High-conductivity cobalt-nitrogen coordination hard carbon negative electrode material and preparation method and application thereof

Abstract

The application relates to the technical field of battery materials, and particularly discloses a preparation method and application of a high-conductivity cobalt-nitrogen coordination hard carbon negative electrode material. In the application, nano carbon particles are doped with nitrogen and cobalt and modified by sulfuration to prepare a hard carbon negative electrode material with high conductivity. The hard carbon negative electrode material does not need to add a conductive additive, fundamentally improves the overall conductivity of a sodium ion battery, simultaneously inhibits the volume expansion and even structure collapse caused by the rapid embedding and disembedding of sodium ions, realizes the improvement of the cycle and rate performance of the sodium ion battery, and realizes the development of the hard carbon negative electrode material with high conductivity. The hard carbon negative electrode material provided by the application effectively solves the problems of low conductivity of the hard carbon negative electrode material in the prior art, the need to add an additional carbon-based conductive additive, high process cost and complicated operation.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of battery materials, and particularly discloses a high-conductivity cobalt-nitrogen coordinated hard carbon negative electrode material and a preparation method and application thereof. BACKGROUND

[0002] Sodium ion batteries are similar to lithium ion batteries in mass energy density, but are widely concerned due to the advantages of rich resources, low cost, safety and environmental protection, and can be widely applied to large-scale energy storage systems and power devices of low-speed electric vehicles as a supplement. Unlike the use of graphite in the negative electrode material of lithium ion batteries, the negative electrode material of sodium ion batteries is mainly hard carbon negative electrode material, but the graphitization degree of the hard carbon material is relatively low, and the conductive performance is poor compared with graphite.

[0003] Generally speaking, the increase of the graphitization degree can improve the conductivity of the carbon material, but it is very difficult to graphitize the hard carbon, and the graphitization temperature above 2500 DEG C will cause a sharp increase in cost. In the prior art, the doping of heteroatoms on the carbon matrix is often used to improve the conductivity, but the improvement of the conductivity caused by the doping is often inhibited by the graphitized carbon, so additional carbon-based conductive additives are needed to enhance the overall conductivity, which is complex and increases the production cost. Therefore, it is of great practical significance to develop a hard carbon negative electrode material which is simple to operate, low in cost and high in conductivity. SUMMARY

[0004] In view of the problems of low conductivity of the hard carbon negative electrode material in the prior art, the need for additional carbon-based conductive additives and high process cost and complex operation, the application provides a high-conductivity cobalt-nitrogen coordinated hard carbon negative electrode material and a preparation method and application thereof. The application prepares a hard carbon negative electrode material with high conductivity by doping cobalt and nitrogen on nano carbon particles and sulfidation modification, without adding conductive additives, fundamentally improves the overall conductivity of the sodium ion battery, and inhibits the volume expansion and even structural collapse caused by the rapid embedding and extraction of sodium ions, realizes the improvement of the cycle and rate performance of the sodium ion battery and the development of the hard carbon negative electrode material with high conductivity.

[0005] To achieve the above-mentioned application purposes, the application provides the following technical scheme:

[0006] The first aspect of the application provides a preparation method of a high-conductivity cobalt-nitrogen coordinated hard carbon negative electrode material, comprising the following steps:

[0007] Step one, dissolving a carbon source and a nitrogen source in an alcohol solution, hydrothermal reaction, centrifugation, washing, drying, and obtaining a precursor powder;

[0008] Step two, dispersing the precursor powder in deionized water to obtain solution A; dissolving zinc salt and cobalt salt in deionized water to obtain solution B; mixing solution A and solution B uniformly, reacting at 40-50 DEG C for 20-30 hours, centrifuging, washing, drying to obtain intermediate product;

[0009] Step three, mixing the intermediate product and sulfurizing agent uniformly, under inert atmosphere, once heating to 300-400 DEG C for 2-4 hours, continuing to heat to 900-1100 DEG C for 5-7 hours, cooling, dispersing in acid solution, stirring, solid-liquid separation, drying to obtain high-conductivity cobalt-nitrogen coordination hard carbon negative electrode material.

[0010] Compared with the prior art, the application provides a preparation method of high-conductivity cobalt-nitrogen coordination hard carbon negative electrode material, the carbon source material and the nitrogen source material are pyrolyzed first to obtain nano carbon particles with carboxyl functional groups on the surface, the nano carbon particles have the advantages of small particle size and large specific surface area, and can adsorb and stabilize metal particles; on this basis, metal zinc and metal cobalt are introduced, the metal zinc acts as a template, and in the subsequent high-temperature carbonization process, the zinc evaporates, the nano carbon particles become hollow porous structures, the active adsorption sites are increased, the electrolyte contact surface area is significantly increased, the interface wettability is improved, the intrinsic conductivity of the electrode material is improved, and thus the ion conductivity is improved; the introduction of cobalt can catalyze the nano carbon particles to form local graphite microcrystals in the high-temperature carbonization process, so as to improve the internal electronic conductivity; at the same time, the nitrogen in the nano carbon particles can form Co-N bonds with cobalt, effectively promoting the uniform dispersion of cobalt particles in the nano carbon particles, and the highly dispersed cobalt particles can form a three-dimensional conductive network with the Co-N groups, enhancing the electronic conductivity of the nano carbon particles, reducing the diffusion energy barrier, promoting charge transfer and sodium ion adsorption; the cobalt-nitrogen doped nano carbon particles are further modified by sulfurization, the sulfurizing agent can form sulfur-containing groups with the lattice oxygen in the nano carbon particles, the sulfur-containing groups can be doped into the carbon layers of the nano carbon particles, the space between the carbon layers is increased, rich migration channels and more active sodium storage points are provided, the rapid transfer and storage of sodium ions are more favorable, the problems of volume expansion and even structure collapse caused by the rapid embedding and extraction of sodium ions are avoided, and the cycle and rate performance of the sodium ion battery are improved.

[0011] Preferably, in step one, the carbon source material is glucose.

[0012] Preferably, in step one, the nitrogen source material is melamine.

[0013] Preferably, in step one, the mass ratio of the carbon source material to the nitrogen source material is 2-4:1-2.

[0014] Preferably, in step one, the alcohol solution is an ethanol aqueous solution with a mass concentration of 45%-55%.

[0015] Preferably, in step one, the temperature of the hydrothermal reaction is 200-280℃, and the time of the hydrothermal reaction is 9-11h.

[0016] Preferably, in step one, the speed of the centrifugation is 800-1500r / min, and the time of the centrifugation is 5-10min.

[0017] Preferably, in step one, the temperature of the drying is 50-90℃, and the time of the drying is 8-12h.

[0018] Preferably, in step two, the zinc salt is any one of zinc nitrate, zinc sulfate or zinc chloride.

[0019] Preferably, in step two, the cobalt salt is any one of cobalt nitrate, cobalt chloride or cobalt sulfate.

[0020] Preferably, in step two, the molar ratio of the zinc salt to the cobalt salt is 2-3:1.

[0021] Preferably, in step two, the mass concentration of the A solution is 0.008-0.012g / mL.

[0022] Preferably, in step two, the total mass concentration of the cobalt salt and the zinc salt in the B solution is 0.004-0.006g / mL.

[0023] Preferably, in step two, the speed of the centrifugation is 1000-2000r / min, and the time of the centrifugation is 5-10min.

[0024] Preferably, in step two, the temperature of the drying is 50-70℃, and the time of the drying is 8-12h.

[0025] Preferably, in step three, the mass ratio of the intermediate product to the sulfurizing agent is 1:2-2.2.

[0026] Preferably, in step three, the sulfurizing agent is a mixture of elemental sulfur and thiourea with a mass ratio of 1:2-2.5.

[0027] Preferably, in step three, the acid solution is a hydrochloric acid solution with a concentration of 1-3mol / L.

[0028] Preferably, in step three, both the first temperature rising and the second temperature rising are programmed temperature rising, and the temperature rising rate of the programmed temperature rising is 4-6℃ / min.

[0029] Preferably, in step three, the temperature of the drying is 60-100℃, and the time of the drying is 6-10h.

[0030] The second aspect of the present application provides a high-conductivity cobalt-nitrogen coordination hard carbon negative material, which is prepared by the preparation method of the high-conductivity cobalt-nitrogen coordination hard carbon negative material.

[0031] The third aspect of the present application provides an application of the high-conductivity cobalt-nitrogen coordination hard carbon negative material in a sodium ion battery.

[0032] In summary, the present application provides a high-conductivity cobalt-nitrogen coordination hard carbon negative material, which is prepared by doping and sulfidizing modification of nano-carbon particles with nitrogen and cobalt, thereby obtaining a hard carbon negative material with high conductivity. The problems of low conductivity of the hard carbon negative material used in the sodium ion battery, the need to add additional carbon-based conductive additives, and high process cost and complex operation in the prior art are effectively solved. The hard carbon negative material provided by the present application has high conductivity, and the sodium ion battery prepared by using the hard carbon negative material has excellent electrochemical performance. The first-cycle specific capacity of the sodium ion battery can reach 458.3 mAh / g at a current density of 0.5 A / g, and the capacity retention rate is still as high as 96.2% after 500 cycles. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0034] Embodiment 1

[0035] The present embodiment provides a preparation method of a high-conductivity cobalt-nitrogen coordination hard carbon negative material, which specifically comprises the following steps:

[0036] Step one, 0.3 g of glucose and 0.15 g of melamine are mixed and dissolved in a mixed solution of 15 ml of deionized water and 15 ml of ethanol, and stirring is performed under a 50℃ water bath for half an hour to ensure complete dissolution. Then, the mixture is transferred to a 100 mL hydrothermal reaction kettle, and hydrothermal reaction is performed at 240℃ for 10 h. The product is centrifuged at a centrifugal speed of 900 r / min for 10 min, and the supernatant is discarded. The obtained solid material is washed with 20 mL of deionized water for three times and then washed with 20 mL of ethanol for two times. The obtained solid material is dried at 60℃ for 10 h to obtain a precursor powder.

[0037] Step two, the 0.5g precursor powder is dispersed in 50ml deionized water, stirred uniformly to form solution A; 0.15g zinc nitrate and 0.07g cobalt nitrate are dissolved in 50ml deionized water to form solution B; then the solution A and solution B are mixed, stirred under 45℃ water bath for 24h; after stirring, the obtained product is centrifuged at 1300r / min for 10min, the supernatant is discarded, the obtained solid material is washed with 20ml deionized water for three times, and the obtained solid material is dried at 60℃ for 10h to obtain an intermediate product;

[0038] Step three, the obtained intermediate product and sulfurizing agent (0.064g sulfur and 0.152g thiourea powder) are mixed in a mass ratio of 1:2 in a agate mortar, then the mixed powder is transferred to a ceramic canister, heated to 350℃ at a rate of 5℃ / min in an inert atmosphere for 3h, then continues to heat to 1000℃ at a rate of 5℃ / min for 6h, waits for its natural cooling, the obtained product is dispersed in 2mol / L dilute hydrochloric acid, stirred for 12h, suction filtered, and dried at 70℃ for 8h to obtain a high-conductivity cobalt-nitrogen-coordinated hard carbon negative electrode material.

[0039] Example 2

[0040] The embodiment provides a preparation method of a high-conductivity cobalt-nitrogen-coordinated hard carbon negative electrode material, which specifically comprises the following steps:

[0041] Step one, 0.3g glucose and 0.2g melamine are mixed and dissolved in a mixed solution of 20ml deionized water and 18ml ethanol, stirred under 50℃ water bath for half an hour to ensure complete dissolution, then transferred to a 100ml hydrothermal reaction kettle, and hydrothermally reacted at 260℃ for 10h; the product is centrifuged at 1000r / min for 10min, the supernatant is discarded, the obtained solid material is washed with 20ml deionized water for three times, and then washed with 20ml ethanol for two times; the obtained solid material is dried at 70℃ for 9h to obtain a precursor powder;

[0042] Step two, the 0.5g precursor powder is dispersed in 50ml deionized water, stirred uniformly to form solution A; 0.15g zinc nitrate and 0.07g cobalt nitrate are dissolved in 50ml deionized water to form solution B; then the solution A and solution B are mixed, stirred under 45℃ water bath for 24h; after stirring, the obtained product is centrifuged at 1300r / min for 10min, the supernatant is discarded, the obtained solid material is washed with 20ml deionized water for three times, and the obtained solid material is dried at 60℃ for 10h to obtain an intermediate product;

[0043] Step three, the obtained intermediate product and vulcanizing agent (0.064g sulfur and 0.152g thiourea powder) were mixed in a mass ratio of 1:2.1 in a agate mortar, and then the mixed powder was transferred to a ceramic capsule, heated to 360℃ at a rate of 4℃ / min in an inert atmosphere for 3h, and then continued to heat to 1050℃ at a rate of 4℃ / min for 6h, and then naturally cooled, the obtained product was dispersed in dilute hydrochloric acid with a concentration of 2mol / L, stirred for 12h, suction filtered, and dried at 70℃ for 8h to obtain a high-conductivity cobalt-nitrogen-coordinated hard carbon negative electrode material.

[0044] Example 3

[0045] The embodiment provides a preparation method of a high-conductivity cobalt-nitrogen-coordinated hard carbon negative electrode material, which specifically comprises the following steps:

[0046] Step one, 0.3g glucose and 0.15g melamine were mixed and dissolved in a mixed solution of 15ml deionized water and 18ml ethanol, stirring was performed under a water bath at 50℃ for half an hour to ensure complete dissolution, and then the solution was transferred to a 100mL hydrothermal reactor, and hydrothermal reaction was performed at 280℃ for 9h, the product was centrifuged at a centrifugal speed of 1300r / min for 5min, the supernatant was discarded, the obtained solid material was washed with 20mL deionized water for three times, and then washed with 20mL ethanol for two times, and the obtained solid material was dried at 60℃ for 10h to obtain a precursor powder;

[0047] Step two, the 0.5g precursor powder was dispersed in 55ml deionized water to form an A solution, 0.15g zinc nitrate and 0.07g cobalt nitrate were dissolved in 55mL deionized water to form a B solution, and then the A solution and the B solution were mixed and stirred under a water bath at 50℃ for 24h; after stirring, the obtained product was centrifuged at a centrifugal speed of 1700r / min for 10min, the supernatant was discarded, the obtained solid material was washed with 20mL deionized water for three times, and the obtained solid material was dried at 60℃ for 10h to obtain an intermediate product;

[0048] Step three, the obtained intermediate product and vulcanizing agent (0.064g sulfur and 0.152g thiourea powder) were mixed in a mass ratio of 1:2.2 in a agate mortar, and then the mixed powder was transferred to a ceramic capsule, heated to 400℃ at a rate of 6℃ / min in an inert atmosphere for 3h, and then continued to heat to 1100℃ at a rate of 6℃ / min for 6h, and then naturally cooled, the obtained product was dispersed in dilute hydrochloric acid with a concentration of 1.5mol / L, stirred for 12h, suction filtered, and dried at 90℃ for 6h to obtain a high-conductivity cobalt-nitrogen-coordinated hard carbon negative electrode material.

[0049] Comparative example 1

[0050] The present comparative example provides a hard carbon negative electrode material, which is different from that of Example 1 in that the present comparative example does not employ nitrogen doping, and specifically comprises the following steps:

[0051] Step one, 0.3 g of glucose was dissolved in a mixed solution of 15 ml of deionized water and 15 ml of ethanol, and stirring was carried out under a 50°C water bath for half an hour to ensure its complete dissolution, and then it was transferred to a 100 ml hydrothermal reactor, and hydrothermal reaction was carried out at 240°C for 10 h, the product was centrifuged at a centrifugal speed of 900 r / min for 10 min, the supernatant was discarded, the obtained solid material was washed with 20 mL of deionized water for three times, and then washed with 20 mL of ethanol for two times, and the obtained solid material was dried at 60°C for 10 h to obtain a precursor powder;

[0052] Step two, the 0.5 g of precursor powder was dispersed in 50 ml of deionized water, and stirring was carried out to form an A solution; 0.15 g of zinc nitrate and 0.07 g of cobalt nitrate were dissolved in 50 mL of deionized water to form a B solution; then the A solution and the B solution were mixed, and stirring was carried out under a 45°C water bath for 24 h; after the stirring was completed, the obtained product was centrifuged at a centrifugal speed of 1300 r / min for 10 min, the supernatant was discarded, the obtained solid material was washed with 20 mL of deionized water for three times, and the obtained solid material was dried at 60°C for 10 h to obtain an intermediate product;

[0053] Step three, the obtained intermediate product and a sulfurizing agent (0.064 g of sulfur and 0.152 g of thiourea powder) were mixed in a mass ratio of 1:2 in a corundum mortar, and then the mixed powder was transferred to a ceramic capsule, and heated to 350°C at a rate of 5°C / min in an inert atmosphere for 3 h, and then continued to be heated to 1000°C at a rate of 5°C / min for 6 h, and then naturally cooled, the obtained product was dispersed in dilute hydrochloric acid with a concentration of 2 mol / L, and stirring was carried out for 12 h, and then suction filtration was carried out, and drying was carried out at 70°C for 8 h to obtain a high-conductivity cobalt-nitrogen-coordinated hard carbon negative electrode material.

[0054] Comparative Example 2

[0055] The present comparative example provides a hard carbon negative electrode material, which is different from that of Example 1 in that the present comparative example does not employ cobalt doping, and specifically comprises the following steps:

[0056] Step one, 0.3g glucose and 0.15g melamine were mixed and dissolved in a mixed solution of 15ml deionized water and 15ml ethanol, stirred at 50℃ water bath for half an hour to ensure complete dissolution, then transferred to a 100ml hydrothermal reactor, hydrothermal reaction at 240℃ for 10h, the product was centrifuged at 900r / min for 10min, the supernatant was discarded, the obtained solid material was washed with 20ml deionized water for three times, and then washed with 20ml ethanol for two times, the obtained solid material was dried at 60℃ for 10h, and the precursor powder was obtained;

[0057] Step two, the 0.5g precursor powder was dispersed in 50ml deionized water, stirred uniformly to form A solution; 0.15g zinc nitrate was dissolved in 50ml deionized water to form B solution; then A solution and B solution were mixed, stirred at 45℃ water bath for 24h; after stirring, the obtained product was centrifuged at 1300r / min for 10min, the supernatant was discarded, the obtained solid material was washed with 20ml deionized water for three times, and then dried at 60℃ for 10h, and the intermediate product was obtained;

[0058] Step three, the obtained intermediate product was mixed with sulfurizing agent (0.064g sulfur and 0.152g thiourea powder) in a mass ratio of 1:2 in a agate mortar, then the mixed powder was transferred to a ceramic capsule, heated to 350℃ at a rate of 5℃ / min in an inert atmosphere for 3h, then continued to heat to 1000℃ at a rate of 5℃ / min for 6h, and then naturally cooled, the obtained product was dispersed in 2mol / L dilute hydrochloric acid, stirred for 12h, filtered, and dried at 70℃ for 8h to obtain a high-conductivity cobalt-nitrogen coordination hard carbon negative electrode material.

[0059] Comparative example 3

[0060] This comparative example provides a hard carbon negative electrode material, which is different from example 1 in that metal nickel is used instead of metal zinc as a template, which specifically includes the following steps:

[0061] Step one, 0.3g glucose and 0.15g melamine were mixed and dissolved in a mixed solution of 15ml deionized water and 15ml ethanol, stirred at 50℃ water bath for half an hour to ensure complete dissolution, then transferred to a 100ml hydrothermal reactor, hydrothermal reaction at 240℃ for 10h, the product was centrifuged at 900r / min for 10min, the supernatant was discarded, the obtained solid material was washed with 20ml deionized water for three times, and then washed with 20ml ethanol for two times, the obtained solid material was dried at 60℃ for 10h, and the precursor powder was obtained;

[0062] Step two, the 0.5g precursor powder was dispersed in 50ml deionized water, stirred uniformly, to form A solution; 0.15g of nickel nitrate and 0.07g of cobalt nitrate were dissolved in 50ml deionized water to form B solution; then A solution and B solution were mixed, stirred under 40℃ water bath for 24h; after stirring, the obtained product was centrifuged at 1300r / min for 10min, the supernatant was discarded, the obtained solid material was washed with 20ml deionized water for three times, and the obtained solid material was dried at 60℃ for 10h to obtain an intermediate product;

[0063] Step three, the obtained intermediate product and sulfurizing agent (0.064g of elemental sulfur and 0.152g of thiourea powder) were mixed in a mass ratio of 1:2 in a agate mortar, then the mixed powder was transferred to a ceramic canister, heated to 350℃ at a rate of 5℃ / min in an inert atmosphere, and kept for 3h, then continued to heat to 1000℃ at a rate of 5℃ / min and kept for 6h, and then naturally cooled, the obtained product was dispersed in 2mol / L dilute hydrochloric acid, stirred for 12h, suction filtered, and dried at 70℃ for 8h to obtain a hard carbon negative electrode material.

[0064] Comparative example 4

[0065] This comparative example provides a hard carbon negative electrode material, which is different from example 1 in that no sulfurizing agent is used for modification in step three, and other contents and components are unchanged, which specifically includes the following steps:

[0066] Step one, 0.3g of glucose and 0.15g of melamine were mixed and dissolved in a mixed solution of 15ml deionized water and 15ml ethanol, stirred in a 50℃ water bath for half an hour to ensure complete dissolution, then transferred to a 100ml hydrothermal reactor, and hydrothermally reacted at 240℃ for 10h, the product was centrifuged at 900r / min for 10min, the supernatant was discarded, the obtained solid material was washed with 20ml deionized water for three times, and then washed with 20ml ethanol for two times, and the obtained solid material was dried at 60℃ for 10h to obtain a precursor powder;

[0067] Step two, the 0.5g precursor powder was dispersed in 50ml deionized water, stirred uniformly, to form A solution; 0.15g of nickel nitrate and 0.07g of cobalt nitrate were dissolved in 50ml deionized water to form B solution; then A solution and B solution were mixed, stirred under 40℃ water bath for 24h; after stirring, the obtained product was centrifuged at 1300r / min for 10min, the supernatant was discarded, the obtained solid material was washed with 20ml deionized water for three times, and the obtained solid material was dried at 60℃ for 10h to obtain an intermediate product;

[0068] Step three, the obtained intermediate product mixed powder was transferred to a ceramic capsule, heated to 350℃ at a rate of 5℃ / min in an inert atmosphere for 3h, then continued to heat to 1000℃ at a rate of 5℃ / min for 6h, waited for its natural cooling, dispersed the obtained product in dilute hydrochloric acid with a concentration of 2mol / L, stirred for 12h, suction filtered, and dried at 70℃ for 8h to obtain the high-conductivity cobalt-nitrogen coordinated hard carbon negative electrode material.

[0069] Test Example 1

[0070] The high-conductivity cobalt-nitrogen coordinated hard carbon negative electrode material obtained in Example 1 was prepared into a sodium ion battery, and the specific operation was as follows:

[0071] Step one, 0.9g of the high-conductivity cobalt-nitrogen coordinated hard carbon negative electrode material and 0.1g of polyvinylidene fluoride were mixed uniformly and dispersed in 0.5mL of N-methylpyrrolidone, stirred for 10min to obtain a mixed slurry;

[0072] Step two, the mixed slurry was coated on a copper foil with a thickness of 100μm, and vacuum dried at 80℃ for 12h, and a circular electrode was punched out from the copper foil;

[0073] Step three, the circular electrode was transferred to an argon-filled glove box for button cell assembly; a sodium metal was used as a reference electrode to make a battery; and a sodium bis(fluorosulfonyl)imide with a concentration of 1mol / L dissolved in dimethyl ether was used as an electrolyte.

[0074] Test Example 2

[0075] The high-conductivity cobalt-nitrogen coordinated hard carbon negative electrode material obtained in Example 2 was prepared into a sodium ion battery, and the specific operation was the same as that in Test Example 1.

[0076] Test Example 3

[0077] The high-conductivity cobalt-nitrogen coordinated hard carbon negative electrode material obtained in Example 3 was prepared into a sodium ion battery, and the specific operation was the same as that in Test Example 1.

[0078] Test Example 4

[0079] The hard carbon negative electrode material obtained in Comparative Example 1 was prepared into a sodium ion battery, and the specific operation was the same as that in Test Example 1.

[0080] Test Example 5

[0081] The hard carbon negative electrode material obtained in Comparative Example 2 was prepared into a sodium ion battery, and the specific operation was the same as that in Test Example 1.

[0082] Test Example 6

[0083] The hard carbon negative electrode material obtained in Comparative Example 3 was prepared into a sodium ion battery, and the specific operation was the same as that in Test Example 1.

[0084] Test Example 7

[0085] The hard carbon negative material obtained in Comparative Example 4 was prepared into a sodium ion battery, and the specific operation was the same as that in Test Example 1.

[0086] To further embody the application of the high-conductivity cobalt-nitrogen coordination hard carbon negative material provided by the present application in sodium ion batteries, the sodium ion batteries obtained in each test example were subjected to electrochemical performance test under different current densities by a blue light test system, and the current density used in the test was 0.5 A / g, and the results are shown in Table 1.

[0087] Table 1: Test results of sodium ion batteries obtained in each test example

[0088]

[0089]

[0090] According to the data in Table 1, it can be seen that the high-conductivity cobalt-nitrogen coordination hard carbon negative material provided by the present application has excellent electrochemical performance in sodium ion batteries, especially the sodium ion battery prepared from the high-conductivity cobalt-nitrogen coordination hard carbon negative material obtained in Example 1 has a first cycle discharge capacity of 458.3 mAh / g and a first cycle charge capacity of 396.5 mAh / g under the same current density, and the capacity retention rate is still as high as 96.2% after 500 cycles. It can be seen that the high-conductivity cobalt-nitrogen coordination hard carbon negative material provided by the present application not only has high conductivity but also has high stability, effectively solving the problems of low conductivity rate of hard carbon negative material used in sodium ion batteries, the need to add additional carbon-based conductive additives, and high process cost and complex operation in the prior art.

[0091] The above only describes the preferred embodiments of the present application and should not be used to limit the present application. Any modification, equivalent replacement or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a high-conductivity cobalt-nitrogen coordination hard carbon negative electrode material, characterized by comprising the following steps: Comprising the following steps: ​ Step one, dissolving carbon source and nitrogen source in alcohol solution, hydrothermal reaction, centrifugation, washing, drying, to get precursor powder; Step two, dispersing the precursor powder in deionized water to get A solution; dissolving zinc salt and cobalt salt in deionized water to get B solution; mixing A solution and B solution uniformly, reacting at 40-50℃ for 20-30h, centrifugation, washing, drying, to get intermediate product; Step three, mixing the intermediate product and sulfurizing agent uniformly, under inert atmosphere, once heating to 300-400℃ for 2-4h, continuing twice heating to 900-1100℃ for 5-7h, cooling, dispersing in acid solution, stirring, solid-liquid separation, drying, to get high-conductivity cobalt-nitrogen coordination hard carbon negative electrode material.

2. The preparation method of the high-conductivity cobalt-nitrogen coordination hard carbon negative electrode material according to claim 1, characterized in that: In step one, the carbon source is glucose; and / or In step one, the nitrogen source is melamine; and / or In step one, the mass ratio of carbon source to nitrogen source is 2-4:1-2.

3. The method for preparing the highly conductive cobalt-nitrogen coordinated hard carbon anode material as described in claim 1, characterized in that: In step one, the alcohol solution is 45-55% ethanol aqueous solution; and / or In step one, the hydrothermal reaction temperature is 200-280℃, and the hydrothermal reaction time is 9-11h.

4. The method for preparing the highly conductive cobalt-nitrogen coordinated hard carbon anode material as described in claim 1, characterized in that: In step two, the zinc salt is any one of zinc nitrate, zinc sulfate or zinc chloride; and / or In step two, the cobalt salt is any one of cobalt nitrate, cobalt chloride or cobalt sulfate; and / or In step two, the molar ratio of zinc salt to cobalt salt is 2-3:

1.

5. The method for preparing the highly conductive cobalt-nitrogen coordinated hard carbon anode material as described in claim 1, characterized in that: In step two, the mass concentration of A solution is 0.008-0.012g / mL; and / or In step two, the total mass concentration of cobalt salt and zinc salt in B solution is 0.004-0.006g / mL.

6. The method for preparing the highly conductive cobalt-nitrogen coordinated hard carbon anode material as described in claim 1, characterized in that: In step three, the mass ratio of intermediate product to sulfurizing agent is 1:2-2.

2.

7. The method for preparing the highly conductive cobalt-nitrogen coordinated hard carbon anode material as described in claim 1, characterized in that: In step three, the sulfurizing agent is a mixture of sulfur and thiourea with a mass ratio of 1:2-2.5; and / or In step three, the acid solution is 1-3mol / L hydrochloric acid solution.

8. The method for preparing the highly conductive cobalt-nitrogen coordinated hard carbon anode material as described in claim 1, characterized in that: In step three, both the first heating and the second heating use programmed heating, and the heating rate of the programmed heating is 4-6℃ / min.

9. A high-conductivity cobalt-nitrogen-coordinated hard carbon negative electrode material, characterized in that: The high-conductivity cobalt-nitrogen coordination hard carbon negative electrode material is prepared by the method of any one of claims 1-8.

10. The use of the high-conductivity cobalt-nitrogen coordination hard carbon negative electrode material of claim 9 in sodium ion battery.

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