Transition metal sulfide hard carbon composite material and preparation method and application thereof

Abstract

The embodiment of the invention relates to a transition metal sulfide hard carbon composite material and a preparation method and application thereof. The preparation method comprises the following steps: dissolving a transition metal compound in a solvent to form a solution with the molar concentration of 3-10%, adding a high-molecular polymer containing an exchange group, and fully stirring to obtain a high-molecular polymer with transition metal ions; putting the mixture into heat treatment equipment, carrying out heat treatment for 5-20 hours in a protective atmosphere environment at 700-1600 DEG C, and carrying out carbonization treatment, crushing and grading, so as to obtain a primary carbonized material; the primary carbonized material is subjected to heat preservation for 1-2 hours at the temperature of 600-2500 DEG C in a protective atmosphere environment, so that transition metal elements in the primary carbonized material escape through pore parts of the material, and a precursor material is obtained; and mixing the precursor material with sulfur powder, heating, and introducing a mixed gas containing a carbon source gas for chemical vapor deposition coating to obtain the transition metal sulfide hard carbon composite material.

Description

Technical Field

[0001] The technical field of battery materials specifically relates to a transition metal sulfide hard carbon composite material and a preparation method and application thereof. Background Art

[0002] With the rise of the energy storage market, sodium-ion batteries have attracted widespread attention. For the main negative electrode hard carbon materials of sodium-ion batteries, the current market specific capacity fluctuates around 300mAh / g, which is difficult to meet the current development and application of high-capacity sodium-ion batteries.

[0003] Transition metal sulfides, such as ferrous sulfide, cobalt disulfide, and nickel sulfide, can be used as a high-capacity sodium-ion negative electrode battery material, with a capacity of up to 600 mAh / g and a simple material synthesis process. However, transition metal sulfide electrode materials have volume expansion problems, low initial efficiency, poor rate performance, and poor cycle performance, which limit their practical application in high-capacity sodium-ion battery materials. Summary of the invention

[0004] The purpose of the present invention is to provide a transition metal sulfide hard carbon composite material and its preparation method and application. By modifying the transition metal sulfide material during the preparation process, the transition metal sulfide material of the composite hard carbon has significantly improved capacity and conductivity, and the volume expansion problem is also alleviated.

[0005] In a first aspect, an embodiment of the present invention provides a method for preparing a transition metal sulfide hard carbon composite material, the preparation method comprising:

[0006] Dissolving a transition metal compound in a solvent to form a solution with a molar concentration of 3% to 10%, adding a polymer containing an exchange group to the solution, stirring the solution at a speed of 100 to 600 r / min to allow the transition metal ions to undergo ion exchange with the exchange groups of the polymer, filtering and washing, and drying to obtain a polymer containing transition metal ions;

[0007] Placing the high molecular polymer having transition metal ions in a heat treatment device, and heat treating it at 700° C. to 1600° C. in a protective atmosphere for 5 to 20 hours to carbonize the high molecular polymer having transition metal ions, and then crushing and classifying the carbonized material to obtain a primary carbonized material;

[0008] Put the primary carbonized material into an induction furnace, heat it to 1600°C - 2100°C at a rate of 1°C / min - 10°C / min under a protective atmosphere environment, and keep it warm for 1 hour - 5 hours, so that the transition metal elements inside the primary carbonized material escape through the pore part of the material to obtain a precursor material;

[0009] Mix the precursor material and sulfur powder in a mass ratio of 10:1 - 1:1, heat it to 600°C - 1000°C in a rotary furnace under a protective atmosphere environment, keep it warm for 1 hour - 10 hours, then introduce a mixed gas composed of a carbon source gas and a protective gas, and perform coating by chemical vapor deposition. The coating temperature is 600 - 1000°C, and the coating time is 1 - 12h to obtain the transition metal sulfide hard carbon composite material.

[0010] Preferably, the transition metal compound includes: one or more of iron-containing compounds, cobalt-containing compounds, and nickel-containing compounds;

[0011] The exchange group includes: sulfonic acid group (-SO 3 H) and / or carboxyl group (-COOH);

[0012] The polymer includes: one or more of polystyrene, polyethylene oxide, urea-formaldehyde resin, and acrylic resin;

[0013] During the carbonization process, the polymer with transition metal ions first forms a material with a cementite structure, and as the process progresses, the transition metal ions diffuse into the interior of the material to form an onion carbon layer on the outer layer of the material.

[0014] Preferably, the mass ratio of the precursor material to sulfur powder is 2:1 - 1:1;

[0015] The carbon source gas is one or more of methane, acetylene, ethylene, and propylene; the mixed volume ratio of the protective gas and the carbon source gas is 4:1 - 1:2.

[0016] More preferably, the mixed volume ratio of the protective gas and the carbon source gas is 1:1 - 2:1; the coating time is 4 - 8h.

[0017] Preferably, the protective atmosphere environment is an environment into which the protective gas is introduced, and the protective gas includes: nitrogen or argon.

[0018] Preferably, the solvent includes water or polar organic solvents.

[0019] Preferably, the transition metal compound specifically includes: one or more of sulfates, nitrates, carbonates, and chlorides of iron and / or cobalt and / or nickel.

[0020] Second aspect, an embodiment of the present invention provides a transition metal sulfide hard carbon composite material prepared by the preparation method described in the first aspect above.

[0021] Third aspect, an embodiment of the present invention provides a negative electrode for a sodium ion battery, comprising the transition metal sulfide hard carbon composite material described in the second aspect above.

[0022] Fourth aspect, an embodiment of the present invention provides a sodium ion battery, comprising the negative electrode for a sodium ion battery described in the third aspect above.

[0023] The preparation method of the transition metal sulfide hard carbon composite material provided by the embodiment of the present invention successfully prepares a novel sulfide hard carbon composite material through steps such as ion exchange, formation of cementite structure, and carbon coating.

[0024] The technical solution of the present invention solves the problem of the composite strength between hard carbon and transition metal sulfide: through the methods of ion exchange and formation of cementite structure, the obtained structure has a high composite strength between hard carbon and transition metal sulfide, realizing the efficient composite between hard carbon and transition metal sulfide.

[0025] The technical solution of the present invention solves the problem of the expansion of transition metal sulfide: by using uniformly dispersed nano-transition metal sulfide prepared from cementite and sulfurization, the expansion stress effect of particles is effectively reduced. During the high-temperature process, some transition metal elements are gasified and removed to form pore channels, and at the same time, a buffer space is formed in the hard carbon layer, providing sufficient buffer space for volume transformation. Compared with the traditional method, this preparation method solves the problems of agglomeration and uneven dispersion in one step.

[0026] The technical solution of the present invention solves the problem of poor conductivity of transition metal sulfide: by constructing a transition metal sulfide with a hard carbon layer structure and combining a dense structure, the conductivity of transition metal sulfide particles is significantly improved. This design effectively improves the problem of poor conductivity of sulfide and greatly improves the rate performance at the same time.

[0027] In summary, the present invention introduces transition metal ions into a polymer, and forms a material containing a cementite structure through high-temperature treatment. This structural design helps to reduce the expansion stress of the material and improve the cycle stability. At the same time, carbon coating is carried out on the material by chemical vapor deposition, improving the performance of the material as a battery negative electrode material, including the first Coulomb efficiency, cycle performance, and conductivity. Description of the Drawings

[0028] Figure 1 It is a flowchart of the preparation method of the transition metal sulfide hard carbon composite material provided by the embodiment of the present invention;

[0029] Figure 2This is a transmission electron microscope (TEM) image of the transition metal sulfide hard carbon composite material provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0031] The present invention provides a transition metal sulfide hard carbon composite material. The preparation method thereof comprises the following steps: Figure 1 As shown, including:

[0032] Step 110, dissolving the transition metal compound in a solvent to form a solution with a molar concentration of 3%-10%, adding a polymer containing exchange groups to the solution, and stirring at a speed of 100r / min-600r / min to allow the transition metal ions to undergo and complete ion exchange with the exchange groups of the polymer, and then filtering and washing, and drying to obtain the polymer containing transition metal ions.

[0033] Specifically, the transition metal compound includes: one or more of iron-containing compounds, cobalt-containing compounds, and nickel-containing compounds, and specifically includes: one or more of sulfates, nitrates, carbonates, and chlorides of iron and / or cobalt and / or nickel.

[0034] The solvent may include water or a polar organic solvent.

[0035] High molecular weight polymer refers to a high molecular weight (usually up to 104-106) compound formed by repeated covalent bonds, mainly including: one or more of polystyrene, polyethylene oxide, urea-formaldehyde resin, acrylic resin; Q exchange groups include: sulfonic acid group (-SO 3 H) and / or carboxyl (-COOH) groups, etc.

[0036] Step 120, placing the high molecular polymer having transition metal ions in a heat treatment device, and heat treating it at 700°C to 1600°C in a protective atmosphere for 5 hours to 20 hours to carbonize the high molecular polymer having transition metal ions, and then crushing and classifying the carbonized material to obtain a primary carbonized material.

[0037] Specifically, the protective atmosphere environment is an environment in which a protective gas is introduced, and the protective gas includes: nitrogen or argon.

[0038] During the carbonization process, the high molecular polymer with transition metal ions first forms a material with a cementite structure, and as the treatment progresses, the transition metal ions diffuse into the interior of the material to form an onion carbon layer on the outer layer of the material.

[0039] Step 130: Put the primary carbonized material into an induction furnace, heat it from room temperature to 1600°C - 2100°C at a rate of 1°C / min - 10°C / min in a protective atmosphere environment, and hold for 1 hour - 5 hours, so that the transition metal elements inside the primary carbonized material escape through the pore part of the material, obtaining a precursor material.

[0040] Preferably, the temperature is 1800°C - 2100°C.

[0041] Step 140: Mix the precursor material and sulfur powder at a mass ratio of 10:1 - 1:1, heat it to 600°C - 1000°C in a protective atmosphere environment in a rotary furnace, hold for 1 hour - 10 hours, then introduce a mixed gas composed of a carbon source gas and a protective gas, and perform coating by chemical vapor deposition. The coating temperature is 600 - 1000°C, and the coating time is 1 - 12 h, obtaining a transition metal sulfide hard carbon composite material.

[0042] Among them, the carbon source gas is one or more of methane, acetylene, ethylene, and propylene; in the mixed gas, the volume ratio of the protective gas to the carbon source gas is 4:1 - 1:2, more preferably 1:1 - 2:1.

[0043] The mass ratio of the precursor material to sulfur powder is preferably 2:1 - 1:1; the coating time is preferably 4 - 8 h.

[0044] The preparation method of the transition metal sulfide hard carbon composite provided by the embodiment of the present invention uses cementite and sulfidation and coating processes to prepare the transition metal sulfide hard carbon composite, which can effectively reduce the expansion stress of the material and improve the cycle stability of the material. By using the penetrant to form nanoparticles containing transition metal inside the carbon material, under the further action of high temperature, some transition metal elements are gasified and removed to form pore channels in the outer carbon material layer, and then transition metal sulfide is generated through a sulfidation reaction. The transition metal sulfide hard carbon composite prepared by the method provided by the above embodiment has high composite strength and stable cycle performance. Part of the reason is that the space formed after the gasification and removal of some transition metals also provides sufficient buffer space for the volume change of the subsequently formed transition metal sulfide and the material during the charge and discharge cycle. At the same time, the onion carbon layer formed by cementite in the hard carbon matrix forms a graphite conductive layer between the formed transition metal sulfide and the hard carbon matrix, which improves its electron conductivity and the rate performance of the whole composite. Compared with the existing method of separately preparing nanosized transition metal sulfide and then performing carbon material composite, it can solve the agglomeration problem in one step and solve a series of problems such as uneven dispersion during the composite process of nanosized transition metal sulfide and carbon material. The composite structure of the transition metal sulfide and the carbon material layer structure formed by this preparation method is tightly combined, greatly improving the conductivity of the transition metal sulfide particles, improving its rate performance, and enhancing the rate performance of the material.

[0045] In order to more clearly illustrate the purpose and advantages of the present invention, the following further elaborates on the present invention in combination with embodiments. In addition, the embodiments described in the present invention are only partial embodiments. All other embodiments obtained by those skilled in the art without creative efforts based on the embodiments described in the present invention belong to the protection scope of the present invention. Additionally, it should be understood that these embodiments are only for more detailed illustration and should not be construed as limiting the present invention in any form, that is, it is not intended to limit the protection scope of the present invention.

[0046] Example 1

[0047] This example provides a preparation method of a transition metal sulfide hard carbon composite, and the specific preparation steps are as follows.

[0048] Dissolve 200 g of iron nitrate in 2190 ml of deionized water to prepare a solution with a concentration of about 5%. Add a polymer containing sulfonic acid groups (-SO 3H) 220 g of polystyrene polymer (exchange capacity of about 4.5 mmol / g) as an exchange group, at a speed of 100 r / min, fully stirred for 6 hours until the ion exchange is completed, filtered and washed 3 times, and dried to obtain a polymer with iron ions;

[0049] The dried sample was placed in an atmosphere furnace, heated to 700°C under a nitrogen atmosphere and kept warm for 48 hours, and the sample was crushed and classified to obtain 150 g of primary carbonized material;

[0050] 150 g of primary carbonized material was placed in an induction furnace, heated to 2100°C at 1°C / min in an argon atmosphere, and kept at this temperature for 2 hours before discharging the material;

[0051] The material obtained by discharging is mixed with sulfur powder in a mass ratio of 1:1, heated to 700°C in a nitrogen atmosphere in a rotary furnace for 10 hours, then heated to 900°C, and a mixed gas consisting of nitrogen and acetylene in a volume ratio of 3:1 is introduced for carbon coating for 6 hours. After discharging, a transition metal sulfide hard carbon composite material is obtained. Figure 2 This is a transmission electron microscope (TEM) image of the transition metal sulfide hard carbon composite material prepared in Example 1 of the present invention.

[0052] Example 2

[0053] This embodiment provides a method for preparing a transition metal sulfide hard carbon composite material, and the specific preparation steps are as follows.

[0054] Dissolve 200g of nickel sulfate in 2190ml of deionized water to prepare a solution with a concentration of about 5%. Add a sulfonic acid group (-SO 3 H) 220 g of polystyrene polymer (exchange capacity of about 4.5 mmol / g) as an exchange group, at a speed of 100 r / min, fully stirred for 6 hours until the ion exchange is completed, filtered and washed 3 times, and dried to obtain a polymer with iron ions;

[0055] The dried sample was placed in an atmosphere furnace, heated to 700°C under a nitrogen protective atmosphere and kept warm for 48 hours, and the material was crushed and classified to obtain 145g of primary carbonized material;

[0056] 145 g of primary carbonized material was placed in an induction furnace, heated to 2100°C at 1°C / min in an argon atmosphere, and kept at this temperature for 2 hours before discharging the material;

[0057] After mixing the material obtained from discharging with sulfur powder at a mass ratio of 1:1, it is heated to 700 °C in a rotary furnace under a nitrogen atmosphere and kept warm for 10 hours, then the temperature is raised to 900 °C, and a mixed gas composed of nitrogen and acetylene with a volume ratio of 3:1 is introduced for carbon coating for 6 hours. After discharging, the transition metal sulfide hard carbon composite material is obtained.

[0058] Example 3

[0059] This example provides a preparation method of a transition metal sulfide hard carbon composite material, and the specific preparation steps are as follows.

[0060] Dissolve 200 g of cobalt sulfate in 2190 ml of deionized water to prepare a solution with a concentration of about 5%. Add 220 g of polystyrene polymer (exchange capacity is about 4.5 mmol / g) containing sulfonic acid group (-SO 3 H) as the exchange group according to the molar ratio of iron ions to the exchange groups in the polymer of 1:2. Stir thoroughly at a speed of 100 r / min for 6 hours until the ion exchange is completed, then filter and wash 3 times, and dry to obtain the polymer with iron ions.

[0061] Put the dried sample into an atmosphere furnace, heat it to 700 °C under a nitrogen protection atmosphere and keep warm for 48 hours, discharge and crush and classify to obtain 147 g of primary carbonized material.

[0062] Put 147 g of the primary carbonized material into an induction furnace, heat it to 2100 °C at a rate of 1 °C / min under an argon atmosphere, and discharge after keeping warm for 2 hours.

[0063] After mixing the material obtained from discharging with sulfur powder at a mass ratio of 1:1, it is heated to 700 °C in a rotary furnace under a nitrogen atmosphere and kept warm for 10 hours, then the temperature is raised to 900 °C, and a mixed gas composed of nitrogen and acetylene with a volume ratio of 3:1 is introduced for carbon coating for 6 hours. After discharging, the transition metal sulfide hard carbon composite material is obtained.

[0064] Example 4

[0065] This example provides a preparation method of a transition metal sulfide hard carbon composite material, and the specific preparation steps are as follows.

[0066] Dissolve 200 g of iron nitrate in 2190 ml of deionized water to prepare a solution with a concentration of about 5%. Add 220 g of polystyrene polymer (exchange capacity is about 4.5 mmol / g) containing sulfonic acid group (-SO 3H) 220 g of polystyrene high polymer as an exchange group (exchange capacity is about 4.5 mmol / g), with a rotation speed of 100 r / min, fully stirred for 6 hours until the ion exchange is completed, then filtered and washed 3 times, and after drying, a high polymer with iron ions is obtained;

[0067] Put the dried sample into an atmosphere furnace, heat it up to 1600 °C under a nitrogen protection atmosphere and keep it warm for 48 hours, then discharge and crush and classify it to obtain 150 g of primary carbonized material;

[0068] Put 150 g of the primary carbonized material into an induction furnace, heat it up to 2100 °C at a rate of 1 °C / min under an argon atmosphere, and discharge after keeping it warm for 2 hours;

[0069] Mix the discharged material with sulfur powder in a mass ratio of 1:1, heat it in a rotary furnace under a nitrogen atmosphere to 700 °C and keep it warm for 10 hours, then raise the temperature to 900 °C, and introduce a mixed gas composed of nitrogen and acetylene with a volume ratio of 3:1 for carbon coating for 6 hours. After discharging, the transition metal sulfide hard carbon composite material is obtained.

[0070] Example 5

[0071] This example provides a preparation method of a transition metal sulfide hard carbon composite material, and the specific preparation steps are as follows.

[0072] Dissolve 200 g of iron nitrate in 2190 ml of deionized water to prepare a solution with a concentration of about 5%, and add 220 g of polystyrene high polymer with sulfonic acid group (-SO 3 H) as an exchange group (exchange capacity is about 4.5 mmol / g) according to the molar ratio of iron ions to the exchange groups in the high polymer of 1:2. With a rotation speed of 100 r / min, fully stir for 6 hours until the ion exchange is completed, then filter and wash 3 times, and after drying, a high polymer with iron ions is obtained;

[0073] Put the dried sample into an atmosphere furnace, heat it up to 700 °C under a nitrogen protection atmosphere and keep it warm for 48 hours, then discharge and crush and classify it to obtain 150 g of primary carbonized material;

[0074] Put 150 g of the primary carbonized material into an induction furnace, heat it up to 1800 °C at a rate of 1 °C / min under an argon atmosphere, and discharge after keeping it warm for 2 hours;

[0075] Mix the discharged material with sulfur powder in a mass ratio of 1:1, heat it in a rotary furnace under a nitrogen atmosphere to 700 °C and keep it warm for 10 hours, then raise the temperature to 900 °C, and introduce a mixed gas composed of nitrogen and acetylene with a volume ratio of 3:1 for carbon coating for 6 hours. After discharging, the transition metal sulfide hard carbon composite material is obtained.

[0076] Example 6

[0077] This example provides a method for preparing a transition metal sulfide hard carbon composite material, and the specific preparation steps are as follows.

[0078] Dissolve 200 g of iron nitrate in 2190 ml of deionized water to prepare a solution with a concentration of about 5%. Add 220 g of polystyrene polymer containing sulfonic acid group (-SO 3 H) as the exchange group (exchange capacity is about 4.5 mmol / g) according to the molar ratio of iron ions to the exchange group in the polymer of 1:2. Stir at a speed of 100 r / min for 6 hours until the ion exchange is completed, then filter and wash 3 times, and dry to obtain a polymer with iron ions;

[0079] Put the dried sample into an atmosphere furnace, heat it to 700 °C under a nitrogen protection atmosphere and keep it for 48 hours, then take out the material, crush and classify it to obtain 150 g of primary carbonized material;

[0080] Put 150 g of the primary carbonized material into an induction furnace, heat it to 2100 °C at a rate of 1 °C / min under an argon atmosphere, and take out the material after keeping it for 2 hours;

[0081] Mix the obtained material after discharging with sulfur powder according to a mass ratio of 1:1, heat it to 700 °C in a rotary furnace under a nitrogen atmosphere and keep it for 10 hours, then raise the temperature to 900 °C, and introduce a mixed gas composed of nitrogen and methane with a volume ratio of 3:1 for carbon coating for 6 hours. After discharging, the transition metal sulfide hard carbon composite material is obtained.

[0082] Example 7

[0083] This example provides a method for preparing a transition metal sulfide hard carbon composite material, and the specific preparation steps are as follows.

[0084] Dissolve 200 g of iron nitrate in 2190 ml of deionized water to prepare a solution with a concentration of about 5%. Add 220 g of polystyrene polymer containing sulfonic acid group (-SO 3 H) as the exchange group (exchange capacity is about 4.5 mmol / g) according to the molar ratio of iron ions to the exchange group in the polymer of 1:2. Stir at a speed of 100 r / min for 6 hours until the ion exchange is completed, then filter and wash 3 times, and dry to obtain a polymer with iron ions;

[0085] Put the dried sample into an atmosphere furnace, heat it to 700 °C under a nitrogen protection atmosphere and keep it for 48 hours, then take out the material, crush and classify it to obtain 150 g of primary carbonized material;

[0086] 150 g of primary carbonized material was placed in an induction furnace, heated to 2100°C at 1°C / min in an argon atmosphere, and kept at this temperature for 2 hours before discharging the material;

[0087] The material obtained by discharging was mixed with sulfur powder in a mass ratio of 1:1, heated to 700°C in a nitrogen atmosphere in a rotary furnace for 10 hours, then heated to 900°C, and a mixed gas consisting of nitrogen and acetylene in a volume ratio of 10:1 was introduced for carbon coating for 6 hours. After discharging, a transition metal sulfide hard carbon composite material was obtained.

[0088] Example 8

[0089] This embodiment provides a method for preparing a transition metal sulfide hard carbon composite material, and the specific preparation steps are as follows.

[0090] Dissolve 200g of ferric nitrate in 2190ml of deionized water to prepare a solution with a concentration of about 5%. Add a sulfonic acid group (-SO 3 H) 220 g of polystyrene polymer (exchange capacity of about 4.5 mmol / g) as an exchange group, at a speed of 100 r / min, fully stirred for 6 hours until the ion exchange is completed, filtered and washed 3 times, and dried to obtain a polymer with iron ions;

[0091] The dried sample was placed in an atmosphere furnace, heated to 700°C under a nitrogen atmosphere and kept warm for 48 hours, and the sample was crushed and classified to obtain 150 g of primary carbonized material;

[0092] 150 g of primary carbonized material was placed in an induction furnace, heated to 2100°C at 1°C / min in an argon atmosphere, and kept at this temperature for 2 hours before discharging the material;

[0093] The material obtained by discharging is mixed with sulfur powder in a mass ratio of 1:1, heated to 700°C in a nitrogen atmosphere in a rotary furnace for 10 hours, then heated to 900°C, and a mixed gas consisting of nitrogen and acetylene in a volume ratio of 3:1 is introduced for carbon coating for 10 hours. After discharging, a transition metal sulfide hard carbon composite material is obtained.

[0094] Comparative Example 1

[0095] This comparative example 1 is used to prepare nano ferrous sulfide particles for comparison.

[0096] 200 g of ferrous sulfide particles were ball-milled, the main plate speed of the planetary ball mill was 60 r / min, the speed of the ball mill was 800 r / min, and the ball-milling time was 6 hours to obtain nano ferrous sulfide particles for comparison.

[0097] Comparative Example 2

[0098] Comparative Example 2 is used to prepare a hard carbon composite carbon material containing nano-ferrous sulfide for comparison.

[0099] 20 g of ferrous sulfide particles were ball-milled. The main disk speed of the planetary ball mill was 60 r / min, the ball mill tank speed was 800 r / min, and the ball milling time was 6 hours. Then, 400 g of phenolic resin was added, and the main disk speed of the planetary ball mill was 60 r / min, the ball mill tank speed was 400 r / min, and the ball milling time was 2 hours.

[0100] 200 g of the ball-milled product was placed in an atmosphere furnace, heated to 1200 °C under a nitrogen protection atmosphere and held for 6 hours, and then the product was discharged, pulverized and classified to obtain a hard carbon composite carbon material containing nano-ferrous sulfide.

[0101] In order to verify the electrochemical performance of the transition metal sulfide hard carbon composite material obtained in the examples of the present invention as a negative electrode material for sodium ion batteries, the materials prepared in each example and the comparative example were used as negative electrode active materials, and after slurry preparation, electrode sheet preparation and battery assembly, relevant electrical performance tests were carried out as follows:

[0102] The negative electrode material, conductive additive carbon black, and binder (sodium carboxymethyl cellulose and styrene-butadiene rubber with a volume ratio of 1:1) were weighed according to a mass ratio of 95:2:3. Slurry preparation was carried out in a pulper at room temperature. The prepared slurry was evenly coated on aluminum foil. After drying in a blast drying oven at 50 °C for 2 hours, it was cut into electrode sheets of 8×8 mm and vacuum dried in a vacuum drying oven at 100 °C for 10 hours. The dried electrode sheets were immediately transferred into a glove box for standby to assemble the battery.

[0103] The assembly of the simulated battery was carried out in a glove box containing a high-purity Ar atmosphere. Metallic sodium was used as the counter electrode, and a solution of 1 mol / L LiPF6 in ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio 1:1) was used as the electrolyte to assemble the battery. A constant current charge-discharge mode test was carried out using a charge-discharge instrument. The discharge cut-off voltage was 0.005 V, the charge cut-off voltage was 1.5 V, and the charge-discharge test was carried out at a current density of C / 10. The charge specific capacity and first cycle efficiency obtained from the test are recorded in Table 1 data.

[0104] Using a layered oxide cathode material Na 0.67 Mn 0.45 Ni 0.22 Co 0.33 O 2As the positive electrode active material, it is mixed with the conductive agent Super P and the binder polyvinylidene fluoride (PVDF) in a mass ratio of 90:5:5 to obtain the positive electrode slurry. The positive electrode slurry is coated on the current collector aluminum foil using an automatic coater with a coating thickness of 100 μm, and the positive electrode sheet is obtained after drying. The positive electrode case, the positive electrode sheet, the separator, the electrolyte, the negative electrode, the gasket, the shrapnel, and the negative electrode case are stacked and assembled in sequence to obtain the battery. Among them, the separator uses a polypropylene (PP) base film, and the electrolyte uses a conventional sodium ion electrolyte 1 mol / L NaPF 6 @ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) = 1:1:1 (volume ratio). Assemble two groups of batteries according to the above method. One group of batteries is cycled at 0.1C for 1 cycle in the voltage range of 1.5 - 3.9V, and then cycled at 0.5C, and the cycle capacity retention rates at 10 weeks, 50 weeks, 100 weeks, 200 weeks, and 300 weeks are tested respectively. Another group of batteries is cycled at 0.1C for 1 cycle in the same voltage range,

[0105] and then cycled at 1C, 2C, and 5C rates for 5 weeks respectively to test the capacity retention rates at different rates. The test 5 The obtained data are recorded in Table 1.

[0106]

[0107] Table 1

[0108] It can be seen from the data comparison in Table 1 that in Comparative Example 1, the nano-ferrous sulfide material can maintain a relatively high capacity in the first week, but due to the volume expansion during the charge and discharge process, the capacity decays rapidly during the cycle. In Comparative Example 2, a hard carbon material formed by phenolic resin is used for compounding, but because it is difficult to achieve uniform dispersion of nano-ferrous sulfide particles under the existing ball milling compounding technology, and the stability of its composite structure is poor, it is easy to powder and fall off during the cycle, resulting in obvious attenuation of the cycle performance. For the novel transition metal sulfide hard carbon composite materials prepared in Examples 1 - 8, in the first step, ion exchange is used to ensure the uniform distribution of metal ions in the matrix, and nano-transition metal particles formed by cementite are utilized. Then, the size of the nano-metal particles is reduced by an induction furnace to leave a buffer pore diameter and form pores, which is convenient for the later infiltration of sulfur vapor and the formation of transition metal sulfides with nano-metal particles. The transition metal sulfide hard carbon composite materials constructed in this way have excellent cycle stability.

[0109] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a transition metal sulfide hard carbon composite material, It is characterized in that The preparation method comprises: Dissolving a transition metal compound in a solvent to form a solution with a molar concentration of 3% to 10%, adding a polymer containing an exchange group to the solution, stirring the solution at a speed of 100 to 600 r / min to allow the transition metal ions to undergo ion exchange with the exchange groups of the polymer, filtering and washing, and drying to obtain a polymer containing transition metal ions; Placing the high molecular polymer having transition metal ions in a heat treatment device, and heat treating it at 700° C. to 1600° C. in a protective atmosphere for 5 to 20 hours to carbonize the high molecular polymer having transition metal ions, and then crushing and classifying the carbonized material to obtain a primary carbonized material; The primary carbonized material is placed in an induction furnace, and the temperature is raised to 1600° C. to 2100° C. at a rate of 1° C. / min to 10° C. / min in a protective atmosphere, and the temperature is kept for 1 to 5 hours, so that the transition metal elements in the primary carbonized material escape through the pores of the material to obtain a precursor material; The precursor material and sulfur powder are mixed in a mass ratio of 10:1 to 1:1, heated to 600°C to 1000°C in a protective atmosphere in a rotary furnace, and kept warm for 1 to 10 hours, and then a carbon source gas and a protective gas are introduced to form a mixed gas, and coated by chemical vapor deposition, the coating temperature is 600 to 1000°C, and the coating time is 1 to 12 hours, to obtain the transition metal sulfide hard carbon composite material.

2. The preparation method according to claim 1, It is characterized in that The transition metal compound includes: one or more of an iron-containing compound, a cobalt-containing compound, and a nickel-containing compound; The exchange groups include: sulfonic acid group (-SO 3 H) and / or carboxyl group (-COOH); The high molecular polymer includes: one or more of polystyrene, polyethylene oxide, urea-formaldehyde resin, and acrylic resin; During the carbonization treatment, the high molecular polymer having transition metal ions first forms a material having a cementite structure, and as the treatment progresses, the transition metal ions diffuse into the interior of the material to form an onion carbon layer on the outer layer of the material.

3. The preparation method according to claim 1, It is characterized in that The mass ratio of the precursor material to the sulfur powder is 2:1 to 1:1; The carbon source gas is one or more of methane, acetylene, ethylene, and propylene; the mixed volume ratio of the protective gas and the carbon source gas is 4:1 to 1:

2.

4. The preparation method according to claim 3, It is characterized in that The mixed volume ratio of the protective gas and the carbon source gas is 1:1 to 2:1; and the coating time is 4 to 8 hours.

5. The preparation method according to claim 1, It is characterized in that The protective atmosphere environment is an environment into which the protective gas is introduced, and the protective gas includes: nitrogen or argon.

6. The preparation method according to claim 1, It is characterized in that The solvent includes water or a polar organic solvent.

7. The preparation method according to claim 1, It is characterized in that Specifically, the transition metal compound includes one or more of sulfates, nitrates, carbonates, and chlorides of iron and / or cobalt and / or nickel.

8. A transition metal sulfide hard carbon composite material prepared by the preparation method according to any one of claims 1-7 above.

9. A negative electrode for a sodium ion battery Characterized in that The negative electrode for a sodium ion battery includes the transition metal sulfide hard carbon composite material according to claim 8 above.

10. A sodium ion battery Characterized in that The sodium ion battery includes the negative electrode for a sodium ion battery according to claim 9 above.

Images