CN114335520B - Nitride high-energy-storage-density negative electrode material and preparation method thereof - Google Patents
Nitride high-energy-storage-density negative electrode material and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a nitride high energy storage density anode material, which belongs to the technical field of electrochemical energy storage and comprises graphite nitride, silicon nitride, titanium nitride and vanadium nitride. The invention also provides a preparation method of the nitride high-energy-storage-density anode material, which utilizes graphite oxide to coat silicon nitride, effectively solves the problem of volume expansion of the silicon nitride in the circulation process, slows down capacity attenuation caused by surface oxidation and dissolution of the nitride, and greatly improves the circulation stability of the nitride electrode material. The invention has obvious effect and is suitable for wide popularization.
Description
Technical Field
The invention relates to the technical field of electrochemical energy storage, in particular to a nitride anode material with high energy storage density and a preparation method thereof.
Background
With the rapid improvement of the life quality of people and the rapid development of the automobile industry, automobiles become an indispensable transportation means for people to travel daily, the holding quantity of the automobiles is increased continuously, and the problem of exhaust emission caused by the continuous increase of the holding quantity of the automobiles is one of important influencing factors of environmental pollution. Under the extremely high popularization of government and automobile manufacturers, electric automobiles are rapidly applied and developed. The cruising mileage of an electric automobile is a key factor for the popularization and development of the electric automobile, and the improvement of the energy density of a battery is a necessary condition for helping the electric automobile to prolong cruising and accelerate popularization. One specific object of improvement is the negative electrode material of the battery, and the negative electrode material is one of the most main components of the electric automobile power battery pack, and the performance of the negative electrode material directly influences whether the battery pack can work normally or not. At present, the theoretical gram capacity of the traditional graphite cathode is about 372mAh/g, and the requirements of the rapidly-growing electric vehicle market on the large capacity and the miniaturization of batteries cannot be met, so that the development of a high-density cathode material with more excellent performance is urgent. The theoretical gram capacity of the nitride anode can reach 1500mAh/g, so that the addition of a small amount of nitride material into the traditional anode material is the main trend of improving the gram capacity of the anode for battery manufacturers at present. However, the negative electrode added with the nitride material may damage the overall structure of the negative electrode due to excessive volume expansion of the nitride particles during charge and discharge, or significantly reduce the conductivity of the electrode material, ultimately resulting in poor cycle performance of the battery.
The existing method for improving the nitride anode obviously improves the electrochemical performance of the anode, enables electrolyte to easily enter a channel structure, shortens the transmission path of ions, but still has the problem of capacity attenuation caused by larger irreversible reaction in the circulating process, and needs to be further improved in the aspects of rate performance, stability, ion and electronic conductivity.
In view of the above, the existing scientific research work is eagerly seeking to alleviate this situation by using a new anode material or designing a new preparation method, buffer the volume expansion of the nitride anode particles, and maintain the stability of the structure. Therefore, there is a need to develop an ideal negative electrode material that allows lithium ion batteries to have long cycling stability while having high energy density.
Disclosure of Invention
Aiming at the defects, the invention solves the technical problems of providing a nitride anode material with high energy storage density and a preparation method thereof, so as to solve the problems of volume expansion of nitride anode particles and poor structural stability in the prior art; the large irreversible reaction during cycling causes capacity fade problems.
The invention provides a nitride high-energy-storage-density anode material, which comprises a nitride material group, wherein the nitride material group comprises graphite nitride, silicon nitride, titanium nitride and vanadium nitride, the graphite nitride is obtained by converting graphite oxide and has the same structure as the graphite oxide, and the nitride material group has the same three-dimensional intra-layer space structure as the graphite oxide.
Preferably, the nitride material comprises the following components in percentage by mass: 30% -45% of silicon nitride, 30% -45% of graphite nitride, 20% -35% of vanadium nitride and 5% -20% of titanium nitride.
Preferably, the particle size of the graphite nitride particles is 10nm to 5 μm.
Preferably, the silicon nitride particles have a particle diameter of 10nm to 10 μm.
Preferably, the vanadium nitride particles have a particle size of 10nm to 10 μm.
Preferably, the particle size of the titanium nitride particles is 10nm to 10 μm.
The invention also provides a preparation method of the nitride high-energy-storage-density anode material, which is used for preparing any one of the nitride high-energy-storage-density anode materials, and comprises the following steps:
step 1, preparing silicon nitride powder coated by graphite nitride;
step 2, fully mixing vanadium nitride powder and titanium nitride powder in a certain mass ratio to prepare mixed titanium nitride-vanadium nitride powder;
and 3, placing the mixed powder of vanadium nitride and titanium nitride and the silicon nitride powder coated by the graphite nitride in a high-temperature high-pressure reaction kettle according to a certain mass ratio, sealing, heating, and ball-milling the heated sample for 24-72 hours to obtain the nitride high-energy-storage-density anode material.
Preferably, the mass ratio of silicon nitride in the silicon nitride powder coated by the graphite nitride in the step 1 is less than 50%.
Preferably, the specific steps of the step 1 include:
step 1.1, preparing expanded graphite oxide by using natural flaky graphite as a raw material and adopting a Hummers method;
step 1.2, mixing expanded graphite oxide with tetraethyl orthosilicate to obtain graphite oxide coated silicon dioxide;
step 1.3, grinding the silicon dioxide coated with the graphite oxide into powder, and then adding the powder into acetonitrile solvent according to a certain mass ratio for full dispersion;
step 1.4, completely immersing the silicon dioxide powder coated by graphite oxide in an acetonitrile solvent into a liquid ammonia atmosphere for nitriding to obtain silicon nitride coated by graphite nitride;
and 1.5, freeze-drying the sample for 24-72 hours, and fully grinding to obtain the silicon nitride powder coated with the graphite nitride.
Preferably, the specific step of the step 1.4 is that in a glove box protected by high-purity nitrogen, acetonitrile solvent containing graphite oxide coated silicon dioxide powder is placed in a cold trap at minus 60 ℃ to minus 130 ℃, then high-purity ammonia gas is introduced into a mixed solvent, ammonia gas is condensed into liquid ammonia, and the graphite oxide coated silicon dioxide powder in the acetonitrile solvent is completely immersed into the liquid ammonia atmosphere for nitriding for 4 to 24 hours, so that the graphite nitride coated silicon nitride is obtained.
Preferably, the specific step of step 2 includes:
step 2.1, heating titanium oxide powder to 800-1200 ℃, introducing ammonia gas at the temperature, and maintaining for 5-24 hours to fully nitridize the titanium oxide to obtain titanium nitride powder;
2.2, heating the vanadium pentoxide powder to 800-1200 ℃, introducing ammonia gas at the temperature, and maintaining for 5-24 h to fully nitridize the vanadium oxide to obtain vanadium nitride powder;
and 2.3, adding the vanadium nitride powder and the titanium nitride powder into a ball milling tank, and ball milling for 24 hours to obtain the vanadium nitride-titanium nitride powder.
Preferably, the mass ratio of the vanadium nitride powder to the titanium nitride powder in the step 2.3 is 4:1, a step of; the rotation speed of the ball milling tank is 750-850 revolutions.
Preferably, the mass fraction of the acetonitrile solvent in the step 1.3 is 3-20 w%.
Preferably, the mass ratio of the vanadium nitride-titanium nitride mixed powder mixed and reacted in the step 3 to the silicon nitride powder coated by the graphite nitride is 1:1.9 to 2.1; the reaction kettle is put into a box-type furnace to be heated, the heating temperature is 200-600 ℃, and the heating time is 24-72 h.
Preferably, the nitriding conditions preset in the cold trap of step 1.4 include: the cooling rate is 2-10 ℃/min, the temperature of the cold hydrazine is minus 60 ℃ to minus 130 ℃, and the nitriding time is 4-24 hours.
Preferably, the specific steps of the step 1.1 include:
step 1.1.1, adding natural graphite into mixed acid of concentrated sulfuric acid and concentrated phosphoric acid, slowly adding potassium permanganate while stirring, and controlling the temperature of the solution below 20 ℃ in the process;
step 1.1.2, after the potassium permanganate is added, the temperature of the reaction solution is raised to 50 ℃ and stirred for reaction for 12 hours;
step 1.1.3, pouring the reaction solution onto ice cubes containing hydrogen peroxide to terminate the reaction;
step 1.1.4, after the reaction solution is cooled to room temperature, centrifugally washing for 3 times by using hydrochloric acid and deionized water respectively to obtain gel graphite oxide;
step 1.1.5, fully drying the gel graphite oxide at the temperature of 100 ℃ for 24 hours in a forced air oven, and then putting the gel graphite oxide into a muffle furnace to heat to 300 ℃ and keeping the temperature for 3min to prepare the expanded graphite oxide.
Preferably, the specific steps of the step 1.2 include:
step 1.2.1, adding expanded graphite oxide into absolute ethyl alcohol, performing ultrasonic dispersion for 30min, stirring for 10min, adding hydrochloric acid, uniformly mixing, adding tetraethyl orthosilicate solution, and stirring for 10min;
step 1.2.1, pouring the solution into a PTFE culture dish, covering with aluminum foil and punching a plurality of small holes to prevent the solution from volatilizing too fast in the air, standing and drying for 24 hours, drying the sample in a blast oven at 100 ℃ for 6 hours, and grinding into powder by a mortar to obtain the graphite oxide and silicon dioxide sample.
According to the scheme, the nitride high-energy-storage-density anode material comprises graphite nitride, silicon nitride, titanium nitride and vanadium nitride, wherein the silicon nitride is coated in a three-dimensional inner space of the graphite nitride, the graphite nitride can provide enough buffer space for volume expansion of the silicon nitride in the anode charge-discharge process, the problem of the volume expansion of the silicon nitride in the circulation process is effectively solved, capacity attenuation caused by surface oxidation and dissolution of the nitride is slowed down, so that damage of the silicon nitride to the overall structure of the anode in the charge-discharge circulation process is avoided, and the cycle performance of the battery is improved; in the nitride cathode, titanium nitride has high ion conductivity, vanadium nitride has high capacity, and the invention combines the two nitrides to form a composite structure, so that the synergistic effect can be shown, the vanadium nitride provides large specific capacity, the titanium nitride provides a conductive network structure, and the ion conductivity and the cycle performance of the cathode are obviously improved. And because the graphite nitride coats the silicon nitride, stronger acting force is generated between the silicon nitride and the titanium nitride as well as between the silicon nitride and the vanadium nitride, thereby forming a stable conductive network and further being beneficial to the overall high energy density and the cycling stability of the battery. The invention also provides a preparation method of the nitride high energy storage density anode material, which utilizes graphite oxide to coat silicon nitride, effectively solves the problem of volume expansion of the silicon nitride in the circulation process, slows down capacity attenuation caused by surface oxidation and dissolution of the nitride, and greatly improves the circulation stability of the nitride electrode material; meanwhile, the titanium nitride-vanadium nitride compound is added, so that the ion conductivity and the cycle performance of the cathode are obviously improved. The invention has obvious effect and is suitable for wide popularization.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is an optical photograph of expanded graphite oxide in a nitride high energy storage density anode material of the present invention;
FIG. 2 is a scanning electron microscope image of a nitride high energy storage density anode material of the present invention, wherein the mass ratio of graphite nitride to silicon nitride is 1:1;
FIG. 3 is a scanning electron microscope image of a nitride high energy storage density anode material of the present invention, wherein the mass ratio of graphite nitride to silicon nitride is 1:1.5;
FIG. 4 is a scanning electron microscope image of a nitride high energy storage density anode material of the present invention, wherein the mass ratio of graphite nitride to silicon nitride is 1:2;
FIG. 5 is a scanning electron microscope image of a nitride high energy storage density anode material of the present invention, wherein the mass ratio of graphite nitride to silicon nitride is 1:2.5;
FIG. 6 is a scanning electron microscope image of a nitride high energy storage density anode material of the present invention, wherein the mass ratio of graphite nitride to silicon nitride is 1:3;
FIG. 7 is a scanning electron microscope image of a nitride high energy storage density anode material of the present invention, wherein the mass ratio of graphite nitride to silicon nitride is 1:4;
FIG. 8 is a scanning electron microscope image of a nitride high energy storage density anode material of the present invention, wherein the mass ratio of graphite nitride to silicon nitride is 1:8;
fig. 9 is a scanning electron microscope image of graphite nitride according to the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only 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.
It should be understood that the terms "comprises" and "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is also to be understood that the terminology used in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be further understood that the term "and/or" as used in the present specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations.
Various structural schematic diagrams according to the disclosed embodiments of the present invention are shown in the accompanying drawings. The figures are not drawn to scale, wherein certain details are exaggerated for clarity of presentation and may have been omitted. The shapes of the various regions, layers and their relative sizes, positional relationships shown in the drawings are merely exemplary, may in practice deviate due to manufacturing tolerances or technical limitations, and one skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions as actually required.
At present, the synthesis method of nitride is mainly divided into two major categories, namely a physical method and a chemical method, wherein the physical method mainly comprises physical vapor deposition, pulse laser deposition, a plasma method and the like. Physical methods generally require high energy or high voltage devices, and the morphology of the prepared nitrides is not easy to control and the variety is limited. The chemical method is to make use of the chemical reaction of transition metal precursor and nitrogen-containing substance under a certain temperature condition to form transition metal nitride. The transition metal precursor mainly comprises metal, transition metal oxide and transition metal salt, and the nitrogen-containing substance is generally nitrogen, ammonia or urea. The chemical method is a commonly applicable method for preparing transition metal nitrides, and a large number of holes are usually formed on the surface of the transition metal nitrides due to the structural change and the etching action of nitrogen-containing gas in the process of converting the transition metal precursors into the nitrides, so that the transition metal nitrides have larger specific surface area. Compared with a physical method, the chemical method for preparing the transition metal nitride has the advantages of rich morphology and simple preparation.
The large-scale application of a simple silicon nitride anode is faced with a lot of barriers at present, firstly, the volume expansion of the silicon nitride anode is up to 300% in the circulating process, and active substances can be caused to fall off from a current collector, so that the electrochemical performance is invalid; secondly, the volume expansion of the silicon nitride anode can also cause the SEI film formed in the first lithium intercalation process to be broken, the SEI film is continuously generated in the next lithium intercalation process, and the electrolyte and the lithium source material are continuously consumed repeatedly; and the conductivity of the silicon nitride is low, the intermediate product is easy to dissolve, the shuttle effect is generated to cause the loss of active substances, the charge and discharge efficiency is low, and the like, so that the adverse factors prevent the commercialized application of the silicon nitride cathode.
The graphite nitride coated silicon nitride has a plurality of advantages in theory, firstly, the graphite nitride is of a layered structure, and two adjacent layers are combined together through van der Waals force with weaker strength, so that the graphite nitride can reversibly expand/shrink in the Li+ embedding/extracting process, and has very good structural stability; secondly, the graphite nitride can form a stable SEI film with the electrolyte, thereby avoiding side reactions and ensuring the high reversibility of electrode reactions; thirdly, graphite nitride has good conductivity and chemical stability.
Aiming at the problems of the existing nitride cathode, currently, the improvement methods tried by researchers mainly comprise the following three methods: the first is to compound the nitride with high energy density with the carbon material with excellent mechanical property and chemical stability, and the synergistic effect between the two can be used to obtain the negative electrode material with high energy density, such as to load the nitride on the carbon structure (such as carbon fiber and CNT array) to form the composite electrode; the second is to mix silicon nitride and graphene by ball milling, peel off the graphene layer into nano-sheets, and physically mix the nitride and graphene to form a composite electrode, wherein a three-dimensional integrated network is formed inside the material; and thirdly, a thin carbon layer is coated on the surface of the nitride, and when the graphite-coated nitride is directly used as a negative electrode material of a lithium ion battery, the prepared graphite-coated nitride has excellent lithium storage performance.
Referring to fig. 1 to 9, an embodiment of a nitride high energy storage density anode material according to the present invention will now be described. The nitride high energy storage density anode material comprises a nitride material group, wherein the nitride material group comprises graphite nitride, silicon nitride, titanium nitride and vanadium nitride, the graphite nitride is obtained by converting graphite oxide and has the same structure as that of the graphite oxide, and the nitride material group has the same spatial structure as that of the graphite oxide in a three-dimensional layer, namely, the nitride high energy storage density anode material is prepared based on the spatial structure in the three-dimensional layer of the graphite oxide.
In the embodiment, graphite nitride, silicon nitride, titanium nitride and vanadium nitride are mixed to obtain the nitride high-energy-storage-density anode material, wherein the mass percentages of the components in the nitride material are as follows: 30% -45% of silicon nitride, 30% -45% of graphite nitride, 20% -35% of vanadium nitride and 5% -20% of titanium nitride. Illustratively, the mass percentages of the components are respectively: 33% of silicon nitride, 33% of graphite nitride, 27% of vanadium nitride and 7% of titanium nitride. The proportion of each component in the nitride material group is used for ensuring that the nitride anode has better cycle stability and capacity.
Since more lithium ions are consumed in forming a solid electrolyte interface (SEI film) when the silicon nitride content is excessive and irreversible in the next cycle, it is easy to cause a low coulombic efficiency of the first ring of the nitride anode; secondly, because when graphite oxide is too much, the nitride particles in the graphite oxide are tightly packed, so that the nitride particles cannot exert high capacity and high conductivity, and finally the cycle stability and the rate performance of the nitride negative electrode are affected, the embodiment ensures that the nitride negative electrode has better cycle stability and capacity by setting the nitride negative electrode material to the weight ratio so that the content of graphite nitride, silicon nitride, titanium nitride and vanadium nitride is proper.
In this embodiment, the particle diameter of the nitride particles is 10nm to 10 μm, more specifically, the particle diameter of the graphite nitride particles is 10nm to 5 μm; the particle size of the silicon nitride particles is 10nm-10 mu m; the grain diameter of the vanadium nitride particles is 10nm-10 mu m; the particle size of the titanium nitride particles is 10nm-10 μm. The particle size of each component in the nitride material group is set to ensure that the prepared nitride anode has better cycle performance. Since the volume change of the nitride particles is large in the charge and discharge process when the particle size of the nitride particles is large, the nitride negative electrode is easy to be pulverized too severely, and the prepared nitride negative electrode has better cycle performance by selecting the nitride particles with the particle size of 10nm-100 nm.
Compared with the prior art, in the nitride high energy storage density anode material, as the graphite nitride, the silicon nitride, the titanium nitride and the vanadium nitride anode material are coated in the three-dimensional inner space of the graphite oxide, the graphite oxide can provide enough buffer space for the volume expansion of nitride particles in the anode charge-discharge process, so that the rupture of the integral structure of the nitride anode is avoided, and the cycle performance of the battery is improved; meanwhile, in the nitride anode material, graphite oxide coats the nitride anode material, so that carbon and silicon nitride generate stronger acting force with titanium nitride and vanadium nitride, a stable conductive network is formed, the whole structure of the nitride anode is prevented from being damaged due to volume expansion in the charge and discharge process of nitride particles, and the cycle performance of the battery is finally improved. In addition, the graphite oxide has good conductivity, and the titanium nitride and the graphite nitride can form a stable conductive network, so that the conductivity of the nitride anode is improved, and the high gram capacity performance of the silicon nitride particles is fully exerted. In addition, since silicon nitride can provide a nitride anode with a high capacity, it is advantageous to increase the capacity of the battery, thereby being advantageous to increase the energy density of the battery, and since graphite oxide has a large specific surface area, it can provide a site for infiltration of an electrolyte in the nitride anode.
Referring to fig. 1 to 9, a specific embodiment of a method for preparing a nitride anode material with high energy storage density according to the present invention will now be described. The preparation method of the nitride high-energy-storage-density anode material is used for preparing the nitride high-energy-storage-density anode material, and comprises the following specific steps of:
s1, preparing silicon nitride powder coated by graphite nitride;
and S1, the mass ratio of silicon nitride in the silicon nitride powder coated by the graphite nitride is less than 50%.
The specific steps of S1 include:
s1.1, preparing expanded graphite oxide by taking natural flaky graphite as a raw material and adopting a Hummers method to perform oxidation treatment;
the specific steps of S1.1 comprise:
s1.1.1, adding natural graphite into mixed acid of concentrated sulfuric acid and concentrated phosphoric acid, slowly adding potassium permanganate while stirring, and controlling the temperature of the solution below 20 ℃ in the process;
s1.1.2, after adding potassium permanganate, raising the temperature of the reaction solution to 50 ℃ and stirring for reaction for 12 hours;
s1.1.3 pouring the reaction solution onto ice cubes containing hydrogen peroxide to terminate the reaction;
s1.1.4 after the reaction solution is cooled to room temperature, centrifugally washing for 3 times by using hydrochloric acid and deionized water respectively to obtain gel graphite oxide;
S1.1.5 the gel-like graphite oxide was dried at 100℃for 24 hours, and then placed in a muffle furnace and heated to 300℃for 3 minutes to obtain an expanded graphite oxide.
S1.2, mixing the expanded graphite oxide with tetraethyl orthosilicate to obtain graphite oxide coated silicon dioxide;
the specific steps of S1.2 include:
s1.2.1, adding expanded graphite oxide into absolute ethyl alcohol, performing ultrasonic dispersion for 30min, stirring for 10min, adding hydrochloric acid, uniformly mixing, adding tetraethyl orthosilicate solution, and stirring for 10min;
s1.2.1, pouring the solution into a PTFE culture dish, covering with aluminum foil and punching a plurality of small holes to prevent the solution from volatilizing too fast in the air, standing and drying for 24 hours, drying the sample in a blast oven at 100 ℃ for 6 hours, and grinding into powder by a mortar to prepare the sample of graphite oxide and silicon dioxide.
S1.3, grinding the silicon dioxide coated with the graphite oxide into powder, and then adding the powder into acetonitrile solvent according to a certain mass ratio for full dispersion;
the mass fraction of the acetonitrile solvent in S1.3 is 3-20 w%.
S1.4, completely immersing the silicon dioxide powder coated by graphite oxide in an acetonitrile solvent into a liquid ammonia atmosphere for nitriding to obtain graphite nitride coated silicon nitride;
The preset nitriding conditions in the cold trap of S1.4 comprise: the cooling rate is 2-10 ℃/min, the temperature of the cold hydrazine is minus 60 ℃ to minus 130 ℃, and the nitriding time is 4-24 hours.
The specific steps of S1.4 are that in a glove box protected by high-purity nitrogen, acetonitrile solvent containing graphite oxide coated silicon dioxide powder is placed in a cold trap with the cooling rate of 2-10 ℃/min and the cold hydrazine temperature of minus 60 ℃ to minus 130 ℃, then high-purity ammonia gas is introduced into a mixed solvent, ammonia gas is condensed into liquid ammonia, and the graphite oxide coated silicon dioxide powder in the acetonitrile solvent is completely immersed into the liquid ammonia atmosphere for nitriding for 4-24 hours, so that the graphite nitride coated silicon nitride is obtained.
S1.5, freeze-drying the sample for 24-72 hours, and fully grinding to obtain the silicon nitride powder coated with the graphite nitride.
S2, fully mixing vanadium nitride powder and titanium nitride powder in a certain mass ratio to prepare mixed titanium nitride-vanadium nitride powder;
the specific steps of S2 include:
s2.1, heating titanium oxide powder to 800-1200 ℃, introducing ammonia gas at the temperature, and maintaining for 5-24 hours to fully nitridize the titanium oxide to obtain titanium nitride powder;
s2.2, heating the vanadium pentoxide powder to 800-1200 ℃, introducing ammonia gas at the temperature, and maintaining for 5-24 hours to fully nitridize the vanadium oxide to obtain vanadium nitride powder;
S2.3, adding the vanadium nitride powder and the titanium nitride powder into a ball milling tank, and ball milling for 24 hours to obtain the vanadium nitride-titanium nitride powder.
The mass ratio of the vanadium nitride powder to the titanium nitride powder in S2.3 is 4:1, a step of; the rotation speed of the ball milling tank is 750-850 revolutions.
And S3, placing the mixed powder of vanadium nitride and titanium nitride and the silicon nitride powder coated by the graphite nitride in a high-temperature high-pressure reaction kettle according to a certain mass ratio, sealing, heating, and ball-milling the heated sample for 24-72 hours to obtain the nitride high-energy-storage-density anode material.
The mass ratio of the mixed powder of vanadium nitride and titanium nitride in the S3 to the silicon nitride powder coated by the graphite nitride is 1:1.9 to 2.1; the reaction kettle is put into a box-type furnace to be heated, the heating temperature is 200-600 ℃, and the heating time is 24-72 h.
Vanadium nitride has extremely high specific capacity of 1500mAh/g, but has serious polarization problem in the battery cycle process, and the ionic conductivity of the material is low. Titanium nitride is an excellent conductive material with high conductivity. The invention combines the two nitrides to form a composite structure, the vanadium nitride provides a large specific capacity, the titanium nitride provides a conductive network structure, and electrochemical test results show that the capacity performance of the titanium nitride-vanadium nitride composite structure is superior to that of the titanium nitride and the multiplying power performance is superior to that of the vanadium nitride.
Compared with the prior art, the invention utilizes graphite oxide to coat silicon nitride, effectively solves the problem of volume expansion of the silicon nitride in the circulation process, slows down capacity attenuation caused by surface oxidation and dissolution of nitride, and greatly improves the circulation stability of the nitride electrode material; meanwhile, the titanium nitride-vanadium nitride compound is added, so that the ion conductivity and the cycle performance of the cathode are obviously improved.
Exemplary: the performance of the batteries obtained by different preparation methods is tested, and an experimental group and a control group are arranged in the test process, wherein the experimental group is used for preparing the batteries by the preparation method, and the control group is used for obtaining the corresponding batteries by changing some variables, and the specific implementation steps are as follows:
experimental group
S1.1, firstly, oxidizing natural crystalline flake graphite to obtain graphene oxide;
s1.1.1, adding 1.5g of natural graphite into 180mL of mixed acid of concentrated sulfuric acid and 20mL of concentrated phosphoric acid, slowly adding 9g of potassium permanganate while stirring, and controlling the temperature of the solution below 20 ℃;
s1.1.2, after adding potassium permanganate, raising the temperature of the reaction solution to 50 ℃ and stirring for reaction for 12 hours;
s1.1.3 the reaction solution is poured onto ice cubes (200 mL) containing 3mL of 30% hydrogen peroxide to terminate the reaction;
S1.1.4 after the reaction solution is cooled to room temperature, centrifugally washing for 3 times by using 10% hydrochloric acid and deionized water respectively to obtain gel graphite oxide;
s1.1.5 after the gel-like graphite oxide was sufficiently dried at 100℃for 24 hours in a forced air oven, the gel-like graphite oxide was heated to 300℃in a muffle furnace at a heating rate of 5℃per minute and held for 3 minutes to prepare expanded graphite oxide, as shown in FIG. 1.
S1.2, mixing expanded graphite oxide with tetraethyl orthosilicate to obtain graphite oxide coated silicon dioxide;
s1.2.1, adding 100mg of expanded graphite oxide into 3.4g of absolute ethyl alcohol, performing ultrasonic dispersion for 30min, stirring for 10min, then adding 0.136g of 1mol/L hydrochloric acid, uniformly mixing, adding 347mg of tetraethyl orthosilicate solution (M=208), and stirring for 10min;
s1.2.1, pouring the solution into a PTFE culture dish, covering with aluminum foil and punching a plurality of small holes to prevent the solution from volatilizing too fast in the air, standing and drying for 24 hours, drying the sample in a blast oven at 100 ℃ for 6 hours, and grinding into powder by a mortar to prepare graphite oxide and silicon dioxide with the following weight: 1 mass ratio of sample.
S1.3 0.5g of 1: grinding the graphite oxide coated silicon dioxide with the mass ratio of 1 into powder, adding the powder into 50mL of acetonitrile solvent, and fully dispersing the powder by using an emulsifier;
S1.4, in a glove box protected by high-purity nitrogen, placing an acetonitrile solvent containing graphite oxide coated silicon dioxide powder in a cold trap at-60 ℃ to-130 ℃, then introducing high-purity ammonia gas into a mixed solvent, condensing the ammonia gas into liquid ammonia, completely immersing the graphite oxide coated silicon dioxide powder in the acetonitrile solvent into a liquid ammonia atmosphere, and nitriding for 24 hours to obtain graphite nitride coated silicon nitride;
s1.5, freeze-drying the sample for 24-72 hours, and fully grinding to obtain 1: the mass ratio of the silicon nitride powder coated by the graphite nitride is 1, and a scanning electron microscope image is shown in figure 2;
s2, preparing a mixed titanium nitride-vanadium nitride sample:
s2.1, adding 2g of titanium oxide powder into a tube furnace, heating to 800 ℃, and introducing ammonia gas at the temperature for 24 hours to fully nitridize the titanium oxide to obtain a titanium nitride sample;
s2.2, heating 2g of vanadium pentoxide powder to 800 ℃ in a tubular furnace, and introducing ammonia gas at the temperature for 24 hours to fully nitridize vanadium oxide to obtain vanadium nitride powder;
s2.3, mixing vanadium nitride with titanium nitride according to a ratio of 4: adding the mixture into a ball milling tank according to the mass ratio of 1, and ball milling for 24 hours at 800 rotational speed to obtain a vanadium nitride-titanium nitride sample;
s3, weighing 2.5g of vanadium nitride-titanium nitride mixed powder and 5g of silicon nitride powder coated with graphite in a glove box in a high-purity argon environment, putting the mixed powder and the 5g of silicon nitride powder into a high-temperature high-pressure reaction kettle, sealing the mixed powder and the silicon nitride powder, putting the mixed powder into a box furnace, heating the mixed powder to 300 ℃ and keeping the temperature for 72 hours, and then ball-milling a sample for 24 hours to obtain the nitride anode material with high energy storage density;
S4, assembling the prepared nitride high-energy-storage-density anode material, polytetrafluoroethylene acetylene black serving as a conductive agent and PTFE serving as a binder in a mass ratio of 8:1:1 into a positive electrode, taking a lithium sheet as a negative electrode, taking DOL of 1mol/L LiPF6 and DME solution (the volume ratio of DOL to DME is 1:1) as electrolyte, and assembling the button cell by taking a porous polypropylene film Celgard-2300 as a diaphragm.
The battery assembled by the method is charged and discharged by a current of 0.01mA, and the voltage interval is 0.01-1.5V.
The experimental result shows that the specific charge and discharge capacity of the battery assembled by the method in the experimental group can reach 750mAh/g, and the material is proved to be a cathode material with extremely high energy density.
Control group 1
S1, preparing an expanded graphite oxide by the same method as an experimental group; in the same manner, 100mg of expanded graphite oxide was mixed with 520.5mg of tetraethyl orthosilicate to obtain 1:1.5 mass ratio of graphite oxide coated silica powder; immersing the mixture into a liquid ammonia atmosphere for nitriding for 24 hours to obtain 1:1.5 mass percent of silicon nitride powder coated by graphite nitride, and a scanning electron microscope image is shown in figure 3;
s2, preparing a titanium nitride-vanadium nitride sample by the same method:
s2.1, adding 2g of titanium oxide powder into a tube furnace, heating to 800 ℃, and introducing ammonia gas at the temperature for 24 hours to fully nitridize the titanium oxide to obtain a titanium nitride sample;
S2.2, heating 2g of vanadium pentoxide powder to 800 ℃ in a tube furnace, and introducing ammonia gas at the temperature for 24 hours to fully nitridize vanadium oxide to obtain vanadium nitride powder;
s2.3, mixing vanadium nitride with titanium nitride according to a ratio of 4: adding the mixture into a ball milling tank according to the mass ratio of 1, and ball milling for 24 hours at 800 rotational speed to obtain a vanadium nitride-titanium nitride sample;
s3, weighing 2.5g of vanadium nitride-titanium nitride mixed powder and 5g of graphite nitride coated with graphite oxide and silicon nitride powder in a glove box in a high-purity argon environment, putting the mixture into a high-temperature high-pressure reaction kettle, sealing, heating to 300 ℃ in a box furnace, keeping the temperature for 72 hours, and ball-milling a sample for 24 hours to obtain a composite nitride anode material;
s4, assembling the prepared nitride anode material coated with the mass ratio of 1:1.5, polytetrafluoroethylene acetylene black serving as a conductive agent, PTFE serving as a binder, a lithium sheet serving as an anode, DOL of LiPF6 and DME solution (the volume ratio of DOL to DME is 1:1) serving as electrolyte, and a porous polypropylene film Celgard-2300 serving as a diaphragm to assemble the button cell.
The battery assembled by the method is charged and discharged by a current of 0.01mA, and the voltage interval is 0.01-1.5V.
The experimental result shows that the specific charge and discharge capacity of the battery assembled by the method in the control group 1 is 461mAh/g, and the experimental result proves that the feasibility of the preparation mode of the nitride anode material is shown, but the capacity and stability of the battery are obviously reduced due to the fact that the silicon nitride in the control group 1 occupies a relatively high proportion.
Control group 2
S1, preparing an expanded graphite oxide by the same method as in the first embodiment; in the same manner, 100mg of expanded graphite oxide was mixed with 694mg of tetraethyl orthosilicate to obtain 1:2 mass ratio of graphite oxide coated silicon dioxide powder, immersing the silicon dioxide powder into a liquid ammonia atmosphere for nitriding for 24 hours to obtain 1: the mass ratio of the silicon nitride powder coated by the graphite nitride is 2, and a scanning electron microscope image is shown in figure 4;
s2, preparing a titanium nitride-vanadium nitride sample by the same method: adding 2g of titanium oxide powder into a tube furnace, heating to 800 ℃, and introducing ammonia gas at the temperature for 24 hours to fully nitridize the titanium oxide to obtain a titanium nitride sample; heating 2g of vanadium pentoxide powder to 800 ℃ in a tube furnace, and introducing ammonia gas at the temperature for 24 hours to fully nitridize the vanadium oxide to obtain vanadium nitride powder; vanadium nitride and titanium nitride were mixed in a ratio of 4: adding the mixture into a ball milling tank according to the mass ratio of 1, and ball milling for 24 hours at 800 rotational speed to obtain a vanadium nitride-titanium nitride sample;
S3, weighing 2.5g of vanadium nitride-titanium nitride mixed powder and 5g of graphite nitride coated with graphite oxide and silicon nitride powder in a glove box in a high-purity argon environment, putting the mixture into a high-temperature high-pressure reaction kettle, sealing, heating to 300 ℃ in a box furnace, keeping the temperature for 72 hours, and ball-milling a sample for 24 hours to obtain a nitride anode material;
s4, assembling the prepared nitride anode material coated with the mass ratio of 1:2, polytetrafluoroethylene acetylene black serving as a conductive agent and PTFE serving as a binder into a positive electrode in a mass ratio of 8:1:1, taking a lithium sheet as a negative electrode, taking DOL of LiPF6 and DME solution (the volume ratio of DOL to DME is 1:1) as electrolyte, and assembling the button cell by taking a porous polypropylene film Celgard-2300 as a diaphragm.
The battery assembled by the method is charged and discharged by a current of 0.01mA, and the voltage interval is 0.01-1.5V.
The experimental result shows that the specific charge and discharge capacity of the battery assembled by the method in the control group 2 is 270mAh/g, and the capacity and stability of the battery are further reduced.
Control group 3
S1, preparing an expanded graphite oxide by the same method as in the first embodiment; in a similar manner, 100mg of expanded graphite oxide was mixed with 867.5mg of tetraethyl orthosilicate to obtain 1:2.5 mass ratio of graphite oxide coated silica powder, and immersing the silica powder in a liquid ammonia atmosphere for nitriding for 24 hours to obtain 1:2.5 mass ratio of the silicon nitride powder coated with the graphite nitride, and a scanning electron microscope image is shown in FIG. 5;
S2, preparing a titanium nitride-vanadium nitride sample by the same method: adding 2g of titanium oxide powder into a tube furnace, heating to 800 ℃, and introducing ammonia gas at the temperature for 24 hours to fully nitridize the titanium oxide to obtain a titanium nitride sample; heating 2g of vanadium pentoxide powder to 800 ℃ in a tube furnace, and introducing ammonia gas at the temperature for 24 hours to fully nitridize the vanadium oxide to obtain vanadium nitride powder; vanadium nitride and titanium nitride were mixed in a ratio of 4: adding the mixture into a ball milling tank according to the mass ratio of 1, and ball milling for 24 hours at 800 rotational speed to obtain a vanadium nitride-titanium nitride sample;
s3, weighing 2.5g of vanadium nitride-titanium nitride mixed powder and 5g of graphite nitride coated with graphite oxide and silicon nitride powder in a glove box in a high-purity argon environment, putting the mixture into a high-temperature high-pressure reaction kettle, sealing, heating to 300 ℃ in a box furnace, keeping the temperature for 72 hours, and ball-milling a sample for 24 hours to obtain a nitride anode material;
s4, assembling the prepared nitride anode material coated with the mass ratio of 1:2.5, polytetrafluoroethylene acetylene black serving as a conductive agent, PTFE serving as a binder, a lithium sheet serving as an anode, DOL of LiPF6 and DME solution (the volume ratio of DOL to DME is 1:1) serving as electrolyte, and a porous polypropylene film Celgard-2300 serving as a diaphragm to assemble the button cell.
The battery assembled by the method is charged and discharged by a current of 0.01mA, and the voltage interval is 0.01-1.5V.
The experimental result shows that the specific charge and discharge capacity of the battery assembled by the method in the control group 3 is 236mAh/g, and the capacity and stability of the battery are continuously reduced due to excessive silicon nitride.
Control group 4
S1, preparing an expanded graphite oxide by the same method as in the first embodiment; in the same manner, 100mg of expanded graphite oxide was mixed with 1041mg of tetraethyl orthosilicate to obtain 1:3, immersing the graphite oxide coated silicon dioxide powder in a liquid ammonia atmosphere for nitriding for 24 hours to obtain 1:3 mass ratio of the silicon nitride powder coated by the graphite nitride, and a scanning electron microscope image is shown in figure 6;
s2, preparing a titanium nitride-vanadium nitride sample by the same method: adding 2g of titanium oxide powder into a tube furnace, heating to 800 ℃, and introducing ammonia gas at the temperature for 24 hours to fully nitridize the titanium oxide to obtain a titanium nitride sample; heating 2g of vanadium pentoxide powder to 800 ℃ in a tube furnace, and introducing ammonia gas at the temperature for 24 hours to fully nitridize the vanadium oxide to obtain vanadium nitride powder; vanadium nitride and titanium nitride were mixed in a ratio of 4: adding the mixture into a ball milling tank according to the mass ratio of 1, and ball milling for 24 hours at 800 rotational speed to obtain a vanadium nitride-titanium nitride sample;
S3, weighing 2.5g of vanadium nitride-titanium nitride mixed powder and 5g of graphite nitride coated with graphite oxide and silicon nitride powder in a glove box in a high-purity argon environment, putting the mixture into a high-temperature high-pressure reaction kettle, sealing, heating to 300 ℃ in a box furnace, keeping the temperature for 72 hours, and ball-milling a sample for 24 hours to obtain a nitride anode material;
s4, assembling the prepared nitride anode material coated with the mass ratio of 1:3, polytetrafluoroethylene acetylene black serving as a conductive agent and PTFE serving as a binder into a positive electrode in a mass ratio of 8:1:1, taking a lithium sheet as a negative electrode, taking DOL of LiPF6 and DME solution (the volume ratio of DOL to DME is 1:1) as electrolyte, and assembling the button cell by taking a porous polypropylene film Celgard-2300 as a diaphragm.
The battery assembled by the method is charged and discharged by a current of 0.01mA, and the voltage interval is 0.01-1.5V.
The experimental result shows that the specific charge and discharge capacity of the battery assembled by the method in the control group 4 is 230mAh/g, and the fact that the capacity and the stability of the battery are continuously reduced but the trend is slowed down due to excessive silicon nitride is proved.
Control group 5
S1, preparing an expanded graphite oxide by the same method as in the first embodiment; in the same manner, 100mg of expanded graphite oxide was mixed with 1388mg of tetraethyl orthosilicate to obtain 1:4 mass ratio of graphite oxide coated silicon dioxide powder, immersing the silicon dioxide powder into a liquid ammonia atmosphere for nitriding for 24 hours to obtain 1: the mass ratio of the silicon nitride powder coated by the graphite nitride is 4, and a scanning electron microscope image is shown in figure 7;
S2, preparing a titanium nitride-vanadium nitride sample by the same method: adding 2g of titanium oxide powder into a tube furnace, heating to 800 ℃, and introducing ammonia gas at the temperature for 24 hours to fully nitridize the titanium oxide to obtain a titanium nitride sample; heating 2g of vanadium pentoxide powder to 800 ℃ in a tube furnace, and introducing ammonia gas at the temperature for 24 hours to fully nitridize the vanadium oxide to obtain vanadium nitride powder; vanadium nitride and titanium nitride were mixed in a ratio of 4: adding the mixture into a ball milling tank according to the mass ratio of 1, and ball milling for 24 hours at 800 rotational speed to obtain a vanadium nitride-titanium nitride sample;
s3, weighing 2.5g of vanadium nitride-titanium nitride mixed powder and 5g of graphite nitride coated with graphite oxide and silicon nitride powder in a glove box in a high-purity argon environment, putting the mixture into a high-temperature high-pressure reaction kettle, sealing, heating to 300 ℃ in a box furnace, keeping the temperature for 72 hours, and ball-milling a sample for 24 hours to obtain a nitride anode material;
s4, assembling the prepared nitride anode material coated with the mass ratio of 1:4, polytetrafluoroethylene acetylene black serving as a conductive agent, PTFE serving as a binder, a lithium sheet serving as an anode, DOL of LiPF6 and DME solution (the volume ratio of DOL to DME is 1:1) serving as electrolyte, and a porous polypropylene film Celgard-2300 serving as a diaphragm to assemble the button cell.
The battery assembled by the method is charged and discharged by a current of 0.01mA, and the voltage interval is 0.01-1.5V.
The experimental result shows that the specific charge and discharge capacity of the battery assembled by the method in the control group 5 is 173mAh/g, and the fact that the capacity and stability of the battery are continuously reduced due to excessive silicon nitride is proved, and the capacity performance can not reach the energy density of the traditional graphite.
Control group 6
S1, preparing an expanded graphite oxide by the same method as in the first embodiment; in the same manner, 100mg of expanded graphite oxide was mixed with 2776mg of tetraethyl orthosilicate to obtain 1:8 mass ratio of graphite oxide coated silicon dioxide powder, immersing the silicon dioxide powder into a liquid ammonia atmosphere for nitriding for 24 hours to obtain 1: the mass ratio of the silicon nitride powder coated by the graphite nitride is 8, and a scanning electron microscope image is shown in FIG. 8;
s2, preparing a titanium nitride-vanadium nitride sample by the same method: adding 2g of titanium oxide powder into a tube furnace, heating to 800 ℃, and introducing ammonia gas at the temperature for 24 hours to fully nitridize the titanium oxide to obtain a titanium nitride sample; heating 2g of vanadium pentoxide powder to 800 ℃ in a tube furnace, and introducing ammonia gas at the temperature for 24 hours to fully nitridize the vanadium oxide to obtain vanadium nitride powder; vanadium nitride and titanium nitride were mixed in a ratio of 4: adding the mixture into a ball milling tank according to the mass ratio of 1, and ball milling for 24 hours at 800 rotational speed to obtain a vanadium nitride-titanium nitride sample;
S3, weighing 2.5g of vanadium nitride-titanium nitride mixed powder and 5g of graphite nitride coated with graphite oxide and silicon nitride powder in a glove box in a high-purity argon environment, putting the mixture into a high-temperature high-pressure reaction kettle, sealing, heating to 300 ℃ in a box furnace, keeping the temperature for 72 hours, and ball-milling a sample for 24 hours to obtain a nitride-degree anode material;
s4, assembling the prepared nitride anode material coated with the mass ratio of 1:8, polytetrafluoroethylene acetylene black serving as a conductive agent, PTFE serving as a binder, a lithium sheet serving as an anode, DOL of LiPF6 and DME solution (the volume ratio of DOL to DME is 1:1) serving as electrolyte, and a porous polypropylene film Celgard-2300 serving as a diaphragm to assemble the button cell.
The battery assembled by the method is charged and discharged by a current of 0.01mA, and the voltage interval is 0.01-1.5V.
The experimental result shows that the specific charge and discharge capacity of the battery assembled by the method in the control group 6 is 152mAh/g, and the fact that the capacity and stability of the battery are continuously reduced due to excessive silicon nitride is proved, and the capacity performance can not reach the energy density of the traditional graphite.
Control groups 1 to 6 showed that the nitride anode could not maintain a good capacity performance when the mass ratio of silica in graphite oxide was 50% or more, and the cycle stability of the nitride anode was inferior when the mass ratio of silica was higher. The method is characterized in that when the silicon element is too much, the medium graphite nitride of the nitride negative electrode cannot fully wrap the silicon nitride and vanadium nitride particles, so that the nitride particles have insufficient buffer space when the volume of the nitride particles expands in the charge and discharge process, the nitride negative electrode is easy to pulverize, and the cycle stability of the nitride negative electrode is finally affected.
Control group 7
S1, preparing an expanded graphite oxide by the same method as in the first embodiment; the group is a pure expanded graphite oxide comparative example, the graphite oxide is immersed in a liquid ammonia atmosphere for nitriding for 24 hours without being mixed with tetraethyl orthosilicate, and graphite nitride is obtained, and a scanning electron microscope image is shown in fig. 9;
s2, preparing a titanium nitride-vanadium nitride sample by the same method: adding 2g of titanium oxide powder into a tube furnace, heating to 800 ℃, and introducing ammonia gas at the temperature for 24 hours to fully nitridize the titanium oxide to obtain a titanium nitride sample; heating 2g of vanadium pentoxide powder to 800 ℃ in a tube furnace, and introducing ammonia gas at the temperature for 24 hours to fully nitridize the vanadium oxide to obtain vanadium nitride powder; vanadium nitride and titanium nitride were mixed in a ratio of 4: adding the mixture into a ball milling tank according to the mass ratio of 1, and ball milling for 24 hours at 800 rotational speed to obtain a vanadium nitride-titanium nitride sample;
s3, weighing 2.5g of vanadium nitride-titanium nitride mixed powder and 5g of graphite nitride powder in a glove box in a high-purity argon environment, putting the mixed powder and the 5g of graphite nitride powder into a high-temperature high-pressure reaction kettle, sealing, putting the mixed powder and the graphite nitride powder into a box furnace, heating to 300 ℃ and keeping the temperature for 72 hours, and then ball-milling a sample for 24 hours to obtain the nitride-degree anode material;
S4, assembling the prepared nitride anode material, polytetrafluoroethylene acetylene black serving as a conductive agent and PTFE serving as a binder in a mass ratio of 8:1:1 to form a positive electrode, taking a lithium sheet as a negative electrode, taking DOL of LiPF6 with 1mol/L and DME solution (the volume ratio of DOL to DME is 1:1) as electrolyte, and assembling the button cell by taking a porous polypropylene film Celgard-2300 as a diaphragm.
The battery assembled by the method is charged and discharged by a current of 0.01mA, and the voltage interval is 0.01-1.5V.
Experimental results show that the specific charge and discharge capacity of the battery assembled by the method in the control group 7 is 554mAh/g, and the feasibility of the preparation mode of the nitride anode material is proved, and the specific capacity of the anode material is obviously improved by adding vanadium nitride and silicon nitride compared with the traditional graphite anode although the capacity of the battery is reduced compared with that of the first example because of not coating silicon nitride.
From the data, the nitride anode material and the preparation method thereof provided by the invention can effectively relieve the volume expansion of nitride particles in the charge and discharge process, so as to avoid damaging the integral structure of the nitride anode, thereby improving the cycle performance of the battery. The preparation effect of the battery by using the method is very remarkable.
In summary, the embodiment of the invention provides a preparation method of a nitride high-energy-storage anode material, so that silicon nitride, vanadium nitride and titanium nitride realize high fusion and full advantage complementation, and when the mass ratio of silicon nitride in graphite nitride is 50%, the specific capacity of the nitride material can reach 750mAh/g, and the nitride material is an ideal battery material. When the mass ratio of the silicon nitride in the graphite nitride is below 50%, the graphite nitride effectively coats the silicon nitride, so that stronger acting force is generated among the graphite nitride, the silicon nitride, the titanium nitride and the vanadium nitride, a stable conductive network is formed, the whole structure of the negative electrode is prevented from being damaged due to volume expansion in the charge and discharge process of the nitriding negative electrode material, the lithium storage activity of the silicon nitride is fully exerted, the capacity attenuation caused by surface oxidation and dissolution of the nitride is slowed down, and the cycle performance of the battery is improved; the vanadium nitride provides large specific capacity, the titanium nitride provides a conductive network structure, the ion conductivity and the cycle performance of the anode are obviously improved, the advantages are incomparable with those of the conventional nitride or graphite materials at present, if the anode material is used for replacing the classical graphite anode, the energy density of a battery core is greatly improved, and the overall performance of a power battery is also greatly improved, so that the anode material with high energy storage density of the nitride has important development significance and wide application space.
In this specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, so that the same or similar parts between the embodiments are referred to each other. What is not described in detail in the embodiments of the present invention belongs to the prior art known to those skilled in the art.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (1)
1. The preparation method of the nitride high-energy-storage-density anode material is characterized by comprising the following steps of:
step 1, preparing silicon nitride powder coated by graphite nitride;
step 2, fully mixing vanadium nitride powder and titanium nitride powder in a certain mass ratio to prepare mixed titanium nitride-vanadium nitride powder;
Step 3, putting the mixed powder of vanadium nitride and titanium nitride and the silicon nitride powder coated by the graphite nitride in a high-temperature high-pressure reaction kettle according to a certain mass ratio, heating the mixed powder, ball-milling the heated sample for 24-72 hours, and obtaining the nitride high-energy-storage-density anode material;
the mass ratio of silicon nitride in the silicon nitride powder coated by the graphite nitride in the step 1 is less than 50%;
the specific steps of the step 1 comprise:
step 1.1, preparing expanded graphite oxide by using natural flaky graphite as a raw material and adopting a Hummers method;
step 1.2, mixing expanded graphite oxide with tetraethyl orthosilicate to obtain graphite oxide coated silicon dioxide;
step 1.3, grinding the silicon dioxide coated with the graphite oxide into powder, and then adding the powder into acetonitrile solvent according to a certain mass ratio for full dispersion;
step 1.4, completely immersing the silicon dioxide powder coated by graphite oxide in an acetonitrile solvent into a liquid ammonia atmosphere for nitriding to obtain silicon nitride coated by graphite nitride;
step 1.5, freeze-drying a sample for 24-72 hours, and fully grinding to obtain silicon nitride powder coated with graphite nitride;
the specific steps of the step 2 include:
step 2.1, heating titanium oxide powder to 800-1200 ℃, introducing ammonia gas at the temperature, and maintaining for 5-24 hours to fully nitridize the titanium oxide to obtain titanium nitride powder;
2.2, heating the vanadium pentoxide powder to 800-1200 ℃, introducing ammonia gas at the temperature, and maintaining for 5-24 h to fully nitridize the vanadium oxide to obtain vanadium nitride powder;
step 2.3, adding the vanadium nitride powder and the titanium nitride powder into a ball milling tank, and ball milling for 24 hours to obtain vanadium nitride-titanium nitride powder;
the mass ratio of the mixed powder of vanadium nitride and titanium nitride to the silicon nitride powder coated by the graphite nitride in the step 3 is 1:1.9 to 2.1; heating the reaction kettle in a box-type furnace at 200-600 ℃ for 24-72 h;
the specific steps of the step 1.1 comprise:
step 1.1.1, adding natural flake graphite into mixed acid of concentrated sulfuric acid and concentrated phosphoric acid, slowly adding potassium permanganate while stirring, and controlling the temperature of the solution below 20 ℃ in the process;
step 1.1.2, after the potassium permanganate is added, the temperature of the reaction solution is raised to 50 ℃ and stirred for reaction for 12 hours;
step 1.1.3, pouring the reaction solution onto ice cubes containing hydrogen peroxide to terminate the reaction;
step 1.1.4, after the reaction solution is cooled to room temperature, centrifugally washing for 3 times by using hydrochloric acid and deionized water respectively to obtain gel graphite oxide;
Step 1.1.5, fully drying gel graphite oxide at the temperature of 100 ℃ for 24 hours in a forced air oven, and then putting the gel graphite oxide into a muffle furnace to be heated to 300 ℃ and kept for 3min to prepare expanded graphite oxide;
the specific steps of the step 1.2 comprise:
step 1.2.1, adding expanded graphite oxide into absolute ethyl alcohol, performing ultrasonic dispersion for 30min, stirring for 10min, adding hydrochloric acid, uniformly mixing, adding tetraethyl orthosilicate solution, and stirring for 10min;
step 1.2.2, pouring the solution into a PTFE culture dish, covering with aluminum foil and punching a plurality of small holes to prevent the solution from volatilizing too fast in the air, standing and drying for 24 hours, drying the sample in a blast oven at 100 ℃ for 6 hours, and grinding into powder by a mortar to prepare the silica coated with graphite oxide.
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