CN116374991A

CN116374991A - Preparation method of sodium ion battery anode material based on resin precursor

Info

Publication number: CN116374991A
Application number: CN202310383305.4A
Authority: CN
Inventors: 殷雅侠; 肖书浩; 郭玉国
Original assignee: Institute of Chemistry CAS
Current assignee: Institute of Chemistry CAS
Priority date: 2023-04-12
Filing date: 2023-04-12
Publication date: 2023-07-04
Anticipated expiration: 2043-04-12
Also published as: CN116374991B

Abstract

The invention relates to a preparation method of a sodium ion battery anode material based on a resin precursor, which uses an industrialized organic polymer with low price and mature technology as a raw material, increases the crosslinking degree of the precursor through pre-oxidation, and adds a volatile polymer and a zinc-containing inorganic compound in the high-temperature cracking process, thereby obviously improving the capacity and the first coulombic efficiency of a hard carbon material. The preparation method of the hard carbon material has the advantages of low cost, simple process, high carbon yield, suitability for large-scale production, excellent multiplying power performance, stable cycle performance and high energy density when the hard carbon material is used for sodium ion batteries.

Description

Preparation method of sodium ion battery anode material based on resin precursor

Technical Field

The invention belongs to the technical field of battery anode materials, and particularly relates to a preparation method of a sodium ion battery anode material based on a resin precursor.

Background

Due to the shortage of fossil energy and the emission of greenhouse gases, it is increasingly important to develop clean renewable energy. Renewable new energy sources such as wind energy, solar energy and the like often have strong territory and intermittence, so the energy power station needs to be matched with large-scale energy storage equipment to adapt to the grid connection requirement of the energy power station. In recent years, lithium ion batteries have been widely used in portable electronic devices and electric vehicles because of their long service life and high energy and power density. However, with the increase of the usage amount of lithium ion batteries and the shortage and uneven distribution of lithium ores, the price of metal lithium is high year by year, and it is difficult to meet the requirement of large-scale energy storage. Because of the abundant sodium resources, the sodium ion battery has wide distribution and low cost, and has great cost advantage in the application of a large-scale energy storage system. However, due to thermodynamic limitations, sodium ions are difficult to intercalate into commercial graphite negative electrodes, so graphite as a negative electrode of a sodium ion battery hardly shows sodium storage activity, and development of a novel high-capacity low-cost negative electrode material becomes a key for commercialization of the sodium ion battery.

Among the sodium ion battery negative electrode materials which are common at present, the hard carbon material has high energy density and long cycle life, is one of the most promising sodium ion battery negative electrode materials, and the carbon material which is common at present has specific capacity smaller than 300mAh/g and low initial circle coulomb efficiency (< 70%), so the development of the sodium ion battery with high capacity and high coulomb efficiency as the negative electrode material is the key point and hot point of the current research and development. The resin organic polymer has the advantages of good stability, high carbon residue rate and the like, and can be used as one of the hard carbon material precursors. However, the problems of low initial coulombic efficiency, poor multiplying power performance and the like still exist after the direct carbonization, the application of the polymer electrolyte in the negative electrode of the sodium ion battery is limited to a great extent.

Many prior art discloses methods for preparing hard carbon negative electrode materials using resinous materials as carbon precursors, such as CN115458742a, CN114597404A, CN114436237a. The general process is that the polymer resin is oxidized/crosslinked by presintering, and then the hard carbon anode material is obtained by heating and calcining. However, the capacity and the first coulombic efficiency of the obtained hard carbon anode material are still poor, and the requirement of the current energy source on the battery can not be met.

WO2017/057416, WO2021/070825, by japan corporation, discloses a method for increasing the initial capacity of a battery by calcining a volatile polymer such as polystyrene, polyethylene, polypropylene, or the like together with a carbon precursor to form a carbonaceous coating on the surface of the carbon precursor, wherein the specific surface area of the resulting hard carbon material is reduced, while suppressing the formation of a solid electrolyte phase interface (SEI) between the hard carbon material and lithium, and reducing the irreversible capacity; on the other hand, the formed carbonaceous coating can participate in doping and dedoping lithium, and the capacity of the battery is improved under the combined action. However, the capacity of the hard carbon material obtained by using only polystyrene is still unsatisfactory, and the standard for industrial mass use cannot be met.

Disclosure of Invention

In order to overcome the defect that the electrochemical performance of a hard carbon negative electrode material prepared by taking high polymer resin as a carbon precursor in the prior art is not excellent enough, particularly the sodium storage capacity and the first coulombic efficiency are not satisfactory, the invention provides a preparation method of a sodium ion battery negative electrode material based on the resin precursor.

The aim of the invention is achieved by the following technical scheme:

the preparation method of the sodium ion battery anode material based on the resin precursor comprises the following steps:

(S1) pretreatment: pre-oxidizing a high molecular resin substance serving as a carbon precursor in an oxygen-containing atmosphere;

(S2) precarbonization: grinding the pretreated material in the step (S1), and carrying out heating heat treatment under inert atmosphere to carry out pre-carbonization;

(S3) mixing: fully mixing the pre-carbonized material particles in the step (S2) with a pore canal modifier; the pore canal modifier comprises a non-carbon-forming polymer and a zinc-containing inorganic compound;

(S4) carbonization: and (3) carbonizing the mixed material in the step (S3) at a high temperature in an inert atmosphere or a hydrocarbon gas atmosphere to obtain a hard carbon material.

Further, in the step (S1), the polymer resin is at least one selected from the group consisting of a phenolic resin, an epoxy resin, and a furfural resin.

Further, in the step (S1), the oxygen-containing atmosphere means that the oxygen content is more than 20%, such as air, oxygen, a mixed gas of air and oxygen; the pretreatment is to heat up to 200-300 ℃ at a heating rate of 2-10 ℃/min under the oxygen-containing atmosphere, and keep the temperature for 5-10h.

Further, in the step (S2), the pre-carbonization is performed under an inert atmosphere, the temperature is raised to 500-800 ℃ and kept for 2-5 hours, and the inert atmosphere is under an argon atmosphere, and the temperature raising rate is 1-3 ℃/min.

Further, in the step (S3), the pore canal modifier is a combination of a non-carbon-forming polymer and a zinc-containing inorganic compound; the non-carbon-forming polymer is at least one selected from polystyrene, polyethylene, polypropylene, polydiene and polymethyl (meth) acrylate; the zinc-containing inorganic compound is at least one selected from zinc oxide, zinc chloride, zinc sulfate and basic zinc carbonate. Preferably, the number average molecular weight of the non-carbon-forming polymer is 50000-100000g/mol, and the molecular weight distribution of the non-carbon-forming polymer is not particularly limited.

The inventors have previously described in patent CN202310329720.1, CN202310329756.X that the use of a combination of non-carbon forming polymers and oils as pore modifying agents can significantly improve the electrochemical properties of the resulting hard carbon anode material. However, it was found that the combination of non-carbon forming polymers and oils is more suitable for pitch-based as well as biomass-based carbon precursors, and that there is limited performance improvement for polymeric resin-based carbon precursors. The inventors have unexpectedly found that the combination of a certain proportion of non-carbon-forming polymer and zinc-containing inorganic compound, especially basic zinc carbonate, has the most remarkable effect on modifying the pore channels of the material after calcining and carbonizing the high molecular resin carbon precursor, and the obtained hard carbon anode material has optimal electrochemical performance.

Further, in the step (S3), the pore canal modifier is a compound of a non-carbon-forming polymer and a zinc-containing inorganic compound according to a mass ratio of 3-7:1. More preferably, the pore canal modifier is a combination of polystyrene and basic zinc carbonate according to a mass ratio of 3-7:1, so that a hard carbon anode material with optimal capacity and initial coulombic efficiency can be obtained, and presumably, the reason is that zinc ions are reduced into metallic zinc simple substances at high temperature and then volatilized at about 900 ℃ to generate a large number of pores; the small molecular carbon chain broken by the polystyrene in high-temperature cracking can repair the defects of the graphite-like layer and convert the generated pores into closed pores, so that the hard carbon has high capacity and high first coulombic efficiency.

Further, in step (S3), the pore canal modifier accounts for 5-15wt%, preferably 8-10wt%, such as 9wt%,9.5wt% of the mass of the pre-carbonized material particles.

Further, in the step (S3), the manner of sufficiently mixing is not particularly limited, and includes, but is not limited to, ink-ball, grinding, sanding, and the like. Preferably ball milling, ball-to-material ratio of 10-20:1, the rotating speed is 400-700rpm, and the ball milling time is 3-10h.

Further, in the step (S4), the inert atmosphere is argon, and the hydrocarbon gas is at least one selected from methane, ethane, propane, butane, ethylene, acetylene, and toluene. Calcination in a hydrocarbon gas atmosphere is preferred to facilitate further enhancement of the first effect and capacity of the hard carbon material.

Further, in the step (S4), the high-temperature carbonization is performed by heating to 1300-1600 ℃ at a heating rate of 5-10 ℃/min, and performing heat preservation and calcination for 5-10 hours. And (3) the temperature rising rate is slow in the pre-carbonization in the step (S3), so that a uniform and disordered cross-linked structure is formed. In contrast, if the temperature rise rate is too high, the cross-linking copolymerization is insufficient, which will cause the direct polycondensation of the local region polymer carbonaceous material into mesophase carbon microspheres with lamellar ordered macromolecules, and the subsequent high-temperature calcination will generate graphene layers which are ordered in long range and are tightly stacked, which is not beneficial to the storage of sodium ions and is not beneficial to the capacity improvement of materials.

Further, in the step (S4), after high-temperature carbonization is finished, an acid washing step is further carried out, namely, the carbonized material is mixed and stirred in inorganic acid for 10-24 hours, washed and dried, and the hard carbon anode material is obtained. The purpose of the acid washing is to remove impurities.

The invention also provides a sodium ion battery anode material which comprises a hard carbon material, a conductive additive and a binder, wherein the hard carbon material is prepared by the preparation method.

The invention has the excellent effect of providing a preparation method and application of the organic polymer sodium ion battery negative electrode material. The invention uses the low-cost and mature industrial organic polymer as the raw material, increases the crosslinking degree of the precursor through pre-oxidation, and adds the volatile polymer and the zinc-containing inorganic compound in the high-temperature cracking process, thereby obviously improving the capacity and the first coulombic efficiency of the hard carbon material. The preparation method of the hard carbon material has the advantages of low cost, simple process and high carbon yield, and is suitable for large-scale production, and the hard carbon material is used as a negative electrode material for sodium ion secondary batteries. Zinc ions are reduced into metallic zinc simple substance at high temperature, and then volatilize at about 900 ℃ to generate a large number of pores; the volatile organic polymer is broken into small molecular carbon chains in the high-temperature cracking process, and the small molecules have a repairing effect on the defects of the graphite-like layer at high temperature, so that the obtained hard carbon material has the advantages of excellent multiplying power performance, stable cycle performance, high energy density and the like when being used for sodium ion batteries.

Drawings

FIG. 1 is an SEM image of the hard carbon material of example 1.

FIG. 2 is a TEM image of the hard carbon material obtained in example 1.

Fig. 3 is a constant current charge-discharge curve of the sodium ion battery provided in example 1.

Fig. 4 is a cycle chart of a sodium ion battery provided in example 1.

Fig. 5 is a graph of the rate performance of a sodium ion battery provided in example 1.

Fig. 6 is an SEM image of the hard carbon material produced in comparative example 1.

Fig. 7 is an SEM image of the hard carbon material produced in comparative example 2.

FIG. 8 is an SEM image of the hard carbon material of comparative example 3.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. The following examples facilitate a better understanding of the present invention, but are not intended to limit the same. The experimental methods in the following examples are conventional methods unless otherwise specified.

Example 1

(S1) placing the phenolic resin into a muffle furnace, heating in air at a heating rate of 5 ℃/min, heating at 200 ℃, preserving heat for 8 hours, and cooling to obtain pre-oxidized particles.

(S2) grinding the pre-oxidized particles in the step (1) into powder, then placing the powder into a tube furnace for calcination, heating to the temperature of 600 ℃ at the speed of 3 ℃/min, and preserving the heat for 2 hours in the atmosphere of Ar gas to obtain a pre-carbonized precursor, and then grinding and refining the precursor, and sieving the precursor through 200 meshes.

(S3) weighing 100 parts by mass of a pre-carbonized precursor, 7.5 parts by mass of polystyrene (with the number average molecular weight of about 100000 g/mol) and 2.5 parts by mass of basic zinc carbonate, placing the mixture into a ball milling tank, and controlling the ball-to-material ratio to be 20:1, setting the rotating speed of the ball mill to 450rpm, performing forward and reverse rotation modes, and performing ball milling for 4 hours to obtain a mixed precursor.

And (S4) placing the mixed precursor in a high-temperature tube furnace, introducing toluene gas, calcining under the toluene gas atmosphere, heating to a temperature of 1300 ℃ at a speed of 10 ℃/min, preserving heat for 7 hours, cooling to room temperature to obtain the hard carbon negative electrode material, calcining, cooling to room temperature, grinding, adding hydrochloric acid solution, stirring for 24 hours, washing with deionized water, and drying to obtain the hard carbon negative electrode material.

FIG. 1 is an SEM image of the hard carbon material of example 1; FIG. 2 is a TEM image of the hard carbon material obtained in example 1. It can be seen that the hard carbon material particles obtained in example 1 are dense in surface and flat and smooth, and no pore structure appears; however, a closed cell structure consisting of a stack of intact graphite-like layers was observed in the TEM images.

Example 2

Other conditions were the same as in example 1 except that in step (S1), the heating temperature was changed from 200℃to 300℃and the holding time was changed from 8 hours to 5 hours.

Example 3

Otherwise, the procedure was the same as in example 1 except that in step (S3), the cell-site modifier was changed from 7.5 parts by mass of polystyrene to 7.5 parts by mass of polyethylene (number average molecular weight: about 50000 g/mol).

Example 4

Other conditions were the same as in example 1 except that in step (S3), the pore-modifying agent was 8.75 parts by mass of polystyrene (number average molecular weight: about 100000 g/mol) and 1.25 parts by mass of basic zinc carbonate.

Example 5

Other conditions were the same as in example 1 except that in step (S3), the pore canal modifier was 6 parts by mass of polystyrene and 2 parts by mass of basic zinc carbonate.

Example 6

Otherwise, the procedure is the same as in example 1, except that in step (S3), basic zinc carbonate is replaced with zinc oxide of equal mass fraction.

Example 7

Otherwise, the procedure is as in example 1, except that in step (S3), basic zinc carbonate is replaced with zinc acetate of equal mass fraction.

Example 8

Otherwise, the procedure is as in example 1, except that in step (S3), basic zinc carbonate is replaced with zinc chloride of equal mass fraction.

Example 9

Other conditions were the same as in example 1 except that in step (S3), the pore-modifying agent was 5 parts by mass of polystyrene and 5 parts by mass of basic zinc carbonate.

Example 10

Other conditions, the operation was the same as in example 1 except that in step (S4), the calcination temperature was changed from 1300 ℃ to 1600 ℃.

Example 11

Other conditions were the same as in example 1 except that in step (S2), the temperature raising rate was 10℃per minute.

Comparative example 1

Otherwise, the procedure is the same as in example 1, except that step (S3) is omitted, i.e., no pore-modifying agent is added.

Comparative example 2

Other conditions were the same as in example 1 except that in step (S3), the pore-modifying agent was 10 parts by mass of polystyrene.

Comparative example 3

Other conditions were the same as in example 1 except that in step (S3), the pore canal modifier was 10 parts by mass of basic zinc carbonate.

Application example

The preparation and testing method of the anode material comprises the following steps: the hard carbon anode materials, super P and binder CMC/SBR obtained in the above examples and comparative examples were mixed according to a mass ratio of 94:2:4, mixing, adding a proper amount of water, and pulping to obtain uniformly mixed electrode slurry; uniformly coating the prepared electrode slurry on a carbon-coated aluminum foil, drying the electrode slurry in vacuum at 60 ℃ for 12 hours, and slicing the electrode slurry; sodium metal sheet is used as counter electrode, glass fiber is used as diaphragm, 1mol/L NaPF ₆ (the solvent is ethylene carbonate and diethyl carbonate with the volume ratio of 1:1) as electrolyte, and the button cell is assembled in a glove box protected by argon. Constant current charge and discharge tests were conducted, the current density was 20mA/g, the charge and discharge voltage interval was 0.001-2.0V, and the test results are shown in Table 1.

Table 1 electrochemical Performance test of hard carbon negative electrode materials

As can be seen from fig. 1, the hard carbon material prepared in example 1 has a smooth and tight surface.

As can be seen from fig. 2, the hard carbon material added with the pore canal modifier during the preparation process shows a clear graphite-like layer structure and is crosslinked with each other to form closed pores. This is because zinc ions are reduced to elemental metallic zinc at high temperatures and then volatilize at around 900 ℃ to create a large number of pores; the volatile organic polymer is broken into small molecular carbon chains in the high-temperature cracking process, and the small molecules have a repairing effect on the defects of the graphite-like layer at high temperature. The formation of a closed cell structure may provide favorable conditions for sodium ions to form metalloid sodium clusters within the hard carbon, while the increased interlayer spacing facilitates sodium ion diffusion between the layers. As can be seen from fig. 6 and 7, the samples without the addition of the pore modifying agent or with the addition of only polystyrene also have smooth surfaces. As can be seen from fig. 8, the surface of the hard carbon sample particle to which only basic zinc carbonate is added is covered with defects and pore structures, and the defects interact with the electrolyte and sodium salt during the first discharge, thereby generating a large amount of SEI film, and reducing the first coulombic efficiency of the material.

Fig. 3 is a constant current charge-discharge curve of the sodium ion battery provided in example 1. Fig. 4 is a cycle chart of a sodium ion battery provided in example 1. Fig. 5 is a graph of the rate performance of a sodium ion battery provided in example 1. It can be seen that the hard carbon material prepared by the method has high reversible specific capacity and first-circle coulomb efficiency.

From the results of the half-cell testing of the examples in table 1, it can be seen that: after the pore canal modifier is added in the preparation process, the capacity and the first coulombic efficiency of the obtained hard carbon sample are obviously improved. For example, example 7, a hard carbon material having 374.3mAh g after co-firing with polystyrene and zinc acetate ^-1 And a first coulombic efficiency of up to 91.5%. However, the capacity and the first coulombic efficiency of the comparative example 1, which is not added with the pore canal modifier and is subjected to mixed firing, are only 210.5mAh/g and 80.8%; comparative example 2, in which only the polystyrene co-firing agent was added, had improved first coulombic efficiency, but had limited capacity improvement; comparative example 3, in which only basic zinc carbonate was added, had a greatly improved capacity, but its initial coulombic efficiency was much reduced.

Claims

1. The preparation method of the sodium ion battery anode material based on the resin precursor is characterized by comprising the following steps of:

2. The method according to claim 1, wherein in the step (S1), the polymer resin is at least one selected from the group consisting of a phenolic resin, an epoxy resin, and a furfural resin.

3. The method according to claim 1, wherein in the step (S1), the oxygen-containing atmosphere means that the oxygen content is more than 20%; the pretreatment is to heat up to 200-300 ℃ at a heating rate of 2-10 ℃/min under the oxygen-containing atmosphere, and keep the temperature for 5-10h.

4. The method according to claim 1, wherein in the step (S2), the pre-carbonization is performed under an inert atmosphere, the temperature is raised to 500-800 ℃ and maintained for 2-5 hours, and the inert atmosphere is performed under an argon atmosphere, and the temperature raising rate is 1-3 ℃/min; in the step (S4), the high-temperature carbonization is performed by heating to 1300-1600 ℃ at a heating rate of 5-10 ℃/min, and calcining for 5-10h.

5. The method of claim 1, wherein in step (S3), the pore modifier is a combination of a non-carbon-forming polymer and a zinc-containing inorganic compound; the non-carbon-forming polymer is at least one selected from polystyrene, polyethylene, polypropylene, polydiene and polymethyl (meth) acrylate; the zinc-containing inorganic compound is at least one selected from zinc oxide, zinc chloride, zinc sulfate and basic zinc carbonate.

6. The process according to claim 5, wherein the non-carbon-forming polymer has a number average molecular weight of 50000-100000g/mol.

7. The preparation method of claim 5, wherein in the step (S3), the pore canal modifier is a combination of a non-carbon-forming polymer and a zinc-containing inorganic compound according to a mass ratio of 3-7:1; preferably, the pore canal modifier is a compound of polystyrene and basic zinc carbonate according to a mass ratio of 3-7:1.

8. The method according to claim 5, wherein in the step (S3), the pore canal modifier accounts for 5-15wt% of the mass of the pre-carbonized material particles.

9. The method according to claim 5, wherein in the step (S4), the inert atmosphere is argon, and the hydrocarbon gas is at least one selected from the group consisting of methane, ethane, propane, butane, ethylene, acetylene, and toluene.

10. A sodium ion battery anode material comprising a hard carbon material, a conductive additive, a binder, the hard carbon material being produced by the production method of any one of claims 1-9.