A method for preparing titanium-iron-niobium oxide electrode

Abstract

The present invention discloses a method for preparing a titanium-iron-niobium oxide electrode, comprising the following steps: S1, mixing a titanium source, an iron source and a niobium source in proportion to obtain a suspension; S2, drying the suspension to obtain a powder and then performing a high-temperature annealing treatment; S3, performing natural cooling to obtain a titanium-iron-niobium oxide electrode material. In the oxide, the three elements of titanium, iron and niobium randomly occupy the center of the octahedron, and the octahedrons are connected by common vertices or common edges, and the space formed can reversibly embed / extract lithium ions. Compared with traditional titanium-niobium oxide, the material exhibits better rate performance and cycle performance. According to the present invention, the problem of poor electronic and ionic conductivity inherent in niobium oxide and titanium-niobium oxide is solved, and the overall electronic conductivity of the material and the diffusion rate of lithium ions can be significantly improved.

Description

Technical Field

[0001] The invention relates to the technical field of materials science, and in particular to a method for preparing a titanium-iron-niobium oxide electrode. Background Art

[0002] In today's society, pure electric vehicles (EV) and hybrid electric vehicles (HEV) are widely developed and researched due to the large amount of environmental pollution caused by traditional fuel vehicles. Among them, lithium-ion batteries (LIBs) are considered to be the most promising electrochemical energy storage systems for pure electric vehicles and hybrid electric vehicles. However, LIBs using graphite anodes cannot meet the requirements of high power density and safety in practical applications, because lithium embedded in the carbon anode will form a solid electrolyte interface (SEI) layer, resulting in irreversible initial capacity and poor rate performance. In addition, during rapid charging and discharging, lithium dendrites are easily formed, which may cause internal short circuits, greatly reducing their safety. Summary of the invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing a titanium-iron-niobium oxide electrode, which solves the problem of poor electronic and ionic conductivity inherent in niobium oxide and titanium-niobium oxide, and can significantly improve the overall electronic conductivity of the material and the diffusion rate of lithium ions. In order to achieve the above-mentioned purpose and other advantages according to the present invention, a method for preparing a titanium-iron-niobium oxide electrode is provided, comprising:

[0004] S1, titanium source, iron source and niobium source are mixed in proportion to obtain a suspension;

[0005] S2, drying the suspension to obtain a powder and then subjecting it to high temperature annealing treatment;

[0006] S3. Perform natural cooling to obtain titanium-iron-niobium oxide electrode material.

[0007] Preferably, the titanium source in step S1 can be one or more of metatitanic acid, rutile titanium dioxide, anatase titanium dioxide, P25 titanium dioxide; or a solid organic alcohol, acid or ester compound containing titanium.

[0008] Preferably, the iron source in step S1 can be one of ferric oxide, ferrous oxide, ferrous oxide, ferric chloride, ferric fluoride, ferric sulfate, ferric sulfide, ferrous sulfide, ferrous carbonate, ferric hydroxide and ferrous hydroxide.

[0009] Preferably, the niobium source in step S1 may be one of niobium oxide, niobium pentachloride, niobium pentafluoride and niobium ethoxide.

[0010] Preferably, the titanium-iron-niobium oxide is Ti x Fe y Nb z O(4x+3y+5z) / 2 To express it, the ratio is x:y=1:0.5~1:2, y:z=1:10~1:1, x:z=1:0.01~1:100.

[0011] Preferably, in step S2, the obtained suspension is placed in a 100° C. forced air drying oven and dried for 12 h, and the obtained powder is ground and then placed in a nitrogen-filled tubular furnace and calcined at 900-1400° C. for 10 h.

[0012] Preferably, in step S2, high temperature annealing is performed in an annealing atmosphere, and the annealing atmosphere is any one of air, oxygen, argon, nitrogen, helium, a mixed gas of argon and hydrogen, or a mixed gas of nitrogen and hydrogen, and the volume percentage content of hydrogen in the mixed gas is 10% to 40%.

[0013] TiFeNb 10 O 28.5-δ A method for assembling a half-cell from materials, comprising the following steps:

[0014] (1) The prepared material was mixed with 7 wt % of a binder and 8 wt % of a conductive agent, stirred evenly, coated on a copper foil, and dried in an oven at 60-80° C.;

[0015] (2) Punching the electrode into a plate with a diameter of 10 to 16 mm, drying it in a vacuum oven at 60 to 120° C. for 4 to 12 hours, and then transferring it to a glove box filled with argon;

[0016] (3) Using metallic lithium as the counter electrode, the electrolyte solvent is ethyl carbonate (EC): dimethyl carbonate (DMC) = 1:1, and the electrolyte contains 1% LiPF6 to assemble into a CR2032 button cell.

[0017] Compared with the prior art, the present invention has the following beneficial effects: the material has a sheared ReO3 type crystal structure, which ensures the structural stability of the lithium insertion / extraction process. Compared with niobium oxide and titanium niobium oxide with similar structures, trivalent iron ions promote the transformation of tetravalent titanium ions and pentavalent niobium ions to their respective reduced states, thereby generating more oxygen vacancies, improving the intrinsic electronic and ionic conductivity of the material, thereby being able to exhibit faster lithium ion insertion / extraction capabilities and more stable cycle performance. It is suitable for the application of high-power lithium-ion battery negative electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 An X-ray diffraction spectrum of titanium iron niobium oxide according to the preparation method of titanium iron niobium oxide electrode of the present invention;

[0019] Figure 2A charge and discharge curve diagram of the titanium iron niobium oxide in the potential range of 1-3V at a 1C rate according to the preparation method of the titanium iron niobium oxide electrode of the present invention;

[0020] Figure 3 A scanning electron microscope image of titanium iron niobium oxide according to the preparation method of titanium iron niobium oxide electrode of the present invention;

[0021] Figure 4 A charge and discharge curve diagram of the titanium iron niobium oxide in the potential range of 1-3V at a 1C rate according to the preparation method of the titanium iron niobium oxide electrode of the present invention;

[0022] Figure 5 This is a rate performance diagram of the titanium iron niobium oxide electrode material according to the preparation method of the titanium iron niobium oxide electrode of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Reference Figure 1-5 , a method for preparing a titanium-iron-niobium oxide electrode, comprising:

[0025] Example 1

[0026] TiFeNb 10 O 28.5-δ Synthesis, structural characterization and electrochemical performance testing of materials.

[0027] According to the preparation method of 0.01 mol TiFeNb 10 O 28.5 0.8 g of anatase titanium dioxide, 0.8 g of ferric oxide and 10.9 g of niobium pentoxide were dispersed in anhydrous ethanol in a stoichiometric ratio and transferred to a 100 mL zirconium oxide ball mill. The mixture was ball milled at a speed of 500 rpm for 5 h according to a ball-to-material ratio of 5:1 to fully mix the mixture. The obtained suspension was dried in a 70 ° C forced air drying oven for 12 h. The obtained powder was ground and placed in a muffle furnace and calcined in air at 1000 ° C for 10 h. After natural cooling, TiFeNb 10 O 28.5-δ (Since Ti and Nb are partially reduced, "δ" is subtracted after the oxygen atom in the molecular formula).

[0028] TiFeNb 10 O 28.5-δThe X-ray diffraction spectrum of the electrode material is as follows Figure 1 As shown, Figure 1 The diffraction peak of the sample belongs to the monoclinic Wadsley-Roth spatial structure (PDF#13-0317). 10 O 28.5-δ The materials are assembled into a half-cell according to the following steps: the prepared material is mixed with 7wt% of a binder (4wt% PVDF in NMP solution) and 8wt% of a conductive agent (Super P conductive carbon black), stirred evenly and coated on a copper foil, and placed in an oven to dry at 60-80°C. Then, a punch with a diameter of 10-16mm is used to punch out the pole pieces, which are placed in a vacuum oven and dried at 60-120°C for 4-12h, and then transferred to an argon-filled glove box. Metal lithium is used as the counter electrode, and the electrolyte solvent is ethyl carbonate (EC): dimethyl carbonate (DMC) = 1:1, containing 1% LiPF6. The electrolyte is assembled into a CR2032 button cell and the constant current charge and discharge performance test is carried out on the LAND battery test system (provided by Wuhan Jinnuo Electronics Co., Ltd.). The charge and discharge cut-off voltage is relative to Li / Li + The charge and discharge test at 1C rate is as follows Figure 2 As shown, the discharge capacity reaches 172 mAh g at a 1C rate (charge and discharge time is 1 h each). -1 .

[0029] Example 2

[0030] TiFe 0.1 Nb 1.9 O 7-δ Synthesis, morphology characterization and electrochemical performance testing of materials.

[0031] According to the preparation of 0.02 mol TiFe 0.1 Nb 1.9 O 7-δ 1.96 g of metatitanic acid, 0.21 g of ferric hydroxide and 10.28 g of niobium pentachloride were dispersed in water in a stoichiometric ratio. After magnetic stirring for 2 h, the obtained suspension was placed in a 100 ° C forced air drying oven and dried for 12 h. The obtained powder was ground and placed in a nitrogen-filled tubular furnace and calcined at 1300 ° C for 10 h. After natural cooling, TiFe 0.1 Nb 1.9 O 7-δ (Since Ti and Nb are partially reduced, "δ" is subtracted after the oxygen atom in the molecular formula).

[0032] TiFe 0.1 Nb 1.9 O 7-δ The scanning electron microscope image of the electrode material is as follows Figure 3The TiFe prepared in Example 2 is in the form of a block with a width of about 2-5 microns. 0.1 Nb 1.9 O 7-δ The materials were assembled into half-cells according to the steps of Example 1, and then the constant current charge and discharge performance test was carried out on the LAND battery test system (provided by Wuhan Jinnuo Electronics Co., Ltd.). The charge and discharge cut-off voltage was relative to Li / Li + The charge and discharge current density is 100mA g -1 The following charge and discharge tests are Figure 4 The discharge capacity shown reaches 205mAh g -1 . Rate performance such as Figure 5 As shown, at 5A g -1 At a current density of 80 mAh g -1 . And then return to 100mA g -1 After the current density is 200 mAh g -1 .

[0033] Embodiment 3 to Embodiment 5

[0034]

[0035] According to the above experimental parameters and referring to the method of Example 1 or Example 2, the titanium-iron-niobium oxide electrode material can be obtained.

[0036] In summary, the titanium-iron-niobium oxide disclosed in the present invention not only has the function of stabilizing Li + The structure of the deintercalation and extraction, and because there are trivalent iron, tetravalent titanium and pentavalent niobium in the transition metal, the transition metal valence state can be balanced, and oxygen vacancies can be introduced into the structure, which can significantly improve the overall electronic conductivity of the material and the diffusion rate of lithium ions, and improve the electrochemical performance as an electrode material. This advanced invention solves the problem of poor electronic and ionic conductivity inherent in niobium oxide and titanium niobium oxide.

[0037] The number of devices and processing scales described here are used to simplify the description of the present invention, and the application, modification and variation of the present invention will be obvious to those skilled in the art.

[0038] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for preparing a titanium-iron-niobium oxide electrode, characterized in that: The following steps are involved: S1. Disperse 1.96 g of metatitanic acid, 0.21 g of ferric hydroxide and 10.28 g of niobium pentachloride in water, stir magnetically for 2 h, and obtain a suspension; S2, drying the suspension to obtain a powder, and then drying it in a 100°C forced air drying oven for 12 hours. The obtained powder is ground and then placed in a nitrogen-filled tubular furnace for high-temperature annealing treatment at 1300°C for 10 hours; S3, naturally cool to obtain TiFe 0.1 Nb 1.9 O 7-δ Electrode materials; TiFe 0.1 Nb 1.9 O 7-δ It has a shear ReO3 type crystal structure and has a stable Li + The embedding and de-embedding structure, due to the presence of trivalent iron, tetravalent titanium and pentavalent niobium in the transition metals, balances the valence states of the transition metals and introduces oxygen vacancies into the structure.

2. The TiFe prepared according to claim 1 0.1 Nb 1.9 O 7-δ A method for assembling a half-cell from a material, characterized in that: The following steps are involved: (1) The prepared material was mixed with 7 wt% of a binder and 8 wt% of a conductive agent, stirred evenly, coated on a copper foil, and dried in an oven at 60-80°C; (2) Punch the electrode into a plate with a diameter of 10 to 16 mm, dry it in a vacuum oven at 60 to 120 °C for 4 to 12 hours, and then transfer it to a glove box filled with argon gas; (3) Using metallic lithium as the counter electrode, the electrolyte solvent is ethyl carbonate: dimethyl carbonate = 1:1, and the electrolyte contains 1% LiPF6 to assemble into a CR2032 button cell.

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