Separator and preparation method therefor, battery, and electric device

Abstract

A separator and a preparation method therefor, a battery, and an electric device, relating to the field of batteries. The separator comprises a polymer-based film, the polymer-based film has a three-dimensional network pore structure that is formed by interwoven polymer fibers and has pores communicated with each other, and the polymer fibers each contain a porphyrin compound and a polymer resin, wherein the porphyrin compound is dispersed in the polymer resin. The separator has better porosity and ionic conductivity, and during the battery cycling process, the porphyrin compound can coordinate with transition metal dissolved from a positive electrode active material to generate transition metal porphyrin, so that the dissolved transition metal is inhibited or prevented from migrating and depositing onto the surface of a negative electrode sheet to damage an SEI film, thereby improving the cycling capacity retention ratio and the rate capability of batteries.

Description

Diaphragm and preparation method thereof, battery and electrical device

[0001] Cross-references

[0002] This application claims priority to Chinese Patent Application No. 202410268976.0, filed on March 8, 2024, entitled “Diaphragm and its preparation method, 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 batteries, and more specifically, to a diaphragm and a preparation method thereof, a battery, and an electrical device. Background Art

[0004] During the battery cycle, the dissolution of transition metals in the positive electrode active material is a common and unavoidable phenomenon. After dissolution, these transition metals will migrate to the negative electrode surface and deposit, destroying the solid electrolyte membrane (SEI membrane), causing problems such as increased electrode impedance and negative electrode gas production, thereby leading to battery capacity attenuation and deterioration of cycle capacity retention.

[0005] Summary of the Invention

[0006] In view of the above problems, the present application proposes a diaphragm and a preparation method thereof, a battery and an electrical device, which can improve the technical problems of battery capacity attenuation and life deterioration.

[0007] In a first aspect, an embodiment of the present application provides a diaphragm, which includes a polymer base membrane having a three-dimensional network pore structure formed by interweaving polymer fibers and penetrating each other, wherein the polymer fibers contain a porphyrin compound and a polymer resin, wherein the porphyrin compound is dispersed in the polymer resin.

[0008] In the technical solution of the embodiment of the present application, the polymer fiber contains a porphyrin compound and a polymer resin, and the porphyrin compound is dispersed in the polymer resin, so that the diaphragm not only has better porosity and ionic conductivity, but also during the battery cycle, the porphyrin compound can coordinate with the transition metal dissolved from the positive electrode active material to generate transition metal porphyrin, inhibiting or preventing the dissolved transition metal from migrating and depositing on the surface of the negative electrode sheet to destroy the SEI film, which is beneficial to improving the battery's cycle capacity retention rate and rate performance.

[0009] In some embodiments, the ionic conductivity of the polymer-based membrane is 2 mS / cm-6 mS / cm. The ionic conductivity of the polymer-based membrane is 2 mS / cm-6 mS / cm, which is beneficial for improving the capacity and rate performance of the battery.

[0010] In some embodiments, the polymer base film has a thickness of 3 μm to 16 μm and a porosity of 20% to 40%. The polymer base film has a high porosity within the above thickness range, which is beneficial to improving battery performance.

[0011] In some embodiments, the mass ratio of the porphyrin compound to the polymer resin is greater than 0 and less than or equal to 5. By controlling the mass ratio of the porphyrin compound to the polymer resin to be greater than 0 and less than or equal to 5, the battery can be applied to achieve both better cycle capacity retention and rate performance.

[0012] In some embodiments, the mass ratio of the porphyrin compound to the polymer resin is 1-5.

[0013] In some embodiments, the porphyrin compound has the structural formula:

[0014] wherein R1 is independently hydrogen, hydroxyl, carboxyl, phenyl, sulfonic acid, halogen or pyridyl, and the phenyl group may be substituted by alkyl, alkoxy, carboxyl, amino, aryloxy, halogen or other heteroatoms and any combination thereof on carbon atoms 2, 3, 4, 5 and 6 of the phenyl ring;

[0015] R2 is hydrogen, alkyl, alkoxy, aryl, aryloxy, halogen, nitro or other heteroatoms and any combination thereof located on the carbon 2 or 3 of each pyrrole ring of the porphyrin compound.

[0016] In some embodiments, the porphyrin compound includes at least one of tetrasulfonate porphyrin, tetraaminoporphyrin, tetracarboxy porphyrin, tetraaminophenyl porphyrin, tetracarboxyphenyl porphyrin, para-chlorotetraphenyl porphyrin, tetraphenyl porphyrin, tetra(4-pyridyl)porphyrin, tetra(2-pyridyl)porphyrin, 5,15-di(4-pyridyl)10,20-diphenyl porphyrin, 5,15-di(4-pyridyl)10,20-dicarboxyphenyl porphyrin, and tetrahydroxy porphyrin.

[0017] In some embodiments, the polymer resin includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyacetal, polycarbonate, polyimide, polyetherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalate, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, polyacrylonitrile, poly(p-phenylene benzobisoxazole), and polyarylate. Each of the above porphyrin compounds can coordinate with the transition metal dissolved from the positive electrode active material to form a transition metal porphyrin, which can alleviate the migration of the dissolved transition metal and its deposition on the surface of the negative electrode to destroy the SEI film, thereby improving the cycle capacity retention and rate performance of the battery.

[0018] In some embodiments, the diaphragm further comprises a coating layer on the surface of the base film. The coating layer can be provided to specifically enhance the performance of the diaphragm, and the coating layer can be selected according to actual needs.

[0019] In some embodiments, the coating includes an aluminum oxide ceramic coating on a surface of the base film, and a polyvinylidene fluoride coating on a surface of the aluminum oxide ceramic coating.

[0020] In some embodiments, the ionic conductivity of the separator is greater than 2 mS / cm, the thickness of the separator is 4-20 μm, and the porosity of the separator is 20%-40%.

[0021] The above-mentioned diaphragm not only takes into account better porosity and ionic conductivity, but also during the battery cycle, the porphyrin compound can inhibit or prevent the dissolved transition metal from migrating and depositing on the surface of the negative electrode to destroy the SEI film, which is beneficial to improving the battery's cycle capacity retention rate and rate performance. In a second aspect, the present application provides a method for preparing the diaphragm in the above-mentioned embodiment, which includes: a step of dispersing and / or dissolving the porphyrin compound in an organic solution of a polymer resin to obtain a mixed solution, and a step of phase separation of the mixed solution to obtain a polymer-based membrane.

[0022] The preparation method provided in the present application adopts a phase separation method to prepare the above-mentioned polymer-based membrane. The operation is simple and controllable, and the porosity can be easily adjusted. In addition, the polymer fibers in the final polymer-based membrane are interwoven to form a three-dimensional network pore structure that is interconnected. The polymer fibers include porphyrin compounds and polymer resins, and the porphyrin compounds are uniformly dispersed in the polymer resin in a bulk phase distribution, which is beneficial to improving the ionic conductivity of the polymer-based membrane. In addition, during the battery cycle, the porphyrin compound can inhibit or prevent the dissolved transition metal from migrating and depositing on the surface of the negative electrode to destroy the SEI film, which is beneficial to improving the battery's cycle capacity retention rate and rate performance.

[0023] In some embodiments, the method of causing the mixed liquid to phase separate comprises:

[0024] First, a non-solvent is added to an organic solution of a polymer resin, and then a porphyrin compound is added and mixed to obtain a mixed solution as a phase separation liquid;

[0025] The phase separation liquid is then coated or cast on a substrate, evaporated to form a film, and dried;

[0026] The non-solvent comprises at least one of water, methanol, ethanol, isopropanol, ethylene glycol, and glycerol. The non-solvent-induced phase separation method using a phase separation liquid to prepare a diaphragm is simple and controllable, can be industrially produced, and can form a film without stretching. The prepared diaphragm has sufficient mechanical properties and can effectively inhibit or prevent dissolved transition metals from migrating and depositing on the surface of the negative electrode sheet to destroy the SEI film, thereby improving the battery's cycle capacity retention and rate performance.

[0027] In some embodiments, drying comprises vacuum drying at 60-100° C. for at least 12 hours, while maintaining a good drying efficiency and avoiding affecting the quality of the separator.

[0028] In some embodiments, the amount of organic solvent added to the organic solution of the polymer resin is 10-30 times the mass of the polymer resin, and / or the amount of non-solvent added is 3-10 times the mass of the polymer resin. Controlling the amount within these ranges can improve the quality of the separator and enhance the cycle capacity retention and rate performance of the battery.

[0029] In some embodiments, the organic solvent used in the organic solution of the polymer resin includes at least one of toluene, xylene, amyl acetate, and trichloroethylene.

[0030] In a third aspect, the present application provides a battery comprising a positive electrode sheet and the separator in the above embodiment, wherein the positive electrode sheet comprises a positive electrode active material containing a transition metal.

[0031] In a fourth aspect, the present application provides an electrical device, which includes the battery in the above embodiment, and the battery is used to provide electrical energy.

[0032] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Various other advantages and benefits will become apparent to those skilled in the art by reading the detailed description of the preferred embodiment below.The accompanying drawings are only for the purpose of illustrating the preferred embodiment and are not to be considered as limiting the present application.

[0034] Moreover, in all the drawings, the same reference numerals are used to denote the same parts. In the drawings:

[0035] FIG1 is a schematic structural diagram of a vehicle according to some embodiments of the present application;

[0036] FIG2 is a schematic diagram of the exploded structure of a battery according to some embodiments of the present application;

[0037] FIG3 is a schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application.

[0038] The accompanying drawings in the specific implementation manner are as follows:

[0039] 1000-vehicles;

[0040] 100-battery; 200-controller; 300-motor;

[0041] 10- box body; 11- first part; 12- second part;

[0042] 20 - battery cell; 21 - housing; 22 - electrode assembly; 23 - electrode terminal; 24 - pressure relief structure;

[0043] 211-shell; 212-cover. DETAILED DESCRIPTION

[0044] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0046] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0047] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0048] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0049] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0050] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0051] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0052] Currently, market developments indicate that power batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. As power battery applications continue to expand, market demand is also growing.

[0053] However, during the battery cycle, the dissolution of transition metals from positive electrode active materials containing transition metals is a common and unavoidable phenomenon, which leads to battery capacity decay, poor cycle performance, and shortened life.

[0054] Porphyrin compounds are a class of macrocyclic compounds with a conjugated skeleton (porphin) formed by four pyrrole rings connected by methine groups, in which at least one of the eight β-positions and four meso-position hydrogen atoms of the four pyrrole rings in the molecular structure is replaced by other groups to generate porphine derivatives.

[0055] Porphyrin compounds have good electrochemical properties, and porphyrin compounds can undergo coordination reactions with transition metals, so that the transition metals are located inside the porphyrin compounds to generate transition metal porphyrins.

[0056] Therefore, in order to alleviate the problem of battery capacity attenuation and cycle performance degradation caused by the dissolution of transition metals, the present application attempts to introduce porphyrin compounds into the separator.

[0057] The present application provides a diaphragm, which includes a polymer base membrane, the polymer base membrane has a three-dimensional network pore structure formed by interweaving polymer fibers and penetrating each other, the polymer fibers contain a porphyrin compound and a polymer resin, wherein the porphyrin compound is dispersed in the polymer resin.

[0058] The diaphragm provided in the present application utilizes a configuration in which polymer fibers contain a porphyrin compound and a polymer resin, and the porphyrin compound is dispersed in the polymer resin, so that the diaphragm not only has better porosity and ionic conductivity, but also during the battery cycle, the porphyrin compound can coordinate with the transition metal dissolved from the positive electrode active material to generate transition metal porphyrin, inhibiting or preventing the dissolved transition metal from migrating and depositing on the surface of the negative electrode sheet to destroy the SEI film, which is beneficial to improving the battery's cycle capacity retention rate and rate performance.

[0059] The batteries disclosed in the embodiments of this application can be used, but are not limited to, in electrical devices such as vehicles, ships, or aircraft. A power supply system comprising the batteries disclosed in this application can be used to construct such electrical devices, thereby facilitating and improving battery rate performance and cycle capacity retention.

[0060] The present invention provides an electric device that uses a battery as a power source. The electric device may be, but is not limited to, a mobile phone, a tablet, a laptop computer, an electric toy, an electric tool, a battery-powered vehicle, an electric car, a ship, a spacecraft, etc. The electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy, etc. The spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft, etc.

[0061] For the convenience of description, the following embodiments are described by taking a vehicle 1000 as an example of an electrical device according to an embodiment of the present application.

[0062] Please refer to Figure 1, which is a schematic structural diagram of a vehicle 1000 provided in some embodiments of the present application. The vehicle 1000 can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 can be provided at the bottom, head or tail of the vehicle 1000. The battery 100 can be used to power the vehicle 1000. For example, the battery 100 can serve as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0063] In some embodiments of the present application, the battery 100 can serve not only as an operating power source for the vehicle 1000, but also as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0064] In this application, the battery 100 refers to a single physical module that includes one or more battery cells 20 to provide a certain voltage and capacity. It can be in the form of a battery pack, a battery module, etc. The battery 100 may also include a box 10 for encapsulating one or more battery cells 20. The box 10 can prevent liquid or other foreign matter from affecting the charging or discharging of the battery cells 20.

[0065] Please refer to Figure 2, which is an exploded view of a battery 100 provided in some embodiments of the present application. The battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 provides a storage space for the battery cell 20 and can have various structures. In some embodiments, the housing 10 can include a first portion 11 and a second portion 12, which overlap each other and together define a storage space for the battery cell 20. The second portion 12 can be a hollow structure with one end open. The first portion 11 can be a plate-like structure, with the first portion 11 overlapping the open side of the second portion 12, so that the first portion 11 and the second portion 12 together define a storage space. Alternatively, the first portion 11 and the second portion 12 can each be a hollow structure with one end open, with the open side of the first portion 11 overlapping the open side of the second portion 12. Of course, the housing 10 formed by the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0066] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections among the multiple battery cells 20. The multiple battery cells 20 may be directly connected in series, in parallel, or in a hybrid connection, and then the entire battery cell 20 may be housed within the housing 10. Alternatively, the battery 100 may be constructed by first connecting multiple battery cells 20 in series, in parallel, or in a hybrid connection to form a battery module, which is then connected in series, in parallel, or in a hybrid connection to form a complete battery module, and then housed within the housing 10. The battery 100 may also include other structures, such as a busbar assembly for electrically connecting the multiple battery cells 20.

[0067] The battery cell 20 refers to the smallest unit constituting the battery 100. The battery cell 20 may be a lithium-ion battery, a lithium-sulfur battery, or a sodium-ion battery, but is not limited thereto.

[0068] Please refer to Figure 3, which is a schematic diagram of the exploded structure of a battery cell 20 provided in some embodiments of the present application. Referring to Figure 3, the battery cell 20 may include a housing 21, an electrode assembly 22, and an electrolyte, wherein the electrode assembly 22 and the electrolyte are both contained within the housing 21.

[0069] The outer shell 21 may include a shell 211 and a cover 212. The shell 211 is a component used to cooperate with the cover 212 to form an internal sealed space of the battery cell 20, wherein the formed sealed space can be used to accommodate the electrode assembly 22, electrolyte and other components. The cover 212 refers to a component that covers the opening of the shell 211 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the cover 212 can be adapted to the shape of the shell 211 to cooperate with the shell 211. Functional components such as electrode terminals 23 and pressure relief structures 24 can also be provided on the cover 212. A sealing ring can be configured between the opening of the shell 211 and the cover 212 to achieve sealing between the shell 211 and the cover 212.

[0070] The shell 211 and the cover 212 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shapes of the shell 211 and the cover 212 can be determined according to the specific shape and size of the electrode assembly 22. The material of the shell 211 and the cover 212 can be various, such as but not limited to metals such as copper, iron, aluminum, stainless steel, and aluminum alloy. The material of the sealing ring can be various, such as but not limited to PP (polypropylene), PC (polycarbonate), PET (polyethylene terephthalate) and other materials that are resistant to electrolyte corrosion, high toughness and fatigue resistance. A coating can be formed on the outer surface of the shell 211, and the material of the coating can be various, such as but not limited to corrosion-resistant materials such as Ni and Cr.

[0071] The battery cell 20 may also be in the form of a soft pack, such as a pouch-type soft pack. The soft pack may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0072] The electrode assembly 22 includes a negative electrode sheet, a separator, and a positive electrode sheet. The battery cell 20 primarily operates by the movement of metal ions between the positive and negative electrode sheets. During the charge and discharge process, active ions are embedded in and released from the positive and negative electrode sheets. The separator, located between the positive and negative electrode sheets, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through. The electrode assembly 22 can be a wound or laminated structure, but the embodiments of the present application are not limited thereto.

[0073] The negative electrode sheet includes a negative electrode current collector, a negative electrode tab and a negative electrode active material layer. The negative electrode active material layer is arranged on at least one side of the negative electrode current collector. A primer layer may also be arranged between the negative electrode current collector and the negative electrode active material layer. The negative electrode tab protrudes from the negative electrode current collector. The negative electrode tab is located at one end or two opposite ends of the negative electrode current collector, for example.

[0074] Among them, the negative electrode current collector can be a metal foil or a composite current collector. For example, the material of the negative electrode current collector and the negative electrode tab can be copper. The composite current collector may include a polymer material base layer and a metal layer formed on at least one side of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0075] The negative electrode active material in the negative electrode active material layer includes at least one of graphite, silicon, silicon-carbon negative electrode material, and the like.

[0076] In some embodiments, the negative electrode active material layer may further include a binder. The binder may be selected from at least one 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).

[0077] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0078] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0079] The positive electrode sheet includes a positive electrode collector, a positive electrode tab and a positive electrode active material layer. The positive electrode active material layer is arranged on at least one side of the positive electrode collector, and a primer layer may also be arranged between the positive electrode active material layer and the positive electrode collector; the positive electrode tab protrudes from the positive electrode collector, and the positive electrode tab is located at one end or two opposite ends of the positive electrode collector, for example.

[0080] The positive electrode active material layer includes a positive electrode active material containing a transition metal.

[0081] It is understood that the positive electrode active material contains transition metals including:

[0082] (1) The positive electrode active material itself contains transition metal.

[0083] Illustratively, the positive electrode active material includes but is not limited to lithium-containing transition metal oxides or lithium-containing transition metal phosphates.

[0084] Exemplarily, the lithium-containing transition metal oxide includes LiNi 1-x-y Co x Mn y O2, wherein 0<x<1, 0<y<1, illustratively, the lithium-containing transition metal oxide includes Li x M y N 1-y O 2-α A β , M is at least one of Ni, Co, and Mn, N is at least one of Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Ra, Al, Ga, In, Ge, Sn, Sc, Ti, B, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, W, Ru, Rh, Pd, Ag, Cd, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, A is at least one of N, F, P, S, Cl, and Se; 0.8≤x≤1.3, 0.6≤y≤1.0, 0≤α≤0.2, and 0≤β≤0.4,

[0085] For example, lithium-containing transition metal phosphates include LiFePO4, LiMn α Fe 1-α PO4 (0.6≤α<1) or LiFe (1-x- y) Mn x M y PO4, 0≤x≤1, 0≤y≤0.1, M is selected from one or more transition metal elements excluding Fe and Mn and non-transition metal elements.

[0086] (2) Positive electrode active material with a transition metal coating layer.

[0087] It should be noted that the positive electrode active material includes but is not limited to the components exemplified above, and other common transition metal-containing positive electrode active materials in the art may also be used.

[0088] The positive electrode current collector may be a metal foil or a composite current collector. For example, the positive electrode current collector and the positive electrode tab may be made of aluminum. The composite current collector may include a polymer material base layer and a metal layer formed on at least one side of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0089] In some embodiments, the positive electrode active material 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.

[0090] In some embodiments, the positive electrode active material 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.

[0091] The diaphragm is located between the positive electrode and the negative electrode, and plays an isolating role.

[0092] The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0093] The following is a detailed description of the diaphragm and its preparation method, battery and electrical device proposed in the embodiments of the present application in conjunction with the accompanying drawings.

[0094] According to some embodiments of the present application, some embodiments of the present application provide a diaphragm, which includes a polymer base membrane, the polymer base membrane having a three-dimensional network pore structure formed by interweaving polymer fibers and penetrating each other, the polymer fibers containing a porphyrin compound and a polymer resin, wherein the porphyrin compound is dispersed in the polymer resin.

[0095] Porphyrins are a class of macrocyclic compounds with a conjugated skeleton (porphin) consisting of four pyrrole rings connected by methine groups. These macrocyclic compounds are porphine derivatives in which at least one of the eight β-positions and four meso-position hydrogen atoms of the four pyrrole rings in the molecular structure is replaced by another group. Porphyrins exhibit excellent electrochemical properties and can coordinate with transition metals, localizing the transition metal within the porphyrin to form a stable transition metal porphyrin. This prevents transition metals dissolved from the positive electrode active material from migrating and depositing on the surface of the negative electrode, thereby destroying the SEI film.

[0096] The porphyrin compound can be a porphyrin derivative in which at least one of the eight β-position and four meso-position hydrogen atoms is substituted with another group. For example, the porphyrin compound is a porphyrin derivative in which at least one of the eight β-position hydrogen atoms is substituted with another group. Alternatively, the porphyrin compound can be a meso-substituted porphyrin, or a porphyrin compound can be at least partially β- and at least partially meso-substituted porphyrin, without limitation.

[0097] Polymer resin is a raw material for the separator that exists between the positive and negative electrodes of a battery to maintain insulation and prevent short circuits.

[0098] Dispersing the porphyrin compound in the polymer resin means that the porphyrin compound is uniformly dispersed within the continuous phase of the polymer resin. This arrangement not only improves the stability between the two phases, enhancing battery cycling performance, but also uniformly enhances the ionic conductivity of the separator, thereby improving the battery's rate capability. This polymer-based membrane can be analyzed for elemental distribution using cross-sectional ICP (inductively coupled plasma spectrometry). For example, N element distribution analysis reveals uniformly distributed porphyrin compounds.

[0099] In summary, the diaphragm provided in the present application utilizes a configuration in which a polymer fiber contains a porphyrin compound and a polymer resin, and the porphyrin compound is dispersed in the polymer resin, so that the diaphragm not only has better porosity and ionic conductivity, but also during the battery cycle, the porphyrin compound can coordinate with the transition metal dissolved from the positive electrode active material to generate transition metal porphyrin, inhibiting or preventing the dissolved transition metal from migrating and depositing on the surface of the negative electrode sheet to destroy the SEI film, which is beneficial to improving the battery's cycle capacity retention rate and rate performance.

[0100] According to some embodiments of the present application, the ionic conductivity of the polymer-based membrane is 2 mS / cm-6 mS / cm.

[0101] By dispersing the porphyrin compound in the polymer resin in the polymer base membrane, the ionic conductivity of the polymer base membrane is effectively improved, making its ionic conductivity 2mS / cm-6mS / cm, which is beneficial to improving the cycle capacity retention rate and rate performance of the battery.

[0102] Illustratively, the ionic conductivity of the polymer-based membrane is any one of 2 mS / cm, 3 mS / cm, 4 mS / cm, 5 mS / cm or 6 mS / cm, or is between any two values.

[0103] According to some embodiments of the present application, the thickness of the polymer-based film is 3 μm-16 μm, and the porosity of the polymer-based film is 20%-40%.

[0104] That is, the polymer-based membrane has a better porosity when the thickness is 3 μm-16 μm, which is beneficial to improving the electrochemical performance of the battery.

[0105] Illustratively, the thickness of the polymer-based film is any value of 3 μm, 4 μm, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 16 μm, or between any two values.

[0106] Illustratively, the porosity of the polymer-based membrane is any value among 20%, 25%, 30%, 35%, 40%, or between any two values.

[0107] According to some embodiments of the present application, the mass ratio of the porphyrin compound to the polymer resin is greater than 0 and less than or equal to 5.

[0108] Adding too much porphyrin compound will cause the porosity of the diaphragm to be too small, which cannot meet the relevant application requirements. Therefore, by controlling the mass ratio of porphyrin compound to polymer resin to be less than or equal to 5, it can be used in the battery to achieve better cycle capacity retention and rate performance.

[0109] Illustratively, the mass ratio of the porphyrin compound to the polymer resin is any one of 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, or between any two values.

[0110] Optionally, the mass ratio of the porphyrin compound to the polymer resin is 1-5.

[0111] If the amount of porphyrin compound added is too small, the ionic conductivity of the formed diaphragm cannot be significantly improved, and there is not enough porphyrin compound to react with the transition metal dissolved from the positive electrode active material for ligand reaction, and the battery rate performance and cycle capacity retention rate are not improved well. Therefore, controlling the mass ratio of the porphyrin compound to the polymer resin to 1-5 can effectively improve the cycle capacity retention rate and rate performance under the premise that the diaphragm can be used in the battery.

[0112] Illustratively, the mass ratio of the porphyrin compound to the polymer resin is any one of 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 or between any two values.

[0113] In some optional embodiments, the structural formula of the porphyrin compound is:

[0114] wherein R1 is independently hydrogen, hydroxyl, carboxyl, phenyl, sulfonic acid, halogen or pyridyl, and the phenyl group may be substituted by alkyl, alkoxy, carboxyl, amino, aryloxy, halogen or other heteroatoms and any combination thereof on carbon atoms 2, 3, 4, 5 and 6 of the phenyl ring;

[0115] R2 is hydrogen, alkyl, alkoxy, aryl, aryloxy, halogen, nitro or other heteroatoms and any combination thereof located on the carbon 2 or 3 of each pyrrole ring of the porphyrin compound.

[0116] It should be noted that the above structural formula of the porphyrin compound is only a list of optional porphyrin compounds in some embodiments and is not exhaustive. In actual operation, other porphyrin compounds not covered by the above structural formula can be selected.

[0117] According to some embodiments of the present application, the porphyrin compound includes at least one of tetrasulfonate porphyrin, tetraaminoporphyrin, tetracarboxy porphyrin, tetraaminophenyl porphyrin, tetracarboxyphenyl porphyrin, para-chlorotetraphenyl porphyrin, tetraphenyl porphyrin, tetra(4-pyridyl)porphyrin, tetra(2-pyridyl)porphyrin, 5,15-di(4-pyridyl)10,20-diphenyl porphyrin, 5,15-di(4-pyridyl)10,20-dicarboxyphenyl porphyrin, and tetrahydroxy porphyrin.

[0118] The above-mentioned porphyrin compounds are easy to obtain and can improve the ionic conductivity of the polymer-based membrane to a certain extent. In addition, during the battery cycle, the porphyrin compounds can coordinate with the transition metal dissolved from the positive electrode active material to generate transition metal porphyrin, which alleviates the migration of the dissolved transition metal and deposits it on the surface of the negative electrode to destroy the SEI film, which is beneficial to improving the battery's cycle capacity retention rate and rate performance.

[0119] It should be noted that the porphyrin compound in the present application may be a water-soluble porphyrin compound or an ester-soluble porphyrin compound. For example, the above-mentioned tetrasulfonate porphyrin, tetraaminoporphyrin, tetracarboxyl porphyrin, etc. are water-soluble porphyrin compounds, which are generally soluble in hydrophilic solvents such as water, methanol, acetone, and acetonitrile; tetraphenylporphyrin, tetrachlorophenylporphyrin, etc. are ester-soluble porphyrins, which are generally soluble in solvents such as benzene, dichloromethane, pyridine, and N,N-dimethylformamide (DMF).

[0120] Polymer resins are commonly used as separator substrates.

[0121] According to some embodiments of the present application, the polymer resin includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyacetal, polycarbonate, polyimide, polyetherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalate, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, polyacrylonitrile, polyparaphenylene benzobisazole and polyarylate.

[0122] Each of the above polymers can be used to prepare polymer-based membranes by phase separation.

[0123] According to some embodiments of the present application, the separator further includes a coating layer located on the surface of the polymer base film.

[0124] It should be noted that the polymer base film has two opposite surfaces, wherein the coating can be provided on only one of the surfaces, or both surfaces can be provided with the coating.

[0125] The performance of the diaphragm can be improved in a targeted manner by setting the coating, and the coating can be selected according to actual needs.

[0126] By way of example, the coating includes, but is not limited to, at least one of a ceramic coating, a solid electrolyte coating, and a polymer coating. The ceramic coating is used to allow lithium ions to pass through and provide support and protection, maintaining the structure of the separator and preventing loss of separation between the positive and negative electrodes due to melting or large-scale shrinkage of the substrate layer, thereby preventing short circuits between the positive and negative electrodes. The ceramic material in the ceramic coating includes, but is not limited to, one or a mixture of alumina, silica, titania, zirconia, magnesium oxide, and boehmite.

[0127] According to some embodiments of the present application, the coating includes an aluminum oxide ceramic coating located on a surface of the polymer base film, and a polyvinylidene fluoride coating located on a surface of the aluminum oxide ceramic coating.

[0128] The alumina ceramic coating uses alumina ceramic as the functional component, and can also be added with appropriate proportions of dispersants, thickeners, and binders. The specific ingredients and ratios can be selected based on actual needs. The polyvinylidene fluoride coating uses polyvinylidene fluoride as the functional component, and can also be added with appropriate proportions of dispersants, thickeners, and binders. The specific ingredients and ratios can be selected based on actual needs. For example, the dispersant includes, but is not limited to, potassium polyacrylate, the thickener includes, but is not limited to, sodium carboxymethyl cellulose, and the binder includes, but is not limited to, polyurethane acrylate.

[0129] According to some embodiments of the present application, the ionic conductivity of the separator is greater than 2 mS / cm, the thickness of the separator is 4-20 μm, and the porosity of the separator is 20%-40%.

[0130] The above-mentioned diaphragm not only has better porosity and ionic conductivity, but also during the battery cycle, the porphyrin compound can inhibit or prevent the dissolved transition metal from migrating and depositing on the surface of the negative electrode to destroy the SEI film, which is beneficial to improving the battery's cycle capacity retention rate and rate performance.

[0131] Illustratively, the thickness of the separator is any value of 4 μm, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 16 μm, 18 μm, or 20 μm, or is between any two values.

[0132] Illustratively, the porosity of the separator is any value among 20%, 25%, 30%, 35%, 40%, or between any two values.

[0133] According to some embodiments of the present application, the present application further provides a method for preparing the diaphragm provided by any of the above solutions, which comprises:

[0134] The invention also provides a step of dispersing and / or dissolving the porphyrin compound in an organic solution of a polymer resin to obtain a mixed solution, and a step of subjecting the mixed solution to phase separation to obtain a polymer-based film.

[0135] The porphyrin compound can be dissolved and / or dispersed in the organic solution of the polymer resin, that is, the mixed solution can be a suspension in which the porphyrin compound is both dissolved and dispersed, or it can be a solution.

[0136] It should be noted that any method can be used to disperse and / or dissolve the porphyrin compound in the organic solution of the polymer resin. For example, a stirred mixture can be used, or ultrasonic mixing or other methods can be used to disperse and / or dissolve the porphyrin compound in the organic solution of the polymer resin.

[0137] Phase separation can be achieved by non-solvent induced phase separation method. The non-solvent induced phase separation method uses certain physical methods to cause the organic solvent and non-solvent in a homogeneous polymer resin solution of a certain composition to undergo double diffusion, so as to change the thermodynamically unstable state of the polymer resin solution, that is, liquid-liquid phase separation occurs, and finally converted into a three-dimensional macromolecular network gel structure (that is, polymer rich phase solidification). After the polymer poor phase is eluted, a porous structure is formed, and the three-dimensional network gel structure constitutes the main body of the polymer base membrane.

[0138] Exemplarily, phase separation can be achieved by applying the organic solution in which the porphyrin compound is dissolved and / or dispersed and the polymer resin is dissolved onto a substrate, and immersing the substrate in a non-solvent to produce phase separation. The non-solvent refers to a liquid that cannot dissolve the polymer resin but is miscible with the organic solvent used in the organic solution of the polymer resin, and the addition of the non-solvent can remove or replace part of the organic solvent, thereby producing phase separation to form a polymer resin-rich phase and a polymer resin-poor phase, and forming three-dimensional pores by interconnecting the polymer resin-poor phases. The polymer resin-rich phase (that is, the polymer fiber comprising the porphyrin compound and the polymer resin in this application) constitutes the three-dimensional network body of the membrane.

[0139] The preparation method provided in the present application adopts a phase separation method to prepare the above-mentioned polymer-based membrane. The operation is simple and controllable, and the porosity can be easily adjusted. In addition, the polymer fibers in the final polymer-based membrane are interwoven and interconnected to form a three-dimensional network pore structure. The polymer fibers include porphyrin compounds and polymer resins. The porphyrin compounds are uniformly dispersed in the polymer resin in a bulk phase distribution, which is beneficial to improving the ionic conductivity of the polymer-based membrane. In addition, during the battery cycle, the porphyrin compounds can inhibit or prevent the dissolved transition metals from migrating and depositing on the surface of the negative electrode to destroy the SEI film, which is beneficial to improving the battery's cycle capacity retention rate and rate performance.

[0140] According to some embodiments of the present application, the method of phase separation of the mixed liquid includes:

[0141] First, a non-solvent is added to an organic solution of a polymer resin, and then a porphyrin compound is added and mixed to obtain a mixed solution as a phase separation liquid;

[0142] The phase separation liquid is then coated or cast on a substrate, evaporated to form a film, and dried;

[0143] The non-solvent includes at least one of water, methanol, ethanol, isopropanol, ethylene glycol and glycerol.

[0144] Volatile film formation refers to slowly volatilizing the solvent to form a film at room temperature, which is beneficial for controlling the porosity of the final product. For example, the volatilization film formation is achieved by standing at 20-35°C for 8-15 hours. For example, the volatilization film formation is achieved by standing at 20°C, 23°C, 25°C, 28°C, 30°C, 33°C, or 35°C for 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, or 15 hours.

[0145] In the preparation method adopted in the present application, a polymer-based membrane is prepared by a non-solvent-induced phase separation method using a phase separation liquid. The operation is simple and controllable, and it can be industrially produced. The membrane can be formed without stretching, and the prepared polymer-based membrane has sufficient mechanical properties. When used in a battery, it can effectively inhibit or prevent the dissolved transition metal from migrating and depositing on the surface of the negative electrode to destroy the SEI film, which is beneficial to improving the battery's cycle capacity retention rate and rate performance.

[0146] In order to improve the uniformity of the phase separation liquid, the preparation process of the phase separation liquid includes:

[0147] First, the polymer resin is dissolved in an organic solvent to obtain a resin solution. A non-solvent is then added dropwise to the resin solution until the solution becomes transparent. Finally, the porphyrin compound is added to the transparent solution and stirred at room temperature for 8-15 hours to obtain a suspension that serves as the casting solution. Alternatively, the polymer resin is first dissolved in an organic solvent to obtain a resin solution. The porphyrin compound is then added to the resin solution. Finally, a non-solvent is added dropwise and stirred at room temperature for 8-15 hours to obtain a suspension that serves as the phase separation solution.

[0148] According to some embodiments of the present application, drying comprises vacuum drying at 60-100° C. for at least 12 hours.

[0149] The selection of the above drying temperature is beneficial to avoid affecting the quality of the diaphragm while maintaining better drying efficiency.

[0150] Illustratively, drying comprises vacuum drying at a temperature of 60°C, 70°C, 80°C, 90°C, 100°C, etc. for at least 12 hours.

[0151] According to some embodiments of the present application, in the organic solution of the polymer resin, the amount of the organic solvent added is 10-30 times the mass of the polymer resin, and / or,

[0152] The amount of non-solvent added is 3-10 times the mass of the polymer resin.

[0153] By controlling within the above range, it is beneficial to improve the quality of the polymer base film and to improve the cycle capacity retention rate and rate performance of the battery.

[0154] By controlling the amount of organic solvent added to 10-30 times the mass of the polymer resin, it is beneficial to fully dissolve the polymer resin, facilitate subsequent sufficient and uniform phase separation, and improve the quality of various parts of the diaphragm. For example, the amount of organic solvent added is 10 times, 13 times, 15 times, 17 times, 20 times, 23 times, 25 times, 28 times or 30 times the mass of the polymer resin.

[0155] By controlling the amount of the non-solvent added within the above range, it is beneficial to fully promote and initiate phase separation. For example, the amount of the non-solvent added is 3 times, 5 times, 7 times, 9 times or 10 times the mass of the polymer resin.

[0156] According to some embodiments of the present application, the organic solvent used in the organic solution of the polymer resin includes at least one of toluene, xylene, amyl acetate, and trichloroethylene.

[0157] Each of the above organic solvents can effectively dissolve the polymer resin.

[0158] In some examples, the preparation method further includes the step of coating the surface of the polymer base film to form a coating layer.

[0159] By setting the above steps, a coating is formed on the surface of the polymer base film to improve the performance of the diaphragm.

[0160] According to some embodiments of the present application, the present application further provides a battery, comprising the separator of any of the above schemes, and the positive electrode sheet comprises a positive electrode active material containing a transition metal.

[0161] According to some embodiments of the present application, the present application further provides an electrical device, comprising a battery according to any of the above solutions, and the battery is used to provide electrical energy to the electrical device.

[0162] The power-consuming device may be any of the aforementioned devices or systems using batteries.

[0163] Some specific embodiments are listed below to better illustrate the present application.

[0164] Examples 1-11 and Comparative Examples 1-2

[0165] The steps for preparing the polymer base film in Example 1 include:

[0166] 3g of polyethylene was added to 81g of toluene solution and stirred at 65°C for 3 hours to obtain a first solution. 10g of anhydrous ethanol was then added dropwise to the first solution until the solution became transparent, obtaining a second solution. 3g of tetraphenylporphyrin powder was then added to the second solution and stirred at room temperature for 12 hours to obtain a suspension that served as the casting solution.

[0167] The casting solution was spread on a glass plate with a blade and allowed to stand at room temperature for 12 hours to evaporate the solvent to form a film. The obtained film was further vacuum dried at 80° C. for 14 hours to finally obtain a polymer-based film with a thickness of 7 μm.

[0168] The differences in the polymer base films prepared in Examples 1-11 and Comparative Examples 1-2 are shown in Table 1.

[0169] Table 1 Differences in the preparation of polymer base films in various embodiments and comparative examples

[0170]

[0171] The difference between the polymer base film of Comparative Example 1 and the polymer base film of Example 1 is that the polymer base film does not contain tetraphenylporphyrin, that is, the polymer base film is directly prepared using polyethylene.

[0172] The polymer base film in Comparative Example 2 is the same as the polymer base film in Comparative Example 1.

[0173] A 2 μm aluminum oxide coating was coated on both sides of the polymer base film of each embodiment and comparative examples 1-2 by micro-gravure coating, dried, and then a 3 μm PVDF coating was coated on the surface of the aluminum oxide coating by micro-gravure coating, dried to obtain a separator.

[0174] The aluminum oxide coating contains 88 wt% aluminum oxide as a functional component, 3 wt% potassium polyacrylate as a dispersant, 2 wt% sodium carboxymethyl cellulose as a thickener, and 8 wt% polyurethane acrylate as a binder.

[0175] The PVDF coating in each embodiment and comparative example 1 contains 92 wt% PVDF as a functional component, 2 wt% potassium polyacrylate as a dispersant, 2 wt% sodium carboxymethyl cellulose as a thickener, and 4 wt% polyurethane acrylate as a binder. The coating is applied by micro-gravure coating.

[0176] The PVDF coating in Comparative Example 2 contains 80 wt% PVDF as a functional component, 12 wt% tetraphenylporphyrin as an additive, 2 wt% potassium polyacrylate as a dispersant, 2 wt% sodium carboxymethyl cellulose as a thickener, and 4 wt% polyurethane acrylate as a binder. The coating is applied by micro-gravure coating.

[0177] The polymer-based films, separators, and lithium-ion batteries assembled with the corresponding separators corresponding to the embodiments and comparative examples were tested respectively.

[0178] Among them, lithium-ion battery assembly includes:

[0179] (1) Preparation of positive electrode sheet

[0180] NCM523 was mixed with conductive carbon black and binder PVDF in a mass ratio of 96.7:1.7:1.6, and an appropriate amount of solvent NMP was added. The positive electrode slurry was obtained in a vacuum mixer. The positive electrode slurry was evenly coated on both surfaces of the aluminum foil current collector. The positive electrode sheet was then obtained after vacuum drying at 70°C for 12 hours, cold pressing, and stripping.

[0181] (2) Preparation of negative electrode sheet

[0182] Artificial graphite, conductive carbon black, binder carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) and solvent water are uniformly mixed in a weight ratio of 93:2:2:3:100 to form a negative electrode slurry; the negative electrode slurry is then evenly coated on both surfaces of the copper foil current collector; dried at 110°C, cold pressed, and slit to obtain the negative electrode sheet.

[0183] (3) Preparation of electrolyte

[0184] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent; LiPF6 is dissolved in the above organic solvent, and fluoroethylene carbonate (FEC) is added and mixed evenly to obtain an electrolyte; wherein the concentration of LiPF6 is 1 mol / L.

[0185] (4) Diaphragm

[0186] The diaphragm used was the diaphragm prepared in the above embodiment and comparative example.

[0187] (5) Preparation of lithium-ion batteries

[0188] The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator placed between the positive and negative electrodes to act as an isolate, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, injected with the prepared electrolyte and packaged, and a lithium-ion battery is obtained through a process of formation, degassing, and trimming.

[0189] The test method is as follows:

[0190] 1. Porosity test method: The pore volume is obtained based on low-temperature nitrogen adsorption.

[0191] 2. Ionic Conductivity Test Method: Cut four circular membrane samples with a diameter of 50 mm, place them in the electrolyte, and soak them in a sealed container for 1 hour. Place the four membrane samples sequentially into the test mold and measure them using an electrochemical workstation, reading the resistance values ​​R1, R2, R3, and R4. Calculate Sheet Resistance: Plot the number of layers as the horizontal axis and the corresponding resistance values ​​for different numbers of layers as the vertical axis. Calculate the slope A of the curve. The sample sheet resistance R = A·S, where S is the effective electrode area tested. Measure the membrane thickness D, and the membrane ionic conductivity = D / R.

[0192] 3. Interface adhesion test method: Take a diaphragm with intact membrane surface and normal appearance, and punch it into samples with a width of 25 mm and a length of 100 mm. Take two punched diaphragm samples and stack them together. Hot press them on a hot press at a pressure of 1 MPa, a temperature of 100 degrees, and a speed of 100 mm / min. Use a tensile testing machine to test the tensile force (in N) of the two diaphragms bonded together. Adhesion force = tension / 0.025 (unit is N / m).

[0193] 4. 1C rate test method: 1 / 3C charge, 1 / 3C discharge (capacity is recorded as C1), 1 / 3C charge, 1C discharge (capacity is recorded as C2), each charge and discharge is completed with an interval of 1 minute, and the 1C rate is C1 / C2.

[0194] 5. 1C cycle 1000 cycle capacity retention rate test method: 1C charge and 1C discharge are continuously charged and discharged for 1000 cycles, with a 1 minute interval after each charge and discharge. The capacity retention rate at the 1000th cycle is recorded as 1C / 1C capacity retention rate 1000cycle.

[0195] 6. Transition metal content test method: Disassemble the lithium-ion battery after 1000 cycles, remove the negative electrode, and use an inductively coupled plasma emission spectrometer (ICP) to test the transition metal content.

[0196] The test results are shown in Table 2.

[0197] Table 2 Test results

[0198]

[0199] Combining Table 1 and Table 2, and comparing Examples 1-12 with Comparative Examples 1-2, it can be seen that in Comparative Example 2, due to the addition of tetraphenylporphyrin to the PVDF coating, although the cycle capacity retention rate and rate performance of the battery can be improved to a certain extent compared with Comparative Example 1, the interfacial adhesion force is significantly reduced, and the rate performance and cycle capacity retention rate are limited.

[0200] The polymer-based membrane and diaphragm provided in the present application, compared with comparative example 1, can not only significantly improve the ionic conductivity of the polymer-based membrane, but also have better cycle capacity retention and rate performance.

[0201] According to Examples 1-5, it can be seen that, under the premise of keeping the amount of polymer resin added unchanged, the mass ratio of the porphyrin compound to the polymer resin affects the electrochemical performance of the polymer base film, the separator, and the battery. Specifically, when the mass ratio of the porphyrin compound to the polymer resin is 0.5-5, the cycle capacity retention rate and rate performance of the battery can be effectively improved. When the mass ratio of the porphyrin compound to the polymer resin is 1-5, the cycle capacity retention rate and rate performance of the battery are even better.

[0202] According to Examples 1, 6-8, the above-mentioned porphyrin compounds can be used as additives to prepare polymer-based membranes, and the polymer-based membranes have both good porosity and electrical conductivity. Moreover, after the diaphragm prepared based on the polymer-based membrane is applied to the battery, the battery can have better cycle capacity retention and rate performance.

[0203] By comparing Example 1 with Example 9, it can be seen that different polymer resins can all be used to prepare polymer-based films using the above-mentioned preparation method, and can effectively inhibit or prevent the dissolved transition metal from migrating and depositing on the surface of the negative electrode to destroy the SEI film, which is beneficial to improving the battery's cycle capacity retention rate and rate performance.

[0204] According to Examples 1 and 10-11, the drying temperature affects the performance of the diaphragm to a certain extent, and a drying temperature of 60-100° C. is conducive to obtaining better diaphragm quality while maintaining better drying efficiency.

[0205] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A diaphragm, wherein: The invention comprises a polymer base film having a three-dimensional network pore structure formed by interweaving polymer fibers and penetrating each other. The polymer fibers contain a porphyrin compound and a polymer resin, wherein the porphyrin compound is dispersed in the polymer resin.

2. The diaphragm according to claim 1, wherein The ionic conductivity of the polymer-based membrane is 2 mS / cm-6 mS / cm.

3. The diaphragm according to claim 1, wherein The thickness of the polymer-based film is 3 μm-16 μm, and the porosity of the polymer-based film is 20%-40%.

4. The diaphragm according to any one of claims 1 to 3, wherein: The mass ratio of the porphyrin compound to the polymer resin is greater than 0 and less than or equal to 5.

5. The diaphragm according to any one of claims 1 to 3, wherein: The mass ratio of the porphyrin compound to the polymer resin is 1-5.

6. The diaphragm according to any one of claims 1 to 5, wherein: The structural formula of the porphyrin compound is: wherein R1 is independently hydrogen, hydroxyl, carboxyl, phenyl, sulfonic acid, halogen or pyridyl, and the phenyl group may be substituted by alkyl, alkoxy, carboxyl, amino, aryloxy, halogen or other heteroatoms and any combination thereof on carbon atoms 2, 3, 4, 5 and 6 of the phenyl ring; R2 is hydrogen, alkyl, alkoxy, aryl, aryloxy, halogen, nitro or other heteroatoms and any combination thereof located on the carbon 2 or 3 of each pyrrole ring of the porphyrin compound.

7. The diaphragm according to any one of claims 1 to 5, wherein: The porphyrin compound includes at least one of tetrasulfonate porphyrin, tetraaminoporphyrin, tetracarboxy porphyrin, tetraaminophenyl porphyrin, tetracarboxyphenyl porphyrin, para-chlorotetraphenyl porphyrin, tetraphenyl porphyrin, tetra-(4-pyridyl)porphyrin, tetra-(2-pyridyl)porphyrin, 5,15-di(4-pyridyl)-10,20-diphenyl porphyrin, 5,15-di(4-pyridyl)-10,20-dicarboxyphenyl porphyrin, and tetrahydroxy porphyrin.

8. The diaphragm according to any one of claims 1 to 7, wherein: The polymer resin includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyacetal, polycarbonate, polyimide, polyetherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalate, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, polyacrylonitrile, poly(p-phenylene benzobisoxazole) and polyarylate.

9. The diaphragm according to any one of claims 1 to 8, wherein: The diaphragm further includes a coating layer located on the surface of the base film.

10. The diaphragm according to claim 9, wherein The coating comprises an aluminum oxide ceramic coating located on the surface of the base film and a polyvinylidene fluoride coating located on the surface of the aluminum oxide ceramic coating. The diaphragm according to claim 10 , wherein: The ion conductivity of the diaphragm is greater than 2 mS / cm, the thickness of the diaphragm is 4-20 μm, and the porosity of the diaphragm is 20%-40%.

12. The method for preparing a diaphragm according to any one of claims 1 to 11, wherein: include: The invention also provides a step of dispersing and / or dissolving the porphyrin compound in the organic solution of the polymer resin to obtain a mixed solution, and a step of subjecting the mixed solution to phase separation to obtain the polymer-based film.

13. The preparation method according to claim 12, wherein The method for phase separation of the mixed solution comprises: First, a non-solvent is added to the organic solution of the polymer resin, and then the porphyrin compound is added and mixed to obtain the mixed solution as a phase separation liquid; Then, the phase separation liquid is coated or cast on a substrate, volatilized to form a film, and dried; Wherein, the non-solvent includes at least one of water, methanol, ethanol, isopropanol, ethylene glycol and glycerol.

14. The preparation method according to claim 12, wherein The drying comprises vacuum drying at 60-100° C. for at least 12 hours.

15. The preparation method according to claim 12 or 13, wherein In the organic solution of the polymer resin, the amount of the organic solvent added is 10-30 times the mass of the polymer resin, and / or, The amount of the non-solvent added is 3-10 times the mass of the polymer resin.

16. The preparation method according to any one of claims 12 to 15, wherein: The organic solvent used in the organic solution of the polymer resin includes at least one of toluene, xylene, amyl acetate and trichloroethylene.

17. A battery, wherein: The invention comprises a positive electrode sheet and the separator according to any one of claims 1 to 11, wherein the positive electrode sheet comprises a positive electrode active material containing a transition metal.

18. An electrical device, wherein: It comprises the battery according to claim 17, wherein the battery is used to provide electrical energy.

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