Positive electrode active material and preparation method thereof, battery and electric equipment

Abstract

The invention relates to a positive electrode active material and a preparation method thereof, a battery and electric equipment. The positive electrode active material comprises lithium-containing phosphate; the lithium-containing phosphate has a Pnma spatial configuration; the material satisfies the following conditions: 0.09 degree < = FWHM {020} < = 0.4 degree; 0.04 DEG < = FWHM {200} < = 0.07 DEG; 0.04 DEG < = FWHM {111} < = 0.07 DEG; fWHM {020} is the half-peak width of {020} diffraction peaks in an X diffraction spectrum of the positive electrode active material; fWHM {200} is the half-peak width of {200} diffraction peaks in an X diffraction spectrum of the positive electrode active material; fWHM {111} is the half-peak width of {111} diffraction peaks in an X diffraction spectrum of the positive electrode active material. According to the positive electrode active material, through the arrangement, the dynamic performance is improved, and the material capacity exertion is facilitated.

Description

Technical Field

[0001] The present application relates to a positive electrode active material, a preparation method thereof, a battery, and an electrical device. Background Art

[0002] In recent years, with the development of lithium-ion secondary battery technology, lithium-ion 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 power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. Due to the great development of lithium-ion secondary batteries, higher requirements are also put forward for their kinetic performance and capacity. Summary of the Invention

[0003] The purpose of the present application is to provide a positive electrode active material, a preparation method thereof, a battery, and an electrical device to improve the capacity and cycle performance of the battery.

[0004] The embodiments of the present application are implemented as follows:

[0005] In a first aspect, an embodiment of the present application provides a positive electrode active material, which includes: lithium-containing phosphate with an olivine structure; the chemical formula of the lithium-containing phosphate with an olivine structure includes: Li 1+x A 1-y B y PO z , -0.1 ≤ x ≤ 0.3, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 4; wherein, element A includes one or more elements of Co, Ni, Fe, Mn, or V; element B includes one or more elements of Ta, Ir, Te, Ti, Mg, Ca, Sr, Cr, In, Cu, Zn, Zr, Y, Mo, Nb, Al, W, or La; the lithium-containing phosphate with an olivine structure has a Pnma space configuration;

[0006] The positive electrode active material satisfies:

[0007] 0.09° ≤ FWHM{020} ≤ 0.4°; 0.04° ≤ FWHM{200} ≤ 0.07°; 0.04° ≤ FWHM{111} ≤ 0.07°;

[0008] FWHM{020} is the full width at half maximum of the {020} diffraction peak in the X-ray diffraction pattern of the positive electrode active material;

[0009] FWHM{200} is the full width at half maximum of the {200} diffraction peak in the X-ray diffraction pattern of the positive electrode active material;

[0010] FWHM{111} is the full width at half maximum of the {111} diffraction peak in the X-ray diffraction pattern of the positive electrode active material.

[0011] In the technical solution of the above embodiment of the present application, by setting the cathode active material to satisfy 0.09° ≤ FWHM{020} ≤ 0.4°; 0.04° ≤ FWHM{200} ≤ 0.07°; 0.04° ≤ FWHM{111} ≤ 0.07°, it is beneficial to the initial charge-discharge specific capacity of the battery and can also take into account the improvement of the cycle performance.

[0012] In some alternative embodiments, 0.25° ≤ FWHM{020} ≤ 0.4°; 0.059° ≤ FWHM{200} ≤ 0.07°; 0.065° ≤ FWHM{111} ≤ 0.07°.

[0013] In the above technical solution, by setting 0.25° ≤ FWHM{020} ≤ 0.4°; 0.059° ≤ FWHM{200} ≤ 0.07°; 0.065° ≤ FWHM{111} ≤ 0.07°; it is more beneficial to take into account the initial charge-discharge specific capacity and cycle performance of the battery.

[0014] In some alternative embodiments, the primary particle size of the cathode active material is greater than or equal to 50 nm. Optionally, the primary particle size of the cathode active material is 50 nm to 200 nm.

[0015] In the above technical solution, by setting the primary particle size of the cathode active material within the above range, it can not only shorten the migration path of lithium ions, which is beneficial to the capacity utilization of the cathode material; but also prevent the specific surface area of the cathode material from being too large, and can effectively improve the cycle performance.

[0016] In some alternative embodiments, the specific surface area of the cathode active material is 5 m 2 / g to 15 m 2 / g. Optionally, the specific surface area of the cathode active material is 7 m 2 / g to 8.8 m 2 / g.

[0017] In the above technical solution, by setting the specific surface area of the cathode active material within the above range, the side reactions on the material surface can be slowed down; even at ultra-high voltages (above 4.8 V), side reactions are not likely to occur, which is beneficial to the improvement of the cycle performance.

[0018] In some alternative embodiments, the cathode active material further includes a carbon coating layer covering at least part of the surface of the lithium-containing phosphate in the olivine structure.

[0019] As a fast conductor, the carbon coating layer is beneficial to the electron conductivity. In the above technical solution, by setting the carbon coating layer, the conductivity of the cathode material can be improved; thus, it is beneficial to the improvement of the kinetic performance of the cathode material.

[0020] In some alternative embodiments, the carbon content in the positive electrode active material is 0.2 wt% to 10 wt%.

[0021] In the above technical solution, by setting the mass ratio of the carbon coating layer in the positive electrode active material to be 0.2% to 10%, it is beneficial to obtain excellent kinetic performance.

[0022] In some alternative embodiments, the lithium-containing phosphate with an olivine structure includes lithium cobalt phosphate.

[0023] Second, an embodiment of the present application provides a method for preparing a positive electrode active material. The preparation method includes:

[0024] Mix a lithium source, an A source, a B source, a phosphorus source, and a crystal form control agent to obtain a mixture;

[0025] Sinter the mixture to obtain the positive electrode active material;

[0026] Among them, the positive electrode active material includes: lithium-containing phosphate with an olivine structure; the chemical formula of the lithium-containing phosphate with an olivine structure includes: Li 1+x A 1-y B y PO z , -0.1 ≤ x ≤ 0.3, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 4; where the A element includes one or more elements of Co, Ni, Fe, Mn, or V; the B element includes one or more elements of Ta, Ir, Te, Ti, Mg, Ca, Sr, Cr, In, Cu, Zn, Zr, Y, Mo, Nb, Al, W, or La; the lithium-containing phosphate with an olivine structure has a Pnma space configuration;

[0027] The positive electrode active material satisfies:

[0028] 0.09° ≤ FWHM{020} ≤ 0.4°; 0.04° ≤ FWHM{200} ≤ 0.07°; 0.04° ≤ FWHM{111} ≤ 0.07°;

[0029] FWHM{020} is the full width at half maximum of the {020} diffraction peak in the X-ray diffraction pattern of the positive electrode active material;

[0030] FWHM{200} is the full width at half maximum of the {200} diffraction peak in the X-ray diffraction pattern of the positive electrode active material;

[0031] FWHM{111} is the full width at half maximum of the {111} diffraction peak in the X-ray diffraction pattern of the positive electrode active material.

[0032] In the above technical solution, adopting the above preparation method is beneficial to regulating a material with a short lithium ion migration path and moderate primary grains; furthermore, it is beneficial to significantly improving the kinetic performance of the lithium phosphate material with an olivine structure, slowing down the interfacial side reactions, and improving the comprehensive performance of the lithium phosphate material with an olivine structure.

[0033] In some alternative embodiments, 0.25° ≤ FWHM{020} ≤ 0.4°; 0.059° ≤ FWHM{200} ≤ 0.07°; 0.065° ≤ FWHM{111} ≤ 0.07°.

[0034] In some alternative embodiments, the primary particle size of the positive electrode active material is greater than or equal to 50 nm; optionally, the primary particle size of the positive electrode active material is 50 nm to 200 nm.

[0035] In some alternative embodiments, the specific surface area of the positive electrode active material is 5 m 2 / g to 15 m 2 / g; optionally, the specific surface area of the positive electrode active material is 7 m 2 / g to 8.8 m 2 / g.

[0036] In some alternative embodiments, the positive electrode active material further includes a carbon coating layer covering at least a part of the surface of the lithium-containing phosphate with an olivine structure.

[0037] In some alternative embodiments, the carbon content in the positive electrode active material is 0.2 wt% to 10 wt%.

[0038] In some alternative embodiments, the lithium-containing phosphate with an olivine structure includes lithium cobalt phosphate.

[0039] In some alternative embodiments, the sintering includes: The sintering includes:

[0040] Performing a first sintering on the mixture to obtain a product of the first sintering;

[0041] Crushing the product of the first sintering and then performing a second sintering;

[0042] Optionally, the conditions for the first sintering include: the sintering temperature is 500°C to 800°C, and the heat preservation time is 1 h to 15 h;

[0043] Optionally, the conditions for the second sintering include: the sintering temperature is 500°C to 800°C, and the heat preservation time is 5 h to 30 h.

[0044] In the above technical solution, the sintering is divided into two sintering processes. Through the first sintering, the nucleation size of the grains can be controlled; the second sintering can further repair and round the edges and corners of the particles. By controlling the sintering to be divided into two-stage sintering, it is easier to regulate the growth of grains along specific crystal planes, so as to minimize the grain size on {020} and increase the grain size on other crystal planes without affecting the primary particle size, preventing the specific surface area of the material from being too large. This is beneficial for regulating a material with a short lithium-ion migration path and moderate primary grains; furthermore, it is conducive to significantly improving the kinetic performance of the lithium phosphate material with an olivine structure, slowing down the interfacial side reactions, and improving the comprehensive performance of the lithium phosphate material with an olivine structure.

[0045] In some alternative embodiments, the preparation method further includes: mixing the mixture with a coating precursor to obtain a raw material mixture;

[0046] The sintering includes: subjecting the raw material mixture to a first sintering to obtain a product of the first sintering;

[0047] Crushing the product of the first sintering and then subjecting it to a second sintering to obtain a product of the second sintering;

[0048] Crushing the product of the second sintering and then subjecting it to a third sintering;

[0049] Optionally, the conditions for the first sintering include: a sintering temperature of 200°C to 500°C and a holding time of 1 h to 15 h;

[0050] Optionally, the conditions for the second sintering include: a sintering temperature of 500°C to 800°C and a holding time of 5 h to 30 h;

[0051] Optionally, the conditions for the third sintering include: a sintering temperature of 500°C to 800°C and a holding time of 1 h to 15 h.

[0052] When the cathode active material includes a lithium phosphate with an olivine structure and a carbon coating layer, the sintering is divided into three sintering processes. Through the first sintering, the fast conductor (carbon coating layer) can be uniformly coated; the second sintering can control the nucleation size of the grains; the third sintering can further repair and round the edges and corners of the particles. By controlling the sintering to be divided into three-stage sintering, it is easier to regulate the growth of grains along specific crystal planes, so as to minimize the grain size on {020} and increase the grain size on other crystal planes without affecting the primary particle size, preventing the specific surface area of the material from being too large. This is beneficial for regulating a material with a short lithium-ion migration path and moderate primary grains; furthermore, it is conducive to significantly improving the kinetic performance of the lithium phosphate material with an olivine structure, slowing down the interfacial side reactions, and improving the comprehensive performance of the lithium phosphate material with an olivine structure.

[0053] In some alternative embodiments, the coating precursor includes at least one of glucose, sucrose, fructose, cellulose, acetylene black, pitch, carbon nanotubes, starch, citric acid, polyacrylic acid, or dopamine.

[0054] In some alternative embodiments, the mass percentage of the crystal form control agent in the mixture is 0.1 wt% to 10 wt%; optionally, the mass percentage of the crystal form control agent is 3 wt% to 7 wt%.

[0055] In the above technical solution, by setting the mass percentage of the crystal form control agent in the mixture of the raw materials of the positive electrode active material within the above range, it is beneficial to obtain a material with a short lithium ion migration path and moderate primary crystal grains; and further beneficial to the kinetic performance.

[0056] In some alternative embodiments, the crystal form control agent includes a polymer inducer and / or a cation inducer;

[0057] Optionally, the polymer inducer includes at least one of polyethylene glycol or polyvinylpyrrolidone;

[0058] The cation inducer includes Ta 5+ , Ir 3+ , Y 3+ , Te 4+ , In 3+ or Ga 3+ and at least one of their oxides or salts.

[0059] In the above technical solution, the polymer inducer and / or the cation inducer can affect the growth rate of the particles, thereby regulating the grain size on different crystal planes. Thus, the grain size of the {020}, {200}, and {111} crystal planes of the lithium-containing phosphate material with an olivine structure can be regulated; it is beneficial to obtain a material with a short lithium ion migration path and moderate primary crystal grains; and further beneficial to the kinetic performance.

[0060] In some alternative embodiments, the lithium source includes at least one of lithium salts, lithium hydroxide, or lithium oxide; optionally, the A source includes at least one of salts, oxides, or hydroxides containing element A; optionally, the B source includes at least one of salts, oxides, or hydroxides containing element B; optionally, the phosphorus source includes at least one of phosphates or phosphoric acid.

[0061] The positive electrode sheet can effectively improve the kinetic performance of the lithium ion battery by using the positive electrode active material provided in the first aspect or the positive electrode active material prepared by the preparation method of the positive electrode active material provided in the second aspect.

[0062] In a third aspect, an embodiment of the present application provides a battery, which includes the positive electrode sheet provided in the third aspect.

[0063] In the above technical solution, by providing the positive electrode active material provided in the first aspect, or the positive electrode active material prepared by the preparation method of the positive electrode active material provided in the second aspect, the kinetic performance of the lithium-ion battery can be effectively improved.

[0064] In a fourth aspect, an embodiment of the present application provides an electrical device, which includes the battery provided in the fourth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0066] Figure 1 Structural schematic diagram of a vehicle provided in some embodiments of the present application;

[0067] Figure 2 Explosion diagram of a battery provided in some embodiments of the present application;

[0068] Figure 3 For Figure 2 Explosion diagram of the battery cell shown;

[0069] Figure 4 Partial structural schematic diagram of an electrode assembly provided in some embodiments of the present application;

[0070] Figure 5 Partial structural schematic diagram of a positive electrode sheet provided in some embodiments of the present application.

[0071] ICON:

[0072] Vehicle 1000;

[0073] Battery 100; Controller 200; Motor 300;

[0074] Box body 10; First part 11; Second part 12; Accommodating space 13;

[0075] Battery cell 20; Outer shell 21; Electrode assembly 22; Electrode terminal 23; Pressure relief structure 24;

[0076] Shell 211; Cover 212; Positive electrode sheet 221; Negative electrode sheet 222; Separator 223;

[0077] Positive current collector 2211; Positive active material layer 2212;

[0078] Negative current collector 2221; Negative active material layer 2222. Detailed implementation manners

[0079] The embodiments of the technical solutions of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solutions of the present application more clearly, so they are only examples and cannot be used to limit the protection scope of the present application.

[0080] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field 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 drawings are intended to cover non-exclusive inclusion.

[0081] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features.

[0082] In the description of the embodiments of this application, the orientation or positional relationship indicated by technical terms such as "inside" and "outside" is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of this application and simplifying the description, rather than indicating or implying 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 this application.

[0083] In the description of the embodiments of this application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "connection", and "fixation" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of this application can be understood according to specific circumstances.

[0084] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0085] In the embodiments of the present application, the same reference numerals denote the same components, and for the sake of brevity, in different embodiments, the detailed description of the same components is omitted. It should be understood that the heights, lengths, widths, etc. of various components in the embodiments of the present application shown in the drawings, as well as the overall height, length, width, etc. of the integrated device are only for illustrative purposes and should not constitute any limitation to the present application.

[0086] When the lithium phosphate material with olivine structure is used in a battery, due to its extremely high lithium deintercalation / insertion potential (4.85 V vs Li / Li + ), a serious side reaction occurs between the cathode material and the electrolyte, the electrolyte is consumed to generate a large amount of gas, and the capacity decay is accelerated. At the same time, the relatively low conductivity and low lithium ion mobility of the lithium phosphate material with olivine structure result in poor kinetics and it is difficult to exert its capacity.

[0087] The embodiments of the present application provide a cathode active material, which includes:

[0088] Lithium-containing phosphate with olivine structure; the chemical formula of the lithium-containing phosphate with olivine structure includes: Li 1+x A 1- y B y PO z , -0.1 ≤ x ≤ 0.3, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 4; wherein, the A element includes one or more elements of Co, Ni, Fe, Mn or V; the B element includes one or more elements of Ta, Ir, Te, Ti, Mg, Ca, Sr, Cr, In, Cu, Zn, Zr, Y, Mo, Nb, Al, W or La; the lithium-containing phosphate with olivine structure has a Pnma space configuration;

[0089] The cathode active material satisfies:

[0090] 0.09° ≤ FWHM{020} ≤ 0.4°; 0.04° ≤ FWHM{200} ≤ 0.07°; 0.04° ≤ FWHM{111} ≤ 0.07°;

[0091] FWHM{020} is the full width at half maximum of the {020} diffraction peak in the X-ray diffraction pattern of the cathode active material;

[0092] FWHM{200} is the full width at half maximum of the {200} diffraction peak in the X-ray diffraction pattern of the cathode active material;

[0093] FWHM{111} is the full width at half maximum of the {111} diffraction peak in the X-ray diffraction pattern of the cathode active material.

[0094] In the lithium phosphate material with olivine structure, Li +The transmission path of [Li] mainly passes through the {020} crystal plane. Shortening the grain size on this crystal plane is beneficial to shortening the Li + migration path; however, the primary grain size cannot be made too small at the same time; if the primary grain size is too small, the specific surface area of the material will be too large, which may bring some side reactions and deteriorate the cycling performance.

[0095] Therefore, it is desired to design a material that can shorten the migration path of lithium ions while the primary grain size is above 50 nm. In the lithium-containing phosphate material, the Li + transmission path mainly passes through the {020} crystal plane. Reducing the grain size on this crystal plane is beneficial to shortening the Li + migration path. At the same time, increasing the grain size on the crystal planes where other non-primary Li + is transmitted can ensure that the primary grains are not too small.

[0096] Generally, the full-width at half-maximum data can be obtained through XRD testing, and then the grain size on each crystal plane can be calculated according to the Scherrer formula. It should be noted that if the full-width at half-maximum is too small and the grains are too large (above 200 nm), the error in calculating the grain size using the Scherrer formula is relatively large.

[0097] Therefore, it is necessary to regulate the full-width at half-maximum of at least three different crystal planes to regulate a material with a short lithium ion migration path and moderate primary grains. Therefore, the full-width at half-maximum ranges of {020} (Li + conduction plane), {200} (perpendicular to {020}), and {111} (with a relatively large full-width at half-maximum and a small error) are limited. Specifically: controlling the full-width at half-maximum FWHM of each crystal plane of the above-mentioned positive electrode active material to satisfy:

[0098] 0.09° ≤ FWHM{020} ≤ 0.4°; 0.04° ≤ FWHM{200} ≤ 0.07°; 0.04° ≤ FWHM{111} ≤ 0.07°; This can reduce the grain size growing on the {020} crystal plane, which is beneficial to the utilization of the material capacity; and make the primary grain size moderate, thus being beneficial to improving the kinetic performance; and can slow down the interfacial side reactions, which is beneficial to improving the cycling performance of the material.

[0099] Furthermore, due to the low lithium-ion mobility and electronic conductivity of the lithium phosphate material with an olivine structure, the kinetic performance is very poor. To shorten the lithium-ion migration path, the material can be nano-processed so that the material can exert its capacity as much as possible. However, this method of nano-processing the material may result in an excessively large specific surface area of the material, which exacerbates the side reaction between the positive electrode material and the electrolyte at ultra-high voltages (above 4.8 V), leading to severe capacity decay. Compared with this direct method of nano-processing the material, the technical solution of the above embodiment of the present application controls the full width at half maximum (FWHM) of each crystal plane of the above positive electrode active material to satisfy: 0.09° ≤ FWHM{020} ≤ 0.4°; 0.04° ≤ FWHM{200} ≤ 0.07°; 0.04° ≤ FWHM{111} ≤ 0.07°; thereby enabling the regulation of a material with a short lithium-ion migration path and moderate primary grains; not only can effectively shorten the lithium-ion migration path, which is beneficial to the first charge-discharge specific capacity of the battery, but also will not cause the specific surface area of the material to be too large, thus being able to take into account the improvement of the cycle performance.

[0100] The present application provides a positive electrode plate including the aforementioned positive electrode active material.

[0101] By providing the positive electrode active material provided by the aforementioned embodiment, the kinetic performance of the lithium-ion battery can be improved.

[0102] The present application provides a battery including the aforementioned positive electrode plate.

[0103] By providing the positive electrode plate provided by the aforementioned embodiment, it is beneficial to improve the kinetic performance of the battery.

[0104] The present application provides an electrical equipment including the aforementioned battery.

[0105] By providing the battery provided by the aforementioned embodiment, the comprehensive performance of the electrical equipment is improved.

[0106] See Figure 1 , Figure 1 is a schematic structural diagram of a vehicle 1000 provided by some embodiments of the present application. The vehicle 1000 can be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. The vehicle 1000 is internally provided with a battery 100, and the battery 100 can be arranged at the bottom, head or tail of the vehicle 1000. The battery 100 can be used for the power supply of the vehicle 1000. For example, the battery 100 can be used as the operating power source of the vehicle 1000. The vehicle 1000 can also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300. For example, it is used for the working power requirements during the start, navigation and driving of the vehicle 1000.

[0107] 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.

[0108] In the present application, the battery 100 refers to a single physical module including one or more battery cells 20 to provide voltage and capacity. The battery 100 generally includes a box 10 for encapsulating one or more battery cells 20. The box 10 can prevent liquids or other foreign objects from affecting the charging or discharging of the battery cells 20.

[0109] See Figure 2 , Figure 2 is an exploded view of the battery 100 provided in some embodiments of the present application. The battery 100 can include a box 10 and battery cells 20, and the battery cells 20 are accommodated in the box 10. Among them, the box 10 is used to accommodate the battery cells 20, and the box 10 can be of various structures. In some embodiments, the box 10 can include a first part 11 and a second part 12. The first part 11 and the second part 12 are covered with each other, and the first part 11 and the second part 12 jointly define an accommodation space 13 for accommodating the battery cells 20. The second part 12 can be a hollow structure with one end open, and the first part 11 is a plate-like structure. The first part 11 covers the open side of the second part 12 to form the box 10 with the accommodation space 13; the first part 11 and the second part 12 can also both be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12 to form the box 10 with the accommodation space 13. Of course, the first part 11 and the second part 12 can be of various shapes, such as a cylinder, a cuboid, etc.

[0110] In the battery 100, the number of battery cells 20 can be one or more. If there are multiple battery cells 20, the multiple battery cells 20 can be connected in series, parallel or in a mixed connection. A mixed connection means that there are both series and parallel connections among the multiple battery cells 20. The multiple battery cells 20 can be directly connected in series, parallel or in a mixed connection together, and then the whole formed by the multiple battery cells 20 is accommodated in the box 10. It can also be that multiple battery cells 20 are first connected in series, parallel or in a mixed connection to form modules, and then multiple modules are connected in series, parallel or in a mixed connection to form a whole and are accommodated in the box 10. The battery 100 can also include other structures. For example, the multiple battery cells 20 can be electrically connected through a busbar component to achieve parallel, series or mixed connection of the multiple battery cells 20.

[0111] See Figure 3 , Figure 3 is for Figure 2Exploded view of the battery cell 20 shown. The battery cell 20 refers to the smallest unit that makes up the battery 100. The battery cell 20 may include a housing 21, an electrode assembly 22, and an electrolyte, and both the electrode assembly 22 and the electrolyte are accommodated within the housing 21.

[0112] The housing 21 may include a housing body 211 and a cover body 212. The housing body 211 is a component for cooperating with the cover body 212 to form an internal sealed space of the battery cell 20, wherein the formed sealed space can be used to accommodate the electrode assembly 22, the electrolyte, and other components. The cover body 212 refers to a component that covers the opening of the housing body 211 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the cover body 212 can be adapted to the shape of the housing body 211 to cooperate with the housing body 211, and functional components such as electrode terminals 23 and pressure relief structures 24 may also be provided on the cover body 212. A sealing ring may be arranged between the opening of the housing body 211 and the cover body 212 for achieving the seal between the housing body 211 and the cover body 212.

[0113] The housing body 211 and the cover body 212 can be of various shapes and various sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shapes of the housing body 211 and the cover body 212 can be determined according to the specific shape and size of the electrode assembly 22. The materials of the housing body 211 and the cover body 212 can be various, such as but not limited to metals such as copper, iron, aluminum, stainless steel, and aluminum alloy. The materials of the sealing ring can be various, such as but not limited to materials that are resistant to electrolyte corrosion, have high toughness, and are fatigue-resistant, such as PP (polypropylene), PC (polycarbonate), and PET (polyethylene terephthalate). A coating can be formed on the outer surface of the housing body 211, and the materials of the coating can be various, such as but not limited to corrosion-resistant materials such as Ni and Cr.

[0114] See Figure 4 , the electrode assembly 22 may be composed of a positive electrode tab 221, a negative electrode tab 222, and a separator 223. The separator 223 is in the middle of the positive electrode tab 221 and the negative electrode tab 222 to play a role in isolation. The electrode assembly 22 can be a wound structure or a stacked structure, and the embodiments of the present application are not limited thereto.

[0115] See Figure 5 , the negative electrode tab 222 includes a negative electrode current collector 2221 and a negative electrode active material layer 2222. The material of the negative electrode current collector 2221 can be copper, and the negative electrode active material layer 2222 includes a negative electrode active material. The negative electrode active material includes at least one of graphite, silicon, silicon alloy, or tin alloy.

[0116] Please continue to see Figure 5, the positive electrode plate 221 includes a positive electrode current collector 2211 and a positive electrode active material layer 2212. Taking a lithium-ion battery cell as an example, the material of the positive electrode current collector 2211 can be aluminum. The positive electrode active material layer 2212 includes a positive electrode active material.

[0117] In some embodiments of the present application, the above-mentioned positive electrode active material includes:

[0118] Lithium-containing phosphate with an olivine structure; the chemical formula of the lithium-containing phosphate with an olivine structure includes: Li 1+x A 1- y B y PO z , -0.1 ≤ x ≤ 0.3, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 4; wherein, element A includes one or more elements of Co, Ni, Fe, Mn or V; element B includes one or more elements of Ta, Ir, Te, Ti, Mg, Ca, Sr, Cr, In, Cu, Zn, Zr, Y, Mo, Nb, Al, W or La; the lithium-containing phosphate with an olivine structure has a Pnma space configuration;

[0119] The positive electrode active material satisfies:

[0120] 0.09° ≤ FWHM{020} ≤ 0.4°; 0.04° ≤ FWHM{200} ≤ 0.07°; 0.04° ≤ FWHM{111} ≤ 0.07°;

[0121] FWHM{020} is the full width at half maximum of the {020} diffraction peak in the X-ray diffraction pattern of the positive electrode active material;

[0122] FWHM{200} is the full width at half maximum of the {200} diffraction peak in the X-ray diffraction pattern of the positive electrode active material;

[0123] FWHM{111} is the full width at half maximum of the {111} diffraction peak in the X-ray diffraction pattern of the positive electrode active material.

[0124] In the above technical solution, the full width at half maximum: refers to the peak width at half of the diffraction peak height, that is, a straight line parallel to the peak bottom is drawn through the midpoint of the peak height, and the distance between the two intersection points of this straight line and the two sides of the peak.

[0125] Further, in some embodiments of the present application, the above-mentioned full width at half maximum can be obtained by analyzing the XRD pattern of the material using analysis software Jade or highscore.

[0126] Further, in some embodiments of the present application, the XRD pattern can refer to the General Rules for X-ray Diffraction Analysis of JIS K0131-1996. The powder is pressed into a sheet, and the step-scanning method is used to measure the X-ray diffraction pattern of the positive electrode active material using CuKα1 radiation. The wavelength of CuKα1 radiation is 0.1540562 nm. Scanning speed: 2° / min; scanning range: 2θ = 10° to 80°; a {020} diffraction peak is observed in the range of 2θ = 30.15° ± 0.5°; a {200} diffraction peak is observed in the range of 2θ = 17.37° ± 0.5°; a {111} diffraction peak is observed in the range of 2θ = 25.4° ± 0.5°.

[0127] Further, in some embodiments of the present application, the chemical formula of the positive electrode active material includes: Li 1+x A 1- y B y PO z , -0.1 ≤ x ≤ 0.3, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 4; wherein, A includes one or more elements of Co, Ni, Fe, Mn, or V; B includes one or more elements of Ta, Ir, Te, Ti, Mg, Ca, Sr, Cr, In, Cu, Zn, Zr, Y, Mo, Nb, Al, W, or La.

[0128] Further, by way of example, in some embodiments of the present application, the above Li 1+x A 1-y B y PO z in, x can be selected from -0.1, -0.08, -0.05, 0, 0.05, 0.1, 0.2, 0.28, 0.3 or the range between any two of the foregoing values; y can be selected from 0, 0.01, 0.02, 0.05, 0.1, 0.15, 0.18, 0.2 or the range between any two of the foregoing values.

[0129] Further, by way of example, in some embodiments of the present application, the above Li 1+x A 1-y B y PO z can be LiCoPO 4 、LiNiPO 4 、LiFePO 4 、LiMnPO 4 、LiVPO 4 、LiCo 0.9 Ta 0.1 PO 4 、LiNi 0.9 Ir 0.1PO 4 、LiFe 0.9 Te 0.1 PO 4 、LiMn 0.9 Ti 0.1 PO 4 Or LiV 0.9 Mg 0.1 PO 4 。

[0130] When Li 1+x A 1-y B y PO z selects two or more elements for A in, it satisfies Li 1+x (A1A2) 1-y B y PO 4 ; that is, the sum of A1 and A2 satisfies 1 - y, and the proportion of A1 and A2 can be arbitrarily selected; for example, LiCo 0.45 Ni 0.45 Ta 0.1 PO 4 ; LiCo 0.40 Ni 0.50 Ta 0.1 PO 4 。

[0131] When Li 1+x A 1-y B y PO z selects two or more elements for B in as well, it satisfies Li x (A1A2) 1-y (B1B2) y PO 4 ; that is, the sum of B1 and B2 satisfies y, and the proportion of B1 and B2 can be arbitrarily selected; for example, LiCo 0.45 Ni 0.45 Ca 0.05 Sr 0.05 PO 4 ; LiCo 0.45 Ni 0.45 Cu 0.01 Zn 0.09 PO 4 ;

[0132] It should be further noted that during the charge and discharge process of the battery, the insertion and extraction and consumption of Li will occur, and the molar content of Li is different when the battery is discharged to different states. In the listing of the positive active material in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive active material is applied to the battery system, after charge and discharge cycles, the molar content of Li will change.

[0133] In the listing of the positive active material in this application, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0134] The above-mentioned Li 1+x A 1-y B y PO z When the material is doped with elements in the manner described above, it is beneficial to stabilize the bulk structure of the lithium phosphate material with an olivine structure.

[0135] Furthermore, in the above technical solution, by controlling the full width at half maximum FWHM of each crystal plane of the above positive active material to satisfy:

[0136] 0.09° ≤ FWHM{020} ≤ 0.4°; 0.04° ≤ FWHM{200} ≤ 0.07°; 0.04° ≤ FWHM{111} ≤ 0.07°; thus, a material with a short lithium ion migration path and moderate primary grains is regulated; furthermore, it is beneficial to significantly improve the kinetic performance of the lithium phosphate material with an olivine structure, slow down the interfacial side reactions, and improve the comprehensive performance of the lithium phosphate material with an olivine structure.

[0137] Further optionally, in some embodiments of this application, 0.25° ≤ FWHM{020} ≤ 0.4°; 0.059° ≤ FWHM{200} ≤ 0.07°; 0.065° ≤ FWHM{111} ≤ 0.07°.

[0138] Exemplarily, in some embodiments of this application, FWHM{020} is 0.25°, 0.26°, 0.27°, 0.28°, 0.29°, 0.30°, 0.31°, 0.35°, 0.4° or the range between any two of the foregoing values. FWHM{200} is 0.059°, 0.060°, 0.061°, 0.062°, 0.063°, 0.064°, 0.065°, 0.066°, 0.067°, 0.068°, 0.07° or the range between any two of the foregoing values. FWHM{111} is 0.065°, 0.066°, 0.067°, 0.068°, 0.069°, 0.07° or the range between any two of the foregoing values.

[0139] Further, in some embodiments of the present application, the grain size D of each crystal plane of the positive electrode active material satisfies:

[0140] 20nm ≤ D{020} ≤ 90nm; 114nm ≤ D{200} ≤ 199nm; 115nm ≤ D{111} ≤ 201nm.

[0141] In the above technical solution, the crystal plane refers to: during the spontaneous growth process of a crystal, a polyhedral shape composed of planes with different orientations can be developed, and the planes in these polyhedral shapes are called crystal planes.

[0142] In the above technical solution, the grain size D refers to the average grain size on the (hkl) crystal plane.

[0143] Exemplarily, D{020} is the average grain size on the (020) plane; D{200} is the average grain size on the (200) plane; D{111} is the average grain size on the (111) plane.

[0144] It should also be noted that the above "grain" refers to primary grains or primary particles.

[0145] Further, in some embodiments of the present application, the test method for the grain size D of each crystal plane described above includes:

[0146] By performing XRD testing on the material and using Jade analysis software to obtain the full width at half maximum of different diffraction peaks, selecting the stronger peaks {020}, {200}, {111}, and calculating the grain size under the corresponding crystal plane through the Scherrer formula D = Kγ / Bcosθ (where D is the grain size, K is the Scherrer constant, γ is the X-ray wavelength, B is the full width at half maximum of the corresponding diffraction peak, and θ is the diffraction angle).

[0147] In the above technical solution, by setting the grain size D of each crystal plane of the positive electrode active material to satisfy: 20nm ≤ D{020} ≤ 90nm; 114nm ≤ D{200} ≤ 199nm; 115nm ≤ D{111} ≤ 201nm; it is possible to minimize the grain size on {020} and increase the grain size on other crystal planes to the greatest extent without affecting the size of the primary particles, thereby effectively obtaining a material with a short lithium ion migration path and moderate primary grains, and further improving the first charge-discharge specific capacity and cycle performance of the material.

[0148] Further optionally, in some embodiments of the present application, 20nm ≤ D{020} ≤ 33nm; 114nm ≤ D{200} ≤ 134nm; 115nm ≤ D{111} ≤ 124nm.

[0149] Exemplarily, in some embodiments of the present application, D{020} is 20 nm, 22 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 nm, 32 nm, 33 nm, or a range between any two of the foregoing values. D{200} is 114 nm, 115 nm, 117 nm, 118 nm, 120 nm, 125 nm, 130 nm, 132 nm, 133 nm, 134 nm, or a range between any two of the foregoing values. D{111} is 115 nm, 116 nm, 118 nm, 120 nm, 123 nm, 124 nm, or a range between any two of the foregoing values.

[0150] Further, in some embodiments of the present application, the primary particle size of the positive electrode active material is greater than or equal to 50 nm.

[0151] The "primary particle size" of the above positive electrode material is the "grain size of the primary grains" of the lithium-containing phosphate crystal with an olivine structure.

[0152] Further, in some embodiments of the present application, the test method for the primary particle size of the positive electrode active material is as follows:

[0153] By performing XRD testing on the material and using Jade analysis software to obtain the full width at half maximum (FWHM) of different diffraction peaks, select the stronger peaks {020}, {200}, {111}, and calculate the grain size under the corresponding crystal plane through the Scherrer formula D = Kγ / Bcosθ (where D is the grain size, K is the Scherrer constant, γ is the X-ray wavelength, B is the FWHM of the corresponding diffraction peak, and θ is the diffraction angle). Then sum up the grain sizes under the {020}, {200}, {111} corresponding crystal planes obtained by calculation and take the average value to obtain the average grain size. The average grain size is the primary particle size.

[0154] Further optionally, in some embodiments of the present application, the primary particle size of the positive electrode active material is 50 nm to 200 nm.

[0155] Exemplarily, in some embodiments of the present application, the primary particle size of the positive electrode active material is 50 nm, 51 nm, 53 nm, 55 nm, 58 nm, 60 nm, 65 nm, 70 nm, 80 nm, 90 nm, 95 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, or a range between any two of the foregoing values.

[0156] Further optionally, in some embodiments of the present application, the primary particle size of the positive electrode active material is 91 nm to 92 nm.

[0157] In the above technical solution, by setting the primary particle size of the positive electrode active material within the above range, the migration path of lithium ions can be shortened, and the specific surface area of the positive electrode material will not be too large; thus, the first charge-discharge specific capacity and cycle performance of the material can be improved simultaneously.

[0158] Further, in some embodiments of the present application, the specific surface area of the positive electrode active material is 5 m 2 / g to 15 m 2 / g.

[0159] The above specific surface area refers to the total area possessed by a unit mass of the material.

[0160] In some embodiments of the present application, the above specific surface area can be obtained by the following method:

[0161] According to GB / T 19587-2004 gas adsorption BET method, after the sample is heated and degassed, at a constant low temperature, the adsorption amount of gas on the solid surface under different adsorption pressures is measured, and based on the BET multi-layer adsorption theory and its formula, the monolayer adsorption amount of the sample is obtained, so as to calculate the specific surface area of the unit mass solid sample.

[0162] Exemplarily, in some embodiments of the present application, the specific surface area of the above positive electrode active material is 5 m 2 / g, 5.2 m 2 / g, 5.5 m 2 / g, 5.8 m 2 / g, 6 m 2 / g, 7 m 2 / g, 8 m 2 / g, 9 m 2 / g, 10 m 2 / g, 11 m 2 / g, 12 m 2 / g, 13 m 2 / g, 14 m 2 / g, 15 m 2 / g or the range between any two of the foregoing values.

[0163] Further optionally, in some embodiments of the present application, the specific surface area of the positive electrode active material is 7 m 2 / g to 8.8 m 2 / g. In the above technical solution, by setting the specific surface area of the positive electrode active material within the above range, the side reactions on the material surface can be slowed down; even at ultra-high voltages (above 4.8 V), side reactions are not likely to occur, which is beneficial to the cycle performance of the material.

[0164] Further, in some embodiments of the present application, the D of the positive electrode active materialv The D50 is from 0.1 μm to 10 μm.

[0165] The above-mentioned D V The D50 refers to the average particle size of the positive electrode active material powder. When the positive electrode active material particles are accumulated from small to large, and when the accumulation reaches 50% of the total volume, if the particle size of the positive electrode active material particles is all less than a certain value at this time, then this value is the D50 value. V The value of D50.

[0166] In some embodiments of the present application, the above-mentioned D v The D50 is measured by referring to GB / T 19077-2016 / ISO 13320:2009 laser diffraction method for particle size distribution, using the equipment Malvern 3000.

[0167] Exemplarily, in some embodiments of the present application, the D50 of the positive electrode active material v is 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or the range between any two of the foregoing values.

[0168] In the above technical solution, by setting the D50 of the positive electrode active material v to be from 0.1 μm to 10 μm, parameters such as specific surface area can be better regulated, which is beneficial to the exertion of kinetic performance and material capacity.

[0169] Further, in some embodiments of the present application, the positive electrode active material further includes a carbon coating layer covering at least part of the surface of the lithium-containing phosphate in the olivine structure.

[0170] Further, in some embodiments of the present application, the carbon coating layer covering at least part of the surface of the lithium-containing phosphate in the olivine structure includes: the carbon coating layer completely covers the surface of the lithium-containing phosphate in the olivine structure; or part of the surface of the lithium-containing phosphate in the olivine structure is covered by the carbon coating layer, and part of the surface is exposed.

[0171] As a fast conductor, the carbon coating layer is beneficial to the conductivity of electrons. In the above technical solution, by setting the carbon coating layer, the conductivity of the positive electrode material can be improved; thus, it is beneficial to the improvement of the kinetic performance of the positive electrode material.

[0172] Further, in some embodiments of the present application, the lithium-containing phosphate in the olivine structure includes lithium cobalt phosphate as lithium cobalt phosphate (LiCoPO 4 ).

[0173] Further, in some embodiments of the present application, the positive electrode active material further includes a coating covering lithium cobalt phosphate (LiCoPO 4A carbon coating layer on at least a part of the surface.

[0174] Further, in some embodiments of the present application, the above-mentioned carbon coating layer is coated on at least a part of the surface of LiCoPO 4 At least a part of the surface including: the carbon coating layer completely coats the surface of LiCoPO 4 The surface; or a part of the surface of LiCoPO 4 A part of the surface is coated with a carbon coating layer, and a part of the surface is exposed.

[0175] The carbon coating layer is coated on at least a part of the surface of LiCoPO 4 At least a part of the surface is beneficial to improving the electronic conductivity of LiCoPO 4 Thereby, it is beneficial to improve the kinetic performance of the cathode material.

[0176] Further, in some embodiments of the present application, the carbon content in the cathode active material is 0.2 wt% to 10 wt%.

[0177] Exemplarily, the carbon content in the cathode active material is 0.2 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt% or the range between any two of the foregoing values.

[0178] In the above technical solution, by setting the carbon content in the cathode active material within the above range, it is beneficial to obtain excellent kinetic performance.

[0179] Further, in some embodiments of the present application, the carbon content in the above-mentioned cathode active material is tested according to the following test method:

[0180] Referring to the General Rules for the Determination of Carbon and Sulfur Contents of GB / T 20123-2006 / ISO, an appropriate amount of the sample is weighed into a special crucible, an appropriate amount of flux is added and mixed evenly. The sample is burned in oxygen to convert carbon into CO 2 After entering the absorption cell, it is converted into a corresponding signal by the detector. This signal is sampled by the computer, and after linear correction, it is converted into a value proportional to the concentration of CO 2 The values obtained during the entire analysis process are accumulated. After the analysis is completed, this accumulated value is divided by the weight value in the computer, then multiplied by the correction factor, and the blank is deducted to obtain the percentage content of carbon in the sample.

[0181] Some embodiments of the present application provide a preparation method for a cathode active material, and the preparation method includes:

[0182] Mixing a lithium source, an A source, a B source, a phosphorus source and a crystal form control agent to obtain a mixture;

[0183] Sinter the mixture to obtain the positive electrode active material;

[0184] Among them, the positive electrode active material includes: lithium-containing phosphate with an olivine structure; the chemical formula of the lithium-containing phosphate with an olivine structure includes: Li 1+x A 1-y B y PO z , -0.1 ≤ x ≤ 0.3, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 4; where, element A includes one or more elements of Co, Ni, Fe, Mn or V; element B includes one or more elements of Ta, Ir, Te, Ti, Mg, Ca, Sr, Cr, In, Cu, Zn, Zr, Y, Mo, Nb, Al, W or La; the lithium-containing phosphate with an olivine structure has a Pnma space configuration;

[0185] The positive electrode active material satisfies:

[0186] 0.09° ≤ FWHM{020} ≤ 0.4°; 0.04° ≤ FWHM{200} ≤ 0.07°; 0.04° ≤ FWHM{111} ≤ 0.07°;

[0187] FWHM{020} is the full width at half maximum of the {020} diffraction peak in the X-ray diffraction pattern of the positive electrode active material;

[0188] FWHM{200} is the full width at half maximum of the {200} diffraction peak in the X-ray diffraction pattern of the positive electrode active material;

[0189] FWHM{111} is the full width at half maximum of the {111} diffraction peak in the X-ray diffraction pattern of the positive electrode active material.

[0190] In the above technical solution, adopting the above preparation method is beneficial to regulating a material with a short lithium ion migration path and moderate primary grains; furthermore, it is beneficial to significantly improving the kinetic performance of the lithium phosphate material with an olivine structure, slowing down the interfacial side reaction, and improving the comprehensive performance of the lithium phosphate material with an olivine structure.

[0191] Further optionally, in some embodiments of the present application, 0.25° ≤ FWHM{020} ≤ 0.4°; 0.059° ≤ FWHM{200} ≤ 0.07°; 0.065° ≤ FWHM{111} ≤ 0.07°.

[0192] Furthermore, in some embodiments of the present application, the primary particle size of the positive electrode active material is greater than or equal to 50 nm; optionally, the primary particle size of the positive electrode active material is 50 nm to 200 nm.

[0193] Furthermore, in some embodiments of the present application, the specific surface area of the positive electrode active material is 5 m 2 / g to 15 m 2 / g; optionally, the specific surface area of the positive electrode active material is 7 m 2 / g to 8.8 m 2 / g.

[0194] Furthermore, in some embodiments of the present application, the positive electrode active material further includes a carbon coating layer covering at least a part of the surface of the lithium-containing phosphate in the olivine structure.

[0195] Furthermore, in some embodiments of the present application, the carbon content in the positive electrode active material is 0.2 wt% to 10 wt%.

[0196] Furthermore, in some embodiments of the present application, the lithium-containing phosphate in the olivine structure includes lithium cobalt phosphate. Furthermore, in some embodiments of the present application, the sintering includes:

[0197] Performing a first sintering on the mixture to obtain a product of the first sintering;

[0198] Crushing the product of the first sintering and then performing a second sintering;

[0199] Optionally, the conditions of the first sintering include: the sintering temperature is 500 °C to 800 °C, and the heat preservation time is 1 h to 15 h;

[0200] Optionally, the conditions of the second sintering include: the sintering temperature is 500 °C to 800 °C, and the heat preservation time is 5 h to 30 h.

[0201] Exemplarily, in some embodiments of the present application, the above-mentioned first sintering temperature is 510 °C, 520 °C, 550 °C, 580 °C, 600 °C, 650 °C, 700 °C, 750 °C, 800 °C or the range between any two of the foregoing values.

[0202] Exemplarily, in some embodiments of the present application, the above-mentioned second sintering temperature is 510 °C, 520 °C, 550 °C, 580 °C, 600 °C, 650 °C, 700 °C, 750 °C, 800 °C or the range between any two of the foregoing values.

[0203] By using a crystal form control agent, the grain sizes of the {020}, {200}, and {111} crystal planes of the lithium-containing phosphate in the olivine structure can be regulated.

[0204] In the above technical solution, the sintering is divided into two stages. By the first sintering, the nucleation size of the grains can be controlled; the second sintering can further repair and round the edges and corners of the particles. By controlling the sintering in two stages, it is easier to regulate the growth of the grains along specific crystal planes, so as to minimize the grain size on the {020} plane and increase the grain size on other crystal planes without affecting the size of the primary particles, preventing the specific surface area of the material from being too large. This is conducive to regulating a material with a short lithium ion migration path and moderate primary grains; and further conducive to significantly improving the kinetic performance of the lithium phosphate material with an olivine structure, slowing down the interfacial side reactions, and improving the comprehensive performance of the lithium phosphate material with an olivine structure.

[0205] Further, in some embodiments of the present application, when the positive electrode active material includes a lithium-containing phosphate with an olivine structure and a carbon coating layer, the preparation method further includes: mixing the mixture with a coating layer precursor to obtain a raw material mixture;

[0206] The sintering includes: subjecting the raw material mixture to a first sintering to obtain a product of the first sintering;

[0207] Crushing the product of the first sintering and then subjecting it to a second sintering to obtain a product of the second sintering;

[0208] Crushing the product of the second sintering and then subjecting it to a third sintering;

[0209] Optionally, the conditions for the first sintering include: a sintering temperature of 200°C to 500°C and a holding time of 1 h to 15 h;

[0210] Optionally, the conditions for the second sintering include: a sintering temperature of 500°C to 800°C and a holding time of 5 h to 30 h;

[0211] Optionally, the conditions for the third sintering include: a sintering temperature of 500°C to 800°C and a holding time of 1 h to 15 h.

[0212] Exemplarily, in some embodiments of the present application, the above first sintering temperature is 200°C, 210°C, 260°C, 300°C, 350°C, 400°C or a range between any two of the foregoing values.

[0213] Exemplarily, in some embodiments of the present application, the above second sintering temperature is 510°C, 520°C, 550°C, 580°C, 600°C, 650°C, 700°C, 750°C, 800°C or a range between any two of the foregoing values.

[0214] Exemplarily, in some embodiments of the present application, the above-mentioned third sintering temperature is 510 °C, 520 °C, 550 °C, 580 °C, 600 °C, 650 °C, 700 °C, 750 °C, 800 °C or the range between any two of the foregoing values.

[0215] In the above technical solution, the sintering is divided into three times. Through the first sintering, the uniform coating of the fast conductor can be achieved. Through the second sintering, the nucleation size of the grains can be controlled. The third sintering can further repair and round the edges and corners of the particles. By controlling the sintering in three stages, it is easier to regulate the growth of the grains along specific crystal planes, so as to minimize the grain size on {020} and increase the grain size on other crystal planes without affecting the size of the primary particles, so that the specific surface area of the material is not too large. It is beneficial to regulate a material with a short lithium ion migration path and moderate primary grains; and then it is beneficial to significantly improve the kinetic performance of the lithium phosphate material with an olivine structure, slow down the interfacial side reaction, and improve the comprehensive performance of the lithium phosphate material with an olivine structure.

[0216] Further, in some embodiments of the present application, the heat preservation time of the first sintering is 1 h to 15 h.

[0217] Exemplarily, in some embodiments of the present application, the heat preservation time of the first sintering is 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h or the range between any two of the foregoing values.

[0218] In the above technical solution, by setting the heat preservation time of the first sintering to be 1 h to 15 h, it is beneficial to obtain a material with a short lithium ion migration path and moderate primary grains; and then it is beneficial to the kinetic performance.

[0219] Further, in some embodiments of the present application, the heat preservation time of the second sintering is 5 h to 30 h.

[0220] Exemplarily, in some embodiments of the present application, the heat preservation time of the second sintering is 5 h, 6 h, 8 h, 10 h, 12 h, 15 h, 20 h, 25 h, 30 h or the range between any two of the foregoing values.

[0221] In the above technical solution, by setting the heat preservation time of the second sintering to be 5 h to 30 h, it is beneficial to obtain a material with a short lithium ion migration path and moderate primary grains; and then it is beneficial to the kinetic performance.

[0222] Further, in some embodiments of the present application, the heat preservation time of the third sintering is 1 h to 15 h.

[0223] Exemplarily, in some embodiments of the present application, the heat preservation time of the third sintering is 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, or a range between any two of the foregoing values.

[0224] In the above technical solution, by setting the heat preservation time of the third sintering to be 1 h to 15 h, it is beneficial to obtain a material with a short lithium ion migration path and moderate primary grains; and further beneficial to the kinetic performance.

[0225] Further, in some embodiments of the present application, the above sintering can select a solid-phase mixing and sintering process or a spray drying and sintering process for the raw materials.

[0226] Further, in some embodiments of the present application, the crystal form control agent includes a polymer inducer and / or a cation inducer.

[0227] Further, in some embodiments of the present application, the crystal form control agent can be selected from any one of the polymer inducer or the cation inducer alone; or in some embodiments of the present application, the crystal form control agent can be selected from a mixture of the polymer inducer and the cation inducer alone, and the two can be mixed in any ratio in the mixture.

[0228] In the above technical solution, the polymer inducer and / or the cation inducer can affect the growth rate of the particles, thereby regulating the grain size on different crystal planes. Thus, the grain size of the {020}, {200}, and {111} crystal planes of the lithium-containing phosphate material with an olivine structure can be regulated; it is beneficial to obtain a material with a short lithium ion migration path and moderate primary grains; and further beneficial to the kinetic performance.

[0229] Further, in some embodiments of the present application, the polymer inducer includes at least one of polyethylene glycol or polyvinylpyrrolidone.

[0230] Exemplarily, in some embodiments of the present application, the polymer inducer is selected from any one of polyethylene glycol or polyvinylpyrrolidone; or the polymer inducer is selected from a mixture of polyethylene glycol and polyvinylpyrrolidone, and the two are in any ratio in the mixture.

[0231] Further, in some embodiments of the present application, the cation inducer includes Ta 5+ 、Ir 3+ 、Y 3+ 、Te 4+ 、In 3+ or Ga 3+ and at least one of the oxides or salts thereof.

[0232] Exemplarily, in some embodiments of the present application, the cation inducer is selected from oxides or salts of any one of Ta 5+ , Ir 3+ , Y 3+ , Te 4+ , In 3+ or Ga 3+ ; or the cation inducer is selected from a mixture of oxides or salts of Ta 5+ , Ir 3+ , Y 3+ , Te 4+ , In 3+ , Ga 3+ , and the cations in the mixture can be mixed in any proportion; or the cation inducer is selected from a mixture of oxides or salts of Ta 5+ , Ir 3+ , and the cations in the mixture can be mixed in any proportion; or the cation inducer is selected from a mixture of oxides or salts of Te 4+ , In 3+ , Ga 3+ , and the cations in the mixture can be mixed in any proportion.

[0233] Furthermore, in some embodiments of the present application, in the mixture of the raw materials of the positive electrode active material and the crystal form control agent, the mass percentage of the crystal form control agent is 0.1% to 10%. Exemplarily, in some embodiments of the present application, in the mixture of the raw materials of the positive electrode active material and the crystal form control agent, the mass percentage of the crystal form control agent is 0.1%, 0.2%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10% or the range between any two of the foregoing values.

[0234] Further optionally, in some embodiments of the present application, the mass percentage of the crystal form control agent is 3% to 7%. In the above technical solution, by setting the mass percentage of the crystal form control agent in the mixture of the raw materials of the positive electrode active material and the crystal form control agent within the above range, it is beneficial to obtain a material with a short lithium ion migration path and moderate primary grains; and further beneficial to the kinetic performance.

[0235] Furthermore, in some embodiments of the present application, the lithium source includes at least one of lithium salts, lithium hydroxide or lithium oxide.

[0236] Furthermore, in some embodiments of the present application, the A source includes at least one of salts, oxides or hydroxides containing element A.

[0237] Furthermore, in some embodiments of the present application, the B source includes at least one of salts, oxides or hydroxides containing element B.

[0238] Further, in some embodiments of the present application, the phosphorus source includes at least one of phosphate or phosphoric acid.

[0239] Further optionally, by way of example, in some embodiments of the present application, the above lithium salt includes: Li 2 CO 3 , LiOH, LiNO 3 , Li 2 O, Li 3 PO 4 , LiCl, Li 2 SO 4 , LiC 2 H 3 O 2 or LiHSO 4 or at least one of them.

[0240] Further optionally, by way of example, in some embodiments of the present application, the above A source includes a salt, oxide or hydroxide containing element A; by way of example, Co(OH) 2 , NiSO 4 , FeO, MnO or V 2 O 5 or at least one of them.

[0241] Further optionally, by way of example, in some embodiments of the present application, the above B source includes a salt, oxide or hydroxide containing element B; by way of example, Ta 2 O 5 , IrO 2 , TeO, TiO 2 , MgCO, Ca(OH), SrO, Cr 2 (SO4) 3 , In 2 O 3 , CuO, ZnO, ZrO 2 , Y 2 O 3 , MoO 3 , Nb 2 O 5 , Al 2 O 3 , WO 3 or La 2 O 3 or at least one of them.

[0242] Further optionally, by way of example, in some embodiments of the present application, the above phosphate includes NH 3 H 2 PO 4, (NH 4 ) 2 HPO 4 , KH 2 PO 4 , NaH 2 PO 4 or H 3 PO 4 at least one of them.

[0243] Furthermore, in some embodiments of the present application, the coating precursor includes at least one of glucose, sucrose, fructose, cellulose, acetylene black, asphalt, carbon nanotubes, starch, citric acid, polyacrylic acid or dopamine.

[0244] The above-mentioned glucose, sucrose, fructose, cellulose, acetylene black, asphalt, carbon nanotubes, starch, citric acid, polyacrylic acid or dopamine can form a carbon coating layer, which, as a fast conductor, is beneficial to improving the electronic conductivity of the material, and thus beneficial to the improvement of the kinetic performance of the cathode material.

[0245] Some specific embodiments are listed below to better illustrate the present application.

[0246] Example 1

[0247] Provide a battery, which is prepared according to the following steps:

[0248] I.

Preparation method of cathode active material

[0249] Step S1: Based on the stoichiometric ratio of LiCoPO 4 , mix Li 2 CO 3 , Co(OH) 2 , NH 3 H 2 PO 4 in a molar ratio of 1:1:1 for the Li element in Li 2 CO 3 , the Co element in Co(OH) 2 , and the P element in NH 3 H 2 PO 4 to obtain raw materials; then add the crystal form control agent polyethylene glycol and the coating precursor glucose to obtain a raw material mixture; by mass percentage, the addition amount of the crystal form control agent is 5 wt% of the total mass of the raw materials and the crystal form control agent; the addition amount of the coating precursor is 3 wt% of the mass of the raw materials.

[0250] Step S2: Then mix the raw material mixture evenly, and obtain a raw material mixture powder after spray drying at 90°C - 180°C;

[0251] Step S3: Subject the above raw material mixture powder to the first sintering in an N 2 atmosphere: Heat it to 350 °C, hold for 8 hours, and then cool to room temperature; then perform mechanical ball milling, and conduct the second sintering: heat it to 600 °C, hold for 15 hours, and then cool to room temperature; then perform secondary mechanical ball milling, and conduct the third sintering: heat it to 600 °C, hold for 5 hours, and then cool to room temperature to obtain the positive electrode active material.

[0252] II.

Preparation of Positive Electrode Sheet

[0253] Prepare the positive electrode sheet using the positive electrode active material obtained in each of the foregoing examples or comparative examples.

[0254] Mix the positive electrode active material, conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) in a weight ratio of 96:2.5:1.5. Add an appropriate amount of solvent N-methylpyrrolidone (NMP), stir evenly to obtain the positive electrode slurry. Coat the positive electrode slurry on the aluminum foil, and dry it after coating to obtain the positive electrode sheet.

[0255] III.

Preparation of Electrolyte

[0256] The electrolyte is prepared according to the following method:

[0257] In a glove box with an argon atmosphere having a water content of <10 ppm, mix ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) in a weight ratio of EC:PC:DMC = 3:3:3 to obtain a mixed solvent, and then add LiPF 6 , vinylene carbonate (VC), divinyl sulfite (DTD), and 1,3-propane sultone (PS), stir evenly to obtain the electrolyte. Among them, the concentration of LiPF 6 in the electrolyte is 1 mol / L, and the mass percentages of VC, DTD, and PS are 3%, 1%, and 1% in sequence.

[0258] IV.

Preparation of Coin-Type Half Cell

[0259] Using a polypropylene film with a thickness of 12 μm as the separator, place the above-prepared positive electrode sheet, separator, and lithium sheet in sequence, with the separator in the middle of the positive and negative electrode sheets to play a separating role, inject the electrolyte, and process it into shape.

[0260] The preparation process parameters of Example 1 are shown in Table 1 in detail.

[0261] Comparative Example 1

[0262] The difference from Example 1 lies in Step S1 in the first step

Preparation Method of Positive Electrode Active Material

[0263] Based on the stoichiometry of LiCoPO 4 and according to the molar ratio of Li element in Li 2 CO 3 CO(OH) 2 Co element in Co(OH) 3 H 2 PO 4 P element in NH 2 CO 3 CO(OH) 2 NH 3 H 2 PO 4 which is 1:1:1, mix them to obtain the raw materials. Then add the coating precursor glucose to obtain the raw material mixture. The addition amount of the coating precursor is 3wt% of the mass of the raw materials. See Table 1 for details.

[0264] Comparative Example 2

[0265] The difference from Example 1 lies in Steps S1 and S3 in the first step [Preparation method of the positive electrode active material]:

[0266] Step S1: Based on the stoichiometry of LiCoPO 4 and according to the molar ratio of Li element in Li 2 CO 3 CO(OH) 2 Co element in Co(OH) 3 H 2 PO 4 P element in NH 2 CO 3 CO(OH) 2 NH 3 H 2 PO 4 which is 1:1:1, mix them to obtain the raw materials. Then add the coating precursor glucose to obtain the raw material mixture. The addition amount of the coating precursor is 3wt% of the mass of the raw materials.

[0267] Step S3: In an N 2 atmosphere, conduct the first sintering on the above raw material mixture powder: heat up to 350°C, keep warm for 8 hours, and then cool to room temperature; then conduct mechanical ball milling treatment, and conduct the second sintering: heat up to 600°C, keep warm for 15 hours, and then cool to room temperature; then conduct secondary mechanical ball milling treatment, and conduct the third sintering: heat up to 750°C, keep warm for 15 hours, and then cool to room temperature to obtain the positive electrode active material. See Table 1 for details.

[0268] Comparative Example 3

[0269] The difference from Example 1 lies in Step S3 in the first step [Preparation method of the positive electrode active material]:

[0270] The above raw material mixture powder is sintered for the first time in an N 2 atmosphere: heated to 350 °C, held for 8 hours, and then cooled to room temperature; then subjected to mechanical ball milling treatment, and sintered for the second time: heated to 600 °C, held for 15 hours, and then cooled to room temperature; then subjected to secondary mechanical ball milling treatment, and sintered for the third time: heated to 850 °C, held for 15 hours, and then cooled to room temperature to obtain the cathode active material. See Table 1 for details.

[0271] Example 2

[0272] The difference from Example 1 is that step S1 in the first step [Preparation method of cathode active material] is:

[0273] Based on the stoichiometric ratio of LiCo 0.9 Ta 0.1 PO 4 , Li 2 CO 3 , Co(OH) 2 , Ta 2 O 5 , NH 3 H 2 PO 4 are mixed according to the molar ratio of Li 2 CO 3 in Li element, Co(OH) 2 in Co element, Ta 2 O 5 in Ta element, NH 3 H 2 PO 4 being 1:0.9:0.1:1 to obtain the raw materials; then adding the coating precursor glucose to obtain the raw material mixture; (in this example, Ta 2 O 5 acts as both a doping element and a crystal form control agent; by mass percentage, the addition amount of Ta 2 O 5 as the crystal form control agent is 9 wt% of the total mass of the raw materials and the crystal form control agent); the addition amount of the coating precursor is: the addition amount of the coating precursor is 3 wt% of the mass of the raw materials. See Table 1 for details.

[0274] Examples 3 and 5

[0275] The difference from Example 1 is that the addition amount of the crystal form control agent in step S1 of the first step [Preparation method of cathode active material] is different; and the holding temperature of the third sintering in step S3 is different. See Table 1 for details.

[0276] Example 4

[0277] The difference from Example 1 lies in that the addition amount of the crystal form control agent in step S1 of the first step [Preparation method of the positive electrode active material] is different; and the heat preservation time of the first sintering is different; see Table 1 for details.

[0278] Example 6

[0279] The difference from Example 1 lies in that the addition amount of the crystal form control agent in step S1 of the first step [Preparation method of the positive electrode active material] is different. See Table 1 for details.

[0280] Example 7

[0281] The difference from Example 1 lies in that the addition amount of the crystal form control agent in step S1 of the first step [Preparation method of the positive electrode active material] is different; and the heat preservation time of the first sintering, the heat preservation temperature and time of the third sintering are different; see Table 1 for details. Example 8

[0282] The difference from Example 1 lies in that the addition amount of the crystal form control agent in step S1 of the first step [Preparation method of the positive electrode active material] is different; and the heat preservation time of the third sintering in step S3 is different. See Table 1 for details.

[0283] Example 9

[0284] The difference from Example 1 lies in that the addition amount of the crystal form control agent in step S1 of the first step [Preparation method of the positive electrode active material] is different; and the heat preservation time of the first sintering and the heat preservation time of the third sintering are different; see Table 1 for details.

[0285] Example 10

[0286] The difference from Example 1 lies in that the addition amount of the crystal form control agent in step S1 of the first step [Preparation method of the positive electrode active material] is different; and the heat preservation temperature of the third sintering in step S3 is different. See Table 1 for details.

[0287] Example 11

[0288] The difference from Example 1 lies in that the addition amount of the crystal form control agent in step S1 of the first step [Preparation method of the positive electrode active material] is different; and the heat preservation time of the third sintering in step S3 is different. See Table 1 for details.

[0289] Example 12

[0290] The difference from Example 1 lies in that the addition amount of the crystal form control agent in step S1 of the first step [Preparation method of the positive electrode active material] is different; and the temperatures of the second sintering and the third sintering in step S3 are different. See Table 1 for details.

[0291] Example 13

[0292] The difference from Example 1 lies in that the heat preservation time of the second sintering in step S3 of the first step [Preparation method of the positive electrode active material] is different; see Table 1 for details.

[0293] Example 14

[0294] The differences from Example 1 are as follows: in step S1 of the first step [Preparation method of the positive electrode active material], the addition amount of the crystal form control agent is different; and the heat preservation time of the first sintering is different, and the heat preservation temperature of the third sintering is different; see Table 1 for details. Example 15

[0295] The difference from Example 1 lies in step S1 of the first step [Preparation method of the positive electrode active material]:

[0296] Based on the stoichiometric ratio of LiCo 0.9 Mo 0.1 PO 4 Mix Li 2 CO 3 , Co(OH) 2 , MoO 3 , NH 3 H 2 PO 4 According to the molar ratio of Li 2 CO 3 in Li element, Co(OH) 2 in Co element, MoO 3 in Mo element, NH 3 H 2 PO 4 being 1:0.9:0.1:1 for P element in, to obtain raw materials; then add the crystal form control agent polyethylene glycol and the coating layer precursor glucose to obtain a raw material mixture; calculated by mass percentage, the addition amount of the crystal form control agent is 5% of the total mass of the raw materials and the crystal form control agent; the addition amount of the coating layer precursor is 3 wt% of the mass of the raw materials. See Table 1 for details.

[0297] The performance parameters of the positive electrode active materials prepared in each example and comparative example are shown in Table 2 for details.

[0298]

Battery performance test

[0299] The button-type half-cells prepared in each of the examples or comparative examples were used as the test objects. At 25 °C, the battery was charged at a constant current of 0.1C until the voltage reached 5V, and then charged at a constant voltage of 5V until the current reached 0.02C. After standing for 5 minutes, the battery was discharged at a constant current of 0.1C until the voltage reached 3.0V. This was one charge-discharge cycle process, and the first charge-discharge gram capacity (which could be directly read on the blue battery test equipment) was obtained. Then, the cyclic charge-discharge test was carried out according to the above method until the discharge specific capacity decayed to 80% of the first discharge specific capacity, and the number of cycles of the batteries corresponding to each example or comparative example was recorded to obtain the cycle performance in Table 2.

[0300] The test results of the battery performance of each example and comparative example are shown in Table 2.

[0301] Table 1

[0302]

[0303] Table 2

[0304]

[0305]

[0306] It can be seen from the above tabular data that:

[0307] Compared with the comparative examples, for the positive active material of the examples of the present application, within the range of

[0308] 0.09° ≤ FWHM{020} ≤ 0.4°; 0.04° ≤ FWHM{200} ≤ 0.07°; 0.04° ≤ FWHM{111} ≤ 0.07°, the prepared batteries can take into account both the first charge-discharge gram capacity and the cycle performance; for the scheme of Comparative Example 1, the cycle performance is significantly reduced, and it can be seen that the scheme of Comparative Example 1 cannot take into account both the first charge-discharge gram capacity and the cycle performance; similarly, for the scheme of Comparative Example 2, the first charge-discharge gram capacity is significantly reduced, and it can be seen that the scheme of Comparative Example 2 also cannot take into account both the first charge-discharge gram capacity and the cycle performance. For the scheme of Comparative Example 3, the first charge-discharge gram capacity is significantly reduced, and it can be seen that the scheme of Comparative Example 3 also cannot take into account both the first charge-discharge gram capacity and the cycle performance.

[0309] The embodiments described above are some, but not all, of the embodiments of the present application. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application claimed, but merely represents the selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts fall within the scope of protection of the present application.

Claims

1. A positive electrode active material, characterized in that, The positive electrode active material includes: lithium-containing phosphate with an olivine structure; the chemical formula of the lithium-containing phosphate with an olivine structure includes: Li 1+x A 1-y B y PO z , -0.1 ≤ x ≤ 0.3, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 4; wherein, the A element includes one or more elements of Co, Ni, Fe, Mn or V; the B element includes one or more elements of Ta, Ir, Te, Ti, Mg, Ca, Sr, Cr, In, Cu, Zn, Zr, Y, Mo, Nb, Al, W or La; the lithium-containing phosphate with an olivine structure has a Pnma space configuration; the positive electrode active material satisfies: 0.09° ≤ FWHM{020} ≤ 0.4°; 0.04° ≤ FWHM{200} ≤ 0.07°; 0.04° ≤ FWHM{111} ≤ 0.07°; the FWHM{020} is the full width at half maximum of the {020} diffraction peak in the X-ray diffraction pattern of the positive electrode active material; the FWHM{200} is the full width at half maximum of the {200} diffraction peak in the X-ray diffraction pattern of the positive electrode active material; the FWHM{111} is the full width at half maximum of the {111} diffraction peak in the X-ray diffraction pattern of the positive electrode active material.

2. The positive electrode active material according to claim 1, characterized in that, 0.25° ≤ FWHM{020} ≤ 0.4°; 0.059° ≤ FWHM{200} ≤ 0.07°; 0.065° ≤ FWHM{111} ≤ 0.07°.

3. The positive electrode active material according to claim 1 or 2, characterized in that, the primary particle size of the positive electrode active material is greater than or equal to 50 nm; optionally, the primary particle size of the positive electrode active material is 50 nm to 200 nm.

4. The positive electrode active material according to any one of claims 1-3, characterized in that, The specific surface area of the positive electrode active material is 5 m 2 / g to 15 m 2 / g; optionally, the specific surface area of the positive electrode active material is 7 m 2 / g to 8.8 m 2 / g.

5. The positive electrode active material according to any one of claims 1-4, characterized in that, the positive electrode active material further includes a carbon coating layer covering at least a part of the surface of the lithium-containing phosphate in the olivine structure.

6. The positive electrode active material according to any one of claims 1-5, characterized in that, the carbon content in the positive electrode active material is 0.2 wt% to 10 wt%.

7. The positive electrode active material according to any one of claims 1-6, characterized in that, the lithium-containing phosphate in the olivine structure includes lithium cobalt phosphate.

8. A method for preparing a positive electrode active material, characterized in that, the preparation method includes: mixing a lithium source, an A source, a B source, a phosphorus source and a crystal form control agent to obtain a mixture; sintering the mixture to obtain a positive electrode active material; Among them, the positive electrode active material includes: lithium-containing phosphate with an olivine structure; the chemical formula of the lithium-containing phosphate with an olivine structure includes: Li 1+x A 1-y B y PO z , -0.1 ≤ x ≤ 0.3, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 4; wherein, the A element includes one or more elements of Co, Ni, Fe, Mn or V; the B element includes one or more elements of Ta, Ir, Te, Ti, Mg, Ca, Sr, Cr, In, Cu, Zn, Zr, Y, Mo, Nb, Al, W or La; the lithium-containing phosphate with an olivine structure has a Pnma space configuration; the positive electrode active material satisfies: 0.09° ≤ FWHM{020} ≤ 0.4°; 0.04° ≤ FWHM{200} ≤ 0.07°; 0.04° ≤ FWHM{111} ≤ 0.07°; the FWHM{020} is the full width at half maximum of the {020} diffraction peak in the X-ray diffraction pattern of the positive electrode active material; the FWHM{200} is the full width at half maximum of the {200} diffraction peak in the X-ray diffraction pattern of the positive electrode active material; the FWHM{111} is the full width at half maximum of the {111} diffraction peak in the X-ray diffraction pattern of the positive electrode active material.

9. The method for preparing a positive electrode active material according to claim 8, characterized in that, the sintering includes: performing a first sintering on the mixture to obtain a product of the first sintering; crushing the product of the first sintering and then performing a second sintering; optionally, the conditions of the first sintering include: the sintering temperature is 500°C to 800°C, and the heat preservation time is 1 h to 15 h; Optionally, the conditions for the second sintering include: a sintering temperature of 500°C to 800°C and a heat preservation time of 5 h to 30 h.

10. The method for preparing a positive electrode active material according to claim 8, wherein, the preparation method further includes: mixing the mixture with a coating precursor to obtain a raw material mixture; the sintering includes: performing a first sintering on the raw material mixture to obtain a product of the first sintering; crushing the product of the first sintering and then performing a second sintering to obtain a product of the second sintering; crushing the product of the second sintering and then performing a third sintering; Optionally, the conditions for the first sintering include: a sintering temperature of 200°C to 500°C and a heat preservation time of 1 h to 15 h; Optionally, the conditions for the second sintering include: a sintering temperature of 500°C to 800°C and a heat preservation time of 5 h to 30 h; Optionally, the conditions for the third sintering include: a sintering temperature of 500°C to 800°C and a heat preservation time of 1 h to 15 h.

11. The method for preparing a positive electrode active material according to claim 10, wherein, the coating precursor includes at least one of glucose, sucrose, fructose, cellulose, acetylene black, asphalt, carbon nanotubes, starch, citric acid, polyacrylic acid, or dopamine.

12. The method for preparing a positive electrode active material according to any one of claims 8-11, wherein, the mass percentage of the crystal form control agent in the mixture is 0.1 wt% to 10 wt%; optionally, the mass percentage of the crystal form control agent is 3 wt% to 7 wt%.

13. The method for preparing a positive electrode active material according to any one of claims 8-12, wherein, the crystal form control agent includes a polymer inducer and / or a cation inducer; Optionally, the polymer inducer includes at least one of polyethylene glycol or polyvinylpyrrolidone; Optionally, the cation inducer includes an oxide or salt containing at least one element of Ta, Ir, Y, Te, In, or Ga.

14. The method for preparing a positive electrode active material according to any one of claims 8-13, wherein, the lithium source includes at least one of a lithium salt, lithium hydroxide, or lithium oxide; optionally, the A source includes at least one of a salt, oxide, or hydroxide containing element A; optionally, the B source includes at least one of a salt, oxide, or hydroxide containing element B; optionally, the phosphorus source includes at least one of a phosphate or phosphoric acid.

15. A battery, wherein, the battery includes the positive electrode active material according to any one of claims 1-7 or the positive electrode active material prepared by the preparation method according to any one of claims 8-14.

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

Images