阅读说明：本技术 一种片状硅材料、其制备方法和用途 (Sheet silicon material, preparation method and application thereof ) 是由 赵增华 段春阳 钱建华 于 2021-08-03 设计创作，主要内容包括：本申请公开了一种片状硅材料的制备方法,所述方法包括：将分散有硅颗粒的悬浮液通入流通通道逐级变窄的微流道内,通过在所述微流道内流动进行微流道降级,获得片状硅材料；所述微流道能够提供沿管路圆周切向的剪切作用。所述制备方法采用物理方法将硅材料进行片层化,能够保留硅原料的晶型构象,克服了化学方法造成的试剂残留,对硅颗粒原料的制备方法兼容性好,降低了硅材料的制备门槛。(The application discloses a preparation method of a sheet-shaped silicon material, which comprises the following steps: introducing the suspension dispersed with the silicon particles into a micro-channel with a flow channel gradually narrowed, and degrading the micro-channel by flowing in the micro-channel to obtain a sheet-shaped silicon material; the microchannels can provide a shearing action tangential to the circumference of the tubing. The preparation method adopts a physical method to carry out the laminarization of the silicon material, can keep the crystal form conformation of the silicon raw material, overcomes the reagent residue caused by a chemical method, has good compatibility with the preparation method of the silicon particle raw material, and reduces the preparation threshold of the silicon material.)

1. A method for preparing a sheet-like silicon material, the method comprising:

introducing the suspension dispersed with the silicon particles into a micro-channel with a flow channel gradually narrowed, and degrading the micro-channel by flowing in the micro-channel to obtain a sheet-shaped silicon material;

the microchannels can provide a shearing action tangential to the circumference of the tubing.

2. The method of claim 1, wherein the shear rate of the shearing is not less than 10000s^-1；

Preferably, the number of times the suspension in which the silicon particles are dispersed is passed into the micro flow channel is more than 1.

3. The method of claim 1 wherein the flow channel of the microchannel is provided with at least two sizing sections and at least one reducing section of different flow channel sizes;

preferably, the length of the sizing section is more than 10 times, preferably 10-40 times, of the length of the variable diameter section connected with the upstream of the sizing section along the flowing direction of the liquid in the micro flow channel.

4. The method of claim 3, wherein the sizing section has a flow channel dimension of any value from 0.5mm to 5.0 mm;

preferably, along the flowing direction of liquid in the flow channel of the micro-flow channel, the size of the flow channel of the first sizing section is 2-5 mm, and the size of the flow channel of the last sizing section is 0.5-0.8 mm;

preferably, the flow channel of the microchannel is provided with at least three sizing sections and at least two reducing sections.

5. The method according to claim 3 or 4, wherein the micro flow channel comprises a flow channel housing and a rotating shaft member provided inside the flow channel housing to be rotatable around an axis, a flow channel of the micro flow channel is constituted from a gap between the housing and the rotating shaft member, a diameter of the rotating shaft member is fixed, and a change in a size of the flow channel of the micro flow channel is effected by a change in an inner diameter of the flow channel housing;

or, the microchannel includes a channel housing and a rotating shaft member provided in the channel housing and rotatable around an axis, and a channel of the microchannel is constituted by a gap between the housing and the rotating shaft member, and the channel housing has a fixed inner diameter, and a change in channel size of the microchannel is realized by a change in size of the rotating shaft member.

6. A method according to claim 5, characterized in that the rotating shaft part rotates at a speed of more than or equal to 5000rpm, preferably between 8000rpm and 15000 rpm.

7. The production method according to any one of claims 1 to 6, wherein in the suspension in which the silicon particles are dispersed, a solid-to-liquid ratio is 1g/L to 50g/L, preferably 20g/L to 30 g/L;

preferably, the solvent of the suspension of dispersed oily silicon particles includes any one of water and an organic solvent or a combination of at least two thereof;

preferably, the viscosity of the organic solvent at 20 ℃ is less than or equal to 1.2cps, and the boiling point is more than or equal to 65 ℃;

preferably, the flow rate of the suspension flowing in the micro flow channel is 1-50L/min, preferably 15-25L/min.

8. The production method according to any one of claims 1 to 7, wherein the silicon particles comprise any one of metallurgical-grade silicon, solar-grade silicon, or electronic-grade silicon, or a combination of at least two of them;

preferably, the purity of the silicon particles is more than or equal to 90 percent;

preferably, the silicon particles include any one of or a combination of at least two of single crystal silicon particles, polycrystalline silicon particles, or amorphous silicon particles;

preferably, the largest dimension of the silicon particles is less than or equal to 0.1 mm.

9. The silicon material prepared by the preparation method of any one of claims 1 to 8, wherein the nano silicon material is in a sheet shape, the diameter-thickness ratio of the nano silicon material is not less than 5, the sheet diameter size is not less than 10nm, and the thickness is not more than 5 μm.

10. The silicon material of claim 9, wherein the nano silicon material is single crystal silicon, the nano silicon material is prepared by the preparation method of any one of claims 1 to 8, and the silicon particles are single crystal silicon;

or, the nano silicon material is polysilicon, the nano silicon material is prepared by the preparation method of any one of claims 1 to 8, and the silicon particles are polysilicon;

or, the nano silicon material is amorphous silicon, the nano silicon material is prepared by the preparation method of any one of claims 1 to 8, and the silicon particles are amorphous silicon.

11. Use of a silicon material according to claim 9 or 10 as any one of, or in combination with at least two of, a lithium ion battery negative electrode material, an organosilicon preparation precursor, a refractory protective layer, a binder additive.

Technical Field

The invention belongs to the field of preparation of silicon materials, and particularly relates to a sheet silicon material, a preparation method and application thereof, in particular to a method for preparing the sheet silicon material, the sheet silicon material prepared by the method and the application of the silicon material.

Background

In a lithium ion battery, artificial natural graphite is a preferred negative electrode material for a long time, but the reversible capacity limit value of graphite is 372mAh/g, commercial high-end graphite products reach 360-365 mAh/g and are very close to theoretical capacity.

The theoretical capacity of the silicon material is 3580mAh/g, and is always considered to be an ideal element for replacing graphite in the negative electrode. However, the very large volume change (about 300%) during the Si/electrolyte cycling results in pulverization and aging, which affects the number of charge and discharge cycles, and is a technical obstacle to the use of silicon materials.

How to solve the problem of volume expansion of silicon materials is a technical problem to be solved in the field.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a preparation method of a sheet-shaped silicon material, which comprises the following steps:

introducing the suspension dispersed with the silicon particles into a micro-channel with the inner diameter gradually narrowed, and degrading the micro-channel by flowing in the micro-channel to obtain a sheet-shaped silicon material;

the microchannels can provide a shearing action tangential to the circumference of the tubing.

The invention provides a preparation method of a sheet-shaped silicon material, which realizes the laminarization of silicon particles by introducing a suspension of silicon particles into a micro-channel with a flow channel gradually narrowed and a circumferential tangential shearing action. The silicon particles are arranged in the micro-channel, the micro-channel is gradually narrowed, and in the process that the flow channel is gradually narrowed, the pressure and the shearing stress of a flow field are changed, so that the silicon particles are sheared in the flow direction; on the other hand, under the action of circumferential tangential shearing, the silicon particles are subjected to circumferential shearing action; on the contrary, in the radial direction of the circumference, the shearing effect is very small; and finally, thinning the Si-Si bonds of the silicon particles in a direction parallel to the flow direction of the flow channel by the combined force of the two shearing actions, and cutting the surfaces of the silicon particles in the flow direction and the circumferential tangential direction to obtain the sheet-shaped silicon material. In the micro-channel which is gradually narrowed, the flow speed of the suspension is suddenly changed due to the reduction of the size of the flow channel, and the liquid acts as a blade to cut silicon particles and cuts the silicon particles along the flow direction of the flow channel; the silicon particles are cut along the circumferential direction under the action of circumferential tangential shearing; finally, the effect of layering the silicon particles is realized.

In the preparation method provided by the invention, the laminarization of the silicon particles is only a physical process, so that the crystal structure of the silicon particles is not changed, namely, the laminarization silicon material prepared by the silicon particles being single crystals is single crystals, the laminarization silicon material prepared by the silicon particles being polycrystalline is polycrystalline, and the laminarization silicon material prepared by the silicon particles being amorphous is amorphous.

Preferably, the shear rate of the shearing action is more than or equal to 10000s^-1E.g. 10000s^-1、15000s^-1、20000s^-1、25000s^-1、30000s^-1、35000s^-1、40000s^-1And the like.

Preferably, the number of times the suspension in which the silicon particles are dispersed is passed into the micro flow channel is more than 1.

In the preparation method of the sheet-like silicon material, the suspension in which the silicon particles are dispersed is introduced into the micro flow channel for more than 1 (e.g., 2 times, 3 times, 5 times, 8 times, 10 times, 20 times, 50 times, 100 times, etc.), that is, the suspension can repeatedly pass through the micro flow channel to realize the sheet formation of the silicon particles.

Namely, the suspension in which the silicon particles are dispersed is subjected to shearing action after being introduced into the micro flow channel to carry out primary laminarization, and then the suspension subjected to primary laminarization is continuously introduced into the micro flow channel and is continuously subjected to secondary laminarization under the shearing action, and the steps are repeated.

In the actual operation process, the number of times the suspension in which the silicon particles are dispersed is introduced into the micro flow channel can be calculated by the length and the flow rate of the micro flow channel.

Preferably, the flow channel of the micro flow channel is provided with at least two fixed diameter sections and at least one variable diameter section, wherein the sizes of the flow channels are different.

The sizing section means that the size of the flow channel is constant, and the sizing section is understood to be a channel with a specific size; the variable diameter section means that the size of the flow channel changes, and can be understood as a truncated cone-shaped channel.

At least two sizing sections with different inner diameters are arranged in a micro-channel with a gradually narrowed flow channel to narrow the flow channel, so that silicon particles are sheared in the micro-channel and are laminated under the action of fluid flow force. The connection of the sizing section is realized by the reducing section, the longer the length of the reducing section is, the slower the inner diameter is reduced, the radial force can be applied to the suspension in the flowing process, the layering effect of the silicon material is degraded, and the faster the inner diameter is reduced, the force can be weakened quickly, and the force can enter the range with larger shearing force in the flow channel direction and the circumferential direction quickly, so that the layering of the silicon particles is realized.

Preferably, the length of the sizing section is 10 times or more (e.g., 11 times, 12 times, 13 times, 14 times, 15 times, 16 times, 17 times, 18 times, 19 times, 22 times, 25 times, 28 times, 30 times, 34 times, 37 times, 39 times, etc.), preferably 10 to 40 times, the length of the variable diameter section connected upstream of the sizing section in the flow direction of the liquid in the flow channel of the micro flow channel.

The length of the sizing section is too small, meaning that the sizing section is relatively long, and the sizing section can cause a radial force to the silicon particles, which affects the laminarization of the silicon material.

In addition, the force of the silicon particles in the sizing section along the flowing direction of the liquid in the micro-flow channel is smaller and smaller along with the stratification of the silicon particles until a balance is reached, and the length of the sizing section is increased continuously, so that the effect is not increased obviously, and the length of the sizing section is preferably within 40 times of the length of the reducing section connected with the sizing section.

Preferably, the flow passage size of the sizing section is any value from 0.5mm to 5.0mm (e.g., 0.6mm, 0.8mm, 1.5mm, 1.8mm, 2.5mm, 3.5mm, 4.0mm, 4.5mm, 4.8mm, etc.).

Preferably, the flow channel size of the first sizing section is 2 to 5mm (e.g., 2.1mm, 2.4mm, 2.8mm, 3.3mm, 3.5mm, 3.7mm, 3.8mm, 4.1mm, 4.3mm, 4.5mm, 4.7mm, 4.9mm, etc.) and the flow channel size of the last sizing section is 0.5 to 0.8mm (e.g., 0.6mm, 0.7mm, etc.) in the flow direction of the liquid in the flow channel of the micro flow channel.

Preferably, the flow channel of the microchannel is provided with at least three sizing sections and at least two reducing sections.

The specific size of the micro flow channel is not specific, and those skilled in the art can design the micro flow channel according to the size of the silicon particle raw material and the morphology of the target sheet-like silicon material. When the maximum dimension of a silicon particle raw material is less than or equal to 0.1mm and is used for preparing a sheet-shaped silicon material with the diameter-thickness ratio of more than or equal to 5, the sheet diameter size of more than or equal to 10nm and the thickness of less than or equal to 5 microns, the flow channel size of the sizing section of the micro-channel is preferably any value of 0.5mm to 5.0mm, the flow channel size of the first sizing section is 2mm to 5mm and the flow channel size of the last sizing section is 0.5mm to 0.8mm along the flow direction of liquid in the flow channel of the micro-channel, and the design can ensure smooth circulation of silicon particles, provide proper shearing action and prepare the sheet-shaped silicon material more efficiently.

In a preferred embodiment, the microchannel includes a channel housing and a rotating shaft member provided in the channel housing and rotatable around an axis, the channel of the microchannel is formed by a gap between the housing and the rotating shaft member, the diameter of the rotating shaft member is fixed, and the change in the channel size of the microchannel is achieved by changing the inner diameter of the channel housing.

In another preferred embodiment, the microchannel includes a channel housing and a rotating shaft member provided in the channel housing and rotatable around an axis, the channel of the microchannel is formed by a gap between the housing and the rotating shaft member, the channel housing has a fixed inner diameter, and the channel size of the microchannel is changed by changing the size of the rotating shaft member.

In both of the above solutions, the shearing action in the circumferential tangential direction is provided by the fluid disturbance to the microchannel caused by the rotation of the rotating shaft.

Preferably, the rotation speed of the rotating shaft is not less than 5000rpm, preferably 8000-15000 rpm, such as 8500rpm, 9000rpm, 9500rpm, 10000rpm, 10500rpm, 11000rpm, 11500rpm, 12000rpm, 12500rpm, 13000rpm, 13500rpm, 14000rpm, 14500rpm and the like.

The rotating shaft with the rotating speed of more than or equal to 5000rpm is more beneficial to providing the shearing rate of more than or equal to10000s^-1If the rotating speed of the rotating shaft is too low, the shearing rate of the suspension with higher viscosity is difficult to reach 10000s^-1The above.

Preferably, the solid-to-liquid ratio in the suspension in which the silicon particles are dispersed is 1g/L to 50g/L, for example, 5g/L, 10g/L, 15g/L, 20g/L, 25g/L, 30g/L, 35g/L, 40g/L, 45g/L, 48g/L, etc., preferably 20g/L to 30 g/L.

The solid-to-liquid ratio of the suspension in which the silicon particles are dispersed represents the concentration of the suspension, and the flow rate of the lamellar suspension in the microchannel is higher as the concentration is higher, but the viscosity of the suspension is increased as the concentration is too high, so that the shearing action of the silicon particles in the microchannel is weakened, and the lamellar efficiency is reduced.

Preferably, the flow rate of the suspension flowing in the micro flow channel is 1-50L/min, such as 3L/min, 6L/min, 9L/min, 13L/min, 16L/min, 23L/min, 27L/min, 32L/min, 38L/min, 43L/min, 48L/min, etc., preferably 15-25L/min.

The flow rate of the suspension is small, which results in a small shearing action and a low efficiency of the silicon particle sheet formation.

Preferably, the solvent of the suspension of dispersed oily silicon particles includes any one of water and an organic solvent or a combination of at least two thereof.

Preferably, the organic solvent has a viscosity of 1.2cps (e.g., 1.1cps, 1.0cps, 0.8cps, 0.5cps, etc.) at 20 deg.C and a boiling point of 65 deg.C (e.g., 67 deg.C, 70 deg.C, 75 deg.C, 80 deg.C, 83 deg.C, 95 deg.C, etc.).

The viscosity of the organic solvent influences the viscosity of the suspension to a certain extent, and the high viscosity of the organic solvent can cause the viscosity of the suspension to be increased, reduce the shearing action of silicon particles and influence the lamellar effect.

Also, the specific operation of the micro flow channel is not specific, and those skilled in the art can design the micro flow channel according to the size of the silicon particle raw material and the morphology of the target sheet-like silicon material. When the maximum dimension of the silicon particle raw material is less than or equal to 0.1mm, the silicon particle raw material is used for preparing the sheet-shaped silicon material with the sheet diameter ratio of more than or equal to 5, the sheet diameter size of more than or equal to 10nm and the thickness of less than or equal to 5 microns, the flow rate of the suspension is 1-50L/min, the rotating speed of the rotating shaft is more than or equal to 5000rpm, the solid-liquid ratio is 1-50 g/L, the solvent comprises water and an organic solvent (the viscosity at 20 ℃ is less than or equal to 1.2cps, the boiling point is more than or equal to 65 ℃), and the sheet-shaped silicon material can be prepared more efficiently at low cost. One skilled in the art can also select appropriate flow rate, rotation speed, solid-to-liquid ratio and solvent according to the size of the silicon particle raw material and the size of the target sheet silicon material.

Preferably, the silicon particles comprise any one of metallurgical grade silicon, solar grade silicon or electronic grade silicon or a combination of at least two of the same.

Preferably, the purity of the silicon particles is ≥ 90%, e.g. 92%, 95%, 97%, etc.

Preferably, the silicon particles include any one of or a combination of at least two of single crystal silicon particles, polycrystalline silicon particles, or amorphous silicon particles.

The method provided by the application is a physical method, and does not obviously influence the crystal form, purity and the like of silicon in the raw materials, so that the characteristics of the crystal form, purity and the like in the raw materials can be reserved.

Preferably, the silicon particles have a largest dimension of ≦ 0.1mm, such as 0.08mm, 0.06mm, 0.05mm, 0.03mm, and the like.

The invention also aims to provide a silicon material, wherein the nano silicon material is in a sheet shape, the sheet diameter ratio of the nano silicon material is more than or equal to 5, the sheet diameter size is more than or equal to 10nm, and the thickness is less than or equal to 5 mu m.

Preferably, the silicon material is prepared by the preparation method described in one of the purposes.

Preferably, the nano silicon material is monocrystalline silicon, the nano silicon material is prepared by the preparation method of one of the purposes, and the silicon particles are monocrystalline silicon;

or the nano silicon material is polysilicon, the nano silicon material is prepared by the preparation method of one of the purposes, and the silicon particles are polysilicon;

or the nano silicon material is amorphous silicon, the nano silicon material is prepared by the preparation method of one of the purposes, and the silicon particles are amorphous silicon.

The third purpose of the invention is to provide the application of the silicon material according to the second purpose, wherein the silicon material is used as any one or the combination of at least two of a lithium ion battery negative electrode material, an organic silicon preparation precursor, a refractory material protection layer and a binder additive.

Compared with the prior art, the invention has the following beneficial effects:

(1) the invention provides a preparation method of a sheet silicon material, which adopts a physical method to carry out sheet lamination on the silicon material, can keep the crystal form conformation of a silicon raw material, overcomes the reagent residue caused by a chemical method, has good compatibility with the preparation method of a silicon particle raw material, and reduces the preparation threshold of the silicon material.

(2) The preparation method of the sheet-shaped silicon material provided by the invention has controllability on the size of the sheet-shaped silicon material, namely in an optimal scheme, the preparation of the sheet-shaped silicon material with different sizes can be realized through the design, the operating conditions and the like of the micro-channel.

Drawings

FIG. 1 is a schematic view showing the structure of a microchannel device;

FIG. 2 is an SEM image of a sheet silicon material obtained in example 1;

FIG. 3 is a TEM image of a sheet-like silicon material obtained in example 1;

FIG. 4 is an SEM image of a sheet silicon material obtained in example 2;

FIG. 5 is a schematic view showing the structure of another microchannel device;

FIG. 6 is an SEM image of a sheet silicon material obtained in example 3;

FIG. 7 is an SEM image of a sheet silicon material obtained in example 4;

FIG. 8 is an SEM photograph of the flaky silicon nanomaterial obtained in example 5;

FIG. 9 is an SEM image of a sheet silicon material obtained in example 6;

FIG. 10 is an SEM image of a sheet silicon material obtained in example 7;

fig. 11 is an SEM image of the sheet silicon material obtained in comparative example 1;

fig. 12 is an SEM image of the sheet silicon material obtained in comparative example 2.

Detailed Description

The technical solution of the present invention will be further described in detail with reference to specific embodiments. The following examples are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of the invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.

Example 1

A preparation method of a sheet silicon material comprises the following steps:

(1) dispersing polysilicon particle powder (model PS100, purity 99%) in water to prepare silicon particle suspension with a solid-to-liquid ratio of 25 g/L; the size of the silicon particles is 100 meshes;

(2) introducing the silicon particle suspension into a micro flow channel device shown in FIG. 1 (FIG. 1 is a schematic structural view of a micro flow channel device), starting a motor, and starting a rotating shaft 120 at 8000rpm^-1Rotating downwards, closing the inlet valve 140 and the outlet valve 150, starting the circulating pump 160, allowing the silicon particle suspension to enter the micro-channel device at a speed of 20L/min, and circulating in the micro-channel device for 2 hours (at this time, the number of times of circulation of the suspension in the micro-channel is more than 10), thereby obtaining a sheet-like silicon material;

the micro flow channel device has 3 micro flow channels connected in parallel, the micro flow channel has a housing 110, a rotating shaft 120 disposed inside the housing 110, the housing includes a first diameter fixing section 111, a second diameter fixing section 112, a third diameter fixing section 113, a first diameter changing section 114 connecting the first diameter fixing section 111 and the second diameter fixing section 112, and a second diameter changing section 115 connecting the second diameter fixing section 112 and the third diameter fixing section 113 in a liquid flow direction; the length of the first diameter section 111 is 300mm, and the inner diameter is 15 mm; the length of the second sizing section 112 is 500mm, and the inner diameter is 12 mm; the length of the third sizing section 113 is 700mm, and the inner diameter is 10.6 mm; the first reducer section 114 is 20mm in length; the second reducer section 115 is 20mm long; the outer diameter of the rotating shaft 120 is 10 mm; the micro flow channel device is further provided with a motor 130 electrically connected with the rotating shaft 120 of the micro flow channel for providing rotating power; an inlet valve 140 and an outlet valve 150 for controlling the input and output of the suspension; a circulation pump 160 is used to control the circulation flow of the suspension.

The SEM image and TEM image of the sheet silicon material obtained in this example are shown in fig. 2 and 3; it can be seen from fig. 2 that the sheet size of the sheet silicon material prepared in this embodiment is 150nm on average, the average thickness is 10nm, that is, the aspect ratio is 15 on average, and it can be seen from fig. 3 that the sheet silicon material prepared in this embodiment has a polycrystalline morphology.

Example 2

A preparation method of a sheet silicon material comprises the following steps:

(1) dispersing metallurgical silicon powder (model MS50, purity 98%) in water to prepare silicon particle suspension with solid-to-liquid ratio of 30 g/L; the size of the silicon particles is 50 meshes;

(2) introducing the silicon particle suspension into a micro flow channel device shown in fig. 1 (fig. 1 is a schematic structural diagram of the micro flow channel device), starting a motor, starting a rotating shaft 120 to rotate at 12000rpm, closing an inlet valve 140 and an outlet valve 150, starting a circulating pump 160, introducing the silicon particle suspension into the micro flow channel device at a speed of 15L/min, and circulating the silicon particle suspension in the micro flow channel device for 2 hours (at this time, the circulation frequency of the suspension in the micro flow channel is more than 10 times); obtaining a sheet-shaped silicon material;

the micro flow channel device has 3 micro flow channels connected in parallel, the micro flow channel has a housing 110, a rotating shaft 120 disposed inside the housing 110, the housing includes a first diameter fixing section 111, a second diameter fixing section 112, a third diameter fixing section 113, a first diameter changing section 114 connecting the first diameter fixing section 111 and the second diameter fixing section 112, and a second diameter changing section 115 connecting the second diameter fixing section 112 and the third diameter fixing section 113 in a liquid flow direction; the length of the first diameter section 111 is 600mm, and the inner diameter is 12 mm; the length of the second sizing section 112 is 600mm, and the inner diameter is 10.5 mm; the third sizing section 113 is 600mm in length and 8.6mm in inner diameter; the first reducer section 114 is 20mm in length; the second reducer section 115 is 15mm in length; the outer diameter of the rotating shaft 120 is 8 mm; the micro flow channel device is further provided with a motor 130 electrically connected with the rotating shaft 120 of the micro flow channel for providing rotating power; an inlet valve 140 and an outlet valve 150 for controlling the input and output of the suspension; a circulation pump 160 is used to control the circulation flow of the suspension.

An SEM image of the sheet silicon material obtained in this example is shown in fig. 4; it can be seen from fig. 4 that the silicon material prepared in this example is flaky, the average size of the lamella is 500nm, the average thickness is 20nm, i.e. the aspect ratio is 25 on average.

Example 3

A preparation method of a sheet silicon material comprises the following steps:

(1) dispersing monocrystalline silicon powder (type SS100, purity of 99.9%) in water, and preparing silicon particle suspension with solid-to-liquid ratio of 20 g/L; the size of the silicon particles is 300 meshes;

(2) introducing the silicon particle suspension into a micro flow channel device shown in fig. 5 (fig. 5 is a schematic structural diagram of another micro flow channel device), starting a motor, starting a rotating shaft 220 to rotate at 5000rpm, closing an inlet valve 240 and an outlet valve 250, starting a circulating pump 260, introducing the silicon particle suspension into the micro flow channel device at a speed of 20L/min, and circulating the silicon particle suspension in the micro flow channel device for 1.5 hours (at this time, the number of times of circulation of the suspension in the micro flow channel is more than 8); obtaining a sheet-shaped silicon material;

the micro flow channel device has 3 micro flow channels connected in parallel, the micro flow channel has a housing 210, a rotating shaft 220 provided inside the housing 210, the rotating shaft 220 includes a first diameter fixing shaft 221, a second diameter fixing shaft 222, a third diameter fixing shaft 223, a first diameter changing shaft 224 connecting the first diameter fixing shaft 221 and the second diameter fixing shaft 222, and a second diameter changing shaft 225 connecting the second diameter fixing shaft 222 and the third diameter fixing shaft 223 in a liquid flow direction; the length of the first diameter shaft 221 is 300mm, and the outer diameter is 10.0 mm; the length of the second diameter fixing shaft 222 is 400mm, and the outer diameter is 14.0 mm; the length of the third diameter fixing shaft 223 is 500mm, and the outer diameter is 19.0 mm; the first reducer shaft 224 has a length of 20 mm; the second reducer shaft 225 has a length of 25 mm; the inner diameter of the housing 210 is 20 mm; the micro flow channel device is further provided with a motor 230 electrically connected with the rotating shaft 220 of the micro flow channel for providing rotating power; an inlet valve 240 and an outlet valve 250 for controlling the input and output of the suspension; a circulation pump 260 is used to control the circulation flow of the suspension.

An SEM image of the sheet silicon material obtained in this example is shown in fig. 6; it can be seen from fig. 6 that the silicon material prepared in this example is flaky, the average size of the lamella is 300nm, the average thickness is 15nm, i.e. the aspect ratio is 20 on average.

Example 4

The difference from example 3 is that step (2): introducing the silicon particle suspension into a micro-flow channel device shown in fig. 1 (fig. 1 is a schematic structural diagram of the micro-flow channel device), starting a motor, starting a rotating shaft 120 to rotate at 10000rpm, closing an inlet valve 140 and an outlet valve 150, starting a circulating pump 160, introducing the silicon particle suspension into the micro-flow channel device at a speed of 25L/min, and circulating the silicon particle suspension in the micro-flow channel device for 2 hours (at this time, the circulation frequency of the suspension in the micro-flow channel is more than 12 times); a sheet-like silicon material is obtained.

An SEM image of the sheet silicon material obtained in this example is shown in fig. 7; it can be seen from fig. 7 that the silicon material prepared in this example is flaky, the average size of the sheet layer is 200nm, the average thickness is 10nm, i.e. the aspect ratio is 20 on average.

Example 5

A method for preparing a sheet-like silicon material, which differs from example 1 only in that:

in the micro-channel of the micro-channel device used in the step (2), the length of the first reducing section 114 is 40 mm; the second reducer section 115 has a length of 60 mm.

The sheet diameter of the sheet-like silicon material obtained in this example was about 10 μm on average, the average thickness of the sheet layer was about 2 μm, and the aspect ratio was 5 on average. Although the material prepared in fig. 8 is still in a sheet shape, the thickness of the sheet layer is in a micron order, and the diameter-thickness ratio is small, which indicates that although the micro-channel with the gradually narrowed flow channel and the shearing action along the circumferential direction of the pipeline can sheet the granular silicon powder, the increase of the length of the variable diameter section directly leads to the deterioration of the morphology of the sheet material.

Example 6

A method for preparing a sheet-like silicon material, differing from example 1 only in that,

in the micro-channel of the micro-channel device used in the step (2), the micro-channel device is provided with 3 micro-channels which are connected in parallel, the micro-channel is provided with a shell and a rotating shaft arranged in the shell, and the shell comprises a first diameter fixing section, a second diameter fixing section and a first diameter changing section which is connected with the first diameter fixing section and the second diameter fixing section; the length of the first diameter section is 900mm, and the inner diameter of the first diameter section is 5 mm; the length of the second sizing section is 600mm, and the inner diameter of the second sizing section is 2 mm; the length of the first variable diameter section is 20 mm; the outer diameter of the rotating shaft is 0.3 mm; the micro-channel device is also provided with a motor which is electrically connected with a rotating shaft of the micro-channel to provide rotating power; an inlet valve and an outlet valve for controlling the input and output of the suspension; a circulation pump is used to control the circulation flow of the suspension.

The sheet-like silicon material obtained in this example exhibited a pronounced sheet morphology. As shown in FIG. 9, the sheet-like material had an average size of 3 μm, an average thickness of 200nm for the sheet layer, and an average aspect ratio of 15.

Example 7

A method for preparing a sheet-like silicon material, which differs from example 1 only in that:

and (2) dispersing the polycrystalline silicon particle powder (model PS100, purity of 99%) in the step (1) in an ethanol/water mixed solution, wherein the volume ratio of ethanol to water is 3:1, and the solid-to-liquid ratio of the silicon particle suspension is 25 g/L.

The SEM image of the silicon sheet material obtained in this example is shown in fig. 10, and it can be seen from fig. 10 that the average size of the sheet layer and the average thickness of the silicon sheet material prepared in this example are 120nm and 6nm, i.e. the aspect ratio is 20 on average.

Examples 8 to 9

A method for preparing a sheet-like silicon material, which differs from example 1 only in that: the concentration of the silicon particle suspension in the step (1) is 1g/L (example 8) and 50g/L (example 9).

The sheet size of the sheet-like silicon material obtained in example 8 was 180nm on average, the average thickness was 12nm, and the aspect ratio was 15 on average.

The sheet size of the sheet-like silicon material obtained in example 9 was 240nm on average, the average thickness was 20nm, and the aspect ratio was 12 on average.

Comparative example 1

A method for preparing a sheet-like silicon material, which is different from example 1 in that:

the microchannel device used in the step (2) does not have a rotary shaft 120 in the microchannel.

The morphology of the silicon material prepared in comparative example 1 was similar to that of the starting material, and was silicon particles having an average particle diameter of 100 μm, as shown in fig. 11.

Comparative example 2

A method for preparing a sheet-like silicon material, which is different from example 1 in that:

the inner diameter of the housing 110 of the micro flow channel device used in the step (2) is not changed, specifically 5 mm.

The silicon material prepared in comparative example 2 was a micron-sized sheet silicon material having an average diameter of 10 μm, an average thickness of 1 μm, and an average aspect ratio of 10, as shown in fig. 12.

Comparative example 3

Comparative example 3 was a spherical silicon particle of 100nm size of commercial Shanghai Aladdin reagent S130844.

And (3) performance testing:

the silicon materials obtained in the examples and comparative examples were subjected to the following performance tests:

and assembling the silicon materials obtained in the embodiment and the comparative example into a button lithium ion battery for testing the specific capacity and the cycling stability of the button lithium ion battery. The specific process is as follows:

the silicon material, the conductive carbon black and the LA133 binder are put into deionized water in a beaker according to the mass ratio of 7:2:1 and stirred for 8 hours to obtain black slurry. And then transferring the slurry to the surface of the carbon-coated copper foil, uniformly coating the slurry on the copper foil by using an automatic film coating machine, wherein the film coating thickness is 120 mu m, and then drying the copper foil coated with the slurry in an oven at 80 ℃ for 6 h. And cutting the dried copper foil into electrode slices with the diameter of 15mm by using a perforating machine, compacting the electrode slices by using a tablet press, and then putting the electrode slices into a vacuum drying oven for drying for 8 hours. And weighing and recording the mass of each pole piece in sequence, and multiplying the mass difference between the pole piece and the blank copper foil wafer by the proportion of the silicon material to obtain the mass of the silicon material of the pole piece. In the glove box, half batteries are assembled according to the sequence of button battery negative electrode cover-pole piece-electrolyte-diaphragm-electrolyte-metal lithium piece-button battery positive electrode cover (electrolyte is selected from 1mol/L lithium hexafluorophosphate, solvent is a mixed solution of dimethyl carbonate and ethylene carbonate (volume ratio is 1:1), and diaphragm is a coating-treated polyester film). And after the battery is assembled, taking out the button battery, and standing for 10 hours at room temperature so as to enable the electrolyte to fully infiltrate the pole piece and the diaphragm. And then, the electrochemical performance of the battery is tested by using a button cell full-automatic testing system (LAND CT 2001A). The test voltage range of the constant current charge-discharge test (GCD) is 0.01-1.5V.

(1) Mass specific capacity: the testing method comprises connecting the button cell into a full-automatic testing system (LAND CT2001A) and testing at a current density of 200mA g^-1Under the condition of (1), testing a constant current charge-discharge curve, and calculating the mass specific capacity according to the mass of the silicon material in the electrode plate of the button cell.

(2) And (3) cyclic stability: the testing method comprises connecting the button cell into a full-automatic testing system (LAND CT2001A) and testing at a current density of 200mA g^-1Under the condition (1), the constant-current charge-discharge performance is tested circularly, the test is stopped when the specific capacity is reduced to 70% of the initial capacity, and the circulating stability is represented by the circulating times when the capacity is 70% of the initial capacity.

(3) Volume change rate: and testing the lithium battery by using a method for testing the cycling stability, stopping testing when the specific capacity of the battery is reduced to 70% of the initial capacity, disassembling the button battery, testing the thickness of the negative electrode, testing five point positions and taking the average number as the thickness of the negative electrode after testing. And finally, taking the ratio of the difference value of the thickness of the tested negative electrode and the thickness of the negative electrode before testing to the thickness of the negative electrode before testing as the volume change rate.

The test results are shown in table 1:

TABLE 1

	Specific capacity (mA h g)-1)	Circulation stability (subcircuit)	Volume change rate (%)
				Example 1	1462	132	53
Example 2	761	43	127
				Example 3	935	93	91
Example 4	1142	120	72
				Example 5	379	4	248
Example 6	534	12	150
				Example 7	1745	158	51
Example 8	1375	126	58
				Example 9	1173	119	64
Comparative example 1	231	2	230
				Comparative example 2	425	3	215
Comparative example 3	1235	21	85

As can be seen from Table 1, the radius-thickness ratios of the flaky silicon materials prepared in the examples are all above 5, and the sheet radius size is less than or equal to 50nm, which proves that the method provided by the application can be used for layering the silicon particles with larger sizes to obtain the flaky nano-scale silicon particles.

As can be seen from the comparison between example 5 and example 1, the increase in the length of the variable diameter section of the micro flow channel acts on the silicon particles in the radial direction, and the shearing action in the circumferential direction and the flow channel direction is weakened to deteriorate the sheet morphology of the sheet layer, but example 5 still has an obvious sheet morphology compared with comparative example 1 and comparative example 2, that is, the micro flow channel of the present application can be used to obtain the sheet-like silicon material. As can be seen from the results in table 1, the silicon material provided in example 5, due to the thicker sheet layer, has significantly lower cycling stability than the other examples, but still achieves a volume change rate of more than 200% after 4 cycles. Example 5 still shows significant advantages over comparative examples 1 and 2, where a volume change rate of more than 200% is achieved with only 2 or 3 cycles. Namely, the micro-channel provided by the application can effectively laminate silicon materials and provide good electrical properties.

As can be seen from example 6, the arrangement of the 3 sizing sections with different flow channel sizes is more beneficial to the delamination of the silicon material, and the electrical properties with good cycle performance and small volume change rate are obtained. This is probably because the sizing sections with 3 different flow channel sizes can more effectively slice the silicon particles, and under the same cycle time, the 3 different flow channel sizes can be sliced more times in the same time, so as to obtain the slice effect of the silicon material.

As can be seen from example 7, the solvent of the suspension in which the silicon particles are dispersed can disperse the silicon particles and has a certain fluidity, and the flaking of the silicon material in the micro flow channel can be realized.

It can be seen from comparative example 1 that, in the micro flow channel without the rotating shaft, the silicon particles could not be laminated due to lack of the axial shearing action, and the obtained silicon particles could be subjected to only 2 cycles with a volume change rate of 200% or more.

It can be seen from comparative example 2 that, in the micro flow channel without the multi-stage flow channel size, the function in the flow direction is lacked, the lamella of the silicon particles cannot be effectively degraded and laminated, and the obtained silicon particles can only be subjected to 3 cycles, and the volume change rate is more than 200%.

As can be seen from comparative example 3, the specific capacitance of the silicon material can be increased to 1000mA h g by selecting the nano-sized silicon particles^-1As described above, compared to examples 1, 4, 6, 7, 8, and 9 having the same size, the silicon material provided in comparative example 3 has poor cycle stability and poor volume change rate, which confirms that the lamellar structure can effectively reduce the volume change rate of the silicon material and improve the cycle stability of the battery.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.