Method for regenerating alkali lignin as negative electrode material of sodium-ion battery, negative electrode material of sodium-ion battery

Abstract

The application provides a method for regenerating alkali lignin into a sodium ion battery negative material, and comprises the following steps: subjecting alkali lignin to heat treatment to obtain alkali lignin biochar; adding the alkali lignin biochar into a metal ion-containing aqueous solution containing Cd 2+ and Zn 2+ , using the alkali lignin biochar to adsorb Cd 2+ and Zn 2+ in the metal ion-containing aqueous solution, and obtaining alkali lignin biochar adsorbed with heavy metals; placing the alkali lignin biochar adsorbed with heavy metals and a sulfur source in a furnace body, introducing an inert gas into the furnace body to maintain an inert atmosphere in the furnace body, and performing sintering to obtain a sodium ion battery negative material, i.e., alkali lignin biochar loaded with Cd and Zn sulfides, wherein the gas flow direction of the inert gas is from the sulfur source to the alkali lignin biochar. The regenerated sodium ion battery negative material has good electrochemical performance and good application prospect. In addition, the method can realize resource utilization of alkali lignin, and has the advantages of rich raw materials, low sintering temperature, low energy consumption, low regeneration cost, and wide application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid waste resource utilization, and particularly relates to regenerated utilization of alkali lignin. BACKGROUND

[0002] Since the 21st century, the rapid consumption of fossil fuels has led to rapid global warming, and the development of green and friendly renewable energy is imminent. With the development of industry, a large amount of industrial solid waste is produced, and using waste as a cheap raw material to reduce costs and improve performance may be an important measure to solve this problem. Therefore, using waste biomass as an energy storage electrode material has great potential.

[0003] In recent years, many different waste biomasses have been used for lithium batteries, such as coffee grounds, wheat flour, and sisal fibers, which have achieved good results. According to the World Energy Statistics Review 2022, the price of lithium carbonate has risen by 58%, with an average of 11,000 US dollars per ton. The high price of lithium is not in line with our original intention of researching waste biomass, and sodium batteries as a substitute for lithium batteries have attracted people's attention. Unlike lithium, there is a rich storage of sodium on earth, so the cost is low. Although sodium ions are abundant and relatively inexpensive, the preparation cost of some high-performance negative electrode materials (such as hard carbon, transition metal oxides, etc.) is high, which directly affects the overall cost of the battery.

[0004] The prior art discloses some methods of using titanium-based composite materials and metal-organic frameworks as negative electrode materials for sodium ion batteries. However, the price is expensive, the preparation process is complex, and it is not suitable for large-scale application. Hard carbon, as the most widely used negative electrode material for sodium ion batteries, although the raw material cost of hard carbon is not high, but the preparation process is complex and the energy consumption is high, which increases the cost of the final product. SUMMARY

[0005] To solve the above technical problems, the application provides a method for regenerating alkali lignin as a negative electrode material for a sodium ion battery and a negative electrode material for a sodium ion battery.

[0006] To achieve the above-mentioned purpose, the application provides the following solutions:

[0007] In a first aspect, a method for regenerating alkali lignin as a negative electrode material for a sodium ion battery is provided, comprising:

[0008] The alkali lignin is subjected to heat treatment to obtain alkali lignin biochar; the alkali lignin biochar is added to an aqueous solution containing metal ions containing Cd 2+ and Zn 2+ , and the alkali lignin biochar is used to adsorb Cd 2+ and Zn 2+The heavy metal ions are adsorbed on the alkali lignin biochar; the alkali lignin biochar adsorbed with the heavy metal ions and a sulfur source are placed in a furnace body, inert gas is introduced into the furnace body to maintain an inert atmosphere in the furnace body, sintering is carried out, and alkali lignin biochar loaded with Cd and Zn sulfides are obtained, and the flow direction of the inert gas is from the sulfur source to the alkali lignin biochar.

[0009] As preferred, the molar concentration ratio of Cd 2+ and Zn 2+ in the metal ion-containing aqueous solution is 2.8-3.3:1.

[0010] As preferred, the concentration of Cd 2+ ions in the metal ion-containing aqueous solution is 150-1200 ppm.

[0011] As preferred, the adsorption time is 1-2 h; and the adsorption is carried out under the assistance of mechanical force.

[0012] As preferred, after the adsorption treatment, a step of drying the alkali lignin biochar adsorbed with the heavy metal ions is further included.

[0013] As preferred, when the alkali lignin biochar is used to adsorb Cd 2+ and Zn 2+ ions in the metal ion-containing aqueous solution, the dosage of the alkali lignin biochar is 0.1-0.3 g per 100 mL of the metal ion-containing aqueous solution.

[0014] As preferred, the sulfur source is thiourea; and the mass ratio of the sulfur source to the alkali lignin biochar is 2:1-5:1.

[0015] As preferred, the sintering temperature is 500-700℃; and the sintering time is 1-4 h.

[0016] As preferred, the preparation method of the alkali lignin biochar comprises: subjecting alkali lignin to microwave sintering carbonization under an inert gas atmosphere to obtain alkali lignin biochar.

[0017] As preferred, after carbonization, grinding is carried out; and preferably, the particle size of the obtained alkali lignin biochar is less than 100 mesh.

[0018] As preferred, the obtained alkali lignin biochar is stored in a vacuum environment.

[0019] As preferred, the microwave sintering temperature is 400-500℃; and the microwave sintering time is 15-60 minutes.

[0020] As preferred, the Cd and Zn sulfides loaded on the alkali lignin biochar obtained by sintering are also subjected to PDA (polydopamine) coating modification.

[0021] As preferred, the Cd and Zn sulfides are Cd 7.23 Zn 2.77 S 10 .

[0022] In a second aspect, a sodium ion battery negative electrode material is provided, which is prepared by the method described above.

[0023] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects:

[0024] The Cd and Zn sulfides loaded on the alkali lignin biochar negative electrode material of the sodium ion battery regenerated by the method have good electrochemical performance and good application prospect.

[0025] The method can use alkali lignin and other agricultural wastes as carbon-based materials, and regenerate them into sodium ion battery negative electrode materials. The raw materials required by the treatment method are abundant, the sintering temperature is low, the required energy consumption is low, and the cost required for regeneration is low, so the method can be widely applied. The treatment method can realize the resource utilization of alkali lignin which accounts for a large proportion in agricultural wastes. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0027] Figure 1 XRD pattern of the composite negative electrode material prepared in Example 1, 2, 3.

[0028] Figure 2 SEM pattern of the composite negative electrode material prepared in Example 1 under different magnifications.

[0029] Figure 3 The (a) charge-discharge curves of the first three circles and (b) cycle performance curves of the coin cell assembled by the composite negative electrode material prepared in Example 1 at 100 mA / g.

[0030] Figure 4 The (a) charge-discharge curves of the first three circles and (b) cycle performance curves of the coin cell assembled by the composite negative electrode material prepared in Example 1 at 500 mA / g.

[0031] Figure 5 SEM images of the composite anode material prepared for Example 2 at different magnifications.

[0032] Figure 6 Surface distribution element analysis of the composite anode material prepared for Example 2.

[0033] Figure 7 Charge-discharge curves of the first three cycles (a) and cycle performance curves (b) of the coin cell assembled with the composite anode material prepared for Example 2 at 100 mA / g.

[0034] Figure 8 Charge-discharge curves of the first three cycles (a) and cycle performance curves (b) of the coin cell assembled with the composite anode material prepared for Example 2 at 500 mA / g.

[0035] Figure 9 SEM images of the composite anode material prepared for Example 3 at different magnifications.

[0036] Figure 10 Charge-discharge curves of the first three cycles (a) and cycle performance curves (b) of the coin cell assembled with the composite anode material prepared for Example 3 at 100 mA / g.

[0037] Figure 11 Charge-discharge curves of the first three cycles (a) and cycle performance curves (b) of the coin cell assembled with the composite anode material prepared for Example 3 at 500 mA / g.

[0038] Figure 12 Cycle performance curves of the coin cell assembled with the anode material prepared for Comparative Example 1 at 500 mA / g.

[0039] Figure 13 Cycle performance curves of the coin cell assembled with the anode material prepared for Comparative Example 2 at 100 mA / g.

[0040] Figure 14 Cycle performance curves of the coin cell assembled with the anode material prepared for Comparative Example 3 at 100 mA / g.

[0041] Figure 15 Cycle performance curves of the coin cell assembled with the coated modified composite anode material prepared for Example 4 at 100 mA / g. DETAILED DESCRIPTION

[0042] In view of the high cost problem of using hard carbon as negative electrode material in the prior art, the applicant attempts to use common waste alkali lignin to regenerate biochar as negative electrode material. However, the applicant found that the capacity of alkali lignin biochar obtained by conventional heat treatment is extremely low when used as negative electrode material. In view of this phenomenon, the applicant found that after adsorbing cadmium ions and zinc ions on the obtained alkali lignin biochar and high-temperature sulfidation, the prepared alkali lignin biochar loaded with Cd 7.23 Zn 2.77 S 10 The electrical performance of the negative electrode material is greatly improved. Based on this, the present application is completed.

[0043] The method for regenerating alkali lignin as a negative electrode material of a sodium ion battery comprises the following steps:

[0044] The alkali lignin is heat treated to obtain alkali lignin biochar; the alkali lignin biochar is added into a metal ion-containing aqueous solution containing Cd 2+ and Zn 2+ , the Cd 2+ and Zn 2+ ions in the metal ion-containing aqueous solution are adsorbed on the alkali lignin biochar to obtain alkali lignin biochar adsorbed with heavy metals; the alkali lignin biochar adsorbed with heavy metals and a sulfur source are placed in a furnace body, inert gas is introduced into the furnace body to maintain an inert atmosphere in the furnace body, sintering is performed to obtain an alkali lignin biochar loaded with Cd and Zn sulfide negative electrode material, and the gas flow direction of the inert gas is from the sulfur source to the alkali lignin biochar.

[0045] In some preferred embodiments, the molar concentration ratio of Cd 2+ and Zn 2+ in the metal ion-containing aqueous solution is 2.8-3.3:1.

[0046] In some preferred embodiments, the concentration of Cd 2+ ions in the metal ion-containing aqueous solution is 150-1200 ppm.

[0047] In some preferred embodiments, the adsorption time is 1-4 h; and the adsorption is performed under the assistance of mechanical force, which can be realized by, for example, shaking, ultrasonic or stirring.

[0048] In some preferred embodiments, after the adsorption treatment, the alkali lignin biochar adsorbed with heavy metals is dried.

[0049] In some preferred embodiments, the Cd2+ and Zn 2+ When the metal ions are Zn2+, the dosage of the alkali lignin biochar is 0.1-0.3 g per 100 mL of the aqueous solution containing the metal ions.

[0050] In some preferred embodiments, the sulfur source is thiourea; and the mass ratio of the sulfur source to the alkali lignin biochar is 2:1-4:1.

[0051] In some preferred embodiments, the sintering temperature is 500-700℃; and the sintering time is 1-4 h.

[0052] In some preferred embodiments, the method for preparing the alkali lignin biochar comprises: subjecting alkali lignin to microwave sintering carbonization under an inert gas atmosphere to obtain the alkali lignin biochar.

[0053] Preferably, the obtained alkali lignin biochar is ground after carbonization; and preferably, the particle size of the alkali lignin biochar obtained after grinding is less than 100 mesh.

[0054] Preferably, the obtained alkali lignin biochar is stored in a vacuum environment.

[0055] In some preferred embodiments, the microwave sintering temperature is 400-500℃; and the microwave sintering time is 15-60 minutes.

[0056] In some preferred embodiments, the inert gas is one or both of nitrogen and argon.

[0057] The sintering can be performed in a tube furnace, and the time for which the tube furnace is subjected to argon flow should be determined according to the volume of the tube furnace and the rate of argon flow, and should be at least more than 30 minutes. The tube furnace can also be replaced by a furnace that can provide a high-vacuum environment or an argon-filled environment and high temperature.

[0058] In some preferred embodiments, the method further comprises PDA coating modification of the sulfides of Cd and Zn loaded on the alkali lignin biochar obtained by sintering. The PDA coating modification can be performed by using existing conventional coating methods, for example, a tris-hydroxymethyl aminomethane hydrochloride buffer solution is prepared, then hydrochloric acid dopamine is added, mixed uniformly to obtain a hydrochloric acid dopamine solution, then the negative electrode material is added to the hydrochloric acid dopamine solution, after stirring and reaction, washing and drying, a PDA-coated modified composite negative electrode material is obtained.

[0059] The application also provides a sodium ion battery negative electrode material, which is prepared by using the method described above. Preferably, the sodium ion battery negative electrode material is a composite material of alkali lignin biochar and Cd 7.23 and Zn 2.77 S 10 a composite material of the negative electrode material, and the Cd 7.23 and Zn2.77 S 10 The negative electrode material is loaded on the alkali lignin biochar.

[0060] For the purpose of facilitating the understanding of the present application, the present application will be described in more detail below in conjunction with the drawings and preferred embodiments, but the scope of protection of the present application is not limited to the following specific embodiments.

[0061] Example 1

[0062] The alkali lignin was placed in a porcelain boat and heated at 400°C for 15 minutes in a microwave tube furnace under argon atmosphere to obtain alkali lignin biochar. The alkali lignin biochar was ground with a corundum mortar to obtain finer particles, which were then sieved and vacuum-sealed in a bag for storage.

[0063] A 1L Cd 2+ metal solution with an ion concentration of 150 ppm, Zn 2+ metal solution with an ion concentration of 50 ppm. 0.4 g of alkali lignin biochar was weighed into 200 mL of the metal solution, shaken for 1 h, filtered, and dried in an oven at 60°C to obtain material 1.

[0064] The porcelain boat containing material 1 was placed in a tube furnace, and a porcelain boat containing 0.8 g of thiourea was placed beside it (air inlet end). After purging the air, the obtained negative electrode material was sulfidized at 700°C for 2 h under argon atmosphere. Figure 1 The XRD pattern of the obtained negative electrode material is shown in Figure 1 It can be seen that the obtained negative electrode material has Cd 7.23 Zn 2.77 S 10 characteristic peaks of the material, and no characteristic peaks of ZnS and CdS can be seen. Combined with the raw material, it can be determined that the finally prepared negative electrode material is a composite material of carbon and Cd 7.23 Zn 2.77 S 10 material. The SEM images of the obtained negative electrode material at different magnifications (5000 times and 20000 times) are shown in Figure 2 From Figure 2 It can be seen that the obtained composite negative electrode material is in a granular form when the metal ion concentration in the metal solution is low.

[0065] The obtained negative electrode material was assembled into a sodium ion button-type half-cell for charge and discharge tests.

[0066] The prepared electrode sheet was transferred into an inert atmosphere glove box, and button cell assembly components were prepared: negative electrode shell, metal sodium sheet, separator, gasket, spring sheet, positive electrode shell, electrolyte, and sheet pressing mold, pipette, and insulating tweezers.

[0067] Assembly process: Place the negative shell on the insulating table, place the metal sodium sheet in the center of the negative shell, and flatten the metal sodium sheet with the tablet mold, then place the separator on the upper layer of the sodium sheet, and use a pipette to add an appropriate amount of electrolyte to the surface of the separator. Use an insulating tweezer to place the test electrode, gasket, spring sheet and positive shell on the upper layer of the separator in turn. Place the button cell with the negative side up on the button cell sealing machine mold with an insulating tweezer. Paper towels can be used to pad the top of the battery to absorb the spilled electrolyte. Adjust the pressure and press for 30 s to complete the assembly of the button cell. Take it out with an insulating tweezer, observe whether the appearance is complete, and wipe it clean with a paper towel.

[0068] The (a) first three cycles of charge-discharge curves and (b) cycle performance curves of the button cell assembled by the negative electrode material prepared in this example at 100 mA / g are shown in Figure 3 , the (a) first three cycles of charge-discharge curves and (b) cycle performance curves at 500 mA / g are shown in Figure 4 .

[0069] From Figure 3 and Figure 4 , it can be seen that when discharged at a constant current of 100 mA, the first discharge capacity is measured to be 658 mAh / g, and after 100 cycles, the discharge capacity is 178 mAh / g; when discharged at a constant current of 500 mA, the first discharge capacity is measured to be 615 mAh / g, and after 100 cycles, the discharge capacity is 156 mAh / g.

[0070] Example 2

[0071] Place the alkali lignin in a porcelain boat and heat it at 400°C for 15 minutes in a microwave tube furnace under an argon atmosphere to obtain alkali lignin biochar. Grind with a maroon mortar to obtain finer particles, then sieve and store in a vacuum-sealed bag.

[0072] Prepare 1L Cd 2+ ion concentration of 300 ppm, Zn 2+ ion concentration of 100 ppm metal solution. Weigh 0.4 g of alkali lignin biochar and place it in 200 mL of metal solution, shake for 1 h, filter, and dry in an oven at 60°C to obtain material 1.

[0073] Place the porcelain boat containing material 1 into a tube furnace, and place a porcelain boat containing 0.8 g of thiourea beside it (air inlet end), pass high-purity argon, and after removing the air in the tube furnace, sulfide at 700°C for 2 h under an argon atmosphere to obtain a negative electrode material. The XRD pattern of the obtained negative electrode material is shown in Figure 1 , from Figure 1 , it can be seen that the obtained negative electrode material has Cd 7.23 Zn 2.77 S 10The characteristic peaks of the material can be seen, and the characteristic peaks of ZnS and CdS cannot be seen, and combined with the raw material, it can be determined that the finally prepared negative electrode material is carbon and Cd 7.23 Zn 2.77 S 10 The composite material of the material. The SEM images of the obtained negative electrode material at different magnifications (5000 times and 20000 times) are as shown in Figure 5 From Figure 5 It can be seen that as the concentration of metal ions in the metal solution increases, the obtained composite negative electrode material appears rod-shaped crystals. The surface distribution composition analysis diagram of the obtained negative electrode material is as shown in Figure 6 From Figure 6 It can be seen that the Cd, Zn and S elements in the prepared negative electrode material are uniformly distributed.

[0074] The obtained negative electrode material is assembled into a sodium ion button-type half cell, and a charge-discharge test is carried out.

[0075] The charge-discharge curves of the first three circles of the button-type battery assembled by the negative electrode material prepared in this embodiment at 100mA / g (a) and the cycle performance curves (b) are as shown in Figure 7 The charge-discharge curves of the first three circles at 500mA / g (a) and the cycle performance curves (b) are as shown in Figure 8

[0076] From Figure 7 and Figure 8 It can be seen that when the assembled button-type battery is discharged at a constant current of 100mA, the initial discharge capacity is 735mAh / g, the discharge specific capacity is about 270mAh / g after 50 cycles, and the discharge capacity is 211mAh / g after 100 cycles; when discharged at a constant current of 500mA, the initial discharge capacity is 676mAh / g, and the discharge capacity is 185mAh / g after 100 cycles.

[0077] Example 3

[0078] The alkali lignin is placed in a porcelain boat and heated at 400℃ for 15 minutes in a microwave tube furnace under an argon atmosphere to obtain alkali lignin biochar. The fine particles are obtained by grinding with a maroon mortar, and then sieved and vacuum sealed in a bag for storage.

[0079] Prepare a metal solution of 1L Cd 2+ ion concentration is 600ppm, Zn 2+ ion concentration is 200ppm. 0.4 g of alkali lignin biochar is weighed and placed in 200mL of metal solution, shaken for 1h, filtered, and dried in an oven at 60℃ to obtain material 1.

[0080] ​The porcelain boat containing material 1 was placed in a tube furnace, and a porcelain boat containing 0.8 g of thiourea was placed beside it (air inlet end), high-purity argon was passed, after the hollow air was removed, the obtained negative electrode material was obtained by sulfidation treatment at 700°C for 2 h under an argon atmosphere. The XRD pattern of the obtained negative electrode material is shown in Figure 1 From Figure 1 It can be seen that the obtained negative electrode material has Cd 7.23 Zn 2.77 S 10 characteristic peaks of the material, and the characteristic peaks of ZnS and CdS cannot be observed, and combined with the raw material, it can be determined that the finally prepared negative electrode material is a composite material of carbon and Cd 7.23 Zn 2.77 S 10 material. It can be seen from the XRD patterns of the negative electrode materials obtained in Comparative Examples 1-3 that changing the concentration does not affect the generation of the crystal phase.

[0081] The SEM images of the obtained negative electrode material at different magnifications (5000 times and 20000 times) are shown in Figure 9 From Figure 9 It can be seen that as the concentration of metal ions in the metal solution further increases, the material clusters into spheres. It is found that the morphology of the negative electrode material prepared in Comparative Examples 1-3 changes as the concentration of metal ions changes, and after analysis, this rod-shaped and spherical morphology substance corresponds to the sulfide in the composite material.

[0082] The obtained negative electrode material was assembled into a sodium ion button-type half-cell, and charge-discharge test was performed.

[0083] The charge-discharge curves of the first three circles and the cycle performance curves of the button-type battery assembled by the negative electrode material prepared in this example at 100 mA / g are shown in Figure 10 (a) and (b) at 500 mA / g are shown in Figure 11 .

[0084] From Figure 10 and Figure 11 It can be seen that when the button-type battery assembled by the negative electrode material prepared in this example is discharged at a constant current of 100 mA, the measured initial specific discharge capacity is 680 mAh / g, and after 100 cycles, the specific discharge capacity is 144 mAh / g; when the button-type battery assembled by the negative electrode material prepared in this example is discharged at a constant current of 500 mA, the measured initial specific discharge capacity is 630 mAh / g, and after 100 cycles, the measured specific discharge capacity is 125 mAh / g.

[0085] Comparative Example 1

[0086] The alkali lignin was placed in a porcelain boat and heated at 400℃ for 15 minutes under argon atmosphere in a microwave tube furnace to obtain alkali lignin biochar. The alkali lignin biochar was ground into fine particles using a maroon mortar and then sieved and stored in a vacuum sealed bag.

[0087] The alkali lignin biochar was placed in a porcelain boat and heated at 400℃ for 15 minutes under argon atmosphere in a microwave tube furnace to obtain alkali lignin biochar. The alkali lignin biochar was ground into fine particles using a maroon mortar and then sieved and stored in a vacuum sealed bag.

[0088] The obtained negative electrode material was assembled into a sodium ion button half cell for charge and discharge test.

[0089] The cycle performance curve of the sodium ion button half cell assembled with the negative electrode material prepared in Comparative Example 1 at 500 mA / g is shown in FIG. 2. Figure 12 As shown in FIG. 2, the cycle performance curves of the examples and Comparative Example 1 were compared, and it can be seen that the electrical properties of the alkali lignin biochar modified by the composite in each example were greatly improved.

[0090] Comparative Example 2

[0091] The alkali lignin was placed in a porcelain boat and heated at 400℃ for 15 minutes under argon atmosphere in a microwave tube furnace to obtain alkali lignin biochar. The alkali lignin biochar was ground into fine particles using a maroon mortar and then sieved and stored in a vacuum sealed bag.

[0092] A 1L Cd 2+ ion solution with a concentration of 400 ppm was prepared. 0.4 g of alkali lignin biochar was placed in 200 mL of the metal solution, shaken for 1 h, filtered, and dried in an oven at 60℃ to obtain material 1.

[0093] The porcelain boat containing material 1 was placed in a tube furnace, and a porcelain boat containing 0.8 g of thiourea was placed beside it (on the gas inlet side). After purging the air, the negative electrode material was obtained by sulfidation treatment at 700℃ for 2 h under argon atmosphere.

[0094] The obtained negative electrode material was assembled into a sodium ion button half cell for charge and discharge test.

[0095] The cycle performance curve of the sodium ion button half cell assembled with the negative electrode material prepared in Comparative Example 2 at 100 mA / g is shown in FIG. 4. Figure 13 As shown in FIG. 4, the cycle performance curves of Comparative Example 2 and Example 2 were compared, and it can be seen that the electrical properties of the alkali lignin biochar modified by the composite in Example 2 were obviously improved compared to the alkali lignin biochar modified by single CdS. Figure 13 As shown in FIG. 4, the cycle performance curves of Comparative Example 2 and Example 2 were compared, and it can be seen that the electrical properties of the alkali lignin biochar modified by the composite in Example 2 were obviously improved compared to the alkali lignin biochar modified by single CdS.

[0096] Comparative Example 2 and Example 2 were compared, and it can be seen that the electrical properties of the alkali lignin biochar modified by the composite in Example 2 were obviously improved compared to the alkali lignin biochar modified by single CdS.

[0097] Comparative Example 3

[0098] The alkali lignin was placed in a porcelain boat and heated at 400°C for 15 minutes in a microwave tube furnace under argon atmosphere to obtain alkali lignin biochar. The alkali lignin biochar was ground with a corundum mortar to obtain finer particles, which were then sieved and stored in a vacuum-sealed bag.

[0099] A 1 L Zn 2+ The metal solution had an ion concentration of 400 ppm. 0.4 g of alkali lignin biochar was weighed into 200 mL of the metal solution, shaken for 1 h, filtered, and dried in an oven at 60°C to obtain material 1.

[0100] The porcelain boat containing material 1 was placed in a tube furnace, and a porcelain boat containing 0.8 g of thiourea was placed beside it (air inlet end). After purging the hollow with high-purity argon, the negative electrode material was obtained by sulfidation treatment at 700°C for 2 h under argon atmosphere.

[0101] The obtained negative electrode material was assembled into a sodium-ion button half-cell for charge-discharge testing.

[0102] The cycle performance curve of the sodium-ion button half-cell assembled with the negative electrode material prepared in Comparative Example 3 at 100 mA / g is shown in Figure 14 As can be seen from Figure 14 , the initial discharge specific capacity was about 729 mAh / g, and the discharge specific capacity after 50 cycles was about 190 mAh / g.

[0103] Comparing the button cells assembled with Comparative Example 2 and Comparative Example 3, it can be seen that the electrical performance of the composite-modified alkali lignin biochar prepared in Example 2 was significantly improved compared to the single ZnS-modified alkali lignin biochar.

[0104] Comparing the electrical performance of the button cells assembled with the modified alkali lignin biochar of Comparative Example 2, Comparative Example 2, and Comparative Example 3, it can be found that the electrical performance of the composite-modified alkali lignin biochar is better than that of the CdS-modified alkali lignin biochar of Comparative Example 2, and the modification effect is more significant than that of the single ZnS-modified alkali lignin biochar of Comparative Example 3.

[0105] Example 4

[0106] The difference between this example and Example 2 is that it further includes the step of continuing PDA coating modification of the prepared composite-modified alkali lignin biochar negative electrode material, which specifically includes:

[0107] First, 100 mL of 10 mmol / L Tris-HCl buffer solution was prepared, and the pH was adjusted to 8.5 with 0.1 mol / L hydrochloric acid; then 0.2 g of dopamine hydrochloride was added and ultrasonicated for 5 min; 1 g of the composite material prepared in Example 2 was added to the dopamine hydrochloride solution, and stirred at room temperature for 24 h. After washing with ultrapure water, it was placed in a 60°C oven for drying for 12 h, and then bagged for storage.

[0108] The cycle performance curve of the obtained coated modified composite negative electrode material assembled in a button cell at a current density of 100 mA / g is shown in FIG. 4, from which it can be seen that the initial specific discharge capacity of the battery is 753 mAh / g, and the specific discharge capacity after 50 cycles is about 286 mAh / g. Figure 15 Figure 15 It can be seen from the data of Comparative Example 2 and Example 4 that the cycle performance of the battery can be further improved by further coating modification with PDA, and analysis shows that this may be due to the inhibition of the expansion of the negative electrode material by PDA coating, which improves the structural stability thereof.

[0109] The above only describes the preferred embodiments of the present application, and it should be noted that those of ordinary skill in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.​

Claims

1. A method for the regeneration of alkali lignin as a negative electrode material for sodium-ion batteries, characterized by, The application relates to a method for preparing a sodium ion battery negative electrode material of alkali lignin biochar loaded with Cd and Zn sulfide. The alkali lignin is subjected to heat treatment to obtain alkali lignin biochar; the alkali lignin biochar is added into a metal ion-containing aqueous solution containing Cd 2+ and Zn 2+ , the alkali lignin biochar is used to adsorb Cd 2+ and Zn 2+ in the metal ion-containing aqueous solution, and alkali lignin biochar adsorbing heavy metals is obtained. The adsorption time is 1-2 hours; and the adsorption is carried out under the assistance of mechanical force.

2. The method of regenerating alkali lignin into sodium-ion battery anode material according to claim 1, characterized in that, Cd in the metal ion-containing aqueous solution 2+ and Zn 2+ at a molar concentration ratio of 2.8-3.3:1; Cd in the metal ion-containing aqueous solution 2+ The ion concentration is 150-1200 ppm.

3. The method of regenerating alkali lignin into sodium-ion battery anode material according to claim 1, characterized in that, The method further comprises a drying step of the alkali lignin biochar loaded with heavy metals after the adsorption treatment.

4. The method of regenerating alkali lignin into sodium-ion battery anode material according to claim 1, characterized in that, The sulfur source is thiourea; and the mass ratio of the sulfur source to the alkali lignin biochar is 2:1-5:

1.

5. The method of regenerating alkali lignin into sodium-ion battery anode material according to claim 1, characterized in that, The application discloses a method for adsorbing Cd ions in a metal ion-containing aqueous solution by using alkali lignin biochar 2+ and Zn 2+ ions, wherein the dosage of the alkali lignin biochar is 0.1-0.3 g per 100 mL of the metal ion-containing aqueous solution.

6. The method of regenerating alkali lignin into sodium-ion battery anode material according to claim 1, characterized in that, The sintering temperature is 500-700 DEG C; and the sintering time is 1-4 hours.

7. The method of regenerating alkali lignin into sodium-ion battery anode material according to claim 1, characterized in that, The preparation method of the alkali lignin biochar comprises the following steps: microwave sintering carbonization of alkali lignin under an inert gas atmosphere to obtain alkali lignin biochar.

8. The method of regenerating alkali lignin into sodium-ion battery anode material according to claim 1, characterized in that, The alkali lignin biochar obtained after the carbonization is ground; and the particle size of the alkali lignin biochar obtained after the grinding is less than 100 mesh.

9. The method of regenerating alkali lignin into sodium-ion battery anode material according to claim 8, characterized in that, The obtained alkali lignin biochar is stored in a vacuum environment. The microwave sintering temperature is 400-500 DEG C; and the microwave sintering time is 15-60 minutes.

10. The method of regenerating alkali lignin into sodium-ion battery anode material as claimed in claim 8, wherein the step of regenerating the alkali lignin into sodium-ion battery anode material is performed at a temperature ranging from 60 °C to 80 °C. The method further comprises PDA coating modification of the alkali lignin biochar loaded with Cd and Zn sulfide obtained after the sintering.

11. The method of regenerating alkali lignin into sodium-ion battery anode material as claimed in claim 1, wherein, The method is prepared by the method in any one of claims 1-12.

12. The method of regenerating alkali lignin into sodium-ion battery anode material as claimed in claim 1, wherein, The sulfides of Cd and Zn are Cd 7.23 Zn 2.77 S 10 .

13. A sodium-ion battery anode material, characterized in that, ​

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