Layered Cathode Material Sintering to Cut Residual Alkali
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Solution Overview
Problem
Layered positive electrode materials in lithium-ion batteries face issues of high surface residual alkali (LiOH and Li2CO3) and high pH value, leading to gelation during homogenization, which complicates the production process, causes lithium loss, and pollutes water resources.
Innovation Solution
A preparation method involving primary sintering of nickel-cobalt-manganese hydroxide with a lithium source in an oxygen atmosphere, followed by secondary sintering in sulfur dioxide gas to react with residual alkali, reducing surface impurities and enhancing conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If water washing method is used to reduce residual alkali, then residual alkali content is reduced, but production process becomes complicated and production period is extended
Solution Approach 1:
The patent changes the chemical environment parameter from aqueous (water washing) to gaseous (sulfur dioxide atmosphere). By conducting the treatment in a SO2 gas atmosphere at controlled temperatures (300-600°C), the process transforms from a multi-step washing and drying procedure to a single-step thermal treatment, thereby reducing process complexity and time while achieving the same alkali removal effect.
2Manufacturing precision
If water washing method is used to reduce residual alkali, then residual alkali content is reduced, but lithium loss occurs and water resources are polluted
Solution Approach 1:
The patent employs an inert/gas atmosphere (sulfur dioxide) instead of water for the treatment process. This gas-phase environment prevents lithium dissolution and loss that occurs during water washing, while also eliminating water consumption and associated pollution. The sulfur dioxide atmosphere selectively reacts with residual alkali without causing harmful side effects.
Solution Approach 2:
The patent converts the potentially harmful sulfur dioxide gas into a beneficial reagent that selectively reacts with residual alkali (LiOH and Li2CO3) on the material surface. The SO2 transforms the harmful residual alkali into removable sulfur-containing compounds, thereby eliminating the alkali problem while avoiding lithium loss and water pollution associated with conventional washing methods.
3Ease of manufacture
If high surface residual alkali and high pH value are present, then material is easier to process, but gelation occurs during homogenization
Solution Approach 1:
The patent performs preliminary treatment of the positive electrode material by heating it in a sulfur dioxide atmosphere before the homogenization step. This pre-treatment reduces the surface residual alkali and adjusts the surface pH, preventing gelation issues that would otherwise occur during subsequent homogenization. By addressing the alkali problem in advance, the material becomes suitable for standard processing procedures.
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, improves processability, and enhances electrochemical performance of the electrode material without lithium loss, resulting in improved battery capacity and efficiency.
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 primary sintering in an oxygen atmosphere... performing a secondary sintering on the primary sintered product in step (1) in a sulfur dioxide gas
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.