Hemp activated carbon loaded nickel disulfide material and application thereof in preparation of lithium-sulfur battery diaphragm

Abstract

The invention belongs to the field of nano materials and lithium-sulfur batteries, and discloses a hemp activated carbon loaded nickel disulfide material and application thereof in preparation of a lithium-sulfur battery diaphragm. The preparation method of the China-hemp activated carbon loaded nickel disulfide material comprises the following steps: placing China-hemp stem core powder in a muffle furnace for carbonization to obtain carbonized China-hemp powder; mixing the carbonized China-hemp powder with zinc chloride, activating in an inert atmosphere, and then washing and drying to obtain China-hemp activated carbon HPC; uniformly mixing the obtained HPC with Ni (NO3) 2.6 H2O, absolute ethyl alcohol and water, then uniformly mixing the mixture with a Na2S solution, then introducing the mixture into a reaction kettle for hydro-thermal treatment, suction filtration, washing and drying to obtain NiS2-coated HPC, namely the China-hemp activated carbon loaded nickel disulfide material. The nickel disulfide loaded China-hemp activated carbon powder material is used as a diaphragm modification layer and is coated on a commercial diaphragm by a scraper method, and the electrochemical performance of a lithium-sulfur battery can be effectively improved when the nickel disulfide loaded China-hemp activated carbon powder material is applied to the lithium-sulfur battery.

Description

Technical Field

[0001] The invention belongs to the field of nano materials and lithium-sulfur batteries, and particularly relates to a hemp activated carbon loaded nickel disulfide material and application thereof in preparing a lithium-sulfur battery diaphragm. Background Art

[0002] In the field of energy storage, with the rapid development and large-scale application of renewable energy, the demand for efficient energy storage systems is becoming increasingly urgent. As a new generation of energy storage technology, lithium-sulfur batteries have shown significant advantages over traditional lithium-ion batteries. First, the theoretical specific energy of lithium-sulfur batteries is as high as 2600Whkg-1, which is 3-5 times that of lithium-ion batteries, and can meet the needs of long-range and high-energy density energy storage devices. Secondly, the sulfur resources in lithium-sulfur batteries are abundant and low in cost, which significantly reduces the production cost and has higher economic efficiency. In addition, the environmentally friendly properties of sulfur make lithium-sulfur batteries more competitive in the field of green energy storage. In high-efficiency energy storage applications such as renewable energy grid connection, electric vehicles and portable devices, lithium-sulfur batteries are gradually becoming an ideal alternative to lithium-ion batteries.

[0003] However, lithium-sulfur batteries have not yet reached the scale of commercial application. The main reasons are: 1. The shuttle effect of lithium polysulfide, an intermediate product of charge and discharge, reduces the utilization rate of sulfur source of positive electrode active material, resulting in battery capacity loss and shortened cycle life; 2. During the discharge process, the conversion rate of liquid phase high-order lithium polysulfide to solid phase discharge product lithium sulfide is too slow, resulting in some active materials unable to participate in electrochemical reactions, increased battery polarization, aggravated shuttle effect, and greater capacity loss. 3. The negative electrode lithium dendrites and dead lithium caused by the shuttle effect cover the lithium surface, limiting the transmission efficiency of lithium ions during charge and discharge, resulting in a decrease in available lithium ions, gradual attenuation of battery capacity, and an increased risk of thermal runaway of the battery.

[0004] Recent research on lithium-sulfur batteries is devoted to improving the performance of batteries in order to realize the practical application of lithium-sulfur batteries. Among them, the modified layer catalyst with significant catalytic conversion effect on lithium polysulfide in lithium-sulfur batteries is the research focus. The main research method is: a composite material with physical confinement and chemical bonding effect on lithium polysulfide is combined with a commercial diaphragm as a modified layer. Compared with commercial diaphragms, the resulting new diaphragm has the advantages of simple operation and easy use, so the modification of commercial diaphragms has been more widely studied. After carbonization and reactivation of biomass, porous activated carbon with a large specific surface area is formed. As one of the traditional excellent substrate catalytic materials, porous activated carbon materials have good conductivity, stability and good physical confinement ability for lithium polysulfide, which can effectively stabilize the discharge capacity of lithium-sulfur batteries in the high-voltage range. However, the affinity between polar lithium polysulfide and non-polar carbon materials is weak, which is not enough to effectively block the shuttle effect, and cannot accelerate the conversion of liquid-phase high-order lithium polysulfide to solid-phase discharge product lithium sulfide. Transition metal sulfides have a strong affinity for lithium polysulfides, can fully anchor lithium polysulfides, and can accelerate the rate-determining step of lithium polysulfide reduction. Therefore, exploring the composite of biomass porous activated carbon and transition metal sulfides to form a diaphragm modification layer with a large specific surface area, rich active sites, strong physical confinement-chemical bonding, and accelerated lithium polysulfide reduction rate is an effective way to achieve commercial application of lithium-sulfur batteries. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a method for preparing hemp activated carbon and hemp activated carbon loaded with nickel disulfide material.

[0006] Another object of the present invention is to provide hemp activated carbon prepared by the above method and hemp activated carbon loaded with nickel disulfide material.

[0007] Another object of the present invention is to provide the use of the above-mentioned hemp activated carbon and the hemp activated carbon loaded with nickel disulfide material in the preparation of lithium-sulfur battery separators.

[0008] The purpose of the present invention is achieved through the following solutions:

[0009] A method for preparing hemp activated carbon comprises the following steps:

[0010] (1) preparing carbonized hemp powder: placing hemp stalk core powder in a muffle furnace for carbonization to obtain carbonized hemp powder;

[0011] (2) Preparation of hemp activated carbon material: The carbonized hemp powder obtained in step (1) is mixed with zinc chloride, activated under an inert atmosphere, and then washed and dried to obtain hemp activated carbon HPC.

[0012] A method for preparing a hemp activated carbon-loaded nickel disulfide material comprises the following steps:

[0013] (3) HPC and Ni(NO) obtained in step (2) 3 ) 2 6H 2 O, anhydrous ethanol and water are mixed evenly, and then mixed with Na 2 The S solution was mixed evenly, then passed into the reactor for hydrothermal treatment, filtered, washed and dried to obtain NiS 2 @HPC, that is, hemp activated carbon loaded with nickel disulfide material.

[0014] The hemp stalk core powder described in step (1) also includes a de-impurity step before carbonization, which is as follows: the hemp stalk core powder is de-impurized in a heated hydrochloric acid solution, and then washed and dried; wherein the concentration of the hydrochloric acid solution is 1-3 mol / L, preferably 3 mol / L, the heating temperature and the drying temperature are relatively independently 70-100°C, preferably 80°C, and the heating time and the drying time are relatively independently 6-12h, preferably 8h.

[0015] The carbonization in step (1) refers to keeping the temperature at 200-500° C. for 1-3 hours, preferably keeping the temperature at 400° C. for 3 hours.

[0016] After the carbonization in step (1), washing is required to remove the tar on the surface of the carbonized hemp, and then the carbonized hemp powder is obtained after drying.

[0017] The mass ratio of the carbonized hemp powder to zinc chloride in step (2) is 1:0.5-3, preferably 1:1-2.

[0018] The activation described in step (2) refers to keeping warm at 600-800°C for 2-4 hours, using step temperature activation, preferably keeping warm at 732°C for 2 hours and then keeping warm at 750°C for 1 hour.

[0019] The inert atmosphere in step (2) is preferably nitrogen.

[0020] The hemp activated carbon HPC described in step (3) and Ni(NO 3 ) 2 6H 2 O mass ratio is 1:1-3, preferably 1:1-2; the amount of water used is such that the water completely immerses the hemp activated carbon HPC and Ni(NO 3 ) 2 6H 2 O; the amount of anhydrous ethanol is such that the volume of anhydrous ethanol is 25%-50% of the volume of water, and anhydrous ethanol is used to prevent agglomeration during the hydrothermal process:

[0021] In step (3), HPC and Ni(NO 3) 2 6H 2 O, anhydrous ethanol and water are mixed evenly to make Ni(NO 3 ) 2 6H 2 O is fully dispersed in the pores of HPC, preferably by mixing by at least one of ultrasound and stirring, more preferably by stirring at room temperature for more than 1 hour and ultrasound at room temperature for more than 1 hour to make the raw materials uniformly mixed.

[0022] The Na used in step (3) 2 The concentration of the S solution is 0.03-0.1M, preferably 0.05M; the Na 2 The amount of S solution is sufficient to meet the Na 2 S and Ni(NO 3 ) 2 6H 2 O has a molar ratio of greater than or equal to 2:1. 2 The S solution is preferably mixed uniformly by ultrasonic mixing.

[0023] The hydrothermal treatment temperature and time in step (3) are 100°C-200°C, 5-10h, preferably 150°C, 6-8h.

[0024] Preferably, when the mass ratio of the carbonized hemp powder to zinc chloride in step (2) is 1:2, the activation conditions are keeping warm at 732°C for 2 hours and then keeping warm at 750°C for 1 hour, the obtained product is a hemp activated carbon powder material, denoted as HPC.

[0025] Preferably, when the mass ratio of carbonized hemp powder to zinc chloride in step (2) is 1:2, and the activation condition is to keep warm at 732°C for 3h, the obtained product is hemp activated carbon powder material, denoted as HPC 0.5 .

[0026] Preferably, when the mass ratio of carbonized hemp powder to zinc chloride in step (2) is 1:2, and the activation condition is to keep warm at 750°C for 3h, the obtained product is hemp activated carbon powder material, denoted as HPC 0.8 .

[0027] Preferably, when the hemp activated carbon HPC described in step (3) is mixed with Ni(NO 3 ) 2 6H 2 The mass ratio of O is 1:1-2, and the Na 2 The concentration of S solution was 0.05M, the hydrothermal treatment temperature and time were 150℃, 6-8h, and the obtained product was hemp activated carbon powder material loaded with nickel disulfide, denoted as NiS 2 @HPC.

[0028] Preferably, when the hemp activated carbon HPC described in step (3) is mixed with Ni(NO 3 ) 2 6H 2 O mass ratio is greater than 1:1 and less than 1:3, and the Na 2 The concentration of S solution was 0.05M, the hydrothermal treatment temperature and time were 150℃, 6-8h, and the obtained product was hemp activated carbon powder material loaded with nickel sulfide, denoted as Ni x S x @HPC.

[0029] A hemp activated carbon prepared by the above method and a hemp activated carbon loaded with nickel disulfide material.

[0030] The application of the above-mentioned hemp activated carbon and hemp activated carbon loaded with nickel disulfide material in the preparation of lithium-sulfur battery separators.

[0031] A lithium-sulfur battery separator is prepared by the following method: the above-mentioned hemp activated carbon and / or hemp activated carbon loaded with nickel disulfide material, conductive agent and binder are stirred and mixed evenly in a solvent, and then the obtained slurry is evenly coated on a commercial separator by a scraper method, and a lithium-sulfur battery separator is formed after vacuum drying.

[0032] Compared with ordinary commercial separators, the modified separators greatly improve the discharge capacity and cycle stability of lithium-sulfur batteries.

[0033] The conductive agent is preferably a conductive agent Super P Li; the binder is preferably PVDF; and the solvent is preferably N-methylpyrrolidone.

[0034] The mass ratio of the hemp activated carbon and / or hemp activated carbon loaded with nickel disulfide material, the conductive agent and the binder is preferably 8:1:1.

[0035] The method first uses hydrochloric acid to pickle and remove impurities from biomass hemp powder, then carbonizes it at high temperature in a muffle furnace, and then heats it in a tubular furnace N 2 Under the protection of the environment, the carbonized hemp powder and zinc chloride are activated at high temperature. In this process, the carbonization mainly destroys the main chain structure of cellulose and hemicellulose of biomass hemp and the aromatic groups of lignin, so that the biomass hemp is initially carbonized. In this process, the step-by-step high-temperature activation is mainly to make the carbonized hemp completely graphitized. At the same time, 732℃ is the boiling point of zinc chloride, which can etch the surface of graphitized hemp carbon to produce macropores and mesoporous structures. The temperature is further raised to 750℃ to fully gasify the zinc chloride, which can produce micropores on the inner walls of macropores and mesopores. After the reaction is completed, hemp activated carbon can be obtained. On this basis, the hemp activated carbon is further mixed with Ni(NO 3 ) 2 6H 2O in a mass ratio of 1:1-2 and then add 0.05M Na 2 S solution, after hydrothermal treatment, the obtained product is hemp activated carbon powder material loaded with nickel disulfide. The hemp activated carbon powder material loaded with nickel disulfide is used as a diaphragm modification layer and coated on a commercial diaphragm by a doctor blade method. It can be used in lithium-sulfur batteries to effectively improve the electrochemical performance of lithium-sulfur batteries.

[0036] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0037] (1) The synthesis process of the hemp activated carbon (HPC) of the present invention is simple. Compared with the traditional potassium salt one-step high-temperature activation method, the temperature rises too fast, the biomass material is difficult to fully graphitize, the potassium salt activation reaction is violent, the carbon material burnout rate is high, the yield is low, etc. The step-by-step treatment of the present invention is divided into carbonization, activation, and pore regulation. The step-by-step high-temperature graphitization treatment makes the carbon skeleton more stable, the electronic conductivity is higher, and the pore structure is more uniform and controllable, which can realize large-scale industrial production.

[0038] (2) The hemp activated carbon powder material (NiS 2 @HPC) as a transition metal sulfide porous carbon-based material, used in the separator modification layer of lithium-sulfur batteries can greatly improve the electrochemical performance of lithium-sulfur batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 HPC, NiS prepared in Examples 1, 2 and Comparative Examples 1, 2 2 @HPC and HPC 0.5 、HPC 0.8 、Ni x S x @X-ray diffraction (XRD) spectrum of HPC materials.

[0040] Figure 2 HPC, NiS prepared in Examples 1, 2 and Comparative Example 1 2 @HPC, HPC 0.8 、HPC 0.5 Scanning electron microscope (SEM) image of the material.

[0041] Figure 3 The NiS prepared in Example 2 2 @Transmission electron microscope (TEM) image of HPC material.

[0042] Figure 4 HPC / PP, NiS prepared in Examples 1, 2 and Comparative Example 1 2 @HPC / PP and HPC 0.5 / PP、HPC0.8 First cycle specific capacity-voltage diagram of / PP and PP lithium-sulfur batteries at 0.5C.

[0043] Figure 5 HPC / PP, NiS prepared in Examples 1, 2 and Comparative Example 1 2 @HPC / PP and HPC 0.5 / PP、HPC 0.8 / PP and PP lithium-sulfur batteries 200 cycles performance at 0.5C.

[0044] Figure 6 HPC / PP, NiS prepared in Examples 1, 2 and Comparative Example 1 2 @HPC / PP and HPC 0.5 / PP、HPC 0.8 / PP and PP lithium-sulfur batteries discharge rate performance from 0.1C to 5C.

[0045] Figure 7 NiS prepared in Example 2 2 @1000-cycle long cycle performance diagram of HPC / PP and PP lithium-sulfur batteries at 1C. DETAILED DESCRIPTION

[0046] The present invention is further described in detail below in conjunction with the examples and drawings, but the embodiments of the present invention are not limited thereto. If specific conditions are not specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0047] Unless otherwise specified, the reagents used in the examples can be purchased from the market.

[0048] Example 1

[0049] The assembly and testing methods of the lithium-sulfur battery described in the embodiment are as follows:

[0050] (1) HPC / PP and NiS 2 Preparation of HPC / PP modified diaphragm: Hemp activated carbon (HPC, HPC 0.8 、HPC 0.5 ) or hemp activated carbon loaded with nickel disulfide (NiS 2 @HPC), conductive agent Super PLi and binder PVDF were mixed in a mass ratio of 8:1:1, solvent N-methylpyrrolidone (NMP) was added and ball milled for 6 hours to mix evenly, and then the obtained slurry was evenly coated on the commercial diaphragm Celgard2500 (PP) by a doctor blade method. After vacuum drying, the obtained diaphragm was cut into discs with a diameter of 19 mm.

[0051] (2) Preparation of positive electrode: Ketjen black ECP-200L and sublimed sulfur were thoroughly ground and mixed in an agate mortar at a mass ratio of 1:3 for 15 min and placed in a porcelain boat. 2 In the atmosphere, the temperature was kept at 155℃ for 12h, and then kept at 200℃ for 30min. The reaction was completed to obtain a C / S composite material. 80wt% C / S, 10wt% Super P Li and 10wt% LA133 water-based binder (acrylonitrile multipolymer, 5wt%) were mixed evenly by ball milling for 6h with deionized water as solvent, and then the obtained slurry was evenly coated on the surface of the carbon-coated layer of the carbon-coated aluminum foil by a doctor blade method. After vacuum drying, the obtained pole piece was cut into a disc with a diameter of 12mm.

[0052] (3) Assembly of button cells: The following operations were all carried out in a glove box filled with argon. The assembly of CR2032 button cells was performed using a lithium sheet as the negative electrode, a C / S sheet as the positive electrode, a modified separator as the separator, and a LiTFSI electrolyte (1.0 mol / L LiTFSI in DME / DOL = 1:1 vol% with 1.0 wt% LiNO 3 , Suzhou Zhongyan Chemical Technology Co., Ltd.) is the electrolyte, and the amount of the electrolyte used is 30 μL for each battery.

[0053] (4) Test of the cycle stability of lithium-sulfur batteries: After the assembled button cells were left to stand for 12 hours, constant current charge and discharge tests were performed on them at different current densities using the Newwell battery test system. The operating voltage range of the battery was 1.7-2.8V.

[0054] Example 1

[0055] The preparation method of hemp activated carbon (HPC) in this embodiment comprises the following specific steps:

[0056] 15 g of hemp stalk core powder was dispersed in 150 mL of 3 mol / L HCl solution, then magnetically stirred in an oil bath at 60 °C for 12 h, filtered, washed, dried at 60 °C, and then kept at 400 °C in a muffle furnace for 3 h at a heating rate of 5 °C min -1 , carbonized hemp is obtained, and the carbonized hemp is mixed with ZnCl 2 Mix them evenly in a mass ratio of 1:2, place them in a tube furnace, and heat them under N 2 At 3℃min under the protection of atmosphere -1 The heating rate was raised to 732°C, high temperature activation was performed for 2 hours, and then the sample obtained after being kept at 750°C for 1 hour was HPC. The step activation temperature of carbonized hemp powder and zinc chloride will affect the specific surface area of ​​the product. The XRD pattern of HPC in this embodiment is shown in FIG. Figure 1As shown in Figure 2, there are two obvious main peaks in the diffraction pattern of HPC material, at 26.6° and 44.0°, respectively. The characteristic peak at 2θ = 26.6° corresponds to the (0 0 2) crystal plane of graphite carbon, as shown in Figure 2. Figure 3 As shown in Figure 1, the TEM lattice fringe spacing of HPC is 0.342nm, which corresponds to the fringe spacing of the (0 0 2) crystal plane of graphite carbon, indicating that the synthesized HPC has a high degree of graphitization. Figure 2 As shown, it can be clearly observed that the surface of the HPC material is covered with abundant mesopores and micropores.

[0057] The synthesized HPC was used to modify the commercial separator PP, and then assembled into an HPC / PP lithium-sulfur battery. The first charge and discharge specific capacity-voltage diagram of the lithium-sulfur battery at 0.5C is shown in Figure 4 As shown in the figure, it can be seen that the initial discharge capacity of the HPC / PP battery is as high as 1032.0mA hg -1 , higher than HPC 0.8 / PP(957.2mAh g -1 ), HPC 0.5 / PP(836.9mAh g -1 ) and PP (675.4 mA hg -1 ); and from Figure 5 It can be observed from the cycling performance diagram at 0.5C that after 200 cycles, the discharge capacity of the HPC / PP battery remains at 746.8 mAh g -1 The capacity retention rate is as high as 72.3%, which is much higher than that of the commercial PP separator battery without modification (398.2mAh g -1 , 60.3%) from Figure 6 The rate performance test shows that the capacity of HPC / PP batteries at different rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, and 5C is higher than that of HPC 0.8 / PP battery, HPC 0.5 / PP batteries and PP batteries.

[0058] Example 2

[0059] The hemp activated carbon in this example is loaded with nickel disulfide (NiS 2 The preparation method of @HPC) comprises the following specific steps:

[0060] HPC and Ni(NO 3 ) 2 6H 2 O in a mass ratio of 1:2, deionized water (to submerge the solid) and anhydrous ethanol (25% of the volume of deionized water) were added, and ultrasonic and stirring treatments were performed for 1 hour each. Then, 0.05 M Na 2S solution, 0.25 mmol Ni(NO 3 ) 2 6H 2 O corresponds to 10 ml Na 2 S solution, and then ultrasonically and stirred for 1 hour each, and hydrothermally treated at 150 ° C for 6 hours. After the reaction, it was filtered, washed (deionized water and anhydrous ethanol were alternately cleaned at least 3 times), and dried. The obtained sample is NiS 2 @HPC.

[0061] In this embodiment, NiS 2 @HPC's XRD pattern is as follows Figure 1 As shown, NiS 2 @Diffraction peaks of HPC materials and NiS 2 The PDF card information corresponds to the strongest peak at 31.4° corresponding to NiS 2 The (200) crystal plane, combined with Figure 3 Medium 2 @HPC TEM image shows that the lattice fringe spacing is 0.285nm, which corresponds to the lattice fringe spacing of the (200) crystal plane, indicating that nickel disulfide is successfully loaded on the surface of hemp activated carbon. 2 SEM images of @HPC Figure 2 As shown, when magnified to 200 nm, the uniformly distributed pores can be seen. Figure 3 TEM image, showing both the lattice fringes of HPC and NiS 2 The lattice fringes of NiS 2 Evenly distributed on the HPC surface.

[0062] The synthesized NiS 2 @HPC is used to modify the commercial separator PP and then assembled into NiS 2 @HPC / PP lithium-sulfur battery. The first charge and discharge specific capacity-voltage diagram of the lithium-sulfur battery at 0.5C is as follows Figure 4 As shown in the figure, it can be seen that NiS 2 @HPC / PP battery initial discharge capacity up to 1194.6mAh g -1 , higher than HPC / PP battery (1032.0mA hg -1 ), HPC 0.8 / PP battery (957.2mA hg -1 ), HPC 0.5 / PP battery (836.9mA hg -1 ) and PP (675.4 mA hg -1 ); and from Figure 5 It can be observed from the cycling performance diagram at 0.5C that after 200 cycles, NiS2 @HPC / PP battery discharge capacity remains at 942.8mA hg -1 The capacity retention rate is as high as 79.2%, which is much higher than that of HPC / PP batteries (746.8mAh g -1 , 72.3%) and the unmodified commercial PP separator battery (398.2mAh g -1 , 60.3%) from Figure 6 The rate performance test shows that NiS 2 @HPC / PP battery has higher capacity than HPC / PP battery and HPC at different rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 3C and 5C. 0.8 / PP battery, HPC 0.5 / PP battery and PP battery. In order to highlight the NiS 2 @HPC / PP battery has high rate and long cycle advantages, such as Figure 7 As shown in the figure, after 1000 cycles at 1C rate, the PP battery capacity increased from 631.4 mAh g -1 Up to 241.2mAh g -1 , the capacity retention rate is 38.2%, while NiS 2 @HPC / PP battery capacity is 1031.8mAh g -1 Up to 582.8mAh g -1 , the capacity retention rate is 56.5%, which is much higher than that of PP battery.

[0063] Comparative Example 1

[0064] The hemp activated carbon (HPC 0.5 、HPC 0.8 ), the specific steps are as follows:

[0065] 15 g of hemp stalk core powder was dispersed in 150 mL of 3 mol / L HCl solution, then magnetically stirred in an oil bath at 60 °C for 12 h, filtered, washed, dried at 60 °C, and then kept at 400 °C in a muffle furnace for 3 h at a heating rate of 5 °C min -1 , carbonized hemp is obtained, and the carbonized hemp is mixed with ZnCl 2 Mix them evenly in a ratio of 1:2 and place them in a tube furnace under N 2 At 3℃min under the protection of atmosphere -1 The heating rate was increased to 732℃ and the sample was HPC after high temperature activation for 3h. 0.5 . And at 3℃min -1 The heating rate was increased to 750℃ and the sample was HPC after high temperature activation for 3h. 0.8 .

[0066] In this embodiment, HPC0.5 and HPC 0.8 The XRD pattern of Figure 1 As shown, HPC 0.8 There are two obvious main peaks in the diffraction pattern of the material, at 26.6° and 44.0° respectively. The characteristic peak at 2θ=26.6° corresponds to the (0 0 2) crystal plane of graphite carbon, indicating that HPC was successfully synthesized. 0.8 . 0.5 The diffraction peaks of the material at 26.6° and 44.0° are weak, indicating that the degree of graphitization is insufficient. Figure 2 Comparison of different SEMs shows that HPC 0.5 The porosity of HPC is low. 0.8 The pore structure of MgO is rich, but not as rich as that of HPC, which indirectly confirms that the step-by-step high-temperature activation method can significantly improve the graphitization and porosity of the material.

[0067] The synthesized HPC 0.5 and HPC 0.8 Used to modify commercial separator PP and then assembled into HPC 0.5 / PP and HPC 0.8 / PP lithium-sulfur battery, the first charge and discharge specific capacity-voltage diagram of the lithium-sulfur battery at 0.5C is as follows Figure 4 As shown in the figure, it can be seen that HPC 0.5 / PP and HPC 0.8 The initial discharge specific capacity of the PP battery is 824.2 mAh g -1 、931.8mAh g -1 , lower than the 1032mAh g of HPC / PP battery -1 ; and from Figure 5 It can be observed from the cycle performance diagram at 0.5C that after 200 cycles, the discharge capacity remains at 575.4 mAh g -1 and 612.5mAh g -1 , the capacity retention rate is 69.8% and 65.7%, which is lower than the 72.3% of HPC / PP battery. Figure 6 The capacity comparison at different rates shows that HPC 0.5 / PP battery capacity is lower than HPC 0.8 / PP battery and HPC / PP battery, and HPC 0.5 / PP battery capacity at 0.2C~5C rate is much lower than HPC 0.8 / PP battery, description HPC 0.5 The low degree of graphitization of the material has a poor effect on the gain of battery capacity, while HPC 0.8 / PP battery rate capacity is higher than HPC 0.5 / PP battery, but not exceeding HPC / PP battery, and HPC 0.8 The graphitization degree of HPC material is similar to that of HPC material, which indicates that 0.8 The lower porosity of the material has no significant effect on the gain in battery capacity.

[0068] Comparative Example 2

[0069] The hemp activated carbon loaded with nickel disulfide (Ni x S x The preparation method of @HPC) comprises the following specific steps:

[0070] HPC and Ni(NO 3 ) 2 6H 2 O in a mass ratio greater than 1:1 or less than 1:3, add deionized water (to submerge the solid) and anhydrous ethanol (25% of the volume of deionized water), ultrasonicate and stir for 1 hour each, and add 0.05M Na 2 S solution, 0.25 mmol Ni(NO 3 ) 2 6H 2 O corresponds to 10 ml Na 2 S solution, and then ultrasonic and stirring for 1 hour each, and then hydrothermal treatment at 150 ° C for 6 hours. After the reaction is completed, it is filtered, washed (deionized water and anhydrous ethanol are alternately cleaned at least 3 times), and dried. The obtained sample is Ni x S x @HPC.

[0071] HPC and Ni(NO 3 ) 2 6H 2 Whether the mass ratio of O is greater than 1:1 (such as 1:0.5) or less than 1:3 (such as 1:5), the obtained Ni x S x @HPC's XRD patterns are all the same, Figure 1 As shown, the diffraction spectrum shows an unknown peak of nickel sulfide, and NiS 2 diffraction peaks, which may be caused by the Ni(NO 3 )·6H 2 Excessive or insufficient use of O leads to excessive or insufficient use of O. 3 )·6H 2 The amount of O used will affect the formation of the target product.

[0072] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing hemp activated carbon, characterized in that The following steps are involved: (1) preparing carbonized hemp powder: placing hemp stalk core powder in a muffle furnace for carbonization to obtain carbonized hemp powder; (2) Preparation of hemp activated carbon material: The carbonized hemp powder obtained in step (1) is mixed with zinc chloride, activated under an inert atmosphere, and then washed and dried to obtain hemp activated carbon HPC.

2. The method for preparing hemp activated carbon according to claim 1, characterized in that: The hemp stalk core powder described in step (1) further includes a step of removing impurities before carbonization, which is specifically as follows: removing impurities from the hemp stalk core powder in a heated hydrochloric acid solution, and then washing and drying; The concentration of the hydrochloric acid solution is 1-3 mol / L, the heating temperature and the drying temperature are relatively independently 70-100° C., and the heating time and the drying time are relatively independently 6-12 hours.

3. The method for preparing hemp activated carbon according to claim 1, characterized in that: The carbonization described in step (1) refers to keeping the temperature at 200-500° C. for 1-3 hours.

4. The method for preparing hemp activated carbon according to claim 1, characterized in that: The mass ratio of the carbonized hemp powder to zinc chloride in step (2) is 1:0.5-3, preferably 1:1-2; The activation described in step (2) refers to keeping warm at 600-800°C for 2-4 hours; preferably, step temperature activation is adopted, keeping warm at 732°C for 2 hours and then keeping warm at 750°C for 1 hour.

5. Hemp activated carbon prepared by the method according to any one of claims 1 to 4.

6. A method for preparing hemp activated carbon loaded with nickel disulfide material, characterized in that The following steps are involved: The hemp activated carbon HPC described in claim 5 is evenly mixed with Ni(NO3)2·6H2O, anhydrous ethanol and water, and then evenly mixed with Na2S solution, and then introduced into a reactor for hydrothermal treatment, and filtered, washed and dried to obtain NiS2@HPC, that is, hemp activated carbon loaded with nickel disulfide material.

7. The method for preparing the hemp activated carbon loaded nickel disulfide material according to claim 6, characterized in that The following steps are involved: The mass ratio of the hemp activated carbon HPC to Ni(NO3)2·6H2O is 1:1-3, preferably 1:1-2; the amount of water used satisfies: the water completely immerses the hemp activated carbon HPC and Ni(NO3)2·6H2O; the amount of anhydrous ethanol used satisfies: the volume of anhydrous ethanol is 25%-50% of the volume of water: The concentration of the Na2S solution used is 0.03-0.1 mol / L; the amount of the Na2S solution used satisfies that the molar ratio of Na2S to Ni(NO3)2·6H2O is greater than or equal to 2:1; The hydrothermal treatment temperature and time are 100°C-200°C and 5-10h.

8. A hemp activated carbon loaded with nickel disulfide material prepared according to the method according to any one of claims 6-7.

9. Use of the hemp activated carbon according to claim 5 and the hemp activated carbon loaded with nickel disulfide material according to claim 8 in the preparation of lithium-sulfur battery separators.

10. A lithium-sulfur battery separator, characterized in that The method is as follows: the hemp activated carbon described in claim 5 and / or the hemp activated carbon loaded with nickel disulfide material described in claim 8, a conductive agent and a binder are stirred and mixed evenly in a solvent, and then the obtained slurry is evenly coated on a commercial diaphragm by a scraper method, and a lithium-sulfur battery diaphragm is formed after vacuum drying.

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