Intermediate structure and preparation method, lithium secondary battery electrode and preparation method

Abstract

The present application relates to the technical field of lithium secondary battery materials, and in particular to an intermediate structure and preparation method, a lithium secondary battery electrode and preparation method. The intermediate structure is used to prepare lithium secondary battery electrodes on one side and / or both sides, and the preparation method of the intermediate structure includes the following steps: composite film materials on one side and / or both sides of a substrate, and form a through hole in the film material, and the central axis of the through hole is perpendicular to the plane of the substrate; wherein the substrate is a conductive substrate, and the film material is a flexible polymer film; grow a conductive material in the through hole to form a one-dimensional columnar structure perpendicular to the substrate in the through hole; remove the film material to obtain the intermediate structure. The film material used in the preparation method of the intermediate structure when synthesizing the template is a flexible polymer film, which not only has the advantage of low manufacturing cost, but also its soft characteristics enable it to be curled and made into a coil to achieve mass production, which is convenient for large-area synthesis of the template.

Description

Technical Field

[0001] The present application relates to the technical field of lithium secondary battery materials, and in particular to an intermediate structure for preparing a lithium secondary battery electrode and a preparation method thereof, a lithium secondary battery electrode and a preparation method thereof. Background Art

[0002] At present, the negative electrode of lithium secondary batteries often uses graphite negative electrode, which has mature technology and stable mass production. However, the lithium insertion capacity of graphite negative electrode is limited, resulting in limited performance improvement of lithium secondary batteries. Studies have shown that when materials such as silicon, germanium or tin are used as the negative electrode of lithium secondary batteries, the lithium insertion capacity is relatively high. For example, when silicon is used as the negative electrode material of lithium secondary batteries, the theoretical maximum lithium insertion capacity reaches 4200mAh / g, which is much higher than the currently commonly used graphite negative electrode. However, silicon materials themselves also have certain disadvantages that limit their application as negative electrodes for lithium secondary batteries, especially the application of alloy negative electrode materials such as silicon materials in the form of one-dimensional structural materials as negative electrodes for lithium secondary batteries, which is currently difficult to achieve mass production.

[0003] The reason why it is difficult to achieve mass production application is mainly due to the limitations of various synthesis methods of one-dimensional structural materials. The main methods for preparing one-dimensional structural materials include etching method, self-growth method and template method. Among them, etching method and self-growth method are difficult to ensure the consistency of one-dimensional structural materials, and it is easy to make the growth direction of one-dimensional structural materials disordered and easy to agglomerate, which is difficult to apply on a large scale. The template method often uses anodized aluminum templates, but due to the manufacturing process and structural characteristics of anodized aluminum, its manufacturing cost is very high and it is difficult to produce on a large scale. It is currently limited to the laboratory research stage and is also difficult to achieve mass production application. Summary of the invention

[0004] The embodiments of the present application disclose an intermediate structure for preparing a lithium secondary battery electrode and a preparation method thereof, a lithium secondary battery electrode and a preparation method thereof, so as to solve the problem that a lithium secondary battery negative electrode with a one-dimensional structure is difficult to mass produce.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing an intermediate structure, wherein the intermediate structure is used to prepare a lithium secondary battery electrode on one side and / or on both sides, and the method for preparing the intermediate structure comprises the following steps:

[0006] Synthetic template: a composite film material is formed on one side and / or both sides of a substrate, and the film material is provided with a through hole, wherein the central axis of the through hole is perpendicular to the plane of the substrate; wherein the substrate is a conductive substrate, and the film material is a flexible polymer film;

[0007] Growth: growing a conductive material in the through hole so that a one-dimensional columnar structure perpendicular to the substrate is formed in the through hole;

[0008] Removing the membrane material: removing the membrane material to obtain the intermediate structure.

[0009] Furthermore, the step of synthesizing the template is: bonding the film material to the substrate through an adhesive layer, and both the film material and the adhesive layer are formed with the through holes.

[0010] Furthermore, the step of synthesizing the template includes:

[0011] Processing the film material through an ion track etching process to obtain the through hole, printing or spraying the adhesive layer on the film material having the through hole, and the adhesive layer exposes at least a portion of the through hole;

[0012] The film material formed with the adhesive layer is bonded to the substrate through the adhesive layer by hot pressing to obtain the template.

[0013] Furthermore, the step of synthesizing the template includes:

[0014] The adhesive layer is coated on the film material without the through hole, and the film material coated with the adhesive layer is processed by an ion track etching process so that the through hole is formed on both the adhesive layer and the film material;

[0015] The template is obtained by bonding the film material with the through holes formed therein to the substrate through heat pressing.

[0016] Furthermore, the step of synthesizing the template includes:

[0017] Coating the adhesive layer on the film material where the through hole is not formed;

[0018] Bonding the film material formed with the adhesive layer to the substrate through the adhesive layer by heat pressing;

[0019] The film material and the adhesive layer bonded to the substrate are processed by an ion track etching process so that the through holes are formed in the film material and the adhesive layer.

[0020] Furthermore, the conditions of the ion track etching process include: bombarding with heavy ions, irradiating for 0.5s to 200s at an irradiation power of 2000KW to 10000KW.

[0021] Furthermore, the conditions of the ion track etching process include: the etching solution is an alkaline solution, and the etching time is 5 minutes to 30 minutes.

[0022] Furthermore, the adhesive layer is made of at least one of PVDF (polyvinylidene difluoride, PVDF for short) or conductive adhesive.

[0023] Furthermore, the step of synthesizing the template includes:

[0024] Processing the film material through an ion track etching process to obtain the through hole;

[0025] Pre-plating a first metal layer on the film material having the through hole formed therein by physical vapor deposition;

[0026] The second metal layer is electroplated on the first metal layer to form the substrate, and the substrate is plated on the film material with the through holes to form the template.

[0027] Furthermore, the through hole has a diameter of 10 nm to 50 μm, and / or,

[0028] The hole density of the through hole is 10 5 Pieces / cm 2 ~10 8 Pieces / cm 2 , and / or,

[0029] The thickness of the film material is 2 μm to 50 μm, and / or,

[0030] The aspect ratio of the thickness of the membrane material to the aperture of the through hole is 1:3 to 3:1.

[0031] Furthermore, the through hole has a diameter of 5 μm to 30 μm, and / or,

[0032] The through-hole density is 400,000 / cm 2 ~2 million / cm 2 , and / or,

[0033] The thickness of the film material is 15 μm to 50 μm, and / or,

[0034] The aspect ratio of the thickness of the membrane material to the aperture of the through hole is 1:1 to 3:1.

[0035] Furthermore, the step of synthesizing the template includes:

[0036] Performing impurity removal pretreatment on the substrate;

[0037] Coating a dry film on one side and / or both sides of the substrate after pretreatment;

[0038] The dry film is exposed, developed, and etched to obtain the template with the through holes formed on the dry film.

[0039] Furthermore, the through hole has a diameter of 5 μm to 30 μm, and / or,

[0040] The thickness of the film material is 5 μm to 30 μm, and / or,

[0041] The aspect ratio of the thickness of the film material to the aperture of the through hole is 1:3 to 3:1, and / or,

[0042] The hole spacing between adjacent through holes is 5 μm to 20 μm.

[0043] Furthermore, in the growing step, the method of growing the conductive material in the through hole adopts one of physical vapor deposition, electroplating, chemical plating or chemical vapor deposition.

[0044] Furthermore, in the step of removing the film material, the method of removing the film material adopts one of mechanical stripping, chemical corrosion or vacuum sintering.

[0045] Furthermore, the diameter of the one-dimensional columnar structure is 5 μm to 30 μm, the height of the one-dimensional columnar structure is 15 μm to 50 μm, and the aspect ratio of the one-dimensional columnar structure is 3:1 to 1:1.

[0046] Furthermore, the one-dimensional columnar structure includes a plurality of regularly distributed columns, and the spacing between adjacent columns is 5 μm to 20 μm; or, the one-dimensional columnar structure includes a plurality of irregularly distributed columns.

[0047] Furthermore, the substrate is at least one of a copper foil substrate, a nickel foil substrate, and a stainless steel substrate.

[0048] Furthermore, the polymer film is at least one of PTFE (polytetrafluoroethylene, Poly tetra fluoroethylene, abbreviated as PTFE) film, PET (polyethylene glycol terephthalate, abbreviated as PET) film, PP (polypropylene, abbreviated as PP) film, PC (polycarbonate, Polycarbonate, abbreviated as PC) film or PI (polyimide, Polyimide, abbreviated as PC) film.

[0049] Furthermore, the conductive material is at least one of copper, nickel or carbon.

[0050] In the second aspect, an embodiment of the present application provides an intermediate structure, which is used for preparing lithium secondary battery electrodes on one side and / or both sides. The intermediate structure is prepared by the preparation method described in the first aspect, and the intermediate structure includes the substrate and the one-dimensional columnar structure grown vertically on the substrate.

[0051] Furthermore, the diameter of the one-dimensional columnar structure is 5 μm to 30 μm, the height of the one-dimensional columnar structure is 15 μm to 50 μm, and the aspect ratio of the one-dimensional columnar structure is 3:1 to 1:1.

[0052] Furthermore, the one-dimensional columnar structure includes a plurality of regularly distributed columns, and the spacing between adjacent columns is 5 μm to 20 μm, or the one-dimensional columnar structure includes a plurality of irregularly distributed columns.

[0053] In a third aspect, an embodiment of the present application provides a method for preparing a lithium secondary battery electrode, the method for preparing a lithium secondary battery electrode comprising the following steps:

[0054] The outer surface of the one-dimensional columnar structure of the intermediate structure prepared by the preparation method according to the first aspect is coated with an electrode active material to form an active material layer;

[0055] The outer surface of the active material layer is coated with a protective layer to obtain the lithium secondary battery electrode.

[0056] Optionally, the electrode active material is at least one of silicon, germanium or tin.

[0057] Optionally, the material of the protective layer is carbon or metal oxide.

[0058] Furthermore, the method of coating the electrode active material includes chemical vapor deposition, physical vapor deposition or electroplating.

[0059] Furthermore, the method of coating the protective layer includes hydrothermal method, physical vapor deposition or chemical vapor deposition.

[0060] In a fourth aspect, an embodiment of the present application provides a lithium secondary battery electrode, wherein the lithium secondary battery electrode is manufactured by the method for preparing a lithium secondary battery electrode according to the third aspect, and the lithium secondary battery electrode comprises:

[0061] A substrate, wherein the substrate is a conductive substrate;

[0062] A one-dimensional columnar structure, which is grown on the substrate perpendicular to the plane where the substrate is located, and the one-dimensional columnar structure is a conductive one-dimensional columnar structure;

[0063] An active material layer is located on the substrate perpendicular to the plane of the substrate and covers the outer surface of the one-dimensional columnar structure;

[0064] The protective layer is located on the substrate perpendicular to the plane where the substrate is located and covers the outer surface of the active material layer.

[0065] Compared with the related art, the embodiments of the present application have the following beneficial effects:

[0066] The intermediate structure provided in the embodiment of the present application can, on the one hand, use the substrate to provide good mechanical support for the one-dimensional columnar structure. On the other hand, the one-dimensional columnar structure perpendicular to the substrate can serve as a support for the subsequent growth of electrode active materials and play a rigid support role. Moreover, due to its conductive ability, it is beneficial to improve the conductivity between the subsequently grown electrode active materials and the conductive substrate, thereby improving the performance of lithium secondary battery electrodes. The film material used in the preparation method of the intermediate structure when synthesizing the template is a flexible polymer film, which not only has the advantage of low manufacturing cost, but also its soft properties enable it to be curled and made into a coil to achieve mass production, which is convenient for large-area synthesis of the template. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0068] Figure 1 is a structural schematic diagram of the intermediate structure of the first embodiment;

[0069] Figure 2 is a scanning electron microscope image of the intermediate structure of Example 1;

[0070] Figure 3 is a flow chart of the preparation process of the intermediate structure of Example 1;

[0071] Figure 4 is a scanning electron microscope image of the template synthesized during the preparation of the intermediate structure of Example 1;

[0072] Figure 5 is a flow chart of the preparation process of the lithium secondary battery electrode of Example 1;

[0073] Figure 6 is a schematic structural diagram of the intermediate structure of Embodiment 8;

[0074] Figure 7 It is a graph showing the cycle performance test results of button batteries assembled in Example 1 and the comparative example. DETAILED DESCRIPTION

[0075] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0076] In the present invention, the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like are based on the directions or positional relationships shown in the drawings. These terms are mainly used to better describe the present invention and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific direction, or to be constructed and operated in a specific direction.

[0077] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those skilled in the art, the specific meanings of these terms in the present invention can be understood according to specific circumstances.

[0078] In addition, the terms "installed", "set", "provided with", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0079] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.

[0080] The technical solution of the present application will be further described below in conjunction with specific embodiments and drawings.

[0081] Since silicon, germanium or tin and other materials have a high lithium insertion capacity when used as negative electrode materials for lithium secondary batteries, which is much higher than the graphite negative electrode currently used on the market, these materials are lithium secondary battery negative electrode materials with development prospects. However, these materials themselves also have certain defects. Taking silicon as an example, silicon's own electrical conductivity is worse than that of graphite, and its rate performance is poor. In addition, silicon expands too much in volume during the cycle process, which can easily lead to the breakage and differentiation of negative electrode material particles and damage the solid electrolyte interface membrane, resulting in rapid capacity decay, which limits the promotion and application of silicon as a negative electrode material.

[0082] Although it is possible to solve the above problems by making alloy-type negative electrode materials such as silicon into a one-dimensional structure, the limitations of the synthesis method of one-dimensional structural materials make it difficult to truly mass-produce lithium secondary battery negative electrode materials with this structure, and related technologies are only in the laboratory research stage.

[0083] Specifically, the preparation methods for synthesizing one-dimensional structural materials in the relevant technology mainly include etching method, self-growth method and template method. Among them, etching method and self-growth method are difficult to ensure the consistency of one-dimensional structural materials, and the growth direction of one-dimensional structural materials is easy to be disordered and easy to agglomerate, which is difficult to apply on a large scale. The most commonly used template method is anodized aluminum template, which is usually made by anodizing high-purity aluminum sheets in an acidic solution. Due to its manufacturing process and the structural characteristics of the anodized aluminum template itself, it has the following limitations: First, the manufacturing cost is high, and second, after in-depth research and actual investigation, the applicant learned that it is difficult to manufacture large-area anodized aluminum templates in the industrial production process. At present, the maximum size of anodized aluminum templates is only at the unit level of centimeters × centimeters. These two points make the research on synthesizing one-dimensional structural materials using anodized aluminum templates mainly concentrated in the laboratory research stage of universities and research institutes, but the relevant process technology is difficult to apply in industrial mass production. This makes it difficult to synthesize one-dimensional structural materials in large quantities using the template method, and to apply one-dimensional structural materials in lithium secondary battery electrode materials, which ultimately limits the optimization and upgrading of lithium secondary battery electrode materials in actual industrial production.

[0084] Based on the analysis of the above problems, the embodiments of the present application provide an intermediate structure and preparation method for preparing a lithium secondary battery electrode, a lithium secondary battery electrode and a preparation method. By optimizing the preparation method of the intermediate structure, its mass production use in actual industrial production is realized, and then the mass production manufacturing of lithium secondary electrode materials in actual industrial production is realized, and finally a lithium secondary battery electrode with improved electrode performance and mass production is obtained.

[0085] In a first aspect, an embodiment of the present application provides an intermediate structure for preparing a lithium secondary battery electrode on one side and / or on both sides, the intermediate structure comprising a substrate and a one-dimensional columnar structure vertically grown on the substrate. The preparation method of the intermediate structure comprises the following steps:

[0086] Synthetic template: composite film material on one side and / or both sides of a substrate, and form through holes in the film material, the central axis of the through hole is perpendicular to the plane of the substrate; wherein the substrate is a conductive substrate, and the film material is a flexible polymer film;

[0087] Growth: growing a conductive material in the through hole to form a one-dimensional columnar structure perpendicular to the substrate in the through hole;

[0088] Removing membrane material: Remove the membrane material of the template to obtain the intermediate structure.

[0089] The substrate is at least one of a copper foil substrate, a nickel foil substrate, and a stainless steel substrate, and preferably the substrate is a copper foil substrate or a nickel foil substrate. The polymer film is at least one of a PTFE film, a PET film, a PP film, a PC film, or a PI film, and preferably the polymer film is a PET film. The conductive material is at least one of copper, nickel, or carbon.

[0090] Among them, the intermediate structure is used to prepare lithium secondary battery electrodes on one side and / or on both sides, which means that in the process of preparing the intermediate structure, when synthesizing the template, a film material with through holes can be compounded on one surface of the substrate, and a single side of the template can be used to obtain a one-dimensional columnar structure connected on the single side of the substrate, thereby preparing a single-sided lithium secondary battery electrode; or a film material with through holes can be compounded on two opposite surfaces of the substrate, and both sides of the template can be used to obtain a one-dimensional columnar structure connected on both sides of the substrate, thereby preparing a double-sided lithium secondary battery electrode.

[0091] The embodiment of the present application provides an intermediate structure and a preparation method thereof used in the scenario of preparing lithium secondary battery electrodes on one side and / or both sides. A film material with through holes is composited on one side and / or both sides of a conductive substrate, and one-dimensional columnar structure materials such as nanowires or micron wires are grown using the through holes, thereby obtaining an intermediate structure in which a substrate with conductive properties is vertically connected to a one-dimensional columnar structure with conductive properties.

[0092] From the structural perspective of the intermediate structure, on the one hand, the intermediate structure can utilize the characteristics of the substrate being a copper foil substrate, a nickel foil substrate or a stainless steel substrate with a certain strength, and play a good mechanical support role for the one-dimensional columnar structure material in the subsequent preparation of lithium secondary battery electrodes. On the other hand, the one-dimensional columnar structure perpendicular to the substrate can serve as a support for the subsequent growth of electrode active materials and play a rigid support role. Moreover, because of its conductive ability, it is beneficial to improve the conductivity between the subsequently grown electrode active materials and the conductive substrate, thereby improving the performance of lithium secondary battery electrodes.

[0093] From the process perspective of the intermediate structure, the preparation method of the intermediate structure is to first synthesize the template, and then synthesize the intermediate structure based on the template. Among them, the film material used for the synthetic template is a flexible polymer film, which not only has the advantage of low manufacturing cost, but also its soft characteristics enable it to be curled and made into a coil to achieve mass production, which is convenient for large-area synthesis of the template. For example, in a feasible production scenario, a large-area substrate is located on a conveyor belt in the production process, and a commercially purchased film material (i.e., a flexible polymer film) is installed on a roller in the form of a coil. By compounding the film material on the substrate and forming a through hole in the film material, a large-area template is obtained. Among them, a large area refers to at least a specification size of decimeter × decimeter or more, and can also be a specification size of meter × meter. The larger the area, the more conducive it is to reducing the cost of mass production. On the basis that the production and manufacturing of the above-mentioned template can be mass-produced, the process of growing a conductive material in the through hole of the template and then removing the film material can also be mass-produced.

[0094] It can be seen that compared with the conventional one-dimensional material made by using anodized aluminum template, the method of preparing the intermediate structure by using a flexible polymer film as a template and the intermediate structure in the embodiment of the present application have the following obvious advantages at least in terms of industrial mass production:

[0095] First, the optimization of material properties and process methods makes the template easier to realize through industrial mass production. On the one hand, as mentioned above, the embodiment of the present application uses a flexible polymer film as the membrane material. Its flexibility and rollability enable the production and manufacturing of the template itself to achieve large-scale industrial mass production, which is difficult for anodized aluminum templates to do. It is precisely because the production and manufacturing of the template itself can achieve industrial mass production that the process of using the template to make the intermediate structure can achieve industrial mass production. On the other hand, the embodiment of the present application directly uses a conductive material as a conductive substrate, which has the advantage of a simplified production process compared to the related art of using a non-conductive substrate such as a glass substrate and then sputtering a metal layer to achieve the conductive function.

[0096] Secondly, the product performance is optimized, so that the subsequent production of lithium secondary battery electrodes has a better cost-effectiveness and is more suitable for mass production. On the one hand, the embodiment of the present application can achieve a firm fit between the substrate and the film material by gluing, which can ensure the stability of the subsequent pore-making process operation, and will not affect the pore-making effect or the stability of the template structure because the substrate and the film material are easily separated, thereby ensuring the performance stability of the intermediate structure of the lithium secondary battery electrode, including ensuring the stability of the production process and the stability of the structural connection and electrical connection between the one-dimensional columnar structure and the conductive substrate. On the other hand, the present application performs a perforation treatment on the glue layer to ensure that the through hole of the film material is connected to the conductive substrate, thereby ensuring the direct contact between the one-dimensional columnar structure of the subsequent lithium secondary battery intermediate structure and the conductive substrate, and the substrate directly uses a conductive substrate, so the overall conductivity is better. However, when using an anodized aluminum template to make a one-dimensional material, even if it is glued, it will not make holes in the glue layer, so the generated one-dimensional nanomaterial cannot achieve true direct contact with the substrate, and the conductivity of its overall structure is relatively low.

[0097] Moreover, according to the microstructure parameters of the through holes in the template of the embodiment of the present application (such as pore size, film thickness, aspect ratio, pore density, etc.), and the scanning electron microscope image of the template obtained by the specific embodiment of the text application, it can be known that the one-dimensional columnar structure in the intermediate structure prepared by the template of the embodiment of the present application is closer to a short and thick column at the micron level. Such a microstructure morphology can enable the one-dimensional columnar structure to maintain good verticality relative to the conductive substrate, and secondly, a certain interval can be formed between the columns. However, the one-dimensional nanomaterial made by the anodized aluminum template is more likely to grow into a thinner diameter and higher height slender microstructure. This structure has problems such as the ends of adjacent one-dimensional nanomaterials are easy to agglomerate and the overall verticality relative to the substrate is poor, which leads to the unsuitability of such one-dimensional nanomaterials as intermediate structures for preparing lithium secondary battery electrodes.

[0098] The steps of synthesizing the template in the method for preparing the intermediate structure are introduced below.

[0099] In an optional embodiment, the step of synthesizing the template includes: bonding the film material to the substrate via an adhesive layer, and both the film material and the adhesive layer are formed with through holes.

[0100] The adhesive layer is made of at least one of PVDF and conductive adhesive.

[0101] By setting a glue layer on the film material, the glue layer can be used to achieve a reliable connection between the film material and the substrate, and it is also convenient to realize mass production of the template manufacturing process. More importantly, the embodiment of the present application also performs special treatment on the glue layer, and a through hole corresponding to the film material is also formed on the glue layer, that is, the glue layer also forms a through hole at the position corresponding to the through hole formed in the film material. In other words, the glue layer can achieve a reliable connection between the film material and the substrate, and will not block the connectivity between the through hole and the substrate. In this way, when one-dimensional columnar structure materials such as nanowires or micron wires are subsequently grown in the through hole, these one-dimensional columnar structure materials can have good contact with the substrate with conductive properties, and can ensure good electrical contact between the one-dimensional columnar structure material and the conductive substrate while mass production. In addition, the applicant found that in the related art, special pore-making treatment is rarely performed on the glue layer. It is speculated that, on the one hand, the related art does not pay attention to the connectivity between the through holes of the template and the substrate. Even if pores are formed, the carbon layer coated on the substrate is formed by sintering, etc., and its porosity is also low. The pore-making effect is not obvious, which will affect the difficulty of subsequent electroplating or deposition of conductive materials in the holes. More importantly, this is different from the idea of ​​directly making holes in the glue layer in the present application; on the other hand, if the related art wants to remove the film material and the glue layer without making holes in the glue layer, leaving only the substrate and the grown one-dimensional material, a more complicated operation is required - first remove the film material, then remove the glue layer, but the process of removing the glue layer will affect the connection stability between the grown one-dimensional material and the substrate, resulting in the one-dimensional material scattering from the substrate or functional detachment, and even partial collapse and agglomeration of the one-dimensional material. These phenomena are not conducive to the subsequent preparation of lithium secondary battery electrode performance improvement.

[0102] It should be noted that the corresponding through holes formed on the adhesive layer can either completely expose the through holes of the film material, that is, the adhesive layer does not cover the through holes of the film layer at all, or partially expose the through holes of the film material, that is, the adhesive layer covers part of the through holes of the film layer and exposes the other part. As long as there is exposed space for the through holes, the connectivity between the through holes and the conductive substrate is ensured, thereby ensuring good electrical contact between the one-dimensional columnar structure material and the conductive substrate when the one-dimensional columnar structure material is subsequently synthesized.

[0103] In addition, the applicant would like to emphasize that the anodized aluminum template is limited by its own synthesis process. It is usually first to process the columnar aluminum oxide into a hollow tubular aluminum oxide, and then form a substrate on multiple hollow tubular aluminum oxides to form an anodized aluminum template. This makes the anodized aluminum template only able to synthesize lithium secondary battery electrodes on a single side of the substrate, but not on both sides of the substrate. However, the embodiment of the present application connects the membrane material and the substrate by means of adhesive bonding, which can realize the composite film material with through holes on a single side of the substrate, and then prepare lithium secondary battery electrodes on a single side of the template, and can also realize the composite film material with through holes on both sides of the substrate, and then prepare lithium secondary battery electrodes on both sides of the template. While realizing mass production synthesis of templates and lithium secondary battery electrodes, lithium secondary battery electrodes are prepared on both sides of the template, which is difficult to achieve in the prior art and is also one of the important inventive points of the embodiment of the present application.

[0104] The following introduces three specific implementation methods of bonding the film material to the substrate through the adhesive layer.

[0105] In the first embodiment, the steps of synthesizing the template include: treating the membrane material through an ion track etching process to obtain through holes, printing or spraying a glue layer on the membrane material with the through holes, and the glue layer exposes at least part of the through holes; and hot-pressing the membrane material with the glue layer to the substrate through the glue layer to obtain a template.

[0106] After the membrane material is processed by ion track etching process to obtain through holes, a layer of adhesive layer is screen printed or sprayed on the membrane material with through holes, and the adhesive layer is subjected to special hole-making treatment to ensure that the adhesive layer can partially or completely expose the through holes, and ensure that the adhesive layer does not completely cover the through holes, so as to avoid isolation between the through holes and the substrate. Then, the membrane material with through holes is hot-pressed and bonded to the substrate through the adhesive layer with holes, so as to achieve reliable connection of the membrane material on the substrate, and the through holes between the membrane material and the substrate are not completely covered by the adhesive layer, so as to ensure connectivity between the through holes and the substrate.

[0107] Preferably, the glue layer does not completely cover the through hole, so that there will be no excess residual glue between the through hole and the substrate, which can avoid affecting the electrical contact between the subsequently synthesized one-dimensional columnar structure material and the substrate due to the residual glue, including causing the impedance of the overall structure of the one-dimensional columnar structure material and the substrate to increase, thereby affecting the performance of the subsequent lithium secondary battery electrode material.

[0108] In the second embodiment, the steps of synthesizing the template include: coating a glue layer on a membrane material without through holes, treating the membrane material coated with the glue layer by an ion track etching process so that both the glue layer and the membrane material are formed with through holes; and bonding the membrane material with through holes to a substrate by hot pressing to obtain a template.

[0109] In this embodiment, the adhesive layer is first coated on the film material, so that the adhesive layer is evenly and densely coated on the film material, ensuring that the subsequent hot pressing bonding operation can make the connection between the film material and the substrate more reliable. Then, the film material and the adhesive layer are subjected to ion track etching process to form holes on both, so as to ensure the connectivity between the through hole and the substrate, thereby ensuring that the one-dimensional columnar structure material subsequently made by the template has good electrical contact with the substrate.

[0110] In a third embodiment, the step of synthesizing the template comprises:

[0111] Coating a glue layer on the film material without through holes;

[0112] Bonding the film material with the adhesive layer to the substrate through the adhesive layer by hot pressing;

[0113] The film material and the adhesive layer bonded to the substrate are treated by ion track etching to form through holes in the film material and the adhesive layer.

[0114] This implementation method is to first coat a glue layer on the film material and hot press it to improve the connection reliability between the film material and the substrate, and then make holes in the already composited template. Specifically, holes are made in the film material and the glue layer to form through holes on both, ensuring the connectivity between the through holes and the substrate, and then ensuring that the one-dimensional columnar structure material subsequently made by the template has good electrical contact with the substrate.

[0115] In the above three implementations, when making holes in membrane materials or membrane materials and adhesive layers, the ion track etching process is mainly used for hole making. The process itself is a conventional process, but some key parameters in the process will have a key impact on the important parameters of the through holes such as the pore size and pore arrangement density formed. These influences will play an important role in the subsequent preparation of one-dimensional columnar structure materials and lithium secondary battery electrode preparation in the template using the through holes. Therefore, the embodiments of the present application have conducted a lot of research on the key parameters of the ion track etching process.

[0116] In the embodiment of the present application, the conditions of the ion track etching process include: bombardment with heavy ions, irradiation for 0.5s to 200s at an irradiation power of 2000KW to 10000KW; in addition, the etching solution used in the ion track etching process is an alkaline solution, for example, a sodium hydroxide etching solution with a mass fraction of 10% to 50%, etching the membrane material or the membrane material and the adhesive layer for 5min to 30min. In addition, for etching the adhesive layer, different etching solutions can also be selected according to the type of adhesive layer used. When the adhesive layer uses PVDF, the etching solution can be selected as NMP (i.e., N-methylpyrrolidone) etching solution.

[0117] Within the above-mentioned irradiation power and irradiation time range, it is beneficial to obtain through holes with a pore density and pore diameter that are suitable for making lithium secondary battery electrodes. In addition, within the above-mentioned etching solution concentration and etching time range, it is beneficial to control the appropriate through hole etching depth, and then control the parameters to affect the height of the subsequent one-dimensional columnar structure material.

[0118] Wherein, the irradiation power is 2000KW-10000KW including any value within the power range, for example, the irradiation power is 2000KW, 3000KW, 5000KW, 6000KW, 8000KW or 10000KW. The irradiation time is 0.5s-200s including any value within the time range, for example, the irradiation time is 0.5s, 1s, 5s, 10s, 20s, 50s, 60s, 80s, 100s, 120s, 150s, 180s or 200s.

[0119] In another optional embodiment, the step of synthesizing the template includes:

[0120] Processing the film material through an ion track etching process to obtain a through hole;

[0121] Pre-plating a first metal layer on the film material with through holes formed thereon by physical vapor deposition;

[0122] The second metal layer is electroplated on the first metal layer to form a substrate, and the substrate is plated on the film material with through holes to form a template.

[0123] In addition to ensuring the connection reliability between the film material and the substrate and the connectivity between the through hole and the substrate by setting a glue layer and performing a special hole-making treatment on the glue layer, thereby ensuring the good electrical contact relationship between the one-dimensional columnar structure material and the substrate generated in the through hole, the embodiment of the present application can also form holes by first performing an ion track etching treatment on the film material, and then forming a substrate on the film material with the through hole formed. Specifically, the embodiment of the present application first pre-plates a thinner first metal layer by physical vapor deposition to create a good electron channel at the through hole position of the film material as much as possible. This process does not require the metal layer to cover the film layer densely. Then, the second metal layer is further electroplated on the thinner first metal layer, and the thickness of the overall metal layer is increased by the electroplating process, thereby improving the structural strength of the substrate. It can be understood that the first metal layer and the second metal layer can be the same or different types of metals, preferably the same type of metal, for example, the first metal layer and the second metal layer are both copper layers.

[0124] It should be noted that if the first metal layer is pre-plated by physical vapor deposition directly on the film material with through holes, and the second metal layer is not electroplated to be thickened, it is impossible to form a template composed of the substrate and the film material, and it is impossible to obtain a specific intermediate structure and lithium secondary battery electrode in the subsequent production process. This is because if only the first metal layer is pre-plated by physical vapor deposition on the film material with through holes, it can only obtain a metal coating on the surface of the film material, but cannot cover the through hole position, that is, after pre-plating, a film material with through holes and a first metal layer is obtained on the surface. This thin metal layer (thickness is about <1μm) itself has the characteristics of looseness, porosity and non-denseness. First, it can provide limited electronic channels, and second, it cannot play an effective structural support role. If one-dimensional nanowires are directly made on this basis, the conductive material is electroplated into the through hole and the film material is removed, but only one-dimensional nanowires or small-area clusters of wires can be obtained, and a one-dimensional columnar structure vertically grown on a conductive substrate cannot be obtained.

[0125] However, the embodiment of the present application is not to obtain one-dimensional nanowires, but to use a conductive substrate with a vertically grown one-dimensional columnar structure as an intermediate structure to produce a lithium secondary battery electrode structure different from the conventional structure. Therefore, after pre-plating the first metal layer, the embodiment of the present application electroplates a thickened second metal layer on the basis of the first metal layer. The purpose is to: by pre-plating the first metal layer, the insulating film material has a certain electron channel, providing good electrical conditions for the electroplated thickened second metal layer, and the adhesion of a thicker and denser second metal layer can be achieved through electroplating, and the second metal layer is mainly used as a conductive substrate that can play a good conductive role and a good structural support role.

[0126] By using the above template preparation method, a substrate with the following characteristics can be obtained, in which the aperture of the through hole is 10nm to 50μm, the thickness of the film material is 2μm to 50μm, and the hole density of the through hole is 10 5 Pieces / cm 2 ~10 8 Pieces / cm 2 The aspect ratio of the thickness of the membrane material to the aperture of the through hole is 1:3 to 3:1. Preferably, the aperture of the through hole is 5 μm to 30 μm, the thickness of the membrane material is 15 μm to 50 μm, and the hole density of the through hole is 400,000 / cm 2 ~2 million / cm 2 The aspect ratio of the thickness of the film material to the aperture of the through hole is 1:1 to 3:1. The template within this structural parameter range has a more optimized performance of the lithium secondary battery electrode subsequently prepared.

[0127] The pore size of the through hole is 10nm to 50μm, including any value within the pore size range, for example, the pore size of the through hole is 10nm, 20nm, 50nm, 100nm, 200nm, 500nm, 1μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm or 50μm. The thickness of the membrane material is 2μm to 50μm, including any value within the thickness range, for example, the thickness of the membrane material is 2μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm or 50μm. The pore density of the through hole is 10 5 Pieces / cm 2 ~10 8 Pieces / cm 2 Include any point value within this density range, for example, the hole density of the through hole is 10 5 Pieces / cm 2 , 10 6 Pieces / cm 2 , 10 7 Pieces / cm 2 or 10 8 Pieces / cm 2 . The aspect ratio of the thickness of the membrane material to the aperture of the through hole is 1:3 to 3:1, including any point value within the ratio range, for example, the aspect ratio of the thickness of the membrane material to the aperture of the through hole is 1:3, 1:2, 1:1, 2:1 or 3:1. It should be noted that the aspect ratio in the embodiments of the present application refers to the ratio of the thickness of the membrane material to the aperture of the through hole, that is, the "length" refers to the thickness of the membrane material, and the "diameter" refers to the aperture of the through hole, which is also the aperture of the through hole.

[0128] According to the structural parameters of the formed through-holes, the embodiments of the present application can obtain a micron-level through-hole structure on a flexible polymer film material through an ion track etching process, which can meet the requirements for the subsequent production of one-dimensional columnar structure materials and lithium secondary battery electrodes, so that the lithium secondary battery electrodes have more performance advantages than ordinary lithium secondary battery electrodes because they can form a one-dimensional micron structure.

[0129] Among them, the aperture of the through hole, the thickness of the film material, and the aspect ratio range determine the diameter, height, and aspect ratio of the one-dimensional columnar structure material subsequently grown in the through hole, which will further affect the relevant performance of the lithium secondary battery electrode. Although from the perspective of preparing lithium secondary battery electrodes and their application in lithium batteries, the larger the aspect ratio, the better, the applicant has found that when the aspect ratio exceeds the ratio range of 1:3 to 3:1, the thickness of the film material needs to be made thicker and / or the through hole needs to be etched into a smaller aperture, which not only increases the difficulty of etching, but also makes it difficult to ensure the rigidity of the one-dimensional columnar structure material subsequently grown in the through hole, and it is easy to break. Therefore, the present application controls the key parameters of the ion track etching process, including the optimization control of a series of process parameters such as irradiation power, irradiation time, etching solution concentration and etching time, to control the thickness of the film material and the aspect ratio of the through hole within 1:3 to 3:1, preferably within the range of 1:1 to 3:1, which is beneficial to reduce the difficulty of etching, ensure the rigidity of the subsequently grown one-dimensional columnar structure material, and also facilitate the performance optimization of the one-dimensional columnar structure material for the further prepared lithium secondary battery electrode.

[0130] In yet another optional embodiment, the step of synthesizing the template comprises:

[0131] Performing pre-treatment of the substrate to remove impurities;

[0132] Applying a dry film on one side and / or both sides of a pre-treated substrate;

[0133] The dry film is exposed, developed, and etched to obtain a template with through holes formed on the dry film.

[0134] In addition to using a specially treated adhesive layer to realize the composite of the film material and the substrate or using a composite method of directly forming a substrate on the film material of the through hole, the embodiment of the present application can also realize the composite of the two by etching a dry film on the substrate. When performing dry film etching in the related art, an insulating substrate is usually used. It is necessary to first form a layer of conductive film on the insulating substrate, and then apply a dry film and photoresist for etching. Since the embodiment of the present application is to be applied to the production of lithium secondary battery electrodes, the substrate directly uses a conductive substrate, and there is no need to form a conductive film additionally. The process is simpler and more conducive to reducing the mass production cost of the template and the subsequent preparation of lithium secondary battery electrodes.

[0135] By the above-mentioned template preparation method, a substrate with the following characteristics can be obtained, in which the pore diameter of the through hole is 5μm~30μm, the thickness of the film material is 5μm~30μm, the aspect ratio of the thickness of the film material to the through hole is 1:3~3:1, and the spacing between adjacent through holes is 5μm~20μm.

[0136] Among them, the pore size of the through hole is 5μm to 30μm, including any point value within the pore size range, for example, the pore size of the through hole is 5μm, 10μm, 15μm, 20μm, 25μm or 30μm. The thickness of the membrane material is 5μm to 30μm, including any point value within the thickness range, for example, the thickness of the membrane material is 5μm, 10μm, 15μm, 20μm, 25μm or 30μm. The aspect ratio of the thickness of the membrane material to the pore size of the through hole is 1:3 to 3:1, including any point value within the ratio range, for example, the aspect ratio of the thickness of the membrane material to the pore size of the through hole is 1:3, 1:2, 1:1, 2:1 or 3:1. It should be noted that the aspect ratio in the embodiment of the present application refers to the ratio of the thickness of the membrane material to the pore size of the through hole, that is, the "length" refers to the thickness of the membrane material, and the "diameter" refers to the pore size of the through hole, which is also the pore size of the through hole. In addition, the hole spacing between adjacent through holes is 5 μm to 20 μm, including any point value within the hole spacing range, for example, the hole spacing between adjacent through holes is 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm or 20 μm.

[0137] According to the structural parameters of the formed through-holes, the embodiments of the present application can obtain a micron-level through-hole structure on a flexible polymer film material through an ion track etching process, which can meet the requirements for the subsequent production of one-dimensional columnar structure materials and lithium secondary battery electrodes, so that the lithium secondary battery electrodes have more performance advantages than ordinary lithium secondary battery electrodes because they can form a one-dimensional micron structure.

[0138] Among them, the aperture of the through hole, the thickness of the film material, and the aspect ratio range determine the diameter, height, and aspect ratio of the one-dimensional columnar structure material subsequently grown in the through hole, which will further affect the relevant performance of the lithium secondary battery electrode. Although from the perspective of preparing lithium secondary battery electrodes and their applications in lithium secondary batteries, the larger the aspect ratio, the better, the applicant has found that when the aspect ratio exceeds the ratio range of 1:3 to 3:1, the thickness of the film material needs to be made thicker and / or the through hole needs to be etched into a smaller aperture, which not only increases the difficulty of etching, but also makes it difficult to ensure the rigidity of the one-dimensional columnar structure material subsequently grown in the through hole, and it is easy to break. Therefore, the present application controls the key parameters of the ion track etching process, including the optimization control of a series of process parameters such as irradiation power, irradiation time, etching solution concentration and etching time, to control the thickness of the film material and the aspect ratio of the through hole within the range of 1:3 to 3:1, preferably within the range of 1:1 to 3:1, which is beneficial to reduce the difficulty of etching, ensure the rigidity of the subsequently grown one-dimensional columnar structure material, and also facilitate the performance optimization of the one-dimensional columnar structure material for the further prepared lithium secondary battery electrode.

[0139] In addition, when the hole spacing between adjacent through holes is controlled within the above range, it can provide a favorable deposition space for the subsequent coating of active materials in the lithium secondary battery electrode. When the hole spacing is less than 5μm, the number of through holes is too large and the distribution is too dense. Although it can provide a larger active area for the attachment of electrode active materials, it will also cause the reserved gap between the columnar one-dimensional columnar structure materials to be too small, which is not conducive to further deposition of electrode active materials on the peripheral walls of these one-dimensional columnar structure materials. On the contrary, when the hole spacing is greater than 20μm, the density of the through holes is low, and the attachment area that can be provided for the electrode active material is limited, which affects the subsequent loading amount of the electrode active material, and further affects the capacity and other performance of the lithium secondary battery electrode.

[0140] The steps of growth and film material removal in the preparation method of the intermediate structure are introduced below.

[0141] Optionally, in the step of growing, the method of growing the conductive material in the through hole adopts one of physical vapor deposition, electroplating, chemical plating or chemical vapor deposition. Optionally, in the step of removing the film material, the method of removing the film material adopts one of mechanical stripping, chemical etching or vacuum sintering.

[0142] When the conductive material is a metal such as copper or nickel, copper or nickel can be deposited in the through-holes of the template by physical vapor deposition (such as magnetron sputtering or evaporation), electroplating or chemical plating, and the resulting composite structure can be, for example, a copper foil substrate-copper column one-dimensional columnar structure, a copper foil substrate-nickel column one-dimensional columnar structure, a nickel foil substrate-nickel column one-dimensional columnar structure, a nickel foil substrate-copper column one-dimensional columnar structure, and a copper foil substrate-carbon-based one-dimensional columnar structure. When the substrate and the film material have good temperature resistance, a chemical vapor deposition process can also be selected to grow a one-dimensional columnar structure.

[0143] The intermediate structure obtained by the above-mentioned preparation method has structural parameters similar to those of the through-holes because the one-dimensional columnar structure is grown in the through-holes of the template. The diameter of the one-dimensional columnar structure is 5nm to 30μm, the height of the one-dimensional columnar structure is 15μm to 50μm, and the height-to-diameter ratio of the one-dimensional columnar structure is 3:1 to 1:1. When the structural parameters of the one-dimensional columnar structure are controlled within the above-mentioned range, the difficulty of the mass production process and the performance of the lithium secondary battery electrode finally prepared can be well balanced, and a lithium secondary battery electrode with stable structural parameters and optimized performance can be prepared by a relatively stable and easy-to-implement mass production process.

[0144] Among them, the diameter of the one-dimensional columnar structure is 5μm to 30μm, including any point value within the diameter range, for example, the diameter of the one-dimensional columnar structure is 5μm, 10μm, 15μm, 20μm, 25μm or 30μm. The height of the one-dimensional columnar structure is 15μm to 50μm, including any point value within the height range, for example, the height of the one-dimensional columnar structure is 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm or 50μm. The height-to-diameter ratio of the one-dimensional columnar structure is 3:1 to 1:1, including any point value within the height-to-diameter ratio range, for example, the height-to-diameter ratio of the one-dimensional columnar structure is 3:1, 2.5:1, 2:1, 1.5:1 or 1:1.

[0145] Furthermore, the distribution of the one-dimensional columnar structure on the substrate can be regular distribution or irregular distribution according to the template manufacturing method. In the art, both the regular distribution and the irregular distribution can be referred to as a columnar array structure. When the one-dimensional columnar structure is regularly distributed on the substrate, the one-dimensional columnar structure includes a plurality of regularly distributed columns, and the spacing between adjacent columns is 5 μm to 20 μm.

[0146] The spacing between adjacent columns is 5 μm to 20 μm, including any point value within the spacing range, for example, the spacing between adjacent columns is 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm or 20 μm.

[0147] The applicant found that when the spacing between adjacent columns is greater than 20 μm, the number of one-dimensional columnar structures per unit area on the substrate is relatively small, the space utilization rate is low, and the surface area available for subsequent deposition of electrode active materials is small; when the spacing between adjacent columns is less than 5 μm, the spacing between adjacent columns is too small, which will increase the difficulty of subsequent deposition of active materials on the side walls of the columns and / or further coating with other materials, and will result in insufficient space reserved for radial expansion of the electrode active materials during the charge and discharge cycle, which is not conducive to the performance optimization of lithium secondary batteries.

[0148] In a second aspect, the present application also provides a lithium secondary battery electrode, specifically a lithium secondary battery negative electrode, the lithium secondary battery electrode comprising:

[0149] A substrate, the substrate is a conductive substrate;

[0150] A one-dimensional columnar structure is grown on the substrate perpendicular to the plane where the substrate is located, and the one-dimensional columnar structure is a conductive one-dimensional columnar structure;

[0151] The active material layer is located on the substrate perpendicular to the plane of the substrate and covers the outer surface of the one-dimensional columnar structure;

[0152] The protective layer is located on the substrate perpendicular to the plane where the substrate is located, and covers the outer surface of the active material layer.

[0153] The method for manufacturing the lithium secondary battery electrode comprises the following steps:

[0154] The outer surface of the one-dimensional columnar structure of the intermediate structure prepared in the first aspect is coated with an electrode active material to form an active material layer;

[0155] The outer surface of the active material layer is coated with a protective layer to obtain a lithium secondary battery electrode.

[0156] Optionally, the electrode active material is at least one of silicon, germanium or tin. Optionally, the material of the protective layer is carbon or a metal oxide. Optionally, the method of coating the electrode active material comprises chemical vapor deposition, physical vapor deposition or electroplating. Optionally, the method of coating the protective layer comprises hydrothermal method, physical vapor deposition or chemical vapor deposition.

[0157] The above-mentioned lithium secondary battery electrode structure is a coaxial composite one-dimensional columnar structure electrode material. The substrate serves as the current collector of the lithium secondary battery electrode. A one-dimensional columnar structure perpendicular to the current collector is set, and the one-dimensional columnar structure is used as the core layer. The active material layer and the protective layer of the lithium secondary battery electrode are sequentially wrapped on the outer surface. Compared with the battery structure flat on the current collector, this structural setting method that is perpendicular to the current collector will make the overall conductive environment of the lithium secondary battery electrode better.

[0158] Specifically, the one-dimensional columnar structure serves as a core layer perpendicular to the substrate, which can play an effective supporting role and provide a conductive channel for charging and discharging electrons perpendicular to the substrate. It does not require additional conductive agents when used in the electrode structure of lithium secondary batteries. The active material layer of the electrode can be directly coated on the surface of the substrate and the core layer by physical vapor deposition, chemical vapor deposition, electroplating, etc., without the need for additional binders. The outermost protective layer maintains the structural characteristics of being coaxial with the one-dimensional columnar structure core layer and the active material layer.

[0159] The electrode active material in the lithium secondary battery electrode of the above coaxial structure can be selected from at least one of silicon, silicide, germanium or tin. In particular, when the obtained columnar array structure electrode active material selects silicon, silicide, etc. as the active material layer, it not only has the advantage of high gram capacity (the theoretical maximum lithium insertion capacity of silicon negative electrode material reaches 4200mAh / g, which is much higher than the current graphite negative electrode), but also can utilize the good electrical contact between the conductive core layer and the conductive substrate to overcome the problem of poor conductivity of silicon-based negative electrode materials. In addition, the existence of the axial gap between adjacent columns of the one-dimensional columnar structure can better buffer the volume change of the above active material layer during the charge and discharge process, release stress, and improve cycle stability.

[0160] In addition, the protective layer can be coated on the outside of the active material layer by hydrothermal method, physical vapor deposition or chemical vapor deposition and other processes, and the thickness of the protective layer is less than the thickness of the active material layer, that is, the thickness of the protective layer is thin. The presence of such a protective layer can effectively avoid direct contact between the active material layer and the electrolyte in the lithium secondary battery, reduce the irreversible loss of lithium source and further inhibit the volume expansion during the cycle.

[0161] In order to provide a more detailed description of the technical solution and technical effects of the present application, the embodiments of the present application will be further described below through more specific embodiments, application examples and performance test results.

[0162] Embodiment 1

[0163] Combination Figure 1 As shown, this embodiment provides an intermediate structure for preparing a lithium secondary battery electrode on a single side, the intermediate structure comprising a substrate 1 and a one-dimensional columnar structure 2 vertically grown on the substrate 1, wherein the substrate 1 is a copper foil substrate 1, and the one-dimensional columnar structure 2 is a one-dimensional copper column structure. In the intermediate structure, the one-dimensional columnar structure perpendicular to the substrate 1 has the following structural parameters: the diameter of the one-dimensional columnar structure 2 is 5μm to 10μm, the height of the one-dimensional columnar structure 2 is 15μm, and the height-to-diameter ratio of the one-dimensional columnar structure 2 is 3:1 to 3:2. Figure 2 Shown is a scanning electron microscope image of the intermediate structure of this embodiment.

[0164] Combination Figure 3 As shown, the preparation method of the intermediate structure comprises the following steps:

[0165] Synthetic template: a composite film material 3 is formed on a single side of a substrate 1, and a through hole 31 is formed on the film material 3, and the central axis of the through hole 31 is perpendicular to the plane of the substrate 1; the film material 3 is a flexible PC film;

[0166] Growth: growing metal copper in the through hole 31 of the template by physical vapor deposition process, so that a one-dimensional columnar structure 2 perpendicular to the substrate 1 is formed in the through hole 31;

[0167] Removing the film material 3: The film material 3 of the template is removed by a mechanical stripping process to obtain the intermediate structure of this embodiment.

[0168] The steps of synthesizing the template include:

[0169] Hole formation: the membrane material 3 is processed by an ion track etching process to obtain a through hole 31, and a glue layer 4 is screen-printed on the membrane material 3 having the through hole 31, and the glue layer 4 does not cover the through hole 31 so that the through hole 31 is exposed; the conditions of the ion track etching process include: bombarding with heavy ions, irradiating for 200 seconds at an irradiation power of 5000KW, selecting a sodium hydroxide solution with a mass fraction of 20% as an etching solution for the membrane material 3, etching for 20 minutes, so that a through hole 31 is formed on the membrane material 3; the glue layer 4 is selected from PVDF, and NMP etching solution is selected for the glue layer 4, and the glue layer 4 is etched so that the glue layer 4 does not cover the through hole 31 of the membrane material 3;

[0170] Hot pressing: The film material 3 formed with the adhesive layer 4 is bonded to the copper foil substrate 1 by hot pressing through the adhesive layer 4 to obtain a template. Since the adhesive layer 4 is subjected to special pore-forming treatment, the through holes 31 of the template are connected to the copper foil substrate 1.

[0171] The template obtained by the above-mentioned manufacturing method has a through hole 31 with a diameter of 5 μm to 10 μm, a thickness of the membrane 3 of 15 μm, and a hole density of 4×10 6 Pieces / cm 2 .like Figure 4 The figure shows a scanning electron microscope image of the template of this embodiment. From the image, it can be seen that the through holes obtained in this embodiment are irregularly distributed in the film material.

[0172] It should be noted that although the through holes obtained by the ion track etching process are irregularly distributed, since the present embodiment is to use the template to prepare intermediate structures and lithium secondary battery electrodes in batches, that is, the template is used in the field of electrode material production for lithium secondary batteries, the number of through holes on the film material is particularly important for the template. This is because the number of through holes in the template determines the number of one-dimensional columnar structures grown in the through holes when the intermediate structure is produced, and further determines the amount of active material loading in the production of lithium secondary battery electrodes, and the amount of active material loading directly affects the electrical properties of lithium secondary battery electrodes. In addition, with regard to the regularity of the through-hole distribution, the through-hole distribution can be made closer to a regular uniform distribution to a certain extent by increasing the hole density. Specifically in the present embodiment, due to Figure 4 The through holes of the template are enlarged by a certain multiple, so they appear irregularly distributed. However, since the hole density of the through holes can reach 4×10 6 Pieces / cm 2 Therefore, overall, the template can meet the performance requirements of the subsequent production of lithium secondary battery electrodes in terms of the number of holes.

[0173] This embodiment also provides a lithium secondary battery electrode, specifically a lithium secondary battery negative electrode, combined with Figure 5As shown, the lithium secondary battery electrode includes: a substrate 1, a one-dimensional columnar structure, an active material layer 5 with silicon as an electrode active material coated on the outer surface of the one-dimensional columnar structure, and a carbon-based protective layer 6 coated on the outer surface of the active material layer 5, wherein the one-dimensional columnar structure grows on the substrate 1 perpendicular to the plane where the substrate 1 is located, and the active material layer 5 and the protective layer 6 are both perpendicular to the plane where the substrate 1 is located and are located on the substrate 1, thereby forming a lithium secondary battery electrode composed of a one-dimensional columnar structure with the substrate 1 as a current collector, a core layer perpendicular to the substrate 1 and coaxially arranged, the active material layer 5 and the protective layer 6.

[0174] Combination Figure 5 As shown, the method for manufacturing the lithium secondary battery electrode comprises the following steps:

[0175] In this embodiment, the outer surface of the one-dimensional columnar structure of the intermediate structure is coated with silicon electrode active material by physical vapor deposition process to form active material layer 5;

[0176] The carbon-based protective layer 6 is coated on the outer surface of the active material layer 5 by a physical vapor deposition process to obtain a lithium secondary battery electrode.

[0177] Embodiment 2

[0178] The only difference between this embodiment and embodiment 1 is that the ion track etching process conditions when synthesizing the template in this embodiment are different. In the step of synthesizing the template in this embodiment, the conditions of the ion track etching process include: bombarding with heavy ions, irradiating for 0.5s at an irradiation power of 10000KW, selecting a sodium hydroxide solution with a mass fraction of 50% as the etching solution for the membrane material, etching for 5 minutes, so that through holes are formed on the membrane material.

[0179] Embodiment 3

[0180] The only difference between this embodiment and the first embodiment is that the ion track etching process conditions when synthesizing the template in this embodiment are different. In the template manufacturing method of this embodiment, the conditions of the ion track etching process include: bombarding with heavy ions, irradiating for 20 seconds at an irradiation power of 2000KW, selecting a sodium hydroxide solution with a mass fraction of 20% as the etching solution for the membrane material, etching for 30 minutes, so that through holes are formed on the membrane material.

[0181] Embodiment 4

[0182] The only difference between this embodiment and the first embodiment is that the substrate of this embodiment is a nickel foil substrate, the film material is a flexible PET film, and the steps of synthesizing the template of this embodiment are different.

[0183] In this embodiment, the steps of synthesizing the template include:

[0184] Gluing: Apply glue layer on the membrane material without through-holes to make the glue layer uniform and dense;

[0185] Hole making: The film material coated with the adhesive layer is treated by an ion track etching process, so that both the adhesive layer and the film material are formed with through holes; wherein the conditions of the ion track etching process include: bombarding with heavy ions, irradiating for 200s at an irradiation power of 5000KW, selecting a sodium hydroxide solution with a mass fraction of 20% as an etching solution for the film material, etching for 20 minutes, so that through holes are formed on the film material; the adhesive layer is selected from PVDF, and NMP etching solution is selected for the adhesive layer, and the adhesive layer is etched so that the adhesive layer does not cover the through holes of the film material;

[0186] Hot pressing: The film material with through holes is bonded to the nickel foil substrate by hot pressing to obtain a template. Since the film layer and the adhesive layer are subjected to special pore-making treatment, the through holes of the template are connected to the nickel foil substrate.

[0187] The template obtained by the above steps has a through hole diameter of 5 μm to 10 μm, a film thickness of 15 μm to 50 μm, and a through hole density of 10 5 Pieces / cm 2 ~10 8 Pieces / cm 2 .

[0188] Embodiment 5

[0189] The only difference between this embodiment and the first embodiment is that the membrane material of this embodiment is a flexible PI film, the steps of synthesizing the template of this embodiment are different, and the one-dimensional columnar structure of this embodiment is a one-dimensional nickel column structure.

[0190] In this embodiment, the steps of synthesizing the template include:

[0191] Gluing: coating a glue layer on the membrane material without through holes to make the glue layer uniform and dense;

[0192] Hot pressing: The film material with the adhesive layer is bonded to the substrate through the adhesive layer by hot pressing;

[0193] Hole making: The membrane material and the adhesive layer bonded to the substrate are treated by ion track etching to form through holes in the membrane material and the adhesive layer; the conditions of the ion track etching process include: bombarding with heavy ions, irradiating for 200s at an irradiation power of 5000KW, selecting a sodium hydroxide solution with a mass fraction of 20% as an etching solution for the membrane material, etching for 20 minutes, so that through holes are formed on the membrane material; PVDF is selected for the adhesive layer, and NMP etching solution is selected for the adhesive layer to etch the adhesive layer so that the adhesive layer will not cover the through holes of the membrane material.

[0194] Since the film layer and the adhesive layer are subjected to special pore-forming treatment, the through holes of the template are connected with the substrate.

[0195] The template obtained by the above-mentioned preparation method has a through hole diameter of 5 μm to 10 μm, a film thickness of 15 μm to 50 μm, and a through hole density of 10 5 Pieces / cm 2 ~10 8 Pieces / cm 2 .

[0196] Embodiment 6

[0197] The difference between this embodiment and the first embodiment is that the steps of synthesizing the template are different, and the electrode active material used in the active material layer of the lithium secondary electrode is different.

[0198] The steps of synthesizing the template in this embodiment include:

[0199] Hole making: The membrane material is processed by ion track etching process to obtain through holes;

[0200] Pre-plating: Pre-plating a first metal layer on the film material with through holes by physical vapor deposition;

[0201] A second metal layer is electroplated on the first metal layer to form a substrate, so that the substrate is plated on the film material with through holes to form a template, wherein the second metal layer and the first metal layer are both copper layers, and the thickness of the second metal layer is greater than that of the first metal layer.

[0202] In addition, in the lithium secondary battery electrode, the active material layer uses germanium active material.

[0203] Embodiment 7

[0204] The difference between this embodiment and the first embodiment is that the steps of synthesizing the template are different, and the electrode active material used in the active material layer of the lithium secondary battery electrode is different.

[0205] The steps of synthesizing the template in this embodiment include:

[0206] Pre-treatment: pre-treatment of the substrate to remove impurities, specifically, pre-treatment of the substrate to remove oil and impurities;

[0207] Dry film coating: coating a dry film on one side of the pre-treated substrate;

[0208] Hole making: The dry film is exposed, developed, and etched to obtain a template with through holes formed on the dry film.

[0209] The template obtained by the above-mentioned manufacturing method has regularly distributed through holes 31, the pore size of the through holes 31 is 5μm to 30μm, the thickness of the membrane material is 5μm to 30μm, the aspect ratio of the thickness of the membrane material to the pore size of the through holes is 1:3 to 3:1, and the spacing between adjacent through holes is 5μm to 20μm.

[0210] In addition, in the lithium secondary battery electrode, the active material layer uses a tin active material.

[0211] Embodiment 8

[0212] The difference between this embodiment and the seventh embodiment is that in this embodiment, a film material with through holes is compounded on both the upper and lower surfaces of the copper foil substrate, that is, the template is a template with through holes on both sides. The intermediate structure prepared by using the template of this embodiment also has a one-dimensional copper column structure grown on both sides of the substrate, such as Figure 6 The intermediate structure of this embodiment is shown in the scanning electron microscope image. Further, the lithium secondary battery electrode prepared using the intermediate structure of this embodiment also forms a coaxial one-dimensional columnar structure on both sides of the copper foil substrate.

[0213] Comparative Example

[0214] The only difference between this comparative example and Example 1 is that this comparative example does not use a template to make the intermediate structure and the lithium secondary battery electrode, but directly uses the same electrode making conditions as Example 1 to make the lithium secondary battery electrode on the substrate. That is, in this comparative example, the silicon electrode active material is directly deposited on the copper foil substrate by a physical vapor deposition process to form an active material layer flattened on the copper foil substrate, and then a carbon-based protective layer is deposited on the active material layer by a physical vapor deposition process to obtain a lithium secondary battery electrode.

[0215] Performance Testing

[0216] The lithium secondary battery electrodes of Example 1 and the comparative example were used as the battery negative electrode and assembled into button batteries together with other conventional lithium secondary battery materials. The cycle performance test was carried out. The results are as follows: Figure 7 The cycle performance test results show that the button cell assembled with the lithium secondary battery electrode of Example 1 has a gram capacity test result of about 1426 mAh / g, and after 30 cycles, the discharge capacity retention rate is 64%. The button cell assembled with the lithium secondary battery electrode of the comparative example has an initial gram capacity of about 1347 mAh / g, and after 30 cycles, the discharge capacity retention rate is only 6%.

[0217] It can be seen that although in this control experiment, the active material loading on the lithium secondary battery electrode of Example 1 and the comparative example is the same, resulting in the initial gram capacity level of the lithium secondary battery assembled using the two being close. However, as the cycle performance test experiment proceeds, the discharge specific capacity of the comparative lithium secondary battery decreases significantly. This is because the negative electrode of the battery in the comparative example adopts a silicon thin film negative electrode structure, which has a large volume expansion during the charge and discharge cycle. Under the action of stress, the silicon particles and the interface between the silicon and the copper foil current collector are easy to fall off, and the electrical contact is lost, which ultimately leads to a rapid capacity decay. After 30 cycles, the discharge capacity retention rate is only 6%. From the performance test results of the lithium secondary battery electrode of Example 1, it can be seen that since the embodiment of the present application is a one-dimensional columnar structure in which a conductive material is vertically grown on the copper foil current collector, and the outer peripheral wall of the one-dimensional columnar structure is sequentially coated with active substances such as silicon and a protective layer, the reserved gaps between adjacent one-dimensional columnar structures can effectively buffer the volume expansion of active substances such as silicon during the charge and discharge cycle, and slow down the phenomenon of active substances such as silicon falling off and losing electrical contact due to expansion, thereby greatly improving the cycle stability of the lithium secondary battery.

[0218] The above is a detailed introduction to the intermediate structure and preparation method for preparing the lithium secondary battery electrode, the lithium secondary battery electrode and the preparation method disclosed in the embodiments of the present application. The principles and implementation methods of the present application are described in detail using specific examples herein. The description of the above embodiments is only used to help understand the technical solution and core ideas of the present application. At the same time, for those of ordinary skill in the art, according to the ideas of the present application, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for preparing an intermediate structure, characterized in that: The intermediate structure is used to prepare a lithium secondary battery electrode on one side or both sides, and the preparation method of the intermediate structure comprises the following steps: Synthetic template: treating a film material by an ion track etching process to obtain a through hole; pre-plating a first metal layer on the film material with the through hole by physical vapor deposition; electroplating a second metal layer on the first metal layer to form a substrate, so that the film material with the through hole is plated with the substrate to form the template; wherein the central axis of the through hole is perpendicular to the plane of the substrate, the substrate is a conductive substrate, the film material is a flexible polymer film, and the polymer film is at least one of a PTFE film, a PET film, a PP film, a PC film or a PI film; Growth: growing a conductive material in the through hole so that a one-dimensional columnar structure perpendicular to the substrate is formed in the through hole; Removing the membrane material: removing the membrane material to obtain the intermediate structure.

2. The method for preparing the intermediate structure according to claim 1, characterized in that: The conditions of the ion track etching process include: bombarding with heavy ions, irradiating for 0.5 s to 200 s at an irradiation power of 2000 KW to 10000 KW.

3. The method for preparing the intermediate structure according to claim 1, characterized in that: The conditions of the ion track etching process include: the etching solution is an alkaline solution, and the etching time is 5 min to 30 min.

4. The method for preparing the intermediate structure according to claim 1, characterized in that: The through hole has a pore diameter of 10 nm to 50 μm.

5. The method for preparing the intermediate structure according to claim 4, characterized in that: The through hole has a diameter of 5 μm to 30 μm.

6. The method for preparing the intermediate structure according to claim 1, characterized in that: The hole density of the through holes is 105 / cm 2 ~108 pieces / cm 2 .

7. The method for preparing the intermediate structure according to claim 6, characterized in that: The through-hole density is 400,000 / cm 2 ~2 million / cm 2 .

8. The method for preparing the intermediate structure according to claim 1, characterized in that: The thickness of the membrane material is 2 μm to 50 μm.

9. The method for preparing the intermediate structure according to claim 8, characterized in that: The thickness of the membrane material is 15 μm to 50 μm.

10. The method for preparing the intermediate structure according to claim 1, characterized in that: The aspect ratio of the thickness of the membrane material to the aperture of the through hole is 1:3-3:

1.

11. The method for preparing the intermediate structure according to claim 10, characterized in that: The aspect ratio of the thickness of the membrane material to the aperture of the through hole is 1:1-3:

1.

12. The method for preparing the intermediate structure according to claim 1, characterized in that: In the step of growing, the method of growing the conductive material in the through hole adopts one of physical vapor deposition, electroplating, chemical plating or chemical vapor deposition; and / or, In the step of removing the film material, the method of removing the film material adopts one of mechanical stripping, chemical etching or vacuum sintering.

13. The method for preparing the intermediate structure according to claim 1, characterized in that: The diameter of the one-dimensional columnar structure is 5 μm to 30 μm, the height of the one-dimensional columnar structure is 15 μm to 50 μm, and the aspect ratio of the one-dimensional columnar structure is 3:1 to 1:

1.

14. The method for preparing the intermediate structure according to claim 1, characterized in that: The one-dimensional columnar structure includes a plurality of regularly distributed columns, and the spacing between adjacent columns is 5 μm to 20 μm; or, the one-dimensional columnar structure includes a plurality of irregularly distributed columns.

15. The method for preparing an intermediate structure according to any one of claims 1 to 14, characterized in that: The substrate is at least one of a copper foil substrate, a nickel foil substrate, and a stainless steel substrate; and / or, The conductive material is at least one of copper, nickel or carbon.

16. An intermediate structure, characterized in that The intermediate structure is used for preparing lithium secondary battery electrodes on one side or both sides, and the intermediate structure is prepared by the preparation method according to any one of claims 1 to 15, and the intermediate structure includes the substrate and the one-dimensional columnar structure vertically grown on the substrate.

17. The intermediate structure according to claim 16, characterized in that The diameter of the one-dimensional columnar structure is 5 μm to 30 μm, the height of the one-dimensional columnar structure is 15 μm to 50 μm, and the aspect ratio of the one-dimensional columnar structure is 3:1 to 1:

1.

18. The intermediate structure according to claim 17, characterized in that The one-dimensional columnar structure includes a plurality of regularly distributed columns, and the spacing between adjacent columns is 5 μm to 20 μm; or, the one-dimensional columnar structure includes a plurality of irregularly distributed columns.

19. A method for preparing a lithium secondary battery electrode, characterized in that: The method for preparing the lithium secondary battery electrode comprises the following steps: The outer surface of the one-dimensional columnar structure of the intermediate structure prepared by the preparation method according to any one of claims 1 to 15 is coated with an electrode active material to form an active material layer; The outer surface of the active material layer is coated with a protective layer to obtain the lithium secondary battery electrode.

20. The method for preparing a lithium secondary battery electrode according to claim 19, characterized in that: The electrode active material is at least one of silicon, germanium or tin.

21. The method for preparing a lithium secondary battery electrode according to claim 19, characterized in that: The material of the protective layer is carbon or metal oxide.

22. The method for preparing a lithium secondary battery electrode according to claim 19, characterized in that: Methods for coating the electrode active material include chemical vapor deposition, physical vapor deposition or electroplating.

23. The method for preparing a lithium secondary battery electrode according to claim 19, characterized in that: The method of coating the protective layer includes a hydrothermal method, a physical vapor deposition method or a chemical vapor deposition method.

24. A lithium secondary battery electrode, characterized in that: The lithium secondary battery electrode is manufactured by the method for preparing a lithium secondary battery electrode according to any one of claims 19 to 23, and the lithium secondary battery electrode comprises: A substrate, wherein the substrate is a conductive substrate; A one-dimensional columnar structure, which is grown on the substrate perpendicular to the plane where the substrate is located, and the one-dimensional columnar structure is a conductive one-dimensional columnar structure; An active material layer is located on the substrate perpendicular to the plane of the substrate and covers the outer surface of the one-dimensional columnar structure; The protective layer is located on the substrate perpendicular to the plane where the substrate is located and covers the outer surface of the active material layer.

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