Preparation method of molybdenum phosphide / titanium nitride composite material and battery positive electrode material and lithium-carbon dioxide battery

Abstract

The invention provides a preparation method of a molybdenum phosphide / titanium nitride composite material and a battery positive electrode material and a lithium-carbon dioxide battery, and belongs to the technical field of new energy materials. And then a titanium nitride conductor layer is deposited on the molybdenum phosphide by using an atomic layer deposition technology to prepare the molybdenum phosphide / titanium nitride, the molybdenum phosphide is combined as a transition metal phosphide to have stable catalytic performance, and the titanium nitride is used as a conductor to have excellent conductivity. The lithium-carbon dioxide battery positive electrode catalyst with high catalytic activity, high conductivity and excellent stability is obtained through the synergistic effect of the two materials, and when the lithium-carbon dioxide battery positive electrode catalyst is applied to a lithium battery, higher energy density, longer cycle life and better rate capability are shown, so that the overall performance of the battery is improved, and the application prospect is wide. The requirements on high-performance batteries in the fields of electric automobiles, energy storage systems and the like are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy materials, and more specifically, relates to a molybdenum phosphide / titanium nitride composite material, a preparation method of a battery cathode material, and a lithium-carbon dioxide battery. Background Art

[0002] With the continuous consumption of fossil energy, human society has realized the importance of green energy, and lithium-ion batteries are widely used in the fields of consumer batteries, power batteries, and energy storage batteries. However, the energy density of traditional lithium-ion batteries is gradually difficult to meet the human use requirements, and metal-air batteries have begun to come into the view of researchers. Among a series of metal-air batteries, the lithium-carbon dioxide battery has a considerable theoretical energy density.

[0003] During the discharge and charge processes of a lithium-carbon dioxide battery, the intermediate product lithium carbonate is generated and decomposed. Lithium carbonate is a stable insulating product and is not easily decomposed. The reversibility of a lithium-carbon dioxide battery lies in the decomposition of lithium carbonate. During the charging process, the too-high decomposition potential of lithium carbonate will also cause the decomposition of the electrolyte, thus affecting the stability of the battery. Therefore, reducing the decomposition potential of lithium carbonate is crucial for improving the stability of the lithium-carbon dioxide battery.

[0004] Transition metal nitrides have a good catalytic effect on reducing the charging potential of lithium-carbon dioxide batteries, but limited by their conductivity, it is difficult to maintain high-efficiency catalytic performance for a long time. Therefore, it is necessary to improve the conductivity on this basis. Summary of the Invention

[0005] The purpose of the present invention is to address the above deficiencies and provide a molybdenum phosphide / titanium nitride composite material, a preparation method of a battery cathode material, and a lithium-carbon dioxide battery, so as to provide new ideas for optimizing transition metal-based phosphides as catalysts for energy storage batteries.

[0006] To achieve the above object, the present invention is realized through the following technical solutions: In the first aspect, the present invention provides a preparation method of a molybdenum phosphide / titanium nitride composite material, including: Adding a molybdenum source compound to a strong acid solution and completely dissolving it to obtain a mixed solution A; Adding the mixed solution A into a polytetrafluoroethylene inner liner and heating it in a sealed reaction space to obtain a molybdenum source oxide; Placing the obtained molybdenum source oxide downstream of a tube furnace and placing a phosphorus source compound upstream of the tube furnace, and heating it in an atmosphere of a reducing gas to obtain molybdenum phosphide; the mass ratio of the molybdenum source compound to the phosphorus source compound is 1:(40 - 80); The obtained molybdenum phosphide is placed in the cavity of an atomic deposition equipment equipped with a titanium source and a nitrogen source. Using an inert gas as the carrier gas, a titanium nitride layer is prepared by plasma-assisted cyclic deposition. After the reaction is completed, a molybdenum phosphide / titanium nitride composite material is obtained.

[0007] By preparing the molybdenum phosphide / titanium nitride composite material through the above method, combining molybdenum phosphide and titanium nitride can make full use of the excellent properties of both, forming a new composite material with higher performance. This composite material exhibits higher catalytic activity, better conductivity, and more excellent stability; compared with other preparation methods, the reaction conditions in the whole preparation process are relatively mild, easy to control, and conducive to realizing industrial production; using atomic layer deposition technology to deposit a uniform and dense titanium nitride conductor layer on the surface of molybdenum phosphide has excellent uniformity and controllability, thereby further improving the performance of the composite material.

[0008] Further, the strong acid is concentrated nitric acid or concentrated sulfuric acid, and the volume ratio of deionized water to the strong acid in the strong acid solution is (5~2):1; the mass ratio of the molybdenum source compound to the strong acid solution is 1:(30~50).

[0009] In the above scheme, using concentrated nitric acid or concentrated sulfuric acid can provide strong oxidizing properties. Both are chemically substances with strong corrosiveness. By mixing with deionized water to dilute their concentrations, the harm to experimental equipment and experimental personnel can be reduced, making the operation safer; at the same time, by diluting the strong acid, the reaction rate can be adjusted, the reaction conditions can be optimized, and the selectivity of the target product can be improved; due to the pure nature of deionized water, using it to dilute the strong acid can ensure the stability and consistency of the experimental conditions, thereby improving the repeatability of the experiment.

[0010] Further, the molybdenum source compound is any one or more of ammonium molybdate, ammonium molybdate tetrahydrate, or ammonium molybdate hexahydrate; the phosphorus source compound is sodium hypophosphite; the molybdenum source oxide is molybdenum trioxide or molybdenum dioxide.

[0011] In the above scheme, ammonium molybdate and its hydrates as the preparation catalyst of the cathode material can promote the reaction to occur, improve the reaction rate, and the reaction conditions are relatively mild, which helps to reduce the energy consumption and cost in the preparation process; ammonium molybdate and its hydrates are easy to obtain and usually exist in a relatively high-purity form, which helps to prepare high-purity molybdenum source oxides, and is environmentally friendly. The pollution generated during their preparation and use is less, which helps to reduce the environmental impact of battery production.

[0012] By selecting appropriate molybdenum source oxides and reaction conditions, the crystal form and microstructure of molybdenum phosphide can be regulated. Different crystal forms and microstructures have significant effects on the properties of molybdenum phosphide, such as electrical conductivity, catalytic activity, etc.; Using molybdenum trioxide or molybdenum dioxide as molybdenum source oxides to react with phosphorus source to generate molybdenum phosphide can provide high-quality molybdenum elements, thus ensuring the purity and performance of molybdenum phosphide; And it has high reaction activity, making the reaction process more efficient while reducing the generation of by-products; The thermal decomposition temperature of sodium hypophosphite is moderate, usually it can decompose to produce phosphine at about 200 °C, which makes the reaction process relatively mild and easy to control; At the same time, the decomposition product phosphine of sodium hypophosphite has high reaction activity and can react quickly with the molybdenum source to generate the target product molybdenum phosphide, improving the reaction efficiency.

[0013] Further, the heating in the atmosphere of reducing gas includes: Introduce argon-hydrogen mixed gas at a flow rate of 60 ml / min to 100 ml / min, where the hydrogen content accounts for 7% to 10%; Heat up to 600 °C to 1000 °C at a heating rate of 5 °C / min to 8 °C / min and keep it for 1 h to 3 h.

[0014] In the above solution, the argon-hydrogen mixed gas, as a reducing atmosphere, can effectively prevent the oxidation of the material surface during the heating process; Hydrogen has reducibility and can react with the oxides on the material surface to reduce them to metals or low-valent compounds, which helps to remove impurities on the material surface and improve the purity of the material; By adjusting the ratio of argon and hydrogen, the reducibility and inertness of the atmosphere can be precisely controlled. Argon, as an inert gas, can dilute hydrogen, lower its explosion limit, and improve the safety of operation; Controlling the heating rate can ensure that the material is heated evenly during the heating process, avoiding problems such as excessive thermal stress and material cracking caused by too fast heating; Through precise temperature control, it can ensure that the material reacts within a specific temperature range, thus obtaining a material with specific structure and properties.

[0015] Further, the titanium source is titanium tetraisopropoxide; the nitrogen source is ammonia gas; the inert gas is argon or nitrogen.

[0016] In the above solution, titanium tetraisopropoxide is a high-purity titanium source with a stable molecular structure, which is not prone to hydrolysis or decomposition reactions, thus ensuring a stable supply of titanium elements during the deposition process; its chemical properties are relatively stable, so the reaction conditions can be more easily controlled during the deposition process, which helps to form a uniform and dense titanium nitride layer during the deposition process; ammonia is a nitrogen source with relatively high activity and can undergo an efficient nitridation reaction with the titanium source to generate a high-quality titanium nitride layer; argon and nitrogen are both inert gases and will not react with the titanium source or nitrogen source during the deposition process, thus playing a role of protective atmosphere and preventing the titanium nitride layer from being oxidized or contaminated.

[0017] Further, the source bottle temperature of the titanium source is 50°C to 80°C; the nitrogen source flow rate is 1.0 sccm to 3.0 sccm; the inert gas flow rate is 60.0 sccm to 100.0 sccm.

[0018] In the above solution, the temperature control of the source bottle can ensure that the titanium source evaporates at a stable rate, thus providing a continuous and uniform supply of the titanium source and preventing the titanium source from decomposing or agglomerating during the evaporation process, thereby maintaining the chemical stability and activity of the titanium source, which helps to ensure the effective utilization of titanium elements during the deposition process and the high quality of the titanium nitride layer; the control of the nitrogen source flow rate can precisely control the rate of the nitridation reaction, which helps to form a titanium nitride layer with a specific thickness and structure during the deposition process to meet different application requirements; an appropriate nitrogen source flow rate can ensure that the nitrogen element content in the titanium nitride layer is moderate, thereby optimizing the hardness, wear resistance, corrosion resistance and other properties of the titanium nitride layer. An excessive nitrogen source may cause the nitrogen element content in the titanium nitride layer to be too high, forming unnecessary nitride impurities; controlling the inert gas flow rate can form a stable protective atmosphere. An appropriate inert gas flow rate can promote gas flow and heat transfer during the deposition process, thereby improving the deposition efficiency, and can also carry away the heat and by-products generated during the deposition process, thereby improving the uniformity of the deposited layer, which helps to ensure the uniform distribution and consistent properties of the titanium nitride layer on the entire substrate surface.

[0019] Further, the preparation of the titanium nitride layer by plasma-assisted cyclic deposition includes: Maintaining the chamber vacuum at 0.1 Torr to 0.2 Torr, and preparing the titanium nitride layer by cyclic deposition 1000 to 3000 times under the condition that the chamber temperature is 300°C to 400°C. Each cycle period is successively passing a titanium source pulse for 0.1 s to 0.3 s, standing still for 10 s to 15 s, passing the nitrogen source and turning on the plasma generator for reaction for 10 s to 20 s, and purging the waste gas for 30 s to 40 s; after completion, cooling down to 80°C to 100°C.

[0020] In a second aspect, the present invention also provides a method for preparing a cathode material for a battery, comprising: grinding and mixing the molybdenum phosphide / titanium nitride composite material prepared by the method described in the first aspect with a binder in a mass ratio of 8:2.

[0021] In the above solution, titanium nitride has an electron-rich charge transfer ability and good electrical conductivity, which can effectively promote electron transfer, thereby improving the charge and discharge rate and overall performance of the battery. Moreover, it has high capacity and the characteristic of maintaining a stable structure during charge and discharge. Its application in the cathode material of lithium-ion batteries can improve the energy density and power density of the battery; molybdenum phosphide also has high electrical conductivity, and the electron transfer efficiency between phosphorus atoms and molybdenum atoms in its metal phosphide structure is relatively high. Its high catalytic activity and high specific surface area contribute to enhancing the energy storage capacity and power output of the composite material; when molybdenum phosphide is combined with titanium nitride, the two produce a synergistic effect. The molybdenum phosphide / titanium nitride composite material, as a cathode material for a battery, exhibits higher energy density, longer cycle life, and better rate performance, which helps to improve the overall performance of the battery and meet the requirements for high-performance batteries in fields such as electric vehicles and energy storage systems.

[0022] Further, the binder is polyvinylidene fluoride.

[0023] Polyvinylidene fluoride has extremely high viscosity and can effectively bond the positive or negative electrode active materials, conductive agents, and current collectors in the battery tightly together. This excellent bonding performance helps to ensure that the active materials are not easily detached during the charge and discharge process of the battery, thereby improving the cycle stability and service life of the battery; it has excellent anti-aging, chemical resistance, weather resistance, and ultraviolet radiation resistance, etc., can resist the erosion of the electrolyte, does not dissolve, has little swelling, and maintains good bonding performance in an organic electrolyte environment; it can also improve the safety of the battery.

[0024] In a third aspect, the present invention provides a lithium-carbon dioxide battery, and the positive electrode of the battery is the cathode material prepared by the method described in the second aspect uniformly coated on a carbon material substrate.

[0025] In the above solution, molybdenum phosphide, as a transition metal-based material, can effectively catalyze the decomposition of lithium carbonate, thereby reducing the charging voltage of the battery, improving the cycle stability and rate performance of the battery, and showing good electrocatalytic performance in lithium-carbon dioxide batteries; titanium nitride has good electrical conductivity and stability, which can further enhance the electrocatalytic performance of the composite material; the combination of molybdenum phosphide and titanium nitride can form a stable structure to prevent the structural change of the material during charge and discharge, thereby prolonging the service life of the battery. The carbon material substrate provides good support and electrical conductivity, which helps to maintain the stability and performance of the composite material; applying the molybdenum phosphide / titanium nitride composite material on the carbon material substrate can optimize the cathode structure of the battery and improve the energy density and power density of the battery; at the same time, the carbon material substrate also has a certain cost advantage, making the cost of the entire cathode material more controllable.

[0026] Further, the battery is a button battery, which is stacked in the order of a negative electrode case, a shrapnel, a gasket, a lithium sheet, a separator, a positive electrode, a stainless steel mesh, and a positive electrode case, and then compacted to obtain.

[0027] In the above solution, stacking the battery components in a specific order can ensure that the components inside the battery are closely arranged, reduce space waste, and make the battery structure more compact. The compact structure and optimized component arrangement help to reduce the ineffective space inside the battery, thereby increasing the energy density of the battery; this stacking method can also simplify the battery assembly process, reduce the production difficulty and cost, and is also convenient for disassembling and maintaining the battery when needed; the compact structure and standardized component arrangement help to realize the automated production and detection of the battery, further improving the production efficiency and quality stability.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention first oxidizes a molybdenum source compound with a strong acid to obtain molybdenum oxide, then phosphates it with sodium hypophosphite to obtain molybdenum phosphide, and then uses atomic layer deposition technology to deposit a titanium nitride conductor layer on the molybdenum phosphide to prepare molybdenum phosphide / titanium nitride. Combining the stable catalytic performance of molybdenum phosphide as a transition metal phosphide and the excellent electrical conductivity of titanium nitride as a conductor, the two act synergistically to exhibit high catalytic activity, high electrical conductivity, and excellent stability, making it widely used in fields such as batteries, microelectronics, and aerospace; Using this molybdenum phosphide / titanium nitride composite material as the cathode material of the battery and applying it to a lithium battery shows higher energy density, longer cycle life, and better rate performance, which helps to improve the overall performance of the battery and meet the requirements for high-performance batteries in fields such as electric vehicles and energy storage systems; The present invention provides a method for preparing molybdenum phosphide / titanium nitride composite materials, and for the first time, it is used as a positive electrode catalyst for lithium-carbon dioxide batteries, enabling the lithium-carbon dioxide batteries to have a lower charging potential, which is beneficial to reducing battery polarization and extending the service life of the batteries. Description of the Drawings

[0029] Figure 1 Scanning electron micrograph of the molybdenum phosphide / titanium nitride composite material prepared in Example 1; Figure 2 X-ray diffraction pattern of the molybdenum phosphide / titanium nitride composite material prepared in Example 1; Figure 3 X-ray photoelectron spectroscopy pattern of Ti 2p in the molybdenum phosphide / titanium nitride composite material prepared in Example 1; Figure 4 X-ray photoelectron spectroscopy pattern of N 1s in the molybdenum phosphide / titanium nitride composite material prepared in Example 1; Figure 5 Transmission electron micrograph of the molybdenum phosphide / titanium nitride composite material prepared in Example 1; Figure 6 Schematic structural diagram of the lithium-carbon dioxide battery described in Example 5; Figure 7 Rate charge-discharge curves of the lithium-carbon dioxide battery in Example 5 at current densities of 50, 100, 200, 300, 400, and 500 mA·g-1; Figure 8 Cyclic charge-discharge curve of the lithium-carbon dioxide battery in Example 5 at a current density of 250 mA·g-1.

[0030] In the figure: 1, negative electrode case; 2, shrapnel; 3, gasket; 4, lithium sheet; 5, separator; 6, positive electrode; 7, stainless steel mesh; 8, perforated positive electrode case. Detailed Description of the Embodiments

[0031] The preferred embodiments of the present invention will be described in more detail below in conjunction with the drawings and specific embodiments.

[0032] Example 1: This example provides a method for preparing a molybdenum phosphide / titanium nitride composite material, including the following steps: Take 20 ml of concentrated nitric acid and dissolve it in 60 ml of deionized water to obtain a nitric acid solution; weigh 2 g of ammonium molybdate and add it to the nitric acid solution, and ultrasonically vibrate for 3 min to obtain a mixed solution A.

[0033] Add the mixed solution A into a 150 ml polytetrafluoroethylene liner, seal it with a reaction kettle and then put it into an oven. Heat it from 25 °C to 180 °C at a rate of 5 °C / min and keep it warm for 24 h. After the hydrothermal reaction, filter the mixed solution in the polytetrafluoroethylene liner to obtain a white precipitate. Place the white precipitate in an oven at 60 °C for drying to obtain white molybdenum trioxide powder.

[0034] Take 100 mg of molybdenum trioxide powder and 4000 mg of sodium hypophosphite and place them in two porcelain boats respectively. The porcelain boat containing sodium hypophosphite is placed upstream of the tubular furnace, and the porcelain boat containing molybdenum trioxide is placed downstream of the tubular furnace. Introduce an argon-hydrogen mixed gas at a flow rate of 80 ml / min, in which the hydrogen content is 10%, and heat it to 800 °C at a heating rate of 5 °C / min and keep it warm for 2 h to phosphorate the molybdenum trioxide. After the reaction, cool it naturally to room temperature to obtain black molybdenum phosphide powder.

[0035] Place the obtained black molybdenum phosphide powder in the cavity of an atomic deposition equipment. Use titanium tetraisopropoxide (C 12 H 28 O 4 Ti) as the titanium source, high-purity argon as the carrier gas, and ammonia (NH 3 ) as the nitrogen source to react through a 250 W radio frequency plasma generator. Set the temperature of the C 12 H 28 O 4 Ti source bottle to 75 °C, the argon flow rate to 80.0 sccm, and the ammonia flow rate to 2.0 sccm, and keep the cavity vacuum at 0.15 Torr (1 Torr = 1.33×10 2 Pa). Under the condition of a chamber temperature of 350 °C, prepare a titanium nitride layer through 1000 cycles of deposition. Each cycle is successively passing the C 12 H 28 O 4 Ti pulse for 0.2 s, standing still for 10 s, introducing NH3 and turning on the plasma generator to react for 20 s, purging the waste gas for 30 s. After completion, cool it to 100 °C and take it out to obtain molybdenum phosphide / titanium nitride powder, that is, the molybdenum phosphide / titanium nitride composite material.

[0036] Figure 1 This is the scanning electron microscope image of the molybdenum phosphide / titanium nitride composite material prepared in this example. It can be seen from the figure that the molybdenum phosphide / titanium nitride is a rod-shaped composite with an uneven surface, which can provide a large active specific surface area.

[0037] Figure 2X-ray diffraction pattern of the molybdenum phosphide / titanium nitride composite material prepared in this example. It can be seen from the figure that the composite material has typical molybdenum phosphide peaks, indicating that the composite material contains molybdenum phosphide. However, due to the thin titanium nitride layer, it cannot be reflected in the X-ray diffraction pattern.

[0038] Figure 3 X-ray photoelectron spectroscopy of Ti 2p in the molybdenum phosphide / titanium nitride composite material prepared in this example. It can be seen from the figure that the material has the binding energy of Ti-N bonds, indicating that the composite material contains TiN.

[0039] Figure 4 X-ray photoelectron spectroscopy of N 1s in the molybdenum phosphide / titanium nitride composite material prepared in this example. It can be seen from the figure that the material has the binding energy of Ti-N bonds, indicating that the composite material contains TiN.

[0040] Figure 5 Transmission electron microscopy image of the molybdenum phosphide / titanium nitride composite material prepared in this example. It can be seen from the figure that the composite material has a heterojunction structure, which can prove that a layer of titanium nitride is deposited on the outside of molybdenum phosphide by atomic deposition.

[0041] Example 2: This example provides a method for preparing a molybdenum phosphide / titanium nitride composite material, which includes the following steps: Take 20 ml of concentrated nitric acid and dissolve it in 80 ml of deionized water to obtain a nitric acid solution. Weigh 3 g of ammonium molybdate and add it to the nitric acid solution, and ultrasonically vibrate for 5 min to obtain a mixed solution A.

[0042] Add the mixed solution A into a 150-ml polytetrafluoroethylene inner liner, seal it with a reaction kettle, and then put it into an oven. Heat it from 25 °C to 180 °C at a rate of 5 °C / min and keep it warm for 24 h; after the hydrothermal reaction, filter the mixed solution in the polytetrafluoroethylene inner liner to obtain a white precipitate; place the white precipitate in an oven at 60 °C for drying to obtain white molybdenum trioxide powder.

[0043] Take 100 mg of molybdenum trioxide powder and 4000 mg of sodium hypophosphite and place them in two porcelain boats respectively. The porcelain boat containing sodium hypophosphite is placed upstream of the tube furnace, and the porcelain boat containing molybdenum trioxide is placed downstream of the tube furnace. Pass 60 ml / min of argon-hydrogen mixed gas, in which the hydrogen content is 8%, and heat it to 1000 °C at a heating rate of 5 °C / min and keep it warm for 1 h to phosphorate the molybdenum trioxide. After the reaction, cool it naturally to room temperature to obtain black molybdenum phosphide powder.

[0044] Place the obtained black molybdenum phosphide powder in the cavity of the atomic deposition equipment, and use titanium tetraisopropoxide (C 12 H 28 O 4Titanium is used as the titanium source, high-purity argon is used as the carrier gas, and ammonia (NH 3 is used as the nitrogen source, and the reaction is carried out by a 250 W radio frequency plasma generator; set C 12 H 28 O 4 The temperature of the titanium source bottle is 70 °C, the argon flow rate is 70.0 sccm, and the ammonia flow rate is 3.0 sccm, so that the chamber vacuum is maintained at 0.2 Torr (1 Torr = 1.33×10 2 Pa), and cyclic deposition is carried out 3000 times at a chamber temperature of 350 °C. Each cycle is successively passing C 12 H 28 O 4 Ti pulse for 0.1 s, standing for 12 s, passing NH 3 and turning on the plasma generator to react for 10 s, purging the waste gas for 35 s. After completion, it is cooled to 90 °C and taken out to obtain molybdenum phosphide / titanium nitride powder, that is, the molybdenum phosphide / titanium nitride composite material.

[0045] Example 3: This example provides a method for preparing a molybdenum phosphide / titanium nitride composite material, including the following steps: Take 20 ml of concentrated nitric acid and dissolve it in 100 ml of deionized water to obtain a nitric acid solution. Weigh 2.8 g of ammonium molybdate and add it to the nitric acid solution, and ultrasonically vibrate for 4 min to obtain a mixed solution A.

[0046] Add the mixed solution A into a 150 ml polytetrafluoroethylene inner liner, seal it with a reaction kettle and put it into an oven, and heat it from room temperature to 200 °C at a rate of 3 °C / min and keep it warm for 20 h; after the hydrothermal reaction, filter the mixed solution in the polytetrafluoroethylene inner liner to obtain a white precipitate; place the white precipitate in an oven at 60 °C for drying to obtain white molybdenum trioxide powder.

[0047] Take 100 mg of molybdenum trioxide powder and 4000 mg of sodium hypophosphite and place them in two porcelain boats respectively. The porcelain boat containing sodium hypophosphite is placed upstream of the tube furnace, and the porcelain boat containing molybdenum trioxide is placed downstream of the tube furnace. Pass 100 ml / min of argon-hydrogen mixed gas, in which the hydrogen content accounts for 7%, and heat it to 900 °C at a heating rate of 5 °C / min and keep it warm for 1.5 h to phosphorate the molybdenum trioxide. After the reaction, it is naturally cooled to room temperature to obtain black molybdenum phosphide powder.

[0048] Place the obtained black molybdenum phosphide powder in the cavity of the atomic deposition equipment, and use titanium tetraisopropoxide (C 12 H 28 O 4 Ti) as the titanium source, high-purity argon as the carrier gas, ammonia (NH 3) as nitrogen source, and reacted by a 250 W radio frequency plasma generator; C 12 H 28 O 4 The temperature of the Ti source bottle was 80°C, the argon flow rate was 90.0 sccm, and the ammonia flow rate was 1.0 sccm, so that the vacuum degree of the chamber was maintained at 0.1 Torr (1 Torr = 1.33 × 10 2 Pa), and the chamber temperature was 400 ° C for 1500 cycles of deposition. Each cycle was followed by the introduction of C 12 H 28 O 4 Ti pulse 0.15s, stand for 15s, pass NH 3 The plasma generator was turned on for 15 seconds to react and the exhaust gas was purged for 40 seconds. After completion, the temperature was lowered to 80° C. and taken out to obtain molybdenum phosphide / titanium nitride powder, namely the molybdenum phosphide / titanium nitride composite material.

[0049] Embodiment 4: This embodiment provides a method for preparing a positive electrode material for a battery, comprising the following steps: The molybdenum phosphide / titanium nitride powder prepared in Example 1 and polyvinylidene fluoride were added into a grinding mortar at a mass ratio of 8:2, mixed and ground to obtain a mixed material, i.e., a positive electrode material for a battery.

[0050] Embodiment 5: This embodiment provides a lithium-carbon dioxide battery, the positive electrode of which is obtained by evenly coating the positive electrode material prepared in Example 4 on a carbon material substrate.

[0051] Specifically, the preparation method of the battery includes the following steps: 0.2 mg of battery positive electrode material was evenly spread on a 1×1 cm square carbon cloth to obtain a lithium-carbon dioxide battery positive electrode; like Figure 6 As shown, the negative electrode shell 1, the spring sheet 2, the gasket 3, the lithium sheet 4, the separator 5, the positive electrode 6, the stainless steel mesh 7 and the positive electrode shell with holes 8 are stacked in order and compacted with a hydraulic press to obtain a button battery.

[0052] The button cell obtained above was placed in a test box with a carbon dioxide atmosphere and subjected to a rate test with a current density of 50-500 mA / g and a cut-off capacity of 500 mAh / g. The test results are as follows: Figure 7As shown, as the current density increases, the charging potential of the battery gradually increases and the polarization becomes larger. However, it is still less than 4.25 V under the condition of 500 mAh / g. When the current density is less than 200 mAh / g, the charging potential is less than 3 V, with an extremely low charging potential and a very small overpotential, which is beneficial to the long-cycle stability of the battery. A cycle test was carried out at a current density of 250 mA / g and a cut-off capacity of 500 mAh / g. The test results are as Figure 8 shown. When the charging potential is less than 4.25 V, the battery cycled 62 times, having good cycle stability while having a relatively low charging potential.

[0053] The embodiments of the present invention have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those of ordinary skill in the art without departing from the scope and technical principle of the described embodiments. These modifications and changes should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a molybdenum phosphide / titanium nitride composite material, characterized in that: include: Adding a molybdenum source compound into a strong acid solution and completely dissolving the compound to obtain a mixed solution A; Adding the mixed solution A into the polytetrafluoroethylene liner and heating it in a sealed reaction space to obtain a molybdenum source oxide; The obtained molybdenum source oxide is placed downstream of the tube furnace, and the phosphorus source compound is placed upstream of the tube furnace, and heated in an atmosphere of reducing gas to obtain molybdenum phosphide; the mass ratio of the molybdenum source compound to the phosphorus source compound is 1: (40-80); The obtained molybdenum phosphide is placed in the chamber of an atomic deposition device equipped with a titanium source and a nitrogen source, and an inert gas is used as a carrier gas to prepare a titanium nitride layer through plasma-assisted cyclic deposition. After the reaction is completed, a molybdenum phosphide / titanium nitride composite material is obtained.

2. The method for preparing the molybdenum phosphide / titanium nitride composite material according to claim 1, characterized in that: The strong acid is concentrated nitric acid or concentrated sulfuric acid, and the volume ratio of deionized water to strong acid in the strong acid solution is (5-2):1; the mass ratio of the molybdenum source compound to the strong acid solution is 1:(30-50).

3. The method for preparing the molybdenum phosphide / titanium nitride composite material according to claim 1, characterized in that: The molybdenum source compound is any one or more of ammonium molybdate, ammonium molybdate tetrahydrate or ammonium molybdate hexahydrate; The phosphorus source compound is sodium hypophosphite; The molybdenum source oxide is molybdenum trioxide or molybdenum dioxide.

4. The method for preparing the molybdenum phosphide / titanium nitride composite material according to claim 1, characterized in that: The heating under a reducing gas atmosphere comprises: Introduce argon-hydrogen mixed gas at a rate of 60ml / min~100ml / min, of which the hydrogen content accounts for 7%~10%; Increase the temperature to 600℃~1000℃ at a rate of 5℃ / min~8℃ / min and keep it at this temperature for 1h~3h.

5. The method for preparing the molybdenum phosphide / titanium nitride composite material according to claim 1, characterized in that: The titanium source is titanium tetraisopropoxide; and / or the nitrogen source is ammonia; and / or the inert gas is argon or nitrogen.

6. The method for preparing the molybdenum phosphide / titanium nitride composite material according to claim 5, characterized in that: The source bottle temperature of the titanium source is 50° C. to 80° C.; and / or the flow rate of the nitrogen source is 1.0 sccm to 3.0 sccm; and / or the flow rate of the inert gas is 60.0 sccm to 100.0 sccm.

7. The method for preparing the molybdenum phosphide / titanium nitride composite material according to claim 1, characterized in that: The method of preparing the titanium nitride layer by plasma-assisted cyclic deposition comprises: The vacuum degree of the chamber is maintained at 0.1 Torr ~ 0.2 Torr, and the titanium nitride layer is prepared by 1000 ~ 3000 cycles of deposition at a chamber room temperature of 300 ° C ~ 400 ° C. Each cycle period is to introduce a titanium source pulse for 0.1 s ~ 0.3 s, stand for 10s ~ 15s, introduce a nitrogen source and start the plasma generator to react for 10s ~ 20s, and purge the exhaust gas for 30s ~ 40s; after completion, the temperature is lowered to 80 ° C ~ 100 ° C.

8. A method for preparing a positive electrode material for a battery, characterized in that: include: The molybdenum phosphide / titanium nitride composite material prepared by the method according to any one of claims 1 to 7 is ground and mixed with a binder at a mass ratio of 8:

2.

9. The method for preparing a positive electrode material for a battery according to claim 8, characterized in that: The binder is polyvinylidene fluoride.

10. A lithium-carbon dioxide battery, characterized in that: The positive electrode of the battery is prepared by evenly coating the positive electrode material prepared by the method of claim 8 on a carbon material substrate.

11. The lithium-carbon dioxide battery according to claim 10, characterized in that: The battery is a button-type battery, which is manufactured by stacking and compacting a negative electrode shell, a spring sheet, a gasket, a lithium sheet, a separator, a positive electrode, a stainless steel mesh and a positive electrode shell in this order.

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