Fluoride nanocomposite and method of making same

Abstract

The application discloses a fluoride nanocomposite and a preparation method thereof in the field of battery material preparation. A manganese source and a cobalt source are dissolved in deionized water, a reducing alcohol aqueous solution is added, and a bimetallic ion oxide precursor material is obtained through a hydrothermal reaction; then, sodium chloride, the bimetallic ion oxide precursor material and an organic carbon source are dissolved in deionized water, freeze-drying is performed, calcination is performed in an inert atmosphere, the sodium chloride is washed clean with deionized water, and then placed in a reaction container; a fluorination reaction is performed with a fluorine source gas under high-temperature conditions, and after natural cooling to room temperature, the nanocomposite with a bimetallic oxide as an inner core, a metal fluoride as an intermediate layer and an outer fluoride layer is obtained. The method realizes synchronous compatibility improvement of a voltage platform, a conductive layer and an active capacity of a fluorinated carbon material, and the nanometer structure shortens the lithium ion migration path and increases the reaction active sites, so that the voltage platform, the energy density and the power output performance of the fluorinated carbon battery are effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of battery material preparation, and specifically relates to a fluoride nanocomposite material and its preparation method. Background Technology

[0002] Lithium-carbon fluoride (LCF) batteries boast a theoretical energy density of up to 2180 Wh / kg, nearly double that of lithium manganese dioxide (LCD) batteries (1005 Wh / kg), making them the highest energy density battery series among existing lithium primary battery systems. Besides their high energy density, LCF batteries also exhibit excellent storage performance, long shelf life, and low self-discharge rate, making them a promising energy source for commercial applications. However, as the positive electrode active material in LCF batteries, fluorinated carbon materials (CF₂)... x ,0< x ≤1) Due to the high CF bond energy and poor conductivity, although lithium fluorocarbon batteries have high specific energy, they suffer from voltage lag, high heat generation, and severe volume expansion in the early stage of discharge under high rate (≥1C) discharge conditions, which seriously affects the commercial application scope of lithium fluorocarbon batteries.

[0003] To address the aforementioned issues, existing technologies increase the amount of conductive agent by adjusting the particle size or proportion of fluorinated carbon material in the fluorinated carbon electrode. This method can improve the high-rate discharge capability of fluorinated carbon batteries, but it does not fundamentally solve the problems existing in the application of fluorinated carbon materials and also results in a certain degree of loss in the energy density of lithium fluorinated carbon batteries. Another approach involves replacing fluorinated carbon materials with metal oxide active materials (such as vanadium pentoxide and manganese dioxide), which have more stable material structures, higher discharge platforms, lower heat generation, and smaller volume expansion, forming a metal oxide / fluorinated carbon hybrid cathode material. During discharge, both materials can exert their own capacity normally, and the entire reaction process involves first oxide, then oxide / fluorinated carbon mixing, and finally fluorinated carbon discharge. This can, to some extent, solve the problems of voltage lag, volume expansion, and low voltage platform in lithium fluorinated carbon batteries during high-rate discharge. However, metal oxide / fluorinated carbon hybrid cathode materials are currently mainly prepared by direct mixing and compounding. The particle size and compaction density of metal oxide and fluorinated carbon differ significantly, making it difficult to disperse the slurry in the resulting fluorinated carbon composite material. In the electrode preparation process, issues such as the actual dispersion state of the two active materials, the uniformity of the distribution of conductive agents and active materials, the viscosity and adhesion of the slurry, and the difficulty in accurately controlling the actual ratio are involved. As a result, the preparation process of metal oxide / fluorinated carbon hybrid cathode sheets has high requirements, and the capacity of both metal oxide and fluorinated carbon active materials is lost to varying degrees in battery applications, which is not conducive to improving the overall performance of lithium fluorinated carbon batteries.

[0004] Therefore, there is an urgent need to develop a material that is structurally stable, has a high voltage platform, and excellent capacity performance, and can be easily applied to lithium fluorocarbon batteries. Summary of the Invention

[0005] The present invention aims to provide a fluoride nanocomposite material that solves the problems of poor conductivity and low voltage platform of fluorinated carbon materials in the prior art, poor mixing uniformity and difficulty in controlling the proportion when compounded with other materials to form composite materials, and difficulty in dispersing slurry in the compounded fluorinated carbon composite material.

[0006] The preparation method of a fluoride nanocomposite material in this scheme includes the following steps: S1. Dissolve manganese and cobalt sources in deionized water, add reducing alcohol aqueous solution, and obtain bimetallic ion oxide precursor material through hydrothermal reaction; S2. Dissolve sodium chloride, an organic carbon source, and the bimetallic ion oxide precursor material in deionized water, freeze-dry, and calcine in an inert atmosphere to obtain a sodium chloride crystal template. Rinse the sodium chloride crystal template with deionized water and dry to obtain a bimetallic ion oxide composite material MN with in-situ carbon coating on the surface. x O y @C, where 1≤x≤3, 2≤y≤3; S3, the bimetallic ion oxide composite material MN x O y @C is placed in a reaction vessel and reacts with a gaseous fluorine source under high temperature conditions. After being naturally cooled to room temperature, it is removed to obtain the fluoride nanocomposite material. The core of the fluoride nanocomposite material is a bimetallic oxide, the middle is a metal fluoride, and the outside is a fluoride nanocomposite material.

[0007] The working principle of this invention is as follows: This invention uses reducing alcohol and metal source as raw materials to prepare bimetallic ion oxide precursor materials. In the reducing alcohol aqueous solution, the reducing alcohol induces the metal ion complex to spontaneously copolymerize to form a metal ion water and hydroxyl copolymer, thereby obtaining a composite metal oxide precursor material with a bimetallic center (bimetallic ion oxide precursor). The method is simple and easy to implement, and the particle size of the precursor material is uniform and controllable.

[0008] Sodium chloride, the bimetallic ion oxide precursor material, and the organic carbon source were dissolved in a solution, and a mixture powder was obtained by freeze-drying. In this process, sodium chloride acts as a template, confining the bimetallic ion oxide precursor and the organic carbon source within a limited nanoscale space. Following high-temperature calcination, the bimetallic ion oxide precursor material decomposes to form a composite metal ion oxide, while the organic carbon source carbonizes. Because carbon has strong reducing properties at high temperatures, it ensures that the metal ions remain in a low valence state. Finally, sodium chloride is removed by washing with water, yielding a composite structure (carbon-coated bimetallic ion oxide nanocomposite material) with bimetallic ion oxide particles in situ embedded in a continuous carbon coating layer.

[0009] Under high-temperature fluorine source atmosphere, metal oxides and carbon coatings undergo fluorination reactions to varying degrees to form fluoride nanocomposites. These fluoride nanocomposites are composed of three active substances: a core of bimetallic oxides with a high-voltage platform, a middle layer of metal fluorides that form high-conductivity metals from the reaction products, and an outer layer of fluoride nanocomposites with high-capacity fluorinated carbon active substances. The proportion of these three active substances can be adjusted by regulating the organic carbon source, the metal ion oxide precursor, and the degree of high-temperature fluorination. By controlling the reaction temperature and reaction time, the metal oxides and the surface carbon coating can undergo reactions to varying degrees.

[0010] The roles of the three active materials in terms of their proportions: a high content of metal oxides can increase the initial voltage of the fluoride electrode, buffering the voltage lag pressure during high current loading; a high content of metal fluorides can increase the working voltage platform of the fluoride electrode; and the formed elemental metal products can help increase the discharge voltage platform of the fluoride shell material. Increasing the thickness or content of the fluoride shell can increase the overall capacity of the fluoride material.

[0011] The beneficial technical effects of this invention are: 1. In conventional technology, fluorinated carbon composite materials are prepared by mixing processes such as metal oxide doping or mixing. The method of this application directly reduces the mixing process steps in the prior art, effectively shortens the material synthesis and composite ratio adjustment process time, and solves the problem of uniform dispersion of nano-metal oxides and nano-fluorinated carbon materials in the slurry preparation process.

[0012] 2. The fluoride nanocomposite material prepared by this method has a core of high-voltage plateau metal oxide, a middle layer of metal fluoride forming a high-conductivity metal from the reaction products, and an outer layer of high-capacity fluorinated carbon active material. This achieves simultaneous improvement in the voltage plateau, conductive layer, and active capacity of the fluorinated carbon material. The nanostructure shortens the lithium-ion migration path and increases the reactive sites, effectively improving the full wetting space between the electrode and the electrolyte, and achieving an overall improvement in the high-rate discharge voltage plateau.

[0013] Further, in S1, manganese and cobalt sources are dissolved in deionized water, and a reducing alcohol aqueous solution is added. After magnetic stirring for 10-30 min, a brown precursor solution is obtained. The solution is then transferred to a reaction vessel and heated at 80-150℃ for 2-6 h. After cooling, the precipitate is separated by centrifugation and washed with deionized water until the supernatant is transparent. The solution is then transferred to a vacuum chamber and dried at 60-100℃ for 2-8 h to obtain the bimetallic ion oxide precursor material.

[0014] Further, in step S2, 0.1-1M sodium chloride, 0.1-1M bimetallic ion oxide precursor material, and a certain amount of organic carbon source are dissolved in deionized water to obtain a mixed solution. The mixed solution is transferred to a low-temperature chamber and frozen at -20 to 0°C for 4-24 hours, and then vacuum freeze-dried at -40 to -80°C. The dried mixed powder is calcined at 600-800°C for 2-10 hours under an inert atmosphere and then cooled to obtain a sodium chloride crystal template. The sodium chloride crystal template is rinsed clean with deionized water and then dried in an oven at 40-100°C for 8-24 hours to obtain the bimetallic ion oxide composite material MN. x O y @C.

[0015] Furthermore, in S3, the bimetallic ion oxide composite material MN x O y @C is arranged in a reaction vessel, and nitrogen or argon is introduced into the reactor to achieve an internal pressure of 0.05~0.3 MPa. The pressure is maintained for 12~15 h, and the reactor temperature is controlled at 600~800℃. Then, the reactor is continuously charged with reaction gas for 4~8 h and then naturally cooled to room temperature to obtain the fluoride nanocomposite material. The reaction gas is a mixture of gaseous fluorine source and dilution gas. The volume fraction of gaseous fluorine source in the reaction gas is 6%~10%, and the gaseous fluorine source content is 0.08 ml / min~0.20 ml / min. The dilution gas is nitrogen or argon.

[0016] Furthermore, the manganese source is one of potassium permanganate and manganese acetate, with a concentration of 10~500 mM.

[0017] Furthermore, the cobalt source is one of cobalt nitrate and cobalt acetate, with a concentration of 5~50 mM.

[0018] Furthermore, the reducing alcohol is one of citric acid, salicylic acid, and sodium alginate, and the concentration of the reducing alcohol aqueous solution is 10~500 mM.

[0019] Furthermore, the organic carbon source is one of sucrose, lactose, and glucose, and the concentration of the organic carbon source is 10~500mM.

[0020] Furthermore, the gaseous fluorine source is either fluorine or nitrogen trifluoride. Attached Figure Description

[0021] Figure 1 This is a flowchart of a method for preparing a fluoride nanocomposite material according to the present invention; Figure 2 Discharge curves of fluorinated carbon and fluoride nanocomposites at 1 C rate. Detailed Implementation

[0022] The following detailed description illustrates the specific implementation method: Combination Figure 1 The process is further explained in detail below through specific implementation methods: Implementation Case 1: A method for preparing a fluoride nanocomposite material, the steps of which are as follows: S1. Dissolve 10 mM potassium permanganate and 5 mM cobalt nitrate in deionized water, add 10 mM citric acid aqueous solution, and stir magnetically for 10 min to obtain a brown precursor solution. Transfer the solution to a reaction vessel and heat at 80°C for 2 h. After cooling, centrifuge to separate the precipitate, and wash with deionized water until the supernatant is transparent. Transfer the supernatant to a vacuum chamber and dry at 60°C for 2 h to obtain the bimetallic ion oxide precursor material.

[0023] S2. Dissolve 0.1M sodium chloride, 1M bimetallic ion oxide precursor material, and 10mM sucrose in deionized water to obtain a mixed solution. Transfer the mixed solution to a low-temperature chamber and freeze at -20°C for 4 hours, then freeze-dry under vacuum at -40°C. Calcine the dried mixed powder at 600°C for 2 hours under an inert atmosphere and then cool to obtain a sodium chloride crystal template. Rinse the sodium chloride crystal template with deionized water and then dry it in a 40°C oven for 24 hours to obtain the bimetallic ion oxide composite material CoMn2O3@C.

[0024] S3. The bimetallic ion oxide composite material CoMn2O3@C was arranged in a reaction vessel, and nitrogen or argon gas was introduced into the reactor to achieve an internal pressure of 0.05 MPa. This pressure was maintained for 12 h, and the reactor temperature was controlled at 600℃. Then, the reactor was continuously charged with reaction gas for 4 h, followed by natural cooling to room temperature to obtain the fluoride nanocomposite material. The reaction gas was a mixture of fluorine and nitrogen, with a fluorine volume fraction of 6% and a fluorine concentration of 0.08 ml / min.

[0025] Implementation Case 2: A method for preparing a fluoride nanocomposite material, the steps of which are as follows: S1. Dissolve 500 mM potassium permanganate and 50 mM cobalt nitrate in deionized water, add 500 mM salicylic acid aqueous solution, and stir magnetically for 30 min to obtain a brown precursor solution. Transfer the solution to a reaction vessel and heat at 150 °C for 6 h. After cooling, centrifuge to separate the precipitate, and wash with deionized water until the supernatant is transparent. Transfer the supernatant to a vacuum chamber and dry at 100 °C for 8 h to obtain the bimetallic ion oxide precursor material.

[0026] S2. Dissolve 1 M sodium chloride, 0.1 M bimetallic ion oxide precursor material, and 500 mM glucose in deionized water to obtain a mixed solution. Transfer the mixed solution to a low-temperature chamber and freeze at -20°C for 24 h, then freeze-dry under vacuum at -80°C. Calcine the dried mixed powder at 800°C for 10 h under an inert atmosphere and then cool to obtain a sodium chloride crystal template. Rinse the sodium chloride crystal template with deionized water and then dry it in a 100°C oven for 24 h to obtain the bimetallic ion oxide composite material CoMnO3@C.

[0027] S3. The bimetallic ion oxide composite material CoMnO3@C is arranged in a reaction vessel, and nitrogen or argon gas is introduced into the reactor to make the internal pressure reach 0.3 MPa. The pressure is maintained for 15 h, the reactor temperature is controlled at 800℃, and then the reactor is continuously charged with reaction gas for 8 h. After natural cooling to room temperature, the fluoride nanocomposite material is obtained. The reaction gas is a mixture of fluorine and nitrogen, with a fluorine volume fraction of 10% and a fluorine content of 0.20 ml / min.

[0028] Implementation Case 3: A method for preparing a fluoride nanocomposite material, the steps of which are as follows: 200 mM potassium permanganate and 20 mM cobalt nitrate were dissolved in deionized water, and 500 mM sodium alginate aqueous solution was added. After magnetic stirring for 20 min, a brown precursor solution was obtained, which was transferred to a reaction vessel and heated at 100 °C for 4 h. After cooling, the precipitate was separated by centrifugation and washed with deionized water until the supernatant was transparent. The supernatant was then dried in a vacuum chamber at 80 °C for 6 h to obtain the bimetallic ion oxide precursor material.

[0029] 0.6 M sodium chloride, 0.5 M bimetallic ion oxide precursor material, and 200 mM lactose were dissolved in deionized water to obtain a mixed solution. The mixed solution was transferred to a low-temperature chamber and frozen at -5 °C for 10 h, and then vacuum freeze-dried at -50 °C. The dried mixed powder was calcined at 700 °C for 6 h under an inert atmosphere and then cooled to obtain a sodium chloride crystal template. The sodium chloride crystal template was rinsed clean with deionized water and then dried in an oven at 80 °C for 10 h to obtain the bimetallic ion oxide composite material CoMnO2@C.

[0030] The bimetallic ion oxide composite material CoMnO2@C was arranged in a reaction vessel, and nitrogen or argon gas was introduced into the reactor to achieve an internal pressure of 0.15 MPa. This pressure was maintained for 14 h, and the reactor temperature was controlled at 700℃. Then, the reactor was continuously charged with reaction gas for 6 h, followed by natural cooling to room temperature to obtain the fluoride nanocomposite material. The reaction gas was a mixture of fluorine and nitrogen, with a fluorine source volume fraction of 8% and a fluorine source concentration of 0.10 ml / min.

[0031] The fluoride nanocomposite material prepared in Example 3 was compared with existing commercial fluorinated carbon materials (CF2). 0.5 Experimental comparisons were conducted. The specific experimental procedure was as follows: Fluoride nanocomposite materials prepared in Example 1 were used as the positive electrode material, SP and CNTS as conductive agents, and CMC+SBR as binders. A positive electrode slurry was uniformly mixed according to a mass ratio of positive electrode material: conductive agent: binder = 80:10:10, coated onto aluminum foil, and dried at 100 °C. Lithium metal was used as the negative electrode, and a set of lithium fluoride carbon batteries were assembled in a 1% drying chamber. Then, commercial fluoride carbon materials were used as the positive electrode material, with everything else identical to Example 1, to assemble another set of lithium fluoride carbon batteries. Both sets of lithium fluoride carbon batteries were simultaneously subjected to discharge tests at room temperature (25 °C) and a 1C rate. The comparison of rate performance and low-voltage hysteresis performance is shown in the attached figure. Figure 2 As shown.

[0032] Figure 2 The discharge curves for fluorinated carbon and fluoride nanocomposites at a 1 C rate are shown, corresponding to discharge capacities of 706.3 and 660.1 mAh / g, respectively. This is because the theoretical specific capacity of the fluoride nanocomposites is lower than that of pure fluorinated carbon. Figure 2 As can be seen, the on-state voltage of the fluoride nanocomposite material as the electrode active material is greater than 3.75V. The entire discharge process is divided into three discharge stages, and the corresponding voltage plateaus are all higher than those of pure fluorinated carbon materials. This indicates that α-MnO2, metal fluorides, and CF xAll three materials act as discharge active substances in the composite materials. In the first stage, the voltage plateau is 2.68 V, corresponding to the discharge process of the metal oxide. In the second stage, the discharge process of the fluorinated metal material corresponds to a median voltage of 2.57 V. The third stage corresponds to the discharge process of the fluorinated carbon material, and the voltage plateau is significantly higher than that of the conventional fluorinated carbon material. This is because the discharge products formed in the first and second discharge stages are conductive elemental metals Mn and Co, which improve the conductivity of the electrode and thus increase the working voltage of the fluorinated carbon material in the third stage discharge process, reaching 2.50 V. Compared with the working voltage plateau of 2.39 V of the fluorinated carbon material, the overall improvement is 0.27 V (an improvement rate of 11%), demonstrating that fluoride nanocomposites can effectively improve battery voltage hysteresis and rate output performance during the discharge process.

Claims

1. A method for preparing a fluoride nanocomposite material for lithium fluoride carbon batteries, characterized in that... Includes the following steps: S1. Dissolve manganese and cobalt sources in deionized water, and add one of citric acid aqueous solution, salicylic acid aqueous solution, or sodium alginate aqueous solution to obtain bimetallic ion oxide precursor material through hydrothermal reaction. S2. Dissolve the sodium chloride template, organic carbon source, and the bimetallic ion oxide precursor material in deionized water, freeze-dry, calcine in an inert atmosphere, then remove the sodium chloride by washing with deionized water, and dry to obtain a bimetallic ion oxide composite material MN with in-situ carbon coating on the surface. x O y @C, where 1≤x≤3, 2≤y≤3; S3, the bimetallic ion oxide composite material MN x O y @C is placed in a reaction vessel and reacts with a gaseous fluorine source under high temperature conditions. After being naturally cooled to room temperature, it is removed to obtain the fluoride nanocomposite material. The core of the fluoride nanocomposite material is a bimetallic oxide, the middle is a metal fluoride, and the outside is fluorinated carbon.

2. The method for preparing the fluoride nanocomposite material according to claim 1, characterized in that: In S1, manganese and cobalt sources are dissolved in deionized water, and one of citric acid aqueous solution, salicylic acid aqueous solution, or sodium alginate aqueous solution is added. After magnetic stirring for 10-30 min, a brown precursor solution is obtained. The solution is transferred to a reaction vessel and heated at 80-150℃ for 2-6 h. After cooling, the precipitate is separated by centrifugation and washed with deionized water until the supernatant is transparent. The solution is then transferred to a vacuum chamber and dried at 60-100℃ for 2-8 h to obtain the bimetallic ion oxide precursor material.

3. The method for preparing the fluoride nanocomposite material according to claim 2, characterized in that: In step S2, 0.1-1M sodium chloride template, 0.1-1M bimetallic ion oxide precursor material, and a certain amount of organic carbon source are dissolved in deionized water to obtain a mixed solution. The mixed solution is transferred to a low-temperature chamber and frozen at -20 to 0°C for 4-24 hours, followed by vacuum freeze-drying at -40 to -80°C. The dried mixed powder is then calcined at 600-800°C for 2-10 hours under an inert atmosphere. Sodium chloride is then removed by washing with deionized water, and the powder is dried in an oven at 40-100°C for 8-24 hours to obtain the bimetallic ion oxide composite material MN. x O y @C.

4. The method for preparing the fluoride nanocomposite material according to claim 3, characterized in that: S3 will include the bimetallic ion oxide composite material MN x O y @C is arranged in a reaction vessel, and nitrogen or argon is introduced into the reactor to achieve an internal pressure of 0.05~0.3 MPa. The pressure is maintained for 12~15 h, and the reactor temperature is controlled at 600~800℃. Then, the reactor is continuously charged with reaction gas for 4~8 h and then naturally cooled to room temperature to obtain the fluoride nanocomposite material. The reaction gas is a mixture of gaseous fluorine source and dilution gas. The volume fraction of gaseous fluorine source in the reaction gas is 6%~10%, and the gaseous fluorine source content is 0.08 ml / min~0.20 ml / min. The dilution gas is nitrogen or argon.

5. The method for preparing the fluoride nanocomposite material according to claim 1, characterized in that: The manganese source is either potassium permanganate or manganese acetate, with a concentration of 10~500 mM.

6. The method for preparing the fluoride nanocomposite material according to claim 1, characterized in that: The cobalt source is one of cobalt nitrate and cobalt acetate, with a concentration of 5~50 mM.

7. The method for preparing the fluoride nanocomposite material according to claim 1, characterized in that: The concentration of the citric acid aqueous solution, salicylic acid aqueous solution, or sodium alginate aqueous solution is 10~500 mM.

8. The method for preparing the fluoride nanocomposite material according to claim 1, characterized in that: The organic carbon source is one of sucrose, lactose, or glucose, and the concentration of the organic carbon source is 10~500 mM.

9. The method for preparing the fluoride nanocomposite material according to claim 1, characterized in that: The gaseous fluorine source is either fluorine or nitrogen trifluoride.

10. A fluoride nanocomposite material for lithium fluoride carbon batteries, characterized in that... The fluoride nanocomposite material is prepared by the method described in any one of claims 1 to 9.

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