Preparation method of bimetallic sulfide ZnIn2S4 and application thereof

Abstract

This invention relates to a bimetallic sulfide ZnIn2S4(V s The preparation method of ZnIn2S4 and its application as a negative electrode material for sodium-ion batteries are described. The preparation steps are as follows: a) ZnIn2S4 is obtained by reacting an aqueous solution containing ZnCl2InCl3·4H2O and thioacetamide TAA in a low-temperature water bath; b) ZnIn2S4 is annealed in an Ar atmosphere to obtain V with sulfur vacancies and recombination reaction mechanism. s -ZnIn2S4. As a negative electrode material for sodium-ion batteries, V s -ZnIn2S4 exhibits high discharge capacity at 0.5 Ag ‑1 The discharge capacity after 100 cycles at the current density is 505.2 mAh g. ‑1 Excellent rate performance at 80A g ‑1 The capacity is 222.7mAh g. ‑1 ; and excellent cycling stability at 10A g ‑1 The capacity after 2000 cycles is 349.6 mAh g. ‑1 This invention provides a new approach for developing sodium-ion battery anode materials with excellent overall performance.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of a double metal sulfide ZnIn2S4(V s and its application as a negative electrode material of a sodium ion battery. BACKGROUND

[0002] Lithium ion batteries have high energy density and power density, and have been widely used in various energy storage devices. However, the limited reserves and rising prices of lithium resources limit the application of lithium ion batteries in large-scale energy storage. In recent years, sodium ion batteries have attracted more and more attention due to abundant sodium resources and similar energy storage mechanisms to lithium ion batteries. However, Na + has a larger radius, resulting in poor electrochemical performance of the negative electrode of the sodium ion battery. Therefore, it is still a great challenge to find a sodium ion battery negative electrode material with excellent rate performance and cycle stability. Recently, researchers have studied many sodium ion battery negative electrode materials, such as carbon-based materials, transition metal oxides / sulfides / selenides, metals and alloys, etc. Among them, metal sulfides have been widely studied due to their high theoretical capacity and abundant reserves. However, they will undergo large volume expansion during the cycle process, resulting in poor cycle and rate performance.

[0003] By preparing a double metal sulfide with a composite reaction mechanism (such as intercalation-transformation / alloying), the cycle performance can be effectively improved. On the one hand, the double metal sulfide has the advantages of rich types, easy to produce active sites and defects, Na + diffusion channels and high theoretical capacity. On the other hand, the double metal sulfide can be transformed into different types of compounds (such as metals and metal sulfides) during the cycle process, thereby producing different types of reactions (such as transformation and alloying reactions). If intercalation reactions also exist during the cycle process, the intercalation-type compounds produced by the reaction have excellent structural stability like carbon materials (amorphous carbon, graphene, etc.), thereby inhibiting the large volume expansion caused by transformation / alloying reactions. Therefore, under the combined action of intercalation and transformation / alloying reactions, the negative electrode material can not only obtain high specific capacity, but also reduce volume change and achieve good cycle stability. It is well known that the rate performance of the battery is mainly affected by the redox reaction rate and ion / charge transfer kinetics, and the presence of vacancies can effectively improve the reaction kinetics of the electrode material. Therefore, constructing vacancies has become an effective strategy. It has the following advantages: i) vacancies can enrich electrons and attract a large amount of Na + , thereby accelerating the Na +i) the diffusion of sodium ions; ii) the vacancies can act as electron-accepting groups, thereby improving the conductivity of the electrode; iii) the vacancies can provide abundant active sites and adsorb a large number of ions, thereby improving the sodium storage performance of the electrode material. In summary, preparing a new type of double-metal sulfide with a composite reaction mechanism (intercalation and conversion / alloying reaction) and sulfur vacancies is a very effective method. Such a negative electrode not only has a high discharge capacity, but also has excellent cycle stability. Based on the above strategy, the present application is committed to preparing a sodium ion battery negative electrode material with excellent rate performance and cycle stability. SUMMARY

[0004] In view of the above problems, the present application prepares a double-metal sulfide ZnIn2S4(V s -ZnIn2S4), and uses it as a sodium ion battery negative electrode material.

[0005] V s -ZnIn2S4 has a nanosheet structure. This material has the following characteristics: first, the ultra-thin nanosheets can relieve the mechanical stress caused by the volume change of the electrode material; second, the sulfur vacancies improve the conductivity of the material, enhance the Na + adsorption capacity, and improve the sodium storage capacity; third, the intercalation compound formed under the action of the composite reaction mechanism can act as a buffer during the charge and discharge process, reduce the strain caused by the volume change, enhance the structural stability, and improve the cycle performance. Therefore, V s -ZnIn2S4 as a sodium ion battery negative electrode material exhibits excellent comprehensive electrochemical performance.

[0006] The above object of the present application is achieved by the following technical scheme:

[0007] A preparation method of a double-metal sulfide ZnIn2S4, comprising the following steps:

[0008] a, preparing ZnIn2S4: 0.14-0.16g of ZnCl2 and 0.24-0.26g of InCl3·4H2O are respectively dissolved in 50ml of deionized water, after stirring for 10-15 minutes, the pH value of the above solution is adjusted to 2.5 using a hydrochloric acid solution, and then stirring for another 30-40 minutes, then 0.15-0.2g of thioacetamide TAA is added to the solution, and stirring is continued for 10-15 minutes, finally the solution is placed in a water bath at a temperature of 80-90℃ and continuously stirred for 2-2.5h, after centrifugation, washing and drying, ZnIn2S4 is collected;

[0009] b, preparing V s -ZnIn2S4: ZnIn2S4 is annealed at 400-600℃ for 2-2.5h in an Ar atmosphere to obtain V sZnIn2S4.

[0010] Further, in step a, ZnCl2is not added to obtain un-annealed In2S3(Un-In2S3), and the Un-In2S3 is annealed at 500℃ for 2h in Ar atmosphere at a rate of 5℃ min -1 to obtain In2S3.

[0011] Further, in step b, ZnIn2S4is annealed at 500℃ for 2h in Ar atmosphere to obtain V s -ZnIn2S4.

[0012] Further, in step b, the annealing temperature and time can be adjusted to control the crystallization degree of V s -ZnIn2S4.

[0013] The bimetallic sulfide ZnIn2S4obtained by the above preparation method is subjected to electrochemical performance test as a negative electrode material of a sodium ion battery, including the following steps:

[0014] a. Working electrode preparation: the active material, i.e. V s -ZnIn2S4, ZnIn2S4or In2S3, is mixed with conductive carbon black and binder sodium carboxymethyl cellulose in a ratio of 7:2:1 in water, and then coated on a copper foil, vacuum dried at 70-100℃ for 10-12h, and then cut into a circular electrode sheet with a diameter of 11-12mm;

[0015] b. Sodium ion battery assembly: the active material is used as the working electrode, a sodium sheet is used as the counter electrode / reference electrode, a separator is Whatman glass fiber, and an electrolyte is 1.0M NaCF3SO3dissolved in diglyme, and a CR2025 type button cell is assembled in an argon-filled glove box, and the water and oxygen values of the glove box are [O2]<1ppm and [H2O]<1ppm, respectively;

[0016] c. Cyclic voltammetry test is performed using an IVIUM electrochemical workstation, with a scan rate of 0.1-1.0mV s -1 , and a voltage range of 0.3-2.5V;

[0017] d. Electrochemical impedance test is performed at room temperature, with a frequency range of 100kHz to 10mHz;

[0018] e. Constant current charge-discharge cycle test is performed using a LAND CT2001A battery test system, with a voltage range of 0.3-2.5V;

[0019] f, disassembly characterization of the battery: after the charge-discharge test, the button cell is disassembled in a glove box, the electrode sheet is taken out, soaked in dimethyl carbonate solution for 20-24h, cleaned with ethanol for 3-6 times, dried and then characterized by transmission electron microscope (TEM), the water and oxygen values of the glove box are [O2]<1ppm and [H2O]<1ppm respectively;

[0020] g, in-situ X-ray diffraction (XRD) characterization: V s -ZnIn2S4 electrode as the working electrode, sodium sheet as the counter electrode / reference electrode, the separator is Whatman glass fiber, the electrolyte is 1.0M NaCF3SO3 dissolved in diglycol dimethyl ether, the in-situ battery is assembled in an argon-filled glove box using an in-situ battery device, and then the in-situ battery during the charge-discharge process is characterized by XRD, the water and oxygen values of the glove box are [O2]<1ppm and [H2O]<1ppm respectively.

[0021] The technical effects of the present application are:

[0022] The bimetallic sulfide ZnIn2S4 prepared by the present application can effectively relieve the mechanical stress caused by volume change, improve the pseudo-capacitance effect; the sulfur vacancy can improve the conductivity, enhance the adsorption capacity of Na + , thereby improving the sodium storage capacity; the intercalation compound formed under the action of the composite reaction mechanism can play a buffering role in the charge-discharge process, reduce the strain caused by volume change, enhance the structural stability and improve the cycle stability. As the negative electrode material of the sodium ion battery, V s -ZnIn2S4 exhibits high discharge capacity (505.2mAh g -1 under 0.5A g -1 current density after 100 cycles), excellent rate performance (222.7mAh g -1 under 80A g -1 ), and outstanding cycle stability (349.6mAh g -1 under 10A g -1 after 2000 cycles). The present application provides a new idea for developing sodium ion battery negative electrode materials with excellent comprehensive performance. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The V s -ZnIn2S4 prepared in Example 1 of the present application, ZnIn2S4 and In2S3 as the rate performance of the negative electrode of the sodium ion battery.

[0024] Figure 2 The V sFlowchart of -ZnIn2S4.

[0025] Figure 3 V prepared in Example 1 of this invention s XRD patterns of ZnIn2S4 and In2S3.

[0026] Figure 4 XRD pattern of ZnIn2S4 prepared in Example 1 of this invention.

[0027] Figure 5 V prepared in Example 1 of this invention s FESEM image of ZnIn2S4.

[0028] Figure 6 V prepared in Example 1 of this invention s TEM image of ZnIn2S4.

[0029] Figure 7 V prepared in Example 1 of this invention s -HRTEM image of ZnIn2S4.

[0030] Figure 8 V prepared in Example 1 of this invention s -HRTEM image of ZnIn2S4.

[0031] Figure 9 V prepared in Example 1 of this invention s SAED photo of ZnIn2S4.

[0032] Figure 10 V prepared in Example 1 of this invention s - EPR spectra of ZnIn2S4 and ZnIn2S4.

[0033] Figure 11 V prepared in Example 1 of this invention s -XPS full spectrum of ZnIn2S4 and ZnIn2S4.

[0034] Figure 12 V prepared in Example 1 of this invention s - S2p XPS high-resolution spectra of ZnIn2S4 and ZnIn2S4.

[0035] Figure 13 V prepared in Example 1 of this invention s -In 3d XPS high-resolution spectra of ZnIn2S4 and ZnIn2S4.

[0036] Figure 14 V prepared in Example 1 of this inventions - ZnIn2S4 and Zn 2p XPS high-resolution spectra of ZnIn2S4.

[0037] Figure 15 V prepared in Example 1 of this invention s In-situ XRD pattern of ZnIn2S4 electrode.

[0038] Figure 16 V prepared in Example 1 of this invention s -HRTEM image of a ZnIn2S4 electrode discharged to 1.0V.

[0039] Figure 17 V prepared in Example 1 of this invention s -HRTEM image of a ZnIn2S4 electrode discharged to 0.6V.

[0040] Figure 18 V prepared in Example 1 of this invention s -HRTEM image of a ZnIn2S4 electrode discharged to 0.3V.

[0041] Figure 19 V prepared in Example 1 of this invention s -HRTEM image of a ZnIn2S4 electrode charged to 0.9V.

[0042] Figure 20 V prepared in Example 1 of this invention s -HRTEM image of a ZnIn2S4 electrode charged to 1.4V.

[0043] Figure 21 V prepared in Example 1 of this invention s -HRTEM image of a ZnIn2S4 electrode charged to 2.5V.

[0044] Figure 22 V prepared in Example 1 of this invention s -ZnIn2S4, ZnIn2S4 and In2S3 electrodes in sodium-ion batteries 0.5Ag -1 Cyclic performance at current density.

[0045] Figure 23 V prepared in Example 1 of this invention s -ZnIn2S4 electrode in sodium-ion battery 0.5A g -1 Constant current charge-discharge curves at current density.

[0046] Figure 24 V prepared in Example 1 of this invention s-ZnIn2S4, ZnIn2S4 and In2S3 electrodes in sodium-ion batteries 10Ag -1 Cyclic performance at current density.

[0047] Figure 25 V prepared in Example 1 of this invention s -ZnIn2S4 electrode at different scan rates (0.2–1.0 mV s) in sodium-ion batteries -1 Cyclic volt-ampere curves under ( ).

[0048] Figure 26 V prepared in Example 1 of this invention s Linear relationship of log(i)-log(v) for ZnIn2S4 electrode under different redox states in sodium-ion battery.

[0049] Figure 27 V prepared in Example 1 of this invention s - Contribution of capacitance and diffusion storage to capacity normalization of ZnIn2S4 electrode at different scan rates in sodium-ion battery.

[0050] Figure 28 V prepared in Example 1 of this invention s GITT curves of ZnIn2S4, ZnIn2S4 and In2S3 electrodes in sodium-ion batteries.

[0051] Figure 29 V prepared in Example 1 of this invention s Sodium ion diffusion coefficient diagram of ZnIn2S4, ZnIn2S4 and In2S3 electrodes in sodium-ion batteries

[0052] Figure 30 V prepared in Example 2 of this invention s FESEM image of ZnIn2S4-400.

[0053] Figure 31 V prepared in Example 2 of this invention s -ZnIn2S4-400 and V prepared in Example 1 s XRD pattern of ZnIn2S4.

[0054] Figure 32 V prepared in Example 3 of this invention s FESEM image of ZnIn2S4-600.

[0055] Figure 33 V prepared in Example 3 of this invention s -ZnIn2S4-600 and V prepared in Example 1 sXRD pattern of ZnIn2S4. Detailed Implementation

[0056] The specific content and implementation methods of the present invention will now be further described with reference to the embodiments. However, the embodiments are merely illustrative and should not be construed as limiting the technical solution of the present invention. The following is a detailed description of Embodiment 1. Embodiments 2 and 3 of the present invention are similar in content to Embodiment 1.

[0057] The embodiments of the present invention are now described below:

[0058] Example 1

[0059] The preparation process and steps in this embodiment are as follows:

[0060] (1) Preparation of ZnIn2S4: Dissolve 0.14-0.16g ZnCl2 and 0.24-0.26g InCl3·4H2O in 50ml of deionized water respectively. After stirring for 10-15 minutes, adjust the pH of the solution to 2.5 with hydrochloric acid solution and then stir for 30-40 minutes. Then add 0.15-0.2g TAA to the solution and continue stirring for 10-15 minutes. Finally, place the solution in a water bath at 80-90℃ and stir continuously for 2-2.5h. After centrifugation, washing and drying, collect ZnIn2S4.

[0061] (2) Preparation of V s -ZnIn2S4: ZnIn2S4 was annealed at 500℃ for 2–2.5 h in an Ar atmosphere to obtain V s -ZnIn2S4.

[0062] As a comparative experiment, Un-In2S3 can be obtained by removing the addition of ZnCl2 in step (1). Un-In2S3 is then annealed at 500℃ in Ar atmosphere for 2 to 2.5 h to obtain In2S3.

[0063] As a comparative experiment, ZnIn2S4 in step (1) was used directly as the final product without annealing.

[0064] V obtained by the above preparation method s The electrochemical performance of ZnIn2S4 as a negative electrode material for sodium-ion batteries was tested, including the following steps:

[0065] a. Preparation of working electrode: First, the active material, namely V... s-ZnIn2S4, ZnIn2S4 or In2S3, are mixed evenly with conductive carbon black and binder sodium carboxymethyl cellulose in water at a ratio of 7:2:1 and then coated onto copper foil. The mixture is then vacuum dried at 70-100℃ for 10-12 hours and then cut into circular electrode sheets with a diameter of 11-12 mm.

[0066] b. Sodium-ion battery assembly: The active material is used as the working electrode, the sodium sheet is used as the counter electrode / reference electrode, the separator is Whatman glass fiber, and the electrolyte is 1.0M NaCF3SO3 dissolved in diethylene glycol dimethyl ether. The CR2025 button battery is assembled in an argon-filled glove box. The water oxygen value of the glove box is [O2] < 1ppm and [H2O] < 1ppm.

[0067] c. Cyclic voltammetry tests were performed using an IVIUM electrochemical workstation at a scan rate of 0.1–1.0 mV / s. -1 The voltage range is 0.3 to 2.5V;

[0068] d. Electrochemical impedance spectroscopy was performed at room temperature, with a frequency range of 100 kHz to 10 mHz.

[0069] e. Perform constant current charge-discharge cycle testing using the LAND CT2001A battery testing system, with a voltage range of 0.3–2.5V;

[0070] f. Battery disassembly and characterization: After the charge and discharge test, the button battery was disassembled in a glove box, the electrode plates were removed, and the battery was soaked in dimethyl carbonate solution for 20-24 hours. Then it was washed with ethanol 3-6 times, dried, and then subjected to TEM characterization. The water oxygen values ​​in the glove box were [O2] < 1 ppm and [H2O] < 1 ppm, respectively.

[0071] g. In-situ XRD characterization: V s The ZnIn2S4 electrode was used as the working electrode, the sodium sheet as the counter / reference electrode, the diaphragm was made of Whatman glass fiber, and the electrolyte was 1.0 M NaCF3SO3 dissolved in diethylene glycol dimethyl ether. An in-situ battery was assembled in an argon-filled glove box using an in-situ battery device. The in-situ battery was then characterized by XRD during the charge and discharge process. The water oxygen values ​​in the glove box were [O2] < 1 ppm and [H2O] < 1 ppm, respectively.

[0072] Bimetallic sulfide ZnIn2S4(V s Morphological and structural characterization of ZnIn2S4:

[0073] Preparation of V s The process of -ZnIn2S4 is as follows Figure 2As shown. First, ZnCl2 and InCl3•4H2O were dissolved in deionized water, and then the pH was adjusted to 2.5 using HCl solution. Next, thioacetamide (TAA) was added, stirred until dissolved, and then reacted in a low-temperature water bath to obtain ZnIn2S4. Finally, ZnIn2S4 was annealed under an Ar atmosphere to obtain V. s -ZnIn2S4. We characterized V by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). s The structure and morphology of ZnIn2S4. Figure 3 For V s XRD patterns of ZnIn2S4 (JCPDS No. 65-2023) and In2S3 (JCPDS No. 73-1366). (Compared with...) Figure 4 A comparison of the XRD patterns of ZnIn2S4 shows that, corresponding to V s The angles of the diffraction peaks on the (006), (102), and (110) crystal planes of ZnIn2S4 all decrease, indicating that in V s -S vacancies may have formed in ZnIn2S4. Figure 5 and Figure 6 V s FESEM and TEM images of ZnIn2S4 show that the material is composed of ultrathin nanosheets. Figure 7 For V s A high-resolution TEM (HRTEM) image of ZnIn2S4 shows that the thickness of its nanosheets is about 12 nm (about 25 atomic layers thick), with each atomic layer being 0.494 nm thick, corresponding to the (005) crystal plane of ZnIn2S4. Figure 8 For V s -HRTEM image of ZnIn2S4, where the interplanar spacings of 0.293 and 0.309 nm correspond to the (104) and (008) / (013) planes of ZnIn2S4, respectively. Figure 9 For V s The selected area electron diffraction (SAED) pattern of ZnIn2S4 clearly shows the diffraction rings of ZnIn2S4, consistent with the XRD results. Next, we confirmed the presence of V using X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). s -The existence of S vacancy in ZnIn2S4. Figure 10 For V s The EPR spectra of ZnIn2S4 and ZnIn2S4 show that V s -ZnIn2S4 exhibits a strong EPR signal at g = 2.003, indicating the presence of abundant S vacancies.Figure 11 For V s The XPS full spectra of ZnIn2S4 and ZnIn2S4 can be seen from the figure. s -ZnIn2S4 and ZnIn2S4 contain Zn, In and S elements. Figure 12 For V s - S2p XPS high-resolution spectra of ZnIn2S4 and ZnIn2S4, compared with ZnIn2S4, V s The peak of -ZnIn2S4 shifted by +0.24 eV, while Figure 13 V s The In 3d XPS high-resolution spectra of ZnIn2S4 and ZnIn2S4 show that their peaks are not shifted, which further verifies V s -ZnIn2S4 contains vacant S-positions. Furthermore... Figure 14 For V s The Zn 2p XPS high-resolution spectra of ZnIn2S4 and ZnIn2S4 show that V s The characteristic peaks of -ZnIn2S4 also showed a slight shift, which may be due to the formation of sulfur vacancies around Zn atoms.

[0074] To clarify V s We characterized the reaction mechanism of the ZnIn2S4 electrode during charge and discharge processes using in-situ XRD and ex-situ HRTEM. Figure 15 As shown, the peak at approximately 38.3° corresponds to BeO in the in-situ cell. Before the discharge begins, the two peaks at 21.2° and 27.4° correspond to the (006) and (102) crystal planes of ZnIn2S4 (JCPDS No. 65-2023), respectively. When the discharge reaches 1.05V, the peak at approximately 21.2° disappears, the peak at approximately 27.4° gradually shifts to a lower angle, and a new peak appears at approximately 31.0°. These phenomena indicate that Na... + Successfully inserted into V s -ZnIn2S4 and Na formed x -ZnIn2S4 phase. During the discharge process from 1.05 to 0.41V, Na x The peak of -ZnIn2S4 gradually disappears and new Na2S and Na are formed. y -In2S3 peak. Due to the small particle size or low crystallinity of zinc, no Zn peak was observed. Subsequently, Na... y -In2S3 gradually transforms into Na z -In6S7, metallic zinc also undergoes an alloying reaction with Na to form NaZn. 13 As the discharge process continues until its end, due to Na...+ Continuously inserted into Na z In In6S7, Na z The diffraction peaks of -In6S7 gradually shifted to lower angles. Subsequently, during charging to 0.9V, Na... z The diffraction peaks of -In6S7 gradually returned to higher angles and then disappeared. During this process, Na was observed when charging to 0.6V. y The diffraction peak of -In2S3 indicates that some Na2S3 was produced during the above reaction process. z -In6S7 is converted to Na y -In2S3, while due to NaZn 13 A dealloying reaction occurs, and its diffraction peaks disappear. When charged to 1.16V, Na... y The disappearance of the diffraction peaks of In2S3 and Na2S indicates that Na y In In2S3, Zn and Na2S are completely converted to Na. x -ZnIn2S4. During the subsequent charging process from 1.16V to 1.60V, due to Na... x -ZnIn2S4 has poor crystallinity; no Na was observed in the XRD pattern. x - Diffraction peaks of ZnIn2S4. As the charging process proceeds, Na... + Continuously from Na x - It is extracted from ZnIn2S4. After full charging, the diffraction peaks of ZnIn2S4 reappeared in the XRD pattern. The above results indicate that V s The reaction mechanism of ZnIn2S4 during the charge and discharge process is an insertion-conversion-alloy reaction with good reversibility. Figures 16 to 21 V s -HRTEM images of ZnIn2S4 at different charge and discharge potentials. When discharged to 1.0V, from Figure 16 The generated Na can be seen in x -ZnIn2S4 phase indicates Na + Successfully inserted into V s In ZnIn2S4. When discharged to 0.6V, due to the alloying and conversion reactions, from Figure 17 New NaZn can be seen forming. 13 , Na2S and Na y -In2S3. After complete discharge, from Figure 18 Na can be seen in y -In6S7 NaZn 13 The (420) and (265) crystal planes of Na₂S indicate that a transformation reaction occurred. When charged to 0.9V, due to the occurrence of transformation and dealloying reactions, [the following text appears to be incomplete and requires further context: "from..."]Figure 19 The formation of Zn, Na2S, and Na can be observed. b -In2S3. Then, when charged to 1.40V, from... Figure 20 Zn, Na2S and Na can be seen in it. b -In2S3 was completely converted into Na. c -ZnIn2S4. When fully charged to 2.5V, from Figure 21 Na can be seen in c The lattice spacing of -ZnIn2S4 decreases, indicating that Na + Successfully from Na c Extracted from ZnIn2S4. All the above non-in-situ HRTEM results are consistent with the in-situ XRD results. Based on the above analysis, V s The detailed electrochemical reaction of ZnIn2S4 is as follows:

[0075] Discharge process:

[0076] Insertion reaction: ZnIn2S4 + xNa + +xe - →Na x -ZnIn2S4 (1) Transformation reaction: Na x -ZnIn2S4+(2+yx)Na + +(2+yx)e - →Na₂S + Na y -In2S3+Zn (2) Alloy reaction: 13Zn + Na + +e - →NaZn 13 (3) Transformation reaction: 3Na y -In2S3+(4+z-3y)Na + +(4+z-3y)e - →2Na₂S + Na z -In6S7 (4) Insertion reaction: Na z -In6S7+aNa + +ae - →Na a+z -In6S7 (5) Charging process:

[0077] Insertion reaction: Na a+z -In6S7→Na a -In6S7+zNa + +ze - (6)

[0078] Dealloying reaction: NaZn 13 →13Zn+Na + +e - (7)

[0079] Transformation reaction: Na a -In6S7 + 2Na2S → 3Na b -In2S3+(a+4-3b)Na + +(a+4-3b)e - (8)

[0080] Transformation and insertion reaction: Na₂S + Na b -In2S3+Zn→Na c -ZnIn2S4+(b+2-c)Na + +(b+2-c)e - (9)

[0081] In summary, V s The ZnIn2S4 electrode undergoes a reversible intercalation-conversion-alloying reaction. During the electrochemical reaction, the presence of alloying and conversion reactions provides a significant capacity contribution to the electrode. The alloy formed during the alloying reaction can also improve the conductivity of the electrode material. However, both of these reactions lead to a large volume expansion of the electrode material, thus compromising its structural stability. Conversely, the intercalation reaction produces a smaller volume change, thus ensuring the structural stability of the electrode material. Therefore, the intercalated compound (Na) formed in the intercalation reaction... z -In6S7) exhibits good structural stability, which can effectively suppress volume changes during electrochemical reactions, thereby improving the cycle performance of the electrode. As a composite material with Na... z -In6S7 is a compound of the same type as Na y -In2S3 (intercalation type) also exhibits similarities to Na z -In6S7 has the same effect.

[0082] To test V s To assess the electrochemical performance of ZnIn2S4 as a negative electrode material in sodium-ion batteries, we assembled samples into half-cells and performed electrochemical tests at room temperature. It should be noted that all capacities in this work are based on Va. s Calculation of the total mass of ZnIn2S4. Figure 22 For V s -ZnIn2S4, ZnIn2S4 and In2S3 electrodes at 0.5A g -1 The cycle performance curve under the following conditions, V s The reversible capacity of the ZnIn2S4 electrode after 100 cycles is 505.2 mAh g.-1 It is far superior to ZnIn2S4 (401.6mAh g) -1 ) and In2S3 (317.5mAh g -1 ). Figure 23 For a current density of 0.5 A g -1 At that time, V s - Constant current charge-discharge curves of the ZnIn2S4 electrode. V s The initial discharge and charge capacities of the ZnIn2S4 electrode are 682.8 and 530.5 mAh g, respectively. -1 The corresponding initial coulombic efficiency is 78%. The irreversible capacity in the first cycle is due to the formation of a solid electrolyte membrane. Figure 1 For V s Rate performance test results for ZnIn2S4, ZnIn2S4 and In2S3 electrodes. Current densities of 0.1, 0.2, 0.5, 1.0, 2.0, 5.0, 10.0, 20.0 and 50.0 Ag. -1 At that time, V s The average discharge capacities corresponding to the ZnIn2S4 electrode were 499.5, 493.5, 480.9, 465.1, 444.1, 410.7, 373.6, 334.4 and 270.8 mAh g, respectively. -1 Even at 80.0A g -1 At current density, V s The average discharge capacity of the ZnIn2S4 electrode remains as high as 222.7 mAh g. -1 It is far higher than ZnIn2S4 (148.2mAh g). -1 ) and In2S3 (74.4mAh g -1 When the current density returns to 0.1 A g -1 At that time, V s The capacity of the ZnIn2S4 electrode can be restored to 496.7 mAh g. -1 And it gradually stabilizes during subsequent charge-discharge cycles. Figure 24 For V s -ZnIn2S4, ZnIn2S4 and In2S3 electrodes at 10 A g -1 Cyclic stability test results at current density. After 2000 cycles, V s The discharge capacity of the ZnIn2S4 electrode remains as high as 349.6 mAh g. -1 Furthermore, the capacity decay per cycle is only 0.006%. In contrast, the discharge capacities of ZnIn2S4 and In2S3 are both lower than V. s-ZnIn2S4, and decays rapidly. The aforementioned ultrafast and ultrastable sodium storage performance demonstrates that S vacancies and the intercalation-conversion-alloying reaction mechanism greatly enhance V... s - Rate and cycle performance of ZnIn2S4.

[0083] To better understand V s The ZnIn2S4 electrode exhibits excellent high-rate discharge performance, which we tested at different scan rates (0.2–1.0 mV / s). -1 The cyclic voltammetry test under the following conditions yielded the following results: Figure 25 As shown. Typically, the scan rate (v) and test current (i) follow the following relationship:

[0084] i = av b (10)

[0085] Where a and b are adjustable parameters. Equation 10 can also be expressed in the following form.

[0086] log(i) = blog(v) + log(a) (11)

[0087] Here, b is the slope of the linear relationship between log(i) and log(v), and its magnitude can characterize Na. + Storage mechanism. b = 0.5 indicates that the electrode electrochemical reaction is Na. + Intercalation / extraction reactions are diffusion-controlled processes; b=1 indicates that the electrode electrochemical reaction is capacitive, controlled by surface reactions, representing a capacitively controlled process. Through Figure 26 The slope values ​​b obtained from the relationship between log(i) and log(v) are 0.86 (peak O1), 0.99 (peak O2), 0.79 (peak R1), 0.87 (peak R2), and 0.63 (peak R3), respectively, indicating that V s The kinetics of the ZnIn2S4 electrode are primarily capacitively controlled. Furthermore, capacitive behavior (k1v) and diffusion behavior (k2v) at a fixed potential are also observed. 1 / 2 The relative contribution of ) can be obtained from the following equation:

[0088] i(V) = k1v + k2v 1 / 2 (12)

[0089] Where k1 and k2 are adjustable parameters. Equation 12 can also be expressed in the following form.

[0090] i(V) / v 1 / 2 = k1v 1 / 2 + k2 (13)

[0091] By calculating the value of k1, the specific proportion of capacitance stored in the entire electrochemical process can be determined. For example... Figure 27 As shown, as the scan rate increases from 0.2 to 1.0 mV s -1 At that time, V s The capacitance contribution of the ZnIn2S4 electrode increased from 80.2% to 95.5%, and this ultra-high capacitance contribution rate greatly promoted the electron / ion diffusion kinetics. In addition, we used galvanostatic intermittent titration (GITT) to calculate V. s Na-ZnIn2S4 electrode + diffusion coefficient The results are as follows Figure 28 As shown. Typically, The value of can be calculated using Fick's second law as follows:

[0092]

[0093] like Figure 29 As shown, V s -ZnIn2S4 electrode The reaction is much larger than that of ZnIn2S4 and In2S3 electrodes, demonstrating its rapid reaction kinetics.

[0094] In summary, we prepared the bimetallic sulfide ZnIn2S4 via a safe and simple low-temperature water bath reaction followed by annealing. The ultrathin nanosheets of this material can effectively alleviate the mechanical stress caused by volume changes and improve the pseudocapacitive effect; sulfur vacancies can improve conductivity and enhance Na+. + The adsorption capacity enhances sodium storage capacity; the intercalated compound formed under the complex reaction mechanism acts as a buffer during charge and discharge, reducing strain caused by volume changes, enhancing structural stability, and improving cycle performance. Therefore, this material exhibits excellent electrochemical performance as a negative electrode for sodium-ion batteries and is expected to be applied in high-performance sodium-ion batteries.

[0095] Example 2

[0096] The preparation process and steps in this embodiment are as follows:

[0097] (1) Preparation of ZnIn2S4: Dissolve 0.14-0.16g ZnCl2 and 0.24-0.26g InCl3·4H2O in 50ml of deionized water respectively. After stirring for 10-15 minutes, adjust the pH of the solution to 2.5 with hydrochloric acid solution and then stir for 30-40 minutes. Then add 0.15-0.2g TAA to the solution and continue stirring for 10-15 minutes. Finally, place the solution in a water bath at 80-90℃ and stir continuously for 2-2.5h. After centrifugation, washing and drying, collect ZnIn2S4.

[0098] (2) Preparation of V s -ZnIn2S4: ZnIn2S4 was annealed at 400℃ for 2–2.5 h in an Ar atmosphere to obtain V s -ZnIn2S4-400.

[0099] V obtained by the above preparation method s The electrochemical performance of ZnIn2S4-400 material as a negative electrode material for sodium-ion batteries was tested, including the following steps:

[0100] a. Preparation of working electrode: First, the active material, namely V... s -ZnIn2S4, ZnIn2S4 or In2S3, are mixed evenly with conductive carbon black and binder sodium carboxymethyl cellulose in water at a ratio of 7:2:1 and then coated onto copper foil. The mixture is then vacuum dried at 70-100℃ for 10-12 hours and then cut into circular electrode sheets with a diameter of 11-12 mm.

[0101] b. Sodium-ion battery assembly: The active material is used as the working electrode, the sodium sheet is used as the counter electrode / reference electrode, the separator is Whatman glass fiber, and the electrolyte is 1.0M NaCF3SO3 dissolved in diethylene glycol dimethyl ether. The CR2025 button battery is assembled in an argon-filled glove box. The water oxygen value of the glove box is [O2]<1ppm, [H2O]<1ppm.

[0102] c. Cyclic voltammetry tests were performed using an IVIUM electrochemical workstation at a scan rate of 0.1–1.0 mV / s. -1 The voltage range is 0.3 to 2.5V;

[0103] d. Electrochemical impedance spectroscopy was performed at room temperature, with a frequency range of 100 kHz to 10 mHz.

[0104] e. Perform constant current charge-discharge cycle testing using the LAND CT2001A battery testing system, with a voltage range of 0.3–2.5V;

[0105] f. Battery disassembly characterization: After the charge and discharge test, the button battery was disassembled in a glove box, the electrode plates were removed, and the battery was immersed in dimethyl carbonate solution for 20-24 hours. Then it was washed with ethanol 3-6 times, dried, and then TEM characterized. The water oxygen values ​​in the glove box were [O2] < 1 ppm and [H2O] < 1 ppm, respectively.

[0106] g. In-situ XRD characterization: V s The ZnIn2S4 electrode was used as the working electrode, the sodium sheet as the counter / reference electrode, the diaphragm was made of Whatman glass fiber, and the electrolyte was 1.0 M NaCF3SO3 dissolved in diethylene glycol dimethyl ether. An in-situ battery was assembled in an argon-filled glove box using an in-situ battery device. The in-situ battery was then characterized by XRD during the charge and discharge process. The water oxygen values ​​in the glove box were [O2] < 1 ppm and [H2O] < 1 ppm, respectively.

[0107] The V obtained in this embodiment s -FESEM images of ZnIn2S4-400 as shown Figure 30 As shown in the figure, the material prepared in this embodiment has a similar nanosheet morphology to the material prepared in Example 1, which is beneficial for the storage of sodium ions. Figure 31 For V s -ZnIn2S4-400 and V s The XRD pattern of ZnIn2S4 shows that, compared with the material prepared in Example 1, V increases with decreasing annealing temperature. s The degree of crystallization of ZnIn2S4-400 also decreases accordingly.

[0108] Example 3

[0109] The preparation process and steps in this embodiment are as follows:

[0110] (1) Preparation of ZnIn2S4: Dissolve 0.14-0.16g ZnCl2 and 0.24-0.26g InCl3·4H2O in 50ml of deionized water respectively. After stirring for 10-15 minutes, adjust the pH of the solution to 2.5 with hydrochloric acid solution and then stir for 30-40 minutes. Then add 0.15-0.2g TAA to the solution and continue stirring for 10-15 minutes. Finally, place the solution in a water bath at 80-90℃ and stir continuously for 2-2.5h. After centrifugation, washing and drying, collect ZnIn2S4.

[0111] (2) Preparation of V s -ZnIn2S4: ZnIn2S4 was annealed at 600℃ for 2–2.5 h in an Ar atmosphere to obtain V s -ZnIn2S4-600.

[0112] V obtained by the above preparation method s The electrochemical performance of ZnIn2S4-600 material as a negative electrode material for sodium-ion batteries was tested, including the following steps:

[0113] a. Preparation of working electrode: First, the active material, namely V... s -ZnIn2S4, ZnIn2S4 or In2S3, are mixed evenly with conductive carbon black and binder sodium carboxymethyl cellulose in water at a ratio of 7:2:1 and then coated onto copper foil. The mixture is then vacuum dried at 70-100℃ for 10-12 hours and then cut into circular electrode sheets with a diameter of 11-12 mm.

[0114] b. Sodium-ion battery assembly: The active material is used as the working electrode, the sodium sheet is used as the counter electrode / reference electrode, the separator is Whatman glass fiber, and the electrolyte is 1.0M NaCF3SO3 dissolved in diethylene glycol dimethyl ether. The CR2025 button battery is assembled in an argon-filled glove box. The water oxygen value of the glove box is [O2] < 1ppm and [H2O] < 1ppm.

[0115] c. Cyclic voltammetry tests were performed using an IVIUM electrochemical workstation at a scan rate of 0.1–1.0 mV / s. -1 The voltage range is 0.3 to 2.5V;

[0116] d. Electrochemical impedance spectroscopy was performed at room temperature, with a frequency range of 100 kHz to 10 mHz.

[0117] e. Perform constant current charge-discharge tests using the LAND CT2001A battery testing system, with a voltage range of 0.3–2.5V;

[0118] f. Battery disassembly characterization: After the charge and discharge test, the button battery was disassembled in a glove box, the electrode plates were removed, and the battery was immersed in dimethyl carbonate solution for 20-24 hours. Then it was washed with ethanol 3-6 times, dried, and then TEM characterized. The water oxygen values ​​in the glove box were [O2] < 1 ppm and [H2O] < 1 ppm, respectively.

[0119] g. In-situ XRD characterization: V s The ZnIn2S4 electrode was used as the working electrode, the sodium sheet as the counter / reference electrode, the diaphragm was made of Whatman glass fiber, and the electrolyte was 1.0 M NaCF3SO3 dissolved in diethylene glycol dimethyl ether. An in-situ battery was assembled in an argon-filled glove box using an in-situ battery device. The in-situ battery was then characterized by XRD during the charge and discharge process. The water oxygen values ​​in the glove box were [O2] < 1 ppm and [H2O] < 1 ppm, respectively.

[0120] The V obtained in this embodiments -FESEM images of ZnIn2S4-600 as shown Figure 32 As shown in the figure, the material prepared in this embodiment has a similar nanosheet morphology to the material prepared in Example 1, which is beneficial for the storage of sodium ions. Figure 33 For V s -ZnIn2S4-600 and V s The XRD pattern of ZnIn2S4 shows that, compared with the material prepared in Example 1, V increases with increasing annealing temperature. s The degree of crystallinity of ZnIn2S4-600 also increases accordingly. The above embodiments are merely several implementation methods within the scope of this invention, and not all of them. They should not be used to limit the scope of protection of this invention. All equivalent changes or modifications made in accordance with the spirit and essence of this invention should be covered within the scope of protection of this invention.

Claims

1. Application of nanosheet-like double-metal sulfide ZnIn2S4 as negative electrode material of sodium-ion battery, comprising the following steps: a. Preparation of ZnIn2S4: 0.14-0.16 g of ZnCl2and 0.24-0.26 g of InCl3.4H2O were dissolved in 50 ml of deionized water, respectively, and after stirring for 10-15 minutes, the pH of the above mixture was adjusted to 2.5 using a hydrochloric acid solution, and then stirred for another 30-40 minutes. After that, 0.15-0.2 g of thioacetamide (TAA) was added to the solution, and the stirring was continued for 10-15 minutes. Finally, the solution was placed in a water bath at a temperature of 80-90°C of C and continuously stirred for 2-2.5 h, and after centrifugation, washing and drying, ZnIn2S4was collected. 0 C. Preparation of ZnIn2S4: 0.14-0.16 g of ZnCl2and 0.24-0.26 g of InCl3.4H2O were dissolved in 50 ml of deionized water, respectively, and after stirring for 10-15 minutes, the pH of the above mixture was adjusted to 2.5 using a hydrochloric acid solution, and then stirred for another 30-40 minutes. After that, 0.15-0.2 g of thioacetamide (TAA) was added to the solution, and the stirring was continued for 10-15 minutes. Finally, the solution was placed in a water bath at a temperature of 80-90°C of C and continuously stirred for 2-2.5 h, and after centrifugation, washing and drying, ZnIn2S4 b. Preparation of V s - ZnIn2S4: ZnIn2S4was annealed at 400-600 °C for 2-2.5 h in Ar atmosphere to obtain V s - ZnIn2S4; The crystallization degree of ZnIn2S4 is controlled by adjusting the annealing temperature and time in step b.

2. Use of a nanosheet-like double metal sulfide ZnIn2S4 as a negative electrode material for sodium ion batteries according to claim 1, characterized in that, The ZnIn2S4 prepared in step b was annealed at 500 °C for 2 h with a temperature increase of 5 °C min -1 under Ar atmosphere, and finally V-ZnIn2S4 with rich sulfur vacancies was obtained. s -ZnIn2S4.

3. Application of nanosheet-like double-metal sulfide ZnIn2S4 as negative electrode material of sodium-ion battery according to claim 1 or 2, comprising the following steps: a) Working electrode preparation: First, the active material, i.e. V s ZnIn2S4, conductive carbon black and binder sodium carboxymethyl cellulose were mixed in a ratio of 7:2:1 in water and coated on a copper foil, vacuum dried at 70-100 °C for 10-12 h, and then cut into a circular electrode sheet with a diameter of 11-12 mm; b. Sodium-ion battery assembly: the active material is used as the working electrode, the sodium sheet is used as the counter electrode / reference electrode, the diaphragm is Whatman glass fiber, and the electrolyte is 1.0 M NaCF3SO3 dissolved in diglyme, and a CR2025 type button cell is assembled in an argon-filled glove box, and the water and oxygen values of the glove box are [O2]<1 ppm and [H2O]<1 ppm, respectively; c. Cyclic voltammetry test was performed using IVIUM electrochemical workstation with a scan rate of 0.1-1.0 mV s -1 and a voltage range of 0.3-2.5 V. d. Electrochemical impedance test is carried out at room temperature, and the frequency range is 100 kHz to 10 mHz; e. Constant current charge-discharge cycle test is carried out using LAND CT2001A battery test system, and the voltage range is 0.3-2.5 V; f. Disassembly characterization of the battery: the button cell after charge-discharge test is disassembled in the glove box, the electrode sheet is taken out, soaked in dimethyl carbonate solution for 20-24 h, cleaned with ethanol for 3-6 times, dried, and then characterized by transmission electron microscope (TEM), and the water and oxygen values of the glove box are [O2]<1 ppm and [H2O]<1 ppm, respectively. g. In-situ X-ray diffraction (XRD) characterization: V s - ZnIn2S4 electrode as working electrode, sodium sheet as counter electrode / reference electrode, separator as Whatman glass fiber, electrolyte as 1.0 M NaCF3SO3 dissolved in diglyme, in-situ battery was assembled in an argon-filled glove box using in-situ battery device, then the in-situ battery during charging and discharging process was characterized by XRD, the water and oxygen values of the glove box were [O2] < 1 ppm, [H2O] < 1 ppm, respectively.

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