Spinel-type lithium-containing manganese composite oxide, method for producing same, positive electrode sheet, secondary battery, and electric device

Abstract

A spinel-type lithium-containing manganese composite oxide having a chemical composition of Li 1+x M y Mn 2‑y O 4‑k , -0.1≤x≤0.2, 0≤y≤0.3, 0≤k≤0.2, M comprises at least one of B, Na, Mg, Al, Si, P, K, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Mo, W and Te; the crystal grain of the spinel-type lithium-containing manganese composite oxide has a spherical-like morphology; the surface of a single crystal grain is connected by a continuous curved surface to a limited surface circumscribing the continuous curved surface, or is a continuous curved surface; the number of limited surfaces circumscribing the continuous curved surface of a single crystal grain observable in a SEM photograph is ≤5, and the ratio of the diameter dA of the limited surface circumscribing the continuous curved surface to the diameter dV of the crystal grain satisfies dA / dV≤0.5; optionally, dA / dV≤0.3.

Description

[0001] Cross-referencing

[0002] This application incorporates, in its entirety, PCT / CN2022 / 118189, entitled “Spinel-type lithium-manganese composite oxide and its preparation method, positive electrode, secondary battery and power device,” filed on September 9, 2022, which is hereby incorporated by reference. Technical Field

[0003] This application relates to the field of secondary batteries, and in particular to a spinel-type lithium-manganese composite oxide and its preparation method, positive electrode sheet, secondary battery and power device. Background Technology

[0004] Lithium-ion batteries are widely used in electric vehicles, consumer electronics, and other fields due to their high energy density, good cycle performance, and high average output voltage. The positive electrode active material is the material in a lithium-ion battery that can insert and extract lithium ions. Manganese-rich lithium-ion positive electrode materials have advantages such as low price, high energy density, environmental friendliness, and high safety performance. Among them, spinel-structured lithium manganese oxide has a significant cost advantage and outstanding safety performance due to its low Li content. However, conventional spinel lithium manganese oxide has a sharp-edged crystal morphology, making it prone to cracking and stress corrosion, which affects the electrochemical performance of lithium-ion batteries. Summary of the Invention

[0005] Based on the above problems, this application provides a spinel-type lithium manganese composite oxide and its preparation method, positive electrode sheet, secondary battery and power device. The spinel-type lithium manganese composite oxide has grains that are not easily cracked or corroded, and its use in the preparation of secondary batteries can improve the service life of secondary batteries.

[0006] One aspect of this application provides a spinel-type lithium-manganese composite oxide with a chemical composition of Li. 1+ x M y Mn 2-y O 4-k Where -0.1≤x≤0.2, 0≤y≤0.3, 0≤k≤0.2, and M includes at least one of B, Na, Mg, Al, Si, P, K, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Mo, W, and Te; the spinel-type lithium-manganese composite oxide grains have a near-spherical morphology; the surface of a single grain is a continuous curved surface, or consists of a continuous curved surface and a finite surface whose contour is circumscribed on the continuous curved surface; the complete field of view is D. V50 ~10D V50 In the SEM images, the number of finite faces that can be observed in a single grain is ≤5, and the ratio of the diameter dA of the finite face to the diameter dV of the grain satisfies dA / dV≤0.5.

[0007] In some embodiments, dA / dV ≤ 0.3.

[0008] In some implementations, the surfaces of individual grains do not have a finite number of adjacent surfaces.

[0009] In some embodiments, the ratio of the major axis L to the minor axis S of the spinel-type lithium manganese composite oxide grains satisfies 1 ≤ L / S ≤ 1.3.

[0010] In some embodiments, 1 ≤ L / S ≤ 1.2, or 1 ≤ L / S ≤ 1.1.

[0011] In some embodiments, the spinel-type lithium-manganese composite oxide particles have a single crystal or near-single crystal morphology.

[0012] In some embodiments, the average grain diameter d of the spinel-type lithium-manganese composite oxide V50 The volume median particle size D of the powder particles V50 The ratio satisfies 0.3 ≤ d V50 / D V50 ≤1.

[0013] In some embodiments, 0.4 ≤ d V50 / D V50 ≤1, 0.5≤d V50 / D V50 ≤1, or 0.6≤d V50 / D V50 ≤1.

[0014] In some embodiments, the spinel-type lithium-manganese composite oxide D V50 The range is from 2 micrometers (μm) to 20 micrometers (μm).

[0015] In some embodiments, the Dvs0 of spinel-type lithium manganese composite oxide is 3 μm to 15 μm.

[0016] In some embodiments, M includes at least two of Na, Al, P, Mo, W, and Te, 0 <y≤0.3。

[0017] In some embodiments, 0.001 ≤ y ≤ 0.1.

[0018] In some embodiments, 0.005 ≤ y ≤ 0.05.

[0019] Secondly, this application also provides a method for preparing the above-mentioned spinel-type lithium-manganese composite oxide, comprising the following steps:

[0020] Prepare raw materials based on the chemical composition of spinel-type lithium-manganese composite oxides;

[0021] The raw materials are mixed and subjected to a first heat treatment in an oxygen-containing atmosphere to prepare an intermediate.

[0022] The intermediate is subjected to a second heat treatment in an oxygen-containing atmosphere;

[0023] The first heat treatment is performed at temperature T1 for a time of 2 hours to 50 hours; the second heat treatment is performed at temperature T2 for a time of 0.5 hours to 20 hours.

[0024] T1 and T2 satisfy the following conditions: 800 degrees Celsius (°C) ≤ T1 ≤ 1100 degrees Celsius (°C), T1 - 200°C ≤ T2 ≤ T1, and T2 ≥ 800°C.

[0025] In some implementations, T1 and T2 satisfy the following condition: T1-100℃≤T2≤T1.

[0026] In some implementations, T1 and T2 satisfy the following condition: 850℃≤T1≤950℃.

[0027] In some embodiments, after the first heat treatment step, the reaction system is further cooled to room temperature to obtain an intermediate; the room temperature is 20°C to 45°C.

[0028] In some embodiments, the volume content of oxygen in the oxygen-containing atmosphere is greater than or equal to 20%;

[0029] In some embodiments, the oxygen-containing atmosphere is air.

[0030] In some embodiments, the raw materials include lithium-containing compounds and manganese-containing compounds.

[0031] In some embodiments, the raw material further includes a dopant compound, wherein the dopant element M in the dopant compound includes at least one of B, Na, Mg, Al, Si, P, K, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Mo, W, and Te.

[0032] In some embodiments, the lithium-containing compound includes at least one of lithium carbonate, lithium oxide, lithium hydroxide, and lithium nitrate; the manganese-containing compound includes at least one of manganese tetroxide, manganese carbonate, manganese trioxide, and manganese hydroxide.

[0033] Thirdly, this application also provides a spinel-type lithium-manganese composite oxide with a chemical composition of Li 1+ x M y Mn 2-x-y O 4-k-0.1≤x≤0.2, 0≤y≤0.3, 0≤k≤0.2, M includes at least one of B, Na, Mg, Al, Si, P, K, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Mo, W and Te; the spinel-type lithium manganese composite oxide grains have a spherical morphology; the surface of a single grain is connected by a continuous surface to a finite surface of the circumscribed continuous surface, or is a continuous surface; the number of finite surfaces of the circumscribed continuous surface that can be observed in the SEM image of a single grain is ≤5, and the ratio of the diameter dA of the finite surface to the diameter dV of the grain satisfies dA / dV≤0.5.

[0034] Fourthly, this application also provides a positive electrode sheet, comprising a spinel-type lithium-manganese composite oxide according to the preparation method of the spinel-type lithium-manganese composite oxide according to the first aspect or a spinel-type lithium-manganese composite oxide according to the preparation method of the second aspect.

[0035] Fifthly, this application also provides a secondary battery, including the positive electrode sheet of the third aspect.

[0036] Sixthly, a battery module comprising the secondary battery of the fourth aspect.

[0037] A seventh aspect is a battery pack, comprising at least one of the secondary battery of the fifth aspect and the battery module of the sixth aspect.

[0038] Eighth aspect, an electrical device comprising at least one selected from the fifth aspect of a secondary battery, the sixth aspect of a battery module, and the seventh aspect of a battery pack.

[0039] The spinel-type lithium manganese composite oxide of this application has a near-spherical morphology of grains, which can prevent cracking and corrosion of the grain surface of the spinel lithium manganese composite oxide due to stress concentration, slow down Mn dissolution, reduce gas production, and thus improve the service life of secondary batteries.

[0040] Details of one or more embodiments of this application are set forth in the following drawings and description, and other features, objects and advantages of this application will become apparent from the specification, drawings and claims. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort. In the drawings:

[0042] Figure 1A scanning electron microscope (SEM) image of a spinel-type lithium-manganese composite oxide according to an embodiment of this application;

[0043] Figure 2 This is a schematic diagram of a secondary battery according to one embodiment of this application;

[0044] Figure 3 for Figure 2 An exploded view of a secondary battery according to an embodiment of this application is shown.

[0045] Figure 4 This is a schematic diagram of a battery module according to one embodiment of this application;

[0046] Figure 5 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0047] Figure 6 for Figure 5 An exploded view of a battery pack according to one embodiment of this application is shown;

[0048] Figure 7 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to an embodiment of this application.

[0049] Explanation of reference numerals in the attached figures:

[0050] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Cover plate; 6 Electrical device. Detailed Implementation

[0051] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0053] This application provides a spinel-type lithium-manganese composite oxide and its preparation method, as well as a positive electrode sheet, secondary battery, battery module, battery pack, and electrical device using the spinel-type lithium-manganese composite oxide. This secondary battery is suitable for various battery-powered electrical devices, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, electric vehicles, ships, and spacecraft, including aircraft, rockets, space shuttles, and spacecraft.

[0054] One embodiment of this application provides a spinel-type lithium-manganese composite oxide with a chemical composition of Li. 1+ x M y Mn 2-y O 4-k Where -0.1≤x≤0.2, 0≤y≤0.3, 0≤k≤0.2, and M includes at least one of B, Na, Mg, Al, Si, P, K, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Mo, W, and Te. The spinel-type lithium-manganese composite oxide grains have a near-spherical morphology. The surface of a single grain is a continuous curved surface, or consists of a continuous curved surface and a finite surface whose contour is circumscribed by the continuous curved surface; within a complete field of view of size D... V50 ~10D V50 In the SEM images, the number of observable finite faces of a single grain is ≤5, and the ratio of the diameter dA of the finite face to the diameter dV of the grain satisfies dA / / dV≤0.5.

[0055] In some embodiments, the grain is a small, irregularly shaped single crystal that makes up a polycrystalline material; that is, the molecules and atoms within the grain are arranged in a regular manner, and the grain is a single crystal separated by independent grain boundaries. D V50 This refers to the particle size at which the cumulative particle size distribution reaches 50% in the volumetric cumulative distribution curve. Physically, it means that 50% of the grains have a particle size smaller than (or larger than) this value. As an example, D... V50 Particle size distribution can be conveniently determined using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK, in accordance with GB / T 19077-2016 Laser Diffraction Method.

[0056] See Figure 1 The image shows a scanning electron microscope photograph of a spinel-type lithium-manganese composite oxide according to an embodiment of this application, along with a statistical diagram of the finite facets, finite facet diameters, and grain diameters. Figure 1 In the diagram, 'a' represents a continuous surface and 'b' represents a finite surface. It can be seen that the spinel-type lithium-manganese composite oxide grains have a spherical morphology, and the area of ​​the finite surface accounts for a relatively small proportion.

[0057] In some embodiments, the number of finite faces whose contours circumscribe a continuous surface can be 1, 2, 3, 4, or 5. The case where the surface of a single grain is a continuous surface can also be understood as the number of finite faces whose contours circumscribe the continuous surface being 0.

[0058] In some embodiments, if the number of finite faces whose contours circumscribe a continuous surface is 0, then the dA / dV value is also 0.

[0059] Meanwhile, in this application, dA / dV is used to characterize the roundness of the surface of the spinel-type lithium-containing manganese composite oxide grains. The smaller the value of dA / dV, the smaller the proportion of the area of the discontinuous surface and the larger the proportion of the area of the continuous surface on the grain surface. Therefore, the grains are closer to spherical grains.

[0060] In some embodiments, dA / dV ≤ 0.3.

[0061] In some embodiments, the dA / dV value can be statistically obtained by the following method: Referring again to Figure 1 , for the three diameters dV1, dV2, and dV3 (with an included angle of 60 ± 10° between each pair) of the ellipse circumscribed by the grain contour, the average value is dV, and for the three diameters dA1, dA2, and dA3 (with an included angle of 60 ± 10° between each pair) of the ellipse circumscribed by the finite face contour, the average value is dA. The number of grains for statistics is not less than 50. Calculate the dA / dV value of each statistically counted grain and take its average value. The statistically counted grains meet the conditions: In the SEM photo with a field size of 5D V50 ~20D V50 , select one or more dense and gapless regions of the grains, and count them from the largest grain. Stop when the sum of the field areas of each grain counted accounts for 80% of the total area of this dense region.

[0062] In this application, by controlling the number of finite faces whose contours circumscribe a continuous surface and dA / dV within a certain range on the surface of the spinel-type lithium-containing manganese composite oxide grains, the spherical-like morphology of the grains can be controlled, thereby enhancing the stability of the subsequent processing and application of the spinel-type lithium-containing manganese composite oxide, avoiding cracking and corrosion of the surface of the spinel-type lithium-containing manganese composite oxide grains due to stress concentration, slowing down Mn dissolution, reducing gas generation, and thus enhancing the service life of the secondary battery.

[0063] In some embodiments, M includes at least two of Na, Al, P, Mo, W, and Te, and 0 < y ≤ 0.3. Doping at least two of the above elements in the spinel-type lithium-containing manganese composite oxide can significantly increase the entropy and make the material more stable.

[0064] In some embodiments, 0.001 ≤ y ≤ 0.1, or 0.005 ≤ y ≤ 0.05.

[0065] In some embodiments, there are no connected finite faces on the surface of individual grains. Understandably, the non-connected finite faces on the surface of the spinel-type lithium manganese composite oxide of this application avoid the formation of sharp edges. This effectively prevents the corners of the spinel-type lithium manganese composite oxide grains from cracking or corroding due to stress concentration during subsequent cell processing and use, thereby slowing down the dissolution of Mn from the spinel-type lithium manganese composite oxide and reducing gas production in the secondary battery.

[0066] In some embodiments, the ratio of the major diameter L to the minor diameter S of the spinel-type lithium manganese composite oxide grains satisfies 1 ≤ L / S ≤ 1.3. The minimum ratio L / S is 1, meaning the grain is closest to a spherical grain; the smaller the L / S ratio, the closer the grain is to a spherical grain, which helps reduce stress concentration and improve the stability of the spinel-type lithium manganese composite oxide.

[0067] In some embodiments, the L / S value can be 1, 1.05, 1.1, 1.15, 1.2, 1.25 or 1.3.

[0068] In some embodiments, 1 ≤ L / S ≤ 1.2 or 1 ≤ L / S ≤ 1.1.

[0069] In some embodiments, the particle morphology of spinel-type lithium-manganese composite oxide is single crystal or near-single crystal. The particles are composed of one or more grains; it should be noted that when a particle consists of a single grain, the particle and the grain are equivalent, but when a particle consists of multiple grains, the particle and the grain are not equivalent. In this embodiment, single crystal refers to a dispersed particle of spinel-type lithium-manganese composite oxide containing only one grain. Near-single crystal (or quasi-single crystal) refers to a dispersed particle of spinel-type lithium-manganese composite oxide composed of a few or a dozen grains. Single crystal or near-single crystal lithium-manganese composite oxides have high mechanical strength and are not easily broken, which can improve the gas generation problem caused by particle breakage.

[0070] In this application, the measurement method for the major axis L and minor axis S of the spinel-type lithium manganese composite oxide grains can be performed using methods known in the art. As an example, the following method can be used: [See again...] Figure 1 The major axis of the circumscribed ellipse of the grain profile is L, and the minor axis of the inscribed ellipse is S. At least 50 grains are counted, and their average value is taken. The counted grains meet the condition that the field of view size is 5D. V50 ~20D V50 In the SEM image, select one or more dense, gapless regions and count them from largest to smallest grains. The count ends when the sum of the field of view areas of each grain accounts for 80% of the total area of ​​the dense region.

[0071] In some embodiments, the average grain diameter dV50 The volume median particle size D of the powder particles V50 The ratio satisfies 0.3 ≤ d V50 / D V50 ≤1. Average grain diameter d V50 The following statistical methods were used to obtain the results: At a field of view size of 5D... V50 ~20D V50 In the SEM images, select one or more dense, gapless regions and count them from largest to smallest grains. Stop counting when the sum of the field of view areas of all grains accounts for 80% of the total area of ​​the dense region. Count the grain sizes d1, d2, ..., dn and calculate the average grain diameter d according to the volume distribution function. V50 = [(d13+d23+……+dn3) / n](1 / 3). The statistical methods for d1, d2, ..., dn are the same as for dV. V50 / D V50 The minimum value is 0, and the maximum value is 1. d V50 / D V50 When d = 1, it is considered a single crystal in the traditional academic sense, with only one grain per particle. In the embodiments of this application, 0.3 ≤ d V50 / D V50 ≤1.

[0072] Furthermore, 0.4≤d V50 / D V50 ≤1, 0.5≤d V50 / D V50 ≤1, or 0.6≤d V50 / D V50 ≤1. d V50 / D V50 A value >0.4 indicates that the material is close to single-crystal particles and has fewer easily cracked grain boundaries. Therefore, the probability of cracking and exposing unstable new surfaces and generating sharp edges during production, processing, and cell use is low, which can further improve the service life of secondary batteries.

[0073] In some embodiments, d V50 / D V50 It can be a range of any of the following values: 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.

[0074] In some embodiments, the D of spinel-type lithium-manganese composite oxide V50 The diameter ranges from 2 μm to 20 μm. Ds of spinel-type lithium-manganese composite oxides... V50 Within the aforementioned range, it can achieve both good dynamic performance and long cycle life.

[0075] In some embodiments, the D of spinel-type lithium-manganese composite oxide V50It can be a range of any of the following values: 2μm, 3μm, 4μm, 5μm, 61μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, or 20μm.

[0076] In some embodiments, the D of spinel-type lithium-manganese composite oxide V50 The size ranges from 3μm to 15μm.

[0077] Another embodiment of this application also provides a method for preparing the above-mentioned spinel-type lithium-manganese composite oxide, including steps S110 to S130:

[0078] Step S110: Prepare raw materials according to the chemical composition of spinel-type lithium manganese composite oxide.

[0079] Step S120: Mix the raw materials and perform a first heat treatment under an oxygen-containing atmosphere to prepare an intermediate.

[0080] Step S130: The intermediate is subjected to a second heat treatment in an oxygen-containing atmosphere.

[0081] The first heat treatment is carried out at a temperature of T1 for a duration of 2 hours to 50 hours; the second heat treatment is carried out at a temperature of T2 for a duration of 0.5 hours to 20 hours. T1 and T2 satisfy the following conditions: 800℃ ≤ T1 ≤ 1100℃, T1 - 200℃ ≤ T2 ≤ T1, and T2 ≥ 800℃. T1 can be selected from any of the following values: 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, or 1100℃.

[0082] The above-mentioned method for preparing spinel-type lithium manganese composite oxides, by reasonably controlling the temperature and time of heat treatment, produces spinel-type lithium manganese composite oxides with a near-spherical morphology and good stability. It can reduce Mn dissolution and gas production, and can improve the service life of secondary batteries.

[0083] In some embodiments, T1 and T2 satisfy the condition: T1-100℃≤T2≤T1. By controlling T1 and T2 to satisfy the above condition, the prepared material is closer to a spherical morphology.

[0084] In some embodiments, T1 and T2 satisfy the condition: 850℃≤T1≤950℃. By controlling T1 within the above range, the prepared spinel-type lithium-manganese composite oxide can achieve both good kinetic performance and stability.

[0085] In some embodiments, after step S120 and before step S130, the method further includes: cooling the reaction system to room temperature to obtain an intermediate; the room temperature is 20°C to 45°C. Through the above cooling step, the spinel-type lithium-manganese composite oxide prepared has a morphology closer to spherical.

[0086] In some embodiments, the volume content of oxygen in the oxygen-containing atmosphere during steps S120 and S130 is greater than or equal to 20%.

[0087] In some embodiments, the oxygen-containing atmosphere is air.

[0088] In some embodiments, the raw materials include lithium-containing compounds and manganese-containing compounds.

[0089] In some embodiments, the lithium-containing compound includes at least one of lithium carbonate, lithium oxide, lithium hydroxide, and lithium nitrate.

[0090] In some embodiments, the lithium-containing compound includes lithium carbonate.

[0091] In some embodiments, the manganese-containing compound includes at least one of manganese tetroxide, manganese carbonate, manganese trioxide, and manganese hydroxide.

[0092] In some embodiments, the manganese-containing compound includes manganese tetroxide.

[0093] In some embodiments, the raw material further includes a dopant compound, wherein the dopant element M in the dopant compound includes at least one of B, Na, Mg, Al, Si, P, K, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Mo, W, and Te.

[0094] In some embodiments, the Na-doped compound includes one or more of sodium hydroxide, sodium carbonate, sodium nitrate, and sodium sulfate.

[0095] In some embodiments, the Al-doped compound includes aluminum oxide, aluminum hydroxide, aluminum carbonate, and lithium aluminate.

[0096] In some embodiments, the Mg-doped compound includes magnesium oxide, magnesium hydroxide, magnesium carbonate, and magnesium nitrate.

[0097] In some embodiments, the Te-doped compound includes TeO2, TeO3, Te2O5, H2TeO3, and H2TeO5.

[0098] In some embodiments, the P-doped compounds include NH4H2PO4, (NH4)3PO4, Li3PO4, and P2O5.

[0099] Another embodiment of this application provides a spinel-type lithium-manganese composite oxide with a chemical composition of Li. 1+x M y Mn2 -x-y O 4-k -0.1≤x≤0.2, 0≤y≤0.3, 0≤k≤0.2, M includes at least one of B, Na, Mg, Al, Si, P, K, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Mo, W and Te; the spinel-type lithium manganese composite oxide grains have a spherical morphology; the surface of a single grain is connected by a continuous surface to a finite surface of the circumscribed continuous surface, or is a continuous surface; the number of finite surfaces of the circumscribed continuous surface that can be observed in the SEM image of a single grain is ≤5, and the ratio of the diameter dA of the finite surface to the diameter dV of the grain satisfies dA / dV≤0.5.

[0100] In addition, the secondary battery, battery module, battery pack and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0101] In one embodiment of this application, a secondary battery is provided.

[0102] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0103] Positive electrode sheet

[0104] The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector. The positive active material layer includes a positive active material, which includes the aforementioned spinel-type lithium-manganese composite oxide.

[0105] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0106] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy on the polymer substrate. The polymer substrate includes substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0107] In some embodiments, the positive electrode active material may optionally include positive electrode active materials for batteries known in the art. As an example, the positive electrode active material may optionally include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, at least one of lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium nickel cobalt oxides, lithium nickel cobalt aluminum oxides, lithium nickel cobalt manganese oxides, and their modified compounds. The modified compounds of lithium nickel cobalt aluminum oxides or lithium nickel cobalt manganese oxides may use the molecular formula Li 1+a2 Ni x2 Co y2 M 1-x2-y2 O2 characterization, 0.5≤a2≤2, 0≤x2≤1, 0≤y2≤1, M includes at least one of Mn, Al, Ti, Mg, Zn, Zr, B, Ca) Examples of lithium phosphates with olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0108] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0109] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0110] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0111] Negative electrode sheet

[0112] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, wherein the negative active material layer includes a negative active material.

[0113] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0114] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy on the polymer substrate. The polymer substrate includes substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0115] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0116] In some embodiments, the negative electrode active material layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0117] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0118] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0119] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0120] electrolytes

[0121] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0122] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0123] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0124] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0125] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0126] Separating membrane

[0127] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0128] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0129] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding process or a stacking process.

[0130] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0131] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The soft pack can be made of plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0132] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 This is an example of a square-structured secondary battery 5.

[0133] In some of these embodiments, reference is made to Figure 3 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0134] In some embodiments, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0135] Figure 4 This is battery module 4, used as an example. (See reference...) Figure 4 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0136] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0137] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0138] Figure 5 and Figure 6 This is battery pack 1 as an example. (See reference...) Figure 5 and Figure 6 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0139] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to.

[0140] As an electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0141] Figure 7This is an example of an electrical device 6. This electrical device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0142] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0143] Example

[0144] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0145] Example 1

[0146] (1) Preparation of lithium-manganese composite oxides: according to the target composition Li 1.05 Mn 2.00 O4 weighs Li2CO3 and Mn3O4 powders in the corresponding stoichiometric ratio, then mixes them evenly to obtain a raw material mixture powder; the above mixture powder is heated to 950℃ in an oxygen atmosphere and held for 10 hours, then cooled to room temperature to obtain an intermediate; the above intermediate is heated to 800℃ and held for 2 hours, then cooled to room temperature to obtain a lithium-manganese composite oxide.

[0147] (2) Preparation of the positive electrode sheet: The lithium manganese composite oxide prepared in step (1) above is mixed with conductive carbon black and PVDF at a mass ratio of 96:2.5:1.5. N-methylpyrrolidone (NMP) is added and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is coated onto aluminum foil and dried to obtain the positive electrode sheet. The loading of lithium manganese composite oxide on the positive electrode sheet is 0.02 g / cm³. 2 .

[0148] (3) Preparation of negative electrode sheet: Artificial graphite (negative electrode active material), carbon black (Super P) (conductive agent), styrene-butadiene rubber (binder), and sodium carboxymethyl cellulose (thickener) are mixed thoroughly in an appropriate amount of deionized water at a mass ratio of 96:1:1:2 to form a uniform negative electrode slurry. The negative electrode slurry is then uniformly coated onto the surface of the copper foil of the negative electrode current collector. After drying and cold pressing, the negative electrode sheet is obtained. The loading of the negative electrode active material on one side of the negative electrode current collector is 0.008 g / cm³. 2 .

[0149] (4) Electrolyte preparation: In an argon atmosphere glove box with a water content of <10ppm, equal volumes of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed to obtain an organic solvent. Then, 1 mol / L of LiPF6 is uniformly dissolved in the organic solvent to obtain the electrolyte.

[0150] (5) Preparation of pouch battery: Using a 12μm thick polypropylene film as the separator, the above-prepared positive electrode, separator, and negative electrode are arranged in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The mixture is then wound into shape and packaged in an aluminum-plastic bag. The electrolyte is injected, and after encapsulation, the capacity is determined to obtain a pouch battery.

[0151] Examples 2-12, Comparative Examples 1-3:

[0152] The difference between Examples 2-12, Comparative Examples 1-3 and Example 1 is that (1) the preparation parameters T1, t1, T2, and t2 of the lithium-manganese composite oxide are different.

[0153] Examples 13-14:

[0154] The difference between Examples 13-14 and Example 1 is that (1) the types of lithium-containing compounds and manganese-containing compounds used in the preparation of lithium-manganese composite oxides are different, and T2 and t2 are different.

[0155] Examples 15-24:

[0156] The difference between Examples 15-24 and Example 1 is that the chemical composition of the lithium-manganese composite oxide is different, the lithium-manganese composite oxide contains dopant element M, and the raw materials include dopant element compounds; T2 and t2 are different.

[0157] Comparative Example 4:

[0158] The difference between Comparative Example 4 and Example 24 is that the chemical composition of the lithium-manganese composite oxide is different.

[0159] Comparative Example 5:

[0160] The chemical composition of the lithium-manganese composite oxide in Comparative Example 5 is Li 1.10 Mn 1.9 Al 0.1 The preparation of lithium-manganese composite oxides includes: weighing Li2CO3, Mn3O4 and Al2O3 powders according to the target composition in the corresponding stoichiometric ratio, then mixing them evenly to obtain a raw material mixture powder; heating the above mixture powder to 900℃ in an oxygen atmosphere and holding it for 10 hours, then cooling it to room temperature to obtain lithium-manganese composite oxides.

[0161] The preparation parameters of the lithium-containing manganese composite oxides in Examples 1-24 and Comparative Examples 1-5 are recorded in Table 1.

[0162] Test section:

[0163] Morphology testing of lithium-manganese composite oxides:

[0164] The samples were tested using a ZEISS Sigma 300 scanning electron microscope, and then tested according to standard JY / T010-1996. The morphology of the samples was observed, and the number of finite surfaces, dA / dV, L / S, and d of the circumscribed continuous surface of the lithium manganese composite oxide were statistically analyzed. V50 Specifically, the average of the three diameters (with pairwise angles of 60±10°) of the circumscribed ellipse of the grain profile is dV, and the average of the three diameters (with pairwise angles of 60±10°) of the circumscribed ellipse of the finite surface profile is dA. At least 50 grains are counted, and the dA / dV value of each counted grain is calculated, then the average is taken. The major axis of the circumscribed ellipse of the grain profile is L, and the minor axis of the inscribed ellipse is S. At least 50 grains are counted, and their average is taken. Based on the statistically obtained L and S, the L / S of the grain is calculated. The counted grains meet the condition that the field of view size is 5D. V50 ~20D V50 In the SEM images, one or more dense, gapless regions are selected, and statistical analysis is performed on the grains from largest to smallest. The analysis stops when the sum of the field-of-view areas of all grains accounts for 80% of the total area of ​​the dense region. The average grain diameter d is then calculated. V50 The following statistical methods were used to obtain the results: At a field of view size of 5D... V50 ~20D V50 In the SEM images, select one or more dense, gapless regions and count them from largest to smallest grains. Stop counting when the sum of the field of view areas of all grains accounts for 80% of the total area of ​​the dense region. Count the grain sizes d1, d2, ..., dn and calculate the average grain diameter d according to the volume distribution function. V50 = [(d13+d23+……+dn3) / h](1 / 3). The statistical methods for d1, d2, ..., dn are the same as those for dV.

[0165] Initial discharge capacity test of pouch battery:

[0166] At 25°C, the pouch battery is charged at a constant current of 1C to a voltage of 4.35V, then charged at a constant voltage of 4.35V to a current of 0.05C. After standing for 5 minutes, the pouch battery is discharged at a constant current of 1C to a voltage of 3.0V. This discharge capacity is the first discharge capacity of the secondary battery.

[0167] High-temperature cycle performance test of pouch batteries:

[0168] At 45℃, the pouch cell is charged at a constant current of 1C to a voltage of 4.35V, then charged at a constant voltage of 4.35V to a current of 0.05C. After resting for 5 minutes, the pouch cell is discharged at a constant current of 1C to a voltage of 3.0V. This constitutes one charging cycle, and the discharge capacity of this cycle is the discharge capacity of the first cycle. Repeated charging and discharging are performed until the discharge capacity decays to 80% of the initial value; the number of cycles is the cycle life.

[0169] The morphological parameters and corresponding secondary battery electrochemical performance of the lithium-manganese composite oxides of Examples 1-24 and Comparative Examples 1-5 are recorded in Table 2.

[0170] Table 1. Preparation parameters of lithium-manganese composite oxides in Examples 1-24 and Comparative Examples 1-5

[0171]

[0172]

[0173] Table 2. Morphology of lithium-manganese composite oxides in Examples 1-24 and Comparative Examples 1-5 and their corresponding electrochemical performance in secondary batteries.

[0174]

[0175]

[0176] As can be seen from the relevant data in Tables 1 and 2, the number of finite faces of the circumscribed continuous surfaces of the lithium-manganese composite oxide profiles in Examples 1 to 24 is 0 to 4, 0 ≤ dA / dV ≤ 0.5, 1.02 ≤ L / S ≤ 1.27, and 0.31 ≤ d V50 / D V50 ≤0.78, D V50 The grains of the lithium-manganese composite oxide have a size of 8.7 μm to 19.4 μm and a near-spherical morphology. The corresponding secondary battery exhibits an initial discharge capacity of 103 mAh / g to 125 mAh / g, and the number of cycles at 45°C where the discharge capacity decays to 80% is 445 cls to 976 cls. The secondary battery demonstrates high capacity and long cycle life. Data from Examples 1-14 and Examples 15-24 show that the doped lithium-manganese composite oxide has a longer cycle life than lithium manganese oxide.

[0177] Comparative Examples 1 and 3, by adjusting the heat treatment conditions during the preparation of lithium-manganese composite oxides, produced lithium-manganese composite oxide grains with an octahedral structure. The corresponding secondary batteries exhibited initial discharge capacities of 118 mAh / g and 115 mAh / g, respectively, and 315 and 277 cycles, respectively, at 45°C, respectively, indicating a significant deterioration in cycle life. Comparative Example 2 produced lithium-manganese composite oxide grains with a near-spherical morphology, but with dA / dV > 0.5. Its corresponding secondary battery had an initial discharge capacity of 117 mAh / g, and 388 cycles, respectively, at 45°C, resulted in a capacity decay to 80%. The cycle life of this secondary battery was slightly better than that of Comparative Examples 1 and 3, but significantly worse than the cycle performance of the secondary batteries in Examples 1–24.

[0178] The chemical composition of the lithium-manganese composite oxide in Comparative Example 4 differs from that of the lithium-manganese composite oxide in this application. Its finite number of circumscribed continuous surfaces is 0, L / S is 1.02, and d... V50 / D V50 It is 0.78, D V50 The size is 10.1 μm, and the grains of the lithium manganese composite oxide have a near-spherical morphology. The corresponding secondary battery has an initial discharge capacity of 91 mAh / g and 934 cycles at 45℃ when the discharge capacity decays to 80%. It can be seen that the secondary battery prepared by the lithium manganese composite oxide in Comparative Example 4 has a longer cycle life, but the initial discharge capacity is significantly reduced, making it difficult to balance battery capacity and cycle performance.

[0179] Comparative Example 5: Lithium-containing manganese composite oxide Li 1.10 Mn 1.9 Al 0.1 O4 was prepared using a traditional process. SEM observation showed that the grain morphology was octahedral or irregular polycrystalline structure. The initial discharge capacity of the corresponding secondary battery was 105 mAh / g, and the number of cycles at which the discharge capacity decayed to 80% at 45°C was 604. Its discharge capacity and cycle life were both inferior to the secondary batteries in Examples 15-24.

[0180] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0181] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A spinel-type lithium-manganese composite oxide, the chemical composition of which is Li 1+x M y Mn 2-y O 4-k , -0.1≤x≤0.2, 0≤y≤0.3, 0≤k≤0.2, M includes at least one of B, Na, Mg, Al, Si, P, K, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Mo, W and Te; the spinel-type lithium manganese composite oxide grains have a near-spherical morphology; the surface of a single grain is connected by a continuous surface to a finite surface of the circumscribed continuous surface, or is a continuous surface; the number of finite surfaces of the circumscribed continuous surface that can be observed in the SEM image of a single grain is ≤5, and the ratio of the diameter dA of the finite surface to the diameter dV of the grain satisfies dA / dV≤0.

5.

2. The spinel-type lithium-manganese composite oxide according to claim 1, wherein, dA / dV≤0.

3.

3. The spinel-type lithium-manganese composite oxide according to claim 1 or 2, wherein, The surface of a single grain does not have a finite number of interconnected surfaces.

4. The spinel-type lithium-manganese composite oxide according to claim 1 or 2, wherein, The ratio of the major axis L to the minor axis S of the spinel-type lithium manganese composite oxide grains satisfies 1 ≤ L / S ≤ 1.

3.

5. The spinel-type lithium-manganese composite oxide according to claim 4, wherein, 1≤L / S≤1.

2.

6. The spinel-type lithium-manganese composite oxide according to claim 4, wherein, 1≤L / S≤1.

1.

7. The spinel-type lithium-manganese composite oxide according to claim 1 or 2, wherein, The spinel-type lithium-manganese composite oxide has a particle morphology of single crystal or near-single crystal.

8. The spinel-type lithium-manganese composite oxide according to claim 1 or 2, wherein, The average grain diameter d of the spinel-type lithium-manganese composite oxide according to volume distribution statistics V50 The volume median particle size D of the powder particles V50 The ratio satisfies: 0.3 ≤ d V50 / D V50 ≤1.

9. The spinel-type lithium-manganese composite oxide according to claim 8, wherein, 0.4≤d V50 / D V50 ≤1。 10. The spinel-type lithium-manganese composite oxide according to claim 8, wherein, 0.5≤d V50 / D V50 ≤1。 11. The spinel-type lithium-manganese composite oxide according to claim 8, wherein, 0.6≤d V50 / D V50 ≤1。 12. The spinel-type lithium-manganese composite oxide according to claim 1 or 2, wherein, The spinel-type lithium-manganese composite oxide D V50 The range is 2μm to 20μm.

13. The spinel-type lithium-manganese composite oxide according to claim 12, wherein, The spinel-type lithium-manganese composite oxide D V50 The size ranges from 3μm to 15μm.

14. The spinel-type lithium-manganese composite oxide according to claim 1 or 2, wherein, M includes at least two of Na, Al, P, Mo, W, and Te, and 0 < y ≤ 0.

3.

15. The spinel-type lithium-manganese composite oxide according to claim 14, wherein, 0.001≤y≤0.1。 16. The spinel-type lithium-manganese composite oxide according to claim 14, wherein, 0.005≤y≤0.05。 17. A method for preparing the spinel-type lithium-manganese composite oxide according to any one of claims 1 to 16, comprising the following steps: Prepare raw materials according to the chemical composition of the spinel-type lithium-manganese composite oxide; The raw materials are mixed and subjected to a first heat treatment in an oxygen-containing atmosphere to prepare an intermediate. The intermediate is subjected to a second heat treatment in an oxygen-containing atmosphere; The first heat treatment is performed at a temperature of T1 for a time of 2 hours to 50 hours; the second heat treatment is performed at a temperature of T2 for a time of 0.5 hours to 20 hours. T1 and T2 satisfy the following conditions: 800℃≤T1≤1100℃, T1-200℃≤T2≤T1, and T2≥800℃.

18. The method for preparing spinel-type lithium-manganese composite oxide according to claim 17, wherein, The conditions T1 and T2 satisfy: T1-100℃≤T2≤T1.

19. The method for preparing spinel-type lithium-manganese composite oxide according to claim 17 or 18, wherein, The conditions T1 and T2 satisfy: 850℃≤T1≤950℃.

20. The method for preparing spinel-type lithium-manganese composite oxide according to claim 17 or 18, wherein, Following the first heat treatment step, the process further includes: cooling the reaction system to room temperature to obtain the intermediate; the room temperature is 20°C to 45°C.

21. The method for preparing spinel-type lithium-manganese composite oxide according to claim 17 or 18, wherein, The oxygen content in the oxygen-containing atmosphere is greater than or equal to 20% by volume.

22. The method for preparing spinel-type lithium-manganese composite oxide according to claim 21, wherein, The oxygen-containing atmosphere is air.

23. The method for preparing spinel-type lithium-manganese composite oxide according to claim 17 or 18, wherein, The raw materials include lithium-containing compounds and manganese-containing compounds.

24. The method for preparing spinel-type lithium-manganese composite oxide according to claim 23, wherein, The raw material also includes a dopant compound, wherein the dopant element M in the dopant compound includes at least one of B, Na, Mg, Al, Si, P, K, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Mo, W and Te.

25. The method for preparing spinel-type lithium-manganese composite oxide according to claim 23, wherein, The lithium-containing compound includes at least one of lithium carbonate, lithium oxide, lithium hydroxide, and lithium nitrate; The manganese-containing compound includes at least one of manganese tetroxide, manganese carbonate, manganese trioxide, and manganese hydroxide.

26. A spinel-type lithium-manganese composite oxide, the chemical composition of which is Li 1+x M y Mn 2-x-y O 4-k , -0.1≤x≤0.2, 0≤y≤0.3, 0≤k≤0.2, M includes at least one of B, Na, Mg, Al, Si, P, K, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Mo, W and Te; the spinel-type lithium manganese composite oxide grains have a near-spherical morphology; the surface of a single grain is connected by a continuous surface to a finite surface of the circumscribed continuous surface, or is a continuous surface; the number of finite surfaces of the circumscribed continuous surface that can be observed in the SEM image of a single grain is ≤5, and the ratio of the diameter dA of the finite surface to the diameter dV of the grain satisfies dA / dV≤0.

5.

27. A positive electrode, comprising the spinel-type lithium-manganese composite oxide according to any one of claims 1 to 16 or the spinel-type lithium-manganese composite oxide prepared by the preparation method according to any one of claims 17 to 25.

28. A secondary battery comprising the positive electrode sheet as described in claim 27.

29. A battery module comprising the secondary battery of claim 28.

30. A battery pack comprising at least one of the secondary battery of claim 28 and the battery module of claim 29.

31. An electrical device comprising at least one selected from the secondary battery of claim 28, the battery module of claim 29, and the battery pack of claim 30.

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