High-performance electrolyte for molten carbonate fuel cells

Abstract

A molten carbonate fuel cell includes an anode and a cathode separated by an electrolyte. The electrolyte includes Li2CO3, Na2CO3, and K2CO3. K2CO3 is present in a concentration of less than or equal to 3.5 mol% of the electrolyte.

Description

Atty. Dkt. No.: 106876-2268HIGH-PERFORMANCE ELECTROLYTE FOR MOLTEN CARBONATE FUEL CELLS CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of and priority to U. S. Provisional Application No. 63 / 730,784, filed December 11, 2024, the entire disclosure of which is incorporated herein by reference.TECHNICAL FIELD[00021 The present disclosure relates generally to the field of electrochemical cells. In particular, the present disclosure relates to electrolytes for fuel cells.BACKGROUND

[0003] A fuel cell is a type of electrochemical cell that uses an electrochemical reaction to convert chemical energy stored in a fuel such as hydrogen or methane into electrical energy. In general, fuel cells typically include an anode and a cathode separated by an electrolyte contained in an electrolyte matrix. Fuel is supplied to the anode, and an oxidant is supplied to the cathode via the second flow field. The fuel cell may oxidize the fuel in an electrochemical reaction, which releases a flow of electrons between the anode and cathode, thereby converting chemical energy into electrical energy.SUMMARY

[0004] At least one aspect of the present disclosure is directed to a molten carbonate fuel cell. The molten carbonate fuel cell includes an anode and a cathode separated by an electrolyte. The electrolyte includes Li2CO3, Na2CO3, and K2CO3. K2CO3 is present in a concentration of less than or equal to 3.5 mol% of the electrolyte.-1- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268[0005[ Another aspect of the present disclosure is directed to an electrolyte. The electrolyte includes Li2CO3, Na2CO3, and K2CO3. K2CO3 is present in a concentration of less than or equal to 3.5 mol% of the electrolyte.|0006] The summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices and / or processes described herein, as defined solely by the claims, will become apparent in the detailed description set forth herein and taken in conjunction with the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS[0007[ The details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

[0008] FIG. 1 is a schematic diagram of a portion of a molten carbonate fuel cell stack, according to an exemplary embodiment.

[0009] FIG. 2 is a plot of heat flow vs. temperature for electrolytes, according to an exemplary embodiment.

[0010] FIG. 3 is a plot of voltage vs. temperature for electrolytes, according to an exemplary embodiment.

[0011] FIG. 4 is a plot of cathode polarization vs. temperature for electrolytes, according to an exemplary embodiment.

[0012] FIG. 5 is a plot of voltage vs. temperature for electrolytes, according to an exemplary embodiment.

[0013] It will be recognized that the figures are schematic representations for purposes of illustration. The figures are provided for the purpose of illustrating one or more implementations -2- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268with the explicit understanding that the figures will not be used to limit the scope of the meaning of the claims. Like reference numbers and designations in the various drawings indicate like elements.DETAILED DESCRIPTION

[0014] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and made part of this disclosure.

[0015] Disclosed herein are systems and methods for electrolytes for fuel cells. Molten carbonate fuel cells (MCFCs) operate by passing a reactant fuel gas through the anode, while oxidizing gas is passed through the cathode. The anode and the cathode of MCFCs are isolated from one another by a porous electrolyte matrix which is saturated with carbonate electrolyte. MCFCs can include a carbonate electrolyte stored in the pores of the anode and of the cathode and in gas passages formed in the anode and cathode current collectors. Generally MCFCs operate at intermediate temperatures, and the electrolyte melts during the initial heat up of the fuel cell and redistributes among the pores of the anode, the cathode, and the electrolyte matrix due to the capillary forces of the pores.[0016| Lithium carbonate and sodium carbonate electrolytes can have low oxygen gas solubility, which can affect fuel cell performance particularly at low temperatures (e.g., temperatures less than 600°C). Lithium carbonate and sodium carbonate electrolytes that include 52 mol% lithium carbonate and 48 mol% sodium carbonate can exhibit poor performance at low temperatures-3- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268compared to lithium carbonate and potassium carbonate electrolytes that include 62 mol% lithium carbonate and 38 mol% potassium carbonate. This can be due to high cathode polarization due to low oxygen solubility. Lithium carbonate and sodium carbonate electrolytes doped with additives (e.g., Rb2CO3, CS2CO3, or Bi2O3) can improve fuel cell performance at the low temperatures. However, these additives can exhibit high vapor pressure, which can negatively impact the fuel cell voltage decay and reforming catalyst stability as well as accelerate electrolyte loss, decrease direct internal reforming catalyst stability, shorten fuel cell lifetime. Additionally, the additives can clog downstream equipment of the balance of plant (BOP). BOP components can include components of the fuel cell except the stack itself.

[0017] The systems and methods of the present disclosure can include an electrolyte for molten carbonate fuel cells. The electrolyte can have a high oxygen solubility and high performance at low cell temperatures (e.g., temperatures less than 575-600°C). Fuel cells of the present disclosure can have decreased cathode flooding, improved anode wetting, and low vapor pressure additives able to improve oxygen gas solubility in the melt. The electrolyte of the present disclosure can improve the performance of lithium carbonate and sodium carbonate electrolyte-based cells over baseline cells by greater than 10-15 mV at temperatures less than 600°C. The electrolyte of the present disclosure can improve the performance of lithium carbonate and sodium carbonate electrolyte-based cells over lithium carbonate and potassium carbonate electrolyte-based cells by greater than 55-60 mV at temperatures less than 600°C. The electrolyte of the present disclosure can have high ionic conductivity, low vapor pressure, and low cathode dissolution. The electrolyte of the present disclosure can decrease cathode polarization at low temperature and improve electrolyte distribution between active components (e.g., anode, cathode, and matrix) to avoid cathode flooding and high mass-transfer resistance. The electrolyte of the present disclosure can increase electrolyte distribution. The electrolyte of the present disclosure can decrease cathode polarization. The electrolyte of the present disclosure can decrease electrolyte vapor loss. The electrolyte of the present disclosure can decrease direct internal reforming catalyst poisoning. The electrolyte of the present disclosure can extend the fuel cell lifetime or fuel cell stack lifetime. The electrolyte of the present disclosure can allow for-4- 4916-7700-5175.1Atty. Dkt. No.: 106876-226810°C-15°C lower fuel cell or fuel cell stack operation temperatures, leading to decreased degradation and extended fuel cell lifetime or fuel cell stack lifetime.

[0018] Compared to lithium carbonate and sodium carbonate electrolytes doped with additives such as Rb2CC>3, CS2CO3, or Bi2O3, the electrolyte of the present disclosure can have improved voltage (e.g., greater than 10-15 mV). Compared to electrolytes that include 62 mol% lithium carbonate and 38 mol% potassium carbonate, the electrolyte of the present disclosure can have improved voltage (e g., greater than 60 mV). Compared to electrolytes that include 52 mol% lithium carbonate and 48 mol% sodium carbonate, the electrolyte of the present disclosure can have improved voltage (e.g., greater than 150-200 mV).

[0019] FIG. 1 is a schematic diagram of a portion of a molten carbonate fuel cell stack. The portion of the stack shown in FIG. 1 corresponds to a fuel cell 100. To isolate the fuel cell 100 from adjacent fuel cells in the stack and / or other elements in the stack, the fuel cell 100 includes separator plates 110 and 111. In FIG. 1, the fuel cell 100 includes an anode 130 and a cathode 150. In various aspects, the cathode 150 can correspond to a dual-layer (or multi-layer) cathode. The cathode 150 can be formed from a porous sintered NiO material. Anode current collector 120 provides electrical contact between the anode 130 and the other anodes in the fuel cell stack, while cathode current collector 160 provides similar electrical contact between the cathode 150 and the other cathodes in the fuel cell stack. Additionally, the anode current collector 120 allows for introduction and exhaust of gases from the anode 130, while cathode current collector 160 allows for introduction and exhaust of gases from the cathode 150. The cathode current collector 160 can be configured to support the cathode 150.

[0020] The anode 130 can be made of nickel or a nickel alloy. For example, the anode 130 can include at least one of Ni4Cr (e.g., nickel alloy with 4 wt% Cr) or Ni3Al (e.g., nickel alloy with 3 wt% Al). The mixture of Ni4Cr and Ni3Al in the anode 130 can improve anode electrolyte storage capacity and reduce cathode flooding. The anode 130 can be formed from a porous Ni-Al, Ni-Cr, or Ni-Cr-Al material. Ni4Cr can be present in a concentration range of 25 wt% to 45 wt% of the anode 130. For example, the anode 130 can include a range of 25 wt% Ni4Cr to 30-5- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268wt% Ni4Cr, 25 wt% Ni4Cr to 35 wt% Ni4Cr, 25 wt% Ni4Cr to 40 wt% Ni4Cr, 25 wt% Ni4Cr to 45 wt% Ni4Cr, 30 wt% Ni4Cr to 35 wt% Ni4Cr, 30 wt% Ni4Cr to 40 wt% Ni4Cr, 30 wt% Ni4Cr to 45 wt% Ni4Cr, 35 wt% Ni4Cr to 40 wt% Ni4Cr, 35 wt% Ni4Cr to 45 wt% Ni4Cr, or 40 wt% Ni4Cr to 45 wt% Ni4Cr. The concentration of Ni4Cr present in the anode 130 can improve anode electrolyte storage capacity and reduce cathode flooding. In some embodiments, Ni4Cr is present in a concentration range of 20 wt% to 45 wt% of the anode 130. A concentration of greater than 45 wt% Ni4Cr can lead to anode flooding. Ni3 Al can be present in a concentration range of 60 wt% to 80 wt% of the anode 130. For example, the anode 130 can include a range of 60 wt% Ni3Al to 65 wt% Ni3 Al, 60 wt% Ni3Al to 70 wt% Ni3Al, 60 wt% Ni3Al to 75 wt% Ni3Al, 60 wt% Ni3Al to 80 wt% Ni3Al, 65 wt% Ni3Al to 70 wt% Ni3Al, 65 wt% Ni3Al to 75 wt% Ni3Al, 65 wt% Ni3Al to 80 wt% Ni3Al, 70 wt% Ni3Al to 75 wt% Ni3Al, 70 wt% Ni3Al to 80 wt% Ni3Al, or 75 wt% Ni3Al to 80 wt% Ni3Al. In some embodiments, Ni4Cr is present in a concentration of 30 wt% of the anode 130 and Ni3Al can be present in a concentration of 70 wt% of the anode 130. The anode 130 having 30 wt% Ni4Cr and 70 wt% Ni3Al can enhance electrolyte retention and wetting.[00211 The anode 130 and the cathode 150 are separated by an electrolyte matrix 140. For example, the electrolyte matrix 140 can be disposed between the anode 130 and the cathode 150. The electrolyte matrix 140 can be formed from a ceramic material (e.g., porous ceramic material). The electrolyte matrix 140 can include a mixture of LiAlO2and BaCO3. The electrolyte matrix 140 can be made of LiAlO2. The electrolyte matrix 140 can be doped with BaCO3. For example, the electrolyte matrix 140 can include LiAlO2doped with BaCO3. BaCO3can be stored initially in the electrolyte matrix 140 (e.g., green electrolyte matrix) to facilitate or accelerate matrix electrolyte filling during initial start-up and prevent gas crossover. BaCO3can be present in a concentration of 1 wt% to 2 wt% of the electrolyte matrix 140. For example, the electrolyte matrix 140 can include a range of 1 wt% BaCO3to 1.2 wt% BaCO3, 1 wt% BaCO3to 1.4 wt% BaCO3, 1 wt% BaCO3to 1.6 wt% BaCO3, 1 wt% BaCO3to 1.8 wt% BaCO3, 1 wt% BaCO3to 2 wt% BaCO3, 1.2 wt% BaCO3to 1.4 wt% BaCO3, 1.2 wt% BaCO3to 1.6 wt% BaCO3, 1.2 wt% BaCO3to 1.8 wt% BaCO3, 1.2 wt% BaCO3to 2 wt% BaCO3, 1.4 wt% BaCO3-6- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268to 1.6 wt% BaCO3, 1.4 wt% BaCO3to 1.8 wt% BaCOs, 1.4 wt% BaCO3to 2 wt% BaCO3, 1.6 wt% BaCO3to 1.8 wt% BaCO3, 1.6 wt% BaCO3to 2 wt% BaCO3, or 1.8 wt% BaCO3to 2 wt% BaCO3. In some embodiments, BaCO3is present in a concentration of 0.5 wt% to 2.5 wt% of the electrolyte matrix 140. BaCO3can accelerate matrix filling during MCFC conditioning. The electrolyte matrix 140 can include at least one of BaO, SrO, or SrCO3. BaO, SrO, and / or SrCO3can be used to accelerate filling of the electrolyte matrix 140 during initial conditioning of the fuel cell 100. The content of BaO, SrO, and / or SrCO3can be in a range of 1 wt% to 3 wt%.

[0022] An electrolyte 142 can be disposed in the electrolyte matrix 140. For example, the electrolyte matrix 140 can contain the electrolyte 142. The electrolyte 142 can include a first electrolyte. The anode 130 and the cathode 150 can be separated by the electrolyte 142. During operation of the fuel cell stack, the electrolyte matrix 140 can be saturated with the electrolyte 142. The electrolyte 142 can be stored, prior to operation of the fuel cell stack, in at least the pores of the cathode 150. The electrolyte 142 may be stored in the electrolyte matrix 140. The electrolyte 142 may be stored in the anode 130. The cathode 150 can be filled with the electrolyte 142 prior to assembly into the fuel cell 100. After the cathode 150 is assembled into the fuel cell stack, and during conditioning and operation of the fuel cell stack, the electrolyte 142 stored in the cathode 150 can melt and permeate the electrolyte matrix 140. The electrolyte 142 can be disposed in the cathode 150. The electrolyte 142 can be distributed between active components (e.g., anode 130, cathode 150, and electrolyte matrix 140). This distribution can allow for lower cathode polarization and higher performance at temperatures less than 600°C. After electrolyte redistribution during the beginning of the life of the fuel cell 100 or the fuel cell stack, BaCO3can promote an enhanced oxygen solubility in the electrolyte 142 and lead to reduced cathode polarization loss.

[0023] The electrolyte 142 (e.g., first electrolyte) can have a composition including lithium carbonate (Li2CO3), sodium carbonate (Na2CO3) and potassium carbonate (K2CO3). The electrolyte 142 can be free of additives that have a high vapor pressure. For example, the electrolyte 142 may be free of (e.g., not include) Rb2CO3, CS2CO3, and / or Bi2O3. The additives that have high vapor pressure can increase the vapor pressure of the electrolyte 142. The-7- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268additives that have high vapor pressure can clog downstream equipment of the BOP and impact electrolyte inventory for long-term operation, reducing fuel cell life and overall performance at low temperatures (e.g., temperatures less than 600°C, T < 600°C).10024] The electrolyte 142 can include K2CO3 present in a concentration of less than or equal to 3.5 mol% of the electrolyte 142. For example, the electrolyte 142 can have a concentration range of greater than 0 mol% K2CO3 to less than or equal to 3.5 mol% K2CO3. The electrolyte 142 can have a concentration of K2CO3 in a range of greater than 0 mol% to 0.5 mol%, greater than 0 mol% to 1 mol%, greater than 0 mol% to 1.5 mol%, greater than 0 mol% to 2 mol%, greater than 0 mol% to 2.5 mol%, greater than 0 mol% to 3 mol%, greater than 0 mol% to 3.5 mol%, 0.5 mol% to 1 mol%, 0.5 mol% to 1.5 mol%, 0.5 mol% to 2 mol%, 0.5 mol% to 2.5 mol%, 0.5 mol% to 3 mol%, 0.5 mol% to 3.5 mol%, 1 mol% to 1.5 mol%, 1 mol% to 2 mol%, 1 mol% to 2.5 mol%, 1 mol% to 3 mol%, 1 mol% to 3.5 mol%, 1.5 mol% to 2 mol%, 1.5 mol% to 2.5 mol%, 1.5 mol% to 3 mol%, 1.5 mol% to 3.5 mol%, 2 mol% to 2.5 mol%, 2 mol% to 3 mol%, 2 mol% to 3.5 mol%, 2.5 mol% to 3 mol%, 2.5 mol% to 3.5 mol%, or 3 mol% to 3.5 mol%. A concentration of greater than 3.5 mol% K2CO3 in the electrolyte 142 can lower the melting point of the electrolyte 142, which may negatively hinder binder burnout during an initial conditioning process of the MCFC stack. This conditioning process can occur at a temperature of less than 410°C.

[0025] The electrolyte 142 can include K2CO3 present in a concentration range of 1.5 mol% to 3 mol% of the electrolyte 142. For example, the electrolyte 142 can have a concentration of K2CO3 in a range of 1.5 mol% to 3 mol% of the electrolyte 142. This concentration range of the electrolyte 142 can mitigate early electrolyte melting issues. The electrolyte 142 can have a concentration of K2CO3 in a range of 1.5 mol% to 2 mol%, 1.5 mol% to 2.5 mol%, 1.5 mol% to 3 mol%, 1.5 mol% to 3.5 mol%, 2 mol% to 2.5 mol%, 2 mol% to 3 mol%, 2 mol% to 3.5 mol%, 2.5 mol% to 3 mol%, 2.5 mol% to 3.5 mol%, or 3 mol% to 3.5 mol%. The electrolyte 142 can include K2CO3 present in a concentration of 2.9 mol% of the electrolyte 142.-8- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268[0026| The electrolyte 142 can include a eutectic mixture of Li2CO3and Na2CO3. For example, the eutectic mixture of Li2CO3 andNa2CO3can include 52 mol% LJ2CO3 and 48 mol% Na2CC>3. The electrolyte 142 can include a eutectic mixture of Li2CO3and Na2CO3doped with K2CO3. For example, the electrolyte 142 can include a eutectic mixture of Li2CO3and Na2CC>3 doped with greater than 0 mol% K2CO3 and less than or equal to 3.5 mol% K2CO3.[0027J For the eutectic mixture of Li2CO3and Na2CO3doped with K2CO3, the electrolyte 142 can have a concentration of Li2CO3in a range of 50 mol% to 53 mol% of the electrolyte 142. The electrolyte 142 can have a concentration of Li2CO3 in a range of 50 mol% to 50.5 mol%, 50 mol% to 51 mol%, 50 mol% to 51.5 mol%, 50 mol% to 52 mol%, 50 mol% to 52.5 mol%, 50 mol% to 53 mol%, 50.5 mol% to 51 mol%, 50.5 mol% to 51.5 mol%, 50.5 mol% to 52 mol%, 50.5 mol% to 52.5 mol%, 50.5 mol% to 53 mol%, 51 mol% to 51.5 mol%, 51 mol% to 52 mol%, 51 mol% to 52.5 mol%, 51 mol% to 53 mol%, 51.5 mol% to 52 mol%, 51.5 mol% to 52.5 mol%, 51.5 mol% to 53 mol%, 52 mol% to 52.5 mol%, 52 mol% to 53 mol%, or 52.5 mol% to 53 mol%.

[0028] For the eutectic mixture of Li2CO3and Na2CO3doped with K2CO3, the electrolyte 142 can have a concentration of Na2CC>3 in a range of 46 mol% to 48 mol% of the electrolyte 142. The electrolyte 142 can have a concentration of Na2CC>3 in a range of 46 mol% to 46.5 mol%, 46 mol% to 47 mol%, 46 mol% to 47.5 mol%, 46 mol% to 48 mol%, 46.5 mol% to 47 mol%, 46.5 mol% to 47.5 mol%, 46.5 mol% to 48 mol%, 47 mol% to 47.5 mol%, 47 mol% to 48 mol%, or 47.5 mol% to 48 mol%.[Q029J The electrolyte 142 can include an off-eutectic mixture of Li2CO3and N 2CO3. For example, the off-eutectic mixture of LJ2CO3 and Na2CC>3 can include 54.4 mol% Li2CO3and 45.6 mol% Na2CC>3. The electrolyte 142 can include an off-eutectic mixture of Li2CO3 and Na2CO3 doped with K2CO3. For example, the electrolyte 142 can include an off-eutectic mixture of Li2CO3and Na2CO3 doped with greater than 0 mol% K2CO3 and less than or equal to 3.5 mol% K2CO3.4916-7700-5175.1Atty. Dkt. No.: 106876-2268[0030| For the off-eutectic mixture of Li2CO3and Na C03 doped with K2CO3, the electrolyte 142 can have a concentration of Li2CO3in a range of 52 mol% to 54 mol% of the electrolyte 142. The electrolyte 142 can have a concentration of Li2CO3in a range of 52 mol% to 52.5 mol%, 52 mol% to 53 mol%, 52 mol% to 53.5 mol%, 52 mol% to 54 mol%, 52.5 mol% to 53 mol%, 52.5 mol% to 53.5 mol%, 52.5 mol% to 54 mol%, 53 mol% to 53.5 mol%, 53 mol% to 54 mol%, or 53.5 mol% to 54 mol%.

[0031] For the off-eutectic mixture of Li2CO3and Na2CO3doped with K2CO3, the electrolyte 142 can have a concentration of Na2CO3 in a range of 44 mol% to 45 mol% of the electrolyte 142. The electrolyte 142 can have a concentration of Na2CC>3 in a range of 44 mol% to 44.2 mol%, 44 mol% to 44.4 mol%, 44 mol% to 44.6 mol%, 44 mol% to 44.8 mol%, 44 mol% to 45 mol%, 44.2 mol% to 44.4 mol%, 44.2 mol% to 44.6 mol%, 44.2 mol% to 44.8 mol%, 44.2 mol% to 45 mol%, 44.4 mol% to 44.6 mol%, 44.4 mol% to 44.8 mol%, 44.4 mol% to 45 mol%, 44.6 mol% to 44.8 mol%, 44.6 mol% to 45 mol%, or 44.8 mol% to 45 mol%.

[0032] In some embodiments, the electrolyte 142 includes Li2CO3present in a concentration of 52.8 mol% of the electrolyte 142. The electrolyte 142 can include Na2CC>3 present in a concentration of 44.3 mol% of the electrolyte 142. The electrolyte 142 can include K2CO3 present in a concentration of 2.9 mol% of the electrolyte 142. The electrolyte 142 can include combining an electrolyte composition in the cathode 150 made with an off-eutectic mixture of lithium carbonate and sodium carbonate doped with potassium carbonate. The off-eutectic mixture of lithium carbonate and sodium carbonate can include 54.4 mol% Li2CO3and 45.6 mol% Na2CO3before the K2CO3 is added. After the K2CO3 is added to the off-eutectic mixture of lithium carbonate and sodium carbonate, the composition of the electrolyte can include 52.8 mol% Li2CO3, 44.3 mol% Na2CO3, and 2.9 mol% K2CO3.

[0033] The electrolyte 142 can include a second electrolyte. The second electrolyte can be disposed in the cathode current collector 160. The cathode current collector 160 can store a predetermined amount of the second electrolyte. The second electrolyte can be stored in passages formed by the cathode current collector 160. The second electrolyte can include a mixture of-10- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268Li2CO3, Na C03, K2CO3, and lanthanum oxide (La2O3). The second electrolyte can be free of additives that have a high vapor pressure that may compromise electrolyte loss and / or reforming (e.g., direct internal reforming, DIR) catalyst performance stability. For example, the second electrolyte may be free of (e.g., not include) Rb2CC>3, CS2CO3, and / or Bi2C>3. The second electrolyte can include an off-eutectic mixture of Li2CO3and Na2CO3. For example, the off-eutectic mixture of Li2CO3 and Na2CO3 can include 93 mol% Li2CO3and 7 mol% Na2CO3. The second electrolyte can include an off-eutectic mixture of Li2CO3and Na2CC>3 doped with K2CO3 and / or La2O3. The concentration of K2CO3 in the electrolyte disposed in the cathode current collector 160 can be the same as or different from the concentration of K2CO3 in the electrolyte disposed in the cathode 150. The concentration of K2CO3 in the electrolyte disposed in the cathode current collector 160 can be the same as or different from the concentration of K2CO3 in the electrolyte disposed in the electrolyte matrix 140.|0034] The second electrolyte can include Li2CO3present in a concentration of 88 mol% to 91 mol% of the second electrolyte. For example, the second electrolyte can have a concentration of Li2CO3 in a range of 88 mol% to 91 mol% of the second electrolyte. The second electrolyte can have a concentration of Li2CO3in a range of 88 mol% to 88.5 mol%, 88 mol% to 89 mol%, 88 mol% to 89.5 mol%, 88 mol% to 90 mol%, 88 mol% to 90.5 mol%, 88 mol% to 91 mol%, 88.5 mol% to 89 mol%, 88.5 mol% to 89.5 mol%, 88.5 mol% to 90 mol%, 88.5 mol% to 90.5 mol%, 88.5 mol% to 91 mol%, 89 mol% to 89.5 mol%, 89 mol% to 90 mol%, 89 mol% to 90.5 mol%, 89 mol% to 91 mol%, 89.5 mol% to 90 mol%, 89.5 mol% to 90.5 mol%, 89.5 mol% to 91 mol%, 90 mol% to 90.5 mol%, 90 mol% to 91 mol%, or 90.5 mol% to 91 mol%.

[0035] The second electrolyte can include K2CO3 present in a concentration range of 1.5 mol% to 3 mol% of the second electrolyte. For example, the second electrolyte can have a concentration of K2CO3 in a range of 1.5 mol% to 3 mol% of the second electrolyte. The second electrolyte can have a concentration of K2CO3 in a range of 1.5 mol% to 2 mol%, 1.5 mol% to 2.5 mol%, 1.5 mol% to 3 mol%, 1.5 mol% to 3.5 mol%, 2 mol% to 2.5 mol%, 2 mol% to 3 mol%, 2 mol% to 3.5 mol%, 2.5 mol% to 3 mol%, 2.5 mol% to 3.5 mol%, or 3 mol% to 3.5-11- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268mol%. In some embodiments, the second electrolyte has a concentration of K2CO3 in a range of 1 mol% to 3.5 mol%. The second electrolyte can be doped with less than 2.5 mol% K2CO3.

[0036] The second electrolyte can include La2C>3 present in a concentration range of 1 mol% to 2 mol% of the second electrolyte. For example, the second electrolyte can have a concentration of La2C>3 in a range of 1 mol% to 2 mol% of the second electrolyte. The second electrolyte can have a concentration of La2C>3 in a range of 1 mol% to 1.2 mol%, 1 mol% to 1.4 mol%, 1 mol% to 1.6 mol%, 1 mol% to 1.8 mol%, 1 mol% to 2 mol%, 1.2 mol% to 1.4 mol%, 1.2 mol% to 1.6 mol%, 1.2 mol% to 1.8 mol%, 1.2 mol% to 2 mol%, 1.4 mol% to 1.6 mol%, 1.4 mol% to 1.8 mol%, 1.4 mol% to 2 mol%, 1.6 mol% to 1.8 mol%, 1.6 mol% to 2 mol%, or 1.8 mol% to 2 mol%. In some embodiments, the second electrolyte has a concentration of La2O3 in a range of 0.5 mol% to 2.5 mol%.[0037| In some embodiments, the second electrolyte includes Li2CO3present in a concentration of 89 mol% of the second electrolyte. The second electrolyte can include Na2CO3present in a concentration of 7 mol% of the second electrolyte. The second electrolyte can include K2CO3 present in a concentration of 2.5 mol% of the second electrolyte. The second electrolyte can include La2C>3 present in a concentration of 1.5 mol% of the second electrolyte. The second electrolyte can include combining an electrolyte composition in the cathode current collector 160 made with an off-eutectic mixture of lithium carbonate and sodium carbonate doped with potassium carbonate and lanthanum oxide. The off-eutectic mixture of lithium carbonate and sodium carbonate can include 92.7 mol% Li2CO3and 7.3 mol% Na2CC>3 before the K2CO3 and La2C>3 are added. After the K2CO3 and La2C>3 are added to the off-eutectic mixture of lithium carbonate and sodium carbonate, the composition of the electrolyte can include 89 mol% Li2CO3, 7 mol% Na2CO3, 2.5 mol% K2CO3, and 1.5 mol% La2O3.

[0038] In some embodiments, a system can include a cathode electrode (e.g., cathode 150) filled with an electrolyte (e g., electrolyte 142) having a first electrolyte composition. The first electrolyte composition can include a eutectic mixture of 52 mol% Li2CO3 and 48 mol% Na2CC>3 doped with less than 3.5 mol% (e.g., small amounts) of K2CO3. The first electrolyte composition-12- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268can include an off-eutectic mixture of 54.4 mol% Li2CO3and 45.6 mol% Na2CO3doped with less than 3.5 mol% of K2CO3. The first electrolyte composition can include K2CO3 present in a concentration of greater than 1.5 mol% and less than 3 mol%. The first electrolyte composition can include K2CO3 present in a concentration of 2.9 mol%. The presence of the small amount of K2CO3 in the eutectic mixture or off-eutectic mixture of Li2CO3and Na2CO3 can mitigate early electrolyte melting issues. The system can include an anode electrode (e.g., anode 130) that includes Ni4Cr and Ni3Al. The anode electrode can include Ni4Cr present in a concentration of 30 wt% to 45 wt%. This can improve the anode electrolyte storage capacity and reduce cathode flooding. The system can include the electrolyte matrix 140 disposed between the anode electrode and the cathode electrode. The electrolyte matrix 140 can be made of a mixture of LiAlO2and BaCO3. The electrolyte matrix 140 can include BaO, SrO, or SrCO3and / or a mixture of SrO and BaO or BaCOi. The electrolyte matrix 140 can include BaCO3present in a concentration of greater than 1 wt% to 2 wt%. This can accelerate electrolyte filling during initial conditioning of the MCFC. The system can include the cathode current collector 160 configured to support the cathode electrode. The system can include a second electrolyte (e.g., electrolyte 142) having a second electrolyte composition. The second electrolyte composition can include an off-eutectic mixture of 92.7 mol% Li2CO3and 7.3 mol% Na2CO3, K2CO3, and La2C>3 stored in the cathode current collector 160. The second electrolyte composition can include an off-eutectic mixture of 93 mol% Li2CO3and 7 mol% Na2CC>3 doped with greater than 1.5 mol% to less than 3 mol% K2CO3. The second electrolyte composition can include an off-eutectic mixture of 93 mol% Li2CO3 and 7 mol% Na2CO3doped 2.5 mol% K2CO3. The second electrolyte composition can include La2O3present in a concentration of greater than 1 mol% to 2 mol%.

[0039] In some embodiments, the system can include an electrolyte (e.g., electrolyte 142) having a first electrolyte composition. The first electrolyte can be disposed in a cathode. The first electrolyte composition can include a mixture of 52.8 mol% Li2CO3, 44.3 mol% Na2CO3, and 2.9 mol% K2CO3. The system can include a porous anode made of 30 wt% Ni4Cr and 70% Ni3Al. The system can include a porous electrolyte matrix (e.g., electrolyte matrix 140). The-13- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268electrolyte matrix 140 can be made of L1AIO2 and 1.5 wt% BaCO3. The system can include a second electrolyte having a second electrolyte composition. The second electrolyte can be stored in the cathode current collector 160. The second electrolyte can include a mixture of 89 mol% Li2CO3, 7 mol% Na2CO3, 2.5 mol% K2CO3, and 1.5 mol% La2O3.

[0040] During operation of the fuel cell stack, CO2is passed into the cathode current collector 160 along with O2. The CO2and O2diffuse into the cathode 150 (e.g., porous cathode) and travel to a cathode interface region near the boundary of the cathode 150 and the electrolyte matrix 140. In the cathode interface region, a portion of the electrolyte 142 can be present in the pores of the cathode 150. The CO2and O2can be converted near / in the cathode interface region to a carbonate ion (CO32), which can then be transported across the electrolyte 142 (and therefore across the electrolyte matrix 140) to facilitate generation of electrical current. In aspects where alternative ion transport is occurring, a portion of the O2can be converted to an alternative ion, such as a hydroxide ion or a peroxide ion, for transport in the electrolyte 142. After transport across the electrolyte 142, the carbonate ion (or alternative ion) can reach an anode interface region near the boundary of the electrolyte matrix 140 and the anode 130. The carbonate ion can be converted back to CO2and H2O in the presence of H2, releasing electrons that are used to form the current generated by the fuel cell. The H2and / or a hydrocarbon suitable for forming H2are introduced into the anode 130 via the anode current collector 120.

[0041] FIG. 2 is a plot 200 of heat flow (mW / mg) vs. temperature (°C) for electrolytes. FIG. 2 is a plot 200 of differential scanning calorimetry of lithium carbonate and sodium carbonate doped with different amounts of potassium carbonate. Electrolyte A includes 52.9 mol% Li2CO3, 44.3 mol% Na2CO3, and 2.9 mol% K2CO3. Electrolyte B includes 53.5 mol% Li2CO3, 41.1 mol% Na2CO3, and 5.4 mol% K2CO3. The plot 200 show that increasing K2CO3concentration (e.g., content) in a lithium carbonate and sodium carbonate electrolyte from 2.9 mol% K2CO3to 5.4 mol% K2CO3leads to a more pronounced early melting of a portion of the electrolyte at a temperature of approximately 400°C. Electrolyte B has a more pronounced early melting of a portion of the electrolyte at a temperature of approximately 400°C compared to Electrolyte A.-14- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268[0042| Electrolyte melting at a temperature of approximately 400°C (e.g., low temperature melting) can lead to incomplete combustion (e.g., burnout) of organic species (e.g., binder) present in the electrolyte matrix. Incomplete combustion can lead to carbon formation that can reduce the electrolyte matrix wetting and filling with the electrolyte, which can cause higher gas cross-over. The electrolyte 142 can include Electrolyte A. The concentration of K2CO3 in the electrolyte 142 can be in a range of 1.5 mol% and 3 mol%. The concentration of K2CO3 in the electrolyte 142 can reduce the surface tension of Li2CC>3 and Na2CO3. The concentration of K2CO3 in the electrolyte 142 can improve electrolyte wetting and spreading during the cathode filling process. The concentration of K2CO3 in the cathode 150 can be less than 3 mol%. The concentration of K2CO3 in the cathode current collector 160 can be less than 3 mol%.

[0043] FIG. 3 is a plot 300 of voltage vs. temperature (°C) for electrolytes. The plot 300 shows performance data of single cells using the high-performance (e.g., advanced) electrolyte of the present disclosure (e.g., electrolyte 142), an electrolyte that includes 62 mol% lithium carbonate and 38 mol% potassium carbonate, and an electrolyte that includes lithium carbonate and sodium carbonate (e.g., baseline electrolyte). The single cells can have an average active surface area of 250 cm2. The lithium carbonate and sodium carbonate electrolyte is doped with additives such as Rb2CC>3, CS2CO3, or Bi2C>3. The tests were performed in single cells (250 cm2) to evaluate the performance benefit of the high-performance electrolyte. Each single cell assembly using the high-performance electrolyte includes a porous anode made of 30 wt% Ni4Cr and 70 wt% Ni3Al and a porous in-situ oxidized and lithiated NiO cathode filled with a predetermined amount (e.g., 86 g to 90 g) of 52.8 mol% Li2CO3 / 44.3 mol% Na2CO3 / 2.9 mol% K2CO3. The assembly includes a BaCOs (1 wt%-2 wt%)-doped porous ceramic matrix (LiAlO2). The assembly includes a predetermined amount (e.g., 14 g to 15 g) of an off-eutectic electrolyte (89 mol% Li2CC>3 / 7 mol% Na2CC>3 / 2.5 K2CO3 / I.5 mol% La2Os) stored in the cathode current collector. The cells were operated at 160 mA / cm2and 75% fuel utilization and 75% CO2 utilization.

[0044] Results showed that the high-performance electrolyte offers greater than 60 mV performance improvement compared to an electrolyte that includes 62 mol% lithium carbonate and 38 mol% potassium carbonate. The high-performance electrolyte offers greater than 10-20 -15- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268mV performance improvement compared to the electrolyte that includes lithium carbonate and sodium carbonate doped with additives. The high-performance electrolyte offers greater than 150-200 mV performance improvement compared to the electrolyte that include 52 mol% lithium carbonate and 48 mol% sodium carbonate. This improvement can stem from lower cathode polarization at T < 600°C due to improved electrolyte distribution between active components (e.g., less cathode flooding) leading to reduced mass-transfer resistance and improved gas-diffusion.

[0045] FIG. 4 is a plot 400 of cathode polarization (mV) vs. temperature (°C) for electrolytes. The plot 400 shows polarization studies at low temperatures (e.g., 575°C to 650°C) in button cells for the high-performance electrolyte of the present disclosure (e.g., electrolyte 142), an electrolyte that includes 52 mol% lithium carbonate and 48 mol% sodium carbonate (e.g., conventional electrolyte), and an electrolyte that includes lithium carbonate and sodium carbonate (e.g., baseline electrolyte). The baseline electrolyte is doped with additives such as Rb2CC>3, CS2CO3, or Bi2C>3. Each button cell assembly using the high-performance electrolyte includes a porous anode made of 30 wt% Ni4Cr and 70 wt% Ni3Al and a porous in-situ oxidized and lithiated NiO cathode filled with a predetermined amount (e.g., 0.250 g to 0.300 g) of 52.8 mol% Li2CC>3 / 44.3 mol% Na2CC>3 / 2.9 mol% K2CO3. The button cell can have an average active surface area of 3 cm2. The assembly includes a BaCO3(1 wt%-2 wt%)-doped porous ceramic matrix (LiAlO2). The assembly includes a predetermined amount (e.g., 0.250 g to 0.350 g) of an off-eutectic electrolyte (89 mol% Li2CC>3 / 7 mol% Na2CO3 / 2.5 K2CO3 / I.5 mol% La2C>3) stored in the cathode current collector. The combination of improved anode wetting using 30 wt% Ni4Cr, 52.8 mol% Li2CC>3 / 44.3 mol% Na2CC>3 / 2.9 mol% K2CO3, and BaCO3-doped matrix can provide greater than 20 mV lower cathode polarization than the baseline electrolyte and greater than 100 mV lower cathode loss than the electrolyte that includes 52 mol% lithium carbonate and 48 mol% sodium carbonate. The cells were operated at 160 mA / cm2and 5% fuel utilization.

[0046] FIG. 5 is a plot 500 of voltage (mV) vs. temperature (°C) for electrolytes. The plot 500 shows studies conducted to determine the effect of anode composition in single cells (e.g., with an area of about 250 cm2) for the high-performance electrolytes of the present disclosure (e.g.,-16- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268electrolyte 142) and an electrolyte that includes lithium carbonate and sodium carbonate (e.g., baseline). The baseline electrolyte is doped with additives such as Rb2CO3, Cs2CO3, or Bi2O3. The content of Ni4Cr in the anode affects the fuel cell performance. For example, a fuel cell made with 20 wt% Ni4Cr displays greater than 10 mV to 15 mV lower performance (e.g., voltage) than the baseline. The fuel cell made with 20 wt% Ni4Cr includes an electrolyte that includes 52.8 mol% Li2CO3 / 44.3 mol% Na2CC> / 2.9 mol% K2CO3. The fuel cell made with 20 wt% Ni4Cr includes a BaCO3-doped porous ceramic matrix. A fuel cell made with 30 wt% Ni4Cr displays greater than 8 mV to 10 mV higher voltage than the baseline. The fuel cell made with 30 wt% Ni4Cr includes an electrolyte that includes 52.8 mol% Li2CO3 / 44.3 mol% Na2CC>3 / 2.9 mol% K2CO3. The fuel cell made with 30 wt% Ni4Cr includes a BaCO3-doped porous ceramic matrix. Increasing the amount of Ni4Cr in the anode composition can improve the wetting due to the formation of lithium chromate during conditioning (e.g., lithiation of Cr present in Ni4Cr). This can lead to more electrolyte storage in the anode, thus reducing the cathode fill level and resulting in lower polarization and higher performance. The cells were operated at 160 mA / cm2and 75% fuel utilization and 75% CO2 utilization.

[0047] The following provides an overview of some Aspects of the present disclosure.[0048| Aspect 1. A molten carbonate fuel cell, comprising: an anode and a cathode separated by an electrolyte, the electrolyte comprising: Li2CO3; Na2CO3; and K2CO3, wherein K2CO3 is present in a concentration of less than or equal to 3.5 mol% of the electrolyte.

[0049] Aspect 2. The molten carbonate fuel cell of aspect 1, wherein the anode comprises at least one of Ni4Cr or Ni3Al.

[0050] Aspect 3. The molten carbonate fuel cell of any of aspects 1-2, wherein Ni4Cr is present in a concentration range of 25 wt% to 45 wt% of the anode.

[0051] Aspect 4. The molten carbonate fuel cell of any of aspects 1-3, comprising an electrolyte matrix disposed between the anode and the cathode.-17- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268[00521 Aspect 5. The molten carbonate fuel cell of aspect 4, wherein the electrolyte matrix comprises a mixture of LiAlO2and BaCO3.

[0053] Aspect 6. The molten carbonate fuel cell of aspect 5, wherein BaCO3is present in a concentration of 1 wt% to 2 wt% of the electrolyte matrix.

[0054] Aspect 7. The molten carbonate fuel cell of any of aspects 4-6, wherein the electrolyte matrix comprises at least one of BaO, SrO, or SrCO3.

[0055] Aspect 8. The molten carbonate fuel cell of any of aspects 4-7, wherein: the anode comprises 30 wt% Ni4Cr; and the electrolyte matrix comprises LiAlO2doped with BaCO3.

[0056] Aspect 9. The molten carbonate fuel cell of aspect 8, wherein the electrolyte comprises a first electrolyte, the molten carbonate fuel cell comprising: a cathode current collector; and a second electrolyte disposed in the cathode current collector.

[0057] Aspect 10. The molten carbonate fuel cell of aspect 9, wherein the second electrolyte comprises a mixture of LizCCh, Na2CO3, K2CO3, and La2Ch.10058] Aspect 11. The molten carbonate fuel cell of any of aspects 9-10, wherein the second electrolyte comprises 93 mol% Li2COa and 7 mol% Na2CO3of the second electrolyte.

[0059] Aspect 12. The molten carbonate fuel cell of any of aspects 9-11, wherein the second electrolyte comprises La2O3present in a concentration range of 1 mol% to 2 mol% of the second electrolyte.

[0060] Aspect 13. The molten carbonate fuel cell of any of aspects 9-12, wherein the second electrolyte comprises K2CO3 present in a concentration range of 1.5 mol% to 3 mol% of the second electrolyte.

[0061] Aspect 14. The molten carbonate fuel cell of any of aspects 9-13, wherein the second electrolyte comprises: Li2CC>3 present in a concentration of 89 mol% of the second electrolyte; Na2CC>3 present in a concentration of 7 mol% of the second electrolyte; K2CO3 present in a -18- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268concentration of 2.5 mol% of the second electrolyte; and La2O3present in a concentration of 1.5 mol% of the second electrolyte.

[0062] Aspect 15. The molten carbonate fuel cell of any of aspects 1-14, wherein the electrolyte comprises: Li2CO3present in a concentration of 52.8 mol% of the electrolyte; Na2CO3present in a concentration of 44.3 mol% of the electrolyte; and K2CO3 present in a concentration of 2.9 mol% of the electrolyte.

[0063] Aspect 16. The molten carbonate fuel cell of any of aspects 1-15, wherein the anode comprises: Ni4Cr present in a concentration of 30 wt% of the anode; and Ni3Al present in a concentration of 70 wt% of the anode.

[0064] Aspect 17. An electrolyte, comprising: Li2CO3; Na2CC>3; and K2CO3, wherein K2CO3 is present in a concentration of less than or equal to 3.5 mol% of the electrolyte.

[0065] Aspect 18. The electrolyte of aspect 17, wherein K2CO3 is present in a concentration range of between 1.5 mol% and 3 mol%.

[0066] Aspect 19. The electrolyte of any of aspects 17-18, comprising: Li2CO3 present in a concentration of 52.8 mol% of the electrolyte; Na2CO3present in a concentration of 44.3 mol% of the electrolyte; and K2CO3 present in a concentration of 2.9 mol% of the electrolyte.

[0067] Aspect 20. The electrolyte of any of aspects 17-19, comprising a eutectic mixture or off-eutectic mixture of Li2CC>3 and Na2CO3.

[0068] Having now described some illustrative implementations, it is apparent that the foregoing is illustrative and not limiting, having been presented by way of example. In particular, although many of the examples presented herein involve specific combinations of method acts or system elements, those acts and those elements may be combined in other ways to accomplish the same objectives. Acts, elements and features discussed in connection with one implementation are not intended to be excluded from a similar role in other implementations or implementations.-19- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268

[0069] The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” “having,” “containing,” “involving,” “characterized by,” “characterized in that,” and variations thereof herein, is meant to encompass the items listed thereafter, equivalents thereof, and additional items, as well as alternate implementations consisting of the items listed thereafter exclusively. In one implementation, the systems and methods described herein consist of one, each combination of more than one, or all of the described elements, acts, or components.

[0070] Any references to implementations or elements or acts of the systems and methods herein referred to in the singular can include implementations including a plurality of these elements, and any references in plural to any implementation or element or act herein can include implementations including only a single element. References in the singular or plural form are not intended to limit the presently disclosed systems or methods, their components, acts, or elements to single or plural configurations. References to any act or element being based on any information, act or element may include implementations where the act or element is based at least in part on any information, act, or element.

[0071] Any implementation disclosed herein may be combined with any other implementation, and references to “an implementation,” “some implementations,” “an alternate implementation,” “various implementations,” “one implementation” or the like are not necessarily mutually exclusive and are intended to indicate that a particular feature, structure, or characteristic described in connection with the implementation may be included in at least one implementation. Such terms as used herein are not necessarily all referring to the same implementation. Any implementation may be combined with any other implementation, inclusively or exclusively, in any manner consistent with the aspects and implementations disclosed herein.

[0072] References to “or” may be construed as inclusive so that any terms described using “or” may indicate any of a single, more than one, and all of the described terms. References to at least one of a conjunctive list of terms may be construed as an inclusive OR to indicate any of a single, more than one, and all of the described terms. For example, a reference to “at least one of-20- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268‘A’ and ‘B’” can include only ‘A’, only ‘B’, as well as both ‘A’ and ‘B’. Elements other than ‘A’ and ‘B’ can also be included.

[0073] As utilized herein, the terms “approximately,” “about,” “substantially”, and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the invention as recited in the appended claims.

[0074] The terms “coupled,” “connected,” and the like as used herein mean the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another.

[0075] References herein to the positions of elements (e.g., “top,” “bottom,” “above,” “below,” etc.) are merely used to describe the orientation of various elements in the Figures. It should be noted that the orientation of various elements may differ according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure.

[0076] The systems and methods described herein may be embodied in other specific forms without departing from the characteristics thereof. The foregoing implementations are illustrative rather than limiting of the described systems and methods.

[0077] Where technical features in the drawings, detailed description or any claim are followed by reference signs, the reference signs have been included to increase the intelligibility of the -21- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268drawings, detailed description, and claims. Accordingly, neither the reference signs nor their absence have any limiting effect on the scope of any claim elements.

[0078] The systems and methods described herein may be embodied in other specific forms without departing from the characteristics thereof. The foregoing implementations are illustrative rather than limiting of the described systems and methods. Scope of the systems and methods described herein is thus indicated by the appended claims, rather than the foregoing description, and changes that come within the meaning and range of equivalency of the claims are embraced therein.

[0079] It is important to note that the construction and arrangement of the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process or method steps may be varied or resequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.-22- 4916-7700-5175.1

Claims

Atty. Dkt. No.: 106876-2268WHAT IS CLAIMED IS:

1. A molten carbonate fuel cell, comprising:an anode and a cathode separated by an electrolyte, the electrolyte comprising:Li2CO3;Na2CO3; andK2CO3, wherein K2CO3 is present in a concentration of less than or equal to 3.5 mol% of the electrolyte.

2. The molten carbonate fuel cell of claim 1, wherein the anode comprises at least one of Ni4Cr or Ni3Al.

3. The molten carbonate fuel cell of claim 1, wherein Ni4Cr is present in a concentration range of 25 wt% to 45 wt% of the anode.

4. The molten carbonate fuel cell of claim 1, comprising an electrolyte matrix disposed between the anode and the cathode.

5. The molten carbonate fuel cell of claim 4, wherein the electrolyte matrix comprises a mixture of LiAlO2and BaCO3.

6. The molten carbonate fuel cell of claim 5, wherein BaCO3is present in a concentration of 1 wt% to 2 wt% of the electrolyte matrix.

7. The molten carbonate fuel cell of claim 4, wherein the electrolyte matrix comprises at least one of BaO, SrO, or SrCO3.

8. The molten carbonate fuel cell of claim 4, wherein:the anode comprises 30 wt% Ni4Cr; and-23- 4916-7700-5175.1Atty. Dkt. No.: 106876-2268the electrolyte matrix comprises LiAlO2doped with BaCO3.

9. The molten carbonate fuel cell of claim 8, wherein the electrolyte comprises a first electrolyte, the molten carbonate fuel cell comprising:a cathode current collector; anda second electrolyte disposed in the cathode current collector.

10. The molten carbonate fuel cell of claim 9, wherein the second electrolyte comprises a mixture of Li2CO3, Na2CO3, K2CO3, and La2O3.

11. The molten carbonate fuel cell of claim 9, wherein the second electrolyte comprises 93 mol% Li2CO3and 7 mol% Na2CC>3 of the second electrolyte.

12. The molten carbonate fuel cell of claim 9, wherein the second electrolyte comprises La2O3 present in a concentration range of 1 mol% to 2 mol% of the second electrolyte.

13. The molten carbonate fuel cell of claim 9, wherein the second electrolyte comprises K2CO3 present in a concentration range of 1.5 mol% to 3 mol% of the second electrolyte.

14. The molten carbonate fuel cell of claim 9, wherein the second electrolyte comprises:Li2CO3 present in a concentration of 89 mol% of the second electrolyte;Na2CO3 present in a concentration of 7 mol% of the second electrolyte;K2CO3 present in a concentration of 2.5 mol% of the second electrolyte; andLa2C>3 present in a concentration of 1.5 mol% of the second electrolyte.

15. The molten carbonate fuel cell of claim 1, wherein the electrolyte comprises:Li2CO3 present in a concentration of 52.8 mol% of the electrolyte;Na2CO3 present in a concentration of 44.3 mol% of the electrolyte; andK2CO3 present in a concentration of 2.9 mol% of the electrolyte.-24- 4916-7700-5175.1Atty. Dkt. No.: 106876-226816. The molten carbonate fuel cell of claim 1, wherein the anode comprises:Ni4Cr present in a concentration of 30 wt% of the anode; andNi3Al present in a concentration of 70 wt% of the anode.

17. An electrolyte, comprising:Li2CO3;Na2CO3; andK2CO3, wherein K2CO3is present in a concentration of less than or equal to 3.5 mol% of the electrolyte.

18. The electrolyte of claim 17, wherein K2CO3is present in a concentration range of between 1.5 mol% and 3 mol%.

19. The electrolyte of claim 17, comprising:Li2CO3present in a concentration of 52.8 mol% of the electrolyte;Na2CO3 present in a concentration of 44.3 mol% of the electrolyte; andK2CC>3 present in a concentration of 2.9 mol% of the electrolyte.

20. The electrolyte of claim 17, comprising a eutectic mixture or off-eutectic mixture of Li2CO3and Na2CC>3.-25- 4916-7700-5175.1

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