Preparation method and application of a sheet-shaped manganese phosphide / carbon composite material

Abstract

The application relates to a preparation method of a flaky manganese phosphide / carbon composite material and belongs to the technical field of composite material preparation. The preparation method comprises the following steps: step (1), mixing a manganese source, a carbon source and an acid according to a certain mass ratio, continuously grinding at room temperature for 10-60 minutes to obtain a precursor; and step (2), under a protective gas, heating the precursor to 600-1000 DEG C at a rate of 1-10 DEG C / min, keeping the temperature for 2-10 h, and cooling to room temperature with the furnace to obtain the flaky manganese phosphide / carbon composite material. The preparation method can solve the agglomeration problem of manganese phosphide particles and ensure the long cycle stability of the manganese phosphide particles as lithium / potassium ion battery electrode materials.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite material preparation, and particularly relates to a preparation method and application of a sheet-shaped manganese phosphide / carbon composite material. BACKGROUND

[0002] Lithium ion batteries have been widely used in electric vehicles, and in order to further meet the demand of people for longer cycle life, it is necessary to explore and develop electrode materials with high cycle stability. Among the materials studied, compared with transition metal oxides and transition metal sulfides, transition metal phosphides can theoretically have higher theoretical capacity based on conversion reaction mechanism or alloy reaction mechanism. In addition, transition metal phosphides are also potential electrode materials for sodium ion batteries and potassium ion batteries due to their good electrical conductivity. Among transition metal phosphides, manganese phosphide can achieve a reversible lithium storage capacity of 870 mAh·g -1 based on alloy reaction mechanism for the first time, which is a potential electrode material. However, the current synthesis route of manganese phosphide is mainly through ball milling or integrating multiple steps using sodium hypophosphite (NaH2PO2) or high-boiling organic solvents as phosphorus sources as a result, which is not cost-competitive in large-scale production. In addition, the capacity of manganese phosphide will quickly decay after multiple cycles due to particle agglomeration. It is also difficult to avoid the agglomeration of manganese phosphide particles by coating a layer of carbon on the manganese phosphide particles. Therefore, an effective method for limiting the agglomeration of manganese phosphide should be developed to ensure the long cycle stability of manganese phosphide electrode material. SUMMARY

[0003] The purpose of the present application is to provide a preparation method of sheet-shaped manganese phosphide / carbon composite material, which can solve the problem of agglomeration of manganese phosphide particles and ensure the long cycle stability of the material as a lithium / potassium ion battery electrode material.

[0004] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0005] A preparation method of sheet-shaped manganese phosphide / carbon composite material, comprising the following steps:

[0006] Step (1), mix manganese source, carbon source and acid according to a certain mass ratio, continuously grind at room temperature for 10-60 minutes to obtain a precursor; the precursor obtained after reaction is a structure in which the carbon source connects the generated manganese phosphide precursor as a crosslinked network, the reaction mechanism is that the manganese source and the phosphorus-containing acid form the manganese phosphide precursor through polymerization reaction, the functional groups on the surface of the first generated manganese phosphide precursor can attract the functional groups on the surface of the carbon source, so that the manganese phosphide precursor is uniformly distributed in the carbon source;

[0007] Step (2), the precursor is heated to 600-1000℃ at a rate of 1-10℃ / min under a protective gas, and is kept for 2-10h, and is cooled to room temperature with the furnace, to obtain a sheet-shaped manganese phosphide / carbon composite material. During the heat treatment, the manganese phosphide precursor is phosphorized to generate manganese phosphide, and the carbon source acting as a cross-linked network in the precursor is carbonized to form sheet-shaped carbon.

[0008] Further, in the step (1), the mass ratio of the manganese source, the carbon source and the acid is 1:5-8:20-25.

[0009] Further, in the step (1), the manganese source is one, two or more of manganese chloride, manganese acetate, manganese nitrate tetrahydrate and manganese sulfate.

[0010] Further, in the step (1), the carbon source is one, two or more of glucose, citric acid and melamine.

[0011] Further, in the step (1), the acid is phosphoric acid or / and phytic acid.

[0012] Further, in the step (2), the flow rate of the protective gas is 0.5-2 L / min.

[0013] Further, in the step (2), the protective gas is one of nitrogen, argon and carbon dioxide.

[0014] The sheet-shaped manganese phosphide / carbon composite material prepared by the above method is used as a negative electrode material in a lithium ion battery or a potassium ion battery.

[0015] Compared with the prior art, the present application has the following advantages:

[0016] 1. In the preparation method of the sheet-shaped manganese phosphide / carbon composite material, the acid containing phosphorus is added as a phosphorus source, and the in-situ polymerization method is used to disperse the manganese phosphide precursor into the carbon precursor framework. After heat treatment, the manganese phosphide is dispersed into the carbon framework, and the source of the carbon framework is the carbon source which has a charge attraction effect on the manganese phosphide precursor. The carbon source connects the dispersed manganese phosphide precursor, and the manganese phosphide can be dispersed into the carbon framework after heat treatment. The carbon framework can further improve the conductivity of the manganese phosphide, and can effectively inhibit the agglomeration of the manganese phosphide during the cycle process. The sheet-shaped manganese phosphide / carbon composite material synthesized by the present application has a large specific surface area, and the lithium / potassium ion battery prepared by using the sheet-shaped manganese phosphide / carbon composite material as a negative electrode material has good cycle performance.

[0017] 2. The sheet-shaped manganese phosphide / carbon composite material synthesized by the present application is used to form a test battery with metal lithium / potassium, and the battery has a capacity of 500 / 100 mA·g -1The current density is 0.01-3V, and the capacity is 150 / 65.1mAh / g after 520 / 260 cycles, and the capacity retention rate is 83.6 / 84.4%. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 X-ray diffraction pattern (XRD) of the manganese phosphide / carbon material prepared in Example 1;

[0019] Figure 2 Field emission scanning electron microscope (FESEM) of the manganese phosphide / carbon material prepared in Example 1;

[0020] Figure 3 Nitrogen adsorption-desorption curve (a) and pore size distribution curve (b) of the manganese phosphide / carbon material prepared in Example 1;

[0021] Figure 4 Cycle performance of the lithium battery composed of the manganese phosphide / carbon material prepared in Example 1 and lithium metal sheet;

[0022] Figure 5 Rate performance of the lithium battery composed of the manganese phosphide / carbon material prepared in Example 1 and lithium metal sheet;

[0023] Figure 6 Cycle performance of the lithium battery composed of the manganese phosphide / carbon material prepared in Example 1 and potassium metal sheet;

[0024] Figure 7 Rate performance of the lithium battery composed of the manganese phosphide / carbon material prepared in Example 1 and potassium metal sheet;

[0025] Figure 8 X-ray diffraction pattern (XRD) comparison of the manganese phosphide / carbon materials prepared in Example 1 and Example 2;

[0026] Figure 9 Field emission scanning electron microscope (FESEM) of the manganese phosphide / carbon material prepared in Example 2;

[0027] Figure 10 Cycle performance comparison of the lithium battery composed of the manganese phosphide / carbon materials prepared in Example 1 and Example 2 and lithium metal sheet;

[0028] Figure 11 Rate performance comparison of the lithium battery composed of the manganese phosphide / carbon materials prepared in Example 1 and Example 2 and lithium metal sheet. IMPLEMENTATION

[0029] The technical solutions and effects of the present application will be further described below in combination with the drawings and specific examples, but the protection scope of the present application is not limited thereto. EXAMPLE

[0030] A method for preparing a sheet-shaped manganese phosphide / carbon composite, comprising the following steps:

[0031] Step one, preparing a precursor manganese phosphide / carbon material by a solvothermal method, the specific steps are: grinding and mixing manganese chloride tetrahydrate, melamine and phytic acid, the mass ratio of manganese chloride tetrahydrate, melamine and phytic acid is 1:6:24; during grinding, the three are allowed to fully undergo polymerization reaction, then the ground and mixed uniform material is transferred to a drying oven, heated to 80℃, dried for 2h, remove excess phytic acid, cool to room temperature, obtain the precursor manganese phosphide / carbon material;

[0032] Step two, transferring the precursor manganese phosphide / carbon material obtained in step one to a corundum boat, and using a corundum cover to cover 1 / 2 of the upper opening end of the corundum boat to control the appropriate gas release speed (during carbonization);

[0033] Step three, transferring the precursor manganese phosphide / carbon material obtained in step two to a tube furnace, placing it directly below a thermocouple, passing argon gas in the tube furnace at a gas flow rate of 1L / min, then heating to 900℃ at a heating rate of 5℃ / min, holding for 2h, then cooling to room temperature, and grinding to obtain the manganese phosphide / carbon material.

[0034] According to the drawings, the manganese phosphide / carbon material prepared in Example 1 is observed by X-ray diffractometer and field emission scanning electron microscope; by Figure 1 comparing the X-ray diffraction pattern of the prepared manganese phosphide / carbon material with the standard card PDF #30-0823 (Mn 5.64 P3), it is found that the diffraction angles and diffraction peaks, and the intensity changes of the diffraction peaks of the two are completely consistent, indicating that the prepared manganese phosphide / carbon material is hexagonal system Mn 5.64 P3. By Figure 2 observing the microstructure photos of the prepared manganese phosphide / carbon material, it is shown that the prepared manganese phosphide / carbon material is sheet-shaped structure.

[0035] Meanwhile, the manganese phosphide / carbon material prepared in Example 1 is measured in the following aspects:

[0036] 1. The pore size distribution of the manganese phosphide / carbon material, such as Figure 3 (b);

[0037] 2. The nitrogen adsorption / desorption performance of the manganese phosphide / carbon material, such as Figure 3(a); The specific surface area and pore size distribution of the manganese phosphide / carbon material prepared by low-temperature nitrogen adsorption-desorption test are shown in Figure (a). The nitrogen adsorption-desorption hysteresis curve of the mesoporous material is shown. The specific surface area of ​​the prepared manganese phosphide / carbon material is calculated to be 187.05 m² according to the Brunauer-Emmett-Teller method. 2 g -1 Figure (b) shows that the pore size distribution of the prepared manganese phosphide / carbon material is almost entirely within the mesoporous range, indicating that the prepared manganese phosphide / carbon material has a rich mesoporous structure.

[0038] 3. Lithium storage performance of manganese phosphide / carbon materials, such as Figure 4 and 5 As shown; Figure 4 This indicates that at 500 mA·g -1 The current density of the lithium battery composed of the prepared manganese phosphide / carbon material and lithium metal sheet was measured. After 520 constant current charge-discharge cycles, the capacity was still 150 mAh / g, with a capacity retention rate of 83.6% and a coulombic efficiency of almost 100%. Figure 5 This indicates the values ​​as 200, 500, 1000, 2000, 5000, and then back to 200 mA·g. -1 The prepared manganese phosphide / carbon material was used to construct a lithium battery with lithium metal sheets. Constant current charge-discharge rate tests were conducted, as shown in the figure. At different current densities, the reversible capacity was approximately 211.3, 156.4, 118.4, 77.2, and 37.5 mAh / g, respectively. When the current density returned to 200 mA·g... -1 At that time, its reversible capacity was approximately 206.2 mAh / g, demonstrating good capacity recovery performance. Furthermore, after the initial 200 mA·g... -1 Constant current charge-discharge rate test showed that the charging curve and the discharging curve almost completely overlapped, indicating that the manganese phosphide / carbon material has good reversible lithium insertion / extraction performance.

[0039] 4. Potassium storage performance of manganese phosphide / carbon materials, such as Figure 6 and 7 As shown; Figure 6 This indicates that at 100 mA·g -1 The current density, after 260 constant current charge-discharge cycles, still has a capacity of 65.1 mAh / g, with a capacity retention of 84.4%, and the coulombic efficiency remains almost 100%. Figure 7 This indicates values ​​of 50, 100, 200, 500, 1000, and then back to 50 mA·g. -1current density, the lithium battery composed of the prepared manganese phosphide / carbon material and lithium metal sheet is subjected to constant current charge-discharge rate test, as shown in the figure, and the reversible capacity thereof is about 181.0, 151.2, 128.3, 100.9, 77.7 mAh / g at different current densities, respectively, when the current density returns to 50 mA·g -1 , the reversible capacity thereof is about 159.8 mAh / g, which shows good capacity recovery performance. In addition, after the initial 50 mA·g -1 constant current charge-discharge rate test, the charge curve and the discharge curve are almost completely coincided, which indicates that the manganese phosphide / carbon material has good reversible deintercalation lithium performance.

[0040] The manganese phosphide / carbon material prepared in the application has abundant mesoporous structure, high specific surface area of 187.05 m 2 ·g -1 , which is beneficial to electrolyte infiltration and can provide more electrochemical active sites, and has good application prospect in the energy storage field.

[0041] The preparation steps and equipment in the application are simple, low in cost and easy for industrial production, and have wide application prospect. Embodiment

[0042] A preparation method of a manganese phosphide / carbon sheet-shaped composite comprises the following steps:

[0043] Step one, a precursor manganese phosphide / carbon material is prepared by a solvothermal method, and the specific steps are as follows: manganese sulfate heptahydrate, melamine and phytic acid are ground and mixed, and the mass ratio of manganese sulfate heptahydrate, melamine and phytic acid is 0.2:6:24; during the grinding process, the three are allowed to fully undergo polymerization reaction, then the ground and mixed material is transferred to a drying oven, heated to 80℃, dried for 2h to remove excess phytic acid, and cooled to room temperature to obtain the precursor manganese phosphide / carbon material;

[0044] Step two, the precursor manganese phosphide / carbon material obtained in step one is transferred to a corundum boat, and a corundum cover is used to cover 4 / 5 of the upper opening end of the corundum boat to control the appropriate gas release speed during the carbonization process;

[0045] Step three, the precursor manganese phosphide / carbon material obtained in step two is transferred to a tube furnace and placed directly below a thermocouple, argon gas is passed through the tube furnace at a flow rate of 1L / min, then heated to 900℃ at a heating rate of 5℃ / min, kept for 2h, then cooled to room temperature, and ground to obtain the manganese phosphide / carbon material.

[0046] According to the drawings, the manganese phosphide / carbon material prepared in Example 2 is observed by an X-ray diffractometer and a field emission scanning electron microscope, as shown in the figures. Figure 8 and Figure 9shown; by Figure 8 The X-ray diffraction patterns of the manganese phosphide / carbon materials prepared in Comparative Example 1 and Example 2 were found to have completely consistent diffraction angles and diffraction peaks, as well as intensity changes of the diffraction peaks, indicating that the manganese phosphide / carbon materials prepared were hexagonal Mn 5.64 P3. By Figure 9 Observation of the microstructure photographs of the manganese phosphide / carbon materials prepared showed that the manganese phosphide / carbon materials prepared were micron-scale spherical particles.

[0047] Meanwhile, the manganese phosphide / carbon material prepared in Example 2 was measured for the following aspects of performance:

[0048] 1. The lithium storage performance cycle test of the manganese phosphide / carbon material, as shown in Figure 10 ; Figure 10 The cycle performance of lithium batteries composed of the manganese phosphide / carbon materials prepared in Example 1 and Example 2 and lithium metal sheets was compared, indicating that the manganese phosphide / carbon material prepared in Example 2 exhibited a lower specific capacity under a constant current charge and discharge at a current density of 500 mA·g -1 . The manganese phosphide / carbon material prepared in Example 1 exhibited a higher specific capacity, and exhibited a high capacity of about 183.1 mAh / g after 200 cycles at a current density of 100 mA·g -1 . Even after 300 cycles at a high current density of 1 A·g -1 , the capacity was still 99.1 mAh / g, and the coulombic efficiency was almost maintained at 100%.

[0049] 2. The lithium storage performance rate test of the manganese phosphide / carbon material, as shown in Figure 11 ; Figure 11 The rate performance of lithium batteries composed of the manganese phosphide / carbon materials prepared in Example 1 and Example 2 and lithium metal sheets was compared, and the test current densities were 200, 500, 1000, 2000, and 5000, and then returned to 200 mA·g -1 . Comparison showed that the manganese phosphide / carbon material prepared in Example 1 exhibited better rate performance than the manganese phosphide / carbon material prepared in Example 2.

[0050] Although embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for producing a sheet-shaped manganese phosphide / carbon composite material, characterized by, The preparation method comprises the following steps: Step (1), a manganese source, a carbon source and an acid are mixed in a certain mass ratio, and are continuously ground at room temperature for 10-60 minutes to obtain a precursor; the precursor obtained after the reaction is a structure in which the generated manganese phosphide precursor is connected by the carbon source as a crosslinked network, and the reaction mechanism is that the manganese source and the phosphorus-containing acid form the manganese phosphide precursor through a polymerization reaction, the functional groups on the surface of the first generated manganese phosphide precursor can be attracted to the functional groups on the surface of the carbon source, so that the manganese phosphide precursor is uniformly distributed in the carbon source; Step (2), the precursor is heated at a rate of 1-10 ℃ / min to 600-1000 ℃ under a protective gas, is kept for 2-10 h, is cooled to room temperature with the furnace, and a flaky manganese phosphide / carbon composite material is obtained; the manganese phosphide precursor is phosphatized to generate manganese phosphide during the heat treatment process, and the carbon source as a crosslinked network in the precursor is carbonized to form flaky carbon; In the step (1), the mass ratio of the manganese source, the carbon source and the acid is 1:5-8:20-25; In the step (1), the manganese source is one, two or more of manganese chloride, manganese acetate, manganese nitrate tetrahydrate and manganese sulfate; In the step (1), the carbon source is one, two or more of glucose, citric acid and melamine; In the step (1), the acid is phosphoric acid or / and phytic acid; In the step (2), the flow rate of the protective gas is 0.5-2 L / min; In the step (2), the protective gas is one of nitrogen, argon and carbon dioxide.

2. The flaky manganese phosphide / carbon composite material prepared by the preparation method of the flaky manganese phosphide / carbon composite material of claim 1 is applied to a lithium ion battery or a potassium ion battery as a negative electrode material.

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