Method for preparing a continuous self-supporting electrolyte membrane, electrolyte membrane and applications

Abstract

The application discloses a preparation method of a continuous self-supporting electrolyte membrane, the electrolyte membrane and application, wherein the preparation method of the self-supporting electrolyte membrane comprises the following steps: preparing a skeleton membrane and a base film, coating slurry containing an electrolyte on the base film by using a gravure coater, forming an electrolyte membrane layer on the base film after first drying, and attaching the electrolyte membrane layer on both sides of the skeleton membrane to obtain the self-supporting electrolyte membrane. In the embodiment of the application, the skeleton membrane is introduced, the skeleton membrane has a supporting effect on the electrolyte membrane layer, and the skeleton membrane is favorable for improving the short-circuit problem of the electrolyte membrane layer when the electrolyte membrane layer is applied to a battery. Meanwhile, the slurry is coated on the base film by using the gravure coater to form the electrolyte membrane layer, and the electrolyte membrane layer with higher coating precision can be obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrolyte membranes, in particular to a preparation method of a continuous self-supporting electrolyte membrane, an electrolyte membrane and application. BACKGROUND

[0002] Based on the requirements of high energy density and high safety of batteries, all-solid-state batteries have become a research hotspot. All-solid-state batteries are mainly divided into oxide all-solid-state batteries, polymer all-solid-state batteries and sulfide all-solid-state batteries, among which sulfide all-solid-state batteries have become the main system due to their excellent ionic conductivity and good mechanical flexibility. However, the sulfide all-solid-state battery is still in the pressure mold assembly stage, and only a few companies try to assemble small capacity soft packs, which is mainly due to the mechanical performance of the sulfide electrolyte membrane limiting the assembly method of the soft pack.

[0003] In addition, since the thickness of the electrolyte membrane is directly related to the overall energy density and volume energy density of the battery, it is necessary to ensure the high energy density advantage of the all-solid-state battery, which requires as thin as possible electrolyte membrane. Based on the process characteristics, the dry process is limited by the equipment precision and is difficult to prepare an electrolyte membrane with a thickness of less than 20 microns. At present, the wet process can realize the coating of an electrolyte membrane with a thickness of less than 20 microns, but the too thin electrolyte membrane is difficult to be self-supporting, and when applied to the battery, it is prone to short circuit due to poor uniformity.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a continuous self-supporting electrolyte membrane, a self-supporting ultra-thin electrolyte membrane and an all-solid-state battery.

[0006] The present application is realized as follows:

[0007] In a first aspect, the present application provides a preparation method of a continuous self-supporting electrolyte membrane, comprising:

[0008] Preparation of a skeleton membrane and a base film, coating a slurry containing an electrolyte on the base film by using a gravure coater, and forming an electrolyte film layer on the base film after first drying;

[0009] Attaching the electrolyte film layer to both sides of the skeleton membrane to obtain the self-supporting electrolyte membrane.

[0010] In an optional embodiment, the electrolyte film layer is transferred and attached to both sides of the skeleton membrane by rolling;

[0011] Preferably, when the electrolyte film layer is transferred, the skeleton membrane and the base film move synchronously under the action of an external force towards the rolling equipment, and the electrolyte film layer is transferred and attached to the surface of the skeleton membrane.

[0012] In an optional embodiment, before laminating the electrolyte membrane layer on the skeleton membrane, the method further comprises pre-treating the skeleton membrane, the pre-treatment is loading the affinity agent on the skeleton membrane;

[0013] Preferably, the affinity agent is selected from at least one of n-heptane, n-hexane, n-hexane, n-butyl ether and butyl butyrate;

[0014] Preferably, the loading amount of the affinity agent in the skeleton membrane is 500-2000 ppm;

[0015] Preferably, the pre-treatment comprises: placing the skeleton membrane in an atmosphere of affinity agent vapor, so that the affinity agent molecules are immersed in the skeleton membrane.

[0016] Preferably, after laminating the electrolyte membrane layer on the skeleton membrane loaded with the affinity agent, the skeleton membrane laminated with the electrolyte membrane layer is further subjected to a second drying to obtain the self-supporting electrolyte membrane;

[0017] Preferably, the skeleton membrane is a resin fiber membrane or a glass fiber membrane, and has a thickness of 5-15 μm and a porosity of 60-95%.

[0018] In an optional embodiment, the electrolyte membrane layer comprises a sulfide electrolyte and a binder, the mass fraction of the sulfide electrolyte is 90-99 wt%, and the mass fraction of the binder is 1-10 wt%;

[0019] Preferably, the thickness of the single-layer electrolyte membrane layer is 0.1 μm-10 μm; more preferably, the error range of the thickness of the electrolyte membrane layer is ±1%;

[0020] Preferably, the sulfide electrolyte is selected from at least one of Li6PS5Cl, Li3PS4 and Li2S-P2S5;

[0021] Preferably, the D50 of the sulfide electrolyte is 0.2-1 μm;

[0022] Preferably, the binder is selected from at least one of methyl vinyl silicone rubber, nitrile rubber, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene and styrene-butadiene rubber.

[0023] In an optional embodiment, the slurry comprises an electrolyte, a binder and a solvent;

[0024] Preferably, the solid content of the slurry is 50-65%;

[0025] Preferably, the coating speed is 0.005-0.015 m / min;

[0026] Preferably, the solvent is selected from at least one of n-heptane, methyl vinyl ketone, n-hexane, isobutyl isobutyrate, butyl butyrate xylene and toluene.

[0027] In an optional embodiment, the base film is one of aluminum foil, stainless steel, release film and release paper.

[0028] Preferably, the thickness of the base film is 2.5-20 μm.

[0029] Preferably, the release force of the base film is 1-5 g.

[0030] In an optional embodiment, the first drying temperature is 45-150 °C, and the drying is performed to a residual amount of the solvent less than 2000 ppm.

[0031] And / or, the second drying temperature is 80-200 °C, and the drying is performed to a residual amount of the affinity agent and the solvent less than 100 ppm.

[0032] In a second aspect, the present application provides a self-supporting ultra-thin electrolyte membrane, which is obtained by the preparation method of the self-supporting electrolyte membrane according to any one of the preceding embodiments.

[0033] In an optional embodiment, the thickness of the self-supporting electrolyte membrane is less than 24 μm, and preferably, the thickness of the self-supporting electrolyte membrane is 14-15 μm.

[0034] In a third aspect, the present application provides a full solid-state battery, which comprises the self-supporting ultra-thin electrolyte membrane according to the preceding embodiments.

[0035] The present application has the following beneficial effects:

[0036] The present application introduces a skeleton film, which has a supporting effect on the electrolyte membrane layer, and is conducive to improving the problem of easy short circuit when the electrolyte membrane layer is applied in a battery. At the same time, the gravure coater is used to coat the slurry on the base film to form the electrolyte membrane layer, which is conducive to obtaining an electrolyte membrane layer with higher coating precision. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0038] Figure 1 FIG. 1 is a schematic diagram of the preparation process of the self-supporting electrolyte membrane in Embodiment 1 of the present application. DETAILED DESCRIPTION

[0039] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. If specific conditions are not specified in the embodiments, conventional conditions or manufacturer recommended conditions are adopted. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased in the market.

[0040] The present embodiment provides a preparation method of a continuous self-supporting electrolyte membrane, comprising:

[0041] A skeleton membrane and a base membrane are prepared, a slurry containing an electrolyte is coated on the base membrane by using a gravure coater, and after first drying, an electrolyte membrane layer is formed on the base membrane;

[0042] The electrolyte membrane layer is attached to both sides of the skeleton membrane to obtain the self-supporting electrolyte membrane.

[0043] At present, the ultra-thin electrolyte membrane coated on the base membrane is difficult to be self-supporting, and is often transferred to the positive or negative electrode sheet for use, which will cause two problems, one is that defects may occur during the entire transfer process, such as incomplete transfer in some areas; the other is that the negative or positive electrode and the electrolyte membrane are wound and unwound after transfer, and the stress of the positive or negative electrode and the electrolyte membrane is different, and the contact between the two is easily damaged during curling. Therefore, short circuit is prone to occur when it is applied in a battery, which causes waste of positive and negative electrode sheets and electrolyte membranes and affects production efficiency. The present embodiment introduces a skeleton membrane, which has a supporting effect on the electrolyte membrane layer and is beneficial to improve the problem of easy short circuit when applied in a battery.

[0044] The ultra-thin electrolyte membrane applied in a battery has higher requirements for the uniformity of the electrolyte membrane, otherwise short circuit phenomenon is prone to occur. At present, the dry process is rarely applied to the preparation of ultra-thin electrolyte membrane due to the limitation of equipment precision; the wet process is considered to be the mainstream process that can realize the preparation of ultra-thin electrolyte membrane at present. The common mature continuous coating equipment, such as transfer coating and extrusion coating, is difficult to be below 20 μm in thickness, and the precision of these equipment is about ± 1.5 μm. For 20 μm or below ultra-thin electrolyte membrane, the thickness error can reach ± 7.5%, that is, the electrolyte membrane is very uneven. Even if the electrolyte membrane is relatively uniform after pressing, the internal structure of the thin film will be uneven due to the difference in density at different positions, and the uneven electrolyte layer will affect the transmission of ions, and most importantly, affect the uniformity of the multi-layer battery.

[0045] One of the difficulties in transferring the electrolyte layer to the skeleton film is that the electrolyte layer is difficult to be thin and uniform, which leads to the final three-layer composite electrolyte film with high thickness. The dry layer thickness of micro gravure printing coating is 0.1-10 μm, and its coating precision is ±1%, and for 20 μm electrolyte film, considering the subsequent two-layer composite, the maximum error is only 2%; and even if 2 layers are transferred together to composite the 3-layer electrolyte film structure of the skeleton film, the thickness can be controlled to be less than 20 μm, or even less than 15 μm, so the coating form of gravure printing introduced in the embodiment of the application can not only prepare thinner electrolyte film, but also improve the coating precision of electrolyte film, and solve the uniformity problem of ultra-thin electrolyte film.

[0046] In an optional embodiment, the electrolyte film layer is transferred and attached to both sides of the skeleton film by rolling.

[0047] Preferably, when the electrolyte film layer is transferred, the skeleton film and the base film are synchronously moved towards the rolling device under the action of an external force, so as to transfer and attach the electrolyte film layer to the surface of the skeleton film.

[0048] If the electrolyte film is prepared by mold pressing, flat pressing or warm isostatic pressing, the precision of the electrolyte film prepared in this way is relatively high, but the size is limited and cannot support continuous production. In the embodiment of the application, the rolling combined with the transfer mode is adopted, which is beneficial to improve the uniformity of the electrolyte film and realize continuous production.

[0049] At present, the production efficiency of all-solid-state batteries is very low, one of the main reasons is that the electrolyte film is difficult to be continuously coiled like the liquid battery separator, and it is difficult to adopt the winding and stacking mode of the liquid battery. On the one hand, the mechanical toughness of the electrolyte film is a problem, on the other hand, the electrolyte film cannot be continuously coiled. Based on this, the embodiment of the application improves the mechanical properties of the electrolyte film by using the skeleton film, and combines the continuous rolling process to transfer the 2-layer electrolyte layer to the skeleton film, which can realize continuous production and support the diversification of the soft packaging form of the rear end, such as stacking, winding, and stacking, etc., which guarantees the efficient and continuous production of the rear end of the all-solid-state battery.

[0050] In an optional embodiment, before the electrolyte film layer is attached to the skeleton film, the skeleton film is pretreated, and the pretreatment is to load an affinity agent on the skeleton film.

[0051] During the transfer, if only relying on pressure to transfer the electrolyte membrane layer to the skeleton membrane, it is easy to cause part of the residual material to fail to be successfully transferred, which seriously reduces the production efficiency during continuous production. The introduction of the skeleton membrane and the pretreatment of the skeleton membrane in the embodiment of the application is beneficial to enhancing the affinity of the skeleton membrane to the electrolyte membrane layer, improving the transfer success rate of the electrolyte membrane layer, and ensuring the production efficiency. In addition, the affinity agent of the skeleton membrane is also helpful for the movement of the electrolyte particles (such as sulfide electrolyte particles) in the electrolyte membrane layer, which is beneficial to further improving the density of the electrolyte layer.

[0052] The introduction of the skeleton membrane and the pretreatment of the skeleton membrane in the embodiment of the application make the affinity agent loaded on the skeleton membrane after the pretreatment have a certain solubility to the binder in the electrolyte membrane layer, so that the electrolyte membrane layer has a certain adhesion, which is helpful to improve the bonding strength between the skeleton membrane and the electrolyte membrane. In combination with the use of the aforementioned gravure coater, the preparation of the self-supporting ultrathin electrolyte membrane can be realized, and the problem of easy short circuit caused by poor uniformity when the electrolyte membrane is applied in the battery can be solved.

[0053] In an optional embodiment, the affinity agent is selected from at least one of n-heptane, n-hexane, n-hexane, n-butyl ether and butyl butyrate, which has good compatibility with the sulfide electrolyte.

[0054] In an optional embodiment, the loading amount of the affinity agent in the skeleton membrane is 500-2000 ppm. If the content of the affinity agent is too low, the effect is not obvious, but if the content of the affinity agent is too high, the effect of improving the affinity between the skeleton membrane and the electrolyte membrane layer is not obvious, and part of the solvent may affect the ionic conductivity of the electrolyte. In addition, it also increases the energy consumption of subsequent removal of the affinity agent, and may also affect the uniformity of the electrolyte membrane.

[0055] The affinity agent can be added to the skeleton membrane by spraying, dripping, soaking or coating and the like. In one embodiment, the pretreatment comprises: placing the skeleton membrane in an atmosphere of affinity agent vapor so that the affinity agent molecules are immersed in the skeleton membrane. Placing the skeleton membrane in an atmosphere of affinity agent vapor is beneficial to the uniform dispersion of the affinity agent in the skeleton membrane. In some embodiments, in order to reduce the introduction of other impurities, the skeleton membrane and the affinity agent are placed in a vacuum environment, and then heated to evaporate or gasify the affinity agent. The heating temperature can be any temperature that can gasify the affinity agent into vapor.

[0056] In an optional embodiment, after the electrolyte membrane layer is attached to the skeleton membrane loaded with the affinity agent, the skeleton membrane attached with the electrolyte membrane layer is subjected to a second drying to obtain the self-supporting electrolyte membrane. If the skeleton membrane loaded with the affinity agent is used, the electrolyte membrane layer needs to be dried after being attached.

[0057] In an optional embodiment, the skeleton film is a resin fiber film or a glass fiber film, with a thickness of 5-15 pm and a porosity of 60-95%. Since the skeleton film has poor electrical conductivity, in order to minimize the negative impact of the skeleton film on the performance of the electrolyte film, and considering the need for the electrolyte film to be as thin as possible, the thickness of the skeleton film is as thin as possible while ensuring the mechanical properties of the electrolyte film. In addition, a larger porosity is conducive to further reducing the amount of skeleton film and further reducing the negative impact of the skeleton film on the performance of the electrolyte film; at the same time, the electrolyte film layers on both sides of the skeleton film can be in contact with each other through the hollows on the skeleton film, thereby improving the bonding strength of the three layers in the electrolyte film.

[0058] In an optional embodiment, the electrolyte film layer comprises a sulfide electrolyte and a binder, the mass fraction of the sulfide electrolyte being 90-99 wt%, and the mass fraction of the binder being 1-10 wt%.

[0059] In an optional embodiment, the dry layer thickness of a single electrolyte film layer is 0.1 pm-10 pm; more preferably, the error range of the thickness of the electrolyte film layer is ±1%, for example, if the thickness of the electrolyte film is 0.5 pm, then the thickness deviation of each position of the film layer is within ±0.005 pm, and if the thickness of the electrolyte film is set to 1 pm, then the thickness deviation of each position of the film layer is within ±0.01 pm.

[0060] In some embodiments, after the slurry is coated on the base film using a gravure coater, a coating layer with a wet thickness of 2-20 pm is formed on the base film, and after the coating layer is dried, a thin and uniform electrolyte film layer can be obtained.

[0061] In an optional embodiment, the sulfide electrolyte is selected from at least one of Li6PS5Cl, Li3PS4, and Li2S-P2S5.

[0062] In an optional embodiment, the D50 of the sulfide electrolyte is 0.2-1 pm. If the particle size of the sulfide electrolyte is too large, the mechanical properties and uniformity of the electrolyte film layer will be reduced, and if the particle size of the sulfide electrolyte layer is too small, the amount of binder needs to be increased, which will in turn reduce the proportion of the sulfide electrolyte in the electrolyte film and affect the electrical conductivity of the electrolyte film.

[0063] In an optional embodiment, the binder is selected from at least one of methyl vinyl silicone rubber, nitrile rubber, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, and styrene-butadiene rubber.

[0064] In an optional embodiment, the slurry comprises an electrolyte, a binder, and a solvent.

[0065] In an optional embodiment, the solid content of the slurry is 50-65%, which ensures the uniformity of the electrolyte membrane while reducing the energy consumption of the subsequent solvent removal.

[0066] In an optional embodiment, the coating speed is 0.005-0.015 m / min.

[0067] In an optional embodiment, the solvent is at least one selected from the group consisting of n-heptane, methyl vinyl ketone, n-hexane, isobutyl isobutyrate, butyl butyrate, xylene and toluene.

[0068] In an optional embodiment, the base film is one of an aluminum foil, a stainless steel, a release film and a release paper.

[0069] In an optional embodiment, the thickness of the base film is 2.5-20 μm, which ensures the electrolyte layer to be affected by the base film as little as possible while having a supporting effect.

[0070] In an optional embodiment, the release force of the base film is 1-5 g, which controls the release force of the base film to ensure the release of the electrolyte layer and the winding of the base film at the back end.

[0071] In an optional embodiment, the first drying temperature is 45-150°C, and the drying is performed until the residual amount of the solvent is less than 2000 ppm. If the residual amount of the solvent is too large, deformation may occur during the rolling or winding, which in turn affects the uniformity of the electrolyte membrane.

[0072] In an optional embodiment, the second drying is performed in a drying tunnel, and the second drying temperature is 80-200°C, and the drying is performed until the residual amount of the affinity agent and the solvent is less than 100 ppm. Specifically, the second drying can be performed at one time or in multiple times. In some embodiments, a drying tunnel of 3-20 m in length is provided on the production line, and the composite electrolyte membrane passes through the drying tunnel at a speed of 0.5-3 m / s to preliminarily remove the affinity agent. If the affinity agent still remains, a subsequent supplemental drying is performed, and then the battery is assembled.

[0073] Another embodiment of the present application provides a self-supporting ultrathin electrolyte membrane obtained by the method for preparing a continuous self-supporting electrolyte membrane according to any one of the preceding embodiments.

[0074] In an optional embodiment, the thickness of the self-supporting electrolyte membrane is less than 24 μm; preferably, the thickness of the self-supporting electrolyte membrane is 14-15 μm.

[0075] Another embodiment of the present application provides a full solid-state battery comprising the self-supporting ultrathin electrolyte membrane according to the preceding embodiments.

[0076] The features and performances of the present application are further described in detail below in combination with the embodiments.

[0077] Example 1

[0078] The present example provides a method for preparing a continuous self- supporting electrolyte membrane, comprising the following steps:

[0079] Preparation of electrolyte membrane-1:

[0080] 0.98 kg of Li6PS5Cl, 0.02 kg of PVDF and 0.8181 kg of butyl butyrate were weighed and then mixed in a high-speed centrifuge at a speed of 1000 rpm for 2 h. Then, the mixture was coated on a base film (5 μm in thickness, 3-5 g in release force) using a gravure coater, with a coating wet thickness of 10 μm, a coating speed of 0.01 m / min, followed by drying at a temperature of 145 °C, and then winding after drying. The electrolyte membrane-1 was obtained.

[0081] Treatment of the skeleton membrane:

[0082] A 200-meter-long skeleton membrane (10 μm in thickness, 91% in porosity, and 3 N / 50 mm in tensile strength) with a width of 200 mm was placed in a vacuum oven (Keli DZF-6050-53L) with 20 mL of n-heptane, at a temperature of 100 °C for 3 h, to obtain a skeleton membrane with a n-heptane content of 1000 ppm.

[0083] Preparation of a continuous self-supporting ultrathin electrolyte membrane-2

[0084] The electrolyte membrane-1 and the skeleton membrane were combined by the process as shown in Figure 1 , followed by drying in a drying tunnel with a length of 5 m and a temperature of 100 °C, to obtain a three-layer self-supporting electrolyte membrane-2 with the electrolyte membrane layers on the top and bottom and the skeleton membrane in the middle.

[0085] Example 2:

[0086] During the preparation of the electrolyte-1, the coating wet thickness was controlled to be 4 μm.

[0087] The rest was the same as in Example 1.

[0088] Example 3:

[0089] The skeleton membrane was replaced by a skeleton membrane with a thickness of 10 μm, a porosity of 83%, and a tensile strength of 3 N / 50 mm.

[0090] The rest was the same as in Example 2.

[0091] Example 4

[0092] The skeleton membrane was not treated, and the rest was the same as in Example 3.

[0093] Example 5

[0094] After the treatment of the skeleton film, the n-heptane content in the skeleton film was 1500 ppm, and the rest was the same as in Example 1.

[0095] Comparative Example 1:

[0096] The base film (thickness 5 μm, release force 3-5 g) was coated directly with a doctor blade coating method, and the theoretical thickness of the electrolyte film was controlled to be the same as that of the electrolyte film-2 in Example 1, and was used in the negative electrode sheet by transfer printing.

[0097] Comparative Example 2:

[0098] The base film (thickness 5 μm, release force 3-5 g) was coated directly with a doctor blade coating method, and the theoretical thickness of the electrolyte film was controlled to be the same as that of the electrolyte film-2 in Example 1, and was used in the negative electrode sheet by transfer printing.

[0099] Comparative Example 3:

[0100] In the preparation of the electrolyte film-1, the electrolyte film was coated by a doctor blade coating method, and the wet thickness was controlled to be 20 μm by controlling the doctor blade slit, and the rest was the same as in Example 1.

[0101] Comparative Example 4:

[0102] The base film (thickness 5 μm, release force 3-5 g) was coated directly with a doctor blade coating method, and the theoretical thickness of the electrolyte film was controlled to be the same as that of the electrolyte film-2 in Example 1, and was used in the negative electrode sheet by transfer printing.

[0103] The thickness and ionic conductivity of the electrolyte film-2 obtained in the above examples and comparative examples were tested, and the results are shown in Table 1.

[0104] Table 1

[0105]

[0106] It can be seen from the comparison of Example 1 and Comparative Example 1 that the introduction of the skeleton film slightly reduces the ionic conductivity of the electrolyte film, but is within an acceptable range (according to the standard of liquid batteries, an ionic conductivity of 1 mS is considered to be able to support normal charging and discharging of the battery). However, as can be seen from the comparison of the example and the comparative example, whether coated directly on the base film or on the skeleton film and using other coating forms, the uniformity of the prepared electrolyte is poor, with an error of up to 10.9%. The application of such non-uniform electrolyte film to the battery will cause lithium to be unable to be uniformly deposited, inducing the formation of lithium dendrites, which is easy to cause short circuit of the battery. In addition, as can be seen from the comparison of the comparative example and the comparative example, due to the precision problem of conventional coating equipment, it is not possible to prepare a uniform electrolyte film with a thickness of less than 20 μm at one time; even if the gravure coating technology with higher precision is used in combination with the skeleton film, it is not possible to prepare a uniform electrolyte film with a thickness of less than 20 μm at one time. The gravure coating technology can ensure the precision of the coating relative to the flat base film. However, the microstructure of the skeleton film is not flat due to the presence of porosity, which will bring about coating errors. Moreover, due to the presence of the pores of the skeleton film, it can only be coated on one side. Thus, the thickness of the electrolyte layer on the other side is not the same as that on the coated side, and therefore the uniformity cannot meet the standard.

[0107] The positive and negative electrode sheets were prepared by combining the wet process, wherein the positive electrode was Ni83 ternary positive electrode material, and the negative electrode was silicon-carbon 450, and the surface capacity of the positive and negative electrodes was 4.2 mAh / cm 2 The electrolyte film-2 obtained in each of the above examples and comparative examples was assembled into a single sheet battery, and the forming pressure of the battery was 300 mPa. The open circuit voltage and the cycle performance of the battery were tested, and the test temperature was 45°C, the voltage range was 2.5V-4.2V, and the rate was 0.05C. The results are shown in Table 2.

[0108] Table 2

[0109]

[0110] Comparing the comparative examples and the examples, it can be seen that the uniformity of the electrolyte membrane has a great influence on the battery. In the examples, the battery assembled with the electrolyte membrane with high uniformity and thickness less than 15 μm is not short-circuited and is in normal cycle. In the comparative examples, the batteries assembled with the electrolyte membranes with thickness less than 30 μm are directly short-circuited without open circuit voltage. After increasing the thickness, the battery assembled with the electrolyte membrane in comparative example 3 has open circuit voltage, but is short-circuited after less than 10 cycles, which is mainly due to the non-uniformity of the electrolyte membrane inducing lithium dendrite in the charging process, thereby causing the battery to be short-circuited. Compared with comparative example 2, the uniformity of the electrolyte membrane prepared by gravure coating combined with the skeleton membrane in one step is improved in comparative example 4, and the battery assembled with the electrolyte membrane has normal open circuit voltage, but is short-circuited in the cycle process, which is mainly because although the precision of the gravure coater is sufficient to ensure that the coating layer is uniform, when coating directly on the skeleton membrane, the other side of the coating relies on the slurry to penetrate, so that the thickness of the electrolyte layer on both sides of the skeleton membrane is uneven in a large area, and therefore the charge distribution is uneven in the charging and discharging process, thereby inducing dendrite generation and causing the battery to be short-circuited in the cycle process.

[0111] The above only describes the preferred embodiments of the present application and is not used to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a self-supporting electrolyte membrane, characterized by, The preparation method comprises the following steps: preparing a skeleton film and a base film, coating a slurry containing electrolyte on the base film by using a gravure coater, and forming an electrolyte film layer on the base film after first drying; attaching the electrolyte film layer on both sides of the skeleton film to obtain the self-supporting electrolyte film; Before attaching the electrolyte film layer on the skeleton film, the method further comprises pretreating the skeleton film, wherein the pretreatment is loading an affinity agent on the skeleton film; the affinity agent is selected from at least one of n-heptane, n-hexane, n-hexyl, n-butyl ether and butyl butyrate; the loading amount of the affinity agent in the skeleton film is 500-2000 ppm; the skeleton film is a resin fiber film or a glass fiber film, the thickness is 5-15 μm, and the porosity is 60-95%; the electrolyte film layer comprises a sulfide electrolyte and a binder; the thickness of the single-layer electrolyte film layer is 0.1 μm-10 μm, and the error range of the thickness of the electrolyte film layer is ±1%.

2. The method of claim 1, wherein the self-supporting electrolyte film is prepared by the steps of: The electrolyte film layer is transferred and attached to both sides of the skeleton film by using a rolling method.

3. The method of claim 2, wherein the self-supporting electrolyte film is prepared by the steps of: When the electrolyte film layer is transferred, the skeleton film and the base film are synchronously moved towards the rolling equipment under the action of an external force, so that the electrolyte film layer is transferred and attached to the surface of the skeleton film.

4. The method of claim 1, wherein the self-supporting electrolyte film is prepared by the steps of: The pretreatment comprises placing the skeleton film in an atmosphere of affinity agent vapor, so that the affinity agent molecules are immersed in the skeleton film.

5. The method for preparing a self-supporting electrolyte membrane according to claim 1, characterized in that, After the electrolyte film layer is attached on the skeleton film loaded with the affinity agent, the skeleton film attached with the electrolyte film layer is subjected to second drying to obtain the self-supporting electrolyte film.

6. The method for preparing a self-supporting electrolyte membrane according to claim 1, characterized in that, The mass fraction of the sulfide electrolyte in the electrolyte film layer is 90-99 wt%, and the mass fraction of the binder is 1-10 wt%.

7. The method for preparing a self-supporting electrolyte membrane according to claim 1, characterized in that, The sulfide electrolyte is selected from at least one of Li6PS5Cl, Li3PS4 and Li2S-P2S5.

8. The method for preparing a self-supporting electrolyte membrane according to claim 1, characterized in that, The D50 of the sulfide electrolyte is 0.2-1 μm.

9. The method for preparing a self-supporting electrolyte membrane according to claim 1, characterized in that, The binder is selected from at least one of methyl vinyl silicone rubber, nitrile rubber, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene and styrene butadiene rubber.

10. The method for preparing a self-supporting electrolyte membrane according to claim 1, characterized in that, The slurry comprises electrolyte, binder and solvent.

11. The method of claim 10, wherein the self-supporting electrolyte film is prepared by a method comprising: The solid content of the slurry is 50-65%.

12. The method for preparing a self-supporting electrolyte membrane according to claim 10, characterized in that, The coating speed is 0.005-0.015 m / min.

13. The method for preparing a self-supporting electrolyte membrane according to claim 10, characterized in that, The solvent is selected from at least one of n-heptane, methyl vinyl ketone, n-hexane, isobutyl isobutyrate, butyl butyrate xylene and toluene.

14. The method for preparing a self-supporting electrolyte membrane according to claim 1, characterized in that, The base film is one of aluminum foil, stainless steel, release film and release paper.

15. The method for preparing a self-supporting electrolyte membrane according to claim 14, characterized in that, The thickness of the base film is 2.5-20 μm.

16. The method of claim 14, wherein the self-supporting electrolyte film is prepared by a method comprising: The release force of the base film is 1-5 g.

17. The method for preparing a self-supporting electrolyte membrane according to claim 1, characterized in that, The first drying temperature is 45-150 ℃, and the drying is performed until the residual amount of the solvent is less than 2000 ppm.

18. The method for preparing a self-supporting electrolyte membrane according to claim 5, characterized in that, The second drying temperature is 80-200 ℃, and the drying is performed until the residual amount of the affinity agent and the solvent is less than 100 ppm.

19. A self-supporting electrolyte membrane, characterized by, The self-supporting electrolyte film is obtained by the preparation method of any one of claims 1-17.

20. The self-supporting electrolyte film of claim 19, wherein, The thickness of the self-supporting electrolyte film is less than 24 μm.

21. The self-supporting electrolyte film of claim 19, wherein, The thickness of the self-supporting electrolyte film is 14-15 μm.

22. An all-solid-state battery, characterized by comprising: The self-supporting electrolyte film comprises the self-supporting electrolyte film of any one of claims 19-21.

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