Secondary battery and electric apparatus

Abstract

A secondary battery and an electric apparatus. The secondary battery comprises a positive electrode sheet, wherein the positive electrode sheet comprises a current collector; the current collector comprises a substrate, and a lithium-supplementing agent thin film and a coating which are located on at least the same side of the substrate; the coating includes a reducing agent; when the lithium-supplementing agent thin film is located on at least one side of the substrate, the coating is located on the side that is adjacent to the lithium-supplementing agent thin film and is away from the substrate; and when the coating is located on at least one side of the substrate, the lithium-supplementing agent thin film is located on the side that is adjacent to the coating and is away from the substrate. The secondary battery has good cycle performance and long service life.

Description

Secondary batteries and electrical devices Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a secondary battery and an electrical device. Background Art

[0002] Lithium-ion batteries (LIBs), a type of secondary battery, boast high energy density, long service life, and are energy-efficient and environmentally friendly. However, during the initial charge and discharge process of a lithium-ion battery, the electrolyte forms a solid electrolyte interface film (SEI) on the surface of the negative electrode. This SEI film formation consumes a large amount of active lithium ions. Furthermore, during the battery's charge and discharge cycles, the cracking and shattering of the positive electrode active material particles, and the thickening and repair of the SEI film, all consume active lithium ions, easily leading to a decrease in the battery's cycle capacity and shortening its service life.

[0003] Summary of the Invention

[0004] The present application is made in view of the above-mentioned problems, and its purpose is to provide a secondary battery, aiming to solve the technical problem of how to improve the cycle performance of the secondary battery and extend the service life of the battery.

[0005] A first aspect of the present application provides a secondary battery, comprising a positive electrode plate, the positive electrode plate comprising a current collector, the current collector comprising a substrate, and a lithium supplement film and a coating located on at least the same side of the substrate, the coating comprising a reducing agent,

[0006] When the lithium supplement film is located on at least one side of the substrate, the coating is located on a side adjacent to the lithium supplement film and away from the substrate;

[0007] When the coating layer is located on at least one side of the substrate, the lithium replenisher film is located on a side adjacent to the coating layer and away from the substrate.

[0008] When the lithium supplement agent is in the form of a thin film and the reducing agent is in the form of a coating on one side of the current collector matrix, the thin film and the coating form surface-to-surface contact, so that the lithium supplement agent and the reducing agent can form point-surface contact, which can increase the contact area between the lithium supplement agent and the reducing agent, increase the degree of reaction between the lithium supplement agent and the reducing agent, and improve the lithium supplement efficiency of the lithium supplement agent. At the same time, the lithium supplement agent and the reducing agent are coated on the surface of the current collector matrix, and the good conductivity of the current collector matrix can be used to improve the conductive network between the lithium supplement agent and the reducing agent, provide more electron transmission pathways, increase the degree of reaction between the lithium supplement agent and the reducing agent, and improve the lithium supplement efficiency of the lithium supplement agent.

[0009] In summary, by using the secondary battery of the present application, the contact area between the lithium supplement agent and the reducing agent is increased, and the degree of reaction between the two is increased. The lithium supplement agent can maximize its lithium supplement effect, improve the lithium supplement efficiency of the lithium supplement agent, provide a large amount of active lithium for lithium supplementation during the cycle process, and the battery has an excellent cycle number and a long service life.

[0010] In any embodiment, the mass ratio of the lithium replenisher film to the reducing agent is 0.5-50.

[0011] In any embodiment, the mass ratio of the lithium replenisher film to the reducing agent is 1-20.

[0012] The mass ratio of the lithium replenisher film to the reducing agent is within an appropriate range, which allows the lithium replenisher and the reducing agent to fully react to improve the lithium replenishment efficiency while avoiding excessive residual lithium replenisher or reducing agent affecting the battery's rate performance and energy density.

[0013] In any embodiment, the coating further comprises a conductive agent.

[0014] The coating containing the reducing agent also includes a conductive agent, which can further improve the conductive network between the lithium supplement agent and the reducing agent, form a continuous electron transmission path between the lithium supplement agent and the reducing agent, improve the lithium supplement efficiency of the lithium supplement agent, and improve the cycle performance of the battery.

[0015] In any embodiment, the mass ratio of the reducing agent to the conducting agent is 0.05-20.

[0016] In any embodiment, the mass ratio of the reducing agent to the conducting agent is 0.2-10.

[0017] The mass ratio of the reducing agent to the conductive agent in the coating is within an appropriate range. While improving the conductive network between the lithium supplement agent and the reducing agent, it also ensures that the reducing agent in the coating and the lithium supplement agent film have sufficient contact sites, thereby achieving the purpose of increasing the contact area between the lithium supplement agent and the reducing agent, and jointly achieving the purpose of improving the lithium supplement efficiency of the lithium supplement agent and extending the service life of the battery.

[0018] In any embodiment, the positive electrode plate further includes a positive electrode film layer, and based on the total mass of the positive electrode film layer, the mass percentage of the lithium supplement film is 0.5%-20%.

[0019] In any embodiment, based on the total mass of the positive electrode film, the mass percentage of the lithium supplement film is 1%-10%.

[0020] The mass percentage of the lithium replenisher film is within an appropriate range. On the one hand, the lithium replenisher film can fully exert its lithium replenishing effect and improve the cycle performance of the battery. On the other hand, it also avoids excessive lithium replenisher film from having an adverse effect on the battery's rate performance, available capacity and safety performance.

[0021] In any embodiment, based on the total mass of the positive electrode film layer, the mass percentage of the reducing agent is 0.01%-10%.

[0022] In any embodiment, based on the total mass of the positive electrode film layer, the mass percentage of the reducing agent is 0.02%-5%.

[0023] The mass percentage of the reducing agent is within an appropriate range. On the one hand, the lithium replenisher film reacts fully with a sufficient amount of reducing agent, so that the lithium replenisher can maximize its lithium replenishing effect and improve the cycle performance of the battery. On the other hand, it also avoids the adverse effects of excessive reducing agent on the available capacity and safety performance.

[0024] In any embodiment, the lithium replenisher film includes one or more of a lithium nickelate film, a lithium-rich lithium nickelate film, a lithium ferrite film, a lithium-rich lithium ferrite film, a lithium oxalate film, a lithium quartz film, a lithium metasilicate film, a lithium orthosilicate film, a lithium carbonate film, a lithium sulfate film, a lithium hydroxide film, a lithium phosphate film, a lithium oxide film, a lithium peroxide film, a lithium borate film, and a lithium metaborate film.

[0025] The lithium replenisher film has high irreversible capacity and good lithium replenishment effect. In addition, the lithium replenisher film has good stability in the air and good compatibility with the existing battery production process, which is conducive to industrial production.

[0026] In any embodiment, the reducing agent includes one or more of elemental selenium, metal compounds of selenium, elemental sulfur, metal compounds of sulfur, elemental phosphorus, metal compounds of phosphorus, elemental boron, metal compounds of boron, elemental tellurium, metal compounds of tellurium, elemental antimony, metal compounds of antimony, elemental bismuth, metal compounds of bismuth, and selenium disulfide.

[0027] The above-mentioned reducing agent can chemically react with the lithium supplement agent film to reduce the decomposition potential of the lithium supplement agent, achieve low-potential lithium supplementation, improve the decomposition efficiency and utilization rate of the lithium supplement agent, improve the capacity retention rate of the battery, and increase the battery life.

[0028] In any embodiment, the preparation method of the lithium supplement agent film includes at least one of chemical vapor deposition, physical vapor deposition, atomic layer deposition, and molecular layer deposition.

[0029] In any embodiment, the surface of the conductive agent is coated with a reducing agent.

[0030] Coating the reducing agent on the surface of the conductive agent can further improve the conductive network between the lithium replenishing agent and the reducing agent, which is beneficial to improving the lithium replenishing efficiency of the lithium replenishing agent and improving the cycle performance of the battery.

[0031] In any embodiment, the thickness of the lithium supplement agent film is 50 nm to 500 nm; and / or the thickness of the coating layer is 0.5 μm to 5 μm.

[0032] In any embodiment, the lithium replenishment efficiency of the lithium replenishment agent film is greater than or equal to 85%.

[0033] In any embodiment, the lithium replenishing efficiency of the lithium replenishing agent film is 90%-100%.

[0034] A second aspect of the present application provides an electrical device comprising the secondary battery of the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG1 is a schematic diagram of a current collector in one embodiment of the present application;

[0036] FIG2 is a schematic diagram of a current collector in one embodiment of the present application;

[0037] FIG3 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0038] FIG4 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG3 ;

[0039] FIG5 is a schematic diagram of a battery module according to an embodiment of the present application;

[0040] FIG6 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0041] FIG7 is an exploded view of the battery pack shown in FIG6 according to an embodiment of the present application;

[0042] FIG8 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0043] Reference numerals: 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 housing; 52 electrode assembly; 53 cover plate; 6 current collector; 61 substrate; 62 lithium supplement film; 63 coating. DETAILED DESCRIPTION

[0044] Below, the embodiments of the secondary battery and the electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0045] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0047] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0048] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0049] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0050] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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).

[0051] All active lithium in lithium-ion batteries is provided by the positive electrode active material. However, during the initial charging process of the lithium-ion battery, the formation of the solid electrolyte membrane (SEI membrane) on the negative electrode surface and other chemical side reactions during the subsequent charge and discharge cycles will consume active lithium ions, deteriorating the battery's cycle performance. To improve the cycle performance of lithium-ion batteries, the industry's commonly used solution is to add positive electrode lithium replenishers to the battery's positive electrode. Commonly used positive electrode lithium replenishers generally include binary lithium-containing compounds, ternary lithium-containing compounds, or organic lithium salts. However, most positive electrode lithium replenishers have a high decomposition voltage, which will affect the battery's cycle performance and safety performance. In order to solve the problem of high decomposition potential of positive electrode lithium replenishers, lithium replenishers and reducing agents are often added to the positive electrode film layer or the lithium replenishing bottom coating layer in the form of additives. However, the reducing agent and the lithium replenisher in the positive electrode film layer or the lithium replenishing bottom coating layer are both in particle state, and the contact between the two is point-to-point contact. In addition, the conductive agent, positive electrode active material and binder in the positive electrode film layer will isolate the two, or the binder in the lithium replenishing bottom coating layer will isolate the two. The reducing agent and the lithium replenisher cannot fully contact and react with each other. The lithium replenisher cannot play its lithium replenishing role, the lithium replenishing efficiency is low, and the purpose of improving the cycle performance of the battery cannot be achieved.

[0052] [Secondary battery]

[0053] The present application provides a secondary battery, comprising a positive electrode plate, the positive electrode plate comprising a current collector, the current collector comprising a substrate, and a lithium supplement film and a coating located on at least the same side of the substrate, the coating comprising a reducing agent,

[0054] When the lithium supplement film is located on at least one side of the substrate, the coating is located on a side adjacent to the lithium supplement film and away from the substrate;

[0055] When the coating layer is located on at least one side of the substrate, the lithium replenisher film is located on a side adjacent to the coating layer and away from the substrate.

[0056] In this article, the term "lithium supplement" refers to a material that can undergo a decomposition reaction and provide active lithium within the operating range of a secondary battery, and the active lithium will not be back-intercalated during the discharge process, thereby compensating for the loss of active lithium.

[0057] In this article, the term "reducing agent" refers to a compound that can reduce the lithium supplement agent, so that the lithium supplement agent produces lithium ions at a lower voltage platform, reducing the decomposition voltage of the lithium supplement agent, thereby enabling lithium supplement agents with higher capacity to have a stronger application space.

[0058] In this article, the term "lithium supplement agent film" refers to a thin film formed by depositing, coating or other processes a lithium supplement agent on a substrate or a coating, and the lithium supplement agent film layer does not contain a binder.

[0059] Schematic diagrams of the current collector structure of an embodiment of the present application are shown in Figures 1 and 2. In Figure 1, the current collector 6 includes a substrate 61, a lithium replenisher film 62, and a coating 63 located on the same side of the substrate 61. The coating 63 contains a reducing agent. When the lithium replenisher film 62 is located on one side of the substrate 61, the coating 63 is located on a side adjacent to the lithium replenisher film 62 and away from the substrate 61. In Figure 2, the current collector 6 includes a substrate 61, a lithium replenisher film 62, and a coating 63 located on the same side of the substrate 61. The coating 63 contains a reducing agent. When the coating 63 is located on one side of the substrate 61, the lithium replenisher film 62 is located on a side adjacent to the coating 63 and away from the substrate 61.

[0060] In some embodiments, both sides of the substrate contain a lithium replenisher film and a coating.

[0061] In some embodiments, the substrate may be a metal foil or a composite substrate. For example, aluminum foil may be used as the metal foil. The composite substrate may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite substrate 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 polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0062] When the lithium supplement agent is in the form of a thin film and the reducing agent is in the form of a coating on one side of the current collector matrix, the thin film and the coating form direct surface-to-surface contact. Compared with the lithium supplement agent and the reducing agent both being present in the form of additives in the positive electrode film layer or the lithium supplement coating, the two form point-point contact or direct non-contact. The lithium supplement agent and the reducing agent of the present application can form point-surface contact, which can increase the contact area between the lithium supplement agent and the reducing agent, increase the reaction degree of the lithium supplement agent and the reducing agent, and improve the lithium supplement efficiency of the lithium supplement agent. At the same time, the lithium supplement agent and the reducing agent are coated on the surface of the current collector matrix, and the good conductivity of the current collector matrix can be used to improve the conductive network between the lithium supplement agent and the reducing agent, provide more electron transmission pathways, increase the reaction degree of the lithium supplement agent and the reducing agent, and improve the lithium supplement efficiency of the lithium supplement agent.

[0063] In summary, by using the secondary battery of the present application, the contact area between the lithium supplement agent and the reducing agent is increased, and the degree of reaction between the two is increased. The lithium supplement agent can maximize its lithium supplement effect, improve the lithium supplement efficiency of the lithium supplement agent, provide a large amount of active lithium for lithium supplementation during the cycle process, and the battery has an excellent cycle number and a long service life.

[0064] In some embodiments, the mass ratio of the lithium replenishing agent film to the reducing agent is 0.5-50. In some embodiments, the mass ratio of the lithium replenishing agent film to the reducing agent can be selected from 0.5, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 or any range therebetween.

[0065] In some embodiments, the mass ratio of the lithium replenishing agent film to the reducing agent is 1 to 20. In some embodiments, the mass ratio of the lithium replenishing agent film to the reducing agent can be selected from 1, 5, 10, 15, 20 or any range therebetween.

[0066] The mass ratio of the lithium replenisher film to the reducing agent is within an appropriate range, which allows the lithium replenisher and the reducing agent to fully react to improve the lithium replenishment efficiency while avoiding excessive residual lithium replenisher or reducing agent affecting the battery's rate performance and energy density.

[0067] In some embodiments, the coating further comprises a conductive agent.

[0068] In some embodiments, the conductive agent comprises at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0069] The coating containing the reducing agent also includes a conductive agent, which can further improve the conductive network between the lithium supplement agent and the reducing agent, form a continuous electron transmission path between the lithium supplement agent and the reducing agent, improve the lithium supplement efficiency of the lithium supplement agent, and improve the cycle performance of the battery.

[0070] In some embodiments, the coating further comprises a binder.

[0071] In some embodiments, the binder comprises any one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), polyacrylate, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0072] In some embodiments, the mass ratio of the reducing agent to the conducting agent is 0.05 to 20. In some embodiments, the mass ratio of the reducing agent to the conducting agent is 0.05, 0.1, 0.5, 1, 5, 10, 15, 20, or any range therebetween.

[0073] In some embodiments, the mass ratio of the reducing agent to the conducting agent is 0.2 to 10. In some embodiments, the mass ratio of the reducing agent to the conducting agent is 0.2, 0.5, 1, 3, 4, 6, 8, 10, or any range therebetween.

[0074] The mass ratio of the reducing agent to the conductive agent in the coating is within an appropriate range. While improving the conductive network between the lithium supplement agent and the reducing agent, it also ensures that the reducing agent in the coating and the lithium supplement agent film have sufficient contact sites, thereby achieving the purpose of increasing the contact area between the lithium supplement agent and the reducing agent, and jointly achieving the purpose of improving the lithium supplement efficiency of the lithium supplement agent and extending the service life of the battery.

[0075] In some embodiments, the positive electrode plate further includes a positive electrode film layer, and based on the total mass of the positive electrode film layer, the mass percentage of the lithium supplement film is 0.5%-20%.

[0076] In some embodiments, the positive electrode sheet includes a current collector and a positive electrode film layer disposed on at least one surface of the current collector.

[0077] In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage of the lithium supplement film can be selected as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% or any numerical range therebetween.

[0078] In some embodiments, the mass percentage of the lithium replenisher film is 1%-10% based on the total mass of the positive electrode film layer. In some embodiments, the mass percentage of the lithium replenisher film is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any range therebetween, based on the total mass of the positive electrode film layer.

[0079] The mass percentage of the lithium replenisher film is within an appropriate range. On the one hand, the lithium replenisher film can fully exert its lithium replenishing effect and improve the cycle performance of the battery. On the other hand, it also avoids excessive lithium replenisher film from having an adverse effect on the battery's rate performance, available capacity and safety performance.

[0080] In some embodiments, the mass percentage of the reducing agent is 0.01%-10% based on the total mass of the positive electrode film layer. In some embodiments, the mass percentage of the reducing material is 0.01%, 0.05%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any range therebetween, based on the total mass of the positive electrode film layer.

[0081] In some embodiments, the mass percentage of the reducing agent is 0.02%-5% based on the total mass of the positive electrode film layer. In some embodiments, the mass percentage of the reducing agent is 0.02%, 0.05%, 1%, 2%, 3%, 4%, 5%, or any range therebetween based on the total mass of the positive electrode film layer.

[0082] The mass percentage of the reducing agent is within an appropriate range. On the one hand, the lithium replenisher film reacts fully with a sufficient amount of reducing agent, so that the lithium replenisher can maximize its lithium replenishing effect and improve the cycle performance of the battery. On the other hand, it also avoids the adverse effects of excessive reducing agent on the available capacity and safety performance.

[0083] In some embodiments, the lithium replenisher film includes one or more of a lithium nickelate film, a lithium-rich lithium nickelate film, a lithium ferrite film, a lithium-rich lithium ferrite film, a lithium oxalate film, a lithium quartz film, a lithium metasilicate film, a lithium orthosilicate film, a lithium carbonate film, a lithium sulfate film, a lithium hydroxide film, a lithium phosphate film, a lithium oxide film, a lithium peroxide film, a lithium borate film, and a lithium metaborate film.

[0084] The lithium replenisher film has high irreversible capacity and good lithium replenishment effect. In addition, the lithium replenisher film has good stability in the air and good compatibility with the existing battery production process, which is conducive to industrial production.

[0085] In some embodiments, the lithium replenisher film includes one or more of a lithium-rich lithium nickelate film, a lithium metasilicate film, a lithium orthosilicate film, a lithium sulfate film, a lithium hydroxide film, a lithium borate film, a lithium metaborate film, and a lithium phosphate film.

[0086] The combination of a suitable lithium-supplementing agent film and a reducing agent in the coating can not only reduce the decomposition potential of the lithium-supplementing agent, fully utilizing its lithium-supplementing effect, but also eliminate the presence of gases such as oxygen, carbon dioxide, or nitrogen in the reaction products, reducing the likelihood of gassing and their impact on battery safety and cycling performance. Furthermore, the decomposition products of the lithium-supplementing agent, including silicon oxide, nickel oxide, lithium oxide, boron oxide, or lithium sulfate, possess excellent ionic conductivity, which helps improve the electrode's ionic conductivity and enhances the battery's rate capability and cycling performance.

[0087] In some embodiments, the lithium replenisher film includes one or both of a lithium metasilicate film and a lithium orthosilicate film.

[0088] The decomposition potential of lithium metasilicate or lithium orthosilicate is low, which enables lithium supplements with higher capacity to have a stronger application space. The decomposition products contain silicon dioxide and lithium sulfate, which have good ion conductivity, can enhance the ion conductivity of the positive electrode sheet and improve the battery's rate performance and cycle performance.

[0089] In some embodiments, the reducing agent includes one or more of elemental selenium, metal compounds of selenium, elemental sulfur, metal compounds of sulfur, elemental phosphorus, metal compounds of phosphorus, elemental boron, metal compounds of boron, elemental tellurium, metal compounds of tellurium, elemental antimony, metal compounds of antimony, elemental bismuth, metal compounds of bismuth, and selenium disulfide.

[0090] As used herein, the term "selenium metal compound" refers to a compound formed by selenium and a metal element, wherein the chemical valence of selenium in the selenium metal compound is negative, wherein the selenium metal compound includes but is not limited to lithium selenide, sodium selenide or calcium selenide.

[0091] As used herein, the term "sulfur metal compound" refers to a compound formed by sulfur and a metal element, wherein the chemical valence of sulfur in the sulfur metal compound is negative, wherein the sulfur metal compound includes but is not limited to calcium sulfide, lithium sulfide, sodium sulfide, zinc sulfide or iron sulfide.

[0092] As used herein, the term "phosphorus metal compound" refers to a compound formed by phosphorus and a metal element, wherein the chemical valence state of phosphorus in the phosphorus metal compound is negative, wherein the phosphorus metal compound includes but is not limited to lithium phosphide, sodium phosphide, iron phosphide, calcium phosphide, zinc phosphide, aluminum phosphide or copper phosphide.

[0093] As used herein, the term "boron metal compound" refers to a compound formed by boron and a metal element, wherein the chemical valence of boron in the boron metal compound is negative, wherein the boron metal compound includes but is not limited to titanium diboride, calcium hexaboride, molybdenum boride or cobalt boride.

[0094] Herein, the term "tellurium metal compound" refers to a compound formed by tellurium and a metal element, wherein the chemical valence state of tellurium in the tellurium metal compound is negative, wherein the tellurium metal compound includes but is not limited to copper telluride or molybdenum telluride.

[0095] Herein, the term "antimony metal compound" refers to a compound formed by antimony and a metal element, wherein the chemical valence of antimony in the antimony metal compound is negative, wherein the antimony metal compound includes but is not limited to lithium antimonide, sodium antimonide or indium antimonide.

[0096] Herein, the term "bismuth metal compound" refers to a compound formed by bismuth and a metal element, wherein the chemical valence state of bismuth in the bismuth metal compound is negative, wherein the bismuth metal compound includes but is not limited to sodium bismuthide.

[0097] The above-mentioned reducing agent can chemically react with the lithium supplement agent film, reduce the decomposition potential of the lithium supplement agent, achieve low-potential lithium supplementation, improve the decomposition efficiency and utilization rate of the lithium supplement agent film, improve the capacity retention rate of the battery, and increase the battery life.

[0098] In some embodiments, the reducing agent includes one or more of elemental selenium, non-transition metal compounds of selenium, elemental sulfur, non-transition metal compounds of sulfur, elemental phosphorus, non-transition metal compounds of phosphorus, elemental boron, non-transition metal compounds of boron, elemental tellurium, non-transition metal compounds of tellurium, elemental antimony, non-transition metal compounds of antimony, elemental bismuth, non-transition metal compounds of bismuth, and selenium disulfide.

[0099] In this article, the term "non-transition metal compound of selenium" refers to a compound formed by selenium and a non-transition metal element, wherein the chemical valence state of selenium in the non-transition metal compound of selenium is negative, wherein the metal compound of selenium includes but is not limited to lithium selenide, sodium selenide or calcium selenide.

[0100] As used herein, the term "non-transition metal compound of sulfur" refers to a compound formed by sulfur and a non-transition metal element, wherein the chemical valence of sulfur in the non-transition metal compound of sulfur is negative, wherein the non-transition metal compound of sulfur includes but is not limited to calcium sulfide, lithium sulfide or sodium sulfide.

[0101] As used herein, the term "non-transition metal compound of phosphorus" refers to a compound formed by phosphorus and a non-transition metal element, wherein the chemical valence state of phosphorus in the non-transition metal compound of phosphorus is negative, and the non-transition metal compound of phosphorus includes but is not limited to lithium phosphide, sodium phosphide, iron phosphide, calcium phosphide, and aluminum phosphide.

[0102] As used herein, the term "non-transition metal compound of boron" refers to a compound formed by boron and a non-transition metal element, wherein the chemical valence state of boron in the non-transition metal compound of boron is negative, wherein the non-transition metal compound of boron includes but is not limited to calcium hexaboride.

[0103] As used herein, the term "non-transition metal compound of tellurium" refers to a compound formed by tellurium and a non-transition metal element, wherein the chemical valence state of tellurium in the non-transition metal compound of tellurium is negative, and the non-transition metal compound of tellurium includes but is not limited to lithium telluride and sodium telluride.

[0104] In this article, the term "non-transition compound of antimony" refers to a compound formed by antimony and a non-transition metal element, wherein the chemical valence state of antimony in the non-transition metal compound of antimony is negative, wherein the non-transition metal compound of antimony includes but is not limited to lithium antimonide, sodium antimonide or indium antimonide.

[0105] Herein, the term "non-transition metal compound of bismuth" refers to a compound formed by bismuth and a non-transition metal element, wherein the chemical valence state of bismuth in the non-transition metal compound of bismuth is negative, wherein the non-transition metal compound of bismuth includes but is not limited to sodium bismuth.

[0106] The above-mentioned reducing agent does not contain transition metal elements, which can reduce the impact of the catalytic oxidation reaction between the transition metal elements and the electrolyte on the cycle or safety performance of the battery.

[0107] In some embodiments, the reducing agent includes one or more of elemental selenium, elemental sulfur, elemental phosphorus, elemental boron, elemental tellurium, elemental antimony, elemental bismuth, and selenium disulfide.

[0108] The above-mentioned reducing agent is a single substance, which can reduce the impact of the catalytic oxidation reaction between the transition metal element and the electrolyte on the cycle or safety performance of the battery. At the same time, the relative molecular mass of the single substance reducing agent is low, and the same mass content of reducing agent can react with more lithium supplement film, thereby improving the mass utilization rate of the reducing agent.

[0109] In some embodiments, the reducing agent includes one or more of elemental selenium, metal compounds of selenium, elemental sulfur, metal compounds of sulfur, and selenium disulfide.

[0110] The reducing agent has a strong reducing property. When added in a low amount, it can reduce the decomposition potential of the lithium replenisher, give full play to the lithium replenishing effect of the lithium replenisher film, improve the lithium replenishing efficiency of the lithium replenisher film, and increase the cycle number of the battery.

[0111] In some embodiments, the preparation method of the lithium supplement film includes at least one of chemical vapor deposition, physical vapor deposition, atomic layer deposition, and molecular layer deposition.

[0112] In some embodiments, physical vapor deposition includes thermal evaporation, magnetron sputtering, or ion plating.

[0113] Chemical vapor deposition, physical vapor deposition, atomic layer deposition, and molecular layer deposition are conventional processes for preparing thin films. A suitable process is selected according to the type of lithium replenisher to prepare the lithium replenisher film.

[0114] By using the above-mentioned chemical vapor deposition, physical vapor deposition, atomic layer deposition, and molecular layer deposition, a uniform and dense lithium supplement film can be formed on a substrate or a coating.

[0115] In some embodiments, the surface of the conductive agent is coated with a reducing agent.

[0116] Coating the reducing agent on the surface of the conductive agent can further improve the conductive network between the lithium replenishing agent and the reducing agent, which is beneficial to improving the lithium replenishing efficiency of the lithium replenishing agent and improving the cycle performance of the battery.

[0117] In some embodiments, the thickness of the lithium supplementing agent film is 50 nm to 500 nm. In some embodiments, the thickness of the lithium supplementing agent film is 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or any range therebetween.

[0118] The thickness of the lithium replenisher film is within an appropriate range, so that a sufficient amount of lithium replenisher reacts with the reducing agent in the coating to provide enough active lithium to improve the cycle performance of the battery, while also avoiding the lithium replenisher film being too thick to affect the volume energy density of the battery.

[0119] In some embodiments, the coating has a thickness of 0.5 μm to 5 μm. In some embodiments, the coating has a thickness of 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or any range therebetween.

[0120] The thickness of the coating is within an appropriate range, so that a sufficient amount of reducing agent reacts with the lithium replenisher film, thereby improving the lithium replenishment efficiency of the lithium replenisher film and improving the cycle performance of the battery, while also avoiding the coating being too thick to affect the volume energy density of the battery.

[0121] In some embodiments, the lithium replenishment efficiency of the lithium replenisher film is greater than or equal to 85%.

[0122] In some embodiments, the lithium replenishment efficiency of the lithium replenisher film is 90%-100%.

[0123] In some embodiments, the lithium replenishment efficiency of the lithium replenishment agent film can be selected to be 85%, 87%, 90%, 94%, 95%, 97%, 98%, 99%, 100% or any range therebetween.

[0124] The lithium replenisher film has high lithium replenishment efficiency, improves the cycle performance of the battery, and extends the service life of the battery.

[0125] In some embodiments, the current collector can be prepared as follows: a reducing agent, a binder, and any other components are dispersed in a solvent (e.g., deionized water) to form a coating slurry, which is then applied to a substrate to form a coating; and a lithium replenisher raw material is deposited on the coating surface using chemical vapor deposition, physical vapor deposition, atomic layer deposition, or molecular layer deposition to form a lithium replenisher thin film to obtain a current collector.

[0126] In some embodiments, the current collector can be prepared as follows: a reducing agent, a binder, a conductive agent, and any other components are dispersed in a solvent (e.g., deionized water) to form a coating slurry, which is then applied to a substrate to form a coating; and a lithium replenisher raw material is used to form a lithium replenisher thin film on the coating surface by chemical vapor deposition, physical vapor deposition, atomic layer deposition, or molecular layer deposition to obtain a current collector.

[0127] In some embodiments, the current collector can be prepared by: forming a lithium replenisher film on the surface of the substrate using chemical vapor deposition, physical vapor deposition, atomic layer deposition or molecular layer deposition methods using a lithium replenisher raw material; dispersing a reducing agent, a binder and any other components in a solvent (such as deionized water) to form a coating slurry, which is applied on the lithium replenisher film to form a coating to obtain a current collector.

[0128] In some embodiments, the current collector can be prepared by: forming a lithium replenisher film on the surface of the substrate using chemical vapor deposition, physical vapor deposition, atomic layer deposition or molecular layer deposition methods using a lithium replenisher raw material; dispersing a reducing agent, a binder, a conductive agent and any other components in a solvent (such as deionized water) to form a coating slurry, which is applied on the lithium replenisher film to form a coating to obtain a current collector.

[0129] In the above method, during the preparation of the lithium replenisher film, the lithium replenisher raw materials can be conventionally selected based on the type of the target lithium replenisher film and the preparation process of the lithium replenisher film. For example, if the target lithium replenisher film is a lithium metasilicate film and the selected process is atomic layer deposition, the lithium replenisher raw materials are lithium oxide and silicon dioxide. For example, if the target lithium replenisher film is a lithium metasilicate film and the selected process is chemical vapor deposition, the lithium replenisher raw materials are lithium carbonate and tetramethyl orthosilicate. For example, if the target lithium replenisher film is a lithium silicate film and the selected process is physical vapor deposition, the lithium replenisher raw materials are lithium silicate.

[0130] In one embodiment, the secondary battery comprises a lithium-ion battery. Specifically, it comprises a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive and negative electrodes. During the battery's charge and discharge processes, active ions are intercalated and released between the positive and negative electrodes. The electrolyte acts as an ion conductor between the positive and negative electrodes. The separator, disposed between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0131] In some embodiments, the cathode film layer includes a cathode active material.

[0132] In some embodiments, the positive electrode active material includes a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials. These positive electrode active materials can be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds, etc. Examples of lithium phosphates containing olivine structure may include but are not limited to lithium iron phosphate (such as LiFePO 4( It can also be referred to as LFP), at least one of a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0133] In some embodiments, the positive electrode active material includes lithium iron phosphate or a modified form of lithium iron phosphate, wherein the modified form includes one or more of doping modification and coating modification.

[0134] In some embodiments, the positive electrode film layer further includes a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0135] In some embodiments, the positive electrode film layer further includes a binder, which may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.

[0136] In some embodiments, the positive electrode sheet can be prepared by the following method: the positive electrode active material, binder, conductive agent and any other components in the above embodiment are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0137] [Negative electrode]

[0138] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0139] As an example, the negative electrode current collector has two surfaces opposite to each other in its 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.

[0140] 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 base layer and a metal layer formed on at least one surface of the polymer base material. 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 base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0141] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0142] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0143] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0144] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0145] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0146] [Electrolytes]

[0147] In some embodiments, the electrolyte acts as a conductive medium between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte may be selected based on specific needs. For example, the electrolyte may be liquid, gel, or solid.

[0148] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0149] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0150] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0151] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0152] [Diaphragm]

[0153] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0154] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven 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.

[0155] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0156] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0157] 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. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0158] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0159] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0160] 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. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0161] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape. For example, FIG3 shows a secondary battery 5 having a square structure as an example.

[0162] In some embodiments, referring to Figure 4, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0163] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0164] Figure 5 shows an example battery module 4. Referring to Figure 5 , within the battery module 4, multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple secondary batteries 5 may be secured together using fasteners.

[0165] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0166] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0167] Figures 6 and 7 illustrate an example battery pack 1. Referring to Figures 6 and 7 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0168] In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present 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 mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0169] As an electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0170] Figure 8 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0171] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0172] Example

[0173] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0174] 1. Preparation method

[0175] Example 1

[0176] 1) Preparation of positive electrode sheet

[0177] Coating: Dissolve polyacrylate binder and elemental sulfur in deionized water at a mass ratio of 80%:20%, stir and mix thoroughly, and then apply to one side of the positive electrode aluminum foil substrate to form a coating with a coating weight of 6.25 mg / 1540.25 mm 2 ;

[0178] Lithium oxide and silicon dioxide are deposited on the surface of the coating using an atomic layer deposition process. The specific process is as follows: first, in a nitrogen atmosphere, lithium tert-butoxide / H2O and tetraethyl orthosilicate / H2O are alternately introduced into the first chamber and the second chamber to obtain a lithium oxide precursor and a silicon dioxide precursor, respectively. The reaction temperature of lithium tert-butoxide / H2O is 170°C, and the reaction temperature of tetraethyl orthosilicate / H2O is 65°C. The introduction and diffusion times of lithium tert-butoxide, tetraethyl orthosilicate, and H2O are 1s / 15s, 2s / 15s, and 2s / 20s, respectively. Under a nitrogen atmosphere, the current collector with the above coating is placed in the sample chamber of the atomic layer deposition equipment and heated to 235°C. The lithium oxide precursor and silicon dioxide precursor obtained above are alternately introduced as one cycle. The loading amount of lithium metasilicate is monitored by controlling the number of cycles, so that the target weight of the lithium supplement film is 6.25mg / 1540.25mm2 .

[0179] Positive electrode film: The positive electrode active material lithium iron phosphate, conductive carbon (SP), and binder are dissolved in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 96%:2%:2%, and the mixture is fully stirred and mixed to prepare a positive electrode film slurry. The positive electrode film slurry is coated on the lithium metasilicate film, wherein the coating weight of the positive electrode film is 250mg / 1540.25mm 2 After that, it is dried at 100°C, cold pressed at 40T, and cut to obtain the positive electrode sheet. Based on the total mass of the positive electrode film layer, the mass percentage of the lithium metasilicate film is 2.50%, and the percentage of elemental sulfur is 0.5%.

[0180] 2) Preparation of negative electrode sheet

[0181] The active material graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are thoroughly stirred and mixed in an appropriate amount of deionized water solvent system in a weight ratio of 96.5%:0.7%:1.8%:1% to obtain a negative electrode slurry. The negative electrode slurry is then coated on a Cu foil, and then dried, cold pressed, and cut to obtain a negative electrode sheet.

[0182] 3) Isolation film

[0183] A polyethylene porous polymer film is used as the separator.

[0184] 4) Preparation of electrolyte

[0185] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0186] 6) Preparation of batteries

[0187] The positive electrode sheet, separator, and negative electrode sheet are stacked in order and wound to obtain a battery cell. The battery cell is placed in an outer package, and the above-mentioned electrolyte is added. After packaging, standing, formation, aging and other processes, a secondary battery is obtained.

[0188] Example 2

[0189] Compared with Example 1, Example 2 differs in that the preparation method of the positive electrode sheet is adjusted, as follows:

[0190] Lithium oxide and silicon dioxide are deposited on the surface of the coating using an atomic layer deposition process. The specific process is as follows: first, in a nitrogen atmosphere, lithium tert-butoxide / H2O and tetraethyl orthosilicate / H2O are alternately introduced into the first chamber and the second chamber, respectively, to obtain a lithium oxide precursor and a silicon dioxide precursor, respectively. The reaction temperature of lithium tert-butoxide / H2O is 170°C, and the reaction temperature of tetraethyl orthosilicate / H2O is 65°C. The introduction and diffusion times of lithium tert-butoxide, tetraethyl orthosilicate, and H2O are 1s / 15s, 2s / 15s, and 2s / 20s, respectively. Under a nitrogen atmosphere, an aluminum foil substrate is placed in the sample chamber of the atomic layer deposition equipment and heated to 235°C. The lithium oxide precursor and silicon dioxide precursor obtained above are alternately introduced as one cycle. The loading amount of lithium metasilicate is monitored by controlling the number of introduction cycles, so that the target weight of the lithium supplement film is 6.25mg / 1540.25mm 2 .

[0191] Coating: Dissolve polyacrylate binder and elemental sulfur in deionized water at a mass ratio of 80%:20%, stir and mix thoroughly, then apply to the lithium metasilicate film to form a coating. The coating weight is 6.25mg / 1540.25mm 2 ;

[0192] Positive electrode film: The positive electrode active material lithium iron phosphate, conductive carbon (SP), and binder are dissolved in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 96%:2%:2%, and the mixture is fully stirred and evenly mixed to prepare a positive electrode film slurry. The positive electrode film slurry is coated on the coating, wherein the coating weight of the positive electrode film is 250mg / 1540.25mm 2 After that, it is dried at 100°C, cold pressed at 40T, and cut to obtain the positive electrode sheet. Based on the total mass of the positive electrode film layer, the mass percentage of the lithium metasilicate film is 2.50%, and the percentage of elemental sulfur is 0.5%.

[0193] Example 3

[0194] Compared with Example 1, Example 3 differs in that the preparation method of the coating is adjusted, as follows:

[0195] Conductive carbon, polyacrylate binder, and elemental sulfur were dissolved in deionized water at a mass ratio of 40%:40%:20%, stirred and mixed thoroughly, and then coated on one side of the positive electrode aluminum foil substrate to form a coating with a coating weight of 6.25 mg / 1540.25 mm 2 .

[0196] Example 4

[0197] Compared with Example 2, Example 4 differs in that the preparation method of the coating is adjusted, as follows:

[0198] Conductive carbon, polyacrylate binder, and elemental sulfur were dissolved in deionized water at a mass ratio of 40%:40%:20%, stirred and mixed thoroughly, and then coated on the surface of the lithium metasilicate film to form a coating with a coating weight of 6.25 mg / 1540.25 mm 2 .

[0199] Example 5

[0200] Compared with Example 3, the difference is that the preparation method of the positive electrode sheet is adjusted, as follows:

[0201] Coating: Dissolve conductive carbon, polyacrylate binder, and elemental selenium in deionized water at a mass ratio of 40%:40%:20%, stir and mix thoroughly, and then apply to one side of the positive electrode aluminum foil substrate to form a coating with a coating weight of 6.25 mg / 1540.25 mm 2 ;

[0202] A lithium silicate target was used to form a lithium silicate film on the coating surface by magnetron sputtering. The specific process was as follows: the current collector with the above coating was placed on the sample tray of the magnetron sputtering equipment, the lithium silicate target was placed in the target position of the equipment, the temperature was heated to 310°C, the power was adjusted to 120W, the air pressure was adjusted to 1.2Pa, and the load weight of the lithium silicate film was adjusted to 6.25mg / 1540.25mm by controlling the magnetron sputtering time. 2 ;

[0203] Positive electrode film: The positive electrode active material lithium iron phosphate, conductive carbon (SP), and binder are dissolved in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 96%:2%:2%, and the mixture is thoroughly stirred and mixed to prepare a positive electrode film slurry. The positive electrode film slurry is coated on the lithium silicate film, wherein the coating weight of the positive electrode film is 250mg / 1540.25mm 2 After that, it is dried at 100°C, cold pressed at 40T, and cut to obtain the positive electrode sheet, in which the mass percentage of the lithium silicate film is 2.50% and the percentage of elemental selenium is 0.5% based on the total mass of the positive electrode film layer.

[0204] Example 6

[0205] Compared with Example 3, the difference is that the preparation method of the positive electrode sheet is adjusted, as follows:

[0206] Coating: Dissolve conductive carbon, polyacrylate binder, and elemental tellurium in deionized water at a mass ratio of 40%:40%:20%, stir and mix thoroughly, and then apply to one side of the positive electrode aluminum foil substrate to form a coating with a coating weight of 6.25 mg / 1540.25 mm 2 ;

[0207] Lithium carbonate and tetramethyl orthosilicate were used as precursors to form a lithium metasilicate film on the surface of the first coating using a chemical vapor deposition process. The specific process was as follows: a current collector having the above coating was placed on a porous alumina substrate, lithium carbonate and polyvinyl alcohol were composited and impregnated on the surface, the reaction chamber temperature was heated to 400°C, and tetramethyl orthosilicate precursor was introduced under a N2 atmosphere at a flow rate of 5g / min. The coating mass of lithium metasilicate was regulated to 6.25mg / 1540.25mm by controlling the introduction time. 2 ;

[0208] Positive electrode film: The positive electrode active material lithium iron phosphate, conductive carbon (SP), and binder are dissolved in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 96%:2%:2%, and the mixture is thoroughly stirred and mixed to prepare a positive electrode film slurry. The positive electrode film slurry is coated on the lithium metaborate film, wherein the coating weight of the positive electrode film is 250mg / 1540.25mm 2 After that, it is dried at 100°C, cold pressed at 40T, and cut to obtain the positive electrode sheet. Based on the total mass of the positive electrode film layer, the mass percentage of the lithium metasilicate film is 2.50%, and the percentage of elemental tellurium is 0.5%.

[0209] Example 7

[0210] Compared with Example 3, the difference is that the preparation method of the positive electrode sheet is adjusted, as follows:

[0211] Coating: Dissolve conductive carbon, polyacrylate binder, and selenium disulfide in deionized water at a mass ratio of 40%:40%:20%, stir and mix thoroughly, and then apply to one side of the positive electrode aluminum foil substrate to form a coating with a coating weight of 6.25 mg / 1540.25 mm 2 ;

[0212] A lithium borate target was used to form a lithium borate film on the coating surface by magnetron sputtering. The specific process was as follows: the current collector with the above coating was placed on the sample tray of the magnetron sputtering equipment, the lithium borate target was placed in the target position of the equipment, the temperature was heated to 250°C, the power was adjusted to 100W, the air pressure was adjusted to 1Pa, and the load weight of the lithium borate film was adjusted to 6.25mg / 1540.25mm by controlling the magnetron sputtering time. 2 ;

[0213] Positive electrode film: The positive electrode active material lithium iron phosphate, conductive carbon (SP), and binder are dissolved in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 96%:2%:2%, and the mixture is thoroughly stirred and mixed to prepare a positive electrode film slurry. The positive electrode film slurry is coated on the lithium borate film, wherein the coating weight of the positive electrode film is 250mg / 1540.25mm 2After that, it is dried at 100°C, cold pressed at 40T, and cut to obtain the positive electrode sheet, in which the mass percentage of the lithium borate film is 2.50% and the percentage of selenium disulfide is 0.5% based on the total mass of the positive electrode film layer.

[0214] Examples 8-11

[0215] Compared with Example 3, the difference is that the preparation method of the coating is adjusted, as follows:

[0216] Example 8: Conductive carbon, polyacrylate binder, and elemental sulfur were dissolved in deionized water at a mass ratio of 40%:58%:2%, stirred thoroughly, and then coated on one side of the positive electrode aluminum foil substrate to form a coating with a coating weight of 62.5 mg / 1540.25 mm 2 .

[0217] Example 9: Conductive carbon, polyacrylate binder, and elemental sulfur were dissolved in deionized water at a mass ratio of 40%:52%:8%, stirred thoroughly, and then coated on one side of the positive electrode aluminum foil substrate to form a coating with a coating weight of 15.625 mg / 1540.25 mm 2 .

[0218] Example 10: Conductive carbon, polyacrylate binder, and elemental sulfur were dissolved in deionized water at a mass ratio of 2%:78%:20%, stirred thoroughly, and then coated on one side of the positive electrode aluminum foil substrate to form a coating with a coating weight of 6.25 mg / 1540.25 mm 2 .

[0219] Example 11: Conductive carbon, polyacrylate binder, and elemental sulfur were dissolved in deionized water at a mass ratio of 1%:79%:20%, stirred thoroughly, and then coated on one side of the positive electrode aluminum foil substrate to form a coating with a coating weight of 6.25 mg / 1540.25 mm 2 .

[0220] Comparative Example 1

[0221] Compared with Example 1, the preparation method of the positive electrode sheet was adjusted as follows:

[0222] Lithium iron phosphate, conductive carbon (SP), and binder were dissolved in N-methylpyrrolidone (NMP) solvent in a mass ratio of 96%:2%:2%, and the mixture was thoroughly stirred and mixed to prepare a positive electrode film slurry. The positive electrode film slurry was coated on the positive electrode current collector aluminum foil, and then dried at 100°C, cold pressed, and cut to obtain the positive electrode sheet.

[0223] Comparative Example 2

[0224] Compared with Example 1, the preparation method of the positive electrode sheet was adjusted as follows:

[0225] Lithium iron phosphate, lithium metasilicate, elemental sulfur, conductive carbon, and binder are dissolved in a solvent N-methylpyrrolidone (NMP) in a mass ratio of 93%:2.5%:0.5%:2%:2%, and the mixture is thoroughly stirred and mixed to prepare a positive electrode slurry. The positive electrode slurry is coated on the positive electrode current collector aluminum foil, and then dried at 100°C, cold pressed, and cut to obtain a positive electrode sheet.

[0226] Comparative Example 3

[0227] Compared with Example 1, the preparation method of the positive electrode sheet was adjusted as follows:

[0228] Polyacrylate binder, lithium metasilicate, and elemental sulfur were dissolved in deionized water at a mass ratio of 40%:40%:20%, stirred and mixed thoroughly, and then coated on one side of the positive electrode aluminum foil substrate to form a coating with a coating weight of 6.25 mg / 1540.25 mm 2 ;

[0229] The positive electrode active material lithium iron phosphate, conductive carbon (SP), and binder are dissolved in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 96%:2%:2%, and the mixture is stirred and mixed thoroughly to prepare a positive electrode film slurry. The positive electrode film slurry is coated on the coating, wherein the coating weight of the positive electrode film is 250 mg / 1540.25 mm 2 After that, it is dried at 100°C, cold pressed at 40T, and cut to obtain a positive electrode sheet, in which the mass percentage of lithium metasilicate is 2.50% and the mass percentage of elemental sulfur is 0.5% based on the total mass of the positive electrode film layer.

[0230] Comparative Example 4

[0231] The difference from Example 1 is that the preparation method of the positive electrode sheet is adjusted, as follows:

[0232] The polyacrylate binder and elemental sulfur were dissolved in deionized water at a mass ratio of 80%:20%, stirred and mixed thoroughly, and then coated on one side of the positive electrode aluminum foil substrate to form a first coating with a coating weight of 6.25 mg / 1540.25 mm 2 ;

[0233] Dissolve polyacrylate binder and lithium metasilicate in deionized water at a mass ratio of 50%:50%, stir and mix thoroughly, and then apply on the first coating to form a second coating. The coating weight is 12.5 mg / 1540.25 mm 2 ;

[0234] The positive electrode active material lithium iron phosphate, conductive carbon (SP), and binder are dissolved in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 96%:2%:2%, and the mixture is fully stirred and mixed to prepare a positive electrode film slurry. The positive electrode film slurry is coated on the second coating layer, wherein the coating weight of the positive electrode film is 250 mg / 1540.25 mm 2 After that, it is dried at 100°C, cold pressed at 40T, and cut to obtain the positive electrode sheet, in which the mass percentage of lithium metasilicate is 2.50% and the mass percentage of elemental sulfur is 0.5% based on the total mass of the positive electrode film layer.

[0235] 2. Test Method

[0236] 1. Number of battery cycles

[0237] The secondary batteries prepared in each example and comparative example were charged at a constant current rate of 0.5C to a charge cutoff voltage of 4.2V. They were then charged at a constant voltage rate to a current of ≤0.05C, allowed to rest for 5 minutes, and then discharged at a constant current rate of 0.33C to a discharge cutoff voltage of 2V. The batteries were allowed to rest for 5 minutes. This constituted the first charge-discharge cycle. At the start of the second cycle, the charge voltage was reduced to 3.8V, while all other parameters remained unchanged. The batteries were then cyclically charged and discharged in this manner until the battery capacity decayed to 70%. The number of cycles at this point is the battery's cycle life at 25°C.

[0238] 2. Lithium replenishment efficiency of lithium replenisher film

[0239] The lithium-ion batteries of the embodiment and comparative example were charged at 25°C at a rate of 0.05C to 4.2V, and the charge capacity C1 was recorded, where the mass of the lithium supplement film in the positive electrode sheet was recorded as m0, and the mass of the positive electrode active material was recorded as m1;

[0240] The lithium-ion battery of Comparative Example 1 is used as a blank control. The charge capacity measured under the above test conditions is recorded as C2. The mass of the positive electrode active material in the positive electrode sheet of Comparative Example 1 is recorded as m2. The gram capacity of the positive electrode active material is B = C2 / m2;

[0241] The actual gram capacity of the lithium replenisher film A1 = (C1-B×m1) / m0, where the theoretical gram capacity of the lithium replenisher film is A0, and the lithium replenishment efficiency of the lithium replenisher film = the actual gram capacity of the lithium replenisher film / theoretical gram capacity of the lithium replenisher film = A1 / A0×100%.

[0242] 3. Analysis of test results of various embodiments and comparative examples

[0243] Secondary batteries of various examples and comparative examples were prepared according to the above methods, and various parameters were measured. The results are shown in the table below.

[0244] Table 1

[0245] The secondary batteries in Examples 1-11 of the present application include a positive electrode plate, which includes a current collector, which includes an aluminum foil substrate, and a lithium metasilicate film, a lithium silicate film, or a lithium borate film, and a coating containing elemental sulfur, elemental selenium, elemental tellurium, or selenium disulfide, located on at least the same side of the aluminum foil substrate. When the coating containing elemental sulfur, elemental selenium, elemental tellurium, or selenium disulfide in Examples 1, 3, 5-11 is located on at least one side of the aluminum foil substrate, the lithium metasilicate film, lithium silicate film, or lithium borate film is located on a side adjacent to the coating and away from the aluminum foil substrate; when the lithium metasilicate film layer in Examples 2 and 4 is located on at least one side of the aluminum foil substrate, the coating containing elemental sulfur is located on a side adjacent to the lithium metasilicate film and away from the aluminum foil substrate.

[0246] From the comparison of Examples 1-11 and Comparative Example 1, it can be seen that compared with the secondary battery without the lithium replenisher film and the coating containing the reducing agent, the secondary battery of the present application can increase the number of battery cycles and extend the battery life.

[0247] From the comparison of Examples 1-11 and Comparative Example 2, it can be seen that compared with secondary batteries in which the lithium replenisher and the reducing agent are added to the positive electrode film layer in the form of additives, the secondary battery using the present application can improve the lithium replenishment efficiency of the lithium replenisher film, increase the number of battery cycles, and extend the battery life.

[0248] From the comparison of Examples 1-11 and Comparative Example 3, it can be seen that compared with the secondary battery containing both a lithium replenisher and a reducing agent in the coating, the secondary battery using the present application can improve the lithium replenishment efficiency of the lithium replenisher film, increase the number of battery cycles, and extend the battery life.

[0249] From the comparison of Examples 1-11 and Comparative Example 4, it can be seen that compared with the secondary battery including a coating containing a lithium replenisher and a coating containing a reducing agent, the secondary battery of the present application can improve the lithium replenishment efficiency of the lithium replenisher film, increase the number of battery cycles, and extend the battery life.

[0250] From the comparison between Example 3 and Example 1, and from the comparison between Example 4 and Example 2, it can be seen that the coating containing the reducing agent contains the conductive agent, which can further improve the lithium replenishment efficiency of the lithium replenishment agent film, increase the number of battery cycles, and extend the battery life.

[0251] As can be seen from Examples 3 and 8-11, when the mass ratio of the reducing agent to the conductive agent in the coating is 0.05-20, the lithium replenisher has a high lithium replenishment efficiency and the battery has an excellent cycle life. A comparison of Examples 3, 9-10 with Examples 8 and 11 shows that when the mass ratio of the reducing agent to the conductive agent in the coating is 0.2-10, the lithium replenisher film's lithium replenishment efficiency can be further improved, the battery cycle life can be increased, and the battery life can be further extended.

[0252] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A secondary battery comprising a positive electrode plate, characterized in that: The positive electrode plate includes a current collector, the current collector includes a substrate, and a lithium supplement film and a coating located on at least the same side of the substrate, the coating containing a reducing agent, When the lithium supplement film is located on at least one side of the substrate, the coating is located on a side adjacent to the lithium supplement film and away from the substrate; When the coating is located on at least one side of the substrate, the lithium replenisher film is located on a side adjacent to the coating and away from the substrate.

2. The secondary battery according to claim 1, wherein The mass ratio of the lithium supplement film to the reducing agent is 0.5-50.

3. The secondary battery according to claim 1 or 2, characterized in that The mass ratio of the lithium replenisher film to the reducing agent is 1-20.

4. The secondary battery according to any one of claims 1 to 3, characterized in that The coating also includes a conductive agent.

5. The secondary battery according to claim 4, wherein The mass ratio of the reducing agent to the conducting agent is 0.05-20.

6. The secondary battery according to claim 4, characterized in that The mass ratio of the reducing agent to the conducting agent is 0.2-10.

7. The secondary battery according to any one of claims 1 to 6, characterized in that The positive electrode plate further includes a positive electrode film layer. Based on the total mass of the positive electrode film layer, the mass percentage of the lithium supplement film is 0.5%-20%.

8. The secondary battery according to claim 7, wherein: Based on the total mass of the positive electrode film layer, the mass percentage of the lithium supplement film is 1%-10%.

9. The secondary battery according to claim 7 or 8, characterized in that: Based on the total mass of the positive electrode film layer, the mass percentage of the reducing agent is 0.01%-10%.

10. The secondary battery according to any one of claims 7 to 9, characterized in that Based on the total mass of the positive electrode film layer, the mass percentage of the reducing agent is 0.02%-5%.

11. The secondary battery according to any one of claims 1 to 10, characterized in that: The lithium replenisher film includes one or more of lithium nickelate film, lithium-rich lithium nickelate film, lithium ferrite film, lithium-rich lithium ferrite film, lithium oxalate film, lithium squarate film, lithium metasilicate film, lithium orthosilicate film, lithium carbonate film, lithium sulfate film, lithium hydroxide film, lithium phosphate film, lithium oxide film, lithium peroxide film, lithium borate film, and lithium metaborate film.

12. The secondary battery according to any one of claims 1 to 11, characterized in that: The reducing agent includes one or more of elemental selenium, selenium metal compounds, elemental sulfur, sulfur metal compounds, elemental phosphorus, phosphorus metal compounds, elemental boron, boron metal compounds, elemental tellurium, tellurium metal compounds, elemental antimony, antimony metal compounds, elemental bismuth, bismuth metal compounds, and selenium disulfide.

13. The secondary battery according to any one of claims 1 to 12, characterized in that: The preparation method of the lithium supplement film includes at least one of chemical vapor deposition, physical vapor deposition, atomic layer deposition, and molecular layer deposition.

14. The secondary battery according to any one of claims 4 to 13, characterized in that: The surface of the conductive agent is coated with the reducing agent.

15. The secondary battery according to any one of claims 1 to 14, characterized in that The lithium replenishment efficiency of the lithium replenishment agent film is greater than or equal to 85%.

16. The secondary battery according to any one of claims 1 to 14, characterized in that: The lithium replenishing efficiency of the lithium replenishing agent film is 90%-100%.

17. The secondary battery according to any one of claims 1 to 16, characterized in that: The thickness of the lithium supplement film is 50 nm to 500 nm; and / or the thickness of the coating is 0.5 μm to 5 μm.

18. An electrical device, characterized in that: A secondary battery comprising the secondary battery according to any one of claims 1 to 17.

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