Lithium tungstate, its preparation method and application

Abstract

The present disclosure belongs to the technical field of lithium batteries, and specifically relates to lithium tungstate, a preparation method thereof, and an application thereof. Using lithium hydroxide, a tungsten source, and an easily decomposable ammonium salt as raw materials, and taking advantage of the property that the ammonium salt is easily decomposed by heat to absorb the heat generated during the reaction process, the thermal field distribution during the reaction process can be made uniform, preventing the morphology of lithium tungstate from changing due to local overheating. Nanoscale cubic lithium tungstate can be prepared by a solid-phase reaction at room temperature. Compared with the conventional high-temperature solid-phase method, the preparation method provided by the present disclosure does not require high-temperature conditions, and the energy consumption is significantly reduced, making it suitable for large-scale industrial production.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of lithium batteries, and more particularly, relates to lithium tungstate, a preparation method thereof, and an application thereof. Background Art

[0002] With the widespread application of new energy vehicles, higher requirements are put forward for their performance. Currently, the main problems of new energy vehicles are the battery range and lifespan issues. Improving the energy density and cycle performance of the battery is the key to solving the above technical problems. Compared with lithium iron phosphate, the ternary Li[Ni x Co y Mn (1-x-y) O 2 material as the cathode has a higher specific capacity and is more likely to meet the requirements.

[0003] For ternary materials, with the increase of nickel content, although the energy density is improved, the cycle performance will deteriorate accordingly. To solve this problem, there are mainly two mainstream solutions: (1) Using other elements to dope and replace transition metal elements or oxygen elements to improve the structural stability of the material itself. (2) Using oxides with good structural stability or metal lithium salts with fast ion conduction characteristics. Among them, the coating of metal lithium salts with fast ion conduction characteristics can not only effectively block the erosion of the electrolyte on the cathode material and inhibit the occurrence of parasitic reactions, but also block the release of lattice oxygen and inhibit the growth of the SEI film, providing a fast and stable channel for the transmission of lithium ions, which has a great improvement effect on battery capacity and cycle performance.

[0004] Coating the ternary cathode material with lithium tungstate can effectively improve the cycle stability of the battery. However, the existing synthesis methods of lithium tungstate mainly include the liquid phase method and the high-temperature solid phase method. The solidification method needs to be carried out under high-temperature conditions, with high energy consumption and difficult to achieve industrial mass production.

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

[0006] The object of the present disclosure includes providing a lithium tungstate and a preparation method thereof, aiming to prepare lithium tungstate by solid-phase reaction at room temperature.

[0007] Another object of the present disclosure includes providing a cathode material, a preparation method thereof, and an application thereof, aiming to improve the capacity and cycle performance of the material simultaneously.

[0008] To achieve the above objects of the present disclosure, the following technical solutions can be adopted:

[0009] In a first aspect, the solution provided by the present disclosure includes a preparation method of lithium tungstate, including: mixing lithium hydroxide, a tungsten source, and an ammonium salt, and preparing lithium tungstate by solid-phase reaction;

[0010] Among them, the decomposition temperature of the ammonium salt is less than 200 °C.

[0011] In some embodiments of the present disclosure, the ammonium salt is selected from at least one of ammonium bicarbonate, ammonium carbonate, and ammonium acetate.

[0012] In some embodiments of the present disclosure, the ammonium salt is ammonium bicarbonate.

[0013] In some embodiments of the present disclosure, the mass ratio of the amount of the ammonium salt to the total mass of lithium hydroxide and tungsten source is (0.1 - 0.5):100.

[0014] In some embodiments of the present disclosure, by controlling the amounts of lithium hydroxide and tungsten source, the molar ratio of lithium and tungsten elements is (2.0 - 2.2):1.

[0015] In some embodiments of the present disclosure, the tungsten source is selected from WO 3 and H 2 WO 4 and at least one of them.

[0016] In some embodiments of the present disclosure, the process of the solid-phase method reaction includes: mixing and ball-milling lithium hydroxide, tungsten source, and ammonium salt.

[0017] In some embodiments of the present disclosure, during the ball-milling process, the ball-to-material ratio is controlled to be (0.8 - 1.2):1.

[0018] In some embodiments of the present disclosure, the ball-to-material ratio is controlled to be (0.9 - 1.1):1.

[0019] In some embodiments of the present disclosure, the ball-milling time is 3 min - 20 min.

[0020] In some embodiments of the present disclosure, the ball-milling time is 5 min - 10 min.

[0021] In some embodiments of the present disclosure, the ball-milling is carried out under normal temperature conditions.

[0022] 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-milling tank.

[0023] In some embodiments of the present disclosure, it further includes: drying and pulverizing after ball-milling.

[0024] In some embodiments of the present disclosure, the drying temperature is controlled to be 50 °C - 100 °C, and the drying time is 4 h - 24 h.

[0025] In some embodiments of the present disclosure, the particle size D50 after pulverization is controlled to be 2 μm - 10 μm.

[0026] In some embodiments of the present disclosure, the pulverization method is selected from at least one of traditional Chinese medicine pulverization and air flow pulverization.

[0027] In a second aspect, the present disclosure also provides a lithium tungstate, which is prepared by the preparation method in any of the above embodiments.

[0028] In some embodiments of the present disclosure, the particle size of the lithium tungstate is 2 μm - 10 μm, and it is cubic phase particles.

[0029] In a third aspect, the present disclosure also provides a preparation method for a cathode material, including: coating the cathode material substrate with the lithium tungstate in any of the above embodiments.

[0030] In some embodiments of the present disclosure, the lithium tungstate and the cathode material substrate are mixed and sintered, wherein the cathode material substrate is lithium nickel cobalt manganese oxide.

[0031] In some embodiments of the present disclosure, the coating amount of the lithium tungstate is controlled to be 500 ppm - 2000 ppm.

[0032] In some embodiments of the present disclosure, the sintering temperature is 550 °C - 700 °C, and the sintering time is 4 h - 8 h.

[0033] In some embodiments of the present disclosure, in lithium nickel cobalt manganese oxide, the mass proportion of nickel in the total transition metals is greater than 90%.

[0034] In a fourth aspect, the present disclosure also provides a cathode material, which is prepared by the preparation method in any of the above embodiments.

[0035] In a fifth aspect, the present disclosure also provides a lithium ion battery, including the cathode material in any of the above embodiments.

[0036] In a sixth aspect, the present disclosure also provides an electrical device, including the lithium ion battery in any of the above embodiments.

[0037] Using lithium hydroxide, tungsten source and easily decomposable ammonium salt as raw materials, and utilizing the characteristic that the ammonium salt is easily decomposed by heat to absorb the heat generated during the reaction process, the thermal field distribution during the reaction process can be made uniform, preventing the change of the morphology of lithium tungstate caused by local overheating, and nano-scale cubic phase lithium tungstate can be prepared by solid-phase reaction at room temperature. Compared with the conventional high-temperature solid-phase method, the preparation method provided by the present disclosure does not require high-temperature conditions, and the energy consumption is significantly reduced, which is suitable for industrial large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show certain embodiments of the present disclosure and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0039] Figure 1 Electron micrographs of lithium tungstate prepared for the examples and comparative examples;

[0040] Figure 2 XRD pattern of lithium tungstate prepared in Example 1;

[0041] Figure 3 Charge-discharge curves of the positive electrode materials prepared in Example 1 and Comparative Example 1;

[0042] Figure 4 Rate performance curves of the positive electrode materials prepared in Example 1 and Comparative Example 1;

[0043] Figure 5 Cycling performance curves of the positive electrode materials prepared in Example 1 and Comparative Example 1. Specific Embodiments

[0044] The following will describe the implementation schemes of the present disclosure in detail in combination with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present disclosure and should not be regarded as limiting the scope of the present disclosure. For those not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0045] In the ranges disclosed in the present disclosure, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values and individual point values of each range, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0046] The embodiments of the present disclosure provide a method for preparing lithium tungstate, including: mixing lithium hydroxide, tungsten source and ammonium salt for reaction to prepare lithium tungstate, and using the solid-phase method for preparation. Specifically, it includes the following steps:

[0047] S1. Weighing

[0048] Weigh lithium hydroxide, tungsten source and ammonium salt respectively and set aside.

[0049] In some embodiments, lithium hydroxide can be LiOH·H2 O, but not limited thereto. The tungsten source is selected from WO 3 and H 2 WO 4 At least one of them can be any one or several of the above. The above raw materials are all suitable as tungsten sources and can react with lithium hydroxide.

[0050] Furthermore, the decomposition temperature of the ammonium salt is less than 200 °C. During the mixing reaction, the ammonium salt decomposes when heated. Due to the endothermic decomposition, the thermal field distribution in the mixing process can be made uniform, and it can effectively prevent the morphology of lithium tungstate from changing due to local overheating.

[0051] 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 several of the above. Preferably, it is ammonium bicarbonate. The gas generated during the decomposition can be discharged without affecting the composition of the product.

[0052] In some embodiments, the mass ratio of the amount of ammonium salt to the total mass of lithium hydroxide and tungsten source is (0.1 - 0.5):100. It is appropriate to control the amount of ammonium salt within the above range to keep the thermal field distribution uniform. Specifically, the mass ratio of the amount of ammonium salt to the total mass of lithium hydroxide and tungsten source can be 0.1:100, 0.2:100, 0.3:100, 0.4:100, 0.5:100, etc.

[0053] In some embodiments, by controlling the amounts of lithium hydroxide and tungsten source, the molar ratio of lithium and tungsten elements is (2.0 - 2.2):1. When preparing lithium tungstate (Li 2 WO 4 ), the theoretical molar ratio of lithium and tungsten elements in the raw materials is 2:1. To make the reaction proceed fully, lithium can be made slightly excessive. Specifically, the molar ratio of lithium and tungsten elements can be 2.0:1, 2.1:1, 2.2:1, etc.

[0054] S2. Ball milling and mixing

[0055] Mix lithium hydroxide, tungsten source, and ammonium salt by ball milling. During the ball milling process, a solid-phase reaction occurs, and the uniformity of the reaction is better.

[0056] In some embodiments, during the ball milling process, control the ball-to-material ratio to be (0.8 - 1.2):1, preferably (0.9 - 1.1):1; control the ball milling time to be 3 min - 20 min, preferably 5 min - 10 min. By further controlling the ball-to-material ratio and ball milling time, it is further ensured that the morphology of the lithium tungstate product presents a uniform cubic phase. Excessive ball-to-material ratio and too long ball milling time will cause local overheating and lead to changes in the morphology of the generated lithium tungstate.

[0057] 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.

[0058] Further, the ball milling is carried out under normal temperature conditions without temperature intervention. The so-called "normal temperature" refers to a temperature of 15°C - 30°C. Control the volume of the mixed raw materials to account for 10% - 50% of the volume of the ball milling tank. Since gas is generated during the reaction, too much mixed raw material should not be added, as excessive mixed raw material will lead to too high reaction pressure, which is not conducive to obtaining a product with uniform morphology.

[0059] Specifically, the volume of the mixed raw materials accounts for 10%, 20%, 30%, 40%, 50%, etc. of the volume of the ball milling tank.

[0060] S3. Post-treatment

[0061] After ball milling, drying and pulverization are carried out to obtain a lithium tungstate material with good dispersibility in the cubic phase; if not pulverized, it is not conducive to subsequent uniform coating and the electrochemical performance of the coated cathode material.

[0062] In some embodiments, control the drying temperature to be 50°C - 100°C and the drying time to be 4 h - 24 h, and remove the moisture on the particle surface through 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 h, 5 h, 10 h, 15 h, 20 h, 24 h, etc.

[0063] In some embodiments, control the D50 of the particle size after pulverization to be 2 μm - 10 μm. This particle size range can ensure the processing performance while also ensuring the dispersibility required for uniform coating. Specifically, the D50 of the particle size after pulverization can be 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, etc.

[0064] In some embodiments, the pulverization method is selected from at least one of Chinese herbal medicine pulverization and air flow pulverization. Using the above methods for pulverization can make the dispersibility of the product better. Chinese herbal medicine pulverization can be processed using a general Chinese herbal medicine pulverizer; air flow pulverization can be processed using a general air flow pulverizer.

[0065] The embodiments of the present disclosure also provide a lithium tungstate, which is prepared by the above preparation method and has the advantages of low preparation cost and easy industrial production.

[0066] In some embodiments, the particle size of lithium tungstate is 2 μm - 10 μm and it is cubic phase particles, which is convenient for coating the cathode material substrate and can significantly improve the electrochemical performance of the cathode material.

[0067] The embodiments of the present disclosure also provide a method for preparing a cathode material, including: coating a cathode material substrate with lithium tungstate prepared by the above-mentioned implementation manner. The lithium tungstate provided by the present disclosure has better coating uniformity, and the obtained modified cathode material has more excellent electrochemical performance.

[0068] In some embodiments, lithium tungstate and a cathode material substrate can be mixed and sintered to form a surface coating. Among them, the cathode material substrate can be lithium nickel cobalt manganese oxide, and the capacity and cycle stability of the coated lithium nickel cobalt manganese oxide material are both improved.

[0069] In some embodiments, the coating amount of lithium tungstate is controlled to be 500 ppm - 2000 ppm. Within this range, the coated cathode material has more excellent electrochemical performance. Specifically, the coating amount of lithium tungstate can be 500 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1500 ppm, 1800 ppm, 2000 ppm, etc. The coating amount of lithium tungstate refers to the mass ratio of tungsten element in lithium tungstate to the cathode material substrate.

[0070] In some embodiments, the sintering temperature is 550 °C - 700 °C, and the sintering time is 4 h - 8 h, so that lithium tungstate is uniformly coated on the material surface. Specifically, the sintering temperature can be 550 °C, 600 °C, 650 °C, 700 °C, etc.; the sintering time can be 4 h, 6 h, 8 h, etc.

[0071] In some embodiments, in lithium nickel cobalt manganese oxide, the mass proportion of nickel in the total transition metals is greater than 90%, that is, at least one selected from NCM with a nickel proportion greater than 90%.

[0072] The embodiments of the present disclosure also provide a cathode material prepared by the above-mentioned preparation method. The surface of this cathode material is uniformly coated with lithium tungstate material, which isolates the direct erosion of the electrolyte on the cathode material, and improves both the capacity and cycle stability.

[0073] It should be added that after the cathode material substrate is coated with the lithium tungstate prepared in the embodiments of the present disclosure, the capacity basically does not decrease, and even increases, and the cycle performance is significantly improved. Compared with the coating of lithium tungstate with other morphologies, it has better electrochemical performance.

[0074] It should be added that in the prior art process of directly coating a tungsten source on a cathode material to in-situ form lithium tungstate, due to the formation mechanism of lithium tungstate mainly being the reaction of residual lithium and the tungsten source, generally the mixing time parameter is too large considering the mixing effect. The morphology and structure of the generated lithium tungstate are different from those of the lithium tungstate synthesized in the present disclosure (specifically, see the comparative example). Obviously, the nanoscale particles prepared in the embodiments of the present disclosure will have a better coating effect.

[0075] Embodiments of the present disclosure also provide a lithium-ion battery, including the above-mentioned positive electrode material. Through the optimization of the positive electrode material, the electrochemical performance of the lithium-ion battery is significantly improved.

[0076] Embodiments of the present disclosure also provide an electrical device, including the above-mentioned lithium-ion battery, and may also include electrical appliances, etc., and the specific types are not limited.

[0077] The following further describes the features and performance of the present disclosure in detail with reference to embodiments.

[0078] Example 1

[0079] This example provides a preparation method of lithium tungstate (Li 2 WO 4 ), including the following steps:

[0080] (1) Weigh LiOH·H 2 O and WO 3 in a molar ratio of 2:1; then weigh ammonium bicarbonate (NH 4 HCO 3 ). The amount of ammonium bicarbonate weighed is in a mass ratio of 0.4:100 to the total amount of LiOH·H 2 O and WO 3 .

[0081] (2) Place the samples weighed in step (1) in a ball mill jar for mixing reaction. The volume of the samples is 15% of the volume of the ball mill jar, the ball-to-material mass ratio is 1.1, and the time is 5 min.

[0082] (3) Vacuum-dry the materials after the reaction in step (2) for 8 h, and the drying temperature is 80 °C.

[0083] (4) After pulverizing the materials in step (3) with a Chinese herbal medicine pulverizer, a cubic-phase lithium tungstate material with good dispersibility can be obtained, and the particle size D50 is 5 ± 0.5 μm.

[0084] This example also provides a preparation method of a ternary positive electrode material, including the following steps:

[0085] (1) Weigh the pulverized lithium tungstate in this example and lithium nickel cobalt manganese oxide (LiNi 0.94 Co 0.03 Mn 0.03 O 2 , the same below) in proportion. The amount of lithium tungstate is 500 ppm, and the used lithium nickel cobalt manganese oxide is provided by Guangdong Bump Recycling Technology Co., Ltd.

[0086] (2) Mix the samples weighed in step (1) evenly so that the lithium tungstate is evenly coated on the surface of the lithium nickel cobalt manganese oxide material.

[0087] (3) Sinter the mixed sample in step (2) at a sintering temperature of 600 °C for 6 h.

[0088] Example 2:

[0089] This example provides a preparation method of lithium tungstate (Li 2 WO 4 ), which includes the following steps:

[0090] (1) Weigh LiOH·H 2 O and WO 3 in a molar ratio of 2:1, and then weigh ammonium bicarbonate (NH 4 HCO 3 ). The amount of ammonium bicarbonate weighed is in a mass ratio of 0.2:100 to the total amount of LiOH·H 2 O and WO 3 .

[0091] (2) Place the samples weighed in step (1) in a ball milling tank for mixing reaction. The sample volume is 25% of the ball milling tank volume, the ball-to-material mass ratio is 1.0, and the time is 10 min.

[0092] (3) Vacuum dry the materials after the reaction in step (2) for 8 h at a temperature of 80 °C.

[0093] (4) After airflow pulverization of the materials in step (3), a cubic lithium tungstate material with good dispersibility can be obtained, and the particle size D50 is 5 ± 0.5 μm.

[0094] This example also provides a preparation method of a ternary cathode material, which includes the following steps:

[0095] (1) Weigh the pulverized lithium tungstate and lithium nickel cobalt manganese oxide in this example in proportion, where the amount of lithium tungstate is 1000 ppm, and the used lithium nickel cobalt manganese oxide is provided by Guangdong Bump Recycling Technology Co., Ltd.

[0096] (2) Mix the samples weighed in step (1) evenly so that the lithium tungstate is uniformly coated on the surface of the lithium nickel cobalt manganese oxide material.

[0097] (3) Sinter the mixed sample in step (2) at a sintering temperature of 600 °C for 8 h.

[0098] Example 3

[0099] This example provides a preparation method of lithium tungstate (Li 2 WO 4 ), which includes the following steps:

[0100] (1) Weigh LiOH·H 2 O and WO 3 in a molar ratio of 2:1; then weigh ammonium bicarbonate (NH 4 HCO 3 ). The amount of ammonium bicarbonate weighed is in a mass ratio of 0.15:100 to the total amount of LiOH·H 2 O and WO 3 .

[0101] (2) Place the samples weighed in step (1) in a ball milling jar for mixing and reaction. The sample volume is 30% of the ball milling jar volume, the ball-to-material mass ratio is 0.8, and the time is 15 min.

[0102] (3) Vacuum dry the materials after the reaction in step (2) for 4 h at a temperature of 90 °C.

[0103] (4) After pulverizing the materials in step (3) with a Chinese herbal medicine pulverizer, a lithium tungstate material with good dispersibility in cubic phase can be obtained, and the particle size D50 is 5 ± 0.5 μm.

[0104] This example also provides a preparation method for a ternary cathode material, including the following steps:

[0105] (1) Weigh the pulverized lithium tungstate and lithium nickel cobalt manganese oxide in this example in proportion. The amount of lithium tungstate is 800 ppm, and the lithium nickel cobalt manganese oxide used is provided by Guangdong Bump Recycling Technology Co., Ltd.

[0106] (2) Mix the samples weighed in step (1) evenly so that the lithium tungstate is uniformly coated on the surface of the lithium nickel cobalt manganese oxide material.

[0107] (3) Sinter the evenly mixed samples in step (2) at a sintering temperature of 600 °C for 7 h.

[0108] Example 4

[0109] This example provides a preparation method for lithium tungstate (Li 2 WO 4 ), which is only different from Example 1 in that: when preparing lithium tungstate, the dosage of ammonium bicarbonate is different, and the mass ratio of the amount of ammonium bicarbonate to the total amount of LiOH·H 2 O and WO 3 is 0.05:100.

[0110] This example also provides a preparation method for a ternary cathode material, which is prepared by using the pulverized lithium tungstate in this example and lithium nickel cobalt manganese oxide. The specific steps refer to Example 1.

[0111] Example 5

[0112] This embodiment provides a preparation method of lithium tungstate (Li 2 WO 4 ), which is only different from that of Embodiment 1 in that: when preparing lithium tungstate, the dosage of ammonium bicarbonate is different, and the mass ratio of the amount of ammonium bicarbonate to the total amount of LiOH·H 2 O and WO 3 is 0.8:100.

[0113] This embodiment also provides a preparation method of a ternary cathode material, which is prepared by using the lithium tungstate pulverized in this embodiment and lithium nickel cobalt manganate, and the specific steps refer to Embodiment 1.

[0114] Example 6

[0115] This embodiment provides a preparation method of lithium tungstate (Li 2 WO 4 ), which is only different from that of Embodiment 1 in that: when preparing lithium tungstate, the ball milling time is 3 min.

[0116] This embodiment also provides a preparation method of a ternary cathode material, which is prepared by using the lithium tungstate pulverized in this embodiment and lithium nickel cobalt manganate, and the specific steps refer to Embodiment 1.

[0117] Example 7

[0118] This embodiment provides a preparation method of lithium tungstate (Li 2 WO 4 ), which is only different from that of Embodiment 1 in that: when preparing lithium tungstate, the ball milling time is 20 min.

[0119] This embodiment also provides a preparation method of a ternary cathode material, which is prepared by using the lithium tungstate pulverized in this embodiment and lithium nickel cobalt manganate, and the specific steps refer to Embodiment 1.

[0120] Example 8

[0121] This embodiment provides a preparation method of lithium tungstate (Li 2 WO 4 ), which is only different from that of Embodiment 1 in that: ammonium bicarbonate is replaced with an equal amount of ammonium carbonate.

[0122] This embodiment also provides a preparation method of a ternary cathode material, which is prepared by using the lithium tungstate pulverized in this embodiment and lithium nickel cobalt manganate, and the specific steps refer to Embodiment 1.

[0123] Comparative Example 1

[0124] The comparative example is lithium nickel cobalt manganate (LiNi 0.94 Co 0.03 Mn 0.03 O provided by Guangdong Bump Recycling Technology Co., Ltd.2 ), but without coating the lithium tungstate synthesized in the embodiments of the present disclosure.

[0125] Comparative Example 2

[0126] This comparative example provides a preparation method of lithium tungstate (Li 2 WO 4 ), and the difference from Example 1 is only that: when preparing lithium tungstate, ammonium bicarbonate is not added.

[0127] This comparative example also provides a preparation method of a ternary cathode material, using the lithium tungstate pulverized in this comparative example and lithium nickel cobalt manganese oxide (LiNi 0.94 Co 0.03 Mn 0.03 O 2 ) for preparation, and the specific steps refer to Example 1.

[0128] Comparative Example 3

[0129] This comparative example provides a preparation method of an existing lithium tungstate (Li 2 WO 4 ), which is prepared by a liquid phase method, and the specific steps are as follows:

[0130] (1) Weigh LiOH·H 2 O and WO 3 in a molar ratio of 2:1;

[0131] (2) Pour the sample weighed in step (1) into ethanol that can submerge the weighed sample and stir to react;

[0132] (3) Vacuum dry the material after the reaction in step (2) for 8 h at a temperature of 80 °C;

[0133] (4) Pulverize the material in step (3) using Chinese herbal medicine, and the particle size D50 is 5 ± 0.5 μm.

[0134] This comparative example also provides a preparation method of a ternary cathode material, using the lithium tungstate pulverized in this comparative example and lithium nickel cobalt manganese oxide (LiNi 0.94 Co 0.03 Mn 0.03 O 2 ) for preparation, and the specific steps refer to Example 1.

[0135] Test Example 1

[0136] Test the SEM images of the lithium tungstate prepared in the examples and comparative examples, and the results are as Figure 1As shown, it can be seen that the lithium tungstate prepared in this embodiment is in a cubic phase. As the amount of ammonium bicarbonate added increases, the thermal field distribution during the reaction becomes more uniform, and the morphology uniformity of the prepared lithium tungstate is better. When the mass ratio of the amount of ammonium bicarbonate to the total amount of LiOH·H 2 O and WO 3 is 0.4:100, almost no impurity phase can be seen from the electron microscopy results; however, as the addition amount further increases, the gas generated by decomposition causes excessive internal pressure, resulting in a great change in morphology. Figure 1 There are impurity phases in the circled areas of Example 2 and Example 4 in Figure 1 , indicating that different addition amounts of ammonium bicarbonate have a certain impact on the obtained products.

[0137] The XRD pattern of the lithium tungstate prepared in Test Example 1 was tested and compared with the standard card (PDF#35-0826), and the results are as Figure 2 shown. It can be seen that the lithium tungstate prepared in this embodiment is confirmed to be in a cubic phase structure through comparison with the PDF card retrieval.

[0138] Test 2

[0139] The performance of the positive electrode materials prepared in the test examples and comparative examples was tested, and the results are shown in Table 1. The performance comparison between Example 1 and Comparative Example 1 is as Figure 3 、 Figure 4 and Figure 5 shown.

[0140] Testing method:

[0141] (1) Assembled into a lithium-ion coin half-cell: Using the positive electrode materials provided by the test examples and comparative examples, with PVDF as the binder, activated carbon as the conductive agent, and the mass ratio of the three being 90:5:5, and N-methylpyrrolidone as the solvent; first, stir the activated carbon, PVDF, and N-methylpyrrolidone into a slurry, then mix it with the positive electrode material and stir, and then uniformly coat it on the aluminum foil using a coater. After drying and rolling, punch it into a positive electrode sheet. Finally, assemble it into a coin half-cell in the glove box in the order of the negative electrode shell (lithium sheet), nickel foam, lithium sheet, separator (PP or PE), positive electrode sheet, and positive electrode shell. The main components of the electrolyte used are LiPF 6 / EC / DMC and other additives.

[0142] (2) Testing conditions: The first charge-discharge rate is 0.1C, and the cycle test rate is 1C.

[0143] Table 1 Summary of data for test examples and comparative examples

[0144]

[0145]

[0146] From the data comparison between the examples and the comparative examples, it can be seen that after synthesizing the nanoscale cubic lithium tungstate coating material in the examples of the present disclosure, the capacity, cycle performance, and rate performance of lithium nickel cobalt manganese oxide have all been improved; moreover, there are obvious advantages in both capacity and cycle compared with the comparative examples coated with other lithium tungstates. This is mainly attributed to the fact that the nanoscale lithium tungstate can be more evenly coated on the material surface after being pulverized, which is beneficial to the insertion and extraction of lithium ions and effectively prevents the erosion of the electrolyte.

[0147] As can be seen from Table 1, although Comparative Example 3 has good cycle performance, its initial discharge capacity is significantly lower than that of the example, and its comprehensive performance is worse than that of the example. Under the same coating amount as Example 1, the comprehensive performance is significantly worse than that of Example 1.

[0148] Industrial Applicability

[0149] The present disclosure uses lithium hydroxide, a tungsten source, and an easily decomposable ammonium salt as raw materials. Utilizing the characteristic that the ammonium salt is easily decomposed by heat to absorb the heat generated during the reaction process can make the thermal field distribution in the reaction process uniform, prevent the change of the morphology of lithium tungstate caused by local overheating, and can prepare nanoscale cubic lithium tungstate by solid-phase reaction at room temperature. Compared with the conventional high-temperature solid-phase method, the preparation method provided by the present disclosure does not require high-temperature conditions, and the energy consumption is significantly reduced, having very good industrial applicability.

Claims

1. A preparation method of lithium tungstate, characterized in that, comprising: mixing lithium hydroxide, a tungsten source and an ammonium salt, and preparing lithium tungstate by a solid-phase method reaction; The process of the solid-phase method reaction includes: mixing and ball-milling lithium hydroxide, the tungsten source and the ammonium salt; 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 claim 1, characterized in that, the mass ratio of the dosage of the ammonium salt to the total mass of lithium hydroxide and the tungsten source is (0.1-0.5):

100.

5. The preparation method according to claim 1, characterized in that, by controlling the dosages of lithium hydroxide and the tungsten source, the molar ratio of lithium and tungsten elements is (2.0-2.2):

1.

6. The preparation method according to claim 1, characterized in that, The tungsten source is selected from WO 3 and H 2 WO 4 and at least one of them.

7. The preparation method according to claim 1, characterized in that, during the ball-milling process, controlling the ball-to-material ratio to be (0.8-1.2):

1.

8. The preparation method according to claim 7, characterized in that, controlling the ball-to-material ratio to be (0.9-1.1):

1.

9. The preparation method according to claim 1, characterized in that, the ball-milling time is 3 min - 20 min.

10. The preparation method according to claim 9, characterized in that, the ball-milling time is 5 min - 10 min.

11. The preparation method according to claim 1, characterized in that, the ball-milling is carried out at room temperature.

12. The preparation method according to claim 1, characterized in that, controlling the volume of the mixed raw materials to account for 10% - 50% of the volume of the ball-milling tank.

13. The preparation method according to claim 1, characterized in that, further comprising: drying and pulverizing after ball-milling.

14. The preparation method according to claim 13, characterized in that, controlling the drying temperature to be 50 °C - 100 °C and the drying time to be 4 h - 24 h.

15. The preparation method according to claim 13, characterized in that, controlling the D50 of the pulverized particle size to be 2 μm - 10 μm.

16. The preparation method according to any one of claims 13 - 15, characterized in that, the pulverizing method is selected from at least one of Chinese herbal medicine pulverization and air-flow pulverization.

17. A lithium tungstate, characterized in that, it is prepared by the preparation method according to any one of claims 1 - 16.

18. The lithium tungstate according to claim 17, characterized in that, the particle size of the lithium tungstate is 2 μm - 10 μm and it is cubic-phase particles.

19. A preparation method of a cathode material, characterized in that, comprising: coating a cathode material substrate with the lithium tungstate according to claim 17 or 18.

20. The preparation method according to claim 19, characterized in that, mixing and sintering the lithium tungstate and the cathode material substrate, wherein the cathode material substrate is lithium nickel cobalt manganese oxide.

21. The preparation method according to claim 20, characterized in that, the coating amount of lithium tungstate is controlled to be 500 ppm - 2000 ppm.

22. The preparation method according to claim 20, characterized in that, the sintering temperature is 550 °C - 700 °C, and the sintering time is 4 h - 8 h.

23. The preparation method according to claim 20, characterized in that, in lithium nickel cobalt manganese oxide, the mass ratio of nickel content in the total transition metals is greater than 90%.

24. A cathode material, characterized in that, it is prepared by the preparation method described in any one of claims 19 - 23.

25. A lithium-ion battery, characterized in that, it includes the cathode material described in claim 24.

26. An electrical device, characterized in that, it includes the lithium-ion battery described in claim 25.

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