Negative electrode material, manufacturing method thereof, and lithium ion battery

Abstract

The present application relates to a negative electrode material and a manufacturing method thereof, and to a lithium ion battery, and belongs to the technical field of energy storage materials. The negative electrode material is Li x M y The Li x M y The SiO4 material and the carbon material both form a network structure, which in the negative electrode material independently form a first skeleton and a second skeleton, respectively, and the first skeleton and the second skeleton are intertwined with each other, and the Li x M y The nanosilicon is distributed in and / or on the surface of a SiO4 material matrix, among which the Li x M y In the SiO4 material, the values ​​of x and y satisfy the charge balance, and M includes a metal element other than Li that can reduce silicon oxide. The negative electrode material has better electrical conductivity, more stable structure, lower volume expansion, higher electrical conductivity, initial efficiency and excellent multiplication performance.

Description

[Technical Field]

[0001] This application claims priority from a Chinese patent application filed with the China Patent Office on December 31, 2021, bearing application number 2021116652522 and entitled "Negative electrode material and manufacturing method thereof, and lithium ion battery," the entire contents of which are incorporated herein by reference. The present application relates to the technical field of energy storage materials, and in particular to anode materials and methods for producing the same, and lithium ion batteries. [Background technology]

[0002] Currently, graphite is the most widely used anode material for lithium batteries, but its low theoretical capacity (372 mAh / g) makes it difficult to meet the demand for high energy density. Silicon has a high theoretical capacity (4200 mAh / g) and is considered a new generation anode material for lithium batteries, attracting extensive attention and research from industry personnel.

[0003] However, silicon also has obvious drawbacks. For example, silicon has low electrical conductivity. It also undergoes large volume expansion and changes during silicon cycling, making it prone to pulverization. This can cause the active material and current collector to lose electrical contact and even fall off the current collector, ultimately resulting in a serious decline in cycle performance. Furthermore, the SEI film formed by the expansion can rupture, exposing a new interface and continuing to form a new SEI film. After cycling, the SEI film on the outer layer of the silicon particles becomes increasingly thick, ultimately blocking lithium ion insertion.

[0004] How to more effectively mitigate the volume expansion of silicon, ensure the cycling stability of silicon anodes, and obtain silicon anode materials with lower volume expansion, higher initial efficiency, and longer cycle life are currently technical hot spots in the lithium battery field that need to be resolved as soon as possible.

[0005] Composites of graphite and silicon can solve the above problems to some extent; however, conventional silicon carbon composites generally coat the silicon within the carbon layer, which reduces the initial efficiency of the silicon carbon composite. Summary of the Invention [Problem to be solved by the invention]

[0006] The present application provides a negative electrode material that can improve the volume expansion of the negative electrode material and enhance its initial efficiency and cycle performance, a method for producing the same, and a lithium ion battery. [Means for solving the problem]

[0007] In a first aspect, an embodiment of the present application provides an anode material, the anode material including a composite material, the composite material including a first framework, a second framework, and nanosilicon entangled with each other, the first framework including Li x M y The second skeleton includes a carbon material, and the Li x M y The nanosilicon is distributed within and / or on the surface of a matrix made of SiO4 material.

[0008] In accordance with the first aspect, in some embodiments of the present application, the negative electrode material further comprises a coating carbon layer present on the surface of the composite material. In some examples of the present application, including the first aspect, the thickness of the coated carbon layer is 5 nm to 80 nm. In conjunction with the first aspect, in some embodiments of the present application, Li x M y In the SiO4 material, 2≦x≦3.4 and 0.4≦y≦1. In accordance with the first aspect, in some embodiments of the present application, M comprises Mg or / and Al. In some examples of the present application, including the first aspect, the particle size of the nanosilicon is 5 nm to 200 nm. In accordance with the first aspect, in some embodiments of the present application, the carbon material includes a combination of one or two of soft carbon and hard carbon. In accordance with the first aspect, in some embodiments of the present application, the specific surface area of ​​the negative electrode material is 1 m 2 / g~3m 2 / g. In some examples of the present application, including the first aspect, the negative electrode material has a spherical particle shape, and the average particle size (D50) of the negative electrode material particles is 5 μm to 30 μm. In accordance with the first aspect, in some examples of the present application, the diameter of the second skeleton is 10 nm to 500 nm. In accordance with the first aspect, in some examples of the present application, the diameter of the first skeleton is 10 nm to 400 nm. In conjunction with the first aspect, in some embodiments of the present application, Li x M y The content of the SiO4 material in the negative electrode material is 5% by mass to 30% by mass. In some examples of the present application, including the first aspect, the content of nanosilicon in the negative electrode material is 30% by mass to 60% by mass. In some examples of the present application, including the first aspect, the content of the carbon material in the negative electrode material is 10% by mass to 65% by mass. In accordance with the first aspect, in some embodiments of the present application, the coated carbon layer comprises the carbon material.

[0009] In a second aspect, embodiments of the present application provide a negative electrode material, the negative electrode material comprising Li x M y SiO4 (where M includes a metal element other than Li that can reduce silicon oxide. The values ​​of x and y satisfy the charge balance.) materials, carbon materials, and nanosilicon, Li x M y SiO4 material has a porous structure and Li x M y The pores of the SiO4 material are filled with carbon material, and Lix M y Nanosilicon is distributed within and / or on the surface of a matrix made of SiO4 material.

[0010] In accordance with the second aspect, in some embodiments of the present application, the negative electrode material further comprises a coating carbon layer present on at least a portion of the surface of the composite material. In some examples of the present application, including the second aspect, the thickness of the coated carbon layer is 5 nm to 80 nm. In conjunction with the second aspect, in some embodiments of the present application, Li x M y In the SiO4 material, 2≦x≦3.4 and 0.4≦y≦1. In accordance with the second aspect, in some embodiments of the present application, M comprises Mg or / and Al. In some embodiments of the present application, including the second aspect, the particle size of the nanosilicon is 5 nm to 200 nm. In accordance with the second aspect, in some embodiments of the present application, the carbon material includes a combination of one or two of soft carbon and hard carbon. In accordance with the second aspect, in some embodiments of the present application, the specific surface area of ​​the negative electrode material is 1 m 2 / g~3m2 / g. In some examples of the present application, including the second aspect, the negative electrode material has a spherical particle shape, and the average particle size (D50) of the negative electrode material particles is 5 μm to 30 μm. In conjunction with the second aspect, in some embodiments of the present application, Li x M y The porosity of the SiO4 material is 30% to 46%. In conjunction with the second aspect, in some embodiments of the present application, Li x M y The content of the SiO4 material in the negative electrode material is 5% by mass to 30% by mass. In some examples of the present application, including the second aspect, the content of nanosilicon in the negative electrode material is 30% by mass to 60% by mass. In some examples of the present application, including the second aspect, the content of the carbon material in the negative electrode material is 10% by mass to 65% by mass. In accordance with the second aspect, in some embodiments of the present application, the coated carbon layer comprises a carbon material.

[0011] In a third aspect, embodiments of the present application provide a lithium-ion battery, the lithium-ion battery comprising the negative electrode material provided by the first or second aspect.

[0012] In a fourth aspect, an embodiment of the present application provides a method for producing a negative electrode material, the method comprising: Li with nanosilicon distributed within and / or on the surface of the matrix and having a porous or network structure x M y forming a SiO4 material (where M includes any metal element other than Li that can reduce silicon oxide); Li x M y and filling a carbon material into the pores of the porous structure or the voids of the network structure of the SiO4 material to obtain the negative electrode material.

[0013] In accordance with the fourth aspect, in some embodiments of the present application, the manufacturing method comprises: A framework material having a network structure or a porous structure is mixed with a lithium salt, and then calcined to form a Li x M y Obtaining SiO4 material and Li x M y forming a carbon material within the pores or voids of the SiO4 material to obtain an anode material; Alternatively, the method includes mixing a framework material having a network structure or a porous structure with a lithium salt and an organic carbon source, followed by heat treatment to obtain a negative electrode material, wherein the framework material includes nanosilicon, silicon oxide supported on the surface of the nanosilicon, and metal M oxide.

[0014] In conjunction with the fourth aspect, in some embodiments of the present application, Li x M yForming a carbon material in the pores or voids of an SiO4 material to obtain a negative electrode material is x M y combining and calcining the SiO4 material and the organic carbon source to carbonize the organic carbon source to form a carbon material; Or Li by chemical vapor deposition method x M y forming a carbon material within the pores or voids of the SiO4 material; Alternatively, mixing the framework material having a network structure or a porous structure, the lithium salt, and the organic carbon source includes mixing the framework material having a network structure or a porous structure with the lithium salt, and further mixing it with the organic carbon source.

[0015] In accordance with the fourth aspect, in some embodiments of the present application, a method for producing a scaffold material comprises: mixing silicon oxide and an adhesive and then granulating the mixture to obtain a first precursor; Mixing a first precursor, a metal M powder and a molten salt, and performing a thermal reaction to reduce at least a part of the silicon oxide to nanosilicon to obtain a second precursor; and washing the second precursor with an acid to remove some of the metal M oxide, thereby forming a skeleton material with a porous structure or a network structure.

[0016] In accordance with the fourth aspect, in some examples of the present application, silicon oxide and an adhesive are dispersed in a solution and spray-granulated to obtain a first precursor. In some embodiments of the present application, including the fourth aspect, the mass ratio of silicon oxide to adhesive is (40-100):1. 。 In some examples of the present application, including the fourth aspect, the mass ratio of the first precursor, the molten salt, and the metal M powder is 1:(3 to 8):(0.5 to 1.5) in this order. In accordance with the fourth aspect, in some embodiments of the present application, the metal M powder includes a combination of one or more of Mg powder, Al powder, and MgAl alloy powder. In accordance with the fourth aspect, in some examples of the present application, the framework material is mixed with a soluble lithium salt and water, stirred uniformly, and then dried. [Effects of the Invention]

[0017] Compared with the prior art, the present application can achieve the following beneficial effects: Regarding the negative electrode material of the first embodiment, Li x M y The addition of SiO4 material (M includes metal elements other than Li that can reduce silicon oxide) can supplement lithium into the anode material to improve its initial efficiency, and Li x M y SiO4 material has better lithium ion and electron conductivity, and the Li x M y The SiO4 material is intertwined with the network-structured carbon material, and the network-structured carbon material is basically distributed throughout the negative electrode material, which can increase the conductivity of the negative electrode material and also improve the Li x M y The nanosilicon is distributed within and / or on the surface of the SiO4 material matrix, and the addition of nanosilicon can increase the capacity of the material. The nanosilicon particle size is small and uniformly distributed. During charging and discharging, the nanosilicon expands in volume, but the intertwined network structure of Li x M y The action of SiO4 material and network structure carbon material can limit the expansion of nano silicon, and to some extent, can avoid the structural collapse caused by the volume expansion of nano silicon. The negative electrode material has better conductivity, more stable structure, lower volume expansion, high conductivity, expensive It can have first-time efficiency and excellent magnification performance.

[0018] Regarding the negative electrode material of the second embodiment, Li x M yThe addition of SiO4 material (M includes metal elements other than Li that can reduce silicon oxide) can supplement lithium into the anode material to improve its initial efficiency, and Li x M y SiO4 material has better lithium ion and electron conductivity, and the conductivity of the material can be improved by porous Li x M y The carbon material is distributed in the pores of the SiO4 material, which increases the conductivity of the negative electrode material and also increases the x M y The nanosilicon is distributed within and / or on the surface of the SiO4 material matrix, and the addition of nanosilicon can increase the capacity of the material. The nanosilicon particle size is small and uniformly distributed. The nanosilicon expands in volume during charging and discharging, but the porous structure of Li x M y The carbon material in the SiO4 material and its pores can restrict the expansion of the nanosilicon, and to some extent avoid the structural collapse caused by the volume expansion of the nanosilicon. The negative electrode material has better conductivity, a more stable structure, and lower volume expansion, high conductivity, expensive It can have first-time efficiency and excellent magnification performance.

[0019] Regarding the manufacturing method of the negative electrode material, Li forming a porous structure or a skeletal structure x M y The SiO4 material is composed of nano-silicon and Li x M y The distribution between the SiO4 material and the nanosilicon becomes uniform, and the Li x M y Located in the matrix or / and on the surface of the SiO4 material, after being composited with the carbon material, the resulting negative electrode material has better conductivity, a more stable structure, low volume expansion, high conductivity, expensive It has excellent initial efficiency and magnification performance.

[0020] For lithium ion batteries, by using the negative electrode material provided by the present application, the lithium ion battery can have lower volume expansion, high initial efficiency and excellent power-up performance. [Brief explanation of the drawings]

[0021] In order to more clearly explain the technical solutions of the embodiments of the present application, the following briefly introduces drawings necessary for the embodiments. Obviously, the following drawings only illustrate some embodiments of the present application, and therefore should not be considered as limiting the scope. Those skilled in the art can obtain other relevant drawings based on these drawings without any creative efforts.

[0022] [Figure 1] 1 is a cross-sectional schematic diagram of a negative electrode material provided in an example of the present application. [Figure 2] FIG. 1 is a process flow diagram of a method for manufacturing a negative electrode material provided by an example of the present application. [Figure 3] 1 shows a scanning electron microscope image and an EDS map of the fifth precursor in Example 1. [Figure 4] 1 is an XRD chart of a negative electrode material provided in Example 1 of the present application. [Figure 5] FIG. 1 is a scanning electron microscope view of the negative electrode material provided in Example 1 of the present application. [Explanation of symbols]

[0023] 110-Li x M y SiO4 material, 120-carbon material, 130-nano silicon. DETAILED DESCRIPTION OF THE INVENTION

[0024] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the following provides a clear and complete description of the technical solutions of the present application.

[0025] The inventors have found through their research that silicon can improve the capacity of the negative electrode material, but it is prone to volume expansion, and the oxide layer on the silicon surface reduces the initial efficiency of the battery. Carbon can improve the conductivity of the negative electrode material, but its capacity is low. x M y SiO4 can capture lithium in the negative electrode material, thereby improving the initial efficiency and Li x M y SiO4 material has excellent lithium ion and electron conductivity, and can improve the conductivity of the material. Therefore, the inventors believe that by combining these three, the negative electrode material will have lower volume expansion, higher conductivity, and expensive To provide a negative electrode material having initial efficiency and excellent multiplier performance.

[0026] FIG. 1 is a cross-sectional view of a negative electrode material provided in an embodiment of the present application. Referring to FIG. 1, the black part in FIG. 1 represents Li x M y The SiO4 material 110, the white part is nanosilicon 130, and the grey part is carbon material 120.

[0027] Continuing with reference to FIG. 1, the negative electrode material includes first and second skeletons entangled with each other, and nanosilicon 130, the first skeleton being Li x M y The second skeleton includes a carbon material 120, of which Li x M y Nanosilicon 130 is distributed within and / or on the surface of the SiO4 material 110. x M y In the SiO4 material, the values ​​of x and y satisfy the charge balance, and M includes a metal element other than Li that can reduce silicon oxide.

[0028] The first and second skeletons are intertwined to form a composite skeleton, and the Li x M y The carbon material 120 of the second skeleton is entangled in the SiO4 material 110, and the Li of the first skeleton is entangled in the carbon material 120 of the second skeleton.x M y The SiO4 material 110 is intertwined, making the structure of the negative electrode material more stable, and the carbon material 120 is distributed more uniformly throughout the negative electrode material, making the material more conductive.

[0029] Li x M y The addition of SiO4 material 110 (where M includes a metal element other than Li that can reduce silicon oxide) can supplement the anode material with lithium, thereby improving its initial efficiency, and nanosilicon 130 can supplement Li x M y The nanosilicon 130 is distributed within and / or on the surface of the SiO4 material 110 matrix, which can increase the capacity of the negative electrode material. The nanosilicon 130 expands in volume during charging and discharging, but the intertwined Li x M y The SiO4 material 110 and the carbon material 120 can restrict the expansion of the nanosilicon 130, and to some extent avoid the structural collapse caused by the volume expansion of the nanosilicon 130. The negative electrode material has better conductivity, a more stable structure, and lower volume expansion, high conductivity, expensive It can have first-time efficiency and excellent magnification performance.

[0030] Li x M y The SiO4 material 110 and the carbon material 120 may both have a network structure. x M y The action of the SiO4 material 110 and the network-structured carbon material 120 can better restrict the expansion of the nanosilicon 130 and prevent the structure from collapsing due to the volume expansion of the nanosilicon 130. This improves the conductivity of the negative electrode material, makes the structure more stable, and has low volume expansion, high conductivity, expensive It can have first-time efficiency and excellent magnification performance.

[0031] Note that the network structure here does not refer to the structure of an intangible computer network, but to the network structure of a tangible substance, and this network structure corresponds to a solid structure. For example, in a spherical material, if there are no voids inside and it matches the surface structure of the spherical material, it is called a solid structure; if there are large voids inside, it is called a hollow structure; and if there are many voids inside and the voids have the potential to be partially conductive, it is called a network structure.

[0032] For example, a certain material is called a metal mesh, and its general structure is a metal mesh woven with multiple metal wires to form a multiple pore structure. The network structure in the present application differs from this in that the substrate of the network structure in the present application is basically a three-dimensional structure (for example, a spherical structure, a cubic structure, a rectangular parallelepiped structure, or other irregular three-dimensional structure), and has many pores inside and on the surface (for example, similar to a three-dimensional foam metal structure, but with different materials and possibly different pore structures), thereby forming a network structure.

[0033] Therefore, the network structure in this application is a three-dimensional Li x M y This refers to a structure in which there are many voids inside and on the surfaces of the SiO4 material 110 and the carbon material 120, thereby intertwining the voids and materials of both materials. The voids in the network structure here are not limited to uniformly distributed voids, but may be large in some areas and small in other areas, or may be irregular voids.

[0034] Nano Silicon 130 is Li x M y Distributing within and / or on the surface of the SiO4 material 110 is Li x M y Nano silicon 130 is distributed on the surface of the SiO4 material 110, or Li x M y Nanosilicon 130 is distributed within the matrix of SiO4 material 110, or Li x M yThis refers to the fact that nanosilicon 130 is distributed both on the surface of the SiO4 material 110 and within the matrix.

[0035] Nano silicon 130 mainly refers to silicon material with nano-scale particle size. Under the condition that the particle size of the silicon material is small and the silicon content is the same, nano silicon 130 with small particle size can be used in combination with Li x M y The SiO4 material 110 tends to distribute it evenly.

[0036] This application claims that nanosilicon 130 is Li x M y Although it has been described that Li is distributed within the matrix and / or on the surface of the SiO4 material 110, x M y There is no limitation that the mass of the SiO4 material 110 is greater than the mass of the nanosilicon 130. In fact, Li x M y The mass of the SiO4 material 110 may be greater than the mass of the nanosilicon 130, and the mass of the nanosilicon 130 may be greater than the mass of the Li x M y The mass of the SiO4 material 110 may be larger than that of the Li x M y The mass of the SiO 4 material 110 may correspond to the mass of the nanosilicon 130.

[0037] With continued reference to FIG. 1, the negative electrode material is Li x M y The material includes an SiO4 material 110, a carbon material 120, and nanosilicon 130, and Li x M y The SiO4 material 110 has a porous structure and x M y The pores of the SiO4 material 110 are filled with a carbon material 120, of which Li x M y Nanosilicon 130 is distributed within the matrix and / or on the surface of the SiO4 material 110, the values ​​of x and y satisfy the charge balance, and M includes a metal other than Li that can reduce silicon oxide.

[0038] Porous Li x M y The carbon material 120 is filled into the pores of the SiO4 material 110, which makes the structure of the negative electrode material more stable, and the carbon material 120 is distributed almost uniformly throughout the negative electrode material, which makes the conductivity of the material stronger. x M y The addition of SiO4 material 110 (where M includes a metal element other than Li that can reduce silicon oxide) can supplement the anode material with lithium, thereby improving its initial efficiency, and nanosilicon 130 can supplement Li x M y The nanosilicon 130 is distributed within and / or on the surface of the SiO4 material 110 matrix, which can increase the capacity of the negative electrode material. The nanosilicon 130 expands in volume during charging and discharging, but the Li x M y The SiO4 material 110 and the porous carbon material 120 can restrict the expansion of the nanosilicon 130, and to some extent avoid the structural collapse caused by the volume expansion of the nanosilicon 130. The negative electrode material has better conductivity, a more stable structure, and lower volume expansion, high conductivity, expensive It can have first-time efficiency and excellent magnification performance.

[0039] For example, porous Li x M y The porosity of the SiO4 material 110 is 30% to 46%, for example, 30%, 32%, 35%, 40%, 43%, 46%, etc., i.e., Li x M y It can ensure that the SiO4 material has sufficient volume to fill the carbon material, improve the conductivity of the composite negative electrode material, reduce the expansion rate of the composite negative electrode material, and ensure that the capacity is not too low.

[0040] The carbon material 120 can be considered to have a porous structure, and the porous structure here refers to the following: Li x M yThe SiO4 material 110 and the carbon material 120 basically have a three-dimensional structure and have many pores inside and / or on their surfaces, some of which may be interconnected or some of which may not be interconnected, and the two materials can be filled with each other. The pores in the porous structure here are not limited to uniformly distributed pores or pores with the same pore size; they may have large pores in some areas and small pores in other areas, or they may have irregular pores.

[0041] Regardless of whether the carbon material 120 has a porous structure or a network structure, the skeletal diameter of the carbon material 120 is preferably 10 nm to 500 nm. x M y The skeletal diameter of the SiO4 material 110 is 10 nm to 400 nm, which is the carbon material 120 and Li x M y It is not necessary that the diameter of all the skeletons of the SiO4 material 110 be within the above range. Generally, as long as the diameter of 70% or more of the skeletons is within the above range, Li x M y It is easy to realize mutual packing or intertwining of the SiO4 material 110 and the carbon material 120. At the same time, it is not limited that the skeleton diameters of different parts are the same, and the diameters of different parts of the skeleton of the same particle may be different.

[0042] For example, the skeletal diameter of the carbon material 120 is 10 nm to 100 nm, and Li x M y The skeletal diameter of the SiO4 material 110 is 10 nm to 90 nm, or the skeletal diameter of the carbon material 120 is 100 nm to 300 nm, and Li x M y The skeletal diameter of the SiO4 material 110 is 90 nm to 200 nm, or the skeletal diameter of the carbon material 120 is 300 nm to 500 nm, and Li x M y The skeletal diameter of the SiO4 material 110 is 200 nm to 400 nm, which can be observed using a scanning electron microscope.

[0043] Continuing with Figure 1, Li x M yThe carbon material filled in the pores of the SiO4 material further x M y The carbon nanotubes are distributed on the outer surface of the SiO4 material, forming a coating carbon layer, which on the one hand improves the conductivity of the negative electrode material, and on the other hand, can limit the volume expansion of the nanosilicon 130, protect the internal structure, and make the overall structure of the material more stable.

[0044] The coated carbon layer is explained below. For example, as shown in Figure 1, the porous structure of Li x M y The diameter of the SiO4 material 110 is D1(Li x M y The SiO4 material 110 has a porous structure or a network structure, but the basic outer contour is spherical, and the diameter of the spherical outer contour is D1. x M y The diameter of the filled carbon filled in the SiO4 material is also D1 (the filled carbon also has a porous structure, but the basic outer contour is spherical, and the diameter of the spherical outer contour is D1), and the particle size of the negative electrode material is D2, the coated carbon layer refers to the sphere where D2 is located minus the area of ​​the sphere where D1 is located in Figure 1. The coated carbon layer is Li x M y It refers to a carbon layer structure coated with other than SiO4 material 110, and is basically Li x M y There is no intertwining or interfilling relationship between the SiO4 material 110.

[0045] Preferably, the thickness of the coated carbon layer is 5 nm to 80 nm. The thickness of the coated carbon layer is determined by the amount of Li in the carbon layer. x M y It refers to the absence of a thickness of the outermost layer of the SiO4 material 110, for example, the value of D in Fig. 1 is (D2-D1) / 2. The covering carbon layer of this thickness can, on the one hand, make the structure of the material relatively stable, on the other hand, effectively restrain the volume expansion of silicon, and on the other hand, enhance the overall performance of the anode material by interposing the nanosilicon 130 and Li x M yThe mass proportion of the SiO4 material 110 can be rationalized.

[0046] For example, the thickness of the coated carbon layer may be 5 nm to 20 nm, or 20 nm to 40 nm, or 40 nm to 60 nm, or 60 nm to 80 nm. As shown in Figure 1, the coated carbon layer has a roughly spherical layered structure, and the thicknesses of different positions on the sphere may be the same or different, and the present application is not limited thereto.

[0047] In addition, in Fig. 1, the Li x M y Although the outer contour of the SiO4 material 110 has a spherical structure, or the outer contour of the particulate negative electrode material has a spherical structure, these are only exemplary shapes or structures, and they are not necessarily limited to a spherical structure; any solution that resembles a spherical structure or can form a particulate structure is within the scope of protection of the present application.

[0048] Preferably, Li x M y In the SiO4 material 110, 2≦x≦3.4 and 0.4≦y≦1, and the values ​​of x and y satisfy the charge balance.

[0049] In some possible embodiments, M comprises Mg or / and Al, while it reacts with silicon oxides and metal oxides to form Li x M y The SiO4 material 110 is easy to obtain, on the one hand, its origin is wide and easy to obtain, and on the other hand, its prelithiation effect is high, and the performance of the negative electrode material is higher.

[0050] Preferably, Li x M y The SiO4 material 110 may be lithium magnesium silicate, or Li x M yThe SiO4 material 110 may be lithium aluminum silicate, or the LixMySiO4 material 110 may be a mixture of lithium magnesium silicate and lithium aluminum silicate.

[0051] In other embodiments, M may further include Ca or / and Zn.

[0052] In some possible embodiments, the particle size of the nanosilicon 130 is 5 nm to 200 nm, which makes it easier for the nanosilicon 130 to be distributed more uniformly in the LixMySiO4 material 110, and the nanosilicon 130 with this particle size can be obtained by directly reducing silicon oxide, making it more convenient to manufacture.

[0053] Li x M y A large number of nanosilicon 130 are distributed in the SiO4 material 110, and the particle size of each nanosilicon 130 is not limited to the same size, but generally, the particle size of the nanosilicon 130 is basically within a range, and the particle distribution of the nanosilicon 130 is uniform. Illustratively, the particle size of the nanosilicon 130 is 5 nm to 50 nm, or 50 nm to 100 nm, or 100 nm to 150 nm, or 150 nm to 200 nm.

[0054] In some possible embodiments, the carbon material 120 includes one or more combinations of hard carbon, soft carbon.

[0055] In some possible embodiments, the specific surface area of ​​the negative electrode material is 1 m 2 / g~3m 2 The specific surface area of ​​the negative electrode material is small, and there are few or only a small number of pores, which makes the overall structure of the negative electrode material more stable.

[0056] For example, the specific surface area of ​​the negative electrode material is 1m 2 / g, 1.5m 2 / g, 2m2 / g, 2.5m 2 / g, or 3m 2 / g.

[0057] Preferably, the shape of the negative electrode material is spherical particles, and the average particle size (D50) of the negative electrode material particles is 5 μm to 30 μm. The spherical particles here are not limited to regular spheres, but may be irregular spherical particles, for example, particles with a small number of recesses on the surface and an ellipsoidal overall structure. The average particle size here may refer to the average particle size of different particles, or may be the average particle size of the same particle in different directions, and is not limited thereto.

[0058] The average particle size (D50) of the spherical particles of the negative electrode material is in the range of 5 μm to 30 μm, which allows the size of the negative electrode material to be uniform, thereby resulting in high capacity retention and good performance. For example, the average particle size (D50) of the negative electrode material particles is 5 μm to 10 μm, or the average particle size (D50) of the negative electrode material particles is 10 μm to 20 μm, or the average particle size (D50) of the negative electrode material particles is 20 μm to 30 μm.

[0059] For example, the average particle size (D50) of the spherical particles of the negative electrode material is 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, or 30 μm.

[0060] In some possible embodiments, Li x M y The content of the SiO4 material 110 in the negative electrode material is 5% to 30% by mass, the content of the nanosilicon 130 in the negative electrode material is 30% to 60% by mass, and the content of the carbon material 120 in the negative electrode material is 10% to 65% by mass. x M y The contents of the SiO4 material 110, the nanosilicon 130 and the carbon material 120 are limited within the above ranges, so that the composition of the negative electrode material can be more reasonable and the overall performance of the negative electrode material can be improved.

[0061] In one embodiment, Li xM y The content of the SiO4 material 110 in the negative electrode material is 5% to 10% by mass, the content of the nanosilicon 130 in the negative electrode material is 30% to 40% by mass, and the content of the carbon material 120 in the negative electrode material is 50% to 65% by mass. x M y The content of SiO4 material 110 is relatively low, and the content of nanosilicon 130 and carbon material 120 is relatively high, which can effectively improve the initial efficiency of the negative electrode material. At the same time, the addition of a large amount of carbon material 120 can effectively limit the expansion of nanosilicon 130 during the charge and discharge process, thereby improving the performance of the negative electrode material.

[0062] In another embodiment, Li x M y The content of the SiO4 material 110 in the negative electrode material is 10% to 20% by mass, the content of the nanosilicon 130 in the negative electrode material is 30% to 40% by mass, and the content of the carbon material 120 in the negative electrode material is 50% to 60% by mass.

[0063] In another embodiment, Li x M y The content of the SiO4 material 110 in the negative electrode material is 20% to 30% by mass, the content of the nanosilicon 130 in the negative electrode material is 40% to 60% by mass, and the content of the carbon material 120 in the negative electrode material is 10% to 30% by mass.

[0064] For example, Li x M y The content of the SiO4 material 110 in the negative electrode material is 5 mass %, the content of the nanosilicon 130 in the negative electrode material is 60 mass %, and the content of the carbon material 120 in the negative electrode material is 35 mass %, or x M y The content of the SiO4 material 110 in the negative electrode material is 10 mass %, the content of the nanosilicon 130 in the negative electrode material is 50 mass %, and the content of the carbon material 120 in the negative electrode material is 40 mass %, or x My The content of the SiO4 material 110 in the negative electrode material is 20 mass %, the content of the nanosilicon 130 in the negative electrode material is 45 mass %, and the content of the carbon material 120 in the negative electrode material is 35 mass %, or x M y The content of the SiO4 material 110 in the negative electrode material is 30 mass %, the content of the nanosilicon 130 in the negative electrode material is 30 mass %, and the content of the carbon material 120 in the negative electrode material is 40 mass %.

[0065] The negative electrode material is used to manufacture a lithium ion battery, and the resulting lithium ion battery has lower volume expansion, high initial efficiency and excellent power-up performance.

[0066] The lithium ion battery is used to provide electrical energy to electrical devices and has a better driving range.

[0067] The above introduces the negative electrode material and its applications, and the following describes its manufacturing method. The method includes: x M y SiO4 material is Li x M y The negative electrode material is obtained by filling the pore paths of the porous structure or the voids of the network structure of the SiO4 material with a carbon material, where M contains a metal element other than Li that can reduce silicon oxide.

[0068] Lithium nanosilicon surface porous or network structure based on silicon oxide x M y By forming SiO4 material, nano-silicon and Li x M y The distribution between the SiO4 material is uniform, and the nanosilicon is Li x M y Located in the matrix or / and on the surface of the SiO4 material, after being composited with the carbon material, the resulting negative electrode material has better conductivity, a more stable structure, low volume expansion, high conductivity, expensiveIt has excellent initial efficiency and magnification performance.

[0069] The manufacturing method will be described in detail below. FIG. 2 is a process flow diagram of the manufacturing method of the negative electrode material provided in the embodiment of the present application. Referring to FIG. 2, the manufacturing method includes: S110 includes mixing silicon oxide with a binder and then granulating the mixture to obtain a first precursor. The addition of the binder allows the particles to be more uniform, and also facilitates the subsequent formation of a skeleton having a porous or network structure.

[0070] Preferably, the silicon oxide and adhesive are dispersed in a solution and then spray-granulated to obtain the first precursor. By dispersing the silicon oxide and adhesive more uniformly, particles with a more uniform particle size can be obtained.

[0071] In some possible implementation ranges, the mass ratio of silicon oxide to adhesive is (40-100): 1. The content of silicon oxide is significantly higher than the content of the sintering agent, and the main component of the first precursor after granulation is silicon oxide, with the sintering agent being used only as an adhesive material for granulation.

[0072] Exemplarily, the mass ratio of silicon oxide to adhesive is (40-60): 1, or the mass ratio of silicon oxide to adhesive is (60-80): 1, or the mass ratio of silicon oxide to adhesive is (80-100): 1. For example, the mass ratio of silicon oxide to binder is 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, or 100:1.

[0073] In some possible embodiments, the silicon oxide is a combination of one or more of SiO, SiO, and Si0. For example, the silicon oxide is silicon dioxide, which is stable and has a wider range of origins.

[0074] In some possible embodiments, the adhesive is one or more of the following: epoxy resin, phenolic resin, furfural resin, urea resin, polyvinyl alcohol, polyvinyl chloride, polyethylene glycol, polyethylene oxide, polyvinylidene fluoride, glucose, sucrose, asphalt, polystyrene, polypyrrole, polyaniline, sodium carboxymethylcellulose, polyvinylpyrrolidone.

[0075] Preferably, silicon oxide is dispersed in an aqueous solution, and after uniform stirring, an adhesive is added to the solution, and the mass ratio of silicon oxide to adhesive is (40-60):1, followed by uniform stirring and then spray granulation to obtain the first precursor.

[0076] In S120, the first precursor, metal M powder, and molten salt are mixed and subjected to a thermal reaction to reduce at least a portion of the silicon oxide to nanosilicon, thereby obtaining a second precursor, where M includes a metal element other than Li that can reduce silicon oxide. During the thermal reaction, the silicon oxide is reduced to nanosilicon by the metal M, and the metal M is converted into metal M oxide, resulting in particles that essentially have a nanosilicon core and a metal M oxide surface, with molten salt distributed between the particles.

[0077] It should be noted that this does not necessarily mean that all silicon oxide is reduced, nor that all metal M oxide is attached to the surface of the nanosilicon. In actual manufacturing processes, in more situations, most silicon oxide is reduced, and the metal M oxide on the nanosilicon generally covers only part of the surface of the nanosilicon, and some of the surface of the nanosilicon may be exposed.

[0078] At the same time, nanosilicon particles (particles with nanosilicon inside and metal oxide on the surface) )of The molten salt may be distributed between some of the nanosilicon particles, or may bond between some of the nanosilicon particles.

[0079] The addition of molten salt can control the reaction conditions of the thermal reaction, avoid violent reaction to a certain extent, and prevent adhesion or aggregation between particles, so that the particles finally form a more uniform negative electrode material and the reaction is easier to control, which is conducive to the formation of a more porous structure after the molten salt is later removed.

[0080] In some possible embodiments, the mass ratio of the first precursor, molten salt, and metal M powder is 1:(3-8):(0.5-1), in order. The content of the molten salt is high, which basically does not participate in the reaction, and after the molten salt is subsequently removed, a porous structure or network structure can be formed, which is convenient for producing a negative electrode material. When the mass ratio of the first precursor to metal M powder is within the above range, more silicon oxide can be reduced and nanosilicon can be obtained.

[0081] For example, the mass ratio of the first precursor, the molten salt, and the metal M powder is 1:(3-5):(0.8-1), or the mass ratio of the first precursor, the molten salt, and the metal M powder is 1:(5-8):(0.5-0.8), or the mass ratio of the first precursor, the molten salt, and the metal M powder is 1:(3-6):(0.5-0.7), or

[0082] For example, the mass ratio of the first precursor, the molten salt, and the metal M powder is, in order, 1:3:0.8, 1:4:0.8, 1:5:0.8, 1:6:0.8, 1:7:0.8, 1:8:0.8, 1:3:0.9, 1:4:0.9, 1:5:0.9, 1:6:0.9, 1:7:0.9, 1:8:0.9, 1:3:1, 1:4:1, 1:5:1, 1:6:1, 1:7:1, or 1:8:1, etc.

[0083] In some possible embodiments, the metal M powder comprises one or more of Mg powder, Al powder, and MgAl alloy powder in combination. During the thermal reaction, an oxidation-reduction reaction occurs, so the metal M powder comes into contact with silicon oxide, and the metal M oxide is mostly formed on the surface of the nanosilicon. However, this is not limited to the fact that all of the metal M oxide is on the surface of the nanosilicon, and some of the metal M oxide may not be formed on the surface of the nanosilicon.

[0084] In another embodiment, the metal M powder may further include calcium powder, zinc powder, etc.

[0085] In some possible embodiments, the molten salt is one or a combination of more of magnesium chloride, sodium chloride, potassium chloride, calcium chloride, copper chloride, sodium sulfate, calcium sulfate, barium sulfate, aluminum sulfate, sodium nitrate, potassium nitrate, ammonium nitrate, calcium nitrate, lead nitrate, cerium nitrate, sodium fluoride, potassium fluoride, and calcium fluoride.

[0086] Preferably, the thermal reaction is carried out in an inert gas atmosphere at a temperature of 400°C to 800°C for 1 to 10 hours. In the inert gas atmosphere, the metal M powder is not oxidized by oxygen and undergoes a redox reaction with silicon oxide, thereby converting the silicon oxide into nanosilicon. The temperature and time of the thermal reaction within the above ranges can achieve a better reduction effect of silicon oxide.

[0087] For example, the thermal reaction conditions are a reaction in a nitrogen atmosphere at a temperature of 400°C to 500°C for 8 hours to 10 hours, or a reaction in a nitrogen atmosphere at a temperature of 500°C to 600°C for 6 hours to 8 hours, or a reaction in a nitrogen atmosphere at a temperature of 600°C to 700°C for 1 hour to 6 hours, or a reaction in a nitrogen atmosphere at a temperature of 700°C to 800°C for 1 hour to 6 hours.

[0088] Preferably, the first precursor, metal M powder, and molten salt are mixed together, with the mass ratio of the first precursor, molten salt, and metal M powder being 1:(3-8):(0.5-1.5), respectively, and after mixing, the mixture is placed in a nitrogen atmosphere and reacted at a temperature of 400°C to 800°C for 1 hour to 10 hours to obtain the second precursor.

[0089] In S130, the second precursor is pickled to remove some of the metal M oxide, thereby forming a third precursor. The pickling step is performed in an acid solution. After mixing the second precursor with the acid solution, some of the metal M oxide on the nanosilicon surface dissolves in the acid solution, and the molten salt dissolves in the acid solution, forming a nanosilicon aggregate with a porous or network structure. The nanosilicon surface may be partially covered with the metal M oxide and partially exposed. The third precursor is a network or porous framework material, which includes nanosilicon, silicon oxide supported on the nanosilicon surface, and metal M oxide. The silicon oxide may be unreduced silicon oxide or silicon oxide naturally formed on the surface after the nanosilicon is exposed.

[0090] In some possible embodiments, the acid solution is a combination of one or more of a nitric acid solution, a hydrochloric acid solution, and a sulfuric acid solution.

[0091] Preferably, the mass concentration of the nitric acid solution is 5% to 15%, the mass concentration of the hydrochloric acid solution is 5% to 15%, and the mass concentration of the sulfuric acid solution is 5% to 15%.

[0092] Preferably, the amount of the acid solution added is 10% to 120% of the mass of the second precursor. Exemplarily, the amount of the acid solution added is 10% to 30% of the mass of the second precursor, or 30% to 50% of the mass of the second precursor, or 50% to 80% of the mass of the second precursor, or 80% to 120% of the mass of the second precursor.

[0093] For example, the amount of acid solution added is 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, or 120% of the mass of the second precursor.

[0094] Preferably, the second precursor is mixed with a hydrochloric acid solution having a mass concentration of 5% to 15%, and the mixture is immersed for 0.3 h to 1 h; salt Acid solution concentration Adjustments for By adjusting the soaking time and the amount of silicon dioxide present, some of the metal oxides are removed, and then the resulting mixture is washed with water to separate the solid and liquid, after which impurities are removed (the solid and liquid separation method can be centrifugation, filtration, suction filtration, etc.), and then dried to obtain a porous or network structured framework material, which includes nanosilicon, silicon oxide supported on the surface of the nanosilicon, and metal M oxide.

[0095] Steps S110 to S130 may or may not be performed, and a skeleton material with a porous structure or a network structure may be obtained using other methods.

[0096] In S140, the third precursor and lithium salt are mixed and baked to form a porous or network structure Li x M y Obtain SiO4 material. Among them, Li x M y Nanosilicon is distributed within and / or on the surface of the SiO4 material matrix, and the values ​​of x and y satisfy the charge balance.

[0097] The second precursor is immersed in an acid solution of a certain concentration for a certain time, which can remove some of the metal M oxide in the second precursor, exposing a large amount of nano-silicon and forming a pore structure (skeleton of a porous structure or network structure). After mixing the lithium salt with the third precursor, the lithium salt comes into contact with the nano-silicon, metal M oxide, and silicon oxide (the silicon oxide may be unreduced silicon oxide or silicon oxide naturally formed on the surface after the nano-silicon is exposed). During calcination, some of the silicon oxide and metal M oxide react with the lithium salt, forming the Lix M y SiO4 material was obtained, and at this time, Li x M y Nanosilicon is distributed both within the matrix and / or on the surface of the SiO4 material.

[0098] In some possible embodiments, the lithium salt is one or more of lithium acetate, lithium oxalate, lithium carbonate, lithium hydroxide, lithium formate, lithium benzoate, lithium chloride, lithium sulfate, and lithium nitrate.

[0099] Preferably, the firing conditions are an inert gas atmosphere at a temperature of 600°C to 1200°C for 1 hour to 10 hours. Exemplary firing conditions are a nitrogen atmosphere at a temperature of 600°C to 800°C for 8 hours to 10 hours, a nitrogen atmosphere at a temperature of 800°C to 1000°C for 5 hours to 8 hours, or a nitrogen atmosphere at a temperature of 1000°C to 1200°C for 1 hour to 5 hours.

[0100] Preferably, the third precursor, the soluble lithium salt, and water are mixed, stirred uniformly, dried, and then baked in an inert gas atmosphere at a temperature of 600°C to 1200°C for 1 hour to 10 hours to obtain Li x M y Obtain SiO4 material.

[0101] The soluble lithium salt is mixed with the third precursor in water, and a layer of the soluble lithium salt is uniformly adsorbed on the surface of the third precursor. After drying, the lithium salt is adsorbed on the surface of the third precursor. When the third precursor is subsequently calcined, the Li x M y It is convenient to control the amount of SiO4 material, and the nano silicon is x M y It can also be distributed uniformly in the SiO4 material.

[0102] In the S150, Li x M y A carbon material is formed in the pores of the SiO4 material to obtain the negative electrode material. x My The SiO4 material has a porous or network structure and Li x M y Nano-silicon is distributed within and / or on the surface of the SiO44 material matrix, and Li x M y The SiO4 material has many pores inside, and the carbon material x M y The Li x M y The carbon material is filled with or intertwined with the SiO4 material to obtain the negative electrode material. In addition, if the carbon material has a large mass, a coating carbon layer can be formed on the surface, resulting in a negative electrode material with better performance.

[0103] In one embodiment, Li x M y By mixing SiO4 material with an organic carbon source and calcining it, This carbonizes the organic carbon source to form a carbon material. x M y After mixing the SiO4 material with the organic carbon source, some of the organic carbon source was converted to Li x M y Some organic carbon sources enter the pores of the SiO4 material and are transported to Li x M y When coated on the surface of SiO4 material and calcined, Li x M y The carbon material can be formed by inter-packing the SiO4 material with the carbon material, and a coating carbon layer can be formed on the surface.

[0104] The organic carbon source is one or a combination of polymers, sugars, organic acids, asphalt, and polymeric materials. For example, the organic carbon source is polyvinyl chloride, polyvinyl butyral, sucrose, glucose, citric acid, asphalt, furfural resin, epoxy resin, phenolic resin, polyacrylic acid, etc.

[0105] Preferably, Li x M y The mixing method of the SiO4 material and the organic carbon source can be a hot press coating method.x M y After uniformly mixing the SiO4 material and the organic carbon source, place it in a calcination furnace and calcinate it in an inert gas atmosphere at a pressure of 5 MPa to 20 MPa and a temperature of 700°C to 1200°C for 1 hour to 10 hours to carbonize the organic carbon source.

[0106] By hot pressing coating method, organic carbon source is coated on porous Li x M y The organic carbon source may be hot pressed into the pores or voids of the SiO4 material, thereby forming a porous Li x M y The carbon material fills the pores or voids in the SiO4 material.

[0107] For example, the conditions for carbonizing the organic carbon source are a reaction in a nitrogen atmosphere at a temperature of 700°C to 800°C for 8 hours to 10 hours, a reaction in a nitrogen atmosphere at a temperature of 800°C to 1000°C for 5 hours to 8 hours, or a reaction in a nitrogen atmosphere at a temperature of 1000°C to 1200°C for 1 hour to 5 hours.

[0108] The pressure in the hot press furnace is 5Mpa to 20Mpa, and the pressure is high, so the calcination process In this case, after the organic carbon source is carbonized, the volume decreases, so the carbon material is Porous structure of Li x M y The porous carbon material and the porous Li were hot pressed into the SiO4 material. x M y The tighter the entanglement between the SiO4 materials, the tighter the packing, and the better the performance of the negative electrode material.

[0109] For example, the conditions for carbonizing the organic carbon source are to react for 8 to 10 hours in an inert gas atmosphere at a pressure of 5 to 10 MPa and a temperature of 700 to 800°C, or to react for 5 to 8 hours in an inert gas atmosphere at a pressure of 10 to 15 MPa and a temperature of 800 to 1000°C, or to react for 1 to 5 hours in an inert gas atmosphere at a pressure of 15 to 20 MPa and a temperature of 1000 to 1200°C.

[0110] In another embodiment, Li x M y The SiO4 material is placed in a chemical vapor deposition furnace and Li is deposited by chemical vapor deposition. x M y Carbon material is formed in the pores and on the surface of the SiO4 material. The carbon material is formed by chemical vapor deposition, and Li x M y The pores of the SiO4 material are filled with the material, and the filling effect is high. Even if the pores are small, the Li x M y The porous structure of the carbon material and the porous structure of the Li x M y SiO4 material can be formed.

[0111] Preferably, the chemical vapor deposition is carried out under the conditions of using acetylene, methane or acetone as a carbon source, argon gas or nitrogen gas as a protective gas, and performing vapor deposition at 750°C to 1200°C.

[0112] The steps S140 and S150 are performed twice, by firing and calcining, respectively. However, the present application is not limited to performing the heat treatment in two steps, and it may be produced by a single heat treatment.

[0113] Preferably, the third precursor and a lithium salt are mixed with an organic carbon source, followed by heat treatment to obtain the negative electrode material, wherein the third precursor is a porous or network structured framework material, and the framework material comprises nanosilicon, silicon oxide on the surface of the nanosilicon, and metal oxide.

[0114] When heat treatment is performed, some nanosilicon, silicon oxide, and metal oxide react with lithium salt to form porous or network structure Li x M y In addition to obtaining SiO4 material, the organic carbon source is carbonized, and the carbonized carbon material and Li x M y The SiO4 materials can be packed together or intertwined with each other.

[0115] Preferably, the third precursor is mixed with a lithium salt, and then mixed with an organic carbon source, followed by heat treatment to obtain a negative electrode material. For example, the third precursor, a soluble lithium salt, and water are mixed, uniformly stirred, and then dried. Then, the organic carbon source is coated on the surface and inside of the mixture, and the mixture is heat-treated in an inert gas atmosphere at a temperature of 700 to 1200°C for 1 to 10 hours to carbonize the organic carbon source and form a carbon material, while the lithium salt reacts to form Li x M y Obtain SiO4 material.

[0116] The negative electrode material prepared by the above method is composed of Li particles intertwined or packed together. x M y Contains SiO4 material and carbon material, and Li x M y Nano silicon is distributed in and / or on the surface of the SiO4 material matrix, which can make the structure of the negative electrode material more stable, and also has low volume expansion, high conductivity, expensive It has excellent initial efficiency and magnification performance.

[0117] In order to clarify the objectives, technical solutions and advantages of the examples of this application, the following will clearly and completely explain the technical solutions in the examples of this application. In the examples, unless specific conditions are specified, they are carried out according to the general conditions or conditions provided by the manufacturer. For reagents or equipment used, unless the manufacturer is specified, they are all conventional products obtained by commercial purchase.

[0118] Example 1 The method for producing the negative electrode material includes the following steps. (1) Take 500g of nano-silicon dioxide, disperse it in 10kg of aqueous solution, and add 10g of sodium carboxymethylcellulose after uniform stirring. After uniform stirring, spray granulation is performed to obtain the first precursor. (2) The first precursor is mixed with molten sodium chloride and magnesium powder. The mass ratio of the first precursor, sodium chloride, and magnesium powder is 1:5:0.8, respectively. After uniform mixing, the mixture is reacted in a nitrogen atmosphere at 700°C for 5 hours to obtain the second precursor. (3) The second precursor is placed in an aqueous solution, with the ratio of the second precursor to water being 1:4. After uniform stirring, an industrial hydrochloric acid solution with a weight ratio of 1:1 to the second precursor is added thereto. After reacting for 0.5 hours, the mixture is centrifuged and washed with water to remove impurities, and the third precursor is obtained. (4) The third precursor is dispersed in an aqueous solution, the ratio of the framework material to water is 1:5, and lithium carbonate is added thereto in a weight ratio of 10:1 to the framework material. The solvent is evaporated to dryness under stirring conditions to obtain a fourth precursor. (5) The fourth precursor is placed in a rotary furnace and calcined at 1100°C for 3 hours under inert gas conditions to obtain the fifth precursor. (6) After mixing the fifth precursor with asphalt, place it in a hot press furnace and calcinate it at 800°C under a pressure of 10 MPa for 3 hours. After calcination, the calcined material is crushed and sieved to obtain the negative electrode material.

[0119] FIG. 3 shows a scanning electron microscope image (left side of FIG. 3) and an EDS map (right side of FIG. 3) of the fifth precursor in Example 1. As can be seen from FIG. 3, the fifth precursor has a porous structure and contains lithium magnesium silicate material and nanosilicon, and the nanosilicon is uniformly dispersed in the lithium magnesium silicate matrix.

[0120] FIG. 4 is an XRD chart of the negative electrode material provided by Example 1. As can be seen from FIG. 4, the negative electrode material provided by Example 1 contains Li x M yIt contains SiO4 material, carbon material and nano silicon.

[0121] FIG. 5 is a scanning electron microscope image of the negative electrode material provided in Example 1. As can be seen from FIG. 5, the negative electrode material is uniform, and all of its surfaces are coated with a carbon layer.

[0122] Based on the above diagrams and methods, the negative electrode material obtained in this example comprises a first skeleton, a second skeleton, and nanosilicon that are intertwined with each other, the first skeleton being a lithium magnesium silicate material with a network structure, and the second skeleton being a carbon material with a network structure, among which the nanosilicon is distributed within and on the surface of the lithium magnesium silicate material matrix.

[0123] Based on the analysis of the above drawings and methods, it can be seen that the negative electrode material obtained in this example comprises a lithium magnesium silicate material, a carbon material and nanosilicon, the lithium magnesium silicate material has a porous structure, the pores of the lithium magnesium silicate material are filled with a carbon material, and the nanosilicon is distributed within the matrix and on the surface of the lithium magnesium silicate material.

[0124] Example 2 This example is basically the same as the method and steps of Example 1, except that steps (5) and (6) are combined to mix the fourth precursor with asphalt, place it in a hot press furnace, and heat-treat it at 800°C under a pressure of 10 MPa for 3 hours. After the heat-treatment, the material is crushed and sieved to obtain the negative electrode material.

[0125] From the scanning electron microscope images, EDS maps and XRD charts, as well as the analysis of the content of the methods and steps, it can be seen that a single heat treatment not only reacts lithium carbonate to obtain lithium magnesium silicate material, but also carbonizes asphalt to obtain carbon material, and the two tend to intertwine or form a structure in which they are mutually intertwined or filled with each other.

[0126] The negative electrode material obtained in this example includes a first skeleton, a second skeleton, and nanosilicon that are entangled with each other, the first skeleton being a lithium magnesium silicate material with a network structure, and the second skeleton being a carbon material with a network structure, with nanosilicon distributed within and on the surface of the lithium magnesium silicate material matrix.

[0127] The negative electrode material obtained in this example includes a lithium magnesium silicate material, a carbon material, and nanosilicon. The lithium magnesium silicate material has a porous structure, and the pores of the lithium magnesium silicate material are filled with a carbon material, with nanosilicon distributed within the matrix and on the surface of the lithium magnesium silicate material.

[0128] Example 3 This example is basically the same as the method and steps of Example 1, except that in step (6), the fifth precursor is mixed with asphalt, placed in a calcination furnace, and calcined at 800°C for 3 hours. The calcined material is then crushed and sieved to obtain the negative electrode material.

[0129] From the scanning electron microscope images, EDS maps and XRD charts, and the analysis of the method and step contents, it can be seen that the hot pressing process was not performed during the calcination process. Without the need for a carbon material, asphalt can be carbonized by calcination to obtain a carbon material. can be allowed to fill the pores of the lithium magnesium silicate material.

[0130] The negative electrode material obtained in this example includes a first skeleton, a second skeleton, and nanosilicon that are entangled with each other, the first skeleton being a lithium magnesium silicate material with a network structure, and the second skeleton being a carbon material with a network structure, with nanosilicon distributed within and on the surface of the lithium magnesium silicate material matrix.

[0131] The negative electrode material obtained in this example includes a lithium magnesium silicate material, a carbon material, and nanosilicon. The lithium magnesium silicate material has a porous structure, and the pores of the lithium magnesium silicate material are filled with a carbon material, with nanosilicon distributed within the matrix and on the surface of the lithium magnesium silicate material.

[0132] Example 4 This example is basically the same as the method and steps of Example 1, except that in step (6), the fifth precursor is placed in a chemical vapor deposition furnace, methane is introduced, and the deposition is carried out at 800°C for 3 hours. After deposition, the material is crushed and sieved to obtain the negative electrode material.

[0133] From the scanning electron microscope images, EDS maps and XRD charts, as well as the analysis of the method and step contents, it can be seen that the carbon material can be formed in the pores or voids of the magnesium lithium silicate material by chemical vapor deposition.

[0134] The negative electrode material obtained in this example includes a first skeleton, a second skeleton, and nanosilicon that are entangled with each other, the first skeleton being a lithium magnesium silicate material with a network structure, and the second skeleton being a carbon material with a network structure, with nanosilicon distributed within and on the surface of the lithium magnesium silicate material matrix.

[0135] The negative electrode material obtained in this example includes a lithium magnesium silicate material, a carbon material, and nanosilicon. The lithium magnesium silicate material has a porous structure, and the pores of the lithium magnesium silicate material are filled with a carbon material, with nanosilicon distributed within the matrix and on the surface of the lithium magnesium silicate material.

[0136] Example 5 This example is basically the same as the method and steps of Example 1, except that in step (2), the first precursor is mixed with sodium chloride and aluminum powder in a mass ratio of 1:5:0.9, respectively, and after uniform mixing, the mixture is reacted in a nitrogen atmosphere at 700°C for 5 hours to obtain a second precursor.

[0137] From the scanning electron microscope images, EDS maps and XRD charts, as well as the analysis of the process and steps, it can be seen that the process uses aluminum powder to reduce silicon dioxide, and finally forms lithium aluminum silicate material.

[0138] The negative electrode material obtained in this example includes a first skeleton, a second skeleton, and nanosilicon that are entangled with each other, the first skeleton being a lithium aluminum silicate material with a network structure, and the second skeleton being a carbon material with a network structure, with nanosilicon distributed within and on the surface of the lithium aluminum silicate material matrix.

[0139] The negative electrode material obtained in this example includes a lithium aluminum silicate material, a carbon material, and nanosilicon. The lithium magnesium silicate material has a porous structure, with the carbon material filling the pores of the lithium aluminum silicate material, and nanosilicon distributed within and on the surface of the lithium magnesium silicate material matrix.

[0140] Example 6 This example is basically the same as the method and steps of Example 1, except that in step (2), the first precursor is mixed with sodium chloride, magnesium powder, and aluminum powder in a mass ratio of 1:5:0.45:0.4, respectively, and after uniform mixing, the mixture is reacted in a nitrogen atmosphere at 700°C for 5 hours to obtain a second precursor.

[0141] From the scanning electron microscope images, EDS maps and XRD charts, as well as the analysis of the process and steps, it can be seen that the process uses aluminum powder and magnesium powder to simultaneously reduce silicon dioxide, ultimately forming lithium aluminum silicate material and lithium magnesium silicate material.

[0142] The negative electrode material obtained in this example includes a first skeleton, a second skeleton, and nanosilicon that are entangled with each other. The first skeleton is a mixed material of lithium aluminum silicate and lithium magnesium silicate with a network structure, and the second skeleton is a carbon material with a network structure, in which nanosilicon is distributed within and on the surface of the mixed material matrix of lithium aluminum silicate and lithium magnesium silicate.

[0143] The negative electrode material obtained in this example includes a mixed material of lithium aluminum silicate and lithium magnesium silicate, a carbon material, and nanosilicon, and the mixed material of lithium magnesium silicate and lithium magnesium silicate has a porous structure, with the pores of the lithium aluminum silicate material filled with carbon material, and nanosilicon distributed within and on the surface of the mixed material matrix of lithium magnesium silicate and lithium magnesium silicate.

[0144] Example 7 The method and steps of this embodiment are basically the same as those of the first embodiment, with the following differences: In step (3), the second precursor is placed in an aqueous solution, the ratio of the second precursor to water is 1:4, and after uniform stirring, an industrial hydrochloric acid solution with a weight ratio of 10:8 to the second precursor is added thereto. After reacting for 0.5 hours, the mixture is centrifuged and washed with water to remove impurities, thereby obtaining a third precursor.

[0145] In step (4), the third precursor is dispersed in an aqueous solution, the ratio of the framework material to water is 1:5, and lithium carbonate is added thereto in a weight ratio of 8:1 to the framework material, and the solvent is evaporated to dryness under stirring conditions to obtain a fourth precursor.

[0146] The negative electrode material obtained in this example includes a first skeleton, a second skeleton, and nanosilicon that are entangled with each other, the first skeleton being a lithium magnesium silicate material with a network structure, and the second skeleton being a carbon material with a network structure, with nanosilicon distributed within and on the surface of the lithium magnesium silicate material matrix.

[0147] The negative electrode material obtained in this example includes a lithium magnesium silicate material, a carbon material, and nanosilicon. The lithium magnesium silicate material has a porous structure, and the pores of the lithium magnesium silicate material are filled with a carbon material, with nanosilicon distributed within the matrix and on the surface of the lithium magnesium silicate material.

[0148] Example 8 This example is basically the same as the method and steps of Example 1, with the exception that (1) 500 g of nano-silicon dioxide is taken, dispersed in 10 kg of aqueous solution, and after uniform stirring, 40 g of sodium carboxymethylcellulose is added thereto, and after uniform stirring, spray granulation is performed to obtain the first precursor. In step (6), the fifth precursor is placed in a chemical vapor deposition furnace, methane is introduced, and the deposition is performed at 800 °C for 5 hours. The deposited material is then pulverized and sieved to obtain the negative electrode material.

[0149] The negative electrode material obtained in this example includes a first skeleton, a second skeleton, and nanosilicon that are entangled with each other, the first skeleton being a lithium magnesium silicate material with a network structure, and the second skeleton being a carbon material with a network structure, with nanosilicon distributed within and on the surface of the lithium magnesium silicate material matrix.

[0150] The negative electrode material obtained in this example includes a lithium magnesium silicate material, a carbon material, and nanosilicon. The lithium magnesium silicate material has a porous structure, and the pores of the lithium magnesium silicate material are filled with a carbon material, with nanosilicon distributed within the matrix and on the surface of the lithium magnesium silicate material.

[0151] Example 9 This example is basically the same as the method and steps of Example 1, except that (6) the fifth precursor is mixed with asphalt, placed in a hot press furnace, and calcined at 800°C under 30 MPa for 3 hours. The calcined material is then crushed and sieved to obtain the negative electrode material.

[0152] The negative electrode material obtained in this example includes a first skeleton, a second skeleton, and nanosilicon that are entangled with each other, the first skeleton being a lithium magnesium silicate material with a network structure, and the second skeleton being a carbon material with a network structure, with nanosilicon distributed within and on the surface of the lithium magnesium silicate material matrix.

[0153] The negative electrode material obtained in this example includes a lithium magnesium silicate material, a carbon material, and nanosilicon. The lithium magnesium silicate material has a porous structure, and the pores of the lithium magnesium silicate material are filled with a carbon material, with nanosilicon distributed within the matrix and on the surface of the lithium magnesium silicate material.

[0154] Example 10 This example is basically the same as the method and steps of Example 1, except that (6) the fifth precursor is mixed with asphalt, placed in a hot press furnace, and calcined at 800°C under atmospheric pressure for 3 hours. The calcined material is then crushed and sieved to obtain the negative electrode material.

[0155] The negative electrode material obtained in this example includes a first skeleton, a second skeleton, and nanosilicon that are entangled with each other, the first skeleton being a lithium magnesium silicate material with a network structure, and the second skeleton being a carbon material with a network structure, with nanosilicon distributed within and on the surface of the lithium magnesium silicate material matrix.

[0156] The negative electrode material obtained in this example includes a lithium magnesium silicate material, a carbon material, and nanosilicon. The lithium magnesium silicate material has a porous structure, and the pores of the lithium magnesium silicate material are filled with a carbon material, with nanosilicon distributed within the matrix and on the surface of the lithium magnesium silicate material.

[0157] [Table 1]

[0158] In addition, Li x M y The sum of the mass percentage content of the SiO4 material, the mass percentage content of the nanosilicon, and the mass percentage content of the carbon material is close to 100%, which is due to the possibility that one or more impurities may be contained in the negative electrode material when it is produced, such as one or more impurities including incompletely reacted silicon oxide, MgO, by-product MgSiO4, etc.

[0159] The thickness of the carbon coating layer is measured by cross-sectional SEM testing.

[0160] The test method for the specific surface area of ​​the negative electrode material is a Micro Specific Surface Area Analyzer.

[0161] D50 test method for negative electrode materials : Malvern Laser Particle Sizer 3000 The cumulative 50% particle diameter based on the volume-based particle size distribution obtained using do.

[0162] Li x M y The test method for the mass percentage content of SiO4 material is the total dissolved component analysis method.

[0163] The test method for the mass percentage content of nanosilicon is X-ray fluorescence analysis.

[0164] The test method for the mass percentage content of carbon materials is an infrared carbon-sulfur analyzer.

[0165] The porosity test method is to measure the porosity by mercury intrusion. The porosity is measured at least three times, and the arithmetic mean value of the three measurements is used as the measurement result.

[0166] The skeletal diameter distribution range test method is to measure the skeletal diameter at selected different points in the fixed area using a scanning electron microscope to obtain the skeletal diameter distribution range.

[0167] Comparative Example 1 This comparative example is basically the same as the method and steps of Example 1, except that step (4) is not performed and no magnesium lithium silicate material is ultimately formed.

[0168] Comparative Example 2 This comparative example is basically the same as the method and steps of Example 1, except that step (4) and step (6) are not performed, and the magnesium lithium silicate material and carbon material are not finally formed.

[0169] Comparative Example 3 This comparative example is basically the same as the method and steps of Example 1, except that in step (2), molten sodium chloride is not added and a porous or network structure skeleton is not formed.

[0170] Comparative Example 4 This comparative example is basically the same as the method and steps of Example 1, except that the hydrochloric acid washing reaction in step (3) is not carried out, and a porous magnesium lithium silicate material is not formed.

[0171] The performance of the negative electrode materials obtained in Examples 1 to 6 and Comparative Examples 1 to 4 was measured and is shown in Table 2.

[0172] The composite negative electrode materials, conductive agent, and adhesive of Examples 1 to 6 and Comparative Examples 1 to 4 were mixed in a solvent in a mass ratio of 93:2:5. The resulting mixed slurry was applied to a copper foil current collector and vacuum-dried to produce a negative electrode strip. CR2016 button batteries were then assembled using a conventional process with a 1 mol / L LiPF6 / EC+DMC+EMC (v / v=1:1:1) electrolyte, a SK (12 μm) separator, and a housing. Electrochemical performance tests were conducted at a current density of 1 C equal to 1000 mAh / g. The capacity and initial efficiency of the materials were tested at 0.1 C, and the retention rate and volume expansion rate after 100 charge / discharge cycles were also tested at 1 C.

[0173] [Table 2]

[0174] As can be seen from the manufacturing method of the negative electrode material, Tables 1 and 2, the negative electrode material according to the examples of the present application has a high initial efficiency, a high cycle retention rate, and a small volume expansion coefficient.

[0175] Comparing Example 1 and Comparative Example 1, it can be seen that in Comparative Example 1, the lithium magnesium silicate material is prepared without adding lithium carbonate, and the initial efficiency and cycle retention are low. In addition, since there is no limitation on the lithium magnesium silicate material, the volume expansion coefficient of the negative electrode material is high.

[0176] As can be seen from a comparison between Example 1 and Comparative Example 2, the lithium magnesium silicate material in Comparative Example 2 was produced without adding lithium carbonate and without carbon coating. The resulting negative electrode material had a high capacity, but its volume expansion coefficient was very high, its cycle retention rate was very low, and its initial efficiency was also low.

[0177] Comparing Example 1 and Comparative Example 3, it can be seen that when no molten salt was added in Comparative Example 3 to prepare the lithium magnesium silicate material, almost no pores were formed, and it was difficult to form an entangled structure between the carbon material and the lithium magnesium silicate material, resulting in a low cycle retention rate of the obtained product.

[0178] As can be seen from a comparison between Example 1 and Comparative Example 4, in Comparative Example 4, a molten salt was added but pickling with hydrochloric acid was not performed, and the resulting negative electrode material contained a large amount of molten salt, making it difficult to form a porous lithium magnesium silicate material, and the capacity, initial efficiency, and cycle retention were all low, and the volume expansion coefficient was also high.

[0179] As can be seen from the comparison between Example 1 and Example 2, in Example 1, firstly, the magnesium lithium silicate material was obtained by firing, and then further calcined to obtain a carbon material; in Example 2, The negative electrode material is made of lithium magnesium silicate and carbon material by a single heat treatment, and there is no significant difference in the performance of the resulting material. Is it possible to manufacture it in stages by firing and calcining, or by a single heat treatment? It will be explained that either of these can improve the performance of the resulting negative electrode material.

[0180] As can be seen from a comparison between Example 1 and Example 3, Example 1 is pressure-coated and Example 3 is pressure-coated, and the performance of the negative electrode material obtained by pressure-coating is relatively better.

[0181] As can be seen from a comparison between Example 1 and Example 4, the carbon material in Example 1 was prepared using the asphalt coating method, while the carbon material in Example 4 was prepared using the chemical vapor deposition method, and the performance of the resulting negative electrode material is comparable.

[0182] As can be seen from a comparison of Examples 1, 5, and 6, Li in Example 1 x M yThe M metal in SiO4 is magnesium, the M metal in Example 5 is aluminum, and the M metal in Example 6 is a mixture of magnesium and aluminum, and the performance of the final negative electrode material corresponds to these.

[0183] Comparing Examples 1, 7 and 8, it can be seen that the diameter of the first skeleton in the negative electrode material of Example 7 is too large, resulting in a decrease in the gram capacity and initial efficiency of the material, and no significant improvement in cycle performance and expansion performance. This is because the large size of the first skeleton makes it difficult for lithium ions to desorb from the nanosilicon particles, resulting in a decrease in the capacity and initial efficiency of the material. The diameter of the second skeleton in the negative electrode material of Example 8 is too large, resulting in a decrease in electrical performance. This is because the diameter of the second skeleton increases, increasing the carbon content in the material. The capacity and initial efficiency of the carbon material are both lower than those of nanosilicon, resulting in a decrease in the capacity and initial efficiency of the composite material.

[0184] Comparing Examples 1, 9, and 10, it can be seen that the porosity of the negative electrode material in Example 9 is too small, resulting in large expansion of the material. This reduces the porosity of the material, and the space available to accommodate the volumetric expansion of the nanosilicon during charging and discharging is relatively reduced, resulting in large cycling expansion of the material. The porosity of Example 10 is too large, resulting in a large specific surface area of ​​the material and poor cycling performance. This is because the voids increase, making it easier for the electrolyte to penetrate into the material, increasing side reactions between the nanosilicon and the electrolyte and resulting in poor cycling performance.

[0185] The above-described embodiments are only a portion of the present application, not all of the embodiments. The detailed description of the embodiments of the present application does not limit the scope of the claimed application, but only shows selected embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments in the present application without the need for creative labor fall within the scope of protection of the present application.

Claims

1. A negative electrode material comprising a composite material and a coated carbon layer present on a surface of the composite material, the composite material includes a first skeleton, a second skeleton, and nanosilicon that are entangled with each other; The first skeleton is Li x M y SiO 4 (wherein M includes Mg and / or Al, and the values ​​of x and y satisfy a charge balance.) material, and the second skeleton includes a carbon material, The Li x M y SiO 4 The nanosilicon is distributed within and / or on the surface of a matrix of a material; the diameter of the first skeleton is 10 nm to 400 nm, and the diameter of the second skeleton is 10 nm to 500 nm; The diameter of the first skeleton and the diameter of the second skeleton are obtained by measuring in a scanning electron microscope image.

2. 2. The negative electrode material according to claim 1, wherein the thickness of the carbon coating layer is 5 nm to 80 nm.

3. the coated carbon layer contains a carbon material, The carbon material includes one or a combination of two of soft carbon and hard carbon; and The Li x M y SiO 4 2. The negative electrode material according to claim 1, wherein the porosity of the material is 30% to 46%.

4. The Li x M y SiO 4 2. The negative electrode material according to claim 1, wherein 2≦x≦3.4 and 0.4≦y≦1.

5. The particle size of the nanosilicon is 5 nm to 200 nm; The specific surface area of ​​the negative electrode material is 1 m 2 / g to 3m 2 / g, The negative electrode material according to claim 1, characterized in that the shape of the negative electrode material is spherical particles, the average particle size (D50) of the particles of the negative electrode material is 5 μm to 30 μm, and the D50 is a cumulative 50% particle size based on a volume-based particle size distribution obtained using a laser diffraction particle size analyzer.

6. The Li x M y SiO 4 The content of the material in the negative electrode material is 5% by mass to 30% by mass, The content of the nanosilicon in the negative electrode material is 30% by mass to 60% by mass, and 2. The negative electrode material according to claim 1, wherein the content of the carbon material in the negative electrode material is 10% by mass to 65% by mass.

7. The Li x M y SiO 4 The material has a porous structure, and the Li x M y SiO 4 The pores of the material are filled with the carbon material, The Li x M y SiO 4 2. The negative electrode material according to claim 1, wherein the nanosilicon is distributed within and / or on the surface of a matrix made of the material.

8. A lithium ion battery comprising the negative electrode material according to any one of claims 1 to 7.

9. A method for producing a negative electrode material, comprising: Lithium-ion nanosilicon is distributed within and / or on the surface of the matrix, and has a porous or network structure. x M y SiO 4 (wherein M includes Mg and / or Al) forming a material; The Li x M y SiO 4 filling a carbon material into the pores of the porous structure or the voids of the network structure of the material to obtain the negative electrode material; The manufacturing method includes: A framework material having a network structure or a porous structure is mixed with a lithium salt, and then calcined to form the Li x M y SiO 4 Obtaining the material, and x M y SiO 4 forming the carbon material within the pores or voids of a material to obtain the negative electrode material; Or, The method includes mixing a framework material having a network structure or a porous structure, a lithium salt, and an organic carbon source, and then performing a heat treatment to obtain the negative electrode material; The method for producing a negative electrode material, wherein the framework material comprises nanosilicon, silicon oxide supported on the surface of the nanosilicon, and metal M oxide.

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