WO2019161648A1

WO2019161648A1 - Composite material and preparation method therefor

Info

Publication number: WO2019161648A1
Application number: PCT/CN2018/102343
Authority: WO
Inventors: 苏航; 李阳兴; 于哲勋; 王平华
Original assignee: 华为技术有限公司
Priority date: 2018-02-26
Filing date: 2018-08-24
Publication date: 2019-08-29
Also published as: CN110197896A

Abstract

A composite material and a preparation method therefor, being used for solving the problem in the prior art that a silicon negative electrode material in a battery is easily broken and pulverized. The composite material comprises a lamellar silicon inner core and a plurality of graphene layers, the lamellar silicon inner core comprising a plurality of silicon-based material layers; there is an interlayer gap between two adjacent silicon-based material layers; the silicon-based material layers comprise silicon or silicon oxide; each graphene layer is provided in the interlayer gap between two adjacent silicon-based material layers; there is a gap between each graphene layer and at least one silicon-based material layer in two adjacent silicon-based materials.

Description

一种复合材料及其制备方法Composite material and preparation method thereof

本申请要求于2018年2月26日提交中国专利局、申请号为201810159595.3、申请名称为“一种复合材料及其制备方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。The present application claims priority to Chinese Patent Application No. 201101159595.3, the entire disclosure of which is hereby incorporated by reference. in.

技术领域Technical field

本申请涉及材料技术领域，尤其涉及一种复合材料及其制备方法。The present application relates to the field of material technology, and in particular, to a composite material and a preparation method thereof.

背景技术Background technique

锂离子电池通常采用石墨作为负极材料，石墨的理论克容量为372mAh/g，而当前实际使用的石墨的克容量已超过360mAh/g，已接近理论极限值，很难再有上升的空间，制约电池的能量密度的进一步提升。Lithium-ion batteries usually use graphite as the anode material. The theoretical gram capacity of graphite is 372 mAh/g, and the current gram capacity of graphite has exceeded 360 mAh/g, which is close to the theoretical limit value. It is difficult to have any room for further increase. A further increase in the energy density of the battery.

硅的理论克容量远大于石墨，达到4200mAh/g，很有希望被用作电池负极材料。但是，在电池的充放电过程中，硅基负极材料不断在满嵌锂状态与脱锂状态下转换，而硅基负极材料在满嵌锂状态下体积相对于脱锂状态下体积增大可达约300％至400％，频繁且剧烈的体积变化导致硅基负极材料容易发生破裂和粉化，降低电池寿命。The theoretical gram capacity of silicon is much larger than that of graphite, reaching 4200 mAh/g, and it is promising to be used as a battery anode material. However, during the charging and discharging process of the battery, the silicon-based anode material is continuously converted in the state of full lithium insertion and de-lithium, and the volume of the silicon-based anode material is increased in the state of full lithium insertion relative to the delithiation state. From about 300% to 400%, frequent and severe volume changes cause the silicon-based negative electrode material to be susceptible to cracking and chalking, reducing battery life.

发明内容Summary of the invention

本申请提供一种复合材料及其制备方法，用以解决现有技术中存在的电池中硅负极材料容易破裂和粉化的问题。The present application provides a composite material and a preparation method thereof for solving the problem that the silicon negative electrode material in the battery existing in the prior art is easily broken and pulverized.

第一方面，本申请提供一种复合材料，包括：层状硅内核以及多个石墨烯层，其中，所述层状硅内核包括至少两个硅基材料层，该硅基材料层包括硅或硅的氧化物，如一氧化硅等。相邻两个所述硅基材料层之间具有层间空隙，该层间空隙的大小在相邻两个硅基材料层不同位置处可以不同，且不同的相邻两层的层间空隙的大小也可以不同。石墨烯层位于相邻两个所述硅基材料层的层间空隙中，且每个所述石墨烯层与相邻的两个所述硅基材料层中的一个或两个硅基材料层之间具有空隙。In a first aspect, the present application provides a composite material comprising: a layered silicon core and a plurality of graphene layers, wherein the layered silicon core comprises at least two layers of silicon-based material, the layer of silicon-based material comprising silicon or An oxide of silicon, such as silicon monoxide. There are interlayer voids between two adjacent silicon-based material layers, and the size of the interlayer voids may be different at different positions of two adjacent silicon-based material layers, and different adjacent two layers of interlayer voids The size can also be different. a graphene layer is located in an interlayer gap of two adjacent ones of the silicon-based material layers, and one or two silicon-based material layers of each of the graphene layer and two adjacent ones of the silicon-based material layers There is a gap between them.

上述复合材料的相邻两个硅基材料层之间具有层间空隙，该层间空隙可以抑制复合材料在嵌锂时的膨胀压力，减少复合材料因体积变化较大而破裂或粉化的几率。不仅如此，相邻两个硅基材料层的层间空隙中还填充有石墨烯层，石墨烯层可以层状硅内核进行纵向支撑，提高层状硅内核的强度，防止层状硅内核在反复膨胀收缩后发生结构坍塌。再者，石墨烯还具有优良的导电性也，有助于电子传输，能够提高复合材料的导电性能。The interlayer of the two adjacent silicon-based materials of the composite material has interlayer voids, which can suppress the expansion pressure of the composite material during lithium insertion, and reduce the probability of the composite material being broken or pulverized due to large volume change. . Moreover, the interlayer voids of the adjacent two silicon-based material layers are also filled with a graphene layer, and the graphene layer can be longitudinally supported by the layered silicon core to improve the strength of the layered silicon core and prevent the layered silicon core from being repeated. Structural collapse occurs after expansion and contraction. Furthermore, graphene also has excellent electrical conductivity, contributes to electron transport, and can improve the electrical conductivity of the composite.

在一些可选的实现方式中，还包括覆盖在层状硅内核外表面的石墨烯覆盖层，该石墨烯覆盖层可以进一步提高复合材料的导电性能，而且石墨烯覆盖层良好的柔韧性也能够对复合材料在电池充放电过程的膨胀起到良好的缓冲作用，抑制复合材料破裂和粉化。In some optional implementations, a graphene coating layer covering the outer surface of the layered silicon core layer is further included, the graphene coating layer can further improve the electrical conductivity of the composite material, and the graphene coating layer can also have good flexibility. The composite material has a good buffering effect on the expansion of the battery during charging and discharging, and inhibits the cracking and pulverization of the composite material.

在一些可选的实现方式中，石墨烯层与其相邻的两个硅基材料层中的一个或两个硅基材料层相连，以增强层状硅内核的结构强度以及硅基材料层的层间导电性能。In some alternative implementations, the graphene layer is coupled to one or both of the two silicon-based material layers adjacent thereto to enhance the structural strength of the layered silicon core and the layer of the silicon-based material layer Conductive performance.

在一些可选的实现方式中，相邻的两个硅基材料层相连，以增强层状硅内核的结构强度以及硅基材料层的层间导电性能。In some alternative implementations, adjacent layers of two silicon-based materials are joined to enhance the structural strength of the layered silicon core and the interlayer conductivity of the layer of silicon-based material.

在一些可选的实现方式中，复合材料还包括包覆所述层状硅内核的包覆层，该包覆层将层状硅内核包覆在内部，该包覆层可以为碳包覆层、无机化合物包覆层或有机物包覆层。该包覆层可以减少层状硅内核与电解液的直接接触，减缓电池容量衰减，而且，包覆层为碳包覆层时，还可以提供高效的导电界面，提升电池的功率性能。In some optional implementations, the composite material further includes a cladding layer covering the layered silicon core, the cladding layer coating the layered silicon core inside, the cladding layer may be a carbon coating layer An inorganic compound coating layer or an organic coating layer. The coating layer can reduce the direct contact between the layered silicon core and the electrolyte, and slow down the battery capacity attenuation. Moreover, when the cladding layer is a carbon coating layer, it can also provide a highly efficient conductive interface and improve the power performance of the battery.

在一些可选的实现方式中，在脱锂状态下，层状硅内核110的相邻两个硅基材料层111之间的层间空隙的大小在10纳米(nm)至10微米(μm)范围内，例如，相邻两个硅基材料层111之间的层间空隙可以为10nm、40nm、120nm、660nm、1μm、5μm、8μm、10μm等。上述大小的层间空隙可以让层状硅内核110在脱离状态与嵌锂状态之间转换时，具有较小的体积变化，降低复合材料破裂和粉化的几率。In some alternative implementations, the interlaminar gap between two adjacent silicon-based material layers 111 of the layered silicon core 110 is between 10 nanometers (nm) and 10 micrometers (μm) in the delithiated state. In the range, for example, the interlayer gap between two adjacent silicon-based material layers 111 may be 10 nm, 40 nm, 120 nm, 660 nm, 1 μm, 5 μm, 8 μm, 10 μm, or the like. The inter-layer voids of the above size allow the layered silicon core 110 to have a small volume change when switching between the detached state and the lithium-intercalated state, reducing the probability of cracking and pulverization of the composite.

第二方面，本申请提供一种制备复合材料的方法，包括：将金属硅化物与金属脱除剂进行反应，得到层状硅内核，该金属硅化物可以为成品，也可以由金属与硅基材料反应制备，金属脱除剂可以为乙醇、丙醇、丁醇、异丙醇、CuCl2、SnCl2、HCl等，得到的该层状硅内核包括至少两个硅基材料层，相邻两个所述硅基材料层之间具有层间空隙，所述硅基材料层包括硅或硅的氧化物。然后，在所述层状硅内核上制备多个石墨烯层，石墨烯层位于相邻两个所述硅基材料层的层间空隙中，且所述石墨烯层与其相邻的两个所述硅基材料层中的一个或两个硅基材料层之间具有空隙。其中，石墨烯层可以为一层或多层石墨烯，且不同的石墨烯层的厚度可以不同。In a second aspect, the present application provides a method for preparing a composite material, comprising: reacting a metal silicide with a metal remover to obtain a layered silicon core, which may be a finished product or a metal and a silicon base. The material is prepared by reaction, and the metal removing agent may be ethanol, propanol, butanol, isopropanol, CuCl2, SnCl2, HCl, etc., and the layered silicon core obtained includes at least two layers of silicon-based materials, two adjacent There are inter-layer spaces between the silicon-based material layers, and the silicon-based material layer includes an oxide of silicon or silicon. Then, a plurality of graphene layers are prepared on the layered silicon core, the graphene layer is located in the interlayer gap of two adjacent silicon-based material layers, and the graphene layer is adjacent to the two There is a gap between one or two layers of silicon-based material in the layer of silicon-based material. Wherein, the graphene layer may be one or more layers of graphene, and different graphene layers may have different thicknesses.

采用上述方法制备的复合材料的相邻两个硅基材料层之间具有层间空隙，该层间空隙可以抑制复合材料在嵌锂时的膨胀压力，减少复合材料因体积变化较大而破裂或粉化的几率。不仅如此，相邻两个硅基材料层的层间空隙中还填充有石墨烯层，石墨烯层可以层状硅内核进行纵向支撑，提高层状硅内核的强度，防止层状硅内核在反复膨胀收缩后发生结构坍塌。再者，石墨烯还具有优良的导电性也，有助于电子传输，能够提高复合材料的导电性能。The composite material prepared by the above method has interlayer voids between adjacent two silicon-based material layers, and the interlayer voids can suppress the expansion pressure of the composite material during lithium insertion, and reduce the composite material to be broken due to large volume change or The chance of chalking. Moreover, the interlayer voids of the adjacent two silicon-based material layers are also filled with a graphene layer, and the graphene layer can be longitudinally supported by the layered silicon core to improve the strength of the layered silicon core and prevent the layered silicon core from being repeated. Structural collapse occurs after expansion and contraction. Furthermore, graphene also has excellent electrical conductivity, contributes to electron transport, and can improve the electrical conductivity of the composite.

在一些可选的实现方式中，还在所述层状硅内核的外表面制备石墨烯覆盖层，该石墨烯覆盖层可以进一步提高复合材料的导电性能，而且石墨烯覆盖层良好的柔韧性也能够对复合材料在电池充放电过程的膨胀起到良好的缓冲作用，抑制复合材料破裂和粉化。In some optional implementations, a graphene cap layer is further prepared on the outer surface of the layered silicon core, the graphene cap layer can further improve the electrical conductivity of the composite material, and the graphene cover layer has good flexibility. It can well buffer the expansion of the composite during the charging and discharging process of the battery, and inhibit the cracking and pulverization of the composite.

在一些可选的实现方式中，还包括：在形成有多个石墨烯层的层状硅内核的外表面制备包覆层，所述包覆层将所述层状硅内核包覆在所述包覆层内。所述包覆层将所述层状硅内核包覆在所述包覆层内。该包覆层可以为无定形的碳包覆层，也可以为无机化合物包覆层，如钛酸锂包覆层，还可以为有机物包覆层，如聚苯胺包覆层。该包覆层的制备工艺可以为蒸发、溅射、电镀、化学气相淀积(chemical vapor deposition，CVD)等。该包覆层可以减少层状硅内核与电解液的直接接触，减缓电池容量衰减，而且，包覆层为碳包覆层时还可以提供高效的导电界面，提升电池的功率性能。In some optional implementations, the method further includes: preparing a cladding layer on an outer surface of the layered silicon core layer formed with the plurality of graphene layers, the cladding layer coating the layered silicon core in the Inside the coating. The cladding layer encapsulates the layered silicon core within the cladding layer. The coating layer may be an amorphous carbon coating layer, or may be an inorganic compound coating layer such as a lithium titanate coating layer, or may be an organic coating layer such as a polyaniline coating layer. The preparation process of the coating layer may be evaporation, sputtering, electroplating, chemical vapor deposition (CVD) or the like. The coating layer can reduce the direct contact between the layered silicon core and the electrolyte, and slow down the battery capacity attenuation. Moreover, when the cladding layer is a carbon coating layer, it can also provide a highly efficient conductive interface and improve the power performance of the battery.

在一些可选的实现方式中，还包括：在形成有石墨烯覆盖层的层状硅内核的外表面制备包覆层，所述包覆层将所述层状硅内核包覆在所述包覆层内。所述包覆层将所述层状硅内核包覆在所述包覆层内。该包覆层可以为无定形的碳包覆层，也可以为无机化合物包覆层，如钛酸锂包覆层，还可以为有机物包覆层，如聚苯胺包覆层。该包覆层的制备工艺可以为蒸发、溅射、电镀、CVD等。该包覆层可以减少层状硅内核与电解液的直接接触，减缓电池容量衰减，而且，包覆层为碳包覆层时还可以提供高效的导电界面，提升电池的功率性能。In some optional implementations, the method further includes: preparing a cladding layer on an outer surface of the layered silicon core layer formed with the graphene coating layer, the cladding layer coating the layered silicon core in the package Inside the cladding. The cladding layer encapsulates the layered silicon core within the cladding layer. The coating layer may be an amorphous carbon coating layer, or may be an inorganic compound coating layer such as a lithium titanate coating layer, or may be an organic coating layer such as a polyaniline coating layer. The preparation process of the cladding layer may be evaporation, sputtering, electroplating, CVD, or the like. The coating layer can reduce the direct contact between the layered silicon core and the electrolyte, and slow down the battery capacity attenuation. Moreover, when the cladding layer is a carbon coating layer, it can also provide an efficient conductive interface and improve the power performance of the battery.

在一些可选的实现方式中，采用化学气相沉积CVD工艺在所述层状硅内核的层间空隙中生长石墨烯层。该制备具有孔洞的硅基材料的方法成本较低，效率较高。In some alternative implementations, a graphene layer is grown in the inter-layer voids of the layered silicon core using a chemical vapor deposition CVD process. The method of preparing a silicon-based material having pores is relatively low in cost and high in efficiency.

在一些可选的实现方式中，将制备的石墨烯或石墨烯成品迁移至所述层状硅内核的层间空隙。该制备具有孔洞的硅基材料的方法成本较低，效率较高。In some alternative implementations, the prepared graphene or graphene finished product migrates to the interlaminar voids of the layered silicon core. The method of preparing a silicon-based material having pores is relatively low in cost and high in efficiency.

在一些可选的实现方式中，金属硅化物中的金属包括碱金属或碱土金属。In some alternative implementations, the metal in the metal silicide includes an alkali metal or an alkaline earth metal.

第三方面，本申请提供一种电池，包括：正极、电解液以及负极，正极的电极材料可以为含锂的化合物，如锰酸锂、磷酸铁锂、镍钴锰酸锂等，负极的电极材料为第一方面或第一方面的任意可选方式所述的复合材料，或者，负极的电极材料根据第二方面或第二方面的任意可选方式所述的方法制备，电解液可以为.碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯、碳酸二甲酯、碳酸甲乙酯、五氟化磷以及氢氟酸等。In a third aspect, the present application provides a battery comprising: a positive electrode, an electrolyte, and a negative electrode; and the electrode material of the positive electrode may be a lithium-containing compound, such as lithium manganate, lithium iron phosphate, lithium nickel cobalt manganese oxide, etc. The composite material according to the first aspect or the optional aspect of the first aspect, or the electrode material of the negative electrode is prepared according to the method of any of the second aspect or the second aspect, the electrolyte may be: Ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, phosphorus pentafluoride, hydrofluoric acid, and the like.

第四方面，本申请提供一种改良锂离子电池负极材料的方法，该方法包括：将层状硅内核作为硅负极材料的主体，所谓层状硅内核包括多个硅基材料层，相邻两个所述硅基材料层之间具有层间空隙，所述硅基材料层包括硅或硅的氧化物。该层状硅内核的相邻两层之间的层间空隙可以缓解硅负极材料在嵌锂状态下的膨胀压力，因为硅基材料层在嵌锂后可以向层间空隙扩张，进而减小整个层状硅内核的体积变化，降低复合材料破裂和粉化的几率。进一步，该方法中，还在层状硅内核内部设置多个石墨烯层，每个所述石墨烯层位于相邻两个所述硅基材料层的层间空隙中，且每个所述石墨烯层与相邻的两个所述硅基材料层中的至少一个所述硅基材料层之间具有空隙。层状硅内核的层间空隙中的石墨烯层具有较强的强度，能够给复合材料提供稳固的层间支撑。不仅如此，层状硅内核的层间空隙中的石墨烯层还能够增强硅基材料层111的层间电子传导，增强复合材料的导电性能，进而提高电池的性能。In a fourth aspect, the present application provides a method for improving a negative electrode material of a lithium ion battery, the method comprising: using a layered silicon core as a main body of a silicon negative electrode material, wherein the layered silicon core comprises a plurality of silicon-based material layers, adjacent to two There is an interlayer gap between the layers of the silicon-based material, and the silicon-based material layer includes an oxide of silicon or silicon. The interlayer gap between two adjacent layers of the layered silicon core can alleviate the expansion pressure of the silicon anode material in the lithium intercalation state, because the silicon-based material layer can expand to the interlayer gap after intercalating lithium, thereby reducing the entire The volume change of the layered silicon core reduces the probability of cracking and chalking of the composite. Further, in the method, a plurality of graphene layers are further disposed inside the layered silicon core, each of the graphene layers being located in an interlayer gap of two adjacent ones of the silicon-based material layers, and each of the graphites The olefin layer has a void between at least one of the two of the silicon-based material layers. The graphene layer in the interlaminar voids of the layered silicon core has strong strength and can provide stable interlayer support to the composite. Moreover, the graphene layer in the interlaminar void of the layered silicon core can also enhance the interlayer electron conduction of the silicon-based material layer 111, enhance the electrical conductivity of the composite material, and thereby improve the performance of the battery.

附图说明DRAWINGS

图1为本申请实施例提供的复合材料的结构示意图；1 is a schematic structural view of a composite material provided by an embodiment of the present application;

图2a-图2d为本申请实施例中石墨烯层的示意图；2a-2d are schematic views of a graphene layer in an embodiment of the present application;

图3为复合材料在脱锂状态以及嵌锂状态下的示意图；3 is a schematic view of the composite material in a delithiated state and a lithium intercalation state;

图4为石墨烯覆盖层的示意图；Figure 4 is a schematic view of a graphene cover layer;

图5a-图5b为复合材料的包覆层的示意图；5a-5b are schematic views of a cladding layer of a composite material;

图6为相邻硅基材料层之间层间空隙的示意图；Figure 6 is a schematic view of interlayer voids between adjacent silicon-based material layers;

图7为制备复合材料的方法的流程示意图；7 is a schematic flow chart of a method of preparing a composite material;

图8为层状硅内核的形成过程的示意图；Figure 8 is a schematic view showing a process of forming a layered silicon core;

图9为本申请实施例提供的电池的结构示意图。FIG. 9 is a schematic structural diagram of a battery provided by an embodiment of the present application.

具体实施方式Detailed ways

为了使本申请的目的、技术方案和优点更加清楚，下面将结合附图对本申请作进一步地详细描述。In order to make the objects, technical solutions and advantages of the present application more clear, the present application will be further described in detail below with reference to the accompanying drawings.

本申请中所涉及的多个，是指两个或两个以上。另外，本申请中术语“和/或”，仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。The plurality referred to in the present application means two or more. In addition, the term “and/or” in the present application is merely an association relationship describing an associated object, indicating that there may be three relationships, for example, A and/or B, which may indicate that A exists separately, and A and B exist simultaneously. There are three cases of B alone.

下面先介绍本申请实施例涉及的一些概念。The following refers to some concepts involved in the embodiments of the present application.

石墨烯(graphene)，是一种由碳(C)原子按六边形晶格整齐排布形成的只有一层原子厚度的二维晶体。石墨烯不仅具有优良的力学性能，具有较强的强度，还具有优异的导电性能。Graphene is a two-dimensional crystal with a thickness of one atom formed by a carbon (C) atom arranged neatly in a hexagonal lattice. Graphene not only has excellent mechanical properties, but also has strong strength and excellent electrical conductivity.

化学气相淀积(chemical vapor deposition，CVD)：指把含有构成目标物质的元素的气态反应剂或液态反应剂的蒸气及反应所需其它气体引入反应室，在衬底表面发生化学反应生成薄膜、颗粒的过程。Chemical vapor deposition (CVD): refers to introducing a vapor containing a gaseous reactant or a liquid reactant constituting an element of a target substance and other gases required for the reaction into a reaction chamber, and chemically reacting on the surface of the substrate to form a thin film. The process of particles.

固体电解质界面(solid electrolyte interface，SEI)膜：在液态锂离子电池首次充放电过程中，电极的材料与电解液在固液相界面上发生反应，形成一层覆盖于电极表面的钝化层，该钝化膜能有效地阻止溶剂分子的通过，但锂离子却可以经过该钝化层自由地嵌入和脱出，具有固体电解质的特征，因此这层钝化膜被称为固体电解质界面膜。Solid electrolyte interface (SEI) membrane: During the first charge and discharge of a liquid lithium ion battery, the material of the electrode reacts with the electrolyte at the solid-liquid phase interface to form a passivation layer covering the surface of the electrode. The passivation film can effectively prevent the passage of solvent molecules, but lithium ions can be freely embedded and removed through the passivation layer, and have the characteristics of a solid electrolyte. Therefore, this passivation film is called a solid electrolyte interface film.

图1示出本申请提供的复合材料100的结构，复合材料100包括层状硅内核110和多个石墨烯层120。1 shows the structure of a composite 100 provided by the present application. The composite 100 includes a layered silicon core 110 and a plurality of graphene layers 120.

图1左侧为层状硅内核110的结构，层状硅内核110包括多个硅基材料层111，相邻的两个硅基材料层111之间具有层间空隙。该硅基材料层111可以为硅(Si)层或硅的氧化物层，例如一氧化硅(SiO)层。可选的，硅基材料层111还可以包括二氧化硅，但不全部为二氧化硅，以提高嵌锂能力。在硅基材料层111为Si层时，其厚度可以为一个或多个原子层的厚度，在硅基材料层111为硅的氧化物层时，其厚度可以为一个或多个分子层的厚度，且不同硅基材料层111的厚度可以相同，也可以不同。The left side of FIG. 1 is the structure of the layered silicon core 110, and the layered silicon core 110 includes a plurality of silicon-based material layers 111 with interlayer voids between adjacent two silicon-based material layers 111. The silicon-based material layer 111 may be a silicon (Si) layer or an oxide layer of silicon, such as a silicon oxide (SiO) layer. Alternatively, the silicon-based material layer 111 may further include silicon dioxide, but not all of silicon dioxide to improve lithium intercalation capability. When the silicon-based material layer 111 is a Si layer, the thickness thereof may be the thickness of one or more atomic layers, and when the silicon-based material layer 111 is an oxide layer of silicon, the thickness may be the thickness of one or more molecular layers. The thickness of the different silicon-based material layers 111 may be the same or different.

参见图1右侧，石墨烯层120位于层状硅内核的相邻两个硅基材料层的层间空隙，该石墨烯层的厚度可以为一层，也可以为两层或两层以上。另外，相邻两个硅基材料层之间的一个石墨烯层的厚度可以不均匀，例如，参见图2a至图2b，石墨烯层120的A位置处的厚度较大，A位置处石墨烯可以与上下两个硅基材料层111相连，而石墨烯层120的B位置的厚度较小，B位置处石墨烯可以只与一个硅基材料层111相连。再者，位于不同的硅基材料层之间的石墨烯层的厚度可以相同，也可以不同，例如，参见图2c，石墨烯层120-a位于硅基材料层111-a、111-b之间，石墨烯层120-b位于硅基材料层111-b、111-c之间，石墨烯层120-c位于硅基材料层111-c、111-d之间，石墨烯层120-a的厚度与石墨烯层120-c的厚度相等，且大于石墨烯层120-b的厚度。Referring to the right side of FIG. 1, the graphene layer 120 is located in the interlayer gap of two adjacent silicon-based material layers of the layered silicon core. The graphene layer may have a thickness of one layer or two or more layers. In addition, the thickness of one graphene layer between adjacent two silicon-based material layers may be non-uniform. For example, referring to FIG. 2a to FIG. 2b, the graphene layer 120 has a larger thickness at the A position, and the graphene at the A position. It may be connected to the upper and lower silicon-based material layers 111, and the thickness of the B-site of the graphene layer 120 is small, and the graphene at the B-position may be connected to only one silicon-based material layer 111. Furthermore, the thickness of the graphene layer between different silicon-based material layers may be the same or different. For example, referring to FIG. 2c, the graphene layer 120-a is located in the silicon-based material layers 111-a, 111-b. Meanwhile, the graphene layer 120-b is located between the silicon-based material layers 111-b, 111-c, the graphene layer 120-c is located between the silicon-based material layers 111-c, 111-d, and the graphene layer 120-a The thickness is equal to the thickness of the graphene layer 120-c and greater than the thickness of the graphene layer 120-b.

应理解，石墨烯层120占据层状硅内核110的层间空隙的一部分空间，但并未填满整个层间空隙，层状硅内核110的相邻两个硅基材料层之间仍然具有层间空隙，亦即：每个所述石墨烯层120与相邻的两个硅基材料层111中的至少一个硅基材料层之间具有空隙。It should be understood that the graphene layer 120 occupies a portion of the inter-layer voids of the layered silicon core 110, but does not fill the entire inter-layer voids, and there are still layers between the adjacent two silicon-based material layers of the layered silicon core 110. The inter-space, that is, each of the graphene layer 120 has a gap between at least one of the two adjacent silicon-based material layers 111.

参见图3，在层状硅内核110处于嵌锂状态下时，锂离子嵌入硅基材料层111，硅基材料层111的体积变大，硅基材料层111之间的层间空隙变小，层状硅内核110的层间空隙变小可以减少层状硅内核110整体向外的扩张程度。因此，层状硅内核110结构可以减少复合材料100在脱锂状态-嵌锂状态转换过程中的体积变化，降低复合材料破裂和粉化的几率。另外，层状硅内核110的层间空隙中的石墨烯层120具有较强的强度，能够给复合材料100提供稳固的层间支撑。不仅如此，层状硅内核110的层间空隙中的石墨烯层120还能够增强硅基材料层111的层间电子传导，增强复合材料100的导电性能，进而提高电池的性能。Referring to FIG. 3, when the layered silicon core 110 is in the lithium intercalation state, lithium ions are intercalated into the silicon-based material layer 111, the volume of the silicon-based material layer 111 becomes large, and the interlayer gap between the silicon-based material layers 111 becomes small. The reduced inter-layer voids of the layered silicon core 110 can reduce the overall outward extent of the layered silicon core 110. Therefore, the layered silicon core 110 structure can reduce the volume change of the composite material 100 during the delithiation state-lithium state transition, and reduce the probability of composite cracking and pulverization. In addition, the graphene layer 120 in the interlaminar spaces of the layered silicon core 110 has a strong strength and can provide the composite material 100 with stable interlayer support. Moreover, the graphene layer 120 in the interlaminar spaces of the layered silicon core 110 can also enhance the interlayer electron conduction of the silicon-based material layer 111, enhance the electrical conductivity of the composite material 100, and thereby improve the performance of the battery.

在一些可选的设计中，两个相邻的硅基材料层111之间最多有一个硅基材料层。而在另一些可选的实施例中，两个相邻的硅基材料层111之间可以有一个、两个或两个以上的硅基材料层，如图2d所示，两个硅基材料层之间存在两个石墨烯层，每个石墨烯层依附在一个硅基材料层上。In some alternative designs, there is at most one layer of silicon-based material between two adjacent layers of silicon-based material 111. In still other alternative embodiments, there may be one, two or more layers of silicon-based material between two adjacent layers of silicon-based material 111, as shown in Figure 2d, two silicon-based materials. There are two graphene layers between the layers, each of which is attached to a layer of silicon-based material.

在一些可选的设计中，参见图4，复合材料还包括石墨烯覆盖层121，该石墨烯覆盖层121覆盖在层状硅内核110的外表面。应理解，石墨烯覆盖层121可以覆盖在层状硅内核110的外表面的局部位置，也可以完全覆盖层状硅内核110的外表面。In some alternative designs, referring to FIG. 4, the composite further includes a graphene cap layer 121 overlying the outer surface of the layered silicon core 110. It should be understood that the graphene cap layer 121 may cover a local portion of the outer surface of the layered silicon core 110 or may completely cover the outer surface of the layered silicon core 110.

上述技术方案中，在层状硅内核110的外表面覆盖石墨烯覆盖层121，可以进一步提高层状硅内核110的导电性能，而且石墨烯覆盖层121良好的柔韧性也能够对层状硅内核110在电池充放电过程的膨胀起到良好的缓冲作用，抑制复合材料100破裂和粉化。再者，层状硅内核与电解液直接接触将导致硅与电解液不断产生新的SEI膜，导致电解液消耗殆尽，电池容量迅速衰减，而在层状硅内核110的外表面覆盖石墨烯覆盖层121可以减少层状硅内核与电解液的直接接触，减缓电池容量衰减。In the above technical solution, the outer surface of the layered silicon core 110 is covered with the graphene cover layer 121, which can further improve the conductivity of the layered silicon core 110, and the good flexibility of the graphene cover layer 121 can also be applied to the layered silicon core. The expansion of the battery during charging and discharging of the battery serves as a good buffering effect, inhibiting cracking and chalking of the composite material 100. Furthermore, direct contact of the layered silicon core with the electrolyte results in a continuous generation of a new SEI film between the silicon and the electrolyte, resulting in exhaustion of the electrolyte, rapid decay of the battery capacity, and coverage of the graphene on the outer surface of the layered silicon core 110. The cover layer 121 can reduce the direct contact of the layered silicon core with the electrolyte and slow down the battery capacity attenuation.

在一些可选的设计中，相邻两个硅基材料层111之间可以有一部分相连，以增强层状硅内核110的结构强度以及硅基材料层111的层间导电性能。需要说明的是，为了更好地体现层状硅内核110的层间空隙，在图1至图4以及后面的示意图中，相邻的两个硅基材料层111被简化为相分离。In some alternative designs, a portion of the adjacent two silicon-based material layers 111 may be connected to enhance the structural strength of the layered silicon core 110 and the interlayer conductivity of the silicon-based material layer 111. It should be noted that, in order to better embody the interlaminar voids of the layered silicon core 110, in the schematic views of FIGS. 1 to 4 and the following, the adjacent two silicon-based material layers 111 are simplified to phase separation.

在一些可选的设计中，例如图2a所示，石墨烯层120可以与相邻的上下两层硅基材料层中的一个或两个硅基材料层相连，以增强层状硅内核110的结构强度以及硅基材料层111的层间导电性能。In some alternative designs, such as shown in FIG. 2a, the graphene layer 120 may be connected to one or two of the adjacent upper and lower silicon-based material layers to enhance the layered silicon core 110. Structural strength and interlayer conductivity of the silicon-based material layer 111.

在一些可选的设计中，参见图5a至图5b，复合材料100还包括：包覆层状硅内核110的包覆层130，该包覆层130将层状硅内核110包覆在内。图5a中，层状硅内核110的外表面包覆包覆层130，没有覆盖石墨烯覆盖层121；而在图5b中，层状硅内核110的外表面先覆盖石墨烯覆盖层121，然后，在石墨烯覆盖层121之上，再包覆包覆层130。该包覆层130可以为无定形的碳包覆层，也可以为无机化合物包覆层，如钛酸锂包覆层，还可以为有机物包覆层，如聚苯胺包覆层。需要说明的是，图5a-图5b中包覆层的截面形状简化为圆形，在具体实施时，包覆层的截面形状可以为椭圆形等其他形状，也可以为不规则形状。In some alternative designs, referring to FIGS. 5a-5b, the composite material 100 further includes a cladding layer 130 covering the layered silicon core 110, the cladding layer 130 encasing the layered silicon core 110. In FIG. 5a, the outer surface of the layered silicon core 110 is covered with a cladding layer 130 without covering the graphene cover layer 121; and in FIG. 5b, the outer surface of the layered silicon core 110 is first covered with a graphene cover layer 121, and then On the graphene cover layer 121, the cladding layer 130 is further coated. The coating layer 130 may be an amorphous carbon coating layer, or may be an inorganic compound coating layer, such as a lithium titanate coating layer, or may be an organic coating layer, such as a polyaniline coating layer. It should be noted that the cross-sectional shape of the cladding layer in FIGS. 5 a to 5 b is simplified to a circular shape. In a specific implementation, the cross-sectional shape of the cladding layer may be other shapes such as an elliptical shape, or may be an irregular shape.

上述技术方案中，在层状硅内核110的外表面制备包覆层130，可以减少层状硅内核与电解液的直接接触，减缓电池容量衰减，而且，包覆层130为碳包覆层时，还可以提供高效的导电界面，提升电池的功率性能。In the above technical solution, the coating layer 130 is prepared on the outer surface of the layered silicon core 110, which can reduce the direct contact between the layered silicon core and the electrolyte, and slow down the battery capacity attenuation. Moreover, when the cladding layer 130 is a carbon coating layer. It also provides an efficient conductive interface to enhance the power performance of the battery.

在一些可选的设计中，在脱锂状态下，层状硅内核110的相邻两个硅基材料层111之间的层间空隙的大小在10纳米(nm)至10微米(μm)范围内，例如，相邻两个硅基材料层111之间的层间空隙可以为10nm、40nm、120nm、660nm、1μm、5μm、8μm、10μm等。上述大小的层间空隙可以让层状硅内核110在脱离状态与嵌锂状态之间转换时，具有较小的体积变化，降低复合材料破裂和粉化的几率。In some alternative designs, the interlaminar gap between adjacent two silicon-based material layers 111 of the layered silicon core 110 is in the range of 10 nanometers (nm) to 10 micrometers (μm) in the delithiated state. For example, the interlayer gap between two adjacent silicon-based material layers 111 may be 10 nm, 40 nm, 120 nm, 660 nm, 1 μm, 5 μm, 8 μm, 10 μm, or the like. The inter-layer voids of the above size allow the layered silicon core 110 to have a small volume change when switching between the detached state and the lithium-intercalated state, reducing the probability of cracking and pulverization of the composite.

应理解，相邻两层之间的层间空隙的大小在不同位置处可以不同，如图6所示，相邻的硅基材料层111-e与硅基材料层111-f的层间空隙的大小不是固定值，在位置C处具有最小的层间空隙(Cmin)，在位置D处具有最大的层间空隙(Cmax)。It should be understood that the size of the interlayer gap between two adjacent layers may be different at different positions, as shown in FIG. 6, the interlayer gap between the adjacent silicon-based material layer 111-e and the silicon-based material layer 111-f. The size is not a fixed value, with a minimum inter-layer gap (Cmin) at position C and a maximum inter-layer gap (Cmax) at position D.

本申请实施例提供一种制备复合材料的方法，参见图7，该方法包括：The embodiment of the present application provides a method for preparing a composite material. Referring to FIG. 7, the method includes:

步骤21、将金属硅化物与金属脱除剂进行反应，得到层状硅内核。层状硅内核包括至少两层硅基材料，至少两层硅基材料的相邻两层之间具有层间空隙。该硅基材料包括硅或硅的氧化物中的至少一种，例如，硅基材料可以为硅、一氧化硅中的任意一种，或者硅基材料同时包括硅、二氧化硅、一氧化硅中的两种，或者同时包括三者。 Step 21. The metal silicide is reacted with a metal remover to obtain a layered silicon core. The layered silicon core comprises at least two layers of silicon-based material with inter-layer voids between adjacent two layers of at least two layers of silicon-based material. The silicon-based material includes at least one of silicon or silicon oxide. For example, the silicon-based material may be any one of silicon and silicon monoxide, or the silicon-based material includes silicon, silicon dioxide, and silicon oxide. Two of them, or both.

上述金属硅化物可以为成品，也可以根据金属与硅(或硅的氧化物)之间的反应生成。金属硅化物的制备方法包括但不限于：烧结、蒸发、溅射、电镀、CVD等。金属硅化物中的金属元素可以为碱金属或碱土金属，如Li、Na、Ca、Mg等。在一些实施例中，只使用一种金属制备金属硅化物，例如，将二氧化硅与镁(Mg)混合加热，形成Mg2Si。在另一些实施例中，可以使用两种或以上的金属制备金属硅化物，例如，根据锂、钠与硅形成的Li3NaSi6。The above metal silicide may be a finished product or may be formed according to a reaction between a metal and silicon (or an oxide of silicon). Methods of preparing metal silicides include, but are not limited to, sintering, evaporation, sputtering, electroplating, CVD, and the like. The metal element in the metal silicide may be an alkali metal or an alkaline earth metal such as Li, Na, Ca, Mg or the like. In some embodiments, the metal silicide is prepared using only one metal, for example, by mixing silica with magnesium (Mg) to form Mg2Si. In other embodiments, metal silicides may be prepared using two or more metals, for example, Li3NaSi6 formed from lithium, sodium, and silicon.

金属脱除剂用于与金属硅化物发生脱金属反应，金属脱除剂根据金属硅化物的种类不同而可以不同。例如，当金属硅化物为锂的硅化物(LiSix)时，金属脱除剂为化学脱锂试剂，包括但不限于乙醇、丙醇、丁醇、异丙醇等。当金属硅化物为硅化钙(CaSi2)时，金属脱除剂可以为氧化性试剂或酸溶液，包括但不限于CuCl2、SnCl2、HCl等。The metal remover is used for demetallization reaction with the metal silicide, and the metal remover may be different depending on the type of the metal silicide. For example, when the metal silicide is a lithium silicide (LiSix), the metal remover is a chemical delithiation reagent including, but not limited to, ethanol, propanol, butanol, isopropanol, and the like. When the metal silicide is calcium silicide (CaSi2), the metal remover may be an oxidizing agent or an acid solution including, but not limited to, CuCl2, SnCl2, HCl, and the like.

金属硅化物与金属脱除剂在不同的反应介质中反应，可以得到不同氧化态的硅基材料，例如，当反应介质为醇类时，硅化钙与金属脱除剂反应可以得到二氧化硅之外的硅的其他氧化物，表示为SiOx；当反应介质为熔盐时，硅化钙与金属脱除剂进行反应得到纯Si。The metal silicide and the metal remover react in different reaction media to obtain silicon-based materials in different oxidation states. For example, when the reaction medium is an alcohol, the calcium silicide reacts with the metal remover to obtain silica. The other oxide of the outer silicon is represented by SiOx; when the reaction medium is a molten salt, the calcium silicide is reacted with the metal remover to obtain pure Si.

由于该硅基材料由从金属硅化物中脱去金属形成，所有硅基材料中存在大量脱去金属所形成的空隙，使得硅基材料呈现层状。下面以MgSi为例，介绍MgSi脱除金属后，形成层状硅内核的机制。图8示出MgSi的晶胞结构，其中，Si粒子形成面心立方结构，Mg粒子形成简立方结构，整个MgSi的晶胞分可以为a～e五层。MgSi在与金属脱除剂反应后，b层与d层的Mg粒子被脱除，a层与c层之间以及c层与e层之间的间隙较大，即形成层间空隙。应理解，上述机制为理论上阐述层状硅内核的形成机制，由于制备的金属硅化物的晶胞结构存在各种畸变(如线缺陷、面缺陷以及体缺陷等)，金属硅化物在脱除金属后所形成的层状硅内核的不同硅基材料层的厚度可以不同，不同的相邻硅基材料层之间的层间空隙的大小也可以不同。Since the silicon-based material is formed by removing metal from the metal silicide, a large amount of voids formed by the removal of the metal exist in all of the silicon-based materials, so that the silicon-based material is layered. Taking MgSi as an example, the mechanism of forming a layered silicon core after removing metal from MgSi is described. Fig. 8 shows a unit cell structure of MgSi in which Si particles form a face-centered cubic structure, Mg particles form a simple cubic structure, and the unit cell of the entire MgSi may have a layer of a to e. After the MgSi is reacted with the metal removing agent, the Mg particles of the b layer and the d layer are removed, and the gap between the a layer and the c layer and between the c layer and the e layer is large, that is, an interlayer gap is formed. It should be understood that the above mechanism theoretically explains the formation mechanism of the layered silicon core, and the metal silicide is removed due to various distortions (such as line defects, surface defects, and body defects) in the unit cell structure of the prepared metal silicide. The thickness of the different silicon-based material layers of the layered silicon core formed after the metal may be different, and the size of the interlayer gaps between different adjacent silicon-based material layers may also be different.

在将层状硅内核作为电池的负极材料时，层状硅内核的大量层间空隙能够缓减负极材料在嵌锂(或电池正极释放的其他离子)状态下的膨胀压力，减小充放电过程中的电池负极材料体积的变化，有效避免电池负极材料的粉化，提高电池负极材料的使用寿命。When the layered silicon core is used as the negative electrode material of the battery, a large number of interlayer voids of the layered silicon core can reduce the expansion pressure of the anode material in the state of lithium insertion (or other ions released from the positive electrode of the battery), and reduce the charge and discharge process. The change of the volume of the battery anode material in the battery effectively avoids the powdering of the battery anode material and improves the service life of the battery anode material.

步骤22，在层状硅内核上制备多个石墨烯层，石墨烯层位于相邻两个硅基材料层的层间空隙中，且石墨烯层与相邻的两个硅基材料层中的至少一个硅基材料层之间具有空隙。 Step 22, preparing a plurality of graphene layers on the layered silicon core, the graphene layer being located in the interlayer gap of the adjacent two silicon-based material layers, and the graphene layer and the adjacent two silicon-based material layers There is a gap between the at least one layer of silicon-based material.

本申请实施例中，可以通过多种方式在层状硅内核的层间空隙中制备石墨烯层，包括但不限于以下方式：In the embodiments of the present application, the graphene layer can be prepared in the inter-layer voids of the layered silicon core by various means, including but not limited to the following manners:

方式1，在层状硅内核的层间空隙中原位生长石墨烯层。In the first embodiment, the graphene layer is grown in situ in the interlayer void of the layered silicon core.

如采用CVD工艺在层状硅内核的层间空隙中生长石墨烯，具体过程可以为：对层状硅内核进行加热，升温至设定温度后，持续通入氢气H ₂和气态碳源，并保持一段时间，然后关闭气态碳源，并通入氩Ar气冷却，便可在层状硅内核的层间空隙中形成石墨烯层。其中，气态碳源可以为含碳的气态烃类物质，包括但不限于甲烷、乙烷、丙烷、乙烯、丙烯、乙炔等。 If the graphene is grown in the interlayer void of the layered silicon core by a CVD process, the specific process may be: heating the layered silicon core, heating to a set temperature, continuously introducing hydrogen H ₂ and a gaseous carbon source, and The graphene layer is formed in the interlayer voids of the layered silicon core by holding it for a while, then turning off the gaseous carbon source and cooling it with argon Ar gas. The gaseous carbon source may be a gaseous hydrocarbon containing carbon, including but not limited to methane, ethane, propane, ethylene, propylene, acetylene, and the like.

方式2，将已经制备好的层状石墨烯迁移至层状硅内核的层间空隙中，在层状硅内核的层间空隙中形成石墨烯层。例如，将生长在其他衬底上的石墨烯浸入溶液内，例如酒精，异丙醇胺(Isopropanolamine，IPA)等溶剂，然后将长有石墨烯的衬底腐蚀掉，在液相中将石墨烯迁移至层状硅内核的层间空隙中。In the second embodiment, the layered graphene which has been prepared is migrated into the interlayer gap of the layered silicon core to form a graphene layer in the interlayer gap of the layered silicon core. For example, graphene grown on other substrates is immersed in a solution, such as alcohol, isopropanolamine (IPA), etc., and then the graphene-rich substrate is etched away, and graphene is precipitated in the liquid phase. Migrating into the inter-layer voids of the layered silicon core.

上述技术方案中，制备形成层状硅内核，利用层状硅内核的层间空隙有效抑制复合材料在嵌锂时的膨胀压力，减小充放电过程中的复合材料体积的变化，提高电池负极材料的使用寿命。不仅如此，还在层状硅内核的层间空隙中填充石墨烯，利用石墨烯对硅基材料的层间进行支撑，提高层状硅内核的强度，防止层状硅内核在反复膨胀收缩后发生结构坍塌。再者，石墨烯具有优良的导电性也，有助于电子传输，能够提高复合材料的导电性能。In the above technical solution, a layered silicon core is prepared, and the interlayer void of the layered silicon core is used to effectively suppress the expansion pressure of the composite during lithium insertion, reduce the volume change of the composite during charge and discharge, and improve the battery anode material. The service life. In addition, graphene is filled in the interlaminar spaces of the layered silicon core, and the layers of the silicon-based material are supported by graphene to increase the strength of the layered silicon core and prevent the layered silicon core from undergoing repeated expansion and contraction. The structure collapsed. Furthermore, graphene has excellent electrical conductivity, contributes to electron transport, and can improve the electrical conductivity of the composite.

作为一种可选的方式，除了在层状硅内核的层间空隙中制备石墨烯层之外，还可以在层状硅内核的外表面制备石墨烯覆盖层。例如，在采用CVD工艺生长石墨烯时，石墨烯可以生长在层状硅内核的层间空隙以及层状硅内核的外表面。又例如，在采用迁移的方式将石墨烯迁移至层状硅内核的层间空隙时，还可以将一部分石墨烯迁移至层状硅内核的外表面。As an alternative, in addition to preparing the graphene layer in the interlaminar voids of the layered silicon core, a graphene cap layer may be prepared on the outer surface of the layered silicon core. For example, when graphene is grown by a CVD process, graphene can be grown on the interlaminar voids of the layered silicon core and the outer surface of the layered silicon core. For another example, when the graphene is migrated to the interlayer gap of the layered silicon core by migration, a part of the graphene may be migrated to the outer surface of the layered silicon core.

上述技术方案中，在层状硅内核的外表面形成石墨烯覆盖层，可以进一步提高层状硅内核的导电性能，而且位于层状硅内核外表面的石墨烯覆盖层具有良好的柔韧性，能够对层状硅内核的膨胀起到良好的缓冲作用。In the above technical solution, a graphene coating layer is formed on the outer surface of the layered silicon core, which can further improve the conductivity of the layered silicon core, and the graphene coating layer on the outer surface of the layered silicon core has good flexibility and can It has a good buffering effect on the expansion of the layered silicon core.

作为一种可选的方式，在步骤22之后，还包括：As an optional manner, after step 22, the method further includes:

步骤23，在层状硅内核的外表面制备包覆层，该包覆层将层状硅内核包覆在内。该包覆层可以为无定形的碳包覆层，也可以为无机化合物包覆层，如钛酸锂包覆层，还可以为有机物包覆层，如聚苯胺包覆层。In step 23, a cladding layer is prepared on the outer surface of the layered silicon core, which coats the layered silicon core. The coating layer may be an amorphous carbon coating layer, or may be an inorganic compound coating layer such as a lithium titanate coating layer, or may be an organic coating layer such as a polyaniline coating layer.

以碳包覆层为例，本申请实施例中可以采用多种方式制备碳包覆层，包括但不限于：蒸发、溅射、电镀、CVD等。例如，将步骤22形成的层状硅-石墨烯复合材料与碳源混合，在高温下裂解，在层状硅-石墨烯复合材料的外表面形成碳包覆层。其中，所述的碳源为气态碳源、液态碳源或固态碳源，其中，气态碳源包括但不限于甲烷、乙烷、乙烯、乙炔、丙烯、一氧化碳等；液态碳源包括但不限于甲醇、乙醇、正己烷、环己烷、苯、甲苯、二甲苯等；固态碳源包括但不限于聚乙烯、聚丙烯、聚氯乙烯、聚偏氟乙烯、聚丙烯腈、聚苯乙烯、环氧树脂、酚醛树脂、葡萄糖、果糖、蔗糖、麦芽糖、煤焦油沥青、石油沥青等。Taking the carbon coating layer as an example, the carbon coating layer can be prepared in various manners in the embodiments of the present application, including but not limited to: evaporation, sputtering, electroplating, CVD, and the like. For example, the layered silicon-graphene composite material formed in step 22 is mixed with a carbon source and cracked at a high temperature to form a carbon coating layer on the outer surface of the layered silicon-graphene composite material. Wherein, the carbon source is a gaseous carbon source, a liquid carbon source or a solid carbon source, wherein the gaseous carbon source includes but is not limited to methane, ethane, ethylene, acetylene, propylene, carbon monoxide, etc.; the liquid carbon source includes but is not limited to Methanol, ethanol, n-hexane, cyclohexane, benzene, toluene, xylene, etc.; solid carbon sources include, but are not limited to, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polyacrylonitrile, polystyrene, rings Oxygen resin, phenolic resin, glucose, fructose, sucrose, maltose, coal tar pitch, petroleum pitch, and the like.

应理解，步骤23还可以在层状硅内核的外表面制备石墨烯覆盖层之后执行。It should be understood that step 23 can also be performed after the graphene cap layer is prepared on the outer surface of the layered silicon core.

上述技术方案中，在层状硅内核的外表面制备包覆层，可以固化层状硅内核，避免层状硅内核与电解液直接接触，减少副反应，防止长期循环过程中硅的粉化，进一步提高循环性能。另外，在采用碳包覆层包覆层状硅内核时，还可以提供高效的导电界面，提升功率性能。In the above technical solution, a coating layer is prepared on the outer surface of the layered silicon core to solidify the layered silicon core, thereby avoiding direct contact between the layered silicon core and the electrolyte, reducing side reactions and preventing powdering of silicon during long-term circulation. Further improve cycle performance. In addition, when a layered silicon core is coated with a carbon coating, an efficient conductive interface can be provided to improve power performance.

在一些可选的设计中，两个相邻的硅基材料层111之间最多有一个硅基材料层。而在另一些可选的实施例中，两个相邻的硅基材料层111之间可以有两个或两个以上的硅基材料层。In some alternative designs, there is at most one layer of silicon-based material between two adjacent layers of silicon-based material 111. In still other alternative embodiments, there may be two or more layers of silicon-based material between two adjacent layers of silicon-based material 111.

下面介绍制备上述复合材料的几种可能的应用实例。Several possible application examples for preparing the above composite materials are described below.

应用实例1、采用硅锂化合物前驱体制备复合材料。Application Example 1. A composite material was prepared using a silicon lithium compound precursor.

步骤一，制备硅锂化合物前驱体：将化学计量比的硅Si块与锂Li带(考虑到锂Li的蒸发损失，Li需要过量7％)在氩气Ar环境中通过电弧熔化进行反应，生成Li ₁₂Si ₇化合物。当冷却下来以后，将得到的块状物在充满Ar氩气的手套箱中用研钵研磨成粉末。 Step 1: Preparation of a lithium-lithium compound precursor: a stoichiometric ratio of a silicon Si block to a lithium Li band (in consideration of evaporation loss of lithium Li, Li requires an excess of 7%) is reacted by arc melting in an Ar gas environment to generate Li ₁₂ Si ₇ compound. After cooling down, the resulting cake was ground into a powder in a mortar box filled with Ar argon.

步骤二，制备无定型层状硅：取上述Li ₁₂Si ₇粉末1.0g置于装有磁力搅拌的三颈烧瓶中，放入充满Ar气的手套箱。烧瓶中加入120mL乙醇，持续搅拌，反应数个小时，将产物转移入布氏漏斗中用滤纸过滤，滤渣用蒸馏水和1M HCl分别清洗三次，再用蒸馏水洗至中性，得到黑色不溶于水的产物。产物在Ar气保护下在管式炉中120℃加热3h，得到无定型层状硅材料。 Step 2: Preparation of amorphous layered silicon: 1.0 g of the above Li ₁₂ Si ₇ powder was placed in a three-necked flask equipped with magnetic stirring, and placed in a glove box filled with Ar gas. 120 mL of ethanol was added to the flask, stirring was continued for several hours, and the product was transferred into a Buchner funnel and filtered with a filter paper. The filter residue was washed three times with distilled water and 1 M HCl, and then washed with distilled water until neutral to obtain a black water-insoluble solution. product. The product was heated at 120 ° C for 3 h in a tube furnace under the protection of Ar gas to obtain an amorphous layered silicon material.

步骤三，制备层状硅-石墨烯复合材料：将得到的无定型层状硅材料置于干净的石英舟中，并转移至炉中，通入保护气体(如氢氩混合气)，以20℃/min的速率升至1000℃，维持20min；然后停止通入保护气体，并通入碳源气体(如甲烷)，反应30～120min，反应完成；在保护气氛下冷却至室温，得到层状硅-石墨烯复合材料。Step 3: preparing a layered silicon-graphene composite material: placing the obtained amorphous layered silicon material in a clean quartz boat, transferring it to a furnace, and introducing a shielding gas (such as a hydrogen-argon mixed gas) to 20 The rate of °C/min is raised to 1000 °C for 20 min; then the protective gas is stopped, and a carbon source gas (such as methane) is introduced, and the reaction is completed for 30-120 min. The reaction is completed; the mixture is cooled to room temperature under a protective atmosphere to obtain a layered layer. Silicon-graphene composite.

应用实例2、采用硅钙化合物前驱体制备复合材料。Application Example 2: A composite material was prepared using a silicon calcium compound precursor.

步骤一，制备硅钙化合物前驱体：将纯钙屑与纯硅粉混合均匀，放在硬质素烧瓷舟中，迅速将瓷舟放入石英反应管内，通入CO ₂，瓷舟处已加热到1000℃，只需几秒钟，混合物熔融，反应随之激烈进行。取出瓷舟，生成物CaSi即刻凝结，得到有金属光泽的铅灰色多孔块状物CaSi，将其粉碎。将CaSi与计算量的Si粉混合均匀，放在镍舟中，在H ₂气流中加热1000℃。反应的最后阶段进行缓慢，需要加热15h，即可得到CaSi ₂。 Step one: preparing a precursor of a calcium-calcium compound: mixing the pure calcium powder with the pure silicon powder uniformly, placing it in a hard-burning porcelain boat, rapidly placing the porcelain boat into the quartz reaction tube, and introducing the CO ₂ , the porcelain boat has been When heated to 1000 ° C, it takes only a few seconds for the mixture to melt and the reaction proceeds intensely. The porcelain boat was taken out, and the product CaSi was immediately condensed to obtain a metallic gray lead-colored porous mass CaSi, which was pulverized. CaSi was mixed uniformly with a calculated amount of Si powder, placed in a nickel boat, and heated at 1000 ° C in a H ₂ gas stream. The final stage of the reaction proceeds slowly and requires heating for 15 h to obtain CaSi ₂ .

步骤二，制备无定型层状硅基材料，其中，步骤一制备的CaSi ₂与金属脱除剂在不同的反应介质中反应，可以得到不同氧化态的硅基材料，包括但不限于以下方式： Step 2, preparing an amorphous layered silicon-based material, wherein the CaSi ₂ prepared in the first step and the metal removing agent are reacted in different reaction media to obtain silicon-based materials of different oxidation states, including but not limited to the following manners:

方式a、制备无定型层状二氧化硅SiO ₂：将0.2g CaSi ₂与20mL 0.2M CuCl ₂水溶液混合，在室温下搅拌2h。所得产物过滤，用水和乙醇洗涤，然后80℃真空干燥24h。生成的Cu纳米颗粒用CuCl ₂水溶液除去，得到层状结构的无定型SiO ₂。反应式如下： Mode a, Preparation of Amorphous Layered Silica SiO ₂ : 0.2 g of CaSi _{2 was} mixed with 20 mL of a 0.2 M CuCl ₂ aqueous solution, and stirred at room temperature for 2 hours. The product obtained was filtered, washed with water and ethanol, then dried at 80 ° C for 24h. The resulting Cu nanoparticles were removed with a CuCl ₂ aqueous solution to obtain a layered amorphous SiO ₂ . The reaction formula is as follows:

CaSi ₂+CuCl ₂→CaCl ₂+2Si+Cu； CaSi ₂ +CuCl ₂ →CaCl ₂ +2Si+Cu;

2Si+4H ₂O→2SiO ₂+4H ₂。 2Si+4H ₂ O→2SiO ₂ +4H ₂ .

方式b、制备无定型层状SiO _x：将0.2g CaSi2与40mL 0.1M SnCl2乙醇溶液混合，在60℃下搅拌反应10h。所得产物过滤，用乙醇洗涤，然后80℃真空干燥24h。生成的Sn纳米颗粒用HCl乙醇溶液除去，得到层状结构的无定型SiO _x。反应式如下： Method b, Preparation of amorphous layered SiO _x : 0.2 g of CaSi 2 was mixed with 40 mL of 0.1 M SnCl 2 ethanol solution, and the reaction was stirred at 60 ° C for 10 h. The product obtained was filtered, washed with ethanol and dried under vacuum at 80 ° C for 24 h. Sn nanoparticles resulting solution was removed with HCl in ethanol to give the amorphous SiO _x layer structure. The reaction formula is as follows:

CaSi ₂+SnCl ₂→2Si+CaCl ₂+Sn； CaSi ₂ +SnCl ₂ →2Si+CaCl ₂ +Sn;

Si+CH ₃CH ₂OH→SiO _x+reduzate，式中reduzate表示还原沉积物。 Si+CH ₃ CH ₂ OH→SiO _x + reduzate, where reduzate represents a reduced deposit.

方式c、制备无定型层状Si：将1g CaSi ₂/SnCl ₂(摩尔比1:1.5)与10g LiCl/KCl(摩尔比59:41)混合，在充满Ar气的手套箱中研磨均匀，得到的粉末置于陶瓷坩埚中在Ar气保护下400℃烧结5h。所得产物用乙醇洗涤，然后80℃真空干燥24h。生成的锡Sn纳米颗粒用HCl乙醇溶液除去，得到层状结构的无定型硅Si。反应是如下： Method c, preparing amorphous layered Si: 1 g of CaSi ₂ /SnCl ₂ (molar ratio 1:1.5) was mixed with 10 g of LiCl/KCl (molar ratio 59:41), and uniformly ground in a glove box filled with Ar gas to obtain The powder was placed in a ceramic crucible and sintered at 400 ° C for 5 h under Ar gas protection. The obtained product was washed with ethanol and then dried under vacuum at 80 ° C for 24 h. The resulting tin Sn nanoparticles were removed with a solution of HCl in ethanol to obtain a layered amorphous Si. The response is as follows:

CaSi ₂+SnCl ₂→2Si+CaCl ₂+Sn。 CaSi ₂ +SnCl ₂ →2Si+CaCl ₂ +Sn.

3)制备层状硅-石墨烯复合材料：将步骤二中得到的无定型层状硅材料置于干净的石英舟中，并转移至炉中，通入保护气体(如氢氩混合气)，以20℃/min的速率升至1000℃，维持20min；然后停止通入保护气体，并通入碳源气体(如甲烷)，反应30～120min，反应完成；在保护气氛下冷却至室温，得到层状硅-石墨烯复合材料。3) Preparation of layered silicon-graphene composite material: the amorphous layered silicon material obtained in step 2 is placed in a clean quartz boat, and transferred to a furnace, and a protective gas (such as a mixture of hydrogen and argon) is introduced. Raise to 1000 ° C at a rate of 20 ° C / min, for 20 min; then stop the introduction of shielding gas, and pass a carbon source gas (such as methane), the reaction is 30 ~ 120min, the reaction is completed; cooled to room temperature under a protective atmosphere, Layered silicon-graphene composite.

上述制备复合材料的工艺简单、成本较低，且制备的层状硅-石墨烯复合材料在用作电池负极时，不仅具有较强的强度以及导电性能，而且在电池充放电过程中体积变化较小，结构稳定、使用寿命较长。The above process for preparing the composite material is simple and the cost is low, and the prepared layered silicon-graphene composite material not only has strong strength and electrical conductivity when used as a battery negative electrode, but also has a volume change during charge and discharge of the battery. Small, stable structure and long service life.

图9示出本申请实施例提供的一种电池，包括：壳体301、正极302、负极303以及电解液304。其中，正极302、负极303以及电解液304容置与壳体301内。上述正极302的电极材料可以为含锂的化合物，如锰酸锂、磷酸铁锂、镍钴锰酸锂等。上述负极303的电极材料为前述复合材料100，或者，负极303的电极材料采用前述步骤21～步骤22或步骤21～步骤23的方法制备。在电池充电时，正极302释放阳离子，如锂离子，正极释放的锂离子通过电解液移动至负极303，嵌入负极材料。反之，在电池放电时，负极303释放阳离子，阳离子通过电解液移动至正极302，嵌入正极材料。上述电解液304可以为.碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯、碳酸二甲酯、碳酸甲乙酯、五氟化磷以及氢氟酸等。应理解，电池还可以包括隔膜305、引出电极等结构。FIG. 9 shows a battery provided by an embodiment of the present application, including a housing 301, a positive electrode 302, a negative electrode 303, and an electrolyte 304. The positive electrode 302, the negative electrode 303, and the electrolyte 304 are housed in the casing 301. The electrode material of the above positive electrode 302 may be a lithium-containing compound such as lithium manganate, lithium iron phosphate, lithium nickel cobalt manganese oxide or the like. The electrode material of the negative electrode 303 is the composite material 100, or the electrode material of the negative electrode 303 is prepared by the above steps 21 to 22 or steps 21 to 23. When the battery is charged, the positive electrode 302 releases a cation such as lithium ion, and the lithium ion released from the positive electrode moves to the negative electrode 303 through the electrolyte to be embedded in the negative electrode material. On the contrary, when the battery is discharged, the anode 303 releases the cation, and the cation moves to the cathode 302 through the electrolyte to be embedded in the cathode material. The electrolyte 304 may be ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, phosphorus pentafluoride, hydrofluoric acid or the like. It should be understood that the battery may also include a structure such as a diaphragm 305, an extraction electrode, and the like.

由于制备负极303的复合材料100处于嵌锂状态下时，锂离子嵌入硅基材料层111，硅基材料层111的体积变大，硅基材料层111之间的层间空隙变小，层状硅内核110的层间空隙变小可以减少层状硅内核110整体向外的扩张程度。因此，层状硅内核110结构可以减少复合材料100在脱锂状态-嵌锂状态转换过程中的体积变化，降低复合材料破裂和粉化的几率。另外，层状硅内核110的层间空隙中的石墨烯层120具有较强的强度，能够给复合材料100提供稳固的层间支撑。不仅如此，层状硅内核110的层间空隙中的石墨烯层120还能够增强硅基材料层111的层间电子传导，增强复合材料100的导电性能，进而提高电池的性能。Since the composite material 100 for preparing the anode 303 is in the lithium intercalation state, lithium ions are intercalated into the silicon-based material layer 111, the volume of the silicon-based material layer 111 becomes large, and the inter-layer gap between the silicon-based material layers 111 becomes small, and the layer is The reduced inter-layer voids of the silicon core 110 can reduce the overall outward extent of the layered silicon core 110. Therefore, the layered silicon core 110 structure can reduce the volume change of the composite material 100 during the delithiation state-lithium state transition, and reduce the probability of composite cracking and pulverization. In addition, the graphene layer 120 in the interlaminar spaces of the layered silicon core 110 has a strong strength and can provide the composite material 100 with stable interlayer support. Moreover, the graphene layer 120 in the interlaminar spaces of the layered silicon core 110 can also enhance the interlayer electron conduction of the silicon-based material layer 111, enhance the electrical conductivity of the composite material 100, and thereby improve the performance of the battery.

本申请实施例提供一种改良锂离子电池的硅负极材料的方法，以解决硅负极材料容易破裂和粉化的问题。该方法为：将层状硅内核作为硅负极材料的主体，所谓层状硅内核包括多个硅基材料层，相邻两个所述硅基材料层之间具有层间空隙，所述硅基材料层包括硅或硅的氧化物。该层状硅内核的相邻两层之间的层间空隙可以缓解硅负极材料在嵌锂状态下的膨胀压力，因为硅基材料层在嵌锂后可以向层间空隙扩张，进而减小整个层状硅内核的体积变化，降低复合材料破裂和粉化的几率。进一步，该方法中，还在层状硅内核内部设置多个石墨烯层，每个所述石墨烯层位于相邻两个所述硅基材料层的层间空隙中，且每个所述石墨烯层与相邻的两个所述硅基材料层中的至少一个硅基材料层之间具有空隙。层状硅内核的层间空隙中的石墨烯层具有较强的强度，能够给复合材料提供稳固的层间支撑。不仅如此，层状硅内核的层间空隙中的石墨烯层还能够增强硅基材料层111的层间电子传导，增强复合材料的导电性能，进而提高电池的性能。The embodiment of the present application provides a method for improving a silicon negative electrode material of a lithium ion battery to solve the problem that the silicon negative electrode material is easily broken and pulverized. The method comprises: using a layered silicon core as a main body of a silicon anode material, wherein the layered silicon core comprises a plurality of silicon-based material layers, and between the two adjacent silicon-based material layers, an interlayer gap, the silicon base The material layer includes an oxide of silicon or silicon. The interlayer gap between two adjacent layers of the layered silicon core can alleviate the expansion pressure of the silicon anode material in the lithium intercalation state, because the silicon-based material layer can expand to the interlayer gap after intercalating lithium, thereby reducing the entire The volume change of the layered silicon core reduces the probability of cracking and chalking of the composite. Further, in the method, a plurality of graphene layers are further disposed inside the layered silicon core, each of the graphene layers being located in an interlayer gap of two adjacent ones of the silicon-based material layers, and each of the graphites The olefin layer has a void between at least one of the two adjacent silicon-based material layers. The graphene layer in the interlaminar voids of the layered silicon core has strong strength and can provide stable interlayer support to the composite. Moreover, the graphene layer in the interlaminar void of the layered silicon core can also enhance the interlayer electron conduction of the silicon-based material layer 111, enhance the electrical conductivity of the composite material, and thereby improve the performance of the battery.

以上，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。The above is only a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto, and any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present application, and should cover Within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of protection of the claims.

Claims

一种复合材料，其特征在于，包括：A composite material characterized by comprising:

层状硅内核，所述层状硅内核包括多个硅基材料层，相邻两个所述硅基材料层之间具有层间空隙，所述硅基材料层包括硅或硅的氧化物；a layered silicon core comprising a plurality of layers of a silicon-based material having interlayer voids between two adjacent layers of the silicon-based material, the layer of silicon-based material comprising an oxide of silicon or silicon;

相邻两个所述硅基材料层的层间空隙中置有石墨烯层，所述石墨烯层与相邻的两个所述硅基材料层中的至少一个所述硅基材料层之间具有空隙。a graphene layer is disposed in an interlayer gap of two adjacent silicon-based material layers, and between the graphene layer and at least one of the two adjacent ones of the silicon-based material layers Has a gap.
根据权利要求1所述的复合材料，其特征在于，还包括：The composite material of claim 1 further comprising:

石墨烯覆盖层，覆盖在所述层状硅内核的外表面。A graphene overlay covering the outer surface of the layered silicon core.
根据权利要求1或2所述的复合材料，其特征在于，所述石墨烯层与对应的相邻的两个所述硅基材料层中的至少一个所述硅基材料层相连。The composite material according to claim 1 or 2, wherein the graphene layer is connected to at least one of the corresponding two of the silicon-based material layers.
根据权利要求1至3任一项所述的复合材料，其特征在于，还包括：The composite material according to any one of claims 1 to 3, further comprising:

包覆层，用于将所述层状硅内核包覆在内。a cladding layer for coating the layered silicon core.
根据权利要求1至4任一项所述的复合材料，其特征在于，相邻两个所述硅基材料层之间的层间空隙的大小在10nm～10μm范围内。The composite material according to any one of claims 1 to 4, wherein the size of the interlayer gap between two adjacent silicon-based material layers is in the range of 10 nm to 10 μm.
一种制备复合材料的方法，其特征在于，包括：A method of preparing a composite material, comprising:

将金属硅化物与金属脱除剂进行反应得到层状硅内核，所述层状硅内核包括至少两个硅基材料层，相邻两个所述硅基材料层之间具有层间空隙，所述硅基材料层包括硅或硅的氧化物；The metal silicide is reacted with a metal stripper to obtain a layered silicon core, the layered silicon core comprising at least two layers of silicon-based material, and between two adjacent layers of the silicon-based material having interlayer voids The silicon-based material layer comprises an oxide of silicon or silicon;

在所述层状硅内核上制备多个石墨烯层，所述石墨烯层位于相邻两个所述硅基材料层的层间空隙中，且所述石墨烯层与相邻的两个所述硅基材料层中的至少一个所述硅基材料层之间具有空隙。Preparing a plurality of graphene layers on the layered silicon core, the graphene layer being located in interlayer voids of two adjacent ones of the silicon-based material layers, and the graphene layer and two adjacent ones There is a gap between at least one of the silicon-based material layers in the silicon-based material layer.
根据权利要求6所述的方法，其特征在于，还包括：The method of claim 6 further comprising:

在所述层状硅内核的外表面制备石墨烯覆盖层。A graphene cap layer is prepared on the outer surface of the layered silicon core.
根据权利要求6所述的方法，其特征在于，还包括：The method of claim 6 further comprising:

在形成有所述多个石墨烯层的层状硅内核的外表面制备包覆层，所述包覆层将所述层状硅内核包覆在所述包覆层内。A coating layer is prepared on an outer surface of the layered silicon core having the plurality of graphene layers formed, the cladding layer coating the layered silicon core in the cladding layer.
根据权利要求7所述的方法，其特征在于，还包括：The method of claim 7 further comprising:

在形成有所述石墨烯覆盖层的层状硅内核的外表面制备包覆层，所述包覆层将所述层状硅内核包覆在所述包覆层内。A coating layer is prepared on an outer surface of the layered silicon core layer on which the graphene coating layer is formed, the cladding layer coating the layered silicon core in the cladding layer.
根据权利要求6至9任一项所述的方法，其特征在于，在所述层状硅内核上制备多个石墨烯层，包括：The method according to any one of claims 6 to 9, wherein preparing a plurality of graphene layers on the layered silicon core comprises:

采用化学气相沉积CVD工艺在所述层状硅内核上生长多个石墨烯层，所述石墨烯层位于相邻两个所述硅基材料层的层间空隙中，且所述石墨烯层与相邻的两个所述硅基材料层中的至少一个所述硅基材料层之间具有空隙；或者Depositing a plurality of graphene layers on the layered silicon core by a chemical vapor deposition CVD process, the graphene layer being located in interlayer voids of two adjacent ones of the silicon-based material layers, and the graphene layer and Having a gap between at least one of the two adjacent silicon-based material layers; or

将多个层状石墨烯迁移至所述层状硅内核内，所述层状石墨烯位于相邻两个所述硅基材料层的层间空隙中，且所述层状石墨烯与相邻的两个所述硅基材料层中的至少一个所述硅基材料层之间具有空隙。Moving a plurality of layered graphene into the layered silicon core, the layered graphene being located in an interlayer gap of two adjacent silicon-based material layers, and the layered graphene and adjacent There is a gap between at least one of the two silicon-based material layers.
根据权利要求6至10任一项所述的方法，其特征在于，所述金属硅化物为碱金属或碱土金属的硅化物。The method according to any one of claims 6 to 10, characterized in that the metal silicide is an alkali metal or alkaline earth metal silicide.
一种电池，包括：正极、电解液以及负极，其特征在于，所述负极的电极材料为如权利要求1至5中任一项所述的复合材料，或者，所述负极的电极材料根据权利要求6至11中任一项所述的方法制备。A battery comprising: a positive electrode, an electrolyte, and a negative electrode, wherein the electrode material of the negative electrode is the composite material according to any one of claims 1 to 5, or the electrode material of the negative electrode is according to the right The method of any one of 6 to 11 is prepared.