioxide reacts with residual alkali to produce lithium sulfate, reducing surface alkali and pH, and improving the material's processability and electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If water washing method is used to remove residual alkali, then residual alkali content is reduced, but lithium loss occurs and production process becomes complicated
Solution Approach 1:
The patent changes the chemical environment parameter from aqueous (water washing) to gaseous (sulfur dioxide atmosphere). By conducting the alkali removal process in a sulfur dioxide gas atmosphere at elevated temperatures (900-1100°C), the method transforms the washing mechanism from liquid-phase dissolution to gas-phase chemical reaction, thereby eliminating lithium loss while effectively removing residual alkali through formation of lithium sulfate.
Solution Approach 2:
The patent converts the harmful residual alkali (LiOH and Li2CO3) into beneficial lithium sulfate (Li2SO4) through reaction with sulfur dioxide. The previously harmful substance becomes a stable, non-gelling product that improves material processability. The reaction LiOH + SO2 → Li2SO4 transforms the problem of residual alkali into a solution where the alkali is chemically converted into a beneficial compound.
2Object-generated harmful factors
If water washing method is used to remove residual alkali, then residual alkali content is reduced, but production time increases and water resources are polluted
Solution Approach 1:
The patent replaces the mechanical/physical water washing system with a thermal-chemical gas treatment system. Instead of using liquid water to physically wash and dissolve residual alkali, the method uses sulfur dioxide gas in a high-temperature atmosphere to chemically react with and convert the residual alkali, thereby eliminating the need for water consumption, washing time, and subsequent drying time.
Solution Approach 2:
The patent changes the process parameters from ambient temperature liquid washing to elevated temperature gas-phase reaction. By conducting the treatment at 900-1100°C in a sulfur dioxide atmosphere, the method accelerates the alkali removal process and eliminates the multi-step washing and drying procedure, thereby reducing overall production time.
3Object-generated harmful factors
If water washing method is used to remove residual alkali, then residual alkali content is reduced, but process complexity increases
Solution Approach 1:
The patent merges the alkali removal process with the existing sintering process. By conducting the sulfur dioxide treatment during or after the sintering step (at 900-1100°C), the method combines two separate operations (sintering and alkali removal) into one integrated process, thereby eliminating the need for separate washing, filtration, and drying equipment and procedures.
Solution Approach 2:
The patent converts the harmful residual alkali into beneficial lithium sulfate through chemical reaction with sulfur dioxide. This transformation not only removes the harmful substance but also produces a compound that improves material properties, thereby simplifying subsequent processing steps and reducing overall process complexity.
4Quantity of substance
If traditional sintering method is used, then material is formed, but residual alkali remains high causing gelation during homogenization
Solution Approach 1:
The patent changes the atmospheric parameter from conventional air or oxygen atmosphere to sulfur dioxide atmosphere during the sintering process. This parameter change enables simultaneous material formation and alkali removal, as the sulfur dioxide reacts with residual alkali on the material surface during sintering, preventing gelation during subsequent homogenization.
Solution Approach 2:
The patent converts the harmful residual alkali that causes gelation into beneficial lithium sulfate through reaction with sulfur dioxide during sintering. This in-situ conversion during the material formation process eliminates the gelation problem without requiring separate treatment steps.
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 effectively reduces residual alkali and pH on the surface of the positive electrode material, enhancing its conductivity and electrochemical performance while minimizing lithium loss and simplifying the production process compared to traditional water washing methods.
Implementation Method 1
sulfur dioxide reacts with the residual alkali on the surface of the positive electrode material to produce lithium sulfate
Implementation Method 2
performing a secondary sintering on the primary sintered product in step (1) in a sulfur dioxide atmosphere
Data Source
AI summary
Provided is a method for preparing a layered positive electrode material, comprising the following steps: (1) mixing layered nickel cobalt manganese hydroxide with a lithium source, carrying out primary sintering in an oxygen atmosphere, pulverizing and sieving to obtain a primary sintering product; and (2) carrying out secondary sintering on the primary sintering product in a sulfur dioxide atmosphere to obtain a layered positive electrode material, of which the chemical formula is NiaCobMnc(OH)2, wherein 0.3≤a≤0.95, 0.03≤b≤0.12, 0.01≤c≤0.10, and a+b+c=1. Also provided are a layered positive electrode material obtained by the preparation method and a lithium-ion battery comprising the layered positive electrode material. In the preparation method, the secondary sintering is carried out in a sulfur dioxide atmosphere to cause the sulfur dioxide and the primary sintering product to be in full contact with each other and reacted, the sulfur dioxide reacts with residual alkali on the surface of the positive electrode material to produce lithium sulfate, thereby achieving the objective of reducing the surface residual alkali and pH value and improving electrochemical performance of the material.