Sodium-Ion Cathode Washing for Residual Alkali Without Crystal Damage
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Solution Overview
Problem
Sodium-ion batteries face challenges due to high residual alkali content on the surface of positive active materials, which affects their electrochemical performance and capacity, especially the first-cycle charge and discharge capacities, and existing washing methods either damage the crystal structure or are costly.
Innovation Solution
A method involving washing the positive active material with deionized water or an acidic solution at a temperature below 20°C, followed by filtering and drying, to reduce residual alkali content while maintaining the crystal structure, using a pH value between 4.0 and 7.0, and incorporating specific solutes like boric acid to form stable sodium salts that act as a coating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional washing methods are used to remove residual alkali, then residual alkali content is reduced, but crystal structure is damaged
Solution Approach 1:
The patent changes the temperature parameter of the washing process to below 20°C, which reduces the dissolution rate of sodium ions from the crystal structure while still allowing effective removal of residual alkali on the surface. This parameter optimization resolves the contradiction between removing residual alkali and preserving crystal structure.
Solution Approach 2:
The patent introduces an acidic solution as an intermediary washing medium that reacts with residual alkali to form soluble salts, enabling more effective removal of residual alkali without requiring aggressive washing conditions that would damage the crystal structure.
2Productivity
If washing temperature is increased to improve washing efficiency, then residual alkali removal is enhanced, but sodium ion dissolution from crystal structure increases
Solution Approach 1:
The patent optimizes the temperature parameter to below 20°C, creating a balance point where washing efficiency is sufficient to remove residual alkali while the dissolution rate of sodium ions from the crystal structure is minimized. This resolves the contradiction between productivity and substance loss.
3Quantity of substance
If high concentration acidic solution is used to remove residual alkali quickly, then residual alkali content is reduced significantly, but crystal structure stability is compromised
Solution Approach 1:
The patent optimizes the concentration parameter of the acidic solution to a moderate level (pH 4.0-7.0), which provides sufficient washing effectiveness to remove residual alkali while avoiding the excessive acidity that would compromise crystal structure stability and cause sodium ion dissolution.
4Quantity of substance
If additional washing equipment is added to improve washing effectiveness, then residual alkali removal is enhanced, but manufacturing cost increases
Solution Approach 1:
The patent achieves improved washing effectiveness by optimizing existing process parameters (temperature below 20°C, acidic solution with pH 4.0-7.0) rather than adding complex equipment. This resolves the contradiction between washing effectiveness and manufacturing cost by improving the process itself.
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
This approach significantly reduces residual alkali on the surface, enhances the first-cycle charge and discharge capacities, and improves the structural and thermal stability of the positive active material without damaging the crystal structure, making the process cost-effective and efficient.
Implementation Method 1
mixing a positive active material for use in a sodium-ion battery with, and causing the positive active material to react with, a washing solution
Implementation Method 2
When the positive active material is washed at a temperature falling within the specified range, a dissolution speed of sodium ions in a crystal structure of the positive active material for use in a sodium-ion battery can be reduced
Implementation Method 3
incorporating specific solutes like boric acid to form stable sodium salts that act as a coating layer
Data Source
AI summary
Provided are a positive active material for use in a sodium-ion battery, a method for preparing same, a positive electrode plate containing same, a sodium-ion battery, and an electrical device. The method for preparing a positive active material for use in a sodium-ion battery includes the following steps: mixing a positive active material for use in a sodium-ion battery with, and causing the positive active material to react with, a washing solution at a temperature of T1, and filtering and drying a product of the reaction to obtain a washed positive active material for use in a sodium-ion battery, where the washing solution is deionized water or an acidic solution with a pH value lower than 7.0, and 0° C.≤T1<20° C.