Secondary battery, negative current collector, preparation method of negative current collector and electric device

Abstract

The invention provides a secondary battery, a negative electrode current collector, a preparation method of the negative electrode current collector and an electric device. The secondary battery comprises a positive pole piece, a negative pole piece, an isolating membrane and an electrolyte, the isolating membrane and the electrolyte are arranged between the negative pole piece and the positive pole piece, the negative pole piece comprises a negative current collector, and the negative current collector comprises a porous membrane layer and a coating arranged on at least part of the surface of at least one side of the porous membrane layer. The coating comprises an inorganic substance, a conductive agent and a binder, and the inorganic substance comprises at least one of a metal oxide or silicon oxide. In the negative electrode current collector of the secondary battery, the coating can be well coated on the porous membrane layer to provide conductivity for the negative electrode current collector; the porous membrane layer can provide a porous structure for the negative electrode current collector, and the rate capability of the secondary battery can be improved.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to a secondary battery, a negative electrode current collector, a method for preparing the same, and an electrical device thereof. Background Technology

[0002] In recent years, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0003] With the widespread application of batteries in various fields, people have increasingly higher requirements for their performance. How to further improve the rate performance of batteries has become a key focus of attention. Summary of the Invention

[0004] This application is made in view of the aforementioned issues and aims to at least solve one of the technical problems existing in the prior art. To this end, this application provides a secondary battery, a negative electrode current collector, a method for preparing the same, and an electrical device thereof. The secondary battery of this application has good rate performance.

[0005] The first aspect of this application provides a secondary battery, the secondary battery comprising a positive electrode, a negative electrode, a separator disposed between the negative electrode and the positive electrode, and an electrolyte, wherein the negative electrode comprises a negative current collector, the negative current collector comprises a porous film layer and a coating disposed on at least a portion of the surface of at least one side of the porous film layer, the coating comprising an inorganic material, a conductive agent, and a binder, wherein the inorganic material comprises at least one of a metal oxide or silicon oxide.

[0006] As a component of the negative electrode current collector, the porous membrane layer in the secondary battery of this application embodiment has a porous structure and is permeable to electrolyte. The porous structure and good electrolyte permeability help to shorten the migration path of metal ions such as sodium ions and lithium ions, improve the transport speed of metal ions, and improve the rate performance of the secondary battery.

[0007] Under high-rate conditions, when the migration of metal ions on the negative electrode side is hindered, metal precipitation and dendrite formation are more likely to occur. When dendrites pierce the separator, a short circuit can occur between the positive and negative electrode plates, thereby affecting the safety performance of the secondary battery. Furthermore, in the negative electrode current collector of the secondary battery in this application embodiment, on the one hand, the porous structure and electrolyte permeability facilitate the migration of metal ions, reducing the formation of metal dendrites; on the other hand, the porous structure helps provide more deposition sites for metal ions, allowing the negative electrode metal to be deposited more extensively within the porous structure, i.e., uniformly deposited on the porous structure, reducing the formation of lithium or sodium dendrites, which is beneficial for improving the cycle performance and safety performance of the secondary battery.

[0008] Porous membranes generally lack the conductivity required for negative electrode current collectors. The negative electrode current collector of this application provides conductivity to the formed current collector by coating a porous membrane.

[0009] Traditional compositions of conductive agents and binders have poor adhesion to porous membranes, easily leading to powder shedding and detachment, which significantly affects the cycle performance of the battery. This application addresses this by incorporating the aforementioned inorganic material into the coating. This inorganic material acts as a tenon and mortise joint, effectively anchoring the conductive agent, binder, and porous membrane, greatly increasing the adhesion between the coating and the porous membrane. Simultaneously, it enhances the thermal and mechanical stability of the current collector and reduces the film-forming properties of the binder. The coating in the secondary battery of this application exhibits superior coating performance. The current collector coated on the porous membrane possesses conductivity, a porous structure, electrolyte permeability, good mechanical strength, and thermal stability, resulting in a secondary battery with excellent rate performance.

[0010] In any embodiment, the metal oxide includes at least one of aluminum oxide, boehmite, magnesium oxide, iron oxide, zirconium oxide, titanium oxide, or zinc oxide.

[0011] When the inorganic material is of the type described above, it has better affinity with porous membranes, as well as better mechanical and thermal stability, which is beneficial for further improving the cycle performance and rate performance of secondary batteries.

[0012] In any embodiment, the adhesive comprises at least one of acrylic monomer homopolymers and / or copolymers, acrylate monomer homopolymers and / or copolymers, polyol monomer-polyisocyanate monomer copolymers, diamine monomer-dianhydride monomer copolymers, butadiene monomer-styrene monomer copolymers, styrene monomer-acrylate monomer copolymers, or derivatives thereof, or modified species thereof.

[0013] The binder provides adhesion to the various components of the coating.

[0014] In any embodiment, the adhesive comprises at least one of butadiene monomer unit-styrene monomer unit copolymer, styrene monomer unit-acrylate monomer unit copolymer, methyl acrylate monomer unit homopolymer, ethyl acrylate monomer unit homopolymer, butyl acrylate monomer unit homopolymer, isooctyl acrylate monomer unit homopolymer, acrylate monomer unit copolymer, or derivatives thereof, or modified species thereof.

[0015] The above-mentioned type of binder has lower surface tension, which is beneficial to further improve the adhesion of the coating to the porous membrane and further improve the cycle performance of the secondary battery.

[0016] In any embodiment, the conductive agent includes at least one of conductive carbon black, carbon nanotubes, graphene, superconducting carbon, acetylene black, Ketjen black, carbon dots, or carbon nanofibers.

[0017] Conductive agents can form a conductive network, providing conductivity to the current collector and facilitating electron transport.

[0018] In any embodiment, the inorganic matter contains 40%-55% by mass, based on the mass of the coating.

[0019] In any embodiment, the inorganic matter has a mass percentage of 45%-50%, calculated based on the mass of the coating.

[0020] When the content of inorganic matter in the coating is appropriate, the coating and porous membrane have better adhesion, which is beneficial to further improve the cycle performance of the secondary battery, further reduce the impact on the conductivity of the current collector, and further improve the rate performance of the secondary battery.

[0021] In any embodiment, the adhesive content is 20%-35% by mass, based on the mass of the coating.

[0022] In any embodiment, the adhesive content is 25%-30% by mass, based on the mass of the coating.

[0023] When the binder content in the coating is appropriate, it helps to further reduce the powder shedding of the coating, thereby further improving the adhesion between the coating and the porous membrane layer, and further improving the cycle performance of the secondary battery.

[0024] In any embodiment, the conductive agent has a mass percentage content of 5%-15%, calculated based on the mass of the coating.

[0025] In any embodiment, the conductive agent has a mass percentage content of 8%-12%, calculated based on the mass of the coating.

[0026] When the content of conductive agent in the coating is appropriate, it is beneficial to improve the conductivity of the negative electrode current collector, thereby further improving the rate performance of the secondary battery. Furthermore, the conductive agent has poor affinity with the porous film layer, and since it possesses active groups, excessive conductive agent may consume the deposited metal on the negative electrode. Therefore, an appropriate conductive agent content also helps to further improve the affinity between the coating and the porous film layer, reduce the consumption of the deposited metal on the negative electrode, and thus contribute to further improving the cycle performance and initial coulombic efficiency of the secondary battery.

[0027] In any embodiment, the coating further includes a dispersant.

[0028] In any embodiment, the dispersant includes at least one of carboxymethyl cellulose, methyl cellulose, sodium starch phosphate, sodium carboxymethyl cellulose, sodium polyacrylate, polyoxyethylene, or polyvinylpyrrolidone.

[0029] Adding a dispersant to the coating helps to better disperse inorganic and conductive agents, reduces their sedimentation and agglomeration, and helps the inorganic and conductive agents to further perform their respective functions.

[0030] In any embodiment, the mass percentage of the dispersant is 0%-10%, calculated based on the mass of the coating.

[0031] In any embodiment, the mass percentage of the dispersant is greater than 0%, calculated based on the mass of the coating.

[0032] In coatings, a suitable amount of dispersant helps to further improve their dispersing ability.

[0033] In any embodiment, the coating weight per unit area is 1-5 mg / cm². 2 .

[0034] In any embodiment, the coating weight per unit area is 2-3 mg / cm². 2 .

[0035] The coating has a suitable coating weight per unit area, which helps to coat it more evenly on the porous membrane, thereby further reducing the possibility of missed coating, providing better conductivity for the current collector, and further improving the rate performance of the secondary battery; furthermore, the suitable coating weight per unit area also helps to improve the cycle performance of the secondary battery.

[0036] In any embodiment, the porosity of the porous membrane layer is 30%-60%.

[0037] In any embodiment, the porosity of the porous membrane layer is 40%-50%.

[0038] An appropriate number of porous structures helps to further improve the transport rate of metal ions, thereby further improving the rate performance of the secondary battery; it also helps to provide a more suitable number of deposition sites, making the deposition of negative electrode metal more uniform, further reducing the formation of lithium or sodium dendrites, and thus further improving the cycle performance and safety performance of the secondary battery. Furthermore, an appropriate number of porous structures is more conducive to the effective application of coatings.

[0039] In any embodiment, the porous membrane layer includes at least one of porous polyolefin membrane, porous glass fiber, porous nonwoven fabric, porous polyimide membrane, porous polyvinylidene fluoride membrane, or porous polyterephthalate.

[0040] The porous membranes of the above type have a porous structure and good electrolyte permeability, which is beneficial to further improve the rate performance of the secondary battery of this application, reduce dendrite formation, and improve the safety performance of the secondary battery.

[0041] In any embodiment, the thickness of the porous membrane layer is 6-15 μm.

[0042] A porous membrane of suitable thickness is beneficial for providing a suitable transmission distance and for further improving the rate performance of secondary batteries.

[0043] In any embodiment, the coating is disposed on at least a portion of the surface of one side of the porous membrane layer.

[0044] In any embodiment, the coating is disposed on at least a portion of the surface on both sides of the porous membrane layer.

[0045] When the coating is disposed on at least a portion of the surface on one side of the porous membrane layer, the secondary battery of this application embodiment exhibits high rate performance. The coating being disposed on at least a portion of the surfaces on both sides of the porous membrane layer further enhances the rate performance of the secondary battery of this application embodiment.

[0046] In any embodiment, the secondary battery includes a metal battery without a negative electrode.

[0047] In any embodiment, the secondary battery includes a negative electrode-free sodium metal battery or a negative electrode-free lithium metal battery.

[0048] Generally, in metal-free batteries, the negative electrode is made of metal foil such as copper or aluminum foil. These foils lack a porous structure and have poor electrolyte wettability. Therefore, the negative electrode current collector in a metal-free battery may hinder the migration of metal ions, such as sodium or lithium ions, and increase their migration path, thus reducing the battery's rate performance. Furthermore, in this case, metal dendrites, such as sodium or lithium dendrites, are more likely to form. Applying the negative electrode current collector of the present application to metal-free batteries is more beneficial for improving the rate performance of the secondary battery; furthermore, it helps to better reduce dendrite formation.

[0049] In any embodiment, the negative electrode sheet includes a negative electrode film layer disposed on at least one side of the negative electrode current collector, the negative electrode film layer including a negative electrode active material, the negative electrode active material including at least one of artificial graphite, natural graphite, soft carbon, hard carbon or silicon-based materials.

[0050] The negative electrode current collector in the secondary battery of this application embodiment is beneficial to improving the rate performance of the ion battery.

[0051] A second aspect of this application provides a negative electrode current collector comprising a porous membrane layer and a coating disposed on at least a portion of the surface of at least one side of the porous membrane layer, the coating comprising an inorganic material, a conductive agent, and a binder, wherein the inorganic material comprises a metal oxide or silicon oxide.

[0052] As a component of the negative electrode current collector, the porous membrane layer in this application embodiment has a porous structure and is permeable to electrolyte. The porous structure and good electrolyte permeability help to shorten the migration path of metal ions such as sodium ions and lithium ions, increase the transport speed of metal ions, and improve the rate performance of the secondary battery.

[0053] Under high-rate conditions, when the migration of metal ions on the negative electrode side is hindered, metal precipitation and dendrite formation are more likely to occur. When dendrites pierce the separator, they can cause a short circuit between the positive and negative electrode plates, thereby affecting the safety performance of the secondary battery. Furthermore, in the negative electrode current collector of this application embodiment, on the one hand, the porous structure and electrolyte permeability facilitate the migration of metal ions, reducing the formation of metal dendrites; on the other hand, the porous structure helps provide more deposition sites for metal ions, allowing the negative electrode metal to be deposited more extensively within the porous structure, i.e., uniformly deposited on the porous structure, reducing the formation of lithium or sodium dendrites, which is beneficial for improving the cycle performance and safety performance of the secondary battery.

[0054] Porous membranes generally lack the conductivity required for negative electrode current collectors. This application provides conductivity to the current collector by coating a porous membrane. Traditional combinations of conductive agents and binders have poor adhesion to porous membranes, potentially leading to powder shedding and detachment, significantly impacting battery cycle performance. This application, by incorporating the aforementioned inorganic material into the coating, which acts as a tenon and mortise joint, effectively anchors the conductive agent, binder, and porous membrane, greatly increasing the adhesion between the coating and the porous membrane. Simultaneously, it enhances the thermal and mechanical stability of the current collector and reduces the film-forming properties of the binder. The coating of this embodiment exhibits superior coating performance; the current collector coated on the porous membrane possesses conductivity, a porous structure, electrolyte permeability, good mechanical strength, and thermal stability, resulting in a secondary battery with excellent rate performance.

[0055] In any embodiment, the metal oxide includes at least one of aluminum oxide, boehmite, magnesium oxide, iron oxide, zirconium oxide, titanium oxide, or zinc oxide.

[0056] When the inorganic material is of the type described above, it has better affinity with porous membranes, as well as better mechanical and thermal stability, which is beneficial for further improving the cycle performance and rate performance of secondary batteries.

[0057] In any embodiment, the adhesive comprises at least one of acrylic monomer homopolymers and / or copolymers, acrylate monomer homopolymers and / or copolymers, polyol monomer-polyisocyanate monomer copolymers, diamine monomer-dianhydride monomer copolymers, butadiene monomer-styrene monomer copolymers, styrene monomer-acrylate monomer copolymers, or derivatives thereof, or modified species thereof.

[0058] The binder provides adhesion to the various components of the coating.

[0059] In any embodiment, the conductive agent includes at least one of conductive carbon black, carbon nanotubes, graphene, superconducting carbon, acetylene black, Ketjen black, carbon dots, or carbon nanofibers.

[0060] Conductive agents can form a conductive network, providing conductivity to the current collector and facilitating electron transport.

[0061] In any embodiment, the inorganic matter contains 40%-55% by mass, based on the mass of the coating.

[0062] When the content of inorganic matter in the coating is appropriate, the coating and porous membrane have better adhesion, which is beneficial to further improve the cycle performance of the secondary battery, further reduce the impact on the conductivity of the current collector, and further improve the rate performance of the secondary battery.

[0063] In any embodiment, the adhesive content is 20%-35% by mass, based on the mass of the coating.

[0064] When the binder content in the coating is appropriate, it helps to further reduce the powder shedding of the coating, thereby further improving the adhesion between the coating and the porous membrane layer, and further improving the cycle performance of the secondary battery.

[0065] In any embodiment, the conductive agent has a mass percentage content of 5%-15%, calculated based on the mass of the coating.

[0066] When the content of conductive agent in the coating is appropriate, it is beneficial to improve the conductivity of the negative electrode current collector, thereby further improving the rate performance of the secondary battery. Furthermore, the conductive agent has poor affinity with the porous film layer, and since it possesses active groups, excessive conductive agent may consume the deposited metal on the negative electrode. Therefore, an appropriate conductive agent content also helps to further improve the affinity between the coating and the porous film layer, reduce the consumption of the deposited metal on the negative electrode, and thus contribute to further improving the cycle performance and initial coulombic efficiency of the secondary battery.

[0067] In any embodiment, the coating further includes a dispersant.

[0068] In any embodiment, the dispersant includes at least one of carboxymethyl cellulose, methyl cellulose, sodium starch phosphate, sodium carboxymethyl cellulose, sodium polyacrylate, polyoxyethylene, or polyvinylpyrrolidone.

[0069] Adding a dispersant to the coating helps to better disperse inorganic and conductive agents, reduces their sedimentation and agglomeration, and helps the inorganic and conductive agents to further perform their respective functions.

[0070] In any embodiment, the coating weight per unit area is 1-5 mg / cm². 2 .

[0071] The coating has a suitable coating weight per unit area, which helps to coat it more evenly on the porous membrane, thereby further reducing the possibility of missed coating, providing better conductivity for the current collector, and further improving the rate performance of the secondary battery; furthermore, the suitable coating weight per unit area also helps to improve the cycle performance of the secondary battery.

[0072] In any embodiment, the porosity of the porous membrane layer is 30%-60%.

[0073] An appropriate number of porous structures helps to further improve the transport rate of metal ions, thereby further improving the rate performance of the secondary battery; it also helps to provide a more suitable number of deposition sites, making the deposition of negative electrode metal more uniform, further reducing the formation of lithium or sodium dendrites, and thus further improving the cycle performance and safety performance of the secondary battery. Furthermore, an appropriate number of porous structures is more conducive to the effective application of coatings.

[0074] In any embodiment, the porous membrane layer includes at least one of porous polyolefin membrane, porous glass fiber, porous nonwoven fabric, porous polyimide membrane, porous polyvinylidene fluoride membrane, or porous polyterephthalate.

[0075] The porous membranes of the above type have a porous structure and good electrolyte permeability, which is beneficial to further improve the rate performance of the secondary battery of this application, reduce dendrite formation, and improve the safety performance of the secondary battery.

[0076] In any embodiment, the coating is disposed on at least a portion of the surface of one side of the porous membrane layer.

[0077] In any embodiment, the coating is disposed on at least a portion of the surface on both sides of the porous membrane layer.

[0078] When the coating is disposed on at least a portion of the surface on one side of the porous membrane layer, the secondary battery of this application embodiment exhibits high rate performance. The coating being disposed on at least a portion of the surfaces on both sides of the porous membrane layer further enhances the rate performance of the secondary battery of this application embodiment.

[0079] A third aspect of this application provides a method for preparing a negative electrode current collector, the method comprising at least the following steps:

[0080] The raw materials are dissolved in a solvent and stirred to form a coating slurry;

[0081] The coating slurry is applied to at least a portion of the surface of at least one side of the porous membrane to obtain the negative electrode current collector;

[0082] The raw materials include inorganic substances, binders, and conductive agents, wherein the inorganic substances include at least one of metal oxides or silicon oxide.

[0083] The above preparation method can be used to prepare the negative electrode current collector of this application.

[0084] In any embodiment, the metal oxide includes at least one of aluminum oxide, boehmite, magnesium oxide, iron oxide, zirconium oxide, titanium oxide, or zinc oxide.

[0085] When the inorganic material is of the type described above, it has better affinity with porous membranes, as well as better mechanical and thermal stability, which is beneficial for further improving the cycle performance and rate performance of secondary batteries.

[0086] In any embodiment, the adhesive comprises at least one of acrylic monomer homopolymers and / or copolymers, acrylate monomer homopolymers and / or copolymers, polyol monomer-polyisocyanate monomer copolymers, diamine monomer-dianhydride monomer copolymers, butadiene monomer-styrene monomer copolymers, styrene monomer-acrylate monomer copolymers, or derivatives thereof, or modified species thereof.

[0087] The binder provides adhesion to the various components of the coating.

[0088] In any embodiment, the inorganic matter has a mass percentage content of 40%-55%, calculated based on the mass of the raw material.

[0089] When the content of inorganic matter is appropriate, the coating slurry and porous membrane have better adhesion, which is beneficial to further improve the cycle performance of the secondary battery, further reduce the impact on the conductivity of the current collector, and further improve the rate performance of the secondary battery.

[0090] In any embodiment, the adhesive content is 20%-35% by mass, based on the mass of the raw materials.

[0091] When the binder content is appropriate, it helps to further reduce the powder shedding of the coating, thereby further improving the adhesion between the coating and the porous membrane layer, and further improving the cycle performance of the secondary battery.

[0092] In any embodiment, the conductive agent has a mass percentage content of 5%-15%, calculated based on the mass of the raw material.

[0093] When the content of the conductive agent is appropriate, it is beneficial to improve the conductivity of the negative electrode current collector, thereby further improving the rate performance of the secondary battery. Furthermore, the conductive agent has poor affinity with porous films, and because it possesses active groups, excessive conductive agent may consume the deposited metal on the negative electrode. Therefore, an appropriate conductive agent content also helps to further improve the affinity between the coating and the porous film, reduce the consumption of deposited metal on the negative electrode, and thus contribute to further improving the cycle performance and initial coulombic efficiency of the secondary battery.

[0094] In any embodiment, the raw material further includes a dispersant.

[0095] Adding a dispersant to the coating slurry helps to better disperse inorganic and conductive agents, reduces their sedimentation and agglomeration, and helps the inorganic and conductive agents to further exert their respective functions.

[0096] A fourth aspect of this application provides an electrical device comprising a secondary battery as described in this application or a negative current collector as described in this application.

[0097] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0098] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0099] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0100] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0101] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0102] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0103] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0104] Explanation of reference numerals in the attached figures:

[0105] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0106] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode active material, its manufacturing method, positive electrode sheet, secondary battery, battery module, battery pack, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0107] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated 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.

[0108] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0109] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0110] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0111] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0112] Unless otherwise specified, the term "or" is inclusive in this application. 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 any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0113] With the increasing application of rechargeable batteries, the requirements for their electrical performance, such as rate performance, are gradually increasing. The negative electrode current collector in these batteries is typically made of metal foil, such as copper foil. However, this type of current collector may hinder the migration of metal ions and increase their migration paths, which is detrimental to improving the rate performance of the rechargeable battery.

[0114] [Rechargeable Battery]

[0115] Based on this, this application provides a secondary battery, which includes a positive electrode, a negative electrode, a separator disposed between the negative electrode and the positive electrode, and an electrolyte. The negative electrode includes a negative current collector, which includes a porous film layer and a coating disposed on at least a portion of the surface of at least one side of the porous film layer. The coating includes an inorganic substance, a conductive agent, and a binder. The inorganic substance includes at least one of a metal oxide or silicon oxide.

[0116] When used in this document, the term "metal oxide" refers to a binary compound consisting of oxygen and a metal.

[0117] The structure and inorganic composition of the negative electrode current collector can be measured using methods and equipment known in the art. As an example, a battery is disassembled to obtain the negative electrode sheet. If a negative electrode film layer is present on the negative electrode sheet, this film layer is peeled off to obtain the negative electrode current collector. If no negative electrode film layer is present on the negative electrode sheet, the following operation can be performed directly: the negative electrode current collector is cut into a cross-section using an electron beam or other similar means (e.g., a cutter). The cross-section can be directly observed using a scanning electron microscope, revealing at least two layers of the porous film layer and coating of the negative electrode current collector (specifically, a two-layer structure consisting of a porous film layer and a coating layer on one side of the porous film layer; a three-layer structure consisting of a porous film layer and coating layers on both sides of the porous film layer). Further, the obtained negative electrode current collector is subjected to a powder scraping operation to obtain coating powder. The coating powder is calcined in air or oxygen at a certain temperature (e.g., 500°C) until the powder weight no longer changes; the remaining powder is inorganic. The remaining material can be tested using an X-ray diffractometer and compared with standard spectra to confirm the composition of the inorganic substances. Simultaneously, X-ray fluorescence spectroscopy (XRF) or inductively coupled plasma (ICP) analysis can be performed on the remaining material to analyze its elemental composition, cross-validating the results with the X-ray diffractometer findings to further determine the specific composition of the inorganic substances.

[0118] In some implementations, the porous membrane allows the electrolyte to pass through from one side to the other along the thickness of the porous membrane.

[0119] As a component of the negative electrode current collector, the porous membrane layer in the secondary battery of this application embodiment has a porous structure and is permeable to electrolyte. The porous structure and good electrolyte permeability help to shorten the migration path of metal ions such as sodium ions and lithium ions, improve the transport speed of metal ions, and improve the rate performance of the secondary battery.

[0120] Under high-rate conditions, when the migration of metal ions on the negative electrode side is hindered, metal precipitation and dendrite formation are more likely to occur. When dendrites pierce the separator, they can cause a short circuit between the positive and negative electrode plates, thereby affecting the safety performance of the secondary battery. Furthermore, in the negative electrode current collector of the secondary battery in this application embodiment, on the one hand, the porous structure and electrolyte permeability of the negative electrode current collector are conducive to the migration of metal ions, which can reduce the formation of metal dendrites; on the other hand, the porous structure helps to provide more deposition sites for metal ions, allowing the negative electrode metal to be deposited to a greater extent in the porous structure, i.e., uniformly deposited on the porous structure, reducing the formation of lithium or sodium dendrites, which is beneficial to improving the cycle performance and safety performance of the secondary battery.

[0121] Porous membranes generally lack the conductivity required for negative electrode current collectors. The secondary battery of this application provides conductivity to the current collector by coating the porous membrane. Traditional compositions of conductive agents and binders have poor adhesion to porous membranes, potentially leading to powder shedding and detachment, significantly impacting battery cycle performance. This application, by adding inorganic materials to the coating, which act as interlocking elements, can effectively connect the conductive agent, binder, and porous membrane, greatly increasing the adhesion between the coating and the porous membrane. It also enhances the thermal and mechanical stability of the current collector and reduces the film-forming properties of the binder. The coating in the secondary battery of this application exhibits good adhesion to the porous membrane. The current collector coated on the porous membrane possesses conductivity, a porous structure, electrolyte permeability, good mechanical strength, and thermal stability, resulting in a secondary battery with excellent rate performance.

[0122] In some embodiments, the metal oxide includes at least one of aluminum oxide, boehmite, magnesium oxide, iron oxide, zirconium oxide, titanium oxide, or zinc oxide.

[0123] In some embodiments, the metal oxide includes at least one of aluminum oxide, boehmite, or titanium oxide.

[0124] When the inorganic material is of the type described above, it has better affinity with porous membranes, as well as better mechanical and thermal stability, which is beneficial for further improving the cycle performance and rate performance of secondary batteries.

[0125] In some embodiments, the binder includes at least one of acrylic monomer homopolymers and / or copolymers, acrylate monomer homopolymers and / or copolymers, polyol monomer-polyisocyanate monomer copolymers, diamine monomer-dianhydride monomer copolymers, butadiene monomer-styrene monomer copolymers, styrene monomer-acrylate monomer copolymers, or derivatives thereof, or modified species thereof.

[0126] When used in this document, the term "homogeneous polymer" refers to a polymer formed by the polymerization of a single monomer.

[0127] As used herein, the term "copolymer" refers to a polymer formed by the polymerization of two or more monomers, comprising two or more monomer units. Based on the arrangement of the monomers in the copolymer molecular chain, copolymers can be classified as random copolymers, alternating copolymers, block copolymers, and graft copolymers.

[0128] When used in this document, the term "derivative" refers to a substance derived from which a group on the original molecule, such as a hydrogen atom, is replaced by another group.

[0129] When used in this article, the term "modified substance" refers to a substance formed by further modifying the original molecule through various means, such as physical or chemical means, to change a certain physical or chemical property.

[0130] In some embodiments, the binder includes at least one of acrylic monomer homopolymers and / or copolymers, acrylate monomer homopolymers and / or copolymers, butadiene monomer-styrene monomer copolymers, styrene monomer-acrylate monomer copolymers, or derivatives thereof, or modified species thereof.

[0131] The binder provides adhesion to the various components of the coating.

[0132] In some embodiments, the binder includes at least one of butadiene monomer unit-styrene monomer unit copolymer, styrene monomer unit-acrylate monomer unit copolymer, methyl acrylate monomer unit homopolymer, ethyl acrylate monomer unit homopolymer, butyl acrylate monomer unit homopolymer, isooctyl acrylate monomer unit homopolymer, acrylate monomer unit copolymer, or derivatives thereof, or modified species thereof.

[0133] In this article, the term "butadiene monomer unit-styrene monomer unit copolymer" refers to a copolymer formed by butadiene monomer and styrene monomer.

[0134] In this document, the term "styrene monomer unit-acrylate monomer unit copolymer" refers to a copolymer formed by styrene monomer and acrylate monomer, wherein the acrylate may include at least one of methyl acrylate, ethyl acrylate, butyl acrylate or isooctyl acrylate.

[0135] In this paper, the term "methyl acrylate monomer homopolymer" refers to a homopolymer obtained by free radical polymerization of methyl acrylate monomers. Ethyl acrylate monomer homopolymer, butyl acrylate monomer homopolymer, and isooctyl acrylate monomer homopolymer have similar definitions.

[0136] In some embodiments, the binder includes at least one of butadiene monomer unit-styrene monomer unit copolymer, styrene monomer unit-acrylate monomer unit copolymer, ethyl acrylate monomer unit homopolymer, or derivatives thereof, or modified species thereof.

[0137] In some embodiments, the styrene monomer unit-acrylate monomer unit copolymer includes at least one of the following: styrene monomer unit-methyl acrylate monomer unit copolymer, styrene monomer unit-ethyl acrylate monomer unit copolymer, styrene monomer unit-butyl acrylate monomer unit copolymer, and styrene monomer unit-isooctyl acrylate monomer unit copolymer.

[0138] In some embodiments, the butadiene monomer unit-styrene monomer unit copolymer has a copolymer molar ratio of butadiene monomer unit to styrene monomer unit of (7-3):(3-7).

[0139] In some embodiments, the copolymer molar ratio of butadiene monomer units to styrene monomer units in the butadiene monomer unit-styrene monomer unit copolymer can be 7:3, 6:4, 5:5, 4:6, 3:7, or a range of any two of the above copolymer molar ratios or a value within that range.

[0140] In some embodiments, the copolymerization molar ratio of styrene monomer unit to acrylate monomer unit in the styrene monomer unit-acrylate monomer unit copolymer is (3-5):(7-5).

[0141] In some embodiments, in the styrene monomer unit-acrylate monomer unit copolymer, the copolymer molar ratio of styrene monomer and acrylate monomer can be 3:7, 4:6, 5:5, or a range of any two of the above copolymer molar ratios, or a value within that range.

[0142] The above-mentioned type of binder has lower surface tension, which is beneficial to further improve the adhesion of the coating to the porous film.

[0143] In some embodiments, the conductive agent includes at least one of conductive carbon black, carbon nanotubes, graphene, superconducting carbon, acetylene black, Ketjen black, carbon dots, or carbon nanofibers.

[0144] Conductive agents can form a conductive network, providing conductivity to the current collector and facilitating electron transport.

[0145] In some implementations, the inorganic content is 40%-55% by mass, calculated based on the mass of the coating.

[0146] In the coating, the mass of the inorganic material can be measured using methods and equipment known in the art. A specific example is as follows: Disassemble a battery to obtain the negative electrode. If the negative electrode has a negative electrode film layer, peel off the negative electrode film layer to obtain the negative electrode current collector. If the negative electrode does not have a negative electrode film layer, directly perform the following operation: scrape off the obtained negative electrode current collector to obtain coating powder, and weigh its mass as M1. Calcine the coating powder in air or oxygen at a certain temperature (e.g., 500°C) until the powder weight no longer changes. The remaining powder is the inorganic material, and its mass is weighed as M0. The mass percentage of the inorganic material = (M0 / M1) × 100%.

[0147] In some embodiments, the mass percentage of inorganic matter can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, or 55%, or a range of any two of the above mass percentages, or a value within that range.

[0148] In some implementations, the inorganic content is 45%-50% by mass, calculated based on the mass of the coating.

[0149] When the content of inorganic matter in the coating is appropriate, the coating and porous membrane have better adhesion, which is beneficial to further improve the cycle performance of the secondary battery, further reduce the impact on the conductivity of the current collector, and thus further improve the rate performance of the secondary battery.

[0150] In some implementations, the adhesive content is 20%-35% by mass, calculated based on the quality of the coating.

[0151] In some embodiments, the mass percentage of the adhesive can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, or 35%, or a range of any two of the above mass percentages, or a value within that range.

[0152] In some implementations, the adhesive content is 25%-30% by mass, calculated based on the quality of the coating.

[0153] When the binder content in the coating is appropriate, it helps to further reduce the powder shedding of the coating, thereby further improving the adhesion between the coating and the porous membrane layer and improving the cycle performance of the secondary battery.

[0154] In some implementations, the mass percentage of the conductive agent is 5%-15%, calculated based on the mass of the coating.

[0155] In some embodiments, the mass percentage of the conductive agent can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%, or a range of any two of the above mass percentages, or a value within that range, based on the mass percentage of the coating.

[0156] In some implementations, the conductive agent content is 8%-12% by mass, calculated based on the quality of the coating.

[0157] When the content of conductive agent in the coating is appropriate, it is beneficial to further improve the conductivity of the negative electrode current collector, thereby further improving the rate performance of the secondary battery. Conductive agents have poor affinity with porous films, and because they possess active groups, excessive amounts may consume the deposited metal on the negative electrode. Therefore, an appropriate conductive agent content also helps to further improve the affinity between the coating and the porous film, reduce the consumption of deposited metal on the negative electrode, and thus contribute to further improving the cycle performance and initial coulombic efficiency of the secondary battery.

[0158] In some embodiments, the coating also includes a dispersant.

[0159] In some embodiments, the dispersant includes at least one of carboxymethyl cellulose, methyl cellulose, sodium starch phosphate, sodium carboxymethyl cellulose, sodium polyacrylate, polyoxyethylene, or polyvinylpyrrolidone.

[0160] In some embodiments, the dispersant includes at least one of carboxymethyl cellulose or sodium carboxymethyl cellulose.

[0161] Adding a dispersant to the coating helps to better disperse inorganic and conductive agents, reduces their sedimentation and agglomeration, and helps the inorganic and conductive agents to further perform their respective functions.

[0162] In some implementations, the mass percentage of the dispersant is 0%-10%, calculated based on the quality of the coating.

[0163] In some embodiments, the mass percentage of the dispersant can be 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range of any two of the above mass percentages, or a value within that range, based on the mass percentage of the coating.

[0164] In some implementations, the mass percentage of the dispersant is greater than 0%, with the coating mass as the calculation basis.

[0165] In coatings, a suitable amount of dispersant helps to further improve the dispersibility of the coating.

[0166] In some embodiments, the coating weight per unit area is 1-5 mg / cm². 2 .

[0167] In some embodiments, the coating weight per unit area can be 1 mg / cm². 2 1.5 mg / cm 2 2mg / cm 2 2.5 mg / cm 2 3mg / cm 2 3.5 mg / cm 2 4mg / cm 2 4.5 mg / cm 2 5mg / cm 2 , or a range consisting of any two of the above mass percentage contents, or a value within the range of contents.

[0168] In some embodiments, the coating weight per unit area is 2-3 mg / cm². 2 .

[0169] The coating has a suitable coating weight per unit area, which helps to coat it more evenly on the porous membrane, thereby further reducing the possibility of missed coating, providing better conductivity for the current collector, and further improving the rate performance of the secondary battery; furthermore, the suitable coating weight per unit area also helps to improve the cycle performance of the secondary battery.

[0170] In some embodiments, the porosity of the porous membrane is 30%-60%.

[0171] When used in this document, the term "porosity" refers to the percentage of pore volume in a material to the total volume of the material in its natural state.

[0172] In some embodiments, the porosity of the porous membrane layer can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, or a range of any two of the above porosities, or a value within that range.

[0173] In some embodiments, the porosity of the porous membrane layer is 40%-50%.

[0174] The porosity of porous membranes can be measured using methods and equipment known in the art. A specific example involves placing the porous membrane sample to be tested in a mercury porosimeter, ensuring a good seal between the sample and the instrument; injecting mercury into the instrument and gradually increasing the mercury pressure; observing the volume change of the porous membrane sample and recording the volume values ​​at different pressures; plotting a pressure-volume curve based on the relationship between volume change and mercury pressure; and calculating the porosity of the porous membrane based on the pressure-volume curve.

[0175] An appropriate number of porous structures helps to further improve the transport rate of metal ions, thereby further improving the rate performance of the secondary battery; it also helps to provide a more suitable number of deposition sites, making the deposition of negative electrode metal more uniform, further reducing the formation of lithium or sodium dendrites, and thus further improving the cycle performance and safety performance of the secondary battery. Furthermore, an appropriate number of porous structures is more conducive to the effective application of coatings.

[0176] In some embodiments, the porous membrane layer includes at least one of porous polyolefin membrane, porous glass fiber, porous nonwoven fabric, porous polyimide membrane, porous polyvinylidene fluoride membrane, or porous polyterephthalate.

[0177] In some embodiments, the porous membrane layer can be a single-layer thin film or a multi-layer composite thin film. When the porous membrane layer is a multi-layer composite thin film, the materials of each layer can be the same or different.

[0178] The porous membranes of the above type have a porous structure and good electrolyte permeability, which is beneficial to further improve the rate performance of the secondary battery of this application, reduce dendrite formation, improve the cycle performance of the secondary battery, and even the safety performance.

[0179] In some implementations, the thickness of the porous membrane layer is 6-15 μm.

[0180] In some embodiments, the thickness of the porous membrane is 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or a range of any two of the above thicknesses or a value within that range.

[0181] The thickness of the porous film can be measured using methods and equipment known in the art. Specifically, a battery can be disassembled to obtain the negative electrode. If a negative electrode film is present on the negative electrode, it can be peeled off to obtain the negative current collector. If no negative electrode film is present on the negative electrode, the following steps can be performed directly: the negative current collector can be cleaned with a suitable solvent (e.g., water) to remove the coating and obtain the porous film. The thickness of the porous film can then be measured using a micrometer.

[0182] A porous membrane of suitable thickness is beneficial for providing a suitable transmission distance and for further improving the rate performance of secondary batteries.

[0183] In some embodiments, the coating is disposed on at least a portion of the surface of one side of the porous membrane layer.

[0184] In some embodiments, the coating is applied to the entire surface of one side of the porous membrane layer.

[0185] In some implementations, the coating is disposed on the side away from the release membrane.

[0186] In some implementations, the coating is applied to the side close to the release membrane.

[0187] In some embodiments, the coating is disposed on at least a portion of the surface on both sides of the porous membrane layer.

[0188] In some embodiments, the coating is applied to all surfaces on both sides of the porous membrane layer.

[0189] When the coating is disposed on at least a portion of the surface on one side of the porous membrane layer, the secondary battery of this application embodiment exhibits high rate performance. The coating being disposed on at least a portion of the surfaces on both sides of the porous membrane layer further enhances the rate performance of the secondary battery of this application embodiment.

[0190] In some implementations, the secondary battery includes a metal battery without a negative electrode.

[0191] In some implementations, the secondary battery includes a negative electrode-free sodium metal battery or a negative electrode-free lithium metal battery.

[0192] In this document, the term "metal-free battery" refers to a battery in which no negative electrode active material layer is actively deposited on the negative electrode side during the battery manufacturing process. For example, during battery manufacturing, no negative electrode active material layer is formed at the negative electrode through processes such as coating or deposition of sodium, lithium, or carbonaceous active materials. During the first charge, metal ions, such as sodium or lithium ions, gain electrons on the anode side and deposit metals, such as sodium or lithium, on the current collector surface to form a metal phase, such as a sodium metal phase or a lithium metal phase. During discharge, the metals, such as sodium or lithium, can be converted back into metal ions, such as sodium or lithium ions, and return to the positive electrode, achieving cyclic charging and discharging.

[0193] Generally, in metal-free batteries, the negative electrode current collector is made of metal foil such as copper foil. This type of metal foil lacks a porous structure and has poor electrolyte wettability. Therefore, the negative electrode current collector in a metal-free battery may hinder the migration of metal ions, such as sodium or lithium ions, and increase their migration path, thus reducing the battery's rate performance. Furthermore, in this case, metal dendrites, such as sodium or lithium dendrites, are more likely to form. Applying the negative electrode current collector of the present application embodiment to a metal-free battery is more beneficial for improving the rate performance of the secondary battery; furthermore, it helps to better reduce dendrite formation.

[0194] In some implementations, the secondary battery includes an ion battery.

[0195] In some implementations, the secondary battery includes a lithium-ion battery or a sodium-ion battery.

[0196] In some embodiments, the negative electrode sheet includes a negative electrode film layer disposed on at least one side of the negative electrode current collector, the negative electrode film layer including a negative electrode active material, the negative electrode active material including at least one of artificial graphite, natural graphite, soft carbon, hard carbon or silicon-based materials.

[0197] In some implementations, in an ion battery, as an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0198] The negative electrode current collector in the secondary battery of this application embodiment is beneficial to improving the rate performance of the ion battery.

[0199] In some embodiments, the negative electrode film layer includes 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).

[0200] In some embodiments, the negative electrode film layer includes a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0201] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0202] In some embodiments, the negative electrode sheet of an ion battery can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector of this application, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0203] [Negative electrode current collector]

[0204] This application provides a negative electrode current collector, which includes a porous film layer and a coating disposed on at least a portion of the surface of at least one side of the porous film layer. The coating includes an inorganic material, a conductive agent, and a binder, wherein the inorganic material includes at least one of a metal oxide or silicon oxide. In some embodiments, the negative electrode current collector includes a porous film layer and a coating disposed on at least a portion of the surface of one side of the porous film layer.

[0205] As a component of the negative electrode current collector, the porous membrane layer in this application embodiment has a porous structure and is permeable to electrolyte. The porous structure and good electrolyte permeability help to shorten the migration path of metal ions such as sodium ions and lithium ions, increase the transport speed of metal ions, and improve the rate performance of the secondary battery.

[0206] Under high-rate conditions, when the migration of metal ions on the negative electrode side is hindered, metal precipitation and dendrite formation are more likely to occur. When dendrites pierce the separator, a short circuit can occur between the positive and negative electrode plates, thereby affecting the safety performance of the secondary battery. Furthermore, in the negative electrode current collector of this application embodiment, on the one hand, the porous structure and electrolyte permeability of the negative electrode current collector facilitate the migration of metal ions and reduce the formation of metal dendrites; on the other hand, the porous structure helps provide more deposition sites for metal ions, allowing the negative electrode metal to be deposited more extensively within the porous structure, i.e., uniformly deposited on the porous structure, reducing the formation of lithium or sodium dendrites, which is beneficial for improving the cycle performance and safety performance of the secondary battery.

[0207] Porous membranes generally lack the conductivity required for negative electrode current collectors. This application provides conductivity to the formed current collector by coating a porous membrane.

[0208] Traditional compositions of conductive agents and binders have poor adhesion to porous membranes, potentially leading to powder shedding and detachment, significantly impacting battery cycle performance. This application addresses this by incorporating inorganic materials into the coating. These inorganic materials act as interlocking components, connecting the conductive agent, binder, and porous membrane, greatly increasing the adhesion between the coating and the porous membrane. Simultaneously, it enhances the thermal and mechanical stability of the current collector and reduces the film-forming properties of the binder. The coating of this application exhibits superior coating performance. The current collector coated on the porous membrane possesses conductivity, a porous structure, electrolyte permeability, good mechanical strength, and thermal stability, resulting in a secondary battery with excellent rate performance.

[0209] In some embodiments, the metal oxide includes at least one of aluminum oxide, boehmite, magnesium oxide, iron oxide, zirconium oxide, titanium oxide, or zinc oxide.

[0210] In some embodiments, the metal oxide includes at least one of aluminum oxide, boehmite, or titanium oxide.

[0211] When the inorganic material is of the type described above, it has better affinity with porous membranes, as well as better mechanical and thermal stability, which is beneficial for further improving the cycle performance and rate performance of secondary batteries.

[0212] In some embodiments, the binder includes at least one of acrylic monomer homopolymers and / or copolymers, acrylate monomer homopolymers and / or copolymers, polyol monomer-polyisocyanate monomer copolymers, diamine monomer-dianhydride monomer copolymers, butadiene monomer-styrene monomer copolymers, styrene monomer-acrylate monomer copolymers, or derivatives thereof, or modified species thereof.

[0213] In some embodiments, the binder includes at least one of acrylic monomer homopolymers and / or copolymers, acrylate monomer homopolymers and / or copolymers, butadiene monomer-styrene monomer copolymers, styrene monomer-acrylate monomer copolymers, or derivatives thereof, or modified species thereof.

[0214] The binder provides adhesion to the various components of the coating.

[0215] In some embodiments, the binder includes at least one of butadiene monomer unit-styrene monomer unit copolymer, styrene monomer unit-acrylate monomer unit copolymer, methyl acrylate monomer unit homopolymer, ethyl acrylate monomer unit homopolymer, butyl acrylate monomer unit homopolymer, isooctyl acrylate monomer unit homopolymer, acrylate monomer unit copolymer, or derivatives thereof, or modified species thereof.

[0216] In some embodiments, the binder includes at least one of butadiene monomer unit-styrene monomer unit copolymer, styrene monomer unit-acrylate monomer unit copolymer, ethyl acrylate monomer unit homopolymer, or derivatives thereof, or modified species thereof.

[0217] In some embodiments, the styrene monomer unit-acrylate monomer unit copolymer includes at least one of the following: styrene monomer unit-methyl acrylate monomer unit copolymer, styrene monomer unit-ethyl acrylate monomer unit copolymer, styrene monomer unit-butyl acrylate monomer unit copolymer, and styrene monomer unit-isooctyl acrylate monomer unit copolymer.

[0218] In some embodiments, the butadiene monomer unit-styrene monomer unit copolymer has a copolymer molar ratio of butadiene monomer unit to styrene monomer unit of (7-3):(3-7).

[0219] In some embodiments, the copolymer molar ratio of butadiene monomer units to styrene monomer units in the butadiene monomer unit-styrene monomer unit copolymer can be 7:3, 6:4, 5:5, 4:6, 3:7, or a range of any two of the above copolymer molar ratios or a value within that range.

[0220] In some embodiments, the copolymerization molar ratio of styrene monomer unit to acrylate monomer unit in the styrene monomer unit-acrylate monomer unit copolymer is (3-5):(7-5).

[0221] In some embodiments, in the styrene monomer unit-acrylate monomer unit copolymer, the copolymer molar ratio of styrene monomer and acrylate monomer can be 3:7, 4:6, 5:5, or a range of any two of the above copolymer molar ratios, or a value within that range.

[0222] The above-mentioned type of binder has lower surface tension, which is beneficial to further improve the adhesion of the coating to the porous film.

[0223] In some embodiments, the conductive agent includes at least one of conductive carbon black, carbon nanotubes, graphene, superconducting carbon, acetylene black, Ketjen black, carbon dots, or carbon nanofibers.

[0224] Conductive agents can form a conductive network, providing conductivity to the current collector and facilitating electron transport.

[0225] In some implementations, the inorganic content is 40%-55% by mass, calculated based on the mass of the coating.

[0226] In some embodiments, the mass percentage of inorganic matter can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, or 55%, or a range of any two of the above mass percentages, or a value within that range.

[0227] In some implementations, the inorganic content is 45%-50% by mass, calculated based on the mass of the coating.

[0228] When the content of inorganic matter in the coating is appropriate, the coating and porous membrane have better adhesion, which is beneficial to further improve the cycle performance of the secondary battery, further reduce the impact on the conductivity of the current collector, and thus further improve the rate performance of the secondary battery.

[0229] In some implementations, the adhesive content is 20%-35% by mass, calculated based on the quality of the coating.

[0230] In some embodiments, the mass percentage of the adhesive can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, or 35%, or a range of any two of the above mass percentages, or a value within that range.

[0231] In some implementations, the adhesive content is 25%-30% by mass, calculated based on the quality of the coating.

[0232] When the binder content in the coating is appropriate, it helps to further reduce the powder shedding of the coating, thereby further improving the adhesion between the coating and the porous membrane layer and improving the cycle performance of the secondary battery.

[0233] In some implementations, the mass percentage of the conductive agent is 5%-15%, calculated based on the mass of the coating.

[0234] In some embodiments, the mass percentage of the conductive agent can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%, or a range of any two of the above mass percentages, or a value within that range, based on the mass percentage of the coating.

[0235] In some implementations, the conductive agent content is 8%-12% by mass, calculated based on the quality of the coating.

[0236] When the content of conductive agent in the coating is appropriate, it is beneficial to further improve the conductivity of the negative electrode current collector, thereby further improving the rate performance of the secondary battery. Conductive agents have poor affinity with porous films, and because they possess active groups, excessive amounts may consume the deposited metal on the negative electrode. Therefore, an appropriate conductive agent content also helps to further improve the affinity between the coating and the porous film, reduce the consumption of deposited metal on the negative electrode, and thus contribute to further improving the cycle performance and initial coulombic efficiency of the secondary battery.

[0237] In some embodiments, the coating also includes a dispersant.

[0238] In some embodiments, the dispersant includes at least one of carboxymethyl cellulose, methyl cellulose, sodium starch phosphate, sodium carboxymethyl cellulose, sodium polyacrylate, polyoxyethylene, or polyvinylpyrrolidone.

[0239] In some embodiments, the dispersant includes at least one of carboxymethyl cellulose or sodium carboxymethyl cellulose.

[0240] Adding a dispersant to the coating helps to better disperse inorganic and conductive agents, reduces their sedimentation and agglomeration, and helps the inorganic and conductive agents to further perform their respective functions.

[0241] In some implementations, the mass percentage of the dispersant is 0%-10%, calculated based on the quality of the coating.

[0242] In some embodiments, the mass percentage of the dispersant can be 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range of any two of the above mass percentages, or a value within that range, based on the mass percentage of the coating.

[0243] In some implementations, the mass percentage of the dispersant is greater than 0%, with the coating mass as the calculation basis.

[0244] In coatings, a suitable amount of dispersant helps to further improve the dispersibility of the coating.

[0245] In some embodiments, the coating weight per unit area is 1-5 mg / cm². 2 .

[0246] In some embodiments, the coating weight per unit area can be 1 mg / cm². 2 1.5 mg / cm 2 2mg / cm 2 2.5 mg / cm 2 3mg / cm 2 3.5 mg / cm 24mg / cm 2 4.5 mg / cm 2 5mg / cm 2 , or a range consisting of any two of the above mass percentage contents, or a value within the range of contents.

[0247] In some embodiments, the coating weight per unit area is 2-3 mg / cm². 2 .

[0248] The coating has a suitable coating weight per unit area, which helps to coat it more evenly on the porous membrane, thereby further reducing the possibility of missed coating, providing better conductivity for the current collector, and further improving the rate performance of the secondary battery; furthermore, the suitable coating weight per unit area also helps to improve the cycle performance of the secondary battery.

[0249] In some embodiments, the porosity of the porous membrane is 30%-60%.

[0250] In some embodiments, the porosity of the porous membrane layer can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, or a range of any two of the above porosities, or a value within that range.

[0251] In some embodiments, the porosity of the porous membrane layer is 40%-50%.

[0252] An appropriate number of porous structures helps to further improve the transport rate of metal ions, thereby further improving the rate performance of the secondary battery; it also helps to provide a more suitable number of deposition sites, making the deposition of negative electrode metal more uniform, further reducing the formation of lithium or sodium dendrites, and thus further improving the cycle performance and safety performance of the secondary battery. Furthermore, an appropriate number of porous structures is more conducive to the effective application of coatings.

[0253] In some embodiments, the porous membrane layer includes at least one of porous polyolefin membrane, porous glass fiber, porous nonwoven fabric, porous polyimide membrane, porous polyvinylidene fluoride membrane, or porous polyterephthalate.

[0254] In some embodiments, the porous membrane layer can be a single-layer thin film or a multi-layer composite thin film. When the porous membrane layer is a multi-layer composite thin film, the materials of each layer can be the same or different.

[0255] The porous membranes of the above type have a porous structure and good electrolyte permeability, which is beneficial to further improve the rate performance of the secondary battery of this application, reduce dendrite formation, improve the cycle performance of the secondary battery, and even the safety performance.

[0256] In some implementations, the thickness of the porous membrane layer is 6-15 μm.

[0257] In some embodiments, the thickness of the porous membrane is 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or a range of any two of the above thicknesses or a value within that range.

[0258] A porous membrane of suitable thickness is beneficial for providing a suitable transmission distance and for further improving the rate performance of secondary batteries.

[0259] In some embodiments, the coating is disposed on at least a portion of the surface of one side of the porous membrane layer.

[0260] In some embodiments, the coating is applied to the entire surface of one side of the porous membrane layer.

[0261] In some embodiments, the coating is disposed on at least a portion of the surface on both sides of the porous membrane layer.

[0262] In some embodiments, the coating is applied to all surfaces on both sides of the porous membrane layer.

[0263] When the coating is disposed on at least a portion of the surface on one side of the porous membrane layer, the secondary battery of this application embodiment exhibits high rate performance. Disposing the coating on at least a portion of the surfaces on both sides of the porous membrane layer further enhances the rate performance of the secondary battery of this application embodiment.

[0264] [Preparation method of negative electrode current collector]

[0265] This application provides a method for preparing a negative electrode current collector, the method comprising at least the following steps:

[0266] The raw materials are dissolved in a solvent and stirred to form a coating slurry;

[0267] A coating slurry is applied to at least a portion of the surface of at least one side of a porous membrane to obtain a negative electrode current collector;

[0268] The raw materials include inorganic substances, binders, and conductive agents, and the inorganic substances include at least one of metal oxides or silicon oxide.

[0269] In some embodiments, the preparation method of this application can prepare the negative electrode current collector of this application.

[0270] In some embodiments, the coating slurry has a coating weight per unit area of ​​1-5 mg / cm². 2 .

[0271] In some embodiments, a coating slurry is applied to at least a portion of the surface of one side of the porous membrane layer.

[0272] In some embodiments, the coating slurry is applied to the entire surface of one side of the porous membrane layer.

[0273] In some embodiments, a coating slurry is applied to at least a portion of the surface on both sides of the porous membrane layer.

[0274] In some embodiments, the coating slurry is applied to all surfaces on both sides of the porous membrane layer.

[0275] In some implementations, the solvent includes a water-soluble solvent.

[0276] In some implementations, the solvent includes water.

[0277] In some embodiments, the porous membrane includes at least one of porous polyolefin membrane, porous glass fiber, porous nonwoven fabric, porous polyimide membrane, porous polyvinylidene fluoride membrane, or porous polyterephthalate.

[0278] The above preparation method can be used to prepare the negative electrode current collector of this application.

[0279] In some embodiments, the metal oxide includes at least one of aluminum oxide, boehmite, magnesium oxide, iron oxide, zirconium oxide, titanium oxide, or zinc oxide.

[0280] When the inorganic material is of the type described above, it has better affinity with porous membranes, as well as better mechanical and thermal stability, which is beneficial for further improving the cycle performance and rate performance of secondary batteries.

[0281] In some embodiments, the binder includes at least one of acrylic monomer homopolymers and / or copolymers, acrylate monomer homopolymers and / or copolymers, polyol monomer-polyisocyanate monomer copolymers, diamine monomer-dianhydride monomer copolymers, butadiene monomer-styrene monomer copolymers, styrene monomer-acrylate monomer copolymers, or derivatives thereof, or modified species thereof.

[0282] In some embodiments, the adhesive comprises at least one of butadiene monomer unit-styrene monomer unit copolymer, styrene monomer unit-acrylate monomer unit copolymer, methyl acrylate monomer unit homopolymer, ethyl acrylate monomer unit homopolymer, butyl acrylate monomer unit homopolymer, isooctyl acrylate monomer unit homopolymer, acrylate monomer unit copolymer, or derivatives thereof, or modified species thereof.

[0283] The binder provides adhesion to the various components of the coating.

[0284] In some implementations, the inorganic content is 40%-55% by mass, calculated based on the mass of the raw materials.

[0285] When the content of inorganic matter is appropriate, the coating slurry and porous membrane have better adhesion, which is beneficial to further improve the cycle performance of the secondary battery, further reduce the impact on the conductivity of the current collector, and further improve the rate performance of the secondary battery.

[0286] In some implementations, the binder content is 20%-35% by mass, calculated based on the mass of the raw materials.

[0287] When the binder content is appropriate, it helps to further reduce the powder shedding of the coating, thereby further improving the adhesion between the coating slurry and the porous membrane layer, and further improving the cycle performance of the secondary battery.

[0288] In some implementations, the mass percentage of the conductive agent is 5%-15%, calculated based on the mass of the raw materials.

[0289] When the content of the conductive agent is appropriate, it is beneficial to improve the conductivity of the negative electrode current collector, thereby further improving the rate performance of the secondary battery. Furthermore, the conductive agent has poor affinity with porous films, and because it possesses active groups, excessive conductive agent may consume the deposited metal on the negative electrode. Therefore, an appropriate conductive agent content also helps to further improve the affinity between the coating and the porous film, reduce the consumption of deposited metal on the negative electrode, and thus contribute to further improving the cycle performance and initial coulombic efficiency of the secondary battery.

[0290] In some embodiments, the raw materials also include dispersants.

[0291] In some implementations, the mass percentage of the dispersant is 0%-10%, calculated based on the mass of the raw materials.

[0292] In some implementations, the mass percentage of the dispersant is greater than 0%, calculated based on the mass of the raw materials.

[0293] Adding a dispersant to the coating slurry helps to better disperse inorganic and conductive agents, reduces their sedimentation and agglomeration, and helps the inorganic and conductive agents to further exert their respective functions.

[0294] [Positive electrode plate]

[0295] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0296] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As an example, the positive electrode active material for a sodium secondary battery may include at least one of the following materials: Prussian blue compounds, sodium-containing layered oxides, sodium-containing polyanionic compounds, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of Prussian blue compounds include, but are not limited to, iron-based Prussian blue or manganese-based Prussian blue; examples of sodium-containing layered oxides include, but are not limited to, iron-based layered oxides, manganese-based layered oxides, iron-manganese-based layered oxides, and one or more iron-based layered oxides doped with transition metal elements (such as Ti, Cu, Ni). Exemplarily, iron-based layered oxides include, but are not limited to, NaFeO2; manganese-based layered oxides include, but are not limited to, NaMnO2; and iron-manganese-based layered oxides include, but are not limited to, Na… x Fe y Mn 1-y O2 (x=0.2~1, y=0.1~0.9, such as Na 0.67 Fe 0.5 Mn 0.5 O2, Na 0.67 Fe 0.45 Mn 0.65 O2); Sodium-containing polyanionic compounds include, but are not limited to, one or more of sodium-containing phosphates, sodium-containing pyrophosphates, sodium-containing fluorophosphates, and sodium-containing mixed phosphates, wherein sodium-containing phosphates include, but are not limited to, Na3V2(PO4)3 and Na4Mn. V One or more of (PO4)3, sodium pyrophosphates including but not limited to one or more of NaFeP2O7, NaMnP2O7, and NaCoP2O7, sodium fluorophosphates including but not limited to NaVPO4F, and sodium mixed phosphates including but not limited to one or more of Na4Fe3(PO4)2P2O7 and Na4Mn3(PO4)2P2O7.

[0297] As an example, the positive electrode active material of a lithium secondary battery may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials of batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0298] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0299] In some embodiments, the positive current collector can be a conductive carbon sheet, a metal foil, a carbon-coated metal foil, a porous metal plate, or a composite current collector. The conductive carbon material of the conductive carbon sheet can be selected from one or more of Super P, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers. The metal material of the metal foil, carbon-coated metal foil, and porous metal plate is independently selected from at least one of copper, aluminum, nickel, and stainless steel. The composite current collector can be a composite current collector formed by combining a metal foil with a polymer base film.

[0300] In some embodiments, the positive electrode film layer further includes a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA), and carboxymethyl chitosan (CMCS).

[0301] In some embodiments, the positive electrode film layer further includes a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0302] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, additives, conductive agents, binders and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto a positive current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0303] Electrolyte

[0304] The electrolyte plays a role in conducting ions between the positive and negative electrode plates.

[0305] In some implementations, the electrolyte is liquid, gel peptide, or all-solid.

[0306] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0307] In some embodiments, the electrolyte salt is a sodium salt. Exemplary examples include one or more of sodium hexafluorophosphate (NaPF6), sodium chlorate (NaClO4), sodium chloride (NaCl), sodium tetrafluoroborate (NaBF4), sodium nitrate (NaNO3), sodium cyanide (NaCN), or sodium bisulfate (NaHSO4).

[0308] In some embodiments, the electrolyte salt is a lithium salt. Exemplary examples include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalate borate) (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate phosphate (LiDFOP), or lithium tetrafluorooxalate phosphate (LiTFOP).

[0309] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0310] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0311] [Isolation membrane]

[0312] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0313] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0314] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0315] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0316] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0317] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0318] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0319] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0320] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0321] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0322] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0323] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0324] [Electrical appliances]

[0325] This application provides an electrical device, which includes the secondary battery of this application or the negative electrode current collector of this application.

[0326] In some embodiments, the electrical device of this application may further include at least one of a battery module or a battery pack. A secondary battery, battery module, or battery pack can be used as the power source for the electrical device or as the energy storage unit of the electrical device. The electrical 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.), electric trains, ships and satellites, energy storage systems, etc.

[0327] As an electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0328] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0329] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0330] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application.

[0331] Example

[0332] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0333] I. Preparation Method

[0334] Example 1

[0335] 1) Preparation of positive electrode sheet

[0336] The positive electrode active material NFPP (Na4Fe3(PO4)2P2O7), conductive agent conductive carbon black, and binder polyvinylidene fluoride were thoroughly mixed in N-methylpyrrolidone at a mass percentage of 96:1:3 to form a uniform positive electrode slurry. The positive electrode slurry was then mixed at a concentration of 20 mg / cm³. 2 The single-sided weight is coated on aluminum foil. After coating, it is cold-pressed and cut to obtain the positive electrode sheet.

[0337] 2) Preparation of negative electrode sheet

[0338] Inorganic alumina, binder styrene-butadiene emulsion (butadiene monomer unit-styrene monomer unit copolymer, A&L Corporation, Japan, model SBR-1002), conductive agent conductive carbon black (Super-P), and dispersant carboxymethyl cellulose (CMC) were thoroughly mixed in water at a mass percentage of 50:30:10:10 to form a coating slurry. The coating slurry was then mixed at a concentration of 3 mg / cm³. 2 The single-sided coating weight is applied to both sides of a polypropylene membrane, wherein the polypropylene membrane has a porosity of 45% and a thickness of 12μm. After coating, the membrane is cut to obtain a negative electrode current collector, which is the negative electrode sheet.

[0339] 4) Preparation of the separating membrane

[0340] Polypropylene film is used as the separator.

[0341] 5) Preparation of electrolyte

[0342] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), sodium hexafluorophosphate (NaPF6) was dissolved in the organic solvent propylene carbonate (PC) with 5% FEC fluoroethylene carbonate by mass, and stirred until homogeneous to obtain an electrolyte with a sodium salt concentration of 1 mol / L.

[0343] 6) Battery manufacturing

[0344] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The cells are then wound to obtain a bare cell. Tabs are welded onto the bare cell, which is then placed in an aluminum casing and baked in a vacuum oven at 100°C for 8 hours. Electrolyte is then injected and the casing is sealed to obtain a non-charged battery. The non-charged battery is then subjected to a series of processes, including settling, hot and cold pressing, formation, shaping, and capacity testing, to obtain the sodium metal battery without a negative electrode as described in Example 1.

[0345] The battery preparation methods of Examples 2-3 are the same as those of Example 1, except that the types of inorganic materials in the coating of the negative electrode current collector are different. Specifically, the inorganic material in Example 2 is boehmite, and the inorganic material in Example 3 is titanium dioxide. Other parameters are shown in Table 1.

[0346] The battery preparation methods of Examples 4-5 are the same as those of Example 1, except that the type of binder in the coating of the negative electrode current collector is different. Specifically, the binder of the coating in Example 4 is styrene-acrylic emulsion (styrene monomer unit-acrylate monomer unit copolymer, Risennoco Co., Ltd., Japan, model LB-150J), and the binder of the coating in Example 5 is polyethyl acrylate emulsion (BASF (China) Co., Ltd., model Acronal ECO 6370). Other parameters are shown in Table 1.

[0347] Examples 6-10 are prepared using the same battery method as Example 1, except that the mass percentage of each component in the coating of the negative electrode current collector is different, as shown in Table 1.

[0348] Examples 11-12 are prepared using the same battery method as Example 1, except that the coating weight per unit area of ​​the negative electrode current collector coating is different, as shown in Table 1.

[0349] Example 13 uses the same battery preparation method as Example 1, the difference being the positive electrode active material. The positive electrode active material in Example 13 is LiNi. 0.8 Co 0.1 Mn 0.1 O2.

[0350] Example 14 uses the same battery preparation method as Example 1, the difference being that Example 14 is a conventional sodium-ion battery. The negative electrode preparation method for Example 14 is as follows:

[0351] The negative electrode active material hard carbon, conductive agent carbon black, thickener carboxymethyl cellulose, and binder styrene-butadiene rubber were added to deionized water in a mass ratio of 97:0.5:0.5:2 and stirred evenly to obtain the negative electrode slurry.

[0352] Then the negative electrode slurry was prepared at 10 mg / cm³. 2 The single-sided weight is uniformly coated on the negative electrode current collector. After double-sided coating is completed, it is dried, cold-pressed, and cut to obtain the negative electrode sheet. The preparation method of the negative electrode current collector is the same as in Example 1.

[0353] The battery preparation method of Comparative Example 1 is the same as that of Example 1, except that the negative electrode current collector of Comparative Example 1 is copper foil.

[0354] The battery preparation method of Comparative Example 2 is the same as that of Example 1, except that the coating of the negative electrode current collector in Comparative Example 2 does not include inorganic matter, and the mass ratio of binder, conductive agent and dispersant is 35:55:10.

[0355] The battery preparation method for Comparative Example 3 is the same as that for Example 1, except that the negative electrode preparation method for Comparative Example 3 is as follows:

[0356] The negative electrode active material hard carbon, conductive agent carbon black, thickener carboxymethyl cellulose, and binder styrene-butadiene rubber were added to deionized water in a mass ratio of 97:0.5:0.5:2 and stirred evenly to obtain the negative electrode slurry.

[0357] Then the negative electrode slurry was prepared at 10 mg / cm³. 2 The single-sided weight is uniformly coated on the copper foil. After double-sided coating is completed, it is dried, cold-pressed, and cut to obtain the negative electrode sheet. The preparation method of the negative electrode current collector is the same as in Example 1.

[0358] II. Performance Testing

[0359] 1. Testing of negative electrode current collector and negative electrode sheet

[0360] 1) Testing of inorganic components and content in the coating

[0361] Inorganic content mass percentage test: Disassemble the battery to obtain the negative electrode sheet. If the negative electrode sheet has a negative electrode film layer, peel off the negative electrode film layer to obtain the negative electrode current collector. If the negative electrode sheet does not have a negative electrode film layer, the following operation can be performed directly: scrape the obtained negative electrode current collector to obtain a coating powder, and weigh its mass as M1. Calcinate the coating powder in air or oxygen at 500℃ until the powder weight no longer changes. The remaining powder is inorganic matter, and its mass is weighed as M0. The inorganic content mass percentage = (M0 / M1) × 100%.

[0362] Inorganic composition testing: Disassemble the battery to obtain the negative electrode. If the negative electrode has a negative electrode film, peel off the film to obtain the negative current collector. If there is no film, scrape off the current collector to obtain a coating powder. Calcine the coating powder in air or oxygen at a certain temperature (e.g., 500°C) until the powder weight no longer changes. The remaining powder is inorganic. Test the remaining material using X-ray diffraction (XRF) and compare it with a standard spectrum to confirm the inorganic composition. Alternatively, X-ray fluorescence spectroscopy (XRF) or inductively coupled plasma atomic absorption spectrometry (ICP) can be used to analyze the elemental composition of the remaining material. This analysis can be cross-validated with the X-ray diffraction results to further determine the specific inorganic composition.

[0363] 2) Porosity testing of porous membranes

[0364] Place the porous membrane sample to be tested in a mercury porosimeter, ensuring a good seal between the sample and the instrument; inject mercury into the instrument and gradually increase the mercury pressure; observe the volume change of the porous membrane sample and record the volume values ​​under different pressures; plot a pressure-volume curve based on the relationship between volume change and mercury pressure; calculate the porosity of the porous membrane based on the pressure-volume curve.

[0365] 2. Battery performance testing

[0366] 1) Cyclic performance testing

[0367] At 25°C, the prepared battery was charged to 3.65V with a constant current of 1C, and then charged to 0.05C with a constant voltage of 3.65V. After standing for 10 minutes, it was discharged to 1.5V with a constant current of 1C. This is one charge / discharge cycle of the battery. The capacity of the first discharge is taken as 100%, and the charge / discharge cycle is repeated. When the discharge capacity decays to 80%, the test is stopped, and the number of cycles is recorded. The number of cycles in which the capacity retention rate reaches 80% is used as the indicator to evaluate the cycle performance of the battery.

[0368] 2) Testing of high-rate performance

[0369] 4C rate charging capacity retention: After battery assembly and 10 hours of rest at 25℃, charge and discharge tests were conducted. The secondary battery was first charged to 3.65V with a constant current at different rates (specifically 0.33C and 4C), and the charging capacity value C was recorded. The 4C rate charging capacity retention rate = C4 / C 0.33 (C 0.33 This refers to the basic charging capacity, with a charging capacity retention rate of 100%.

[0370] 4C discharge rate capacity retention: After battery assembly and resting for 10 hours at 25℃, the battery is charged to 100% SOC and then discharged at constant current at different rates (specifically 0.33C and 4C) to the lower cutoff voltage of 1.5V. This discharge capacity value is recorded as D. The discharge capacity retention at 4C rate = D4 / D 0.33 (D 0.33 This is the base discharge capacity, with a capacity retention rate of 100%.

[0371] 3) First Coulomb efficiency test

[0372] After assembling the battery and letting it rest for 10 hours at 25℃, the first charge-discharge test was conducted. First, the secondary battery was charged to 3.65V with a constant current of 0.33C. Then, it was charged to 0.05C with a constant voltage of 3.65V. The charging capacity was recorded as C0. Then, it was discharged to the lower cutoff voltage of 1.5V with a constant current of 0.33C. The discharge capacity was recorded as D0. The initial coulombic efficiency FCE = D0 / C0.

[0373] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0374] Batteries for each embodiment and comparative example were prepared according to the above method, and various performance parameters were measured. The relevant parameters of the secondary batteries are shown in Table 1, and the battery performance test results are shown in Table 2.

[0375] Table 1. Relevant Parameters of Secondary Batteries

[0376]

[0377]

[0378] Continued from Table 1: Relevant Parameters of Secondary Batteries

[0379]

[0380] Table 2. Performance test results of secondary batteries

[0381]

[0382]

[0383] As shown in Examples 1-14, the negative electrode current collector of the battery in this application embodiment includes a porous film layer and a coating disposed on at least a portion of the surface of at least one side of the porous film layer. The coating includes an inorganic material, a conductive agent, and a binder. The inorganic material includes metal oxides or silicon oxide. The secondary battery in this application embodiment has high rate performance.

[0384] As can be seen from the comparison between Examples 1-13 and Comparative Example 1, and from the comparison between Example 14 and Comparative Example 3, the negative electrode current collector of the battery in this application has a porous film layer, and the porous structure on the porous film layer is beneficial to improving the rate performance of the secondary battery.

[0385] As can be seen from the comparison between Examples 1-14 and Comparative Example 2, adding inorganic materials to the coating is beneficial to improving the cycle performance of the secondary battery.

[0386] As shown in Examples 1-3, the coating of this application embodiment can use a variety of inorganic materials. Among them, when the inorganic material is aluminum oxide, it is beneficial to further improve the cycle performance of the secondary battery. As shown in Examples 1 and 4-5, the coating of this application embodiment can use a variety of binders. Among them, using butadiene monomer structural unit-styrene monomer structural unit is beneficial to further improve the rate performance and cycle performance of the secondary battery.

[0387] As can be seen from Examples 1 and 6-10, appropriate mass percentages of inorganic substances, binders, and conductive agents are beneficial for further improving the cycle performance, rate performance, and / or initial coulombic efficiency of secondary batteries.

[0388] As can be seen from Examples 1 and 11-12, a suitable coating weight per unit area is beneficial to further improve the cycle performance, rate performance and initial coulombic efficiency of secondary batteries.

[0389] As can be seen from Examples 13 and 14, the negative electrode current collector of this application is also applicable to scenarios of negative electrode-less lithium metal batteries and ion batteries.

[0390] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A secondary battery, characterized in that, The secondary battery includes a positive electrode, a negative electrode, a separator disposed between the negative electrode and the positive electrode, and an electrolyte. The negative electrode includes a negative current collector, which includes a porous film layer and a coating disposed on at least a portion of the surface of at least one side of the porous film layer. The coating includes an inorganic material, a conductive agent, and a binder. The inorganic material includes at least one of a metal oxide or silicon oxide.

2. The secondary battery according to claim 1, characterized in that, The metal oxide includes at least one of aluminum oxide, boehmite, magnesium oxide, iron oxide, zirconium oxide, titanium oxide, or zinc oxide.

3. The secondary battery according to claim 1 or 2, characterized in that, The adhesive comprises at least one of the following: acrylic monomer homopolymers and / or copolymers, acrylate monomer homopolymers and / or copolymers, polyol monomer-polyisocyanate monomer copolymers, diamine monomer-dianhydride monomer copolymers, butadiene monomer-styrene monomer copolymers, styrene monomer-acrylate monomer copolymers, or derivatives thereof, or modified species thereof.

4. The secondary battery according to any one of claims 1-3, characterized in that, The adhesive comprises at least one of butadiene monomer unit-styrene monomer unit copolymer, styrene monomer unit-acrylate monomer unit copolymer, methyl acrylate monomer unit homopolymer, ethyl acrylate monomer unit homopolymer, butyl acrylate monomer unit homopolymer, isooctyl acrylate monomer unit homopolymer, acrylate monomer unit copolymer, or its derivatives or modified species.

5. The secondary battery according to any one of claims 1-4, characterized in that, The conductive agent includes at least one of conductive carbon black, carbon nanotubes, graphene, superconducting carbon, acetylene black, Ketjen black, carbon dots, or carbon nanofibers.

6. The secondary battery according to any one of claims 1-5, characterized in that, Based on the mass of the coating, the inorganic content is 40%-55% by mass.

7. The secondary battery according to any one of claims 1-6, characterized in that, Based on the mass of the coating, the inorganic content is 45%-50% by mass.

8. The secondary battery according to any one of claims 1-7, characterized in that, Based on the quality of the coating, the adhesive has a mass percentage content of 20%-35%.

9. The secondary battery according to any one of claims 1-8, characterized in that, Based on the quality of the coating, the adhesive has a mass percentage of 25%-30%.

10. The secondary battery according to any one of claims 1-9, characterized in that, Based on the mass of the coating, the mass percentage of the conductive agent is 5%-15%.

11. The secondary battery according to any one of claims 1-10, characterized in that, Based on the mass of the coating, the conductive agent has a mass percentage content of 8%-12%.

12. The secondary battery according to any one of claims 1-11, characterized in that, The coating also includes a dispersant.

13. The secondary battery according to claim 12, characterized in that, The dispersant includes at least one of carboxymethyl cellulose, methyl cellulose, sodium starch phosphate, sodium carboxymethyl cellulose, sodium polyacrylate, polyoxyethylene, or polyvinylpyrrolidone.

14. The secondary battery according to claim 12 or 13, characterized in that, Based on the mass of the coating, the dispersant has a mass percentage content of 0%-10%.

15. The secondary battery according to any one of claims 12-14, characterized in that, Based on the mass of the coating, the mass percentage of the dispersant is greater than 0%.

16. The secondary battery according to any one of claims 1-15, characterized in that, The coating weight per unit area on one side is 1-5 mg / cm². 2 .

17. The secondary battery according to any one of claims 1-16, characterized in that, The coating weight per unit area is 2-3 mg / cm³. 2 .

18. The secondary battery according to any one of claims 1-17, characterized in that, The porosity of the porous membrane layer is 30%-60%.

19. The secondary battery according to any one of claims 1-18, characterized in that, The porosity of the porous membrane layer is 40%-50%.

20. The secondary battery according to any one of claims 1-19, characterized in that, The porous membrane layer includes at least one of porous polyolefin membrane, porous glass fiber, porous nonwoven fabric, porous polyimide membrane, porous polyvinylidene fluoride membrane, or porous polyterephthalate.

21. The secondary battery according to any one of claims 1-20, characterized in that, The thickness of the porous membrane is 6-15 μm.

22. The secondary battery according to any one of claims 1-21, characterized in that, The coating is disposed on at least a portion of the surface of one side of the porous membrane layer, or the coating is disposed on at least a portion of the surface of both sides of the porous membrane layer.

23. The secondary battery according to any one of claims 1-22, characterized in that, The secondary battery includes a negative electrode-free metal battery, and optionally, the secondary battery includes a negative electrode-free sodium metal battery or a negative electrode-free lithium metal battery.

24. The secondary battery according to any one of claims 1-23, characterized in that, The negative electrode sheet includes a negative electrode film layer disposed on at least one side of the negative electrode current collector, the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon or silicon-based materials.

25. A negative electrode current collector, characterized in that, The negative electrode current collector includes a porous membrane layer and a coating disposed on at least a portion of the surface of at least one side of the porous membrane layer. The coating includes an inorganic material, a conductive agent, and a binder, wherein the inorganic material includes at least one of a metal oxide or silicon oxide.

26. The negative electrode current collector according to claim 25, characterized in that, The metal oxide includes at least one of aluminum oxide, boehmite, magnesium oxide, iron oxide, zirconium oxide, titanium oxide, or zinc oxide.

27. The negative electrode current collector according to claim 25 or 26, characterized in that, The adhesive comprises at least one of the following: acrylic monomer homopolymers and / or copolymers, acrylate monomer homopolymers and / or copolymers, polyol monomer-polyisocyanate monomer copolymers, diamine monomer-dianhydride monomer copolymers, butadiene monomer-styrene monomer copolymers, styrene monomer-acrylate monomer copolymers, or derivatives thereof, or modified species thereof.

28. The negative electrode current collector according to any one of claims 25-27, characterized in that, The conductive agent includes at least one of conductive carbon black, carbon nanotubes, graphene, superconducting carbon, acetylene black, Ketjen black, carbon dots, or carbon nanofibers.

29. The negative electrode current collector according to any one of claims 25-28, characterized in that, Based on the mass of the coating, the inorganic content is 40%-55% by mass.

30. The negative electrode current collector according to any one of claims 25-29, characterized in that, Based on the quality of the coating, the adhesive has a mass percentage content of 20%-35%.

31. The negative electrode current collector according to any one of claims 25-30, characterized in that, Based on the mass of the coating, the mass percentage of the conductive agent is 5%-15%.

32. The negative electrode current collector according to any one of claims 25-31, characterized in that, The coating also includes a dispersant.

33. The negative electrode current collector according to claim 32, characterized in that, The dispersant includes at least one of carboxymethyl cellulose, methyl cellulose, sodium starch phosphate, sodium carboxymethyl cellulose, sodium polyacrylate, polyoxyethylene, or polyvinylpyrrolidone.

34. The negative electrode current collector according to any one of claims 25-33, characterized in that, The coating weight per unit area on one side is 1-5 mg / cm². 2 .

35. The negative electrode current collector according to any one of claims 25-34, characterized in that, The porosity of the porous membrane layer is 30%-60%.

36. The negative electrode current collector according to any one of claims 25-35, characterized in that, The porous membrane layer includes at least one of porous polyolefin membrane, porous glass fiber, porous nonwoven fabric, porous polyimide membrane, porous polyvinylidene fluoride membrane, or porous polyterephthalate.

37. The negative electrode current collector according to any one of claims 25-36, characterized in that, The coating is disposed on at least a portion of the surface of one side of the porous membrane layer, or the coating is disposed on at least a portion of the surface of both sides of the porous membrane layer.

38. A method for preparing a negative electrode current collector, characterized in that, The method includes at least the following steps: The raw materials are dissolved in a solvent and stirred to form a coating slurry; The coating slurry is applied to at least a portion of the surface of at least one side of the porous membrane to obtain the negative electrode current collector; The raw materials include inorganic substances, binders, and conductive agents, wherein the inorganic substances include at least one of metal oxides or silicon oxide.

39. The method according to claim 38, characterized in that, The metal oxide includes at least one of aluminum oxide, boehmite, magnesium oxide, iron oxide, zirconium oxide, titanium oxide, or zinc oxide.

40. The negative electrode current collector according to claim 38 or 39, characterized in that, The adhesive comprises at least one of the following: acrylic monomer homopolymers and / or copolymers, acrylate monomer homopolymers and / or copolymers, polyol monomer-polyisocyanate monomer copolymers, diamine monomer-dianhydride monomer copolymers, butadiene monomer-styrene monomer copolymers, styrene monomer-acrylate monomer copolymers, or derivatives thereof, or modified species thereof.

41. The negative electrode current collector according to any one of claims 38-40, characterized in that, Based on the mass of the raw materials, the inorganic matter has a mass percentage content of 40%-55%.

42. The negative electrode current collector according to any one of claims 38-41, characterized in that, Based on the mass of the raw materials, the adhesive has a mass percentage content of 20%-35%.

43. The negative electrode current collector according to any one of claims 38-42, characterized in that, Based on the mass of the raw materials, the mass percentage of the conductive agent is 5%-15%.

44. The negative electrode current collector according to any one of claims 38-43, characterized in that, The raw materials also include dispersants.

45. An electrical appliance, characterized in that, The electrical device includes a secondary battery as described in any one of claims 1-24 or a negative electrode current collector as described in any one of claims 25-37.

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