Method for manufacturing sodium or potassium ion battery cells

Abstract

The present disclosure generally relates to a method for manufacturing a sodium or potassium ion battery cell that includes a Prussian blue analog (PBA) as a cathode active material. The present disclosure also relates to a sodium or potassium ion battery manufactured by the method.

Description

[Technical Field]

[0001] The present disclosure generally relates to a method for producing a sodium or potassium ion battery cell that includes a Prussian blue analog (PBA) as a cathode active material. The present disclosure also relates to a sodium or potassium ion battery cell produced by the method. [Background technology]

[0002] Lithium-ion batteries dominate the rechargeable battery market. However, this technology has drawbacks, particularly due to the relatively scarce availability of lithium. Although superior to previous generations of secondary battery technology, lithium-ion batteries are not considered environmentally friendly and are costly from a recycling perspective.

[0003] These drawbacks have triggered a search for alternatives to lithium-ion batteries. Sodium or potassium-ion batteries represent an attractive alternative and are also a viable means of supporting renewable energy sources for the purposes of load leveling and excess energy storage.

[0004] The performance of sodium or potassium ion batteries depends heavily on the properties of the electrode materials.

[0005] A typical process for manufacturing an electrode, e.g., a cathode, is to mix an active material with a solvent, a conductive additive, and a binder to form a slurry. The slurry is then coated onto a current collector to form the cathode. The cathode is then assembled with an anode and any other components used to form a battery, such as a separator.

[0006] In conventional battery manufacturing, all steps of the process typically must be performed in a dry room, a room in which the moisture content of the air is controlled to a specific level. Exposure of a battery or any of its components to moisture during assembly can lead to degradation, such as reduced charge capacity and overall performance.

[0007] Prussian blue analogue (PBA) cathode materials have emerged as promising cathode materials for use in sodium or potassium ion batteries. Prussian blue analogues have a unique crystalline structure with an open three-dimensional framework and large interstitial voids, allowing them to store sodium (and potassium) ions.

[0008] Drying is particularly important when PBA is used as a cathode active material because any water present in the PBA structure must be removed in order for the active material to fully utilize its capacity in a battery cell. The presence of water can adversely affect the electrochemical potential and cycling stability of battery cells containing PBA as the cathode material.

[0009] Therefore, it is essential to remove any water present in the PBA material when it is used in a final battery cell. However, even once the water is removed from the PBA material, the PBA material still has a strong affinity for water. PBA is highly hygroscopic and can rapidly transition from anhydrous to hydrated upon exposure to air or moisture.

[0010] Therefore, the use of a dry room is an essential part of the process for preparing sodium or potassium ion batteries that utilize Prussian blue analog cathode materials. Furthermore, drying times are typically long.

[0011] However, there are various drawbacks associated with the use of dry rooms in battery manufacturing. First, dry rooms require high investment costs. Furthermore, the large amount of air that needs to be temperature controlled and dried results in high energy demands. Another drawback of dry rooms is that they are not a pleasant environment for personnel to work in.

[0012] Therefore, there is a need to provide an improved method for manufacturing sodium or potassium ion batteries that is simple, inexpensive, and does not require the use of a dry room. Furthermore, the method should be suitable for large-scale manufacturing of sodium or potassium ion batteries. Summary of the Invention

[0013] In view of the above and other shortcomings of the prior art, it is an object of the present disclosure to provide improvements related to sodium or potassium ion batteries, and in particular to providing a simple and inexpensive manufacturing method for producing such batteries on a large industrial scale.

[0014] According to a first aspect of the present disclosure, there is provided a method for manufacturing a sodium or potassium ion battery, comprising the steps of: a) providing a slurry comprising a Prussian blue analogue, wherein the Prussian blue analogue can exist in a first hydrated phase and a second dehydrated phase, the slurry comprising the first hydrated phase of the Prussian blue analogue; b) applying the slurry to a current collector to form a cathode; c) assembling the cathode with the anode and a separator to form an electrode stack; d) drying the electrode stack under conditions that allow the Prussian blue analog to be converted from a first hydrated phase to a second dehydrated phase, the drying being carried out at a drying temperature t1 of 150 to 300°C and for a drying time of 1 minute to less than 4 hours; e) placing the electrode stack within a cell casing; f) adding an electrolyte to the cell casing; g) sealing the battery casing to form a battery cell; Including, A method is provided wherein steps e) to g) are carried out under conditions that allow the Prussian blue analogue to be maintained in the second dehydrated phase throughout steps e) to g) of the method.

[0015] Prussian blue analogs (PBAs) can exist in a hydrated phase, i.e., a hydrated phase, or in a dehydrated phase, i.e., an anhydrous phase from which water has been removed. The present inventors have discovered that a method for producing sodium or potassium ion battery cells can be significantly improved if the conversion of a first hydrated phase of Prussian blue analog to a second dehydrated phase occurs late in the process, and if the converted dehydrated phase is maintained throughout the process steps. Thus, undesired conversion between the dehydrated and hydrated phases is prevented.

[0016] In the first hydrated phase of the Prussian blue analog, the material has a monoclinic crystal structure. PBA materials generally exist in the monoclinic structure in the slurry and in processes preceding the drying step.

[0017] In the second, dehydrated phase, the PBA material has a rhombohedral crystal structure. In battery applications, the dehydrated rhombohedral phase of PBA is desirably utilized to maximize the energy density and cycling stability of the battery cell.

[0018] The transition from the first to the second phase involves distortion of the monoclinic crystal lattice, resulting in a significant change in volume. The phase transition is associated with a substantial increase in sensitivity to moisture. The dehydrated rhombohedral structure of Prussian blue analogs is highly susceptible to reversion to the first hydrated phase, i.e., the monoclinic structure. However, such reversion is undesirable because it can significantly damage the PBA structure, rendering the material unsuitable for use in battery cells. Furthermore, significant amounts of sodium or potassium can be lost during such reversion.

[0019] It is therefore important that the PBA material, after transitioning to the second dehydration phase, remain in this phase, i.e., maintain its rhombohedral crystal structure, throughout the remaining steps of the process, which is achieved by the methods of the present disclosure.

[0020] In an exemplary embodiment, steps e)-g) are carried out under inert conditions.

[0021] Therefore, these steps are carried out in an oxygen- and water-free atmosphere.

[0022] Thus, after the drying step (step d), the Prussian blue analogue (PBA) is maintained in a second dehydrated phase, preventing undesired conversion of the PBA material between the dehydrated and hydrated phases.

[0023] Typically, the drying step (step d) is also carried out under inert conditions.

[0024] In an exemplary embodiment, steps e)-g) are performed in the same apparatus or multiple connected apparatuses, where the apparatus contains an inert gas or dry air having a moisture content of less than 50 ppm H2O.

[0025] Dry air is substantially free of moisture that can react with the PBA material.

[0026] By carrying out the steps in the same equipment or in multiple connected equipment, the atmosphere within these equipment is controlled, ensuring that the Prussian blue analogue (PBA) is maintained in the second dehydrated phase and that undesired phase transitions are avoided, and personnel can still work and operate under normal conditions (e.g., compared to a dry room where personnel may find it less comfortable to work).

[0027] Typically, the drying step (step d) is also carried out in the same apparatus or in several connected apparatuses.

[0028] Thus, in an exemplary embodiment, steps d) to g) are performed in the same apparatus or multiple connected apparatuses, the apparatuses containing inert gas or dry air having a moisture content of less than 50 ppm HO.

[0029] The inventors further found that the drying time can be significantly reduced when the drying temperature t1 is within the range of 150 to 300°C. A drying time of less than 4 hours is sufficient for efficient conversion of the first hydrated PBA phase to the second dehydrated PBA phase. Therefore, the disclosed method leads to a significant improvement in the large-scale industrial production of sodium and potassium ion batteries. A rapid, efficient, and simplified method is provided.

[0030] In an exemplary embodiment, steps a) through c) of the method are carried out at ambient conditions.

[0031] The slurry containing the Prussian blue analogue is typically an aqueous slurry, so that the Prussian blue analogue can be maintained in the first hydrated phase in the slurry.

[0032] The inventors have found that it is desirable to keep the Prussian blue analogue in the first hydrated phase until the drying step (step d), i.e., until the phase transition occurs. In this way, undesired transitions between the first and second phases are avoided and only one phase transition takes place (during the drying step).

[0033] This allows the steps preceding the drying step to be carried out under ambient conditions, which is a significant advantage compared to conventional battery manufacturing techniques, which typically require all method steps to be carried out in a dry room.

[0034] Thus, the steps of providing the PBA slurry (step a), applying the slurry to a current collector (step b), and assembling the cathode with additional battery components (step c) can be performed at ambient conditions. During these stages of the process, the PBA material is less sensitive because it has not yet been converted to the second dehydrated phase.

[0035] The Prussian blue analogue is preferably present in a first hydrated phase in steps a) to c) of the method.

[0036] With the disclosed method, significant improvements in capacity and cycling performance have been observed. Even very short exposures to ambient atmosphere resulted in undesirable PBA conversion and degradation of battery cell performance (see Example 2).

[0037] The disclosed method does not require the use of a dry room during any step of battery manufacturing, thus providing a simple and cost-effective method suitable for large-scale battery manufacturing.

[0038] In an exemplary embodiment, step d) of drying the electrode stack is carried out at a drying temperature t1 of 170-250°C.

[0039] As demonstrated in the examples, the inventors have found that drying temperatures within this range can result in high capacity battery cells even with short drying times, i.e., as short as 30 minutes (see Example 1).

[0040] These drying conditions are suitable for enabling a phase transition from a first hydrated phase of the Prussian blue analog to a second dehydrated phase of the PBA. Furthermore, these drying conditions allow for the removal of any water present in the first phase of the PBA material and potentially present in any other portion of the battery cell. Furthermore, these drying conditions do not adversely affect the PBA structure or any other components of the battery cell.

[0041] In an exemplary embodiment, the drying time is between 5 minutes and 2 hours.

[0042] Such short drying times offer significant advantages for large scale manufacturing of sodium and potassium ion batteries.

[0043] In an exemplary embodiment, the separator has a melting temperature t2 that is greater than the drying temperature t1.

[0044] The separator prevents electrical short circuits between the negative and positive electrodes and provides mechanical stability to the battery cell. The separator material may include any material that is chemically stable and electrically insulating. The separator is preferably thermally stable at a temperature of 170 °C to 320 °C, for example 200 °C to 270 °C.

[0045] With the short drying times made possible by the process of the present disclosure, there are fewer requirements for the separator despite the high temperatures during drying.

[0046] In an exemplary embodiment, the drying step d) is performed at a pressure below ambient pressure.

[0047] Since the drying time can be further shortened, it is desirable to utilize a vacuum.

[0048] In an exemplary embodiment, the Prussian blue analog has the formula A a M b [M’ c (CN)6] d where A is sodium or potassium, 1 < a ≤ 2, M and M’ are transition metals, preferably selected from iron and / or manganese, 0 < b < 2, 1 < c < 2, and 1 < d < 2.

[0049] Preferably, the Prussian blue analog is Prussian white having the formula A a Fe[Fe(CN)6], where A is sodium or potassium, 1.8 < a ≤ 2, preferably 1.9 < a ≤ 2.

[0050] Prussian white is associated with high battery capacity and an improved ability to store sodium (and potassium) ions. Prussian white is also environmentally friendly and can be produced at low cost.

[0051] In an exemplary embodiment, the battery casing is a pouch cell or a cylindrical cell.

[0052] Typically, the casing is a pouch cell.

[0053] The pouch cells may be formed from a flexible material such as foil, so the battery casing is flexible, lightweight, and can be made into a variety of sizes and shapes.

[0054] The sealed battery casing surrounds and seals the battery cells and acts as a barrier to the transmission of any air or moisture into or out of the battery cells.

[0055] In an exemplary embodiment, applying the slurry to the current collector comprises applying a slurry of 5 mg / cm 2 ~70mg / cm 2 , preferably 10 mg / cm 2 ~40mg / cm 2 The method includes coating the slurry onto a current collector at a coating weight of 1000 ppm.

[0056] The thickness of the coating on the current collector can vary depending on the particular application and purpose. For example, the thickness of the PBA coating can be in the range of 50 μm to 500 μm, such as 100 μm to 250 μm.

[0057] The electrodes can then be cut to the desired shape by techniques well known in the art.

[0058] The cathode may be assembled with the anode by stacking or winding the electrode together with a separator.

[0059] According to another aspect, there is provided a sodium or potassium ion battery cell manufactured according to the foregoing method.

[0060] In an exemplary embodiment, the battery cell comprises a Na + / More than 3.9V vs. Na or K + The electrochemical cycling curves have no voltage plateau above 4.1 V vs. / K.

[0061] Each is 3.9V(Na+ / Na) and 4.1 (K + The absence of a voltage plateau above 3.9 V (Na / K) is an indication that water has been removed from the battery cell and the PBA material is in a second, dehydrated phase. Such a battery cell exhibits stable behavior during subsequent charge and discharge and has a high initial coulombic efficiency. + / Na), and 4.1(K + / K) is associated with water extraction and is an indication that the PBA material contains a first hydrated phase of the PBA material.

[0062] In an exemplary embodiment, the battery cell comprises a Na + Between 3.0 and 3.9 V vs. Na, or K + The electrochemical cycling curves show one voltage plateau between 3.8 and 4.1 vs. K, and there are no additional voltage plateaus in the electrochemical cycling curves.

[0063] The presence of one clear voltage plateau within the above range indicates that the battery cell is devoid of water and no side reactions caused by water or moisture occur.

[0064] Further features and advantages of the present disclosure will become apparent upon review of the appended claims and the following description. Those skilled in the art will appreciate that different features of the present disclosure can be combined to create embodiments other than those described below without departing from the scope of the disclosure.

[0065] The various aspects of the present disclosure, including particular features and advantages thereof, will be readily understood from the following detailed description and the accompanying drawings. [Brief explanation of the drawings]

[0066] [Figure 1] 1 is a diagram illustrating the steps of the method of the present disclosure. [Figure 2] FIG. 1 is a schematic diagram of a sodium or potassium ion battery according to an exemplary embodiment of the present disclosure. [Figure 3a]1 is a graph showing cycle data for a sodium-ion battery cell manufactured according to an exemplary embodiment of the method of the present disclosure. [Figure 3b] FIG. 3c is a graph showing cycling data for a sodium-ion battery cell fabricated under the same conditions as the battery cell of FIG. 3a, except that the step of placing the electrode stack within the battery casing (step e) was performed at ambient conditions. [Figure 3c] 3b is a graph showing cycling data for sodium-ion battery cells fabricated under the same conditions as the battery cell of FIG. 3a, but differing with respect to the drying temperature and drying time utilized. DETAILED DESCRIPTION OF THE INVENTION

[0067] The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which presently preferred embodiments of the disclosure are shown. However, the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided for thoroughness and completeness, so as to fully convey the scope of the present disclosure to those skilled in the art.

[0068] FIG. 1a generally outlines the steps of a method (100) for manufacturing a sodium or potassium ion battery cell of the present disclosure.

[0069] The method comprises, in sequential order: a) providing a slurry comprising a Prussian blue analogue, wherein the Prussian blue analogue can exist in a first hydrated phase and a second dehydrated phase, the slurry comprising the first hydrated phase of the Prussian blue analogue (step 101); b) applying the slurry to a current collector to form a cathode (step 102); c) assembling the cathode with the anode and a separator to form an electrode stack (step 103); d) drying the electrode stack under conditions that allow the Prussian blue analog to be converted from a first hydrated phase to a second dehydrated phase, the drying being carried out at a drying temperature t1 of 150 to 300°C and for a drying time of 1 minute to less than 4 hours (step 104); e) placing the electrode stack within a cell casing (step 105); f) adding electrolyte to the cell casing (step 106); g) sealing the battery casing to form a battery cell (step 107); Including, Steps e) through g) are carried out under conditions that allow the Prussian blue analogue to be maintained in a second dehydrated phase throughout steps e) through g) of the method.

[0070] An important feature of the disclosed method is that steps e)-g) are carried out under conditions that prevent the reaction and undesired conversion of the PBA material.

[0071] It is important to ensure that the electrode stack is not exposed to moisture or air during the steps following drying step d). The disclosed process ensures that only one phase transition occurs between the first hydrated phase and the second dehydrated phase of the PBA analog. Thus, undesirable reversion between the first and second phases of the PBA material, which can result in swelling and damage to the material, is prevented.

[0072] In an exemplary embodiment, steps e)-g) (steps 105-107) can be carried out under inert conditions.

[0073] As used herein, the term "inert conditions" means an atmosphere that is free of oxygen and water.

[0074] Preferably, the drying step (step d) is also carried out under inert conditions.

[0075] In an exemplary embodiment, steps e)-g) (steps 105-107) are performed in the same apparatus or multiple connected apparatuses, where the apparatuses contain inert gas or dry air having a moisture content of less than 50 ppm HO, e.g., less than 30 ppm HO.

[0076] Dry air is substantially free of moisture that can react with the PBA material.

[0077] The drying step (step d) is also preferably carried out in the same apparatus or in several connected apparatuses.

[0078] Thus, steps d) to g) of the method, ie steps 104 to 107, can be performed in the same device or in multiple connected devices.

[0079] One or more closed chambers filled with inert gas or dry air having a moisture content of less than 50 ppm HO, for example less than 30 ppm HO, can be utilized in steps e) to g), preferably steps d) to g).

[0080] For example, step f) (step 106) may be performed in an electrolyte injection apparatus such as a glove box. A glove box is a closed apparatus for electrolyte injection that may include sealed gloves. In an exemplary embodiment, the glove box is filled with an inert gas, such as argon (Ar) gas. In an alternative embodiment, the glove box is filled with dry air having a moisture content of less than 50 ppm HO.

[0081] Steps e) (step 105) and / or g) (step 106) can be performed within the electrolyte injector or in a separate device directly connected to the electrolyte injector.

[0082] The drying step (step d)) may be carried out in a drying device such as a closed drying chamber. The drying device may be connected to or integrated into the electrolyte injection device. The drying device may comprise means for applying a vacuum.

[0083] By carrying out the process in the same equipment or in multiple connected equipment, the atmosphere within these equipment is controlled, ensuring that the electrode stack is not undesirably exposed to moisture and ambient air. Thus, the Prussian blue analogue (PBA) can be maintained in a second, dehydrated phase after transitioning from a first, hydrated phase. Furthermore, undesirable phase transitions are avoided. Workers can still work and operate under normal conditions (e.g., compared to a dry room, which is less comfortable for workers to work in).

[0084] The inventors have found that battery cells fabricated according to the disclosed method exhibit significant improvements in capacity and cycling performance, resulting in battery cells with stable cycling performance and avoiding undesirable side reactions due to exposure to ambient air (see Figures 3a and 3b, respectively).

[0085] The step of providing a slurry (Step 101) may include mixing a Prussian blue analog in powder form with a conductive additive and a binder.

[0086] The mixing can be accomplished by stirring and / or mixing for at least 1 hour.

[0087] The conductive additive may be any type of conductive additive known to those skilled in the art, such as various types of carbon compounds, such as super P, C65, C45, and carbon black, such as Ketjenblack.

[0088] The binder is not limited to a specific binder, and examples thereof include alginate, carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), and polyvinylidene fluoride (PVdF).

[0089] Prussian blue analogue (PBA) powder can be prepared by means known in the art.

[0090] The slurry containing the Prussian blue analogue is typically an aqueous slurry, and therefore the Prussian blue analogue exists in a first hydrated phase in the slurry.

[0091] The step (102) of applying the slurry to the current collector is carried out at a concentration of 5 mg / cm 2 ~70mg / cm 2 , preferably 10 mg / cm 2 ~40mg / cm 2 The method may include coating the slurry onto a current collector at a coating weight of

[0092] The slurry is preferably applied uniformly to at least one surface of a current collector, which is typically a metal foil or sheet.

[0093] The current collector can be coated on one side or two sides. When coated on two sides, the coating weight can be increased. In this case, the coating weight can be, for example, 30 to 50 mg / cm. 2 may be.

[0094] The coating process is not limited to a specific coating technique and can utilize any means for coating the slurry onto the current collector, such as slot die coating. Preferably, the coating is uniformly distributed over at least one surface of the current collector.

[0095] The thickness of the coating on the current collector can vary depending on the particular application and purpose. For example, the thickness of the PBA coating can be in the range of 50 μm to 500 μm, such as 100 μm to 250 μm.

[0096] The coated PBA active material may then be pressed and compressed onto the current collector, for example, by calendering using a roller press calender, thus achieving a coating of consistent thickness and density.

[0097] The electrode can then be cut to the desired shape by techniques well known in the art, for example, any type of slitting machine can be utilized.

[0098] In step 103, the cathode is assembled with the anode by stacking or winding the electrode with a separator. Any technique known in the art can be used.

[0099] As previously mentioned, the separator prevents electrical shorts between the negative and positive electrodes and provides mechanical stability to the battery cell. The separator material may include any chemically stable and electrically insulating material.

[0100] The separator has a melting temperature t2 that is higher than the drying temperature t1.

[0101] The separator is preferably thermally stable at temperatures between 170°C and 320°C, for example between 200°C and 270°C.

[0102] The separator material can include any chemically stable, electrically insulating material, for example, a polymer film such as a film comprising polypropylene, polyethylene, or a combination thereof.

[0103] The first steps of the method, ie steps a) to c) (steps 101 to 103), may be carried out at ambient conditions.

[0104] Steps a) to c) (steps 101 to 103) may be carried out at room temperature.

[0105] As used herein, "ambient conditions" refers to the general temperature and relative humidity at which the process is carried out. Steps a) through c) may be carried out at relative humidity (RH) levels relative to room temperature (e.g., 40-60% RH). The process is not limited to any particular requirements or equipment for these first steps of the method.

[0106] The Prussian blue analogue is preferably present in a first hydrated phase in steps a) to c) of the method.

[0107] In step 104, the electrode stack is dried at a drying temperature t1 of 150 to 300° C. and for a drying time of 1 minute to less than 4 hours.

[0108] Under these conditions, the Prussian blue analogue can be converted from a first, hydrated phase to a second, dehydrated phase.

[0109] Preferably, the drying step is carried out at a temperature in the range of 170° C. to 250° C., for example, 190° C. to 230° C. The drying time is preferably 5 minutes to 2 hours, more preferably 20 minutes to 1.5 hours.

[0110] Therefore, sodium or potassium ion batteries with improved capacity and cycling performance can be obtained, and these drying conditions do not adversely affect the PBA structure.

[0111] Preferably, the drying step is carried out at sub-ambient temperature and pressure.

[0112] Preferably, the drying step is carried out under vacuum.

[0113] This is beneficial in reducing the drying time required for the phase transition of the PBA analogue.

[0114] The drying process is 10 -3 It can be carried out at a pressure of up to 100 mbar, for example, the pressure may be 0.01 to 1 mbar.

[0115] However, the pressure is highly dependent on the temperature utilized in the drying process, and therefore the pressure may vary depending on the temperature used during drying.

[0116] It is important that the drying step ensures the removal of any water present in the PBA active material and any water potentially present in any other part of the battery cell.

[0117] By dehydrated PBA material, it is meant that the PBA material does not contain water, which would affect the electrochemical behavior of a battery cell containing the PBA material.

[0118] After the drying step (step 104), the battery cells are placed into a battery casing (step 105).

[0119] Battery casings can vary depending on the intended use and preference. The battery casing surrounds and seals the battery cells, acting as a barrier to any air or moisture penetration into or out of the battery cells.

[0120] Preferably, the battery casing is a pouch cell, that is, the battery casing may be in the form of a pouch made of a flexible material such as foil, so that the casing is flexible, lightweight, and can be made into a variety of sizes and shapes.

[0121] For example, the pouch cell may comprise a polymer-coated metal foil, which may comprise a polymer coating on one or both sides of the foil.

[0122] When the electrode stack is inserted into the pouch cell, the pouch cell may be partially sealed.

[0123] The method further includes adding an electrolyte to the cell casing (step 106).

[0124] The methods of the present disclosure are not limited to the use of any particular electrolyte.

[0125] Preferably, the electrolyte is a non-aqueous electrolyte. The non-aqueous electrolyte prevents water from interfering with the PBA-coated cathode. Furthermore, the non-aqueous electrolyte provides a larger potential window compared to aqueous electrolytes. Also, because the battery cell is dry and the PBA is dehydrated, there is substantially no water present in the PBA active material or in the battery cell that could interfere with the non-aqueous electrolyte.

[0126] The non-aqueous electrolyte typically includes a solvent or blend of solvents, and at least one dissolved salt.

[0127] For example, the non-aqueous electrolyte may include, for example, ethylene carbonate, diethyl carbonate, dimethyl carbonate, and / or any mixture thereof. The non-aqueous electrolyte may include a salt such as sodium hexafluorophosphate (NaPF6), or sodium tetrafluoroborate (NaBF4). The non-aqueous electrolyte may also include additives.

[0128] In an exemplary embodiment, the non-aqueous electrolyte includes an alkali metal bis(oxalato)borate salt, and the alkali metal ion is selected from sodium (Na + ), and potassium (K + ). Such non-aqueous electrolytes are fluoride-free, environmentally friendly, safe, and have high ionic conductivity and electrochemical stability.

[0129] Thereafter, the battery casing is sealed (step 107).

[0130] In an exemplary embodiment, the Prussian blue analog has the formula A a M b [M’ c (CN)6] d where A is sodium or potassium, 1 < a ≦ 2, M and M’ are transition metals, preferably selected from iron and / or manganese, 0 < b < 2, 1 < c < 2, and 1 < d < 2.

[0131] In one embodiment, the Prussian blue analog is Prussian white having the formula A a Fe[Fe(CN)6], where A is sodium or potassium, 1.8 < a ≦ 2, preferably 1.9 < a ≦ 2.

[0132] Prussian white is associated with high battery capacity and improved storage of sodium (and potassium) ions. It is also environmentally friendly and can be produced at low cost.

[0133] In embodiments where the Prussian blue analog is a Prussian white material, this material can be prepared according to the methods described in WO 2018 / 056890, assigned to Altris AB.

[0134] According to another aspect, there is provided a sodium or potassium ion battery cell manufactured according to the foregoing method.

[0135] Figure 2 shows the general principle of a sodium or potassium ion battery 200, which utilizes sodium or potassium ions 201 as charge carriers. The battery stores energy in chemical bonds at the negative electrode, or anode 202. When the battery 200 is charged, the Na + or K + Ions 201 are forced to deintercalate from the positive electrode, i.e., cathode 203, and move toward the anode 202. During discharge, the process is reversed. Upon completing the circuit, electrons return from the anode 202 to the cathode 203, transporting Na + or K + The ions 201 return to the cathode 203. During battery discharge, oxidation occurs at the anode 202 while reduction occurs at the cathode 203, as shown in Figure 2. Current flow is determined by the potential difference between the cathode 203 and the anode 202, i.e., the cell voltage.

[0136] The two electrodes are separated by a separator 205 that is impregnated with an electrolyte 204 .

[0137] As used herein, the term "battery" means a device that includes one or more battery cells.

[0138] A "battery cell" contains a positive electrode, or cathode, a negative electrode, or anode, and a separator. In a battery cell, chemical energy is converted to electricity by reduction and oxidation (redox) reactions at the electrodes.

[0139] The cathode 203 utilized in the sodium or potassium ion batteries of the present disclosure includes a current collector coated with the Prussian blue analog material described above.

[0140] The negative electrode material, i.e., anode 202, is not particularly limited as long as it is a material capable of storing and releasing sodium or potassium ions. Examples include metal composite oxides, sodium metal, sodium alloys, silicon, silicon-based alloys, tin-based alloys, bismuth-based alloys, metal oxides, conductive polymers, Na-Co-Ni-based materials, and hard carbon. The anode may also be a metal foil coated with an anode active material.

[0141] Preferably, the battery cell is + / Na > 3.9V and K + The electrochemical cycling curves have no voltage plateau above 4.1 V vs. / K. Such a voltage plateau is associated with water extraction and is an indication that the PBA has not completely transitioned from the first hydrated phase to the second dehydrated phase.

[0142] As used herein, "Na + / More than 3.9V vs. Na or K + The term "there is no voltage plateau above 4.1 V vs. / K" means that there is no additional capacity after 3.9 V and 4.1 V, respectively. + / More than 3.9V vs. Na or K +Above 4.1 V vs. K, there is no moisture-induced reaction. This is illustrated by the vertically upward-sloping electrochemical cycling curve in Figure 3b. The anodes used for electrochemical cycling tests are typically carbon-based (hard carbon) anodes. The electrochemical cycling tests shown in Figures 3a-c were performed at a C-rate of 0.05 C for three charge / discharge cycles, with voltage cutoff limits set at 4.2 V and 2.0 V, respectively.

[0143] The presence of water or side reactions caused by water or moisture may be + / Na (see Figure 3b), or K + This can be evidenced by a slope of the curve greater than 4.1 V vs. / K. This can also be evidenced by the presence of two or more voltage plateaus in the electrochemical cycling curve.

[0144] The battery cell is Na + Between 3.0 and 3.9 V vs. Na, or K + The electrochemical cycling curve may have an electrochemical cycling curve that exhibits one voltage plateau between 3.9 and 4.1 V vs. / K, and no additional voltage plateaus in the electrochemical cycling curve.

[0145] Therefore, a water-free, stable and high-performance battery cell is achieved.

[0146] A key advantage of the disclosed method is that no dry room is required at any stage of battery manufacturing, making the method significantly simplified, inexpensive, and suitable for large-scale battery manufacturing.

[0147] example Example 1 The prototype Prussian White half-cell was fabricated with a heat-resistant separator and a 12 mg / cm 2 The prototype was stacked with an electrode mass loading of 2 × 10. To remove any water from the electrode, the stacked prototype was placed in a high vacuum oven (2 × 10). -2The stack was dried at 210°C under a pressure of less than 1000 mBar for 0.5 hours. After drying was complete, the cell stack was transferred from the oven to a pouch cell casing under an inert atmosphere for electrolyte injection and sealing. After drying was complete, the cell stack was injected with electrolyte and sealed without exposure to ambient atmosphere.

[0148] The half-cells were charged / discharged under controlled conditions using constant current cycling with a Neware BTS4000 galvanostat. The current was kept constant at 0.05 C during the measurements, and the voltage cut-off limits were set at 4.2 V and 2.0 V, respectively. A total of three charge / discharge cycles were recorded.

[0149] The cycling data in Figure 3a show that the electrode stack contains only the anhydrous, i.e., rhombohedral, phase of Prussian white, as clearly evidenced by the absence of a voltage plateau above 3.9 volts that appears at the end of charge (such a voltage plateau is associated with the extraction of water from the cathode).

[0150] Example 2 The prototype Prussian White half-cell was fabricated with a heat-resistant separator and a 12 mg / cm 2 The prototype was stacked with an electrode mass loading of 2 × 10. To remove any water from the electrode, the stacked prototype was placed in a high vacuum oven (2 × 10). -2 The electrode stack was dried at 210°C under a pressure of <100 mBar for 0.5 hours. After drying was complete, the cell stack was transferred from the oven to a pouch cell casing. This procedure involved briefly exposing the electrode stack to ambient conditions (<3 minutes) before returning it to the inert atmosphere for electrolyte injection and sealing.

[0151] The cycling data in Figure 3b show that the electrode stack contains both the anhydrous and hydrated phases of Prussian white, i.e., both rhombohedral and monoclinic structures. This is clearly evidenced by the voltage plateau above 3.9 V that appears at the end of charge and is associated with the extraction of water from the cathode. The water content within the cell caused gassing within the cell, making discharge impossible.

[0152] Example 3 A similar electrochemical cycling evaluation was performed as described in Example 1, except that in this test the temperature used to dry the laminated prototypes was 130°C and the drying time was 15 hours.

[0153] As shown in Figure 3c, a voltage plateau above 3.9 V appeared at the end of charging, which is associated with the extraction of water from the cathode. The water content in the cell caused gas generation within the cell, making discharge impossible. Therefore, similar to the results of Example 2, the electrode stack contained both the anhydrous phase of Prussian white and the hydrated phase of Prussian white, i.e., both the rhombohedral and monoclinic structures.

[0154] The terms, definitions, and embodiments of all aspects of this disclosure apply mutatis mutandis to the other aspects of this disclosure.

[0155] Although the present disclosure has been described with reference to specific exemplary embodiments thereof, many different alterations, modifications and the like will become apparent to those skilled in the art.

[0156] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the present disclosure, from a study of the drawings, the disclosure, and the appended claims. Moreover, in the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

Claims

1. 1. A method for manufacturing a sodium or potassium ion battery cell, comprising: a) providing a slurry comprising a Prussian blue analogue, wherein the Prussian blue analogue can exist in a first hydrated phase and a second dehydrated phase, the slurry comprising the first hydrated phase of the Prussian blue analogue; b) applying the slurry to a current collector to form a cathode; c) assembling the cathode with an anode and a separator to form an electrode stack; d) drying the electrode stack under conditions capable of converting the Prussian blue analogue from the first hydrated phase to the second dehydrated phase, wherein the drying is carried out at a drying temperature t1 of 150 to 300°C and for a drying time of 1 minute to less than 4 hours; e) placing the electrode stack within a cell casing; f) adding an electrolyte to the cell casing; g) sealing the battery casing to form a battery cell; Including, The method wherein steps e) through g) are carried out under conditions capable of maintaining the Prussian blue analogue in the second dehydration phase throughout steps e) through g) of the method.

2. The method of claim 1, wherein steps e) to g) are carried out under inert conditions.

3. The steps e) to g) are carried out in the same apparatus or in a number of connected apparatuses, the apparatus being preferably inert gas or 50 ppm H ２ 3. The method of claim 1 or 2, comprising drying air having a moisture content of less than O.

4. The method according to any one of claims 1 to 3, wherein steps a) to c) of the method are carried out at ambient conditions.

5. The process according to any one of claims 1 to 4, wherein step d) of drying the electrode stack is carried out at a drying temperature t1 of 170 to 250°C.

6. The process of any one of claims 1 to 5, wherein the drying time is from 5 minutes to 2 hours.

7. 7. The process of claim 1, wherein the separator has a melting temperature t2 that is higher than the drying temperature t1.

8. 8. The method according to any one of claims 1 to 7, wherein the drying step d) is carried out under a pressure below ambient pressure.

9. The Prussian blue analogue has the formula A ａ M ｂ [M' ｃ (CN) ６ ] ｄ wherein A is sodium or potassium; 9. The method according to any one of claims 1 to 8, wherein 1<a≦2, M and M' are transition metals, preferably selected from iron and / or manganese, 0<b<2, 1<c<2 and 1<d<2.

10. The Prussian blue analogue has the formula A ａ Fe[Fe(CN) ６ 10. The method according to claim 1, wherein A is sodium or potassium, and 1.8<a≦2, preferably 1.9<a≦2.

11. 11. The method of claim 1, wherein the battery casing is a pouch cell.

12. The step of applying the slurry to the current collector has a thickness of 5 mg / cm ２ ~70 mg / cm ２ , preferably 10 mg / cm ２ ~40 mg / cm ２ 12. The method of claim 1, comprising coating the slurry onto the current collector at a coating weight of

13. 13. A sodium or potassium ion battery cell manufactured according to the method of any one of claims 1 to 12.

14. The battery cell is ＋ / more than 3.9 V vs. Na, or K ＋ 14. The sodium or potassium ion battery cell of claim 13, having an electrochemical cycling curve with no voltage plateau above 4.1 V vs. / K.

15. The battery cell is ＋ / Between 3.0 and 3.9 V vs. Na, or K ＋ 15. The sodium or potassium ion battery cell of claim 13 or 14, having an electrochemical cycling curve exhibiting one voltage plateau between 3.8 and 4.1 vs. / K, and no additional voltage plateaus in the electrochemical cycling curve.

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