CN119297260A

CN119297260A - A metal-doped silicon-based negative electrode material and its preparation method and application

Info

Publication number: CN119297260A
Application number: CN202411807220.5A
Authority: CN
Inventors: 岳之浩; 马浩强; 金晨鑫; 徐国军; 温丽君
Original assignee: Gongqingcheng Optical Hydrogen Storage Technology Research Institute Of Nanchang University; Nanchang University
Current assignee: Gongqingcheng Optical Hydrogen Storage Technology Research Institute Of Nanchang University; Nanchang University
Priority date: 2024-12-10
Filing date: 2024-12-10
Publication date: 2025-01-10
Anticipated expiration: 2044-12-10
Also published as: CN119297260B

Abstract

The present invention provides a metal-doped silicon-based negative electrode material and a preparation method and application thereof, and relates to the technical field of new energy battery materials. The preparation method provided by the present invention comprises: stirring and mixing the surface-activated silicon-based material in a metal organic framework nanosheet suspension and separating and drying to obtain a composite precursor; stirring and mixing the composite precursor in a coating solution and separating and drying to obtain a composite intermediate; stirring and mixing the composite intermediate in a transition metal solution, dripping an organic ligand, stirring and reacting, and separating and drying to obtain a doped intermediate; pre-sintering the doped intermediate in an oxygen-containing atmosphere at 100°C-150°C for 0.5h-1h, calcining and cooling in an inert atmosphere at 1000°C-1200°C to obtain a metal-doped silicon-based negative electrode material. The preparation method provided by the present invention is simple to operate, does not require the use of complex mechanical equipment, and the obtained metal-doped silicon-based negative electrode material has good capacity performance and cycle stability.

Description

Metal doped silicon-based anode material and preparation method and application thereof

Technical Field

The invention relates to the technical field of new energy battery materials, in particular to a metal doped silicon-based anode material, and a preparation method and application thereof.

Background

The negative electrode material is used as one of four main materials of the lithium battery, the performance of the negative electrode material has a key influence on the battery performance, and the graphite has good cycle stability and excellent electric conductivity, and the layered structure of the graphite has good lithium intercalation space, so that the lithium battery manufacturer mainly uses a graphite negative electrode to be applied to the lithium battery. However, with the continuous increase of the performance requirements of lithium batteries, the development of lithium batteries is restricted by the natural limitations of graphite negative electrodes (such as low theoretical gram specific capacity, easy stripping and falling off during long cycle, etc.).

Silicon materials with higher theoretical specific capacities have become cathode materials with great potential, however, there are some problems to be solved when the silicon materials are applied to lithium batteries, for example, the silicon materials have huge volume changes, which easily cause cathode cracking and pulverization, and huge capacity loss and even battery failure can be caused in the battery cycle process. Currently, in the application of silicon materials, the silicon materials are generally subjected to modification treatment so as to improve the problem of volume expansion of the silicon materials and to increase the capacity of the silicon materials.

The modification method of the silicon material in the prior art is to compound with a carbon material, a metal material or other materials with high conductivity, for example, the silicon material and the metal material are compounded by adopting a high-energy ball milling method, so that silicon and metal can be fully mixed, but the morphological structure of the silicon material can be greatly destroyed, and the expansion problem of the silicon material can be improved, but the actual specific capacity of the final material is still far lower than the theoretical specific capacity. It is therefore desirable to provide a solution to the above-mentioned problems.

Disclosure of Invention

The invention aims to provide a metal doped silicon-based anode material, a preparation method and application thereof, the preparation method provided by the invention has simple operation, the metal doped silicon-based anode material prepared by the method has good capacity performance and cycle stability without using complex mechanical equipment.

The preparation method of the metal doped silicon-based anode material comprises the steps of stirring, mixing, separating and drying a silicon-based material with activated surface in a metal organic framework nanosheet suspension to obtain a composite precursor, stirring, mixing, separating and drying the composite precursor in a coating solution to obtain a composite intermediate, stirring, mixing, dripping an organic ligand, stirring, reacting, separating and drying to obtain a doped intermediate, presintering the doped intermediate in an oxygen-containing atmosphere of 100-150 ℃ for 0.5-1 h, calcining in an inert atmosphere of 1000-1200 ℃ and cooling to obtain the metal doped silicon-based anode material.

Optionally, the preparation method of the silicon-based material comprises the steps of stirring and mixing silicon powder and cellulose, carbonizing and crushing to obtain a silicon-carbon mixture, ultrasonically mixing the silicon-carbon mixture in an alcohol solution, adding a cross-linking agent, stirring and mixing, separating and drying to obtain a silicon-carbon composite, carbonizing the silicon-carbon composite at 600-700 ℃, and crushing to obtain the silicon-based material.

Optionally, the mass ratio of the silicon powder to the cellulose is 1 (1-1.5).

Optionally, the silicon powder and cellulose are carbonized and crushed under 10MPa-50MPa and 300-400 ℃.

Optionally, the alcohol solution comprises one of methanol and ethanol.

Optionally, the solid-to-liquid ratio of the silicon-carbon mixture in the alcohol solution is 0.05g/mL-0.08g/mL.

Optionally, the cross-linking agent comprises one of 1, 3-propanedithiol, 1, 5-pentanedithiol, and 1, 9-nonanedithiol.

Optionally, the mass ratio of the silicon-carbon mixture to the cross-linking agent is 1 (0.1-0.2).

Optionally, the average particle size of the silicon-based material is 50nm-100nm.

Optionally, the surface-activated silicon-based material is prepared by surface treatment of the silicon-based material in a titanate coupling agent and/or a nitrogen-containing coupling agent.

Alternatively, the process may be carried out in a single-stage, the titanate coupling agent comprises triiso isopropyl stearyl titanate one of the isopropoxy tricarboxyl titanate esters.

Optionally, the nitrogen-containing coupling agent comprises one of 3-piperazinylpropyl methyl dimethoxy silane and N- (aminoethyl) -3-aminopropyl methyl dimethoxy silane.

Optionally, the silicon-based material is immersed in an active solution in which a titanate coupling agent and/or a nitrogen-containing coupling agent are dissolved, and then separated and dried to obtain the silicon-based material with the activated surface.

Optionally, the mass ratio of the silicon-based material to the coupling agent is 1 (0.05-0.10), and the coupling agent is a titanate coupling agent and/or a nitrogen-containing coupling agent.

Optionally, the mass ratio of the silicon-based material after surface activation to the metal organic framework nanosheets in the metal organic framework nanosheet suspension is 1 (0.1-0.2).

Optionally, the length of the metal organic framework nano-sheets in the metal organic framework nano-sheet suspension is 1-10 μm, and the thickness is 50-200 nm.

Optionally, the solvent in the metal organic framework nanosheet suspension comprises one of methanol and ethanol.

Optionally, the solute in the coating solution comprises melamine.

Alternatively, the mass ratio of the composite precursor to the solute in the coating solution is 1 (0.2-0.3).

Optionally, the composite precursor is stirred and mixed in a coating solution at 40-50 ℃.

Optionally, the composite precursor is ultrasonically dispersed within the coating solution.

Optionally, after mixing the composite precursor with stirring in the coating solution, the composite precursor is isolated and dried in a 60 ℃ to 80 ℃ vacuum environment.

Optionally, the transition metal element in the transition metal solution includes one of cobalt, copper, titanium, manganese, zinc, magnesium, and platinum.

Optionally, the organic ligand comprises one of 2-methylimidazole, terephthalic acid, 2, 5-thiophene dicarboxylic acid.

Optionally, the mass ratio of the composite intermediate to the transition metal element in the transition metal solution to the organic ligand is 1 (0.2-0.3) (0.05-0.08).

Optionally, the oxygen volume fraction in the oxygen-containing atmosphere is 10% -100%.

Optionally, the doped intermediate is warmed to 100 ℃ to 150 ℃ at a rate of 1 ℃ to 10 ℃ per minute in an oxygen-containing atmosphere.

Optionally, after pre-sintering the doped intermediate in an oxygen-containing atmosphere at 100 ℃ to 150 ℃ for 0.5h to 1h, the temperature is raised to 1000 ℃ to 1200 ℃ at a rate of 1 ℃ to 10 ℃ per minute under an inert atmosphere.

Optionally, the calcination is carried out for 2-3 hours in an inert atmosphere at 1000-1200 ℃.

In a second aspect, the invention also provides a metal doped silicon-based anode material prepared by any one of the above optional preparation methods.

In a third aspect, the invention also provides an application of the metal doped silicon-based anode material prepared by any one of the optional preparation methods in a lithium ion battery.

Drawings

Fig. 1 is a flow chart of a preparation method of a metal doped silicon-based anode material provided by the invention.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. Unless otherwise defined, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs.

Referring to fig. 1, the invention provides a preparation method of a metal doped silicon-based anode material, which comprises the following steps:

S1, stirring and mixing the surface-activated silicon-based material in a metal organic framework nanosheet suspension, and separating and drying to obtain a composite precursor;

S2, stirring and mixing the composite precursor in a coating solution, and separating and drying to obtain a composite intermediate;

S3, stirring and mixing the composite intermediate in a transition metal solution, dropwise adding an organic ligand, stirring and reacting, separating and drying to obtain a doped intermediate;

S4, pre-sintering the doped intermediate in an oxygen-containing atmosphere at 100-150 ℃ for 0.5-1 h, calcining in an inert atmosphere at 1000-1200 ℃ and cooling to obtain the metal doped silicon-based anode material.

In fact, in the step S1, after the surface activation treatment is performed on the silicon-based material, the reactivity of the surface of the silicon-based material can be effectively improved, and then when stirring is performed in the metal organic framework nanosheet suspension, the adhesion of the metal organic framework nanosheets on the surface of the silicon-based material is promoted by the shearing force generated by stirring, and then the nanosheet coating layer with a loose structure can be formed on the surface of the silicon-based material, and meanwhile, the stirring process is favorable for improving the uniformity of the nanosheet coating layer, so that the silicon-based material in the nanosheet coating layer can be protected.

In some embodiments, the step S1 of pre-treating the surface of the silicon-based material comprises the step of preparing the surface-activated silicon-based material after the surface treatment of the silicon-based material in the titanate coupling agent and/or the nitrogen-containing coupling agent. In practice, after the surface treatment of the silicon-based material is performed by adopting the titanate coupling agent and/or the nitrogenous coupling agent, different active groups can be introduced on the surface of the silicon-based material, so that the dispersibility and interface bonding performance of the silicon-based material can be effectively improved, and the adhesion and coating of the metal organic framework nano-sheet on the surface of the silicon-based material are facilitated.

In some embodiments, the titanate coupling agent used in the pre-surface treatment of the silicon-based material comprises one of isopropyl triisostearate titanate and isopropyl tricarboxyl titanate. In fact, the titanate coupling agent has titanium central atoms in the molecules, and can be condensed with silicon-hydroxyl groups on the surface of the silicon-based material in a reaction way, so that silicon-oxygen-titanium bonds are introduced on the surface of the silicon-based material.

In some embodiments, the nitrogen-containing coupling agent used in the pre-surface treatment of the silicon-based material comprises one of 3-piperazinylpropyl methyl dimethoxy silane, N- (aminoethyl) -3-aminopropyl methyl dimethoxy silane. In fact, the molecule of the nitrogen-containing coupling agent contains amino, and the amino has stronger nucleophilicity and can react with hydroxyl on the surface of silicon base, so that silicon-oxygen-silicon bond is introduced on the surface of the silicon base material.

In practice, when the surface treatment is performed on the silicon-based material in advance, the titanate coupling agent and the nitrogen-containing coupling agent can be used for compounding, so that the richness of the surface active groups of the silicon-based material can be improved. Specifically, when the surface treatment is carried out, the mass ratio of the silicon-based material to the coupling agent (titanate coupling agent and/or nitrogen-containing coupling agent) is 1 (0.05-0.10).

In some embodiments, when the surface treatment is performed on the silicon-based material in advance, the silicon-based material is immersed in an active solution in which a titanate coupling agent and/or a nitrogen-containing coupling agent are dissolved, and then separated and dried to obtain the silicon-based material with the activated surface. Specifically, the silicon-based material is immersed in the active solution, which is favorable for fully contacting the silicon-based material by the coupling agent, thereby being favorable for improving the surface activation effect and simultaneously improving the activation efficiency.

In practice, after the silicon-based material is added into the active solution, the silicon-based material is dispersed and impregnated by adding ultrasound, so that agglomeration and sedimentation of the silicon-based material during activation treatment are avoided, and meanwhile, the dispersion uniformity of the silicon-based material in the active solution can be further improved, and further, the activation effect and activation efficiency are improved.

In some embodiments, after the silicon-based material is immersed in the active solution, solid-liquid separation may be performed by common separation means such as filtration separation and suction filtration separation, and then the obtained solid is dried in an environment of 30-60 ℃ to obtain the silicon-based material with activated surface. In practice, after the solids are obtained, a rinse with deionized water may also be used to remove surface-adhering impurities.

The preparation method of the silicon-based material used in the step S1 comprises the steps of stirring and mixing silicon powder and cellulose, carbonizing and crushing to obtain a silicon-carbon mixture, ultrasonically mixing the silicon-carbon mixture in an alcohol solution, adding a cross-linking agent, stirring and mixing, separating and drying to obtain a silicon-carbon composite, carbonizing the silicon-carbon composite at 600-700 ℃, and crushing to obtain the silicon-based material.

In practice, when the silicon-based material is prepared, the silicon powder and the cellulose are stirred and mixed in advance, so that the dispersion uniformity between the silicon powder and the cellulose is improved, a compact carbon network can be formed by the carbonized cellulose, the silicon powder is anchored and coated, and a uniform silicon-carbon structure can be formed. Meanwhile, after the carbonized silicon powder and cellulose are crushed, the particle size of the silicon-carbon mixture is reduced, the specific surface area and the surface defects are improved, and the reactivity is improved.

Specifically, the mixing ratio of silicon powder to cellulose is 1 (1-1.5) when preparing silicon-based materials. In fact, in the silicon-based material formed by mixing the silicon powder and the cellulose in the proportion, the carbon network can well anchor and connect the silicon powder, so that the structural stability of the silicon-based material is effectively improved, and meanwhile, the volume change and the theoretical energy storage capacity of the silicon-based material in the charging and discharging processes can be balanced.

In some embodiments, the silicon powder is carbonized and crushed at 10MPa-50MPa, 300-400 ℃ after being mixed with cellulose in the preparation of the silicon-based material. In fact, when carbonization treatment is carried out in a high-pressure environment, the close contact between silicon powder and cellulose is facilitated, meanwhile, the diffusion of gas can be restrained in the cellulose pyrolysis process, pore structures can be carried out in the silicon-carbon material, and the surface defects and the reactivity of the silicon-carbon material are facilitated to be improved.

In practice, when the silicon-based material is prepared, the silicon-carbon mixture is subjected to ultrasonic mixing in the alcohol solution, so that the dispersion uniformity of the silicon-carbon mixture in the alcohol solution can be improved by utilizing the cavitation effect brought by ultrasonic waves, and meanwhile, the silicon-carbon mixture is prevented from sedimentation in the alcohol solution. In addition, after the crosslinking agent is dripped and stirred for reaction, the reaction can be carried out on the silicon powder and the surface of a carbon network in the silicon-carbon mixture, so that the connection stability of the silicon powder and cellulose to form the carbon network after carbonization is improved.

Specifically, the alcohol solution used comprises one of methanol and ethanol, and in addition, the alcohol solution can also be a mixed solution of methanol, ethanol and deionized water, wherein the volume fraction of the methanol and/or the ethanol is greater than or equal to 50%. Meanwhile, the solid-to-liquid ratio of the suspension formed after the silicon-carbon mixture is dispersed in the alcohol solution is 0.05g/mL-0.08g/mL, so that the silicon-carbon mixture is fully dispersed.

Specifically, the crosslinking agent added dropwise during the preparation of the silicon-based material comprises one of 1, 3-propanedithiol, 1, 5-pentanedithiol and 1, 9-nonanedithiol. In fact, since the added cross-linking agent contains mercaptan, the mercaptan can react with active groups such as hydroxyl groups and unsaturated bonds on the surfaces of silicon powder and carbon networks during the cross-linking reaction, so that the purpose of connecting the silicon powder and the carbon networks is achieved, meanwhile, part of sulfur elements can be introduced into the silicon-based material, S-C, S-Si bonds are formed in the silicon-based material, and the adaptability of the silicon-based material to volume changes during the charging and discharging processes can be improved.

Specifically, when the silicon-based material is prepared, the mass ratio of the crosslinking agent added dropwise to the silicon-carbon mixture dispersed in the alcohol solution is (0.1-0.2): 1, so that the crosslinking agent is favorable for uniformly crosslinking the silicon-carbon mixture. In fact, when the amount of the cross-linking agent is too small, the cross-linking points formed in the silicon-carbon mixture are relatively small, the formed cross-linking network is relatively open, the formed pores in the silicon-based material are large, the structural stability is insufficient, and when the amount of the cross-linking agent is too large, the formed cross-linking network in the silicon-carbon mixture is more compact, the structural stability is stronger, but the capacity of the pores to resist volume expansion change is poor.

In some embodiments, when preparing the silicon-based material, the average grain size of the silicon powder is 30nm-50nm, the cellulose is biomass cellulose, specifically wheat straw cellulose with grain size of 0.1mm-0.5mm and water content of less than 10%, and in addition, the grain size of the obtained silicon-based material is 50nm-100nm after carbonization and crushing is carried out after the silicon-based material is prepared. In practice, the particle size of the silicon-based material is controlled, so that the specific surface area of the silicon-based material is improved, more adsorption and intercalation sites can be provided for lithium ions, the battery capacity can be effectively improved, the diffusion rate of ions can be improved, the polarization phenomenon is reduced, in addition, the stress concentration phenomenon caused by volume change can be better relieved by the small-particle-size silicon-based material, the silicon-based material is prevented from being split and pulverized in the charging and discharging process, and the service life of the cathode material can be effectively prolonged.

Specifically, in the step S1, the mass ratio of the surface-activated silicon-based material to the metal organic framework nano-sheets in the metal organic framework nano-sheet suspension is 1 (0.1-0.2). In practice, the coating amount, compactness and uniformity of the metal organic frame nano-sheets on the surface of the silicon-based material can be regulated and controlled by regulating and controlling the dosage of the metal organic frame nano-sheets. In addition, the metal organic frame nano-sheets are prepared into suspension in advance, so that uniformity of the metal organic frame nano-sheets is improved, and even loading on the surface of the silicon-based material is facilitated.

Specifically, the metal-organic framework nanoplatelets used in step S1 have a length of 1 μm to 10 μm and a thickness of 50nm to 200nm. In fact, when the metal organic frame nano sheets are compounded on the surface of the silicon-based material, a complex two-dimensional network structure can be formed on the surface of the silicon-based material through mutual covering, penetrating, winding and stacking of the metal organic frame nano sheets, an ion transmission channel can be provided for lithium ions, and then the ion transmission efficiency is effectively improved.

Specifically, the metal ion in the metal-organic framework nanoplatelets used in step S1 may be one of cobalt, copper, titanium, manganese, zinc, magnesium, platinum. In fact, the metal organic frame nano-sheets can be mixed by adopting a plurality of different metal elements as cores, so that a coating structure with different metal cores can be formed on the surface of the silicon-based material, and then a framework with different metal doping can be formed after the subsequent carbonization and calcination treatment, thereby being beneficial to comprehensively improving the conductivity and the circulation stability of the cathode material.

In practice, the solvent in the metal organic framework nanosheet suspension used in step S1 comprises one of methanol, ethanol. Specifically, in some embodiments, a coupling agent may also be added to the metal-organic framework nanosheet suspension to increase the surface activity of the metal-organic framework nanosheets and avoid agglomeration and sedimentation of the metal-organic framework nanosheets in the suspension.

In some embodiments, the solute of the coating solution used in step S2 comprises melamine. In practice, by stirring and mixing the composite precursor in the coating solution, the solute in the coating solution is favorable for coating the surfaces of the metal organic frame nano sheets in the composite precursor, so that the metal organic frame coating layer can be coated, the surface activity of the metal organic frame coating layer can be improved, and further, the subsequent growth of the metal organic frame nano material on the surface of the metal organic frame nano sheet is favorable, and the pore structure of the metal organic frame nano sheets can be modified. Meanwhile, a solute in the coating solution, such as melamine, can also introduce nitrogen element on the surface of the metal organic framework nano-sheet.

In some embodiments, the mass ratio of the composite precursor to the solute in the coating solution in step S2 is 1 (0.2-0.3). In practice, by adjusting this mass range, the coating amount of the solute in the coating solution on the surface of the composite precursor can be controlled, thereby achieving uniform coating of the metal-organic framework nanoplatelets on the composite precursor.

In some embodiments, the composite precursor is stirred and mixed in step S2 within the coating solution at 40-50 ℃. In practice, the coating treatment is carried out at 40-50 ℃, which is favorable for improving the reactivity of the composite precursor and the solute in the coating solution, further ensuring that the solute in the coating solution has a stable coating structure on the surface of the composite precursor, and simultaneously, mixing by stirring is favorable for improving the coating uniformity. Specifically, the composite precursor may be ultrasonically dispersed in a coating solution.

In some embodiments, after the composite precursor is stirred and mixed in the coating solution in step S2, solid materials may be separated and dried in a vacuum environment of 60 ℃ to 80 ℃ by solid-liquid separation means commonly used in the art, such as filtration separation and suction filtration separation. In fact, the solute coated on the surface of the composite precursor can be promoted to be combined with the metal organic framework nano-sheets on the surface of the composite precursor in the drying process, and meanwhile cracking of the composite precursor between the silicon-based material and the metal organic framework nano-sheets in the drying process is avoided.

In fact, in step S3, the composite intermediate is stirred and mixed in the transition metal solution in advance, which is favorable for promoting the transition metal ions in the transition metal solution to be pre-combined on the surface of the composite intermediate, and then after the organic ligand is dripped, the metal organic framework nano particles can be generated on the surface of the composite intermediate in situ, and further, the pore structure of the metal organic framework nano sheet can be modified, which is favorable for improving the adaptability to volume change, the circulation stability and the capacity performance.

In practice, the coating solution is applied to the surface of the composite precursor, so that the growth of the metal-organic framework particles along the shape of the surface metal-organic framework nano-sheets in the step S3 can be avoided, the pore structure of the metal-organic framework nano-sheets cannot be modified, and the cycle performance and the capacity performance of the negative electrode material in use are difficult to improve.

In some embodiments, the transition metal element in the transition metal solution used in step S3 includes one of cobalt, copper, titanium, manganese, zinc, magnesium, platinum. In practice, different types of transition metal elements are used, so that metal organic framework nano particles with different forms can be grown on the surface of the composite intermediate, and further modification of different forms can be performed on the metal organic framework nano sheet. Specifically, the transition metal element in the transition metal solution is the same as the metal element in the metal organic framework nano-sheet, so that the metal organic framework material with different shapes and the same quality can be formed on the surface of the silicon-based material.

In some embodiments, the organic ligand used in step S3 comprises one of 2-methylimidazole, terephthalic acid, 2, 5-thiophenedicarboxylic acid. In practice, 2-methylimidazole molecules contain an imidazole ring structure in which the nitrogen atom has an arc pair electron, and can form a coordination bond with a transition metal ion, thereby generating a metal organic framework nanoparticle on the surface of the composite intermediate, while terephthalic acid molecules have a benzene ring and two carboxyl groups, and the carboxyl groups can coordinate with the transition metal ion, thereby enabling one terephthalic acid molecule to coordinate with two transition metal ions, while 2, 5-thiophene dicarboxylic acid molecules contain a thiophene ring and two carboxyl groups, and can coordinate with two transition metal ions as well.

Specifically, zinc can be used as transition metal and 2-methylimidazole as organic ligand in the step S3, and 2-methylimidazole zinc salt (ZIF-8) can be generated in situ on the surface of the composite intermediate, or cobalt can be used as transition metal and 2-methylimidazole to react to generate 2-methylimidazole cobalt (ZIF-67). In practice, the metal-organic framework nanoplatelets used in step S2 may be ZIF-8 nanoplatelets or ZIF-67 nanoplatelets.

In some embodiments, the mass ratio of the composite intermediate, the transition metal element in the transition metal solution, and the organic ligand in step S3 is 1 (0.2-0.3): 0.05-0.08. In practice, the amount of the composite intermediate and the amount of the transition metal element are regulated and controlled, so that the amount of the metal organic framework nano particles generated on the surface of the composite intermediate in situ can be controlled, and the modification degree of the metal organic framework nano particles on the pores can be regulated and controlled. In practice, the composite intermediate is dispersed into a transition metal solution in step S3, and the transition metal solution is able to sufficiently infiltrate into the surface pores of the composite intermediate, thereby achieving the prefilling of the transition metal ions.

In fact, in the step S4, the doped intermediate is subjected to pre-sintering treatment at 100 ℃ to 150 ℃, which is favorable for improving the bonding stability of the metal organic framework nanosheets and the metal organic framework nanoparticles, and in addition, the pre-sintering time is controlled to be 0.5h to 1.0h, so that the doped intermediate can be prevented from being subjected to transitional oxidation, and the electrochemical performance of the anode material is affected. In particular, the oxygen-containing atmosphere used may have a volume fraction of oxygen of 10% to 100%, in particular the oxygen-containing atmosphere may be clean air and oxygen.

In some embodiments, the doped intermediate is placed in the hearth of a tube furnace in step S4 and pre-sintered with an incubation at a temperature ramp rate of 1 ℃ to 10 ℃ per minute to 100 to 150 ℃ in an oxygen-containing atmosphere. In fact, the temperature change is too severe by controlling the temperature rising rate, so that cracking and chalking of the doped intermediate due to uneven temperature rising can be avoided.

In some embodiments, after pre-sintering the doped intermediate in an oxygen-containing atmosphere at 100-150 ℃ for 0.5-1 h in step S4, the doped intermediate is calcined at a rate of 1-10 ℃ to 1000-1200 ℃ for 2-3 h under an inert atmosphere. In practice, calcination at 1000-1200 ℃ is beneficial to diffusion and retake of transition metal atoms in the doped intermediate, so that a more uniform metal-carbon skeleton can be formed on the surface of the silicon-based material, and meanwhile, the metal-carbon skeleton and the silicon-based material can be promoted to crosslink, so that the structural stability is effectively improved, in addition, calcination in an inert atmosphere can be avoided, and the silicon-based material can be prevented from being severely oxidized, so that the chemical stability and the structural integrity are improved.

The invention also provides a metal-doped silicon-based anode material prepared by the preparation method in any embodiment, which comprises a silicon-based substrate and a metal carbonized skeleton carbonized and coated on the silicon-based substrate, wherein the metal carbonized skeleton is prepared by carbonizing a metal organic frame material in an inert atmosphere at 1000-1200 ℃. In practice, the silicon-based matrix is provided with silicon powder and a carbon skeleton coated outside the silicon powder, and the carbon skeleton is prepared by carbonizing cellulose.

The invention also provides an application of the metal doped silicon-based anode material prepared by the preparation method in any embodiment in a lithium ion battery. The cathode material, the adhesive and the conductive agent are mixed to prepare conductive slurry, the conductive slurry is coated on a current collector to be dried and molded to prepare a cathode, and the cathode, the anode, the diaphragm and the electrolyte are assembled to prepare the lithium ion battery.

Preparation example 1

The preparation example 1 provides a preparation method of a silicon-based material, which comprises the following steps:

Y1, ultrasonically dispersing nano silicon powder with the average particle size of 50nm and cellulose with the average particle size of 0.3mm in deionized water according to a mass ratio of 1:1, filtering and separating, drying in a 70 ℃ vacuum drying oven to constant weight, transferring into a high-pressure atmosphere furnace, carbonizing for 3 hours under 30MPa and 350 ℃, cooling to room temperature along with the furnace, and crushing to obtain a silicon-carbon mixture;

Y2, ultrasonically mixing a silicon-carbon mixture in a methanol solution at a frequency of 20kHz for 10min to obtain a silicon-carbon mixed methanol suspension, dropwise adding a methanol solution of 1, 3-propanedithiol into the silicon-carbon mixed methanol suspension, controlling the dropwise adding time to be 30min, stirring and mixing for 30min after the dropwise adding is finished, filtering and separating, flushing the obtained solid by using methanol, and drying in a 50 ℃ oven to constant weight to obtain a silicon-carbon compound, wherein the mass ratio of the silicon-carbon mixture to the 1, 3-propanedithiol is 1:0.1;

And Y3, placing the silicon-carbon composite in a hearth of a tube furnace, introducing nitrogen as protective gas, heating the tube furnace to 650 ℃ at a rate of 5 ℃ per min, preserving heat and carbonizing for 2 hours, cooling the tube furnace to room temperature, and crushing to obtain the silicon-based material with the average particle size of 100 nm.

Preparation example 2

The preparation example 2 provides a surface activation method of a silicon-based material, which comprises the following steps:

Y4, dissolving triisostearyl isopropyl titanate (CAS: 61417-49-0, purchased from Jiangxi Chen Guangguang New Material Co., ltd.) in absolute ethyl alcohol in advance to prepare an active solution, adding the silicon-based material prepared in preparation example 1 into the active solution, ultrasonically mixing in a water bath environment at 40 ℃, performing vacuum filtration, washing the obtained fixed object by using absolute ethyl alcohol, and drying in a 50 ℃ oven until the weight is constant to obtain the surface-activated silicon-based material, wherein the mass ratio of the silicon-based material to the triisostearyl isopropyl titanate is 1:0.08.

Preparation example 3

The preparation example 3 provides a surface activation method of a silicon-based material, which comprises the following steps:

And Y4, uniformly mixing N- (aminoethyl) -3-aminopropyl methyl dimethoxy silane (KH-602, CAS: 3069-29-2) and absolute ethyl alcohol in a volume ratio of 1:10 in advance to obtain an active solution, putting the silicon-based material prepared in preparation example 1 into the active solution, ultrasonically mixing in a water bath environment at 40 ℃, performing vacuum filtration, washing the obtained fixture by using absolute ethyl alcohol, and drying in a 50 ℃ oven to constant weight to obtain the surface-activated silicon-based material, wherein the mass ratio of the silicon-based material to the N- (aminoethyl) -3-aminopropyl methyl dimethoxy silane is 1:0.08.

Preparation example 4

The preparation example 4 provides a preparation method of a metal organic frame nanosheet suspension, which comprises the steps of mixing a cobalt chloride solution with the concentration of 1mol/L and a 2-methylimidazole aqueous solution with the concentration of 5mol/L in a volume ratio of 1:1, ultrasonically mixing for 10min at the frequency of 20kHz, preserving heat for 2h in a water bath environment at 40 ℃, filtering, separating, flushing precipitate by deionized water, drying in a vacuum environment at 40 ℃ until the weight is constant, and dispersing the obtained metal organic frame nanosheets in methanol to obtain the metal organic frame nanosheet suspension with the solid-to-liquid ratio of 0.08 g/mL.

Example 1

The embodiment 1 provides a preparation method of a metal doped silicon-based anode material, which comprises the following steps:

S1, adding the surface-activated silicon-based material prepared in preparation example 2 into the metal organic frame nanosheet suspension prepared in preparation example 4, controlling the mass ratio of the surface-activated silicon-based material to the metal organic frame nanosheets to be 1:0.1, carrying out ultrasonic treatment at a frequency of 20kHz for 10min, preserving heat at 50 ℃ and stirring at a rotating speed of 200rpm for 30min, carrying out vacuum filtration, washing the obtained solid by using deionized water, and drying at 50 ℃ to constant weight to obtain a composite precursor;

S2, adding the composite precursor into a melamine solution, controlling the mass ratio of the composite precursor to the melamine to be 1:0.25, carrying out ultrasonic mixing at a frequency of 20kHz for 10min, then preserving heat for 1h in a water bath environment at 45 ℃, carrying out vacuum filtration, washing the obtained solid by using absolute ethyl alcohol, and drying in a hot air drying box at 40 ℃ until the weight is constant to obtain a composite intermediate;

S3, after the composite intermediate is ultrasonically mixed in a cobalt chloride aqueous solution for 10min at the frequency of 20kHz, dropwise adding a 2-methylimidazole aqueous solution in a water bath environment of 50 ℃ and 200rpm, controlling the mass ratio of the composite intermediate to cobalt ions to 2-methylimidazole to be 1:0.25:0.07, after the dropwise adding is finished, stirring in the water bath environment of 50 ℃ and preserving heat for 30min, filtering and separating, washing the obtained precipitate by using deionized water, and drying in a 50 ℃ hot air drying box until the weight is constant to obtain a doped intermediate;

S4, placing the doped intermediate in a hearth of a tubular furnace, heating the tubular furnace to 120 ℃ at 5 ℃ per min under an air atmosphere, preserving heat, presintering for 1h, introducing argon into the tubular furnace for gas replacement, heating the tubular furnace to 1100 ℃ at a rate of 5 ℃ per min under the argon atmosphere, calcining for 2h, and cooling to room temperature along with the furnace to obtain the metal doped silicon-based anode material.

Example 2

This example 2 provides a method for preparing a metal-doped silicon-based anode material, which is different from example 1 in that the surface-activated silicon-based material prepared in preparation example 3 is used in step S1.

Example 3

The present example 3 provides a method for preparing a metal doped silicon-based anode material, which is different from example 1 in that in step S3, after ultrasonic mixing of the composite intermediate in a zinc chloride aqueous solution at a frequency of 20kHz for 10min, 2-methylimidazole aqueous solution is dropwise added in a water bath environment of 50 ℃ and 200rpm, and the mass ratio of the composite intermediate, zinc ions and 2-methylimidazole is controlled to be 1:0.25:0.07.

Comparative example 1

The present comparative example 1 provides a method for preparing a metal-doped silicon-based negative electrode material, which is different from example 1 in that the silicon-based material prepared in preparation example 1 is added into the metal-organic framework nanosheet suspension prepared in preparation example 4 in step S1, and the mass ratio of the silicon-based material to the metal-organic framework nanosheets is controlled to be 1:0.1.

Comparative example 2

The comparative example 2 provides a preparation method of a metal doped silicon-based anode material, which is different from the example 1 in that the step S2 is not performed, in the step S3, after the composite precursor is directly ultrasonically mixed with the cobalt chloride aqueous solution at the frequency of 20kHz for 10min, 2-methylimidazole aqueous solution is dropwise added in a water bath environment of 50 ℃ and 200rpm, and the mass ratio of the composite precursor, cobalt ions and 2-methylimidazole is controlled to be 1:0.25:0.07.

Comparative example 3

This comparative example 3 provides a method for producing a metal-doped silicon-based anode material, which is different from example 1 in that step S3 is not performed, and in step S4, the composite intermediate is directly placed in a tube furnace to be subjected to temperature-raising calcination.

Performance detection

The metal-doped silicon-based anode materials prepared in examples 1 to 3 and comparative examples 1 to 3 were used as active materials, LA133 was used as an adhesive, acetylene black was used as a conductive agent, and after being uniformly mixed in a mass ratio of 8:1:1, the materials were coated on a copper foil, vacuum-dried, rolled, and cut into anode sheets with a diameter of 14mm, lithium metal was used as a cathode sheet, lithium hexafluorophosphate was used as an electrolyte, and a polypropylene microporous membrane was used as a separator, and assembled into a button lithium battery in a glove box to perform the following electrochemical performance test.

The first coulomb efficiency test, which is to discharge to 0.01V at normal temperature with a constant current density of 0.1C, then discharge to 0.005V with a constant current density of 0.02C, and finally charge to 1.5V with a constant current density of 0.1C, measure the capacity when charging to 1.5V as the first reversible specific capacity, and calculate the first coulomb efficiency, the result of which is shown in Table 1 below;

And (3) testing the cycle performance, namely performing constant-current charge and discharge at the normal temperature with the current density of 0.1C, limiting the charge and discharge voltage to 0.005V-1.5V, measuring the charge specific capacity after 100 cycles, and calculating the capacity retention rate after 100 cycles, wherein the results are shown in the following table 1.

TABLE 1 electrochemical Performance test results

,

As can be seen from table 1, when the example 1 and the example 2 are combined, the surface of the silicon-based material is modified by using different coupling agents, so that the combination stability of the surface of the silicon-based material and the metal organic framework nano-sheet can be improved, and the obtained negative electrode material can show higher capacity and cycle stability after being applied to a lithium ion battery.

By combining examples 1 to 3, it can be seen from table 1 that homogeneous metal-organic framework nanoparticles are doped on the metal-organic framework nanosheets on the surface of the composite intermediate, and the metal-organic framework nanosheets have better combination performance, so that the structural stability of the anode material is improved, and higher cycle stability is further shown.

As can be seen from table 1, in combination with example 1 and comparative example 1, the surface activation treatment of the silicon-based material was not performed in comparative example 1, and although the coating treatment of the metal-organic framework nano-sheets was also possible, the bonding strength was remarkably decreased, which was shown to be a large decrease in the cycle stability, indicating that the bonding stability of the silicon-based material and the metal-organic framework nano-sheets could be effectively improved by performing the surface treatment of the silicon-based material in advance.

In combination with example 1 and comparative example 2, as can be seen from table 1, in comparative example 2, the surface melamine coating treatment was not performed on the composite precursor, but when the metal organic framework nano-particle formation was performed in step S3, the growth of the nano-sheet was easily continued along the direction of the metal organic framework nano-sheet, and the effect of filling the pores was difficult to be performed, so that the larger pore structure on the surface of the silicon-based material had poor structural stability, and the cyclic stability was significantly reduced.

In combination with example 1 and comparative example 3, and as can be seen from table 1, in comparative example 3, the growth of metal organic framework nanoparticles was not performed on the surface of the composite intermediate, and after the coating treatment was performed on the surface using only melamine, the binding force of melamine between the metal organic framework nanoplatelets was used to reduce the pore size, and the binding strength between the metal organic framework layers and the silicon-based material was further improved, so that the cycle stability was improved.

While embodiments of the present invention have been described in detail hereinabove, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. It is to be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the following claims. Moreover, the invention described herein is capable of other embodiments and of being practiced or of being carried out in various ways.

Claims

1. A preparation method of a metal doped silicon-based anode material is characterized by comprising the steps of stirring, mixing, separating and drying a silicon-based material with activated surface in a metal organic framework nanosheet suspension to obtain a composite precursor, stirring, mixing, separating and drying the composite precursor in a coating solution to obtain a composite intermediate, stirring, mixing, dripping an organic ligand, stirring, reacting, separating and drying to obtain a doped intermediate, presintering the doped intermediate in an oxygen-containing atmosphere at 100-150 ℃ for 0.5-1 h, calcining in an inert atmosphere at 1000-1200 ℃ and cooling to obtain the metal doped silicon-based anode material.

2. The preparation method of the silicon-based material according to claim 1, wherein the preparation method comprises the steps of stirring and mixing silicon powder and cellulose, carbonizing and crushing the mixture to obtain a silicon-carbon mixture, ultrasonically mixing the silicon-carbon mixture in an alcohol solution, adding a cross-linking agent, stirring and mixing the mixture, separating and drying the mixture to obtain a silicon-carbon composite, and carbonizing the silicon-carbon composite at 600-700 ℃ and crushing the carbonized silicon-carbon composite to obtain the silicon-based material.

3. A production method according to claim 2, wherein the mass ratio of the silicon powder to the cellulose is 1 (1-1.5), and/or the silicon powder is carbonized and pulverized at 10MPa-50MPa and 300-400 ℃ after being mixed with the cellulose, and/or the alcohol solution comprises one of methanol and ethanol, and/or the solid-to-liquid ratio of the silicon-carbon mixture in the alcohol solution is 0.05g/mL-0.08g/mL, and/or the crosslinking agent comprises one of 1, 3-propanedithiol, 1, 5-pentanedithiol and 1, 9-nonanedithiol, and/or the mass ratio of the silicon-carbon mixture to the crosslinking agent is 1 (0.1-0.2), and/or the average particle diameter of the silicon-based material is 50nm-100nm.

4. The preparation method of the surface-activated silicon-based material according to claim 1, wherein the silicon-based material is prepared by carrying out surface treatment in a titanate coupling agent and/or a nitrogen-containing coupling agent, wherein the titanate coupling agent comprises one of triisostearoyl isopropyl titanate and isopropoxy tricarboxyl titanate, and/or the nitrogen-containing coupling agent comprises one of 3-piperazinyl propyl methyl dimethoxy silane and N- (aminoethyl) -3-aminopropyl methyl dimethoxy silane, and/or the silicon-based material is separated and dried after being immersed in an active solution dissolved with the titanate coupling agent and/or the nitrogen-containing coupling agent to obtain the silicon-based material with the surface activated, and/or the mass ratio of the silicon-based material to the coupling agent is 1 (0.05-0.10), and/or the coupling agent is the titanate coupling agent and/or the nitrogen-containing coupling agent.

5. The method according to claim 1, wherein the mass ratio of the surface-activated silicon-based material to the metal organic framework nano-sheets in the metal organic framework nano-sheet suspension is 1 (0.1-0.2), and/or the metal organic framework nano-sheets in the metal organic framework nano-sheet suspension have a length of 1-10 μm and a thickness of 50-200 nm, and/or the solvent in the metal organic framework nano-sheet suspension comprises one of methanol and ethanol.

6. The method according to claim 1, wherein the solute in the coating solution comprises melamine, and/or the mass ratio of the composite precursor to the solute in the coating solution is 1 (0.2-0.3), and/or the composite precursor is mixed in the coating solution at 40-50 ℃, and/or the composite precursor is ultrasonically dispersed in the coating solution, and/or the composite precursor is separated and dried in a vacuum environment at 60-80 ℃ after being mixed in the coating solution.

7. The method according to claim 1, wherein the transition metal element in the transition metal solution comprises one of cobalt, copper, titanium, manganese, zinc, magnesium, and platinum, and/or the organic ligand comprises one of 2-methylimidazole, terephthalic acid, and 2, 5-thiophene dicarboxylic acid, and/or the mass ratio of the composite intermediate, the transition metal element in the transition metal solution, and the organic ligand is 1 (0.2-0.3): 0.05-0.08.

8. The method according to claim 1, wherein the oxygen content in the oxygen-containing atmosphere is 10-100%, and/or the doping intermediate is heated to 100-150 ℃ at a rate of 1-10 ℃ per minute in the oxygen-containing atmosphere, and/or the doping intermediate is pre-sintered for 0.5-1 h in the oxygen-containing atmosphere at 100-150 ℃ and then heated to 1000-1200 ℃ at a rate of 1-10 ℃ per minute in the inert atmosphere, and/or the doping intermediate is calcined for 2-3 h in the inert atmosphere at 1000-1200 ℃.

9. A metal doped silicon-based negative electrode material prepared by the method of any one of claims 1 to 8.

10. Use of a metal-doped silicon-based negative electrode material prepared by the preparation method according to any one of claims 1 to 8 in a lithium ion battery.