A water-soluble organic titanium compound and its preparation method and application

Abstract

The present invention discloses a water-soluble organic titanium compound having a general formula shown in structural formula I, (R1O) a -Ti(O(R2)C=CH-CO-O-(CH2)2(CH3)-PEG-Y) 4‑a (I), wherein R1 is methyl, ethyl or isopropyl, R2 is methyl or ethyl, PEG is a polyethylene glycol segment with a molecular weight of less than 500, and Y is -(CH2) m NH(CH2)2NH2 represents an ethylenediamine group, wherein m is 2 or 3, and a satisfies 0

Description

Technical Field

[0001] The present invention relates to the technical field of organotitanium, and particularly to a water-soluble organotitanium compound, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, lithium-ion batteries have been widely used in fields such as electric vehicles. Among them, lithium iron phosphate has become the preferred cathode material for lithium-ion power batteries due to its good safety performance, low cost, and excellent cycle performance. However, the poor electronic conductivity and ionic conductivity of lithium iron phosphate limit its larger-scale application.

[0003] At present, researchers have proposed to improve the intrinsic conductivity of lithium iron phosphate and improve the material performance by doping elements into the lithium iron phosphate material. The currently common method is to add solid titanium dioxide as the doping source of titanium element. However, solid titanium dioxide particles have a certain particle size. Even if nanoscale titanium dioxide is used for doping, it is difficult to disperse evenly. In addition, as a solid particle, nanoscale titanium dioxide undergoes a solid-solid reaction in the manufacture of iron lithium, resulting in a long ion migration path and requiring a relatively large addition amount.

[0004] Therefore, developing a soluble organotitanium compound as a doping agent for lithium iron phosphate is of great significance for improving the performance of lithium iron phosphate products. Summary of the Invention

[0005] In view of the deficiencies of the above technologies, the present invention provides a water-soluble organotitanium compound for doping lithium iron phosphate.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A water-soluble organotitanium compound has a general formula shown in Structural Formula I,

[0008] [[ID='28']](R1O)[[ID=2'9]]

[0010] , m , -Ti(O(R2)C=CH-CO-O-(CH2)2(CH3)-PEG-Y) 4-a (I),

[0009] In the formula, R1 is methyl, ethyl or isopropyl, R2 is methyl or ethyl, PEG is a polyethylene glycol chain segment with a molecular weight less than 500, Y is an ethylenediamine group represented by -(CH2) m NH(CH2)2NH2, where m is 2 or 3, a is a number satisfying 0 < a < 4, a is preferably a number satisfying 0.5 ≤ a ≤ 3.5, and more preferably 2. <000003'2>As a preferred technical solution, the organic titanium compound is a reaction product of a polyethylene glycol derivative having a β-ketoester structure represented by the following general formula (a) and a tetraalkyl titanate.

[0011] (a)

[0012] In the general formula (a), R2 is a methyl group or an ethyl group, n is a natural number, and Y is -(CH2) m An ethylenediamine group represented by NH(CH2)2NH2, wherein m is 2 or 3.

[0013] As a preferred technical solution, the tetraalkyl titanate is at least one of tetraethyl titanate, tetrapropyl titanate, and tetraisopropyl titanate.

[0014] As a preferred technical solution, the polyethylene glycol derivative represented by general formula (a) is obtained from terminal hydroxyethylenediamine, ethylene oxide and oxiranylmethyl acetoacetate through a ring-opening polymerization reaction of epoxy groups under certain conditions.

[0015] As a preferred technical solution, the terminal hydroxyethylenediamine is N-(3-hydroxypropyl)ethylenediamine and / or hydroxyethylethylenediamine.

[0016] The second aspect of the present invention is to provide a method for preparing the water-soluble organic titanium compound as described above, the preparation method comprising the following steps:

[0017] S1: first reacting terminal hydroxyethylenediamine with di-tert-butyl dicarbonate under alkaline conditions, introducing a hydroxyethylamine compound with a tert-butyloxycarbonyl protecting group for standby use; allowing ethylene oxide to self-polymerize under the catalysis of aluminum isopropoxide for a certain period of time, and then sequentially adding oxiranylmethyl acetoacetate and the hydroxyethylamine compound to react; finally, removing the tert-butyloxycarbonyl protecting group under strong acid conditions to obtain the polyethylene glycol derivative represented by general formula (a);

[0018] S2: reacting the polyethylene glycol derivative obtained in step S1 with tetraalkyl titanate to obtain an organic titanium compound having structural formula I;

[0019] (R1O) a -Ti(O(R2)C=CH-CO-O-(CH2)2(CH3)-PEG-Y) 4-a (I),

[0020] In the formula, R1 is methyl, ethyl or isopropyl, R2 is methyl or ethyl, PEG is a polyethylene glycol segment with a molecular weight of less than 500, and Y is -(CH2) mAn ethylenediamine group represented by NH(CH2)2NH2, where m is 2 or 3, and a is a number satisfying 0 < a < 4.

[0021] The third aspect of the present invention is the application of the water-soluble organotitanium compound as described above. The organotitanium compound is used as a titanium element dopant in the preparation process of lithium iron phosphate.

[0022] As a preferred technical solution, the application of the organotitanium compound in the preparation of lithium iron phosphate specifically includes the following operating steps:

[0023] S1: Add water, the organotitanium compound, iron phosphate, lithium carbonate and other carbon sources to the batching tank in sequence. Start the emulsification circulation operation when the iron phosphate starts to be added or when half of it has been added.

[0024] S2: After the feeding in step S1 is completed, emulsify for 30 - 60 min, and then perform coarse grinding, fine grinding and spray drying operations in sequence.

[0025] S3: Subject the material completed in step S2 to high-temperature sintering, and finally obtain the target product lithium iron phosphate.

[0026] As a preferred technical solution, the mass ratio of the water, the organotitanium compound, iron phosphate, lithium carbonate and other carbon sources is 105 - 115:1.5 - 2.5:90 - 110:20 - 30:10 - 11.

[0027] As a preferred technical solution, the temperature of the high-temperature sintering is 800 ± 10 °C, and the time is 8 - 12 h.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] (1) The organotitanium compound prepared in the present invention shows the function of a wetting agent by introducing PEG segments, ethylenediamine functional groups and acetoacetate groups, breaking the bubbles between microparticles and wetting the particle surface; further, by forming an enclosure on the surface of solid particles with hydrophilic groups facing outwards to bind water molecules, a synovial effect is generated between particles, reducing the viscosity of the mixture, showing a good dispersion effect of a dispersant; at the same time, by reducing the surface tension or interfacial tension of solid materials, the generation of foam is inhibited, and thus the function of an antifoaming agent is shown. Finally, the organotitanium compound of the present invention can be used as a titanium element dopant in the preparation process of lithium iron phosphate, effectively increasing the solid content and achieving uniform dispersion. During the sintering process, the carbon residue coating of the molecular segments of the organotitanium compound is also beneficial to reducing the internal resistance of the material.

[0030] (2) Adding the organic titanium compound prepared by the present invention to the raw materials in the lithium iron phosphate preparation process not only allows the various components of the raw materials to be evenly dispersed, but also significantly increases the solid content of the raw materials, thereby reducing the energy consumption in the lithium iron phosphate production process and generating significant economic benefits;

[0031] (3) The cycle performance and charge-discharge performance of the doped lithium iron phosphate are improved, and at the same time, more capacity is exerted while the primary particles are made larger (compaction density and energy density are increased). DETAILED DESCRIPTION

[0032] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are merely examples, and those skilled in the art may conceive of other obvious variations.

[0033] [Example 1]

[0034] The water-soluble organic titanium compound of this embodiment has the general formula shown in Structural Formula I-1,

[0035] (I-1).

[0036] The preparation method of the water-soluble organic titanium compound of this embodiment comprises the following steps:

[0037] S1: First, at room temperature, 0.2 mol of N-(3-hydroxypropyl)ethylenediamine and 0.5 mol of di-tert-butyl dicarbonate (Boc2O) were added to 500 mL of an alkaline solution prepared by mixing sodium hydroxide solution and tetrahydrofuran solvent (pH value was controlled at 12) to react for 2 hours to introduce a hydroxyethylamine compound with a tert-butyloxycarbonyl protecting group. Subsequently, 1.6 mol of ethylene oxide was subjected to a self-polymerization reaction under the catalysis of aluminum isopropoxide. The self-polymerization reaction was carried out at 60°C for 2 hours. The amount of aluminum isopropoxide used was 1.2% of the mass of ethylene oxide. After the self-polymerization reaction, 1 mol equivalent of oxiranylmethylacetoacetate and 1 mol equivalent of the above-obtained hydroxyethylamine compound were added in sequence. The reaction was continued at room temperature for 4 hours to form a precursor of a polyethylene glycol derivative. Subsequently, the reaction mixture was cooled to 0°C, and then 2 mol equivalents of hydrochloric acid solution were slowly added. The mixture was stirred at this temperature for 1 hour to ensure complete removal of the protecting group. After the reaction is completed, the target product is purified by extraction, washing, drying and vacuum distillation to finally obtain the polyethylene glycol derivative represented by general formula (I-1).

[0038] (a).

[0039] S2: 0.2 mol of the polyethylene glycol derivative obtained in step S1 is reacted with 0.4 mol of tetraethyl titanate, and the reaction is stirred at room temperature for 24 hours. The by-product ethanol is distilled off to finally obtain a yellow-brown organic titanium compound having the structural formula I-1.

[0040] [Example 2]

[0041] The water-soluble organic titanium compound of this embodiment has the general formula shown in Structural Formula I-2,

[0042] (I-2),

[0043] The preparation method of the water-soluble organic titanium compound of this embodiment comprises the following steps:

[0044] S1: First, at room temperature, 0.2 mol of hydroxyethylethylenediamine and 0.5 mol of di-tert-butyl dicarbonate (Boc2O) were added to 500 mL of an alkaline solution prepared by mixing sodium hydroxide solution and tetrahydrofuran solvent (pH value was controlled at 12) to react for 2 hours to introduce a hydroxyethylamine compound with a tert-butyloxycarbonyl protecting group. Subsequently, 2 mol of ethylene oxide was subjected to a self-polymerization reaction under the catalysis of aluminum isopropoxide. The self-polymerization reaction was carried out at 60°C for 2.5 hours, and the amount of aluminum isopropoxide used was 1.2% of the mass of ethylene oxide. After the self-polymerization reaction, 1 mol equivalent of oxiranylmethylacetoacetate and 1 mol equivalent of the above-obtained hydroxyethylamine compound were added in sequence, and the reaction was continued at room temperature for 4 hours to form a precursor of a polyethylene glycol derivative. Subsequently, the reaction mixture was cooled to 0°C, and then 2 mol equivalents of hydrochloric acid solution were slowly added, and the mixture was stirred at this temperature for 1 hour to ensure complete removal of the protecting group. After the reaction is completed, the target product is purified by extraction, washing, drying and vacuum distillation to finally obtain the polyethylene glycol derivative represented by general formula (I-2).

[0045] (a).

[0046] S2: 0.2 mol of the polyethylene glycol derivative obtained in step S1 is reacted with 0.4 mol of tetraisopropyl titanate, and the reaction is stirred at room temperature for 24 hours. The by-product isopropyl alcohol is distilled off to finally obtain a yellow-brown organic titanium compound having structural formula I-1.

[0047] [Example 3]

[0048] By weight, 110 parts of water, 2 parts of the organic titanium compound prepared in Example 1, 100 parts of iron phosphate, 25 parts of lithium carbonate and 10.5 parts of glucose were added to the batching tank in sequence. When half of the iron phosphate was added, the emulsification cycle was started and emulsified for 60 minutes. Then, coarse grinding, fine grinding and spray drying operations were carried out in sequence. Finally, the material was sintered at a high temperature of 800°C for 10 hours to obtain the target product, lithium iron phosphate.

[0049] [Example 4]

[0050] By weight, 110 parts of water, 2 parts of the organic titanium compound prepared in Example 2, 100 parts of iron phosphate, 25 parts of lithium carbonate and 10.5 parts of glucose as other carbon sources were added to the batching tank in sequence. When half of the iron phosphate was added, the emulsification cycle was started and emulsified for 60 minutes. Then, coarse grinding, fine grinding and spray drying were carried out in sequence. Finally, the material was sintered at 800°C for 10 hours to obtain the target product, lithium iron phosphate.

[0051] [Comparative Example 1]

[0052] By weight, 220 parts of water, 100 parts of iron phosphate, 25 parts of lithium carbonate and 10.5 parts of glucose as other carbon sources are added to the batching tank in sequence. When half of the iron phosphate is added, the emulsification cycle operation is started. After the addition is completed, emulsification is carried out for 60 minutes, and then coarse grinding, fine grinding and spray drying operations are carried out in sequence. Finally, it is sintered at a high temperature of 800°C for 10 hours to obtain the target product, lithium iron phosphate.

[0053] It is worth mentioning that, since no water-soluble organic titanium compound is added in Comparative Example 1, the amount of water added is significantly increased, which also reduces the solid content of the mixture.

[0054] [Comparative Example 2]

[0055] By weight, 220 parts of water, 2 parts of nano-titanium dioxide, 100 parts of iron phosphate, 25 parts of lithium carbonate and 10.5 parts of glucose as other carbon sources are added to the batching tank in sequence. When half of the iron phosphate is added, the emulsification cycle operation is started; after the addition is completed, emulsification is carried out for 60 minutes, and then coarse grinding, fine grinding and spray drying operations are carried out in sequence, and finally sintered at a high temperature of 800°C for 10 hours to obtain the target product, lithium iron phosphate.

[0056] Electrochemical performance testing was conducted on the lithium iron phosphate prepared in Examples 3 and 4 and Comparative Examples 1 and 2. Testing method: The lithium iron phosphate positive electrode material, conductive agent, and adhesive were mixed in a solvent at a ratio of 9:0.5:0.5 to obtain an electrode slurry. This slurry was then coated onto aluminum foil to form an electrode membrane. In a glove box, the electrode membrane (positive electrode), lithium metal sheet (negative electrode), separator, and electrolyte were combined to form a button-type battery. Battery performance was then tested over a charge and discharge voltage range of 2.0V to 4.0V. The specific preparation and testing methods are conventional techniques in the art and will not be described in detail in this application. The test results are shown in Table 1.

[0057] Table 1

[0058]

[0059] Through comparative analysis of Comparative Example 1 and Examples 3 and 4, it can be seen that by adding the water-soluble organic titanium compound prepared in Example 1, the charge and discharge performance and cycle performance of the lithium battery are improved.

[0060] Through comparative analysis of Example 2 and Examples 3 and 4, it can be seen that adding water-soluble organic titanium compounds can further improve the charge and discharge performance and cycle performance of the battery than adding nano-titanium dioxide. This is mainly because when using water-soluble organic titanium compounds, Ti 4+ Replace Fe 2+ into the LiFePO4 lattice, resulting in Li + The deintercalation / embedding path is shortened and the migration efficiency is accelerated, thereby improving the discharge capacity, rate and cycle performance of LiFePO4, thereby improving the electrical properties of lithium iron phosphate.

[0061] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. Various changes and improvements are possible without departing from the spirit and scope of the present invention, and such changes and improvements fall within the scope of the invention as claimed.

Claims

1. A water-soluble organic titanium compound, characterized in that The organic titanium compound has the general formula shown in Structural Formula I, (R1O) a -Ti(O(R2)C=CH-CO-O-CH2CH(CH3)-PEG-Y) 4-a (I), In the formula, R1 is methyl, ethyl or isopropyl, R2 is methyl or ethyl, PEG is a polyethylene glycol segment with a molecular weight less than 500, and Y is an ethylenediamine group represented by -(CH2) m NH(CH2)2NH2, where m is 2 or 3, and a is a number satisfying 0 < a < 4.

2. A method for preparing a water-soluble organic titanium compound as claimed in claim 1, characterized in that: The organic titanium compound is a reaction product of a polyethylene glycol derivative having a β-ketoester structure represented by the following general formula (a) and a tetraalkyl titanate. （a） In the general formula (a), R2 is a methyl group or an ethyl group, n is a natural number, and Y is -(CH2) m An ethylenediamine group represented by NH(CH2)2NH2, wherein m is 2 or 3.

3. The method for preparing a water-soluble organic titanium compound according to claim 2, wherein: The tetraalkyl titanate is at least one of tetraethyl titanate and tetraisopropyl titanate.

4. The method for preparing a water-soluble organic titanium compound according to claim 2, wherein: The polyethylene glycol derivative represented by general formula (a) is obtained from terminal hydroxyethylenediamine, ethylene oxide and oxiranylmethyl acetoacetate through the ring-opening polymerization reaction of epoxy groups.

5. The method for preparing a water-soluble organic titanium compound according to claim 4, wherein: The terminal hydroxy ethylenediamine is N-(3-hydroxypropyl)ethylenediamine.

6. The method for preparing a water-soluble organic titanium compound according to claim 4, wherein: The terminal hydroxyethylenediamine is hydroxyethylethylenediamine.

7. A method for preparing a water-soluble organic titanium compound as claimed in claim 1, characterized in that: The preparation method comprises the following steps: S1: first reacting terminal hydroxyethylenediamine with di-tert-butyl dicarbonate under alkaline conditions, introducing a hydroxyethylamine compound with a tert-butyloxycarbonyl protecting group for standby use; subjecting ethylene oxide to a self-polymerization reaction under the catalysis of aluminum isopropoxide, and then sequentially adding oxiranylmethyl acetoacetate and the hydroxyethylamine compound to react; finally, removing the tert-butyloxycarbonyl protecting group under strong acid conditions to obtain a polyethylene glycol derivative represented by general formula (a); （a） In the general formula (a), R2 is a methyl group or an ethyl group, n is a natural number, and Y is -(CH2) m An ethylenediamine group represented by NH(CH2)2NH2, wherein m is 2 or 3; S2: reacting the polyethylene glycol derivative obtained in step S1 with tetraalkyl titanate to obtain an organic titanium compound having structural formula I; (R1O) a -Ti(O(R2)C=CH-CO-O-CH2CH(CH3)-PEG-Y) 4-a (I), In the formula, R1 is methyl, ethyl or isopropyl, R2 is methyl or ethyl, PEG is a polyethylene glycol chain segment with a molecular weight less than 500, and Y is an ethylenediamine group represented by -(CH2) m NH(CH2)2NH2, where m is 2 or 3 and a is a number satisfying 0 < a < 4.

8. A use of the water-soluble organic titanium compound as claimed in claim 1, characterized in that: The organic titanium compound is used as a titanium dopant in the preparation process of lithium iron phosphate.

9. The use of the water-soluble organic titanium compound according to claim 8, characterized in that: The organic titanium compound is used in the preparation of lithium iron phosphate, which includes the following steps: S1: adding water, organic titanium compound, iron phosphate, lithium carbonate and other carbon sources into the batching tank in sequence, and starting the emulsification cycle operation when the iron phosphate is added or half of it is added; S2: After the addition of step S1 is completed, emulsify for 30 to 60 minutes, and then perform coarse grinding, fine grinding and spray drying operations in sequence; S3: The material obtained in step S2 is sintered at high temperature to obtain the target product, lithium iron phosphate.

10. The use of the water-soluble organic titanium compound according to claim 9, characterized in that: The mass ratio of the water, the organic titanium compound, the iron phosphate, the lithium carbonate and the other carbon sources is 105-115:1.5-2.5:90-110:20-30:10-11.

11. The use of the water-soluble organic titanium compound according to claim 9, characterized in that: The high-temperature sintering temperature is 800±10°C and the time is 8 to 12 hours.

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