ZnS@FeNC negative electrode material and preparation method thereof

Abstract

The present invention discloses a ZnS@FeNC negative electrode material and a preparation method thereof. The ZnS@FeNC negative electrode material is composed of a ZnS core and an iron-nitrogen co-doped carbon shell coated on the outside of the core. The preparation method of the ZnS@FeNC negative electrode material comprises heating ZIF8, an iron source, a sulfur source, and 1,1-phenanthroline in a solution and calcining at high temperature. The ZnS@FeNC negative electrode material prepared by the present invention combines the advantages of ZnS nanoparticles and Fe-N co-doped carbon, has a large specific surface area, high conductivity, alleviated volume expansion, and has high mass specific capacity and high energy density. It can be used in potassium ion batteries and potassium ion hybrid capacitors to significantly improve the electrochemical performance of potassium ion batteries and potassium ion hybrid capacitors.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of negative electrode materials for potassium ion batteries and potassium ion hybrid capacitors, and in particular to a ZnS@FeNC negative electrode material and a preparation method thereof. Background Art

[0002] Large-scale energy storage plays a key role in enhancing the stability, security, and reliability of the power grid. Electrochemical energy storage devices, due to their high energy density, flexibility, and scalability, have become an important solution for grid energy storage for intermittent renewable energy sources. For example, sodium-sulfur batteries and lead-acid batteries have been used for grid energy storage. However, traditional lead-acid batteries struggle to meet high-rate energy storage requirements, while demand for lithium-ion batteries, which are currently used in electric vehicles and portable electronic devices, is also growing. Furthermore, the scarcity and increasing costs of lithium and cobalt pose challenges to the further development of lithium-ion batteries. In contrast, potassium-ion batteries (KIBs) exhibit great potential due to their abundant raw materials, fast ion transport kinetics in the electrolyte, and low cost. These factors are particularly evident in the following aspects: potassium is abundant and widely distributed, accounting for 1.5 wt% of the Earth's crust, while lithium accounts for only 0.0017%; potassium ions have a low standard reduction potential of -2.93 V vs. SHE, compared to -3.04 V and -2.71 V vs. SHE, respectively, for lithium and sodium ions; and potassium ions in propylene carbonate solvents are relatively stable. + The standard voltage of the K redox couple is lower than that of the Li + / Li and Na + / Na; Potassium ions have a smaller Stokes radius, potassium ions (K + ) <Sodium ion <Lithium-ion In propylene carbonate (PC) K + Has higher ionic conductivity, about 10mS·cm in 1M PC -1 ; In ethylene carbonate K + The desolvation energy required is the lowest, (K + 4.12eV, Na + 4.72eV, Li + 5.85eV), thus having a faster K + Diffusion rate; Potassium does not form an alloy with aluminum, so cheaper aluminum foil can be used as the positive and negative current collectors.

[0003] To date, research on potassium-ion batteries has made great progress in electrode material optimization (such as crystal morphology, reaction mechanism, interface control), synthesis methods, and full-cell manufacturing. As energy storage devices, they show great development potential, especially in the field of large-scale energy storage, and are increasingly receiving attention from the industry. Currently, researchers have explored many metal sulfides as negative electrode materials for potassium-ion batteries, such as cobalt sulfide, NiS, CuS, and iron sulfide. For example, patent CN110137460A discloses a method for preparing hollow V3S4@C nanotube negative electrode materials for lithium / sodium / potassium ion batteries. When used as a negative electrode material for potassium-ion batteries, its unique structure shortens the ion transmission path during the charge and discharge process, which is beneficial to the battery's cycle performance. CN110729478A discloses an antimony trisulfide nanodot / sulfur-doped carbon composite material, its preparation method, and its application in sodium / potassium ion batteries. The Sb2S3 in the composite material is a nanodot material with unique volume effect, surface effect, quantum size effect, and macroscopic quantum tunneling effect, which can effectively improve the electrochemical performance of the composite material. The sulfur-doped carbon carrier can improve the conductivity of the composite material and at the same time alleviate the large volume expansion of the antimony trisulfide material during the charging and discharging process. When used in sodium ion and potassium ion batteries, it exhibits high capacity and good cycle stability.

[0004] However, the metal sulfide materials prepared by the above method still have large volume changes, strong agglomeration, and low conductivity when used in potassium ion batteries, resulting in capacity attenuation and poor rate performance, which cannot meet performance requirements. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a ZnS@FeNC anode material for potassium ion batteries and potassium ion hybrid capacitors, which can significantly improve the specific capacity and rate performance.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A ZnS@FeNC anode material consists of a ZnS core and an iron-nitrogen co-doped carbon shell covering the core.

[0008] The present invention also provides a method for preparing a ZnS@FeNC negative electrode material, comprising heating ZIF8, an iron source, a sulfur source and o-phenanthroline in a solution for reaction and calcining at a high temperature.

[0009] Preferably, the preparation method of the ZnS@FeNC negative electrode material specifically comprises the following steps:

[0010] S1. ZIF8, an iron source, a sulfur source, and o-phenanthroline were added to ethanol, stirred to obtain a mixed solution, and then heated under stirring conditions. After the reaction was completed, the ethanol was evaporated and cooled to obtain a red powder;

[0011] S2. The red powder obtained in step S1 was placed in a vacuum drying oven and dried under vacuum;

[0012] S3. The red powder dried in step S2 is calcined at high temperature in a nitrogen atmosphere and cooled to obtain the ZnS@FeNC negative electrode material.

[0013] Preferably, the molar ratio of ZIF8, iron source, sulfur source and 1,1-phenanthroline is (5-7):(1-3):(1-3):(3-9).

[0014] Preferably, the iron source is at least one of ferrous sulfate and ferric sulfate.

[0015] Preferably, the sulfur source is at least one of thiourea and thioacetamide.

[0016] Preferably, in step S1, the heating reaction temperature is 60-90° C. and the time is 3-6 hours.

[0017] Preferably, in step S2, the vacuum drying is carried out at a temperature of 70 to 100° C. and for a time of 6 to 12 hours.

[0018] Preferably, in step S3, the high-temperature calcination is carried out at a temperature of 800 to 1000° C. and for a time of 2 to 4 hours.

[0019] The present invention also provides the use of the ZnS@FeNC negative electrode material in potassium ion batteries and potassium ion hybrid capacitors.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The ZnS@FeNC anode material prepared in this invention combines the advantages of ZnS nanoparticles and Fe and N co-doped carbon. It boasts a large specific surface area, high conductivity, mitigated volume expansion, and high mass specific capacity and energy density. Its application in potassium-ion batteries and potassium-ion hybrid capacitors can significantly improve their electrochemical performance.

[0022] At the same time, the raw materials for preparing the ZnS@FeNC negative electrode material of the present invention are easily available and low in price, the preparation process is simple, the repeatability is high, the reaction conditions are mild, and it can be produced on a large scale and industrialized. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1This is a scanning electron microscope photograph of the ZnS@FeNC anode material of Example 1;

[0024] Figure 2 This is a transmission electron microscope photograph of the ZnS@FeNC negative electrode material of Example 1;

[0025] Figure 3 This is an EDS element distribution comparison diagram of the ZnS@FeNC negative electrode material of Example 1;

[0026] Figure 4 This is the XRD pattern of the ZnS@FeNC negative electrode material of Example 1;

[0027] Figure 5 The potassium ion battery of Example 1 is at 0.1 mV·s -1 CV curve diagram under the scanning rate;

[0028] Figure 6 The potassium ion battery of Example 1 is at 1A·g -1 Cycling performance diagram at current density of ;

[0029] Figure 7 This is an impedance diagram of the potassium ion battery of Example 1;

[0030] Figure 8 1 is the charge and discharge curve of the potassium ion hybrid capacitor of Example 1;

[0031] Figure 9 This is a rate diagram of the potassium ion hybrid capacitor of Example 1;

[0032] Figure 10 This is a scanning electron microscope photograph of the ZnS@FeNC negative electrode material of Example 2;

[0033] Figure 11 The potassium ion battery of the comparative example is at 1A·g -1 Cycling performance diagram at current density of . DETAILED DESCRIPTION

[0034] The principles and features of the present invention are described below in conjunction with specific embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0035] An embodiment of the present invention provides a ZnS@FeNC anode material, which is composed of a ZnS core and an iron-nitrogen co-doped carbon shell covering the core.

[0036] The preparation method of the ZnS@FeNC negative electrode material provided in an embodiment of the present invention comprises heating ZIF8, an iron source, a sulfur source and o-phenanthroline in a solution and calcining at a high temperature.

[0037] Specifically, the method for preparing the ZnS@FeNC negative electrode material provided in the embodiment of the present invention includes the following steps:

[0038] S1. ZIF8, an iron source, a sulfur source, and o-phenanthroline were added to ethanol, stirred to obtain a mixed solution, and then heated under stirring conditions. After the reaction was completed, the ethanol was evaporated and cooled to obtain a red powder;

[0039] S2. The red powder obtained in step S1 was placed in a vacuum drying oven and dried under vacuum;

[0040] S3. The red powder dried in step S2 is calcined at high temperature in a nitrogen atmosphere and cooled to obtain the ZnS@FeNC negative electrode material.

[0041] In some preferred embodiments, the molar ratio of ZIF8, iron source, sulfur source and 1,1-phenanthroline is (5-7):(1-3):(1-3):(3-9).

[0042] In some preferred embodiments, the iron source is selected from at least one of ferrous sulfate and ferric sulfate.

[0043] In some preferred embodiments, the sulfur source is selected from at least one of thiourea and thioacetamide.

[0044] In some preferred embodiments, in step S1, the heating reaction temperature is 60-90° C. and the time is 3-6 hours.

[0045] In some preferred embodiments, in step S2, the vacuum drying temperature is 70-100° C. and the time is 6-12 hours.

[0046] In some preferred embodiments, in step S3, the high-temperature calcination temperature is 800-1000° C. and the time is 2-4 hours.

[0047] The ZnS@FeNC negative electrode material provided in the embodiment of the present invention is used for potassium ion batteries and potassium ion hybrid capacitors, and conventional methods can be used to assemble potassium ion batteries and potassium ion hybrid capacitors.

[0048] Example 1

[0049] 0.2 mmol of ferrous sulfate, 0.2 mmol of thiourea and 0.6 mmol of o-phenanthroline were added to 10 mL of ethanol and mixed evenly. 0.6 mmol of ZIF8 was added and ultrasonicated for 30 min. The mixture was stirred at 400 rpm at 60 °C for 3 h. The ethanol was then evaporated and cooled to obtain a red powder.

[0050] The red powder was placed in a vacuum oven and vacuum dried at 70°C for 6 h. It was taken out and transferred to a tube furnace, calcined at 900°C for 2 h, and cooled to obtain the ZnS@FeNC negative electrode material.

[0051] Figure 1 This is a scanning electron microscope photograph of the ZnS@FeNC negative electrode material obtained in this example. It can be seen that it presents a dodecahedral structure similar to ZIF8.

[0052] Figure 2 This is a transmission electron microscope photo of the ZnS@FeNC negative electrode material obtained in this example. Figure 3 The corresponding EDS element distribution comparison diagram shows that it is a core-shell structure, the internal core is nano-ZnS, and the external shell is iron-nitrogen co-doped carbon.

[0053] Figure 4 This is the XRD pattern of the ZnS@FeNC negative electrode material obtained in this example, from which it can be seen that its core is ZnS.

[0054] Potassium ion batteries and potassium ion hybrid capacitors were assembled using the ZnS@FeNC negative electrode material obtained in this example, and their performance was tested using a blue electric test system.

[0055] Figure 5 For potassium ion batteries at 0.1mV·s -1 The CV curves measured at a scan rate of 1.5 volts show that the peak at 1.35 V during the initial cathodic scan is attributed to the appearance of the solid electrolyte interface (SEI) layer and the reduction of ZnS. In addition, the overlapping CV curves of subsequent cycles show the good electrochemical reversibility of the ZnS@FeNC-2 anode during potassium ion storage.

[0056] Figure 6 For potassium ion batteries at 1A·g -1 The performance diagram after 1400 cycles at a current density of 10000 cycles shows that the battery capacity is stable at 270mAh g after 1400 cycles. -1 This indicates that the material has good cycle stability as the negative electrode of potassium ion battery.

[0057] Figure 7 This is the impedance diagram of the potassium ion battery. It can be seen that the charge transfer resistance Rct of the potassium ion battery is about 2700 ohms.

[0058] Figure 8 The charge and discharge curve of the potassium ion hybrid capacitor shows that the energy density of the potassium ion hybrid capacitor is about 140Wh·kg- 1 .

[0059] Figure 9This is the rate diagram of the potassium ion hybrid capacitor. It can be seen that the potassium ion hybrid capacitor has good rate performance.

[0060] Example 2

[0061] 0.1 mmol of ferrous sulfate, 0.2 mmol of thiourea and 0.3 mmol of o-phenanthroline were added to 10 mL of ethanol and mixed evenly. 0.6 mmol of ZIF8 was added and ultrasonicated for 30 min. The mixture was stirred at 400 rpm at 60 °C for 3 h. The ethanol was then evaporated and cooled to obtain a red powder.

[0062] The red powder was placed in a vacuum oven and vacuum dried at 70°C for 6 h. It was taken out and transferred to a tube furnace, calcined at 900°C for 2 h, and cooled to obtain the ZnS@FeNC negative electrode material.

[0063] Figure 10 This is a scanning electron microscope photograph of the ZnS@FeNC negative electrode material obtained in this example. It can be seen that it presents a dodecahedral structure similar to ZIF8.

[0064] Example 3

[0065] 0.2 mmol of ferrous sulfate, 0.2 mmol of thioacetamide and 0.6 mmol of o-phenanthroline were added to 10 mL of ethanol and mixed evenly. 0.6 mmol of ZIF8 was added and ultrasonicated for 30 min. The mixture was stirred at 400 rpm at 60 °C for 3 h. The ethanol was then evaporated and cooled to obtain a red powder.

[0066] The red powder was placed in a vacuum oven and vacuum dried at 100°C for 6 h. It was taken out and transferred to a tube furnace, calcined at 1000°C for 4 h, and cooled to obtain the ZnS@FeNC negative electrode material.

[0067] Example 4

[0068] 0.3 mmol of ferrous sulfate, 0.3 mmol of thioacetamide and 0.9 mmol of o-phenanthroline were added to 10 mL of ethanol and mixed evenly. 0.7 mmol of ZIF8 was added and ultrasonicated for 30 min. The mixture was stirred at 400 rpm at 90 °C for 6 h. The ethanol was then evaporated and cooled to obtain a red powder.

[0069] The red powder was placed in a vacuum oven and vacuum dried at 80°C for 5 h. It was taken out and transferred to a tube furnace, calcined at 800°C for 2 h, and cooled to obtain the ZnS@FeNC negative electrode material.

[0070] Example 5

[0071] 0.2 mmol of ferric sulfate, 0.3 mmol of thioacetamide and 0.6 mmol of o-phenanthroline were added to 10 mL of ethanol and mixed evenly. 0.6 mmol of ZIF8 was added and ultrasonicated for 30 min. The mixture was stirred at 400 rpm at 60 °C for 3 h. The ethanol was then evaporated and cooled to obtain a red powder.

[0072] The red powder was placed in a vacuum oven and vacuum dried at 80°C for 5 h. It was taken out and transferred to a tube furnace, calcined at 900°C for 2 h, and cooled to obtain the ZnS@FeNC negative electrode material.

[0073] Comparative Example 1

[0074] 0.2 mmol of thiourea and 0.6 mmol of ZIF8 were added to 10 mL of ethanol, mixed evenly, and ultrasonicated for 30 min. The mixture was stirred at 400 rpm at 60°C for 3 h. The ethanol was then evaporated and cooled to obtain a white powder.

[0075] The white powder was placed in a vacuum oven and vacuum dried at 70°C for 6 h. The powder was taken out and transferred to a tube furnace, calcined at 900°C for 2 h, and cooled to obtain a black powder.

[0076] The black powder material obtained in this comparative example was used to assemble a potassium ion battery, and its cycle performance was measured as follows: Figure 11 As shown in the figure, it can be seen that the battery capacity is stable at 100mAh g after 800 cycles. -1 It is about 1:1, which is far lower than the effect of Example 1 of the present invention.

[0077] Table 1 shows the battery performance test results of the negative electrode materials and the assembled potassium ion batteries of the embodiments of the present invention and the comparative example. It can be seen that the ZnS@FeNC negative electrode material of the embodiment of the present invention has good cycle stability when used in potassium ion batteries.

[0078] Table 1 Performance test results of negative electrode materials and potassium ion batteries of the embodiments and comparative examples

[0079] Test example Conductivity Number of cycles <![CDATA[Specific capacity (mAh·g -1 )]]> Example 1 good 1400 270 Example 2 good 1180 200 Example 3 good 1070 150 Example 4 good 1190 190 Example 5 good 1040 170 Comparative Example 1 Poor 800 100

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit 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 ZnS@FeNC negative electrode material, characterized in that: It consists of a ZnS core and an iron-nitrogen co-doped carbon shell covering the core. The preparation method of the ZnS@FeNC negative electrode material comprises heating ZIF8, an iron source, a sulfur source, and o-phenanthroline in a solution and reacting and calcining at a high temperature, specifically comprising the following steps: S1. ZIF8, an iron source, a sulfur source, and o-phenanthroline were added to ethanol, stirred to obtain a mixed solution, and then heated under stirring conditions. After the reaction was completed, the ethanol was evaporated and cooled to obtain a red powder; S2. The red powder obtained in step S1 was placed in a vacuum drying oven and dried under vacuum; S3. The red powder dried in step S2 was calcined at high temperature in a nitrogen atmosphere and cooled to obtain the ZnS@FeNC anode material; The molar ratio of ZIF8, iron source, sulfur source and 1,1-phenanthroline is 3:1:1:3; The iron source is ferrous sulfate; The sulfur source is thiourea; The heating reaction temperature is 60°C and the time is 3h; The vacuum drying temperature is 70°C and the time is 6 hours; The high temperature calcination temperature is 900° C. and the time is 2 hours.

2. Use of the ZnS@FeNC negative electrode material according to claim 1 in potassium ion batteries and potassium ion hybrid capacitors.

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