Secondary battery, battery device, and electric device

Abstract

The invention discloses a secondary battery, a battery device and a power utilization device. The secondary battery comprises a first electrode, a second electrode and a diaphragm, the diaphragm is located between the first electrode and the second electrode, the secondary battery comprises an SEI film stabilizer, the SEI film stabilizer contains an S element, the SEI film stabilizer is located on the first electrode and / or the second electrode, and the SEI film stabilizer contains an S element. At least a portion of the SEI film stabilizer is covered by the active layer of the first electrode and / or the second electrode. The secondary battery has the advantages of being capable of stabilizing SEI film formation and prolonging the service life of the battery.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to secondary batteries, battery devices, and electrical devices. Background Technology

[0002] With the development of lithium-ion battery technology, the application of lithium-ion and other secondary batteries in consumer electronics, electric vehicles, energy storage, and other markets is gradually expanding. Lithium-ion and other secondary batteries form a solid electrolyte interphase (SEI) film on the electrode surface. The SEI film can effectively isolate the electrolyte from the electrode active materials, improve safety performance, and reduce side reactions.

[0003] However, the stability and other properties of the SEI film still need to be improved, so current secondary batteries, battery devices and power devices still need to be improved. Summary of the Invention

[0004] In view of the above problems, this application provides a secondary battery and battery device that, by adding an SEI film stabilizer, can promote the reaction and decomposition of electrolyte components used to form the SEI film into more stable substances, thereby improving the stability of the SEI film and improving the storage performance of the secondary battery.

[0005] In one aspect of this application, a secondary battery is provided. The secondary battery includes a first electrode, a second electrode, and a separator, the separator being located between the first and second electrodes. The secondary battery includes an SEI film stabilizer containing sulfur (S), the SEI film stabilizer being located on the first and / or second electrodes, and at least a portion of the SEI film stabilizer being covered by the active layer of the first and / or second electrodes.

[0006] In the technical solution of this application embodiment, by adding an SEI film stabilizer containing specific elements, S... 2- Plasma promotes the chemical process of electrolyte components such as ethylene carbonate (EC) decomposing into polyethylene oxide (PEO) and polysulfide polymers, thereby stabilizing SEI film formation and improving battery life.

[0007] In some embodiments, the first electrode and / or the second electrode includes: a current collector; a first SEI film stabilizer layer having the SEI film stabilizer therein; and an active layer located on the side of the SEI film stabilizer layer away from the current collector. Thus, the active layer can be used to protect the SEI film stabilizer, improving the effectiveness of the SEI film stabilizer in stabilizing the SEI film.

[0008] In some embodiments, the mass percentage of the SEI film stabilizer in the first SEI film stabilizer layer is 0.1-5%. This further enhances the effect of the SEI film stabilizer on improving SEI film stability.

[0009] In some embodiments, the first SEI film stabilizer layer comprises: 0.5-1.5% of the SEI film stabilizer; 0.1-1.5% of a conductive agent; and an electrode active material. This can further improve battery performance, such as lifespan.

[0010] In some embodiments, the first electrode and / or the second electrode includes a first SEI film stabilizer layer in contact with the current collector, the active layer being located on the side of the first SEI film stabilizer layer away from the current collector, and the thickness ratio of the first SEI film stabilizer layer to the active layer is 0.05-1.3; or the first electrode and / or the second electrode includes a first active layer and a second active layer located on the same side as the current collector, the first SEI film stabilizer layer being located between the first active layer and the second active layer, the thickness of the first SEI film stabilizer layer accounting for 10-50% of the total thickness of the film layer on one side of the electrode, and the total thickness of the film layer on one side of the electrode is the sum of the thicknesses of the first active layer, the second active layer, and the first SEI film stabilizer layer.

[0011] In some embodiments, the current collector of the first electrode and / or the second electrode has a concave structure, and the SEI film stabilizer is present at the concave structure. This can further improve battery performance such as lifespan.

[0012] In some embodiments, the SEI film stabilizer is located within a second SEI film stabilizer layer at the concave plate structure. The second SEI film stabilizer layer contains carbon, and the mass percentage of the SEI film stabilizer in the second SEI film stabilizer layer is 0.5-1.5%; and / or the thickness of the second SEI film stabilizer layer is 0.1-3 μm; and / or the mass percentage of the carbon in the second SEI film stabilizer layer is 20-30%. This can further improve battery performance, such as lifespan.

[0013] In some embodiments, the positive electrode of the secondary battery has the SEI film stabilizer. This can further improve battery performance, such as lifespan.

[0014] In some embodiments, the SEI film stabilizer includes Li2S x It contains at least one of Li3PS4, where x is 1-8. This can further improve battery performance, such as lifespan.

[0015] In another aspect of this application, a battery device is proposed. This battery device includes a plurality of the aforementioned secondary batteries.

[0016] In another aspect of this application, an electrical device is provided. This electrical device includes a secondary battery or a battery device as described above, which is used to provide or store electrical energy. Attached Figure Description

[0017] To more clearly illustrate the technical solution of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without any creative effort.

[0018] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0019] Figure 2 for Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0020] Figure 3 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0021] Figure 4 This is a schematic diagram of the electrode structure of a secondary battery according to one embodiment of this application.

[0022] Figure 5 This is a schematic diagram of the electrode structure of a secondary battery according to another embodiment of this application.

[0023] Figure 6 This is a graph showing the results of a 45°C cyclic charge-discharge test in one of the embodiments of this application.

[0024] Figure 7 This is a graph showing the test results of 97% SOC storage (7 days) at 45°C in some embodiments of this application.

[0025] To better describe and illustrate embodiments and / or examples of the inventions disclosed herein, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed inventions, the currently described embodiments and / or examples, or the best mode of these inventions as currently understood. Detailed Implementation

[0026] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion.

[0028] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0029] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0030] In the description of the embodiments in this application, the term "and / or" 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, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0031] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0032] In the description of the embodiments of this application, the technical terms "upper", "lower", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0033] Unless otherwise stated, the terms used in this application have their common meanings as commonly understood by those skilled in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0034] As mentioned earlier, the formation of an SEI film on the electrode surface of lithium-ion and other secondary batteries helps improve interfacial stability and, to a certain extent, isolates the active material of the electrode and the electrolyte, reducing side reactions between them. Therefore, improving the stability of the SEI film is beneficial to the interfacial performance and cycle performance of the battery to be improved.

[0035] To further improve the stability of the SEI film formed in secondary batteries, this application incorporates elements such as sulfur at locations in the battery, such as electrodes, that can contact the electrolyte. 2- SEI film stabilizers utilize inorganic negative ions to promote the decomposition of electrolyte components such as ethylene carbonate (EC) into components with superior interfacial properties, such as polyethylene oxide (PEO) and polysulfide polymers. This stabilizes SEI film formation and improves battery life.

[0036] In one aspect of this application, a secondary battery is provided. The secondary battery includes a first electrode, a second electrode, and a separator, the separator being located between the first and second electrodes. The secondary battery includes an SEI film stabilizer containing sulfur (S), the SEI film stabilizer being located on the first and / or second electrodes, and at least a portion of the SEI film stabilizer being covered by the active layer of the first and / or second electrodes.

[0037] In the technical solution of this application embodiment, Sn is added to the location where it can contact the electrolyte. 2- S 2- Inorganic elements such as ethylene carbonate (EC) are used as SEI film stabilizers, and an active layer is used to protect the SEI film stabilizers. In this way, inorganic ions can be used to promote the decomposition of electrolyte components such as ethylene carbonate (EC) into polyethylene oxide (PEO) and polysulfide polymers during the SEI film production process, thereby stabilizing the SEI film formation and improving the battery life.

[0038] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0039] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0040] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate. This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 1.

[0041] In some implementations, refer to Figure 2 The outer packaging may include a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The shell 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator can be formed into an electrode assembly 12 by a winding process or a stacking process. The electrode assembly 12 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 12. The secondary battery 1 may contain one or more electrode assemblies 12, which can be selected by those skilled in the art according to specific practical needs.

[0042] In some embodiments, the specific composition of the SEI film stabilizer may be selected to contain S x 2- For example, S 2- The compounds can include, for example, at least one of Li₂S and Li₃PS₄. In addition to stabilizing SEI film formation as described above, substances such as Li₂S can also replenish lithium. This can further improve battery life and other performance characteristics.

[0043] In some embodiments, the SEI film stabilizer may be located on the electrodes of the secondary battery. For example, in some embodiments, both the first electrode and the second electrode may have a current collector and an active layer located on the current collector. At least one of the first electrode and the second electrode has an SEI film stabilizer, and at least a portion of the SEI film stabilizer located on the electrode is covered by the active layer. Thus, the active layer can be used to protect the SEI film stabilizer, improving the effect of the SEI film stabilizer in stabilizing the SEI film.

[0044] Especially when the SEI film stabilizer includes inorganic substances such as lithium sulfides, which are sensitive to water and oxygen, such as Li2S, the reaction of Li2S with moisture will lead to the decomposition of Li2S and the generation of gas. This not only causes the SEI film stabilizer to fail but also produces H2S gas. Therefore, having at least a portion of the SEI film stabilizer covered by the active layer can reduce the probability of the SEI film stabilizer coming into contact with reactants such as moisture, thereby improving its effect on stabilizing the SEI film.

[0045] In secondary batteries, moisture sources may include moisture contained in the positive and negative electrode slurries, as well as moisture from the environment and equipment during the production process. Therefore, if at least part of the SEI film stabilizer can be covered with an active layer, the probability of the SEI film stabilizer coming into contact with moisture will be significantly reduced. Furthermore, the SEI film stabilizer covered by the active layer can participate in the formation of the SEI film in a "slow-release" manner, thereby further improving the stability of the formed SEI film.

[0046] In this application, one of the first electrode and the second electrode is a positive electrode, and the other is a negative electrode. Those skilled in the art will understand that the description of the first electrode and the second electrode is for distinction only and should not be construed as a limitation on the type of electrode, etc. For example, the SEI film stabilizer can be located on the positive electrode. Since the solvents and other components used in the positive electrode slurry have lower water content, placing the SEI film stabilizer on the positive electrode is beneficial for further improving the stability of the SEI film.

[0047] In some embodiments, the SEI membrane stabilizer may be located within one or more electrode membrane layers. For example, the electrode may include a multilayer structure, and the SEI membrane stabilizer may be located in the outermost layer and / or the innermost layer. When the electrode includes a multilayer structure, the membrane layer closest to the current collector is the innermost layer. This is beneficial for further improving the sustained-release effect of the SEI membrane stabilizer.

[0048] In some embodiments, the SEI film stabilizer may be disposed in the first SEI film stabilizer layer. (See reference...) Figure 4 The first and / or second electrode may include a first SEI film stabilizer layer 200 and an active layer 300 located on the side of the first SEI film stabilizer layer away from the current collector 100. The first SEI film stabilizer layer 200 may be in direct contact with the current collector 100. In other embodiments, the first and / or second electrode may include multiple active layers, at least two of which are located on the same side of the current collector. Active layers may be present on both sides of the first SEI film stabilizer layer. (See reference...) Figure 5 In this embodiment, the first electrode and / or the second electrode may include a first active layer 300A and a second active layer 300B located on the same side of the current collector 100, and a first SEI film stabilizer layer 200 located between the first active layer 300A and the second active layer 300B.

[0049] In some embodiments, the first electrode and / or the second electrode may have a double-sided coated structure. That is, both the upper and lower sides of the current collector 100 may have an active layer 300, or both the upper and lower sides of the current collector 100 may have an active layer 300 and a first SEI film stabilizer layer 200. The structures of the upper and lower sides of the current collector 100 may be symmetrical. Figure 4 as well as Figure 5The diagram only shows the case of single-sided coating. When the first electrode and / or the second electrode have a double-sided coating structure, the structure of the other side of the current collector 100 can be the same as... Figure 4 , Figure 5 The active layer 300 and the first SEI film stabilizer layer 200 shown are symmetrical.

[0050] In some embodiments, the mass percentage of SEI film stabilizer in the first SEI film stabilizer layer can be 0.1-5%. For example, it can be 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%. More specifically, it can be 0.5-1.5%. When the mass percentage of SEI film stabilizer in the first SEI film stabilizer layer is within the above range, on the one hand, the stabilizing effect on the SEI film can be guaranteed, on the other hand, the prepareability of the first SEI film stabilizer layer can be improved, and the integrity of the SEI film stabilizer layer itself can be maintained after the SEI film stabilizer reaction takes effect.

[0051] In some embodiments, the thickness of the first SEI film stabilizer layer can be adjusted according to the overall situation of the film layer on the current collector surface. Specifically, the thickness of the first SEI film stabilizer layer can account for 10-50% of the total thickness of the film layer on one side of the current collector.

[0052] For example, the structure of the first and / or second electrodes can be as follows: Figure 4 The diagram shows a first SEI film stabilizer layer in direct contact with the current collector, and an active layer located on the side of the first SEI film stabilizer layer facing away from the current collector. The thickness ratio of the first SEI film stabilizer layer to the active layer is 0.05-1.3. Specifically, the thickness ratio of the first SEI film stabilizer layer to the active layer can be (5-55):(25-95).

[0053] For example, refer to Figure 5 Two active layers may be present on the same side of the current collector 100, with a first SEI film stabilizer layer located between the two active layers. The thickness of the first SEI film stabilizer layer accounts for 10-50% of the total thickness of the film layers on one side of the electrode, for example, it can be 10%, 20%, 30%, 40%, or 50%. The total thickness of the film layers on one side of the electrode is the sum of the thicknesses of the two active layers and the first SEI film stabilizer layer.

[0054] In some embodiments, based on the total mass of the first SEI film stabilizer layer, it may include 0.5-1.5% of the SEI film stabilizer; 0.1-1.5% of a conductive agent; and an electrode active material, such as a positive or negative electrode active material. When the first SEI film stabilizer layer includes the above composition, it can be formed by formulating a slurry and coating it, thus having the advantage of lower processing difficulty. Furthermore, when the SEI film stabilizer is made of Li... x When substances such as S (x is 1-2) are formed, after the conductive agent is solidified inside the first SEI film stabilizer layer, it can affect S. x 2- By confining and adsorbing byproducts, S can be reduced. x 2- The consumption of lithium ions by byproducts can improve the initial charge and discharge capacity of secondary batteries.

[0055] In some embodiments, the composition of the first SEI film stabilizer layer may be similar to that of the active layer. In some embodiments, to reduce the probability of the SEI film stabilizer coming into contact with moisture in the environment, the active layer may not contain an SEI film stabilizer. When the composition of the SEI film stabilizer layer and the active layer are similar, on the one hand, the interfacial compatibility between the two film layers is better and the interfacial adhesion is stronger; on the other hand, the electrode fabrication process can be simplified, and the first and / or second electrodes can be obtained by multiple coating processes.

[0056] In this application, when the compositions of the first SEI film stabilizer layer and the active layer are similar, the boundary between them may not be very clear when observed using testing methods such as scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) of the electrode cross-section can be performed to distinguish the first SEI film stabilizer layer and the active layer by the position of specific elements in the SEI film stabilizer. For example, when the SEI film stabilizer contains sulfur (S), a surface scan of this element can be performed to determine the boundary between the first SEI film stabilizer layer and the active layer based on the distribution position of the S element. For instance, a line parallel to the current collector can be drawn from the position of the S element distribution at the top (the side furthest from the current collector is considered the top) as the boundary between the first SEI film stabilizer layer and the active layer, which can be used to calculate the thickness of the first SEI film stabilizer layer and the active layer. Alternatively, since the distribution of the SEI film stabilizer in the first SEI film stabilizer layer means that the position above the uppermost S element may still be the first SEI film stabilizer layer, the position 0.5-1 micrometers above the uppermost S element can be defined as the boundary between the first SEI film stabilizer layer and the active layer.

[0057] In some embodiments, the current collector having the first and / or second electrodes with the SEI film stabilizer may also have a concave structure. The SEI film stabilizer may be located at the concave structure. This can further improve battery performance such as lifespan. Specifically, the SEI film stabilizer may be located within a second SEI film stabilizer layer at the concave structure. This film layer may contain carbon and the SEI film stabilizer, and the content of the SEI film stabilizer in the second SEI film stabilizer layer may be 0.5-1.5%. The thickness of the second SEI film stabilizer layer at the concave structure is 0.1-3 μm. The carbon content in the second SEI film stabilizer layer is 20-30%. This can further improve battery performance such as lifespan. The side of the film layer at the current collector concave structure facing away from the current collector may be an active layer.

[0058] The secondary battery with the structure proposed in this application exhibits improved stability of the SEI film on the electrode surface, thus enhancing cycle performance. After 50 cycles at 45°C, the battery capacity retention rate can be increased by more than 0.5%, and after 7 days of storage at 45°C, the battery's SOC can still be maintained at over 95% of 97%.

[0059] In another aspect, the present invention provides a positive electrode. This positive electrode includes a current collector and an active layer located on the surface of the current collector, the active layer comprising an SEI film stabilizer. This positive electrode has advantages such as the ability to stabilize the SEI film and improve the lifespan of secondary batteries utilizing this positive electrode.

[0060] In some embodiments, the positive electrode may be the positive electrode of the secondary battery described above, and the SEI film stabilizer may be the SEI film stabilizer used in the secondary battery described above. The positive electrode may have the structure of the first and / or second electrodes with the SEI film stabilizer described above.

[0061] In some embodiments, at least a portion of the SEI film stabilizer is covered by the electrode active material.

[0062] In some embodiments, the positive electrode may have the following characteristics: Figure 4 or Figure 5 The structure shown, or a structure with double-sided coating, has symmetrical film layers on both sides of the current collector, and the structure on one side of the current collector is as follows: Figure 4 or Figure 5 As shown, the surface of the positive electrode current collector may have an active layer and a first SEI film stabilizer layer. The structure of the active layer and the first SEI film stabilizer layer, as well as the composition of the first SEI film stabilizer layer, may be consistent with the corresponding film layers in the first and / or second electrodes of the secondary battery described above.

[0063] In another aspect of this application, a battery device is proposed. This battery device includes a plurality of the aforementioned secondary batteries. Thus, this battery device possesses all the features and advantages of the aforementioned secondary batteries. In general, this battery device has the advantage of better cycle performance.

[0064] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, specifically multiple secondary batteries as described above. These battery cells are connected in series, parallel, or mixed connections via a busbar.

[0065] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0066] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0067] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0068] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0069] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0070] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0071] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0072] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0073] In another aspect of this application, an electrical device is provided. This electrical device includes a secondary battery or battery device as described above, which is used to provide or store electrical energy.

[0074] In this application, the electrical device can be such as a mobile phone, tablet, laptop, electric toy, power tool, electric vehicle, electric car, ship, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0075] As for the aforementioned electrical device, a secondary battery can be selected according to its usage requirements.

[0076] Figure 3 Here is an example of an electrical device 2. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0077] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0078] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0079] Preparation of secondary batteries

[0080] Example 1

[0081] A secondary battery was prepared by adding Li₂S as an SEI film stabilizer to the positive electrode. The fabrication process of the secondary battery is as follows:

[0082] Positive electrode: The active layer uses lithium iron phosphate (LFP) as the positive electrode active material, and a slurry is formed by mixing 97.2 wt% LFP, 2 wt% PVDF, and 0.8 wt% acetylene black. SEI film stabilizer layer: The active layer slurry is used, with 1% (based on the total mass of the formed slurry) of Li2S added as an SEI film stabilizer to form the slurry, and the PVDF content in the slurry is reduced accordingly. An SEI film stabilizer layer and an active layer are sequentially formed on the current collector surface through a layered coating process, and then cold-pressed to obtain the final product. The thickness of the Li2S layer accounts for 30% of the total thickness of the film layers on the electrode surface (active layer and Li2S layer).

[0083] Negative electrode sheet: The active layer of the electrode is obtained by cold pressing a slurry containing graphite, sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR);

[0084] Separator: PE film is used as the battery separator;

[0085] Electrolyte: Lithium bis(fluorosulfonyl)imide (LiFSI) is the lithium salt, and ethylene carbonate (EC) is used as the solvent.

[0086] The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator acting as a separator between the positive and negative electrode sheets. The stacked sheets are then stacked to obtain small stacks. The bare cell is placed in the outer packaging of the lithium battery. After drying, electrolyte is injected into the outer packaging of the battery. After vacuum sealing, settling, formation, and shaping, a secondary battery is obtained.

[0087] The negative electrode, separator, and electrolyte of the remaining embodiments and comparative examples are the same as in Example 1. The difference is that the amount and location of Li2S added in the positive electrode are changed. When the amount of Li2S added is changed, the PVDF content in the SEI film stabilizer layer slurry is changed accordingly to ensure that the sum of the percentage contents of each component is 100%. Comparative Example 1 only forms an active layer and does not add Li2S. In Example 6, the SEI film stabilizer is located in the carbon layer at the current collector gravure plate, and in addition to the SEI film stabilizer layer, it also includes two active layers. For ease of normalization and comparison, the thickness of the Li2S layer is expressed as a percentage, with the total thickness of all active layers and the Li2S layer on the electrode surface being 100%. See Table 1 below for details.

[0088] Table 1

[0089]

[0090] Secondary battery performance test

[0091] The performance of the secondary batteries prepared in each of the embodiments and comparative examples in Table 1 below was tested:

[0092] Cyclic charge-discharge test at 1.45℃:

[0093] Using the same charge-discharge strategy, cyclic charge-discharge tests were conducted on each embodiment and comparative example at 45°C. The capacity retention and cycle number curves are shown below. Figure 6 As shown in Table 2, with the capacity of Comparative Example 1 at a specific number of cycles as 100%, the capacity decay rates of the other embodiments and comparative examples at different numbers of cycles were calculated.

[0094] 2.45℃ 97% SOC storage test:

[0095] Using the same charge / discharge strategy, 97% SOC storage calendar tests were conducted on each embodiment and the comparative example at 45°C. The reversible capacity retention and storage days curves are shown below. Figure 7 As shown in Table 2 below, with the initial charge / discharge capacity as 100% SOC and the capacity of Comparative Example 1 at the corresponding number of days as 100%, the improvement in storage performance of the remaining embodiments and comparative examples when the capacity decays to 97% SOC is calculated.

[0096] Table 2

[0097]

[0098] The results of some embodiments and Comparative Example 1 are as follows: Figure 6 as well as Figure 7 As shown. Refer to Table 2 above and... Figure 6 and Figure 7 The cycling performance of the embodiments of this application is improved, and under the same conditions, the capacity decay is less than that of Comparative Example 1 without Li2S.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A secondary battery, characterized in that, include: The secondary battery comprises a first electrode, a second electrode, and a separator, wherein the separator is located between the first electrode and the second electrode, and the secondary battery includes an SEI film stabilizer containing sulfur. The SEI film stabilizer is located on the first electrode and / or the second electrode, and at least a portion of the SEI film stabilizer is covered by the active layer of the first electrode and / or the second electrode.

2. The secondary battery according to claim 1, characterized in that, The first electrode and / or the second electrode include: current collector; A first SEI film stabilizer layer, wherein the first SEI film stabilizer layer contains the SEI film stabilizer; The active layer is located on the side of the first SEI film stabilizer layer away from the current collector.

3. The secondary battery according to claim 2, characterized in that, Based on the total mass of the first SEI film stabilizer layer, the mass percentage of the SEI film stabilizer in the first SEI film stabilizer layer is 0.1-5%.

4. The secondary battery according to claim 2 or 3, characterized in that, The first SEI film stabilizer layer includes: 0.5-1.5% of the SEI film stabilizer; 0.1-1.5% conductive agent; and Electrode active materials.

5. The secondary battery according to any one of claims 2-4, characterized in that, The first electrode and / or the second electrode includes a first SEI film stabilizer layer in contact with the current collector, the active layer being located on the side of the first SEI film stabilizer layer facing away from the current collector, and the ratio of the thickness of the first SEI film stabilizer layer to the thickness of the active layer being 0.05-1.3; or The first electrode and / or the second electrode include a first active layer and a second active layer located on the same side as the current collector, the first SEI film stabilizer layer is located between the first active layer and the second active layer, the thickness of the first SEI film stabilizer layer accounts for 10-50% of the total thickness of the film layer on one side of the electrode, and the total thickness of the film layer on one side of the electrode is the sum of the thicknesses of the first active layer, the second active layer and the first SEI film stabilizer layer.

6. The secondary battery according to claim 1, characterized in that, The current collector of the first electrode and / or the second electrode has a concave plate structure, and the concave plate structure has the SEI film stabilizer.

7. The secondary battery according to claim 6, characterized in that, The SEI film stabilizer is located within the second SEI film stabilizer layer at the concave plate structure, and the second SEI film stabilizer layer contains carbon. The SEI film stabilizer in the second SEI film stabilizer layer has a mass percentage content of 0.5-1.5%; and / or The thickness of the second SEI film stabilizer layer is 0.1-3 μm; and / or The carbon content in the second SEI film stabilizer layer is 20-30% by mass.

8. The secondary battery according to any one of claims 1-7, characterized in that, The positive electrode of the secondary battery contains the SEI film stabilizer.

9. The secondary battery according to any one of claims 1-8, characterized in that, The SEI film stabilizer includes Li2S. x At least one of Li3PS4, Where x ranges from 1 to 8.

10. A battery device, characterized in that, Includes the secondary battery as described in any one of claims 1-9.

11. An electrical appliance, characterized in that, The electrical device includes a secondary battery as described in any one of claims 1-9 or a battery device as described in claim 10, wherein the secondary battery or battery device is used to provide or store electrical energy.

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