A heterogeneous material, its preparation method and application

Abstract

This invention provides a heterogeneous material, its preparation method, and its application. The heterogeneous material comprises nickel foam and nickel sulfide and nickel phosphide supported on the nickel foam. The heterogeneous material is prepared by heat treatment following a mixture of nickel foam, a sulfur source, and a phosphorus source. This heterogeneous material is used to prepare anode materials for sodium metal batteries. It exhibits a low Fermi level, which can prevent electrolyte decomposition, induce a uniform solid-state electrolyte interface, thereby limiting sodium dendrite growth and restricting the volume change of the anode material during sodium metal deposition / stripping, resulting in lower nucleation overpotential and better cycle performance. This anode material shows promising application prospects in the development of high-performance, long-life sodium metal battery systems.

Description

Technical Field

[0001] This invention relates to the technical field of metal batteries, specifically to a heterogeneous material, its preparation method, and its application. Background Technology

[0002] Sodium metal anodes have a capacity of 1166 mAh g. -1 Sodium metal anodes are considered potential candidate anodes for sodium-based batteries due to their high capacity and low redox potential (-2.714 V, standard hydrogen electrode). However, dendrite growth, safety concerns, and poor cycling performance hinder the practical application of sodium metal anodes. In existing technologies, high-surface-area current collectors with abundant sodium nucleation sites have been shown to reduce local current density, decrease sodium nucleus size, and lead to uniform sodium dendrite growth. Furthermore, optimizing electrolyte composition, constructing engineered functional membranes, and building artificial solid electrolyte layers (SEIs) can also effectively improve sodium dendrite growth.

[0003] Studies have reported that the initial stage of sodium nucleation behavior and the properties of the SEI formed on the current collector are very important because they control the sequential evolution of sodium deposition states, and the microstructure of the SEI and the sodium nucleation behavior can be modified by adjusting the Fermi level on the current collector surface. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a heterogeneous material, its preparation method, and its application. When used to prepare sodium metal anode materials, the heterogeneous material exhibits a lower Fermi level, can induce a uniform solid-electrolyte interface, suppress sodium dendrite formation, and limit volume changes during sodium metal deposition / exfoliation.

[0005] In a first aspect, the present invention provides a heterogeneous material comprising nickel foam and nickel sulfide and nickel phosphide loaded on said nickel foam.

[0006] Preferably, the mass ratio of the nickel foam, nickel sulfide, and nickel phosphide is (5-20):(0.1-0.9):(0.1-0.9).

[0007] Preferably, the nickel sulfide and nickel phosphide are loaded in situ onto the nickel foam.

[0008] Secondly, the present invention provides a method for preparing the heterogeneous material, comprising the following steps:

[0009] The heterogeneous material is obtained by mixing nickel foam, sulfur source, and phosphorus source and then heat-treating them.

[0010] Preferably, the sulfur source includes any one or more of phenylthiourea, thiourea, thioacetamide, disulfiram, or thiophenic acid.

[0011] Preferably, the phosphorus source includes any one or more of triphenylphosphine, tribenzylphosphine, cyclohexylphosphine, tributylphosphine, or phenylphosphonic acid.

[0012] Preferably, the heat treatment temperature is 700–900°C, and the heat treatment time is 6–8 hours.

[0013] Thirdly, the present invention provides a sodium metal anode material, comprising a heterogeneous material and sodium metal deposited on the surface of the heterogeneous material;

[0014] The heterogeneous material includes nickel foam and nickel sulfide and nickel phosphide loaded on the nickel foam.

[0015] Preferably, the mass ratio of the nickel foam, nickel sulfide, and nickel phosphide is (5-20):(0.1-0.9):(0.1-0.9).

[0016] Preferably, the nickel sulfide and nickel phosphide are loaded in situ onto the nickel foam.

[0017] Fourthly, the present invention provides a sodium metal battery, comprising the aforementioned sodium metal anode material.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] This invention provides a nickel foam-supported nickel sulfide and nickel phosphide heterostructure for preparing sodium metal battery anode materials. This material exhibits a low Fermi level, which can prevent electrolyte decomposition, induce a uniform solid-state electrolyte interface, thereby limiting sodium dendrite growth and restricting the volume change of the anode material during sodium metal deposition / stripping, resulting in lower nucleation overpotential and better cycle performance. This anode material shows promising application prospects in the development of high-performance, long-life sodium metal battery systems. Attached Figure Description

[0020] Figure 1 XRD patterns of Ni3S2 / Ni3P@NF, Ni3S2@NF and Ni3P@NF materials;

[0021] Figure 2 SEM images of Ni3S2 / Ni3P@NF, Ni3S2@NF, and Ni3P@NF materials, where, Figure 2 a is a SEM image of the Ni3S2 / Ni3P@NF material. Figure 2 b is the SEM image of Ni3S2@NF material. Figure 2 c is a SEM image of the Ni3P@NF material;

[0022] Figure 3 For Ni3S2 / Ni3P@NF, Ni3S2@NF, and Ni3P@NF materials, at 1 mA cm-2 Current density deposition of 1mAh cm -2 Cyclic coulombic efficiency diagram of sodium metal;

[0023] Figure 4 For Ni3S2 / Ni3P@NF, Ni3S2@NF, and Ni3P@NF materials, at 1 mA cm -2 Current density deposition of 1mAh cm -2 Electroplating curves of sodium metal with varying capacity;

[0024] Figure 5 The cycle time-voltage curves of symmetrical cells assembled with Ni3S2 / Ni3P@NF@Na, Ni3S2@NF@Na and Ni3P@NF@Na as counter electrodes are shown.

[0025] Figure 6 The UPS diagrams of Ni3S2 / Ni3P@NF, Ni3S2@NF, and Ni3P@NF materials are shown at the initial potential, discharged to 1.0V, and discharged to 0.01V, respectively. Figure 6 a shows the UPS diagrams of Ni3P@NF at initial potential, discharged to 1.0V, and discharged to 0.01V. Figure 6 b shows the UPS diagrams of Ni3S2@NF at initial potential, discharged to 1.0V, and discharged to 0.01V. Figure 6 c shows the UPS diagrams of Ni3S2 / Ni3P@NF at initial potential, discharged to 1.0V, and discharged to 0.01V;

[0026] Figure 6 In a, 1, 2, and 3 represent the conditions of Ni3P@NF being discharged to 0.01V, discharged to 1.0V, and at the initial potential (0cv), respectively. Figure 6 In b, 1, 2, and 3 represent the conditions of Ni3S2@NF being discharged to 0.01V, discharged to 1.0V, and at the initial potential (0cv), respectively. Figure 6 In c, 1, 2, and 3 represent the cases of discharging to 0.01V, discharging to 1.0V, and the initial potential (0cv), respectively.

[0027] Figure 7 The figure shows the Fermi level variation with discharge potential after sodium treatment of Ni3S2 / Ni3P@NF, Ni3S2@NF, and Ni3P@NF. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention does not impose any special restrictions on the source of any of the raw materials involved; they can be purchased from the market or prepared according to conventional preparation methods known to those skilled in the art.

[0030] The present invention provides a heterogeneous material comprising nickel foam and nickel sulfide and nickel phosphide loaded on said nickel foam.

[0031] In this invention, the nickel sulfide and nickel phosphide are preferably loaded in situ onto the nickel foam. The mass ratio of the nickel foam, nickel sulfide, and nickel phosphide is preferably (5-20):(0.1-0.9):(0.1-0.9), more preferably (5-15):(0.1-0.9):(0.1-0.9), and most preferably 10:(0.1-0.9):(0.1-0.9).

[0032] It should be noted that since nickel sulfide and nickel phosphide are generated by reacting with nickel foam through sulfur and phosphorus sources, and the solids generated by reacting with nickel foam during the reaction are only nickel sulfide and nickel phosphide, the total mass percentage of nickel sulfide and nickel phosphide is 100%. That is, in the above mass ratio, when the value of nickel sulfide is 0.1, the value of nickel phosphide is 0.9.

[0033] The present invention also provides a method for preparing the heterogeneous material, comprising the following steps:

[0034] The heterogeneous material is obtained by mixing nickel foam, sulfur source, and phosphorus source and then heat-treating them.

[0035] This invention does not impose any particular restrictions on the source of the nickel foam; commercially available products are acceptable. In this invention, before mixing the nickel foam with the phosphorus and sulfur sources, it is preferable to pretreat the nickel foam with a solvent to remove some impurities present on its surface. In this invention, the solvent preferably includes one or more of water, ethanol, or acetone, and the water includes one or more of ultrapure water, deionized water, or purified water, more preferably deionized water. In this invention, to ensure thorough removal of impurities from the surface of the nickel foam, it is more preferable to clean the nickel foam with water, ethanol, and acetone respectively. The cleaning is preferably performed under ultrasonic conditions, and the cleaning time is preferably 20–40 minutes, more preferably 20–30 minutes.

[0036] In this invention, after cleaning, the nickel foam is preferably cut into a 1.5×15cm shape, placed in a quartz sealed tube, and then a sulfur source and a phosphorus source are added. After sealing the tube, heat treatment is performed. The sulfur source preferably includes one or more of phenylthiourea, thiourea, thioacetamide, disulfiram, or thiophenic acid. The phosphorus source preferably includes one or more of triphenylphosphine, tribenzylphosphine, cyclohexylphosphine, tributylphosphine, or phenylphosphonic acid. The heat treatment temperature is preferably 700–900℃, more preferably 700–800℃, and the heat treatment time is preferably 6–8 hours, more preferably 6–7 hours. In this invention, during the heat treatment process, the phosphorus source and sulfur source react with the nickel foam to generate a heterogeneous structure of nickel sulfide and nickel phosphide in situ on the surface of the nickel foam.

[0037] The preparation method of this invention is simple. Preferably, it utilizes sulfur and phosphorus sources containing carbon elements to react with nickel foam, eliminating the need for additional carbon sources. Nickel sulfide and nickel phosphide are generated in situ on the surface of the nickel foam through a one-step sintering process, resulting in a heterogeneous material with a three-dimensional porous structure. This material can serve as an ideal nickel-based current collector for sodium metal anodes, and can then be used to construct safe, high coulombic efficiency, and long-life sodium metal batteries. The nickel foam acts as both a nickel source and a supporting framework, significantly increasing the specific surface area and electronic conductivity of the material. The heterogeneous structure of nickel sulfide and nickel phosphide possesses abundant sodium-loving adsorption sites, which can alleviate the tip discharge effect, reduce local current density, uniformize sodium ion flow, and promote uniform sodium metal deposition, thereby inhibiting sodium dendrite growth. Furthermore, the sodium-modified heterogeneous structure of nickel sulfide and nickel phosphide exhibits a lower Fermi level, effectively preventing continuous electrolyte decomposition and resulting in a more uniform solid electrolyte film, which is beneficial for improving the battery's coulombic efficiency and cycle stability.

[0038] This invention also provides a sodium metal anode material, comprising a heteromaterial and sodium metal deposited on the surface of the heteromaterial. The heteromaterial comprises nickel foam and nickel sulfide and nickel phosphide loaded on the nickel foam. The preferred mass ratio of the nickel foam, nickel sulfide, and nickel phosphide is (5-20):(0.1-0.9):(0.1-0.9), more preferably (5-15):(0.1-0.9):(0.1-0.9), and most preferably 10:(0.1-0.9):(0.1-0.9). It should be noted that since nickel sulfide and nickel phosphide are generated by reacting nickel foam with a sulfur source and a phosphorus source, and the solids generated by reacting with nickel foam during the reaction are only nickel sulfide and nickel phosphide, the total mass percentage of nickel sulfide and nickel phosphide is 100%. That is, in the above mass ratio, when the value of nickel sulfide is 0.1, the value of nickel phosphide is 0.9.

[0039] In this invention, the nickel sulfide and nickel phosphide are preferably loaded in situ on the nickel foam.

[0040] In this invention, the sodium metal anode material is preferably prepared by electrodeposition, and the specific steps are as follows:

[0041] Using a heterogeneous material as the positive electrode and metallic sodium as the negative electrode, a 1M NaClO4 solution of diethyl carbonate / ethylene carbonate (EC / DEC) containing 5% fluoroethylene carbonate (FEC) was used as the electrolyte. Assembly was carried out in a glove box under argon protection (water and oxygen content were both below 1 ppm), at 1 mA cm⁻¹. -2 Current density, 5mAh cm -2 Under the condition of surface capacity discharge, sodium metal is deposited on the surface of a heterogeneous material to obtain a sodium metal anode material.

[0042] This invention also provides a sodium metal battery, wherein the sodium metal battery preferably uses glass fiber as a separator, Na3V2(PO4)3(NVP) as the positive electrode, and sodium metal as the negative electrode. In this invention, there are no special limitations on the electrolyte of the sodium metal battery; preferably, a 1M NaClO4 solution containing 5% fluoroethylene carbonate (FEC) in diethyl carbonate / ethylene carbonate (EC / DEC) is used as the electrolyte.

[0043] This invention utilizes a heterogeneous material of nickel sulfide and nickel phosphide supported on nickel foam for the preparation of anode materials for sodium metal batteries. This material exhibits a low Fermi level, which can prevent electrolyte decomposition and induce a uniform solid-state electrolyte interface, thereby limiting sodium dendrite growth and restricting the volume change of the anode material during sodium metal deposition / stripping. This results in lower nucleation overpotential and better cycle performance. The anode material shows promising application prospects in the development of high-performance, long-life sodium metal battery systems.

[0044] To further illustrate the present invention, the following examples provide a detailed description. The source of the experimental materials used in the following examples is not particularly limited; they can be purchased from the market or prepared using conventional methods well-known to those skilled in the art. In the following examples and comparative examples, the nickel foam was purchased from Guangxi Guangjiayuan New Materials Co., Ltd., and its specifications were 240mm × 300mm × 0.25mm.

[0045] Example 1

[0046] This embodiment provides a heterogeneous material, the preparation method of which is as follows:

[0047] First, the nickel foam was ultrasonically treated in acetone, ethanol, and deionized water for 30 minutes each, then dried for later use. Next, the treated nickel foam was cut into 1.5cm × 15cm shapes, placed in a quartz tube, and then 100mg of phenylthiourea and 100mg of triphenylphosphine were added. After sealing, the tube was annealed and carbonized at 700℃ for 6 hours. The resulting heteromaterial was named Ni3S2 / Ni3P@NF.

[0048] Comparative Example 1

[0049] First, the nickel foam was ultrasonically treated in acetone, ethanol, and deionized water for 30 minutes each, then dried for later use. Next, the treated nickel foam was cut into 1.5cm × 15cm shapes, placed in a quartz tube, and 100mg of phenylthiourea was added. After sealing, the tube was annealed and carbonized at 700℃ for 6 hours. The resulting material was named Ni3S2@NF.

[0050] Comparative Example 2

[0051] First, the nickel foam was ultrasonically treated in acetone, ethanol, and deionized water for 30 minutes each, then dried for later use. Next, the treated nickel foam was cut into 1.5cm × 15cm shapes, placed in quartz tubes, and 100mg of triphenylphosphine was added. After sealing, the tubes were annealed and carbonized at 700℃ for 6 hours. The resulting material was named Ni3P@NF.

[0052] Performance testing

[0053] The materials obtained in Example 1, Comparative Example 1, and Comparative Example 2 were characterized by XRD, and the results are as follows: Figure 1 As shown, the components of Ni3S2 / Ni3P@NF are Ni3S2, Ni3P, and Ni; the components of Ni3S2@NF are Ni3S2 and Ni; and the components of Ni3P@NF are Ni3P and Ni.

[0054] The surface morphology of the materials obtained in Example 1, Comparative Example 1, and Comparative Example 2 was characterized using scanning electron microscopy, and the results are as follows: Figure 2 As shown, where Figure 2 a is a SEM image of the Ni3S2 / Ni3P@NF material. Figure 2 b is the SEM image of Ni3S2@NF material. Figure 2 c is the SEM image of the Ni3P@NF material, where Figure 2 The top right corner of a~2c is a random pair Figure 2 A magnified image of a specific part in diagrams a through 2c. Figure 2 As can be seen, Ni3S2 / Ni3P particles are loaded on the surface of the nickel foam without damaging its morphology, and the particle size of the Ni3S2 / Ni3P particles is 1–2 μm. Figure 2 As can be seen from b, the particle size of Ni3S2 is 100-200 nm. (From...) Figure 2 c shows that the particle size of Ni3P particles is between 1 and 2 μm.

[0055] In a glove box under argon protection (water and oxygen content both below 1 ppm), Ni3S2 / Ni3P@NF, Ni3S2@NF, and Ni3P@NF were used as positive electrodes, metallic sodium as the negative electrode, and a 1 M NaClO4 solution of diethyl carbonate / ethylene carbonate (EC / DEC) containing 5% fluoroethylene carbonate (FEC) was used as the electrolyte. An 1 mA cm⁻¹ flow rate was applied. -2 Current density deposition of 1mAh cm -2 Cyclic coulombic efficiency plots for Ni3S2 / Ni3P@NF, Ni3S2@NF, and Ni3P@NF were obtained using sodium metal. The test results are shown below. Figure 3 As shown, Ni3S2 / Ni3P@NF exhibits excellent cycling performance, maintaining an average coulombic efficiency of 99.3% after 700 cycles, while Ni3S2@NF and Ni3P@NF begin to show varying degrees of degradation after 100 cycles.

[0056] In a glove box under argon protection (water and oxygen content both below 1 ppm), Ni3S2 / Ni3P@NF, Ni3S2@NF, and Ni3P@NF were used as positive electrodes, metallic sodium as the negative electrode, and a 1 M NaClO4 solution of diethyl carbonate / ethylene carbonate (EC / DEC) containing 5% fluoroethylene carbonate (FEC) was used as the electrolyte. An 1 mA cm⁻¹ flow rate was applied. -2 Current density deposition of 1mAh cm -2 Electroplating curves for Ni3S2 / Ni3P@NF, Ni3S2@NF, and Ni3P@NF were obtained using sodium metal. The test results are as follows: Figure 4 As shown, calculations show that the nucleation overpotentials of Ni3S2 / Ni3P@NF, Ni3S2@NF, and Ni3P@NF materials during the first cycle are 27mV, 32mV, and 60mV, respectively. This indicates that Ni3S2 / Ni3P@NF has abundant sodium deposition sites and a good affinity for sodium, which can effectively inhibit the growth of sodium dendrites and improve the electrochemical performance of the sodium metal anode.

[0057] Electrodeposition was used to deposit metallic sodium on the surface of the heterogeneous materials obtained in Example 1 and Comparative Examples 1-2. The specific steps are as follows:

[0058] In a glove box under argon protection (water and oxygen content both below 1 ppm), Ni3S2 / Ni3P@NF, Ni3S2@NF, and Ni3P@NF were used as positive electrodes, metallic sodium as the negative electrode, and a 1 M NaClO4 solution of diethyl carbonate / ethylene carbonate (EC / DEC) containing 5% fluoroethylene carbonate (FEC) was used as the electrolyte. The electrolyte was maintained at 1 mA cm⁻¹. -2 Current density and 5mAh cm -2 Under the condition of areal capacity, metallic sodium is deposited on Ni3S2 / Ni3P@NF, Ni3S2@NF, and Ni3P@NF to obtain sodium metal anode materials, namely Ni3S2 / Ni3P@NF@Na, Ni3S2@NF@Na, and Ni3P@NF@Na.

[0059] Assemble a 2032-type symmetrical coin cell: Using glass fiber as the separator, and two Ni3S2 / Ni3P@NF@Na, Ni3S2@NF@Na, and Ni3P@NF@Na as the counter electrode materials, respectively, assemble symmetrical coin cells. Place the fully assembled symmetrical cell in a battery tester at a current density of 0.5 mA cm⁻¹. -2 The surface area capacity is 0.5mAh cm⁻¹ -2 The cycle time-voltage curves of the symmetrical battery were tested under the specified conditions. The test results are as follows: Figure 5 As shown, Ni3S2 / Ni3P@NF@Na exhibits the lowest polarization voltage and cycle life, with a very low polarization voltage even after 990 cycles. However, Ni3S2@NF@Na and Ni3P@NF@Na begin to show polarization voltage instability after 50 cycles.

[0060] Ultraviolet photoelectron spectroscopy (UPS) was used to obtain UPS plots of Ni3P@NF, Ni3S2@NF, and Ni3S2 / Ni3P@NF at initial potentials and different discharge potentials. The Fermi level variation of the three materials with discharge potential was calculated. The test results are as follows: Figure 6 As shown, where, Figure 6 a shows the UPS diagrams of Ni3P@NF at initial potential, discharged to 1.0V, and discharged to 0.01V. Figure 6 b shows the UPS diagrams of Ni3S2@NF at initial potential, discharged to 1.0V, and discharged to 0.01V. Figure 6 c shows the UPS diagrams of Ni3S2 / Ni3P@NF at initial potential, discharged to 1.0V, and discharged to 0.01V. Figure 6 The numbers 1, 2, and 3 in a to 6c represent the discharge conditions of Ni3P@NF, Ni3S2@NF, and Ni3S2 / Ni3P@NF at 0.01V, 1.0V, and the initial potential (OCV), respectively.

[0061] against Figure 6 The results were used to calculate the Fermi levels of Ni3S2 / Ni3P@NF, Ni3S2@NF, and Ni3P@NF as a function of discharge potential (e.g., Figure 7 (As shown). By Figure 7 It can be seen that after Ni3S2 / Ni3P@NF is discharged to 0.01V (sodium plating), the Fermi level is significantly lower than that of Ni3P@NF and Ni3S2@NF when discharged to 0.01V (sodium plating). This indicates that after sodium plating, the surface of Ni3S2 / Ni3P@NF is less susceptible to electrolyte decomposition, thereby inhibiting further SEI thickening and irreversible capacity loss.

[0062] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A sodium metal anode material, characterized in that, Includes heterogeneous materials and sodium metal deposited on the surface of the heterogeneous materials; The heterogeneous material is formed of nickel foam and nickel sulfide and nickel phosphide loaded on the nickel foam; The mass ratio of the nickel foam, nickel sulfide, and nickel phosphide is (5~20):(0.1~0.9):(0.1~0.9). The nickel sulfide is Ni3S2, and the nickel phosphide is Ni3P.

2. The sodium metal anode material according to claim 1, characterized in that, The nickel sulfide and nickel phosphide are loaded in situ on the nickel foam.

3. The sodium metal anode material according to claim 1, characterized in that, The method for preparing the heterogeneous material includes the following steps: The heterogeneous material is obtained by mixing nickel foam, sulfur source, and phosphorus source and then heat-treating them.

4. The sodium metal anode material according to claim 3, characterized in that, The sulfur source includes any one or more of phenylthiourea, thiourea, thioacetamide, disulfiram, or thiophenic acid. The phosphorus source includes any one or more of triphenylphosphine, tribenzylphosphine, cyclohexylphosphine, tributylphosphine, or phenylphosphonic acid.

5. The sodium metal anode material according to claim 3, characterized in that, The heat treatment temperature is 700~900℃, and the heat treatment time is 6~8 h.

6. A sodium metal battery, characterized in that, Includes the sodium metal anode material as described in any one of claims 1 to 5.

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