1. The invention belongs to the field of solid-state lithium-ion battery materials and relates to a dry-process pole piece of a carbon-based solid-state lithium battery, a solid-state electrolyte membrane, a preparation method, and a battery cell.

Background technique:

2. Solid-state lithium-ion batteries have attracted much attention for their application prospects such as high energy density, small size, safety, flexibility, and deformability.

3. The three key components of solid-state lithium-ion batteries are positive and negative electrodes and solid-state electrolytes, of which solid-state electrolytes include polymer systems (conductivity 10-7-10-5

s/cm), oxide system (conductivity 10-6-10-3

s/cm), sulfide system (conductivity 10-3-10-2

sec/cm); compared to conventional liquid electrolytes (conductivity 10-2

s/cm) has a lower conductivity. Moreover, when used in a battery, due to the small contact area between the solid/solid interface between the electrode and the electrolyte and the high interfacial impedance, the transmission of lithium ions between the interfaces is hindered, which directly leads to a solid-state lithium battery. Poor and unstable circulation limits its application.

4. The flexibility and ease of processing of polymer solid electrolytes, and good contact with the electrode interface, can reduce the interface resistance of solid-state batteries, and more and more attention has been paid to all-solid-state batteries. Polyvinylidene fluoride polymer, a common polymer solid-state electrolyte, has attracted attention because of its stable electrochemical and mechanical properties, and its ability to dissociate lithium salts well to improve its conductivity. However, due to its high crystallinity and a high proportion of crystallized regions, lithium ions cannot be transported rapidly in the PVDF crystal structure, and the ion conductivity at room temperature is poor, about 10-5s·

cm-1

. In general, gelation increases electrical conductivity, which in turn leads to a decrease in mechanical properties. The introduction of ceramic fillers () or oxide-like solid electrolytes () to form a composite polymer electrolyte enhances its stability and mechanical properties, but the introduction of inorganic fillers is likely to cause its side reactions, leading to problems such as excessive self-discharge and poor cycle performance of the battery.

5. At present, the positive and negative electrodes are mainly prepared by a wet coating process. The wet coating cannot increase the energy density of batteries by making thick electrodes, and because the cathode uses a large amount of toxic volatile organic compounds amp, it not only causes environmental pollution but also consumes a lot of energy during the solvent drying process. Therefore, the dry electrode technology that does not rely on solvents has attracted more and more attention from the lithium battery industry and is expected to become the key to breaking the performance bottleneck of lithium batteries. Patent literature discloses a dry method for preparing positive and negative electrodes of lithium batteries. It is made by mixing the active material, conductive agent, binder, and solid electrolyte powder in a certain proportion and a certain order, without solvent. The liquid forms a dry electrode, which can reduce the polarization of the battery and reduce the battery impedance, but the biggest problem with this method is that the prepared dry electrode is brittle and easy to break, which is not conducive to reducing the usage rate.

Technical realization elements:

6. The present invention aims at poor PVDF-based solid electrolyte interface contact, high solid/solid interface impedance, hindered lithium ion transmission between interfaces, low room temperature ion conductivity, poor mechanical properties, and easily caused side reactions, etc., by adding polyphenylene sulfide The ether forms a composite polymer solid electrolyte, improves the crystallinity of PVDF, improves the mechanical properties of the solid electrolyte membrane, increases the ionic conductivity, and at the same time achieves the lithium-ion rectification effect, reduces the concentration polarization, and effectively inhibits the growth of lithium dendrites. In addition, for insoluble

There are many problems in the preparation process of dry electrodes, such as high brittleness, easy fracture, and high binder content. The introduction of the semi-dry electrode sheet preparation process can reduce the amount of binder, increase the flexibility of the electrode sheet, and obtain good cycle performance and low internal resistance. High energy density solid-state battery.

7. The object of the present invention is achieved through the following technical solutions: A method for preparing a carbon-based solid-state lithium-ion battery dry-process electrode sheet, characterized in that the preparation of a dry-process positive electrode sheet comprises the following steps: adding lithium-ion battery positive electrode powder or Lithium-ion battery negative electrode powder, polytetrafluoroethylene (PTFE) binder and conductive agent are placed in a low-temperature mixer below 0°C at a mass percentage of 90-96: 2-5:1-5 After mixing evenly, the stirring speed is 30 -500r/min; Use a supersonic jet mill to mix the dry powder, and the air inlet pressure is 1-2MPa; Then knead the mixed dry powder with an organic solvent in an internal mixer to form a ball, and the stirring speed is 30-500r/min. The solid content of the dough is ≥50%. The dough-like material is extruded by a screw extruder to obtain a continuous thin broadband with a thickness of 500-1000 μm; the positive and negative electrode dry-process film materials with a thickness of 50-120 μm are produced by a hot roll press, and the horizontal roll pressure is 2-10t; The positive or negative electrode dry film material is placed on a horizontal hot roller press at a temperature of 150°C-200°C for double-sided thermal lamination, and the pressure of the horizontal roller is 2-10 tons; finally, a dry positive electrode sheet or a dry method negative plate.

8. Preferably, the highly conductive coating is one or more graphene, carbon nanotubes, or highly conductive graphite.

9. Preferably, the added organic solvent is any one or combination of the following: water, ethanol, ethylene glycol, propylene glycol, glycerin, isopropanol, n, n-dimethylformamide, tetrahydrofuran, n-formaldehyde base pyrrolidone.

10. Preferably, the lithium-ion battery negative electrode powder is any one or combination of the following: natural graphite, artificial graphite, mcm, hard carbon, soft carbon, carbon nanotubes, graphene, carbon fiber, activated carbon, oxide Si@ and @.

11. A carbon-based solid-state lithium-ion battery dry-process positive electrode sheet or dry-process negative electrode sheet, prepared by the preparation method of the dry-process electrode sheet.

12. A preparation method for a carbon-based solid-state lithium-ion battery solid-state electrolyte membrane, characterized in that, at first polyphenylene sulfide powder and polyvinylidene fluoride (PVDF) are premixed in a planetary mixer or a kneader 1- 2 hours, slowly add organic solvent to the solid content of 40-60%, semi-dry mixing for 1-5 hours, until the material is mixed evenly; add lithium salt, continue mixing for 1-5 hours, then add organic solvent to the solid content of 10- 30% for high-speed dispersion mixing, dispersion speed 2000-, dispersion time 1-2h to obtain solid electrolyte slurry; use a doctor blade coater to coat the obtained solid electrolyte slurry into a film with a thickness of 25 μm-50 μm, put the solid electrolyte membrane put into a vacuum oven at a temperature of 60-100° C. and dry for 10-24 hours to finally obtain a solid electrolyte membrane.

13. Preferably, the added organic solvent is any one or combination of the following: water, ethanol, ethylene glycol, propylene glycol, glycerin, isopropanol, n, n-dimethylformamide, tetrahydrofuran, n-formaldehyde base pyrrolidone.

14. Preferably, the lithium salt is a double salt of neutralization, and the mass ratio of the double salt to neutralization is 1:1-1.5.

15. A solid electrolyte membrane prepared by a method for preparing a solid electrolyte membrane, characterized in that the polymer solid electrolyte membrane is composed of continuous phase PVDF, reinforcing phase pps, lithium salt, and an organic solvent; wherein the mass percentage of PVDF is 30% -40%, the mass percentage of pps is 30%-40%, the mass percentage of lithium salt is 20-25%, and the percentage of organic solvent is 5-15%.

16. A battery, is characterized in that it comprises the dry-process positive electrode sheet and the dry-process negative electrode sheet according to claim 5, and the polymer solid electrolyte membrane according to claim 9, and the solid electrolyte membrane is located on the positive electrode. The electrode sheet and the negative electrode sheet are connected by an adhesive and then assembled by thermal compounding. The adhesive contains or entirely contains solid electrolyte slurry.

17. Compared with the prior art, the present invention has the following advantages:

The polymer solid electrolyte slurry can partially replace the binder, effectively reduce the contact resistance between the inside of the active particles and the electrode/electrolyte interface, and has beneficial effects on reducing the polarization internal resistance of the battery and improving the cycle performance of the battery.

18. Adding polyphenylene sulfide can improve the mechanical strength of the PVDF solid electrolyte membrane and enhance the ion conductivity at the same time. Because polyphenylene sulfide in electrochemical lithium plating can chelate anions, prevent concentration polarization, improve the directional migration of lithium ions along the sulfur (s) site channel, and achieve lithium ion rectification, thereby effectively inhibiting the growth of lithium dendrites, which helps to form a dense sei layer on the surface of the graphite negative electrode to prevent lithium precipitation.

19. The polymer solid-state electrolyte membrane has the advantages of high decomposition voltage, large lithium-ion migration number, and high ion conductivity, which can effectively improve the electrochemical rate performance of carbon-based solid-state lithium-ion batteries and meet the requirements of commercial solid-state lithium-ion battery applications.

20. The semi-dry electrode sheet preparation process can reduce the amount of binder and increase the flexibility of the electrode sheet. The battery assembled with a thermally composited polymer solid electrolyte membrane has the characteristics of good cycle performance, low internal resistance, and high energy density.

21. Provide a simple and efficient preparation method for polymer solid electrolyte membranes. Through the simple blending method, the film-making process is simple, the film is formed quickly, and the efficiency is high. The conventional equipment used is easy to control and operate, and the polymer solid electrolyte membrane can be prepared in large quantities. Electrolyte and separator for commercial solid-state lithium battery production.

Drawing Description

22. Figure 1 is the physical picture of the polymer solid electrolyte membrane of Example 1; Figure 2 is the SEM photo of the polymer solid electrolyte membrane of Example 1; Figure 3 is the tensile property diagram of the polymer solid electrolyte membrane of Example 1; FIG. 4 is a diagram of the decomposition voltage (lv) of the polymer solid electrolyte of Example 1. FIG.

implement

23. The following examples are descriptions of the specific experimental operations of the present invention, and are only used to illustrate the present invention, and cannot be construed as limiting the present invention.

example

24. Put lithium iron phosphate, polytetrafluoroethylene (PTFE) binder, and p-conductive agent in a mass percentage of 96:2:2 into a mixer at -5°C, and stir evenly at a speed of 100r/min, mix the dry powder with a supersonic airflow mill, and the inlet pressure is 1mpa; then knead the mixed dry powder with a mixed solvent of water and ethanol in an internal mixer at a stirring speed of 200r/min to form a dough with a solid content of 90% materials. The dough-like material was extruded with a screw extruder to obtain a continuous strip with a thickness of 500 μm and then rolled into a positive dry self-supporting film C with a thickness of 90 μm by a 120° horizontal hot roll under a pressure of 5 tons. Then, the positive self-supporting film and the conductive layer-coated aluminum foil current collector were hot-compressed and composited on a horizontal hot roller press at 180°C and a pressure of 5 tons, and finally a dry-process positive electrode sheet was obtained.

25. Artificial graphite, polytetrafluoroethylene (PTFE) binder, and p conductive agent are mixed in a mixer at -5°C at 100r/min according to the mass percentage of lithium-ion battery negative electrode powder at a ratio of 97:2:1 and then mixed at a speed Evenly, mix the dry powder with a supersonic airflow mill, and the inlet pressure is 1mpa; then knead the mixed dry powder and the mixed solvent of water and ethanol in an internal mixer at a stirring speed of 200r/min to form a dough with a solid content of 85% thing. The dough-like material was extruded with a screw extruder to obtain a continuous strip with a thickness of 500 μm and then rolled into a negative dry self-supporting film C with a thickness of 80 μm by a 120° horizontal hot roll under a pressure of 5 tons. Then, the positive electrode self-supporting film was hot-compressed and composited with the conductive layer-coated copper foil current collector on a horizontal hot roller press at 180°C and a pressure of 5t, and finally a dry-process negative electrode sheet was obtained. get.

26. Grind the polyphenylene sulfide particles with a high-speed grinder for 30 minutes, pass through a 500-mesh sieve, and then disperse them ultrasonically in an ethanol solvent for 40 minutes, and dry them in a vacuum at 60°C for 20 hours. Mix 50 g of dry polyphenylene sulfide powder with 50 g of 80 Put the PVDF dried at ℃ for 24 hours into a planetary mixer and stir for 2 hours, slowly add n,n-dimethylformamide (DMF), stir for 2 hours, then add 33g of compound salt, continue mixing for 2 hours, and then Add amp organic solvent, set the dispersion speed to, disperse for 1 hour, disperse and mix at high speed to obtain solid electrolyte slurry. The solid electrolyte slurry was coated into a film with a thickness of 30 μm on a knife coater, and then placed in a vacuum oven and dried at 100 °C for 24 hours to obtain a polymer solid electrolyte membrane, as shown in Figure 1. The surface of the solid electrolyte membrane can be observed using a scanning electron microscope (SEM), as shown in Figure 2, and it can be observed that the pps are uniformly distributed in the continuous phase of PVDF. The conductivity of the solid electrolyte membrane measured by the AC impedance method is 1.27

x

10-4 sec/cm. The tensile strength measured by the electronic universal testing machine is 4mpa, as shown in Figure 3, the electrochemical window of the linear volt-ampere test of the lithium sheet/solid electrolyte membrane/steel plate half-cell is 4.3v, and the linear volt-ampere curve is as shown in Figure 4 Show.

27. Use a button battery for electrochemical testing, put the above-mentioned dry-process positive and negative electrodes in an oven and dry them at 60°C for 2 hours, use a cutting machine to cut the positive electrode sheet with a diameter of 12mm, use a sheet with a diameter of 15mm for the negative electrode, and use a solid electrolyte The membrane was cut to a diameter of 19 mm. After the pole pieces were dried in a vacuum oven at 100°C for 20 hours, a button battery was assembled in a glove box, the solid electrolyte membrane was placed between the positive and negative electrodes, and 5 μl of lithium hexafluorophosphate commercial electrolyte was added to the positive and negative sides respectively to achieve wetting The effect of the pole piece, the 0.2C rate charge and discharge test is carried out on the charge and discharge tester, and the discharge specific capacity is /g.

28. The preparation method of Examples 2-6 is the same as that of Example 1, except that the proportions of polyphenylene sulfide, PVDF, and a lithium salt, and the organic solvents used for preparing pole pieces and electrolytes are different.

29. The preparation method of this comparative example 1 is the same as that of the above-mentioned example 1, except that polyphenylene sulfide powder PVDF and lithium salt polymer electrolyte are not added.

30. The preparation method of the electrolyte in this comparative example 2 is the same as that in the above-mentioned example 1, except that the traditional commercially available wet-coated pole pieces are used, and the semi-dry method electrode pole pieces are not used.

31. The materials and electrochemical properties of specific examples 1-6 and comparative examples 1-2 are shown in Table 1.

32. Table 1 Different examples of electrode preparation methods and polymer electrolyte components and their electrochemical properties Although the examples of the present invention have been described, those of ordinary skill in the art can understand that without departing from the principles and principles of the present invention Various changes, modifications, substitutions, and variations may be made to these embodiments within the scope of the present invention as defined by the appended claims and their equivalents.

Technical Features:

1. A preparation method of a carbon-based solid-state lithium-ion battery dry-process electrode sheet, characterized in that, the dry-process positive electrode sheet is prepared by the following steps: lithium-ion battery positive electrode powder or lithium-ion battery negative electrode powder, polymer tetrafluoroethylene Ethylene (ptfe) binder and conductive agent are mixed according to the mass percentage of 90-96:2-5:1-5 in a low-temperature mixer below 0°C, and the stirring speed is 30-500 rpm; the dry powder is supersonic Air jet mill mixing, air inlet pressure 1-2mpa; knead the mixed dry powder and organic solvent in the internal mixer to form a lump material, stirring speed 30-500r/min, the density of the lump substance content ≥ 50% ; Extrude the dough-like material with a screw extruder to obtain a continuous thin strip with a thickness of 500-1000 μm; then press the continuous thin strip through a horizontal hot roller press with a temperature below 150 ° C to a thickness of 50-120 μm For the positive and negative electrode dry process film materials, the horizontal pressure roller is 2-10t; then the positive and negative electrode dry process film materials and the aluminum foil collectors coated with high conductive coating on both sides are placed at 150°C-200°C Horizontal hot rolling at a certain temperature, double-sided hot pressing on the machine, the pressure of the horizontal roller is 2-10t; finally a dry positive electrode sheet or a dry negative electrode sheet is obtained.  2. The preparation method of lithium-ion battery dry electrode sheets according to claim 1, wherein the highly conductive coating is one or more of graphene, carbon nanotubes, or highly conductive graphite.  3. the preparation method of carbon-based solid-state lithium-ion battery dry-process electrode sheet according to claim 1, is characterized in that, the organic solvent described adding is following any one or its combination: water, ethanol, ethylene glycol, propylene glycol, glycerin, isopropanol, n,n-dimethylformamide, tetrahydrofuran, n-methyl pyrrolidone.

4. the preparation method of carbon-based solid-state lithium-ion battery dry-process electrode sheet according to claim 1, is characterized in that, described lithium-ion battery negative electrode powder is following any one or its combination: natural graphite, artificial graphite, mcm, hard carbon, soft carbon, carbon nanotubes, graphene, carbon fiber, activated carbon, silica@carbon, and silicon@carbon.  5. A carbon-based solid-state lithium ion battery dry-process positive electrode sheet or dry-process negative electrode sheet, which is prepared by the preparation method of the dry-process electrode sheet described in any one of claims 1-4.  6. A preparation method for a carbon-based solid-state lithium-ion battery solid-state electrolyte membrane, characterized in that, first polyphenylene sulfide powder (pps) and polyvinylidene fluoride (pvdf) are carried out in a planetary mixer or a kneader Pre-mix for 1-2 hours, slowly add organic solvent to solid content of 40-60%, semi-dry mixing for 1-5 hours, until the material is mixed evenly; add lithium salt, continue mixing for 1-5 hours, then add organic solvent to solid content of 10 %-30% for high-speed dispersion mixing, dispersion speed 2000-, dispersion time 1-2h, to obtain a solid electrolyte slurry; use a doctor blade coater to coat the obtained solid electrolyte slurry coating into a solid electrolyte membrane with a thickness of 25μm-50μm , placed in a vacuum oven at a temperature of 60-100°C and dried for 10-24 hours to finally obtain a solid electrolyte membrane.  7. the preparation method of carbon-based solid-state lithium-ion battery solid-state electrolyte membrane according to claim 6 is characterized in that, the organic solvent described adding is following any one or its combination: water, ethanol, ethylene glycol, propylene glycol, glycerin, isopropanol, n,n-dimethylformamide, tetrahydrofuran, n-methyl pyrrolidone.

8. the preparation method of carbon-based solid-state lithium-ion battery dry-process electrode sheet and solid-state electrolyte membrane according to claim 6, is characterized in that, the described lithium salt is and the double salt of and, in the double salt described in mass fraction And the ratio is 1:1~1.5.  9. The solid electrolyte membrane prepared by the preparation method of the solid electrolyte membrane according to claim 6, wherein the polymer solid electrolyte membrane is composed of a continuous phase PVDF, a reinforcing phase pps, a lithium salt, and an organic solvent; wherein PVDF The mass percentage of pps is 30%-40%, the mass percentage of pps is 30%-40%, the mass percentage of lithium salt is 20-25%, and the mass percentage of organic solvent is 5-15%. 10. A battery, characterized in that, comprising the dry positive electrode sheet and dry negative electrode sheet according to claim 5, and the polymer solid electrolyte membrane according to claim 9, the solid electrolyte membrane is located on the positive electrode sheet, Negative electrode sheets are connected by adhesive

Then, by Thermo composite assembly, the binder contains or is all solid electrolyte paste.

Technical overview

The invention relates to the field of solid-state lithium-ion batteries and discloses a carbon-based solid-state lithium battery dry-process electrode sheet, a solid-state electrolyte membrane, a preparation method, and a battery cell. After the active material, conductive agent, and binder are used in a certain proportion, a dry electrode is prepared by a semi-dry method; the polymer is mixed and dispersed at a high speed by a continuous phase PVDF, a reinforcing phase PPS, lithium salt and an organic solvent to prepare a solid electrolyte membrane. Finally, a carbon-based solid-state lithium-ion battery is assembled by thermal compounding. The carbon-based solid lithium-ion battery prepared by the method of the invention has a higher specific capacity, specific energy density, and safety. and safe. and safe.

Technical R&D personnel: Gao Hongquan, Wang Baojun, Zhou Haitao, Wu Jianchun, Sun Yongling, Xu Teng, Wang Xin, Sun Pengfei

Protected Technology User: Jiangsu University

Technology R&D Day: 2023.01.16

Technical bulletin date: 2023/4/25