A secondary battery, a method of manufacturing a corresponding positive electrode active material, a battery module, a battery pack, and a power-using device

Abstract

The application relates to a secondary battery, comprising (1) a positive electrode sheet; (2) an electrolyte; characterized in that the positive electrode active material is an active material A containing A and B double cations with the following chemical formula x B 1‑x MeO2 or A x B 1‑x MPO4, wherein Me, M, A, B, x have the definitions described in the specification; and the electrolyte comprises an A and B double cation electrolyte salt, wherein A and B are the same as the definitions in the positive electrode active material; and a corresponding preparation method of the positive electrode active material, a corresponding battery module, a battery pack and a power utilization device. The secondary battery of the application comprises a positive electrode active material containing A and B double cations and the same double cation salt electrolyte, which improves the stability of the positive electrode active material and the negative electrode active material, thereby improving the cycle stability of the battery.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to a secondary battery, a method for preparing a corresponding positive electrode active material, a battery module, a battery pack, and an electrical device. Background Technology

[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 plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. Due to the significant development of secondary batteries, especially lithium-ion batteries, higher requirements have been placed on their energy density, cycle performance, and safety performance. Furthermore, with increasingly limited choices of positive electrode active materials, the adjustment of the structure of positive electrode active materials has been increasingly studied by those skilled in the art.

[0003] Improving the rate performance and cycle performance of materials through coating or doping are currently effective methods. However, existing methods all lead to varying degrees of damage to battery performance, such as reduced specific capacity and worsened cycle performance. Therefore, existing coated or doped cathode active materials still need improvement. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a secondary battery that includes a positive electrode active material containing A and B dual cations and the same dual cation salt electrolyte, thereby improving the stability of the positive electrode active material and the negative electrode active material, and thus improving the cycle stability of the battery.

[0005] The first aspect of this application provides a secondary battery comprising (1) a positive electrode sheet, which includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and containing a positive electrode active material; (2) an electrolyte; characterized in that the positive electrode active material is an active material containing A and B dual cations having the following chemical formula.

[0006] A x B 1-x MeO2 or A x B 1-x MPO4,

[0007] in

[0008] Me is selected from one or more of the elements Mn, Fe, Ni, Co, V, Cu, and Cr;

[0009] M is selected from one or more of Mn, Fe, Ni, and Co;

[0010] A is K or Na,

[0011] B is either Na or Li;

[0012] The ionic radius of A is larger than that of B, and A and B are of different species;

[0013] x is between 0.001 and 0.05; and

[0014] The electrolyte contains A and B dual-cation electrolyte salts, wherein A and B are defined in the same way as in the positive electrode active material.

[0015] Therefore, the battery of this application comprises a positive electrode active material containing dual cations A and B and the same dual-cation salt electrolyte, which significantly improves its cycle performance. On the one hand, the larger-radius cation A plays a role in stabilizing the structure of the positive electrode active material and reducing the loss of the positive electrode active material. On the other hand, the larger-radius cation A is embedded in the negative electrode active material through the electrolyte containing the ion salt, supporting the structure of the negative electrode active material, reducing the loss of active lithium ions, thereby improving the cycle performance of the battery.

[0016] In any embodiment, the molar concentration ratio of the two cations in the electrolyte is greater than or equal to the stoichiometric ratio of the two cations in the positive electrode active material. This is more conducive to the stability of the negative electrode active material, thereby improving the cycle stability of the battery.

[0017] In any embodiment, the dual-cation electrolyte salt is selected from at least one inorganic and organic salt of two or more elements selected from lithium, sodium, and potassium. The inorganic salt is selected from at least one of hexafluorophosphate, perchlorate, hexafluoroarsenate, tetrafluoroborate, and difluorophosphate; the organic salt is selected from at least one of bis(oxalate)borate, oxalate difluoroborate, bis(fluorosulfonyl)imide, and bis(trifluoromethyl)sulfonyl)imide. This makes the electrolyte more conducive to the transport of dual cations and improves the cycle stability of the battery.

[0018] In any embodiment, the chemical formula A x B 1-x The positive electrode active material of MeO2 is selected from chemical formula A x B 1- x NiO2, A x B 1-x MnO2, A x B 1-x CoO2, A x B 1-x Ni y Co z Mn 1-y-z O2, A x B 1-x Ni y Co z Al 1-y-zThe active material of O2 and at least one of its coating and doping products; wherein A, B and x are defined as described above; 0≤z≤1, 0≤y≤1. Thus, by including the specific positive electrode active material, the cycle stability of the secondary battery is improved.

[0019] In any embodiment, the chemical formula A x B 1-x The positive electrode active material of MPO4 is selected from chemical formula A x B 1- x FePO4, A x B 1-x At least one of the active materials selected from CoPO4; wherein A, B, and x are as defined above. This improves the cycle stability of the secondary battery by incorporating the specific positive electrode active material.

[0020] A second aspect of this application also provides a method for preparing the positive electrode active material for a secondary battery as described in the first aspect of this application, comprising the following steps:

[0021] 1) Provide precursors for Me or M transition metals.

[0022] 2) The precursor is mixed evenly with metal salt A and metal salt B, and then ground; the ground powder is then calcined and cooled to room temperature to obtain the positive electrode active material;

[0023] Wherein Me or M, A, B are as defined in the first aspect of this application.

[0024] Therefore, the positive electrode active material required for the battery of the first aspect of this application can be prepared, the structural stability of the positive electrode active material is improved, and thus the cycle stability of the secondary battery is improved.

[0025] In any embodiment, metal salt A and metal salt B are at least one of carbonates and hydroxides. Thus, the active material of this application can be obtained using metal salts of this type to improve the cycle stability of secondary batteries.

[0026] In any embodiment, the molar ratio of the precursor to metal salt A or metal salt B is 105%-109% of its stoichiometric ratio. This ratio of precursor to metal salt A or metal salt B allows for the acquisition of the active material of this application, thereby improving the cycle stability of the secondary battery.

[0027] A third aspect of this application provides a battery module, including the secondary battery of the first aspect of this application.

[0028] A fourth aspect of this application provides a battery pack that includes the battery module of the third aspect of this application.

[0029] The fifth aspect of this application provides an electrical device, including at least one selected from the second-generation battery of the first aspect of this application, the battery module of the third aspect of this application, or the battery pack of the fourth aspect of this application.

[0030] The battery of this application significantly improves its cycle performance by incorporating a positive electrode active material containing dual cations A and B and the same dual-cation salt electrolyte. On one hand, the larger-radius cation A stabilizes the structure of the positive electrode active material, reducing its loss. On the other hand, the A and B dual cations of the dual-cation positive electrode active material can be intercalated into the negative electrode active material through the dual-cation salt electrolyte. The larger-radius cation A acts as a support in the negative electrode active material, thereby reducing the expansion / contraction of the negative electrode active material caused by the smaller-radius ion B during intercalation / deintercalation. This improves the stability of the SEI film (solid electrolyte interphase), reduces active lithium ion consumption, and thus enhances the battery's cycle stability. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0032] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0033] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0034] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0035] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0036] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0037] Explanation of reference numerals in the attached figures:

[0038] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Casing; 52 Electrode assembly; 53 Top cover assembly Detailed Implementation

[0039] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of a secondary battery, a method for preparing a corresponding positive electrode active material, a positive electrode sheet, a battery module, a battery pack, and an electrical device. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0040] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0042] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0043] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0044] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0045] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0046] As the selection of positive electrode active materials becomes increasingly limited, the adjustment of the structure of positive electrode active materials has been increasingly studied by those skilled in the art. Improving the rate performance and cycle performance of materials through coating or doping are currently effective methods; however, existing methods all lead to varying degrees of damage to battery performance, such as reduced specific capacity and deteriorated cycle performance. Therefore, existing coated or doped positive electrode active materials still need improvement. The inventors have discovered that the secondary battery of the first aspect of this application significantly improves its cycle performance by using a positive electrode active material containing cations with larger radii and an electrolyte containing the ionic salt. On the one hand, the larger radii of the cations stabilize the structure of the positive electrode active material, reducing its loss. On the other hand, the larger radii of the cations are embedded in the negative electrode active material through the electrolyte containing the ionic salt, supporting the structure of the negative electrode active material, reducing the loss of active lithium ions, thereby improving the battery's cycle performance.

[0047] Secondary batteries

[0048] In one embodiment of this application, a secondary battery is provided, comprising (1) a positive electrode sheet, which includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and containing a positive electrode active material; (2) an electrolyte; characterized in that the positive electrode active material is an active material containing A and B dual cations having the following chemical formula.

[0049] A x B 1-x MeO2 or A x B 1-x MPO4,

[0050] in

[0051] Me is selected from one or more of the elements Mn, Fe, Ni, Co, V, Cu, and Cr;

[0052] M is selected from one or more of Mn, Fe, Ni, and Co;

[0053] A is K or Na,

[0054] B is either Na or Li;

[0055] The ionic radius of A is larger than that of B, and A and B are of different species;

[0056] x is 0.001-0.05, preferably 0.001-0.025; and

[0057] The electrolyte contains A and B dual-cation electrolyte salts, wherein A and B are defined in the same way as in the positive electrode active material.

[0058] Unbound by any particular theory, this application unexpectedly discovers that the battery of this application, comprising a positive electrode active material containing dual cations A and B and the same dual-cation salt electrolyte, significantly improves its cycle performance. On one hand, the larger-radius cation A stabilizes the structure of the positive electrode active material, reducing its loss. On the other hand, the larger-radius cation A is embedded in the negative electrode active material through the electrolyte containing this ion salt, supporting the structure of the negative electrode active material, reducing active lithium loss, thereby improving the battery's cycle performance.

[0059] In some embodiments, the cations in the dual-cation electrolyte salt are the same as those in the positive electrode active material; and the molar ratio of the two cations in the electrolyte is greater than or equal to the stoichiometric ratio of the two cations in the positive electrode active material. This is more conducive to the stability of the negative electrode active material, thereby improving the cycle stability of the battery.

[0060] In some embodiments, the dicationic electrolyte salt refers to an electrolyte salt used in the electrolyte that contains the same two cations as the positive electrode active material, i.e., a mixture of A and B cation salts.

[0061] In some embodiments, the dual-cation electrolyte salt is selected from at least one inorganic and organic salt of two or more elements selected from lithium, sodium, and potassium. The inorganic salt is selected from at least one of hexafluorophosphate, perchlorate, hexafluoroarsenate, tetrafluoroborate, and difluorophosphate, optionally hexafluorophosphate; the organic salt is selected from at least one of bis(oxalate)borate, oxalate difluoroborate, bis(fluorosulfonyl)imide, and bis(trifluoromethyl)sulfonyl)imide. This makes the electrolyte more conducive to the transport of dual cations and improves the cycle stability of the battery.

[0062] In some embodiments, the chemical formula A x B 1-x The positive electrode active material of MeO2 is selected from chemical formula A x B 1- x NiO2, A x B 1-x MnO2, A x B 1-x CoO2, A x B 1-x Ni y Co z Mn 1-y-z O2, A x B 1-x Ni y Co z Al 1-y-z At least one of the active materials of O2 and their coating and doping products, wherein A, B and x are defined as described above; 0≤z≤1, 0≤y≤1; and may be chemical formula A. x B 1-x Ni y Co z Mn 1-y-z The active material is O2, wherein A, B, and x are defined as described above, y = 0.5, and z = 0.2. This improves the cycle stability of the secondary battery by incorporating the specific positive electrode active material.

[0063] In some embodiments, the chemical formula A x B 1-x The positive electrode active material of MPO4 is selected from chemical formula A x B 1- x FePO4, A x B 1-xAt least one of the active materials of CoPO4 and their coating and doping products, wherein A, B and x are defined as described above; the optional chemical formula is A x B 1-x The active material is FePO4, wherein A, B, and x are defined as described above. This improves the cycle stability of the secondary battery by incorporating the specific positive electrode active material.

[0064] A second aspect of this application also provides a method for preparing the positive electrode active material for a secondary battery as described in the first aspect of this application, comprising the following steps:

[0065] 1) Provide precursors for Me or M transition metals.

[0066] 2) The precursor is mixed evenly with metal salt A and metal salt B, and then ground; the ground powder is then calcined and cooled to room temperature to obtain the positive electrode active material;

[0067] Wherein Me or M, A, B are as defined in the first aspect of this application.

[0068] Therefore, the positive electrode active material required for the battery of the first aspect of this application can be prepared, the structural stability of the positive electrode active material is improved, and thus the cycle stability of the secondary battery is improved.

[0069] In some embodiments, the precursor of the Me or M transition metal may be commercially available or may be prepared according to methods known to those skilled in the art.

[0070] In some embodiments, metal salt A and metal salt B are at least one of carbonates and hydroxides, optionally a carbonate. Thus, the active material of this application can be obtained using metal salts of this type to improve the cycle stability of secondary batteries.

[0071] In some embodiments, the molar ratio of the precursor to metal salt A or metal salt B is 105%-109% of its stoichiometric ratio. This ratio of precursor to metal salt A or metal salt B allows for the acquisition of the active material of this application, thereby improving the cycle stability of the secondary battery.

[0072] In some embodiments, in step 2), the calcination is usually carried out in a high-temperature furnace, first pre-calcining at a low temperature of 300-600°C for 3-7 hours, and then calcining at a high temperature of 700-900°C for 9-15 hours.

[0073] In some embodiments, the secondary battery comprises (1) a negative electrode sheet including a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and containing a negative electrode active material; (2) a positive electrode sheet including a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and containing a positive electrode active material; and (3) an electrolyte; characterized in that the positive electrode active material and the electrolyte have the definitions described above.

[0074] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0075] [Positive electrode tablets]

[0076] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material as described above.

[0077] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0078] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0079] In some embodiments, the positive electrode active material is a positive electrode active material containing A and B dual cations as described above, and the preparation method of the positive electrode active material is as described in the second aspect of this application.

[0080] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0081] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0082] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive electrode active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0083] [Negative electrode plate]

[0084] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0085] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0086] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0087] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. 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, and lithium titanate, optionally artificial graphite or natural graphite. 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, this application is not limited to these materials, and other conventional 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.

[0088] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0089] In some embodiments, the negative electrode film may optionally include a conductive agent. 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.

[0090] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0091] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0092] [Electrolytes]

[0093] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0094] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0095] In some embodiments, the electrolyte salt is the dication electrolyte salt described in the first aspect of this application.

[0096] In some embodiments, the solvent may be selected from at least one of ethylene carbonate (EC), propylene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate, dimethyl carbonate (DMC), dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0097] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0098] [Isolation membrane]

[0099] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0100] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0101] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0102] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0103] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0104] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0105] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0106] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0107] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0108] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0109] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0110] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0111] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0112] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0113] Figure 6This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0114] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0115] Example

[0116] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0117] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0118] I. Preparation of Positive Electrode Active Materials

[0119] Comparative Example 1.1 Single-cation positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O2 preparation

[0120] Commercially available Ni 0.5 Co 0.2 Mn 0.3 The (OH)₂ precursor and lithium carbonate were mixed evenly in a molar ratio of 1:1.07 and ground using an agate mortar. The excess lithium carbonate was used to compensate for lithium loss during high-temperature calcination. The thoroughly ground solid powder was transferred to a crucible and calcined in a muffle furnace with a programmed temperature rise. The calcination program was as follows: pre-calcination at 500℃ for 5 hours from room temperature, followed by calcination at 800℃ for 12 hours, with a heating rate of 3℃ / min. -1 Then, it was cooled to room temperature to obtain LiNi. 0.5 Co 0.2 Mn 0.3 O2 materials.

[0121] Comparative Example 1.2 Preparation of LiFePO4 cathode active material

[0122] Lithium carbonate, ferric nitrate, and ammonium dihydrogen phosphate in a molar ratio of 1:1:1 were added to a nitric acid solution, and a citric acid complexing agent was added to adjust the pH to 3. A carbon source composed of glucose was added, with the carbon source accounting for 25% of the total mass of lithium carbonate, ferric nitrate, and ammonium dihydrogen phosphate. The mixture was stirred and stirred until homogeneous to obtain a mixed solution. The mixed solution underwent an exothermic reaction, and after evaporating the mixed solution to dryness, a precursor was obtained. The precursor was vacuum dried at 150°C for 12 hours and then ball-milled.

[0123] Take 1 kg of the precursor after ball milling and sinter it in an atmosphere furnace under nitrogen protection. The temperature is increased to 500℃ at a rate of 2℃ / min for the first sintering time of 4 hours. Then, the temperature is increased to 700℃ at a rate of 10℃ / min and 200 mL of ethanol-water mixture gas with a mass fraction of 80% is introduced for the second sintering time of 8 hours. After natural cooling, the LiFePO4 material product is collected.

[0124] Example 1.1 Dual-cation positive electrode active material Na 0.003 Li 0.997 Ni 0.5 Co 0.2 Mn 0.3 O2 preparation

[0125] Commercially available Ni 0.5 Co 0.2 Mn 0.3 The (OH)₂ precursor, lithium carbonate, and sodium carbonate were mixed uniformly in a molar ratio of 1:1.06679:0.0032, and then ground. The excess lithium carbonate was added to compensate for lithium loss during high-temperature calcination. The thoroughly ground solid powder was transferred to a crucible and placed in a muffle furnace with a programmed temperature rise. The calcination program was as follows: pre-calcination at 500℃ for 5 hours from room temperature, followed by calcination at 800℃ for 12 hours, with a heating rate of 3℃ / min. -1 Na was then collected after cooling to room temperature. 0.003 Li 0.997 Ni 0.5 Co 0.2 Mn 0.3 O2 materials.

[0126] Example 1.2 Dual-cation positive electrode active material Na 0.015 Li 0.985 Ni 0.5 Co 0.2 Mn 0.3 O2

[0127] Commercially available Ni 0.5 Co 0.2 Mn 0.3The (OH)₂ precursor, lithium carbonate, and sodium carbonate were mixed uniformly in a molar ratio of 1:1.054:0.016, and then ground. The excess lithium carbonate was added to compensate for lithium loss during high-temperature calcination. The thoroughly ground solid powder was transferred to a crucible and placed in a muffle furnace with a programmed temperature rise. The calcination program was as follows: pre-calcination at 500℃ for 5 hours from room temperature, followed by calcination at 800℃ for 12 hours, with a heating rate of 3℃ / min. -1 Na was then collected after cooling to room temperature. 0.0015 Li 0.985 Ni 0.5 Co 0.2 Mn 0.3 O2 materials.

[0128] Example 1.3 Dual-cation positive electrode active material Na 0.025 Li 0.975 Ni 0.5 Co 0.2 Mn 0.3 O2 preparation

[0129] Commercially available Ni 0.5 Co 0.2 Mn 0.3 The (OH)₂ precursor was mixed evenly with lithium carbonate and sodium carbonate in a molar ratio of 1:1.0432:0.0268, and then ground. The excess lithium carbonate was added to compensate for lithium loss during high-temperature calcination. The thoroughly ground solid powder was transferred to a crucible and placed in a muffle furnace with a programmed temperature rise. The calcination program was as follows: pre-calcination at 500℃ for 5 hours from room temperature, followed by calcination at 800℃ for 12 hours, with a heating rate of 3℃ / min. -1 Na was then collected after cooling to room temperature. 0.025 Li 0.975 Ni 0.5 Co 0.2 Mn 0.3 O2 materials.

[0130] Example 1.4 Dual-cation positive electrode active material Na 0.03 Li 0.97 Ni 0.5 Co 0.2 Mn 0.3 O2 preparation

[0131] Commercially available Ni 0.5 Co 0.2 Mn 0.3The (OH)₂ precursor was mixed evenly with lithium carbonate and sodium carbonate in a molar ratio of 1:1.0379:0.0321, and then ground. The excess lithium carbonate was added to compensate for lithium loss during high-temperature calcination. The thoroughly ground solid powder was transferred to a crucible and placed in a muffle furnace with a programmed temperature rise. The calcination program was as follows: pre-calcination at 500℃ for 5 hours from room temperature, followed by calcination at 800℃ for 12 hours, with a heating rate of 3℃ / min. -1 Na was then collected after cooling to room temperature. 0.03 Li 0.97 Ni 0.5 Co 0.2 Mn 0.3 O2 materials.

[0132] Example 1.5 Dual-cation positive electrode active material Na 0.05 Li 0.95 Ni 0.5 Co 0.2 Mn 0.3 O2 preparation

[0133] Commercially available Ni 0.5 Co 0.2 Mn 0.3 The (OH)₂ precursor, lithium carbonate, and sodium carbonate were mixed evenly in a molar ratio of 1:1.0165:0.0535 and ground. The excess lithium carbonate was used to compensate for lithium loss during high-temperature calcination. The thoroughly ground solid powder was transferred to a crucible and calcined in a muffle furnace with a programmed temperature rise. The calcination program was as follows: pre-calcination at 500℃ for 5 hours from room temperature, followed by calcination at 800℃ for 12 hours, with a heating rate of 3℃ / min. -1 Na was then collected after cooling to room temperature. 0.05 Li 0.95 Ni 0.5 Co 0.2 Mn 0.3 O2 materials.

[0134] Example 1.6 Positive electrode active material with dual cations of Li and K K 0.003 Li 0.997 Ni 0.5 Co 0.2 Mn 0.3 O2

[0135] Commercially available Ni 0.5 Co 0.2 Mn 0.3The (OH)₂ precursor, lithium carbonate, and potassium carbonate were mixed uniformly in a molar ratio of 1:1.06679:0.0032, and then ground. The excess lithium carbonate was added to compensate for lithium loss during high-temperature calcination. The thoroughly ground solid powder was transferred to a crucible and placed in a muffle furnace with a programmed temperature rise. The calcination program was as follows: pre-calcination at 500℃ for 5 hours from room temperature, followed by calcination at 800℃ for 12 hours, with a heating rate of 3℃ / min. -1 K was then collected after cooling to room temperature. 0.003 Li 0.997 Ni 0.5 Co 0.2 Mn 0.3 O2 materials.

[0136] Example 1.7 Positive electrode active material of trications K and Na Na 0.0015 K 0.0015 Li 0.997 Ni 0.5 Co 0.2 Mn 0.3 O2

[0137] Commercially available Ni 0.5 Co 0.2 Mn 0.3 The (OH)₂ precursor was mixed with lithium carbonate, sodium carbonate, and potassium carbonate in a molar ratio of 1:1.06679:0.0016:0.0016 until homogeneous, and then ground. Excess lithium carbonate was added to compensate for lithium loss during high-temperature calcination. The thoroughly ground solid powder was transferred to a crucible and placed in a muffle furnace with a programmed temperature rise. The calcination program was as follows: pre-calcination at 500℃ for 5 hours from room temperature, followed by calcination at 800℃ for 12 hours, with a heating rate of 3℃ / min. -1 Na was then collected after cooling to room temperature. 0.0015 K 0.0015 Li 0.997 Ni 0.5 Co 0.2 Mn 0.3 O2 materials.

[0138] Example 1.8 Preparation of Sodium Iron Phosphate-Based Dual-Cation Positive Electrode Active Material Na 0.003 Li 0.997 FePO4

[0139] Lithium carbonate, sodium carbonate, ferric nitrate, and ammonium dihydrogen phosphate in a molar ratio of 0.003:0.997:1:1 were added to a nitric acid solution, and a citric acid complexing agent was added to adjust the pH to 3. A carbon source composed of glucose was added, with the carbon source accounting for 25% of the total mass of lithium carbonate, ferric nitrate, and ammonium dihydrogen phosphate. The mixture was stirred and stirred until homogeneous to obtain a mixed solution. The mixed solution underwent an exothermic reaction, and after evaporating the mixed solution to dryness, a precursor was obtained. The precursor was vacuum dried at 150°C for 12 hours and then ball-milled.

[0140] 1 kg of the ball-milled precursor was sintered in an atmosphere furnace under a nitrogen protective atmosphere at a rate of 2 °C / min to 500 °C for 4 hours. Then, the temperature was increased to 700 °C at a rate of 10 °C / min, and 200 mL of an 80% ethanol-water mixture was introduced for a second sintering process for 8 hours. After natural cooling, Na was collected. 0.003 Li 0.997 FePO4 material finished product.

[0141] Example 1.9 Preparation of sodium-potassium iron phosphate dual-cation positive electrode active material K 0.0015 Na 0.0015 Li 0.997 Lithium carbonate, sodium carbonate, potassium carbonate, ferric nitrate, and ammonium dihydrogen phosphate in a molar ratio of 0.0015:0.0015:0.997:1:1 were added to a nitric acid solution, and citric acid complexing agent was added to adjust the pH to 3. A carbon source composed of glucose was added, with the carbon source accounting for 25% of the total mass of lithium carbonate, ferric nitrate, and ammonium dihydrogen phosphate. The mixture was stirred and stirred until homogeneous to obtain a mixed solution. The mixed solution underwent an exothermic reaction, and the solution was evaporated to dryness to obtain the precursor. The precursor was vacuum dried at 150°C for 12 hours and then ball-milled.

[0142] Take 1 kg of the ball-milled precursor and sinter it in an atmosphere furnace under a nitrogen protective atmosphere at a rate of 2 °C / min to 500 °C for the first time, and sinter for 4 hours. Then, sinter it at a rate of 10 °C / min to 700 °C and introduce 200 mL of 80% ethanol-water mixture gas for the second time, and sinter for 8 hours. After natural cooling, collect K. 0.o015 Na 0.0015 Li 0.997 FePO4 material finished product.

[0143] II. Preparation of Secondary Batteries

[0144] Example 1

[0145] 1. Preparation of positive electrode sheet

[0146] The positive electrode active material, conductive agent acetylene black, and binder PVDF from Example 1.1 were mixed in a weight ratio of 95:4:1. N-methylpyrrolidone solvent was added, and the mixture was thoroughly stirred to obtain a uniform positive electrode slurry. This slurry was then coated onto both surfaces of the positive electrode current collector aluminum foil, with a coating weight per unit area of ​​0.250 g / 1540.25 mm². 2 (Based on weight excluding solvent), then dried and cold-pressed to obtain the positive electrode sheet.

[0147] 2. Electrolyte preparation

[0148] 1M LiPF6 was dissolved in a solution composed of EC:EMC:DMC = 1:1:1.

[0149] 3. Preparation of negative electrode sheet

[0150] Artificial graphite (negative electrode active material), acetylene black (conductive agent), and SBR+CMC (binder) were mixed in a weight ratio of 95:1.5:3.1:0.4. Deionized water was added as a solvent, and the mixture was stirred thoroughly to obtain a uniform negative electrode slurry. This slurry was then coated onto both surfaces of the copper foil used as the negative electrode current collector. The coating weight per unit area of ​​the negative electrode film was 0.140 g / 1540.25 mm². 2 (Based on weight excluding solvent), the negative electrode sheet is obtained after drying and cold pressing.

[0151] 4. Preparation of the separating membrane

[0152] Polyethylene porous membrane is used as the separation membrane.

[0153] 5. Preparation of secondary batteries

[0154] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. They are then wound to obtain a bare battery cell. The bare battery cell is placed in an outer package, electrolyte is injected, and it is sealed to obtain a secondary battery, which is then subjected to performance testing.

[0155] The secondary batteries of Examples 2-11 and Comparative Examples 1-2 are prepared in a similar manner to the secondary battery of Example 1, but the composition of the positive electrode active material and electrolyte is adjusted. The different product parameters are detailed in Table 1.

[0156] II. Battery Performance Testing

[0157] Battery 45°C Cycling Performance Test

[0158] At 45°C, a lithium-ion battery is charged at a constant current of 1C to 4.45V, then charged at a constant voltage of 4.45V until the current is less than 0.05C. The battery is then discharged at a constant current of 1C to 2.8V, yielding the initial discharge capacity C0, which is recorded as the first cycle. This charging and discharging process is repeated, and the number of cycles required for the lithium-ion battery's discharge capacity to decay to 80% of C0 is calculated.

[0159] III. Test Results of Each Embodiment and Comparative Example

[0160] Batteries for each embodiment and comparative example were prepared according to the above method, and various performance parameters were measured. The results are shown in Table 1 below.

[0161] Table 1. Battery composition and cycle performance of each embodiment and comparative example.

[0162]

[0163] Incorporating sodium and potassium ions into the positive electrode active material of lithium-ion batteries improves the cell's cycle performance. The cycle performance initially increases and then decreases with increasing doping concentration, with an optimal sodium doping concentration of 0.025%. Sodium and potassium ion doping enhances the structural stability of the positive electrode active material, thereby improving the battery's cycle performance.

[0164] A comparison of Examples 1, 8, and 9 with Comparative Example 1 shows that positive electrode active materials containing sodium ions, combined with electrolytes containing sodium salts, can significantly improve the cycle performance of secondary batteries. After adding sodium salts to the electrolyte, sodium ions in the positive electrode active material can be intercalated into the graphite layer through the electrolyte, providing support and reducing expansion / contraction caused by lithium ion intercalation / extraction. This reduces SEI degradation, minimizes active lithium loss, and improves battery cycle performance.

[0165] As can be seen from the comparison of Examples 8 and 12 and Comparative Example 1, different electrolyte salts can significantly improve the battery cycle performance.

[0166] In summary, incorporating larger-radius ions into the positive electrode active material, combined with an electrolyte containing that ion salt, significantly improves the battery's cycle performance. On one hand, the larger-radius ions stabilize the cathode's layered structure, reducing material loss. On the other hand, the larger-radius ions embed into the graphite material through the electrolyte containing the ion salt, supporting the graphite's layered structure, reducing active lithium loss, and improving the battery's cycle performance.

[0167] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A secondary battery, comprising (1) a positive electrode sheet, which includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and containing a positive active material; (2) an electrolyte; characterized in that, The positive electrode active material is an active material containing two cations, A and B, having the following chemical formula; A x B 1-x MeO2orA x B 1-x MPO4, in, Me is selected from one or more of the elements Mn, Fe, Ni, Co, V, Cu, and Cr; M is selected from one or more of Mn, Fe, Ni, and Co; A is K or Na, B is either Na or Li; The ionic radius of A is larger than that of B, and A and B are of different species; x is between 0.001 and 0.05; and The electrolyte contains A and B dual-cation electrolyte salts, wherein A and B are defined in the same way as in the positive electrode active material; the molar ratio of the two cations in the electrolyte is greater than or equal to the stoichiometric ratio of the two cations in the positive electrode active material.

2. The secondary battery according to claim 1, characterized in that, The dication electrolyte salt is selected from at least one inorganic and organic salt of two or more elements selected from lithium, sodium, and potassium. The inorganic salt is selected from at least one of hexafluorophosphate, perchlorate, hexafluoroarsenate, tetrafluoroborate, and difluorophosphate. The organic salt is selected from at least one of dioxalate borate, difluorooxalate borate, difluorosulfonamide salt, and ditrifluoromethylsulfonamide salt.

3. The secondary battery according to any one of claims 1-2, characterized in that, The chemical formula A x B 1-x The positive electrode active material of MeO2 is selected from chemical formula A x B 1-x NiO2, A x B 1-x MnO2, A x B 1-x CoO2, A x B 1-x Ni y Co z Mn 1-y-z O2, A x B 1- x Ni y Co z Al 1-y-z At least one of the active materials of O2 and their coating and doping products; wherein A, B and x are as defined in claim 1; 0 ≤ z ≤ 1, 0 ≤ y ≤ 1.

4. The secondary battery according to claim 1, characterized in that, The chemical formula A x B 1-x The positive electrode active material of MPO4 is selected from chemical formula A x B 1-x FePO4, A x B 1-x At least one of the active materials of CoPO4; wherein A, B and x are as defined in claim 1.

5. A method for preparing a positive electrode active material for a secondary battery according to any one of claims 1-4, characterized in that, Includes the following steps: 1) Provide precursors of Me or M transition metals; 2) The precursor is mixed evenly with metal salt A and metal salt B, and then ground; the ground powder is then calcined and cooled to room temperature to obtain the positive electrode active material; Me or M, A, B as defined in any one of claims 1-4.

6. The method according to claim 5, characterized in that, The metal salt A and metal salt B are at least one of carbonates and hydroxides.

7. The method according to claim 5 or 6, characterized in that, The molar ratio of the precursor to metal salt A or metal salt B is 105%-109% of its stoichiometric ratio.

8. A battery module, characterized in that, The secondary battery includes any one of claims 1-7.

9. A battery pack, characterized in that, Includes the battery module as described in claim 8.

10. An electrical device, characterized in that, It includes at least one selected from the secondary battery of any one of claims 1-4, the battery module of claim 8, or the battery pack of claim 9.

Images