Negative electrode additive, negative electrode sheet containing the same and secondary battery

Abstract

The present application provides a negative electrode additive, including a substrate, the substrate including porous carbon; a functionalized material, the functionalized material including a transition metal phosphide; and a magnetic substance, the magnetic substance including one or more of a magnetic metal element or a magnetic metal oxide.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a negative electrode additive, a negative electrode plate containing the negative electrode additive, and a 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. Compared with traditional cars, the biggest disadvantage of electric vehicles is the charging time. Usually, the charging time of electric vehicles is more than ten hours, which seriously limits the application of electric vehicles. Therefore, if electric vehicles are to replace traditional fuel vehicles, charging speed is one of the key technologies that must be overcome, and it is also an important indicator that affects user experience.

[0003] Taking lithium-ion batteries as an example, for thick-coated graphite negative electrodes in fast-charging state, the fast-charging capacity is insufficient, which easily causes lithium deposition on the surface of the graphite negative electrode, causing a series of problems. Therefore, how to improve the fast-charging capacity of secondary batteries is still an urgent problem to be solved. Summary of the invention

[0004] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a negative electrode additive, including a substrate, the substrate includes porous carbon; a functionalized material, the functionalized material includes a transition metal phosphide; a magnetic substance, the magnetic substance includes one or more of a magnetic metal element or a magnetic metal oxide.

[0005] Therefore, the present application prepares a negative electrode additive by introducing functional materials and magnetic substances into the base material, thereby achieving rapid transfer of alkali metal ions in the negative electrode, inhibiting lithium plating on the negative electrode surface, and further improving the internal pore structure of the additive, thereby improving the fast charging capability of the secondary battery.

[0006] In any embodiment, the substrate includes one or both of porous carbon nanofibers or hollow tubular structure carbon fibers.

[0007] In any embodiment, the functionalized material includes one or more of Ni, Mn, and Mo-based phosphides.

[0008] In any embodiment, the functionalized material comprises MoP x , where 0 <x≤2。

[0009] In any embodiment, the magnetic material includes one or more of Ni, Co, Fe, Fe3O4, and Co3O4; optionally, it includes one or more of Fe3O4 and Co3O4.

[0010] In any embodiment, the negative electrode additive includes a magnetic substance; the magnetic substance is selected from one or more of metal elements such as Ni, Co, Fe, or metal oxides such as Fe3O4, Co3O4, etc.

[0011] In any embodiment, the mass proportion of the substrate in the negative electrode additive is greater than or equal to 60%, and can be optionally 60%-80%.

[0012] In any embodiment, the mass proportion of the functionalized material in the negative electrode additive is less than or equal to 30%, and can be optionally 10%-20%.

[0013] In any embodiment, the mass proportion of the magnetic substance in the negative electrode additive is less than or equal to 20%, and can be optionally 5%-20%.

[0014] In any embodiment, the negative electrode additive is a tubular structure with a diameter of 500 nm to 800 nm.

[0015] The second aspect of the present application also provides a method for preparing a negative electrode additive, which comprises the following steps:

[0016] S1: dissolving a carbon source and a transition metal salt into a solution, and stirring to obtain a spinning solution;

[0017] S2: electrospinning the spinning solution to obtain an intermediate material;

[0018] S3: subjecting the intermediate to high temperature carbonization and phosphating treatment to obtain a composite material;

[0019] S4: adding the composite material to an iron salt solution and performing hydrothermal synthesis to obtain a negative electrode additive;

[0020] Among them, the carbon source includes one or more of polyacrylonitrile, polyvinyl pyrrolidone, and polyvinyl alcohol, the transition metal salt includes at least one of molybdenum acetylacetonate or nickel acetylacetonate, and the iron salt includes one or more of FeCl3, Fe(NO3)3, and Fe2(SO4)3.

[0021] Therefore, according to the preparation method provided in the present application, the metal phosphide is embedded in the surface of the porous carbon nanofiber or coated by the hollow tubular structure carbon fiber, and the internal pore structure of the negative electrode additive is optimized by adding magnetic material, which plays a role in enhancing lithium ion transmission and inhibiting lithium precipitation, thereby improving the fast charging capability of the secondary battery.

[0022] In any embodiment, step S1 further includes a step of using a pore-forming agent to form pores, and the pore-forming agent includes one or more of polystyrene, polymethyl methacrylate, and silicon dioxide and is added into the spinning solution for use.

[0023] The third aspect of the present application provides a negative electrode plate, comprising the negative electrode active material of the first aspect of the present application or the negative electrode active material prepared according to the method of the second aspect of the present application.

[0024] In any embodiment, the mass proportion of the negative electrode additive in the negative electrode film layer is less than or equal to 2%, and can be optionally 0.05%-2%.

[0025] The fourth aspect of the present application provides a secondary battery, comprising the negative electrode plate of the third aspect of the present application.

[0026] A fifth aspect of the present application provides an electrical device, comprising the secondary battery of the fourth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of the additive according to one embodiment of the present application and a partially enlarged schematic diagram.

[0028] Figure 2 is a schematic diagram of a secondary battery according to one embodiment of the present application.

[0029] Figure 3 yes Figure 2 An exploded view of a secondary battery according to an embodiment of the present application is shown.

[0030] Figure 4 is a schematic diagram of a battery module according to an embodiment of the present application.

[0031] Figure 5 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0032] Figure 6 yes Figure 5 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0033] Figure 7 FIG. 1 is a schematic diagram of an electric device using a secondary battery according to an embodiment of the present application as a power source.

[0034] Description of reference numerals:

[0035] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0036] Below, the embodiments of the separator, positive electrode sheet, negative electrode sheet, electrolyte, secondary battery, battery module, battery pack and power device of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there are 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 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 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.

[0037] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a 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 a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present 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 real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it 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.

[0038] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0039] 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.

[0040] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means 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), which means 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.

[0041] 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.

[0042] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": 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).

[0043] [Secondary battery]

[0044] Secondary batteries, also known as rechargeable batteries or storage batteries, refer to batteries that can be recharged to activate active materials and continue to be used after the battery is discharged. Usually, secondary batteries include positive electrode sheets, negative electrode sheets, separators and electrolytes. During the battery charging and discharging process, active ions (such as lithium ions) are embedded and released back and forth between the positive electrode sheets and the negative electrode sheets. The separator is arranged between the positive electrode sheets and the negative electrode sheets, and its main function is to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The electrolyte is between the positive electrode sheets and the negative electrode sheets, and its main function is to conduct active ions.

[0045] [Anode additives]

[0046] One embodiment of the present application provides a negative electrode additive, comprising

[0047] The substrate comprises porous carbon; the functionalized material comprises transition metal phosphide; and the magnetic material comprises one or more of magnetic metal elements or magnetic metal oxides.

[0048] The negative electrode additive prepared in this application introduces functional materials and magnetic substances into the substrate material. During the fast charging process, it can promote the rapid transfer of lithium ions in graphite and is conducive to the rapid infiltration of the electrolyte. Especially for the thick coating method, it is difficult for lithium ions to embed into the graphite far from the separator, resulting in low utilization rate of graphite and easy lithium deposition on the graphite surface, forming lithium dendrites that pierce the separator and cause short circuits inside the battery cell. The negative electrode additive of this application can optimize the internal pore structure of the additive, reduce the tortuosity of the additive material. From D eff = Dε / τ (D eff is the effective diffusion coefficient, ε is the porosity, D is the intrinsic diffusion coefficient, and τ is the tortuosity), it can be known that when the intrinsic diffusion coefficient of the electrolyte salt and the porosity of the electrode sheet are constant, the lower the tortuosity of the electrode sheet, the greater the effective diffusion coefficient of the electrolyte salt in the graphite negative electrode. The negative electrode additive material introduced in this application has the above beneficial effects, can effectively accelerate the rapid transfer of lithium ions in graphite, slow down the lithium deposition problem during the fast charging process of the battery, and thus improve the purpose of accelerating lithium ion transmission to achieve 4C fast charging.

[0049] In some embodiments, the substrate includes one or both of porous carbon nanofibers or hollow tubular structure carbon fibers.

[0050] The porous carbon has specific rich channels, which is conducive to the coating of the metal phosphide selected as the negative electrode active material of this application. The functional material can be embedded on the surface of the porous carbon nanofibers or coated by the hollow tubular structure carbon fibers, forming various through or surface lithium ion transmission channels inside, which accelerates the transmission rate of lithium ions in the graphite negative electrode.

[0051] In some embodiments, the functional material includes one or several of Ni, Mn, Mo-based phosphides.

[0052] During the fast charging process, the metal phosphide introduced in this application can not only utilize its characteristic of lithium intercalation at a relatively high potential to achieve a rapid lithium intercalation process, but also effectively reduce the diffusion energy barrier of lithium ions in graphite and promote the rapid transfer of lithium ions in graphite.

[0053] In some embodiments, the functional material is selected from MoP x , where 0 < x ≤ 2. Compared with other metal phosphides, molybdenum phosphide has a lower adsorption energy for lithium ions, which is conducive to realizing the rapid kinetic process of lithium ions.

[0054] In some embodiments, the magnetic substance includes one or several of Ni, Co, Fe, Fe3O4, Co3O4; optionally, it includes one or several of Fe3O4, Co3O4.

[0055] In some embodiments, the mass proportion of the substrate in the negative electrode additive is greater than or equal to 60%, and can be optionally 60%-80%.

[0056] In some embodiments, the mass proportion of the functionalized material in the negative electrode additive is less than or equal to 30%, and can be optionally 10%-20%.

[0057] In some embodiments, the mass proportion of the magnetic substance in the negative electrode additive is less than or equal to 20%, and can be optionally 5%-20%.

[0058] In some embodiments, the negative electrode additive is a tubular structure with a diameter of 500nm-800nm. When the size is controlled between 500nm-800nm, the specific surface area of ​​the negative electrode additive is small, resulting in fewer surface side reactions, and is conducive to building a continuous conductive network structure.

[0059] In some embodiments, the schematic diagram of the structure of the negative electrode additive is as follows Figure 1 The morphology of the prepared additive is shown in the schematic diagram. Figure 1 The locally enlarged schematic diagram in the figure shows that in the additive of the present application, there are two ways to combine the functionalized material and the carbon substrate, depending on the selection of the carbon substrate. The functionalized material can be embedded in the surface of the porous carbon nanofiber or coated by the hollow tubular structure carbon fiber.

[0060] [Method for preparing negative electrode additive]

[0061] One embodiment of the present application provides a method for preparing a negative electrode additive, comprising the following steps:

[0062] S1: dissolving a carbon source and a transition metal salt into a solution, and stirring to obtain a spinning solution;

[0063] S2: electrospinning the spinning solution to obtain an intermediate material;

[0064] S3: subjecting the intermediate to high temperature carbonization and phosphating treatment to obtain a composite material;

[0065] S4: adding the composite material to an iron salt solution and performing hydrothermal synthesis to obtain the negative electrode additive;

[0066] Among them, the carbon source includes one or more of polyacrylonitrile, polyvinyl pyrrolidone, and polyvinyl alcohol, the transition metal salt includes at least one of acetylacetonate molybdenum or acetylacetonate nickel, and the iron salt includes one or more of FeCl3, Fe(NO3)3, and Fe2(SO4)3.

[0067] In some embodiments, step S1 further includes a step of using a pore-forming agent to form pores, wherein the pore-forming agent includes one or more of polystyrene, polymethyl methacrylate, and silicon dioxide and is added to the spinning solution for use. The pore-forming agent is introduced into the preparation method of the present application, and the pore structure inside the additive can be regulated by the mass ratio of the pore-forming agent to the carbon source.

[0068] [Negative electrode]

[0069] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material and a negative electrode additive provided in the present application.

[0070] In some embodiments, the mass proportion of the negative electrode additive in the negative electrode film layer is less than or equal to 2%, and may be 0.05%-2%.

[0071] 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 any one or both of the two opposite surfaces of the negative electrode current collector.

[0072] 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.).

[0073] In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery 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 oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, 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.

[0074] 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).

[0075] 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.

[0076] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0077] In some embodiments, the negative electrode sheet can be prepared in the following manner: 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 collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0078] [Positive electrode]

[0079] The positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0080] 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 disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0081] 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.).

[0082] In some embodiments, the positive electrode active material may adopt a positive electrode active material for a battery that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, 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 Co 0.2 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.

[0083] 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.

[0084] 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.

[0085] 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 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.

[0086] [Electrolytes]

[0087] The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0088] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0089] In some embodiments, the electrolyte salt can 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.

[0090] 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, methyl propyl carbonate, ethyl propyl 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 sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0091] In some embodiments, the electrolyte may further include additives. As examples, 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, additives that improve battery high or low temperature performance, etc.

[0092] [Isolation film]

[0093] 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 stability and mechanical stability can be selected.

[0094] 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.

[0095] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0096] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0097] In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0098] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square or any other shape. Figure 2 The secondary battery 5 is a square structure as an example.

[0099] In some embodiments, reference Figure 3 , the outer packaging may include a shell 51 and a cover plate 53. Among them, 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 form 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.

[0100] 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.

[0101] Figure 4 4 is an example of a battery module. Figure 4 In the battery module 4, the plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.

[0102] 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.

[0103] 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.

[0104] Figure 5 and Figure 6 1 is a battery pack 1 as an example. Figure 5 and Figure 6 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0105] 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 thereto.

[0106] As the electrical device, a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.

[0107] Figure 7 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the high power and high energy density requirements of the power consumption device for the secondary battery, a battery pack or a battery module can be used.

[0108] [Example]

[0109] 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.

[0110] Example 1

[0111] Preparation of negative electrode additives

[0112] Weigh a certain mass of pore-forming agent polystyrene and add it to 5mL N,N-dimethylformamide for ultrasonic dispersion, add 0.2g of molybdenum acetylacetonate and stir at 600rpm for 30min to obtain a uniform mixed solution. Then, under stirring at 800rpm, add 0.5g of polyacrylonitrile and stir at room temperature for 48h to obtain a uniform electrospinning slurry. Electrospinning was carried out under the conditions of positive high voltage 11.00kV, negative high voltage -3.03kV, receiving distance of 17cm, and injection speed of 0.15mm / min. After the electrospinning was completed, the collected samples were vacuum dried at 60℃ for 12h. The collected samples were heated to 250℃ at a heating rate of 1℃ / min in an air atmosphere and kept warm for 3h. Subsequently, the obtained samples were phosphated. Finally, 30mL1.0mol / L FeCl3 solution was added to the obtained product, and the hydrothermal time was controlled to 6h to obtain the negative electrode additive.

[0113] Preparation of negative electrode

[0114] The active material artificial graphite, the conductive agent carbon black, the binder styrene-butadiene rubber (SBR), the thickener sodium hydroxymethyl cellulose (CMC) and the negative electrode additive are dissolved in the solvent deionized water in a weight ratio of 96.2:0.8:0.8:1.2:1, and the negative electrode slurry is prepared after being evenly mixed; the negative electrode slurry is evenly coated on the negative electrode collector copper foil once or multiple times, and the negative electrode sheet is obtained after drying, cold pressing and slitting.

[0115] Preparation of positive electrode

[0116] The nickel-cobalt-manganese (NCM) ternary material, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are stirred and mixed evenly in a weight ratio of 96.7:2.5:0.8 to obtain a positive electrode slurry; the positive electrode slurry is then evenly coated on the positive electrode collector, and then dried, cold pressed, and cut to obtain a positive electrode sheet.

[0117] Preparation of electrolyte

[0118] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), the organic solvent ethylene carbonate (EC) / ethyl methyl carbonate (EMC) was mixed evenly in a volume ratio of 3 / 7, 12.5% ​​LiPF6 lithium salt was added and dissolved in the organic solvent, and stirred evenly to obtain the electrolyte of Example 1.

[0119] Isolation film

[0120] Polypropylene film is used as the isolation film.

[0121] Preparation of secondary batteries

[0122] The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is added. After packaging, standing, forming, aging and other processes, a secondary battery is obtained.

[0123] Example 2-12

[0124] The other steps of Examples 2-12 are the same as those of Example 1, except that the masses of molybdenum acetylacetonate are respectively changed to 0.32g, 0.1g, 0.14g, 0.12g, 0.15g, 0.14g, 0.3g, 0.37g, 0.16g, 0.12g and 0.15g and the hydrothermal time is adjusted to 3h, 6h, 4h, 3h, 6h, 5h, 6h, 1h, 7h, 1h, 6h,

[0125] Embodiment 13

[0126] On the basis of Example 1, the hydrothermal synthesis step was changed to adding 30 mL of 1.0 mol / L CoCl2 solution, and hydrothermal synthesis was performed for 5 h to obtain Example 13.

[0127] Embodiment 14

[0128] On the basis of Example 1, the mass of molybdenum acetylacetonate was changed to 0.18 g, the hydrothermal solution was replaced with 30 mL of 1.0 mol / L CoCl2 solution, and hydrothermal synthesis was performed for 3 h to obtain Example 14.

[0129] Comparative Examples 1-3

[0130] On the basis of Example 1, without adding molybdenum salt, a carbon base material is first obtained, and comparative examples 1-3 can be obtained by controlling the hydrothermal time of the material and the FeCl3 solution to 10 h, 8 h and 7.5 h.

[0131] Comparative Examples 4-6

[0132] On the basis of Example 1, the addition amounts of molybdenum acetylacetonate were changed to 0.42 g, 0.3 g and 0.2 g respectively, to obtain Comparative Examples 4-6.

[0133] The product parameters of Examples 1-14 and Comparative Examples 1-6 prepared according to the above method are shown in Table 1.

[0134] Table 1: Product parameters of Examples 1-14 and Comparative Examples 1-6

[0135]

[0136]

[0137] Material Testing

[0138] (1) Morphology test

[0139] All the examples were characterized by scanning electron microscopy and transmission electron microscopy. The uniform tubular structure can be observed by scanning electron microscopy, and the tube diameter of the prepared negative electrode additive can be measured at the same time; the multi-porous structure can be observed from the interface of the tube. The multi-porous structure inside can be further confirmed by transmission electron microscopy, and it can also be observed that the molybdenum phosphide particles are uniformly embedded in the multi-porous structure. High-resolution transmission electron microscopy can further confirm the presence of molybdenum phosphide.

[0140] (2) Structural analysis

[0141] All embodiments were characterized by X-ray crystal diffraction, and the test angle range was 5°-90°. Among them, the peak position of 5° is attributed to the characteristic peak of amorphous carbon derived from the carbon source, the peak position of 43° corresponds to the characteristic peak of the MoP (JCPDS: No.24-0771) (101) crystal plane, the peak position of 46° corresponds to the characteristic peak of the CoP (JCPDS: No.29-0497) (211) crystal plane, and the peak position of 35° corresponds to the characteristic peak of the Fe3O4 (JCPDS: No.65-3107) (311) crystal plane. The characteristic peaks of MoP, CoP and Fe3O4 were compared with the standard cards of each substance to determine the presence of MoP, CoP and Fe3O4 in the composite material.

[0142] (3) Thermogravimetric analysis

[0143] Weigh a certain mass of material and heat it to 800℃ at a heating rate of 5℃ / min in a dry air atmosphere. The weight loss before 200℃ is attributed to the water adsorbed in the material. As the temperature gradually increases, MoP and CoP are converted into MoO3 and Co3O4 respectively. The mass fraction of MoP or CoP in the negative electrode additive can be determined based on the final material content. The content of Fe3O4 is estimated based on the weight difference before and after Fe3O4 loading.

[0144] (4) Three-electrode test

[0145] The prepared three-electrode battery cell was subjected to a three-electrode test, with a voltage test window of 2.5-4.4V and a test temperature of 25°C. First, the actual charge capacity of each battery cell (capacity is recorded as C0) was measured, and then different current densities (0.5C0, 1.0C0, 1.5C0 and 2.0C0) were used for charging, and the anode potential was monitored. Once the anode potential reached -10mV, charging was terminated. The charge cut-off capacity C tDivide by C0 to get the SOC state of the battery cell at 2C charging current density. At a charging current density of 2C, the higher the SOC of the battery cell, the stronger the charging capacity of the battery cell at a high current density.

[0146] Electrochemical performance test

[0147] At 25°C, charge the assembled battery at 4C to 4.4V, leave it for 10 minutes, and then discharge it at 1C to 2.5V. Repeat the above steps for the same battery and record the battery capacity after 300 cycles. The capacity after 300cyls cycle / initial capacity is the 300cyls capacity retention rate.

[0148] The above tests were performed on Examples 1-10 and Comparative Examples 1-5, and the performance test results are shown in Table 2.

[0149] Table 2: Performance test results of Examples 1-10 and Comparative Examples 1-5

[0150]

[0151]

[0152] According to the above results, in Examples 1-14, the negative electrode additives of the present application were used in the secondary battery, which effectively improved the capacity and the capacity retention rate after multiple cycles, and the SOC achieved by 2C charging was higher. The negative electrode additives provided by the present application can adapt to the high current density charging environment and improve the fast charging capability of the secondary battery.

[0153] In contrast, in Comparative Examples 1-6, additives that meet the conditions of this application are not used. In the absence of functional materials or magnetic substances, their capacity, capacity retention rate and SOC achieved by 2C charging are effectively improved, and the secondary batteries prepared using them lack fast charging capability.

[0154] 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 negative electrode additive comprising a substrate comprising porous carbon; Functionalized material, the functionalized material includes transition metal phosphide, the functionalized material includes one or more of Ni, Mn, and Mo-based phosphides; The magnetic material includes one or more of a magnetic metal element or a magnetic metal oxide.

2. The negative electrode additive according to claim 1, characterized in that The substrate includes one or both of porous carbon nanofibers and hollow tubular carbon fibers.

3. The negative electrode additive according to claim 1 or 2, characterized in that: The functionalized material includes MoP x , where 0 <x≤2。 4. The negative electrode additive according to claim 1 or 2, characterized in that: The magnetic material includes one or more of Ni, Co, Fe, Fe3O4, and Co3O4.

5. The negative electrode additive according to claim 4, characterized in that: The magnetic material includes one or more of Fe3O4 and Co3O4.

6. The negative electrode additive according to claim 1 or 2, characterized in that: The mass proportion of the substrate in the negative electrode additive is greater than or equal to 60%.

7. The negative electrode additive according to claim 6, characterized in that: The mass proportion of the substrate in the negative electrode additive is 60%-80%.

8. The negative electrode additive according to claim 1 or 2, characterized in that: The mass proportion of the functionalized material in the negative electrode additive is less than or equal to 30%.

9. The negative electrode additive according to claim 8, characterized in that: The mass proportion of the functionalized material in the negative electrode additive is 10%-20%.

10. The negative electrode additive according to claim 1 or 2, characterized in that: The mass proportion of the magnetic substance in the negative electrode additive is less than or equal to 20%.

11. The negative electrode additive according to claim 10, characterized in that: The mass proportion of the magnetic substance in the negative electrode additive is 5%-20%.

12. The negative electrode additive according to claim 1 or 2, characterized in that: The fiber diameter of the negative electrode additive is 500nm-800nm.

13. A method for preparing a negative electrode additive, characterized in that: The steps include: S1: dissolving a carbon source and a transition metal salt into a solution, and stirring to obtain a spinning solution; S2: electrospinning the spinning solution to obtain an intermediate material; S3: subjecting the intermediate to high temperature carbonization and phosphating treatment to obtain a composite material; S4: adding the composite material to an iron salt solution and performing hydrothermal synthesis to obtain the negative electrode additive; Among them, the carbon source includes one or more of polyacrylonitrile, polyvinyl pyrrolidone, and polyvinyl alcohol, the transition metal salt includes at least one of acetylacetonate molybdenum or acetylacetonate nickel, and the iron salt includes one or more of FeCl3, Fe(NO3)3, and Fe2(SO4)3.

14. The preparation method according to claim 13, characterized in that: Step S1 also includes a step of using a pore-forming agent to form pores. The pore-forming agent includes one or more of polystyrene, polymethyl methacrylate, and silicon dioxide and is added into the spinning solution for use.

15. A negative electrode plate, comprising the negative electrode additive according to any one of claims 1 to 12 or the negative electrode additive prepared according to the preparation method provided in claim 13 or 14.

16. The negative electrode sheet according to claim 15, characterized in that: The mass proportion of the negative electrode additive in the negative electrode film layer is less than or equal to 2%.

17. The negative electrode sheet according to claim 16, characterized in that: The mass proportion of the negative electrode additive in the negative electrode film layer is 0.05%-2%.

18. A secondary battery, characterized in that: Comprising the negative electrode sheet as described in any one of claims 15-17.

19. An electrical device, characterized in that: A secondary battery selected from the group consisting of:

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