CuF2@void@se i@sa electrode material and preparation method and application thereof

Abstract

The present application relates to the technical field of lithium ion battery electrode material, in particular to CuF2@void@SEI@SA electrode material and its preparation method and application. The present application uses the electrolyte of waste lithium ion battery to fluorinate the three-dimensional porous metal conductive frame of foam copper by a simple solvothermal method, in-situ synthesizes CuF2@void@SEI electrode material with pomegranate morphology on the surface of the three-dimensional porous metal conductive frame, solves the problems of large volume expansion and poor conductivity of CuF2 in the charging and discharging process, then in-situ coats a sodium alginate layer on the SEI, and further solves the problem of CuF2 dissolution in organic electrolyte. The synthesized CuF2@void@SEI@SA electrode material shows excellent reversible capacity and excellent cycle stability. The present application conforms to the development concept of green environmental protection, and comprehensively realizes the unity of economic benefit, social benefit and environmental benefit.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery electrode materials, in particular to a CuF2@void@SEI@SA electrode material and a preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries (LIBs) as a kind of energy storage devices with high energy density and high voltage have been widely used in portable electronic devices, electric tools, hybrid electric vehicles and electric vehicles. In particular, with the rapid development of electric vehicles, the demand for LIBs is increasing every year. It is predicted that the demand for LIBs for electric vehicles worldwide will reach 221 billion US dollars by 2024. However, the service life of LIBs is usually 3-8 years, and more than 2 million tons of waste LIBs will be generated every year. Under the social background of strengthening environmental protection and improving resource utilization, such a huge inventory means that the recycling of waste LIBs and their materials will pose a challenge to society in the future. The solution to this problem lies in the comprehensive realization of the unity of economic, social and environmental benefits.

[0003] Because the main components of the electrolyte in the waste battery are lithium hexafluorophosphate and carbonate, these substances generated by lithium salt and solvent are easy to dissolve and diffuse into water, soil and air, causing serious pollution to the environment and posing a potential threat to human life. At present, the recycling methods of lithium ion battery electrolyte mainly include high-temperature calcination method, room temperature dry method and room temperature wet method. When using the high-temperature calcination method, the organic solvent volatilizes or decomposes to generate greenhouse gas CO2, and lithium hexafluorophosphate decomposes into phosphate and fluoride solid compounds. Although this method can handle waste batteries on a large scale, the electrolyte loses its own value, and a large amount of polluting waste gas is generated, so the treatment cost is high. The room temperature dry method and the room temperature wet method can realize the higher recycling value of the electrolyte, but the high treatment cost and great technical difficulty lead to low overall recycling efficiency.

[0004] Compared with transition metal oxides, transition metal fluorides exhibit high ionic characteristics of metal-fluoride bonds, so they have the highest redox potential and can exhibit the highest discharge platform of about ~3.3V as cathode materials of lithium ion batteries, which is beneficial to obtain higher energy density. Among various metal fluorides, CuF2 has a high theoretical capacity of 528mAh g -1 and a high redox potential of ~3.55V, and the energy density reaches 1874Wh kg -1CuF2 is a promising and competitive cathode material. However, CuF2 has some deficiencies, which hinder its large-scale application, mainly embodied in: a, poor intrinsic conductivity; b, large volume expansion in the cycle process, difficult to prepare, high cost, and need to use highly polluting and dangerous hydrofluoric acid as raw material; c, CuF2 is easily dissolved in organic electrolyte, so the stability is poor.

[0005] Based on the above problems, researchers have carried out extensive research. In order to improve the electrochemical activity, Badway embeds CuF2 nanoparticles in oxide mixed conductive matrix, such as MoO3, VO2 and V2O5, and the initial discharge capacity is 510mAh g -1 However, due to the irreversibility of redox reaction, the capacity is greatly attenuated after several cycles. 2+ / 0 Seo reduces the direct contact of CuF2 with electrolyte by coating NiO on the surface of CuF2, thereby inhibiting the dissolution of Cu, and NiO as an artificial SEI layer improves the reversibility of Cu-based material. Unfortunately, the capacity loss of NiO-CuF2 / C electrode in the initial cycle and the voltage hysteresis in the charge and discharge process are large, which hinders its practical application in rechargeable batteries. Recently, Dai designed a high-concentration fluorinated electrolyte, which weakens the solvation of copper ions and inhibits the dissolution of copper. However, CuF2-Ketjen Black nanocomposite cathode lacks long cycle performance.

[0006] Therefore, how to overcome the technical defects of CuF2 itself and realize the unity of high capacity and long cycle of CuF2 is still the main problem that puzzles researchers. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application provides a CuF2@void@SEI@SA electrode material and a preparation method and application thereof. The present application uses a simple solvothermal method to fluorinate the three-dimensional porous metal conductive framework of waste lithium ion battery electrolyte on the surface of the three-dimensional porous metal conductive framework. In-situ synthesis of CuF2@void@SEI electrode material with pomegranate morphology, solves the problems of large volume expansion of CuF2 in the charge and discharge process and poor conductivity, and in-situ coating of SA layer on the surface of SEI, further solves the problem of dissolution of CuF2 in organic electrolyte, and realizes the unity of high capacity and long cycle of CuF2.

[0008] To solve the above technical problems, the present application adopts the following technical scheme:

[0009] The preparation method of CuF2@void@SEI@SA electrode material comprises the following steps:

[0010] The foam copper is cleaned to remove impurities and grease on the surface of the foam copper, and clean foam copper is obtained.

[0011] The clean foam copper is mixed with the electrolyte of the waste lithium ion battery, and then subjected to a solvothermal reaction. 2+ After dissolution, F - is obtained by decomposing the lithium salt at high temperature. 2+ The CuF2 nanoparticles are generated by reaction and are wrapped in the SEI formed by the lithium salt and the solvent after the decomposition of the lithium salt, and a CuF2@void@SEI electrode material is obtained.

[0012] The lithium salt in the electrolyte of the waste lithium ion battery is a fluorine-containing lithium salt.

[0013] The CuF2@void@SEI electrode material is immersed in a sodium alginate aqueous solution until the sodium alginate is coated on the surface of the CuF2@void@SEI electrode material. 2+ The SA aqueous solution is combined with the dissolved Cu 2+ to form a viscous hydrogel and is coated on the surface of the CuF2@void@SEI electrode material, and a SA-Cu 2+ hydrogel effectively hinders the shuttling of Cu 2+ and inhibits the further dissolution of CuF2 in the organic solvent.

[0014] Preferably, the solvothermal reaction is performed at 100-140℃ for 4-10h.

[0015] Preferably, the solvothermal reaction is performed at 120℃ for 6h.

[0016] Preferably, the fluorine-containing lithium salt is selected from lithium hexafluorophosphate, lithium cobalt hexafluorophosphate or lithium iron hexafluorophosphate.

[0017] Preferably, the mass ratio of the clean foam copper to the electrolyte of the waste lithium ion battery is 1:10-40.

[0018] Preferably, the mass ratio of sodium alginate to CuF2@void@SEI electrode material is 100-400:1, and the thickness of sodium alginate is too thin to affect the volume deformation resistance of the SA film, which is not conducive to the stability of the structure; and the thickness of the sodium alginate film is too thick to cause the lithium ion transmission efficiency to decrease.

[0019] The application also protects the CuF2@void@SEI@SA electrode material prepared by the above preparation method.

[0020] The application also protects the application of the above CuF2@void@SEI@SA electrode material in preparing a lithium ion battery positive electrode sheet.

[0021] Preferably, the application method is:

[0022] Preparation of the negative electrode sheet: the metal lithium is pressed and cut;

[0023] Preparation of the electrolyte: LiClO4 is dissolved in an organic reagent to prepare a LiClO4 electrolyte with a concentration of 4 mol / L;

[0024] The organic solvent is composed of dimethyl carbonate and propylene carbonate in a volume ratio of 1:1;

[0025] Preparation of the lithium ion battery: the negative electrode sheet, Cellgard2400 separator, electrolyte and CuF2@void@SEI@SA electrode material are sequentially assembled to prepare a lithium ion battery.

[0026] Compared with the prior art, the application has the following beneficial effects:

[0027] 1. The preparation principle of the application is: in the process of synthesizing the CuF2@void@SEI electrode material by using the solvent thermal method, the Cu 2+ After dissolution, F - reacts with the F obtained by the decomposition of the lithium salt at high temperature to form CuF2 nanoparticles, which are wrapped in the SEI formed by the decomposition of the lithium salt and the solvent to form a core-shell structure, and because the CuF2 nanoparticles are easily dissolved in the organic electrolyte, the internal CuF2 will shrink in size after the formation of the core-shell structure due to further dissolution, forming a CuF2@void@SEI electrode material with a pomegranate morphology, and in the CuF2@void@SEI electrode material, the space between CuF2 and SEI relieves the problem of volume expansion of CuF2 in the cycle process;

[0028] In order to avoid the internal CuF2 from being dissolved in the electrolyte during the test, the application also coats an SA layer on the surface of the CuF2@void@SEI electrode material to form a CuF2@void@SEI@SA electrode material, and the SA aqueous solution can react with the dissolved Cu2+ A viscous hydrogel is formed by cross-linking and coated on the surface of the CuF2@void@SEI electrode material, SA-Cu 2+ Hydrogels can effectively inhibit Cu 2+ The shuttle, inhibiting Cu 2+ This prevents further dissolution of CuF2 in organic solvents, thus ensuring the stability of the CuF2@void@SEI@SA electrode material. It is worth noting that due to the partial Cu within the SEI layer... 2+ By forming a hydrogel with SA, the size of CuF2 nanoparticles is further reduced, leaving more space inside the SEI layer to alleviate the volume expansion of CuF2 during cycling.

[0029] 2. This invention involves in-situ fluorination of copper foam in waste lithium-ion electrolyte, followed by coating with sodium alginate to obtain CuF2@void@SEI@SA electrode material. This CuF2@void@SEI@SA electrode material is then used as the positive electrode material in lithium-ion batteries. Results show that the synthesized CuF2@void@SEI@SA electrode material exhibits good performance in 0.05 Ag... -1 It has a capacity of 535mAh g -1 The invention exhibits high reversible capacity, demonstrating excellent reversible capacity and superior cycle stability. It aligns with the concept of green and environmentally friendly development, comprehensively achieving a balance between economic, social, and environmental benefits. Attached Figure Description

[0030] Figure 1 This is a schematic diagram illustrating the fabrication principle of the CuF2@void@SEI@SA electrode material of this invention.

[0031] Figure 2Figure 1 is a TEM image of the CuF2@void@SEI@SA electrode material of Example 1; Figure 2 is a Raman spectrum of the CuF2@void@SEI@SA electrode material of Example 1 and commercial CuF2 powder at 100 cm-400 cm-1; Figure 3 is a Raman spectrum of the CuF2@void@SEI@SA electrode material of Example 1 and commercial CuF2 powder at 1100 cm-1800 cm-1; Figure 4 is a TEM image of the CuF2@void@SEI@SA electrode material of Comparative Example 1; Figure 5 is a TEM image of the CuF2@void@SEI@SA electrode material of Example 1 at high magnification; Figure 6 is a TEM image of the CuF2@void@SEI@SA electrode material of Comparative Example 2; Figure 7 is a mapping test image of the CuF2@void@SEI@SA electrode material of Example 1; Figures 8a-8d are mapping images of Cu element, F element, C element and O element, respectively, of the CuF2@void@SEI@SA electrode material of Example 1.

[0032] Figure 3 Figure 9 is a plot of the CuF2@void@SEI@SA electrode material of Example 1 at a current density of 0.05 Ag-1at 1-3.5 V, 0.2 mV s-1. -1 Figure 10 is a plot of the CV curves of the CuF2@void@SEI@SA electrode material of Example 1 at 1-3.5 V, 0.2 mV s-1.

[0033] Figure 4 Figure 11 is a plot of the galvanostatic charge-discharge curves of the CuF2@void@SEI@SA electrode material of Example 1 at a current density of 0.05 Ag-1at 1-3.5 V, 0.2 mV s-1. -1 Figure 12 is a plot of the galvanostatic charge-discharge curves of the CuF2@void@SEI@SA electrode material of Example 1 at 1-3.5 V, 0.2 mV s-1.

[0034] Figure 5 Figure 13 is a plot of the charge-discharge capacity of the CuF2@void@SEI@SA electrode material of Example 1 at different current densities.

[0035] Figure 6 Figure 14 is a Nyquist plot of the CuF2@void@SEI@SA electrode material of Example 1 at a frequency of 10 mHz-100 kHz, Figure 6 the inset in Figure 14 is a magnified view of the high frequency region of the EIS.

[0036] Figure 7 Figure 15 is a plot of the cycle stability test of the CuF2@void@SEI@SA electrode material of Example 1 at a current density of 0.05 Ag-1at 1-3.5 V, 0.2 mV s-1. -1 Figure 16 is a plot of the cycle stability test of the CuF2@void@SEI@SA electrode material of Example 1 at 1-3.5 V, 0.2 mV s-1.

[0037] Figure 8 Figure 17 is a plot of the comparison of the capacity of the CuF2@void@SEI@SA electrode material of Example 1 with the capacity reported in the prior art.

[0038] Figure 9The calculation graph of the capacitive contribution of the CuF2@void@SEI@SA electrode material of Example 1; wherein a is the cyclic voltammogram of the CuF2@void@SEI@SA electrode material at 1-3.5V voltage window, 0.2mV s -1 , 0.4mV s -1 , 0.6mV s -1 , 0.8mV s -1 and 1.0mV s -1 ; b is the corresponding relationship graph of the logarithm of the peak current density in a and the logarithm of the scan rate; c is the capacitive storage contribution graph of the CuF2@void@SEI@SA electrode material at 0.6mV s -1 ; d is the capacitive contribution graph of the CuF2@void@SEI@SA electrode material at different scan rates. DETAILED DESCRIPTION

[0039] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings, but it should be understood that the scope of protection of the present application is not limited by the specific embodiments. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present application.

[0040] The present application uses the electrolyte of the waste lithium ion battery as raw material, and reacts F - obtained by decomposing the electrolyte of the waste lithium ion battery with the surface Cu 2+ of the three-dimensional porous foam copper, on the one hand, realizes the secondary utilization of the electrolyte of the waste lithium ion battery, and on the other hand, overcomes the problems of high preparation difficulty, high cost and the need to use highly polluting and dangerous hydrofluoric acid as raw material in the preparation of existing copper fluoride;

[0041] In the CuF2@void@SEI@SA electrode material of the present application, the CuF2 nanoparticles are wrapped in the SEI formed by the decomposition of the lithium salt and the solvent, forming a core-shell structure. The SEI not only protects the CuF2, but also reserves space inside the SEI layer to relieve the volume expansion of CuF2 during the cycle process;

[0042] Considering that copper fluoride has the problem of high intrinsic theoretical specific capacity but poor conductivity, the present application grows copper fluoride in situ on the foam copper substrate. Since the foam copper is conductive, the conductivity of the copper fluoride is improved by using the foam copper, overcoming the problem of poor conductivity of copper fluoride;

[0043] The application solves the problems of poor inherent conductivity, large volume expansion in the cycle process and easy dissolution in the organic electrolyte of CuF2, so that the CuF2@void@SEI@SA electrode material realizes the unification of high capacity and long cycle of CuF2.

[0044] In the application, the void is empty position, the SEI is solid electrolyte interface, and the SA is sodium alginate.

[0045] The technical scheme of the application is further explained and described below by using examples and comparative examples, and the specific embodiments are as follows:

[0046] Example 1

[0047] The preparation method of the CuF2@void@SEI@SA electrode material comprises the following steps:

[0048] S1, cleaning the foamed copper by sequentially ultrasonic cleaning with acetone, anhydrous ethanol, deionized water, 1 mol / L hydrochloric acid solution and deionized water for 15 min, 15 min, 15 min, 30 min and 15 min, respectively, to obtain clean foamed copper;

[0049] S2, placing the 2cm*2cm clean foamed copper in 40mL waste lithium ion battery electrolyte with lithium hexafluorophosphate as lithium salt, and carrying out solvothermal reaction at 120℃ in a high-pressure reaction kettle for 6h, taking out the foamed copper after the solvothermal reaction is completed, then sequentially washing with deionized water and anhydrous ethanol, and then placing in a vacuum drying oven for drying, with a drying temperature of 60℃ and a drying time of 8h, to obtain the CuF2@void@SEI electrode material;

[0050] S3, placing the CuF2@void@SEI electrode material in a sodium alginate aqueous solution for soaking for 4h, the sodium alginate aqueous solution is obtained by dissolving 0.5g of sodium alginate in 100mL of deionized water, and after the soaking is completed, placing in a vacuum drying oven for drying, with a drying temperature of 60℃ and a drying time of 8h, to obtain the CuF2@void@SEI@SA electrode material.

[0051] Example 2

[0052] The preparation method of the CuF2@void@SEI@SA electrode material comprises the following steps:

[0053] S1, cleaning the foamed copper by sequentially ultrasonic cleaning with acetone, anhydrous ethanol, deionized water, 1 mol / L hydrochloric acid solution and deionized water for 15 min, 15 min, 15 min, 30 min and 15 min, respectively, to obtain clean foamed copper;

[0054] S2, 2cm*2cm clean foam copper was placed in 40mL waste lithium-ion battery electrolyte with lithium hexafluorophosphate as lithium salt, and was solvothermal reacted at 100℃ for 10h in a high-pressure reaction kettle. After the solvothermal reaction was completed, the foam copper was taken out, and then was sequentially rinsed with deionized water and anhydrous ethanol, and then was placed in a vacuum drying oven for drying, the drying temperature was 60℃, and the drying time was 8h, to obtain a CuF2@void@SEI electrode material;

[0055] S3, the CuF2@void@SEI electrode material was placed in a sodium alginate aqueous solution for soaking for 4h, the sodium alginate aqueous solution was 1.0g sodium alginate dissolved in 100mL deionized water, after the soaking was completed, it was placed in a vacuum drying oven for drying, the drying temperature was 60℃, and the drying time was 8h, to obtain a CuF2@void@SEI@SA electrode material.

[0056] Example 3

[0057] The preparation method of the CuF2@void@SEI@SA electrode material comprises the following steps:

[0058] S1, the foam copper was sequentially ultrasonically cleaned with acetone, anhydrous ethanol, deionized water, 1mol / L hydrochloric acid solution and deionized water for 15min, 15min, 15min, 30min and 15min, to obtain clean foam copper;

[0059] S2, 2cm*2cm clean foam copper was placed in 40mL waste lithium-ion battery electrolyte with lithium hexafluorophosphate as lithium salt, and was solvothermal reacted at 100℃ for 10h in a high-pressure reaction kettle. After the solvothermal reaction was completed, the foam copper was taken out, and then was sequentially rinsed with deionized water and anhydrous ethanol, and then was placed in a vacuum drying oven for drying, the drying temperature was 60℃, and the drying time was 8h, to obtain a CuF2@void@SEI electrode material;

[0060] S3, the CuF2@void@SEI electrode material was placed in a sodium alginate aqueous solution for soaking for 4h, the sodium alginate aqueous solution was 1.0g sodium alginate dissolved in 100mL deionized water, after the soaking was completed, it was placed in a vacuum drying oven for drying, the drying temperature was 60℃, and the drying time was 8h, to obtain a CuF2@void@SEI@SA electrode material.

[0061] Comparative Example 1

[0062] The preparation method of the CuF2@void@SEI@SA electrode material is the same as that of Example 1, except that the solvothermal time is replaced by 1h instead of 6h, comprising the following steps:

[0063] S1, clean the foamed copper with acetone, anhydrous ethanol, deionized water, 1 mol / L hydrochloric acid solution and deionized water in sequence for 15 min, 15 min, 15 min, 30 min and 15 min respectively by ultrasonic cleaning, to obtain clean foamed copper;

[0064] S2, place the clean foamed copper with a size of 2cm*2cm in 40mL waste lithium-ion battery electrolyte with lithium hexafluorophosphate as lithium salt, and perform solvothermal reaction at 120℃ in a high-pressure reaction kettle for 1h, then take out the foamed copper, and then sequentially wash with deionized water and anhydrous ethanol, and then place in a vacuum drying oven for drying, with a drying temperature of 60℃ and a drying time of 8h, to obtain CuF2@void@SEI electrode material;

[0065] S3, immerse the CuF2@void@SEI electrode material in a sodium alginate aqueous solution for 4h, the sodium alginate aqueous solution is prepared by dissolving 0.5g of sodium alginate in 100mL of deionized water, and then place in a vacuum drying oven for drying after immersion, with a drying temperature of 60℃ and a drying time of 8h, to obtain CuF2@void@SEI@SA electrode material.

[0066] Comparative Example 2

[0067] The preparation method of the CuF2@void@SEI@SA electrode material is the same as that of Example 1, except that the solvothermal time is replaced by 12h instead of 6h, including the following steps:

[0068] S1, clean the foamed copper with acetone, anhydrous ethanol, deionized water, 1 mol / L hydrochloric acid solution and deionized water in sequence for 15 min, 15 min, 15 min, 30 min and 15 min respectively by ultrasonic cleaning, to obtain clean foamed copper;

[0069] S2, place the clean foamed copper with a size of 2cm*2cm in 40mL waste lithium-ion battery electrolyte with lithium hexafluorophosphate as lithium salt, and perform solvothermal reaction at 120℃ in a high-pressure reaction kettle for 1h, then take out the foamed copper, and then sequentially wash with deionized water and anhydrous ethanol, and then place in a vacuum drying oven for drying, with a drying temperature of 60℃ and a drying time of 8h, to obtain CuF2@void@SEI electrode material;

[0070] S3, immerse the CuF2@void@SEI electrode material in a sodium alginate aqueous solution for 4h, the sodium alginate aqueous solution is prepared by dissolving 0.5g of sodium alginate in 100mL of deionized water, and then place in a vacuum drying oven for drying after immersion, with a drying temperature of 60℃ and a drying time of 8h, to obtain CuF2@void@SEI@SA electrode material.

[0071] The CuF2@void@SEI@SA electrode material solving the problems of large volume expansion, poor conductivity of CuF2 in the charging and discharging process, and dissolution of CuF2 in organic electrolyte is prepared in Examples 1-3 of the present application. The CuF2@void@SEI@SA electrode material prepared in Example 1 and Comparative Examples 1-2 is taken as an example for research, and the specific research method and results are shown as follows.

[0072] Figure 1 The preparation principle diagram of the CuF2@void@SEI@SA electrode material of the present application.

[0073] I. Characterization of CuF2@void@SEI@SA electrode material:

[0074] Figure 2 a is the TEM image of the CuF2@void@SEI electrode material of Example 1. Clean foam copper and waste LiPF6 electrolyte are kept at 120℃ for 6h, during which LiPF6 decomposes to release F - , and reacts with the foam copper to generate CuF2 in situ on the surface of the foam copper, and the size of the CuF2 nanoparticles is 100nm; at the same time, the organic solvent in the electrolyte spontaneously generates a SEI-like protective layer with a thickness of 50nm around the CuF2, and the thickness of the SEI layer is 50nm; it can be clearly observed from the figure that there is a single CuF2 nanoparticle inside each SEI layer, and the volume expansion of the prepared CuF2@void@SEI electrode material in the charging and discharging process is effectively alleviated due to the reserved space between the SEI layer and the CuF2 nanoparticles.

[0075] Raman characterization of CuF2@void@SEI@SA electrode and CuF2 powder is carried out, as shown in Figure 2 b, in the range of 200-400cm -1 , the CuF2 powder has four strong Raman bands, two Bg modes and two Ag modes. The characteristic peaks of CuF2@void@SEI@SA electrode at 216cm -1 and 283cm -1 are consistent with the characteristic peaks of the commercial CuF2 powder Bg mode.

[0076] At the same time, compared with the commercial CuF2 powder, the CuF2@void@SEI@SA electrode has obvious characteristic peaks related to the SEI layer at 1357cm -1 and 1595cm -1 , as shown in Figure 2 c, which are respectively marked as D band and G band, which is Figure 2The mapping test results in g are consistent. The above results fully confirm the successful synthesis of the CuF2@void@SEI@SA electrode.

[0077] As shown in Figure 2 As shown in d-2f, with the extension of the solvothermal treatment time, the CuF2 nanoparticles gradually decrease until completely disappear. The CuF2@void@SEI electrode prepared under the condition of a solvothermal time of 6 h has a more excellent microstructure, which is beneficial to relieve the volume expansion of CuF2 and prolong the cycle life of the electrode.

[0078] As shown in Figure 2 As shown in g-2k, from Figure 2 The mapping diagram of the CuF2@void@SEI@SA electrode material in g can clearly observe that the Cu element and the F element are concentrated on the central nanoparticles, which confirms the existence of CuF2 in the electrode material. The annular SEI layer around the CuF2 nanoparticles is mainly composed of C element and O element, and the C element and O element are mainly derived from the organic solvent in the electrolyte. It is worth noting that since the main element composition of SA is also C and O, the delamination of SEI and SA is not effectively observed in the mapping diagram.

[0079] II. Electrochemical performance test:

[0080] (1) Battery assembly:

[0081] The CuF2@void@SEI@SA electrode material of Example 1 was cut into a size of 0.5 cm x 0.5 cm, and CR2025 button batteries were assembled in an argon-filled glove box, O2 and H2O in the glove box <1 ppm, with a metal lithium foil as the counter electrode and reference electrode, 4 mol / L LiClO4 as the electrolyte, and the organic solvent consisting of dimethyl carbonate and propylene carbonate in a volume ratio of 1:1.

[0082] The battery was subjected to electrochemical test. When cyclic voltammetry scanning was performed, the range of cyclic voltammetry characteristic curve was set to 1V-3.5V, and the scanning rate was 0.2mVs -1 -1mVs -1 . When constant current charge and discharge test was performed, the voltage interval was set to 1V-3.5V, and the current intensity was 10μA-640μA. When impedance test was performed, the frequency range was set to 100kHz-10mHz, and the voltage amplitude was 10mV. When using constant current charge and discharge for cycle stability test, the voltage interval was set to 1V-3.5V, the current density was set to 0.05Ag -1 , and the cycle number was 70 times.

[0083] (2) Performance determination:

[0084] The electrochemical performance of the CuF2@void@SEI@SA electrode material was investigated by assembling a coin-shaped lithium-ion battery with CuF2@void@SEI@SA electrode material as the working electrode, lithium foil as the counter electrode and reference electrode. The electrode material exhibited excellent performance at 0.2 mV / s. -1 The first four cycles of cyclic voltammetry curves are as follows: Figure 3 As shown, during the first discharge cycle, two relatively obvious reduction peaks appeared at ~3.34V and ~1.49V, corresponding to the lithiation reaction peaks of CuF2. 2+ Reduced to Cu 0 The reaction formula is CuF₂ + 2Li + 2e⁻ - →Cu + 2LiF. During the first charging cycle, besides a significant oxidation peak at ~1.49V, there is also a small oxidation peak at ~3.32V, corresponding to the delithiation process of the electrode material. 0 Oxidized to Cu 2+ The reaction is Cu + 2LiF → CuF₂ + 2Li + 2e⁻ - The lithiation / delithiation reactions during the above charge-discharge process demonstrate that the CuF2@void@SEI@SA electrode material exhibits high redox reversibility during charge-discharge. With increasing scan count, the reduction peak positions gradually stabilize at ~1.53V and ~3.29V during discharge cycles 2-4, while the oxidation peak positions gradually stabilize at ~2.49V and ~3.32V during charging. Compared to the initial charge-discharge process, the shift in peak positions is mainly attributed to the fact that some electrode material was not fully activated during the initial charge-discharge process; as the reaction progresses, the electrode material eventually stabilizes.

[0085] Notably, the CV curves of the CuF2@void@SEI@SA electrode material show a good match between cycles 2 and 4, indicating excellent reversibility during repeated electrochemical cycling. This superior reversibility is primarily attributed to the SEI-like layer in the electrode structure, which effectively mitigates structural breakage caused by the volume expansion of CuF2 nanoparticles during cycling. Simultaneously, the SA layer surrounding the CuF2@void@SEI@SA electrode interacts with the Cu... 2+ Cross-linked hydrogel films can prevent Cu 2+ The shuttle movement, thereby inhibiting Cu 2+ Dissolution in organic solvents.

[0086] like Figure 4 As shown, the charge / discharge capacity of the CuF2@void@SEI@SA electrode material in Example 1 is stable at 464 mAh g. -1 and 480mAhg -1, the coulombic efficiency is close to 96.5%. Benefiting from the internal reserved space of the SEI layer in the structure of the CuF2@void@SEI@SA electrode material, the structure breakage caused by the volume expansion of CuF2 nanoparticles during the cycle process can be effectively alleviated, and the CuF2@void@SEI@SA electrode material has excellent redox reversibility.

[0087] As shown in Figure 5 , the CuF2@void@SEI@SA electrode material has superior rate performance and can realize deep charge and discharge at high current density.

[0088] As shown in Figure 6 , the impedance data show that the intrinsic resistance of the CuF2@void@SEI@SA electrode material is about 21.48Ω before cycling and about 22.86Ω after cycling. The lower resistance is helpful for the transmission of electrons and ions, improves the utilization rate of CuF2, and the change of resistance before and after cycling is small, indicating that the structure of the CuF2@void@SEI@SA electrode material is stable.

[0089] The cycle stability of the CuF2@void@SEI@SA electrode material is further verified by long-time charge and discharge, as shown in Figure 7 , after 70 cycles, the capacity is maintained at 535mAhg -1 , showing excellent lithium storage capacity and excellent cycle stability. During the entire cycle process, the coulombic efficiency of the CuF2@void@SEI@SA electrode material is maintained at a level close to 100%.

[0090] As shown in Figure 8 , compared with other fluoride-based electrode materials of the prior art, the CuF2@void@SEI@SA electrode material of the present application has excellent capacity. The references corresponding to the samples in the figure are shown in Table 1:

[0091] Table 1 Reference Table

[0092]

[0093]

[0094] As shown in Figure 9 , by studying the capacitive contribution of the CuF2@void@SEI@SA electrode material, the utilization rate of CuF2 in the CuF2@void@SEI@SA electrode material is calculated to be about 79.5%.

[0095] Obviously, various modifications and changes can be made to the present application by those skilled in the art without departing from the spirit and scope of the present application. Accordingly, it is intended that the present application embrace all such modifications and changes as fall within the scope of the claims and their equivalents. The above examples are merely illustrative of the best modes presently contemplated for carrying out the present application. This application is intended to cover any and all adaptations or variations of the various embodiments of the application disclosed above.

Claims

1. A method for preparing CuF2@void@SEI@SA electrode material, characterized in that, The method comprises the following steps: The cleaning treatment is performed on the foamed copper to obtain clean foamed copper; The clean foam copper is mixed with waste lithium ion battery electrolyte, the lithium salt in the waste lithium ion battery electrolyte is fluorine-containing lithium salt, then solvent thermal reaction is carried out, in the solvent thermal reaction process, Cu 2+ After dissolution, F - Reaction with lithium salt decomposed at high temperature, CuF2 nanoparticles are generated, and are wrapped in SEI formed by lithium salt decomposition and solvent, to obtain CuF2@void@SEI electrode material; The CuF2@void@SEI electrode material is immersed into a sodium alginate aqueous solution until the sodium alginate is coated on the surface of the CuF2@void@SEI electrode material, the sodium alginate is used to inhibit the dissolution of CuF2 in the organic electrolyte, and the CuF2@void@SEI@SA electrode material is obtained after drying.

2. The method for preparing the CuF2@void@SEI@SA electrode material according to claim 1, characterized in that, The conditions of the solvothermal reaction are as follows: the solvothermal reaction is performed at 100-140 ℃ for 4-10 h.

3. The method for preparing the CuF2@void@SEI@SA electrode material according to claim 2, characterized in that, The conditions of the solvothermal reaction are as follows: the solvothermal reaction is performed at 120 ℃ for 6 h.

4. The method for preparing the CuF2@void@SEI@SA electrode material according to claim 1, characterized in that, The fluorine-containing lithium salt is selected from lithium hexafluorophosphate, lithium cobalt hexafluorophosphate or lithium iron hexafluorophosphate.

5. The method for preparing the CuF2@void@SEI@SA electrode material according to claim 1, characterized in that, The mass ratio of the clean foamed copper to the electrolyte of the waste lithium ion battery is 1:10-40.

6. The method of claim 1, wherein the CuF2@void@SEI@SA electrode material is prepared by the process comprising: The mass ratio of the sodium alginate to the CuF2@void@SEI electrode material is 100-400:

1. 7.A CuF2@void@SEI@SA electrode material prepared by the preparation method of any one of claims 1-6. 8.The application of the CuF2@void@SEI@SA electrode material of claim 7 in the preparation of a lithium ion battery positive electrode sheet.

9. Use according to claim 8, characterized in that, The application method is as follows: Preparation of the negative electrode sheet: the metal lithium is pressed and cut; Preparation of the electrolyte: LiClO4 is dissolved in an organic solvent to prepare a LiClO4 electrolyte with a concentration of 4 mol / L; The organic solvent is composed of dimethyl carbonate and propylene carbonate at a volume ratio of 1:1; Preparation of the lithium ion battery: the negative electrode sheet, a Cellgard2400 separator, the electrolyte and the CuF2@void@SEI@SA electrode material are sequentially assembled to prepare the lithium ion battery.

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