Secondary battery, battery module, battery pack, and electrical device

Abstract

This application relates to a secondary battery. The secondary battery includes a positive electrode plate, a negative electrode plate, and an electrolytic solution. The positive electrode plate includes 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 contains a positive electrode active material. The positive electrode active material includes S1) a lithium-containing compound having an olivine structure, and S2) a vanadium oxide represented by the general formula j(M2O)·kVO X where M is one or more of alkali metals, 0 ≦ j ≦ 1, 1 ≦ k ≦ 5, 1 ≦ x ≦ 2.5, and the difference in discharge plateau voltage between S1 and S2 is E, and 0.2V ≦ E ≦ 2.8V. The secondary battery has very good low-temperature performance while ensuring excellent cycle performance and gram capacity, and can maintain a very good low-temperature capacity retention rate even at a high discharge rate, for example.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and particularly to secondary batteries, battery modules, battery packs, and electrical devices.

Background Art

[0002] In recent years, as the application range of lithium-ion batteries has become increasingly wide, the market's requirements for lithium-ion batteries have been on the rise. While demanding energy density, the research and development and industrialization of high-rate low-temperature-resistant batteries have attracted more and more attention in the industry. Military applications of devices such as electromagnetic interference, electromagnetic rail launchers, and magnetrons, and civilian applications such as in-vehicle cold start power supplies in low-temperature regions, high-power electric tools, and power supplies for communication base stations in extremely cold regions can be cited. The above application scenarios have more stringent requirements for low-temperature performance and rate performance. The cathode material of the battery is a crucial factor that determines the electrochemical performance, safety performance, energy density, etc. of the battery system.

[0003] Phosphate-based cathode materials having an olivine structure (LiMPO4, where M can be one or a combination of two or more of Fe, Co, Zn, Ni, Cu, and Mn) are one of the currently commercially available cathode materials on a large scale. They can exhibit high gram capacity, have a high discharge voltage, and the output of the discharge voltage is stable. The cost of synthetic raw materials is low, the lifespan is excellent, the safety performance is good, and they are widely applied in the fields of power batteries and energy storage batteries.

[0004] As shown by tests, LiMPO4-type cathode materials have very low electron conductivity and ion conductivity. Taking the lithium iron phosphate material as an example, the drawbacks of LiFePO4 are low electron conductivity and ion conductivity, which are respectively 10 -9 S·cm1 and 10 -10 ~10 -15It is cm2·s1. When applied to a lithium-ion battery as a positive electrode material, its rate performance and low-temperature discharge performance are inferior. Improving the rate performance and low-temperature performance of the material by means such as coating or doping is currently a relatively effective means, but the electrochemical performance still does not yield satisfactory results. Seeking an appropriate low-temperature auxiliary agent and adopting an appropriate composite means is an effective route to improve the lithium iron phosphate positive electrode material.

Summary of the Invention

[0005] This application is made in view of the above problems, and its purpose is that the positive electrode film layer contains a vanadium oxide of the general formula j(M2O)·kVO X By including this, a secondary battery is provided that has excellent cycle performance and gram capacity while having very good low-temperature performance, and can maintain a very good low-temperature capacity retention rate even at a high discharge rate, for example.

[0006] The first aspect of this application is a secondary battery including a positive electrode plate, a negative electrode plate, and an electrolytic solution. The positive electrode plate includes 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 contains 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 of the general formula j(M2O)·kVO X where M is one or more of alkali metals, 0≦j≦1, 1≦k≦5, 1≦x≦2.5, and the difference in discharge plateau voltage between S1 and S2 is E, and 0.2V≦E≦2.8V. A secondary battery is provided.

[0007] Thereby, in this application, since the positive electrode active material contains two specific active materials with specific discharge plateau voltages, the secondary battery has very good low-temperature performance while guaranteeing excellent cycle performance, and can maintain a very good low-temperature capacity retention rate even at a high discharge rate, for example.

[0008] In any embodiment, in component S2, M is selected from one or both of Li and Na, preferably Li, 0 ≦ j / k ≦ 1, preferably 0.2 ≦ j / k ≦ 0.6. Thereby, it is more preferably vanadium oxide, which can contribute to improving the content of active lithium or sodium in the low-temperature promoter, improving the capacity performance of the secondary battery at low temperatures, and maintaining a good low-temperature capacity retention rate at the same time.

[0009] In any embodiment, S1 is a compound of the general formula LiA 1-n*y / 2 M y PO4, where 0 ≦ y ≦ 0.1, A is selected from at least one of Fe, Co, Ni, Cu, Mn, Zn, n is the valence of the M metal, and n = +2, +3, +4 or +5, M is selected from at least one of Cr, Pb, Ca, Sr, Ti, Mg, V, Nb, Zr, A and M are the same or different.

[0010] Thereby, by using the lithium phosphate-based cathode active material of the above type and combining it with vanadium oxide, the low-temperature performance of the battery can be further enhanced, and at the same time, its cycle performance can be guaranteed.

[0011] In any embodiment, component S1 is a compound of LiFe 1-n*y / 2 M y PO4, where y, M and n are as defined above, S2 is LiVO3, Li3V2O5, Li4V3O8, LiV3O8, Li2VO3, LiVO2, V2O5, V2O3, V3O4, and the Li 0.95 Na 0.05 VO3, Li 2.95 Na 0.05 V2O5, Li 3.95 Na 0.05It contains V3O8. By using the above type of lithium phosphate cathode active material and combining it with vanadium oxide, the low-temperature performance of the battery can be further improved while ensuring its cycle performance.

[0012] In any embodiment, based on the weight of the cathode active material, the content of vanadium element is 1 wt% - 5 wt%. In the cathode active material, the molar ratio of vanadium element to lithium element is 1:5 - 20, preferably 1:6 - 10. Thereby, by controlling the content and relative ratio of lithium and vanadium in the cathode active material, the low-temperature performance of the battery can be further improved.

[0013] In any embodiment, the weight ratio of S1 component to S2 component is 3 - 30:1, preferably 4 - 10:1. Thereby, by controlling the weight ratio of S1 component to 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 guaranteed.

[0014] In any embodiment, the discharge plateau voltage of S1 component is 3.1 - 4.8V, and the discharge plateau voltage of S2 component is 1.0 - 3.0V. Thereby, by controlling the discharge plateau voltages of S1 component and 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 guaranteed.

[0015] In any embodiment, S2 component is coated with carbon or coated with a conductive polymer. Thereby, by controlling the composition of 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 guaranteed.

[0016] The second aspect of the present application further provides a battery module including the secondary battery according to the first aspect of the present application.

[0017] The third aspect of the present application provides a battery pack including the battery module according to the second aspect of the present application.

[0018] A fourth aspect of the present application provides an electrical device including at least one selected from the secondary battery according to the first aspect of the present application, the battery module according to the second aspect of the present application, or the battery pack according to the third aspect of the present application.

[0019] In the secondary battery of the present application, a lithium-containing compound and vanadium oxide are included in the positive electrode active material, and by ensuring that the difference in discharge plateau voltage between the two is within a specific range, the secondary battery can have very good low-temperature performance while ensuring excellent cycle performance. For example, even at a high discharge rate, it can maintain a good low-temperature capacity retention rate, and the capacity of the battery at low temperature can be more preferably exhibited.

Brief Description of the Drawings

[0020]

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Embodiments for Carrying Out the Invention

[0021] Hereinafter, embodiments specifically disclosing the positive electrode active material of the present application, a method for manufacturing the same, a positive electrode plate, a secondary battery, a battery module, a battery pack, and an electrical device will be described in detail with appropriate reference to the drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and duplicate descriptions of substantially the same structure may be omitted. This is to avoid the following description from becoming unnecessarily redundant and to enable those skilled in the art to easily understand. Also, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the gist described in the claims.

[0022] The "range" disclosed in the present application is limited in the form of a lower limit and an upper limit. A predetermined range is limited by selecting one lower limit and one upper limit, and the selected lower limit and upper limit define the boundary of the predetermined range. The range thus limited may include both end values or may not include both end values, and can be arbitrarily combined, that is, any lower limit can form a range in combination with any upper limit. For example, when ranges of 60 to 120 and 80 to 110 are listed for a certain parameter, ranges of 60 to 110 and 80 to 120 are also understood to be expected. Also, when 1 and 2 are listed as the values of the minimum range and 3, 4, and 5 are listed as the values of the maximum range, ranges of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all predictable. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviated expression of any combination of real numbers between a and b, and both a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are listed in this specification, and "0 to 5" is simply an abbreviated expression of the combination of these numerical values. Note that when it is described that a certain parameter is an integer ≧ 2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0023] Unless otherwise specifically stated, all embodiments and alternative embodiments of the present application can be combined with each other to form new technical solutions.

[0024] Unless otherwise specified, all technical features of this application and optional technical features can be combined with each other to form new technical solutions.

[0025] Unless otherwise specified, all steps of this application may be performed in sequence or randomly, but preferably in sequence. For example, the fact that the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b).

[0026] Unless otherwise specified, the terms "comprise" and "include" as used in this application represent an open-ended form, but may also be in a closed-ended form. For example, the "comprise" and "include" can mean that they may further comprise or include other components not listed, or may comprise or include only the listed components.

[0027] Unless otherwise specified, the term "or" in this application is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the conditions that 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) satisfies the condition "A or B".

[0028] The phosphate-based cathode material with an olivine structure (LiMPO4, where M can be one or a combination of two or more of Fe, Co, Zn, Ni, and Cu) is one of the currently commercially available cathode materials on a large scale. It can exhibit a high gram capacity and has a high discharge voltage. Moreover, the output of the discharge voltage is stable, the cost of synthetic raw materials is low, the lifespan is excellent, the safety performance is good, and it is widely applied in the fields of power batteries and energy storage batteries.

[0029] As shown by tests, the LiMPO4-type cathode material has very low electronic conductivity and ionic conductivity. Taking the lithium iron phosphate material as an example, the disadvantages of LiFePO4 are that its electronic conductivity and ionic conductivity are low, being 10 -9 S·cm1 and 10 -10 ~10 -15 cm2·s1 respectively. When applied to a lithium-ion battery as a cathode material, its rate performance and low-temperature discharge performance are inferior. Although means such as coating or doping are currently relatively effective means to improve the rate performance and low-temperature performance of the material, the electrochemical performance still does not achieve satisfactory results. Seeking appropriate low-temperature aids and adopting appropriate composite means is an effective route to improve the lithium iron phosphate cathode material. As the applicant has found through research, the secondary battery according to the first aspect of the present application contains a lithium-containing compound and vanadium oxide in its cathode active material, and by ensuring that the difference in the discharge plateau voltage between the two is within a specific range, the secondary battery can have excellent cycle performance and gram capacity while having very good low-temperature performance. For example, even at a high discharge rate, it can maintain a good low-temperature capacity retention rate, and the battery at a low SOC exhibits excellent power performance.

[0030] Secondary battery The first aspect of the present application is a secondary battery including a positive electrode plate, a negative electrode plate, and an electrolyte. The positive electrode plate includes 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 contains a positive electrode active material, and the positive electrode active material includes S1) a lithium-containing compound with an olivine structure, and S2) a general formula of j(M2O)·kVOX It includes vanadium oxide, M is one or more of alkali metals, 0 ≦ j ≦ 1, 1 ≦ k ≦ 5, 1 ≦ x ≦ 2.5, the difference in discharge plateau voltage between S1 and S2 is E, and a secondary battery with 0.2V ≦ E ≦ 2.8V is provided.

[0031] Without being limited to any theory, currently, when the battery discharges to a low state of charge (SOC), the discharge power of the battery rapidly decays, and this phenomenon is more obvious during low-temperature discharge. Improving the discharge power under the low SOC discharge conditions of the battery becomes particularly important. In the present application, by ensuring that the positive electrode active material contains a lithium-containing compound and vanadium oxide, and the difference in discharge plateau voltage between the two is within a specific range, the battery can provide energy output through the reaction of vanadium oxide at low temperature, and at the same time, the internal temperature of the cell can be increased, the discharge capacity of the cell can be enhanced, and the secondary battery can have very good low-temperature performance while ensuring excellent cycle performance. For example, even at a high discharge rate, a good low-temperature capacity retention rate can be maintained, and the capacity of the battery at low temperature can be more preferably exerted.

[0032] In some embodiments, in component S2, M is selected from one or both of Li or Na, optionally Li, 0 ≦ j / k ≦ 1, preferably 0.2 ≦ j / k ≦ 0.6. Thereby, it is more preferably vanadium oxide, which contributes to improving the capacity performance of the secondary battery at low temperature and maintaining a good low-temperature capacity retention rate at the same time.

[0033] In some embodiments, S1 is a compound of the general formula LiA 1-n*y / 2 M y PO4, 0 ≦ y ≦ 0.1, A is selected from at least one of Fe, Co, Ni, Cu, Mn, Zn, n is the valence of the M metal, n = +2, +3, +4 or +5 valence, M is selected from at least one of Cr, Pb, Ca, Sr, Ti, Mg, V, Nb, Zr, A and M are the same or different.

[0034] Thereby, by using the lithium phosphate-based cathode active material of the above type and combining it with vanadium oxide, the low-temperature performance of the battery is further improved, and at the same time its cycle performance is guaranteed.

[0035] In some embodiments, the S1 component is optionally LiFe 1-n*y / 2 M y PO4 compound, where y, M, n are as defined above, preferably 0 < y ≤ 0.1, M and n are as defined above, more preferably LiFePO4, LiFe 1-n*y / 2 M y PO4, still more 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 as defined above, 0.005 ≤ x ≤ 0.1, most preferably LiFePO4, LiTi y Fe 1-n*y / 2 PO4, where y and n are as defined above.

[0036] In some embodiments, S2 is LiVO3, Li3V2O5, Li4V3O8, LiV3O8, Li2VO3, Li3VO 4、 LiVO2, V2O5, V2O3, V3O4, and the corresponding Na dopants of the above components, namely Li 3-x Na x VO4, Li 1-x Na x V3O8 and Li 1-x Na x VO3, etc., 0.005 ≤ x ≤ 0.1, preferably Li3VO4, V2O5, LiV3O8, LiVO3 and its Na dopant, namely Li 0.95 Na0.05 VO3, Li 2.95 Na 0.05 V2O5, Li 3.95 Na 0.05 It is V3O8. Since the forms of acid groups formed by vanadium and oxygen are very rich, such as orthovanadate groups, metavanadate groups, pyrovanadate groups, polyvanadate groups, etc., the S2 component is not limited to the above compounds. Thereby, by using the above type of lithium phosphate cathode active material and combining it with vanadium oxide, the low-temperature performance of the battery can be further improved while ensuring its cycle performance.

[0037] In some embodiments, based on the weight of the cathode active material, the content of vanadium element is 1 wt% - 5 wt%, preferably 2 wt% - 4 wt%. In the cathode active material, the molar ratio of lithium element to vanadium element is 5 - 20:1, preferably 6 - 10:1. Thereby, by controlling the contents and relative ratios of lithium and vanadium in the cathode active material, the low-temperature performance of the battery can be further improved.

[0038] In some embodiments, the weight ratio of S1 component to S2 component is 3 - 20:1, preferably 4 - 10:1. Thereby, by controlling the weight ratio of S1 component to 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 guaranteed.

[0039] In some embodiments, the discharge plateau voltage of the S1 component is 3.1 - 4.8V, and the discharge plateau voltage of the S2 component is 1.0 - 3.0V. Thereby, by controlling the discharge plateau voltages 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 guaranteed. When the S1 or S2 component has multiple discharge plateau voltages, the discharge plateau voltage of S1 or S2 described in the present invention is its highest discharge plateau voltage.

[0040] In some embodiments, the S2 component is coated with carbon or a conductive polymer. Thereby, 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 to guarantee the cycle performance of the battery. In some embodiments, the surface-modified carbon or conductive polymer can be selected from one or more of amorphous carbon, graphene, graphitized carbon layer, polyacetylene, polypyrrole, polythiophene, polyphenylene, polyphenylacetylene, polyaniline, polydopamine, etc.

[0041] In some embodiments, the average volume particle size Dv50 of the S1 component is 1 to 5 μm. The average volume particle size Dv50 is the particle size corresponding to the case where the volume cumulative distribution percentage of the sample reaches 50%, and is measured by adopting a laser particle size analyzer, for example, Mastersizer 3000 type laser particle size analyzer manufactured by Malvern Instruments, UK.

[0042] In some embodiments, the positive electrode active material can be manufactured by methods known in the art. For example, the positive electrode active material can be obtained by physically mixing the S1 component and the S2 component, or by coating the surface of the S1 component with the S2 component or doping the surface of the S1 component with the S2 component.

[0043] In some embodiments, when coating the surface of the S1 component with the S2 component or doping the surface of the S1 component with the S2 component, the positive electrode active material is usually manufactured as follows. A lithium source, an A metal source, a phosphorus source, and an M metal source are mixed in a certain molar ratio to form a mixture. A carbon source and an auxiliary agent are added to the mixture, and the above mixture is polished to form a uniform mixture slurry. The obtained slurry is spray-dried to obtain a precursor. The precursor is fired in an inert atmosphere to obtain an S1 component material coated with carbon. The obtained S1 component material and an optionally selected lithium source and a metal vanadium source are mixed in a certain ratio, and a certain amount of carbon source is further supplemented, and the firing is continued in an inert atmosphere to obtain the positive electrode active material of the present application.

[0044] In the mixture, the lithium source, the A metal source, the phosphorus source, and the M metal are mixed so that the molar ratio of Li:A:P:M is 0.95-1:0.95-1:0.95-1:0-0.05.

[0045] The lithium source is one or a combination of 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.

[0046] The A metal source includes an iron source, a copper source, a cobalt source, a nickel source, a zinc source, and a manganese source, preferably an iron source and a manganese source. For example, it is one or a combination of iron (manganese) phosphate, ferrous (manganese) phosphate, ferrous (manganese) pyrophosphate, ferrous (manganese) carbonate, ferrous (manganese) chloride, ferrous (manganese) hydroxide, ferrous (manganese) nitrate, ferrous (manganese) oxalate, ferric (manganese) chloride, ferric (manganese) hydroxide, ferric (manganese) nitrate, ferric (manganese) citrate, and ferric (manganese) oxide.

[0047] The phosphorus source is one or a combination of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, iron phosphate, and lithium dihydrogen phosphate.

[0048] The M metal source further includes one or a combination of compounds of copper, vanadium, magnesium, aluminum, zinc, manganese, titanium, zirconium, niobium, chromium, and rare earth element compounds.

[0049] The carbon source is one or a combination of citric acid, malic acid, tartaric acid, oxalic acid, salicylic acid, succinic acid, glycine, ethylenediaminetetraacetic acid, sucrose, and glucose.

[0050] The solvent is one or a combination of more than one of water, methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, n-pentanol, n-hexanol, n-heptanol, acetone, butanone, butanedione, pentanone, cyclopentanone, hexanone, cyclohexanone, cycloheptanone.

[0051] The auxiliary agent is one or a combination of more than one of polyvinyl alcohol, polyethylene glycol, polyoxyethylene, sodium polystyrene sulfonate, polyoxyethylene nonyl phenyl ether, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide.

[0052] The vanadium metal source is one or more of vanadium pentoxide, vanadium dioxide, vanadium metal powder, vanadium chloride, ammonium metavanadate.

[0053] Next, the secondary battery of the present application will be described with appropriate reference to the drawings.

[0054] Normally, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are repeatedly inserted and desorbed between the positive electrode plate and the negative electrode plate. The electrolyte plays a role of conducting ions between the positive electrode plate and the negative electrode plate. The separator is provided between the positive electrode plate and the negative electrode plate, mainly plays a role of preventing short circuit between the positive and negative electrodes, and at the same time can allow ions to pass through.

[0055] [Positive Electrode Plate] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, and the positive electrode film layer contains a positive electrode active material. FIG. 1 is a cross-sectional SEM diagram of the electrode plate containing the positive electrode active material of the present invention, and FIG. 2 is an EDS surface scanning diagram of the electrode plate containing the positive electrode active material of the present invention for characterizing the distribution of phosphorus, vanadium, and oxygen elements.

[0056] As an example, the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0057] In some embodiments, as the positive electrode current collector, a metal foil or a composite current collector can be employed. For example, as the metal foil, an aluminum foil can be used. The composite current collector can 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 a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material substrate (such as substrates of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0058] In some embodiments, the positive electrode active material can also include other positive electrode active materials known in the art for batteries. As an example, the other positive electrode active material can further include at least one of materials such as olivine-structured lithium-containing phosphates, lithium transition metal oxides, and modified compounds thereof. In addition to these materials, other conventional materials used as positive electrode active materials for batteries may also be used. These other positive electrode active materials can be used alone or in combination of two or more. Examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (abbreviated as NCM 333 as well), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM 523(also abbreviated as), LiNi 0.5 Co 0.25 Mn 0.25 O2 (NCM 211 (also abbreviated as), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM 622 (also abbreviated as), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM 811 (also abbreviated as)), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 O2) and at least one of its modified compounds, etc., but not limited thereto. Examples of olivine-structured lithium-containing phosphates include lithium iron phosphate (e.g., LiFePO4 (also abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon, but not limited thereto. Based on the total weight of the positive electrode film layer, the weight ratio of the positive electrode active material in the positive electrode film layer is 80 to 100% by weight.

[0059] In some embodiments, the positive electrode film layer optionally further includes a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of vinylidene fluoride, tetrafluoroethylene, and propylene, a terpolymer of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene, a copolymer of tetrafluoroethylene and hexafluoropropylene, and a fluorine-containing acrylate resin. Based on the total weight of the positive electrode film layer, the weight ratio of the binder in the positive electrode film layer is 0 to 20% by weight.

[0060] In some embodiments, the positive electrode film layer further selectively includes a conductive agent. As an example, the conductive agent can include one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Based on the total weight of the positive electrode film layer, the weight ratio of the conductive agent in the positive electrode film layer is 0 to 20 wt%.

[0061] In some embodiments, the positive electrode plate can be manufactured by the following method. Components for manufacturing the above-described positive electrode plate, such as a positive electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry. The solid content of the positive electrode slurry is 40 to 80 wt%, and the viscosity at room temperature is adjusted to 5000 to 25000 mPa·s. The positive electrode slurry is applied to the surface of the positive electrode current collector, baked, and then cold-pressed by a cold rolling machine to form a positive electrode plate. The unit surface density of the applied positive electrode powder is 150 to 350 g / m 2 and the compression density of the positive electrode plate is 1 to 5 g / cm 3 and preferably 2.0 to 2.6 g / cm 3 .

[0062] [Negative Electrode Plate] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0063] As an example, the negative electrode current collector has two surfaces facing each other in its own thickness direction, and the negative electrode film layer is provided on either one or both of the two facing surfaces of the negative electrode current collector.

[0064] In some embodiments, a metal foil or a composite current collector can be employed as the negative electrode current collector. For example, a copper foil can be used as the metal foil. The composite current collector can include a metal layer formed on at least one surface of a polymer material base layer and a polymer material substrate. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material substrate (such as substrates of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0065] In some embodiments, the type of the negative electrode active material can be a negative electrode active material for a battery known in the art. As an example, the negative electrode active material can include at least one of materials such as artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material can be selected from at least one of elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials used as the negative electrode active material of the battery may also be used. These negative electrode active materials can be used alone or in combination of two or more. Based on the total weight of the negative electrode film layer, the weight ratio of the negative electrode active material in the negative electrode film layer is 80 to 100% by weight.

[0066] In some embodiments, the negative electrode film layer optionally further comprises a binder. The binder can 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). Based on the total weight of the negative electrode film layer, the weight ratio of the binder in the negative electrode film layer is 0 to 20% by weight.

[0067] In some embodiments, the negative electrode film layer optionally further comprises a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Based on the total weight of the negative electrode film layer, the weight ratio of the conductive agent in the negative electrode film layer is 0 to 20% by weight.

[0068] In some embodiments, the negative electrode film layer optionally further comprises other auxiliaries such as a thickening agent (for example, sodium carboxymethyl cellulose (CMC-Na)). Based on the total weight of the negative electrode film layer, the weight ratio of the other auxiliaries in the negative electrode film layer is 0 to 15% by weight.

[0069] In some embodiments, a negative electrode plate can be manufactured by the following method. Components for manufacturing the above-described negative electrode plate, such as a negative electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (for example, deionized water) to form a negative electrode slurry, the solid content of the negative electrode slurry is 30 to 70 wt%, the viscosity at room temperature is adjusted to 2000 to 10000 mPa·s, the obtained negative electrode slurry is applied to a negative electrode current collector, and after undergoing cold pressing such as a drying process and rolling, a negative electrode plate is obtained. The unit surface density of the applied negative electrode powder is 75 to 220 g / m 2 and the compression density of the negative electrode plate is 1.2 to 2.0 g / cm 3 is.

[0070] [Electrolyte] The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. In the present application, the type of the electrolyte is not specifically limited and can be selected according to needs. For example, the electrolyte may be liquid, gel-like or all-solid.

[0071] In some embodiments, an electrolytic solution is adopted as the electrolyte. The electrolytic solution contains an electrolyte salt and a solvent.

[0072] In some embodiments, the electrolyte salt can 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 difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalato phosphate (LiDFOP), and lithium tetrafluorooxalato phosphate (LiTFOP). The concentration of the electrolyte salt is usually 0.5 to 5 mol / L.

[0073] In some embodiments, the solvent can be selected from one or more of 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 (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).

[0074] In some embodiments, the electrolyte further selectively contains additives. For example, the additives can include negative electrode film-forming additives and positive electrode film-forming additives, and can also include additives that can improve a predetermined performance of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high-temperature performance or low-temperature performance of the battery, and the like.

[0075] [Separator] In some embodiments, the secondary battery further includes a separator. In the present application, there is no particular limitation on the type of the separator, and any known separator having a porous structure with good chemical stability and mechanical stability can be selected.

[0076] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, and are not particularly limited.

[0077] In some embodiments, the thickness of the separator is 6 to 40 μm, and optionally 12 to 20 μm.

[0078] In some embodiments, the positive electrode plate, the negative electrode plate, and the separator can be manufactured as an electrode assembly by a winding process or a lamination process.

[0079] In some embodiments, the secondary battery can include an exterior body. The exterior body can be used to package the electrode assembly and the electrolyte.

[0080] In some embodiments, the exterior body of the secondary battery may be a rigid case such as a rigid plastic case, an aluminum case, or a steel case. The exterior body of the secondary battery may be a soft pack such as a pouch-type soft pack. The material of the soft pack may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0081] In the present application, the shape of the secondary battery is not particularly limited, and it may be cylindrical, square, or any other arbitrary shape. For example, FIG. 3 shows a secondary battery 5 having a square structure as an example.

[0082] In some embodiments, referring to FIG. 4, the exterior body can include a case 51 and a cover plate 53. The case 51 can include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates surround to form a housing chamber. The case 51 has an opening communicating with the housing chamber, and the cover plate 53 can cover the opening so as to seal the housing chamber. The positive electrode plate, the negative electrode plate, and the separator can form an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is packaged in the housing chamber. The electrolyte infiltrates the electrode assembly 52. The number of electrode assemblies 52 included in the lithium-ion battery 5 may be one or more, and those skilled in the art can select according to specific actual requirements.

[0083] In some embodiments, the secondary battery can be assembled into a battery module. The number of secondary batteries included in the battery module may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0084] FIG. 5 shows a battery module 4 as an example. Referring to FIG. 5, in the battery module 4, a plurality of secondary batteries 5 may be arranged in sequence along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other form. Further, the plurality of secondary batteries 5 may be fixed by fastening members.

[0085] Optionally, the battery module 4 can further include a housing having an accommodation space, and the plurality of secondary batteries 5 are accommodated in the accommodation space.

[0086] In some embodiments, the above battery module can be further assembled into a battery pack. The number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0087] FIGS. 6 and 7 show a battery pack 1 as an example. Referring to FIGS. 6 and 7, the battery pack 1 can include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box includes an upper box 2 and a lower box 3. The upper box 2 covers the lower box 3 and can form a sealed space for accommodating the battery module 4. The plurality of battery modules 4 can be arranged in the battery box according to any form.

[0088] Furthermore, the present application further provides an electrical device including 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 as an energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as secondary battery electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric cars, ships, satellites, energy storage systems, and the like.

[0089] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to the needs in its use.

[0090] FIG. 8 shows an electrical device as an example. The electrical device is, for example, a secondary battery electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the requirements for high power and high energy density for the secondary battery of the electrical device, a battery pack or a battery module can be adopted.

[0091] Another example of the device may be a mobile phone, a tablet, a notebook computer, etc. The device usually requires weight reduction and thinning, and a secondary battery can be adopted as a power source.

[0092] Examples In order to more clearly illustrate the technical problems to be solved, technical solutions, and beneficial effects of the present application, the present application will be further described in detail below in conjunction with examples and drawings. Obviously, the described examples are only some examples of the present application, not all examples. The following description of at least one exemplary embodiment is actually only for the purpose of explanation and does not limit the present application and its application in any way. Based on the examples in the present application, all other examples obtained without creative efforts by those skilled in the art belong to the protection scope of the present application.

[0093] When specific technologies or conditions are not specified in the examples, the technologies or conditions described in the literature of the relevant field or the product specifications shall be followed. When the manufacturer of the reagents or equipment used is not specified, they are all ordinary commercially available products.

[0094] I. Manufacturing Examples Manufacturing Example 1 (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, PEG, and citric acid surfactant with a weight ratio of 3:1:0.3 were added to the mixture. Glucose accounted for 10% of the total weight of all raw materials, and citric acid accounted for 1% of the total weight of all raw materials. 1000 mL of water was added as a dispersion medium. Subsequently, the above mixture was ground in a sand mill at 1000 rpm for 4 hours to form a uniform mixture slurry, and the solid content of the slurry was 40%. The obtained slurry was spray-dried by a spray dryer to obtain a precursor of the S1 component.

[0095] (2) The precursor of the S1 component was fired in a nitrogen inert atmosphere (with the oxygen atmosphere controlled within 20 ppm). The heating rate was 10 °C / min, and the temperature was raised at a constant rate to 760 °C, held for 10 h, and then purged with cold nitrogen for 5 h to cool down, and the temperature was lowered until the surface temperature of the material reached 40 °C. The fired material was pulverized by an air flow, and the obtained S1 component had a molecular formula of LiTi 0.005 Fe 0.99 PO4 and an average volume particle size Dv50 of 1.5 um.

[0096] (3) The material of the S1 component, lithium carbonate, ammonium metavanadate, and glucose as a carbon source were further mixed. Based on the total weight of the mixture, the weight ratio of the S1 component was 80%, the weight ratios of lithium carbonate and ammonium metavanadate were 15%, the weight ratio of glucose as a carbon source was 5%, and the molar ratio of lithium carbonate to ammonium metavanadate was 1.5:1.

[0097] (4) The mixture was ball-milled in a ball mill apparatus for 2 hours. Subsequently, the mixture was fired under nitrogen protection conditions, with a heating rate of 10 °C / min, heated at a constant rate up to 560 °C, held for 10 h, and then purged with cold nitrogen for 5 h to cool down until the surface temperature of the material reached 40 °C. The entire firing process was protected by a nitrogen atmosphere, and the oxygen atmosphere of the atmosphere was controlled within 20 ppm. Finally, a positive electrode active material of the present invention coated with 1.5Li2O·VO 2.5 was obtained, and its average volume particle size Dv50 was 1.8 μm.

[0098] Production Examples 2 to 12 The positive electrode active material is similar to the production method of the positive electrode active material in Production Example 1, but the composition of the raw materials and the parameters of the product are adjusted. The details of the different product parameters are as shown in Table 1.

[0099] Production Example 13 In steps (1) and (2) of the production method of the positive electrode active material in Production Example 1, the S1 component was produced. Lithium carbonate, ammonium metavanadate, and glucose as a carbon source were mixed. Based on the total weight of the mixture, the weight ratios of lithium carbonate and ammonium metavanadate were 75%, the weight ratio of glucose as the carbon source was 25%, and the molar ratio of lithium carbonate to ammonium metavanadate was 1.5:1. The mixture was ball-milled in a ball mill apparatus for 2 hours. Subsequently, the mixture was fired under nitrogen protection conditions, with a heating rate of 10 °C / min, heated at a constant rate up to 560 °C, held for 10 h, and then purged with cold nitrogen for 5 h to cool down until the surface temperature of the material reached 40 °C to obtain the S2 component. The entire firing process was protected by a nitrogen atmosphere, and the oxygen atmosphere of the atmosphere was controlled within 20 ppm. The S1 component and the S2 component obtained above were physically mixed at a weight ratio of 8:1 to obtain the positive electrode active material of the present invention. The details of the different product parameters are as shown in Table 1.

[0100] Production Comparative Example 1 Only steps (1) and (2) of Production Example 1 were performed to obtain the S1 component and used it as the positive electrode active material. The details of the different product parameters are as shown in Table 1.

[0101]

Table 1

[0102] II. Applicable Examples Example 1 1) Production of the positive electrode plate The positive electrode active material powder, conductive agent, and binder of Production Example 1 were dry-mixed at a weight ratio of 96:2:2, and an NMP solvent was added. Stir vigorously until a uniform positive electrode slurry is formed by the action of a vacuum mixer. The solid content of the slurry is 60 wt%, the viscosity at room temperature is adjusted to 8000 mPa·s, the positive electrode slurry is applied to the surface of the aluminum foil of the positive electrode current collector, cold-pressed by a cold rolling machine after baking, and then the positive electrode plate is formed. The unit surface density of the applied positive electrode powder is controlled to 200 g / m 2 as shown in Table 1. The compression density of the positive electrode plate is as shown in Table 1.

[0103] 2) Production of the negative electrode plate Graphite of the negative electrode active material, sodium carboxymethyl cellulose (CMC-Na) as the thickener, styrene-butadiene rubber (SBR) as the binder, and carbon black as the conductive agent were mixed at a mass ratio of 97:1:1:1, deionized water was added, and they were uniformly stirred and mixed to obtain a negative electrode slurry. The solid content of the slurry is 50 wt%, the viscosity at room temperature is adjusted to 4000 mPa·s, the obtained negative electrode slurry is applied to the copper foil, and after passing through a drying process and rolling, a negative electrode plate is obtained. The unit surface density of the applied negative electrode powder is controlled to 145 g / m 2 The compression density of the negative electrode plate was 1.35 g / m 3 at that time.

[0104] 3) Separator A polyethylene film with a thickness of 0.012 mm was used as the separator.

[0105] 4) Production of the electrolyte 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. Subsequently, the well-dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0106] 5) Battery manufacturing The positive electrode plate, separator, and negative electrode plate manufactured above were stacked in sequence, and the separator was interposed between the positive and negative electrode plates to play a role in isolation. Subsequently, it was wound to obtain a bare cell with a capacity of 3 Ah. The bare cell was placed in an outer packaging case, and after drying, 10 g of the electrolyte solution was injected. Through processes such as vacuum packaging, standing, formation, and shaping, a lithium-ion battery was obtained.

[0107] The secondary batteries of Examples 2 to 13 and the secondary battery of Comparative Example 1 were similar to the manufacturing method of the secondary battery of Example 1, but the positive electrode active materials obtained in the corresponding manufacturing examples were used.

[0108] III. Battery performance test 1. Performance test at a low temperature of -20°C At 25°C, first, the battery was charged to 3.65 V at a constant current of 0.5 C, and then charged at a constant voltage of 3.65 V until the current reached 0.025 C. After standing for 2 h, subsequently, the battery was discharged to 2.0 V at a constant current of 1 C, and the discharge capacity was recorded as C0. Then, it was left standing at 25°C for 2 h. Repeatedly, the battery was charged to 3.65 V at a constant current of 0.5 C and charged at a constant current until 0.025 C. The battery was left standing at -20°C for 2 h. Subsequently, the battery was discharged to 2.0 V at a constant current of 1 C, and the discharge capacity was recorded as D1. Then, it was left standing at 25°C for 2 h. Repeatedly, the battery was charged to 3.65 V at a constant current of 0.5 C and charged at a constant current until 0.025 C. The battery was left standing at -20°C for 2 h. Subsequently, the battery was discharged to 2.0 V at a constant current of 3 C, and the discharge capacity was recorded as D3. The capacity retention rates D1 / D0 and D3 / D0 of the cell when discharging at rates of 1 C and 3 C at -20°C were calculated respectively.

[0109] 2. Cycle performance test At 25°C, 1. First, charge the battery at a constant current of 0.5C until 3.65V, 2. Then, charge at a constant voltage of 3.65V until the current reaches 0.025C, record the first charging capacity, 3. Let it stand for 3.2h, 4. Subsequently, discharge the battery at a constant current of 1C until 2.0V, record the first discharge capacity, 5. Then, let it stand at 25°C for 2h, repeat the process of 1 - 4, record the charging capacity and discharge capacity in each cycle process, and divide the 500th discharge capacity by the first discharge capacity to obtain the capacity retention rate of the nth cycle of the battery.

[0110] 3. Test of the gram capacity of the discharge capacity at 0.5C At 25°C, first charge the battery at a constant current of 0.5C until 3.65V, then charge at a constant voltage of 3.65V until the current reaches 0.025C, let it stand for 2h, and then discharge the battery at a constant current of 0.5C until 2.0V, record the discharge capacity as C 放 and record the gram capacity c = C 放 / mass of the positive electrode material.

[0111] IV. Test results of each example and comparative example Manufacture the batteries of each example and comparative example respectively by the above method, measure each performance parameter, and the results are shown in Table 2 below.

[0112]

Table 2

[0113] According to Examples 1 - 7, by coating the surface of LiTi 0.005 Fe 0.99 PO4 to form a coating layer of 1.5Li2O·VO 2.5 the low - temperature performance of the mixed positive electrode material can be improved, and the low - temperature performance is clearly higher than that of Comparative Example 1 in all cases. On the other hand, as the proportion of lithium vanadium oxide increases, the cycle life of the cell becomes shorter. This is mainly because during the process of lithium desorption and lithium insertion of lithium vanadium oxide, the conversion of multiple valences of vanadium elements is involved, and the structural attenuation rate is higher than that of the lithium iron phosphate material. Further analysis of the data shows that 1.5Li2O·VO 2.5When the content is appropriate, it is found that the mixed cathode material has optimal low-temperature discharge performance, and it is shown that the overall performance of the battery is the best under the conditions of Example 3.

[0114] At the same time, lithium vanadium oxide can play a role in replenishing lithium in the cathode, and significantly improve the performance of the gram capacity of the battery. Furthermore, in Example 12, 1.5Li2O·VO 2.5 Na ions were doped into the components of the compound to obtain 1.45Li2O·0.05Na2O·VO 2.5 and the overall performance of the battery could be further improved. This is because Na and Li are homologous elements, the radius of Na ions (0.1 nm) is larger than the radius of Li ions (0.7 nm), and by replacing Li+ with appropriate Na+, the interlayer pitch of the material is widened, providing a larger space for the diffusion of lithium ions in the bulk phase of the material, reducing the diffusion resistance, and improving the rate performance and low-temperature performance of the material.

[0115] In Examples 8 to 11, 0.5Li2O·3VO 2.5 low-temperature aids were adopted. Compared with Examples 1 to 7, since the j value was relatively low, the performance of the gram capacity of the battery decreased, and the degree of low-temperature improvement of the battery improved accordingly. This is because the proportion of the vanadium oxygen matrix in lithium vanadium oxide increased, the resistance in the transmission process of lithium ions decreased, and it had a significant effect on the improvement of low-temperature performance. In Examples 8 to 11, 0.5Li2O·3VO 2.5 As the addition amount of the low-temperature aid increased, a tendency similar to that of Examples 1 to 7 was shown.

[0116] Compared with Example 3, in Example 12, the mixing means of the low-temperature aid and the main material were changed, and a simple physical mixing means was adopted, that is, S1 and S2 were synthesized respectively, and S1 and S2 were combined with other aids in the formulation of the cathode to produce a cathode plate. From the test results, it was found that Example 12 also showed good improvement in low-temperature performance.

[0117] Note that this application is not limited to the above embodiments. The above embodiments are merely examples, and embodiments that have substantially the same configuration within the scope of the technical solution of this application, exhibit the same functions and effects, are all included within the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that those skilled in the art can conceive of are added to the embodiments, and other forms constituted by combining some components in the embodiments are also included within the scope of this application.

Description of Reference Numerals

[0118] 1 Battery pack 2 Upper box 3 Lower box 4 Battery module 5 Secondary battery 51 Case 52 Electrode assembly 53 Top cover

Claims

1. A secondary battery including a positive electrode plate, a negative electrode plate, and an electrolytic solution, wherein the positive electrode plate includes 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 contains a positive electrode active material, and the positive electrode active material includes S1) a lithium-containing compound having an olivine structure, and S2) a vanadium oxide represented by the general formula j(M ２ O)·kV O Ｘ where M is one or more of alkali metals, 0 ≦ j ≦ 1, 1 ≦ k ≦ 5, 1 ≦ x ≦ 2.5, and the difference in discharge plateau voltage between S1 and S2 is E, and 0.2 V ≦ E ≦ 2.8 V.

2. 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, the secondary battery according to Claim 1.

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

4. The S1 component is selectively LiFe １－ｎ＊ｙ／２ M ｙ PO ４ a compound of, where n, y, and M are as defined in claim 3, S2 is LiVO ３ 、Li ３ V ２ O ５ 、Li ４ V ３ O ８ 、LiVO ３ O ８ 、Li ２ VO ３ 、LiVO ２ 、V ２ O ５ 、V ２ O ３ 、V ３ O ４ 、and 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 secondary battery according to any one of claims 1 to 3, characterized by comprising

5. Based on the weight of the positive electrode active material, the content of vanadium element is 1 wt% to 5 wt%, and in the positive electrode active material, the molar ratio of vanadium element to lithium element is 1:5 to 20, preferably 1:6 to 10, the secondary battery according to any one of Claims 1 to 4.

6. The weight ratio of component S1 to component S2 is 3 to 20:1, preferably 4 to 10:1, the secondary battery according to any one of Claims 1 to 5.

7. The discharge plateau voltage of component S1 is 3.1 to 4.8 V, and the discharge plateau voltage of component S2 is 1.0 to 3.0 V, the secondary battery according to any one of Claims 1 to 6.

8. Component S2 is coated with carbon or coated with a conductive polymer, the secondary battery according to any one of Claims 1 to 7.

9. A battery module comprising the secondary battery according to any one of Claims 1 to 8.

10. A battery pack comprising the battery module according to Claim 9.

11. An electrical device comprising at least one selected from the secondary battery according to any one of Claims 1 to 8, the battery module according to Claim 9, or the battery pack according to Claim 10.

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