Metal phosphide composite material as well as preparation method and application thereof
By using carbon-coated high-entropy transition metal phosphide composite materials in the negative electrode materials of lithium-ion batteries, the problems of volume expansion and low conductivity are solved, and longer cycle life and better rate performance are achieved.
Patent Information
- Application Number
- CN202510154038.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-12
- Publication Date
- 2025-05-16
AI Technical Summary
The transition metal phosphides in the negative electrode materials of existing lithium-ion batteries expand severely during charging and discharging, resulting in the shedding of the electrode powder, low cycle life, and low intrinsic conductivity, affecting the rate performance.
The carbon-coated high-entropy transition metal phosphide composite material is prepared by sol-gel method to form a core-shell structure with a uniform carbon coating layer to improve the conductivity and structural stability of the phosphide.
It effectively inhibits the volume expansion of phosphides, improves the stability of composite materials and the transmission rate of lithium ions, and significantly improves the cycle life and rate performance of transition metal phosphides.
Smart Images
Figure CN120004229A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of negative electrode materials for lithium ion batteries, and in particular to a metal phosphide composite material and a preparation method and application thereof. Background Art
[0002] With the competition and rapid development of various industries in the field of new energy, the energy density and cycle life of existing lithium-ion batteries can no longer meet the needs of the current society. In the existing lithium-ion battery negative electrode material system, transition metal phosphides have the advantages of high gram-to-gram capacity and low price, and are strong competitors for the next generation of lithium-ion battery systems. However, due to the higher gram-to-gram capacity, transition metal phosphides have a larger volume expansion during the charge and discharge process, which will cause the electrode powder to fall off, resulting in a low cycle life, and the continuously broken and reorganized SEI film will greatly consume the electrolyte, causing lithium loss and a large amount of gas generation. In addition, the intrinsic conductivity of transition metal phosphides is low, resulting in a lower lithium ion migration rate, making its rate performance poor. These defects seriously hinder the application of transition metal phosphides in lithium-ion batteries. Therefore, how to improve the problem of severe volume expansion and poor conductivity of transition metal phosphides in applications is the key to promoting their large-scale commercial application. Summary of the invention
[0003] Based on the technical problems existing in the background technology, the present invention proposes a metal phosphide composite material and a preparation method and application thereof.
[0004] The present invention provides a method for preparing a metal phosphide composite material, comprising the following steps:
[0005] S1. Add metal salt, phosphate, citric acid and carbon source into water, heat and stir evenly, add nucleation control agent, stir to obtain gel material;
[0006] S2, subjecting the gel-like material to a first carbonization treatment, grinding, and then subjecting the gel-like material to a second carbonization treatment to obtain.
[0007] The carbon-coated high-entropy transition metal phosphide composite material of the present invention has a high-entropy transition metal phosphide as a core and is coated with a uniform carbon layer on the surface. Among them, the high-entropy design can improve the intrinsic conductivity of the phosphide, enhance the crystal structure stability of the phosphide, and effectively improve the transmission rate of lithium ions. In addition, the coated carbon layer can further inhibit the volume expansion of the phosphide, improve the overall stability of the composite material, and effectively improve the cycle life of the transition metal phosphide.
[0008] Citric acid is an acidic organic substance that has a good buffering effect in the sol-gel method and can adjust the pH value of the solution. In addition, citric acid contains multiple hydroxyl and carboxyl groups, which can coordinate with metal ions in the solution, promote the stable dispersion of metal ions in the sol, and facilitate the formation of gel.
[0009] Preferably, in the S1, the molar ratio of the metal salt, phosphate, citric acid and carbon source is (1-3): (0.5-1.5): (2-4): (0.1-2).
[0010] The molar ratio of metal salt, phosphate, citric acid and carbon source within a certain range is helpful to uniformly disperse the metal phosphide, and the appropriate proportion of carbon source is helpful to form a carbon coating layer of appropriate thickness.
[0011] Preferably, in S1, the metal salt is selected from one or more of chromium salts, manganese salts, iron salts, cobalt salts and nickel salts.
[0012] More preferably, the chromium salt is selected from one or more of chromium nitrate, chromium chloride, and chromium sulfate; the manganese salt is selected from one or more of manganese nitrate, manganese chloride, and manganese sulfate; the iron salt is selected from one or more of iron nitrate, iron chloride, and iron sulfate; the cobalt salt is selected from one or more of cobalt nitrate, cobalt chloride, and cobalt sulfate; the nickel salt is selected from one or more of nickel nitrate, nickel chloride, and nickel sulfate.
[0013] Preferably, in S1, the phosphate is selected from one or more of diammonium phosphate and diammonium hydrogen phosphate.
[0014] The role of inorganic phosphates is to coordinate with metal ions to form metal phosphate precursors.
[0015] Preferably, in S1, the carbon source is selected from one or more of glucose and sucrose.
[0016] The carbon source added during the gelling process can make the composite material have a uniform carbon coating layer, which can effectively alleviate the volume expansion of the transition metal phosphide during the cycle process and improve the conductivity of the composite material.
[0017] Preferably, in said S1, the heating temperature is 100-150°C.
[0018] Preferably, in S1, the nucleation control agent is selected from one or more of ethylene glycol, isopropanol and n-butanol.
[0019] The role of nucleation control agents is to regulate the nucleation process of materials so that the particles have a more uniform particle size distribution.
[0020] Preferably, in the S1, the volume ratio of water to nucleation control agent is 100:(5-15).
[0021] Preferably, in S2, the first carbonization treatment comprises carbonization in the first atmosphere at 250-350° C. for 1-3 hours.
[0022] The purpose of the first carbonization treatment is to promote the formation of phosphate precursors.
[0023] More preferably, the first atmosphere is selected from nitrogen and argon.
[0024] Preferably, in the S2, the particle size D50 after grinding is 10 to 30 μm.
[0025] Preferably, in said S2, the second carbonization treatment comprises carbonization in a second atmosphere at 500-700°C for 6-10 hours.
[0026] After two carbonization treatments, the coated carbon layer can further inhibit the volume expansion of the phosphide, improve the overall stability of the composite material, and effectively increase the cycle life of the transition metal phosphide.
[0027] More preferably, the second atmosphere is selected from one of argon / hydrogen mixed gas and nitrogen / hydrogen mixed gas.
[0028] More preferably, the volume fraction of hydrogen gas in the argon / hydrogen mixed gas is 1% to 10%.
[0029] More preferably, the volume fraction of hydrogen gas in the nitrogen / hydrogen mixed gas is 4% to 6%.
[0030] The present invention also provides a metal phosphide composite material prepared by the above preparation method, which has a core-shell structure, wherein the outer layer is a conductive carbon layer and the inner core is a metal phosphide.
[0031] A negative electrode sheet comprises a negative electrode active material, wherein the negative electrode active material comprises the above-mentioned metal phosphide composite material.
[0032] A lithium-ion battery comprises the above-mentioned negative electrode sheet.
[0033] The battery provided by the present invention has a higher cycle life and rate performance because it includes the carbon-coated high-entropy transition metal phosphide composite material with the above specific structure.
[0034] The beneficial effects of the present invention are:
[0035] The invention discloses a method for preparing a metal phosphide composite material. The prepared composite material has a core-shell structure, wherein the outer layer is a conductive carbon layer and the inner core is a high-entropy transition metal phosphide.
[0036] The method for preparing a carbon-coated high-entropy transition metal phosphide composite material provided by the present invention can make the composite material have a uniform carbon coating layer by the carbon source added during the gelling process, can effectively alleviate the volume expansion of the transition metal phosphide during the cycle process, and improve the conductivity of the composite material. The added ethylene glycol can regulate the nucleation process of the material so that the particles have a more uniform particle size distribution. Thus, a composite material with excellent cycle life and rate performance is prepared simply and efficiently. BRIEF DESCRIPTION OF THE DRAWINGS
[0037] Figure 1 This is a SEM image of the metal phosphide composite material prepared in Example 1 of the present invention.
[0038] Figure 2 This is the XRD spectrum of the metal phosphide composite material prepared in Example 1 of the present invention.
[0039] Figure 3 It is a comparison chart of the rate performance of the embodiment and the comparative example. DETAILED DESCRIPTION
[0040] The technical solution of the present invention is described in detail through specific embodiments.
[0041] Unless otherwise specified, the materials, reagents, etc. used in the following examples and comparative examples can be obtained from commercial sources.
[0042] Example 1
[0043] A method for preparing a metal phosphide composite material comprises the following steps:
[0044] S1. Weigh 10 mmol of metal salts (2 mmol each of chromium nitrate, manganese nitrate, iron nitrate, cobalt nitrate and nickel nitrate), 5 mmol of diammonium phosphate, 15 mmol of citric acid and 5 mmol of glucose, dissolve in 50 mL of deionized water, stir at 120 ° C for 4 hours, slowly add 5 mL of ethylene glycol to the solution with a rubber dropper, continue stirring until it is in a gel state, and obtain a gel material;
[0045] S2. Place the gel-like material in a corundum boat, then place the corundum boat in a tubular furnace, carbonize at 300°C for 2 hours in a nitrogen atmosphere, take out after natural cooling, and grind into a powder with a D50 particle size of 20 μm; place the powder in a corundum boat, send it into a tubular furnace, carbonize at 600°C for 8 hours in an atmosphere of argon / hydrogen mixed gas (5% hydrogen), take out after natural cooling, and grind into a black powder to obtain a metal phosphide composite material, recorded as C@(CrMnFeCoNi)2P-1.
[0046] Example 2
[0047] A method for preparing a metal phosphide composite material comprises the following steps:
[0048] S1. Weigh 15 mmol of metal salts (3 mmol each of chromium nitrate, manganese nitrate, iron nitrate, cobalt nitrate and nickel nitrate), 7.5 mmol of ammonium dihydrogen phosphate, 10 mmol of citric acid and 2.5 mmol of glucose, dissolve in 50 mL of deionized water, stir at 120 ° C for 4 hours, slowly add 7.5 mL of ethylene glycol to the solution with a rubber dropper, continue stirring until it is in a gel state, and obtain a gel material;
[0049] S2. Place the gel-like material in a corundum boat, then place the corundum boat in a tubular furnace, carbonize at 250°C for 2h in a nitrogen atmosphere, take out after natural cooling, and grind into a powder with a D50 particle size of 20μm; place the powder in a corundum boat, send it into a tubular furnace, carbonize at 500°C for 6h in an atmosphere of argon / hydrogen mixed gas (10% hydrogen), take out after natural cooling, and grind into a black powder to obtain a metal phosphide composite material, recorded as C@(CrMnFeCoNi)2P-2.
[0050] Example 3
[0051] A method for preparing a metal phosphide composite material comprises the following steps:
[0052] S1. Weigh 5 mmol of metal salts (1 mmol each of chromium nitrate, manganese nitrate, iron nitrate, cobalt nitrate and nickel nitrate), 2.5 mmol of diammonium phosphate, 20 mmol of citric acid and 10 mmol of glucose, dissolve in 50 mL of deionized water, stir at 120 ° C for 4 hours, slowly add 5 mL of ethylene glycol to the solution with a rubber dropper, continue stirring until it is in a gel state, and obtain a gel-like material;
[0053] S2. Place the gel-like material in a corundum boat, then place the corundum boat in a tubular furnace, carbonize at 350°C for 2h in a nitrogen atmosphere, take out after natural cooling, and grind into a powder with a D50 particle size of 20μm; place the powder in a corundum boat, send it into a tubular furnace, carbonize at 700°C for 10h in an atmosphere of argon / hydrogen mixed gas (1% hydrogen), take out after natural cooling, and grind into a black powder to obtain a metal phosphide composite material, recorded as C@(CrMnFeCoNi)2P-3.
[0054] Comparative Example 1
[0055] A method for preparing a metal phosphide composite material comprises the following steps:
[0056] S1. Weigh 10 mmol of metal salts (2 mmol each of chromium nitrate, manganese nitrate, iron nitrate, cobalt nitrate and nickel nitrate), 5 mmol of ammonium dihydrogen phosphate and 15 mmol of citric acid, dissolve in 50 mL of deionized water, stir at 120 ° C for 4 hours, slowly add 5 mL of ethylene glycol to the solution with a rubber dropper, continue stirring until it is in a gel state, and obtain a gel material;
[0057] S2. Place the gel-like material in a corundum boat, then place the corundum boat in a tubular furnace, carbonize at 300°C for 2 hours in a nitrogen atmosphere, take out after natural cooling, and grind into a powder with a D50 particle size of 20 μm; place the powder in a corundum boat, send it into a tubular furnace, carbonize at 600°C for 8 hours in an atmosphere of argon / hydrogen mixed gas (5% hydrogen), take out after natural cooling, and grind into a black powder to obtain a metal phosphide composite material, recorded as (CrMnFeCoNi)2P.
[0058] Comparative Example 2
[0059] A method for preparing a metal phosphide composite material comprises the following steps:
[0060] S1. Weigh 10 mmol of ferric nitrate, 5 mmol of ammonium dihydrogen phosphate, 15 mmol of citric acid and 5 mmol of glucose, dissolve them in 50 mL of deionized water, stir at 120 °C for 4 hours, slowly add 5 mL of ethylene glycol to the solution with a rubber dropper, and continue stirring until it becomes a gel to obtain a gel material;
[0061] S2. Place the gel-like material in a corundum boat, then place the corundum boat in a tubular furnace, carbonize at 300°C for 2 hours in a nitrogen atmosphere, take out after natural cooling, and grind into a powder with a D50 particle size of 20 μm; place the powder in a corundum boat, send it into a tubular furnace, carbonize at 600°C for 8 hours in an atmosphere of argon / hydrogen mixed gas (5% hydrogen), take out after natural cooling, and grind into a black powder to obtain a metal phosphide composite material, recorded as C@Fe2P.
[0062] Preparation Example
[0063] The metal phosphide composite materials of the above embodiments and comparative examples are used as negative electrode active materials to prepare negative electrode sheets and then assemble button batteries. The specific steps are as follows: 1) 80wt% of negative electrode active materials, 10wt% of Super P, 5wt% of CMC and 5wt% of SBR are dissolved in a certain amount of deionized water with a solid content of 20wt%. Stir continuously to form a uniform electrode slurry. The electrode slurry is coated on the surface of copper foil and vacuum dried at 100°C for 12h. The loading amount of active material in the final electrode sheet is about 1.5mg / cm 2. 2) The electrode sheet was used as the working electrode, metallic lithium was used as the reference electrode and the counter electrode, a 25 μm PP / PE / PP composite film was used as the separator, the electrolyte was diethyl carbonate and ethylene carbonate in a volume ratio of 1:1, and the electrolyte was 1 mol / L lithium hexafluorophosphate. A 2032-type button cell was assembled in a glove box under an argon atmosphere. The electrochemical performance of the battery was tested, and the test results are shown in Table 1.
[0064] Table 1
[0065]
[0066]
[0067] From the data in Table 1, it can be seen that by comparing Examples 1 to 3 and Comparative Examples 1 to 2, the carbon-coated high entropy transition metal phosphide composite material prepared by using metal salt, phosphate, citric acid and carbon source as raw materials has high specific capacity, high initial efficiency and long cycle stability. By comparing different embodiments, it can be seen that the appropriate raw material ratio, carbonization temperature and carbonization atmosphere are crucial to the lithium ion storage performance of the composite material.
[0068] By comparing Example 1, Example 2 and Comparative Example 1, it can be seen that more metal phosphides can provide higher initial discharge specific capacity, but the first week coulomb efficiency and cycle life are low, which is caused by the irreversible behavior and large volume expansion of metal phosphides during the charge and discharge process. It can be seen from Example 3 that when the carbon coating is excessive, the cycle life of the electrode material is longer, but because the specific capacity of carbon is very low, the overall gram capacity decreases.
[0069] By comparing Example 1 with Comparative Example 2, it can be seen that the doping of high entropy transition metal elements affects the performance of the composite material. Since the doping of high entropy elements enhances the stability of the crystal structure and inhibits the lattice deformation during the charge and discharge process, the high entropy phosphide exhibits better cycle stability.
[0070] like Figure 1 As shown in the figure, the SEM image of the metal phosphide composite material prepared in Example 1 of the present invention shows that C@(CrMnFeCoNi)2P-1 has a honeycomb structure, and the phosphide particles are connected by a carbon substrate, which greatly shortens the migration distance of lithium ions. In addition, the rich carbon substrate forms a continuous conductive network, providing a "high-speed channel" for charge transfer. This structure can greatly improve the rate performance of electrode materials. Figure 2The XRD spectrum shows that C@(CrMnFeCoNi)2P-1 is a single phase, proving the formation of high-entropy phosphide. The doping of high-entropy transition metal elements can improve the intrinsic conductivity of phosphide and promote the transmission of lithium ions. In addition, the interaction between different transition metals can enhance the stability of the crystal structure and effectively inhibit the lattice deformation during the charge and discharge process.
[0071] from Figure 3 The rate performance comparison shows that the rate performance of Example 1 is the best, at 2000mA g -1 At a current density of 1.5 %, its capacity can still be maintained at 667 mAh g -1 , the retention rate reaches 70%. The rate performance of comparative example 1 without carbon coating is the worst, and the capacity retention rate is only 30.6%. This is because the metal phosphide itself has poor conductivity and cannot quickly transport lithium ions.
[0072] In summary, the metal phosphide composite material provided by the present invention has excellent rate performance and long cycle life.
[0073] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.
Claims
1. A method for preparing a metal phosphide composite material, characterized in that: The following steps are involved: S1. Add metal salt, phosphate, citric acid and carbon source into water, heat and stir evenly, add nucleation control agent, stir to obtain gel material; S2, subjecting the gel-like material to a first carbonization treatment, grinding, and then subjecting the gel-like material to a second carbonization treatment to obtain.
2. The preparation method according to claim 1, characterized in that: In the S1, the molar ratio of metal salt, phosphate, citric acid and carbon source is (1-3): (0.5-1.5): (2-4): (0.1-2); the metal salt is selected from one or more of chromium salt, manganese salt, iron salt, cobalt salt and nickel salt.
3. The preparation method according to claim 1, characterized in that: In the S1, the phosphate is selected from one or more of diammonium phosphate and diammonium hydrogen phosphate; the carbon source is selected from one or more of glucose and sucrose.
4. The preparation method according to claim 1, characterized in that: In the S1, the nucleation control agent is selected from one or more of ethylene glycol, isopropanol, and n-butanol; the volume ratio of water to the nucleation control agent is 100:(5-15).
5. The preparation method according to claim 1, characterized in that: In the above-mentioned S2, the first carbonization treatment includes carbonization at 250-350° C. for 1-3 hours in a first atmosphere; the first atmosphere is selected from one of nitrogen and argon; and the particle size D50 after grinding is 10-30 μm.
6. The preparation method according to claim 1, characterized in that: In the S2, the second carbonization treatment includes carbonization at 500-700°C for 6-10 hours in a second atmosphere; the second atmosphere is selected from one of argon / hydrogen mixed gas and nitrogen / hydrogen mixed gas.
7. The preparation method according to claim 6, characterized in that: The volume fraction of hydrogen gas in the argon / hydrogen mixed gas is 1% to 10%; the volume fraction of hydrogen gas in the nitrogen / hydrogen mixed gas is 4% to 6%.
8. A metal phosphide composite material obtained by the preparation method according to any one of claims 1 to 7, characterized in that: The metal phosphide composite material has a core-shell structure, wherein the outer layer is a conductive carbon layer and the inner core is a metal phosphide.
9. A negative electrode sheet, characterized in that: It comprises a negative electrode active material, wherein the negative electrode active material comprises the metal phosphide composite material according to claim 8.
10. A lithium ion battery, characterized in that: Including the negative electrode sheet as claimed in claim 9.