Secondary battery and electric device

Abstract

The invention provides a secondary battery and an electric device. The secondary battery comprises a positive pole piece, the positive pole piece comprises a positive pole film layer, the positive pole film layer comprises a lithium supplementing composition, the lithium supplementing composition comprises a lithium supplementing agent and a reducing agent, and the electronic conductivity of the reducing agent is greater than or equal to 10 <-6 > S / cm. The secondary battery has excellent 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] The first aspect of the present application provides a secondary battery, comprising a positive electrode plate, the positive electrode plate comprising a positive electrode film layer, the positive electrode film layer comprising a lithium supplement composition, the lithium supplement composition comprising a lithium supplement agent and a reducing agent, the electronic conductivity of the reducing agent being greater than or equal to 10 -6 S / cm.

[0006] Adding lithium replenisher and reducing agent to the positive electrode film layer, on the one hand, the reducing agent has reducing property, which can change the reaction path of the lithium replenisher and reduce the decomposition potential of the lithium replenisher, so that the lithium replenisher can play its lithium replenishing role as much as possible, improve the lithium replenishing efficiency of the lithium replenisher, provide a large amount of active lithium for lithium replenishment during the cycle, and the battery has an excellent cycle number and a long service life; on the other hand, the electronic conductivity of the reducing agent is greater than or equal to 10 - 6 S / cm, the reducing agent has excellent electronic conductivity and can form a good electron transport pathway with the lithium supplement agent, so that the lithium supplement agent is decomposed as much as possible to generate a reaction product with excellent ion conductivity. At the same time, in order to make the lithium supplement agent fully react, the reducing agent will generally be excessive. The residual reducing agent with excellent electronic conductivity and the lithium supplement product with excellent ion conductivity can be used to reduce the DC impedance of the battery and improve the battery's rate performance.

[0007] In any embodiment, the electronic conductivity of the reducing agent is 10 -5 S / cm-10 6 S / cm.

[0008] The reducing agent has excellent electronic conductivity, and builds a good electron transport network between the lithium replenisher and the reducing agent, thereby improving the lithium replenishment efficiency of the lithium replenisher. At the same time, the residual reducing agent can further reduce the DC impedance of the battery and improve the battery's rate performance.

[0009] In any embodiment, the reducing agent includes one or more of elemental selenium, elemental tellurium, elemental antimony, elemental bismuth, selenium disulfide, lithium selenide, sodium selenide, copper selenide, and sodium bismuth.

[0010] In any embodiment, the reducing agent includes one or more of elemental tellurium, elemental antimony, elemental bismuth, lithium selenide, sodium selenide, copper selenide, and sodium bismuth.

[0011] The above-mentioned reducing agent has reducing properties and high electronic conductivity. When it undergoes a reduction reaction with the lithium replenisher, the lithium replenisher can achieve low-potential lithium replenishment while further reducing the film resistance of the electrode and the DC impedance of the battery, thereby improving the rate performance.

[0012] In any embodiment, the lithium supplement includes one or more of lithium nickelate, lithium-rich lithium nickelate, lithium ferrite, lithium-rich lithium ferrite, lithium oxalate, lithium quartz, lithium metasilicate, lithium orthosilicate, lithium carbonate, lithium sulfate, lithium hydroxide, lithium phosphate, lithium oxide, lithium peroxide, lithium borate, and lithium metaborate.

[0013] The lithium supplement agent has a high irreversible capacity and a good lithium supplement effect. In addition, the lithium supplement agent has good stability in the air and is compatible with the existing battery production process, which is conducive to industrial production.

[0014] In any embodiment, the mass ratio of the lithium supplement agent to the reducing agent is 0.5-20.

[0015] In any embodiment, the mass ratio of the lithium supplement agent to the reducing agent is 1-10.

[0016] The mass ratio of the lithium supplement agent to the reducing agent is within an appropriate range, so that the lithium supplement agent and the reducing agent fully react with each other, thereby improving the lithium supplement efficiency of the lithium supplement agent, giving full play to the lithium supplement effect of the lithium supplement agent, and achieving the purpose of improving the cycle performance of the battery.

[0017] In any embodiment, the mass fraction of the reducing agent is 0.1%-10% based on the total mass of the positive electrode film layer.

[0018] In any embodiment, based on the total mass of the positive electrode film layer, the mass fraction of the reducing agent is 0.4%-2%.

[0019] The reducing agent has an appropriate mass fraction so that the lithium supplement agent can be fully reduced, providing enough lithium ions, improving the lithium supplement efficiency of the lithium supplement agent, and improving the cycle performance of the battery. At the same time, the reducing agent with excellent electronic conductivity has an appropriate mass fraction, which can reduce the DC impedance of the battery and improve the battery's rate performance.

[0020] In any embodiment, based on the total mass of the positive electrode film layer, the mass fraction of the lithium supplement agent is 0.9%-20%.

[0021] The mass fraction of the lithium supplement agent is within an appropriate range. On the one hand, the lithium supplement agent can fully exert its lithium supplement effect and improve the cycle performance of the battery. On the other hand, it also avoids excessive lithium supplement agent from having adverse effects on the diaphragm resistance of the electrode and the rate performance, available capacity and safety performance of the battery.

[0022] In any embodiment, the reducing agent coats the lithium replenishing agent.

[0023] The reducing agent is coated on the surface of the lithium supplement agent, which can increase the contact degree between the lithium supplement agent and the reducing agent and improve the reaction degree between the two. At the same time, coating the reducing agent with excellent electronic conductivity on the surface of the lithium supplement agent can improve the ability of the lithium supplement agent to gain or lose electrons, thereby maximizing the reaction degree between the lithium supplement agent and the reducing agent, achieving efficient lithium supplementation, and improving the cycle performance of the battery.

[0024] In any embodiment, the sheet resistance of the positive electrode sheet is less than or equal to 0.07Ω.

[0025] The second aspect of the present application provides an electric device, comprising the secondary battery of the first aspect BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0027] FIG2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG1 ;

[0028] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0029] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0030] FIG5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG4 ;

[0031] FIG6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0032] 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. DETAILED DESCRIPTION

[0033] 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.

[0034] " 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.

[0035] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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).

[0040] 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 a positive electrode lithium replenisher 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 with high lithium capacity also have a high decomposition voltage, which will affect the battery's cycle performance and safety performance. To address the high decomposition potential of positive electrode lithium supplements, a lithium supplement composition containing a lithium supplement and a reducing agent is often added to the lithium supplement layer on the surface of the positive electrode active material. However, current reducing agents have poor electronic conductivity, and the lithium supplement is also a poor conductor of electrons, making it difficult for the reducing agent and the lithium supplement to form an effective conductive network structure, affecting the lithium supplement's ability to gain or lose electrons, making it difficult for the lithium supplement to effectively exert its lithium supplement capacity. In addition, in order to maximize the reduction and decomposition of the lithium supplement, an excess of reducing agent is generally added. However, traditional reducing agents have low electronic conductivity, and residual reducing agent will affect the battery's rate performance.

[0041] [Secondary battery]

[0042] The present application provides a secondary battery, comprising a positive electrode plate, wherein the positive electrode plate comprises a positive electrode film layer, wherein the positive electrode film layer comprises a lithium supplement composition, wherein the lithium supplement composition comprises a lithium supplement agent and a reducing agent, wherein the electronic conductivity of the reducing agent is greater than or equal to 10 -6 S / cm.

[0043] 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.

[0044] 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.

[0045] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.

[0046] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is provided on either or both of the two opposite surfaces of the positive electrode current collector.

[0047] In some embodiments, the electronic conductivity of the reducing agent may be greater than or equal to 10 - 6 S / cm, greater than or equal to 3×10 -6 S / cm, greater than or equal to 10 -5 S / cm, greater than or equal to 5×10 - 5 S / cm, greater than or equal to 10 -4 S / cm, greater than or equal to 5×10 -4 S / cm, greater than or equal to 10 - 3 S / cm, greater than or equal to 5×10 -3 S / cm, greater than or equal to 10 -2 S / cm, greater than or equal to 5×10 - 2 S / cm, greater than or equal to 10 -1 S / cm, greater than or equal to 5×10 -1 S / cm, greater than or equal to 1S / cm, greater than or equal to 40S / cm, greater than or equal to 10 2 S / cm, greater than or equal to 10 3 S / cm, greater than or equal to 10 4 S / cm, greater than or equal to 10 5 S / cm, greater than or equal to 5×10 5Any of S / cm.

[0048] The electronic conductivity of the reducing agent can be tested using any method known in the art. For example, the reducing agent is spread in a conventional mold, molded under a pressure of 8 MPa to obtain a sample, and subjected to DC polarization under a certain bias voltage (V). After polarization, the current is I, and the electronic conductivity of the reducing agent is Where L is the sample thickness and S is the sample bottom area.

[0049] Adding lithium replenisher and reducing agent to the positive electrode film layer, on the one hand, the reducing agent has reducing property, which can change the reaction path of the lithium replenisher and reduce the decomposition potential of the lithium replenisher, so that the lithium replenisher can play its lithium replenishing role as much as possible, improve the lithium replenishing efficiency of the lithium replenisher, provide a large amount of active lithium for lithium replenishment during the cycle, and the battery has an excellent cycle number and a long service life; on the other hand, the electronic conductivity of the reducing agent is greater than or equal to 10 - 6 S / cm, the reducing agent has excellent electronic conductivity and can form a good electron transport pathway with the lithium supplement agent, so that the lithium supplement agent is decomposed as much as possible to generate a reaction product with excellent ion conductivity. At the same time, in order to make the lithium supplement agent fully react, the reducing agent will be excessive. The residual reducing agent can improve the electronic conductivity of the film layer and improve the conductive network of the electrode. It can also be used together with the lithium supplement product that improves the ion conductivity of the film layer to improve the electronic and ion conductivity of the positive electrode film layer, reduce the DC impedance of the battery, and improve the rate performance of the battery.

[0050] In summary, the electronic conductivity is greater than or equal to 10 -6 S / cm reducing agent is combined with lithium supplement agent, which can improve the cycle performance of the battery while improving the rate performance of the battery, and comprehensively improve the cycle performance and rate performance of the battery. The lithium supplement composition of the present application is more suitable for improving the cycle performance of power batteries.

[0051] In some embodiments, the electronic conductivity of the reducing agent is 10 -5 S / cm-10 6 S / cm.

[0052] In some embodiments, the electronic conductivity of the reducing agent can be selected to be 10 -5 S / cm, 10 -4 S / cm, 10 -3 S / cm, 10 -2 S / cm, 10 -1 S / cm, 1S / cm, 10S / cm, 10 2 S / cm, 10 3 S / cm, 10 4 S / cm, 10 5S / cm, 10 6 S / cm or any range of values ​​therebetween.

[0053] The reducing agent has excellent electronic conductivity, and builds a good electron transport network between the lithium replenisher and the reducing agent, thereby improving the lithium replenishment efficiency of the lithium replenisher. At the same time, the residual reducing agent can further reduce the DC impedance of the battery and improve the battery's rate performance.

[0054] In some embodiments, the reducing agent includes one or more of elemental selenium, elemental tellurium, elemental antimony, elemental bismuth, selenium disulfide, lithium selenide, sodium selenide, copper selenide, and sodium bismuth.

[0055] In some embodiments, the electronic conductivity of elemental selenium is 10 -3 S / cm. In some embodiments, the electronic conductivity of elemental tellurium is 40 S / cm. In some embodiments, the electronic conductivity of elemental antimony is 2×10 4 S / cm. In some embodiments, the electronic conductivity of elemental bismuth is 5×10 5 S / cm. In some embodiments, the electronic conductivity of selenium disulfide is 3×10 -6 S / cm. In some embodiments, the electronic conductivity of copper selenide is 2×10 3 S / cm. In some embodiments, the electronic conductivity of lithium selenide is 2×10 -2 S / cm. In some embodiments, the electronic conductivity of sodium selenide is 5×10 -2 S / cm. In some embodiments,

[0056] The above-mentioned reducing agent has excellent reducing agent and good electronic conductivity, which can reduce the decomposition potential of the lithium supplement agent and improve the cycle performance of the battery. At the same time, the residual reducing agent is also beneficial to improve the electronic conductivity of the film layer, reduce the DC impedance of the battery, and improve the battery's rate performance.

[0057] In some embodiments, the reducing agent includes one or more of elemental tellurium, elemental antimony, elemental bismuth, lithium selenide, sodium selenide, copper selenide, and sodium bismuthide.

[0058] The above-mentioned reducing agent has high electronic conductivity, which can further reduce the film resistance of the electrode, improve the electronic conductivity of the positive electrode film layer, reduce the DC impedance of the battery, and improve the rate performance.

[0059] In some embodiments, the lithium supplement includes one or more of lithium nickelate, lithium-rich lithium nickelate, lithium ferrite, lithium-rich lithium ferrite, lithium oxalate, lithium quartz, lithium metasilicate, lithium orthosilicate, lithium carbonate, lithium sulfate, lithium hydroxide, lithium phosphate, lithium oxide, lithium peroxide, lithium borate, and lithium metaborate.

[0060] The lithium supplement agent has a high irreversible capacity and a good lithium supplement effect. In addition, the lithium supplement agent has good stability in the air and is compatible with the existing battery production process, which is conducive to industrial production.

[0061] In some embodiments, the lithium supplement includes one or more of lithium-rich nickelate, lithium metasilicate, lithium orthosilicate, lithium sulfate, lithium hydroxide, lithium borate, lithium metaborate, and lithium phosphate.

[0062] The combination of a suitable lithium supplement and a reducing agent can not only lower the decomposition potential of the lithium supplement, fully utilizing the lithium supplement's replenishing effect, but also eliminate the presence of gases such as oxygen, carbon dioxide, or nitrogen in the reaction product, reducing the likelihood of battery gassing and minimizing their impact on battery safety and cycling performance. Furthermore, the decomposition products of the lithium supplement may include silicon oxide, nickel oxide, lithium oxide, boron oxide, or lithium sulfate, which possess excellent ionic conductivity, thereby improving the electrode's ion conductivity and enhancing the battery's rate performance.

[0063] In some embodiments, the lithium supplement comprises one or both of lithium metasilicate and lithium orthosilicate.

[0064] 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.

[0065] In some embodiments, the mass ratio of the lithium supplement agent to the reducing agent is 0.5-20. In some embodiments, the mass ratio of the lithium supplement agent to the reducing agent can be selected from 0.5, 1, 5, 10, 15, 20 or any range therebetween.

[0066] In some embodiments, the mass ratio of the lithium supplement agent to the reducing agent is 1 to 10. In some embodiments, the mass ratio of the lithium supplement agent to the reducing agent can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or any range therebetween.

[0067] The mass ratio of the lithium supplement agent to the reducing agent is within an appropriate range, so that the lithium supplement agent and the reducing agent fully react with each other, thereby improving the lithium supplement efficiency of the lithium supplement agent, giving full play to the lithium supplement effect of the lithium supplement agent, and achieving the purpose of improving the cycle performance of the battery.

[0068] In some embodiments, the mass fraction of the reducing agent is 0.1%-10% based on the total mass of the positive electrode film layer. In some embodiments, the mass fraction of the reducing agent is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.5%, 5%, 6%, 7%, 8%, 9%, 10% or any range therebetween based on the mass of the positive electrode film layer.

[0069] In some embodiments, the mass fraction of the reducing agent is 0.4%-2% based on the total mass of the positive electrode film layer. In some embodiments, the mass fraction of the reducing agent is 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, or any range therebetween, based on the mass of the positive electrode film layer.

[0070] The reducing agent has an appropriate mass fraction so that the lithium supplement agent can be fully reduced, providing enough lithium ions, improving the lithium supplement efficiency of the lithium supplement agent, and improving the cycle performance of the battery. At the same time, the reducing agent with excellent electronic conductivity has an appropriate mass fraction, which can reduce the DC impedance of the battery and improve the battery's rate performance.

[0071] In some embodiments, the mass fraction of the lithium supplement agent is 0.9%-20% based on the total mass of the positive electrode film layer. In some embodiments, the mass fraction of the lithium supplement agent is 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 12%, 14%, 16%, 18%, 20%, or any range therebetween, based on the mass of the positive electrode film layer.

[0072] The mass fraction of the lithium supplement agent is within an appropriate range. On the one hand, the lithium supplement agent can fully exert its lithium supplement effect and improve the cycle performance of the battery. On the other hand, it also avoids excessive lithium supplement agent from having adverse effects on the diaphragm resistance of the electrode and the rate performance, available capacity and safety performance of the battery.

[0073] In some embodiments, the reducing agent coats the lithium supplementing agent.

[0074] The reducing agent is coated on the surface of the lithium supplement agent, which can increase the contact degree between the lithium supplement agent and the reducing agent and improve the reaction degree between the two. At the same time, coating the reducing agent with excellent electronic conductivity on the surface of the lithium supplement agent can improve the ability of the lithium supplement agent to gain or lose electrons, thereby maximizing the reaction degree between the lithium supplement agent and the reducing agent, achieving efficient lithium supplementation, and improving the cycle performance of the battery.

[0075] In some embodiments, the sheet resistance of the positive electrode plate is less than or equal to 0.07Ω.

[0076] The positive electrode sheet has low membrane resistance, which is conducive to the construction of a good electronic conductive network of the positive electrode sheet, and is conducive to the full reaction of the lithium replenisher and the reducing agent, thereby improving the lithium replenishment efficiency of the lithium replenisher and improving the cycle performance of the battery. At the same time, the positive electrode sheet has low membrane electrons, which is also conducive to reducing the DC impedance of the battery and improving the battery temperature rate performance.

[0077] In some embodiments, the positive electrode 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 material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0078] In some embodiments, the positive electrode plate 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.

[0079] In some embodiments, the positive electrode plate 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.

[0080] In some embodiments, the positive electrode sheet can be prepared by the following method: the positive electrode active material, binder, conductive agent, lithium supplement agent, reducing 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 positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0081] [Negative electrode]

[0082] 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.

[0083] 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.

[0084] 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.).

[0085] 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.

[0086] 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).

[0087] 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.

[0088] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0089] 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.

[0090] [Electrolytes]

[0091] 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.

[0092] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] [Diaphragm]

[0097] 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.

[0098] 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.

[0099] 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.

[0100] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0101] 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.

[0102] 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.

[0103] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0104] 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.

[0105] 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, FIG1 shows a secondary battery 5 having a square structure as an example.

[0106] In some embodiments, referring to FIG2 , the outer package 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.

[0107] 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.

[0108] Figure 3 shows an example battery module 4. Referring to Figure 3 , 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.

[0109] 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.

[0110] 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.

[0111] Figures 4 and 5 illustrate an example battery pack 1. 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 comprises an upper case 2 and a lower case 3. The upper case 2 can be placed 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.

[0112] 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.

[0113] As an electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0114] Figure 6 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.

[0115] 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.

[0116] Example

[0117] 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.

[0118] 1. Preparation method

[0119] Example 1

[0120] 1) Preparation of positive electrode sheet

[0121] Lithium iron phosphate, lithium orthosilicate, selenium powder, conductive carbon, and binder are dissolved in a solvent N-methylpyrrolidone (NMP) in a mass ratio of 92%:2.8%:1.2%:1%:1%, and the mixture is thoroughly stirred and mixed to prepare a positive electrode film slurry. The positive electrode film 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.

[0122] 2) Preparation of negative electrode sheet

[0123] 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.

[0124] 3) Isolation film

[0125] A polyethylene porous polymer film is used as the separator.

[0126] 4) Preparation of electrolyte

[0127] 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.

[0128] 6) Preparation of batteries

[0129] 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.

[0130] Examples 2-6

[0131] Compared with Example 1, Examples 2-6 replace the reducing agent with elemental tellurium, elemental antimony, elemental bismuth, selenium disulfide, and copper selenide. See Table 1 for specific parameters.

[0132] Examples 7-9

[0133] Compared with Example 2, Examples 7-9 replace the lithium supplement with lithium metasilicate, lithium-rich lithium nickelate, or lithium-rich lithium ferrite. For specific parameters, see Table 1.

[0134] Examples 10-13

[0135] Compared with Example 2, the mass contents of the lithium supplement agent and the reducing agent were adjusted in Examples 10-13. For specific parameters, see Table 1.

[0136] Example 14

[0137] Compared with Example 2, the preparation method of the positive electrode sheet was adjusted as follows:

[0138] 1.2 g of tellurium element is treated at 450° C. to generate tellurium vapor, which is then diffused onto the surface of 2.8 g of lithium orthosilicate, so that the tellurium element is evenly coated on the surface of the lithium orthosilicate in the form of vapor, thereby forming tellurium-coated lithium orthosilicate;

[0139] Tellurium-coated lithium orthosilicate, lithium iron phosphate, conductive carbon, and binder are dissolved in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 4%:92%:1%:1%, and the mixture is thoroughly stirred and mixed to prepare a positive electrode film slurry. The positive electrode film 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.

[0140] Comparative Example 1

[0141] Compared with Example 1, the preparation method of the positive electrode sheet was adjusted as follows:

[0142] Lithium iron phosphate, conductive carbon (SP), and binder are dissolved in a solvent N-methylpyrrolidone (NMP) in a mass ratio of 98%:1%:1%, and the mixture is thoroughly stirred and mixed to prepare a positive electrode film slurry. The positive electrode film 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.

[0143] Comparative Examples 2-3

[0144] Compared with Example 1, the reducing agent is replaced with sulfur or boron. See Table 1 for details.

[0145] 2. Test Method

[0146] 1. Diaphragm resistance of the electrode

[0147] Cut the dried electrode sheet at the left, center, and right sides of the electrode into small discs with a diameter of 10mm. Turn on the Yuanneng Technology electrode resistance meter, place it in the appropriate position on the "probe" of the electrode resistance meter, click the "Start" button, and wait for the reading to stabilize before reading. Test two positions on each small disc, and calculate the average of the six measurements to obtain the film resistance of the electrode.

[0148] 2. Number of battery cycles

[0149] 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 4.0V. 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 0.5C 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 beginning 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 according to this method until the battery capacity decayed to 70%. The number of cycles at this point is the battery's cycle life at 25°C.

[0150] 3. Battery DC resistance (DCR)

[0151] At 25°C, charge the battery at a constant current of 0.33C to 4.3V, then charge at a constant voltage of 4.3V to a current of 0.05C, let it stand for 60s, and then discharge it at 0.33C to SOC = 50% (remaining capacity). After standing for 5 minutes, record the voltage V1, then discharge it at 3C for 30s and record the voltage V2. The DC resistance DCR of the battery is DCR = (V1-V2) / 3C.

[0152] 3. Analysis of test results of various embodiments and comparative examples

[0153] 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.

[0154] Table 1

[0155] As can be seen from Table 1, the secondary batteries of Examples 1-14 of the present application include a positive electrode sheet, the positive electrode sheet includes a positive electrode film layer, the positive electrode film layer includes a lithium replenishing composition, the lithium replenishing composition includes lithium orthosilicate, lithium metasilicate, lithium nickel-rich lithium or lithium ferrite-rich lithium replenishing agent and elemental selenium, elemental tellurium, elemental antimony, elemental bismuth, selenium disulfide or copper selenide reducing agent, and the electronic conductivity of elemental selenium, elemental tellurium, elemental antimony, elemental bismuth, selenium disulfide or copper selenide reducing agent is greater than or equal to 10 -6 S / cm.

[0156] Comparing Examples 1-14 with Comparative Example 1, the use of lithium supplementing agents and reducing agents can significantly increase the number of battery cycles and improve the cycle life of the battery.

[0157] From the comparison between Examples 1-6 and Comparative Examples 2-3, it can be seen that the use of an electronic conductivity greater than or equal to 10 -6 S / cm reducing agent, while the battery has excellent cycle performance, can also reduce the diaphragm resistance of the electrode, reduce the DC impedance of the battery, and improve the battery's rate performance.

[0158] From the comparison between Examples 1-4, 6 and Example 5, it can be seen that the electron conductivity is 10 - 5 S / cm-10 6 S / cm of elemental selenium, elemental tellurium, elemental antimony, elemental bismuth or copper selenide reducing agent, while maintaining an excellent number of cycles of the battery, further reduce the diaphragm resistance of the electrode and the DC impedance of the battery, and comprehensively improve the cycle performance and rate performance of the battery.

[0159] From the comparison of Examples 2-4 and 6 with Examples 1 and 5, it can be seen that the use of reducing agents such as elemental tellurium, elemental antimony, elemental bismuth or copper selenide can further increase the number of battery cycles, reduce the diaphragm resistance of the electrode and the DC impedance of the battery, and improve the cycle performance and rate performance of the battery.

[0160] As can be seen from Examples 2, 10-13, a reducing agent mass fraction of 0.1%-10%, based on the total mass of the positive electrode film layer, results in low sheet resistance for the positive electrode sheet, low DC impedance for the battery, and a long cycle life. Comparing Examples 2, 11-12 with Examples 10 and 13, a reducing agent mass fraction of 0.4%-2.0%, based on the total mass of the positive electrode film layer, further reduces the DC impedance of the battery, increases the number of cycles, and improves the battery's rate performance and cycling performance.

[0161] From the comparison between Example 14 and Example 2, it can be seen that coating the surface of lithium orthosilicate with elemental tellurium can further reduce the DC impedance of the battery, increase the number of cycles of the battery, and improve the rate performance and cycle performance of the battery.

[0162] 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 sheet includes a positive electrode film layer, the positive electrode film layer includes a lithium supplement composition, the lithium supplement composition includes a lithium supplement agent and a reducing agent, and the electronic conductivity of the reducing agent is greater than or equal to 10 -6 S / cm.

2. The secondary battery according to claim 1, wherein The electronic conductivity of the reducing agent is 10 -5 S / cm-10 6 S / cm.

3. The secondary battery according to claim 1 or 2, characterized in that The reducing agent includes one or more of elemental selenium, elemental tellurium, elemental antimony, elemental bismuth, selenium disulfide, lithium selenide, sodium selenide, copper selenide, and sodium bismuth.

4. The secondary battery according to claim 1 or 2, characterized in that The reducing agent includes one or more of elemental tellurium, elemental antimony, elemental bismuth, lithium selenide, sodium selenide, copper selenide, and sodium bismuthide.

5. The secondary battery according to any one of claims 1 to 4, characterized in that The lithium supplement includes one or more of lithium nickelate, lithium-rich lithium nickelate, lithium ferrite, lithium-rich lithium ferrite, lithium oxalate, lithium squarate, lithium metasilicate, lithium orthosilicate, lithium carbonate, lithium sulfate, lithium hydroxide, lithium phosphate, lithium oxide, lithium peroxide, lithium borate, and lithium metaborate.

6. The secondary battery according to any one of claims 1 to 5, characterized in that The mass of the lithium supplement agent and the reducing agent is 0.5-20.

7. The secondary battery according to any one of claims 1 to 5, characterized in that The mass of the lithium supplement agent and the reducing agent is 1-10.

8. The secondary battery according to any one of claims 1 to 7, characterized in that Based on the total mass of the positive electrode film layer, the mass fraction of the reducing agent is 0.1%-10%.

9. The secondary battery according to any one of claims 1 to 7, characterized in that Based on the total mass of the positive electrode film layer, the mass fraction of the reducing agent is 0.4%-2%.

10. The secondary battery according to any one of claims 1 to 9, characterized in that Based on the total mass of the positive electrode film layer, the mass fraction of the lithium supplement agent is 0.9%-20%.

11. The secondary battery according to any one of claims 1 to 10, characterized in that: The reducing agent covers the lithium supplement agent.

12. The secondary battery according to any one of claims 1 to 11, characterized in that: The membrane resistance of the positive electrode plate is less than or equal to 0.07Ω.

13. An electrical device, characterized in that: A secondary battery comprising the secondary battery according to any one of claims 1 to 12.

Images