Method for preparing hard carbon negative electrode material based on bi-crosslinking reaction of organic phosphoric acid and Schiff base and application of hard carbon negative electrode material in sodium battery

Abstract

The invention relates to a method for preparing a hard carbon negative electrode material based on a bi-crosslinking reaction of organic phosphoric acid and Schiff base and application of the hard carbon negative electrode material in a sodium battery. The method comprises the following steps: step 1, crosslinking biomass and organic phosphonic acid through a C-O-P bond; step 2, converting rich hydroxyl (-OH) in cellulose into aldehyde group (-CHO) through the oxidation effect of oxidizing acid on the material obtained in the step 1; step 3, carrying out secondary crosslinking on-CHO in the material obtained in the step 2 and-NH2 in the diamino compound through a Schiff base reaction; and 4, carbonizing the material obtained in the step 3 in an inert atmosphere at a high temperature, cooling, and assembling into the sodium ion battery. Compared with the prior art, the method has the following advantages: (1) the operation method is simple and reliable, the consumed time is short, and high-end instruments are not needed; and (2) the improvement efficiency is excellent, and large-scale production can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion batteries, and specifically relates to a method for preparing a hard carbon negative electrode material based on a double cross-linking reaction of organic phosphoric acid and Schiff base, and an application of the method in a sodium battery. Background Art

[0002] In recent years, there has been a worldwide consensus to reconstruct the energy system and pursue sustainable development, and replacing traditional fossil fuels with renewable energy is considered an effective strategy to achieve this goal. However, due to the intermittent nature of renewable energy (such as wind and solar energy), energy storage systems are required in practical applications to mitigate time domain limitations and relieve grid pressure. Batteries, as a portable chemical energy storage device with high conversion efficiency, have played a key role in many fields in recent years. In large-scale energy storage solutions, sodium-ion batteries have attracted much attention due to their abundant sodium resources, good low-temperature performance, and high cost-effectiveness potential.

[0003] The development of high-performance sodium-ion batteries depends largely on the progress of electrode materials, especially the anode materials, which are currently limited in choice. Therefore, the development of new anode materials that meet the special needs of sodium-ion batteries is crucial for their practical application. Among many carbon-based materials, hard carbon stands out as a candidate material for large-scale electrochemical energy storage. Hard carbon has a low operating voltage (<0.3V vs. Na + / Na), appropriate interlayer spacing (>0.34nm) and numerous sodium adsorption sites, showing a high theoretical sodium storage capacity, which is expected to significantly improve the energy density of sodium-ion batteries. However, hard carbon anodes still face some key challenges, such as small reversible capacity, low initial Coulombic efficiency, poor rate performance and limited long-cycle stability. Therefore, developing a simple and effective hard carbon preparation strategy is of great significance to promote the practical application of sodium-ion batteries. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of low reversible capacity, low first-cycle coulombic efficiency, and poor rate performance of hard carbon negative electrodes, and to provide a method for preparing hard carbon negative electrode materials based on a double cross-linking reaction of organic phosphoric acid and Schiff base and its application in sodium batteries, wherein organic phosphonic acid and organic amine are used as cross-linking agents in sequence to improve the micromorphology and electrochemical properties of biomass-derived hard carbon negative electrodes.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A method for preparing a hard carbon negative electrode material based on a double cross-linking reaction of an organic phosphoric acid and a Schiff base, the method comprising:

[0007] Step 1: biomass, organic phosphonic acid and water are mixed in a mass ratio of 1:1 to 2:8, stirred at room temperature for 10 hours, filtered, and dried in an oven for 12 hours to obtain a No. 1 precursor; in this step, the first cross-linking reaction occurs inside the biomass to generate a large number of COP groups;

[0008] Step 2: Precursor No. 1, oxidizing acid and water are mixed in a mass ratio of 1:1 to 2:8, stirred at room temperature for 10 hours, filtered, and placed in an oven to dry for 12 hours to obtain precursor No. 2; in this step, precursor No. 1 is oxidized with an oxidizing acid, and -OH is converted to -CHO for subsequent Schiff base reaction;

[0009] Step 3: The No. 2 precursor and the diamine compound undergo a Schiff base reaction to perform a second crosslinking. The No. 2 precursor, the diamine compound and water are mixed in a mass ratio of 1:1 to 2:8, and a Schiff base reaction is performed at 80°C. After stirring for 10 hours, a large amount of -RC=N- groups are generated. The precursor is filtered and placed in an oven to dry for 12 hours to obtain a No. 3 precursor.

[0010] Step 4: Add the No. 3 precursor into an alumina crucible, place it in a tubular furnace, introduce an inert gas as a protective gas, carbonize at high temperature, and cool naturally to obtain an N / P co-doped hard carbon negative electrode material.

[0011] Furthermore, in step one, the biomass includes at least one of agricultural by-products such as sesame shells, almond shells, corn cobs, and corn stalks.

[0012] Furthermore, in step 1, the organic phosphonic acid includes at least one of aminotri(methylenephosphonic acid), ethylenediaminetetra(methylenephosphonic acid), phytic acid, and phosphonoacetic acid.

[0013] Furthermore, in step 2, the oxidizing acid includes at least one of nitric acid, perchloric acid, and periodic acid.

[0014] Furthermore, in step three, the diamine compound includes at least one of ethylenediamine, 1,2-diaminobenzene, diethylenetriamine, and triethylenetetramine.

[0015] Furthermore, in step 4, the high temperature carbonization is specifically: heating from room temperature to 1200-1400° C. at a rate of 5° C. / min, and the heat preservation time is 2-3 hours.

[0016] An application of a hard carbon negative electrode material prepared by the above preparation method through a double cross-linking reaction in a sodium ion battery.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] (1) Based on this double cross-linking effect, the cellulose chains widely present in biomass can be closely arranged, and rich N / P elements can be in situ doped in the biomass, so that in the subsequent high-temperature carbonization, N / P co-doped hard carbon materials with lower specific surface area can be prepared. Based on the synergistic effect of the above two points, the prepared hard carbon materials can have higher reversible capacity, initial coulombic efficiency, cycle stability and excellent rate performance.

[0019] (2) The operation is simple and effective, takes little time and has low instrument requirements.

[0020] (3) The improvement effect is excellent and can be realized in large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a constant current charge and discharge diagram of a half-cell before and after double cross-linking in Example 1.

[0022] Figure 2 This is a constant current charge and discharge diagram of the half-cell before and after double cross-linking in Example 2.

[0023] Figure 3 This is a constant current charge and discharge diagram of the half-cell before and after double cross-linking in Example 3.

[0024] Figure 4 This is a half-cell rate performance diagram comparing before and after double cross-linking.

[0025] Figure 5 This is a comparison of the long cycle performance of the half-cell before and after double cross-linking.

[0026] The control group was a hard carbon negative electrode prepared without double cross-linking reaction. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described below in conjunction with the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0028] In the present invention, the biomass contains a large number of long cellulose chains, which can form POC bonds with PO in the organic phosphonic acid, thereby achieving cross-linking through the organic phosphonic acid, and combining the parallel long cellulose chains into a cellulose network. Thereafter, an oxidizing acid is used to oxidize a large number of -OH functional groups in the cellulose network into -CHO functional groups, and then placed in an aqueous solution of a diamine compound to undergo a Schiff base reaction, thereby further achieving cross-linking between chains.

[0029] Embodiment 1:

[0030] Step 1: Mix aminotri(methylenephosphonic acid), almond shell and water in a mass ratio of 1:1:8 in a beaker equipped with a magnetic stirrer. Stir at room temperature for 10 hours, filter, rinse with deionized water until neutral, and dry in an oven for 12 hours to obtain precursor No. 1.

[0031] Step 2: Mix precursor No. 1, nitric acid and water in a beaker equipped with a magnetic stirrer in a mass ratio of 1:2:8, stir at room temperature for 10 hours, filter, rinse with deionized water until neutral, and dry in an oven for 12 hours to obtain precursor No. 2.

[0032] Step 3: Mix precursor No. 2, ethylenediamine and water in a mass ratio of 1:2:8 in a beaker equipped with a magnetic stirrer, stir at 80°C for 10 hours, filter, rinse with deionized water several times, and dry in an oven for 12 hours to obtain precursor No. 3.

[0033] Step 4: Add 10g of precursor No. 3 into an alumina crucible, place it in a tubular furnace, introduce argon as a protective gas, heat to 1200°C at a rate of 5°C / min, keep warm for 3h, and cool naturally to obtain N / P co-doped hard carbon material.

[0034] Embodiment 2:

[0035] Step 1: Mix phytic acid, corn cobs and water in a beaker equipped with a magnetic stirrer in a mass ratio of 1:1:8, stir at room temperature for 10 hours, filter, rinse with deionized water until neutral, and dry in an oven for 12 hours to obtain precursor No. 1.

[0036] Step 2: Mix precursor No. 1, perchloric acid and water in a beaker equipped with a magnetic stirrer in a mass ratio of 1:1:8, stir at room temperature for 10 hours, filter, rinse with deionized water until neutral, and dry in an oven for 12 hours to obtain precursor No. 2.

[0037] Step 3: Mix precursor No. 2, 1,2-diaminobenzene and water in a mass ratio of 1:1:8 in a beaker equipped with a magnetic stirrer, stir at 80°C for 10 hours, filter, rinse with deionized water several times, and dry in an oven for 12 hours to obtain precursor No. 3.

[0038] Step 4: Add 10g of precursor No. 3 into an alumina crucible, place it in a tubular furnace, introduce argon as a protective gas, heat to 1300°C at a rate of 5°C / min, keep warm for 2h, and then cool naturally to obtain N / P co-doped hard carbon material.

[0039] Embodiment 3:

[0040] Step 1: Mix ethylenediaminetetramethylenephosphonic acid, sesame shells and water in a mass ratio of 1:2:8 in a beaker equipped with a magnetic stirrer. Stir at room temperature for 10 hours, filter, rinse with deionized water until neutral, and dry in an oven for 12 hours to obtain precursor No. 1.

[0041] Step 2: Mix precursor No. 1, periodic acid and water in a beaker equipped with a magnetic stirrer in a mass ratio of 1:2:8. Stir at room temperature for 10 hours, filter, rinse with deionized water until neutral, and dry in an oven for 12 hours to obtain precursor No. 2.

[0042] Step 3: Mix precursor No. 2, 1,2-diaminobenzene and water in a mass ratio of 1:1:8 in a beaker equipped with a magnetic stirrer, stir at 80°C for 10 hours, filter, rinse with deionized water several times, and dry in an oven for 12 hours to obtain precursor No. 3.

[0043] Step 4: Add 10g of precursor No. 3 into an alumina crucible, place it in a tubular furnace, introduce argon as a protective gas, heat to 1400°C at a rate of 5°C / min, keep warm for 2h, and then cool naturally to obtain N / P co-doped hard carbon material.

[0044] Comparative Example

[0045] The untreated biomass was washed with water to remove dust and ground into powder, and then directly placed in a tube furnace for high-temperature carbonization using the same process parameters as step 4 of Example 1.

[0046] The hard carbon materials prepared in the comparative example and the example are respectively used as negative electrode materials of sodium ion batteries and assembled into button batteries. The preparation method is as follows:

[0047] In 1000mg water, add 180mg sample, 10mg Super P (conductive agent), and 10mg carboxymethyl cellulose (binder), stir thoroughly for 30 minutes, evenly apply the mixed slurry on a flat copper foil, dry and slice to obtain the electrode; use 1mol / L NaPF6 diethylene glycol dimethyl ether solution as the electrolyte; use metallic sodium as the counter electrode.

[0048] Depend on Figures 1 to 3 It can be seen that the hard carbon negative electrodes prepared by the double cross-linking reaction in each embodiment have a larger reversible capacity and a higher first cycle coulombic efficiency (ICE) than those in the comparative example. Figure 4 This shows that Example 1 prepared by double cross-linking has significantly improved rate performance. Figure 5 This shows that the double cross-linking reaction also plays a significant role in improving the long-cycle performance of sodium-ion batteries.

Claims

1. A method for preparing a hard carbon negative electrode material based on a double cross-linking reaction of an organic phosphoric acid and a Schiff base, characterized in that: The method is: Step 1: biomass, organic phosphonic acid and water are mixed in a mass ratio of 1:1 to 2:8, stirred at room temperature for 10 hours, filtered, and dried in an oven for 12 hours to obtain a precursor No. 1; Step 2: Precursor No. 1, oxidizing acid and water are mixed in a mass ratio of 1:1 to 2:8, stirred at room temperature for 10 hours, filtered, and dried in an oven for 12 hours to obtain precursor No. 2; Step 3: Precursor No. 2, diamine compound and water are mixed in a mass ratio of 1:1 to 2:8, and a Schiff base reaction is carried out at 80°C. After stirring for 10 hours, the mixture is filtered and placed in an oven to dry for 12 hours to obtain precursor No. 3; Step 4: Add the No. 3 precursor into an alumina crucible, place it in a tubular furnace, introduce an inert gas as a protective gas, carbonize at high temperature, and cool naturally to obtain an N / P co-doped hard carbon negative electrode material.

2. The method for preparing a hard carbon negative electrode material based on a double cross-linking reaction of an organic phosphoric acid and a Schiff base according to claim 1, characterized in that: In step 1, the biomass includes at least one of agricultural by-products such as sesame shells, almond shells, corn cobs, and corn stalks.

3. The method for preparing a hard carbon negative electrode material based on a double cross-linking reaction of an organic phosphoric acid and a Schiff base according to claim 1, characterized in that: In step 1, the organic phosphonic acid includes at least one of aminotri(methylenephosphonic acid), ethylenediaminetetra(methylenephosphonic acid), phytic acid, and phosphonoacetic acid.

4. The method for preparing a hard carbon negative electrode material based on a double cross-linking reaction of an organic phosphoric acid and a Schiff base according to claim 1, characterized in that: In step 2, the oxidizing acid includes at least one of nitric acid, perchloric acid and periodic acid.

5. The method for preparing a hard carbon negative electrode material based on a double cross-linking reaction of an organic phosphoric acid and a Schiff base according to claim 1, characterized in that: In step three, the diamine compound includes at least one of ethylenediamine, 1,2-diaminobenzene, diethylenetriamine, and triethylenetetramine.

6. The method for preparing a hard carbon negative electrode material based on a double cross-linking reaction of an organic phosphoric acid and a Schiff base according to claim 1, characterized in that: In step 4, the high temperature carbonization is specifically: heating from room temperature to 1200-1400° C. at a rate of 5° C. / min, and the heat preservation time is 2-3 hours.

7. Use of a hard carbon negative electrode material prepared by the preparation method according to any one of claims 1 to 6 in a sodium ion battery.

Images