Negative electrode material and preparation method thereof and potassium ion battery

Abstract

The present application provides a negative electrode material comprising arsenic-doped graphene, layered stannous sulfide anchored on the arsenic-doped graphene, and phosphate ions in situ introduced between the stannous sulfide layers. The negative electrode material provided herein has high conductivity, high cycle stability, and high kinetic performance. The present application also provides a method for preparing the negative electrode material, which is simple to operate. The present application also provides the use of the negative electrode material of the present application in a potassium ion battery.

Description

Technical Field

[0001] The present application relates to the technical field of potassium-based energy storage devices, and in particular to a negative electrode material and a preparation method thereof, and a potassium ion battery. Background Art

[0002] Currently, the development of lithium-based energy storage devices is limited by resource scarcity and high costs. New energy storage devices are urgently needed to solve current environmental and resource problems. Potassium-ion batteries (PIBs) have attracted widespread attention in recent years as an ideal alternative to potassium-ion batteries due to their high earth abundance and low potassium cost. + Not only does it have the advantage of higher energy density due to its lower redox potential, but K + It can also undergo intercalation reactions with commercial graphite anodes, laying the foundation for the future practical application of PIBs. However, when commercial graphite is used as the anode material, its electrochemical performance is often poor due to low cycling stability, low capacity, and large volume changes during charge and discharge that lead to graphite skeleton collapse, making it difficult to meet the requirements of high-capacity and long-term stable energy storage devices. Therefore, the development of efficient and stable potassium storage anode materials is a top priority for realizing high-performance energy storage devices. Summary of the Invention

[0003] The purpose of this application is to provide a negative electrode material and a preparation method thereof and a potassium ion battery. The negative electrode material has high kinetic performance and excellent cycle stability.

[0004] In a first aspect, the present application provides a negative electrode material, comprising: arsenic-doped graphene, layered stannous sulfide anchored on the arsenic-doped graphene, and phosphate ions in situ introduced between the stannous sulfide layers.

[0005] In some embodiments, the mass content of the arsenic-doped graphene is 4%-8% relative to the total weight of the negative electrode material.

[0006] The second aspect of the present application further provides a method for preparing the negative electrode material according to the first aspect of the present application, comprising the following steps:

[0007] Tin source, arsenic pentoxide, sodium hydroxide, phosphorus source, and thiourea are sequentially added to a graphene oxide dispersion having a concentration of 0.4-1.0 mg / mL and stirred to dissolve to form a precursor solution.

[0008] The precursor solution is subjected to a hydrothermal reaction to obtain a precursor powder,

[0009] The precursor powder is annealed to obtain the negative electrode material.

[0010] In some embodiments, the hydrothermal reaction comprises: o C-180o C for 10-12 h.

[0011] In some embodiments, the annealing treatment includes 2-5 o Annealing at a heating rate of 500 °C / min o C-600 o C, keep warm for 4-6 hours.

[0012] In some embodiments, the tin source is SnCl 4 ·5H 2 O.

[0013] In some embodiments, the phosphorus source is selected from phytic acid or phosphoric acid.

[0014] In some embodiments, in the precursor solution, the mass ratio of graphene oxide, arsenic pentoxide, sodium hydroxide, tin source, phosphorus source, and thiourea is 1-3:26:24:144:55:6.

[0015] In some embodiments, the precursor solution is subjected to high-energy ball milling before the hydrothermal reaction.

[0016] The third aspect of the present application also provides a potassium ion battery, comprising the negative electrode material described in the first aspect of the present application.

[0017] In some embodiments, the potassium ion battery includes a potassium ion secondary battery and a potassium ion full battery.

[0018] In the negative electrode material provided by the present application, arsenic doping of graphene can effectively change the electronic structure of graphene, revealing more active sites and significantly improving the conductivity of the material. In addition, changes in these electronic properties can reduce the reaction energy gap, which is beneficial to electron transfer during the redox reaction. By anchoring layered stannous sulfide on arsenic-doped graphene, it is beneficial to improve the conductivity of the negative electrode material, achieve rapid transport of potassium ions, and improve the kinetic performance of the electrode material during full charge and discharge. The in-situ introduction of phosphate ions between the stannous sulfide (SnS) layers can expand the lattice spacing in the SnS crystal, thereby relieving the lattice expansion during potassium insertion, thereby allowing the electrode material to maintain longer-term cycle stability during repeated charge and discharge. The in-situ introduction of phosphate ions between the stannous sulfide (SnS) layers can adjust the electronic structure of the SnS crystal, and through the Sn-OP bridging covalent bond as an electronic bridge, it effectively shortens the ion diffusion distance and promotes the storage kinetics of potassium ions. The present invention's method for preparing anode materials uses unoxidized arsenic and sodium hydroxide as raw materials. Arsenic atoms are doped into the carbon structure of graphene through a hydrothermal reaction and annealing treatment. Phosphate ions are simultaneously introduced between stannous sulfide (SnS) layers, thereby increasing the interlayer spacing between graphene and stannous sulfide and improving the potassium ion storage kinetics of the prepared anode material. This method is simple and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 This is a scanning electron microscope (SEM) image of the negative electrode material prepared in Example 1 of the present application.

[0021] Figure 2 This is a transmission electron microscope (TEM) image of the negative electrode material prepared in Example 1 of the present application.

[0022] Figure 3 This is the infrared spectrum of the negative electrode material prepared in Example 1 of the present application.

[0023] Figure 4 It is a comparison chart of the battery rate cycle performance of Examples 1 and 3 of the present application and Comparative Examples 1-2.

[0024] Figure 5 This is a comparison chart of the high current cycle performance of Examples 1 and 4 of the present application and Comparative Example 1.

[0025] Figure 6 The battery K of Example 1 and Comparative Example 1 of the present application + Diffusion rate comparison chart.

[0026] Figure 7 This is an energy density cycling performance diagram of the full battery of Example 6 of the present application at a rate current density. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the present application, the following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0028] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0029] Transition metal sulfides (TMSs) have shown considerable theoretical capacity in potassium storage due to their multi-electron reaction and multi-reaction mechanism. Tin sulfide (SnS) is a two-dimensional (2D) transition metal sulfide with high theoretical capacity and unique layered structure. However, SnS has inherently poor electrical conductivity, resulting in large ion diffusion barriers, unsatisfactory intrinsic conductivity, and its layered structure is difficult to store at large K. + Severe structural collapse and agglomeration are very likely to occur during the potassium insertion / depotassium process, triggering irreversible phase changes, causing the active material to pulverize and fall off from the current collector and continuous side reactions, ultimately resulting in poor rate capability and cycle stability.

[0030] In view of this, the present application provides a negative electrode material, which includes arsenic-doped graphene, layered stannous sulfide anchored on the arsenic-doped graphene, and phosphate ions in situ introduced between the stannous sulfide layers.

[0031] In this application, arsenic-doped graphene changes its electronic structure, revealing more active sites and significantly improving its conductivity. These changes in electronic properties can reduce the energy gap, facilitating electron transfer during redox reactions. Furthermore, more active sites are exposed, increasing the reactivity of the material. By anchoring layered stannous sulfide to arsenic-doped graphene through, for example, van der Waals forces, the structural stability and electronic conductivity of the negative electrode material are improved, enabling rapid potassium ion transport and enhancing the kinetic performance of the electrode material during full charge and discharge cycles. In situ introduction of phosphate ions between stannous sulfide (SnS) layers can expand the lattice spacing in the SnS crystal, thereby alleviating lattice expansion during potassium insertion and enabling the electrode material to maintain longer-term cyclic stability during repeated charge and discharge cycles. In situ introduction of phosphate ions between stannous sulfide (SnS) layers can adjust the electronic structure of the SnS crystal, effectively shortening the ion diffusion distance and promoting potassium ion storage kinetics through Sn-OP bridging covalent bonds as electron bridges.

[0032] In some embodiments, the mass content of the arsenic-doped graphene is 4%-8% relative to the total weight of the negative electrode material. This helps prevent the aggregation of SnS particles anchored to the graphene surface layer during cycling; it also improves the conductivity of the composite electrode material and can buffer changes in the electrode volume during potassium storage. Secondly, the insertion of phosphate ions into the two-dimensional SnS interlayers not only modifies the SnS micromorphology but also forms Sn-OP bridging covalent bonds between the SnS layers, adjusting the interlayer spacing and electronic structure of the SnS.

[0033] The present application also provides a method for preparing the above-mentioned negative electrode material, comprising the following steps:

[0034] Add tin source, arsenic pentoxide, sodium hydroxide, phosphorus source and thiourea to the graphene oxide dispersion with a concentration of 0.4 mg / mL-1.0 mg / mL, stir and dissolve, and form a precursor solution.

[0035] The precursor solution is subjected to a hydrothermal reaction to obtain a precursor powder,

[0036] The precursor powder is annealed to obtain the negative electrode material.

[0037] In the preparation method of the present application, arsenic pentoxide is an acidic oxide that reacts with sodium hydroxide during a hydrothermal reaction to form sodium arsenate. The arsenate is then incorporated into the carbon lattice of graphene during annealing. Furthermore, a combined hydrothermal-annealing method is used to anchor SnS nanosheets with a two-dimensional structure to arsenic-doped graphene sheets, while simultaneously introducing phosphate ions in situ between SnS layers to prepare the negative electrode material (PO4-SnS@AsG) of the present application. This negative electrode material has an extended interlayer spacing, which is beneficial for improving the cycle stability and kinetic performance of the negative electrode material. The method of the present invention uses a combined hydrothermal-annealing method to simultaneously complete the doping of arsenic into graphene, the synthesis of SnS, and the insertion of phosphate ions during the preparation process, resulting in simple operation.

[0038] In the present application, graphene oxide can be prepared by methods known to those skilled in the art or obtained commercially. For example, graphene oxide can be prepared by methods such as the Hummers method, the Brodie method, and the Staudenmaier method. In some embodiments, the method for preparing the graphene oxide dispersion of the present application includes: using natural graphite powder as a raw material, modifying it by the Hummers method to prepare a flaky GO solution; and ultrasonicating the GO solution at room temperature for 5-6 hours.

[0039] The Hummers method involves mixing graphite powder with concentrated sulfuric acid, adding potassium permanganate, and reacting to produce manganese heptoxide. The reaction is then continued in an ice-water bath to produce graphite oxide. Hydrogen peroxide is added to terminate the reaction, and the graphite flakes are exfoliated into graphene oxide through vigorous stirring. After multiple centrifugal washings with deionized water, the graphene oxide forms a stable, light brown monolayer suspension in water.

[0040] In the present application, a tin source, arsenic pentoxide, sodium hydroxide, a phosphorus source, and thiourea are sequentially added to a graphene oxide dispersion and stirred and dissolved to form a precursor solution, which is then prepared by a hydrothermal method. In some embodiments, the precursor is subjected to a high-energy spheroidal graphitization treatment prior to the hydrothermal reaction. This high-energy spheroidal graphitization treatment mechanically grinds the graphite material, destroying its layered structure and gradually exfoliating the single-layer graphene. It also allows for more uniform mixing of the raw materials in the precursor solution, thereby facilitating the uniform doping of arsenic atoms into the graphene crystal structure and the uniform insertion of phosphate ions into the interlayers of tin sulfide. In the present application, the high-energy spheroidal graphitization treatment can be performed using conventional equipment in the art. For example, the high-energy spheroidal graphitization can be performed using a vibrating high-energy ball mill. In some embodiments, the high-energy spheroidal graphitization rate is 2700-4000 rpm, and the ball milling time is 2-3 hours.

[0041] The method of the present application obtains a precursor by a single hydrothermal reaction, and the operation steps and reaction conditions are simple. Exemplarily, the step of preparing the precursor solution includes: ultrasonically converting graphene oxide into a few-layer graphene oxide, adding an appropriate amount of tin source, arsenic pentoxide and sodium hydroxide to the few-layer graphene oxide dispersion, dissolving under stirring, keeping stirring, then adding an appropriate amount of phosphorus source, mixing evenly, adding an appropriate amount of thiourea, and mixing evenly to obtain a precursor solution. It will be understood that stirring can be carried out by means well known in the art, for example, by magnetic stirring, mechanical stirring and other methods. The present application does not specifically limit the stirring time. All raw materials are stirred until dissolved and mixed evenly. Those skilled in the art can select the stirring time as needed. Exemplarily, the stirring time for each time is 0.5h.

[0042] In some embodiments, in the precursor solution, the mass ratio of graphene oxide, tin source, arsenic pentoxide, sodium hydroxide, phosphorus source, and thiourea is 1-3:26:24:144:55:6.

[0043] In some embodiments, the tin source is SnCl 4 ·5H 2 O.

[0044] In some embodiments, the phosphorus source is selected from phytic acid or phosphoric acid.

[0045] In some embodiments, the hydrothermal reaction comprises: o C-180 oC is maintained for 10h-12h. It will be understood that the hydrothermal reaction can be carried out by equipment or means well known to those skilled in the art. Illustratively, the hydrothermal reaction is carried out in a polytetrafluoroethylene-lined stainless steel autoclave. After the hydrothermal reaction is completed, the obtained black precipitate is separated and washed multiple times, and the precursor powder is obtained after drying. Separation can be carried out by methods such as filtration and centrifugation. In some embodiments, washing includes washing with anhydrous ethanol and deionized water three times respectively. The unreacted reactants and impurity ions on the surface of the precursor are removed by washing. In some embodiments, drying is carried out by freeze drying. Freeze drying allows the water to be directly sublimated, and the prepared material is more fluffy, which is beneficial to increase the specific surface area of ​​the negative electrode material, thereby improving the kinetic properties of the material.

[0046] In this application, the precursor powder is annealed to obtain the negative electrode material. The annealing process further dopes arsenic atoms into the carbon matrix and further improves the crystallinity of SnS. This helps improve the structural stability of the prepared negative electrode material.

[0047] In some embodiments, the annealing treatment includes 2-5 o Annealing at a heating rate of 500 °C / min o C-600 o C, keep warm for 4h-6h. The negative electrode material obtained by annealing in the above steps has better cycle stability and kinetic performance. For example, the annealing temperature can be 500 o C. 550 o C. 600 o C or a value between any two of them. As the annealing temperature increases, the annealing process may cause the destruction of the lamella structure of stannous sulfide and the loss of a portion of the phosphate ions. In some preferred embodiments, the annealing temperature is 500 o C-550 o By keeping the annealing temperature within this range, the damage to the stannous sulfide structure and the loss of phosphate ions during the annealing process can be reduced, further improving the cycle stability and capacity retention of the material.

[0048] The present application also provides a potassium ion battery comprising the aforementioned negative electrode material. The negative electrode material of the present application is used to prepare a negative electrode plate of a potassium ion battery, which can provide the potassium ion battery with improved cycle stability and kinetic performance.

[0049] In some embodiments, the potassium ion battery includes a potassium ion secondary battery and a potassium ion full battery.

[0050] The present application will be further described below with reference to specific embodiments. Example

[0051] It is understood that the following examples are illustrative and are intended only to explain the present application and are not to be construed as limiting the present application. Specific techniques and conditions not indicated in the examples were performed in accordance with those described in the literature in the art or in accordance with the product specifications. Reagents or instruments used without manufacturer designation are commercially available conventional products.

[0052] Sources of reagents used in the following examples: stannous chloride pentahydrate, arsenic pentoxide, sodium hydroxide, thiourea, phytic acid, and potassium metal were purchased from Aladdin Chemical Reagent Co., Ltd.

[0053] The manufacturers and models of the instruments used in the experiment are as follows:

[0054] The desktop centrifuge was a TG16-WS desktop centrifuge manufactured by Hunan Xiangyi Instrument Co., Ltd.

[0055] The single-temperature zone tube furnace is the OTF-1200X single-temperature zone tube furnace produced by Hefei Kejing Materials Technology Co., Ltd.

[0056] The magnetic stirrer was the HJ-6B magnetic stirrer from Shanghai Yidian Scientific Instrument Co., Ltd.

[0057] The polytetrafluoroethylene high-pressure reactor was from Shanghai Baikal Technology Co., Ltd.

[0058] The electrochemical workstation is the Lvium electrochemical workstation from IVIUM Technologies BV, the Netherlands;

[0059] The battery testing system is the LAND-CT2001A battery testing system of Wuhan Landian Electronics Co., Ltd.

[0060] The precision balance is an EX125DZH balance from Ohaus Instruments;

[0061] The vibrating high-energy ball mill is Kejing MSK-SFM-12M;

[0062] The glove box was an MB-Labstar glove box from Braun Inert Gas Co., Ltd.

[0063] Example 1

[0064] Preparation of negative electrode materials

[0065] Using natural graphite powder as raw material, the GO flake solution was prepared by Hummers method. The concentration was 0.4 mg / mL. -1 , 65 mL of GO dispersion was ultrasonicated at room temperature for 5 h to form a few-layer graphene oxide dispersion.

[0066] 0.701 g of SnCl4·5H2O was dissolved in the above graphene oxide dispersion under magnetic stirring and stirred for 0.5 h until no obvious particles were formed.

[0067] Add 0.216 g of arsenic pentoxide and 1.294 g of sodium hydroxide to the above mixture and continue stirring for 0.5 h until the solution is homogeneous.

[0068] 1.0 mL of phytic acid was added to the above solution and stirred for 0.5 h until the solution was homogeneous.

[0069] 0.152 g of thiourea was added to the above solution and stirred for 1 h until the solution became homogeneous to obtain a precursor solution.

[0070] The precursor solution was transferred to a polytetrafluoroethylene-lined stainless steel autoclave for hydrothermal reaction at a temperature of 180 o C, maintain for 12 h.

[0071] The black precipitate obtained by the hydrothermal reaction was centrifuged, washed three times with anhydrous ethanol and deionized water respectively, and then freeze-dried at -80°C for 12 h to obtain a black precursor powder.

[0072] The black precursor powder was placed on a magnetic boat and placed in a tube furnace filled with argon at 2 o Annealing at a heating rate of 500 °C / min o C, and kept warm for 4 h to finally obtain the negative electrode material (denoted as PO4-SnS@AsG).

[0073] The obtained negative electrode material was tested by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). During the TEM observation, three points on the material were randomly selected and the average arsenic content at the three selected points was tested using TEM accessory energy dispersive X-ray spectroscopy (EDX). The arsenic content was expressed as a percentage. The SEM image obtained by the test is shown in Figure 1 , transmission electron microscopy images are shown in Figure 2 The mass percentage of arsenic is shown in Table 1. Figure 1 It can be seen that PO4-SnS@AsG presents a fluffy tremella-like structure, and PO4-SnS crystal nanosheets with a size of 6-15 nm are uniformly attached to the thin layer of graphene. Figure 2 The three lattice arrangements of PO4-SnS@AsG are clearly visible, with lattice spacings of 0.305, 0.287, and 0.367 nm, corresponding to the (101), (111), and (120) planes of SnS crystals. Compared with the SnS lattice data previously recorded in the literature, the spacings are enlarged. This indicates that PO4 3- The introduction of α-HgO2 enlarges the lattice spacing of SnS.

[0074] The obtained negative electrode material was tested by Fourier transform infrared spectroscopy (FT-IR), and the test results are shown in Figure 3 .Depend on Figure 3 Visible at 1090 and 1630 cm -1 The vibration at 1083 cm is attributed to the OPO and PO bonds. -1 The vibration at 542 cm is attributed to the Sn-S bond, while the -1 The peak at corresponds to the infrared vibration of Sn-O bond, confirming that PO4 3- After the addition of SnS, Sn-OP covalent bonds are formed with Sn atoms, which serve as conductive pillars to buffer the volume expansion of SnS.

[0075] Preparation of negative electrode sheet

[0076] Weigh 8 parts by weight of PO4-SnS@AsG, 1 part by weight of superconducting carbon and 1 part by weight of carboxymethyl cellulose binder (CMC), and dissolve and disperse them in a mixed solution of ethanol / water to obtain PO4-SnS@AsG negative electrode slurry. 2 The loading amount is coated on the copper foil current collector and the negative electrode sheet is obtained after drying.

[0077] Battery Assembly

[0078] The negative electrode sheet is combined with the counter electrode potassium block and the separator, and the electrolyte is added and assembled into a battery casing to obtain a battery.

[0079] Diaphragm material: GF / A (Whatman), purchased from Whatman Ltd., UK.

[0080] Electrolyte: 2 M potassium bis(fluorosulfonyl)imide (KFSI) in triethyl phosphate (TEP).

[0081] Battery performance test method:

[0082] Cyclic performance test:

[0083] Using a Wuhan Blue Electric test system in China, the battery's constant current charge-discharge (GCD) curve was measured at a constant temperature of 28°C. The battery was discharged at a current density of 100 mA / g to 0.01 V, then charged at a current density of 100 mA / g to 3.0 V. This was recorded as the first cycle, and the reversible capacity (D1) of the first cycle was recorded. This charge-discharge process was repeated, and the reversible capacity (Dn) at the nth cycle was recorded. The capacity retention at the nth cycle was calculated. The capacity retention after 600 cycles is calculated as D600 / D1 x 100%.

[0084] High current cycle performance test:

[0085] The battery's constant current charge-discharge (GCD) curve was tested at a constant temperature of 28°C using the Wuhan Blue Electric test system in China. The battery was discharged to 0.01 V at a current density of 1000 mA / g, and then charged to 3.0 V at a current density of 1000 mA / g. This was recorded as the first cycle. The aforementioned charge-discharge process was repeated, and the reversible capacity of the nth cycle was recorded.

[0086] Rate cycling performance: The constant current charge and discharge (GCD) curve of the battery was tested using the Wuhan Blue Electric test system in China. The battery was discharged to 0.01 V at current densities of 100, 200, 300, 500, 800, 1000, 2000 and 3000 mA / g, and then charged to 3.0 V at the same current density. Ten cycles were repeated at each current density.

[0087] K + Diffusion rate test:

[0088] The test was conducted on the Wuhan Blue Electric test system in China. The battery system was first subjected to cross-current charge and discharge at a low current of 50 mA / g for 15 minutes. The applied current was then cut off and kept at rest for 2 hours to allow potassium to fully diffuse within the active material and reach equilibrium. By analyzing the relationship between the electrode potential change and the relaxation time, and combining the physical and chemical parameters of the negative electrode material, the potassium ion diffusion coefficient Dk was calculated. Among them, D K The value of can be calculated based on the simplified Fick's second law, as follows:

[0089]

[0090] in: t represents the pulse duration, m B， V M， and M B are the mass, molar volume and molar mass of the corresponding electrode, A is considered to be the interfacial area between the electrode and the electrolyte, ΔE s Indicates the voltage change (V) caused by the current pulse, ΔE t It represents the voltage change (V) during constant current discharge / charge after deducting the voltage change (iR drop) caused by the battery's internal resistance.

[0091] Example 2: All steps are the same as those in Example 1, except that the phytic acid solution is replaced by a phosphoric acid solution in the preparation of the negative electrode material.

[0092] Example 3: All steps are the same as in Example 1, but the preparation material is changed to 65 mL of GO dispersion with a concentration of 0.8 mg / mL.

[0093] Example 4:

[0094] A negative electrode material was prepared in a manner similar to that of Example 1, and a battery was prepared using the prepared negative electrode material, except that the annealing temperature during the preparation of the negative electrode material was changed to 600°C.

[0095] Example 5

[0096] A negative electrode material was prepared using a method similar to that of Example 1, and a battery was fabricated using the prepared negative electrode material. The difference was that the precursor solution was subjected to a high-energy ball milling treatment before the hydrothermal reaction. The treatment was performed using a vibrating high-energy ball mill. Milling balls with a diameter of 1 mm and the precursor solution were placed in a high-energy ball mill tube at a mass ratio of 1:1. The milling was then performed at a vibration rate of 3000 rpm for 3 minutes.

[0097] Comparative Example 1

[0098] A negative electrode material was prepared in a manner similar to that of Example 1, and a battery was prepared using the prepared negative electrode material, except that no phytic acid solution was added during the preparation of the negative electrode material.

[0099] Comparative Example 2

[0100] A negative electrode material was prepared in a manner similar to that of Example 1, and a battery was prepared using the prepared negative electrode material, except that no graphene oxide solution was added during the preparation of the negative electrode material.

[0101] The EDX test results of Example 1 and Example 5 are shown in Table 1.

[0102] Table 1

[0103]

[0104] Furthermore, as can be seen from the data in Table 1, the arsenic content in Example 5 is higher than that in Example 1. This is because high-energy ball milling allows for more arsenic to be fixed to the graphene. Vibratory high-energy ball milling, compared to rotary ball milling, produces higher collision energy, effectively generating a mechanochemical reaction that allows arsenic pentoxide particles to collide with graphene particles, thereby increasing the arsenic content fixed to the graphene surface.

[0105] The prepared batteries were tested for performance according to the battery performance test method described in Example 1. The cycle performance test results of Examples 1-5 and Comparative Examples 1-2 are shown in Table 2, and the rate cycle test results of Examples 1, 3 and Comparative Examples 1-2 are shown in Table 2. Figure 4 The high current cycle performance test results of Example 1, Example 4 and Comparative Example 1 are shown in Figure 5 , K of Example 1 and Comparative Example 1 +The diffusion rate test results are shown in Figure 6 .

[0106] Table 2

[0107]

[0108] From the results in Table 2 above, it can be seen that the specific capacity of Comparative Example 1 continues to decay at a current density of 100 mA / g, and only maintains a specific capacity of 150.4 mA / g after 600 cycles. However, Example 1 maintains a high specific capacity of 374.4 mAh / g after 600 stable cycles, and the capacity decay rate of each cycle is close to zero. This is because the arsenic-doped graphene in Example 1 effectively prevents material aggregation during the cycle, and PO4 3- The introduction of the group constructs a PO4-SnS@AsG three-dimensional conductive material with an expanded interlayer spacing, which provides potassium ions with a wider ion channel during the insertion and removal process, effectively alleviating the pulverization of the material when storing potassium, and ensuring the stability of potassium storage. Therefore, Example 1 has a higher capacity retention rate. In Comparative Example 1, due to the lack of a large interlayer spacing expanded by phosphate groups, SnS is inherently less conductive and its layered structure is very prone to severe structural collapse and agglomeration during the potassium insertion / depotassium insertion process, triggering an irreversible phase change, causing the active material to pulverize and fall off from the current collector and side reactions to occur continuously. Therefore, the capacity retention rate of Comparative Example 1 is poor. This proves the structural stability of the present invention when storing potassium at low current density. The capacity of Example 5 in the first 200 cycles is higher than that of Example 1, which is provided by more arsenic elements and their SnS particles anchored in the surface layer of graphene. However, the integrity of some graphene may have been destroyed during the high-energy ball milling process, and its capacity retention rate is slightly lower than that of Example 1.

[0109] Figure 4 Shown are the rate performance test results of Examples 1 and 3 of the present invention and Comparative Examples 1 and 2. Figure 4 It shows that in Example 1, PO4 3- The introduction of groups improves the conductivity of SnS. Arsenic-doped graphene effectively fixes SnS particles anchored on the graphene surface layer, preventing particle aggregation during the cycle, so that the material can still maintain high specific capacity and cycle stability after cycling at different current densities, indicating that the material has excellent potassium storage reaction kinetics and structural stability. In the negative electrode materials prepared in Examples 1 and 3, PO4 3- The introduction of these groups creates a three-dimensional conductive material with expanded interlayer spacing, PO4-SnS@AsG, altering the electronic structure of SnS and improving its conductivity, resulting in better rate performance. In contrast, Comparative Examples 1 and 2, which lack phosphate or graphene oxide, exhibit poor rate performance due to the inherently low conductivity of SnS.

[0110] Figure 5 Shown are the high current cycle test results of Examples 1 and 4 of the present invention and Comparative Example 1 tested at a current of 1000 mA / g. Figure 5 The results show that the presence of phosphate and graphene oxide in Example 1 improves the conductivity and structural stability of the negative electrode material, thereby exhibiting higher capacity and stable cycling ability at high current density. In contrast, in Comparative Example 1, there is no phosphate intercalation to improve the interlayer spacing and conductivity of SnS, thus exhibiting a lower specific capacity.

[0111] Figure 6 Shown as K of Example 1 and Comparative Example 1 + Diffusion rate test results. Figure 6 It shows that the K + The diffusion rate of Example 1 is higher than that of Comparative Example 1. 3- The groups effectively expand the interlayer spacing of SnS and improve the conductivity of SnS, making Example 1 have a fast K + Transfer kinetics. Comparative Example 1 exhibits a slower K transfer due to the poor intrinsic conductivity of SnS. + Transfer kinetics. In Example 1, PO4 3- The introduction of groups gives the negative electrode material an extended interlayer spacing and covalent bond charge bridge, allowing potassium ions with a larger radius to be quickly transported in the electrode structure and alleviating the lattice expansion during potassium ion insertion, thereby achieving excellent rate performance.

[0112] Example 6

[0113] A negative electrode plate was prepared in the same manner as in Example 1, except that the negative electrode plate was pre-potassium treated.

[0114] Positive electrode sheet: 3,4,9,10-perylenetetracarboxylic dianhydride is prepared as an organic positive electrode sheet, wherein the mass of 3,4,9,10-perylenetetracarboxylic dianhydride is twice the amount of the negative electrode loading.

[0115] The pre-potassium-treated negative electrode sheet was combined with the positive electrode sheet and the separator, and the electrolyte was added and assembled into a full battery after being placed in the battery casing. The separator material was GF / A (Whatman), purchased from Whatman Ltd. in the UK; the electrolyte was a 2M potassium bis(fluorosulfonyl)imide (KFSI) solution in triethyl phosphate (TEP).

[0116] The prepared full battery was tested according to the above-mentioned rate cycle performance test method, and the test results are shown in Figure 7 .

[0117] Figure 7A schematic diagram shows the rate energy density cycling of a full cell from Example 1, using a pre-potassium-treated electrode as the negative electrode and 3,4,9,10-perylenetetracarboxylic dianhydride as the organic positive electrode. Due to the expanded interlayer spacing and improved conductivity, the assembled full cell exhibits high energy density and cycling stability at various current densities.

[0118] In addition, the descriptions of the terms "some embodiments", "other embodiments", etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this application, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this application and the features of the different embodiments or examples, unless they are mutually inconsistent.

[0119] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A method for preparing a negative electrode material for a potassium ion battery, characterized in that: The following steps are involved: Tin source, arsenic pentoxide, sodium hydroxide, phosphorus source, and thiourea are sequentially added to a graphene oxide dispersion having a concentration of 0.4 mg / mL-1.0 mg / mL, and the mixture is stirred and dissolved to form a precursor solution. The precursor solution is subjected to a hydrothermal reaction to obtain a precursor powder, Annealing the precursor powder to obtain the potassium ion battery negative electrode material; wherein the hydrothermal reaction comprises maintaining the temperature at 160°C-180°C for 10-12 hours; The annealing treatment includes annealing to 500-550°C at a heating rate of 2-5°C / min and keeping the temperature for 4-6 hours; In the precursor solution, the mass ratio of graphene oxide, tin source, arsenic pentoxide, sodium hydroxide, phosphorus source, and thiourea is 1-3:26:24:144:55:6; Before the hydrothermal reaction, the precursor solution is subjected to high-energy ball milling treatment, specifically using a vibrating high-energy ball mill for high-energy ball milling treatment; The potassium ion battery negative electrode material comprises: Arsenic-doped graphene, layered tin sulfide anchored on the arsenic-doped graphene, and In situ introduction of phosphate ions between the stannous sulfide layers; The mass content of the arsenic-doped graphene is 4%-8% relative to the total weight of the potassium ion battery negative electrode material; The phosphorus source is phosphoric acid.

2. The preparation method according to claim 1, characterized in that The tin source is SnCl4·5H2O.

3. A potassium ion battery negative electrode material, characterized in that The method according to claim 1 or 2 is used to prepare the product.

4. A potassium ion battery, characterized in that The potassium ion battery negative electrode material according to claim 3 is included, wherein the potassium ion battery comprises a potassium ion secondary battery.

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