CN115763773A - Negative electrode slurry, negative electrode plate, all-solid-state battery and preparation method thereof - Google Patents
Negative electrode slurry, negative electrode plate, all-solid-state battery and preparation method thereof Download PDFInfo
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Abstract
The invention provides a negative electrode slurry, a negative electrode plate, an all-solid-state battery and a preparation method thereof, wherein the negative electrode slurry comprises first micron silicon particles, second micron silicon particles, third micron silicon particles, a solvent and a first binder; wherein the grain diameter of the first micron silicon grains is less than that of the second micron silicon grains and less than that of the third micron silicon grains, and the grain diameter difference between the first micron silicon grains and the second micron silicon grains is between 0.5 and 2.5 mu m; the difference of the particle size of the second micron silicon particles and the third micron silicon particles is between 2 and 19 mu m. The negative pole piece prepared by the negative pole slurry has the advantages of low pole piece expansion rate, high silicon content of the pole piece, excellent electrochemical performance of the all-solid-state battery, wide source of micron silicon particles, better environmental friendliness, low manufacturing cost and better industrial application prospect, and the negative pole piece can be prepared by only a simple preparation method.
Description
Technical Field
The invention relates to the field of all-solid-state lithium ion batteries, in particular to a negative electrode slurry, a negative electrode plate, an all-solid-state battery and a preparation method thereof.
Background
As the gram capacity of the graphite cathode in the lithium ion battery is brought into play to the theoretical capacity (375 mAh/g), the energy density of the battery is gradually reduced, and the silicon material has the characteristics of high gram capacity (4200 mAh/g), wide raw material source and environmental friendliness, so that the silicon material is widely concerned. Conventionally, a silicon negative electrode is used as an additive for improving capacity by mixing with a graphite negative electrode, and a pure silicon negative electrode has not been commercially used. Mainly because the pure silicon cathode is easy to generate Li during the lithium intercalation process 3.75 Si alloy, which causes its volume to change, can expand to 300% of its original volume. During the charging and discharging processes of the battery, the silicon electrode can promote the continuous rupture and formation of a solid electrolyte interface film on the surface of the silicon, and can also cause the negative active material to be separated from a current collector, so that the negative capacity is rapidly attenuated, and the cycle performance of the battery is poor. Therefore, the silicon negative electrode is more suitable for use in an all-solid battery than a conventional liquid lithium ion battery. The method is mainly based on that the all-solid-state battery adopts the solid electrolyte to replace the liquid electrolyte, and the silicon cathode is only contacted with the surface of the solid electrolyte, so that the phenomena of cracking and forming of a solid electrolyte interface film on the surface of a large number of silicon particles can not occur.
In the prior art, in order to alleviate the problem of expansion of the silicon negative electrode, the adopted method mainly comprises the steps of using a complex silicon nano structure and combining carbon composite materials and an elastic adhesive matrix or polymer and the like to prepare a silicon negative electrode pole piece, but the pole piece prepared by the method is low in compactness, complex in preparation method and high in cost, so that the possibility of large-scale application is not provided, and the commercial application of the silicon negative electrode is further hindered. The Chinese invention patent (application number: CN 201910534209.9) discloses an all-solid-state battery adopting a silicon cathode and a sulfide solid electrolyte, wherein a composite silicon cathode is prepared by mixing silicon and the sulfide solid electrolyte so as to relieve the problem of volume expansion of the silicon. However, the effective silicon content of the composite silicon negative electrode is less than 60wt% in the working process, so that the high-capacity characteristic of a silicon material cannot be exerted, the energy density of an all-solid-state battery is reduced, and the consumption of sulfide electrolyte is increased, so that the cost is greatly increased.
In summary, the silicon negative electrode material prepared in the prior art has the problems of serious volume expansion, low silicon content of the material, high preparation cost of the material, and the like in the specific application process. Based on this, it is highly desirable to provide a silicon anode material to improve the above problems.
Disclosure of Invention
The invention mainly aims to provide a negative electrode slurry, a negative electrode plate, an all-solid-state battery and a preparation method thereof, and aims to solve the problems that the conventional silicon negative electrode has serious volume expansion, low silicon content of a material or high preparation cost of the material.
In order to achieve the above object, according to one aspect of the present invention, there is provided an anode slurry including first, second, and third micro silicon particles, a solvent, and a first binder; wherein the grain diameter of the first micron silicon grains is less than that of the second micron silicon grains and less than that of the third micron silicon grains, and the grain diameter difference between the first micron silicon grains and the second micron silicon grains is between 0.5 and 2.5 mu m; the difference of the particle size of the second micron silicon particles and the third micron silicon particles is between 2 and 19 mu m.
Further, the grain diameter of the first micron silicon particles is 0.3-0.7 μm, the grain diameter of the second micron silicon particles is 1-2 μm, and the grain diameter of the third micron silicon particles is 4-20 μm; preferably, the weight ratio of the first micron silicon particles to the second micron silicon particles to the third micron silicon particles is (0.1-10): (0.1-50): 50-90); further preferably, the weight ratio of the first micron silicon particles, the second micron silicon particles and the third micron silicon particles is (5-10), (30-50) and (50-65).
Furthermore, the ratio of the total weight of the first micron silicon particles, the second micron silicon particles and the third micron silicon particles to the weight of the first binder is (90-99.9): (0.1-10); preferably, the ratio of the total weight of the first micron silicon particles, the second micron silicon particles and the third micron silicon particles to the weight of the first binder is (95-99.9) to (0.1-5).
Further, the first binder is selected from one or more of PVDF, SBS, NBR, PAA, CMC or PTFE; preferably the solvent is selected from one or more of N-methylpyrrolidone, cyclohexane, toluene, benzene, methyl ethyl ketone, ethyl acetate, dichloroethane or water; the amount of the solvent is preferably 0.8 to 1.5 times the total weight of the first, second and third silicon micro-particles.
According to another aspect of the invention, a negative electrode plate is provided, and the negative electrode plate is obtained by performing first drying and molding on the negative electrode slurry.
Furthermore, the porosity of the negative pole piece is 20-60%, preferably 40-50%; preferably, the silicon loading of the negative pole piece is 0.2-5.0 mg/cm 2 More preferably 0.8 to 1.8mg/cm 2 (ii) a The thickness of the negative electrode sheet is preferably 10 to 50 μm, more preferably 20 to 30 μm.
Further, the treatment temperature of the first drying is 70-120 ℃, and the treatment time is 8-15 h.
According to another aspect of the present invention, an all-solid-state battery is provided, which includes a positive electrode plate, a solid electrolyte layer, and a negative electrode plate, which are stacked in sequence, wherein the negative electrode plate is the above negative electrode plate.
Further, the positive active material in the positive pole piece comprises a base material and a coating layer coated on the outer surface of the base material; the preferred matrix material has the formula LiNi x Co y Mn z M n O 2 Wherein x is more than or equal to 0.7 and less than or equal to 0.92, y is more than or equal to 0 and less than or equal to 0.2, z is more than or equal to 0 and less than or equal to 0.2, n is more than or equal to 0 and less than or equal to 0.2, and x + y + z + n =1; m is one or more selected from Al, mg, fe, ti, V, zr, la, mo, zn, cu or Y.
Go to oneThe material of the coating layer is LiNbO 3 、Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 、Li 3 BO 3 、LiPO 3 、Li 2 ZrO 3 、Li 7 La 3 Zr 2 O 12 、Li 2 TiO 3 、LiTaO 3 Or Al 2 O 3 One or more of; preferably, the positive electrode active material is in the form of particles, and the average particle diameter of the positive electrode active material is 1 to 15 μm.
Further, the material of the solid electrolyte layer is a sulfide solid electrolyte and/or a halide solid electrolyte; preferably the sulfide solid electrolyte is selected from Li 6 PS 5 Cl、Li 6 PS 5 Cl 0.5 Br 0.5 、Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 、Li 10 GeP 2 S 12 、Li 7 P 3 S 11 、LiPON、Li 10 SnP 2 S 12 、LiS-SiS 2 Or xLi 2 S·yP 2 S 5 Wherein x is more than or equal to 100 and more than or equal to 70, and y is more than or equal to 30 and more than or equal to 0; more preferably the halide solid state electrolyte is selected from Li 3 InCl 6 、Li 3 YBr 6 、Li 3 InBr 6 、Li 2 ZrCl 6 、Li 3 ErCl 6 Or Li 3 YCl 6 One or more of (a).
According to another aspect of the present invention, there is provided a method of manufacturing an all-solid battery, the method including the steps of: step S1, providing the negative pole piece, wherein the negative pole piece is provided with a first surface and a second surface which are oppositely arranged; s2, arranging a solid electrolyte layer on the first surface of the negative pole piece; and S3, arranging a positive pole piece on the outer surface of the solid electrolyte layer far away from the first surface.
Further, in step S2, mixing the material of the solid electrolyte layer with a second binder to obtain a mixed slurry, coating the mixed slurry on the first surface of the negative electrode plate, and performing second drying to form the solid electrolyte layer; preferably, the material of the solid electrolyte layer is in the form of particles, and the average particle diameter of the material of the solid electrolyte layer is 1 to 100 μm; preferably, the weight ratio of the material of the solid electrolyte layer to the second binder is (90-100): 0.1-10; the second drying treatment temperature is preferably 60-80 ℃, and the treatment time is 12-24 h.
The negative pole piece prepared by the negative pole slurry has the advantages of low pole piece expansion rate, high silicon content of the pole piece, excellent electrochemical performance of the all-solid-state battery, wide source of micron silicon particles, better environmental friendliness, lower product manufacturing cost and better industrial application prospect, and the negative pole piece can be prepared by only a simple preparation method.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
fig. 1 shows a schematic structural view of an all-solid battery in one embodiment of the present invention.
Wherein the figures include the following reference numerals:
10. a positive electrode plate; 20. a solid electrolyte layer; 30. a negative pole piece;
11. a first current collector; 12. a positive electrode active material layer;
31. a negative electrode active material layer; 32. a second current collector.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.
As described in the background of the invention section, the silicon negative electrode material prepared in the prior art has problems of serious volume expansion, low silicon content of the material, high preparation cost of the material itself, and the like in the specific application process. In order to solve the problem, the invention provides a negative electrode slurry, which comprises first micron silicon particles, second micron silicon particles, third micron silicon particles, a solvent and a first binder; wherein the grain diameter of the first micron silicon grains is less than that of the second micron silicon grains and less than that of the third micron silicon grains, and the grain diameter difference between the first micron silicon grains and the second micron silicon grains is between 0.5 and 2.5 mu m; the difference of the particle size of the second micron silicon particles and the third micron silicon particles is between 2 and 19 mu m.
Although silicon has a high gram capacity, a negative electrode sheet, which is generally composed of a pure silicon material, forms Li when lithium is intercalated 3.75 A Si alloy, the alloy having a volume expansion greater than 300%. Therefore, in liquid lithium ions, the silicon negative electrode can continuously generate volume change in the charging and discharging processes, so that a solid electrolyte interface film on the silicon surface can be continuously broken and formed, and meanwhile, an active material can be separated from a current collector, so that the capacity of the negative electrode is quickly attenuated, and the cycle performance does not reach the standard. Thus, in the prior art, the silicon negative electrode is usually used only as a capacity-enhancing additive in combination with a graphite negative electrode, such as the commonly used composite silicon-carbon (e.g., S)i/C or SiO/C) negative electrode material.
The invention unexpectedly uses the cooperation of micron silicon particles with different particle sizes to form the negative electrode slurry, and the negative electrode slurry can form a proper porous structure in a negative electrode plate when the negative electrode plate is formed later (detailed below), so that the negative electrode plate is promoted to have a porous structure with excellent performance. The porous structure can promote the negative pole piece to greatly relieve the transverse volume expansion change generated when the negative pole piece is embedded with lithium under the condition of high silicon content (the silicon content is higher than 99wt%, and the gram capacity is more than 2500 mAh/g), so that the phenomena of cracking or pulverization and the like of the negative pole piece are avoided, and the all-solid-state battery can simultaneously take better capacity performance, cycle performance and energy density into consideration. Meanwhile, the micron silicon particles are wide in source and better in environmental protection, the negative pole piece can be prepared by a simple preparation method, the manufacturing cost of the product is lower, and the industrial application prospect is better.
In order to further obtain a negative electrode plate with more excellent structural performance and reduce the transverse volume expansion change of the negative electrode material during lithium intercalation, the particle size of the first micron silicon particles is preferably 0.3-0.7 μm, the particle size of the second micron silicon particles is preferably 1-2 μm, and the particle size of the third micron silicon particles is preferably 4-20 μm. Based on this, the subsequently obtained negative pole piece has more suitable porosity, and the battery can simultaneously give consideration to better capacity performance, cycle performance and energy density. Further preferably, the weight ratio of the first micrometer silicon particles, the second micrometer silicon particles and the third micrometer silicon particles is (0.1-10): 0.1-50): 50-90, more preferably (5-10): 30-50): 50-65. In order to further improve the stability and performance uniformity of the negative electrode plate, the ratio of the total weight of the first micron silicon particles, the second micron silicon particles and the third micron silicon particles to the weight of the first binder is preferably (90-99.9): 0.1-10).
In order to further improve the stability, dispersion uniformity and safety of the negative electrode slurry, so that the micron silicon particles with different particle sizes can be better bonded to each other, and thus the electrochemical performance can be better exerted, the first binder is preferably selected from one or more of PVDF, SBS, NBR, PAA, CMC or PTFE. Further preferably, the solvent is selected from one or more of NMP, cyclohexane, toluene, benzene, methyl ethyl ketone, ethyl acetate or dichloroethane, and more preferably, the amount of the solvent is 0.8 to 1.5 times the total weight of the first micron silicon particles, the second micron silicon particles and the third micron silicon particles.
In an alternative embodiment, the above-mentioned anode slurry may be obtained by the following preparation method by those skilled in the art: dissolving the binder in a solvent to prepare a glue solution, then mixing the micron silicon particles with different particle sizes, and finally adding the glue solution into the mixture to form the cathode slurry.
The invention provides a negative pole piece which is obtained by carrying out first drying and forming on the negative pole slurry. Based on the reasons, the negative pole piece has a porous structure with excellent performance. The porous structure can promote the negative pole piece to greatly relieve the transverse volume expansion change generated when the negative pole piece is embedded with lithium under the condition of high silicon content (the silicon content is higher than 99wt%, and the gram capacity is more than 2500 mAh/g), thereby avoiding the phenomena of cracking or pulverization and the like of the negative pole piece, and further ensuring that the all-solid-state battery can simultaneously give consideration to better capacity performance, cycle performance and energy density. Meanwhile, the micron silicon particles are wide in source and better in environmental protection, and can be used as a raw material for preparing the negative pole piece, the negative pole piece can be prepared by a simple preparation method, and the product is lower in manufacturing cost and better in industrial application prospect.
Specifically, those skilled in the art can obtain the negative electrode sheet by the following preparation method: and coating the negative electrode slurry on a copper foil by using a scraper to form a film, and further performing first drying on the film to obtain a negative electrode plate.
In a preferred embodiment, in order to better relieve the transverse volume expansion change of the negative electrode material during lithium intercalation, thereby avoiding the phenomena of cracking or pulverization of the negative electrode material and further improving the capacity performance and the cycle performance of the all-solid-state battery. The porosity of the negative pole piece is preferably 20-60%, and more preferably 40-50%; the silicon loading of the negative pole piece is 0.2-5.0 mg/cm 2 More preferably 0.8 to 1.8mg/cm 2 . The negative pole piece has higher silicon content, so that the thickness is smaller on the basis of products with the same surface capacity. In view of further promoting the interfacial contact of the negative electrode tab with the current collector and the solid electrolyte membrane, the applicant prefers that the thickness of the negative electrode tab be 10 to 50 μm, more preferably 20 to 30 μm, on the basis of alleviating the volume expansion of the negative electrode material in the longitudinal direction of the battery.
And further improving the stability of the negative pole piece and the electrochemical performance of the battery, and carrying out first drying and forming on the negative pole slurry to obtain the negative pole piece, wherein the first drying treatment temperature is preferably 70-120 ℃, and the treatment time is preferably 8-15 h.
The invention also provides an all-solid-state battery, which comprises a positive pole piece, a solid electrolyte layer and a negative pole piece which are sequentially stacked, wherein the negative pole piece is the negative pole piece. The all-solid-state battery has the characteristics of small volume expansion change, high silicon content and excellent cycle performance and electrochemical performance, and as shown in fig. 1, the all-solid-state battery comprises a positive pole piece 10, a solid electrolyte layer 20 and a negative pole piece 30, wherein the positive pole piece 10 comprises a first current collector 11 and a positive active material 12; the negative electrode tab 30 includes a negative active material 31 and a second current collector 32.
In a preferred embodiment, in order to further improve the electrochemical performance and the cycle performance of the battery, the positive active material in the positive pole piece of the all-solid-state battery comprises a base material and a coating layer coated on the outer surface of the base material, and preferably, the base material has the structural formula of LiNi x Co y Mn z M n O 2 Wherein x is more than or equal to 0.7 and less than or equal to 0.92, y is more than or equal to 0 and less than or equal to 0.2, z is more than or equal to 0 and less than or equal to 0.2, n is more than or equal to 0 and less than or equal to 0.2, and x + y + z + n =1; m is one or more selected from Al, mg, fe, ti, V, zr, la, mo, zn, cu or Y. In order to further improve the performance of the positive electrode plate, and enable the positive electrode plate to be cooperated with the negative electrode plate and the solid electrolyte layer to enable the battery to have better chemical performance, the material of the coating layer is preferably selected from LiNbO 3 、Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 、Li 3 BO 3 、LiPO 3 、Li 2 ZrO 3 、Li 7 La 3 Zr 2 O 12 、Li 2 TiO 3 、LiTaO 3 Or Al 2 O 3 One or more of (a). It is further preferable that the positive electrode active material is in the form of particles, and the average particle diameter of the positive electrode active material is 1 to 15 μm.
In order to further improve the electrochemical properties and the cycle performance of the battery, the material of the solid electrolyte layer is preferably a sulfide solid electrolyte and/or a halide solid electrolyte; more preferably the sulfide solid electrolyte is selected from Li 6 PS 5 Cl、Li 6 PS 5 Cl 0.5 Br 0.5 、Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 、Li 10 GeP 2 S 12 、Li 7 P 3 S 11 、LiPON、Li 10 SnP 2 S 12 、LiS-SiS 2 Or xLi 2 S·yP 2 S 5 Wherein x is more than or equal to 100 and more than or equal to 70, and y is more than or equal to 30 and more than or equal to 0; more preferably the halide solid state electrolyte is selected from Li 3 InCl 6 、Li 3 YBr 6 、Li 3 InBr 6 、Li 2 ZrCl 6 、Li 3 ErCl 6 Or Li 3 YCl 6 One or more of (a).
The invention also provides a preparation method of the all-solid-state battery, which comprises the following steps: step S1, providing the negative pole piece, wherein the negative pole piece is provided with a first surface and a second surface which are oppositely arranged; s2, arranging a solid electrolyte layer on the first surface of the negative pole piece; and S3, arranging a positive pole piece on the outer surface of the solid electrolyte layer far away from the first surface.
The technical personnel in the field can select a negative pole piece with a first surface and a second surface which are oppositely arranged, then a solid electrolyte layer is coated on the first surface of the negative pole piece, finally a positive pole piece is arranged on the outer surface of the solid electrolyte layer far away from the first surface, an all-solid battery is assembled by compaction, and the all-solid battery is pressed for 2-10 min under 300-400 MPa, thus obtaining the final all-solid battery. The all-solid-state battery prepared by the method has the advantages that the solid electrolyte layer is coated on the negative electrode plate, and compared with the traditional method that the solid electrolyte is independently formed into a film, the use amount of the second binder can be further reduced, so that the all-solid-state battery has higher ionic conductivity, and the all-solid-state battery has better rate performance at room temperature.
In order to further improve the chemical performance and the cycle performance of the all-solid-state battery, in the preparation step S2 of the all-solid-state battery, the material of the solid-state electrolyte layer is mixed with the second binder to obtain a mixed slurry, the mixed slurry is coated on the first surface of the negative electrode plate, and the solid-state electrolyte layer is formed after the second drying. Preferably, the weight ratio of the material of the solid electrolyte layer to the second binder is (90-100): (0.1-10), the material of the solid electrolyte layer is granular, and the average grain diameter of the material of the solid electrolyte layer is 1-100 μm; more preferably, the temperature of the second drying is 60-80 ℃ and the time of the second drying is 12-24 h.
The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.
Example 1
And (3) negative electrode slurry: the particle size of the first micron silicon particles is 0.7 mu m, the particle size of the second micron silicon particles is 1.7 mu m, the particle size of the third micron silicon particles is 10.0 mu m, the particle size difference between the first micron silicon particles and the second micron silicon particles is 1.0 mu m, and the particle size difference between the second micron silicon particles and the third micron silicon particles is 8.3 mu m; the weight ratio of the first, second and third silicon microparticles was 7.
The preparation method of the negative pole piece comprises the following steps: and (3) taking the negative electrode slurry, coating the slurry into a film by using a scraper, and performing first drying in a vacuum drying oven at the processing temperature of 90 ℃ for 12 hours to obtain a negative electrode plate.
The preparation steps of the solid electrolyte layer are as follows: the solid electrolyte is sulfide solid electrolyte, and the structure of the solid electrolyte is Li 6 PS 5 Cl, the material particle size of the solid electrolyte layer is 15 μm, and the second binder is SBS. Firstly, mixing materials in the solid electrolyte layer with a second binder to obtain mixed slurry, then coating the mixed slurry on the first surface of the negative pole piece, and performing second drying to form the solid electrolyte layer. Wherein the weight ratio of the material in the solid electrolyte layer to the second binder is 98, the second drying temperature is 80 ℃, and the processing time is 12h.
The preparation method of the positive pole piece comprises the following steps: the structure of the anode base material is LiNi 0.8 Co 0.1 Mn 0.1 O 3 The material of the coating layer is LiNbO 3 The particle size of the anode active material is 5 mu m, the third binder is SBS, and the conductive agent is VCGF carbon. And (3) carrying out first stirring on the positive electrode material, the material in the solid electrolyte layer and the conductive agent in a mixer to obtain a mixed material, wherein the first stirring speed is 1200rpm, and the first stirring time is 0.2h. Then, the third binder is dissolved inIn anisole, a third binder solution is obtained. And adding a third binder solution into the mixed material, and performing second stirring to form coating slurry. Wherein the second stirring speed is 1200rpm, and the second stirring time is 0.15h. Then the film is coated by a scraper to form a film, and the film is dried in a vacuum drying oven for 12 hours at 80 ℃.
The preparation method of the all-solid-state battery comprises the following steps: and cutting the positive pole piece and the negative pole piece coated with the solid electrolyte layer into small wafers with the diameter of 10mm, and compacting the direct contact surface of the negative pole side coated with the solid electrolyte layer to the positive pole piece to form the all-solid-state lithium ion battery. The all-solid-state battery is firstly pressed for 5min under 400MPa, and then electrochemical performance test is carried out under 80 MPa.
Example 2
The only differences from example 1 are: the particle size of the first micron silicon particles is 0.5 μm, the particle size of the second micron silicon particles is 1 μm, the particle size of the third micron silicon particles is 20 μm, the difference between the particle sizes of the first micron silicon particles and the second micron silicon particles is 0.5 μm, and the difference between the particle sizes of the second micron silicon particles and the third micron silicon particles is 19 μm.
Example 3
The only differences from example 1 are: the particle size of the first micron silicon particles is 0.3 mu m, the particle size of the second micron silicon particles is 1 mu m, the particle size of the third micron silicon particles is 4 mu m, the difference between the particle sizes of the first micron silicon particles and the second micron silicon particles is 0.7 mu m, and the difference between the particle sizes of the second micron silicon particles and the third micron silicon particles is 3 mu m.
Example 4
The only differences from example 1 are: the weight ratio of the first micron silicon particles, the second micron silicon particles and the third micron silicon particles is 3.
Example 5
The only differences from example 1 are: the weight ratio of the first micron silicon particles, the second micron silicon particles and the third micron silicon particles is 3.
Example 6
The only differences from example 1 are: the weight ratio of the first micron silicon particles, the second micron silicon particles and the third micron silicon particles is 8.
Comparative example 1
The only differences from example 1 are: the negative electrode slurry included only the micro silicon particles having a particle diameter of 1.7 μm.
Comparative example 2
The only differences from example 1 are: the first micrometer silicon particles in the negative paste were 0.7 μm and the second micrometer silicon particles were 1.7 μm.
Comparative example 3
The only differences from example 1 are: the particle size of the first micron silicon particles is 0.7 mu m, the particle size of the second micron silicon particles is 5.7 mu m, the particle size of the third micron silicon particles is 30.7 mu m, and the difference value between the particle sizes of the first micron silicon particles and the second micron silicon particles is 5 mu m; the difference in particle size between the second micron silicon particles and the third micron silicon particles was 25 μm.
Comparative example 4
The only differences from example 1 are: the particle size of the first micron silicon particles is 0.7 mu m, the particle size of the second micron silicon particles is 0.75 mu m, the particle size of the third micron silicon particles is 1.25 mu m, and the difference between the particle sizes of the first micron silicon particles and the second micron silicon particles is 0.05 mu m; the difference in particle size between the second micron silicon particles and the third micron silicon particles was 0.5 μm.
Comparative example 5
The only differences from example 1 are: the negative electrode slurry included only the micro silicon particles having a particle size of 0.7 μm.
Comparative example 6
The only differences from example 1 are: the negative electrode slurry included only the micro silicon particles having a particle size of 4.0 μm.
Comparative example 7
The only differences from example 1 are: the weight ratio of the first micron silicon particles, the second micron silicon particles and the third micron silicon particles is 25.
And (3) performance testing:
(1) Electrochemical Performance test
The all-solid-state battery is subjected to charge and discharge performance test at 0.1C multiplying power, the test voltage interval is 2.5-4.2V, and the test temperature is 30 ℃. The method mainly comprises the steps of testing the first effect, the 0.1C specific discharge capacity and the cycle performance of the all-solid-state battery (the capacity retention rate of the battery circulating for 100 circles at 0.1C).
(2) Porosity test
The specific formula is calculated by the ratio of the real density to the theoretical density as follows:
porosity =1- (true density/theoretical density), where true density is the ratio of the mass of the active material layer on the pole piece to the volume of the active material layer, and theoretical density is the theoretical density of the high-purity silicon material (2.34 g/cm) 3 )。
(3) Silicon loading
Cutting the negative pole piece into a wafer with the diameter of 10mm to obtain the mass m 1 And cutting the same size of optical foil (without cathode material) to obtain the mass m 2 Silicon loading equal to mass m 1 And mass m 2 And multiplying by the ratio of silicon to the sum of silicon and binder to obtain the silicon loading.
(4) Expansion rate of pole piece thickness
The pole piece expansion rate of the negative pole piece passes through professional expansive force test equipment and an in-situ expansion analysis system, the equipment model is swe2110, and the test conditions are as follows: the measurement was carried out at a constant pressure of 628 kg.
The specific test results of the negative electrode sheet and the all-solid-state battery prepared in the above examples and comparative examples are shown in table 1.
TABLE 1
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:
from the test data of the embodiments 1, 2 and 3 and the comparative examples 1, 2, 5 and 6, it can be found that when the negative electrode slurry provided by the invention is adopted, the negative electrode slurry comprises the first micron silicon particles, the second micron silicon particles, the third micron silicon particles, the solvent and the first binder, and the particle size of the first micron silicon particles is smaller than that of the second micron silicon particles and smaller than that of the third micron silicon particles, the prepared negative electrode plate has a lower electrode plate expansion rate and excellent electrochemical performance, the sources of the micron silicon particles are wider, the environmental protection performance is better, the negative electrode plate can be prepared by only a simple preparation method, the product manufacturing cost is lower, and the industrial application prospect is better. When only one kind of silicon micron particles (comparative examples 1, 5 and 6) and two kinds of silicon micron particles (comparative example 2) are adopted, the silicon micron particles have single particle size or the difference of the two kinds of silicon micron particles is small, so that the porosity of the pole piece is low, the expansion rate of the obtained negative pole piece is obviously increased, and finally the electrochemical performance is poor.
From the test data of examples 1, 2, 3 and comparative examples 3, 4, it can be found that when the preparation method of the present invention is employed, the difference in particle size between the first-micrometer silicon particles and the second-micrometer silicon particles is between 0.5 and 2.5 μm; when the particle size difference value of the second micron silicon particles and the third micron silicon particles is between 2 and 19 microns, the particle size of the first micron silicon particles is between 0.3 and 0.7 micron, the particle size of the second micron silicon particles is between 1 and 2 microns, and the particle size of the third micron silicon particles is between 4 and 20 microns, the prepared negative pole piece has lower pole piece expansion rate and excellent electrochemical performance, the sources of the micron silicon particles are wider, the environmental protection performance is better, the negative pole piece can be prepared by only a simple preparation method, the product manufacturing cost is lower, and the industrial application prospect is better. When the particle sizes of the three adopted silicon particles are not within the above range, or the particle sizes of the first silicon particle and the second silicon particle and the particle size difference of the second silicon particle and the third silicon particle are not within the above range (for example, comparative examples 3 and 4), the porosity of the negative electrode plate is reduced due to the undersize or oversize particle sizes of the silicon particles, so that the expansion rate of the obtained negative electrode plate is obviously increased, and the electrochemical performance is poor.
From the test data of examples 4, 5, 6 and comparative example 7, it can be found that when the preparation method of the present invention is adopted, wherein the weight ratio of the first micron silicon particles, the second micron silicon particles and the third micron silicon particles is (0.1-10) to (0.1-50) within the range (e.g., 3. When the weight ratio of the first micron silicon particles, the second micron silicon particles and the third micron silicon particles is (0.1-10) to (0.1-50) to (50-90) (for example, 25 of comparative example 7.
In conclusion, the negative pole piece prepared by the negative pole slurry has the advantages of low pole piece expansion rate, high silicon content of the pole piece, excellent electrochemical performance of the battery, wide source of micron silicon particles, better environmental friendliness, lower product manufacturing cost and better industrial application prospect, and the negative pole piece can be prepared by only a simple preparation method.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The negative electrode slurry is characterized by comprising first micrometer silicon particles, second micrometer silicon particles, third micrometer silicon particles, a solvent and a first binder;
wherein the grain size of the first micron silicon particles is less than that of the second micron silicon particles is less than that of the third micron silicon particles, and the grain size difference between the first micron silicon particles and the second micron silicon particles is between 0.5 and 2.5 microns; the difference of the particle sizes of the second micron silicon particles and the third micron silicon particles is between 2 and 19 mu m.
2. The negative electrode slurry according to claim 1, wherein the first micrometer silicon particles have a particle size of 0.3 to 0.7 μm, the second micrometer silicon particles have a particle size of 1 to 2 μm, and the third micrometer silicon particles have a particle size of 4 to 20 μm;
preferably, the weight ratio of the first micron silicon particles, the second micron silicon particles and the third micron silicon particles is (0.1-10): 0.1-50): 50-90; further preferably, the weight ratio of the first micron silicon particles, the second micron silicon particles and the third micron silicon particles is (5-10): 30-50): 50-65;
preferably, the ratio of the total weight of the first micron silicon particles, the second micron silicon particles and the third micron silicon particles to the weight of the first binder is (90-99.9): (0.1-10); further preferably, the ratio of the total weight of the first micron silicon particles, the second micron silicon particles and the third micron silicon particles to the weight of the first binder is (95-99.9): (0.1-5).
3. The negative electrode paste of claim 1 or 2, wherein the first binder is selected from one or more of PVDF, SBS, NBR, PAA, CMC or PTFE;
preferably, the solvent is selected from one or more of N-methylpyrrolidone, cyclohexane, toluene, benzene, methyl ethyl ketone, ethyl acetate, dichloroethane or water;
preferably, the amount of the solvent is 0.8 to 1.5 times of the total weight of the first micron silicon particles, the second micron silicon particles and the third micron silicon particles.
4. A negative pole piece is characterized in that the negative pole piece is obtained by carrying out first drying and forming on the negative pole slurry of any one of claims 1 to 3.
5. The negative electrode plate of claim 4, wherein the porosity of the negative electrode plate is 20-60%, more preferably 40-50%;
preferably, the silicon loading of the negative pole piece is 0.2-5.0 mg/cm 2 More preferably 0.8 to 1.8mg/cm 2 ；
Preferably, the thickness of the negative electrode sheet is 10 to 50 μm, and more preferably 20 to 30 μm.
6. The negative electrode plate as claimed in claim 4 or 5, wherein the first drying temperature is 70-120 ℃ and the processing time is 8-15 h.
7. An all-solid-state battery, which comprises a positive pole piece, a solid electrolyte layer and a negative pole piece which are sequentially stacked, wherein the negative pole piece is the negative pole piece of any one of claims 4 to 6.
8. The all-solid battery according to claim 7, wherein the positive active material in the positive electrode plate comprises a base material and a coating layer coated on the outer surface of the base material;
preferably, the structural formula of the matrix material is LiNi x Co y Mn z M n O 2 Wherein x is more than or equal to 0.7 and less than or equal to 0.92, y is more than or equal to 0 and less than or equal to 0.2, z is more than or equal to 0 and less than or equal to 0.2, n is more than or equal to 0 and less than or equal to 0.2, and x + y + z + n =1; m is selected from one or more of Al, mg, fe, ti, V, zr, la, mo, zn, cu or Y;
preferably, the material of the coating layer is selected from LiNbO 3 、Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 、Li 3 BO 3 、LiPO 3 、Li 2 ZrO 3 、Li 7 La 3 Zr 2 O 12 、Li 2 TiO 3 、LiTaO 3 Or Al 2 O 3 One or more of;
preferably, the positive electrode active material is in a granular form, and the average particle diameter of the positive electrode active material is 1 to 15 μm;
preferably, the material of the solid electrolyte layer is vulcanizedA solid electrolyte and/or a halide solid electrolyte; more preferably, the sulfide solid electrolyte is selected from Li 6 PS 5 Cl、Li 6 PS 5 Cl 0.5 Br 0.5 、Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 、Li 10 GeP 2 S 12 、Li 7 P 3 S 11 、LiPON、Li 10 SnP 2 S 12 、LiS-SiS 2 Or xLi 2 S·yP 2 S 5 Wherein x is more than or equal to 100 and more than or equal to 70, and y is more than or equal to 30 and more than or equal to 0; more preferably, the halide solid state electrolyte is selected from Li 3 InCl 6 、Li 3 YBr 6 、Li 3 InBr 6 、Li 2 ZrCl 6 、Li 3 ErCl 6 Or Li 3 YCl 6 One or more of (a).
9. A method for producing the all-solid battery according to claim 7 or 8, characterized by comprising the steps of:
step S1, providing the negative pole piece of any one of claims 4 to 6, wherein the negative pole piece is provided with a first surface and a second surface which are oppositely arranged;
step S2, arranging a solid electrolyte layer on the first surface of the negative pole piece;
and S3, arranging a positive pole piece on the outer surface of the solid electrolyte layer far away from the first surface.
10. The method according to claim 9, wherein in step S2, a material of the solid electrolyte layer is mixed with a second binder to obtain a mixed slurry, the mixed slurry is coated on the first surface of the negative electrode plate, and the solid electrolyte layer is formed after the second drying;
preferably, the material of the solid electrolyte layer is in a granular form, and the average particle diameter of the material of the solid electrolyte layer is 1 to 100 μm;
preferably, the weight ratio of the material of the solid electrolyte layer to the second binder is (90-100): 0.1-10;
preferably, the treatment temperature of the second drying is 60-80 ℃, and the treatment time is 12-24 h.
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