Composite material and preparation method thereof, negative electrode-free current collector and battery

Abstract

The present invention relates to the field of battery technology, and in particular to a composite material and a preparation method thereof, a negative electrode-free current collector, and a battery. The provided composite material comprises: an inner core, a first coating layer, and a second coating layer, wherein the inner core comprises a metal and has a frame structure; the first coating layer is coated on at least a portion of the surface of the inner core, and the first coating layer comprises a conductive polymer; the second coating layer is coated on at least a portion of the surface of the first coating layer, and the second coating layer comprises a ceramic material. The preparation method of the composite material comprises: mixing a porous template agent with a metal compound solution, adding a reducing agent, and performing a first drying to obtain an inner core with a frame structure; applying a slurry containing a conductive polymer to the surface of the inner core to form a first coating layer; and applying a slurry containing a ceramic material to the surface of the first coating layer to form a second coating layer. The present application can improve the deposition uniformity of lithium ions and improve the safety performance of lithium batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a composite material and a preparation method thereof, a negative electrode-free current collector and a battery. Background Art

[0002] In order to increase the energy density of batteries (such as lithium batteries), more and more research efforts are being invested in battery weight reduction design. Because the negative electrode-free structure does not require negative electrode active materials, it can significantly reduce the mass of the battery and increase the energy density of the lithium battery. However, the current negative electrode-free structure batteries face a serious problem, that is, without the lithium embedded in the negative electrode active material, where should the lithium ions released from the positive electrode go? Although conventional copper foil negative electrodes can deposit lithium, they face the risk of uneven lithium deposition, forming lithium dendrites, causing puncture of the diaphragm, causing contact short circuits between the positive and negative electrodes, and causing safety issues. Therefore, how to solve the problem of uneven lithium deposition in negative electrode-free batteries is one of the key points of negative electrode-free structure applications.

[0003] In view of this, this application is hereby filed. Summary of the Invention

[0004] In view of this, the present invention aims to at least partially address one of the technical problems in the related art. To this end, the present invention provides a composite material and a preparation method thereof, a negative electrode-free current collector, and a battery, which are beneficial for improving the uniformity of lithium ion deposition and alleviating the problem of lithium dendrites.

[0005] In order to solve the above technical problems, this application is implemented as follows:

[0006] According to one aspect of the present application, the present application provides a composite material, comprising:

[0007] a core comprising metal and having a frame structure;

[0008] a first coating layer, the first coating layer coating at least a portion of the surface of the core, the first coating layer comprising a conductive polymer; and

[0009] A second coating layer is coated on at least a portion of the surface of the first coating layer, and the second coating layer includes a ceramic material.

[0010] In any embodiment, the metal comprises at least one of a transition metal or a post-transition metal.

[0011] In any embodiment, the metal includes at least one of copper, tin, silver, or zinc.

[0012] In any embodiment, the inner core further comprises a first binder.

[0013] In any embodiment, the mass ratio of the metal to the first binder is (95-98):(2-5).

[0014] In any embodiment, the first binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyacrylamide, polyimide or polyamide.

[0015] In any embodiment, the pore size of the pores in the framework structure ranges from 100 nm to 500 nm.

[0016] In any embodiment, the porosity of the inner core is 20% to 50%.

[0017] In any embodiment, the average particle size of the core is in the range of 2 μm to 5 μm.

[0018] In any embodiment, the conductive polymer includes at least one of conductive polyimide, conductive polyaniline, or conductive polypyrrole.

[0019] In any embodiment, the first coating layer further includes a second binder.

[0020] In any embodiment, the mass ratio of the conductive polymer to the second binder is (80-90):(10-20).

[0021] In any embodiment, the second binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyacrylamide, polyimide or polyamide.

[0022] In any embodiment, the average particle size of the conductive polymer is in the range of 100 nm to 500 nm.

[0023] In any embodiment, the thickness of the first coating layer is 2 μm to 5 μm.

[0024] In any embodiment, the ceramic material includes at least one of aluminum oxide, zirconium oxide, aluminum nitride, silicon nitride, magnesium oxide, tin oxide, or titanium oxide.

[0025] In any embodiment, the second coating layer further includes a third binder.

[0026] In any embodiment, the mass ratio of the ceramic material to the third binder is (80-90):(10-20).

[0027] In any embodiment, the third binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyacrylamide, polyimide or polyamide.

[0028] In any embodiment, the second coating layer has a porous structure.

[0029] In any embodiment, the porosity of the second coating layer is 5% to 20%.

[0030] In any embodiment, the thickness of the second coating layer is 2 μm to 5 μm.

[0031] According to another aspect of the present application, the present application provides a method for preparing a composite material, the method comprising the following steps:

[0032] The porous template agent is mixed with a metal compound solution, a reducing agent is added, and then a first drying is performed to obtain a core having a framework structure;

[0033] applying a slurry containing a conductive polymer to the surface of the core to form a first coating layer on at least a portion of the surface of the core;

[0034] A slurry containing a ceramic material is applied to the surface of the first coating layer to form a second coating layer on at least a portion of the surface of the first coating layer.

[0035] In any embodiment, the preparation of the porous template agent includes: grinding the template agent and the pore-forming agent to obtain particles with an average particle size of 100nm to 500nm; uniformly mixing the particles with a first binder and a first solvent to obtain a slurry; coating the slurry into a thin film on a substrate, and obtaining the porous template agent after a second drying and pulverization process.

[0036] In any embodiment, the average particle size of the porous template agent is in the range of 500 nm to 1000 nm.

[0037] In any embodiment, the stencil agent includes at least one of polyethylene, polyethylene glycol, polyvinyl pyrrolidone, or cetyltrimethylammonium bromide.

[0038] In any embodiment, the pore former comprises at least one of ammonium bicarbonate, ammonium carbonate, ammonium nitrate, or ammonium sulfate.

[0039] In any embodiment, the mass ratio of the first binder, the template agent and the pore-forming agent is (60-80): (10-20): (10-20).

[0040] In any embodiment, the first solvent comprises at least one of N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide, or water.

[0041] In any embodiment, the second drying temperature is 60°C to 100°C.

[0042] In any embodiment, mixing the porous template agent with the metal compound solution comprises: soaking the porous template agent in the metal compound solution for 2 hours to 4 hours.

[0043] In any embodiment, the metal ions in the metal compound solution include at least one of copper ions, tin ions, silver ions, or zinc ions.

[0044] In any embodiment, the anions in the metal compound solution include at least one of nitrate, sulfate, chloride or acetate.

[0045] In any embodiment, the reducing agent comprises at least one of iron, zinc or hydrazine hydrate.

[0046] In any embodiment, after the first drying, the method further comprises: soaking the porous metal-deposited template after the first drying in a benzene solvent for 4 to 12 hours, and then washing and drying for the third time to obtain the core having a framework structure.

[0047] In any embodiment, the first drying temperature is 60°C to 100°C.

[0048] In any embodiment, the third drying temperature is 60°C to 100°C.

[0049] In any embodiment, the paste containing a conductive polymer contains a conductive polymer, a second binder, and a second solvent.

[0050] In any embodiment, the mass ratio of the conductive polymer to the second binder is (80-90):(10-20).

[0051] In any embodiment, the second solvent comprises at least one of N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide, or water.

[0052] In any embodiment, the average particle size of the conductive polymer is in the range of 100 nm to 500 nm.

[0053] In any embodiment, after coating the slurry containing the conductive polymer on the surface of the core, a fourth drying is performed, and the temperature of the fourth drying is 60° C. to 100° C.

[0054] In any embodiment, the ceramic-containing slurry comprises a ceramic material, a third binder, and a third solvent.

[0055] In any embodiment, the ceramic-containing slurry further includes a pore former.

[0056] In any embodiment, the mass ratio of the ceramic material, the pore former and the third binder is (70-80): (10-20): (10-20).

[0057] In any embodiment, the third solvent comprises at least one of N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide or water.

[0058] In any embodiment, after the slurry containing the ceramic material is coated on the surface of the first coating layer, heat treatment is performed, and the heat treatment temperature is 100° C. to 150° C. and the time is 4 hours to 8 hours.

[0059] According to another aspect of the present application, the present application provides a negative electrode-free current collector, which includes a substrate and a coating arranged on at least one side of the surface of the substrate, and the coating includes the composite material as described above, or includes a composite material prepared by the preparation method as described above.

[0060] In any embodiment, the coating further includes a fourth binder and a conductive agent.

[0061] In any embodiment, the fourth binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyacrylamide, polyimide or polyamide.

[0062] In any embodiment, the conductive agent includes at least one of conductive carbon black, conductive graphite, carbon nanotubes, carbon fibers, or graphene.

[0063] In any embodiment, the mass ratio of the composite material, the fourth binder and the conductive agent is (70-80): (10-20): (10-20).

[0064] In any embodiment, the substrate includes a copper-based substrate or a composite substrate, and the composite substrate includes a substrate formed by a composite of a polymer material and a metal.

[0065] In any embodiment, the coating has a thickness of 2 μm to 10 μm.

[0066] According to another aspect of the present application, the present application provides a battery, which includes the composite material as described above, or includes the composite material prepared by the preparation method as described above, or includes the aforementioned negative electrode-free current collector.

[0067] The implementation of the technical solution of the present invention has at least the following beneficial effects:

[0068] In an embodiment of the present application, the provided composite material can be applied to anode-free battery structures, such as anode-free current collectors of cathode-free lithium batteries. The composite material is provided with a core of a metal material, which can form a framework structure, thereby increasing its specific surface area, improving its affinity with active ions such as lithium ions, and promoting the deposition of lithium ions. Furthermore, a first coating layer comprising a conductive polymer is provided on the surface of the core, which can utilize the physical adsorption of the conductive polymer to improve the directional transport capability of lithium ions and further improve the uniformity of lithium ion deposition. At the same time, a second coating layer comprising a ceramic material is provided on the surface of the first coating layer, which can be used to stabilize the first coating layer comprising the conductive polymer and can also be used to inhibit the excessive growth of lithium dendrites and improve safety performance. Thus, the composite material not only helps to improve the uniformity of lithium ion deposition, but also improves the safety performance of lithium batteries, and has good application prospects in the field of cathode-free batteries.

[0069] Additional aspects and advantages of the present application will be given in part in the following description and in part will become obvious from the following description or will be learned through practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 Shown is a schematic structural diagram of a composite material provided by an embodiment of the present invention.

[0071] Description of reference numerals:

[0072] 10-core; 101-hole;

[0073] 20-first coating layer;

[0074] 30-Second coating layer. DETAILED DESCRIPTION

[0075] The present application will be further described below with reference to specific examples. It should be understood that these examples are only used to illustrate the present application and are not intended to limit the scope of the present application.

[0076] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range or the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0077] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0078] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0079] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0080] Generally speaking, a negative electrode-free battery refers to a battery without negative electrode active material. By not using negative electrode active material, the negative electrode-free battery can improve the energy density of the battery. The technical principle of the negative electrode-free battery is to deposit the lithium in the positive electrode on the negative electrode current collector through formation charging, or during the first charging process of the battery. However, the negative electrode-free battery in the related art has the problem of lithium dendrites caused by uneven deposition of lithium. The lithium dendrites formed can easily pierce the diaphragm, causing a contact short circuit between the positive and negative electrodes, thereby causing safety problems or affecting the cycle life of the battery. Therefore, how to solve the problem of uneven lithium deposition in the negative electrode-free battery structure is one of the key points of the application of the negative electrode-free structure. Based on this, some research and improvements have been made to the negative electrode-free battery structure in the relevant technology. For example, the patent with publication number CN113013417A discloses a negative electrode-free structure, which coats an electronic conductive layer and an ion conductive layer on the outer layer of the traditional negative electrode material. Although this method can accommodate the lithium source detached from the positive electrode, the scheme adopts the method of directly immersing the copper foil in the ion coating glue. The coating does not have a large number of pores, thereby hindering the deposition rate of lithium ions on the copper foil surface, and the efficiency of lithium deposition is low. In severe cases, it will lead to the deposition of lithium ions on the coating surface due to untimely deposition (high rate charging), causing lithium dendrites to pierce the diaphragm and cause a short circuit; and the ion conductive layer is difficult to prepare, and the traditional negative electrode metal substrate has a large mass, which affects the energy density of the battery. For example, the patent with publication number CN116581361A discloses a negative electrode-free structure, which provides lithium insertion space and avoids direct reaction with the electrolyte by setting a lithium titanate layer for lithium insertion in combination with a solid electrolyte. However, the current solid electrolyte has problems with low ion transfer rate and interface contact, which affects the power performance of the battery. In addition, the setting of the lithium titanate layer also brings about weight gain, which is not conducive to improving the energy density of the negative electrode-free battery.

[0081] In view of this, the technical solutions of the embodiments of the present application provide a composite material and a method for preparing the composite material. The composite material can be used in anode-free batteries, such as in a current collector for anode-free batteries (anode-free battery anode current collector), as well as anode-free current collectors and batteries containing the composite material. The technical solutions of the embodiments of the present application can alleviate the problem of lithium dendrites in existing anode-free batteries, thereby enhancing the uniformity of lithium deposition and improving the safety performance and cycle life of anode-free batteries. A description of the specific technical solutions is provided below.

[0082] [Composite Materials]

[0083] See also Figure 1 As shown, in some embodiments, a composite material is provided, the composite material comprising:

[0084] The core 10 includes metal and has a frame structure;

[0085] a first coating layer 20 , the first coating layer 20 coating at least a portion of the surface of the core 10 , the first coating layer 20 comprising a conductive polymer; and

[0086] The second coating layer 30 covers at least a portion of the surface of the first coating layer 20 , and the second coating layer 30 includes a ceramic material.

[0087] It should be pointed out that in this application, the "coating" is not limited to direct coating, but also includes indirect coating. For example, the first coating layer 20 coats the core 10, and there may be no other structure between the first coating layer 20 and the outer surface of the core 10, or there may be one or more layers of other structures between the first coating layer 20 and the outer surface of the core 10. Preferably, there is no other structure between the first coating layer 20 and the outer surface of the core 10; in this way, it is more conducive to the uniformity of the deposition of active ions such as lithium ions and improves the directional transport capability of active ions such as lithium ions. Similarly, the second coating layer 30 coats the first coating layer 20, and there may be no other structure between the second coating layer 30 and the outer surface of the first coating layer 20, or there may be one or more layers of other structures between the second coating layer 30 and the outer surface of the first coating layer 20; in this way, it is more conducive to improving the uniformity of the deposition of active ions such as lithium ions and improving the stability of the structure.

[0088] The first coating layer 20 is formed or coated on at least a portion of the surface of the core 10, which can protect or further improve the core 10, and can be used to improve the conductivity of the composite material and further improve the uniformity of lithium ion deposition. The first coating layer 20 is formed on at least a portion of the surface of the core 10, which means that the first coating layer 20 can completely encapsulate the core 10 within the first coating layer 20, or the first coating layer 20 can only coat a portion of the outer surface of the core; that is, the first coating layer 20 can completely coat the core 10, or it can coat a portion of the surface of the core 10, preferably completely; in this way, it can better play a protective or improvement role.

[0089] The second coating layer 30 is formed or coated on at least a portion of the surface of the first coating layer 20, which can protect and improve the core 10 and the first coating layer 20, and can be used to improve the stability of the structure, enhance the electrochemical properties of the composite material, and inhibit the excessive growth of lithium dendrites, thereby further improving the safety performance. The second coating layer 30 is formed on at least a portion of the surface of the first coating layer 20, which means that the second coating layer 30 can completely encapsulate the first coating layer 20 within the second coating layer 30, or the second coating layer 30 can only coat a portion of the outer surface of the first coating layer 20; that is, the second coating layer 30 can completely coat the first coating layer 20, or can coat a portion of the surface of the first coating layer 20, preferably completely coating; in this way, it is more conducive to improving the stability of the structure and better playing a protective or improvement role.

[0090] The provided composite material has a core-shell structure, comprising an inner core 10 and an outer shell. The inner core 10 is made of a metal material, and the metal can form a framework structure, resulting in an inner core 10 having a porous structure 101. The outer shell comprises a first coating layer 20 and a second coating layer 30, wherein the first coating layer 20 comprises a conductive polymer, and the second coating layer 30 comprises a ceramic material. Thus, by providing an active metal on the inner core 10 and forming a framework structure, its specific surface area can be increased, and its binding ability with active ions such as lithium ions can be enhanced, thereby promoting the deposition of lithium ions. Furthermore, by providing the first coating layer 20 comprising a conductive polymer on the surface of the inner core 10, the physical adsorption properties of the conductive polymer can be utilized to enhance the directional transport of lithium ions, further improving the uniformity of lithium ion deposition. Simultaneously, by providing the second coating layer 30 comprising a ceramic material on the surface of the first coating layer 20, the second coating layer 30 comprising a ceramic material can be used to stabilize the first coating layer 20 comprising a conductive polymer, and can also be used to inhibit the excessive growth of lithium dendrites, thereby improving safety performance. In some preferred embodiments, the second coating layer 30 also has a porous structure. The porous property of the second coating layer 30 can be used to improve the diffusion of lithium ions into the composite material and improve the uniformity of lithium ion deposition.

[0091] Therefore, the composite material adopts a multi-layer coating structure by sequentially arranging the first coating layer 20 and the second coating layer 30 on the surface of the core 10 with a frame structure. Through reasonable structural design, it not only improves the structural stability of the composite material and improves the conductivity of the composite material, but also helps to improve the deposition uniformity of lithium ions, which can improve the safety performance of lithium batteries and has good application prospects in the field of negative electrode-free batteries.

[0092] The inventors have found through in-depth research that when the composite material of the present application satisfies the above-mentioned design conditions and optionally satisfies one or more of the following conditions, the performance of the composite material can be further improved.

[0093] In embodiments of the present invention, the high-performance composite material provided can be used in anode-free batteries, such as in anode-free current collectors for anode-free batteries. As a coating material, it comprises, from the inside out, a core, a first coating layer, and a second coating layer. The core can also be referred to as a metal core, the first coating layer can also be referred to as a conductive polymer layer, and the second coating layer can also be referred to as a porous ceramic coating. This composite material primarily promotes uniform lithium ion deposition through the electronic adsorption of lithium ions by the active metal and the physical adsorption of lithium ions by the conductive polymer. The ceramic coating stabilizes the structure and inhibits the growth of lithium dendrites, thereby improving safety.

[0094] In some embodiments, the metal in the core 10 includes at least one of a transition metal and a post-transition metal.

[0095] In this application, transition metals primarily refer to elements in the d-block (Groups 3 to 12) of the periodic table, whose atoms have their valence electrons filled in d orbitals (e.g., iron, copper, zinc, etc.). Transition metals have incomplete d orbitals (or can form cations with incomplete d orbitals).

[0096] Late transition metals generally refer to the main group metals located to the right of the transition metals (d-block) in the periodic table, encompassing some of the metallic elements in Groups 13 to 15 (IIIA to VA). These elements possess metal-like physical properties (such as ductility and conductivity), but their chemical behavior lies between that of typical metals and metalloids (such as arsenic and antimony). For example, common late transition metals include aluminum (Al), gallium (Ga), indium (In), tin (Sn), lead (Pb), and bismuth (Bi).

[0097] The core metal material in the composite material of the present application can be selected from transition metals, post-transition metals, or one or more of these. Thus, by utilizing the electron adsorption properties of these active metals for lithium ions and increasing their specific surface area through modification, the core metal can enhance its ability to bind lithium ions and promote lithium ion deposition.

[0098] In some preferred embodiments, the metal includes, but is not limited to, any one or a combination of at least two of copper (Cu), tin (Sn), silver (Ag) or zinc (Zn); wherein copper (Cu), silver (Ag) and zinc (Zn) are transition metals, and tin (Sn) is a post-transition metal.

[0099] The above-mentioned active metals such as Cu, Sn, Ag, Zn, etc. are not only widely available and easy to obtain, but also have strong lithium affinity, which is more conducive to promoting the uniform deposition of lithium ions, improving the lithium dendrite problem, and thus more conducive to improving the safety of the battery.

[0100] In some embodiments, the core 10 is modified to have porous 101 characteristics, that is, after the modification, the metal forms a framework structure with a porous 101 form; wherein, the modification treatment can, for example, be to add pore-forming agents, template agents and other ingredients during the preparation process, and decompose or volatilize the pore-forming agents, template agents, etc. through heating treatment to form a porous structure.

[0101] Optionally, the pore size range of the pores 101 in the framework structure of the porous 101 is 100nm to 500nm; illustratively, the pore size of the framework structure of the porous 101 can be any point value among 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm or a range value between any two of them.

[0102] During the preparation of the above-mentioned core 10, a porous template agent is added. The porous template agent will be decomposed by a solvent in the subsequent treatment, thereby forming a porous framework structure. That is, these pores (holes) are left after the porous template agent is digested. Therefore, the size of the pore size is related to the added porous template agent. For example, the size of the pore size can be adapted to the particle size of the added porous template agent. In this application, by limiting the pore size range to 100nm to 500nm, a certain structural strength and compaction density can be met, which is conducive to increasing the specific surface area and improving the binding ability with lithium ions, thereby promoting the uniform deposition of lithium ions; if the pore size is too large, it will reduce the structural strength of the composite material and reduce the compaction density; if the pore size is too small, it will reduce the effect of promoting the uniform deposition of lithium ions.

[0103] Optionally, the porosity of the inner core 10 with the porous framework structure 101 is 20% to 50%; illustratively, its porosity can be any point value among 20%, 25%, 30%, 35%, 40%, 45%, 50% or a range value between any two of them.

[0104] In the present application, by making the porosity of the inner core 10 within the range of 20% to 50%, the compaction density and specific surface area can be increased while meeting a certain structural strength. It can also accommodate multiple particles and reserve sufficient pores for deposition and plastic dipping, thereby promoting the uniform deposition of lithium ions.

[0105] In some embodiments, the core 10 also includes a first binder; that is, the core is mainly composed of metal and a first binder, wherein the metal has a porous framework structure, and the first binder component may exist in the holes or gaps in the porous framework structure, that is, the first binder may be attached to at least part of the holes in the porous framework structure.

[0106] Taking into account the small amount and low density of the first binder itself, optionally, the mass ratio of the metal to the first binder is (95-98): (2-5); illustratively, the mass ratio of the metal to the first binder is any one of 95:5, 96:4, 97:3, 97.5:2.5, 98:2 or a range value between any two of them.

[0107] Therefore, by making the ratio of the metal to the first binder within the above range, the electron adsorption of the metal can be ensured, and the core can also have a certain degree of adhesion, thereby improving the connection strength between the core and the first coating layer.

[0108] Optionally, the first binder includes, but is not limited to, any one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC-Na), potassium carboxymethyl cellulose (CMC-K), styrene-butadiene rubber (SBR), polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyacrylamide, polyimide or polyamide.

[0109] The first binder in the above-mentioned core can be various binders known in the art, preferably selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber (SBR), etc., which have wider sources, are easier to obtain, and have better application effects.

[0110] In some embodiments, the average particle size of the core is in the range of 2 μm to 5 μm. For example, the average particle size of the core can be any one of 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, and 5 μm, or a range between any two of them.

[0111] By making the average particle size of the inner core within the above range, multiple particles can be accommodated, and sufficient pores can be reserved for deposition and plastic dipping, which is not only beneficial for processing and preparation, but also helps promote the uniform deposition of lithium ions.

[0112] In some embodiments, the conductive polymer in the first coating layer 20 includes, but is not limited to, any one or more combinations of conductive polyimide, conductive polyaniline, or conductive polypyrrole.

[0113] By coating the core surface with the aforementioned conductive polymers, not only is conductivity enhanced, but the electronic adsorption of lithium ions by the active metal and the physical adsorption of lithium ions by the conductive polymers can also promote uniform lithium ion deposition. Furthermore, the physical adsorption properties of these conductive polymers can enhance the directional transport of lithium ions, further improving the uniformity of lithium ion deposition.

[0114] In some embodiments, the average particle size of the conductive polymer ranges from 100 nm to 500 nm. For example, the average particle size of the conductive polymer can be any one of 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, and 500 nm, or a range therebetween. A particle size of the conductive polymer within this range helps ensure good processing properties of the composite material and improves the electrochemical properties of the resulting composite material.

[0115] In some embodiments, the first cladding layer 20 further includes a second binder; that is, the first cladding layer mainly consists of the conductive polymer and the second binder.

[0116] Optionally, the mass ratio of the conductive polymer to the second binder is (80-90):(10-20); illustratively, the mass ratio of the conductive polymer to the second binder is any one of 80:20, 82:18, 85:15, 88:12, 90:10 or a range between any two of them.

[0117] Therefore, by making the ratio of the conductive polymer and the second binder within the above range, it is possible to avoid the influence of excessive addition of the second binder on the performance of the conductive polymer, and it is also possible to meet the bonding requirements of the first coating layer, so that the first coating layer has a certain bonding property, thereby improving the connection strength between the core and the first coating layer and between the first coating layer and the second coating layer.

[0118] Optionally, the second binder includes, but is not limited to, any one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC-Na), potassium carboxymethyl cellulose (CMC-K), styrene-butadiene rubber (SBR), polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyacrylamide, polyimide or polyamide.

[0119] The second binder in the first coating layer 20 can be various binders known in the art, preferably selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber (SBR), etc., which are more widely available, easier to obtain, and have better application effects.

[0120] In the present application, the types of the first adhesive and the second adhesive may be the same or different, and there is no limitation on this.

[0121] In some embodiments, the thickness of the first coating layer 20 is 2 μm to 5 μm. For example, the thickness of the first coating layer can be any one of 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, and 5 μm, or a range between any two of the values.

[0122] The thickness of the first coating layer can be adjusted according to the size of the core. An appropriate thickness of the first coating layer can ensure that the composite material has good processing performance, while avoiding excessive thickness, excessive first coating material increasing battery impedance or affecting the cycle performance of the battery cell, or excessively thin thickness that is insufficient to effectively exert the modification effect of the first coating layer.

[0123] In some embodiments, the ceramic material of the second coating layer 30 includes, but is not limited to, any one or more combinations of aluminum oxide, zirconium oxide, aluminum nitride, silicon nitride, magnesium oxide, tin oxide, or titanium oxide. Preferably, based on a comprehensive consideration of raw material source, cost, and performance, aluminum oxide, zirconium oxide, aluminum nitride, and silicon nitride are more preferred.

[0124] By coating the surface of the first coating layer with the above-mentioned ceramic materials, the structural stability of the first coating layer can be improved, the first coating layer can be protected, the overall performance or structural stability of the composite material can be ensured, and the excessive growth of lithium dendrites can be prevented, thereby improving safety performance.

[0125] In some embodiments, the second coating layer 30 further includes a third binder; that is, the second coating layer is mainly composed of a ceramic material and the third binder.

[0126] Optionally, the mass ratio of the ceramic material and the third binder is (80-90):(10-20); illustratively, the mass ratio of the ceramic material and the third binder is any one of 80:20, 82:18, 85:15, 88:12, 90:10 or a range between any two of them.

[0127] Therefore, by making the ratio of the ceramic material and the third binder within the above range, it is possible to avoid the influence of excessive addition of the third binder on the performance of the ceramic material, and it is also possible to meet the bonding requirements of the second coating layer, so that the second coating layer has a certain bonding property, thereby improving the connection strength between the first coating layer and the second coating layer and ensuring the structural stability of the composite material.

[0128] Optionally, the third binder includes, but is not limited to, any one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC-Na), potassium carboxymethyl cellulose (CMC-K), styrene-butadiene rubber (SBR), polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyacrylamide, polyimide or polyamide.

[0129] The third binder in the second coating layer can be various binders known in the art, preferably selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber (SBR), etc., which are more widely available, easier to obtain, and have better application effects.

[0130] In the present application, the types of the first adhesive, the second adhesive, and the third adhesive may be the same or different, and there is no limitation on this.

[0131] In some embodiments, the second coating layer 30 has a porous structure. The second coating layer of the present application is a porous ceramic coating. By making the second coating layer have a porous structure, its porous properties can be utilized to enhance the diffusion of lithium ions into the composite material, thereby improving the uniformity of lithium ion deposition.

[0132] In some embodiments, the porosity of the second coating layer is 5% to 20%. For example, the porosity of the second coating layer can be any one of 5%, 10%, 15%, 18%, and 20%, or a range therebetween.

[0133] By controlling the porosity of the second coating layer within the above-mentioned suitable range, the diffusion of lithium ions into the interior of the composite material can be improved and the structural strength can be ensured.

[0134] In some embodiments, the thickness of the second coating layer is 2 μm to 5 μm. For example, the thickness of the second coating layer can be any one of 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, and 5 μm, or a range between any two of the values.

[0135] By controlling the thickness of the second coating layer within the above-mentioned appropriate range, it is possible to ensure that the composite material has good processing performance, while avoiding the situation where the thickness is too thick, the second coating material increases the battery impedance or affects the cycle performance of the battery cell, or the thickness is too thin to effectively exert the modification effect of the second coating layer.

[0136] Thus, the composite material provided by the present application has an active metal arranged in the core and forms a porous framework structure. By modifying the composite material, its specific surface area is increased, the affinity with lithium ions is increased, and the deposition of lithium ions is promoted. A first coating layer comprising a conductive polymer is arranged in the middle layer, and the physical adsorption of the conductive polymer is utilized to improve the directional transmission capability of lithium ions and further improve the uniformity of lithium ion deposition. A second coating layer comprising a porous ceramic material is arranged in the outermost layer. On the one hand, the ceramic coating, i.e., the second coating layer, can stabilize the structure of the first coating layer. On the other hand, it can also inhibit the excessive growth of lithium dendrites and improve safety performance. Moreover, the porous performance of the second coating layer can improve the diffusion of lithium ions into the interior of the composite material. The present invention not only improves the deposition uniformity of lithium ions but also improves the safety performance of lithium batteries through reasonable structural design. In addition, the composite material has a simple preparation process and therefore has good application prospects in the field of negative electrode-free batteries.

[0137] [Method for preparing composite materials]

[0138] Accordingly, in some embodiments, a method for preparing a composite material is provided, the method comprising the following steps:

[0139] The porous template agent is mixed with a metal compound solution, a reducing agent is added, and then a first drying is performed to obtain a core having a framework structure;

[0140] applying a slurry containing a conductive polymer to the surface of the core to form a first coating layer on at least a portion of the surface of the core;

[0141] A slurry containing a ceramic material is applied to the surface of the first coating layer to form a second coating layer on at least a portion of the surface of the first coating layer.

[0142] The method provided by the present invention can first prepare a metal core, that is, a core with a porous framework structure, and then form a first coating layer containing a conductive polymer on the surface of the core, and then form a second coating layer containing a ceramic material on the surface of the first coating layer, thereby forming a core-shell structure composite material.

[0143] The preparation method provided by the embodiment of the present invention has simple process, convenient operation, strong feasibility, and is easy to industrialize; the composite material that can be prepared by this method is beneficial to improving the uniformity of lithium ion deposition, alleviating the problem of lithium dendrites, and thus improving the safety performance of the battery.

[0144] It should be understood that all the features and advantages described above for the “composite material” are also applicable to the “method for preparing the composite material” and will not be described in detail here.

[0145] In some specific embodiments, the preparation method of the positive electrode lithium supplement comprises the following steps (a) to (c):

[0146] (a) Preparation of the core.

[0147] In step (a), preparing the inner core includes: first preparing a porous template agent, then mixing the porous template agent with a metal compound solution, adding a reducing agent, and performing a first drying to obtain an inner core having a framework structure.

[0148] During the preparation process of the core of the present application, a porous template agent is added. The porous template agent will be decomposed by the solvent in the subsequent treatment to form a porous framework structure. That is, the porous template agent leaves holes after decomposition, so that the core has a porous framework structure.

[0149] In some embodiments, in step (a), the preparation of the porous template agent comprises:

[0150] Grinding the template agent and the pore-forming agent to obtain particles with an average particle size of 100 nm to 500 nm;

[0151] uniformly mixing the particles with a first binder and a first solvent to obtain a slurry;

[0152] The slurry is coated on a substrate to form a thin film, and after a second drying and pulverization process, a porous stencil agent is obtained.

[0153] As previously mentioned, the particle size of the aforementioned particles is compatible with the pore size of the framework structure, and particles of this size can form a pore structure of corresponding size. By limiting the average particle size range of 100nm to 500nm, a certain structural strength and compaction density can be achieved, which helps to increase the specific surface area and enhance the binding capacity with lithium ions, thereby promoting uniform deposition of lithium ions. If the particle size is too large, the structural strength of the composite material will be reduced, reducing the compaction density. If the particle size is too small, the effect of promoting uniform deposition of lithium ions will be reduced.

[0154] In any embodiment, after the above-mentioned crushing treatment, particles with an average particle size of 500nm to 1000nm are obtained, that is, a porous template agent is obtained; as an example, the average particle size of the porous template agent can be any one point value among 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm or a range value between any two of them.

[0155] Optionally, the template agent includes, but is not limited to, at least one of polyethylene, polyethylene glycol, polyvinyl pyrrolidone, or hexadecyltrimethylammonium bromide. The template agent can be selected from substances that can be dissolved in toluene solvent.

[0156] In some preferred embodiments, the template agent is selected from polyethylene. By selecting polyethylene as the template agent, it can be dissolved by toluene solvent in subsequent processing, thereby forming holes in the metal core.

[0157] Optionally, the pore forming agent includes, but is not limited to, at least one of ammonium bicarbonate, ammonium carbonate, ammonium nitrate or ammonium sulfate.

[0158] In some preferred embodiments, the pore-forming agent is selected from ammonium bicarbonate. By selecting ammonium bicarbonate as the pore-forming agent, it is easy to decompose to form a pore structure, thereby making the template agent porous.

[0159] In some embodiments, in step (a), the mass ratio of the first binder, the template agent and the pore-forming agent is (60-80): (10-20): (10-20); illustratively, the mass ratio of the first binder, the template agent and the pore-forming agent is 60:20:20, 65:15:20, 65:18:17, 70:15:15, 75:12:13, 80:10:10, etc.

[0160] In some embodiments, in step (a), the first solvent includes, but is not limited to, at least one of N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), dimethylformamide (DMF), or water.

[0161] In some embodiments, in step (a), the second drying temperature is 60° C. to 100° C.; as an example, the second drying temperature can be any one of 60° C., 70° C., 80° C., 90° C., and 100° C., or a range between any two thereof;

[0162] The temperature of the second drying can be selected and set according to the decomposition temperature of the pore-forming agent. For example, ammonium bicarbonate-like substances decompose under heat, generally above 60°C. Therefore, the second drying temperature is 60°C to 100°C to decompose the ammonium bicarbonate-like pore-forming agent in the mixed particles, thus obtaining a porous template agent, such as porous polyethylene particles.

[0163] In some embodiments, in step (a), after preparing the porous template agent, the porous template agent is mixed with a metal compound solution, specifically comprising: soaking the porous template agent in the metal compound solution for 2 hours to 4 hours; as an example, the soaking time can be any one of 2 hours, 2.5 hours, 3 hours, 3.5 hours, and 4 hours, or a range between any two of them.

[0164] By soaking the porous template agent in the metal compound for 2 hours to 4 hours, the porous template agent and the metal compound solution can be fully mixed, thereby improving mixing uniformity.

[0165] Optionally, the metal ions in the metal compound solution include at least one of copper ions, tin ions, silver ions, or zinc ions. The metal ions may be one or more transition metal ions or post-transition metal ions, preferably selected from a combination of any one or more of copper ions, tin ions, silver ions, or zinc ions. This improves lithiophilicity and facilitates improved uniformity of lithium ion deposition.

[0166] Optionally, the anions in the metal compound solution include at least one of nitrate, sulfate, chloride or acetate.

[0167] As an example, the metal compound solution may be a solution of copper nitrate, tin nitrate, silver nitrate, zinc nitrate, copper sulfate, tin sulfate, silver sulfate, zinc sulfate, copper acetate, tin acetate, silver acetate, zinc acetate, or the like.

[0168] In some embodiments, in step (a), after the porous template agent is mixed with the metal compound solution, a reducing agent is added to the solution to reduce the metal in the metal compound solution. The reducing agent includes, but is not limited to, at least one of iron, zinc, or hydrazine hydrate.

[0169] Therefore, by adding the above-mentioned reducing agents to the solution, the metal in the metal compound can be reduced to obtain metal-deposited porous template microspheres, such as metal-deposited porous polyethylene microspheres.

[0170] In some embodiments, in step (a), after adding the reducing agent, a first drying step is performed, and the temperature of the first drying step can be a conventional temperature, such as a temperature of 60°C to 100°C. Furthermore, after the first drying step, the method further comprises: soaking the porous metal-deposited template after the first drying step in a benzene solvent for 4 to 12 hours, followed by washing and a third drying step, and the temperature of the third drying step can also be a conventional temperature, such as a temperature of 60°C to 100°C, to obtain a core having a framework structure;

[0171] Optionally, the benzene solvent may be toluene, but is not limited thereto, as long as it can be used to dissolve template agents such as polyethylene.

[0172] Therefore, after the porous template agent for metal deposition is immersed in a benzene solvent such as toluene, the porous template agent can be dissolved, that is, the porous template agent can be decomposed to form a metal core with a porous framework structure.

[0173] Illustratively, the above step (a) specifically includes: grinding a template agent (such as polyethylene, etc.) and a pore-forming agent (such as ammonium bicarbonate, etc.) to obtain particles with an average particle size of 100nm to 500nm; then uniformly mixing the particles with a first binder in a first solvent and stirring to obtain a slurry; wherein the mass ratio of the first binder, the template agent and the pore-forming agent is (60-80): (10-20): (10-20); coating the slurry on a substrate (the substrate mainly refers to a bottom plate that can support the slurry coating into a film, such as a glass plate, a plastic plate, etc.), and after a second drying, removing the film from the substrate and then crushing it to obtain particles of a suitable particle size, that is, obtaining a porous template agent.

[0174] Then, the porous template agent is immersed in a solution containing metal ions, that is, a metal compound solution, for 2 hours to 4 hours, and then a reducing agent, such as iron, zinc or hydrazine hydrate, is added to the solution to obtain a metal-deposited porous template agent, such as metal-deposited porous polyethylene microspheres; the metal-deposited porous template agent is then dried and immersed in a benzene solvent such as toluene solvent for 4 hours to 12 hours, and then washed (such as with water) and dried for a third time to obtain a metal core with a porous framework structure.

[0175] In this application, after a porous template is immersed in a solution containing metal ions, the metal compound solution will penetrate into the porous template, such as porous polyethylene mixed particles, along the pores. Subsequently, the corresponding metal ions can be reduced to metal by a reducing agent. Repeating this process multiple times will result in a metal layer of a certain thickness, which is referred to as the metal-based core. In other embodiments, the metal core can also be obtained by gas-phase reduction, such as mixing porous polyethylene mixed particles soaked in metal salts with a reducing gas such as hydrogen to reduce the metal and obtain a porous metal-based core.

[0176] (b) Preparing the first coating layer.

[0177] In step (b), preparing the first coating layer includes: first preparing a slurry containing a conductive polymer, and then coating the slurry containing the conductive polymer on the surface of the core to form the first coating layer on at least a portion of the surface of the core.

[0178] In some embodiments, in step (b), the slurry containing the conductive polymer includes a conductive polymer, a second binder, and a second solvent.

[0179] Optionally, the mass ratio of the conductive polymer to the second binder is (80-90):(10-20);

[0180] Optionally, the second solvent includes, but is not limited to, at least one of N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide or water.

[0181] Optionally, the average particle size of the conductive polymer ranges from 100 nm to 500 nm;

[0182] In some embodiments, in step (b), after the slurry containing the conductive polymer is coated on the surface of the core, a fourth drying is performed, and the temperature of the fourth drying is 60° C. to 100° C.

[0183] Exemplarily, the above-mentioned step (b) specifically includes: uniformly mixing a conductive polymer such as conductive polyimide with a suitable particle size, such as an average particle size range of 100 nm to 500 nm, and a second binder in a second solvent such as NMP in a mass ratio of (80 to 90): (10 to 20), and then spraying the slurry onto the surface of the metal-based core obtained in step (a) by spray coating. After the fourth drying, a first coating layer is formed on the surface of the core.

[0184] (c) Preparing a second coating layer.

[0185] In step (c), preparing the second coating layer includes: first preparing a slurry containing a ceramic material, and then coating the slurry containing the ceramic material on the surface of the first coating layer to form the second coating layer on at least a portion of the surface of the first coating layer.

[0186] In some embodiments, in step (c), the ceramic-containing slurry comprises a ceramic material, a third binder, and a third solvent.

[0187] Optionally, the slurry containing ceramics further includes a pore former, that is, the slurry containing ceramics includes a ceramic material, a third binder, a pore former, and a third solvent. The pore former may be an ammonium bicarbonate pore former.

[0188] In some embodiments, in step (c), the mass ratio of the ceramic material, the pore former and the third binder is (70-80): (10-20): (10-20).

[0189] Optionally, the third solvent includes, but is not limited to, at least one of N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide or water;

[0190] In some embodiments, in step (c), after applying the slurry containing the ceramic material to the surface of the first coating layer, a heat treatment is performed at a temperature of 100°C to 150°C for a time of 4 to 8 hours. As an example, the heat treatment temperature can be any one of 100°C, 110°C, 120°C, 130°C, 140°C, and 150°C, or a range between any two thereof; and the heat treatment time can be any one of 4 hours, 5 hours, 6 hours, 7 hours, and 8 hours, or a range between any two thereof.

[0191] Illustratively, the above-mentioned step (c) specifically includes: uniformly mixing a ceramic material such as an alumina ceramic material, a pore-forming agent, and a third binder in a third solvent such as NMP in a mass ratio of (70-80): (10-20): (10-20), and then spraying the slurry onto the surface of the material obtained in step (b) by spray coating. After heat treatment at 100°C to 150°C for 4h to 8h (such as standing in an environment of 100°C to 150°C for 4h to 8h), a second coating layer is formed on the surface of the first coating layer to obtain a composite material.

[0192] The preparation method of the composite material provided in the embodiments of the present application has simple process, strong feasibility, high efficiency and environmental protection, and is easy to achieve large-scale production.

[0193] [No negative electrode current collector]

[0194] Accordingly, in some embodiments, a negative electrode-free current collector is provided, which includes a substrate and a coating disposed on at least one surface of the substrate, the coating including the aforementioned composite material, or including a composite material prepared by the aforementioned preparation method.

[0195] The negative electrode-free current collector of the present application includes a substrate and a coating arranged on at least one side surface of the substrate, and the coating contains the above-mentioned composite material, thereby improving the uniformity of lithium ion deposition, inhibiting the growth of lithium dendrites, and improving the safety of the battery.

[0196] The coating can be provided on at least one surface of the substrate, which means that the coating can be provided on one surface of the substrate along its thickness direction, or on both surfaces of the substrate along its thickness direction. The "surface" here can be the entire area of ​​the substrate or a portion of the substrate, and this application is not particularly limited, as long as the purpose of this application can be achieved.

[0197] Optionally, in this embodiment, the substrate has two surfaces opposite to each other in its thickness direction, and the coating is provided on the two opposite surfaces of the substrate. It is understood that in other embodiments, the coating can also be provided on either of the two surfaces of the substrate. Preferably, when the coating is provided on one surface of the substrate, the coating is provided on the side close to the negative electrode.

[0198] In the present application, the substrate may be a copper-based substrate or a composite substrate. The composite substrate includes a substrate formed by a composite of a polymer material and a metal.

[0199] As an example, the substrate can be a sheet-like metal foil material conventionally used in the field of negative electrode current collectors, such as copper foil, porous copper foil, foam copper and the like, which are widely available, low in cost and easy to obtain.

[0200] Alternatively, the substrate can also be a substrate formed by a composite of a polymer material and a metal. For example, a composite substrate can be formed by forming a metal material such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy on a substrate of a polymer material such as polypropylene, polyethylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, etc.

[0201] In some embodiments, the coating further includes a fourth binder and a conductive agent, that is, the coating mainly includes the composite material, the fourth binder and the conductive agent.

[0202] Optionally, the fourth binder includes, but is not limited to, at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyacrylamide, polyimide or polyamide.

[0203] Optionally, the conductive agent includes, but is not limited to, at least one of conductive carbon black, conductive graphite, carbon nanotubes, carbon fibers or graphene.

[0204] It should be noted that the fourth binder and conductive agent are not limited to the substances listed above and can be used in the coating of the battery. This does not limit the purpose of the present invention. Other similar binders and conductive agents can also be used in the present invention.

[0205] Optionally, the mass ratio of the composite material, the fourth binder, and the conductive agent is (70-80):(10-20):(10-20). For example, the mass ratio of the composite material, the fourth binder, and the conductive agent is 70:15:15, 72:10:18, 75:10:15, 80:10:10, etc.

[0206] In some embodiments, the coating has a thickness of 2 μm to 10 μm. For example, the coating may have a thickness of 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, or a range between any two of the values.

[0207] Optionally, the surface density of the coating may be 0.05 to 0.1 g / cm.

[0208] [Battery]

[0209] In some embodiments, a battery is provided, comprising the above-mentioned negative electrode-free current collector; the battery further comprises a positive electrode sheet, a separator, and an electrolyte; the separator is located between the positive electrode sheet and the negative electrode-free current collector.

[0210] The electrochemical cell may be a secondary battery having high cycle performance and high safety, and may be specifically a lithium secondary battery.

[0211] The battery includes the above-mentioned negative electrode-free current collector provided in the embodiments of the present application. Therefore, the battery, such as a lithium-ion secondary battery, also has excellent electrochemical properties, such as long cycle life and good rate performance.

[0212] The battery provided in this application is a negative electrode-free battery, which can greatly improve the energy density of the battery compared with conventional lithium-ion batteries using carbon materials or silicon materials as negative electrode active materials.

[0213] The battery provided in the present application uses the negative electrode-free current collector provided in the present application, which can induce uniform lithium deposition, reduce or avoid lithium dendrites, improve the safety performance of the battery, and also improve the cycle performance of the battery.

[0214] In the embodiments of the present application, in the battery, there is no limitation on the specific materials and structures of the positive electrode sheet, separator, and electrolyte. Components and structures that are well known in the art and can be used for secondary batteries can be selected as long as the purpose of the present application can be achieved.

[0215] The battery of this application also includes a packaging case for housing the positive electrode sheet, separator, current collector (negative electrode current collector for batteries without negative electrodes), electrolyte, and other components known in the art for lithium batteries. This application does not limit these other components. This application does not specifically limit the packaging case and can be any packaging case known in the art, as long as it can achieve the objectives of this application.

[0216] The present invention has no particular limitation on the method for preparing the battery, and any technical solution for preparing a positive electrode material into a battery, such as a secondary battery, which is well known to those skilled in the art can be used.

[0217] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents, materials, or instruments used that do not specify the manufacturer are all conventional products that can be purchased commercially.

[0218] Example 1

[0219] 1. Preparation of composite materials, including the following steps:

[0220] (a) First, polyethylene (template agent) and ammonium bicarbonate (pore-forming agent) particles are ground into particles with a size of approximately 200 nm. Then, PVDF (first binder), polyethylene particles, and ammonium bicarbonate are uniformly mixed in a solvent NMP at a ratio of 60:20:20 and stirred into a slurry. The slurry is coated onto a substrate into a thin film. After drying, the film is removed and pulverized into particles with a size of approximately 800 nm, namely, porous polyethylene particles.

[0221] The porous polyethylene microsphere material is immersed in a tin sulfate solution with a solubility of 0.1 mol / L for 4 hours, and then a hydrazine hydrate reducing agent is added to the solution to obtain porous polyethylene microspheres with tin metal deposition. The metal-deposited porous polyethylene microspheres are dried and then immersed in a toluene solvent for 8 hours to dissolve the polyethylene microspheres. After washing with water and drying, a porous metal-based core (tin-based core) is obtained. The porosity of the core is 40%.

[0222] (b) Conductive polymer particles, such as conductive polyimide, having a particle size of approximately 500 nm are prepared, and the conductive polymer and PVDF (a second binder) are uniformly mixed in a solvent, NMP, at a mass ratio of 90:10. The mixed slurry is then sprayed onto the surface of a porous tin metal core by spray coating. After drying, a first coating layer having a thickness of 3 μm is formed on the surface of the core.

[0223] (c) Alumina ceramic material, ammonium bicarbonate (pore former), and PVDF (third binder) are uniformly mixed in a solvent NMP at a mass ratio of 80:10:10, and then the slurry is sprayed onto the surface of the material prepared in step (b) by spray coating. After heat treatment at 120° C. for 6 h, a second coating layer is formed on the surface of the first coating layer. The second coating layer has a thickness of 3 μm and a porosity of 10%, thereby obtaining a composite material.

[0224] 2. Preparation of anode-free current collector, including:

[0225] The above-mentioned composite material, PVDF (fourth binder), and conductive carbon black (conductive agent) are evenly mixed in a solvent water in a mass ratio of 80:10:10 to prepare a coating slurry. The coating slurry is then coated on a conventional copper foil substrate by coating. The coating thickness is 5 μm to obtain a negative electrode-free current collector.

[0226] 3. Preparation of batteries, including:

[0227] Preparation of positive electrode sheet: The positive electrode active material NCM811, conductive agent conductive carbon black (SP), carbon nanotubes, and binder polyvinylidene fluoride (PVDF5130) are mixed in a mass ratio of 97:1.5:0.5:1, and then N-methylpyrrolidone (NMP) is added. Stir and mix to form a stable positive electrode slurry; the positive electrode slurry is evenly coated on a 13μm aluminum foil of the positive electrode current collector with a coating surface density of 195g / m 2 , and then after drying, cold pressing and cutting, the positive electrode sheet is obtained; the compaction density is 3.4 g / cm 3 .

[0228] Isolation membrane: A polypropylene film with a thickness of 9 μm is selected as the isolation membrane base membrane, and the isolation membrane also includes a ceramic coating with a thickness of 3 μm on one side (ceramic coating is set on both sides).

[0229] Electrolyte: In a glove box filled with inert gas, ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate were mixed in a mass ratio of 1:1:1 to obtain an organic solvent. LiPF6 was then dissolved in the organic solvent to a concentration of 1.2 mol / L to obtain an electrolyte.

[0230] Battery Assembly: Arrange the positive electrode sheet, separator, and negative electrode current collector in order, using a winding method. Electrolyte is injected into the dry cell, soaking it for 24 hours before formation at 45°C. The formation process involves charging at 0.05C to 3.4V, then 0.2C to 3.75V. After aging at room temperature for 24 hours, the battery is complete.

[0231] Example 2

[0232] The composite material of Example 2 was prepared according to the preparation method of Example 1, with the following differences:

[0233] In step (b), the thickness of the first coating layer is 5 μm.

[0234] Example 3

[0235] The composite material of Example 3 was prepared according to the preparation method of Example 1, with the following differences:

[0236] In step (b), the thickness of the first coating layer is 2 μm.

[0237] Example 4

[0238] The composite material of Example 4 was prepared according to the preparation method of Example 1, with the following differences:

[0239] In step (a), the particle size of the porous polyethylene particles is 1000 nm.

[0240] Example 5

[0241] The composite material of Example 5 was prepared according to the preparation method of Example 1, with the following differences:

[0242] In step (a), the particle size of the porous polyethylene particles is 500 nm.

[0243] Example 6

[0244] The composite material of Example 6 was prepared according to the preparation method of Example 1, with the following differences:

[0245] In step (c), the porosity of the second coating layer is about 20% by adjusting the mass ratio of alumina ceramic, ammonium bicarbonate, and binder.

[0246] Example 7

[0247] The composite material of Example 7 was prepared according to the preparation method of Example 1, with the following differences:

[0248] In step (c), the porosity of the second coating layer is about 5% by adjusting the mass ratio of alumina ceramic, ammonium bicarbonate, and binder.

[0249] Example 8

[0250] The composite material of Example 8 was prepared according to the preparation method of Example 1, with the following differences:

[0251] In step (c), the thickness of the second coating layer is 5 μm.

[0252] Example 9

[0253] The composite material of Example 9 was prepared according to the preparation method of Example 1, with the following differences:

[0254] In step (c), the thickness of the second coating layer is 2 μm.

[0255] Example 10

[0256] The composite material of Example 10 was prepared according to the preparation method of Example 1, with the following differences:

[0257] In step (a), the metal is made of copper.

[0258] In step (b), the conductive polymer is conductive polyaniline.

[0259] In step (c), the ceramic material is zirconium oxide.

[0260] Example 11

[0261] The composite material of Example 11 was prepared according to the preparation method of Example 1, with the following differences:

[0262] In step (a), the metal is made of zinc.

[0263] In step (b), the conductive polymer is conductive polypyrrole.

[0264] In step (c), the ceramic material is aluminum nitride.

[0265] Example 12

[0266] The composite material of Example 12 was prepared according to the preparation method of Example 1, with the following differences:

[0267] In step (b), the thickness of the first coating layer is 1 μm.

[0268] Example 13

[0269] The composite material of Example 13 was prepared according to the preparation method of Example 1, with the following differences:

[0270] In step (c), the thickness of the second coating layer is 8 μm.

[0271] Example 14

[0272] The composite material of Example 14 was prepared according to the preparation method of Example 1, with the following differences:

[0273] In step (c), the porosity of the second coating layer is 40%.

[0274] Example 15

[0275] The composite material of Example 15 was prepared according to the preparation method of Example 1, with the following differences:

[0276] In step (a), the particle size of polyethylene (template agent) and ammonium bicarbonate (pore-forming agent) is too large, here 1000 nm;

[0277] The porosity of the prepared core was 68%.

[0278] Comparative Example 1

[0279] The composite material of Comparative Example 1 was prepared according to the preparation method of Example 1, with the following differences:

[0280] In step (a), the metal modification treatment is omitted, that is, the porous feature is not set, and tin metal is directly used as the core. The prepared tin-based core does not have a porous feature, that is, does not have a framework structure.

[0281] Comparative Example 2

[0282] The composite material of Comparative Example 2 was prepared according to the preparation method of Example 1, with the following differences:

[0283] Step (b) was omitted, that is, the first coating layer was not provided.

[0284] Comparative Example 3

[0285] The composite material of Comparative Example 3 was prepared according to the preparation method of Example 1, with the following differences:

[0286] Step (c) was omitted, that is, the second coating layer was not provided.

[0287] Performance Testing

[0288] 1. The composite materials and negative electrode-free current collectors prepared in the above embodiments and comparative examples were subjected to performance tests, including:

[0289] (1) Specific surface area: The specific surface area is measured by the N2 adsorption method, and the specific surface area of ​​the composite material is characterized by the amount of gas adsorbed.

[0290] (2) Maximum compaction density: The above-mentioned negative electrode-free current collector was passed through a roller press under different pressure conditions in turn. Under compaction densities of 3.2T, 3.3T, 3.4T, 3.5T, and 3.6T, the SEM and CP of the cross section were used to determine whether the composite material in the coating was broken, and the maximum compaction density was recorded.

[0291] (3) Conductivity: The measurement of conductivity is a powder-level resistivity test. A certain amount of composite material is placed in a test container. The same mass of composite material is pressed into a dense block under certain pressure conditions, such as 3-10 tons of pressure, and its resistivity is tested in this state.

[0292] The test results are shown in Table 1 below.

[0293] Table 1

[0294]

[0295] It can be seen from the relevant physical and chemical performance tests in Table 1 above that, in general, compared with comparative examples 1-3, the composite materials and negative electrode-free current collectors provided by Examples 1-15 of the present invention have a larger specific surface area, a more suitable maximum compaction density and a higher conductivity. This shows that the negative electrode-free current collector of the present invention can provide more lithium deposition sites, which is beneficial to improving the uniformity of lithium ion deposition and improving the lithium dendrite problem.

[0296] A comparison of Comparative Example 1 with Examples 1-11 shows that the core of Comparative Example 1 is unmodified and lacks a porous structure, while the composite materials of Examples 1-11, after modification of the metal core substrate, significantly increase their specific surface area, thereby providing more lithium deposition sites. A comparison of Example 1 with Examples 12-15 shows that if the second coating layer, or ceramic coating, is too thick, it significantly reduces the conductivity of the electrode, hindering the improvement of power performance. Although the increased porosity of the ceramic coating can increase the lithium ion transmission channel, excessive pores can reduce its structural stability, resulting in a low compaction density, which hinders the improvement of the energy density of the lithium battery. Although the thickness of the first coating layer, or conductive polymer layer, is reduced, although there is no significant change in physical and chemical properties, the reduction in conductive polymer reduces the number of particles available for physical adsorption of lithium ions, resulting in uneven lithium ion adsorption, ultimately affecting the capacity and life of the battery. The particle size of the pore-forming agent and template agent is related to the structural strength of the composite material. If it is too large, the composite material will have larger pores and easily break under pressure, thus affecting safety performance.

[0297] In addition, it can be seen from Examples 10-11 that changing the metal base type and the type of material of the coating layer does not have a significant impact on the final physical and chemical properties, and all have relatively similar properties. By comparing the embodiment with Comparative Example 2, it can be seen that Comparative Example 2 does not provide a first coating layer, that is, Comparative Example 2 cancels the conductive polymer layer, which directly reduces the conductivity of the overall composite particles, which will affect the power performance of the battery, and the cancellation of the conductive polymer will also affect the deposition stability of lithium ions. By comparing the embodiment with Comparative Example 3, it can be seen that Comparative Example 3 does not provide a second coating layer, that is, Comparative Example 3 cancels the outer layer of alumina ceramic coating. Although no obvious difference is seen in the physical and chemical properties of the material end, the coating plays a role in protecting lithium ion deposition and avoiding the risk of lithium ion dendrite overflow, and therefore may affect the safety performance of the battery.

[0298] 2. The batteries prepared in the above embodiments and comparative examples were subjected to performance tests, including:

[0299] (1) Internal resistance test (DC internal resistance ACR test): Charge the battery according to the standard 0.5C / 1C charge and discharge system, charge the battery cell to 4.25V according to the standard 0.5C constant current constant voltage, let it stand for 30 minutes, then discharge it at a constant current of 1C for 30 minutes, let it stand for 60 minutes, and use a DC internal resistance meter to test the DC internal resistance of the battery.

[0300] (2) Capacity retention test (1C cycle 500 cycles capacity retention): Perform charge and discharge test according to the standard test process 0.5C / 1C system. Charge the battery cell to 4.25V at a standard 0.5C constant current, let it stand for 30 minutes, then discharge it to 2.5V at a 1C constant current, let it stand for 30 minutes, and perform cycle test in sequence until the discharge capacity of the battery is lower than 80% of the initial capacity.

[0301] (3) 1C energy density test: 1C energy density = 1C discharge capacity * 1C discharge average voltage / total weight of the battery.

[0302] (4) 5C rate capacity retention test: The battery cell is charged to 4.25V at a standard 0.5C constant current, left to stand for 30 minutes, and then discharged to 2.5V at a 1C constant current, and left to stand for 30 minutes; it is again charged to 4.25V at a 0.5C constant current and constant voltage, left to stand for 30 minutes, and then discharged to 2.5V at a 5C constant current, then the 5C capacity retention rate = 5C discharge capacity / 1C discharge capacity.

[0303] (5) Maximum charge rate test: The battery is repeatedly charged and discharged at a rate of 1C\2C\3C... in sequence, and the charge and discharge test is carried out according to the standard test process 0.5C / XC system. The battery cell is charged to 4.25V at a standard 0.5C constant current and constant voltage, and left to stand for 30 minutes. Then, it is discharged to 2.5V at a XC constant current, and left to stand for 30 minutes until the battery has thermal runaway. The rate at this time is the maximum safe rate of the battery without negative electrode current collector, which indirectly reflects the safety performance of the structure without negative electrode current collector.

[0304] The test results are shown in Table 2 below.

[0305] Table 2

[0306]

[0307] It can be seen from the data in Table 2 above that Examples 1-11 show good performance in terms of comprehensive electrochemical performance within the appropriate range of the present invention. Compared with Example 1, the metal substrate shown in Comparative Example 1 has no porous setting. Although the compaction density of the composite material can be improved, the specific surface area of ​​the composite material is reduced due to the lack of a porous setting, and the effective lithium ion deposition area is reduced, which will cause the unevenness of lithium ion deposition and the growth of lithium dendrites, resulting in poor high-rate performance and safety performance. In addition, compared with Example 1, Examples 12-15 have a reduced thickness of the conductive polymer layer, resulting in a small amount of polymer added and a reduced ability to physically adsorb lithium ions. This will also cause uneven lithium ion deposition, affecting safety and other performance. The increase in the thickness of the second coating layer, that is, the ceramic coating, significantly worsens the internal resistance of the battery, resulting in poor cycle stability. In addition, due to the increase in thickness, the quality is improved, resulting in a decrease in energy density, and due to the deterioration of the polarization phenomenon, the rate performance and safety of the battery are also worsened. Compared with Example 1, Examples 14 and 15 are equivalent to increased pores and larger holes. The final result will cause the pressure resistance of the composite material to decrease, leading to particle breakage, affecting the deposition uniformity of lithium ions, and worsening the battery's high rate and safety performance. In addition, due to the breakage of particles, it will also affect the battery capacity, resulting in a decrease in energy density and deterioration of cycle performance.

[0308] In addition, in Examples 10 and 11, the effects of fine-tuning the metal base on battery performance are basically the same, with little difference. In Comparative Example 2, since the first coating layer, also known as the conductive polymer layer, is eliminated, the polarization of the battery is increased due to the reduction in conductivity, thus affecting the cycle performance and rate retention rate. In addition, the conductive polymer layer also has the function of promoting lithium ion deposition, so the maximum charge rate of this group is reduced, that is, the safety performance is reduced. In Comparative Example 3, since the second coating layer, also known as the ceramic coating, is eliminated, the function of the protective layer is lost. Therefore, the cycle performance and charging capacity of the battery are reduced due to the easy lithium precipitation, and the overall performance of the battery is reduced.

[0309] Parts of the present invention that are not described in detail are well known to those skilled in the art.

[0310] The basic principles of the present invention have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in the present invention are merely illustrative and non-limiting, and should not be construed as necessarily possessed by each embodiment of the present invention. Furthermore, the specific details disclosed above are provided for illustrative purposes and to facilitate understanding, and are not intended to be limiting. These details do not necessarily limit the present invention to being implemented using these specific details.

[0311] It should be noted that the terms "and / or" or " / " used herein are merely a description of an association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B may represent three situations: A exists alone, A and B exist at the same time, and B exists alone. The singular forms "a," "the," and "the" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0312] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0313] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A composite material, characterized in that The composite material comprises: A core, the core comprising metal, the core having a porous framework structure; the pores in the porous framework structure have a pore size ranging from 100 nm to 500 nm; a first coating layer, the first coating layer coating at least a portion of the surface of the core, the first coating layer comprising a conductive polymer; and a second coating layer, the second coating layer coating at least a portion of the surface of the first coating layer, the second coating layer comprising a ceramic material; The thickness of the first coating layer is 2 μm to 5 μm; The thickness of the second coating layer is 2 μm to 5 μm; The porosity of the second coating layer is 5% to 20%.

2. The composite material according to claim 1, characterized in that The core, the first cladding layer, and the second cladding layer satisfy at least one of the following characteristics (1) to (10): (1) The metal comprises at least one of a transition metal or a post-transition metal; (2) The core further includes a first binder; (3) The porosity of the core is 20% to 50%; (4) The average particle size of the core is in the range of 2 μm to 5 μm; (5) The conductive polymer includes at least one of conductive polyimide, conductive polyaniline or conductive polypyrrole; (6) The first coating layer further includes a second binder; (7) The average particle size of the conductive polymer is in the range of 100 nm to 500 nm; (8) The ceramic material includes at least one of aluminum oxide, zirconium oxide, aluminum nitride, silicon nitride, magnesium oxide, tin oxide or titanium oxide; (9) The second coating layer further includes a third binder; (10) The second coating layer has a porous structure.

3. The composite material according to claim 2, characterized in that The kernel satisfies at least one of the following characteristics (1) to (3): (1) The metal includes at least one of copper, tin, silver or zinc; (2) The mass ratio of the metal to the first binder is (95-98):(2-5); (3) The first binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyacrylamide, polyimide or polyamide.

4. The composite material according to claim 2, characterized in that The first coating layer and the second coating layer satisfy at least one of the following characteristics (1) to (4): (1) The mass ratio of the conductive polymer to the second binder is (80-90):(10-20); (2) the second binder comprises at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyacrylamide, polyimide or polyamide; (3) The mass ratio of the ceramic material to the third binder is (80-90):(10-20); (4) The third binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyacrylamide, polyimide or polyamide.

5. A method for preparing the composite material according to any one of claims 1 to 4, characterized in that: The following steps are involved: The porous template agent is mixed with a metal compound solution, a reducing agent is added, and then a first drying is performed to obtain a core having a porous framework structure; applying a slurry containing a conductive polymer to the surface of the core to form a first coating layer on at least a portion of the surface of the core; A slurry containing a ceramic material is applied to the surface of the first coating layer to form a second coating layer on at least a portion of the surface of the first coating layer.

6. The method for preparing a composite material according to claim 5, characterized in that: The preparation method satisfies at least one of the following characteristics (1) to (8): (1) The preparation of the porous template agent includes: Grinding the template agent and the pore-forming agent to obtain particles with an average particle size of 100 nm to 500 nm; uniformly mixing the particles with a first binder and a first solvent to obtain a slurry; The slurry is coated on a substrate to form a thin film, and after a second drying and pulverization process, the porous stencil agent is obtained; (2) The step of mixing the porous template agent with the metal compound solution comprises: Soaking the porous template agent in the metal compound solution for 2 hours to 4 hours; (3) The reducing agent includes at least one of iron, zinc or hydrazine hydrate; (4) After the first drying, the method further includes: soaking the porous metal-deposited template after the first drying in a benzene solvent for 4 to 12 hours, and then washing and drying for the third time to obtain the core having the porous framework structure; (5) The slurry containing the conductive polymer contains a conductive polymer, a second binder and a second solvent; (6) After the conductive polymer slurry is applied to the surface of the core, a fourth drying step is performed, wherein the temperature of the fourth drying step is 60° C. to 100° C.; (7) The ceramic slurry comprises a ceramic material, a third binder, and a third solvent; (8) After the slurry containing the ceramic material is coated on the surface of the first coating layer, heat treatment is performed, wherein the heat treatment temperature is 100° C. to 150° C. and the time is 4 hours to 8 hours.

7. The method for preparing a composite material according to claim 6, characterized in that: The preparation method satisfies at least one of the following characteristics (1) to (16): (1) The average particle size of the porous template agent is in the range of 500 nm to 1000 nm; (2) The template agent includes at least one of polyethylene, polyethylene glycol, polyvinyl pyrrolidone or hexadecyltrimethylammonium bromide; (3) the pore-forming agent comprises at least one of ammonium bicarbonate, ammonium carbonate, ammonium nitrate or ammonium sulfate; (4) The mass ratio of the first binder, the template agent and the pore-forming agent is (60-80): (10-20): (10-20); (5) The first solvent includes at least one of N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide or water; (6) The temperature of the second drying is 60°C to 100°C; (7) The metal ions in the metal compound solution include at least one of copper ions, tin ions, silver ions, or zinc ions; (8) The anions in the metal compound solution include at least one of nitrate, sulfate, chloride or acetate; (9) The temperature of the first drying is 60°C to 100°C; (10) The temperature of the third drying is 60°C to 100°C; (11) The mass ratio of the conductive polymer to the second binder is (80-90): (10-20); (12) The second solvent comprises at least one of N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide or water; (13) The average particle size of the conductive polymer is in the range of 100 nm to 500 nm; (14) The ceramic slurry further includes a pore-forming agent; (15) The mass ratio of the ceramic material, the pore former and the third binder is (70-80): (10-20): (10-20); (16) The third solvent includes at least one of N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide or water.

8. A negative electrode-free current collector, characterized in that: The negative electrode-free current collector includes a substrate and a coating provided on at least one surface of the substrate, wherein the coating includes the composite material according to any one of claims 1 to 4 and / or includes a composite material prepared by the preparation method according to any one of claims 5 to 7.

9. The negative electrode-free current collector according to claim 8, characterized in that: The coating further includes a fourth binder and a conductive agent; The fourth binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyacrylamide, polyimide or polyamide; the conductive agent includes at least one of conductive carbon black, conductive graphite, carbon nanotubes, carbon fibers or graphene; The mass ratio of the composite material, the fourth binder and the conductive agent is (70-80): (10-20): (10-20); And / or, the substrate comprises a copper-based substrate or a composite substrate, and the composite substrate comprises a substrate formed by a composite of a polymer material and a metal; And / or, the coating has a thickness of 2 μm to 10 μm.

10. A battery, characterized in that: The battery comprises the composite material according to any one of claims 1 to 4, or the composite material prepared by the preparation method according to any one of claims 5 to 7, or the negative electrode-free current collector according to claim 8 or 9.

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