Sodium-ion battery cell, secondary battery, and electric device

Abstract

The application provides a sodium ion battery monomer, a secondary battery and an electric device. The sodium ion battery monomer comprises an electrode assembly and a shell, the shell is cylindrical, the shell has a containing cavity inside, and the electrode assembly is located inside the containing cavity; the electrode assembly comprises a negative electrode sheet, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer located on at least one surface of the negative electrode current collector, the density of the negative electrode current collector is ≤5.0 g / cm 3 , and the group margin of the sodium ion battery monomer satisfies 0.95≤group margin<1, wherein the group margin is the ratio of the diameter of the electrode assembly to the diameter of the containing cavity. By adopting the negative electrode current collector with small density, cooperating with the large group margin, and adopting the cylindrical structure, the battery monomer can have high mass energy density, high volume energy density and good cycle performance, which is beneficial to promote the development of small size and light weight of the battery monomer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary batteries, in particular to a sodium-ion battery monomer, a secondary battery and an electric device. BACKGROUND

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute the prior art.

[0003] Sodium-ion batteries have good cost advantages, which are conducive to expanding the use range of sodium-ion batteries. However, it is difficult to effectively balance the mass energy density and the volume energy density of sodium-ion batteries, which restricts the development of miniaturization and light weight of sodium-ion batteries. SUMMARY

[0004] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a sodium-ion battery monomer, comprising an electrode assembly and a shell, the shell is cylindrical, the shell has a containing cavity inside, and the electrode assembly is located inside the containing cavity; the electrode assembly comprises a negative electrode sheet, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer located on at least one surface of the negative electrode current collector, the density of the negative electrode current collector is ≤5.0 g / cm 3 , and the group margin of the sodium-ion battery monomer satisfies: 0.95≤group margin<1, wherein the group margin is the ratio of the diameter of the electrode assembly to the diameter of the containing cavity.

[0005] The above-mentioned sodium-ion battery monomer can have higher mass energy density and volume energy density at the same time by adopting a negative electrode current collector with smaller density, a larger group margin, and a cylindrical structure, and can also have better cycle performance.

[0006] In some embodiments, the density of the negative electrode current collector is 1.3 g / cm 3 ~3.5 g / cm 3 . The density of the negative electrode current collector in this range can further reduce the weight of the negative electrode current collector, thereby further improving the mass energy density of the battery monomer.

[0007] In some embodiments, the group margin of the sodium-ion battery monomer is 0.95~0.97. The group margin of the sodium-ion battery monomer in this range can simultaneously balance the higher energy density and the better cycle performance.

[0008] In some embodiments, the negative current collector has an elongation ≥ 3%. The negative current collector has a large elongation, which can have good pressure resistance during preparation of the negative electrode sheet, can reduce the risk of fracture of the negative electrode sheet during cold pressing, and is conducive to promoting the increase of the compaction density of the negative active layer. Optionally, the negative current collector has an elongation of 3.5% to 5.0%.

[0009] In some embodiments, the ratio of the thickness of the negative current collector to the thickness of the negative active layer is ≤ 0.2. At this time, the thickness of the negative active layer can be further increased, which is conducive to further improving the mass energy density and volume energy density of the battery cell. Optionally, the ratio of the thickness of the negative current collector to the thickness of the negative active layer is 0.03 to 0.15.

[0010] In some embodiments, the negative current collector has a thickness of 6 μm to 12 μm. The negative current collector has a thickness in this range, which can make the negative current collector play its own role, and at the same time make the negative electrode sheet have a more appropriate thickness, and thus make the battery cell have a suitable volume energy density. Optionally, the negative current collector has a thickness of 6.5 μm to 10 μm.

[0011] In some embodiments, the negative current collector comprises an aluminum foil or a metal / polymer composite current collector.

[0012] In some embodiments, the metal / polymer composite current collector comprises a polymer substrate layer and a metal layer located on at least one surface of the polymer substrate layer. Optionally, the polymer substrate layer comprises at least one of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, and polyethylene. Optionally, the metal layer comprises at least one of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.

[0013] In some embodiments, the sodium-ion battery cell further comprises an electrolyte, the electrolyte is located inside the accommodation cavity; the sodium-ion battery cell satisfies: m / C0≤6 g / Ah, wherein m represents the mass of the electrolyte, the unit is g, and C0 represents the rated capacity of the sodium-ion battery cell, the unit is Ah. m / C0 in this range can make the battery cell have a large group margin on the basis of maintaining good electrical performance, which is conducive to further improving the volume energy density of the battery cell. Optionally, 4 g / Ah≤m / C0≤5 g / Ah.

[0014] In some embodiments, the negative active layer has a compaction density of 0.7 g / cm 3 ~ 1.3 g / cm 3The compaction density of the negative active layer in the range can make the battery cell have a higher energy density. Optionally, the compaction density of the negative active layer is 0.8 g / cm 3 ~ 1.2 g / cm 3 .

[0015] In some embodiments, the ratio of the height of the battery cell to the diameter of the battery cell is greater than or equal to 3.5, optionally 4-6.

[0016] In some embodiments, the height of the battery cell is greater than or equal to 60 mm, optionally 70 mm-300 mm.

[0017] In some embodiments, the diameter of the battery cell is greater than or equal to 21 mm, optionally 30 mm-60 mm.

[0018] The second aspect of the present application provides a secondary battery comprising the sodium-ion battery cell.

[0019] The third aspect of the present application provides an electric device comprising at least one of the sodium-ion battery cell and the secondary battery. DETAILED DESCRIPTION

[0020] For the purpose of facilitating the understanding of the present application, the present application will be described more fully below with reference to the relevant embodiments. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein only for the purpose of describing specific embodiments and is not intended to limit the present application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] "ranges" disclosed herein can be defined, for example, by the lower and upper values. Any lower limit can independently be combined with any upper limit to define a range of any value. For example, if a range of 60-120 and 80-110 is listed, it is understood that a range of 60-110 and 80-120 is also contemplated. Furthermore, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is also listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, the use of "a" and "an" to describe a single item can be taken as equivalent to the use of "one" or "at least one," unless otherwise limited by context. In this application, the use of "or" as a conjunction can be taken as

[0023] In this application, the use of "a" and "an" to describe a single item can be taken as equivalent to the use of "one" or "at least one," unless otherwise limited by context. In this application, the use of "or" as a conjunction can be taken as

[0024] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, if not specifically stated.

[0025] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment or implementation of the application. The appearances of the phrase that the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of other embodiments. It is explicitly understood that the embodiments described herein are combinable with each other. Reference herein to "an implementation" has a similar understanding.

[0026] Those skilled in the art can understand that the order of writing each step in the method of each embodiment or example does not mean a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. If not specifically stated, all steps of the present application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0027] In the present application, the open technical features or technical solutions described by the words "containing", "including", "comprising" and the like do not exclude additional members other than the listed members, and can be regarded as providing both a closed feature or solution composed of the listed members and an open feature or solution including additional members in addition to the listed members. For example, A includes a1, a2 and a3, and unless otherwise specified, it can also include other members or can not include additional members, and can be regarded as providing both the feature or solution that "A is composed of a1, a2 and a3" and the feature or solution that "A includes a1, a2 and a3, and also includes other members".

[0028] In the present application, A (such as B) means that B is a non-limiting example of A, and A can be understood to be limited to B.

[0029] In the present application, "optionally", "optional" and "optional" mean that it can or can not be present, i.e. it means to choose from either of the two parallel solutions "yes" or "no". If there are multiple "options" in a technical solution, and unless otherwise specified, and there is no contradiction or mutual restriction, each "option" is independent.

[0030] An embodiment of the present application provides a sodium ion battery monomer. The sodium ion battery monomer comprises an electrode assembly and a shell, the shell is cylindrical, the shell has a receiving cavity inside, and the electrode assembly is located inside the receiving cavity; the electrode assembly comprises a negative electrode sheet, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer located on at least one surface of the negative electrode current collector, the density of the negative electrode current collector is ≤5.0 g / cm 3 The group margin of the sodium ion battery monomer satisfies: 0.95 ≤ group margin < 1, wherein the group margin is the ratio of the diameter of the electrode assembly to the diameter of the receiving cavity.

[0031] The sodium-ion battery cell in the embodiment can effectively improve the mass energy density of the battery by adopting a negative electrode current collector with a smaller density, but the thickness design of the current collector with a small density in the prior art is usually thick, which has a certain influence on the volume energy density of the battery. In order to improve the volume energy density, the group margin of the battery can be increased, but after the group margin is increased, the local stress of the battery cell in the expansion process may be too large to affect the cycle performance of the battery. If a cylindrical structure is adopted, the stress of the battery cell inside the battery is more balanced, which can effectively alleviate the problem. Further, by adopting the specific battery structure, the negative electrode current collector and the mutual cooperation of the group margin in the embodiment, the battery can have good cycle performance while taking into account the higher mass energy density and volume energy density.

[0032] It can be understood that, in the sodium-ion battery cell, the accommodation cavity can be represented as a cavity enclosed by the shell. It can also be understood that the sodium-ion battery cell further includes a cover plate, which cooperates with the shell to seal the accommodation cavity.

[0033] In some embodiments, the density of the negative electrode current collector is 1.3 g / cm 3 ~ 3.5 g / cm 3 . The density of the negative electrode current collector in this range can further reduce the weight of the negative electrode current collector, thereby further improving the mass energy density of the battery cell. Alternatively, the density of the negative electrode current collector can be 1.3 g / cm 3 , 1.5 g / cm 3 , 1.8 g / cm 3 , 2 g / cm 3 , 2.3 g / cm 3 , 2.5 g / cm 3 , 2.8 g / cm 3 , 3 g / cm 3 , 3.2 g / cm 3 , 3.5 g / cm 3 , etc.

[0034] In some embodiments, the group margin of the sodium-ion battery cell is 0.95~0.97. The group margin of the sodium-ion battery cell in this range can improve the space utilization rate of the accommodation cavity, further improving the volume energy density of the battery cell. Alternatively, the group margin of the sodium-ion battery can be 0.955, 0.96, 0.965, 0.97, etc.

[0035] In some embodiments, the negative current collector has an elongation of ≥ 3%. The negative current collector has a large elongation, which can have good pressure resistance during preparation of the negative electrode sheet, can reduce the risk of fracture of the negative electrode sheet during cold pressing, and is conducive to further improving the energy density and cycle performance. Optionally, the negative current collector has an elongation of 3.5% to 5.0%. For example, the negative current collector can have an elongation of 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0036] The elongation of the negative current collector can be tested by the following method: recording the initial length H1 of the negative current collector. A tensile test is performed using a high-iron tensile machine, and a tensile force is applied to both ends of the length direction of the negative current collector at a stretching speed of 2 mm / min. The two ends of the stretching machine need to be tightly attached with corrugated rubber to prevent the negative current collector from relaxing and falling off during stretching, and the negative current collector needs to be kept vertical and straight during stretching. The negative current collector needs to be broken at a certain point in the middle, and the breaking data at both ends of the clamp is discarded. When the negative current collector is broken, the length H2 of the negative current collector at the breaking point is recorded. The elongation δ of the negative current collector is calculated, and the elongation δ = (H2-H1) / H1 x 100%. Optionally, H1 is 50 mm.

[0037] In some embodiments, the ratio of the thickness of the negative current collector to the thickness of the negative active layer is ≤ 0.2. This can further increase the thickness of the negative active layer, which is conducive to further improving the mass energy density and volume energy density of the battery cell. Optionally, the ratio of the thickness of the negative current collector to the thickness of the negative active layer is 0.03 to 0.15. For example, the ratio of the thickness of the negative current collector to the thickness of the negative active layer can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, etc.

[0038] In some embodiments, the negative current collector includes an aluminum foil or a metal / polymer composite current collector, and the metal / polymer composite current collector includes a polymer substrate layer and a metal layer on at least one surface of the polymer substrate layer. Optionally, the polymer substrate layer includes one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc. Optionally, the metal layer includes at least one of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.

[0039] In some embodiments, the polymer substrate layer of the metal / polymer composite current collector includes polypropylene, and the metal layer includes at least one of copper or copper alloy.

[0040] In some embodiments, the polymer substrate layer of the metal / polymer composite current collector comprises at least one of polyethylene terephthalate, polybutylene terephthalate, and the metal layer comprises at least one of aluminum or aluminum alloy.

[0041] The density of the composite current collector can be adjusted by adjusting the kind or the ratio of the polymer and the metal. Alternatively, when the metal layer comprises copper or copper alloy, the density of the composite current collector can be adjusted in the range of 1.0 g / cm 3 - 8.9 g / cm 3 . Alternatively, when the metal layer comprises aluminum or aluminum alloy, the density of the composite current collector can be adjusted in the range of 1.4 g / cm 3 - 2.7 g / cm 3 .

[0042] Alternatively, as some examples of the thickness of the negative electrode current collector, the thickness of the negative electrode current collector is 6 μm to 12 μm. The thickness of the negative electrode current collector in this range can make the negative electrode current collector play its own role on the basis of making the negative electrode sheet have a more appropriate thickness, and thus making the battery monomer have a suitable volumetric energy density. Alternatively, the thickness of the negative electrode current collector can be 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, etc. Further alternatively, the thickness of the negative electrode current collector is 6.5 μm to 10 μm.

[0043] It can be understood that the sodium-ion battery monomer further comprises an electrolyte, and the electrolyte is located inside the accommodation cavity. Alternatively, the electrolyte can be an electrolyte solution.

[0044] In some embodiments, the sodium-ion battery monomer satisfies: m / C0≤6 g / Ah, wherein m represents the mass of the electrolyte, and C0 represents the rated capacity of the sodium-ion battery monomer, in Ah. m / C0 in this range can make the battery monomer have a larger group margin on the basis of maintaining good electrical performance, which is conducive to further improving the volumetric energy density of the battery monomer. Alternatively, 4 g / Ah≤m / C0≤5 g / Ah. Further alternatively, m / C0 can be 3 g / Ah, 3.5 g / Ah, 4 g / Ah, 4.5 g / Ah, 5 g / Ah, 5.5 g / Ah, 6 g / Ah, etc. It can be understood that C0 can be measured by the following method: discharging the battery monomer at 0.33C to 1.5V, standing for 10 min; charging at 0.33C to 3.9V, standing for 10 min; discharging at 0.33C to 1.5V, and recording the discharge capacity at this time as the rated capacity.

[0045] It is also understood that the mass m of the electrolyte in the battery cell can be measured by the following method: taking a battery cell sample, weighing the initial mass m1 of the battery cell, disassembling the battery cell, cleaning the shell and the electrode assembly with dimethyl carbonate for more than three times, drying the shell and the electrode assembly after cleaning, weighing the mass m2 of the shell and the mass m3 of the electrode assembly respectively. The mass m of the electrolyte = m1-m2-m3.

[0046] In some embodiments, the compaction density of the negative active layer is 0.7 g / cm 3 ~ 1.3 g / cm 3 . The compaction density of the negative active layer in this range can make the battery cell have a higher energy density. Optionally, the compaction density of the negative active layer is 0.8 g / cm 3 ~ 1.2 g / cm 3 . Further optionally, the compaction density of the negative active layer can be 0.8 g / cm 3 , 0.9 g / cm 3 , 1 g / cm 3 , 1.1 g / cm 3 , 1.2 g / cm 3 , 1.3 g / cm 3 , etc.

[0047] In some embodiments, the ratio of the height of the battery cell to the diameter of the battery cell is greater than or equal to 3.5. Optionally, the ratio of the height of the battery cell to the diameter of the battery cell is 4-6. Further optionally, the ratio of the height of the battery cell to the diameter of the battery cell can be 3.5, 4, 4.5, 5, 5.5, 6, etc.

[0048] Optionally, the height of the battery cell is greater than or equal to 60 mm. Further optionally, the height of the battery cell is 70-300 mm. For example, the height of the battery cell can be 60 mm, 65 mm, 70 mm, 75 mm, 80 mm, 90 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, etc.

[0049] Optionally, the diameter of the battery cell is greater than or equal to 21 mm. Further optionally, the diameter of the battery cell is 30-60 mm. For example, the diameter of the battery cell can be 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, etc.

[0050] The electrode assembly further comprises a positive electrode tab, the positive electrode tab comprising a positive current collector and a positive active layer located on at least one surface of the positive current collector. The positive active layer comprises a positive active material.

[0051] Optionally, the positive active material includes at least one of a sodium-containing transition metal oxide, a Prussian blue material, and a polyanion material.

[0052] Further optionally, the sodium-containing transition metal oxide includes a chemical formula of Na x Cu y Fe z Mn a M 1-y-z-a O2, a sodium-iron composite oxide, a sodium-cobalt composite oxide, a sodium-chromium composite oxide, a sodium-manganese composite oxide, a sodium-nickel composite oxide, a sodium-nickel-titanium composite oxide, a sodium-nickel-manganese composite oxide, a sodium-iron-manganese composite oxide, a sodium-nickel-iron-manganese composite oxide, and a sodium-nickel-cobalt-manganese composite oxide. In the chemical formula of Na x Cu y Fe z Mn a M 1-y-z-a O2, M includes at least one of Li, Ni, Mg, Zn, Co, Al, Zr, and Ti, 0 < x ≤ 1, 0 < y ≤ 0.5, 0 < z ≤ 0.5, and 0 < a ≤ 0.5. It can be understood that the values of x, y, z, and a satisfy the charge balance of the chemical formula.

[0053] Further optionally, the Prussian blue material includes a chemical formula of A x M[M'(CN)6] y zH2O, wherein A is one or more of an alkali metal cation, an alkaline earth metal cation, Zn 2+ , Al 3+ , M is a transition metal, M' is a transition metal, 0 < x ≤ 2, 0.8 ≤ y < 1, and 0 < z ≤ 20.

[0054] Further optionally, the polyanion material includes at least one of a phosphate, a fluorophosphate, a pyrophosphate, and a sulfate. Further optionally, the polyanion material includes at least one of a sodium-iron phosphate compound, a sodium-manganese phosphate compound, and a sodium-cobalt phosphate compound. Further optionally, the polyanion material includes at least one of NaFePO4, Na3V2(PO4)3, NaM"PO4F, and Na3(VO c )2(PO4)2F 3-2c , wherein M" includes at least one of V, Fe, Mn, and Ni, and 0 ≤ c ≤ 1.

[0055] In some embodiments, the positive active layer has a compacted density of 2 g / cm 3 ~ 3.3 g / cm 3 . Optionally, the positive active layer has a compacted density of 2 g / cm 3 , 2.1 g / cm 32.2 g / cm 3 2.3 g / cm 3 2.4 g / cm 3 2.5 g / cm 3 2.6 g / cm 3 2.7 g / cm 3 2.8 g / cm 3 2.9 g / cm 3 3 g / cm 3 3.1 g / cm 3 3.2 g / cm 3 and the like. Further optionally, the compaction density of the positive active layer is 2.5 g / cm 3 ~ 3 g / cm 3 .

[0056] The application also has an embodiment to provide a secondary battery. The secondary battery includes any of the above sodium-ion battery cells.

[0057] The application also has an embodiment to provide an electric device. The electric device includes at least one of the above sodium-ion battery cell or the above secondary battery.

[0058] The secondary battery and the electric device of the application are described below.

[0059] Generally, the secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the short circuit of the positive and negative electrodes, while allowing ions to pass through.

[0060] Positive electrode sheet

[0061] The positive electrode sheet includes a positive current collector and a positive active layer arranged on at least one surface of the positive current collector, wherein the positive active layer includes a positive active material.

[0062] As a non-limiting example, the positive current collector has two opposite surfaces in the thickness direction of itself, and the positive active layer is arranged on any one or both of the two opposite surfaces of the positive current collector.

[0063] In some embodiments, the positive electrode current collector can employ a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be employed. The composite current collector can include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite current collector can be obtained by forming a metal material on the polymer base layer. Non-limiting examples of the metal material in the positive electrode current collector can include one or more of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, a silver alloy, and the like. Non-limiting examples of the polymer base layer in the positive electrode current collector can include one or more of a polypropylene (PP), a polyethylene terephthalate (PET), a polybutylene terephthalate (PBT), a polystyrene (PS), a polyethylene (PE), and the like.

[0064] In some embodiments, the positive electrode active material can employ a positive electrode active material for a sodium ion battery known in the art. As an example, the positive electrode active material can be used alone only in one kind, or two or more kinds can be combined. Among them, the positive electrode active material can be selected from a sodium-iron composite oxide, a sodium-cobalt composite oxide, a sodium-chromium composite oxide, a sodium-manganese composite oxide, a sodium-nickel composite oxide, a sodium-nickel-titanium composite oxide, a sodium-nickel-manganese composite oxide, a sodium-iron-manganese composite oxide, a sodium-nickel-iron-manganese composite oxide, a sodium-nickel-cobalt-manganese composite oxide, a sodium-iron-phosphate compound, a sodium-manganese-phosphate compound, a sodium-cobalt-phosphate compound, a Prussian blue-based material, a polyanion material, and the like, but the present application is not limited to these materials, and other conventionally known materials that can be used as a positive electrode active material for a sodium ion battery can also be used. Optionally, the sodium-iron composite oxide includes NaFeO2. The sodium-cobalt composite oxide includes NaCoO2. The sodium-chromium composite oxide includes NaCrO2. The sodium-manganese composite oxide includes NaMnO2. The sodium-nickel composite oxide includes NaNiO2. The sodium-nickel-titanium composite oxide includes NaNi 1 / 2 Ti 1 / 2 O2. The sodium-nickel-manganese composite oxide includes NaNi 1 / 2Mn 1 / 2 O2. The sodium-iron-manganese composite oxide includes Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2. The sodium-nickel-cobalt-manganese composite oxide includes NaNi 1 / 3 Co 1 / 3Mn 1 / 3 O2. The sodium-iron-phosphate compound includes NaFePO4. The sodium-manganese-phosphate compound includes NaMnPO4. The sodium-cobalt-phosphate compound includes NaCoPO4. The polyanion material includes at least one of a phosphate, a fluorophosphate, a pyrophosphate, and a sulfate.

[0065] In some embodiments, the positive electrode active layer optionally further includes a binder. As non-limiting examples, the binder can include one or more 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.

[0066] In some embodiments, the positive electrode active layer optionally further includes a conductive agent. As non-limiting examples, the conductive agent can include one or more of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0067] In some embodiments, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one side surface of the positive electrode current collector; and subjecting the positive electrode current collector to a drying, cold-pressing, or other process to obtain the positive electrode tab. The solvent can be selected from, but is not limited to, any of the above-mentioned embodiments, such as N-methylpyrrolidone (NMP). The positive electrode slurry can be coated on a single surface of the positive electrode current collector, or on both surfaces of the positive electrode current collector.

[0068] Negative electrode tab

[0069] The negative electrode tab includes a negative electrode current collector and a negative electrode active layer disposed on at least one surface of the negative electrode current collector, the negative electrode active layer including a negative electrode active material.

[0070] As non-limiting examples, the negative electrode current collector has two opposite surfaces in the thickness direction of the negative electrode current collector, and the negative electrode active layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector.

[0071] The negative electrode current collector can be the above-mentioned metal foil or metal / polymer composite current collector.

[0072] In some embodiments, the negative active material can employ a negative active material for a battery known in the art. As non-limiting examples, the negative active material can include one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate, etc. The silicon-based material can include one or more of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can include one or more of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative active material for a battery can also be used. These negative active materials can be used alone or in combination of two or more. In some embodiments, the negative active material includes hard carbon.

[0073] In some embodiments, the negative active layer can also optionally include a binder. The binder can include one or more of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0074] In some embodiments, the negative film layer can also optionally include a conductive agent. The conductive agent can include one or more of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0075] In some embodiments, the negative active layer can also optionally include other auxiliary agents, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)), etc.

[0076] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry on at least one side surface of the negative current collector, and after processes such as drying, cold pressing, etc., the negative electrode sheet can be obtained. The surface of the negative current collector coated with the negative electrode slurry can be on a single surface of the negative current collector, or on both surfaces of the negative current collector.

[0077] Electrolyte

[0078] The electrolyte has the function of conducting ions between the positive electrode sheet and the negative electrode sheet. The present application does not have a particular limitation on the type of electrolyte, which can be selected as needed. For example, the electrolyte can be liquid, gel, or all-solid.

[0079] In some embodiments, the electrolyte employs an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0080] In some embodiments, the electrolyte salt can include one or more of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bisfluorosulfonylimide (NaFSI), sodium bis-trifluoromethanesulfonylimide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorophosphate (NaPO2F2), sodium difluoro-oxalato-borate (NaDFOB), sodium bis-oxalato-borate (NaBOB), sodium difluoro-bis-oxalato-phosphate (NaDFOP), and sodium tetrafluoro-oxalato-phosphate (NaTFOP).

[0081] In some embodiments, the solvent can include one or more of ethylene carbonate (EC, ), propylene carbonate (PC, ), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BEC), fluorinated ethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, methyl ethyl sulfone, and diethyl sulfone. In some embodiments, the electrolyte solution can further include one or more of fluorinated ethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), and the like.

[0082] In some embodiments, the electrolyte solution can further include one or more of fluorinated ethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), and the like.

[0083] In some embodiments, the electrolyte solution can further include one or more of fluorinated ethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), and the like.

[0084] Separator film

[0085] In some embodiments, the secondary battery further includes a separator film. The type of the separator film is not particularly limited in the present application, and any known porous structure separator film having good chemical stability and mechanical stability can be used.

[0086] In some embodiments, the material of the separator film can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0087] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator film can be made into an electrode assembly through a winding process.

[0088] In the present application, unless otherwise specified, a "battery cell" refers to a basic unit capable of realizing mutual conversion between chemical energy and electrical energy. Further, in general, at least includes a positive electrode sheet, a separator film, a negative electrode sheet, and an electrolyte. During the charging and discharging process of the battery, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. The separator film is arranged between the positive electrode sheet and the negative electrode sheet, which can be electrically insulated to prevent internal short circuit, while allowing active ions to pass through and move between the positive and negative electrodes. The electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0089] In some embodiments, the secondary battery can be a battery module or a battery pack.

[0090] The battery module includes at least one battery cell. The number of battery cells included in the battery module can be one or more, and a person skilled in the art can select an appropriate number according to the application and capacity of the battery module.

[0091] In the battery module, the plurality of battery cells can be arranged in sequence along the length direction of the battery module. Of course, they can also be arranged in any other manner. Further, the plurality of battery cells can be fixed by fasteners.

[0092] Optionally, the battery module can further include a housing having an accommodation space, and the plurality of battery cells are accommodated in the accommodation space.

[0093] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules included in the battery pack can be one or more, and a person skilled in the art can select an appropriate number according to the application and capacity of the battery pack.

[0094] The battery pack can include a battery box and a plurality of battery modules arranged in the battery box. The battery box includes an upper box body and a lower box body, and the upper box body can be arranged on the lower box body to form a closed space for accommodating the battery modules. The plurality of battery modules can be arranged in the battery box in any manner.

[0095] In addition, the present application also provides a power utilization device, which includes the secondary battery provided by the present application. The secondary battery can be used as a power source of the power utilization device, or as an energy storage unit of the power utilization device. The power utilization device can include a mobile device, an electric vehicle, an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto. Among them, the mobile device can be a mobile phone, a notebook computer, etc.; the electric vehicle can be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but is not limited thereto.

[0096] As the power consuming device, a secondary battery can be selected according to its use requirement.

[0097] As an example of the power consuming device, a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. can be used. In order to meet the requirement of high power and high energy density of the power consuming device for the secondary battery, a battery pack or a battery module can be used.

[0098] As another example of the device, a mobile phone, a tablet computer, a notebook computer, etc. can be used. The device usually requires thin and light, and a secondary battery monomer can be used as the power source.

[0099] In order to make the technical problems, technical solutions and beneficial effects solved in the present application clearer, the present application will be further described in detail below in combination with embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0100] Unless otherwise specified in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. Unless otherwise specified, the reagents or instruments used are conventional products that can be obtained from the market.

[0101] The preparation method of the battery monomer in the examples and comparative examples is as follows:

[0102] (1) Preparation of the positive electrode sheet

[0103] The positive electrode active material NaNi 0.22 Cu 0.11 Fe 0.33 Mn 0.34 O2, a conductive agent acetylene black, and a binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 97:2:1 and added to a solvent N-methyl pyrrolidone (NMP) to prepare a positive electrode slurry; the positive electrode slurry was uniformly coated on a positive electrode current collector aluminum foil, dried, cold-pressed, and then cut and striped to prepare a positive electrode sheet.

[0104] (2) Preparation of the negative electrode sheet

[0105] The negative active material hard carbon, conductive agent acetylene black, thickening agent sodium hydroxymethyl cellulose, and binder styrene-butadiene rubber were added into water in a mass ratio of 96:2:1:1, mixed uniformly, and a negative electrode slurry was prepared. The negative electrode slurry was uniformly coated on a negative electrode current collector, dried, cold-pressed, and then cut and divided into strips to prepare a negative electrode sheet. The types of the negative electrode current collector are shown in Table 1.

[0106] (3) Preparation of electrolyte

[0107] Sodium hexafluorophosphate was dissolved in a mixed solvent of ethylmethyl carbonate (EMC) and propylene carbonate (PC) (volume ratio of ethylmethyl carbonate to propylene carbonate was 58:42), and a vinyl fluoride carbonate (FEC) additive was added to obtain an electrolyte. The concentration of sodium hexafluorophosphate in the electrolyte was 1 mol / L, and the mass percentage of FEC was 5 wt%.

[0108] (4) Separation film

[0109] A polyethylene separation film was used.

[0110] (5) Preparation of battery monomer

[0111] The positive electrode sheet, the separation film, and the negative electrode sheet were stacked in order, with the separation film between the positive and negative electrodes to play a separation role, and were wound to obtain an electrode assembly. The electrode assembly was placed in a cylindrical shell and subjected to processes such as packaging, liquid injection, formation, and exhaust to obtain a sodium ion battery monomer. The size of the battery monomer was 32.6 mm x 130 mm.

[0112] The diameter L1 of the electrode assembly, the diameter L2 of the accommodating cavity of the shell, the population margin L1 / L2, and the density of the negative electrode current collector in the battery monomer of Example 1 are shown in Table 1.

[0113] Examples 2-10 were prepared by a method similar to that of Example 1, and the differences are shown in Table 1.

[0114] Comparative Example 1

[0115] A method similar to that of Example 1 was used, except that in the preparation of the battery monomer, the positive electrode sheet, the separation film, and the negative electrode sheet were stacked in order, with the separation film between the positive and negative electrodes to play a separation role, and were wound to obtain an electrode assembly. The electrode assembly was placed in a square shell and subjected to processes such as packaging, liquid injection, formation, and exhaust to obtain a sodium ion battery monomer. The size of the battery monomer was 15 mm x 100 mm x 80 mm.

[0116] The length L3 of the electrode assembly, the length L4 of the accommodating cavity of the shell, the population margin L3 / L4, and the density of the negative electrode current collector in the battery monomer of Comparative Example 1 are shown in Table 1.

[0117] Comparative Examples 2-4 were prepared in a similar manner to Comparative Example 1, except as detailed in Table 1.

[0118] Test Example

[0119] (1) Volume energy density test of the battery cell: after discharging the battery cell to the cut-off voltage 1.5 V at 0.33 C, it was left for 10 min; it was charged to the cut-off voltage 3.9 V at 0.33 C, left for 10 min, and then discharged to the cut-off voltage 1.5 V at 0.33 C, and the discharged energy was taken as the energy E of the battery cell. The volume V of the shell of the battery cell was measured. The volume energy density of the battery cell = E / V, with the unit of Wh / L. The test results are shown in Table 1.

[0120] (2) Mass energy density test of the battery cell: after discharging the battery cell to the cut-off voltage 1.5 V at 0.33 C, it was left for 10 min; it was charged to the cut-off voltage 3.9 V at 0.33 C, left for 10 min, and then discharged to the cut-off voltage 1.5 V at 0.33 C, and the discharged energy was taken as the energy E of the battery cell. The mass M of the battery cell was measured. The volume energy density of the battery cell = E / M, with the unit of Wh / kg. The test results are shown in Table 1.

[0121] (3) Cycle performance test of the battery: at 25℃, the battery was charged to the cut-off voltage 3.9 V at 0.33 C, left for 5 min, discharged to the cut-off voltage 1.5 V at 0.33 C, and the capacity C1 of this one cycle was recorded. The cycle was repeated until C n / C1x 100% = 80%, and the cycle number n at this time was recorded. The test results are shown in Table 1.

[0122] Table 1

[0123]

[0124] In Table 1, L1 is the diameter of the electrode assembly in the battery cell, with the unit of mm. L2 is the diameter of the accommodating cavity of the shell, with the unit of mm. L3 is the length of the electrode assembly in the battery cell, with the unit of mm. L4 is the length of the accommodating cavity of the shell, with the unit of mm. L1 / L2 is the group allowance of the cylindrical battery. L3 / L4 is the group allowance of the square battery. The thickness of the negative electrode current collector has the unit of μm. The density of the negative electrode current collector has the unit of g / cm3. The volume energy density has the unit of Wh / L. The mass energy density has the unit of Wh / kg. The cycle number has the unit of times.

[0125] As can be seen from Examples 1-10 and Comparative Examples 1-4, when the sodium-ion battery cell adopts a negative electrode current collector with a smaller density, cooperates with a larger group allowance, and simultaneously adopts a cylindrical shell, the battery cell has higher volume energy density and mass energy density, while taking into account better cycle performance.

[0126] As can be seen from Examples 1-5, when the group margin of the battery cells is 0.95-0.97, better cycle performance can be achieved.

[0127] As can be seen from the comparison between Example 6 and Example 1, when the negative current collector is a metal / polymer composite current collector, the battery cell has higher volumetric energy density, mass energy density and cycle performance.

[0128] As can be seen from the comparison between Example 3 and Examples 7-10, when the elongation of the negative current collector is within a suitable range, especially 3.5%-5.0%, the battery cell can simultaneously have higher volumetric energy density, mass energy density and cycle performance.

[0129] The technical features of the above-described examples can be combined in any manner. For the sake of brevity, not all possible combinations of the technical features in the above-described examples are described, however, as long as the combinations of the technical features do not contradict each other, they should be considered within the scope of the present disclosure.

[0130] The above-described examples only express several embodiments of the present application, and the description is relatively specific and detailed, but it should not be construed as limiting the scope of the patent. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the scope of the patent of the present application should be subject to the appended claims.

Claims

1. A sodium-ion battery cell, characterized in that, The application relates to a sodium ion battery cell, which comprises an electrode assembly and a shell, the shell is cylindrical, the shell has a containing cavity inside, and the electrode assembly is located inside the containing cavity; the electrode assembly comprises a negative electrode sheet, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer located on at least one surface of the negative electrode current collector, the density of the negative electrode current collector is less than or equal to 5.0 g / cm 3 , and the group margin of the sodium ion battery cell is 0.95 to 0.97, wherein the group margin is the ratio of the diameter of the electrode assembly to the diameter of the containing cavity.

2. The sodium-ion battery cell of claim 1, wherein, The density of the negative current collector is 1.3 g / cm 3 3.5 g / cm 3 .

3. The sodium-ion battery cell of any one of claims 1-2, wherein, The negative current collector has an elongation of ≥ 3%.

4. The sodium-ion battery cell of any one of claims 1-3, wherein, The negative current collector has an elongation of 3.5% to 5.0%.

5. The sodium-ion battery cell of any one of claims 1-4, wherein, The ratio of the thickness of the negative current collector to the thickness of the negative active layer is ≤ 0.

2.

6. The sodium-ion battery cell of any one of claims 1-5, wherein, The ratio of the thickness of the negative current collector to the thickness of the negative active layer is 0.03 to 0.

15.

7. The sodium-ion battery cell of any one of claims 1-6, wherein, The thickness of the negative current collector is 6 μm to 12 μm.

8. The sodium-ion battery cell of any one of claims 1-7, wherein, The thickness of the negative current collector is 6.5 μm to 10 μm.

9. The sodium-ion battery cell of any one of claims 1-8, wherein, The negative current collector comprises at least one of a metal foil or a metal / polymer composite current collector.

10. The sodium-ion battery cell of claim 9, wherein, The metal / polymer composite current collector comprises a polymer substrate layer and a metal layer on at least one surface of the polymer substrate layer.

11. The sodium-ion battery cell of claim 10, wherein, The polymer substrate layer comprises at least one of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, and polyethylene.

12. The sodium-ion battery cell according to claim 10 or 11, characterized in that, The metal layer comprises at least one of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.

13. The sodium-ion battery cell of any one of claims 1-12, wherein, The sodium-ion battery cell further comprises an electrolyte, the electrolyte being located inside the accommodation cavity; the sodium-ion battery cell satisfies: m / C0≤6 g / Ah, wherein m represents the mass of the electrolyte, the unit being g, and C0 represents the rated capacity of the sodium-ion battery cell, the unit being Ah.

14. The sodium-ion battery cell of claim 13, wherein, 4 g / Ah≤m / C0≤5 g / Ah.

15. The sodium-ion battery cell of any one of claims 1-14, wherein, The compaction density of the negative active layer is 0.7 g / cm 3 1.3 g / cm 3 .

16. The sodium-ion battery cell of any one of claims 1-15, wherein, The compaction density of the negative active layer is 0.8 g / cm 3 ~1.2 g / cm 3 .

17. The sodium-ion battery cell of any one of claims 1-16, wherein, The ratio of the height of the battery cell to the diameter of the battery cell is greater than or equal to 3.

5.

18. The sodium-ion battery cell of any one of claims 1-17, wherein, The ratio of the height of the battery cell to the diameter of the battery cell is 4 to 6.

19. The sodium-ion battery cell of any one of claims 1-18, wherein, The height of the battery cell is greater than or equal to 60 mm.

20. The sodium-ion battery cell of any one of claims 1-19, wherein, The height of the battery cell is 70 mm to 300 mm.

21. The sodium-ion battery cell of any one of claims 1-20, wherein, The diameter of the battery cell is greater than or equal to 21 mm.

22. The sodium-ion battery cell of any one of claims 1-21, wherein, The diameter of the battery cell is 30 mm to 60 mm.

23. A secondary battery characterized by comprising: The sodium-ion battery cell of any one of claims 1 to 22.

24. An electrical device, comprising: At least one of the sodium-ion battery cell of any one of claims 1 to 22 or the secondary battery of claim 23.

Images