阅读说明：本技术 碳包覆磷酸钛钠材料的制备方法、制得的碳包覆磷酸钛钠材料及应用 (Preparation method of carbon-coated sodium titanium phosphate material, prepared carbon-coated sodium titanium phosphate material and application ) 是由 唐爱菊 梁栋栋 陈晨 刘海宁 王辉 毕超奇 于 2021-09-13 设计创作，主要内容包括：本发明公开一种碳包覆磷酸钛钠材料的制备方法,涉及锂离子电池技术领域,本发明包括以下步骤：(1)将氧化石墨烯、阳离子表面活性剂、碳源、钛酸酯类化合物和磷酸二氢钠加入醇类溶剂中分散形成混合溶液；(2)将步骤(1)中的混合溶液进行保温反应,冷却后洗涤并分散,然后进行干燥；(3)将干燥后的产物进行煅烧和烧结处理。本发明还提供采用上述方法制得的碳包覆磷酸钛钠材料及其应用。本发明的有益效果在于：本发明工艺简单,适合大规模工业化生产制备,碳包覆的材料具有良好的电子导电性,表现出优异的循环稳定性和较高的容量,匹配的全电池也具有较好的循环稳定性和1.5V左右的电压。(The invention discloses a preparation method of a carbon-coated sodium titanium phosphate material, which relates to the technical field of lithium ion batteries and comprises the following steps: (1) adding graphene oxide, a cationic surfactant, a carbon source, a titanate compound and sodium dihydrogen phosphate into an alcohol solvent for dispersing to form a mixed solution; (2) carrying out heat preservation reaction on the mixed solution in the step (1), cooling, washing and dispersing, and then drying; (3) and calcining and sintering the dried product. The invention also provides the carbon-coated sodium titanium phosphate material prepared by the method and application thereof. The invention has the beneficial effects that: the method has simple process, is suitable for large-scale industrial production and preparation, the carbon-coated material has good electronic conductivity, shows excellent cycling stability and higher capacity, and the matched full battery also has good cycling stability and voltage of about 1.5V.)

1. A preparation method of a carbon-coated sodium titanium phosphate material is characterized by comprising the following steps: the method comprises the following steps:

(1) adding graphene oxide, a cationic surfactant, a carbon source, a titanate compound and sodium dihydrogen phosphate into an alcohol solvent for dispersing to form a mixed solution;

(2) carrying out heat preservation reaction on the mixed solution in the step (1), cooling, washing and dispersing, and then drying;

(3) and calcining and sintering the dried product to obtain the carbon-coated sodium titanium phosphate material.

2. The method for preparing a carbon-coated sodium titanium phosphate material according to claim 1, wherein: the cationic surfactant is one of CTAB, diethanolamine, N-alkyl diethylenetriamine and N-alkyl polyethylenepolyamine.

3. The method for preparing a carbon-coated sodium titanium phosphate material according to claim 1, wherein: the carbon source is one of oxalic acid, citric acid, sodium citrate and sodium oleate.

4. The method for preparing a carbon-coated sodium titanium phosphate material according to claim 1, wherein: the total mass fraction of the graphene oxide and the carbon source is maintained at 20-40%, and the mass ratio of the graphene oxide to the carbon source is (1-5): 1 to 5.

5. The method for preparing a carbon-coated sodium titanium phosphate material according to claim 1, wherein: the titanate compound is one of tetraethyl titanate, tetraisopropyl titanate and tetrabutyl titanate.

6. The method for preparing a carbon-coated sodium titanium phosphate material according to claim 1, wherein: in the step (3), the calcining temperature is 350-550 ℃, the calcining time is 1-4 hours, the sintering temperature is 600-900 ℃, and the sintering time is 6-9 hours.

7. The carbon-coated sodium titanium phosphate material prepared by the preparation method of any one of claims 1 to 6.

8. The application of the carbon-coated sodium titanium phosphate material prepared by the preparation method of any one of claims 1 to 6 in preparing a negative plate is characterized in that: the preparation method of the negative plate comprises the following steps: and mixing the prepared carbon-coated sodium titanium phosphate material with a conductive agent and a binder to prepare slurry, and loading the slurry on a negative current collector to obtain a negative plate.

9. The application of the carbon-coated sodium titanium phosphate material prepared by the preparation method of any one of claims 1 to 6 in the preparation of an aqueous sodium ion battery is characterized in that: the preparation method of the aqueous sodium-ion battery comprises the following steps:

(1) preparing a positive plate: mixing a manganese oxide positive electrode material with a conductive agent and a binder to prepare slurry, and loading the slurry on a positive electrode current collector to obtain a positive electrode plate;

(2) preparing a negative plate: mixing the prepared carbon-coated sodium titanium phosphate material with a conductive agent and a binder to prepare slurry, and loading the slurry on a negative current collector to obtain a negative plate;

(3) assembling: and (3) taking the solution added with the surfactant as electrolyte, and respectively placing the positive plate and the negative plate at two ends of the diaphragm to assemble the water-system sodium-ion full battery.

10. The use of the carbon-coated sodium titanium phosphate material according to claim 9 in the preparation of an aqueous sodium ion battery, wherein: the surfactant is one of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium carboxymethyl cellulose, sodium fatty acid and sodium alkyl polyoxyethylene ether sulfate.

Technical Field

The invention relates to the technical field of lithium ion batteries, in particular to a preparation method of a carbon-coated sodium titanium phosphate material, the prepared carbon-coated sodium titanium phosphate material and application.

Background

Among various energy storage technologies, the secondary battery has the advantages of strong flexibility, higher energy density, high energy conversion efficiency and the like, and is a promising large-scale energy storage method. However, lithium is unevenly distributed in the crust and the reserve is not abundant, so that the price of lithium is continuously increased along with the continuous increase of the demand for lithium metal, meanwhile, the cost of the lithium ion battery is greatly increased in an oxygen-free and water-free environment, and great potential safety hazards exist in the using process. The aqueous battery adopts a saline solution as an electrolyte, has certain disadvantages in terms of energy density and working voltage compared with an organic lithium ion battery, but has the characteristics of simple preparation environment, high safety performance, better environmental friendliness, low cost and the like, and also has wide application value in the current society.

The sodium ion battery has good development prospect, not only has a rocking chair type energy storage mechanism similar to that of the lithium ion battery, but also has rich sodium element in the earth crust and low cost. The main factor affecting the development of sodium ion batteries is the lack of high performance electrode materials, especially negative electrode materials. NaTi₂(PO4)₃Is composed of 2 pieces of [ TiO ]₆]Octahedron and 3 [ PO ]₄]The tetrahedrons form individual basic units in an angle connection mode to form a three-dimensional open structure, which is beneficial to the rapid desorption/intercalation of sodium ions. NaTi₂(PO4)₃Has high ion conductivity, small volume expansion rate in the circulation process and excellent chemical stability. However, sodium ions are removed from the crystal lattice of sodium titanium phosphate due to the larger radius of the sodium ionsThe intercalation resistance is large, so that the crystal structure of the sodium titanium phosphate is easy to collapse, the charge-discharge reversibility of the electrode material is poor, especially the irreversible capacity loss under the heavy current density is large, and the further application and development of the sodium titanium phosphate material in a high-performance sodium ion battery are hindered. The existing methods for improving the electrochemical performance of materials mainly comprise the following methods: (1) adding NaTi₂(PO₄)₃The particles are nano-sized, so that the diffusion path of sodium ions can be shortened; (2) the conductive layer is coated, so that the electronic conductivity of the composite electrode material is improved; (3) heteroatom doping is also one of the effective methods to improve electron conductivity.

In the existing aqueous ion battery system, the electron conductivity of the sodium titanium phosphate material is poor, and the sodium titanium phosphate material is easily decomposed to a certain degree in an aqueous electrolyte, so that the circulation stability in an aqueous full battery is poor, and the full performance of the battery is seriously influenced.

Patent publication No. CN107732167A discloses a method for preparing a sodium titanium phosphate cathode material for an aqueous ion battery, wherein the obtained sodium titanium phosphate cathode material has good cycling stability, but the preparation process is complex, involves multiple coating steps, and has poor cycling stability when no secondary coating is performed.

Disclosure of Invention

The invention aims to solve the technical problems that in the prior art, a preparation method of a sodium titanium phosphate material is complex, multiple coating steps are involved, and the circulation stability is poor when secondary coating is not carried out, and provides a preparation method for preparing a simple carbon-coated sodium titanium phosphate material, the prepared carbon-coated sodium titanium phosphate material and application thereof.

The invention solves the technical problems through the following technical means:

a preparation method of a carbon-coated sodium titanium phosphate material comprises the following steps:

(1) adding graphene oxide, a cationic surfactant, a carbon source, a titanate compound and sodium dihydrogen phosphate into an alcohol solvent for dispersing to form a mixed solution;

(2) carrying out heat preservation reaction on the mixed solution in the step (1), cooling, washing and dispersing, and then drying;

(3) and calcining and sintering the dried product to obtain the carbon-coated sodium titanium phosphate material.

Has the advantages that: the preparation method is simple, the problem of poor electronic conductivity of the titanium sodium phosphate can be solved by coating the titanium sodium phosphate with the graphene/pyrolytic carbon, the graphene forms a three-dimensional conductive network, the problem of graphene agglomeration in the synthesis process is effectively solved by the cationic surfactant, the electronic conductivity of the material can be further improved, and the battery has excellent cycling stability.

Preferably, ultrasonic dispersion is used in the step (1) to form a mixed solution.

Preferably, the time of the ultrasonic treatment is 0.5-2 h.

Preferably, the cationic surfactant is one of CTAB, diethanolamine, N-alkyl diethylenetriamine, N-alkyl polyethylenepolyamine.

Preferably, the carbon source is one of oxalic acid, citric acid, sodium citrate and sodium oleate.

Preferably, the total mass fraction of the graphene oxide and the carbon source is maintained at 20-40%, and the mass ratio of the graphene oxide to the carbon source is 1-5: 1 to 5.

Has the advantages that: the material has high capacity and optimal cycle stability by adjusting the proportion of the graphene oxide and the raw materials.

Preferably, the titanate compound is one of tetraethyl titanate, tetraisopropyl titanate and tetrabutyl titanate.

Preferably, the temperature in the step (2) is kept at 120-160 ℃ for 10-24 h.

Preferably, in the step (3), the calcining temperature is 350-550 ℃, the calcining time is 1-4 hours, the sintering temperature is 600-900 ℃, and the sintering time is 6-9 hours.

Preferably, the ratio of the titanate compound to the sodium dihydrogen phosphate is NaTi₂(PO₄)₃The stoichiometric ratio of (a).

Preferably, the alcohol solvent is one of ethanol, ethylene glycol, n-butanol and glycerol.

Preferably, the drying in the step (2) adopts spray drying, and the temperature of the spray drying is 120-180 ℃.

A carbon-coated sodium titanium phosphate material prepared by the preparation method.

Has the advantages that: the carbon-coated sodium titanium phosphate material prepared by the invention can solve the problem of poor electronic conductivity of sodium titanium phosphate, and can form a three-dimensional conductive network with graphene oxide, so that the electronic conductivity of the material can be further improved, and the battery can obtain excellent cycling stability.

The application of the carbon-coated sodium titanium phosphate material prepared by the preparation method in preparing the negative plate comprises the following steps: and mixing the prepared carbon-coated sodium titanium phosphate material with a conductive agent and a binder to prepare slurry, and loading the slurry on a negative current collector to obtain a negative plate.

Has the advantages that: the graphene/pyrolytic carbon coated titanium sodium phosphate cathode material prepared by a hydrothermal method is simple in process and suitable for large-scale industrial production and preparation.

Preferably, the mass ratio of the carbon-coated sodium titanium phosphate material to the conductive agent to the binder is 6-8: 1-2: 1 to 2.

The application of the carbon-coated sodium titanium phosphate material prepared by the preparation method in preparing the water system sodium ion battery comprises the following steps:

(1) preparing a positive plate: mixing a manganese oxide positive electrode material with a conductive agent and a binder to prepare slurry, and loading the slurry on a positive electrode current collector to obtain a positive electrode plate;

(2) preparing a negative plate: mixing the prepared carbon-coated sodium titanium phosphate material with a conductive agent and a binder to prepare slurry, and loading the slurry on a negative current collector to obtain a negative plate;

(3) assembling: and (3) taking the solution added with the surfactant as electrolyte, and respectively placing the positive plate and the negative plate at two ends of the diaphragm to assemble the water-system sodium-ion full battery.

Has the advantages that: according to the water system sodium ion full cell, the surfactant is introduced into the electrolyte, so that a hydrophobic layer can be formed on the surface of a material, and the contact between water and an electrode is reduced. Meanwhile, the addition of the surfactant can widen a potential window, slow down the decomposition of water, effectively improve the cycling stability of the battery and have a voltage of about 1.5V.

The invention adopts a hydrothermal method to prepare the water system sodium ion full cell, has simple process and is suitable for large-scale industrial production and preparation.

Preferably, the concentration of the sodium sulfate is 0.5-2 mol/L.

Preferably, the electrolyte is a sodium sulfate solution added with a surfactant.

Preferably, the surfactant is one of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium carboxymethyl cellulose, sodium fatty acid, and sodium alkyl polyoxyethylene ether sulfate.

Preferably, the addition amount of the surfactant accounts for 1-5% of the total mass of the electrolyte.

Preferably, the mass ratio of the manganese oxide positive electrode material to the conductive agent to the binder is 6-8: 1-2: 1 to 2.

Preferably, the mass ratio of the carbon-coated sodium titanium phosphate material to the conductive agent to the binder is 6-8: 1-2: 1 to 2.

Preferably, the manganese-based oxide is NaMnO₂Or Na_0.44MnO₂。

The invention has the advantages that: according to the invention, the graphene/pyrolytic carbon is adopted to coat the titanium sodium phosphate, the problem of poor electronic conductivity of the titanium sodium phosphate can be solved by coating the titanium sodium phosphate with the pyrolytic carbon, and meanwhile, the graphene forms a three-dimensional conductive network, so that the electronic conductivity of the material can be further improved, and the battery can obtain excellent cycling stability.

The graphene/pyrolytic carbon coated titanium sodium phosphate cathode material prepared by a hydrothermal method is simple in process and suitable for large-scale industrial production and preparation.

According to the water system sodium ion full cell, the surfactant is introduced into the electrolyte, so that a hydrophobic layer can be formed on the surface of a material, and the contact between water and an electrode is reduced. Meanwhile, the addition of the surfactant can widen a potential window, slow down the decomposition of water, effectively improve the cycling stability of the battery and have a voltage of about 1.5V.

The invention adopts a hydrothermal method to prepare the water system sodium ion full cell, has simple process and is suitable for large-scale industrial production and preparation.

Drawings

FIG. 1 is a scanning electron micrograph of a carbon-coated sodium titanium phosphate material according to example 1 of the present invention;

FIG. 2 is a transmission electron micrograph of a carbon-coated sodium titanium phosphate material according to comparative example 1 of the present invention;

fig. 3 is a graph showing the cycle performance of a battery made of the carbon-coated sodium titanium phosphate material in example 1 of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Test materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

The specific techniques or conditions not specified in the examples can be performed according to the techniques or conditions described in the literature in the field or according to the product specification.

Example 1

The preparation of the battery with the cathode active material of carbon-coated sodium titanium phosphate material comprises the following steps:

(1) preparing a positive plate: manganese series oxide anode material NaMnO₂Mixing with acetylene black serving as a conductive agent and PTFE serving as a binder according to the weight ratio of 7: 1: 2, preparing slurry, and loading the slurry on a positive current collector by using a roller press to obtain a positive plate;

(2) preparation of a negative electrode active material: adding 0.1mg CTAB surfactant into 300mL of 10mg/mL graphene ethanol solution, performing ultrasonic dispersion for 1h, then ultrasonically dispersing the graphene ethanol solution, 10g oxalic acid, 17g tetrabutyl titanate and 9g sodium dihydrogen phosphate in 200mL ethanol for 0.5h, transferring to a stainless steel reaction kettle, and preserving heat in an environment at 140 ℃ for 10 h. After cooling, washing the product with distilled water and absolute ethyl alcohol for several times, adding distilled water to form mixed slurry, and spray drying at 130 ℃. Placing the product in a tubular furnace, presintering for 2h at 450 ℃ in a nitrogen atmosphere, and then sintering for 8h at 750 ℃ to obtain a graphene/pyrolytic carbon coated sodium titanium phosphate material with high crystallinity;

(3) preparing a negative plate: mixing the graphene/pyrolytic carbon coated sodium titanium phosphate cathode material, conductive agent acetylene black and binder PTFE according to the weight ratio of 7: 1: 2, preparing slurry, and loading the slurry on a negative current collector by using a roller press to obtain a negative plate;

(4) assembling the battery: and taking a sodium sulfate solution with the mass fraction of 2% added with 0.5mol/L of surfactant lauryl sodium sulfate as an electrolyte, and respectively placing the positive plate and the negative plate at two ends of the diaphragm to assemble the water system sodium ion full cell.

Fig. 1 and 2 are SEM and TEM images of the product of example 1, from which it can be seen that the material is in a uniform sheet-like shape like an ellipse, and a thin carbon layer around the material can be seen, forming a three-dimensional carbon conductive network, improving the electron conductivity of the material. Fig. 3 shows that the reversible capacity of the full-cell 2C made of the carbon-coated sodium titanium phosphate negative electrode material of the embodiment is 98.85mAh/g, and the capacity residual rate after 100-week circulation is 86.1%.

Example 2

The preparation of the battery with the cathode active material of carbon-coated sodium titanium phosphate material comprises the following steps:

(1) preparing a positive plate: manganese series oxide anode material NaMnO₂Mixing with acetylene black serving as a conductive agent and PTFE serving as a binder according to the weight ratio of 7: 1: 2, preparing slurry, and loading the slurry on a positive current collector by using a roller press to obtain a positive plate;

(2) preparation of a negative electrode active material: adding 0.1mg CTAB surfactant into 200mL of 10mg/mL graphene ethanol solution, performing ultrasonic dispersion for 1h, then ultrasonically dispersing the graphene ethanol solution, 15g oxalic acid, 17g tetrabutyl titanate and 9g sodium dihydrogen phosphate in 200mL ethanol for 0.5h, transferring to a stainless steel reaction kettle, and preserving heat in an environment at 140 ℃ for 10 h. After cooling, washing the product with distilled water and absolute ethyl alcohol for several times, adding distilled water to form mixed slurry, and spray drying at 130 ℃. Placing the product in a tubular furnace, presintering for 2h at 450 ℃ in a nitrogen atmosphere, and then sintering for 8h at 750 ℃ to obtain a graphene/pyrolytic carbon coated sodium titanium phosphate material with high crystallinity;

(3) preparing a negative plate: mixing the graphene/pyrolytic carbon coated sodium titanium phosphate cathode material, conductive agent acetylene black and binder PTFE according to the weight ratio of 7: 1: 2, preparing slurry, and loading the slurry on a negative current collector by using a roller press to obtain a negative plate;

(4) assembling the battery: and taking a sodium sulfate solution of which the mass fraction is 2% and which is 0.5mol/L added with a surfactant of sodium dodecyl sulfate as an electrolyte, and respectively placing the positive plate and the negative plate at two ends of the diaphragm to assemble the water system sodium ion full cell.

Example 3

This embodiment is different from embodiment 1 in that: the electrolyte used in the battery assembly process is 0.5mol/L sodium sulfate solution added with 2% of surfactant sodium carboxymethyl cellulose, and other steps are the same as those in example 1.

Example 4

This embodiment is different from embodiment 1 in that: add 0.1mg diethanolamine surfactant, the other steps are the same.

Example 5

This embodiment is different from embodiment 1 in that: 0.1mg of N-alkyl diethylenetriamine surfactant was added, and the other steps were the same.

Example 6

Preparation of a negative electrode active material: adding 0.1mg CTAB surfactant into 300mL of 10mg/mL graphene ethanol solution, performing ultrasonic dispersion for 1h, then ultrasonically dispersing the graphene ethanol solution, 10g citric acid, 17g tetrabutyl titanate and 9g sodium dihydrogen phosphate in 200mL ethanol for 0.5h, transferring to a stainless steel reaction kettle, and preserving heat in an environment at 140 ℃ for 10 h. After cooling, washing the product with distilled water and absolute ethyl alcohol for several times, adding distilled water to form mixed slurry, and spray drying at 130 ℃. And placing the product in a tubular furnace, presintering for 2 hours at 450 ℃ in a nitrogen atmosphere, and then sintering for 8 hours at 750 ℃ to obtain the graphene/pyrolytic carbon coated sodium titanium phosphate material with high crystallinity, wherein the other steps are the same as those in the example 1.

Example 7

This embodiment is different from embodiment 1 in that: the carbon source was sodium citrate and the other steps were the same as in example 1.

Example 8

This embodiment is different from embodiment 1 in that: transferring the negative active material into a stainless steel reaction kettle in the preparation process of the negative active material, and preserving the heat for 10 hours in an environment of 120 ℃. The other steps are the same as in example 1.

Example 9

This embodiment is different from embodiment 1 in that: preparation of a negative electrode active material: transferring the mixture into a stainless steel reaction kettle, and keeping the temperature for 24 hours in an environment of 160 ℃. The other steps are the same as in example 1.

Example 10

This embodiment is different from embodiment 1 in that: the calcining temperature is 350 ℃, the calcining time is 4 hours, the sintering temperature is 600 ℃, and the sintering time is 9 hours.

Example 11

This embodiment is different from embodiment 1 in that: the calcining temperature is 550 ℃, the calcining time is 1h, the sintering temperature is 900 ℃, and the sintering time is 6 h.

Comparative example 1

This comparative example differs from example 1 in that: in the preparation process of the negative active material, 20g of oxalic acid, 17g of tetrabutyl titanate and 9g of sodium dihydrogen phosphate are taken to be ultrasonically dispersed in 200mL of ethanol for 0.5h, transferred to a stainless steel reaction kettle and kept at the temperature of 140 ℃ for 10 h. After cooling, washing the product with distilled water and absolute ethyl alcohol for several times, adding distilled water to form mixed slurry, and spray drying at 130 ℃. And taking out the dried pre-product, placing the pre-product in a tubular furnace, pre-sintering for 2 hours at 450 ℃ in a nitrogen atmosphere, and sintering for 8 hours at 750 ℃ to obtain the graphene/pyrolytic carbon coated sodium titanium phosphate material with high crystallinity. The other steps were the same as in example 1.

Comparative example 2

This comparative example differs from example 1 in that: in the preparation process of the negative active material, 17g of tetrabutyl titanate and 9g of sodium dihydrogen phosphate are uniformly mixed in 200mL of ethanol, transferred to a stainless steel reaction kettle and kept at the temperature of 140 ℃ for 10 hours. After cooling, washing the product with distilled water and absolute ethyl alcohol for several times, adding distilled water to form mixed slurry, and spray drying at 130 ℃. And taking out the dried pre-product, placing the pre-product in a tubular furnace, pre-sintering for 2 hours at 450 ℃ in a nitrogen atmosphere, and sintering for 8 hours at 750 ℃ to obtain the graphene/pyrolytic carbon coated sodium titanium phosphate material with high crystallinity. The other steps were the same as in example 1.

Comparative example 3

This comparative example differs from example 1 in that: the electrolyte used in the battery assembly process was a 0.5mol/L sodium sulfate solution without any surfactant, and the other steps were the same as in example 1.

Experimental data and analysis:

the cell performance was measured in examples 1 to 3 and comparative examples 1 to 3, and the measurement results are shown in table 1.

Table 1 shows the results of the measurement of the cell performance of each of the examples and comparative examples

From table 1, it can be seen that the reversible specific capacity of sodium titanium phosphate is smaller and the cycle performance is also poorer without adding graphene or pyrolytic carbon. The graphene/pyrolytic carbon coated sodium titanium phosphate of example 1 has the largest specific capacity and the optimal cycle retention rate, and when no surfactant is added to the electrolyte, the cycle stability of the battery is reduced.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.