Preparation method of mn-ln-mof type lithium ion battery negative electrode material

Abstract

The application belongs to the field of functional material preparation, and particularly relates to a preparation method of a Mn-Ln-MOF type lithium ion battery negative electrode material, which comprises the following steps: (1) dispersing manganese metal powder, rare earth chloride, 3,5-pyrazole dicarboxylic acid monohydrate and lithium hydroxide in an aqueous solution to form a mixed slurry, and stirring under room temperature air atmosphere; (2) transferring the obtained solution to a high-pressure reaction kettle to perform a heating reaction, and naturally cooling to room temperature after the reaction is completed, so as to obtain a light yellow translucent crystal; (3) washing and drying the obtained light yellow translucent crystal to obtain the Mn-Ln-MOF material; and (4) mixing and grinding the obtained Mn-La-MOF material with PVDF, conductive graphite and N-methyl pyrrolidone, uniformly coating the mixture on the surface of a copper foil, and then performing drying and tabletting treatment, so as to obtain the target product. The application has high structural stability, good crystal morphology reproducibility and excellent electrochemical performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of functional material preparation, and particularly relates to a preparation method of Mn-Ln-MOF type lithium ion battery negative electrode material. BACKGROUND

[0002] Lithium ion batteries are widely used in mobile phones, notebook computers, satellites and transportation and are a very promising power source. The materials of lithium ion batteries depend on various chemical reactions. At present, inorganic materials are mainly used, and the commonly used materials include carbon materials, alloy materials and organic materials such as conjugated conductive polymers, sulfur-containing molecules and metal organic framework materials. With the decrease of fossil fuels, lithium ion batteries (LIBs) have attracted more and more attention worldwide due to their high energy density, long cycle life, low cost and flexibility in manufacturing batteries of various shapes and sizes.

[0003] Metal organic framework (MOF) is a new type of organic-inorganic hybrid crystalline porous material, which has the advantages of diverse structure and pore, adjustable size, excellent thermal stability and chemical stability, and potential applications in energy gas storage, catalysis, optics, electricity, magnetism and biomedicine. We have witnessed the rapid development of MOFs, and currently they have been applied in batteries. However, single metal MOF materials usually have the disadvantage of poor structural stability, which hinders their application in the field of electrochemistry to some extent. With the gradual deepening of the commercialization of electrode materials, people's demand for the safety and long cycle stability of new energy batteries is increasing. Lithium iron phosphate has a low capacity but is relatively stable, while the capacity of ternary composite material is high but its safety decreases with the increase of capacity. The safety hidden danger existing in the intercalation lithium storage mechanism also leads many enterprises to still prefer to use lithium iron phosphate with lower capacity but higher safety as the electrode material of new energy batteries. SUMMARY

[0004] The application aims to overcome the deficiencies of the prior art and provide a preparation method of Mn-Ln-MOF type lithium ion battery negative electrode material with high structural stability, good crystal morphology reproducibility and excellent electrochemical performance.

[0005] To solve the above technical problems, the application is implemented as follows:

[0006] A preparation method of Mn-Ln-MOF type lithium ion battery negative electrode material is implemented in the following steps in sequence:

[0007] (1) dispersing manganese metal powder, rare earth chloride, 3, 5-pyrazole dicarboxylic acid monohydrate and lithium hydroxide in an aqueous solution to form a mixed slurry, and stirring under room temperature air atmosphere;

[0008] (2) transferring the solution obtained in step (1) to a high-pressure reaction kettle for heating reaction, and naturally cooling to room temperature after the reaction is completed, to obtain a light yellow translucent crystal;

[0009] (3) washing and drying the light yellow translucent crystal obtained in step (2) to obtain a Mn-Ln-MOF material;

[0010] (4) mixing and grinding the Mn-La-MOF material obtained in step (3) with PVDF, conductive graphite and N-methyl pyrrolidone respectively, and uniformly coating on the surface of a copper foil, and then performing drying and tabletting treatment to obtain the target product.

[0011] Further, in step (1) of the present application, 0.6-0.8 g of 3, 5-pyrazole dicarboxylic acid monohydrate, 0.4-0.6 g of rare earth chloride, 0.1-0.2 g of lithium hydroxide and 0.1-0.2 g of manganese metal powder are dispersed in 18-20 g of deionized water solution, and the above solution is placed in a polytetrafluoroethylene reaction kettle inner container.

[0012] Further, in step (2) of the present application, the solution obtained in step (1) is transferred to a 25 mL high-pressure reaction kettle, and constant temperature heating is performed in an oven at 180-200 DEG C; the reaction time is 48-50 h, and after the reaction is completed, natural cooling to room temperature is performed to obtain a light yellow translucent crystal.

[0013] Further, in step (3) of the present application, the obtained light yellow translucent crystal is washed with deionized water for 2-3 times, and dried under natural conditions for 10-12 h to obtain a Mn-Ln-MOF material.

[0014] Further, in step (4) of the present application, drying is performed in a vacuum drying box with a vacuum degree of -0.1 Mpa at 110 DEG C for 12 h.

[0015] Further, Ln in the Mn-Ln-MOF material of the present application is La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er, Tm or Yb.

[0016] Ln-MOFs are coordination polymers with specific sizes and shapes of cavity structures, formed by the self-assembly of rare-earth ions (lanthanide: Ln) and rigid organic polydentate ligands. They typically possess high-dimensional 2D or 3D structures and permanently open channels. The structure of Ln-MOFs is determined by the structure of secondary building unions (SBUs), which are small structural units formed by coordination groups encapsulating lanthanide metal ions. These SBUs replace the role of the lanthanide ions in Ln-MOFs and directly determine the final topology. Carboxylic acid ligands have significant advantages in constructing Ln-MOFs, such as relatively good solubility, strong coordination ability, high thermal stability of the resulting framework structure, and, more importantly, the participation of the oxygen atom in the carboxyl group in coordination, resulting in diverse coordination modes with metal ions and thus forming a variety of novel Ln-MOF structures. Ln-MOFs have shown particularly outstanding value in fluorescence emission, but reports on their electrochemical applications are rare. my country is a major producer of rare earth elements, so exploring and researching a method for producing rare earth lithium-ion battery anode materials is very inspiring.

[0017] This invention relates to a series of twelve Mn-Ln-MOF (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er, Tm, Yb) lithium-ion battery anode materials and their preparation methods, belonging to the fields of materials chemistry, inorganic synthesis, and energy materials. The materials used are 3,5-pyrazole dicarboxylic acid monohydrate, rare earth chlorides, lithium hydroxide, and manganese metal powder. The synthesized Mn-Ln-MOF materials are excellent anode materials with an extremely stable cubic structure that maintains its stability even after cycling. This extraordinary stability is particularly noteworthy given that direct application of MOF materials to lithium-ion battery anodes often results in phase transitions. Electrochemical tests were conducted on button batteries made from this material, which exhibited interesting electrochemical performance. The first discharge capacity was 1581.2 mAh / g, and the specific capacity began to drop sharply after the second cycle. The discharge specific capacity reached 185.1 mAh / g at the twentieth cycle and bottomed out at 175.98 mAh / g at the thirtieth cycle. After that, it began to rise steadily, and the discharge specific capacity was 182.75 mAh / g at the fiftieth cycle. After 100 cycles, the charging capacity dropped to 230.28 mAh / g.

[0018] The process of this invention is simple and has good reproducibility, resulting in a novel Mn-La-MOF material with excellent morphology and structure and novel electrochemical performance. Utilizing the inherent structural characteristics of the 3d-4f cubic single crystal, it effectively prevents structural collapse caused by continuous insertion and extraction, thus exhibiting extremely high safety and long-cycle stability. This provides a solid foundation for further development by enterprises and has greater application value. Furthermore, most of the energy storage is contributed by the capacitance provided by rare earth elements; this mechanism is believed to provide a better basis for further modification to enhance its performance, particularly in areas such as fast charging.

[0019] my country is a major province for rare earth elements, but rare earth itself is not rare; what is rare is how to put it into practical use and achieve real-world applications. Among rare earth materials, La and Ce are relatively inexpensive. If they can be effectively applied to the development of the times and the advancement of science and technology, it would be a win-win situation. Our designed and manufactured Mn-Ln-MOF lithium-ion battery anode material system, based on a cubic structure and stable cycle performance of independent single crystals, will bring a new option to the market. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The scope of protection of the present invention is not limited to the following description.

[0021] Figure 1 This is a microscopic image of the Mn-La-MOF crystal morphology of the present invention.

[0022] Figure 2 The image shows the XRD characterization of the Mn-La-MOF single crystal of this invention.

[0023] Figure 3 Here is a SEM characterization image of the Mn-La-MOF of this invention;

[0024] Figure 4 This is a constant current charge-discharge cycle curve of the Mn-La-MOF of the present invention. Detailed Implementation

[0025] As shown in the figure, the preparation method of Mn-Ln-MOF type lithium-ion battery anode material is carried out in the following steps:

[0026] (1) Manganese metal powder, rare earth chloride, 3,5-pyrazole dicarboxylic acid monohydrate, and lithium hydroxide were dispersed in an aqueous solution, and the solution was placed in a polytetrafluoroethylene reactor. The resulting slurry was stirred for 30 min at room temperature in an air atmosphere;

[0027] (2) Transfer the mixture after stirring in step (1) to a 25 mL high-pressure reactor and react at 180-200 °C for 48-50 h. After the reaction is completed, allow it to cool naturally to room temperature to obtain pale yellow translucent crystals.

[0028] (3) Wash the pale yellow translucent crystals obtained in step (2) with deionized water 2 to 3 times, and dry them under natural conditions for 10 to 12 hours to obtain Mn-La-MOF material;

[0029] (4) Grind the Mn-La-MOF material, PVDF (polyvinylidene fluoride), conductive graphite, and N-methylpyrrolidone (NMP) obtained in step (3) thoroughly. Apply the resulting slurry evenly to the cleaned copper foil surface using a tool. Then, place the coated electrode sheet in a vacuum drying oven (-0.1 MPa) at 90°C for 12 hours. After cooling to room temperature, remove the electrode sheet, weigh it, wrap it in paper, and press it under 10 MPa pressure for 30 seconds on a tablet press to prevent the material from falling off during weighing and installation. Current surges during cycling can also cause the material to fall off. Weigh each cut electrode sheet and subtract the mass of the copper foil to calculate the mass of the active material according to the addition ratio. Then, perform battery assembly and electrochemical testing.

[0030] Example 1

[0031] The method for preparing Mn-Ln-MOF type lithium-ion battery anode material is characterized by the following steps being carried out sequentially:

[0032] (1) Disperse 0.6 g of 3,5-pyrazole dicarboxylic acid monohydrate, 0.4 g of rare earth chloride, 0.1 g of lithium hydroxide, and 0.1 g of manganese metal powder in 18 g of deionized water solution, and place the above solution in the inner liner of a polytetrafluoroethylene reactor. Stir the resulting yellow slurry for 30 min at room temperature in an air atmosphere;

[0033] (2) Transfer the mixture after stirring in step (1) to a 25 mL high-pressure reactor and heat it at a constant temperature in an oven at 180 °C. The reaction time is 48 h. After the reaction is completed, cool it naturally to room temperature to obtain light yellow translucent crystals.

[0034] (3) Wash the pale yellow transparent crystals obtained in step (2) with deionized water 2 to 3 times, and dry them under natural conditions for 10 hours to obtain Mn-Ln-MOF material;

[0035] (4) The Mn-Ln-MOF material, PVDF (polyvinylidene fluoride), conductive graphite, and N-methylpyrrolidone (NMP) obtained in step (3) are thoroughly ground, and the resulting slurry is evenly coated onto the cleaned copper foil surface using a tool. The coated electrode sheet is then placed in a vacuum drying oven (-0.1 MPa) and dried at 110°C for 12 hours. After cooling to room temperature, the electrode sheet is removed for stamping and slicing. The battery is assembled in a vacuum glove box filled with argon gas, and the assembled battery is subjected to electrochemical testing after standing for 20 hours. Test results: The initial discharge capacity of Mn-La-MOF was 1581.2 mAh / g. After the second cycle, the specific capacity began to drop sharply, reaching 185.1 mAh / g at the twentieth cycle, and bottoming out at 175.98 mAh / g at the thirtieth cycle. Afterward, it began to rise steadily, reaching 182.75 mAh / g at the fiftieth cycle. After 100 cycles, the charging capacity decreased to 230.28 mAh / g. The material has low equipment requirements and is easy to operate. The synthesized Mn-Ln-MOF material has a stable structure and is a novel lithium-ion battery anode material.

[0036] Example 2

[0037] The method for preparing Mn-Ln-MOF type lithium-ion battery anode material is characterized by the following steps being carried out sequentially:

[0038] (1) Disperse 0.8 g of 3,5-pyrazole dicarboxylic acid monohydrate, 0.6 g of rare earth chloride, 0.2 g of lithium hydroxide, and 0.2 g of manganese metal powder in 20 g of deionized water solution, and place the above solution in the inner liner of a polytetrafluoroethylene reactor. Stir the resulting yellow slurry for 30 min at room temperature in air atmosphere;

[0039] (2) Transfer the mixture after stirring in step (1) to a 25 mL high-pressure reactor and heat it at a constant temperature in an oven at 200 °C for 50 h. After the reaction is completed, cool it naturally to room temperature to obtain light yellow translucent crystals.

[0040] (3) Wash the pale yellow transparent crystals obtained in step (2) with deionized water 2 to 3 times, and dry them under natural conditions for 12 hours to obtain Mn-Ln-MOF material;

[0041] (4) The Mn-Ln-MOF material, PVDF (polyvinylidene fluoride), conductive graphite, and N-methylpyrrolidone (NMP) obtained in step (3) are thoroughly ground, and the resulting slurry is evenly coated onto the cleaned copper foil surface using a tool. The coated electrode sheet is then placed in a vacuum drying oven (-0.1 MPa) and dried at 110°C for 12 hours. After cooling to room temperature, the electrode sheet is removed for stamping and slicing. The battery is assembled in a vacuum glove box filled with argon gas, and the assembled battery is subjected to electrochemical testing after standing for 24 hours.

[0042] The process method involved in this invention has good reproducibility, and the novel Mn-Ln-MOF material obtained has excellent morphology and structure and novel electrochemical properties. This method uses deionized water as the reaction solvent, which is environmentally friendly and readily available. This concept aligns with the current trend of green and low-cost processes. my country is a major producer of rare earth elements, and the rare earth and lithium bimetallic coordination polymers prepared therefrom exhibit excellent morphology and structure and superior electrochemical performance, possessing great application prospects and market value.

[0043] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a Mn-Ln-MOF type lithium-ion battery anode material, characterized in that, Follow these steps in sequence: (1) Disperse 0.6-0.8g of 3,5-pyrazole dicarboxylic acid monohydrate, 0.4-0.6g of rare earth chloride, 0.1-0.2g of lithium hydroxide and 0.1-0.2g of manganese metal powder in 18-20g of deionized water to form a mixed slurry, and stir it at room temperature in air atmosphere; (2) Transfer the solution obtained in step (1) to a 25 mL high-pressure reactor and heat it at a constant temperature of 180-200 °C in an oven. The reaction time is 48-50 h. After the reaction is completed, cool it naturally to room temperature to obtain light yellow translucent crystals. (3) Wash the pale yellow translucent crystals obtained in step (2) with deionized water 2 to 3 times and dry them under natural conditions for 10 to 12 hours to obtain Mn-Ln-MOF material; (4) The Mn-Ln-MOF material obtained in step (3) is mixed and ground with PVDF, conductive graphite and N-methylpyrrolidone respectively, and then uniformly coated on the surface of copper foil. It is then dried at 110°C for 12 hours in a vacuum drying oven with a vacuum degree of -0.1 MPa and pressed into tablets to obtain the target product. The Ln in the Mn-Ln-MOF material is La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er, Tm or Yb.

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