Multi-component composite negative electrode material as well as preparation method and application thereof

Abstract

The embodiment of the invention relates to a multi-component composite negative electrode material as well as a preparation method and application thereof. The preparation method comprises the following steps: putting charcoal and an activated pore-forming agent into a ball-milling tank for ball-milling, putting a mixture subjected to ball-milling into a tubular furnace for carbonization, taking out the carbonized mixture, and carrying out acid pickling, suction filtration and drying to form porous carbon; weighing a proper amount of a lanthanum source and the porous carbon, ultrasonically dispersing the lanthanum source and the porous carbon into absolute ethyl alcohol to form a mixed solution, adding an organic ligand, a sulfur source and a coagulator into the mixed solution under a continuous stirring condition, and heating to a set temperature, so that a molecular chain of the coagulator is broken and dissolved, and the mixed solution forms sol; standing the sol at room temperature to obtain solid gel; placing the solid gel in a vacuum freeze dryer for pre-freezing, and then performing vacuum drying to obtain a lanthanum sulfide / porous carbon composite material precursor; and calcining the lanthanum sulfide / porous carbon composite material precursor in an inert atmosphere, and cooling to room temperature to obtain the lanthanum sulfide / porous carbon composite material.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy materials, and in particular to a multi-component composite negative electrode material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries are one of the new energy storage devices, with high energy density, high rate charging and excellent thermal stability. In order to further improve the electrochemical performance of lithium batteries, scientific researchers are committed to exploring efficient lithium-ion battery negative electrode materials.

[0003] Lanthanum sulfide is a binary alloy. Its unique electronic structure is mainly attributed to the fact that after sulfur atoms occupy the metal lattice, the interaction between metal atoms is weakened, the center of the d band is shifted, and the state density of the Fermi level is increased. Therefore, using lanthanum sulfide with unique physical and chemical properties as a negative electrode material for lithium batteries has the advantages of high initial discharge and reversible capacity, small electrode polarization, and outstanding cycle performance. However, single-phase lanthanum sulfide is not only very easy to agglomerate during the preparation process, but also after multiple cycles of charge / discharge, the material expands in volume, and the particles are crushed and detached; at the same time, the decomposition of the electrolyte continuously produces an unstable solid electrolyte interface, which seriously affects the battery cycle life and causes poor battery performance. Composite porous carbon with high specific capacity, good cycle stability and low price and lanthanum sulfide can improve the electrochemical activity of the material. However, conventional methods for preparing composite materials, such as wet stirring, may have uneven reactions and poor particle dispersion, which will affect the consistency of the materials obtained by the preparation method and may affect the electrochemical properties of the materials. Summary of the invention

[0004] The purpose of the present invention is to provide a multi-component composite negative electrode material and its preparation method and application, which can effectively alleviate the volume expansion after cyclic charge and discharge, prevent the composite negative electrode material from pulverizing and falling off; at the same time, it can also improve the conductivity of the composite negative electrode material, and improve the kinetics and electrochemical properties of the composite negative electrode material. The negative electrode material synthesized by the present invention has good reversible capacity, first coulomb efficiency and cycle stability, and the preparation method is simple, which is suitable for large-scale industrial production.

[0005] To this end, in a first aspect, an embodiment of the present invention provides a method for preparing a multi-component composite negative electrode material, comprising:

[0006] The biochar and the activated pore-forming agent are placed in a ball mill for ball milling, the ball-milled mixture is placed in a tube furnace for carbonization, and then taken out for acid washing, suction filtration, and drying to form porous carbon;

[0007] Weighing an appropriate amount of lanthanum source and the porous carbon and ultrasonically dispersing them in anhydrous ethanol to form a mixed solution, and adding an organic ligand, a sulfur source and a coagulant to the mixed solution under continuous stirring, heating the solution to a set temperature, so that the molecular chain of the coagulant is broken and dissolved, and the mixed solution forms a sol; and leaving the sol to stand at room temperature to obtain a solid gel;

[0008] The solid gel is placed in a vacuum freeze dryer for pre-freezing, and then vacuum dried to obtain a lanthanum sulfide / porous carbon composite material precursor;

[0009] The lanthanum sulfide / porous carbon composite material precursor is heat-treated under an inert atmosphere and then cooled to room temperature to obtain a lanthanum sulfide / porous carbon composite material, which is the multi-component composite negative electrode material.

[0010] Preferably, the biochar is formed by pre-carbonization using trees as a carbon source;

[0011] The tree includes one of eucalyptus, poinciana, sycamore, cypress and paulownia;

[0012] The pre-carbonization process is specifically as follows: placing the carbon source in a tubular furnace, heating the temperature to 400°C-600°C at a heating rate of 2°C / min-5°C / min under a nitrogen atmosphere, maintaining the temperature for 2h-4h, and forming biochar.

[0013] Preferably, the activated pore-forming agent comprises: at least one of potassium bicarbonate, sodium bicarbonate, potassium carbonate, sodium carbonate, and magnesium carbonate;

[0014] The addition ratio of the biochar to the activated pore-forming agent is 1:4-1:8 by mass;

[0015] The ball milling speed is 300-500 rpm, and the ball milling time is 0.2-1 h;

[0016] The carbonization process is specifically as follows: in a nitrogen atmosphere, heating to 800°C-1000°C at a heating rate of 2°C / min-10°C / min, and keeping the temperature for 2h-4h;

[0017] The acid washing specifically comprises: dispersing the sample in a 0.1 mol / L-1 mol / L hydrochloric acid solution, using a magnetic stirrer, maintaining a rotation speed of 300-500 rpm at 40° C.-80° C., and acid washing for 1-3 hours.

[0018] Preferably, the lanthanum source includes: one or more of lanthanum nitrate, lanthanum sulfate, and lanthanum chloride;

[0019] The mass ratio of the porous carbon to the lanthanum source is 1:0.2-1:0.8;

[0020] The solid-liquid ratio of the total mass of the porous carbon and the lanthanum source to anhydrous ethanol is 1 g / 50 mL;

[0021] The organic ligand includes: ethylenediaminetetraacetic acid;

[0022] The sulfur source includes: at least one of sodium sulfite and potassium sulfite;

[0023] The coagulant includes: one or more of agar, carrageenan, gelatin, gum arabic, pectin and xanthan gum;

[0024] The mass ratio of the lanthanum source to the organic ligand is 1:5-1:10;

[0025] The mass ratio of the lanthanum source to the sulfur source is 1:5-1:15;

[0026] The ratio of the total mass of the porous carbon, the lanthanum source and the sulfur source to the mass of the coagulant is 1:2-1:8;

[0027] The set temperature is 80°C-100°C, and the set temperature is maintained for 0.5h-1h.

[0028] Preferably, the pre-freezing temperature is -40°C and the time is 4-6h;

[0029] The vacuum drying time is 24-48h.

[0030] Preferably, the inert atmosphere is nitrogen or argon;

[0031] The heat treatment is specifically as follows: heating to 600°C-1000°C at a heating rate of 2°C / min-10°C / min, and keeping the temperature for 2h-8h.

[0032] In a second aspect, an embodiment of the present invention provides a multi-component composite negative electrode material prepared by the preparation method described in the first aspect above.

[0033] In a third aspect, an embodiment of the present invention provides a negative electrode plate, comprising the negative electrode material described in the second aspect above.

[0034] In a fourth aspect, an embodiment of the present invention provides a lithium-ion battery, wherein the lithium-ion battery comprises the negative electrode sheet described in the third aspect.

[0035] The method for preparing a multi-component composite negative electrode material provided in an embodiment of the present invention uses wood with a well-developed pore structure, rich pore structure, and high mechanical strength as a porous carbon precursor, and synthesizes a multi-component composite material by a sol-gel method, thereby alleviating the potential problems of single-phase porous carbon or lanthanum sulfide in volume expansion, low cycle life, and poor conductivity during use. In addition, the sol-gel method can significantly improve the dispersion and uniformity of lanthanum sulfide in porous carbon, and the vacuum drying technology can well avoid the agglomeration phenomenon during the material synthesis process. The combination of the two further improves the electrochemical performance of the composite negative electrode material, and it is expected to obtain a lithium battery negative electrode material with high capacity, high stability, high conductivity, and commercial application. The materials used in the preparation method provided in an embodiment of the present invention are low-cost and easy to obtain, the preparation process is simple to operate, the process time is short, and it is suitable for large-scale industrial development. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A flow chart of a method for preparing a multi-component composite negative electrode material provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0038] The present invention provides a method for preparing a multi-component composite negative electrode material. Figure 1 As shown, the main steps include:

[0039] Step 110, placing the biochar and the activated pore-forming agent in a ball mill for ball milling, placing the ball-milled mixture in a tube furnace for carbonization, taking it out for acid washing, filtering, and drying to form porous carbon.

[0040] Among them, biochar is formed by pre-carbonization using trees as carbon sources; the trees include one of eucalyptus, poinciana, sycamore, cypress, and paulownia; the pre-carbonization process is specifically as follows: placing the trees as carbon sources in a tubular furnace, heating them to 400°C-600°C at a heating rate of 2°C / min-5°C / min under a nitrogen atmosphere, maintaining for 2h-4h, to form biochar.

[0041] The activated pore-forming agent includes: at least one of potassium bicarbonate, sodium bicarbonate, potassium carbonate, sodium carbonate, and magnesium carbonate; the addition ratio of biochar to the activated pore-forming agent is 1:4-1:8 by mass.

[0042] The ball milling speed is 300-500rpm, and the ball milling time is 0.2-1h.

[0043] The specific carbonization process is: in a nitrogen atmosphere, heating to 800°C-1000°C at a heating rate of 2°C / min-10°C / min, and keeping the temperature for 2h-4h.

[0044] The acid pickling is specifically as follows: the sample is dispersed in a 0.1 mol / L-1 mol / L hydrochloric acid solution, and the sample is pickled for 1-3 hours at a temperature of 40°C-80°C and a rotation speed of 300-500 rpm using a magnetic stirrer.

[0045] Step 120, weigh appropriate amounts of lanthanum source and porous carbon and ultrasonically disperse them in anhydrous ethanol to form a mixed solution, and add organic ligands, sulfur sources and coagulants to the mixed solution under continuous stirring, and heat the mixture to a set temperature to break the molecular chains of the coagulant and dissolve it, so that the mixed solution forms a sol; and the sol is allowed to stand at room temperature to obtain a solid gel.

[0046] The lanthanum source includes one or more of lanthanum nitrate, lanthanum sulfate and lanthanum chloride, and the added amount is 1:0.2-1:0.8 according to the mass ratio of porous carbon to lanthanum source, and the solid-liquid ratio of the total mass of porous carbon and lanthanum source to anhydrous ethanol is 1g / 50mL.

[0047] The organic ligand includes ethylenediaminetetraacetic acid, the sulfur source includes at least one of sodium sulfite and potassium sulfite, and the coagulant includes one or more of agar, carrageenan, gelatin, gum arabic, pectin and xanthan gum. The added amount is based on the mass ratio of lanthanum source to organic ligand of 1:5-1:10, the mass ratio of lanthanum source to sulfur source of 1:5-1:15, and the total mass ratio of porous carbon, lanthanum source and sulfur source to the mass ratio of coagulant of 1:2-1:8.

[0048] The set temperature for breaking the molecular chain of the coagulant and dissolving it is 80°C-100°C, and the set temperature is maintained for 0.5h-1h.

[0049] Step 130, placing the solid gel in a vacuum freeze dryer for pre-freezing, and then vacuum drying to obtain a lanthanum sulfide / porous carbon composite material precursor.

[0050] The pre-freezing temperature is -40°C and the time is 4-6 hours; the vacuum drying time is 24-48 hours.

[0051] Step 140, heat-treating the lanthanum sulfide / porous carbon composite material precursor under an inert atmosphere, and then cooling it to room temperature to obtain a lanthanum sulfide / porous carbon composite material, which is a multi-component composite negative electrode material.

[0052] The inert atmosphere is nitrogen or argon, and the heat treatment is specifically as follows: heating to 600°C-1000°C at a heating rate of 2°C / min-10°C / min, and keeping the temperature for 2h-8h.

[0053] The multi-component composite material prepared by the preparation method of the embodiment of the present invention can be used as a negative electrode material for lithium-ion batteries and applied to lithium battery pole pieces and lithium batteries.

[0054] The above method of the present invention converts biochar into porous carbon through ball milling and carbonization steps, thereby increasing the specific surface area of ​​the material. The porous structure helps to increase the contact area between the electrode and the electrolyte, and improves the electrochemical performance of the electrode material; the addition of an activated pore-forming agent helps to further increase the pore structure of the porous carbon, improve the adsorption performance of the electrode, and enhance the diffusion rate of lithium ions in the electrode material; by introducing a lanthanum source, a proper amount of lanthanum source is compounded with porous carbon, which helps to improve the conductivity of the electrode material and the kinetic characteristics of lithium ion insertion / deinsertion reaction; the sol-gel method can significantly improve the dispersion and uniformity of lanthanum sulfide in porous carbon; the lanthanum sulfide / porous carbon composite material precursor is prepared by a vacuum freeze-drying method, which helps to retain the porous structure, prevent the collapse of the material, and can also well avoid the agglomeration phenomenon in the material synthesis process, further improving the electrochemical performance of the composite negative electrode material. The final heat treatment step is carried out under an inert atmosphere, which helps to form the final lanthanum sulfide / porous carbon composite material, and can achieve an ideal structure and performance by controlling a suitable heating rate and insulation time. The multi-component composite negative electrode material finally obtained by this method performs well in lithium-ion batteries, has high specific energy, long cycle life and good electrochemical properties, and can be used as a lithium battery negative electrode material with high capacity, high stability, high conductivity and commercial application.

[0055] In order to more clearly illustrate the purpose and advantages of the present invention, the present invention is further described below in conjunction with the embodiments. In addition, the embodiments described in the present invention are only partial embodiments. Based on the embodiments described in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present invention. In addition, it should be understood that these embodiments are only used for more detailed description and should not be understood as limiting the present invention in any form, that is, they are not intended to limit the protection scope of the present invention.

[0056] Example 1

[0057] This embodiment provides a method for preparing a multi-component composite negative electrode material and testing its performance, and the specific method is as follows.

[0058] Eucalyptus was placed in a tubular furnace, heated to 600°C at a heating rate of 2°C / min under a nitrogen atmosphere, and maintained for 2 hours to form biochar. 10g of biochar and 40g of potassium bicarbonate were weighed and placed in a ball mill, the speed was maintained at 400rpm, and the ball milling was performed for 0.5 hours. The mixture obtained by ball milling was placed in a tubular furnace, heated to 1000°C at 2°C / min under nitrogen, and maintained for 2 hours. The product was dispersed in a 0.5mol / L hydrochloric acid solution, at 60°C, the speed was 400rpm, acid washed for 2 hours, filtered, and dried to form porous carbon.

[0059] Weigh 5g of porous carbon and 1g of lanthanum nitrate and disperse them in 300mL of anhydrous ethanol, and ultrasonicate for 0.5h. Under continuous stirring, add 5g of ethylenediaminetetraacetic acid, 5g of sodium sulfite and 22g of agar to the mixed solution, heat it to 80℃, maintain it for 1h, dissolve the coagulant and form a sol; let the sol stand at room temperature to obtain a solid gel. The solid gel is placed in a vacuum freeze dryer, pre-frozen at -40℃ for 4h, and vacuum dried for 48h to obtain a lanthanum sulfide / porous carbon composite material precursor. The obtained precursor is heated to 600℃ at 10℃ / min in a nitrogen atmosphere, maintained for 8h, and cooled to room temperature to obtain a lanthanum sulfide / porous carbon composite material.

[0060] The multi-component composite negative electrode material prepared in this embodiment is used to prepare a negative electrode sheet and assemble a battery for testing. The specific process is as follows:

[0061] The prepared lanthanum sulfide / porous carbon composite material was used as a battery negative electrode material and weighed with conductive carbon black, sodium carboxymethyl cellulose and styrene-butadiene rubber in a mass ratio of 92%:2%:3%:3%, and evenly mixed using a beater in an aqueous solvent. The battery slurry was coated on a copper foil, dried, cut into pieces, and assembled into button-type half-cells in a glove box, and their electrochemical properties were evaluated.

[0062] The electrochemical test mode is: the first week is 0.1C discharge to 0.005V, 0.05C discharge to 0.005V, 0.02C discharge to 0.005V. After standing for 5s, charge to 1V at 0.1C. The subsequent cycles are 0.5C discharge to 0.005V, 0.2C discharge to 0.005V, 0.05C discharge to 0.005V, 0.02C discharge to 0.005V, and charge to 1V at 0.5C after standing for 5s.

[0063] The discharge in the above electrochemical test is the process of lithium insertion in the negative electrode, which corresponds to the charge in the full battery; the charge in the above electrochemical test is the process of lithium removal in the negative electrode, which corresponds to the discharge of the full battery.

[0064] The prepared negative electrode material was coated on copper foil in the same proportion as described above to prepare a negative electrode, and lithium cobalt oxide was used as the positive electrode to assemble a 1Ah soft-pack battery, and its cycle performance at 0.5C was tested.

[0065] The test results of the first-week charge and discharge coulomb efficiency of the half-cell prepared in this embodiment and the 100-week cycle capacity retention rate of the soft-pack battery are recorded in Table 1.

[0066] Example 2

[0067] Eucalyptus was placed in a tubular furnace, heated to 400°C at a heating rate of 5°C / min under a nitrogen atmosphere, and maintained for 4 hours to form biochar. 10g of biochar and 80g of potassium bicarbonate were weighed and placed in a ball mill, the speed was maintained at 400rpm, and the ball milling was performed for 0.5h. The mixture was placed in a tubular furnace, heated to 800°C at 10°C / min under nitrogen, and maintained for 4 hours. The product was dispersed in a 0.5mol / L hydrochloric acid solution, at 60°C, the speed was 400rpm, acid washed for 2 hours, filtered, and dried to form porous carbon.

[0068] Weigh 5g of porous carbon and 4g of lanthanum nitrate and disperse them in 450mL of anhydrous ethanol, and ultrasonicate for 0.5h. Under continuous stirring, add 20g of ethylenediaminetetraacetic acid, 24g of sodium sulfite and 99g of agar to the obtained mixed solution, heat it to 100℃, maintain it for 0.5h, dissolve the coagulant, form a sol, and let the sol stand at room temperature to obtain a solid gel. The solid gel is placed in a vacuum freeze dryer, pre-frozen at -40℃ for 6h, and vacuum dried for 40h to obtain a lanthanum sulfide / porous carbon composite material precursor. The obtained precursor is heated to 1000℃ at 2℃ / min in a nitrogen atmosphere, maintained for 2h, and cooled to room temperature to obtain a lanthanum sulfide / porous carbon composite material.

[0069] According to the test method of Example 1, the multi-component composite negative electrode material prepared in this example was used to prepare the electrode sheet and assembled the battery for testing. The test results are shown in Table 1.

[0070] Example 3

[0071] Place the royal poinciana in a tube furnace, and heat it to 560°C at a heating rate of 4°C / min in a nitrogen atmosphere, and maintain it for 2.5 hours to form biochar. Weigh 10g of biochar and 50g of potassium carbonate and place them in a ball mill, keep the speed at 400rpm, and ball mill for 0.5h. Place the mixture in a tube furnace, heat it to 900°C at 3°C / min under nitrogen, and maintain it for 3h. Disperse the product in a 0.5mol / L hydrochloric acid solution, at 60°C, at a speed of 400rpm, acid wash for 2h, filter and dry to form porous carbon.

[0072] Weigh 5g of porous carbon and 1g of lanthanum nitrate and disperse them in 300mL of anhydrous ethanol, and ultrasonicate for 0.5h. Under continuous stirring, add 10g of ethylenediaminetetraacetic acid, 15g of sodium sulfite and 168g of carrageenan to the obtained mixed solution, heat it to 100℃, maintain it for 1h, dissolve the coagulant, form a sol, and let the sol stand at room temperature to obtain a solid gel. The solid gel is placed in a vacuum freeze dryer, pre-frozen at -40℃ for 4h, and vacuum dried for 48h to obtain a lanthanum sulfide / porous carbon composite material precursor. The obtained precursor is heated to 950℃ at 5℃ / min in a nitrogen atmosphere, maintained for 4h, and cooled to room temperature to obtain a lanthanum sulfide / porous carbon composite material.

[0073] According to the test method of Example 1, the multi-component composite negative electrode material prepared in this example was used to prepare the electrode sheet and assembled the battery for testing. The test results are shown in Table 1.

[0074] Example 4

[0075] Place the royal poinciana in a tube furnace, and heat it to 550°C at a heating rate of 5°C / min in a nitrogen atmosphere, and maintain it for 2.5 hours to form biochar. Weigh 10g of biochar and 60g of potassium carbonate and place them in a ball mill, keep the speed at 400rpm, and ball mill for 0.5h. Place the mixture in a tube furnace, heat it to 900°C at 3°C / min under nitrogen, and maintain it for 3h. Disperse the product in a 0.5mol / L hydrochloric acid solution, at 60°C, at a speed of 400rpm, acid wash for 2h, filter and dry to form porous carbon.

[0076] Weigh 5g of porous carbon and 1.5g of lanthanum nitrate and disperse them in 325mL of anhydrous ethanol, and ultrasonicate for 0.5h. Under continuous stirring, add 9g of ethylenediaminetetraacetic acid, 9g of sodium sulfite and 46.5g of carrageenan to the mixed solution, heat it to 90℃, maintain it for 0.75h, dissolve the coagulant, form a sol, and let the sol stand at room temperature to obtain a solid gel. The solid gel is placed in a vacuum freeze dryer, pre-frozen at -40℃ for 4h, and vacuum dried for 48h to obtain a lanthanum sulfide / porous carbon composite material precursor. The obtained precursor is heated to 800℃ at 4℃ / min in a nitrogen atmosphere, maintained for 6h, and cooled to room temperature to obtain a lanthanum sulfide / porous carbon composite material.

[0077] According to the test method of Example 1, the multi-component composite negative electrode material prepared in this example was used to prepare the electrode sheet and assembled the battery for testing. The test results are shown in Table 1.

[0078] Example 5

[0079] The paulownia wood was placed in a tubular furnace, heated to 550°C at a heating rate of 5°C / min under a nitrogen atmosphere, and maintained for 2.5 hours to form biochar. 10g of biochar and 55g of sodium bicarbonate were weighed and placed in a ball mill, the speed was maintained at 400rpm, and the ball milling was performed for 0.5 hours. The mixture was placed in a tubular furnace, heated to 900°C at 3°C / min under nitrogen, and maintained for 3 hours. The product was dispersed in a 0.5mol / L hydrochloric acid solution, at 60°C, the speed was 400rpm, acid washed for 2 hours, filtered, and dried to form porous carbon.

[0080] Weigh 5g of porous carbon and 2g of lanthanum sulfate and disperse them in 350mL of anhydrous ethanol, and ultrasonicate for 0.5h. Under continuous stirring, add 12g of ethylenediaminetetraacetic acid, 14g of potassium sulfite and 42g of gelatin to the mixed solution, heat it to 95℃, maintain it for 0.8h, dissolve the coagulant, form a sol, and let the sol stand at room temperature to obtain a solid gel. The solid gel is placed in a vacuum freeze dryer, pre-frozen at -40℃ for 4h, and vacuum dried for 48h to obtain a lanthanum sulfide / porous carbon composite material precursor. The obtained precursor is heated to 980℃ at 8℃ / min in a nitrogen atmosphere, maintained for 4.5h, and cooled to room temperature to obtain a lanthanum sulfide / porous carbon composite material.

[0081] According to the test method of Example 1, the multi-component composite negative electrode material prepared in this example was used to prepare the electrode sheet and assembled the battery for testing. The test results are shown in Table 1.

[0082] Example 6

[0083] The paulownia wood was placed in a tubular furnace, heated to 550°C at a heating rate of 5°C / min under a nitrogen atmosphere, and maintained for 2.5 hours to form biochar. 10g of biochar and 65g of sodium bicarbonate were weighed and placed in a ball mill, the speed was maintained at 400rpm, and the ball milling was performed for 0.5 hours. The mixture was placed in a tubular furnace, heated to 960°C at 3°C / min under nitrogen, and maintained for 2.8 hours. The product was dispersed in a 0.5mol / L hydrochloric acid solution, at 60°C, the speed was 400rpm, acid washed for 2 hours, filtered, and dried to form porous carbon.

[0084] Weigh 5g of porous carbon and 2.5g of lanthanum sulfate and disperse them in 375mL of anhydrous ethanol, and ultrasonicate for 0.5h. Under continuous stirring, add 12.5g of ethylenediaminetetraacetic acid, 15g of potassium sulfite and 45g of gelatin to the mixed solution, heat it to 95℃, maintain it for 0.8h, dissolve the coagulant, form a sol, and let the sol stand at room temperature to obtain a solid gel. The solid gel is placed in a vacuum freeze dryer, pre-frozen at -40℃ for 4h, and vacuum dried for 48h to obtain a lanthanum sulfide / porous carbon composite material precursor. The obtained precursor is heated to 850℃ at 5℃ / min in a nitrogen atmosphere, maintained for 7h, and cooled to room temperature to obtain a lanthanum sulfide / porous carbon composite material.

[0085] According to the test method of Example 1, the multi-component composite negative electrode material prepared in this example was used to prepare the electrode sheet and assembled the battery for testing. The test results are shown in Table 1.

[0086] Example 7

[0087] Cypress wood was placed in a tube furnace, heated to 550°C at a heating rate of 5°C / min under a nitrogen atmosphere, and maintained for 2.5 hours to form biochar. 10g of biochar and 40g of sodium carbonate were weighed and placed in a ball mill, kept at a speed of 400rpm, and ball milled for 0.5h. The mixture was placed in a tube furnace, heated to 900°C at 2°C / min under nitrogen, and maintained for 3h. The product was dispersed in a 0.5mol / L hydrochloric acid solution, at 60°C, at a speed of 400rpm, acid washed for 2h, filtered, and dried to form porous carbon.

[0088] Weigh 5g of porous carbon and 1g of lanthanum chloride and disperse them in 300mL of anhydrous ethanol, and ultrasonicate for 0.5h. Under continuous stirring, add 8g of ethylenediaminetetraacetic acid, 10g of potassium sulfite and 18g of gum arabic to the mixed solution, heat it to 80℃, maintain it for 1h, dissolve the coagulant, form a sol, and let the sol stand at room temperature to obtain a solid gel. The solid gel is placed in a vacuum freeze dryer, pre-frozen at -40℃ for 4h, and vacuum dried for 48h to obtain a lanthanum sulfide / porous carbon composite material precursor. The obtained precursor is heated to 1000℃ at 5℃ / min in a nitrogen atmosphere, maintained for 2.5h, and cooled to room temperature to obtain a lanthanum sulfide / porous carbon composite material.

[0089] According to the test method of Example 1, the multi-component composite negative electrode material prepared in this example was used to prepare the electrode sheet and assembled the battery for testing. The test results are shown in Table 1.

[0090] Example 8

[0091] Paulownia wood was placed in a tubular furnace, heated to 550°C at a heating rate of 5°C / min under a nitrogen atmosphere, and maintained for 2.5 hours to form biochar. 10g of biochar and 65g of magnesium carbonate were weighed and placed in a ball mill, the speed was maintained at 400rpm, and the ball milling was performed for 0.5 hours. The mixture was placed in a tubular furnace, heated to 960°C at 3°C / min under nitrogen, and maintained for 2.8 hours. The product was dispersed in a 0.5mol / L hydrochloric acid solution, at 60°C, the speed was 400rpm, acid washed for 2 hours, filtered, and dried to form porous carbon.

[0092] Weigh 5g of porous carbon and 1.5g of lanthanum chloride and disperse them in 325mL of anhydrous ethanol, and ultrasonicate for 0.5h. Under continuous stirring, add 7.5g of ethylenediaminetetraacetic acid, 7.5g of potassium sulfite and 35g of pectin to the mixed solution, heat it to 95℃, maintain it for 0.8h, dissolve the coagulant, form a sol, and let the sol stand at room temperature to obtain a solid gel. The solid gel is placed in a vacuum freeze dryer, pre-frozen at -40℃ for 4h, and vacuum dried for 36h to obtain a lanthanum sulfide / porous carbon composite material precursor. The obtained precursor is heated to 1000℃ at 5℃ / min in a nitrogen atmosphere, maintained for 3h, and cooled to room temperature to obtain a lanthanum sulfide / porous carbon composite material.

[0093] According to the test method of Example 1, the multi-component composite negative electrode material prepared in this example was used to prepare the electrode sheet and assembled the battery for testing. The test results are shown in Table 1.

[0094] In order to better illustrate the effect of the embodiment of the present invention, a comparative example is compared with the above embodiment.

[0095] Comparative Example 1

[0096] This comparative example provides a preparation process and performance test of a negative electrode material, and the specific preparation process is as follows.

[0097] Eucalyptus was placed in a tubular furnace, heated to 600°C at a heating rate of 2°C / min under a nitrogen atmosphere, and maintained for 2 hours to form biochar. 10g of biochar and 40g of potassium bicarbonate were weighed and placed in a ball mill, the speed was maintained at 400rpm, and the ball milling was performed for 0.5 hours. The mixture was placed in a tubular furnace, heated to 1000°C at 2°C / min under nitrogen, and maintained for 2 hours. The product was dispersed in a 0.5mol / L hydrochloric acid solution, at 60°C, the speed was 400rpm, acid washed for 2 hours, filtered, and dried to form porous carbon.

[0098] Weigh 5g of porous carbon and 1g of lanthanum nitrate and disperse them in 300mL of anhydrous ethanol, and ultrasonicate for 0.5h. Under continuous stirring, add 5g of ethylenediaminetetraacetic acid and 5g of sodium sulfite to the mixed solution, and dry it to obtain a lanthanum sulfide / porous carbon composite material precursor. The obtained precursor is heated to 600℃ at 10℃ / min in a nitrogen atmosphere, maintained for 8h, and cooled to room temperature to obtain a lanthanum sulfide / porous carbon composite material.

[0099] The negative electrode material prepared in this comparative example was used to prepare a negative electrode plate and assemble a battery for testing. The specific process was the same as that in Example 1. The test results are shown in Table 1.

[0100] Comparative Example 2

[0101] This comparative example provides a preparation process and performance test of a negative electrode material, and the specific preparation process is as follows.

[0102] Eucalyptus was placed in a tubular furnace, heated to 600°C at a heating rate of 2°C / min under a nitrogen atmosphere, and maintained for 2 hours to form biochar. 10g of biochar and 40g of potassium bicarbonate were weighed and placed in a ball mill, the speed was maintained at 400rpm, and the ball milling was performed for 0.5 hours. The mixture was placed in a tubular furnace, heated to 1000°C at 2°C / min under nitrogen, and maintained for 2 hours. The product was dispersed in a 0.5mol / L hydrochloric acid solution, at 60°C, the speed was 400rpm, acid washed for 2 hours, filtered, and dried to form a porous carbon negative electrode material.

[0103] The negative electrode material prepared in this comparative example was used to prepare a negative electrode plate and assemble a battery for testing. The specific process was the same as that in Example 1. The test results are shown in Table 1.

[0104] Comparative Example 3

[0105] This comparative example provides a preparation process and performance test of a negative electrode material, and the specific preparation process is as follows.

[0106] Weigh 5g of lanthanum nitrate and disperse it in 250mL of anhydrous ethanol, and ultrasonicate for 0.5h. Under continuous stirring, add 25g of ethylenediaminetetraacetic acid and 25g of sodium sulfite to the mixed solution, and dry it to obtain a lanthanum sulfide negative electrode material precursor. The obtained precursor is heated to 600℃ at 10℃ / min in a nitrogen atmosphere, maintained for 8h, and cooled to room temperature to obtain a lanthanum sulfide negative electrode material.

[0107] The negative electrode material prepared in this comparative example was used to prepare a negative electrode plate and assemble a battery for testing. The specific process was the same as that in Example 1. The test results are shown in Table 1.

[0108] Table 1 shows the test comparison data of the first-cycle charge and discharge coulomb efficiency and 100-cycle capacity retention rate of the negative electrode materials prepared in Examples 1-8 and Comparative Examples 1-3.

[0109]

[0110]

[0111] Table 1

[0112] It can be seen from the test data in Table 1 that the first-week coulombic efficiency and cycle capacity retention rate of Examples 1-8 are better than those of Comparative Examples 1-3, which further verifies that the preparation method of the multi-component composite negative electrode material provided by the embodiment of the present invention is easy to control, safe and efficient. The natural wood used in the present invention has high mechanical strength, and its inherent internal tissue framework provides a good loading space for lanthanum sulfide. The multi-component composite material is synthesized by the sol-gel method to alleviate the potential problems of single-phase porous carbon or lanthanum sulfide during use, significantly improve the dispersion and uniformity of lanthanum sulfide in porous carbon, and well avoid agglomeration in the material synthesis process. Therefore, the multi-component composite negative electrode material provided by the present invention has excellent electrochemical performance and cycle performance, has ideal first-week coulombic efficiency, cycle stability and safety performance, and has broad application prospects.

[0113] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a multi-component composite negative electrode material, It is characterized in that The preparation method comprises: The biochar and the activated pore-forming agent are placed in a ball mill for ball milling, the ball-milled mixture is placed in a tube furnace for carbonization, and then taken out for acid washing, suction filtration, and drying to form porous carbon; Weighing an appropriate amount of lanthanum source and the porous carbon and ultrasonically dispersing them in anhydrous ethanol to form a mixed solution, and adding an organic ligand, a sulfur source and a coagulant to the mixed solution under continuous stirring, heating the solution to a set temperature, so that the molecular chain of the coagulant is broken and dissolved, and the mixed solution forms a sol; and leaving the sol to stand at room temperature to obtain a solid gel; The solid gel is placed in a vacuum freeze dryer for pre-freezing, and then vacuum dried to obtain a lanthanum sulfide / porous carbon composite material precursor; The lanthanum sulfide / porous carbon composite material precursor is heat-treated under an inert atmosphere and then cooled to room temperature to obtain a lanthanum sulfide / porous carbon composite material, which is the multi-component composite negative electrode material.

2. The preparation method according to claim 1, It is characterized in that The biochar is formed by pre-carbonization using trees as a carbon source; The tree includes one of eucalyptus, poinciana, sycamore, cypress and paulownia; The pre-carbonization process is specifically as follows: placing the carbon source in a tubular furnace, heating the temperature to 400°C-600°C at a heating rate of 2°C / min-5°C / min under a nitrogen atmosphere, maintaining the temperature for 2h-4h, and forming biochar.

3. The preparation method according to claim 1, It is characterized in that The activated pore-forming agent comprises: at least one of potassium bicarbonate, sodium bicarbonate, potassium carbonate, sodium carbonate, and magnesium carbonate; The addition ratio of the biochar to the activated pore-forming agent is 1:4-1:8 by mass; The ball milling speed is 300-500 rpm, and the ball milling time is 0.2-1 h; The carbonization process is specifically as follows: in a nitrogen atmosphere, heating to 800°C-1000°C at a heating rate of 2°C / min-10°C / min, and keeping the temperature for 2h-4h; The acid washing specifically comprises: dispersing the sample in a 0.1 mol / L-1 mol / L hydrochloric acid solution, using a magnetic stirrer, maintaining a rotation speed of 300-500 rpm at 40° C.-80° C., and acid washing for 1-3 hours.

4. The preparation method according to claim 1, It is characterized in that The lanthanum source includes: one or more of lanthanum nitrate, lanthanum sulfate, and lanthanum chloride; The mass ratio of the porous carbon to the lanthanum source is 1:0.2-1:0.8; The solid-liquid ratio of the total mass of the porous carbon and the lanthanum source to anhydrous ethanol is 1 g / 50 mL; The organic ligand includes: ethylenediaminetetraacetic acid; The sulfur source includes: at least one of sodium sulfite and potassium sulfite; The coagulant includes: one or more of agar, carrageenan, gelatin, gum arabic, pectin and xanthan gum; The mass ratio of the lanthanum source to the organic ligand is 1:5-1:10; The mass ratio of the lanthanum source to the sulfur source is 1:5-1:15; The ratio of the total mass of the porous carbon, the lanthanum source and the sulfur source to the mass of the coagulant is 1:2-1:8; The set temperature is 80°C-100°C, and the set temperature is maintained for 0.5h-1h.

5. The preparation method according to claim 1, It is characterized in that The pre-freezing temperature is -40°C and the time is 4-6 hours; The vacuum drying time is 24-48h.

6. The preparation method according to claim 1, It is characterized in that The inert atmosphere is nitrogen or argon; The heat treatment is specifically as follows: heating to 600°C-1000°C at a heating rate of 2°C / min-10°C / min, and keeping the temperature for 2h-8h.

7. A multi-component composite negative electrode material prepared by the preparation method according to any one of claims 1 to 6.

8. A negative electrode sheet, It is characterized in that The negative electrode sheet comprises the negative electrode material as described in claim 7 above.

9. A lithium ion battery, It is characterized in that The lithium-ion battery comprises the negative electrode sheet as described in claim 8 above.

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