Lithium tungstate, and preparation method therefor and use thereof

Abstract

The present disclosure belongs to the technical field of lithium batteries, and specifically relates to lithium tungstate, and a preparation method therefor and the use thereof. In the present disclosure, lithium hydroxide, a tungsten source and an easily decomposable ammonium salt are used as raw materials, and heat generated in a reaction process is absorbed by utilizing the characteristic of the ammonium salt being easily decomposed with heat; therefore, a thermal field can be uniformly distributed in the reaction process, preventing morphological changes of lithium tungstate caused by local overheating, and nano-scale cubic-phase lithium tungstate can be prepared by means of a solid-phase reaction at normal temperature. Compared with a conventional high-temperature solid-phase method, the preparation method provided in the present disclosure does not require high-temperature conditions, the energy consumption involved therein is significantly reduced, and same is suitable for industrial mass production.

Description

A lithium tungstate and its preparation method and application Technical Field

[0001] The present disclosure belongs to the field of lithium battery technology, and specifically relates to lithium tungstate and its preparation method and application. Background Art

[0002] As new energy vehicles are widely used, people have put forward higher requirements for their performance. At present, the main problem of new energy vehicles is the battery life and lifespan. Improving the energy density and cycle performance of batteries is the key to solving the above technical problems. Compared with lithium iron phosphate, ternary Li[Ni x Co y Mn (1-x-y) ]O2 material as the positive electrode has a higher specific capacity and is more likely to meet the requirements.

[0003] For ternary materials, as the nickel content increases, although the energy density increases, the cycle performance will deteriorate accordingly. In order to solve this problem, there are two main mainstream solutions: (1) using other elements to replace transition metal elements or oxygen elements to improve the stability of the material structure itself. (2) using oxides with good structural stability or metal lithium salts with fast ion conductivity. Among them, the coating of metal lithium salts with fast ion conductivity can not only effectively prevent the electrolyte from corroding the positive electrode material and inhibit the occurrence of parasitic reactions, but also prevent the escape of lattice oxygen, inhibit the growth of SEI film, and provide a fast and stable channel for the transmission of lithium ions, which has a huge improvement on the battery capacity and cycle performance.

[0004] Using lithium tungstate to coat ternary cathode materials can effectively improve the battery's cycling stability. However, existing lithium tungstate synthesis methods mainly include liquid-phase and high-temperature solid-phase methods. The solidification method requires high temperatures, consumes a lot of energy, and is difficult to achieve industrial mass production.

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

[0006] Summary of the Invention

[0007] The purpose of the present disclosure includes providing a lithium tungstate and a preparation method thereof, aiming to realize the preparation of lithium tungstate by solid-phase reaction at room temperature.

[0008] Another object of the present disclosure includes providing a positive electrode material and a preparation method and application thereof, aiming to simultaneously improve the capacity and cycle performance of the material.

[0009] In order to achieve the above-mentioned purpose of the present disclosure, the following technical solutions can be adopted:

[0010] In a first aspect, the present disclosure provides a method for preparing lithium tungstate, comprising: mixing lithium hydroxide, a tungsten source, and an ammonium salt, and preparing lithium tungstate by a solid-phase reaction;

[0011] Among them, the decomposition temperature of ammonium salt is less than 200°C.

[0012] In some embodiments of the present disclosure, the ammonium salt is selected from at least one of ammonium bicarbonate, ammonium carbonate, and ammonium acetate.

[0013] In some embodiments of the present disclosure, the ammonium salt is ammonium bicarbonate.

[0014] In some embodiments of the present disclosure, the mass ratio of the amount of the ammonium salt to the total mass of the lithium hydroxide and the tungsten source is (0.1-0.5):100.

[0015] In some embodiments of the present disclosure, the amount of lithium hydroxide and tungsten source is controlled so that the molar ratio of lithium to tungsten is (2.0-2.2):1.

[0016] In some embodiments of the present disclosure, the tungsten source is selected from at least one of WO 3 and H 2 WO 4 .

[0017] In some embodiments of the present disclosure, the solid phase reaction process includes: mixing lithium hydroxide, a tungsten source, and an ammonium salt and ball milling them.

[0018] In some embodiments of the present disclosure, during the ball milling process, the ball-to-material ratio is controlled to (0.8-1.2):1.

[0019] In some embodiments of the present disclosure, the ball-to-material ratio is controlled to be (0.9-1.1):1.

[0020] In some embodiments of the present disclosure, the ball milling time is 3 min-20 min.

[0021] In some embodiments of the present disclosure, the ball milling time is 5 min-10 min.

[0022] In some embodiments of the present disclosure, ball milling is performed at room temperature.

[0023] In some embodiments of the present disclosure, the volume of the mixed raw materials is controlled to account for 10%-50% of the volume of the ball mill.

[0024] In some embodiments of the present disclosure, the process further comprises drying and pulverizing after ball milling.

[0025] In some embodiments of the present disclosure, the drying temperature is controlled to be 50° C.-100° C., and the drying time is controlled to be 4 h-24 h.

[0026] In some embodiments of the present disclosure, the particle size D50 after pulverization is controlled to be 2 μm-10 μm.

[0027] In some embodiments of the present disclosure, the pulverization method is selected from at least one of Chinese herbal medicine pulverization and air flow pulverization.

[0028] In a second aspect, the present disclosure further provides lithium tungstate, which is prepared by the preparation method in any of the above embodiments.

[0029] In some embodiments of the present disclosure, the particle size of lithium tungstate is 2 μm-10 μm, and the particles are cubic phase particles.

[0030] In a third aspect, the present disclosure further provides a method for preparing a positive electrode material, comprising: coating a positive electrode material substrate with the lithium tungstate in any of the above embodiments.

[0031] In some embodiments of the present disclosure, lithium tungstate and a positive electrode material substrate are mixed and sintered, wherein the positive electrode material substrate is lithium nickel cobalt manganese oxide.

[0032] In some embodiments of the present disclosure, the coating amount of lithium tungstate is controlled to be 500 ppm-2000 ppm.

[0033] In some embodiments of the present disclosure, the sintering temperature is 550° C.-700° C., and the sintering time is 4 h-8 h.

[0034] In some embodiments of the present disclosure, in lithium nickel cobalt manganese oxide, the mass content of nickel in the total transition metals is greater than 90%.

[0035] In a fourth aspect, the present disclosure further provides a positive electrode material prepared by the preparation method in any of the above embodiments.

[0036] In a fifth aspect, the present disclosure further provides a lithium-ion battery comprising the positive electrode material in any of the above embodiments.

[0037] In a sixth aspect, the present disclosure further provides an electrical device comprising a lithium-ion battery in any of the above embodiments.

[0038] Using lithium hydroxide, a tungsten source, and a readily decomposable ammonium salt as raw materials, the method utilizes the ammonium salt's readily decomposable nature when heated to absorb the heat generated during the reaction. This allows for a uniform distribution of the thermal field during the reaction, preventing local overheating that could alter the lithium tungstate's morphology. Nanoscale cubic lithium tungstate can be prepared through a solid-phase reaction at room temperature. Compared to conventional high-temperature solid-phase methods, the preparation method provided in this disclosure does not require high temperatures, significantly reduces energy consumption, and is suitable for industrial mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] 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.

[0040] FIG1 is an electron microscope image of lithium tungstate prepared in Example and Comparative Example;

[0041] FIG2 is an XRD pattern of lithium tungstate prepared in Example 1;

[0042] FIG3 is a charge and discharge curve diagram of the positive electrode materials prepared in Example 1 and Comparative Example 1;

[0043] FIG4 is a rate performance curve diagram of the positive electrode materials prepared in Example 1 and Comparative Example 1;

[0044] FIG5 is a cycle performance curve diagram of the positive electrode materials prepared in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0045] 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.

[0046] 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.

[0047] The present disclosure provides a method for preparing lithium tungstate, comprising: preparing lithium tungstate by mixing lithium hydroxide, a tungsten source, and an ammonium salt, using a solid phase method. Specifically, the method comprises the following steps:

[0048] S1. Ingredients

[0049] Weigh lithium hydroxide, tungsten source and ammonium salt separately and set aside.

[0050] In some embodiments, the lithium hydroxide may be LiOH·H2O, but is not limited thereto. The tungsten source is selected from at least one of WO3 and H2WO4, and may be any one or more of the above. All of the above raw materials are suitable as tungsten sources and can react with lithium hydroxide.

[0051] Furthermore, the decomposition temperature of the ammonium salt is less than 200° C. During the mixing reaction, the ammonium salt decomposes due to heat. Since the decomposition absorbs heat, the thermal field distribution during the mixing process can be uniform, which can effectively prevent local overheating from causing changes in the morphology of lithium tungstate.

[0052] In some embodiments, the ammonium salt is selected from at least one of ammonium bicarbonate, ammonium carbonate and ammonium acetate, and can be any one or more of the above, preferably ammonium bicarbonate. The gas generated during the decomposition process can be discharged without affecting the composition of the product.

[0053] In some embodiments, the mass ratio of the ammonium salt to the total mass of the lithium hydroxide and the tungsten source is (0.1-0.5):100. The amount of the ammonium salt is preferably controlled within the above range to maintain a uniform distribution of the thermal field. Specifically, the mass ratio of the ammonium salt to the total mass of the lithium hydroxide and the tungsten source can be 0.1:100, 0.2:100, 0.3:100, 0.4:100, 0.5:100, etc.

[0054] In some embodiments, the amount of lithium hydroxide and tungsten source is controlled to achieve a molar ratio of lithium to tungsten of (2.0-2.2):1. Theoretically, the molar ratio of lithium to tungsten in the raw materials for preparing lithium tungstate (Li2WO4) is 2:1. A slight excess of lithium can be used to ensure a sufficient reaction. Specifically, the molar ratio of lithium to tungsten can be 2.0:1, 2.1:1, 2.2:1, etc.

[0055] S2, ball milling

[0056] The lithium hydroxide, tungsten source and ammonium salt are mixed and ball-milled, and a solid phase reaction is carried out during the ball-milling process, and the reaction uniformity is good.

[0057] In some embodiments, during the ball milling process, the ball-to-material ratio is controlled to be (0.8-1.2):1, preferably (0.9-1.1):1; and the ball milling time is controlled to be 3 min-20 min, preferably 5 min-10 min. Further controlling the ball-to-material ratio and ball milling time can further ensure that the morphology of the lithium tungstate product presents a uniform cubic phase. Excessive ball-to-material ratio and excessively long ball milling time can cause local overheating, resulting in changes in the morphology of the generated lithium tungstate.

[0058] Specifically, the ball-to-material ratio can be 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, etc., and the ball milling time can be 3 min, 5 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, etc.

[0059] Furthermore, ball milling is performed at room temperature, meaning 15°C to 30°C, without temperature control. The volume of the mixed raw materials is controlled to account for 10% to 50% of the volume of the ball mill. Due to the generation of gas during the reaction, excessive addition of mixed raw materials is not recommended. This can lead to excessive reaction pressure, which is detrimental to obtaining a uniform product.

[0060] Specifically, the volume of the mixed raw materials accounts for 10%, 20%, 30%, 40%, 50%, etc. of the volume of the ball mill.

[0061] S3, post-processing

[0062] After ball milling, drying and crushing are performed to obtain a cubic phase lithium tungstate material with good dispersion. If it is not crushed, it will be detrimental to subsequent uniform coating and the electrochemical performance of the positive electrode material after coating.

[0063] In some embodiments, the drying temperature is controlled to be 50° C. to 100° C., and the drying time is 4 hours to 24 hours, and moisture on the surface of the particles is removed by drying. Specifically, the drying temperature can be 50° C., 60° C., 70° C., 80° C., 90° C., 100° C., etc., and the drying time can be 4 hours, 5 hours, 10 hours, 15 hours, 20 hours, 24 hours, etc.

[0064] In some embodiments, the particle size D50 after pulverization is controlled to be 2 μm-10 μm. This particle size range can ensure both processability and the dispersion required for uniform coating. Specifically, the particle size D50 after pulverization can be 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, etc.

[0065] In some embodiments, the pulverization method is selected from at least one of Chinese herbal medicine pulverization and air flow pulverization. The pulverization method can improve the dispersibility of the product. The Chinese herbal medicine pulverization can be performed using a conventional Chinese herbal medicine pulverizer; the air flow pulverization can be performed using a conventional air flow pulverizer.

[0066] The disclosed embodiments also provide a lithium tungstate, which is prepared by the above-mentioned preparation method and has the advantages of low preparation cost and easy industrial production.

[0067] In some embodiments, the particle size of lithium tungstate is 2 μm-10 μm and is a cubic phase particle, which is convenient for coating the positive electrode material substrate and can significantly improve the electrochemical performance of the positive electrode material.

[0068] The embodiments of the present disclosure also provide a method for preparing a positive electrode material, comprising: coating a positive electrode material substrate with the lithium tungstate prepared according to the above embodiment. The lithium tungstate provided by the present disclosure has better coating uniformity, and the obtained modified positive electrode material has better electrochemical properties.

[0069] In some embodiments, lithium tungstate and a positive electrode material substrate may be mixed and sintered to form a surface coating, wherein the positive electrode material substrate may be lithium nickel cobalt manganese oxide, and the capacity and cycle stability of the coated lithium nickel cobalt manganese oxide material are improved.

[0070] In some embodiments, the coating amount of lithium tungstate is controlled to be between 500ppm and 2000ppm. Within this range, the coated positive electrode material has better electrochemical performance. Specifically, the coating amount of lithium tungstate can be 500ppm, 800ppm, 1000ppm, 1200ppm, 1500ppm, 1800ppm, 2000ppm, etc. The coating amount of lithium tungstate refers to the mass ratio of the tungsten element in the lithium tungstate to the positive electrode material substrate.

[0071] In some embodiments, the sintering temperature is 550°C-700°C and the sintering time is 4 hours-8 hours to uniformly coat the surface of the material with lithium tungstate. Specifically, the sintering temperature can be 550°C, 600°C, 650°C, 700°C, etc.; and the sintering time can be 4 hours, 6 hours, 8 hours, etc.

[0072] In some embodiments, in lithium nickel cobalt manganese oxide, the nickel content in the total transition metal content is greater than 90% by mass, that is, at least one NCM is selected from the group consisting of NCMs having a nickel content greater than 90%.

[0073] The disclosed embodiments also provide a positive electrode material prepared by the above-mentioned preparation method. The surface of the positive electrode material is evenly coated with lithium tungstate material, which isolates the positive electrode material from direct corrosion by the electrolyte, thereby improving both capacity and cycle stability.

[0074] It should be noted that after the positive electrode substrate is coated with the lithium tungstate prepared in the embodiment of the present disclosure, the capacity is basically unchanged and even increases, and the cycle performance is significantly improved. Compared with other morphologies of lithium tungstate, the coating has better electrochemical performance.

[0075] It should be added that in the prior art, the positive electrode material is directly coated with the tungsten source to form lithium tungstate in situ. Since the formation mechanism of lithium tungstate is mainly the reaction between residual lithium and tungsten source, for the consideration of mixing effect, the mixing time parameter is generally too large, and the morphology and structure of the generated lithium tungstate are different from those of the lithium tungstate synthesized in the present disclosure (see the comparative example for details). Obviously, the nano-scale particles prepared in the embodiment of the present disclosure will have a better coating effect.

[0076] The embodiments of the present disclosure further provide a lithium-ion battery, comprising the above-mentioned positive electrode material, wherein the electrochemical performance of the lithium-ion battery is significantly improved by optimizing the positive electrode material.

[0077] The embodiments of the present disclosure further provide an electrical device, including the lithium-ion battery described above, and may also include electrical appliances, etc., with no limitation to the specific types.

[0078] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0079] Example 1

[0080] This embodiment provides a method for preparing lithium tungstate (Li2WO4), comprising the following steps:

[0081] (1) LiOH·H2O and WO3 were weighed in a molar ratio of 2:1; then ammonium bicarbonate (NH4HCO3) was weighed, and the mass ratio of the weighed ammonium bicarbonate to the total amount of LiOH·H2O and WO3 was 0.4:100.

[0082] (2) The sample weighed in step (1) was placed in a ball mill for mixing and reaction. The sample volume was 15% of the volume of the ball mill, the ball-to-material mass ratio was 1.1, and the reaction time was 5 min.

[0083] (3) The material after the reaction in step (2) was vacuum dried for 8 h at a drying temperature of 80°C.

[0084] (4) The material in step (3) is crushed by a Chinese herbal medicine grinder to obtain a cubic lithium tungstate material with good dispersibility and a particle size D50 of 5±0.5 μm.

[0085] This embodiment also provides a method for preparing a ternary positive electrode material, comprising the following steps:

[0086] (1) The lithium tungstate and lithium nickel cobalt manganese oxide (LiNi 0.94 Co 0.03 Mn 0.03 O2, the same below) was weighed in proportion, wherein the amount of lithium tungstate was 500ppm, and the lithium nickel cobalt manganese oxide used was provided by Guangdong Brunp Recycling Technology Co., Ltd.

[0087] (2) The sample weighed in step (1) is mixed evenly so that the lithium tungstate is evenly coated on the surface of the lithium nickel cobalt manganese oxide material.

[0088] (3) The sample mixed in step (2) was sintered at a temperature of 600° C. for 6 h.

[0089] Example 2:

[0090] This embodiment provides a method for preparing lithium tungstate (Li2WO4), comprising the following steps:

[0091] (1) LiOH·H2O and WO3 were weighed in a molar ratio of 2:1, and then ammonium bicarbonate (NH4HCO3) was weighed. The mass ratio of the weighed ammonium bicarbonate to the total amount of LiOH·H2O and WO3 was 0.2:100.

[0092] (2) The sample weighed in step (1) was placed in a ball mill for mixing and reaction. The sample volume was 25% of the volume of the ball mill, the ball-to-material mass ratio was 1.0, and the reaction time was 10 min.

[0093] (3) The material after the reaction in step (2) was vacuum dried for 8 h at a temperature of 80°C.

[0094] (4) After the material in step (3) is subjected to air flow pulverization, a cubic lithium tungstate material with good dispersion can be obtained, and the particle size D50 is 5±0.5 μm.

[0095] This embodiment also provides a method for preparing a ternary cathode material, comprising the following steps:

[0096] (1) The lithium tungstate and lithium nickel cobalt manganese oxide crushed in this example were weighed in proportion, wherein the amount of lithium tungstate was 1000 ppm. The lithium nickel cobalt manganese oxide used was provided by Guangdong Brunp Recycling Technology Co., Ltd.

[0097] (2) The sample weighed in step (1) is mixed evenly so that the lithium tungstate is evenly coated on the surface of the lithium nickel cobalt manganese oxide material.

[0098] (3) The sample mixed in step (2) was sintered at a temperature of 600° C. for 8 h.

[0099] Example 3

[0100] This embodiment provides a method for preparing lithium tungstate (Li2WO4), comprising the following steps:

[0101] (1) LiOH·H2O and WO3 were weighed in a molar ratio of 2:1; then ammonium bicarbonate (NH4HCO3) was weighed, and the mass ratio of the weighed ammonium bicarbonate to the total amount of LiOH·H2O and WO3 was 0.15:100.

[0102] (2) The sample weighed in step (1) was placed in a ball mill for mixing and reaction. The sample volume was 30% of the volume of the ball mill, the ball-to-material mass ratio was 0.8, and the reaction time was 15 min.

[0103] (3) The material after the reaction in step (2) was vacuum dried for 4 h at a temperature of 90°C.

[0104] (4) The material in step (3) is crushed by a Chinese herbal medicine grinder to obtain a cubic lithium tungstate material with good dispersibility and a particle size D50 of 5±0.5 μm.

[0105] This embodiment also provides a method for preparing a ternary cathode material, comprising the following steps:

[0106] (1) The lithium tungstate and lithium nickel cobalt manganese oxide crushed in this example were weighed in proportion, wherein the amount of lithium tungstate was 800 ppm. The lithium nickel cobalt manganese oxide used was provided by Guangdong Brunp Recycling Technology Co., Ltd.

[0107] (2) The sample weighed in step (1) is mixed evenly so that the lithium tungstate is evenly coated on the surface of the lithium nickel cobalt manganese oxide material.

[0108] (3) The sample mixed in step (2) was sintered at a temperature of 600° C. for 7 h.

[0109] Example 4

[0110] This embodiment provides a method for preparing lithium tungstate (Li2WO4). The only difference from Example 1 is that when preparing lithium tungstate, the amount of ammonium bicarbonate used is different, and the mass ratio of the amount of ammonium bicarbonate to the total amount of LiOH·H2O and WO3 is 0.05:100.

[0111] This embodiment also provides a method for preparing a ternary positive electrode material, which is prepared using the pulverized lithium tungstate and lithium nickel cobalt manganese oxide of this embodiment. The specific steps are as described in Example 1.

[0112] Example 5

[0113] This embodiment provides a method for preparing lithium tungstate (Li2WO4). The only difference from Example 1 is that when preparing lithium tungstate, the amount of ammonium bicarbonate used is different, and the mass ratio of the amount of ammonium bicarbonate to the total amount of LiOH·H2O and WO3 is 0.8:100.

[0114] This embodiment also provides a method for preparing a ternary positive electrode material, which is prepared using the pulverized lithium tungstate and lithium nickel cobalt manganese oxide of this embodiment. The specific steps are as described in Example 1.

[0115] Example 6

[0116] This embodiment provides a method for preparing lithium tungstate (Li2WO4), which differs from Example 1 only in that the ball milling time is 3 minutes when preparing lithium tungstate.

[0117] This embodiment also provides a method for preparing a ternary positive electrode material, which is prepared using the pulverized lithium tungstate and lithium nickel cobalt manganese oxide of this embodiment. The specific steps are as described in Example 1.

[0118] Example 7

[0119] This embodiment provides a method for preparing lithium tungstate (Li2WO4), which differs from Example 1 only in that the ball milling time is 20 minutes when preparing lithium tungstate.

[0120] This embodiment also provides a method for preparing a ternary positive electrode material, which is prepared using the pulverized lithium tungstate and lithium nickel cobalt manganese oxide of this embodiment. The specific steps are as described in Example 1.

[0121] Example 8

[0122] This embodiment provides a method for preparing lithium tungstate (Li2WO4), which differs from Example 1 only in that ammonium bicarbonate is replaced by an equal amount of ammonium carbonate.

[0123] This embodiment also provides a method for preparing a ternary positive electrode material, which is prepared using the pulverized lithium tungstate and lithium nickel cobalt manganese oxide of this embodiment. The specific steps are as described in Example 1.

[0124] Comparative Example 1

[0125] The comparative example is lithium nickel cobalt manganese oxide (LiNi 0.94 Co 0.03 Mn 0.03 O2), but without coating the lithium tungstate synthesized in the embodiment of the present disclosure.

[0126] Comparative Example 2

[0127] This comparative example provides a method for preparing lithium tungstate (Li2WO4), which differs from Example 1 only in that ammonium bicarbonate is not added during the preparation of lithium tungstate.

[0128] This comparative example also provides a method for preparing a ternary positive electrode material by using the pulverized lithium tungstate and lithium nickel cobalt manganese oxide (LiNi 0.94 Co 0.03 Mn 0.03 O2) was prepared, and the specific steps were as shown in Example 1.

[0129] Comparative Example 3

[0130] This comparative example provides an existing method for preparing lithium tungstate (Li2WO4), which is prepared by a liquid phase method. The specific steps are as follows:

[0131] (1) Weigh LiOH·H2O and WO3 in a molar ratio of 2:1;

[0132] (2) Pour the sample weighed in step (1) into ethanol that can cover the sample and stir to react;

[0133] (3) The material after the reaction in step (2) was vacuum dried for 8 hours at 80°C;

[0134] (4) The material in step (3) is crushed using Chinese herbal medicine, and the particle size D50 is 5±0.5 μm.

[0135] This comparative example also provides a method for preparing a ternary positive electrode material by using the pulverized lithium tungstate and lithium nickel cobalt manganese oxide (LiNi 0.94 Co 0.03 Mn 0.03 O2) was prepared, and the specific steps were as shown in Example 1.

[0136] Test Example 1

[0137] The SEM images of lithium tungstate prepared in the test examples and comparative examples are shown in Figure 1. It can be seen that the lithium tungstate prepared in this example presents a cubic phase. As the amount of ammonium bicarbonate added increases, the thermal field distribution during the reaction becomes more uniform, and the morphological uniformity of the prepared lithium tungstate is improved. When the mass ratio of ammonium bicarbonate to the total amount of LiOH·H2O and WO3 is 0.4:100, the presence of impurities is almost invisible from the electron microscopy results; however, as the addition amount increases further, the decomposition gas causes excessive internal pressure, resulting in a significant change in morphology. The presence of impurities in the circled areas of Examples 2 and 4 in Figure 1 indicates that different amounts of ammonium bicarbonate added have a certain impact on the resulting products.

[0138] The XRD pattern of lithium tungstate prepared in Test Example 1 was compared with the standard card (PDF#35-0826), and the results are shown in Figure 2. It can be seen that the lithium tungstate prepared in this example was confirmed to have a cubic phase structure through PDF card retrieval and comparison.

[0139] Test 2

[0140] The performance of the positive electrode materials prepared in the examples and comparative examples was tested. The results are shown in Table 1. The performance comparisons of Example 1 and Comparative Example 1 are shown in Figures 3, 4 and 5.

[0141] Test method:

[0142] (1) Assembling into a lithium-ion button half-cell: using the positive electrode materials provided in the examples and comparative examples, with PVDF as a binder and activated carbon as a conductive agent, the mass ratio of the three being 90:5:5, and N-methylpyrrolidone as a solvent; first, stirring the activated carbon, PVDF, and N-methylpyrrolidone into a slurry, then mixing and stirring with the positive electrode material, and evenly coating it on an aluminum foil using a coating machine, drying and rolling, and punching out to obtain a positive electrode sheet; finally, in a glove box, assembling into a button half-cell in the order of a negative electrode shell (lithium sheet), nickel foam, lithium sheet, diaphragm (PP or PE), positive electrode sheet, and positive electrode shell, the electrolyte used mainly comprises LiPF6 / EC / DMC and other additives.

[0143] (2) Test conditions: The first charge and discharge rate is 0.1C, and the cycle test rate is 1C.

[0144] Table 1 Summary of Examples and Comparative Examples

[0145] From the comparison of the data of the embodiment and the comparative example, it can be seen that after the nano-cubic phase lithium tungstate coating material synthesized in the embodiment of the present invention, the capacity, cycle and rate performance of lithium nickel cobalt manganese oxide are improved; and compared with other comparative examples coated with lithium tungstate, it has obvious advantages in both capacity and cycle. This is mainly due to the fact that the nano-scale morphology of lithium tungstate can be more evenly coated on the surface of the material after crushing, which is conducive to the embedding and extraction of lithium ions and effectively prevents the erosion of the electrolyte.

[0146] As can be seen from Table 1, although the cycle performance of Comparative Example 3 is good, the first discharge capacity is significantly lower than that of the Example, and the overall performance is worse than that of the Example. When the coating amount is the same as that of Example 1, the overall performance is significantly worse than that of Example 1. Industrial Applicability

[0147] The present invention uses lithium hydroxide, a tungsten source, and an easily decomposable ammonium salt as raw materials. By utilizing the ammonium salt's readily decomposable nature upon heating, it absorbs the heat generated during the reaction, resulting in a uniform distribution of the thermal field during the reaction and preventing local overheating that could alter the lithium tungstate's morphology. Nanoscale cubic lithium tungstate can be prepared through a solid-phase reaction at room temperature. Compared to conventional high-temperature solid-phase methods, the preparation method provided by the present invention does not require high temperature conditions, significantly reduces energy consumption, and has excellent industrial applicability.

Claims

1. A method for preparing lithium tungstate, characterized in that: include: The lithium hydroxide, tungsten source and ammonium salt are mixed to prepare lithium tungstate by solid phase reaction; Wherein, the decomposition temperature of the ammonium salt is less than 200°C.

2. The preparation method according to claim 1, characterized in that: The ammonium salt is selected from at least one of ammonium bicarbonate, ammonium carbonate and ammonium acetate.

3. The preparation method according to claim 2, characterized in that: The ammonium salt is ammonium bicarbonate.

4. The preparation method according to any one of claims 1 to 3, characterized in that The mass ratio of the amount of the ammonium salt to the total mass of the lithium hydroxide and the tungsten source is (0.1-0.5):

100.

5. The preparation method according to any one of claims 1 to 4, characterized in that: By controlling the dosage of the lithium hydroxide and the tungsten source, the molar ratio of lithium to tungsten element is (2.0-2.2):

1.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The tungsten source is selected from at least one of WO3 and H2WO4.

7. The preparation method according to any one of claims 1 to 6, characterized in that The solid phase reaction process comprises: mixing and ball milling lithium hydroxide, the tungsten source and the ammonium salt.

8. The preparation method according to claim 7, characterized in that: During the ball milling process, the ball-to-material ratio is controlled at (0.8-1.2):

1.

9. The preparation method according to claim 8, characterized in that: Control the ball-to-material ratio to (0.9-1.1):

1.

10. The preparation method according to any one of claims 7 to 9, characterized in that: The ball milling time is 3min-20min.

11. The preparation method according to claim 10, characterized in that: The ball milling time is 5min-10min.

12. The preparation method according to any one of claims 7 to 11, characterized in that: Ball milling is carried out at room temperature.

13. The preparation method according to any one of claims 7 to 12, characterized in that: The volume of the mixed raw materials is controlled to account for 10%-50% of the volume of the ball mill.

14. The preparation method according to any one of claims 7 to 13, characterized in that: Also includes: After ball milling, it is dried and pulverized.

15. The preparation method according to claim 14, characterized in that: Control the drying temperature to 50℃-100℃ and the drying time to 4h-24h.

16. The preparation method according to claim 14 or 15, characterized in that: The particle size D50 after crushing is controlled to be 2μm-10μm.

17. The preparation method according to any one of claims 14 to 16, characterized in that: The pulverizing method is selected from at least one of Chinese herbal medicine pulverizing and air flow pulverizing.

18. A lithium tungstate, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 17.

19. The lithium tungstate according to claim 18, characterized in that: The lithium tungstate has a particle size of 2 μm-10 μm and is a cubic phase particle.

20. A method for preparing a positive electrode material, characterized in that: include: The positive electrode material substrate is coated with the lithium tungstate described in claim 18 or 19.

21. The preparation method according to claim 20, characterized in that: The lithium tungstate and the positive electrode material substrate are mixed and sintered, wherein the positive electrode material substrate is lithium nickel cobalt manganese oxide.

22. The preparation method according to claim 21, characterized in that: The coating amount of lithium tungstate is controlled to be 500ppm-2000ppm.

23. The preparation method according to claim 21 or 22, characterized in that: The sintering temperature is 550°C-700°C, and the sintering time is 4h-8h.

24. The preparation method according to any one of claims 21 to 23, characterized in that: In lithium nickel cobalt manganese oxide, the nickel content accounts for more than 90% by mass of the total transition metals.

25. A positive electrode material, characterized in that It is prepared by the preparation method described in any one of claims 20 to 24.

26. A lithium ion battery, characterized in that: Comprising the positive electrode material as described in claim 25.

27. An electrical device, characterized in that: Comprising the lithium ion battery as claimed in claim 26.

Images