Active material for positive electrodes, positive electrode plate, lithium-ion secondary battery and corresponding battery module, battery pack and device

Abstract

A positive electrode plate, consisting of a positive electrode current collector and an active material layer of the positive electrode, which is arranged on the positive electrode current collector, wherein the active material layer of the positive electrode comprises an active material of the positive electrode, wherein the active material of the positive electrode comprises a lithium nickel cobalt manganese oxide, wherein the molar content of nickel in the lithium nickel cobalt manganese oxide is 60% to 90% of the total molar content of nickel, cobalt and manganese, and the lithium nickel cobalt manganese oxide has a layered crystal structure with the space group R3 m; a transition metal layer of lithium nickel cobalt manganese oxide containing a doping element; and in a differential scanning calorimetry spectrum of the active material of the positive electrode in a 78% delithiated state, an initial exothermic temperature of an exothermic main peak is 200 °C or more and an integral area of ​​the exothermic main peak is 100 J / g or less.

Description

[0001] This utility model claims priority over Chinese patent application No. 201910824127,8 entitled “POSITIVE ELECTRODEACTIVE MATERIAL, POSITIVE ELECTRODE PLATE AND LITHIUM ION SECONDARY BATTERY”, which was filed on September 2, 2019. TECHNICAL AREA

[0002] This application belongs to the technical field of secondary batteries and relates in particular to an active material for a positive electrode, a positive electrode plate, a lithium-ion secondary battery, as well as a battery module, a battery set and a device. BACKGROUND

[0003] The lithium-ion secondary battery is a type of rechargeable battery that relies primarily on the movement of lithium ions between the positive and negative electrodes and is currently a widely used clean energy source. A key component of a lithium-ion secondary battery is an active material at the positive electrode, which supplies lithium ions that move back and forth between the positive and negative electrodes to enable the charging and discharging process. Therefore, the active material at the positive electrode is crucial for the battery's performance.

[0004] Lithium nickel cobalt manganese oxide has a relatively high theoretical capacity, and a lithium-ion secondary battery using lithium nickel cobalt manganese oxide as the active material for the positive electrode should exhibit a relatively high energy density. However, the question of how the lithium-ion secondary battery can achieve both a higher energy density and good high-temperature cycle stability has become a pressing engineering problem. SUMMARY

[0005] A first aspect of the present application provides an active material for a positive electrode, which contains a lithium nickel cobalt manganese oxide, wherein the molar content of nickel in the lithium nickel cobalt manganese oxide is 60% to 90% of the total molar content of nickel, cobalt and manganese, and the lithium nickel cobalt manganese oxide has a layered crystal structure with space group R3m; a transition metal layer of the lithium nickel cobalt manganese oxide contains a dopant, and the local mass concentration of the dopant in particles of the active material of the positive electrode has a relative deviation of 20% or less;and in a differential scanning calorimetry spectrum of the active material of the positive electrode in a 78% delithiated state, the initial exothermic temperature of an exothermic main peak is 200 °C or more, and the integral area of ​​the exothermic main peak is 100 J / g or less.

[0006] The active material of the positive electrode in this application comprises lithium nickel cobalt manganese oxide with a high nickel content, which exhibits a relatively high charge / discharge voltage and specific capacity. By using this active material in the positive electrode, lithium-ion secondary batteries can achieve higher capacity and energy density.Simultaneously, the lithium nickel cobalt manganese oxide also contains dopants, and the relative deviation of the local mass concentration of the dopants in the particles of the positive electrode active material is 20% or less; and in a differential scanning calorimetry spectrum of the positive electrode active material in the 78% delithiated state, the initial exothermic temperature of an exothermic main peak is 200°C or higher, and the integral area of ​​the exothermic main peak is 100 J / g or less; these parameters can confer higher thermal stability and high-temperature cycle stability to the positive electrode active material. Therefore, the use of this active material for the positive electrode in the present application can also result in the lithium-ion secondary battery exhibiting higher high-temperature cycle stability.

[0007] In each of the above-mentioned embodiments, the half-width of the exothermic main peak can be 30 °C or less. The active material of the positive electrode, which meets the above-mentioned conditions, can achieve higher thermal stability and high-temperature cycle stability, thereby further improving the high-temperature cycle stability of the lithium-ion secondary battery.

[0008] In each of the above-mentioned embodiments, the peak temperature of the exothermic main peak can be 230 °C or higher. If the above-mentioned conditions are met, the thermal stability of the active material of the positive electrode can be further improved, thereby increasing the high-temperature cycle stability of the battery.

[0009] In each of the aforementioned embodiments, the relative deviation of the local mass concentration of the doping element in the particles of the active material of the positive electrode is 15% or less. A battery using such an active material for the positive electrode can achieve a higher energy density and high-temperature cycle stability.

[0010] In each of the above embodiments, the dopant can have a valence of +3 or higher when the positive electrode active material is in a 78% delithiated state, and optionally a valence of one or more of the values ​​+4, +5, +6, +7, and +8. High-valence dopants can effectively bind oxygen atoms and also increase the initial exothermic temperature and the maximum exothermic temperature of the main exothermic peak in the DSC diagram of the positive electrode active material after delithiation, as well as decrease the integrated area and the full width at half maximum of the main exothermic peak. The positive electrode active material thus exhibits higher thermal stability and high-temperature cycle stability, further improving the energy density and high-temperature cycle stability of the battery.

[0011] In each of the embodiments described above, the doping element can contain one or more of the following elements: Al, Si, Ti, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Te, and W. Optionally, the doping element can contain one or more of the following elements: Al, Si, Ge, Se, Zr, Nb, Ru, Sb, Te, and W. Optionally, the doping element M can contain one or more of the elements Si, Ge, Se, Ru, Sb, Te, and W. These doping elements can enhance the effects mentioned above and further increase the energy density and high-temperature cycle stability of the lithium-ion secondary battery.

[0012] In each of the embodiments described above, the active material of the positive electrode can have a true density ρ true exhibiting 4.6 g / cm³ 3 ≤ ρ true ≤ 4.9 g / cm³ 3This requirement is met. Such an active material with a positive electrode can have a relatively high specific capacity, which can increase the energy density of the battery.

[0013] In each embodiment described above, the active material of the positive electrode can have a true doping concentration ω of 2300 µg / cm². 3 ≤ ω ≤ 49500 µg / cm 3 fulfilled, optionally 3000 µg / cm² 3 ≤ ω ≤ 35000 µg / cm 3 , optional 14810 µg / cm 3 ≤ ω ≤ 36710 µg / cm 3By using an active material for the positive electrode whose actual doping concentration lies within the appropriate range, the initial exothermic temperature and the maximum exothermic temperature of the main exothermic peak in the DSC diagram of the active material for the positive electrode in the "78% delithiated state" can be further improved, and the integrated area and the full width at half maximum of the exothermic peak can be reduced. At the same time, this ensures that the active material of the positive electrode exhibits good lithium-ion transport performance, which can improve the energy density and high-temperature cycle stability of the battery.

[0014] In each of the embodiments described above, the deviation ε of the mass concentration of the dopant in the active material of the positive electrode, relative to the average mass concentration of the dopant in the particles of the active material of the positive electrode, satisfies the conditions ε < 50%, optionally ε ≤ 30%, and optionally ε ≤ 20%. By using the active material of the positive electrode whose ε lies within the aforementioned ranges, the active material of the positive electrode can exhibit relatively good macroscopic and microscopic consistency. During the charge and discharge cycle of the active material of the positive electrode, the expansion and contraction of the particles remain constant, and the stability of the particles is high, resulting in higher capacity development and cycle stability at room temperature and elevated temperatures. This also improves the corresponding performance of the battery.

[0015] In each of the embodiments described above, the active material of the positive electrode can have a volume-averaged particle diameter D. v 50 from 5 µm to 20 µm, optionally from 8 µm to 15 µm and further optionally from 9 µm to 11 µm. By using the active material for the positive electrode with a D v A value of 50 within the aforementioned ranges can further improve the transfer and diffusion performance of lithium ions and electrons, thereby enhancing the cycle stability and rate performance of the lithium-ion secondary battery. The active material of the positive electrode can also have a higher density, which can improve the battery's energy density.

[0016] In each of the embodiments described above, the active material of the positive electrode can have a specific surface area of ​​0.2 m². 2 / g up to 1.5 m 2 / g, optionally from 0.3 m 2 / g to 1 m 2 exhibit / g. By using the active material of the positive electrode with a specific surface area within the above-mentioned ranges, the capacity and cycle life of the active material of the positive electrode can be improved, and the processing performance of the positive electrode paste can also be improved, so that the battery can achieve a higher energy density and cycle stability.

[0017] In all embodiments described above, the active material of the positive electrode can have a bulk density of 2.3 g / cm³. 3 up to 2.8 g / cm³ 3 exhibiting the following characteristics: The bulk density of the active material of the positive electrode lies within the aforementioned range, which gives the lithium-ion secondary battery a higher energy density.

[0018] In each embodiment described above, the active material of the positive electrode can achieve a compacted density of 3.1 g / cm³ under a pressure of 5 tons (equivalent to 49 kN). 3 up to 3.8 g / cm³ 3 exhibiting these characteristics. By using the active material of the positive electrode with a density within the aforementioned range, a relatively high energy density and high cycle stability of the battery can be achieved.

[0019] In each embodiment as described above, the lithium nickel cobalt manganese oxide of chemical formula Li 1+a [Ni x Co y Mn z M b ]O2 correspond, in which M is the doping element and M is selected from one or more of the following elements: Al, Si, Ti, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Te and W, 0.7 ≤ x ≤ 0.9, 0 < y < 0.3, 0 < z < 0.3, 0 ≤ a < 0.2, 0 < b < 0.3, and x+y+z+b=1.

[0020] In each embodiment as described above, the lithium nickel cobalt manganese oxide of chemical formula Li 1+c [Ni r-d Co s M n1 M' d ]O2 correspond, in which M' is the doping element and M is selected from one or more of the following elements: Al, Si, Ti, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Te and W, 0.7 ≤ r - d ≤ 0.9, 0 < s < 0.3, 0 < t < 0.3, 0 ≤ c < 0.2, 0 < d < 0.3, and r + s + t = 1.

[0021] A second unclaimed aspect of the present application provides for a method for producing an active material for positive electrodes, comprising the following steps: Mixing a precursor for an active material for a positive electrode, a lithium source and a precursor for a doping element to obtain a mixed material, wherein the precursor for the active material for the positive electrode is selected from one or more oxides, hydroxides and carbonates containing Ni, Co and Mn and the molar content of nickel is 60% to 90% of the total molar content of nickel, cobalt and manganese; Subjecting the mixed material to a sintering treatment to obtain the active material of the positive electrode; wherein the active material of the positive electrode comprises a lithium nickel cobalt manganese oxide, and the lithium nickel cobalt manganese oxide has a layered crystal structure of the space group R 3 m; a transition metal layer of lithium nickel cobalt manganese oxide includes a doping element, and the local mass concentration of the doping element in particles of the active material of the positive electrode has a relative deviation of 20% or less; and In a differential scanning calorimetry spectrum of the active material of the positive electrode in a 78% delithiated state, the initial exothermic temperature of an exothermic main peak is 200 °C or more, and the integral area of ​​the exothermic main peak is 100 J / g or less.

[0022] The positive electrode active material provided by this application comprises high-nickel lithium nickel cobalt manganese oxide, which also includes dopants. The local mass concentration of the dopants in the particles of the positive electrode active material has a relative deviation of 20% or less. In a differential scanning calorimetry spectrum of the positive electrode active material in a 78% delithiated state, the initial exothermic temperature of an exothermic main peak is 200°C or higher, and the integral area of ​​the exothermic main peak is 100 J / g or less. As a result, the lithium-ion secondary battery utilizing this positive electrode active material exhibits higher energy density and higher high-temperature cycle stability.

[0023] In each of the embodiments described above, the precursor of the doping element can be selected from one or more of the following elements: aluminum oxide, silicon oxide, titanium oxide, vanadium oxide, germanium oxide, selenium oxide, zirconium oxide, niobium oxide, ruthenium oxide, palladium oxide, antimony oxide, tellurium oxide, and tungsten oxide. Optionally, the precursor of the doping element can be selected from one or more of the following elements: Al₂O₃, SiO₂, SiO₂, TiO₂, TiO₂, V₂O₅, V₂O₄, V₂O₃, GeO₂, SeO₂, ZrO₂, Nb₂O₅, NbO₂, RuO₂, PdO, Sb₂O₅, Sb₂O₃, TeO₂, WO₂, and WO₃.

[0024] In each of the aforementioned embodiments, the atmosphere of the sintering process is an oxygen-containing atmosphere; optionally, the oxygen concentration of the sintering atmosphere is 70% to 100% and optionally 75% to 95%.

[0025] In each of the aforementioned embodiments, the sintering temperature is 600 °C to 1000 °C, optionally 700 °C to 900 °C.

[0026] In each of the aforementioned embodiments, the sintering time is 5 to 25 hours, optionally 10 to 20 hours.

[0027] In each of the embodiments described above, the dopant precursor can be divided uniformly or randomly into L parts for L batches of doping, where L is between 1 and 5, optionally between 2 and 3. Optionally, the embodiments include: mixing the active material precursor for the positive electrode, the lithium source, and the first batch of the dopant precursor, followed by a first sintering process; mixing the product obtained from the first sintering process with the second batch of the dopant precursor, followed by a second sintering process; and so on, until the product obtained from the L-1 sintering process is mixed with the L-batch of dopant precursor, followed by the L-th sintering treatment to obtain an active material for the positive electrode.

[0028] In each of the aforementioned embodiments, the temperature for each of the sintering processes can be between 600 °C and 1000 °C, optionally between 700 °C and 900 °C and optionally between 800 °C and 850 °C.

[0029] In each of the aforementioned embodiments, the duration of the individual sintering processes can range from 3 to 25 hours, optionally from 5 to 10 hours.

[0030] In each of the aforementioned embodiments, the total sintering time can range from 5 to 25 hours, optionally from 15 to 25 hours.

[0031] A third aspect of the present application provides a positive electrode plate comprising a positive electrode current collector and an active material layer of the positive electrode arranged on the positive electrode current collector, wherein the active material layer of the positive electrode comprises the active material of the positive electrode of the first aspect of the present application or the active material of the positive electrode obtained according to the method of the second aspect of the present application.

[0032] Since the positive electrode plate of the present application contains the positive electrode active material described herein, the lithium-ion secondary battery containing the positive electrode plate can exhibit a relatively high energy density and high-temperature cycle performance.

[0033] A fourth aspect of the present application relates to a lithium-ion secondary battery comprising the positive electrode plate according to the third aspect.

[0034] Since the lithium-ion secondary battery of the present application contains the positive electrode plate, it can exhibit a relatively high energy density and high-temperature cycle performance.

[0035] A fifth aspect of the present application provides a battery module that contains the lithium-ion secondary battery of the fourth aspect of the present application.

[0036] A sixth aspect of the present application provides a battery set that includes the lithium-ion secondary battery of the fourth aspect of the present application or the battery module of the fifth aspect of the present application.

[0037] A seventh aspect of the present application provides for a device that includes at least one of the following components: the lithium-ion secondary battery of the fourth aspect of the present application, the battery module of the fifth aspect of the present application, or the battery pack of the sixth aspect of the present application.

[0038] The battery module, battery pack and device of the present application contain the lithium-ion secondary battery of the present application and thus have at least the same or similar effects as the lithium-ion secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] To more clearly explain the technical solutions of the embodiments of the present application, the drawings that must be used in these embodiments are briefly presented below. The drawings described below represent only some embodiments of the present application. A person skilled in the art can create other drawings based on these without any creative effort. Fig. is a diagram of the exothermic curve measured with a differential scanning calorimeter (DSC) for an active material with a positive electrode according to an embodiment of this application, i.e., the differential scanning calorimetry spectrogram referred to as the DSC diagram. Fig.is a cross-sectional view of the particles of the active material of the positive electrode from Example 1, in which bright dots in the image indicate the doping elements and the doping elements are evenly distributed in the particles. Fig. is a schematic diagram showing the locations used to test the relative deviation of the local mass concentration of the doping elements in the particles of the active materials of the positive electrodes of examples 1 to 21 and of the comparison examples 1 to 7. Fig. Figure 1 is a schematic representation of a lithium-ion secondary battery according to an embodiment of the present application. Fig. is an exploded view of Fig. . Fig. Figure 1 is a schematic representation of a battery module according to an embodiment of the present application. Fig.Figure 1 is a schematic representation of a battery pack according to one embodiment of the present application. Fig. is an exploded view of Fig. . Fig. Figure 1 is a schematic representation of a device according to an embodiment of the present application in which a lithium-ion secondary battery is used as the energy source. DETAILED DESCRIPTION

[0040] To clarify the subject matter, the technical solution, and the technical effects of the present application, the present application is described in detail below with reference to the embodiments. It is understood that the embodiments described in this description serve only to illustrate the present application and are not intended to limit it.

[0041] For the sake of brevity, only specific ranges of numbers are explicitly mentioned here. However, any lower bound can be combined with any upper bound to form an unspecified range; and any lower bound can be combined with any other lower bound to form an unspecified range; and any upper bound can be combined with any other upper bound to form an unspecified range. Although not explicitly stated, any point or individual value between the endpoints of a range is included in the range. Thus, any point or individual value can be combined with any other point or individual value, or with other lower or upper bounds, to form an unspecified range.

[0042] In this description, it should be noted that, unless otherwise specified, the use of "above" and "below" to refer to ranges of numbers includes all numbers within that range, including the endpoints. Unless otherwise specified, the terms "one," "an," "the," "at least one," and "one or more" are used synonymously in this document, with "more" in the phrase "one or more" including two or more.

[0043] In this description, unless otherwise stated, the term "or" is comprehensive. For example, the phrase "A or B" means "A, B, or both A and B." More precisely, each of the following conditions satisfies the "A or B" condition: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0044] The above summary of this application is not intended to describe every disclosed embodiment or implementation in this application. Exemplary embodiments are further explained in the following description. At many points in the application, guidance is provided by a series of examples that can be used in various combinations. In each case, the list represents only a representative group and is not intended to be exhaustive. Active material of the positive electrode

[0045] The active material of the positive electrode of the first aspect of the present application comprises a lithium nickel cobalt manganese oxide, wherein the molar content of nickel in the lithium nickel cobalt manganese oxide is 60% to 90% of the total molar content of nickel, cobalt and manganese, and the lithium nickel cobalt manganese oxide has a layered crystal structure with space group R3m; a transition metal layer of the lithium nickel cobalt manganese oxide comprises a dopant, and the local mass concentration of the dopant in particles of the active material of the positive electrode has a relative deviation of 20% or less; and in a differential scanning calorimetry diagram of the active material of the positive electrode in a 78% delithiated state, an initial exothermic temperature of an exothermic main peak is 200 °C or more and an integral area of ​​the exothermic main peak is 100 J / g or less.

[0046] In this application, the local mass concentration of the dopant in the particles of the positive electrode active material is the mass concentration of the dopant in all elements within the finite volume element at any location within the particles, obtainable by EDX (energy-dispersive X-ray spectroscopy) or EDS elemental analysis in combination with TEM (transmission electron microscopy) or SEM (scanning electron microscopy) single-point scanning of the elemental concentration distribution, or other similar methods. When the EDX or EDS elemental analysis is combined with the TEM or SEM single-point scanning test, the mass concentration of the dopant at different locations within the particles of the positive electrode active material, expressed in µg / g, is denoted as η1, η2, η3, ..., η4. n denoted by , where n is a positive integer greater than 15.

[0047] The average mass concentration of dopants in the particles of the positive electrode active material is the mass concentration of dopants in all elements within one or more particles of the positive electrode active material, which can be obtained by EDX or EDS elemental analysis in conjunction with TEM or SEM surface scanning of the elemental concentration distribution or other similar methods. When EDX or EDS elemental analysis is combined with TEM or SEM surface scanning of the elemental concentration distribution, the tested surface includes all points of the aforementioned single-point test. The average

[0048] Mass concentration of the doping elements in the particles of the active material of the positive electrode is expressed in η µg / g specified.

[0049] The relative deviation σ of the local mass concentration of the doping elements in the particles of the active material of the positive electrode can be calculated according to formula (1): σ=max{|η1−η¯|,|η2−η¯|,|η3−η¯|,⋯,|ηn−η¯|}η¯

[0050] The term "78% delithiated state" used here refers to the state in which the molar content of lithium deintercalated from the active material of the positive electrode is 78% of the theoretical lithium content during the battery's charging process. In actual use of a secondary battery, a "full charge" and a corresponding "charge cut-off voltage" are generally set to ensure safe battery operation. "Full charge" means that the secondary battery's state of charge (SOC) is 100%. In other words, the secondary battery, with the positive electrode containing the aforementioned active material, is charged to the charge cut-off voltage within the reversible charging and discharging range.The "fully charged state" or "final charging voltage" can vary due to different active positive electrodes or differing safety requirements. When the secondary battery, consisting of active material in the positive electrode containing lithium nickel cobalt manganese oxide, is in a "fully charged state," the degree of delithiation of the active material in the positive electrode is generally around "78% delithiated state" to ensure normal use.

[0051] In this application, the active material of the positive electrode in the "78% delithiated state" is investigated in combination with the corresponding relationship between the "delithiated state" and the charging voltage. Specifically, a series of batteries using the active material of the positive electrode are charged at a rate of 0.1 C to 2.8 V, 2.9 V, 3.0 V, 3.1 V, 3.2 V, 3.3 V, ... 4.0 V, 4.1 V, 4.2 V, 4.3 V, 4.4 V and 4.5 V (i.e.The battery is charged at a charging voltage interval of 0.1 V. Then, the positive electrode plate is removed and washed to remove the electrolyte. The active material of the positive electrode is extracted, and the mass concentration of lithium, transition metals (Ni, Co, Mn), and oxygen elements in the active material is tested using an inductively coupled plasma optical emission spectrometer (ICP-OES). The stoichiometric ratios of the elements in the active material at the charging voltage are calculated, and the chemical formula of the active material at the charging voltage is determined. Thus, the charging voltage corresponding to the "78% de-lithium state" is achieved.

[0052] The battery containing the active material of the positive electrode under test is charged to the voltage corresponding to the “78% delithiated state” and then disassembled to obtain the active material of the positive electrode in the “78% delithiated state” for further investigation.

[0053] The DSC diagram of the active material of the positive electrode in the “78% delithiated state” is measured with a differential scanning calorimeter. Fig. shows a DSC diagram of an active material for a positive electrode as an example. As in Fig.As depicted, the DSC diagram is a graph in which the heat flux rate is plotted on the ordinate and the temperature on the abscissa. In this application, the most important exothermic peak is the peak with the largest integrated area in the DSC diagram, which arises from the irreversible phase transition of the layered phase structure of the active material of the positive electrode due to the release of oxygen. The exothermic starting temperature of the main peak is the intersection point A of the tangent at the point of maximum slope on the low-temperature side of the main peak and the extension of the baseline ef before the peak (i.e., the extrapolated starting point).The integral area of ​​the exothermic main peak is the area of ​​the region enclosed by the exothermic peak and the inscribed baseline fg, which is used to characterize the heat emitted by the active material of the positive electrode per unit weight in this interval.

[0054] The active material of the positive electrode according to the embodiment of this application comprises lithium nickel cobalt manganese oxide, and the molar content of nickel is 60% to 90% of the total molar content of nickel, cobalt, and manganese. The high-nickel lithium nickel cobalt manganese oxide has a higher charge and discharge voltage and specific capacity characteristics, so that the lithium-ion secondary battery using it can exhibit higher capacity performance and energy density.

[0055] The lithium nickel cobalt manganese oxide according to the embodiment of this application further comprises a dopant, and the relative deviation σ of the local mass concentration of the dopant in the particles of the positive electrode active material is 20% or less. The distribution of the dopant in the particles of the positive electrode active material is uniform, and the properties within the particles remain constant. The dopant can improve the structural stability at any position of the particles and prevent oxygen release and structural phase transitions at any position of the particles. It is advantageous to increase the initial exothermic temperature of the exothermic main peak in the DSC diagram of the active material of the positive electrode in the "78% delithiated state" and to decrease the integral area of ​​the exothermic main peak.

[0056] In the DSC diagram of the active material of the positive electrode in the "78% delithiated state," the initial exothermic temperature of the main exothermic peak is 200 °C or higher and can also be 205 °C or higher, 207 °C or higher, or 210 °C or higher. The initial exothermic temperature of the main exothermic peak is relatively high, so the active material of the positive electrode exhibits high structural stability during the high-temperature cycle and heating conditions, consistently maintaining a strongly electrochemically active layered phase state in which the oxygen atoms cannot easily leave their original lattice positions.The active material of the positive electrode does not tend to undergo irreversible structural phase transitions, so it can exhibit higher thermal stability and high-temperature cycle stability, thereby improving the high-temperature cycle strength and safety performance of the lithium-ion secondary battery.

[0057] In the DSC diagram of the positive electrode active material in the "78% delithiated state," the integrated area of ​​the exothermic main peak is 100 J / g or less and can be 85 J / g or less, 74 J / g or less, 67 J / g or less, 55 J / g or less, or 48 J / g or less. The small integral area of ​​the exothermic main peak means that the amount of heat released by the positive electrode active material during high-temperature cycling and heating conditions is lower, indicating a lesser risk of irreversible reaction or structural failure of the positive electrode active material during these conditions.The thermal stability and high-temperature cycle stability of the active material of the positive electrode are effectively improved, which can significantly improve the high-temperature cycle strength and safety performance of the lithium-ion secondary battery.

[0058] Furthermore, the migration and diffusion capacity of lithium ions in the various regions of the particles within the uniformly doped active material of the positive electrode is at the same level, resulting in higher lithium-ion transport performance for the active material of the positive electrode. This contributes to improved capacity, energy density, and cycle life of the battery. In the uniformly doped active material for the positive electrode, the structural stability and deformation resistance of the particles are closely matched, ensuring a uniform stress distribution within the particles.The particles of the active material of the positive electrode do not tend to crack, thus preventing side reactions and a deterioration of capacity and cycle stability due to the fresh surface exposed by cracking, which further improves the high-temperature cycle stability of the battery.

[0059] The use of the active material of the positive electrode according to the present application enables the lithium-ion secondary battery to simultaneously achieve higher capacity performance, energy density and high temperature cycle stability.

[0060] The lithium nickel cobalt manganese oxide contains dopants, and the relative deviation σ of the local mass concentration of the dopants in the particles of the active material of the positive electrode is 20% or less, which can also improve the maximum exothermic temperature of the exothermic main peak in the DSC diagram of the active material of the positive electrode in the “78% delithiated state” and reduce the half-width of the exothermic main peak.

[0061] In some embodiments, in the DSC diagram of the active material of the positive electrode in the "78% delithiated state", the full width at half maximum (FWHM) of the exothermic main peak is optionally 30 °C or less, and further optionally 28 °C or less. In this application, the FWHM of the exothermic main peak is the peak width at half the peak height mn, where n is the intersection of a line perpendicular to the abscissa (peak apex m of the exothermic main peak) and the inscribed baseline fg.

[0062] The half-width of the exothermic main peak lies within the range described above. This means that the irreversible reaction or structural damage to the active material of the positive electrode in the "78% delithiated state" during the high-temperature cycle and heating conditions is further reduced, and the thermal stability and high-temperature cycle stability of the active material of the positive electrode are further improved, thereby further enhancing the performance of the lithium-ion secondary battery.

[0063] The half-width of the exothermic main peak lies within the aforementioned range, which also means that doping the active material of the positive electrode does not generate any obvious new phases. The doping element is essentially a doping and substitution at one or more nickel, manganese, and cobalt sites, and the active material of the positive electrode retains a well-layered crystal structure. The active material of the positive electrode can serve as a good support for the deintercalation of lithium ions, which is advantageous for the intercalation and deintercalation of lithium ions.It can prevent reversible lithium ions from being consumed on the electrode surface or in the electrolyte, and effectively reduce the irreversible capacity, thereby giving the active material of the positive electrode a high initial capacity and cycle capacity retention rate to improve the energy density as well as the room temperature and high-temperature cycle stability of the battery.

[0064] In some embodiments, the peak temperature of the exothermic main peak in the DSC diagram of the positive electrode active material in the "78% delithiated state" is optionally 225 °C or above, and further optionally 230 °C or above. Such positive electrode active materials do not tend to release oxygen during heating and high-temperature cycling and effectively prevent the irreversible phase transition of the positive electrode active material after delithation, thereby improving the thermal stability of the positive electrode active material and increasing the high-temperature cycle stability of the battery.

[0065] In some optional embodiments, the relative deviation σ of the local mass concentration of the doping element in the particles of the active material of the positive electrode is 15% or less, optionally 12% or less, and optionally 10% or less. The battery utilizing this active material of the positive electrode can achieve a higher energy density and high-temperature cycle stability.

[0066] In the active material of the positive electrode according to the embodiments of the present application, the dopant can be selected from one or more transition metal elements other than nickel, cobalt, and manganese, and elements of groups IIA to VIA other than carbon, nitrogen, oxygen, and sulfur. Optionally, the dopant in the active material of the positive electrode in the "78% delithiated state" has a valence higher than +3, and further optionally, a valence higher than +3. For example, in the active material of the positive electrode in the "78% delithiated state," the dopant has one or more valences of +4, +5, +6, +7, and +8, and for example, one or more valences of +4, +5, and +6.

[0067] The higher-valence doping element has a stronger ability to bond with oxygen atoms; that is, the bonding energy with oxygen atoms is greater. This allows oxygen atoms to be effectively bound, preventing the active material of the positive electrode from releasing oxygen during heating and the high-temperature cycling process after delithation. This suppresses the irreversible structural phase transition, increases the initial exothermic temperature and the maximum exothermic temperature of the main exothermic peak in the DSC diagram of the active material of the positive electrode after delithation, and decreases the integral area and the full width at half maximum of the exothermic peak.The active material of the positive electrode can exhibit high thermal stability and high-temperature cycle stability, further improving the energy density and high-temperature cycle stability of the battery.

[0068] Dopants with a higher valence can contribute more electrons to the active material of the positive electrode, which can help the positive electrode release more lithium ions, thus further improving the battery's energy density. Specifically, the dopant has a valence state greater than +3, exceeding the average valence state (+3) of nickel, cobalt, and manganese in lithium nickel cobalt manganese oxide, and the number of electrons contributing to the active material of the positive electrode is further increased, which can further improve the battery's capacity and energy density.

[0069] In the present application, the battery containing the active material of the positive electrode under test is charged to a voltage corresponding to the "78% delithiated state" and then disassembled to obtain the active material of the positive electrode in this "78% delithiated state". The valence state of the dopant M in the "78% delithiated state" of the active material of the positive electrode can be determined by X-ray photoelectron spectroscopy (XPS). More precisely, it can be determined by synchrotron radiation photoelectron spectroscopy (SRPES).

[0070] In some embodiments, the doping element M comprises one or more of the elements Al, Si, Ti, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Te, and W. Optionally, the doping element M comprises one or more of the elements Al, Si, Ge, Se, Zr, Ru, Sb, Te, and W. Optionally, the doping element M comprises one or more of the elements Si, Ge, Se, Zr, Ru, Sb, Te, and W. These doping elements can enhance the effects mentioned above and further improve the energy density and high-temperature cycle stability of the lithium-ion secondary battery.

[0071] In some optional embodiments, the actual doping concentration ω in the active material of the positive electrode meets 1500 µg / cm². 3 ≤ ω ≤ 60000 µg / cm 3 , optionally 2300 µg / cm² 3 ≤ ω ≤ 49500 µg / cm 3 ; optional 3000 µg / cm 3 ≤ ω ≤ 35000 µg / cm 3 ; optional 14810 µg / cm 3 ≤ ω ≤ 36710 µg / cm 3 ; optional 24900 µg / cm 3≤ ω ≤ 25510 µg / cm 3 .

[0072] In this application, the actual doping concentration ω in the active material of the positive electrode can be calculated according to formula (2): ω=φ×ρtrue

[0073] In formula (2) ω is the actual doping concentration in the active material of the positive electrode in µg / cm². 3 .

[0074] ρ true is the actual density of the active material of the positive electrode in g / cm³ 3 and is equal to the ratio of the mass of the active material of the positive electrode to the actual volume of the active material of the positive electrode, where the actual volume is the actual volume of the solid material excluding the pores within and between the particles of the active material of the positive electrode. ρ truecan be measured using known instruments and methods in engineering, e.g. the gas volume method, which can be carried out with a powder density tester.

[0075] φ is the mass concentration of the dopant in the active material of the positive electrode in µg / g, i.e., the mass of the dopant contained in each gram of the active material of the positive electrode. φ represents the content of dopant elements in the entire macroscopic active material of the positive electrode, including the dopant incorporated into the particles of the active material of the positive electrode, the dopant enriched in other phases on the surface of the particles of the active material of the positive electrode, and the dopant between the particles of the active material of the positive electrode. φ can be determined from the absorption spectrum of the solution of the active material of the positive electrode, e.g., by ICP (inductively coupled plasma emission spectrometry), XAFS (X-ray absorption fine structure spectroscopy), and other tests.

[0076] The actual doping concentration of the positive electrode active material is within a reasonable range, which allows the initial exothermic temperature and the maximum exothermic main peak temperature in the DSC diagram of the positive electrode active material in the "78% delithiated state" to be increased, and the integral area and the full width at half maximum of the exothermic main peak to be reduced, thus ensuring that the positive electrode active material has a good layered crystal structure and that the positive electrode active material exhibits good lithium-ion deintercalation / intercalation performance, so that the positive electrode active material has a relatively high initial capacity and cycle capacity retention rate, thus improving the energy density and high-temperature cycle stability of the battery.

[0077] Furthermore, by using the active material for the positive electrode, which has a true doping concentration within the aforementioned ranges, it is ensured that the doping element is incorporated into the transition metal layer, thus preventing the doping element from penetrating the lithium layer, and that the particles of the active material for the positive electrode have a relatively high capacity for the transfer and diffusion of lithium ions, so that the battery has a higher capacity and cycle stability.

[0078] In some alternative embodiments, the deviation of the mass concentration φ of the doping elements in the active material of the positive electrode in relation to the average mass concentration is η'¯ The doping elements in the particles of the active material of the positive electrode ε, and ε fulfills the condition ε < 50%. Optionally, ε ≤ 30%. Optionally, ε ≤ 20%. Furthermore, ε ≤ 15% or ≤ 13%.

[0079] The deviation ε of the mass concentration φ of the doping elements in the active material of the positive electrode in relation to the average mass concentration of the doping elements in η of the particle concentration of the active material of the positive electrode can be calculated according to the following formula (3): ε=|φ−η¯|φ

[0080] The active material for the positive electrode, which fulfills ε within the aforementioned range, means that the dopants are uniformly incorporated into the particles of the active material for the positive electrode and that the content of dopants dispersed in other phases on the particle surface and of dopants embedded in the spaces between the particles is lower, resulting in better macro- and micro-consistency and a uniform structure of the active material for the positive electrode. During the charge-discharge cycle of the active material of the positive electrode, the expansion and contraction of the particles are uniform, and the particle stability is high, contributing to higher capacity and high-temperature cycle stability.

[0081] The active material of the positive electrode according to the embodiments of the present application can optionally be doped uniformly within the above-mentioned true doping concentration range to ensure the consistency of the microscopic distribution and macroscopic content of the doping elements, which can more effectively improve the thermal stability and high-temperature cycle stability of the active material of the positive electrode in order to further improve the energy density and high-temperature cycle performance of the battery.

[0082] In some optional embodiments, the true density ρ satisfies true The active material of the positive electrode has a value of 4.6 g / cm². 3 ≤ ρ true ≤ 4.9 g / cm³ 3 , so that the active material of the positive electrode can have a higher specific capacity, thereby improving the capacity performance and energy density of the battery.

[0083] In some optional embodiments, the molar nickel content in the lithium nickel cobalt manganese oxide is 70% to 90% of the total molar content of nickel, cobalt, and manganese, e.g., 75% to 85%. The active material of the positive electrode exhibits a higher specific capacity and can improve the capacity performance and energy density of the lithium-ion secondary battery.

[0084] Some examples: Lithium nickel cobalt manganese oxide can have the chemical formula Li 1+a [Ni x Co y Mn z M b]O2 correspond, in which M is a doping element that is doped and substituted at one or more of the positions nickel, cobalt and manganese, and 0.6 ≤ x ≤ 0.9, 0 ≤ y <0.3, 0 ≤ z <0.3, 0 ≤ a <0.2, 0

[0085] Optional: 0.7 ≤ x ≤ 0.9, 0 <y <0,3, 0 <z <0,3. Das aktive Material der ternären positiven Elektrode mit hohem Nickelgehalt hat eine hohe Energiedichte und eine gute strukturelle Stabilität, was der Batterie eine hohe Energiedichte und eine lange Lebensdauer verleiht.

[0086] ​Optionally, M is selected from one or more of the elements Al, Si, Ti, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Te, and W. Optionally, M can contain one or more of the elements Al, Si, Ge, Se, Zr, Ru, Sb, Te, and W. The doping element M ensures that the active material of the high-nickel ternary positive electrode exhibits high thermal stability and high temperature cycle stability, thus improving the overall performance of the battery.

[0087] Furthermore, due to its higher valence, the doping element M can introduce more electrons into the active material of the positive electrode and assist the ternary active material of the high nickel positive electrode in releasing more lithium ions, thereby improving the capacity performance and energy density of the battery.

[0088] Other examples include lithium nickel cobalt manganese oxides, which have the chemical formula Li 1+c [Ni r-d Cos Mn t M' d ]O2 satisfy, where M' is a doping element that partially replaces the nickel site, and 0.6 ≤ r - d ≤ 0.9, 0 ≤ s <0.3, 0 ≤ t <0.3, 0 ≤ c <0.2, 0 <d <0,3, r + s + t = 1. Durch die Verwendung des ternären aktiven Materials für die positive Elektrode mit hohem Nickelgehalt kann die Lithium-Ionen-Sekundärbatterie eine höhere Kapazität, Energiedichte und Zyklenfestigkeit bei Raumtemperatur und hohen Temperaturen aufweisen.

[0089] Optional: 0.7 ≤ rd ≤ 0.9, 0

[0090] ​Optionally, M' can be selected from one or more of the following elements: Al, Si, Ti, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Te, and W. Similarly, the doping element M' ensures that the high-nickel ternary active material of the positive electrode exhibits high thermal stability and high-temperature cycle stability, thus improving the overall battery performance. Furthermore, the doping element M' can assist the high-nickel ternary active material of the positive electrode in releasing more lithium ions, thereby improving the capacity and energy density of the lithium-ion secondary battery.

[0091] The various lithium nickel cobalt manganese oxides in the examples above can be used independently as the active material for the positive electrode, or a combination of two or more lithium nickel cobalt manganese oxides can be used as the active material for the positive electrode.

[0092] The volume-averaged particle size D v 50% of the particles of the active material of the positive electrode can optionally be between 5 µm and 20 µm, optionally between 8 µm and 15 µm, and optionally between 9 µm and 11 µm. By using active material for the positive electrode with D vWithin the aforementioned areas, the migration path of lithium ions and electrons in the materials is relatively short, which can further improve the transfer and diffusion performance of lithium ions and electrons in the active material for the positive electrode and reduce the polarization of the battery, thereby improving the cycle stability and rate performance of the lithium-ion secondary battery; in addition, the active material for the positive electrode can have a higher condensed density and improve the energy density of the battery.

[0093] By using active material for the positive electrode with D v50 Within the above-mentioned areas, it is also advantageous to reduce the side reactions of the electrolyte on the surface of the active material for the positive electrode and to decrease the agglomeration between the particles of the active material for the positive electrode, thereby improving the performance of the active material for normal temperature and high temperature cycles as well as the safety performance of the positive electrode.

[0094] The active material of the positive electrode can have a specific surface area of ​​optionally 0.2 m². 2 / g up to 1.5 m 2 / g, optionally from 0.3 m 2 / g to 1 m 2 / g. By using active material for the positive electrode with a specific surface area within the above-mentioned ranges, it can be ensured that the active material for the positive electrode has a higher active specific surface area and simultaneously helps to reduce the side reactions of the electrolyte on the surface of the active material for the positive electrode, thereby improving the capacity and cycle life of the active material for the positive electrode; furthermore, agglomeration between the particles of the active material for the positive electrode can be prevented during paste production and during charging and discharging, which can improve the energy density and cycle stability of the battery.

[0095] The active material of the positive electrode can have a bulk density of 2.3 g / cm³. 3 up to 2.8 g / cm³ 3By using the active material of the positive electrode with a conductivity density within the aforementioned range, the lithium-ion secondary battery can exhibit a relatively high capacity and energy density.

[0096] The active material of the positive electrode can achieve a compacted density of 3.1 g / cm³ under a pressure of 5 tons (equivalent to 49 kN). 3 up to 3.8 g / cm³ 3 exhibiting. By using the active material of the positive electrode, which has a condensed density within the aforementioned range, the lithium-ion secondary battery can exhibit a relatively high capacity and energy density, while simultaneously offering good normal-temperature cycle stability and high-temperature cycle stability.

[0097] Optionally, the particles of the active material of the positive electrode can have a morphology of one or more spheres and be nearly spherical.

[0098] In some embodiments, the active material of the positive electrode comprises secondary particles that arise from the aggregation of primary particles. In these embodiments, the aforementioned "particles" also include secondary particles.

[0099] In this application, the volume-averaged particle size D v The median particle size of the active material of the positive electrode, also known as the median particle size, has a well-known meaning in engineering and represents the particle size that corresponds to 50% of the volume distribution of the particles of the active material of the positive electrode. v 50% of the active material of the positive electrode can be measured using known instruments and methods, e.g., with a laser particle size analyzer (such as the Mastersizer 3000 from Malvern Instruments Co., Ltd., UK).

[0100] The specific surface area of ​​the active material of the positive electrode has a well-established significance in engineering and can be measured using established instruments and methods. For example, it can be measured using the specific surface area analysis method with nitrogen adsorption and calculated using the BET (Brunauer-Emmett-Teller) method. The test procedure for specific surface area analysis with nitrogen adsorption can be performed with the NOVA 2000e, a specific surface area and pore size analysis instrument from Quantachrome Instruments, USA. A specific example of the test procedure is as follows: Extraction of 8,000 g to 15...000 g of the active material of the positive electrode in a weighed empty sample tube, stirring and weighing of the active material of the positive electrode and placement of the sample tube in the NOVA 2000e degassing station for degassing, weighing of the total mass of the active material of the positive electrode and the sample tube after degassing and calculation of the mass of the active material of the positive electrode after degassing by subtracting the mass of the empty sample tube from the total mass G.Inserting the sample tube into the NOVA 2000e, measuring the amount of nitrogen adsorption on the surface of the active material of the positive electrode under different relative pressures, calculating the single-layer adsorption amount based on the Brunauer-Emmett-Teller multi-layer adsorption theory and equation, and subsequently calculating the total surface area A of the active material of the positive electrode and the specific surface area of ​​the active material of the positive electrode by A / G.

[0101] The bulk density of the active material of the positive electrode has a known significance in engineering and can be measured using a known instrument and method in engineering, e.g. it can be conveniently measured with a bulk density meter (e.g. type FZS4-4B).

[0102] The compacted density of the active material of the positive electrode has a significance known in engineering and can be measured with an instrument and method known in engineering; for example, it can be conveniently measured with an electronic pressure tester (e.g., type UTM7305).

[0103] A process for producing an active material for a positive electrode is then schematically illustrated. Any of the above-mentioned active materials for positive electrodes can be produced using such a process. An exemplary production process includes:

[0104] Mixing the precursor of the positive electrode active material, the lithium source and the precursor of the doping element and sintering to obtain the positive electrode active material.

[0105] The precursor of the active material for the positive electrode can consist of one or more oxides, hydroxides and carbonates containing Ni, Co and Mn in a stoichiometric ratio, for example hydroxides containing Ni, Co and Mn in a stoichiometric ratio.

[0106] The precursor of the active material for the positive electrode can be produced by a process known in engineering, for example by a co-precipitation process, a gel process or a solid-state process.

[0107] As an example, the Ni source, the Co source, and the Mn source are dispersed in a solvent to obtain a mixed solution; in a continuous cocurrent reaction, the mixed solution, the strong alkali solution, and the complexing agent solution are simultaneously pumped into a stirred reactor, with the pH of the reaction solution controlled in a range of 10 to 13 and the temperature in the reactor controlled in a range of 25 °C to 90 °C under inert gas protection during the reaction; after completion of the reaction and after aging, filtration, washing, and vacuum drying, a hydroxide containing Ni, Co, and Mn is obtained.

[0108] The nickel source may be a soluble nickel salt, such as one or more of the elements nickel sulfate, nickel nitrate, nickel chloride, nickel oxalate, and nickel acetate; in particular, one or more of the elements nickel sulfate and nickel nitrate; in particular, nickel sulfate. The cobalt source may be a soluble cobalt salt, such as one or more of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt oxalate, and cobalt acetate; in particular, one or more of cobalt sulfate and cobalt nitrate; in particular, cobalt sulfate. The manganese source may be a soluble manganese salt, such as one or more of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, and manganese acetate; in particular, one or more of manganese sulfate and manganese nitrate; in particular, manganese sulfate.

[0109] The strong base can include one or more of the following substances: LiOH, NaOH, and KOH, for example, NaOH. The complexing agent can include one or more of the following substances: ammonia, ammonium sulfate, ammonium nitrate, ammonium chloride, ammonium citrate, and disodium ethylenediaminetetraacetate (EDTA), for example, ammonia.

[0110] There are no special restrictions on the solvents used in the mixed solution, the strong base solution, and the complexing agent solution. For example, the solvents in the mixed solution, the strong base solution, and the complexing agent solution can each be, independently of one another, one or more of the following: deionized water, methanol, ethanol, acetone, isopropanol, and n-hexanol; for example, deionized water.

[0111] The inert gas introduced during the reaction is, for example, one or more of the gases nitrogen, argon and helium.

[0112] The lithium source can be one or more of the following: lithium oxide (Li₂O), lithium phosphate (Li₃PO₄), lithium dihydrogen phosphate (LiH₂PO₄), lithium acetate (CH₃COOLi), lithium hydroxide (LiOH), lithium carbonate (Li₂CO₃), and lithium nitrate (LiNO₃). The lithium source is, in particular, lithium carbonate, lithium hydroxide, or lithium nitrate; specifically, the lithium source is lithium carbonate.

[0113] The precursor of the doping element can be one or more oxides, nitric acid compounds, carbonic acid compounds, hydroxide compounds and acetic acid compounds of doping elements. The precursor of the doping element can consist, for example, of oxides of doping elements such as one or more aluminum oxides (such as Al2O3, etc.), silicon oxides (such as SiO2, SiO, etc.), titanium oxides (such as TiO2, TiO, etc.), vanadium oxides (such as V2O5, V2O4, V2O3, etc.), germanium oxides (such as GeO2, etc.), selenium oxide (such as SeO2, etc.), zirconium dioxide (such as ZrO2, etc.), niobium oxide (such as Nb2O5, NbO2, etc.), ruthenium oxide (such as RuO2, etc.), palladium oxide (such as PdO, etc.), antimony oxide (such as Sb2O5, Sb2O3, etc.), tellurium oxide (such as TeO2, etc.), and tungsten oxide (such as WO2, WO3, etc.).

[0114] The precursor of the active material for the positive electrode, the lithium source, and the precursor of the dopant can be mixed using a ball mill mixer or a high-speed mixer. The mixed materials are placed in an atmospheric sintering furnace and sintered. The sintering atmosphere is an oxygen-containing atmosphere, such as air or oxygen. The sintering atmosphere can have an oxygen concentration of 70% to 100%, for example, 75% to 95%. The sintering temperature is typically between 600°C and 1000°C. Optionally, the sintering temperature can be between 700°C and 900°C, which contributes to a more uniform distribution of the dopant. The sintering time can be adjusted depending on the situation, for example, from 5 to 25 hours or from 10 to 20 hours.

[0115] It should be noted that when preparing the active material for the positive electrode, there are numerous theoretically feasible ways to control the exothermic DSC initial temperature and the exothermic peak area of ​​the nickel-cobalt-manganese oxide active material, such as the type and concentration of the dopant, the sintering time, the sintering temperature, the number of sinterings, and the oxygen concentration during sintering. This application outlines some measures for doping solid-state sintering processes. By adjusting the number of sinterings, batch doping, controlling the total sintering time and temperature, and controlling the sintering oxygen concentration, the molar nickel content in the resulting lithium nickel-cobalt-manganese oxide ranges from 60% to 90% of the total molar content of nickel, cobalt, and manganese.The lithium nickel cobalt manganese oxide has a layered crystal structure belonging to the R3m space group; the transition metal layer includes dopants, and the deviation of the local mass concentration of the dopants anywhere in the particles of the active material of the positive electrode is 20% or less; and when the material of the positive electrode is delithiated to the 78% delithiated state for the purpose of performing a DSC test, the initial exothermic temperature of the main exothermic peak is 200°C or more, and the integral area of ​​the main exothermic peak is 100 J / g or less. It is understood that the methods described in this description serve only to illustrate the present application and are not intended to limit it.

[0116] For example, the dopant precursor can be divided into L batches, where L can be between 1 and 5, for example, between 2 and 5 or between 2 and 3. In these embodiments, the process for producing the active material for the positive electrode can include the following steps: mixing the active material precursor for the positive electrode, the lithium source, and the first batch of the dopant precursor, followed by a first sintering process; mixing the product obtained from the first sintering process with the second batch of the dopant precursor, followed by a second sintering process; and so on, until the product obtained from the L-1 sintering process is mixed with the L batch of the dopant precursor, followed by the L-th sintering process to obtain an active material for the positive electrode.

[0117] The precursor of the doping element can be divided uniformly or arbitrarily into L parts to perform L batches of doping.

[0118] The temperature can be the same or different for each sintering process. The time for each sintering process can also be the same or different. Experts can adjust the temperature and time for sintering depending on the type and amount of dopants. For example, the temperature for each sintering process can range from 600°C to 1000°C, such as between 700°C and 900°C, and even between 800°C and 850°C; the time for each sintering process can range from 3 hours to 25 hours, such as between 5 hours and 10 hours. The total sintering time can range from 5 to 25 hours, for example, between 15 and 25 hours.

[0119] For elements that are more difficult to dope, e.g., elements with a large atomic radius, the uniformity of doping can be improved by increasing the sintering temperature and / or extending the sintering time.

[0120] In some embodiments, the sintered product can also be comminuted and sieved to obtain an active material for positive electrodes with an optimized particle size distribution and specific surface area. There are no particular restrictions on the comminution method; it can be determined as required, e.g., by using a particle crusher. Positive electrode plate

[0121] This application provides a positive electrode plate containing one or more of the active materials for positive electrodes of this application.

[0122] By using the active material of the positive electrode of the present application in the positive electrode plate of embodiments of the present application, the lithium-ion secondary battery can simultaneously exhibit good room temperature and high temperature cycle stability and a higher energy density.

[0123] In particular, the positive electrode plate comprises a positive electrode current collector and an active material layer of the positive electrode, which is arranged on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two opposing surfaces in its own thickness direction, and the active material layer of the positive electrode is laminated onto one or both of the two opposing surfaces of the positive electrode current collector.

[0124] The active material layer of the positive electrode comprises one or more of the active materials for the positive electrode from the present application.

[0125] Furthermore, the active material layer of the positive electrode can contain a conductive material and a binder. In this application, there are no specific restrictions on the types of conductive materials and binders used in the active material layer of the positive electrode; these can be determined according to the actual requirements.

[0126] For example, the conductivity agent may comprise one or more of the following materials: graphite, superconducting carbon, carbon black, carbon black, carbon black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binder may comprise one or more of the following materials: styrene-butadiene rubber (SBR), waterborne acrylic resins, carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer (EVA), vinylidene fluoride-tetrafluoroethylene propylene terpolymer, vinylidene fluoride-hexafluoropropylene tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylic resin, and polyvinyl alcohol (PVA).

[0127] The positive electrode current collector can be a metal foil or a porous metal plate with good electrical conductivity and good mechanical properties, and the material of the positive electrode current collector can be one or more of the following: aluminum, copper, nickel, titanium, silver, and their respective alloys. For example, the positive electrode current collector is an aluminum foil.

[0128] The positive electrode plate can be manufactured using the usual method. For example, an active material for a positive electrode, a conductive agent, and a binder are dispersed in a solvent, which can be, for example, N-methylpyrrolidone (NMP) and deionized water, to form a uniform positive electrode paste; the positive electrode paste is applied to a positive electrode current collector; after processes that include drying and rolling, a positive electrode plate is obtained. Lithium-ion secondary battery

[0129] The present application provides a lithium-ion secondary battery comprising a positive electrode plate, a negative electrode plate, a separator and an electrolyte, wherein the positive electrode plate is any positive electrode plate of the application.

[0130] By using the positive electrode plate of the present application, the lithium-ion secondary battery can exhibit good cycle stability and high energy density at room temperature and high temperatures.

[0131] The negative electrode plate can be a metallic lithium plate.

[0132] The negative electrode plate can also include a negative electrode current collector and an active material layer for the negative electrode, which is arranged on at least one surface of the negative electrode current collector. For example, the negative electrode current collector has two opposing surfaces in its own thickness direction, and the active material layer of the negative electrode is laminated onto one or both of the two opposing surfaces of the negative electrode current collector.

[0133] The active material layer of the negative electrode contains the active material for the negative electrode in the present application. In the embodiments of the present application, there is no specific limitation on the types of active materials for negative electrodes, which can be determined according to actual needs. For example, the active material of the negative electrode can be one or more of the following: natural graphite, synthetic graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite material, SiO₂. m (0 < m <2, e.g. m = 1), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, lithium titanate Li4Ti5O 12 with spinel structure, Li-Al alloy and lithium metal.

[0134] The active material layer for the negative electrode may also contain a conductive material and a binder. In the embodiments of the present application, there is no specific limitation on the types of conductive materials and binders in the active layer of the negative electrode, which can be determined according to actual needs. The conductive material may be, for example, one or more of the following: graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binders may consist of one or more of the following: styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), and water-based acrylic resin.

[0135] The layer of active material for the negative electrode may optionally also contain a thickening agent, such as sodium carboxymethylcellulose (CMC-Na).

[0136] The negative electrode current collector can be a metal foil or a porous metal plate with good electrical conductivity and good mechanical properties, and the material of the negative electrode current collector can be one or more of the following: copper, nickel, titanium, iron, and their respective alloys. For example, the negative electrode current collector is a copper foil.

[0137] The negative electrode plate can be manufactured using the usual method. For example, an active material for a negative electrode, a conductive agent, a binder, and a thickening agent are dispersed in a solvent, which can be, for example, N-methylpyrrolidone (NMP) or deionized water, to form a uniform paste for the negative electrode; the paste for the negative electrode is applied to a negative electrode current collector; after processes such as drying and rolling, a negative electrode plate is obtained.

[0138] In the lithium-ion secondary battery of the embodiments of the present application, the electrolyte can be a solid electrolyte, such as a polymer electrolyte or an inorganic solid electrolyte, but is not limited to these. An electrolyte solution can also be used. The electrolyte solution mentioned above can contain a solvent and a lithium salt dissolved in the solvent.

[0139] The solvent may be a non-aqueous organic solvent, such as one or more, e.g., two or more, of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), and ethyl butyrate (EB).

[0140] The lithium salt can be one or more of the following: LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiAsF6 (lithium hexafluoroarsenate), LiFSI (lithium bisfluorosulfonimide), LiTFSI (lithium bistrifluoromethanesulfonimide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium bisoxalate borate), LiPO2F2 (lithium difluorophosphate), LiDFOP (lithium difluorooxalate phosphate), and LiTFOP (lithium tetrafluorooxalate phosphate), such as one or more of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiBOB (lithium bisoxalate borate), LiDFOB (lithium difluorooxalate borate), LiTFSI (Lithium bistrifluoromethanesulfonimide) and LiFSI (Lithium bisfluorosulfonimide).

[0141] The electrolyte solution may optionally contain other additives, such as... B. one or more of the following substances: vinylene carbonate (VC), vinylethylene carbonate (VEC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoropropylene carbonate (TFPC), succinonitrile (SN), adiponitrile (ADN), glutaronitrile (GLN), hexanetrinitrile (HTN), 1,3-propane sultone (1,3-PS), ethylene sulfate (or 1,3,2-dioxathiolane-2,2-dioxide, DTD), methylenemethanedisulfonate (MMDS), 1-propane-1,3-sultone (PST), 4-methylvinyl sulfate (PCS, or propane-1,2-cyclic sulfate), 4-ethylvinyl sulfate (PES), 4-propylethylene sulfate (PEGLST), propylene sulfate (TS), 1,4-butane sultone (1,4-BS), ethylene sulfite (DTO), dimethyl sulfite (DMS), diethyl sulfite (DES), cyclic quaternary ammonium salt of sulfonic acid esters, tris(trimethylsilane) phosphate (TMSP) and tris(trimethylsilane) borate (TMSB), but not limited to these.

[0142] There are no specific restrictions on the separator in the lithium-ion secondary battery of the embodiments of the present application, and any known separator with a porous structure that is electrochemically and mechanically stable can be used, such as one or more single- or multi-layer films of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP) and polyvinylidene fluoride (PVDF).

[0143] The positive and negative electrode plates are stacked alternately, and a separator is placed between them to separate the positive and negative electrode plates, forming an electrode assembly (optionally after winding). The electrode assembly is then inserted into a housing into which an electrolyte is injected, and the housing is sealed, creating a lithium-ion secondary battery.

[0144] The shape of the lithium-ion secondary battery is not particularly restricted within the scope of the present application and can be cylindrical, rectangular or any other shape. Fig. Figure 5 shows, as an example, a lithium-ion secondary battery with a rectangular structure.

[0145] In some embodiments, the secondary battery may contain an outer casing. The positive electrode plate, the negative electrode plate, and the electrolyte are encapsulated within the outer casing.

[0146] In some embodiments (see Fig. The outer packaging can comprise a housing 51 and a cover plate 53. In one example, the housing 51 can comprise a base plate and a side plate connected to the base plate, and the base plate and side plate are combined to form a receiving space. The housing 51 has an opening that connects to the receiving space, and the cover plate 53 can cover the opening to close the receiving space.

[0147] The positive electrode plate, the negative electrode plate, and the separator can be stacked or wound to form an electrode assembly 52. ​​The electrode assembly 52 is encapsulated in the receiving space. The electrolyte can be an electrolytic solution, which is infiltrated into the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the lithium-ion secondary battery 5 can be one or more, as required.

[0148] In some embodiments, the outer packaging of the lithium-ion secondary battery can be a rigid casing, such as a hard plastic casing, an aluminum casing, a steel casing, or the like. The outer packaging of the secondary battery can also be a flexible casing, such as a bag-like soft pack. The material of the flexible casing can be, for example, plastic, including polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), and the like.

[0149] In some embodiments, the lithium-ion secondary battery can be assembled into a battery module. The battery module can contain a variety of lithium-ion secondary batteries, the specific number of which can be adapted depending on the application and the capacity of the battery module.

[0150] Fig. shows, as an example, battery module 4. As in Fig.As shown in Figure 6, several lithium-ion secondary batteries 5 are arranged in series along the length of the battery module 4. The secondary batteries 5 can, of course, also be arranged in any other way. Furthermore, a large number of lithium-ion secondary batteries 5 can be secured with a fastening element.

[0151] Optionally, the battery module 4 can also include a housing with a receiving space in which several lithium-ion secondary batteries 5 can be accommodated.

[0152] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted depending on the application and capacity of the battery pack.

[0153] The Fig. show an example of a battery set 1. As can be seen from the Fig.As can be seen, the battery assembly 1 can comprise a battery housing and a plurality of battery modules 4 housed within the battery housing. The battery housing consists of an upper housing body 2 and a lower housing body 3. The upper housing body 2 can cover the lower housing body 3 to form an enclosed space for receiving the battery modules 4. Multiple battery modules 4 can be arranged within the battery housing in any configuration.

[0154] This application also provides a device, the device comprising at least one lithium-ion secondary battery, battery module, or battery pack as described in this application. The lithium-ion secondary battery, battery module, or battery pack can be used as the device's power source or energy storage device. The device may be, but is not limited to, a mobile device (e.g., a mobile phone, laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck), an electric train, a ship, a satellite, an energy storage system, etc. The device may use a lithium-ion secondary battery, a battery module, or a battery pack, depending on the application's requirements.

[0155] Fig.This shows an example of a device. The device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high performance and high energy density of the secondary batteries, a battery pack or battery module can be used.

[0156] Another example: The device could be a mobile phone, a tablet computer, a notebook, etc. The device generally needs to be thin and light, and a lithium-ion secondary battery can be used as a power source. Examples

[0157] The following examples are for illustrative purposes only and are intended to further describe the present application. Various modifications and variations within the scope of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios described in the following embodiments refer to weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further treatment, and all instruments used in the embodiments are commercially available. Example 1: Production of the active material of the positive electrode

[0158] The doping element was Sb. The precursor of the doping element antimony oxide Sb2O3 was divided approximately equally into three batches for the Sb doping.

[0159] The precursor of the active material of the positive electrode [Ni0,8Co 0,1 Mn 0,1 ](OH)₂, lithium hydroxide LiOH, and the first batch of antimony oxide Sb₂O₃ were placed in the high-speed mixer and mixed for 1 hour to obtain a mixture. The molar ratio of the positive electrode active material precursor to lithium hydroxide Li / Me was 1.05, where Me represented the total molar amount of Ni, Co, and Mn in the positive electrode active material precursor; the mixture was placed in the atmospheric sintering furnace for sintering. Sintering was carried out at a sintering temperature of 830 °C and for a sintering time of 5 hours under an oxygenated atmosphere with an O₂ concentration of 90%.

[0160] The product from the first sintering and the second batch of antimony oxide were placed in the high-speed mixer for one hour to perform the second sintering. The second sintering was carried out at the same sintering temperature, sintering time, and sintering atmosphere as the first sintering.

[0161] The product from the second sintering and the third batch of antimony oxide were placed in the high-speed mixer for one hour, after which the third sintering took place. The sintering temperature and atmosphere were the same as in the two previous sinterings, and the sintering time was 10 hours. The total sintering time was 20 hours.

[0162] The product of the third sintering was crushed and sieved to obtain the high-nickel ternary active material for the positive electrode. Antimony oxide was added in such a quantity that the actual doping concentration of Sb in the active material of the positive electrode was 25,110 µg / cm³. 3 fraud. Preparation of the electrolyte solution

[0163] After mixing EC, DEC and DMC in a volume ratio of 1:1:1, a solvent was obtained, and then the lithium salt LiPF6 was dissolved in the above solvent to obtain an electrolyte solution in which the concentration of LiPF6 was 1 mol / L. Preparing the button battery

[0164] The active material of the positive electrode, prepared as above—carbon black as a conductive medium and PVDF as a binder in a weight ratio of 90:5:5—was dispersed in the solvent N-methylpyrrolidone (NMP). After uniform mixing, a positive electrode paste was obtained. This paste was then evenly applied to an aluminum foil to form the positive electrode current collector. After drying and cold pressing, a positive electrode plate was obtained.

[0165] In a button battery housing, the positive electrode plate, a separator and a metal lithium sheet were successively laminated and the aforementioned electrolyte solution injected to assemble a button battery. Preparing a fully charged battery

[0166] The active material of the positive electrode, prepared as above, consisting of acetylene black as a conductive agent and PVDF as a binder in a weight ratio of 94:3:3, was dispersed in the solvent NMP. After uniform mixing, a positive electrode paste was obtained. This paste was then evenly applied to the aluminum foil of the positive electrode current collector. After drying and cold pressing, a positive electrode plate was obtained.

[0167] Synthetic graphite and hard carbon as the active material for the negative electrode, acetylene black as a conductive agent, styrene-butadiene rubber (SBR) as a binder, and sodium carboxymethylcellulose (CMC-Na) as a thickener in a weight ratio of 90:5:2:2:1 were dispersed in deionized water; after uniform mixing, a negative electrode paste was obtained; the negative electrode paste was applied evenly to the aluminum foil of the negative electrode current collector. After drying and cold pressing, the negative electrode plate was obtained.

[0168] A porous polyethylene (PE) film was used as a separator. The positive electrode plate, the separator, and the negative electrode plate were laminated sequentially to obtain a bare electrode assembly; the bare electrode assembly was placed in an outer packaging, followed by injection of the aforementioned electrolyte solution into the outer packaging, and then, after the formation steps and the like, the outer packaging was sealed to obtain a complete battery. Examples 2 to 11, examples 13 to 17 and comparative examples 1 to 4

[0169] Example 1 was repeated, except that the relevant parameters in the manufacturing step of the active material of the positive electrode were changed; the type and amount of dopants in each batch, the sintering temperature (600 °C to 900 °C), the sintering atmosphere (an oxygenated atmosphere with an O2 concentration of 75% to 95%), and the total sintering time (10 h to 20 h) were adjusted to obtain the active material of the positive electrode with a predetermined type of dopants, a predetermined amount of dopants, and a predetermined doping uniformity. Examples 4 and 5 involve the doping of multiple elements, while the amounts of dopants were substantially the same in each case. In Comparative Example 1, no dopants were added. The remaining parameters are listed in Table 1 and Table 2. Example 12 and Comparative Example 5

[0170] Example 1 was repeated, except that the dopant in Example 12 was added in a single batch and the sintering temperature was 720 °C; the dopant in Comparative Example 5 was added in a single batch and the sintering temperature was 650 °C; the other parameters are listed in Table 1 and Table 2. Examples 18 to 19

[0171] In Example 18, Example 1 was repeated, except that the temperature for the first sintering was 800 °C and the time for the first sintering was 7 hours; the temperature for the second sintering was 750 °C and the time for the second sintering was 2 hours; and the temperature for the third sintering was 100 °C and the time for the third sintering was 2 hours, with the amount of the second batch of dopants being 40% and the amount of the third batch of dopants being 10%, based on the total amount of dopants. The remaining parameters are listed in Table 1 and Table 2.

[0172] In Example 19, Example 1 was repeated, except that the temperature for the first sintering was 750 °C and the time for the first sintering was 6 hours; the temperature for the second sintering was 700 °C and the time for the second sintering was 1 hour; and the temperature for the third sintering was 650 °C and the time for the third sintering was 1 hour, with the quantity of the second batch of dopants being 50% and the quantity of the third batch of dopants being 20%, based on the total quantity of dopants. The remaining parameters are listed in Table 1 and Table 2. Examples 20 to 21 and comparative examples 6 to 7

[0173] Example 1 was repeated, except that in Examples 20 and 21, as well as in Comparative Example 7, the precursor for the active material of the positive electrode [Ni 0,6 Co 0,2 Mn 0,2](OH)2 were and various types of doping elements were added; in comparative example 6, the precursor for the active material of the positive electrode was [Ni 0,6 Co 0,2 Mn0 ,2 ](OH)2, without the addition of doping elements; the other parameters are given in Table 1 and Table 2. Test section 1) DSC test of the “78% delithiated state” of the active material of the positive electrode

[0174] At 25 °C, 18 button batteries were charged with a constant current of 1 C up to the upper limit of the charge / discharge cut-off voltage, then charged with constant voltage until the current was ≤0.05 mA, and after a 2-minute standby period, discharged with a constant current of 1 C up to the lower limit of the charge / discharge cut-off voltage.

[0175] Subsequently, the 18 button batteries were charged and discharged as described above to 2.8 V, 2.9 V, 3.0 V, 3.1 V, 3.2 V, 3.3 V, ... 4.0 V, 4.1 V, 4.2 V, 4.3 V, 4.4 V, 4.5 V (i.e., the charging voltage interval was 0.1 V) at a rate of 0.1 C. The positive electrode plate of each charged button battery was removed in a drying chamber and taken as a sample. After weighing and recording the sample mass, the sample was placed in a digestion vessel, followed by the slow addition of 10 ml of aqua regia as a digestion reagent; the digestion vessel was then placed in the CEM-Mars5 microwave digestion unit, with digestion carried out at a microwave emission frequency of 2450 Hz. The decongested sample solution was transferred to a volumetric flask and shaken, and the sample was placed in the ICP-OES sampling system PE7000DV.The mass concentrations of Li, O, Ni, Co, Mn, and dopant elements were measured for the active material of the positive electrode under 0.6 MPa argon pressure at 1300 W radio frequency power. Based on the mass concentrations of the elements, the chemical formula for each voltage, and thus the delithiated state for each voltage, was determined after conversion. If the chemical formula of the active material of the positive electrode is Li... 0,22 Ni 0,8 Co 0,1 Mn 0,1 O2 was, the corresponding delithiated state was (1-0.22)×100 %=78 %, and the corresponding voltage was the voltage that corresponded to the 78 % delithiated state.

[0176] A button cell battery was charged at a rate of 0.1 C to the voltage corresponding to a 78% delithiated state. The battery was then cut open in the drying room using scissors, and the entire positive electrode plate was removed and placed in a beaker into which an appropriate amount of high-purity anhydrous dimethyl carbonate (DMC) was poured and then replaced every 8 hours. After the sample was washed three times consecutively, it was placed in the vacuum chamber in the drying room and pumped to a vacuum of -0.096 MPa and dried for 12 hours. The dried positive electrode plate was scraped with a blade in the drying room, and 4.95 mg to 5.05 mg of the active material powder from the positive electrode were weighed into the high-pressure crucible of the STA449F3-QMS403C differential scanning calorimeter and sealed.The sample was heated at a heating rate of 10 °C / min, and the data of the heat flux change of the sample as a function of temperature were recorded to obtain the DSC diagram and thus the exothermic initial temperature, the full width at half maximum, the integral area, and the maximum exothermic temperature of the exothermic main peak.

[0177] The positive electrode in the button battery can also be a positive electrode plate that was removed from the full battery in a drying room, and the middle area was selected to be punched out to a suitable size as the positive electrode plate of the button battery. 2) Testing the relative deviation σ of the local mass concentration of the doping elements in the particles of the active material of the positive electrode

[0178] 2 g of the positive electrode active material were weighed out and evenly sprinkled onto the sample stage using conductive adhesive, followed by light pressure to fix the powder; or a 1 cm × 1 cm electrode plate was cut from the battery's positive electrode plate and glued to the sample stage as the test sample. The sample stage was loaded and secured in the vacuum sample chamber, and the JEOL-manufactured IB-09010CP cross-sectional polisher was used to create a cross-section of the positive electrode active material (as shown in Fig. shown). As in Fig.As shown, points were recorded at 17 positions in the cross-section of the secondary particles, with each point having an area of ​​20 nm × 20 nm. The X-Max energy spectrometer (EDS) detector from the Oxford Instruments Group in the United Kingdom was used in combination with the Sigma-02-33 scanning electron microscope (SEM) from ZEISS in Germany to test the mass concentrations of dopants at the 17 positions using the following test method: configuring Li, O, Ni, Co, Mn and dopants as elements to be detected and setting the SEM parameters, including 20 kV accelerating voltage, 60 µm aperture, 8.5 mm working distance, 2.335 A current, performing the EDS-SEM test until the spectral range reached 250,000 cts or more (controlled by acquisition time and acquisition rate), and collecting data to determine the mass concentrations η1, η2, η3, ..., η 17the doping elements at the positions.

[0179] The average mass concentration η of the doping element in the particles of the active material of the positive electrode was determined as follows: using the EDS-SEM test method mentioned above, with the area under investigation being as shown in the dashed box in Fig. shown, covering all the above-mentioned points in the particles a of the active material of the positive electrode without exceeding the cross-section of the secondary particle.

[0180] The relative deviation σ of the local mass concentration of the doping elements in the particles of the active material of the positive electrode was calculated according to formula (1).

[0181] To test the active material of the battery's positive electrode, the battery was disassembled with scissors in the drying room, the entire positive electrode plate was removed and placed in a beaker, and covered with an appropriate amount of high-purity anhydrous dimethyl carbonate (DMC). The DMC was replaced every 8 hours. After three consecutive washes, the sample was placed in the vacuum chamber in the drying room, pumped to a vacuum of -0.096 MPa, and dried for 12 hours. A 1 cm × 1 cm electrode plate was cut from the battery's positive electrode plate and glued to the sample stage with conductive adhesive. Alternatively, 2 g of active material powder was scraped from the positive electrode in the drying room, and the sample was then tested as described above. 3) Verification of the actual doping concentration of the active material of the positive electrode:

[0182] The actual density ρ true The density of the active material of the positive electrode was measured using the TD2400 powder density tester from Beijing Builder Electronic Technology Co., Ltd., using the following test method: A specific mass of the active material of the positive electrode was extracted and placed in a sample cup at 25 °C; the mass m of the active material of the positive electrode was recorded; the sample cup containing the active material of the positive electrode was placed in the test chamber of the density tester; the test system was sealed; an inert gas with a small molecular diameter, such as helium or nitrogen, was introduced; the gas pressure in the sample chamber and the expansion chamber was measured; and the true volume V of the measured material was then measured according to Bohr's law PV = nRT, and the true density ρ was calculated. trueof the secondary particles by m / V. n was the molar mass of the gas in the sample beaker; R was the ideal gas constant, 8.314; T was the ambient temperature, 298.15 K.

[0183] The sampling system of the inductively coupled plasma optical emission spectrometer (ICP-OES) 7000DV, available from PerkinElmer (PE) in the United States, was used to test the mass concentration φ of the dopants in the active material of the positive electrode, using the following test procedure: extraction of an electrode plate containing the active material of the positive electrode and punching in a disc with a total mass of more than 0.5 g or extraction of a powder sample of at least 5 g of the active material of the positive electrode, weighing and recording the sample mass and placing the sample in a digestion vessel, slow addition of 10 ml of aqua regia as a digestion reagent, assembly, placement of the digestion vessel in the CEM Mars5 microwave digestion unit and performance of the digestion at a microwave emission frequency of 2450 Hz;Transfer the decongested sample solution into a volumetric flask, shake, sample and insert into the ICP-OES sampling system, test the mass concentration of doping elements in the active material of the positive electrode under 0.6 MPa argon pressure at 1300 W high-frequency power.

[0184] Then the actual doping concentration ω of the active material of the positive electrode was calculated according to the formula (2) mentioned above. 4) Testing the chemical valence of the doping element M in the “78% delithiated state” of the active material of the positive electrode

[0185] A battery containing the positive electrode active material under test was charged to the voltage corresponding to a 78% delithiated state. The battery was then cut open in the drying room using scissors, the entire positive electrode plate was removed, placed in a beaker, and covered with an appropriate amount of high-purity anhydrous dimethyl carbonate (DMC), with the DMC being replaced every 8 hours. After three consecutive correct washes, the sample was placed in the vacuum chamber in the drying room, pumped to a vacuum of -0.096 MPa, and dried for 12 hours. The dried positive electrode plate was then used as the sample for the XPS test.

[0186] The plate sample was adhered to the sample stage of the Kratos AXIS Supra XPS using 3M insulating tape. After automated sample injection, the system was vacuum-pumped for at least one hour. A monochromatic aluminum target (Al Kα, 1486.6 eV) was used as the excitation source, and the fine spectra of the dopants were scanned with a step size of 0.1 eV and a through energy of 40 eV. The valence state of the elements was determined by splitting the peaks of specific elements with reference to the characteristic standard XPS peaks. 5) Testing the initial gram capacity of the button battery

[0187] At 25 °C, button cells were charged at a constant current of 0.1 C to the upper limit of the charge / discharge cut-off voltage, then charged at a constant voltage until the current was 0.05 mA or less, and after being left for 2 minutes, discharged at a constant current of 0.1 C to the lower limit of the charge / discharge cut-off voltage. The discharge capacity at this point corresponded to the initial gram capacity of the button cell. 6) Testing the initial gram capacity of a fully charged battery

[0188] At 25°C, the battery was charged at a constant current of 1 / 3 C to the upper limit of the charge / discharge cut-off voltage, then charged at a constant voltage until the current was 0.05 mA or less, and after standing for 5 minutes, it was then discharged at a constant current of 1 / 3 C to the lower limit of the charge / discharge cut-off voltage. The discharge capacity at this point corresponded to the initial gram capacity of the fully charged battery. 7) High-temperature cycle stability tests of a fully charged battery

[0189] At 45 °C, the battery was charged at a constant current of 1C to the upper limit of the charge / discharge cut-off voltage, then charged at a constant voltage until the current was 0.05 mA or less, and after standing for 5 minutes, it was then discharged at a constant current of 1C to the lower limit of the charge / discharge cut-off voltage. This constituted one charge and discharge cycle. The discharge capacity at this point was recorded as the discharge-specific capacity Di at the first cycle. The battery was subjected to 400 charge and discharge cycles using the method described above, and the discharge capacity after the 400th cycle, D, was recorded. 400 , was recorded. Capacity retention rate of a fully charged battery at 45 °C, 1 C / 1 C 400 cycles (%) = D 400 / D1 × 100%

[0190] In the above-mentioned tests 1), 5), 6) and 7): In examples 1 to 19 and comparison examples 1 to 5, the charge / discharge cut-off voltage of the button battery was between 2.8 V and 4.25 V, and the charge / discharge cut-off voltage of the fully charged battery was between 2.8 V and 4.2 V; in examples 20 to 21 and comparison examples 6 to 7, the charge / discharge cut-off voltage of the button battery was between 2.8 V and 4.35 V, and the charge / discharge cut-off voltage of the fully charged battery was between 2.8 V and 4.3 V.

[0191] The test results of examples (Ex.) 1 to 21 and comparison examples (V.Ex.) 1 to 7 are listed in Tables 2 and 3. Table 1 Nr. Type of doping element Mass ratio of the batches Oxygen concentration in the sinter atmosphere (%) First sintering Second sintering Third sintering Temp.(°C) Time (h) Temp.(°C) Time (h) Temp.(°C) Time (h) Example 1 Sb 1:1:1 90 830 5 830 5 830 10 Example 2 Te 1:2:1 85 825 4 800 7 815 8 Example 3 Si 2:3:2 88 785 5 825 4 835 10 Example 4 Zr+W 1:2:3 79 810 7 805 5 845 6 Example 5 Sb+Ru+Te 1:2:1 83 800 3 835 6 795 11 Example 6 Sb 2:3:4 82 825 5 800 8 825 5 Example 7 Sb 2:3:2 83 830 3 785 7 815 8 Example 8 Sb 1:2:2 86 825 6 805 4 830 7 Example 9 Sb 1:2:1 84 810 4 815 5 825 6 Example 10 Sb 1:2:3 85 835 6 825 3 845 9 Example 11 Ru 1:1:2 83 800 3 795 6 825 10 Example 12 Ru / 78 Single-batch doping; one sintering at 720 °C for 20 hours Example 13 Ti 1:2:2 80 805 5 835 4 800 10 Example 14 Zr 1:2:1 81 825 4 810 6 815 6 Example 15 Al 1:2:3 85 810 5 825 3 830 8 Example 16 Ge 1:2:2 82 815 6 795 4 825 7 Example 17 See 2:3:2 81 800 5 785 5 825 7 Example 18 Sb 5:4:1 78 800 7 750 2 700 2 Example 19 Sb 3:5:2 77 750 6 700 1 650 1 Example 1 / / 89 Sintering at 830 °C for 20 hours Example 2 Y 1:1:2 87 815 5 810 3 825 10 Example 3 Sb 1:2:1 88 825 6 805 5 835 8 Example 4 Sb 1:2:3 91 830 4 785 7 845 7 Example 5 Ru / 76 Single-batch doping; one sintering at 650 °C for 20 h Example 20 Sb 2:3:2 85 800 4 835 5 800 10 Example 21 Ru 1:2:2 87 815 6 825 7 795 7 Example 6 / / 88 Sintering at 830 °C for 20 hours Example 7 Y 1:1:2 85 825 7 835 5 805 8

[0192] In Table 1, the mass ratio of the batches is: Mass of the first batch of doping element precursors: Mass of the second batch of doping element precursors: Mass of the third batch of doping element precursors. Table 2 Nr. Chemical Valence ω(µg / cm3) Σ(%) E(%) Exothermic initial temperature (°C) Integral area of ​​the exothermic peak (J / g) Full width at half maximum (°C) Maximum exothermic temperature (°C) Example 1 +5 25110 10 12 212 50 23 235 Example 2 +6 25480 9 10 208 74 25 233 Example 3 +4 25390 11 13 207 83 27 234 Example 4 +6 25210 10 9 213 42 19 232 Example 5 +8 25510 9 11 218 48 22 240 Example 6 +5 2290 10 9 201 77 30 231 Example 7 +5 14810 12 11 205 55 28 233 Example 8 +5 25220 9 10 211 52 23 234 Example 9 +5 36710 15 8 209 53 23 232 Example 10 +5 49090 9 12 208 85 26 234 Example 11 +8 25410 8 10 208 67 25 233 Example 12 +8 25280 20 11 201 95 28 229 Example 13 +4 25130 12 9 206 57 26 232 Example 14 +4 25310 13 10 209 52 25 234 Example 15 +3 25220 10 8 210 52 27 237 Example 16 +4 25290 9 11 212 47 25 237 Example 17 +6 25410 12 10 213 44 25 238 Example 18 +5 25000 11 29 205 72 29 230 Example 19 +5 25080 16 48 201 98 33 225 Example 1 / / / / 185 136 35 220 Example 2 +3 25090 9 10 196 113 30 226 Example 3 +5 1510 8 9 197 105 31 228 Example 4 +5 57990 9 11 199 113 33 232 Example 5 +8 25510 33 9 194 123 32 226 Example 20 +5 25100 13 12 226 43 22 248 Example 21 +8 24900 8 10 224 51 26 250 Example 6 / / / / 205 112 34 239 Example 7 +3 25300 10 12 208 105 31 239

[0193] The valence shown in Table 2 was the highest valence of the doping element in the “78% delithiated state” of the active material of the positive electrode. Table 3 Nr. Initial capacity of the button cell battery in grams (mAh / g) Initial capacity of a fully charged battery in grams (mAh / g) Capacity retention rate of a fully charged battery at 45 °C, 1 C / 1 C, 400 cycles (%) Ex. 1 208,1 197,4 94,03 Ex. 2 206,7 195,1 92,37 Ex. 3 206,2 196,2 92,09 Ex. 4 207,6 197,1 93,48 Ex. 5 207,0 196,3 92,24 Ex,6 202,1 193,3 85,20 Ex. 7 205,8 195,5 91,75 Ex. 8 207,2 196,7 93,31 Ex. 9 205,6 196,2 92,14 Ex. 10 204,2 194,0 90,22 Ex. 11 205,9 195,9 91,87 Ex. 12 201,2 192,6 85,73 Ex. 13 203,6 194,4 89,35 Ex. 14 205,5 196,8 91,28 Ex. 15 203,7 197,8 91,13 Ex. 16 206,5 197,6 92,62 Ex. 17 206,7 198,4 93,31 Ex. 18 204,9 195,7 91,94 Ex. 19 202,7 193,4 89,27 CE. 1 196,9 186,5 80,74 CE. 2 201,2 191,4 83,38 CE. 3 201,4 190,7 84,22 CE. 4 202,3 191,6 85,71 CE. 5 198,6 191,7 84,76 Ex. 20 184,6 180,4 95,53 Ex. 21 183,7 179,3 94,81 CE. 6 172,0 168,3 86,03 CE. 7 179,5 174,2 88,22

[0194] From the comparative results of Examples 1 to 5, 13 to 17, and Comparative Examples 1 to 2, Examples 20 to 21, and Comparative Examples 6 to 7, it is evident that the molar content of nickel in lithium nickel cobalt manganese oxide is 60% to 90% of the total molar content of nickel when the active material of the positive electrode consists of layered lithium nickel cobalt manganese oxide, the cobalt and manganese content was high, the transition metal layer included dopants, the relative deviation of the local mass concentration in the particles of the active material of the positive electrode was 20% or less, the DSC diagram of the active material of the positive electrode was in the “78% delithiated state”, the exothermic initial temperature of the exothermic main peak was 200 °C or more, and the integral area of ​​the exothermic main peak was 100 J / g was, or less, what led to this,that the lithium-ion secondary battery had both a higher capacity and a higher high-temperature cycle stability.

[0195] The results from Examples 6 to 10 and the comparative examples 3 to 4 show that with a low doping concentration, the dopant exhibited insufficient binding capacity for oxygen atoms in the positive electrode material, and the structural stability of the positive electrode structure remained poor. This resulted in lower initial and maximum exothermic temperatures during the heating process of the material in the DSC, and relatively large corresponding exothermic integral area and half-width. The unstable structure of the active material of the positive electrode leads to lower capacity and poor high-temperature cycle stability of the battery.If the doping amount was large, an excessively high dopant destroyed the original structure of the active material in the positive electrode, resulting in poor thermal stability of the active material. Simultaneously, the battery capacity and the cycle capacity retention rate at 45 °C were also reduced.

[0196] From the results of Examples 11, 12 and Comparative Example 5, it is evident that when the relative deviation of the local mass concentration of the dopant within the particles of the active material of the positive electrode was 20% or less, the dopant was very uniformly distributed within the active material of the positive electrode, and thus the improvement in the stability of the active material of the positive electrode was evident, the thermal stability of the material was good, and the capacity and high-temperature cycle stability of the corresponding battery were better. Conversely, when the relative deviation of the local mass concentration of the dopant exceeds 20%, the grid strain in the uniform doping area is high, which degrades the capacity and high-temperature cycle stability of the battery.

[0197] The results from Examples 1, 18, and 19 show that when ε is less than 30%, this indicates that the dopant can be smoothly incorporated into the particles of the positive electrode's active material and that the dopant can fully improve the structural stability of the positive electrode's active material, which in turn improves the thermal stability of the active material, thus enhancing battery capacity and high-temperature cycle stability. When ε is greater than 30%, more dopant elements are distributed in the gaps or on the surface of the positive electrode's active particles, the improvement effect of the dopant is less pronounced, and the thermal stability of the positive electrode material is poor.However, the doping elements distributed on the surface cause a certain coating and insulation of the electrolyte's side reaction, so that the cell's capacity and high-temperature cycle stability are slightly reduced at this point.

[0198] The descriptions mentioned above only show certain embodiments of the present application and are not intended to limit the scope of protection of the present application. Various equivalent modifications or substitutions that a person skilled in the art could readily devise within the technical framework disclosed in the present application fall within the scope of protection of the present application. The scope of protection of the present application is therefore determined by the scope of protection of the claims. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] CN 201910824127,8

[0001] Cited non-patent literature

[0000] POSITIVE ELECTRODENACTIVE MATERIAL, POSITIVE ELECTRODE PLATE AND LITHIUM-ION SECONDARY BATTERY”, published on September 2, 2019

[0001]

Claims

[1] A positive electrode plate, consisting of a positive electrode current collector and an active material layer of the positive electrode, which is arranged on the positive electrode current collector, wherein the active material layer of the positive electrode comprises an active material of the positive electrode, wherein the active material of the positive electrode comprises a lithium nickel cobalt manganese oxide, wherein the molar content of nickel in the lithium nickel cobalt manganese oxide is 60% to 90% of the total molar content of nickel, cobalt and manganese, and the lithium nickel cobalt manganese oxide has a layered crystal structure with the space group R3 m; a transition metal layer of lithium nickel cobalt manganese oxide containing a doping element; and in a differential scanning calorimetry spectrum of the active material of the positive electrode in a 78% delithiated state, an initial exothermic temperature of an exothermic main peak is 200 °C or more and an integral area of ​​the exothermic main peak is 100 J / g or less. [2] The positive electrode plate according to claim 1, wherein the half-width of the exothermic main peak is 30 °C or less; or the peak temperature of the exothermic main peak is 230 °C or higher. [3] The positive electrode plate according to claim 1 or 2, wherein the local mass concentration of the doping element in the particles of the active material of the positive electrode has a relative deviation of 15% or less. [4] The positive electrode plate according to any one of claims 1 to 3, wherein, when the active material of the positive electrode is in the 78% delithiated state, the doping element has a valence greater than +3 and optionally has a valence selected from one or more of the following: +4, +5, +6, +7 and +8. [5] The positive electrode plate according to any one of claims 1 to 4, wherein the doping element comprises one or more of the elements Al, Si, Ti, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Te and W; optionally the doping element comprises one or more of the elements Al, Si, Ge, Se, Zr, Ru, Sb, Te and W; and optionally the doping element comprises one or more of the elements Si, Ge, Se, Ru, Sb, Te and W. [6] The positive electrode plate according to any one of claims 1 to 5, wherein the active material of the positive electrode has a true density ρ true has a satisfactory value: 4.6 g / cm³ 3 ≤ ρ true≤ 4.9 g / cm³ 3 . [7] The positive electrode plate according to any one of claims 1 to 6, wherein the active material of the positive electrode has a true doping concentration ω that meets the following conditions: 2300 µg / cm² 3 ≤ ω ≤ 49500 µg / cm 3 ; optional 3000 µg / cm 3 ≤ ω ≤ 35000 µg / cm 3 ; and optionally 14810 µg / cm³ 3 ≤ ω ≤ 36710 µg / cm 3 . [8] The positive electrode plate according to any one of claims 1 to 7, wherein the mass concentration of the doping element in the active material of the positive electrode has a deviation ε < 50 %, optionally ε ≤ 30 %, and further optionally ε ≤ 20 %, based on an average mass concentration of the doping element in the particles of the active material of the positive electrode. [9] The positive electrode plate according to any one of claims 1 to 8, wherein the active material of the positive electrode also fulfills one or more of the following points (1) to (4): (1) the active material of the positive electrode has a volume-averaged particle size D v 50 from 5 µm to 20 µm, optionally from 8 µm to 15 µm and further optionally from 9 µm to 11 µm; (2) the active material of the positive electrode has a specific surface area of ​​0.2 m² 2 / g up to 1.5 m 2 / g and optionally from 0.3 m 2 / g to 1 m 2 / g exhibits; (3) The active material of the positive electrode has a bulk density of 2.3 g / cm³ 3 up to 2.8 g / cm³ 3 ; and (4) The active material of the positive electrode has a condensed density of 3.1 g / cm³ 3 - 3.8 g / cm³ 3 under a pressure of 5 tons (equivalent to 49 kN). [10] The positive electrode plate according to any one of claims 1 to 9, wherein the lithium nickel cobalt manganese oxide has the chemical formula Li 1+a [Ni x Co y Mn z M b ]O2 satisfies, where M is the doping element, M is selected from one or more of Al, Si, Ti, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Te and W, 0.7 ≤ x ≤ 0.9, 0 < y < 0.3, 0 < z < 0.3, 0 ≤ a < 0.2, 0 < b < 0.3, and x + y + z + b = 1; or Lithium nickel cobalt manganese oxide has the chemical formula Li 1+c [Ni r-d Co s M nt M' d ]O2 satisfies, where M' is the doping element, M' is selected from one or more of Al, Si, Ti, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Te and W, 0.7 ≤ r - d ≤ 0.9, 0 < s < 0.3, 0 < t < 0.3, 0 ≤ c < 0.2, 0 < d < 0.3, and r + s + t = 1. [11] A lithium-ion secondary battery comprising the positive electrode plate according to any one of claims 1 to 10. [12] The battery module comprising the lithium-ion secondary battery according to claim 11. [13] The battery assembly comprising the lithium-ion secondary battery according to claim 11 or the battery module according to claim 12. [14] A device comprising at least one lithium-ion secondary battery according to claim 11, a battery module according to claim 12 or a battery pack according to claim 13.

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