Solid electrolyte and preparation method therefor, separator coating slurry and separator, and battery and electrical apparatus

Abstract

A solid electrolyte and a preparation method therefor, a separator coating slurry and a separator, and a battery and an electrical apparatus, belonging to the field of batteries. The solid electrolyte is: Li1+xAlxTi2-x(PO4)3, where 0.01≤x≤0.5; the moisture content of the solid electrolyte is <500 ppm; the ionic conductivity of the solid electrolyte is >0.5 mS / cm; and the particle size of the solid electrolyte is in the range of 0.1-2 um. The present solid electrolyte can effectively reduce moisture of a solid electrolyte coating prepared from separator coating slurry, and can effectively reduce alternating current impedance, improving battery safety, and battery capacity retention rate at normal temperatures and low temperatures.

Description

Solid electrolyte and preparation method thereof, diaphragm coating slurry and diaphragm, battery and electrical device

[0001] Cross-references

[0002] This application claims priority to Chinese Patent Application No. 202410178089.4 filed on February 8, 2024, entitled “Solid electrolyte and preparation method thereof, diaphragm coating slurry and diaphragm, battery and electrical device,” and the entire contents of that application are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of batteries, and more specifically, to a solid electrolyte and a preparation method thereof, a diaphragm coating slurry and a diaphragm, a battery, and an electrical device. Background Art

[0004] In solid-state or semi-solid-state lithium batteries, the problem of insufficient contact between the solid electrolyte and the electrode is easy to occur, and the solid-liquid interface between the electrode material and the electrolyte will partially transform into the solid-solid interface between the electrode material and the solid electrolyte. The mutual diffusion and even reaction between the components will form vacancy charge layers, etc., which will lead to the increase of the internal resistance of the lithium battery and the deterioration of the battery capacity retention rate.

[0005] Summary of the Invention

[0006] The present application provides a solid electrolyte and a preparation method thereof, a diaphragm coating slurry and a diaphragm, a battery and an electrical device. The diaphragm coating slurry is conducive to reducing the difficulty of drying the diaphragm. The solid electrolyte can effectively reduce the moisture content of the solid electrolyte coating prepared from the diaphragm coating slurry, and can effectively reduce the AC impedance, thereby improving the safety of the battery and the capacity retention rate of the battery at room temperature and low temperature.

[0007] The embodiment of the present application is implemented as follows:

[0008] In the first aspect, the present application example provides a solid electrolyte, which is: Li1+xAlxTi2-x(PO4)3, 0.01≤x≤0.5, the moisture value of the solid electrolyte is <500ppm, the ionic conductivity of the solid electrolyte is >0.5mS / cm, and the particle size of the solid electrolyte is in the range of 0.1~2um.

[0009] The solid electrolyte used in this application utilizes its characteristics of ionic conductivity greater than 0.5mS / cm, particle size in the range of 0.1 to 2um, and powder moisture value less than 500ppm. When it is used as a raw material for diaphragm coating slurry to prepare a diaphragm, it is beneficial to reduce the difficulty of drying the diaphragm. It can not only effectively reduce the moisture content of the solid electrolyte coating prepared from the diaphragm coating slurry, but also effectively reduce the AC impedance, improve the safety of the battery and the capacity retention rate of the battery at room temperature and low temperature.

[0010] In the second aspect, the present application provides an example of a method for preparing the above-mentioned solid electrolyte, which includes: obtaining a solid electrolyte sintered material; wet-milling the solid electrolyte sintered material to a target particle size, centrifuging to remove the supernatant, filtering and spray-drying to obtain a coarse powder; deagglomerating the coarse powder, and then drying it at 150-250°C for at least 6 hours to obtain the solid electrolyte with a powder moisture value of <500ppm.

[0011] The preparation method of the solid electrolyte used in this application is simple and controllable, and can prepare a solid electrolyte with an ion conductivity greater than 0.5 mS / cm, a particle size in the range of 0.1 to 2 μm, and a powder moisture value less than 500 ppm.

[0012] In a third aspect, the present application provides an example of a separator coating slurry, wherein the separator coating slurry includes the solid electrolyte provided in the first aspect.

[0013] In the diaphragm coating slurry used in this application, a solid electrolyte with an ion conductivity greater than 0.5mS / cm, a particle size in the range of 0.1 to 2um, and a powder moisture value less than 500ppm is used as a raw material, which is beneficial to reducing the difficulty of drying the diaphragm. It can not only effectively reduce the moisture content of the solid electrolyte coating prepared from the diaphragm coating slurry, but also effectively reduce the AC impedance, thereby improving the safety of the battery and the capacity retention rate of the battery at room temperature and low temperature.

[0014] In a fourth aspect, the present application provides an example of a diaphragm, which includes a diaphragm body and a solid electrolyte coating provided on at least one surface of the diaphragm body, wherein the solid electrolyte coating is made from the diaphragm coating slurry provided in the third aspect of the present application.

[0015] The diaphragm provided in the present application, which contains a solid electrolyte coating made from the above-mentioned diaphragm coating slurry, not only has a low water content, but also can effectively reduce the AC impedance when used in the battery, improve the safety of the battery and the capacity retention rate of the battery at room temperature and low temperature.

[0016] In a fifth aspect, the present application provides an example of a battery comprising the separator provided in the third aspect of the present application.

[0017] In a sixth aspect, the present application example provides an electrical device, which includes the battery provided in the fifth aspect of the present application, and the battery is used to provide electrical energy. DETAILED DESCRIPTION

[0018] The embodiments of the present application will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0019] To improve the increased internal resistance and poor capacity retention in solid-state or semi-solid-state lithium batteries, solid electrolytes can be added to the diaphragm coating slurry. However, diaphragms are typically produced by applying the diaphragm coating slurry to the surface of a base film and then drying it. After the base film is coated with the diaphragm coating slurry, the moisture content of the diaphragm typically increases dramatically. Excessive moisture content in the diaphragm can severely affect the insulation and heat dissipation properties of the diaphragm, directly affecting the conductivity of the subsequent battery and even affecting the safety of the battery.

[0020] The current method for controlling the moisture content of battery separators is to place the separators in a drying room for drying. However, this method suffers from long drying times, poor drying results, and low efficiency. The inventors discovered that the moisture content of the solid electrolyte itself significantly affects the drying effect. However, the moisture content of commercially available solid electrolyte powders is generally well above 500ppm. Due to the small size of solid electrolyte particles, it is impossible to reduce the powder moisture content to less than 500ppm through simple drying in actual operation, which does not meet the application requirements.

[0021] The following is a detailed description of the solid electrolyte and its preparation method, diaphragm coating slurry and diaphragm, battery and electrical device of the embodiments of the present application:

[0022] The present application provides a solid electrolyte, which is: Li 1+x Al x Ti 2-x (PO4)3, 0.01≤x≤0.5, the moisture value of the solid electrolyte is less than 500 ppm, the ionic conductivity of the solid electrolyte is greater than 0.5 mS / cm, and the particle size of the solid electrolyte is in the range of 0.1 to 2 um.

[0023] It is understood that the solid electrolyte exists in the form of powder. The moisture value of the solid electrolyte refers to the moisture content of the solid electrolyte powder, which can be measured using a moisture meter according to GB / T 6283-2008.

[0024] The solid electrolyte used in this application utilizes its characteristics of ionic conductivity greater than 0.5mS / cm, particle size in the range of 0.1 to 2um, and powder moisture value less than 500ppm. When it is used as a raw material for diaphragm coating slurry to prepare a diaphragm, it is beneficial to reduce the difficulty of drying the diaphragm. It can not only effectively reduce the moisture content of the solid electrolyte coating prepared from the diaphragm coating slurry, but also effectively reduce the AC impedance, improve the safety of the battery and the capacity retention rate of the battery at room temperature and low temperature.

[0025] For example, the solid electrolyte includes but is not limited to Li 1.3 Al 0.3 Ti 1.7 (PO4)3.Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP) is a NASICON solid electrolyte that not only has low toxicity but also has a high -3 S cm -1 It has the additional advantages of high ionic conductivity, excellent electrochemical stability and easy preparation.

[0026] It should be noted that the particle size distribution and particle morphology of the solid electrolyte are not limited and can be selected according to different application purposes.

[0027] In some embodiments, the solid electrolyte has a volume particle size distribution Dv50 of 0.1 to 1.0 μm.

[0028] Solid electrolytes have the characteristics of particle size distribution concentrated towards medium particle size, resulting in high particle size concentration and small specific surface area, which can indirectly reduce the amount of binder used, thereby reducing water absorption and pore blocking of the binder polymer after drying, and reducing the moisture and air permeability of the coated diaphragm;

[0029] Illustratively, the volume particle size distribution Dv50 of the solid electrolyte is any value of 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, 1.0 μm, or between any two values.

[0030] Therefore, the present application provides a method for preparing the above-mentioned solid electrolyte, the preparation method comprising:

[0031] obtaining a solid electrolyte sintered material;

[0032] The solid electrolyte sintered material is wet-ball-milled to a target particle size, centrifuged to remove the supernatant, filtered, and then spray-dried to obtain a coarse powder;

[0033] The coarse powder is deagglomerated and then dried at 150-250° C. for at least 6 hours to obtain a solid electrolyte with a powder moisture value of less than 500 ppm.

[0034] Since the powder moisture value of solid electrolytes sold on the market is basically far greater than 500ppm, it is impossible to reduce the powder moisture value to less than 500ppm by simple drying during actual operation. It is necessary to treat it in the manner shown in this application to achieve a powder moisture value of less than 500ppm. Therefore, it can be understood that the powder moisture value of the solid electrolyte sintered material here is greater than 500ppm.

[0035] During the actual operation, since the coarse powder is actually in a clumping state after spray drying, it needs to be dissociated to transform it from lumps into particles. The dissociation methods include but are not limited to air flow crushing dissociation, vibration crushing dissociation or mechanical crushing dissociation, among which the vibration dissociation method is, for example, ultrasonic vibration dissociation.

[0036] The preparation method adopted in the present application utilizes a method of ball milling the solid electrolyte sintered material and then centrifuging it. Small particles of powder can be removed in the process of removing the supernatant. Since small particles of powder have a large specific surface area, they will absorb more water. Removing small particles contributes to moisture reduction. The subsequent filter press can remove most of the water, thereby improving the drying efficiency of the next step. In addition, small particles of powder will also be adsorbed on the filter press bag, which also has the effect of removing small particles to achieve moisture reduction. Then spray drying is carried out; ultrasonic vibration is then used to deagglomerate the agglomerated powder after spray drying to avoid affecting the particle size. Finally, the drying time is at 150-250°C for at least 6 hours to effectively control the powder moisture to <500ppm and the particle size distribution is concentrated towards the medium particle size of the solid electrolyte.

[0037] Among them, solid electrolyte sintering materials can be prepared by oneself or purchased directly on the market.

[0038] In some embodiments, the solid electrolyte sintered material is prepared by:

[0039] A lithium salt, an aluminum source, a titanium source and an orthophosphate are mixed uniformly according to a molar ratio of lithium element, aluminum element, titanium element and phosphate ion of (1+x+a):x:(2-x):3 to obtain a mixed material, wherein 0.01≤x≤0.5, 5%(1+x)≤a≤15%(1+x).

[0040] The mixed material is first sintered at a low temperature of 250-350°C for 1.5-2.5 hours, then heated to a high temperature of 600-800°C for sintering for 3.5-4.5 hours, and then cooled in the furnace.

[0041] In the above preparation method, 5% (1 + x) ≤ a ≤ 15% (1 + x) is used to make the lithium element in the lithium salt 5% to 15% in excess to compensate for the loss caused by lithium volatilization during the calcination process. Then, specific low-temperature sintering and high-temperature sintering are performed on it, which is conducive to obtaining a solid electrolyte sintered material with higher electrical conductivity.

[0042] For example, lithium salts include, but are not limited to, Li2CO3 or LiOH, aluminum sources include, but are not limited to, Al2O3 or Al(OH)3, titanium sources include, but are not limited to, TiO2 or Ti(OH)4, and orthophosphates include, but are not limited to, NH4H2PO4 or (NH4)2HPO4. These raw materials are readily available and do not introduce impurities during the sintering process.

[0043] Exemplarily, the temperature of low-temperature sintering is any value among 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 320℃, 320℃, 330℃, 340℃, 350℃ or between any two values, and the time of low-temperature sintering is any value among 1.5h, 2h, 2.5h or between any two values.

[0044] Illustratively, the high-temperature sintering temperature is any value among 600°C, 630°C, 650°C, 680°C, 700°C, 730°C, 750°C, 770°C, 800°C or between any two values, and the high-temperature sintering time is any value among 3.5h, 4h, 4.5h or between any two values.

[0045] The present application provides a diaphragm coating slurry, which includes the above-mentioned solid electrolyte.

[0046] The diaphragm coating slurry used in this application uses a solid electrolyte Li with an ion conductivity greater than 0.5mS / cm, a particle size in the range of 0.1 to 2um, and a powder moisture value less than 500ppm. 1+x Al x Ti 2-x (PO4)3 as a raw material is helpful in reducing the difficulty of drying the diaphragm. It can not only effectively reduce the moisture content of the solid electrolyte coating made from the diaphragm coating slurry, but also effectively reduce the AC impedance, improve the safety of the battery and the capacity retention rate of the battery at room temperature and low temperature.

[0047] In some embodiments, the solid electrolyte coating further comprises a dispersion stabilizer, a thickener, a binder, and an interfacial tension regulator;

[0048] Based on the total volume of the solid electrolyte particles, dispersion stabilizer, thickener, binder, and interfacial tension regulator being 100 parts, the volume of the solid electrolyte ceramic particles is 76.0 to 85.5 parts, the volume of the dispersion stabilizer is 1.0 to 4.0 parts, the volume of the thickener is 1.0 to 4.0 parts, the volume of the binder is 12.0 to 15.0 parts, and the volume of the interfacial tension regulator is 0.5 to 1.0 part.

[0049] The rational combination of the above-mentioned components is conducive to improving the consistency of the solid electrolyte coating prepared from the diaphragm coating slurry, which not only makes the air permeability and thermal shrinkage of the prepared diaphragm meet the relevant requirements, but also helps to improve the safety of the battery and improve the capacity retention rate of the battery at room temperature and low temperature.

[0050] It should be noted that the diaphragm coating slurry is an aqueous slurry, that is, the diaphragm coating slurry is actually composed of solid electrolyte particles, a dispersion stabilizer, a thickener, a binder, an interfacial tension regulator and water. The amount of water added to the diaphragm coating slurry can be adjusted according to the actual solid content required by the diaphragm coating slurry, and is not limited here.

[0051] In some embodiments, the dispersion stabilizer is a hydrophilically modified polymer, wherein the main chain of the polymer is connected with an affinity group that is affinity to the solid electrolyte and a compatibility group that is compatible with the binder.

[0052] By using the above-mentioned dispersion stabilizer, the long-term stability of the solid electrolyte ceramic particles in the aqueous dispersion system is achieved by using electrostatic stabilization and steric stabilization.

[0053] Optionally, the dispersion stabilizer includes at least one of a sulfonated polystyrene oxide resin having a weight average molecular weight of 5000 to 15000 and a polyoxyethylene ether having a weight average molecular weight of 500 to 1000.

[0054] The main chain of the above-mentioned dispersion stabilizer is connected with an affinity group that is affinity to the solid electrolyte and a compatible group that is compatible with the binder, which is conducive to using electrostatic stabilization and steric stabilization to achieve long-term stability of solid electrolyte ceramic particles in the aqueous dispersion system.

[0055] In some embodiments, the thickener comprises an anionic cellulose ether having a pH of 6.5 to 8.0 and a degree of substitution of 0.5 to 1.0.

[0056] The thickener can effectively improve the wettability of the substrate solid electrolyte ceramic particles, facilitate uniform dispersion, and cooperate with the binder to improve the bonding force between the solid electrolyte coating formed by the diaphragm coating slurry and the diaphragm body.

[0057] The degree of polymerization of the anionic cellulose ether is not limited and can be selected according to different application purposes.

[0058] Optionally, the thickening agent comprises sodium carboxymethylcellulose and / or lithium carboxymethylcellulose.

[0059] The selection of the above two thickeners is beneficial to improving the stability of the diaphragm coating slurry and improving the capacity retention rate of the battery at room temperature and low temperature.

[0060] In some embodiments, the binder includes an acrylate copolymer.

[0061] Acrylate copolymers have excellent electrolyte resistance, which allows the battery to maintain the stability of the binder material itself in high or low temperature storage environments and prevent the solid electrolyte coating from falling off.

[0062] The pH value, Tg, viscosity and particle size of the acrylic copolymer are not limited herein, and those skilled in the art may select them according to different application purposes.

[0063] Optionally, the binder includes at least one of polybutyl acrylate, polybutyl methacrylate, and poly(ethyl acrylate-styrene-acrylamide).

[0064] Each of the above binders can enable the battery to maintain the stability of the binder material itself in high-temperature or low-temperature storage environments, which is beneficial to improving the capacity retention and safety of the battery at room temperature and low temperature.

[0065] In some embodiments, the interfacial tension adjuster includes an organosilicon-based interfacial tension adjuster having a static surface tension of 19 to 25 mN / m.

[0066] The above-mentioned silicone interfacial tension regulator is composed of two parts: a lipophilic group and a hydrophilic group. During the actual coating process, it can reduce the interfacial tension between the surface of the polymer base film and the slurry, so that the aqueous slurry can well wet the surface of the hydrophobic polymer base film, which is beneficial to the uniformity of the coating and improves the stability between the solid electrolyte coating and the polymer base film.

[0067] Optionally, the interfacial tension adjuster includes polyether-modified polysiloxane.

[0068] The polyether-modified polysiloxane can reduce the interfacial tension between the surface of the polymer base film and the slurry during the actual coating process, so that the aqueous slurry can well wet the surface of the hydrophobic polymer base film.

[0069] The present application provides a diaphragm, which includes a diaphragm body and a solid electrolyte coating provided on at least one surface of the diaphragm body, wherein the solid electrolyte coating is made from the diaphragm coating slurry provided in the above embodiments.

[0070] It can be understood that the solid electrolyte coating on at least one surface of the diaphragm body means that the diaphragm body has two surfaces opposite to each other along the thickness direction, and any one or both surfaces are provided with the solid electrolyte coating.

[0071] The diaphragm provided in the present application, which contains a solid electrolyte coating made from the above-mentioned diaphragm coating slurry, not only has a low water content, but also can effectively reduce the AC impedance when used in the battery, improve the safety of the battery and the capacity retention rate of the battery at room temperature and low temperature.

[0072] In some embodiments, the diaphragm body is a polymer-based membrane.

[0073] That is, the above-mentioned diaphragm coating slurry is directly coated on the surface of the polymer base membrane to form a solid electrolyte coating, which is beneficial to improving the ionic conductivity.

[0074] The material of the polymer base film is a high molecular polymer commonly used in the art, and those skilled in the art can select it according to actual needs.

[0075] In some embodiments, the diaphragm body includes a polymer base film and a ceramic coating formed on at least one surface of the polymer base film; wherein the solid electrolyte coating is coated on the surface of the ceramic coating, and / or the solid electrolyte coating is coated on the surface of the polymer base film.

[0076] The ceramic coating is used to allow lithium ions to pass through and provide support and protection, maintaining the structure of the diaphragm. It will not lose its function of separating the positive and negative electrodes due to melting or large-scale shrinkage of the substrate layer, thus avoiding short circuits between the positive and negative electrodes, preventing the battery from burning or even exploding, and improving battery safety.

[0077] The ceramic coating formed on at least one surface of the polymer base film means that the polymer base film has two surfaces opposite to each other in the thickness direction, and the ceramic coating is formed on only one surface of the polymer base film, or on two opposite surfaces of the polymer base film.

[0078] When the ceramic coating is formed only on any surface of the polymer base film, the diaphragm body includes the polymer base film and the ceramic coating formed on any surface of the polymer base film. At this time, the solid electrolyte coating can be formed only on the surface of the ceramic coating, or only on the other surface of the polymer base film away from the ceramic coating, or the solid electrolyte coating is formed on the surface of the ceramic coating and the other surface of the polymer base film away from the ceramic coating.

[0079] When the ceramic coating is formed only on two opposite surfaces of the polymer base membrane, the diaphragm body includes the polymer base membrane and the ceramic coating formed on both surfaces of the polymer base membrane. At this time, the solid electrolyte coating can be formed only on the surface of the ceramic coating located on either side of the polymer base membrane, or the solid electrolyte coating can be formed on the surfaces of the ceramic coating located on both sides of the polymer base membrane.

[0080] In other words, the introduction of ceramic coating is conducive to improving battery safety.

[0081] The ceramic material in the ceramic coating includes but is not limited to one or a mixture of alumina, silica, titania, zirconia, magnesia and boehmite.

[0082] In some embodiments, the ceramic coating includes an α-Al 2 O 3 ceramic coating, and the thickness of the ceramic coating is 1 to 2 μm.

[0083] In some embodiments, the polymer-based film satisfies at least one of the following (a1) to (a3):

[0084] (a1) The polymer base film includes ultra-high molecular weight polyethylene, linear polyethylene, branched polyethylene with a weight average molecular weight of 600,000 or more, and a density between 0.941 and 0.960 g / cm 3 High-density polyethylene with a density between 0.915 and 0.940 g / cm 3 A copolymer formed between one or more of low-density polyethylene, cross-linked polyethylene, and polypropylene.

[0085] (a2) The porosity of the polymer-based membrane is 30% to 60%.

[0086] Illustratively, the porosity of the polymer-based membrane is any value among 30%, 35%, 40%, 45%, 50%, 55%, 60%, or between any two values.

[0087] (a3) The thickness of the polymer base film is 5 to 10 μm.

[0088] Illustratively, the thickness of the polymer base film is any value among 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or between any two values.

[0089] In some embodiments, the solid electrolyte coating has a thickness of 0.5 to 6 μm.

[0090] The thickness of the solid electrolyte coating is within the above range, which is beneficial to improving the ionic conductivity of the separator.

[0091] Exemplarily, the thickness of the solid electrolyte coating is any value of 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, or between any two values.

[0092] The present application also provides a method for preparing the above-mentioned diaphragm, which at least comprises:

[0093] Step S1, obtaining a diaphragm coating slurry.

[0094] Among them, the preparation process of the diaphragm coating slurry includes: first adding the solid electrolyte powder into water and stirring, and there is no limit on the stirring equipment, stirring speed and stirring time, as long as a uniform mixed liquid without precipitation is obtained; then dispersing the solid electrolyte particles to obtain a dispersion liquid, and there is no limit on the dispersion equipment and parameters, as long as a dispersion liquid without particle agglomeration is obtained; then adding a dispersion stabilizer, a binder and an interfacial tension regulator to the dispersion liquid in sequence and stirring, and there is no limit on the stirring equipment, stirring speed and stirring time, as long as a uniformly mixed diaphragm coating slurry can be obtained.

[0095] In step S2, a diaphragm body is provided, and the diaphragm coating slurry is coated on at least one surface of the diaphragm body, and then dried to obtain a coated diaphragm. Drying can be performed by various methods such as heating and air drying, for example, in an oven.

[0096] The coating method may be gravure roller coating or wire rod coating.

[0097] The present application provides a battery, which includes the separator provided by the above embodiments.

[0098] The battery includes but is not limited to a semi-solid battery and can also be a solid-state battery.

[0099] Optionally, the battery is a semi-solid state battery.

[0100] The present application provides an electrical device, which includes the battery provided in the present application, and the battery is used to provide electrical energy.

[0101] Electrical devices include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, battery-powered vehicles, electric cars, ships, spacecraft, etc. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys.

[0102] The following is a further detailed description of the diaphragm coating slurry, diaphragm, battery and electrical device of the present application in conjunction with the embodiments.

[0103] In the following embodiments, the preparation method of the solid electrolyte powder includes:

[0104] According to Li 1.3 Al 0.3 Ti 1.7 1. Weigh the raw materials Li2CO3, Al2O3, TiO2, and NH4H2PO4 in the stoichiometric ratio of (PO4)3, among which Li2CO3 is in excess of 10% to compensate for the loss caused by Li volatilization during calcination, and mix the above four raw materials evenly; 2. Sintering: The heating rate is 5°C per hour, sintering at 300°C for 2h, sintering at 700°C for 4h, and naturally cooling to obtain the sintered material.

[0105] The sintering material is divided into a first part and a second part.

[0106] The first part of the sintered material was divided into 5 parts, and each part was ground to the target particle size; the supernatant was removed after centrifugation to remove small particles of powder, and the powder was spray-dried after filtration; ultrasonic vibration was used to deagglomerate the agglomerated powder after drying; the powder was dried at 200°C for at least 6 hours, and the moisture content of the powder was controlled to <500ppm, respectively, as the solid electrolyte powder added in Examples 1-5.

[0107] The second portion of sintered material was directly ground and pulverized, and sieved to obtain a solid electrolyte with a target particle size as the solid electrolyte powder added in Comparative Example 2.

[0108] Example 1

[0109] The preparation steps of the diaphragm coating slurry are as follows:

[0110] Based on the total volume of solid electrolyte particles, dispersion stabilizer, thickener, binder, and interfacial tension regulator being 100 parts, the solid electrolyte in the volume fractions shown in Table 1 was added to water and stirred for 120 minutes to disperse to obtain a dispersion without particle agglomeration. Then, the dispersion stabilizer, binder, and interfacial tension regulator were added to the dispersion in sequence and stirred. After each addition, the next component was added after stirring for 10 minutes to obtain a diaphragm coating slurry.

[0111] The solid electrolyte is LATP, with a Dv50 of 0.5 μm and a powder moisture content of 353 ppm. The dispersion stabilizer is a sulfonated polystyrene oxide resin with a weight-average molecular weight of 5,000 to 15,000. The thickener is sodium carboxymethyl cellulose. The binder is polybutyl acrylate. The interfacial tension modifier is a polyether-modified polysiloxane.

[0112] A wet-process PE substrate as shown in Table 1 was obtained as a polymer base membrane. One surface of the wet-process PE substrate was provided with a traditional ceramic α-Al2O3 coating as an upper coating, and the other side was coated with the above-mentioned diaphragm coating slurry and then dried to form a solid electrolyte coating (LATP coating).

[0113] Examples 2-5 and Comparative Examples 1-2

[0114] The differences between Examples 2-5 and Comparative Examples 1-2 and Example 1 are shown in Table 1.

[0115] Table 1 Composition of Examples 1-5 and Comparative Examples 1-2

[0116]

[0117] In Table 1, the lower coating layer is: 1um traditional ceramic α-Al2O3 coating + 1um LATP coating, which means that the lower coating layer is composed of a 1um thick traditional ceramic α-Al2O3 coating on the surface of a wet-process PE substrate and a 1um thick LATP coating on the surface of the traditional ceramic α-Al2O3 coating.

[0118] In Table 1, the moisture content of the solid electrolyte powder was measured using a Swiss Metrohm 851+885 Karl Fischer moisture analyzer in accordance with GB / T 6283-2008.

[0119] In Table 1, according to GB / T 20245.3-2013, the calculation formula of the electrolyte ionic conductivity at room temperature is k=j / E [where k represents the conductivity of the electrolyte, the unit is Siemens per meter (S / m), j represents the current density, the unit is ampere per square meter (A / m 2 ), E represents the electric field strength, the unit is volt per meter (V / m)] to calculate the ionic conductivity of the solid electrolyte powder (1S / m = 10mS / cm).

[0120] Test Example 1

[0121] The membranes prepared in Examples 1-5 and Comparative Examples 1-2 were tested according to the following method to obtain membrane performance or parameter test results:

[0122] 1. Thickness (GB / T 6672-2001)

[0123] The thickness of the film was measured using a Millimar C1208 film thickness gauge (Millimar, Germany).

[0124] 2. Heat shrinkage (GB / T 12027-2004)

[0125] At room temperature, measure the original length L0 of the sample along the machine direction and perpendicular to the machine direction T0. Heat the sample at the test temperature for the specified time in a constant temperature and humidity controlled oven and then cool it to the original test conditions. Measure the length L1 of the sample along the machine direction and the length T1 perpendicular to the machine direction at this time. The calculation formula is as follows:

[0126] MD%=(L1-L0) / L0×100%;

[0127] TD%=(T1-T0) / T0×100%.

[0128] 3. Surface density (GB / T 36363-2018)

[0129] Cut a test sample with a diaphragm length of 6 cm and a diaphragm width of 4 cm, and use a Mettler QSR205 analytical balance to measure the mass of the diaphragm. The calculation formula is as follows:

[0130] Diaphragm surface density = diaphragm mass / (diaphragm length × diaphragm width), unit is g / m 2 .

[0131] 4. Breathability (GB / T 36363-2018)

[0132] At room temperature, humidity, and standard atmospheric pressure, the test instrument applies a pressure of 1.21 kPa, and 100 mL of air passes through an area of ​​6.45 cm 2 The time required for the diaphragm to be tested was measured using a Wangyan permeability tester (EG01-55-1MR, manufactured by Asahi Seiko).

[0133] 5. Moisture (GB / T 6283-2008)

[0134] The moisture content of the solid electrolyte powder and the separator was determined using a Swiss Metrohm 851+885 Karl Fischer moisture analyzer.

[0135] The test results are shown in Table 2.

[0136] Table 2 Diaphragm test results

[0137]

[0138] According to Table 2, when the solid electrolyte powder is not dried and dehydrated, the moisture content of the powder is greater than 5000 ppm, and the moisture content of the solid electrolyte coating separator made of this powder is also high. The test value in Comparative Example 2 is 2632 ppm; the moisture content of the powder after drying and dehydration is less than 500 ppm, and the moisture content of the solid electrolyte separator made of this powder is as shown in Examples 1 to 5. The test values ​​are all less than

[0139] 1400ppm.

[0140] The test results of thickness and surface density in Examples 1 to 5 and Comparative Examples 1 and 2 show that the consistency of each group of diaphragms controlled by the coating process is good, and the air permeability and thermal shrinkage test results show that the slurry formula design is relatively reasonable.

[0141] Test Example 2

[0142] The separators prepared in Example 1, Example 2 and Comparative Example 1 were assembled into soft-pack batteries for battery performance testing: positive electrode: NCM523, negative electrode: AG, capacity: 3000 mAh; electrolyte composition and content: 1 mol LiPF6,

[0143] EC / EMC / DMC=1:1:1Vol%.

[0144] The soft-pack batteries corresponding to Example 1, Example 2 and Comparative Example 1 are divided into battery sample 1 and battery sample 2 according to the different liquid injection amounts.

[0145] The specific test methods for the performance of each battery sample prepared in Examples 1, 2 and Comparative Example 1 are described as follows:

[0146] 1. Battery AC internal resistance ACIR test

[0147] Under normal temperature, humidity, and standard atmospheric pressure, a BS-VR3 battery internal resistance meter was used to test the battery's ACIR. Power supply: 220VAC, 50Hz, 10W. Once the battery is placed in the fixture, the battery's voltage and internal resistance are measured in real time. The left side of the digital display shows the battery's internal resistance, and the right side shows the battery's voltage. The voltage range is 0V-4.999V, with a resolution of 1mV, and the internal resistance range is 1mΩ-199.9mΩ, with a resolution of 0.1mΩ.

[0148] 2. Battery rate discharge performance test (QC / T 743-2006 "Lithium-ion batteries for electric vehicles")

[0149] 2.1 Test conditions

[0150] The test is usually carried out under the standard laboratory temperature and humidity conditions specified in QC / T 743-2006. The same temperature conditions should be used for the same set of tests or multiple sets of comparative tests.

[0151] 2.2 Testing equipment

[0152] 2.2.1 All measuring instruments and meters used in the test shall comply with the requirements of QC / T 743-2006.

[0153] 2.2.2 Xinwei charging and discharging system: It shall comply with the provisions of QC / T 743-2006, have a force measurement accuracy of 0.5 level voltage and current, and a time force measurement accuracy of ±0.1%. Adopting industrial-grade 32 embedded platform, the work step file is downloaded to the device for execution; up to 10Hz data recording; supports DCIR (direct current internal resistance) test, and the test price can be automatically calculated by taking points; supports pulse and discharge functions, and the error of pulse mode work step time control is ≤1ms; each pulse step supports 32 different pulse segments; pulse mode supports: current, power, and small pulse width up to 100ms; test mode supports: constant current, constant voltage, constant current and constant voltage, constant power, constant resistance, and pulse; each channel is independently programmed and supports a maximum of 254 work steps; 65535 cycles, which can be nested in 3 layers; supports setting recording conditions and protection conditions for a single work step; supports setting recording conditions in sections within the work step; hardware reverse connection protection; voltage curve, current curve, and capacity curve abnormality protection; the switching time from charge to discharge is less than 10ms (pulse mode) supports offline testing and supports 1GB of data storage space. Based on TCP / IP protocol, it supports LAN remote monitoring; it uses Database to centrally manage test data, with powerful data retrieval and traceability functions; it supports curve comparison, customizable automatic reports, and supports report formats such as Excel, TXT, and PDF.

[0154] 2.2.3 High and Low Temperature Chamber: The high and low temperature chamber used to measure batteries should comply with the provisions of QC / T 743-2006 and have a temperature measurement accuracy of ±0.5°C. The high and low temperature chamber should be connected to the charging and discharging system, be able to provide the temperature required for the experiment, and the accuracy should meet the requirements of national standards. Xinwei's high and low temperature chamber can provide a temperature range of -40°C to 150°C, with a storage space of up to 225L. The indicated temperature accuracy (T-type thermocouple): measurement accuracy of ±0.3°C, indication accuracy (full scale): ±(0.07%FS+1digit) (ambient temperature 23°C±1°C) time: less than 30 seconds per month; performance is guaranteed at an ambient temperature of 25°C±5°C and humidity of 15%RH~90%RH (without condensation); operation is guaranteed at an ambient temperature of 0°C~+60°C and humidity of 15%RH~90%RH (without condensation). Equipment information prompt function, tracing function, resettable time accumulator, manual drainage function, time signal function, input disconnection detection function, power failure protection function, upper and lower limit temperature (humidity) alarm function, refrigeration system automatic operation function, self-diagnosis function, alarm display function, timing function, help function.

[0155] 2.3 Preparation before testing

[0156] 2.3.1 Conditioning of samples and test pieces: Unless otherwise specified, the test should be carried out at a temperature of 15°C to 35°C and a relative humidity of

[0157] The process is carried out in an environment with a pressure range of 25% to 85% and an atmospheric pressure of 86kPa to 106kPa. A single battery is a basic unit device that directly converts chemical energy into electrical energy, including electrodes, separators, electrolytes, casings, and terminals, and is designed to be rechargeable.

[0158] 2.3.2 Preparation of samples: Soft-pack batteries are prepared by winding and lamination processes. The cells that have passed the Hi-pot test are made into initial test samples after liquid injection, hot and cold pressing, and formation.

[0159] 2.3.3 Test quantity: Standard QC / T 743-2006 stipulates that the specific number of samples in each group is 2, that is, two parallel samples are set for each battery sample.

[0160] 2.4 Standard 20℃, 3C rate discharge test steps

[0161] Place the sample in the charging and discharging cabinet, fix the battery with a clamp, and make sure the positive and negative poles are not reversed. When the temperature is 20±5℃, turn on the charging and discharging system, set the test steps according to standard QC / T 743-2006, start the test, and record the data.

[0162] a) Charge according to the charging method specified by the enterprise; or charge at a constant current of 0.33C to the charging termination voltage specified by the enterprise, then switch to constant voltage charging and stop charging when the charging termination current drops to 0.033C;

[0163] b) Shelved for no less than 30 minutes or under the shelving conditions specified by the enterprise;

[0164] c) Discharge at 3C until the discharge termination condition specified by the enterprise, and record the discharge capacity;

[0165] d) Measure the discharge capacity (in Ah) and express it as a percentage of the rated capacity.

[0166] 2.5 Standard 20℃, 5C rate discharge test steps

[0167] Place the sample in the charging and discharging cabinet, fix the battery with a clamp, and make sure the positive and negative poles are not reversed. When the temperature is 20±5℃, turn on the charging and discharging system, set the test steps according to standard QC / T 743-2006, start the test, and record the data.

[0168] a) Charge according to the charging method specified by the enterprise; or charge at a constant current of 0.33C to the charging termination voltage specified by the enterprise, then switch to constant voltage charging and stop charging when the charging termination current drops to 0.033C;

[0169] b) Shelved for no less than 30 minutes or under the shelving conditions specified by the enterprise;

[0170] c) Discharge at 5C until the discharge termination condition specified by the enterprise, and record the discharge capacity;

[0171] d) Measure the discharge capacity (in Ah) and express it as a percentage of the rated capacity.

[0172] 2.6-20℃ low temperature 1C rate discharge test steps

[0173] Place the sample in a temperature chamber and secure the battery with a clamp, making sure the positive and negative poles are not reversed. Open the temperature chamber and set the chamber temperature to 25°C. Turn on the charge and discharge system and set the test steps according to standard QC / T 743-2006. After the chamber temperature stabilizes at 25°C for 1 hour, begin the test and record the data.

[0174] a) Charge at a temperature of 25±2°C according to the charging method specified by the manufacturer; or charge at a constant current of 0.33C to the charging termination voltage specified by the manufacturer, then switch to constant voltage charging and stop charging when the charging termination current drops to 0.033C;

[0175] b) Place in an environment of -20℃±2℃ for 20h;

[0176] c) Discharge at 1C until the discharge termination condition specified by the enterprise, and record the discharge capacity;

[0177] d) Measure the discharge capacity (in Ah) and express it as a percentage of the rated capacity.

[0178] 3. Battery cell puncture test

[0179] Test conditions: Charging voltage 4.2V, constant current-constant voltage mode, 5mm diameter, high-temperature resistant steel needle with a tip angle of 50 degrees, speed of 25±2mm / s, the steel needle stays in the battery for 10 minutes, then is pulled out and observed for 1 hour. The endpoint voltage and maximum temperature of the battery cell are recorded to observe whether there is fire or smoke.

[0180] The test results of the battery of the embodiment and the comparative example are shown in Table 3.

[0181] Table 3 Test results

[0182]

[0183] As can be seen from Table 3, at 100% liquid injection, the AC internal resistance ACIR result is: battery 1 of Example 1 < battery 1 corresponding to Example 2 < battery 1 corresponding to Comparative Example 1, that is, when the diaphragm contains a solid electrolyte LATP coating, it shows a lower AC internal resistance.

[0184] At 70% liquid filling, the results of ACIR are: Battery 2 of Example 1 < Battery 2 corresponding to Example 2 < Battery 2 corresponding to Comparative Example 1, that is, when the diaphragm contains a solid electrolyte LATP coating, it shows a lower AC internal resistance, and compared with 100% liquid filling, the 70% liquid filling rate makes the diaphragm containing the solid electrolyte LATP coating show more obvious advantages.

[0185] As can be seen from Table 3, at 100% liquid filling, the 3C / 5C rate discharge capacity retention results are: Battery 1 of Example 1 > Battery 1 corresponding to Example 2 > Battery 1 corresponding to Comparative Example 1. At 70% liquid filling, the 3C / 5C rate discharge capacity retention results are: Battery 2 of Example 1 > Battery 2 corresponding to Example 2 > Battery 2 corresponding to Comparative Example 1. In other words, the rate performance results show that the thicker the solid electrolyte LATP coating, the more significant the rate performance advantage; the advantage of the solid electrolyte LATP coating is even more obvious at a 70% liquid filling ratio.

[0186] According to the needle penetration test results of battery 2 corresponding to Example 1 and battery 2 corresponding to Comparative Example 1, it is shown that the solid electrolyte LATP coated separator can improve the safety of the battery cell.

[0187] In summary, the diaphragm coating slurry and diaphragm, battery and electrical device provided in this application, the diaphragm coating slurry is conducive to reducing the difficulty of drying the diaphragm, can effectively reduce the moisture content of the solid electrolyte coating prepared by the diaphragm coating slurry, and can effectively reduce the AC impedance, improve the safety of the battery and the capacity retention rate of the battery at room temperature and low temperature.

[0188] The above are merely specific embodiments of the present application and are not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A solid electrolyte, wherein: The solid electrolyte is: Li 1+x Al x Ti 2-x (PO4)3, 0.01≤x≤0.5, the moisture value of the solid electrolyte is less than 500 ppm, the ionic conductivity of the solid electrolyte is greater than 0.5 mS / cm, and the particle size of the solid electrolyte is in the range of 0.1 to 2 um.

2. The solid electrolyte according to claim 1, wherein The volume particle size distribution Dv50 of the solid electrolyte is 0.1 to 1.0 μm.

3. The method for preparing a solid electrolyte according to claim 1 or 2, wherein: The preparation method of the solid electrolyte comprises: obtaining a solid electrolyte sintered material; Wet-milling the solid electrolyte sintered material to a target particle size, centrifuging to remove the supernatant, filtering, and spray-drying to obtain a coarse powder; The coarse powder is deagglomerated and then dried at 150-250° C. for at least 6 hours to obtain the solid electrolyte having a powder moisture value of less than 500 ppm.

4. The method for preparing a solid electrolyte according to claim 3, wherein: The solid electrolyte sintered material is prepared by the following method: Mixing a lithium salt, an aluminum source, a titanium source and an orthophosphate in a molar ratio of lithium element, aluminum element, titanium element and phosphate radical of (1+x+a):x:(2-x):3 to obtain a mixed material, wherein 0.01≤x≤0.5, 5%(1+x)≤a≤15%(1+x); The mixed material is first sintered at a low temperature of 250-350° C. for 1.5-2.5 hours, then heated to a high temperature of 600-800° C. for sintering for 3.5-4.5 hours, and then cooled in the furnace.

5. A diaphragm coating slurry, wherein: The separator coating slurry comprises the solid electrolyte according to claim 1 or 2.

6. The diaphragm coating slurry according to claim 5, wherein: The diaphragm coating slurry further includes a dispersion stabilizer, a thickener, a binder and an interfacial tension regulator; Based on the total volume of the solid electrolyte particles, the dispersion stabilizer, the thickener, the binder, and the interfacial tension regulator being 100 parts, the volume of the solid electrolyte ceramic particles is 76.0 to 85.5 parts, the volume of the dispersion stabilizer is 1.0 to 4.0 parts, the volume of the thickener is 1.0 to 4.0 parts, the volume of the binder is 12.0 to 15.0 parts, and the volume of the interfacial tension regulator is 0.5 to 1.0 parts.

7. The diaphragm coating slurry according to claim 6, wherein: The dispersion stabilizer is a hydrophilically modified polymer, the main chain of which is connected with an affinity group that is affinity with the solid electrolyte and a compatibility group that is compatible with the binder; Optionally, the dispersion stabilizer includes at least one of a sulfonated polystyrene oxide resin having a weight average molecular weight of 5000 to 15000 and a polyoxyethylene ether having a weight average molecular weight of 500 to 1000.

8. The diaphragm coating slurry according to claim 6, wherein: The thickener includes an anionic cellulose ether having a pH value of 6.5 to 8.0 and a degree of substitution of 0.5 to 1.0; Optionally, the thickener comprises sodium carboxymethyl cellulose and / or lithium carboxymethyl cellulose.

9. The diaphragm coating slurry according to claim 6, wherein: The binder includes an acrylic copolymer; Optionally, the binder includes at least one of polybutyl acrylate, polybutyl methacrylate, and poly(ethyl acrylate-styrene-acrylamide).

10. The diaphragm coating slurry according to claim 6, wherein: The interfacial tension regulator includes an organic silicon interfacial tension regulator having a static surface tension of 19 to 25 mN / m; Optionally, the interfacial tension regulator includes polyether-modified polysiloxane.

11. A diaphragm, wherein: The invention comprises a diaphragm body and a solid electrolyte coating provided on at least one surface of the diaphragm body, wherein the solid electrolyte coating is made from the diaphragm coating slurry according to any one of claims 5 to 10.

12. The diaphragm according to claim 11, wherein The diaphragm body is a polymer-based membrane.

13. The diaphragm according to claim 11, wherein The diaphragm body includes a polymer base film and a ceramic coating formed on at least one surface of the polymer base film; Wherein, the solid electrolyte coating is coated on the surface of the ceramic coating, and / or the solid electrolyte coating is coated on the surface of the polymer base film; Optionally, the ceramic coating includes an α-Al 2 O 3 ceramic coating, and the thickness of the ceramic coating is 1 to 2 μm.

14. The diaphragm according to claim 12 or 13, wherein The polymer base film satisfies at least one of the following (a1) to (a3): (a1) The polymer base film includes ultra-high molecular weight polyethylene, linear polyethylene, branched polyethylene with a weight average molecular weight of 600,000 or more, and a density between 0.941 and 0.960 g / cm 3 High-density polyethylene with a density between 0.915 and 0.940 g / cm 3 A copolymer formed by one or more of low-density polyethylene, cross-linked polyethylene, and polypropylene; (a2) the porosity of the polymer-based membrane is 30% to 60%; (a3) The thickness of the polymer base film is 5 to 10 μm.

15. The separator according to any one of claims 11 to 13, wherein The thickness of the solid electrolyte coating is 0.5 to 6 μm.

16. A battery, wherein: A diaphragm comprising any one of claims 11 to 15; Optionally, the battery is a semi-solid-state battery.

17. An electrical device, wherein: It comprises the battery according to claim 16, wherein the battery is used to provide electrical energy.

Images