NL2030456B1

NL2030456B1 - Cathode Material Coated In situ by Copper Foam/lithium Metal Battery

Info

Publication number: NL2030456B1
Application number: NL2030456A
Authority: NL
Inventors: Liu Yuhua; Wang Weijie; Li Dongwei; Gu Qianqian; Tao Yuanyuan; Li Yong; Wang Kang
Original assignee: Advanced Mat Institute Shandong Academy Of Sciences
Priority date: 2021-11-05
Filing date: 2022-01-07
Publication date: 2023-01-03
Also published as: CN114039033A

Abstract

The disclosure relates to the technical field of cathode material for lithium metal battery, in 5 particular to a method for preparing a cathode material coated in situ by copper foam/lithium metal. Specifically, a surface - modified copper foam 3D current collector is provided with copper foam as the framework material, wherein the surface of copper foam is oxidized in situ to generate cuprous oxide; the cleaned and dried copper foam is oxidized by cyclic voltammetry and then dried to prepare the surface - modified copper foam 3D current collector. A 3D collector with 10 secondary structure for lithium metal battery that can inhibit the growth of lithium dendrites and improve the long - cycle stability with high electrochemical performance of lithium metal anode is prepared according to the present disclosure, and the prepared 3D collector has a large specific surface area, lithium ion diffusion coefficient and excellent electrical conductivity, and exhibits excellent long - cycle stability and high electrochemical performance.

Description

Cathode Material Coated In situ by Copper Foam/lithium Metal Battery

TECHNICAL FIELD The disclosure relates to the technical field of cathode material for lithium metal battery, in particular to a method for preparing a cathode material coated in situ by copper foam/lithium metal.

BACKGROUND The booming portable electronic devices and electric vehicles imposes urgent demand on the development of new generation of high - energy - density rechargeable lithium batteries. With extremely high theoretical capacity (3,860 mAh/g 1), low standard electrochemical potential (-3.04 V vs. SHE) and excellent intrinsic conductivity, lithium has become the best choice of anode materials. However, its commercialization as anode materials has been hindered by the uncontrollable dendrites growth, relatively unlimited volume expansion and serious side reactions. Among these problems, dendrites growth is considered to be the most severe obstacle. Dendrites can easily penetrate the separator to cause short circuits, thermal runaway, fires and even explosions. In addition, dendrites are prone to react with the electrolyte to irreversibly consume the active material, moreover, dead lithium caused by uneven dissolution of lithium dendrites will further reduce the battery life.

Researchers nowadays usually adopt the following methods to solve various problems of lithium metal battery, including electrolyte additive modification, artificial SEI layer, solid state electrolytes and mechanical separator with high shear modulus, etc.

For inhibiting the growth of lithium dendrites, there is a feasible way of designing a functional three - dimensional (3D) framework, which not only reduces the inhomogeneity of current density distribution, but also limits the volume change of Li stripping/plating. Still, most 3D frameworks show lithophilic. Therefore, it is urgently needed to modify the framework surface by a lithophilic layer to realize the large - scale application of thermal infusion strategy on the 3D framework.

SUMMARY One of the objectives of the disclosure is to provide a method for preparing a cathode material coated in situ by copper foam/lithium metal by using cyclic voltammetry to oxidize copper foam and grow a layer of lithophilic copper oxide in situ on the surface of copper foam to obtain a 3D current collector with secondary structure for lithium metal batteries that can inhibit the growth of lithium dendrites and improve the long - cycle stability and excellent electrochemical performance of lithium metal anodes. The 3D current collector prepared herein has a large specific surface area, high lithium ion diffusion coefficient and excellent electrical conductivity, and exhibits excellent long - cycle stability and high electrochemical performance.

According to one of the technical schemes of the disclosure, a surface - modified copper foam 3D current collector takes copper foam as material of framework, wherein the surface of copper foam is oxidized in situ to generate cuprous oxide.

Further, the thickness of the copper foam is 0.5 - 1.5 mm with porosity of 110 - 130 ppi, and the cuprous oxide has a spike - like structure.

Copper foam is selected as the 3D current collector and copper source of lithium metal cathode with relatively uniform 3D macropores, large supporting area and high conductivity, it also has the following characteristics: a 3D framework structure that can guide the uniform plating of lithium; and a large number of cavity structures that can provide buffer space for the growth of lithium dendrites and therefore delays the volume expansion. Nonetheless, it should be noted that commercial copper foam bears certain shortcomings, such as low specific surface area and weak affinity with lithium. Based upon that, the present disclosure adopts copper foam as substrate and modifies it to prepare a 3D current collector that meeting the needs against lithium metal cathode. In view of the thickness and porosity of copper foam that influencing the morphology and performance of the final product, experiments show that the product with the thickness of 0.5 -

1.5 mm and the porosity of 110 - 130 ppi has the best performance.

According to another technical scheme of the disclosure, the method for preparing the surface - modified copper foam 3D current collector comprises the following steps: the cleaned and dried copper foam is oxidized by cyclic voltammetry and then dried to prepare the surface - modified copper foam 3D current collector. Such method is simple with no toxicity and can be applied on a large scale without requiring surfactant. Active substance grows on the conductive substrate in situ, which therefore makes adhesive or conductive agent not required while ensuring good interface contact between the active substance and the substrate as well as good conductivity.

Further, the cleaned and dried copper foam is prepared by ultrasonic cleaning copper foam with hydrochloric acid solution and acetone in turn; specifically, the pre - cut copper foam sheet is ultrasonically cleaned firstly with hydrochloric acid solution to remove the oxide on the surface ofthe copper foam, then the copper foam after hydrochloric acid cleaning is taken out and washed with deionized water for three times, and then immersed in acetone solution for ultrasonic cleaning to remove the oil stain on the surface of the copper foam sheet. The cleaned copper foam is washed repeatedly with deionized water and dried at 50°C for later use.

The conditions for cyclic voltammetry are as follows: voltage range of -0.3 - 0.3 V, scanning speed of 1 mV/s, number of scanning cycles of 1, drying temperature is 50°C, and the drying duration is 5 - 6 hours. The specific conditions of cyclic voltammetry mentioned above can ensure that the electrochemical oxidation occurs on the surface of copper foam and cuprous oxide generates on the surface of copper foam. Spike morphology provides a significantly increased specific surface area of copper foam, which means a larger contact area for copper foam and molten lithium in the subsequent process of preparing composite lithium cathode by melting method in addition to accelerated melting rate of lithium through greater capillary effect; meanwhile, a large number of nucleation sites and charge centres for the plating of lithium is provided on the cathode, which is conducive for reducing the current density, guiding the uniform plating of lithium and forming a flat and smooth plane, and developing a stable SEI layer as a result.

Further, the concentration of hydrochloric acid solution is 0.5 - 1 mol/l, the ultrasonic cleaning duration is 15 min, and that concentration of the potassium hydroxide solution is 0.5 - 1 mol/l.

For electrochemical oxidation in alkaline solution, the concentration is related with the reaction duration, that is, a higher concentration results in a short reaction duration.

Another technical scheme of the present disclosure is an application of the surface - modified copper foam 3D current collector in preparing cathode material for lithium metal battery.

A further technical scheme of the present disclosure is a cathode material for lithium metal battery prepared by directly compounding the surface - modified copper foam 3D current collector as a skeleton material with lithium metal. Specifically, the embedding of lithium metal is achieved by melting lithium metal and perfusing under high - temperature.

Another technical scheme of the present disclosure is a method for preparing the cathode material for lithium metal battery, which includes the following steps: in an inert environment, the surface - modified copper foam 3D current collector is immersed in molten liquid lithium metal, then taken out and cooled to room temperature to prepare the cathode material for lithium metal battery.

Specifically, the surface - modified copper foam 3D current collector is transferred to a glove box filled with argon gas of high - purity; firstly, the lithium sheet is melted into liquid lithium in the battery case on the heating table, and the surface - modified copper foam 3D current collector is immersed into the liquid lithium, wherein the liquid lithium will be quickly absorbed into the porous skeleton structure of the surface - modified copper foam 3D current collector; then the modified copper foam filled with lithium is taken out and moved to a clean crucible for cooling to prepare the cathode material for lithium metal battery.

Further, the lithium metal sheet in the battery case is heated to 320°C, and the value of oxygen of that high - purity argon gas is less than 0.1 ppm.

The surface - modified copper foam 3D current collector prepared by the disclosure has a layer of cuprous oxide with spike structure loaded in situ on the surface of copper foam structure, the lithium - affinity and spike structure of cuprous oxide can quicken up the melting and perfusion of high - temperature lithium metal; the special structure works to reduce the local current density, effectively delays the growth of lithium dendrite and provides a large number of nucleation sites for lithium plating, which is conducive to the uniform plating of lithium to form a smoath plane and a stable SEI layer.

Another technical scheme of the present disclosure is an application of the cathode material for lithium metal battery in preparing battery.

Further, the battery is a symmetrical battery or a full battery.

Further, when the battery is a symmetrical battery, the electrode sheets of both the anode and the cathode of the symmetric battery are of the above - mentioned cathode material for lithium metal battery.

Further, when the battery is a full battery, the aluminium foil current collector coated with LiFePO,4 is used as material of anode, and the cathode material for lithium metal battery mentioned above is used as the cathode material.

Furthermore, the above two batteries are assembled in a glove box filled with argon gas of high - purity; the electrolyte of symmetrical battery is 1 mol of LiTFSI dissolved in 1 L of DME: DOL mixed solution, wherein the volume ratio of DME to DOL in the electrolyte is 1:1, and a LiNO:3 additive with a mass percentage of 2% is contained; the electrolyte of the full battery is 1 mol of LiPFs dissolved in 1 L of EC:DEC mixed solution, wherein the volume ratio of EC to DEC in the electrolyte is 1:1.

Furthermore, the separator used in the symmetrical battery and the full battery are polypropylene (PP) separator.

Compared with the prior art, the disclosure has the following beneficial effects: commonly used copper foam current collector with good conductivity and strong toughness is used as 3D framework in this disclosure to effectively control the volume change of lithium metal and reduce the current density; performance of the 3D framework is improved since no excessive inactive substances have been introduced in the process of surface modification; the cathode 3D current collector for lithium metal battery prepared by the method can not only be used as the site of lithium ion plating, but also may be used to effectively reduce the local current density of the electrode through its larger specific surface area, and its internal space can also inhibit the volume expansion of the electrode, therefore effectively inhibit the growth of lithium dendrite or the formation of "dead lithium" on the electrode surface of the lithium metal battery, thus improving the CE (Coulomb efficiency) of the lithium metal battery, and prolonging the cyclic service life and the safety and stability in the application.

By applying this simple and convenient method for preparing the cathode 3D current collector for the lithium metal battery, the cost for producing the lithium metal battery can be reduced and the commercialization of the lithium metal battery can hence be promoted.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1. XRD pattern of the surface - modified copper foam 3D current collector in Embodiment 1 of the present disclosure; FIG. 2. SEM image of the surface - modified copper foam 3D current collector in Embodiment 1 of the present disclosure;

FIG. 3. Galvanostatic cycling performance of symmetric cell using the surface - modified copper foam 3D current collector in Embodiment 1 of the present disclosure (grey), and the bare Li foils (black) at a current density of 1, and 3 mA cm’? with a stripping/plating capacity of 1MmAh cm 5 FIG. 4. Full battery cycle stability test in Embodiment 1 of the present disclosure; FIG. 5. SEM image of the surface - modified copper foam 3D current collector in Embodiment 2 of the present disclosure; FIG. 6. Galvanostatic cycling performance of symmetric cell using the surface - modified copper foam 3D current collector in Embodiment 2 of the present disclosure (grey), and the bare Li foils (black) at a current density of 1, and 3 mA cm’? with a stripping/plating capacity of 1mAh cm FIG. 7. SEM image of the surface - modified copper foam 3D current collector in Embodiment 3 of the present disclosure; in which a is the SEM image of the material at 500 times magnification, b is the SEM image of the material at 10,000 times magnification and c is the SEM image of the material at 100,000 times of magnification; FIG. 8. SEM image of the surface - modified copper foam 3D current collector in Embodiment 4 of the present disclosure; wherein a is the SEM image of the material at 1,000 times of magnification, b is the SEM image of the material at 10,000 times of magnification; FIG. 9. SEM image of the surface - modified copper foam 3D current collector in Embodiment 5 of the present disclosure, wherein a is the SEM image of the material at 1000 times of magnification, and b is the SEM image of the material at 10,000 times of magnification; FIG. 10. SEM image of the surface - modified copper foam 3D current collector of Comparative Embodiment 1 in the present disclosure, wherein a is the SEM image of the material at 1,000 times of magnification, b is the SEM image of the material at 10,000 times of magnification and c is the SEM image of the material at 20,000 times of magnification.

DESCRIPTION OF THE INVENTION Now, various exemplary embodiments of the present disclosure will be described in detail, and such detailed description should not be considered as a limitation of the present disclosure, but should be understood as a more detailed description of some aspects, characteristics and embodiments of the present disclosure.

It should be understood that the terms used in this disclosure are only for describing specific embodiments, and are not used to limit the disclosure. In addition, for the numerical range in the present disclosure, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Any stated value or intermediate value within the stated range and any other stated value or every smaller range between intermediate values within the stated range are also included in the present disclosure.

The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by the ordinary technicians in the field of this disclosure.

Although the present disclosure only describes the preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and/or materials related to the documents. In case of conflict with any incorporated documents, the contents of this specification shall prevail.

Without departing from the scope or spirit of the present disclosure, it is obvious to those skilled in the art that many modifications and changes can be made to the specific embodiments of the present disclosure. Other embodiments obtained from the description of the present disclosure will be obvious to the skilled person. The description and embodiments of that present disclosure are exemplary only.

The words "comprising", "including", "having" and "containing" used in this paper are all open terms, that is, they mean including but not limited to.

The reagents and instruments used in the following embodiments of the disclosure are as follows: Scanning electron microscope test: the model of scanning electron microscope is JEOL JSM - 7800F,; X - ray powder diffraction (XRD). the model of X - Ray diffractometer is Bruker D8 advance with test range of 10 - 80 degrees; Charge and discharge tester: the model is testing system of Wuhan LAND Electronic Co.Ltd; Copper foam: purchased from Shanxi Lizhiyuan Battery Materials Co., Ltd.; Lithium metal sheet: purchased from China Energy Lithium Co., Ltd.

Where no specific conditions are specifically indicated in the embodiments, operation according to the conventional steps described in the literature in the art is acceptable. The reagents used are all conventional products commercially available.

Embodiment 1 (1) A copper foam sheet with thickness of 0.8 mm, porosity of 130 ppi and size of 2 cm*2 cm is ultrasonically cleaned with 1 mol/l hydrochloric acid solution for 15 min to remove the oxide on the surface of copper foam, then the copper foam after hydrochloric acid cleaning is taken out and washed with deionized water for three times, and then immersed in acetone solution for ultrasonic cleaning for 15 min to remove the oil stain on the surface of the copper foam sheet. The cleaned copper foam is washed repeatedly with deionized water and dried at 50°C for later use.

(2) 1 mol/l potassium hydroxide solution is prepared, and the copper foam in step (1) is oxidized in potassium hydroxide solution by cyclic voltammetry (voltage range of -0.3 -0.3V, scanning rate of 1 mV/s, and the number of scanning cycles is 1), and then dried at 50°C for 5 hours to generate a layer of lithiophilic cuprous oxide on the surface layer, thus obtaining the surface - modified copper foam 3D current collector.

XRD test of surface - modified copper foam 3D current collector shows that the main components are copper and cuprous oxide, and further SEM test (FIG. 2) shows that a layer of cuprous oxide is grown on the framework of copper foam, specifically, a spike - structured oxide is generated from the smooth surface. (3) Preparation of cathode material for lithium metal battery: in a glove box filled with argon gas, the lithium sheet is melted at 320°C on the heating table to obtain liquid lithium metal, after the modified copper foam current collector is contacted with the liquid lithium metal, the liquid lithium metal is quickly filled into the copper foam framework, and the modified copper foam filled with lithium is taken out and moved to a clean crucible for cooling to obtain the cathode material for lithium metal battery. (4) Assembling symmetrical batteries: 1 mol of LiTFSI is dissolved in 1 L of DME:DOL (the volume ratio of DME to DOL is 1:1) mixed solution, and 2% LiNO:3 additive is added according to the mass percentage to obtain electrolyte; 70 pL of the above electrolyte is used to assemble a 2025 button - type symmetric cell in a glove box protected by an argon atmosphere with the lithium metal cell cathode material prepared in step (3) as the electrode sheet for the positive and cathode electrodes of the symmetric cell and the PP separator as the separator; the prepared symmetrical electrodes are charged and discharged 1 mAh/cm? at 1 and 3 mA/cm? current densities, and the cycle stability tests are performed with commercial lithium tablets as controls; the results shown in FIG. 3 indicate that when the current density is 1 mA/cm? and the cycle capacity is 1 mAh/cm?, the Li@Cu.O - Cu symmetrical battery can be cycled stably for 800 h with an overpotential of 25 mV without short circuit.

However, the commercial lithium sheet symmetric battery exhibits an overpotential of 30 mV at the beginning of the cycle, and it increases continuously with the cycle.

After about 500 hours of cycle, the overpotential exceeds 130 mV, which is caused by the growth of dendrite on the electrode surface and the accumulation of dead lithium.

When the current density is 3 mA/cm? and the cycle capacity is 1 mAh/cm?, the overpotential of the commercial lithium cathode symmetrical battery exceeds 100 mV after 200 h of cycle, while the initial polarization voltage of the symmetrical battery is about 50 mV, and the cycle life is as long as 400 h with no obvious voltage fluctuation. (5) Full battery assembling: 1 mol of LiPFs is dissolved in 1 L of EC:DEC mixed solution (the volume ratio of EC to DEC is 1:1) to obtain electrolyte, 70 pL of the electrolyte is used, the aluminium foil current collector coated with LiFePQ4 is used as the anode material, the cathode material for lithium metal battery prepared in step (3) is used as the cathode material, and the PP separator is used as the separator to assemble the full battery in a glove box protected by argon atmosphere.

The cycle performance of the full battery is tested at rate of 1 C, and the results shown in FIG. 4 indicate that after 400 cycles, the full battery can still maintain 80% of specific capacity, indicating an effectively improved service life of the full battery. Embodiment 2 Same as Embodiment 1 except the difference that the copper foam sheet specifications is as follows: thickness of 0.8 mm, porosity of 110 ppi, size of 2 cm*2 cm; SEM test is carried out on the prepared surface - modified copper foam 3D current collector, and the results shown in FIG. 5 proves that a large number of rod - like nanostructures have grown on the surface. The length of nanorods is about 1 - 2 ym and the diameter is about 100 nm. The morphology of the grown cuprous oxide can be controlled by adjusting the porosity of the copper foam, and the substrate with large and small porosity induces the generation of nanorod structures. At the current density of 1 and 3 mA/ecm?, charging and discharging 1 mAh/cm? are carried out, and the cyclic stability of the prepared symmetrical electrode is tested. The results shown in FIG. 6 indicates that when the current density is 1 mA/cm? and the cycle capacity is 1 mAh/cm?, the composite electrode symmetric battery can stably cycle for 600 h with an overpotential of 30 mV without short circuit; the current increases as much as 3 mA/cm?, then the composite electrode symmetric battery can stably cycle for 330 h, which is worse than that of Embodiment

1.

Embodiment 3 (1) A copper foam sheet with thickness of 0.5 mm, porosity of 110 ppi and size of 2 cm*2 cm is ultrasonically cleaned with 0.5 mol/l hydrochloric acid solution for 15 min to remove the oxide on the surface of copper foam, then copper foam after hydrochloric acid cleaning is taken out and washed with deionized water for three times, and then immersed in acetone solution for ultrasonic cleaning for 15 min to remove the oil stain on the surface of the copper foam sheet. The cleaned copper foam is washed repeatedly with deionized water and dried at 50°C for later use. (2) 0.5 mol/l potassium hydroxide solution is prepared, and the copper foam in step (1) is oxidized in potassium hydroxide solution by cyclic voltammetry (voltage range of -0.3 -0.3 V, scanning speed of 1 mV/s, and the number of scanning cycles is 1), and then dried at 50°C for 5 hours to form a layer of lithiophilic cuprous oxide on the surface layer, thus preparing the surface - modified copper foam 3D current collector. The surface - modified copper foam 3D current collector is tested by SEM, and the results are shown in FIG. 7. Compared with Embodiment 1, a large number of nanorods are grown on the surface, and each nanorod is composed a regular array of nanosheets with a thickness of about 10 nm. Step (3) and step (4) are the same as in Embodiment 1.

Embodiment 4 (1) A copper foam sheet with a thickness of 1.5 mm, porosity of 110 ppi and a size of 2 cm*2 cm is ultrasonically cleaned with 1 mol/l hydrochloric acid solution for 15 min to remove the oxide on the surface of copper foam, then the copper foam after hydrochloric acid cleaning is taken out and washed with deionized water for three times, and then immersed in acetone solution for ultrasonic cleaning for 15 min to remove the oil stain on the surface of the copper foam sheet. The cleaned copper foam is washed repeatedly with deionized water and dried at 50°C for later use. (2) 1 mol/l potassium hydroxide solution is prepared, and the copper foam in step (1) is oxidized in potassium hydroxide solution by cyclic voltammetry {voltage range of -0.3 -0.3 V, scanning speed of 1 mV/s, and the number of scanning cycles is 1), and then dried at 50°C for 5 hours to generate a layer of lithiophilic cuprous oxide on the surface layer, thus preparing the surface - modified copper foam 3D current collector. The surface - modified copper foam 3D current collector is tested by SEM, and the results are shown in FIG. 8. Compared with Embodiment 1, a large number of nanorods are grown on the surface, each nanorod is composed of a nanosheet array with a thickness of about 50 nm and poor uniformity, which indicates that the thickness of copper foam would affect the uniformity of the generated cuprous oxide morphology. Step (3) and step (4) are the same as in Embodiment 1.

Embodiment 5 (1) A copper foam sheet with a thickness of 1.5 mm, porosity of 130 ppi and a size of 2 cm*2 cm is ultrasonically cleaned with 1 mol/l hydrochloric acid solution for 15 min to remove the oxide on the surface of copper foam, then the copper foam after hydrochloric acid cleaning is taken out and washed with deionized water for three times, and then immersed in acetone solution for ultrasonic cleaning for 15 min to remove the oil stain on the surface of the copper foam sheet. The cleaned copper foam is washed repeatedly with deionized water and dried at 50°C for later use. (2) 1 mol/l potassium hydroxide solution is prepared, and the copper foam in step (1) is oxidized in potassium hydroxide solution by cyclic voltammetry (voltage range -0.3 -0.3 V, scanning rate of 1 mV/s, and the number of scanning cycles is 1}, and then dried at 50°C for 5 hours to generate a layer of lithiophilic cuprous oxide on the surface layer, thus preparing the surface - modified copper foam 3D current collector. The surface - modified copper foam 3D current collector is tested by SEM, and the results are shown in FIG. 8. Compared with Embodiment 1, a large number of nanorods are grown on the surface, and each nanorod is composed of an array of nanosheets. Step (3) and step (4) are the same as in Embodiment 1.

The symmetrical batteries assembled in Embodiments 3 - 5 are tested for cyclic stability, and the results are shown in Table 1. Table 1 Jom semen Comparing the results of Embodiments 1 - 5, it can be concluded that the copper foam with a thickness of 0.8 mm and porosity of 130 ppi is the best substrate.

Comparative embodiment 1 Same as Embodiment 1, but the difference is that the voltage range herein is -0.3 -0.3 V, the scanning speed is 1 mV/s, and the number of scanning circles is 2. SEM analysis of the prepared current collector is shown in FIG. 10, compared with Embodiment 1, a large number of flower - like nanostructures are grown on the surface, and the nanorods are about 300 nm in length, gathered together in a petal - like manner, and each petal is about 3 - 5 um in diameter.

Cyclic stability test of the assembled symmetrical battery and the full battery shows that when the current density is 1 mA/cm? and the cycling capacity is 1 mAh/cm?, the composite electrode symmetrical battery can be cycled stably for 500 hours with an overpotential of 30 mV without short circuit; the current increases as much as 3 mA/cm?, then the composite electrode symmetrical battery can be cycled stably for 200 hours.

What has been described above is only the preferred embodiments of the disclosure, and it is not intended to limit the disclosure.

Any modification, equivalent replacement and improvement within the spirit and principle of the disclosure should be included in the scope of protection of the disclosure.

Claims

CONCLUSIONS

1. A surface-modified copper foam 3D current collector, characterized in that copper foam is used as the framework material, and the surface of copper foam is oxidized in situ to form copper oxide.

The surface-modified 3D copper foam current collector according to claim 1, characterized in that the thickness of the copper foam is 0.5-1.5mm, the porosity of the copper foam is 110-130 ppi, and the copper oxide has a spike- like structure.

A process for preparing the surface-modified copper foam 3D current collector according to claim 1, comprising the steps of: - oxidizing cleaned and dried copper foam oxidized by cyclic voltammetry and - drying about the surface-modified copper foam 3D current collector to obtain.

The method for preparing the surface-modified copper foam 3D current collector according to claim 3, characterized in that the cleaned and dried copper foam is prepared by ultrasonic cleaning copper foam with hydrochloric acid solution and acetone alternately; the surface oxidation treatment is performed in a potassium hydroxide solution where the cyclic voltammetry conditions are as follows: voltage range of -0.3 - 0.3 V, scan rate of 1 mV/s, number of scan cycles of 1; a drying temperature of 50°C, and a drying time of 5 - 6 hours.

The method for preparing the surface-modified copper foam 3D current collector according to claim 4, characterized in that the concentration of hydrochloric acid solution is 0.5-1 mol/L, and the ultrasonic cleaning time is 15 min, and the concentration of the potassium hydroxide solution is 0.5 - 1 mol/l.

Use of the surface-modified copper foam 3D current collector according to claim 1 or 2 in the preparation of the cathode material for lithium metal batteries.

A cathode material for lithium metal batteries, characterized in that the surface-modified copper foam 3D current collector according to claim 1 or 2 is used as a framework material and directly compounded with lithium metal.

A method for preparing cathode material for lithium metal batteries according to claim 7, comprising the steps of: placing the surface-modified 3D current collector according to claim 1 or 2 in an inert environment in molten liquid lithium metal, and after immersion removing and cooling at room temperature to prepare the cathode material for lithium metal batteries.

Use of the lithium metal battery cathode material according to claim 7 in battery manufacturing.

The application according to claim 9, characterized in that the battery is a symmetrical battery or a full battery; wherein when the battery is a symmetrical battery, the electrode plates of the anode and the cathode of the symmetrical battery are all of the cathode material of the lithium metal battery according to claim 7, and when the battery is a complete battery, the aluminum foil current collector is lined with LiFePO4 used as the anode material of the whole battery, and the cathode material for lithium metal batteries according to claim 7 is used as the cathode material.