Preparation method and application of titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material

Abstract

A preparation method and application of a titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material, belonging to the field of secondary batteries, uses a high-temperature solid phase method to first synthesize a titanium niobate material, and then evenly mixes the tantalum source, titanium source, niobium source, and tungsten source required for preparing the titanium tantalate and tungsten niobium oxide materials to obtain a precursor, and evenly mixes the precursor with the synthesized titanium niobate material, and sinters in a tubular furnace to generate a titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material. The present invention prepares a titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material for the first time, utilizes the unique advantages of the heterojunction material interface, and generates electronic structure complementarity and energy band rearrangement, combined with the built-in electric field effect of the heterojunction, significantly improves the electronic conductivity and ionic conductivity of the titanium niobate material, and improves its discharge capacity, high rate performance, long cycle life and other electrochemical properties in low-temperature batteries.

Description

Technical Field

[0001] The present invention belongs to the field of secondary batteries, and specifically relates to a preparation method of a titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material and its application in a negative electrode of a low-temperature lithium-ion battery. Background Art

[0002] As an important component of new energy storage devices, lithium-ion batteries have the advantages of high energy density, high discharge voltage, and relatively long service life compared to traditional secondary batteries. They have been widely used in military and civilian energy storage appliances. Graphite is the most commonly used negative electrode material for commercial lithium-ion batteries, but the electrochemical performance of graphite negative electrodes is poor under low temperature conditions, with obvious capacity decay and poor high-rate discharge performance. It is also easy to produce lithium dendrites at low temperatures, leading to safety issues. Therefore, it is necessary to find a lithium-ion battery negative electrode material with intrinsic safety, high-rate performance, high energy density and high capacity retention rate under low temperature conditions to meet the use requirements of lithium-ion batteries under low temperature conditions.

[0003] In recent years, titanium niobate has attracted much attention as a low-temperature, high-capacity negative electrode material for lithium-ion batteries and is expected to replace lithium titanate. As a typical intercalation negative electrode material, its excellent electrochemical performance is mainly attributed to the unique structure of titanium niobate. The disordered arrangement of Nb atoms and Ti atoms occupies the center of NbO6 and TiO6 octahedra, respectively. At the same time, NbO6 octahedra and TiO6 octahedra share edges and vertices and form an open tunnel-type gap space that can accommodate the transmission of lithium ions. Due to the structure of titanium niobate, the insertion and extraction of lithium ions are relatively easy, so it has excellent rate performance. Titanium niobate not only has the advantages of conventional lithium titanate materials in terms of cycle stability and long life, but also has the advantages of Ti 3+ / Ti 4+ , Nb 4+ / Nb 5+ and Nb 3+ / Nb 4+ Compared with traditional batteries, the titanium niobate anode has a higher theoretical specific capacity (387.6 mA hg -1 , much higher than lithium titanate, and even higher than graphite negative electrode); the working potential is similar to that of lithium titanate (1.6V vs Li + / Li), which can effectively prevent the formation of lithium dendrites and the reduction and decomposition of the electrolyte, and has intrinsic safety; the unique pseudocapacitive lithium storage mechanism ensures that ion diffusion is not limited by the mass transfer process under low temperature conditions, and the high rate performance and capacity retention rate are much better than graphite negative electrode materials. However, conventional titanium niobate materials also have serious problems. The electronic conductivity and ionic conductivity of this material are relatively low, which limits its further large-scale application in high-rate and low-temperature environments. Therefore, it is urgent to invent a method that can improve the electronic conductivity and ionic conductivity of titanium niobate materials. Summary of the invention

[0004] Based on the above background technology, the present invention provides a preparation method and application of a titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material, aiming to improve the electronic conductivity and ionic conductivity of the titanium niobate material, and improve its electrochemical properties such as discharge capacity, high rate performance, and long cycle life in low-temperature batteries.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for synthesizing a titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material comprises the following steps:

[0007] Step 1: Prepare titanium niobate material by traditional high-temperature solid phase method. The synthesis method is as follows: weigh TiO2 and Nb2O5 with a molar ratio of 1:1 and disperse them in anhydrous ethanol, and use magnetic stirring or ball milling to fully mix TiO2 and Nb2O5. The stirring or ball milling time is 4 hours, and then transfer to a blast drying oven for drying. After drying, grind to obtain a powder material precursor C, transfer the powder material precursor C to a tubular furnace and calcine at 800℃~900℃ for 12-18 hours to obtain a white powder titanium niobate sample;

[0008] Step 2: Prepare titanium tantalate and tungsten niobium oxide precursor materials. The synthesis method is as follows: weigh TiO2, Ta2O5, Nb2O5, and WO3 with a molar ratio of 8:8:8:5 and disperse them in anhydrous ethanol, and use magnetic stirring or ball milling to fully mix the above substances for 6 hours, and then transfer them to a blast drying oven for drying, and grind them after drying to obtain a powder material precursor A;

[0009] Step 3: Disperse the titanium niobate powder material obtained in step 1 and the powder material precursor A obtained in step 2 in anhydrous ethanol at a mass ratio of 1:5, and fully mix the above substances by magnetic stirring or ball milling. The stirring or ball milling time is 4 hours, and then transfer to a blast drying oven for drying. After drying, grind to obtain a powder material precursor B;

[0010] Step 4: Use a high-temperature solid phase method to in-situ generate titanium tantalate / tungsten niobium oxide material on the surface of titanium niobate material to form a powder material with three-phase heterojunction structural characteristics. The synthesis method is as follows: transfer the powder material precursor B in step 3 to a vacuum tube furnace for sintering reaction at 1300℃~1400℃ for 2-4h, cool to room temperature and grind to obtain titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material;

[0011] An application of a titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material prepared by the preparation method, wherein the titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material is used as a negative electrode material in a negative electrode of a low-temperature lithium-ion battery.

[0012] Furthermore, the titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material is used as a negative electrode active material and is dispersed in a solvent with a conductive agent and a binder in a certain mass ratio to obtain a negative electrode slurry. The negative electrode slurry is coated on a negative electrode collector, dried, rolled, and punched to obtain a negative electrode sheet, and then a button battery is assembled.

[0013] Preferably, the binder is polyvinylidene fluoride (PVDF), the conductive agent is acetylene black, and the solvent is N-methylpyrrolidone (NMP). The mass ratio of negative electrode active material: conductive agent: binder is 80%:10%:10%.

[0014] Furthermore, the operating temperature range of the low-temperature lithium-ion battery is -50°C to 40°C.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1) The present invention is the first to in-situ generate titanium tantalate and tungsten niobium oxide materials on the surface of titanium niobate material to obtain a titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material. By utilizing the heterostructure formed on the surface of titanium tantalate and tungsten niobium oxide materials with the titanium niobate material, electronic structure complementarity and energy band rearrangement occur at the three-phase heterojunction to form a built-in electric field of the heterojunction, thereby improving the electronic conductivity and ionic conductivity of the titanium niobate material, and improving its electrochemical properties such as discharge capacity, high rate performance, and long cycle life in low-temperature batteries.

[0017] 2) The present invention mainly adopts a high-temperature solid phase method to synthesize materials, which has a simple preparation method, low cost, low equipment requirements, and is suitable for large-scale production.

[0018] 3) The present invention uses TiO2, Ta2O5, Nb2O5, and WO3 as raw materials for forming titanium tantalate and tungsten niobium oxide heterojunctions on the surface of titanium niobate materials. Titanium tantalate and tungsten niobium oxide are more stable forms within the synthesis temperature range set by the present invention. During the synthesis process, it can be ensured that no other forms of compounds can exist stably. In addition, the molar ratio of TiO2, Ta2O5, Nb2O5, and WO3 raw materials is controlled to be 8:8:8:5, so that the molar ratio of Ta and Nb elements in the titanium tantalate / tungsten niobium oxide heterojunction formed on the surface of the titanium niobate material is the same, and it can be ensured that no excessive reactants remain on the surface of the titanium niobate material during the synthesis process, so as to better regulate the specific composition of the three-phase heterojunction.

[0019] 4) The synthesis temperatures of the titanium tantalate and tungsten niobium oxide materials designed in the present invention are similar and can be synthesized together to promote the formation of a multiphase heterojunction interface. However, the synthesis temperature of the titanium niobate material is relatively low. The selected TiO2 and Nb2O5 raw materials can be used to synthesize titanium niobate alone at a relatively low temperature. However, under the conditions of sufficient tantalum source and tungsten source and high temperature, titanium tantalate and tungsten niobium oxide materials are mainly generated respectively. In order to avoid the inability to effectively form the titanium niobate material and form an effective heterojunction on its surface, the present invention synthesizes a stable titanium niobate material alone, and then synthesizes the titanium tantalate and tungsten niobium oxide materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a comparison chart of the rate performance of titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material and ordinary titanium niobate material at -20°C;

[0021] Figure 2 This is a comparison chart of the cycling performance of titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material and ordinary titanium niobate material at -20°C and 5C rate;

[0022] Figure 3 This is a comparison chart of the ultra-low temperature (-30℃, -40℃, -50℃) performance of titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material and ordinary titanium niobate material at 5C rate. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] A method for preparing a titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material comprises the following steps:

[0026] Step 1, weigh 0.08g of TiO2 and 0.266g of Nb2O5 and disperse them in 50ml of anhydrous ethanol, stir them magnetically for 4h, and then transfer them to a blast drying oven at 80°C for drying. After drying, grind them to obtain a powder material precursor C, transfer the powder material precursor C to a tube furnace, calcine at 850°C for 18h in an air atmosphere, with a heating rate of 5°C / min, cool them naturally to room temperature, and grind them to obtain a white powdery titanium niobate material;

[0027] Step 2: Weigh 0.256 g of TiO2, 1.414 g of Ta2O5, 0.851 g of Nb2O5, and 0.464 g of WO3, disperse them in 100 ml of anhydrous ethanol, stir them magnetically for 6 hours, and then transfer them to a blast drying oven at 80°C for drying. After drying, grind them to obtain a powder material precursor A;

[0028] Step 3, weigh 0.200 g of titanium niobate powder material and 1.000 g of powder material precursor A in 100 ml of anhydrous ethanol, stir magnetically for 4 hours, transfer to a forced air drying oven at 80° C. and dry, and grind to obtain powder material precursor B after drying;

[0029] Step 4: Transfer the powder material precursor B to a vacuum tube furnace, calcine at 1350°C for 4 hours at a heating rate of 5°C / min, cool naturally to room temperature, and grind to obtain a titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material.

[0030] The prepared titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material is used as the negative electrode active material, dispersed in N-methylpyrrolidone (NMP) solvent with a binder polyvinylidene fluoride (PVDF) and a conductive agent acetylene black in a mass ratio of 8:1:1 to obtain a negative electrode slurry, and the negative electrode slurry is coated on the negative electrode collector, dried, rolled and punched to obtain a negative electrode sheet, and then button batteries are assembled.

[0031] Example 2

[0032] The difference between the preparation of titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material in this embodiment and that in embodiment 1 is that the calcination time of the obtained powder material precursor C in the tube furnace is 16 hours. The rest is the same as in embodiment 1. The shortening of the calcination time is conducive to the reduction of industrial production costs.

[0033] Example 3

[0034] The difference between the preparation of titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material in this embodiment and that in embodiment 1 is that the calcination time of the obtained powder material precursor C in the tube furnace is 12 hours. The rest is the same as in embodiment 1, and the shortening of the calcination time is conducive to the reduction of industrial production costs.

[0035] Example 4

[0036] The difference between the preparation of titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material in this embodiment and that in embodiment 1 is that the calcination time of the obtained powder material precursor B in the tube furnace is 3 hours. The rest is the same as in embodiment 1, and the shortening of the calcination time is conducive to the reduction of industrial production costs.

[0037] Example 5

[0038] The difference between the preparation of titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material in this embodiment and that in embodiment 1 is that the calcination time of the obtained powder material precursor B in the tube furnace is 2 hours. The rest is the same as in embodiment 1. The shortening of the calcination time is conducive to the reduction of industrial production costs.

[0039] Example 6

[0040] The difference between the preparation of titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material in this embodiment and that in embodiment 1 is that the calcination temperature of the obtained powder material precursor C in the tube furnace is 900° C. The rest is the same as in embodiment 1.

[0041] Example 7

[0042] The difference between the preparation of titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material in this embodiment and that in embodiment 1 is that the calcination temperature of the obtained powder material precursor C in the tube furnace is 800° C. The rest is the same as in embodiment 1.

[0043] Example 8

[0044] The difference between the preparation of titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material in this embodiment and that in embodiment 1 is that the calcination temperature of the obtained powder material precursor B in the tube furnace is 1400° C. The rest is the same as in embodiment 1.

[0045] Example 9

[0046] The difference between the preparation of titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material in this embodiment and that in embodiment 1 is that the calcination temperature of the obtained powder material precursor B in the tube furnace is 1300° C. The rest is the same as in embodiment 1.

[0047] Comparative Example 1

[0048] The titanium niobate prepared in step 1 of Example 1 is used as the negative electrode active material, and the conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) are dispersed in N-methylpyrrolidone (NMP) solvent at a mass ratio of 8:1:1 to obtain a negative electrode slurry, and the negative electrode slurry is coated on the negative electrode collector, dried, rolled, and punched to obtain a negative electrode pole piece, and the pole piece prepared by the titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material and the pole piece prepared in this comparative example are respectively assembled into button batteries. The negative electrode pole piece prepared by this conventional titanium niobate material has low electronic conductivity and ionic conductivity, which is not conducive to the rapid transmission of lithium ions and has poor low temperature performance.

[0049] The rate performance test was carried out at -20 degrees Celsius. Figure 1As shown. Under -20℃, the rate performance of titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material is significantly better than that of ordinary titanium niobate material, and it can release more effective capacity at low temperature and high rate. The long cycle performance test was compared at -20℃ and 5C rate, as shown Figure 2 As shown. Under low temperature and high rate discharge conditions, the capacity retention rate of the titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material is as high as 94.67% after 500 cycles, which is better than the 88.13% of ordinary titanium niobate materials, and the low temperature and high rate cycle stability is good. Ultra-low temperature (-30℃, -40℃, -50℃) performance test comparison is carried out at 5C rate, as shown Figure 3 The discharge capacity and capacity retention rate of the titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material in ultra-low temperature environment are significantly higher than those of ordinary titanium niobate materials. It can be charged and discharged normally in ultra-low temperature environment and has better application potential.

[0050] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing a titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material, characterized in that: The following steps are involved: Step 1, prepare titanium niobate powder; the synthesis method of titanium niobate is: disperse TiO2 and Nb2O5 with a molar ratio of 1:1 in anhydrous ethanol and mix them thoroughly, dry and grind to obtain a powder material precursor C, and calcine the powder material precursor C to obtain titanium niobate powder, the calcination temperature is 800-900°C, and the time is 12-18h; Step 2: Disperse TiO2, Ta2O5, Nb2O5 and WO3 in a molar ratio of 8:8:8:5 in anhydrous ethanol and mix them thoroughly, dry them and grind them to obtain a powder material precursor A; Step 3: Disperse titanium niobate powder and powder material precursor A in anhydrous ethanol at a mass ratio of 1:5 and fully mix, dry and grind to obtain powder material precursor B; Step 4: Sinter the powder material precursor B at 1300° C. to 1400° C. to generate titanium tantalate / tungsten niobium oxide material on the surface of the titanium niobate material, thereby forming a titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material.

2. The preparation method according to claim 1, characterized in that: In step 1, the method of thorough mixing is magnetic stirring or ball milling.

3. The preparation method according to claim 1, characterized in that: In step 2 and step 3, the method used for sufficient mixing is magnetic stirring or ball milling.

4. The preparation method according to claim 1, characterized in that: In step 4, the sintering time is 2 to 4 hours.

5. An application of a titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material prepared by the preparation method according to any one of claims 1 to 4, characterized in that: The titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material is used as a negative electrode material in the negative electrode of a low-temperature lithium-ion battery.

6. The use according to claim 5, characterized in that: The titanium niobate / titanium tantalate / tungsten niobium oxide three-phase heterojunction material is dispersed in a solvent as a negative electrode active material with a conductive agent and a binder to obtain a negative electrode slurry, which is then coated on a negative electrode current collector, and then dried, rolled, and punched to obtain a negative electrode sheet.

7. The use according to claim 6, characterized in that: The mass ratio of the negative electrode active material: the conductive agent: the binder is 80%: 10%: 10%.

8. The use according to claim 5, characterized in that: The operating temperature range of the low-temperature lithium-ion battery is -50°C to 40°C.

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