Diaphragm and preparation method thereof, battery and electric device

Abstract

The invention discloses a diaphragm and a preparation method thereof, a battery and an electric device. The separator includes a separator substrate and a metal ion trapping layer. Wherein the metal ion capture layer is arranged on at least one surface of the diaphragm base material and comprises an inorganic adsorbent and an organic adsorbent. The diaphragm can effectively relieve the passing of non-active metal ions released by a positive electrode material in the circulation process through the contained metal ion capture layer, so that the content of impurity metal ions on a negative electrode interface in a battery cell is effectively reduced, the phenomenon of generating impurity dendritic crystals on the negative electrode interface and the generation amount are obviously relieved, and the safety performance of the battery cell is improved. The battery comprises the diaphragm.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to a separator and its preparation method, a battery, and an electrical device. Background Technology

[0002] With the widespread application of batteries in fields including energy storage systems and new energy vehicles, battery safety and cycle performance are receiving increasing attention. Cathode materials play a crucial role in the electrochemical performance of batteries, including safety and cycle performance. Among them, inorganic cathode materials are widely used in lithium-ion batteries due to their relatively superior electrochemical performance, stability, and cost-effectiveness.

[0003] However, inorganic cathode materials generally possess various crystal structures, and during battery charging and discharging, the insertion and extraction of active metal ions often lead to phase transitions and structural changes. These changes can cause the inorganic cathode material to expand or contract in volume, thereby disrupting its structural integrity and releasing inactive metal ions. Simultaneously, during battery cycling, trace amounts of water and acid are often generated within the cell, also causing the release of inactive metal ions from the inorganic cathode material. These inactive metal ions migrate to the negative electrode through the separator and are easily reduced in low-potential environments, leading to the formation of impurity metal dendrites at the negative electrode interface, thus increasing battery safety risks. However, existing separators either do not effectively impede the passage of inactive metal ions or their effect is inadequate. Summary of the Invention

[0004] In view of the above problems, this application provides a separator, a method for preparing the separator, and a battery containing the separator, to solve the technical problem that existing separators do not have the function of preventing the passage of inactive metal ions or the function of preventing the passage of inactive metal ions is not ideal.

[0005] In a first aspect, embodiments of this application provide a diaphragm. The diaphragm of this application includes a diaphragm substrate and a metal ion trapping layer disposed on at least one surface of the diaphragm substrate; wherein the metal ion trapping layer comprises an inorganic adsorbent and an organic adsorbent.

[0006] The inorganic adsorbent in the metal ion capture layer of the membrane in this embodiment possesses high surface area, porous structure, and / or specific chemical properties, enabling it to physically adsorb and / or precipitate inactive metal ions. The organic adsorbent, with its abundant pore structure, pore size distribution, and functional groups, can also physically adsorb and / or complex inactive metal ions. Furthermore, by adjusting the distribution of inorganic and organic adsorbents in the metal ion capture layer and flexibly selecting their types, the inorganic and organic adsorbents can interact, resulting in a synergistic and enhanced effect in capturing inactive metal ions. This improves the capture capacity of the metal ion capture layer for inactive metal ions and reduces their permeability through the membrane. Therefore, the membrane in this embodiment, through the addition of a metal ion capture layer, endows the metal ion capture layer with the ability to capture inactive metal ions, effectively hindering their passage and reducing the permeability of the membrane to inactive metal ions. When the separator of the present application embodiment is used as a separator in the battery cell, it can effectively alleviate the inactive metal ions released by the positive electrode material during the battery cell cycle through the separator, thereby effectively reducing the content of impurity metal ions at the negative electrode interface, significantly alleviating the phenomenon and amount of impurity dendrite formation at the negative electrode interface, and improving the safety performance of the battery cell.

[0007] In some embodiments, the inorganic and organic adsorbents form a mixture in the metal ion trapping layer. By forming a mixture of inorganic and organic adsorbents and distributing it in the metal ion trapping layer, both adsorbents can perform their respective functions. The inorganic adsorbent can form a stable three-dimensional framework structure in the metal ion trapping layer, working synergistically with the organic adsorbent to give the metal ion trapping layer a specific pore structure, thereby improving the trapping effect of the metal ion trapping layer on inactive metal ions. Alternatively, the inorganic adsorbent can also change the charge distribution of the groups contained in the organic adsorbent, thereby enhancing the adsorption and / or complexation effects of the organic adsorbent on inactive metal ions. Therefore, when the inorganic and organic adsorbents form a mixture, they can play a synergistic and enhanced role in the metal ion trapping layer, thereby improving the trapping effect of the metal ion trapping layer on inactive metal ions and further reducing the permeability of the membrane to inactive metal ions in the embodiments of this application.

[0008] In the embodiments, in the metal ion capture layer formed by the mixture of inorganic and organic adsorbents, the mass ratio of the inorganic adsorbent to the organic adsorbent is 1:(0.05~1). This mass ratio range, while fully utilizing the adsorption effect of both on inactive metal ions, can enhance the adsorption synergistic effect of both on inactive metal ions, further improving the capture effect of the metal ion capture layer on inactive metal ions, thereby further reducing the permeability of the membrane to inactive metal ions in the embodiments of this application.

[0009] In this embodiment, the metal ion capture layer, which is a mixture of inorganic and organic adsorbents, further includes a binder. The binder forms a mixture with the inorganic and organic adsorbents, and the mass ratio of the inorganic adsorbent, the organic adsorbent, and the binder is 1:(0.05–1):(0.01–0.05). This content range of binder effectively binds the inorganic and organic adsorbents, improving the stability of their function in the metal ion capture layer and enhancing the mechanical properties of the membrane. This, in turn, improves the stability of the synergistic effect between the inorganic and organic adsorbents and enhances the stability of the metal ion capture layer for capturing inactive metal ions.

[0010] In the embodiments, in the metal ion capturing layer formed by the mixture of inorganic and organic adsorbents, the thickness of the metal ion capturing layer is 200–500 nm. This thickness range allows for adjustment of the metal ion capturing layer's thickness ratio within the membrane and its modification effect on the membrane surface. It also allows for adjustment of the content of inorganic and organic adsorbents within the membrane, thereby improving the capturing effect of the metal ion capturing layer on inactive metal ions and further reducing the permeability of the membrane to inactive metal ions in this embodiment.

[0011] In the embodiments, in the metal ion capturing layer formed by the mixture of inorganic and organic adsorbents, the porosity of the metal ion capturing layer is 20% to 50%. This porosity range allows the metal ion capturing layer, together with the membrane substrate, to adjust the total porosity of the membrane in this embodiment. While fully utilizing the capturing effect of the metal ion capturing layer on inactive metal ions, it also allows for further adjustment of the membrane's active metal ion flux and electrolyte wettability.

[0012] In some embodiments, the metal ion capture layer includes an inorganic adsorption layer and a porous organic adsorption layer stacked with the inorganic adsorption layer, and either the inorganic adsorption layer or the porous organic adsorption layer is stacked with the surface of the membrane substrate, wherein the inorganic adsorption layer contains the inorganic adsorbent and the porous organic adsorption layer contains the organic adsorbent.

[0013] By forming an inorganic adsorbent and an organic adsorbent in a stacked manner, an inorganic adsorbent layer and a porous organic adsorbent layer are formed, respectively. The two adsorbent layers can perform a relay adsorption of inactive metal ions, so that inactive metal ions can be adsorbed and captured in the corresponding adsorbent layers in sequence. This improves the capture effect of the metal ion capture layer on inactive metal ions and further reduces the permeability of the membrane of this embodiment to inactive metal ions.

[0014] In this embodiment, the thickness ratio of the inorganic adsorption layer to the porous organic adsorption layer is 1:(0.1~1.0).

[0015] In this embodiment, the porosity of the metal ion trapping layer is 20% to 50%.

[0016] By controlling the thickness ratio of the two adsorption layers and the porosity of the metal ion capturing layer within this range, the metal ion capturing layer and the membrane substrate can be used to adjust the total thickness and pore structure of the membrane in this embodiment, thereby adjusting the migration path of inactive metal ions. This can further reduce the permeability of the membrane to inactive metal ions and adjust the wettability of the membrane to the electrolyte.

[0017] In the embodiments, the thickness of the inorganic adsorption layer is 200–600 nm.

[0018] In the embodiments, the thickness of the porous organic adsorption layer is 50–300 nm.

[0019] The inorganic adsorption layer and the porous organic adsorption layer within this thickness range together can adjust the thickness ratio of the metal ion capture layer in the membrane and the content of the inorganic adsorption layer and the porous organic adsorption layer in the membrane, thereby improving the capture effect of the metal ion capture layer on inactive metal ions and further reducing the permeability of the membrane to inactive metal ions in the embodiments of this application.

[0020] In the embodiment, the inorganic adsorption layer further includes a first binder, the first binder and the inorganic adsorbent forming a mixture, and the mass ratio of the inorganic adsorbent to the first binder is 1:(0.01~0.05);

[0021] In the embodiments, the porous organic adsorption layer further includes a second binder, which forms a mixture with the organic adsorbent, and the mass ratio of the organic adsorbent to the second binder is 1:(0.01~0.05).

[0022] By adding binders to the inorganic adsorption layer and the porous organic adsorption layer respectively, and controlling the binder content in the two layers within the above-mentioned range, the structural stability of the inorganic adsorption layer and the porous organic adsorption layer can be improved respectively, thereby improving the stability of the metal ion capture layer composed of the inorganic adsorption layer and the porous organic adsorption layer in capturing inactive metal ions.

[0023] In some embodiments, the membrane substrate includes a first membrane substrate and a second membrane substrate, and the metal ion capturing layer is stacked between the first membrane substrate and the second membrane substrate. In this case, the first membrane substrate, the second membrane substrate, and the metal ion capturing layer constitute a sandwich structure. This sandwich structure membrane is stable, and its effect and performance in adsorbing inactive metal ions are relatively stable.

[0024] In the embodiments, the thicknesses of the first and second membrane substrates are the same or different, ranging from 2.5 to 25 μm. This thickness range allows the first and second membrane substrates to improve the flux of active metal ions in the membrane of this embodiment, while also adjusting the total thickness and mechanical properties of the membrane.

[0025] In some embodiments, the particle size (Dv50) of at least one of the inorganic adsorbent and the organic adsorbent is the same or different, ranging from 50 to 150 nm. This particle size range can improve the pore structure of the metal ion trapping layer and enhance the adsorption of inactive metals by the inorganic adsorbent and the organic adsorbent.

[0026] In some embodiments, the inorganic adsorbent includes at least one of a metal ion precipitant and an inorganic porous adsorbent.

[0027] In the embodiments, the metal ion precipitant includes at least one of phosphate salts, silicate salts, carbonate salts, and oxalate salts.

[0028] In the embodiments, the inorganic porous adsorbent is at least one of bentonite, attapulgite, hydroxyapatite, molecular sieve, alumina, silica gel, and zinc oxide.

[0029] In some embodiments, the organic adsorbent comprises a porous organic adsorbent.

[0030] In the embodiments, the porous organic adsorbent includes at least one of covalent organic frameworks, organosulfur, metal-organic frameworks, hydrogen-bonded organic frameworks, and crystalline porous organic salts.

[0031] These types of inorganic and organic adsorbents can perform at least one of the following actions on inactive metal ions that migrate to the metal ion capture layer: precipitation, complexation, and adsorption. This firmly adsorbs the inactive metal ions into the metal ion capture layer, reducing the migration of inactive metal ions to the negative electrode through the membrane. As a result, it effectively reduces the occurrence of undesirable phenomena such as crystallization of impurity metal ions or further growth of impurity dendrites at the negative electrode interface.

[0032] In some embodiments, the thickness of the membrane is 4–50 μm. This thickness range allows for further adjustment of the proportion of inorganic and organic adsorbents in the membrane and regulation of the migration pathway of inactive metal ions, thereby improving the membrane's ability to capture inactive metal ions and reducing the permeability of inactive metal ions through the membrane.

[0033] In some embodiments, the porosity of the membrane is 20% to 60%. This range of porosity can improve the ion transport efficiency and electrolyte wettability of the membrane in the embodiments of this application.

[0034] Secondly, embodiments of this application provide a method for preparing a diaphragm. The method for preparing a diaphragm according to embodiments of this application includes the following steps:

[0035] A metal ion trapping layer is formed on at least one surface of a diaphragm substrate to obtain a diaphragm;

[0036] The metal ion capture layer includes inorganic adsorbents and organic adsorbents.

[0037] The membrane preparation method of this application directly forms a metal ion trapping layer containing inorganic and organic adsorbents on at least one surface of the membrane substrate. The formed metal ion trapping layer has an adsorption effect on inactive metal ions, and together with the membrane substrate, it can hinder the passage of inactive metal ions, thereby reducing the permeability of inactive metal ions.

[0038] In some embodiments, the method of forming a metal ion trapping layer on at least one surface of the diaphragm substrate includes the following steps:

[0039] The inorganic adsorbent and the organic adsorbent are mixed with a binder to form a slurry;

[0040] The mixture slurry is subjected to a film-forming treatment on at least one surface of the diaphragm substrate to form the metal ion trapping layer.

[0041] This method can form a metal ion capturing layer containing a mixture of inorganic and organic adsorbents, which makes the two evenly dispersed and can enhance the adsorption of inactive metal ions, thereby improving the capturing effect of the metal ion capturing layer on inactive metal ions and further reducing the permeability of the membrane to inactive metal ions in the embodiments of this application.

[0042] In the embodiment, the mass ratio of the inorganic adsorbent, the organic adsorbent, and the binder in the mixture slurry is 1:(0.05~1):(0.01~0.05).

[0043] In the embodiments, the viscosity of the mixture slurry is 500-3000 nm.

[0044] The mass ratio of inorganic adsorbent, organic adsorbent, and binder within a certain range, as well as the viscosity range of the slurry constituting the mixture, can improve the quality and mechanical properties of the metal ion capture layer, and enhance the capture effect of the metal ion capture layer on inactive metal ions.

[0045] In some embodiments, the method of forming a metal ion trapping layer on at least one surface of the diaphragm substrate includes the following steps:

[0046] The inorganic adsorbent and the first binder are combined to form a first mixture slurry;

[0047] The organic adsorbent is combined with the second binder to form a second mixture slurry;

[0048] The first mixture slurry is subjected to a first film-forming treatment on at least one surface of the diaphragm substrate to form an inorganic adsorption layer, and then the second mixture slurry is subjected to a second film-forming treatment on the surface of the inorganic adsorption layer opposite to the diaphragm substrate to form a porous organic adsorption layer; or, the second mixture slurry is subjected to a first film-forming treatment on at least one surface of the diaphragm substrate to form a porous organic adsorption layer, and then the first mixture slurry is subjected to a second film-forming treatment on the surface of the porous organic adsorption layer opposite to the diaphragm substrate to form an inorganic adsorption layer.

[0049] The formation of an inorganic adsorption layer and a porous organic adsorption layer stacked together can improve the capture effect of the metal ion capture layer on inactive metal ions, and further reduce the permeability of the membrane of this embodiment to inactive metal ions.

[0050] In the embodiment, the mass ratio of the inorganic adsorbent to the first binder in the first mixture slurry is 1:(0.01~0.05).

[0051] In the embodiments, the viscosity of the first mixture slurry is 500-2500 nm.

[0052] The range of mass ratios of the inorganic adsorbent to the first binder and the viscosity range of the slurry constituting the first mixture can improve the membrane quality and mechanical properties of the inorganic adsorbent layer, and enhance the adsorption of inactive metal ions by the inorganic adsorbent layer.

[0053] In the embodiment, the mass ratio of the organic adsorbent to the second binder in the second mixture slurry is 1:(0.01~0.05).

[0054] In the embodiment, the viscosity of the second mixture slurry is 500-3000 nm.

[0055] The range of mass ratios of the organic adsorbent to the second binder and the viscosity range of the slurry constituting the second mixture can improve the membrane quality and mechanical properties of the porous organic adsorption layer, and enhance the adsorption of inactive metal ions by the porous organic adsorption layer.

[0056] In some embodiments, the membrane substrate includes a first membrane substrate and a second membrane substrate. The metal ion trapping layer is formed on one surface of the first membrane substrate, and then the second membrane substrate is stacked on the surface of the metal ion trapping layer opposite to the first membrane substrate. Forming the metal ion trapping layer between the two membrane substrates creates a sandwich structure, which can improve the structural stability of the membrane and the stability of its ability to trap inactive metal ions.

[0057] Thirdly, embodiments of this application provide a battery. The battery of this application embodiment includes a separator according to embodiments of this application or a separator prepared by the separator preparation method of embodiments of this application.

[0058] The separator in the battery of this application embodiment can effectively reduce the amount of inactive metal ions passing through and migrating to the negative electrode, thereby significantly mitigating the content of impurity metal ions at the negative electrode interface, thus alleviating the phenomenon of impurity metal crystallization at the negative electrode interface and reducing the amount of impurity dendrite formation. Therefore, the safety of the battery cell in this application embodiment is significantly improved.

[0059] Fourthly, embodiments of this application provide an electrical device. The electrical device in this application includes the battery described in this application.

[0060] The electrical devices described in this application have high safety and long service life.

[0061] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0062] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0063] Figure 1 This is a schematic diagram of the structure of a diaphragm according to an embodiment of this application;

[0064] Figure 2 This is a schematic diagram of another structure of the diaphragm according to an embodiment of this application;

[0065] Figure 3 This is a schematic diagram of a third structure of the diaphragm according to an embodiment of this application;

[0066] Figure 4 This is a schematic diagram of the structure of the metal ion capture layer of the diaphragm in the embodiments of this application, which includes an inorganic adsorption layer and a porous organic adsorption layer;

[0067] Figure 5 This is a schematic diagram of the structure of a single battery cell according to an embodiment of this application;

[0068] Figure 6 for Figure 5 The diagram shows an exploded view of a single battery cell.

[0069] Figure 7 This is a schematic diagram of one embodiment of the battery module of this application;

[0070] Figure 8 This is an exploded view of the battery pack according to an embodiment of this application;

[0071] Figure 9 This is a schematic diagram of one embodiment of an electrical device that uses a battery as a power source, as described in the present application.

[0072] The reference numerals in the detailed embodiments are as follows:

[0073] 10-September;

[0074] 11-Separator substrate, 111-First diaphragm substrate, 112-Second diaphragm substrate;

[0075] 12-Metal ion trapping layer, 121-Inorganic adsorption layer, 122-Porous organic adsorption layer;

[0076] 20-Battery cell, 21-Casing, 22-Electrode assembly, 23-Cover plate;

[0077] 30-Battery Module;

[0078] 40 - Battery pack, 41 - Upper casing, 42 - Lower casing. Detailed Implementation

[0079] 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.

[0080] 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, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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).

[0085] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" 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 are not intended to 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.

[0086] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0087] Batteries, especially lithium-ion batteries, are widely used in electric vehicles, smartphones, tablets, and other fields as an important energy storage device. Battery performance and safety are crucial for the normal operation of devices and the safety of users. With technological advancements and societal progress, people are placing higher demands on battery safety.

[0088] A battery consists of a positive electrode, a negative electrode, and a separator between them. The positive electrode and separator, as crucial components, play a vital role in the battery's electrochemical performance, including safety. The separator isolates the positive and negative electrodes, prevents short circuits, and allows lithium ions to pass through, thus significantly contributing to the safety of lithium-ion batteries. The theoretical energy density of the positive electrode material determines the upper limit of the battery's energy density; the stability and degradation rate of the positive electrode material affect the battery's cycle life; and the thermal and chemical stability of the positive electrode material significantly impacts the battery's safety performance. Inorganic positive electrode materials are widely used in lithium-ion batteries due to their relatively superior electrochemical performance, stability, and cost-effectiveness.

[0089] However, inorganic cathode materials generally possess multiple crystal structures. During battery charging and discharging, the insertion and extraction of active metal ions often lead to phase transitions and structural changes. These changes can cause the inorganic cathode material to expand or contract, thereby disrupting its structural integrity and releasing inactive metal ions. Simultaneously, during battery cycling, trace amounts of water and acid are often generated within the cell, further contributing to the release of inactive metal ions from the inorganic cathode material. This release reduces the cathode material's capacity and can migrate through the separator to the negative electrode, accumulating at the negative electrode interface. Furthermore, these inactive metal ions are easily reduced in low-potential environments, leading to the formation of impurity metal dendrites at the negative electrode interface, thus increasing battery safety risks. Although the separator is positioned between the positive and negative electrodes, existing separators either lack the ability to impede the passage of inactive metal ions or their effect is inadequate, failing to effectively mitigate the permeation and migration of released inactive metal ions from the cathode material to the negative electrode, thereby increasing battery safety risks.

[0090] Although there are currently public reports of coatings containing inorganic substances on the surface of separators, these coatings are often intended to enhance the thermal stability of the separator and reduce the risk of thermal runaway in the battery. They are unlikely to effectively prevent or alleviate the permeation and migration of inactive metal ions released from the positive electrode material to the negative electrode. Instead, they can lead to other problems with the separator, such as reducing the overall permeability and wettability of the separator, which in turn affects the overall migration efficiency of active metal ions.

[0091] Therefore, in order to effectively mitigate the permeation and migration of inactive metal ions released from the positive electrode material to the negative electrode, reduce the amount of impurity dendrites growing at the negative electrode interface, and improve the safety of the battery cell, research has found that setting a metal ion capture layer containing inorganic and organic adsorbent materials on the surface of the separator substrate can effectively mitigate the permeation and aggregation of inactive metal ions released from the positive electrode material by the adsorption of inorganic and organic adsorbents at the negative electrode interface. This effectively reduces the content of inactive metal ions at the negative electrode interface, thereby effectively mitigating the formation of impurity dendrites at the negative electrode interface and reducing the amount of dendrites, thus improving the safety performance of the battery cell.

[0092] Diaphragm:

[0093] In a first aspect, embodiments of this application provide a diaphragm. The diaphragm of this application includes a diaphragm substrate and a metal ion trapping layer, the metal ion trapping layer being disposed on at least one surface of the diaphragm substrate. The metal ion trapping layer comprises an inorganic adsorbent and an organic adsorbent.

[0094] In the separator of this application embodiment, the separator substrate serves as the base layer for supporting the metal ion trapping layer, and also functions as a conventional separator in the battery cell. The surface of the separator refers to its two opposing surfaces. In this case, the metal ion trapping layer can be disposed on one of the separator surfaces or simultaneously on both opposing surfaces, forming a composite separator structure with two or more layers on the separator substrate. The metal ion trapping layer is a functional membrane layer formed from adsorbent materials including inorganic and organic adsorbents. This functional membrane layer adsorbs inactive metal ions, thereby reducing the ability of inactive metal ions to pass through the metal ion trapping layer, but has almost no impact on the passage of active metal ions such as lithium ions or sodium ions. Therefore, the metal ion trapping layer has a porous structure that allows at least active metal ions to pass through. Inactive metal ions, relative to the active metal ions contained in the positive electrode material, refer to other metal ions in the positive electrode material besides monovalent metal ions such as lithium ions or sodium ions, such as divalent or higher-valent metal ions. In the example, the inactive metal ions may include Fe... 3+ Cu 2+ Cr 3+ Ni 2+ At least one of the following; active metal ions refer to monovalent metal lithium ions (Li... + ) and sodium ions (Na + Low-valence metal ions, such as those that impart capacity to cathode materials, contribute to their performance.

[0095] The diaphragm in this application incorporates a metal ion trapping layer on at least one surface of the diaphragm substrate. This metal ion trapping layer modifies the surface of the diaphragm substrate, preventing the passage of inactive metal ions. Specifically, inorganic adsorbents, due to their high surface area, porous structure, and / or specific chemical properties, can physically adsorb and / or precipitate inactive metal ions. Organic adsorbents, with their abundant pore structure, pore size distribution, and functional groups, can physically adsorb and / or complex inactive metal ions. Therefore, both inorganic and organic adsorbents can effectively trap inactive metal ions, reducing their passage through the diaphragm.

[0096] Furthermore, by adjusting the distribution of inorganic and organic adsorbents in the metal ion capture layer and flexibly selecting the types of inorganic and organic adsorbents, the inorganic and organic adsorbents can interact with each other, such as forming a specific membrane structure or influencing each other's charge properties. This allows the two to play a synergistic and enhancing role in capturing inactive metal ions in the metal ion capture layer, thereby improving the capture capacity of the metal ion capture layer for inactive metal ions and reducing the effect of inactive metal ions passing through the membrane.

[0097] Therefore, the separator in this embodiment forms a metal ion trapping layer using inorganic and organic adsorbents, thereby endowing the metal ion trapping layer with the function of trapping inactive metal ions. This effectively prevents inactive metal ions from passing through the separator, reducing its permeability. Thus, when the separator is used as a separator in a battery cell, it effectively mitigates the accumulation of inactive metal ions released from the positive electrode material during cell cycling, thereby reducing the content of impurity metal ions at the negative electrode interface. This significantly reduces the formation and amount of impurity dendrites at the negative electrode interface, improving the safety performance of the battery cell.

[0098] Meanwhile, since inactive metal ions have a significantly higher charge and a significantly larger ion diameter than active metal ions, and active metal ions are almost impossible to precipitate, the metal ion capture layer, which includes inorganic and organic adsorbents, can significantly reduce the permeability of the membrane in this embodiment to high-valence inactive metal ions, and has almost no adverse effect on the passage of active metal ions through the membrane.

[0099] Based on the relationship between the membrane substrate and the metal ion trapping layer in the diaphragm of the embodiments of this application described above, in some embodiments, the diaphragm of the embodiments of this application may be as follows: Figures 1 to 3 Any of the structures shown:

[0100] In some embodiments, the structure of the diaphragm in this application can be as follows: Figure 1 As shown, the diaphragm 10 in this embodiment includes a diaphragm substrate 11, which has two surfaces disposed opposite to each other, and a metal ion trapping layer 12 is disposed on one of the surfaces of the diaphragm substrate 11.

[0101] In some embodiments, the structure of the diaphragm in this application can be as follows: Figure 2 As shown, the diaphragm 10 in this embodiment includes a diaphragm substrate 11, which has two surfaces disposed opposite to each other, and metal ion trapping layers 12 are respectively disposed on the two surfaces disposed opposite to each other.

[0102] In some embodiments, the structure of the diaphragm in this application can be as follows: Figure 3 As shown, the diaphragm 10 in this embodiment includes a diaphragm substrate 11 and a metal ion trapping layer 12. The diaphragm substrate 11 includes a first diaphragm substrate 111 and a second diaphragm substrate 112. The first diaphragm substrate 111 and the second diaphragm substrate 112 each have two surfaces disposed opposite to each other. The metal ion trapping layer 12 is stacked between the first diaphragm substrate 111 and the second diaphragm substrate 112 to form a sandwich structure.

[0103] Regardless of the structure of the diaphragm in the embodiments of this application as described above Figures 1 to 3 In any structure, the metal ion trapping layer 12 can act as a modified film layer that adsorbs inactive metal ions, thereby preventing inactive metal ions released from the positive electrode material from passing through the separator 10 of this embodiment. This reduces the content of inactive metal ions at the negative electrode interface in the battery cell, significantly alleviating adverse phenomena such as crystallization of impurity metal ions and further dendrite formation at the negative electrode interface, thus improving the safety of the battery cell. Figure 3 The sandwich structure diaphragm shown is relatively Figure 1 and Figure 2 The membrane shown, with the first membrane substrate 111 and the second membrane substrate 112, can effectively protect the metal ion capture layer 12, making the membrane structure of the metal ion capture layer 12 relatively stable, and making the membrane's function and performance in adsorbing inactive metal ions relatively stable.

[0104] In some embodiments, the thickness of the diaphragm in this application can be 4–50 μm, optionally 5–18 μm. In exemplary examples, it can be a typical but non-limiting thickness such as 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, 30 μm, 40 μm, 50 μm, or any range between two thickness values. Here, the thickness of the diaphragm refers to the sum of the thickness of the diaphragm substrate and the thickness of the metal ion trapping layer, such as… Figure 1 The sum of the thickness a of the diaphragm substrate 11 and the thickness b of the metal ion trapping layer 12 (i.e., a+b), or as... Figure 2 The sum of the thickness 'a' of the diaphragm substrate 11 and the thickness 'b' of the two metal ion trapping layers 12 (i.e., a + 2b), or as follows: Figure 3 The thickness a1 of the membrane substrate 111, the thickness a2 of the membrane substrate 112, and the thickness b of the metal ion trapping layer 12 (i.e., a1+a2+b) are considered together. Within this thickness range, the proportions of inorganic and organic adsorbents in the membrane can be further adjusted. This enhances the ability of the metal ion trapping layer to trap inactive metal ions, while also regulating the pore structure of the membrane substrate. This modulates the migration path of inactive metal ions and, by utilizing the significantly larger radius of inactive metal ions compared to active metal ions, reduces the permeability of inactive metal ions through the membrane. The thickness of this membrane can be measured using a micrometer or a thickness gauge, or more precisely, using a scanning electron microscope.

[0105] In some embodiments, the porosity of the diaphragm in this application embodiment can be 20% to 60%, optionally 30% to 50%. In exemplary examples, it can be typical but not limiting porosities such as 20%, 30%, 35%, 37%, 40%, 42%, 44%, 48%, 50%, 55%, and 60%, or any range between two porosity values. Here, the porosity of the diaphragm refers to the porosity of the composite membrane layer formed by the diaphragm substrate and the metal ion trapping layer. This range of porosity can improve the ion transport efficiency and electrolyte wettability of the diaphragm in this application embodiment.

[0106] [Separator Substrate]

[0107] In the diaphragm of this application embodiment, the diaphragm substrate it contains constitutes the diaphragm matrix, performs the function of a conventional diaphragm, and at the same time serves as a carrier for loading the metal ion capture layer.

[0108] In this embodiment, the thickness of the membrane substrate is the difference between the total thickness of the membrane and the thickness of the metal ion selectively permeable membrane layer. In some embodiments, the thickness of the membrane substrate can be 3–48 μm, optionally 4–16 μm. In exemplary examples, it can be typical but not limiting thicknesses such as 3 μm, 4 μm, 5 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 13 μm, 15 μm, 16 μm, 18 μm, 20 μm, 30 μm, 40 μm, and 48 μm, or any range between two thickness values. The thickness of the membrane substrate can be as follows: Figure 1 and Figure 2 The thickness 'a' of the single-layer diaphragm substrate 11, or as follows: Figure 3 The thickness a1 of the first diaphragm substrate 111 and the thickness a2 of the second diaphragm substrate 112 are combined. This thickness range of the diaphragm substrate can improve the flux of active metal ions in the diaphragm of this embodiment, and can also adjust the total thickness and mechanical properties of the diaphragm, thereby improving the electrochemical performance of the battery cell, including energy density. The thickness of the diaphragm substrate can be measured using a micrometer or a thickness gauge, or it can be precisely measured using a scanning electron microscope.

[0109] In some embodiments, the membrane substrate may comprise a single-layer or multi-layer membrane formed of at least one material selected from polyolefins, polyvinylidene fluoride (PVDF), polyimide, glass fiber, spandex, aramid, etc. In an exemplary example, the polyolefin may comprise at least one material selected from polyethylene (PE), polypropylene (PP), etc. When the membrane substrate comprises such... Figure 3When the first diaphragm substrate 111 and the second diaphragm substrate 112 are used, the materials of the first diaphragm substrate 111 and the second diaphragm substrate 112 can be the same or different. Diaphragm substrates of these material types have properties such as high thermal stability, chemical stability, corrosion resistance and good mechanical strength, thereby improving the thermal stability, chemical stability, corrosion resistance and good mechanical strength of the diaphragm in the embodiments of this application.

[0110] In this embodiment, the thickness of the first diaphragm substrate and the second diaphragm substrate can be as follows: Figures 1 to 2 The thickness of the diaphragm substrate is half (1 / 2). Therefore, in the embodiments, the thicknesses of the first diaphragm substrate and the second diaphragm substrate can be the same or different, ranging from 2.5 to 25 μm.

[0111] [Metal ion trapping layer]

[0112] In the metal ion trapping layer, the inorganic and organic adsorbents it contains adsorb inactive metal ions. In the embodiments, the inorganic and organic adsorbents can form a mixture and be distributed in the same adsorption layer, or they can be distributed in different adsorption layers, exerting a synergistic trapping effect on inactive metal ions. Therefore, the metal ion trapping layer can have the following structure:

[0113] In some embodiments, such as Figure 4 As shown, the metal ion trapping layer 12 includes an inorganic adsorption layer 121 and a porous organic adsorption layer 122, which are stacked together. The inorganic adsorption layer 121 and the porous organic adsorption layer 122 are, as shown in the figure. Figure 1 or Figure 2 The membrane substrate 11 shown is provided with layers stacked on its surface. Alternatively, it could be a porous organic adsorption layer 122 and, as shown... Figure 1 or Figure 2 The membrane substrate 11 shown is laminated on the surface. Alternatively, a composite layer of the inorganic adsorption layer 121 and the porous organic adsorption layer 122 is laminated as shown. Figure 3 The first membrane substrate 111 and the second membrane substrate 112 are shown. The inorganic adsorption layer 121 contains an inorganic adsorbent, and the porous organic adsorption layer 122 contains an organic adsorbent.

[0114] A composite membrane structure is formed by an inorganic adsorption layer 121 containing an inorganic adsorbent and a porous organic adsorption layer 122 containing an organic adsorbent. When inactive metal ions migrate to the inorganic adsorption layer 121 first, the inorganic adsorption layer 121 can precipitate or adsorb the inactive metal ions, thereby capturing at least a portion of the inactive metal ions. The remaining inactive metal ions pass through the porous organic adsorption layer 122 and are adsorbed and complexed by the porous organic adsorption layer 122, thereby capturing at least a portion of the remaining inactive metal ions in the porous organic adsorption layer 122. The same applies when inactive metal ions migrate to the porous organic adsorption layer 122 first; the two layers can play a relay capture role. Therefore, the composite membrane structure formed by the inorganic adsorption layer 121 and the porous organic adsorption layer 122 can synergistically adsorb inactive metal ions, thereby improving the capture effect of the metal ion capture layer 12 on inactive metal ions, further reducing the permeability of the membrane to inactive metal ions in this embodiment, so as to further reduce the enrichment of inactive metal ions at the negative electrode interface, thereby further reducing the formation and amount of impurity dendrites at the negative electrode interface, and further improving the safety performance of the battery cell.

[0115] In the embodiments, in such Figure 4 In the metal ion trapping layer 12 shown, the total porosity of the metal ion trapping layer 12 formed by the inorganic adsorption layer 121 and the porous organic adsorption layer 122 can be 20% to 50%, and can be selected as 25% to 35%. In the exemplary example, it can be a typical but non-limiting porosity such as 20%, 25%, 26%, 27%, 28%, 29%, 30%, 35%, 40%, 45%, 50%, or any range between two porosity values. The porosity of the metal ion trapping layer 12 refers to the total porosity of the metal ion trapping layer 12 formed by the inorganic adsorption layer 121 and the porous organic adsorption layer 122 disposed on a surface of the membrane substrate 11. The porosity within this range, together with the membrane substrate 11, can adjust the total porosity of the membrane in this embodiment. If the total porosity of the membrane is adjusted to the range mentioned above, while fully utilizing the metal ion trapping layer 12's ability to trap inactive metal ions, the ion transport efficiency and electrolyte wettability of the membrane in this embodiment can be further improved. The porosity of the metal ion trapping layer 12 can be measured using conventional nitrogen adsorption or conventional mercury intrusion porosimetry after the membrane substrate in this embodiment has been peeled off.

[0116] In the embodiments, in such Figure 4In the metal ion capturing layer 12 shown, the thickness ratio of the inorganic adsorption layer 121 to the porous organic adsorption layer 122 is 1:(0.1 to 1.0), optionally 1:(0.3 to 0.8). In the exemplary example, typical but non-limiting thickness ratios such as 1:0.1, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, and 1:1, or any range between two thickness ratios, are possible. This thickness ratio range of the two adsorption layers can further enhance the synergistic capture effect of the inorganic adsorption layer 121 and the porous organic adsorption layer 122 on inactive metal ions. Simultaneously, this thickness ratio range of the two adsorption layers can also adjust the total thickness and pore structure of the membrane in this embodiment, thereby adjusting the migration path of inactive metal ions to further reduce the permeability of the membrane to inactive metal ions, and can also adjust the wettability of the membrane to the electrolyte. At this point, the thickness of the monolayer metal ion trapping layer 12 is the sum of the thicknesses of the inorganic adsorption layer 121 and the porous organic adsorption layer 122 (that is, as shown below). Figure 4 (b1+b2 in the text). The thickness of the inorganic adsorption layer 121 and the porous organic adsorption layer 122 can be measured using a thickness gauge, or it can be measured using electron microscopy, such as scanning electron microscopy and X-ray photoelectron spectroscopy (XPS).

[0117] In the embodiments, in such Figure 4 In the metal ion trapping layer 12 shown, the thickness of the inorganic adsorption layer 121 can be 200-600 nm, or optionally 300-500 nm. In the exemplary example, it can be a typical but non-limiting thickness such as 200 nm, 300 nm, 320 nm, 340 nm, 360 nm, 380 nm, 400 nm, 500 nm, or any range between two thickness values.

[0118] In the embodiments, in such Figure 4 In the metal ion trapping layer 12 shown, the thickness of the porous organic adsorption layer 122 can be 50-300 nm, or optionally 100-250 nm. In the exemplary example, it can be a typical but non-limiting thickness such as 50 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, 250 nm, 300 nm, or any range between two thickness values.

[0119] The inorganic adsorption layer 121 and the porous organic adsorption layer 122 within this thickness range can together adjust the thickness ratio of the metal ion capture layer 12 in the membrane and the content of the inorganic adsorption layer and the porous organic adsorption layer in the membrane, thereby improving the capture effect of the metal ion capture layer 12 on inactive metal ions and further reducing the permeability of the membrane to inactive metal ions in the embodiments of this application.

[0120] In the embodiments, in such Figure 4In the metal ion capturing layer 12 shown, the inorganic adsorption layer 121 further includes a first binder, which forms a mixture with the inorganic adsorbent, and the mass ratio of the inorganic adsorbent to the first binder is 1:(0.01 to 0.05), which can be selected as 1:(0.01 to 0.03). In the exemplary example, it can be a typical but non-limiting mass ratio or a range between any two mass ratios, such as 1:0.01, 1:0.012, 1:0.014, 1:0.016, 1:0.018, 1:0.02, 1:0.03, 1:0.04, 1:0.05.

[0121] In the embodiments, in such Figure 4 In the metal ion capturing layer 12 shown, the porous organic adsorption layer 122 further includes a second binder, which forms a mixture with the organic adsorbent. The mass ratio of the organic adsorbent to the second binder can be 1:(0.01 to 0.05), or optionally 1:(0.015 to 0.035). In the exemplary example, it can be a typical but non-limiting mass ratio or a range between any two mass ratios, such as 1:0.01, 1:0.015, 1:0.018, 1:0.021, 1:0.024, 1:0.027, 1:0.03, 1:0.035, 1:0.04, 1:0.05.

[0122] Through such Figure 4 The inorganic adsorption layer 121 and the porous organic adsorption layer 122 shown are respectively provided with binders, and the contents of the first binder in the inorganic adsorption layer 121 and the second binder in the porous organic adsorption layer 122 are respectively controlled within the above range. This can improve the mechanical properties and structural stability of the membrane of the inorganic adsorption layer 121 and the porous organic adsorption layer 122, thereby improving the stability of the metal ion capture layer 12 composed of the inorganic adsorption layer 121 and the porous organic adsorption layer 122 in capturing inactive metal ions.

[0123] In the embodiments, the first binder in the inorganic adsorption layer 121 and the second binder in the porous organic adsorption layer 122 may be the same or the same, including at least one of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyvinyl ketone (PVP), and polymethyl methacrylate (PMMA). These binders can effectively improve the structural stability of the inorganic adsorption layer 121 and the porous organic adsorption layer 122.

[0124] In some embodiments, the metal ion capturing layer contained in the diaphragm of this application may also be a single layer, and the inorganic adsorbent and organic adsorbent form a mixture in the metal ion capturing layer. By setting the inorganic and organic adsorbents in a single layer, their respective adsorption effects on inactive metal ions can be utilized. Specifically, the inorganic adsorbent can precipitate or adsorb inactive metal ions, and the organic adsorbent can adsorb and complex inactive metal ions.

[0125] Meanwhile, since inorganic and organic adsorbents are distributed as a mixture within the metal ion trapping layer, and both can simultaneously enhance the adsorption of inactive metal ions, specifically, when the inorganic adsorbent is an inorganic porous adsorbent material, its high specific surface area, porous structure, and specific chemical properties allow it to form a stable three-dimensional framework structure within the metal ion trapping layer. The organic adsorbent can be distributed based on this three-dimensional framework structure. On the one hand, this effectively improves the mechanical properties of the metal ion trapping layer; on the other hand, it endows the metal ion trapping layer with a specific pore structure. This allows both inorganic and organic adsorbents to exert their respective adsorption effects while simultaneously enhancing the adsorption of inactive metal ions, thereby improving the trapping effect of the metal ion trapping layer on inactive metal ions. When the inorganic adsorbent is a precipitant that can precipitate inactive metal ions, the negative ions it contains, during the precipitation reaction with inactive metal ions, can alter the charge distribution of the functional groups in the organic adsorbent, thereby enhancing the adsorption and / or complexation effects of the organic adsorbent on inactive metal ions. Therefore, when inorganic and organic adsorbents form a mixture, they can work synergistically and enhance each other in the metal ion capture layer, thereby improving the capture effect of the metal ion capture layer on inactive metal ions and further reducing the permeability of the membrane to inactive metal ions in the embodiments of this application.

[0126] In the embodiments, in the metal ion capture layer formed by the mixture of inorganic and organic adsorbents, the mass ratio of the inorganic adsorbent to the organic adsorbent can be 1:(0.05-1), optionally 1:(0.1-0.7). In exemplary examples, typical but non-limiting mass ratios such as 1:0.05, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, and 1:1, or any range between two mass ratios, can be used. This mass ratio range, while fully utilizing the adsorption effect of both adsorbents on inactive metal ions, can enhance the adsorption synergistic effect of both adsorbents on inactive metal ions in the metal ion capture layer as described above, further improving the capture effect of the metal ion capture layer on inactive metal ions, thereby further reducing the permeability of the membrane to inactive metal ions in the embodiments of this application. Simultaneously, the porosity and pore size of the metal ion trapping layer can be further adjusted, thereby further regulating the flux of the metal ion trapping layer to active metal ions. In the metal ion trapping layer containing a mixture of inorganic and organic adsorbents, the respective mass content of the inorganic and organic adsorbents can be detected by methods such as thermogravimetric analysis (TGA) and X-ray fluorescence analysis (XRF).

[0127] In the embodiments, in the metal ion capturing layer in which the inorganic adsorbent and the organic adsorbent form a mixture, the metal ion capturing layer further contains a binder (designated as a third binder), which forms a mixture with the inorganic adsorbent and the organic adsorbent. The mass ratio of the inorganic adsorbent, organic adsorbent, and binder can be 1:(0.05~1):(0.01~0.05), or optionally 1:(0.1~0.7):(0.01~0.05). In the examples, it can be a typical but non-limiting mass ratio or a range between any two mass ratios, such as 1:0.05:0.01, 1:0.05:0.03, 1:0.05:0.05, 1:0.1:0.03, 1:0.2:0.03, 1:0.3:0.03, 1:0.4:0.03, 1:0.5:0.03, 1:0.6:0.03, 1:0.7:0.03, 1:0.8:0.03, 1:0.9:0.03, 1:1:0.03. By adding a binder to the metal ion capture layer, the inorganic and organic adsorbents can be bound together. By controlling their content within a certain range, the stability of the inorganic and organic adsorbents in the metal ion capture layer and the mechanical properties of the membrane can be improved, thereby enhancing the stability of the metal ion capture layer for capturing inactive metal ions.

[0128] In the embodiments, in the metal ion capturing layer formed by the mixture of inorganic and organic adsorbents, the thickness of the metal ion capturing layer can be 200–500 nm, optionally 250–400 nm. In exemplary examples, typical but non-limiting thicknesses such as 200 nm, 250 nm, 280 nm, 310 nm, 340 nm, 370 nm, 400 nm, and 500 nm, or any range between two thickness values, are possible. Here, the thickness of the metal ion capturing layer refers to the thickness of the metal ion capturing layer disposed on one surface of the membrane substrate, such as… Figure 1 The thickness b of the metal ion capturing layer 12. This thickness range allows for adjustment of the metal ion capturing layer's thickness ratio in the membrane and its modification effect on the membrane surface. It also allows for adjustment of the content of inorganic and organic adsorbents in the membrane, thereby improving the metal ion capturing effect on inactive metal ions and further reducing the permeability of the membrane to inactive metal ions in this embodiment.

[0129] In the embodiments, in the metal ion capturing layer formed by the mixture of inorganic and organic adsorbents, the porosity of the metal ion capturing layer can be 20% to 50%, optionally 25% to 35%. In exemplary examples, it can be typical but not limiting porosities such as 20%, 25%, 26%, 27%, 28%, 30%, 35%, and 40%, or any range between two porosity values. Here, the porosity of the metal ion capturing layer refers to the porosity of the metal ion capturing layer disposed on one surface of the membrane substrate, such as... Figure 1 The porosity of the metal ion trapping layer 12. A porosity within this range allows the metal ion trapping layer, together with the membrane substrate, to adjust the total porosity of the membrane in this embodiment. If the total porosity of the membrane in this embodiment is adjusted to the range mentioned above, while fully utilizing the trapping effect of the metal ion trapping layer on inactive metal ions, the active metal ion flux and electrolyte wettability of the membrane can be further adjusted. The porosity of the metal ion trapping layer can be measured by conventional nitrogen adsorption or conventional mercury intrusion porosimetry after peeling off the membrane substrate contained in the membrane of this embodiment.

[0130] In some embodiments, the particle size (Dv50) of at least one of the inorganic and organic adsorbents contained in the metal ion trapping layer of the membrane in the above embodiments is the same or different, ranging from 50 to 150 nm, optionally from 60 to 100 nm. In exemplary examples, typical but non-limiting particle sizes such as 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, and 150 nm, or any range between two particle size values, can be used. This particle size range can improve the pore structure of the metal ion trapping layer and enhance the adsorption of inactive metals by the inorganic and organic adsorbents.

[0131] In some embodiments, the inorganic adsorbent contained in the metal ion capturing layer of the membrane in the above embodiments may include at least one of a metal ion precipitant and an inorganic porous adsorbent. The metal ion precipitant refers to a precipitant that can undergo a precipitation reaction with inactive metal ions; the inorganic porous adsorbent has a porous structure containing abundant pores of different diameters, and its porous framework may also contain abundant functional groups, thereby effectively adsorbing and complexing inactive metal ions.

[0132] In the example, the metal ion precipitant may include at least one of phosphate, silicate, carbonate, and oxalate salts. These types of metal ion precipitants can react with the corresponding inactive metal ions to form a precipitation reaction, preventing the inactive metal ions from migrating further to the negative electrode. For instance, when the metal ion precipitant contains phosphate and the positive electrode material in the battery cell contains iron, during charging and discharging, the positive electrode material undergoes a precipitation reaction with iron ions (Fe²⁺). 3+ After precipitation, when the iron ions migrate to the metal ion trapping layer in the membrane of this embodiment, the phosphate ions provided by the phosphate salt contained in the metal ion trapping layer can undergo a precipitation reaction with the iron ions as follows: when the metal ion precipitant contains at least one salt of silicate salt, carbonate salt, oxalate salt, etc., it can undergo a similar precipitation reaction with high-valence non-reactive metal ions:

[0133] PO4 3+ +Fe 3+ →Fe2(PO4)3↓

[0134] In the example, the inorganic porous adsorbent may include at least one of the following: bentonite, attapulgite, hydroxyapatite, molecular sieve, alumina, silica gel, and zinc oxide. These types of inorganic porous adsorbents have a porous structure containing abundant pores of varying diameters. Furthermore, their porous framework may contain abundant functional groups, enabling them to adsorb inactive metal ions migrating to the metal ion trapping layer into the porous structure. Simultaneously, they undergo electrostatic adsorption with the inactive metal ions, thus firmly adsorbing them into the metal ion trapping layer. This reduces the migration of inactive metal ions to the negative electrode through the membrane, lowers the content of impurity ions at the negative electrode interface, and effectively reduces undesirable phenomena such as crystallization of impurity metal ions or further growth of impurity dendrites at the negative electrode interface.

[0135] In some embodiments, the organic adsorbent contained in the metal ion capture layer of the membrane in the above embodiments may include a porous organic adsorbent. In these embodiments, the porous organic adsorbent may include at least one of a covalent organic framework (COF), organosulfur (TMT), metal-organic frameworks (MOFs), hydrogen-bonded organic frameworks (HOFs), and crystalline porous organic salts (CPOSs). These types of organic adsorbents are similar to inorganic porous adsorbents, possessing a porous structure with abundant pores of varying diameters. They can also complex inactive metal ions, thereby adsorbing inactive metal ions migrating to the metal ion capture layer into the porous structure and / or undergoing complexation reactions with inactive metal ions. This effectively adsorbs inactive metal ions firmly into the metal ion capture layer, reducing their migration through the membrane to the negative electrode, lowering the content of impurity ions at the negative electrode interface, and thus effectively reducing undesirable phenomena such as crystallization of impurity metal ions or further growth of impurity dendrites at the negative electrode interface.

[0136] Diaphragm preparation method:

[0137] Secondly, embodiments of this application provide a method for preparing the diaphragm according to the embodiments of the above application.

[0138] In some embodiments, the membrane preparation method of this application includes the following steps:

[0139] S10: A metal ion trapping layer is formed on at least one surface of the diaphragm substrate to obtain a diaphragm.

[0140] In the preparation method of the diaphragm in this application embodiment, the diaphragm substrate in step S10 can be the diaphragm substrate contained in the diaphragm of the above application embodiment, and the formed metal ion capturing layer is also the metal ion capturing layer contained in the diaphragm of the above application embodiment. Therefore, the formed metal ion capturing layer contains inorganic adsorbent and organic adsorbent.

[0141] Thus, the membrane preparation method of this application directly forms a metal ion trapping layer containing inorganic and organic adsorbents on at least one surface of the membrane substrate, so that the formed metal ion trapping layer has an adsorption effect on inactive metal ions, and together with the membrane substrate, it can play a role in hindering the passage of inactive metal ions, thereby reducing the permeability of the prepared membrane to inactive metal ions.

[0142] In some embodiments, the method of forming a metal ion trapping layer on the surface of the diaphragm substrate may include the following steps:

[0143] S11: Form a first mixture slurry by combining the inorganic adsorbent with the first binder;

[0144] S12: The organic adsorbent and the second binder are combined to form a second mixture slurry;

[0145] S13: The first mixture slurry is subjected to a first film-forming treatment on at least one surface of the diaphragm substrate to form an inorganic adsorption layer, and then the second mixture slurry is subjected to a second film-forming treatment on the surface of the inorganic adsorption layer opposite to the diaphragm substrate to form a porous organic adsorption layer.

[0146] or,

[0147] S13': The second mixture slurry is subjected to a first film-forming treatment on at least one surface of the diaphragm substrate to form a porous organic adsorption layer, and then the first mixture slurry is subjected to a second film-forming treatment on the surface of the porous organic adsorption layer opposite to the diaphragm substrate to form an inorganic adsorption layer.

[0148] By separately depositing a first mixture slurry containing an inorganic adsorbent and a second mixture slurry containing an organic adsorbent onto the surface of a membrane substrate, a stacked inorganic adsorption layer and a porous organic adsorption layer are formed, respectively. Specifically, this can result in... Figure 4 The metal ion capturing layer 12 shown comprises a layered inorganic adsorption layer 121 and a porous organic adsorption layer 122. In this case, the two adsorption layers in the metal ion capturing layer can synergistically capture inactive metal ions, thereby improving the capturing effect of the metal ion capturing layer on inactive metal ions and further reducing the permeability of the membrane to inactive metal ions in this embodiment.

[0149] In step S11, the inorganic adsorbent and the first binder can both be the inorganic adsorbent and the first binder contained in the metal ion capture layer of the membrane in the above-described embodiments.

[0150] In this embodiment, the mass ratio of the inorganic adsorbent to the first binder in the first mixture slurry is 1:(0.01 to 0.05), and can be optionally 1:(0.01 to 0.03). This mass ratio range can improve the quality and mechanical properties of the inorganic adsorbent layer formed in step S13, and enhance the adsorption of inactive metal ions by the inorganic adsorbent layer.

[0151] In the embodiments, the viscosity of the first mixture slurry is 500–2500 mPa·s (viscosity test temperature is 25±3℃), optionally 1000–2000 mPa·s. In the exemplary examples, typical but non-limiting viscosities such as 500 mPa·s, 1000 mPa·s, 1200 mPa·s, 1400 mPa·s, 1600 mPa·s, 1800 mPa·s, 2000 mPa·s, 2300 mPa·s, and 2500 mPa·s, or any range between two viscosity values, can be used. Viscosities within this range can improve the film quality of the inorganic adsorption layer and enhance the uniformity of the inorganic adsorbent dispersion within the inorganic adsorption layer. The viscosity of the first mixture slurry refers to the viscosity value at 25±3℃, and all viscosity values ​​below refer to the viscosity value at 25±3℃.

[0152] In step S12, both the organic adsorbent and the second binder can be the organic adsorbent and the second binder contained in the metal ion capture layer of the membrane in the above-described embodiments.

[0153] In this embodiment, the mass ratio of the organic adsorbent to the second binder in the second mixture slurry is 1:(0.01-0.05), which can be optionally 1:(0.01-0.03). This mass ratio range can improve the membrane quality and mechanical properties of the porous organic adsorbent layer formed in step S13, and enhance the adsorption of inactive metal ions by the porous organic adsorbent layer.

[0154] In the embodiments, the viscosity of the second mixture slurry is 500–3000 mPa·s (viscosity test temperature 25±3℃), optionally 1500–2500 mPa·s. In exemplary cases, typical but non-limiting viscosities such as 500 mPa·s, 1000 mPa·s, 1500 mPa·s, 1600 mPa·s, 1700 mPa·s, 1800 mPa·s, 1900 mPa·s, 2000 mPa·s, 2300 mPa·s, 2500 mPa·s, and 3000 mPa·s, or any range between two viscosity values, can be used. Viscosities within this range can improve the membrane quality of the porous organic adsorption layer and enhance the uniformity of the organic adsorbent dispersion within the porous organic adsorption layer.

[0155] In addition, there is no existing order for steps 11 and 12.

[0156] The inorganic adsorption layer and porous organic adsorption layer formed in step S13 or step S13' can be as follows: Figure 4 The inorganic adsorption layer 121 and the porous organic adsorption layer 122 shown form a composite layer structure in which the metal ion trapping layer comprises an inorganic adsorption layer and a porous organic adsorption layer stacked together. Furthermore, the thicknesses of the formed inorganic adsorption layer and the porous organic adsorption layer can be as follows: Figure 4 The thickness ranges shown in b1 and b2 are as follows.

[0157] In the embodiments, the first film-forming treatment and the second film-forming treatment in step S13 or step S13' can be film-forming methods such as spraying film-forming, printing film-forming, coating film-forming, etc., on the corresponding base film by applying the first mixture slurry or the second mixture slurry to the corresponding base film.

[0158] In this embodiment, before performing the first film-forming treatment on the surface of the diaphragm substrate, a surface treatment is further performed on the surface of the diaphragm substrate. In an exemplary example, the surface treatment may include at least one of cleaning, ionization treatment, etc. The cleaning treatment can remove impurities from the surface of the diaphragm substrate. The ionization treatment can modify the surface of the diaphragm substrate, improve the film-forming quality of the first film-forming treatment, and improve the mechanical strength of the bond between the corresponding film layer and the diaphragm substrate surface.

[0159] In some embodiments, the method for forming a metal ion trapping layer on the surface of the diaphragm substrate may further include the following steps:

[0160] S14: A mixture of inorganic and organic adsorbents with a binder is formed into a slurry.

[0161] S15: The mixture slurry is subjected to a film-forming treatment on at least one surface of the diaphragm substrate to form a metal ion trapping layer.

[0162] In step S14, the inorganic and organic adsorbents can be the same inorganic and organic adsorbents contained in the metal ion capture layer of the membrane in the above-described embodiments. The binder in step S14 can be a third binder contained in the metal ion capture layer of the membrane in the above-described embodiments. Therefore, the mixing ratio of the inorganic and organic adsorbents and the binder in step S14 can be within the mass ratio range of the three components in the metal ion capture layer containing the mixture of inorganic and organic adsorbents in the membrane of the above-described embodiments. For example, in the embodiment, the mass ratio of the inorganic adsorbent, organic adsorbent, and binder in the mixture slurry is 1:(0.05~1):(0.01~0.05).

[0163] In this embodiment, the viscosity of the mixture slurry in step S14 can be 500–3000 mPa·s (viscosity test temperature 25±3℃), and can be selected as 1500–2500 mPa·s. In the exemplary example, it can be typical but not limiting viscosities such as 500 mPa·s, 1000 mPa·s, 1500 mPa·s, 1600 mPa·s, 1700 mPa·s, 1800 mPa·s, 1900 mPa·s, 2000 mPa·s, 2300 mPa·s, 2500 mPa·s, and 3000 mPa·s, or any range between two viscosity values. This viscosity range can improve the uniformity of dispersion of the inorganic and organic adsorbents in the formed metal ion trapping layer, and simultaneously improve the film quality of the metal ion trapping layer.

[0164] In the embodiment, the film-forming process in step S15 may be the same as or different from the first film-forming process and the second film-forming process in step S13 or step S13'. For example, it may be to form a film on the surface of the diaphragm substrate by methods such as spraying, printing, coating, etc.

[0165] Furthermore, the step numbers of step S14 above and steps S11 to S13 or step S13' above do not represent the order of the process steps.

[0166] In some embodiments, after step S10 described above, step S20 is further included;

[0167] Step S20: Another membrane substrate is stacked on the surface of the metal ion trapping layer away from the membrane substrate, thereby making the prepared membrane structure as shown in the figure. Figure 3 The sandwich structure shown consists of a first diaphragm substrate, a metal ion capture layer, and a first diaphragm substrate stacked sequentially.

[0168] In step S20, the other membrane substrate, namely the second membrane substrate, may be the same as or different from the membrane substrate in step S10.

[0169] In this embodiment, after the second diaphragm substrate is laminated, the sandwich-structured diaphragm can be hot-pressed. Hot-pressing improves the structural stability of the sandwich-structured diaphragm. In this embodiment, the hot-pressing temperature can be 80–100°C, the pressure can be 1–1000 kg, and the time can be 1–5 seconds. Hot-pressing under these conditions effectively improves the structural stability of the sandwich-structured diaphragm and ensures abundant porosity in the diaphragm.

[0170] Battery:

[0171] Thirdly, embodiments of this application also provide a battery.

[0172] In the embodiments of this application, the battery may include any one of a battery cell, a battery module, or a battery pack.

[0173] Battery cell:

[0174] A battery cell, also known as a battery pack, refers to the battery including its outer packaging and the electrode assembly encapsulated within it. A battery cell can contain one or more electrode assemblies, which can be adjusted according to actual needs.

[0175] The outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell; or it can be a soft package, such as a pouch. The soft package material can be plastic, such as polypropylene, polybutylene terephthalate, or polybutylene succinate. The shape of the outer packaging can be cylindrical, square, or any other arbitrary shape. This outer packaging shape determines the shape of the battery cell; therefore, the shape of the battery cell can also be cylindrical, square, or any other arbitrary shape corresponding to the shape of the outer packaging. In the example, the battery cell can be as follows: Figure 5 The shown is a square-structured battery cell 20.

[0176] In some embodiments, such as Figure 6 As shown, the outer packaging of the battery cell 20 may include a housing 21 and a cover plate 23. The housing 21 may include a base plate and side plates connected to the base plate, the base plate and side plates enclosing a receiving cavity. The housing 21 has an opening communicating with the receiving cavity, and the cover plate 23 is used to cover the opening to close the receiving cavity. One or more electrode assemblies 22 are encapsulated within the receiving cavity.

[0177] In this embodiment, the battery cell can be a liquid battery cell containing a separator, or a semi-solid battery cell containing a separator and a solid electrolyte. It can also be a lithium-ion battery cell or a sodium-ion battery cell.

[0178] Regardless of whether the battery cell in this application is a liquid battery cell or a semi-solid battery cell, the electrode assembly contained in the battery cell in this application typically includes a positive electrode, a negative electrode, and a separator. The positive and negative electrode cells are alternately stacked, and the separator is stacked between the positive and negative electrode cells to provide isolation, separating them. The positive electrode, separator, and negative electrode can be formed into a stacked electrode assembly using a lamination process, or into a wound electrode assembly using a winding process. The electrode assembly containing the separator is placed in an outer packaging, injected with electrolyte to wet the electrode assembly, and then packaged to obtain the battery cell.

[0179] In this embodiment, the separator in the battery cell is the same as the separator described in the previous embodiment. Thus, the separator in the battery cell of this embodiment can effectively reduce the amount of inactive metal ions passing through and migrating to the negative electrode, thereby significantly reducing the content of impurity metal ions at the negative electrode interface, thus mitigating impurity metal crystallization at the negative electrode interface and reducing the amount of impurity dendrite formation. Therefore, the safety of the battery cell in this embodiment is significantly improved.

[0180] In the embodiments, when the battery cell of this application embodiment is a semi-solid battery cell, that is, when the battery cell of this application embodiment contains a solid electrolyte in addition to a separator, the solid electrolyte contained in the battery cell may include at least one of polymer solid electrolyte, oxide electrolyte, sulfide electrolyte, borohydride electrolyte, composite solid electrolyte, etc.

[0181] In each of the above-mentioned battery cells, the positive electrode sheet contained in the battery cell of the present application embodiment includes a positive electrode current collector and a positive electrode active material layer bonded to at least one surface of the positive electrode current collector.

[0182] In the embodiments of this application, the positive electrode current collector contained in the positive electrode sheet of the battery cell may include, but is not limited to, metal current collectors, carbon current collectors, conductive resin current collectors, and composite current collectors of metal and resin, and more specifically, aluminum, copper, nickel, titanium, iron and their respective alloys, stainless steel, carbon fiber, carbon nanotubes (CNTs), graphite, etc. In the embodiments, the current collector may also be a dense film layer or a porous film layer. In the embodiments, the current collector may be, but is not limited to, aluminum foil or porous aluminum foil.

[0183] In this embodiment, the positive electrode active material layer contained in the positive electrode sheet may be bonded to one surface of the positive electrode current collector, or it may be bonded to two opposing surfaces of the positive electrode current collector. When the surface layer of the positive electrode current collector has a porous structure or the positive electrode current collector itself has a porous structure, the positive electrode active material layer may be at least partially embedded in the current collector.

[0184] In the embodiments, the mass content of the positive electrode active material in the positive electrode active material layer of the above-mentioned positive electrode sheet can be 90% to 98%, optionally 92% to 96%. In exemplary examples, it can be typical but non-limiting contents such as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, and 98%, or any range between two contents. Positive electrode active materials within this content range can effectively improve the energy density of the positive electrode sheet.

[0185] In the embodiments, the positive electrode active material may include sodium-ion positive electrode active material or lithium-ion positive electrode active material. When containing sodium-ion positive electrode active material, the battery cell in this application embodiment may be a sodium battery cell; when containing lithium-ion positive electrode active material, the battery cell in this application embodiment may be a lithium battery cell. In the exemplary embodiment, the sodium-ion positive electrode active material may include one or more of sodium layered oxides, polyanionic compounds, and Prussian blue compounds. In the exemplary embodiment, the lithium-ion positive electrode active material may include, but is not limited to, at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and ternary materials. These types of sodium-ion positive electrode active materials or lithium-ion positive electrode active materials have high specific capacity, or further have high structural stability and good cycle performance. At this time, when the positive electrode active material is sodium layered oxide, the sodium layered oxide may contain inactive metal ions such as cobalt, nickel, and iron; when the positive electrode active material is lithium iron phosphate, the lithium iron phosphate contains inactive metal ions such as iron and manganese.

[0186] In the embodiments, the positive electrode active material layer contained in the above-mentioned positive electrode sheet generally includes components such as binders and conductive agents in addition to the positive electrode active material components mentioned above. The binder can enhance the mechanical properties between the positive electrode active material layer itself and the current collector. The conductive agent can effectively improve the conductivity of the positive electrode sheet. In the exemplary example, the binder and conductive agent contained in the positive electrode sheet can be the binder and conductive agent in the negative electrode sheet of the above-mentioned application embodiments, respectively. To save space, the binder and conductive agent will not be described in detail here.

[0187] In each of the above-mentioned battery cells, the negative electrode sheet contained in the battery cell of the present application embodiment includes a negative electrode current collector, and optionally may also include a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer containing a negative electrode active material.

[0188] In the embodiments of this application, the negative electrode current collector contained in the negative electrode sheet of the battery cell may include, but is not limited to, metal or composite current collectors. For example, as a metal, sodium, sodium alloy, lithium, lithium alloy, copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc. may be used. When sodium or sodium alloy is used as the negative electrode current collector, sodium or sodium alloy itself can also serve as a negative electrode active material; similarly, when lithium or lithium alloy is used as the negative electrode current collector, lithium or lithium alloy itself can also serve as a negative electrode active material; therefore, the negative electrode sheet may not contain a negative electrode active material layer, and sodium, sodium alloy or lithium, lithium alloy serves as both the current collector and the negative electrode active material.

[0189] Composite current collectors can include composite materials of polymers and metals. In the embodiments, the polymers may include, but are not limited to, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE). In the embodiments, the metals may include, but are not limited to, sodium, lithium, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Composite current collectors can be obtained by blending polymers and metals, or they can be coated onto at least one side of the polymer material through electroplating, coating, or other methods.

[0190] When the negative electrode includes a negative electrode active material layer, the negative electrode active material in the negative electrode active material layer may be a mixture or composite material formed from any one or more of carbon-based materials, alloy materials, titanium-based materials, sodium metal, and lithium metal. Specifically, carbon-based materials include, but are not limited to, one or more of graphite, soft carbon, hard carbon, carbon microspheres, and carbon fibers; alloy materials include, but are not limited to, one or more of sodium-tin alloys, sodium-germanium alloys, and sodium-antimony alloys, or alloy materials include, but are not limited to, one or more of lithium-tin alloys, lithium-germanium alloys, and lithium-antimony alloys; and titanium-based materials include, but are not limited to, one or more of titanium dioxide, titanates, and titanium phosphates.

[0191] The mass content of the negative electrode active material in the negative electrode active material layer can be 85% to 98%, and can be selected as 95% to 98%. In the example, it can be a typical but non-limiting content such as 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or any range between two content values.

[0192] The negative electrode active material layer may also include at least one of a conductive agent and a binder. The conductive agent is used to collect current between the negative electrode active materials and between the active materials and the current collector, thereby improving electronic conductivity. Simultaneously, the conductive agent can also promote the wetting of the negative electrode sheet by the electrolyte. The binder can improve the bonding strength between the substances in the negative electrode active material layer and between the negative electrode active material layer and the current collector.

[0193] In the embodiments, the mass content of the conductive agent in the negative electrode active material layer can be 0.5% to 10%. In exemplary examples, it can be a typical but non-limiting content such as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range between any two content values. Other contents can also be set as needed. In exemplary examples, the conductive agent includes one or more of acetylene black (SP), carbon nanotubes, conductive carbon black (super-P), Ketjen black, carbon fiber, and graphene.

[0194] In the embodiments, the mass content of the binder in the negative electrode active material layer can be 0.5% to 10%. In the exemplary examples, it can be a typical but non-limiting content such as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range between any two content values. Other contents can also be set as needed. In the exemplary examples, the binder includes, but is not limited to, one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, polyimide, polytetrafluoroethylene, polybutyl acrylate, polyacrylonitrile, carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylate, polyvinyl alcohol, sodium alginate, cyclodextrin, styrene-butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber.

[0195] In the embodiments, the negative electrode active material layer may optionally include a thickener, such as, but not limited to, carboxymethyl cellulose (CMC). The mass content of the thickener in the negative electrode active material layer can be set to 0.5% to 5%, and in exemplary examples, it can be a typical but non-limiting content such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range between any two content values.

[0196] Battery module:

[0197] When the battery in the embodiments of this application is a battery module, the battery module refers to the assembly of the above-mentioned battery cells, that is, it can contain multiple of the above-mentioned battery cells, and the specific number can be adjusted according to the application and capacity of the battery module.

[0198] In some embodiments, Figure 7 This is a schematic diagram of battery module 30 as an example. (See diagram below.) Figure 7 As shown, in the battery module 30, multiple battery cells 20 can be arranged sequentially along the length of the battery module 30. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 20 can be fixed in place using fasteners.

[0199] Optionally, the battery module 30 may also include a housing with a receiving space in which multiple battery cells 20 are received.

[0200] Battery pack:

[0201] When the battery in this application embodiment is a battery pack, the battery pack refers to the assembly of the aforementioned battery cells, that is, it can contain multiple battery cells, and these multiple battery cells are assembled into the aforementioned battery module. The specific number of battery cells or battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0202] In some embodiments, Figure 8This is a schematic diagram of a battery pack 40 as an example. The battery pack 40 may include a battery compartment and multiple battery modules 30 disposed within the battery compartment. The battery compartment includes an upper compartment 41 and a lower compartment 42. The upper compartment 41 covers the lower compartment 42, forming a closed space for accommodating the battery modules 30. The multiple battery modules 30 can be arranged in any manner within the battery compartment.

[0203] Electrical appliances:

[0204] Fourthly, this application also provides an electrical device. The electrical device of this application includes a power supply unit or an energy storage unit, and may also include other auxiliary or necessary components. The power supply unit or energy storage unit contains the battery described in the above application embodiment. For example, it may be a single battery cell, a battery module, or a battery pack. Because the electrical device of this application embodiment contains the battery described in the above application embodiment, the power supply unit or energy storage unit of the electrical device of this application embodiment has high safety and a long service life, and the standby or battery life of the electrical device of this application embodiment is long.

[0205] In this embodiment, the electrical device may include, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc. As the electrical device, battery cells, battery modules, or battery packs can be selected according to their usage requirements.

[0206] Figure 9 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0207] In this embodiment, when the electrical device includes an energy storage unit, the electrical device can be an energy storage device, which includes the energy storage unit and may also include other auxiliary or necessary components. The energy storage unit contains the battery described in the above-described embodiment. The energy storage unit may contain one or more batteries. When there are multiple batteries, they can form a battery module or battery pack. Because the energy storage device in this embodiment includes the battery described in the above-described embodiment, the energy storage device has high safety.

[0208] Example:

[0209] 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.

[0210] 1. Examples of diaphragm and its preparation method:

[0211] Example A1:

[0212] This embodiment A1 provides a diaphragm and its preparation method. The diaphragm includes a first diaphragm substrate, a metal ion trapping layer, and a second diaphragm substrate, which are sequentially stacked to form a sandwich composite structure.

[0213] The first and second diaphragm substrates are 5μm polyethylene membrane substrates (PE diaphragm substrates), and the metal ion capture layer contains a mixture of inorganic and organic adsorbents. The diaphragm-related characteristic parameters provided in Example A1 are shown in Table 1 below.

[0214] The membrane preparation method includes the following steps:

[0215] S1: The surface of the polyethylene membrane substrate (first diaphragm substrate) is subjected to plasma treatment using a plasma beam to obtain a plasma-treated polyethylene membrane substrate;

[0216] S2: A metal ion trapping layer slurry with a viscosity of 1500 mPa·s is coated onto the plasma-treated surface of a polyethylene film substrate to form a wet film, which is then dried to form a metal ion trapping layer.

[0217] The metal ion capture layer slurry contains inorganic adsorbent, organic adsorbent and binder in a mass ratio of 1:0.1:0.03, and the inorganic adsorbent is hydroxyapatite, the organic adsorbent is COF and the binder is polyvinylidene fluoride.

[0218] S3: The surface of another polyethylene membrane substrate (second diaphragm substrate) treated with plasma beam is attached to the outer surface of the metal ion capture layer, and then subjected to hot pressing treatment at a temperature of 90-100℃ and a pressure of 500kg for 3 seconds to form a sandwich structure diaphragm.

[0219] Examples A2 to A19:

[0220] Examples A2 to A19 respectively provide a diaphragm and its preparation method.

[0221] Among them, the difference between the membrane in Examples A2 to A7 and that in Example A1 is that the types of inorganic and organic adsorbents contained in the metal ion capture layer are different, while the rest are the same as in Example A1.

[0222] The difference between Examples A8 to A10 and the membrane in Example A1 lies in the different mixing ratios of inorganic and organic adsorbents in the formed metal ion capture layer; otherwise, they are the same as in Example A1.

[0223] The difference between Examples A11 to A15 and the diaphragm in Example A1 is that the thickness of the formed metal ion trapping layer is different; otherwise, they are the same as in Example A1.

[0224] The difference between the diaphragm in Example A16 and that in Example A1 is the thickness and number of layers of the diaphragm substrate (the diaphragm substrate in Example A16 contains only one layer), while the rest is the same as in Example A1.

[0225] The difference between Examples A17 to A19 and the membrane in Example A1 is that the metal ion capture layer includes an inorganic adsorption layer and a porous organic adsorption layer; otherwise, they are the same as in Example A1.

[0226] The diaphragm-related characteristic parameters in Examples A2 to A19 are shown in Table 1 below.

[0227] The membrane preparation methods in Examples A2 to A19 are the same as those in Example A1, with adjustments made to the materials and conditions of the corresponding steps based on the membrane material and membrane properties in each example. For instance, in Examples A17 to A19, when preparing the metal ion trapping layer, inorganic adsorption layer slurry and porous organic adsorption layer slurry are prepared respectively, and the inorganic adsorption layer and porous organic adsorption layer are formed sequentially along the direction away from the surface of the membrane substrate, or the porous organic adsorption layer and inorganic adsorption layer are formed sequentially, thus forming the metal ion trapping layer.

[0228] Comparative Example A1:

[0229] Comparative Example A1 provides a diaphragm and its preparation method.

[0230] The difference between Comparative Example A1 and the membrane in Example A17 is that the metal ion capture layer contains only inorganic adsorbent material and no organic adsorbent material. The relevant characteristic parameters of the membrane in Comparative Example A1 are shown in Table 1 below.

[0231] The diaphragm in Comparative Example A1 was prepared using the same method as the diaphragm in Example A17.

[0232] Comparative Example A2:

[0233] Comparative Example A2 provides a diaphragm and its preparation method.

[0234] The difference between Comparative Example A2 and the membrane in Example A17 is that the metal ion capture layer contains only organic adsorbent material and no inorganic adsorbent material. The relevant characteristic parameters of the membrane in Comparative Example A2 are shown in Table 1 below.

[0235] The diaphragm in Comparative Example A2 was prepared using the same method as the diaphragm in Example A17.

[0236] Comparative Example A3:

[0237] Comparative Example A3 provides a diaphragm, which is the diaphragm substrate of Example A1. That is, compared with the diaphragm in Example A1, it does not contain a metal ion trapping layer.

[0238] 2. Performance tests of the diaphragm in each embodiment:

[0239] The diaphragms provided in Examples A1 to A19 and Comparative Examples A1 to A3 were subjected to the relevant feature detection methods shown in Table 1 below, and the results are shown in Table 1. The relevant feature detection methods for the diaphragms in Table 1 are as follows:

[0240] The thickness of the metal ion trapping layer and the diaphragm was measured using X-ray photoelectron spectroscopy (XPS).

[0241] Porosity detection method (nitrogen adsorption method): First, place the membrane sample into the sample device of the ammonia adsorption instrument, then turn off the device and evacuate it using a vacuum pump. After the vacuum stabilizes, set the required test parameters, including temperature, test mode, and equilibrium time, through the control panel of the ammonia adsorption instrument. Then, turn on the gas pump and its control switch to allow ammonia to enter the test tube until the required pressure range is reached. After maintaining this pressure for a period of time, turn off the vacuum pump, open the sample chamber door, and allow nitrogen to enter the sample pores. Finally, based on the pressure and temperature changes recorded by the nitrogen adsorption instrument during the adsorption and desorption processes, the porosity and pore size of the membrane can be calculated using the specific surface area equation and pore size distribution model.

[0242] Testing the membrane's ability to block high-valence metal ions:

[0243] Formulated with 102ppm Fe 3+ 101ppm Fe 2+ 102ppm Cu 2+ A standard aqueous solution was prepared, and the metal ions in the solution were subjected to the same pressure to migrate from one side of the diaphragm provided in Examples A1 to A19 and Comparative Examples A1 to A3 to the other side. Finally, ICP was used to detect the Fe content in the filtered standard aqueous solution. 3+ Fe 2+Cu 2+ The concentration in.

[0244] Table 1

[0245]

[0246]

[0247] Based on the ICP detection results in Table 1, and comparing Examples A1 to A10, it can be seen that the types and ratios of inorganic and organic adsorbents in the metal ion capture layer all contribute to the membrane's ability to capture high-valence inactive metal ions. Furthermore, the combination of different types of inorganic and organic adsorbents has a certain impact on the membrane's ability to capture high-valence metal ions. For example, when hydroxyapatite is combined with organosulfur (TMT), calcium carbonate with organic framework (COF), or hydroxyapatite with polystyrene sulfonic acid, the membrane's ability to capture high-valence metal ions is relatively strong.

[0248] Comparing Examples A1, A11 to A15, it can be seen that the thickness of the metal ion trapping layer can adjust the trapping effect of the membrane on high-valence inactive metal ions. For example, when the thickness of the metal ion trapping layer is between 250 nm and 400 nm, especially 400 nm, the trapping effect of the membrane on high-valence inactive metal ions is relatively obvious.

[0249] Comparative examples A17 to A19 show that when the metal ion capturing layer is a composite membrane of an inorganic adsorption layer and a porous organic adsorption layer, it can also endow the membrane with a good capturing effect on high-valence inactive metal ions.

[0250] Comparing Comparative Examples A1 to A19 with Comparative Examples A1 to A3, it is evident that the membranes in Examples A1 to A19 exhibit significantly superior capture performance of high-valence inactive metal ions compared to those in Comparative Examples A1 to A3. This demonstrates that inorganic and organic adsorbents play a synergistic and enhancing role in capturing high-valence inactive metal ions within the metal ion capture layer.

[0251] 3. Example of a single lithium-ion battery cell:

[0252] Examples B1 to B19 and Comparative Examples B1 to B3:

[0253] Examples B1 to B19 and Comparative Examples B1 to B3 each provide a lithium-ion battery cell. Each lithium-ion battery cell includes an electrode assembly formed by a positive electrode, a separator, and a negative electrode, and also includes an electrolyte.

[0254] The lithium-ion battery cells in Examples B1 to B19 and Comparative Examples B1 to B3 are assembled as follows:

[0255] Positive electrode sheet: Lithium iron phosphate, conductive carbon black, and binder polyvinylidene fluoride (PVDF) are mixed thoroughly in an appropriate amount of solvent N-methylpyrrolidone at a weight ratio of 8:1:1 to form a uniform positive electrode slurry. The positive electrode slurry is uniformly coated on both surfaces of a 13μm positive electrode current collector aluminum foil. After drying and cold pressing, it is cut to obtain the positive electrode sheet. The positive electrode sheet is rolled into a film roll, and a ceramic slurry is sprayed onto the cut surface of the film roll. In the ceramic slurry, the ceramic material is boehmite, accounting for 39wt%; the binder is polyacrylate, accounting for 5wt%; the solvent is N-methylpyrrolidone; the solid content of the slurry is 10%; and the viscosity of the slurry is 8000mPa·s.

[0256] Negative electrode sheet: Artificial graphite, conductive carbon black, binder carboxymethyl cellulose (CMC) and solvent water are thoroughly mixed in a weight ratio of 95:2:3:100 to obtain a uniform negative electrode slurry; the negative electrode slurry is uniformly coated on both surfaces of a 6μm copper foil, dried, cold-pressed, and then cut to obtain the negative electrode sheet;

[0257] 3) Separator: The separators provided in Examples A1 to A19 and Comparative Examples A1 to A3 are used as separators; wherein, the cell in Example B1 contains the separator in Example A1, the cell in Example B2 contains the separator in Example A2, and so on, and the cell in Comparative Example B2 contains the separator in Comparative Example A2.

[0258] 4) Electrolyte: Vinyl acetate, diethyl carbonate, and dimethyl carbonate are mixed in a volume ratio of 1:1:1. LiPF6 is dissolved in the above solution to obtain the electrolyte; the concentration of LiPF6 in the electrolyte is 1 mol / L.

[0259] 5) Battery Assembly: The positive electrode, separator, and negative electrode are stacked sequentially, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode assembly is then obtained through a winding process. Each electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, the ion battery cells of Examples B1 to B19 and Comparative Examples B1 to B3 are obtained.

[0260] 4. Electrochemical performance testing of individual ion battery cells in each embodiment:

[0261] The ion battery cells provided in Examples B1 to B19 and Comparative Examples B1 to B3 were subjected to the relevant electrochemical performance tests listed in Table 2 below, using the methods described below. The results are shown in Table 2. The methods for testing the relevant performance of the ion battery cells in Table 2 are as follows:

[0262] High-temperature storage voltage drop: ① Charge the secondary battery to 4.25V at a constant current of 0.33C at 25℃, let it rest for 3 minutes, and test cell OCV1; ② Then store it in an environment of 45℃ for 60 days. After storage, cool the cell to 25℃ and test cell OCV2; ③ High-temperature storage voltage drop = OCV1 - OCV2.

[0263] Cycle life (number of cycles): The number of cycles is calculated by charging the secondary battery at a constant current of 0.33C to 4.25V at 25℃, then charging it at a constant voltage of 4.25V to a current of 0.05C, and then discharging it at a constant current of 1C to 2.8V.

[0264] Cell calendar life: ① Charge the secondary battery at a constant current of 0.33C to 4.25V at 25℃, ② then store it in a 45℃ environment for 30 days; ③ after 30 days of storage, charge it at a constant voltage of 4.25V until the current drops to 0.05C, then discharge it at a constant current of 0.33C to 2.8V, repeat this charge-discharge cycle until the 3rd cycle, and record the cell capacity retention rate; ④ if the capacity retention rate is >80% in the above steps, continue with ①-③, if the capacity retention rate is <80%, stop the test and record the total number of times step ② is performed, n; ⑤ calendar life = 30*n days.

[0265] Table 2

[0266]

[0267] Referring to Table 1, the data in Table 2 shows that in the lithium-ion batteries of this application, the high-temperature storage voltage drop of the battery cells in Examples B1 to B19 is higher than that of the battery cells in Examples B1 to B3. This indicates that the separator in Examples A1 to A19 significantly improves the high-temperature storage voltage drop of the battery cells. This demonstrates that the metal ion trapping layer in the separator of this application, through the inorganic and organic adsorbents it contains, can impart a trapping effect on high-valence inactive metal ions. Furthermore, both adsorbents and organic adsorbents in the separator can synergistically and effectively trap high-valence inactive metal ions, thereby significantly reducing the permeability of the separator to high-valence inactive metal ions. This effectively alleviates the aggregation of inactive metal ions at the negative electrode interface, reducing the content of impurity metal ions at the negative electrode interface. Consequently, it can significantly alleviate the formation and amount of impurity dendrites at the negative electrode interface, effectively suppressing physical self-discharge caused by metal impurities inside the cell and improving the safety performance of the cell.

[0268] Meanwhile, the cell calendar life and cell cycle life of the lithium-ion battery cells in Examples B1 to B19 were not significantly reduced compared to the lithium-ion battery cells in Examples B1 to B3, and some were even improved. This indicates that the metal ion trapping layer has almost no adverse effect on the active metal ions (lithium ions) in the cell, and the metal ion trapping layer can also improve the pore structure of the separator substrate to a certain extent, thereby improving the cycle performance and other properties of the cell.

[0269] 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 diaphragm, comprising a diaphragm substrate, characterized in that, It also includes a metal ion trapping layer disposed on at least one surface of the membrane substrate; wherein the metal ion trapping layer comprises an inorganic adsorbent and an organic adsorbent.

2. The diaphragm as described in claim 1, characterized in that: In the metal ion capture layer, the inorganic adsorbent and the organic adsorbent form a mixture.

3. The diaphragm as described in claim 1 or 2, characterized in that: The metal ion trapping layer includes at least one of the following (1) to (4): (1) The mass ratio of the inorganic adsorbent to the organic adsorbent is 1:(0.05~1); (2) It also includes a binder, wherein the binder forms a mixture with the inorganic adsorbent and the organic adsorbent, and the mass ratio of the inorganic adsorbent, the organic adsorbent and the binder is 1:(0.05~1):(0.01~0.05); (3) The thickness of the metal ion trapping layer is 200-500 nm; (4) The porosity of the metal ion trapping layer is 20% to 50%.

4. The diaphragm as described in claim 1, characterized in that: The metal ion capture layer includes an inorganic adsorption layer and a porous organic adsorption layer stacked with the inorganic adsorption layer, wherein either the inorganic adsorption layer or the porous organic adsorption layer is stacked with the surface of the membrane substrate, wherein the inorganic adsorption layer contains the inorganic adsorbent and the porous organic adsorption layer contains the organic adsorbent.

5. The diaphragm as described in claim 4, characterized in that: The thickness ratio of the inorganic adsorption layer to the porous organic adsorption layer is 1:(0.1~1.0); and / or The porosity of the metal ion trapping layer is 20% to 50%.

6. The diaphragm as described in any one of claims 4 or 5, characterized in that: The inorganic adsorption layer includes at least one of the following (1) to (2): (1) The thickness of the inorganic adsorption layer is 200-600 nm; (2) It also includes a first binder, which forms a mixture with the inorganic adsorbent, and the mass ratio of the inorganic adsorbent to the first binder is 1:(0.01 to 0.05); and / or The porous organic adsorption layer comprises at least one of the following (1) to (2): (1) The thickness of the porous organic adsorption layer is 50-300 nm; (2) It also includes a second binder, which forms a mixture with the organic adsorbent, and the mass ratio of the organic adsorbent to the second binder is 1:(0.01 to 0.05).

7. The diaphragm according to any one of claims 1 to 6, characterized in that: The membrane substrate includes a first membrane substrate and a second membrane substrate, and the metal ion capture layer is stacked between the first membrane substrate and the second membrane substrate.

8. The diaphragm as described in claim 7, characterized in that: The thickness of the first diaphragm substrate and the second diaphragm substrate is the same or different, ranging from 2.5 to 25 μm.

9. The diaphragm according to any one of claims 1 to 8, characterized in that: The inorganic adsorbent includes at least one of a metal ion precipitant and an inorganic porous adsorbent; and / or The organic adsorbent includes porous organic adsorbents; and / or The particle size (Dv50) of at least one of the inorganic adsorbents and the organic adsorbents is either the same or different, ranging from 50 to 150 nm.

10. The diaphragm as described in claim 9, characterized in that: The metal ion precipitant includes at least one of phosphate, silicate, carbonate, and oxalate salts; and / or The inorganic porous adsorbent includes at least one of bentonite, attapulgite, hydroxyapatite, molecular sieve, alumina, silica gel, and zinc oxide.

11. The diaphragm as described in claim 9 or 10, characterized in that: The porous organic adsorbent includes at least one of covalent organic frameworks, organosulfur, metal-organic frameworks, hydrogen-bonded organic frameworks, and crystalline porous organic salts.

12. The diaphragm according to any one of claims 1 to 11, characterized in that: The diaphragm includes at least one of the following (1) to (2): (1) The thickness of the diaphragm is 4 to 50 μm; (2) The porosity of the diaphragm is 20% to 60%.

13. A method for preparing a diaphragm, characterized in that, Includes the following steps: A metal ion trapping layer is formed on at least one surface of a diaphragm substrate to obtain a diaphragm; The metal ion capture layer includes inorganic adsorbents and organic adsorbents.

14. The preparation method according to claim 13, characterized in that, The method for forming a metal ion trapping layer on at least one surface of a diaphragm substrate includes the following steps: The inorganic adsorbent and the organic adsorbent are mixed with a binder to form a slurry; The mixture slurry is subjected to a film-forming treatment on at least one surface of the diaphragm substrate to form the metal ion trapping layer.

15. The preparation method according to claim 14, characterized in that: In the mixture slurry, the mass ratio of the inorganic adsorbent, the organic adsorbent, and the binder is 1:(0.05~1):(0.01~0.05); and / or The viscosity of the mixture slurry is 500–3000 nm.

16. The preparation method according to claim 13, characterized in that, The method for forming a metal ion trapping layer on at least one surface of a diaphragm substrate includes the following steps: The inorganic adsorbent and the first binder are combined to form a first mixture slurry; The organic adsorbent is combined with the second binder to form a second mixture slurry; The first mixture slurry is subjected to a first film-forming treatment on at least one surface of the diaphragm substrate to form an inorganic adsorption layer, and then the second mixture slurry is subjected to a second film-forming treatment on the surface of the inorganic adsorption layer opposite to the diaphragm substrate to form a porous organic adsorption layer; or, the second mixture slurry is subjected to a first film-forming treatment on at least one surface of the diaphragm substrate to form a porous organic adsorption layer, and then the first mixture slurry is subjected to a second film-forming treatment on the surface of the porous organic adsorption layer opposite to the diaphragm substrate to form an inorganic adsorption layer.

17. The preparation method according to claim 16, characterized in that, The first mixture slurry includes at least one of (1) to (2): (1) In the first mixture slurry, the mass ratio of the inorganic adsorbent to the first binder is 1:(0.01~0.05); (2) The viscosity of the first mixture slurry is 500-2500 nm; and / or The second mixture slurry includes at least one of (1) to (2): (1) In the second mixture slurry, the mass ratio of the organic adsorbent to the second binder is 1:(0.01~0.05); (2) The viscosity of the second mixture slurry is 500-3000 nm.

18. The preparation method according to any one of claims 13 to 17, characterized in that, The diaphragm substrate includes a first diaphragm substrate and a second diaphragm substrate. The metal ion capturing layer is formed on one surface of the first diaphragm substrate, and the second diaphragm substrate is stacked on the surface of the metal ion capturing layer opposite to the first diaphragm substrate.

19. A battery, characterized in that, It includes the diaphragm according to any one of claims 1 to 12 or the diaphragm prepared by the preparation method according to any one of claims 13 to 18.

20. An electrical appliance, characterized in that: Includes the battery as described in claim 19.

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