CN108321375B - In-situ doped nano-molybdenum-based material, preparation method and use - Google Patents

Abstract

The invention discloses an in-situ doped nano-molybdenum-based material, a preparation method and use thereof, belonging to the field of lithium ion battery preparation. , strontium chloride and phosphoric acid are used as starting materials, and a manganese-substituted organic-inorganic hybrid phosphomolybdate material is synthesized by a medium-temperature hydrothermal one-pot synthesis method. Using the modified phosphomolybdate derivatives as precursors, porous doped nano-molybdenum-based composites were successfully prepared by high temperature firing in nitrogen atmosphere. The in-situ doping of various elements improves the activity and stability of the material surface and fundamentally improves the electrochemical performance. In addition, the coral-shaped porous nanostructures formed by the precursor method can control the morphology, particle size distribution, specific surface area and tap density of molybdenum-based materials, thereby improving the performance of lithium-ion batteries. After 300 cycles at a high current density of 500 mA/g, the reversible capacity of the lithium-ion capacitor battery is still higher than 95%.

Description

In-situ doped nano-molybdenum-based material, preparation method and use

technical field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to an in-situ doped nano-molybdenum-based material, a preparation method and an application thereof.

Background technique

As a new generation of clean energy, lithium-ion batteries have significant advantages such as small size, large storage energy, high operating voltage, long cycle life, and no memory effect. They are widely used in smart phones, notebook computers, digital cameras, electronic watches and other fields. .

As a key part of lithium-ion batteries, electrode materials account for more than 50% of the cost of the entire battery. At present, graphite is a commonly used anode material for commercial lithium-ion batteries, but the energy density and power density of graphite are low, and its low lithium intercalation potential is also prone to safety problems. A negative electrode material with lithium intercalation potential is very necessary. Compared with graphite, transition metal oxides, tin-based, and silicon-based anode materials have attracted widespread attention in recent years due to their high specific capacity, high potential, and abundant reserves. However, these negative electrode materials will experience large expansion and contraction in volume when lithium is deintercalated. Large volume changes will lead to changes in the internal stress of the particles, resulting in particle cracking and pulverization, and the active material will peel off from the current collector. And the loss of electrical contact between the active material and the current collector causes capacity fading. Due to the volume expansion of the electrode material, it cannot generate a stable solid electrolyte interface (SEI) in the electrolyte. During the cycle, the electrolyte is continuously consumed to form a new SEI layer, resulting in low reversible capacity and poor electrode performance. Cyclic Stability. To this end, various strategies have been adopted to improve the electrochemical performance of such anode materials: (1) To obtain more space through nanostructure design to buffer the stress caused by volume expansion. For example: hollow structure, porous structure, eggshell structure, etc. (2) Buffer stress by compounding with other flexible materials, such as constructing a compound with carbon, graphene, carbon nanotubes, etc. In this paper, the structure design and preparation strategy of this type of volume-expandable lithium battery anode material will be described in combination with the research progress in this field in recent years. (3) The existing materials are modified and modified by doping and surface coating, and the multi-component composite materials with amorphous or porous structure are prepared by using the synergistic effect of various conductive materials. However, the current strategy can only achieve the purpose of improving the electrochemical performance of the material by changing its morphology and particle size distribution. It is difficult to control the amount of coating and doping, as well as the uniformity of the surface, so as to fundamentally regulate and improve the electrode material. compatibility performance.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies of the prior art, and to provide an in-situ doped nano-molybdenum-based material, a preparation method and an application.

For achieving the above object, the technical scheme adopted in the present invention is as follows:

A preparation method of an in-situ doped nano-molybdenum-based material, comprising the following steps:

S1, using 1,6-bis(triazole) hexane, ammonium heptamolybdate, manganese chloride, strontium chloride and phosphoric acid as starting materials, using water as a solvent, mixing and stirring for 60min, adjusting the pH value to be 3 to 4, to obtain a mixed solution, wherein the molar ratio of the 1,6-bis(triazole)hexane, ammonium heptamolybdate, manganese chloride, strontium chloride, phosphoric acid and water is 1:2:4 :3:30:2000～2500;

S2, transfer the mixed solution obtained in S1 to the reaction kettle, and react at 160° C. for 4 to 6 days. After the reaction is completed, naturally cool to room temperature to obtain a dark blue polyacid precursor;

S3. The precursor obtained in S2 is washed, filtered, dried, and calcined at 600-700 ° C for 6-8 h in a tube furnace under the protection of inert gas. After the calcination is completed, it is naturally cooled to room temperature to obtain a calcined product. Then, the calcined product is ground for 30-50 minutes and passed through a 400-mesh sieve to obtain an in-situ doped nano-molybdenum-based lithium ion battery negative electrode material.

The present invention is also characterized in that the inert gas in S3 is N ₂ .

Another technical solution of the present invention is to provide an in-situ doped nano-molybdenum-based material prepared by the above method.

Another technical solution of the present invention is to provide the use of the above-mentioned in-situ doped nano-molybdenum-based material as a negative electrode material for a lithium ion battery.

The present invention is also characterized in that the process of using the in-situ doped nano-molybdenum-based material as a negative electrode material for a lithium ion battery includes the following steps: adding the in-situ doped nano-molybdenum-based material, a conductive agent and a binder into an appropriate amount of solvent Mix evenly to make the mixture into a paste, then coat it on the current collector, and dry it at 80 to 120 ° C for 6 to 12 hours to obtain a lithium-ion battery negative electrode material, wherein the in-situ doped nano-molybdenum-based material, the conductive agent and the adhesive The mass ratio of the binder is 8.0-9.5:0.2-1.0:0.3-1.0.

The present invention is also characterized in that the solvent is N-methyl-2-pyrrolidone (NMP).

The present invention is also characterized in that the conductive agent is one or a combination of two or more selected from acetylene black, carbon nanotubes and graphene.

The present invention is also characterized in that the binder is polyvinylidene fluoride.

The present invention is also characterized in that the current collector is one of copper foil and nickel foam.

The advantages and positive effects that the present invention has are:

The invention utilizes a medium-temperature hydrothermal one-pot synthesis method to synthesize a manganese-substituted organic-inorganic hybrid phosphomolybdate material. Using the modified phosphomolybdate derivatives as precursors, porous doped nano-molybdenum-based composites were successfully prepared by high temperature firing in nitrogen atmosphere. The in-situ doping of various elements improves the activity and stability of the material surface and fundamentally improves the electrochemical performance. In addition, the uniform and porous nanostructures formed by the precursor method realize the regulation of the morphology, particle size distribution, specific surface area, and tap density of molybdenum-based materials, thereby improving the performance of lithium-ion batteries. This in-situ doped nano-molybdenum-based material was used as a negative electrode material for lithium-ion batteries and assembled into a CR2025 button battery, which showed high discharge specific capacity (1108mAh/g), rate performance and good cycle performance. After 300 cycles at a high current density of 500mA/g, the capacity of the lithium-ion capacitor battery is still higher than 95%. Its electrode performance is better than that of currently commonly used electrode materials.

Description of drawings

Figure 1 is a SEM image of the in-situ doped nano-Mo-based material.

Fig. 2 is a charge-discharge curve diagram of the in-situ doped nano-molybdenum-based material at a current density of 100 mA/g for the 10th cycle.

Figure 3 is a graph showing the rate performance of the in-situ doped nano-Mo-based material at current densities of 100, 200, 500, 800, and 1000 mA/g.

Figure 4 shows the cycle performance of the in-situ doped nano-Mo-based material at a high current density of 500 mA/g for 300 cycles.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

In the following examples, the prepared lithium ion battery negative electrode material is used as the working electrode, the lithium sheet is the counter electrode, and 1MLiPF ₆ (1:1:1 volume ratio of ethylene carbonate, dimethyl carbonate and diethyl carbonate is mixed solvent) as the electrolyte, Celgard 2500 as the separator, and assembled together to form a CR2025 button cell, wherein the active material loading of the working electrode is 1-3 mg/cm ^-2 .

Example 1

An in-situ doped nano-molybdenum-based material provided by an embodiment of the present invention, the preparation method of which specifically includes the following steps:

S1. Using 0.2200g of 1,6-bis(triazole)hexane, 2.4000g of ammonium heptamolybdate, 0.6475g of manganese chloride, 0.7999g of strontium chloride and 2.00mL of phosphoric acid as starting materials, and 36.00mL of water As a solvent, mix and stir for 60min, and adjust the pH value with sodium hydroxide to be 3 to obtain a mixed solution;

S2, transfer the mixed solution obtained in S1 into the reactor, react at 160 ° C for 4 days, after the reaction is completed, naturally cool to room temperature to obtain the precursor reactant crystal;

S3. The precursor reactant crystals obtained in S2 are washed, filtered, dried, and calcined at 600 °C for 8 h in a tube furnace under the protection of N ₂ . After the calcination is completed, naturally cool to room temperature to obtain a calcined product, The calcined product was ground for 30 minutes and passed through a 400-mesh sieve to obtain an in-situ doped nano-molybdenum-based material.

The process of using the in-situ doped nano-molybdenum-based material as the negative electrode material of a lithium ion battery provided in the embodiment of the present invention specifically includes the following steps: adding 480 mg of the in-situ doped nano-molybdenum-based lithium ion battery negative electrode material, 60 mg of acetylene black and 60 mg of polymer Vinylidene fluoride was added to an appropriate amount of NMP to make the mixture into a paste, which was then coated on copper foil and dried at 80°C for 12 hours to obtain a negative electrode material for lithium ion batteries.

Example 2

An in-situ doped nano-molybdenum-based material provided by an embodiment of the present invention, the preparation method of which specifically includes the following steps:

S1. Using 0.2200g of 1,6-bis(triazole)hexane, 2.4000g of ammonium heptamolybdate, 0.6475g of manganese chloride, 0.7999g of strontium chloride and 2.00mL of phosphoric acid as starting materials, and 40.50mL of water As a solvent, mix and stir for 60min, and adjust the pH value with sodium hydroxide to be 3.5 to obtain a mixed solution;

S2, the mixed solution obtained in S1 is transferred to the reactor, reacted at 160 ° C for 5 days, after the reaction is finished, naturally cooled to room temperature to obtain a reaction solution;

S3. The reaction solution obtained in S2 is washed, filtered, dried, and calcined at 650° C. for 7h in a tube furnace under the protection of N ₂ . After the calcination is completed, it is naturally cooled to room temperature to obtain a calcined product. Grind for 40 min, pass through a 400-mesh sieve, and obtain an in-situ doped nano-molybdenum-based material.

The process of using the in-situ doped nano-molybdenum-based material as the negative electrode material of a lithium ion battery provided in the embodiment of the present invention specifically includes the following steps: adding 510 mg of the in-situ doped nano-molybdenum-based lithium ion battery negative electrode material, 54 mg of acetylene black and 36 mg of polymer Vinylidene fluoride was added to an appropriate amount of NMP to make the mixture into a paste, which was then coated on copper foil and dried at 100° C. for 10 hours to obtain a negative electrode material for lithium ion batteries.

Example 3

An in-situ doped nano-molybdenum-based material provided by an embodiment of the present invention, the preparation method of which specifically includes the following steps:

S1. Using 0.2200g of 1,6-bis(triazole)hexane, 2.4000g of ammonium heptamolybdate, 0.6475g of manganese chloride, 0.7999g of strontium chloride and 2.00mL of phosphoric acid as starting materials, and 45.00mL of water As a solvent, mix and stir for 60min, and adjust the pH value with sodium hydroxide to be 4 to obtain a mixed solution;

S2, the mixed solution obtained in S1 is transferred to the reactor, reacted at 160 ° C for 6 days, and after the reaction is finished, naturally cooled to room temperature to obtain a reaction solution;

S3. The reaction solution obtained in S2 is washed, filtered, dried, and calcined at 700° C. for 6 h in a tube furnace under the protection of N ₂ . After the calcination is completed, it is naturally cooled to room temperature to obtain a calcined product. Grind for 50 min, pass through a 400-mesh sieve, and obtain an in-situ doped nano-molybdenum-based material.

The process of using the in-situ doped nano-molybdenum-based material as the negative electrode material of a lithium ion battery provided by the embodiment of the present invention specifically includes the following steps: adding 540 mg of the in-situ doped nano-molybdenum-based lithium ion battery negative electrode material, 30 mg of acetylene black and 30 mg of polymer Vinylidene fluoride was added to an appropriate amount of NMP to make the mixture into a paste, which was then coated on copper foil and dried at 120° C. for 6 hours to obtain a negative electrode material for lithium ion batteries.

In the specific embodiment of the present invention, the morphology of the material is characterized by scanning electron microscope (SEM), and the assembled battery is tested for charge and discharge, rate performance and cycle performance through the Xinwei constant current charge and discharge test system. The potential range was 0.01-3.0 V (vs. Li/Li ⁺ ), and the tested current densities were 100, 200, 500, 800, 1000 mA/g.

Figure 1a and Figure 1b are the SEM images of the in-situ doped nano-Mo-based material at different magnifications, respectively. It can be seen from Figure 1a and Figure 1b that the fired Mo-based material has a coral-like three-dimensional porous surface. The morphology greatly increases the surface area of the material, making it possible to store and release a large amount of charge in a very short period of time.

Fig. 2 is a charge-discharge curve diagram of the in-situ doped nano-molybdenum-based material at a current density of 100 mA/g for the 10th cycle. It can be seen from Figure 2 that the reversible capacity of the in-situ doped nano-Mo-based material after the 10th cycle is 1108 mAh/g.

Figure 3 is a graph showing the rate performance of the in-situ doped nano-Mo-based material at current densities of 100, 200, 500, 800, and 1000 mA/g. It can be seen from Figure 3 that the corresponding reversible capacities of the in-situ doped nano-Mo-based materials at current densities of 100, 200, 500, 800, and 1000 mA/g are 1059, 957, 839, 726, and 652 mAh/g, respectively. .

Figure 4 shows the cycle performance of the in-situ doped nano-Mo-based material at a high current density of 500 mA/g for 300 cycles. It can be seen from Figure 4 that the in-situ doped nano-molybdenum-based material has an initial discharge capacity of 852mAh/g at a large current density of 500mA/g, and after 300 cycles, the discharge capacity remains at 826mAh/g. The retention rate is still above 95%.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (8)

1. a preparation method of in-situ doped nano-molybdenum-based material, is characterized in that, comprises the steps: S1, using 1,6-bis(triazole) hexane, ammonium heptamolybdate, manganese chloride, strontium chloride and phosphoric acid as starting materials, using water as a solvent, mixing and stirring for 60min, adjusting the pH value to be 3 to 4, to obtain a mixed solution, wherein the molar ratio of the 1,6-bis(triazole)hexane, ammonium heptamolybdate, manganese chloride, strontium chloride, phosphoric acid and water is 1:2:4 :3:30:2000～2500; S2, transfer the mixed solution obtained in S1 to the reaction kettle, and react at 160° C. for 4 to 6 days. After the reaction is completed, naturally cool to room temperature to obtain a dark blue polyacid precursor; S3. The precursor obtained in S2 is washed, filtered, dried, and calcined at 600-700 ° C for 6-8 h in a tube furnace under the protection of a nitrogen atmosphere. After the calcination is completed, it is naturally cooled to room temperature to obtain a calcined product. Then, the calcined product is ground for 30-50 minutes and passed through a 400-mesh sieve to obtain an in-situ doped nano-molybdenum-based material. 2. The in-situ doped nano-molybdenum-based material prepared by the method of claim 1. 3. Use of the in-situ doped nano-molybdenum-based material as claimed in claim 2 as a negative electrode material for a lithium ion battery. 4. purposes according to claim 3 is characterized in that, the process that described in-situ doped nano-molybdenum-based material is used as negative electrode material of lithium ion battery specifically comprises the following steps: the in-situ doped nano-molybdenum-based material, The conductive agent and the binder are added to an appropriate amount of solvent and mixed evenly to make the mixture form a paste, which is then coated on the current collector and dried at 80-120 ° C for 6-12 hours to obtain a negative electrode material for a lithium ion battery, wherein the original The mass ratio of site-doped nano-molybdenum-based material, conductive agent and binder is 8.0-9.5:0.2-1.0:0.3-1.0. 5 . The use of the in-situ doped nano-molybdenum-based material as claimed in claim 4 , wherein the solvent is N-methyl-2-pyrrolidone. 6 . 6. The purposes of the in-situ doped nano-molybdenum-based material according to claim 4 as a negative electrode material for a lithium ion battery, wherein the conductive agent is one of acetylene black, carbon nanotubes, and graphene or two or more combinations. 7 . The use of the in-situ doped nano-molybdenum-based material as claimed in claim 4 , wherein the binder is polyvinylidene fluoride. 8 . 8 . The use of the in-situ doped nano-molybdenum-based material as claimed in claim 4 , wherein the current collector is one of copper foil and nickel foam. 9 .

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