Preparation method and application of negative electrode material of fast-charging lithium ion battery

Abstract

The invention relates to the field of lithium ion batteries, in particular to a preparation method and application of a negative electrode material of a fast-charging lithium ion battery, and the preparation method comprises the following steps: dissolving PTA in DMF, stirring until complete dissolution, adding niobium pentachloride and ferric trichloride hexahydrate, stirring again until complete dissolution to obtain an intermediate product, filtering, washing, and drying to obtain the negative electrode material of the fast-charging lithium ion battery. Transferring the intermediate product into a drying oven, preserving heat at 200 DEG C, centrifuging the intermediate product in the drying oven to obtain a precipitate, washing the precipitate with ethanol, drying in the drying oven at 60 DEG C to obtain dry powder, and calcining the dry powder in an air atmosphere at 800 DEG C to obtain a finished product. According to the invention, a Fe source is added, Fe atoms replace a small amount of Nb atoms, and the FeNb11O29 electrode material is innovatively synthesized; the synthesized FeNb11O29 can be used for a lithium ion battery, can be rapidly charged and discharged, and can still be circulated for a long time under the large current of 30A / g; the method disclosed by the invention is simple to operate, and the adopted ferric salt is low in cost, environment-friendly and easy for large-scale production.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion batteries, and specifically to a method for preparing a negative electrode material for a fast-charging lithium-ion battery and its application. Background Art

[0002] The massive consumption of global petroleum energy has led to increasingly serious environmental pollution, so the world is promoting green new energy vehicles. Compared with traditional fuel vehicles, new energy electric vehicles driven by lithium-ion batteries have the advantages of environmental protection, pollution-free and economical charging costs. However, the long charging time has become a major concern for potential users in the market, which directly affects the market acceptance of electric vehicles. Therefore, the development of lithium-ion battery fast charging technology that can shorten the charging time has become the key to meeting market demand and promoting the popularization of electric vehicles.

[0003] Currently, the main negative electrode for lithium-ion fast charging is commercial graphite negative electrode, but the working potential of graphite is relatively low, about 0.08V vs. Li+ / Li, which may lead to electrolyte decomposition, electrode cracks and lithium plating, thus reducing the cycle stability and rate performance of the battery and causing a series of safety problems. The working potential of niobium-based oxides is relatively high (>1V vs. Li+ / Li), which can solve the safety problems caused by lithium plating; on the basis of high safety, due to the good redox property of niobium, FeNb 11 O 29 The material can achieve a theoretical specific capacity of up to 400 mAh / g. In addition, the Wadsely-Roth structure (a crystal structure) of niobium-based materials is stable, which can promote stable and rapid ion transport. However, the current research on FeNb 11 O 29 research has not yet reached its potential.

[0004] At present, FeNb 11 O 29 The synthesis methods include ball milling and calcination, electrospinning and solution combustion. The ball milling and calcination method requires a long time of grinding, which may cause structural changes or damage during the grinding process. At the same time, the powder particles obtained are not uniform enough, and it is difficult to control the size and morphology of the particles. During the ball milling process, the material is in an open system, which may cause the sample to react with substances in the air. The electrospinning method requires specific equipment, including a high-voltage power supply and a spinning device, which may be more expensive than equipment for heating solvents. It is usually used to prepare fibrous or film-like materials with low yields. At the same time, the prepared samples and morphology are not precisely controlled, and large-scale production is not easy to achieve. The solution combustion method generally requires heating the solution to a higher reaction temperature after mixing, which may cause decomposition or structural changes of certain heat-sensitive materials; a large amount of gas may be produced during the reaction, and the obtained materials may require subsequent complicated purification steps. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a method for preparing a negative electrode material for a fast-charging lithium-ion battery.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing a negative electrode material for a fast-charging lithium-ion battery comprises the following steps:

[0008] 2 g of terephthalic acid (PTA) was dissolved in 80 mL of N, N-dimethylformamide (DMF) and stirred until completely dissolved. Then, 4.0 mmol of niobium pentachloride and 1.6 mmol-2.0 mmol of ferric chloride hexahydrate were added thereto and stirred again until completely dissolved to obtain an intermediate product. The intermediate product was moved into an oven and kept warm at 200° C., and then the intermediate product in the oven was centrifuged to obtain a precipitate. The precipitate was washed with ethanol and dried in an oven at 60° C. to obtain a dry powder. The dry powder was calcined at 800° C. in an air atmosphere to obtain a finished product FeNb 11 O 29 Powder particles. The present invention synthesizes a precursor by a solvent thermal method, and calcines the precursor to generate an organic carbon shell, which can accelerate electron conduction. The ferric chloride hexahydrate in the present invention can be replaced with other iron sources, such as ferric nitrate, ferric nitrate hexahydrate, etc. The amount of the iron source can also be reduced in the present invention, which is called niobium pentoxide doped with Fe.

[0009] As a further solution of the present invention: the stirring time is 0.8-1.5h.

[0010] As a further solution of the present invention: the intermediate product is poured into a 100 mL polytetrafluoroethylene liner before being moved into the oven.

[0011] As a further solution of the present invention: the insulation time at 200° C. is 10-14 h, and the drying time at 60° C. is 8-12 h.

[0012] As a further solution of the present invention: the centrifugal speed is 3000-4500 rpm, and the centrifugal time is 20-30 min.

[0013] As a further solution of the present invention: the number of ethanol washing is four times.

[0014] The invention also provides the application of the finished product obtained by the preparation method in preparing the negative electrode of a lithium ion battery.

[0015] Compared with the prior art, the invention has the following advantages: the invention adopts the method of adding Fe source, replacing a small amount of Nb atoms with Fe atoms, and innovatively synthesizing FeNb 11 O 29Electrode material: Synthetic FeNb 11 O 29 The method can be used for lithium-ion batteries for rapid charge and discharge, and can still be cycled for a long time at a large current of 30A / g. The method of the invention is simple to operate, and the iron salt used is low in cost, is environmentally friendly, and is easy to mass produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 In the embodiment of the present invention, FeNb 11 O 29 XRD phase diagram.

[0017] Figure 2 In the embodiment of the present invention, FeNb 11 O 29 SEM morphology of the samples.

[0018] Figure 3 In the embodiment of the present invention, FeNb 11 O 29 TEM image of.

[0019] Figure 4 In the embodiment of the present invention, FeNb 11 O 29 TEM mapping image.

[0020] Figure 5 is FeNb in the embodiment of the present invention 11 O 29 Graph of rate performance of lithium-ion half-cell assembled from electrode materials.

[0021] Figure 6 In the embodiment of the present invention, FeNb 11 O 29 Lithium-ion half-cells assembled from electrode materials at 30A g -1 Cycle diagram under high current density. DETAILED DESCRIPTION

[0022] 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.

[0023] Currently, the fast-charging negative electrode of commercial lithium-ion batteries is still mainly based on traditional graphite, but its low working potential (about 0.08Vvs.Li + / Li) may lead to safety issues. However, niobium-based oxide anodes have improved the working potential (>1V vs.Li + / Li), it can solve the safety problem; it also has a high theoretical specific capacity (400mAh / g) and high stability (Wadesely-Roth framework structure); but the performance of niobium-based materials as fast charging and fast charging still needs to be further improved. The principle of the present invention is as follows: The Nb source and the Fe source are respectively added to the organic solvent. During the solvothermal process, the metal ions Fe and the metal ions Nb respectively undergo mismatch reactions with the organic ligands (PTA) to obtain small-sized amorphous metal ligands (precursors). It is then calcined at a high temperature, with one part of the precursor undergoing organic carbonization and the other part undergoing carbon oxidation. After the organic ligand precursor is calcined and decomposed at a high temperature, its organic carbon shell provides excellent electron conduction, which makes FeNb 11 O 29 The method of the present invention synthesizes FeNb by solvent thermal method and air calcination method. 11 O 29 The material has a simple preparation process, is safe and efficient, and has successfully improved FeNb 11 O 29 Fast charging performance and stability at 30A g -1 At a current density of about 100 mAh g -1 Around, it perfectly improves the fast charging performance of niobium-based materials.

[0024] Example 1: Reference Figure 1-Figure 6 , a method for preparing a negative electrode material for a fast-charging lithium-ion battery, comprising the following steps:

[0025] Prepare terephthalic acid, ferric chloride hexahydrate and niobium pentachloride. Dissolve 2g of terephthalic acid (PTA) in 80mL N,N-dimethylformamide (DMF) and stir for 1h until completely dissolved. Then add 4.0mmol niobium pentachloride and 1.8mmol (effective range) ferric chloride hexahydrate and stir again. After complete dissolution, pour the above liquid into 100mL of polytetrafluoroethylene liner, move into an oven, and keep warm at 200°C for 12h. Centrifuge the solvent-heated mixture to obtain a precipitate, then wash it with ethanol 4 times and dry it in an oven at 60°C overnight. The obtained powder sample was calcined at 800 degrees Celsius for 2h in a tube furnace under an air atmosphere to finally obtain FeNb 11 O 29 Powder particles.

[0026] The powder sample of Example 1, the conductive agent (acetylene black), and the binder (PVDF, polyvinylidene fluoride) were mixed in a solvent (NMP, N-methylpyrrolidone) at a mass ratio of 7:2:1, ground and coated, and dried to obtain an electrode sheet. The electrode sheet and the lithium sheet were assembled into a lithium ion half-cell.-1 The rate performance of the battery was tested at a current density of 30A g -1 The cycling performance of the battery was tested at a high current density.

[0027] Figure 1 FeNb 11 O 29 From the XRD phase diagram, we can see that the XRD and PDF cards are consistent with each other.

[0028] Figure 2 FeNb 11 O 29 From the SEM morphology, we can see that the particles are blocky and uniform in size.

[0029] Figure 3 FeNb 11 O 29 From the TEM image, we can see that the particles are blocky. Figure 2 The SEM images of the samples are consistent with each other, and the size is about 200nm.

[0030] Figure 4 FeNb 11 O 29 TEM mapping of Figure 4 It shows that Fe, Nb, and O elements are evenly distributed in the bulk particles.

[0031] Figure 5 FeNb 11 O 29 Lithium-ion half-cell rate performance diagram assembled with electrode materials, Figure 5 It can be seen that at 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 30A g -1 At the current density, the capacity is 280 mAh g -1 , 266mAh g -1 , 249mAh g -1 , 233mAh g -1 , 218mAh g -1 , 193mAh g -1 , 170mAh g -1 , 141mAh g -1 , 120mAh g -1 , indicating that its rate performance is very excellent.

[0032] Figure 6 FeNb 11 O 29 Lithium-ion half-cells assembled from electrode materials at 30A g -1 The cycle diagram under high current density, Figure 6It can be seen that under high current, the material is slowly activated and the capacity is slowly increased. After 3000 cycles, the capacity retention rate is 94.2%, which has high cycle stability.

[0033] 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 negative electrode material for a fast-charged lithium-ion battery, characterized in that: The following steps are involved: 2 g of terephthalic acid (PTA) is dissolved in 80 mL of N,N-dimethylformamide (DMF), and stirred until completely dissolved. Then, 4.0 mmol of niobium pentachloride and 1.6 mmol-2.0 mmol of ferric chloride hexahydrate are added thereto, and stirred again until completely dissolved to obtain an intermediate product. The intermediate product is transferred into an oven and kept warm at 200° C., and then the intermediate product in the oven is centrifuged to obtain a precipitate. The precipitate is washed with ethanol and dried in an oven at 60° C. to obtain a dry powder. The dry powder is calcined at 800° C. in an air atmosphere to obtain a finished product.

2. The method for preparing the negative electrode material for a fast-charged lithium-ion battery according to claim 1, characterized in that: The stirring time is 0.8-1.5h.

3. The method for preparing a negative electrode material for a fast-charged lithium-ion battery according to claim 1 or 2, characterized in that: The intermediate product was poured into a 100 mL polytetrafluoroethylene liner before being moved into the oven.

4. The method for preparing a negative electrode material for a fast-charged lithium-ion battery according to claim 1, characterized in that: The 200° C. insulation time is 10-14 hours, and the 60° C. drying time is 8-12 hours.

5. The method for preparing the negative electrode material for a fast-charged lithium-ion battery according to claim 1, characterized in that: The centrifugal speed is 3000-4500 rpm, and the centrifugal time is 20-30 min.

6. The method for preparing the negative electrode material for a fast-charged lithium-ion battery according to claim 1, characterized in that: The number of ethanol washes was four times.

7. Use of a finished product obtained by the method for preparing a negative electrode material for a fast-charged lithium-ion battery as described in any one of claims 1 to 6 in preparing a negative electrode for a lithium-ion battery.

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