Preparation method of negative electrode of lithium battery and lithium battery

Abstract

The invention relates to a preparation method of a lithium battery negative electrode and a lithium battery, and relates to the field of new energy, the method comprises the following steps: providing foamed nickel with a porous structure; placing the foamed nickel in a predetermined electrolyte for electrodeposition so as to prepare polypyrrole on the surface of the foamed nickel and obtain a prefabricated current collector coated with polypyrrole on the surface; performing heat treatment on the prefabricated current collector in an inert atmosphere to carbonize polypyrrole on the surface of the prefabricated current collector to obtain the current collector with the porous structure; lithium metal is prepared on the surface of the current collector, the lithium battery negative electrode is obtained, and the predetermined electrolyte is electrolyte containing pyrrole. The preparation method of the lithium battery negative electrode provided by the invention has the beneficial effect of enabling deposition and stripping of lithium metal to be more ordered.

Description

Technical Field

[0001] The present application relates to the field of new energy, and in particular to lithium batteries. Background Art

[0002] Lithium metal is considered to be one of the most promising negative electrode materials for lithium batteries due to its high specific capacity, low working potential and high energy density. Guiding the orderly deposition and stripping of lithium metal, inhibiting the growth of lithium dendrites and the volume expansion during lithium deposition and desorption can effectively improve the coulombic efficiency and cycle life of lithium metal negative electrodes. Loading lithium-philic materials on the current collector is conducive to guiding the orderly deposition of lithium metal. Nitrogen-containing compounds have been proven to be materials with high lithium affinity and are currently lithium-philic materials commonly loaded on the surface of the current collector. However, although loading nitrogen-containing compounds on the surface of the current collector can make the deposition and stripping of lithium metal more orderly, the lithium-philic sites are still very limited, and the effect of improving the orderliness of lithium metal deposition and stripping needs to be improved. Summary of the invention

[0003] The embodiments of the present application provide a method for preparing a negative electrode of a lithium battery and a lithium battery to solve the technical problem that the effect of improving the orderliness of the deposition and stripping of lithium metal by loading nitrogen-containing compounds on the surface of a current collector needs to be improved.

[0004] In a first aspect, an embodiment of the present application provides a method for preparing a negative electrode of a lithium battery, the method comprising the following steps:

[0005] Providing nickel foam with a porous structure;

[0006] Placing the nickel foam in a predetermined electrolyte for electrodeposition to prepare polypyrrole on the surface of the nickel foam, thereby obtaining a prefabricated current collector having a surface coated with polypyrrole;

[0007] heat-treating the prefabricated current collector under an inert atmosphere to carbonize the polypyrrole on the surface of the prefabricated current collector to obtain a current collector having the porous structure;

[0008] Lithium metal is prepared on the surface of the current collector to obtain the negative electrode of the lithium battery,

[0009] Wherein, the predetermined electrolyte is an electrolyte containing pyrrole.

[0010] In some embodiments of the present application, the step of preparing lithium metal on the surface of the current collector comprises the following steps:

[0011] In an inert atmosphere, filling molten lithium metal into the porous structure of the current collector;

[0012] The molten lithium metal in the porous structure of the current collector is cooled and solidified to obtain the negative electrode of the lithium battery.

[0013] In some embodiments of the present application, filling molten lithium metal into the porous structure of the current collector in an inert atmosphere comprises the following steps:

[0014] In an inert atmosphere, the current collector is immersed in molten lithium metal for at least 5 minutes, so that the molten lithium metal is filled into the porous structure of the current collector.

[0015] In some embodiments of the present application, the preparation of lithium metal on the surface of the current collector is performed in a glove box.

[0016] In some embodiments of the present application, the electrolyte in the predetermined electrolyte includes a lithium salt.

[0017] In some embodiments of the present application, the predetermined electrolyte is an aqueous solution, the lithium salt is lithium carbonate, and the electrolyte in the predetermined electrolyte further includes a water-soluble carbonate whose cation does not contain lithium.

[0018] In some embodiments of the present application, the temperature of the heat treatment is 800-1000° C.; and / or,

[0019] The heat treatment time is 1 to 3 hours.

[0020] In a second aspect, an embodiment of the present application provides a lithium battery, wherein the negative electrode of the lithium battery is a lithium battery negative electrode prepared by the method described in any embodiment of the first aspect.

[0021] In some embodiments of the present application, the lithium battery further includes a separator and a liquid electrolyte.

[0022] In some embodiments of the present application, the lithium battery also includes a solid electrolyte.

[0023] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0024] The method for preparing the negative electrode of a lithium battery provided in an embodiment of the present application is to deposit a layer of polypyrrole on the surface of nickel foam by electrodeposition, and then carbonize the polypyrrole to obtain a current collector whose surface is coated with nitrogen-doped carbon. Since the nitrogen content of polypyrrole is relatively high, the nitrogen-doped carbon has abundant nitride lithium-affinity sites. Since the surface of the nitrogen-doped carbon-coated current collector has a relatively large contact area with lithium metal as a whole, there are a large number of nitride lithium-affinity sites on the surface of the current collector, which can effectively guide the orderly deposition and stripping of lithium metal, thereby improving the coulombic efficiency and cycle life of the lithium metal negative electrode. In addition, the matrix material of the current collector is nickel foam, which has a porous structure similar to nickel foam. The porous structure can accommodate lithium dendrites and limit the growth of lithium dendrites, which can further make the deposition and stripping of lithium metal more orderly. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0027] Figure 1 A schematic diagram of a process for preparing a negative electrode for a lithium battery provided in an embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0029] Unless otherwise specified, the terms used herein should be understood as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. In the event of a conflict, this specification takes precedence.

[0030] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0031] Currently, there is a technical problem that the improvement effect of loading nitrogen-containing compounds on the surface of the current collector to improve the orderliness of the deposition and stripping of lithium metal needs to be improved.

[0032] The technical solution provided by the embodiments of the present application is to solve the above technical problems, and the overall idea is as follows:

[0033] In a first aspect, an embodiment of the present application provides a method for preparing a negative electrode of a lithium battery, the method comprising the following steps:

[0034] S1: providing a nickel foam having a porous structure;

[0035] S2: placing the nickel foam in a predetermined electrolyte for electrodeposition to prepare polypyrrole on the surface of the nickel foam, thereby obtaining a prefabricated current collector having a surface coated with polypyrrole;

[0036] S3: heat-treating the prefabricated current collector under an inert atmosphere to carbonize the polypyrrole on the surface of the prefabricated current collector to obtain a current collector having the porous structure;

[0037] S4: preparing lithium metal on the surface of the current collector to obtain the negative electrode of the lithium battery,

[0038] Wherein, the predetermined electrolyte is an electrolyte containing pyrrole.

[0039] Nickel foam has a three-dimensional fully through mesh structure. It is a porous metal material with a porosity of up to 96-98%. Its bulk density is only one-fiftieth of that of nickel. The nickel skeleton is hollow and interconnected in a metallurgical state. Nickel foam has the following physical properties: 1. Large specific surface area: This property enables it to perform well in many application scenarios. For example, when used as a catalytic carrier substrate, it can provide more reaction sites; 2. Good thermal conductivity: It can effectively conduct heat and can be used as a damping material or a high-efficiency thermal conductive "wick" material for "heat pipes" in the thermal field, which can double the efficiency; 3. It has wide-frequency sound absorption characteristics: In the field of functional materials, it can be used as a damping material to absorb wave energy, and can also be used for silencing, vibration absorption, and buffering; 4. Strong processability: It can be cut, bent, and simply pasted, which is convenient for processing and use according to actual needs; 5. Homogeneous three-dimensional mesh structure: This structure enables nickel foam to have a filtering effect, and the flow stability of gas and fluid during filtering is super strong. The beneficial effect of selecting nickel foam as the matrix material of the current collector in this application is that the nickel foam has a rich porous structure inside that can be used to accommodate lithium metal, and the current collector still retains this porous structure, and the deposition of lithium metal can be carried out inside the current collector, and the lithium dendrites have less impact on the diaphragm; lithium metal is deposited in a porous structure with a smaller space, and the growth of lithium dendrites is limited, reducing the uneven growth of lithium dendrites, thereby increasing the orderliness of the lithium metal deposition and stripping process. In addition, as a starting material, nickel foam has good conductivity and electrolyte permeability due to its porous structure, providing an ideal substrate for subsequent lithium metal deposition.

[0040] The present application can prepare lithium metal on the surface of the current collector by any feasible implementation method. As an example, the present application can prepare lithium metal on the surface of the current collector by electrochemical deposition, vapor deposition, impregnation of hot-melt lithium metal, etc. It should be noted that the current collector structure of the present application is based on nickel foam, which has a rich porous structure. The surface of the current collector described in the present application includes both a visible external surface and an internal surface formed by the porous structure.

[0041] In some embodiments, for electrochemical deposition, the present application can use the current collector as an initial lithium-free negative electrode and assemble it with a lithium-rich positive electrode material into a prefabricated lithium battery whose negative electrode does not contain lithium, and achieve the deposition of lithium metal on the current collector by charging the prefabricated lithium battery.

[0042] It is easy to understand that polypyrrole has a high nitrogen content. It is a polymer formed by polymerization of pyrrole monomers and has a conjugated structure. From the microscopic structure, polypyrrole is described as quasi-one-dimensional and one-dimensional because there are some cross-linking and chain skipping, and its polymerization degree is different and presents different states. Undoped and doped polypyrrole is insoluble in solvents but swellable, and doping makes it brittle. The surface of the polypyrrole material presents fractal characteristics, and ion diffusion shows an abnormal diffusion pattern. After the polypyrrole on the surface of the prefabricated current collector is carbonized, nitrogen-doped carbon with abundant nitride lithium-philic sites is formed. And since the prefabricated current collector with a surface coated with polypyrrole is formed after the electrodeposition is completed, the current collector formed after the polypyrrole on the surface of the prefabricated current collector is carbonized is also a form of surface coated with nitrogen-doped carbon. As a conductive polymer, polypyrrole can further enhance the conductivity of the current collector, and its unique chemical properties contribute to the subsequent carbonization process.

[0043] The present application deposits a layer of polypyrrole on the surface of nickel foam by electrodeposition, and then carbonizes the polypyrrole to obtain a current collector coated with nitrogen-doped carbon on the surface. Since the nitrogen content of polypyrrole is relatively high, the nitrogen-doped carbon has abundant nitride lithium-philic sites. Since the surface of the nitrogen-doped carbon-coated current collector has a relatively large contact area with lithium metal as a whole, there are a large number of nitride lithium-philic sites on the surface of the current collector, which can effectively guide the orderly deposition and stripping of lithium metal, thereby improving the coulombic efficiency and cycle life of the lithium metal negative electrode. In addition, the matrix material of the current collector is nickel foam, which has a porous structure similar to nickel foam. The porous structure can accommodate lithium dendrites and limit the growth of lithium dendrites, which can further make the deposition and stripping of lithium metal more orderly. The carbonization process not only improves the thermal stability and chemical stability of the current collector, but also provides a more uniform and stable interface for subsequent lithium metal deposition.

[0044] In some embodiments of the present application, the step of preparing lithium metal on the surface of the current collector comprises the following steps:

[0045] S31: filling molten lithium metal into the porous structure of the current collector in an inert atmosphere;

[0046] S32: Cooling and solidifying the molten lithium metal in the porous structure of the current collector to obtain the negative electrode of the lithium battery.

[0047] It is easy to understand that lithium metal has poor mechanical processing performance, high chemical reactivity with moisture and oxygen under ambient conditions, and poor electrochemical reversibility, which makes ultra-thin lithium metal negative electrodes, whether prepared by mechanical processing or electrochemical deposition, have high requirements for the preparation process and preparation environment. The present application fills the porous structure of the current collector with molten lithium metal, and only needs to provide an inert atmosphere and heating conditions that can melt the lithium metal. The implementation is relatively simple, and the lithium metal can be relatively fully filled into the porous structure of the current collector.

[0048] In addition, it should be noted that the nitrogen-doped carbon has chemical inertness and good affinity to the strongly reducing molten lithium metal.

[0049] In some embodiments of the present application, filling molten lithium metal into the porous structure of the current collector in an inert atmosphere comprises the following steps:

[0050] S311: In an inert atmosphere, immersing the current collector in molten lithium metal for at least 5 minutes, so that the molten lithium metal fills the porous structure of the current collector.

[0051] In some embodiments of the present application, the preparation of lithium metal on the surface of the current collector is performed in a glove box.

[0052] It is easy to understand that the glove box is a commonly used equipment in the lithium battery field and can provide an inert atmosphere and heating conditions.

[0053] In some embodiments of the present application, the electrolyte in the predetermined electrolyte includes a lithium salt.

[0054] It is easy to understand that the beneficial effect of the electrolyte in the predetermined electrolyte including a lithium salt is that lithium ions are present in the polypyrrole, and ultimately lithium ions are present in the nitrogen-doped carbon, which is beneficial to increase the affinity of the nitrogen-doped carbon with molten lithium metal, thereby increasing the wettability of the molten lithium metal on the surface of the nitrogen-doped carbon.

[0055] In some embodiments of the present application, the predetermined electrolyte is an aqueous solution, the lithium salt is lithium carbonate, and the electrolyte in the predetermined electrolyte further includes a water-soluble carbonate whose cation does not contain lithium.

[0056] The predetermined electrolyte is an aqueous solution, which has the advantages of being cheap and easy to prepare.

[0057] The water-soluble carbonate serves to further increase the conductivity of the predetermined electrolyte.

[0058] In some embodiments of the present application, the temperature of the heat treatment is 800-1000° C.; and / or,

[0059] The heat treatment time is 1 to 3 hours.

[0060] The beneficial effect of the heat treatment temperature being 800-1000° C. is that the energy consumption can be reduced as much as possible while ensuring sufficient carbonization of the polypyrrole.

[0061] The beneficial effect of the heat treatment time being 1 to 3 hours is that the energy consumption can be reduced as much as possible while ensuring sufficient carbonization of the polypyrrole.

[0062] As an example, the temperature of the heat treatment may be 800°C, 850°C, 900°C, 950°C, 1000°C.

[0063] As an example, the heat treatment time can be 1 h, 1.5 h, 2 h, 2.5 h, or 3 h.

[0064] In summary, the present invention provides a method for preparing a negative electrode for a lithium battery, which has the following technical advantages:

[0065] 1. Ordering of lithium metal deposition and stripping:

[0066] Through this preparation method, especially the introduction and carbonization of polypyrrole, the deposition and stripping behavior of lithium metal on the current collector surface is effectively improved. The carbon layer provides a more uniform and stable deposition interface, which helps to reduce the dendrite growth of lithium metal during the charge and discharge process, thereby extending the service life and safety of the battery.

[0067] 2. Improve battery performance:

[0068] The ordered lithium metal deposition and stripping process helps improve the battery's cycle stability and Coulombic efficiency. In addition, the introduction of porous nickel foam and carbon layer also enhances the battery's conductivity and electrolyte permeability, further improving the battery's overall performance.

[0069] 3. Application prospects

[0070] The lithium battery negative electrode preparation method and lithium battery provided in this application have broad application prospects in the fields of new energy vehicles, energy storage systems, etc. By optimizing the negative electrode structure, not only can the energy density and cycle life of the lithium battery be improved, but also the cost and environmental impact of the battery can be reduced, contributing to the development of the new energy industry.

[0071] Therefore, this application successfully achieved the optimization of the negative electrode structure of lithium batteries through innovative preparation methods and material selection, providing new ideas and solutions for improving the performance of lithium batteries and promoting the development of the new energy industry.

[0072] In a second aspect, an embodiment of the present application provides a lithium battery, wherein the negative electrode of the lithium battery is a lithium battery negative electrode prepared by the method described in any embodiment of the first aspect.

[0073] The lithium battery is realized by a lithium battery negative electrode prepared by the method described in any embodiment of the first aspect. The specific implementation of the lithium battery can refer to the above embodiments and common knowledge in the art. Since the lithium battery adopts part or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0074] In some embodiments of the present application, the lithium battery further includes a separator and a liquid electrolyte.

[0075] It is easy to understand that in the lithium battery negative electrode described in the present application, lithium dendrites mainly exist in the porous structure of the current collector, and fewer lithium dendrites are generated on the surface where the current collector contacts the diaphragm, which has less impact on the diaphragm. Therefore, the lithium battery negative electrode described in the present application can be applied to traditional lithium batteries including a diaphragm and a liquid electrolyte.

[0076] In some embodiments of the present application, the lithium battery also includes a solid electrolyte.

[0077] It is easy to understand that the lithium battery negative electrode described in the present application is suitable for lithium batteries that do not contain a separator and use a solid electrolyte.

[0078] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0079] Example 1

[0080] This embodiment provides a lithium battery negative electrode, which is prepared by the following method:

[0081] 1.5 g of lithium carbonate, 3 g of sodium carbonate and 2 g of pyrrole were added to 200 mL of water and stirred for 30 min to obtain a prefabricated electrolyte;

[0082] Using nickel foam as a working electrode, a carbon rod as a reference and counter electrode, and the prefabricated electrolyte as an electrolyte, a constant potential oxidation method is adopted, a voltage of 0.8 V is used, and the reaction is continued for 10 minutes to obtain a prefabricated current collector;

[0083] The prefabricated current collector was placed in a tube furnace and reacted at 800°C for 2 h in an Ar atmosphere to obtain a current collector;

[0084] In a glove box filled with nitrogen, the current collector was immersed in molten metal Li and taken out after 5 minutes to obtain the negative electrode of the lithium battery.

[0085] This embodiment also provides a lithium battery, which is prepared by the following method:

[0086] Providing a positive electrode plate, the positive electrode plate is composed of a positive electrode active material, a conductive agent, and a binder in a mass ratio of 95:3:2, wherein the positive electrode active material is lithium cobalt oxide, the conductive agent is SUPER P carbon black, and the binder is sodium carboxymethyl cellulose;

[0087] Providing a polyethylene diaphragm and an electrolyte, wherein the electrolyte is an ethylene carbonate solution of lithium hexafluorophosphate;

[0088] The positive electrode plate and the polyethylene separator are stacked in a Z-shaped stacking manner, and a 1Ah lithium battery is prepared through welding, liquid injection, pre-charging, secondary sealing, and formation processes.

[0089] Example 2

[0090] The only difference between this embodiment and embodiment 1 is that the carbonization temperature of polypyrrole is 900°C.

[0091] The present embodiment is as follows:

[0092] This embodiment provides a lithium battery negative electrode, which is prepared by the following method:

[0093] 1.5 g of lithium carbonate, 3 g of sodium carbonate and 2 g of pyrrole were added to 200 mL of water and stirred for 30 min to obtain a prefabricated electrolyte;

[0094] Using nickel foam as a working electrode, a carbon rod as a reference and counter electrode, and the prefabricated electrolyte as an electrolyte, a constant potential oxidation method is adopted, a voltage of 0.8 V is used, and the reaction is continued for 10 minutes to obtain a prefabricated current collector;

[0095] The prefabricated current collector was placed in a tube furnace and reacted at 900°C for 2 h in an Ar atmosphere to obtain a current collector;

[0096] In a glove box filled with nitrogen, the current collector was immersed in molten metal Li and taken out after 5 minutes to obtain the negative electrode of the lithium battery.

[0097] This embodiment also provides a lithium battery, which is prepared by the following method:

[0098] Providing a positive electrode plate, the positive electrode plate is composed of a positive electrode active material, a conductive agent, and a binder in a mass ratio of 95:3:2, wherein the positive electrode active material is lithium cobalt oxide, the conductive agent is SUPER P carbon black, and the binder is sodium carboxymethyl cellulose;

[0099] Providing a polyethylene diaphragm and an electrolyte, wherein the electrolyte is an ethylene carbonate solution of lithium hexafluorophosphate;

[0100] The positive electrode plate and the polyethylene separator are stacked in a Z-shaped stacking manner, and a 1Ah lithium battery is prepared through welding, liquid injection, pre-charging, secondary sealing, and formation processes.

[0101] Example 3

[0102] The only difference between this embodiment and embodiment 1 is that the carbonization temperature of polypyrrole is 1000°C.

[0103] The present embodiment is as follows:

[0104] This embodiment provides a lithium battery negative electrode, which is prepared by the following method:

[0105] 1.5 g of lithium carbonate, 3 g of sodium carbonate and 2 g of pyrrole were added to 200 mL of water and stirred for 30 min to obtain a prefabricated electrolyte;

[0106] Using nickel foam as a working electrode, a carbon rod as a reference and counter electrode, and the prefabricated electrolyte as an electrolyte, a constant potential oxidation method is adopted, a voltage of 0.8 V is used, and the reaction is continued for 10 minutes to obtain a prefabricated current collector;

[0107] The prefabricated current collector was placed in a tube furnace and reacted at 1000°C for 2 h in an Ar atmosphere to obtain a current collector;

[0108] In a glove box filled with nitrogen, the current collector was immersed in molten metal Li and taken out after 5 minutes to obtain the negative electrode of the lithium battery.

[0109] This embodiment also provides a lithium battery, which is prepared by the following method:

[0110] Providing a positive electrode plate, the positive electrode plate is composed of a positive electrode active material, a conductive agent, and a binder in a mass ratio of 95:3:2, wherein the positive electrode active material is lithium cobalt oxide, the conductive agent is SUPERP carbon black, and the binder is sodium carboxymethyl cellulose;

[0111] Providing a polyethylene diaphragm and an electrolyte, wherein the electrolyte is an ethylene carbonate solution of lithium hexafluorophosphate;

[0112] The positive electrode plate and the polyethylene separator are stacked in a Z-shaped stacking manner, and a 1Ah lithium battery is prepared through welding, liquid injection, pre-charging, secondary sealing, and formation processes.

[0113] Comparative Example

[0114] The only difference between this comparative example and Example 1 is that this comparative example directly uses foamed nickel as the current collector.

[0115] The details are as follows:

[0116] This comparative example provides a lithium battery negative electrode, which is prepared by the following method:

[0117] In a glove box filled with nitrogen, the foamed nickel was immersed in molten metal Li and taken out after 5 minutes to obtain the negative electrode of the lithium battery.

[0118] This embodiment also provides a lithium battery, which is prepared by the following method:

[0119] Providing a positive electrode plate, the positive electrode plate is composed of a positive electrode active material, a conductive agent, and a binder in a mass ratio of 95:3:2, wherein the positive electrode active material is lithium cobalt oxide, the conductive agent is SUPERP carbon black, and the binder is sodium carboxymethyl cellulose;

[0120] Providing a polyethylene diaphragm and an electrolyte, wherein the electrolyte is an ethylene carbonate solution of lithium hexafluorophosphate;

[0121] The positive electrode plate and the polyethylene separator are stacked in a Z-shaped stacking manner, and a 1Ah lithium battery is prepared through welding, liquid injection, pre-charging, secondary sealing, and formation processes.

[0122] Related experiments and effect data:

[0123] At a current of 1C, the lithium batteries of Examples 1 to 3 and the comparative example were subjected to cyclic charge and discharge tests, and the statistically obtained capacity retention rate after 30 cycles and the number of cycles at which the capacity retention rate was 80% are shown in Table 1.

[0124] Table 1

[0125] Capacity retention after 30 cycles Cycle number for 80% capacity retention Example 1 94％ 200 Example 2 95％ 280 Example 2 90％ 170 Comparative Example 1 83％ 40

[0126] It can be found from Table 1 that for the lithium batteries provided in Examples 1 to 3, the capacity retention rate after 30 cycles and the number of cycles at which the capacity retention rate is 80% are both at a relatively high level. However, for the lithium batteries provided in the comparative example, the capacity retention rate after 30 cycles and the number of cycles at which the capacity retention rate is 80% are significantly lower than those in Examples 1 to 3. This indicates that for the lithium batteries in Examples 1 to 3, the nitrogen-doped carbon coated on the surface of the current collector can effectively improve the orderliness of the deposition and stripping of lithium metal, thereby having better cycle performance.

[0127] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0128] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present application specification, the terms "including", "comprising", etc. refer to "including but not limited to". Moreover, the terms "including", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the sentence "including..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements. In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. For the association relationship of more than three associated objects described by "and / or", it means that any one of these three associated objects can exist alone, or any at least two of them exist at the same time. For example, for A, and / or B, and / or C, it can be represented that any one of A, B, and C exists alone, or any two of them exist at the same time, or three of them exist at the same time. In this article, "at least one" refers to one or more, and "multiple" refers to two or more. "At least one", "the following at least one (individual)" or similar expressions refer to any combination of these items, including any combination of single items (individuals) or plural items (individuals). For example, "at least one (individual) of a, b, or c", or "at least one (individual) of a, b, and c", can all represent: a, b, c, ab (i.e. a and b), ac, bc, or abc, wherein a, b, c can be single or multiple respectively. The "number of parts" involved in this application, such as weight parts, mass parts, etc., represent the proportional relationship between each component. In the proportional relationship involved in the present application, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, if the mass ratio of substance A, substance B and substance C is 1:2:3, then substance A, substance B and substance C should correspond one-to-one with the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0129] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing a negative electrode of a lithium battery, characterized in that: The method comprises the following steps: Providing nickel foam with a porous structure; Placing the nickel foam in a predetermined electrolyte for electrodeposition to prepare polypyrrole on the surface of the nickel foam, thereby obtaining a prefabricated current collector having a surface coated with polypyrrole; heat-treating the prefabricated current collector under an inert atmosphere to carbonize the polypyrrole on the surface of the prefabricated current collector to obtain a current collector having the porous structure; Lithium metal is prepared on the surface of the current collector to obtain the negative electrode of the lithium battery, Wherein, the predetermined electrolyte is an electrolyte containing pyrrole.

2. The method for preparing a negative electrode of a lithium battery according to claim 1, characterized in that: The step of preparing lithium metal on the surface of the current collector comprises the following steps: In an inert atmosphere, filling molten lithium metal into the porous structure of the current collector; The molten lithium metal in the porous structure of the current collector is cooled and solidified to obtain the negative electrode of the lithium battery.

3. The method for preparing a negative electrode of a lithium battery according to claim 2, characterized in that: The step of filling molten lithium metal into the porous structure of the current collector in an inert atmosphere comprises the following steps: In an inert atmosphere, the current collector is immersed in molten lithium metal for at least 5 minutes, so that the molten lithium metal is filled into the porous structure of the current collector.

4. The method for preparing a negative electrode of a lithium battery according to claim 1, characterized in that: The preparation of lithium metal on the surface of the current collector is performed in a glove box.

5. The method for preparing a negative electrode of a lithium battery according to claim 1, characterized in that: The electrolyte in the predetermined electrolyte solution includes a lithium salt.

6. The method for preparing a negative electrode of a lithium battery according to claim 5, characterized in that: The predetermined electrolyte is an aqueous solution, the lithium salt is lithium carbonate, and the electrolyte in the predetermined electrolyte further includes a water-soluble carbonate whose cation does not contain lithium.

7. The method for preparing a negative electrode for a lithium battery according to claim 1, characterized in that: The heat treatment temperature is 800-1000°C; and / or, The heat treatment time is 1 to 3 hours.

8. A lithium battery, characterized in that: The negative electrode of the lithium battery is a negative electrode of the lithium battery prepared by the method according to any one of claims 1 to 7.

9. The lithium battery according to claim 8, characterized in that: The lithium battery also includes a separator and a liquid electrolyte.

10. The lithium battery according to claim 8, characterized in that: The lithium battery also includes a solid electrolyte.

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