A heterogeneous hard carbon material, its preparation method and application
By preparing heterogeneous hard carbon materials using biomass aggregates, the problem of poor cycle stability of hard carbon materials in secondary batteries was solved, achieving high specific capacity and good rate performance, and applied to the anode of sodium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUANGDONG UNIV OF TECH
- Filing Date
- 2024-07-16
- Publication Date
- 2026-05-26
Smart Images
Figure CN119038517B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of materials technology, and particularly relates to a heterogeneous hard carbon material, its preparation method, and its application. Background Technology
[0002] With the rapid development of electric vehicles and the increasing demand for large-scale energy storage in the power grid, the demand for lithium and cobalt resources is rising rapidly, leading to increased raw material prices. As research into batteries continues, the commercialization of batteries is becoming increasingly urgent. Among the many materials available, hard carbon is the most mature and currently the only material with the potential for commercialization as a battery anode material.
[0003] Hard carbon has a low sodium storage voltage, many closed nanopores, high mechanical hardness, and its microstructure remains largely unchanged at different temperatures. It also exhibits stable electrochemical performance, low cost, and a larger interlayer spacing than graphite. Its amorphous structure can provide more defects than soft carbon, resulting in high performance.
[0004] Hard carbon also has drawbacks: its discharge voltage varies greatly with capacity, its initial charge-discharge efficiency is lower than that of graphitized carbon, and its cycle stability is poor. In practical applications, hard carbon anodes cannot simultaneously achieve high initial coulombic efficiency, high specific capacity, and good rate performance, mainly because the hard carbon structure is difficult to controllably adjust. Summary of the Invention
[0005] In view of this, the present invention provides a heterogeneous hard carbon material, its preparation method and application, which uses biomass as aggregate and introduces small molecules through a conduit structure to form a heterogeneous structure, effectively solving a series of problems such as structural instability of secondary battery negative electrode active materials during cycling.
[0006] The technical solution of this invention is implemented as follows:
[0007] A method for preparing a heterogeneous hard carbon material specifically includes the following steps:
[0008] S01. The biomass aggregate is ground into powder and sieved to obtain biomass aggregate powder. After washing, drying and ball milling, the sample before calcination is obtained.
[0009] S02. The sample before calcination is calcined in a calcining atmosphere to obtain a preliminary sample;
[0010] S03. The preliminary sample is washed with acid and alkali and then dried to obtain the sample after acid and alkali washing;
[0011] S04. The heterogeneous component mixture solution is ultrasonically broken, and then polymerized, condensed and refluxed to obtain the sample before carbonization;
[0012] S05. Carbonize the sample before carbonization in a carbonization atmosphere to obtain heterogeneous hard carbon material.
[0013] Preferably, in step S01,
[0014] The biomass aggregate is selected from walnut shells or bamboo;
[0015] The sieve mesh size is 100~400 mesh;
[0016] The drying temperature is 50~100℃.
[0017] More preferably, the biomass aggregate is walnut shell; the sieve mesh size is 200 mesh; and the drying temperature is 60 ℃.
[0018] Preferably, in step S02,
[0019] The calcination atmosphere is N2;
[0020] The calcination temperature is 300~600 ℃, the heating rate is 2~6 ℃ / min, and the calcination time is 1~4 h.
[0021] More preferably, the calcination temperature is 500 ℃; the heating rate is 5 ℃ / min; and the calcination time is 2 h.
[0022] Preferably, in step S03...
[0023] The acid-base washing includes acid washing and alkali washing. The acid washing uses an aqueous solution of hydrochloric acid, and the alkali washing uses an aqueous solution of sodium hydroxide.
[0024] The pickling process specifically involves adding 40-60 mL of hydrochloric acid and 40-60 mL of deionized water to the initial sample, pickling for 1-3 hours using a reflux condenser, and then rinsing three times with deionized water.
[0025] The alkaline washing process specifically involves using 10-30 g NaOH and 50-100 mL deionized water, reflux condensing for 2-5 hours, followed by filtration with deionized water and drying.
[0026] More preferably, the acid washing specifically involves adding 56.7 mL of hydrochloric acid and 43.3 mL of deionized water to the preliminary sample, and the acid washing time is 2 h; the alkaline washing specifically involves using 20 g of NaOH and 80 mL of deionized water, and the alkaline washing time is 4 h.
[0027] Preferably, in step S04...
[0028] The heterogeneous component mixture solution is a mixture of formaldehyde, resorcinol, the sample after acid and alkali washing, ammonia, anhydrous ethanol, and deionized water.
[0029] The amounts used in the heterogeneous component mixture solution are: 0.2~2 mL formaldehyde, 0.1~2 g resorcinol, 0.1~2 g sample after acid and alkali washing, 0.1~1 mL ammonia water, 1~100 mL anhydrous ethanol and 10~100 mL deionized water;
[0030] The ultrasonic fragmentation time is 1-3 hours;
[0031] The conditions for polymerization reflux are: polymerization reflux at 60~120 ℃ for 20~30 h.
[0032] The polymerization reflux is preferably carried out in a three-necked flask.
[0033] More preferably, the amounts of the heterogeneous component mixture solution are: 0.56 mL formaldehyde, 0.4 g resorcinol, 0.4 g acid-base washed sample, 0.2 mL ammonia, 16 mL anhydrous ethanol and 40 mL deionized water; the ultrasonic disruption time is 1 h; and the polymerization reflux conditions are: polymerization reflux at 100 °C for 24 h.
[0034] Preferably, in step S05...
[0035] The carbonization atmosphere is N2; the carbonization temperature is 1000~1400 ℃, and the carbonization time is 1~3 h.
[0036] More preferably, the carbonization temperature is 1200 °C and the carbonization time is 2 h.
[0037] A heterogeneous hard carbon material was obtained by the above preparation method.
[0038] The aforementioned heterogeneous hard carbon material is used in the negative electrode of a secondary battery; preferably, the heterogeneous hard carbon material is used in the negative electrode of a sodium-ion battery.
[0039] Compared with the prior art, the technical solution of the present invention has the following advantages:
[0040] This invention uses biomass aggregate as material and obtains heterogeneous hard carbon material through pulverization, ball milling, calcination, acid and alkali washing, polymerization, condensation and reflux, and carbonization. The obtained heterogeneous hard carbon material is applied to the negative electrode of sodium-ion batteries. After cycling the same number of times at different current densities, the charge-discharge specific capacity and capacity retention rate are both high. It can effectively solve the problem of structural instability of the battery negative electrode active material during cycling. Attached Figure Description
[0041] Figure 1The following are SEM images of BBHC-1200-N2 at different magnifications in the examples: (a) is a 35,000x SEM image of BBHC-1200-N2, (b) is a 65,000x SEM image of BBHC-1200-N2, and (c) is a 100,000x SEM image of BBHC-1200-N2. Detailed Implementation
[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0043] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.
[0044] This invention provides a heterogeneous hard carbon material, its preparation method, and its application, which can effectively solve problems such as instability that occur in some battery negative electrode active materials during cycling.
[0045] All raw materials used in the following examples are either commercially available or homemade.
[0046] Example 1
[0047] This invention provides a first method for preparing a heterogeneous hard carbon material, and applies the heterogeneous hard carbon material as a negative electrode active material in the preparation of a sodium-ion battery. The sodium-ion battery includes a negative electrode, a separator, an electrolyte, and a positive electrode. The negative electrode includes a negative electrode current collector and a negative electrode active material, with Whatman glass fiber used as the separator. The positive electrode includes a positive electrode current collector and a positive electrode active material. The specific preparation method is as follows:
[0048] 1. The preparation method of heterogeneous hard carbon materials is as follows:
[0049] 1.1 Crush the walnut shells into powder, pass them through a 200-mesh sieve, take 10 g of the walnut shell powder, dissolve the walnut shell powder in deionized water in a beaker, wash it three times with acetone and deionized water respectively, and dry it in an oven at 60 ℃. Roll the dried sample into powder using a mortar and pestle, weigh it, and divide it evenly into four ball mill jars. After ball milling, rinse the sample out of the ball mill jars with deionized water, collect it in a beaker, wash it three times with acetone and deionized water respectively, and dry it in an oven at 60 ℃ to obtain the sample before calcination.
[0050] 1.2. The dried sample before calcination was rolled into powder in a mortar and calcined in a tube furnace under a high-purity N2 atmosphere at 500 ℃. The heating rate was 5 ℃ / min. After calcination for 2 h, the sample was cooled to room temperature to obtain a preliminary sample.
[0051] 1.3 Add 56.7 mL of hydrochloric acid and 43.3 mL of deionized water, use a reflux condenser to acid wash for 2 h, then wash three times with a large amount of deionized water and dry. Then use 20 g of NaOH and 80 mL of deionized water to alkali wash for 4 h using a reflux condenser, then filter with a large amount of deionized water and dry to obtain the acid-alkali washed sample.
[0052] 1.4. 0.56 mL of formaldehyde, 0.4 g of resorcinol, 0.4 g of acid- and alkali-washed sample, 0.2 mL of ammonia, 16 mL of anhydrous ethanol and 40 mL of deionized water were ultrasonically crushed for 1 h, and then polymerized and refluxed at 100 °C for 24 h in a three-necked flask to obtain the sample before carbonization.
[0053] 1.5 Carbonization was carried out in a tube furnace under a high-purity N2 atmosphere at 1200 ℃ for 2 h, with a heating rate of 5 ℃ / min. After cooling to room temperature, a heterogeneous hard carbon material was obtained, labeled as WHC-XYZ (W is walnut shell, X is carbonization temperature, Y is carbonization atmosphere, and Z is the battery used).
[0054] 2. Preparation of negative electrode: The carbonized heterogeneous hard carbon material is used as the negative electrode active material, conductive carbon black is used as the conductive agent, and polytetrafluoroethylene (PTFE) is used as the binder. 6mg of sample, 3mg of conductive carbon black and 1mg of polytetrafluoroethylene (PTFE) are weighed in a mass ratio of 6:3:1. After being thoroughly ground in a mortar, the mixture is rolled into a round thin sheet and then covered on a 12mm diameter copper foam. After being compacted in a tablet press, it is placed in a vacuum drying oven and dried at 120℃ for later use as the negative electrode.
[0055] Preparation of diaphragm: Cut Whatman glass fiber diaphragm into 16mm diameter round pieces using a cutting machine, and dry them for later use as diaphragms;
[0056] Electrolyte preparation: 1.0 M NaPF6 in DME was prepared as the electrolyte using dimethyl ether (DME) as the solvent;
[0057] Preparation of the positive electrode: Roll out metallic sodium into a thin sheet and cut out a circular piece with a diameter of 12 mm as the positive electrode;
[0058] 4. Assembly: The prepared positive electrode, separator, and negative electrode are stacked tightly in sequence, and electrolyte is added to completely wet the separator. Then, the stacked parts are placed in a button cell packaging machine to seal them, thus completing the assembly of the sodium-ion battery.
[0059] Comparative Example 1
[0060] This invention provides a first control battery, which is prepared in a similar manner to Example 1. The difference is that the carbonization atmosphere used in this example is Ar or Ar / H2, which is used as the active material of the negative electrode of the sodium-ion battery. The rest is the same as in Example 1.
[0061] Comparative Example 2
[0062] This invention provides a second control battery, which is prepared in a similar manner to Example 1. The difference is that the carbonization temperature used in this example is 1000 ℃ and 1400 ℃, which are used as the active material for the negative electrode of the sodium-ion battery. The rest is the same as in Example 1.
[0063] Comparative Example 3
[0064] This invention provides a third control battery, the preparation method of which is similar to that of Example 1. The difference is that this example uses bamboo as the biomass aggregate as the active material for the negative electrode of the sodium-ion battery. Otherwise, it is the same as Example 1. A heterogeneous hard carbon material is obtained, labeled BBHC-XYZ (BB represents bamboo, X represents carbonization temperature, Y represents carbonization atmosphere, and Z represents the battery used).
[0065] Comparative Example 4
[0066] This invention provides a fourth control battery, which is prepared in a similar manner to Example 1. The difference is that the positive electrode used in this example is metallic lithium, which is used as the active material of the negative electrode of the lithium-ion battery. Otherwise, it is the same as Example 1.
[0067] Detection Example 1
[0068] Electrochemical performance tests were performed on the batteries of Example 1 and Comparative Examples 1-2:
[0069] Cyclic performance was tested using conventional battery testing methods. The charge-discharge specific capacity at different current densities and the capacity retention rate after different cycles were tested. The sodium-ion battery using walnut shells as biomass aggregate under different temperatures and atmospheres was labeled WHC-XY. The results are shown in Table 1. Table 1 shows the electrochemical performance of the batteries prepared in Example 1 and Comparative Examples 1-2 provided by the present invention. As can be seen from Table 1, the heterogeneous hard carbon anode active material of the sodium-ion battery provided by the present invention has a high charge-discharge specific capacity and capacity retention rate after the same number of cycles at different carbonization temperatures and different current densities. Compared with the carbonization atmosphere treatment with N2, the carbonization atmosphere treatment with Ar and Ar / H2 resulted in a decrease in both rate capability and number of cycles.
[0070] Table 1
[0071]
[0072] Detection Example 2
[0073] Electrochemical performance tests were conducted on the batteries of Example 1 and Comparative Examples 3-4:
[0074] The cycle performance was tested using conventional battery testing methods. The charge-discharge specific capacity at different current densities and the capacity retention rate after different cycles were tested. The results are shown in Table 2. Table 2 shows the electrochemical performance of the batteries prepared in Example 1 and Comparative Examples 3-4 provided by the present invention. The heterogeneous hard carbon with walnut shells and bamboo as biomass aggregates in the application scenario is labeled as WHC / BBHC-N2-Z. As can be seen from Table 2, the heterogeneous hard carbon anode active material provided by the present invention has a high charge-discharge specific capacity and capacity retention rate after the same number of cycles under different biomass aggregates, different application scenarios and different current densities.
[0075] like Figure 1 The images shown are SEM images of BBHC-1200-N2 at different magnifications; where: (a) is a SEM image of BBHC-1200-N2 at 35,000x magnification, (b) is a SEM image of BBHC-1200-N2 at 65,000x magnification, and (c) is a SEM image of BBHC-1200-N2 at 100,000x magnification.
[0076] Table 2
[0077]
[0078] Compared with the prior art, the technical solution of the present invention has the following advantages:
[0079] This invention uses biomass aggregate as material and obtains heterogeneous hard carbon material through pulverization, ball milling, calcination, acid and alkali washing, polymerization, condensation and reflux, and carbonization. The obtained heterogeneous hard carbon material is applied to the negative electrode of sodium-ion batteries. After cycling the same number of times at different current densities, the charge-discharge specific capacity and capacity retention rate are both high. It can effectively solve the problem of structural instability of the battery negative electrode active material during cycling.
[0080] 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, and improvements 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 of preparing a heterogeneous hard carbon material, characterized by: Specifically, the following steps are included: S01. The biomass aggregate is ground into powder and sieved to obtain biomass aggregate powder. After washing, drying and ball milling, the sample before calcination is obtained. S02. The sample before calcination is calcined in a calcining atmosphere to obtain a preliminary sample; S03. The preliminary sample is washed with acid and alkali and then dried to obtain the sample after acid and alkali washing; S04. The heterogeneous component mixture solution is ultrasonically broken, and then polymerized, condensed and refluxed to obtain the sample before carbonization; S05. Carbonize the sample before carbonization in a carbonization atmosphere to obtain heterogeneous hard carbon material. In step S04, the heterogeneous component mixture solution is a mixture of formaldehyde, resorcinol, the sample after acid and alkali washing, ammonia, anhydrous ethanol and deionized water. The amounts used in the heterogeneous component mixture solution are: 0.2~2 mL formaldehyde, 0.1~2 g resorcinol, 0.1~2 g sample after acid and alkali washing, 0.1~1 mL ammonia water, 1~100 mL anhydrous ethanol and 10~100 mL deionized water; The conditions for polymerization reflux are: polymerization reflux at 60~120 ℃ for 20~30 h.
2. The method of claim 1, wherein: In step S01, The biomass aggregate is selected from walnut shells or bamboo; The sieve mesh size is 100~400 mesh; The drying temperature is 50~100℃.
3. The method of claim 1, wherein: In step S02, The calcination atmosphere is N2; The calcination temperature is 300~600 ℃, the heating rate is 2~6 ℃ / min, and the calcination time is 1~4 h.
4. The method for preparing heterogeneous hard carbon material according to claim 1, characterized in that: In step S03, The acid-base washing includes acid washing and alkali washing. The acid washing uses an aqueous solution of hydrochloric acid, and the alkali washing uses an aqueous solution of sodium hydroxide.
5. The method for preparing heterogeneous hard carbon material according to claim 4, characterized in that: The pickling process specifically involves adding 40-60 mL of hydrochloric acid and 40-60 mL of deionized water to the initial sample, pickling for 1-3 hours using a reflux condenser, and then rinsing three times with deionized water. The alkaline washing process specifically involves using 10-30 g NaOH and 50-100 mL deionized water, reflux condensing for 2-5 hours, followed by filtration with deionized water and drying.
6. The method for preparing heterogeneous hard carbon material according to claim 1, characterized in that: In step S04, The ultrasonic fragmentation time is 1~3 hours.
7. The method for preparing heterogeneous hard carbon material according to claim 1, characterized in that: In step S05, The carbonization atmosphere is N2; the carbonization temperature is 1000~1400 ℃, and the carbonization time is 1~3 h.
8. A heterogeneous hard carbon material is obtained by the preparation method according to any one of claims 1-7.
9. The application of the heterogeneous hard carbon material according to claim 8 in the negative electrode of a sodium-ion battery.