Electrolyte Design Method and System

Abstract

Electrochemical system comprising an aqueous electrolyte, at least one chelating agent configured to bind at least one harmful ionic species, and particulate deposition sites. A method of forming an electrochemical system comprising the steps of: creating a housing having an interior volume; disposing at least one electrode within the interior volume; adding at least one chelating agent configured to bind at least one harmful ionic species to the interior volume; and adding particulate deposition sites to the interior volume.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Provisional Application No. 62 / 957,407, filed on January 6, 2020, the entire disclosure of which is incorporated herein by reference as if fully set forth herein.

[0002] Technical Field The embodiments described herein generally relate to electrochemical systems comprising an aqueous electrolyte, and more particularly to electrochemical systems and methods configured to use a particulate deposition site in combination with at least one chelating agent to bind to harmful ionic species.

Background Art

[0003] Background Power sources such as metal - water cells have become a popular alternative energy source for underwater applications. These types of cells generally include a hydrogen - generating cathode that decomposes water according to the reaction 2H2O→H2 + 2OH - The hydroxide ions are then used to react with a metal material such as aluminum. The cell can be discharged at a constant voltage or constant power, or under other load profiles, and the type and amount of discharge can affect the general patterns described herein.

[0004] Metal-water electrochemical cells, such as aluminum-water cells, that include an aqueous electrolyte have a break-in period during which the cell performance degrades and recovers due to several factors. When the cell operates under a constant voltage, this effect manifests as a decrease in the cell's current output, and proportionally decreases the power output. After this induction period, the cell can reach steady-state operation for most of the discharge. This behavior causes either 1) the user to have to accept a mission profile that includes a period of low power output during startup, or 2) the battery system to be designed to meet a minimum discharge specification at the lowest performance point during the transition period, which can result in a poor system fit for long-term steady-state discharge.

[0005] The maximum current output of an aluminum-water cell is typically limited by the corrosion rate of aluminum, which is a function of several variables including the hydroxide concentration of the electrolyte. Aluminate (Al(OH)4 - ) binds more hydroxyl groups than the final waste product (Al(OH)3), reducing the hydroxyl concentration. As aluminate accumulates in the solution, the hydroxyl concentration and current output decrease. This trend reverses when aluminum hydroxide begins to precipitate from the electrolyte at a significant rate, replenishing the hydroxyl concentration. There can be precipitation reactions that include heterogeneous precipitation onto the substrate or onto solid particles in the electrolyte, or several mechanisms by which aluminate can nucleate in solution to form aluminum hydroxide particles. Steady-state discharge can be reached when the rate of aluminate formation from the electrochemical reaction is approximately equal to the rate of precipitation of aluminate to aluminum hydroxide, with other factors held constant (temperature, water injection to replenish consumed water, etc.).

[0006] The power source can be used in fresh water, salt water, brackish water, or any combination thereof. Some power sources can be used in impure water, and the precipitation process can include, but is not limited to, Si 4+ , Mg 2+ , Ca2+ , Sr 2+ , Fe 2+ and Fe 3+ can be complicated by the presence of certain ionic species such as.

[0007] Existing power sources can be sensitive to contamination or blockage of the active electrode surface area. Contamination can be caused by ambient metal ions or other particulates in the water. There are multiple mechanisms by which these ions can interact with the system, including interaction with aluminates, to prevent these ions from depositing. When water from an environmental source is used as a component in the electrolyte mixture, either as part of an initial fill or by periodic replenishment, these ions can be present at a certain concentration. The term "water from an environmental source" is intended to include all forms of surface water and groundwater, such as seawater, freshwater sources such as rivers and lakes, marshes, wetlands or stagnant ponds, and brackish water sources such as those derived from industrial or agricultural runoff.

[0008] Therefore, there is a need for methods and devices that overcome the drawbacks of existing power sources. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEM

[0009] Overview This overview is presented to introduce a selection of concepts in a simplified form that are further described in the following detailed description. This overview is not meant to identify or exclude key or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0010] According to one aspect, embodiments relate to an electrochemical system. In some embodiments, the electrochemical system includes an aqueous electrolyte; at least one chelating agent configured to bind to at least one harmful ionic species; and a particulate deposition site.

[0011] In some embodiments, the particulate deposition site is suspended in an aqueous electrolyte.

[0012] In some embodiments, the electrochemical system is a metal-water system.

[0013] In some embodiments, the electrochemical system is a metal-oxygen system.

[0014] In some embodiments, the chelating agent is a corrosion inhibitor for the anode in the electrochemical system.

[0015] In some embodiments, the particulate deposition site includes aluminum hydroxide, silicon dioxide, aluminum oxide, aluminum oxyhydroxide, boehmite, sodium aluminate, calcium oxide, potassium aluminum sulfate, ammonium aluminum sulfate, or dissolved aluminum species.

[0016] In some embodiments, the chelating agent is configured to selectively coordinate with at least one dissolved species in the aqueous electrolyte.

[0017] In some embodiments, the aqueous electrolyte includes at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, seawater, fresh water, brackish water, or any combination thereof.

[0018] In some embodiments, at least one harmful ion species is Ca 2+ , Mg 2+ , Fe 2+ or Fe 3+ and includes at least one of them.

[0019] In some embodiments, the particulate deposition site is a nucleation site.

[0020] In another aspect, embodiments relate to a method of forming an electrochemical system. In some embodiments, the method includes fabricating a housing having an internal volume, disposing at least one electrode within the internal volume, adding to the internal volume at least one chelating agent configured to bind to at least one species of harmful ionic species, and adding a particulate deposition site to the internal volume.

[0021] In some embodiments, the method further includes adding an electrolyte to the internal volume.

[0022] In some embodiments, adding an electrolyte to the internal volume includes at least partially immersing the housing in a liquid containing water.

[0023] In some embodiments, the particulate deposition site is either suspended or dissolved in an aqueous electrolyte.

[0024] In some embodiments, the aqueous electrolyte includes at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, seawater, fresh water, brackish water, or any combination thereof.

[0025] In some embodiments, the electrochemical system is a metal-water system.

[0026] In some embodiments, the chelating agent is a corrosion inhibitor for an anode in the electrochemical system.

[0027] In some embodiments, the chelating agent is configured to selectively coordinate to at least one dissolved species in the aqueous electrolyte within the housing.

[0028] In some embodiments, at least one species of harmful ionic species includes at least one of Ca 2+ , Mg 2+ , Fe 2+ or Fe 3+ and includes at least one of them.

[0029] In some embodiments, the electrode comprises at least one of an aluminum anode, a lithium anode, a magnesium anode, a zinc anode, or an iron anode.

[0030] Non-limiting embodiments of the present invention are described with reference to the accompanying drawings, which are schematic diagrams and are not intended to be drawn to scale. In the figures, the same or substantially the same components that are illustrated are generally represented by a single number each. For clarity, not all components are labeled in all figures, and not all components of each embodiment of the present invention are shown where illustration is not necessary for those skilled in the art to understand the present invention. **Brief Description of the Drawings**

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[0045] Detailed Description Various embodiments are described in more detail below with reference to the accompanying drawings, which form a part of this specification and illustrate specific exemplary embodiments. However, the concepts of the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments described herein. These embodiments are provided as a thorough and complete disclosure to fully convey the concepts, techniques, and scope of implementation of the present disclosure to those skilled in the art. The embodiments may be implemented as a method, system, or device. Accordingly, the following detailed description should not be construed in a limiting sense.

[0046] As used herein, the term "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one example implementation or technique according to the present disclosure. The appearances of the phrase "in one embodiment" in various places in this specification are not necessarily all referring to the same embodiment.

[0047] Furthermore, the language used herein has been principally selected for readability and for instructional purposes and may not have been selected to describe or limit the disclosed subject matter. Accordingly, this disclosure is intended to be illustrative and not to limit the scope of the concepts discussed herein.

[0048] Figure 1 shows, for an aluminum-water electrochemical cell, a graph of a typical electrochemical discharge at constant voltage and constant temperature. A typical current over time changes in four individual periods marked on the x-axis of the graph as the time coordinate. These periods include a pre-transition peak 101, a transition trough 102, a recovery point 103, and a post-transition peak 104. The ratio of the pre-transition peak 101 to the post-transition peak 104 is approximately 1:1 in Figure 1, but the ratio depends on the specific discharge conditions and electrode materials selected. In some aluminum-water electrochemical cells, a typical discharge can have a ratio of the pre-transition peak 101 to the post-transition peak 104 that is higher than 1:1, less than 1:1, or approximately equal to 1:1.

[0049] The first period 110 includes the time from startup to the pre-transition peak 101. During startup of the cell, the anode surface may become rough and the cell's current output may increase over time. This is sometimes referred to as the startup period or the transient start state of the discharge.

[0050] The second period 120 is the start of the transition event and ranges from the pre-transition peak 101 to the transition trough 102. In an aluminum-water cell, the accumulation of aluminate by-products increases without sufficient precipitation to counteract the aluminate. This causes the hydroxyl concentration in the aluminum-water cell to decrease and the current output to begin to decline.

[0051] The third period 130 is the recovery period of the transition event and extends from the transition trough 102 to the recovery point 103. Once the aluminate concentration becomes high enough to be favorable for the rate of one of several precipitation reactions, the aluminate begins to crash out of solution as aluminum hydroxide. This releases hydroxyl groups from the aluminate molecules, increasing the hydroxide concentration and the current output. Since there are different reaction rates for the nucleation of aluminum hydroxide and growth on existing particles or surfaces, the shape of this part of the graph can vary depending on which reaction rate is favorable.

[0052] The fourth period 140 or the steady-state region extends from the recovery point 103 to the post-transition peak 104. When these reactions reach equilibrium, the cell approaches a steady-state output where the current output at a constant voltage is nearly constant. The recovery point is indicated by the point where the electrochemical reaction that produces aluminate is in equilibrium with the precipitation reaction of aluminate and the current output stabilizes.

[0053] The induction period 105 or conditioning period extends from startup to the recovery point and is the entire region before the steady state.

[0054] In some aluminum-water cells, the pre-transition peak 101 is the maximum current output observed before the accumulation of aluminate by-products begins and the output of the aluminum-water cell decreases. In some aluminum cells, the pre-transition peak 101 may not be the time when the anode surface becomes completely rough. In most aluminum-water cells, the anode surface can continue to become rough through the recovery point 103. In the literature, the cell can use a sufficiently large reservoir of electrolyte, and as a result, the transition behavior in the second and third periods does not occur, so the pre-transition peak 101 is often reported as the maximum output for a given alloy or cathode composition.

[0055] In some aluminum-water cells, the transition trough 102 is the lowest part of the induction period. The transition trough 102 is the output of the aluminum-water cell at the lowest hydroxide concentration, induced by the reaction rate before the steady state.

[0056] After the third period, a fourth period slightly longer than that observed immediately after the recovery period 130 is caused by further stabilization due to both 1) the consumption of water that slowly increases the hydroxide concentration and 2) the slow shift of the experimental conditions, resulting in a peak output after equilibrium. In some embodiments, the consumption of water is due to the water reduction reaction at the cathode. In some embodiments, the consumption of water may be due to self-corrosion at the anode.

[0057] To improve performance, some embodiments increase the minimum current density throughout the transition induction period, such that the pre-transition peak 101, the transition trough 102, and the post-transition steady state 104 approach the same value. In some embodiments, this improvement in system performance is referred to as dampening. In a fully dampened metal-water cell, the current values of the pre-transition peak 101, the transition trough 102, and the post-transition steady state 104 are equal, and thus the transition trough 102 does not exist.

[0058] To control the break-in period, embodiments can accelerate or dampen the effects of the period over time, such that the engineer can size the battery system appropriately.

[0059] In some embodiments, a chemical agent is added to the electrolyte of an electrochemical system such as a metal-water cell. The chemical agent may include additives such as aluminate or other substances configured to accelerate the precipitation reaction of the system. In some embodiments, this can be a precipitation induction site referred to as a preload. In some embodiments, the preload or preload material may include a solid material such as aluminum hydroxide and may be configured to act as a nucleation site or a preferential precipitation site.

[0060] In some embodiments, the chemical agent includes additives configured to preferentially bind to harmful chemical species present in the electrolyte and remove them, as a result of which precipitation can occur. In some embodiments, this type of chemical agent can be a chelating agent. In some embodiments, a combination of at least one chelating agent and at least one preload may be added to the electrochemical system.

[0061] In some embodiments, the system may include an electrolyte that is not expected to contain a harmful series of chemical species, such as one composed of a particular fresh water source. In some embodiments, a system not expected to contain a harmful series of chemical species can use only a preload, rather than a chelating agent, to accelerate the conditioning period and quickly bring the system to equilibrium. In some embodiments, such as when the electrolyte is composed of seawater, a combination of a chelating agent and a preload can achieve a similar effect. The optimization of the combination of the preload and the chelating agent can be based on the environmental factors and water quality in which the system is intended to operate.

[0062] In some embodiments, the preload includes an aluminum-containing additive. In some embodiments, the preload may be introduced into the electrolyte of an aluminum-water electrochemical cell. In some embodiments, the preload can be solid particles of chemical species such as aluminum hydroxide, aluminum oxide, sodium aluminate or potassium aluminate dissolved in the electrolyte, or any combination thereof. In some metal-water cells, the preload can include a metal-containing additive compatible with the metal-water cell. For example, in some embodiments, if the cell is an iron-water cell, the preload can include an iron-containing additive. In some embodiments, the preload may include a metal-containing additive that is not compatible with the metal-water cell. For example, in some embodiments, if the cell is an aluminum-water cell, the preload can include a magnesium-containing additive.

[0063] In some embodiments, the preload may allow for partial dissolution of aluminum species in the electrolyte, thereby increasing the initial aluminate concentration in the electrolyte. This increase causes the electrolyte to become saturated with aluminate more quickly than in the standard reaction shown in FIG. 1. In some embodiments, the solid residue present in the electrolyte may act as a nucleation site for the aluminum deposition reaction, whereby the reaction is initiated at a lower aluminate concentration. In some embodiments, the solid residue may act as a seed crystal for the aluminum deposition reaction.

[0064] In some embodiments, the combination of rapid saturation of aluminate and the solid residue present in the electrolyte may shorten the induction period and allow the electrochemical system to reach the recovery point more quickly. In some embodiments, rapid saturation of a metal such as aluminate can be a primary mechanism for reaching the rapid recovery point. In some embodiments, the amount of solid residue present in the electrolyte can be a primary mechanism for reaching the rapid recovery point. In some embodiments using a highly soluble seed as the preload, rapid saturation of the metal can be primarily responsible for shortening the induction period of the electrochemical cell. In some embodiments using low-solubility fine particles as the preload, the amount of solid residue present in the electrolyte can be primarily responsible for shortening the induction period of the electrochemical cell.

[0065] In some embodiments, and unlike a batch process, an aluminum-water battery continuously generates aluminate and precipitates aluminum hydroxide. Unlike in industrial processes where the temperature may be imposed above 100 °C, these batteries can function in an environment where temperature control is mostly passive, instead of the variables used to force precipitation. In some embodiments, the battery can function in natural environmental seawater, brackish water, fresh water, or any combination thereof. Some embodiments can function as a galvanic cell that supplies power.

[0066] FIG. 2 shows an electrochemical system 200 according to one embodiment. In some embodiments, the electrochemical system 200 can include an aqueous electrolyte 210, at least one chelating agent 220 configured to bind to at least one harmful ionic species, and a particulate deposition site 230. In some embodiments, the electrochemical system 200 may also include a preload 240.

[0067] In some embodiments, the electrochemical system 200 can include a housing 250 having an internal volume 260 and at least one electrode 270 within the internal volume 260. The housing 250 can also have at least one mechanism for controlling at least one harmful ionic species within the internal volume. The harmful ionic species may be present when the electrolyte 210 is added to the housing and within the internal volume.

[0068] The mechanism for controlling at least one harmful ionic species can include the chelating agent 220, the preload 240, or the particulate deposition site 230. In some embodiments, the mechanism can include any combination of the chelating agent 220, the preload 240, and the particulate deposition site 230. In some embodiments, at least one chelating agent 220 may be added to the internal volume 260. In some embodiments, the preload 240 may be included within the internal volume 260. In some embodiments, the particulate deposition site 230 can also be present within the internal volume 260. In some embodiments, the preload 240 is the particulate deposition site 230. In some embodiments, the particulate deposition site 230 is a nucleation site.

[0069] In some embodiments, the electrochemical system 200 can be a metal-water system. In some embodiments, the electrochemical system 200 can be a metal-oxygen system. In some embodiments, the system 200 may be surrounded by an environment containing a liquid 290. For example, in some embodiments, the system may be at least partially immersed in a liquid containing water, such as brackish water, seawater, fresh water, or deionized water. In some embodiments, the system may be completely immersed in an aqueous environment 290. In some embodiments, the system may be immersed in an environment containing oxygen.

[0070] In some embodiments, the system 200 may use an oxygen-based electrolyte 210. In some embodiments, the system may use an aqueous electrolyte 210. In some embodiments, the aqueous electrolyte 210 may include at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, seawater, fresh water, brackish water, or any combination thereof. The electrolyte 210 may be the same as the surrounding environment 290 of the electrochemical system 200. For example, in some embodiments, the electrochemical system 200 may be surrounded by seawater 290, and the electrochemical system 200 may use seawater as the electrolyte 210 within the internal volume.

[0071] In some embodiments, the electrolyte 210 can have at least one type of harmful ionic species. For example, in some embodiments, the at least one type of harmful ionic species can include at least one of Ca 2+ , Mg 2+ , Fe 2+ or Fe 3+ . The electrode surface 270 may be affected, and metal by-products can accumulate in the cell without sufficient deposition to counteract this, so the harmful ionic species may reduce the current output of the system. In some embodiments, the harmful ionic species may contaminate the electrode 270, such as an aluminum anode, a lithium anode, a magnesium anode, a zinc anode, or an iron anode.

[0072] To reduce contamination and ensure a more efficient electrochemical system, system 200 can include at least one chelating agent 220 or preload 240 in an internal volume 260. In some embodiments, chelating agent 220 is configured to selectively coordinate with at least one dissolved species in aqueous electrolyte 210. In some embodiments, chelating agent 220 acts as a corrosion inhibitor for anode 270 in electrochemical system 200. In some embodiments, as described in further detail below, chelating agent 220 and preload 240 can be selected based on at least one of the type of electrode 270, the type of electrolyte 210, and the type of expected harmful ion species in electrolyte 210 or the ambient environment 290.

[0073] In some embodiments, electrochemical system 200 can include preload 240 or particulate deposition site 230. Particulate deposition site 230 can be a site in electrolyte 210 that collects deposits or accelerates the deposition process. In some embodiments, particulate deposition site 230 can be a nucleation site. In some embodiments, particulate deposition site 230 is suspended in aqueous electrolyte 210. In some embodiments, particulate deposition site 230 is dissolved in aqueous electrolyte 210. In some embodiments, particulate deposition site 230 can include aluminum hydroxide, silicon dioxide, aluminum oxide, aluminum oxyhydroxide, boehmite, sodium aluminate, calcium oxide, potassium aluminum sulfate, ammonium aluminum sulfate, dissolved aluminum species, or any combination thereof. In some embodiments, as described in further detail below, particulate deposition site 230 can be selected based on at least one of the type of electrode 270, the type of electrolyte 210, and the type of expected harmful ion species in electrolyte 210 or the ambient environment 290.

[0074] In some embodiments, the preload 240 is the precipitation site 230. In some embodiments, the particulate precipitation site 230 is a solid particulate site. In some embodiments, the preload 240 can be either a solid particulate precipitation site or a dissolved species.

[0075] Figure 3 shows a table of preload candidates according to various embodiments. In some embodiments, the preload candidates may be used for aluminum hydroxide deposition. In some embodiments, the preload candidates may be added to electrolytes of different phases. For example, in some embodiments, some species may be added as crystalline solids. In some embodiments, some species may be added to an amorphous phase. In some embodiments, the species may be added as salts, synthetic solids, natural solids, or any combination thereof.

[0076] In some embodiments, the preload candidate can be seed particles. In some embodiments, the effectiveness of preloading seed particles into an electrolyte to shorten the induction period depends on three factors: the composition of the seed particles and their solubility in the electrolyte, the surface area of the seed particles in the electrolyte, and the crystal structure or phase of the seed particles. In some embodiments, the preload candidate may be a layered double hydroxide (LDH).

[0077] In some embodiments, particles with low solubility in the electrolyte can have a greater impact on shortening the induction period of the system than particles with high solubility. For example, three aluminum hydroxide [oxide] species, boehmite, bayerite, and gibbsite, have decreasing solubility in alkaline solutions. In the case of boehmite and bayerite additives, little effect was observed, while the introduction of gibbsite resulted in a smaller power drop and a more rapid recovery from the transition period, as shown in FIG. 4. In some embodiments, the steady-state power can be affected by controlling which aluminum hydroxide phase forms after the induction period. For example, if precipitation is pushed to a phase with a faster growth rate, and then the rate of removal of aluminate increases, more hydroxide is released, and the cell operates at a higher current density in some embodiments.

[0078] Figures 4A and B show graphs of the solubility of the preload species and the performance of the electrochemical cell as a function of the preload species in the electrolyte cell, according to one embodiment.

[0079] In some embodiments, seed particles with a high specific surface area corresponding to particles with a high surface area to volume ratio were effective in damping the induction period. In some embodiments, the larger the surface area, the higher the effectiveness of preloading the electrolyte. In FIG. 4, both the 90C gibbsite line and the 63C gibbsite line correspond to the same amount of gibbsite added to the electrolyte, but the 90C gibbsite line corresponds to a particle size smaller than that of the 63C gibbsite line. The transition trough in FIG. 4B for the DI electrolyte containing gibbsite is sufficiently damped such that the discharge approaches a steady-state discharge without a transition trough period. This is a function of the number of active sites for the seed particles, which varies linearly with the increase in surface area. In some embodiments, the absolute surface area of all the particles in the solution can be increased by using a greater amount of smaller particles.

[0080] Regarding the operation of electrochemistry cells designed similarly at the same temperature, similar transition troughs can be observed at about 1 - 2 Ahr to discharge. As shown in Figure 4B, highly soluble species such as boehmite did not have a significant effect on the trough. With the addition of moderately soluble bayerite, the minimum current output occurred at 1.0 Ahr instead of 1.2 Ahr, and the current density was closer to 2 not less than 25 mA / cm 2 . The addition of gibbsite, the least soluble aluminum hydroxide species, resulted in a dampened trough of about 35 mA / cm 2 . In some embodiments, kinetically, the most favorable condition for the precipitation reaction is the gibbsite of the embodiment shown in Figure 4B, which can contribute to accelerating the precipitation rate of aluminate, reducing its concentration in the solution, and increasing the current output. In some embodiments, the time for the particles to completely dissolve varies widely among species. In some embodiments, the dissolution has no effect over the time scale of battery discharge.

[0081] Furthermore, in some embodiments, since the experimental conditions of precipitation have an impact on both the thermodynamically favorable state and the kinetically favorable state of the aluminum hydroxide by - product, the crystal phase of the pre - loaded seed particles is an important factor.

[0082] Figure 5 shows the composition of the precipitated aluminum hydroxide as a function of the electrolyte composition according to one embodiment. In some embodiments, under the conditions where the aluminum-water battery is discharged, gibbsite is the thermodynamically favorable phase for aluminum hydroxide. Kinetically, the first aluminum hydroxide product that forms between cold temperatures, 0 - 25 °C, at atmospheric pressure, and in the absence of additional salts or ionic species, is bayerite. The growth of bayerite has also been observed on other surfaces in electrochemical systems ("heterogeneous waste"). However, in some embodiments, the waste products can form various phases based on the crystal structure underlying the seed particles. For example, at temperatures higher than 25 °C and pH values higher than 14, the primary phase of the aluminum hydroxide precipitate is gibbsite. In some embodiments, the presence of salts of seawater and other insoluble particles, such as calcium hydroxide and magnesium hydroxide that form when seawater is mixed with potassium hydroxide, can also cause a kinetically favorable precipitation state to become gibbsite. As shown in Figure 5, the waste derived from the DI water-based electrolyte contained approximately 60% gibbsite, and the waste derived from the seawater-based electrolyte contained approximately 75% gibbsite. Figure 5 also shows a greater degree of amorphous (non-crystalline) waste that is also present in the seawater-based electrolyte, which causes the total percentage not to add up to 100%.

[0083] The presence of certain ionic species can have an adverse effect on cell performance, which is a unique challenge faced when the electrolyte for an electrochemical cell is formed from an environmental source of water. These sources can include, but are not limited to, seawater, brackish (wetland or marsh) water, agricultural drainage or other forms of wastewater, or other "natural" sources. One common technique used to bind ionic species is chelation, which is a chemical reaction that typically uses organic compounds to bind metal ions in solution.

[0084] Figure 6 shows Ca according to one embodiment 2+shows a chelating agent that forms a complex. Some embodiments may use specific Ca 2+ -binding and Fe 3+ -binding chelating agents in an aqueous electrolyte that is a natural source for an electrochemical cell. Some embodiments may use a chelating agent that can be dissolved in the aqueous electrolyte. Some embodiments may use an agent that cannot be dissolved in the aqueous electrolyte. For example, in some embodiments, the same purpose can be achieved by flowing the electrolyte over a chelating agent or ion exchange resin that is immobilized in a single process unit and then injected into the electrochemical cell. Cationic species can complex with Ca 2+ in solution to continue the reaction and cannot contaminate the cell and inhibit the formation of metal-hydroxide by-products.

[0085] In the case of an aluminum-water cell, cationic species such as Ca 2+ , Sr 2+ and Fe 3+ present in the electrolyte can affect the electrochemistry by various species-dependent mechanisms. Two main mechanisms occur with these species: 1) by contaminating one or the other of the electrode surfaces, preventing one of the half-reactions from occurring, and / or 2) by inhibiting the formation of aluminum hydroxide by-products, increasing the hydroxide and reducing the current output of the electrochemical cell.

[0086] More specifically, the detrimental effects of Fe 3+ ions are caused by the first mechanism. In some embodiments, Fe 3+ may promote the H2 generation reaction to occur at the anode, which may reduce the Coulombic efficiency and the output of the cell. Ca 2+ and Sr 2+The presence of ions can cause the latter mechanism, which has two effects on electrochemistry. Divalent cations can inhibit the formation of aluminum hydroxide by-products and, second, can increase the thickness of the double hydroxyl layer on the anode surface. Both effects reduce the cell's current output by preventing the transport of hydroxide ions to the anode. Both actions can be corrected by the introduction of a chelating agent, such as that shown in Figure 6. In some embodiments, the system can use multiple chelating agents specific to the harmful ions in the electrolyte.

[0087] Figure 7 shows the discharge of an aluminum-water electrochemical cell in an electrolyte formed from DI water containing KOH and various iron additives, according to one embodiment. In some embodiments, as shown in Figure 6, Fe 3+ may interact detrimentally with the cell, potentially reducing the cell's Coulombic efficiency and current output. As shown, the addition of Fe 2+ resulted in a temporary decrease in current density. In some embodiments, the presence of Fe 3+が resulted in a temporary decrease in Coulombic efficiency. In some embodiments, water is reduced by Fe 3+ at the aluminum anode, causing a short circuit, in which case the current output or self-corrosion is not visible in the graph shown in Figure 7.

[0088] Fe 3+ Once completely consumed, the cell can recover to a current output similar to that when Fe is not toxic. For example, looking at Fe(III)Cl3, the output peaks at about 5 - 8 mA / cm 2 while the electrolyte in deionized water peaks at about 40 mA / cm 2 .

[0089] In some embodiments, Ca 2+ (and, by extension, Sr 2+)The presence of certain ions, such as ions, can significantly reduce the effectiveness of the preload scheme. FIG. 8 shows the discharge of an aluminum-water electrochemical cell in an electrolyte formed from seawater and DI water containing KOH, Al(OH)3, and various calcium additives, according to one embodiment. The graph shows DI water containing KOH and Al(OH)3 (solid line), seawater with added KOH and Al(OH)3 preload (dashed line), and the total charge passed through an electrolyte formed from DI water with added KOH, Al(OH)3 preload, and Ca 2+ The graph shows the total charge passed through electrolytes formed from DI water containing KOH and Al(OH)3 (solid line), seawater with added KOH and Al(OH)3 preload (dashed line), and DI water with added KOH, Al(OH)3 preload, and Ca 2+ In some embodiments, the combination of DI water containing the electrolyte and aluminum hydroxide results in a greater total charge passed than a seawater electrolyte combined with aluminum hydroxide. Both of these combinations result in a greater total charge passed than a combination of DI water containing aluminum hydroxide and calcium chloride. As shown in FIG. 8, since the solution becomes saturated with aluminate, there is less decrease in current density in the combination of DI water containing the electrolyte and aluminum hydroxide than when Ca

[0090] FIG. 9 shows the discharge of an aluminum-water electrochemical cell in DI water and seawater electrolytes containing added Al(OH)3 preload and various added salts as a function of the total charge passed through the cell, according to one embodiment. As shown, the average current density for preload-containing electrolytes constructed using DI water, DI water and MgCl2, and DI water and NaCl is higher than the average current density for preload-containing electrolytes constructed from seawater or DI water and CaCl2. In other words, the transition trough decreases for preload-containing electrolytes that do not contain calcium ions.

[0091] FIGS. 10A, 10B, and 10C show three tables of chelating agent candidates studied according to one embodiment. Multiple chemical chelating agents can be used in an electrochemical system to make the system more efficient. Some embodiments include Ca 2+Chelating agents specific to it, generally chelating agents that bind cations, or soluble salts that form insoluble calcium or other metal products precipitating from the solution can be used. In some embodiments, multiple chelating agents can be selected in light of at least one of an environment specific to the electrolyte or specific to the electrode. For example, if a large amount of calcium ions are expected to be present in the electrolyte, the system can include a chelating agent configured to bind to Ca 2+ In some embodiments, the system can include multiple chelating agents. In some embodiments, if a large amount of iron ions and calcium ions are expected to be present in the electrolyte, the system can include a chelating agent configured to bind to at least one of Fe 3+ and Ca 2+ a chelating agent generally configured to bind cations, or multiple chelating agents, and at least one of the multiple chelating agents is configured to bind to Fe 3+ and the other of the multiple chelating agents is configured to bind to Ca 2+ .

[0092] In the experiment, the effect of the chelating agent was measured using the pre-transition current and power density instead. When harmful species are removed from the solution, the cell approaches a discharge profile similar to that of a method performed using an electrolyte formed from deionized / distilled water. Most chelating species bind ions in a 1:1 molar ratio, and thus it was used as a basis for determining how much chelating agent to add. However, in some embodiments, the concentration of the chelating agent may not be exactly 1:1 molar ratio. In some embodiments, the concentration of the chelating agent may be equal to the concentration of Ca 2+ in the solution. In some embodiments, the concentration of the chelating agent may be equal to all the concentrations of divalent and trivalent cation species in the solution, including Ca 2+ , Mg 2+ and Fe 3+ . These are Na + and K +It contains most of the dissolved cation species present in seawater, excluding monovalent cations such as etc.

[0093] Not all species of chelating agents have the same effectiveness. Some embodiments can use various chelating agents depending on the stability of the chelating agent at high alkalinity, the ion selectivity that favors divalent and trivalent cations over other species present, and the solubility of the target species at certain pH conditions. For example, Ca 2+ 、Mg 2+ およびSr 2+ Some target species in alkaline solutions, as, form solid metal hydroxides when exposed to strong bases. Under high pH conditions, the equilibrium favors precipitation, but trace amounts of these species can remain in solution in some embodiments. In some embodiments, consumption of the trace dissolved amount can shift the equilibrium in the direction of solubilizing the metal hydroxide (the metal represented as M in the following scheme) and then chelating the species (the chelating agent represented as Chl below).

Number

[0094] Kinetically, this process can occur over a period of ten-odd minutes to several hours, and significant improvement is generally observed after 15 minutes. The performance of each chelating agent can vary in a particular embodiment, and compounds containing multiple carboxylic acid and nitrile groups perform best, while compounds with fewer functional groups do not bind metal ions as effectively. In some embodiments, when the solid of the metal hydroxide transitions to a more crystalline form, the dissolution rate can slow down and the period required to bind metal ions increases.

[0095] Figure 11 shows the discharge of an aluminum-water electrochemical cell containing a seawater electrolyte under four conditions according to one embodiment. These conditions are: seawater electrolyte; seawater electrolyte and chelating agent; seawater electrolyte, chelating agent and preload; and addition of seawater electrolyte, preload and pre-roughened chelating agent.

[0096] In some embodiments, to pre-roughen the chelating agent, the chelating agent may be sandblasted. In some embodiments, the chelating agent may contain Ca 2+ . In some embodiments, the combination of an effective payload and a suitable chelating agent significantly dampens the induction period, accelerates the discharge to a steady state, and generally improves the performance of the aluminum-water electrochemical cell. As shown in FIG. 11, the seawater electrolyte alone had a large gap between the transition trough and the recovery point. However, the seawater electrolyte containing the payload and the chelating agent has a smaller difference in current density between the transition trough and the recovery point. Pre-roughening the chelating agent significantly reduces that difference as well. Furthermore, the time from the pre-transition peak to the recovery point is shorter for the case of the chelating agent, payload, and seawater electrolyte than for the case of just the seawater electrolyte or the seawater electrolyte and the chelating agent alone.

[0097] FIG. 12A shows a graph comparing the current density of the electrolyte composition throughout the electrochemical discharge process according to one embodiment. FIG. 12B shows a graph comparing the difference in the amount of charge passed for each coulombic efficiency based on various electrolyte compositions. These show compilations of experimental data collected regarding important performance metrics in the discharge of an electrochemical flow cell with respect to the electrolyte in seawater under three conditions: raw seawater electrolyte, seawater electrolyte with payload present, and seawater electrolyte with payload and chelating agent present.

[0098] In some embodiments, the preload, whether introduced alone or in combination with a chelating agent, does not significantly affect the Coulombic efficiency of the cell or the average current density at steady state. However, in some embodiments, the time to transition and the maximum current density before and at the transition trough are significantly improved. The ratio shows further stabilization in some embodiments, indicating that the preload, alone or in combination with a chelating agent, can shorten the induction period and enable the electrochemical system to reach the recovery point more quickly. For example, as shown in FIG. 12A, the average after transition is relatively similar for all three conditions, but the minimum value of the trough is much higher for the seawater electrolyte with the preload and chelating agent than for the raw seawater electrolyte. This indicates that in some embodiments, adding the preload and chelating agent results in a more stable electrochemical system.

[0099] Although some embodiments of the present invention have been described and illustrated herein, those skilled in the art can readily conceive of various other means and / or structures for performing the functions described herein and / or obtaining the results and / or one or more advantages, and each such variation and / or modification is considered to be within the scope of the present invention. More generally, those skilled in the art will recognize that all parameters, dimensions, materials, and configurations described herein are intended to be illustrative, and that the actual parameters, dimensions, materials, and / or configurations depend on the particular application(s) in which the teachings of the present invention are used. Those skilled in the art can recognize or elucidate numerous equivalents to the specific embodiments of the present invention described herein using only routine experimentation. Accordingly, the foregoing embodiments are presented by way of example only, and it should be understood that the present invention can be practiced otherwise than as specifically described and claimed within the scope of the appended claims and their equivalents. The present invention is directed to each of the individual features, systems, articles, materials, and / or methods described herein. Furthermore, any combination of two or more of such features, systems, articles, materials, and / or methods is included within the scope of the present invention if such features, systems, articles, materials, and / or methods are not mutually inconsistent.

[0100] It should be understood that, as used herein in the specification and claims, the indefinite articles "a" and "an" mean "at least one" unless clearly indicated to the contrary.

[0101] As used herein in the specification and claims, the phrase "and / or" should be understood to mean "either or both" of the elements so connected, i.e., in some cases presented conjunctively and in other cases presented disjunctively. Other elements not specifically identified by the "and / or" clause may be present as necessary, whether or not related to those specifically identified elements, unless clearly indicated to the contrary. Thus, by way of non-limiting example, in the case of "A and / or B," when used in conjunction with open-ended language such as "comprising," in one embodiment it may refer to A without B (optionally including elements other than B); in another embodiment, it may refer to B without A (optionally including elements other than A); and in yet another embodiment, it may refer to both A and B (optionally including other elements), etc.

[0102] As used in this specification and the claims, "or" shall be understood to have the same meaning as "and / or" as defined above. For example, when separating items in a list, "or" or "and / or" is inclusive, i.e., it includes the number of elements or at least one of the items in the list, but also includes more than one and, if necessary, additional items not listed. Only terms such as "only one of" or "exactly one of" or, when used in the claims, terms such as "consisting of" that are expressly indicated to the contrary, refer to exactly one element of the number of elements or the list. Generally, the term "or" as used in this specification shall be construed to indicate an exclusive alternative (i.e., "one or the other, but not both") only when preceded by an exclusive term such as "either," "one of," "only one of," or "exactly one of." "Consisting essentially of" shall have its ordinary meaning as used in the field of patent law when used in the claims.

[0103] As used herein, the phrase "at least one" in reference to a list of one or more elements in the specification and claims means at least one element selected from any one or more of the elements in the list of elements, but does not necessarily include at least one of every element specifically listed within the list of elements, and is not to be construed as excluding any combinations of elements in the list of elements. By this definition, elements other than those specifically identified within the list of elements to which the phrase "at least one" refers may also be present, as necessary, regardless of whether or not they are related to the specifically identified elements. Thus, by way of non-limiting example, "at least one of A and B" (or equivalently "at least one of A or B" or equivalently "at least one of A and / or B") can refer, in one embodiment, to at least one, and optionally more than one, A, with no B present, (and optionally including elements other than B); in another embodiment, to at least one, and optionally more than one, B, with no A present (and optionally including elements other than A); and in yet another embodiment, to at least one, and optionally more than one, A, and at least one, and optionally more than one, B (and optionally including other elements), and so forth.

[0104] In the claims, as well as in the specification above, all transitional phrases such as "comprising," "including," "carrying," "having," "containing," "involving," "holding," and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" are to be considered closed or semi-closed transitional phrases, as set forth in item 2111.03 of the United States Patent and Trademark Office's Manual of Patent Examining Procedure. The present invention provides, for example, the following items. (Item 1) An aqueous electrolyte, at least one chelating agent configured to bind to at least one harmful ion species, and a fine particle deposition site An electrochemical system comprising. (Item 2) The electrochemical system according to Item 1, wherein the fine particle deposition site is suspended in the aqueous electrolyte. (Item 3) The electrochemical system according to Item 1, wherein the electrochemical system is a metal-water system. (Item 4) The electrochemical system according to Item 1, wherein the electrochemical system is a metal-oxygen system. (Item 5) The electrochemical system according to Item 1, wherein the chelating agent is a corrosion inhibitor for the anode in the electrochemical system. (Item 6) The electrochemical system according to Item 1, wherein the fine particle deposition site contains aluminum hydroxide, silicon dioxide, aluminum oxide, aluminum oxyhydroxide, boehmite, sodium aluminate, calcium oxide, potassium aluminum sulfate, ammonium aluminum sulfate, or dissolved aluminum species. (Item 7) The electrochemical system according to Item 1, wherein the chelating agent is configured to selectively coordinate with at least one dissolved species in the aqueous electrolyte. (Item 8) The electrochemical system according to Item 1, wherein the aqueous electrolyte contains at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, seawater, fresh water, brackish water, or any combination thereof. (Item 9) The at least one harmful ion species contains at least one of Ca 2+ , Mg 2+ , Fe 2+ or Fe 3+ , The electrochemical system according to Item 1. (Item 10) The electrochemical system according to Item 1, wherein the fine particle deposition site is a nucleation site. (Item 11) A method of forming an electrochemical system, comprising: producing a housing having an internal volume; disposing at least one electrode within the internal volume; adding to the internal volume at least one chelating agent configured to bind to at least one harmful ion species; and adding a fine particle deposition site to the internal volume A method comprising. (Item 12) The method according to item 11, further comprising the step of adding an electrolyte to the internal volume. (Item 13) The method according to item 12, wherein the step of adding the electrolyte to the internal volume includes the step of at least partially immersing the housing in a liquid containing water. (Item 14) The method according to item 11, wherein the particulate deposition site is either suspended or dissolved in an aqueous electrolyte. (Item 15) The method according to item 14, wherein the aqueous electrolyte comprises at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, seawater, fresh water, brackish water, or any combination thereof. (Item 16) The method according to item 11, wherein the electrochemical system is a metal-water system. (Item 17) The method according to item 11, wherein the chelating agent is a corrosion inhibitor for the anode in the electrochemical system. (Item 18) The method according to item 11, wherein the chelating agent is configured to selectively coordinate with at least one dissolved species in the aqueous electrolyte within the housing. (Item 19) The at least one harmful ion species is Ca 2+ Mg 2+ Fe 2+ or Fe 3+ The method according to item 11, comprising at least one of the above. (Item 20) The method according to item 11, wherein the electrode comprises at least one of an aluminum anode, a lithium anode, a magnesium anode, a zinc anode, or an iron anode.

Claims

1. An aqueous electrolyte, at least one chelating agent configured to bind to at least one harmful ion species, and a fine particle deposition site comprising an electrochemical system.

2. The electrochemical system according to Claim 1, further comprising a preload.

3. The electrochemical system according to Claim 1, wherein the electrochemical system is a metal-water system.

4. The electrochemical system according to Claim 1, wherein the fine particle deposition site is a solid fine particle deposition site.

5. The electrochemical system according to Claim 1, wherein the chelating agent is a corrosion inhibitor for an anode in the electrochemical system.

6. The electrochemical system according to Claim 1, wherein the fine particle deposition site comprises aluminum hydroxide, silicon dioxide, aluminum oxide, aluminum oxyhydroxide, boehmite, sodium aluminate, calcium oxide, potassium aluminum sulfate, ammonium aluminum sulfate, or dissolved aluminum species.

7. The electrochemical system according to Claim 1, wherein the chelating agent is configured to selectively coordinate with at least one dissolved species in the aqueous electrolyte.

8. The electrochemical system according to Claim 1, wherein the aqueous electrolyte comprises at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, seawater, fresh water, brackish water, or any combination thereof.

9. wherein the at least one harmful ion species is Ca ２＋ , Mg ２＋ , Fe ２＋ or Fe ３＋ and the electrochemical system according to claim 1 comprises at least one of them.

10. The electrochemical system according to Claim 1, further comprising a preload comprising seed particles.

11. A method of forming an electrochemical system, comprising: producing a housing having an internal volume; disposing at least one electrode within the internal volume; adding to the internal volume at least one chelating agent configured to bind to at least one harmful ion species; and adding a fine particle deposition site to the internal volume A method comprising.

12. The method according to Claim 11, further comprising adding an electrolyte to the internal volume.

13. The method according to Claim 11, further comprising adding at least one preload to the internal volume.

14. The method according to Claim 11, wherein the fine particle deposition site is either suspended or dissolved in the aqueous electrolyte.

15. The method according to claim 14, wherein the aqueous electrolyte contains at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, seawater, fresh water, brackish water, or any combination thereof.

16. The method according to claim 11, wherein the electrochemical system is a metal-water system.

17. The method according to claim 11, wherein the chelating agent is a corrosion inhibitor for the anode in the electrochemical system.

18. The method according to claim 11, wherein the chelating agent is configured to selectively coordinate with at least one dissolved species in the aqueous electrolyte within the housing.

19. wherein said at least one harmful ion species is Ca ２＋ , Mg ２＋ , Fe ２＋ or Fe ３＋ The method according to claim 11, comprising at least one of them.

20. The method according to claim 11, wherein the electrode contains at least one of an aluminum anode, a lithium anode, a magnesium anode, a zinc anode, or an iron anode.

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