An ultrathin flexible self-supporting sodium metal negative electrode protection material and a preparation method and application thereof

Abstract

The application discloses an ultrathin flexible self-supporting sodium metal negative electrode protection material and a preparation method and application thereof, and belongs to the technical field of electrochemical energy storage materials. The preparation method comprises the following steps: S01, placing a precursor in a reactor, then placing the reactor in a deposition device, introducing a carbon source / nitrogen source for reaction, cooling to room temperature after the reaction is completed, and obtaining a sample containing a salt template; S02, adding deionized water to the sample containing the salt template for soaking and drying, and obtaining the ultrathin flexible self-supporting sodium metal negative electrode protection material. The ultrathin flexible self-supporting sodium metal negative electrode protection material can not only make the metal plating layer more uniform and thin, but also slow down the volume change in the repeated cycle process; the surface micropores and the gradient doping are combined to form a good conductive path, promote the transfer of ions / electrons and improve the stable service life of the energy storage device; the material is light and thin and has higher utilization, so that the energy density is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical energy storage materials, in particular to an ultrathin flexible self-supporting sodium metal negative electrode protection material and a preparation method and application thereof. BACKGROUND

[0002] In the past few decades, lithium-ion batteries have become the most common power supply in the market of portable electronic products. However, due to the global shortage of lithium resources and the increasing market demand, the cost of lithium resources is high, in order to solve the existing problems, people have carried out extensive research, and continuously developed rechargeable batteries with high energy density and long cycle life. Sodium metal is an excellent alternative because of its high theoretical specific capacity (1166mAhg -1 ) and low standard electrode potential (-2.71V vs. standard hydrogen electrode, SHE), and it has lower cost and higher natural abundance. However, similar to lithium metal anodes, the development of sodium metal anodes is also hindered by some serious problems. First, uneven deposition can lead to serious dendrite growth during the cycle process, and sodium dendrites near the active site can rapidly and unevenly dissolve, separating them from the substrate and causing "dead sodium" and thus battery short circuit problems. Second, due to the high electrochemical activity of metallic sodium, the repeated expansion and contraction of the metal sodium during electrochemical cycling, the solid electrolyte interface (SEI) between the sodium metal anode and the electrolyte is easily decomposed, leading to side reactions between the electrolyte and the newly exposed metal. The side reaction will continue to deplete the electrolyte and sodium metal, which is an irreversible reaction, accompanied by the thickening of the SEI layer, leading to a significant decrease in the electrochemical performance of the sodium metal battery.

[0003] In order to solve the above problems, researchers have developed a series of optimization methods for metal anodes. Among them, carbon-based carriers are of great concern due to their high chemical stability, good mechanical properties and strong conductivity. Researchers mainly optimize the carbon structure from the following aspects.

[0004] 1) Precise adjustment of the surface structure of carbon at a scale below the critical nucleation size: photolithography, template flash lithography and laser micromachining have been used to obtain patterned voids, trenches or vertically aligned microchannels, but it is difficult to work at the nanoscale. 2) Construction of three-dimensional carriers: three-dimensional conductive / sodium-philic carriers can partially alleviate the problems of sodium dendrite growth and volume expansion compared to traditional two-dimensional carriers. However, metal deposition on three-dimensional carriers often exhibits a "top growth" mode. 3) Protective layer: as a physical barrier to inhibit dendrite growth, its interfacial compatibility is more complex. Designing multifunctional carbon materials will increase the thickness, sacrificing the volume and mass energy density.

[0005] Therefore, it is necessary to prepare carbon materials meeting the requirements of gradient doping of heteroatoms, limitation of metal crystal nucleus size, fine protection layer, lightness and thinness, and application in electrochemical energy storage devices. SUMMARY

[0006] Therefore, the present application provides an ultrathin flexible self-supporting sodium metal negative electrode protection material, a preparation method and application thereof.

[0007] The object of the present application is achieved by the following technical solutions.

[0008] In one aspect, the present application provides a preparation method of an ultrathin flexible self-supporting sodium metal negative electrode protection material, comprising the following steps:

[0009] SO1, placing a precursor in a reactor, then placing the reactor in a deposition device, introducing a carbon source / nitrogen source for reaction, cooling to room temperature after the reaction is completed, and obtaining a sample containing a salt template;

[0010] SO2, taking out the sample containing the salt template in step S01, and adding deionized water to the sample containing the salt template for soaking; after the soaking is completed, drying to obtain an ultrathin flexible self-supporting sodium metal negative electrode protection material.

[0011] As a preferred embodiment, in step SO1,

[0012] The precursor is sodium chloride. By controlling different reaction temperatures, sodium chloride crystals of different sizes after recrystallization can be obtained, which is low in cost and easy to obtain.

[0013] The amount of the precursor is 2.5g. Further preferably, the precursor is piled into a small hill and placed in the reactor.

[0014] The reactor is a silicon wafer placed on a corundum square boat; the deposition device is a plasma enhanced chemical vapor deposition device.

[0015] The carbon source / nitrogen source is a carbon element-containing gas and a carbon and nitrogen element-containing volatile liquid; wherein the carbon element-containing gas is preferably a hydrogen gas mixture with a methane volume content of 30%, and the carbon and nitrogen element-containing volatile liquid is one or a mixture of at least two of pyridine or acetonitrile.

[0016] The carbon and nitrogen element-containing volatile liquid is both a carbon source and a dopant; the carbon and nitrogen element-containing volatile liquid is contained by an external liquid bottle.

[0017] The carbon-containing gas is first introduced into the reaction process, then the carbon-containing gas is closed and the volatile liquid containing carbon and nitrogen elements is introduced. Further preferably, the carbon-containing gas is reacted for 10 min at a flow rate of 150 sccm, the carbon-containing gas is closed, and the volatile liquid containing carbon and nitrogen elements is introduced at a flow rate of 5 sccm to 15 sccm (see the specific control process in the example operation steps).

[0018] The initial temperature of the reaction is 20℃, the reaction temperature of the reaction is 650℃-900℃, the heating rate is 10℃ / min, and the temperature is then reduced to 300℃.

[0019] The reaction time is 90 min-120 min (including the heating time and the deposition time).

[0020] Further preferably, the initial temperature of the reaction is 20℃, the reaction temperature of the reaction is: the heating furnace temperature: 650℃-900℃ (plasma power: 400w-500w) for 10-15 min; the temperature is reduced to 300℃ (plasma power: 150w) for 12 min-22 min.

[0021] The cooling method is to remove the heating device after the reaction is completed, so that the sample is rapidly cooled to room temperature.

[0022] As a preferred embodiment, in step SO2,

[0023] The amount of deionized water is 70ml. By soaking in deionized water, residual salt templates in the reaction process can be removed.

[0024] The soaking time is 24h.

[0025] The soaking is carried out in a 20cm diameter culture dish.

[0026] The soaking and cleaning is performed twice.

[0027] The drying temperature is 60℃, and the drying time is 1h.

[0028] The drying is preferably carried out in an electric heating air drying oven.

[0029] In another aspect, the present application also provides an ultrathin flexible self-supporting sodium metal negative electrode protection material prepared by the above preparation method.

[0030] In another aspect, the ultrathin flexible self-supporting sodium metal negative electrode protection material is applied in a sodium metal battery.

[0031] Compared with the prior art, the application has the following technical effects:

[0032] The ultra-thin flexible self-supporting sodium metal negative electrode protection material obtained by plasma vapor deposition has a smooth surface and a structure of interconnected units in the interior. The small-size interconnected units limit the critical nucleation size, making the metal coating more uniform and thinner, and slowing down the volume change in the cycling process. At the same time, the surface micropore size limits the entry of solvent molecules into the material interior, reducing the occurrence of side reactions; in combination with gradient nitrogen doping, it is beneficial to form a good conductive path, promote the transfer of ions / electrons and improve the stable service life of the energy storage device. The prepared flexible self-supporting carbon film is lighter and thinner than the traditional electrode prepared by brushing and suction filtration, and has higher utilization, thereby effectively improving the energy density. At the same time, the multifunctional integrated flexible self-supporting carbon film can overcome the problem of single function of other carbon carriers. The preparation method of the application is simple, the cost is low, and can be applied to large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0034] Figure 1 SEM and TEM characterization diagrams of the ultra-thin flexible self-supporting sodium metal negative electrode protection material provided for the present embodiment 1 are shown in the following figures:

[0035] Figure 2 SEM and TEM characterization diagrams of the ultra-thin flexible self-supporting sodium metal negative electrode protection material provided for the present embodiment 2 are shown in the following figures:

[0036] Figure 3 SEM and TEM characterization diagrams of the ultra-thin flexible self-supporting sodium metal negative electrode protection material provided for the present embodiment 3 are shown in the following figures:

[0037] Figure 4 The cycle performance test diagram of the sodium metal symmetrical battery prepared in the present embodiment 3 under the condition of discharge depth 100% is shown in the following figure: -2

[0038] Figure 5 TEM characterization diagram and BET test data of the surface layer sheet in the ultra-thin flexible self-supporting sodium metal negative electrode protection material provided for the present embodiments 3 and 4 are shown in the following figures:

[0039] Figure 6 Cross-sectional SEM characterization diagram of the ultra-thin flexible self-supporting sodium metal negative electrode protection material provided for the present embodiment 5 is shown in the following figure: ​

[0040] Figure 7 A cross-sectional SEM characterization of the ultra-thin flexible self-supporting sodium metal anode protection material provided for this Example 6.

[0041] Figure 8 A cross-sectional SEM characterization of the ultra-thin flexible self-supporting sodium metal anode protection material obtained for this Example 3.

[0042] The objectives, functional characteristics and advantages of the present application will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0044] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, top, bottom, etc.), the directional indications are only used to explain the relative positional relationship, movement condition, etc. between components in a certain posture, and if the certain posture changes, the directional indications also change accordingly.

[0045] In the present application, unless otherwise explicitly specified and limited, the terms “mounting”, “connection”, “connecting”, “fixing” and the like should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0046] It should be noted that when an element is referred to as “fixed to” or “disposed on” another element, it can be directly on the other element or there can be a middle element. When an element is referred to as “connected to” another element, it can be directly connected to the other element or there can be a middle element.

[0047] In addition, if the description of "first", "second" and the like is involved in the embodiments of the present application, the description of "first", "second" and the like is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can be explicitly or implicitly included at least one of the features. In addition, the technical solutions of various embodiments can be combined with each other, but it must be based on the realization of ordinary skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, nor in the protection scope required by the present application.

[0048] The ultra-thin flexible self-supporting sodium metal negative electrode protection material prepared in the application not only makes the metal plating layer more uniform and thin, and can slow down the volume change in the repeated cycle process; but also can form a good conductive path by the mutual combination of surface micropores and gradient doping, promote the transfer of ions / electrons and improve the stable life of energy storage devices; The material is light and thin and has higher utilization, thereby effectively improving the energy density. At the same time, the multifunctional integrated flexible self-supporting carbon film can overcome the problem of single function of other carbon carriers.

[0049] To achieve the above object, on the one hand, the present application provides a preparation method of an ultra-thin flexible self-supporting sodium metal negative electrode protection material, comprising the following steps:

[0050] SO1, the precursor is placed in the reactor, then the reactor is placed in the deposition device, the carbon source / nitrogen source is introduced for reaction, and the sample containing salt template is obtained after cooling to room temperature after reaction;

[0051] SO2, the sample containing salt template in step S01 is taken out, and deionized water is added to the sample containing salt template for soaking; after soaking, drying is carried out to obtain an ultra-thin flexible self-supporting sodium metal negative electrode protection material.

[0052] As a preferred embodiment, in step SO1,

[0053] The precursor is sodium chloride, and by controlling different reaction temperatures, sodium chloride crystals of different sizes after recrystallization can be obtained, which is low in cost and easy to obtain.

[0054] The amount of the precursor is 2.5g. The precursor is piled into a small hill and placed in the reactor.

[0055] The reactor is a silicon wafer placed in a corundum square boat; the deposition device is a plasma enhanced chemical vapor deposition device. In a vacuum oxygen-free environment, the plasma bombardment and high-temperature evaporation processes in the deposition device are carried out simultaneously, the carbon source / nitrogen source is cracked into high-energy carbon / nitrogen atoms after being bombarded by a high-energy plasma beam, the precursor is evaporated into a gaseous state in a high-temperature environment, reaches the low-temperature zone, combines with the high-energy carbon / nitrogen atoms, and is deposited on the silicon wafer.

[0056] The carbon source / nitrogen source is a carbon element-containing gas and a carbon-nitrogen element-containing volatile liquid; the carbon element-containing gas is preferably hydrogen mixed gas with a flow rate of 150 sccm and a methane volume content of 30%, and the carbon-nitrogen element-containing volatile liquid is one of pyridine or acetonitrile.

[0057] The carbon-nitrogen element-containing volatile liquid is both a carbon source and a dopant; the carbon-nitrogen element-containing volatile liquid is contained in an external liquid bottle. In the reaction process of introducing the carbon source, the carbon element-containing gas is introduced for a period of time, and then the carbon element-containing volatile liquid is introduced.

[0058] In SO1, the carbon element-containing gas is reacted for 10 min at a flow rate of 150 sccm, and then the carbon element-containing volatile liquid is introduced with a flow rate varying from 5 sccm to 15 sccm.

[0059] The initial temperature of the reaction is 20℃, and the reaction temperature of the reaction is: the heating furnace temperature is 650℃-900℃ (plasma power: 400w-500w), the temperature rising rate is 10℃ / min, and then the temperature is reduced to 300℃.

[0060] The reaction time is 90min-120min (including the temperature rising time and the deposition time).

[0061] Further preferably, the initial temperature of the reaction is 20℃, and the reaction temperature of the reaction is: the heating furnace temperature: 650℃-900℃ (plasma power: 400w-500w) for 10-15min; the temperature is reduced to 300℃ (plasma power: 150w) for 12min-22min.

[0062] The cooling method is to remove the heating device after the reaction is completed, so that the sample is rapidly cooled to room temperature.

[0063] As a preferred embodiment, in step SO2,

[0064] The amount of deionized water is 70ml. By soaking in deionized water, residual salt templates in the reaction process can be removed.

[0065] The soaking time is 24h.

[0066] The soaking is performed in a 20 cm diameter petri dish.

[0067] The soaking cleaning is performed twice.

[0068] The drying temperature is 60°C, and the drying time is 1 h.

[0069] The drying is preferably performed in an electrically heated air drying oven.

[0070] In another aspect, the embodiments of the present application also provide an ultrathin flexible self-supporting sodium metal negative electrode protection material obtained by the above preparation method.

[0071] In another aspect, the embodiments of the present application also provide an ultrathin flexible self-supporting sodium metal negative electrode protection material obtained by the above preparation method.

[0072] The ultrathin flexible self-supporting sodium metal negative electrode protection material prepared by the present application not only makes the metal plating layer more uniform and thin, and can slow down the volume change in the repeated cycle process, but also can form a good conductive path by the mutual combination of the surface micropore and the gradient doping, promote the transfer of ions / electrons and improve the stable service life of the energy storage device; the material is light and thin and has higher utilization, thereby effectively improving the energy density. At the same time, the multifunctional integrated flexible self-supporting carbon film can overcome the problem of single function of other carbon carriers.

[0073] Embodiment 1

[0074] A preparation method of an ultrathin flexible self-supporting sodium metal negative electrode protection material, comprising the following steps:

[0075] SO1, placing a precursor in a reactor, then placing the reactor in a deposition device, introducing a carbon source / nitrogen source for reaction, cooling to room temperature after the reaction is completed, and obtaining a sample containing a salt template;

[0076] SO2, taking out the sample containing the salt template in step S01, and adding deionized water to the sample containing the salt template for soaking; drying after the soaking is completed, and obtaining an ultrathin flexible self-supporting sodium metal negative electrode protection material.

[0077] In step SO1,

[0078] The precursor is sodium chloride.

[0079] The amount of the precursor is 2.5 g.

[0080] The reactor is a silicon wafer placed on a square corundum square boat; and the deposition device is a plasma enhanced chemical vapor deposition device.

[0081] The carbon source / nitrogen source is a hydrogen gas mixture with a methane volume content of 30% and a volatile liquid pyridine containing carbon and nitrogen elements.

[0082] The carbon-containing gas was reacted for 10 min at a flow rate of 150 sccm, after which the flow rate of the carbon-nitrogen-containing volatile liquid pyridine was changed from 5 sccm to 15 sccm (increased at a rate of 0.59 sccm / min using a gas flow meter).

[0083] The initial temperature of the reaction was 20℃, and the reaction temperature of the reaction was a heating furnace temperature of 650℃, a plasma power of 400w, and a temperature increase rate of 10℃ / min; during the deposition process, the temperature was maintained at 650℃ for 10 min, after which the temperature was reduced to 300℃, and the plasma power was maintained at 150w for 17 min.

[0084] The reaction time was 90 min (including the temperature increase time and the deposition time).

[0085] The cooling method was to remove the heating device after the reaction was completed, so that the sample was rapidly cooled to room temperature.

[0086] In step SO2,

[0087] The amount of deionized water used was 70ml. By soaking in deionized water, residual salt templates during the reaction process can be removed.

[0088] The soaking time was 24h.

[0089] The soaking was performed in a 20cm diameter culture dish.

[0090] The soaking and cleaning was performed twice.

[0091] The drying temperature was 60℃, and the drying time was 1h.

[0092] The drying was preferably performed in an electric heating air drying oven.

[0093] Figure 1 SEM characterization diagram of the ultrathin flexible self-supporting sodium metal negative electrode protection material obtained in Example 1; from Figure 1 It can be observed that the surface of the negative electrode material is a layer of uniform sheet, and the inside is a connected structure with a unit size of ~1 microns.

[0094] Example 2

[0095] A preparation method of an ultrathin flexible self-supporting sodium metal negative electrode protection material, comprising the following steps:

[0096] SO1, the precursor was placed in the reactor, and then the reactor was placed in a deposition device, a carbon source / nitrogen source was introduced for reaction, and the sample containing a salt template was obtained after cooling to room temperature;

[0097] SO2, the sample containing the salt template in step S01 is taken out, and deionized water is added to the sample containing the salt template for soaking; after soaking is completed, drying is performed to obtain an ultrathin flexible self-supporting sodium metal negative electrode protection material.

[0098] In step S01,

[0099] The precursor is sodium chloride.

[0100] The amount of the precursor is 2.5 g.

[0101] The reactor is a silicon wafer placed on a square corundum tank; and the deposition device is a plasma enhanced chemical vapor deposition device.

[0102] The carbon source is a hydrogen mixed gas with a methane volume content of 30% and a volatile liquid pyridine containing carbon and nitrogen elements.

[0103] The gas containing carbon elements is reacted for 10 min under a flow rate of 150 sccm, then closed and the volatile liquid containing carbon and nitrogen elements is introduced at a flow rate of 5 sccm to 15 sccm (controlled by a gas flow meter at 0.59 sccm / min).

[0104] The initial temperature of the reaction is 20℃, the reaction temperature of the reaction: the heating furnace temperature is 800℃, the plasma power is 400w, and the heating rate is 10℃ / min; during the deposition process, 800℃ is maintained for 10 min, then the temperature is reduced to 300℃, and the plasma power is 150w for 17 min.

[0105] The reaction time is 105 min (including the heating time and the deposition time).

[0106] The cooling method is to remove the heating device after the reaction is completed, so that the sample is quickly cooled to room temperature.

[0107] In step S02,

[0108] The amount of deionized water is 70 ml. By soaking with deionized water, residual salt templates in the reaction process can be removed.

[0109] The soaking time is 24 h.

[0110] The soaking is performed in a 20 cm diameter culture dish.

[0111] The soaking and cleaning is performed twice.

[0112] The drying temperature is 60℃, and the drying time is 1 h.

[0113] The drying is preferably performed in an electric heating air drying oven.

[0114] Figure 2 SEM characterization figure of the ultra-thin flexible self-supporting sodium metal negative electrode protection material obtained in this embodiment 2; from Figure 2 It can be observed that the surface of the negative electrode material is a layer of uniform flakes, and the inside is a connected structure with a unit size of ~200 nanometers.

[0115] Embodiment 3

[0116] A preparation method of an ultra-thin flexible self-supporting sodium metal negative electrode protection material, comprising the following steps:

[0117] S01, the precursor is placed in a reactor, then the reactor is placed in a deposition device, and a carbon source / nitrogen source is introduced for reaction. After the reaction is completed, it is cooled to room temperature to obtain a sample containing a salt template;

[0118] S02, the sample containing the salt template in step S01 is taken out, and deionized water is added to the sample containing the salt template for soaking; after soaking is completed, it is dried to obtain an ultra-thin flexible self-supporting sodium metal negative electrode protection material.

[0119] In step S01,

[0120] The precursor is sodium chloride.

[0121] The amount of the precursor is 2.5g.

[0122] The reactor is a silicon wafer placed on a square corundum square boat; the deposition device is a plasma enhanced chemical vapor deposition device.

[0123] The carbon source is a mixture of hydrogen gas with a methane volume content of 30% and a volatile liquid pyridine containing carbon and nitrogen elements.

[0124] The gas containing carbon elements is reacted for 10min under a flow rate of 150sccm, then closed and introduced into a volatile liquid containing carbon and nitrogen elements with a flow rate of 5sccm to 15sccm (controlled by a gas flow meter to increase by 0.59sccm / min).

[0125] The initial temperature of the reaction is 20℃, the reaction temperature of the reaction: the heating furnace temperature is 900℃, the plasma power is 400w, and the heating rate is 10℃ / min; during the deposition process, 900℃ is maintained for 10min, then the temperature is reduced to 300℃, and the plasma power is 150w for 17min.

[0126] The reaction time is 115min (including the heating time and the deposition time).

[0127] The cooling method is to remove the heating device after the reaction is completed, and the sample is quickly cooled to room temperature.

[0128] In step SO2,

[0129] The amount of deionized water is 70ml. By soaking in deionized water, residual salt templates in the reaction process can be removed.

[0130] The soaking time is 24h.

[0131] The soaking is carried out in a 20cm diameter culture dish.

[0132] The soaking cleaning is 2 times.

[0133] The drying temperature is 60℃, and the drying time is 1h.

[0134] The drying is preferably carried out in an electric heating air drying oven.

[0135] The self-supporting carbon film prepared in this embodiment 3 is cut into a size of 10mm as an electrode, and 4mAh·cm -2 of sodium metal is pre-deposited; sodium hexafluorophosphate NaPF6 is used as a solute, and dimethyl carbonate DME is used as a solvent to prepare a solution with a concentration of 1mol·L -1 as an electrolyte; finally, a 2032 button-type sodium metal symmetric battery is assembled and subjected to charge and discharge test, and the test voltage window is 0.01V-3V.

[0136] Figure 3 SEM and TEM characterization diagrams of the ultrathin flexible self-supporting sodium metal negative electrode protection material obtained in this embodiment 3; from Figure 3 It can be observed that the surface of the negative electrode material is a layer of uniform sheet, and the inside is a connected structure with a unit size of ~50nm.

[0137] Figure 4 The cycle performance test diagram of the sodium metal symmetric battery prepared in this embodiment 3 under the condition of large current 8mA·cm -2 discharge depth 100%, from Figure 4 It can be seen that after 1300 cycles, it still shows a low hysteresis voltage of 41.9mV, showing good cycle stability.

[0138] Embodiment 4

[0139] A preparation method of an ultrathin flexible self-supporting sodium metal negative electrode protection material, comprising the following steps:

[0140] SO1, the precursor is placed in a reactor, then the reactor is placed in a deposition device, and a carbon source / nitrogen source is introduced for reaction. After the reaction is completed, it is cooled to room temperature to obtain a sample containing a salt template;

[0141] SO2, the sample containing the salt template in step S01 is taken out, and deionized water is added to the sample containing the salt template for soaking; after soaking is completed, drying is performed, to obtain an ultrathin flexible self-supporting sodium metal negative electrode protection material.

[0142] In step S01,

[0143] The precursor is sodium chloride.

[0144] The amount of the precursor is 2.5 g.

[0145] The reactor is a silicon wafer placed on a square corundum tank; and the deposition device is a plasma enhanced chemical vapor deposition device.

[0146] The carbon source is hydrogen mixed gas with a methane volume content of 30% and volatile liquid pyridine containing carbon and nitrogen elements.

[0147] The carbon-containing gas is reacted for 10 min under a flow rate of 150 sccm, and then is closed and the volatile liquid containing carbon and nitrogen elements is introduced at a flow rate of 5 sccm to 15 sccm (controlled by a gas flow meter at an increase of 0.59 sccm / min).

[0148] The initial temperature of the reaction is 20℃, the reaction temperature of the reaction is: the heating furnace temperature is 900℃, the plasma power is 500w, and the heating rate is 10℃ / min; during the deposition process, 900℃ is maintained for 10 min, and then the temperature is reduced to 300℃, and the plasma power is 150w for 17 min.

[0149] The reaction time is 115 min (including the heating time and the deposition time).

[0150] The cooling mode is to remove the heating device after the reaction is completed, so that the sample is rapidly cooled to room temperature.

[0151] In step S02,

[0152] The amount of the deionized water is 70 ml. By soaking with the deionized water, residual salt templates in the reaction process can be removed.

[0153] The soaking time is 24 h.

[0154] The soaking is performed in a culture dish with a diameter of 20 cm.

[0155] The soaking and cleaning are performed twice.

[0156] The drying temperature is 60℃, and the drying time is 1 h.

[0157] The drying is preferably performed in an electric heating air drying oven.

[0158] Figure 5 TEM characterization figures of the surface layer sheet of the ultra-thin flexible self-supporting sodium metal negative electrode protection material obtained in Examples 3 and 4 and the corresponding BET test data thereof are shown in the following table: Figure 5 It can be observed that the pore size of the surface layer material can be controlled under the control of plasma power.

[0159] Example 5

[0160] A preparation method of an ultra-thin flexible self-supporting sodium metal negative electrode protection material, comprising the following steps:

[0161] S01, placing the precursor in a reactor, then placing the reactor in a deposition device, introducing a carbon source / nitrogen source for reaction, and cooling to room temperature after the reaction is completed to obtain a sample containing a salt template;

[0162] S02, taking out the sample containing the salt template in step S01, and adding deionized water to the sample containing the salt template for soaking; after soaking, drying to obtain an ultra-thin flexible self-supporting sodium metal negative electrode protection material.

[0163] In step S01,

[0164] The precursor is sodium chloride.

[0165] The amount of the precursor is 2.5 g.

[0166] The reactor is a silicon wafer placed on a square corundum square boat; the deposition device is a plasma enhanced chemical vapor deposition device.

[0167] The carbon source is a hydrogen gas mixture with a methane volume content of 30% and a volatile liquid pyridine containing carbon and nitrogen elements.

[0168] The carbon-containing gas is reacted for 10 min at a flow rate of 150 sccm, then closed and introduced into a volatile liquid containing carbon and nitrogen elements with a flow rate of 5 sccm to 15 sccm (controlled by a gas flow meter to increase at 0.83 sccm / min).

[0169] The initial temperature of the reaction is 20℃, the reaction temperature of the reaction: the heating furnace temperature is 900℃, the plasma power is 400w, the heating rate is 10℃ / min; during the deposition process, 900℃ for 10min, then the temperature is reduced to 300℃ for 12min.

[0170] The reaction time is 100min (including the heating time and the deposition time).

[0171] The cooling method is to remove the heating device after the reaction is completed, and the sample is quickly cooled to room temperature.

[0172] In step SO2,

[0173] The amount of deionized water is 70 ml. By soaking in deionized water, residual salt templates in the reaction process can be removed.

[0174] The soaking time is 24 h.

[0175] The soaking is carried out in a 20 cm diameter culture dish.

[0176] The soaking cleaning is 2 times.

[0177] The drying temperature is 60℃, and the drying time is 1 h.

[0178] The drying is preferably carried out in an electric heating air drying oven.

[0179] Figure 6 The cross-sectional SEM characterization graph and optical photo of the ultra-thin flexible self-supporting sodium metal negative electrode protection material obtained in this embodiment 5, the thickness is 5 microns.

[0180] Embodiment 6

[0181] A preparation method of an ultra-thin flexible self-supporting sodium metal negative electrode protection material, comprising the following steps:

[0182] SO1, the precursor is placed in the reactor, then the reactor is placed in the deposition device, the carbon source / nitrogen source is introduced for reaction, and after the reaction is completed, it is cooled to room temperature to obtain a sample containing a salt template;

[0183] SO2, the sample containing the salt template in step S01 is taken out, and deionized water is added to the sample containing the salt template for soaking; after the soaking is completed, drying is carried out to obtain an ultra-thin flexible self-supporting sodium metal negative electrode protection material.

[0184] In step SO1,

[0185] The precursor is sodium chloride.

[0186] The amount of the precursor is 2.5 g.

[0187] The reactor is a silicon wafer placed on a square corundum square boat; the deposition device is a plasma enhanced chemical vapor deposition device.

[0188] The carbon source is a hydrogen gas mixture with a methane volume content of 30% and a volatile liquid pyridine containing carbon and nitrogen elements.

[0189] The carbon-containing gas is reacted for 10 min at a flow rate of 150 sccm, after which the flow rate of the carbon-containing volatile liquid is changed from 5 sccm to 15 sccm (controlled by a gas flow meter at an increase of 0.45 sccm / min).

[0190] The initial temperature of the reaction is 20℃, the reaction temperature of the reaction: the heating furnace temperature is 900℃, the plasma power is 400w, and the temperature rising rate is 10℃ / min; during the deposition process, 900℃ is maintained for 10 min, and then the temperature is reduced to 300℃, and the plasma power is 150w for 22 min.

[0191] The reaction time is 120 min (including the temperature rising time and the deposition time).

[0192] The cooling method is to remove the heating device after the reaction is completed, so that the sample is rapidly cooled to room temperature.

[0193] In step S02,

[0194] The amount of deionized water is 70ml. By soaking in deionized water, residual salt templates in the reaction process can be removed.

[0195] The soaking time is 24h.

[0196] The soaking is carried out in a 20cm diameter culture dish.

[0197] The soaking cleaning is performed twice.

[0198] The drying temperature is 60℃, and the drying time is 1h.

[0199] The drying is preferably carried out in an electric heating air drying oven.

[0200] Figure 7 The cross-sectional SEM characterization diagram and optical photograph of the ultra-thin flexible self-supporting sodium metal negative electrode protection material obtained in this embodiment 6 are shown, and the thickness is 15 microns.

[0201] Figure 8 The cross-sectional SEM characterization diagram and optical photograph of the ultra-thin flexible self-supporting sodium metal negative electrode protection material obtained in this embodiment 3 are shown, and the thickness is 10 microns.

[0202] Comparative Example 1

[0203] The preparation method of the ordered mesoporous graphene (OMG) of the present comparative example comprises the following steps:

[0204] (1) Preparation of graphene oxide (GO) aqueous solution: a modified Hummers method was used to prepare the GO aqueous solution, which was then re-dispersed in deionized water with a concentration of about 4 mg mL -1 ;

[0205] (2) Synthesis of iron oleate complex: 7.62 g of sodium oleate was dissolved in 150 mL of water, stirred for 1 h, and then 2.26 g of FeCl3·6H2O was added to prepare the iron oleate complex;

[0206] (3) Preparation of precursor: 0.42 g or 0.21 g of suspended GO was added to the iron oleate complex solution, stirred until uniformly dispersed, and then freeze-dried;

[0207] (4) Calcination treatment: the obtained iron oleate / GO powder was heated to 500℃ in a furnace and calcined for 2 h under an argon (Ar) flow (flow rate of 100 sccm) or under an Ar / H2 (flow rates of 100 sccm / 30 sccm) atmosphere;

[0208] (5) Template removal: the Fe3O4 nanoparticles were removed with hydrochloric acid (HCl), and then washed with water and ethanol three times respectively to obtain ordered mesoporous graphene (OMG)

[0209] Comparison between the method of the present application and Comparative Example 1: the synthesis steps of Comparative Example 1 are complicated, and a carbon material with small-sized interconnected units can be obtained only after a long-time calcination treatment after a multi-step synthesis of a precursor. The long reaction time and complex synthesis steps result in more influencing factors, which to some extent limits the application of the method. The method of the present application can synthesize the material in one step, realizes the template regulation of the interconnected unit size by changing the temperature, and has a relatively simple synthesis step, a shorter reaction time, lower energy consumption, safety and convenience, and can be used for rapidly preparing an ultrathin flexible self-supporting sodium metal negative electrode protection material, and has higher universality.

[0210] Comparative Example 2

[0211] The preparation method of a 3D carbon framework (CMFS) with a "gradient sodium affinity" property in the present comparative example comprises the following steps:

[0212] 1. Preparation of sodium-affinity carbon fiber framework (CFS)

[0213] (1) First, the purchased bacterial cellulose (BC) was soaked in deionized water and ultrasonically cleaned for 1 hour.

[0214] (2) Then, the deionized water was replaced with ethanol and ultrasonically cleaned again for 1 hour.

[0215] (3) Then it was immersed in deionized water for 24 hours, and then dried BC was obtained by freeze-drying.

[0216] The dried BC was cut into a disc with a diameter of 19 mm, and several pieces were placed in a corundum boat and transferred to a tube furnace. Under an argon atmosphere, it was heated to 700℃ at a heating rate of 3℃ / min for carbonization for 2 hours, and the obtained three-dimensional carbon fiber skeleton was named CFS.

[0217] 2. Preparation of "gradient sodium affinity" support (CMFS)

[0218] (1) 40 times of concentrated polytetrafluoroethylene (PTFE) dispersion liquid (60wt.%) was added dropwise to the surface of CFS, and it was left for half an hour to make it fully infiltrated with PTFE.

[0219] (2) Then the PTFE infiltrated CFS was annealed again at 700℃ under an argon atmosphere at a heating rate of 3℃ / min for 1 hour, and the obtained three-dimensional carbon microsphere interwoven fiber skeleton was CMFS. After carbonization, the diameter of CFS and CMFS was 14mm.

[0220] The method of the present application and comparative example 2 were compared: the synthesis steps of comparative example 2 are complicated, and it is necessary to prepare the original material and then react to achieve the purpose of gradient nitrogen doping. But the method of the present application can quickly synthesize gradient-doped three-dimensional interconnected structure in one step, and the nitrogen doping amount can be controlled by adjusting the pyridine flow, which improves the stability of the carbon network and effectively simplifies the steps of preparing gradient-doped three-dimensional carbon carrier with high performance.

[0221] The above only describes the preferred embodiments of the present application and should not be used to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing an ultrathin flexible self-supporting sodium metal anode protection material, characterized by: It comprises the following steps: S01, the precursor is placed in the reactor, then the reactor is placed in the deposition device, the carbon source / nitrogen source is introduced for reaction, and the sample containing the salt template is obtained after cooling to room temperature after the reaction is completed; S02, the sample containing the salt template in step S01 is taken out, and deionized water is added to the sample containing the salt template for soaking; after soaking, drying is performed to obtain an ultrathin flexible self-supporting sodium metal negative electrode protection material; The precursor is sodium chloride; In step S01, the carbon source / nitrogen source is a gas containing carbon elements and a volatile liquid containing carbon and nitrogen elements; wherein the gas containing carbon elements is a hydrogen mixture gas with a methane volume content of 30%, and the volatile liquid containing carbon and nitrogen elements is one or a mixture of at least two of pyridine or acetonitrile; In step S01, the gas containing carbon elements is reacted at a flow rate of 150 sccm for 10 min, the gas containing carbon elements is turned off, and the volatile liquid containing carbon and nitrogen elements is introduced at a flow rate of 5 sccm to 15 sccm; In step S01, the initial temperature of the reaction is 20℃, and the reaction conditions of the reaction are: heating furnace temperature: 650℃-900℃ for 10-15 min; temperature reduction to 300℃ for 12 min-22 min; The ultrathin flexible self-supporting sodium metal negative electrode protection material is a flexible self-supporting carbon film, which has a smooth surface and a structure of interconnected units inside.

2. The preparation method of the ultrathin flexible self-supporting sodium metal anode protective material according to claim 1, characterized in that: In step S01, The amount of the precursor is 2.5g; The precursor is piled into a small hill and placed in the reactor.

3. The preparation method of the ultrathin flexible self-supporting sodium metal anode protective material according to claim 1, characterized in that: In step S01, The reactor is a silicon wafer placed on a corundum square boat; the deposition device is a plasma enhanced chemical vapor deposition device; The cooling method is to remove the heating device after the reaction is completed, so that the sample is rapidly cooled to room temperature.

4. The preparation method of the ultrathin flexible self-supporting sodium metal anode protective material according to claim 1, characterized in that: In step S02, The amount of deionized water is 70ml; The soaking time is 24h; The drying temperature is 60℃, and the drying time is 1h; The drying is performed in an electric heating air drying oven.

5. An ultrathin flexible self-supporting sodium metal anode protection material, characterized in that: Obtained by the preparation method of any one of claims 1-4.

6. The ultrathin flexible self-supporting sodium metal negative electrode protection material of claim 5 is applied in a sodium metal battery.

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