Iron Salt Battery Electrolyte Preparation With pH-Controlled Fe3+ Reduction
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Solution Overview
Problem
Existing methods for preparing FeCl2 solutions for iron salt batteries face safety hazards, high costs, and purity issues, particularly due to the use of concentrated HCl and high-purity FeCl2 salts or byproducts.
Innovation Solution
A method involving the reaction of iron(III) chloride with elemental iron in a dilute hydrochloric acid solution, controlled by pH monitoring, followed by conversion in an electrochemical cell to produce a FeCl2 electrolyte with controlled Fe3+ concentration, using safer and lower-cost materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If concentrated HCl is used to prepare FeCl2 solution, then the FeCl2 solution can be prepared effectively, but safety hazards increase
Solution Approach 1:
The patent changes the concentration parameter of HCl from concentrated to dilute (pH less than 1), which maintains the chemical reaction effectiveness while significantly reducing the safety hazards associated with concentrated acid handling and storage
2Manufacturing precision
If high purity FeCl2 salts are purchased and dissolved, then the electrolyte purity is improved, but the cost increases
Solution Approach 1:
The patent uses inexpensive iron filings as a sacrificial reagent that reacts with FeCl3 to produce FeCl2. The iron filings are consumed in the reaction and do not need to be recovered, providing a cost-effective source of FeCl2 compared to purchasing high-purity salts
Solution Approach 2:
The patent replaces the chemical purification process with an electrochemical reduction process. By applying a small cathodic current, Fe3+ ions are reduced to Fe2+ directly in the electrolyte, achieving high purity without expensive chemical reagents or multiple purification steps
3Ease of manufacture
If FeCl2 is obtained as a byproduct of the chlorine process, then the cost is reduced, but purity issues arise
Solution Approach 1:
The patent uses electrochemical reduction at the cathode to convert Fe3+ to Fe2+ with high selectivity and efficiency. This electrochemical method provides precise control over the reduction process, achieving high purity FeCl2 electrolyte without the contamination issues associated with byproduct recovery from chlorine processes
4Productivity
If FeCl2 solution is prepared by oxidation of metallic iron in concentrated HCl, then the FeCl2 can be produced, but safety hazards and cost issues arise
Solution Approach 1:
The patent changes the HCl concentration from concentrated to dilute (pH less than 1), which is sufficient to dissolve the iron and maintain Fe2+ in solution while dramatically reducing the safety hazards of handling concentrated acid
Solution Approach 2:
Instead of oxidizing iron to produce FeCl2 directly in concentrated acid, the patent first prepares a dilute FeCl3 solution and then reduces it electrochemically to FeCl2. This inverted approach avoids the need for concentrated acid and high-temperature oxidation, improving safety while maintaining productivity
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 a safer, cost-effective, and environmentally friendly production of high-purity FeCl2 electrolyte by reducing hazardous material use and optimizing processing conditions.
Implementation Method 1
supplying elemental iron, Fe, into the reactor, wherein the elemental iron reacts with iron(III) to iron(II)
Implementation Method 2
A flow rate of the reactor solution through the anode is controlled to obtain a final Fe 3+ concentration of less than 5% of the total iron concentration
Data Source
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AI summary
The invention provides a method for preparation of an iron salt battery electrolyte. The method comprises the following steps: supplying iron(III) chloride, FeCl3, into an agitated reactor containing a dilute solution of hydrochloric acid, HCl, having a pH value less than 1; supplying elemental iron, Fe, into the reactor, wherein the elemental iron reacts with iron(III) to iron(II); monitoring the pH value of reactor solution; using the monitored pH value to control supplying additional hydrochloric acid, HCl, into the reactor in order to maintain a pH of the reactor solution less than 1; and converting excess Fe3+ to Fe2+ in an electrochemical cell having a membrane or a separator between an anode and a cathode thereof by directing the reactor solution from the reactor through the anode of the electrochemical cell. A flow rate of the reactor solution through the anode is controlled to obtain a final Fe3+ concentration in the anode outlet FeCl2 stream of 15% or less than 15% of a total dissolved iron concentration as the iron salt battery electrolyte.