Preparation method and application of MAX phase derived polymetallic sulfide

Abstract

The invention provides a preparation method and application of MAX phase derived polymetallic sulfide, and belongs to the field of lithium ion battery negative electrode material preparation. A MAX phase is used as a precursor, metal chlorides such as CuCl2, FeCl2 and CoCl2 are used as etching agents, K2S is used as a sulfur source, and etching in-situ vulcanization is performed under a NaCl / KCl molten salt system to obtain a series of multi-metal sulfide materials. When the prepared multi-metal sulfide material is used as a lithium ion battery negative electrode material, excellent cycle and rate performance is shown.

Description

Technical Field

[0001] The present invention relates to the field of synthesis and preparation of lithium ion battery negative electrode materials, and in particular to a preparation method and application of a MAX phase-derived multimetallic sulfide negative electrode material. Background Art

[0002] The large-scale exploitation of traditional fossil energy sources has led to increasingly serious environmental problems and an urgent energy crisis, necessitating the vigorous development of new renewable energy sources. Furthermore, rising environmental awareness has led to a growing demand for new energy vehicles, driving the rapid development of lithium-ion batteries. Traditional graphite anodes have low capacity and poor stability, necessitating the urgent need to find lithium-ion battery anode materials with improved performance. Conversion-type materials primarily include metal oxides and metal sulfides, which react primarily through the reaction of metal compounds with lithium metal to produce elemental metals and lithium salts. Conversion reactions enable the transfer of multiple electrons and possess a large theoretical capacity. Furthermore, the voltage platform of transition metal sulfides is typically above 1V, effectively reducing the formation of lithium dendrites. Therefore, transition metal sulfides hold great promise for application in lithium-ion battery anodes.

[0003] As a new type of two-dimensional material, MXene has metal-like conductivity and a unique layered structure. It can not only be used as an active electrode material in various electrochemical energy storage systems, but also as a conductive substrate to load various active materials, improve their conductivity, buffer their volume expansion, and thus obtain high-performance energy storage electrode materials. In addition, the general structural formula of MXene is usually M n+1 X n T x (n=1-3), and its structural thermodynamic instability allows it to be transformed into corresponding metal compound materials, including metal oxides, metal sulfides, metal selenides, etc., through hydrothermal and chemical conversion methods.

[0004] The Lewis acid molten salt etching method is a novel approach for the universal preparation of a series of MXene materials by placing the MAX phase in a mixed Lewis acid halide salt at high temperature and in a molten state. Due to the advantages of the molten salt synthesis method, such as rapid reaction kinetics and environmental friendliness, and the ability to precisely control the product morphology and structure by manipulating parameters such as the molten salt composition, reaction temperature, and time, it is expected that by manipulating the composition of the Lewis acid molten salt etching system, a one-step in situ synthesis from MAX phase to MXene and then to transition metal sulfide can be achieved, yielding a series of transition metal sulfide materials with unique morphologies, structures, and compositions. Summary of the Invention

[0005] The present invention aims to provide a preparation method and application of MAX phase-derived polymetallic sulfides, which can be used as negative electrode materials for lithium-ion batteries and have excellent rate performance and cycle performance.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a MAX phase-derived polymetallic sulfide material with excellent rate capability and cycle performance, comprising the following steps:

[0008] (1) Weighing MAX phase, K2S, metal chloride etchant, NaCl, and KCl according to a certain molar ratio;

[0009] (2) Pour the solid powder weighed in (1) into a mortar and grind until the powder is evenly dispersed;

[0010] (3) Transfer the powder in (2) to a corundum boat, heat it to a certain temperature in an inert atmosphere of a tube furnace and keep it warm, then cool it down to 300°C and then cool it naturally to room temperature;

[0011] (4) The solid powder obtained in (3) is washed and collected by vacuum filtration, and then vacuum dried to obtain a polymetallic sulfide material.

[0012] Preferably, the certain molar ratio in step (1) is 1:(2-8):3:3:2.

[0013] Preferably, the MAX phase in step (1) is any one or more of Nb2AlC, Ti3AlC2, V2AlC, TiNbAlC, TiVAlC, Mo2TiAlC2, Mo3AlC2, TiVNbMoAlC3 and TiVCrMoAlC3.

[0014] Preferably, the metal chloride etchant in step (1) can be replaced by any one or more of CuCl2, FeCl2, CoCl2, SnCl2, ZnCl2 and NiCl2.

[0015] Preferably, the holding temperature of the tubular furnace in step (3) is 600-800° C., and the holding time is 2-8 hours.

[0016] Preferably, the inert atmosphere in step (3) is any one of helium, neon, argon and nitrogen, or a mixture of several of them.

[0017] The present invention also provides a MAX phase-derived polymetallic sulfide material prepared by the preparation method described in the above technical solution.

[0018] The present invention also provides the use of the bimetallic sulfide described in the above technical solution in the negative electrode of a lithium ion battery.

[0019] The present invention provides a method for preparing a MAX phase-derived polymetallic sulfide material, comprising the following steps: weighing a MAX phase, K2S, metal chloride, NaCl, and KCl according to a specific molar ratio, grinding the mixture uniformly, and then placing the mixture in a tube furnace for a high-temperature molten salt reaction. After cooling to room temperature, the mixture is collected by filtration with deionized water, washed multiple times with deionized water and anhydrous ethanol, and finally dried in a vacuum oven to obtain the polymetallic sulfide material. The present invention utilizes a molten salt reaction strategy, enabling the preparation of MAX phase-derived polymetallic sulfides in a relatively short time. K2S, which has a high boiling point (912°C) and is not easily volatilized in a molten salt system, is used as a sulfur source. Metal chloride is used as an etchant, allowing metal cations to replace the Al layer in the MAX phase and introduce metal clusters, further catalyzing the sulfurization reaction. A relatively slow heating rate allows the polymetallic sulfide to maintain its original layered morphology, while a low cooling rate ensures the integrity of the material structure. The MAX phase-derived polymetallic sulfide material of the present invention exhibits excellent crystallinity, a flower-like or network-like structure, and exposes a large number of active lithium storage sites. The experimental results show that when the FeTiS material provided by the present invention is used as the negative electrode of lithium ion battery, the -1 At a current density of 729.5 mAh g -1 The specific capacity is 616.6 mAh g after 200 cycles. -1 , and at 1A g -1 After 2000 cycles at a current density of 1.5 GHz, the specific capacity is 623.0 mAh g -1 The bimetallic sulfide material prepared by the present invention not only has a high specific capacity but also has good cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 (a) XRD and (b) SEM images of the MAX phase-derived bimetallic sulfide CuNbS material prepared in Example 1 of the present invention;

[0021] Figure 2 (a) XRD and (b) SEM images of the MAX phase-derived bimetallic sulfide FeNbS material prepared in Example 2 of the present invention;

[0022] Figure 3 (a) 0.1A g -1 Cycling performance under (b) rate performance, (c) 1A g -1 Cycling performance under

[0023] Figure 4 (a) XRD and (b) SEM images of the MAX phase-derived bimetallic sulfide FeTiS material prepared in Example 3 of the present invention;

[0024] Figure 5 (a) 0.1A g -1 Cycling performance under (b) rate performance, (c) 1A g -1 Cycling performance under

[0025] Figure 6 (a) XRD and (b) SEM images of the MAX phase-derived trimetallic sulfide CuTiNbS material prepared in Example 4 of the present invention; DETAILED DESCRIPTION

[0026] The present invention aims to provide a method for preparing and applying MAX phase-derived polymetallic sulfide materials. The method comprises the following steps:

[0027] (1) Weighing MAX phase, K2S, metal chloride etchant, NaCl, and KCl according to a certain molar ratio;

[0028] (2) Pour the solid powder weighed in (1) into a mortar and grind until the powder is evenly dispersed;

[0029] (3) Transfer the powder in (2) to a corundum boat, heat it to a certain temperature in an inert atmosphere of a tube furnace and keep it warm, then cool it down to 300°C and then cool it naturally to room temperature;

[0030] (4) The solid powder obtained in (3) is washed and collected by vacuum filtration, and then vacuum dried to obtain a polymetallic sulfide material.

[0031] In the present invention, the high-temperature molten salt process can effectively improve the reaction efficiency, reduce the reaction time, and facilitate the removal of impurities in the later stage.

[0032] In the present invention, the certain molar ratio includes 1:(2-8):3:3:2, more preferably 1:4:3:3:2; the MAX phase preferably includes Nb2AlC, Ti3AlC2, V2AlC, TiNbAlC, TiVAlC, Mo2TiAlC2, Mo3AlC2, TiVNbMoAlC3 and TiVCrMoAlC3, more preferably Nb2AlC, Ti3AlC2, V2AlC, TiNbAlC, TiVAlC; the metal chloride etchant preferably includes CuCl2, FeCl2, CoCl2, SnCl2, ZnCl2 and NiCl2, more preferably CuCl2, FeCl2, CoCl2; the MAX phase was purchased from Jilin Yiyi Technology Co., Ltd. and Laizhou Kaixi Ceramic Materials Co., Ltd., and the etchant and anhydrous potassium sulfide were purchased from Aladdin Pharmaceutical Co., Ltd.

[0033] In the present invention, the holding temperature of the tube furnace is preferably 600-800° C., more preferably 800° C. Temperature change causes changes in crystallinity, and 800° C. is preferably selected to obtain samples with better crystallinity.

[0034] In the present invention, the inert atmosphere is preferably any one of helium, neon, argon and nitrogen or a mixture of several of them, which can prevent the oxidation of the product.

[0035] The present invention also provides the use of the bimetallic sulfide described in the above technical solution in the negative electrode of a lithium ion battery.

[0036] In the present invention, the characterization and testing methods used when the MAX phase-derived polymetallic sulfide is used as a negative electrode for a lithium-ion battery are not particularly limited, and the application methods of lithium-ion battery negative electrode materials well known to those skilled in the art can be used.

[0037] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] Example 1

[0039] Nb2AlC, K2S, CuCl2, NaCl and KCl were weighed in a molar ratio of 1:4:3:3:2 and ground thoroughly. The mixture was poured into a corundum boat and transferred to a tube furnace. The mixture was heated at 4 °C min under an argon atmosphere. -1 The temperature was raised to 800℃ at a rate of 100℃ and kept at that temperature for 2h, and then the temperature was increased to 5℃min -1 The temperature was lowered to 300°C and then naturally cooled to room temperature. The reaction product was then rinsed with a large amount of deionized water, and the precipitate was collected by vacuum filtration and dried in a vacuum oven to obtain bimetallic sulfide CuNbS.

[0040] The MAX phase-derived CuNbS prepared in Example 1 was tested using an X-ray diffractometer, and the XRD pattern of the CuNbS prepared in Example 1 was obtained as follows: Figure 1 The characteristic peaks at 13.5°, 27.1°, 30.8°, 37.1° and 46.6° correspond to Cu 0.65 The (002), (004), (100), (103) and (105) crystal planes of NbS2 (PDF#65-5077) demonstrate that the MAX phase is derived to form CuNbS material.

[0041] The CuNbS material prepared in Example 1 was tested using a scanning electron microscope, and the SEM spectrum obtained was as follows: Figure 1 The SEM image shows the rough surface of the CuNbS sample, which is composed of numerous tiny nanosheets stacked together to form a flower-like structure. This unique microstructure gives the material a high specific surface area, providing abundant active sites for lithium storage and facilitating electrolyte infiltration.

[0042] Example 2

[0043] Nb2AlC, K2S, FeCl2, NaCl and KCl were weighed in a molar ratio of 1:4:3:3:2 and ground thoroughly. The mixture was poured into a corundum boat and transferred to a tube furnace. The mixture was heated at 4 °C min under an argon atmosphere. -1 The temperature was raised to 800℃ at a rate of 100℃ and kept at that temperature for 2h, and then the temperature was increased to 5℃min -1 The temperature was lowered to 300°C and then naturally cooled to room temperature. The reaction product was then rinsed with a large amount of deionized water, and the precipitate was collected by vacuum filtration and dried in a vacuum oven to obtain bimetallic sulfide FeNbS.

[0044] The MAX phase-derived FeNbS prepared in Example 2 was tested using an X-ray diffractometer, and the XRD pattern of the FeNbS prepared in Example 2 was obtained as shown in FIG. Figure 2 (a) The characteristic peaks at 14.5°, 29.2°, 31.1°, 31.9°, 34.4°, and 43.0° correspond to the (120), (211), (400), (410), (231), and (251) crystal planes of FeNb2S4 (PDF#21-0431), respectively. This indicates that the MAX phase is derived to form FeNbS material.

[0045] The FeNbS material prepared in Example 2 was tested using a scanning electron microscope, and the obtained SEM spectrum is as follows: Figure 2 As shown in Figure 2b, similar to Example 1, the FeNbS sample has a rough surface and a flower-like structure formed by stacking numerous tiny nanosheets. This unique microstructure gives the material a high specific surface area, providing abundant active sites for lithium storage and facilitating electrolyte infiltration.

[0046] Application Example 2

[0047] 70 mg of the MAX phase-derived FeNbS material and 20 mg of the conductive carbon q prepared in Example 2 were fully ground and mixed with carboxymethyl cellulose in a mass ratio of 7:2:1. The mixture was uniformly mixed in a homogenizer to form a slurry. The slurry was then evenly applied on the current collector copper foil. After drying, the slurry was cut into (8×8) mm pieces. 2The electrode was dried at 60°C under vacuum for 10 hours and then transferred to a glove box for later use. The battery was assembled in an Ar atmosphere glove box using a metallic lithium sheet as the counter electrode, a Celgard membrane as the separator, and 1M LiPF6 + EC / DEC (1:1, v:v) + 5wt% FEC as the electrolyte, packaged into a CR2025 lithium-ion half-cell.

[0048] Test Example 2

[0049] The cycle performance test of the battery prepared in Example 2 was carried out under the following conditions: the charge and discharge mode was constant current charging, and the current density was 0.1A g -1 , the discharge cut-off voltage is 0.01V, and the charge cut-off voltage is 3V. The cycle curve of the battery prepared in Application Example 2 is as follows Figure 3 The specific capacity of the battery prepared in Application Example 2 after 200 cycles is 629.8 mAh g -1 In the first 50 cycles or so, the specific capacity decreased due to the activation of the electrode material and the gradual penetration of the electrolyte. In the subsequent cycles, the specific capacity of the battery of Application Example 2 gradually increased.

[0050] The rate performance test of the battery prepared in Example 2 was conducted under the following conditions: the charge and discharge mode was constant current charge and discharge, and the charge and discharge rates were 0.03A g -1 , 0.05A g -1 , 0.1A g -1 , 0.2A g -1 , 0.5A g -1 , 0.8A g -1 , 1A g -1 , 2A g -1 , 5Ag -1 , 10A g -1 , 20A g -1 The battery was cycled for 10 cycles at a current density of , with a discharge cut-off voltage of 0.01 V and a charge cut-off voltage of 3 V. The rate performance of the battery prepared in Application Example 2 is as follows: Figure 3 As shown in b. Figure 3 b It can be seen that the battery made in Application Example 2 is 0.03Ag -1 , 0.05A g -1 , 0.1A g -1 , 0.2A g -1 , 0.5A g -1 , 0.8A g -1 , 1A g -1 , 2A g -1 , 5A g -1 , 10A g -1 , 20Ag -1The specific capacities are 656.4 mAh g -1 , 598.4mAh g -1 、557.0mAh g -1 , 502.4mAh g -1 , 412.5mAh g -1 、349.4mAh g -1 , 321.7mAh g -1 、258.2mAh g -1 、175.2mAh g -1 , 113.9mAh g -1 , 61.1mAh g -1 , with good rate performance.

[0051] The cycle performance test of the battery prepared in Example 2 was carried out under the following conditions: the charge and discharge mode was constant current charging, and the current density was 1A g -1 , the discharge cut-off voltage is 0.01V, and the charge cut-off voltage is 3V. The cycle curve of the battery prepared in Application Example 2 is as follows Figure 3 As shown in c. Figure 3 c It can be seen that the specific capacity of the battery prepared in Example 2 after 2000 cycles is 696.8 mAh g -1 .

[0052] Example 3

[0053] Ti3AlC2, K2S, FeCl2, NaCl and KCl were weighed in a molar ratio of 1:4:3:3:2 and ground thoroughly. The mixture was poured into a corundum boat and transferred to a tube furnace. The mixture was heated at 4 °C min under an argon atmosphere. -1 The temperature was raised to 800℃ at a rate of 100℃ and kept at that temperature for 2h, and then the temperature was increased to 5℃min -1 The temperature was lowered to 300°C and then naturally cooled to room temperature. The reaction product was then rinsed with a large amount of deionized water, and the precipitate was collected by vacuum filtration and dried in a vacuum oven to obtain bimetallic sulfide FeTiS.

[0054] The MAX phase-derived FeTiS prepared in Example 3 was tested using an X-ray diffractometer, and the XRD pattern of the FeTiS prepared in Example 3 was obtained as shown in FIG. Figure 4 (a) The characteristic peaks of this XRD spectrum have a high degree of match with FeTi2S4 (PDF#89-2025), proving that the MAX phase is derived to form FeTiS material.

[0055] The FeTiS material prepared in Example 3 was tested using a scanning electron microscope, and the SEM spectrum obtained was as follows: Figure 4b. The morphology of the bimetallic sulfide CuNbS obtained in Example 1 is similar.

[0056] Application Example 3

[0057] 70 mg of the MAX phase-derived FeTiS material and 20 mg of the conductive carbon q prepared in Example 3 were fully ground and mixed with carboxymethyl cellulose in a mass ratio of 7:2:1. The mixture was uniformly mixed in a homogenizer to form a slurry. The slurry was then evenly applied on the current collector copper foil. After drying, the slurry was cut into (8×8) mm pieces. 2 The electrode was dried at 60°C under vacuum for 10 hours and then transferred to a glove box for later use. The battery was assembled in an Ar atmosphere glove box using a metallic lithium sheet as the counter electrode, a Celgard membrane as the separator, and 1M LiPF6 + EC / DEC (1:1, v:v) + 5wt% FEC as the electrolyte, packaged into a CR2025 lithium-ion half-cell.

[0058] Test Example 3

[0059] The cycle performance test of the battery prepared in Example 3 was carried out under the following conditions: the charge and discharge mode was constant current charging, and the current density was 0.1A g -1 , the discharge cut-off voltage is 0.01V, and the charge cut-off voltage is 3V. The cycle curve of the battery prepared in Application Example 3 is as follows Figure 5 As shown in a. Figure 5 It can be seen from a that the specific capacity of the battery prepared in Example 3 after 200 cycles is 616.6 mAh g -1 In the first 50 cycles or so, the specific capacity decreased due to the activation of the electrode material and the gradual penetration of the electrolyte. In the subsequent cycles, the specific capacity of the battery of Application Example 3 gradually increased.

[0060] The rate performance test of the battery prepared in Example 3 was carried out under the following conditions: the charge and discharge mode was constant current charge and discharge, and the charge and discharge rates were 0.03A g -1 , 0.05A g -1 , 0.1A g -1 , 0.2A g -1 , 0.5A g -1 , 0.8A g -1 , 1A g -1 , 2A g -1 , 5Ag -1 , 10A g -1 , 20A g -1 The battery was cycled for 10 cycles at a current density of 1000V, with a discharge cut-off voltage of 0.01V and a charge cut-off voltage of 3V. The rate performance of the battery prepared in Application Example 3 is as follows: Figure 5 As shown in b. Figure 5 b It can be seen that the battery made in Application Example 3 is 0.03Ag -1 , 0.05A g -1 , 0.1A g -1 , 0.2A g -1 , 0.5A g -1 , 0.8A g -1 , 1A g -1 , 2A g -1 , 5A g -1 , 10A g -1 , 20Ag -1 The specific capacities are 776.6 mAh g -1 、657.8mAh g -1 、597.4mAh g -1 、553.4mAh g -1 、496.7mAh g -1 , 463.8mAh g -1 、452.8mAh g -1 , 407.2mAh g -1 、325.2mAh g -1 、236.1mAh g -1 、122.2mAh g -1 , with good rate performance.

[0061] The cycle performance test of the battery prepared in Example 3 was carried out under the following conditions: the charge and discharge mode was constant current charging, and the current density was 1A g -1 , the discharge cut-off voltage is 0.01V, and the charge cut-off voltage is 3V. The cycle curve of the battery prepared in Application Example 2 is as follows Figure 5 As shown in c. Figure 5 c It can be seen that the specific capacity of the battery prepared in Example 3 after 2000 cycles is 623 mAh g -1 .

[0062] Example 4

[0063] TiNbAlC, K2S, CuCl2, NaCl and KCl were weighed in a molar ratio of 1:4:3:3:2 and ground thoroughly. The mixture was poured into a corundum boat and transferred to a tube furnace. The mixture was heated at 4 °C min under an argon atmosphere. -1 The temperature was raised to 800℃ at a rate of 100℃ and kept at that temperature for 2h, and then the temperature was increased to 5℃min -1 The temperature was lowered to 300°C and then naturally cooled to room temperature. The reaction product was then rinsed with a large amount of deionized water, and the precipitate was collected by vacuum filtration and dried in a vacuum oven to obtain trimetallic sulfide CuTiNbS.

[0064] The MAX phase-derived CuTiNbS prepared in Example 4 was tested using an X-ray diffractometer, and the XRD pattern of the CuTiNbS prepared in Example 3 was obtained as shown in FIG. Figure 6 a. The XRD spectrum contains Cu 0.65 NbS2 (PDF#65-5077) and Cu 0.93 Characteristic peaks of two bimetallic sulfides of Ti2S4 (PDF#80-0279), demonstrating the successful preparation of MAX-phase-derived CuTiNbS materials.

[0065] The CuTiNbS material prepared in Example 4 was tested using a scanning electron microscope, and the SEM spectrum obtained was as follows: Figure 6 As shown in b. The SEM image shows that the surface of the CuTiNbS sample is rough, and many tiny nanosheets are stacked to form a flower-like structure.

Claims

1. A method for preparing MAX phase-derived polymetallic sulfides, comprising the following steps: (1) Weighing MAX phase, K2S, metal chloride etchant, NaCl, and KCl according to a certain molar ratio; (2) Pour the solid powder weighed in (1) into a mortar and grind until the powder is evenly dispersed; (3) Transfer the powder in (2) to a corundum boat, heat it to a certain temperature in an inert atmosphere of a tube furnace and keep it warm, then cool it down to 300°C and then cool it naturally to room temperature; (4) The solid powder obtained in (3) is washed and collected by vacuum filtration, and then vacuum dried to obtain a polymetallic sulfide material.

2. The preparation method according to claim 1, characterized in that The certain molar ratio in the step (1) includes 1:(2-8):3:3:

2.

3. The preparation method according to claim 1, characterized in that The MAX phase in step (1) includes one or more of Nb2AlC, Ti3AlC2, V2AlC, TiNbAlC, TiVAlC, Mo2TiAlC2, Mo3AlC2, TiVNbMoAlC3 and TiVCrMoAlC3.

4. The preparation method according to claim 1, characterized in that The metal chloride etchant in step (1) includes one or more of CuCl2, FeCl2, CoCl2, SnCl2, ZnCl2 and NiCl2.

5. The preparation method according to claim 1, characterized in that The reaction temperature in step (3) is 600-800° C., and the insulation time is 2-8 hours.

6. The preparation method according to claim 1, characterized in that The inert atmosphere in step (3) is any one of helium, neon, argon and nitrogen, or a mixture of several of them.

7. Use of the multimetallic sulfide material prepared by the preparation method according to any one of claims 1 to 6 in the negative electrode of a lithium-ion battery.

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