Alkaline earth metal ion doped copper fluoride and preparation method and application thereof

Abstract

The invention discloses alkaline earth metal ion doped copper fluoride as well as a preparation method and application thereof. The preparation method of the alkaline earth metal ion doped copper fluoride comprises the following steps: respectively preparing a copper salt solution and a basic oxide solution; the copper salt solution and the alkaline oxide solution are mixed and stirred at the temperature of 30-70 DEG C for a reaction, and a precursor mixture is obtained after the reaction is completed; and filtering, washing and drying the precursor mixture to obtain a dried precursor sample, uniformly mixing the dried precursor sample with a fluorine source, and carrying out heat treatment at 240-320 DEG C in a protective atmosphere to obtain the alkaline earth metal ion doped copper fluoride after the heat treatment is finished. According to the invention, the use of water is reduced in the preparation process, so that the wastewater discharge is reduced; meanwhile, the preparation efficiency is improved by simplifying the process, and after the obtained porous copper fluoride is doped with alkaline earth metal ions, the energy band structure is regulated and controlled, and the electrochemical activity is improved.

Description

Technical Field

[0001] The invention belongs to the field of electrode materials, and in particular relates to alkaline earth metal ion-doped copper fluoride and a preparation method and application thereof. Background Art

[0002] The development of new energy vehicles has led to an increasing demand for high energy density lithium-ion batteries. However, existing commercial lithium-ion batteries are limited by the specific capacity of their intercalation compound cathode materials (such as LiCoO2, LiMn2O4, LiFePO4), making it increasingly difficult for their energy density to meet the needs of new energy vehicles. Therefore, conversion materials with higher specific capacity have attracted widespread attention in recent years. Among these materials, transition metal fluorides have high theoretical potentials and theoretical specific capacities, showing high theoretical energy densities, and are considered to be important candidate systems to replace existing cathode materials.

[0003] As one of the transition metal fluorides, CuF2 is considered to have good development potential due to its high theoretical potential (3.55 V), high theoretical specific capacity (528 mAh / g) and high energy density (1874 Wh / Kg). However, due to the high ionic bond strength of Cu-F, its electrical conductivity is low, which seriously affects the electrochemical activity of CuF2. At present, the main measures to improve the electrochemical performance of copper fluoride are as follows: composite with carbon materials, but this method requires the introduction of more inactive substances, which may affect the overall energy density; and doping of copper fluoride can affect its energy band structure and improve electrochemical performance, but the current doping system often leads to a decrease in the voltage of copper fluoride, which in turn affects its energy density. Research in recent years has found that constructing a porous structure of CuF2 can increase the specific surface area of ​​the material, shorten the electron transport distance, and accelerate Li + Diffusion, thereby significantly improving the electrochemical activity of copper fluoride. For example, Hu et al. reported that porous CuF2 prepared by coprecipitation showed excellent electrochemical activity (reference 10.1007 / s10853-023-08668-0). However, this method uses NaOH as a precipitant to synthesize precursors, which makes process control more difficult, has poor stability, and is prone to form impurities, resulting in poor electrochemical performance of the final product; in addition, this method requires the introduction of more water during the synthesis process, which not only increases the environmental burden, but is also not conducive to large-scale preparation. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide an alkaline earth metal ion-doped copper fluoride and its preparation method and application. Compared with the existing method for preparing porous CuF2, the present invention uses MgO, CaO, SrO and BaO as alkaline oxides, whose aqueous solutions are alkaline and can stably and continuously provide OH for the precursor precipitation reaction. -, and generate basic copper acetate precipitate. The preparation process is simple to control, can greatly reduce the amount of water used, and is environmentally friendly. In addition, the alkaline earth metal oxide in the method is used as a precipitant on the one hand, and as a dopant on the other hand to introduce alkaline earth metals into CuF2 to regulate its band structure and improve the electrochemical activity of CuF2.

[0005] The purpose of the present invention is achieved through the following technical solutions: A method for preparing alkaline earth metal ion-doped copper fluoride comprises the following steps: (1) Prepare copper salt solution and alkaline oxide solution respectively; (2) mixing the copper salt solution and the alkaline oxide solution, and stirring them at 30-70° C. to react, and obtaining a precursor mixture after the reaction is completed; (3) The precursor mixture is filtered, washed and dried to obtain a dry precursor sample, which is then uniformly mixed with a fluorine source and heat-treated at 240-320° C. in a protective atmosphere. After the heat treatment is completed, copper fluoride doped with alkaline earth metal ions is obtained.

[0006] Preferably, in step (1), the copper salt solution is prepared as follows: adding the copper salt to water at 30-70° C. and stirring to fully dissolve the water.

[0007] Preferably, the copper salt is copper acetate.

[0008] Preferably, the concentration of the copper salt solution is 0.05-1 mol / L.

[0009] Preferably, in step (1), the alkaline oxide solution is prepared by the following method: adding the alkaline oxide into water at 30-70° C., stirring and fully dispersing the water.

[0010] Preferably, the basic oxide is at least one of MgO, CaO, SrO and BaO.

[0011] Preferably, the concentration of metal ions in the alkaline oxide solution is 0.03-0.75 mol / L.

[0012] Preferably, in step (2), the mass ratio of the copper salt in the copper salt solution to the alkaline oxide in the alkaline oxide solution is 0.9-19.0:0.1-8.0.

[0013] Preferably, in step (2), the stirring time is 30 to 120 minutes.

[0014] Preferably, in step (3), the dried precursor sample is mixed with a fluorine source and fully ground, and then heat-treated.

[0015] Preferably, in step (3), the mass ratio of the fluorine source to the dried precursor sample is 2-10:1.

[0016] Preferably, in step (3), the fluorine source is at least one of ammonium fluoride and ammonium bifluoride.

[0017] Preferably, in step (3), the heat treatment time is 2 to 6 hours.

[0018] Preferably, in step (3), the protective atmosphere is nitrogen or an inert gas.

[0019] Preferably, the inert gas is argon.

[0020] The alkaline earth metal ion-doped copper fluoride is prepared by the preparation method of the alkaline earth metal ion-doped copper fluoride.

[0021] Application of the above alkaline earth metal ion-doped copper fluoride as lithium ion positive electrode material.

[0022] Compared with the prior art, the beneficial effects of the present invention include: (1) The present invention does not introduce much water during the preparation process, which not only reduces the dependence on water resources, but also reduces the wastewater discharge that may be generated during the synthesis process, thereby reducing the burden on the environment.

[0023] (2) The process of the present invention is streamlined and the preparation efficiency is high. The prepared copper fluoride doped with alkaline earth metal ions has a porous structure. The doping of alkaline earth metal ions can regulate its energy band structure and improve the electrochemical activity of CuF2. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the XRD diffraction pattern of the alkaline earth metal ion-doped copper fluoride prepared in Example 1, wherein the right image is a partial enlarged view of the left image.

[0025] Figure 2 This is the first cycle charge and discharge curve of the alkaline earth metal ion-doped copper fluoride prepared in Example 1.

[0026] Figure 3 This is the SEM image of the alkaline earth metal ion-doped copper fluoride prepared in Example 1. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] Example 1 A method for preparing copper fluoride doped with alkaline earth metal ions, comprising the following steps: (1) Weigh 9.07 g of copper acetate and add it to 100 mL of deionized water. Heat and stir at 50°C to fully dissolve it to form a 0.5 mol / L copper acetate solution.

[0029] (2) Weigh 5.4 g of BaO and add it to 100 mL of deionized water. Heat and stir at 50 °C to disperse it evenly to form a 0.35 mol / L oxide solution.

[0030] (3) Slowly drop the copper acetate solution described in step (1) into the oxide solution described in step (2), and stir the mixture for 60 minutes at a water bath temperature of 50° C. to obtain a precursor mixture.

[0031] (4) The precursor mixture is filtered, washed and dried to obtain a dry precursor (containing basic copper acetate).

[0032] (5) The dried precursor and ammonium fluoride are mixed and ground in a mass ratio of 1:2 to obtain a mixed powder after uniform grinding. The mixed powder is placed in a tubular furnace filled with argon gas and heat-treated at 290°C for 4 hours. After the heat treatment, copper fluoride doped with alkaline earth metal ions is obtained.

[0033] Example 2 A method for preparing copper fluoride doped with alkaline earth metal ions, comprising the following steps: (1) Weigh 18 g of copper acetate and add it to 100 mL of deionized water. Heat and stir at 70°C to fully dissolve it to form a 1 mol / L copper acetate solution.

[0034] (2) Weigh 2.24 g of CaO and 5.37 g of BaO and add them to 100 mL of deionized water. Heat and stir at 70°C to disperse them evenly to form a 0.75 mol / L oxide solution.

[0035] (3) Slowly drop the copper acetate solution described in step (1) into the oxide solution described in step (2), and stir the mixture in a water bath at 70° C. for 120 min to obtain a precursor mixture.

[0036] (4) The precursor mixture is filtered, washed and dried to obtain a dry precursor (containing basic copper acetate).

[0037] (5) The dried precursor and ammonium fluoride are mixed and ground in a mass ratio of 1:10 to obtain a mixed powder after uniform grinding. The mixed powder is placed in a tubular furnace filled with argon gas and heat-treated at 240°C for 6 hours. After the heat treatment, copper fluoride doped with alkaline earth metal ions is obtained.

[0038] Example 3 A method for preparing copper fluoride doped with alkaline earth metal ions, comprising the following steps: (1) Weigh 12.7 g of copper acetate and add it to 100 mL of deionized water. Heat and stir at 60°C to fully dissolve it to form a 0.7 mol / L copper acetate solution.

[0039] (2) Weigh 5.2 g of SrO and add it to 100 mL of deionized water. Heat and stir at 60 °C to disperse it evenly to form a 0.5 mol / L oxide solution.

[0040] (3) Slowly drop the copper acetate solution described in step (1) into the oxide solution described in step (2), and stir the mixture for 60 minutes at a water bath temperature of 60° C. to obtain a precursor mixture.

[0041] (4) The precursor mixture is filtered, washed and dried to obtain a dry precursor (containing basic copper acetate).

[0042] (5) The dried precursor and ammonium fluoride are mixed and ground in a mass ratio of 1:6 to obtain a mixed powder after uniform grinding. The mixed powder is placed in a tubular furnace filled with argon gas and heat-treated at 300°C for 2 hours. After the heat treatment, copper fluoride doped with alkaline earth metal ions is obtained.

[0043] Example 4 A method for preparing copper fluoride doped with alkaline earth metal ions, comprising the following steps: (1) Weigh 12.7 g of copper acetate and add it to 100 mL of deionized water. Heat and stir at 50°C to fully dissolve it to form a 0.7 mol / L copper acetate solution.

[0044] (2) Weigh 7.6 g of BaO and add it to 100 mL of deionized water. Heat and stir at 50 °C to disperse it evenly to form a 0.5 mol / L oxide solution.

[0045] (3) Slowly drop the copper acetate solution described in step (1) into the oxide solution described in step (2), and stir the mixture in a water bath at 50° C. for 90 minutes to obtain a precursor mixture.

[0046] (4) The precursor mixture is filtered, washed and dried to obtain a dry precursor (containing basic copper acetate).

[0047] (5) The dried precursor and ammonium fluoride are mixed and ground in a mass ratio of 1:5 to obtain a mixed powder after uniform grinding. The mixed powder is placed in a tubular furnace filled with argon gas and heat-treated at 280°C for 5 hours. After the heat treatment, copper fluoride doped with alkaline earth metal ions is obtained.

[0048] Example 5 A method for preparing copper fluoride doped with alkaline earth metal ions, comprising the following steps: (1) Weigh 0.91 g of copper acetate and add it to 100 mL of deionized water. Heat and stir at 30°C to fully dissolve it to form a 0.05 mol / L copper acetate solution.

[0049] (2) Weigh 0.12 g of MgO and add it to 100 mL of deionized water. Heat and stir at 30°C to disperse it evenly to form a 0.03 mol / L oxide solution.

[0050] (3) Slowly drop the copper acetate solution described in step (1) into the oxide solution described in step (2), and stir the mixture in a water bath at 30° C. for 60 min to obtain a precursor mixture.

[0051] (4) The precursor mixture is filtered, washed and dried to obtain a dry precursor (containing basic copper acetate).

[0052] (5) The dried precursor and ammonium fluoride are mixed and ground in a mass ratio of 1:2 to obtain a mixed powder after uniform grinding. The mixed powder is placed in a tubular furnace filled with argon and heat treated at 300°C for 3 hours. After the heat treatment, copper fluoride doped with alkaline earth metal ions is obtained.

[0053] Example 6 A method for preparing copper fluoride doped with alkaline earth metal ions, comprising the following steps: (1) Weigh 14.52 g of copper acetate and add it to 100 mL of deionized water. Heat and stir at 70°C to fully dissolve it to form a 0.8 mol / L copper acetate solution.

[0054] (2) Weigh 0.8 g of MgO, 1.1 g of CaO, and 3.1 g of BaO and add them to 100 mL of deionized water. Heat and stir at 70 °C to disperse them evenly to form a 0.6 mol / L oxide solution.

[0055] (3) Slowly drop the copper acetate solution described in step (1) into the oxide solution described in step (2), and stir the mixture in a water bath at 70° C. for 120 min to obtain a precursor mixture.

[0056] (4) The precursor mixture is filtered, washed and dried to obtain a dry precursor (containing basic copper acetate).

[0057] (5) The dried precursor and ammonium fluoride are mixed and ground in a mass ratio of 1:7 to obtain a mixed powder after uniform grinding. The mixed powder is placed in a tubular furnace filled with argon gas and heat-treated at 250°C for 4 hours. After the heat treatment, copper fluoride doped with alkaline earth metal ions is obtained.

[0058] The alkaline earth metal ion-doped copper fluoride prepared in the embodiment is used as the positive electrode active material, and polyvinylidene fluoride and carbon black are used as raw materials to prepare the positive electrode, wherein the alkaline earth metal ion-doped copper fluoride accounts for 70wt% of the raw material, polyvinylidene fluoride accounts for 20wt% of the raw material, and carbon black accounts for 10wt% of the raw material. The slurry composed of the above three raw materials is cast on a 10mm thick Al foil sheet to prepare the electrode. The prepared electrode is then placed in a vacuum oven to dry. Using LiTFSI / TMS (1:10) sulfolane electrolyte, Li metal sheet negative electrode, Celgard 2500 diaphragm, R2032 button battery is assembled to characterize its electrochemical performance, and then the button battery is charged and discharged at a voltage of 1.5-4.2V and a current density of 0.1C.

[0059] Figure 1 The XRD diffraction pattern of the alkaline earth metal ion-doped copper fluoride prepared in Example 1, wherein the right figure is a partial enlarged view of the left figure, from Figure 1 We can see that the main diffraction peaks of the obtained XRD diffraction spectrum are consistent with the copper fluoride standard card (JCPDS card no.70-1936). The enlarged image shows that the diffraction peak around 2 Thete = 27.5° shifts to a lower angle, which indicates that the barium ions with a larger ionic radius have been successfully incorporated into the CuF2 positive electrode material.

[0060] Figure 2 The first cycle charge-discharge curve of the alkaline earth metal ion-doped copper fluoride prepared in Example 1 is shown in FIG. Figure 2 We can see that the first-cycle discharge voltage platform of Ba-doped copper fluoride reaches above 2.8V, and the first-cycle discharge capacity reaches 497.77mAh / g.

[0061] Figure 3 This is the SEM image of the alkaline earth metal ion-doped copper fluoride prepared in Example 1. Figure 3 We can see that the prepared alkaline earth metal ion-doped copper fluoride is composed of loose and porous blocks, and the size is mostly concentrated in the range of 2~4μm.

[0062] The electrochemical performance statistics of the battery prepared by using the alkaline earth metal ion doped copper fluoride described in Examples 1 to 6 as the positive electrode material are shown in Table 1.

[0063] Table 1 Electrochemical performance of the batteries corresponding to Examples 1 to 6

[0064] As shown in Table 1, we can know that the alkaline earth metal ion-doped copper fluoride prepared by the present invention is used as a positive electrode material, and the prepared battery has good electrochemical performance.

[0065] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing copper fluoride doped with alkaline earth metal ions, characterized in that: The steps include: (1) Prepare copper salt solution and alkaline oxide solution respectively; (2) mixing the copper salt solution and the alkaline oxide solution, and stirring them at 30-70° C. to react, and obtaining a precursor mixture after the reaction is completed; (3) The precursor mixture is filtered, washed and dried to obtain a dry precursor sample, which is uniformly mixed with a fluorine source and heat-treated at 240-320° C. in a protective atmosphere to obtain the alkaline earth metal ion-doped copper fluoride.

2. The method for preparing alkaline earth metal ion-doped copper fluoride according to claim 1, characterized in that: The copper salt solution in step (1) is prepared as follows: adding copper salt to water at 30-70°C, stirring and fully dissolving the copper salt; The alkaline oxide solution in step (1) is prepared as follows: adding the alkaline oxide into water at 30-70° C., stirring and fully dispersing the water.

3. The method for preparing alkaline earth metal ion-doped copper fluoride according to claim 2, characterized in that: The copper salt is copper acetate; The basic oxide is at least one of MgO, CaO, SrO and BaO.

4. The method for preparing alkaline earth metal ion-doped copper fluoride according to claim 3, characterized in that: The concentration of the copper salt solution is 0.05-1 mol / L; In the alkaline oxide solution, the concentration of metal ions is 0.03-0.75 mol / L.

5. The method for preparing alkaline earth metal ion-doped copper fluoride according to any one of claims 2 to 4, characterized in that: In step (2), the mass ratio of the copper salt in the copper salt solution to the alkaline oxide in the alkaline oxide solution is 0.9-19.0:0.1-8.0; The stirring time in step (2) is 30 to 120 minutes.

6. The method for preparing alkaline earth metal ion-doped copper fluoride according to claim 5, characterized in that: In step (3), the dried precursor sample is mixed with a fluorine source and fully ground, and then heat-treated.

7. The method for preparing alkaline earth metal ion-doped copper fluoride according to claim 6, characterized in that: The mass ratio of the fluorine source to the dried precursor sample in step (3) is 2-10:1; The fluorine source in step (3) is at least one of ammonium fluoride and ammonium bifluoride.

8. The method for preparing alkaline earth metal ion-doped copper fluoride according to claim 1, characterized in that: The heat treatment time in step (3) is 2 to 6 hours; The protective atmosphere in step (3) is nitrogen or an inert gas.

9. Alkaline earth metal ion-doped copper fluoride prepared by the method for preparing alkaline earth metal ion-doped copper fluoride according to any one of claims 1 to 8.

10. Use of the alkaline earth metal ion-doped copper fluoride according to claim 9 as a lithium ion positive electrode material.

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