A hard carbon composite material, a preparation method thereof, a negative electrode material, a sodium ion battery and an electric device

Abstract

The application discloses a hard carbon composite material and a preparation method thereof, a negative electrode material, a sodium ion battery and an electric equipment. The hard carbon composite material comprises a carbon tin inner layer material and a coated outer layer. The carbon tin inner layer material comprises a porous hard carbon base body and a tin-containing compound filled in the pores of the porous hard carbon base body. The coated outer layer is a hard carbon coating layer. The application further discloses a preparation method of the material. The hard carbon composite material prepared by the method effectively buffers the volume expansion of the negative electrode material, and improves the sodium intercalation / deintercalation capacity and the cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sodium ion batteries, in particular to a hard carbon composite material and a preparation method thereof, a negative electrode material, a sodium ion battery and an electric equipment. BACKGROUND

[0002] At present, sodium ion batteries are considered as a highly cost-effective secondary ion battery system, and the wide and low cost of sodium resources can greatly alleviate the shortage of lithium mineral resources and the cost anxiety caused by the high price of lithium carbonate raw materials. Its research and industrialization progress has attracted widespread attention at home and abroad. As one of the negative electrode materials of sodium ion batteries, hard carbon materials have good cycle stability and industrialization production feasibility. However, hard carbon materials also have some application shortcomings: 1) Due to the low specific capacity of hard carbon materials, which is usually less than 300 mAh / g, the energy density of the full battery is greatly limited; 2) Due to the existence of a large number of mesoporous micropores in hard carbon materials, the inherent property of the porous structure makes it easy to produce capillary adsorption phenomenon during storage and use, and absorb moisture in the environment, which seriously affects the production process stability and cycle stability of sodium ion batteries.

[0003] Tin-based materials are a kind of electrode materials with great potential and are favored by researchers. Tin-based materials as negative electrode materials of sodium ion batteries are less studied. They have high theoretical capacity, but the cycle stability is poor, mainly because of the large volume expansion problem during charging and discharging. SUMMARY

[0004] Therefore, the present application provides a hard carbon composite material and a preparation method thereof, a negative electrode material, a sodium ion battery and an electric equipment. The hard carbon composite material comprises a carbon-tin inner layer material and a coated outer layer. The carbon-tin inner layer material comprises a porous hard carbon matrix and a tin-containing compound filled in the pores of the porous hard carbon matrix. The coated outer layer is a hard carbon coating layer. The hard carbon composite material effectively buffers the volume expansion of the negative electrode material and improves the sodium intercalation / deintercalation capacity and cycle performance.

[0005] In one embodiment, the particle size distribution of the porous hard carbon matrix is 1 um≤D50≤20 um.

[0006] In one embodiment, the BET specific surface area of the porous hard carbon matrix is 1-20 m 2 / g, the tap density of the porous hard carbon matrix is ≥0.7 g / cm 3 , and the carbon content of the porous hard carbon matrix is ≥99.10%.

[0007] In one embodiment, the tin-containing compound comprises one or more of SnO, Sn3P4 and SnS.

[0008] In an embodiment, the tin-containing compound has a particle size diameter satisfying 5nm≤D50≤200nm.

[0009] In an embodiment, the tin-containing compound has a mass ratio of 1% to 2% based on the total mass of the hard carbon composite material.

[0010] In an embodiment, the coating outer layer has a thickness of 20nm to 800nm, and a mass ratio of 0.5% to 1% based on the total mass of the hard carbon composite material.

[0011] The hard carbon composite material provided by the first aspect of the present application has a high capacity, the porous internal structure provides a fast transfer channel for ion diffusion and transfer, the porous carbon skeleton can serve as a buffer structure to relieve volume expansion during charging and discharging, the introduced tin-containing compound has a good theoretical capacity, and the capacity of the hard carbon-based material can be improved. The hard carbon composite material of the present application can achieve high sodium intercalation capacity while achieving a long cycle life.

[0012] In a second aspect, the present application further provides a preparation method of a hard carbon composite material, characterized in that the method comprises the following steps:

[0013] S1, acid washing after first carbonization treatment of the first carbon source;

[0014] S2, activating reaction of the acid-washed first carbon source and an activating pore-forming agent;

[0015] S3, second carbonization of the activated first carbon source to obtain a porous hard carbon matrix;

[0016] S4, hydrothermal reaction of the porous hard carbon matrix and a tin source to obtain a carbon-tin inner layer material;

[0017] S5, carbon coating treatment of the carbon-tin inner layer material to obtain a hard carbon composite material.

[0018] In an embodiment, in step S1, the first carbon source comprises biomass waste and coal, the biomass waste comprises one or more of crop straw and crop shell, and the coal comprises one or more of anthracite, bituminous coal and lignite.

[0019] In an embodiment, in step S1, the first carbon source is further coarsely broken, washed and dried, and the particle size of the dried first carbon source is 1mm≤D50≤5mm.

[0020] In an embodiment, the preparation method of the hard carbon composite material further comprises:

[0021] In step S1, the first carbonization treatment has a temperature of 300-600℃ and a treatment time of 10-12 hours, the acid washing uses one or more of hydrochloric acid, sulfuric acid and hydrofluoric acid, and the acid washing temperature is 40-70℃.

[0022] In step S2, the activation reaction temperature is 600-1000℃, and the activation reaction time is 2-6 hours.

[0023] In step S3, the second carbonization temperature is 1000-1700℃, and the second carbonization time is 2-10 hours.

[0024] In step S4, the hydrothermal reaction temperature is 120-180℃, and the hydrothermal reaction time is 4-8 hours.

[0025] In one embodiment, in step S5, the carbon coating treatment step comprises: mixing the carbon tin inner layer material, the second carbon source and the first solvent, and then performing third carbonization, grinding and sieving to obtain the hard carbon composite material.

[0026] In one embodiment, in step S5, the third carbonization temperature is 1000-1300℃, and the third carbonization time is 3-5 hours.

[0027] The preparation method of the hard carbon composite material provided by the second aspect of the present application has simple process, low cost of carbon source, high repeatability, short cycle, low energy consumption, saves production cost, is suitable for large-scale production and preparation, and has good application prospect in the field of sodium ion batteries.

[0028] In a third aspect, the present application provides a negative electrode material comprising the hard carbon composite material provided by the first aspect of the present application. The negative electrode material provided by the present application has small volume change, high cycle capacity and long cycle life during the cycle process.

[0029] In a fourth aspect, the present application provides a sodium ion battery comprising the negative electrode material provided by the third aspect of the present application. The sodium ion battery provided by the present application has high cycle capacity and long cycle life.

[0030] In a fifth aspect, the present application provides an electric device comprising the sodium ion battery. Specifically, the electric device can be an electric vehicle, an electric motorcycle, an electric bicycle, a mobile power supply, a drone, a mobile phone, a computer, a camera, an electric tool, a smart home or a wearable device. The sodium ion battery has long cycle life and high capacity, so that the electric device can be used stably for a long time, which is beneficial to improve the use performance of the electric device. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiment or prior art description will be briefly introduced. The specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0032] Figure 1A cross-sectional view of a hard carbon composite material according to an embodiment of the present application.

[0033] Figure 2 A scanning electron microscope image of a hard carbon material according to Comparative Example 1 of the present application.

[0034] Figure 3 A scanning electron microscope image of a hard carbon composite material according to Example 1 of the present application.

[0035] Figure 4 A TGA curve of a hard carbon composite material according to Example 1.

[0036] Explanation of reference numerals:

[0037] Porous hard carbon matrix - 11, tin-containing compound - 12, coating outer layer - 13. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The use of the terms "and / or" includes a combination of one or more of the associated listed items.

[0040] Some embodiments of the present application will be described in detail below. The following examples and features in the examples can be combined with each other in the case of no conflict.

[0041] Hard carbon materials have attracted increasing attention in sodium-ion batteries. The high specific capacity of hard carbon materials can effectively improve the energy density of batteries. The excellent cycle stability ensures the long-term use of batteries, and the good electrical conductivity enhances the charging and discharging efficiency of batteries. In addition, hard carbon materials have relatively low cost and have the potential for large-scale application.

[0042] However, despite the advantages of hard carbon materials in sodium-ion batteries, there are still many technical challenges and defects. For example, the preparation process of hard carbon materials is complex, the cost is high, and the electrochemical performance is affected by many factors such as preparation conditions, structural defects and surface properties, which limits its large-scale application in sodium-ion batteries. In addition, the problem of volume expansion and contraction of hard carbon materials during charging and discharging process also needs to be solved to further improve its cycle stability and energy density.

[0043] Based on this, the present application provides a hard carbon composite material, which comprises a carbon-tin inner layer material and a coated outer layer. The carbon-tin inner layer material comprises a porous hard carbon matrix and a tin-containing compound filled in the pores of the porous hard carbon matrix, and the coated outer layer is a hard carbon coating layer. The introduced tin-containing compound has good theoretical capacity, which can significantly improve the capacity of the hard carbon base material. Secondly, the tin-containing compound is loaded with a porous hard carbon material, and the hard carbon material with certain conductivity can have good electron transmission path, and the porous internal structure provides a fast transfer channel for ion diffusion and transfer, and the porous carbon skeleton can act as a buffer structure to relieve the volume expansion of the tin-containing compound during charging and discharging, realizing high sodium intercalation capacity and long cycle life. Finally, the surface of the porous hard carbon / tin-containing compound composite material is coated with a layer of carbon material. The carbon coating layer can block the open pore structure on the surface, reduce the contact area with the electrolyte, thereby improving the first coulombic efficiency, and can improve the problem of strong water absorption and difficulty in drying and dehydration of hard carbon material itself due to capillary adsorption.

[0044] In one embodiment, the particle size distribution of the porous hard carbon matrix is: 1um≤D50≤20um. The particle size distribution in this range helps to optimize the structure and performance of the electrode. Smaller particles can be more evenly dispersed in the electrode, increasing the contact area between the electrode and the electrolyte, thereby improving the diffusion rate of sodium ions and reaction efficiency. Secondly, smaller particles can shorten the transmission path of electrons in the electrode, reduce resistance, and thus improve the conductivity of the electrode. This helps to reduce the energy loss of the battery during charging and discharging, and improves the efficiency and cycle life of the battery. Alternatively, the particle size D50 of the porous hard carbon matrix can be 1um, 5um, 10um, 15um, 20um, 25um, 30um, 40um, 50um.

[0045] In one embodiment, the BET specific surface area of the porous hard carbon matrix is 1-20m 2 / g, the tap density of the powder is ≥0.7g / cm 3 , and the carbon content of the porous hard carbon matrix is ≥99.10%. Controlling the BET specific surface area to be 1-20m 2 / g helps to enhance the contact between the electrolyte and the electrode, and improve the sodium ion reaction efficiency. Alternatively, the BET specific surface area of the porous hard carbon matrix can be 1m2 / g, 2m 2 / g, 4m 2 / g, 6m 2 / g, 8m 2 / g, 10m 2 / g, 12m 2 / g, 14m 2 / g, 16m 2 / g, 18m 2 / g, 20m 2 / g; tap density ≥ 0.7 g / cm 3 This ensures that the material is tightly packed, improving the electrical conductivity and energy density of the electrode. At the same time, the carbon content ≥ 99.10% ensures the high purity of the material, reduces side reactions, and improves the cycle stability of the battery.

[0046] In one embodiment, the tin-containing compounds include one or more of SnO, Sn3P4, and SnS. These tin-containing compounds can significantly improve the electrochemical performance of the hard carbon material. Due to their high theoretical capacity, they can increase the storage capacity of sodium-ion batteries after doping, thereby improving the energy density of the battery. Second, the tin-containing compounds have good sodium-ion intercalation and deintercalation capabilities during charging and discharging, which helps to improve the cycle stability and rate performance of the battery. After doping these compounds, the hard carbon material can more effectively accommodate sodium ions, reducing the volume expansion and contraction of the material during charging and discharging, and prolonging the service life of the battery.

[0047] In one embodiment, the particle size diameter of the tin-containing compound satisfies 5 nm ≤ D50 ≤ 200 nm. This range of particle size diameter of the tin-containing compound helps the tin-containing compound to be more uniformly dispersed in the hard carbon material, reducing local concentration differences in the material, and facilitating the full mixing of the tin-containing compound with the hard carbon material and other components, forming a uniform electrode structure, thereby improving the diffusion efficiency of sodium ions in the electrode, and thus enhancing the electrochemical performance of the battery. Alternatively, the particle size diameter D50 of the tin-containing compound can be 5 nm, 10 nm, 20 nm, 30 nm, 50 nm, 70 nm, 90 nm, 110 nm, 130 nm, 150 nm, 170 nm, 200 nm.

[0048] In an embodiment, the tin-containing compound accounts for 1-2% of the total mass of the hard carbon composite. In the present application, the 1-2% tin-containing compound mass ratio is conducive to optimizing and balancing the performance of the material. At this time, the tin-containing compound can be uniformly distributed in the hard carbon matrix and form a good synergistic effect with the hard carbon material. Not only can the conductivity and ion diffusion rate of the electrode be improved, but also the polarization phenomenon of the electrode during charging and discharging can be reduced, and the power density and energy conversion efficiency of the battery can be improved. Alternatively, the tin-containing compound can account for 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2.0% of the total mass of the hard carbon composite.

[0049] In an embodiment, the thickness of the coating outer layer is 20-800 nm, and the mass ratio of the coating outer layer to the total mass of the hard carbon composite is 0.5-1%. The thickness of the coating outer layer affects the electrochemical performance and physical stability of the hard carbon composite. A thickness of 20-800 nm can ensure that the coating layer is neither too thick to cause a decline in the overall performance of the material nor too thin to effectively protect the internal material. A suitable thickness not only helps to improve the conductivity and ion diffusion rate of the electrode, but also prevents the structure of the hard carbon material from being damaged during charging and discharging, thereby improving the cycle life and stability of the battery. Alternatively, the thickness of the coating outer layer can be 20 nm, 50 nm, 1000 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, or 800 nm. Furthermore, a coating outer layer mass ratio of 0.5-1% can provide sufficient protection without affecting the overall performance of the hard carbon composite, improve the interface contact between the electrode and the electrolyte, and improve the sodium ion insertion and extraction efficiency, thereby further improving the overall performance of the sodium ion battery. Alternatively, the mass ratio of the coating outer layer to the total mass of the hard carbon composite can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1.0%.

[0050] The hard carbon composite provided by the present application has high capacity. The porous internal structure provides a fast transfer channel for ion diffusion and transfer, and the porous carbon skeleton can act as a buffer structure to relieve volume expansion during charging and discharging, thereby achieving high sodium insertion capacity and long cycle life.

[0051] The present application also provides a preparation method of a hard carbon composite, characterized by comprising the following steps:

[0052] S1, acid washing the first carbon source after first carbonization treatment;

[0053] S2, activating the acid-washed first carbon source and the pore-forming agent;

[0054] S3, performing second carbonization on the activated first carbon source to obtain a porous hard carbon matrix;

[0055] S4, performing hydrothermal reaction on the porous hard carbon matrix and a tin source to obtain a carbon-tin inner layer material;

[0056] S5, performing carbon coating treatment on the carbon-tin inner layer material to obtain a hard carbon composite material.

[0057] The method provided by the application prepares a hard carbon composite material with excellent electrochemical performance through carbonization treatment, acid pickling, activation pore making, re-carbonization, hydrothermal reaction to introduce a tin source, and finally carbon coating treatment. The hard carbon composite material prepared by the application not only has high storage capacity and cycle stability, but also has good conductivity and ion diffusion performance, which provides strong support for the performance improvement and application expansion of sodium ion batteries.

[0058] In one embodiment, in step S1, the first carbon source includes biomass waste and coal, the biomass waste includes one or more of crop straw and crop shell, and the coal includes one or more of anthracite, bituminous coal and lignite. The use of biomass waste such as crop straw and crop shell not only realizes the recycling of resources, reduces environmental pollution, but also reduces production costs. These biomass wastes are rich in carbon elements and can be converted into carbon materials with good performance after carbonization treatment, providing a sustainable source of raw materials for the preparation of hard carbon composite materials. In addition, the use of biomass waste and coal as a composite carbon source can fully utilize the advantages of both and achieve performance complementation of carbon materials. The porous structure and abundant functional groups of biomass waste help to improve the specific surface area and electrochemical activity of hard carbon materials, while the high carbon content and stability of coal help to improve the conductivity and cycle stability of hard carbon materials.

[0059] In one embodiment, in step S1, the first carbon source is coarsely broken, washed, and dried. After coarse breaking, the particle size of the first carbon source is 1 mm≤D50≤5 mm. The coarse breaking process can break the original first carbon source into smaller particles, which helps to improve the uniformity and efficiency of subsequent processing steps. Larger particles can lead to uneven reactions, affecting the carbonization effect and the performance of the final product. The washing step can remove impurities and contaminants on the surface of the first carbon source. These impurities can affect the quality of carbonization, introduce unnecessary defects or reduce the purity of the material. By washing, the purity of the first carbon source can be ensured, providing high-quality raw materials for subsequent steps. The drying step is to remove moisture from the first carbon source. High moisture content can cause bubbles or cracks during carbonization, affecting the structure and performance of the carbon material. Therefore, by drying, the first carbon source can have a lower moisture content before carbonization. Controlling the particle size of the first carbon source after drying to 1 mm≤D50≤5 mm ensures that the first carbon source has appropriate reaction speed and uniformity in subsequent carbonization and other processing steps. Too large a particle size can lead to incomplete reaction, while too small a particle size can increase the cost and difficulty of preparation. Therefore, by controlling the particle size range, the performance of the material can be ensured while improving the preparation efficiency and reducing the cost. Alternatively, the particle size D50 of the first carbon source after coarse breaking can be 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm.

[0060] In one embodiment, in step S1, the first carbonization treatment temperature is 300-600°C, and the first carbonization treatment time is 10-12 hours. The first carbonization can be carried out in a box furnace. Alternatively, the first carbonization treatment temperature is in the range of 300-600°C, at which the first carbon source can gradually undergo pyrolysis and carbonization to form a carbon material with a certain degree of graphitization. This temperature range can ensure the progress of the carbonization reaction while avoiding excessive graphitization or burning of the carbon material at high temperatures, thereby maintaining its porous structure and high specific surface area. Alternatively, the first carbonization temperature can be 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, or 600°C. The first carbonization treatment time of 10-12 hours can ensure that the first carbon source undergoes sufficient carbonization reaction to form a stable carbon structure. At the same time, appropriate treatment time can also avoid the destruction of the carbon material structure or the decline in performance due to long treatment time. Alternatively, the first carbonization treatment time can be 10 h, 10.5 h, 11 h, 11.5 h, or 12 h.

[0061] In one embodiment, in step S1, the acid washing uses one or more of hydrochloric acid, sulfuric acid, and hydrofluoric acid, and the acid washing temperature is 40-70°C. The main purpose of acid washing is to remove impurities such as metal oxides, inorganic salts, etc. in the first carbon source, so as to improve the purity of the carbon material. Hydrochloric acid, sulfuric acid, and hydrofluoric acid are all strong acids, which can effectively dissolve these impurities, thereby achieving deep cleaning of the carbon source. At the same time, their combined use can be flexibly adjusted according to the specific composition of the carbon source and the type of impurities, so as to achieve the best cleaning effect. Secondly, the selection of the acid washing temperature has an important influence on the acid washing effect. The temperature range of 40-70°C can ensure that the acid washing reaction is carried out under relatively mild conditions, avoiding the destruction of the structure of the carbon material or the rapid volatilization of the acid solution caused by too high a temperature. At the same time, appropriate temperature can also accelerate the acid washing reaction rate and improve the acid washing efficiency. Optionally, the acid washing temperature can be 40°C, 50°C, 60°C, or 70°C.

[0062] In one embodiment, in step S2, the activation reaction temperature is 600-1000°C, and the activation reaction time is 2-6 hours. The activation method can adopt one of KOH activation, steam activation, and CO2 activation. The activation reaction temperature is in the temperature range of 600-1000°C, so that the reaction between the activator and the carbon material can be fully carried out, thereby effectively introducing pores into the carbon material. At the same time, it can avoid excessive ablation or structural damage of the carbon material caused by too high a temperature, and maintain its stability and integrity. Optionally, the activation reaction temperature can be 600°C, 700°C, 800°C, 900°C, or 1000°C. Secondly, the activation reaction time in the range of 2-6 hours can promote the full reaction of the activator and the carbon material, forming a uniform pore distribution. Optionally, the activation reaction time can be 2h, 3h, 4h, 5h, or 6h.

[0063] In one embodiment, in step S3, the second carbonization temperature is 1000-1700°C, and the second carbonization time is 2-10 hours. The carbonization temperature in the range of 1000-1700°C helps the non-carbon elements in the carbon source material to further escape, thereby improving the purity of the carbon material. At this time, the carbon source can fully carry out graphitization reaction, so that the graphitization degree of the carbon material is moderate, which not only retains sufficient pore structure and specific surface area, but also improves the electrical conductivity and structural stability of the material. Optionally, the second carbonization temperature can be 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C, 1600°C, or 1700°C. At the same time, controlling the carbonization time between 2-10 hours can ensure the complete carbonization reaction, and avoid excessive graphitization or structural damage of the carbon material. Optionally, the second carbonization time can be 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, or 10h.

[0064] In an embodiment, in step S4, the hydrothermal reaction temperature is 120-180℃, and the hydrothermal reaction time is 4-8 hours. The hydrothermal reaction temperature is in the range of 120-180℃, the tin source can be well dissolved or dispersed in the hydrothermal medium, and then interact with the hard carbon matrix, which can ensure the full dissolution or dispersion of the tin source, and avoid the volatilization of the tin source or the destruction of the hard carbon matrix structure caused by high temperature. Optionally, the hydrothermal reaction temperature can be 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, or 180℃. At the same time, the reaction time of 4-8 hours of the hydrothermal reaction can promote the tin source to fully diffuse and be uniformly loaded on the hard carbon matrix, avoid the agglomeration of the tin source or the change of the hard carbon matrix structure, form a stable carbon-tin inner layer structure, and optionally, the hydrothermal reaction time can be 4h, 5h, 6h, 7h, or 8h.

[0065] In an embodiment, in step S5, the carbon coating treatment step includes: mixing the carbon-tin inner layer material, the second carbon source, and the first solvent, then performing third carbonization, grinding, and sieving to obtain a hard carbon composite material. In this embodiment, the mixture will be subjected to third carbonization at high temperature, so that the second carbon source is converted into carbon and coated on the surface of the carbon-tin inner layer material. After carbonization, the material is refined by grinding to improve its specific surface area and reactivity, and then oversized or undersized particles are removed by sieving to ensure uniform particle size distribution of the final product. Through a series of carbon coating treatment steps, a hard carbon composite material with excellent performance is obtained. This material not only has high specific capacity and good cycle stability, but also has excellent electrical conductivity and ion diffusion performance, providing an ideal electrode material for sodium ion battery applications. In an embodiment of the present application, the second carbon source is pitch, and the first solvent is petroleum ether.

[0066] The preparation method of the hard carbon composite material provided by the present application has simple process, low cost of carbon source used, high repeatability, short cycle, low energy consumption, saves production cost, and is suitable for large-scale production and preparation, and has good application prospect in the field of sodium ion batteries.

[0067] The present application provides a negative electrode material, which comprises the hard carbon composite material provided in the first aspect of the present application. The negative electrode material provided by the present application has small volume change, high cycle capacity and long cycle life during the cycle process.

[0068] The present application provides a sodium ion battery, which comprises the negative electrode material provided in the third aspect of the present application. The sodium ion battery provided by the present application has high cycle capacity and long cycle life.

[0069] The present application provides an electric device, which comprises a sodium ion battery. The sodium ion battery has long cycle life and high capacity, so that the electric device can be used stably for a long time, which is beneficial to improve the use performance of the electric device.

[0070] The technical solutions of the present application are further illustrated by specific examples and comparative examples.

[0071] Example 1

[0072] The present embodiment provides a hard carbon composite material and a preparation method thereof, and the synthesis process comprises the following steps:

[0073] (1) The waste coconut shell is washed with deionized water for 3 times to remove the surface sludge and other impurities, and then dried in an oven at 120°C for 12h;

[0074] (2) After drying, the coconut shell is coarsely broken, and the sample particle size is controlled in the range of D50=2mm;

[0075] (3) The coarsely broken coconut shell sample is pre-carbonized at 450°C for 10h;

[0076] (4) The sample after pre-carbonization in step (3) is ground in an air flow grinder, and the particle size of the discharged sample is controlled to be D50≈5um;

[0077] (5) The sample after grinding in step (4) is acid washed and purified, and the volume ratio of each component in the mixed acid used is hydrochloric acid:sulfuric acid:hydrofluoric acid=7:2:1; the volume of the mixed acid used per 100g is 500ml, and the acid washing reaction temperature is 50°C. After acid washing, the sample is washed repeatedly with deionized water and dried;

[0078] (6) The sample after acid washing and purification in step (5) is activated with activated pore-forming agent KOH at high temperature, the reaction temperature is 600°C, and the reaction time is 5h;

[0079] (7) The sample after activation in step (6) is carbonized at high temperature, the carbonization reaction temperature is 1300°C, and the reaction time is 6h; after natural cooling, a porous hard carbon skeleton material is obtained;

[0080] (8) 500g of the porous hard carbon powder in step (7) is mixed with 10.86g of SnCl2·2H2O, and then dispersed in deionized water. After sufficient stirring, it is transferred to a polytetrafluoroethylene reaction kettle and subjected to hydrothermal reaction at a reaction temperature of 120°C for 6 hours. The product obtained after the reaction is washed by centrifugation, filtered and dried to obtain a hard carbon / SnO composite material.

[0081] (9) The asphalt is dissolved in petroleum ether, then a certain amount of asphalt is added and stirred until completely dissolved, then the hard carbon / SnO composite material in step (8) above is added to the asphalt-dissolved petroleum ether solution, and stirring is continued for 2 hours, the temperature is raised to 80°C, and the petroleum ether is completely evaporated. The asphalt-coated hard carbon / SnO composite material is carbonized at a high temperature of 1000°C for 3 hours under a nitrogen atmosphere, and then removed after the temperature decreases to room temperature.

[0082] Example 2

[0083] This embodiment provides a hard carbon composite material and a preparation method thereof, and the synthesis process comprises the following steps:

[0084] (1) The waste coconut shell is washed with deionized water for 3 times to remove surface dirt and other impurities, and then dried in an oven at 120°C for 12h;

[0085] (2) After drying, the coconut shell is coarsely broken, and the sample particle size is controlled in the range of D50=2mm;

[0086] (3) The coarsely broken coconut shell sample is pre-carbonized at 450°C for 11h;

[0087] (4) The sample after pre-carbonization in step (3) is ground in an air flow grinder, and the particle size of the discharged sample is controlled to be D50≈8um;

[0088] (5) The sample after grinding in step (4) is acid washed and purified, and the volume ratio of each component in the mixed acid used is hydrochloric acid:sulfuric acid:hydrofluoric acid=7:2:1; the volume of the mixed acid used per 100g is 500ml, and the acid washing reaction temperature is 50°C. After acid washing, the sample is washed repeatedly with deionized water and dried;

[0089] (6) The sample after acid washing and purification in step (5) is activated with activated pore-forming agent KOH at a high temperature, the reaction temperature is 600°C, and the reaction time is 5h;

[0090] (7) The sample after activation in step (6) is carbonized at a high temperature, the carbonization reaction temperature is 1300°C, and the reaction time is 6h; after natural cooling, a porous hard carbon skeleton material is obtained;

[0091] (8) 500g of the porous hard carbon powder in step (7) is mixed with 7.848g of SnCl2·2H2O, then dispersed in deionized water, and after sufficient stirring, transferred to a polytetrafluoroethylene reaction kettle for hydrothermal reaction at a reaction temperature of 120°C, the reaction time is 6 hours, and the product obtained after the reaction is washed by centrifugation, filtration and drying to obtain a hard carbon / SnO composite material.

[0092] (9) The asphalt is dissolved in petroleum ether, then a certain amount of asphalt is added and stirred until completely dissolved, then the hard carbon / SnO composite material in step (8) above is added to the asphalt-dissolved petroleum ether solution, and stirring is continued for 2 hours, the temperature is raised to 80°C, and the petroleum ether is completely evaporated. The asphalt-coated hard carbon / SnO composite material is carbonized at a high temperature of 1000°C for 3 hours under a nitrogen atmosphere, and then removed when the temperature decreases to room temperature.

[0093] Example 3

[0094] The difference from Example 1 is that the mass of SnCl2·2H2O in step (8) is 9.81 g, and the other steps remain the same as Example 1.

[0095] Example 4

[0096] The difference from Example 1 is that the mass of SnCl2·2H2O in step (8) is 13.08 g, and the other steps remain the same as Example 1.

[0097] Example 5

[0098] (Compared with Example 3, using anthracite as the precursor raw material, using water vapor as the activator)

[0099] In this embodiment, the carbon-coated and SnO-loaded modified porous hard carbon negative electrode material and its preparation method, the synthesis process comprises the following steps:

[0100] (1) The anthracite is washed with deionized water for 3 times to remove surface dirt and other impurities, then dried in an oven at 100°C for 24h;

[0101] (2) After drying, the anthracite is coarsely broken, and the sample particle size is controlled in the range of D50=1mm;

[0102] (3) The coarsely broken anthracite is pre-carbonized at 550°C for 3h;

[0103] (4) The sample after pre-carbonization in step (3) above is ground in an air jet mill, and the sample particle size is controlled to D50≈5um;

[0104] (5) The sample after grinding in step (4) above is acid washed and purified, and the volume ratio of each component in the mixed acid used is hydrochloric acid:sulfuric acid:hydrofluoric acid=7:2:1; the volume of the mixed acid used per 100g is 600ml, and the acid washing reaction temperature is 60°C. After acid washing, the sample is washed repeatedly with deionized water and dried;

[0105] (6) The sample after acid washing and purification in step (5) above is subjected to an activation reaction with high-temperature water vapor at a temperature of 600°C for 4h;

[0106] (7) The sample after the activation treatment of step (6) is subjected to a carbonization reaction at a high temperature, and the carbonization reaction temperature is 1200°C, and the reaction time is 6h; and a porous hard carbon skeleton material is obtained after natural cooling;

[0107] (8) The porous hard carbon powder of step (7) is mixed with SnCl2·2H2O, and then is dispersed in deionized water, and after being fully stirred, is transferred to a polytetrafluoroethylene reaction kettle, and is subjected to a hydrothermal reaction at a reaction temperature of 120°C, and the reaction time is 6 hours; and the product obtained after the reaction is washed by centrifugation, filtration and drying to obtain a hard carbon / SnO composite material.

[0108] (9) The pitch is dissolved in petroleum ether, and then a certain amount of pitch is stirred to completely dissolve, and then the hard carbon / SnO composite material in step (8) is added to the petroleum ether solution in which the pitch is dissolved, and stirring is continued for 2 hours, and the temperature is increased to 80°C until the petroleum ether is completely evaporated. The pitch-coated hard carbon / SnO composite material is carbonized at a high temperature of 1000°C for 3 hours under a nitrogen atmosphere, and is taken out after the temperature is reduced to room temperature.

[0109] Example 6

[0110] (Compared with Example 3, lignite is used as a precursor raw material, and CO2 is used as an activator)

[0111] In this embodiment, the carbon-coated and SnO-loaded co-modified porous hard carbon negative electrode material and the preparation method thereof are characterized in that the synthesis process comprises the following steps:

[0112] (1) The lignite is washed with deionized water for 3 times to remove surface dirt and other impurities, and then is dried in an oven at 85°C for 24h;

[0113] (2) After drying, the lignite is coarsely broken, and the sample particle size is controlled in the range of D50=1mm;

[0114] (3) The coarsely broken lignite is subjected to a pre-carbonization treatment at 550°C for 3h;

[0115] (4) The sample after the pre-carbonization treatment of step (3) is ground in an airflow pulverizer, and the sample particle size is controlled to D50≈5um;

[0116] (5) The sample after the grinding treatment of step (4) is subjected to acid washing purification, and the volume ratio of each component in the mixed acid used is hydrochloric acid:sulfuric acid:hydrofluoric acid=7:2:1; the volume of the mixed acid used per 100g is 600ml, and the acid washing reaction temperature is 60°C. After the acid washing is completed, the sample is washed repeatedly with deionized water and dried;

[0117] (6) The sample after acid pickling purification treatment in step (5) is subjected to activation reaction with activated pore-forming agent CO2 at high temperature, the reaction temperature is 900°C, and the reaction time is 4h;

[0118] (7) The sample after activation treatment in step (6) is subjected to carbonization reaction at high temperature, the carbonization reaction temperature is 1250°C, and the reaction time is 6h; after natural cooling, a porous hard carbon skeleton material is obtained;

[0119] (8) The porous hard carbon powder in step (7) is mixed with SnCl2·2H2O, then dispersed in deionized water, after sufficient stirring, transferred to a polytetrafluoroethylene reaction kettle, and subjected to hydrothermal reaction at a reaction temperature of 120°C, the reaction time is 6 hours, and the obtained product is washed by centrifugation, filtration and drying to obtain a hard carbon / SnO composite material.

[0120] (9) The pitch is dissolved in petroleum ether, then a certain amount of pitch is added and stirred until completely dissolved, then the hard carbon / SnO composite material in step (8) is added to the petroleum ether solution with dissolved pitch, and continues to stir for 2 hours, the temperature is raised to 80°C until the petroleum ether is completely evaporated. The pitch-coated hard carbon / SnO composite material is carbonized at 1000°C under nitrogen atmosphere for 3 hours, and then taken out after the temperature is reduced to room temperature.

[0121] Comparative Example 1

[0122] Commercially available Japanese Kureha hard carbon product Type-2. The specific surface area and particle size of the composite material prepared in this comparative example are tested, the specific surface area is 4.5m 2 / g, and the average particle size D50 = 5um.

[0123] Comparative Example 2

[0124] Take 39.84g SnCl2·2H2O, then disperse in deionized water, after sufficient stirring, transfer to a polytetrafluoroethylene reaction kettle, and subject to hydrothermal reaction at a reaction temperature of 120°C, the reaction time is 6 hours, and the obtained product is washed by centrifugation, filtration and drying to obtain SnO material.

[0125] Test method:

[0126] (1) Electrochemical sodium storage performance test

[0127] The composite material obtained in the examples and comparative examples was respectively taken as a negative electrode (the mass ratio of the substances in the formula was hard carbon composite material: carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR): conductive carbon black (SP) = 100: 1.5: 2.5: 1), sodium sheet was taken as a positive electrode, electrolyte was NaPF6 / (PC+EMC) (the volume ratio of the electrolyte solvents PC: EMC = 1: 1), the separator was a glass fiber separator, and the coin half-cell was assembled in a glove box filled with high-purity argon. The electrochemical performance was tested on a Wuhan Lan electric CT2001A battery tester, the charge and discharge voltage range was controlled at 0-2V, the charge and discharge rate was 0.1C, the first cycle sodium intercalation capacity and sodium extraction capacity and the cycle number (sodium extraction capacity decayed to 80% of the first cycle sodium extraction capacity) were recorded, and the first cycle coulombic efficiency (first cycle coulombic efficiency = first cycle sodium extraction capacity / first cycle sodium intercalation capacity) was calculated.

[0128] (2) Specific surface area test

[0129] According to the provisions in GB / T 19587, the specific surface area of the material was determined by using a CANTA NOVA2000e specific surface area analyzer.

[0130] (3) Particle size test

[0131] According to Appendix A in GB / T 24533-2019, the particle size of the material was detected by using a Malvern laser particle size analyzer.

[0132] (4) TGA thermogravimetric test

[0133] A small amount of powder sample was weighed by using a special crucible, and after recording its mass, it was placed in a thermogravimetric analyzer, and a heating test was carried out in an air atmosphere at a heating rate of 5℃ / min, the temperature range was room temperature-900℃, and the remaining mass ratio was the mass ratio of SnO.

[0134] (5) TEM transmission electron microscope test

[0135] A small amount of sample was ultrasonically dispersed in anhydrous ethanol, and then a small amount of drop was sucked by a pipette gun and dropped on a carbon film or microgrid, and after natural drying, the test was carried out, the instrument used was Hitachi-7650 (Japan, 80kV), and HRTEM, JEOL JEM-3000F.

[0136] Table 1 Hard carbon composite material components and preparation, battery test results

[0137]

[0138] It can be found by comparing examples 1-6 and comparative example 1 that the capacity is obviously improved after activation and SnO compounding, which benefits from the more active sites provided by the activation and the more capacity provided by the SnO as active material and the porous hard carbon. The battery in comparative example 2 using SnO as the negative material only has poor cycle stability. Meanwhile, in examples 1-6, the first coulombic efficiency is also improved to a certain extent, which is mainly due to the optimization of the surface structure by the coating layer, reducing the contact area with the electrolyte. Further, when the content of SnO further meets the range of 1-2% in the present application, the sodium ion battery containing the hard carbon composite material has high capacity, high first coulombic efficiency and long cycle life.

[0139] The above is the preferred embodiment of the present application, but it cannot be interpreted as limiting the scope of the present application. It should be noted that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can also be made, which are considered to be within the scope of protection of the present application.

Claims

1. A hard carbon composite material, characterized in that It includes a carbon-tin inner layer material and a coating outer layer, wherein the carbon-tin inner layer material includes a porous hard carbon matrix and a tin-containing compound filled in the pores of the porous hard carbon matrix, and the coating outer layer is a soft carbon coating layer; The hard carbon composite material is prepared by the following steps: S1, performing a first carbonization treatment on the first carbon source and then pickling; S2, activating the first carbon source after acid washing and the activated pore-forming agent; S3, performing a second carbonization on the activated first carbon source to obtain a porous hard carbon matrix; S4, hydrothermally reacting the porous hard carbon matrix and the tin source to obtain a carbon-tin inner layer material; S5. Performing carbon coating treatment on the carbon-tin inner layer material to obtain the hard carbon composite material.

2. The hard carbon composite material according to claim 1, wherein The particle size diameter of the porous hard carbon matrix is: 1um≤D50≤20um.

3. The hard carbon composite material according to claim 1, wherein The BET specific surface area of ​​the porous hard carbon matrix is ​​1-20 m 2 / g, the powder tap density of the porous hard carbon matrix is ​​≥0.7g / cm 3 , the carbon content of the porous hard carbon matrix is ​​≥99.10%.

4. The hard carbon composite material according to claim 1, wherein The tin-containing compound includes one or more of SnO, Sn3P4 and SnS.

5. The hard carbon composite material according to claim 1 or 4, characterized in that The particle diameter of the tin-containing compound satisfies 5nm≤D50≤200nm.

6. The hard carbon composite material according to claim 1, wherein Based on the total mass of the hard carbon composite material, the mass proportion of the tin-containing compound is 1% to 2%.

7. The hard carbon composite material according to claim 1, wherein The thickness of the outer coating layer is 20 to 800 nm, and based on the total mass of the hard carbon composite material, the mass of the outer coating layer accounts for 0.5% to 1%.

8. The hard carbon composite material according to claim 1, wherein In step S1 , the first carbon source includes biomass waste and coal, the biomass waste includes one or more of crop straw and crop husk, and the coal includes one or more of anthracite, bituminous coal and lignite.

9. The hard carbon composite material according to claim 1, wherein Step S1 further includes coarsely crushing, cleaning, and drying the first carbon source, wherein the particle size of the coarsely crushed first carbon source is 1 mm ≤ D50 ≤ 5 mm.

10. The hard carbon composite material according to claim 1, wherein include: In step S1, the temperature of the first carbonization treatment is 300-600°C, the treatment time is 10-12 hours, and the pickling uses one or more of hydrochloric acid, sulfuric acid, and hydrofluoric acid, and the pickling temperature is 40-70°C; In step S2, the activation reaction temperature is 600-1000° C., and the activation reaction time is 2-6 hours; In step S3, the second carbonization temperature is 1000-1700° C., and the second carbonization time is 2-10 hours; In step S4, the temperature of the hydrothermal reaction is 120-180° C., and the time of the hydrothermal reaction is 4-8 hours.

11. The hard carbon composite material according to claim 1, wherein In step S5, the carbon coating treatment step includes: mixing the carbon-tin inner layer material, the second carbon source and the first solvent, performing a third carbonization, grinding and screening to obtain the hard carbon composite material.

12. The hard carbon composite material according to claim 11, wherein In step S5, the third carbonization temperature is 1000-1300° C., and the third carbonization time is 3-5 hours.

13. A negative electrode material, characterized in that The negative electrode material includes the hard carbon composite material according to any one of claims 1 to 12.

14. A sodium ion battery, characterized in that: The sodium ion battery comprises the negative electrode material according to claim 13.

15. An electrical device, characterized in that: The electrical device includes the negative electrode material according to claim 13 or the sodium ion battery according to claim 14.

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