A structured micro battery and a method for preparing the same

Abstract

The embodiments of the present disclosure provide a structured micro-battery and a method for preparing the same. The battery includes a silicon substrate, a silicon nanowire cluster negative electrode structure, an electrolyte layer and a positive electrode material layer; the silicon nanowire cluster negative electrode structure is arranged on the silicon substrate; the silicon nanowire cluster negative electrode structure includes a plurality of silicon nanowire clusters; the electrolyte layer and the positive electrode material layer are sequentially stacked and arranged around the silicon nanowire cluster negative electrode structure. The embodiments of the present disclosure can provide a larger contact interface between the active material and the electrolyte by increasing the surface area of ​​the electrode, and the transmission path of ions and electrons between the electrodes is shorter, which is beneficial to improve the capacity, reaction rate and power density of the battery. At the same time, the softness of silicon nanowires makes it more tolerant to deformation caused by lithium ion insertion / extraction during the charge and discharge cycle, does not cause loosening and breakage of the material, avoids performance degradation, and can comprehensively improve the stability of the battery during the cycle.

Description

Technical Field

[0001] The embodiments of the present disclosure belong to the technical field of structured micro-batteries, and specifically relate to a structured micro-battery and a method for preparing the same. Background Art

[0002] With the rapid development of microelectronics technology, the size of various electronic systems has been continuously miniaturized and their functions have been continuously enhanced. The strict restrictions on the size and weight of these micro-systems have forced the energy carrying capacity to be extremely limited, and even in some scenarios it is difficult to guarantee and meet basic electricity needs. The lack of high-performance integrated energy has become a bottleneck restricting the further development of new electronic systems. After a long period of development, the energy density of lithium-ion battery electrode materials has gradually approached its upper limit. It is difficult to achieve significant comprehensive improvement simply by optimizing the energy storage density of battery active materials. The design and innovation of battery structure are considered to be an effective solution.

[0003] At present, the design and research of structured microbatteries is a hot topic. In the research of structured microbatteries composed of silicon micron-column negative electrodes, it was found that the structured microbattery adopts a 3D structure, which can provide more contact interfaces between active materials and electrolytes by increasing the surface area of ​​the electrode, and the transmission path of ions and electrons between the electrodes is shorter, which is conducive to improving the capacity, reaction rate and power density of the battery. However, after the first few cycles of the battery, its interface impedance increases rapidly, indicating that its cycle stability is poor and the capacity decay is obvious.

[0004] Existing research shows that the increase in microbattery impedance is mainly related to the characteristics of the silicon negative electrode itself. During the charging and discharging process, as lithium ions are inserted and removed, volume expansion and contraction easily occur, resulting in loosening and breakage of the silicon negative electrode material. At the same time, this negative electrode damage will also lead to damage to the microscopic interface inside the battery, hindering the conduction of electrons and ions, thereby causing performance degradation. Summary of the invention

[0005] The embodiments of the present disclosure aim to solve at least one of the technical problems existing in the prior art and provide a structured micro-battery and a method for preparing the same.

[0006] One aspect of the present disclosure provides a structured micro battery, the battery comprising a silicon substrate, a silicon nanowire cluster negative electrode structure, an electrolyte layer and a positive electrode material layer;

[0007] The silicon nanowire cluster cathode structure is disposed on the silicon substrate; the silicon nanowire cluster cathode structure comprises a plurality of silicon nanowire clusters;

[0008] The electrolyte layer and the positive electrode material layer are sequentially stacked and arranged around the silicon nanowire cluster negative electrode structure.

[0009] Optionally, the width of each of the silicon nanowire clusters is 1 μm to 50 μm; and / or the height of each of the silicon nanowire clusters is 10 μm to 200 μm.

[0010] Optionally, the center distance between each of the silicon nanowire clusters is 1 μm to 100 μm.

[0011] Optionally, the spacing between the silicon nanowires in each silicon nanowire cluster is less than 200 nm.

[0012] Optionally, a negative electrode protection layer is further provided between the silicon nanowire cluster negative electrode structure and the electrolyte layer.

[0013] Another aspect of the present disclosure provides a method for preparing a structured microbattery, the method comprising:

[0014] A silicon nanowire cluster cathode structure is formed on the surface of a silicon substrate by a multi-step etching process; the silicon nanowire cluster cathode structure includes a plurality of silicon nanowire clusters;

[0015] forming an electrolyte layer on the surface of the silicon nanowire cluster negative electrode structure;

[0016] The positive electrode slurry of the battery is dripped on the surface of the electrolyte layer, and vacuuming and drying are performed to form a positive electrode material layer.

[0017] Furthermore, the multi-step etching process is used to form a silicon nanowire cluster cathode structure on the surface of the silicon substrate, including:

[0018] A silicon dioxide film is formed on the surface of a silicon substrate by plasma enhanced vapor deposition;

[0019] Spin coating a first photoresist on the silicon dioxide film and performing mask exposure and development to form a periodic array pattern;

[0020] dry etching the silicon dioxide film so that the silicon dioxide film forms a periodic array pattern corresponding to the first photoresist;

[0021] Removing the silicon dioxide film, spin coating the silicon substrate with the silicon micron pillars with a second photoresist, and thinning the second photoresist to expose the tops of the silicon micron pillars;

[0022] Removing the silicon dioxide film, spin-coating a second photoresist on the silicon substrate having the silicon micron pillars and exposing the top of each silicon micron pillar;

[0023] The plurality of silicon micrometer columns are prepared into a plurality of silicon nanowire clusters by wet etching, and the second photoresist is removed to obtain a silicon nanowire cluster cathode structure.

[0024] Further, the thinning of the second photoresist to expose the top of the silicon micron column includes:

[0025] The second photoresist is made flush with the top of the silicon micron column.

[0026] Furthermore, the step of preparing the plurality of silicon micro-pillars into a plurality of silicon nanowire clusters by wet etching, removing the second photoresist, and obtaining a silicon nanowire cluster cathode structure comprises:

[0027] Placing the silicon substrate having the silicon micro-pillars in a noble metal solution to form a porous noble metal coating on the surface of the silicon substrate;

[0028] The silicon substrate with the porous noble metal coating is placed in an etching solution containing hydrogen peroxide and hydrofluoric acid to chemically etch the multiple silicon micro-pillars to form multiple silicon nanowire clusters to obtain a silicon nanowire cluster negative electrode structure.

[0029] Furthermore, after forming the silicon nanowire cluster cathode structure on the surface of the silicon substrate by a multi-step etching process, the method further comprises:

[0030] A negative electrode protection material is conformally grown on the surface of the silicon nanowire cluster negative electrode structure to form a negative electrode protection layer.

[0031] A structured micro-battery and a preparation method thereof according to an embodiment of the present disclosure can provide a larger contact interface between the active material and the electrolyte by increasing the surface area of ​​the electrode, and the transmission path of ions and electrons between the electrodes is shorter, which is beneficial to improving the capacity, reaction rate and power density of the battery. At the same time, due to the softness of silicon nanowires, they have better tolerance to deformation caused by lithium ion insertion / extraction during the charge and discharge cycle, and will not cause loosening and breakage of the material, thereby avoiding performance degradation, and thus can comprehensively improve the stability of the battery during the cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the structure of an existing structured micro battery;

[0033] Figure 2 This is a schematic diagram of the structure of a structured micro battery according to an embodiment of the present disclosure;

[0034] Figure 3 A schematic diagram of a process for preparing a structured micro-battery according to another embodiment of the present disclosure;

[0035] Figure 4 A schematic diagram of a process for preparing a structured micro-battery according to another embodiment of the present disclosure;

[0036] Figure 5A schematic diagram of a process for preparing a structured micro-battery according to another embodiment of the present disclosure;

[0037] Figure 6 A schematic diagram of a process for preparing a structured micro-battery according to another embodiment of the present disclosure;

[0038] Figure 7 FIG. 4 is a schematic diagram of a process for preparing a structured microbattery according to another embodiment of the present disclosure. DETAILED DESCRIPTION

[0039] like Figure 1 The figure shows a schematic diagram of the structure of an existing structured micro-battery, which is composed of a silicon substrate 11, a silicon micro-pillar 12, an electrolyte layer 13 and a positive electrode material layer 14. After cycling, the interface impedance of the battery with this structure increases rapidly, indicating that its cycling stability is poor and the capacity decay is obvious. Analysis shows that the increase in the impedance of the micro-battery is mainly related to the characteristics of the silicon negative electrode itself. During the charging and discharging process, the volume expands and contracts easily with the insertion and extraction of lithium ions, resulting in loosening and fracture of the material, such as Figure 1 The silicon micro-pillar damage is shown in 15. Such damage to the negative electrode surface will cause deformation and fracture of the electrolyte layer 13, and separation of the electrolyte layer 13 from the positive electrode material layer 14, resulting in damage to the microscopic interface inside the battery, hindering the conduction of electrons and ions, and thus causing performance degradation.

[0040] Therefore, in order to solve the above problems, it is necessary to propose an improved structured microbattery.

[0041] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0042] In addition, the described features, structures or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known methods, devices, implementations or operations are not shown or described in detail to avoid blurring the various aspects of the present disclosure.

[0043] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0044] It should be understood that although the terms first, second, third, etc. may be used in this disclosure to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another component. Therefore, the first component discussed below can be referred to as the second component without departing from the teachings of the concepts of the present disclosure. As used in this disclosure, the term "and / or" includes any one of the associated listed items and all combinations of one or more.

[0045] Those skilled in the art will appreciate that the drawings are merely schematic diagrams of example embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing the present disclosure, and therefore cannot be used to limit the protection scope of the present disclosure.

[0046] like Figure 2 As shown, an embodiment of the present disclosure provides a structured micro-battery, the battery comprising a silicon substrate 210, a silicon nanowire cluster negative electrode structure 220, an electrolyte layer 230 and a positive electrode material layer 240. The silicon nanowire cluster negative electrode structure 220 is disposed on the silicon substrate 210. The silicon nanowire cluster negative electrode structure 220 comprises a plurality of silicon nanowire clusters 221. The solid electrolyte layer 230 and the positive electrode material layer 240 are sequentially stacked and arranged around the silicon nanowire cluster negative electrode structure 220.

[0047] Specifically, the silicon substrate 210 can adopt the current mainstream 4-inch to 12-inch single crystal silicon wafer, with a crystal orientation of

[100] , which is an n-type or p-type single-sided polished silicon wafer with a relatively low resistivity. The cross section of each silicon nanowire cluster 221 can be approximately circular or square. The cross section of the silicon nanowire cluster 221 is essentially a collection of silicon nanowires and gaps between nanowires. The specific cross-sectional profile is strongly related to the photolithography pattern used in the preparation process. Each silicon nanowire cluster 221 has a horizontal width of 1 μm to 50 μm and a vertical height of 10 μm to 200 μm, and has a high aspect ratio. It is evenly distributed on the surface of the silicon substrate 210, and the center spacing between each silicon nanowire cluster 221 is 1 μm to 100 μm. In each silicon nanowire cluster 221, a large number of silicon nanowires are distributed. The silicon nanowires are 10 μm to 200 μm long, and the spacing between silicon nanowires is less than 200 nm. There are a large number of micro-nano gaps between the wires, and agglomeration may occur at the top of the wires.

[0048] It should be noted that the typical data given in the embodiments of the structured micro-battery and the negative electrode structure of the silicon nanowire cluster are a range of experimental research and exploration, and it is easy for those skilled in the art to change the structure and size design. The actual silicon nanowire cluster structure may vary due to the actual process, such as cleaning and drying. Figure 2 There are differences in the morphology of the nanowires, such as the clusters of nanowires may gather at the top, but this does not change the fact that they are silicon nanowires, nor does it change their advantage of better tolerance to deformation caused by lithium ion insertion / ejection during charge and discharge cycles compared to silicon micro-pillars. All technical problems mentioned above that are solved by silicon nanowires should fall within the scope of protection of this disclosure.

[0049] For example, Figure 2 As shown, a negative electrode protection layer 250 is further provided between the silicon nanowire cluster negative electrode structure and the electrolyte layer. The negative electrode protection layer 250 can be connected in a mesh or point shape to improve the conductivity of the negative electrode interface.

[0050] A structured microbattery of an embodiment of the present disclosure can provide a larger contact interface between the active material and the electrolyte by increasing the surface area of ​​the electrode, and the transmission path of ions and electrons between the electrodes is shorter, which is beneficial to improving the capacity, reaction rate and power density of the battery. At the same time, due to the softness of silicon nanowires, they have better tolerance to deformation caused by lithium ion insertion / extraction during the charge and discharge cycle, and will not cause loosening and breakage of the material, thereby avoiding performance degradation, and thus can comprehensively improve the stability of the battery during the cycle. In addition, the introduction of the negative electrode protective layer not only enhances the conductivity of the negative electrode, but also further enhances the tolerance of the negative electrode nanowire structure to deformation caused by lithium ion insertion / extraction, thereby further improving the performance and stability of the battery.

[0051] like Figure 3 As shown, an embodiment of the present disclosure provides a method for preparing a structured micro battery, the method comprising:

[0052] Step S1, forming a silicon nanowire cluster cathode structure on the surface of a silicon substrate by a multi-step etching process; the silicon nanowire cluster cathode structure includes a plurality of silicon nanowire clusters.

[0053] Specifically, a silicon substrate is firstly taken, and a silicon dioxide (SiO2) film is formed on the surface of the silicon substrate by plasma enhanced vapor deposition (PECVD); a photoresist is spin-coated on the silicon dioxide film and mask exposure and development are performed to form a periodic array pattern; the silicon dioxide film is dry-etched to form a pattern corresponding to the photoresist; the photoresist is removed, and the silicon dioxide on the surface of the silicon substrate acts as a hard template, and then the silicon substrate is dry-etched according to the periodic array pattern to form a silicon micron column array; the silicon substrate with the silicon micron column is placed in a 5% HF hydrofluoric acid aqueous solution to remove the silicon dioxide film, and the following is obtained: Figure 4 In the structure shown, a plurality of silicon micro-pillars 42 are periodically arranged on a silicon substrate 41 .

[0054] Subsequently, photoresist is spin-coated on the silicon substrate with the silicon micron pillars to completely cover the silicon micron pillars. Then, the photoresist layer is thinned by mask exposure and development, or by plasma bombardment and other processes to expose the tops of the silicon micron pillars and block the rest of the silicon micron pillars with photoresist. To ensure the success rate of subsequent wet etching, the exposed tops of the micron pillars should be substantially flush with the tops of the photoresist formed by the thinned photoresist, and the following is obtained: Figure 5 The structure shown includes a silicon substrate 51 , a plurality of silicon micro-pillars 52 and a photoresist 53 .

[0055] Finally, the plurality of silicon micrometer pillars are prepared into a plurality of silicon nanowire clusters by wet etching to obtain a silicon nanowire cluster negative electrode structure: Figure 5 The silicon substrate structure in the process is placed in a precious metal solution, such as a silver plating solution containing silver nitrate and hydrofluoric acid, and allowed to stand for one minute. The silver ions undergo a reduction reaction due to the electrons obtained from the silicon wafer surface to generate silver single substance particles that are deposited on the silicon wafer surface, completing the chemical deposition of the silver particles on the silicon substrate surface, thereby forming a precious metal coating with a porous structure on the surface of the silicon substrate, namely, a silver coating. The precious metal coating is a discontinuous porous film, and the preparation of a discontinuous porous precious metal film can be achieved by using self-assembled PS beads as a template or controlling the coating time. The silver-plated silicon substrate is then placed in an etching solution containing hydrogen peroxide and hydrofluoric acid to chemically etch the multiple silicon micron columns. The silver particles are oxidized by hydrogen peroxide to generate silver ions, and then the silver ions continue to capture electrons near the silicon substrate to generate silver particles. As the reaction time increases, the silver particles are etched downward along the crystal direction of the silicon substrate, and finally multiple silicon micron columns are prepared as shown in the following figure. Figure 6 A plurality of silicon nanowire clusters 61 are shown in FIG.

[0056] After that, the etched silicon substrate can be placed in an aqueous solution containing nitric acid for ten minutes to remove excess silver particles, and the silicon nanowire clusters can be washed with deionized water for twenty minutes to remove excess solvent impurities. Figure 7 The silicon substrate and silicon nanowire cluster negative electrode structure shown.

[0057] For example, when obtaining Figure 7 After the silicon nanowire cluster negative electrode structure is formed, graphene or other negative electrode protection materials can be conformally grown on the surface of the silicon nanowire cluster negative electrode structure as a negative electrode protection layer. The protection layer only needs to form a mesh or point connection, and does not need to form a continuous film, so as to improve the conductivity of the negative electrode interface.

[0058] Step S2, forming an electrolyte layer on the surface of the silicon nanowire cluster negative electrode structure.

[0059] Specifically, an electrolyte layer is conformally prepared on the surface of the negative electrode structure of the silicon nanowire cluster by atomic layer deposition (ALD), or an electrolyte colloidal material is spin-coated on the surface of the negative electrode structure of the silicon nanowire cluster, thereby forming an electrolyte layer on the surface of the negative electrode structure of the silicon nanowire cluster, and obtaining an electrolyte layer that completely covers the negative electrode structure of the silicon nanowire cluster and its protective layer.

[0060] Step S3, adding battery positive electrode slurry to the surface of the electrolyte layer, and performing vacuuming and drying to form a positive electrode material layer.

[0061] Specifically, a positive electrode slurry of a battery is prepared based on a high-capacity positive electrode material, a conductive agent, a solvent, etc., and a cycle operation of dripping and vacuum is adopted to make the slurry completely fill the gaps in the electrolyte layer, and after drying, a positive electrode material layer is formed on the surface of the electrolyte layer, so as to complete the process as follows: Figure 2 Preparation of the structured microbattery shown.

[0062] A method for preparing a structured micro-battery in an embodiment of the present disclosure can provide a larger contact interface between the active material and the electrolyte by increasing the surface area of ​​the electrode, and the transmission path of ions and electrons between the electrodes is shorter, which is beneficial to improving the capacity, reaction rate and power density of the battery. At the same time, due to the softness of silicon nanowires, they have better tolerance to deformation caused by lithium ion insertion / extraction during the charge and discharge cycle, and will not cause loosening and breakage of the material, thereby avoiding performance degradation, and thus can comprehensively improve the stability of the battery during the cycle. In addition, the introduction of the negative electrode protective layer not only enhances the conductivity of the negative electrode, but also further enhances the tolerance of the negative electrode nanowire structure to deformation caused by lithium ion insertion / extraction, thereby further improving the performance and stability of the battery.

[0063] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present disclosure, but the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and substance of the present disclosure, and these modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A structured microbattery, characterized in that: The battery comprises a silicon substrate, a silicon nanowire cluster negative electrode structure, an electrolyte layer and a positive electrode material layer; The silicon nanowire cluster cathode structure is arranged on the silicon substrate; the silicon nanowire cluster cathode structure comprises a plurality of silicon nanowire clusters, each of which has a width of 1 μm to 50 μm, a height of 10 μm to 200 μm, and a center spacing between each of which has a center spacing of 1 μm to 100 μm; wherein the silicon nanowire cluster cathode structure is prepared by the following method: A silicon dioxide film is formed on the surface of a silicon substrate by plasma enhanced vapor deposition; a first photoresist is spin-coated on the silicon dioxide film and mask exposure and development are performed to form a periodic array pattern; the silicon dioxide film is dry-etched to form a periodic array pattern corresponding to the first photoresist; the first photoresist is removed, and the silicon substrate is dry-etched according to the periodic array pattern to form a plurality of silicon micron columns; the silicon dioxide film is removed, and a second photoresist is spin-coated on the silicon substrate with the silicon micron columns, and the second photoresist is thinned to expose the top of the silicon micron column; the plurality of silicon micron columns are prepared into a plurality of silicon nanowire clusters by wet etching, and the second photoresist is removed to obtain a negative electrode structure of the silicon nanowire cluster; The electrolyte layer and the positive electrode material layer are sequentially stacked and arranged around the silicon nanowire cluster negative electrode structure.

2. The structured microbattery according to claim 1, characterized in that: The distance between each silicon nanowire in each silicon nanowire cluster is less than 200 nm.

3. The structured microbattery according to claim 1 or 2, characterized in that: A negative electrode protection layer is also arranged between the silicon nanowire cluster negative electrode structure and the electrolyte layer.

4. A method for preparing a structured microbattery, used for preparing the structured microbattery according to any one of claims 1 to 3, characterized in that: The preparation method comprises: A silicon nanowire cluster cathode structure is formed on the surface of a silicon substrate by a multi-step etching process, including: forming a silicon dioxide film on the surface of a silicon substrate by plasma enhanced vapor deposition; spin coating a first photoresist on the silicon dioxide film and performing mask exposure and development to form a periodic array pattern; dry etching the silicon dioxide film to form a periodic array pattern corresponding to the first photoresist; removing the first photoresist, and dry etching the silicon substrate according to the periodic array pattern to form a plurality of silicon micron columns; removing the silicon dioxide film, spin coating and covering the silicon substrate with the silicon micron columns with a second photoresist, and thinning the second photoresist to expose the top of the silicon micron column; preparing the plurality of silicon micron columns into a plurality of silicon nanowire clusters by wet etching, and removing the second photoresist to obtain a silicon nanowire cluster cathode structure; the silicon nanowire cluster cathode structure includes a plurality of silicon nanowire clusters; forming an electrolyte layer on the surface of the silicon nanowire cluster negative electrode structure; The positive electrode slurry of the battery is dripped on the surface of the electrolyte layer, and vacuuming and drying are performed to form a positive electrode material layer.

5. The method for preparing a structured microbattery according to claim 4, characterized in that: The step of thinning the second photoresist to expose the top of the silicon micron column comprises: The second photoresist is made flush with the top of the silicon micron column.

6. The method for preparing a structured microbattery according to claim 5, characterized in that: The method of preparing the plurality of silicon micrometer pillars into a plurality of silicon nanowire clusters by wet etching, removing the second photoresist, and obtaining a silicon nanowire cluster cathode structure includes: Placing the silicon substrate having the silicon micro-pillars in a noble metal solution to form a porous noble metal coating on the surface of the silicon substrate; The silicon substrate with the porous noble metal coating is placed in an etching solution containing hydrogen peroxide and hydrofluoric acid to chemically etch the multiple silicon micro-pillars to form multiple silicon nanowire clusters to obtain a silicon nanowire cluster negative electrode structure.

7. The method for preparing a structured microbattery according to any one of claims 4 to 6, characterized in that: After forming a silicon nanowire cluster cathode structure on the surface of the silicon substrate by a multi-step etching process, the method further comprises: A negative electrode protection material is conformally grown on the surface of the silicon nanowire cluster negative electrode structure to form a negative electrode protection layer.

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