Separators and secondary batteries, battery modules, battery packs, and power consumption devices using them.

Abstract

The present application provides a separator including a first base film, a coating layer including ceramic particles, graphene oxide, and a binder, and a second base film, which are sequentially stacked. The separator of the present application has good electrolyte wettability, can effectively inhibit the growth of lithium dendrites, and has low resistance, and can effectively improve the safety performance, dynamic characteristics, and cycle characteristics of the corresponding battery. The present application further provides a secondary battery, a battery module, a battery pack, and a power consumption device using the separator of the present application.

Description

[Technical Field]

[0001] This application relates to lithium battery technology, and more particularly to separators and secondary batteries, battery modules, battery packs, and power consumption devices using the same. [Background technology]

[0002] In recent years, as the range of applications for lithium-ion batteries has expanded, they are now widely used in energy storage systems such as wind, thermal, hydroelectric, and solar power plants, as well as in multiple fields such as power tools and electric bicycles. A lithium-ion battery generally includes an electrolyte, positive and negative electrode sheets, and a separator placed between the positive and negative electrode sheets. The separator is mainly used to prevent short circuits between the positive and negative electrodes while simultaneously allowing ions to pass through freely. Many separators used in conventional technology are polyolefin films. However, polyolefin films have poor permeability to the electrolyte, and lithium dendrites generated during the battery's use can penetrate the separator, causing short circuits and potentially posing a safety risk.

[0003] To solve the above problem, those skilled in the art generally apply a coating layer to the separator to promote the penetration of the electrolyte into the separator and prevent lithium dendrites from penetrating the separator. Ceramic particles are one of the coating layers commonly applied by those skilled in the art. However, due to poor adhesion between the ceramic particles and the polyolefin film, "powder shedding" is a serious problem. For this reason, it is necessary to introduce a binder to increase the adhesion between the ceramic particles and the polyolefin film and reduce powder shedding, but using a large amount of binder increases the resistance of the separator and deteriorates the dynamic characteristics of the secondary battery.

[0004] As this demonstrates, developing a separator that simultaneously possesses good penetration performance and low resistance is an urgent challenge for researchers. [Overview of the Initiative]

[0005] This application is made in view of the above problems, and its object is to provide a separator that simultaneously has good infiltration performance, mechanical properties, and low resistance, and a secondary battery applying the same has good safety performance, dynamic properties, and cycle properties.

[0006] According to the first aspect of the present application, a separator is provided, which includes a first base film, a second base film, and a coating layer located between the first base film and the second base film and stacked in order, and the coating layer includes ceramic particles, graphene oxide, and a binder.

[0007] The separator of the present application has a three-layer composite structure, has good infiltration performance and low resistance to an electrolyte solution, and is helpful for improving the safety performance, dynamic properties, and cycle properties of a secondary battery applying the separator.

[0008] In any embodiment, optionally, the mass ratio of the ceramic particles to the binder is 1:0.001 to 0.3, and optionally 1:0.01 to 0.1.

[0009] When the mass ratio of the ceramic particles to the binder is within the above range, it is advantageous for the coating layer to have appropriate adhesiveness and effectively avoid "powder shedding" of the ceramic particles.

[0010] In any embodiment, optionally, the ratio of the sum of the masses of the ceramic particles and the binder to the mass of the graphene oxide is 2 to 11:1, and optionally 2 to 9:1.

[0011] When the ratio of the sum of the masses of the ceramic particles and the binder to the mass of the graphene oxide is within the above range, it is advantageous to increase the ionic conductivity of the coating layer, improve the wettability of the separator, enhance the lithium dendrite resistance ability, and improve the dynamic properties and safety performance of the corresponding secondary battery.

[0012] In any embodiment, optionally, the mass ratio of the graphene oxide to the ceramic particles is 1:1.5 to 11, and optionally 1:3 to 5.

[0013] When the mass ratio of the graphene oxide to the ceramic particles is within the above range, it is advantageous to promote the formation of intermolecular forces and hydrogen bonding between the oxygen-containing functional groups on the surface of the graphene oxide and the ceramic particles, improve the adhesion of the ceramic particles on the separator, thereby improving the adhesion of the entire coating material, and further avoiding the stacking of graphene oxide sheets to block the pores of the separator.

[0014] In any embodiment, optionally, the graphene oxide is a graphene oxide sheet, and optionally, the maximum lateral dimension of the graphene oxide sheet is 0.01 to 10 μm.

[0015] Graphene oxide with a small diameter can prevent graphite from covering the pores on the separator and reducing the air permeability of the separator, thereby avoiding the inhibition of ion transmission and the increase in the resistance of the separator.

[0016] In any embodiment, optionally, the ceramic particles are one or more selected from oxides, nitrides or oxoacids of Si, Fe, Sn, Ti, Cu, Mg, Ge, Zn, Zr and B elements, optionally one or more selected from silicon oxide, silicon nitride, iron oxide, iron nitride, iron oxoacid salt, tin oxide, titanium oxide, titanium nitride, titanium oxoacid salt, copper oxide, copper nitride, magnesium oxide, germanium oxide, zinc oxide, zirconium oxide, and boron nitride, and further optionally one or more selected from titanium dioxide (TiO2), silicon dioxide (SiO2), tin dioxide (SnO2), zinc oxide (ZnO), zirconium oxide (ZrO2), and lithium titanate.

[0017] When ceramic particles are selected from the above materials, the mechanical strength of the separator, the permeability of the electrolyte, and the electrical and chemical stability can be effectively improved.

[0018] In any embodiment, the particle size of the ceramic particles is selectively 0.01 to 10 μm, and selectively 0.05 to 0.5 μm.

[0019] When the particle size of the ceramic particles falls within the above range, it is advantageous not only in avoiding "powder shedding" due to excessively large particle size, but also in avoiding the blockage of channels in the base film and deterioration of dynamic properties caused by excessively small particle size.

[0020] In any embodiment, the binder is selectively one or more selected from dopamine hydrochloride, polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorine-containing acrylate resin, styrene-butadiene rubber, sodium polyacrylate, polymethacrylic acid, polyacrylamide, polyvinyl alcohol, sodium alginate, carboxymethyl chitosan, and sodium carboxymethylcellulose.

[0021] In any embodiment, the thickness of the coating layer is selectively 0.1 to 10 μm, and selectively 1 to 6 μm.

[0022] When the thickness of the coating layer is within the above range, it is advantageous not only to effectively consume lithium dendrites and prevent them from penetrating the separator and causing safety problems, but also to prevent the coating layer from significantly increasing the resistance of the separator.

[0023] In any embodiment, the first base film and the second base film are each independently one or more selected from polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, polyamide, and polyester.

[0024] In any embodiment, the first base film and / or the second base film are selectively impregnated with a graphene oxide dispersion.

[0025] Pre-treating the base film with a graphene oxide dispersion improves the bonding efficiency between the coating layer and the base film, reduces the use of binder, and lowers the resistance of the separator.

[0026] In any embodiment, the thickness of the first base film and / or the second base film is selectively 3 to 30 μm, and selectively 5 to 25 μm.

[0027] In any embodiment, the separator is optionally ρ s ≤10 7 Satisfying mΩ·cm, selectively ρ s ≤ 5 × 10 6 The condition mΩ·cm is satisfied, where ρ s This indicates the ion resistivity of the separator.

[0028] ρ s When the value falls within the above range, the ion resistivity of the separator is low, which is advantageous for improving the dynamic characteristics of the corresponding secondary battery.

[0029] According to a second aspect of the present application, a secondary battery including the separator of the first aspect of the present application is provided.

[0030] According to a third aspect of the present application, a battery module including a secondary battery according to a second aspect of the present application is provided.

[0031] According to a fourth aspect of the present application, a battery pack is provided that includes at least one of the secondary battery of the second aspect of the present application or the battery module of the third aspect of the present application.

[0032] According to a fifth aspect of the present application, a power consumption device is provided which includes at least one of a secondary battery according to a second aspect of the present application, a battery module according to a third aspect of the present application, or a battery pack according to a fourth aspect of the present application. [Effects of the Invention]

[0033] The separator of this invention has a three-layer composite structure, and the intermediate coating layer contains ceramic particles, graphene oxide, and a binder. The ceramic particles can, on the one hand, promote the infiltration of the electrolyte into the separator, and on the other hand, effectively consume the lithium dendrites that are generated, preventing the lithium dendrites from penetrating the separator and improving safety performance. The surface of the graphene oxide in the coating layer is rich in various polar groups, which can, on the one hand, further promote the infiltration of the electrolyte into the base film, and on the other hand, help reduce resistance through the following actions, thereby improving the dynamic characteristics of the corresponding battery. Firstly, graphene oxide itself can be bonded to the base film by van der Waals forces, reducing the use of binder. Secondly, graphene oxide can provide a large number of channels for ions to be freely transported, improving the ionic conductivity of the separator. Furthermore, the coating layer is located between the first and second base films, and the base film itself can exist as a "barrier layer," effectively preventing direct contact between the ceramic particles and the positive and negative electrode sheets. This helps to further improve the safety performance of the corresponding secondary battery, while also helping to avoid many side reactions, thereby improving the stability and cycle characteristics when using the corresponding battery.

[0034] The battery module, battery pack, and power consumption device of the present invention include a secondary battery provided by the present invention and therefore have at least the same advantages as the said secondary battery. [Brief explanation of the drawing]

[0035] [Figure 1] This is a schematic diagram of the separator of the present invention. [Figure 2] This is a schematic diagram of a secondary battery according to one embodiment of the present invention. [Figure 3] Figure 2 is an exploded view of a secondary battery according to one embodiment of the present invention. [Figure 4] This is a schematic diagram of a battery module according to one embodiment of the present invention. [Figure 5] This is a schematic diagram of a battery pack according to one embodiment of the present invention. [Figure 6] Figure 5 is an exploded view of a battery pack according to one embodiment of the present invention. [Figure 7] This is a schematic diagram of a power consumption device that uses a secondary battery as a power source according to one embodiment of the present invention. [Explanation of symbols]

[0036] 1 Battery pack 2 Upper cabinet 3 Lower cabinet 4 Battery Modules 5 Secondary battery 51 Housing 52 Electrode Assembly 53 Cover Plate 11. First base film 12 Ceramic particles 13 Graphene Oxide Sheet 14. Second base film [Modes for carrying out the invention]

[0037] The following describes in detail embodiments of the separator of the present application and the secondary battery, battery module, battery pack, and power consumption device using the same, with reference to the drawings as appropriate. However, unnecessarily detailed explanations may be omitted. For example, detailed explanations of well-known matters or redundant explanations of substantially identical structures may be omitted. This is to avoid unnecessarily verbose explanations and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following explanation 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.

[0038] The “range” disclosed herein is defined in the form of a lower bound and an upper bound, and a given range is defined by selecting one lower bound and one upper bound, the selected lower and upper bounds defining the boundaries of a particular range. Ranges defined in this manner may or may not include the values ​​at both ends and can be combined in any way, that is, any lower bound can be combined with any upper bound to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also expected. Similarly, if the minimum range values ​​1 and 2 are listed and the maximum range values ​​3, 4 and 5 are listed, the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 are all intended. In this application, unless otherwise specified, the numerical range “a-b” means an abbreviated expression for any combination of real numbers between a and b, where both a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are listed in this specification, and "0 to 5" is merely an abbreviated expression for combinations of these numbers. Also, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0039] All embodiments and optional embodiments of this application can be combined to form new technical solutions unless otherwise specified.

[0040] All of the technical features and selectable technical features of this application can be combined to form new technical solutions, unless otherwise specified.

[0041] All steps of this application may be performed sequentially or randomly unless otherwise specified, preferably in order. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, if the method may further include step (c), it means that step (c) may be added to the method in any order, for example, that the method may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b).

[0042] As used in this application, “includes” and “inclusive” refer to both open and closed forms unless otherwise specified. For example, “includes” and “inclusive” may include or include other components not listed, or may include or include only the listed components.

[0043] In this application, terms related to graphene can be understood by referring to their meanings in the GB / T 30544.13-2018 standard, and related parameters can also be measured by referring to the said standard. For example, according to GB / T 30544.13-2018, the term "two-dimensional material" refers to a material consisting of one or more layers, where atoms in each layer are closely bonded to adjacent atoms in the layer in which it is located, where one dimension (i.e., its thickness) is in nanometers or even smaller units, and the remaining two dimensions are generally in larger units, and the term "lateral dimension" refers to the lateral dimensions of a two-dimensional material sheet.

[0044] In this application, unless otherwise specified, the term “or” is inclusive. For example, the phrase “A or B” means “A, B, or both A and B.” More specifically, the condition “A or B” is satisfied by either A being true (or existing) and B being false (or not existing), A being false (or not existing) and B being true (or existing), or both A and B being true (or existing).

[0045] The inventors noted that in practical applications, the prior art generally involves applying a ceramic coating layer to the surface of a polyolefin film to improve the penetration of the electrolyte into the polyolefin film. However, improving the adhesion between the ceramic particles and the base film requires the use of a large amount of binder, which increases the separator's resistance.

[0046] As a result of numerous experiments, the inventors discovered that by applying a coating layer containing ceramic particles, graphene oxide, and a binder between two base films, it is possible to promote the penetration of the electrolyte into the separator and effectively prevent lithium dendrites from penetrating the separator. Furthermore, it is possible to avoid a significant increase in the resistance of the separator due to the application of the coating layer or the use of large amounts of binder, thereby avoiding the occurrence of many side reactions, improving the operational stability of the corresponding battery, and enhancing the safety performance, dynamic characteristics, and cycle characteristics of secondary batteries using the separator.

[0047] [Separator] According to a first aspect of the present application, a separator is provided comprising a first base film, a second base film, and a coating layer located between the first base film and the second base film, the coating layer comprising ceramic particles, graphene oxide, and a binder.

[0048] The separator of this invention has a three-layer composite structure, and the intermediate coating layer contains ceramic particles, graphene oxide, and a binder. The ceramic particles can, on the one hand, promote the penetration of the electrolyte into the separator, improving the heat resistance and mechanical properties of the separator, and on the other hand, effectively consume the lithium dendrites that are generated, preventing the lithium dendrites from penetrating the separator and improving safety performance. The surface of the graphene oxide in the coating layer is rich in various polar groups, which can, on the one hand, further promote the penetration of the electrolyte into the separator, and on the other hand, help to reduce resistance through the following actions, thereby improving the dynamic characteristics of the corresponding battery. Firstly, graphene oxide itself can be compounded with the base film by van der Waals forces, reducing the use of binder. Secondly, graphene oxide can provide a large number of channels for ions to be freely transported, improving the ionic conductivity of the separator. Furthermore, the coating layer is located between the first and second base films, and the base film itself can exist as a "barrier layer," effectively preventing direct contact between the ceramic particles and the positive and negative electrode sheets. This helps to further improve the safety performance of the corresponding secondary battery, while also helping to avoid many side reactions, thereby improving the stability and cycle characteristics when using the corresponding battery.

[0049] In some embodiments, the mass ratio of the ceramic particles to the binder is selectively 1:0.001 to 0.3, and selectively 1:0.01 to 0.1. For example, the ratio may be in the range of 1:0.001, 1:0.005, 1:0.006, 1:0.01, 1:0.013, 1:0.017, 1:0.02, 1:0.026, 1:0.033, 1:0.05, 1:0.06, 1:0.1, or 1:0.3 and any two of the above ratios.

[0050] When the mass ratio of ceramic particles to binder is within the above range, it is advantageous for the coating layer to have proper adhesion, effectively avoids "powder fall-off" of the ceramic particles, allows the ceramic particles to improve the wetting performance of the separator and fully exert their effect in consuming lithium dendrites, and improves the safety performance of the corresponding secondary battery.

[0051] In some embodiments, the ratio of the sum of the masses of the ceramic particles and the binder to the mass of the graphene oxide is selectively 2 to 11:1, and selectively 2 to 9:1. For example, the ratio may be in the range of 2:1, 3:1, 3.1:1, 5:1, 5.1:1, 5.3:1, 5.5:1, 6.5:1, 8:1, 9:1, 10:1, or 11:1 and any two of the above ratios.

[0052] When the ratio of the sum of the masses of the ceramic particles and the binder to the mass of the graphene oxide is within the above range, it is advantageous for the coating layer to have appropriate adhesion, thereby allowing the ceramic particles to fully exert their function of improving the wetting performance of the separator and consuming lithium dendrites, while the graphene oxide reduces the use of the binder and promotes the free transfer of ions, thereby reducing the resistance of the separator and improving the dynamic characteristics of the corresponding secondary battery.

[0053] In some embodiments, the mass ratio of graphene oxide to ceramic particles is selectively 1:1.5 to 11, and selectively 1:3 to 5. For example, the ratio may be in the range of 1:1.5, 1:1.95, 1:3, 1:5, 1:8, 1:8.95, 1:9, 1:10, or 1:11 and any two of the above ratios.

[0054] The graphene oxide surface is rich in oxygen-containing functional groups, and when the mass ratio of graphene oxide to ceramic particles is within the above range, it is advantageous to promote the formation of intermolecular forces and hydrogen bonds between the oxygen-containing functional groups on the graphene oxide surface and the ceramic particles, thereby improving the adhesion of the ceramic particles to the separator, improving the adhesion of the entire coating material, and further advantageous in preventing the graphene oxide sheets from laminating and blocking the pores of the separator. In addition, when the mass ratio of graphene oxide to ceramic particles is within the above range, it is also advantageous to improve the function of the coating layer in consuming lithium dendrites.

[0055] In some embodiments, the content of graphene oxide is selectively 5-40% and selectively 15-30% relative to the total weight of the coating layer, the content of ceramic particles is 25-95% and selectively 70-85%, and the content of the binder is 0.001-8% and selectively 0.01-0.5%.

[0056] In some embodiments, the mass ratio of graphene oxide:ceramic particles:binder is selectively 0.09 to 1:1:0.001 to 0.3. For example, the above ratio may be in the range of 0.1:1:0.001, 0.2:1:0.001, 0.2:1:0.01, 0.2:1:0.1, 0.2:1:0.3, 0.3:1:0.3, 0.5:1:0.2, or 1:1:0.3 and any two of the above ratios.

[0057] In some embodiments, the graphene oxide is selectively a graphene oxide sheet, and the maximum transverse dimension of the graphene oxide sheet is selectively 0.01 to 10 μm.

[0058] The surface of graphene oxide is rich in oxygen-containing functional groups such as hydroxyl groups, carboxyl groups, and aldehyde groups, which improves the hydrophilicity of the separator and allows the electrolyte to penetrate the separator rapidly. Furthermore, the laminated graphene oxide sheets create a large number of gaps, allowing lithium ions to be freely transmitted within the voids of the sheet layer, thereby improving the ionic conductivity of the separator. In addition, small-diameter graphene oxide is advantageous in preventing the graphene from covering the pores on the separator and reducing the separator's permeability, thereby avoiding inhibition of ion transmission and a significant increase in the separator's resistance.

[0059] In some embodiments, the ceramic particles are selectively one or more selected from oxides, nitrides, or oxoates of elements Si, Fe, Sn, Ti, Cu, Mg, Ge, Zn, Zr, and B. Selectively selected from one or more of the following: oxides of Si, nitrides of Si, oxides of Fe, nitrides of Fe, oxoates of Fe, oxides of Sn, oxides of Ti, nitrides of Ti, oxoates of Ti, oxides of Cu, nitrides of Cu, oxides of Mg, oxides of Ge, oxides of Zn, oxides of zirconium, and boron nitride. Furthermore, it is selectively one or more of titanium dioxide (TiO2), silicon dioxide (SiO2), tin dioxide (SnO2), zinc oxide (ZnO), zirconium oxide (ZrO2), and lithium titanate.

[0060] In this application, the first and second base films have strong hydrophobicity and low affinity for highly polar electrolytes; therefore, the base films cannot absorb and retain the electrolyte. The ceramic particles in this application have strong hydrophilicity, which is advantageous in significantly improving the permeability of the electrolyte to the separator.

[0061] In addition, during several charge-discharge processes of a lithium metal battery, the generation of lithium dendrites cannot be avoided. If not controlled, lithium dendrites will eventually contact and penetrate the separator, resulting in the contact between the positive and negative electrodes and causing safety problems. Components such as silicon dioxide contained in the ceramic particles of the present application can generate a lithium insertion reaction, immediately consume the generated lithium dendrites, and improve the safety performance of the corresponding battery.

[0062] The reaction mechanism by which the ceramic particles of the present application consume lithium dendrites can be divided into an alloying reaction mechanism, an intercalation reaction mechanism, and a redox mechanism.

[0063] 1) Alloying reaction mechanism: When a metal oxide reacts with lithium dendrites, it is accompanied by the generation of a metal single substance, and an alloying reaction further occurs on the generated metal single substance to generate a lithium alloy. The reaction equation is as follows.

[0064]

Number

[0065] Taking tin dioxide as an example, in the discharge process, first, tin single substance and Li2O are generated, and then the tin single substance and Li + react to generate a Li 4.4 Sn compound.

[0066] 2) Intercalation reaction mechanism: In the charge-discharge process, Li + is only inserted into the gaps of the layer structure of the material, and its chemical reaction formula in the charge-discharge process is as follows.

[0067]

Number

[0068] Typical ceramic materials that exhibit intercalation reaction mechanisms include SiO2, TiO2, and lithium titanate.

[0069] 3) Conversion reaction mechanism: Metal oxide and Li + When these undergo a redox reaction, elemental metals and Li2O are produced, and the chemical equation for this reaction is as follows.

[0070]

number

[0071] In some embodiments, the particle size of the ceramic particles is selectively 0.01 to 10 μm, and selectively 0.05 to 0.5 μm.

[0072] If the ceramic particles are too large, the resulting coating layer will have high paste viscosity and difficulty in ensuring uniformity, making it difficult to coat the separator. Furthermore, a "powder fallout" phenomenon is likely to occur during the coating process, resulting in poor adhesion of the powder to the separator surface and an unsatisfactory coating effect. If the particles are too small, when coating with ceramic particles, the particles can clog the voids on the surface of the organic pore material, reducing the separator's air permeability, thereby blocking ion transmission channels and significantly reducing both battery capacity and cycle life.

[0073] Furthermore, if the particle size of the ceramic particles is within the above range, introducing the ceramic particles is advantageous in improving the porosity of the separator, Li + This accelerates diffusion and improves the ionic conductivity of the separator.

[0074] In some embodiments, the binder is selectively one or more selected from dopamine hydrochloride, polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorine-containing acrylate resin, styrene-butadiene rubber, sodium polyacrylate, polymethacrylic acid, polyacrylamide, polyvinyl alcohol, sodium alginate, carboxymethyl chitosan, and sodium carboxymethylcellulose.

[0075] In some embodiments, the thickness of the coating layer is selectively 0.1 to 10 μm, and selectively 1 to 6 μm.

[0076] When the thickness of the coating layer is within the above range, it is advantageous not only to effectively consume lithium dendrites and prevent them from penetrating the separator and causing safety problems, but also to prevent the coating layer from significantly increasing the resistance of the separator.

[0077] In some embodiments, the first base film and the second base film are each independently one or more selected from polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, polyamide, and polyester.

[0078] In some embodiments, the first base film and / or the second base film are selectively impregnated with a graphene oxide dispersion.

[0079] Pre-treating the base film with a graphene oxide dispersion allows for the inclusion of numerous polar groups on the base film's surface, increasing its hydrophilicity and thereby improving the electrolyte's penetration into the base film. Furthermore, the inclusion of many polar groups on the base film's surface helps improve the bonding efficiency between the coating layer and the base film, reducing binder usage and lowering separator resistance.

[0080] In some embodiments, the weight-average molecular weights of the first and second base films are selectively between 100,000 and 1,000,000. The weight-average molecular weight can be measured by methods commonly used in this art, for example, by gel permeation chromatography based on GB / T 21863-2008.

[0081] In some embodiments, the thickness of the first base film and / or the second base film is selectively 3 to 30 μm, and selectively 5 to 25 μm.

[0082] If the separator thickness is too small, the mechanical stability of the separator may deteriorate, and it may be difficult for the separator to adequately perform its role in separating the positive and negative electrode sheets. If the separator thickness is too large, the resistance of the separator will increase, making it more difficult for lithium ions to pass through the separator and be transmitted, which may lead to a decrease in battery performance.

[0083] In some embodiments, the separator is selectively ρ s ≤10 7 Satisfying mΩ·cm, selectively ρ s ≤ 5 × 10 6 The condition mΩ·cm is satisfied. Here, ρ s This indicates the ion resistivity of the separator.

[0084] ρ s When the value falls within the above range, the ion resistivity of the separator is low, which is advantageous for improving the dynamic characteristics of the corresponding secondary battery.

[0085] In some embodiments, the present application further provides a method for manufacturing the separator described herein, comprising at least the following steps 1 to 3.

[0086] In Step 1, graphene oxide, ceramic particles, and binder are thoroughly mixed in an appropriate amount of solvent in a mass ratio of 0.09-1:1:0.001-0.3 to obtain a mixed paste.

[0087] In step 2, the mixed paste obtained in step 1 is coated onto one surface of the first base film and the second base film.

[0088] In step 3, the first base film and the second base film obtained in step 2 are stacked along the coating layer side, and the solvent is removed after hot pressing and drying.

[0089] In some embodiments, the solvent in step 1 is selectively water, NN-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and the like.

[0090] In some embodiments, selectively, the graphene oxide in step 1 is a graphene oxide dispersion.

[0091] In some embodiments, the solid content of the graphene oxide dispersion is selectively 0.1 to 5%, and selectively 0.3 to 3%.

[0092] In some embodiments, the graphene oxide dispersion may be selectively obtained by adding graphene oxide to a solvent and then uniformly dispersing it using ultrasound.

[0093] In some embodiments, the solvent in the graphene oxide dispersion may be selectively selected from one or more of water, ethanol, isopropyl alcohol, n-butanol, and isobutanol.

[0094] In some embodiments, the first and second base films are selectively pretreated with a graphene oxide dispersion before performing step 2.

[0095] In some embodiments, the dispersion used to selectively pre-treat the base film is an aqueous dispersion of graphene oxide or an isopropyl alcohol dispersion of graphene oxide.

[0096] In some embodiments, the pretreatment selectively involves completely immersing the base film in a graphene oxide dispersion, holding it for 15 to 120 seconds, selectively for 30 to 90 seconds, and then removing and drying it.

[0097] In some embodiments, the coating in step 2 may be selectively carried out by coating methods commonly used in the art, such as scraper coating, roller coating, or extrusion coating.

[0098] In some embodiments, the hot pressing in step 3 is selectively performed at a temperature of 90–150°C, and selectively at 120–140°C.

[0099] In some embodiments, the coating density of the coating layer on the separator obtained in step 3 is selectively 1.0 to 6.0 g / m². 2 Therefore, selectively 1.5-4.5 g / m 2 That is the case.

[0100] In some embodiments, selectively, in the separator of the present application, the mass ratio of graphene oxide, ceramic particles, and binder is 0.09 to 1:1:0.001 to 0.3. For example, the ratio may be in the range of 0.2:1:0.02, 0.33:1:0.033, 1.125:1:0.0125, 0.1:1:0.001, 0.2:1:0.01, 0.2:1:0.06, 0.2:1:0.02, 0.2:1:0.001, 0.2:1:0.006, 0.5:1:0.03, 0.1:1:0.006, or 0.09:1:0.004 and any two of the above ratios.

[0101] [Secondary battery] According to a second aspect of the present application, a secondary battery including the separator described in the first aspect of the present application is provided. Generally, in addition to the separator, a secondary battery further includes a positive electrode sheet, a negative electrode sheet, and an electrolyte.

[0102] In particular, the separator described in this application can be used in lithium metal batteries instead of conventional separators. The negative electrode of the lithium metal battery may be lithium metal or a lithium alloy, or it may be a negative electrode-less battery. The corresponding positive electrode materials are as follows. In the case of a negative electrode-less lithium metal battery, the positive electrode material needs to provide a lithium source.

[0103] The manufacture of secondary batteries can be carried out using methods commonly used in this field. For example, an electrode assembly can be formed from a positive electrode sheet, a negative electrode sheet, and a separator via a winding or lamination process, and then an electrolyte can be injected into the electrode assembly and sealed to obtain a secondary battery.

[0104] The following describes each of the above-mentioned components of the secondary battery.

[0105] [Positive electrode sheet] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0106] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. As the metal foil, for example, aluminum foil can be used. The composite current collector may include a polymer substrate layer and a metal layer formed on at least one surface of the polymer substrate layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material base layer (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0107] In this application, the positive electrode material is Li + It is a compound that can be reversibly inserted into and removed from.

[0108] In some embodiments, the positive electrode active material can be a known positive electrode active material for batteries. For example, Li x MO2 or Li y Examples include lithium-containing composite oxides represented as M2O4 (where M is a transition metal, 0≦x≦1, 0≦y≦2), spinel-like oxides, layered metal sulfides, and olivine structures. For example, lithium cobalt oxides such as LiCoO2, lithium manganese oxides such as LiMn2O4, lithium nickel oxides such as LiNiO2, and Li 4 / 3 Ti 5 / 3 Examples include lithium titanium oxides such as O4, lithium manganese nickel composite oxides, lithium manganese nickel cobalt composite oxides, and materials having an olivine-type crystal structure such as LiMPO4 (M=Fe, Mn, Ni).

[0109] In some embodiments, the positive electrode active material is selectively a lithium-containing composite oxide having a layered or spinel-like structure, such as LiCoO2, LiMn2O4, LiNiO2, LiNi 1 / 2 Mn 1 / 2 Lithium manganese nickel cobalt composite oxides, such as O2, LiNi l / 3 Mn 1 / 3 Co 1 / 3 O2, LiLiLi 0.6 Mn 0.2 Co 0.2 Lithium manganese nickel cobalt composite oxides, such as O2, or LiNi 1-x-y-z Co x Al y Mg z This refers to lithium-containing composite oxides such as O2 (wherein the formula 0≦x≦1, 0≦y≦0.1, 0≦z≦0.1, 0≦1-xyz≦1). Furthermore, lithium-containing composite oxides in which some of the constituent elements of the above lithium-containing composite oxide are substituted with additive elements such as Ge, Ti, Zr, Mg, Al, Mo, and Sn are also included within the scope of this application.

[0110] In addition to the positive electrode active materials described above, other conventional materials usable as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used individually or in combination of two or more types. For example, by using a layered lithium-containing composite oxide and a spinel-like lithium-containing composite oxide simultaneously, it is possible to achieve both increased capacity and improved safety.

[0111] In some embodiments, the mass ratio of the positive electrode active material to the positive electrode film is selectively 75% to 99%, and selectively 80% to 97%.

[0112] In some embodiments, the positive electrode film layer may further selectively contain a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0113] In some embodiments, the conductive agent selectively accounts for 0.05 to 5% of the total weight of the positive electrode film layer, and selectively accounts for 0.5 to 3%.

[0114] In some embodiments, the positive electrode film layer further selectively comprises a binder, such as polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene ternpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and polyethylene oxide, which are binders commonly used in the battery field.

[0115] In some embodiments, the binder selectively accounts for 0.1 to 3.5% and selectively for 0.5 to 2.5% of the total weight of the positive electrode film layer.

[0116] In some embodiments, a positive electrode sheet can be manufactured by the following method: Components for manufacturing the positive electrode sheet, such as a positive electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode paste, the positive electrode paste is applied to a positive electrode current collector, and the positive electrode sheet can be obtained through steps such as drying and cold pressing.

[0117] [Negative electrode sheet] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0118] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil. The composite current collector may include a polymer substrate layer and a metal layer formed on at least one surface of the polymer substrate layer. The composite current collector can be formed by forming a metal material (such as copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0119] In this application, the negative electrode material is a lithium metal or a compound capable of inserting and removing lithium.

[0120] In some embodiments, the negative electrode active material can be any negative electrode active material known in the art for batteries. For example, various materials such as alloys or oxides of aluminum, silicon, tin, etc., and carbon materials can be used as negative electrode active materials. Selectively, oxides can include titanium dioxide, and carbon materials can include graphite, pyrolytic carbons, cokes, glassy carbons, calcined organic polymer compounds, mesocarbon microbeads, etc. The tin-based material can be at least one selected from elemental tin, tin oxides, and tin alloys. However, this application is not limited to these materials, and other conventional materials usable as negative electrode active materials for batteries may be used. These negative electrode active materials may be used individually or in combination of two or more types.

[0121] In some embodiments, the mass ratio of the negative electrode active material to the positive electrode film is selectively 75% to 99%, and selectively 80% to 97%.

[0122] In some embodiments, the negative electrode film layer may further selectively contain a conductive agent. The conductive agent may be at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0123] In some embodiments, the conductive agent selectively accounts for 0.05 to 5% of the total weight of the negative electrode film layer, and selectively accounts for 0.5 to 3%.

[0124] In some embodiments, the negative electrode film layer further selectively comprises a binder, such as polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene ternpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and polyethylene oxide, which are binders commonly used in the battery field.

[0125] In some embodiments, the binder selectively accounts for 0.1 to 3.5% of the total weight of the negative electrode film layer, and selectively accounts for 0.5 to 2.5%.

[0126] In some embodiments, the negative electrode film layer further comprises other additives, such as a selective thickener (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0127] In some embodiments, the mass ratio of the thickening agent to the negative electrode film is selectively 0.04% to 5%, and selectively 0.5% to 3%.

[0128] In some embodiments, a negative electrode sheet can be manufactured by the following method. Components for manufacturing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode paste. The negative electrode paste is then applied to a negative electrode current collector, and the negative electrode sheet can be obtained through processes such as drying and cold pressing.

[0129] [Electrolyte] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. This application does not particularly limit the type of electrolyte, and it can be selected as needed. For example, the electrolyte may be a liquid, a gel, or a solid.

[0130] In some embodiments, an electrolyte solution is used as the electrolyte. The electrolyte solution comprises an electrolyte salt and a solvent.

[0131] In some embodiments, a non-aqueous solvent (organic solvent) is used as a non-aqueous electrolyte. Non-aqueous solvents include carbonate esters, ethers, and the like.

[0132] In some embodiments, the carbonate esters include cyclic carbonate esters and linear carbonate esters. Examples of cyclic carbonate esters include ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and thioesters (ethylene glycol sulfide). Examples of linear carbonate esters include low-viscosity polar linear carbonate esters such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, as well as aliphatic branched carbonate ester compounds. A mixed solvent of cyclic carbonate ester (especially ethylene carbonate) and linear carbonate ester is particularly preferred.

[0133] Examples of ethers include tetraethylene glycol dimethyl ether (TEGDME), dimethyl ether (DME), and 1,3-dioxolane (DOL).

[0134] In addition to the non-aqueous solvents mentioned above, other non-aqueous solvents (organic solvents) such as linear alkyl esters including methyl propionate, linear triesters including trimethyl phosphate, nitrile solvents including 3-methoxypropionitrile, and branched compounds having ether bonds, such as dendrimers, can also be used.

[0135] Alternatively, a fluorinated solvent may be used. Examples of fluorinated solvents include H(CF2)2OCH3, C4F9OCH3, H(CF2)2OCH2CH3, H(CF2)2OCH2CF3, H(CF2)2CH2O(CF2)2H, or linear (perfluoroalkyl) alkyl ethers such as CF3CHFCF2OCH3, CF3CHFCF2OCH2CH3, etc., such as 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethylhexafluoropropyl propyl ether, 3-trifluoromethyloctafluorobutyl methyl ether, 3-trifluoromethyloctafluorobutyl ethyl ether, 3-trifluoromethyloctafluorobutyl propyl ether, and 4-trifluoromethyldecafluoropentyl methyl ether. Examples include 4-trifluoromethyl decafluoropentyl ethyl ether, 4-trifluoromethyl decafluoropentyl propyl ether, 5-trifluoromethyl dodecafluorohexyl methyl ether, 5-trifluoromethyl dodecafluorohexyl ethyl ether, 5-trifluoromethyl dodecafluorohexyl propyl ether, 6-trifluoromethyl tetradecafluoroheptyl methyl ether, 6-trifluoromethyl tetradecafluoroheptyl ethyl ether, 6-trifluoromethyl tetradecafluoroheptyl propyl ether, 7-trifluoromethyl hexadecafluorooctyl methyl ether, 7-trifluoromethyl hexadecafluorooctyl ethyl ether, and 7-trifluoromethyl hexadecafluorooctyl propyl ether.

[0136] Alternatively, a mixture of iso(perfluoroalkyl)alkyl ether and a linear (perfluoroalkyl)alkyl ether may be used.

[0137] Lithium salts such as lithium perchlorates, organoboro lithium salts, fluorine-containing lithium salts, and lithium imide salts are preferred as electrolyte salts used in non-aqueous electrolytes.

[0138] Examples of such electrolyte salts include, for example, LiClO4, LiPF6, LiBF4, LiAsF6, LiSbF6, LiCF3SO3, LiCF3CO2, LiC2F4(SO3)2, LiN(C2F5SO2)2, LiC(CF3SO2)3, LiC n F 2n+1 SO3(n≧2), LiN(R f OSO2)2(wherein, R f Examples include lithium salts (where is a fluoroalkyl group). Among these lithium salts, fluorine-containing organolithium salts are particularly preferred. Fluorine-containing organolithium salts are readily soluble in non-aqueous electrolytes because their anionic polarity is high and they easily separate into ions.

[0139] The concentration of the lithium electrolyte salt in the non-aqueous electrolyte is, for example, 0.3 mol / L (moles / liter) or higher, more selectively 0.7 mol / L or higher, selectively 1.7 mol / L or lower, and more selectively 1.2 mol / L or lower. If the concentration of the lithium electrolyte salt is too low, the ionic conductivity will be too low, and if the concentration is too high, there is a risk that undissolved electrolyte salts will precipitate.

[0140] In some embodiments, the electrolyte further selectively includes additives, but the present application is not particularly limited thereto. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and further additives that can improve specific characteristics of the battery, such as additives that improve the overcharge characteristics of the battery, or additives that improve the high-temperature or low-temperature characteristics of the battery.

[0141] [Battery modules, battery packs, and power consumption devices] According to a third aspect of the present application, a battery module including a secondary battery according to a second aspect of the present application is provided. The battery module can be manufactured using methods commonly used in the art.

[0142] A fourth aspect of this application provides a battery pack comprising at least one of a secondary battery according to the second aspect of this application or a battery module according to the third aspect of this application. The battery pack can be manufactured using methods commonly used in the art.

[0143] According to a fifth aspect of the present application, a power consumption device is provided which includes at least one selected from a secondary battery according to a second aspect of the present application, a battery module according to a third aspect of the present application, or a battery pack according to a fourth aspect of the present application.

[0144] Furthermore, the secondary battery, battery module, battery pack, and power consumption device of this application will be described below with reference to the drawings as appropriate.

[0145] In some embodiments, the secondary battery may include an outer casing. This casing is used to enclose the electrode assembly and electrolyte.

[0146] In some embodiments, the casing material of the secondary battery may be a hard case such as a rigid plastic case, an aluminum case, or a steel case. The casing material of the secondary battery may also be a soft pack such as a pouch-type soft pack. The material of the soft pack may be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0147] This invention does not particularly limit the shape of the secondary battery, and it may be cylindrical, prismatic, or any other shape. For example, Figure 2 shows a prismatic secondary battery 5 as an example.

[0148] In some embodiments, referring to Figure 3, the exterior may include a housing 51 and a cover plate 53. The housing 51 includes a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates enclose a housing cavity. The housing 51 has an opening that communicates with the housing cavity, and the cover plate 53 can cover the opening to seal the housing cavity. An electrode assembly 52 can be formed from a positive electrode sheet, a negative electrode sheet, and a separator via a winding or lamination process. The electrode assembly 52 is sealed within the housing cavity. The electrode assembly 52 is impregnated in an electrolyte. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art can select according to specific practical requirements.

[0149] In some embodiments, the secondary battery can constitute a battery module, and the number of secondary batteries included in the battery module may be one or more, the specific number of which can be selected by those skilled in the art depending on the application and capacity of the battery module.

[0150] Figure 4 shows an example of a battery module 4. Referring to Figure 4, in the battery module 4, multiple secondary batteries 5 can be installed in sequence along the length of the battery module 4. Of course, they can be arranged in any other way. Furthermore, these multiple secondary batteries 5 can be fixed in place with fasteners.

[0151] Selectively, the battery module 4 may further comprise an outer case having a housing space for accommodating multiple secondary batteries 5.

[0152] In some embodiments, the battery module can further constitute a battery pack, and the number of battery modules included in the battery pack may be one or more. The specific number can be selected by those skilled in the art depending on the application and capacity of the battery pack.

[0153] Figures 5 and 6 show an example of a battery pack 1. Referring to Figures 5 and 6, the battery pack 1 may include a battery case and a plurality of battery modules 4 installed inside the battery case. The battery case includes an upper housing 2 and a lower housing 3, the upper housing 2 can be placed over the lower housing 3, thereby forming a sealed space for housing the battery modules 4. The plurality of battery modules 4 can be arranged inside the battery case in any way.

[0154] Furthermore, the present application provides a power consumption device comprising at least one of a secondary battery, a battery module, or a battery pack relating to the present application. The secondary battery, battery module, or battery pack may be used as a power source for the power consumption device, or as an energy storage element for the power consumption device. The power consumption device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships and satellites, energy storage systems, etc.

[0155] As the power consumption device, a secondary battery, battery module, or battery pack can be selected according to the usage requirements.

[0156] Figure 7 shows an example of a power consumption device. This power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power output and high energy density requirements for the secondary battery of this power consumption device, a battery pack or battery module can be used.

[0157] Other examples of such devices may include mobile phones, tablet computers, and laptop computers. These devices are generally required to be lightweight and thin, and can use rechargeable batteries as a power source. [Examples]

[0158] The following describes examples of the present application. The examples described below are illustrative and are for illustrative purposes only, and should not be understood as limiting the present application. If specific techniques or conditions are not shown in the examples, they should be carried out in accordance with the techniques or conditions described in the literature in the art, or in accordance with the product instructions. If the manufacturer of the reagents or equipment used is not specified, they are all commercially available common products.

[0159] 1. Separator (Example 1) Step 1: Hydrophilic modification of the polypropylene film A nano-order grade hydrophilic graphene oxide layer is coated onto the surface of a polypropylene film (PP film). A dispersion of 0.02 wt% graphene oxide (GO, purchased from Nanjing Xianfeng Nami Technology Co., Ltd.) in isopropyl alcohol (IPA) is prepared. An aqueous IPA solution with an isopropyl alcohol:water volume fraction ratio of 20:1 is prepared, and 0.02 g of GO is added to 100 g of the aforementioned aqueous IPA solution. The solution is then subjected to ultrasonic vibration for 30 minutes to obtain a dispersion of GO in isopropyl alcohol (IPA). Next, a 7 μm PP film is completely immersed in the dispersion, left to stand for 30 seconds, and then removed and dried. This process is repeated five times to obtain a PP film with a hydrophilic surface.

[0160] Step 2: Manufacturing the mixed paste Mix an aqueous dispersion of GO with a solid content of 1 wt% (preparation method is the same as in step 1, using only water as the solvent, and calculated by wet weight including water, the same applies below), SiO2 (400 nm, calculated by dry weight, the same applies below), and a mixed binder (calculated by the dry weight of the mixed binder, the same applies below) in a mass ratio of 100:5:0.1, and stir at 800 rpm for 30 minutes to uniformly mix the paste and prepare it for use.

[0161] The method for preparing the aforementioned mixed binder is as follows: 0.75 g of dopamine hydrochloride, 0.2 g of sodium carboxymethylcellulose (CMC), and 10 ml of a mixed solution of deionized water and ethanol (1:1, v:v) (aqueous solvent) are uniformly mixed. Then, the pH is adjusted to 8.5 using a 1 mol / L aqueous NaOH solution to obtain the mixed binder.

[0162] Step 3: Coating the separator The paste obtained in Step 2 is uniformly coated onto one side of the GO-modified PP film using a scraper to produce an SiO2 / GO-PP film.

[0163] Composite 2-layer PP film Another SiO2 / GO-PP film is manufactured according to steps 1-3 above. Then, the two SiO2 / GO-PP films are stacked with their coating layers facing each other, hot-pressed at 150°C to bond them, and dried overnight in a vacuum dryer at 60°C until the solvent is completely removed to obtain a 3-layer composite separator made of PP-SiO2 / GO-PP. The ceramic layer of the composite separator has a thickness of 3 μm, and the total thickness is 17 μm.

[0164] (Example 2) Except for changing the particle size of silicon dioxide in Step 2 to 700 nm, the other steps of Example 2 are the same as those of Example 1.

[0165] (Example 3) Except for changing the particle size of silicon dioxide in Step 2 to 200 nm, the other steps of Example 3 are the same as those of Example 1.

[0166] (Example 4) Except for changing the ceramic particles in Step 2 from silicon dioxide to ferric oxide (particle size approximately 100 nm), the other steps of Example 4 are the same as those of Example 1.

[0167] Ferric oxide can be alloyed with lithium dendrites, exhibiting high specific capacity, excellent stability, and low ionic conductivity, which is advantageous for lithium dendrite consumption, while simultaneously reducing internal resistance due to the separator.

[0168] (Example 5) Except for changing the ceramic particles in Step 2 from silicon dioxide to tin dioxide (particle size approximately 100 nm), the other steps of Example 5 are the same as those of Example 1.

[0169] (Example 6) Except for changing the ceramic particles in Step 2 from silicon dioxide to titanium dioxide (particle size approximately 100 nm, anatase type), the other steps of Example 6 are the same as those of Example 1.

[0170] Titanium dioxide can be intercalated with lithium dendrites to produce lithium titanate. It has a high theoretical capacity, a stable structure, and its oxide structure does not change significantly even after lithium insertion.

[0171] (Example 7) Except for changing the ceramic particles in Step 2 from silicon dioxide to copper oxide (CuO, particle size approximately 150 nm), the other steps of Example 7 are the same as those of Example 1.

[0172] Copper oxide reacts with lithium to produce amorphous Li2O and nano-order metallic copper particles. These nano-order copper particles can further react with Li2O to produce oxides, which are given high specific capacity and good cycling properties.

[0173] (Example 8) Except for the fact that the hydrophilic modification of the polypropylene film was performed without using a graphene oxide dispersion in Step 1, all other conditions in Example 8 are the same as in Example 1.

[0174] (Examples 9-14) In Step 2, the mass mixing ratios of a 1 wt% aqueous dispersion of GO (preparation method is the same as in Step 1, using only water as the solvent), SiO2 (400 nm), and the mixed binder were adjusted in order as follows.

[0175] Example 9 100:3:0.1 Example 10 100:8:0.1 Example 11 100:10:0.1 Example 12 100: 5:0.05 Example 13: 100:5:0.3 Example 14: 100:5:0.5

[0176] The rest is the same as in Example 1.

[0177] (Examples 15-17) The other steps are the same as in Example 1, except that the thickness of the coating layer in Step 3 was changed to 4 μm, 5 μm, and 6 μm.

[0178] (Examples 18-20) Except for the mass ratios of ceramic particles to the mixed binder being 1:0.001, 1:0.3, and 1:0.006, the rest of the procedure is the same as in Example 1.

[0179] (Examples 21-24) Except for the ratio of the sum of the masses of the ceramic particles and the mixed binder to the mass of the graphene oxide being 2:1, 3:1, 9:1, and 11:1, the rest of the procedure is the same as in Example 1.

[0180] (Example 25) The conditions for Example 25 are the same as those for Example 1, except that the ceramic particles in Step 2 were changed from silicon dioxide to aluminum oxide (with a particle size of approximately 400 nm).

[0181] (Comparative Example 1) The other steps are the same as in Example 1, except that graphene oxide is not used in Step 2.

[0182] The test results for Examples 1 to 25 and the comparative examples are shown in Table 1.

[0183] 2, secondary battery Manufacturing of positive electrode sheets Lithium iron phosphate (calculated as LiFePO4) as the positive electrode active material, acetylene black as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder are mixed in a mass ratio of 96.5:2:1.5, dissolved in the solvent N-methylpyrrolidone (i.e., NMP), and thoroughly stirred to mix uniformly and obtain a positive electrode paste. The positive electrode paste is uniformly coated onto aluminum foil, and after drying, cold pressing, and cutting, a positive electrode sheet is obtained. The coating surface density of the obtained polar sheet is 19.5 mg / cm². 2 The compacted flour density is 2.4 g / cm³. 3 That is the case.

[0184] Manufacturing of negative electrode sheets Graphite, acetylene black (a conductive agent), PVDF (a binder), and sodium carboxymethylcellulose (CMC) (a thickener) are dissolved in deionized water as a solvent in a mass ratio of 96.5 parts by weight:0.7 parts by weight:1.8 parts by weight:1 part by weight. The mixture is thoroughly stirred to obtain a negative electrode paste. The negative electrode paste is uniformly coated onto the copper foil of the negative electrode current collector, and then dried, cold-pressed, and cut to obtain a negative electrode sheet. The coating surface density of the obtained polar sheet is 9.8 mg / cm³. 2 The compacted flour density is 1.65 g / cm³. 3 That is the case.

[0185] Manufacturing of electrolyte The organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are uniformly mixed in a weight ratio of 50 / 50. LiPF6 is added and dissolved in the organic solvent, and the mixture is uniformly stirred to obtain an electrolyte with a LiPF6 concentration of 1.1 mol / L.

[0186] Separator The separators manufactured in the examples and comparative examples of this application are used as separators for secondary batteries.

[0187] secondary battery A positive electrode sheet, a separator, and a negative electrode sheet are stacked in order (the separator is placed between the positive and negative electrodes to provide isolation), and then wound up to obtain a bare cell. The bare cell is placed in an outer casing, the electrolyte is injected and sealed to obtain a secondary battery. The dimensions of the obtained secondary battery are 60 × 130 × 4 mm.

[0188] Test methods for related parameters 1. Separator performance test 1) Tensile strength (Transverse Direction, TD) test of separators Measurements are performed according to the ASTM D882-09 standard. The separator under test is cut to a size of 10 mm in width and ≥ 150 mm in length, and pulled at a speed of 500 mm / min using a universal tensile device. The maximum load value at which the sample breaks is obtained, and then the tensile strength of the separator is calculated by dividing this value by the cross-sectional area of ​​the separator (width × thickness of the sample).

[0189] 2) Separator peeling force test Using a roller compressor, a standard 20mm wide tape (31B, purchased from Nitto) is applied to the ceramic coating layer of the separator under a constant stress (2kg, 300mm / min). A 180-degree peel test is then performed at a speed of 300mm / min using a tensile testing machine. 50 peel force values ​​are obtained at test distances of 50mm to 120mm, and the average value is calculated.

[0190] 3) Wetness test of the separator The separator under test is cut to a size of 50 mm x 50 mm, 1 ml of standard electrolyte (an electrolyte prepared by dissolving LiPF6 in a mixed solvent with a weight ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) of 1:1:1, with a LiPF6 concentration of 1 mol / l) is dropped onto the sample, and the clamping angle between the droplet and the separator is observed using a contact angle meter.

[0191] 4) Separator liquid absorption rate test The separator to be tested is cut to a size of 200 mm x 15 mm, and the sample is suspended vertically above the electrolyte solvent (a mixed solvent with a weight ratio of EC:DMC:DEC of 1:1:1) in a sealed space, so that the lower end of the separator is in contact with the surface of the solvent. After 15 minutes, the height of the capillary absorption of the separator is recorded, and the absorption rate (absorption height / absorption time) is calculated.

[0192] 2. Particle size testing of ceramic particles Particle size analysis Dv50 is a value that indicates the diameter of particles that make up 50% of the total volume is greater than this value, and the diameter of particles that make up 50% of the total volume is smaller than this value. Dv50 represents the median diameter of the powder.

[0193] When a particle is irradiated with a laser beam, the angle of the scattered light is inversely proportional to the particle diameter, the intensity of the scattered light decreases logarithmically with increasing angle, and the energy distribution of the scattered light is directly related to the particle size distribution. By receiving and measuring the energy distribution of the scattered light, the characteristics of the particle size distribution can be obtained. See the GB / T19077.1-2009 standard for particle size distribution laser diffraction.

[0194] 3. Coating layer surface density (ρ) test The coating surface density (ρ) is given by: coating weight (m) / coating area (A).

[0195] The weight of the separator before coating (m0) and the weight of the separator after coating (m1) are weighed, and the difference between the two is the coating weight. Simultaneously, by measuring the area of ​​the coated separator, the coating surface density can be obtained.

[0196] 4. Ion resistivity of the separator due to the coating layer (ρ s )test Test method: Electrochemical impedance spectroscopy (EIS Law)This study investigates the effect of the separator within the battery on lithium ion permeability. The internal resistance of the battery (related to the separator's resistance) can be obtained from the electrochemical impedance spectrum measured using the AC method, and therefore the charge transfer resistance of the battery can be determined using this method. Tests were conducted using an IVIUM electrochemical workstation, with frequencies ranging from 0.1 Hz to 100 kHz.

[0197] Based on the law of resistance, the Rs of a region-limited symmetric battery is measured using the EIS method for different numbers of separator layers (n) to obtain the separator resistance. Rs and n are then plotted to obtain the slope k, and the ion resistivity of the separator is calculated under known effective area S and separator thickness conditions.

[0198] The actual test generally yields the ion resistance of the battery, i.e., its volume resistance. The ion resistance (R) obtained by measuring in the test b ) refers to a separator resistor (R s ) and the resistance (R) of the electrolyte inside the battery e It is the sum of ) and can be expressed as follows:

[0199]

number

[0200] For the sake of calculation convenience, we can ignore the effect of Re and approximately consider Rs = Rb, and calculate the resistivity of the separator (ρ) based on the following formula. s ) can be calculated.

[0201]

number

[0202] In the formula, ρ s is the resistivity of the separator, S is the effective area of ​​the separator, and d is the average thickness of the separator.

[0203] 5. Solid content measurement The solids content can be tested by referring to GB / T 1725-2007, "Measurement of Non-Volatile Content of Colored Paints, Varnishes and Plastics."

[0204] 6. Performance testing of secondary batteries Coulomb efficiency test 1) Charging conditions: Charge the battery at room temperature using constant current-constant voltage (CC-CV) mode. First, charge in constant current mode with a fixed current of 0.1C until the voltage rises to 3.65V, then switch to constant voltage mode and continue charging until the current reaches 0.02C to fully charge the battery.

[0205] 2) Discharge conditions: Discharge to 2.5V in constant current mode with different discharge rates (C rate: 0.1C / 1C / 3C), and repeat this 200 times.

[0206] 3) Calculate the Coulomb efficiency (discharge capacity / charge capacity * 100%) at different discharge rates after 200 cycles. The results are shown in Table 1.

[0207] Power Test 1) Charging conditions: Charge the battery at room temperature using constant current-constant voltage (CC-CV) mode. First, charge in constant current mode with a fixed current of 0.1C until the voltage rises to 3.65V, then switch to constant voltage mode and charge until the current reaches 0.02C to fully charge the battery.

[0208] 2) Discharge conditions: Discharge to 2.5V in constant current mode with a discharge rate of 0.1C.

[0209] 3) Calculate and record the average power (voltage * current) during the charging and discharging process.

[0210] [Table 1-1]

[0211] [Table 1-2]

[0212] [Table 1-3] remarks 1 The polypropylene film was modified to be hydrophilic without using a graphene oxide dispersion. 2 The coating layer thicknesses for Examples 15-17 were 4 μm, 5 μm, and 6 μm, respectively. 3 Alumina (particle size approximately 400 nm) was used as ceramic particles.

[0213] The results in Table 1 show the following: 1) Separators pretreated with graphene oxide dispersion can contact the ceramic-graphene oxide coating more effectively, which is advantageous in further improving the overall performance of the separator. 2) Using other ceramic particles of this invention compared to alumina can further improve the mechanical properties and wettability of the separator. 3) Graphene oxide helps to improve the adhesion, wettability, and ion conductivity of the separator. 4) The overall performance of the separator can be further improved by adjusting the mixing ratio of graphene oxide, binder, and ceramic particles.

[0214] Furthermore, as can be seen from the results in Table 1, the secondary batteries corresponding to the separator coated with the graphene oxide-ceramic particle mixed coating material have high Coulomb efficiency, maintaining over 99% even after 200 cycles at low rates, and also exhibit high Coulomb efficiency at high rates, indicating that the secondary batteries have good cycle characteristics and a longer service life. At the same time, compared to Comparative Example 1, the secondary batteries using the separator of the present invention have higher power and superior dynamic characteristics. In addition, the separator has good dendrite resistance, allowing lithium dendrites generated during the cycling process to be consumed immediately, thereby ensuring that all corresponding secondary batteries have good safety performance.

[0215] Furthermore, this application is not limited to the embodiments described above. The embodiments described above are merely illustrative, and any embodiment that has substantially the same configuration as the technical idea and exhibits similar effects, within the scope of the technical solutions of this application, is included in the technical scope of this application. In addition, any modifications to the embodiments that can be conceived by a person skilled in the art, or other forms constructed by combining some of the components of the embodiments, are also included in the scope of this application, as long as they do not depart from the spirit of this application.

Claims

1. It includes a first base film, a second base film, and a coating layer located between the first and second base films, which contains ceramic particles, graphene oxide, and a binder, in that order. The ceramic particles are one or more selected from titanium dioxide, silicon dioxide, tin dioxide, zinc oxide, zirconium oxide, lithium titanate, ferric oxide, and copper oxide. A separator for a battery, wherein the surfaces of the first base film and the second base film are coated with a graphene oxide layer.

2. The separator according to claim 1, wherein the mass ratio of the ceramic particles to the binder is 1:0.001 to 0.

3.

3. The separator according to claim 1, wherein the ratio of the sum of the masses of the ceramic particles and the binder to the mass of the graphene oxide is 2 to 11:

1.

4. The separator according to any one of claims 1 to 3, wherein the mass ratio of graphene oxide to the ceramic particles is 1:1.5 to 11.

5. The separator according to any one of claims 1 to 3, wherein the graphene oxide is a graphene oxide sheet.

6. The separator according to claim 5, wherein the maximum lateral dimension of the graphene oxide sheet is 0.01 to 10 μm.

7. The separator according to any one of claims 1 to 3, wherein the median diameter of the ceramic particles is 0.01 to 10 μm.

8. The separator according to any one of claims 1 to 3, wherein the binder is one or more selected from dopamine hydrochloride, polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorine-containing acrylate resin, styrene-butadiene rubber, sodium polyacrylate, polymethacrylic acid, polyacrylamide, polyvinyl alcohol, sodium alginate, carboxymethyl chitosan, and sodium carboxymethylcellulose.

9. The separator according to any one of claims 1 to 3, wherein the thickness of the coating layer is 0.1 to 10 μm.

10. The separator according to any one of claims 1 to 3, wherein the first base film and the second base film are each independently one or more selected from polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, polyamide, and polyester.

11. The separator according to any one of claims 1 to 3, wherein the first base film and / or the second base film are subjected to impregnation treatment with a graphene oxide dispersion.

12. The separator according to any one of claims 1 to 3, wherein the thickness of the first base film and / or the second base film is 3 to 30 μm.

13. The separator is ρ ｓ ≤ 10 ７ The condition mΩ·cm is satisfied (where ρ ｓ The ion resistivity of the separator obtained by testing using an IVIUM electrochemical workstation is shown.), the separator according to any one of claims 1 to 3.

14. A secondary battery comprising a separator according to any one of claims 1 to 3.

15. A battery module including the secondary battery described in claim 14.

16. A battery pack comprising the battery module described in claim 15.

17. A power consumption device including the battery pack described in claim 16.

Images