Metal-doped hard carbon composite material, preparation method and application thereof

Abstract

The embodiment of the present application discloses a kind of metal doped hard carbon composite materials, by silver metal salt, cobalt metal salt, aluminium titanium composite coupling agent mixed aqueous solution as electrolyte, with hard carbon, conductive agent, binder and catalyst mixed hot-pressed hard carbon composite sheet as working electrode, with electrochemical deposition method to obtain doped metal material, then sinter at high temperature, obtain the material.The present application adopts electrochemical deposition metal, with the advantages of good deposition thickness consistency, high deposition density in hard carbon pore, can significantly improve the electronic conductivity of material, while electrochemical deposition has the advantages of controllable process, high efficiency;Metal silver, metal cobalt as doped metal, utilize the good electrical properties and synergistic effect of both, rely on the network structure formed by coupling agent in the pore and surface of hard carbon, improve the cycle and power performance of material.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of lithium ion battery materials, and particularly relates to a metal-doped hard carbon composite material, a preparation method thereof and application thereof. BACKGROUND

[0002] Hard carbon is a lithium ion energy storage negative material that is difficult to graphitize, and is applied in the field of high-power lithium ion batteries due to its large interlayer spacing, wide material sources, excellent high-rate charging and low-temperature performance, etc. However, due to the porous structure of hard carbon itself and its more active points, the specific surface area of the material is large, the first efficiency is low (only about 80%), and thus the first efficiency and energy density of the full battery as a basic material are affected.

[0003] In view of the above problems, at present, the surface of the hard carbon material is mainly coated to reduce the side reaction and improve the first efficiency, but the kinetic performance of the material after coating is reduced, which affects the power and low-temperature performance; for example, patent application No. CN201710361334.5 discloses a hard carbon-metal oxide-soft carbon composite material and a preparation method and application thereof. In the patent, a hydrocarbon is used to prepare a hard carbon precursor by a hydrothermal method in a reaction kettle, a hard carbon precursor and a titanium salt are pre-coated, and pitch is placed in a muffle furnace to perform a low-temperature pyrolysis reaction to obtain a soft carbon precursor; finally, the pre-coated hard carbon precursor and the soft carbon precursor are fully mixed, and a high-temperature pyrolysis reaction is performed under inert gas protection to obtain a product of a hard carbon-metal oxide-soft carbon composite material. Although the first efficiency is improved by coating the soft carbon and the metal oxide, the specific capacity is slightly reduced, and the rate performance is also reduced, and in addition, the solid-phase method is used for preparation, and there are problems such as poor uniformity of coating. SUMMARY

[0004] In order to solve the problems of the prior art, the present application provides a metal-doped hard carbon composite material, which is prepared by an electrochemical deposition method to deposit silver and cobalt metals in the pores of the hard carbon to improve the electronic conductivity of the material and the first efficiency.

[0005] To achieve the above technical purposes, the technical scheme adopted by the present application is as follows:

[0006] The technical purpose of the first aspect of the present application is to provide a preparation method of a metal-doped hard carbon composite material, comprising the following steps:

[0007] Preparation of the mixed solution: silver metal salt and cobalt metal salt are mixed in water, and then aluminum-titanium composite coupling agent is added, wherein the mass ratio of the silver metal salt, the cobalt metal salt and the aluminum-titanium composite coupling agent is 1-5: 1-5: 1;

[0008] Preparation of the hard carbon composite sheet: mixing hard carbon, conductive agent, binder and catalyst, and then pressing into a hard carbon composite sheet by a hot press; wherein the mass ratio of hard carbon, conductive agent, binder and catalyst is 90-95:1-5:1-5:0.5-2;

[0009] Electrochemical deposition of hard carbon composite material: using the mixed solution as the electrolyte, using the hard carbon composite sheet as the working electrode, and using the cyclic voltammetry method for electrochemical deposition;

[0010] High-temperature sintering: washing, drying and sintering the product obtained after electrochemical deposition to obtain the metal-doped hard carbon composite material.

[0011] Further, the preparation process of the mixed solution, the mass concentration of silver metal salt and cobalt metal salt is 0.1-10wt%.

[0012] Further, the silver metal salt is selected from at least one of silver chloride, silver nitrate, silver sulfate, silver bromide, silver sulfide and silver hydroxide.

[0013] Further, the cobalt metal salt is selected from at least one of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt carbonate and cobalt oxalate.

[0014] Further, the chemical structure of the aluminum-titanium composite coupling agent is: (C3H7O) X Al(OCOR1)(OCOR2) n ·(R1O)Ti(OOCR2) n , wherein X is an integer of 2-5, n1 and n2 are independently selected from integers of 1-6, and R1 and R2 are independently selected from C6-C12 alkane.

[0015] Further, the thickness of the prepared hard carbon composite sheet is 1-10mm.

[0016] Further, the working temperature of the hot press is 100-150℃, and the pressure is 1-5Mpa.

[0017] Further, the conductive agent is selected from at least one of graphene, carbon nanotube, carbon black and vapor-grown carbon fiber; the binder is low-temperature pitch with a softening point ≤100℃; and the catalyst is selected from at least one of nano-iron, nano-cobalt and nano-nickel, and the particle size of the catalyst is 100-500nm.

[0018] Further, the operating voltage range of the cyclic voltammetry method is-2V-2V, the scanning speed is 0.1-10mV / S, and the deposition time is 10-120min.

[0019] Further, the sintering is performed in a tube furnace at a temperature of 700-1000℃ for 1-6h.

[0020] The technical purpose of the second aspect of the present application is to provide the metal-doped hard carbon composite material prepared by the above method.

[0021] The technical purpose of the third aspect of the present application is to provide the application of the metal-doped hard carbon composite material as a battery negative electrode material. Specifically, the battery is a lithium ion battery.

[0022] The implementation of the embodiments of the present application will have the following beneficial effects:

[0023] (1) The present application can obviously improve the electronic conductivity of the material by preparing a specific electrolyte and working electrode, and depositing a specific metal on the surface of the hard carbon by using the electrochemical deposition method. The electrochemical deposition has the advantages of good consistency in deposition thickness and high density in the hard carbon pores. The electrochemical deposition has the advantages of controllable process and high efficiency.

[0024] (2) The present application uses silver and cobalt as doping metals. Silver has the characteristics of high electronic conductivity, which can improve the electronic conductivity of the hard carbon. Silver salt has good compatibility with the electrolyte, and can form an alloy with lithium when used as a negative electrode material to improve the structural stability of the material. Cobalt has a catalytic effect, which can play a synergistic effect between silver and cobalt. The coupling agent can form a network structure in the pores and on the surface of the hard carbon, which can improve the cycle and power performance of the material.

[0025] In order to make the concept of the present application and other purposes, advantages, features and effects more clear and easy to understand, the preferred embodiments will be described in detail in the following specific embodiments, and the detailed description will be made with the help of the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiment or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creating any creative labor.

[0027] Among them:

[0028] Figure 1 SEM image of the metal-doped hard carbon composite material prepared in Example 1. DETAILED DESCRIPTION

[0029] With reference to the accompanying drawings on the basis of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0030] The metal-doped hard carbon composite material was prepared in Embodiments 1-3.

[0031] Embodiment 1

[0032] S1, preparation of a mixed solution: 3 g of silver chloride and 3 g of cobalt chloride were added into 200 mL of deionized water and mixed uniformly to obtain a mixed solution with a mass concentration of 3 wt%, and then 1 g of an aluminum-titanium composite coupling agent (structural formula: (C3H7O)2Al(OCOC8H 17 )(OCOC8H 17 )3·(C8H 17 O)Ti(OOCC8H 17 )3) was added and mixed uniformly;

[0033] S2, preparation of a hard carbon composite sheet: 94 g of hard carbon, 2 g of a carbon nanotube conductive agent, 3 g of low-temperature pitch, and 1 g of nano-iron (particle size 300 nm) were mixed uniformly, and then a hard carbon composite sheet with a thickness of 5 mm was pressed by a hot press at a temperature of 120 DEG C and a pressure of 3 MPa;

[0034] S3, electrochemical deposition to prepare a hard carbon composite material: the mixed solution of S1 was transferred into an electrolytic cell, a hard carbon composite sheet was used as a working electrode, a cyclic voltammetry method was adopted, a voltage range was -2 V-2 V, a scanning speed was 5 mV / S, and a deposition time was 60 min, so that a silver-cobalt compound was deposited on the surface of the hard carbon composite sheet;

[0035] S4, high-temperature sintering: then the surface of the electrode sheet was cleaned with deionized water, vacuum drying was performed at 80 DEG C for 24 h, and then the electrode sheet was transferred into a tube furnace and sintered at a temperature of 800 DEG C for 3 h, so that a metal-doped hard carbon composite material was obtained.

[0036] Embodiment 2

[0037] S1, preparation of a mixed solution: 1 g of silver nitrate and 1 g of cobalt nitrate were added into 200 mL of deionized water and mixed uniformly to obtain a mixed solution with a mass concentration of 1 wt%, and then 1 g of an aluminum-titanium composite coupling agent (structural formula: (C3H7O)5Al(OCOC 10 H 21 )(OCOC 10 H 21 )·(C 10 H 21O)Ti(OOCC 10 H 21 )2) mixed uniformly;

[0038] S2, preparation of hard carbon composite sheet: 90 g of hard carbon, 4.5 g of graphene, 5 g of low temperature pitch, 0.5 g of nano cobalt (particle size 100 nm) were mixed uniformly, and then a hard carbon composite sheet with a thickness of 10 mm was pressed by a hot press at a temperature of 100°C and a pressure of 5Mpa;

[0039] S3, preparation of hard carbon composite material by electrochemical deposition: the mixed solution was transferred to an electrolytic cell, the hard carbon composite sheet was used as the working electrode, the cyclic voltammetry method was adopted, the voltage range was-2V-2V, the scanning speed was 0.1mV / S, and the deposition time was 120 min, so that the silver cobalt compound was deposited on the surface of the hard carbon composite sheet;

[0040] S4, high temperature sintering: then the surface of the electrode sheet was washed with deionized water, vacuum dried at 80°C for 24h, and then transferred to a tube furnace, sintered at a temperature of 700°C for 6h, to obtain a metal-doped hard carbon composite material.

[0041] Example 3

[0042] S1, preparation of mixed solution: 5 g of silver sulfate and 5 g of cobalt sulfate were added to 100 mL of deionized water and mixed uniformly, then 1 g of aluminum titanium composite coupling agent (structure formula: (C3H7O)2Al(OCOC9H 19 )(OCOC9H 19 )2·(C9H 19 O)Ti(OOCC9H 19 )2) was added and mixed uniformly to obtain a mixed solution with a mass concentration of 10wt%;

[0043] S2, preparation of hard carbon composite sheet: 95 g of hard carbon, 1.5 g of carbon black, 1.5 g of low temperature pitch, and 2 g of nano nickel (particle size 500 nm) were mixed uniformly, and then a hard carbon composite sheet with a thickness of 1 mm was pressed by a hot press at a temperature of 150°C and a pressure of 1Mpa;

[0044] S3, preparation of hard carbon composite material by electrochemical deposition: the mixed solution of S1 was transferred to an electrolytic cell, the hard carbon composite sheet was used as the working electrode, the cyclic voltammetry method was adopted, the voltage range was-2V-2V, the scanning speed was 10mV / S, and the deposition time was 10 min, so that the silver cobalt compound was deposited on the surface of the hard carbon composite sheet;

[0045] S4, high temperature sintering: then the surface of the electrode sheet was washed with deionized water, vacuum dried at 80°C for 24h, and then transferred to a tube furnace, sintered at a temperature of 1000°C for 1h, to obtain a metal-doped hard carbon composite material.

[0046] Comparative Example 1

[0047] The operation process of S1 and S2 is the same as in Example 1. Then, the hard carbon composite sheet is added to the mixture of S1 and soaked for 24 hours, filtered, vacuum dried at 80°C for 24 hours, and then transferred to a tube furnace and sintered at 800°C for 3 hours to obtain the metal-doped hard carbon composite material.

[0048] Comparative Example 2

[0049] Add 3g of silver chloride and 3g of cobalt chloride to 200mL of deionized water and mix well. Then add 1g of aluminum-titanium composite coupling agent and mix well. Then add 100g of hard carbon, ultrasonically disperse it evenly, filter it, vacuum dry it at 80℃ for 24h, and then transfer it to a tube furnace and sinter it at 800℃ for 3h to obtain metal-doped hard carbon composite material.

[0050] Comparative Example 3

[0051] Except for the addition of 6g of cobalt chloride instead of silver chloride in S1, the other operations are the same as in Example 1, and a hard carbon composite material is obtained.

[0052] Performance testing of the materials prepared in the above embodiments and comparative examples:

[0053] (1) SEM testing

[0054] The phosphorus-iron co-doped hard carbon composite material prepared in Example 1 was subjected to SEM testing, and the test results are as follows: Figure 1 As shown.

[0055] Depend on Figure 1 As can be seen from the results, the composite material prepared in Example 1 exhibits a granular structure with a uniform size distribution and a particle size between 5 and 10 μm.

[0056] (2) Physical and chemical performance testing

[0057] The particle size, tap density, specific surface area, and powder conductivity of the composite materials prepared in the examples and comparative examples were tested. The tests were conducted according to the methods specified in the national standard GB / T-24533-2019, "Graphite Anode Materials for Lithium-ion Batteries". The test results are shown in Table 1.

[0058] Table 1

[0059]

[0060] As can be seen from Table 1, the hard carbon composite materials obtained in Examples 1-3 are superior to the comparative examples in specific surface area, and the tap density is obviously higher than that of the comparative examples. The reason is that the electrochemical deposition method is used to obtain a material with high density and improve the electronic conductivity of the material. At the same time, the metal ions can be more uniformly doped in the hard carbon pores by using the electrochemical deposition method, so as to improve the activity of the material and the discharge specific capacity of the material.

[0061] (3) Button cell test

[0062] The composite materials in the examples and the comparative examples are assembled into button cells as lithium ion battery negative electrode materials. The specific preparation method of the negative electrode material is as follows: a binder, a conductive agent and a solvent are added to the composite material, stirring is performed to prepare a slurry, coating is performed on a copper foil, and drying and rolling are performed to obtain the negative electrode sheet. The conductive agent SP and the solvent are twice distilled water, and the preparation of the negative electrode sheet is performed according to the composite material: CMC: SBR: SP: H2O = 95: 2.5: 1.5: 1: 150 mL. A lithium metal sheet is used as a counter electrode. LiPF6 / EC+DEC is used as an electrolyte, LiPF6 is used as an electrolyte, a mixture of EC and DEC in a volume ratio of 1:1 is used as a solvent, and the electrolyte concentration is 1.3 mol / L. A polyethylene (PE) film is used as a separator. The button cell is assembled in an argon-filled glove box. The electrochemical performance is tested on a Wuhan Lan electric CT2001A battery tester. The charge and discharge voltage range is 0.00V to 1.5V, the charge and discharge rate is 0.5C / 0.5C, the first discharge specific capacity and the first charge and discharge efficiency of the button cell are tested, and the rate performance (2C / 0.1C), the cycle performance (0.5C / 0.5C, 100 cycles) and the DCR (direct current resistance) are tested. The test results are shown in Table 2.

[0063] Table 2

[0064]

[0065] As can be seen from Table 2, the cycle and rate of the button cell made of the hard carbon composite material of Examples 1-3 are obviously higher than those of the comparative examples. The reason is that the hard carbon composite material prepared by the electrochemical deposition method of the present application can uniformly and densely dope the metal compound in the hard carbon, reduce the impedance, improve the kinetic performance and the rate performance, and improve the cycle performance at a large rate.

[0066] (4) Soft package battery test:

[0067] The composite materials in the examples and the comparative examples are prepared into negative electrode sheets by slurry mixing and coating, and a ternary material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2) is a positive electrode, LiPF6 (solvent is EC: DEC: PC = 1: 1: 1 volume ratio 1: 1: 1, electrolyte concentration 1.3 mol / L) is an electrolyte, and Celgard2400 film is a separator. A 5 Ah soft package battery is prepared.

[0068] The liquid absorption rate and liquid retention rate (24h electrolyte volume / 0h electrolyte volume) of the negative electrode sheet are tested according to the national standard GB / T 24533-2019 "Lithium ion battery graphite negative electrode material", and the results are shown in Table 3.

[0069] Table 3

[0070]

[0071] As can be seen from Table 3, the liquid absorption and retention capacity of the negative electrode prepared by using the hard carbon composite material obtained in Examples 1-3 is obviously better than that of the comparative example. The reason is that the hard carbon material of the examples has a high specific surface area, which improves the liquid absorption and retention performance of the electrode sheet.

[0072] The rate performance of the soft package battery is then tested. The charge and discharge voltage range is 2.75-4.2V, the temperature is 25±3.0℃, and the charging is carried out at 1.0C, 3.0C, 5.0C, 10.0C and 20.0C, and the discharging is carried out at 1.0C. The results are shown in Table 4.

[0073] Table 4

[0074]

[0075]

[0076]

[0077] As can be seen from Table 4, the rate charging performance of the soft package battery in Examples 1-3 is obviously better than that of the comparative example, i.e. the charging time is shorter. The reason is that the metal-doped hard carbon material prepared by electrochemical deposition has the advantages of high density and low impedance, thereby reducing the electronic impedance of the material and improving the rate performance.

[0078] The above only discloses the preferred embodiments of the present application, and of course cannot limit the scope of the present application. Therefore, any equivalent changes made according to the claims of the present application are still within the scope of the present application.

Claims

1. A method for preparing a metal-doped hard carbon composite material, comprising the following steps: Preparation of the mixture: Silver metal salt and cobalt metal salt are mixed in water, and then aluminum-titanium composite coupling agent is added. The mass ratio of silver metal salt, cobalt metal salt and aluminum-titanium composite coupling agent is 1-5:1-5:

1. Preparation of hard carbon composite sheets: Hard carbon, conductive agent, binder and catalyst are mixed and then pressed into hard carbon composite sheets by hot press; wherein, the mass ratio of hard carbon, conductive agent, binder and catalyst is 90-95:1-5:1-5:0.5-2. Electrochemical deposition preparation of hard carbon composite materials: using a mixed solution as the electrolyte and a hard carbon composite sheet as the working electrode, electrochemical deposition was carried out using cyclic voltammetry. High-temperature sintering: The product obtained after electrochemical deposition is washed, dried, and sintered to obtain the metal-doped hard carbon composite material.

2. The preparation method according to claim 1, characterized in that, The silver metal salt is selected from at least one of silver chloride, silver nitrate, silver sulfate, silver bromide, and silver sulfide.

3. The preparation method according to claim 1, characterized in that, The cobalt metal salt is selected from at least one of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt carbonate, and cobalt oxalate.

4. The preparation method according to claim 1, characterized in that, The chemical structural formula of the aluminum-titanium composite coupling agent is: (C3H7O)XAl(OCOR1)(OCOR2)n1·(R1O)Ti(OOCR2)n2, where X is an integer from 2 to 5, n1 and n2 are independently selected from integers from 1 to 6, and R1 and R2 are independently selected from alkanes from C6 to C12.

5. The preparation method according to claim 1, characterized in that, The thickness of the prepared hard carbon composite sheet is 1-10 mm.

6. The preparation method according to claim 1, characterized in that, The hot press operates at a temperature of 100-150℃ and a pressure of 1-5MPa.

7. The preparation method according to claim 1, characterized in that, The conductive agent is selected from at least one of graphene, carbon nanotubes, carbon black and vapor-grown carbon fibers; the binder is low-temperature asphalt with a softening point ≤100℃; the catalyst is selected from at least one of nano-iron, nano-cobalt and nano-nickel, and the particle size of the catalyst is 100-500nm.

8. The preparation method according to claim 1, characterized in that, The cyclic voltammetry method operates in the range of -2V to 2V, with a scan rate of 0.1-10mV / s and a deposition time of 10-120min.

9. The metal-doped hard carbon composite material prepared by the preparation method according to any one of claims 1-8.

10. The application of the metal-doped hard carbon composite material of claim 9 as a battery anode material.

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