A battery and an electric device

Abstract

The application belongs to the technical field of batteries, and discloses a battery and a power consumption device. The battery comprises a positive electrode sheet and a diaphragm, wherein the diaphragm comprises a base film and a coating layer arranged on the surface of the base film and facing the positive electrode sheet, and the battery satisfies the condition that the SOC when the battery is overcharged and short-circuited is greater than 130% at 25 DEG C and with a current density of 1 / 3 C. The coating layer arranged on the base film blocks lithium dendrite from piercing the diaphragm, thereby improving the overcharge prevention performance of the battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more particularly to a battery and an electrical device. Background Technology

[0002] In recent years, with the increasingly severe global warming caused by the greenhouse effect, people have paid increasing attention to the issue of greenhouse gas emission reduction. Carbon dioxide, as one of the most important components of greenhouse gases, has prompted many countries to introduce policies to reduce carbon dioxide emissions and promote the rapid development of green energy. Lithium-ion batteries, as an important green energy storage method, are widely used in smart electronic products, new energy vehicles, and other fields due to their advantages such as high energy density and long cycle life. Especially in the field of new energy vehicles, many countries have formulated plans to ban the sale of gasoline-powered vehicles, further promoting the large-scale application of lithium-ion batteries in new energy vehicles.

[0003] Lithium-ion batteries are a core component of new energy vehicles, and their safety performance directly impacts the safety of these vehicles and their occupants. Current statistics show that the majority of electric vehicle fires are battery-related, with over 35% of these battery-related incidents linked to overcharging. Overcharging increases polarization, leading to a series of problems, including lithium dendrites depositing at the anode. These dendrites can puncture the separator, causing short circuits and potentially even fires or explosions. Summary of the Invention

[0004] Therefore, embodiments of this application provide a battery and an electrical device designed to improve the battery's overcharge protection performance, prevent lithium dendrites from piercing the separator, and improve the safety performance of lithium-ion batteries.

[0005] In one aspect, this application provides a battery.

[0006] This application is achieved through the following technical solution:

[0007] A battery includes a positive electrode and a separator, the separator including a base film and a coating disposed on the surface of the base film facing the positive electrode, the battery satisfying that: when charged at 25°C with a current density of 1 / 3C, the state of charge (SOC) of the battery during overcharge and short circuit is greater than 130%.

[0008] In a preferred embodiment of this application, the battery may be further configured to satisfy the following: when charged at 25°C with a current density of 1 / 3C, the state of charge (SOC) of the battery during overcharge and short circuit is greater than or equal to 150%.

[0009] In a preferred embodiment of this application, the coating may be further configured to include an oxidant, which includes a compound capable of undergoing a redox reaction with metallic lithium.

[0010] In a preferred embodiment of this application, the compound capable of undergoing a redox reaction with metallic lithium may be further configured to include one or a mixture of several of sodium thiosulfate, sodium hypochlorite, sodium perborate, iodine, and sodium persulfate.

[0011] In a preferred embodiment of this application, the coating may further include ceramic particles, which may be one or a mixture of several of alumina, magnesium oxide, silicon dioxide, zirconium oxide, titanium dioxide, and hydrotalcite.

[0012] In a preferred embodiment of this application, the coating thickness may be further set to 0.5–5.0 μm.

[0013] In a preferred embodiment of this application, the oxidant content per unit area in the coating may be further set to 0.05-2.5 mg / cm². 2 .

[0014] In a preferred embodiment of this application, the membrane may be further configured such that, after heat treatment at 100°C for 2 hours, the longitudinal shrinkage rate of the membrane is less than 2.5%.

[0015] In a preferred embodiment of this application, the needle penetration strength of the diaphragm may be further configured to be 300-500 gf.

[0016] Secondly, this application provides an electrical appliance.

[0017] This application is achieved through the following technical solution:

[0018] An electrical device comprising the battery described in the first aspect above.

[0019] In summary, compared with the prior art, the beneficial effects of the technical solution provided by the embodiments of this application include at least the following: By providing a coating on the surface of the base film facing the positive electrode, the SOC of the battery at 25°C and 1 / 3 current density during overcharge short circuit is greater than 130%. Coating the base film with a certain thickness of coating ensures the thermal stability of the separator, guarantees good structural stability of the separator even when the lithium-ion battery experiences overcharge temperature rise, and improves the overcharge protection capability of the lithium-ion battery. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of lithium dendrite growth on a separator, provided as an exemplary embodiment of this application. Detailed Implementation

[0021] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] Furthermore, the term "and / or" in this application is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this application, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0024] In this application, the terms "first," "second," etc., are used to distinguish identical or similar items with essentially the same function. It should be understood that there is no logical or temporal dependency between "first," "second," and "nth," nor are there any restrictions on quantity or execution order.

[0025] The battery and electrical device of this application are described in detail below.

[0026] First, it is explained that the battery provided in this application includes a positive electrode and a separator, wherein the separator includes a base film and a coating applied to one surface of the base film, the coating being applied to the side of the base film facing the positive electrode; the battery satisfies the requirement that when charged at 25°C with a current density of 1 / 3C, the SOC of the battery during overcharge and short circuit is greater than 130%.

[0027] The base membrane used is at least one of polyethylene membrane, polypropylene membrane, polyvinylidene fluoride membrane, and polyimide membrane, but is not limited to these materials. It can be a single-layer base membrane material or a combination of the above materials. Specifically, it can be a single-layer polyethylene membrane, a single-layer polypropylene membrane, a single-layer polyvinylidene fluoride membrane, a single-layer polyimide membrane, or a polyethylene / polypropylene / polyethylene membrane composite membrane. These membrane materials are relatively inexpensive, possess certain mechanical and processing strength, and have appropriate porosity to ensure rapid lithium-ion transport during charging and discharging of the lithium-ion battery.

[0028] The porosity of the base membrane is 40%-60%, which can be 40%, 45%, 50%, 55%, or 60%. A suitable porosity can ensure that the lithium-ion battery using this membrane has good lithium-ion transport capability.

[0029] The average pore size of the base film is 0.01 μm-0.3 μm. Preferably, the average pore size is 0.01 μm-0.1 μm, and can be 0.01 μm, 0.02 μm, 0.03 μm, 0.04 μm, 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, or 1.0 μm. When the average pore size is less than 0.01 μm, the lithium-ion transport capacity between the positive and negative electrodes will be affected during the charging and discharging process of the lithium-ion battery, affecting the kinetic performance of the lithium-ion battery. When the average pore size is too large, greater than 0.3 μm, lithium dendrites can easily pierce the separator and cause a short circuit when the battery is overcharged. An average pore size of 0.01 μm-0.3 μm in the base film can ensure good lithium-ion transport capacity.

[0030] In some embodiments of this application, the battery is charged at 25°C with a current density of 1 / 3C, and the state of charge (SOC) at the time of overcharge and short circuit is greater than or equal to 150%. For example, the SOC at the time of overcharge and short circuit is 155%, 160%, 170%, 180%, 185%, 190%, or 195%.

[0031] In some embodiments of this application, the coating disposed on the surface of the base film includes an oxidant, which comprises a compound capable of undergoing a redox reaction with metallic lithium. The compound capable of undergoing a redox reaction with metallic lithium includes one or a mixture of several of sodium thiosulfate (Na₂S₂O₃), sodium hypochlorite (NaClO), sodium perborate (NaBO₃), iodine (I₂), and sodium persulfate (Na₂S₂O₈), but is not limited thereto. For example, the chemical reaction formula between sodium thiosulfate and metallic lithium is: Na₂S₂O₃ + 2Li = Na₂SO₃ + Li₂S; the chemical reaction formula between sodium hypochlorite and metallic lithium is: NaClO + 2Li = NaCl + Li₂O; the chemical reaction formula between iodine and metallic lithium is: I₂ + 2Li = 2LiI; and the chemical reaction formula between sodium persulfate and metallic lithium is: Na₂S₂O₈ + 2Li = Na₂SO₄ + Li₂S.

[0032] In this application, as Figure 1As shown, when an oxidant coating is applied to the surface of the base film and this separator is used in a lithium-ion battery, if the lithium-ion battery is overcharged, excessive lithium ions will be embedded in the negative electrode, resulting in lithium dendrites. Upon contact with the oxidant on the separator, the oxidant can undergo a redox reaction, converting the metallic lithium in the lithium dendrites into insulating species. This effectively prevents the lithium dendrites from piercing the separator, avoiding short circuits and thus preventing dangerous accidents such as fires or explosions. Simultaneously, coating the base film with an oxidant coating can effectively improve the thermal stability of the base film, preventing significant thermal shrinkage due to the continuous rise in internal temperature of the lithium-ion battery when overcharged.

[0033] In some embodiments of this application, the coating also includes ceramic particles. The oxidant and ceramic particles are mixed to coat the ceramic particles with the oxidant, and then coated onto the base film. The ceramic particles used include, but are not limited to, one or a mixture of several of alumina (Al₂O₃), magnesium oxide (MgO), silicon dioxide (SiO₂), zirconium oxide (ZrO₂), titanium dioxide (TiO₂), and hydrotalcite. The ceramic particles have a particle size of 100nm-125nm. The oxidant is coated onto the surface of the ceramic particles and then applied to the surface of the base film. This effectively improves the dispersibility of the oxidant, ensuring it is uniformly dispersed on the base film surface and reducing its aggregation. During overcharging, the uniformly dispersed oxidant on the base film can effectively react with lithium dendrites to increase its utilization rate. Simultaneously, it prevents oxidant buildup from clogging the pores of the base film, thus avoiding interference with lithium-ion transport during charging and discharging. Furthermore, the ceramic particles enhance the mechanical strength of the composite separator, preventing lithium dendrites from piercing the separator during overcharging.

[0034] When preparing an oxidant coating using a mixture of oxidant and ceramic particles, the total mass of the mixture is used as a reference, with the oxidant loading ratio ranging from 25% to 50%. For example, the oxidant loading ratio can be 25%, 30%, 35%, 40%, 45%, or 50%.

[0035] In some embodiments of this application, the coating thickness is 0.5 μm-5.0 μm. This aims to achieve better overcharge protection while maintaining lithium-ion battery capacity. If the coating thickness is too small, the improvement in overcharge protection is poor; however, if the coating thickness is too large, it will sacrifice the ion-conducting ability of the separator and increase the separator's mass, thus reducing the energy density of the battery using the separator.

[0036] In some embodiments of this application, the content of oxidant per unit area in the coating is 0.05-2.5 mg / cm². 2 .

[0037] In some embodiments of this application, the separator is heat-treated at 100°C for 2 hours, and the shrinkage rate of the separator before and after the heat treatment is measured. The longitudinal shrinkage rate of the separator is less than 2.5%. Ordinary separators exhibit significant shrinkage at high temperatures, with severe shrinkage at the edges, which may lead to direct contact between the positive and negative electrodes of the battery, resulting in a serious internal short circuit and thermal runaway. In contrast, the coated separator in this application exhibits better high-temperature resistance, with both lateral and longitudinal shrinkage rates being smaller as the temperature rises. This results in less separator deformation, reducing the risk of short circuits or fires and improving the safety performance of batteries using this separator.

[0038] In some embodiments of this application, the needle penetration strength of the coated separator is 300-500 gf. This separator has high mechanical strength, which can prevent lithium dendrites generated during overcharging from piercing the separator, thus avoiding the risk of short circuits or fires and providing better overcharge protection.

[0039] Methods for preparing the diaphragm:

[0040] This application provides a method for preparing the above-mentioned diaphragm, comprising the following steps:

[0041] Step a: Add a certain amount of oxidant and solvent to a mixing tank and stir to prepare a slurry;

[0042] Alternatively, a certain amount of oxidant and solvent can be added to a mixing tank, followed by ceramic particles, and all materials can be mixed to form a slurry.

[0043] Step b: The slurry prepared in step a is coated onto one surface of the base film facing the positive electrode using a coating machine, and then dried at a temperature of 50℃-90℃ to obtain a coated separator.

[0044] The solvents used in the preparation of the slurry include one or a mixture of two of the following: N-methylpyrrolidone, tetrahydrofuran, methyl ethyl ketone, dimethylformamide, dimethylacetamide, tetramethylurea, tetramethyl phosphate, acetone, dichloromethane, chloroform, dimethylamide, cyclohexane, water, or ethanol.

[0045] Preparation method of positive electrode sheet: Positive electrode active material, conductive agent, and binder are added to a mixing tank according to a certain weight percentage, and an appropriate amount of solvent (N-methylpyrrolidone) is added for stirring and viscosity adjustment to obtain a positive electrode active slurry. The positive electrode active slurry is coated onto aluminum foil, dried, rolled, and cut to obtain the positive electrode sheet. The positive electrode active material can be one or a mixture of two of the following: ternary positive electrode material, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, or lithium nickel manganese oxide.

[0046] Preparation method of negative electrode sheet: The negative electrode active material, conductive agent and binder are added to a mixing tank according to a certain weight percentage, and an appropriate amount of pure water is added for stirring and viscosity adjustment to obtain a negative electrode active slurry. The negative electrode active slurry is coated on copper foil, dried, rolled and cut to obtain the negative electrode sheet. Among them, the negative electrode active material is graphite and / or silicon carbide.

[0047] Electrolyte preparation method: Dissolve 1 mol / L lithium salt (LiPF6) in a mixed solvent of ethyl carbonate (EC) and dimethyl carbonate (DMC), EC:DMC = 1:1 (volume ratio).

[0048] Battery preparation: The positive electrode, separator, and negative electrode prepared above are wound into a cell in sequence, wherein the coated side of the separator faces the positive electrode side. The cell is assembled in the cell shell, dried, injected with electrolyte, and welded and packaged to obtain the battery.

[0049] According to a second aspect of this application, an electrical device is provided, including the aforementioned battery. This electrical device can be a power tool, an electric vehicle, or an energy storage device for a smart grid or communication base station, but is not limited thereto.

[0050] The technical solution of this application will be further illustrated below through specific embodiments. Those skilled in the art should understand that the following embodiments are merely for the purpose of helping to understand the present invention and are not intended to limit the scope of the invention.

[0051] Example 1

[0052] Preparation of the diaphragm:

[0053] Sodium thiosulfate (an oxidant) and water (a solvent) were added to a mixing tank and stirred to prepare a slurry. The slurry was then coated onto one surface of a polyethylene membrane (average pore size 0.1 μm, porosity 45%) using a coating machine. The membrane was then transferred to an oven and dried at 60°C for 6 hours to obtain a diaphragm. The thickness of the coating was 0.5 μm.

[0054] Positive electrode sheet:

[0055] LiNi, the positive electrode active material 0.6 Co 0.2 Mn 0.2 O2, conductive carbon black, and PVDF binder are added to a mixing tank in a ratio of 96%:3%:1%, and an appropriate amount of N-methylpyrrolidone is added for stirring and viscosity adjustment to obtain a positive electrode active slurry. The positive electrode active slurry is coated on aluminum foil, and after drying, rolling, and cutting, a positive electrode sheet is obtained.

[0056] Negative electrode plate:

[0057] The negative electrode active material (graphite), conductive carbon black, and styrene-butadiene rubber latex binder are added to a mixing tank in a ratio of 95%:2.5%:2.5%, and an appropriate amount of purified water is added for stirring and viscosity adjustment to obtain a negative electrode active slurry. The negative electrode active slurry is coated on copper foil, dried, rolled, and cut to obtain a negative electrode sheet.

[0058] Electrolyte: The solvent is a mixture of ethyl carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 1:1, and the lithium salt is 1 mol / L LiPF6.

[0059] Battery manufacturing:

[0060] The above-prepared positive electrode, separator, and negative electrode are wound in sequence to form a bare cell, wherein the coated side of the separator faces the positive electrode side. The bare cell is assembled into a cell shell, dried, injected with electrolyte, and welded and packaged to obtain a battery.

[0061] Example 2

[0062] The positive electrode, negative electrode, and electrolyte are set up in the same way as in Example 1. The difference is that the separator is different. In this example, the coating thickness is 1.0 μm.

[0063] Example 3

[0064] The positive electrode, negative electrode, and electrolyte are set up in the same way as in Example 1. The difference is that the coating thickness is 2.5 μm.

[0065] Example 4

[0066] The positive electrode, negative electrode, and electrolyte are set up in the same way as in Example 1. The difference is that the coating thickness is 5.0 μm.

[0067] Example 5

[0068] The positive electrode, negative electrode, and electrolyte are set up in the same way as in Example 1. The difference lies in the preparation of the separator. In this example, the separator is prepared as follows:

[0069] Oxidant I2 was dissolved in chloroform and added to a mixing tank to prepare a slurry. The slurry was then coated onto one surface of a polyethylene membrane (average pore size 0.1 μm, porosity 45%) using a coating machine. The membrane was then transferred to an oven and dried at 60°C for 6 hours to obtain a diaphragm. The coating thickness was 0.5 μm.

[0070] Example 6

[0071] The positive electrode, negative electrode, and electrolyte are set up in the same way as in Example 1. The difference lies in the preparation of the separator. In this example, the separator is prepared as follows:

[0072] Oxidant I2 was dissolved in chloroform and added to a mixing tank to prepare a slurry. The slurry was then coated onto one surface of a polyethylene-based membrane (average pore size 0.1 μm, porosity 45%) using a coating machine. The membrane was then transferred to an oven and dried at 60°C for 6 hours to obtain a diaphragm. The coating thickness was 1.0 μm.

[0073] Example 7

[0074] The positive electrode, negative electrode, and electrolyte are set up in the same way as in Example 1. The difference lies in the preparation of the separator. In this example, the separator is prepared as follows:

[0075] Oxidant I2 was dissolved in chloroform and added to a mixing tank to prepare a slurry. The slurry was then coated onto one surface of a polyethylene membrane (average pore size 0.1 μm, porosity 45%) using a coating machine. The membrane was then transferred to an oven and dried at 60°C for 6 hours to obtain a diaphragm. The coating thickness was 2.5 μm.

[0076] Example 8

[0077] The positive electrode, negative electrode, and electrolyte are set up in the same way as in Example 1. The difference lies in the preparation of the separator. In this example, the separator is prepared as follows:

[0078] Oxidant I2 was dissolved in chloroform and added to a mixing tank to prepare a slurry. The slurry was then coated onto one surface of a polyethylene membrane (average pore size 0.1 μm, porosity 45%) using a coating machine. The membrane was then transferred to an oven and dried at 60°C for 6 hours to obtain a diaphragm. The coating thickness was 5.0 μm.

[0079] Example 9

[0080] The positive electrode, negative electrode, and electrolyte are set up in the same way as in Example 1. The difference lies in the preparation of the separator. In this example, the separator is prepared as follows:

[0081] Sodium thiosulfate (an oxidant) and water (a solvent) were added to a stirred tank, followed by alumina particles (average particle size 100 nm). All materials were stirred to form a slurry. The prepared slurry was then coated onto one surface of a polyethylene membrane (average pore size 0.1 μm, porosity 45%) using a coating machine. The membrane was then transferred to an oven and dried at 60°C for 6 hours to obtain a diaphragm. The coating thickness was 2.5 μm.

[0082] Example 10

[0083] The positive electrode, negative electrode, and electrolyte are set up in the same way as in Example 1. The difference lies in the preparation of the separator. In this example, the separator is prepared as follows:

[0084] Iodine, an oxidizing agent, was dissolved in chloroform and added to a stirred tank. Alumina particles (average particle size 100 nm) were then added, and all materials were stirred to form a slurry. The prepared slurry was coated onto one surface of a polyethylene-based membrane (average pore size 0.1 μm, porosity 45%) using a coating machine. The membrane was then transferred to an oven and dried at 60°C for 6 hours to obtain a diaphragm. The thickness of the coating was 2.5 μm.

[0085] Example 11

[0086] The positive electrode, negative electrode, and electrolyte are set up in the same way as in Example 1. The difference lies in the preparation of the separator. In this example, the separator is prepared as follows:

[0087] Sodium thiosulfate (an oxidant) and water (a solvent) were added to a mixing tank, followed by hydrotalcite particles (average particle size 100 nm). All materials were stirred to form a slurry. The prepared slurry was then coated onto one surface of a polyethylene membrane (average pore size 0.1 μm, porosity 45%) using a coating machine. The membrane was then transferred to an oven and dried at 60°C for 6 hours to obtain a diaphragm. The coating thickness was 2.5 μm.

[0088] Example 12

[0089] The positive electrode, negative electrode, and electrolyte are set up in the same way as in Example 1. The difference lies in the preparation of the separator. In this example, the separator is prepared as follows:

[0090] Iodine, an oxidizing agent, was dissolved in chloroform and added to a stirred tank. Hydrotalcite particles (average particle size 100 nm) were then added, and all materials were stirred to form a slurry. The prepared slurry was coated onto one surface of a polyethylene-based membrane (average pore size 0.1 μm, porosity 45%) using a coating machine. The membrane was then transferred to an oven and dried at 60°C for 6 hours to obtain a diaphragm. The thickness of the coating was 2.5 μm.

[0091] Example 13

[0092] The positive electrode, negative electrode, and electrolyte settings are the same in this embodiment as in Embodiment 3. The difference is that the oxidant in the membrane coating is sodium hypochlorite.

[0093] Example 14

[0094] The positive electrode, negative electrode, and electrolyte settings in this embodiment are the same as those in Embodiment 3. The difference is that the oxidant in the membrane coating is sodium perborate.

[0095] Example 15

[0096] The positive electrode, negative electrode, and electrolyte settings are the same in this embodiment as in Embodiment 3. The difference is that the oxidant in the membrane coating is sodium persulfate.

[0097] Comparative Example 1

[0098] The positive electrode, negative electrode, and electrolyte are set up in the same way as in Example 1. The difference is that the separator used in the full cell in this example is the polyethylene membrane-based membrane of Example 1 (average pore size is 0.1 μm, porosity is 45%).

[0099] Comparative Example 2

[0100] The preparation of the positive electrode, negative electrode, electrolyte, and separator in this embodiment is the same as in Embodiment 1. The difference is that, in preparing the battery, the coated side of the separator faces the negative electrode side.

[0101] Battery performance test

[0102] The methods for testing the full-cell performance of the examples and comparative examples are as follows:

[0103] Overcharge test:

[0104] Under a constant temperature environment of 25℃, the battery is installed on a charge-discharge test cabinet. The battery is discharged at a constant current until its state of charge (SOC) reaches 0%. After resting for 30 minutes, the battery is charged at a constant current of 1 / 3C until the battery voltage jumps to zero or the battery bursts. The overcharge capacity C1 of the battery at the point where the battery voltage jumps to zero or the battery bursts is recorded. The ratio of the overcharge capacity C1 to the nominal theoretical capacity C0 of the battery is the SOC corresponding to the overcharge short circuit, SOC = C1 / C0 * 100%.

[0105] Shrinkage test:

[0106] The diaphragm was cut into 100mm*50mm shapes and transferred to an oven. The temperature was increased to 100℃ at a rate of 5℃ / min and maintained at 100℃ for 2 hours. The oven was then allowed to cool naturally to room temperature. The diaphragm was removed, and its longitudinal length after heat treatment was measured. The longitudinal shrinkage rate of the diaphragm is the ratio of the difference between the original longitudinal length and the longitudinal length after heat treatment to the original longitudinal length, i.e., the longitudinal shrinkage rate s% = (S0 - S1) / S0, where S0 is the original longitudinal length and S1 is the longitudinal length after heat treatment.

[0107] Needle penetration strength test:

[0108] The diaphragm was cut into test samples with a width greater than 100 mm. The test samples were mounted on the sample fixing ring and pierced with a steel needle with a diameter of 1.0 mm at a speed of 50 mm / min. The load of the steel needle penetrating the sample was read. Five test points were selected for each sample, and the average value was taken.

[0109] The performance of Examples 1-15 and Comparative Example 1 is shown in Table 1:

[0110] Table 1

[0111]

[0112] As can be seen from the table, compared with Comparative Example 1, the batteries using separators coated with oxidant coatings in Examples 1-15 exhibit superior overcharge protection compared to batteries using only the base film. Batteries using only the base film experienced a short circuit when overcharged to 130% SOC, while batteries using separators coated with oxidant coatings showed a significantly higher SOC at the time of short circuit due to overcharge. During overcharge, lithium ions directly deposit metallic lithium on the negative electrode surface, forming lithium dendrites. The oxidant on the separator coated with oxidant coating can react with the lithium dendrites through a redox reaction, converting metallic lithium into insulating species, thereby improving the battery's overcharge protection. It can also be seen that after heat treatment, the base film has a thermal shrinkage rate of 3% and a needle penetration strength of 250 gf. The separator coated with oxidant coating shows significantly improved thermal shrinkage rate and needle penetration strength, giving the separator better thermal stability and mechanical strength, effectively preventing lithium dendrites from piercing the separator, and thus avoiding short circuits in the battery.

[0113] Examples 1-4 and 5-8 compared the overcharge protection capabilities of separators with different coating thicknesses, showing that the overcharge protection capability of the battery increases with the increase of the oxidant coating thickness. This is because the amount of oxidant coated per unit area increases, resulting in an increase in the amount of metallic lithium that can be converted.

[0114] Compared with Examples 3 and 7, and Examples 9-12, it can be seen that loading the oxidant onto ceramic particles such as alumina or hydrotalcite improves the battery's overcharge protection capability. This is because loading the oxidant onto alumina or hydrotalcite increases the dispersion of the oxidant, thereby improving its effective utilization rate.

[0115] Compared with Comparative Example 2, Example 1 shows that coating facing the positive electrode side has better overcharge protection than coating facing the negative electrode side. This is because when the oxidant faces the negative electrode side, the oxidant will react with the lithium-intercalated negative electrode material and will not play a role in redox reaction with lithium dendrites.

[0116] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A battery comprising a positive electrode and a separator, characterized in that, The separator includes a base membrane and a coating disposed on one surface of the base membrane facing the positive electrode. The coating includes an oxidant and ceramic particles. The oxidant is a compound capable of undergoing a redox reaction with metallic lithium. The compound includes one or a mixture of several of sodium thiosulfate, sodium hypochlorite, sodium perborate, and sodium persulfate. The ceramic particles include one or a mixture of several of alumina, magnesium oxide, silicon dioxide, zirconium oxide, titanium dioxide, and hydrotalcite. The battery meets the following requirements: when charged at 25°C with a current density of 1 / 3C, the state of charge (SOC) of the battery during overcharge and short circuit is greater than 130%.

2. The battery according to claim 1, characterized in that, The battery satisfies the following conditions: when charged at 25°C with a current density of 1 / 3C, the state of charge (SOC) of the battery during overcharge and short circuit is greater than or equal to 150%.

3. The battery according to claim 1, characterized in that, The thickness of the coating is 0.5~5.0μm.

4. The battery according to claim 1, characterized in that, The oxidant content per unit area in the coating is 0.05-2.5 mg / cm². 2 .

5. The battery according to claim 1, characterized in that, After the diaphragm is heat-treated at 100°C for 2 hours, the longitudinal shrinkage rate of the diaphragm is less than 2.5%.

6. The battery according to claim 1, characterized in that, The needle penetration strength of the diaphragm is 300-500 gf.

7. An electrical appliance, characterized in that, Includes the battery as described in claims 1 to 6.

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