Nickel-rich multi-element positive electrode material as well as preparation method and application thereof

Abstract

The invention provides a nickel-rich multi-element positive electrode material and a preparation method and application thereof, the nickel-rich multi-element positive electrode material comprises a transition metal element, the transition metal element comprises a nickel element, and the molar content of the nickel element in the transition metal element is greater than or equal to 60%; by mass, the residual alkali content of the nickel-rich multi-element positive electrode material is less than or equal to 3%, and the residual alkali content is the sum of the content of lithium carbonate and the content of lithium carbonate converted from the content of lithium hydroxide. The residual alkali content of the nickel-rich multi-element positive electrode material can be reduced, and the battery performance can be improved.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and in particular to a nickel-rich multi-element positive electrode material and a preparation method and application thereof. Background Art

[0002] With the development of lithium-ion batteries, nickel-rich multi-element positive electrode materials have been widely used due to their advantages such as high energy density and high voltage. However, nickel-rich multi-element positive electrode materials generally have problems such as high residual alkali content, which affects battery performance, specifically leading to problems such as low battery capacity, high impedance, and easy gas production. Summary of the invention

[0003] The present invention provides a nickel-rich multinary positive electrode material and a preparation method and application thereof, which can reduce the residual alkali content of the nickel-rich multinary positive electrode material and improve battery performance. Specifically, it can take into account increasing battery capacity, reducing battery impedance, reducing battery gas production, etc., effectively overcoming the defects of the prior art.

[0004] In one aspect of the present invention, a nickel-rich multinary positive electrode material is provided, wherein the nickel-rich multinary positive electrode material includes a transition metal element, wherein the transition metal element includes a nickel element, and the molar content of the nickel element in the transition metal element is greater than or equal to 60%; the residual alkali content of the nickel-rich multinary positive electrode material is less than or equal to 3% by mass, and the residual alkali content is the sum of the content of lithium carbonate and the content of lithium carbonate converted from the content of lithium hydroxide.

[0005] According to one embodiment of the present invention, the nickel-rich multinary positive electrode material satisfies: the nickel-rich multinary positive electrode material is mixed with water in a mass ratio of (5±0.5):100, and the pH value of the resulting solution is 10-12.5.

[0006] According to one embodiment of the present invention, the specific surface area of ​​the nickel-rich multi-element positive electrode material is 0.2 m 3 / g~1m 3 / g; and / or, the particle size Dv50 of the nickel-rich multi-element positive electrode material is 6μm to 18μm.

[0007] According to one embodiment of the present invention, the nickel-rich multi-element positive electrode material includes a nickel-cobalt-lithium manganese oxide-based ternary material and / or a nickel-cobalt-aluminum oxide-based ternary material.

[0008] According to one embodiment of the present invention, the chemical formula of the nickel-rich multi-element positive electrode material is LiNi a Co b A (1-a-b) M c O 2, 0.6≤a≤1.0, 0<b≤0.4, 0≤c≤0.05, A includes Mn and / or Al, and M includes at least one of Co, Mn, Al, Zn, Mg, Ti, Zr, Sr, Ca, Sb, Nb, Mo, V, Y, La, Ce, W, B, and F.

[0009] Another aspect of the present invention provides a method for preparing the above-mentioned nickel-rich multi-element positive electrode material, comprising the following steps: mixing a nickel-rich precursor with a lithium source, performing a first heat treatment under an oxygen atmosphere to obtain an intermediate; performing a second heat treatment on the intermediate under an oxygen atmosphere to obtain the nickel-rich multi-element positive electrode material; wherein the temperature of the second heat treatment is greater than the temperature of the first heat treatment, the temperature of the first heat treatment is 250-600°C, and the temperature of the second heat treatment is 600-1000°C.

[0010] According to one embodiment of the present invention, the particle size Dv50 of the lithium source is 100 to 400 μm.

[0011] According to one embodiment of the present invention, during the first heat treatment, the oxygen ventilation flow rate is 150-300m 3 / h; and / or, the first heat treatment time is 2 to 8 hours; and / or, the first heat treatment is performed using a rotary kiln; and / or, during the second heat treatment, the oxygen ventilation flow rate is 150 to 300m 3 / h; and / or, the time of the second heat treatment is 5 to 15h; and / or, a roller kiln or a push plate kiln is used for the second heat treatment; and / or, the process of subjecting the intermediate to a second heat treatment in an oxygen atmosphere comprises: mixing the intermediate with an M source containing the M element, and then subjecting the intermediate to a second heat treatment in an oxygen atmosphere to obtain the nickel-rich multi-element positive electrode material.

[0012] Another aspect of the present invention provides a positive electrode sheet, comprising the above-mentioned nickel-rich multi-element positive electrode material.

[0013] According to one embodiment of the present invention, the positive electrode sheet includes a positive electrode collector, and a positive electrode active material layer present on the surface of the positive electrode collector, the positive electrode active material layer includes a positive electrode active material, a conductive agent and a binder, and the positive electrode active material includes the nickel-rich multi-element positive electrode material; wherein, based on the total mass of the positive electrode active material layer, the mass fraction of the positive electrode active material is 80% to 98%, the mass fraction of the conductive agent is 1.5% to 15%, and the mass fraction of the binder is 0.5% to 5%.

[0014] Another aspect of the present invention provides a battery, comprising the positive electrode sheet.

[0015] In the present invention, the nickel-rich multi-element positive electrode material has a high nickel content and a low residual alkali content, which can reduce the residual alkali content while achieving the high energy density of the nickel-rich multi-element positive electrode material, thereby improving battery performance. Specifically, it can take into account increasing battery capacity, reducing battery impedance, and reducing battery gas production.

[0016] In addition, the nickel-rich multi-element positive electrode material of the present invention has the advantages of simple preparation process, high preparation efficiency, and low cost, which is conducive to practical industrial application. DETAILED DESCRIPTION

[0017] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific implementation methods listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0018] With the development of lithium-ion batteries, nickel-rich multi-component positive electrode materials have been widely used due to their high energy density and high voltage. However, due to factors such as the production process of nickel-rich multi-component positive electrode materials, nickel-rich multi-component positive electrode materials generally have problems such as high residual alkali content, which affects battery performance, specifically leading to problems such as low battery capacity, high impedance, and easy gas production.

[0019] Specifically, multi-element positive electrode materials are usually prepared by mixing precursors and lithium salts and then sintering them. For example, when preparing ternary positive electrode materials, the precursors and lithium salts are usually mixed and then directly sintered in a roller kiln at high temperature. During the high-temperature sintering process, the lithium element usually does not enter the bulk phase of the multi-element positive electrode material according to the theoretical stoichiometric ratio, that is, it is difficult to sinter the multi-element positive electrode material with the theoretical stoichiometric ratio, resulting in a large amount of lithium remaining on the surface of the multi-element positive electrode material. These residual lithium (i.e., lithium that has not entered the bulk phase of the multi-element positive electrode material) are easily reacted with water (H 2 O), carbon dioxide (CO 2 ) and other reactions to form residual alkali (or residual lithium, mainly lithium hydroxide (LiOH) and lithium carbonate (Li 2 CO 3 )), remaining on the surface of the multi-electrode positive material, causing residual alkali to exist on the surface of the multi-electrode positive material.

[0020] Among them, the higher the nickel content of the multi-element positive electrode material, the greater its energy density, but the increase in nickel content usually makes the sintering conditions more stringent, and it is more difficult to make the lithium element enter the bulk phase of the multi-element positive electrode material during the sintering process, and it is more difficult to form a multi-element positive electrode material that meets the theoretical stoichiometric ratio, which not only affects the electrochemical properties of the multi-element positive electrode material, but also the lithium element and water (H2 O), carbon dioxide (CO 2 ) and other reactions to form residual alkali that remains on the surface of the multi-electrode positive material, so that residual alkali exists on the surface of the sintered multi-electrode positive material. After the multi-electrode positive material is applied to the battery, the electrochemical properties of the battery, such as gas production, capacity and impedance, are affected.

[0021] Therefore, it is difficult to balance the high nickel content and low residual alkali content of the existing multi-element positive electrode materials. The nickel-rich multi-element positive electrode materials with high nickel content (or high nickel multi-element positive electrode materials) generally have problems such as high residual alkali content. The residual alkali is an inert material in the battery. The presence of residual alkali on the surface of the positive electrode material will affect the electronic conductivity of the positive electrode material, increase the impedance of the positive electrode material, and affect the capacity of the positive electrode material. At the same time, LiOH and Li 2 CO 3 During the charge and discharge process of the battery, residual alkali is easily decomposed in a high oxygen state to produce CO, CO 2 and H 2 O and other byproducts, H 2 The generation of byproducts such as O will further cause the decomposition of electrolyte components and produce gases (such as hydrogen fluoride (HF), etc.), thereby increasing the gas production during the battery cycle and affecting the safety and electrochemical performance of the battery.

[0022] In view of this, an embodiment of the present invention provides a nickel-rich multi-component positive electrode material, which includes a transition metal element, the transition metal element includes a nickel element (Ni), and the molar content of the nickel element in the transition metal element is greater than or equal to 60% (that is, in the nickel-rich multi-component positive electrode material, the molar content of the nickel element accounts for more than 60% of the total molar content of the transition metal element); the residual alkali content of the nickel-rich multi-component positive electrode material is less than or equal to 3% by mass, and the residual alkali content is the sum of the content of lithium carbonate present on the surface of the nickel-rich multi-component positive electrode material and the content of lithium carbonate converted from the content of lithium hydroxide present on the surface of the nickel-rich multi-component positive electrode material.

[0023] The nickel-rich multinary positive electrode material of the embodiment of the present invention has a high nickel content, which can ensure its high energy density and other characteristics. At the same time, the residual alkali content of the nickel-rich multinary positive electrode material is as low as 3% or less, which can ensure its capacity, improve the battery capacity, and improve the electrochemical properties such as the electronic conductivity of the nickel-rich multinary positive electrode material, thereby reducing the battery impedance. At the same time, it can prevent the residual alkali from decomposing during the battery charge and discharge cycle to produce CO and CO 2 and H 2 O and other byproducts, as well as H 2 The production of by-products such as O further leads to the decomposition of the electrolyte, and the resulting production of gases such as HF, thereby reducing the gas production during the battery cycle, while improving the gas production performance of the battery, reducing the gas production of the battery, and improving the safety and electrochemical performance of the battery.

[0024] In general, the residual alkali in the nickel-rich multinary positive electrode material exists on the surface of the nickel-rich multinary positive electrode material. These residual alkalis are mainly lithium hydroxide and lithium carbonate. The residual alkali content of the nickel-rich multinary positive electrode material is basically equal to the sum of the content of lithium carbonate and the content of lithium carbonate converted from the content of lithium hydroxide. Among them, the content of lithium carbonate refers to the mass percentage of lithium carbonate in the nickel-rich multinary positive electrode material (that is, the ratio of the mass of lithium carbonate to the total mass of the nickel-rich multinary positive electrode material), and the content of lithium hydroxide refers to the mass percentage of lithium hydroxide in the nickel-rich multinary positive electrode material (that is, the ratio of the mass of lithium hydroxide to the total mass of the nickel-rich multinary positive electrode material).

[0025] In specific implementation, the residual alkali content of the nickel-rich multi-element positive electrode material can be calculated according to the following formula:

[0026]

[0027] Wherein, w is the residual alkali content of nickel-rich multi-element positive electrode material, d c is the content of lithium carbonate in the nickel-rich multi-element positive electrode material, d H is the content of lithium hydroxide in the nickel-rich multi-element positive electrode material, M c is the molecular weight of lithium carbonate (M c =73.89), M H is the molecular weight of lithium hydroxide (M H =23.94).

[0028] In the embodiment of the present invention, d can be measured by acid-base indicator titration method or automatic potentiometric titration method. c and d H Acid-base indicator titration (using acid-base indicator for titration) and automatic potentiometric titration are conventional operating methods, and conventional titrators in the art can be used for testing.

[0029] After further study, the nickel-rich multi-element positive electrode material can meet the following conditions: the nickel-rich multi-element positive electrode material is mixed with water in a mass ratio of (5±0.5):100, and the pH of the resulting solution is less than or equal to 12.5, preferably 10 to 12.5. In this way, it can further ensure that the residual alkali content of the nickel-rich multi-element positive electrode material is reduced, the electrochemical properties such as the capacity and conductivity of the nickel-rich multi-element positive electrode material are improved, and the battery capacity, the battery impedance and the gas production are improved. The reason for the analysis is that the pH of the resulting solution is a reflection of the hydroxide concentration in the solution. The larger the pH, the stronger the alkalinity of the nickel-rich multi-element positive electrode material, and the smaller the pH, the lower the residual alkali content of LiOH and the like of the nickel-rich multi-element positive electrode material. The pH of the above nickel-rich multi-element positive electrode material mixed with water in a mass ratio of (5±0.5):100 is ≤12.5, which further ensures that the nickel-rich multi-element positive electrode material has a lower residual alkali content, improves the electrochemical properties such as the capacity and conductivity of the nickel-rich multi-element positive electrode material, and improves the battery capacity, reduces the battery impedance and the gas production.

[0030] It is understandable that the pH of the resulting solution is the pH after the solution is stabilized. Specifically, after the nickel-rich multinary positive electrode material is mixed with water, the residual alkali in the nickel-rich multinary positive electrode material will dissolve in the water, increasing the pH of the resulting solution. After the pH of the solution is stabilized (i.e., as the placement time continues to increase, the pH of the solution basically no longer changes), it indicates that the residual alkali in the nickel-rich multinary positive electrode material is basically completely dissolved in the water, and the pH of the solution measured at this time is the pH after the solution is stabilized.

[0031] In a specific implementation, the nickel-rich multi-electrode material is mixed with water in a mass ratio of (5±0.5):100, and the mixture is allowed to stand for 25 to 35 minutes. The pH of the solution is then tested, and the measured pH is the pH of the solution after stabilization.

[0032] Specifically, the nickel-rich multi-element positive electrode material is a layered structure, that is, it is a nickel-rich layered oxide material.

[0033] Generally, the nickel-rich multi-element positive electrode material includes a plurality of transition metal elements. In addition to nickel, the transition metal elements may also include one or more of cobalt (Co), manganese (Mn), and aluminum (Al).

[0034] In addition, the metal elements in the nickel multi-element positive electrode material exist in the form of oxides.

[0035] Specifically, the nickel-rich multi-electrode material may include a ternary positive electrode material, and the ternary positive electrode material may include a nickel cobalt manganese oxide-based ternary material (NCM) and / or a nickel cobalt aluminum oxide-based ternary material (NCA). The ternary positive electrode material may be a ternary positive electrode material doped with a doping element (for example, including NCM doped with a doping element and / or NCA doped with a doping element), or a ternary positive electrode material not doped with a doping element (for example, including NCM not doped with a doping element and / or NCA not doped with a doping element).

[0036] Specifically, when the above-mentioned nickel-rich multi-element material (ternary positive electrode material) is doped with doping elements, that is, the above-mentioned nickel-rich multi-element positive electrode material includes a matrix material and the doping elements doped in the matrix material; the matrix material may include lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide; the doping elements may include one or more of Co, Mn, Al, Zn, Mg, Ti, Zr, Sr, Ca, Sb, Nb, Mo, V, Y, La, Ce, W, B, and F.

[0037] In some embodiments, the chemical formula (average composition) of the nickel-rich multi-element positive electrode material may be LiNi a Co b A (1-a-b) M c O 2 , 0.6≤a≤1.0, 0<b≤0.4, 0≤c≤0.05, A includes Mn and / or Al, M is the above-mentioned doping element, that is, M includes one or more of Co, Mn, Al, Zn, Mg, Ti, Zr, Sr, Ca, Sb, Nb, Mo, V, Y, La, Ce, W, B, and F.

[0038] Exemplarily, a is, for example, 0.6, 0.7, 0.8, 0.9, 1 or a range consisting of any two of them, b is, for example, 0.01, 0.03, 0.05, 0.07, 0.1, 0.12, 0.15, 0.18, 0.2, 0.25, 0.3, 0.35, 0.4 or a range consisting of any two of them, and c is, for example, 0, 0.01, 0.02, 0.03, 0.04, 0.05 or a range consisting of any two of them.

[0039] Specifically, nickel-rich multi-element cathode materials (LiNi a Co b A (1-a-b) M c O 2), Ni, Co, and A are the main transition metal elements that form the nickel-rich multinary positive electrode material. When the nickel-rich multinary positive electrode material contains a doping element M, M is a doping element, and the content of M as a doping element is small (c≤0.05, which is much less than the content of Ni, Co, and A as the main transition metal elements). For the nickel-rich multinary positive electrode material, the molar content of the nickel element in its transition metal elements is greater than or equal to 60%, which specifically refers to the ratio of the amount of nickel element in the main transition metal elements that form the nickel-rich multinary positive electrode material to the total molar amount of the main transition metal elements (i.e., a≥0.6 in the above chemical formula).

[0040] In some embodiments, the nickel-rich multi-element cathode material is a nickel-cobalt-manganese-based ternary material (NCM), and its chemical formula may be LiNi a Co b Mn (1-a-b) O 2 The value ranges of a, b, and c are the same as above and will not be repeated here.

[0041] In other embodiments, the nickel-rich multi-element positive electrode material is a nickel-cobalt-aluminum-based ternary material (NCA), and its chemical formula may be LiNi a Co b Al (1-a-b) O 2 The value ranges of a, b, and c are the same as above and will not be repeated here.

[0042] In the embodiment of the present invention, the nickel-rich multi-element positive electrode material with the above-mentioned average composition has a high nickel content, and has the advantages of high energy density and high voltage. At the same time, the residual alkali content on its surface is less than or equal to 3%, which is more conducive to the capacity of the nickel-rich positive electrode chemical material, and can reduce its impedance and reduce its gas production during the battery charge and discharge cycle, thereby improving the battery capacity and reducing the battery's internal resistance and gas production.

[0043] Generally, the nickel-rich multi-element positive electrode material is in a granular form, which includes polycrystalline particles (ie, secondary particles formed by aggregation of multiple primary particles).

[0044] In some embodiments, the specific surface area (BET) of the nickel-rich multi-element positive electrode material may be 0.2 m 3 / g~1m 3 / g, for example 0.2m 3 / g, 0.3m 3 / g, 0.4m 3 / g, 0.5m 3 / g, 0.6m 3 / g, 0.7m 3 / g, 0.8m 3 / g, 0.9m 3 / g, 1m 3 / g or any two of them, so that the nickel-rich multi-element positive electrode material has a value of not less than 0.2m 3 / g specific surface area, which is more conducive to the capacity of nickel-rich positive electrode multi-materials, increases the lithium ion transmission path, and reduces the internal resistance of the battery. At the same time, the nickel-rich multi-material positive electrode material has a surface area of ​​no more than 1m 3 / g specific surface area can keep the contact area between nickel-rich positive electrode multi-element materials and electrolyte small, and reduce gas generation during battery cycle and storage. Therefore, by controlling the specific surface area (BET) of nickel-rich multi-element positive electrode materials within the above range, it is possible to further improve battery capacity, reduce battery impedance and gas generation.

[0045] In the embodiment of the present invention, the specific surface area of ​​the nickel-rich multi-element positive electrode material can be measured by conventional methods in the art such as nitrogen adsorption-desorption method.

[0046] In some embodiments, the particle size Dv50 of the nickel-rich multi-electrode material can be 6μm to 18μm, for example, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm or a range composed of any two of them, which is beneficial to further balance the improvement of battery capacity, reduction of battery impedance and gas production.

[0047] An embodiment of the present invention also provides a method for preparing the above-mentioned nickel-rich multi-element positive electrode material, comprising the following steps: mixing a nickel-rich precursor with a lithium source, performing a first heat treatment under an oxygen atmosphere to obtain an intermediate; performing a second heat treatment on the intermediate under an oxygen atmosphere to obtain a nickel-rich multi-element positive electrode material; wherein the temperature of the second heat treatment is greater than the temperature of the first heat treatment, the temperature of the first heat treatment is 250-600°C, for example, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C or a range consisting of any two thereof, and the temperature of the second heat treatment is 600-1000°C, for example, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C or a range consisting of any two thereof.

[0048] In an embodiment of the present invention, during the preparation process of the above-mentioned nickel-rich multi-element positive electrode material, water in the nickel-rich precursor and the lithium source is removed by a first heat treatment (low-temperature heat treatment), and lithium enters into the bulk phase of the nickel-rich precursor. Subsequently, a second heat treatment (high-temperature heat treatment) is performed to form a layered structure in the material phase to obtain a nickel-rich layered oxide material (i.e., a nickel-rich multi-element positive electrode material). The obtained nickel-rich multi-element positive electrode material can reduce the residual alkali content (residual alkali content is less than or equal to 3%) of the nickel-rich multi-element positive electrode material while maintaining a high nickel content (the molar content of the nickel element is greater than or equal to 60%).

[0049] After research and analysis, the inventors believe that, on the one hand, the first heat treatment stage can promote the melting and diffusion of lithium salts, ensure the uniformity of the reaction between the nickel-rich precursor and the lithium salt, and make the lithium element more evenly dispersed in the bulk phase of the nickel-rich precursor, thereby reducing residual lithium and further reducing the residual alkali on the surface of the nickel-rich multi-electrode positive material (if the first heat treatment is not performed, but the nickel-rich precursor and the lithium salt are mixed and then directly subjected to the second heat treatment, the lithium salt cannot be fully diffused, and the lithium element cannot be fully and evenly dispersed in the bulk phase of the high-nickel precursor. There are more lithium elements on the surface of the material, and these lithium elements react with water, carbon dioxide, etc. to form residual alkali, which remains on the surface of the obtained nickel-rich multi-electrode positive material).

[0050] On the other hand, by removing moisture from the nickel-rich precursor and the lithium source through the first heat treatment, the moisture content in the reaction atmosphere of the second heat treatment process can be reduced, the amount of residual alkali formed by the reaction of residual lithium and moisture can be reduced, and the residual alkali content of the obtained nickel-rich multi-electrode material can be further reduced.

[0051] In addition, in the related technologies, the preparation process of nickel-rich multi-element cathode materials generally has defects such as low preparation efficiency (low production capacity) and high production cost, which hinders its application process. For example, when preparing ternary cathode materials, the precursor and lithium salt are usually mixed and then directly sintered at high temperature using a roller kiln. In addition to the problem of high residual alkali content in the prepared ternary cathode materials, there are also problems such as low density after the precursor and lithium source are mixed, resulting in low kiln production capacity.

[0052] In the embodiment of the present invention, after the nickel-rich precursor and the lithium source are mixed, the water in the nickel-rich precursor and the lithium source is first removed through a first heat treatment, which can increase the total amount of material during the second heat treatment (for example, when a roller kiln is used for the second heat treatment, the amount of a single boat (that is, the mass of the intermediate loaded in each sagger of the roller kiln)) can be increased, and the time (or cycle) of the second heat treatment can be shortened, and there is basically no quality loss during the second heat treatment, thereby increasing production capacity. It also has the advantages of low heat treatment temperature (sintering temperature), low energy consumption, low equipment loss, and reduced equipment maintenance costs.

[0053] Therefore, the embodiment of the present invention can produce nickel-rich multi-element positive electrode materials and reduce their residual alkali content. At the same time, it also has the advantages of low heat treatment (sintering) temperature, low energy consumption, low cost, and high efficiency, which is of great significance for practical industrial applications.

[0054] In addition, in the related art, the preparation of layered oxide multi-element positive electrode materials usually uses fine-particle lithium sources (such as lithium hydroxide) with smaller particle sizes to ensure the uniformity of the reaction between the precursor and the lithium source, but the cost of the fine-particle lithium source is high, which will increase the cost of the multi-element positive electrode material. In the embodiment of the present invention, the first heat treatment is used to promote the melting and diffusion of the lithium source to ensure the uniformity of the reaction between the precursor and the lithium salt. Therefore, a coarse-particle lithium source with a larger particle size can be used. That is, in the embodiment of the present invention, when a coarse-particle lithium source with a larger particle size is used, the uniformity of the reaction between the precursor and the lithium salt can still be ensured, thereby further reducing the cost.

[0055] Specifically, in an embodiment of the present invention, the particle size Dv50 of the lithium source can be 100 to 400 μm, for example, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm or any two thereof. In this way, while ensuring the uniformity of the reaction between the precursor and the lithium salt and reducing the residual alkali content of the obtained nickel-rich multi-electrode material, the cost can be further reduced.

[0056] In the embodiment of the present invention, the particle size Dv50 of the material (such as the particle size Dv50 of the nickel-rich multinary positive electrode material and the particle size Dv50 of the lithium source) is the median particle size of its volume particle size, that is, in the volume-based particle size distribution, the particle size of the material starting from the small particle size side and reaching 50% of the volume accumulation (that is, in the volume-based particle size distribution of the material, 50% of the particle size is smaller than this value (Dv50), and 50% of the particle size is larger than this value (Dv50), so Dv50 is also called "median particle size"). The particle size Dv50 of the material can be measured by a laser particle size analyzer.

[0057] The embodiments of the present invention may use conventional lithium source materials in the art, for example, the lithium source includes lithium salts such as lithium hydroxide and / or lithium carbonate.

[0058] In an embodiment of the present invention, in the above-mentioned preparation process, the intermediate can be directly subjected to a second heat treatment to obtain a nickel-rich multinary positive electrode material; or, the intermediate and an M source containing the M element can be mixed and then subjected to a second heat treatment to introduce the doping element M into the obtained nickel-rich multinary positive electrode material, that is, the process of subjecting the intermediate to a second heat treatment under an oxygen atmosphere can include: mixing the intermediate with the M source, and then subjecting the intermediate to a second heat treatment under an oxygen atmosphere to obtain a nickel-rich multinary positive electrode material.

[0059] Specifically, the M source may include a compound containing the M element, for example, one or more of an oxide containing M, a salt containing M, and a hydroxide containing M. For example, the M source may include Al(OH) 2 .

[0060] In specific implementation, the amount of materials such as lithium source and nickel-rich precursor can be adjusted to obtain a nickel-rich multi-element positive electrode material with a preset chemical formula. For example, the content of the doping element M in the obtained nickel-rich multi-element positive electrode material can be controlled by adjusting the amount of M source.

[0061] Specifically, the nickel-rich precursor may include a ternary positive electrode material precursor, specifically a nickel cobalt manganese oxide-based ternary material precursor and / or a nickel cobalt aluminum oxide-based ternary material precursor. These precursors are hydroxides of metal elements. Through the above-mentioned first heat treatment and second heat treatment processes, oxides of metal elements are formed, thereby obtaining a nickel-rich multi-element positive electrode material.

[0062] In some embodiments, the chemical formula of the nickel-rich precursor may be Ni a Co b A (1-a-b) M c (OH) 2 , 0.6≤a≤1.0, 0<b≤0.4, 0≤c≤0.05, as mentioned above, A includes Mn and / or Al, M is the above-mentioned doping element, that is, M includes one or more of Co, Mn, Al, Zn, Mg, Ti, Zr, Sr, Ca, Sb, Nb, Mo, V, Y, La, Ce, W, B, and F, a is, for example, 0.6, 0.7, 0.8, 0.9, 1 or a range consisting of any two of them, b is, for example, 0.01, 0.03, 0.05, 0.07, 0.1, 0.12, 0.15, 0.18, 0.2, 0.25, 0.3, 0.35, 0.4 or a range consisting of any two of them, and c is, for example, 0, 0.01, 0.02, 0.03, 0.04, 0.05 or a range consisting of any two of them.

[0063] Specifically, during the first heat treatment, oxygen may be introduced into the first sintering device for the first heat treatment so that the first heat treatment is performed under an oxygen atmosphere, wherein the oxygen flow rate may be 150 to 300 m / s. 3 / h, for example 150m 3 / h、180m 3 / h、200m 3 / h、230m 3 / h、250m 3 / h、280m 3 / h、300m 3 / h or a range consisting of any two thereof.

[0064] Specifically, the first sintering equipment may include a rotary kiln, that is, the first heat treatment may be performed using a rotary kiln. Compared with a roller kiln, a rotary kiln has the advantages of low equipment cost, low maintenance cost, and low energy consumption, which can further reduce costs.

[0065] Specifically, the time of the first heat treatment can be 2 to 8 hours (i.e., during the first heat treatment, the temperature conditions of the first heat treatment are kept warm for 2 to 8 hours), for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours or a range composed of any two of them, which is more conducive to removing moisture from the nickel-rich precursor and the lithium source, and is more suitable for the subsequent second heat treatment process, thereby reducing the residual alkali content of the obtained nickel-rich multi-electrode positive material and increasing the production capacity of the nickel-rich multi-electrode positive material.

[0066] Specifically, during the second heat treatment, oxygen may be introduced into the second sintering device for the second heat treatment so that the second heat treatment is performed under an oxygen atmosphere. The oxygen flow rate may be 150 to 300 m / s. 3 / h, for example 150m 3 / h、180m 3 / h、200m 3 / h、230m 3 / h、250m 3 / h、280m 3 / h、300m 3 / h or a range consisting of any two thereof.

[0067] In addition, a roller kiln or a push plate kiln can be used for the second heat treatment, which is conducive to obtaining the above-mentioned nickel-rich multi-element positive electrode material with low residual alkali content, while increasing production capacity and reducing costs.

[0068] In the embodiment of the present invention, conventional rotary kilns, roller kilns and pusher kilns in the art can be used. For example, the roller kiln used can be a fully automatic four-row double-layer atmosphere roller kiln (that is, its specifications are double-layer, four-row, forming a total of 8 saggers, each sagger is used to load the material to be sintered). Specifically, a four-row double-layer roller kiln with a length of 50m can be used.

[0069] In addition, the time of the second heat treatment can be 5 to 15 hours, for example, 5 hours, 7 hours, 9 hours, 10 hours, 12 hours, 14 hours, 15 hours or a range composed of any two of them, which is beneficial to further balance the improvement of the production capacity of the nickel-rich multi-electrode material and the reduction of the residual alkali content of the nickel-rich multi-electrode material, and improve the electrochemical properties of the nickel-rich multi-electrode material.

[0070] In a specific implementation, after the second heat treatment is completed, the second heat treatment product can be crushed and sieved to obtain a nickel-rich multi-element positive electrode material with characteristics such as a preset particle size.

[0071] The embodiment of the present invention further provides a positive electrode sheet, which includes the above-mentioned nickel-rich multinary positive electrode material and has the advantages corresponding to the above-mentioned nickel-rich multinary positive electrode material, which will not be described in detail.

[0072] Specifically, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer present on the surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, a conductive agent and a binder. The positive electrode active material includes a nickel-rich multi-element positive electrode material.

[0073] Among them, based on the total mass of the positive electrode active material layer, the mass fraction of the positive electrode active material is 80% to 98%, for example, 80%, 83%, 85%, 88%, 90%, 93%, 95%, 98% or a range consisting of any two of them, the mass fraction of the conductive agent is 1.5% to 15%, for example, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% or a range consisting of any two of them, and the mass fraction of the binder is 0.5% to 5%, for example, 0.5%, 1%, 2%, 3%, 4%, 5% or a range consisting of any two of them.

[0074] Specifically, the positive electrode active material layer may be disposed on one surface of the positive electrode current collector, or on both the front and back surfaces of the positive electrode current collector. The positive electrode current collector may include a conventional positive electrode current collector in the art such as aluminum foil.

[0075] An embodiment of the present invention further provides a battery, which includes the above-mentioned positive electrode sheet and has the advantages corresponding to the above-mentioned nickel-rich multi-element positive electrode material, which will not be described in detail.

[0076] Specifically, the battery also includes a negative electrode sheet and a separator located between the positive electrode sheet and the negative electrode sheet, and the separator is used to separate the positive electrode sheet and the negative electrode sheet to prevent the positive electrode sheet and the negative electrode sheet from contacting and short-circuiting.

[0077] The embodiments of the present invention may adopt conventional diaphragms in the art. For example, the diaphragm may include one or more of a polypropylene diaphragm (PP), a polyethylene diaphragm (PE), a polypropylene / polyethylene double-layer composite film (PP / PE), a polyimide electrospinning diaphragm (PI), a polypropylene / polyethylene / polypropylene three-layer composite film (PP / PE / PP), a cellulose non-woven fabric diaphragm, and a diaphragm with a ceramic coating.

[0078] The embodiments of the present invention may adopt conventional negative electrode sheets in the art. For example, the negative electrode sheet may include a lithium metal sheet (lithium sheet), or the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. Specifically, the negative electrode active material layer may be disposed on both the positive and negative surfaces of the negative electrode current collector, respectively. The negative electrode active material layer includes a negative electrode active material, a binder, a conductive agent and a thickener. The negative electrode active material may include one or more of graphite, mesophase carbon microbeads, soft carbon, hard carbon, silicon material, silicon-oxygen material, silicon-carbon material, lithium titanate, etc. The negative electrode current collector may be a conventional negative electrode current collector in the art, for example, including copper foil, etc.

[0079] In some embodiments, based on the total mass of the negative electrode active material layer, the mass fraction of the negative electrode active material may be 90-96%, the mass fraction of the conductive agent may be 1-3%, the mass fraction of the binder may be 2-4%, and the mass fraction of the thickener may be 2-4%.

[0080] In an embodiment of the present invention, the conductive agent in the positive electrode sheet and the negative electrode sheet may be a conventional conductive material in the art, for example, one or more of conductive carbon black (SP), acetylene black, carbon nanotubes, conductive graphite (KS-6), and graphene, and the binder may be a conventional binding material in the art, for example, one or more of polyvinylidene fluoride (PVDF), a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylic acid salt, sodium carboxymethyl cellulose (CMC), polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber (SBR).

[0081] Generally, a battery includes a cell, and the cell includes a positive electrode sheet, a separator and a negative electrode sheet. The cell can be a stacked cell, that is, the positive electrode sheet, the separator and the negative electrode sheet are stacked in sequence, or the cell can be a wound cell, that is, the positive electrode sheet, the separator and the negative electrode sheet are stacked and then wound to form a wound structure.

[0082] In addition, the battery also includes an electrolyte. The embodiment of the present invention may use a conventional electrolyte in the art. For example, the electrolyte is a non-aqueous electrolyte, which may specifically include an organic solvent and a lithium salt. The organic solvent may include ethylene carbonate (EC), propylene carbonate, butylene carbonate, fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), diethyl carbonate (DEC), difluoroethylene carbonate (DFEC), dipropyl carbonate, ethyl methyl carbonate (EMC), ethyl acetate, ethyl propionate, propyl acetate, propyl propionate, sulfolane, γ-butyrolactone, etc. The lithium salt may include lithium hexafluorophosphate (LiPF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).

[0083] In the embodiment of the present invention, the positive electrode sheet and the negative electrode sheet can be prepared by conventional methods in the art, such as by a coating method. Taking the positive electrode sheet as an example, materials such as a positive electrode active material, a conductive agent and a binder can be placed in a solvent to prepare a positive electrode slurry. The solvent used includes, for example, N-methylpyrrolidone (NMP). The positive electrode slurry is then coated on the surface of the positive electrode collector. After drying, rolling and other processes, a positive electrode active material layer is formed on the surface of the collector to prepare a positive electrode sheet.

[0084] In the embodiment of the present invention, the battery further comprises a shell for encapsulating the battery core, and the shell may comprise a soft packaging material (ie, the battery is a soft packaging battery), and may specifically comprise an aluminum-plastic film.

[0085] In the embodiments of the present invention, the battery can be manufactured by conventional methods in the art. For example, the positive electrode sheet, the separator, and the negative electrode sheet can be stacked in sequence and then wound into a wound battery cell. The battery can then be manufactured after processes such as packaging, liquid injection, formation, and capacity separation. These steps / processes are all conventional operations in the art, and the present invention does not impose any particular limitation on this and will not be described in detail.

[0086] The battery of the embodiment of the present invention is a lithium-ion battery, which can be applied to various fields such as electric vehicles, power tools, and smart grids.

[0087] The present invention is further described below through specific examples. In the following examples and comparative examples, unless otherwise specified, the roller kiln used is a four-row double-layer roller kiln with a length of 50 m, the roller kiln has 8 saggers, and the boat loading refers to the mass of the intermediate (material to be sintered) loaded in one sagger; the particle size Dv50 of the lithium source used is about 150 μm.

[0088] Example 1: Ni 0.9 Co 0.05 Mn 0.05 (OH) 2 (nickel-rich precursor) and lithium hydroxide (lithium source) were mixed and placed in a rotary kiln under an oxygen atmosphere (oxygen ventilation flow rate of 200m 3 / h), and kept at 550℃ for 6h to obtain an intermediate; the intermediate was placed in a roller kiln (loading amount was 10kg), and in an oxygen atmosphere (oxygen ventilation flow rate was 200m 3 / h), kept at 770℃ for 8h, and then crushed and sieved the obtained second heat treatment product to obtain a nickel-rich multi-element positive electrode material with a particle size Dv50 of 10μm (its chemical formula is shown in Table 1).

[0089] Example 2: Ni 0.95 Co 0.03 Mn 0.02 (OH) 2 (nickel-rich precursor) and lithium hydroxide (lithium source) were mixed and placed in a rotary kiln under an oxygen atmosphere (oxygen ventilation flow rate of 200m 3 / h), and kept at 500℃ for 6h to obtain an intermediate; the intermediate was placed in a roller kiln (loading amount was 8kg), and in an oxygen atmosphere (oxygen ventilation flow rate was 200m 3 / h), kept at 740℃ for 8h, and then crushed and sieved the obtained second heat treatment product to obtain a nickel-rich multi-element positive electrode material with a particle size Dv50 of 13.5μm (its chemical formula is shown in Table 1).

[0090] Example 3: Ni 0.83 Co 0.12 Mn 0.05 (OH) 2 (nickel-rich precursor) and lithium hydroxide (lithium source) were mixed and placed in a rotary kiln under an oxygen atmosphere (oxygen ventilation flow rate of 200m 3 / h), and kept at 600℃ for 4h to obtain an intermediate; the intermediate was placed in a roller kiln (loading amount was 10kg), and in an oxygen atmosphere (oxygen ventilation flow rate was 180m 3 / h), kept at 800℃ for 10h, and then the obtained second heat treatment product was crushed and sieved to obtain a nickel-rich multi-element positive electrode material with a particle size Dv50 of 9.5μm (its chemical formula is shown in Table 1)

[0091] Example 4: Ni 0.9 Co 0.05 Mn 0.05 (OH) 2 (nickel-rich precursor) and lithium hydroxide (lithium source) were mixed and placed in a rotary kiln under an oxygen atmosphere (oxygen ventilation flow rate of 200m 3 / h), and kept at 550℃ for 6h to obtain an intermediate; the intermediate was placed in a roller kiln (loading amount was 4.5kg), and in an oxygen atmosphere (oxygen ventilation flow rate was 220m 3 / h), kept at 765℃ for 8h, and then crushed and sieved the obtained second heat treatment product to obtain a nickel-rich multi-element positive electrode material with a particle size Dv50 of 10μm (its chemical formula is shown in Table 1).

[0092] The difference between Example 5 and Example 1 is that the nickel-rich multi-element positive electrode material prepared in Example 5 contains the doping element Al. The preparation process of the nickel-rich multi-element positive electrode material in Example 5 is as follows: Ni 0.9 Co 0.05 Mn 0.05 (OH) 2 (nickel-rich precursor), lithium hydroxide (lithium source) and Al(OH) 2 (M source) and placed in a rotary kiln under an oxygen atmosphere (oxygen ventilation flow rate of 200m 3 / h), and kept at 550℃ for 6h to obtain an intermediate; the intermediate was placed in a roller kiln (loading amount was 10kg), and in an oxygen atmosphere (oxygen ventilation flow rate was 200m 3 / h), kept at 770℃ for 8h, and then crushed and sieved the obtained second heat treatment product to obtain a nickel-rich multi-element positive electrode material with a particle size Dv50 of 10μm (its chemical formula is shown in Table 1).

[0093] Comparative Example 1: Ni 0.9 Co 0.05 Mn0.05 (OH) 2 (nickel-rich precursor) and lithium hydroxide (lithium source) were mixed and placed in a roller kiln (boat loading of 4.5 kg) under an oxygen atmosphere (oxygen ventilation flow rate of 200m 3 / h), kept at 770℃ for 10h, and then crushed and sieved the obtained product to obtain a nickel-rich multi-element positive electrode material with a particle size Dv50 of 10μm (its chemical formula is shown in Table 1).

[0094] The specific surface area (BET), production capacity, residual alkali content w of the nickel-rich multi-element positive electrode material in each embodiment and comparative example were measured respectively, and the pH of the solution obtained after dissolving 5g of the nickel-rich multi-element positive electrode material in 100g of water and standing for 30min is shown in Table 1.

[0095] Among them, production capacity refers to the production capacity of the roller kiln, and the unit is tons / month, that is, production capacity refers to the average mass of nickel-rich multi-electrode positive electrode materials produced in one month.

[0096] in, w is the residual alkali content of nickel-rich multi-element positive electrode materials, d c is the content of lithium carbonate in the nickel-rich multi-element positive electrode material, d H is the content of lithium hydroxide in the nickel-rich multi-element positive electrode material, M c =73.89,M H =23.94.

[0097] Among them, the pH of the solution obtained after 5g of nickel-rich multi-electrode material was dissolved in 100g of water and allowed to stand for 30 minutes was tested according to the following process: 5g of nickel-rich multi-electrode material was dissolved in 100g of water, allowed to stand for 30 minutes (after which the pH of the solution basically did not change), and the pH of the solution was tested. The results are shown in Table 1.

[0098] In addition, the nickel-rich multi-element positive electrode materials prepared in each embodiment and comparative example were used to prepare batteries according to the following process, and the battery performance was tested:

[0099] 1. Preparation of positive electrode

[0100] The nickel-rich multi-element positive electrode material, SP, KS-6, and PVDF were mixed in a mass ratio of 95:2:1:2, and NMP was added thereto to prepare a positive electrode slurry;

[0101] The positive electrode slurry is coated on the front and back surfaces of the aluminum foil, and after drying and rolling, a positive electrode active material layer is formed on the front and back surfaces of the aluminum foil to obtain a positive electrode sheet.

[0102] 2. Preparation of negative electrode sheet

[0103] Graphite, SP, SBR and CMC were mixed in a mass ratio of 95:1:2:2, and NMP was added thereto to prepare a negative electrode slurry;

[0104] The positive electrode slurry is coated on the front and back surfaces of the copper foil, and after drying and rolling, a negative electrode active material layer is formed on the front and back surfaces of the copper foil to prepare a negative electrode sheet.

[0105] 3. Preparation of batteries

[0106] The positive electrode sheet, the separator and the negative electrode sheet are stacked in sequence, wound into a wound cell, and packaged with an aluminum-plastic film to assemble a lithium-ion battery; the electrolyte used is an organic solvent and LiPF 6 The organic solvent is a mixed solvent of EC and DMC in a mass ratio of 1:1. The LiPF 6 The concentration is 1 mol / L.

[0107] 4. Battery performance test

[0108] (1) Testing battery capacity: The battery was charged and discharged at a rate of 0.2C with a cycle voltage of 2.8 to 4.25V, and the discharge capacity at 0.2C (i.e., the battery capacity in Table 1) was recorded.

[0109] (2) Test battery impedance: The battery was subjected to a pulse test at 50% SOC and a discharge rate of 4C for 10 s. The voltage change during the 10 s discharge period (ΔU) (the voltage at the beginning of the test minus the voltage at the end of the test) was recorded. Battery impedance = ΔU / 4C. The results are shown in Table 1.

[0110] (3) Test the gas production performance of the battery: When the battery is fully charged at 4.25V, use the drainage method to measure the battery volume V before storage. 前 Then the battery was stored at 70℃ for 7 days. After the storage, the volume V of the battery after storage was measured by the drainage method. 后 , battery gas production rate = (V 后 -V 前 ) / V 前 , the results are shown in Table 1.

[0111] Table 1

[0112]

[0113] It can be seen from Table 1 that, relative to Comparative Example 1, in Examples 1 to 5, while maintaining the prepared nickel-rich multi-component positive electrode material with a high nickel content, the residual alkali content of the nickel-rich multi-component positive electrode material can be reduced, thereby increasing the battery capacity and reducing the battery impedance and gas production, thereby improving the electrochemical performance of the battery, and at the same time significantly improving the production capacity of the nickel-rich multi-component positive electrode material, while maintaining a relatively low sintering temperature and other conditions.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A nickel-rich multi-element positive electrode material, characterized in that: The nickel-rich multi-element positive electrode material includes a transition metal element, the transition metal element includes a nickel element, and the molar content of the nickel element in the transition metal element is greater than or equal to 60%; The residual alkali content of the nickel-rich multi-element positive electrode material is less than or equal to 3% by mass, and the residual alkali content is the sum of the content of lithium carbonate and the content of lithium carbonate converted from the content of lithium hydroxide.

2. The nickel-rich multi-element positive electrode material according to claim 1, characterized in that: The nickel-rich multinary positive electrode material satisfies the following conditions: the nickel-rich multinary positive electrode material is mixed with water in a mass ratio of (5±0.5):100, and the pH value of the resulting solution is 10-12.

5.

3. The nickel-rich multi-element positive electrode material according to claim 1, characterized in that: The specific surface area of ​​the nickel-rich multi-element positive electrode material is 0.2 m 3 / g~1m 3 / g; And / or, the particle size Dv50 of the nickel-rich multi-element positive electrode material is 6 μm to 18 μm.

4. The nickel-rich multi-element positive electrode material according to claim 1, characterized in that: The nickel-rich multi-element positive electrode material includes a nickel-cobalt-lithium manganese oxide-based ternary material and / or a nickel-cobalt-aluminum oxide-based ternary material.

5. The nickel-rich multi-element positive electrode material according to any one of claims 1 to 4, characterized in that: The chemical formula of the nickel-rich multi-element positive electrode material is LiNi a Co b A (1-a-b) M c O2, 0.6≤a≤1.0, 0<b≤0.4, 0≤c≤0.05, A includes Mn and / or Al, and M includes at least one of Co, Mn, Al, Zn, Mg, Ti, Zr, Sr, Ca, Sb, Nb, Mo, V, Y, La, Ce, W, B, and F.

6. A method for preparing the nickel-rich multinary positive electrode material according to any one of claims 1 to 5, characterized in that: The following steps are involved: The nickel-rich precursor is mixed with a lithium source and subjected to a first heat treatment in an oxygen atmosphere to obtain an intermediate; The intermediate is subjected to a second heat treatment in an oxygen atmosphere to obtain the nickel-rich multi-element positive electrode material; The temperature of the second heat treatment is greater than that of the first heat treatment, the temperature of the first heat treatment is 250-600°C, and the temperature of the second heat treatment is 600-1000°C.

7. The preparation method according to claim 6, characterized in that: The particle size Dv50 of the lithium source is 100 to 400 μm.

8. The preparation method according to claim 6 or 7, characterized in that: During the first heat treatment, the oxygen ventilation flow rate is 150-300m 3 / h; And / or, the first heat treatment time is 2 to 8 hours; and / or, using a rotary kiln to carry out the first heat treatment; And / or, during the second heat treatment, the oxygen ventilation flow rate is 150-300m 3 / h; And / or, the second heat treatment time is 5 to 15 hours; and / or, using a roller kiln or a pusher kiln for the second heat treatment; And / or, the process of subjecting the intermediate to a second heat treatment in an oxygen atmosphere includes: mixing the intermediate with an M source containing an M element, and then subjecting the intermediate to a second heat treatment in an oxygen atmosphere to obtain the nickel-rich multi-element positive electrode material.

9. A positive electrode sheet, characterized in that: It comprises the nickel-rich multi-element positive electrode material as described in any one of claims 1 to 5.

10. The positive electrode sheet according to claim 9, characterized in that: The positive electrode sheet includes a positive electrode collector and a positive electrode active material layer present on the surface of the positive electrode collector, the positive electrode active material layer includes a positive electrode active material, a conductive agent and a binder, and the positive electrode active material includes the nickel-rich multi-electrode positive material; wherein, based on the total mass of the positive electrode active material layer, the mass fraction of the positive electrode active material is 80% to 98%, the mass fraction of the conductive agent is 1.5% to 15%, and the mass fraction of the binder is 0.5% to 5%.

11. A battery, characterized in that: The battery comprises the positive electrode sheet according to claim 9 or 10.

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