Negative electrode-free secondary battery and electric device

Abstract

The present application provides a negative electrode-free secondary battery and an electric device. The negative electrode-free secondary battery comprises a negative electrode current collector and a bottom coating which is arranged on at least one side of the negative electrode current collector close to a positive electrode sheet. The bottom coating comprises a linear polymer and a conductive agent, wherein the linear polymer comprises one or more of cellulose ether and a modification thereof, polyimide, nitrile rubber, hydrogenated nitrile rubber, polyvinylpyrrolidone, and hydrogenated styrene-butadiene rubber.

Description

Negative-electrode secondary batteries and electrical devices

[0001] Cross-referencing

[0002] This application incorporates Chinese Patent Application No. 202411215429.2, filed on August 30, 2024, entitled “Anode-free Secondary Battery and Electrical Device,” which is incorporated herein by reference in its entirety. Technical Field

[0003] This application relates to the field of secondary battery technology, and in particular to a negative electrode-free secondary battery and its power supply device. Background Technology

[0004] In recent years, rechargeable 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 power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. With the increasing application of rechargeable batteries, higher requirements have been placed on their cycle performance and service life. Summary of the Invention

[0005] This application is made in view of the above-mentioned problems, and its purpose is to provide a base coating slurry suitable for the preparation of current collectors in negative electrode batteries, which can effectively improve the problem of missed coating caused by traditional aqueous slurries, and thus has greater advantages compared with traditional aqueous slurries.

[0006] To achieve the above objectives, a first aspect of this application provides a negative electrode-free secondary battery, which includes a negative electrode current collector and a base coating disposed on the negative electrode current collector at least on the side close to the positive electrode. The base coating includes a linear polymer and a conductive agent, wherein the linear polymer includes one or more of cellulose ether and its modified forms, polyimide, nitrile rubber, hydrogenated nitrile rubber, polyvinylpyrrolidone, hydrogenated styrene-butadiene rubber, polyurethane, and polyvinylidene fluoride.

[0007] When the slurry provided in this application is used to prepare the current collector, a base coating with a smaller, more complete and denser uncoated area can be formed on the surface of the current collector. This increases the mechanical stability and heat resistance of the current collector base coating, better suppresses the deposition of sodium or lithium on the negative electrode, and suppresses dendrite growth, thereby improving the cycle performance of the negative electrodeless battery.

[0008] In any embodiment, the linear polymer includes cellulose ethers and their modifications.

[0009] In any embodiment, the cellulose ether includes one or more of methylcellulose ether, ethylcellulose ether, hydroxypropylcellulose ether, hydroxyethylcellulose ether, hydroxyethylmethylcellulose ether, and hydroxypropylmethylcellulose ether.

[0010] The linear polymer in the primer slurry mainly acts as a dispersant and binder. When the linear polymer is of the type mentioned above, it can further improve the problem of missed coating of the primer slurry on the current collector surface, thereby further improving the cycle performance of the battery.

[0011] In any embodiment, the weight-average molecular weight of the linear polymer is 5w-80w.

[0012] When the weight-average molecular weight of the linear polymer is within the above range, the problems of easy demolding and high brittleness of the base coating layer can be further improved, thereby further improving the cycle performance of the battery.

[0013] In any implementation, the linear polymer accounts for 70%-90% of the total mass of the base coating.

[0014] When the content of linear polymer is within the above range, it can further improve the uncoated area on the current collector surface, thereby further improving the cycle performance of the battery.

[0015] In any embodiment, the conductive agent includes one or more of conductive carbon black, carbon nanotubes, graphene, acetylene black, and Ketjen black.

[0016] In any embodiment, the conductive agent includes conductive carbon black.

[0017] The conductive agent in the primer slurry mainly serves to construct a conductive network, which facilitates electron transfer and thus improves electrochemical performance. However, traditional conductive agents (such as conductive carbon black) are amorphous carbon, and their preparation process results in numerous defects and micro-nano pores on their surface, leading to problems such as bubbling and missed coating during the coating process. The slurry containing linear polymers provided in this application, when further combined with the aforementioned type of conductive agent, not only improves the bubbling and missed coating problems caused by these conductive agents but also retains the excellent properties of these conductive agents themselves.

[0018] In any embodiment, the conductive agent accounts for 10%-30% of the total mass of the base coating.

[0019] When the content of the conductive agent is within the above range, the base coating has good conductivity and can also avoid excessive consumption of active sodium by the defect sites on the conductive carbon surface, thereby further improving the cycle performance of the battery.

[0020] In any embodiment, the areal density of the base coating is 0.1 mg / cm³. 2 -0.8mg / cm 2 .

[0021] When the areal density of the base coating is within the above range, it can effectively suppress sodium or lithium deposition while avoiding missed coating and preventing the conductive agent from reacting with excessive sodium metal, thereby improving the battery's cycle performance and first-time efficiency.

[0022] In any embodiment, the number of missed areas in the primer coating is no more than 12, and the number of missed areas is defined as an area with a missed area greater than 0.1 mm per square meter. 2 The number of.

[0023] Using the primer slurry provided in this application can effectively improve bubbling and missed coating phenomena during the coating process, thereby forming a current collector primer layer with a smaller missed coating area.

[0024] In any embodiment, the negative electrode current collector is prepared by a rolling pressing method.

[0025] Current collectors prepared by calendering have many excellent properties. However, the surface tension of traditional aqueous slurries is often much higher than that of current collectors (such as aluminum foil) prepared by calendering, which means that the surface of the current collector cannot be completely wetted by the slurry, thus aggravating the problem of incomplete coating. At the same time, there is an oil film on the surface of current collectors (such as aluminum foil) prepared by calendering, which results in a larger area of ​​incomplete coating when using traditional aqueous slurries for coating.

[0026] The slurry containing linear polymer provided in this application has a surface tension that is closer to that of current collectors (such as aluminum foil) prepared by calendering, which can play a better wetting role and thus avoid incomplete coating. When it is used in combination with current collectors prepared by calendering, it can not only improve the problem of easy incomplete coating of calendered current collectors, but also retain the excellent properties of these current collectors themselves.

[0027] In any embodiment, the negative electrode-free secondary battery includes one or more of the negative electrode-free lithium secondary battery and the negative electrode-free sodium secondary battery; and / or, the negative electrode current collector includes one or more of the following: aluminum foil, copper foil, stainless steel substrate, titanium foil, plastic film composite copper foil, and plastic film composite aluminum foil.

[0028] The primer slurry provided in this application can be used in negative electrode-free lithium secondary batteries or negative electrode-free sodium secondary batteries. It can also be used in combination with any negative electrode current collector of the above types. All of these methods can effectively improve the problem of missing coating of the primer layer, thereby improving the cycle performance of the battery.

[0029] In any embodiment, the plastic film is at least one of PET film, PP film, and PI film.

[0030] The above-mentioned types of plastic film composite current collectors have the advantages of high strength, low cost, and easy vapor deposition.

[0031] A second aspect of this application also provides an electrical device, which includes the negative electrode-free secondary battery of this application.

[0032] A third aspect of this application also provides a primer slurry comprising a linear polymer, a conductive agent, and an organic solvent. The linear polymer comprises one or more of cellulose ethers and their modified forms, polyimide, nitrile rubber, hydrogenated nitrile rubber, polyvinylpyrrolidone, hydrogenated styrene-butadiene rubber, polyurethane, and polyvinylidene fluoride.

[0033] The surface tension of traditional aqueous slurries is often much higher than that of current collectors prepared by calendering, which means that the surface of the current collector cannot be completely wetted by the slurry, resulting in problems such as incomplete coating and edge shrinkage. Furthermore, during the coating process of current collectors using traditional aqueous slurries, the surface structure of the pores of traditional conductive agents (such as conductive carbon black) exerts a greater force on water molecules than the surface itself exerts a force on water molecules. This causes water molecules to enter the pores from the surface, resulting in bubbling. Consequently, even current collectors prepared by non-calendering methods have incomplete coating problems.

[0034] The slurry provided in this application contains linear polymers of the aforementioned type, which can effectively avoid the bubbling phenomenon caused by aqueous slurries during the coating process, thus effectively improving the problem of incomplete coating on the surface of current collectors prepared by calendering or non-calendering methods. At the same time, the primer slurry provided in this application also contains organic solvents, which can dissolve residual organic matter on the surface of the current collector, thus further improving the problems of incomplete coating and edge shrinkage existing in traditional slurries. In addition, the surface tension of the slurry provided in this application is closer to that of the current collector surface prepared by calendering, which can play a better wetting role, thereby further improving the problem of incomplete coating on the surface of current collectors prepared by calendering.

[0035] In any embodiment, the linear polymer includes cellulose ethers and their modifications.

[0036] In any embodiment, the cellulose ether includes one or more of methylcellulose ether, ethylcellulose ether, hydroxypropylcellulose ether, hydroxyethylcellulose ether, hydroxyethylmethylcellulose ether, and hydroxypropylmethylcellulose ether.

[0037] The linear polymers in the primer slurry mainly act as dispersants and binders. When the linear polymers are of the types mentioned above, they can further improve the problem of missed coating on the surface of the current collector.

[0038] In any embodiment, the weight-average molecular weight of the linear polymer is 5w-80w.

[0039] When the weight-average molecular weight of the linear polymer is within the above range, the problems of easy demolding and high brittleness of the primer film can be further improved.

[0040] In any embodiment, the linear polymer accounts for 70%-90% of the total mass of the dry material in the primer slurry.

[0041] When the content of linear polymer is within the above range, it can further improve the uncoated area on the surface of the current collector.

[0042] In any embodiment, the conductive agent includes one or more of conductive carbon black, carbon nanotubes, graphene, acetylene black, and Ketjen black.

[0043] In any embodiment, the conductive agent includes conductive carbon black.

[0044] The conductive agent in the primer slurry mainly serves to construct a conductive network, which facilitates electron transfer and thus improves electrochemical performance. However, traditional conductive agents (such as conductive carbon black) are amorphous carbon, and during their preparation, numerous defects and nanoscale pores form on their surface and between secondary particles, leading to problems such as bubbling and missed coating during the coating process. The slurry containing linear polymers provided in this application, when further combined with the aforementioned type of conductive agent, not only improves the bubbling and missed coating problems caused by the conductive agent but also retains the excellent properties of these conductive agents themselves.

[0045] In any implementation, the conductive agent accounts for 10%-30% of the total mass of the dry slurry.

[0046] When the content of the conductive agent is within the above range, the base coating has good conductivity while avoiding excessive consumption of active sodium by the defect sites on the conductive carbon surface.

[0047] In any embodiment, the organic solvent includes one or more of N-methylpyrrolidone, ethanol, acetone, propylene carbonate, methyl ethyl carbonate, dimethyl carbonate, and dimethyl sulfoxide.

[0048] In any embodiment, the organic solvent includes N-methylpyrrolidone.

[0049] When the organic solvent is of the type described above, it can make the primer slurry more oily and distinct from water-based slurries, which can further improve the problem of missed coating during primer slurry application. In addition, the organic solvents of the above type (such as N-methylpyrrolidone) have a very strong adsorption effect on the conductive agent surface, thereby further improving the problem of bubbling during primer slurry application.

[0050] In any embodiment, the solid content of the primer slurry is 2%-20%, and the viscosity of the primer slurry is 3000mPa·s-13000mPa·s.

[0051] When the solid content of the primer is within the above range, the primer can have a suitable viscosity, which makes it easier to apply and further improves the problem of missed coating. Attached Figure Description

[0052] Figure 1 is a schematic diagram of a secondary battery according to an embodiment of this application;

[0053] Figure 2 is an exploded view of a secondary battery according to an embodiment of this application shown in Figure 1;

[0054] Figure 3 is a schematic diagram of a battery module according to an embodiment of this application;

[0055] Figure 4 is a schematic diagram of a battery pack according to an embodiment of this application;

[0056] Figure 5 is an exploded view of the battery pack of one embodiment of this application shown in Figure 4;

[0057] Figure 6 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of this application.

[0058] Explanation of reference numerals in the attached drawings: 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

[0059] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the negative electrode slurry, its preparation method, the negative electrode sheet, the secondary battery, and the power application 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.

[0060] 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.

[0061] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0062] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0063] 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.

[0064] 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.

[0065] 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).

[0066] In a battery system without a negative electrode, the sodium or lithium deposited on the negative electrode side has poor affinity for the negative electrode current collector (such as copper foil or aluminum foil), and there is a lattice difference between the current collector and sodium or lithium, which easily leads to dendrite growth, resulting in poor cycle and storage life of sodium or lithium batteries without a negative electrode.

[0067] To improve sodium or lithium deposition on the negative electrode current collector and to increase its mechanical strength, a conventional approach is to apply an aqueous primer coating, such as PAA and conductive carbon, onto the negative electrode current collector (e.g., copper or aluminum foil). However, such aqueous primer coatings face several problems: First, the surface tension of traditional aqueous slurries is often much higher than that of current collectors prepared by calendering, resulting in incomplete wetting of the slurry surface and problems such as incomplete coating and edge shrinkage. Second, during the coating process using traditional aqueous slurries, the surface structure of the pores of traditional conductive agents (e.g., conductive carbon black) exerts a greater force on water molecules than its surface exerts on water molecules, causing water molecules to enter the pores from the surface and bubbling, resulting in incomplete coating even for current collectors prepared by non-calendering methods. These problems urgently require novel primer coating slurries to solve.

[0068] [Primer coating]

[0069] This application provides a primer slurry comprising a linear polymer, a conductive agent, and an organic solvent. The linear polymer comprises one or more of cellulose ethers and their modified forms, polyimide, nitrile rubber, hydrogenated nitrile rubber, polyvinylpyrrolidone, hydrogenated styrene-butadiene rubber, polyurethane, and polyvinylidene fluoride.

[0070] The slurry provided in this application contains linear polymers of the aforementioned type, whose surface tension is closer to that of current collectors prepared by calendering, thus providing better wetting. Furthermore, its coating process effectively avoids bubbling caused by aqueous slurries, effectively improving the problem of incomplete coating on current collectors prepared by either calendering or non-calendering methods. Simultaneously, the primer slurry provided in this application also contains organic solvents, which can dissolve residual organic matter on the current collector surface, further improving problems such as incomplete coating and edge shrinkage inherent in traditional slurries. Therefore, when using the slurry provided in this application to prepare and coat current collectors, a more complete and dense primer layer with a smaller incomplete coating area can be formed on the current collector surface, increasing the mechanical stability and heat resistance of the primer layer. In some embodiments, the linear polymer includes cellulose ethers and their modified forms.

[0071] In some embodiments, the cellulose ether includes one or more of methylcellulose ether, ethylcellulose ether, hydroxypropylcellulose ether, hydroxyethylcellulose ether, hydroxyethylmethylcellulose ether, and hydroxypropylmethylcellulose ether.

[0072] The linear polymers in the primer slurry mainly act as dispersants and binders. When the linear polymers are of the types mentioned above, they can further improve the problem of missed coating on the surface of the current collector.

[0073] In some embodiments, the linear polymer has a weight-average molecular weight of 5w-80w, such as 5w, 10w, 15w, 20w, 25w, 30w, 35w, 40w, 45w, 50w, 55w, 60w, 65w, 70w, 75w, 80w, or other unlisted values ​​in the range of 5w-80w.

[0074] When the weight-average molecular weight of the linear polymer is within the above range, the problems of easy demolding and high brittleness of the base coating layer can be further improved, thereby further improving the cycle performance of the battery.

[0075] In this document, the term "weight-average molecular weight" refers to the statistical average of the mass fractions of different molecular weights in a polymer. It can be characterized by the sum of the products of the weight fractions of molecules with different molecular weights and their corresponding molecular weights. In this application, the weight-average molecular weight of the polymer can be determined using methods known in the art, such as gel permeation chromatography.

[0076] In some embodiments, the linear polymer accounts for 20%-90% of the total mass of the dry material in the primer slurry, for example, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or other unlisted values ​​within the range of 20%-90%.

[0077] In some embodiments, the linear polymer accounts for 70%-90% of the total mass of the dry material in the primer slurry, for example, 70%, 75%, 80%, 85%, 90%, or other unlisted values ​​within the range of 70%-90%.

[0078] When the content of linear polymer is within the above range, it can further improve the uncoated area on the surface of the current collector.

[0079] In some embodiments, the conductive agent includes one or more of conductive carbon black, carbon nanotubes, graphene, acetylene black, and Ketjen black.

[0080] In some embodiments, the conductive agent includes conductive carbon black.

[0081] The conductive agent in the primer slurry mainly serves to construct a conductive network, which facilitates electron transfer and thus improves electrochemical performance. However, traditional conductive agents (such as conductive carbon black) are amorphous carbon, and during their preparation, numerous defects and nanoscale pores form on their surface, leading to problems such as bubbling and missed coating during the coating process. The slurry containing linear polymers provided in this application, when further combined with the aforementioned type of conductive agent, not only improves the bubbling and missed coating problems caused by the conductive agent but also retains the excellent properties of these conductive agents themselves.

[0082] In some embodiments, the conductive agent accounts for 10%-80% of the total mass of the dry slurry, for example, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or other unlisted values ​​within the range of 10%-80%.

[0083] In some embodiments, the conductive agent accounts for 10%-30% of the total mass of the dry slurry.

[0084] When the content of the conductive agent is within the above range, the base coating has good conductivity while avoiding excessive consumption of active sodium by the defect sites on the conductive carbon surface.

[0085] In some embodiments, the organic solvent includes one or more of N-methylpyrrolidone, ethanol, acetone, propylene carbonate, methyl ethyl carbonate, dimethyl carbonate, and dimethyl sulfoxide.

[0086] In some embodiments, the organic solvent includes N-methylpyrrolidone.

[0087] When the organic solvent is of the type described above, it can make the primer slurry more oily and distinct from water-based slurries, which can further improve the problem of missed coating during primer slurry application. In addition, the organic solvents of the above type (such as N-methylpyrrolidone) have a very strong adsorption effect on the conductive agent surface, thereby further improving the problem of bubbling during primer slurry application.

[0088] In some embodiments, the solid content of the primer slurry is 2%-20%, such as 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, etc., or other unlisted values ​​within the range of 2%-20%.

[0089] In some embodiments, the viscosity of the primer slurry is 3000 mPa·s-13000 mPa·s, such as 3000 mPa·s, 4000 mPa·s, 5000 mPa·s, 6000 mPa·s, 7000 mPa·s, 8000 mPa·s, 9000 mPa·s, 10000 mPa·s, 11000 mPa·s, 12000 mPa·s, 13000 mPa·s, etc., or other unlisted values ​​within the range of 3000 mPa·s-13000 mPa·s.

[0090] When the solid content of the primer is within the above range, the primer can have a suitable viscosity, which makes it easier to apply and further improves the problem of missed coating.

[0091] In this document, the term “viscosity” has the meaning conventionally understood in the art as referring to the resistance a fluid exhibits to flow, and its test method can be found in GB / T10247-2008.

[0092] [Negative electrode current collector and primer coating]

[0093] This application provides a negative electrode-free secondary battery, which includes a negative electrode current collector and a base coating disposed on the negative electrode current collector at least on the side close to the positive electrode.

[0094] In some embodiments, the electrodeless secondary battery includes one or more of the following: electrodeless lithium secondary battery and electrodeless sodium secondary battery.

[0095] The primer slurry provided in this application can be used in both negative electrode-free lithium secondary batteries and negative electrode-free sodium secondary batteries. Both can effectively improve the problem of missing coating of the primer layer, thereby improving the cycle performance of the battery.

[0096] In some embodiments, the base coating comprises a linear polymer and a conductive agent.

[0097] In some embodiments, the linear polymer includes one or more of cellulose ethers and their modifications, polyimide, nitrile rubber, hydrogenated nitrile rubber, polyvinylpyrrolidone, hydrogenated styrene-butadiene rubber, polyurethane, and polyvinylidene fluoride.

[0098] The slurry provided in this application contains linear polymers of the aforementioned type, which can effectively avoid the bubbling phenomenon caused by aqueous slurries during the coating process, thereby effectively improving the problem of missed coating of the primer slurry on the current collector surface. Therefore, when using the slurry provided in this application to prepare a primer coating for coating the current collector, a primer coating with a smaller missed area, greater completeness, and density can be formed on the current collector surface, increasing the mechanical stability and heat resistance of the current collector primer coating, better suppressing the deposition of sodium or lithium on the negative electrode, and suppressing dendrite growth, thereby improving the cycle performance of the battery.

[0099] In some preferred embodiments, the linear polymer comprises cellulose ethers and their modified forms.

[0100] In some preferred embodiments, the cellulose ether includes one or more of methylcellulose ether, ethylcellulose ether, hydroxypropylcellulose ether, hydroxyethylcellulose ether, hydroxyethylmethylcellulose ether, and hydroxypropylmethylcellulose ether.

[0101] The linear polymer in the primer slurry mainly acts as a dispersant and binder. When the type of dispersant is as described above, it can further improve the cycle performance of the battery.

[0102] In some embodiments, the linear polymer has a weight-average molecular weight of 5w-80w, such as 5w, 10w, 15w, 20w, 25w, 30w, 35w, 40w, 45w, 50w, 55w, 60w, 65w, 70w, 75w, 80w, or other unlisted values ​​in the range of 5w-80w.

[0103] When the weight-average molecular weight of the linear polymer is within the above range, it has better solubility and can further improve the problems of easy demolding and high brittleness of the primer film.

[0104] In some embodiments, the linear polymer accounts for 20%-90% of the total mass of the base coating, for example, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or other unlisted values ​​within the range of 20%-90%.

[0105] In some preferred embodiments, the linear polymer accounts for 70%-90% of the total mass of the base coating, for example, 70%, 75%, 80%, 85%, 90%, or other unlisted values ​​within the range of 70%-90%.

[0106] When the content of linear polymer is within the above range, it can further improve the uncoated area on the current collector surface, thereby further improving the cycle performance of the battery.

[0107] In some embodiments, the conductive agent includes one or more of conductive carbon black, carbon nanotubes, graphene, acetylene black, and Ketjen black.

[0108] In some preferred embodiments, the conductive agent comprises conductive carbon black.

[0109] The conductive agent in the primer slurry mainly serves to construct a conductive network, which facilitates electron transfer and thus improves electrochemical performance. However, traditional conductive agents (such as conductive carbon black) are amorphous carbon, and their preparation process results in numerous defects and micro-nano pores on their surface, leading to problems such as bubbling and missed coating during the coating process. The slurry containing linear polymers provided in this application, when further combined with the aforementioned type of conductive agent, not only improves the bubbling and missed coating problems caused by these conductive agents but also retains the excellent properties of these conductive agents themselves.

[0110] In some embodiments, the conductive agent accounts for 10%-80% of the total mass of the base coating, for example, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, etc., or other unlisted values ​​within the range of 10%-80%.

[0111] In some preferred embodiments, the conductive agent accounts for 10%-30% of the total mass of the base coating.

[0112] When the content of the conductive agent is within the above range, the base coating has good conductivity and can also avoid excessive consumption of active sodium by the defect sites on the conductive carbon surface, thereby further improving the cycle performance of the battery.

[0113] In some embodiments, the areal density of the base coating is 0.1 mg / cm³. 2 -0.8mg / cm 2 For example, 0.1 mg / cm 2 0.2 mg / cm 2 0.3 mg / cm 2 0.4 mg / cm 2 0.5 mg / cm 2 0.6 mg / cm 2 0.7 mg / cm 2 0.8 mg / cm 2 etc., or 0.1 mg / cm 2 -0.8mg / cm 2Other values ​​not listed within the range.

[0114] When the areal density of the base coating is within the above range, it can effectively suppress sodium or lithium deposition while avoiding missed coating and preventing the conductive agent from reacting with excessive sodium metal, thereby improving the battery's cycle performance and first-time efficiency.

[0115] In some embodiments, the number of missed areas in the primer coating is no more than 12, and the number of missed areas is defined as an area with a missed area greater than 0.1 mm per square meter. 2 The number of, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc., or other unlisted values ​​within the range of 12.

[0116] Using the primer slurry provided in this application can effectively improve bubbling and missed coating phenomena during the coating process, thereby forming a current collector primer layer with a smaller missed coating area.

[0117] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0118] In some embodiments, the electrodeless secondary battery is an electrodeless lithium secondary battery, and the electrode current collector preferably includes a substrate that will not undergo an alloying reaction, such as copper foil or steel foil.

[0119] In some embodiments, the negative electrode current collector is prepared by a rolling pressing method.

[0120] Current collectors prepared by calendering have many excellent properties. However, the surface tension of traditional aqueous slurries is often much higher than that of current collectors (such as aluminum foil) prepared by calendering, which means that the surface of the current collector cannot be completely wetted by the slurry, thus aggravating the problem of incomplete coating. At the same time, there is an oil film on the surface of current collectors (such as aluminum foil) prepared by calendering, which results in a larger area of ​​incomplete coating when using traditional aqueous slurries for coating.

[0121] The slurry containing linear polymer provided in this application has a surface tension that is closer to that of current collectors (such as aluminum foil) prepared by calendering, which can play a better wetting role and thus avoid incomplete coating. When it is used in combination with current collectors prepared by calendering, it can not only improve the problem of easy incomplete coating of calendered current collectors, but also retain the excellent properties of these current collectors themselves.

[0122] In some embodiments, the negative electrode current collector includes one or more of aluminum foil, copper foil, stainless steel substrate, titanium foil, plastic film composite copper foil, and plastic film composite aluminum foil.

[0123] The primer slurry provided in this application can be used in negative electrode-free lithium secondary batteries or negative electrode-free sodium secondary batteries. It can also be used in combination with any negative electrode current collector of the above types. All of these methods can effectively improve the problem of missing coating of the primer layer, thereby improving the cycle performance of the battery.

[0124] In some embodiments, the plastic film is at least one of PET film, PP film, and PI film.

[0125] The above-mentioned types of plastic film composite current collectors have the advantages of high strength, low cost, and easy vapor deposition.

[0126] [Positive electrode plate]

[0127] The negative electrode-free secondary battery provided in this application also includes a positive electrode.

[0128] 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 the positive electrode active material of the first aspect of this application.

[0129] 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.

[0130] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0131] In some embodiments, the positive electrode active material may be a positive electrode active material known in the art for use in batteries.

[0132] In some embodiments, the negative electrode-free secondary battery is a negative electrode-free sodium secondary battery. As an example, the positive electrode active material includes at least one of layered transition metal oxides, polyanionic compounds, and Prussian blue-like compounds.

[0133] The transition metal in the layered transition metal oxide can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Optionally, the layered transition metal oxide is, for example, NaxMO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x ≤ 1.

[0134] Polyanionic compounds can contain metal ions, transition metal ions, or tetrahedral (YO4) structures. n- A class of compounds with anionic units. The metal ion may be one of sodium, lithium, potassium, or zinc; the transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be at least one of P, S, and Si; n represents (YO4). n- The price state.

[0135] Prussian blue compounds can be a class of compounds containing sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Examples of Prussian blue compounds include Na. a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0136] In some embodiments, the negative electrode-free secondary battery is a negative electrode-free lithium secondary battery. As an example, the positive electrode active material may also 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 for 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 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.

[0137] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0138] In some embodiments, the positive electrode film may optionally include 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.

[0139] 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, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0140] [Electrolytes]

[0141] The electrolyte acts as a conductor of ions between the positive and negative electrode plates. This application does not specifically limit the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, solid, or gel-like.

[0142] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0143] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0144] 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.

[0145] 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.

[0146] [Isolation membrane]

[0147] 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.

[0148] 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.

[0149] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0150] 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.

[0151] 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.

[0152] 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 shows a square-structured secondary battery 5 as an example. Optionally, the secondary battery is a lithium-ion battery or a sodium-ion battery.

[0153] In some embodiments, referring to FIG2, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 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 by a winding process or a 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.

[0154] 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.

[0155] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in the battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple secondary batteries 5 can be fixed in place using fasteners.

[0156] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0157] 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.

[0158] Figures 4 and 5 show a battery pack 1 as an example. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 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.

[0159] [Electrical appliances]

[0160] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, 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.

[0161] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0162] Figure 6 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. 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.

[0163] 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.

[0164] Example

[0165] 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.

[0166] I. Preparation Method

[0167] Example 1

[0168] 1) Preparation of negative electrode sheet

[0169] Methylcellulose ether with a molecular weight of 100,000 and conductive carbon black were weighed and dissolved in N-methylpyrrolidone (NMP) at a mass ratio of 90:10. The mixture was then ultrasonically dispersed to prepare a primer slurry. The resulting primer slurry had a solid content of 10% and a viscosity of 4132 mPa·s. This primer slurry was coated onto the surface of aluminum foil prepared by calendering. After drying, slitting, and cutting, a negative electrode current collector with a primer coating was obtained, wherein the areal density of the primer coating was 0.2 mg / cm³. 2 The uncoated area per square meter of primer layer is larger than the uncoated area specification (0.1mm). 2 The number of ) is less than 2.

[0170] 2) Preparation of positive electrode sheet

[0171] 10 wt% of polyvinylidene fluoride binder was fully dissolved in N-methylpyrrolidone, and 10 wt% of carbon black conductive agent and 80 wt% of positive electrode active material Na4Fe3(PO4)2(P2O7) were added and dispersed evenly to prepare a positive electrode slurry. The positive electrode slurry was uniformly coated on the surface of the positive electrode current collector aluminum foil, and after drying, cold pressing, slitting, and cutting, the positive electrode sheet was obtained.

[0172] 3) Separating membrane

[0173] A 9μm porous polyethylene (PE) polymer film was used as the separator.

[0174] 4) Preparation of electrolyte

[0175] In an argon atmosphere glove box (H2O content <10ppm, O2 content <1ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a mass ratio of 30:70, and sodium NaPF6 was dissolved to obtain an electrolyte with a NaPF6 concentration of 1.0mol / L.

[0176] 5) Preparation of negative electrode-free batteries

[0177] The above-mentioned negative electrode sheet, separator, and positive electrode sheet are stacked in sequence, wound, and hot-pressed to form a battery cell; the battery cell is placed in an outer packaging, the electrolyte prepared above is added, and after processes such as encapsulation, standing, formation, and aging, the negative electrode-free secondary battery of Example 1 is obtained.

[0178] Examples 2-4, 13-14

[0179] The secondary batteries in Examples 2-4 and 13-14 are prepared in a manner similar to that in Example 1, except that the type of linear polymer in the primer slurry is changed, as detailed in Table 1.

[0180] Examples 5-6

[0181] The secondary batteries in Examples 5-6 were prepared in a manner similar to that in Example 1, except that the weight-average molecular weight of the linear polymer was changed, as detailed in Table 1.

[0182] Example 7

[0183] The preparation method of the secondary battery in Example 7 is basically similar to that in Example 1. The difference is that the mass ratio of linear polymer and conductive agent in the primer slurry is changed, as shown in Table 1.

[0184] Examples 8-9

[0185] The secondary batteries of Examples 8-9 are prepared in a similar manner to those of Example 1, except that the solid content of the base coating slurry is changed, as detailed in Table 1.

[0186] Examples 10-11

[0187] The secondary batteries in Examples 10-11 are prepared in a manner similar to that in Example 1, except that the areal density of the base coating is changed, as detailed in Table 1.

[0188] Example 12

[0189] The preparation method of the secondary battery in Example 12 is basically similar to that in Example 1, except that the type of solvent is changed, as detailed in Table 1.

[0190] Comparative Example 1

[0191] The preparation methods of Comparative Example 1 and Example 1 are basically similar, except that the negative electrode sheet is prepared as follows: sodium carboxymethyl cellulose with a molecular weight of 200,000 and conductive carbon black are weighed at a mass ratio of 90:10 and dissolved in deionized water. After ultrasonic dispersion, a base coating slurry is prepared. The solid content of the base coating slurry is 10%, and the viscosity is 18000 mPa·s. This base coating slurry is coated on the surface of aluminum foil prepared by calendering. After drying, slitting, and cutting, a negative electrode current collector with a base coating is obtained, wherein the areal density of the base coating is 0.2 mg / cm³. 2 The uncoated area per square meter of primer layer is larger than the uncoated area specification (0.1mm). 2 The number of ) is 20.

[0192] II. Performance Testing

[0193] (1) Weight-average molecular weight

[0194] Weight-average molecular weight can be determined using methods known in the art, such as gel permeation chromatography (GPC), specifically a Waters 2695 Isocratic HPLC system (differential refractive index detector 2141). The test method uses a 3.0% polystyrene solution as a reference, selecting a suitable column (oil-based: Styragel HT5DMF7.8×300mm + Styragel HT4). A 3.0% dispersant solution is prepared using purified N-methylpyrrolidone (NMP) solvent and allowed to stand for one day. During testing, tetrahydrofuran is first used to flush the solution, repeated several times. Then, 5 ml of the test solution is drawn, air is expelled from the syringe, and the needle tip is dried. Finally, the sample solution is slowly injected into the injection port. After the reading stabilizes, the data is acquired, and the weight-average molecular weight is recorded.

[0195] (2) Solid content

[0196] The formula for expressing solid content is: solid content = (ac) / a, where a is the total weight and the solvent is cg; the solid content is calculated based on the amount of material fed.

[0197] (3) Surface density

[0198] A punching machine is used to punch out electrode sheets of a fixed area, with an area of ​​a cm². 2 Weigh the substrate using an electronic balance and record the mass as bg; under the same conditions, weigh the empty substrate and record the mass as cg. The surface density of the primer coating = (bc) / a mg / cm³ 2 ;

[0199] (4) Viscosity of the slurry

[0200] Referring to the national standard GB / T10247-2008 "Viscosity Measurement Methods", at a certain temperature, when a rotor rotates continuously at a constant speed in a sample, the shear force it experiences causes a spring to generate torque. The torque is proportional to the viscosity, thus yielding the viscosity value. The viscosity of the prepared primer slurry was tested using a digital viscometer.

[0201] (5) Number of missed areas in the primer coating

[0202] Online detection of uncoated areas in the electrode undercoat: Image data of the battery electrodes is acquired by a CCD camera module, received and processed by a processing module to determine whether the electrode surface meets pre-defined parameters, and the corresponding location of defective electrodes after slitting is provided. The machine can record uncoated areas per square meter that are larger than the uncoated specification (0.1mm). 2 The number of missing coatings.

[0203] (6) Capacity retention test procedure

[0204] At 25°C, the prepared battery is charged to 3.8V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 3.8V, left to rest for 5 minutes, and then discharged to 2.0V at 1 / 3C. The resulting discharge capacity is recorded as the initial capacity C0. The above steps are repeated for the same battery, and the discharge capacity Cn of the battery after the nth cycle is recorded. The battery capacity retention rate after each cycle is Pn = (Cn / C0) × 100%. The test is stopped when the battery capacity retention rate Pn ≤ 80%, and the number of cycles at this time is recorded to characterize the battery's cycle performance.

[0205] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0206] Secondary batteries for each embodiment and comparative example were prepared according to the above method, and various performance parameters were measured. The results are shown in Table 1 and Table 2 below.

[0207] Table 1 Preparation parameters of the primer slurry

[0208] Table 2. Preparation and performance parameters of the base coating and battery.

[0209] In Examples 1-14, the primer slurry includes one or more linear polymers such as cellulose ether and its modified forms, polyimide, nitrile rubber, hydrogenated nitrile rubber, polyvinylpyrrolidone, and hydrogenated styrene-butadiene rubber. The primer slurries prepared from these polymers rarely experience missed coating.

[0210] The primer slurry in Comparative Example 1 did not contain the aforementioned linear polymer; instead, it used an aqueous primer slurry with sodium carboxymethyl cellulose as a dispersant. A comparison between Comparative Example 1 and Examples 1-14 shows that the aqueous primer slurry causes significant undercoating during the current collector preparation process; and the undercoated areas develop dendrites, thus deteriorating the cycle performance of the electrodeless battery. Therefore, only by using the primer slurry prepared in Examples 1-14 can the undercoating problem in the current collector preparation of electrodeless batteries be improved.

[0211] In Examples 1-4, the primer slurry incorporated various linear polymers such as methyl cellulose ether, ethyl cellulose ether, hydroxypropyl cellulose ether, and polyimide. Compared to Comparative Example 1, these polymers effectively improved the coating leakage problem in the current collector preparation and enhanced the battery cycle performance. Among them, Example 1, which used methyl cellulose ether, produced the primer slurry with the best performance in both the primer slurry and the negative electrode-free battery.

[0212] Examples 13-14 used oil-based primer slurries containing polyurethane or PVDF, which, compared to Comparative Example 1, effectively improved the coating leakage problem in current collector preparation and slightly improved the battery cycle performance. Meanwhile, a comparison between Examples 13-14 and Examples 1-4 shows that only when one or more of the following are used in the primer slurry: cellulose ether and its modified forms, polyimide, nitrile rubber, hydrogenated nitrile rubber, polyvinylpyrrolidone, and hydrogenated styrene-butadiene rubber, can the coating leakage problem be improved while further improving the battery cycle performance. Using other types of dispersants, such as polyurethane or PVDF, while improving the coating leakage problem, has limited effect on improving battery cycle performance.

[0213] In Examples 1 and 5-6, the linear polymers in the primer slurry had a weight-average molecular weight of 5w-80w, which effectively improved the problem of missing coating in the current collector preparation and improved the cycle performance of the battery compared with Comparative Example 1.

[0214] In Examples 1 and 7, when the mass percentage of linear polymer in the primer slurry is 70%-90% and the mass percentage of conductive agent is 10%-30%, the battery cycle performance can be further improved while the problem of missing coating is improved. The battery prepared using such primer slurry has better performance.

[0215] In Examples 1 and 8-9, the solid content of the primer slurry was 2%-20%, which effectively improved the problem of missing coating in the current collector preparation and improved the cycle performance of the battery compared with Comparative Example 1.

[0216] In Examples 1 and 10-11, the areal density of the base coating was 0.1 mg / cm³. 2 -0.8mg / cm 2 Compared with Comparative Example 1, both of them effectively improved the problem of missing coating in the current collector preparation and improved the cycle performance of the battery.

[0217] In Examples 1 and 12, the organic solvents used in the primer slurry were N-methylpyrrolidone and dimethyl sulfoxide, which, compared with Comparative Example 1, effectively improved the problem of missing coating in the current collector preparation and improved the cycle performance of the battery.

[0218] 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 negative electrode-free secondary battery, characterized in that, The negative electrode-free secondary battery includes a negative electrode current collector and a base coating disposed on the negative electrode current collector at least on the side close to the positive electrode plate. The base coating includes a linear polymer and a conductive agent. The linear polymer includes one or more of cellulose ethers and their modified forms, polyimide, nitrile rubber, hydrogenated nitrile rubber, polyvinylpyrrolidone, hydrogenated styrene-butadiene rubber, polyurethane, and polyvinylidene fluoride.

2. The negative electrode-free secondary battery according to claim 1, characterized in that, The linear polymers include cellulose ethers and their modified forms.

3. The negative electrode-free secondary battery according to claim 1 or 2, characterized in that, The cellulose ether includes one or more of methylcellulose ether, ethylcellulose ether, hydroxypropylcellulose ether, hydroxyethylcellulose ether, hydroxyethylmethylcellulose ether, and hydroxypropylmethylcellulose ether.

4. The negative electrode-free secondary battery according to any one of claims 1 to 3, characterized in that, The linear polymer has a weight-average molecular weight of 5w-80w.

5. The negative electrode-free secondary battery according to any one of claims 1 to 4, characterized in that, Based on the total mass of the base coating, the linear polymer accounts for 70%-90% of the total mass.

6. The negative electrode-free secondary battery according to any one of claims 1 to 5, characterized in that, The conductive agent includes one or more of conductive carbon black, carbon nanotubes, graphene, acetylene black, and Ketjen black.

7. The negative electrode-free secondary battery according to claim 6, characterized in that, The conductive agent includes conductive carbon black.

8. The negative electrode-free secondary battery according to any one of claims 1 to 7, characterized in that, Based on the total mass of the base coating, the conductive agent accounts for 10%-30% of the total mass.

9. The negative electrode-free secondary battery according to any one of claims 1 to 8, characterized in that, The areal density of the base coating is 0.1 mg / cm³. 2 -0.8mg / cm 2 .

10. The negative electrode-free secondary battery according to any one of claims 1 to 9, characterized in that, The number of missed areas in the primer coating is no more than 12, and the number of missed areas is defined as an area with a missed area greater than 0.1 mm per square meter. 2 The number of.

11. The negative electrode-free secondary battery according to any one of claims 1 to 10, characterized in that, The negative electrode current collector is prepared by a rolling pressing method.

12. The negative electrode-free secondary battery according to any one of claims 1 to 11, characterized in that, The negative electrode-free secondary battery includes one or more of the following: negative electrode-free lithium secondary battery and negative electrode-free sodium secondary battery; and / or, The negative electrode current collector includes one or more of the following: aluminum foil, copper foil, stainless steel substrate, titanium foil, plastic film composite copper foil, and plastic film composite aluminum foil.

13. The negative electrode-free secondary battery according to claim 12, characterized in that, The plastic film is at least one of PET film, PP film, and PI film.

14. An electrical appliance, characterized in that, The electrical device includes any one of claims 1 to 13, a negative electrode-free secondary battery.

15. A primer slurry, characterized in that, The primer slurry comprises a linear polymer, a conductive agent, and an organic solvent. The linear polymer comprises one or more of the following: cellulose ether and its modified forms, polyimide, nitrile rubber, hydrogenated nitrile rubber, polyvinylpyrrolidone, hydrogenated styrene-butadiene rubber, polyurethane, and polyvinylidene fluoride.

16. The primer slurry according to claim 15, characterized in that, The linear polymers include cellulose ethers and their modified forms.

17. The primer slurry according to claim 15 or 16, characterized in that, The cellulose ether includes one or more of methylcellulose ether, ethylcellulose ether, hydroxypropylcellulose ether, hydroxyethylcellulose ether, hydroxyethylmethylcellulose ether, and hydroxypropylmethylcellulose ether.

18. The primer slurry according to any one of claims 15 to 17, characterized in that, The linear polymer has a weight-average molecular weight of 5w-80w.

19. The primer slurry according to any one of claims 15 to 18, characterized in that, Based on the total mass of dry material in the primer slurry, the linear polymer accounts for 70%-90% of the mass.

20. The primer slurry according to any one of claims 15 to 19, characterized in that, The conductive agent includes one or more of conductive carbon black, carbon nanotubes, graphene, acetylene black, and Ketjen black.

21. The primer slurry according to claim 20, characterized in that, The conductive agent includes conductive carbon black.

22. The primer slurry according to any one of claims 15 to 21, characterized in that, Based on the total mass of the dry slurry, the conductive agent accounts for 10%-30% of the total mass.

23. The primer slurry according to any one of claims 15 to 22, characterized in that, The organic solvent includes one or more of N-methylpyrrolidone, ethanol, acetone, propylene carbonate, methyl ethyl carbonate, dimethyl carbonate, and dimethyl sulfoxide.

24. The primer slurry according to claim 23, characterized in that, The organic solvent includes N-methylpyrrolidone.

25. The primer slurry according to any one of claims 15 to 24, characterized in that, The solid content of the primer slurry is 2%-20%, and the viscosity of the primer slurry is 3000mPa·s-13000mPa·s.

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