Formation method for metal battery, metal battery and electrical apparatus

Abstract

The present application relates to a formation method for a metal battery, a metal battery and an electrical apparatus. The formation method comprises: successively charging a battery cell n times, n≥2, the charging being in a negative pressure environment, and as the number of charging times increases, used charging rates increasing progressively and the temperatures of temperature conditions for the charging decreasing progressively. Using the formation method can remarkably reduce gas produced by metal batteries in storage and usage processes so as to ameliorate the bulging problem of battery cell pouches, and moreover have certain improvement effects on the cycle performance of the batteries.

Description

Metal battery formation method, metal battery and power-using device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202410010939.X filed on January 2, 2024, entitled “A method for forming a metal battery, a metal battery and an electrical device,” and the entire contents of that application are incorporated herein by reference. Technical Field

[0003] The present application relates to the technical field of metal batteries, and in particular to a metal battery formation method, a metal battery, and an electrical device. Background Art

[0004] As electric vehicles, energy storage, and electronic products continue to expand in scale, higher demands are being placed on electrochemical energy storage technologies. Lithium-ion batteries have been widely used. Furthermore, sodium batteries are widely considered one of the most promising candidates for large-scale energy storage applications due to their abundant reserves, low cost, and similar chemical properties to lithium.

[0005] Alkali metals, represented by sodium, have high theoretical specific capacity and low electrochemical potential, making them promising anode materials. However, research on alkali metal anodes is still in its infancy, and a series of challenges remain to be addressed. In battery manufacturing, the formation process involves multiple charge and discharge cycles, significantly impacting battery performance. For example, in existing technologies, even after formation, metal batteries are susceptible to core swelling during storage and use, adversely affecting the battery's cycle performance and service life.

[0006] Summary of the Invention

[0007] The purpose of the present application is to provide a metal battery formation method, a metal battery and an electrical device. By applying the formation method, the gas production of the metal battery during the storage and use stages can be significantly reduced, and the battery core pack swelling problem can be improved; thereby, the battery cycle performance can also be improved to a certain extent.

[0008] To this end, the present application provides a metal battery formation method, comprising charging the battery cells n times in sequence, where n≥2; the charging is in a negative pressure environment; as the number of charging times increases, the charging rate adopted increases, and the temperature of the charging conditions decreases.

[0009] During the formation process of metal batteries, by simultaneously controlling the increase in charging rate and the decrease in charging temperature, the composition and structure of the SEI film can be affected from the perspectives of thermodynamics and kinetics, which is conducive to the deposition of metal with large-sized morphology on the surface of the negative electrode, thereby helping to reduce the side reactions between the electrolyte and the metal, reduce gas production and dendrite problems, and promote the improvement of battery cycle performance.

[0010] In any embodiment, the charging rate is 0.1C to 1.5C.

[0011] By adopting the above charging rate, the metal deposited on the negative electrode plate is more regular and larger in size.

[0012] In any embodiment, the temperature condition is 45 to 90°C.

[0013] Carrying out chemical formation within the above-mentioned temperature conditions is beneficial to controlling the metal deposited on the negative electrode surface to have a larger nucleation size.

[0014] In any embodiment, the pressure of the negative pressure environment is -80Kpa to -5Kpa.

[0015] Adopting the negative pressure environment pressure within the above range is beneficial to further reduce the gas generation of the core package during the battery formation process.

[0016] In any embodiment, as the number of charging times increases, the pressure of the negative pressure environment during charging increases.

[0017] By gradually increasing the negative pressure, the gas inside the battery cell can be discharged, which helps to reduce the problem of gas production in the core pack during subsequent use and storage.

[0018] In any embodiment, n≤5; for example, the number of charging times can be 2 times, 3 times, 4 times, 5 times, etc.

[0019] In any embodiment, n=3; the formation method of the metal battery comprises: sequentially performing a first charge, a second charge, and a third charge on the battery cell; the first charge, the second charge, and the third charge are all performed under a negative pressure environment;

[0020] In the first charging, charging is performed at a first charging rate and a first temperature; in the second charging, charging is performed at a second charging rate and a second temperature; in the third charging, charging is performed at a third charging rate and a third temperature;

[0021] Among them, the first charging rate, the second charging rate, and the third charging rate increase in sequence; the first temperature, the second temperature, and the third temperature decrease in sequence.

[0022] In any embodiment, the first charging rate is 0.1C to 1.0C, the second charging rate is 0.3C to 1.2C, and the third charging rate is 0.5C to 1.5C.

[0023] The use of the above-mentioned charging rate, combined with decreasing temperature conditions, can have a positive impact on the morphology and size of the metal deposited on the negative electrode, which is conducive to making the metal morphology more regular and the size larger.

[0024] In any embodiment, the first temperature is 60-90°C, the second temperature is 50-70°C, and the third temperature is 45-60°C.

[0025] Adopting the above-mentioned charge rate and performing chemical formation within the above-mentioned temperature conditions is beneficial to controlling the metal deposited on the negative electrode surface to have a larger nucleation size, and is also beneficial to increasing the organic component in the SEI film.

[0026] In any embodiment, the pressures of the negative pressure environments during the first charging, the second charging, and the third charging increase sequentially.

[0027] By gradually increasing the negative pressure, the gas inside the battery cell can be discharged, which helps to reduce the problem of gas production in the core pack during subsequent use and storage.

[0028] In any embodiment, the pressure of the first charging negative pressure environment is -30 to -5 KPa, the pressure of the second charging negative pressure environment is -40 to -20 KPa, and the pressure of the third charging negative pressure environment is -80 to -30 KPa.

[0029] Adopting the negative pressure environment pressure within the above range is conducive to coordinating the charge rate and temperature in different stages of formation, further reducing the gas production problem of the battery during formation, storage and use.

[0030] In any embodiment, the cut-off voltage of the first charge is 2.9 to 3.1; the cut-off voltage of the second charge is 3.1 to 3.15; and the cut-off voltage of the third charge is 3.4 to 3.65.

[0031] In any embodiment, the interval time between the first charge and the second charge, and / or the interval time between the second charge and the third charge are each independently selected from: 0 to 0.5 hours.

[0032] The two charges can be performed continuously or after a period of rest. Resting for a period of time is conducive to sufficient exhaust of the system.

[0033] The second aspect of the present application provides a metal battery, which is prepared by the chemical formation method provided by the first aspect of the present application.

[0034] In any embodiment, the metal battery includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; wherein the negative electrode sheet is a sodium metal negative electrode.

[0035] The third aspect of the present application provides an electrical device, which includes the metal battery described in the second aspect of the present application.

[0036] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Various other advantages and benefits will become apparent to those skilled in the art by reading the detailed description of the preferred embodiment below. The accompanying drawings are only for the purpose of illustrating the preferred embodiment and are not to be considered as limiting the present application. In the accompanying drawings:

[0038] Figure 1: Surface morphology of the negative electrode after formation using different methods;

[0039] Among them, (A) is formed according to a method of an embodiment of the present application, and (B) is formed according to a method of a comparative example; the equipment and conditions used in the imaging of (A) and (B) are exactly the same, and the two have the same scale (not shown in the figure). DETAILED DESCRIPTION

[0040] The exemplary embodiments of the present disclosure will be described in more detail below. It should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Instead, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0041] The "ranges" disclosed in this application are defined in the form of lower limits and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values ​​and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if minimum range values ​​of 1 and 2 are listed, and maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" is an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0042] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0043] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0044] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, it is mentioned that the method may also include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0045] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0046] Research on sodium metal anodes is still in its infancy, and a series of challenges remain to be addressed. In battery manufacturing, the formation process involves multiple charge and discharge cycles, significantly impacting battery performance. For example, in existing technologies, the formation process for metal batteries is prone to swelling of the battery core, potentially adversely affecting cycle performance and lifespan.

[0047] This application mainly improves the charging rate, temperature and negative pressure conditions during the metal battery formation process, significantly reducing the gas production of the metal battery during the formation and storage stages to improve the battery core pack swelling problem; in addition, it also has a certain improvement effect on the battery's cycle performance.

[0048] The technical solutions described in the embodiments of the present application are applicable to a formation method of a metal battery, a metal battery prepared using the formation method, a battery module containing the metal battery, a battery pack using the metal battery or battery module, and an electrical device using at least one of the metal battery, battery module, and battery pack.

[0049] Metal battery formation method

[0050] An embodiment of the present application provides a formation method for a metal battery, which includes charging a battery cell n times in sequence, where n≥2; the charging is performed in a negative pressure environment; as the number of charging times increases, the charging rate used increases, and the temperature of the charging condition decreases.

[0051] During the formation process of metal batteries, by simultaneously controlling the gradual increase in charging rate and the gradual decrease in charging temperature, it is possible to ensure the charging speed while avoiding overheating of the battery cell due to excessive charging current; and by simultaneously controlling the above two conditions, the composition and structure of SEI can be affected from the perspectives of thermodynamics and kinetics, which is conducive to the deposition of metal with large-sized morphology on the surface of the negative electrode, thereby helping to reduce the side reactions between the electrolyte and the metal, reduce gas production and dendrite problems, and promote the improvement of battery cycle performance.

[0052] In some embodiments, the charging rate is 0.1C to 1.5C; for example, it can be selected from about 0.1C, 0.2C, 0.3C, 0.4C, 0.5C, 0.6C, 0.7C, 0.8C, 0.9C, 1C, 1.1C, 1.2C, 1.3C, 1.4C, 1.5C, etc.

[0053] By adopting the above charging rate, the metal deposited on the negative electrode plate is more regular and larger in size.

[0054] In some embodiments, the temperature condition is 45-90°C; for example, it can be selected from about 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, etc.

[0055] Carrying out chemical formation within the above-mentioned temperature conditions is beneficial to controlling the metal deposited on the negative electrode surface to have a larger nucleation size.

[0056] In some embodiments, the pressure of the negative pressure environment is -80Kpa to -5Kpa; for example, it can be selected from about -80Kpa, -70Kpa, -60Kpa, -50Kpa, -40Kpa, -30Kpa, -20Kpa, -10Kpa, -5Kpa, etc.

[0057] Adopting the negative pressure environment pressure within the above range is beneficial to further reduce the gas generation of the core package during the battery formation process.

[0058] In some embodiments, as the number of charging times increases, the pressure of the negative pressure environment during charging increases.

[0059] By gradually increasing the negative pressure, the gas inside the battery cell can be discharged, which helps to reduce the problem of gas production in the core pack during subsequent use and storage.

[0060] In some embodiments, n≤5; for example, the number of charging times may be 2 times, 3 times, 4 times, 5 times, etc.

[0061] In some embodiments, the formation method of the metal battery includes: sequentially performing a first charge, a second charge, and a third charge on the battery cell; the first charge, the second charge, and the third charge are all performed under a negative pressure environment;

[0062] In the first charging, charging is performed at a first charging rate and a first temperature; in the second charging, charging is performed at a second charging rate and a second temperature; in the third charging, charging is performed at a third charging rate and a third temperature;

[0063] Among them, the first charging rate, the second charging rate, and the third charging rate increase in sequence; the first temperature, the second temperature, and the third temperature decrease in sequence.

[0064] In some embodiments, the first charging rate is 0.1C to 1.0C, the second charging rate is 0.3C to 1.2C, and the third charging rate is 0.5C to 1.5C.

[0065] The use of the above-mentioned charging rate, combined with decreasing temperature conditions, can have a positive impact on the morphology and size of the metal deposited on the negative electrode, which is conducive to making the metal morphology more regular and the size larger.

[0066] In some embodiments, the first temperature, the second temperature, and the third temperature are in the range of 45 to 90° C. For example, the first temperature is 60 to 90° C., the second temperature is 50 to 70° C., and the third temperature is 45 to 60° C. As an example, the first temperature may be selected from approximately 60° C., 65° C., 70° C., 75° C., 80° C., 85° C., 90° C., etc.; the second temperature may be selected from approximately 50° C., 55° C., 60° C., 65° C., 70° C., etc.; and the third temperature may be selected from approximately 45° C., 50° C., 55° C., 60° C., etc.

[0067] Adopting the aforementioned charge rate and conducting the formation within the aforementioned temperature range facilitates controlling the morphology of the metal deposited on the negative electrode surface, resulting in a larger nucleus size. The combination of charge rate and temperature conditions thermodynamically influences the nucleus size of the negative electrode metal, while kinetically influencing the metal battery deposition overpotential and interfacial impedance, ultimately resulting in the deposition of metal with a large morphology.

[0068] In some embodiments, the pressures of the negative pressure environments during the first charging, the second charging, and the third charging increase sequentially.

[0069] By gradually increasing the negative pressure, the gas inside the battery cell can be discharged, which helps to reduce the problem of gas production in the core pack during subsequent use and storage.

[0070] In some embodiments, the negative pressure environment has a pressure of -80KPa to -5KPa. For example, the negative pressure environment for the first charging is -30 to -5KPa, the negative pressure environment for the second charging is -40 to -20KPa, and the negative pressure environment for the third charging is -80 to -30KPa. As an example, the pressure of the first charging negative pressure environment can be selected from about -30Kpa, -25Kpa, -20Kpa, -15Kpa, -10Kpa, -5Kpa, etc.; the pressure of the second charging negative pressure environment can be selected from about -40Kpa, -35Kpa, -30Kpa, -25Kpa, -20Kpa, etc.; the pressure of the third charging negative pressure environment can be selected from about -80Kpa, -75Kpa, -70Kpa, -65Kpa, -60Kpa, -55Kpa, -50Kpa, -45Kpa, -40Kpa, -35Kpa, -30Kpa, etc.

[0071] Adopting the negative pressure environment pressure within the above range is conducive to coordinating the charge rate and temperature of different stages of formation, thereby exhausting all gas produced by the system in the formation stage, thereby reducing the gas production problem of the battery during subsequent storage and use.

[0072] In some embodiments, the cut-off voltage of the first charge is 2.9-3.1; the cut-off voltage of the second charge is 3.1-3.15; and the cut-off voltage of the third charge is 3.4-3.65.

[0073] By adopting the above-mentioned cut-off voltage, it is beneficial to keep the charging voltage in the slope area, so that abnormally functioning cells can be screened out during the formation stage.

[0074] In some embodiments, the interval time between the first charge and the second charge, and / or the interval time between the second charge and the third charge are each independently selected from: 0 to 0.5 hours.

[0075] The two charges can be performed continuously or after a period of rest. Leaving the battery for a period of rest is conducive to sufficient exhaust, which can avoid the problem of core package bulging caused by the exhaust speed of the battery cell being lower than the gas production speed.

[0076] Metal batteries

[0077] In some embodiments, a metal battery is provided, which includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte; the metal battery is prepared by the formation method provided in the embodiments of the present application.

[0078] In some embodiments, the metal battery is an alkali metal battery.

[0079] In some embodiments, the metal battery is a sodium metal battery, a lithium metal battery, or a potassium metal battery. For example, the negative electrode of the metal battery is a sodium metal negative electrode, a lithium metal negative electrode, or a potassium metal negative electrode.

[0080] [Positive electrode]

[0081] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0082] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer can be provided on either or both of the two opposite surfaces of the positive electrode current collector.

[0083] Alternatively, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0084] In the embodiment of the present application, the positive electrode active material includes octahedral transition metal oxides and prismatic transition metal oxides. Among them, octahedral transition metal oxides include but are not limited to Na 0.95 Mn 0.33 Fe 0.33 Ni 0.33 O2. Prismatic transition metal oxides include but are not limited to Na 2 / 3 Mg 1 / 4 Mn 3 / 4 O2.

[0085] Alternatively, the positive electrode active material may also include positive electrode active materials for sodium ion batteries that are well known in the art. For example, the positive electrode active material may also include one or more of a polyanionic compound and a Prussian blue compound. As an example, a polyanionic compound may be a class of compounds having sodium ions, transition metal ions and tetrahedral anion units, such as sodium iron phosphate (NaFePO4), sodium vanadium phosphate (Na3V2(PO4)3), etc. A Prussian blue compound may be a class of compounds having sodium ions, transition metal ions and cyanide ions. However, the present application is not limited to these materials, and other materials that can be used as positive electrode active materials for sodium ion batteries may also be used. These positive electrode active materials may be used alone, or two or more materials may be used in combination.

[0086] Optionally, the positive electrode film layer may further include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0087] Optionally, the positive electrode film layer includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as NMP) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0089] [Negative electrode]

[0090] In some embodiments, the negative electrode plate may be a metal sodium plate.

[0091] In some embodiments, the negative electrode sheet includes a negative electrode current collector, or includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0092] In some embodiments, the sodium metal battery is a negative electrode-free sodium metal battery, in which the negative electrode current collector directly serves as the negative electrode plate of the battery, and a sodium layer is deposited in situ on the negative electrode current collector after the first charge and discharge. During the formation and charging process, the sodium ions released from the positive electrode plate are deposited on the negative electrode current collector to form a sodium metal negative electrode, in which sodium metal is the negative electrode active material. In other words, a "negative electrode-free sodium metal battery" means that no negative electrode active material is added during the production of the sodium metal battery, and only the negative electrode current collector is used as the nominal negative electrode; after the first charge of the negative electrode-free sodium metal battery is completed, the metallic sodium in its positive electrode material will migrate to the surface of the negative electrode current collector; part of the sodium metal will remain on the negative electrode current collector, thereby forming a sodium deposition layer of a certain thickness, constituting the actual negative electrode. In other embodiments, in order to ensure the normal use of the negative electrode plate, or to facilitate the deposition of sodium metal on the negative electrode current collector, a conductive film layer can be provided on the negative electrode current collector.

[0093] In some embodiments, the negative electrode current collector has two opposite surfaces in its thickness direction, and the negative electrode film layer may be disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0094] Alternatively, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base layer (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0095] Optionally, the negative electrode active material may include at least one of the following materials: sodium metal, a carbon-based material or metal deposited with sodium metal, an alloy material, a composite material containing sodium metal, an alloy material containing sodium metal, etc. However, the present application is not limited to these materials, and other materials that can be used as negative electrode active materials for sodium ion batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more materials.

[0096] The negative electrode sheet can be prepared according to conventional methods in the art. For example, the negative electrode film layer can be deposited on at least one surface of the negative electrode current collector by methods such as physical vapor deposition (PVD), spin coating, electroplating, and chemical vapor deposition (CVD).

[0097] [Electrolytes]

[0098] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0099] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0100] Optionally, when the metal battery is a sodium metal battery, the electrolyte salt includes NaPF6, NaBCl4, NaSO3CF3 and Na(CH3)C6H4SO3, etc.

[0101] Optionally, the solvent includes a carbonate or ether solvent. Carbonate solvents include cyclic ethylene carbonate (EC), propylene carbonate (PC), fluoroethylene carbonate (FEC) and chain dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), etc.; ether solvents include ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxolane, etc.

[0102] Optionally, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0103] [Isolation film]

[0104] In some embodiments, the metal battery further includes a separator, which can be any known porous separator with good chemical and mechanical stability.

[0105] Optionally, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0106] [Battery Preparation]

[0107] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0108] In some embodiments, the metal battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0109] In some embodiments, the present invention provides an electrochemical device comprising the metal battery of the present invention. The electrochemical device can be any device that undergoes an electrochemical reaction. The use of the electrochemical device of the present invention is not particularly limited, and can be used in, for example, mobile phones, tablet computers, laptop computers, e-book players, portable phones, portable fax machines, portable copiers, headphones, video recorders, televisions, calculators, memory cards, tape recorders, backup power supplies, automobiles, motorcycles, power-assisted bicycles, lighting fixtures, toys, game consoles, clocks, power tools, cameras, and the like.

[0110] Example 1

[0111] This embodiment provides a sodium metal battery and performs relevant tests on it. The specific steps are as follows:

[0112] 1) Preparation of positive electrode sheet

[0113] A positive electrode slurry was prepared by fully dissolving 10 wt% of polyvinylidene fluoride binder in N-methylpyrrolidone, adding 10 wt% of carbon black conductive agent and 80 wt% of positive electrode active material Na4Fe3(PO4)2(P2P7) and dispersing them evenly. This slurry was evenly coated on the surface of the positive electrode current collector aluminum foil. After drying, cold pressing, slitting, and cutting, the positive electrode sheets were obtained.

[0114] 2) Preparation of negative electrode sheet

[0115] Weigh 5g of sodium carboxymethylcellulose (CMC-Na) and dissolve it in 1000mL of water with stirring. Then, add 5g of single-walled carbon nanotubes and disperse them ultrasonically to prepare a slurry. This slurry is coated on the surface of the negative electrode current collector copper foil. After drying, slitting, and cutting, the negative electrode sheet is obtained.

[0116] 3) Battery assembly

[0117] The positive electrode sheet, the polypropylene film serving as the separator, and the negative electrode sheet are stacked in sequence, with the separator being located between the positive electrode sheet and the negative electrode sheet to serve as an isolation film. After winding, an electrode assembly is formed, and the electrode assembly is placed in a packaging shell. A sodium hexafluorophosphate electrolyte with a concentration of 1 mol / L is added, and the battery is packaged to obtain a sodium metal battery to be formed.

[0118] 4) Formation

[0119] The sodium metal battery to be formed is formed in the following steps:

[0120] 1. Place under the conditions of -30Kpa pressure and room temperature for 5 minutes;

[0121] 2. First charge: Under the conditions of -30kPa pressure and 60℃, charge at 0.3C constant current until the voltage reaches 3.0V, then let it stand for 30min.

[0122] 3. Second charge: Under the conditions of -40kPa pressure and 55℃, charge at 0.5C constant current to 3.1V, then let it stand for 30min.

[0123] 4. Third charge: Under the conditions of -50 kPa pressure and 50°C temperature, charge at a constant current of 0.8 C to a voltage of 3.65 V, and then let it stand for 30 minutes; thus, a sodium metal battery is prepared.

[0124] 5) Performance testing

[0125] 1. Morphology characterization

[0126] The surface of the negative electrode obtained in each step of the formation stage was scanned using a scanning electron microscope (SEM). FIG1(A) shows an electron microscope image of the surface of the negative electrode after the third charge is completed.

[0127] 2. Gas production detection in the formation stage

[0128] Before formation, a pipe with the same diameter as the sealing pin hole was placed along the sodium metal battery to be formed. A pressure sensor was connected to the end of the pipe. The battery was clamped with two aluminum plates, with an initial clamp force of 3000N. The calibration was performed three times, with 15-minute intervals between each clamp. The battery was then formed according to the formation steps in step 4). The temperature of all cells was monitored, and the cumulative flow rate was recorded. The gas production during the formation phase (in ml / Ah) was calculated by dividing the cumulative flow rate (ml) by the cell capacity (Ah). The results are shown in Table 1.

[0129] 3. Gas production detection at 25℃ storage

[0130] The formed batteries were piped along the sealing pin weld holes, with the same diameter as the sealing pin holes. A pressure sensor was connected to the end of the pipe. The battery was clamped with two aluminum plates, with an initial clamp force of 3000N. Calibration was performed three times, with 15-minute intervals between each clamp. The batteries were then fully charged to 100% SOC and allowed to stand at room temperature (25°C). The temperature of all cells was monitored, and the cumulative flow rate was recorded daily. The average daily storage gas production (in ml / Ah / D) was calculated by dividing the cumulative flow rate (ml) by the cell capacity (Ah) and the number of days (D). The results are shown in Table 1.

[0131] 4. 25℃ circulating gas production detection

[0132] The formed battery was piped along the weld hole of the sealing nail. The pipe had the same diameter as the sealing nail hole. A pressure sensor was connected to the end of the pipe. The battery was clamped with two aluminum plates. The initial clamp force was set to 3000N. The battery was calibrated three times, with 15 minutes between each clamp. The battery was then charged and discharged at 1C / 1C within the range of 1.5-3.65V at room temperature (25°C). One complete charge and discharge cycle was defined as one cycle. The cumulative flow rate was recorded. The cycle gas production (unit: ml / Ah / cls) was calculated by dividing the cumulative flow rate (ml) by the cell capacity (Ah) and the number of cycles (cls). The results are shown in Table 1.

[0133] Comparative Example 1

[0134] The preparation and testing were carried out in the same manner as in Example 1, except that the first, second, and third charging rates were all 0.3C. The test results are shown in Table 1. FIG1(B) shows an electron microscope image of the surface of the negative electrode after the third charge in the formation stage.

[0135] Comparative Example 2

[0136] The preparation and testing were performed in the same manner as in Example 1, except that the temperatures for the first, second, and third charges were all 45° C. The test results are shown in Table 1.

[0137] Table 1

[0138] Examples 2 to 6

[0139] Except for the difference in the charge rate during the formation stage as shown in Table 2, the preparation and testing were carried out in the same manner as in Example 1. Some of the test results are shown in Table 2.

[0140] Table 2

[0141] Examples 7-8

[0142] Except that the temperature conditions in the formation stage are different as shown in Table 3, the preparation and testing are carried out in the same manner as in Example 1. Some test results are shown in Table 3.

[0143] Table 3

[0144] Examples 9 to 13

[0145] Except that the pressure of the negative pressure environment in the formation stage is different as shown in Table 4, the preparation and testing are carried out in the same manner as in Example 1. Some test results are shown in Table 4.

[0146] Table 4

[0147] The above description is merely a preferred embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A formation method for a metal battery, characterized in that, Including charging the battery cell n times in sequence, where n ≥ 2; the charging is carried out in a negative pressure environment; as the number of charging times increases, the charging rate used increases, and the temperature condition during charging decreases.

2. The formation method of the metal battery according to claim 1, characterized in that, The charging rate is 0.1C to 1.5C.

3. The formation method of the metal battery according to claim 1 or 2, characterized in that The temperature of the temperature condition is 45 to 90 °C.

4. The formation method of the metal battery according to any one of claims 1 to 3, characterized in that, The pressure of the negative pressure environment is -80 Kpa to -5 Kpa.

5. The formation method of the metal battery according to claim 4, wherein, As the number of charging times increases, the pressure of the negative pressure environment where the charging is carried out increases.

6. The forming method of the metal battery according to any one of claims 1 to 5, characterized in that, The number of charging times is three, and the battery cell is charged in sequence for the first charge, the second charge, and the third charge. The first charge, the second charge, and the third charge are all carried out in a negative pressure environment; In the first charge, charging is carried out at the first charging rate, and the temperature condition is the first temperature; in the second charge, charging is carried out at the second charging rate, and the temperature condition is the second temperature; in the third charge, charging is carried out at the third charging rate, and the temperature condition is the third temperature; Among them, the first charging rate, the second charging rate, and the third charging rate increase in sequence; the first temperature, the second temperature, and the third temperature decrease in sequence.

7. The formation method of the metal battery according to claim 6, characterized in that, The first charging rate is 0.1C to 1.0C, the second charging rate is 0.3C to 1.2C, and the third charging rate is 0.5C to 1.5C.

8. The formation method of the metal battery according to claim 6 or 7, characterized in that, The first temperature is 60 to 90 °C, the second temperature is 50 to 70 °C, and the third temperature is 45 to 60 °C.

9. The formation method of the metal battery according to any one of claims 6 to 8, characterized in that, The pressures of the negative pressure environments for the first charge, the second charge, and the third charge increase in sequence; Preferably, the pressure of the negative pressure environment for the first charge is -30 to -5 Kpa, the pressure of the negative pressure environment for the second charge is -40 to -20 Kpa, and the pressure of the negative pressure environment for the third charge is -80 to -30 Kpa.

10. The formation method of the metal battery according to any one of claims 6 to 9, characterized in that, The cut-off voltage for the first charge is 2.9 to 3.1; the cut-off voltage for the second charge is 3.1 to 3.15; the cut-off voltage for the third charge is 3.4 to 3.

65.

11. A metal battery, characterized in that, The metal battery is prepared by the formation method described in any one of claims 1 to 10.

12. An electrical device, characterized in that, The electrical device includes the metal battery described in claim 11.

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