Method and electrochemical filter cell for extracting lithium

Abstract

A novel electrochemical cell for extraction of lithium chloride from brines and release of pure lithium metal is disclosed, wherein the cell is composed of two porous electrodes positioned inside a housing with a narrow gap between them and preferably a third recovery electrode. The working electrode is impregnated with a compound that selectively binds lithium ions such as various manganese oxide and Prussian Blue analogs. The counter electrode is impregnated with a compound that binds chlorine ions such as silver and polypyrrole. Brine is pumped through the charged electrodes and lithium ions selectively bind to the working electrode and chlorine ions bind to the counter electrode while the majority of other salts pass through. When the working electrode is fully loaded, the brine is replaced with a polar organic solvent and the voltage increased to release the chlorine ions from the counter electrode as chlorine gas. Then the polarity of the electrodes is reversed between the capture electrode and the recovery electrode, and the lithium ions are released into the solvent. The solvent with the insoluble lithium ions is collected in an inert tank and the solvent is drained and evaporated, leaving dry pure lithium metal precipitate. This precipitate is melted, drained into an inert canister, and solidified as pure lithium metal ready for use.

1 - 14 . (canceled) 
     
     
         15 . A method using an electrochemical filter cell for producing high-purity concentrated lithium chloride solutions from aqueous solutions containing dilute lithium chloride and other salts comprising:
 a. Providing a stack of porous sheet materials stacked in the following sequence:
 i. Capture electrode ( 51 ) comprising a lithium binding compound 
 ii. Capture electrode current collector ( 52 ) 
 iii. Capture electrode ( 51 ) comprising a lithium binding compound 
 iv. Flow spacer ( 49 ) 
 v. Counter electrode ( 47 ) comprising a chlorine binding compound 
 vi. Counter electrode current collector ( 48 ) 
 vii. Counter electrode ( 47 ) comprising a chlorine binding compound 
 viii. Flow spacer ( 49 ) 
   b. Spirally wrapping the stack around a porous or perforated inner fluid flow pipe   c. Attaching current connectors to the current collectors ( 48 ,  52 )   d. Fitting the filter element with anti-telescoping element endcaps, inserting the filter element inside of a housing, attaching the connector tabs to current connectors, and sealing the housing with two housing endcap assemblies   e. Providing an outer fluid flow channel between the inner surface of the housing wall and the outer surface of the stack   f. Providing gaps in the endcap on the filter cell inlet side such that fluid can flow into the filter cell and to the outer flow channel   g. Providing gaps in the endcap on the filter cell outlet side such that fluid can flow from the inner flow pipe and out of the filter cell   h. Providing a flow of an aqueous solution containing dilute lithium chloride and other salts such that solution enters the filter cell, flows axially through the outer flow channel, flows radially inward through the filter element, flows axially through the inner flow channel, and exits the filter cell   i. Providing a negative charge to the working electrode current collector and a positive charge to the counter electrode current collector   j. Allowing the lithium chloride molecules to disassociate into lithium ions and chlorine ions and selectively bind to the working electrode and counter electrode respectively while the other salts pass through the filter element   k. When the electrodes are fully loaded with ions, flushing the filter cell with air to remove the dilute mixed salt solution   l. Providing a flow of a recovery solvent such as water into the filter cell   m. Reversing the polarity of the electrodes such that the working electrode is now positively charged and the counter electrode is negatively charged   n. Allowing the lithium ions and the chlorine ions to be repelled from their respective electrodes and recombine in the solvent to form a high purity concentrated lithium chloride solution   o. Recycling the solution through the filter cell as necessary to bring all of the lithium chloride into solution   p. Flushing out the filter cell with air to recover all of the solution.   
     
     
         16 . A method using an electrochemical filter cell for producing high-purity concentrated lithium chloride solutions from aqueous solutions containing dilute lithium chloride and other salts comprising:
 q. Providing a first electrochemical filter unit with one or more filter cells each with one or more filter elements that have a working electrode with a lithium binding compound   r. Providing a second electrochemical filter unit with one or more filter cells each with one or more filter elements that have a working electrode with a non-lithium binding compound such as various Prussian blue analogs that bind sodium, calcium, potassium, and magnesium ions   s. Applying a negative electrical charge to the working electrodes and a positive electrical charge to the counter electrodes in the first electrochemical filter unit   t. Providing a flow of an aqueous solution containing dilute lithium chloride and other salts through the first electrochemical filter unit such that lithium ions are selectively intercalated into the working electrodes along with some amount of other ions such as sodium, calcium, potassium, and magnesium, while the majority of these other ions pass through   u. Reversing the polarity of the electrodes in the first electrochemical filter unit and recovering the released lithium and other ions as a concentrated solution in a recovery solvent such as water.   v. Returning the polarity of the electrodes in the first electrochemical filter unit to their original state   w. Passing the recovery solvent with salts from the first pass through the first filter unit for a second pass such that lithium ions are once again selectively intercalated into the working electrodes while most of the other ions pass through   x. Reversing the polarity of the electrodes in the first electrochemical filter unit again and recovering the release lithium ions and much lower concentration of other ions as a concentrated solution in a second recovery solvent such as water   y. Applying a negative electrical charge to the working electrodes and a positive electrical charge to the counter electrodes in the first electrochemical filter unit   z. Passing the second recovery solvent with salts through the second electrochemical filter unit such that most of the lithium chloride passes through but most of the other salts such as sodium, calcium, potassium, and magnesium are selectively intercalated into the working electrodes.   aa. Taking the concentrated solution on now highly pure lithium chloride for further processing   bb. Reversing the polarity of the electrodes in the second electrochemical filter unit   cc. Passing a recovery solvent such as water through the second electrochemical filter to flush out the other intercalated ions and prepare the filter for the next run.