Fe-Substituted Mn Prussian Blue Analogues With Low Vacancy Control
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Solution Overview
Problem
Existing methods for synthesizing transition metal cyanide coordination compounds (TMCCC) materials, particularly Fe-substituted Mn-based PBAs, are inefficient, costly, and result in lower energy density due to high vacancy concentrations, which affect the performance of sodium ion secondary batteries.
Innovation Solution
A method involving the use of bifunctional compounds like ethylene glycol and sulfur-containing reducing agents to control vacancy formation in TMCCC synthesis, resulting in a scalable and cost-effective production of low vacancy Prussian blue analogues with controlled particle size and multiple oxidation-reduction potentials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If acid hydrolysis of sodium hexacyanoferrate is used to suppress vacancy formation, then specific capacity is improved, but production cost increases and energy density decreases due to lower deintercalation/intercalation potentials
Solution Approach 1:
The invention changes the synthesis parameters by using a neutral or basic pH environment instead of acid hydrolysis, and by controlling the molar ratios of reactants (Fe2+:Mn2+:hexacyanoferrate = 1:1:2-3) to achieve low vacancy formation without requiring expensive acid treatments
Solution Approach 2:
The invention replaces expensive and complex acid hydrolysis processes with simple, inexpensive reagents such as sodium carbonate or sodium hydroxide for pH control, and uses readily available iron and manganese salts, making the process cost-effective and suitable for large-scale production
2Reliability
If common cobalt-based Prussian blue analogue is used, then electrochemical performance is improved, but material cost increases significantly
Solution Approach 1:
The invention substitutes expensive cobalt-based materials with inexpensive iron and manganese-based Prussian blue analogues, achieving comparable or superior electrochemical performance while dramatically reducing material costs, making the technology economically viable for large-scale energy storage applications
Solution Approach 2:
The invention creates a composite Fe-substituted Mn-based Prussian blue analogue with a specific stoichiometry (Fe2+:Mn2+:hexacyanoferrate = 1:1:2-3) that combines the advantages of both iron and manganese, achieving high specific capacity and good electrochemical performance at low cost
3Manufacturing precision
If excess alkali ion and chelating agents are used to suppress vacancy formation, then vacancy concentration is reduced, but the method is not effective for Fe-substituted Mn-based TMCCC and limits composition choices
Solution Approach 1:
The invention changes the approach from using chemical additives (chelating agents) to controlling physical-chemical parameters such as pH (using sodium carbonate or sodium hydroxide to maintain neutral or basic conditions) and molar ratios, which is universally applicable to Fe-substituted Mn-based TMCCC and allows flexible composition design
Solution Approach 2:
The invention develops a universal synthesis method using sodium carbonate or sodium hydroxide for pH control that works effectively for all Fe-substituted Mn-based Prussian blue analogues, regardless of specific composition variations, providing a versatile and adaptable synthesis protocol
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 specific capacity and energy density in sodium ion batteries by suppressing vacancy formation, allowing for batch-to-batch reproducibility and using inexpensive reagents, thus enhancing the performance of TMCCC materials.
Implementation Method 1
sulfur-containing reducing agents to control vacancy formation in TMCCC synthesis
Data Source
AI summary
A system and method implementing and manufacturing transition metal cyanide coordination compounds (TMCCC) comprising Na, Fe, Mn, C, H, N, S, and O, wherein the TMCCC have 0-14% hexacyanometallate vacancies such as for application in electrochemical cells, including sodium ion secondary batteries.