A sodium ion battery negative electrode material and its preparation method and application

Abstract

The present invention provides a sodium-ion battery negative electrode material, a preparation method and application thereof, and relates to the technical field of sodium-ion batteries. Specifically, the sodium-ion battery negative electrode material includes a conductive agent, gallium sulfide and nickel sulfide; the conductive agent includes at least one of graphene oxide, carbon nanotubes or MXene. The present invention provides a sodium-ion negative electrode material composed of a conductive agent and two specific metal sulfides, which has good performance in the low-temperature application field of high-capacity power batteries; the sodium-ion battery prepared based on this negative electrode material has good performance in low-temperature rate performance and low-temperature capacity retention, and can improve its reversible capacity at the same time. It still has excellent stability and good fast charging and discharging capabilities during the charge and discharge cycle, and has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a sodium ion battery negative electrode material, a preparation method thereof, and applications thereof. Background Art

[0002] Due to the natural abundance of sodium resources, sodium-ion batteries (SIBs) are considered a promising commercial alternative to lithium-ion batteries. Research on anode materials for sodium-ion batteries operating at or above room temperature has attracted considerable attention. However, when the operating temperature drops below zero, the capacity and stability of the anode drop sharply, limiting the further application of sodium-ion batteries in cold climates or high-altitude areas. For example, at -20°C, hard carbon anodes can only maintain 20% of their room-temperature capacity. In recent years, research and development has focused on improving the low-temperature performance of sodium-ion batteries, such as heating the batteries to 18-20°C and exploring new electrolytes. However, considering the slow sodium ion diffusion and charge transfer kinetics of the anode material at low temperatures, rationally designing a new anode material with suitable sodium ion and electron diffusion kinetics to improve the low-temperature performance of sodium-ion battery anodes is a crucial step.

[0003] Graphene oxide (GO) is a common conductive agent in the battery field. Its flakes contain many oxygen-containing functional groups, which give GO good dispersibility, a high specific surface area, and rich surface chemical properties. It can be closely integrated with the negative electrode active material and significantly improve the electronic conductivity and mechanical stability of the composite material. On the other hand, gallium-based sulfides, due to their high electrical conductivity and excellent interfacial compatibility, help reduce the interfacial resistance within the battery and improve the overall performance of the battery. On the other hand, compared with other transition metal sulfides, nickel sulfide has the advantages of high theoretical specific capacity and relatively high electrochemical reaction activity, and has also attracted widespread attention in SIBs negative electrode materials.

[0004] Therefore, if the advantages of graphene oxide, gallium-based sulfide, and nickel sulfide can be integrated, it will be beneficial to improve the low-temperature performance of sodium-ion batteries. In view of this, the present invention is proposed. Summary of the Invention

[0005] The first object of the present invention is to provide a sodium ion battery negative electrode material, which is mainly used to solve the defects of conventional sodium ion battery negative electrode materials such as slow sodium ion diffusion and slow charge transfer at low temperatures, and is used to improve the low-temperature performance of sodium ion batteries and increase their reversible capacity; the present invention obtains a negative electrode material with close interface contact and compatibility by combining three core components: a conductive agent (preferably graphene oxide), nickel sulfide and gallium sulfide.

[0006] The second object of the present invention is to provide a method for preparing the negative electrode material of a sodium ion battery, which is simple, easy to implement and easy to promote.

[0007] A third object of the present invention is to provide a negative electrode for a sodium ion battery.

[0008] A fourth object of the present invention is to provide a sodium ion battery.

[0009] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0010] A sodium ion battery negative electrode material comprising a conductive agent, gallium sulfide and nickel sulfide;

[0011] The conductive agent includes at least one of graphene oxide, carbon nanotubes or MXene.

[0012] A method for preparing a negative electrode material for a sodium ion battery comprises the following steps:

[0013] A solution containing a conductive agent, a nickel source, a gallium source and urea is prepared, and a hydrothermal reaction is carried out. After cooling, the solution is subjected to solid-liquid separation, washing and drying to obtain a Ga / Ni precursor;

[0014] A solution containing the Ga / Ni precursor and a sulfur source is prepared, the hydrothermal reaction is continued, and after cooling, solid-liquid separation, washing, and drying are performed to obtain the sodium ion battery negative electrode material.

[0015] A sodium ion battery negative electrode comprises the sodium ion battery negative electrode material.

[0016] A sodium ion battery comprises the sodium ion battery negative electrode.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention aims to improve the technical problem of the performance of sodium ion battery negative electrode materials at low temperatures, enhance their reversible capacity, and ensure that the negative electrode materials still have excellent stability and good fast charging and discharging capabilities during the charge and discharge cycle. The present invention provides a sodium battery negative electrode material composed of a conductive agent, nickel sulfide and gallium sulfide, which has significantly improved overall electrochemical performance and performs well in the low-temperature application field of high-capacity power batteries.

[0019] (2) The conductive agent of the present invention preferably uses graphene oxide, which not only serves as a low-resistance network for electron transfer but also prevents phase separation, thereby improving rate capability and cycle stability. By loading a specific metal sulfide on the surface of graphene oxide, the present invention provides a negative electrode material with a low-dimensional nanowire array of vertical porous channels and a hierarchical porous structure, which can provide efficient electron / ion migration with a short path length and an expanded accessible surface area.

[0020] (3) The present invention utilizes a specific sulfide combination of gallium sulfide and nickel sulfide. Like most bimetallic sulfide systems, Ga2S3@Ni3S4 converts to nickel-based sulfide and gallium-based sulfide during the initial discharge process. After the temperature is lowered to subzero, although the gallium-based sulfide loses its electrochemical activity, it can serve as a medium with high ionic conductivity to promote the conversion reaction of nickel sulfide. In the present invention, the use of gallium-based sulfide sacrifices some of its electrical properties at subzero temperatures, but enables nickel sulfide to better adapt to low-temperature changes, thereby effectively improving the overall low-temperature performance of the negative electrode.

[0021] (4) In the negative electrode material preparation process provided by the present invention, a solution containing gallium ions, nickel ions and simple sulfides is used as a precursor, which is simply mixed with a conductive agent, and then a hydrothermal method is used to synthesize the heterostructure porous negative electrode material of the present invention. The hydrothermal reaction directly grows the Ga precursor nanowire array on the graphene oxide. In the subsequent hydrothermal sulfurization process, S 2- The ions directly convert the Ga precursor (mainly gallium hydroxide or basic gallium carbonate) into a nanowire array of gallium sulfide through an anion exchange reaction; at the same time, the graphene oxide loaded with nickel ions is oxidatively etched and sulfurized in a Na2S medium to form Ni3S4 nanosheets, ultimately obtaining the negative electrode material of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 Provided are rate performance diagrams of Example 1 of the present invention at different temperatures;

[0024] Figure 2 A comparison chart of the cycle performance of Example 1 of the present invention and Comparative Example 1 is provided. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. However, it will be understood by those skilled in the art that the following embodiments are only some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially. In addition, the terms "first", "second" and "third" are only used for descriptive purposes and are not to be construed as indicating or implying relative importance.

[0026] A first aspect of the present invention is to provide a sodium ion battery negative electrode material; the sodium ion battery negative electrode material includes a conductive agent, gallium sulfide and nickel sulfide, wherein the conductive agent includes at least one of graphene oxide, carbon nanotubes or MXene.

[0027] As a preferred embodiment, the molar ratio of nickel atoms in the nickel sulfide to gallium atoms in the gallium sulfide is (2.5-3.5):(1.5-2.5). In some more preferred embodiments, the molar ratio is 3:2.

[0028] As a preferred embodiment, in the sodium ion battery negative electrode material, the amount of the conductive agent is 15wt.% to 20wt.%, including but not limited to any one of 15, 16, 17, 18, 19, 20 (wt.%) or a numerical range consisting of any two.

[0029] As a preferred embodiment, the conductive agent includes graphene oxide.

[0030] As a preferred embodiment, the MXene includes one or both of Ti3AlC2 or Ti3C2.

[0031] As a preferred embodiment, the sodium-ion battery negative electrode material includes a conductive agent, and gallium sulfide and nickel sulfide supported on the surface of the conductive agent; wherein the gallium sulfide is arranged in a nanoscale linear array on the surface of the conductive agent; and the nickel sulfide is uniformly distributed outside the nanowires formed by the gallium sulfide and on the surface of the conductive agent, presenting a nanoscale sheet-like structure. The present invention achieves the formation of nanowires through a solution method. After the gallium source dissolves, ion clusters are formed. Based on the temperature difference between the upper and lower solutions in the hydrothermal reaction vessel, strong convection is generated, thereby carrying the saturated solution in the high-temperature area to the low-temperature area, forming a saturated solution. The saturated gallium source uses the conductive agent as a growth interface, undergoing adsorption, decomposition, and desorption, and ultimately crystallizing to form a nanowire array.

[0032] The second aspect of the present invention is to provide a method for preparing a negative electrode material for a sodium ion battery as described in the first aspect; specifically, the method comprises the following steps: (1) preparing a solution comprising a conductive agent, a nickel source, a gallium source and urea, performing a hydrothermal reaction, and after cooling, performing solid-liquid separation, washing, and drying to obtain a Ga / Ni precursor; (2) preparing a solution comprising the Ga / Ni precursor and a sulfur source, continuing the hydrothermal reaction, and after cooling, performing solid-liquid separation, washing, and drying to obtain the negative electrode material for a sodium ion battery.

[0033] As a preferred embodiment, the nickel source includes one or more of nickel nitrate, nickel sulfate, nickel chloride, and nickel acetate; the gallium source includes one or more of gallium nitrate, gallium sulfate, and gallium chloride; and the sulfur source includes one or more of sodium sulfide, potassium sulfide, and ammonium sulfide.

[0034] In the present invention, the urea is used as a surfactant in the preparation process of the positive electrode material to affect the morphology, size and dispersibility of the nanoparticles; specifically, the urea can form a complex with metal ions in a hydrothermal reaction, thereby affecting the morphology and size of the nanoparticles, and obtaining nanoparticles with uniform morphology.

[0035] As a more preferred embodiment, the amount of urea added is 0.3 mol / L to 0.7 mol / L.

[0036] As a preferred embodiment, in the solution, the concentration of nickel atoms in the nickel source is 0.05 mol / L to 0.2 mol / L; since the dosage relationship between the nickel source and the gallium source is still limited in the present invention, those skilled in the art can calculate the concentration of the gallium source in the solution based on the limited relationship; for reference, in the solution, the concentration of nickel atoms in the nickel source is 0.03 mol / L to 0.15 mol / L.

[0037] As a preferred embodiment, in the solution, the solid-liquid ratio of the conductive agent is 0.07 to 0.1, with the unit being g / mL.

[0038] As a preferred embodiment, during the preparation of the solution containing the conductive agent, nickel source, gallium source, and urea, auxiliary methods such as oscillation, stirring, shaking, centrifugation, and ultrasound are used to help accelerate dispersion and obtain a relatively uniform dispersion system.

[0039] As a more preferred embodiment, nickel source, gallium source, urea and conductive agent are sequentially added to water, and then stirred vigorously; the stirring frequency is 1000 rpm to 2000 rpm, and the stirring time is 1.5 h to 3 h.

[0040] As a preferred embodiment, the concentration of the sulfur source is 0.04 mol / L to 0.25 mol / L.

[0041] As a preferred embodiment, the hydrothermal reaction is carried out under closed conditions.

[0042] As a preferred embodiment, the temperature of the hydrothermal reaction is 110°C to 140°C, and the time of the hydrothermal reaction is 6h to 24h; in some optional embodiments, the temperature of the hydrothermal reaction includes but is not limited to any one of 110, 115, 120, 125, 130, 135, 140 (°C) or a numerical range consisting of any two of them, and the time of the hydrothermal reaction is any one of 6, 8, 10, 12, 15, 18, 20, 24 (h) or a numerical range consisting of any two of them.

[0043] As a preferred embodiment, the washing medium is deionized water.

[0044] As a preferred embodiment, the drying temperature is 50° C. to 80° C., and the drying time is 20 h to 28 h.

[0045] The third aspect of the present invention is to provide a sodium ion battery negative electrode, comprising the sodium ion battery negative electrode material as described in the first aspect.

[0046] It is worth noting that, in addition to the sodium ion battery negative electrode material, the sodium ion battery negative electrode may also include one or more functional components or structural elements such as a current collector, a conductive agent, a binder, a dopant, etc. The specific component selection and ratio adopted may be conventional or unconventional. On the basis of meeting the electrical and mechanical properties of the negative electrode of the sodium ion battery, any negative electrode containing the sodium ion battery negative electrode material and applicable can be used as an embodiment of this aspect.

[0047] As a preferred embodiment, the sodium ion battery negative electrode includes the sodium ion battery negative electrode material, a second conductive agent, an adhesive and a current collector; in some optional embodiments, the second conductive agent includes graphite, Ketjen black, acetylene black, etc., the adhesive includes polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, etc., and the current collector includes copper foil.

[0048] As a preferred embodiment, the method for preparing the negative electrode of the sodium ion battery comprises the following steps: preparing a slurry containing the negative electrode material of the sodium ion battery, wherein the solvent of the slurry is preferably N-methylpyrrolidone; coating the slurry on the surface of the current collector and then heat treating the slurry to obtain the negative electrode of the sodium ion battery.

[0049] A fourth aspect of the present invention is to provide a sodium ion battery, comprising the sodium ion battery negative electrode as described in the third aspect.

[0050] It is understandable that, in addition to the sodium ion battery negative electrode, the sodium ion battery should include a positive electrode, a separator, an electrolyte, and other necessary or non-essential functional elements or packaging components, etc., which can be arbitrarily selected and combined by those skilled in the art; when the sodium ion battery includes the sodium ion battery negative electrode, whether or not other composite negative electrodes are used in the sodium ion battery, it can be regarded as an embodiment of the present invention.

[0051] Example 1

[0052] (1) 4 mmol of gallium nitrate and 6 mmol of nickel nitrate were dissolved in 60 mL of deionized water, and then 30 mmol of urea and 5 g of graphene oxide were added. The mixture was vigorously stirred at 1500 rpm for 2 h to form a uniform reaction mixture. The reaction mixture was then transferred to a 100 mL Teflon-lined reactor and heated at 120 °C for 12 h for a hydrothermal reaction. After the mixture was cooled to room temperature, the excess was removed by ultrasonic washing with deionized water and dried at 60 °C to obtain a Ca / Ni precursor.

[0053] (2) The Ca / Ni precursor loaded with graphene oxide substrate was transferred to a 50 mL Teflon-lined reactor, 40 mL of 0.05 mol / L Na2S aqueous solution was added, and the mixture was heated at 120 °C for 6 h for hydrothermal reaction. After cooling, the mixture was rinsed with deionized water and vacuum-dried at 60 °C for 24 h to prepare the porous Ga2S3@Ni3S4@GO heterogeneous material of this embodiment.

[0054] Example 2

[0055] The method is basically the same as Example 1, except that the concentration of the Na2S aqueous solution is replaced with 0.1 mol / L.

[0056] Example 3

[0057] The method is basically the same as Example 1, except that the concentration of the Na2S aqueous solution is replaced with 0.2 mol / L.

[0058] Example 4

[0059] The method is basically the same as Example 1, except that the time for the hydrothermal reaction is replaced with 12 h.

[0060] Example 5

[0061] The method is basically the same as Example 1, except that the time for the hydrothermal reaction is replaced with 24 hours.

[0062] Example 6

[0063] The method is basically the same as Example 1, except that graphene oxide is replaced by carbon nanotubes.

[0064] Example 7

[0065] It is basically the same as Example 1, except that graphene oxide is replaced by MXene (Ti3AlC2, Xianfeng Nano).

[0066] Comparative Example 1

[0067] The method is basically the same as Example 1, except that the addition of graphene oxide is omitted.

[0068] Comparative Example 2

[0069] The method is basically the same as Example 1, except that the addition of gallium nitrate is omitted.

[0070] Comparative Example 3

[0071] The method is basically the same as Example 1, except that the addition of nickel nitrate is omitted.

[0072] The negative electrode battery materials prepared in each embodiment and comparative example were used to prepare the corresponding sodium ion batteries for testing.

[0073] (1) The active electrode material, conductive agent carbon black (super-p) and binder polyvinylidene fluoride (PVDF) in a mass ratio of 80:10:10 were ground and uniformly mixed, and an appropriate amount of N-methylpyrrolidone was added as a solvent to prepare a negative electrode slurry.

[0074] (2) The negative electrode slurry was uniformly stirred on a magnetic stirrer for 10 h, and then 2 Apply it evenly on the copper foil, wait for its surface to dry, and finally dry it in a vacuum oven at 80°C for 12 hours to obtain a negative electrode sheet with a thickness of 69±3μm.

[0075] (3) The negative electrode sheets were assembled in an Ar-filled glove box to produce a 2032 model button battery; glass fiber was used as the battery's diaphragm material, and hand-rolled sodium sheets were used as the counter electrode and reference electrode in the battery.

[0076] Test example

[0077] (a) The sodium ion battery prepared in Example 1 was tested at different rates at different temperatures using the Land battery test system, and the following results were obtained: Figure 1 The test results are shown.

[0078] like Figure 1 It can be seen that at 25℃, Ga2S3@Ni3S4@GO electrode has a-1 and 2Ag -1 The current density is 810 mAh g -1 and 450mAh g -1 When the operating temperature drops to 0°C, the capacity at the corresponding current density drops to 418 mAh g -1 and 253mAh g -1 When the operating temperature drops to -20°C, the capacity at the corresponding current density drops to 322 mAh g -1 and 153mAh g -1 It can be seen from this that even though the battery negative electrode material of the present invention has a certain decrease in battery capacity at low temperatures compared to room temperature, it still has good low-temperature performance.

[0079] (b) The sodium ion batteries prepared in Example 1 and Comparative Example 1 were subjected to capacity cycle tests at -60°C using a Land battery test system, and the following results were obtained: Figure 2 The test results are shown.

[0080] like Figure 2 It can be seen that at -60 °C, the reversible capacity of Example 1 (Ga2S3@Ni3S4@GO) is about 125 mAh g -1 The capacity performance is relatively stable after the number of cycles exceeds 12, while the comparative example 1 (Ga2S3@Ni3S4) has obvious capacity attenuation; this also shows that the introduction of GO buffers the volume expansion during the charge and discharge cycle, thereby enhancing the stability of the cycle capacity.

[0081] (c) The sodium ion batteries prepared in accordance with the examples and comparative examples were tested, and the first discharge capacity, the capacity retention rate after 70 cycles compared with the second discharge capacity, and the 1Ag -1 Discharge capacity at -10℃ and 0.2Ag -1 The first discharge capacity retention rate under the conditions of 100 nm and 100 nm are shown in Table 1.

[0082] Table 1

[0083]

[0084] As can be seen from Table 1, by comparing Examples 1 to 5 with Examples 6 to 7, it can be seen that although all of them use conductive materials, graphene oxide still has obvious electrical performance advantages over carbon nanotubes or MXene; it can be seen from Example 1 and Comparative Example 1 that the conductive material can effectively guarantee the performance in terms of cycle performance; it can be seen from Example 2 and Comparative Examples 2 and 3 that the two sulfides introduced in the present invention are both necessary components and play an important role in the overall electrochemical performance. The reversible capacity and rate capacity of the Ga2S3@Ni3S4@GO of the present invention during the cycle are significantly improved compared with those of single metal sulfides.

[0085] Although the present invention has been illustrated and described using specific embodiments, it should be appreciated that the above embodiments are merely intended to illustrate the technical solutions of the present invention rather than to limit them. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and scope of the present invention. However, these modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A sodium ion battery negative electrode material, characterized in that The preparation method of the sodium ion battery negative electrode material comprises the following steps: A solution containing a conductive agent, a nickel source, a gallium source and urea is prepared, and a hydrothermal reaction is carried out. After cooling, the solution is subjected to solid-liquid separation, washing and drying to obtain a Ga / Ni precursor; preparing a solution comprising the Ga / Ni precursor and a sulfur source, continuing the hydrothermal reaction, and after cooling, performing solid-liquid separation, washing, and drying to obtain the sodium ion battery negative electrode material; The sodium ion battery negative electrode material includes gallium sulfide and nickel sulfide; The conductive agent includes at least one of graphene oxide, carbon nanotubes or MXene.

2. The sodium ion battery negative electrode material according to claim 1, characterized in that The gallium sulfide and the nickel sulfide are loaded on the surface of the conductive agent; and the gallium sulfide is arranged in a nanometer-scale linear array on the surface of the conductive agent.

3. The sodium ion battery negative electrode material according to claim 1, characterized in that The molar ratio of nickel atoms in the nickel sulfide to gallium atoms in the gallium sulfide is (2.5-3.5): (1.5-2.5).

4. The sodium ion battery negative electrode material according to claim 1, characterized in that In the sodium ion battery negative electrode material, the amount of the conductive agent is 15wt.%~20wt.%.

5. The sodium ion battery negative electrode material according to claim 1, characterized in that The nickel source includes at least one of nickel nitrate, nickel sulfate, nickel chloride or nickel acetate; and / or, the gallium source comprises at least one of gallium nitrate, gallium sulfate or gallium chloride; And / or, the sulfur source includes at least one of sodium sulfide, potassium sulfide or ammonium sulfide.

6. The sodium ion battery negative electrode material according to claim 1, characterized in that The preparation of the solution containing the conductive agent, the nickel source, the gallium source and the urea comprises the following steps: sequentially adding the nickel source and the gallium source, the urea and the conductive agent into water, and then stirring; The frequency of the stirring treatment is 1000 rpm to 2000 rpm, and the time of the stirring treatment is 1.5 h to 3 h.

7. The sodium ion battery negative electrode material according to claim 1, characterized in that The temperature of the hydrothermal reaction is 110° C. to 140° C., and the time of the hydrothermal reaction is 6 h to 24 h; The hydrothermal reaction is carried out under closed conditions.

8. A sodium ion battery negative electrode, characterized in that The invention comprises the sodium ion battery negative electrode material according to any one of claims 1 to 7.

9. A sodium ion battery, characterized in that: Comprising the sodium ion battery negative electrode as claimed in claim 8.

Images