Positive electrode active material, positive electrode sheet, secondary battery and electric device

Abstract

The present application relates to a positive electrode active material, a positive electrode sheet, a secondary battery, and an electric device. The positive electrode active material has a molecular formula of Li 1+x Fe 1-y A y P 1-z Q z a first active material containing a compound of O4 and its modified compound, and a second active material having a molecular formula of Li h Ni j Co k M1 d M2 e O f R g and a second active material comprising the compound of formula (I) and a modified compound thereof. The embodiment of the present application can improve the capacity and cycle performance of a secondary battery.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to Chinese Patent Application No. 202310279207.6, entitled "Positive Electrode Active Material, Positive Electrode Sheet, Secondary Battery, and Electrical Device," filed on March 21, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the technical field of batteries, and more particularly to positive electrode active materials, positive electrode sheets, secondary batteries, and electrical devices. [Background technology]

[0003] Secondary batteries have been widely used due to their advantages of reliable operation, pollution-free, no memory effect, etc. For example, with the increasing emphasis on environmental protection issues and the increasing popularity of new energy vehicles, the demand for power secondary batteries is increasing explosively.

[0004] With the development of new energy fields, the requirements for battery performance are gradually increasing, and how to further improve the capacity and cycle performance of secondary batteries has become an issue that needs to be resolved urgently. Summary of the Invention

[0005] The embodiments of the present application provide a positive electrode active material, a positive electrode sheet, a secondary battery, and an electric device, and the embodiments of the present application can improve the capacity and cycle performance of the secondary battery.

[0006] In a first aspect, embodiments of the present application provide a compound having the molecular formula Li 1+x Fe 1-y A y P 1-z Q zCompounds of O4 (where 0 ≤ x < 1, 0 ≤ y ≤ 0.8, 0 ≤ z ≤ 0.1, A includes one or more of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Mn, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and Q includes one or more of B, Si, N, S, F, Cl, and Br) and modified compounds thereof as the first active material, and the molecular formula is Li h Ni j Co k M1 d M2 e O f R g (where 0.75 ≤ h ≤ 1.2, 0.38 < j < 1, 0.03 < k < 0.50, 0 < d < 1, 0 ≤ e ≤ 0.2, 1 ≤ f ≤ 2.5, 0 ≤ g ≤ 1, f + g ≤ 3, M1 includes one or two of Mn or Al, M2 includes one or more of the group consisting of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Ba, Y, W, and Nb, and R includes one or more of the group consisting of N, F, S, and Cl) and modified compounds thereof as the second active material, are provided as the cathode active material.

[0007] Thus, in the embodiments of the present application, by specifically selecting the polyanion-based material, when the first active material and the second active material satisfy the range of the above molecular formula, the voltage platforms of the first active material and the second active material are close, both capacities are exerted together, which is advantageous for improving the cycle performance of the secondary battery.

[0008] In some embodiments, a button-type half-cell is constructed by the cathode sheet per unit area containing the cathode active material and the lithium sheet per unit area, charged at a 0.1C rate to obtain a capacity-voltage derivative curve graph. The capacity-voltage derivative curve graph includes a first peak α corresponding to the abscissa v1 with the unit of V and a second peak β corresponding to the abscissa v2 with the unit of V, where α - β ≤ 0.25 and v2 < v1, and optionally, 3.5 < v1 < 4.0 and / or 3.3 < v2 < 3.6.

[0009] As a result, when the above ranges are satisfied, the embodiment of the present application can further improve the capacity and cycle performance of the secondary battery.

[0010] In some embodiments, a button half-cell is formed by charging the positive electrode sheet per unit area containing the first active material and the lithium sheet per unit area at a 0.1 C rate to obtain a first relationship curve graph between the state of charge (SOC) and the corresponding open-circuit voltage (OCV), where m is a voltage platform in the range of 0-10% SOC in V, and mn≦0.15. In some embodiments, a button half-cell is formed by charging the positive electrode sheet per unit area containing the second active material and the lithium sheet per unit area at a 0.1 C rate to obtain a second relationship curve graph between the state of charge (SOC) and the corresponding open-circuit voltage (OCV), where n is a voltage platform in the range of 0-10% SOC in V, and mn≦0.15.

[0011] As a result, when the above ranges are satisfied, the embodiment of the present application can further improve the capacity and cycle performance of the secondary battery.

[0012] In some embodiments, the first active material satisfies at least one of the following conditions: (1) 0≦x≦0.3; (2) 0≦y≦0.7. Thus, when the above ranges are satisfied, the present embodiment can further improve the capacity and cycle performance of the secondary battery.

[0013] In some embodiments, the first active material satisfies at least one of the following conditions: (I) A includes one or more of Ti, V, Ni, Co, and Mg; and (II) Q includes one or more of B, Si, N, and S.

[0014] As a result, when the above ranges are satisfied, the embodiment of the present application can further improve the capacity and cycle performance of the secondary battery.

[0015] In some embodiments, the first active material is LiMn 0.5 Fe 0.5 PO4, LiMn 0.6 Fe 0.4 PO4, LiMn 0.7 Fe 0.3 PO4 and LiFePO4.

[0016] In some embodiments, the second active material satisfies at least one of the following conditions: (a) 0.50≦j<1, optionally 0.50≦j≦0.95; and (b) M2 includes one or more of Mg, Ti, Ba, and Nb. Thus, when the above ranges are satisfied, the embodiment of the present application can further improve the capacity and cycle performance of the secondary battery.

[0017] In some embodiments, the second active material is LiNi 0.50 Co 0.20 Mn 0.30 O2, LiNi 0.70 Co 0.20 Mn 0.10 O2, LiNi 0.50 Co 0.30 Mn 0.20 O2, LiNi 0.60 Co 0.20 Mn 0.20 O2, LiNi 0.80 Co 0.10 Mn 0.10 O2, LiNi 0.90 Co 0.05 Mn 0.05 O2.

[0018] In some embodiments, the weight percent content of the first active material is A% based on the weight of the positive electrode active material, the weight percent content of the second active material is B% based on the weight of the positive electrode active material, and the positive electrode active material satisfies 1.5≦A / B≦9.0, optionally 2.3≦A / B≦4.0. More optionally, 60≦A≦90, even more optionally, 70≦A≦80, and / or 10≦B≦40, even more optionally, 20≦B≦30. Thus, when the above ranges are satisfied, embodiments of the present application can further improve the capacity and cycle performance of secondary batteries.

[0019] In some embodiments, the first active material includes one or two of single-crystalline particles and quasi-single-crystalline particles, and / or the second active material includes one or more of single-crystalline particles, quasi-single-crystalline particles, and polycrystalline particles, optionally with the second active material including polycrystalline particles.

[0020] In a second aspect, an embodiment of the present application provides a positive electrode sheet including a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes the positive electrode active material according to any one of the embodiments of the first aspect of the present application.

[0021] In a third aspect, an embodiment of the present application provides a secondary battery including the positive electrode sheet according to any one of the embodiments of the second aspect of the present application.

[0022] In a fourth aspect, an embodiment of the present application provides an electrical device comprising the secondary battery according to any one of the embodiments of the third aspect of the present application. [Brief explanation of the drawings]

[0023] In order to more clearly explain the technical solutions of the embodiments of the present application, the drawings used in the embodiments of the present application are briefly described below. The drawings described below are only some embodiments of the present application, and it is obvious that those skilled in the art can obtain other drawings from the drawings without any creative efforts. [Figure 1] 1 is a schematic diagram of an embodiment of a secondary battery of the present application. [Figure 2] FIG. 2 is an exploded schematic view of the embodiment of the secondary battery of FIG. [Figure 3] 1 is a schematic diagram of one embodiment of a battery module of the present application. [Figure 4] 1 is a schematic diagram of one embodiment of a battery pack of the present application. [Figure 5] 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4. [Figure 6] 1 is a schematic diagram of one embodiment of an electrical device that includes the secondary battery of the present application as a power source. [Figure 7] 1 is a graph showing the capacity-voltage derivative curve of a secondary battery according to Example 6 of the present application. The drawings are not necessarily drawn to scale. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, with appropriate reference to the drawings, specific disclosed embodiments of the present application will be described in detail, but unnecessary detailed description may be omitted. For example, detailed description of well-known matters and redundant description of actually identical structures may be omitted. This is to avoid unnecessary redundancy in the following description so as to facilitate understanding by those skilled in the art. Furthermore, 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 scope of the claims.

[0025] The "ranges" disclosed in this application are defined by lower and upper limits. A given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of that particular range. Such defined ranges may or may not include the endpoints and may be arbitrarily combined; that is, any lower limit and any upper limit may be combined to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are recited for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if 1 and 2 are recited as minimum range values ​​and 3, 4, and 5 as maximum range values, the ranges of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all contemplated. In this application, unless otherwise specified, a numerical range of "a to b" represents a shorthand notation for any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers "0 to 5" are fully enumerated in this specification, and "0 to 5" is merely a shorthand notation for combinations of these numerical values. Note that when a parameter is expressed as an integer ≧2, this is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0026] Unless otherwise specified, all embodiments and alternative embodiments in this application can be combined with each other to form new technical solutions.

[0027] Unless otherwise specified, all technical features and alternative technical features in this application can be combined with each other to form a new technical solution.

[0028] Unless otherwise specified, all steps in this application may be performed in order or randomly, preferably in order. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or may include steps (b) and (a) performed in order. For example, the method may further include step (c), which 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 may include steps (a), (c), and (b), or may include steps (c), (a), and (b), or may be other cases.

[0029] Unless otherwise specified, the terms "comprise" and "comprises" in this application are open-ended but may also be closed-ended. For example, the terms "comprise" and "comprises" may indicate that the composition may further include or include other components not listed, or may include or include only the listed components.

[0030] Unless otherwise specified, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if A is true (or exists) and B is false (or does not exist), A is false (or does not exist) but B is true (or exists), or A and B are both true (or exist).

[0031] Positive electrode active materials include, but are not limited to, at least one of transition metal oxides, polyanionic materials (e.g., phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue-based materials. Because performance varies depending on the positive electrode active material, it is common to combine multiple types of positive electrode active materials to improve the overall performance of secondary batteries. However, there can be significant differences between different types of active materials, such as differences in voltage platform, which can cause some active materials to decay more quickly during charge / discharge, affecting the capacity and cycle performance of secondary batteries.

[0032] To address the above-mentioned problems, an embodiment of the present application provides a cathode active material that includes a specific polyanionic material and a ternary material, and by approximating the voltage platforms of the two, contributes to the capacity and cycle performance of a secondary battery. Next, the technical solution of the embodiment of the present application will be described.

[0033] positive electrode active material In a first aspect, embodiments of the present application provide a compound having the molecular formula Li 1+x Fe 1-y A y P 1-z Q z and a first active material including a compound of ZnO4 (where 0≦x<1, 0≦y≦0.8, 0≦z≦0.1, A includes one or more of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Mn, Ni, Co, Ga, Sn, Sb, Nb, and Ge), and a modified compound thereof; and a second active material having a molecular formula of Li h Ni j Co k M1 d M2 e O f R g(However, 0.75 ≦ h ≦ 1.2, 0.38 < j < 1, 0.03 < k < 0.50, 0 < d < 1, 0 ≦ e ≦ 0.2, 1 ≦ f ≦ 2.5, 0 ≦ g ≦ 1, f + g ≦ 3, M1 contains one or two of Mn or Al, M2 contains one or more of the group consisting of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Ba, Y, W and Nb, and R contains one or more of the group consisting of N, F, S and Cl), and a second active material containing a modified compound thereof, to provide a positive electrode active material.

[0034] The first active material is a polyanion-based material that forms a special frame structure that is advantageous for the insertion or desorption of metal ions such as lithium ions or sodium ions by two-dimensional van der Waals bonds or 3D structures. The polyanion-based material can not only rapidly conduct metal ions but also stabilize the redox potential of transition metals in the charge-discharge process. In addition, due to the stability of the P-O bond in the polyanion-based material, the stability of oxygen in the lattice is significantly improved, the stability of the polyanion-based material is improved, which is advantageous for improving the stability of the positive electrode active material. When the secondary battery uses the polyanion-based material as the positive electrode active material, the cycle performance of the secondary battery can be improved.

[0035] The second active material is a ternary material, and the nickel Ni, cobalt Co, M1 element and M2 element have a synergistic effect. For example, the nickel element provides capacity to the second active material, the cobalt element enhances the ionic conductivity of the second active material, and the M1 element and M2 element can improve the stability of the second active material. When the secondary battery uses the ternary material as the positive electrode active material, the capacity, voltage platform, etc. of the secondary battery can be significantly improved.

[0036] The combination of a polyanionic material and a ternary material, where the polyanionic material has excellent thermochemical stability and the ternary material has a higher capacity than the polyanionic material, can improve the reliability of secondary batteries while also increasing their capacity. However, conventional polyanionic materials and conventional ternary materials have significant differences in voltage platform, resulting in significant differences in voltage and rate during charge and discharge. In particular, the actual load rate of the ternary material in a mixed system is higher than the rate of the entire secondary battery. Therefore, when the mixed positive electrode active material is subjected to a long-term cycle test, the capacity of the ternary material rapidly decays, affecting the capacity and cycle performance of the secondary battery.

[0037] In the embodiment of the present application, by specifically selecting the polyanion-based material, when the first active material and the second active material satisfy the above molecular formula range, the voltage platforms of the first active material and the second active material become close to each other, allowing both active materials to exert their capacities, which is advantageous for improving the cycle performance of the secondary battery.

[0038] In the embodiment of the present application, the compound may be modified, and the modified compound may be a doping modification and / or a surface coating modification of the material of the compound.

[0039] In an embodiment of the present application, if the positive electrode active material further satisfies one or more of the following conditions, the capacity and cycle performance of the secondary battery can be further improved.

[0040] In some embodiments, a button-type half-cell is formed by a positive electrode sheet per unit area containing the positive electrode active material and a lithium sheet per unit area, and is charged at a 0.1 C rate to obtain a capacity-voltage derivative curve dQ / dV-V graph, the capacity-voltage derivative curve graph having a first peak α in V and corresponding to abscissa v1, and a second peak β in V and corresponding to abscissa v2, wherein α-β≦0.25, v2 <v1である。

[0041] Optionally, 3.5 < v1 < 4.0. Exemplarily, v1 may be 3.6, 3.7, 3.8, 3.9 or a range consisting of any two of the above numerical values.

[0042] Optionally, 3.3 < v2 < 3.6. Exemplarily, v2 may be 3.35, 3.40, 3.42, 3.45, 3.50, 3.53, 3.55, 3.58 or a range consisting of any two of the above numerical values.

[0043] In an embodiment of the present application, the capacity-voltage curve graph is obtained by constructing a button-type half-cell with a positive electrode sheet per unit area containing the positive electrode active material and a lithium sheet per unit area, charging at a 0.1C rate to obtain a voltage value and a capacity value corresponding to the voltage value, calculating for each adjacent data by Δ capacity / Δ voltage value to obtain a corresponding dQ / dV value, using voltage as the abscissa and dQ / dV as the ordinate, and obtaining a dQ / dV-V curve graph.

[0044] In some embodiments, a button-type half-cell is constructed with a positive electrode sheet per unit area containing the first active material and a lithium sheet per unit area, charged at a 0.1C rate to obtain a first relationship curve graph of the state of charge SOC and the corresponding open circuit voltage OCV. In the first relationship curve graph, the voltage platform at 0 to 10% state of charge SOC is denoted as a, and its unit is V. A button-type half-cell is constructed with a positive electrode sheet per unit area containing the second active material and a lithium sheet per unit area, charged at a 0.1C rate to obtain a second relationship curve graph of the state of charge SOC and the corresponding open circuit voltage OCV. In the second relationship curve graph, the voltage platform at 0 to 10% state of charge SOC is denoted as b, and its unit is V. a - b ≤ 0.15.

[0045] The first relationship curve graph is created with the state of charge SOC as the abscissa and the open circuit voltage OCV as the ordinate. The second relationship curve graph is created with the state of charge SOC as the abscissa and the open circuit voltage OCV as the ordinate.

[0046] When a and b satisfy the above relationship, the difference in voltage platform between the first active material and the second active material is not large, and when a cycle test is performed on a cathode active material consisting of both active materials, there is almost no excessive loss in one of the active materials, which indicates that the capacity and cycle performance of the secondary battery can be improved.

[0047] In the embodiment of the present application, the capacity and cycle performance of the secondary battery can be further improved by further selecting the first active material and the second active material.

[0048] In some embodiments, the first active material satisfies 0≦x≦0.3.

[0049] In some embodiments, the first active material satisfies 0≦y≦0.7.

[0050] In some embodiments, the first active material satisfies A includes one or more of Ti, V, Ni, Co, and Mg.

[0051] In some embodiments, the first active material satisfies Q comprises one or more of B, Si, N, and S.

[0052] Illustratively, the first active material is LiMn 0.5 Fe 0.5 PO4, LiMn 0.6 Fe 0.4 PO4, LiMn 0.7 Fe 0.3 PO4 and LiFePO4.

[0053] To further improve the conductivity of the first active material, in some embodiments, the first active material comprises a modified compound, and a specific modification method is coating modification, i.e., the surface of the particles may be coated with a conductive layer that may comprise one or more of carbon, phosphate, and pyrophosphate.

[0054] In some embodiments, the second active material satisfies 0.50≦j<1.

[0055] In some embodiments, the second active material satisfies 0.50≦j≦0.95.

[0056] In some embodiments, the second active material satisfies M2, wherein M2 comprises one or more of Mg, Ti, Ba, and Nb.

[0057] Exemplarily, the second active material is LiNi 0.50 Co 0.20 Mn 0.30 O2, LiNi 0.70 Co 0.20 Mn 0.10 O2, LiNi 0.50 Co 0.30 Mn 0.20 O2, LiNi 0.60 Co 0.20 Mn 0.20 O2, LiNi 0.80 Co 0.10 Mn 0.10 O2, LiNi 0.90 Co 0.05 Mn 0.05 O2.

[0058] In the present application, the types of the first active material and the second active material can be detected using methods and equipment commonly used in the art, for example, by performing phase analysis using X-ray diffraction (XRD) and / or by confirming the chemical elements and their ratios using an inductively coupled plasma emission spectrometer (ICP).

[0059] In an embodiment of the present application, the capacity and cycle performance of the secondary battery can be further improved by making the positive electrode active material further satisfy one or more of the following conditions.

[0060] In some embodiments, the weight percent content of the first active material is A% based on the weight of the positive electrode active material, the weight percent content of the second active material is B% based on the weight of the positive electrode active material, and the positive electrode active material satisfies 1.5≦A / B≦9.0, optionally 2.3≦A / B≦4.0. Exemplarily, A / B may be 1.5, 1.8, 2.0, 2.3, 2.5, 2.8, 3.0, 3.2, 3.5, 3.8, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 9.0, or a range consisting of any two of the foregoing values.

[0061] When the ratio of the mass percent content of the first active material to the mass percent content of the second active material is within the above range, the first active material and the second active material can fully exert a synergistic effect, thereby improving the capacity and cycle performance of the secondary battery.

[0062] In some embodiments, 60≦A≦90, and optionally, 70≦A≦80. Illustratively, the weight percent content of the first active material is 60, 65, 70, 75, 80, 85, 90, or a range consisting of any two of the foregoing values.

[0063] In some embodiments, 10≦B≦40, and optionally, 20≦B≦30. Illustratively, the weight percent content of the second active material is 10, 15, 20, 25, 30, 35, 40, or a range consisting of any two of the foregoing values.

[0064] In an embodiment of the present application, the contents of the first active material and the second active material can be detected using methods and equipment commonly used in this field. For example, 5 to 100 mg of a sample can be weighed, decomposed with concentrated nitric acid as a decomposition reagent, and the phase can be confirmed by X-ray diffraction (XRD). The proportions of elements can then be determined by inductively coupled plasma atomic emission spectroscopy (ICP). The contents of the first active material and the second active material (content of element / mass percentage of the element in the additive) can be calculated from the measured element contents.

[0065] The embodiments of the present application can also further improve the capacity and cycle performance of the secondary battery by specifically selecting the morphology of the positive electrode active material.

[0066] In some embodiments, the first active material includes one or two of single-crystalline particles and quasi-single-crystalline particles.

[0067] In some embodiments, the second active material comprises one or more of single-crystalline particles, quasi-single-crystalline particles, and polycrystalline particles, and optionally, the second active material comprises polycrystalline particles.

[0068] Polycrystalline particles are secondary spherical particles formed by the aggregation of multiple primary particles, which means that the lithium ion transport path is shorter, the rate performance is better, and in a mixed system, the capacity is less likely to deteriorate at higher rates.

[0069] In an embodiment of the present application, the topographies of the first active material and the second active material can be confirmed by scanning with a scanning electron microscope (SEM). For example, a JSM-5610LV scanning electron microscope manufactured by FEI Corporation, USA, is used to observe the topographic structure after vacuum deposition on a sample, and / or a transmission electron microscope (TEM) is used to confirm the microstructure.

[0070] Positive electrode sheet In a second aspect, an embodiment of the present application provides a positive electrode sheet including a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode current collector has two surfaces opposing each other in a thickness direction of the positive electrode current collector, and the positive electrode film layer is provided on any one or two of the two opposing surfaces of the positive electrode current collector.

[0071] In an embodiment of the present application, the positive electrode membrane layer comprises the positive electrode active material according to any one of the embodiments of the first aspect of the present application.

[0072] In some embodiments, the positive electrode film layer optionally further includes a positive electrode conductive agent. In embodiments of the present application, the type of the positive electrode conductive agent is not particularly limited. For example, the positive electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percent content of the positive electrode conductive agent is ≦5 wt% based on the total weight of the positive electrode film layer.

[0073] In some embodiments, the positive electrode film layer optionally further includes a positive electrode binder. In embodiments of the present application, the type of the positive electrode binder is not particularly limited. For example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin. In some embodiments, the mass percent content of the positive electrode binder is ≦5 wt % based on the total weight of the positive electrode film layer.

[0074] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymeric substrate layer and a metal layer formed on at least one surface of the polymeric substrate layer. For example, the metal layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymeric substrate layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0075] The positive electrode film layer is typically obtained by applying a positive electrode slurry to a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0076] secondary battery In a third aspect, embodiments of the present application further provide a secondary battery.

[0077] A secondary battery, also known as a rechargeable battery or storage battery, refers to a battery that can be used continuously after discharging by activating the active material through charging. Generally, a secondary battery includes an electrode assembly including a positive electrode sheet, a negative electrode sheet, and a separator, and an electrolyte. The separator is disposed between the positive electrode sheet and the negative electrode sheet and mainly serves to prevent short circuits between the positive electrode and the negative electrode, while allowing active ions to pass through.

[0078] In the present application, the type of secondary battery is not particularly limited, and for example, the secondary battery may be a lithium ion battery, a sodium ion battery, etc., and in particular, the secondary battery may be a lithium ion secondary battery.

[0079] In some embodiments, the secondary battery includes a positive electrode sheet according to any one of the embodiments of the second aspect of the present application, or a positive electrode sheet including a positive electrode active material according to any one of the embodiments of the first aspect of the present application, thereby enabling the secondary battery according to the embodiments of the present application to achieve both high capacity and cycle performance.

[0080] [Negative electrode sheet] The secondary battery further includes a negative electrode sheet.

[0081] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer including a negative electrode active material and provided on at least one surface of the negative electrode current collector. For example, the negative electrode current collector has two surfaces facing each other in the thickness direction of the negative electrode current collector, and the negative electrode film layer is provided on one or two of the two facing surfaces of the negative electrode current collector.

[0082] The negative electrode active material may be any known negative electrode active material used in secondary batteries in this field. For example, the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include at least one of silicon elemental, silicon oxide, silicon carbon composite, silicon nitrogen composite, and silicon alloy material. The tin-based material may include at least one of tin elemental, tin oxide, and tin alloy material.

[0083] In some embodiments, the negative electrode film layer optionally further includes a negative electrode conductive agent. In embodiments of the present application, the type of the negative electrode conductive agent is not particularly limited. For example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percent content of the negative electrode conductive agent is ≦5 wt% based on the total weight of the negative electrode film layer.

[0084] In some embodiments, the negative electrode film layer optionally further includes a negative electrode binder. In embodiments of the present application, the type of the negative electrode binder is not particularly limited. For example, the negative electrode binder may include at least one of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-soluble acrylic acid-based resin (e.g., polyacrylic acid (PAA), polymethacrylic acid (PMAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percent content of the negative electrode binder is ≦5 wt % based on the total weight of the negative electrode film layer.

[0085] In some embodiments, the negative electrode membrane layer optionally further includes other additives. For example, the other additives may include a thickener, such as sodium carboxymethyl cellulose (CMC), a PTC thermistor material, etc. In some embodiments, the mass percent content of the other additives is ≦2 wt % based on the total weight of the negative electrode membrane layer.

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

[0087] The negative electrode film layer is typically obtained by applying a negative electrode slurry to a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is typically formed by dispersing a negative electrode active material, an optional conductive agent, an optional binder, and other optional auxiliary agents in a solvent and stirring the resulting mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0088] The negative electrode sheet does not exclude additional functional layers other than the negative electrode film layer. For example, in some examples, the negative electrode sheet described in the embodiments of the present application further includes a conductive undercoat layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and provided on the surface of the negative electrode current collector. In other examples, the negative electrode sheet described in the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0089] [Electrolyte] The secondary battery further includes an electrolyte.

[0090] During the charge and discharge process of a secondary battery, active ions are inserted and removed between the positive electrode sheet and the negative electrode sheet, and the electrolyte serves to conduct the active ions between the positive electrode sheet and the negative electrode sheet. In the embodiments of the present application, the type of electrolyte is not particularly limited and can be selected according to actual needs.

[0091] The electrolyte solution includes an electrolyte salt and a solvent, and the types of the electrolyte salt and the solvent are not specifically limited and may be selected according to actual needs.

[0092] When the secondary battery of the present application is a lithium-ion battery, for example, the electrolyte salt may include at least one of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorobisoxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP), but is not limited thereto.

[0093] When the secondary battery of the present application is a sodium ion battery, for example, the electrolyte salt may include at least one of sodium hexafluorophosphate (NaPF), sodium tetrafluoroborate (NaBF), sodium perchlorate (NaClO), sodium hexafluoroarsenate (NaAsF), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalate borate (NaDFOB), sodium bisoxalate borate (NaBOB), sodium difluorophosphate (NaPOF), sodium difluorobisoxalate phosphate (NaDFOP), and sodium tetrafluorooxalate phosphate (NaTFOP), but is not limited thereto.

[0094] By way of example, the solvent may include, but is not limited to, at least one of 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), fluoroethylene carbonate (FEC), 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).

[0095] In some embodiments, the electrolyte solution optionally further includes an additive. For example, the additive may include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive that can improve some battery performance, such as an additive that improves the overcharge performance of the battery, an additive that improves the high-temperature performance of the battery, or an additive that improves the low-temperature performance of the battery.

[0096] [Separator] The secondary battery further includes a separator.

[0097] In some embodiments, the secondary battery further includes a separator. In the present application, the type of separator is not particularly limited, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0098] In some embodiments, the separator may be made of at least one of glass fiber, nonwoven 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 the layers may be the same or different, and are not particularly limited.

[0099] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be fabricated into an electrode assembly by a winding process and / or a stacking process.

[0100] In some embodiments, the secondary battery may include an exterior body that can be used to enclose the electrode assembly and the electrolyte solution.

[0101] In some embodiments, the exterior of the secondary battery may be a hard case such as a hard plastic case, an aluminum case, or a steel case. The exterior 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, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0102] In the present application, the shape of the secondary battery is not particularly limited, and may be cylindrical, rectangular, or any other shape. For example, Fig. 1 shows an example of a secondary battery 5 having a rectangular structure.

[0103] In some embodiments, as shown in FIG. 2 , the exterior body may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates are surrounded to form a receiving cavity. The case 51 has an opening communicating with the receiving cavity, and the cover plate 53 can cover the opening to seal the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly 52 through a winding process and / or a stacking process. The electrode assembly 52 is sealed in the receiving cavity. The electrode assembly 52 is impregnated with an electrolyte. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more and can be adjusted according to needs.

[0104] Methods for manufacturing the secondary battery of the present application are known. In some embodiments, a secondary battery can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. For example, the positive electrode sheet, the separator, and the negative electrode sheet can be wound and / or stacked to form an electrode assembly, which can then be placed in an outer casing, baked, and then injected with an electrolyte. The secondary battery can then be obtained through processes such as vacuum packaging, standing, chemical conversion, and molding.

[0105] In some embodiments of the present application, the secondary battery according to the present application may be assembled into a battery module, and the number of secondary batteries included in the battery module may be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0106] Fig. 3 is a schematic diagram of an example battery module 4. As shown in Fig. 3, in the battery module 4, the plurality of secondary batteries 5 may be arranged in order along the length of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fastening members.

[0107] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in the accommodating space.

[0108] In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0109] 4 and 5 are schematic diagrams of an example battery pack 1. As shown in FIGS. 4 and 5, the battery pack 1 may 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, and the upper box 2 is covered by the lower box 3 and is used to form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0110] Electrical equipment In a third aspect of an embodiment of the present application, there is provided an electric device including at least one of the secondary battery, battery module, or battery pack according to the present application. The secondary battery, battery module, or battery pack may be used as a power source for the electric device or as an energy storage unit for the electric device. The electric device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), a train, a ship, a satellite, an energy storage system, etc.

[0111] The electric device can be selected from a secondary battery, a battery module, or a battery pack depending on its usage needs.

[0112] 6 is a schematic diagram of an example electric device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, that can use a battery pack or battery module to meet the demand for high power and high energy density.

[0113] Another example of the electrical device may be a mobile phone, a tablet computer, a notebook computer, etc. Such electrical devices are usually required to be lightweight and thin, and may use a secondary battery as a power source.

[0114] Example The following examples further illustrate the disclosure of the present application, but these examples are used for interpretation only, as various modifications and variations within the scope of the disclosure will be obvious to those skilled in the art. Unless otherwise specified, all parts, percentages, and ratios described in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized by common methods and can be used as is without further treatment. All instruments used in the examples are commercially available.

[0115] Example 1. Manufacturing of positive electrode sheets An aluminum foil with a thickness of 12 μm was used as the positive electrode current collector.

[0116] The positive electrode active material, carbon black (conductive agent), and polyvinylidene fluoride (PVDF) (binder) were mixed in a weight ratio of 97.5:1.4:1.1 with an appropriate amount of NMP (solvent) and thoroughly stirred to form a uniform positive electrode slurry. The positive electrode slurry was uniformly applied to the surface of the aluminum foil positive electrode current collector, dried, and cold-pressed to obtain a positive electrode sheet.

[0117] 2. Manufacturing of negative electrode sheets A copper foil with a thickness of 8 μm was used as the negative electrode current collector.

[0118] The negative electrode active material, graphite, the binder, styrene butadiene rubber (SBR), the thickener, sodium carboxymethyl cellulose (CMC-Na), and the conductive agent, carbon black (Super P), were mixed in a weight ratio of 96.2:1.8:1.2:0.8 with an appropriate amount of deionized water as the solvent, and stirred thoroughly to form a uniform negative electrode slurry. The negative electrode slurry was then evenly applied to the surface of the copper foil of the negative electrode current collector, dried, and cold-pressed to obtain a negative electrode sheet.

[0119] 3. Separator A porous polyethylene (PE) film was used as the separator.

[0120] 4. Preparation of electrolyte In an environment with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a 1:1 volume ratio to obtain an electrolyte solvent, and then lithium salt was mixed with the resulting solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0121] 5. Secondary battery manufacturing The positive electrode sheet, separator, and negative electrode sheet were stacked in this order so that the separator served to separate the positive electrode sheet and the negative electrode sheet, and then wound to obtain an electrode assembly. The electrode assembly was then placed in an outer case and dried, after which an electrolyte solution was injected, and the assembly was subjected to processes such as vacuum packaging, standing, chemical conversion, and molding to obtain a lithium ion battery.

[0122] Examples 2 to 17 and Comparative Examples In Examples 2 to 17 and the comparative example, lithium ion batteries were manufactured by the same method as in Example 1, except that they differ from Example 1 in that at least one of the type and content of the first active material and the type and content of the second active material was adjusted.

[0123] The data for the examples and comparative examples are shown in Tables 1 to 3.

[0124] Test Method 1. Cycle performance test of secondary batteries At 25°C, the secondary battery prepared above was charged at a constant current of 0.33 C to a charge cutoff voltage of 4.3 V, then charged at a constant voltage until the current reached 0.05 C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.33 C to a discharge cutoff voltage of 2.5 V, and its initial capacity C0 was recorded. It was then charged at 0.33 C and discharged at 1 C, recording the discharge capacity Cn per cycle. It was stopped until the cycle capacity retention rate (i.e., Cn / C0 × 100%) reached 80%, and the number of cycles was recorded. It was shown that the higher the number of cycles, the better the cycle performance of the secondary battery.

[0125] Test results The test results are shown in Tables 1 to 3.

[0126] [Table 1]

[0127] [Table 2]

[0128] [Table 3]

[0129] In Tables 1 to 3, the material types were specifically as follows: The chemical formula of the first active material 1-1 is LiMn 0.6 Fe 0.4 It was PO4. The chemical formula of the first active material 1-2 was LiFePO4. The chemical formula of the second active material 2-3 is LiNi 0.50 Co 0.30 Mn 0.20 It was O2. The chemical formula of the second active material 2-4 is LiNi 0.60 Co 0.20 Mn 0.20 It was O2. The chemical formula of the second active material 2-5 is LiNi 0.80 Co 0.10 Mn 0.10 It was O2. The chemical formula of the second active material 2-6 is LiNi 0.90 Co 0.05 Mn 0.05 It was O2. The chemical formula of the second active material 2-7 is LiNi 0.90 Co 0.08 Mn 0.02 It was O2.

[0130] In Tables 1 to 3, the calculation formula for "deterioration / improvement of cycle life" is M / N-1, where M is the number of cycles when the cycle capacity in the example has decreased to 80% of the initial capacity, and N is the number of cycles when the cycle capacity in Comparative Example 1 (or Comparative Example 2) has decreased to 80% of the initial capacity.

[0131] As can be seen from Tables 1 to 3, in Comparative Examples 1 and 2, a polyanionic material was used as the positive electrode active material, and the cycle performance was relatively poor. Referring to FIG. 7, compared to the comparative examples, the positive electrode active material according to the examples of the present application uses a polyanionic material with a specific molecular formula in combination with a ternary material with a specific molecular formula, which makes the voltage platforms of the first active material and the second active material close to each other, allowing both active materials to exert their capacities, which is advantageous for improving the cycle performance of the secondary battery.

[0132] Although illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions, and modifications can be made to the embodiments without departing from the spirit, principles, and scope of the present application. [Explanation of symbols]

[0133] 1 battery pack 2 Upper Box 3 Lower Box 4 Battery Module 5 Secondary battery 6. Electrical Equipment 51 cases 52 Electrode assembly 53 Lid plate

Claims

1. The molecular formula is Li １＋ｘ Fe １－ｙ A ｙ P １－ｚ Q ｚ O ４ (wherein 0≦x<1, 0≦y≦0.8, 0≦z≦0.1, A includes one or more of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Mn, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and Q includes one or more of B, Si, N, S, F, Cl, and Br) and modified compounds thereof; and The molecular formula is Li ｈ Ni ｊ Co ｋ M1 ｄ M2 ｅ O ｆ R ｇ and a second active material including a compound of the formula (wherein 0.75≦h≦1.2, 0.38<j<1, 0.03<k<0.50, 0<d<1, 0≦e≦0.2, 1≦f≦2.5, 0≦g≦1, f+g≦3; M1 includes one or two of Mn or Al; M2 includes one or more elements selected from the group consisting of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Ba, Y, W, and Nb; and R includes one or more elements selected from the group consisting of N, F, S, and Cl) or a modified compound thereof.

2. A button-type half-cell is formed by a positive electrode sheet per unit area containing the positive electrode active material and a lithium sheet per unit area, and is charged at a rate of 0.1 C to obtain a capacity-voltage derivative curve graph, and the capacity-voltage derivative curve graph shows: The unit is V, and the abscissa v １ A first peak α corresponding to The unit is V, and the abscissa v ２ and a second peak β corresponding to α−β≦0.25, v2<v1, Optionally, 3.5<v １ < 4.0, and / or 3.3<v ２ 2. The cathode active material of claim 1, wherein R1 is 0.05 or 1.

05.

3. A button-type half-cell is formed by the positive electrode sheet per unit area containing the first active material and the lithium sheet per unit area, and is charged at a rate of 0.1 C to obtain a first relationship curve graph between the state of charge SOC and the corresponding open circuit voltage OCV, in which a voltage platform m in the range of 0 to 10% state of charge SOC is defined as a voltage platform m, and its unit is V; A button-type half-cell is formed by the positive electrode sheet per unit area containing the second active material and the lithium sheet per unit area, and is charged at a rate of 0.1 C to obtain a second relationship curve graph between the state of charge SOC and the corresponding open circuit voltage OCV, in which the voltage platform in the second relationship curve graph between 0% and 10% state of charge SOC is n, and its unit is V; The positive electrode active material according to claim 1 or 2, wherein m-n≦0.

15.

4. The first active material is (1) 0≦x≦0.3; (2) 0≦y≦0.7; The positive electrode active material according to claim 1 , which satisfies at least one of the following conditions:

5. The first active material is (I) A comprises one or more of Ti, V, Ni, Co, and Mg; (II) Q comprises one or more of B, Si, N, and S; The positive electrode active material according to claim 1 , which satisfies at least one of the following conditions:

6. The first active material is LiMn ０．５ Fe ０．５ P.O. ４ , LiMn ０．６ Fe ０．４ P.O. ４ , LiMn ０．７ Fe ０．３ P.O. ４ and LiFePO ４ The positive electrode active material of claim 1 , comprising one or more of:

7. The second active material is (a) 0.50≦j<1, optionally 0.50≦j≦0.95; (b) M2 comprises one or more of Mg, Ti, Ba, and Nb; The positive electrode active material according to claim 1 , which satisfies at least one of the following conditions:

8. The second active material is LiNi ０．５０ Co ０．２０ Mn ０．３０ O ２ , LiNi ０．７０ Co ０．２０ Mn ０．１０ O ２ , LiNi ０．５０ Co ０．３０ Mn ０．２０ O ２ , LiNi ０．６０ Co ０．２０ Mn ０．２０ O ２ , LiNi ０．８０ Co ０．１０ Mn ０．１０ O ２ , LiNi ０．９０ Co ０．０５ Mn ０．０５ O ２ The cathode active material of claim 1 , comprising one or more of:

9. the mass percent content of the first active material is A% based on the mass of the positive electrode active material; the mass percent content of the second active material is B% based on the mass of the positive electrode active material; The positive electrode active material has a composition satisfying the following conditions: 1.5≦A / B≦9.0, optionally 2.3≦A / B≦4.0; Further alternatively, 60≦A≦90, even more alternatively, 70≦A≦80, and / or 9. The cathode active material of claim 1, wherein 10≦B≦40, and even more preferably 20≦B≦30.

10. the first active material includes one or two of single-crystal particles and quasi-single-crystal particles; and / or 10. The cathode active material of claim 1, wherein the second active material comprises one or more of single-crystal particles, quasi-single-crystal particles, and polycrystalline particles, and optionally the second active material comprises polycrystalline particles.

11. 11. A positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises the positive electrode active material according to claim 1.

12. A secondary battery comprising the positive electrode sheet according to claim 11.

13. An electrical device comprising the secondary battery of claim 12.

Images