Cylindrical battery cell, cylindrical battery and electric apparatus

Abstract

Provided in the present application are a cylindrical battery cell, a cylindrical battery and an electric apparatus. The cylindrical battery cell comprises a positive electrode sheet, a negative electrode sheet and a separator, wherein the negative electrode sheet is a negative electrode current collector or a negative electrode current collector with a conductive layer on a surface thereof. The cylindrical battery cell uses a "no negative electrode" design plus a positive electrode sheet, that is, a negative electrode side is not provided with an active material, and is simply provided with a negative electrode current collector or a negative electrode current collector with a conductive layer on a surface thereof, such that there is no hard expansion caused by volume expansion of a negative electrode active material in a negative electrode film layer, and thus the hard expansion on the negative electrode side during a charging process is effectively controlled, thereby effectively reducing the risk of breakage of an electrode sheet and the risk of collapse of a central hole caused by the hard expansion of the electrode sheet.

Description

Cylindrical battery cells, cylindrical batteries and electrical devices

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202410262967.0, filed on March 7, 2024, entitled “Cylindrical Battery Cell, Cylindrical Battery and Electrical Device,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to a cylindrical battery cell, a cylindrical battery, and an electrical device. Background Art

[0004] Cylindrical batteries are a common type of secondary battery. As the capacity of cylindrical batteries increases, the diameter of cylindrical batteries will become larger and larger. As the cycle progresses, the active materials (such as carbon or silicon negative electrode materials) of the cylindrical battery's pole pieces (mainly the negative electrode pieces) undergo hard expansion due to the embedding of active ions during the charging process. This hard expansion consumes the gaps between the pole pieces, causing squeezing between the pole pieces. From the inner circle to the outer circle, the shear force on the pole pieces gradually increases, and there is a risk of outer ring pole piece fracture. As the cylinder diameter increases, the shear force on the outer ring pole piece increases, so the risk of outer ring fracture increases rapidly. At the same time, due to the long-term charging and discharging of secondary batteries, the hard expansion of the pole pieces tends to accumulate. When the compressive stress (pointing to the center of the circle) caused by the expansion of the outer ring pole piece exceeds a critical value, the inner ring pole piece is compressed inward, resulting in center hole collapse. The larger the cylinder diameter, the greater the compressive stress on the inner ring pole piece, and the more likely it is to cause center hole collapse.

[0005] Summary of the Invention

[0006] The present application provides a cylindrical battery cell, a cylindrical battery, and an electrical device to reduce the risk of pole piece breakage and center hole collapse caused by hard expansion of the pole piece.

[0007] A first aspect of the present application provides a cylindrical battery cell comprising a positive electrode sheet, a negative electrode sheet and a separator, wherein the negative electrode sheet is a negative electrode current collector or a negative electrode current collector having a conductive layer on its surface.

[0008] The cylindrical battery cell adopts a "negative electrode-free" design with a positive electrode plate, that is, no active material is set on the negative electrode side, only a negative electrode current collector or a negative electrode current collector with a conductive layer on the surface is set. Then there is no hard expansion caused by the volume expansion of the negative electrode active material in the negative electrode film layer. Therefore, the hard expansion of the negative electrode side during charging is effectively controlled, thereby effectively reducing the risk of electrode plate breakage and the risk of center hole collapse caused by the hard expansion of the electrode plate.

[0009] In any embodiment of the first aspect, the separator comprises a substrate and an organic insulating material layer disposed on the substrate. The substrate has a porosity of 50%-80%. After charging, active metal is deposited on the surface of the negative electrode current collector or the conductive layer, and the active metal may extend into the pores of the substrate. During the cell preparation stage, the substrate reserves more space for metal deposition on the negative electrode side. During charging, metal deposition can occur in this reserved space, further mitigating the risk of fracture of the positive and negative electrode sheets due to increased hard expansion of the active metal layer deposited on the negative electrode side.

[0010] In any embodiment of the first aspect, the porosity of the organic insulating material layer is less than 45%, thereby effectively preventing the active metal entering the substrate from passing through the separator and causing a short circuit between the positive and negative electrodes.

[0011] In any embodiment of the first aspect, the organic insulating material is disposed on a side of the substrate close to the positive electrode tab.

[0012] In any embodiment of the first aspect, the substrate is a nonwoven substrate.

[0013] In any embodiment of the first aspect, the thickness of the substrate is 5 μm to 20 μm, so as to provide more sufficient space for metal deposition on the negative electrode side.

[0014] In any embodiment of the first aspect, the material forming the substrate includes one or more of cellulose, polyethylene terephthalate, polyimide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, and polytetrafluoroethylene.

[0015] In any embodiment of the first aspect, the material forming the organic insulating material layer includes one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0016] In any embodiment of the first aspect, the thickness of the separator is 10 μm-40 μm. Within the above range, the thicker the separator, the more space there is for sodium deposition under the condition that the non-woven fabric has the same porosity.

[0017] In any embodiment of the first aspect, the negative electrode current collector comprises copper foil, aluminum foil, copper-plated polymer foil, or aluminum-plated polymer foil.

[0018] In any embodiment of the first aspect, the conductive layer includes a conductive agent, and the conductive agent includes one or more of carbon nanotubes, conductive carbon black, hard carbon, conductive graphite, and graphene.

[0019] In any embodiment of the first aspect, the thickness of the conductive layer is 2 μm to 40 μm.

[0020] In any embodiment of the first aspect, the diameter of the cylindrical battery core is 46 mm-200 mm.

[0021] A second aspect of the present application provides a cylindrical battery, comprising a cylindrical battery cell and a shell, wherein the cylindrical battery cell comprises the cylindrical battery cell provided by any embodiment of the first aspect.

[0022] A third aspect of the present application provides an electrical device including a cylindrical battery, wherein the cylindrical battery includes the cylindrical battery provided in any embodiment of the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0024] FIG1 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application. DETAILED DESCRIPTION

[0025] The following detailed description of the embodiments of the present application is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present application, but are not intended to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0026] Below, the embodiments of the cylindrical battery cell, cylindrical battery, and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0027] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all 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.

[0028] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0029] 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.

[0030] 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), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating 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.

[0031] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or comprised.

[0032] Unless otherwise specified, the term "or" is inclusive in this application. For example, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0033] [Secondary battery]

[0034] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged to activate the active materials after discharge and continue to be used.

[0035] Typically, a secondary battery includes a cell and a shell. The cell includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the battery's charge and discharge process, active ions (such as lithium ions) are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The electrolyte is between the positive electrode sheet and the negative electrode sheet, mainly to conduct active ions.

[0036] [Cylindrical battery cells]

[0037] As described in the background technology, during long-term charge and discharge cycles, the negative electrode sheet undergoes hard expansion due to the volume expansion of the negative electrode active material (referring to the active material that allows lithium ions or sodium ions to be embedded and extracted), resulting in an increased risk of mutual compression between the electrode sheets, which in turn causes the outer ring electrode sheet to break or the center hole to collapse. In order to reduce the risk of fracture caused by hard expansion of the electrode sheet, the first embodiment of the present application provides a cylindrical battery cell, including a positive electrode sheet, a negative electrode sheet, and a separator, wherein the negative electrode sheet is a negative electrode current collector or a negative electrode current collector with a conductive layer on its surface.

[0038] The cylindrical battery cell of the present application adopts a "negative electrode-free" design with a positive electrode plate, that is, no active material is set on the negative electrode side, only a negative electrode current collector or a negative electrode current collector with a conductive layer on the surface is set, so there is no hard expansion caused by the volume expansion of the negative electrode active material in the negative electrode film layer. Therefore, the hard expansion of the negative electrode side during charging is effectively controlled, thereby effectively reducing the risk of electrode plate breakage and the risk of center hole collapse caused by the hard expansion of the electrode plate.

[0039] In some embodiments, because the negative electrode plate serves as the negative current collector or has a conductive layer on its surface, the cylindrical cell can be referred to as a negative-electrode-free sodium secondary battery cell. The conductive layer helps reduce the overpotential required for sodium deposition during charging and improves the uniformity of sodium metal deposition after the initial charge and discharge.

[0040] A negative-electrode-free sodium secondary battery refers to a battery in which no negative electrode active material layer is actively placed on the negative electrode during the battery manufacturing process. For example, a sodium metal or carbonaceous active material layer is not formed on the negative electrode through coating or deposition. During the initial charge, sodium ions on the negative electrode side gain electrons, and metallic sodium is deposited on the current collector surface to form a sodium metal phase. During discharge, the metallic sodium can be converted into sodium ions and returned to the positive electrode, achieving cyclic charge and discharge. Compared to other sodium secondary batteries, negative-electrode-free sodium secondary batteries can achieve higher energy density due to the lack of a negative electrode active material layer.

[0041] In some embodiments, to improve battery performance, one or both sides of the negative electrode current collector of the negative electrode sheet may be provided with some conventional negative electrode active materials, such as carbonaceous materials, metal oxides, alloys, etc. Although these materials have a certain capacity, due to the small amount of these materials, they are not used as the main negative electrode active material in the battery. Therefore, the sodium secondary battery constructed in this way can still be regarded as a negative electrode-free sodium secondary battery.

[0042] In some embodiments, the CB value of the negative electrode-free sodium secondary battery is less than or equal to 0.1.

[0043] The CB value is the capacity per unit area of ​​the negative electrode in a secondary battery divided by the capacity per unit area of ​​the positive electrode. Since a battery without a negative electrode contains no or only a small amount of negative electrode active material, the capacity per unit area of ​​the negative electrode is relatively small, and the CB value of a secondary battery is less than or equal to 0.1.

[0044] During the winding process of the positive electrode, separator, and negative electrode of a cylindrical battery cell, gaps (i.e., natural gaps) inevitably form between the positive electrode, separator, and negative electrode. Generally, the natural gap between the separator and the negative electrode is usually larger than the thickness of the active metal layer. In this case, the problem caused by volume expansion caused by the deposition of the active metal layer can be effectively alleviated.

[0045] When the energy density of the cylindrical battery cell is further increased, the thickness of the active metal layer that needs to be deposited on the negative electrode increases, and the natural gap between the negative electrode sheet and the separator may not be sufficient to support the thickness of the deposited active metal layer. At this time, the deposited active metal layer will cause extrusion between the positive electrode sheet and the negative electrode sheet. Or in one possible scenario, during the winding process of the battery cell, it is impossible to accurately control the natural gap between the positive electrode sheet, the negative electrode sheet and the separator, resulting in a very small natural gap between the negative electrode sheet and the separator. At this time, the deposited active metal layer will cause extrusion between the positive electrode sheet and the negative electrode sheet. In another possible scenario, when the active metal is deposited on the negative electrode side, it is difficult to form a dense metal layer in an ideal state. For example, there will be a dendrite form. Therefore, its actual deposition thickness will be greater than the theoretical deposition thickness. Especially in high energy density cylindrical batteries, this thickness difference will be more obvious. To address these issues, in some embodiments, a separator comprises a substrate and an organic insulating material layer disposed on the substrate. By controlling the substrate's porosity to 50%-80%, active metal is deposited on the surface of the negative electrode current collector or conductive layer after charging, extending into the substrate's pores. This 50%-80% porosity is richer than that of conventional secondary battery separators. Therefore, the pores of the separator substrate provide ample space for the active metal, thereby mitigating or eliminating the problem of hard expansion caused by active metal deposition.

[0046] The diaphragm and the organic insulating material layer are matched, and the thickness and porosity of the organic insulating material layer can be freely adjusted according to the needs of the diaphragm. In some embodiments, the porosity of the organic insulating material layer is less than 45%, for example, above 20%, above 30% or above 35%. Thus, the organic insulating material layer can effectively prevent the metal dendrites generated when the metal deposition is uneven from piercing the diaphragm, thereby avoiding the problem of battery short circuit. In some embodiments, the porosity of the organic insulating material layer can be 20%, 25%, 30% or 40%, etc., that is, the porosity of the organic insulating material layer can be adjusted according to the porosity of the conventional diaphragm, and this application does not make special requirements.

[0047] The porosity of the substrate or organic insulating material layer is tested by measuring the permeability of the pores to the fluid. The test steps are as follows:

[0048] 1. When the non-woven fabric substrate is compounded in the diaphragm, the non-woven fabric substrate and the organic insulating material are peeled off, and permeate pools are respectively set on both sides of the non-woven fabric substrate, and the permeate is placed in the pools on both sides.

[0049] 2. Apply a certain pressure in the permeate pool to allow the permeate to penetrate through the pores of the non-woven fabric substrate to the other side.

[0050] 3. Measure the pressure change in the liquid pool before and after penetration and the flow rate of the permeate.

[0051] 4. Calculate the porosity of the nonwoven substrate for: Where Q is the permeate flow rate, Δt is the permeation time, A is the area of ​​the nonwoven substrate, and ΔP is the pressure difference.

[0052] The porosity test of the present application can be performed directly on the raw material substrate using the above method; or the substrate can be peeled off from the diaphragm after the battery is 100% discharged, and the porosity of the substrate can be tested using the above method.

[0053] In the present application, a slurry of organic insulating material is coated on one or both sides of a substrate and pressed and dried, or a prepared organic insulating material film layer is pressed against a substrate, thereby providing organic insulating material on one or both sides of the substrate. In some embodiments of the present application, in order to leave more space for metal deposition on the negative electrode side, in some embodiments, the organic insulating material is provided on the side of the substrate close to the positive electrode plate. The substrate close to the negative electrode side has relatively more pores, which is more conducive to the deposition of metal on the negative electrode side, thereby better alleviating the hard expansion caused by the deposition of active metal on the negative electrode side, and the substrate frame also plays a limiting role in the growth of active metal to avoid its excessive growth; the organic insulating material layer is provided on the side close to the positive electrode plate, and the active metal does not need to pass through the organic insulating material layer to enter the substrate pores, which is more conducive to the growth of active metal in the substrate pores. In addition, the organic insulating material can effectively prevent the active metal in the substrate pores from piercing the diaphragm, thereby avoiding internal short circuits between the positive and negative electrodes.

[0054] In some embodiments, the substrate is a non-woven fabric substrate. Non-woven fabric is a non-woven fabric in this field, which refers to a product obtained by orienting or randomly arranging uniformly dispersed fibers using non-woven manufacturing processes such as electrospinning, wet non-woven process, melt-blowing, etc. to form a three-dimensional network structure, and then reinforcing it by physical methods. Non-woven fabric can be prepared from a diaphragm material commonly used in secondary batteries by any of the above non-woven processes. Due to the characteristics of the non-woven fabric manufacturing process, a non-woven fabric substrate with abundant pores can be obtained at a low cost. During the charging process, when metal is deposited on the negative electrode side, the pores of the non-woven fabric substrate serve as a framework to provide abundant space for the deposition of metal, thereby alleviating the hard expansion caused by the large amount of metal deposition on the negative electrode side, thereby alleviating or avoiding the problems of cracking of the pole piece and collapse of the central hole; and the organic insulating material layer provided on the non-woven fabric substrate can effectively prevent the metal dendrites generated when the metal deposition is uneven from piercing the diaphragm, thereby avoiding the problem of battery short circuit. Of course, a film layer with a porosity of 50%-80% that can be obtained by a conventional wet or dry film forming process can also be used in this application.

[0055] In some embodiments, the thickness of the substrate is 5 μm to 20 μm, so as to provide more sufficient space for metal deposition on the negative electrode side.

[0056] In some embodiments, the thickness of the separator is between 10 μm and 40 μm. Adjusting the separator thickness is achieved by adjusting the ratio of the organic insulating material to the substrate. Within this range, a thicker separator provides more space for sodium deposition, provided the substrate has the same porosity.

[0057] In some embodiments, the material forming the substrate includes but is not limited to one or more of cellulose, polyethylene terephthalate (PET), polyimide (PI), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and polytetrafluoroethylene (PTFE).

[0058] The material forming the organic insulating material layer can be selected from commonly used separator materials for secondary batteries. In some embodiments, the organic insulating material includes at least one or more of glass fiber, polyethylene, polypropylene, and polyvinylidene fluoride.

[0059] The negative electrode plate of the present application does not contain negative electrode active material. A battery having such a negative electrode plate is what is commonly known in the art as a "negative electrode-free" battery. The negative electrode current collector used in the cylindrical battery cell of the present application can be the negative electrode current collector used for conventional negative electrode plates. In some embodiments, the negative electrode current collector includes but is not limited to copper foil, aluminum foil, copper-plated polymer foil, or aluminum-plated polymer foil. The thickness of the negative electrode current collector is based on the thickness of the negative electrode current collector in conventional cylindrical batteries and is not further described in this application.

[0060] In some embodiments, the surface of the negative electrode current collector comprises a conductive layer. This conductive layer can reduce the overpotential required for metal deposition on the negative electrode side, improve the uniformity of metal deposition after the initial charge and discharge, and increase the rate of active ion transport, thereby enhancing battery kinetic performance. This conductive layer includes a conductive agent, which can be a commonly used conductive agent for secondary battery negative electrodes. In some embodiments, the conductive agent includes, but is not limited to, one or more of carbon nanotubes, conductive carbon black, hard carbon, conductive graphite, and graphene.

[0061] In order to give full play to the advantages of the conductive layer while avoiding the conductive layer being too thick and causing a reduction in battery energy density, in some embodiments, the thickness of the conductive layer is 2μm-40μm, such as 2μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm or 40μm, optionally 2μm-20μm, and further optionally 2μm-10μm.

[0062] Because the rigid expansion of the cylindrical battery cell of the present application is effectively controlled, the number of winding layers can be further expanded. In some embodiments, the diameter of the cylindrical battery cell is 46mm-200mm. The larger the diameter of the battery cell, the more difficult it is to dissipate heat. To improve the heat dissipation effect, the diameter of the cylindrical battery cell can optionally be 60mm-92mm.

[0063] [Positive electrode]

[0064] The positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0065] 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 is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0066] In some embodiments, 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 of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0067] In some embodiments, the positive electrode active material may adopt the positive electrode active material for batteries that is well known in the art. As an example, when the secondary battery is a lithium ion secondary battery, the positive electrode active material may include at least one of the following materials: lithium phosphates containing olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include but are not limited to lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0068] When the secondary battery is a sodium-ion secondary battery, as an example, the positive electrode active material of the sodium-ion secondary battery may include at least one of the following materials: a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound. However, the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0069] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Sodium transition metal oxide is, for example, Na x MO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0070] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y can be at least one of P, S and Si; n represents (YO4) n- valence.

[0071] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n-A class of compounds containing anion units and halogen anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4) n- valence state; the halogen may be at least one of F, Cl and Br.

[0072] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. Y can be at least one of P, S and Si, and n represents (YO4) n- valence state; Z represents a transition metal, which may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents (ZO y ) m+ valence state; halogen may be at least one of F, Cl and Br, y is selected from any chemically acceptable value.

[0073] In some embodiments, the polyanionic compound is a NACOSION type material, such as NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, referred to as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (M' is one or more of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y The NACOSION material is a fast ion conductor with a low potential barrier and almost no temperature rise, thus reducing heat accumulation in the battery cell, lowering the resulting safety risks, and extending the life of the battery cell.

[0074] Prussian blue compounds can be compounds containing sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds are, for example, Na a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0075] In some embodiments, the positive electrode film layer may further optionally 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.

[0076] In some embodiments, the positive electrode film layer may further include a conductive agent. For 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.

[0077] 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 N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0078] In some embodiments, the cylindrical battery cell is a sodium cylindrical battery cell.

[0079] In a second embodiment of the present application, a cylindrical battery is provided, including a cylindrical battery cell and a shell. The cylindrical battery cell includes the cylindrical battery cell provided in any embodiment of the first embodiment.

[0080] [Electrolytes]

[0081] The cylindrical battery cell also includes an electrolyte, which conducts ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected based on needs. For example, the electrolyte can be liquid, gel, or solid.

[0082] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0083] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0084] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0085] In some embodiments, the electrolyte may optionally 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.

[0086] In some embodiments, the secondary battery housing may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the secondary battery housing may be a soft package, such as a pouch-type soft package. The soft package may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0087] In some embodiments, cylindrical batteries can be assembled into battery modules as monomers. The number of monomers contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0088] In addition, the present application also provides an electrical device, which includes the cylindrical battery provided in the present application. The cylindrical battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0089] As the electrical device, a single cell, a battery module or a battery pack can be selected according to its usage requirements.

[0090] Figure 1 shows an example of an electric device. This device can be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0091] [Example]

[0092] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0093] Example 1

[0094] Preparation of the diaphragm: A polyethylene film (7 nm thick, 40% porosity) was pressed onto one side of a cellulose nonwoven fabric, and then dried in a drying oven to obtain a diaphragm. The thickness and porosity of the nonwoven fabric used are recorded in Table 1.

[0095] Preparation of anode-free sodium metal batteries

[0096] Preparation of positive electrode sheet: The positive electrode active material sodium iron pyrophosphate (whose theoretical gram capacity is 129 mAh / g), the conductive agent carbon nanotubes, and the binder hexafluorophosphate are fully stirred and mixed in N-methylpyrrolidone (NMP) at a mass ratio of 95:2:3 to form a uniform positive electrode slurry; the positive electrode slurry is coated on the surface of the positive electrode current collector aluminum foil, and after drying, cold pressing, and die cutting, a positive electrode sheet with a thickness of 200 μm is obtained, wherein the coating weight of the positive electrode film layer of the positive electrode sheet is 350 mg / 1540.25 mm 2 .

[0097] Preparation of electrolyte: In an argon-filled glove box with a water content of <1 ppm, diethylene glycol dimethyl ether and tetrahydrofuran were mixed in a mass ratio of 1:3, sodium hexafluorophosphate (NaPF6) with a concentration of 1.0 mol / L was added, and the mixture was stirred to obtain an electrolyte.

[0098] Preparation of a negative electrode-free sodium metal battery: stack the positive electrode sheet, separator, and copper foil (8 μm thick) prepared in the above steps in order, so that the separator is located between the positive electrode sheet and the copper foil and can isolate the positive electrode sheet and the copper foil, and the side of the separator with the PE film is close to the positive electrode sheet; then wind the stacked components to obtain a cylindrical battery cell with a diameter of 80 mm; place the electrode assembly in a shell, dry it, and inject the electrolyte; after formation, standing, and other processes, a negative electrode-free sodium metal battery is obtained.

[0099] Examples 2 to 9

[0100] The preparation process of the diaphragm was the same as that of Example 1. The thickness and porosity of the non-woven fabric used are recorded in Table 1. The rest of the preparation was the same as that of Example 1.

[0101] Example 10

[0102] A polyethylene diaphragm (thickness of 17 nm, porosity of 40%, without non-woven fabric) was used to replace the diaphragm of Example 1, and the rest was the same as in Example 1.

[0103] Comparative Example 1

[0104] The separator is a polyethylene separator with a thickness of 17 nm and a porosity of 40%.

[0105] Preparation of negative electrode sheets: The negative electrode active material hard carbon, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are dissolved in deionized water in a weight ratio of 96.2:0.8:0.8:1.2, and a negative electrode slurry is obtained under the action of a vacuum mixer; the negative electrode slurry is evenly coated on a copper foil; the copper foil is dried at room temperature and then transferred to a 120°C oven for drying for 4 hours, and then super-cold pressed and cut to obtain a negative electrode sheet with a negative electrode film layer, and the coating amount per unit area is 0.17g / 1540.25mm 2 .

[0106] The rest is the same as in Example 1.

[0107] The porosity of the non-woven fabric substrate is tested by measuring the permeability of the pores of the non-woven fabric substrate to the fluid. The test steps are as follows:

[0108] 1. Set up permeate pools on both sides of the non-woven fabric substrate, and place the permeate in the pools on both sides.

[0109] 2. Apply a certain pressure in the permeate pool to allow the permeate to penetrate through the pores of the non-woven fabric substrate to the other side.

[0110] 3. Measure the pressure change in the liquid pool before and after penetration and the flow rate of the permeate.

[0111] 4. Calculate the porosity of the nonwoven substrate for: Where Q is the permeate flow rate, Δt is the permeation time, A is the area of ​​the nonwoven substrate, and ΔP is the pressure difference.

[0112] Separator Thickness Test: Prepare the battery sample to be tested and ensure it is in a safe condition. Place the thickness gauge probe on the surface of the battery separator and record the measurement results. Repeat these steps to measure the separator thickness at multiple locations for more accurate data. Analyze the measurement results and calculate the average separator thickness.

[0113] Table 1

[0114] Cycle performance test: Each battery cell is charged at a rate of 0.33C to a voltage of 3.65V at room temperature, and then discharged at a rate of 0.33C to a voltage of 1.5V. The reversible capacity is measured as C0. Repeat the charge and discharge until the discharge capacity of a certain cycle is C0. n / C0≤80%, the total number of cycles is recorded as X-Cycle. n is the reversible capacity at the nth cycle.

[0115] The above test and calculation results are recorded in Table 2.

[0116] Table 2

[0117] During cycling, the negative electrode of the cylindrical battery cell with an 80mm diameter negative electrode in Comparative Example 1 expanded, causing the outer electrode sheet to fracture, leading to a drop in cycle life. The separator in Example 10 lacked a non-woven fabric. When the electrode sheet gap exactly matched the theoretical deposition thickness, there was a tendency for the separator and negative electrode sheet to have no margin, leading to deposited sodium metal dendrites piercing the separator and causing internal shorting. The improvement in cycle life was not significant compared to the other examples.

[0118] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A cylindrical battery cell comprising a positive electrode sheet, a negative electrode sheet and a separator, wherein: The negative electrode plate is a negative electrode current collector or a negative electrode current collector with a conductive layer on its surface.

2. The cylindrical battery cell according to claim 1, wherein: The separator includes a substrate and an organic insulating material layer arranged on the substrate. The porosity of the substrate is 50%-80%. After charging, active metal is deposited on the surface of the negative electrode current collector or the surface of the conductive layer, and the active metal can extend into the pores of the substrate.

3. The cylindrical battery cell according to claim 2, wherein: The porosity of the organic insulating material layer is less than 45%.

4. The cylindrical battery cell according to claim 2 or 3, wherein: The organic insulating material layer is arranged on a side of the substrate close to the positive electrode plate.

5. The cylindrical battery cell according to any one of claims 2 to 3, wherein: The substrate is a non-woven fabric substrate.

6. The cylindrical battery cell according to any one of claims 2 to 5, wherein: The thickness of the substrate is 5 μm-20 μm.

7. The cylindrical battery cell according to any one of claims 2 to 6, wherein: The material forming the substrate includes one or more of cellulose, polyethylene terephthalate, polyimide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, and polytetrafluoroethylene.

8. The cylindrical battery cell according to any one of claims 2 to 7, wherein: The material forming the organic insulating material layer includes one or more of glass fiber, polyethylene, polypropylene and polyvinylidene fluoride.

9. The cylindrical battery cell according to any one of claims 1 to 8, wherein: The thickness of the separator is 10 μm-40 μm.

10. The cylindrical battery cell according to any one of claims 1 to 9, wherein: The negative electrode current collector includes copper foil, aluminum foil, copper-plated polymer foil, or aluminum-plated polymer foil.

11. The cylindrical battery cell according to any one of claims 1 to 10, wherein: The conductive layer includes a conductive agent, and the conductive agent includes one or more of carbon nanotubes, conductive carbon black, hard carbon, conductive graphite, and graphene.

12. The cylindrical battery cell according to any one of claims 1 to 11, wherein: The thickness of the conductive layer is 2 μm-40 μm.

13. The cylindrical battery cell according to any one of claims 1 to 12, wherein: The diameter of the cylindrical battery core is 46mm-200mm.

14. A cylindrical battery comprising a cylindrical cell and a shell, wherein: The cylindrical battery cell comprises the cylindrical battery cell according to any one of claims 1 to 13.

15. An electrical device comprising a cylindrical battery, wherein: The cylindrical battery includes the cylindrical battery according to claim 14.

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