WO2024000101A1 - 一种二次电池、电池模块、电池包和用电装置 - Google Patents

一种二次电池、电池模块、电池包和用电装置 Download PDF

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WO2024000101A1
WO2024000101A1 PCT/CN2022/101487 CN2022101487W WO2024000101A1 WO 2024000101 A1 WO2024000101 A1 WO 2024000101A1 CN 2022101487 W CN2022101487 W CN 2022101487W WO 2024000101 A1 WO2024000101 A1 WO 2024000101A1
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positive electrode
battery
secondary battery
lithium
active material
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PCT/CN2022/101487
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English (en)
French (fr)
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别常峰
朱畅
刘宏宇
董苗苗
欧阳少聪
倪欢
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/101487 priority Critical patent/WO2024000101A1/zh
Priority to CN202280064878.4A priority patent/CN118043995A/zh
Publication of WO2024000101A1 publication Critical patent/WO2024000101A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of lithium batteries, and in particular to a secondary battery, a battery module, a battery pack and an electrical device.
  • the phosphate-based cathode material with an olivine structure (LiMPO 4 , where M can be one or a combination of two or more of Fe, Co, Zn, Ni, Cu, Mn) is one of the currently commercialized cathode materials on a large scale. , has high gram capacity and discharge voltage, and its discharge voltage output is stable, the cost of synthetic raw materials is low, the life is excellent, and the safety performance is good. It has been widely used in power batteries and energy storage batteries.
  • LiMPO 4 cathode material has very low electronic conductivity and ion conductivity.
  • the disadvantage of LiFePO 4 is that the electronic conductivity and ion conductivity are low, respectively 10 - 9 S ⁇ cm1 and 10 -10 -10 -15 cm2 ⁇ s1, used as cathode materials in lithium-ion batteries, show poor rate performance and low temperature discharge performance. Improving the rate performance and low-temperature performance of materials through coating or doping is currently a relatively effective method, but the electrochemical performance still fails to achieve satisfactory results. Finding suitable low-temperature additives and adopting appropriate compounding methods is an effective way to improve lithium iron phosphate cathode materials.
  • This application was made in view of the above problems, and its purpose is to provide a secondary battery whose positive electrode film layer contains vanadium oxide with the general formula j(M 2 O) ⁇ kVO X , so that the secondary battery can Guarantee excellent cycle performance and very good low-temperature performance under gram capacity, such as maintaining good low-temperature capacity retention even at higher discharge rates.
  • a first aspect of the present application provides a secondary battery, which includes a positive electrode sheet, a negative electrode sheet and an electrolyte, wherein the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material
  • the positive electrode active material includes S1) a lithium-containing compound with an olivine structure, and S2) a vanadium oxide with the general formula j(M 2 O) ⁇ kVO X , where M is One or more alkali metals, 0 ⁇ j ⁇ 1, 1 ⁇ k ⁇ 5, 1 ⁇ x ⁇ 2.5; where the difference between the discharge platform voltages of S1 and S2 is E, where 0.2V ⁇ E ⁇ 2.8V .
  • this application includes two specific active materials with specific discharge plateau voltages in the positive electrode active material, so that the secondary battery has very good low-temperature performance while ensuring excellent cycle performance, for example, even at higher discharge Even under high magnification, it can also maintain good low-temperature capacity retention rate.
  • M is one or two selected from Li or Na, optionally Li; 0 ⁇ j/k ⁇ 1, preferably 0.2 ⁇ j/k ⁇ 0.6. Therefore, vanadium oxide is further preferred, which can increase the active lithium or sodium content in low-temperature additives, which is beneficial to improving the capacity of secondary batteries at low temperatures while maintaining good low-temperature capacity retention.
  • S1 is a compound of the formula LiA 1-n*y/2 MyPO 4 , where 0 ⁇ y ⁇ 0.1,
  • A is selected from at least one of Fe, Co, Ni, Cu, Mn, and Zn,
  • M is selected from at least one of Cr, Pb, Ca, Sr, Ti, Mg, V, Nb, and Zr;
  • a and M are the same or different.
  • lithium phosphate cathode active material combined with vanadium oxide, further improves the low-temperature performance of the battery while ensuring its cycle performance.
  • the S1 component is a compound of LiFe 1-n*y/2 My PO 4 , where y, M and n are as defined above;
  • S2 includes LiVO 3 , Li 3 V 2 O 5 , Li 4 V 3 O 8 , LiV 3 O 8 , Li 2 VO 3 , LiVO 2 ; V 2 O 5 , V 2 O 3 , V 3 O 4 ; and the above group Divide the corresponding Na dopants Li 0.95 Na 0.05 VO 3 , Li 2.95 Na 0.05 V 2 O 5 , Li 3.95 Na 0.05 V 3 O 8 .
  • the content of vanadium element is 1%-5% by weight, based on the weight of the cathode active material; in the cathode active material, the molar ratio of vanadium element to lithium element is 1:5-20, Preferably it is 1:6-10.
  • the low-temperature performance of the battery can be further improved.
  • the weight ratio of the S1 component to the S2 component is 3-30:1, preferably 4-10:1. Therefore, by controlling the weight ratio of the S1 component to the S2 component in the cathode active material, the low-temperature performance of the battery can be further improved and the cycle performance of the battery can be ensured.
  • the discharge plateau voltage of the S1 component is 3.1-4.8V
  • the discharge plateau voltage of the S2 component is 1.0-3.0V. Therefore, by controlling the discharge plateau voltage of the S1 component and the S2 component in the cathode active material, the low-temperature performance of the battery can be further improved and the cycle performance of the battery can be ensured.
  • the S2 component is carbon coated or conductive polymer coated. Therefore, by controlling the composition of the S2 component in the cathode active material, the low-temperature performance of the battery can be further improved and the cycle performance of the battery can be ensured.
  • a second aspect of the present application also provides a battery module, including the secondary battery of the first aspect of the present application.
  • a third aspect of the present application provides a battery pack, including the battery module of the second aspect of the present application.
  • a fourth aspect of the present application provides an electrical device, including at least one selected from the secondary battery of the first aspect of the present application, the battery module of the second aspect of the present application, or the battery pack of the third aspect of the present application. kind.
  • the secondary battery of the present application contains a lithium-containing compound and a vanadium oxide in its cathode active material, and ensures that the difference in discharge platform voltage between the two is within a specific range, so that the secondary battery can ensure excellent performance. It has very good low-temperature performance under the cycle performance. For example, it can maintain a good low-temperature capacity retention rate even at a higher discharge rate; and allows the battery to better exert its capacity at low temperatures.
  • FIG. 1 is a scanning electron microscope image of a cathode active material according to an embodiment of the present application.
  • FIG. 2 is an X-ray energy spectrometer (EDS) surface scan of the cathode active material according to an embodiment of the present application.
  • EDS X-ray energy spectrometer
  • FIG. 3 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 4 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 3 .
  • FIG. 5 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 6 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 7 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 6 .
  • FIG. 8 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 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.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • 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).
  • the phosphate-based cathode material with an olivine structure (LiMPO 4 , where M can be one or a combination of two or more of Fe, Co, Zn, Ni, Cu, Mn) is one of the currently commercialized cathode materials on a large scale. , with higher gram capacity play and discharge voltage. Moreover, the discharge voltage output is stable, the cost of synthetic raw materials is low, the life is excellent, and the safety performance is good. It has been widely used in power batteries and energy storage batteries.
  • LiMPO 4 cathode material has very low electronic conductivity and ion conductivity.
  • the disadvantage of LiFePO 4 is that the electronic conductivity and ion conductivity are low, respectively 10 - 9 S ⁇ cm1 and 10 -10 -10 -15 cm2 ⁇ s1, used as cathode materials in lithium-ion batteries, show poor rate performance and low temperature discharge performance. Improving the rate performance and low-temperature performance of materials through coating or doping is currently a relatively effective method, but the electrochemical performance still fails to achieve satisfactory results. Finding suitable low-temperature additives and adopting appropriate compounding methods is an effective way to improve lithium iron phosphate cathode materials.
  • the secondary battery of the first aspect of the present application can achieve the desired result by including a lithium-containing compound and a vanadium oxide in its positive active material and ensuring that the difference in discharge platform voltage between the two is within a specific range.
  • the above-mentioned secondary battery has very good low-temperature performance while ensuring excellent cycle performance and gram capacity. For example, even at higher discharge rates, it can maintain a good low-temperature capacity retention rate and the battery under low SOC exhibits excellent Power performance.
  • a first aspect of the present application provides a secondary battery, which includes a positive electrode sheet, a negative electrode sheet and an electrolyte, wherein the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material
  • the positive electrode active material includes S1) a lithium-containing compound with an olivine structure, and S2) a vanadium oxide with the general formula j(M 2 O) ⁇ kVO X , where M is One or more alkali metals, 0 ⁇ j ⁇ 1, 1 ⁇ k ⁇ 5, 1 ⁇ x ⁇ 2.5; where the difference between the discharge platform voltages of S1 and S2 is E, where 0.2V ⁇ E ⁇ 2.8V .
  • M is one or two selected from Li or Na, optionally Li; 0 ⁇ j/k ⁇ 1, preferably 0.2 ⁇ j/k ⁇ 0.6. Therefore, vanadium oxide is further preferred, which is beneficial to improving the capacity of secondary batteries at low temperatures while maintaining good low-temperature capacity retention.
  • S1 is a compound of the general formula LiA 1-n*y/2 MyPO 4 , where 0 ⁇ y ⁇ 0.1,
  • A is selected from at least one of Fe, Co, Ni, Cu, Mn, and Zn,
  • M is selected from at least one of Cr, Pb, Ca, Sr, Ti, Mg, V, Nb, and Zr;
  • a and M are the same or different.
  • lithium phosphate cathode active material combined with vanadium oxide, further improves the low-temperature performance of the battery while ensuring its cycle performance.
  • the S1 component may be a compound of LiFe 1-n*y/2 My PO 4 , where y, M, and n are as defined above, preferably 0 ⁇ y ⁇ 0.1, and M and n are as above The above definition; further preferably LiFePO 4 , LiFe 1-n*y/2 My PO 4 , more preferably LiTix Fe 1-n*y/2-2x Mny PO 4 , LiTi y Fe 1-n*y/ 2 PO 4 , LiMg x Fe 1-n*y/2-x Mn y PO 4 , LiV x Fe 1- n*y/2-5x/2 Mn y PO 4 , where y and n are as defined above, 0.005 ⁇ x ⁇ 0.1; most preferred are LiFePO 4 and LiTi y Fe 1- n*y/2 PO 4 , where y and n are defined as above.
  • S2 is LiVO 3 , Li 3 V 2 O 5 , Li 4 V 3 O 8 , LiV 3 O 8 , Li 2 VO 3 , Li 3 VO 4, LiVO 2 ; V 2 O 5 , V 2 O 3 , V 3 O 4 ; and Na dopants corresponding to the above components such as Li 3-x Na x VO 4 , Li 1-x Na x V 3 O 8 and Li 1-x Na x VO 3 where 0.005 ⁇ x ⁇ 0.1, preferably Li 3 VO 4 , V 2 O 5 , LiV 3 O 8 , LiVO 3 and its Na dopant Li 0.95 Na 0.05 VO 3 , Li 2.95 Na 0.05 V 2 O 5 , Li 3.95 Na 0.05 V 3 O 8 .
  • the S2 component is not limited to the above compounds.
  • the content of vanadium element is 1% to 5% by weight, preferably 2% to 4% by weight, based on the weight of the cathode active material; in the cathode active material, the ratio between lithium element and vanadium element is The molar ratio is 5-20:1, preferably 6-10:1. Therefore, by controlling the content and relative proportions of lithium and vanadium in the cathode active material, the low-temperature performance of the battery can be further improved.
  • the weight ratio of the S1 component to the S2 component is 3-20:1, preferably 4-10:1. Therefore, by controlling the weight ratio of the S1 component to the S2 component in the cathode active material, the low-temperature performance of the battery can be further improved and the cycle performance of the battery can be ensured.
  • the discharge plateau voltage of the S1 component is 3.1-4.8V
  • the discharge plateau voltage of the S2 component is 1.0-3.0V. Therefore, by controlling the discharge plateau voltage of the S1 component and the S2 component in the cathode active material, the low-temperature performance of the battery can be further improved and the cycle performance of the battery can be ensured. If the S1 or S2 component has multiple discharge plateau voltages, the discharge plateau voltage of S1 or S2 described in the present invention is the highest discharge plateau voltage.
  • the S2 component is carbon coated or conductive polymer coated. Therefore, by controlling the composition of the S2 component in the cathode active material, the low-temperature performance of the battery can be further improved and the cycle performance of the battery can be ensured.
  • the surface-modified carbon or conductive polymer can be selected from the group consisting of amorphous carbon, graphene, graphitized carbon layers, polyacetylene, polypyrrole, polythiophene, polyphenylene, polyphenylene, poly One or more of aniline, polydopamine, etc.
  • the S1 component has an average volume particle size Dv50 of 1-5um.
  • the average volume particle size Dv50 is the particle size corresponding to when the cumulative volume distribution percentage of the sample reaches 50%, and is measured using a laser particle size analyzer, such as the Mastersizer 3000 laser particle size analyzer of Malvern Instruments Co., Ltd. in the UK.
  • the cathode active material can be prepared by methods known in the art.
  • the S1 component and the S2 component are physically mixed to obtain the cathode active material, or the surface of the S2 component is coated or doped with S2.
  • the components obtain the positive active material.
  • the cathode active material is usually prepared as follows:
  • the material is spray-dried to obtain the precursor.
  • the precursor is sintered in 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 metallic vanadium source in a certain proportion, and a certain amount of carbon source is further supplemented.
  • the cathode active material of the present application is obtained.
  • the lithium source, A metal source, phosphorus source, and M metal are mixed in a molar ratio Li:A:P:M of 0.95-1:0.95-1:0.95-1:0-0.05.
  • the lithium source is one of lithium oxide, lithium hydroxide, lithium acetate, lithium carbonate, lithium nitrate, lithium nitrite, lithium phosphate, lithium dihydrogen phosphate, lithium oxalate, lithium chloride, lithium molybdate, lithium vanadate, or Various combinations.
  • a metal source includes iron source, copper source, cobalt source, nickel source, zinc source and manganese source; preferably iron source and manganese source, such as iron 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), iron nitrate (manganese), iron citrate (manganese), ferric oxide (manganese), or a combination of one or more.
  • iron source and manganese source such as iron phosphate (manganese), ferrous phosphate (manganese), ferrous pyrophosphate (manganese) ), ferrous carbonate
  • the phosphorus source is one or a combination of more of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, iron phosphate, and lithium dihydrogen phosphate.
  • the M metal source also includes one or more combinations of copper, vanadium, magnesium, aluminum, zinc, manganese, titanium, zirconium, niobium, chromium compounds and rare earth element compounds.
  • the carbon source is one or a combination of more of citric acid, malic acid, tartaric acid, oxalic acid, salicylic acid, succinic acid, glycine, ethylenediaminetetraacetic acid, sucrose, and glucose.
  • the solvents are water, methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, n-pentanol, n-hexanol, n-heptanol, acetone, ethyl ketone, butanedione, pentanone, cyclopentanone, One or a combination of hexanone, cyclohexanone, and cycloheptanone.
  • the additives are polyvinyl alcohol, polyethylene glycol, polyethylene oxide, sodium polystyrene sulfonate, polyoxyethylene nonyl phenyl ether, cetyltrimethylammonium chloride, cetyltrimethylammonium chloride One or a combination of ammonium bromide, octadecyltrimethylammonium chloride, and octadecyltrimethylammonium bromide.
  • the metal vanadium source is one or more of vanadium pentoxide, vanadium dioxide, vanadium metal powder, vanadium chloride, and ammonium metavanadate.
  • a secondary battery typically includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.
  • Figure 1 shows a cross-sectional SEM image of a pole piece containing the cathode active material of the present invention.
  • Figure 2 shows an EDS surface scan of the pole piece containing the cathode active material of the invention to characterize the phosphorus, vanadium and oxygen elements. distributed.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive active material may also include other positive active materials known in the art for batteries.
  • other cathode active materials may also include at least one of the following materials: olivine-structured lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds.
  • other conventional materials that can be used as positive active materials for batteries can also be used. Only one type of these other positive electrode active materials may be used alone, or two or more types may be used in combination.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (can also be abbreviated to NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (can also be abbreviated to NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (can also be abbreviated to NCM 622 ), LiNi At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as Li Li
  • the olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon. At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • the weight ratio of the positive electrode active material in the positive electrode film layer is 80-100% by weight, based on the total weight of the positive electrode film layer count.
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the weight ratio of the binder in the positive electrode film layer is 0-20% by weight, based on the total weight of the positive electrode film layer.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the weight ratio of the conductive agent in the positive electrode film layer is 0-20% by weight, based on the total weight of the positive electrode film layer.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone), forming a positive electrode slurry, wherein the solid content of the positive electrode slurry is 40-80wt%, the viscosity at room temperature is adjusted to 5000-25000mPa ⁇ s, and the positive electrode slurry is coated on the surface of the positive electrode current collector , dried and cold-pressed by a cold rolling mill to form a positive electrode piece; the unit area density of the positive electrode powder coating is 150-350 mg/m 2 , and the compacted density of the positive electrode piece is 1-5g/cm3, preferably 2.0-2.6g/ m3 .
  • a solvent such as N -methylpyrrolidone
  • 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, where the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • 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.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the weight ratio of the negative active material in the negative electrode film layer is 80-100% by weight, based on the total weight of the negative electrode film layer.
  • the negative electrode film layer optionally further includes a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS polysodium acrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA methacrylic acid
  • CMCS carboxymethyl chitosan
  • the negative electrode film layer optionally further includes 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 weight ratio of the conductive agent in the negative electrode film layer is 0-20% by weight, based on the total weight of the negative electrode film layer.
  • the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • the weight ratio of the other additives in the negative electrode film layer is 0-15% by weight, based on the total weight of the negative electrode film layer.
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water), forming a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30-70wt%, and the viscosity at room temperature is adjusted to 2000-10000mPa ⁇ s; the obtained negative electrode slurry is coated on the negative electrode current collector, After the drying process and cold pressing, such as against rollers, the negative electrode piece is obtained.
  • the negative electrode powder coating unit area density is 75-220mg/m2, and the negative electrode plate compacted density is 1.2-2.0g/m 3 .
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the type of electrolyte in this application can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte is an electrolyte solution.
  • the electrolyte solution includes electrolyte salts and solvents.
  • the electrolyte salt may be selected from lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonimide (LiFSI ), lithium bistrifluoromethanesulfonimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoromethanesulfonylborate (LiDFOB), lithium difluoromethanesulfonylborate (LiBOB), lithium difluorophosphate (LiPO2F2), One or more of lithium difluorodioxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).
  • the concentration of the electrolyte salt is usually 0.5-5 mol/L.
  • the solvent may be selected from fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) ), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate Ester (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB) , one or more of ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl
  • FEC
  • the electrolyte optionally further includes additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the thickness of the isolation film is 6-40um, optionally 12-20um.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 3 shows a square-structured secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG. 5 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application.
  • the secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device.
  • the electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • Figure 8 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery pack or battery module can be used.
  • the device may be a mobile phone, a tablet, a laptop, etc.
  • the device is usually required to be thin and light, and a secondary battery can be used as a power source.
  • the S1 component precursor is sintered under an inert atmosphere of nitrogen (oxygen atmosphere is controlled within 20 ppm), where the heating rate is 10°C/min, the temperature is raised to 760°C at a constant rate, kept for 10 hours, and then purged with cold nitrogen to cool down. 5h, cool down to the surface temperature of the material to 40°C.
  • the sintered material is pulverized by airflow, and the S1 component obtained has a molecular formula of LiTi 0.005 Fe 0.99 PO 4 and an average volume particle size Dv50 of 1.5um.
  • the preparation method of the cathode active material is similar to that of the cathode active material in Preparation Example 1, but the composition of raw materials and product parameters are adjusted. The different product parameters are detailed in Table 1.
  • Lithium carbonate, ammonium metavanadate, and carbon source glucose are mixed, wherein, based on the total weight of the mixture, the weight ratio of lithium carbonate and ammonium metavanadate is 75%, and the weight ratio of carbon source glucose is 25%; wherein lithium carbonate and The molar ratio of ammonium metavanadate is 1.5:1.
  • the mixture was ball milled in a ball mill apparatus for 2 hours.
  • the mixture was then sintered under nitrogen protection conditions, with a heating rate of 10°C/min, a uniform temperature rise to 560°C, and a heat preservation period of 10 hours, and then purging with cold nitrogen for 5 hours to cool down until the surface temperature of the material reached 40°C. S2 component.
  • the entire sintering process is protected by nitrogen atmosphere, and the oxygen atmosphere of the atmosphere is controlled within 20ppm.
  • the S1 component and the S2 component obtained above are physically mixed in a weight ratio of 8:1 to obtain the cathode active material of the present invention.
  • the different product parameters are detailed in Table 1.
  • Table 1 The positive electrode active material composition and related parameters obtained in each preparation example and preparation comparative example
  • the cathode active material powder, conductive agent, and binder of Preparation Example 1 were dry-mixed in a weight ratio of 96:2:2, and NMP solvent was added. Stir vigorously under the action of a vacuum mixer until a uniform positive electrode slurry is formed. The solid content of the slurry is 60wt%, and the viscosity is adjusted to 8000mPa ⁇ s at room temperature. Coat the positive electrode slurry on the surface of the positive electrode current collector aluminum foil and dry it. After cold pressing in a cold rolling mill, the positive electrode sheet is formed. The positive electrode powder coating unit area density is controlled to 200 mg/m 2 , and the compacted density of the positive electrode sheet is as shown in Table 1.
  • the negative active material graphite graphite, thickener sodium carboxymethyl cellulose (CMC-Na), binder styrene-butadiene rubber (SBR), and conductive agent carbon black according to a mass ratio of 97:1:1:1, and add Deionized water, stir and mix evenly to obtain negative electrode slurry.
  • the solid content of the slurry is 50wt%, and the viscosity at room temperature is adjusted to 4000 mPa ⁇ s; the obtained negative electrode slurry is coated on the copper foil, and subjected to a drying process and rolled to obtain a negative electrode piece.
  • the negative electrode powder coating unit area density is controlled to 145 mg/m 2 and the negative electrode sheet compacted density is 1.35 g/m 3 .
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then the fully dried lithium salt LiPF6 is dissolved in the mixture.
  • the final organic solvent prepare an electrolyte solution with a concentration of 1 mol/L.
  • the battery core is placed in the outer packaging shell, and after drying, 10g of electrolyte is injected. After vacuum packaging, standing, formation, shaping and other processes, a lithium-ion battery is obtained.
  • the secondary batteries of Examples 2-13 and the secondary battery of Comparative Example 1 are similar to the secondary batteries of Example 1, but the positive electrode active materials obtained in the corresponding preparation examples are used.
  • lithium vanadium oxide can play the role of replenishing lithium in the positive electrode, which significantly improves the gram capacity of the battery.
  • Na ions are doped into the 1.5Li 2 O ⁇ VO 2.5 compound component to obtain 1.45Li 2 O ⁇ 0.05Na 2 O ⁇ VO 2.5 , which can further improve the overall performance of the battery.
  • the radius of Na ions (0.1nm) is larger than the radius of Li ions (0.7nm).
  • Appropriate replacement of Li+ by Na+ can widen the interlayer spacing of the material and provide more space for lithium ions to diffuse in the bulk phase of the material. Reduce diffusion resistance and improve the rate performance and low-temperature performance of the material.
  • Examples 8-11 use 0.5Li 2 O ⁇ 3VO 2.5 low-temperature additive. Compared with Examples 1-7, the j value is relatively low. Therefore, the gram capacity of the battery is reduced, and the low-temperature improvement range of the battery is accordingly This is because the proportion of vanadium-oxygen matrix in lithium vanadium oxide increases and the resistance during lithium ion transmission decreases, which has a significant effect on improving low-temperature performance. In Examples 8-11, as the addition amount of 0.5Li 2 O ⁇ 3VO 2.5 low-temperature additive increases, similar rules are shown to those in Examples 1-7.
  • Example 12 changed the mixing method of low-temperature additives and main materials, and adopted a simple physical mixing method, that is, synthesizing S1 and S2 respectively, and then preparing S1 and S2 together with other additives of the positive electrode formula. Get the positive electrode piece. The test results found that Example 12 also showed better low-temperature performance improvement.

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Abstract

本申请涉及一种二次电池，其包含正极极片、负极极片和电解液，其中所述正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包含正极活性材料，所述正极活性材料包含S1)橄榄石结构的含锂化合物，和S2)通式为j(M 2O)·kVO X的钒氧化物，其中M为碱金属中的一种或多种，0≤j≤1，1≤k≤5，1≤x≤2.5；其中S1与S2的放电平台电压的差值为E,其中0.2V≤E≤2.8V。所述二次电池在保证优异的循环性能和克容量下具有非常好的低温性能，例如即使在较高的放电倍率下，也能保持很好的低温容量保持率。

Description

一种二次电池、电池模块、电池包和用电装置 技术领域
本申请涉及锂电池技术领域，尤其涉及一种二次电池、电池模块、电池包和用电装置。
背景技术
近年来，随着锂离子电池的应用范围越来越广泛，市场对锂离子电池的要求不断提高。追求能量密度的同时，高倍率耐低温电池的研发和工业化，越来越受到业界的关注，例如军工上的应用，如电磁干扰、电磁轨道发射器、磁控管等设备；在民用方面，如低温地区车载冷启动电源，高功率电动工具，极寒地区通讯基站电源。以上应用场景对于低温性能和倍率性能的要求是更加的严苛。电池正极材料是决定电池系统电化学性能、安全性能、能量密度等的关键因素。
具有橄榄石结构的磷酸系正极材料(LiMPO 4，其中M可以是Fe、Co、Zn、Ni、Cu、Mn中的一种或者两种以上的组合)是当前大规模商业化的正极材料之一，具有较高的克容量发挥和放电电压，并且其放电电压输出稳定，合成原材料成本低，寿命优异，安全性能好，在动力电池和储能电池方面获得了大规模的应用。
通过测试表明，LiMPO 4型正极材料具有非常低的电子导电性和离子导电性，以磷酸铁锂材料为例，LiFePO 4的不足之处在于电子电导率和离子电导率较低，分别为10 -9S·cm1和10 -10-10 -15cm2·s1，作为正极材料应用于锂离子电池表现出较差的倍率性能和低温放电性能。通过包覆或掺杂等手段来改善材料的倍率性能和低温性能等是目前比较有效的手段，但是电化学性能仍未能达到令人满意的结果。寻找合适的低温助剂，采用恰当的复合方式，是改善磷酸铁锂正极材料的一种有效途径。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种二次电池，其正极膜层包含通式为j(M 2O)·kVO X的钒氧化物，使得所述二次电池在保证优异的循环性能和克容量下具有非常好的低温性能，例如即使在较高的放电倍率下，也能保持很好的低温容量 保持率。
本申请的第一方面提供了一种二次电池，其包含正极极片、负极极片和电解液，其中所述正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包含正极活性材料，所述正极活性材料包含S1)橄榄石结构的含锂化合物，和S2)通式为j(M 2O)·kVO X的钒氧化物，其中M为碱金属中的一种或多种，0≤j≤1，1≤k≤5，1≤x≤2.5；其中S1与S2的放电平台电压的差值为E，其中0.2V≤E≤2.8V。
由此，本申请通过在正极活性材料中包含特定放电平台电压的两种特定的活性材料，使得所述二次电池在保证优异的循环性能下具有非常好的低温性能例如即使在较高的放电倍率下，也能保持很好的低温容量保持率。
在任意实施方式中，在组分S2中，M为选自Li或Na中一种或两种，可选地为Li；0≤j/k≤1，优选0.2≤j/k≤0.6。由此，进一步优选钒氧化物，可以提升低温助剂中活性锂或者钠含量，有利于提升低温下二次电池的容量发挥，同时保持很好的低温容量保持率。
在任意实施方式中，S1为通式LiA 1-n*y/2M yPO 4的化合物，其中0≤y≤0.1，
A选自Fe、Co、Ni、Cu、Mn、Zn中的至少一种，
n为M金属的价态，n＝+2、+3、+4或+5价价，
M选自Cr、Pb、Ca、Sr、Ti、Mg、V、Nb、Zr中的至少一种；
A与M相同或不同。
由此，使用上述类型的磷酸锂类正极活性材料，结合钒氧化物，进一步提高了所述电池的低温性能，同时保证其循环性能。
在任意实施方式中，S1组分为LiFe 1-n*y/2M yPO 4的化合物，其中y、M和n如上所述定义；
S2包括LiVO 3、Li 3V 2O 5、Li 4V 3O 8、LiV 3O 8、Li 2VO 3、LiVO 2；V 2O 5、V 2O 3、V 3O 4；以及上述组分相应的Na掺杂物Li 0.95Na 0.05VO 3、Li 2.95Na 0.05V 2O 5、Li 3.95Na 0.05V 3O 8。使用上述类型的磷酸锂类正极活性材料，结合钒氧化物，进一步提高了所述电池的低温性能，同时保证其循环性能。
在任意实施方式中，钒元素的含量为1重量％-5重量％，基于所述正极活性材料的重量计；在正极活性材料中，钒元素与锂元素的摩尔比为1：5-20，优选为1：6-10。由此，通过控制正极活性材料中锂与钒的含量以及相对比例，可以进一步改善所述电池的低温性能。
在任意实施方式中，S1组分与S2组分的重量比为3-30：1，优选为4-10：1。由此，通过控制正极活性材料中S1组分与S2组分的重量比，可以进一步改善所述电池的低温性能并保证电池的循环性能。
在任意实施方式中，S1组分的放电平台电压为3.1-4.8V，S2组分的放电平台电压为1.0-3.0V。由此，通过控制正极活性材料中S1组分与S2组分的放电平台电压，可进一步改善所述电池的低温性能并保证电池的循环性能。
在任意实施方式中，S2组分被碳包覆或者导电聚合物包覆。由此，通过控制正极活性材料中S2组分的组成，可进一步改善所述电池的低温性能并保证电池的循环性能。
本申请的第二方面还提供一种电池模块，包括本申请的第一方面的二次电池。
本申请的第三方面提供一种电池包，包括本申请的第二方面的电池模块。
本申请的第四方面提供一种用电装置，包括选自本申请的第一方面的二次电池、本申请的第二方面的电池模块或本申请的第三方面的电池包中的至少一种。
本申请的二次电池通过其正极活性材料中包含含锂化合物以及钒氧化物，并保证两者之间的放电平台电压的差值在特定范围内，就可以使得所述二次电池在保证优异的循环性能下具有非常好的低温性能例如即使在较高的放电倍率下，也能保持很好的低温容量保持率；而且使得所述电池在低温下容量得到更好地发挥。
附图说明
图1为本申请一实施方式的正极活性材料的扫描电镜图。
图2为本申请一实施方式的正极活性材料的X射线能谱仪(EDS)面扫描图。
图3是本申请一实施方式的二次电池的示意图。
图4是图3所示的本申请一实施方式的二次电池的分解图。
图5是本申请一实施方式的电池模块的示意图。
图6是本申请一实施方式的电池包的示意图。
图7是图6所示的本申请一实施方式的电池包的分解图。
图8是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的正极活性材料及其制造方法、正极极片、二次电池、电池模块、电池包和电学装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组 分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
具有橄榄石结构的磷酸系正极材料(LiMPO 4，其中M可以是Fe、Co、Zn、Ni、Cu、Mn中的一种或者两种以上的组合)是当前大规模商业化的正极材料之一，具有较高的克容量发挥和放电电压。且放电电压输出稳定，合成原材料成本低，寿命优异，安全性能好，在动力电池和储能电池方面获得了大规模的应用。
通过测试表明，LiMPO 4型正极材料具有非常低的电子导电性和离子导电性，以磷酸铁锂材料为例，LiFePO 4的不足之处在于电子电导率和离子电导率较低，分别为10 -9S·cm1和10 -10-10 -15cm2·s1，作为正极材料应用于锂离子电池表现出较差的倍率性能和低温放电性能。通过包覆或掺杂等手段来改善材料的倍率性能和低温性能等是目前比较有效的手段，但是电化学性能仍未能达到令人满意的结果。寻找合适的低温助剂，采用恰当的复合方式，是改善磷酸铁锂正极材料的一种有效途径。申请人研究发现本申请第一方面的二次电池通过其正极活性材料中包含含锂化合物以及钒氧化物，并保证两者之间的放电平台电压的差值在特定范围内，就可以使得所述二次电池在保证优异的循环性能和克容量下具有非常好的低温性能例如即使在较高的放电倍率下，也能保持很好的低温容量保持率以及低SOC下的电池表现出优异的功率性能。
二次电池
本申请的第一方面提供了一种二次电池，其包含正极极片、负极极片和电解液，其中所述正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包含正极活性材料，所述正极活性材料包含S1)橄榄石结构的含锂化合物，和S2)通式为j(M 2O)·kVO X的钒氧化物，其中M为碱金属中的一种或多种，0≤j≤1，1≤k≤5，1≤x≤2.5；其中S1与S2的放电平台电压的差值为E，其中0.2V≤E≤2.8V。
不囿于任何理论，现认为，电池放电到较低的荷电状态(SOC)时，电池的放电功率会急剧衰减，且在低温放电时，该现象更加明显。提升电池低SOC放电条件下的放电功率，显得尤为重要。本申请通过在正极活性材料中包含含锂化合物以及钒氧化物，并保证两者之间的放电平台电压的差值在特定范围内，所述电池在低温下借助钒氧化物 的反应提供能量输出，同时电芯内部温度可以提升，电芯放电容量得以提高，从而使得所述二次电池在保证优异的循环性能下具有非常好的低温性能例如即使在较高的放电倍率下，也能保持很好的低温容量保持率；而且使得所述电池在低温下容量得到更好地发挥。
在一些实施方式中，在组分S2中，M为选自Li或Na中一种或两种，可选地为Li；0≤j/k≤1，优选0.2≤j/k≤0.6。由此，进一步优选钒氧化物，有利于提升低温下二次电池的容量发挥，同时保持很好的低温容量保持率。
在一些实施方式中，S1为通式LiA 1-n*y/2M yPO 4的化合物，其中0≤y≤0.1，
A选自Fe、Co、Ni、Cu、Mn、Zn中的至少一种，
n为M金属的价态，n＝+2、+3、+4或+5价，
M选自Cr、Pb、Ca、Sr、Ti、Mg、V、Nb、Zr中的至少一种；
A与M相同或不同。
由此，使用上述类型的磷酸锂类正极活性材料，结合钒氧化物，进一步提高了所述电池的低温性能，同时保证其循环性能。
在一些实施方式中，S1组分可选为LiFe 1-n*y/2M yPO 4的化合物，其中y、M、n如上所述定义，优选0<y≤0.1，M和n如上所述定义；进一步优选为LiFePO 4、LiFe 1-n*y/2M yPO 4，更优选LiTi xFe 1-n*y/2-2xMn yPO 4、LiTi yFe 1-n*y/2PO 4、LiMg xFe 1-n*y/2-xMn yPO 4、LiV xFe 1- n*y/2-5x/2Mn yPO 4，其中y和n如上所述定义，0.005≤x≤0.1；最优选LiFePO 4、LiTi yFe 1- n*y/2PO 4，其中y和n如上所述定义。
在一些实施方式中，S2为LiVO 3、Li 3V 2O 5、Li 4V 3O 8、LiV 3O 8、Li 2VO 3、Li 3VO 4、LiVO 2；V 2O 5、V 2O 3、V 3O 4；以及上述组分相应的Na掺杂物例如Li 3-xNa xVO 4、Li 1-xNa xV 3O 8和Li 1-xNa xVO 3其中0.005≤x≤0.1，优选为Li 3VO 4、V 2O 5、LiV 3O 8、LiVO 3及其Na掺杂物Li 0.95Na 0.05VO 3、Li 2.95Na 0.05V 2O 5、Li 3.95Na 0.05V 3O 8。由于钒和氧形成的酸根形式非常丰富，例如正钒酸根，偏钒酸根，焦钒酸根，多钒酸根等，因此S2组分不限于以上化合物。由此，使用上述类型的磷酸锂类正极活性材料，结合钒氧化物，进一步提高了所述电池的低温性能，同时保证其循环性能。
在一些实施方式中，钒元素的含量为1重量％-5重量％，优选2重量％-4重量％，基于所述正极活性材料的重量计；在正极活性材料中，锂元素与钒元素的摩尔比为5-20：1，优选为6-10：1。由此，通过控制正极活性材料中锂与钒的含量以及相对比例，可以 进一步改善所述电池的低温性能。
在一些实施方式中，S1组分与S2组分的重量比为3-20：1，优选为4-10：1。由此，通过控制正极活性材料中S1组分与S2组分的重量比，可以进一步改善所述电池的低温性能并保证电池的循环性能。
在一些实施方式中，S1组分的放电平台电压为3.1-4.8V，S2组分的放电平台电压为1.0-3.0V。由此，通过控制正极活性材料中S1组分与S2组分的放电平台电压，可以进一步改善所述电池的低温性能并保证电池的循环性能。如果S1或S2组分具有多个放电平台电压，那么本发明中所述的S1或S2的放电平台电压为其最高的放电平台电压。
在一些实施方式中，S2组分被碳包覆或者导电聚合物包覆。由此，通过控制正极活性材料中S2组分的组成，可以进一步改善所述电池的低温性能并保证电池的循环性能。在一些实施方式中，所述表面修饰的碳或导电聚合物可选自无定形碳、石墨烯、石墨化碳层、聚乙炔、聚吡咯、聚噻吩、聚亚苯基、聚苯乙炔、聚苯胺、聚多巴胺等中的一种或多种。
在一些实施方式中，所述S1组分的平均体积粒径Dv50为1-5um。所述平均体积粒径Dv50为样品的体积累计分布百分数达到50％时对应的粒径，采用激光粒度分析仪测定，例如采用英国马尔文仪器有限公司的Mastersizer 3000型激光粒度分析仪。
在一些实施方式中，所述正极活性材料可以本领域已知的方法制备，例如，S1组分与S2组分物理混合得到所述正极活性材料，或者在S2组分表面包覆或掺杂S2组分得到所述正极活性材料。
在一些实施方式中，在S2组分表面包覆或掺杂S2组分时，所述正极活性材料通常如下制备：
将锂源、A金属源、磷源、M金属源按一定的摩尔比相混合形成混合物，在混合物中加入碳源和助剂，将以上混合物经过研磨形成均匀的混合物浆料，将得到的浆料进行喷雾干燥得到前驱体。将前驱体进行惰性气氛下烧结得到碳包覆的S1组分材料，将得到的S1组分材料和任选的锂源、金属钒源按一定比例进行混合，进一步补充一定量的碳源，继续至于惰性气氛下烧结得到本申请的正极活性材料。
混合物中，锂源、A金属源、磷源、M金属按摩尔比Li∶A∶P∶M为0.95-1∶0.95-1∶0.95-1∶0-0.05的比例混合。
锂源为氧化锂、氢氧化锂、乙酸锂、碳酸锂、硝酸锂、亚硝酸锂、磷酸锂、磷酸二 氢锂、草酸锂、氯化锂、钼酸锂、钒酸锂中的一种或多种的组合。
A金属源包括铁源、铜源、钴源、镍源、锌源、锰源；优选为铁源和锰源，例如磷酸铁(锰)、磷酸亚铁(锰)、焦磷酸亚铁(锰)、碳酸亚铁(锰)、氯化亚铁(锰)、氢氧化亚铁(锰)、硝酸亚铁(锰)、草酸亚铁(锰)、氯化铁(锰)、氢氧化铁(锰)、硝酸铁(锰)、柠檬酸铁(锰)、三氧化二铁(锰)中的一种或多种的组合。
磷源为磷酸、磷酸氢二铵、磷酸二氢铵、磷酸铁、磷酸二氢锂中的一种或多种的组合。
M金属源还包括铜、钒、镁、铝、锌、锰、钛、锆、铌、铬的化合物及稀土元素化合物中的一种或多种的组合。
碳源为柠檬酸、苹果酸、酒石酸、草酸、水杨酸、琥珀酸、甘氨酸、乙二胺四乙酸、蔗糖、葡萄糖中的一种或多种的组合。
溶剂为水、甲醇、乙醇、丙醇、异丙醇、正丁醇、异丁醇、正戊醇、正己醇、正庚醇、丙酮、丁酮、丁二酮、戊酮、环戊酮、己酮、环己酮、环庚酮中的一种或多种的组合。
助剂为聚乙烯醇、聚乙二醇、聚氧化乙烯、聚苯乙烯磺酸钠、聚氧乙烯壬基苯基醚、十六烷基三甲基氯化铵、十六烷基三甲基溴化铵、十八烷基三甲基氯化铵、十八烷基三甲基溴化铵中的一种或多种的组合。
金属钒源为五氧化二钒，二氧化钒，钒金属粉末，氯化钒、偏钒酸铵中的一种或者几种。
另外，以下适当参照附图对本申请的二次电池进行说明。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括本申请第一方面的正极活性材料。图1示出了包含本发明的正极活性材料的极片的剖面SEM图，图2示出了包含本发明的正极活性材料的极片的EDS面扫描图，以表征磷、钒和氧元素的分布。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料还可包含本领域公知的用于电池的其他正极活性材料。作为示例，其他正极活性材料还可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。除了这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些其他正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。所述正极活性材料在正极膜层中的重量比为80-100重量％，基于正极膜层的总重量计。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。所述粘结剂在正极膜层中的重量比为0-20重量％，基于正极膜层的总重量计。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包 括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。所述导电剂在正极膜层中的重量比为0-20重量％，基于正极膜层的总重量计。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料，其中所述正极浆料固含量为40-80wt％，室温下的粘度调整到5000-25000mPa·s，将正极浆料涂覆在正极集流体的表面，烘干后经过冷轧机冷压后形成正极极片；正极粉末涂布单位面密度为150-350mg/m 2，正极极片压实密度为1-5g/cm3，优选2.0-2.6g/m 3。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。所述负极活性材料在负极膜层中的重量比为80-100重量％，基于负极膜层的总重量计。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯 醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。所述粘结剂在负极膜层中的重量比为0-20重量％，基于负极膜层的总重量计。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。所述导电剂在负极膜层中的重量比为0-20重量％，基于负极膜层的总重量计。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。所述其他助剂在负极膜层中的重量比为0-15重量％，基于负极膜层的总重量计。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料，其中所述负极浆料固含量为30-70wt％，室温下的粘度调整到2000-10000mPa·s；将所得到的负极浆料涂覆在负极集流体上，经过干燥工序，冷压例如对辊，得到负极极片。负极粉末涂布单位面密度为75-220mg/m2，负极极片压实密度1.2-2.0g/m 3。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂(LiPF6)、四氟硼酸锂(LiBF4)、高氯酸锂(LiClO4)、六氟砷酸锂(LiAsF6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO2F2)、二氟二草酸磷酸锂(LiDFOP)及四氟草酸磷酸锂(LiTFOP)中的一种或几种。所述电解质盐的浓度通常为0.5-5mol/L。
在一些实施方式中，溶剂可选自氟代碳酸乙烯酯(FEC)、碳酸亚乙酯(EC)、碳酸亚丙基酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、 甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或几种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，所述隔离膜的厚度为6-40um，可选为12-20um。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图3是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图4，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图5是作为一个示例的电池模块4。参照图5，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图6和图7是作为一个示例的电池包1。参照图6和图7，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图8是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
为了使本申请所解决的技术问题、技术方案及有益效果更加清楚，以下将结合实施例和附图对本申请进行进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。以下对至少一个示例性实施例的描述实际上仅仅是说明性 的，决不作为对本申请及其应用的任何限制。基于本申请中的实施例，本领域普通技术人员在没有付出创造性劳动前提下所获得的所有其他实施例都属于本申请保护的范围。
实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
一、制备实施例
制备实施例1
(1)在室温下，将碳酸锂、草酸亚铁、磷酸二氢铵、二氧化钛按摩尔比1：2：2：0.01混合形成混合物。在所述混合物中加入重量比为3:1:0.3的葡萄糖和PEG以及柠檬酸表面活性剂，其中葡萄糖在全部原料重量的10％，柠檬酸占全部原料重量的1％。加入1000mL水作为分散介质。然后采用砂磨机在1000rpm下将以上混合物研磨4小时，形成均匀的混合物浆料，其中浆料的固含量为40％。将得到的浆料使用喷雾干燥设备进行喷雾干燥得到S1组分的前驱体。
(2)将S1组分前驱体进行惰性气氛氮气(氧氛控制在20ppm以内)下烧结，其中升温速率为10℃/min，匀速升温到760℃，保温10h，然后采用冷氮气吹扫进行降温5h，降温到物料表面温度为40℃。将烧结完成的物料进行气流粉碎，获得的S1组分，其分子式为LiTi 0.005Fe 0.99PO 4，平均体积粒径Dv50为1.5um。
(3)将S1组分材料和碳酸锂、偏钒酸铵、碳源葡萄糖进一步混合，其中，基于混合物的总重量计，S1组分的重量比为80％，碳酸锂和偏钒酸铵的重量比15％，碳源葡萄糖的重量比为5％；其中碳酸锂和偏钒酸铵的摩尔比为1.5:1。
(4)将所述混合物在球磨机设备中球磨2小时。然后将所述混合物置于氮气保护条件下烧结，其中升温速率为10℃/min，匀速升温到560℃，保温10h，然后采用冷氮气吹扫进行降温5h，直到物料表面温度为40℃。整个烧结过程采用氮气气氛保护，且气氛的氧氛控制在20ppm以内。最终得到表面包覆1.5Li 2O·VO 2.5的本发明的正极活性材料，其平均体积粒径Dv50为1.8um。
制备实施例2-12
其正极活性材料与制备实施例1的正极活性材料的制备方法相似，但是调整了原料的组成和产品参数，不同的产品参数详见表1。
制备实施例13
以制备实施例1的正极活性材料的制备方法中步骤(1)和(2)制备S1组分；
将碳酸锂、偏钒酸铵、碳源葡萄糖混合，其中，基于混合物的总重量计，碳酸锂和偏钒酸铵的重量比75％，碳源葡萄糖的重量比为25％；其中碳酸锂和偏钒酸铵的摩尔比为1.5:1。将所述混合物在球磨机设备中球磨2小时。然后将所述混合物置于氮气保护条件下烧结，其中升温速率为10℃/min，匀速升温到560℃，保温10h，然后采用冷氮气吹扫进行降温5h，直到物料表面温度为40℃，获得S2组分。整个烧结过程采用氮气气氛保护，且气氛的氧氛控制在20ppm以内。将上述获得的S1组分与S2组分以8：1的重量比物理混合，得到本发明的正极活性材料。不同的产品参数详见表1。
制备对比例1
仅进行制备实施例1的步骤(1)和(2)，得到S1组分用作正极活性材料。不同的产品参数详见表1。
表1各制备实施例和制备对比例获得的正极活性材料组成和相关参数
Figure PCTCN2022101487-appb-000001
二、应用实施例
实施例1
1)正极极片的制备
将制备实施例1的正极活性材料粉末、导电剂、粘结剂按照重量比例96：2：2进行干混，加入NMP溶剂。在真空搅拌机的作用下激烈搅拌直到形成均匀的正极浆料，浆料固含量为60wt％，室温下粘度调整到8000mPa·s，将正极浆料涂覆在正极集流体铝箔的表面，烘干后经过冷轧机冷压后形成正极极片，正极粉末涂布单位面密度控制到200mg/m 2，正极极片压实密度如表1中所示。
2)负极极片的制备
将负极活性材料石墨、增稠剂羧甲基纤维素钠(CMC-Na)、粘接剂丁苯橡胶(SBR)、导电剂炭黑，按照质量比97:1:1:1进行混合，加入去离子水，搅拌混合均匀，得到负极浆料。浆料固含量为50wt％，室温下粘度调整到4000mPa·s；将所得到的负极浆料涂覆在铜箔上，经过干燥工序，对辊，得到负极极片。负极粉末涂布单位面密度控制到145mg/m 2，负极极片压实密度1.35g/m 3。
3)隔离膜
使用厚度0.012mm的聚乙烯膜作为隔离膜。
4)电解液的制备
将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照按体积比1:1:1进行，混合得到有机溶剂，接着将充分干燥的锂盐LiPF6溶解于混合后的有机溶剂中，配制成浓度为1mol/L的电解液。
5)电池的制备
将上述制备的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，然后卷绕得到容量为3Ah的裸电芯；将裸电芯置于外包装壳中，干燥后注入10g电解液，经过真空封装、静置、化成、整形等工序，获得锂离子电池。
实施例2-13的二次电池和对比例1的二次电池与实施例1的二次电池制备方法相似，但是使用了相应制备实施例获得的正极活性材料。
三、电池性能测试
1、-20℃低温性能测试
在25℃下，先以0.5C的恒定电流对电池充电至3.65V，进一步以3.65V恒定电压充电至电流为0.025C，静置2h，然后以1C的恒定电流将电池放电至2.0V，放电容量 记为C0；然后25℃静置2h，重复以0.5C的恒定电流对电池充电至3.65V并横流充电至0.025C,电池置于-20℃条件下静置2h，然后以1C的恒定电流将电池放电至2.0V，放电容量记为D1；然后25℃静置2h，重复以0.5C的恒定电流对电池充电至3.65V并横流充电至0.025C，电池置于-20℃条件下静置2h，然后以3C的恒定电流将电池放电至2.0V，放电容量记为D3。分别计算电芯在-20℃，以1C、3C倍率放电的容量保持率D1/D0和D3/D0。
2、循环性能测试
在25℃下，1.先以0.5C的恒定电流对电池充电至3.65V，2.进一步以3.65V恒定电压充电至电流为0.025C，记录为第1次充电容量，3.静置2h，4.然后以1C的恒定电流将电池放电至2.0V，记录为第1次放电容量；5.然后25℃静置2h，重复1-4过程,记录每一次循环过程中的充电容量和放电容量；以第500次的放电容量除以第一次的放电容量即为电池的第n次循环的容量保持率。
3.0.5C放电容量克容量的测试
在25℃下，先以0.5C的恒定电流对电池充电至3.65V，进一步以3.65V恒定电压充电至电流为0.025C，静置2h，然后以0.5C的恒定电流将电池放电至2.0V，放电容量记为C 放，克容量c＝C 放/正极材料的质量。
四、各实施例、对比例测试结果
按照上述方法分别制备各实施例和对比例的电池，并测量各项性能参数，结果见下表2。
表2各实施例和对比例的电池的性能
Figure PCTCN2022101487-appb-000002
Figure PCTCN2022101487-appb-000003
从实施例1-7，通过在LiTi 0.005Fe 0.99PO 4表面包覆形成1.5Li 2O·VO 2.5包覆层，可提升混合正极材料的低温性能，低温性能明显均高于对比例1。另一方面，随着锂钒氧化物比例的增加，电芯的循环寿命降低，主要原因是锂钒氧化物在脱锂和嵌锂过程中，涉及到钒元素多种价态的变换，结构衰减速度高于磷酸铁锂材料；进一步数据分析，看到当1.5Li 2O·VO 2.5含量合适时，混合正极材料具有最优的低温放电性能；可见在实施例3条件下，电池综合性能最优。
同时，锂钒氧化物可以起到正极补锂的作用，其使得电池的克容量发挥得到显著提升。进一步，实施例12在1.5Li 2O·VO 2.5化合物组分中进行Na离子掺杂，得到1.45Li 2O·0.05Na 2O·VO 2.5，可以进一步改善电池的综合性能，这是因为Na与Li为同族元素，Na离子的半径(0.1nm)大于Li离子半径(0.7nm)，适当的Na+取代Li+的位置可以拓宽材料层间间距，为锂离子在材料体相扩散提供更大的空间，减少扩散阻力，提升材料的倍率性能和低温性能。
实施例8-11，采用0.5Li 2O·3VO 2.5低温助剂，相对于实施例1-7，j值是相对较低的，因此，电池的克容量发挥降低，电池的低温改善幅度随之提升，这是因为锂钒氧化物中钒氧基体占比增加，锂离子传输过程中的阻力降低，对于低温性能提升具有显著的效果。实施例8-11中随着0.5Li 2O·3VO 2.5低温助剂的添加量提升，和1-7实施例表现相似的规律。
实施例12相比于实施例3，改变了低温助剂和主体材料混合的方式，采用了单纯物理混合的方式，即分别合成S1和S2，在将S1和S2连同正极配方其它助剂进行制备得到正极极片。测试结果发现，实施例12同样表现出较好的低温性能提升。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (11)

  1. 一种二次电池，其包含正极极片、负极极片和电解液，其中所述正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包含正极活性材料，所述正极活性材料包含S1)橄榄石结构的含锂化合物，和S2)通式为j(M 2O)·kVO X的钒氧化物，其中M为碱金属中的一种或多种，0≤j≤1，1≤k≤5，1≤x≤2.5；其中S1与S2的放电平台电压的差值为E,其中0.2V≤E≤2.8V。
  2. 根据权利要求1所述的二次电池，其特征在于，在组分S2中，M为选自Li或Na中一种或两种，可选地为Li；0≤j/k≤1，优选0.2≤j/k≤0.6。
  3. 根据权利要求1或2所述的二次电池，其特征在于，S1为通式LiA 1-n*y/2M yPO 4的化合物，其中0≤y≤0.1，
    A选自Fe、Co、Ni、Cu、Mn、Zn中的至少一种，
    n为M金属的价态，n＝+2、+3、+4或+5价价，
    M选自Cr、Pb、Ca、Sr、Ti、Mg、V、Nb、Zr中的至少一种；
    A与M相同或不同。
  4. 根据权利要求1-3中任一项所述的二次电池，其特征在于，S1组分可选为LiFe 1-n*y/2M yPO4的化合物，其中n、y、M如权利要求3所述定义；
    S2包括LiVO 3、Li 3V 2O 5、Li 4V 3O 8、LiV 3O 8、Li 2VO 3、LiVO 2；V 2O 5、V 2O 3、V 3O 4；以及上述组分相应的Na掺杂物Li 0.95Na 0.05VO 3、Li 2.95Na 0.05V 2O 5、Li 3.95Na 0.05V 3O 8。
  5. 根据权利要求1-4中任一项所述的二次电池，其特征在于，钒元素的含量为1重量％-5重量％，基于所述正极活性材料的重量计；在正极活性材料中，钒元素与锂元素的摩尔比为1：5-20，优选为1：6-10。
  6. 根据权利要求1-5中任一项所述的二次电池，其特征在于，S1组分与S2组分的重量比为3-20：1，优选为4-10：1。
  7. 根据权利要求1-6中任一项所述的二次电池，其特征在于，S1组分的放电平台电压为3.1-4.8V，S2组分的放电平台电压为1.0-3.0V。
  8. 根据权利要求1-7中任一项所述的二次电池，其特征在于，S2组分被碳包覆或者导电聚合物包覆。
  9. 一种电池模块，其特征在于，包括权利要求1-8中任一项所述的二次电池。
  10. 一种电池包，其特征在于，包括权利要求9所述的电池模块。
  11. 一种用电装置，其特征在于，包括选自权利要求1-8中任一项所述的二次电池、权利要求9所述的电池模块或权利要求10所述的电池包中的至少一种。
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