Separator for lithium thionyl chloride batteries, and preparation method therefor

Abstract

A preparation method for a separator for lithium thionyl chloride batteries. The preparation method comprises the following steps: (1) adding inorganic fibers and flexible fibers to water, and mixing and dispersing same to obtain a mixed fiber suspension; (2) subjecting the mixed suspension to slurry spreading, and forming same into a wet paper sheet; and (3) applying an adhesive to the surface of the wet paper sheet, and drying same to obtain a separator for lithium thionyl chloride batteries. Inorganic fibers are used as the main material for the battery separator, thereby ensuring the safety performance of the battery separator in a high-temperature environment. Moreover, the battery separator can absorb excess electrolyte to participate in reactions at positive and negative electrodes of a battery, thereby ensuring that the battery has good charging and discharging performance. Furthermore, flexible fibers, an adhesive and inorganic fibers are combined to form the battery separator, wherein the flexible fibers and the adhesive can work synergistically, improving both the strength and ductility of the battery separator, thereby significantly enhancing the assembly capability of the battery separator.

Description

Lithium sulfoxyl chloride battery separator and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery materials, in particular to a lithium sulfoxyl chloride battery and a preparation method thereof. BACKGROUND

[0002] The lithium sulfoxyl chloride battery is a disposable lithium battery, which has the advantages of high energy density, long service life, high working voltage and wide working temperature range, and can be used at a temperature range of-55℃ to 85℃. At the same time, the lithium sulfoxyl chloride battery also has the characteristics of high capacity, high stability and low self-discharge rate, and therefore, the lithium sulfoxyl chloride battery is widely used in the fields of wireless communication, medical equipment, safety alarm and the like.

[0003] The lithium battery separator is an important inner layer component in the structure of a lithium battery, which is located between the positive electrode and the negative electrode of the lithium battery, can effectively prevent the two electrodes from directly contacting, avoid the short circuit of the battery, slow down the aging speed of the battery and prolong the service life of the battery. At the same time, the lithium battery separator also has high porosity and ion conductivity, which can enable lithium ions to transfer between the positive electrode and the negative electrode, so as to realize the charge and discharge performance of the lithium battery. Therefore, the lithium battery separator with excellent performance plays an important role in improving the comprehensive performance of the lithium battery.

[0004] At present, the lithium battery separator is generally made of polypropylene (PP), polyethylene (PE) and other polyolefin materials. However, the safety performance of the battery separator formed by the polyolefin material is low, and when the temperature is high, the battery separator will melt, thereby causing the positive and negative electrodes of the battery to directly contact and short circuit, which seriously affects the application of the lithium battery. Therefore, based on the above problems, it is urgent to provide a lithium sulfoxyl chloride battery separator with high safety in a high-temperature environment and a preparation method thereof.

[0005] SUMMARY

[0006] The present application provides a lithium sulfoxyl chloride battery separator and a preparation method thereof, which has good temperature resistance and liquid absorption performance and will not melt in a high-temperature environment, and has good safety performance.

[0007] In a first aspect, the present application provides a preparation method of a lithium sulfoxyl chloride battery separator, which comprises the following steps:

[0008] (1) adding inorganic fibers and flexible fibers into water to mix and disperse, to obtain a mixed fiber suspension;

[0009] (2) performing cloth pulp on the mixed suspension to obtain a wet paper sheet after forming;

[0010] (3) compounding an adhesive on the surface of the wet paper sheet, and obtaining the lithium sulfoxyl chloride battery separator after drying.

[0011] Preferably, the inorganic fiber is at least one of glass fiber, ceramic fiber, high silica fiber or quartz fiber.

[0012] Preferably, the flexible fiber is at least one of polyester fiber, polyamide fiber, polypropylene fiber, polyimide fiber or polyethylene fiber.

[0013] Preferably, the adhesive is at least one of epoxy resin, phenol resin, silicone resin, polyester resin, acrylic emulsion or polyvinyl alcohol.

[0014] Preferably, the diameter of the inorganic fiber is 0.3-15 μm, and the diameter of the flexible fiber is 5-30 μm.

[0015] Preferably, in step (1), the content of the inorganic fiber is 90-99% by weight, and the content of the flexible fiber is 1-10%.

[0016] Preferably, in step (1), the concentration of the mixed fiber suspension is 0.1-1%.

[0017] Preferably, in step (2), after obtaining the wet paper sheet, the method further comprises a step of pre-drying the wet paper sheet; wherein the pre-drying is performed by hot air drying, and the pre-drying temperature is 60-90℃, and the pre-drying time is 5-15 s.

[0018] Preferably, the humidity of the pre-dried wet paper sheet is 40-70%.

[0019] Preferably, in step (3), the concentration of the adhesive is 0.5-5%.

[0020] Preferably, the compounding method of the adhesive is spraying, overflow or dipping.

[0021] Preferably, the drying is performed by hot air drying or oven drying.

[0022] Preferably, the drying temperature is 120-200℃, and the drying time is 60-120 s.

[0023] In a second aspect, the present application provides a lithium sulfinyl chloride battery separator, which is prepared by the method of any one of the first aspect.

[0024] Compared with the prior art, the present application has at least the following beneficial effects:

[0025] (1) In the present application, by adopting inorganic fibers as the main material of the battery separator, the inorganic fibers have the advantages of high temperature resistance, strong corrosion resistance and good dimensional stability, which can adapt to the extreme environment inside the lithium battery, so that the formed battery separator not only has good temperature resistance, thereby ensuring the safety performance of the battery separator under high temperature environment, and the battery separator can absorb excess electrolyte to participate in the positive and negative electrode reaction of the battery, ensuring that the battery has good charge and discharge performance;

[0026] (2) In the present application, the flexible fiber and the adhesive are used together with the inorganic fiber to form the battery separator, and the flexible fiber can play a synergistic effect with the adhesive, which can not only improve the strength of the battery separator, but also improve the ductility of the battery separator, thereby significantly improving the assembly capability of the battery separator. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings described below are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0028] Figure 1 is a flow chart of a preparation method of a lithium thionyl chloride battery separator according to an embodiment of the present application;

[0029] Figure 2 is a scanning electron microscope (SEM) image of a lithium thionyl chloride battery separator according to an embodiment of the present application;

[0030] Figure 3 is a scanning electron microscope (SEM) image of another lithium thionyl chloride battery separator according to an embodiment of the present application. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0032] The existing lithium battery separator material is generally based on polyolefin material, but the polyolefin material will deform under high temperature condition, and its temperature resistance is poor, so when the battery works beyond a certain temperature, the battery separator will melt, causing the positive and negative electrodes of the battery to directly contact and short circuit; and the battery separator formed by the polyolefin material has low porosity and poor liquid absorption performance, which cannot meet the performance requirements of high-rate charging and discharging of lithium batteries. Based on the above problems, the present inventors first consider using inorganic fibers as the main material of the battery separator, which has the advantages of high temperature resistance, corrosion resistance and good dimensional stability, etc. Although it can make the battery separator have high temperature resistance and liquid absorption performance, if only inorganic fibers are used to form the battery separator, the strength and ductility of the battery separator will be poor, which will make the assembly of the battery separator poor and prone to breakage.

[0033] Therefore, based on the above problems, as shown in FIG. 1, the present embodiment provides a preparation method of a lithium thionyl chloride battery separator, which comprises the following steps:

[0034] (1) adding inorganic fibers and flexible fibers into water to mix and disperse, to obtain a mixed fiber suspension;

[0035] (2) performing pulp distribution on the mixed suspension to obtain a wet paper sheet after forming;

[0036] (3) compounding an adhesive on the surface of the wet paper sheet, and obtaining the lithium thionyl chloride battery separator after drying.

[0037] In the present embodiment, inorganic fibers are used as the main material of the lithium thionyl chloride battery separator (hereinafter referred to as battery separator), which has the advantages of high temperature resistance, strong corrosion resistance and good dimensional stability, etc. It can adapt to the extreme environment inside the lithium battery, so that the formed battery separator not only has good temperature resistance, thereby ensuring the safety performance of the battery separator under high temperature environment, but also can absorb excess electrolyte to participate in the positive and negative electrode reaction of the battery, ensuring good charge and discharge performance of the battery. At the same time, in order to further ensure the good assembly performance of the battery separator, the present inventors consider mixing inorganic fibers and flexible fibers to form a wet paper sheet, and compounding a certain amount of adhesive in the wet paper sheet. The mixed inorganic fibers and flexible fibers can ensure that the wet paper sheet has good temperature resistance and ductility; at the same time, the flexible fibers can play a synergistic effect with the adhesive, so as to not only improve the strength of the battery separator, but also improve the ductility of the battery separator, thereby significantly improving the assembly capacity of the battery separator, ensuring the good assembly efficiency of the lithium battery, avoiding the damage of the separator, and adversely affecting the charge and discharge performance of the lithium battery.

[0038] According to some preferred embodiments, the inorganic fiber is at least one of glass fiber, ceramic fiber, high-silica fiber, or quartz fiber;

[0039] The flexible fiber is at least one of polyester fiber, polyamide fiber, polypropylene fiber, polyimide fiber, or polyethylene fiber.

[0040] The adhesive is at least one of epoxy resin, phenolic resin, silicone resin, polyester resin, acrylic emulsion, or polyvinyl alcohol.

[0041] In the embodiments of the present application, the specific types of the inorganic fiber, the flexible fiber, and the adhesive are preferably within the above ranges. The inorganic fiber is used as the main material of the battery separator. By selecting the inorganic fiber of the above types, the battery separator can have better temperature resistance and electrolyte absorption performance, thereby ensuring better safety performance of the lithium battery. By further selecting the types of the flexible fiber and the adhesive, the flexible fiber can be intertwined with the inorganic fiber during the mixing and forming of the inorganic fiber and the flexible fiber into a wet paper sheet, thereby improving the ductility of the battery separator. When the adhesive of the above types is compounded on the surface of the wet paper sheet formed by the inorganic fiber and the flexible fiber, the adhesive can interact with the molecules on the surface of the wet paper sheet, thereby further improving the tensile strength and toughness of the battery separator.

[0042] According to some preferred embodiments, the diameter of the inorganic fiber is 0.3-15 μm (for example, it can be 0.3 μm, 0.5 μm, 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, or 15 μm), and the diameter of the flexible fiber is 5-30 μm (for example, it can be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, or 30 μm).

[0043] In the embodiments of the present application, by selecting the diameters of the inorganic fiber and the flexible fiber within the above ranges, the inorganic fiber and the flexible fiber can have better dispersibility, thereby ensuring better uniformity of the inorganic fiber and the flexible fiber in the wet paper sheet, and further ensuring better high-temperature resistance and ductility of the final battery separator.

[0044] According to some preferred embodiments, in step (1), the content of the inorganic fiber is 90-99% (for example, it can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%) by weight percentage, and the content of the flexible fiber is 1-10% (for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%) by weight percentage.

[0045] In the embodiment of the present application, the inorganic fiber and the flexible fiber are mixed and dispersed preferably in the above-mentioned content, which is beneficial to ensure that the battery separator has good temperature resistance, liquid absorption performance and ductility. The inorganic fiber mainly serves as the main fiber skeleton of the battery separator. The substrate formed by the inorganic fiber enables the battery separator to have good temperature resistance and good liquid absorption performance, thereby ensuring that the battery has good charge and discharge performance. The flexible fiber will change from a glass state to a high-elasticity state in the subsequent temperature rising and drying process, and the adhesion of the flexible fiber will increase, so as to be entangled with the inorganic fiber, thereby improving the ductility of the battery separator. In the embodiment, if the content of the flexible fiber is too low, the ductility of the battery separator cannot be improved. If the content of the flexible fiber is too high, the content of the inorganic fiber will be reduced accordingly. At this time, the content of the flexible fiber in the battery separator is too high, which is not conducive to improving the high-temperature resistance of the battery separator.

[0046] According to some preferred embodiments, in step (1), the concentration of the mixed fiber suspension is 0.1-1% (for example, it can be 0.1%, 0.3%, 0.5%, 0.8% or 1%).

[0047] In the embodiment of the present application, by preferably selecting the concentration of the mixed fiber suspension in the above-mentioned range, the uniformity of the dispersion of the inorganic fiber and the flexible fiber can be ensured, and the subsequent wet paper sheet forming of the mixed fiber suspension can be ensured in this concentration range. It should be noted that the concentration of the mixed fiber suspension refers to the mass concentration of the mixed fiber formed by the inorganic fiber and the flexible fiber in water.

[0048] According to some preferred embodiments, in step (2), after obtaining the wet paper sheet, a step of pre-drying the wet paper sheet is further included; the pre-drying method is hot air drying, the pre-drying temperature is 60-90℃ (for example, it can be 60℃, 70℃, 80℃ or 90℃), and the time is 5-15s (for example, it can be 5s, 8s, 10s, 12s or 15s).

[0049] According to some preferred embodiments, the humidity of the wet paper sheet after pre-drying is 40-70% (for example, it can be 40%, 50%, 60% or 70%).

[0050] In the embodiment of the present application, the mixed fiber suspension is sequentially stored, sized, and distributed to form a wet paper sheet, and then the wet paper sheet is pre-dried at a certain temperature to make the fibers interweave and entangle with each other. As the number of interweaving points between the fibers increases, the pre-dried wet paper sheet has a certain strength and liquid absorption performance. On the one hand, it can ensure the continuous production of the subsequent web belt, and on the other hand, it can make the adhesive more easily adhere to the fiber surface, fiber interweaving point and fiber pore in the wet paper sheet. After re-drying, the performance of the lithium battery separator is more excellent. The obtained wet paper sheet is pre-dried at the above-mentioned temperature range, so as to ensure that the humidity of the pre-dried wet paper sheet is in the range of 40-70%. In this humidity range, it is not only beneficial to ensure the subsequent composite of the adhesive, but also beneficial to the better adhesion of the adhesive to the fiber surface, fiber interweaving point and fiber pore in the wet paper sheet. If the humidity of the wet paper sheet is too high, the bonding force between the fibers in the wet paper sheet is poor, which is not conducive to the subsequent composite of the adhesive on the surface of the wet paper sheet. If the humidity of the wet paper sheet is too low, the bonding force between the fibers is strong, and after the subsequent composite of the adhesive on the surface of the wet paper sheet, not only the visual effect of the formed battery separator is poor, but also the adhesive is not conducive to adhere to the fiber surface, fiber interweaving point and fiber pore in the wet paper sheet, thereby not conducive to improving the strength of the battery separator.

[0051] It should be noted that in the present application, the pre-drying method includes but is not limited to the above-mentioned method, for example, microwave drying and infrared drying methods can also be used. The present application does not make specific limitations on the conditions of microwave drying and infrared drying, as long as the humidity of the pre-dried wet paper sheet is within the above-mentioned range. At the same time, the specific process of forming the wet paper sheet from the fiber suspension after storage, sizing and distribution is known to those skilled in the art.

[0052] According to some preferred embodiments, in step (3), the concentration of the adhesive is 0.5-5% (for example, 0.5%, 1%, 2%, 3%, 4% or 5%); and the composite method of the adhesive is spraying, overflow or dipping.

[0053] In the embodiment of the present application, the adhesive can be compounded on one side of the wet paper sheet by using a sizing system in the form of spraying, overflow or dipping. The adhesive wets from one side of the wet paper sheet to the other side. By controlling the concentration of the adhesive within the above-mentioned range, the mechanical strength (tensile strength and toughness) of the battery separator can be further improved on the basis of ensuring that the battery separator has good liquid absorption performance. If the concentration of the adhesive is too low, it is not conducive to effectively improving the mechanical strength of the battery separator. However, if the concentration of the adhesive is too high, the porosity of the battery separator will decrease, the liquid absorption performance of the battery separator will decrease, it is not conducive to absorbing a large amount of electrolyte, and thus it cannot ensure the large capacity discharge of the lithium battery.

[0054] In the embodiment, the adhesive can be diluted to a certain concentration, and the content of the adhesive in the wet paper sheet can be controlled by controlling the concentration of the adhesive within the above range. It should be noted that the content of the adhesive in the entire battery separator is 6-10% in the present application.

[0055] According to some preferred embodiments, in step (3), the drying method is hot air drying or oven drying; the drying temperature is 120-200°C (for example, it can be 120°C, 150°C, 180°C or 200°C), and the drying time is 60-120s (for example, it can be 60s, 80s, 100s or 120s).

[0056] In the embodiment of the present application, through the two drying processes of pre-drying and re-drying after compounding the adhesive, the molecular chains of the flexible fibers move, and the flexible fibers change from a glassy state to a high-elasticity state, and the adhesion of the flexible fibers increases, thereby bonding the inorganic fibers together and enhancing the ductility of the battery separator (as shown in FIG. 2); at the same time, after compounding the adhesive on the surface of the wet paper sheet, the adhesive adheres to the fiber surface, fiber interweaving and fiber pores in the wet paper sheet, and in the drying and curing process, the adhesive and the molecules on the fiber surface interact to form chemical bonds or physical bonds, thereby firmly bonding the fibers together, and the formation of these chemical bonds or bonds enhances the friction and surface tension between the fiber surfaces, thereby improving the mechanical strength (tensile strength and toughness) of the battery separator (as shown in FIG. 3).

[0057] In the present application, by using inorganic fibers with high temperature resistance, strong corrosion resistance, good dimensional stability and fine fiber diameter as the base material of the battery separator, the battery separator is endowed with good safety and stability, high porosity and strong liquid absorption capacity, thereby improving the capacity of the battery and ensuring the charge and discharge performance of the battery; and further, the flexible reinforcing agent is used to synergistically enhance the performance of the battery separator, thereby improving the strength performance of the battery separator and improving the ductility of the separator and the assembly capacity of the battery separator.

[0058] In order to more clearly illustrate the technical solutions and advantages of the present application, the following describes in detail a lithium sulfinyl chloride battery separator and a preparation method thereof through several embodiments.

[0059] Embodiment 1:

[0060] (1) 95wt% of inorganic fibers (glass fibers) and 5wt% of flexible fibers (polyester fibers) are added to water for mixing and dispersion to obtain a mixed fiber suspension with a concentration of 0.5%; wherein the diameter of the inorganic fibers is 0.3-0.8μm, and the diameter of the flexible fibers is 8-20μm;

[0061] (2) The mixed fiber suspension is stored, sized, and distributed, and after forming, a wet paper sheet is obtained. The wet paper sheet is hot air dried at 60°C for 15s to ensure that the humidity of the pre-dried wet paper sheet is 50%;

[0062] (3) The adhesive (acrylic emulsion with a concentration of 3%) is compounded on the surface of the pre-dried wet paper sheet in an overflow manner by a sizing system. The wet paper sheet compounded with the adhesive is dried at 180°C for 100s by hot air drying to obtain a lithium sulfonyl chloride battery separator.

[0063] Example 2:

[0064] (1) 97wt% of inorganic fibers (ceramic fibers) and 3wt% of flexible fibers (polypropylene fibers) are added to water and mixed and dispersed to obtain a mixed fiber suspension with a concentration of 0.4%. The diameter of the inorganic fibers is 5-10μm, and the diameter of the flexible fibers is 10-20μm;

[0065] (2) The mixed fiber suspension is stored, sized, and distributed, and after forming, a wet paper sheet is obtained. The wet paper sheet is hot air dried at 80°C for 13s to ensure that the humidity of the pre-dried wet paper sheet is 55%;

[0066] (3) The adhesive (acrylic emulsion with a concentration of 3%) is compounded on the surface of the pre-dried wet paper sheet in an overflow manner by a sizing system. The wet paper sheet compounded with the adhesive is dried at 180°C for 100s by hot air drying to obtain a lithium sulfonyl chloride battery separator.

[0067] Example 3:

[0068] (1) 97wt% of inorganic fibers (ceramic fibers) and 3wt% of flexible fibers (polypropylene fibers) are added to water and mixed and dispersed to obtain a mixed fiber suspension with a concentration of 0.4%. The diameter of the inorganic fibers is 5-10μm, and the diameter of the flexible fibers is 10-20μm;

[0069] (2) The mixed fiber suspension is stored, sized, and distributed, and after forming, a wet paper sheet is obtained. The wet paper sheet is hot air dried at 80°C for 13s to ensure that the humidity of the pre-dried wet paper sheet is 55%;

[0070] (3) The adhesive (acrylic emulsion with a concentration of 3%) is compounded on the surface of the pre-dried wet paper sheet in an overflow manner by a sizing system. The wet paper sheet compounded with the adhesive is dried at 180°C for 100s by hot air drying to obtain a lithium sulfonyl chloride battery separator.

[0071] Example 4:

[0072] (1) adding 93wt% of inorganic fiber (quartz fiber) and 7wt% of flexible fiber (polyethylene fiber) into water to mix and disperse, to obtain a mixed fiber suspension with a concentration of 0.3%; wherein the diameter of the inorganic fiber is 3-8μm, and the diameter of the flexible fiber is 15-25μm;

[0073] (2) storing the mixed fiber suspension, sizing, and distributing the pulp, to form a wet paper sheet, and then hot air drying the wet paper sheet at 90°C for 5s to ensure that the humidity of the pre-dried wet paper sheet is 40%;

[0074] (3) through a sizing system, spraying the adhesive onto the surface of the pre-dried wet paper sheet to form a composite adhesive (an epoxy resin solution with a concentration of 2%), and then drying the wet paper sheet with the composite adhesive at 120°C for 120s by infrared drying, to obtain a lithium sulfinyl chloride battery separator.

[0075] Example 5:

[0076] Example 5 is basically the same as Example 1, except that in step (1), the content of inorganic fiber is 89%, and the content of flexible fiber is 11%.

[0077] Example 6:

[0078] Example 6 is basically the same as Example 1, except that in step (2), the wet paper sheet is hot air dried at 100°C for 5s to ensure that the humidity of the pre-dried wet paper sheet is 35%.

[0079] Example 7:

[0080] Example 7 is basically the same as Example 1, except that in step (2), the wet paper sheet is hot air dried at 50°C for 5s to ensure that the humidity of the pre-dried wet paper sheet is 75%.

[0081] Example 8:

[0082] Example 8 is basically the same as Example 1, except that in step (3), the concentration of the adhesive is 6%.

[0083] Example 9:

[0084] Example 9 is basically the same as Example 1, except that in step (3), the concentration of the adhesive is 0.4%.

[0085] Comparative Example 1:

[0086] (1) adding 100wt% of inorganic fiber (glass fiber) into water to disperse, to obtain a fiber suspension with a concentration of 0.5%; wherein the diameter of the inorganic fiber is 0.3-0.8μm;

[0087] (2) The fiber suspension is stored, sized, and distributed, and after forming, a wet paper sheet is obtained. The wet paper sheet is hot air dried at 60°C for 15s to ensure that the humidity of the pre-dried wet paper sheet is 50%;

[0088] (3) The pre-dried wet paper sheet is dried at 180°C for 100s by hot air drying to obtain a lithium sulfinyl chloride battery separator.

[0089] Comparative Example 2:

[0090] (1) 95wt% of inorganic fibers (glass fibers) and 5wt% of flexible fibers (polyester fibers) are added to water and mixed and dispersed to obtain a mixed fiber suspension with a concentration of 0.5%. The diameter of the inorganic fibers is 0.3-0.8μm, and the diameter of the flexible fibers is 8-20μm;

[0091] (2) The mixed fiber suspension is stored, sized, and distributed, and after forming, a wet paper sheet is obtained. The wet paper sheet is hot air dried at 60°C for 15s to ensure that the humidity of the pre-dried wet paper sheet is 50%;

[0092] (3) The pre-dried wet paper sheet is dried at 180°C for 100s by hot air drying to obtain a lithium sulfinyl chloride battery separator.

[0093] Comparative Example 3:

[0094] (1) 100wt% of inorganic fibers (glass fibers) are added to water and dispersed to obtain a fiber suspension with a concentration of 0.5%. The diameter of the inorganic fibers is 0.3-0.8μm;

[0095] (2) The fiber suspension is stored, sized, and distributed, and after forming, a wet paper sheet is obtained. The wet paper sheet is hot air dried at 60°C for 15s to ensure that the humidity of the pre-dried wet paper sheet is 50%;

[0096] (3) The pre-dried wet paper sheet is dried at 180°C for 100s by hot air drying to obtain a lithium sulfinyl chloride battery separator.

[0097] Comparative Example 4:

[0098] (1) 100wt% of polyethylene fibers are added to water and dispersed to obtain a fiber suspension with a concentration of 0.5%. The diameter of the polyethylene fibers is 8-20μm;

[0099] (2) The fiber suspension is stored, sized, and clothed, and then a wet paper sheet is obtained after forming. The wet paper sheet is hot air dried at 60°C for 15s to ensure that the humidity of the pre-dried wet paper sheet is 50%;

[0100] (3) The pre-dried wet paper sheet is coated with an adhesive (3% acrylic emulsion) by an overflow method through a sizing system, and then the wet paper sheet coated with the adhesive is dried at 180°C for 100s by hot air drying to obtain a lithium sulfinyl chloride battery separator.

[0101] The lithium sulfinyl chloride battery separators prepared in Examples 1 to 9 and Comparative Examples 1 to 4 (hereinafter referred to as samples) are subjected to performance tests, and the test results are shown in Table 1.

[0102] Density test method: The sample is cut into a test sample of 100mm x 100mm, dried at 105°C ± 2°C for 2h, then cooled to room temperature in a desiccator, weighed, and the thickness of the test sample is measured by a thickness gauge. The basis weight of the sample is calculated according to the formula G = m / (l·b·d); wherein G is the basis weight of the test sample, m is the mass of the test sample, l is the length of the test sample, b is the width of the test sample, and d is the thickness of the test sample.

[0103] Liquid absorption rate test method: the test liquid is a 3:7 alcohol solution (volume ratio of anhydrous ethanol to pure water), and the sample is soaked for 2 minutes. The amount of liquid absorbed is calculated according to the following formula:

[0104] Wherein: m - sample mass / (g);

[0105] m1 - sample mass after saturation / (g)

[0106] Tensile strength and elongation test method: tested according to GB / T28535-2018;

[0107] Ignition loss test method: cut 1.5-2g (accurate to 0.0001g) of sample with a knife or scissors, dry in a 100-105°C constant temperature oven for 1h, take out and place in a desiccator, cool to room temperature (25-28°C) and weigh, then dry for another 30min and weigh until the mass is constant, recorded as m0; place the test sample with constant mass in a 500°C muffle furnace and ignite for 1h, take out and place in a desiccator, cool to room temperature and weigh, then dry for another 30min and weigh until the mass is constant, recorded as m; the ignition loss is calculated according to the following formula:

[0108] Table 1

[0109] Note: The liquid absorption rate of polypropylene (PP), polyethylene (PE) and other material separators is <1g / g

[0110] As shown in Table 1, compared with the battery separator material in Comparative Example 4 (a battery separator material commonly used in the prior art), the lithium sulfinyl chloride battery separator prepared from inorganic fibers, flexible fibers and adhesives as raw materials has good liquid absorption performance and temperature resistance, and the temperature resistance is as high as 300°C. As shown in Table 1, the flexible fibers and adhesives can synergistically enhance the performance of the battery separator, improve the mechanical strength of the battery separator, and improve the ductility of the battery separator, thereby ensuring that the battery separator has good assembly performance.

[0111] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions described in the foregoing examples can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of preparing a lithium sulfinyl chloride battery separator, characterized by, The preparation method comprises the following steps: (1) adding inorganic fibers and flexible fibers into water to mix and disperse, to obtain a mixed fiber suspension; (2) performing pulp distribution on the mixed suspension, to obtain a wet paper sheet after forming; (3) compounding an adhesive on the surface of the wet paper sheet, to obtain the lithium sulfinyl chloride battery diaphragm after drying.

2. The preparation method according to claim 1, wherein the inorganic fibers are at least one of glass fibers, ceramic fibers, high-silica fibers or quartz fibers.

3. The preparation method according to claim 1, wherein the flexible fibers are at least one of polyester fibers, polyamide fibers, polypropylene fibers, polyimide fibers or polyethylene fibers.

4. The preparation method according to claim 1, wherein the adhesive is at least one of epoxy resin, phenolic resin, siloxane resin, polyester resin, acrylic emulsion or polyvinyl alcohol. The diameter of the inorganic fibers is 0.3-15 μm, and the diameter of the flexible fibers is 5-30 μm. In step (1), the content of the inorganic fibers is 90-99% by weight, and the content of the flexible fibers is 1-10% by weight. In step (1), the concentration of the mixed fiber suspension is 0.1-1%.

5. The method of claim 1, wherein, In step (2), after obtaining the wet paper sheet, a step of pre-drying the wet paper sheet is further included; wherein the pre-drying is performed by hot air drying, the pre-drying temperature is 60-90°C, and the pre-drying time is 5-15 s.

6. The method of claim 1, wherein, The humidity of the pre-dried wet paper sheet is 40-70%.

7. The preparation method according to claim 1, characterized in that, In step (3), the concentration of the adhesive is 0.5-5%.

8. The method of claim 1, wherein, The compounding method of the adhesive is spraying, overflow or dipping.

9. The production method according to claim 8, characterized by, In step (3), the drying is performed by hot air drying or oven drying.

10. The method of claim 1, wherein, The drying temperature is 120-200°C, and the drying time is 60-120 s.

11. The method of claim 1, wherein, The lithium sulfinyl chloride battery diaphragm is prepared by the preparation method according to any one of claims 1-13.

12. The method of claim 1, wherein, ​ 13. The production method according to claim 1 or 12, characterized by, ​ 14. A lithium sulfinyl chloride battery separator characterized by, ​

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