Secondary battery and electric device including the same

Abstract

The invention provides a secondary battery and a power device including the same. The secondary battery comprises a negative electrode plate, the negative electrode plate comprises a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, and the negative electrode film layer comprises an additive capable of performing nucleophilic reaction with a cyclic carbonate compound. The secondary battery of the present application has high storage performance.

Description

Technical Field

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

[0002] In recent years, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. As secondary batteries have made great progress, higher requirements have been placed on their performance.

[0003] Therefore, how to make secondary batteries have better storage performance has become an urgent problem to be solved in this field. Summary of the invention

[0004] The present application is made in view of the above-mentioned problems, and an object of the present application is to provide a secondary battery and an electric device including the secondary battery, wherein the secondary battery has high storage performance.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a secondary battery, including a negative electrode plate, wherein the negative electrode plate includes a negative electrode collector and a negative electrode film layer arranged on at least one surface of the negative electrode collector, and the negative electrode film layer includes an additive capable of undergoing a nucleophilic reaction with a cyclic carbonate compound.

[0006] Therefore, the storage performance of the secondary battery of the present application is improved by making the negative electrode film layer include an additive capable of undergoing a nucleophilic reaction with the cyclic carbonate compound.

[0007] In any embodiment, the additive includes at least one of a sulfur-containing substance, a selenium-containing substance, a composite of a sulfur-containing substance and a carbon-based material, a composite of a selenium-containing substance and a carbon-based material, a sulfur-containing substance with a carbon coating, and a selenium-containing substance with a carbon coating; optionally, the sulfur-containing substance includes at least one of elemental sulfur, lithium sulfide, and sodium sulfide; optionally, the selenium-containing substance includes at least one of elemental selenium, lithium selenide, sodium selenide, cobalt selenide, and nickel selenide; optionally, the carbon-based material includes a nano-carbon-based material and graphene, and optionally, the nano-carbon-based material includes a carbon nanotube. The sulfur-containing substance and the selenium-containing substance undergo a reduction reaction during battery charging and discharging, undergo a nucleophilic reaction with a cyclic carbonate compound, and participate in the formation of an SEI film. In addition, by being compounded with carbon nanotubes or having a carbon coating, the conductivity and fast charging performance of the battery can be improved.

[0008] In any embodiment, based on the total mass of the negative electrode film layer, the mass proportion of the additive is less than or equal to 10%, and can be optionally 0.5%-5%. Thus, the battery can obtain excellent conductivity and fast charging performance while achieving high storage performance.

[0009] In any embodiment, the particle size Dv50 of the additive is 50nm-500nm, and can be optionally 100nm-200nm. By controlling the particle size within the above range, a larger specific surface area can be obtained, thereby increasing the reaction activity.

[0010] In any embodiment, the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a silicon-based material; optionally, the mass proportion of the silicon-based material in the negative electrode active material is greater than or equal to 5%, and more optionally 5%-25%; optionally, the silicon-based material includes at least one of silicon, silicon-carbon composite materials, and silicon-oxygen compounds. By adding silicon-based materials to the negative electrode film layer, the energy density of the battery can be improved.

[0011] In any embodiment, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, the second negative electrode film layer is arranged between the negative electrode collector and the first negative electrode film layer, and the first negative electrode film layer and / or the second negative electrode film layer includes the additive.

[0012] In any embodiment, in the first negative electrode film layer, the mass proportion of the additive is greater than 0% and less than or equal to 10%, and can be 0.5%-5%; in the second negative electrode film layer, the mass proportion of the additive is 0%-5%, and can be 0.1%-2%.

[0013] In any embodiment, the first negative electrode film layer and the second negative electrode film layer both include the additive, and the additive materials in the first negative electrode film layer and the second negative electrode film layer are the same or different.

[0014] In any embodiment, the first negative electrode film layer and the second negative electrode film layer both include the additive; in the first negative electrode film layer, the mass proportion of the additive is recorded as A1, and in the second negative electrode film layer, the mass proportion of the additive is recorded as A2; the secondary battery satisfies: A1 / A2>1; optionally, 2≤A1 / A2≤10.

[0015] In any embodiment, the first negative electrode film layer includes a first negative electrode active material, the second negative electrode film layer includes a second negative electrode active material, and the first negative electrode active material and / or the second negative electrode active material include the silicon-based material; optionally, both the first negative electrode active material and the second negative electrode active material include the silicon-based material, and the mass proportion of the silicon-based material in the first negative electrode active material is greater than the mass proportion of the silicon-based material in the second negative electrode active material.

[0016] In any embodiment, the mass proportion of the silicon-based material in the first negative electrode active material is greater than or equal to 5%, and can be optionally 5%-25%.

[0017] In any embodiment, the first negative electrode active material and / or the second negative electrode active material further comprises a carbon material; optionally, the carbon material comprises graphite, and more optionally, a powder pressed at 1.8 g / cm 3 Highly compacted graphite above.

[0018] The present application achieves better storage performance and conductivity for the secondary battery by configuring the double-layer negative electrode film layer.

[0019] In any embodiment, the secondary battery includes a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer includes a lithium supplement; optionally, the lithium supplement includes at least one of lithium sulfide, lithium selenide, lithium oxide, and lithium nitride. By including the lithium supplement in the positive electrode film layer, active lithium can be supplemented, so that the secondary battery has high energy density and fast charging performance.

[0020] In any embodiment, the secondary battery includes an electrolyte, and the electrolyte includes a cyclic carbonate compound; optionally, the cyclic carbonate compound includes at least one of ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate, and butylene carbonate. Thus, the cyclic carbonate compound undergoes a nucleophilic reaction with the additive in the negative electrode film layer, participates in the formation of the SEI film, and improves the storage performance of the secondary battery.

[0021] In any embodiment, the negative electrode film layer includes high-valent sulfur and low-valent sulfur at the same time, and / or, the negative electrode film layer includes high-valent selenium and low-valent selenium at the same time; optionally, the high-valent sulfur includes at least one of +4-valent sulfur and +6-valent sulfur; optionally, the S2p spectrum peak of the high-valent sulfur is 168.5eV-171eV; optionally, the low-valent sulfur includes -2-valent sulfur to -1 / 6-valent sulfur, and optionally, the S2p spectrum peak of the low-valent sulfur is 161eV-166.5eV. Optionally, the high-valent selenium includes at least one of +4-valent selenium and +6-valent selenium; optionally, the Se3d spectrum peak of the high-valent selenium is 58.9eV-61.2eV; optionally, the low-valent selenium includes -2-valent selenium; optionally, the Se3d spectrum peak of the low-valent selenium is 54eV-55.1eV.

[0022] A second aspect of the present application provides an electrical device, which includes the secondary battery of the first aspect of the present application.

[0023] Effects of the Invention

[0024] According to the present application, a secondary battery having excellent storage performance and an electric device including the lithium ion battery can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of the negative electrode sheet in the secondary battery of the present application.

[0026] Description of reference numerals:

[0027] 1 negative electrode current collector; 2 negative electrode film layer; 21 first negative electrode film layer; 22 second negative electrode film layer DETAILED DESCRIPTION

[0028] Hereinafter, the secondary battery of the present application and the electrical device including the secondary battery will be described in detail with reference to the accompanying drawings as appropriate. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure 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 descriptions 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.

[0029] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range.

[0030] If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0031] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0032] A secondary battery is a battery that can be used continuously by recharging the active materials after the battery is discharged, such as a lithium-ion battery. Generally, a secondary battery includes a positive electrode, a negative electrode, a separator and an electrolyte. During the battery charge and discharge process, active ions (such as lithium ions) are embedded and released back and forth between the positive electrode and the negative electrode. The electrolyte is between the positive electrode and the negative electrode, and mainly plays the role of conducting active ions.

[0033] One embodiment of the present application provides a secondary battery, including a negative electrode plate, the negative electrode plate including a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, the negative electrode film layer including an additive capable of undergoing a nucleophilic reaction with a cyclic carbonate compound.

[0034] The applicant unexpectedly discovered that when an additive capable of undergoing nucleophilic reaction with cyclic carbonate compounds is added to the negative electrode film layer, the additive reacts with the cyclic carbonate compounds in the electrolyte of the secondary battery, inducing the ring opening thereof to form a highly elastic PEO-like polymer, which participates in SEI formation and strengthens film formation, thereby reducing irreversible capacity loss caused by frequent repair of SEI rupture and consumption of active lithium; at the same time, a conductive network with high ionic conductivity is formed, which is beneficial to the migration of active ions (such as lithium ions, etc.) in the secondary battery, reduces charge transfer impedance and electrochemical polarization, reduces polarization capacity loss, and thus improves the storage performance of the battery.

[0035] As for the additive, as long as it can react with the cyclic carbonate compound by nucleophilic reaction, there is no particular limitation. In some embodiments, as the additive, sulfur-containing substances and / or selenium-containing substances are included, for example, including at least one of elemental sulfur, lithium sulfide, sodium sulfide, selenium-containing elemental substances, lithium selenide, sodium selenide, cobalt selenide, and nickel selenide. These additives undergo reduction reaction during the charge and discharge process of the battery, and further react with the cyclic carbonate electrolyte solvent. For example, lithium sulfide reacts with ethylene carbonate to generate poly (ethylene oxide) (PEO)-type polymers, which participate in the formation of SEI film. The specific reaction is as follows.

[0036]

[0037] In addition, in some embodiments, a carbon-based material is used as a substrate, and a sulfur-containing substance and / or a selenium-containing substance is loaded on the carbon-based material to form a composite. The carbon-based material includes a nano-carbon-based material, graphene, etc. Preferably, the nano-carbon-based material is a carbon nanotube. In addition, carbon, preferably nanoporous carbon, can also be used as a coating material to coat the surface of the above-mentioned sulfur-containing substance and / or selenium-containing substance to form a sulfur-containing substance with a carbon coating layer and a selenium-containing substance with a carbon coating layer. This can improve the conductivity and fast charging performance of the battery while improving the battery storage performance. In addition, the amount of negative electrode conductive agent can be reduced.

[0038] In some embodiments, based on the total mass of the negative electrode film layer, the mass proportion of the additive is less than or equal to 10%, which can be optionally 0.5%-5%. By making the content of the additive within the above range, the storage performance, conductivity and fast charging performance of the battery can be further improved. In some embodiments, the particle size Dv50 of the above additive is 50nm-500nm, which can be optionally 100nm-200nm. By controlling the particle size within the above range, a larger specific surface area can be obtained and the reaction activity can be increased.

[0039] In some embodiments, the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a carbon material, and the carbon material can be at least one of graphite (including artificial graphite, natural graphite), soft carbon, and hard carbon, preferably graphite. The negative electrode active material also includes a silicon-based material. Optionally, the mass proportion of the silicon-based material in the negative electrode active material is greater than or equal to 5%, preferably 5%-25%, and further preferably 5%-20%. As the silicon-based material, for example, it includes at least one of silicon element, silicon-carbon composite material, and silicon oxide compound, preferably, includes silicon oxide compound, the chemical formula is SiOx, wherein 0<x<2, preferably 0.5≤x≤1.5, and further preferably x=1. The silicon oxide compound has high capacity performance and cycle life.

[0040] By including silicon-based materials as negative electrode active materials in the negative electrode film layer, the energy density of the secondary battery can be greatly improved. On the other hand, the silicon-based negative electrode material has a huge volume change during the embedding and de-embedding process of active ions, such as lithium ions. The electrode material is likely to cause internal stress due to the volume effect, resulting in surface SEI rupture, and frequent SEI repair consumes a large amount of active lithium; in addition, it is easy to cause the electrode material to break, thereby losing electrical contact with the current collector, which leads to poor storage performance of the silicon-based negative electrode. However, the negative electrode film layer of the secondary battery of the present application contains the above-mentioned additive. As mentioned above, the additive can form a highly elastic polymer with the cyclic carbonate compound in the electrolyte to participate in SEI film formation, thereby effectively alleviating the volume expansion of the silicon-based material during charging at the negative electrode-electrolyte interface, and improving the battery capacity and the stability of the interface between the negative electrode and the electrolyte. It can be seen from this that through this embodiment, the secondary battery of the present application has high storage performance and high energy density.

[0041] In the present application, preferably, the above-mentioned negative electrode film layer is configured as a double-layer structure, that is, including a first negative electrode film layer and a second negative electrode film layer, the above-mentioned second negative electrode film layer is arranged between the above-mentioned negative electrode current collector and the above-mentioned first negative electrode film layer, and the above-mentioned first negative electrode film layer and / or the above-mentioned second negative electrode film layer include the above-mentioned additive.

[0042] In some embodiments, the mass proportion of the above-mentioned additive in the above-mentioned first negative electrode film layer is greater than 0% and less than or equal to 10%, and can be optionally 0.5%-5%; and / or, the mass proportion of the above-mentioned additive in the above-mentioned second negative electrode film layer is 0%-5%, and can be optionally 0.1%-2%. When both the first negative electrode film layer and the second negative electrode film layer include additives, the additives in the two layers can be the same or different. When the mass proportion of the additive in the first negative electrode film layer is recorded as A1 and the mass proportion of the additive in the second negative electrode film layer is recorded as A2, A1 / A2>1; preferably, 2≤A1 / A2≤10.

[0043] In some embodiments, the first negative electrode film layer includes a first negative electrode active material, the second negative electrode film layer includes a second negative electrode active material, and the first negative electrode active material and / or the second negative electrode active material include the silicon-based material. Optionally, both the first negative electrode active material and the second negative electrode active material include the silicon-based material, and the mass proportion of the silicon-based material in the first negative electrode active material is greater than the mass proportion of the silicon-based material in the second negative electrode active material. The mass proportion of the silicon-based material in the first negative electrode active material is greater than or equal to 5%, preferably 5%-25%, and further preferably 5%-20%. The type of the silicon-based material is the same as described above. In addition to the silicon-based material, the first negative electrode active material also includes a carbon material, and the carbon material includes at least one of graphite, soft carbon, and hard carbon. Preferably, the carbon material includes graphite. In addition, the second negative electrode active material includes a carbon material, which is the same as or different from the carbon material in the negative electrode film layer. Preferably, the carbon material includes a powder pressure of 1.8 g / cm 3 The above high-density graphite materials.

[0044] The negative electrode sheet comprising the first and second negative electrode film layers may be prepared, for example, as follows.

[0045] By double-layer coating technology, firstly, the two sides of the current collector 1 are coated with a powder having a pressure of 1.8 g / cm 3 The above high-pressure graphite and / or additive slurry forms the second negative electrode film layer 22, and then a composite slurry containing graphite, silicon-based materials, additives, etc. is coated on this basis to form the first negative electrode film layer 21, forming a double-layer negative electrode film layer 2, thereby obtaining a negative electrode sheet, such as Figure 1 Through this composite slurry and double-layer coating method, the advantages of graphite and silicon-based materials are fully utilized. Through different distributions in the vertical direction of the current collector, the fast charging performance of the negative electrode plate can be improved, and a negative electrode plate with high fast charging performance and high compaction can be obtained.

[0046] In some embodiments, the negative electrode film layer includes both high-valent sulfur and low-valent sulfur, and / or, the negative electrode film layer includes both high-valent selenium and low-valent selenium. Optionally, the high-valent sulfur includes at least one of +4-valent sulfur and +6-valent sulfur, and the S2p spectrum peak is 168.5eV-171eV; the low-valent sulfur includes -2-valent sulfur to -1 / 6-valent sulfur, and the S2p spectrum peak is 161eV-166.5eV. Optionally, the high-valent selenium includes at least one of +4-valent selenium and +6-valent selenium, and the Se3d spectrum peak of the high-valent selenium is 58.9eV-61.2eV; Optionally, the low-valent selenium includes -2-valent selenium, and the Se3d spectrum peak of the low-valent selenium is 54eV-55.1eV. The generation of the above-mentioned high-valent sulfur and high-valent selenium is due to the oxidation after losing electrons to generate alkyl sulfates and alkyl selenates that participate in SEI film formation, and the generation of low-valent sulfur and low-valent selenium is due to the reduction after gaining electrons to generate PEO polymers that participate in SEI film formation.

[0047] In the secondary battery of the present application, as an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0048] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. 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 substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0049] In some embodiments, the negative electrode film layer may further include a binder. As an example, 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).

[0050] In some embodiments, the negative electrode film layer may further include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0051] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0052] In some embodiments, the negative electrode sheet can be prepared in the following manner: the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material (carbon material and / or silicon-based material), the above-mentioned additives, 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 collector, and after drying, cold pressing and other processes, the negative electrode sheet is obtained.

[0053] The secondary battery of the present application includes a positive electrode sheet.

[0054] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a lithium supplement, and the lithium supplement includes at least one of lithium sulfide, lithium selenide, lithium oxide, and lithium nitride. Since active lithium is consumed in the process of sulfur-containing substances / selenium-containing substances in the negative electrode plate forming lithium polysulfide / lithium polyselenide, by including a lithium supplement in the positive electrode film layer, active lithium can be supplemented, so that the secondary battery has high energy density and fast charging performance.

[0055] 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 and a metal layer formed on at least one surface of the polymer material base. 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 a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0056] In some embodiments, the positive electrode active material in the positive electrode film layer may adopt the positive electrode active material for batteries known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may 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 NCM 333 )、LiNi 0.5 Co0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), 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-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), 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.

[0057] In some embodiments, the positive electrode film layer may also optionally include a binder. As an example, the binder 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.

[0058] In some embodiments, the positive electrode film layer may further include a conductive agent, for example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0059] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder, the lithium supplement and any other components 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.

[0060] In the secondary battery of the present application, the electrolyte includes a cyclic carbonate compound, preferably, the cyclic carbonate compound includes at least one of ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate and butylene carbonate. These compounds can undergo nucleophilic reaction with the additive in the negative electrode film layer, participate in the formation of SEI film, and improve the storage performance of the secondary battery.

[0061] In some embodiments, the electrolyte includes an organic solvent and an electrolyte salt dispersed in the organic solvent. The specific types and compositions of the organic solvent and the lithium salt are not subject to specific restrictions and can be selected according to actual needs. For example, the electrolyte salt can be selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate and lithium tetrafluorooxalate phosphate. For the solvent, in addition to the above-mentioned cyclic carbonate compounds, it can also be selected from ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0062] The secondary battery of the present application also includes a separator. The present application has no particular restrictions on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0063] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0064] The secondary battery of the present application can be prepared by conventional methods, for example, the positive electrode sheet, the separator, and the negative electrode sheet are wound or stacked in sequence, so that the separator is between the positive electrode sheet and the negative electrode sheet to play an isolating role, and the battery cell is placed in an outer package, and the electrolyte is injected to obtain an electrode assembly. The above-mentioned outer package can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The above-mentioned outer package can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed.

[0065] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape.

[0066] In some embodiments, secondary batteries may be assembled into a battery module. The number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0067] 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 according to the application and capacity of the battery pack.

[0068] 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, and can also be used 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 are not limited to these.

[0069] As the above-mentioned electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0070] Example

[0071] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0072] Example 1

[0073] (1) Preparation of negative electrode sheet

[0074] The negative electrode active material (artificial graphite and silicon oxide, the mass ratio of the two is 90%:10%), the additive elemental sulfur (particle size Dv50 = 200nm), the conductive agent Super P, carbon nanotubes (CNTs), the binder styrene butadiene rubber, and the thickener sodium carboxymethyl cellulose are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 94.5%:2%:1%:0.5%:1%:1% to form a negative electrode slurry.

[0075] The negative electrode slurry is coated on the two surfaces of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode sheet is obtained.

[0076] (2) Preparation of positive electrode sheet

[0077] LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent Super P, and binder polyvinylidene fluoride are mixed in a weight ratio of 96%:2%:2%, and an appropriate amount of solvent NMP is added and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is coated on both surfaces of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained.

[0078] (3) Electrolyte

[0079] In an argon atmosphere glove box (H2O<0.01ppm, O2<0.01ppm), the solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed evenly in a volume ratio of 4:6, LiPF6 lithium salt was added thereto to dissolve it, and stirred evenly. The final concentration of LiPF6 lithium salt was 12.5%, which was used as an electrolyte.

[0080] (4) Isolation film

[0081] A polyethylene film is used as the isolation film.

[0082] (5) Lithium-ion battery

[0083] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, the separator is placed between the positive and negative electrode sheets, and wound to obtain a battery cell. The battery cell is placed in a battery outer package, and then injected with electrolyte, packaged, left to stand, formed, shaped, and tested for capacity to prepare a lithium-ion battery having a thickness of 4.2 mm, a width of 42 mm, and a length of 49.5 mm.

[0084] Example 2-14

[0085] The preparation method is similar to that of Example 1, except that different types or contents of additives are used, as shown in Table 1 for details.

[0086] Embodiment 15

[0087] The preparation method is similar to that of Example 1, except that the preparation method of the negative electrode sheet is as follows:

[0088] The first negative electrode active material (artificial graphite and silicon oxide, the mass ratio of the two is 80%:20%), a composite material of elemental sulfur and carbon nanotubes (particle size Dv50 = 200nm), a conductive agent Super P, carbon nanotubes (CNTs), a binder styrene-butadiene rubber, and a thickener sodium carboxymethyl cellulose are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 94.5%:2%:1%:0.5%:1%:1% to form a first slurry.

[0089] The second negative electrode active material (artificial graphite and silicon oxide, the mass ratio of the two is 95%:5%), nanoporous carbon-coated elemental selenium (particle size Dv50 = 200nm), conductive agent Super P, carbon nanotubes (CNTs), binder styrene butadiene rubber, thickener sodium carboxymethyl cellulose are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 96%: 0.5%: 1%: 0.5%: 1%: 1% to form a second slurry.

[0090] The first slurry and the second slurry are extruded simultaneously through a double-chamber coating device. The second slurry is coated on both surfaces of the negative electrode current collector copper foil, and the first slurry is coated on the second slurry; after drying and cold pressing, a negative electrode sheet is obtained.

[0091] Comparative Example 1

[0092] The preparation method is similar to that of Example 1, except that: the preparation method of the negative electrode plate is as follows: the negative electrode active material (artificial graphite and silicon oxide, the mass ratio of the two is 90%:10%), the conductive agent Super P, carbon nanotubes (CNTs), the binder styrene butadiene rubber, and the thickener sodium carboxymethyl cellulose are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 96.5%:1%:0.5%:1%:1% to form a negative electrode slurry.

[0093] The negative electrode slurry is coated on the two surfaces of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode sheet is obtained.

[0094] Comparative Example 2

[0095] The preparation method is similar to that of Example 15, except that the preparation method of the negative electrode sheet is as follows:

[0096] The first active material (artificial graphite and silicon oxide, the mass ratio of the two is 80%:20%), the conductive agent SuperP, carbon nanotubes (CNTs), the binder styrene-butadiene rubber, and the thickener sodium carboxymethyl cellulose are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 96.5%:1%:0.5%:1%:1% to form a first slurry.

[0097] The second active material (artificial graphite and silicon oxide, the mass ratio of the two is 95%:5%), the conductive agent SuperP, carbon nanotubes (CNTs), the binder styrene-butadiene rubber, and the thickener sodium carboxymethyl cellulose are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 96.5%:1%:0.5%:1%:1% to form a second slurry.

[0098] The first slurry and the second slurry are extruded simultaneously through a double-chamber coating device. The second slurry is coated on both surfaces of the negative electrode current collector copper foil, and the first slurry is coated on the second slurry; after drying and cold pressing, a negative electrode sheet is obtained.

[0099] The secondary batteries of the above-mentioned embodiments and comparative examples were subjected to the following tests, and the results are shown in Table 1 below.

[0100] Battery Test

[0101] Storage performance (capacity retention after 100 days storage at 60°C)

[0102] The battery capacity recovery rate test process is as follows: before storage, at 25°C, the batteries of the embodiment and the comparative example are charged to 4.25V at a constant current of 1 / 3C, then charged to 0.05C at a constant voltage of 4.25V, left for 30 minutes, and then discharged to 2.8V at 1 / 3C. The obtained capacity is recorded as the initial capacity C0. After storage at 60°C for 100 days, the battery temperature is cooled to room temperature, and the above steps are repeated. The measured capacity is recorded as Cr. The battery capacity recovery rate after 100 days of storage is H=Cr / C0*100%.

[0103] The higher H is, the better the storage performance is.

[0104] Conductivity (electrode film resistance)

[0105] The rolled film was cut into a rectangular size of about 5 cm × 10 cm and placed between the two electrodes of the film resistance meter. The test pressure was set to 25 MPa and the holding time was set to 25 s on the MRMS software. The software automatically read the film thickness, resistance, resistivity, conductivity and other data and recorded the resistance data.

[0106] The smaller the resistance value, the better the conductivity.

[0107] Fast charging performance (10%-80% SOC fast charging time)

[0108] The test process of 10%-80% SOC charging time is as follows: at 25°C, the batteries in the embodiment and comparative example are charged from 10% SOC to 80% SOC at 1.0C / 0.8C / 0.5C / 0.33C step by step. The charging time when no lithium deposition occurs at the negative electrode is the fast charging time of the battery at this time. The shorter the fast charging time, the better the fast charging performance of the battery.

[0109] Table 1

[0110]

[0111] According to the results in Table 1, compared with Comparative Examples 1 and 2, the secondary batteries of Examples 1 to 15 all achieved excellent storage performance.

[0112] Moreover, compared with Examples 1 to 4, the additives in Examples 5 to 7 not only have excellent storage performance of the battery but also reduce resistance, improve conductivity of the secondary battery, and obtain better fast charging performance by taking the form of a composite with carbon nanotubes or having a carbon coating layer.

[0113] In Examples 8 to 14, compared with Example 14, Examples 8 to 13 obtain excellent storage performance, conductivity and fast charging performance by making the mass proportion of the additive less than or equal to 10% relative to the total mass of the negative electrode film layer. Furthermore, compared with Examples 12 and 13, Examples 8 to 11 obtain even better storage performance, conductivity and fast charging performance by making the mass proportion of the additive 0.5%-5% relative to the total mass of the negative electrode film layer.

[0114] In addition, in Example 15, by making the negative electrode film layer a double-layer structure, the storage performance and fast charging performance of the secondary battery can be further improved.

[0115] In contrast, since Comparative Examples 1 and 2 do not contain the specific additives of the present application, the storage performance is not improved and the technical effect of the present application cannot be obtained.

[0116] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining 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 negative electrode plate, wherein the negative electrode plate comprises 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 comprises an additive capable of undergoing a nucleophilic reaction with a cyclic carbonate compound.

2. The secondary battery according to claim 1, wherein The additive comprises at least one of a sulfur-containing substance, a selenium-containing substance, a composite of a sulfur-containing substance and a carbon-based material, a composite of a selenium-containing substance and a carbon-based material, a sulfur-containing substance with a carbon coating layer, or a selenium-containing substance with a carbon coating layer; Optionally, the sulfur-containing substance includes at least one of elemental sulfur, lithium sulfide, or sodium sulfide; Optionally, the selenium-containing substance includes at least one of selenium, lithium selenide, sodium selenide, cobalt selenide, or nickel selenide; Optionally, the carbon-based material includes nano-carbon-based material and / or graphene. Optionally, the nano-carbon-based material includes carbon nanotubes.

3. The secondary battery according to claim 1 or 2, wherein: Based on the total mass of the negative electrode film layer, the mass proportion of the additive is less than or equal to 10%, and can be optionally 0.5%-5%.

4. The secondary battery according to any one of claims 1 to 3, wherein: The particle size Dv50 of the additive is 50nm-500nm, and can be optionally 100nm-200nm.

5. The secondary battery according to any one of claims 1 to 4, wherein: The negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a silicon-based material. Optionally, the mass proportion of the silicon-based material in the negative electrode active material is greater than or equal to 5%, and optionally greater than or equal to 10%; Optionally, the silicon-based material includes at least one of silicon element, silicon-carbon composite material, and silicon-oxygen compound.

6. The secondary battery according to any one of claims 1 to 5, wherein: The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, wherein the second negative electrode film layer is arranged between the negative electrode current collector and the first negative electrode film layer. The first negative electrode film layer and / or the second negative electrode film layer includes the additive.

7. The secondary battery according to claim 6, wherein In the first negative electrode film layer, the mass proportion of the additive is greater than 0% and less than or equal to 10%, and can be optionally 0.5%-5%. In the second negative electrode film layer, the mass proportion of the additive is 0%-5%, and can be optionally 0.1%-2%.

8. The secondary battery according to claim 6 or 7, wherein: The first negative electrode film layer and the second negative electrode film layer both include the additive; In the first negative electrode film layer, the mass proportion of the additive is recorded as A1, and in the second negative electrode film layer, the mass proportion of the additive is recorded as A2; the secondary battery satisfies: A1 / A2>1; optionally, 2≤A1 / A2≤10.

9. The secondary battery according to any one of claims 6 to 8, wherein The first negative electrode film layer and the second negative electrode film layer both include the additive, and the additive materials in the first negative electrode film layer and the second negative electrode film layer are the same or different.

10. The secondary battery according to any one of claims 6 to 9, wherein The first negative electrode film layer comprises a first negative electrode active material, the second negative electrode film layer comprises a second negative electrode active material, and the first negative electrode active material and / or the second negative electrode active material comprises the silicon-based material; Optionally, both the first negative electrode active material and the second negative electrode active material include the silicon-based material, and the mass proportion of the silicon-based material in the first negative electrode active material is greater than the mass proportion of the silicon-based material in the second negative electrode active material.

11. The negative electrode sheet according to claim 10, wherein: The first negative electrode active material and / or the second negative electrode active material further include a carbon material; optionally, the carbon material includes graphite.

12. The secondary battery according to any one of claims 1 to 11, wherein: The secondary battery comprises a positive electrode plate, the positive electrode plate comprises a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer comprises a lithium supplement; Optionally, the lithium supplement includes at least one of lithium sulfide, lithium selenide, lithium oxide, and lithium nitride.

13. The secondary battery according to any one of claims 1 to 12, wherein: The secondary battery includes an electrolyte, and the electrolyte includes a cyclic carbonate compound; Optionally, the cyclic carbonate compound includes at least one of ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate and butylene carbonate.

14. The secondary battery according to any one of claims 1 to 13, wherein: The negative electrode film layer includes both high-valent sulfur and low-valent sulfur, and / or the negative electrode film layer includes both high-valent selenium and low-valent selenium; Optionally, the high-valent sulfur includes at least one of +4-valent sulfur and +6-valent sulfur; Optionally, the S2p spectrum peak of the high-valent sulfur is 168.5-171 eV; Optionally, the low-valent sulfur includes -2-valent sulfur to -1 / 6-valent sulfur; Optionally, the S2p spectrum peak of the low-valent sulfur is 161-166.5 eV; Optionally, the high-valent selenium includes at least one of +4-valent selenium and +6-valent selenium; Optionally, the Se3d spectrum peak of the high-valent selenium is 58.9-61.2 eV; Optionally, the low-valent selenium includes -2-valent selenium; Optionally, the Se3d spectrum peak of the low-valent selenium is 54-55.1 eV.

15. An electrical device comprising the secondary battery according to any one of claims 1 to 14.

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