1. A multielement (C, N, S, P) doped titanium dioxide cathode material and a preparation method thereof. The method is characterized in that: respectively adding a certain amount of anatase type TiO into a Cetyl Trimethyl Ammonium Bromide (CTAB) aqueous solution with a certain concentration₂The preparation method comprises the steps of electrically stirring and dispersing oxalic acid, tributyl phosphate and pyrrole for 60min, then dropwise adding a certain volume of ammonium persulfate solution, continuing to react for 2-6h after dropwise adding, centrifugally separating the suspension III for 10-30 min, removing the supernatant to obtain a precipitate, placing the precipitate in a tubular furnace, heating to 400-700 ℃ at the speed of 5 ℃/min under the condition of introducing nitrogen, preserving heat for 4-8h, and cooling to obtain (C, N, S, P) doped titanium dioxide cathode material.

2. The method of claim 1, wherein: the mass concentration of the CTAB aqueous solution is 0.5-5%.

3. The method of claim 1, wherein: anatase type TiO₂The addition amount of (b) is 5-10 times of the mass of CTAB.

4. The method of claim 1, wherein: the added amount of oxalic acid is TiO₂The addition amount is 1-2 times.

5. The method of claim 1, wherein: the pyrrole is added in an amount of TiO₂The addition amount is 0.1-1 times.

6. The method of claim 1, wherein: the addition amount of tributyl phosphate is TiO₂The addition amount is 0.1-0.2 times.

7. The method of claim 1, wherein: the concentration of the ammonium persulfate solution is 0.5-4 mol.L^-1The amount added is the same as the amount of pyrrole added (relative error less than 10% is allowed by the amount of substance).

8. The method of claim 1, wherein: after the ammonium persulfate solution is dripped, the continuous reaction time is 2-4 h.

9. The method of claim 1, wherein: the calcining temperature is 400-700 ℃, and the heat preservation time is 4-8 h.

Background

The cathode material is an important component of the lithium ion battery, and the performance of the cathode material directly influences the service life of the lithium ion battery. The current commercialized negative electrode materials are mainly carbon-based materials (such as natural graphite, mesocarbon microbeads, artificial graphite and the like), and have the advantages of good conductivity, low charge-discharge platform and high cost performance. But the carbon potential of the lithium battery is too close to that of metal lithium, lithium dendrite is easy to precipitate in the charging and discharging process to cause short circuit of the battery, potential safety hazards exist, and in addition, the volume change caused by lithium desorption and intercalation is large, so that the cycle performance of the lithium battery is reduced.

Anatase TiO₂The lithium ion battery is a semiconductor material with electric activity for the insertion and extraction of lithium ions, has a high working voltage platform with discharge of 1.75V and charge of 2V, does not generate lithium dendrite and a Solid Electrolyte Interface (SEI) film on the surface of the semiconductor material, and has the volume change of only about 3-4% in the charge-discharge process, namely the volume change caused by the insertion and extraction of Li + in the material is very small, the cycle performance is excellent, the cost is low, and the lithium ion battery is environment-friendly and is a candidate material for replacing graphite. However, its theoretical capacity is low (335mAh g) compared to graphite^-1Per 1mol TiO₂Insertion of 1mol Li⁺) The actual cyclability is lower (only 167.5mAh g)^-1)。

The poor electronic conductivity of titanium dioxide severely restricts the application of titanium dioxide as an electrode material. In recent years, the electrochemical performance of titanium dioxide is improved at home and abroad mainly by methods of morphology and particle size regulation, element doping, carbon coating and the like, but in the prior relevant researches, the discharge capacity of titanium dioxide is not high enough, so that the commercial requirement is difficult to meet. For example, Sung Woo Oh et al prepared 22nm titanium dioxide at 0.4mA cm by hydrothermal method^-2The specific capacity of the first discharge of 100 times of circulation under the current density is 170 mAh.g^-1Porous titania nanosheets synthesized by solvothermal method using Li or the like, and having a molecular weight of 1C (1C ═ 168mA · g)^-1) The first discharge specific capacity under multiplying power is 210 mAh.g^-1(ii) a The nano rod-shaped titanium dioxide cathode material prepared by a hydrothermal method has the current density of 0.1 DEG CThe first discharge capacity under the temperature is about 300 mAh.g^-1And the maximum discharge capacity at 10C charge-discharge rate is 125.9mAh g^-1[ZL201810829882.0]The first discharge capacity of the anatase type layered mesoporous titanium dioxide prepared by the hydrothermal method is about 280 mAh.g at the current density of 0.1C^-1[ZL201010168942.2](ii) a Adding tetrabutyl titanate into urea-choline chloride ionic liquid to prepare nano titanium dioxide, and roasting at high temperature to obtain titanium dioxide cathode material with first discharge specific capacity of 193.2mAh g-1[ ZL201610107105.6 ] at 0.5 DEG C]Molybdenum doped anatase TiO₂The specific capacity of the material at the first discharge under the current density of 0.2C is about 180 mAh.g^-1[ZL201811024033.4]The first discharge capacity of the lithium zirconate modified double-phase lithium titanate/titanium dioxide negative electrode material is about 172mAh g under the current density of 0.1C^-1[ZL201810161587.2]Preparation method of silver-loaded titanium dioxide negative electrode material [ ZL201510149000.2]The discharge specific capacity is 180-280 mAh.g at the current density of 0.1C^-1In the meantime. The first discharge capacity of the carbon-coated titanium dioxide negative electrode material at 0.1C rate is about 220 mAh.g^-1[ZL201710027901.3]。

The invention provides a multielement (C, N, S, P) doped titanium dioxide cathode material and a preparation method thereof in order to overcome the defect of low specific discharge capacity of the conventional titanium dioxide cathode material, and according to the technical scheme of the invention, the preparation method of the multielement (C, N, S, P) doped titanium dioxide cathode material comprises the following steps:

(1) weighing a certain amount of Cetyl Trimethyl Ammonium Bromide (CTAB) and dissolving in 100mL of deionized water to obtain a solution I;

(2) respectively adding a certain amount of anatase type TiO into the solution I₂Oxalic acid, tributyl phosphate and pyrrole, and then electrically stirring and dispersing for 60min to obtain a suspension II;

(3) dropwise adding a certain volume of ammonium persulfate solution into the suspension II at room temperature, and continuously reacting for 2-6h after dropwise adding to obtain a suspension III;

(4) centrifuging the suspension III for 10-30 min, and removing supernatant to obtain a precipitate;

(5) and (3) placing the precipitated product in a tube furnace, heating to 400-700 ℃ at the speed of 5 ℃/min under the condition of introducing nitrogen, preserving the heat for 4-8h, and cooling to obtain (C, N, S, P) doped titanium dioxide cathode material.

Further, in the step (1), the mass concentration of the CTAB aqueous solution is 0.5-5%.

Further, in the step (2), anatase type TiO₂The addition amount of (b) is 5-10 times of the mass of CTAB.

Further, in the step (2), the adding amount of oxalic acid is TiO₂The addition amount is 1-2 times.

Further, in the step (2), the adding amount of pyrrole is TiO₂The addition amount is 0.1-1 times.

Further, in the step (2), the addition amount of tributyl phosphate is TiO₂The addition amount is 0.1-0.2 times.

Further, in the step (3), the concentration of the ammonium persulfate solution is 0.5-4 mol.L^-1The amount added is the same as the amount of pyrrole added (relative error less than 10% is allowed by the amount of substance).

Further, in the step (3), the reaction time is 2-4 h.

Further, the calcining temperature in the step (5) is 400-700 ℃, and the heat preservation time is 4-8 h.

The (C, N, S, P) doped titanium dioxide negative electrode material prepared by the method is prepared into an electrode plate (the preparation method comprises the steps of taking N-methyl-2-pyrrolidone (NMP) as a solvent, uniformly mixing (C, N, S, P) doped titanium dioxide negative electrode material, conductive carbon black and polyvinylidene fluoride according to the mass ratio of 8: 1, stirring for 1-2 h to obtain a slurry substance, coating the slurry substance on a copper foil, drying in vacuum at the temperature of 110-120 ℃ for 12h, uniformly pressing, cutting out a pole piece with the diameter of 14mm, weighing to obtain a positive pole piece with the titanium dioxide negative electrode material as a positive pole), using a lithium piece as a counter electrode, assembling into a button battery, standing for 10h, and carrying out electrochemical performance testing. The results show that at 100mA g^-1The discharge capacity of the first 10 circles can be stabilized to 510mAh g^-1And the specific discharge capacity corresponding to the undoped sampleThe amount is 350mAh g from the first circle^-1140mAh g at 10 th turn^-1(FIG. 2).

Compared with the existing reported titanium dioxide-based negative electrode material, the discharge specific capacity of the (C, N, S, P) doped titanium dioxide negative electrode material prepared by the invention shows obviously improved electrochemical performance, and the preparation method is simple to operate, environment-friendly and easy to implement amplification experiments and industrial production.

Drawings

Fig. 1 is an SEM image of (C, N, S, P) doped titania negative electrode material.

Fig. 2 is a rate performance graph of (C, N, S, P) doped titania anode material.

Detailed Description

The invention is further illustrated by the following examples, but is not limited thereto.

Example 1

(1) Weighing 0.5g of Cetyl Trimethyl Ammonium Bromide (CTAB) and dissolving in 99.5g of deionized water to obtain a solution I with the CTAB mass concentration of 0.5%;

(2) 2.5g of anatase TiO in each case were added to the solution I₂2.5g of oxalic acid, 0.25g of tributyl phosphate and 0.25g (0.003725mol) of pyrrole, and then electrically stirring and dispersing for 60min to obtain suspension II;

(3) 7.45ml of 0.5 mol. L was added dropwise to suspension II at room temperature^-1After the ammonium persulfate solution is added, continuously reacting for 2 hours to obtain suspension III;

(4) centrifuging the suspension III for 10-30 min, and removing supernatant to obtain a precipitate;

(5) and (3) placing the precipitation product in a tube furnace, heating to 400 ℃ at the speed of 5 ℃/min under the condition of introducing nitrogen, preserving the heat for 8h, and cooling to obtain (C, N, S, P) doped titanium dioxide cathode material.

Example 2

(1) Weighing 1g of Cetyl Trimethyl Ammonium Bromide (CTAB) and dissolving in 95g of deionized water to obtain a solution I with the CTAB mass concentration of 1%;

(2) 5g of anatase TiO in each case were added to the solution I₂10g of oxalic acid, 0.5g of tributyl phosphate and 2.5g (0.03725mol) of pyrrole, and then electrically stirring and dispersing for 60min to obtain suspension II;

(3) at room temperature, a certain volume of 12.42ml of 3.0 mol.L is dripped into the suspension II^-1After the ammonium persulfate solution is added, continuously reacting for 3 hours to obtain suspension III;

(4) centrifuging the suspension III for 10-30 min, and removing supernatant to obtain a precipitate;

(5) and (3) placing the precipitation product in a tube furnace, heating to 500 ℃ at the speed of 5 ℃/min under the condition of introducing nitrogen, preserving the heat for 7h, and cooling to obtain (C, N, S, P) doped titanium dioxide cathode material.

Example 3

(1) Weighing 2g of Cetyl Trimethyl Ammonium Bromide (CTAB) and dissolving in 98g of deionized water to obtain a solution I with the CTAB mass concentration of 2%;

(2) 20g of anatase TiO in each case were added to the solution I₂30g of oxalic acid, 4g of tributyl phosphate and 10.1g (0.15mol) of pyrrole, and then electrically stirring and dispersing for 60min to obtain suspension II;

(3) at room temperature, a certain volume of 37.5ml of 4.0 mol.L is added dropwise into the suspension II^-1After the ammonium persulfate solution is added, continuously reacting for 4 hours to obtain suspension III;

(4) centrifuging the suspension III for 10-30 min, and removing supernatant to obtain a precipitate;

(5) and (3) placing the precipitation product in a tube furnace, heating to 600 ℃ at the speed of 5 ℃/min under the condition of introducing nitrogen, preserving the heat for 6h, and cooling to obtain (C, N, S, P) doped titanium dioxide cathode material.

Example 4

(1) Weighing 3g of Cetyl Trimethyl Ammonium Bromide (CTAB) and dissolving in 98g of deionized water to obtain a solution I with 3% of CTAB by mass concentration;

(2) 20g of anatase TiO in each case were added to the solution I₂30g of oxalic acid, 3g of tributyl phosphate and 10.1g (0.15mol) of pyrrole, and then electrically stirring and dispersing for 60min to obtain suspension II;

(3) at room temperature, a certain volume of 75.0ml is added into the suspension II 2.0mol·L^-1After the ammonium persulfate solution is added, continuously reacting for 4 hours to obtain suspension III;

(4) centrifuging the suspension III for 10-30 min, and removing supernatant to obtain a precipitate;

(5) and (3) placing the precipitated product in a tube furnace, heating to 700 ℃ at the speed of 5 ℃/min under the condition of introducing nitrogen, preserving the heat for 4h, and cooling to obtain (C, N, S, P) doped titanium dioxide cathode material.

Example 5

(1) Weighing 4g of Cetyl Trimethyl Ammonium Bromide (CTAB) and dissolving in 95g of deionized water to obtain a solution I with the CTAB mass concentration of 4%;

(2) 25g of anatase TiO in each case were added to the solution I₂30g of oxalic acid, 2.5g of tributyl phosphate and 15g (0.2235mol) of pyrrole, and then electrically stirring and dispersing for 60min to obtain suspension II;

(3) at room temperature, a certain volume of 55.9ml of 4.0 mol.L is added dropwise to the suspension II^-1After the ammonium persulfate solution is added, continuously reacting for 6 hours to obtain suspension III;

(4) centrifuging the suspension III for 10-30 min, and removing supernatant to obtain a precipitate;

(5) and (3) placing the precipitated product in a tubular furnace, heating to 700 ℃ at the speed of 5 ℃/min under the condition of introducing nitrogen, preserving the heat for 3h, and cooling to obtain (C, N, S, P) doped titanium dioxide cathode material.

Example 6

(1) Weighing 5g of Cetyl Trimethyl Ammonium Bromide (CTAB) and dissolving in 95g of deionized water to obtain a solution I with the CTAB mass concentration of 5%;

(2) 25g of anatase TiO in each case were added to the solution I₂50g of oxalic acid, 2.5g of tributyl phosphate and 25g (0.3725mol) of pyrrole, and then electrically stirring and dispersing for 60min to obtain suspension II;

(3) at room temperature, a certain volume of 93.13ml of 4.0 mol.L is added dropwise into the suspension II^-1After the ammonium persulfate solution is added, continuously reacting for 6 hours to obtain suspension III;

(4) centrifuging the suspension III for 10-30 min, and removing supernatant to obtain a precipitate;

(5) and (3) placing the precipitation product in a tube furnace, heating to 500 ℃ at the speed of 5 ℃/min under the condition of introducing nitrogen, preserving the heat for 5 hours, and cooling to obtain (C, N, S, P) doped titanium dioxide cathode material.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.