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 comprises a separator base material and a metal ion selective permeable membrane layer. Wherein the metal ion selective permeable membrane layer is arranged on at least one surface of the diaphragm base material, and the material of the metal ion selective permeable membrane layer contains at least one of a charge group and a steric hindrance group. The diaphragm can effectively relieve the passing of non-active metal ions released by a positive electrode material in a circulation process through the contained metal ion selective permeable membrane layer, so that the content of impurity metal ions on a negative electrode interface in a battery cell is effectively reduced, and the phenomenon of generating impurity metal dendrites 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 multiple 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, further contributing to the release of inactive metal ions from the inorganic cathode material. These inactive metal ions migrate through the separator to the negative electrode and are easily reduced and precipitated at low potentials, forming impurity metal dendrites at the negative electrode interface, thus increasing battery safety risks. However, existing separators either do not effectively prevent the passage of inactive metal ions or their effectiveness in doing so 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 selectively permeable membrane layer, the metal ion selectively permeable membrane layer being disposed on at least one surface of the diaphragm substrate; wherein the material of the metal ion selectively permeable membrane layer contains at least one group selected from charged groups and steric hindrance groups.

[0006] The separator in this embodiment utilizes at least one functional group, including charged groups and steric hindrance groups, contained in the material that allows selective permeability of metal ions. This functional group can effectively generate electrostatic and / or steric hindrance effects on inactive metal ions released by the positive electrode material during cycling. This hinders the passage of inactive metal ions through the separator, reducing the probability of these ions passing through the separator. Consequently, it effectively reduces the content of impurity metal ions at the negative electrode interface in the battery cell, significantly alleviating the formation and amount of impurity dendrites at the negative electrode interface and improving the safety performance of the battery cell.

[0007] In some embodiments, the molar amount of at least one of the charged groups and steric hindrance groups in the metal ion selectively permeable membrane layer is 5% to 30%.

[0008] In some embodiments, the molar amount of at least one of the charged groups and steric hindrance groups in the metal ion selectively permeable membrane layer is 10% to 30%.

[0009] The molar content range includes at least one functional group among charged groups and steric hindrance groups, which can effectively improve the selective permeability of metal ions through the membrane layer to the electrostatic effect and / or steric hindrance effect of inactive metal ions, thereby further reducing the permeability of the membrane to inactive metal ions in the embodiments of this application, reducing the content of impurity metal ions at the negative electrode interface in the battery cell, further alleviating the phenomenon of impurity metal ion crystallization at the negative electrode interface and the amount of further growth of impurity metal dendrites, thereby improving the safety performance of the battery cell.

[0010] In some embodiments, the charged group includes a positively charged group or a negatively charged group; wherein the positively charged group includes at least one of amino, amine, quaternary ammonium, and guanidine, and the negatively charged group includes at least one of sulfonic acid, carboxylic acid, and alcohol.

[0011] In some embodiments, the steric hindrance group includes at least one of a pyromellitic acid group, an orthophthalamide group, and a styrene diacetic acid group.

[0012] The aforementioned charged groups have a relatively strong electrostatic interaction with inactive metal ions, which hinders and reduces the passage of inactive metal ions through the membrane of this embodiment. These steric hindrance groups effectively act as steric hindrance in the metal ion selectively permeable membrane layer, effectively reducing the permeability of the membrane to inactive metal ions. Therefore, the aforementioned charged groups and steric hindrance effectively hinder the passage of inactive metal ions through the membrane of this embodiment, reducing the membrane's permeability to inactive metal ions. Simultaneously, because active metal ions have relatively small diameters and relatively weak charges, the electrostatic interaction of these charged groups on active metal ions is relatively small, and the steric hindrance effect of the steric hindrance groups on active metal ions is weak, hardly affecting the flux of active metal ions through the membrane of this embodiment.

[0013] In some embodiments, the material of the metal ion selectively permeable membrane layer includes at least one of polyethyleneimine, polyetherimine, polyacrylamide, quaternized polyethyleneimine, polystyrene sulfonic acid, polymethacrylic acid, polyacrylic acid, sulfonated polysulfone, trimesoyl chloride-grafted polyetherimine, phthaloyl chloride-grafted polyacrylamide, and sodium styrene diacetate-grafted quaternized polyethyleneimine. The metal ion selectively permeable membrane layer formed by these materials is rich in at least one of charged groups and steric hindrance groups, which can exert electrostatic and / or steric hindrance effects on inactive metal ions, thereby effectively preventing inactive metal ions from passing through the membrane of the embodiments of this application. Furthermore, it has good film-forming properties, improving the uniformity of dispersion of charged groups and steric hindrance groups in the metal ion selectively permeable membrane layer.

[0014] In some embodiments, the metal ion selectively permeable membrane layer includes a permeable base membrane, and at least one of the charged groups and steric hindrance groups is grafted onto the permeable base membrane. By grafting functional groups onto the permeable base membrane, the binding strength of at least one of the charged groups and steric hindrance groups on the metal ion selectively permeable membrane layer can be increased, thereby improving the stability of the membrane in the embodiments of this application in preventing the passage of inactive metal ions.

[0015] In some embodiments, the thickness of the metal ion selectively permeable membrane is 30–100 nm.

[0016] In some embodiments, the thickness of the metal ion selectively permeable membrane is 50–80 nm.

[0017] The metal ion selective permeable membrane layer within this thickness range can increase the content of at least one functional group among the charged groups and steric hindrance groups contained therein. At the same time, it and the membrane substrate play a role in regulating the pore structure of the membrane, so that the metal ion selective permeable membrane layer and the membrane substrate have a synergistic effect in preventing inactive metal ions from passing through the membrane of the present application embodiment, thereby reducing the crystallization phenomenon at the negative electrode interface in the battery cell and reducing the amount of dendrite growth.

[0018] In some embodiments, the metal ions selectively permeate through the membrane layer, which contains pores with a pore size of 10–30 nm.

[0019] In some embodiments, the metal ions selectively permeate through the membrane layer containing pores, and the pore diameter is 15-25 nm.

[0020] The pore size within this range allows metal ions to selectively permeate through the membrane layer and the membrane substrate, thereby adjusting the pore diameter of the membrane. While intercepting inactive metal ions passing through the membrane and reducing the membrane's permeability to inactive metal ions, it can also effectively seal and compensate for pore defects in the membrane substrate, reducing pore defects in the membrane of this embodiment, and simultaneously regulating the flux of active metal ions, thereby alleviating dendrite formation at the negative electrode interface.

[0021] In some embodiments, the membrane substrate includes at least one selected from polyolefin, polyvinylidene fluoride (PVDF), polyimide, glass fiber, spandex, and aramid. These types of membrane substrates possess 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 membrane in the embodiments of this application.

[0022] In some embodiments, the thickness of the diaphragm is 5–50 μm;

[0023] In some embodiments, the thickness of the diaphragm is 7–20 μm.

[0024] The thickness range of the membrane allows for selective permeation of metal ions within an appropriate thickness range, thereby increasing the content of at least one of the charged groups and steric hindrance groups in the membrane and regulating the migration path of inactive metal ions, thus enhancing the membrane's ability to impede the passage of inactive metal ions.

[0025] In some embodiments, the porosity of the diaphragm is 20% to 60%.

[0026] In some embodiments, the porosity of the diaphragm is 30% to 50%.

[0027] This porosity range can improve the ion transport efficiency and electrolyte wettability of the membrane in the embodiments of this application.

[0028] 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:

[0029] A metal ion selectively permeable membrane layer is formed on at least one surface of a membrane substrate to obtain a membrane;

[0030] The material of the metal ion selectively permeable membrane layer contains at least one of charged groups and steric hindrance groups.

[0031] The membrane preparation method of this application directly forms a metal ion selectively permeable membrane layer containing at least one functional group among charged groups and steric hindrance groups on at least one surface of the membrane substrate. The formed metal ion selectively permeable membrane layer exerts an electrostatic effect and / or steric hindrance effect on inactive metal ions, thereby hindering the passage of inactive metal ions and reducing the permeability of the prepared membrane to inactive metal ions.

[0032] In some embodiments, the method of forming a metal ion selectively permeable membrane layer on at least one surface of the membrane substrate includes the following steps:

[0033] A permeable base film is disposed on at least one surface of the diaphragm substrate to form a composite film layer;

[0034] A solution containing grafting reactants is used to form a wet film on the surface of the permeable base membrane opposite to the membrane substrate;

[0035] The grafting reactant is grafted onto the permeable base membrane to obtain the diaphragm;

[0036] The permeable base membrane material and the grafting reactant contain at least one of the following groups: charged groups and steric hindrance groups.

[0037] In some embodiments, the method of forming a metal ion selectively permeable membrane layer on at least one surface of the membrane substrate includes the following steps:

[0038] The permeable base membrane is immersed in a solution containing grafting reactants to carry out a grafting reaction, thereby obtaining the metal ion selectively permeable membrane layer.

[0039] The metal ion selectively permeable membrane layer is bonded to at least one surface of the membrane substrate to obtain the membrane;

[0040] The permeable base membrane material and the grafting reactant contain at least one of the following groups: charged groups and steric hindrance groups.

[0041] By directly forming a wet film on the surface of a permeable base membrane with the grafting reactant, or by immersing the permeable base membrane in a solution containing the reactant, the grafting reactant will penetrate into the interior of the permeable base membrane through the pores and fully contact the permeable base membrane. After the grafting reaction, at least one functional group, including charged groups and steric hindrance groups, can be grafted onto the permeable base membrane, and the uniformity of grafting of these functional groups in the formed metal ion selective permeable membrane layer is improved, thereby reducing the permeability of the membrane to inactive metal ions.

[0042] In the embodiments, the mass content of the grafting reactant in the solution is 1% to 15%. This range of mass content can improve the uniformity of the grafting reactant dispersion in the permeable base membrane.

[0043] In the embodiments, the grafting reactant includes at least one of pyromellitic acid trichloroethylene chloride, phthaloyl chloride, and sodium styrene diacetate. This grafting reactant can undergo a grafting reaction with a permeable base membrane material, grafting at least one of charged groups and steric hindrance groups onto the permeable base membrane, thereby generating a metal ion selectively permeable membrane layer.

[0044] In the embodiments, the material of the permeable base membrane includes at least one of polyetherimide, polyacrylamide, and sulfonamide. These permeable base membrane materials are capable of undergoing a grafting reaction with the grafting reactant.

[0045] 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.

[0046] 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.

[0047] Fourthly, embodiments of this application provide an electrical device. The electrical device in this application includes the battery described in this application.

[0048] The electrical devices described in this application have high safety and long service life.

[0049] 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

[0050] 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:

[0051] Figure 1 This is a schematic diagram of the structure of a diaphragm according to an embodiment of this application;

[0052] Figure 2 This is a schematic diagram of another structure of the diaphragm according to an embodiment of this application;

[0053] Figure 3 This is a schematic diagram of the structure of a single battery cell according to an embodiment of this application;

[0054] Figure 4 for Figure 3 The diagram shows an exploded view of a single battery cell.

[0055] Figure 5 This is a schematic diagram of one embodiment of the battery module of this application;

[0056] Figure 6 This is an exploded view of the battery pack according to an embodiment of this application;

[0057] Figure 7 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.

[0058] Figure 8 The images shown are SEM images of the metal ion selectively permeable membrane layer and the membrane substrate contained in the diaphragm provided in Example A7; wherein, image a is an SEM image of the metal ion selectively permeable membrane layer contained in the diaphragm, image b is an enlarged SEM image of image a, image c is an SEM image of the membrane substrate contained in the diaphragm, and image d is an enlarged SEM image of image c.

[0059] The reference numerals in the detailed embodiments are as follows:

[0060] 10-Separator, 11-Separator substrate, 12-Metal ion selectively permeable membrane layer, 121-Permeable base membrane, 122-Functional group;

[0061] 20-Battery cell, 21-Casing, 22-Electrode assembly, 23-Cover plate;

[0062] 30-Battery Module;

[0063] 40 - Battery pack, 41 - Upper casing, 42 - Lower casing. Detailed Implementation

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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).

[0070] 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.

[0071] 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.

[0072] Batteries, especially lithium-ion batteries, are widely used in electric vehicles, smartphones, tablets, and other fields as important energy storage devices. Battery performance and safety are crucial for the normal operation of devices and the safety of users. With technological advancements and societal progress, higher demands are being placed on the cycle performance and safety of batteries.

[0073] A battery consists of a positive electrode, a negative electrode, and a separator positioned between them. The positive electrode and separator, as crucial components, play a vital role in the battery's electrochemical performance, including safety and cycle life. 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.

[0074] However, inorganic cathode materials generally possess various 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 into the electrolyte. 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 allows these ions to migrate through the separator to the negative electrode. In low-potential environments, these ions are easily reduced and precipitated, forming 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 cannot effectively reduce the permeation and migration of inactive metal ions released from the cathode material to the negative electrode, further increasing battery safety risks.

[0075] 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. However, they are unlikely to effectively mitigate 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.

[0076] Therefore, in order to effectively mitigate the migration of inactive metal ions released from the positive electrode material through the separator to the negative electrode, alleviate the dendrite formation at the negative electrode interface, and improve the safety of the battery cell, research has found that a metal ion selective permeability membrane layer can be formed on the surface of the separator substrate. This membrane layer contains at least one of two groups: charged groups and steric hindrance groups. The charged groups exert a charge effect on the inactive metal ions released from the positive electrode material as they pass through the separator, and / or the steric hindrance groups exert a steric hindrance effect, effectively mitigating the permeation of these inactive metal ions. This significantly reduces the content of inactive metal ions at the negative electrode interface, thereby effectively reducing the amount of impurity dendrites formed at the negative electrode interface and improving the safety performance of the battery cell.

[0077] Diaphragm:

[0078] In a first aspect, embodiments of this application provide a diaphragm. The diaphragm of this application includes a diaphragm substrate and a metal ion selectively permeable membrane layer, the metal ion selectively permeable membrane layer being disposed on at least one surface of the diaphragm substrate. The material of the metal ion selectively permeable membrane layer contains at least one group selected from charged groups and steric hindrance groups.

[0079] In the separator of this application embodiment, the separator substrate serves as the base layer for loading the metal ion selective permeation membrane layer, while also functioning as a conventional separator in the battery cell. The separator surface refers to the two surfaces of the separator that are opposite each other. In this case, the metal ion selective permeation membrane layer can be disposed on one of the separator surfaces or simultaneously on both opposite surfaces, forming a composite separator structure with two or more layers on the separator substrate. The metal ion selective permeation membrane layer refers to a functional membrane layer whose material contains at least one of charged groups and steric hindrance groups, enabling it to exert a charge effect (including repulsion between positively charged and inactive metal ions and / or electrostatic adsorption between negatively charged and inactive metal ions) or a steric hindrance effect on inactive metal ions, thereby effectively reducing the passage of inactive metal ions while barely affecting the passage of active metal ions such as lithium ions or sodium ions. Therefore, this metal ion selective permeation membrane layer has a porous structure that allows at least active metal ions to pass through. In this context, inactive metal ions are those other than monovalent lithium or sodium ions in the cathode material, as opposed to the active metal ions contained in the cathode material. These include divalent or higher-valence metal ions. In the example, these 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.

[0080] The diaphragm in this application improves the permeability of inactive metal ions by adding a metal ion selectively permeable membrane layer to at least one surface of the diaphragm substrate. Specifically, when the material of the metal ion selectively permeable membrane layer contains charged groups, and these groups are positively charged, the positively charged groups exert a relatively strong electrostatic repulsion on inactive metal ions, thereby reducing the probability of inactive metal ions passing through the diaphragm. When the charged groups in the metal ion selectively permeable membrane layer are negatively charged, these negatively charged groups exert a relatively strong electrostatic adsorption on inactive metal ions, thereby reducing the probability of inactive metal ions passing through the diaphragm. Furthermore, since the charge of inactive metal ions is significantly higher than that of active metal ions, the charged groups (whether positively or negatively charged) can significantly exert an electrostatic effect on high-valence inactive metal ions, while the electrostatic effect (electrostatic repulsion or electrostatic adsorption) on active metal ions is relatively weak. Therefore, it does not significantly adversely affect the passage of active metal ions through the diaphragm in this application. Therefore, the charged group can significantly reduce the permeability of the membrane in the present application embodiment to high-valence inactive metal ions, and has almost no adverse effect on the passage of active metal ions through the membrane.

[0081] When the material of the metal ion selectively permeable membrane contains steric hindrance groups, these groups can exert a relatively strong steric hindrance effect on inactive metal ions, thus hindering their passage through the membrane of this embodiment and reducing the permeability of the membrane to high-valence inactive metal ions. Similarly, since the charge and ionic radius of inactive metal ions are significantly higher than those of active metal ions, the steric hindrance groups can only hinder the passage of high-valence inactive metal ions through the membrane of this embodiment, while their steric hindrance effect on active metal ions is relatively weak. Therefore, they do not cause significant adverse effects on the passage of active metal ions through the membrane of this embodiment.

[0082] Therefore, the separator in this embodiment of the application can block inactive metal ions from passing through the separator by at least one functional group among the charged groups and steric hindrance groups contained in the material that allows metal ions to selectively permeate the membrane layer. This effectively reduces the permeability of the separator to inactive metal ions released by the positive electrode material during cycling, effectively reduces the content of impurity metal ions at the negative electrode interface in the battery cell, thereby significantly alleviating the phenomenon and amount of impurity dendrite formation at the negative electrode interface and improving the safety performance of the battery cell.

[0083] Based on the relationship between the membrane substrate and the metal ion selectively permeable membrane 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: Figure 1 or Figure 2 The structure shown:

[0084] 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. A metal ion selectively permeable membrane layer 12 is disposed on one of the surfaces of the diaphragm substrate 11. The material of the metal ion selectively permeable membrane layer 12 contains functional groups 122, and the functional groups 122 include at least one of charge groups and steric hindrance groups.

[0085] 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. Metal ion selectively permeable membrane layers 12 are respectively disposed on the two surfaces disposed opposite to each other. The material of each metal ion selectively permeable membrane layer 12 contains functional groups 122, and the functional groups 122 include at least one of charge groups and steric hindrance groups.

[0086] Regardless of the structure of the separator in this application embodiment, the selectively permeable metal ion membrane layer 12 contained therein can act as a separator to prevent the passage of inactive metal ions, thereby alleviating the passage of inactive metal ions released by the positive electrode material through the separator of this application embodiment, reducing the content of inactive metal ions at the negative electrode interface in the battery cell, significantly alleviating the adverse phenomena such as crystallization of impurity metal ions at the negative electrode interface and further formation of impurity dendrites, thereby improving the safety of the battery cell.

[0087] In some embodiments, the thickness of the diaphragm in this application can be 5–50 μm, optionally 7–20 μm. In exemplary examples, it can be a typical but non-limiting thickness such as 5 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 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 selectively permeable membrane layer, such as… Figure 1 The sum of the thickness 'a' of the diaphragm substrate 11 and the thickness 'b' of the metal ion selectively permeable membrane layer 12 (i.e., a+b), or as... Figure 2The thickness 'a' of the membrane substrate 11 is the sum of the thicknesses 'a+2b' of the two metal ion selective permeable membrane layers 12. Within this thickness range, the metal ion selective permeable membrane layers have an appropriate thickness. On one hand, this thickness can further adjust the content of at least one of the charged groups and steric hindrance groups in the membrane, thereby improving the electrostatic and / or steric hindrance effects of the membrane on migrating inactive metal ions. On the other hand, the metal ion selective permeable membrane layers can regulate the pore size and pore structure of the membrane substrate, adjusting the migration path of inactive metal ions and utilizing the fact that the radius of inactive metal ions is significantly larger than that of active ions to reduce the permeability of inactive ions. Therefore, a membrane with this thickness range can effectively reduce the permeability of inactive metal ions, alleviating their accumulation at the negative electrode interface and further mitigating the formation and amount of impurity dendrites at the negative electrode interface. The thickness of this membrane can be measured using a micrometer or a thickness gauge, or it can be precisely measured using a scanning electron microscope.

[0088] 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 selectively permeable membrane layer. This range of porosity can improve the ion transport efficiency and electrolyte wettability of the diaphragm in this application embodiment.

[0089] [Separator Substrate]

[0090] In the diaphragm of the present application embodiment, the diaphragm substrate it contains constitutes the diaphragm matrix, performs the function of a conventional diaphragm, and at the same time acts as a carrier for selectively permeating metal ions through the membrane layer.

[0091] The membrane substrate can be selected from conventional thicknesses. In the embodiments of this application, 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 is as follows: Figure 1 and Figure 2The thickness 'a' of the diaphragm substrate 11 can be 4–48 μm, optionally 5–17 μm. In exemplary cases, it can be typical but non-limiting thicknesses such as 4 μm, 6 μm, 7 μm, 8 μm, 10 μm, 13 μm, 15 μm, 17 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, and 48 μm, or any range between two thickness values. Diaphragm substrates within this thickness range can improve the flux of active metal ions in the diaphragm of this embodiment, while also adjusting the total thickness and mechanical properties of the diaphragm, thereby improving the electrochemical performance of the battery cell, including energy density and other related properties. The thickness of the diaphragm substrate can be measured using a micrometer or a thickness gauge, or, of course, precisely measured using a scanning electron microscope.

[0092] 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. Membrane substrates made of these materials possess 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 membrane in the embodiments of this application.

[0093] [Metal ion selectively permeable membrane]

[0094] In some embodiments, the total molar amount of any one or two of the charged groups and steric hindrance groups contained in the material of the metal ion selective permeable membrane layer can be 5% to 30%, or optionally 10% to 30%. In exemplary cases, it can be a typical but non-limiting content such as 5%, 10%, 13%, 14%, 15%, 16%, 17%, 20%, 23%, 25%, 27%, 30%, or a range between any two content values. The functional groups within this molar content range can effectively improve the electrostatic and / or steric hindrance effects of the metal ion selective permeable membrane layer on inactive metal ions, thereby further reducing the permeability of the separator in this embodiment to high-valence inactive metal ions, reducing the content of impurity metal ions at the negative electrode interface in the battery cell, further mitigating the phenomenon of impurity metal ion crystallization at the negative electrode interface and the further growth of impurity metal dendrites, thereby improving the safety performance of the battery cell. The total molar content of at least one of the charged groups and sterically hindered groups on the metal ion selectively permeable membrane can be detected and analyzed by methods such as infrared spectroscopy, chromatography combined with mass spectrometry.

[0095] In some embodiments, when metal ions selectively permeate the film containing charged groups, the charged groups can be either positively charged or negatively charged groups.

[0096] In the embodiments, when the metal ion selectively permeable membrane contains positively charged groups, the positively charged groups may include at least one of amino, amine, quaternary ammonium, and guanidine groups.

[0097] Based on these positively charged groups, in the embodiments, the material containing these positively charged groups, that is, the material that allows metal ions to selectively permeate the membrane layer, may include at least one of polyethyleneimine, polyetherimine, polyacrylamide, and quaternized polyethyleneimine.

[0098] In the embodiments, when the metal ion selectively permeable membrane contains negatively charged groups, the negatively charged groups may include at least one of sulfonic acid groups, carboxylic acid groups, and alcohol groups.

[0099] Based on these negatively charged groups, in the embodiments, the material containing these negatively charged groups, that is, the material that allows metal ions to selectively permeate the membrane layer, may include at least one of polystyrene sulfonic acid, polymethacrylic acid, polyacrylic acid, and sulfonated polysulfone.

[0100] The aforementioned positively or negatively charged groups exhibit relatively strong electrostatic interactions with the inactive metal ions released from the positive electrode material. Specifically, the positively charged groups exert a relatively strong electrostatic repulsion on the inactive metal ions, hindering their approach to the membrane and thus reducing their passage rate. Conversely, the negatively charged groups exhibit a relatively strong electrostatic adsorption on the inactive metal ions, attracting them and hindering their passage through the membrane, further reducing the passage rate. Simultaneously, both the positively and negatively charged groups have weak electrostatic interactions with the relatively weakly charged active metal ions, having almost no impact on the flux of active metal ions through the membrane.

[0101] In the embodiments, when the metal ion selectively permeable membrane contains steric hindrance groups, the steric hindrance groups include at least one of pyromellitic acid groups, phthalamide groups, and styrene diacetic acid groups.

[0102] Based on these steric hindrance groups, in the embodiments, the material containing these steric hindrance groups, that is, the material that allows metal ions to selectively permeate the membrane layer, may include at least one of pyromellitic benzoyl chloride-grafted polyetherimide, phthaloyl chloride-grafted polyacrylamide, and sodium styrene diacetate-grafted quaternized polyethyleneimine.

[0103] These steric hindrance groups can effectively hinder the passage of inactive metal ions in the metal ion selectively permeable membrane layer. When inactive metal ions pass through the membrane of this embodiment, the steric hindrance groups can effectively prevent their passage. At the same time, since the diameter of active metal ions is relatively small, the steric hindrance effect of the steric hindrance groups on active metal ions is weak and has almost no impact on the flux of active metal ions through the membrane of this embodiment.

[0104] Of course, in addition to their respective functional groups, the aforementioned materials with positively charged groups, materials with negatively charged groups, and materials containing steric hindrance groups also contain other groups that can hinder the passage of inactive metal ions. For example, materials with negatively charged groups contain not only negatively charged groups but also other groups that can act as steric hindrances. For instance, in polystyrene sulfonic acid, in addition to the negatively charged sulfonic acid groups, the polystyrene backbone can also act as a steric hindrance. Similarly, materials containing steric hindrance groups may contain both positively charged and negatively charged groups.

[0105] In some embodiments, the metal ion selectively permeable membrane layer in the above embodiments includes a permeable base membrane, wherein at least one of the charged groups and sterically hindered groups contained therein is grafted onto the permeable base membrane. In the embodiments, the metal ion selectively permeable membrane layer is as follows: Figure 1 and Figure 2 The metal ion selectively permeable membrane layer 12 described herein includes a permeable base membrane 121, on which at least one functional group 122, selected from charged groups and steric hindrance groups, is grafted. The permeable base membrane is understood to be a porous membrane layer with pathways for the migration of active metal ions, possessing electrolyte wettability, and capable of undergoing a grafting reaction. By grafting functional groups onto the permeable base membrane, the binding strength of at least one functional group, selected from charged groups and steric hindrance groups, on the metal ion selectively permeable membrane layer can be increased, thereby improving the stability of the membrane in the present application embodiment in preventing the passage of inactive metal ions.

[0106] In some embodiments, metal ions selectively permeate through the membrane layer, such as... Figure 1The thickness b of the metal ion selective permeable membrane 12 can be 30-100 nm, or optionally 50-80 nm. In the exemplary example, it can be a typical but non-limiting thickness such as 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm, or any range between two thickness values. The thickness of the metal ion selective permeable membrane refers to the thickness of the metal ion selective permeable membrane disposed on one of the surfaces of the separator substrate. This thickness range of the metal ion selective permeable membrane can increase the content of at least one functional group among the charged groups and steric hindrance groups it contains. Simultaneously, it, together with the separator substrate, regulates the pore structure of the separator and the migration path of inactive metal ions. This results in the metal ion selective permeable membrane and the separator substrate having a synergistic effect in hindering the passage of inactive metal ions through the separator of this embodiment, reducing the content of inactive metal ions at the negative electrode interface, reducing crystallization at the negative electrode interface in the battery cell, and reducing dendrite growth. The thickness of the selectively permeable metal ion membrane 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).

[0107] In some embodiments, the diameter of the vias in the metal ion selective permeable membrane layer can be 10–30 nm, or optionally 15–25 nm. In exemplary cases, it can be typical but non-limiting diameters such as 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 22 nm, 25 nm, 28 nm, and 30 nm, or any range between two diameter values. Here, the diameter of the via refers to the pore size. This range of pore sizes allows the metal ion selective permeable membrane layer and the membrane substrate to adjust the pore diameter of the membrane. On the one hand, by utilizing the characteristic that the diameter of inactive metal ions is significantly larger than that of active metal ions, it intercepts inactive metal ions passing through the membrane, reducing the membrane's permeability to inactive metal ions. On the other hand, the metal ion selective permeable membrane layer can effectively seal and compensate for pore defects in the membrane substrate, reducing pore defects in the membrane of this application embodiment. While intercepting inactive metal ions, it also adjusts the flux of active metal ions, thereby alleviating dendrite formation at the negative electrode interface. The diameter of the pores in the selectively permeable membrane can be precisely measured using scanning electron microscopy (SEM) or transmission electron microscopy (TEM).

[0108] Diaphragm preparation method:

[0109] Secondly, embodiments of this application provide a method for preparing the diaphragm according to the embodiments of the above application.

[0110] In some embodiments, the membrane preparation method of this application includes the following steps:

[0111] S10: A metal ion selectively permeable membrane layer is formed on at least one surface of the membrane substrate to obtain a membrane.

[0112] 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. Therefore, the metal ion selectively permeable membrane layer formed is also the metal ion selectively permeable membrane layer contained in the diaphragm of the above application embodiment. Thus, the material of the formed metal ion selectively permeable membrane layer contains at least one of the following groups: charged groups and steric hindrance groups.

[0113] Thus, the membrane preparation method of this application directly forms a metal ion selectively permeable membrane layer containing at least one of the charged groups and steric hindrance groups on at least one surface of the membrane substrate. The formed metal ion selectively permeable membrane layer exerts an electrostatic effect and / or steric hindrance effect on inactive metal ions, thereby hindering the passage of inactive metal ions and reducing the permeability of the prepared membrane to inactive metal ions.

[0114] In some embodiments, the method of forming a metal ion selectively permeable membrane layer on the surface of the diaphragm substrate may include the following steps:

[0115] S11: A permeable base film is disposed on at least one surface of the diaphragm substrate to form a composite membrane layer;

[0116] S12: A wet film is formed on the surface of a permeable base membrane away from the diaphragm substrate by a solution containing the grafting reactant.

[0117] S13: The grafting reactant is grafted onto a permeable base membrane to obtain a metal ion selectively permeable membrane.

[0118] In step S11, the material of the permeable base membrane and in step S12, the grafting reactant, contain at least one functional group, including at least one charged group and at least one sterically hindered group. By directly forming a wet film on the surface of the permeable base membrane with the grafting reactant, the wet film can penetrate into the interior of the permeable base membrane through its pores, fully contacting it. After the grafting reaction, at least one functional group, including charged groups and sterically hindered groups, can be grafted onto the permeable base membrane, improving the uniformity of the distribution of these functional groups in the formed metal ion selective permeable membrane layer, thereby enhancing the membrane's ability to prevent the passage of inactive metal ions. Furthermore, forming the permeable base membrane first on the surface of the membrane substrate and then forming the wet film with the grafting reactant allows for continuous online production of the membranes described in this application, improving the stability of the membrane quality. For example, mass production can be carried out using a winding device, thereby improving the membrane preparation efficiency.

[0119] In step S11, the material of the permeable base membrane can be a membrane material that can undergo a grafting reaction with the grafting reactant in step S12. For example, in the embodiment, the material of the permeable base membrane is at least one of polyetherimide, polyacrylamide, and sulfonamide.

[0120] In step S11, the thickness of the permeable base film determines the thickness of the metal ion selectively permeable membrane layer. For example, in the embodiment, the thickness of the permeable base film can be 30 to 100 nm, which is the thickness of the metal ion selectively permeable membrane layer formed in the diaphragm of the above-mentioned application embodiment.

[0121] In this embodiment, the method for forming the permeable base film may be to prepare the permeable base film material into a slurry and then spray it onto the surface of the diaphragm substrate to form a film. Of course, other methods can also be used to form the permeable base film.

[0122] In this embodiment, before the solution containing the grafted reactant forms a wet film on the surface of the diaphragm substrate, the surface of the diaphragm substrate is further subjected to surface treatment. In an exemplary example, this 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, improving the film-forming properties of the solution containing the grafted reactant on the modified diaphragm substrate surface, improving the uniformity of the wet film, and enhancing the mechanical strength of the final metal ion selectively permeable membrane layer bonded to the diaphragm substrate surface.

[0123] In step S12, forming a wet film on the surface of the permeable base membrane with the solution of the grafted reactant is to ensure that the grafted reactant is distributed as evenly as possible on the surface of the permeable base membrane. Then, through solution permeation, it can enter the permeable base membrane and fully contact the permeable base membrane material, thereby improving the uniformity of the dispersion of the grafted reactant in the permeable base membrane. This ultimately improves the uniformity of the distribution of at least one functional group, including charged groups and steric hindrance groups, contained in the membrane, and enhances the membrane's effect of blocking the passage of inactive metal ions.

[0124] In the embodiments, the mass content of the grafting reactant in the solution can be 1% to 15%, optionally 5% to 13%. In exemplary cases, it can be a typical but non-limiting mass content such as 1%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, or 15%, or a range between any two mass content values. This range of mass content can improve the membrane quality of the wet membrane, thereby improving the uniformity of the grafting reactant dispersion in the permeable base membrane.

[0125] In the embodiments, by controlling the amount of wet film formed on the surface of the permeable base film, the total molar amount of any one or two of the charged groups and steric hindrance groups in the generated metal ion selective permeable membrane layer after the grafting reaction in step S13 can reach 5% to 30% of the molar amount of at least one of the charged groups and steric hindrance groups contained in the metal ion selective permeable membrane layer in the above-described embodiments.

[0126] In the embodiments, the method for forming a wet film on the surface of a permeable base film using a solution containing the grafting reactant may include, but is not limited to, spray coating, blade coating, or printing. The solution containing the grafting reactant may be a solvent capable of effectively dissolving the grafting reactant, such as, but not limited to, solvents such as diethyl ether, dichloromethane, and benzene.

[0127] In the example, the grafting reactant may include at least one of trimellitic acid chloride (TMC), phthaloyl chloride, and sodium styrene diacetate. This grafting reactant can undergo a grafting reaction with the permeable base membrane material in step S11, grafting at least one of charged groups and steric hindrance groups onto the permeable base membrane, thereby generating a metal ion selectively permeable membrane layer.

[0128] In step S13, during the grafting reaction, a grafting reaction occurs between the grafting reactant in the wet membrane and the permeable base membrane material. For example, in the exemplary case, when the permeable base membrane material is polyetherimide (PEI) and the grafting reactant is trimesoyl chloride (TMC), the PEI and TMC undergo the following grafting reaction to generate PEI-TMC:

[0129] PEI + TMC → PEI-TMC + HCl.

[0130] In the embodiments, the temperature of the grafting reactant can be between 100°C and 350°C. In exemplary cases, typical but non-limiting temperatures such as 180°C, 190°C, 200°C, and 210°C, or any range between two temperature values, can be used. This range of polymerization temperature allows the grafting reactant to fully react with the permeable base membrane material, maximizing the grafting of the aforementioned functional groups onto the permeable base membrane, thereby improving the membrane's ability to impede the passage of inactive metal ions.

[0131] In addition, the grafting reactant should be sufficient. For example, at the grafting reaction temperature of 180℃~210℃ mentioned above, the grafting reaction time can be controlled to be 2h~6h to ensure that the grafting reaction is sufficient.

[0132] In some embodiments, the method for forming a metal ion selectively permeable membrane layer on the surface of the diaphragm substrate may further include the following steps:

[0133] S14: Immerse the permeable base membrane in a solution containing the grafting reactant to carry out the grafting reaction, and obtain a metal ion selectively permeable membrane layer.

[0134] S15: Metal ions are selectively permeated through the membrane layer and bonded to at least one surface of the membrane substrate to obtain a membrane.

[0135] In step S14, the permeable base membrane can be the same as the permeable base membrane in step S11. The grafting reactant and the solution containing the grafting reactant in step S14 can be the same as the grafting reactant and the solution containing the grafting reactant in step S12. The grafting reaction conditions in step S14 can be the same as the grafting reaction conditions in step S13. To save space, these details will not be elaborated further.

[0136] In step S15, the selective permeation of metal ions through the membrane layer and its bonding with the membrane substrate can be achieved by direct lamination or by applying an adhesive to achieve bonding between the two.

[0137] Furthermore, the step numbers of step S14 above and steps S11 to S13 above do not represent the order of the process steps.

[0138] Of course, besides using the above methods to form a metal ion selectively permeable membrane layer on at least one surface of the diaphragm substrate, other methods can also be used to form a metal ion selectively permeable membrane layer on at least one surface of the diaphragm substrate. As in the embodiments, one or more polymer monomers used to form the metal ion selectively permeable membrane layer can be directly formed on the surface of the diaphragm substrate, and then a polymerization reaction is carried out to generate the metal ion selectively permeable membrane layer, thus obtaining the diaphragm. In other embodiments, organic materials such as polymers containing at least one of charged groups and steric hindrance groups can also be used to directly form a metal ion selectively permeable membrane layer on the surface of the diaphragm substrate.

[0139] Battery:

[0140] Thirdly, embodiments of this application also provide a battery.

[0141] In the embodiments of this application, the battery may include any one of a battery cell, a battery module, or a battery pack.

[0142] Battery cell:

[0143] 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.

[0144] 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 3 The shown is a square-structured battery cell 20.

[0145] In some embodiments, such as Figure 4 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] 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 current collector and a positive active material layer bonded to at least one surface of the positive current collector.

[0151] 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.

[0152] 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.

[0153] 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 material within this content range can effectively improve the energy density of the positive electrode sheet.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] 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.

[0165] Battery module:

[0166] 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.

[0167] In some embodiments, Figure 5 This is a schematic diagram of battery module 30 as an example. (See diagram below.) Figure 5 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.

[0168] Optionally, the battery module 30 may also include a housing with a receiving space in which multiple battery cells 20 are received.

[0169] Battery pack:

[0170] 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.

[0171] In some embodiments, Figure 6This 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.

[0172] Electrical appliances:

[0173] 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.

[0174] 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, individual battery cells, battery modules, or battery packs can be selected according to their usage requirements.

[0175] Figure 7 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.

[0176] 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.

[0177] Example:

[0178] 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.

[0179] 1. Examples of diaphragm and its preparation method:

[0180] Example A1:

[0181] This embodiment A1 provides a diaphragm and its preparation method. The diaphragm includes a 7 μm polyethylene membrane substrate (PE diaphragm substrate), and a metal ion selectively permeable membrane layer is disposed on one surface of the polyethylene membrane substrate. The metal ion selectively permeable membrane layer contains trimesoyl chloride (TMC) grafted polyethyleneimine (PEI). The relevant characteristic parameters of the diaphragm provided in Embodiment A1 are shown in Table 1 below.

[0182] The membrane preparation method includes the following steps:

[0183] S1: Plasma treatment is performed on the surface of the polyethylene film substrate using a plasma beam to obtain a plasma-treated polyethylene film substrate.

[0184] S2: A PEI film is formed by spraying 5.5% PEI onto the plasma-treated surface of a polyethylene film substrate.

[0185] S3: A 7.0% TMC solution is sprayed onto the surface of the PEI film away from the polyethylene film substrate to form a wet TMC film.

[0186] S4: The TMC wet film polyethylene film substrate is heated to 60°C to carry out a full grafting reaction. TMC and PEI undergo a grafting reaction to generate a TMC-PEI metal ion selectively permeable membrane layer, thus obtaining a separator.

[0187] In the formation of the TMC wet film, the mass ratio of TMC to PEI in the TMC wet film satisfies the condition that the total molar percentage of functional groups contained in the formed TMC-PEI metal ion selective permeable membrane layer is the molar percentage of functional groups shown in Example A1 of Table 1.

[0188] Examples A2 to A16:

[0189] Examples A2 to A16 each provide a diaphragm and its preparation method.

[0190] Among them, the difference between the membrane in Examples A2 to A7 and that in Example A1 is that the membrane material of the selective permeation membrane layer for metal ions is different. Due to the different membrane material, the types and contents of functional groups in the selective permeation membrane layer for metal ions are different, as are the membranes including porosity. Otherwise, they are the same as in Example A1.

[0191] The difference between the membranes in Examples A8 to A11 and those in Example A1 lies in the different contents of the trimesoamide groups grafted into the metal ion selective permeable membrane layer, which in turn leads to different molar contents of the functional groups contained in the metal ion selective permeable membrane layer. Otherwise, they are the same as in Example A1.

[0192] The differences between the membranes in Examples A12 to A16 and those in Example A1 are the thickness of the membrane layer through which metal ions selectively permeate and the resulting differences in membrane porosity, etc. The other aspects are the same as in Example A1.

[0193] The diaphragm-related characteristic parameters in Examples A2 to A16 are shown in Table 1 below.

[0194] The membrane preparation methods in Examples A2 to A16 are the same as those in Example A1, with adjustments made to the materials and conditions of each step based on the membrane material and membrane properties in each example. For instance, in Example A2, when preparing the metal ion selective permeable membrane, an ethyl sulfonyl chloride graft solution is prepared and then sprayed onto the surface of the PEI membrane away from the polyethylene membrane substrate to form an ethyl sulfonyl chloride wet membrane. Then, the ethyl sulfonyl chloride is triggered to undergo a grafting reaction with PEI to generate an ethyl sulfonyl chloride-PEI metal ion selective permeable membrane. In Example A6, when preparing the metal ion selective permeable membrane, polystyrene sulfonic acid (polystyrene sulfonic acid obtained after sulfonation) is prepared into a solution and sprayed onto the surface of the PEI membrane away from the polyethylene membrane substrate to form a wet membrane. After drying, the metal ion selective permeable membrane is obtained.

[0195] Comparative Example A1:

[0196] Comparative Example A1 provides a diaphragm, which is the diaphragm substrate of Example 1. That is, compared with the diaphragm in Example A1, it does not contain a metal ion selectively permeable membrane layer.

[0197] 2. Performance tests of the diaphragm in each embodiment:

[0198] The diaphragms provided in Examples A1 to A16 and Comparative Example A1 were subjected to the relevant feature detection methods shown in Table 1 below, and the detection results are shown in Table 1. The relevant feature detection methods for the diaphragms in Table 1 are as follows:

[0199] Methods for detecting the types and contents of functional groups in metal ion selectively permeable membranes:

[0200] Samples of metal ion selectively permeable membrane material were obtained from the diaphragm in each embodiment. Fourier transform infrared spectroscopy (FTIR) was used to analyze each sample, and infrared spectra were obtained for each sample. The types of functional groups contained in each sample were determined based on the characteristic absorption peaks in each infrared spectrum. The intensity of each characteristic absorption peak was substituted into the standard curve equation (which was obtained by establishing a standard curve based on the infrared spectroscopy of the corresponding standard sample) to calculate the content of each functional group.

[0201] The thickness of a metal ion selectively permeable membrane was determined using X-ray photoelectron spectroscopy (XPS).

[0202] 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.

[0203] Method for detecting the diameter of pores in a metal ion selectively permeable membrane: Scanning electron microscopy (SEM) is used to measure the diameter range of the pores based on the SEM images. The SEM image of the diaphragm in Example A7 is shown below. Figure 8 As shown. Among them, Figure 8 Figures a and b are SEM images of the metal ion selectively permeable membrane layer in the diaphragm of Example A7, and figures c and d are SEM images of the diaphragm substrate in Example A7. As can be seen from the SEM images, the metal ion selectively permeable membrane layer on the diaphragm surface is a three-dimensional nanofiber membrane layer, which, along with… Figure 8 In comparison, the pore size of the metal ion selective permeable membrane is significantly smaller than that of the membrane substrate. Therefore, while the metal ion selective permeable membrane is rich in functional groups, it, together with the membrane substrate, improves the pore structure of the membrane.

[0204] Testing the membrane's ability to block high-valence metal ions:

[0205] 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 allowed to migrate from one side of the diaphragm provided in Examples A1 to A14 and Comparative Examples A1 to A2 to the other side under the same pressure (room temperature) conditions. Finally, ICP was used to detect the Fe in the filtered standard aqueous solution. 3 + Fe 2+ Cu 2+ The concentration in.

[0206] Table 1

[0207]

[0208]

[0209] As shown in Table 1, the ICP detection results, comparing Examples A1 to A16 with Comparative Example 1, indicate that after membrane filtration treatment in Examples A1 to A16, the target ion content in each standard aqueous solution was significantly lower than that in Comparative Example 1. Therefore, this demonstrates that the functional groups contained in the material of the metal ion selective permeation membrane layer all function, enabling the metal ion selective permeation membrane layer to exert electrostatic and / or steric hindrance effects on high-valence inactive metal ions. This hinders the passage of inactive metal ions through the membrane of this application embodiment, significantly reducing the permeation rate of high-valence inactive metal ions through the membrane of this application embodiment.

[0210] Comparative Examples A1 to A7 show that different functional groups (including at least one of positively charged groups, negatively charged groups, and sterically hindered groups) contained in the membrane material of the metal ion selectively permeable membrane can all hinder inactive metal ions.

[0211] Comparative Examples A8 to A11 show that the higher the content of functional groups (including at least one of positively charged groups, negatively charged groups, and sterically hindered groups) in the membrane material of the metal ion selective permeable membrane, the stronger the barrier effect of the metal ion selective permeable membrane on inactive metal ions, thereby resulting in a lower pass rate of high-valence inactive metal ions through the membrane of this application.

[0212] Comparative Examples A12 to A16 show that the thicker the metal ion selective permeable membrane layer, the higher the content of functional groups (including at least one of positively charged groups, negatively charged groups, and sterically hindered groups) in the membrane, which also makes the metal ion selective permeable membrane layer more resistant to inactive metal ions, thereby making the pass rate of high-valence inactive metal ions through the membrane of this application embodiment lower.

[0213] 3. Example of a single lithium-ion battery cell:

[0214] Examples B1 to B16 and Comparative Example B1:

[0215] Examples B1 to B16 and Comparative Example B1 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.

[0216] The lithium-ion battery cells in Examples B1 to B16 and Comparative Example B1 are assembled as follows:

[0217] 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.

[0218] 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;

[0219] 3) Separator: The separator provided in Examples A1 to A16 and Comparative Example A1 is used as the separator; 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 B1 contains the separator in Comparative Example A1.

[0220] 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.

[0221] 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 B14 and Comparative Examples B1 to B2 are obtained.

[0222] 4. Electrochemical performance testing of individual ion battery cells in each embodiment:

[0223] The ion battery cells provided in Examples B1 to B18 and Comparative Example B1 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. Table 2 lists the relevant performance testing methods for the ion battery cells.

[0224] 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.

[0225] 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.

[0226] 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.

[0227] Table 2

[0228]

[0229] 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 ion battery cells in Examples B1 to B16 is higher than that of the ion battery cell in Example B1. This indicates that the separator in Examples A1 to A16 significantly improves the high-temperature storage voltage drop of the ion battery cells. This demonstrates that the selective permeation of metal ions in the separator of this application, through the functional groups contained therein, plays an electrostatic and / or steric hindrance role on the high-valence inactive metal ions dissolved in the electrolyte, reducing the permeability of these high-valence inactive metal ions through the separator of this application. This reduces the amount of these high-valence inactive metal ions accumulating at the negative electrode interface, significantly alleviating the formation of impurity dendrites at the negative electrode interface and effectively suppressing the physical self-discharge caused by metal impurities inside the cell, thus improving the safety performance of the cell.

[0230] Meanwhile, the cell calendar life and cell cycle life of the lithium-ion battery cells in Examples B1 to B16 were not significantly reduced compared to the lithium-ion battery cell in Example B1, and some were even improved. This indicates that the selective permeation of metal ions through the membrane layer has almost no adverse effect on the active metal ions (lithium ions) in the cell, and the selective permeation of metal ions through the membrane 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.

[0231] 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 selectively permeable membrane layer, which is disposed on at least one surface of the membrane substrate; wherein the material of the metal ion selectively permeable membrane layer contains at least one group selected from charged groups and steric hindrance groups.

2. The diaphragm as described in claim 1, characterized in that: The molar amount of at least one of the charged groups and steric hindrance groups in the metal ion selectively permeable membrane layer is 5% to 30%.

3. The diaphragm as described in claim 1, characterized in that: The molar amount of at least one of the charged groups and steric hindrance groups in the metal ion selectively permeable membrane layer is 10% to 30%.

4. The diaphragm according to any one of claims 1 to 3, characterized in that: The charged groups include positively charged groups or negatively charged groups; wherein, the positively charged groups include at least one selected from amino, amine, quaternary ammonium, and guanidine groups, and the negatively charged groups include at least one selected from sulfonic acid, carboxylic acid, and alcohol groups; and / or The steric hindrance group includes at least one of the following: pyromellitic acid group, phthalamide group, and styrene diacetic acid group.

5. The diaphragm according to any one of claims 1 to 4, characterized in that: The material for the metal ion selectively permeable membrane layer includes at least one of polyethyleneimine, polyetherimine, polyacrylamide, quaternized polyethyleneimine, polystyrene sulfonic acid, polymethacrylic acid, polyacrylic acid, sulfonated polysulfone, pyromellitic acid-grafted polyetherimine, phthaloyl chloride-grafted polyacrylamide, and sodium styrene diacetate-grafted quaternized polyethyleneimine. The diaphragm substrate includes at least one of polyolefin, polyvinylidene fluoride, polyimide, glass fiber, spandex, and aramid.

6. The diaphragm according to any one of claims 1 to 5, characterized in that: The metal ion selectively permeable membrane layer includes a permeable base membrane, and at least one of the charged groups and steric hindrance groups is grafted onto the permeable base membrane.

7. The diaphragm according to any one of claims 1 to 6, characterized in that: The metal ion selectively permeable membrane contains pores with a pore size of 10–30 nm; and / or The thickness of the metal ion selectively permeable membrane is 30–100 nm.

8. The diaphragm according to any one of claims 1 to 6, characterized in that: The metal ion selectively permeable membrane contains pores with a pore size of 15–25 nm; and / or The thickness of the metal ion selectively permeable membrane is 50–80 nm.

9. The diaphragm according to any one of claims 1 to 8, characterized in that: The diaphragm includes at least one of the following (1) to (2): (1) The thickness of the diaphragm is 5 to 50 μm; (2) The porosity of the diaphragm is 20% to 60%.

10. The diaphragm according to any one of claims 1 to 8, characterized in that: The diaphragm includes at least one of the following (1) to (2): (1) The thickness of the diaphragm is 7–20 μm; (2) The porosity of the diaphragm is 30% to 50%.

11. A method for preparing a diaphragm, characterized in that, Includes the following steps: A metal ion selectively permeable membrane layer is formed on at least one surface of a membrane substrate to obtain a membrane; The metal ion selectively permeable membrane layer formed contains at least one of charged groups and steric hindrance groups.

12. The preparation method according to claim 11, characterized in that, The method for forming a metal ion selectively permeable membrane layer on at least one surface of a membrane substrate includes the following steps: A permeable base film is disposed on at least one surface of the diaphragm substrate to form a composite film layer; A solution containing grafting reactants is used to form a wet film on the surface of the permeable base membrane opposite to the membrane substrate; The grafting reactant is grafted onto the permeable base membrane to obtain the diaphragm; The permeable base membrane material and the grafting reactant contain at least one of the following groups: charged groups and sterically hindered groups.

13. The preparation method according to claim 11, characterized in that, The method for forming a metal ion selectively permeable membrane layer on at least one surface of a membrane substrate includes the following steps: The permeable base membrane is immersed in a solution containing grafting reactants to carry out a grafting reaction, thereby obtaining the metal ion selectively permeable membrane layer. The metal ion selectively permeable membrane layer is bonded to at least one surface of the membrane substrate to obtain the membrane; The permeable base membrane material and the grafting reactant contain at least one of the following groups: charged groups and sterically hindered groups.

14. The preparation method according to claim 12 or 13, characterized in that, The grafting reactant has a mass content of 1% to 15% in the solution; The grafting reactant includes at least one of pyromellitic methyl chloride, phthaloyl chloride, and sodium styrene diacetate. The material of the permeable base membrane includes at least one of polyetherimide, polyacrylamide, and sulfonamide.

15. A battery, characterized in that, It includes the diaphragm according to any one of claims 1 to 10 or the diaphragm prepared by the preparation method according to any one of claims 11 to 14.

16. An electrical appliance, characterized in that: Includes the battery as described in claim 15.

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