Secondary battery and preparation method thereof, energy storage system and electrical equipment

Abstract

The present application relates to the field of energy storage, and provides a secondary battery and its preparation method, an energy storage system and an electrical device. The secondary battery includes: a battery shell, the battery shell has a cavity, and the cavity has an electrolyte; a battery cell assembly, the battery cell assembly is located in the cavity, and the battery cell assembly is immersed in the electrolyte; the battery cell assembly includes a wound positive electrode sheet, a separator and a negative electrode sheet, wherein the separator includes: a substrate layer, the substrate layer has a through hole; a functional layer, the functional layer is located on at least one surface of the substrate layer, and the functional layer is composed of a plurality of scale units arranged in a hinged connection structure; the functional layer includes a trigger material, the trigger material is connected to the surface of the scale unit, and the trigger material is used to make the scale unit open and close to form a through hole, and the through hole exposes at least one of the through holes. The secondary battery and its preparation method, the energy storage system and the electrical device provided by the present application can at least improve the thermal runaway problem of the secondary battery.

Description

Technical Field

[0001] The present application relates to the field of energy storage, and in particular to a secondary battery and a preparation method thereof, an energy storage system and electrical equipment. Background Art

[0002] Safety issues are the primary obstacle hindering the large-scale application of lithium-ion batteries in energy storage. As the energy density of lithium-ion batteries continues to increase, improving their safety is increasingly crucial for the development of this sector. Thermal runaway is a key issue in battery safety research. Thermal runaway refers to a rapid rise in the temperature of a lithium-ion battery, either locally or globally. Heat cannot dissipate quickly, accumulating internally and triggering further side reactions, potentially leading to catastrophic accidents such as battery fires and explosions. Common mechanisms for thermal runaway include internal short circuits, overcharging and over-discharging, high-temperature environments, and the characteristics of battery materials.

[0003] Although some measures have been taken to solve the thermal runaway problem, the preparation difficulty and improvement effect are poor. Therefore, the thermal runaway problem of current secondary batteries still needs to be further improved. Summary of the Invention

[0004] The embodiments of the present application provide a secondary battery and a preparation method thereof, an energy storage system, and an electrical device, which are at least beneficial in improving the thermal runaway problem of the secondary battery.

[0005] According to some embodiments of the present application, on one hand, an embodiment of the present application provides a secondary battery, comprising: a battery shell, wherein the battery shell has a cavity, and the cavity has an electrolyte; a battery cell assembly, wherein the battery cell assembly is located in the cavity and the battery cell assembly is immersed in the electrolyte; the battery cell assembly includes a wound positive electrode sheet, a separator and a negative electrode sheet, wherein the separator includes: a substrate layer, wherein the substrate layer has a through hole; a functional layer, wherein the functional layer is located on at least one surface of the substrate layer, and the functional layer is composed of a plurality of scale units arranged in a hinged connection structure; the functional layer includes a trigger material, wherein the trigger material is connected to the surface of the scale unit, and the trigger material is used to make the scale unit open and close to form a through hole, and the through hole exposes at least one of the through holes.

[0006] In some embodiments, the trigger material is a temperature-sensitive material, and the temperature-sensitive material is configured to undergo volume deformation as the temperature changes, thereby driving the scale unit to open and close.

[0007] In some embodiments, the thermosensitive material includes a thermosensitive polymer having an acrylic polymer grafted onto its surface.

[0008] In some embodiments, the material of the thermosensitive polymer includes poly(N-isopropylacrylamide) or polyvinylpyrrolidone.

[0009] In some embodiments, the scale unit includes a structural layer and a connecting layer, the connecting layer is located between the substrate layer and the structural layer, the connecting layer is located at an edge of the structural layer, and the trigger material is connected to the surface of the structural layer.

[0010] In some embodiments, the scale unit further includes: an isolation layer, wherein the isolation layer is located on a side of the structural layer close to the substrate layer.

[0011] In some embodiments, the diaphragm further comprises: a functional modification layer, the functional modification layer being located on the surface of the functional layer close to the substrate layer, and the ionic conductivity of the material of the functional modification layer is 8×10 -5 S / cm~2×10 - ³S / cm.

[0012] In some embodiments, the material of the function modification layer includes lithium aluminum titanium phosphate, lithium lanthanum titanate / lithium lanthanum titanate, or lithium lanthanum zirconate / lithium lanthanum zirconate.

[0013] According to some embodiments of the present application, another aspect of the embodiments of the present application provides a method for preparing a secondary battery, comprising: forming a diaphragm, the diaphragm comprising: a substrate layer; a through hole in the substrate layer; a functional layer, the functional layer being located on at least one surface of the substrate layer, the functional layer being composed of a plurality of scale units arranged in a hinged connection structure; the functional layer comprising a trigger material, the trigger material being connected to the surface of the scale unit, the trigger material being used to make the scale unit open and close to form a through hole, the through hole exposing at least one of the through holes; providing a positive electrode sheet and a negative electrode sheet; stacking the negative electrode sheet, the diaphragm and the positive electrode sheet in sequence, stacking the negative electrode sheet, the diaphragm and the positive electrode sheet in sequence, obtaining a battery cell assembly by winding or laminating, placing the battery cell assembly into a battery shell, injecting electrolyte into the battery shell, and encapsulating to obtain a secondary battery.

[0014] In some embodiments, the scale unit is formed by using a micro-electromechanical process or an ion etching process.

[0015] In some embodiments, the process steps for forming the flake unit include: forming a sacrificial layer on the surface of the substrate layer; patterning the sacrificial layer to form a first hole, wherein the bottom surface of the first hole exposes the substrate layer; forming a connecting layer, wherein the connecting layer is located in the first hole; forming a first film layer, wherein the first film layer is located on the surface of the sacrificial layer and the surface of the connecting layer; patterning the first film layer to form multiple flake-shaped structural layers; and removing the sacrificial layer.

[0016] In some embodiments, the scale units are formed using a laser etching process.

[0017] In some embodiments, the process steps for forming the diaphragm also include: forming prepolymer capsules, the prepolymer capsules including a urea-formaldehyde resin shell and prepolymer particles, the prepolymer particles including a hydroxyl-containing siloxane prepolymer and a platinum catalyst; dispersing the prepolymer capsules in a bonding solution to form a mixed slurry; screen printing the mixed slurry on the surface of the substrate layer, and curing to form an adhesive layer on the surface of the functional layer.

[0018] According to some embodiments of the present application, another aspect of the embodiments of the present application provides an energy storage system, including: a secondary battery prepared by the method for preparing a secondary battery as described in any one of the above embodiments or a secondary battery as described in the above embodiments.

[0019] According to some embodiments of the present application, on the other hand, embodiments of the present application provide an electrical device, including: a secondary battery prepared by the method for preparing a secondary battery as described in any of the above embodiments, a secondary battery as described in the above embodiments, or an energy storage battery pack as described in the above embodiments.

[0020] The technical solution provided by the embodiments of the present application has at least the following advantages:

[0021] The secondary battery provided in the embodiments of the present application is provided with a functional layer on the surface of the substrate layer. The functional layer is composed of a plurality of scale units arranged in an array. The functional layer also includes a trigger material, which is connected to the surface of the scale unit. The trigger material is used to open and close the scale unit to form a through hole. The through hole exposes at least one through hole, instantly opening a large number of additional, low-resistance ion channels on the diaphragm, greatly reducing the ion transmission resistance and making the current distribution more uniform. It can effectively alleviate the severe lithium dendrite precipitation caused by excessive local current density on the negative electrode surface at high temperatures. After a large number of through holes are opened, the electrolyte can flow freely through the diaphragm under the action of convection, which is beneficial to enhance the heat transfer efficiency within the battery. Heat can be diffused more quickly from the hot spot to the entire battery or housing, effectively avoiding the situation where the local temperature rises sharply beyond the critical point or even thermal runaway. The formation of the through hole ensures that the electrolyte can fully penetrate the electrode sheet even at high temperatures, maintaining a relatively normal interface, reducing the local high impedance and severe heat generation side reactions caused by poor wetting, and improving the yield of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] One or more embodiments are exemplified by the figures in the corresponding drawings. These exemplified descriptions do not constitute a limitation on the embodiments. Unless otherwise stated, the figures in the drawings do not constitute a scale limitation. In order to more clearly illustrate the embodiments of the present application or the technical solutions in the traditional technology, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 A cross-sectional view of a cell assembly in a secondary battery provided in one embodiment of the present application;

[0024] Figure 2 A top view of a separator in a secondary battery provided in one embodiment of the present application;

[0025] Figure 3 A cross-sectional view of a separator in a secondary battery provided in one embodiment of the present application;

[0026] Figure 4 Another cross-sectional view of a separator in a secondary battery provided in one embodiment of the present application;

[0027] Figure 5 Another cross-sectional view of a separator in a secondary battery provided in one embodiment of the present application;

[0028] Figure 6 This is another cross-sectional view of a separator in a secondary battery provided in one embodiment of the present application.

[0029] Description of reference numerals:

[0030] 1. Positive electrode sheet; 2. Negative electrode sheet; 3. Separator; 100. Base material layer; 101. Through hole; 110. Flake unit; 11. Functional layer; 111. Trigger material; 112. Structural layer; 113. Connecting layer; 114. Functional modification layer; 12. Through hole; 120. Adhesive layer. DETAILED DESCRIPTION

[0031] As known from the background technology, current secondary batteries have the potential safety hazard of thermal runaway.

[0032] The current solutions to thermal runaway mainly include: 1. Coating and modifying the positive electrode material, improving the compatibility of the electrolyte and the electrode, and improving the thermal conductivity of the battery cell; 2. Selecting a highly safe electrolyte to achieve a flame retardant effect; 3. Selecting a safe and efficient thermal management system to suppress the temperature rise of lithium-ion batteries; 4. Adding fins, embedding foam metal, coating phase change materials, etc.

[0033] However, although coating and modifying the positive electrode material can solve the thermal runaway problem, the preparation cost is high; the higher safety of the electrolyte has limited improvement on the performance of the secondary battery; the use of a thermal management system and the addition of heat dissipation measures increase the difficulty of preparation and reduce the efficiency of preparation.

[0034] An embodiment of the present application provides a secondary battery and a method for preparing the same, by improving the diaphragm so that the diaphragm not only has a conventional through hole but also has a functional layer, and the functional layer is set to include a scale unit and a trigger material to form a through hole, and this through hole is connected to the through hole, thereby greatly improving the problem of thermal runaway.

[0035] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0036] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0037] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0038] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0039] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0040] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0041] In the accompanying drawings corresponding to the embodiments of the present application, the thickness and area of ​​the layers are exaggerated for better understanding and ease of description. When describing a component (such as a layer, film, region, or substrate) as being on another component or on the surface of another component, the component may be "directly" located on the surface of the other component, or a third component may be present between the two components. Conversely, when describing a component as being on the surface of another component or as being formed or provided on the surface of a component, it means that there is no third component between the two components. In addition, when describing a component as being "substantially" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a portion of the edge of the entire surface.

[0042] In the description of the embodiments of this application, when a component "includes" another component, unless otherwise specified, other components are not excluded, and other components may be further included. In addition, when a component such as a layer, film, region, or plate is referred to as being "on / located on" another component, it can be "directly on" the other component (i.e., located on the surface of the other component with no other components between them) or another component can be present between them. In addition, when a component such as a layer, film, region, or plate is "directly on" another component, or when a component such as a layer, film, region, or plate is located on the surface of another component, it means that no other components are located between them.

[0043] The terms used herein in the description of the various embodiments are intended only to describe the specific embodiments and are not intended to be limiting. As used in the description of the various embodiments and the appended claims, "part" is intended to include the plural form unless the context clearly indicates otherwise. A component includes a layer, film, region, or plate.

[0044] The following detailed description of the various embodiments of the present application is provided in conjunction with the accompanying drawings. However, those skilled in the art will appreciate that many technical details are provided in the various embodiments of the present application to facilitate a better understanding of the present application. However, even without these technical details and the various variations and modifications based on the following embodiments, the technical solutions claimed in the present application can still be implemented.

[0045] Figure 1 A cross-sectional view of a cell assembly in a secondary battery provided in one embodiment of the present application; Figure 2 A top view of a separator in a secondary battery provided in one embodiment of the present application; Figure 3 A cross-sectional view of a secondary battery separator provided in one embodiment of the present application.

[0046] It should be noted that in order to explain and distinguish the diaphragm, positive electrode sheet and negative electrode sheet, Figure 1 The dotted line indicates the separator, the thinner solid line indicates the negative electrode, and the thicker solid line indicates the positive electrode, but this does not represent the thickness relationship between the separator, the positive electrode, and the negative electrode. Figure 1 There are gaps between the middle diaphragm, the positive electrode sheet and the negative electrode sheet. This is to clearly indicate the winding correspondence between the diaphragm, the positive electrode sheet and the negative electrode sheet, but it does not mean that there must be a gap between the diaphragm and the positive electrode sheet or between the diaphragm and the negative electrode sheet. In other words, the diaphragm and the positive electrode sheet can contact each other, or the diaphragm and the negative electrode sheet can contact each other.

[0047] According to some embodiments of the present application, on the one hand, the embodiments of the present application provide a secondary battery, including: a battery shell, the battery shell having a cavity, the cavity having an electrolyte; a battery cell assembly, the battery cell assembly is located in the cavity, and the battery cell assembly is immersed in the electrolyte; the battery cell assembly includes a wound positive electrode sheet 1, a diaphragm 3 and a negative electrode sheet 2, wherein the diaphragm 3 includes: a substrate layer 100, the substrate layer 100 has a through hole 101; a functional layer 11, the functional layer 11 is located on at least one surface of the substrate layer 100, and the functional layer 11 is composed of a plurality of scale units 110 arranged in a hinged connection structure; the functional layer 11 includes a trigger material 111, the trigger material 111 is connected to the surface of the scale unit 110, and the trigger material 111 is used to make the scale unit 110 open and close to form a through hole 12, and the through hole 12 exposes at least one through hole 101.

[0048] In the secondary battery provided by the embodiment of the present application, a functional layer 11 is provided on the surface of the substrate layer 100. The functional layer 11 is composed of a plurality of scale units 110 arranged in an array. The functional layer 11 also includes a trigger material 111. The trigger material 111 is connected to the surface of the scale unit 110. The trigger material 111 is used to open and close the scale unit 110 to form a through hole 12. The through hole 12 exposes at least one through hole 101, and instantly opens a large number of additional, low-resistance ion channels on the diaphragm 3, greatly reducing the ion transmission resistance and making the current distribution more uniform. It can effectively alleviate the severe lithium dendrite precipitation caused by excessive local current density on the negative electrode surface at high temperature. After a large number of through holes 12 are opened, the electrolyte can flow freely through the diaphragm 3 under the action of convection, which is beneficial to enhance the heat transfer efficiency inside the battery. Heat can diffuse from the hot spot to the entire battery or shell more quickly, effectively avoiding the situation where the local temperature soars sharply beyond the critical point or even thermal runaway. The formation of the through-hole 12 ensures that the electrolyte can fully infiltrate the electrode sheet even at high temperature, maintain a relatively normal interface, reduce local high impedance and intense heat generation side reactions caused by poor infiltration, and improve the yield of the secondary battery.

[0049] According to the appearance classification, the prepared secondary batteries can be divided into square batteries, round batteries or soft-pack batteries. According to the capacity classification, the secondary batteries can be divided into 50Ah, 100Ah, 150Ah, 200Ah, 280Ah, 306Ah, 314Ah, 500+Ah, 800+Ah and 1000+Ah models. According to the chemical composition and working principle classification of the battery cell components of the secondary battery, the secondary battery can be a lithium-ion battery, a lead-acid battery, a sodium-ion battery or a nickel-metal hydride battery. The embodiment of the present application takes the preparation method of a lithium-ion battery as an example. Those skilled in the art can replace the lithium ions in the positive electrode sheet 1, the negative electrode sheet 2 and the electrolyte with corresponding metal ions according to actual needs. For example, in sodium-ion batteries, the lithium transition metal oxide of the subsequent positive electrode active material is replaced by any of the corresponding layered metal oxides (such as NaFeO2), polyanion compounds (NaFePO4) and Prussian blue compound systems (such as NaMnFe(CN)6-zH2O), and the electrolyte is replaced by any of the organic liquid electrolyte, solid composite electrolyte or solid electrolyte.

[0050] refer to Figure 1 The positive electrode sheet 1 acts as the cathode in the redox reaction. During discharge, the positive electrode material (lithium salt material) releases lithium ions and electrons through a chemical reaction; during charging, it reaccepts lithium ions.

[0051] The positive electrode sheet 1 includes a positive electrode current collector and a positive electrode active layer. The positive electrode current collector can be aluminum foil. Aluminum foil is cheaper than copper foil. A dense oxide film is formed on the surface of the aluminum foil. The oxide film is very thin, which can improve the corrosion resistance of the aluminum foil and enable electrons to conduct electricity through the tunnel effect.

[0052] In some embodiments, the current collector of the positive electrode sheet 1 may also be a composite current collector comprising three stacked layers: an organic middle layer, and upper and lower layers of copper and aluminum plating. The organic material may be PET (polyethylene terephthalate), PP (polypropylene), or PI (polyimide).

[0053] The positive electrode active material within the positive electrode active layer is an energy storage material, typically composed of metal oxides, metal sulfides, or polymers. Its primary function is to chemically react with the lithium ions in the negative electrode during battery charging, thereby storing lithium ions and increasing the lithium ion concentration, which in turn causes the positive electrode of the battery to release a charge current. Simultaneously, during battery discharge, the lithium ions stored in the positive electrode active material migrate toward the negative electrode, reacting with the negative electrode material and creating a potential difference between the positive and negative electrodes of the battery, thereby generating current output.

[0054] The negative electrode sheet 2 acts as the anode in the redox reaction. During discharge, the negative electrode material (such as graphite or silicon-based materials) accepts and stores lithium ions; during charging, the lithium ions are released.

[0055] The negative electrode sheet 2 includes a negative electrode current collector and a negative electrode active layer, and the negative electrode active layer is located on the negative electrode current collector.

[0056] The negative electrode current collector can be copper foil. Copper foil has low electrical conductivity but high electron transport capacity. Copper foil also has weak lithium insertion capacity and captures fewer lithium ions, thereby effectively reducing lithium ion loss. In other embodiments, the negative electrode current collector can also be a foam copper current collector, a copper mesh current collector, or a three-dimensional nano-copper array current collector.

[0057] In some embodiments, the negative electrode current collector can be a composite current collector, including a polymer material layer and a metal coating, the metal coating is located on the upper and lower sides of the polymer material layer, the polymer material layer is PET (polyethylene terephthalate), PP (polypropylene), PI (polyimide), etc., and the metal coating is a copper layer.

[0058] In some embodiments, the negative electrode current collector can also be a carbon-based current collector, that is, a conductive carbon layer is formed on the copper foil. The conductive carbon layer can serve as a protective layer, effectively protecting the current collector from corrosion and thereby improving the life of the current collector. Furthermore, the conductive carbon layer itself has a low resistivity, thus preventing excessive electrical losses. The conductive carbon layer can be made of flake graphite, spherical graphite, carbon nanotubes, graphene, etc.

[0059] In some embodiments, the negative electrode active material particles in the negative electrode active layer are the carriers of the oxidation reaction in the battery cell. The negative electrode active material can be divided into two categories: carbon materials and non-carbon materials: carbon-based materials include graphite materials (natural graphite, artificial graphite and intermediate carbon spheres) and other carbon-based materials (hard carbon, soft carbon and graphene); non-carbon-based materials can be further divided into titanium-based materials, silicon-based materials, tin-based materials, nitrides and metallic lithium, etc.

[0060] In some embodiments, the negative electrode active layer may include a first negative electrode active layer and a second negative electrode active layer, wherein the first negative electrode active layer is located between the negative electrode current collector and the second negative electrode active layer. The first active layer and the second active layer are arranged on the negative electrode current collector. By providing two layers of active material, firstly, the first negative electrode active layer is closer to the negative electrode current collector, so that the stability and conductivity of the lower surface of the negative electrode current collector connected to the active coating layer are better, thereby improving the electrochemical performance and cycle performance of the negative electrode; secondly, the second negative electrode active layer is farther away from the negative electrode current collector and contacts the separator 3. The surface of the negative electrode side thereof is prone to lithium deposition. Therefore, the second negative electrode active layer in contact with the separator 3 can focus on stability and conductivity, thereby facilitating the smooth insertion and extraction of lithium ions into and out of the positive and negative electrode materials.

[0061] The diaphragm 3 is located between the positive electrode sheet 1 and the negative electrode sheet 2 to prevent short circuit problems caused by physical contact between the positive electrode sheet 1 and the negative electrode sheet 2. At the same time, it allows lithium ions to freely shuttle through the micropores and hinders the transmission of electrons, so that the ions and electrons form a circuit during the charging and discharging process of the battery; as a carrier of the electrolyte, it adsorbs the electrolyte to ensure the efficiency of ion transmission; at high temperatures, it closes the pores to block the flow of ions and prevent thermal runaway.

[0062] The diaphragm 3 can be any one of a microporous membrane, a modified microporous membrane, a non-woven fabric diaphragm 3 and a composite diaphragm 3. A microporous membrane is a diaphragm 3 with a pore size in the micrometer range, mainly including polyolefin microporous membranes and other polymer microporous membranes. A modified microporous membrane is a diaphragm 3 obtained by modifying a microporous membrane. Common modification methods include surface treatment, chemical grafting, surface coating, etc. Non-woven fabric diaphragms 3 have a small fiber diameter and generally exhibit a higher porosity than other types of diaphragms 3. Composite diaphragms 3 are prepared by coating or filling an inorganic material in a microporous membrane or a non-woven fabric diaphragm 3, and have higher thermal stability and electrolyte wettability than other types of diaphragms 3.

[0063] The substrate layer 100 is the base of the separator 3 , and the substrate layer 100 may be any one of a microporous membrane, a modified microporous membrane, a non-woven fabric separator 3 , and a composite separator 3 .

[0064] The material of the substrate layer 100 includes polyimide (PI), polypropylene (PP), polyethylene (PE), and nano-silicon dioxide wrapped with PVP.

[0065] The substrate layer 100 may be a 3D mesh structure woven of nanofibers, and the mesh structure is a through hole 101. In this way, a membrane 3 with controllable morphology and adjustable porosity can be obtained by changing the spinning conditions, thereby controlling the conductivity of the membrane 3.

[0066] In some embodiments, the porosity of the substrate layer 100 is 60% to 70%. The porosity of the substrate layer 100 can be 60%, 62%, 64%, 66%, 68% or 70%. In this way, when the scale unit 110 of the functional layer 11 is heated and opened, the high porosity of 60% to 70% of the substrate layer 100 means that its through-hole 101 network is extremely developed. After the through-holes 12 are formed, the electrolyte can flow at high speed through these high-density, large-sized through-holes 101 under the action of convection, quickly transferring the heat from the hot spots inside the core to the electrolyte as a whole, significantly reducing the local temperature rise rate.

[0067] In some embodiments, the substrate layer 100 is a 3D mesh structure woven from PI nanofibers with a porosity of 60% to 70%. PI's glass transition temperature (Tg) is typically above 300°C, and its decomposition temperature is above 500°C. In the early stages of thermal runaway, the PI substrate layer 100 can maintain its rigidity and resist deformation, ensuring the structural stability of the through-holes 101 and preventing a decrease in porosity or contact between the positive and negative electrodes due to softening and shrinkage. In the later stages of thermal runaway, PI can still maintain its skeletal structure, providing a final physical barrier to prevent direct, large-scale short circuits between the positive and negative electrodes. Secondly, PI has high mechanical strength and can maintain high mechanical strength even at high porosity, thereby withstanding the stresses during cell winding or thermal expansion, as well as the dynamic stress of the hinge structure when the scale unit 110 opens and closes without breaking.

[0068] The functional layer 11 acts as a switch, forming a gap when thermal runaway occurs, and allowing the electrolyte to flow freely through the separator 3 .

[0069] The functional layer 11 is composed of a plurality of scale units 110 arranged in an array.

[0070] The scale unit 110 can be as follows Figure 2 As shown, the regular hexagonal shape maximizes coverage when densely packed, minimizing defects such as dangling bonds at the edges. The regular hexagon is one of the most isotropic polygons, evenly distributing stress when subjected to external forces, making it less susceptible to cracking. Compared to pentagons, quadrilaterals, and triangles, the hexagon is less likely to generate localized stress concentrations when bent or stretched.

[0071] In other embodiments, the scale unit 110 may be a pentagon, a quadrilateral, a triangle or an irregular shape, as long as a portion of the scale unit 110 is fixed on the substrate layer 100 and can be opened and closed.

[0072] In some embodiments, the flake unit 110 is a regular hexagon with a side length of 20μm to 25μm. This allows the 20μm to 25μm size to match the resolution of conventional ultraviolet lithography in micro-electromechanical systems (MEMS) lithography processes, eliminating the need for high-cost equipment such as electron beams and reducing manufacturing costs. When the 20μm to 25μm flake is bent on the substrate layer 100, the strain is moderate, preventing breakage. The side lengths of the flake unit 110 can be 20μm, 21μm, 22μm, 23μm, 24μm, or 25μm.

[0073] In some embodiments, the scale unit 110 includes a structural layer 112 and a connecting layer 113 . The connecting layer 113 is located between the substrate layer 100 and the structural layer 112 . The connecting layer 113 is located at the edge of the structural layer 112 . The trigger material 111 is connected to the surface of the structural layer 112 .

[0074] In some embodiments, the structure layer 112 is a regular hexagon with a side length of 20 μm to 25 μm.

[0075] In some embodiments, the material of the structure layer 112 may be polysilicon, silicon nitride, Su-8 photoresist, aluminum oxide, silicon oxide, hexagonal boron nitride (h-BN), or MXenes.

[0076] In some embodiments, the thickness of the structural layer 112 is 1 μm to 10 μm. The thickness of the structural layer 112 can be 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, or 10 μm.

[0077] The connecting layer 113 is used to connect the structural layer 112 and the substrate layer 100 , so that the structural layer 112 can rotate freely along a fixed or movable axis.

[0078] The material of the connection layer 113 can be PI or a metal material, such as aluminum foil or copper foil. In this way, the connection layer 113 can have high strength, so that the scale unit 110 still has high mechanical strength after multiple openings and closings, thereby improving the safety and stability of the secondary battery.

[0079] In some embodiments, the scale unit 110 further includes an isolation layer, which is located on a side of the structural layer 112 close to the substrate layer 100. The isolation layer is used to prevent adhesion between the structural layer 112 and the substrate layer 100, thereby preventing subsequent opening and closing.

[0080] The material of the isolation layer may be aluminum oxide.

[0081] Figure 4 Another cross-sectional view of a separator in a secondary battery provided in one embodiment of the present application.

[0082] In some embodiments, reference Figure 4 The trigger material 111 is a thermosensitive material that changes volume with temperature to drive the scale unit 110 to open and close. The thermosensitive material is combined with the active functional groups on the surface of the structural layer 112 through chemical bonds or strong physical effects. For example, the material of the structural layer 112 is MXenes (Ti3C2T x ), the -O or -OH functional groups on its surface directly esterify with the terminal carboxyl groups of PNIPAM in the thermosensitive material to form covalent bonds (CN or Si-O). The deformation path is that the thermosensitive material expands upon heating, which in turn drives the structural layer 112 to rotate around the hinge of the connecting layer 113. The gaps between the scales expand to form through-holes 12, ensuring that the through-holes 101 are exposed.

[0083] Among them, PNIPAM is poly (N-isopropylacrylamide), the chemical formula is (C6H 11 NO) n , which is polymerized from the monomer N-isopropylacrylamide (NIPAM)

[0084] In some embodiments, the thermosensitive material comprises a thermosensitive polymer with an acrylate polymer grafted onto its surface. The grafted polymer forms a nanoscale brush-like structure on the substrate surface. When heated, the side chains expand synergistically, driving the directional rotation of the scale units 110 and providing higher sensitivity. The acrylate polymer grafted layer shields the thermosensitive groups from direct contact with the electrolyte, preventing swelling failure.

[0085] In some embodiments, the thermosensitive polymer material includes poly(N-isopropylacrylamide) (PNIPAM) or polyvinylpyrrolidone (PVP). By grafting poly(N-isopropylacrylamide), a polymer with a low critical solution temperature (LCST ≈ 32°C), the material undergoes a hydrophilic-to-hydrophobic transition when the set temperature is reached, triggering a rapid volume expansion. This allows for rapid temperature response and secures the safety window.

[0086] In some embodiments, the opening and closing angle of the structural layer 112 is between 0° and 100°. This range allows the structural layer 112 to be opened, exposing more through-holes 101, while preventing deformation of the structural layer 112 from exceeding its mechanical strength, thereby reducing the potential safety hazard of hidden cracks. The opening and closing angle of the structural layer 112 is 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, 90°, or 100°.

[0087] In some embodiments, the molecular weight of the thermosensitive acrylic polymer (AAc) is 20 kDa to 50 kDa, taking both response speed and film-forming properties into consideration.

[0088] In some embodiments, the molar ratio of AAc is less than or equal to 20 mol %. Too much AAc will destroy the temperature sensitivity of PNIPAM, causing the lower critical solution temperature (LCST) to be blurred or even disappear.

[0089] In some embodiments, the trigger material 111 is a shape memory alloy, such as NiTi.

[0090] Figure 5 Another cross-sectional view of a separator in a secondary battery provided in one embodiment of the present application;

[0091] refer to Figure 5 In some embodiments, the diaphragm 3 further includes a functional modification layer 114, which is located on the surface of the functional layer 11 close to the substrate layer 100. The ionic conductivity of the material of the functional modification layer 114 is 8×10 -5 S / cm~2×10 - 3 Thus, at higher temperatures, the functional modification layer 114 can provide good ion transport performance and alleviate thermal runaway.

[0092] In some embodiments, the material of the function modification layer 114 includes lithium aluminum titanium phosphate (LATP), lithium lanthanum titanate / lithium lanthanum titanate (LLTO), or lithium lanthanum zirconate / lithium lanthanum zirconate (LLZO).

[0093] In some embodiments, the thickness of the function modification layer 114 is 180 nm to 220 nm. The thickness of the function modification layer 114 can be 180 nm, 190 nm, 200 nm, 210 nm, or 220 nm.

[0094] Figure 6 This is another cross-sectional view of a separator in a secondary battery provided in one embodiment of the present application.

[0095] Combined with reference Figure 1 and Figure 6 In some embodiments, the separator 3 may be coated with a polyvinylidene fluoride (PVDF) material as an adhesive layer 120 to impart excellent adhesion and flexibility to the separator 3. The excellent adhesion of the separator 3 allows for good contact between the separator 3 and the positive electrode sheet 1 or between the separator 3 and the negative electrode sheet 2, thereby reducing the assembly time of the energy storage cell and effectively lowering the overall production cost of the energy storage cell. The excellent flexibility of the separator 3 also enhances its strength, effectively improving its impact resistance.

[0096] In some embodiments, the secondary battery further includes a positive tab and a negative tab. The positive tab / negative tab is a metal conductor that leads the positive electrode sheet 1 / negative electrode sheet 2 of the energy storage cell from the battery cell. The positive tab / negative tab serves as the contact point between the positive electrode sheet 1 / negative electrode sheet 2 and external contact components during charging and discharging of the battery cell. The external contact component can be a terminal.

[0097] An electrolyte is a carrier that conducts electrons between the positive and negative electrodes in a battery. In some embodiments, the electrolyte can be an electrolyte solution composed of three parts: a solvent, a lithium salt, and additives. The solvent is used to dissolve the lithium salt and can include cyclic carbonates (PC, EC); linear carbonates (DEC, DMC, EMC); and carboxylates (MF, MA, EA, MA, MP, etc.). The lithium salt can be LiPF6, LiClO4, LiBF4, LiAsF6, etc. Additives can include one or more of the following: film-forming additives, conductive additives, flame retardant additives, overcharge protection additives, additives to control the H2O and HF content in the electrolyte, additives to improve low-temperature performance, and multifunctional additives.

[0098] In some embodiments, the secondary battery may further include a top cover, an adapter plate, and a terminal. The top cover engages with the outer shell. The adapter plate is located within the chamber and electrically connected to the terminal tab. The terminal extends through the top cover, and one end of the terminal is electrically connected to the adapter plate.

[0099] Among them, the adapter plate includes at least a first adapter plate and a second adapter plate, the pole includes a positive pole pole and a negative pole pole, the first adapter plate is electrically connected to the positive pole ear and the positive pole pole of the positive pole plate 1 respectively, and the second adapter plate is electrically connected to the negative pole ear and the negative pole pole of the negative pole plate 2 respectively.

[0100] In the secondary battery provided by the embodiment of the present application, a functional layer 11 is provided on the surface of the substrate layer 100. The functional layer 11 is composed of a plurality of scale units 110 arranged in an array. The functional layer 11 also includes a trigger material 111. The trigger material 111 is connected to the surface of the scale unit 110. The trigger material 111 is used to open and close the scale unit 110 to form a through hole 12. The through hole 12 exposes at least one through hole 101, and instantly opens a large number of additional, low-resistance ion channels on the diaphragm 3, greatly reducing the ion transmission resistance and making the current distribution more uniform. It can effectively alleviate the severe lithium dendrite precipitation caused by excessive local current density on the negative electrode surface at high temperature. After a large number of through holes 12 are opened, the electrolyte can flow freely through the diaphragm 3 under the action of convection, which is beneficial to enhance the heat transfer efficiency inside the battery. Heat can diffuse from the hot spot to the entire battery or shell more quickly, effectively avoiding the situation where the local temperature soars sharply beyond the critical point or even thermal runaway. The formation of the through-hole 12 ensures that the electrolyte can fully infiltrate the electrode sheet even at high temperature, maintain a relatively normal interface, reduce local high impedance and intense heat generation side reactions caused by poor infiltration, and improve the yield of the secondary battery.

[0101] Accordingly, according to some embodiments of the present application, another aspect of the present application provides a method for preparing a secondary battery, which is used to prepare the secondary battery provided by the above embodiments. The technical features that are the same as or corresponding to the above embodiments will not be described in detail here.

[0102] The preparation method includes: forming a diaphragm 3, the diaphragm 3 includes: a substrate layer 100; a through hole 101 in the substrate layer 100; a functional layer 11, the functional layer 11 is located on at least one surface of the substrate layer 100, and the functional layer 11 is composed of a plurality of scale units 110 arranged in a hinged connection structure; the functional layer 11 includes a trigger material 111, the trigger material 111 is connected to the surface of the scale unit 110, and the trigger material 111 is used to make the scale unit 110 open and close to form a through hole 12, and the through hole 12 exposes at least one through hole 101.

[0103] The preparation method includes forming a substrate layer 100 .

[0104] The substrate layer 100 was prepared using an electrospinning method. The process steps for forming the substrate layer 100 included preparing a PI solution with a solid content of 13 wt% to 17 wt%, and forming the substrate layer 100 with a fiber diameter of 80 nm to 100 nm, a porosity of 65 ± 5%, and a thickness of 20 μm under process parameters of a voltage of 25 kV, a receiving distance of 15 cm, and a flow rate of 1.2 mL / h.

[0105] The substrate layer 100 was prepared using a sol-gel method. The process steps for forming the substrate layer 100 included preparing a coating solution using polyvinyl pyrrolidone, tetraethyl orthosilicate, and butanol. Nano-sized silica was then mixed into the coating solution. The coating solution was then spin-coated at a speed of 3000 rpm to form a film, which was then dried at 80°C for 2 hours. This produced a substrate layer 100 with a pore size of 50 nm to 200 nm and a thickness of 10 μm to 50 μm.

[0106] In some embodiments, the scale unit 110 is formed using a micro-electromechanical process or an ion etching process.

[0107] In some embodiments, the process steps for forming the flake unit 110 include: forming a sacrificial layer on the surface of the substrate layer 100; patterning the sacrificial layer to form a first hole, with the bottom surface of the first hole exposing the substrate layer 100; forming a connecting layer 113, with the connecting layer 113 being located in the first hole; forming a first film layer, with the first film layer being located on the surface of the sacrificial layer and the surface of the connecting layer 113; patterning the first film layer to form multiple flake-shaped structural layers 112; and removing the sacrificial layer.

[0108] The material of the sacrificial layer may be silicon oxide, borosilicate glass or phosphosilicate glass. The etching solution for removing the sacrificial layer may be a 49% HF solution.

[0109] In some embodiments, the scale unit 110 is formed using a laser etching process.

[0110] In some embodiments, a surface photografting process is used to form a thermosensitive material, including: forming a thermosensitive polymer of an acrylate polymer; mixing the thermosensitive polymer of the acrylate polymer with an initiator, and dropping the thermosensitive polymer at a temperature of 80°C, a pressure of 10Pa, and a deposition rate of 0.1um / min. The initiator in the thermosensitive polymer of the acrylate polymer and the thermosensitive polymer of the acrylate polymer are grafted to the surface of the structural layer 112 through ultraviolet irradiation to form short linear grafted chains, which grow into side chains through continuous ultraviolet irradiation, and finally form a coating composed of the thermosensitive material.

[0111] In some embodiments, a spraying process is used to form a thermosensitive material, including: forming a prepolymer solution, the dispersion liquid is ethanol, the solid content of the thermosensitive polymer of the acrylic polymer is 8%~12%, and the particle size distribution D50 of the thermosensitive polymer of the acrylic polymer is 0.8μm; under the parameters of a nozzle diameter of 100μm, a pressure of 0.2MPa, and a spacing of 5cm, a thermosensitive material with a thickness of 1μm~2μm and a phase change temperature of 45±3°C is formed.

[0112] The process steps for forming the functional modification layer 114 include: providing a material of the functional modification layer as a target material; -4The functional modification layer 114 with a thickness of 200±10 nm is formed by sputtering under the following process parameters: Pa, Ar gas flow rate of 20 sccm, sputtering power of 150 W, substrate temperature of 200° C., and deposition rate of 0.3 nm / s.

[0113] In some embodiments, the process steps for forming the diaphragm 3 also include: forming prepolymer capsules, the prepolymer capsules including a urea-formaldehyde resin shell and prepolymer particles, the prepolymer particles including a hydroxyl-containing siloxane prepolymer and a platinum catalyst; dispersing the prepolymer capsules in an adhesive solution to form a mixed slurry; screen printing, screen printing the mixed slurry on the surface of the substrate layer 100, and curing to form an adhesive layer 120 on the surface of the functional layer 11.

[0114] In some embodiments, the urea-formaldehyde resin shell is obtained by in-situ polymerization of urea:formaldehyde at a molar ratio of 1:(1.2-1.8).

[0115] Provide a positive electrode sheet 1 and a negative electrode sheet 2; stack the negative electrode sheet 2, the separator 3 and the positive electrode sheet 1 in sequence, stack the negative electrode sheet 2, the separator 3 and the positive electrode sheet 1 in sequence, and obtain a battery cell assembly by winding or stacking. Place the battery cell assembly in a battery shell, inject an electrolyte into the battery shell, and encapsulate to obtain a secondary battery.

[0116] According to some embodiments of the present application, another aspect of the embodiments of the present application provides an energy storage system, including: a secondary battery prepared by the method for preparing a secondary battery as in any of the above embodiments or a secondary battery as in the above embodiments.

[0117] According to some embodiments of the present application, on the other hand, embodiments of the present application provide an electrical device, including: a secondary battery prepared by the method for preparing a secondary battery as in any of the above embodiments, a secondary battery as in the above embodiments, or an energy storage battery pack as in the above embodiments.

[0118] The beneficial effects of the embodiments of the present application will be further illustrated below in combination with examples and comparative examples.

[0119] Example 1:

[0120] (1) A diaphragm is prepared, the diaphragm comprising: a PI substrate layer having a through hole in the PI substrate layer; a functional layer, the functional layer being located on at least one surface of the substrate layer, the functional layer being composed of a plurality of scale units arranged in a hinge-type connection structure; the functional layer comprising a trigger material, the trigger material being connected to the surface of the scale unit, the trigger material being used to open and close the scale unit to form a through hole, the through hole exposing at least one through hole.

[0121] (2) Assemble secondary batteries.

[0122] The thermal performance test, mechanical strength test, sensitivity test and electrochemical performance test were carried out on the examples in sequence, and the test results were summarized and recorded in Table 1.

[0123] Thermal performance test: Cut the diaphragm into 100mm square specimens according to GB / T 13542.2. Then hang the specimens in a natural air circulation oven and dry them at 180°C for 1 hour. Then remove the specimens from the oven, cool them to room temperature, and remeasure the dimensions in all directions. The thermal shrinkage is then calculated.

[0124] Puncture resistance test: The puncture strength test of the diaphragm is carried out in accordance with the standard of GB / T 36363, and the thickness is tested at 4 points around the pinhole, the average value is taken, and the puncture strength is calculated.

[0125] Table 1

[0126]

[0127] It can be seen from the data in Table 1 that the secondary battery provided in the embodiment of the present application has high mechanical strength, moderate ionic conductivity, and low thermal shrinkage, thereby maintaining the free penetration of lithium ions and improving thermal runaway.

[0128] Those skilled in the art will appreciate that the above-described embodiments are specific examples for implementing the present application, and that in actual applications, various changes in form and detail may be made thereto without departing from the spirit and scope of the present application. Any person skilled in the art may make various changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined in the claims.

Claims

1. A secondary battery, characterized in that: include: A battery case, wherein the battery case has a cavity therein, and the cavity contains an electrolyte; A battery cell assembly, the battery cell assembly is located in the cavity and immersed in the electrolyte; the battery cell assembly includes a wound positive electrode sheet, a separator and a negative electrode sheet, wherein the separator includes: a substrate layer, wherein the substrate layer has a through hole; A functional layer is located on at least one surface of the substrate layer, and the functional layer is composed of a plurality of scale units arranged in a hinged structure; the functional layer includes a trigger material, and the trigger material is connected to the surface of the scale unit, and the trigger material is used to make the scale unit open and close to form a through hole, and the through hole exposes at least one of the through holes; the trigger material is a temperature-sensitive material, and the temperature-sensitive material is used to undergo volume deformation as the temperature changes to drive the scale unit to open and close.

2. The secondary battery according to claim 1, wherein The temperature-sensitive material includes a temperature-sensitive polymer with an acrylic ester polymer grafted on the surface.

3. The secondary battery according to claim 2, wherein The material of the thermosensitive polymer includes poly(N-isopropylacrylamide) or polyvinylpyrrolidone.

4. The secondary battery according to claim 1, wherein The scale unit includes a structural layer and a connecting layer. The connecting layer is located between the substrate layer and the structural layer. The connecting layer is located at the edge of the structural layer. The trigger material is connected to the surface of the structural layer.

5. The secondary battery according to claim 4, wherein The scale unit further includes an isolation layer, which is located on a side of the structural layer close to the substrate layer.

6. The secondary battery according to claim 1, wherein The diaphragm further comprises a functional modification layer, which is located on the surface of the functional layer close to the substrate layer, and the ionic conductivity of the material of the functional modification layer is 8×10 -5 S / cm~2×10 -3 S / cm.

7. The secondary battery according to claim 6, characterized in that The material of the functional modification layer includes lithium aluminum titanium phosphate, lithium lanthanum titanate / lithium lanthanum titanate or lithium lanthanum zirconate / lithium lanthanum zirconate.

8. A method for preparing a secondary battery, characterized in that: include: A diaphragm is formed, the diaphragm comprising: a substrate layer; a substrate layer having a through hole therein; a functional layer located on at least one surface of the substrate layer, the functional layer being composed of a plurality of scale units arranged in a hinged structure; the functional layer comprising a trigger material connected to the surface of the scale unit, the trigger material being used to cause the scale unit to open and close to form a through hole, wherein the through hole exposes at least one of the through holes; the trigger material being a temperature-sensitive material, the temperature-sensitive material being used to undergo volume deformation as temperature changes, thereby driving the scale unit to open and close; Providing a positive electrode sheet and a negative electrode sheet; stacking the negative electrode sheet, a separator and a positive electrode sheet in sequence, stacking the negative electrode sheet, a separator and a positive electrode sheet in sequence, and obtaining a battery cell assembly by winding or laminating, placing the battery cell assembly into a battery shell, injecting an electrolyte into the battery shell, and encapsulating to obtain a secondary battery.

9. The method for preparing a secondary battery according to claim 8, wherein: The scale unit is formed by using a micro-electromechanical process or an ion etching process.

10. The method for preparing a secondary battery according to claim 9, wherein: The process steps for forming the scale unit include: forming a sacrificial layer on the surface of the substrate layer; Patterning the sacrificial layer to form a first hole, wherein a bottom surface of the first hole exposes the substrate layer; forming a connecting layer, wherein the connecting layer is located in the first hole; forming a first film layer, wherein the first film layer is located on a surface of the sacrificial layer and a surface of the connecting layer; patterning the first film layer to form a plurality of scale-like structural layers; The sacrificial layer is removed.

11. The method for preparing a secondary battery according to claim 8, wherein: The scale units are formed by adopting a laser etching process.

12. The method for preparing a secondary battery according to claim 8, wherein: The process steps for forming the diaphragm also include: forming a prepolymer capsule comprising a urea-formaldehyde resin shell and prepolymer particles, wherein the prepolymer particles comprise a hydroxyl-containing siloxane prepolymer and a platinum catalyst; dispersing the prepolymer capsules in a bonding solution to form a mixed slurry; Screen printing treatment: screen printing the mixed slurry on the surface of the substrate layer, and curing treatment to form an adhesive layer on the surface of the substrate layer away from the functional layer.

13. An energy storage system, characterized in that: include: A secondary battery according to any one of claims 1 to 7 or a secondary battery prepared by the method for preparing a secondary battery according to any one of claims 8 to 12.

14. An electrical device, characterized in that: include: The secondary battery according to any one of claims 1 to 7, the secondary battery prepared by the method for preparing a secondary battery according to any one of claims 8 to 12, or the energy storage system according to claim 13.

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