N / o / p co-doped porous carbon material and preparation method and application thereof

Abstract

The application relates to the technical field of sodium ion battery / capacitor negative electrode materials, and particularly discloses a preparation method and application of N / O / P co-doped porous carbon material. Through element analysis, the carbon material contains nitrogen-containing groups, i.e. pyridine nitrogen, pyrrole nitrogen, graphite nitrogen and nitrogen oxide compounds, and phosphorus-containing groups including C3-P=O, C-P-O and C-O-P, wherein the N content is 10-15 wt.%, the O content is 24-40 wt.% and the P content is 1-10 wt.%. The material is designed from a molecular scale, active groups of polysaccharides are used as anchoring sites to crosslink phosphorus-oxygen acid radicals, the amount of phosphorus-oxygen acid radicals is changed to adjust the microstructure and surface chemical state of the carbon material, and the carbon negative electrode with a fast sodium storage behavior is obtained through low-temperature carbonization. The N / O / P co-doped porous carbon material provided by the application is a sodium ion battery / capacitor negative electrode material, and has high reversible specific capacity, high rate performance and good large-current cycle stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion battery / capacitor negative electrode materials, and particularly relates to a N / O / P co-doped porous carbon material and a preparation method and application thereof. BACKGROUND

[0002] Among various negative electrode materials currently studied, carbon materials are concerned due to low cost, excellent performance, simple preparation and the like. The current research on carbon materials mainly focuses on graphite and amorphous carbon. Graphite is a hybrid ordered carbon with a crystalline hexagonal structure of graphene stacked along the c-axis; amorphous carbon is in an amorphous state and can be divided into soft carbon and hard carbon according to whether it is easy to undergo graphitization transformation at high temperatures. Hard carbon has been widely used and is the most promising sodium storage negative electrode material, because it has a local microcrystalline structure and a large interlayer spacing, and can release a larger reversible capacity at a lower potential (0-0.1V vs. Na / Na 2 ). + However, the capacity provided by hard carbon at a low potential (0-0.1V vs. Na / Na + ) is a diffusion-controlled process, which is limited by slower kinetics to rate performance, and the low voltage close to sodium plating can cause safety problems, especially at high rates. Therefore, carbon negative electrodes suitable for Na + deintercalation should promote a fast storage mechanism of sodium at high potentials (>0.1V vs. Na / Na + ).

[0003] Heteroatom doping can expand the path of ion transport and shorten the distance of ion transport, and is an effective strategy to improve the kinetics of carbon materials. Studies have shown that heteroatom doping (such as N, S, B and P) of carbon materials has the following advantages: (1) expanding the interlayer spacing to reduce the diffusion impedance of Na + in the charging and discharging process, and enhancing the wettability of the electrolyte to the carbon material; (2) increasing the surface groups of the carbon material to provide more active sites for reversible sodium adsorption and desorption; (3) improving the specific capacity of the carbon material at a large current. However, the temperature for preparing conventional hard carbon materials is generally high (>1300℃), and the energy consumption is large. Based on this, developing hard carbon negative electrode materials for high-rate sodium ion batteries / sodium ion capacitors at low temperature has become the focus of current research.

[0004] Patent CN202311412874.3 discloses a preparation method of a low-temperature synthesized high-rate sodium ion battery hard carbon negative electrode material. The disclosed preparation method is complex, and the high-rate performance of the hard carbon material prepared by the method needs to be improved when the hard carbon material is used as a negative electrode of a sodium ion battery. SUMMARY

[0005] The present application aims at providing a preparation method of N / O / P co-doped porous carbon material to solve the above problems of the prior art.

[0006] To achieve the above object, the present application adopts the following technical scheme:

[0007] The first object of the present application is to provide an N / O / P co-doped porous carbon material, which contains nitrogen-containing groups and phosphorus-containing groups by elemental analysis, the nitrogen-containing groups include pyridine nitrogen, pyrrole nitrogen, graphite nitrogen and nitrogen oxide, and the phosphorus-containing groups include C3-P=O, C-P-O and C-O-P, wherein the N content ranges from 10 to 15 wt.%, the O content ranges from 24 to 40 wt.%, and the P content ranges from 1 to 10 wt.%.

[0008] In the present embodiment, the nitrogen-containing groups (pyridine nitrogen, pyrrole nitrogen, graphite nitrogen and nitrogen oxide) and the phosphorus-containing groups (C3-P=O, C-P-O, C-O-P) of the N / O / P co-doped porous carbon material can promote the transmission of sodium ions by changing the electronic structure of the carbon material, providing more sodium reversible adsorption and desorption active sites, and improving the wettability of the carbon material. The present application finds that the content ranges of N, O and P are 10-15 wt.%, 24-40 wt.% and 1-10 wt.% respectively, at which the specific surface area of the carbon material is 44-227 m 2 g -1 , the content of surface functional groups is within a suitable range, the carbon material has excellent reversible specific capacity at high current density, and has high cycle stability.

[0009] Further, the interlayer spacing d(002) of the graphite (002) crystal plane measured by X-ray diffraction satisfies: 0.39 nm < d(002) < 0.43 nm.

[0010] Further, the specific surface area SSA measured by nitrogen adsorption and desorption satisfies: 44 m 2 / g < SSA < 227 m 2 / g.

[0011] Further, the mass percentage of each element in the N / O / P co-doped porous carbon material is: the C content ranges from 35 to 65 wt.%, the N content ranges from 10 to 15 wt.%, the O content ranges from 24 to 40 wt.%, and the P content ranges from 1 to 10 wt.%.

[0012] The second object of the present application is to provide a preparation method of the above N / O / P co-doped porous carbon material, which comprises the following steps:

[0013] S1, mixing polysaccharide, crosslinking agent and deionized water, stirring uniformly to obtain a mixed solution, the molar ratio of amino in the polysaccharide to phosphate in the crosslinking agent is 1:(1-6);

[0014] S2, drying the mixed solution obtained in step S1 to obtain a precursor;

[0015] S3, placing the precursor obtained in step S2 in an inert atmosphere, and carbonizing by programmed heating to 600-800 DEG C, then grinding and washing with hot water, and drying to obtain the final product.

[0016] It should be noted that:

[0017] The polysaccharide in step S1 is a polysaccharide that is more likely to disperse and crosslink with phosphate, the doped nitrogen comes from the polysaccharide, and the doped phosphorus mainly comes from the crosslinking agent, and the molar ratio of amino to phosphate is 1:(1-6);

[0018] In step S1, the drying environment is not limited, and the solvent in the sample can be completely removed;

[0019] In step S3, the carbonization environment is an inert atmosphere, which can be nitrogen, argon, helium, etc., and the gas flow rate can be controlled at 0.1-20 mL / min.

[0020] The preparation method adopts one-step low-temperature carbonization treatment, i.e., carbonization by programmed heating to 600-800 DEG C, which is beneficial to the active groups of the polysaccharide as anchor sites and crosslinking with phosphate oxyacid, in-situ doping to obtain N / O / P co-doped carbon negative electrode, and adjusting the amount of crosslinking agent to adjust the microstructure and surface chemical state of the carbon material to obtain a carbon negative electrode with fast sodium storage behavior.

[0021] Further, in step S2, the drying is performed at 60-65 DEG C for 6-8 h.

[0022] Further, in step S3, the programmed heating rate is 3-5 DEG C / min, and after being raised to 600-800 DEG C, the temperature is kept constant for 2-3 h for carbonization.

[0023] Further, the polysaccharide includes any one of chitooligosaccharide, glucosamine, chitosan or chitin, etc.

[0024] Further, the crosslinking agent includes any one of sodium hexametaphosphate, sodium tripolyphosphate, sodium pyrophosphate, trisodium phosphate, disodium hydrogen phosphate or sodium dihydrogen phosphate, etc.

[0025] The third object of the present application is to provide the use of the above-mentioned N / O / P co-doped porous carbon material in the preparation of a sodium ion battery negative electrode material.

[0026] The fourth object of the present application is to provide a sodium ion battery comprising a sodium ion battery negative electrode material prepared by using the above-mentioned N / O / P co-doped porous carbon material.

[0027] The fifth object of the present application is to provide a sodium ion capacitor comprising positive and negative electrode sheets, wherein the sodium ion capacitor negative electrode material comprises a negative electrode material after pre-sodium treatment by using the above-mentioned N / O / P co-doped porous carbon material.

[0028] Compared with the prior art, the technical scheme provided by the present application has the beneficial effects that:

[0029] (1) The present application provides an N / O / P co-doped porous carbon material, which is designed at a molecular scale, uses active groups of polysaccharides such as chitosan oligosaccharide as anchoring sites for crosslinking with phosphorus oxygen acid radicals, and introduces abundant phosphorus oxygen groups in situ during low-temperature carbonization to obtain an N / O / P co-doped carbon negative electrode. The introduction of N / O / P not only improves the electronegativity of the material, but also expands the distance between carbon layers to produce a large number of defects, realizing efficient adsorption and diffusion of Na + . In the pyrolysis process, the decomposition of phosphorus-containing substances makes the carbon material have abundant pore structures, which can provide a large number of active sites to serve as Na + buffer storage, thereby effectively enhancing the ion diffusion kinetics. By adjusting the amount of phosphorus oxygen acid radicals to adjust the microstructure and surface chemical state of the carbon material, a carbon negative electrode with fast sodium storage behavior is obtained.

[0030] (2) The N / O / P co-doped carbon negative electrode prepared by the present application has more excellent electrochemical performance than commercial hard carbon, with a reversible capacity as high as 225.8 mAh g -1 at 0.1 Ag -1 . Even at 10 A g -1 , it still maintains good rate performance (91.4 mAh g -1 ), and after 1000 cycles at a current density of 2 A g -1 , it still maintains a reversible specific capacity of 142.1 mAh g -1 , and the coulombic efficiency is maintained at 99.9%. The material and the activated carbon prepared by the research group are assembled into a sodium ion capacitor, which has an energy density as high as 105.2 Wh kg -1 at 200 W kg -1 . Moreover, the preparation method is simple, low in cost and high in efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The infrared spectrum comparison chart of the precursors prepared in Examples 1-3;

[0032] Figure 2 The TEM chart of the sample COSP6-3-600 prepared in Example 2;

[0033] Figure 3 Mapping image of sample COSP6-3-600 prepared in Example 2;

[0034] Figure 4 XRD comparison images of samples prepared in Examples 1-3;

[0035] Figure 5 Nitrogen adsorption / desorption isotherms and pore size distribution diagrams of the samples prepared in Examples 1-3;

[0036] Figure 6 XPS image of sample COSP6-3-600 prepared in Example 3;

[0037] Figure 7 A comparison chart of the rate performance of the samples prepared in Examples 1-3;

[0038] Figure 8 The sample COSP6-3-600 prepared for Example 3 was in 2A g -1 The following is a graph showing the cyclic performance.

[0039] Figure 9 Rate performance graph of COSP6-3-600 sample prepared in Example 3 and commercial hard carbon;

[0040] Figure 10 A comparison of the rate performance of sample CSCP6-1-600 prepared in Example 3 and sample COSP6-1-600 in Comparative Example 1.

[0041] Figure 11 The image shows the electrochemical performance of a sodium-ion capacitor assembled with COSP6-3-600 as the negative electrode material and an existing carbon positive electrode in Example 3. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the specific embodiments and accompanying drawings are described in further detail below. Where specific test methods, instruments, or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0043] Example 1

[0044] This embodiment provides a method for preparing N / O / P co-doped porous carbon materials.

[0045] Take 2 g of chitooligosaccharide, then take a certain amount of sodium hexametaphosphate according to the molar ratio of amino to phosphate of 1, and mix them into a certain volume of deionized water solution respectively, and magnetically stir at room temperature for 2 h. The obtained complex is first dried in a 65℃ air drying oven for 6h, and then transferred to a vacuum drying oven for drying for 6h. Then the dried precursor is placed in a tube furnace and carbonized under Ar protection, with a heating rate of 5℃ / min -1 , the carbonization temperature interval is set at 600℃, and the holding time is 2h. After carbonization, the obtained black powder is ground and washed with hot water, and is transferred into a 65℃ oven for full drying for 24h. The obtained material is named as COSP6-1-600.

[0046] Example 2

[0047] The present embodiment provides a preparation method of N / O / P co-doped porous carbon material.

[0048] The preparation method of Example 1 is basically the same, except that the molar ratio of amino to phosphate is 3, and the prepared material is named as COSP6-3-600.

[0049] Example 3

[0050] The present embodiment provides a preparation method of N / O / P co-doped porous carbon material.

[0051] The preparation method of Example 1 is basically the same, except that the molar ratio of amino to phosphate is 6, and the prepared material is named as COSP6-6-600.

[0052] Example 4

[0053] The present embodiment provides a preparation method of N / O / P co-doped porous carbon material.

[0054] The preparation method of Example 2 is basically the same, except that the carbonization temperature interval is set at 700℃, and the prepared material is named as COSP6-3-700.

[0055] Example 5

[0056] The present embodiment provides a preparation method of N / O / P co-doped porous carbon material.

[0057] The preparation method of Example 2 is basically the same, except that the carbonization temperature interval is set at 800℃, and the prepared material is named as COSP6-3-800.

[0058] Example 6

[0059] The present embodiment provides a preparation method of N / O / P co-doped porous carbon material.

[0060] The preparation method of the N / O / P co-doped porous carbon material is provided.

[0061] Example 7

[0062] The preparation method of the N / O / P co-doped porous carbon material is provided.

[0063] The preparation method of the N / O / P co-doped porous carbon material is provided.

[0064] Example 8

[0065] The preparation method of the N / O / P co-doped porous carbon material is provided.

[0066] The preparation method of the N / O / P co-doped porous carbon material is provided.

[0067] Example 9

[0068] The preparation method of the N / O / P co-doped porous carbon material is provided.

[0069] The preparation method of the N / O / P co-doped porous carbon material is provided.

[0070] Comparative Example 1

[0071] The preparation method of the N / O / P co-doped porous carbon material is provided.

[0072] The preparation method of the N / O / P co-doped porous carbon material is provided.

[0073] Performance characterization:

[0074] The N / O / P co-doped porous carbon materials prepared in Examples 1-9 all have similar micro-morphologies and physicochemical characteristics, contain nitrogen-containing groups and phosphorus-containing groups, the nitrogen-containing groups include pyridine nitrogen, pyrrole nitrogen, graphite nitrogen and nitrogen oxide, and the phosphorus-containing groups include C3-P=O, C-P-O and C-O-P, wherein the N content ranges from 10 to 15 wt.%, the O content ranges from 24 to 40 wt.%, and the P content ranges from 1 to 10 wt.%. It is found in the research that the carbonization temperature has a greater influence on the electrochemical performance of the N / O / P co-doped porous carbon material of the present application. It is found that when the carbonization temperature is 600℃, the electrochemical performance of the N / O / P co-doped porous carbon material is better. The following examples 1-3 are described in detail:

[0075] ReferenceFigure 1 The infrared spectra of the precursors prepared in Example 1-3 are compared in the figure; the appearance of the P=O characteristic peak indicates that sodium hexametaphosphate is successfully cross-linked to chitooligosaccharide, and after cross-linking, the disappearance of the N-H bending vibration peak and the shift of the C-N characteristic peak indicate that the amino groups of chitooligosaccharide (COS) are ionically cross-linked with the phosphate groups of sodium hexametaphosphate.

[0076] Reference Figure 2 The TEM (high-resolution transmission electron microscope) image of the sample COSP6-3-600 prepared in Example 2; it can be seen that the microstructure of the sample is long-range disorder, some of which are nanoscale pores, and short-range ordered graphite carbon layers with an interlayer spacing of about 0.424 nm.

[0077] Reference Figure 3 The Mapping (scanning electron microscope energy spectrum surface scanning) image of the sample COSP6-3-600 prepared in Example 2; it can be seen that the sample achieves uniform doping of heteroatoms nitrogen, oxygen and phosphorus. The analysis of the present application obtains the mass percentage of each element in the N / O / P co-doped porous carbon material: the C content ranges from 35 to 65 wt.%, the N content ranges from 10 to 15 wt.%, the O content ranges from 24 to 40 wt.%, and the P content ranges from 1 to 10 wt.%.

[0078] Reference Figure 4 The XRD (X-ray diffraction analysis) comparison chart of the samples prepared in Example 1-3; it can be seen that the COSP6-3-600 sample has the largest interlayer spacing of graphite crystallites, wherein the interlayer spacing d(002) of the (002) crystal plane of the COSP6-1-600 sample is 0.395 nm, the interlayer spacing d(002) of the (002) crystal plane of the COSP6-3-600 sample is 0.431 nm, the interlayer spacing d(002) of the (002) crystal plane of the COSP6-6-600 sample is 0.391 nm, and the interlayer spacing d(002) of the (002) crystal plane of the comparative sample COS-600 sample is 0.388 nm.

[0079] Reference Figure 5 The nitrogen adsorption / desorption isotherm and pore size distribution chart of the samples prepared in Example 1-3; it can be seen that the sample has a hierarchical pore structure, and the specific data are shown in Table 1.

[0080] Table 1.

[0081]

[0082] Reference Figure 6XPS (X-ray photoelectron spectroscopy) chart of sample COSP6-3-600 prepared in Example 3; characteristic peaks of C1s, N1s, O1s and P2p can be observed in the full spectrum chart, confirming the coexistence of carbon, nitrogen, oxygen and phosphorus in the sample.

[0083] Reference Figure 7 Comparison chart of rate performance of samples prepared in Example 1-Example 3; it can be seen that the samples have excellent rate performance, and the reversible capacity of COSP6-3-600 is as high as 225.8 mAh g -1 at 0.1 A g -1 , and it maintains good rate performance (91.4 mAh g -1 ) even at 10 A g -1 .

[0084] Reference Figure 8 Cycle performance chart of sample COSP6-3-600 prepared in Example 3 at 2 A g -1 , which can maintain a reversible specific capacity of 142.1 mAh g -1 after 1000 consecutive cycles at a current density of 2 A g -1 , with a high coulombic efficiency (99.9%).

[0085] Reference Figure 9 Rate performance chart of sample COSP6-3-600 prepared in Example 3 and commercial hard carbon; it can be seen that the rate performance of the COSP6-3-600 sample is superior to that of the commercial hard carbon.

[0086] Reference Figure 10 Comparison chart of rate performance of sample CSCP6-1-600 prepared in Example 3 and sample COSP6-1-600 of Comparative Example 1.

[0087] Example 10

[0088] In this example, the nitrogen / oxygen / phosphorus co-doped carbon negative electrode in Example 3 and the existing carbon positive electrode are assembled into a sodium ion capacitor.

[0089] It is carried out in a glove box under high-purity argon atmosphere, and CR2016 type button shell is used for battery assembly. In the assembly of half-cell system, the prepared electrode is used as the working electrode, the corresponding metal sodium is used as the counter electrode, the glass fiber is used as the separator, and the 1M NaClO4 (EC / DEC, 1 / 1 vol.%) is used as the electrolyte. The assembly is carried out in the order of negative electrode shell-sodium sheet-separator-electrolyte-electrode sheet (COSP6-3-600)-gasket-elastic sheet-positive electrode shell, and then the negative electrode shell is upwardly sealed with a tablet press. After the battery is left to stand for 6 h to wait for the electrolyte to be completely soaked, the electrochemical test is carried out at 0.1 A g -1After 10 cycles under the specified current density, the battery was finally discharged to approximately 0.01V, maintaining the pre-metallized state of the negative electrode. Furthermore, the disassembly of the half-cell and the assembly of the sodium-ion capacitor were both completed within a glove box. The sodium-ion capacitor was assembled in the following order: negative electrode shell - pre-sodium-metallized COSP6-3-600 - separator - electrolyte - positive electrode plate - gasket - spring contact - positive electrode shell.

[0090] like Figure 11 The figure shows the electrochemical performance of a sodium-ion capacitor assembled with COSP6-3-600 as the negative electrode material and an existing carbon positive electrode as described in Example 3. It can be seen that the dual-carbon sodium-ion capacitor assembled with COSP6-3-600 as the negative electrode and activated carbon (KC4) as the positive electrode has excellent energy density and power density.

[0091] Where there is no conflict, the above embodiments and features described herein can be combined with each other.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing N / O / P co-doped porous carbon material, characterized in that, The method comprises the following steps: S1, mixing polysaccharide, crosslinking agent and deionized water, stirring uniformly to obtain a mixed solution, the molar ratio of amino in the polysaccharide to phosphate in the crosslinking agent is 1: (1-6); S2, drying the mixed solution obtained in step S1 to obtain a precursor; S3, placing the precursor obtained in step S2 in an inert atmosphere, and programming to heat to 600-800 ℃ for carbonization, then grinding and washing with hot water the black powder obtained, and drying to obtain the final product; The N / O / P co-doped porous carbon material contains nitrogen-containing groups and phosphorus-containing groups by element analysis, the nitrogen-containing groups include pyridine nitrogen, pyrrole nitrogen, graphite nitrogen and nitrogen oxide, and the phosphorus-containing groups include C3-P=O, C-P-O and C-O-P.

2. The production method according to claim 1, characterized by, In step S2, the drying is performed at 60-65℃ for 6-8 hours; in step S3, the rate of temperature increase is 3-5℃ / min -1 and the carbonization is performed at 600-800℃ for 2-3 hours.

3. The production method according to claim 1, wherein The polysaccharide includes any one of chitooligosaccharide, glucosamine, chitosan or chitin, etc. containing amino polysaccharide; the crosslinking agent includes any one of sodium hexametaphosphate, sodium tripolyphosphate, sodium pyrophosphate, trisodium phosphate, disodium hydrogen phosphate or sodium dihydrogen phosphate, etc. containing phosphate salt.

4. The N / O / P co-doped porous carbon material prepared by the method of any one of claims 1-3, characterized in that, The N content ranges from 10 to 15 wt. %, the O content ranges from 24 to 40 wt. %, the P content ranges from 1 to 10 wt. %, and the C content ranges from 35 to 65 wt. %.

5. The N / O / P co-doped porous carbon material of claim 4, wherein, The interlayer spacing d (002) of the (002) crystal plane measured by X-ray diffraction satisfies: 0.39 nm < d (002) < 0.43 nm.

6. The N / O / P co-doped porous carbon material of claim 4, wherein, The specific surface area SSA is measured by nitrogen adsorption-desorption and is comprised between 44 m 2 / g and 227 m 2 / g.

7. Use of the N / O / P co-doped porous carbon material according to any one of claims 4-6 in the preparation of a sodium ion battery negative electrode material.

8. A sodium-ion battery, characterized in that, A sodium ion battery negative electrode material prepared using the N / O / P co-doped porous carbon material according to any one of claims 4-6.

9. A sodium-ion capacitor comprising positive and negative electrode sheets, characterized by, The sodium ion capacitor negative electrode material includes a negative electrode material after pre-sodium treatment using the N / O / P co-doped porous carbon material according to any one of claims 4-6.

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