Fe-Substituted Mn Prussian Blue With Low Vacancy Synthesis
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Solution Overview
Problem
Current methods for synthesizing transition metal cyanide coordination compounds (TMCCC) are inefficient for all types of Prussian Blue Analogues, particularly for Fe-substituted Mn-based TMCCC, as they require excess acid, generate toxic waste, and result in materials with lower energy density and specific capacity.
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, allowing for the production of TMCCC materials with 0-14% hexacyanometallate vacancies, which are then used in electrochemical cells with improved energy density and batch-to-batch reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If acid decomposition of sodium hexacyanoferrate is used to suppress vacancy formation, then vacancy concentration is reduced, but the synthesis becomes slow, requires excess acid, generates toxic HCN waste, and limits TMCCC composition choices
Solution Approach 1:
The patent changes the chemical parameters of the synthesis system by replacing acid decomposition with a basic precipitation method using NaOH and chelating agents. This fundamental parameter change allows for rapid synthesis while maintaining low vacancy concentrations (0-14%) and avoiding the drawbacks of acid-based methods including slow reaction rates, excess reagent requirements, and toxic waste generation.
Solution Approach 2:
The patent introduces chelating agents (EDTA, citrate, or tartrate) as intermediary substances that mediate the precipitation process. These intermediaries control the formation of TMCCC by coordinating with metal ions during precipitation, enabling precise vacancy control and composition flexibility without requiring acid decomposition or generating toxic waste streams.
2Manufacturing precision
If acid decomposition method is used, then vacancy concentration is controlled, but energy density and deintercalation/intercalation potentials are reduced
Solution Approach 1:
The patent employs parameter changes in the synthesis conditions (basic pH environment, chelating agents, controlled precipitation) to produce TMCCC with optimized vacancy concentrations (0-14%). This results in materials with higher energy density and improved electrochemical performance compared to acid-decomposition methods, while maintaining precise vacancy control.
3Adaptability or versatility
If conventional synthesis methods are used for Fe-substituted Mn-based TMCCC, then synthesis is limited, but new methods enable scalable industrial production with controlled particle size
Solution Approach 1:
The patent develops a universal synthesis method using basic precipitation with chelating agents that works effectively for all types of Prussian Blue Analogues including Fe-substituted Mn-based TMCCC. This multi-functional approach enables scalable industrial production with controlled particle sizes and compositions, overcoming the limitations of conventional methods that were not effective for certain PBA types.
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 combined with higher cell voltage, using inexpensive reagents and enabling scalable industrial production while maintaining well-controlled particle size and energy density in sodium ion batteries.
Implementation Method 1
sulfur-containing reducing agents to convert low vacancy Prussian blue to Prussian white
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.