Prussian Blue Cathode Preparation for Low-Water Sodium-Ion Batteries
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Solution Overview
Problem
Prussian blue analogue materials for sodium ion batteries face issues of poor consistency and high water content, which negatively impact electrochemical performance by reducing sodium storage capacity, hindering ion migration, suppressing electrochemical activity, and leading to irreversible reactions with the electrolyte.
Innovation Solution
A preparation method involving the use of nonionic surfactants and antioxidants in a sodium ferrocyanide solution, followed by a precipitation reaction with a transition metal salt solution under a protective gas atmosphere, and subsequent vacuum drying and soaking in an alcohol solution containing sodium alkoxide to reduce water content, resulting in a positive electrode material with improved consistency and reduced water content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If aqueous phase co-precipitation method or hydrothermal method is used to synthesize Prussian blue analogue materials, then the materials can be easily prepared with high voltage platform and large specific capacity, but the crystal water content in the material becomes greater than 15 wt % which negatively impacts electrochemical performance
Solution Approach 1:
The patent applies preliminary action by conducting vacuum drying at 100-120°C for 12-24 hours before the alcohol soaking step. This preliminary removal of bulk water reduces the crystal water content to below 15 wt%, preparing the material for the subsequent alcohol soaking step that removes remaining coordinated water, thereby achieving low water content while maintaining ease of preparation
Solution Approach 2:
The patent uses parameter changes by transitioning from aqueous environment to alcohol environment, and from atmospheric pressure to vacuum conditions. The vacuum drying changes the pressure parameter to remove water, while the alcohol soaking changes the solvent parameter to further reduce water content to below 15 wt%, resolving the contradiction between easy preparation and low water content
2Ease of manufacture
If crystal water content is high in Prussian blue analogue materials, then the material can be obtained through conventional synthesis methods, but the sodium storage capacity is reduced because crystal water occupies the sodium storage site
Solution Approach 1:
The patent applies the extraction principle by removing crystal water from the Prussian blue analogue material through vacuum drying and alcohol soaking treatments. This extraction of water molecules from the crystal structure vacates the sodium storage sites, enabling high sodium storage capacity while maintaining the material's ease of manufacture through conventional synthesis methods followed by water removal steps
3Ease of manufacture
If crystal water is present in the material, then the material structure is formed through conventional synthesis, but the migration of Na+ is hindered leading to deterioration of electrode dynamics performance
Solution Approach 1:
The patent extracts crystal water from the material through vacuum drying and alcohol soaking, removing the obstacles that hinder Na+ migration. This extraction clears the ion transport pathways in the crystal structure, enabling fast ion migration and high electrode dynamics performance while preserving the ease of manufacture through conventional synthesis followed by water removal
4Ease of manufacture
If coordination water exists in the vacancy gap, then the material is formed through conventional synthesis methods, but the electrochemical activity of the low-spin Fe attached to C is suppressed resulting in failure of high-potential platform capacity
Solution Approach 1:
The patent extracts coordination water from the vacancy gaps through the combined vacuum drying and alcohol soaking process. This extraction removes the suppressing effect of water molecules on the low-spin Fe electrochemical activity, enabling high-potential platform capacity to be achieved while maintaining the ease of manufacture through conventional synthesis followed by water removal treatments
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 achieves high consistency and low water content in the positive electrode material, enhancing sodium storage capacity, electrode dynamics, and electrochemical activity, leading to improved cycling and specific capacity performance.
Implementation Method 1
adding a first nonionic surfactant and an antioxidant to a sodium ferrocyanide solution to obtain a first solution; adding a second nonionic surfactant to a transition metal salt solution to obtain a second solution
Implementation Method 2
adding a first nonionic surfactant and an antioxidant to a sodium ferrocyanide solution to obtain a first solution
Implementation Method 3
vacuum drying the washed precipitate
Implementation Method 4
vacuum drying the washed precipitate
Implementation Method 5
soaking in an alcohol solution containing sodium alkoxide, filtering, and evaporating to dryness to obtain a positive electrode material
Data Source
AI summary
Disclosed is a preparation method for a Prussian blue sodium-ion battery positive electrode material, comprising: adding a first nonionic surfactant and an antioxidant into a sodium ferrocyanide solution to obtain a first solution; adding a second nonionic surfactant into a transition metal salt solution to obtain a second solution; in a protective atmosphere, adding the second solution into the first solution for a precipitation reaction; aging after the reaction has finished; collecting a precipitate, washing same, and carrying out vacuum drying on the washed precipitate; then soaking same in an alcohol solution containing sodium alkoxide; and then filtering same and steam drying to obtain a Prussian blue sodium ion battery positive electrode material. The method may relieve vacuum drying pressure and shorten drying time.