A negative electrode material for potassium ion batteries, a preparation method thereof, and an application thereof

Abstract

The present invention discloses a negative electrode material for a potassium ion battery, a preparation method thereof, and an application thereof, which relate to the field of potassium ion batteries. The negative electrode material for the potassium ion battery of the present invention is an N / Sb co-doped BiOCl@C composite material, and its structure is two-dimensional flaky, which is composed of an Sb-doped BiOCl layer and an N-doped carbon layer coated on the surface of the BiOCl layer. Bi single crystal particles are interspersed in the BiOCl layer, and there are C-O-Sb bonds and C-O-Bi bonds between the Sb-doped BiOCl layer and the N-doped carbon layer. Based on the synergistic effect of several factors such as the two-dimensional flaky structure, Bi single crystal particles, doped Sb, and N-doped C layer, the composite material prepared by the present invention has a high specific capacity, excellent rate performance and long cycle life when used as a negative electrode material for a potassium ion battery, and has a good application prospect in the field of potassium ion batteries.

Description

Technical Field

[0001] The present invention relates to the field of potassium ion batteries, and more particularly, to a negative electrode material for a potassium ion battery, a preparation method thereof, and an application thereof. Background Art

[0002] At present, lithium ion batteries dominate the energy storage field with high energy density and excellent cycle life. However, due to the uneven distribution and extremely limited reserves of lithium resources in the earth's crust, and the high price of lithium resources, the further development of lithium ion batteries is severely restricted. Potassium ion batteries have attracted extensive attention from many scientific research scholars because of their rich resources, low cost, and similar working principles to lithium ion batteries. However, due to the larger radius of potassium ions (0.138 nm) than that of lithium ions (0.076 nm), the electrode material is prone to large volume expansion during charge and discharge, causing the active material to be crushed or even detached from the current collector, resulting in rapid decay of battery performance. Therefore, it is particularly important to develop a low-cost and high specific energy potassium ion negative electrode material.

[0003] Bismuth (Bi) and its compounds (bismuth metal, bismuth oxide, bismuth sulfide, bismuth selenide, bismuth oxychloride, etc.) undergo a redox reaction with multiple electron transfers during potassium storage, and have a high theoretical specific capacity, and are considered to be a class of potassium ion battery negative electrode materials with great application potential. Among Bi-based materials, BiOCl has many advantages. However, due to the weak interfacial electron chemical coupling formed by surface absorption or geometric superposition of BiOCl, a large electron transfer energy barrier will be generated, and there are problems such as volume expansion, resulting in poor battery cycle performance and stability.

[0004] The current prior art discloses a nitrogen-doped carbon-coated nano-antimony bismuth alloy material, which can be used as a negative electrode material for sodium ion batteries. The bismuth in the material can buffer with antimony and reduce the volume expansion that occurs during the alloying process of antimony and sodium ions. However, the technical problems addressed by the prior art are those of antimony-based rather than bismuth-based materials when used as battery negative electrode materials, and the application of the nitrogen-doped carbon-coated nano-antimony bismuth alloy material in the prior art is limited to the negative electrode material for sodium ion batteries, and cannot solve the problems of volume expansion and rapid performance decay of potassium ion battery electrode materials. Summary of the Invention

[0005] In order to solve the problem that bismuth oxychloride (BiOCl) has a high energy barrier for electron transfer and volume expansion during potassium storage, resulting in poor battery cycling performance and stability when used as the anode material for potassium-ion batteries, the present invention provides an N / Sb co-doped BiOCl@C material as the anode material for potassium-ion batteries. Due to the synergistic effects of factors such as the two-dimensional sheet structure, Bi single crystal particles, doped Sb, and N-doped carbon layer, the anode material of the present invention has a high specific capacity, excellent rate performance, and long cycle life.

[0006] Another object of the present invention is to provide a preparation method for the anode material.

[0007] Still another object of the present invention is to provide an application of the anode material in the preparation of potassium-ion batteries.

[0008] Still another object of the present invention is to provide an anode material.

[0009] Yet another object of the present invention is to provide a potassium-ion battery.

[0010] To achieve the above objects, the present invention adopts the following technical solutions:

[0011] An N / Sb co-doped BiOCl@C material with a two-dimensional sheet structure, comprising an Sb-doped BiOCl layer and an N-doped carbon layer coated on the surface of the BiOCl layer. Bi particles are interspersed in the Sb-doped BiOCl layer. There are C-O-Sb bonds and C-O-Bi bonds between the Sb-doped BiOCl layer and the N-doped carbon layer, and the doping amount of Sb in the BiOCl layer is 30-40 wt%.

[0012] The anode material for potassium-ion batteries provided by the present invention has the core material of Sb-doped BiOCl. In the core material, Bi single crystal particles are generated due to the reduction of Bi in BiOCl during calcination. The presence of Bi particles improves the electrical conductivity inside the BiOCl layer.

[0013] The two-dimensional sheet-like N / Sb co-doped BiOCl@C material provided by the present invention also has an N-doped carbon layer coated on the surface of the Sb-doped BiOCl layer. Since BiOCl is layered and the precursor polydopamine layer of the N-doped carbon layer is generated on the surface of the BiOCl layer using the BiOCl layer as a template, the composite material has a two-dimensional sheet-like structure. This structure not only has greater mechanical stability and superior flexibility, can adapt to volume changes and maintain structural stability, but also has a higher carrier mobility and shorter diffusion path during cycling, which can improve the rate performance. The BiOCl core material layer and the surface coating layer are not simply superimposed, but are connected by chemical bonds. There is a C-O-Bi bond between the core material layer and the coating layer. The existence of this chemical bond can prevent the aggregation of Bi particles and thus stabilize the structure, and can also promote the transport of electrons / ions and accelerate the K + reaction kinetics. The Sb doped into the BiOCl layer exists in an amorphous form, but Sb, O provided by BiOCl, and C provided by the N-doped carbon layer can form a C-O-Sb bond. This chemical bond can also inhibit the volume expansion of the material by avoiding the aggregation of Bi, further stabilize the structure of the material, and accelerate charge transport at the same time. The N-doped carbon layer coating has a certain strength, can improve the structural stability of the composite material of the present invention, inhibit structural collapse and the shedding of active substances, and improve the cycle stability of the material. The doped N in the coating layer effectively destroys the electrical neutrality of the carbon layer, opens the band gap of the carbon material, improves the conductivity of the material, and can adsorb K + and accelerate the K + reaction kinetics, thereby improving the cycle performance of the composite material.

[0014] Limiting the doping amount of Sb within the range of 30-40 wt% can reduce the volume expansion that occurs during potassium storage in the material, and can also improve the conductivity of the material; since Sb exists in an amorphous form in the material, when the doping amount is too large, the material cannot form a two-dimensional sheet-like structure well, and the performance of the material will also decline accordingly.

[0015] Preferably, the doping amount of N in the N-doped carbon layer is 4-6 wt%.

[0016] The N-doped carbon layer is obtained by calcining the precursor. The present invention selects hydrochloric acid dopamine as the raw material, deposits a layer of polydopamine as the precursor of the coating layer on the core material layer as the template, and converts the polydopamine layer into an N-doped carbon layer by calcination. The specific doping amount of N in this N-doped carbon layer will vary with different polydopamine deposition amounts, calcination treatment conditions, etc. When the N doping amount is 4-6 wt%, the N / Sb co-doped BiOCl@C material has better electrical properties.

[0017] The present invention also provides a method for preparing a two-dimensional sheet-like N / Sb co-doped BiOCl@C material, and the specific steps are as follows:

[0018] S1. Mix a bismuth source, antimony chloride, ethylene glycol and water, and then carry out a hydrothermal reaction to obtain Sb-doped BiOCl;

[0019] S2. Mix, dissolve and stir Sb-doped BiOCl, dopamine hydrochloride and tris(hydroxymethyl)aminomethane to obtain Sb-doped BiOCl with a polydopamine coating layer on the surface;

[0020] S3. Calcinate the Sb-doped BiOCl with a polydopamine coating layer in an inert atmosphere to obtain N / Sb co-doped BiOCl@C.

[0021] The bismuth source in step S1 can be a conventional bismuth salt in the art.

[0022] The antimony source in step S1 is selected from one of antimony trichloride and antimony pentachloride. Using antimony trichloride and antimony pentachloride as the antimony source also serves the function of providing a chlorine source.

[0023] Preferably, the addition amount of water in step S1 is 9-13 mL.

[0024] The hydrothermal method is a commonly used method for preparing dopants. In the present invention, the addition of deionized water is to provide a hydrothermal reaction pressure condition for the reactants, and the addition amount of water will affect the final morphology of the composite material. Too high or too low an addition amount of water may cause the composite material to agglomerate and stack, eventually forming a three-dimensional structure and unable to form a clearer two-dimensional sheet structure with better electrical properties and structural stability. Limiting the addition amount of deionized water within the above range can finally prepare the N / Sb co-doped BiOCl@C composite material to better form a clear two-dimensional structure.

[0025] Preferably, the molar ratio of Sb-doped BiOCl, tris(hydroxymethyl)aminomethane and dopamine hydrochloride in step S2 is 1:(1-2):(0.5-1).

[0026] In the present invention, limiting the molar ratio of Sb-doped BiOCl, tris(hydroxymethyl)aminomethane and dopamine hydrochloride within the above range can enable the N-doped carbon layer to be more completely deposited and coated on the surface of the core material, and thus enable the coating layer to better play its role.

[0027] Preferably, the calcination treatment in step S3 is carried out at 300-500 °C for 3-5 h.

[0028] More preferably, the calcination treatment in step S3 is carried out at 350 °C for 4 h.

[0029] In the present invention, calcination can not only make the polydopamine layer react to form an N-doped carbon layer, but also reduce the Bi element in BiOCl in the core material layer to elemental particles. The higher the temperature, the more Bi is reduced, and thus the larger the particle size of the accumulated Bi elemental particles, which will also affect the two-dimensional sheet structure of the composite material. Therefore, the calcination temperature needs to be maintained within the above range. When the calcination treatment is carried out at 350 °C for 4 h, the prepared N / Sb co-doped BiOCl@C has the clearest two-dimensional sheet structure.

[0030] The N / Sb co-doped BiOCl@C negative electrode material prepared by the above method has an Sb-doped BiOCl layer and an N-doped carbon layer coated on the surface of the Sb-doped BiOCl composite material layer.

[0031] The present invention also protects the application of an N / Sb co-doped BiOCl@C negative electrode material in the preparation of potassium ion batteries.

[0032] The present invention also protects a negative electrode material prepared from an N / Sb co-doped BiOCl@C material.

[0033] The negative electrode material protected by the present invention has the advantages of low electron transfer energy barrier and small volume expansion, and solves the problems of poor cycle performance and stability of potassium ion batteries due to high electron transfer energy barrier and volume expansion.

[0034] The present invention also protects a potassium ion battery composed of an N / Sb co-doped BiOCl@C material as the negative electrode.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] The potassium ion battery negative electrode material provided by the present invention, based on the synergistic effect brought by the doped Sb, the generated Bi particles, the coated N-doped carbon layer, and the bonding between the core material and the coating layer, has a high specific capacity, excellent rate performance and long cycle life, and solves the problem that the cycle performance and stability of the battery are poor when bismuth oxychloride BiOCl is used as the negative electrode material of the potassium ion battery due to the high energy barrier of electron transfer and volume expansion therein.

[0037] When the negative electrode material of the present invention is used as the negative electrode of a potassium ion battery, the battery has an initial capacity of 520.2 mAh g -1 at a current density of 0.05 A g -1 , indicating that the negative electrode material of the present invention has a very high specific capacity; at a current density of 1.0 A g -1 , after 6000 charge-discharge cycles, the capacity still remains at 100.3 mAh g -1, that is, it has excellent cycle life; the material of the present invention has a less degree of capacity reduction under gradually increasing current density; and when the current density is reduced back to the lowest value, the capacity still remains at the level before the increase in current density, indicating that the prepared anode material has good rate performance and cycle reversibility, and can be widely used in the field of potassium ion batteries. Description of the Drawings

[0038] Figure 1 It is the field emission scanning electron microscope photo and transmission electron microscope photo of the product obtained in Example 1 of the present invention.

[0039] Figure 2 It is the X-ray diffraction pattern of the product obtained in Example 1 of the present invention.

[0040] Figure 3 It is the peak fitting diagram of element C in the X-ray photoelectron spectroscopy of the product obtained in Example 1 of the present invention.

[0041] Figure 4 It is the peak fitting diagram of element N in the X-ray photoelectron spectroscopy of the product obtained in Example 1 of the present invention.

[0042] Figure 5 It is the peak fitting diagram of element O / Sb in the X-ray photoelectron spectroscopy of the product obtained in Example 1 of the present invention.

[0043] Figure 6 It is the peak fitting diagram of element Bi in the X-ray photoelectron spectroscopy of the product obtained in Example 1 of the present invention.

[0044] Figure 7 It is the peak fitting diagram of element Cl in the X-ray photoelectron spectroscopy of the product obtained in Example 1 of the present invention.

[0045] Figure 8 It is the cycle performance diagram at a current density of 1.0 A / g of the product obtained in Example 1 of the present invention.

[0046] Figure 9 It is the field emission scanning electron microscope photo and X-ray diffraction pattern of the product obtained in Comparative Example 1 of the present invention.

[0047] Figure 10 It is the field emission scanning electron microscope photo and X-ray diffraction pattern of the product obtained in Comparative Example 2 of the present invention.

[0048] Figure 11 It is the field emission scanning electron microscope photo and X-ray diffraction pattern of the product obtained in Example 3 of the present invention.

[0049] Figure 12 It is the rate performance diagram of the product obtained in Example 1 of the present invention.

[0050] Figure 13This is a rate performance diagram of the product obtained in Example 3 of the present invention. DETAILED DESCRIPTION

[0051] The following is a specific implementation case of the present invention to further illustrate the present invention in detail. However, the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0052] Example 1

[0053] A N / Sb co-doped BiOCl@C material has a two-dimensional sheet structure and comprises a Sb-doped BiOCl layer and an N-doped carbon layer coated on the surface of the BiOCl layer, wherein Bi particles are interspersed in the Sb-doped BiOCl layer, CO-Sb bonds and CO-Bi bonds exist between the Sb-doped BiOCl layer and the N-doped carbon layer, and the doping amount of Sb in the BiOCl layer is 36.0wt%.

[0054] The doping amount of N in the N-doped carbon layer is 4.2 wt %.

[0055] The preparation method of the N / Sb co-doped BiOCl@C material of the above-mentioned embodiment 1 specifically comprises the following steps:

[0056] S1. 0.5mmol bismuth nitrate and 0.5mmol antimony chloride were added to 60ml ethylene glycol and stirred at 300r / min for 20min. After stirring, 11mL deionized water was quickly added to the solution, and then the solution was transferred to a high-pressure reactor and reacted at 180°C for 12h. After the reaction, the mixture was centrifuged and washed three times with a mixture of deionized water and 95% industrial ethanol, and then washed once with anhydrous ethanol, and then dried in a vacuum oven at 80°C for 12h to obtain Sb-doped BiOCl;

[0057] S2. 0.5 mmol Sb-doped BiOCl, 1 mmol tris(hydroxymethyl)aminomethane) and 0.5 mmol dopamine hydrochloride were added to a mixed solution containing 50 mL deionized water and 50 mL anhydrous ethanol, and stirred at a stirring speed of 500 r / min for 4 h. After stirring, the mixture was centrifuged and washed with anhydrous ethanol for 3 times, and dried under vacuum at 80 °C for 12 h. After drying, Sb-doped BiOCl@PDA was obtained.

[0058] S3. The Sb-doped BiOCl@PDA was placed in a nitrogen atmosphere and heated to 350°C at a heating rate of 2°C / min and calcined at a constant temperature for 4 hours to obtain N / Sb co-doped BiOCl@C (N-doped carbon-coated Sb-doped BiOCl) intercalated with Bi elemental particles.

[0059] Figure 1are the field emission scanning electron microscope and transmission electron microscope photos of the material of Example 1. It can be seen from Figure 1 that the N / Sb co-doped BiOCl@C is a flaky structure, and there is an obvious carbon coating layer on its outside.

[0060] Figure 2 is the X-ray diffraction pattern of the material of Example 1. It can be seen from Figure 2 that all diffraction peaks match well with the PDF cards of BiOCl and Bi, proving the successful synthesis of BiOCl@C.

[0061] Figures 3 to 7 are the peak fitting diagrams of C, N, O / Sb, Bi, and Cl elements in the X-ray photoelectron spectroscopy of the material of Example 1 in sequence. It can be analyzed and proved from the figure that the N / Sb co-doped BiOCl@C is successfully synthesized.

[0062] Figure 8 is the cyclic performance test diagram of the material of Example 1 at a current density of 1.0 A g -1 . It can be seen from Figure 8 that at a current density of 0.05 A g -1 , the initial capacity is 520.2 mAh g -1 ; at a current density of 1.0 A g -1 , after 6000 charge-discharge cycles, the capacity still remains at 100.3 mAh g -1 , indicating that the negative electrode material prepared in Example 1 has excellent cycle life.

[0063] Figure 12 is the rate performance test diagram of the material of Example 1. It can be seen from Figure 12 that at a current density of 0.05 to 2.0 A g -1 , the capacities are 434.2, 379.2, 333.2, 234.4, 162.0, 117.8 mAh g -1 in sequence; when the current returns to a current density of 0.05 A g -1 , the capacity still remains at 375.2 mAh g -1 , indicating that the negative electrode material prepared in Example 1 has good rate performance and cycle reversibility.

[0064] Example 2

[0065] An N / Sb co-doped BiOCl@C material with a two-dimensional sheet-like structure, including an Sb-doped BiOCl layer and an N-doped carbon layer coated on the surface of the BiOCl layer. Bi particles are interspersed in the Sb-doped BiOCl layer. There are C-O-Sb bonds and C-O-Bi bonds between the Sb-doped BiOCl layer and the N-doped carbon layer, and the doping amount of Sb in the BiOCl layer is 30.2 wt%.

[0066] The doping amount of N in the N-doped carbon layer is 5.8 wt%.

[0067] The preparation method of the N / Sb co-doped BiOCl@C material in Example 2 above specifically includes the following steps:

[0068] S1. Add 2 mmol of bismuth nitrate and 1 mmol of antimony chloride to 60 ml of ethylene glycol and stir at a speed of 300 r / min for 20 min. After stirring, continue to quickly drop 11 mL of deionized water into the above solution, then transfer it to a high-pressure reaction kettle and react at 200 °C for 24 h. After the reaction, centrifuge and wash 4 times with a mixed solution of deionized water and 95% industrial ethanol, and then wash 4 times with absolute ethanol. Subsequently, dry it in a vacuum oven at 80 °C for 24 h to obtain Sb-doped BiOCl;

[0069] S2. Add 2 mmol of Sb-doped BiOCl, 3 mmol of tris(hydroxymethyl)aminomethane, and 2 mmol of dopamine hydrochloride to a mixed solution containing 50 mL of deionized water and 50 mL of absolute ethanol, and continuously stir at a stirring speed of 500 r / min for 24 h. After stirring, centrifuge and wash 3 times with absolute ethanol, and dry it under vacuum at 80 °C for 12 h to obtain Sb-doped BiOCl@PDA;

[0070] S3. Place Sb-doped BiOCl@PDA in a nitrogen atmosphere and heat it to 500 °C at a heating rate of 2 °C / min for constant-temperature calcination for 5 h to obtain N / Sb co-doped BiOCl@C (Sb-doped BiOCl coated with N-doped carbon) with Bi single-particle inclusions.

[0071] Example 3

[0072] An N / Sb co-doped BiOCl@C material with a three-dimensional block morphology formed by stacking two-dimensional sheets, including an Sb-doped BiOCl core and an N-doped carbon layer coated on the surface of the BiOCl layer. Bi particles are interspersed in the Sb-doped BiOCl core. There are C-O-Sb bonds and C-O-Bi bonds between the Sb-doped BiOCl layer and the N-doped carbon layer, and the doping amount of Sb in the BiOCl layer is 35.5 wt%.

[0073] The doping amount of N in the N-doped carbon layer is 4.2 wt%.

[0074] The preparation method of the N / Sb co-doped BiOCl@C material of the above-mentioned embodiment 3 specifically comprises the following steps:

[0075] S1. 0.5mmol bismuth nitrate and 0.5mmol antimony chloride were added to 60ml ethylene glycol and stirred at 300r / min for 20min. After stirring, 14mL deionized water was rapidly added to the solution, and then the solution was transferred to a high-pressure reactor and reacted at 180°C for 12h. After the reaction, the mixture was centrifuged and washed three times with a mixture of deionized water and 95% industrial ethanol, and then washed once with anhydrous ethanol, and then dried in a vacuum oven at 80°C for 12h to obtain Sb-doped BiOCl;

[0076] S2. 0.5 mmol Sb-doped BiOCl, 1 mmol tris(hydroxymethyl)aminomethane) and 0.5 mmol dopamine hydrochloride were added to a mixed solution containing 50 mL deionized water and 50 mL anhydrous ethanol, and stirred at a stirring speed of 500 r / min for 4 h. After stirring, the mixture was centrifuged and washed with anhydrous ethanol for 3 times, and dried under vacuum at 80 °C for 12 h. After drying, Sb-doped BiOCl@PDA was obtained.

[0077] S3. The Sb-doped BiOCl@PDA was placed in a nitrogen atmosphere and heated to 350°C at a heating rate of 2°C / min and calcined at a constant temperature for 4 hours to obtain N / Sb co-doped BiOCl@C (N-doped carbon-coated Sb-doped BiOCl) intercalated with Bi elemental particles.

[0078] Figure 11 The following are the field emission scanning electron microscope photos and X-ray diffraction patterns of the material in Example 3. Figure 11 It can be seen that the structure of the material in Example 3 is a three-dimensional block structure formed by stacking two-dimensional sheets, and the PDF cards of all diffraction peaks BiOCl match well, proving that the material in Example 3 was successfully synthesized. The reason why the material with a three-dimensional block structure was obtained in Example 3 is that the amount of water added in the hydrothermal reaction is larger, and the conditions of the hydrothermal reaction are changed.

[0079] Figure 13 This is a rate performance test diagram of the material in Example 3. Figure 13 As can be seen, the material is between 0.05 and 2.0Ag -1 At the current density of , the capacities are 412.0, 332.2, 254.4, 101.2, 76.1, and 42.8 mAh g -1 ; It shows that the rate performance of the negative electrode material prepared in Example 3 is worse than that in Example 1.

[0080] Example 4

[0081] An N / Sb co-doped BiOCl@C material with a two-dimensional sheet structure, including an Sb-doped BiOCl layer and an N-doped carbon layer coated on the surface of the BiOCl layer. Bi particles are interspersed in the Sb-doped BiOCl layer. There are C-O-Sb bonds and C-O-Bi bonds between the Sb-doped BiOCl layer and the N-doped carbon layer, and the doping amount of Sb in the BiOCl layer is 30.6 wt%.

[0082] The doping amount of N in the N-doped carbon layer is 4.8 wt%.

[0083] The preparation method of the N / Sb co-doped BiOCl@C material in Example 4 above specifically includes the following steps:

[0084] S1. Add 1.5 mmol of bismuth nitrate and 1 mmol of antimony chloride to 60 ml of ethylene glycol and stir at a speed of 300 r / min for 20 min. After stirring, continue to quickly drop 9 mL of deionized water into the above solution, then transfer it to a high-pressure reaction kettle and react at 160 °C for 20 h. After the reaction, centrifuge and wash 3 times with a mixed solution of deionized water and 95% industrial ethanol, and then wash 3 times with absolute ethanol. Subsequently, dry it in a vacuum oven at 80 °C for 20 h to obtain Sb-doped BiOCl;

[0085] S2. Add 1.5 mmol of Sb-doped BiOCl, 1.5 mmol of tris(hydroxymethyl)aminomethane, and 1 mmol of dopamine hydrochloride to a mixed solution containing 50 mL of deionized water and 50 mL of absolute ethanol, and continuously stir at a stirring speed of 500 r / min for 12 h. After stirring, centrifuge and wash 3 times with absolute ethanol, and dry it under vacuum at 80 °C for 12 h. After drying, obtain Sb-doped BiOCl@PDA;

[0086] S3. Place Sb-doped BiOCl@PDA in a nitrogen atmosphere and heat it to 450 °C at a heating rate of 2 °C / min for constant temperature calcination for 5 h to obtain N / Sb co-doped BiOCl@Bi@C (Sb-doped BiOCl@Bi coated with N-doped carbon);

[0087] Comparative Example 1

[0088] An Sb-doped BiOCl negative electrode material without an N-doped carbon layer coating, with a two-dimensional sheet structure, and the doping amount of Sb in the BiOCl layer is 37.7 wt%.

[0089] The preparation method of the Sb-doped BiOCl negative electrode material without an N-doped carbon layer coating in the above Comparative Example 1 specifically includes the following steps:

[0090] S1. Add 0.5 mmol of bismuth nitrate and 0.5 mmol of antimony chloride into 60 ml of ethylene glycol, stir at a speed of 300 r / min for 20 min. After stirring, quickly drop 11 mL of deionized water into the above solution, then transfer it to a high-pressure reactor and react at 180 °C for 12 h. After the reaction, centrifuge and wash it 3 times with a mixed solution of deionized water and 95% industrial ethanol, then wash it once with absolute ethanol, and then dry it in a vacuum oven at 80 °C for 12 h to obtain Sb-doped BiOCl;

[0091] S2. Place the Sb-doped BiOCl in a nitrogen atmosphere and heat it to 350 °C at a heating rate of 2 °C / min for constant-temperature calcination for 4 h to obtain Sb-doped BiOCl.

[0092] Figure 9 are the field emission scanning electron microscope photograph and X-ray diffraction pattern of the material of Comparative Example 1. From Figure 9 it can be seen that its structure is a flaky structure, and all diffraction peaks match well with the PDF card of BiOCl, proving that the material of Comparative Example 1 is successfully synthesized.

[0093] Comparative Example 2

[0094] An Sb-free N-doped BiOCl@C anode material, with a two-dimensional flaky structure, including a BiOCl layer and an N-doped carbon layer coated on the surface of the BiOCl layer, and the doping amount of N in the N-doped carbon layer is 5.6 wt%.

[0095] The preparation method of the Sb-free N-doped BiOCl@C anode material of the above Comparative Example 2 specifically includes the following steps:

[0096] S1. Add 0.5 mmol of bismuth nitrate and 0.5 mmol of sodium chloride into 60 ml of ethylene glycol, stir at a speed of 300 r / min for 20 min. After stirring, quickly drop 11 mL of deionized water into the above solution, then transfer it to a high-pressure reactor and react at 180 °C for 12 h. After the reaction, centrifuge and wash it 3 times with a mixed solution of deionized water and 95% industrial ethanol, then wash it once with absolute ethanol, and then dry it in a vacuum oven at 80 °C for 12 h to obtain BiOCl;

[0097] S2. Add 0.5 mmol of BiOCl, 1 mmol of tris(hydroxymethyl)aminomethane, and 0.5 mmol of dopamine hydrochloride into a mixed solution containing 50 mL of deionized water and 50 mL of absolute ethanol, continuously stir at a stirring speed of 500 r / min for 4 h. After stirring, centrifuge and wash it 3 times with absolute ethanol, and dry it in a vacuum state at 80 °C for 12 h. After drying, obtain BiOCl@PDA;

[0098] S3. BiOCl@PDA was placed in a nitrogen atmosphere and heated to 350°C at a heating rate of 2°C / min and calcined at a constant temperature for 4 hours to obtain N-doped BiOCl@C (N-doped carbon-coated BiOCl) intercalated with Bi elemental particles.

[0099] Figure 10 The following are the field emission scanning electron microscope photos and X-ray diffraction patterns of the material in Example 2. Figure 10 It can be seen that its structure is a lamellar structure, and the PDF cards of all diffraction peaks BiOCl and Bi match well, proving that the material of Comparative Example 2 was successfully synthesized.

[0100] Comparative Example 3

[0101] A N / Sb co-doped BiOCl@C material with a lower Sb doping amount than the technical solution of the present invention has a two-dimensional sheet structure, comprising an Sb-doped BiOCl layer and an N-doped carbon layer coated on the surface of the BiOCl layer, the Sb-doped BiOCl layer is interspersed with Bi particles, CO-Sb bonds and CO-Bi bonds exist between the Sb-doped BiOCl layer and the N-doped carbon layer, and the Sb doping amount in the BiOCl layer is 19.5wt%.

[0102] The doping amount of N in the N-doped carbon layer is 4.7 wt %.

[0103] The preparation method of the N / Sb co-doped BiOCl@C material of the comparative example 3 specifically comprises the following steps:

[0104] S1. 0.5mmol bismuth nitrate and 0.2mmol antimony chloride were added to 60ml ethylene glycol and stirred at 300r / min for 20min. After stirring, 11mL deionized water was rapidly added to the solution, and then the solution was transferred to a high-pressure reactor and reacted at 180°C for 12h. After the reaction, the mixture was centrifuged and washed three times with a mixture of deionized water and 95% industrial ethanol, and then washed once with anhydrous ethanol, and then dried in a vacuum oven at 80°C for 12h to obtain Sb-doped BiOCl;

[0105] S2. 0.5 mmol Sb-doped BiOCl, 1 mmol tris(hydroxymethyl)aminomethane) and 0.5 mmol dopamine hydrochloride were added to a mixed solution containing 50 mL deionized water and 50 mL anhydrous ethanol, and stirred at a stirring speed of 500 r / min for 4 h. After stirring, the mixture was centrifuged and washed with anhydrous ethanol for 3 times, and dried under vacuum at 80 °C for 12 h. After drying, Sb-doped BiOCl@PDA was obtained.

[0106] S3. The Sb-doped BiOCl@PDA was placed in a nitrogen atmosphere and heated to 350°C at a heating rate of 2°C / min and calcined at a constant temperature for 4 hours to obtain N / Sb co-doped BiOCl@C (N-doped carbon-coated Sb-doped BiOCl) intercalated with Bi elemental particles.

[0107] Performance Testing

[0108] The test method is as follows:

[0109] Morphology characterization: Field emission scanning electron microscopy (FEI SEM, Thermo scientific Apreo C, USA) and high-resolution transmission electron microscopy (TEM, Talos F200S) were used to observe the morphology of the samples;

[0110] Structural and component analysis: X-ray photoelectron spectroscopy (XPS, Thermo Fisher, Escalab 250Xi) and X-ray diffraction analysis instruments (Japan Rigaku SmartLab-9kW, Cu Kα As anode target, the scanning rate is 10°min -1 , the test diffraction angle range is 5-80°) to analyze the crystal structure and phase composition;

[0111] Electrochemical performance test: Neware battery test system (CT-ZWJ-4'S-T-1U, Shenzhen) was used to conduct constant current charge and discharge tests on the battery.

[0112] The test results are shown in Table 1 and Figures 1 to 13 As shown:

[0113] Table 1. Electrical properties of materials obtained from different examples and comparative examples

[0114]

[0115] According to the data in Table 1, it can be seen that the first cycle capacity and the capacity after 1000 charge and discharge cycles of Comparative Examples 1 to 3 are lower than those of Examples 1 to 4, indicating that the negative electrode material prepared by the present invention has a higher specific capacity and better cycle performance, which is an effect brought about by the two-dimensional sheet structure of the material prepared by the present invention, the doped Sb, Bi single substance particles and the N-doped carbon layer.

[0116] According to the data in Table 1 and the comparison Figure 12 and Figure 13It can be seen that the N / Sb co-doped BiOCl@C anode material with a clearer two-dimensional sheet structure in Example 1 has significantly better rate performance than the N / Sb co-doped BiOCl@C anode material formed by stacking two-dimensional sheets into a three-dimensional block in Example 3. It can be seen that a clearer two-dimensional sheet structure can improve the conductivity and structural stability of the N / Sb co-doped BiOCl@C material, thereby improving the rate performance of the material.

Claims

1. A N / Sb co-doped BiOCl@C material, Characterized in that, The structure of the N / Sb co-doped BiOCl@C material is two-dimensional sheet-like, including an Sb-doped BiOCl layer and an N-doped carbon layer coated on the surface of the BiOCl layer. Bi particles are interspersed in the Sb-doped BiOCl layer, and there are C-O-Sb bonds and C-O-Bi bonds between the Sb-doped BiOCl layer and the N-doped carbon layer. The doping amount of Sb in the BiOCl layer is 30-40 wt%; The preparation method of the N / Sb co-doped BiOCl@C material includes the following steps: S1. Mix 0.5 mmol of bismuth source, 0.5 mmol of antimony chloride, 60 ml of ethylene glycol and water, and carry out hydrothermal reaction to obtain Sb-doped BiOCl; S2. Mix, dissolve and stir Sb-doped BiOCl, dopamine hydrochloride and tris(hydroxymethyl)aminomethane to obtain Sb-doped BiOCl with a polydopamine coating layer on the surface; S3. Calcinate the Sb-doped BiOCl with a polydopamine coating layer in an inert atmosphere to obtain N / Sb co-doped BiOCl@C; Among them, the addition amount of water in step S1 is 9-13 mL; the calcination treatment in step S3 is calcination at 300-500 °C for 3-5 h.

2. The N / Sb co-doped BiOCl@C material according to claim 1, Characterized in that, The doping amount of N in the N-doped carbon layer is 4-6 wt%.

3. The N / Sb co-doped BiOCl@C material according to claim 1, Characterized in that, The molar ratio of the Sb-doped BiOCl, tris(hydroxymethyl)aminomethane, and dopamine hydrochloride in step S2 is 1:(1-2):(0.5-1).

4. The N / Sb co-doped BiOCl@C material according to claim 1, Characterized in that, The calcination treatment in step S3 is calcination at 350 °C for 4 h.

5. The application of the N / Sb co-doped BiOCl@C material according to any one of claims 1 to 4 in the preparation of a negative electrode material for a potassium ion battery.

6. A negative electrode material, Characterized in that, The negative electrode material is prepared from the N / Sb co-doped BiOCl@C material according to any one of claims 1 to 4.

7. A potassium ion battery, Characterized in that, The negative electrode material of the potassium ion battery is the negative electrode material in claim 6.

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