Multi-component phosphorus-based electrode material and rapid preparation method and application thereof

Abstract

The invention discloses a multi-component phosphorus-based electrode material as well as a rapid preparation method and application thereof. The preparation method comprises the following steps: taking raw materials according to a ratio, and carrying out ball milling and mixing to obtain a mixture; filling a heating mold of a Joule heating instrument with the mixture, putting the mixture into the Joule heating instrument, heating from room temperature to 1200-1800 DEG C at a heating rate of 500-800 DEG C / s in an inert atmosphere, and carrying out heat preservation for 6-20 seconds to carry out high-temperature roasting; cooling to 400-800 DEG C at a cooling rate of 1-300 DEG C / s, preserving heat for 6-800 seconds, carrying out low-temperature roasting, naturally cooling to room temperature after the roasting is finished, taking out the material in the Joule heating mold, and grinding the material into powder by using a mortar; according to the preparation method, the multi-component phosphorus-based material is prepared through a simple and rapid method, stable combination between phosphorus and carbon elements is achieved, the stability and electrochemical performance of the material are improved, and the multi-component phosphorus-based electrode material has the advantages of being simple and rapid in preparation method, low in cost and suitable for large-scale popularization and application. And the battery capacity and the cycling stability of the lithium ion battery are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, relates to electrode materials for lithium-ion batteries, and particularly relates to a multi-component phosphorus-based electrode material, a rapid preparation method thereof, and an application thereof. Background Art

[0002] In recent years, in order to get rid of the dependence on traditional fossil energy, China has vigorously promoted the new energy industry. Chemical energy storage devices led by lithium-ion batteries have gradually emerged and developed rapidly on a large scale in China. Especially in the field of new energy vehicles, lithium-ion batteries are the core of the entire new energy vehicle. Currently, the most common anode used is graphite material, which has a relatively low lithium intercalation potential during the reaction process. At the same time, the formed lithium intercalation layer compound replaces the metal lithium anode, and its layered structure is stable, which is the current mainstream anode. However, the graphite anode also has obvious theoretical defects, such as a relatively low theoretical specific capacity (372 mAh·g -1 ), poor high-rate charge and discharge performance, and easy lithium deposition on the anode surface, resulting in attenuation of the battery energy density and exacerbation of the battery polarization problem. Therefore, developing a functional material with higher energy density and high-rate performance is of great significance to the lithium-ion battery system and even the entire energy storage field.

[0003] Phosphorus-based materials show the potential of high-energy density materials due to their relatively high theoretical specific capacity (2596 mAh·g -1 ), and ideal lithiation potential (~0.7 / 0.4 V). However, due to its relatively low conductivity (10-12 S·m -1 ), it is difficult to operate for a long time. Coupled with a large volume expansion of nearly 300% during the cycling process, commercialization is even more difficult. However, compounding phosphorus materials with highly conductive materials can significantly improve the conductivity of red phosphorus, thereby improving its electrochemical performance. Graphite is currently a relatively mature material and has good and stable electrochemical capabilities, making it the first choice for composite materials. Therefore, realizing the combination of phosphorus and carbon is the key to preparing phosphorus-carbon materials. In the prior art, in the carbon-phosphorus composite materials obtained by ball milling and chemical vapor deposition methods, the phosphorus and carbon elements are only mechanically mixed and physically contacted, and no chemical bond is formed between them. This leads to the fact that during the charge and discharge process of the battery, red phosphorus will fall off from the carbon matrix due to volume expansion during the intercalation and deintercalation of lithium ions or sodium ions, affecting the stability and performance of the material and restricting its wide application in fields such as batteries. Therefore, improving the cycle stability of carbon-phosphorus composite materials and reducing the capacity attenuation problem of phosphorus-based materials during the electrochemical cycling process is still a major technical difficulty.

[0004] Secondly, the lithium iron phosphate battery industry has developed rapidly in China, especially in the field of new energy vehicles. In March 2022, the China Automotive Power Battery Industry Innovation Alliance released data showing that lithium iron phosphate batteries accounted for 61.6% of the total installed capacity. However, in the lithium iron phosphate battery system, only lithium has high recycling value. Therefore, a large amount of phosphorus and graphite materials in the lithium-extracted slag need to be urgently solved. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a multi-component phosphorus-based electrode material, its rapid preparation method and application. By a simple and rapid method, a multi-component phosphorus-based material is prepared to achieve a stable combination between phosphorus and carbon elements, improve the stability and electrochemical performance of the material, and be used in lithium-ion batteries to significantly improve the battery capacity and cycle stability.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions to achieve:

[0007] A preparation method of a multi-component phosphorus-based electrode material, comprising the following steps:

[0008] Step 1: Preparation of a mixture;

[0009] Mix and ball-mill iron phosphate salt, carbon material and the first transition series metal powder according to the mass ratio of iron phosphate salt to carbon material being (1-5):1 and the mass ratio of carbon material to the first transition series metal powder being (2-5):1 to obtain a mixture;

[0010] Or mix and ball-mill lithium-extracted slag powder, iron phosphate salt powder and the first transition series metal powder according to the mass ratio of (1-6):(1-4):(0.1-0.5) to obtain a mixture;

[0011] Step 2: Load the mixture into the heating mold of a Joule heating instrument and put it into the Joule heating instrument. Under an inert atmosphere, heat from room temperature to 1200-1800°C at a heating rate of 500-800°C / s, and keep it at this temperature for 6-20 s for high-temperature roasting; then cool down to 400-800°C at a cooling rate of 1-300°C / s and keep it at this temperature for 6-800 s for low-temperature roasting. After that, naturally cool down to room temperature, take out the material in the Joule heating mold, and grind it into powder using a mortar;

[0012] Step 3: Transfer the product obtained in Step 2 to dilute acid for pickling, then wash it with pure water until neutral and dry it to obtain a multi-component phosphorus-based electrode material.

[0013] The present invention also has the following technical features:

[0014] Preferably, the iron phosphate salt described in Step 1 includes any one of iron phosphate, ferrous phosphate and ferrous pyrophosphate;

[0015] The carbon material described in step 1 includes any one of graphite, carbon nanotubes and graphene.

[0016] Preferably, the first transition metal in step 1 includes any one of vanadium, chromium, manganese, iron, cobalt and nickel.

[0017] Preferably, in the ball milling process described in step 1, the ball-to-material ratio ranges from 5 to 15, the rotation speed ranges from 300 to 600 rpm, and the ball milling time is 4 to 8 hours.

[0018] Preferably, the inert atmosphere in step 2 comprises either argon or nitrogen.

[0019] Preferably, the operating voltage of the Joule heater is 10-80V, and the operating current is 40-300A.

[0020] Preferably, the dilute acid in step 3 includes dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid with a concentration of 0.1 to 0.5 mol / L;

[0021] The pickling process described in step three includes: transferring the product into dilute acid, setting the rotation speed to 300-600 rpm, and pickling for 4-8 hours.

[0022] The present invention also protects a multi-component phosphorus-based electrode material prepared by the method as described above and its application in the negative electrode of a lithium ion battery.

[0023] Compared with the prior art, the present invention has the following technical effects:

[0024] The present invention selects iron phosphate as a phosphorus source, mixes it with a carbon material and a first transition metal and prepares it into a precursor, utilizes the rapid heating characteristic of Joule heating technology to gradually reduce the iron phosphate, and then reduces the temperature in the Joule heating chamber by regulating the current, thereby reducing the internal thermodynamics, thereby realizing the combination of carbon and phosphorus, and at the same time, the selected transition metal can be combined with the generated phosphorus element to generate a transition metal phosphide, and then the excess surface material is removed by acid washing to obtain a multi-component phosphorus-based negative electrode material; wherein, the combination between phosphorus and carbon elements is more stable than the conventional indoor combination, thereby improving the stability and electrochemical performance of the material, and being used for lithium-ion batteries to achieve significant improvement in battery capacity and cycle stability; on the other hand, the transition metal phosphide and Li + After the reaction, transition metal and Li3P are generated. The transition metal generated by the reaction is dispersed in the entire electrode, which is beneficial to improve the conductivity. By adjusting the raw material ratio, the transition metal phosphide and Li + The transition metal will eventually reduce the volume expansion of the battery reaction and improve the battery cycle life. The multi-component phosphorus-based negative electrode materials are assembled into a half-cell for electrochemical testing. -1The cyclic specific capacity under [conditions] reaches 420 mAh·g -1 , achieving a double breakthrough in capacity and cycling stability;

[0025] The present invention can use the lithium-extracted slag from waste lithium iron phosphate batteries to prepare multi-component phosphorus-based electrode materials, providing a new idea for the high-value recycling of lithium-extracted slag from waste lithium iron phosphate batteries;

[0026] The present invention selects Joule heating technology to replace traditional tube furnace calcination, greatly shortening the reaction time required, and realizing the decomposition and conversion of iron phosphate through Joule heating;

[0027] The present invention has low raw material costs, a rapid and simple preparation process, good product effects, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a process flow chart of the treatment system of the present invention;

[0029] Figure 2 is an XRD comparison chart of the multi-component phosphorus-based negative electrode material prepared in Example 1 before and after pickling;

[0030] Figure 3 is a Raman comparison chart of the multi-component phosphorus-based negative electrode material prepared in Example 1 and commercial graphite material;

[0031] Figure 4 is a scanning electron microscope image of the multi-component phosphorus-based negative electrode material prepared in Example 1;

[0032] Figure 5 is a scanning electron microscope image of the multi-component phosphorus-based negative electrode material prepared in Example 1;

[0033] Figure 6 is a scanning electron microscope image of the multi-component phosphorus-based negative electrode material prepared in Example 1;

[0034] Figure 7 is a Joule heating temperature-time curve graph;

[0035] Figure 8 is a charge-discharge curve graph of the coin cell prepared with the multi-component phosphorus-based negative electrode material prepared in Example 1 at 0.1 A;

[0036] Figure 9 is a charge-discharge curve graph of the coin cell prepared with the multi-component phosphorus-based negative electrode material prepared in Example 1 at 0.2 A;

[0037] Figure 10 is a rate charge-discharge curve graph of the coin cell prepared with the multi-component phosphorus-based negative electrode material prepared in Example 1 and the coin cell prepared with commercial graphite material;

[0038] Figure 11 Schematic diagram after fixing the Joule heating mold prepared in Example 1;

[0039] The meanings of the labels in the figure are as follows: 1 - graphite paper, 2 - graphite boat, 3 - electrode clamp, 4 - graphite electrode. Specific embodiments

[0040] The following further elaborates on the specific content of the present invention in conjunction with examples.

[0041] As Figure 11 shown, the Joule heating mold of the Joule heating instrument of the present invention is composed of a graphite boat and graphite paper. The mixed material is introduced into the central groove of the graphite boat, and then wrapped with graphite paper. The graphite paper 1 is located on the upper side of the graphite boat 2 of the Joule heating mold. The two sides of the graphite paper 1 are electrode clamps 3, and the two sides of the graphite boat 2 of the Joule heating mold are fixed by graphite electrodes 4.

[0042] The specific operation steps of the Joule heating instrument in the present invention are as follows:

[0043] Put the mold filled with the mixture into the Joule heating instrument, fix it on the experimental bench according to the usage requirements of the Joule heating instrument, close the heating chamber door, and start the Joule heating instrument;

[0044] Open the vacuum valve of the Joule heating instrument, and use the vacuum pump to evacuate the inside of the Joule heating instrument cabin to a negative pressure of -0.01 MPa, then close the vacuum valve, open the air inlet, and supplement the protective gas until it reaches a positive pressure. Repeat 3 - 4 times until the air is exhausted. Set the working parameters, start the program to heat the material, and after heating, let it cool naturally.

[0045] Example 1

[0046] Refer to Figure 1 shown, this example gives a preparation method of a multi-component phosphorus-based electrode material, including the following steps:

[0047] Step 1: Weigh 0.4 g each of iron phosphate powder and graphite negative electrode powder, and 0.1 g of reduced iron powder according to a mass ratio of 1:1, and perform ball milling and mixing. Add ball milling beads according to a ball-to-material ratio of 12:1, set the ball milling speed to 400 rpm, and ball mill for 4 h;

[0048] Step 2: Load the mixture into the heating mold of the Joule heater and place it in the Joule heater. Under a nitrogen atmosphere, set the voltage in the rapid heating stage to 40 V, the working current to 240 A, the heating rate to 600 °C / s, heat from room temperature to 1430 °C, keep the temperature for 15 s. Set the working voltage to 40 V and the working current to 48.5 A during the low-temperature sintering process, cool down at a cooling rate of 100 °C / s to 485 °C, keep the temperature for 500 s. After that, naturally cool down to room temperature, take out the material in the Joule heating mold, and grind it into powder using a mortar.

[0049] Step 3: Transfer the product obtained in Step 2 to 0.1 mol / L dilute hydrochloric acid for pickling, set the rotation speed to 400 rpm, pickle for 5 h, then wash with pure water until neutral and dry to obtain multi-component phosphorus-based electrode materials.

[0050] Use a SHIMADZ 6100 type multi-crystal rotating anode X-ray diffractometer, with a Ni filter, tube current of 20 mA, tube voltage of 20 kV, scanning angle 2θ = 10 - 80°, scanning speed 8°·min -1 Perform X-ray diffraction on the multi-component phosphorus-based electrode materials of this Example 1 to obtain an XRD pattern as Figure 2 shown; from Figure 2 it can be seen that the main diffraction peaks of the multi-component phosphorus-based negative electrode materials of this example can all be indexed; except for the peaks belonging to the typical 2H graphite phase, there are obvious peaks near 30°, which are the peaks of ferrous pyrophosphate, and the removal of iron after pickling weakens the intensity of its peaks. Secondly, the typical 002 peak of graphite shifts to a higher angle because of the doping of red phosphorus.

[0051] Use an InVia Qontor type laser Raman spectrometer to perform Raman spectroscopy analysis on the multi-component phosphorus-based electrode materials of this example, and the results of the obtained Raman spectroscopy are as Figure 3 shown; from Figure 3 it can be seen that the multi-component phosphorus-based negative electrode materials of this example still have the typical D-band and G-band peaks of graphite, but their peak intensities are weak. On the one hand, it comes from the doping of phosphorus elements, adding new groups; on the other hand, the doping of phosphorus elements leads to the surface inhomogeneity.

[0052] Use a Gemini 500 type scanning electron microscope to perform scanning electron microscopy analysis on the multi-component phosphorus-based electrode materials of this example, and the results of the obtained scanning electron microscopy (SEM) are as Figures 4 - 6 shown.

[0053] Use a CR2025 type button battery to characterize the electrochemical performance of the synthesized material:

[0054] First, multiple-component phosphorus-based anode materials, conductive agent acetylene black, and binder (10% mass fraction of PVDF) were mixed at a mass ratio of 8:1:1. Then, an appropriate amount of N-methylpyrrolidone was added as a solvent and stirred well. The resulting slurry was coated on aluminum foil and dried at 80 °C for 12 h under vacuum conditions, and then circular discs with a diameter of 12 mm were punched out using a punching machine and compacted under a condition of 20 Mpa to obtain the positive electrode sheets of button cells. In a glove box filled with argon, metallic lithium was used as the negative electrode, a mixed solution of 1.0 M LiTFSI in DOL:DME (V:V = 1:1) + 1.0 wt% LiNO3 dissolved in EC-DMC (volume ratio of 1:1) was used as the electrolyte, and Celgard 2500 microporous polypropylene membrane was used as the separator. Button cells were prepared in accordance with the assembly sequence of button cells. In this example, a BTS test system from Shenzhen Neware Company was used to conduct constant current charge and discharge tests at 0.01 - 3 V at room temperature.

[0055] Figure 7 is the temperature-time curve graph for the Joule heating process, which records the change of temperature with time during the Joule heating process.

[0056] Figure 8 is the charge and discharge curve graph of the button cell at 0.1 A. Its initial discharge specific capacity at 0.1 A is 484 mAh·g -1 , but the ICE is only 86%, which is because a large amount of lithium is consumed in the formation of SEI during the cycling process. After 40 cycles, its capacity stabilizes at 420 mAh·g -1 , the capacity retention rate is 86.8%, and the Coulomb efficiency is close to 100%.

[0057] Figure 9 is the charge and discharge curve graph of the button cell at 0.2 A. Its initial discharge specific capacity at 0.2 A is 398 mAh·g -1 , the ICE is 92%, which is because a large amount of lithium is consumed in the formation of SEI during the cycling process. After 40 cycles, its capacity stabilizes at 368 mAh·g -1 , the capacity retention rate is 92%, and the Coulomb efficiency is 99%.

[0058] Figure 10 is the charge and discharge curve graph of the rate performance of the button cell. The product P15X from Duoduo Chemical Network was selected as the commercial anode material for comparison. In terms of capacity, the batteries assembled with the multiple-component phosphorus-based anode materials are all higher than the commercial graphite materials, and their cycling stability is also better at high rates. This is because the amorphous phosphorus enhances the capacity, while the transition metals stabilize its structure.

[0059] Example 2

[0060] This example provides a preparation method for a multiple-component phosphorus-based electrode material, including the following steps:

[0061] Step 1: Weigh 1.2 g of iron phosphate powder and 0.4 g of graphite powder according to a mass ratio of 3:1, and then add 0.12 g of nickel powder. Conduct ball milling and mixing on them, add milling beads according to a ball-to-material ratio of 15:1, set the ball milling speed at 400 rpm, and ball mill for 4 h;

[0062] Step 2: Load the mixed material into the heating mold of the Joule heating instrument and place it in the Joule heating instrument. Under an argon atmosphere, set the voltage in the rapid heating stage at 40 V, the working current at 245 A, the heating rate at 600 °C / s, heat from room temperature to 1455 °C, with a holding time of 18 s. Set the working voltage in the low-temperature sintering process at 40 V, the working current at 49.5 A, cool down at a cooling rate of 100 °C / s to 460 °C, with a holding time of 500 s. After completion, naturally cool down to room temperature, take out the material in the Joule heating mold, and grind it into powder using a mortar;

[0063] Step 3: Transfer the product obtained in Step 2 to 0.1 mol / L dilute sulfuric acid for pickling, set the rotation speed at 400 rpm, pickle for 5 h, then wash it with pure water until neutral and dry it to obtain a multi-component phosphorus-based electrode material.

[0064] Example 3

[0065] This example provides a preparation method for a multi-component phosphorus-based electrode material, including the following steps:

[0066] Step 1: Weigh 1 g of ferrous pyrophosphate powder and 0.2 g of graphite powder according to a mass ratio of 5:1, and then add 0.1 g of cobalt powder. Conduct ball milling and mixing on them, add milling beads according to a ball-to-material ratio of 12:1, set the ball milling speed at 400 rpm, and ball mill for 4 h;

[0067] Step 2: Load the mixed material into the heating mold of the Joule heating instrument and place it in the Joule heating instrument. Under a nitrogen atmosphere, set the voltage in the rapid heating stage at 40 V, the working current at 240 A, the heating rate at 600 °C / s, heat from room temperature to 1430 °C, with a holding time of 12 s. Set the working voltage in the low-temperature sintering process at 40 V, the working current at 45.5 A, cool down at a cooling rate of 100 °C / s to 464 °C, with a holding time of 500 s. After completion, naturally cool down to room temperature, take out the material in the Joule heating mold, and grind it into powder using a mortar;

[0068] Step 3: Transfer the product obtained in Step 2 to 0.1 mol / L dilute nitric acid for pickling, set the rotation speed at 400 rpm, pickle for 5 h, then wash it with pure water until neutral and dry it to obtain a multi-component phosphorus-based electrode material.

[0069] Example 4

[0070] This embodiment provides a preparation method for a multi-component phosphorus-based electrode material, including the following steps:

[0071] Step 1: Weigh 1 g of ferrous pyrophosphate powder, 0.2 g of graphite powder, and 0.1 g of vanadium powder according to a mass ratio of 5:1, and perform ball milling and mixing on them. Add ball milling beads according to a ball-to-material ratio of 10:1, set the ball milling speed at 400 rpm, and ball mill for 4 h;

[0072] Step 2: Load the mixed material into the heating mold of a Joule heating instrument and place it in the Joule heating instrument. Under a nitrogen atmosphere, set the voltage in the rapid heating stage at 40 V, the working current at 240 A, the heating rate at 600 °C / s, heat from room temperature to 1423 °C, keep the temperature for 12 s. Set the working voltage in the low-temperature sintering process at 40 V, the working current at 47.5 A, cool down at a cooling rate of 100 °C / s to 463 °C, keep the temperature for 500 s. After that, naturally cool down to room temperature, take out the material in the Joule heating mold, and grind it into powder using a mortar;

[0073] Step 3: Transfer the product obtained in Step 2 to 0.1 mol / L dilute hydrochloric acid for pickling, set the rotation speed at 400 rpm, pickle for 5 h, then wash with pure water until neutral and dry to obtain the multi-component phosphorus-based electrode material.

[0074] Example 5

[0075] This embodiment provides a preparation method for a multi-component phosphorus-based electrode material, including the following steps:

[0076] It is obtained through ICP testing after leaching the slag after lithium extraction from waste lithium iron phosphate with aqua regia. In every 10 g of the slag, the phosphorus element accounts for about 16%, the graphite accounts for about 24%, the iron element accounts for about 33%, the copper element accounts for about 3%, and the aluminum element accounts for about 5%;

[0077] Step 1: Weigh 2 g of lithium extraction slag powder, 1 g of iron phosphate powder, and 0.15 g of iron powder according to a mass ratio of 1:0.5, and perform ball milling and mixing on them. Add ball milling beads according to a ball-to-material ratio of 10:1, set the ball milling speed at 400 rpm, and ball mill for 4 h;

[0078] Step 2: Load the mixture into the heating mold of the Joule heater and place it in the Joule heater. Under a nitrogen atmosphere, set the voltage in the rapid heating stage to 40 V, the working current to 240 A, the heating rate to 550 °C / s, heat from room temperature to 1455 °C, with a holding time of 16 s. Set the working voltage in the low-temperature sintering process to 40 V, the working current to 45.5 A, cool down at a cooling rate of 100 °C / s to 420 °C, with a holding time of 800 s. After that, naturally cool down to room temperature, take out the material in the Joule heating mold, and grind it into powder using a mortar;

[0079] Step 3: Transfer the product obtained in Step 2 to 0.2 mol / L dilute hydrochloric acid for pickling, set the rotation speed to 400 rpm, pickle for 8 h, then wash with pure water until neutral and dry to obtain the multi-component phosphorus-based electrode material.

[0080] Example 6

[0081] This example provides a preparation method for a multi-component phosphorus-based electrode material, including the following steps:

[0082] It is obtained by ICP testing after leaching the slag after lithium extraction from waste lithium iron phosphate with aqua regia. In every 10 g of the slag, the phosphorus element accounts for about 16%, the graphite accounts for about 24%, the iron element accounts for about 33%, the copper element accounts for about 3%, and the aluminum element accounts for about 5%;

[0083] Step 1: Weigh 3 g of lithium extraction slag powder, 2 g of iron phosphate powder, and 0.5 g of iron powder according to a mass ratio of 3:2, and carry out ball milling and mixing. Add ball milling beads according to a ball-to-material ratio of 10:1, set the ball milling speed to 400 rpm, and ball mill for 4 h;

[0084] Step 2: Load the mixture into the heating mold of the Joule heater and place it in the Joule heater. Under a nitrogen atmosphere, set the voltage in the rapid heating stage to 40 V, the working current to 240 A, the heating rate to 550 °C / s, heat from room temperature to 1455 °C, with a holding time of 16 s. Set the working voltage in the low-temperature sintering process to 40 V, the working current to 45.5 A, cool down at a cooling rate of 100 °C / s to 440 °C, with a holding time of 800, heat the material with current. After that, naturally cool down to room temperature, take out the material in the Joule heating mold, and grind it into powder using a mortar;

[0085] Step 3: Transfer the product obtained in Step 2 to 0.2 mol / L dilute sulfuric acid for pickling, set the rotation speed to 400 rpm, pickle for 8 h, then wash with pure water until neutral and dry to obtain the multi-component phosphorus-based electrode material.

[0086] Example 7

[0087] This embodiment provides a preparation method for a multi-component phosphorus-based electrode material, including the following steps:

[0088] It is obtained by leaching the slag after lithium extraction from waste lithium iron phosphate with aqua regia and then testing by ICP. In every 10 g of the slag, the phosphorus element accounts for about 16%, the graphite accounts for about 24%, the iron element accounts for about 33%, the copper element accounts for about 3%, and the aluminum element accounts for about 5%.

[0089] Step 1: Weigh 1 g of lithium extraction slag powder, 1 g of iron phosphate powder, and 0.1 g of iron powder according to a mass ratio of 1:1, and carry out ball milling and mixing. Add ball milling beads according to a ball-to-material ratio of 10:1, set the ball milling speed at 400 rpm, and ball mill for 4 h.

[0090] Step 2: Load the mixed material into the heating mold of the Joule heating instrument and put it into the Joule heating instrument. Under a nitrogen atmosphere, set the voltage in the rapid heating stage at 40 V, the working current at 240 A, the heating rate at 550 °C / s, heat from room temperature to 1455 °C, with a holding time of 16 s. Set the working voltage in the low-temperature sintering process at 40 V, the working current at 45.5 A, cool down at a cooling rate of 100 °C / s to 440 °C, with a holding time of 800, heat the material with the current, and after completion, naturally cool down to room temperature. Take out the material in the Joule heating mold and grind it into powder using a mortar.

[0091] Step 3: Transfer the product obtained in Step 2 to 0.2 mol / L dilute sulfuric acid for pickling, set the rotation speed at 400 rpm, pickle for 8 h, then wash with pure water until neutral and dry to obtain the multi-component phosphorus-based electrode material.

[0092] Example 8

[0093] This embodiment provides a preparation method for a multi-component phosphorus-based electrode material, including the following steps:

[0094] Step 1: Weigh 1 g of iron phosphate powder, 0.2 g of carbon nanotube powder, and 0.04 g of chromium powder according to a mass ratio of 5:1, and carry out ball milling and mixing. Add ball milling beads according to a ball-to-material ratio of 5:1, set the ball milling speed at 300 rpm, and ball mill for 6 h.

[0095] Step 2: Load the mixed material into the heating mold of the Joule heating instrument and put it into the Joule heating instrument. Under a nitrogen atmosphere, set the voltage in the rapid heating stage at 10 V, the working current at 40 A, the heating rate at 500 °C / s, heat from room temperature to 1200 °C, with a holding time of 20 s. Set the working voltage in the low-temperature sintering process at 10 V, the working current at 40 A, cool down at a cooling rate of 1 °C / s to 800 °C, with a holding time of 6 s. After completion, naturally cool down to room temperature. Take out the material in the Joule heating mold and grind it into powder using a mortar.

[0096] Step 3: Transfer the product obtained in Step 2 to 0.4 mol / L dilute hydrochloric acid for pickling, set the rotation speed to 300 rpm, pickle for 8 h, then wash with pure water until neutral and dry to obtain a multi-component phosphorus-based electrode material.

[0097] Example 9

[0098] This example provides a preparation method for a multi-component phosphorus-based electrode material, including the following steps:

[0099] Step 1: Weigh 1 g of ferrous pyrophosphate powder, 0.2 g of graphene powder and 0.04 g of manganese powder according to a mass ratio of 5:1, and perform ball milling and mixing. Add ball milling beads according to a ball-to-material ratio of 5:1, set the ball milling speed to 600 rpm, and ball mill for 8 h;

[0100] Step 2: Load the mixture into the heating mold of the Joule heating instrument and put it into the Joule heating instrument. Under a nitrogen atmosphere, set the voltage in the rapid heating stage to 80 V, the working current to 300 A, the heating rate to 800 °C / s, heat from room temperature to 1800 °C, keep the temperature for 6 s, set the working voltage in the low-temperature sintering process to 80 V, the working current to 300 A, cool down to 400 °C at a cooling rate of 300 °C / s, keep the temperature for 800 s. After that, cool down to room temperature naturally, take out the material in the Joule heating mold, and grind it into powder using a mortar;

[0101] Step 3: Transfer the product obtained in Step 2 to 0.5 mol / L dilute hydrochloric acid for pickling, set the rotation speed to 600 rpm, pickle for 4 h, then wash with pure water until neutral and dry to obtain a multi-component phosphorus-based electrode material.

[0102] Example 10

[0103] This example provides a preparation method for a multi-component phosphorus-based electrode material. Weigh 1 g of lithium extraction slag powder, 4 g of iron phosphate powder and 0.1 g of iron powder according to a mass ratio of 1:4, and the remaining steps are the same as those in Example 7.

[0104] Example 11

[0105] This example provides a preparation method for a multi-component phosphorus-based electrode material. Weigh 6 g of lithium extraction slag powder, 1 g of iron phosphate powder and 0.3 g of iron powder according to a mass ratio of 6:1, and the remaining steps are the same as those in Example 7.

[0106] Comparative Example 1:

[0107] Comparative Example 1 is basically the same as Example 1, except that the Joule heating method is replaced by tube furnace heating. The parameters of the tube furnace are set, and the temperature is raised at a rate of 5 °C / min to 1200 °C and held for 0.5 h, then cooled at a rate of 10 °C / min to 320 °C, held for 4 h, and then cooled to room temperature.

[0108] Comparative Example 2:

[0109] Comparative Example 1 is basically the same as Example 1, except that the added iron phosphate is replaced by nickel phosphate.

[0110] Comparative Example 3:

[0111] Comparative Example 1 is basically the same as Example 4, except that the heating method is replaced by tube furnace heating. The parameters of the tube furnace are set, and the temperature is raised at a rate of 5 °C / min to 1200 °C and held for 0.5 h, then cooled at a rate of 10 °C / min to 320 °C, held for 4 h, and then cooled to room temperature.

[0112] Comparative Example 4:

[0113] Comparative Example 1 is basically the same as Example 5, except that the heating method is replaced by tube furnace heating. The parameters of the tube furnace are set, and the temperature is raised at a rate of 5 °C / min to 1200 °C and held for 0.5 h, then cooled at a rate of 10 °C / min to 320 °C, held for 4 h, and then cooled to room temperature.

[0114] Comparative Example 5:

[0115] Comparative Example 1 is basically the same as Example 6, except that the lithium-extracted slag is replaced by crude phosphate rock.

[0116] The cycle stability of the materials prepared in each example and comparative example was determined by testing the capacity retention rate after the first and 100 cycle numbers of each material, as shown in Table 1 specifically:

[0117] Table 1 Cycle stability of the materials prepared in each example and comparative example

[0118]

[0119]

[0120] The specific examples listed above are for better illustrating the technical solutions of the present invention and do not limit the present invention. Any modification, equivalent replacement, and improvement made within the connotation of the present invention shall fall within the scope defined by the claims of the present invention.

Claims

1. A preparation method of a multi-component phosphorus-based electrode material, characterized in that, It includes the following steps: Step 1: Preparation of the mixture; Mix and ball-mill ferric phosphate salt, carbon material and the first transition series metal powder, with the mass ratio of ferric phosphate salt to carbon material being (1 - 5):1 and the mass ratio of carbon material to the first transition series metal powder being (2 - 5):1 to obtain the mixture; Or mix and ball-mill lithium-extracted slag powder, ferric phosphate salt powder and the first transition series metal powder in the mass ratio of (1 - 6):(1 - 4):(0.1 - 0.5) to obtain the mixture; Step 2: Load the mixture into the heating mold of the Joule heating apparatus and place it in the Joule heating apparatus. Under an inert atmosphere, heat from room temperature to 1200 - 1800 °C at a heating rate of 500 - 800 °C / s, and keep it for 6 - 20 s for high-temperature roasting; then cool it at a cooling rate of 1 - 300 °C / s to 400 - 800 °C, and keep it for 6 - 800 s for low-temperature roasting. After that, cool it naturally to room temperature, take out the material in the Joule heating mold, and grind it into powder using a mortar; Step 3: Transfer the product obtained in Step 2 to dilute acid for pickling, then wash it with pure water until neutral and dry it to obtain the multi-component phosphorus-based electrode material.

2. The preparation method of the multi-component phosphorus-based electrode material according to claim 1, characterized in that The ferric phosphate salt described in Step 1 includes any one of ferric phosphate, ferrous phosphate and ferrous pyrophosphate; The carbon material described in Step 1 includes any one of graphite, carbon nanotubes and graphene; 3. The preparation method of the multi-component phosphorus-based electrode material according to claim 1, characterized in that, The first transition series metal described in Step 1 includes any one of vanadium, chromium, manganese, iron, cobalt and nickel; 4. The preparation method of the multi-component phosphorus-based electrode material according to claim 1, characterized in that, During the ball-milling process described in Step 1, the ball-to-material ratio ranges from 5 to 15, the rotation speed ranges from 300 to 600 rpm, and the ball-milling time is 4 - 8 h.

5. The preparation method of the multi-component phosphorus-based electrode material according to claim 1, characterized in that, The inert atmosphere described in Step 2 includes any one of argon or nitrogen; 6. The preparation method of the multi-component phosphorus-based electrode material according to claim 1, characterized in that, The working voltage of the Joule heating apparatus is 10 - 80 V, and the working current is 40 - 300 A.

7. The preparation method of the multi-component phosphorus-based electrode material according to claim 1, characterized in that, The dilute acid described in Step 3 includes dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid with a concentration of 0.1 - 0.5 mol / L; The pickling process described in Step 3 includes: transfer the product to dilute acid, set the rotation speed to 300 - 600 rpm, and pickle for 4 - 8 h.

8. A multi-component phosphorus-based electrode material prepared by the method according to any one of claims 1 to 7.

9. Application of the multi-component phosphorus-based electrode material according to claim 8 in the negative electrode of a lithium-ion battery.

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