CN117239064A - Silicon negative electrode piece and preparation method and application thereof - Google Patents
Silicon negative electrode piece and preparation method and application thereof Download PDFInfo
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 166
- 239000010703 silicon Substances 0.000 title claims abstract description 166
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 166
- 238000002360 preparation method Methods 0.000 title abstract description 31
- 239000011163 secondary particle Substances 0.000 claims abstract description 101
- 239000011230 binding agent Substances 0.000 claims abstract description 78
- 239000011856 silicon-based particle Substances 0.000 claims abstract description 70
- 239000006258 conductive agent Substances 0.000 claims abstract description 61
- 239000011888 foil Substances 0.000 claims abstract description 59
- 239000000463 material Substances 0.000 claims abstract description 38
- 238000000034 method Methods 0.000 claims abstract description 13
- 238000003756 stirring Methods 0.000 claims description 72
- 239000000243 solution Substances 0.000 claims description 68
- 239000002245 particle Substances 0.000 claims description 54
- 239000011148 porous material Substances 0.000 claims description 42
- 238000002156 mixing Methods 0.000 claims description 36
- 239000011259 mixed solution Substances 0.000 claims description 16
- 238000001035 drying Methods 0.000 claims description 15
- 238000005096 rolling process Methods 0.000 claims description 14
- 238000005507 spraying Methods 0.000 claims description 14
- 229920000178 Acrylic resin Polymers 0.000 claims description 10
- 239000004925 Acrylic resin Substances 0.000 claims description 10
- 239000002153 silicon-carbon composite material Substances 0.000 claims description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 8
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 8
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 8
- 239000002033 PVDF binder Substances 0.000 claims description 7
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 7
- 229920003048 styrene butadiene rubber Polymers 0.000 claims description 6
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 4
- OBNDGIHQAIXEAO-UHFFFAOYSA-N [O].[Si] Chemical class [O].[Si] OBNDGIHQAIXEAO-UHFFFAOYSA-N 0.000 claims description 4
- 239000004917 carbon fiber Substances 0.000 claims description 4
- 229910021389 graphene Inorganic materials 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 4
- -1 polytetrafluoroethylene Polymers 0.000 claims description 4
- 229910000676 Si alloy Inorganic materials 0.000 claims description 2
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical class [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 claims description 2
- 239000002041 carbon nanotube Substances 0.000 claims description 2
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 2
- 229910021487 silica fume Inorganic materials 0.000 claims 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 10
- 229910052744 lithium Inorganic materials 0.000 abstract description 10
- 238000009830 intercalation Methods 0.000 abstract description 6
- 230000001351 cycling effect Effects 0.000 abstract description 4
- 238000009831 deintercalation Methods 0.000 abstract description 3
- 239000011149 active material Substances 0.000 abstract 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 59
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 43
- 239000011889 copper foil Substances 0.000 description 43
- 238000005303 weighing Methods 0.000 description 24
- 239000007787 solid Substances 0.000 description 23
- 239000000377 silicon dioxide Substances 0.000 description 22
- 239000002109 single walled nanotube Substances 0.000 description 16
- 230000000052 comparative effect Effects 0.000 description 15
- 229910052814 silicon oxide Inorganic materials 0.000 description 15
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 5
- 239000002131 composite material Substances 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 230000002687 intercalation Effects 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 229910000519 Ferrosilicon Inorganic materials 0.000 description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- 239000002174 Styrene-butadiene Substances 0.000 description 3
- 239000000853 adhesive Substances 0.000 description 3
- 230000001070 adhesive effect Effects 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 239000005543 nano-size silicon particle Substances 0.000 description 3
- 239000004698 Polyethylene Substances 0.000 description 2
- 239000013543 active substance Substances 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910003481 amorphous carbon Inorganic materials 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000003575 carbonaceous material Substances 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 239000002048 multi walled nanotube Substances 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 238000012935 Averaging Methods 0.000 description 1
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- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
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Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention relates to a silicon negative electrode plate, a preparation method and application thereof, and belongs to the technical field of battery materials. The silicon negative electrode plate provided by the invention comprises a porous foil and active silicon particles embedded in through holes of the porous foil; the active silicon particles comprise silicon-containing secondary particles and a buffer layer coated on the surfaces of the silicon-containing secondary particles; the buffer layer includes a conductive agent and a binder. The silicon negative electrode plate has good energy surface density, multiplying power performance and cycling stability, and the silicon-containing secondary particles establish stable conductive connection with the buffer layer in the cycling process no matter fully intercalating lithium or fully deintercalating lithium, so that the conductive performance of the negative electrode plate is ensured; the preparation method is simple, the process flow can be simplified, the efficiency is improved, and meanwhile, the active material can be continuously coated on the pole piece to prepare the negative pole piece, so that the application prospect is wide.
Description
Technical Field
The invention belongs to the technical field of battery materials, and particularly relates to a silicon negative electrode plate, a preparation method and application thereof.
Background
Because silicon cathodes have a higher specific capacity, silicon-containing batteries are commonly used to meet the increasing energy density demands of the battery market. The silicon-carbon composite material has the advantages of good conductivity, longer cycle life compared with a silicon-oxygen composite material, and has a buffering effect on the expansion of silicon because the coating is a carbon material. However, the preparation process of the raw material porous carbon of the silicon-carbon composite material is difficult to control, and the pore size distribution of the porous carbon is larger, so that the transmission of lithium ions and electrons is blocked, and the rate capability of the silicon-carbon composite material is weaker than that of the silicon-oxygen composite material.
In order to improve the rate capability of the silicon negative electrode sheet, patent CN108475779a provides a novel material with extremely durable lithium intercalation and a method for manufacturing the same, and specifically discloses a composite of silicon and various porous scaffold materials, such as carbon materials containing micropores, mesopores and/or macropores, and a method for manufacturing the same, defining a silicon-carbon composite material preparation method. The material has practicability in various applications, but the patent material has the problems that the pore diameter of part of porous support materials is overlarge in the mass production process, the deposition process of a silicon source is poor in control, the rate performance of a synthesized compound is poor, and the gram capacity exertion capacity fluctuation between batches is large. Patent CN115275107a provides a silicon-based negative electrode with an integral structure and a preparation method thereof, but the thickness of the electrode sheet is thicker, other active substances cannot be coated, the contribution to energy density is small, the combination of nano silicon and amorphous carbon therein is not tight, and when the nano silicon is fully intercalated with lithium and expanded and then delithiated, a gap is formed between the nano silicon and amorphous carbon, so that ion transmission and electron transmission are blocked, and the conductivity of the full battery under low SOC is poor. Meanwhile, the preparation method is complex, the preparation material is not environment-friendly, and the large-scale preparation is not facilitated.
Therefore, the silicon negative electrode plate with simple preparation process, good multiplying power performance and long cycle life has important significance.
Disclosure of Invention
The invention aims to overcome the problems in the prior art and provides a silicon negative electrode plate, and a preparation method and application thereof.
The invention is realized by the following technical scheme:
the invention provides a silicon negative electrode plate, which comprises a porous foil and active silicon particles embedded in through holes of the porous foil; the active silicon particles comprise silicon-containing secondary particles and a buffer layer coated on the surfaces of the silicon-containing secondary particles; the buffer layer includes a conductive agent and a binder.
The silicon negative electrode plate is of an integrated structure and comprises a porous foil and active silicon particles, the active silicon particles are pressed and embedded in through holes of the porous foil, when the cross section of the silicon negative electrode plate is seen, the silicon-containing secondary particles are positioned in the center of the through holes, the buffer layer is filled in the rest hole structure, when the silicon-containing secondary particles expand, the buffer layer is extruded to be compressed, when the silicon-containing secondary particles are delithiated and contracted, the buffer layer can rebound, the existence of the buffer layer ensures that the conductive agent is stably and fully connected with the silicon-containing secondary particles in the whole process of circulation, the conductivity of the electrode plate is ensured, so that the electrode plate has good multiplying power performance, and meanwhile, the silicon-containing secondary particles are embedded in the through holes of the foil, the volume expansion of silicon can be effectively inhibited in the charging and discharging process, and the stability of the electrode is ensured.
The porous foil is a porous metal foil, and the metal is single metal or composite metal; preferably, the porous foil comprises at least one of porous nickel foil and porous copper foil.
As a preferred embodiment of the silicon negative electrode sheet, the silicon-containing secondary particles comprise at least one of micron silicon, silicon-carbon composite material, silicon-oxygen composite material and silicon alloy; the conductive agent comprises at least one of carbon nano tubes, carbon fibers and graphene; the binder includes at least one of acrylic resin (PAA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR).
The conductive agent in the buffer layer is soft and elastic, and can change along with the change of the silicon-containing secondary particles in the charge and discharge process, so that the pole piece has good conductivity; the adhesive in the buffer layer can be extruded and contracted, and the conductive agent can be uniformly dispersed and the structural stability of the conductive agent can be maintained, so that the buffer effect of the buffer layer is ensured.
As a preferred embodiment of the silicon anode piece, the average pore diameter of the porous foil is r, and the range of r is 1-10 mu m; the thickness of the porous foil is t, and the range of t is 4-15 mu m; the pore volume of the porous foil accounts for 5% -80% of the total volume of the porous foil.
As a preferred embodiment of the silicon negative electrode sheet according to the present invention, the t and the r satisfy the relation: t >0.5r.
When t is less than or equal to 0.5r, the active silicon particles can be embedded in the through holes of the porous foil, but the embedding is insufficient, and the embedding effect of the particles is relatively poor.
The foil average pore diameter testing method comprises the following steps: and randomly selecting three positions on the foil by using a microscope or a scanning electron microscope, randomly measuring the pore diameters of 30 pores at each position, and averaging to obtain an average value of the pore diameters of 90 pores in total at the three positions, wherein the obtained average value is the average pore diameter of the foil.
Preferably, r ranges from 3 μm to 10 μm; the t ranges from 4.5 μm to 12 μm, more preferably the t ranges from 5 μm to 12 μm; the pore volume of the porous foil accounts for 20% -40% of the total volume of the porous foil.
As a preferable embodiment of the silicon anode piece, the thickness of the buffer layer is d, and the range of d is 1-6 μm; the average particle diameter of the silicon-containing secondary particles is Dv50, and the Dv50 is in the range of 1 μm to 10 μm.
Preferably, d ranges from 1 μm to 3 μm; the Dv50 ranges from 2 μm to 8 μm.
As a preferred embodiment of the silicon negative electrode sheet of the present invention, the d and Dv50 satisfy: d >1/3Dv 50.
Experiments show that the volume expansion of the silicon-containing secondary particles is 200 times of the original volume expansion of the silicon-containing secondary particles under full lithium intercalation expansion in a full battery, and the expansion is isotropic expansion, namely the average particle size of the silicon-containing secondary particles after full lithium intercalation expansion is increased by 1.3 times of the original average particle size. The buffer layer thickness d must therefore be greater than 0.3dv50. However, further researches show that in the cyclic lithium intercalation and deintercalation expansion process of the silicon-containing secondary particles, the buffer layer cannot be fully compressed, and the thickness of the buffer layer becomes 0.1 times of the original thickness when the buffer layer is compressed to the most limit, so that the electrode plate can have better energy area density when d-0.1d >1.3Dv50-1Dv50, namely d and Dv50 meet d >1/3Dv50 by combining theory and practice.
As a preferred embodiment of the silicon negative electrode sheet of the present invention, the r, the Dv50 and the d satisfy the relation: dv50+0.4d < r < Dv50+1.8d.
According to the invention, when the average pore diameter of the porous foil is too small, the silicon-containing secondary particles with the buffer layer cannot be fully embedded. When the average pore diameter is too large, the silicon-containing secondary particles with a buffer layer are liable to fall off. In theory, the thickness of the buffer layer is d, the average particle diameter of the secondary silicon-containing particles is Dv50, and when the silicon negative electrode plate is prepared, the secondary silicon-containing particles do not intercalate lithium to expand, and at the moment, the maximum size of the secondary silicon-containing particles with the buffer layer is the size of the uncompressed buffer layer, namely Dv50+2d; the smallest dimension of the buffered silicon-containing secondary particles is the dimension at which the buffer layer is compressed to a limit, i.e., dv50+0.2d. That is, the pore size of the porous foil should satisfy: the particle diameter of the active silicon particles is larger than that when the buffer layer is compressed to the most limit, and smaller than that when the buffer layer is not extruded, namely Dv50+0.2d < r < Dv50+2d. However, in the experimental process, it was found that the particles having too large a compression amount of the buffer layer were difficult to embed when r was close to Dv50+0.2d, and the buffer layer was hardly compressed when r was close to Dv50+2d, and easily dropped from the inside of the hole. When the relation of r, dv50 and d satisfies Dv50+0.4d < r < Dv50+1.8d, the silicon negative electrode plate can have good structural stability.
The invention further provides a preparation method of the silicon negative electrode plate, which comprises the following steps:
(1) Stirring and mixing the binder and the conductive agent uniformly to obtain a buffer layer material solution;
(2) Adding the silicon-containing secondary particles into the buffer layer material solution obtained in the step (1), and stirring to obtain a mixed solution;
(3) Drying the mixed solution obtained in the step (2) under the stirring condition to obtain active silicon particles;
(4) And (3) uniformly spraying the active silicon particles obtained in the step (3) on the porous foil, rolling to enable the active silicon particles to be embedded into through holes of the porous foil, and removing the non-embedded active silicon particles to obtain the porous foil.
The preparation method of the silicon negative electrode plate is simple and low in cost, all materials can be obtained commercially, the adhesive and the conductive agent can be fully coated on the surfaces of the silicon-containing secondary particles in the step (2), and silicon active particles which are remained on the surfaces of the foil and are not embedded into the through holes of the foil can be removed in the step (4) through the modes of soaking, cleaning, shaking and the like. The silicon negative electrode plate prepared by the preparation method has good multiplying power performance and circulation stability, and can be suitable for industrial production.
As a preferred embodiment of the preparation method of the silicon negative electrode plate, the mass percentage of the silicon-containing secondary particles is 84.5-91.9%, the mass percentage of the conductive agent is 0.1-0.5% and the mass percentage of the binder is 8-15% calculated by taking the mass percentage of the active silicon particles as 100%.
Preferably, in the step (1), the stirring temperature is 20-60 ℃, the stirring time is 1-2 h, and the rotating speed is 2000-3000 r/min.
Preferably, in the step (2), the stirring temperature is 20-60 ℃, the stirring time is 2-4 h, and the rotating speed is 500-2000 r/min.
Preferably, in the step (3), the stirring temperature is 80-120 ℃, the stirring time is 2-4 h, and the rotating speed is 500-2000 r/min; the vacuum degree of the drying is-20 KPa to-95 KPa.
Preferably, the mass percentage of the conductive agent is 0.1% -0.3%.
Preferably, the mass percentage of the binder is 8% -12%.
Preferably, the mass percentage of the silicon-containing secondary particles is 87% -90%.
Preferably, the step (4) is repeated 1 to 30 times, and the more the number of times, the more active silicon particles are embedded into the through holes of the porous foil.
In the step (1), the conductive agent and the binder can be mixed in the form of a solution, and the solid content of the conductive agent in the conductive agent solution is 0.1% -20%; in the binder solution, the solid content of the binder is 5% -50%.
It is still another object of the present invention to provide a battery including the silicon negative electrode tab.
The silicon negative electrode plate is used in a battery, so that the battery has good multiplying power performance and cycle stability.
The invention has the following beneficial effects:
1. the silicon negative electrode plate provided by the invention can be directly used for preparing a battery, and can show good energy surface density (the energy surface density of the electrode plate is high, so that the volume energy density of a battery core is high, and the endurance mileage of the battery is high), multiplying power performance and cycling stability, and the silicon-containing secondary particles are firmly connected with a buffer layer in a conductive manner in a cycling process no matter fully intercalating lithium or fully deintercalating lithium, so that the conductive performance of the negative electrode plate is ensured.
2. The preparation method of the silicon negative electrode plate is simple, can simplify the process flow, improve the efficiency, and can also continuously coat active substances on the plate to prepare the negative electrode plate, thereby having wide application prospect.
Drawings
FIG. 1 is a schematic cross-sectional view of a silicon negative electrode sheet of the present invention, wherein 1 is a porous foil, 2 is a buffer layer, 3 is silicon-containing secondary particles, d is the thickness of the buffer layer, and Dv50 is the average particle diameter of the silicon-containing secondary particles.
Detailed Description
For a better description of the objects, technical solutions and advantages of the present invention, the present invention will be further described with reference to the following specific examples. It will be appreciated by persons skilled in the art that the specific embodiments described herein are for purposes of illustration only and are not intended to be limiting.
The test methods used in the examples are conventional methods unless otherwise specified; the materials, reagents and the like used, unless otherwise specified, are all commercially available.
The cross section schematic diagram of the silicon negative electrode plate is shown in fig. 1, wherein 1 is a porous foil, 2 is a buffer layer, 3 is silicon-containing secondary particles, d is the thickness of the buffer layer, and Dv50 is the average particle size of the silicon-containing secondary particles.
Example 1
The preparation method of the silicon negative electrode plate comprises the following steps:
(1) Weighing 12wt% of binder acrylic resin (PAA) with effective content and 0.3wt% of conductive agent single-walled carbon nanotube, stirring and mixing for 1h at the rotation speed of 2000r/min and the stirring temperature of 25 ℃ to obtain buffer layer material solution; wherein the binder PAA is a solution, the solid content of the binder PAA is 10wt%, the single-walled carbon nanotube conductive agent is also a solution, and the solid content of the binder PAA is 0.4wt%;
(2) Weighing 87.7wt% of effective content of silica secondary particles, adding the silica secondary particles into the buffer layer material solution obtained in the step (1), stirring and mixing for 2 hours at the rotating speed of 1000r/min and the stirring temperature of 30 ℃ to obtain a mixed solution; wherein the average particle diameter Dv50 of the secondary particles of silica is 5 μm;
(3) Stirring and mixing the solution obtained in the step (2) for 2 hours at 90 ℃, wherein the rotating speed is 800r/min, the vacuum degree is-85 KPa, and drying to obtain silicon active particles, and the thickness of a buffer layer in the silicon active particles is 2 mu m;
(4) Uniformly spraying the active silicon particles obtained in the step (3) on the porous copper foil, rolling, and removing the active silicon particles which are remained on the surface of the copper foil and are not embedded into the copper foil holes in a shaking mode; wherein the thickness of the porous copper foil is 8 mu m, the average pore diameter is 6 mu m, and the pore volume accounts for 40% of the total volume of the foil; repeating the step (4) for 3 times to obtain the silicon negative electrode plate of the embodiment.
It should be noted that: the effective contents of the binder and the conductive agent in the step (1) are 12wt% and 0.3wt%, respectively, and the effective content of the silicon oxide secondary particles in the step (2) is 87.7wt%, meaning that, in the active silicon particles of the buffer layer-coated silicon-containing secondary particles finally prepared in this example, the mass percentages of the binder and the conductive agent are 12wt% and 0.3wt%, respectively, and the mass percentages of the silicon-containing secondary particles are 87.7wt%, calculated on the basis of 100% of the mass of the active silicon particles.
Example 2
The preparation method of the silicon negative electrode plate comprises the following steps:
(1) Weighing 9wt% of binder Styrene Butadiene Rubber (SBR) and 0.3wt% of conductive agent multiwall carbon nanotube, stirring and mixing for 1.5h at the rotation speed of 2000r/min and the stirring temperature of 30 ℃ to obtain buffer layer material solution; wherein the binder SBR is a solution, the solid content of the binder SBR is 48 weight percent, the multi-wall carbon nano tube conductive agent is also a solution, and the solid content of the binder SBR is 0.8 weight percent;
(2) Weighing 90.7wt% of effective content of micrometer silicon, adding into the buffer layer material solution obtained in the step (1), stirring and mixing for 3 hours, wherein the rotating speed is 1500r/min, and the stirring temperature is 25 ℃ to obtain a mixed solution; wherein the average particle diameter Dv50 of the micrometer silicon particles is 8 μm;
(3) Stirring and mixing the solution obtained in the step (2) for 2 hours at 110 ℃, wherein the rotating speed is 1500r/min, the vacuum degree is-30 KPa, and drying is carried out to obtain silicon active particles, and the thickness of a buffer layer in the silicon active particles is 3 mu m;
(4) Uniformly spraying the active silicon particles obtained in the step (3) on a porous nickel foil, rolling, and removing the active silicon particles which are remained on the surface of the nickel foil and are not embedded into the nickel foil holes in a shaking mode; wherein the thickness of the porous nickel foil is 12 mu m, the average pore diameter is 10 mu m, and the pore volume accounts for 30% of the total volume of the foil; repeating the step (4) for 2 times to obtain the silicon negative electrode plate of the embodiment.
It should be noted that: the effective contents of the binder and the conductive agent in the step (1) are 9wt% and 0.3wt%, respectively, and the effective content of the micro-sized silicon secondary particles in the step (2) is 90.7wt%, meaning that, in the active silicon particles of the buffer layer-coated silicon-containing secondary particles finally prepared in this example, the mass percentages of the binder and the conductive agent are 9wt% and 0.3wt%, respectively, and the mass percentages of the silicon-containing secondary particles are 90.7wt%, calculated on the basis of 100% of the mass of the active silicon particles.
Example 3
The preparation method of the silicon negative electrode plate comprises the following steps:
(1) Weighing 15wt% of binder polyvinylidene fluoride (PVDF) and 0.3wt% of conductive agent graphene, stirring and mixing for 1.5h at the rotating speed of 2500r/min and the stirring temperature of 30 ℃ to obtain buffer layer material solution; the binder PVDF is a solution, the solid content of the binder PVDF is 3%, and the graphene is dry powder;
(2) Weighing 84.7wt% of silicon-carbon composite material, adding the silicon-carbon composite material into the buffer layer material solution obtained in the step (1), stirring and mixing for 2 hours, wherein the rotating speed is 2000r/min, and the stirring temperature is 40 ℃ to obtain a mixed solution; wherein the average particle diameter Dv50 of the silicon-carbon composite material is 6 μm;
(3) Stirring and mixing the solution obtained in the step (2) for 2 hours at the temperature of 100 ℃, wherein the rotating speed is 1000r/min, the vacuum degree is-60 KPa, and drying to obtain silicon active particles, and the thickness of a buffer layer in the silicon active particles is 3 mu m;
(4) Uniformly spraying the active silicon particles obtained in the step (3) on a porous aluminum foil, rolling, and removing the active silicon particles which are remained on the surface of the copper foil and are not embedded into the aluminum foil holes in a flushing mode; wherein the thickness of the porous aluminum foil is 7 mu m, the average pore diameter is 8 mu m, and the pore volume accounts for 20% of the total volume of the foil; repeating the step (4) for 2 times to obtain the silicon negative electrode plate of the embodiment.
It should be noted that: the effective contents of the binder and the conductive agent in the step (1) are 15wt% and 0.3wt%, respectively, and the effective content of the silicon-carbon secondary particles in the step (2) is 84.7wt%, which means that, in the active silicon particles of the buffer layer-coated silicon-containing secondary particles finally prepared in this example, the mass percentages of the binder and the conductive agent are 15wt% and 0.3wt%, respectively, and 84.7wt%, based on 100% of the mass of the active silicon particles.
Example 4
The preparation method of the silicon negative electrode plate comprises the following steps:
(1) Weighing binder Polytetrafluoroethylene (PTFE) with the effective content of 8wt% and conductive carbon fiber with the effective content of 0.1wt% and stirring and mixing for 1h at the rotating speed of 2000r/min and the stirring temperature of 25 ℃ to obtain buffer layer material solution; wherein the binder PTFE is a solution, the solid content of the binder PTFE is 10%, the carbon fiber is also a solution, and the solid content of the binder PTFE is 0.5%;
(2) Weighing 91.9 weight percent of effective content of silicon oxide secondary particles, adding the silicon oxide secondary particles into the buffer layer material solution obtained in the step (1), stirring and mixing for 2 hours, wherein the rotating speed is 1000r/min, and the stirring temperature is 30 ℃ to obtain a mixed solution; wherein the average particle diameter Dv50 of the secondary particles of silica is 7 μm;
(3) Stirring and mixing the solution obtained in the step (2) for 2 hours at 90 ℃, wherein the rotating speed is 800r/min, the vacuum degree is-85 KPa, and drying to obtain silicon active particles, and the thickness of a buffer layer in the silicon active particles is 3 mu m;
(4) Uniformly spraying the active silicon particles obtained in the step (3) on the porous copper foil, rolling, and removing the active silicon particles which are remained on the surface of the copper foil and are not embedded into the copper foil holes in a shaking mode; wherein the thickness of the porous copper foil is 9 mu m, the average pore diameter is 10 mu m, and the pore volume accounts for 40% of the total volume of the foil; repeating the step (4) for 3 times to obtain the silicon negative electrode plate of the embodiment.
It should be noted that: the effective contents of the binder and the conductive agent in the step (1) are 8wt% and 0.1wt%, respectively, and the effective content of the silicon oxide secondary particles in the step (2) is 91.9wt%, meaning that, in the active silicon particles of the buffer layer-coated silicon-containing secondary particles finally prepared in this example, the mass percentages of the binder and the conductive agent are 8wt% and 0.1wt%, respectively, and the mass percentages of the silicon-containing secondary particles are 91.9wt%, calculated on the basis of 100% of the mass of the active silicon particles.
Example 5
The preparation method of the silicon negative electrode plate comprises the following steps:
(1) Weighing 10wt% of binder acrylic resin (PAA) with effective content and 0.1wt% of conductive agent single-walled carbon nanotube, stirring and mixing for 1h at the rotation speed of 2000r/min and the stirring temperature of 25 ℃ to obtain buffer layer material solution; wherein the binder PAA is a solution, the solid content of the binder PAA is 10%, the single-walled carbon nanotube conductive agent is also a solution, and the solid content of the binder PAA is 0.4%;
(2) Weighing 89.9wt% of ferrosilicon alloy secondary particles with effective content, adding the ferrosilicon alloy secondary particles into the buffer layer material solution obtained in the step (1), stirring and mixing for 2 hours, wherein the rotating speed is 1000r/min, and the stirring temperature is 30 ℃ to obtain a mixed solution; wherein the average particle diameter Dv50 of the secondary particles of silica is 5 μm;
(3) Stirring and mixing the solution obtained in the step (2) for 2 hours at 90 ℃, wherein the rotating speed is 800r/min, the vacuum degree is-85 KPa, and drying to obtain silicon active particles, and the thickness of a buffer layer in the silicon active particles is 2 mu m;
(4) Uniformly spraying the active silicon particles obtained in the step (3) on the porous copper foil, rolling, and removing the active silicon particles which are remained on the surface of the copper foil and are not embedded into the copper foil holes in a shaking mode; wherein the thickness of the porous copper foil is 8 mu m, the average pore diameter is 8 mu m, and the pore volume accounts for 40% of the total volume of the foil; repeating the step (4) for 3 times to obtain the silicon negative electrode plate of the embodiment.
It should be noted that: the effective contents of the binder and the conductive agent in the step (1) are 10wt% and 0.1wt%, respectively, and the effective content of the ferrosilicon secondary particles in the step (2) is 89.9wt%, which means that, in the active silicon particles of the buffer layer-coated silicon-containing secondary particles finally prepared in this example, the mass percentages of the binder and the conductive agent are 10wt% and 0.1wt%, respectively, and 89.9wt% respectively, based on 100% of the mass of the active silicon particles.
Example 6
The preparation method of the silicon negative electrode plate comprises the following steps:
(1) Weighing 10wt% of binder acrylic resin (PAA) with effective content and 0.1wt% of conductive agent single-walled carbon nanotube, stirring and mixing for 1h at the rotation speed of 2000r/min and the stirring temperature of 25 ℃ to obtain buffer layer material solution; wherein the binder PAA is a solution, the solid content of the binder PAA is 10%, the single-walled carbon nanotube conductive agent is also a solution, and the solid content of the binder PAA is 0.4%;
(2) Weighing 89.9 weight percent of effective content of silicon oxide secondary particles, adding the effective content of the silicon oxide secondary particles into the buffer layer material solution obtained in the step (1), stirring and mixing for 2 hours, wherein the rotating speed is 1000r/min, and the stirring temperature is 30 ℃ to obtain a mixed solution; wherein the average particle diameter Dv50 of the secondary particles of silica is 2 μm;
(3) Stirring and mixing the solution obtained in the step (2) for 2 hours at 90 ℃, wherein the rotating speed is 800r/min, the vacuum degree is-85 KPa, and drying to obtain silicon active particles, and the thickness of a buffer layer in the silicon active particles is 1 mu m;
(4) Uniformly spraying the active silicon particles obtained in the step (3) on the porous copper foil, rolling, and removing the active silicon particles which are remained on the surface of the copper foil and are not embedded into the copper foil holes in a shaking mode; wherein the thickness of the porous copper foil is 5 mu m, the average pore diameter is 3 mu m, and the pore volume accounts for 40% of the total volume of the foil; repeating the step (4) for 3 times to obtain the silicon negative electrode plate of the embodiment.
It should be noted that: the effective contents of the binder and the conductive agent in the step (1) are 10wt% and 0.1wt%, respectively, and the effective content of the silicon oxide secondary particles in the step (2) is 89.9wt%, meaning that, in the active silicon particles of the buffer layer-coated silicon-containing secondary particles finally prepared in this example, the mass percentages of the binder and the conductive agent are 10wt% and 0.1wt%, respectively, and 89.9wt% based on 100% of the mass of the active silicon particles.
Example 7
The preparation method of the silicon negative electrode plate comprises the following steps:
(1) Weighing 12wt% of binder acrylic resin (PAA) with effective content and 0.3wt% of conductive agent single-walled carbon nanotube, stirring and mixing for 1h at the rotation speed of 2000r/min and the stirring temperature of 25 ℃ to obtain buffer layer material solution; wherein the binder PAA is a solution, the solid content of the binder PAA is 10%, the single-walled carbon nanotube conductive agent is also a solution, and the solid content of the binder PAA is 0.4%;
(2) Weighing 87.7wt% of effective content of silica secondary particles, adding the silica secondary particles into the buffer layer material solution obtained in the step (1), stirring and mixing for 2 hours at the rotating speed of 1000r/min and the stirring temperature of 30 ℃ to obtain a mixed solution; wherein the average particle diameter Dv50 of the secondary particles of silica is 5 μm;
(3) Stirring and mixing the solution obtained in the step (2) for 2 hours at 90 ℃, wherein the rotating speed is 800r/min, the vacuum degree is-85 KPa, and drying to obtain silicon active particles, and the thickness of a buffer layer in the silicon active particles is 2 mu m;
(4) Uniformly spraying the active silicon particles obtained in the step (3) on the porous copper foil, rolling, and removing the active silicon particles which are remained on the surface of the copper foil and are not embedded into the copper foil holes in a shaking mode; wherein the thickness of the porous copper foil is 8 mu m, the average pore diameter is 5 mu m, and the pore volume accounts for 40% of the total volume of the foil; repeating the step (4) for 3 times to obtain the silicon negative electrode plate of the embodiment.
It should be noted that: the effective contents of the binder and the conductive agent in the step (1) are 12wt% and 0.3wt%, respectively, and the effective content of the silicon oxide secondary particles in the step (2) is 87.7wt%, meaning that, in the active silicon particles of the buffer layer-coated silicon-containing secondary particles finally prepared in this example, the mass percentages of the binder and the conductive agent are 12wt% and 0.3wt%, respectively, and the mass percentages of the silicon-containing secondary particles are 87.7wt%, calculated on the basis of 100% of the mass of the active silicon particles.
Example 8
The preparation method of the silicon negative electrode plate comprises the following steps:
(1) Weighing 12wt% of binder acrylic resin (PAA) with effective content and 0.3wt% of conductive agent single-walled carbon nanotube, stirring and mixing for 1h at the rotation speed of 2000r/min and the stirring temperature of 25 ℃ to obtain buffer layer material solution; wherein the binder PAA is a solution, the solid content of the binder PAA is 10%, the single-walled carbon nanotube conductive agent is also a solution, and the solid content of the binder PAA is 0.4%;
(2) Weighing 87.7wt% of effective content of silica secondary particles, adding the silica secondary particles into the buffer layer material solution obtained in the step (1), stirring and mixing for 2 hours at the rotating speed of 1000r/min and the stirring temperature of 30 ℃ to obtain a mixed solution; wherein the average particle diameter Dv50 of the secondary particles of silica is 5 μm;
(3) Stirring and mixing the solution obtained in the step (2) for 2 hours at 90 ℃, wherein the rotating speed is 800r/min, the vacuum degree is-85 KPa, and drying to obtain silicon active particles, and the thickness of a buffer layer in the silicon active particles is 2 mu m;
(4) Uniformly spraying the active silicon particles obtained in the step (3) on the porous copper foil, rolling, and removing the active silicon particles which are remained on the surface of the copper foil and are not embedded into the copper foil holes in a shaking mode; wherein the thickness of the porous copper foil is 8 mu m, the average pore diameter is 9 mu m, and the pore volume accounts for 40% of the total volume of the foil; repeating the step (4) for 3 times to obtain the silicon negative electrode plate of the embodiment.
It should be noted that: the effective contents of the binder and the conductive agent in the step (1) are 12wt% and 0.3wt%, respectively, and the effective content of the silicon oxide secondary particles in the step (2) is 87.7wt%, meaning that, in the active silicon particles of the buffer layer-coated silicon-containing secondary particles finally prepared in this example, the mass percentages of the binder and the conductive agent are 12wt% and 0.3wt%, respectively, and the mass percentages of the silicon-containing secondary particles are 87.7wt%, calculated on the basis of 100% of the mass of the active silicon particles.
Example 9
The preparation method of the silicon negative electrode plate comprises the following steps:
(1) Weighing 12wt% of binder acrylic resin (PAA) with effective content and 0.3wt% of conductive agent single-walled carbon nanotube, stirring and mixing for 1h at the rotation speed of 2000r/min and the stirring temperature of 25 ℃ to obtain buffer layer material solution; wherein the binder PAA is a solution, the solid content of the binder PAA is 10%, the single-walled carbon nanotube conductive agent is also a solution, and the solid content of the binder PAA is 0.4%;
(2) Weighing 87.7wt% of effective content of silica secondary particles, adding the silica secondary particles into the buffer layer material solution obtained in the step (1), stirring and mixing for 2 hours at the rotating speed of 1000r/min and the stirring temperature of 30 ℃ to obtain a mixed solution; wherein the average particle diameter Dv50 of the secondary particles of silica is 5 μm;
(3) Stirring and mixing the solution obtained in the step (2) for 2 hours at 90 ℃, wherein the rotating speed is 800r/min, the vacuum degree is-85 KPa, and drying to obtain silicon active particles, and the thickness of a buffer layer in the silicon active particles is 1 mu m;
(4) Uniformly spraying the active silicon particles obtained in the step (3) on the porous copper foil, rolling, and removing the active silicon particles which are remained on the surface of the copper foil and are not embedded into the copper foil holes in a shaking mode; wherein the thickness of the porous copper foil is 8 mu m, the average pore diameter is 6 mu m, and the pore volume accounts for 40% of the total volume of the foil; repeating the step (4) for 3 times to obtain the silicon negative electrode plate of the embodiment.
It should be noted that: the effective contents of the binder and the conductive agent in the step (1) are 12wt% and 0.3wt%, respectively, and the effective content of the silicon oxide secondary particles in the step (2) is 87.7wt%, meaning that, in the active silicon particles of the buffer layer-coated silicon-containing secondary particles finally prepared in this example, the mass percentages of the binder and the conductive agent are 12wt% and 0.3wt%, respectively, and the mass percentages of the silicon-containing secondary particles are 87.7wt%, calculated on the basis of 100% of the mass of the active silicon particles.
Example 10
The preparation method of the silicon negative electrode plate comprises the following steps:
(1) Weighing 8wt% of binder acrylic resin (PAA) with effective content and 0.1wt% of conductive agent single-walled carbon nanotube, stirring and mixing for 1h at the rotation speed of 2000r/min and the stirring temperature of 25 ℃ to obtain buffer layer material solution; wherein the binder PAA is a solution, the solid content of the binder PAA is 10%, the single-walled carbon nanotube conductive agent is also a solution, and the solid content of the binder PAA is 0.4%;
(2) Weighing 91.9 weight percent of effective content of silicon oxide secondary particles, adding the silicon oxide secondary particles into the buffer layer material solution obtained in the step (1), stirring and mixing for 2 hours, wherein the rotating speed is 1000r/min, and the stirring temperature is 30 ℃ to obtain a mixed solution; wherein the average particle diameter Dv50 of the secondary particles of silica is 7 μm;
(3) Stirring and mixing the solution obtained in the step (2) for 2 hours at 90 ℃, wherein the rotating speed is 800r/min, the vacuum degree is-85 KPa, and drying to obtain silicon active particles, and the thickness of a buffer layer in the silicon active particles is 3 mu m;
(4) Uniformly spraying the active silicon particles obtained in the step (3) on the porous copper foil, rolling, and removing the active silicon particles which are remained on the surface of the copper foil and are not embedded into the copper foil holes in a shaking mode; wherein the thickness of the porous copper foil is 4.5 mu m, the average pore diameter is 10 mu m, and the pore volume accounts for 40% of the total volume of the foil; repeating the step (4) for 3 times to obtain the silicon negative electrode plate of the embodiment.
It should be noted that: the effective contents of the binder and the conductive agent in the step (1) are 8wt% and 0.1wt%, respectively, and the effective content of the silicon oxide secondary particles in the step (2) is 91.9wt%, meaning that, in the active silicon particles of the buffer layer-coated silicon-containing secondary particles finally prepared in this example, the mass percentages of the binder and the conductive agent are 8wt% and 0.1wt%, respectively, and the mass percentages of the silicon-containing secondary particles are 91.9wt%, calculated on the basis of 100% of the mass of the active silicon particles.
Comparative example 1
The preparation method of the silicon negative electrode plate of the comparative example comprises the following steps:
(1) Weighing 12wt% of binder acrylic resin (PAA), stirring for 1h at the rotation speed of 2000r/min and the stirring temperature of 25 ℃ to obtain buffer layer material solution; wherein the binder PAA is a solution with a solid content of 10%;
(2) Weighing 88wt% of effective content of silica secondary particles, adding the silica secondary particles into the buffer layer material solution obtained in the step (1), stirring and mixing for 2 hours, wherein the rotating speed is 1000r/min, and the stirring temperature is 30 ℃ to obtain a mixed solution; wherein the average particle diameter Dv50 of the secondary particles of silica is 5 μm;
(3) Stirring and mixing the solution obtained in the step (2) for 2 hours at 90 ℃, wherein the rotating speed is 800r/min, the vacuum degree is-85 KPa, and drying to obtain silicon active particles, and the thickness of a buffer layer in the silicon active particles is 2 mu m;
(4) Uniformly spraying the active silicon particles obtained in the step (3) on the porous copper foil, rolling, and removing the active silicon particles which are remained on the surface of the copper foil and are not embedded into the copper foil holes in a shaking mode; wherein the thickness of the porous copper foil is 8 mu m, the average pore diameter is 6 mu m, and the pore volume accounts for 40% of the total volume of the foil; repeating the step (4) for 3 times to obtain the silicon negative electrode plate of the comparative example.
It should be noted that: the effective content of the binder in step (1) is 12wt% and the effective content of the silicon oxide secondary particles in step (2) is 88wt%, which means that, in the active silicon particles of the buffer layer-coated silicon-containing secondary particles finally prepared in this comparative example, the mass percentage of the binder is 12wt% and the mass percentage of the silicon-containing secondary particles is 88wt% calculated on the basis of 100% of the mass of the active silicon particles.
Comparative example 2
The preparation method of the silicon negative electrode plate of the comparative example comprises the following steps:
(1) Weighing 12.3wt% of conductive agent single-walled carbon nanotube, stirring for 1h at a rotating speed of 2000r/min and a stirring temperature of 25 ℃ to obtain buffer layer material solution; wherein the single-walled carbon nanotube conductive agent is a solution with a solid content of 0.4%;
(2) Weighing 87.7wt% of silica secondary particles, adding the silica secondary particles into the buffer layer material solution obtained in the step (1), stirring and mixing for 2 hours, wherein the rotating speed is 1000r/min, and the stirring temperature is 30 ℃ to obtain a mixed solution; wherein the average particle diameter Dv50 of the secondary particles of silica is 5 μm;
(3) Stirring and mixing the solution obtained in the step (2) for 2 hours at 90 ℃, wherein the rotating speed is 800r/min, the vacuum degree is-85 KPa, and drying to obtain silicon active particles, and the thickness of a buffer layer in the silicon active particles is 2 mu m;
(4) Uniformly spraying the active silicon particles obtained in the step (3) on the porous copper foil, rolling, and removing the active silicon particles which are remained on the surface of the copper foil and are not embedded into the copper foil holes in a shaking mode; wherein the thickness of the porous copper foil is 8 mu m, the average pore diameter is 6 mu m, and the pore volume accounts for 40% of the total volume of the foil; repeating the step (4) for 3 times to obtain the silicon negative electrode plate of the comparative example.
It should be noted that: the effective content of the conductive agent in the step (1) is 12.3wt% and the effective content of the silicon oxide secondary particles in the step (2) is 87.7wt%, which means that, in the active silicon particles of the buffer layer-coated silicon-containing secondary particles finally prepared in this comparative example, the mass percentage of the conductive agent is 12.3wt% and the mass percentage of the silicon-containing secondary particles is 87.7wt% calculated on the basis of 100% of the mass of the active silicon particles.
Preparation of lithium ion secondary battery:
sequentially stacking a positive electrode plate (ternary positive electrode material), a Polyethylene (PE) film, the negative electrode plates prepared in examples 1-10 and comparative examples 1-2, and laminating to obtain an electrode assembly; and adding the electrode assembly into an outer package, adding electrolyte, and performing procedures such as packaging, standing, formation, aging and the like to obtain the lithium ion secondary battery.
Cycle life test:
the batteries prepared in examples 1 to 10 and comparative examples 1 to 2 were charged at a constant current of 1C to a charge cutoff voltage of 4.2V at 25℃and then charged at a constant voltage to a current of 0.05C, and left standing for 10min, and then discharged at a constant current of 1C to a discharge cutoff voltage of 2.8V, and the initial capacity was recorded as C. Then charging to a charge cut-off voltage of 4.2V by using a constant current of 1C, then charging to a current of 0.05C at a constant voltage, standing for 10min, discharging to a discharge cut-off voltage of 2.8V by using a constant current of 1C, recording the discharge capacity Cn of each cycle until the cycle capacity retention rate (Cn/C is 100%) is 80%, and recording the cycle number. The more cycles, the longer the cycle life of the representative battery, and the specific test results are shown in table 1.
And (3) multiplying power performance test:
the batteries prepared in examples 1 to 10 and comparative examples 1 to 2 were charged to a charge cutoff voltage of 4.2V at a constant current of 1C, then charged at a constant voltage to a current of 0.05C, left standing for 10min, and discharged to a discharge cutoff voltage of 2.8V at a constant current of 1/3C, and the initial capacity was recorded as C1. Then charging to a charge cutoff voltage of 4.2V with a constant current of 1C, then charging to a current of 0.05C with a constant voltage, standing for 10min, discharging to a discharge cutoff voltage of 2.8V with a constant current of 2C, and recording a discharge capacity C2 of 2C. The ratio of C2/C1 is the discharge rate of 2C. The higher the 2C discharge rate, the better the rate performance of the representative battery, and the specific test results are shown in table 1.
Table 1 test results of examples and comparative silicon negative electrode sheets
As can be seen from Table 1, the silicon negative electrode sheets of examples 1 to 10 of the present invention are relatively superior in the combination of energy areal density, discharge rate and cycle life to those of comparative examples 1 to 2. As can be obtained from example 1 and comparative example 1 in table 1, when no conductive agent is present, only the adhesive is present between the silicone particles and the foil, the conductive network cannot function, the performance is poor under high rate discharge, and the cycle life is poor. As can be obtained from example 1 and comparative example 2, when there is no binder, poor dispersion of the conductive agent causes uneven dispersion of the buffer layer on the surface of the silicon active particles, and no binder causes poor elasticity of the buffer layer, the silicon active particles are not sufficiently embedded in the porous copper foil, and the energy density of the pole piece is low.
In example 7, since r < Dv50+0.4d does not satisfy Dv50+0.4d < r < Dv50+1.8d, the average pore diameter of the porous foil is too small, and the silicon-containing secondary particles with the buffer layer cannot be sufficiently embedded, resulting in a decrease in the pole piece energy areal density. In example 8, since r > Dv50+1.8d, dv50+0.4d < r < Dv50+1.8d was not satisfied, and the average pore diameter of the porous foil was too large, the silicon-containing secondary particles with the buffer layer were easily detached, and the pole piece energy surface density was also lowered. Example 9 did not meet d >1/3Dv50, the buffer layer was too small to sufficiently buffer the expansion of the silicon secondary particles during circulation, resulting in deformation of the foil by extrusion, and a decrease in circulation performance. Example 10 did not meet t >0.5r, and the thickness of the foil was too small and the silicon-containing secondary particles with buffer layer could not be fully embedded, resulting in a decrease in pole piece energy areal density.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted equally without departing from the spirit and scope of the technical solution of the present invention.
Claims (10)
1. The silicon negative electrode plate is characterized by comprising a porous foil and active silicon particles embedded in through holes of the porous foil; the active silicon particles comprise silicon-containing secondary particles and a buffer layer coated on the surfaces of the silicon-containing secondary particles; the buffer layer includes a conductive agent and a binder.
2. The silicon negative electrode tab of claim 1 wherein the silicon-containing secondary particles comprise at least one of microsilica, silicon-carbon composites, silicon-oxygen composites, silicon alloys; the conductive agent comprises at least one of carbon nano tubes, carbon fibers and graphene; the binder comprises at least one of acrylic resin, polytetrafluoroethylene, polyvinylidene fluoride and styrene-butadiene rubber.
3. The silicon negative electrode tab of claim 1, wherein the porous foil has an average pore size r in the range of 1 μιη -10 μιη; the thickness of the porous foil is t, and the range of t is 4-15 mu m; the pore volume of the porous foil accounts for 5% -80% of the total volume of the porous foil.
4. A silicon negative electrode sheet according to claim 3, wherein t and r satisfy the relation: t >0.5r.
5. A silicon negative electrode sheet according to claim 3, wherein the thickness of the buffer layer is d, the d being in the range 1 μm-6 μm; the secondary average particle diameter of the silicon-containing particles is Dv50, and the Dv50 is in the range of 1 μm to 10 μm.
6. The silicon negative electrode tab of claim 5 wherein d and Dv50 satisfy the relationship: d >1/3Dv 50.
7. The silicon negative electrode tab of claim 5 wherein r, dv50 and d satisfy the relationship: dv50+0.4d < r < Dv50+1.8d.
8. A method for preparing a silicon negative electrode sheet as defined in any one of claims 1 to 7, comprising the steps of:
(1) Stirring and mixing the binder and the conductive agent uniformly to obtain a buffer layer material solution;
(2) Adding the silicon-containing secondary particles into the buffer layer material solution obtained in the step (1), and stirring to obtain a mixed solution;
(3) Drying the mixed solution obtained in the step (2) under the stirring condition to obtain active silicon particles;
(4) And (3) uniformly spraying the active silicon particles obtained in the step (3) on the porous foil, rolling to enable the active silicon particles to be embedded into through holes of the porous foil, and removing the non-embedded active silicon particles to obtain the porous foil.
9. The method for producing a silicon negative electrode sheet according to claim 8, wherein the mass percentage of the silicon-containing secondary particles is 84.5 to 91.9%, the mass percentage of the conductive agent is 0.1 to 0.5%, and the mass percentage of the binder is 8 to 15%, calculated with the mass percentage of the active silicon particles as 100%.
10. A battery comprising a silicon negative electrode tab according to any one of claims 1-7.
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