CN115440983A - Preparation method of B and N co-doped sodium-rich porous carbon and application of B and N co-doped sodium-rich porous carbon in sodium ion battery - Google Patents

Preparation method of B and N co-doped sodium-rich porous carbon and application of B and N co-doped sodium-rich porous carbon in sodium ion battery Download PDF

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CN115440983A
CN115440983A CN202211171574.6A CN202211171574A CN115440983A CN 115440983 A CN115440983 A CN 115440983A CN 202211171574 A CN202211171574 A CN 202211171574A CN 115440983 A CN115440983 A CN 115440983A
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sodium
porous carbon
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李健鹏
肖定书
陈鸿雁
张�杰
刘敏
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Huizhou University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/21—After-treatment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/04—Construction or manufacture in general
    • H01M10/0422—Cells or battery with cylindrical casing
    • H01M10/0427—Button cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes

Abstract

The application discloses a preparation method of B and N co-doped sodium-rich porous carbon and application of the B and N co-doped sodium-rich porous carbon in a sodium ion battery, and relates to the technical field of new energy batteries; which comprises the following steps: s1, soaking a carbon source in strong acid, filtering, washing, drying and replacing; s2, mixing and grinding the carbon source treated in the step S1 with a boron-containing organic substance and a pore-forming agent, and then calcining in a nitrogen atmosphere; s3, immersing the sample treated in the step S2 into an organic sodium solution, washing with an ether solvent, and performing vacuum drying to obtain B and N co-doped sodium-rich porous carbon; wherein the boron-containing organic matter contains sodium element; by adopting the technical scheme provided by the application, the storage capacity of sodium ions can be improved by regulating the quantity of the sodium ions, and the problem of low initial coulomb efficiency in the negative electrode can be solved. The application provides a practical operation scheme for preparing the low-cost and high-performance sodium ion battery.

Description

Preparation method of B and N co-doped sodium-rich porous carbon and application of B and N co-doped sodium-rich porous carbon in sodium ion battery
Technical Field
The application relates to the technical field of new energy batteries, in particular to a preparation method of B and N codoped sodium-rich porous carbon and application of the B and N codoped sodium-rich porous carbon in a sodium ion battery.
Background
Compared with lead-acid batteries and nickel-metal hydride batteries, lithium Ion Batteries (LIBs) have a higher energy density and are widely used in electronic products, electric vehicles, and wearable devices. LIB generally uses a carbon material, lithium metal, silicon oxide, or the like as a negative electrode material. Among many carbon materials, graphite has become a commercial LIB anode material because of its advantages of low cost, wide sources, high conductivity, and cycle stability. However, the limited lithium resources and graphite anodes approaching the capacity limits have forced the search for more suitable energy storage technologies to meet the needs of future developments. Sodium Ion Batteries (SIBs) are gaining favor as a new type of secondary energy storage device because they are cost effective and have a high sodium abundance. The radius of 102pm for sodium ions compared to the radius of 76pm for lithium ions requires an interlayer spacing of >0.37nm graphite for sodium ions to rapidly intercalate between layers to store charge.
Heteroatom doping can effectively widen the interlayer spacing of the carbon material, can also enhance electron conductivity and provide additional storage active sites. For example, in chinese patent (CN 107293750B), an organic substance containing a benzene ring is used as a carbon source and a surfactant is used as an N source, and soft carbon with an interlayer distance of 0.37nm is synthesized by calcination. N and C are in the adjacent position of the periodic table, N atoms are easily doped into the crystal lattice of C to change the properties of carbon, and B doping can further reduce the Fermi level and the Lowest Unfilled Molecular Orbital (LUMO) of the material, so that the carbon can accept sodium electrons more easily and adsorb sodium more easily. Thus, N is an electron donor that can attract positive ions to sodium ions to increase capacitance; and B is an electron acceptor that attracts electrons from the sodium ion to increase capacitance. Co-doping of heteroatoms in carbon materials generally shows significant advantages in improving electrochemical performance due to the synergistic effect of co-doping atoms compared to single doping. For example, chinese patent (201810621963) discloses a B and N double-doped carbon aerogel of methyl cellulose and a preparation method thereof, which can effectively improve the specific surface area and the conductivity of a carbon material, prevent the pulverization and the agglomeration of the material and are used for super capacitor electrode materials.
Although the interlayer spacing of carbon materials can be increased by atomic doping to increase the storage capacity of sodium ions, carbon materials still suffer from a low Initial Coulombic Efficiency (ICE) in SIBs. When hard carbon is used as the SIB negative electrode, its ICE is as low as 40-70%. This is because the defect sites of the carbon material interact with the electrolyte, consuming a large amount of electrolyte and sodium ions in the first sodium modification/sodium removal process, forming a Solid Electrolyte Interphase (SEI), eventually leading to low ICE. In order to overcome this difficulty, the electrochemical pre-intercalation of sodium elements into the carbon-based material during the preparation of the electrode material can effectively compensate for the sodium ions consumed during the first cycle, but this method requires complicated disassembly and reassembly of the battery, and is obviously not compatible with industrial manufacturing. At present, modes of pre-sodium treatment mainly comprise modes of electrochemical pretreatment, physical spraying pretreatment, chemical pretreatment, in-situ pretreatment and the like, which can improve the ICE of the SIB to a certain extent, but cannot realize large-scale industrial preparation, and sodium-containing samples are easy to lose in the washing process, so that the content of sodium element is low.
Disclosure of Invention
The application aims to provide a preparation method of B and N co-doped sodium-rich porous carbon and application of the B and N co-doped sodium-rich porous carbon in a sodium ion battery, and the technical scheme provided by the application realizes regulation and control of sodium element content in a porous carbon material carbon layer and interlayer spacing of a carbon material, and the porous carbon material carbon has the interlayer spacing of more than 0.385nm, and meanwhile has high coulombic efficiency in the ion battery.
In order to reach above-mentioned technical purpose, the application provides a preparation method of B, N codope rich sodium porous carbon and its application in sodium ion battery, and first aspect, the application provides a preparation method of B, N codope rich sodium porous carbon, includes following step:
s1, soaking a carbon source in strong acid, filtering, washing, drying and replacing;
s2, mixing and grinding the carbon source treated in the step S1 with a boron-containing organic substance and a pore-forming agent, and then calcining in a nitrogen atmosphere;
s3, immersing the sample treated in the step S2 into an organic sodium solution, washing with an ether solvent, and drying in vacuum to obtain B and N co-doped sodium-rich porous carbon;
wherein the boron-containing organic substance contains sodium element.
Preferably, the carbon source comprises one or more of petroleum coke, and pitch.
Preferably, the carbon source is petroleum coke, which is classified as low sulfur needle coke.
Preferably, in step S3, the organic sodium solute includes at least one of sodium ethoxide, sodium biphenyl, sodium phenolate, and sodium methoxide.
Further preferably, the organic sodium solution solute is sodium biphenyl.
Preferably, the concentration of the organic sodium solution ranges from 0.1mol/L to 2mol/L.
Further preferably, the concentration of the organic sodium solution is 0.5mol/L.
Preferably, in the step S3, the sample is immersed in the organic sodium solution for a soaking time of 5 to 30 seconds.
Further preferably, in the step S3, the soaking time of the sample in the organic sodium solution is 20 seconds
Preferably, in the step S3, the ether solvent includes one of dimethyl ether, diethyl ether, methylethyl ether and n-butyl ether.
Preferably, the boron-containing organic substance comprises at least one of sodium tetraphenylborate, sodium borate, sodium tetrahydroborate, sodium perborate, (trihydroxy) phenylboronate, sodium tetrakis (1-imidazolyl) borate, and derivatives thereof.
More preferably, the boron-containing organic substance is one or both of sodium borate and sodium tetrahydroborate.
Preferably, the pore-forming agent contains NH 4 + 。
Preferably, the pore-forming agent comprises at least one of ammonium bicarbonate, ammonium carbonate, zinc ammonium carbonate, sodium ammonium carbonate and potassium ammonium carbonate.
Wherein, due to NH content 4+ Salts can be decomposed at low temperatures to form NH 3 The latter is decomposed at high temperature to generate H, NH2 active species, which are further combined with carbon to generate carbon with better stability and crystallinity, so NH-containing active species are used in the carbonization process 4+ The salt favors the formation of more crystalline carbon, thus making the XRD peak of the sample narrower.
Further preferably, the pore-forming agent is one or two of ammonium bicarbonate and ammonium acetate.
Preferably, the strong acid in the step S1 includes one of nitric acid and sulfuric acid or a mixed acid of nitric acid and sulfuric acid;
in the case where the strong acid is a mixed acid of nitric acid and sulfuric acid, the volume ratio of the nitric acid to the sulfuric acid is 1.
Preferably, in the step S2, the mass ratio of the carbon source, the boron-containing organic substance, and the pore-forming agent is 8:0.5-1:1.5-1;
wherein the calcining temperature is 1000-1500 ℃, and the reaction time is 2-4 hours.
In a second aspect, the application provides an application of B and N co-doped sodium-rich porous carbon in a sodium ion battery, wherein the B and N co-doped sodium-rich porous carbon material has a carbon material interlamellar spacing of 0.385nm and above, and the prepared sodium ion battery has high coulombic efficiency.
Compared with the prior art, the beneficial effect of this application lies in: according to the preparation method provided by the application, on the basis of calcination and carbonization, the B element is introduced as a graphitization catalyst, so that the graphitization temperature is reduced; meanwhile, the sodium borate and the sodium tetrahydroborate release Na and B atoms at high temperature, and the ammonium bicarbonate and the ammonium acetate release N element, and the three are doped into the carbon layer to form a B and N co-doped sodium-rich porous carbon material; the material and the preparation method thereof have the following beneficial effects:
(1) The preparation method is simple to prepare, the prepared product is good in reproduction, and the operation is easy.
(2) According to the preparation method, the content of sodium element in the carbon layer and the interlayer spacing of the carbon material can be regulated and controlled by regulating and controlling the using amount of sodium borate or sodium tetrahydroborate.
(3) Subsequent organic solvent soaking treatment and washing, restrained conventional washing sodium ion's loss, remain abundant sodium element, form rich sodium's porous carbon.
(4) The application the unique composition of B, N codope rich sodium porous carbon can provide the interlamellar spacing more than 0.385nm, for the embedding of sodium ion with deviate from and provide favorable storage site, the carbon material of rich sodium can supply the loss of first cycle in-process sodium element simultaneously, improves the ICE of SIB.
(5) According to the B and N co-doped sodium-rich porous carbon prepared by the preparation method, the C atom part of the carbon skeleton is replaced by B and N, the carbon skeleton contains a plurality of mesoporous and microporous structures, and the B and N co-doping widens the interlayer spacing of the carbon material, so that a favorable space is provided for the transportation of sodium ions, and the dynamics of sodium modification/sodium removal is improved; meanwhile, the characteristic of rich sodium element in porous carbon is beneficial to improving the ICE of the electrode material.
(6) The button type half cell is assembled by using NaClO4 as a solute, ethylene carbonate and dimethyl carbonate, adding 5% of fluoroethylene carbonate as a film forming aid by mass ratio, and using metal sodium as a counter electrode and a reference electrode. At the initial current intensity of 0.05A/g, the ICE reaches more than 92.6 percent; taking the prepared B and N codoped sodium-rich porous carbon as a cathode and Na 3 V 2 (PO 4 ) 3 After 50 cycles, the capacity retention rate of the button cell assembled as the positive electrode is more than 60 percent, and the coulomb efficiency is close to 100 percent.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
Fig. 1 is a first and second charge-discharge curve diagram of the B and N co-doped sodium-rich porous carbon prepared in example 1.
FIG. 2 shows B and N co-doped sodium-rich porous carbon and Na prepared in example 1 3 V 2 (PO 4 ) 3 Cycling capacity and coulombic efficiency curves for button cells assembled for the positive electrode.
FIG. 3 is a scanning electron micrograph of the B and N co-doped sodium-rich porous carbon prepared in example 2, wherein a is a scanning electron micrograph at low magnification, B is a scanning electron micrograph at high magnification, c is a transmission electron micrograph at low magnification, and d is a transmission electron micrograph at high magnification.
Fig. 4 is an isothermal adsorption curve and a mesoporous distribution curve of the B and N co-doped sodium-rich porous carbon prepared in example 2.
FIG. 5 is an XRD pattern of B and N co-doped sodium-rich porous carbon prepared in example 2
FIG. 6 is an XPS plot of B and N co-doped sodium-rich porous carbon prepared in example 2 (a is a full spectrum plot; B is a N1s plot; c is a B1s plot; and d is a Na1s plot).
Fig. 7 is a first and second charge-discharge curve plot of B, N co-doped sodium-rich porous carbon prepared in example 2.
FIG. 8 shows B and N co-doped Na-rich porous carbon and Na prepared in example 2 3 V 2 (PO 4 ) 3 Cycling capacity and coulombic efficiency curves for button cells assembled for the positive electrode.
Fig. 9 is a first and second charge-discharge curve plot of B, N co-doped sodium-rich porous carbon prepared in example 3.
FIG. 10 shows B and N co-doped Na-rich porous carbon and Na prepared in example 3 3 V 2 (PO 4 ) 3 Cycling capacity and coulombic efficiency curves for button cells assembled for the positive electrode.
Fig. 11 is a first and second charge-discharge curve diagram of the B and N co-doped sodium-rich porous carbon prepared in comparative example 1.
FIG. 12 shows that B and N codoped sodium-rich porous carbon and Na prepared in comparative example 1 3 V 2 (PO 4 ) 3 Cycling capacity and coulombic efficiency curves for button cells assembled for the positive electrode.
FIG. 13 is an XRD pattern of B and N co-doped sodium-rich porous carbon prepared in example 4
Fig. 14 is a first and second charge-discharge curve diagram of the B, N co-doped sodium-rich porous carbon prepared in example 4.
FIG. 15 shows B and N co-doped Na-rich porous carbon and Na prepared in example 4 3 V 2 (PO 4 ) 3 Cycling capacity and coulombic efficiency curves for button cells assembled for the positive electrode.
FIG. 16 is atomic compositions obtained by XPS in examples 1 to 4 and comparative example 1;
Detailed Description
The present invention will now be described in detail with reference to the following examples, in order to make the objects, features and advantages of the present invention more comprehensible. Several embodiments of the invention are given below. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete:
example 1
The embodiment provides a preparation method of B and N co-doped sodium-rich porous carbon, which comprises the following steps:
s1: 10g of petroleum coke obtained from a refinery is soaked in a mixed acid of nitric acid and sulfuric acid, wherein the volume of the nitric acid and the sulfuric acid is 1:3, the soaking time is 12 hours. After soaking, filtering, washing, and drying in an oven at 80 degrees for later use.
S2: and (2) taking the sample obtained in the step (S1), adding sodium tetrahydroborate and ammonium bicarbonate, and mixing the mixture, wherein the petroleum coke is the mixture of the sodium tetrahydroborate: the mass ratio of ammonium bicarbonate is 8:1:1, grinding to powder, placing in a tube furnace in N 2 Calcining in atmosphere at 1200 deg.C and at a rate of 5 deg.C/min, and keeping the temperatureFor 3 hours.
S3: and (3) soaking the sample obtained in the step (S2) in 0.1mol/L dimethyl ether solution of sodium biphenyl for 20 seconds, washing with dimethyl ether, and drying in vacuum to obtain the required B and N co-doped sodium-rich porous carbon.
S4: the electrode slurry comprises the following components: 80wt% of B and N co-doped sodium-rich porous carbon is used as an active material, 10wt% of acetylene black is used as a conductive additive, 10wt% of polyvinylidene fluoride is used as an adhesive, the mixture is added into an N-methyl-2-pyrrolidone solvent, the mixture is uniformly stirred to a proper viscosity to form slurry, the slurry is coated on a copper foil, the copper foil is dried in vacuum at 80 ℃ for 12 hours, and the slurry is compressed under 10MPa to form a coating film with the thickness of 100 microns. The sheets were punched out by a cutter to obtain circular pieces with a diameter of 12mm, and then assembled into button half cells in a glove box under an Ar atmosphere. The solute of the electrolyte is NaClO 4 The solvent is ethylene carbonate and dimethyl carbonate to which 5% by mass of fluoroethylene carbonate is added (volume ratio 1. The button type half cell adopts metal sodium as a counter electrode and a reference electrode, and glass fiber as a diaphragm.
Referring to fig. 1, first and second charge and discharge curves of the B, N co-doped sodium rich porous carbon prepared in example 1 are shown. As can be seen, the first discharge capacity is 249.8mAh/g, and the ICE is 78.48%. The second CE was 99.8%, close to 100%, indicating that the sodium-rich porous carbon was able to adequately compensate for the first loss of sodium element.
FIG. 2 shows that the B and N co-doped sodium-rich porous carbon prepared in example 1 is used as a negative electrode, and Na is added 3 V 2 (PO 4 ) 3 Cycling capacity and coulombic efficiency curves for the button full cell assembled for the positive electrode. After 50 cycles, the full cell capacity dropped from the initial 134.7mAh/g to 79.7mAh/g, but the coulombic efficiency increased from the initial 69.26% and finally stabilized to 92%.
Example 2
The embodiment provides a preparation method of B and N co-doped sodium-rich porous carbon, which comprises the following steps:
s1: soaking 10g of petroleum coke obtained from a petroleum refinery in a mixed acid of nitric acid and sulfuric acid, wherein the volume of the nitric acid and the sulfuric acid is 1:3, the soaking time is 12 hours. After soaking, filtering, washing, and drying in an oven at 80 ℃ for later use.
S2: and (2) taking the sample obtained in the step S1, adding sodium tetrahydroborate and ammonium bicarbonate, and mixing the mixture, wherein the petroleum coke comprises the following components: the mass ratio of ammonium bicarbonate is 8:1:1, grinding the mixture into powder, placing the powder in a tube furnace, and placing the powder in a N atmosphere 2 Calcining in the atmosphere, wherein the calcining temperature is 1200 ℃, the heating rate is 5 ℃/min, and the heat preservation time is 3 hours.
S3: and (3) soaking the sample obtained in the step (S2) in a dimethyl ether solution of 0.5mol/L sodium biphenyl for 20 seconds, washing with dimethyl ether, and drying in vacuum to obtain the required B and N co-doped sodium-rich porous carbon.
See step S4 in example 1 to prepare a button half cell and perform further testing.
Referring to fig. 3, a scanning electron microscope image of the B and N co-doped sodium-rich porous carbon obtained in example 2 under low magnification shows that (a) and (B) in fig. 3 show that the sample after high-temperature calcination has a layered structure, and a high-magnification scanning electron microscope further shows that each graphite sheet is composed of multiple layers of flaky nano sheets. The transmission electron microscope of (c) and (d) in FIG. 3 shows that these lamellar structures contain a plurality of lattice fringes with an interlayer spacing of 0.401nm.
Referring to fig. 4, the specific surface area of the B and N co-doped sodium-rich porous carbon obtained in example 2 is 237.8m 2 The absorption/desorption curve lags in a high-pressure area, which indicates that a mesoporous structure exists; there is also a certain amount of adsorption in the low pressure zone and a microporous structure. The average pore diameter of the pore size distribution was 6.8nm, and the pore volume was 1.87cm 3 /g。
Referring to fig. 5, the XRD pattern of the B and N co-doped sodium-rich porous carbon obtained in example 2 can find that there is a broad peak at 21.84 °, corresponding to the peak of (002) carbon crystal plane with 0.407nm of interlayer spacing.
Referring to fig. 6, XPS diagram of the B and N co-doped sodium-rich porous carbon obtained in example 2, fig. 4 (a) shows that the prepared sample contains C, B, N, na and a small amount of O elements, and the atomic ratio of the C, B, N, na elements is 74.7:6.3:5.8:9.7:3.5. the high resolution patterns of FIGS. 4 (B) (C) (d) show that the presence of B-N, B-C bonds is advantageous for the stable presence of B on the carbon skeleton.
Referring to fig. 7, first and second charge-discharge curves of the B, N co-doped sodium-rich porous carbon prepared in example 1 are shown. As can be seen, the first discharge capacity is 284.8mAh/g, and the ICE is 92.6%. The second CE was 99.1%, close to 100%, indicating that the sodium-rich porous carbon was able to adequately compensate for the first loss of sodium element.
FIG. 8 shows that the B and N co-doped sodium-rich porous carbon prepared in example 1 is used as a negative electrode, and Na is added 3 V 2 (PO 4 ) 3 Cycling capacity and coulombic efficiency curves for button full cells assembled for the positive electrode. After 50 cycles, the capacity of the full battery is reduced to 85.8mAh/g from the initial 134.7mAh/g, but the coulomb efficiency is increased from the initial 94.26 percent and finally stabilized to 100 percent, which shows that the battery has good reversibility and rapid sodium ion transfer kinetic process in the charging and discharging process.
Example 3
The embodiment provides a preparation method of B and N co-doped sodium-rich porous carbon, which comprises the following steps:
s1: soaking 10g of petroleum coke obtained from a petroleum refinery in a mixed acid of nitric acid and sulfuric acid, wherein the volume of the nitric acid and the sulfuric acid is 1:3, the soaking time is 12 hours. After soaking, filtering, washing, and drying in an oven at 80 ℃ for later use.
S2: and (2) taking the sample obtained in the step (S1), adding sodium tetrahydroborate and ammonium bicarbonate, and mixing the mixture, wherein the petroleum coke is the mixture of the sodium tetrahydroborate: the mass ratio of ammonium bicarbonate is 8:1:1, grinding to powder, placing in a tube furnace in N 2 Calcining in the atmosphere at 1200 deg.C at a heating rate of 5 deg.C/min for 3 hr.
S3: and (3) soaking the sample obtained in the step (S2) in 1mol/L dimethyl ether solution of sodium biphenyl for 20 seconds, washing with dimethyl ether, and drying in vacuum to obtain the required B and N co-doped sodium-rich porous carbon.
See step S4 in example 1 to prepare a button half cell and perform further testing.
Referring to fig. 9, first and second charge and discharge graphs of the B, N co-doped sodium rich porous carbon prepared in example 3. As can be seen from the figure, the first discharge capacity reaches 298.6mAh/g, and the ICE is 98.3%. The second CE was 99.1%, close to 100%, indicating that porous carbon with higher sodium content can adequately compensate for the first loss of sodium.
FIG. 10 shows that the B and N co-doped sodium-rich porous carbon prepared in example 3 is used as a negative electrode, and Na is added 3 V 2 (PO 4 ) 3 Cycling capacity and coulombic efficiency curves for button full cells assembled for the positive electrode. After 50 cycles, the capacity of the full battery is reduced from the initial 141.7mAh/g to 119.7mAh/g, but the coulomb efficiency is increased from the initial 98.06 percent and finally stabilized to 100 percent, which shows that the battery has good reversibility and rapid sodium ion transfer kinetic process in the charging and discharging process.
Example 4
S1: soaking 10g of petroleum coke obtained from a petroleum refinery in a mixed acid of nitric acid and sulfuric acid, wherein the volume of the nitric acid and the sulfuric acid is 1:3, the soaking time is 12 hours. After soaking, filtering, washing, and drying in an oven at 80 ℃ for later use.
S2: and (2) taking the sample obtained in the step (S1), adding sodium tetrahydroborate and ammonium bicarbonate, and mixing the mixture, wherein the petroleum coke is the mixture of the sodium tetrahydroborate: the mass ratio of ammonium bicarbonate is 7:2:1, grinding the mixture into powder, placing the powder in a tube furnace, and placing the powder in a N atmosphere 2 Calcining in the atmosphere at 1200 deg.C at a heating rate of 5 deg.C/min for 3 hr.
S3: and (3) soaking the sample obtained in the step (S2) in a dimethyl ether solution of 0.5mol/L sodium biphenyl for 20 seconds, washing with dimethyl ether, and drying in vacuum to obtain the required B and N co-doped sodium-rich porous carbon.
See step S4 in example 1 to prepare a button half cell and perform further testing.
Example 4 increased the content of sodium tetrahydroborate compared to example 2, and it can be found by XRD of fig. 13 that the peak height of (002) crystal plane was lower than that of example 2 and the crystallinity was lower than that of the sample of example 2, indicating that increasing the content of sodium element in the sample can decrease the crystallinity of the sample.
Referring to fig. 14, first and second charge and discharge graphs of the B, N co-doped sodium rich porous carbon prepared in example 4. As can be seen, the first discharge capacity reaches 312.8mAh/g, and the ICE is 99.7%. The second ICE is 99.2 percent and is close to 100 percent, which shows that the B and N codoped porous carbon with higher sodium content can fully compensate the sodium element lost for the first time and improve the first effect of the electrode.
FIG. 15 shows that the B and N co-doped sodium-rich porous carbon prepared in example 4 is used as a negative electrode, and Na is added 3 V 2 (PO 4 ) 3 Cycling capacity and coulombic efficiency curves for the button full cell assembled for the positive electrode. After 50 cycles, the capacity of the full battery is reduced to 187.4mAh/g from the initial 200.3mAh/g, and the coulomb efficiency is stabilized to 100% from the initial 99.56%, which shows that the battery has good reversibility and rapid sodium ion transfer kinetic process in the charging and discharging process.
Comparative example 1
S1, soaking a carbon source in strong acid, filtering, washing, drying and replacing;
s2, mixing and grinding the carbon source treated in the step S1 with a boron-containing organic substance and a pore-forming agent, and then calcining in a nitrogen atmosphere;
and S3, washing the sample of the S2 by deionized water and absolute ethyl alcohol until the pH value of the mother solution is neutral, and performing vacuum drying to obtain the required B and N co-doped porous carbon.
See step S4 in example 1 to prepare a button half cell and perform further testing.
Referring to fig. 11, first and second charge and discharge curves of the B, N co-doped porous carbon prepared in comparative example 11 are shown. As can be seen, the first discharge capacity reached 184.1mAh/g, and the ICE was 66.9%. The second CE was 72.9%, and the sodium element lost by the first SEI formation could not be compensated for due to the lower content of original sodium between the layers.
FIG. 12 shows that the B and N co-doped sodium-rich porous carbon prepared in comparative example 1 is used as a negative electrode and Na 3 V 2 (PO 4 ) 3 Cycling capacity and coulombic efficiency curves for the button full cell assembled for the positive electrode. After 50 cycles, the capacity of the full cell decreased from the initial 100.4mAh/g to 61.2mAh/g, but the coulombic efficiency decreased from the initial oneThe 70.1% rise to 97.17% of the total mass, which is significantly lower than the samples of examples 1, 2 and 3, because the samples cannot compensate for the loss of sodium element forming SEI, the side reactions are significantly increased, resulting in a decrease in coulombic efficiency.
In summary, the present application has the following beneficial effects:
(1) The preparation method is simple to prepare, the prepared product is good in reproduction, and the operation is easy;
(2) According to the preparation method provided by the application, on the basis of calcination and carbonization, the B element is introduced as a graphitization catalyst, so that the graphitization temperature is reduced; meanwhile, na and B atoms are released by the sodium borate and the sodium tetrahydroborate at high temperature, and N element is released by the ammonium bicarbonate and the ammonium acetate, and the three are doped into the carbon layer to form a B and N co-doped sodium-rich porous carbon material, and the content of the sodium element in the carbon layer and the interlayer spacing of the carbon material can be regulated and controlled by regulating the using amount of the sodium borate or the sodium tetrahydroborate;
(3) The subsequent organic solvent soaking treatment and washing inhibit the loss of conventional washing sodium ions, reserve rich sodium elements and form sodium-rich porous carbon, wherein the sodium element accounts for up to 5.0-12%;
(4) The unique components of the B and N co-doped sodium-rich porous carbon can provide a layer spacing of more than 0.385nm, so that favorable storage sites are provided for the embedding and the releasing of sodium ions, and meanwhile, the sodium-rich carbon material can supplement the loss of sodium element in the first circulation process and improve the ICE of SIB; with example 2 having a layer spacing as high as 0.407.
Furthermore, it should be noted that, in the above embodiments, only some of the influencing factors are subjected to relevant experiments, and the control of other conditions in the experiments also has a certain influence on the final effect presented in the present application, and taking the selection of the type of petroleum coke as an example, the application selects low-sulfur needle coke, that is, the graphite degree of the needle coke is utilized to be higher, and the crystallinity of the carbon presented finally is better; like selection such as calcination temperature, calcination time and reaction temperature amplitude of rise again, it all has certain influence to the presentation effect of end product, and this application is through selecting suitable component promptly, and suitable experimental method is matched with suitable experimental condition, has finally obtained the rich sodium porous carbon material of B, N codope that possesses above-mentioned beneficial effect.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
The above description is only for the preferred embodiment of the present application and should not be taken as limiting the present application in any way, and all simple modifications, equivalent changes and modifications made to the above embodiment according to the technical spirit of the present application are intended to be included within the scope of the present application.

Claims (11)

1. A preparation method of B and N codoped sodium-rich porous carbon is characterized by comprising the following steps: the method comprises the following steps:
s1, soaking a carbon source in strong acid, filtering, washing, drying and replacing;
s2, mixing and grinding the carbon source treated in the step S1 with a boron-containing organic substance and a pore-forming agent, and then calcining in a nitrogen atmosphere;
s3, immersing the sample treated in the step S2 into an organic sodium solution, washing with an ether solvent, and performing vacuum drying to obtain B and N co-doped sodium-rich porous carbon;
wherein the boron-containing organic substance contains sodium element.
2. The preparation method of the B and N co-doped sodium-rich porous carbon according to claim 1, characterized in that: the carbon source comprises one or more of petroleum coke, coke and asphalt.
3. The preparation method of the B and N co-doped sodium-rich porous carbon according to claim 2, characterized in that: the carbon source is petroleum coke, and the category of the petroleum coke is low-sulfur needle coke.
4. The preparation method of the B and N co-doped sodium-rich porous carbon according to claim 1, characterized in that: in the step S3, the organic sodium solute includes at least one of sodium ethoxide, sodium biphenyl, sodium phenolate, and sodium methoxide.
5. The preparation method of the B and N co-doped sodium-rich porous carbon according to claim 4, characterized in that: the concentration range of the organic sodium solution is 0.1-2mol/L.
6. The preparation method of the B and N co-doped sodium-rich porous carbon according to claim 1, characterized in that: the boron-containing organic matter comprises at least one of sodium tetraphenylborate, sodium borate, sodium tetrahydroborate, sodium perborate, (trihydroxy) phenylboronate, sodium tetrakis (1-imidazolyl) borate and derivatives thereof.
7. The preparation method of the B and N co-doped sodium-rich porous carbon according to claim 1, characterized in that: the pore-forming agent contains NH 4 + 。
8. The preparation method of the B and N co-doped sodium-rich porous carbon according to claim 7, characterized in that:
the pore-forming agent comprises at least one of ammonium bicarbonate, ammonium carbonate, ammonium zinc carbonate, ammonium sodium carbonate and ammonium potassium carbonate.
9. The preparation method of the B and N co-doped sodium-rich porous carbon according to claim 1, characterized in that: the strong acid in the step S1 comprises one of nitric acid and sulfuric acid or a mixed acid of nitric acid and sulfuric acid;
in the case where the strong acid is a mixed acid of nitric acid and sulfuric acid, the volume ratio of the nitric acid to the sulfuric acid is 1.
10. The preparation method of the B and N co-doped sodium-rich porous carbon according to claim 1, characterized in that: in the step S2, the mass ratio of the carbon source, the boron-containing organic substance, and the pore-forming agent is 8:0.5-1:1.5-1;
wherein the calcining temperature is 1000-1500 ℃, and the reaction time is 2-4 hours.
11. The use of the B, N co-doped sodium rich porous carbon according to any one of claims 1-10 in a sodium ion battery, wherein: the B and N co-doped sodium-rich porous carbon material has a carbon material interlamellar spacing of 0.385nm and above, and the prepared sodium ion battery has high coulombic efficiency.
CN202211171574.6A 2022-09-26 2022-09-26 Preparation method of B and N co-doped sodium-rich porous carbon and application of B and N co-doped sodium-rich porous carbon in sodium ion battery Pending CN115440983A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116553524A (en) * 2023-07-04 2023-08-08 成都锂能科技有限公司 Hard carbon negative electrode material of sodium ion battery, and preparation process and application thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116553524A (en) * 2023-07-04 2023-08-08 成都锂能科技有限公司 Hard carbon negative electrode material of sodium ion battery, and preparation process and application thereof
CN116553524B (en) * 2023-07-04 2023-09-15 成都锂能科技有限公司 Hard carbon negative electrode material of sodium ion battery, and preparation process and application thereof

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