Diaphragm and preparation method thereof, battery and electric device

Abstract

The invention discloses a diaphragm and a preparation method thereof, a battery and a power utilization device, the diaphragm comprises a porous base membrane and a coating, and the coating is arranged on at least one surface of the porous base membrane; the coating comprises an oxide solid electrolyte and a lithium supplement additive; the oxide solid electrolyte comprises at least one of a sodium fast ion conductor type solid electrolyte, a garnet type solid electrolyte and a perovskite type solid electrolyte; the lithium supplement additive comprises a compound formed by a binary lithium-containing compound and a transition metal. Therefore, the diaphragm disclosed by the invention has excellent electrolyte affinity and electrolyte retention capability, can reduce interface impedance and reduce concentration polarization in the battery, and can promote ion transmission and improve the overall performance of the battery at the same time; in addition, the diaphragm can release lithium ions in the first-circle charging and discharging process, and the loss in the SEI film generation process is supplemented.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a diaphragm and a preparation method thereof, a battery and an electrical device. Background Art

[0002] In lithium-ion power batteries, the formation of the solid electrolyte interface (SEI) is a key chemical reaction during the first charge and discharge process of the battery. At the solid-liquid interface between the electrode material and the electrolyte, a reaction occurs and a passivation layer is formed. The SEI film not only prevents further decomposition of the electrolyte, but also allows lithium ions to pass through while blocking the passage of electrons. However, the loss of active lithium is inevitable during the formation of the SEI film. When soluble organic compounds in the electrolyte react with lithium ions, a portion of the active lithium is consumed. These reactions are usually irreversible, resulting in the inability of the consumed lithium ions to participate in the battery's charge and discharge cycle again. The loss of active lithium directly leads to a decrease in the first charge and discharge efficiency (first efficiency) and reduces the initial capacity of the battery.

[0003] On the other hand, the separator of lithium-ion power batteries is mainly made of high molecular polymer materials such as polyethylene (PE) or polypropylene (PP), and its main function is to separate the positive and negative electrodes and prevent short circuits. Lithium ions are transmitted between the positive and negative electrodes through the porous structure of the separator. However, this type of separator material has poor electrolyte wettability and fewer effective ion transmission channels, which leads to increased battery polarization and cannot meet the needs of high-rate charging and discharging. In addition, the separator that has been stretched at a high rate is prone to shrinkage or melting at high temperatures, increasing the risk of thermal runaway of the battery under abnormal operating conditions.

[0004] Therefore, there is an urgent need to develop a sustainable lithium replenishment technology that is simple to operate and safe, so that it can improve the electrochemical performance of batteries. Summary of the invention

[0005] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, one purpose of the present application is to propose a diaphragm and a preparation method thereof, a battery and an electrical device. The diaphragm of the present application can enable the rapid and uniform transmission of lithium ions in the battery, optimize the rate and cycle performance of the battery, compensate for the loss of active lithium in the first charge and discharge and later cycles, and improve the initial efficiency and capacity.

[0006] Therefore, in the first aspect of the present application, the present application proposes a diaphragm. According to an embodiment of the present application, the diaphragm includes: a porous base film and a coating, the coating is arranged on at least one surface of the porous base film; the coating contains an oxide solid electrolyte and a lithium supplement additive; the oxide solid electrolyte includes at least one of a sodium fast ion conductor (NASICON) type solid electrolyte, a garnet type solid electrolyte, and a perovskite type solid electrolyte; the lithium supplement additive includes a complex formed by a binary lithium-containing compound and a transition metal. As a result, the diaphragm of the present application has excellent electrolyte affinity and liquid retention capacity, can reduce interfacial impedance, reduce concentration polarization in the battery, and can promote ion transport and improve the overall performance of the battery; in addition, the diaphragm can release lithium ions during the first cycle of charge and discharge to supplement the loss during the formation of the SEI film.

[0007] According to an embodiment of the present application, the mass ratio of the oxide solid electrolyte to the lithium supplement additive is (2-10):1.

[0008] According to an embodiment of the present application, the thickness of the coating is 0.01 μm-5 μm.

[0009] According to an embodiment of the present application, the sodium fast ion conductor (NASICON) type solid electrolyte includes at least one of lithium aluminum titanium phosphate (LATP) and lithium aluminum germanium phosphate (LAGP).

[0010] According to an embodiment of the present application, the garnet-type solid electrolyte includes at least one of lithium lanthanum zirconium oxide (LLZO), lithium lanthanum niobium oxide (LLNO), lithium lanthanum zirconium niobium oxide (LLZNO), and lithium lanthanum zirconium tantalum oxide (LLZTO).

[0011] According to an embodiment of the present application, the perovskite-type solid electrolyte includes lithium lanthanum titanium oxide (LLTO).

[0012] According to an embodiment of the present application, the binary lithium-containing compound includes at least one of Li2O, Li2S, LiF, and Li3N.

[0013] According to an embodiment of the present application, the transition metal includes at least one of Fe, Co, and Ni.

[0014] According to an embodiment of the present application, the thickness of the porous base membrane is 5 μm-20 μm.

[0015] According to an embodiment of the present application, the porosity of the porous base membrane is 30% to 50%.

[0016] According to an embodiment of the present application, the pore size of the porous base membrane is 0.01 μm-0.3 μm.

[0017] In the second aspect of the present application, the present application proposes a method for preparing the diaphragm described in the first aspect. According to an embodiment of the present application, the method comprises: loading a slurry containing an oxide solid electrolyte and a lithium supplement additive on at least one surface of a porous base film to form a coating; drying the porous base film with the coating to obtain the diaphragm. Therefore, the method of the present application has a simple preparation process and is easy to operate. It can be applied to industrial production and is easy to quickly achieve mass production. In addition, the diaphragm prepared by this method has excellent heat resistance, mechanical strength and electrolyte wettability, which not only improves the safety performance of the battery, but also can remove active lithium and transfer it to the negative electrode during the first charge, offsetting the capacity loss of SEI film formation, and improving the first charge and discharge efficiency. Those skilled in the art can understand that this method has all the characteristics and advantages of the diaphragm described above, and will not be described in detail here.

[0018] According to an embodiment of the present application, the slurry further includes a solvent, a dispersant, a binder and a wetting agent.

[0019] According to an embodiment of the present application, based on the total mass of the slurry, the total mass of the oxide solid electrolyte and the lithium supplement additive accounts for 10%-30%.

[0020] According to an embodiment of the present application, based on the total mass of the slurry, the mass proportion of the dispersant is 0.1%-2%.

[0021] According to an embodiment of the present application, based on the total mass of the slurry, the mass proportion of the adhesive is 2%-10%.

[0022] According to an embodiment of the present application, based on the total mass of the slurry, the mass proportion of the wetting agent is 0.1%-1%.

[0023] According to an embodiment of the present application, the slurry is prepared by the following method: subjecting the dispersant and the solvent to a first mixing treatment to obtain a first mixed liquid; subjecting the first mixed liquid and the oxide solid electrolyte to a second mixing treatment to obtain a second mixed liquid; subjecting the second mixed liquid and the lithium supplement additive to a third mixing treatment and a sand grinding treatment to obtain a third mixed liquid; subjecting the third mixed liquid and the adhesive and the wetting agent to a fourth mixing treatment and an ultrasonic treatment to obtain the slurry.

[0024] According to an embodiment of the present application, the rotation speed of the sanding process is 500rpm-5000rpm.

[0025] According to an embodiment of the present application, the sanding treatment time is 3h-24h.

[0026] According to an embodiment of the present application, the power of the ultrasonic treatment is 2000 Hz-20000 Hz.

[0027] According to an embodiment of the present application, the ultrasonic treatment time is 0.5h-3h.

[0028] In the third aspect of the present application, the present application proposes a battery. According to an embodiment of the present application, the battery includes the diaphragm described in the first aspect or the diaphragm prepared by the method described in the second aspect. As mentioned above, the diaphragm of the present application not only has excellent electrolyte affinity and liquid retention capacity, can reduce interfacial impedance, reduce concentration polarization in the battery, but also can promote ion transport and improve the initial charge and discharge efficiency. As a result, the battery of the present application has high ionic conductivity, high energy density and good initial charge and discharge efficiency. Those skilled in the art can understand that the battery has all the features and advantages of the diaphragm described above, and will not be elaborated here.

[0029] In the fourth aspect of the present application, the present application proposes an electrical device. According to an embodiment of the present application, the electrical device includes the battery described in the third aspect. As mentioned above, the battery of the present application has high ionic conductivity, high energy density and good initial charge and discharge efficiency. As a result, the electrical device of the present application has good cycle performance, fast charging performance, excellent service life and safety performance. Those skilled in the art will understand that the electrical device has all the features and advantages of the battery described above, and will not be elaborated on here.

[0030] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0032] Figure 1 is a schematic diagram of the diaphragm structure according to an embodiment of the present application;

[0033] Figure 2 is a method for preparing a diaphragm according to an embodiment of the present application;

[0034] Figure 3 A method for preparing a coating slurry according to an embodiment of the present application;

[0035] Figure 4 is a SEM image corresponding to the surface coating of the diaphragm prepared according to Example 1 of the present application;

[0036] Figure 5It is a Li||Li symmetric battery charge and discharge time-voltage curve corresponding to the diaphragm prepared according to Example 1 and Comparative Example 1 of the present application;

[0037] Reference numerals: 01 is a porous base film, and 02 is a coating layer. DETAILED DESCRIPTION

[0038] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0039] For simplicity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and any upper limit can be combined with any other upper limit to form an unspecified range. In addition, each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0041] In this document, the terms "include" or "comprising" are open expressions, that is, including the contents specified in the present application but not excluding other contents.

[0042] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of this application, unless otherwise specified, the meaning of "plurality" is two or more.

[0043] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0044] The composition of the solid electrolyte membrane (SEI membrane) is complex and in a metastable state. It will consume a large amount of active lithium ions during its formation, and this mainly occurs during the first cycle. Generally speaking, the loss of active lithium will lead to permanent loss of lithium in the positive electrode material, which in turn causes the available capacity of the battery to continue to decrease. Pre-lithiation technology can compensate for the loss of lithium ions in the SEI membrane formed on the surface of the negative electrode material, thereby improving the initial coulombic efficiency, cycle capacity, cycle life and actual energy density of the battery, and forming a more stable SEI membrane through artificial regulation, which helps to reduce the consumption of lithium ions in the electrolyte, while reducing the loss of active lithium ions in the positive electrode material, thereby improving the first coulombic efficiency of the lithium-ion battery.

[0045] However, existing pre-lithiation technologies have certain defects. For example, the pre-lithiation efficiency of positive electrode lithium replenishment additives is low, and it often increases the impedance of the positive electrode material and the temperature rise of the battery, reducing the specific capacity of the positive electrode material. In addition, the positive electrode lithium replenishment technology has high requirements for lithium replenishers, and there are currently few types of commercial lithium replenishers. Negative electrode lithium replenishment operations are complex, have strict environmental requirements, and are somewhat dangerous, posing a major challenge to existing battery manufacturing processes. In addition, negative electrode lithium replenishment has compatibility issues with the internal environment of the battery, common solvents, adhesives, and heat treatment, and its overall cost is high, and it does not have the ability to be mass-produced.

[0046] In view of this, the present application proposes a diaphragm. The diaphragm is loaded with a coating containing an oxide solid electrolyte and a lithium supplement additive, which can release lithium ions during the first cycle of charge and discharge to supplement the loss during the formation of the SEI film, while enhancing the diaphragm's wettability to the electrolyte, heat resistance and mechanical strength, further promoting ion transmission and improving the overall performance of the battery. The diaphragm, its preparation method and electrochemical device will be introduced in detail below.

[0047] Diaphragm

[0048] The present application proposes a diaphragm. According to the embodiments of the present application, reference Figure 1 The diaphragm comprises: a porous base membrane 01 and a coating 02, wherein the coating 02 is arranged on at least one surface of the porous base membrane 01; the coating comprises an oxide solid electrolyte and a lithium supplement additive; the oxide solid electrolyte comprises at least one of a sodium fast ion conductor (NASICON) type solid electrolyte, a garnet type solid electrolyte and a perovskite type solid electrolyte; the lithium supplement additive comprises a complex formed by a binary lithium-containing compound and a transition metal.

[0049] The diaphragm of the present application has achieved multiple performance optimizations by introducing oxide solid electrolytes and lithium supplement additives. Among them, the oxide solid electrolyte with high intrinsic ionic conductivity can construct additional ion transmission channels on the surface of the diaphragm, improve kinetics, reduce reaction barriers, regulate ion flux distribution, and induce uniform lithium removal / insertion behavior, thereby preventing lithium dendrite growth and slowing down self-discharge. At the same time, the theoretical specific capacity of the complex formed by the binary lithium-containing compound and the transition metal is high, and there is a significant hysteresis effect in its lithium removal and insertion potential: lithium is easy to be removed during charging, but not easy to be inserted back during discharge. Coating it on the diaphragm as a lithium supplement additive can release active lithium and transfer it to the negative electrode during the first charge, offsetting the capacity loss during the formation of SEI, thereby improving the first charge and discharge efficiency. In addition, the coating containing oxide solid electrolytes and lithium supplement additives can form a dense porous structure on the surface of the diaphragm, significantly improving the electrolyte affinity and liquid retention of the porous base membrane, reducing the interface impedance, and reducing the concentration polarization in the battery. At the same time, this coating also effectively reduces thermal shrinkage, preventing short circuits caused by contact between positive and negative electrodes at high temperatures, thereby delaying the occurrence of thermal runaway.

[0050] In some embodiments of the present application, the mass ratio of the oxide solid electrolyte and the lithium supplement additive is (2-10): 1. For example, it can be 2: 1, 3: 1, 4: 1, 5: 1, 6: 1, 7: 1, 8: 1, 9: 1, 10: 1, etc., or it can be a range composed of any of the above values. Thus, by making the mass ratio of the oxide solid electrolyte and the lithium supplement additive within the above range, while ensuring effective lithium supplementation, the overall ion transmission capacity can be improved, the wettability and liquid retention of the electrolyte can be optimized, the interface impedance and battery polarization can be reduced, and the excessive inactive materials can be avoided to affect the overall performance of the battery.

[0051] In some embodiments of the present application, the thickness of the coating is 0.01 μm-5 μm. For example, it can be 0.01 μm, 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc., or it can be a range composed of any of the above numerical values. Thus, by making the thickness of the coating within the above range, it is possible to ensure that the coating is evenly distributed on the diaphragm, while enabling the oxide solid electrolyte and the lithium supplement additive to function better. A coating that is too thick may increase the internal resistance of the battery and reduce the migration speed of ions; while a coating that is too thin may not be able to perform the functions of the oxide solid electrolyte and the lithium supplement additive well.

[0052] In some embodiments of the present application, the sodium fast ion conductor (NASICON) type solid electrolyte includes at least one of lithium aluminum titanium phosphate (LATP) and lithium aluminum germanium phosphate (LAGP). Thus, the above-mentioned type of sodium fast ion conductor (NASICON) type solid electrolyte can construct additional ion transport channels, improve kinetics, and reduce reaction barriers. The ion flux distribution is regulated to induce uniform lithium removal / insertion behavior, thereby preventing lithium dendrite growth and slowing down self-discharge.

[0053] In some embodiments of the present application, the garnet-type solid electrolyte includes at least one of lithium lanthanum zirconium oxide (LLZO), lithium lanthanum niobium oxide (LLNO), lithium lanthanum zirconium niobium oxide (LLZNO), and lithium lanthanum zirconium tantalum oxide (LLZTO). Thus, the above-mentioned types of garnet-type solid electrolytes can construct additional ion transport channels, improve kinetics, and reduce reaction barriers. The ion flux distribution is regulated to induce uniform lithium removal / lithium insertion behavior, thereby preventing lithium dendrite growth and slowing down self-discharge.

[0054] In some embodiments of the present application, the perovskite solid electrolyte includes lithium lanthanum titanium oxide (LLTO). Thus, the above-mentioned type of perovskite solid electrolyte can construct additional ion transport channels, improve kinetics, and reduce reaction barriers. It regulates the distribution of ion flux and induces uniform lithium removal / insertion behavior, thereby preventing lithium dendrite growth and slowing down self-discharge.

[0055] In some embodiments of the present application, the binary lithium-containing compound includes at least one of Li2O, Li2S, LiF, and Li3N. In some embodiments of the present application, the transition metal includes at least one of Fe, Co, and Ni. According to an embodiment of the present application, the complex formed by the binary lithium-containing compound and the transition metal includes at least one of a complex formed by Li2O and Fe, a complex formed by Li2O and Co, a complex formed by Li2O and Ni, a complex formed by Li2S and Fe, a complex formed by Li2S and Co, a complex formed by Li2S and Ni, a complex formed by LiF and Fe, a complex formed by LiF and Co, a complex formed by LiF and Ni, a complex formed by Li3N and Fe, a complex formed by Li3N and Co, and a complex formed by Li3N and Ni. Therefore, the theoretical specific capacity of the complex formed by the above-mentioned binary lithium-containing compounds and transition metals is relatively high, and the lithium deintercalation potential has a large hysteresis effect, that is, lithium is easier to be removed during charging and will not be reintercalated during discharge. When it is coated on the diaphragm, it can release active lithium and transfer it to the negative electrode during the first charge, offsetting the capacity loss of SEI film formation and improving the initial charge and discharge efficiency.

[0056] In some embodiments of the present application, the thickness of the porous base film is 5 μm-20 μm, for example, 5 μm, 7 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, etc., or a range of any of the above values.

[0057] In some embodiments of the present application, the porosity of the porous base film is 30% to 50%, for example, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, etc., or a range of any of the above values.

[0058] In some embodiments of the present application, the pore size of the porous base membrane is 0.01 μm-0.3 μm, for example, 0.01 μm, 0.05 μm, 0.1 μm, 0.2 μm, 0.3 μm, etc., or a range of any of the above values.

[0059] In some embodiments of the present application, the porous base film includes but is not limited to at least one of polyethylene film, polypropylene film, polyimide film, polyethylene terephthalate film, polyvinylidene fluoride film, polyvinylidene fluoride-hexafluoropropylene copolymer film, polyetheretherketone film, polymethyl methacrylate film, polyetherimide film, polyaramid film and cellulose film. Thus, the porous base film of the above type is a porous structure, which is conducive to the transmission of lithium ions.

[0060] In some embodiments of the present application, the coating can be disposed on one side of the porous base membrane or on both sides of the porous base membrane. When the coating is disposed on both sides of the porous base membrane, the coating thickness on both sides can be the same or different.

[0061] Method for preparing diaphragm

[0062] The present application proposes a method for preparing the aforementioned diaphragm. According to the embodiments of the present application, reference Figure 2 , the method comprising:

[0063] S100: Loading a slurry containing an oxide solid electrolyte and a lithium supplement additive on at least one surface of the porous base film to form a coating

[0064] In some embodiments of the present application, the slurry further includes a solvent, a dispersant, a binder and a wetting agent, wherein the dispersant, the binder and the wetting agent are all dissolved in the solvent.

[0065] In some embodiments of the present application, based on the total mass of the slurry, the total mass of the oxide solid electrolyte and the lithium supplement additive accounts for 10%-30%. For example, it can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, etc., or it can be a range composed of any of the above numerical values. Thus, the total mass of the oxide solid electrolyte and the lithium supplement additive accounts for the above range, which can form a dense porous structure on the surface of the diaphragm under the premise of constructing additional ion transmission channels, promoting ion transmission, and compensating for the loss of active lithium in the first charge and discharge and later cycles, improve the electrolyte affinity and liquid retention of the porous base membrane, reduce the interface impedance, reduce the concentration polarization in the battery, and reduce thermal shrinkage at the same time, prevent the positive and negative electrodes from contacting at high temperatures and causing short circuits, and delay thermal runaway.

[0066] In some embodiments of the present application, the mass ratio of the oxide solid electrolyte and the lithium supplement additive is (2-10): 1. For example, it can be 2: 1, 3: 1, 4: 1, 5: 1, 6: 1, 7: 1, 8: 1, 9: 1, 10: 1, etc., or it can be a range composed of any of the above values. Therefore, by making the mass ratio of the oxide solid electrolyte and the lithium supplement additive within the above range, it is possible to improve the overall ion transmission capacity while ensuring effective lithium supplementation, optimize the wettability and liquid retention of the electrolyte, reduce the interface impedance and battery polarization, and avoid excessive active materials affecting the overall performance of the battery.

[0067] In some embodiments of the present application, based on the total mass of the slurry, the mass proportion of the dispersant is 0.1%-2%. For example, it can be 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, etc., or it can be a range composed of any of the above values. Therefore, by making the mass proportion of the dispersant within the above range, it can assist the oxide solid electrolyte and the lithium supplement additive to be better dispersed in deionized water and oily solvents, which is conducive to the large-scale preparation of diaphragm coating slurry.

[0068] In some embodiments of the present application, based on the total mass of the slurry, the mass proportion of the adhesive is 2%-10%. For example, it can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., or it can be a range composed of any of the above numerical values. In some embodiments of the present application, based on the total mass of the slurry, the mass proportion of the wetting agent is 0.1%-1%. For example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc., or it can be a range composed of any of the above numerical values. Thus, by making the mass proportion of the adhesive and the wetting agent in the above range, the adhesion between the coating and the porous base film can be increased to ensure that the coating will not peel off or fall off during the battery operation process (such as charge and discharge cycles, temperature changes, etc.).

[0069] It should be noted that the present application does not specifically limit the mass proportion of the solvent. The total mass of the oxide solid electrolyte and the lithium supplement additive, the mass of the dispersant, the mass of the adhesive, the mass of the wetting agent and the mass of the solvent is 100%. When the total mass proportion of the oxide solid electrolyte and the lithium supplement additive, the mass proportion of the dispersant, the mass proportion of the adhesive and the mass proportion of the wetting agent are determined respectively, the mass proportion of the solvent can be calculated by subtraction.

[0070] In some embodiments of the present application, the solvent includes but is not limited to at least one of deionized water, N-methylpyrrolidone, N-ethylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, 1,2-dimethoxyethane, dimethyl sulfoxide, diethyl carbonate, ethyl methyl carbonate, tetrahydrofuran, ethanol, ethylene glycol, ethylene glycol dimethyl ether, and isopropanol.

[0071] In some embodiments of the present application, the dispersant includes but is not limited to at least one of polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene glycol, sodium polyacrylate, ammonium polyacrylate, polyacrylamide, carboxylates, and sulfonates.

[0072] In some embodiments of the present application, the adhesive includes but is not limited to at least one of polyacrylic acid, polyvinyl alcohol, polyvinylidene fluoride, polytetrafluoroethylene, carboxymethyl cellulose, carboxymethyl cellulose-sodium, carboxymethyl cellulose-lithium, and styrene-butadiene rubber.

[0073] In some embodiments of the present application, the wetting agent includes but is not limited to at least one of polydimethylsiloxane, polyether modified siloxane, alkylphenol polyoxyethylene ether, alkylamine polyoxyethylene ether, fatty alcohol polyoxyethylene ether, sodium alkylbenzene sulfonate, sodium alkyl sulfate, sodium alkyl phosphate, and sodium alkyl polyoxyethylene ether carboxylate.

[0074] In some embodiments of the present application, reference Figure 3 , the slurry is prepared by the following method:

[0075] S101: First Mixing Process

[0076] In this step, the dispersant and the solvent are subjected to a first mixing process to obtain a first mixed solution, thereby enabling the dispersant to be relatively completely dissolved in the solvent to form a uniform first mixed solution.

[0077] S102: Second Mixing Process

[0078] In this step, the first mixed solution obtained after the first mixing process and the oxide solid electrolyte are subjected to a second mixing process to obtain a second mixed solution, thereby facilitating the more complete dissolution of the oxide solid electrolyte in the first mixed solution.

[0079] S103: Third mixing process and sanding process

[0080] In this step, the second mixed solution obtained after the second mixing process and the lithium supplement additive are first subjected to a third mixing process to form a uniform mixed solution; then the mixed solution is subjected to a sand milling process, so that the particle size D in the third mixed solution is 50 0.1μm-10μm.

[0081] In some embodiments of the present application, the speed of the sand milling treatment is 500rpm-5000rpm. For example, it can be 500rpm, 1000rpm, 1500rpm, 2000rpm, 2500rpm, 3000rpm, 3500rpm, 4000rpm, 4500rpm, 5000rpm, etc., or it can be a range composed of any of the above values. In some embodiments of the present application, the time of the sand milling treatment is 3h-24h. For example, it can be 3h, 5h, 8h, 10h, 13h, 15h, 18h, 20h, 24h, etc., or it can be a range composed of any of the above values. Thus, the particle size D in the third mixed solution can be reduced to 0.1%. 50 Reaching the range of 0.1μm-10μm.

[0082] S104: Fourth mixing process and ultrasonic treatment

[0083] In this step, the third mixed liquid obtained after the third mixing treatment and the sanding treatment, the adhesive and the wetting agent are subjected to a fourth mixing treatment, and then the mixed liquid after the fourth mixing treatment is subjected to ultrasonic treatment to obtain a slurry in which all components are evenly mixed.

[0084] In some embodiments of the present application, the power of the ultrasonic treatment is 2000Hz-20000Hz. For example, it can be 2000Hz, 5000Hz, 8000Hz, 10000Hz, 12000Hz, 15000Hz, 18000Hz, 20000Hz, etc., or it can be the range composed of any of the above numerical values. In some embodiments of the present application, the time of the ultrasonic treatment is 0.5h-3h, for example, it can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, etc., or it can be the range composed of any of the above numerical values. Thus, a uniform slurry can be obtained.

[0085] In some embodiments of the present application, the loading method can be conventional means, as long as the coating can be fixed on the surface of the porous base film. Exemplarily, the loading method can include but is not limited to at least one of spin spraying, dip coating, blade transfer coating, micro-concave roller coating, printing coating, extrusion coating, wire rod coating and vacuum filtration.

[0086] S200: Drying the porous base film with the coating to obtain the separator

[0087] In some embodiments of the present application, the drying process is carried out at 40°C-60°C for 3min-10min. According to an embodiment of the present application, the temperature of the drying process may be 40°C, 45°C, 50°C, 55°C, 60°C, etc., or may be a range consisting of any of the above numerical values. According to an embodiment of the present application, the time of the drying process may be 3min, 5min, 7min, 10min, etc., or may be a range consisting of any of the above numerical values. Thus, it helps to fix the coating on the base film, ensuring that the coating is evenly distributed and not easy to fall off.

[0088] Batteries and electrical devices

[0089] The present application proposes a battery. According to an embodiment of the present application, the battery includes the aforementioned diaphragm or a diaphragm prepared by the aforementioned method. In general, the battery includes an electrolyte, a battery cell, and a packaging material for encapsulating the battery cell. The battery cell includes a positive electrode sheet, a negative electrode sheet, and a diaphragm located between the positive electrode sheet and the negative electrode sheet. The battery can be prepared according to conventional methods in the art, for example, the above-mentioned positive electrode sheet, diaphragm, and negative electrode sheet are stacked in sequence and then wound or stacked into a battery cell, and then the battery cell is encapsulated with a packaging material (such as an aluminum-plastic film, etc.) and injected with an electrolyte, and then vacuum encapsulated, left to stand, formed, shaped, sorted, and other processes to form an electrochemical device.

[0090] Furthermore, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer arranged on the surface of the current collector, the positive electrode active material layer includes a positive electrode active material, a binder, and a conductive agent, wherein the mass percentage of the positive electrode active material is 60%-96%, for example, 60%, 70%, 80%, 90%, 96% or a range consisting of any two thereof; the mass percentage of the conductive agent is 1%-10%, for example, 1%, 2%, 5%, 10% or a range consisting of any two thereof; the mass percentage of the binder is 1%-10%, for example, 1%, 2% , 5%, 10% or any two thereof; wherein the positive electrode active material is selected from one or more of lithium cobalt oxide (LCO), lithium manganese oxide, lithium iron phosphate (LFP), nickel cobalt manganese (NCM) ternary materials, and nickel cobalt aluminum (NCA) layered materials; the positive electrode current collector can be an aluminum foil composed mainly of aluminum, or a composite current collector formed by pressing aluminum foil with other materials (such as polymer materials, etc.), or a composite current collector including aluminum foil and a conductive carbon layer coated on the surface of the aluminum foil, etc., wherein the mass content of aluminum in the aluminum foil is generally not less than 95%.

[0091] For example, in the preparation process of the positive electrode sheet, the positive electrode active material, the binder, and the conductive agent are mixed in a certain weight ratio, and a solvent such as N-methylpyrrolidone (NMP) or water is added, and stirred under the action of a vacuum mixer until the mixed system forms a positive electrode slurry with uniform fluidity; the positive electrode slurry is evenly coated on an aluminum foil with a thickness of 8-15 μm; the aluminum foil coated with the positive electrode slurry is baked and dried in an oven, and then rolled and cut to obtain a positive electrode sheet.

[0092] Further, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the current collector, wherein the negative electrode active material layer includes a negative electrode active material, a binder, and a conductive agent, wherein the mass percentage of the negative electrode active material is 60%-96%, such as 60%, 70%, 80%, 90%, 96% or a range consisting of any two thereof; the mass percentage of the conductive agent is 1%-10%, such as 1%, 2%, 5%, 10% or a range consisting of any two thereof; the mass percentage of the binder is 1%-10%, such as 1%, 2%, 5%, 10% or a range consisting of any two thereof; wherein the negative electrode active material is selected from one or more of artificial graphite, natural graphite, silicon, and silicon dioxide. The negative electrode current collector includes, for example, copper foil, etc.

[0093] For example, in the preparation process of the negative electrode sheet, the negative electrode active material, the conductive agent, and the binder are added to the dispersant to form the negative electrode slurry by a wet process; the negative electrode slurry is evenly coated on a copper foil with a thickness of 4-10 μm; the copper foil coated with the negative electrode slurry is baked and dried in an oven, and then rolled and cut to obtain the negative electrode sheet, wherein the dispersant can be, for example, sodium carboxymethyl cellulose (CMC).

[0094] In the present invention, the conductive agent may include at least one of conductive carbon black (SP), acetylene black, Ketjen black, carbon fiber, etc., and the adhesive may be at least one of polyvinylidene fluoride (PVDF), a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylic acid salt, carboxymethyl cellulose sodium (CMC), polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber (SBR).

[0095] Optionally, the above-mentioned electrolyte may include a non-aqueous electrolyte, whose components may include a non-aqueous solvent and a lithium salt, the non-aqueous solvent includes carbonates and / or carboxylates, such as ethylene carbonate, propylene carbonate, propyl propionate, ethyl propionate; the lithium salt includes lithium hexafluorophosphate (LiPF6) and / or lithium tetrafluoroborate (LiBF4). In addition, the electrolyte may also contain additives, which may be conventional electrolyte additives in the art, such as at least one of lithium trifluoromethyl triethylborate, propenyl-1,3-sultone, and fluoroethylene carbonate.

[0096] The battery of the present application may include a battery cell form, a battery module form and a battery pack form. In some embodiments, the battery cells can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module. In some embodiments, the battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0097] The present application proposes an electrical device. According to an embodiment of the present application, the electrical device includes the aforementioned battery. As mentioned above, the battery has high ionic conductivity, high energy density and good initial charge and discharge efficiency. As a result, the electrical device of the present application has good cycle performance, fast charging performance, and excellent service life and safety performance. Those skilled in the art will understand that the electrical device has all the features and advantages of the aforementioned battery, which will not be elaborated here.

[0098] Battery cells, battery modules, and battery packs can be used as power sources for electrical devices or as energy storage units for electrical devices. Electrical devices may include, but are not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0099] As an electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0100] As an embodiment, the electric device may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electric device for high power and high energy density of the battery, a battery pack or a battery module may be used.

[0101] As another embodiment, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is usually required to be light and thin, and a battery cell may be used as a power source.

[0102] The scheme of the present application will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If no specific technology or conditions are indicated in the embodiments, the technology or conditions described in the literature in this area or the product specification are carried out. The reagents used or the instruments that do not indicate the manufacturer are all conventional products that can be obtained commercially.

[0103] Example 1

[0104] 1. Preparation of coating slurry

[0105] S1. Take 20 mg of sodium polyacrylate dispersant, add 7.75 L of deionized water, and stir at 200 rpm for 30 minutes to obtain dispersion 1;

[0106] S2. Take 1.75 kg of LATP (Li 1.3 Al 0.3 Ti 1.7 (PO4)3) powder was added to dispersion 1 and stirred at 1000 rpm for 1 hour to obtain dispersion 2;

[0107] S3. Take 0.25 kg of Li2O and Co nanocomposite powder (abbreviated as Li2O / Co), add it to dispersion 2, stir at 1000 rpm for 1 hour, and then sand grind at 500 rpm for 2 hours to obtain dispersion 3, the slurry particle size D50 of dispersion 3 is 400 nm;

[0108] S4. Take 20 mg of sodium dodecylbenzene sulfonate wetting agent and 200 mg of carboxymethyl cellulose-sodium (CMC-Na) adhesive, add them to dispersion 3, stir at a speed of 200 rpm for 1 hour, then ultrasonically treat at a frequency of 5000 Hz for 30 minutes, and filter to obtain a coating slurry.

[0109] 2. Preparation of Diaphragm

[0110] The porous base film was selected from a commercial wet-process double-stretched polyethylene diaphragm substrate, with a thickness of 7 μm, a porosity of 42%, and a pore size of 0.05 μm. The above coating slurry was coated on one side of the polyethylene diaphragm substrate (preferably on the side of the porous base film close to the positive electrode) using a micro-concave roll coater, and dried at 50°C for 5 minutes to obtain a composite diaphragm. The surface density of the coating layer was 1.5 g / cm 2 , the coating thickness is 2μm.

[0111] Example 2

[0112] A diaphragm was prepared according to the method described in Example 1, except that, in step S2, 1.25 kg of LATP powder was taken and added to dispersion 1.

[0113] Example 3

[0114] A diaphragm was prepared according to the method described in Example 1, except that, in step S2, 2.5 kg of LATP powder was taken and added to dispersion 1.

[0115] Example 4

[0116] A diaphragm was prepared according to the method described in Example 1, except that, in step S2, 0.25 kg of LATP powder was taken and added to dispersion 1.

[0117] Example 5

[0118] A diaphragm was prepared according to the method described in Example 1, except that, in step S2, 3.75 kg of LATP powder was taken and added to dispersion 1.

[0119] Example 6

[0120] The diaphragm was prepared according to the method described in Example 1, except that in step S2, 1.75 kg of LLZO (Li7La3Zr2O 12 ) powder and add it to dispersion 1.

[0121] Example 7

[0122] The separator was prepared according to the method described in Example 1, except that in step S2, 1.75 kg of LLTO (Li 0.48 La 0.505 TiO3) powder, added to dispersion 1.

[0123] Example 8

[0124] A diaphragm was prepared according to the method described in Example 1, except that, in step S3, 0.25 kg of nanocomposite powder formed by Li2S and Co (abbreviated as Li2S / Co) was taken and added to the dispersion 2.

[0125] Example 9

[0126] The separator was prepared according to the method described in Example 1, except that, in step S3, 0.25 kg of nanocomposite powder formed by LiF and Co (abbreviated as LiF / Co) was taken and added to the dispersion 2.

[0127] Example 10

[0128] A separator was prepared according to the method described in Example 1, except that the coating thickness was 1 μm.

[0129] Embodiment 11

[0130] A separator was prepared according to the method described in Example 1, except that the coating thickness was 3 μm.

[0131] Example 12

[0132] A separator was prepared according to the method described in Example 1, except that the coating thickness was 5 μm.

[0133] Example 13

[0134] A separator was prepared according to the method described in Example 1, except that the coating thickness was 8 μm.

[0135] Embodiment 14

[0136] The diaphragm was prepared according to the method described in Example 1, except that the porous base membrane was selected from a circular commercial polyethylene membrane with a diameter of 4 cm, and the porous base membrane had a thickness of 10 μm, a porosity of 37%, and a pore size of 0.05 μm.

[0137] Embodiment 15

[0138] The diaphragm was prepared according to the method described in Example 1, except that the porous base membrane was selected from a circular commercial polypropylene membrane with a diameter of 4 cm, and the porous base membrane had a thickness of 12 μm, a porosity of 50%, and a pore size of 0.1 μm.

[0139] Comparative Example 1

[0140] The comparative example diaphragm adopts the commercial wet-process double-stretched polyethylene diaphragm substrate described in Example 1 without any modification.

[0141] Comparative Example 2

[0142] In this comparative example, the coating slurry contains only oxide solid electrolyte, solvent and adhesive, and the specific process of preparing the coating slurry is as follows:

[0143] S1. Take 20 mg of sodium polyacrylate dispersant, add 7.75 L of deionized water, and stir at 200 rpm for 30 minutes to obtain dispersion 1;

[0144] S2. Take 1.75 kg of LATP powder and add it to dispersion 1, and stir at 1000 rpm for 1 hour to obtain dispersion 2;

[0145] S3. Take 20 mg of sodium dodecylbenzene sulfonate wetting agent and 200 mg of carboxymethyl cellulose-sodium (CMC-Na) binder, add them to dispersion 2, stir at a speed of 200 rpm for 1 hour, then ultrasonically treat at a frequency of 5000 Hz for 30 minutes, and filter to obtain a coating slurry.

[0146] Comparative Example 3

[0147] In this comparative example, the coating slurry only contains a lithium supplement additive (nanocomposite powder formed by Li2O and Co), a solvent and a binder. The specific process of preparing the coating slurry is as follows:

[0148] S1. Take 20 mg of sodium polyacrylate dispersant, add 7.75 L of deionized water, and stir at 200 rpm for 30 minutes to obtain dispersion 1;

[0149] S2. Take 0.25 kg of Li2O and Co nanocomposite powder, add it to dispersion 1, stir at 1000 rpm for 1 hour, and then sand grind at 500 rpm for 2 hours to obtain dispersion 2, the slurry particle size D50 of dispersion 2 is 400 nm;

[0150] S3. Take 20 mg of sodium dodecylbenzene sulfonate wetting agent and 200 mg of carboxymethyl cellulose-sodium (CMC-Na) binder, add them to dispersion 2, stir at a speed of 200 rpm for 1 hour, then ultrasonically treat at a frequency of 5000 Hz for 30 minutes, and filter to obtain a coating slurry.

[0151] The differences between the diaphragms prepared in Examples 1-15 and Comparative Examples 1-3 are shown in Table 1.

[0152] Table 1

[0153]

[0154]

[0155] Detection and analysis

[0156] 1. SEM morphology analysis

[0157] The surface of the diaphragm prepared in Example 1 was observed using a scanning electron microscope (SEM). Figure 4 As shown, it can be seen that the nanocomposite particles formed by the LATP solid electrolyte particles and Li2O and Co form a dense and uniform porous coating on the polyethylene membrane substrate and cover most of the pores on the membrane substrate.

[0158] The surface microstructure of the membranes prepared in Examples 2-15 was analyzed by scanning electron microscopy. As shown in the above results, it can be seen that the oxide solid electrolyte particles and lithium supplement additive particles formed a dense and uniform porous coating on the polyethylene membrane substrate, covering most of the holes on the membrane substrate.

[0159] 2. Determination of physical properties of diaphragm

[0160] The liquid absorption rate and heat shrinkage test were performed on Examples 1-15 and Comparative Examples 1-3. The specific process is as follows:

[0161] The liquid absorption rate test includes the following steps: Take a diaphragm sample and weigh it, which is recorded as m1. Place the sample in the electrolyte, seal it and soak it for 1 hour, then take it out, wipe the electrolyte on the surface of the sample with a dust-free cloth, weigh it and record it as m2. Liquid absorption rate = ((m2-m1) / m1)×100%.

[0162] Heat shrinkage test: refer to GB / T 36363-2018. Cut a 320mm x 120mm sample in the width direction of the film roll, lay it flat on a piece of quantitative filter paper, press it with another piece of quantitative filter paper, put it in a blast thermostatic box, heat it at 130℃ for 1 hour, and then take it out. That is, the length before heating is L1, the length after heating is L2, and the shrinkage rate after heating S = ((L1-L2) / L1)×100%.

[0163] The experimental results are shown in Table 2. Comparative analysis shows that compared with the diaphragm substrate (Comparative Example 1), the diaphragm coated with oxide solid electrolyte or lithium supplement additive (Comparative Examples 2 and 3), or coated with oxide solid electrolyte and lithium supplement additive (Examples 1-15) slurry at the same time, has a significantly increased liquid absorption rate. This phenomenon shows that the above-mentioned lithium supplement coating can effectively improve the electrolyte affinity of commercial polyethylene diaphragms. In addition, compared with the diaphragm substrate of the comparative example and the diaphragm coated with only one of the materials of the oxide solid electrolyte and the lithium supplement additive slurry, the diaphragm coated with a suitable proportion of oxide solid electrolyte and lithium supplement additive composite slurry in the embodiment has a significantly reduced thermal shrinkage after heating at 130°C for 1 hour, indicating that the lithium supplement coating also has a positive effect on the high temperature stability of commercial polyethylene diaphragms.

[0164] Table 2

[0165]

[0166]

[0167] 3. Electrochemical testing

[0168] 1) Assemble Examples 1-15 and Comparative Examples 1-3 into soft-pack lithium-ion batteries. The positive electrode is lithium nickel cobalt manganese oxide (NCM) 613, the negative electrode is graphite, and the electrolyte is a mixed solvent of ethylene glycol carbonate (EC) and diethylene glycol carbonate (DEC) in a volume ratio of 1:1, containing 1.0M LiPF6 and 10wt% fluoroethylene carbonate (FEC). In an environment of 25±2°C, the prepared soft-pack battery is tested for capacity. First, it is allowed to stand for 30 minutes, then charged to 4.3V at a constant current of 0.5C, and then charged to 0.05C at a constant voltage to obtain the first charging capacity C0; it is allowed to stand for 10 minutes; and then discharged to 2.5V at a constant current of 0.5C to obtain the first discharge capacity C1. The first coulomb efficiency is C1 / C0.

[0169] The experimental results are shown in Table 3. Compared with the diaphragm matrix of the comparative example and the diaphragm coated with only one of the oxide solid electrolyte and the lithium supplement additive slurry, the diaphragm coated with both the oxide solid electrolyte and the lithium supplement additive composite slurry in the embodiment significantly improves the first coulomb efficiency of the soft-pack lithium-ion battery. This shows that the diaphragm of the present application makes up for the active lithium lost in the SEI film formation during the first charge and discharge, and improves the effective capacity of the battery.

[0170] Table 3

[0171] Group <![CDATA[C0(mAh)]]> <![CDATA[C1(mAh)]]> First coulombic efficiency Example 1 2239 1950 87.1％ Example 2 2359 2064 87.5％ Example 3 2393 2106 88％ Example 4 2266 1974 87.1％ Example 5 2324 1989 85.6％ Example 6 2276 1985 87.2％ Example 7 2221 1930 86.9％ Example 8 2363 1953 86.3％ Example 9 2242 1951 87％ Example 10 2183 1871 85.7％ Embodiment 11 2297 2010 87.5％ Example 12 2387 2093 87.7％ Example 13 2298 1958 85.2％ Embodiment 14 2146 1873 87.3％ Embodiment 15 2205 1923 87.2％ Comparative Example 1 2166 1835 84.7％ Comparative Example 2 2230 1898 85.1％ Comparative Example 3 2376 1986 83.6％

[0172] The diaphragms prepared in Examples 1-15 and Comparative Examples 1-3 were cut into discs with a diameter of 19 mm using a punching machine and assembled into Li|Li symmetrical batteries. The metal lithium sheets were cut into discs with a diameter of 1 cm to serve as the positive and negative electrodes of the battery. Using an electrolyte (a mixed solvent of ethylene glycol carbonate (EC) and diethylene glycol carbonate (DEC) with a volume ratio of 1:1, containing 1.0 M LiPF6 and 10 wt % fluoroethylene carbonate (FEC)), a stainless steel 2032 button battery shell and accessories, under an argon atmosphere, the diaphragms prepared in Examples 1-15 and Comparative Examples 1-3 were assembled into 2032 button batteries. Using a Newway multi-channel battery tester (BTS-600), at 1 mA / cm 2 The surface current density and 1mAh / cm 2 The lithium insertion and extraction behavior of Li‖Li symmetric battery was tested at the surface capacity.

[0173] The charge and discharge time-voltage curves of the Li / Li symmetrical batteries of Example 1 and Comparative Example 1 are shown in FIG. Figure 5 As shown. For the button battery assembled using the diaphragm described in Example 1, the activation time is 80 hours before the cycle, and the polarization continues to decrease; for the button battery assembled using the polyethylene diaphragm matrix described in Comparative Example 1, no obvious activation process is observed. For the button battery assembled using the polyethylene diaphragm matrix described in Comparative Example 1, the overpotential increases significantly after about 50 hours of charge and discharge cycles; after about 95 hours of cycling, an overpotential of about 100 mV is observed. In comparison, for the button battery assembled using the diaphragm described in Example 1, the overpotential is less than 100 mV even after 230 hours of cycling. The above results indicate that providing a lithium-replenishing coating comprising a LATP solid electrolyte and a nanocomposite material formed by Li2O and Co as the main material on a commercial polyethylene diaphragm can effectively reduce polarization and improve electrochemical stability.

[0174] The remaining results are shown in Table 4. Compared with the diaphragm substrate of the comparative example and the diaphragm coated only with the lithium replenishing additive slurry, the diaphragm coated only with the oxide solid electrolyte, or coated with the oxide solid electrolyte and the lithium replenishing additive composite slurry at the same time, can reduce the overpotential after the symmetric battery cycle.

[0175] Table 4

[0176] Cycle time (h) Overpotential(mV) Example 1 200 78 Example 2 200 69 Example 3 200 91 Example 4 200 100 Example 5 200 86 Example 6 200 58 Example 7 200 84 Example 8 200 93 Example 9 200 76 Example 10 150 94 Embodiment 11 200 67 Example 12 200 55 Example 13 200 89 Embodiment 14 200 65 Embodiment 15 200 104 Comparative Example 1 100 106 Comparative Example 2 200 85 Comparative Example 3 150 112

[0177] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A diaphragm, characterized in that: include: A porous base membrane and a coating, wherein the coating is disposed on at least one surface of the porous base membrane; The coating comprises an oxide solid electrolyte and a lithium supplement additive; The oxide solid electrolyte includes at least one of a sodium fast ion conductor solid electrolyte, a garnet solid electrolyte, and a perovskite solid electrolyte; The lithium supplement additive comprises a complex formed by a binary lithium-containing compound and a transition metal.

2. The diaphragm according to claim 1, characterized in that The mass ratio of the oxide solid electrolyte to the lithium supplement additive is (2-10):

1.

3. The diaphragm according to claim 1, characterized in that The coating has a thickness of 0.01 μm-5 μm.

4. The diaphragm according to any one of claims 1 to 3, characterized in that: Meet one or more of the following: The sodium fast ion conductor type solid electrolyte comprises at least one of lithium aluminum titanium phosphate and lithium aluminum germanium phosphate; The garnet-type solid electrolyte includes at least one of lithium lanthanum zirconium oxide, lithium lanthanum niobium oxide, lithium lanthanum zirconium niobium oxide, and lithium lanthanum zirconium tantalum oxide; The perovskite-type solid electrolyte includes lithium lanthanum titanium oxide; The binary lithium-containing compound includes at least one of Li2O, Li2S, LiF, and Li3N; The transition metal includes at least one of Fe, Co and Ni.

5. The diaphragm according to claim 1, characterized in that The thickness of the porous base film is 5 μm-20 μm; The porosity of the porous base film is 30% to 50%; The pore size of the porous base membrane is 0.01 μm-0.3 μm.

6. A method for preparing the diaphragm according to any one of claims 1 to 5, characterized in that: include: Loading a slurry containing an oxide solid electrolyte and a lithium supplement additive on at least one surface of the porous base film to form a coating; The porous base film having the coating layer is dried to obtain the separator.

7. The method according to claim 6, characterized in that The slurry further includes a solvent, a dispersant, a binder and a wetting agent.

8. The method according to claim 7, characterized in that Based on the total mass of the slurry, the total mass of the oxide solid electrolyte and the lithium supplement additive accounts for 10%-30%; Based on the total mass of the slurry, the mass proportion of the dispersant is 0.1%-2%; Based on the total mass of the slurry, the mass proportion of the adhesive is 2%-10%; Based on the total mass of the slurry, the mass proportion of the wetting agent is 0.1%-1%.

9. The method according to claim 8, characterized in that The slurry is prepared by the following method: Performing a first mixing process on the dispersant and the solvent to obtain a first mixed liquid; Performing a second mixing process on the first mixed solution and the oxide solid electrolyte to obtain a second mixed solution; The second mixed solution and the lithium supplement additive are subjected to a third mixing process and a sand milling process to obtain a third mixed solution; The third mixed liquid, the adhesive and the wetting agent are subjected to a fourth mixing treatment and an ultrasonic treatment to obtain the slurry.

10. The method according to claim 9, characterized in that The rotation speed of the sand grinding process is 500rpm-5000rpm; The sanding treatment time is 3h-24h; The power of the ultrasonic treatment is 2000Hz-20000Hz; The ultrasonic treatment time is 0.5h-3h.

11. A battery, characterized in that: The invention comprises the diaphragm described in any one of claims 1 to 5 or the diaphragm prepared by the method described in any one of claims 6 to 10.

12. An electrical device, characterized in that: Comprising the battery of claim 11.

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