CN114853075A - Mn-doped FeS/CN bimetallic sulfide material with large lattice spacing as well as preparation method and application thereof - Google Patents

Abstract

The invention discloses a preparation method and application of a Mn-doped FeS/CN bimetallic sulfide material with large lattice spacing ₂ A PVP precursor; finally, the precursor is carbonized at high temperature in inert gas to prepare the carbon nano tube. The material is used as a negative electrode material of a sodium ion battery, and the battery has higher energy density and more durable capacity retention rate; to improve the sheetThe electrochemical properties of metal sulfides offer a promising strategy.

Description

Mn-doped FeS/CN bimetallic sulfide material with large lattice spacing and its preparation method and application

technical field

The invention belongs to the technical field of nanometer materials and electrochemical energy storage, in particular to a Mn-doped FeS/CN bimetallic sulfide material with large lattice spacing and a preparation method and application thereof.

Background technique

Under the current increasingly severe ecological environment, new energy has evolved into a powerful substitute for fossil energy, and the development of a material with efficient energy conversion and storage is an urgent need to utilize these new energy. Lithium-ion batteries (LIBs) are known for their light weight, high energy density, and fast charge and discharge. However, the shortage and uneven distribution of lithium sources make it difficult to meet the growing demand for power equipment. Sodium sources are cheap ($150t ^-1 ), widely distributed on earth (23.6×103 mg·kg ^-1 ), and readily available. The working principle of sodium-ion battery is very similar to that of lithium-ion battery. It has the same "rocking chair" charge and discharge principle as lithium-ion battery, and is a reasonable substitute for lithium-ion battery. The process of charging and discharging of the two batteries generally relies on the shuttle and deintercalation of charged ions in the battery to be completed between the electrode materials of the battery. Sodium-ion batteries, like lithium-ion batteries, are also classified as ion-transfer rocking-chair batteries. This concept was originally defined by Armand et al. in the 1980s by using layered compounds with low lithium intercalation potential as anode materials for lithium-ion batteries, and using layered compounds including lithium elements with high lithium intercalation potential as cathode materials , creating a battery model in which lithium ions cycle back and forth between two electrode materials during charge-discharge cycles. During the charging process of the battery, the electric field force makes the sodium ions deintercalate from the positive electrode material of the battery into the electrolyte, move to the negative electrode material of the battery through the electrolyte, and meet the electrons that reach the negative electrode material of the battery through the external circuit, and finally pass through the sodium ions. The elemental state is embedded in the anode material of sodium-ion batteries. In the process of battery discharge, the sodium in the negative electrode material of the sodium ion battery outputs an electron into sodium ions and enters the electrolyte, moves to the positive electrode through the electrolyte, and combines with the electrons passing through the external circuit, and then becomes sodium element again. The cathode material of the intercalated sodium-ion battery finally completes a charge-discharge cycle.

However, sodium ions (Na ⁺ ) have a larger radius ^{and heavier mass than Li + ,} and cause more structural damage to active electrode materials during cycling; this results in that many electrode materials suitable for lithium ion batteries cannot be for sodium-ion batteries. Therefore, it is crucial to prepare electrode materials suitable for sodium-ion batteries.

Transition metal chalcogenides have been shown to be an alternative anode material due to their open framework structure, high theoretical capacity, and low cost. Iron sulfide is a typical transition metal sulfide with a theoretical specific capacity of up to 609mAh·g ^-1 , low cost, environmental friendliness and abundant resources. Unfortunately, FeS suffers from large volume expansion and low electrical conductivity during cycling, resulting in its poor electrochemical performance. Heteroatom doping is considered as a simple and feasible method to improve the electrochemical performance of single metal sulfides. Doping can enhance electron/ion transport by creating chemical bonds between iron, sulfur and heteroatoms. Greater atomic doping also improves lattice parameters to accommodate more sodium ions. In addition, some doping can change the structure and morphology of the material, fundamentally solving the problem of single metal sulfides.

In the prior art, for example, "Synthesis of Na ₂ MnFe(CN) ₆ @Na ₂ NiFe(CN) ₆ and its application in sodium-ion batteries" (Zhou Shu, Dai Jianyong, etc., "Power Technology Research and Design", 2020 In August, 1108-1111, 1203), a Na ₂ MnFe(CN) ₆ @Na ₂ NiFe(CN) ₆ electrode material that can be used as a cathode material for sodium-ion batteries was provided, and the sodium-ion half-cell using this material was the first time. The specific discharge capacity was 137.1mAh/g, and the capacity retention rate reached 94.91% after 200 charge-discharge cycles. However, due to the presence of crystal water, this material affects the material stability and capacity, and its capacity and cycle stability need to be improved when it is used in the electrode material of sodium-ion batteries.

SUMMARY OF THE INVENTION

In view of the above deficiencies of the prior art, the present invention provides a Mn-doped FeS/CN bimetallic sulfide material with large lattice spacing. Doped FeS ₂ /PVP precursor, and then carbonized the precursor in a multiplicity environment to make the finished product. This finished product has higher capacity and longer lasting cycle stability when used in the anode material of sodium-ion batteries. Specifically, it is realized by the following techniques.

The preparation method of Mn-doped FeS/CN bimetallic sulfide material with large lattice spacing comprises the following steps:

S1. Take the ethylene glycol solution of polyvinylpyrrolidone, add inorganic ferrous salt and inorganic manganese salt and stir until dissolved; then add thiourea and sulfur powder, stir, ultrasonicate for 10-30min, keep at 180°C for 18h, and collect by centrifugation to obtain black powder Mn-doped FeS ₂ /PVP precursor; after washing with deionized water and alcohol, vacuum drying (usually drying in a vacuum oven at 65°C);

S2. Carbonize the Mn-doped FeS ₂ /PVP precursor obtained in step S1 at 500-800° C. for 2-4 hours in an inert gas (generally nitrogen, argon, etc.) environment to obtain a Mn-doped FeS bimetallic sulfide material.

In the above-mentioned preparation method of the Mn-doped FeS/CN bimetallic sulfide material, the inorganic ferrous salt and the inorganic manganese salt in step S1 need to be salts that can be dissolved in ethylene glycol. In order to promote the dissolution of these salts, inorganic ferrous salts and inorganic manganese salts can be ground/pulverized to reduce their particle size, generally 10-100 μm. In order to promote the dissolution of sulfur powder in ethylene glycol, methods such as ultrasound are used.

Preferably, in step S1, the ratio of the mass of polyvinylpyrrolidone to the total amount of the inorganic ferrous salt and the inorganic manganese salt is 50-250 g/mol, and the total amount of the inorganic ferrous salt and the inorganic manganese salt is 50-250 g/mol. The ratio of the amount of thiourea and the amount of sulfur powder is 1:1:(1-2).

More preferably, in step S1 of the above preparation method, the material ratio of the inorganic ferrous salt and the inorganic manganese salt is 4:(1-4).

Further preferably, in step S1 of the above preparation method, the material ratio of the inorganic ferrous salt and the inorganic manganese salt is 3:1.

Preferably, in step S1 of the above preparation method, after adding thiourea and sulfur powder and stirring ultrasonically, the temperature is kept at 180° C. for 18 hours.

More preferably, in step S1, the ratio of the mass of polyvinylpyrrolidone to the total amount of the inorganic ferrous salt and the inorganic manganese salt is 100 g/mol, and the total amount of the inorganic ferrous salt and the inorganic manganese salt is 100 g/mol. The ratio to the amount of thiourea and sulfur powder is 2:2:3.

Preferably, the inorganic ferrous salt is ferrous sulfate and ferrous chloride, and the inorganic manganese salt is manganese chloride.

The present invention also provides a Mn-doped FeS/CN bimetallic sulfide material with large lattice spacing prepared by the above preparation method, and a method for applying this material to the preparation of a negative electrode material for a sodium ion battery.

The above-mentioned Mn-doped FeS/CN bimetallic sulfide material with large lattice spacing provided by the present invention adopts one solvothermal and annealing process to synthesize multi-nuclear Mn-doped FeS/CN. There are four important reasons for selecting Mn atoms as doping atoms in the present invention: (1) the premise of doping is that the radius of the matrix atom (Fe) and the doping atom (Mn) are similar; (2) the atomic radius of Mn (0.067 nm) It is slightly larger than the atomic radius of Fe (0.061nm), so the lattice spacing can be appropriately increased to enhance the storage capacity of sodium; (3) the reserves of manganese ore and iron ore are equally abundant on the earth, and the price is equally low; (4) due to the extra-nuclear Different from electrons, Mn doping brings a large number of holes, which improves the conductivity.

Compared with the prior art, the advantages of the present invention are:

1. The present invention uses the larger lattice spacing caused by the doping of Mn atoms, which provides more space for the storage of sodium ions; the doping of atoms increases the electrical conductivity and enhances the transport and rate performance of carriers ;

2. The existence of multi-nuclear structure and carbon can improve the tolerance of volume expansion, which is beneficial to long-term cycle performance;

3. The detection results of the electrochemical properties of the Mn-doped FeS/CN bimetallic sulfide material show that it has a high reversible capacity as a sib anode, which is 563.3mAh·g ^-1 at 0.5A·g ^-1 ; Better rate performance, 442.8mAh·g ^-1 at 8A·g ^-1 ; longer cycle stability, 206.2mAh·g ^-1 after 8000 cycles; higher energy density and capacity retention; This provides a promising strategy for improving the electrochemical performance of single-metal sulfides.

Description of drawings

1 is a SEM image of the Mn-doped FeS/CN electrode material of Example 1;

2 and 3 are TEM images of the Mn-doped FeS/CN electrode material of Example 1;

4 is an HRTEM image of the Mn-doped FeS/CN electrode material in Example 1;

5 is a SEM image of the Mn-doped FeS/CN electrode material in Example 2;

6 is a SEM image of the Mn-doped FeS/CN electrode material in Example 3;

7 is a SEM image of the composite MnS/FeS electrode material prepared in Comparative Example 1;

8 is a cycle diagram of 1000 cycles of the Mn-doped FeS/CN electrode materials prepared in Examples 1-3 under the condition of 4A·g ⁻¹ ;

9 is a cycle diagram of the FeS electrode material prepared in Comparative Example 2 under the condition of 4A·g ^-1 for 1000 cycles;

Figure 10 is a cycle diagram of the MnS electrode material prepared in Comparative Example 3 under the condition of 4A·g ^-1 for 500 cycles;

11 is a cycle diagram of the Mn-doped FeS/CN electrode material prepared in Example 1 under the condition of 0.5 A·g ⁻¹ for 100 cycles;

12 is a graph of the rate performance of the Mn-doped FeS/CN electrode material prepared in Example 1;

13 is a cycle diagram of the Mn-doped FeS/CN electrode material prepared in Example 1 after 8000 cycles under the condition of 8 A·g ⁻¹ ;

Fig. 14 is the XRD pattern of the Mn-doped FeS/CN electrode material prepared by Example 1-3;

15 is an XRD pattern of the Mn-doped FeS ₂ /PVP precursor of Example 1. FIG.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In the following examples and comparative examples, the polyvinylpyrrolidone (PVP) used was purchased from Sinopharm Corporation, the molecular weight was about 5800, and the degree of polymerization was monomer polymerization; the inorganic ferrous salts used were ferrous chloride tetrahydrate and tetrahydrate Hydrated ferrous sulfate, the inorganic manganese salt used is manganese chloride tetrahydrate, purchased from Sinopharm Group Corporation, and ground to a particle size of 10-100 μm before use; thiourea (chemical formula CH ₄ N ₂ S) and Sulfur powder was purchased from Sinopharm Corporation, with a purity of 99.8%.

Example 1

The preparation method of the Mn-doped FeS/CN bimetallic sulfide material provided by the present embodiment is:

S1, get 0.4g polyvinylpyrrolidone and add it in 50ml ethylene glycol, stir for 30min until dissolving and prepare a solution; add 3mmol ferrous sulfate tetrahydrate, 1mmol tetrahydrate manganese chloride and stir until dissolved; then add 4mmol thiourea and 6mmol sulfur powder, stirred and sonicated for 30 min, then placed in an oven at 180 °C for 18 h, and collected by centrifugation to obtain a black powdery Mn-doped FeS ₂ /PVP precursor; washed with deionized water and alcohol, and dried in a vacuum oven at 65 °C;

S2. Carbonize 100 mg of the Mn-doped FeS ₂ /PVP precursor obtained in step S1 at 600° C. for 3 hours in an argon-protected tube furnace to carbonize the PVP and phase-transform the Mn-doped FeS ₂ to obtain Mn-doped FeS bimetallic sulfide material.

Example 2

The difference between the preparation method of the Mn-doped FeS/CN bimetallic sulfide material provided in this embodiment and the embodiment 1 is that the used ferrous sulfate tetrahydrate is 3.5 mmol, and the manganese chloride tetrahydrate is 0.5 mmol; Urea was 4 mmol and sulfur powder was 4 mmol. That is, the amount of ferrous sulfate tetrahydrate and manganese chloride tetrahydrate is 7:1, and the ratio of the total amount of ferrous sulfate tetrahydrate and manganese chloride tetrahydrate to the amount of thiourea and sulfur powder is 1:1:1.

Example 3

The difference between the preparation method of the Mn-doped FeS/CN bimetallic sulfide material provided in this embodiment and the embodiment 1 is that the used ferrous sulfate tetrahydrate is 2 mmol, the tetrahydrate of manganese chloride is 2 mmol; 4 mmol, sulfur powder is 8 mmol. That is, the amount of ferrous sulfate tetrahydrate and manganese chloride tetrahydrate is 1:1, and the ratio of the total amount of ferrous sulfate tetrahydrate and manganese chloride tetrahydrate to the amount of thiourea and sulfur powder is 1:1:2.

Example 4

The difference between the preparation method of the Mn-doped FeS/CN bimetallic sulfide material provided in this embodiment and Embodiment 1 is that ferrous sulfate tetrahydrate is replaced with ferrous chloride hydrate.

Example 5

The difference between the preparation method of the Mn-doped FeS/CN bimetallic sulfide material provided in this embodiment and the embodiment 1 is that the amount of polyvinylpyrrolidone is 1 g, that is, the mass of polyvinylpyrrolidone is the same as that of the inorganic ferrous salt, The ratio of the total substance amount of the inorganic manganese salt was 250 g/mol.

Example 6

The difference between the preparation method of the Mn-doped FeS/CN bimetallic sulfide material provided in this embodiment and the embodiment 1 is that the amount of polyvinylpyrrolidone is 0.2g, that is, the mass of polyvinylpyrrolidone is the same as that of the inorganic ferrous salt. , the proportion of the total amount of inorganic manganese salts is 50g/mol.

Comparative Example 1

The difference between the negative electrode material of the sodium ion battery provided in this comparative example and that of Example 1 is that manganese chloride tetrahydrate is replaced with manganese oxalate during preparation. The specific preparation method is the same as that of Example 1.

Comparative Example 2

The preparation method of the Mn-doped FeS/CN bimetallic sulfide material provided by this comparative example is as follows: the difference from Example 1 is that no manganese salt such as manganese chloride tetrahydrate is used in step S1, that is, 4 mmol of tetrahydrate is directly used. Hydrated ferrous sulfate; the preparation method is the same as that in Example 1.

Comparative Example 3

The preparation method of the Mn-doped FeS/CN bimetallic sulfide material provided in this comparative example is as follows: the difference from Example 1 is that no ferrous salt such as ferrous sulfate tetrahydrate is used in step S1, that is, 4 mmol is directly used. Manganese chloride tetrahydrate; the preparation method is the same as that of Example 1.

Test Example: Microscopic morphology of electrode materials prepared in Examples 1-3 and Comparative Example 1, as well as Examples 1-5 and Comparative Examples 1-3 and electrochemical performance tests

The microscopic morphology of the Mn-doped FeS/CN bimetallic sulfide material prepared in Example 1 is shown in Figures 1-4, and the microscopic morphology of the Mn-doped FeS/CN bimetallic sulfide material prepared in Examples 2 and 3 is shown in Figures 1-4 5 and 6 are shown. The microscopic morphology of the composite MnS/FeS prepared in Comparative Example 1 is shown in Figure 7. This composite is not a doped sample, and when used as an electrode material for sodium-ion batteries, the reversible capacity is not high.

As shown in Figure 8, under the condition of 4A·g ^-1 , using the Mn-doped FeS/CN electrode material prepared in Examples 1-3, the reversible capacity after 1000 cycles using the blue battery test system was 488mAh· g ^-1 , 370mAh·g ^-1 , 368mAh·g ^-1 .

As shown in Fig. 9, the reversible capacities of the FeS electrode materials prepared in Comparative Example 2 after 1000 cycles were 300 mAh·g ^-1 , respectively.

As shown in Fig. 10, the reversible capacities of the MnS electrode materials prepared in Comparative Example 3 after 500 cycles were 117 mAh·g ^-1 , respectively.

As shown in Figure 11, under the condition of 0.5A·g ^-1 , using the Mn-doped FeS/CN electrode material prepared in Example 1, the reversible capacity after 100 cycles using the blue battery test system is 562.7mAh·g ^-1 .

As shown in Figure 12, under the condition of 8A·g ^-1 , the Mn-doped FeS/CN electrode material prepared in Example 1 has excellent rate performance (270.4mAh·g ^-1 ).

As shown in Figure 13, under the condition of 8A·g ^-1 , the Mn-doped FeS/CN electrode material prepared in Example 1 can still maintain a capacity of 206.2mAh·g ^-1 after 8000 cycles.

14 is the XRD pattern of the electrode materials of Examples 1-3; FIG. 15 is the XRD pattern of the Mn-doped FeS ₂ /PVP precursor in step S1 of Example 1.

From the above test results, it can be found that the Mn-doped FeS/CN electrode material prepared by the preparation method provided by the present invention has a relatively high reversible capacity as a sib anode (563.3mAh·g ^-1 at 0.5A·g ^-1 ) , excellent rate performance (442.8mAh·g ^-1 at 8A·g ^-1 ) and long-lasting cycle stability (206.2mAh·g ^-1 after 8000 cycles), namely high energy density and capacity retention Rate.

The above specific embodiments describe the implementation of the present invention in detail, however, the present invention is not limited to the specific details in the above-mentioned embodiments. Within the scope of the claims and technical concepts of the present invention, various simple modifications and changes can be made to the technical solutions of the present invention, and these simple modifications all belong to the protection scope of the present invention.

Claims (9)

1. The preparation method of the Mn-doped FeS/CN bimetallic sulfide material with large lattice spacing is characterized by comprising the following steps of:

s1, adding inorganic ferrous salt and inorganic manganese salt into a glycol solution of polyvinylpyrrolidone, and stirring until the inorganic ferrous salt and the inorganic manganese salt are dissolved; then adding thiourea and sulfur powder, ultrasonically stirring for 10-30min, keeping at 180 ℃ for 18h, centrifuging and collecting to obtain black powdery Mn-doped FeS ₂ A PVP precursor; washing with deionized water and alcohol, and vacuum drying;

s2, mixing the Mn-coped FeS obtained in the step S1 ₂ The PVP precursor is carbonized for 2-4h at the temperature of 800 ℃ under the inert gas environment of 500-.

2. The method for preparing a Mn-doped FeS/CN bimetallic sulfide material with large lattice spacing according to claim 1, wherein in step S1, the ratio of the mass of polyvinylpyrrolidone to the total mass of the inorganic ferrous salt and the inorganic manganese salt is 50-250g/mol, and the ratio of the total mass of the inorganic ferrous salt and the inorganic manganese salt to the mass of thiourea and sulfur powder is 1:1 (1-2).

3. The method for preparing a Mn-doped FeS/CN bimetallic sulfide material with large lattice spacing according to claim 2, wherein the mass ratio of the inorganic ferrous salt to the inorganic manganese salt is (1-7): 1.

4. The method for preparing a Mn-doped FeS/CN bimetallic sulfide material with large lattice spacing according to claim 3, wherein the mass ratio of the inorganic ferrous salt to the inorganic manganese salt is 3: 1.

5. The method for preparing a Mn-doped FeS/CN bimetallic sulfide material with large lattice spacing according to claim 2, wherein in step S1, the ratio of the mass of polyvinylpyrrolidone to the total mass of the inorganic ferrous salt and the inorganic manganese salt is 100g/mol, and the ratio of the total mass of the inorganic ferrous salt and the inorganic manganese salt to the mass of thiourea and sulfur powder is 2:2: 3.

6. The method for preparing a Mn-doped FeS/CN bimetallic sulfide material with large lattice spacing as claimed in claim 1, wherein the carbonization temperature in the step S2 is 600 ℃ for 3 h.

7. The method for preparing a large-lattice-spacing Mn-doped FeS/CN bimetallic sulfide material as claimed in any one of claims 1 to 6, wherein the inorganic ferrous salt is ferrous sulfate or ferrous chloride, and the inorganic manganese salt is manganese chloride.

8. A Mn-coped FeS/CN bimetallic sulfide material of large lattice spacing prepared by the preparation process of any of claims 1 to 6.

9. The application of the Mn-doped FeS/CN bimetallic sulfide material with large lattice spacing prepared by the preparation method of any one of claims 1 to 6 is characterized by being applied to the preparation of a negative electrode material of a sodium-ion battery.

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