A secondary battery, a battery module, a battery pack, and an electric device

Abstract

The present application relates to a secondary battery comprising a positive electrode sheet, a negative electrode sheet and an electrolyte, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material, the positive electrode active material comprising S1) a lithium-containing compound of olivine structure, and S2) a vanadium oxide of general formula j(M2O)·kVOx, wherein M is one or more of alkali metals, 0≤j≤1, 1≤k≤5, 1≤x≤2.5; wherein the difference between the discharge plateau voltage of S1 and S2 is E, wherein 0.2V≤E≤2.8V. The secondary battery has very good low temperature performance under the guarantee of excellent cycle performance and specific capacity, for example, it can maintain good low temperature capacity retention rate even at a higher discharge rate.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and in particular to a secondary battery, battery module, battery pack and power supply device. Background Technology

[0002] In recent years, with the increasingly widespread application of lithium-ion batteries, market demands for them have been continuously rising. While pursuing higher energy density, the research and industrialization of high-rate, low-temperature resistant batteries have attracted increasing attention from the industry. These applications include military uses such as electromagnetic interference devices, electromagnetic railguns, and magnetrons; and civilian applications such as cold-start power supplies for vehicles in low-temperature regions, high-power power tools, and power supplies for communication base stations in extremely cold areas. These applications place even more stringent requirements on low-temperature performance and rate performance. The battery cathode material is a key factor determining the electrochemical performance, safety performance, and energy density of the battery system.

[0003] Phosphoric acid cathode materials with olivine structure (LiMPO4, where M can be one or more of Fe, Co, Zn, Ni, Cu, and Mn) are among the cathode materials currently available for large-scale commercial use. They have high specific capacity and discharge voltage, stable discharge voltage output, low raw material cost, excellent lifespan, and good safety performance, and have been widely used in power batteries and energy storage batteries.

[0004] Tests show that LiMPO4-type cathode materials have very low electronic and ionic conductivity. Taking lithium iron phosphate as an example, the drawback of LiFePO4 is its low electronic and ionic conductivity, which are 10⁻⁶ and 10⁻⁶ respectively. -9 S·cm1 and 10 -10 -10 -15 Lithium iron phosphate (LFP) cathode materials exhibit poor rate performance and low-temperature discharge performance when used as cathode materials in lithium-ion batteries. While coating or doping are effective methods to improve these properties, satisfactory electrochemical performance remains elusive. Therefore, finding suitable low-temperature additives and employing appropriate composite methods is an effective approach to improving LFP cathode materials. Summary of the Invention

[0005] This application is made in view of the above-mentioned problems, and its object is to provide a secondary battery in which the positive electrode film contains the general formula j(M2O)·kVO X The vanadium oxide content enables the secondary battery to maintain excellent low-temperature performance while ensuring excellent cycle performance and specific capacity. For example, it can maintain a good low-temperature capacity retention rate even at high discharge rates.

[0006] A first aspect of this application provides a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes a positive current collector and a positive electrode film disposed on at least one surface of the positive current collector, the positive electrode film comprising a positive electrode active material, the positive electrode active material comprising (S1) a lithium-containing compound with an olivine structure, and (S2) a compound with the general formula j(M2O)·kVO X Vanadium oxide, wherein M is one or more alkali metals, 0≤j≤1, 1≤k≤5, 1≤x≤2.5; wherein the difference between the discharge plateau voltages of S1 and S2 is E, wherein 0.2V≤E≤2.8V.

[0007] Therefore, by including two specific active materials with specific discharge plateau voltages in the positive electrode active material, this application enables the secondary battery to have very good low-temperature performance while ensuring excellent cycle performance. For example, even at high discharge rates, it can maintain a good low-temperature capacity retention rate.

[0008] In any embodiment, in component S2, M is selected from one or both of Li and Na, optionally Li; 0 ≤ j / k ≤ 1, preferably 0.2 ≤ j / k ≤ 0.6. Therefore, vanadium oxide is further preferred, which can increase the content of active lithium or sodium in the low-temperature additive, which is beneficial to improving the capacity of the secondary battery at low temperatures, while maintaining a good low-temperature capacity retention rate.

[0009] In any implementation, S1 is the general formula LiA 1-n*y / 2 M y Compounds of PO4, where 0 ≤ y ≤ 0.1,

[0010] A is selected from at least one of Fe, Co, Ni, Cu, Mn, and Zn.

[0011] n represents the valence state of metal M, where n = +2, +3, +4, or +5.

[0012] M is selected from at least one of Cr, Pb, Ca, Sr, Ti, Mg, V, Nb, and Zr;

[0013] A and M may be the same or different.

[0014] Therefore, by using the above-mentioned lithium phosphate cathode active material in combination with vanadium oxide, the low-temperature performance of the battery is further improved while ensuring its cycle performance.

[0015] In any embodiment, S1 is composed of LiFe. 1-n*y / 2 M y Compounds of PO4, wherein y, M and n are defined as described above;

[0016] S2 includes LiVO3, Li3V2O5, Li4V3O8, LiV3O8, Li2VO3, LiVO2; V2O5, V2O3, V3O4; and the corresponding Na dopant Li of the above components. 0.95 Na 0.05 VO3, Li 2.95 Na 0.05 V2O5, Li 3.95 Na 0.05 V3O8. By using the above-mentioned lithium phosphate cathode active material, combined with vanadium oxide, the low-temperature performance of the battery is further improved, while ensuring its cycle performance.

[0017] In any embodiment, the vanadium content is 1%-5% by weight, based on the weight of the positive electrode active material; the molar ratio of vanadium to lithium in the positive electrode active material is 1:5-20, preferably 1:6-10. Therefore, by controlling the content and relative ratio of lithium and vanadium in the positive electrode active material, the low-temperature performance of the battery can be further improved.

[0018] In any embodiment, the weight ratio of component S1 to component S2 is 3-30:1, preferably 4-10:1. Therefore, by controlling the weight ratio of component S1 to component S2 in the positive electrode active material, the low-temperature performance of the battery can be further improved and the cycle performance of the battery can be guaranteed.

[0019] In any embodiment, the discharge plateau voltage of component S1 is 3.1-4.8V, and the discharge plateau voltage of component S2 is 1.0-3.0V. Therefore, by controlling the discharge plateau voltages of components S1 and S2 in the positive electrode active material, the low-temperature performance of the battery can be further improved, and the cycle performance of the battery can be guaranteed.

[0020] In any embodiment, the S2 component is coated with carbon or a conductive polymer. Therefore, by controlling the composition of the S2 component in the positive electrode active material, the low-temperature performance of the battery can be further improved and the cycle performance of the battery can be guaranteed.

[0021] A second aspect of this application also provides a battery module, including the secondary battery of the first aspect of this application.

[0022] A third aspect of this application provides a battery pack that includes the battery module of the second aspect of this application.

[0023] A fourth aspect of this application provides an electrical device comprising at least one selected from the secondary battery of the first aspect of this application, the battery module of the second aspect of this application, or the battery pack of the third aspect of this application.

[0024] The secondary battery of this application contains lithium-containing compounds and vanadium oxides in its positive electrode active material, and ensures that the difference between the discharge plateau voltages of the two is within a specific range. This allows the secondary battery to have excellent low-temperature performance while ensuring excellent cycle performance. For example, even at high discharge rates, it can maintain a good low-temperature capacity retention rate. Moreover, it allows the battery to better utilize its capacity at low temperatures. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope image of the positive electrode active material according to one embodiment of this application.

[0026] Figure 2 This is an X-ray energy dispersive spectroscopy (EDS) surface scan of the positive electrode active material according to one embodiment of this application.

[0027] Figure 3 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0028] Figure 4 yes Figure 3 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0029] Figure 5 This is a schematic diagram of a battery module according to one embodiment of this application.

[0030] Figure 6 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0031] Figure 7 yes Figure 6 An exploded view of a battery pack according to one embodiment of this application is shown.

[0032] Figure 8 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.

[0033] Explanation of reference numerals in the attached figures:

[0034] 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

[0035] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode active material, its manufacturing method, positive electrode sheet, secondary battery, battery module, battery pack, and electrical device of this application. 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 for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0036] 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.

[0037] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0038] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0039] 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.

[0040] 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.

[0041] 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).

[0042] Phosphoric acid-based cathode materials with an olivine structure (LiMPO4, where M can be one or more of Fe, Co, Zn, Ni, Cu, and Mn) are among the most commercially available cathode materials currently available. They exhibit high specific capacity and discharge voltage, stable discharge voltage output, low raw material cost, excellent lifespan, and good safety performance, leading to their widespread application in power batteries and energy storage batteries.

[0043] Tests show that LiMPO4-type cathode materials have very low electronic and ionic conductivity. Taking lithium iron phosphate as an example, the drawback of LiFePO4 is its low electronic and ionic conductivity, which are 10⁻⁶ and 10⁻⁶ respectively. -9 S·cm1 and 10 -10 -10 -15Lithium iron phosphate (LFP) cathode materials exhibit poor rate performance and low-temperature discharge performance when used as cathode materials in lithium-ion batteries. While coating or doping are effective methods to improve these properties, satisfactory electrochemical performance remains elusive. Finding suitable low-temperature additives and employing appropriate composite methods is an effective approach to improving LFP cathode materials. The applicant's research has found that the secondary battery of the first aspect of this application, by including lithium-containing compounds and vanadium oxides in its cathode active material and ensuring the difference in discharge plateau voltage between them is within a specific range, can achieve excellent low-temperature performance while maintaining good cycle performance and specific capacity. For example, even at high discharge rates, it maintains good low-temperature capacity retention, and the battery exhibits excellent power performance at low SOC.

[0044] Secondary batteries

[0045] A first aspect of this application provides a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes a positive current collector and a positive electrode film disposed on at least one surface of the positive current collector, the positive electrode film comprising a positive electrode active material, the positive electrode active material comprising (S1) a lithium-containing compound with an olivine structure, and (S2) a compound with the general formula j(M2O)·kVO X Vanadium oxide, wherein M is one or more alkali metals, 0≤j≤1, 1≤k≤5, 1≤x≤2.5; wherein the difference between the discharge plateau voltages of S1 and S2 is E, wherein 0.2V≤E≤2.8V.

[0046] Regardless of any particular theory, it is now believed that when a battery discharges to a lower state of charge (SOC), its discharge power decreases sharply, and this phenomenon is more pronounced at low temperatures. Therefore, improving the discharge power of a battery under low SOC conditions is particularly important. This application addresses this issue by including lithium compounds and vanadium oxides in the positive electrode active material, ensuring that the difference in discharge plateau voltage between the two is within a specific range. The battery provides energy output at low temperatures through the reaction of vanadium oxides, while simultaneously increasing the internal temperature of the cell and improving its discharge capacity. This results in a secondary battery that maintains excellent low-temperature performance while ensuring superior cycle performance; for example, it retains good low-temperature capacity even at high discharge rates. Furthermore, it allows the battery to better utilize its capacity at low temperatures.

[0047] In some embodiments, in component S2, M is selected from one or both of Li and Na, optionally Li; 0 ≤ j / k ≤ 1, preferably 0.2 ≤ j / k ≤ 0.6. Therefore, vanadium oxide is further preferred, which is beneficial for improving the capacity performance of the secondary battery at low temperatures while maintaining good low-temperature capacity retention.

[0048] In some implementations, S1 is of the general formula LiA 1-n*y / 2 M y Compounds of PO4, where 0 ≤ y ≤ 0.1,

[0049] A is selected from at least one of Fe, Co, Ni, Cu, Mn, and Zn.

[0050] n represents the valence state of metal M, where n = +2, +3, +4, or +5.

[0051] M is selected from at least one of Cr, Pb, Ca, Sr, Ti, Mg, V, Nb, and Zr;

[0052] A and M may be the same or different.

[0053] Therefore, by using the above-mentioned lithium phosphate cathode active material in combination with vanadium oxide, the low-temperature performance of the battery is further improved while ensuring its cycle performance.

[0054] In some embodiments, the S1 component may be LiFe. 1-n*y / 2 M y Compounds of PO4, wherein y, M, and n are defined as described above, preferably 0 < y ≤ 0.1, and M and n are defined as described above; more preferably LiFePO4, LiFe 1-n*y / 2 M y PO4, preferably LiTi x Fe 1-n*y / 2-2x Mn y PO4, LiTi y Fe 1-n*y / 2 PO4, LiMg x Fe 1-n*y / 2-x Mn y PO4, LiV x Fe 1-n*y / 2-5x / 2 Mn y PO4, where y and n are defined as described above, 0.005 ≤ x ≤ 0.1; the most preferred are LiFePO4 and LiTi. y Fe 1-n*y / 2 PO4, where y and n are defined as described above.

[0055] In some embodiments, S2 is LiVO3, Li3V2O5, Li4V3O8, LiV3O8, Li2VO3, Li3VO4, LiVO2; V2O5, V2O3, V3O4; and the corresponding Na dopant of the above components, such as Li. 3-x Na x VO4, Li 1-x Na x V3O8 and Li 1-x Nax VO3, wherein 0.005 ≤ x ≤ 0.1, is preferably Li3VO4, V2O5, LiV3O8, LiVO3 and its Na dopant Li 0.95 Na 0.05 VO3, Li 2.95 Na 0.05 V2O5, Li 3.95 Na 0.05 V3O8. Since vanadium and oxygen form a wide variety of anions, such as orthovanadate, metavanadate, pyrovanadate, and polyvanadate, the S2 component is not limited to the compounds mentioned above. Therefore, by using the above-mentioned type of lithium phosphate cathode active material, combined with vanadium oxide, the low-temperature performance of the battery is further improved, while ensuring its cycle performance.

[0056] In some embodiments, the vanadium content is 1%-5% by weight, preferably 2%-4% by weight, based on the weight of the positive electrode active material; in the positive electrode active material, the molar ratio of lithium to vanadium is 5-20:1, preferably 6-10:1. Therefore, by controlling the content and relative ratio of lithium and vanadium in the positive electrode active material, the low-temperature performance of the battery can be further improved.

[0057] In some embodiments, the weight ratio of component S1 to component S2 is 3-20:1, preferably 4-10:1. Therefore, by controlling the weight ratio of component S1 to component S2 in the positive electrode active material, the low-temperature performance of the battery can be further improved and the cycle performance of the battery can be guaranteed.

[0058] In some embodiments, the discharge plateau voltage of component S1 is 3.1-4.8V, and the discharge plateau voltage of component S2 is 1.0-3.0V. Therefore, by controlling the discharge plateau voltages of components S1 and S2 in the positive electrode active material, the low-temperature performance of the battery can be further improved and the cycle performance of the battery can be guaranteed. If component S1 or S2 has multiple discharge plateau voltages, then the discharge plateau voltage of S1 or S2 described in this invention is its highest discharge plateau voltage.

[0059] In some embodiments, the S2 component is coated with carbon or a conductive polymer. Therefore, by controlling the composition of the S2 component in the positive electrode active material, the low-temperature performance of the battery can be further improved and the cycle performance of the battery can be guaranteed. In some embodiments, the surface-modified carbon or conductive polymer may be selected from one or more of amorphous carbon, graphene, graphitized carbon layers, polyacetylene, polypyrrole, polythiophene, polyphenylene, polyphenylacetylene, polyaniline, polydopamine, etc.

[0060] In some embodiments, the average volumetric particle size Dv50 of the S1 component is 1-5 μm. The average volumetric particle size Dv50 is the particle size corresponding to a cumulative volume distribution percentage of 50% for the sample, and is determined using a laser particle size analyzer, such as the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0061] In some embodiments, the positive electrode active material can be prepared by methods known in the art, such as physically mixing the S1 component and the S2 component to obtain the positive electrode active material, or coating or doping the S2 component on the surface of the S2 component to obtain the positive electrode active material.

[0062] In some embodiments, when the S2 component is coated or doped on the surface of the S2 component, the positive electrode active material is typically prepared as follows:

[0063] A lithium source, an A-metal source, a phosphorus source, and an M-metal source are mixed in a specific molar ratio to form a mixture. A carbon source and additives are added to the mixture. The mixture is then ground to form a homogeneous slurry. The resulting slurry is spray-dried to obtain a precursor. The precursor is sintered under an inert atmosphere to obtain a carbon-coated S1 component material. The obtained S1 component material is mixed with an optional lithium source and a vanadium metal source in a specific ratio, and a certain amount of carbon source is added. The mixture is then sintered again under an inert atmosphere to obtain the positive electrode active material of this application.

[0064] In the mixture, the lithium source, metal A source, phosphorus source, and metal M are mixed in a molar ratio of Li:A:P:M of 0.95-1:0.95-1:0.95-1:0-0.05.

[0065] The lithium source is one or more of the following: lithium oxide, lithium hydroxide, lithium acetate, lithium carbonate, lithium nitrate, lithium nitrite, lithium phosphate, lithium dihydrogen phosphate, lithium oxalate, lithium chloride, lithium molybdate, and lithium vanadate.

[0066] Metal source A includes iron source, copper source, cobalt source, nickel source, zinc source, and manganese source; preferably iron source and manganese source, such as one or more combinations of ferric phosphate (manganese), ferrous phosphate (manganese), ferrous pyrophosphate (manganese), ferrous carbonate (manganese), ferrous chloride (manganese), ferrous hydroxide (manganese), ferrous nitrate (manganese), ferrous oxalate (manganese), ferric chloride (manganese), ferric hydroxide (manganese), ferric nitrate (manganese), ferric citrate (manganese), and ferric oxide (manganese).

[0067] The phosphorus source is one or more of the following: phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, iron phosphate, and lithium dihydrogen phosphate.

[0068] M metal sources also include one or more combinations of compounds of copper, vanadium, magnesium, aluminum, zinc, manganese, titanium, zirconium, niobium, chromium, and rare earth element compounds.

[0069] The carbon source is one or more of the following: citric acid, malic acid, tartaric acid, oxalic acid, salicylic acid, succinic acid, glycine, ethylenediaminetetraacetic acid, sucrose, and glucose.

[0070] The solvent is one or more of the following: water, methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, n-pentanol, n-hexanol, n-heptanol, acetone, butanone, diacetone, pentanone, cyclopentanone, hexanone, cyclohexanone, and cycloheptanone.

[0071] The additives are one or more of the following: polyvinyl alcohol, polyethylene glycol, polyethylene oxide, sodium polystyrene sulfonate, polyoxyethylene nonylphenyl ether, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, and octadecyltrimethylammonium bromide.

[0072] The vanadium source is one or more of vanadium pentoxide, vanadium dioxide, vanadium metal powder, vanadium chloride, and ammonium metavanadate.

[0073] In addition, the secondary battery of this application will be described below with appropriate reference to the accompanying drawings.

[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 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 plate]

[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 of the first aspect of this application. Figure 1 A cross-sectional SEM image of an electrode containing the positive electrode active material of the present invention is shown. Figure 2 An EDS surface scan of an electrode containing the positive electrode active material of the present invention is shown to characterize the distribution of phosphorus, vanadium and oxygen elements.

[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 may also comprise other positive electrode active materials known in the art for use in batteries. As an example, other positive electrode active materials may include at least one of the following: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. In addition to these materials, other conventional materials that can be used as positive electrode active materials for batteries may also be used. These other positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. The positive electrode active material accounts for 80-100% by weight in the positive electrode film, based on the total weight of the positive electrode film.

[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), a terpolymer of PVDF-tetrafluoroethylene-propylene, a terpolymer of PVDF-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorinated acrylate resin. The binder constitutes 0-20% by weight of the positive electrode film layer, based on the total weight of the positive electrode film layer.

[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. The conductive agent accounts for 0-20% by weight of the positive electrode film, based on the total weight of the positive electrode film.

[0082] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, wherein the solid content of the positive electrode slurry is 40-80 wt%, and the viscosity at room temperature is adjusted to 5000-25000 mPa·s. The positive electrode slurry is coated on the surface of the positive electrode current collector, dried, and then cold-pressed using a cold rolling mill to form the positive electrode sheet; the areal density of the positive electrode powder coating is 150-350 mg / m³. 2 The compaction density of the positive electrode sheet is 1-5 g / cm³, preferably 2.0-2.6 g / cm³. 3 .

[0083] [Negative electrode plate]

[0084] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative 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, 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, 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. The weight percentage of the negative electrode active material in the negative electrode film layer is 80-100% by weight, based on the total weight of the negative electrode film layer.

[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). The binder accounts for 0-20% by weight of the negative electrode film layer, based on the total weight of the negative electrode film layer.

[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. The conductive agent accounts for 0-20% by weight of the negative electrode film, based on the total weight of the negative electrode film.

[0090] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)). The other additives constitute 0-15% by weight of the negative electrode film, based on the total weight of the negative electrode film.

[0091] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30-70 wt%, and the viscosity at room temperature is adjusted to 2000-10000 mPa·s; the obtained negative electrode slurry is coated onto a negative electrode current collector, and after a drying process, it is cold-pressed, for example, by rollers, to obtain the negative electrode sheet. The areal density of the negative electrode powder coating is 75-220 mg / m², and the compacted density of the negative electrode sheet is 1.2-2.0 g / m². 3 .

[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 may be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP). The concentration of the electrolyte salt is typically 0.5-5 mol / L.

[0096] In some embodiments, the solvent may be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[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 embodiments, the thickness of the separator is 6-40 μm, optionally 12-20 μm.

[0102] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0103] 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.

[0104] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. 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.

[0105] 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 3 This is an example of a square-structured secondary battery 5.

[0106] In some implementations, refer to Figure 4The 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.

[0107] 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.

[0108] Figure 5 This is battery module 4, used as an example. (See reference...) Figure 5 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.

[0109] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0110] 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.

[0111] Figure 6 and Figure 7 This is battery pack 1 as an example. (See reference...) Figure 6 and Figure 7 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.

[0112] 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.

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

[0114] Figure 8 This 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.

[0115] 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.

[0116] Example

[0117] 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.

[0118] 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.

[0119] I. Preparation Examples

[0120] Preparation Example 1

[0121] (1) At room temperature, lithium carbonate, ferrous oxalate, ammonium dihydrogen phosphate, and titanium dioxide were mixed in a molar ratio of 1:2:2:0.01 to form a mixture. Glucose and PEG, along with citric acid surfactant, were added to the mixture in a weight ratio of 3:1:0.3, wherein glucose accounted for 10% of the total raw material weight and citric acid accounted for 1% of the total raw material weight. 1000 mL of water was added as a dispersion medium. The mixture was then ground in a sand mill at 1000 rpm for 4 hours to form a homogeneous slurry with a solid content of 40%. The obtained slurry was spray-dried using a spray drying device to obtain the precursor of component S1.

[0122] (2) The S1 component precursor was sintered under an inert nitrogen atmosphere (oxygen atmosphere controlled below 20 ppm) with a heating rate of 10 °C / min, uniformly heated to 760 °C, held for 10 h, and then cooled by purging with cold nitrogen for 5 h until the material surface temperature reached 40 °C. The sintered material was then subjected to air jet milling to obtain the S1 component, whose molecular formula is LiTi. 0.005 Fe 0.99 PO4 has an average volumetric particle size (Dv50) of 1.5 μm.

[0123] (3) Further mix the S1 component material with lithium carbonate, ammonium metavanadate and carbon source glucose, wherein, based on the total weight of the mixture, the weight ratio of S1 component is 80%, the weight ratio of lithium carbonate and ammonium metavanadate is 15%, and the weight ratio of carbon source glucose is 5%; wherein the molar ratio of lithium carbonate and ammonium metavanadate is 1.5:1.

[0124] (4) The mixture was ball-milled for 2 hours. Then, the mixture was sintered under nitrogen protection, with a heating rate of 10℃ / min, uniformly heated to 560℃, held for 10 hours, and then cooled by purging with cold nitrogen for 5 hours until the material surface temperature reached 40℃. The entire sintering process was carried out under nitrogen atmosphere protection, with the oxygen concentration controlled below 20 ppm. The final product was a 1.5Li₂O·VO₄ coating. 2.5 The positive electrode active material of the present invention has an average volume particle size Dv50 of 1.8 μm.

[0125] Preparation Examples 2-12

[0126] The preparation method of its positive electrode active material is similar to that of the positive electrode active material in Example 1, but the composition of the raw materials and the product parameters are adjusted. The different product parameters are detailed in Table 1.

[0127] Preparation Example 13

[0128] The S1 component was prepared using steps (1) and (2) of the method for preparing the positive electrode active material of Example 1;

[0129] Lithium carbonate, ammonium metavanadate, and glucose as a carbon source were mixed, wherein, based on the total weight of the mixture, the weight ratio of lithium carbonate to ammonium metavanadate was 75%, and the weight ratio of glucose as a carbon source was 25%; the molar ratio of lithium carbonate to ammonium metavanadate was 1.5:1. The mixture was ball-milled for 2 hours. Then, the mixture was sintered under nitrogen protection, with a heating rate of 10°C / min, uniformly heated to 560°C, held at that temperature for 10 hours, and then cooled by purging with cold nitrogen for 5 hours until the surface temperature of the material reached 40°C, obtaining component S2. The entire sintering process was carried out under a nitrogen atmosphere, with the oxygen concentration controlled below 20 ppm. Component S1 and component S2 were physically mixed at a weight ratio of 8:1 to obtain the positive electrode active material of this invention. Different product parameters are detailed in Table 1.

[0130] Preparation of Comparative Example 1

[0131] By performing only steps (1) and (2) of Preparation Example 1, the S1 component was obtained and used as the positive electrode active material. See Table 1 for details of the different product parameters.

[0132] Table 1. Composition and related parameters of the positive electrode active materials obtained in each preparation example and comparative example.

[0133]

[0134] II. Application Examples

[0135] Example 1

[0136] 1) Preparation of positive electrode sheet

[0137] The positive electrode active material powder, conductive agent, and binder prepared in Example 1 were dry-mixed in a weight ratio of 96:2:2, and NMP solvent was added. The mixture was vigorously stirred under vacuum until a uniform positive electrode slurry was formed. The slurry had a solid content of 60 wt% and its viscosity was adjusted to 8000 mPa·s at room temperature. The positive electrode slurry was coated onto the surface of the positive electrode current collector aluminum foil, dried, and then cold-pressed using a cold rolling mill to form the positive electrode sheet. The surface density of the positive electrode powder coating was controlled to 200 mg / m². 2 The compaction density of the positive electrode sheet is shown in Table 1.

[0138] 2) Preparation of negative electrode sheet

[0139] Graphite (negative electrode active material), sodium carboxymethyl cellulose (CMC-Na) thickener, styrene-butadiene rubber (SBR) binder, and carbon black conductive agent were mixed in a mass ratio of 97:1:1:1. Deionized water was added, and the mixture was stirred until homogeneous to obtain a negative electrode slurry. The slurry had a solid content of 50 wt% and its viscosity was adjusted to 4000 mPa·s at room temperature. The obtained negative electrode slurry was coated onto copper foil, dried, and then rolled to obtain the negative electrode sheet. The areal density of the negative electrode powder coating was controlled to 145 mg / m². 2 The compaction density of the negative electrode sheet is 1.35 g / m³. 3 .

[0140] 3) Separating membrane

[0141] A polyethylene film with a thickness of 0.012 mm was used as the separator.

[0142] 4) Preparation of electrolyte

[0143] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0144] 5) Battery manufacturing

[0145] The positive electrode, separator, and negative electrode prepared above are stacked in sequence, with the separator acting as a separator between the positive and negative electrode sheets. Then, they are wound to obtain a bare cell with a capacity of 3Ah. The bare cell is placed in an outer packaging shell, dried, and then injected with 10g of electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0146] The secondary batteries in Examples 2-13 and Comparative Example 1 were prepared using methods similar to those in Example 1, but the positive electrode active materials obtained in the corresponding preparation examples were used.

[0147] III. Battery Performance Testing

[0148] 1. Low-temperature performance test at -20℃

[0149] At 25℃, the battery is first charged to 3.65V with a constant current of 0.5C, then further charged to 0.025C with a constant voltage of 3.65V. After resting for 2 hours, the battery is discharged to 2.0V with a constant current of 1C. The discharge capacity is recorded as C0. Then, the battery is rested at 25℃ for 2 hours, and the process of charging the battery to 3.65V with a constant current of 0.5C and then charging it with a constant current to 0.025C is repeated. The battery is then placed at -20℃ for 2 hours, and then discharged to 2.0V with a constant current of 1C. The discharge capacity is recorded as D1. Then, the battery is rested at 25℃ for 2 hours, and the process of charging the battery to 3.65V with a constant current of 0.5C and then charging it with a constant current to 0.025C is repeated. The battery is then placed at -20℃ for 2 hours, and then discharged to 2.0V with a constant current of 3C. The discharge capacity is recorded as D3. Calculate the capacity retention rates D1 / D0 and D3 / D0 of the battery cell at -20℃ and discharged at 1C and 3C rates, respectively.

[0150] 2. Cyclic performance test

[0151] At 25℃, 1. First, charge the battery to 3.65V with a constant current of 0.5C; 2. Further charge it to 0.025C with a constant voltage of 3.65V, and record this as the first charge capacity; 3. Let it stand for 2 hours; 4. Then discharge the battery to 2.0V with a constant current of 1C, and record this as the first discharge capacity; 5. Then let it stand at 25℃ for 2 hours, and repeat steps 1-4, recording the charge capacity and discharge capacity in each cycle; the capacity retention rate of the battery in the nth cycle is obtained by dividing the discharge capacity of the 500th cycle by the discharge capacity of the first cycle.

[0152] 3. Testing of 0.5C discharge capacity (specific capacity)

[0153] At 25℃, the battery was first charged to 3.65V at a constant current of 0.5C, then further charged to 0.025C at a constant voltage of 3.65V. After resting for 2 hours, the battery was discharged to 2.0V at a constant current of 0.5C. The discharge capacity is denoted as C. 放 Capacity c = C 放 / The quality of the cathode material.

[0154] IV. Test Results of Each Embodiment and Comparative Example

[0155] 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 2 below.

[0156] Table 2 shows the battery performance of each embodiment and comparative example.

[0157]

[0158]

[0159] From Examples 1-7, through LiTi 0.005 Fe 0.99 PO4 surface is coated with 1.5Li2O·VO 2.5 The coating layer can improve the low-temperature performance of the hybrid cathode material, with significantly higher performance than Comparative Example 1. On the other hand, with the increase of the lithium vanadium oxide ratio, the cycle life of the cell decreases. This is mainly because lithium vanadium oxide involves multiple valence state changes of vanadium during delithiation and lithium insertion, resulting in a higher structural decay rate than lithium iron phosphate materials. Further data analysis shows that when 1.5Li₂O·VO₄... 2.5 When the content is appropriate, the mixed cathode material has the best low-temperature discharge performance; it can be seen that the battery has the best overall performance under the conditions of Example 3.

[0160] Meanwhile, lithium vanadium oxide can act as a lithium replenishment agent in the positive electrode, which significantly improves the specific capacity of the battery. Furthermore, in Example 12, 1.5Li₂O·VO₄ 2.5 Na ion doping was performed on the compound components to obtain 1.45Li₂O·0.05Na₂O·VO₄ 2.5 This can further improve the overall performance of the battery. This is because Na and Li are elements in the same group. The radius of Na ions (0.1 nm) is larger than that of Li ions (0.7 nm). Appropriate substitution of Li+ by Na+ can widen the interlayer spacing of the material, providing more space for lithium ions to diffuse in the bulk phase of the material, reducing diffusion resistance, and improving the rate performance and low-temperature performance of the material.

[0161] Examples 8-11 use 0.5Li₂O·₃VO 2.5 Compared to Examples 1-7, the low-temperature additive has a relatively low j value, thus reducing the specific capacity of the battery. However, the improvement in low-temperature performance is correspondingly increased. This is because the increased proportion of vanadium oxides in lithium vanadium oxide reduces resistance during lithium-ion transport, significantly improving low-temperature performance. In Examples 8-11, with the addition of 0.5Li₂O·₃VO₄... 2.5 The increase in the amount of low-temperature additives followed a similar pattern to that observed in Examples 1-7.

[0162] Compared to Example 3, Example 12 changed the mixing method of the low-temperature additive and the main material, adopting a simple physical mixing method, that is, S1 and S2 were synthesized separately, and then S1 and S2, together with other additives in the positive electrode formulation, were used to prepare the positive electrode sheet. Test results showed that Example 12 also exhibited a good improvement in low-temperature performance.

[0163] 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 a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode comprises a positive current collector and a positive electrode film disposed on at least one surface of the positive current collector, the positive electrode film comprising a positive electrode active material, the positive electrode active material comprising S1) a lithium-containing compound with an olivine structure, and S2) a compound with the general formula j(M2O)·kVO X Vanadium oxide, wherein M is one or more alkali metals, 0≤j≤1, 1≤k≤5, 1≤x≤2.5; wherein the difference between the discharge plateau voltages of S1 and S2 is E, wherein 0.2V≤E≤2.8V; The average volumetric particle size Dv50 of the S1 component is 1μm-5μm.

2. The secondary battery according to claim 1, characterized in that, In component S2, M is selected from one or both of Li and Na.

3. The secondary battery according to claim 1 or 2, characterized in that, In component S2, M is Li.

4. The secondary battery according to any one of claims 1-3, characterized in that, 0≤j / k≤1.

5. The secondary battery according to any one of claims 1-3, characterized in that, 0.2≤j / k≤0.

6.

6. The secondary battery according to any one of claims 1-5, characterized in that, S1 is a general formula LiA 1-n*y / 2 M y Compounds of PO4, where 0 ≤ y ≤ 0.1, A is selected from at least one of Fe, Co, Ni, Cu, Mn, and Zn. n represents the valence state of metal M, where n = +2, +3, +4, or +5. M is selected from at least one of Cr, Pb, Ca, Sr, Ti, Mg, V, Nb, and Zr; A and M may be the same or different.

7. The secondary battery according to any one of claims 1-6, characterized in that, S1 component is LiFe 1-n*y / 2 M y Compounds of PO4, wherein n, y, and M are as defined in claim 6; S2 includes LiVO3, Li3V2O5, Li4V3O8, LiV3O8, Li2VO3, LiVO2; V2O5, V2O3, V3O4; and the corresponding Na dopant Li of the above components. 0.95 Na 0.05 VO3, Li 2.95 Na 0.05 V2O5, Li 3.95 Na 0.05 V3O8.

8. The secondary battery according to any one of claims 1-7, characterized in that, The vanadium content is 1%-5% by weight, based on the weight of the positive electrode active material; in the positive electrode active material, the molar ratio of vanadium to lithium is 1:(5-20).

9. The secondary battery according to claim 8, characterized in that, In the positive electrode active material, the molar ratio of vanadium to lithium is 1:(6-10).

10. The secondary battery according to any one of claims 1-9, characterized in that, The weight ratio of component S1 to component S2 is (3-20):

1.

11. The secondary battery according to claim 10, characterized in that, The weight ratio of component S1 to component S2 is (4-10):

1.

12. The secondary battery according to any one of claims 1-11, characterized in that, The discharge plateau voltage of component S1 is 3.1-4.8V, and the discharge plateau voltage of component S2 is 1.0-3.0V.

13. The secondary battery according to any one of claims 1-12, characterized in that, The S2 component is coated with carbon or a conductive polymer.

14. A battery module, characterized in that, The secondary battery includes any one of claims 1-13.

15. A battery pack, characterized in that, Includes the battery module as described in claim 14.

16. An electrical appliance, characterized in that, It includes at least one selected from the secondary battery of any one of claims 1-13, the battery module of claim 14, or the battery pack of claim 15.

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