A modification method of lithium manganese-based positive electrode material, lithium-rich manganese-based positive electrode material, positive electrode sheet, battery cell and secondary battery

Abstract

The present application provides a method for modifying a lithium-manganese-based positive electrode material, a lithium-rich manganese-based positive electrode material, a positive electrode sheet, a battery cell and a secondary battery, and belongs to the field of battery technology. The method for modifying a lithium-manganese-based positive electrode material includes doping the lithium-manganese-based positive electrode material with lithium, and the lithium-doped ions include cations larger than the lithium ion radius, and increasing the manganese content in the lithium-manganese-based positive electrode material to obtain a lithium-rich manganese-based positive electrode material. By replacing part of the lithium sites in the lithium-manganese-based positive electrode material with cations larger than the lithium ion radius, the cations larger than the lithium ion radius can play a supporting role at the lithium site, enhance the energy barrier between transition metal layers, improve the manganese dissolution effect, and increase the manganese content in the lithium-doped lithium-manganese-based positive electrode material, reduce the cost of the positive electrode material, improve the safety and structural stability of the positive electrode material, and be able to keep the manganese dissolution amount within an appropriate range, improve the storage performance and safety of the battery, and realize the large-scale application of manganese-rich batteries.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a method for modifying a lithium-manganese-based positive electrode material, a lithium-rich manganese-based positive electrode material, a positive electrode sheet, a battery cell, and a secondary battery. Background Art

[0002] The demand and design of layered cathodes has evolved from the earliest common ternary materials to today's lithium-rich manganese-based materials. In addition to the conventional increase in nickel content, the increase in manganese content also brings a series of side reactions. This is because manganese ions dissolve manganese under the Jahn-Teller effect. Manganese ions deposit on the negative electrode surface, destroying the SEI film. During the initial charge and discharge process of lithium-ion batteries, the electrode material and electrolyte react at the solid-liquid interface to form a passivation layer covering the electrode material surface, which in turn affects the battery's storage life and safety. Summary of the Invention

[0003] In view of the above problems, the present application provides a method for modifying lithium manganese-based positive electrode materials, a lithium-rich manganese-based positive electrode material, a positive electrode plate, a battery cell and a secondary battery, which can improve the problem of manganese dissolution in lithium manganese-rich positive electrode materials and improve the storage life and safety of the battery.

[0004] In a first aspect, the present application provides a method for modifying a lithium-manganese-based positive electrode material, which comprises: performing lithium-site doping on the lithium-manganese-based positive electrode material, wherein the lithium-site doping ions include cations with a larger radius than the lithium ion, and increasing the manganese content in the lithium-manganese-based positive electrode material to obtain a lithium-rich manganese-based positive electrode material.

[0005] In the technical solution of the embodiment of the present application, the modification method of the lithium manganese-based positive electrode material of the present application replaces part of the lithium sites in the lithium manganese-based positive electrode material with cations larger than the lithium ion radius. The cations larger than the lithium ion radius can play a supporting role at the lithium site, enhance the energy barrier between the transition metal layers, improve the manganese dissolution effect, and increase the manganese content in the lithium-site doped lithium manganese-based positive electrode material. This can not only reduce the cost of the positive electrode material, improve the safety and structural stability of the positive electrode material, but also maintain the manganese dissolution amount within an appropriate range, thereby improving the storage performance and safety of the battery and realizing the large-scale application of manganese-rich batteries.

[0006] In some embodiments, the chemical formula of the lithium manganese-based cathode material is Li a+x Ni b0 Co c0 Mn d0 M 1-b0-c0-d0 O e E f The chemical formula of lithium-rich manganese-based cathode material is Li a L x Ni b Co c Mnd M 1-b-c-d O e E f . Wherein, L is a lithium dopant ion, M is a transition metal dopant ion, E is an oxygen dopant ion, 0<x≤0.8, a>0, b>0, b0>0, c>0, c0>0, e>0, f≥0. d=d0+Kx, K>0, d0>0. The manganese content in the lithium-rich manganese-based positive electrode material of the present application is the manganese content in the lithium-manganese-based positive electrode material before modification plus a value, and this value is proportional to the lithium dopant ion content.

[0007] In some embodiments, L includes any one or more of Na, K, Rb, Cs, Mg, Ca, Sr, Bi, and Y. The cations of these elements have a larger radius than lithium ions and can play a supporting role at the lithium site, thereby enhancing the energy barrier between transition metal layers and improving the manganese dissolution effect, thereby improving the storage performance and safety of the battery.

[0008] In some embodiments, 0.001≤x≤0.5; alternatively, 0.001≤x≤0.1. When the content of the lithium-site dopant ions satisfies 0.001≤x≤0.5, the lithium-site dopant ions not only play a supporting role at the lithium site, enhancing the energy barrier between transition metal layers and improving the manganese dissolution effect, but also the lithium-site dopant ions will not precipitate or will precipitate in a small amount, thereby having little impact on the battery's cycle performance, storage performance, and rate performance.

[0009] In some embodiments, 0<a<2. Alternatively, 0<a≤1.5. The lithium content in common lithium manganese-based positive electrode materials is within this range.

[0010] In some embodiments, 0<b≤0.96, 0<c<1, and 0<d<1. Alternatively, 0<c≤0.5. Alternatively, 0<b+c+d≤1. The cobalt content in common lithium manganese-based positive electrode materials is within this range.

[0011] In some embodiments, M includes any one or more of Mg, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La. Doping with transition metal dopants can improve other battery performance, with specific performance depending on the element's properties. For example, Al doping can improve battery safety, while Zr doping can improve battery rate performance.

[0012] In some embodiments, E includes any one or more of F, S, and P. Doping with oxygen dopant ions can improve other performances of the battery, and the specific performance depends on the performance of the elements.

[0013] In some embodiments, 0<e≤2, 0≤f<2. Alternatively, 1<e≤2, 0≤f<1. The oxygen-site dopant ions may partially replace the oxygen element.

[0014] In a second aspect, the present application provides a lithium-rich manganese-based positive electrode material, which is modified according to the modification method of the lithium-manganese-based positive electrode material in the above embodiment.

[0015] In the technical solution of the embodiment of the present application, the lithium-rich manganese-based positive electrode material of the present application has the advantages of low cost, material safety and high structural stability, and can also maintain a low manganese dissolution amount when applied to batteries, thereby improving the storage performance and safety of the battery.

[0016] In a third aspect, the present application provides a positive electrode plate, which includes the lithium-rich manganese-based positive electrode material in the above embodiment.

[0017] In a fourth aspect, the present application provides a battery cell comprising the positive electrode plate in the above embodiment.

[0018] In a fifth aspect, the present application provides a secondary battery comprising the battery cell in the above embodiment.

[0019] In a sixth aspect, the present application provides an electrical device, which includes the secondary battery in the above embodiment, and the secondary battery is used to provide electrical energy.

[0020] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0022] Figure 1 A schematic structural diagram of a vehicle according to some embodiments of the present application;

[0023] Figure 2 Schematic diagram of the exploded structure of batteries according to some embodiments of the present application;

[0024] Figure 3 This is a schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application.

[0025] The accompanying drawings in the specific implementation manner are as follows:

[0026] 1000-Vehicle; 100-Battery; 200-Controller; 300-Motor;

[0027] 10- box body; 11- first part; 12- second part;

[0028] 20 - battery cell; 21 - end cap; 22 - housing; 23 - electrode assembly. DETAILED DESCRIPTION

[0029] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0031] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0032] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0033] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0034] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0035] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0036] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0037] Currently, market developments indicate that power batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. As power battery applications continue to expand, market demand is also growing.

[0038] The demand and design of layered positive electrodes have evolved from the earliest ordinary ternary materials to today's lithium-rich manganese-based materials. In addition to the conventional increase in nickel content, the increase in manganese content also brings about a series of side reactions. The role of manganese in positive electrode materials is to reduce material costs and improve the safety and structural stability of materials. However, because manganese ions will cause manganese to dissolve under the Jahn-Taylor effect, manganese ions will deposit on the surface of the negative electrode and destroy the SEI film. During the first charge and discharge process of lithium-ion batteries, the electrode material and the electrolyte react at the solid-liquid interface to form a passivation layer covering the surface of the electrode material. The higher the manganese content in the positive electrode material, the more obvious the manganese dissolution, which in turn affects the storage life and safety of the battery.

[0039] In order to improve the problem of high manganese dissolution in lithium-rich manganese-based positive electrode materials, the embodiments of the present application found that ions with a larger radius than lithium ions, such as sodium ions and potassium ions in the positive electrode material, can play a supporting role at the lithium site, enhance the energy barrier between transition metal layers, and improve the manganese dissolution effect.

[0040] Based on the above considerations, in order to prepare a lithium-rich manganese-based positive electrode material with low manganese dissolution, the embodiment of the present application replaces part of the lithium sites in the lithium-manganese-based positive electrode material with cations larger than the lithium ion radius. The cations larger than the lithium ion radius can play a supporting role at the lithium site, enhance the energy barrier between the transition metal layers, improve the manganese dissolution effect, and increase the manganese content in the lithium-doped lithium-manganese-based positive electrode material. This can not only reduce the cost of the positive electrode material, improve the safety and structural stability of the positive electrode material, but also maintain the manganese dissolution amount within an appropriate range, thereby improving the storage performance and safety of the battery and realizing large-scale application of manganese-rich batteries.

[0041] The battery referred to in the embodiments of this application refers to a single physical module that includes multiple battery cells to provide higher voltage and capacity. The battery generally includes a battery box for enclosing multiple battery cells. The battery box can prevent liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0042] Each battery cell is a secondary battery; it can be a lithium-ion battery or a lithium-sulfur battery, but is not limited to these. Battery cells can be cylindrical, flat, rectangular, or other shapes. Battery cells are generally categorized into three types based on packaging: cylindrical, prismatic, and pouch-type.

[0043] A battery cell includes an electrode assembly and an electrolyte. The electrode assembly consists of a positive electrode sheet, a negative electrode sheet, and a separator. A battery cell primarily operates by the movement of metal ions between the positive and negative electrode sheets. The positive electrode sheet includes a positive current collector and a positive active material layer. The positive active material layer is coated on the surface of the positive electrode collector. The uncoated positive electrode collector protrudes from the coated positive electrode collector. This serves as the positive electrode tab. For lithium-ion batteries, for example, the positive electrode current collector can be made of aluminum, and the positive electrode active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide. The negative electrode sheet includes a negative current collector and a negative active material layer. The negative active material layer is coated on the surface of the negative electrode collector. The uncoated negative electrode collector protrudes from the coated negative electrode collector. This serves as the negative electrode tab. The negative electrode current collector can be made of copper. To ensure that high currents can pass without melting, multiple positive electrode tabs are stacked together, and multiple negative electrode tabs are stacked together. The separator can be made of polypropylene (PP) or polyethylene (PE). In addition, the electrode assembly can be a wound structure or a laminated structure, but the embodiments of the present application are not limited to this.

[0044] The battery cell also includes a current collecting component, which is used to electrically connect the tabs and electrode terminals of the battery cell to transmit electrical energy from the electrode assembly to the electrode terminals, and then to the outside of the battery cell through the electrode terminals; multiple battery cells are electrically connected through the current collecting component to realize series, parallel or mixed connection of multiple battery cells.

[0045] The battery also includes sampling terminals and a battery management system. The sampling terminals are connected to the busbar and are used to collect information about the battery cells, such as voltage or temperature. The sampling terminals transmit the collected battery cell information to the battery management system. If the battery management system detects that the battery cell information is outside the normal range, it will limit the battery's output power for safety protection.

[0046] It will be appreciated that the electrical devices applicable to the batteries described in the embodiments of the present application may be in various forms, for example, mobile phones, portable devices, laptop computers, electric vehicles, electric cars, ships, spacecraft, electric toys and electric tools, etc. For example, spacecraft include airplanes, rockets, space shuttles and spacecraft, etc. Electric toys include fixed or mobile electric toys, for example, game consoles, electric car toys, electric ship toys and electric airplane toys, etc. Electric tools include metal cutting power tools, grinding power tools, assembly power tools and railway power tools, for example, electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers.

[0047] The battery cells and batteries described in the embodiments of the present application are not limited to the electrical devices described above, but can also be applied to all electrical devices using battery cells and batteries. However, for the sake of simplicity, the following embodiments are described using electric vehicles as an example.

[0048] See also Figure 1 , Figure 1 A schematic diagram of the structure of a vehicle provided for some embodiments of the present application. The vehicle 1000 can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 can be provided at the bottom, head or tail of the vehicle 1000. The battery 100 can be used to power the vehicle 1000. For example, the battery 100 can serve as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0049] In some embodiments of the present application, the battery 100 can not only serve as the operating power source of the vehicle 1000, but also serve as the driving power source of the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0050] Please refer to Figure 2 , Figure 2 An exploded view of a battery provided in some embodiments of the present application. The battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 is used to provide a storage space for the battery cell 20, and the housing 10 can have a variety of structures. In some embodiments, the housing 10 can include a first structure 11 and a second structure 12, which overlap each other and together define a storage space for the battery cell 20. The second structure 12 can be a hollow structure with one end open, and the first structure 11 can be a plate-like structure, with the first structure 11 overlapping the open side of the second structure 12, so that the first structure 11 and the second structure 12 together define a storage space. The first structure 11 and the second structure 12 can also be hollow structures with one end open, with the open side of the first structure 11 overlapping the open side of the second structure 12. Of course, the housing 10 formed by the first structure 11 and the second structure 12 can have a variety of shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0051] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections among the multiple battery cells 20. The multiple battery cells 20 may be directly connected in series, in parallel, or in a hybrid connection, and then the entire battery cell 20 may be housed within the housing 10. Alternatively, the battery 100 may be constructed by first connecting multiple battery cells 20 in series, in parallel, or in a hybrid connection to form a battery module, which is then connected in series, in parallel, or in a hybrid connection to form a complete battery module, and then housed within the housing 10. The battery 100 may also include other structures, such as a busbar assembly for electrically connecting the multiple battery cells 20.

[0052] Each battery cell 20 is a secondary battery, which may be a lithium-ion battery, a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 20 may be cylindrical, flat, rectangular, or in other shapes.

[0053] Please refer to Figure 3 , Figure 3 The first battery cell 20 is a schematic diagram of the decomposition structure of some embodiments of the present application. The battery cell 20 refers to the smallest unit that makes up the battery. Figure 3 The battery cell 20 includes an end cap 21, a shell 22, an electrode assembly 23 and other functional components.

[0054] The end cap 21 is a component that covers the opening of the housing 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 21 can be adapted to the shape of the housing 22 to match the housing 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as an aluminum alloy). This prevents the end cap 21 from deforming when subjected to compression or collision, allowing the battery cell 20 to have higher structural strength and improved safety. Functional components such as electrode terminals can be provided on the end cap 21. The electrode terminals can be used to electrically connect to the electrode assembly 23 for outputting or inputting electrical energy into or out of the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism for relieving internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The end cap 21 can also be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application are not particularly limited in this regard. In some embodiments, an insulating member may be provided inside the end cap 21 to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating member may be made of plastic, rubber, or the like.

[0055] The housing 22 is a component that cooperates with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can be used to accommodate the electrode assembly 23, electrolyte, and other components. The housing 22 and end cap 21 can be separate components. An opening can be provided in the housing 22, and the end cap 21 is placed over the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and housing 22 can be integrated. Specifically, the end cap 21 and housing 22 can form a common connection surface before other components are inserted into the housing. When the interior of the housing 22 needs to be enclosed, the end cap 21 is placed over the housing 22. The housing 22 can have a variety of shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, or a hexagonal prism. Specifically, the shape of the housing 22 can be determined based on the specific shape and size of the electrode assembly 23. The housing 22 can be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this embodiment of the present application does not impose any particular limitations on this.

[0056] The electrode assembly 23 is a component in the battery cell 20 where electrochemical reactions occur. One or more electrode assemblies 23 may be contained in the housing 22. The electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and a separator is usually provided between the positive and negative electrode sheets. The parts of the positive and negative electrode sheets with active materials constitute the main body of the electrode assembly, and the parts of the positive and negative electrode sheets without active materials each constitute a tab. The positive and negative electrode tabs may be located together at one end of the main body or respectively at both ends of the main body. During the charge and discharge process of the battery, the positive electrode active material and the negative electrode active material react with the electrolyte, and the tabs connect the electrode terminals to form a current loop.

[0057] According to some embodiments of the present application, the present application provides a method for modifying a lithium-manganese-based positive electrode material, which includes: performing lithium-site doping on the lithium-manganese-based positive electrode material, and the lithium-site doping ions include cations with a larger radius than the lithium ion, and increasing the manganese content in the lithium-manganese-based positive electrode material to obtain a lithium-rich manganese-based positive electrode material.

[0058] After designing the lithium doping amount of the lithium-manganese-based positive electrode material and the increased manganese content value, the lithium element content of the lithium-manganese-based positive electrode material is appropriately reduced, and the content of at least one of the cobalt element and the nickel element is reduced. Then, the raw material ratio of the lithium-rich manganese-based positive electrode material is redesigned to prepare the lithium-rich manganese-based positive electrode material.

[0059] The preparation method of the lithium-rich manganese-based positive electrode material includes: calcining a first mixture including a nickel-cobalt-manganese precursor, a lithium precursor and an L metal precursor at 400°C to 600°C for 3h to 7h, and then calcining it at 700°C to 900°C for 10h to 14h to obtain a lithium-rich manganese-based positive electrode material.

[0060] Excess lithium precursor can make up for the loss of lithium during high-temperature calcination.

[0061] Optionally, the heating rate is 1°C / min to 5°C / min.

[0062] Among them, the nickel-cobalt-manganese precursor can be prepared by the following method:

[0063] A second mixture including a nickel precursor, a cobalt precursor and a manganese precursor is added to water according to a ratio and dispersed evenly to obtain a salt solution. A sodium carbonate solution is then added to the salt solution, rapidly stirred and reacted for 7 to 12 hours, and then allowed to stand and age for 3 to 5 hours. The standing and aging can allow primary particles to grow to obtain a dispersion containing nickel-cobalt-manganese precursor particles. The nickel-cobalt-manganese precursor particles are washed with water for 2 to 5 times, and after drying, the dried solid is collected as the nickel-cobalt-manganese precursor.

[0064] Optionally, the nickel precursor includes nickel acetate.

[0065] Optionally, the cobalt precursor comprises cobalt acetate.

[0066] Optionally, the manganese precursor comprises manganese acetate.

[0067] Optionally, the drying comprises vacuum drying at 80° C. to 120° C. for 8 h to 16 h.

[0068] Optionally, when the lithium-rich manganese-based positive electrode material is designed to be doped with transition metal ions, the second mixture further includes a transition metal precursor.

[0069] The modification method of the lithium-manganese-based positive electrode material of the present application replaces part of the lithium sites in the lithium-manganese-based positive electrode material with cations larger than the lithium ion radius. The cations larger than the lithium ion radius can play a supporting role at the lithium site, enhance the energy barrier between transition metal layers, improve the manganese dissolution effect, and increase the manganese content in the lithium-site-doped lithium-manganese-based positive electrode material. This method can not only reduce the cost of the positive electrode material, improve the safety and structural stability of the positive electrode material, but also maintain the manganese dissolution amount within an appropriate range, thereby improving the storage performance and safety of the battery and realizing the large-scale application of manganese-rich batteries.

[0070] According to some embodiments of the present application, optionally, the chemical formula of the lithium manganese-based positive electrode material is Li a+ x Ni b0 Co c0 Mn d0 M 1-b0-c0-d0 O e E f The chemical formula of lithium-rich manganese-based cathode material is Li a L x Ni b Co c Mn d M 1-b-c-d O e E f Wherein, L is a lithium dopant ion, M is a transition metal dopant ion, E is an oxygen dopant ion, 0<x≤0.8, a>0, b>0, b0>0, c>0, c0>0, e>0, f≥0. d=d0+Kx, K>0, d0>0.

[0071] As an example, the value of x may be 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8.

[0072] d0 is the manganese content of the lithium manganese-based positive electrode material before modification.

[0073] Since K>0 and 0<x≤0.8, d-d0=Kx>0.

[0074] The manganese content in the lithium-rich manganese-based positive electrode material of the present application is the manganese content in the lithium-manganese-based positive electrode material before modification plus a value, and this value is proportional to the lithium-doped ion content.

[0075] According to some embodiments of the present application, L includes any one or more of Na, K, Rb, Cs, Mg, Ca, Sr, Bi and Y.

[0076] As an example, L may be Na, K, Rb, Cs, Mg, Ca, Sr, Bi, or Y, or may include Na and K simultaneously, or may include Na and Rb simultaneously, or may include Na and Cs simultaneously, or may include Na, K, and Rb simultaneously, or may include Na and Mg simultaneously, or may include Na, K, and Ca simultaneously.

[0077] The cations of the above elements have a larger radius than lithium ions, and can play a supporting role at the lithium site, enhance the energy barrier between transition metal layers, improve the manganese dissolution effect, and thus improve the storage performance and safety of the battery.

[0078] According to some embodiments of the present application, optionally, 0.001≤x≤0.5.

[0079] As an example, the value of x may be 0.001, 0.002, 0.005, 0.008, 0.01, 0.02, 0.05, 0.08, 0.1, 0.2, 0.3, 0.4, or 0.5.

[0080] Optionally, 0.001≤x≤0.1.

[0081] When the content of lithium-site doping ions satisfies 0.001≤x≤0.5, the lithium-site doping ions can not only play a supporting role at the lithium site, enhance the energy barrier between transition metal layers, and improve the manganese dissolution effect; but also because the lithium-site doping ions will not precipitate or the amount of precipitation is small, the impact on the battery's cycle performance, storage performance and rate performance is small.

[0082] According to some embodiments of the present application, optionally, 0<a<2.

[0083] As an example, the value of a can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, or 1.9.

[0084] Optionally, 0<a≤1.5.

[0085] The lithium content in common lithium manganese-based positive electrode materials is within this range.

[0086] According to some embodiments of the present application, optionally, 0<b≤0.96, 0<c<1, 0<d<1.

[0087] As an example, the value of b may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 0.96.

[0088] As an example, the value of c may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9.

[0089] As an example, the value of d may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9.

[0090] Optionally, 0<c≤0.5.

[0091] Optionally, 0<b+c+d≤1.

[0092] As an example, the value of b+c+d may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.

[0093] And when the value of b+c+d is 1, the lithium-rich manganese-based positive electrode material has no transition metal site doping.

[0094] The cobalt content in common lithium manganese-based positive electrode materials is within this range.

[0095] According to some embodiments of the present application, optionally, M includes any one or more of Mg, Zr, Al, B, Ta, Mo, W, Nb, Sb and La.

[0096] As examples, M may be Mg, Zr, Al, B, Ta, Mo, W, Nb, Sb, or La, or may include Mg and Al simultaneously, or may include B and Ta simultaneously, or may include Mg, Zr, and Al simultaneously.

[0097] Doping with transition metal ions can improve other battery properties, with specific performance depending on the element's properties. For example, Al doping can improve battery safety, while Zr doping can improve battery rate performance.

[0098] According to some embodiments of the present application, optionally, E includes any one or more of F, S and P.

[0099] As examples, E may be F, S, or P, or may include F and S simultaneously, or may include S and P simultaneously, or may include F and P simultaneously, or may include F, S, and P simultaneously.

[0100] The doping of oxygen-doped ions can bring some other performance improvements to the battery, and the specific performance depends on the performance of the elements.

[0101] According to some embodiments of the present application, optionally, 0<e≤2, 0≤f<2.

[0102] As an example, the value of e can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.

[0103] As an example, the value of f can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, or 1.9.

[0104] And when the value of e is 2 and the value of f is 0, the lithium-rich manganese-based positive electrode material is not doped with oxygen sites.

[0105] Optionally, 1<e≤2, 0≤f<1.

[0106] Oxygen-site doping ions can partially replace oxygen elements.

[0107] According to some embodiments of the present application, optionally, the present application provides a lithium-rich manganese-based positive electrode material, which is modified according to the modification method of the lithium-manganese-based positive electrode material in the above embodiment.

[0108] The lithium-rich manganese-based positive electrode material of the present application has the advantages of low cost, material safety and high structural stability, and can also maintain a low manganese dissolution amount when used in batteries, thereby improving the storage performance and safety of the battery.

[0109] When the lithium manganese-based positive electrode material is NCM333, the chemical formula of the lithium manganese-based positive electrode material is Li(Ni 0.333 Co 0.333 Mn 0.333 )O2, the chemical formula of lithium-rich manganese-based positive electrode material is Li a L x (Ni b Co c Mn 0.333+K1x )O2, 0.5≤K1≤2.7.

[0110] When the lithium manganese-based positive electrode material is NCM523, the chemical formula of the lithium manganese-based positive electrode material is Li(Ni 0.5 Co 0.2 Mn 0.3 )O2, the chemical formula of lithium-rich manganese-based positive electrode material is Li a L x (Nib Co c Mn 0.3+K2x )O2, 0.2≤K2≤1.2.

[0111] When the lithium manganese-based positive electrode material is NCM622, the chemical formula of the lithium manganese-based positive electrode material is Li(Ni 0.6 Co 0.2 Mn 0.2 )O2, the chemical formula of lithium-rich manganese-based positive electrode material is Li a L x (Ni b Co c Mn 0.2+K3x )O2, 0.3≤K3≤1.5.

[0112] When the lithium manganese-based positive electrode material is NCM811, the chemical formula of the lithium manganese-based positive electrode material is Li(Ni 0.8 Co 0.1 Mn 0.1 )O2, the chemical formula of lithium-rich manganese-based positive electrode material is Li a L x (Ni b Co c Mn 0.1+K4x )O2, 0.25≤K4≤1.3.

[0113] When the lithium manganese-based cathode material is NCM9 series, the chemical formula of the lithium manganese-based cathode material is Li(Ni 0.9 Co 0.05 Mn 0.05 )O2, the chemical formula of lithium-rich manganese-based positive electrode material is Li a L x (Ni b Co c Mn 0.05+K5x )O2, 0.3≤K5≤1.5.

[0114] The following is a further detailed description of a modification method of a lithium manganese-based positive electrode material and a lithium-rich manganese-based positive electrode material of the present application in conjunction with the embodiments.

[0115] The parameters of the lithium manganese-based positive electrode materials and lithium-rich manganese-based positive electrode materials of the examples and comparative examples of the present application are shown in Table 1.

[0116] Table 1 Parameters of lithium manganese-based positive electrode materials and lithium-rich manganese-based positive electrode materials of the embodiments and comparative examples

[0117]

[0118]

[0119] Among them, the lithium-rich manganese-based positive electrode material is prepared by the following method:

[0120] According to the stoichiometric ratio, the nickel precursor, cobalt precursor and manganese precursor are added to deionized water and dispersed evenly to obtain a salt solution. The sodium carbonate solution is then quickly poured into the salt solution, and the reaction is continued for 9 hours. It is then allowed to stand and age for 4 hours to allow primary particles to grow, thereby obtaining a dispersion containing nickel-cobalt-manganese precursor particles. The nickel-cobalt-manganese precursor particles are washed three times with deionized water, dried in a blower dryer, and then vacuum dried at 100°C for 12 hours. The dried solid is collected as the nickel-cobalt-manganese precursor.

[0121] The nickel-cobalt-manganese precursor, lithium precursor and L metal precursor are mixed evenly in proportion and ground, with an excess of lithium precursor. The fully ground solid powder is transferred to a crucible and placed in a programmed temperature muffle furnace for calcination. The calcination procedure is: pre-calcination from room temperature to 500°C for 5h, then raised to a high temperature of 800°C for 12h, with a heating rate of 3°C / min. After cooling to room temperature, it is collected to obtain a lithium-rich manganese-based positive electrode material.

[0122] Test Example 1

[0123] The lithium manganese-based positive electrode materials and lithium-rich manganese-based positive electrode materials of the embodiment and comparative example were all prepared into positive electrode sheets and battery cells using the same method. The storage days at 60°C @ 80% SOH, the 60°C EOL / BOL manganese content retention rate and the post-EOL external short test were measured, and the results are shown in Table 2.

[0124] The method of making a battery cell is as follows:

[0125] Positive electrode sheet: The positive electrode material, polyvinylidene fluoride and carbon black Super P prepared as described above are mixed in a mass ratio of 90:5:5, and N-methyl-pyrrolidone is used as the solvent. The amount of solvent added is adjusted to control the viscosity of the slurry at 100-20000 mPa.s. Use a coating machine to apply the slurry on the surface of the aluminum foil, and then transfer it to a vacuum drying oven for complete drying. After drying at 85°C, cold pressing is carried out, and then the edges, pieces, and strips are trimmed, and then dried at 85°C under vacuum conditions for 4 hours. The ears are welded to make positive electrode sheets. The total coating amount of the positive electrode active material on the obtained sheet is 0.3g / 1540.25mm 2 .

[0126] Negative electrode sheet: Graphite, carbon black Super-P, carboxymethyl cellulose and styrene-butadiene latex are added to deionized water in a mass ratio of 96.5:1.0:1.0:1.5 and mixed evenly to form an anode slurry; the anode slurry is coated on the current collector copper foil and dried at 85°C, and then trimmed, cut into pieces, and divided into strips, and then dried at 110°C under vacuum conditions for 4 hours, and the tabs are welded to form the negative electrode sheet.

[0127] Electrolyte: A mixture of ethylene carbonate, propylene carbonate, and diethyl carbonate was used as a non-aqueous organic solvent, wherein the mass ratio of each component was ethylene carbonate:propylene carbonate:diethyl carbonate = 30:30:40, and lithium hexafluorophosphate (LiPF6) was used as the lithium salt to prepare an electrolyte with a concentration of 1 mol / L.

[0128] Separator film: A 12 μm thick polypropylene film was used as the separator.

[0129] Battery cell: Stack the positive electrode sheet, separator, and negative electrode sheet as described above in order, so that the separator is between the positive electrode sheet and the negative electrode sheet to play an isolating role, add the above-mentioned electrolyte to assemble into a stacked battery, which is a battery cell.

[0130] 60℃ Storage Days @80% SOH Testing Method:

[0131] A fresh battery cell was charged to 100% SOC at 0.33C current and stored in a constant temperature box at 60°C. The capacity value of the 0.33C discharge was measured every 30 days until it decayed to 80% of the initial capacity, and the number of days was recorded.

[0132] 60℃ EOL / BOL manganese content retention rate detection method:

[0133] The fresh battery cells were disassembled, the negative electrode pieces were taken, and the mass ratio of Mn element on the positive electrode piece was measured by inductively coupled plasma emission spectroscopy (ICP). BOL The same method was used to measure the mass ratio of Mn element on the positive electrode of EOL battery cells. EOL Calculate M EOL / M BOL That is the Mn content retention rate.

[0134] Detection method of external short test after EOL:

[0135] Charge to 100% SOC at 0.33C, let stand for 5 minutes, then short-circuit with a 1.5mohm resistor for 10 minutes; observe whether the battery cell explodes or catches fire.

[0136] Overcharge test detection method:

[0137] Charge a fresh battery cell at a current of 0.33C until the battery cell experiences runaway, and record the SOC when runaway occurs.

[0138] Heating test detection method:

[0139] A fresh battery cell was charged to 100% SOC at a current of 0.33C, and the temperature was raised at a heating rate of 5°C / min at room temperature until the battery cell experienced thermal runaway, and the temperature at which runaway occurred was recorded.

[0140] Table 2 Parameters of battery cells prepared in Examples and Comparative Examples

[0141]

[0142]

[0143]

[0144] When the lithium manganese-based positive electrode material is NCM333, it can be seen from the comparison between Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, Example 3 and Comparative Example 3, and Example 4 and Comparative Example 4 that the NCM333 positive electrode material is lithium-doped and the manganese content in the NCM333 positive electrode material is increased. Compared with only increasing the manganese content in the NCM333 positive electrode material, at the same manganese content, the battery cell prepared by the lithium-doped lithium-rich manganese-based positive electrode material has a higher 60°C EOL / BOL manganese content retention rate, a longer 60°C storage number of days @80% SOH, and no fire or explosion in the EOL external short test, that is, manganese dissolution and storage performance are significantly improved, and the safety of the battery cell is improved; from the comparison between the NCM333 positive electrode material and Examples 1 to 4, it can be seen that after the manganese content in the lithium-rich manganese-based positive electrode material is increased, the SOC of the battery cell when runaway occurs is higher, and the temperature at which runaway occurs is higher, that is, increasing the manganese content in the lithium-doped lithium manganese-based positive electrode material can improve the safety of the positive electrode material.

[0145] When the lithium manganese-based positive electrode material is NCM523, it can be seen from the comparison between Example 5 and Comparative Example 5, Example 6 and Comparative Example 6, Example 7 and Comparative Example 7, and Example 8 and Comparative Example 8 that the NCM523 positive electrode material is lithium-doped and the manganese content in the NCM523 positive electrode material is increased. Compared with only increasing the manganese content in the NCM523 positive electrode material, at the same manganese content, the battery cell prepared by the lithium-doped lithium-rich manganese-based positive electrode material has a higher 60°C EOL / BOL manganese content retention rate, a longer 60°C storage number of days @80% SOH, and no fire or explosion in the EOL external short test, that is, manganese dissolution and storage performance are significantly improved, and the safety of the battery cell is improved; from the comparison between the NCM523 positive electrode material and Examples 5 to 8, it can be seen that after the manganese content in the lithium-rich manganese-based positive electrode material is increased, the SOC of the battery cell when runaway occurs is higher, and the temperature at which runaway occurs is higher, that is, increasing the manganese content in the lithium-doped lithium manganese-based positive electrode material can improve the safety of the positive electrode material.

[0146] When the lithium manganese-based positive electrode material is NCM622, it can be seen from the comparison between Example 9 and Comparative Example 9, Example 10 and Comparative Example 10, Example 11 and Comparative Example 11, and Example 12 and Comparative Example 12 that the NCM622 positive electrode material is lithium-doped and the manganese content in the NCM622 positive electrode material is increased. Compared with only increasing the manganese content in the NCM622 positive electrode material, the 60°C EOL / BOL of the battery cell made of the lithium-rich manganese-based positive electrode material with the same manganese content is The manganese content retention rate is higher, the storage days at 60°C @80% SOH are longer, and the EOL external short test is non-flammable and non-explosive, that is, the manganese dissolution and storage performance are significantly improved, and the safety of the battery cell is improved; from the comparison between the NCM622 positive electrode material and Examples 9 to 12, it can be seen that after the manganese content in the lithium-rich manganese-based positive electrode material is increased, the SOC of the battery cell when runaway occurs is higher, and the temperature at which runaway occurs is higher, that is, increasing the manganese content in the lithium-doped lithium manganese-based positive electrode material can improve the safety of the positive electrode material.

[0147] When the lithium manganese-based positive electrode material is NCM811, it can be seen from the comparison between Example 13 and Comparative Example 13, Example 14 and Comparative Example 14, Example 15 and Comparative Example 15, and Example 16 and Comparative Example 16 that the NCM811 positive electrode material is lithium-doped and the manganese content in the NCM811 positive electrode material is increased. Compared with only increasing the manganese content in the NCM811 positive electrode material, at the same manganese content, the 60°C EOL / BOL manganese content of the battery cell made of the lithium-rich manganese-based positive electrode material that is lithium-doped is lower than that of the battery cell made of the lithium-rich manganese-based positive electrode material that is lithium-doped. The amount retention rate is higher, the storage days at 60°C @80% SOH are longer, and the EOL external short test is fire without explosion or no fire and no explosion, that is, manganese dissolution and storage performance are significantly improved, and the safety of the battery cell is improved; from the comparison of NCM811 positive electrode material and Examples 13 to 16, it can be seen that after the manganese content in the lithium-rich manganese-based positive electrode material is increased, the SOC of the battery cell when runaway occurs is higher, and the temperature at which runaway occurs is higher, that is, increasing the manganese content in the lithium-doped lithium manganese-based positive electrode material can improve the safety of the positive electrode material.

[0148] When the lithium manganese-based positive electrode material is NCM9 series, it can be seen from the comparison between Example 17 and Comparative Example 17, Example 18 and Comparative Example 18, Example 19 and Comparative Example 19, and Example 20 and Comparative Example 20 that the NCM9 series positive electrode material is lithium-doped and the manganese content in the NCM9 series positive electrode material is increased. Compared with only increasing the manganese content in the NCM9 series positive electrode material, at the same manganese content, the 60°C EOL / BOL manganese content of the battery cell made of the lithium-doped lithium-rich manganese-based positive electrode material is maintained at 100%. The retention rate is higher, the storage days at 60°C @80% SOH are longer, and the EOL external short test is fire without explosion or no fire and no explosion, that is, manganese dissolution and storage performance are significantly improved, and the safety of the battery cell is improved; from the comparison of the NCM9 series positive electrode material and Examples 17 to 20, it can be seen that after the manganese content in the lithium-rich manganese-based positive electrode material is increased, the SOC of the battery cell when runaway occurs is higher, and the temperature at which runaway occurs is higher, that is, increasing the manganese content in the lithium-doped lithium manganese-based positive electrode material can improve the safety of the positive electrode material.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for modifying a lithium manganese-based positive electrode material, characterized in that: The modification method of the lithium manganese-based positive electrode material comprises: performing lithium doping on the lithium manganese-based positive electrode material, wherein the lithium doping ions include cations with a radius larger than that of lithium ions, and increasing the manganese content in the lithium manganese-based positive electrode material to obtain a lithium-rich manganese-based positive electrode material; The chemical formula of the lithium manganese-based positive electrode material is Li a+x Ni b0 Co c0 Mn d0 M 1-b0-c0-d0 O e E f The chemical formula of the lithium-rich manganese-based positive electrode material is Li a L x Ni b Co c Mn d M 1-b-c-d O e E f ; Wherein, L is the lithium doping ion, M is the transition metal doping ion, E is the oxygen doping ion, 0<x≤0.8, a>0, b>0, b0>0, c>0, c0>0, e>0, f≥0; d=d0+Kx,K>0,d0>0.

2. The method for modifying the lithium manganese-based positive electrode material according to claim 1, characterized in that: The L includes any one or more of Na, K, Rb, Cs, Mg, Ca, Sr, Bi and Y.

3. The method for modifying the lithium manganese-based positive electrode material according to claim 1, characterized in that: 0.001≤x≤0.5。 4. The method for modifying the lithium manganese-based positive electrode material according to claim 3, characterized in that: 0.001≤x≤0.1。 5. The method for modifying the lithium manganese-based positive electrode material according to claim 1, wherein: 0＜a＜2。 6. The method for modifying the lithium manganese-based positive electrode material according to claim 5, characterized in that: 0＜a≤1.5。 7. The method for modifying the lithium manganese-based positive electrode material according to claim 1, characterized in that: 0<b≤0.96, 0<c<1, 0<d<1.

8. The method for modifying the lithium manganese-based positive electrode material according to claim 7, characterized in that: 0＜c≤0.5。 9. The method for modifying the lithium manganese-based positive electrode material according to claim 7, characterized in that: 0<b+c+d≤1.

10. The method for modifying a lithium manganese-based positive electrode material according to any one of claims 1 to 9, wherein: The M includes any one or more of Mg, Zr, Al, B, Ta, Mo, W, Nb, Sb and La.

11. The method for modifying a lithium manganese-based positive electrode material according to any one of claims 1 to 9, wherein: The E includes any one or more of F, S and P.

12. The method for modifying a lithium manganese-based positive electrode material according to any one of claims 1 to 9, wherein: 0<e≤2,0≤f<2.

13. The method for modifying a lithium manganese-based positive electrode material according to any one of claims 1 to 9, wherein: 1<e≤2,0≤f<1.

14. A lithium-rich manganese-based positive electrode material, characterized in that The lithium-rich manganese-based positive electrode material is modified according to the method for modifying the lithium-manganese-based positive electrode material according to any one of claims 1 to 13.

15. A positive electrode plate, characterized in that: The positive electrode plate includes the lithium-rich manganese-based positive electrode material according to claim 14.

16. A battery cell, characterized in that: The battery cell includes the positive electrode sheet according to claim 15 .

17. A secondary battery, characterized in that: The secondary battery includes the battery cell according to claim 16 .

18. An electrical device, characterized in that: The electric device comprises the secondary battery according to claim 17, and the secondary battery is used to provide electric energy.

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