Nitrogen and phosphorus doped porous blocky C (at) ZnO material as well as preparation method and application thereof
By preparing nitrogen and phosphorus-doped porous bulk C@ZnO materials, the problems of low capacity of graphite anodes and poor conductivity of zinc oxide anodes in lithium-ion batteries were solved, achieving high efficiency in cycle stability and improved electrochemical performance, making it suitable for lithium-ion battery anodes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-27
- Publication Date
- 2026-04-10
AI Technical Summary
The actual capacity of existing graphite anode materials for lithium-ion batteries is lower than the theoretical value, and zinc oxide anodes have poor conductivity and severe volume expansion, resulting in decreased cycle stability and battery performance. High-performance composite materials are also costly to manufacture.
A porous, bulk C@ZnO material doped with nitrogen and phosphorus was used. Using biomass sunflower pollen as raw material, a simple preparation method was employed to attach zinc oxide particles to the porous carbon surface, providing a buffer space and improving cycle stability.
It improves the cycle stability and electrochemical capacity of lithium-ion batteries, reduces manufacturing costs, and is suitable for next-generation lithium-ion battery anodes.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of lithium ion battery electrode materials, in particular to a nitrogen and phosphorus doped porous blocky C@ZnO material and a preparation method, and especially to the application of the nitrogen and phosphorus doped porous blocky carbon / zinc oxide composite material (i.e. the nitrogen and phosphorus doped porous blocky C@ZnO material) in a lithium ion battery negative electrode. BACKGROUND
[0002] A lithium ion battery (LIB) is a kind of secondary battery, which mainly relies on the movement of lithium ions between the positive electrode and the negative electrode. The current commercialized lithium ion battery positive active material is mainly lithium iron phosphate, lithium manganate or lithium cobaltate, nickel cobalt manganate, etc.; and the negative active material is mainly graphite. When the battery is charged, lithium ions are generated on the positive electrode of the battery, and the generated lithium ions move to the negative electrode through the electrolyte. The number of lithium ions embedded and extracted in the electrode material directly determines the specific capacity of the battery. The theoretical capacity of the current commercial graphite negative electrode is 372 mAh / g, but due to the generation of the solid electrolyte interface film (SEI) in the actual charging and discharging process of the battery, the inevitable side reactions and a small amount of carbon atoms that do not participate in the process of lithium extraction, the actual capacity exhibited by the graphite negative electrode is often much smaller than 372 mAh / g. In addition, graphite needs high-temperature treatment during production, which often needs to reach more than 2000℃ to graphitize, increasing the preparation cost and environmental hazards. Therefore, it is necessary to explore new cheap and efficient carbon-based materials suitable for lithium ion battery negative electrodes.
[0003] The combination of carbon material improvement, structure regulation and component doping is an effective way to improve the electrochemical performance. Porous carbon materials, especially heteroatom (such as nitrogen (N), phosphorus (P) and boron (P) atoms, etc.) doped carbon materials, have higher specific surface area and porosity than traditional graphite materials, and have more excellent electrochemical performance. When used as lithium ion battery negative active materials, they can exhibit higher reversible capacity. Therefore, exploring an economical and simple method to prepare doped porous carbon to replace the current commonly used graphite negative electrode material of lithium ion battery has an important role in further improving the energy density of lithium ion batteries.
[0004] In addition to improving carbon materials, developing transition metal oxide materials as lithium ion battery anodes to improve battery energy density is also a strategy, for example, the theoretical specific capacity of zinc oxide (ZnO) as a lithium ion battery anode is 978 mAh / g, which is higher than the theoretical specific capacity of graphite 372 mAh / g. However, there are also some deficiencies in using zinc oxide as a lithium ion battery anode: 1) poor electrical conductivity, that is, the electrical conductivity of zinc oxide is relatively poor, which will cause the internal resistance of the battery to increase, affecting the charge and discharge efficiency and power performance. 2) serious volume expansion problem, that is, during the charging and discharging process, zinc oxide will undergo significant volume expansion and contraction, which is easy to make the particles quickly powder, resulting in the loss of electrical contact between the active material and the electrode, and then the battery capacity is sharply attenuated and the cycle performance is poor.
[0005] Therefore, the core advantage of preparing zinc oxide / carbon composite material as a lithium ion battery anode is to compensate for the inherent shortcomings of zinc oxide through carbon material, while retaining its high capacity characteristics. However, there are still some problems to be optimized in zinc oxide / carbon composite material. 1) Poor cycle stability of zinc oxide / carbon composite material, interface separation may occur during long-term charge and discharge cycling, leading to destruction of the conductive network, and then causing capacity attenuation, and side reactions may also occur at the interface, affecting the coulombic efficiency of the battery. 2) High-performance zinc oxide / carbon composite materials (such as core-shell structure, heterojunction structure) usually require precise control of the preparation process (such as high-temperature calcination, hydrothermal synthesis), and the process steps are more, the condition requirement is high, compared with pure zinc oxide or traditional graphite, the cost of large-scale production is higher. SUMMARY
[0006] In view of the above deficiencies of the prior art, the purpose of the present application is to provide a nitrogen and phosphorus doped porous blocky C@ZnO material and a preparation method and use thereof. The raw materials for preparing the nitrogen and phosphorus doped porous blocky C@ZnO material are easy to obtain and the preparation steps are simple. The nitrogen and phosphorus doped porous blocky C@ZnO material has a porous block structure, and zinc oxide is attached to the surface of the porous block. The buffer space provided by the carbon spikes between the materials helps to alleviate the volume expansion of zinc oxide during the charging and discharging process, thereby improving the cycle stability.
[0007] To solve the above technical problems, the present application provides a preparation method of a nitrogen and phosphorus doped porous blocky C@ZnO material, comprising the following steps: Sunflower pollen is added to deionized water for ultrasonic treatment and room temperature stirring treatment. After treatment, it is filtered and washed to obtain sunflower pollen particles as a carbon precursor.
[0008] Zinc chloride is added to deionized water and stirred to disperse it fully. Sunflower pollen particles are then added and stirred. Sodium hydroxide solution is added dropwise, and after the dropwise addition is completed, the reaction is continued. After the reaction, the reaction precursor is obtained by filtering and drying treatment. Under an argon atmosphere, the reaction precursor is calcined and carbonized by increasing the temperature from room temperature to 550-650 DEG C at a rate of 1-10 DEG C / min, and then naturally cooled to room temperature, to obtain a porous blocky C@ZnO material doped with nitrogen and phosphorus.
[0009] Preferably, the sunflower pollen after suction filtration needs to be washed alternately with deionized water and anhydrous ethanol.
[0010] To ensure the conventional operation of cleaning, at least 3 times of washing ensures the cleaning of the sunflower pollen, and the alternately washing with water and anhydrous ethanol can avoid the limitation of a single solvent (such as water washing cannot remove oil stains, and ethanol washing cannot remove electrolyte salts), and the circulation of water washing to remove polar impurities, ethanol washing to remove non-polar impurities and to remove residual moisture can realize the deep purification of the material surface.
[0011] Preferably, the mass ratio of the zinc chloride to the sunflower pollen is 1.7-6.8:1.
[0012] When the mass ratio of the zinc chloride to the sunflower pollen is less than 1.7:1, the loading amount of the zinc oxide formed finally is insufficient, and the theoretical capacity of the material is reduced; when the mass ratio of the zinc chloride to the sunflower pollen is higher than 6.8:1, the amount of the zinc oxide is too much, the volume effect is obvious, and the cycle stability is reduced.
[0013] Preferably, the molar concentration ratio of the zinc chloride solution to the sodium hydroxide solution is 0.5-2:1, and preferably the mass ratio of the zinc chloride to the sunflower pollen is 1:1.
[0014] When the molar concentration ratio of the zinc chloride solution to the sodium hydroxide solution is higher than 2:1, the prepared sodium hydroxide is too dilute, the dropwise synthesis time is increased, and the time cost is increased; when the molar concentration ratio of the zinc chloride solution to the sodium hydroxide solution is lower than 0.5:1, the concentration of the sodium hydroxide is high, the precipitation conversion is too fast, and poor dispersion is easily caused, which affects the electrochemical performance of the material.
[0015] Preferably, the calcination of the reaction precursor is performed at a rate of 1-10 DEG C / min, and preferably the rate is 5 DEG C / min.
[0016] When the calcination of the reaction precursor is performed at a rate lower than 1 DEG C / min, the heating time is prolonged, and the energy consumption and the time cost are increased; when the rate is higher than 10 DEG C / min, the heating rate is accelerated, and the final morphology of the material is not easy to maintain integrity.
[0017] Preferably, the reaction precursor is calcined and carbonized by increasing the temperature from room temperature to 550-650 DEG C at a rate of 1-10 DEG C / min and then naturally cooled to room temperature.
[0018] When the temperature is lower than 600 DEG C, the carbonization process is affected, the graphitization degree of the material is further reduced, the conductivity is deteriorated, and the electrochemical performance of the material is affected; when the temperature is higher than 600 DEG C, the energy consumption is increased, and the electrochemical performance has no obvious advantage, and the optimal temperature is from room temperature to 600 DEG C, and the temperature is kept for 2h-4h.
[0019] The application provides a preparation method of nitrogen and phosphorus doped porous blocky C@ZnO material.
[0020] The application provides application of the nitrogen and phosphorus doped porous blocky C@ZnO material as a negative electrode of a lithium ion battery.
[0021] Preferably, the ICE of the nitrogen and phosphorus doped porous blocky C@ZnO material is 70%-80% at a current density of 200mA / g, and preferably, the ICE of the nitrogen and phosphorus doped porous blocky C@ZnO material is 79.34% at a current density of 200mA / g.
[0022] Preferably, after 100 charge-discharge cycles, the reversible capacity of the nitrogen and phosphorus doped porous blocky C@ZnO material can be maintained at 400mAh / g-570mAh / g at a current density of 200mA / g, and the highest value is 565.9mAh / g.
[0023] Compared with the prior art, the application has the following beneficial effects: The sunflower pollen applied in the preparation method contains rich elements such as phosphorus P, sulfur S and nitrogen N, and the sunflower pollen is porous and blocky, the morphology of the sunflower pollen is still retained after calcination, the zinc oxide particles are attached and dispersed on the surface of the porous block carbon, the obtained nitrogen and phosphorus doped porous blocky C@ZnO material has a unique porous block structure. The unique nitrogen and phosphorus doped porous blocky C@ZnO material contains rich N atoms and P atoms, the pores between the zinc oxide particles and the zinc oxide particles can provide a buffer space for volume expansion, avoid the structure pulverization caused by extrusion between particles, reduce the interface extrusion mechanical stress, improve the interface stability and prevent the collapse of the electrode structure, so that the cycle stability of the material is improved, the material actually exhibits a high electrochemical capacity, and has a high potential for application in a new generation of lithium ion batteries.
[0024] The raw material used for preparing the nitrogen and phosphorus doped porous blocky C@ZnO material is low in cost, the biomass sunflower pollen contains rich protein, polysaccharide and fat and other substances, and contains a large amount of N and P elements, so that the additional addition of chemical reagents for introducing N and P elements into the carbon material is avoided. Meanwhile, compared with the high-performance zinc oxide / carbon composite material (such as core-shell structure, heterojunction structure) which usually needs to precisely control the preparation process (such as high-temperature calcination, hydrothermal synthesis) of the precursor, and the process steps are many and the requirements for the conditions are high, the preparation method given in the application uses the low-cost waste biomass pollen to give the spherical structure, so that the high-temperature calcination and hydrothermal synthesis steps are saved, and the preparation process of the precursor does not need to be precisely controlled, the method used in the application is simple in operation and mild in reaction conditions, the product can be made through expansion of the experiment, a reasonable process flow is designed, the yield is improved, and cost-benefit evaluation is carried out, and finally the market is realized. BRIEF DESCRIPTION OF DRAWINGS
[0025] Figure 1 The XRD pattern of the nitrogen and phosphorus doped porous blocky C@ZnO material prepared in Example 1 of the application.
[0026] Figure 2 The Raman spectrum of the nitrogen and phosphorus doped porous blocky C@ZnO material prepared in Example 1 of the application.
[0027] Figure 3 The SEM image of the surface of the nitrogen and phosphorus doped porous blocky C@ZnO material prepared in Example 1 of the application.
[0028] Figure 4 The nitrogen and phosphorus doped porous blocky C@ZnO material prepared in the application Figure 3 The local magnified SEM image of the surface of the nitrogen and phosphorus doped porous blocky C@ZnO material prepared in Example 1 of the application.
[0029] Figure 5 The SEM-EDX of the nitrogen and phosphorus doped porous blocky C@ZnO material prepared in Example 1 of the application.
[0030] Figure 6 The reversible capacity test value of the button cell assembled by the nitrogen and phosphorus doped porous blocky C@ZnO material prepared in Example 1 of the application in the charge-discharge cycle process at 100mA / g.
[0031] Figure 7 The reversible capacity test value of the button cell assembled by the ZnO material prepared in Comparative Example 1 of the application in the charge-discharge cycle process.
[0032] Figure 8 The average coulombic efficiency test chart of the button cell assembled by the nitrogen and phosphorus doped porous blocky C@ZnO material prepared in Example 1 of the application.
[0033] Figure 9 The average coulombic efficiency test chart of the button cell assembled by the ZnO material prepared in the present application comparative example 1. DETAILED DESCRIPTION
[0034] The specific embodiments of the present application are described in detail below, but it should be understood that the scope of protection of the present application is not limited by the specific embodiments. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application. The experimental methods described in the embodiments of the present application are conventional methods unless otherwise specified.
[0035] It should be noted that when numerical ranges are involved in the present application, both endpoints of each numerical range and any number between the two endpoints can be selected. Since the steps and examples 1-9 are the same, in order to avoid repetition, the present application describes preferred examples, but the present application is not limited thereto, but can also be embodied in other ways within the scope of the technical solutions defined in the appended claims. The various raw materials, reagents, instruments and equipment used in the following embodiments of the present application can be purchased from the market or prepared by existing methods.
[0036] The technical solutions in the embodiments of the present application are described clearly and completely in the following embodiments of the present application in combination with preferred embodiments and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.
[0037] Example 1 A preparation method of a nitrogen and phosphorus doped porous blocky C@ZnO material, comprising the following steps: (1) Preparation of carbon precursor: 2g of sunflower pollen was weighed, added to 50mL of deionized water, ultrasonically treated for 30min, magnetically stirred at room temperature for 1h, and the washed pollen particles were collected by suction filtration (in the process, deionized water and anhydrous ethanol were used to wash alternately for 3 times), to obtain sunflower pollen particles as the carbon precursor.
[0038] (2) Preparation of precursor by precipitation method: Put 3.4 g of zinc chloride into 50 mL of deionized water, stir for 10 min to fully dissolve, add the cleaned sunflower pollen particles into the above solution, continue to stir for 5 h, slowly add 100 mL of 0.5 mol / L sodium hydroxide, after the addition is completed, stir for another 30 min, then filter to collect the product, and dry in an oven at 80℃ to obtain the reaction precursor.
[0039] (3) Preparation of nitrogen and phosphorus doped porous blocky C@ZnO material: Put the reaction precursor into a porcelain boat and place it in a tube furnace, heat to 600℃ at a heating rate of 5℃ / min under argon atmosphere, and keep the temperature for 2 h. Naturally cool to room temperature to obtain the nitrogen and phosphorus doped porous blocky C@ZnO material.
[0040] Example 2 A method for preparing a nitrogen and phosphorus doped porous blocky C@ZnO material, comprising the following steps: (1) Preparation of carbon precursor: Weigh 2 g of sunflower pollen, add 50 mL of deionized water, ultrasonic treatment for 30 min, magnetic stirring at room temperature for 1 h, and collect the cleaned pollen particles by suction filtration (intermittently washed with deionized water and anhydrous ethanol for 3 times) to obtain sunflower pollen particles as the carbon precursor.
[0041] (2) Preparation of precursor by precipitation method: Put 4 g of zinc chloride into 50 mL of deionized water, stir for 10 min to fully dissolve, add the cleaned sunflower pollen particles into the above solution, continue to stir for 5 h, slowly add 117 mL of 0.5 mol / L sodium hydroxide, after the addition is completed, stir for another 30 min, then filter to collect the product, and dry in an oven at 80℃ to obtain the reaction precursor.
[0042] (3) Preparation of nitrogen and phosphorus doped porous blocky C@ZnO material: Put the reaction precursor into a porcelain boat and place it in a tube furnace, heat to 600℃ at a heating rate of 5℃ / min under argon atmosphere, and keep the temperature for 2 h. Naturally cool to room temperature to obtain the nitrogen and phosphorus doped porous blocky C@ZnO material.
[0043] Example 3 A method for preparing a nitrogen and phosphorus doped porous blocky C@ZnO material, comprising the following steps: (1) Preparation of carbon precursor: Weigh 2 g of sunflower pollen, add 50 mL of deionized water, ultrasonic treatment for 30 min, magnetic stirring at room temperature for 1 h, and collect the cleaned pollen particles by suction filtration (intermittently washed with deionized water and anhydrous ethanol for 3 times) to obtain sunflower pollen particles as the carbon precursor.
[0044] (2) Preparation of precursor by precipitation method: Add 13.64 g of zinc chloride into 50 mL of deionized water, stir for 10 min to fully dissolve, add the cleaned sunflower pollen particles into the above solution, continuously stir for 5 h, slowly add 200 mL of 1 mol / L sodium hydroxide, after the addition is completed, stir for another 30 min, then collect the product by filtration, and dry in an oven at 80°C to obtain the reaction precursor.
[0045] (3) Preparation of nitrogen and phosphorus doped porous blocky C@ZnO material: Transfer the reaction precursor into a porcelain boat, place it into a tube furnace, heat to 600°C at a heating rate of 5°C / min under argon atmosphere, and keep the temperature for 2 h. Naturally cool to room temperature to obtain the nitrogen and phosphorus doped porous blocky C@ZnO material.
[0046] Example 4 A method for preparing a nitrogen and phosphorus doped porous blocky C@ZnO material, comprising the following steps: (1) Preparation of carbon precursor: Weigh 2 g of sunflower pollen, add 50 mL of deionized water, ultrasonic treatment for 30 min, room temperature magnetic stirring for 1 h, and collect the cleaned pollen particles by suction filtration (in the process, use deionized water and anhydrous ethanol to clean alternately for 3 times) to obtain the sunflower pollen particles as the carbon precursor.
[0047] (2) Preparation of precursor by precipitation method: Add 6 g of zinc chloride into 50 mL of deionized water, stir for 10 min to fully dissolve, add the cleaned sunflower pollen particles into the above solution, continuously stir for 5 h, slowly add 176 mL of 0.5 mol / L sodium hydroxide, after the addition is completed, stir for another 30 min, then collect the product by filtration, and dry in an oven at 80°C to obtain the reaction precursor.
[0048] (3) Preparation of nitrogen and phosphorus doped porous blocky C@ZnO material: Transfer the reaction precursor into a porcelain boat, place it into a tube furnace, heat to 600°C at a heating rate of 5°C / min under argon atmosphere, and keep the temperature for 2 h. Naturally cool to room temperature to obtain the nitrogen and phosphorus doped porous blocky C@ZnO material.
[0049] Example 5 A method for preparing a nitrogen and phosphorus doped porous blocky C@ZnO material, comprising the following steps: (1) Preparation of carbon precursor: Weigh 2g sunflower pollen, add 50mL deionized water, ultrasonic treatment for 30min, magnetic stirring at room temperature for 1h, and collect the cleaned pollen particles by suction filtration (intermittently washed with deionized water and anhydrous ethanol for 3 times) to obtain sunflower pollen particles as carbon precursors.
[0050] (2) Preparation of precursors by precipitation method: Add 3.4g zinc chloride to 50mL deionized water, stir for 10min to fully dissolve, and then add the cleaned sunflower pollen particles to the above solution, continuously stir for 5h, slowly add 50mL of 1.0moL / L sodium hydroxide, and after the addition is completed, stir for another 30min before filtering to collect the product, and dry treatment in an oven at 80℃ to obtain the reaction precursors.
[0051] (3) Preparation of nitrogen and phosphorus doped porous blocky C@ZnO material: Transfer the reaction precursors to a porcelain boat and place it in a tube furnace, heat to 600℃ at a heating rate of 5℃ / min under argon atmosphere, and then keep the temperature for 2h. Naturally cool to room temperature to obtain the nitrogen and phosphorus doped porous blocky C@ZnO material.
[0052] Example 6 A method for preparing a nitrogen and phosphorus doped porous blocky C@ZnO material, comprising the following steps: (1) Preparation of carbon precursors: Weigh 2g sunflower pollen, add 50mL deionized water, ultrasonic treatment for 30min, magnetic stirring at room temperature for 1h, and collect the cleaned pollen particles by suction filtration (intermittently washed with deionized water and anhydrous ethanol for 3 times) to obtain sunflower pollen particles as carbon precursors.
[0053] (2) Preparation of precursors by precipitation method: Add 8g zinc chloride to 50mL deionized water, stir for 10min to fully dissolve, and then add the cleaned sunflower pollen particles to the above solution, continuously stir for 5h, slowly add 117mL of 1moL / L sodium hydroxide, and after the addition is completed, stir for another 30min before filtering to collect the product, and dry treatment in an oven at 80℃ to obtain the reaction precursors.
[0054] (3) Preparation of nitrogen and phosphorus doped porous blocky C@ZnO material: Transfer the reaction precursors to a porcelain boat and place it in a tube furnace, heat to 600℃ at a heating rate of 5℃ / min under argon atmosphere, and then keep the temperature for 2h. Naturally cool to room temperature to obtain the nitrogen and phosphorus doped porous blocky C@ZnO material.
[0055] Example 7 A method for preparing a nitrogen and phosphorus doped porous blocky C@ZnO material, comprising the following steps: (1) Preparation of carbon precursor: 2g of sunflower pollen was weighed, added to 50mL of deionized water, ultrasonic treated for 30min, magnetically stirred at room temperature for 1h, and the cleaned pollen particles were collected by suction filtration (the process was washed with deionized water and anhydrous ethanol alternately for 3 times) to obtain sunflower pollen particles as carbon precursor.
[0056] (2) Preparation of precursor by precipitation method: 3.4g of zinc chloride was added to 50mL of deionized water, stirred for 10min to dissolve completely, and the cleaned sunflower pollen particles were added to the above solution, continuously stirred for 5h, 62mL of 0.8moL / L sodium hydroxide was slowly added dropwise, and after stirring for another 30min after the dropwise addition was completed, the product was collected by filtration and dried in an oven at 80℃ to obtain the reaction precursor.
[0057] (3) Preparation of nitrogen and phosphorus doped porous blocky C@ZnO material: The reaction precursor was transferred to a porcelain boat and placed in a tube furnace, heated to 600℃ at a heating rate of 5℃ / min under argon atmosphere, and then kept for 2h. Naturally cooled to room temperature to obtain the nitrogen and phosphorus doped porous blocky C@ZnO material.
[0058] Example 8 The difference between this example and Example 1 is only in the heating rate and the holding time.
[0059] A method for preparing a nitrogen and phosphorus doped porous blocky C@ZnO material, comprising the following steps: (1) Preparation of carbon precursor: 2g of sunflower pollen was weighed, added to 50mL of deionized water, ultrasonic treated for 30min, magnetically stirred at room temperature for 1h, and the cleaned pollen particles were collected by suction filtration (the process was washed with deionized water and anhydrous ethanol alternately for 3 times) to obtain sunflower pollen particles as carbon precursor.
[0060] (2) Preparation of precursor by precipitation method: 3.4g of zinc chloride was added to 50mL of deionized water, stirred for 10min to dissolve completely, and the cleaned sunflower pollen particles were added to the above solution, continuously stirred for 5h, 100mL of 0.5moL / L sodium hydroxide was slowly added dropwise, and after stirring for another 30min after the dropwise addition was completed, the product was collected by filtration and dried in an oven at 80℃ to obtain the reaction precursor.
[0061] (3) Preparation of nitrogen and phosphorus doped porous blocky C@ZnO material: The reaction precursor is transferred to a porcelain boat, placed in a tube furnace, and heated to 550℃ at a heating rate of 1℃ / min under an argon atmosphere, and then kept for 4h. It is naturally cooled to room temperature to obtain the nitrogen and phosphorus doped porous blocky C@ZnO material.
[0062] Example 9 The only difference between this example and Example 1 is the heating rate and the holding time.
[0063] A preparation method of a nitrogen and phosphorus doped porous blocky C@ZnO material, comprising the following steps: (1) Preparation of carbon precursor: 2g of sunflower pollen is weighed, added to 50mL of deionized water, ultrasonically treated for 30min, magnetically stirred at room temperature for 1h, and the cleaned pollen particles are collected by filtration (the process is washed with deionized water and anhydrous ethanol alternately for 3 times), to obtain sunflower pollen particles as the carbon precursor.
[0064] (2) Preparation of precursor by precipitation method: 3.4g of zinc chloride is added to 50mL of deionized water, stirred for 10min to dissolve completely, and the cleaned sunflower pollen particles are added to the above solution, continuously stirred for 5h, 100mL of 0.5moL / L sodium hydroxide is slowly added dropwise, and after stirring for 30min after the dropwise addition is completed, the product is collected by filtration and dried in an oven at 80℃ to obtain the reaction precursor.
[0065] (3) Preparation of nitrogen and phosphorus doped porous blocky C@ZnO material: The reaction precursor is transferred to a porcelain boat, placed in a tube furnace, and heated to 650℃ at a heating rate of 10℃ / min under an argon atmosphere, and then kept for 3h. It is naturally cooled to room temperature to obtain the nitrogen and phosphorus doped porous blocky C@ZnO material.
[0066] The preparation methods of the nitrogen and phosphorus doped porous blocky C@ZnO material (i.e. C@ZnO material) given in the above Examples 1-9 can all be used to prepare the nitrogen and phosphorus doped porous blocky C@ZnO material. The structure confirmation and performance analysis of the C@ZnO material prepared in Example 1 are taken as an example.
[0067] The specific research methods and results are shown as follows: I. Structure confirmation: (1) XRD Figure 1 The XRD pattern of the C@ZnO material. The XRD pattern is used to characterize the phase and composition of the material, and the SEM pattern is used to characterize the morphology of the material, from which it can be seen that the C@ZnO material has a porous blocky structure. Figure 1It can be seen that there is a clear bulge at 23°, indicating that the carbon component in the product C@ZnO material is mainly amorphous carbon material. The 2θ angle is about 31.77° corresponding to the (100) crystal face, 34.42° corresponding to the (002) crystal face, 36.25° corresponding to the (101) crystal face, 47.54° corresponding to the (102) crystal face, 56.60° corresponding to the (110) crystal face, 62.86° corresponding to the (103) crystal face, and 67.98° corresponding to the (112) crystal face, and the (101) crystal face diffraction peak intensity is the highest, which is consistent with the typical XRD characteristics of hexagonal wurtzite structure zinc oxide, which is amorphous carbon.
[0068] (2) Raman spectrum Figure 2 The Raman spectrum of the C@ZnO material is shown in FIG. 5, from which it can be seen that the ratio of the D peak (peak position about 1360 cm -1 ) and the G peak (peak position about 1590 cm -1 ) can also indicate the graphitization degree of the C@ZnO material, Figure 2 D I G The value of the C@ZnO material is relatively high (~ 0.80), indicating that the graphitization degree of the carbon material in the C@ZnO material is relatively low, and the proportion of disordered carbon component is high. I (3) SEM image
[0069] The SEM image of the C@ZnO material is shown in FIG. 6, from which it can be seen that the C@ZnO material as a whole presents a porous cubic structure assembled by 10 micrometer level spheres, and smaller size zinc oxide particles are attached to the surface Figure 3 (4) SEM image Figure 3 The SEM image of the surface of the C@ZnO material is shown in FIG. 7, from which it can be seen that the surface is attached to several hundred nanometer to several micrometer size zinc oxide particles. Figure 4 (5) SEM-EDX image
[0070] The SEM-EDX image of the C@ZnO material is shown in FIG. 8, from which it can be seen that the measured elements contained in the C@ZnO material are carbon, zinc, oxygen, nitrogen, phosphorus, and the mass proportions are 60.1%, 12.4%, 25.9%, 1.3% and 0.3% respectively. Figure 5 0, Performance research: The C@ZnO material prepared in Example 1 was used as the working electrode, and the metal lithium was used as the counter electrode to assemble a button cell, and the electrochemical properties of the button cell were studied.
[0071] As shown in FIG. 9, the C@ZnO material prepared in Example 1 has a good electrochemical performance.
[0072] As shown in FIG. 9, the C@ZnO material prepared in Example 1 has a good electrochemical performance. Figure 6 As shown, the ICE (initial charge capacity / initial discharge capacity) of the C@ZnO material is 79.34% at a current density of 100 mA / g. The irreversible capacity occurring in the first cycle is related to the growth of the SEI film, which is widely present in any negative electrode material. During the subsequent charge-discharge cycle process, the capacity gradually tends to be stable. After 100 charge-discharge cycles, the reversible capacity of the C@ZnO material is maintained at 565.9 mAh / g.
[0073] The pure ZnO in Comparative Example 1 was used as the working electrode of the negative electrode material, and lithium metal was used as the counter electrode to assemble a coin cell. The electrochemical properties of the coin cell were studied, such as Figure 7 As shown, the ICE (initial charge capacity / initial discharge capacity) of the ZnO is 73.32%, which is lower than that of the C@ZnO material, indicating that the ZnO material has more serious side reactions during the first discharge process. After 100 charge-discharge cycles, the capacity of the ZnO material is only 43.0 mAh / g, and the capacity retention rate is much lower than that of the C@ZnO material.
[0074] In addition, as shown in Figure 8 Within 100 cycles, the average coulombic efficiency of the coin cell assembled using the C@ZnO material prepared in Example 1 is 99.18%, and except for the lower first coulombic efficiency, it exceeds 99% from the 7th cycle, close to 100%, indicating that the material can reach a stable state after a small number of cycles. It is proved that the structural combination between the zinc oxide particles and the carbon component in the prepared C@ZnO material is stable, and there is almost no subsequent side reaction.
[0075] In contrast, as shown in Figure 9 The average coulombic efficiency of the coin cell assembled using the pure zinc oxide material given in Comparative Example 1 is 96.99%, and it still does not reach 98% after nearly 20 cycles, indicating that during the entire charge-discharge cycle process, the zinc oxide material is always accompanied by more serious side reactions due to the obvious volume effect during the deintercalation of lithium, and the electrode is difficult to achieve an electrochemical stable process. In contrast, due to the unique porous block structure of the C@ZnO material (buffer space can be provided around the spikes) and the dispersion of the carbon component, a moderate expansion buffer space and mechanical toughness are provided, thereby improving the overall cycle stability of the material.
[0076] In summary, the C@ZnO material is much higher than the pure zinc oxide material in terms of cycle stability, and the capacity after 100 cycles is higher than that of the graphite negative electrode and the zinc oxide material on the market, indicating that the C@ZnO material is suitable as a negative electrode for lithium ion batteries.
[0077] Obviously, many modifications and variations of the present application are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.
Claims
1. A method for preparing a nitrogen-phosphorus-doped porous bulk C@ZnO material, characterized in that, Includes the following steps: Sunflower pollen was added to deionized water and subjected to ultrasonic and room temperature stirring. After treatment, it was filtered and washed to obtain sunflower pollen particles as carbon precursors. Zinc chloride was added to deionized water and stirred to disperse it fully. Then, sunflower pollen granules were added and stirring continued. Sodium hydroxide solution was added dropwise, and stirring was continued after the addition was complete. After the reaction, the mixture was filtered and dried to obtain the reaction precursor. Under an argon atmosphere, the temperature is increased from room temperature to 550℃~650℃ at a heating rate of 1℃ / min~10℃ / min and held for 2h~4h. After the reaction precursor is calcined and carbonized, it is naturally cooled to room temperature to obtain nitrogen and phosphorus doped porous bulk C@ZnO material.
2. The method for preparing nitrogen-phosphorus doped porous bulk C@ZnO material according to claim 1, characterized in that, The filtered sunflower pollen needs to be washed alternately with deionized water and anhydrous ethanol.
3. The method for preparing nitrogen-phosphorus doped porous bulk C@ZnO material according to claim 1, characterized in that, The mass ratio of zinc chloride to sunflower pollen is 1.7~6.8:
1.
4. The method for preparing nitrogen-phosphorus doped porous bulk C@ZnO material according to claim 1, characterized in that, The molar ratio of the zinc chloride solution to the sodium hydroxide solution is 0.5 to 2:
1.
5. The method for preparing nitrogen-phosphorus doped porous bulk C@ZnO material according to claim 1, characterized in that, The heating rate is 5℃ / min.
6. The method for preparing nitrogen-phosphorus doped porous bulk C@ZnO material according to claim 1, characterized in that, The reaction precursor was calcined and carbonized by heating from room temperature to 600°C.
7. The nitrogen-phosphorus-doped porous bulk C@ZnO material prepared by the method according to any one of claims 1 to 6.
8. The application of the nitrogen-phosphorus doped porous bulk C@ZnO material according to claim 7 as a negative electrode for lithium-ion batteries.
9. The application according to claim 8, characterized in that, At a current density of 200 mA / g, the ICE of nitrogen-phosphorus doped porous bulk C@ZnO materials is 70%~80%.
10. The application according to claim 8, characterized in that, After 100 charge-discharge cycles, the reversible capacity of the nitrogen-phosphorus doped porous bulk C@ZnO material remained at 400 mAh / g to 570 mAh / g at a current density of 200 mA / g.