Positive electrode active material and preparation method thereof, positive electrode plate, battery and electric device

Abstract

The invention provides a positive active material and a preparation method thereof, a positive pole piece, a battery and an electric device. The positive electrode active material disclosed by the invention comprises (1-a) LiNi < x > M < 1y > M < 2 > (1-x-y-z) Nb < z > O < 2 >. ALi < 2 > MnO < 3 >, m1 comprises one or two elements of Mn and Al; m2 comprises one or more of transition metal elements except the Mn element, the Ni element and the Nb element. The positive electrode active material provided by the invention can improve the cycling stability of the battery and the battery capacity after cycling.

Description

Positive electrode active material, preparation method thereof, positive electrode sheet, battery and electrical device Technical Field

[0001] This application relates to the technical field of lithium secondary batteries, and particularly relates to a positive electrode active material, a preparation method of the positive electrode active material, a positive electrode sheet, a battery and an electrical device. Background Art

[0002] In recent years, with the increasingly wide application range of lithium secondary batteries, lithium secondary batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind and solar power stations, as well as in multiple fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. Due to the great development of lithium secondary batteries, the cycle performance and capacity of the batteries need to be improved urgently.

[0003] Summary of the Invention

[0004] This application is made in view of the above problems, and its purpose is to provide a positive electrode active material, a preparation method of the positive electrode active material, a positive electrode sheet, a battery and an electrical device. The positive electrode active material of this application improves the cycle stability of the battery and the battery capacity after cycling.

[0005] To achieve the above object, in the first aspect of this application, a positive electrode active material is provided, including (1 - a)LiNi x M1 y M2 (1-x-y-z) Nb z O2·aLi2MnO3; wherein,

[0006] M1 includes one or both elements of Mn and Al;

[0007] M2 includes one or more of transition metal elements other than Mn element, Ni element and Nb element;

[0008] 0 < a < 1; 0.6 ≤ x < 1, 0 ≤ y < 0.4, 0 < z ≤ 0.15, and 0.6 < x + y + z ≤ ı.

[0009] Although the conventional lithium-rich manganese-based positive electrode active material has a relatively high theoretical capacity, as the battery charge-discharge cycle progresses, part of the Li2MnO3 phase decomposes, resulting in a rapid decay of the battery capacity after cycling.

[0010] In this application, by doping an appropriate amount of Nb element and optionally doping M1 element and M2 element into the lithium-rich manganese-based positive electrode active material, it is beneficial to improve the particle fragmentation of the material, stabilize the crystal lattice structure of the material, improve the cycle stability of the battery, thereby inhibiting the decay of the battery capacity after cycling, and improving the battery capacity after cycling. And, this application further improves the battery capacity by increasing the content of Ni element.

[0011] In any embodiment, 4≤x / z≤14, and may be 6≤x / z≤10. Thus, a content ratio of Ni to Nb in the solid solution within a certain range is beneficial to improving the cycle stability and capacity of the battery, thereby increasing the battery capacity after cycling.

[0012] In any embodiment, 0.7≤x≤0.85. Thus, the cycle stability and capacity of the battery are improved, thereby increasing the battery capacity after cycling.

[0013] In any embodiment, 0.05≤z≤0.15, and may be 0.1≤z≤0.15. Thus, the cycle stability and capacity of the battery are improved, thereby increasing the battery capacity after cycling.

[0014] In any embodiment, 0.05≤a≤0.6, optionally 0.1≤a≤0.5. Thus, the solid solution of the lithium-rich manganese-based positive electrode active material contains a certain proportion of relatively stable layered LiNi x M1 y M2 (1-x-y-z) Nb z O2 and Li2MnO3 with higher lithium content and higher capacity improve the cycle stability and capacity of the battery and improve the battery capacity after cycling.

[0015] In any embodiment, M2 includes one or more of Co, Mo, and Zr; optionally, M2 includes Co. Thus, doping M2 is beneficial to improving the cycle stability of the battery.

[0016] In any embodiment, the positive electrode active material includes a polycrystalline material, and the primary particles of the polycrystalline material have a particle size greater than or equal to 0.1 μm and less than or equal to 1.5 μm, optionally greater than 0.3 μm and less than or equal to 1.5 μm, and more preferably greater than or equal to 0.4 μm and less than or equal to 1 μm. As a result, during the battery charge and discharge cycle, the volume change of the material can be slowed down, the degree of particle breakage can be reduced, and the cycle stability of the battery can be improved.

[0017] In any embodiment, the volume average particle size Dv50 of the positive electrode active material is 1-10 μm; and / or,

[0018] The specific surface area of ​​the positive electrode active material is 0.2-2m 2 / g; and / or,

[0019] The tap density of the positive electrode active material is 1.5-2.5g / cm 3 .

[0020] The second aspect of the present application also provides a method for preparing a positive electrode active material, comprising the following steps:

[0021] Providing a solution containing a nickel source, the solution optionally also containing a source of an M1 element and / or a source of an M2 element;

[0022] reacting the solution with an alkaline solution to obtain a precipitate;

[0023] The precipitate is mixed with a lithium source and a niobium source, and calcined to obtain a positive electrode active material;

[0024] Among them, the positive electrode active material includes (1-a) LiNi x M1 y M2 (1-x-y-z) Nb z O2·aLi2MnO3, wherein M1, M2, a, x, y and z are as defined in the first aspect of the present application.

[0025] Therefore, the present application improves the material particle breakage, stabilizes the material lattice structure, and improves the battery's cycling stability by doping an appropriate amount of Nb and optionally doping M1 and M2 elements, thereby suppressing the battery capacity decay after cycling and increasing the battery capacity after cycling. Furthermore, the present application further increases the battery capacity by increasing the Ni content. Furthermore, the method of the present application is simple, efficient, safe, highly operable, and adaptable, making it easy to mass-produce.

[0026] In any embodiment, the molar ratio of nickel in the solution to niobium in the niobium source is 4-14, and can be 6-10.

[0027] In any embodiment, the content of nickel in the solution is 0.1-1 mol / L, optionally 0.2-0.8 mol / L; and / or,

[0028] In the solution, the content of M1 element is 0-0.9 mol / L, optionally 0-0.7 mol / L; and / or,

[0029] In the solution, the content of the M2 element is 0-0.3 mol / L, and can be optionally 0-0.1 mol / L.

[0030] In any embodiment, the molar ratio of lithium in the lithium source to niobium in the niobium source is 7-32, and can be 10-22.

[0031] In any embodiment, the alkaline solution includes sodium hydroxide and / or NH3·H2O; and / or,

[0032] The calcination temperature is 700°C-800°C; and / or,

[0033] The roasting time is 4-15 hours.

[0034] The third aspect of the present application provides a positive electrode plate, comprising the positive electrode active material of the first aspect of the present application or the positive electrode active material prepared by the method of the second aspect of the present application.

[0035] The fourth aspect of the present application provides a battery, comprising the positive electrode active material of the first aspect of the present application, the positive electrode active material prepared by the method of the second aspect of the present application, or the positive electrode plate of the third aspect of the present application.

[0036] In any embodiment, the battery may include, but is not limited to, a secondary battery, a battery module, or a battery pack.

[0037] The fifth aspect of the present application provides an electrical device comprising the battery of the fourth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0039] FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .

[0040] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0041] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0042] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.

[0043] FIG6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0044] Explanation of reference numerals: 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 housing; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0045] Below, with appropriate reference to the accompanying drawings, the embodiments of the positive electrode active material and its preparation method, the positive electrode sheet, the secondary battery, the battery module, the battery pack and the electric device of the present application are specifically disclosed in detail. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0046] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0047] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0048] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0049] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which indicates that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0050] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may indicate that other components not listed may also be included or that only the listed components are included.

[0051] Unless otherwise specified, the term "or" is used in this application to be 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 any of the following conditions are met: 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).

[0052] Unless otherwise specified, in this application, the term "solid solution" is a homogeneous mixture of multiple crystalline solids that share a common crystal lattice. A solid solution is usually composed of multiple atoms or molecules that share a common crystal lattice. x M1 y M2 (1-x-y-z) Nb z O2 and Li2MnO3 have a common lattice structure.

[0053] Unless otherwise specified, in the present application, the term "volume average particle size Dv50" refers to a particle size at which the cumulative volume reaches 50% from the smallest particle size side in a volume-based particle size distribution.

[0054] [Secondary battery]

[0055] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged to activate the active materials after discharge and continue to be used.

[0056] Typically, a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the battery's charge and discharge process, active ions (such as lithium ions) are embedded and released back and forth between the positive and negative electrode sheets. The separator is set between the positive and negative electrode sheets, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The electrolyte between the positive and negative electrode sheets mainly plays the role of conducting active ions.

[0057] [Positive electrode active material]

[0058] One embodiment of the present application provides a positive electrode active material, including (1-a) LiNi x M1 y M2 (1-x-y-z) Nb z O2·aLi2MnO3; among them,

[0059] M1 includes one or two elements of Mn and Al;

[0060] M2 includes one or more transition metal elements other than Mn, Ni and Nb;

[0061] a is typically greater than 0 and less than 1; x is typically greater than or equal to 0.6 and less than 1; y is typically greater than or equal to 0 and less than 0.4; z is typically greater than 0 and less than or equal to 0.15; and the sum of x, y, and z is greater than 0.6 and less than or equal to 1.

[0062] It should be noted that, for convenience, the atomic ratio of oxygen in the positive electrode active material composition formula is expressed as 2 or 3, but a certain degree of non-stoichiometric ratio may exist. In addition, the molar ratio of elements in the positive electrode active material composition formula is the ratio of materials charged during the production stage.

[0063] Although conventional lithium-rich manganese-based positive electrode active materials have a high theoretical capacity, as the battery charge and discharge cycle proceeds, part of the Li2MnO3 phase decomposes, resulting in rapid attenuation of the battery capacity after cycling.

[0064] Although the mechanism remains unclear, the applicant unexpectedly discovered that by doping with an appropriate amount of Nb and optionally with M1 and M2 elements, the present invention improves material fragmentation, stabilizes the material lattice structure, and enhances battery cycling stability, thereby suppressing post-cycling battery capacity decay and increasing post-cycling battery capacity. Furthermore, the present invention further enhances battery capacity by increasing the Ni content.

[0065] In some embodiments, 4≤x / z≤14, optionally 6≤x / z≤10, for example, x / z is 4, 4.5, 5, 5.5, 6, 6.4, 7, 7.6, 8, 8.4, 9, 9.6, 10, 10.5, 11, 11.4, 12, 12.3, 13, 13.5, 14, and any range thereof. Thus, a content ratio of Ni to Nb in the solid solution within a certain range is beneficial to improving the cycle stability and capacity of the battery, thereby increasing the battery capacity after cycling.

[0066] In some embodiments, 0.7≤x≤0.85, such as 0.7, 0.73, 0.8, 0.85, and any range thereof, thereby improving the cycle stability and capacity of the battery, thereby improving the battery capacity after cycling.

[0067] In some embodiments, 0.05≤z≤0.15, optionally 0.1≤z≤0.15, such as 0.05, 0.07, 0.1, 0.12, 0.15, and any range thereof, thereby improving the cycle stability and capacity of the battery, thereby improving the battery capacity after cycling.

[0068] In some embodiments, 0.05≤a≤0.6, optionally 0.1≤a≤0.5, for example, a is 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 and any range of the above values. Thus, the lithium-rich manganese-based positive electrode active material solid solution contains a certain proportion of relatively stable layered LiNi x M1 y M2 (1-x-y-z) Nb z O2 and Li2MnO3 with higher lithium content and higher capacity improve the cycle stability and capacity of the battery and improve the battery capacity after cycling.

[0069] In some embodiments, batteries on the market are typically aged after assembly. After battery aging, some layered Li2MnO3 phases may transform into molten salt phase LiMn2O4 at voltages above 4.5 V. In this case, in composition analysis, 0<a≤0.4.

[0070] In some embodiments, M2 includes one or more of Co, Mo, and Zr; optionally, M2 includes Co. Thus, doping M2 is beneficial to improving the cycle stability of the battery.

[0071] In some embodiments, the positive electrode active material comprises a solid solution (1-a)LiNi x M1 y M2 (1- x-y-z) Nb z O2·aLi2MnO3; wherein, M1, M2, a, x, y and z are as defined above in this application.

[0072] In some embodiments, the volume average particle size Dv50 of the positive electrode active material is 1-10 μm, for example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm and any range consisting of the above values.

[0073] In some embodiments, the volume average particle size Dv50 is measured using a Mastersizer 3000 laser particle size analyzer according to the method in the national standard GB / T19077-2016.

[0074] In some embodiments, the positive electrode active material includes a polycrystalline material, and the particle size of the primary particles of the polycrystalline material is greater than or equal to 0.1 μm and less than or equal to 1.5 μm, optionally greater than 0.3 μm and less than or equal to 1.5 μm, and more optionally greater than or equal to 0.4 μm and less than or equal to 1 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm and any range of the above values. Thus, during the charge and discharge cycle of the battery, the volume change of the material can be slowed down, the degree of particle breakage can be reduced, and the cycle stability of the battery can be improved.

[0075] In some embodiments, the primary particle size is measured using a Sigma 300 scanning electron microscope according to the method in JY / T010-1996.

[0076] In some embodiments, the specific surface area of ​​the positive electrode active material is 0.2-2 m 2 / g; and / or, the tap density of the positive electrode active material is 1.5-2.5g / cm 3 .

[0077] In some embodiments, the specific surface area of ​​the positive electrode active material may be, for example, 0.2 m 2 / g, 0.5m 2 / g, 0.8m 2 / g、1m 2 / g, 1.2m 2 / g, 1.5m 2 / g, 1.7m 2 / g, 1.9m 2 / g, 2m 2 / g and any range consisting of the above numerical values.

[0078] In some embodiments, the tap density of the positive electrode active material may be, for example, 1.5 g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 , 2.0g / cm 3 , 2.1g / cm 3 , 2.2g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3 and any range consisting of the above numerical values.

[0079] In some embodiments, the specific surface area of ​​the positive electrode active material can be measured using the BET method. For example, the specific surface area can be measured using a BELSORP-mini II from BEL Japan based on nitrogen absorption at liquid nitrogen temperature (77K).

[0080] In some embodiments, the tap density of the positive electrode active material may be measured using a general tap density measuring device, for example, the tap density may be measured using Logan's Tap-2S.

[0081] In some embodiments, the interlayer spacing of the positive electrode active material is 0.45-0.50 nm.

[0082] [Method for preparing positive electrode active material]

[0083] One embodiment of the present application provides a method for preparing a positive electrode active material, comprising the following steps:

[0084] Providing a solution containing a nickel source, the solution optionally also containing a source of an M1 element and / or a source of an M2 element;

[0085] reacting the solution with an alkaline solution to obtain a precipitate;

[0086] The precipitate is mixed with a lithium source and a niobium source, and calcined to obtain a positive electrode active material;

[0087] Among them, the positive electrode active material includes (1-a) LiNi x M1 y M2 (1-x-y-z) Nb z O2·aLi2MnO3, wherein M1, M2, a, x, y and z are as defined above in this application.

[0088] Therefore, the present application improves the material particle breakage, stabilizes the material lattice structure, and improves the battery's cycle stability by doping the lithium-rich manganese-based positive electrode material with an appropriate amount of Nb and optionally with M1 and M2 elements, thereby suppressing the battery capacity decay after cycling and increasing the battery capacity after cycling. In addition, the present application further increases the battery capacity by increasing the Ni content. Moreover, the method of the present application is simple, efficient, safe, highly operable and adaptable, and is convenient for large-scale production.

[0089] In any embodiment, the molar ratio of nickel in the solution to niobium in the niobium source is 4-14, and can be 6-10, for example, 4, 4.5, 5, 5.5, 6, 6.4, 7, 7.6, 8, 8.4, 9, 9.6, 10, 10.5, 11, 11.4, 12, 12.3, 13, 13.5, 14 and any range consisting of the above values.

[0090] In some embodiments, the content of nickel in the solution is 0.1-1 mol / L, optionally 0.2-0.8 mol / L, for example, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, 0.85 mol / L, 0.9 mol / L, 0.95 mol / L and any range consisting of the above values; and / or,

[0091] In the solution, the content of the M1 element is 0-0.9 mol / L, optionally 0-0.7 mol / L, for example, 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.56 mol / L, 0.6 mol / L, 0.67 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L and any range consisting of the above values; and / or,

[0092] In the solution, the content of M2 element is 0-0.3mol / L, which can be optionally 0-0.1mol / L, for example, 0.005mol / L, 0.01mol / L, 0.02mol / L, 0.03mol / L, 0.04mol / L, 0.05mol / L, 0.06mol / L, 0.07mol / L, 0.08mol / L, 0.1mol / L, 0.13mol / L, 0.14mol / L, 0.16mol / L, 0.2mol / L, 0.22mol / L, 0.25mol / L, 0.27mol / L, 0.28mol / L and any range consisting of the above numerical values.

[0093] In some embodiments, the molar ratio of lithium in the lithium source to niobium in the niobium source is 7-32, and can be optionally 10-22, for example, 7, 8, 9, 10, 11, 13, 15, 16, 18, 20, 21, 22, 24, 25, 26, 28, 29, 30, 31, 32, and any range consisting of the above values.

[0094] In some embodiments, the alkaline solution includes sodium hydroxide and / or NH3·H2O; and / or,

[0095] The calcination temperature is 700° C.-800° C., for example, 700° C., 720° C., 750° C., 780° C., 800° C., and any range thereof; and / or,

[0096] The calcination time is 4-15 hours, for example, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 12 hours, 13 hours, 14 hours, 15 hours and any range thereof.

[0097] In some embodiments, the nickel source, the source of the M1 element, the source of the M2 element, the lithium source, and the niobium source each independently include, but are not limited to, nitrates, chlorides, sulfates, nitrites, sulfites, hydroxides, and oxides.

[0098] In some embodiments, the ratio of the molar amount of sodium hydroxide in the alkaline solution to the total molar amount of the nickel source, the source of the M1 element, and the source of the M2 element in the solution is 0.95:1-20:1, for example, 1:1, 2:1, 4:1, 6:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1, 19:1, and any range consisting of the above values.

[0099] In some embodiments, the ratio of the molar amount of ammonia water (calculated as NH3·H2O) in the alkaline solution to the total molar amount of the nickel source, the source of the M1 element, and the source of the M2 element in the solution is 0.56:1-11.8:1, for example, 0.7:1, 1:1, 2:1, 4:1, 6:1, 8:1, 10:1, 11:1, and any range consisting of the above values.

[0100] In some embodiments, the volume ratio of the solution to the alkaline solution is 1:1-2:1, such as 1.2:1, 1.6:1, 1.8:1, 2:1, and any range thereof.

[0101] [Positive electrode]

[0102] The positive electrode sheet generally 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 includes the positive electrode active material mentioned above or the positive electrode active material prepared by the above method.

[0103] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0104] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0105] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0106] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0107] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0108] [Negative electrode]

[0109] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0110] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0111] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0112] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0113] In some embodiments, the negative electrode film layer may further include a binder. For example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0114] In some embodiments, the negative electrode film layer may further include a conductive agent. For example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0115] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0116] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0117] [Electrolytes]

[0118] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0119] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0120] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0121] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0122] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0123] [Isolation film]

[0124] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0125] 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 can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0126] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0127] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0128] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0129] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape. For example, FIG1 shows a secondary battery 5 with a square structure as an example.

[0130] In some embodiments, referring to FIG2 , the outer package may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0131] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0132] Figure 3 shows an example battery module 4. Referring to Figure 3 , within the battery module 4, multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple secondary batteries 5 may be secured together using fasteners.

[0133] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0134] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0135] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0136] In the present application, the battery may include but is not limited to the aforementioned secondary battery, battery module, and battery pack.

[0137] In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0138] As an electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0139] Figure 6 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0140] [Example]

[0141] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0142] Example 1

[0143] 1. Preparation of positive electrode active material: 0.235 mol manganese nitrate, 0.045 mol cobalt nitrate and 0.63 mol nickel nitrate were dissolved in 1000 ml deionized water to obtain a solution; 500 mL of 4 M NaOH aqueous solution and 116 mL of 10.2 M NH3·H2O aqueous solution were added to the solution, stirred to obtain a precipitate, filtered and collected, and dried at 110 ° C to constant weight to obtain a precursor material. All the precursor materials were mixed evenly with 1.1 mol LiOH and 0.045 mol Nb2O5, and calcined at 750 ° C for 9 h to obtain Nb-doped high nickel-rich lithium positive electrode active material 0.9LiNi 0.7 Mn 0.15 Co 0.05 Nb 0.1 O2·0.1Li2MnO3.

[0144] 2. Preparation of positive electrode sheets: The positive electrode active material, conductive agent acetylene black, and binder PVDF (polyvinylidene fluoride) are mixed in a mass ratio of 8:1:1 with N-methylpyrrolidone NMP as solvent to form a slurry, which is then coated on aluminum foil. After drying at 80°C for 12 hours, the slurry is rolled and punched into discs with a diameter of 10 mm as the positive electrode sheets.

[0145] 3. Negative electrode: metallic lithium sheet.

[0146] 4. Isolation membrane: PE diaphragm is used.

[0147] 5. Preparation of electrolyte: Ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1, and then LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L.

[0148] 6. Preparation of battery: Assemble the above-mentioned positive electrode sheet, separator, negative electrode sheet and electrolyte into a CR2032 button battery.

[0149] The secondary battery preparation methods of Examples 2-20 and Comparative Examples 1-5 are similar to those of Example 1, but the preparation methods and product parameters of the positive electrode active materials are different. The differences between the preparation methods of the positive electrode active materials and Example 1 are detailed in Table 1, and the differences between the product parameters and Example 1 are detailed in Table 2.

[0150] Except for the parameters in Table 1, the preparation method of the positive electrode active material of Example 15 is the same as that of Example 13, except that 500 mL of 4M NaOH aqueous solution is changed to 450 mL and the calcination process is changed to calcination at 800° C. for 10 h.

[0151] Except for the parameters in Table 1, the preparation method of the positive electrode active material of Example 16 is the same as that of Example 11, except that 500 mL of 4M NaOH aqueous solution is changed to 400 mL and the calcination process is changed to calcination at 800° C. for 10 h.

[0152]

[0153]

[0154]

[0155] Test Case

[0156] (1) Primary particle size test: The particle size was measured using a Sigma 300 scanning electron microscope according to the method in JY / T010-1996.

[0157] (2) 0.5C battery capacity test: At room temperature, the battery was tested on the Xinwei battery test system, and constant current charge and discharge were performed three times at a current density of 0.5C. The charge and discharge voltage range was 2.5-4.8V, and the third discharge capacity value was taken as the 0.5C battery capacity.

[0158] (3) Test of battery capacity after 100 cycles at 0.5C: Continue to cycle the battery according to the method in item (3) above until 100 cycles are completed. The discharge capacity at the 100th cycle is taken as the battery capacity after 100 cycles at 0.5C.

[0159] (4) Cyclic performance test: Based on the results of (3) and (4), the cycle capacity retention rate at 0.5C for 100 cycles was calculated according to the following formula;

[0160] The results of item (1) are shown in Table 2, and the results of items (2)-(4) are shown in Tables 3-4.

[0161] Table 3: Test results of battery capacity after 100 cycles at 0.5C for Examples 1-20 and Comparative Examples 1-5

[0162] As can be seen from Table 3, compared with comparative examples 1-5, the battery capacity of the battery in the embodiment of the present application after 100 cycles at 0.5C is significantly higher.

[0163] Table 4: Test results of cycle capacity retention, 0.5C battery capacity and battery capacity after 100 cycles at 0.5C for Examples 1-20

[0164] From Table 4 we can see that:

[0165] Compared with Example 4, the cycle capacity retention rate of Examples 1-3, 6, and 8 of the present application is significantly improved, the 0.5C battery capacity is significantly improved, and the battery capacity after 100 cycles at 0.5C is significantly improved; compared with Example 5, the cycle capacity retention rate of Examples 1-3, 6, and 8 of the present application is significantly improved, and the battery capacity after 100 cycles at 0.5C is significantly improved;

[0166] Compared with Examples 7, 12, 14, and 19, the 0.5C battery capacity of Examples 1-3, 6, and 8 of the present application is significantly improved, and the battery capacity after 100 cycles at 0.5C is significantly improved;

[0167] Compared with Examples 13, 15, and 16, the cycle capacity retention rate of Examples 1-3, 6, and 8 of the present application is significantly improved, the 0.5C battery capacity is significantly improved, and the battery capacity after 100 cycles at 0.5C is significantly improved; compared with Example 11, the 0.5C battery capacity of Examples 1-3, 6, and 8 of the present application is significantly improved, and the battery capacity after 100 cycles at 0.5C is significantly improved;

[0168] Compared with Example 10, the cycle capacity retention rate of Examples 1-3, 6, and 8 of the present application is significantly improved, the 0.5C battery capacity is significantly improved, and the battery capacity after 100 cycles at 0.5C is significantly improved; compared with Example 9, the 0.5C battery capacity of Examples 1-3, 6, and 8 of the present application is significantly improved, and the battery capacity after 100 cycles at 0.5C is significantly improved.

[0169] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A positive electrode active material comprising (1-a) LiNi x M1 y M2 (1-x-y- z) Nb z O2·aLi2MnO3; among them, The M1 includes one or two elements of Mn and Al; The M2 includes one or more of transition metal elements other than Mn element, Ni element and Nb element; 0 < a < 1; 0.6 ≤ x < 1, 0 ≤ y < 0.4, 0 < z ≤ 0.15, and 0.6 < x + y + z ≤ 1.

2. The positive electrode active material according to claim 1, wherein 4 ≤ x / z ≤ 14, and optionally 6 ≤ x / z ≤ 10.

3. The positive electrode active material according to claim 1 or 2, wherein 0.7≤x≤0.85。 4. The positive electrode active material according to any one of claims 1 to 3, wherein 0.05 ≤ z ≤ 0.15, and optionally 0.1 ≤ z ≤ 0.

15.

5. The positive electrode active material according to any one of claims 1 to 4, wherein 0.05 ≤ a ≤ 0.6, and optionally 0.1 ≤ a ≤ 0.

5.

6. The positive electrode active material according to any one of claims 1 to 5, wherein The M2 includes one or more of Co, Mo and Zr; optionally, the M2 includes Co element.

7. The positive electrode active material according to any one of claims 1 to 6, wherein The positive electrode active material includes a polycrystalline material, and the particle size of the primary particles of the polycrystalline material is greater than or equal to 0.1 μm and less than or equal to 1.5 μm, optionally greater than 0.3 μm and less than or equal to 1.5 μm, and more optionally greater than or equal to 0.4 μm and less than or equal to 1 μm.

8. The positive electrode active material according to any one of claims 1 to 7, wherein The volume average particle size Dv50 of the positive electrode active material is 1 - 10 μm; and / or, The specific surface area of ​​the positive electrode active material is 0.2-2m 2 / g; and / or, The tap density of the positive electrode active material is 1.5-2.5 g / cm 3 .

9. A method for preparing a positive electrode active material, comprising the following steps: Providing a solution containing a nickel source, and the solution may further optionally contain a source of M1 element and / or a source of M2 element; Reacting the solution with an alkali solution to obtain a precipitate; Mixing the precipitate with a lithium source and a niobium source, and calcining to obtain a positive electrode active material; in, The positive electrode active material includes (1-a) LiNi x M1 y M2 (1-x-y- z) Nb z O2·aLi2MnO3, wherein M1, M2, a, x, y and z are as defined in any one of claims 1 to 8.

10. The method according to claim 9, wherein: The molar ratio of nickel element in the solution to niobium element in the niobium source is 4 - 14, and optionally 6 - 10.

11. The method according to claim 9 or 10, wherein: In the solution, the content of nickel element is 0.1 - 1 mol / L, and optionally 0.2 - 0.8 mol / L; and / or, In the solution, the content of M1 element is 0 - 0.9 mol / L, and optionally 0 - 0.7 mol / L; and / or, In the solution, the content of M2 element is 0 - 0.3 mol / L, and optionally 0 - 0.1 mol / L.

12. The method according to any one of claims 9 to 11, wherein: The molar ratio of lithium element in the lithium source to niobium element in the niobium source is 7 - 32, and optionally 10 - 22.

13. The method according to any one of claims 9 to 12, wherein: The alkali solution includes sodium hydroxide and / or NH3·H2O; and / or, The temperature of the calcination is 700°C - 800°C; and / or, The time of the calcination is 4 - 15 hours.

14. A positive electrode sheet, comprising the positive electrode active material according to any one of claims 1 to 8 or the positive electrode active material prepared by the method according to any one of claims 9 to 13.

15. A battery, comprising the positive electrode active material according to any one of claims 1 to 8, the positive electrode active material prepared by the method according to any one of claims 9 to 13 or the positive electrode sheet according to claim 14.

16. An electrical device, comprising the battery according to claim 15.

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