Lithium-rich manganese-based positive electrode material, and preparation method and application thereof

Abstract

The present disclosure belongs to the field of lithium battery technology, and specifically relates to a lithium-rich manganese-based positive electrode material, and a preparation method and an application thereof. By means of performing surface oxidation of a dried lithium-rich manganese-based precursor and by means of precisely controlling the oxidation temperature and time, the manganese element can achieve a shallow oxidation effect, during a sintering process with a lithium salt, a layer of spinel structure can be formed on the surface of the material, the spinel structure has a three-dimensional lithium ion diffusion channel, and the channel can accelerate the transmission rate of lithium ions and can effectively improve the electrochemical performance of the material.

Description

A lithium-rich manganese-based positive electrode material, preparation method and application thereof Technical Field

[0001] The present disclosure belongs to the technical field of lithium batteries, and in particular relates to a lithium-rich manganese-based positive electrode material, a preparation method thereof, and applications. Background Art

[0002] Lithium-ion batteries have the advantages of good cycle performance, high capacity, low price, ease of use, safety, and environmental protection, and have been widely used. With the development of transportation equipment such as electric vehicles, higher and higher requirements are placed on the performance of lithium batteries. Lithium-rich manganese-based cathode materials have high specific capacity (greater than 250mAh / g) and a wide operating voltage window (2-4.8V), and are most likely to become the next generation of high-performance lithium-ion battery materials. However, the current lithium-rich manganese-based cathode materials have obvious defects such as low rate performance and poor cycle stability, which seriously limit their use.

[0003] During the first charge of lithium-rich manganese-based cathode materials, part of the Li + It is released in the form of Li2O but cannot be re-embedded during the discharge process, resulting in low initial charge and discharge efficiency of this material. The release of Li2O will cause some lattice oxygen to be released to generate oxygen. The generation of oxygen will damage the surface of the electrode, causing the interior of the electrode to be corroded by the electrolyte, resulting in poor stability. It will also cause changes in the surface composition and structure of the material and gradually spread to the interior, further increasing the battery impedance and affecting the cycle performance and battery life.

[0004] Therefore, it is necessary to use surface modification and other means to change the surface structure of lithium-rich manganese-based materials and optimize the performance of lithium-rich manganese-based positive electrode materials. Metal oxides, metal fluorides, phosphates, etc. are usually used to modify lithium-rich manganese-based positive electrode materials to stabilize the surface structure of the particles, thereby improving the performance of lithium-rich manganese-based positive electrode materials at room temperature and high temperature. However, when using the above materials to optimize lithium-rich manganese-based positive electrode materials, the coating layer formed on the surface is often intermittent and discontinuous, and cannot achieve satisfactory results in improving rate performance and cycle stability.

[0005] In view of this, the present disclosure is proposed.

[0006] Summary of the Invention

[0007] The present disclosure aims to provide a lithium-rich manganese-based cathode material, a preparation method and an application thereof, in order to significantly improve the electrochemical performance of the lithium-rich manganese-based material.

[0008] In order to achieve the above-mentioned purpose of the present disclosure, the following technical solutions can be adopted:

[0009] The solution provided by the present disclosure includes a method for preparing a lithium-rich manganese-based positive electrode material, comprising: surface oxidation of a dried lithium-rich manganese-based precursor in an oxygen-containing atmosphere, and then mixing and sintering the precursor with a lithium salt;

[0010] In the process of surface oxidation, the oxidation temperature is controlled to be 60° C.-150° C., and the oxidation time is 1 h-10 h.

[0011] In some embodiments of the present disclosure, during the surface oxidation process, the oxidation temperature is controlled to be 80° C.-100° C., and the oxidation time is controlled to be 1 h-3 h.

[0012] In some embodiments of the present disclosure, the oxygen-containing atmosphere is selected from at least one of air and oxygen.

[0013] In some embodiments of the present disclosure, when the oxygen-containing atmosphere is air, the flow rate of the oxygen-containing atmosphere is 6m 3 / h-15m 3 / h;

[0014] When the oxygen-containing atmosphere is oxygen, the flow rate of the oxygen-containing atmosphere is 0.5m 3 / h-5m 3 / h.

[0015] In some embodiments of the present disclosure, the oxygen-containing atmosphere is air, and the flow rate of the oxygen-containing atmosphere is 6m 3 / h-10m 3 / h.

[0016] In some embodiments of the present disclosure, the lithium-rich manganese-based precursor is a hydroxide or a carbonate;

[0017] When the lithium-rich manganese-based precursor is hydroxide, the chemical formula is Ni y Co z Mn 1-y-z (OH)2, 0≤y<1, 0≤z<1, (y+z)<1;

[0018] When the lithium-rich manganese-based precursor is a carbonate, the chemical formula is Ni y Co z Mn 1-y-z CO3, 0≤y<1, 0≤z<1, (y+z)<1.

[0019] In some embodiments of the present disclosure, the preparation process of the dry lithium-rich manganese-based precursor includes: drying the wet lithium-rich manganese-based precursor, wherein the oxygen content in the drying atmosphere is less than 0.1% by volume.

[0020] In some embodiments of the present disclosure, the drying temperature is 80° C.-180° C., and the drying time is 8 h-20 h.

[0021] In some embodiments of the present disclosure, the drying temperature is 90° C.-130° C., and the drying time is 10 h-15 h.

[0022] In some embodiments of the present disclosure, the drying process is performed in an inert atmosphere or a vacuum state.

[0023] In some embodiments of the present disclosure, the inert atmosphere is selected from at least one of nitrogen and argon.

[0024] In some embodiments of the present disclosure, the flow rate of the inert atmosphere is 0.5 m 3 / h-10m 3 / h.

[0025] In some embodiments of the present disclosure, the preparation process of the lithium-rich manganese-based precursor wet material includes: preparing a slurry containing the precursor by a co-precipitation method, obtaining a solid material after solid-liquid separation, and washing and solid-liquid separation of the solid material.

[0026] In some embodiments of the present disclosure, the particle size of the precursor contained in the slurry is 1 μm-15 μm.

[0027] In some embodiments of the present disclosure, when the surface-oxidized lithium-rich manganese-based precursor is mixed with a lithium salt and sintered, the molar ratio of the total amount of metal elements in the lithium-rich manganese-based precursor to the lithium element is controlled to be 1:(1.05-1.65).

[0028] In some embodiments of the present disclosure, the sintering process includes: low-temperature sintering first and then high-temperature sintering, the low-temperature sintering temperature is 480°C-650°C, and the high-temperature sintering temperature is 800°C-1000°C.

[0029] In some embodiments of the present disclosure, the low-temperature sintering time is 1 hour to 15 hours.

[0030] In some embodiments of the present disclosure, the high temperature sintering time is 1 hour to 15 hours.

[0031] In some embodiments of the present disclosure, the sintering process is carried out in an air atmosphere or an oxygen atmosphere, and the flow rate of air or oxygen is 0.5m 3 / h-10m 3 / h.

[0032] In a second aspect, the solution provided by the present disclosure also includes a lithium-rich manganese-based positive electrode material prepared by the preparation method in any of the above embodiments.

[0033] In some embodiments of the present disclosure, the surface of the lithium-rich manganese-based cathode material has a spinel phase.

[0034] In some embodiments of the present disclosure, the chemical formula of the lithium-rich manganese-based cathode material is Li 1+x Ni y Co z Mn 1-y-z O2; wherein 0<x≤1, 0≤y<1, 0≤z<1, (y+z)<1.

[0035] In some embodiments of the present disclosure, the tap density of the lithium-rich manganese-based positive electrode material is 2.5 g / cm 3 -3.2g / cm 3 .

[0036] In a third aspect, the solution provided by the present disclosure also includes a positive electrode plate, comprising the lithium-rich manganese-based positive electrode material in any of the above embodiments.

[0037] In a fourth aspect, the solution provided by the present disclosure also includes a lithium battery, including the positive electrode plate in the above embodiment.

[0038] In a fifth aspect, the solution provided by the present disclosure also includes an electrical device, including the lithium battery in the above embodiment.

[0039] By subjecting a dry, lithium-rich manganese-based precursor to surface oxidation and precisely controlling the oxidation temperature and time, the manganese element achieves shallow oxidation. During the sintering process with the lithium salt, a spinel structure forms on the material's surface. The surface-constructed spinel structure exhibits a high interfacial bonding strength with the matrix's layered structure, resulting in not only high structural stability but also interconnected lithium-ion diffusion channels within the two crystal structures, ensuring smooth flow during charge and discharge. Furthermore, the spinel structure possesses three-dimensional lithium-ion diffusion channels that accelerate lithium-ion transport, effectively improving the material's electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0041] FIG1 is a first process flow chart provided by an embodiment of the present disclosure;

[0042] FIG2 is a second process flow chart provided by an embodiment of the present disclosure;

[0043] FIG3 is an XRD diagram of lithium-rich manganese-based positive electrode materials prepared in the embodiments of the present disclosure and the comparative examples;

[0044] FIG4 is a comparison of the rate performance of lithium-rich manganese-based positive electrode materials prepared in the embodiment of the present disclosure and the comparative example;

[0045] FIG5 is a cyclic discharge curve diagram of the lithium-rich manganese-based positive electrode materials prepared in the embodiment of the present disclosure and the comparative example. DETAILED DESCRIPTION

[0046] The embodiments of the present disclosure will be described in detail below with reference to the examples. However, those skilled in the art will appreciate that the following examples are intended only to illustrate the present disclosure and should not be construed as limiting the scope of the present disclosure. Where specific conditions are not specified in the examples, the experiments were performed under conventional conditions or the conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments is not specified, all are commercially available conventional products.

[0047] The endpoints of the ranges and any values ​​disclosed in this disclosure are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0048] Please refer to Figure 1. An embodiment of the present disclosure provides a method for preparing a lithium-rich manganese-based positive electrode material, which is prepared by surface-oxidizing a dry lithium-rich manganese-based precursor in an oxygen-containing atmosphere, and then mixing it with a lithium salt and sintering it, thereby obtaining a positive electrode material with a spinel structure, which can significantly improve the rate performance and cycle performance of the material.

[0049] As shown in FIG2 , the preparation method may specifically include the following steps:

[0050] S1. Preparation of lithium-rich manganese-based precursors by co-precipitation

[0051] A co-precipitation method is used to prepare a slurry containing a precursor. The principle of the co-precipitation method can refer to the existing technology, and transition metal salts such as nickel salts and manganese salts are used for co-precipitation to obtain a powdered precursor. The particle size of the precursor powder is 1μm-15μm, such as 1μm, 3μm, 5μm, 8μm, 10μm, 12μm, 15μm, etc.

[0052] In some embodiments, the lithium-rich manganese-based precursor is a hydroxide or a carbonate, and can be a hydroxide or a carbonate. When the lithium-rich manganese-based precursor is a hydroxide, the chemical formula is Ni y Co z Mn 1-y-z (OH)2, 0≤y<1, 0≤z<1, (y+z)<1; when the lithium-rich manganese-based precursor is carbonate, the chemical formula is Ni y Coz Mn 1-y-z CO3, 0≤y<1, 0≤z<1, (y+z)<1.

[0053] Specifically, the value of y can be 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc., and the value of z can be 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc., and (y+z)<1.

[0054] In actual operation, a base liquid containing a complexing agent (such as ammonia) is placed in a reactor and added until it covers the bottom stirring paddle. Nitrogen is introduced into the reactor as a protective gas. A mixed solution of transition metal salts, such as nickel, cobalt, and manganese salts, is then introduced into the reactor. Ammonia is also introduced as a complexing agent, and alkaline solution is introduced as a precipitant. The pH value in the reactor is adjusted within a certain range for precipitation. The reaction is stopped when the precursor particles in the reactor grow to a specified size. During the reaction, the molar ratio of elements such as nickel, cobalt, and manganese is controlled to obtain a precursor with the required element ratio.

[0055] S2. Solid-liquid separation

[0056] The slurry containing the precursor obtained after coprecipitation is subjected to solid-liquid separation to obtain a solid material.

[0057] There is no limit to the method of solid-liquid separation, and filtration means such as suction filtration can be used to perform the operation. After filtration, a filter cake is obtained and enters the next process.

[0058] S3, washing

[0059] The solid material obtained in S2 is washed to remove surface ions, and after washing, solid-liquid separation is performed to obtain a lithium-rich manganese-based precursor wet material.

[0060] In actual operation, pure water washing can be used, and washing can be repeated multiple times to fully remove residual ions on the surface.

[0061] S4. Drying

[0062] The lithium-rich manganese-based wet precursor prepared in S3 is dried to a drying atmosphere having an oxygen content of less than 0.1% by volume. During the drying process, the lithium-rich manganese-based wet precursor must be placed in a near-oxygen-free environment to prevent excessive oxidation of the manganese element in the bulk phase of the material during the drying process.

[0063] In some embodiments, the drying temperature is 80-180°C and the drying time is 8-20 hours; preferably, the drying temperature is 90-130°C and the drying time is 10-15 hours. If the drying temperature is too high or the drying time is too long, the precursor will decompose, and the bulk and surface phases of the material will undergo: Ni x Mn 1-x (OH)2→Ni x (OH) 2x +(1-x)MnO+(1-x)H2O;

[0064] When MnO comes into contact with air, both its bulk and surface phases undergo the reaction 2MnO+O2=2MnO2. When prepared as a material, the surface and bulk phases of the material are prone to forming a spinel structure. Excessive spinel structure in the bulk phase can severely impact the sample's capacity. Therefore, drying must be performed in a near-oxygen-free atmosphere to maintain the sample's bulk phase structure as much as possible, allowing the reaction to generate xLi2MnO3.(1-x)LiMO2. If the drying time is too short or the drying temperature is too low, the material will not be completely dried.

[0065] Specifically, the drying temperature can be 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, etc.; the drying time can be 8h, 10h, 12h, 15h, 17h, 20h, etc.

[0066] In some embodiments, the drying process is carried out in an inert atmosphere or vacuum state so that the oxygen content in the drying atmosphere meets the requirements. The inert atmosphere is selected from at least one of nitrogen and argon, and can be any one or more of the above; the flow rate of the inert atmosphere is 0.5m 3 / h-10m 3 / h, such as 0.5m 3 / h、1.0m 3 / h, 2.0m 3 / h、3.0m 3 / h、4.0m 3 / h、5.0m 3 / h、6.0m 3 / h、7.0m 3 / h、8.0m 3 / h、9.0m 3 / h、10.0m 3 / h, etc.

[0067] S5. Surface oxidation

[0068] The dried lithium-rich manganese-based precursor is surface-oxidized in an oxygen-containing atmosphere. The dried material is then placed in an oxygen-containing environment, oxidizing only the manganese on the surface of the precursor. The surface-oxidized manganese tends to form a spinel structure on the surface during sintering. Lithium-rich manganese-based cathode materials with a spinel interface not only facilitate lithium-ion transport but also prevent the surface spinel structure from shedding during charge-discharge cycles due to structural stress, improving the structural stability of the electrode material during repeated charge-discharge cycles. The preparation process is simple, easy to operate, and has a high yield.

[0069] During the surface oxidation process, the oxidation temperature is controlled to be 60°C-150°C, and the oxidation time is 1h-10h; preferably, the oxidation temperature is controlled to be 80°C-100°C, and the oxidation time is 1h-3h. If the oxidation temperature is too high, the precursor will decompose; if the oxidation time is too long, the manganese element on the surface and in the bulk of the precursor will be excessively oxidized; if the oxidation temperature is too low and the oxidation time is too short, the degree of oxidation on the surface of the precursor is shallow, and the spinel structure cannot be well constructed on the surface during sintering. The oxidation in this step is only to form a layer of manganese oxide or oxyhydroxide on the surface of the precursor. During the sample preparation process, high-valent manganese elements are more inclined to form a spinel structure.

[0070] In some embodiments, the oxygen-containing atmosphere is selected from at least one of air and oxygen, and can be air or oxygen, with air containing a lower content.

[0071] Furthermore, when the oxygen-containing atmosphere is air, the flow rate of the oxygen-containing atmosphere is 6m 3 / h-15m 3 / h, preferably 6m 3 / h-10m 3 / h, such as 6.0m 3 / h、7.0m 3 / h、8.0m 3 / h、9.0m 3 / h、10.0m 3 / h、11.0m 3 / h、12.0m 3 / h、13.0m 3 / h、14.0m 3 / h、15.0m 3 / h, etc. When the oxygen-containing atmosphere is oxygen, the flow rate of the oxygen-containing atmosphere is 0.5m 3 / h-5m 3 / h, such as 0.5m 3 / h、0.8m 3 / h、1.0m 3 / h, 2.0m 3 / h、3.0m3 / h、4.0m 3 / h、5.0m 3 / h, etc.

[0072] S6. Sintering

[0073] The surface-oxidized lithium-rich manganese-based precursor obtained in S5 is mixed with a lithium salt and sintered to obtain a lithium-rich manganese-based positive electrode material with a spinel interface constructed on the surface.

[0074] In some embodiments, when the surface-oxidized lithium-rich manganese-based precursor is mixed and sintered with a lithium salt, the molar ratio of the total amount of metal elements in the lithium-rich manganese-based precursor to the lithium element is controlled to be 1:(1.05-1.65), such as 1:1.05, 1:1.10, 1:1.15, 1:1.20, 1:1.25, 1:1.30, 1:1.35, 1:1.40, 1:1.45, 1:1.50, 1:1.55, 1:1.60, 1:1.65, etc.

[0075] In some embodiments, the sintering process includes: first low-temperature sintering at a temperature of 480°C to 650°C, and then high-temperature sintering at a temperature of 800°C to 1000°C. The material is first held at a low temperature for a period of time to allow decomposition, then the temperature is raised and held for a period of time. After the holding period, the material can be cooled, crushed, and sieved to obtain a lithium-rich manganese-based cathode material with a spinel interface on its surface.

[0076] In some embodiments, the low-temperature sintering time is 1 hour to 15 hours, and the high-temperature sintering time is 1 hour to 15 hours. It is preferable that the low-temperature sintering time and the high-temperature sintering time be controlled within the above range.

[0077] Specifically, the temperature of low-temperature sintering can be 480°C, 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, 620°C, 650°C, etc., and the time of low-temperature sintering can be 1 hour, 3 hours, 5 hours, 8 hours, 10 hours, 12 hours, 15 hours, etc. The temperature of high-temperature sintering can be 800°C, 850°C, 900°C, 950°C, 1000°C, etc., and the time of high-temperature sintering can be 1 hour, 3 hours, 5 hours, 8 hours, 10 hours, 12 hours, 15 hours, etc.

[0078] In some embodiments, the entire sintering process is carried out in an air atmosphere or an oxygen atmosphere, and the flow rate of air or oxygen is 0.5m 3 / h-10m 3 / h, such as 0.5m 3 / h、0.8m 3 / h、1.0m 3 / h, 2.0m 3 / h、3.0m3 / h、4.0m 3 / h、5.0m 3 / h、6.0m 3 / h、7.0m 3 / h、8.0m 3 / h、9.0m 3 / h、10.0m 3 / h, etc.

[0079] The disclosed embodiments also provide a lithium-rich manganese-based positive electrode material, which is prepared by the above-mentioned preparation method. The surface layer of the positive electrode material has a spinel structure, which can significantly improve the electrochemical performance of the material; due to the simple preparation process, the introduction of impurities is reduced.

[0080] In some embodiments, the chemical formula of the lithium-rich manganese-based cathode material is Li 1+x Ni y Co z Mn 1-y-z O2; wherein 0<x≤1, 0≤y<1, 0≤z<1. The value of x can be 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, etc., the value of y can be 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc., and the value of z can be 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc., and (y+z)<1.

[0081] In some embodiments, the tap density of the lithium-rich manganese-based cathode material is 2.5 g / cm 3 -3.2g / cm 3 , such as 2.5g / cm 3 , 2.8g / cm 3 , 3.0g / cm 3 、3.2g / cm 3 wait.

[0082] The solution also provided by the embodiment of the present disclosure also includes a positive electrode plate, including the above-mentioned lithium-rich manganese-based positive electrode material. A slurry containing the lithium-rich manganese-based positive electrode material is applied to the positive electrode collector, and the positive electrode plate is obtained after drying. The type of positive electrode collector is not limited.

[0083] The embodiments of the present disclosure also provide a lithium battery, which includes the above-mentioned positive electrode plate, and may also include a negative electrode plate, an electrolyte, a separator, etc., to form a complete lithium battery structure.

[0084] The embodiments of the present disclosure further provide an electrical device, which includes the above-mentioned lithium battery and may also include an electrical appliance, using the lithium battery as a power source for the electrical appliance.

[0085] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0086] Example 1

[0087] This embodiment provides a method for preparing a lithium-rich manganese-based positive electrode material, comprising the following steps:

[0088] (1) Preparation of lithium-rich manganese-based precursor powder Ni by co-precipitation 0.35 Mn 0.65 (OH)2, the average particle size of the precursor material is 5.5μm. The specific operation process is as follows:

[0089] According to the required molar ratio of nickel, cobalt and manganese elements, i.e., 0.35:0.65, nickel nitrate and manganese nitrate are respectively selected as raw materials to prepare a nickel-manganese mixed salt solution with a total molar concentration of metal ions of 2.0 mol / L; a sodium hydroxide solution with a concentration of 5.0 mol / L; and an ammonia solution with a concentration of 4.0 mol / L.

[0090] The pH value of the aqueous ammonia solution and the aqueous sodium hydroxide solution was adjusted to 10 to obtain a base solution.

[0091] The base liquid is placed in a reactor, and metal salt solution, ammonia solution and sodium hydroxide solution are respectively introduced into the reactor. The pH value in the reactor is controlled to be 10-12, and the ammonia value is controlled to be 0.2 mol / L. The reaction is stopped when the average particle size of the particles in the reactor reaches 5.5 μm.

[0092] (2) The material in the kettle obtained in step (1) is filtered to obtain a filter cake.

[0093] (3) The filter cake obtained in step (2) is washed with pure water and then filtered to obtain a wet material.

[0094] (4) The wet material obtained in step (3) is placed in a drying oven and introduced with nitrogen at a flow rate of 5m 3 The precursor was dried at 110°C for 12 hours to obtain a dry precursor, which was then passed through a 300-mesh sieve and the sieve material was taken.

[0095] (5) Place the material obtained in step (4) into a drying oven and introduce air at a flow rate of 6m 3 / h. Keep the temperature at 90°C for 2h to obtain a surface-oxidized lithium-rich manganese-based precursor.

[0096] (6) The lithium-rich manganese-based precursor material powder obtained in the weighing step (5) is uniformly mixed with lithium carbonate, and the molar ratio of the total amount of metal elements in the lithium-rich manganese-based precursor to the lithium element is 1:1.3.

[0097] (7) The material obtained in step (6) was placed in a sintering furnace and air was introduced at a flow rate of 5m 3 / h. The material was held at 550°C for 5 hours in the low-temperature zone to decompose, then the temperature was raised to 850°C and held for 15 hours to generate a layered lithium-rich manganese-based cathode material. After the holding period, the material was cooled, crushed to 300 mesh, and then passed through a 300-mesh sieve to obtain a lithium-rich manganese-based cathode material with a spinel interface on the surface.

[0098] Example 2

[0099] This embodiment provides a method for preparing a lithium-rich manganese-based positive electrode material, comprising the following steps:

[0100] (1) Preparation of lithium-rich manganese-based precursor powder Ni by co-precipitation 0.37 Mn 0.63 (OH)2; the average particle size of the precursor material is 5.5μm.

[0101] The specific steps are similar to those in Example 1, with the only difference being that the ratio of nickel and manganese elements in the metal salt solution is changed.

[0102] (2) The material in the kettle obtained in step (1) is filtered to obtain a filter cake.

[0103] (3) The filter cake obtained in step (2) is washed with pure water and then filtered to obtain a wet material.

[0104] (4) The wet material obtained in step (3) is placed in a drying oven and introduced with nitrogen at a flow rate of 5m 3 The drying temperature was kept at 110°C for 12 hours to obtain a dry precursor, which was then sieved.

[0105] (5) Place the material from step (4) in a drying oven and introduce air at a flow rate of 6 m 3 / h. Keep the temperature at 90°C for 2h to obtain a surface-oxidized lithium-rich manganese-based precursor.

[0106] (6) The lithium-rich manganese-based precursor material powder in step (5) is weighed and uniformly mixed with lithium carbonate, and the molar ratio of the total amount of metal elements in the lithium-rich manganese-based precursor to the lithium element is 1:1.28.

[0107] (7) The material obtained in step (6) was placed in a sintering furnace and air was introduced at a flow rate of 5m 3 / h. The material was held at 550°C for 5 hours in the low-temperature zone to decompose, then the temperature was raised to 850°C and held for 15 hours to generate a layered lithium-rich manganese-based cathode material. After the holding period, the material was cooled, crushed to 300 mesh, and then passed through a 300-mesh sieve to obtain a lithium-rich manganese-based cathode material with a spinel interface on the surface.

[0108] Example 3

[0109] The only difference from Example 1 is that the oxidation temperature in step (5) is controlled to 80° C. and the holding time is 3 h.

[0110] Example 4

[0111] The only difference from Example 1 is that the oxidation temperature in step (5) is controlled to 100° C. and the holding time is 1 h.

[0112] Example 5

[0113] The only difference from Example 1 is that the oxidation temperature in step (5) is controlled to 60° C. and the holding time is 5 h.

[0114] Example 6

[0115] The only difference from Example 1 is that the oxidation temperature in step (5) is controlled to 120° C. and the holding time is 0.5 h.

[0116] Example 7

[0117] The only difference from Example 1 is that the oxidation temperature in step (5) is controlled to be 150° C. and the holding time is 0.5 h.

[0118] Example 8

[0119] The only difference from Example 1 is that nitrogen is not introduced in step (4), and drying is performed under air atmosphere.

[0120] Example 9

[0121] The only difference from Example 1 is that the drying temperature in step (4) is 200°C.

[0122] Comparative Example 1

[0123] This comparative example provides a method for preparing a lithium-rich manganese-based positive electrode material. The only difference from Example 2 is that nitrogen is not introduced during drying in step (4), step (5) is not performed, and the material is directly mixed with a lithium salt and sintered after step (4). The specific steps are as follows:

[0124] (1) Preparation of lithium-rich manganese-based precursor powder Ni by co-precipitation 0.35 Mn 0.65 (OH)2; the average particle size of the precursor material is 5.5μm.

[0125] (2) The material in the kettle obtained in step (1) is filtered to obtain a filter cake.

[0126] (3) The filter cake obtained in step (2) is washed with pure water and then filtered to obtain a wet material.

[0127] (4) The wet material obtained in step (3) is placed in a drying furnace and kept warm at a drying temperature of 110° C. for 12 hours to obtain a dry precursor, which is then sieved.

[0128] (5) The lithium-rich manganese-based precursor material powder in step (4) is weighed and uniformly mixed with lithium carbonate, and the molar ratio of the total amount of metal elements in the lithium-rich manganese-based precursor to the lithium element is 1:1.3.

[0129] (6) The material obtained in step (5) is placed in a sintering furnace and air is introduced at a flow rate of 5m 3 / h. The material was held at 550°C for 5 hours in the low-temperature zone to decompose, then the temperature was raised to 850°C and held for 15 hours to generate a layered lithium-rich manganese-based cathode material. After the holding period, the material was cooled, crushed to 300 mesh, and then passed through a 300-mesh sieve to obtain a lithium-rich manganese-based cathode material with a spinel interface on the surface.

[0130] Comparative Example 2

[0131] The only difference from Example 1 is that the oxidation temperature in step (5) is controlled to 50° C. and the holding time is 6 h.

[0132] Comparative Example 3

[0133] The only difference from Example 1 is that the oxidation temperature in step (5) is controlled to 160° C. and the holding time is 0.5 h.

[0134] Test Example 1

[0135] The XRD patterns of the positive electrode materials prepared in Test Example 1 and Comparative Example 1 are shown in FIG3 .

[0136] As can be seen from Figure 3, the surface of the lithium-rich manganese-based cathode material with a spinel interface does not change the main crystal structure of the original lithium-rich manganese-based cathode material. Both are typical α-NaFeO2 structures, belonging to the R-3m space group, with obvious splitting of the (006) / (012) and (018) / (110) peaks, and the superlattice peak of Li2MnO3 appears between θ = 20 and 22 degrees. The peak positions of the modified cathode materials from θ = 4.3 to 45 degrees and θ = 58 to 60 degrees are shifted to lower angles relative to the original lithium-rich manganese-based cathode material, indicating that the interlayer spacing of the modified cathode material is larger than that of the original lithium-rich manganese-based cathode material, which will be conducive to the insertion and extraction of lithium ions, and the surface of the surface-modified sample has a spinel phase.

[0137] Test Example 2

[0138] The rate performance and cycle performance of the positive electrode materials prepared in the test examples and comparative examples were obtained.

[0139] Electrode preparation and battery assembly: The prepared lithium-rich manganese-based positive electrode material was weighed and fully mixed with super carbon black and polyvinylidene fluoride (PVDF) in a mass ratio of 9:0.5:0.5, coated on aluminum foil, and placed in a vacuum dryer at 100°C for 5 hours. After taking it out, it was placed on a roller press and rolled several times, and then cut into discs. It was used as the positive electrode, the metal lithium sheet as the negative electrode, the polypropylene microporous membrane as the separator, and 1 mol / L LiPF6+EC / DMC / EMC as the electrolyte. The CR2430 stainless steel button battery was assembled in a glove box filled with argon and with a moisture content of less than 0.1ppm; after standing for 10 hours, its charge and discharge performance was tested.

[0140] Figure 4 compares the rate performance of the positive electrode materials prepared in Example 1 and Comparative Example 1. It can be seen that under the test voltage of 2.0-4.8V, the rate performance of the example is inferior to that of the comparative example. This is due to the spinel structure formed on the surface of the lithium-rich manganese-based material, which has three-dimensional lithium ion diffusion channels. These channels can accelerate the transmission rate of lithium ions and improve the rate performance of the material.

[0141] Figure 5 shows the cycle performance curves of Example 1 and Comparative Example 1. It can be seen that under the test conditions of voltage of 2.0-4.8V and rate of 0.1C, after 100 cycles, the discharge capacity is still 202.6mA / g, and the capacity retention rate is 86.2%.

[0142] The positive electrode material prepared in Example 2 exhibited an initial discharge capacity of 235.6 mAh / g and a first efficiency of 82.5 under test conditions of a voltage of 2.0-4.8 V and a rate of 0.1C. After 100 cycles at 0.1C, the discharge capacity remained at 203.3 mAh / g, with a capacity retention of 86.3%.

[0143] The material synthesized in Comparative Example 1 exhibited an initial discharge capacity of 230 mAh / g and an initial efficiency of 83.9% under test conditions of a voltage of 2.0-4.8 V and a rate of 0.1C. After 100 cycles at 0.1C, the discharge capacity remained at 184.3 mAh / g, with a capacity retention rate of 80.1%.

[0144] Test Example 3

[0145] The first cycle charge-discharge performance and cycle performance of the positive electrode materials prepared in Example 2-9 and Comparative Example 2-3 were tested. The test method was similar to that in Test Example 2. The test results are shown in Table 1.

[0146] Table 1 First cycle charge and discharge performance and cycle performance test results

[0147] It can be seen that the cycle performance of the positive electrode material prepared in the present disclosure is significantly better than that of the comparative example. Industrial Applicability

[0148] The present invention involves surface oxidation of a dried lithium-rich manganese-based precursor. By precisely controlling the oxidation temperature and time, the manganese element achieves shallow oxidation. During sintering with a lithium salt, a spinel structure is formed on the surface of the material. The spinel structure has three-dimensional lithium ion diffusion channels that accelerate the transport rate of lithium ions and effectively improve the electrochemical performance of the material. The solution provided by the present invention is easy to operate, simple to implement, and has excellent industrial applicability.

Claims

1. A method for preparing a lithium-rich manganese-based positive electrode material, characterized in that: include: The dried lithium-rich manganese-based precursor is surface-oxidized in an oxygen-containing atmosphere and then mixed with a lithium salt and sintered; Wherein, during the surface oxidation process, the oxidation temperature is controlled to be 60° C.-150° C., and the oxidation time is 1 h-10 h.

2. The preparation method according to claim 1, characterized in that: During the surface oxidation process, the oxidation temperature is controlled to be 80° C.-100° C., and the oxidation time is controlled to be 1 h-3 h.

3. The preparation method according to claim 1 or 2, characterized in that: The oxygen-containing atmosphere is selected from at least one of air and oxygen.

4. The preparation method according to claim 3, characterized in that: When the oxygen-containing atmosphere is air, the flow rate of the oxygen-containing atmosphere is 6m 3 / h-15m 3 / h; When the oxygen-containing atmosphere is oxygen, the flow rate of the oxygen-containing atmosphere is 0.5 m 3 / h-5m 3 / h.

5. The preparation method according to claim 4, characterized in that: The oxygen-containing atmosphere is air, and the flow rate of the oxygen-containing atmosphere is 6m 3 / h-10m 3 / h.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The lithium-rich manganese-based precursor is a hydroxide or a carbonate; When the lithium-rich manganese-based precursor is a hydroxide, the chemical formula is Ni y Co z Mn 1-y-z (OH)2, 0≤y<1, 0≤z<1, (y+z)<1; When the lithium-rich manganese-based precursor is a carbonate, the chemical formula is Ni y Co z Mn 1-y-z CO3, 0≤y<1, 0≤z<1, (y+z)<1.

7. The preparation method according to any one of claims 1 to 6, characterized in that The preparation process of the dry lithium-rich manganese-based precursor includes: drying the wet lithium-rich manganese-based precursor, and the oxygen content in the drying atmosphere is less than 0.1% by volume.

8. The preparation method according to claim 7, characterized in that: The drying temperature is 80℃-180℃, and the drying time is 8h-20h.

9. The preparation method according to claim 8, characterized in that: The drying temperature is 90℃-130℃, and the drying time is 10h-15h.

10. The preparation method according to any one of claims 7 to 9, characterized in that: The drying process is carried out in an inert atmosphere or under vacuum.

11. The preparation method according to claim 10, characterized in that: The inert atmosphere is selected from at least one of nitrogen and argon.

12. The preparation method according to claim 10 or 11, characterized in that: The flow rate of the inert atmosphere is 0.5m 3 / h-10m 3 / h.

13. The preparation method according to any one of claims 7 to 12, characterized in that: The preparation process of the lithium-rich manganese-based precursor wet material includes: preparing a slurry containing the precursor by a coprecipitation method, obtaining a solid material after solid-liquid separation, and washing and solid-liquid separation of the solid material.

14. The preparation method according to claim 13, characterized in that: The particle size of the precursor contained in the slurry is 1 μm-15 μm.

15. The preparation method according to any one of claims 1 to 14, characterized in that: When the surface-oxidized lithium-rich manganese-based precursor is mixed with a lithium salt for sintering, the molar ratio of the total amount of metal elements in the lithium-rich manganese-based precursor to the lithium element is controlled to be 1:(1.05-1.65).

16. The preparation method according to any one of claims 1 to 15, characterized in that: The sintering process includes: firstly low-temperature sintering and then high-temperature sintering, wherein the temperature of the low-temperature sintering is 480°C-650°C, and the temperature of the high-temperature sintering is 800°C-1000°C.

17. The preparation method according to claim 16, characterized in that: The low temperature sintering time is 1h-15h.

18. The preparation method according to claim 16 or 17, characterized in that: The high temperature sintering time is 1h-15h.

19. The preparation method according to any one of claims 16 to 18, characterized in that: The sintering process is carried out in an air atmosphere or an oxygen atmosphere, and the flow rate of air or oxygen is 0.5m 3 / h-10m 3 / h.

20. A lithium-rich manganese-based positive electrode material, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 19.

21. The lithium-rich manganese-based positive electrode material according to claim 20, characterized in that: The surface of the lithium-rich manganese-based positive electrode material has a spinel phase.

22. The lithium-rich manganese-based positive electrode material according to claim 20 or 21, characterized in that: The chemical formula of the lithium-rich manganese-based positive electrode material is Li 1+x Ni y Co z Mn 1-y-z O2; wherein 0<x≤1, 0≤y<1, 0≤z<1, (y+z)<1.

23. The lithium-rich manganese-based positive electrode material according to any one of claims 20 to 22, characterized in that: The tap density of the lithium-rich manganese-based positive electrode material is 2.5 g / cm 3 -3.2g / cm 3 .

24. A positive electrode plate, characterized in that: Comprising the lithium-rich manganese-based positive electrode material described in any one of claims 20-23.

25. A lithium battery, characterized in that: Including the positive electrode sheet as described in claim 24.

26. An electrical device, characterized in that: Including the lithium battery as described in claim 25.

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