Applications of secondary batteries, electrical devices, and silicate complex salts

Abstract

This application provides a secondary battery in which at least one of the positive electrode active material layer and the negative electrode active material layer contains a silicate composite salt, the chemical formula of which is selected from YSi2Z. 1 Z 2 O8 and X 1 X 2 Si2Z 1 Z 2 At least one of O8, Y is selected from Group 2, and X is selected from... 1 and X 2 Each element is independently selected from the first primary race element, Z. 1 and Z 2 Each element is selected from the third primary race.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to secondary batteries, electrical devices, and the application of silicate complex salts. Background Technology

[0002] The statements herein are provided only as background information in connection with this application and do not necessarily constitute prior art.

[0003] With the accelerating pace of life and the widespread adoption and development of various electronic products such as smartphones, tablets, smart wearables, power tools, and electric vehicles, electronic products are becoming increasingly feature-rich and diversified. People are spending more and more time using electronic products in their daily lives, which poses a greater challenge to the lifespan of these products.

[0004] Therefore, there is an urgent need to further improve the lifespan of secondary battery products. Summary of the Invention

[0005] In view of the above problems, this application provides a secondary battery, an electrical device, and the application of silicate composite salt. The secondary battery uses silicate composite salt as an interface stabilizer in the electrode plates, which can improve the wetting performance of the electrolyte, stabilize the electrode-electrolyte interface, improve cycle performance, and extend the battery life.

[0006] In a first aspect, this application provides a secondary battery, which includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the separator is located between the positive electrode and the negative electrode; the positive electrode includes a positive active material layer, and the negative electrode includes a negative active material layer;

[0007] At least one of the positive electrode active material layer and the negative electrode active material layer contains a silicate composite salt;

[0008] The chemical formula of the silicate complex salt is selected from YSi2Z. 1 Z 2 O8 and X 1 X 2 Si2Z 1 Z 2 At least one of O8;

[0009] in,

[0010] Y is selected from the second main group element;

[0011] X 1 and X 2 Each element is independently selected from the first primary race.

[0012] Z 1 and Z 2 Each element is selected from the third primary race.

[0013] By employing a special silicate composite salt as an interface stabilizer in the electrode plates of a secondary battery, the wetting performance of the electrolyte can be improved, the electrode-electrolyte interface can be stabilized, cycle performance can be improved, and battery life can be extended. The silicate composite salt of this application contains specific short-period Group I to III main group elements. These short-period main group elements can participate in the formation of the electrolyte interface film. The silicate composite salt of this application can act as an interface stabilizer, improving the wetting performance of the electrolyte, stabilizing the electrode-electrolyte interface, improving the cycle performance and storage performance of the secondary battery, and extending the battery's lifespan. This silicate composite salt can stabilize both the positive electrode electrolyte interface (CEI) and the negative electrode electrolyte interface (SEI). In comparison, the interaction between Group IV to VII main group elements and oxygen is weaker, or they contain more lone pairs of electrons and are more prone to oxidation reactions; in addition, long-period transition metal elements have more empty orbitals, which can catalyze the redox reactions of the electrolyte.

[0014] In some embodiments of this application, the structural formula of the silicate complex salt is selected from at least one of Formula I and Formula II:

[0015]

[0016] In some embodiments of this application, the secondary battery satisfies any one or more of the following characteristics:

[0017] Y is either Mg or Be;

[0018] X 1 and X 2 Each can be either Li or Na;

[0019] In the same molecule, X 1 and X 2 same;

[0020] Z 1 and Z 2 Each is independently Al or B; and

[0021] In the same molecule, Z 1 and Z 2 same.

[0022] In some embodiments of this application, the silicate composite salt is selected from one or more of magnesium aluminum silicate, magnesium boron silicate, beryllium aluminum silicate, beryllium boron silicate, lithium aluminum silicate, lithium boron silicate, sodium aluminum silicate, and sodium boron silicate.

[0023] The various silicate composite salts used in this application possess excellent three-dimensional spatial structures and exhibit superior physicochemical properties in one or more aspects, such as spreadability, viscosity increase, film-forming assistance, thickening, rheology, thixotropy, suspension, colloidal solubility, and emulsion stabilizing effects. Adding these special silicate composite salts to the active material layer of the electrode sheet helps improve the wetting performance of the electrolyte and stabilize the electrode-electrolyte interface. Furthermore, the silicate composite salts used in this application also possess a certain degree of alkalinity, which can remove acidic substances from the electrolyte and inhibit the damage to the interfacial structure caused by hydrofluoric acid (HF).

[0024] Taking magnesium aluminum silicate as an example, it possesses a unique three-dimensional chain structure and special needle-like and rod-shaped crystal structures, thus exhibiting special colloidal and adsorption properties. It also possesses excellent thickening, suspending, and colloidal solubility properties, and can form a "card-like" associated network structure in aqueous media. Magnesium aluminum silicate has a certain degree of spreadability, which can increase viscosity and assist in film formation, thereby improving the wetting performance of the electrolyte at the electrode interface. Magnesium aluminum silicate also has a certain degree of viscosity, allowing it to coat the interface of the positive or negative electrode active materials like glue. It can also improve the stability of the decomposition products of electrolyte additives (such as carbonates or other additives) at the electrolyte interface, thus enhancing the wetting performance of the electrolyte and stabilizing the electrode-electrolyte interface. Magnesium aluminum silicate also has a certain degree of alkalinity, which can remove acidic substances in the electrolyte and inhibit the damage to the interface structure caused by HF and other substances.

[0025] In some embodiments of this application, the positive electrode active material layer comprises a positive electrode active substance and the silicate composite salt;

[0026] Optionally, the positive electrode active material layer satisfies one or more of the following characteristics:

[0027] In the positive electrode active material layer, the mass percentage of the silicate composite salt relative to the positive electrode active material is selected from 0.001% to 2%; optionally, the mass percentage of the silicate composite salt relative to the positive electrode active material is selected from 0.01% to 2%; optionally, the mass percentage of the silicate composite salt relative to the positive electrode active material is selected from 0.1% to 2%.

[0028] In the positive electrode active material layer, the ratio of the mass of the silicate composite salt to the specific surface area of ​​the positive electrode active material is selected from 0.01 mg / m². 2 ~100mg / m 2 Optionally, the ratio of the mass of the silicate composite salt to the specific surface area of ​​the positive electrode active material is selected from 0.1 mg / m². 2 ~30mg / m 2 ;

[0029] The areal density of the silicate composite salt in the positive electrode sheet is selected from 0.001 g / cm³. 2 ~0.5g / cm 2 Optionally, the areal density of the silicate composite salt in the positive electrode sheet is selected from 0.01 g / cm³. 2 ~0.1g / cm 2 ;and,

[0030] The positive electrode includes a CEI film, which is located on the surface of the positive active material layer away from the positive current collector, and contains the silicate composite salt.

[0031] Adding the silica composite salt of this application to the positive electrode active material layer of the positive electrode sheet is beneficial to reducing impedance deterioration during cycling, improving the stability of the positive electrode electrolyte interface (CEI), and improving the cycle capacity retention rate, which can play a certain role in improving the cycle stability and capacity performance of the cell.

[0032] In the positive electrode active material layer, when the amount of silicate complex salt added is relatively small, the dispersion uniformity of silicate complex salt on the surface of the positive electrode material is reduced, which affects the full play of the CEI interface protection function. When the amount of silicate complex salt added is relatively high, excessive silicate complex salt may accumulate at the interface of the positive electrode material. In addition, the poor conductivity of silicate complex salt may generate a large interfacial internal resistance, which deteriorates the cell performance.

[0033] In some embodiments of this application, the secondary battery is a lithium-ion secondary battery or a sodium-ion secondary battery.

[0034] In some embodiments of this application, the positive electrode active material includes lithium-ion materials;

[0035] Optionally, the lithium-ion material includes at least one of lithium phosphate and lithium transition metal oxide.

[0036] The basic principles and electrochemical reaction properties of lithium-ion and sodium-ion secondary batteries are similar, both utilizing the insertion and extraction of active ions at the electrodes and their transport in the electrolyte to achieve the charging and discharging process. Generally, the active ion in a lithium-ion secondary battery is lithium ions, and the active ion in a sodium-ion secondary battery is sodium ions, but this is not the only possibility. The silicate composite salt of this application can be used to optimize the performance of both lithium-ion and sodium-ion secondary batteries. In both battery systems, it can improve the wetting performance of the electrolyte, stabilize the electrode-electrolyte interface, improve the cycle performance and storage performance of the secondary battery, and extend its service life. Furthermore, the silicate composite salt of this application can stabilize the electrode-electrolyte interface and improve cell performance in various secondary batteries containing different types of positive electrode active materials.

[0037] The positive electrode active material can be selected from materials that can undergo volume changes during the extraction and insertion of active ions (such as lithium ions, sodium ions, or potassium ions) and that have a catalytic effect on the electrolyte at the active material interface.

[0038] In some embodiments of this application, the negative electrode active material layer comprises a negative electrode active substance and the silicate composite salt;

[0039] Optionally, the negative electrode active material layer satisfies one or more of the following characteristics:

[0040] In the negative electrode active material layer, the mass percentage of the silicate composite salt relative to the negative electrode active material is selected from 0.005% to 5%; optionally, the mass percentage of the silicate composite salt relative to the negative electrode active material is selected from 0.02% to 3%; optionally, the mass percentage of the silicate composite salt relative to the negative electrode active material is selected from 0.1% to 3%.

[0041] In the negative electrode active material layer, the ratio of the mass of the silicate composite salt to the specific surface area of ​​the negative electrode active material is selected from 0.01 mg / m². 2 ~100mg / m 2 Optionally, the ratio of the mass of the silicate composite salt to the specific surface area of ​​the negative electrode active material is selected from 0.1 mg / m². 2 ~30mg / m 2 ;

[0042] The areal density of the silicate composite salt in the negative electrode sheet is selected from 0.0005 g / cm³. 2 ~0.5g / cm 2 Optionally, the areal density of the silicate composite salt in the negative electrode sheet is selected from 0.001 g / cm³. 2 ~0.3g / cm 2 ;and,

[0043] The negative electrode includes an SEI film, which is located on the surface of the negative electrode active material layer away from the negative electrode current collector, and the SEI film contains the silicate composite salt.

[0044] Adding the silica composite salt of this application to the negative electrode active material layer is also beneficial to reduce impedance deterioration during cycling, improve the stability of the negative electrode electrolyte interface (SEI), and improve the cycle capacity retention rate, which can play a certain role in improving the cycle stability and capacity of the cell.

[0045] In the negative electrode active material layer, when the amount of silicate composite salt added is relatively small, the dispersion uniformity of silicate composite salt on the surface of the negative electrode material is reduced, which affects the full play of the interface protection function. When the amount of silicate composite salt added is relatively high, excessive silicate composite salt is easy to accumulate at the material interface. In addition, the poor conductivity of silicate composite salt can easily generate a large interfacial internal resistance, which deteriorates the cell performance.

[0046] In some embodiments of this application, the secondary battery is a lithium-ion battery, and the negative electrode active material includes graphite;

[0047] Optionally, the mass percentage of graphite in the negative electrode active material is greater than 50%;

[0048] Optionally, the mass percentage of graphite in the negative electrode active material is selected from 70% to 100%;

[0049] Optionally, the mass percentage of graphite in the negative electrode active material is selected from 80% to 100%;

[0050] Optionally, the mass percentage of graphite in the negative electrode active material is selected from 90% to 100%;

[0051] Optionally, graphite comprises 100% by mass in the negative electrode active material.

[0052] In some embodiments of this application, the secondary battery is a lithium-ion battery, and the negative electrode active material includes a silicon-carbon composite.

[0053] Optionally, the silicon-carbon composite accounts for more than 50% of the mass of the negative electrode active material;

[0054] Optionally, the mass percentage of the silicon-carbon composite in the negative electrode active material is selected from 70% to 100%;

[0055] Optionally, the mass percentage of the silicon-carbon composite in the negative electrode active material is selected from 80% to 100%;

[0056] Optionally, the mass percentage of the silicon-carbon composite in the negative electrode active material is selected from 90% to 100%;

[0057] Optionally, the silicon-carbon composite accounts for 100% of the mass of the negative electrode active material.

[0058] The silicate composite salts described in this application can be used to improve the electrode-electrolyte interface stability, cycle capacity, and other performance characteristics of various secondary batteries. Applicable secondary batteries include, but are not limited to, existing lithium-ion secondary batteries. Some non-limiting examples include, as mentioned above, lithium-ion batteries with graphite as the negative electrode active material and lithium-ion batteries with silicon-carbon composites as the negative electrode active material.

[0059] In the active material layer of the electrode sheet, when the amount of silicate composite salt added is relatively small, the dispersion uniformity of silicate composite salt on the electrode material surface is reduced, affecting the full play of the interface protection function; while when the amount of silicate composite salt added is relatively high, excessive silicate composite salt is prone to accumulate at the electrode material interface. In addition, the poor conductivity of silicate composite salt can easily generate a large interfacial internal resistance, which deteriorates the cell performance.

[0060] In a second aspect, an electrical device is provided, which includes the secondary battery described in the first aspect of this application.

[0061] Using the secondary battery described in the first aspect of this application in an electrical device can improve cycle performance and extend service life by utilizing the interfacial stabilizing effect of the aforementioned special silicate composite salt.

[0062] Thirdly, the application of silicate composite salts in the preparation of secondary batteries is provided, wherein the silicate composite salts are as defined in the first aspect of this application;

[0063] The applications include at least one of preparing a positive electrode containing the silicate composite salt and preparing a negative electrode containing the silicate composite salt;

[0064] Optionally, the application includes preparing a positive electrode containing the silicate composite salt;

[0065] Optionally, the application includes preparing a negative electrode sheet containing the silicate composite salt;

[0066] Optionally, the application includes preparing a positive electrode containing the silicate composite salt and a negative electrode containing the silicate composite salt.

[0067] The use of the aforementioned special silicate composite salt to prepare secondary batteries (including but not limited to the secondary batteries described in the first aspect of this application) can improve the wetting performance of the electrolyte, increase the stability of the electrode-electrolyte interface, improve the battery cycle capacity, and extend the battery life.

[0068] In some embodiments of this application, the preparation of the positive electrode sheet containing the silicate composite salt includes: coating a positive electrode slurry onto at least one surface of a positive electrode current collector, drying, and compacting; wherein the positive electrode slurry includes a positive electrode active material, the silicate composite salt, a conductive agent, a binder, and a solvent;

[0069] Optionally, in the positive electrode slurry, the mass percentage of the silicate composite salt relative to the positive electrode active material is selected from 0.001% to 2%; alternatively, the mass percentage of the silicate composite salt relative to the positive electrode active material is selected from 0.01% to 2%; alternatively, the mass percentage of the silicate composite salt relative to the positive electrode active material is selected from 0.1% to 2%.

[0070] Optionally, in the positive electrode slurry, the ratio of the mass of the silicate composite salt to the specific surface area of ​​the positive electrode active material is selected from 0.01 mg / m². 2 ~100mg / m 2 Optionally, the ratio of the mass of the silicate composite salt to the specific surface area of ​​the positive electrode active material is selected from 0.1 mg / m². 2 ~30mg / m 2 ;

[0071] Optionally, the areal density of the silicate composite salt in the positive electrode sheet is selected from 0.001 g / cm³. 2 ~0.5g / cm 2 Optionally, the areal density of the silicate composite salt in the positive electrode sheet is selected from 0.01 g / cm³. 2 ~0.1g / cm 2 .

[0072] In some embodiments of this application, the preparation of the negative electrode sheet containing the silicate composite salt includes: coating a negative electrode slurry onto at least one surface of a negative electrode current collector, drying, and compacting; wherein the negative electrode slurry includes a negative electrode active material, the silicate composite salt, a conductive agent, a binder, and a solvent;

[0073] Optionally, in the negative electrode slurry, the mass percentage of the silicate composite salt relative to the negative electrode active material is selected from 0.005% to 5%; optionally, the mass percentage of the silicate composite salt relative to the negative electrode active material is selected from 0.02% to 3%; optionally, the mass percentage of the silicate composite salt relative to the negative electrode active material is selected from 0.1% to 3%.

[0074] Optionally, in the negative electrode slurry, the mass ratio of the silicate composite salt to the specific surface area of ​​the negative electrode active material is selected from 0.01 to 100 mg / m². 2 Optionally, the ratio of the mass of the silicate composite salt to the specific surface area of ​​the negative electrode active material is selected from 0.1 to 30 mg / m². 2 ;

[0075] Optionally, the areal density of the silicate composite salt in the positive electrode sheet is selected from 0.001 to 0.5 g / cm³. 2 Optionally, the areal density of the silicate composite salt in the positive electrode sheet is selected from 0.01 to 0.1 g / cm³. 2 .

[0076] The various silicate composite salts used in this application possess excellent three-dimensional spatial structures and exhibit superior physicochemical properties in one or more aspects, such as spreadability, viscosity enhancement, film-forming assistance, thickening, rheology, thixotropy, suspension, colloidal solubility, and emulsion stabilizing effects. Adding these special silicate composite salts to the positive or negative electrode slurry can increase the system stability of the positive or negative electrode slurry, improve the uniformity of the film layer when coated on the positive or negative electrode current collector, and enhance the quality stability of the electrode and the secondary battery.

[0077] In some embodiments of this application, the secondary battery is as defined in the first aspect of this application. The secondary battery prepared by the third aspect of this application can be any suitable secondary battery of the first aspect of this application, and has the characteristic of long life.

[0078] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0079] To better describe and illustrate embodiments or examples of the applications disclosed herein, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the embodiments or examples currently described, or the best mode of conduct of these applications as currently understood. Furthermore, throughout the drawings, the same reference numerals denote the same parts. In the drawings:

[0080] Figure 1 This is a schematic diagram of a secondary battery according to an embodiment of this application;

[0081] Figure 2 yes Figure 1 An exploded view of a secondary battery according to an embodiment of this application is shown;

[0082] Figure 3 This is a schematic diagram of an electrical device in which a secondary battery is used as a power source, according to an embodiment of this application.

[0083] Explanation of reference numerals in the attached figures:

[0084] 5. Secondary battery; 51. Housing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device. Detailed Implementation

[0085] The following detailed description, with appropriate reference to the accompanying drawings, discloses some embodiments of the secondary battery, electrical device, and application of silicate complex salts of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0086] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this document; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, stating that a parameter is an integer ≥2 is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, stating that a parameter is an integer selected from "2-10" is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0087] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0088] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0089] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0090] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0091] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". Further, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0092] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0093] The terms “combinations of,” “any combination of,” and “any combination of” used in this article include all suitable combinations of any two or more of the listed items.

[0094] In this document, the term "suitable" as used in "suitable combination", "suitable method", "any suitable method", etc., refers to the technical solution that enables the implementation of this application.

[0095] In this document, terms such as "preferred," "better," "more suitable," and "ideal" are merely descriptions of more effective implementation methods or embodiments, and should be understood not to limit the scope of protection of this application. If multiple "preferred" terms appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "preferred" term shall be independent.

[0096] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0097] In this application, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0098] In this application, the term "room temperature" generally refers to 4℃ to 35℃, and may refer to 20℃ ± 5℃. In some embodiments of this application, room temperature refers to 20℃ to 30℃.

[0099] In this application, if the unit of a data range is only followed by the right endpoint, it indicates that the units of the left and right endpoints are the same. For example, 3~5h or 3-5h both indicate that the units of the left endpoint "3" and the right endpoint "5" are both in hours (h).

[0100] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Furthermore, the weights mentioned in the embodiments of this application can be well-known units of mass in the chemical industry, such as μg, mg, g, and kg.

[0101] There is an urgent need to further improve the cycle life of rechargeable battery products. Through experimental research, the inventors of this application discovered that the volume effect of active materials during cycling and the increased interfacial activity under high SOC conditions easily damage the interfacial structure. Therefore, improving interfacial stability can be a strategy to improve the cycle life of rechargeable batteries. To adapt to the volume effect during cycling and suppress excessive electrolyte consumption, the approach can be taken from the perspective of stabilizing the interfacial components.

[0102] Currently, modifications to the electrode-electrolyte interface mainly employ either in-situ or ex-situ methods, coating the material interface with an interfacial component. However, most of these methods fail to effectively improve interfacial stability, particularly under high state of charge (SOC). The inventors of this application speculate that this may be because the interfacial structure generated by ex-situ coating cannot achieve uniform coating or remain stable during charge and discharge. On the other hand, the method of generating the interfacial component in situ using electrolyte additives often results in inorganic components in the inner layer of the interface consisting primarily of crystalline oxides or salts. This inorganic inner layer is prone to breakage during the volume changes of lithium insertion / extraction, leading to direct contact between the active component and the electrolyte, excessive consumption of both electrolyte and active lithium, and deterioration of cell performance.

[0103] To address the aforementioned common technical problems, in a first aspect, this application provides a secondary battery, wherein at least one of the positive electrode active material layer of the positive electrode and the negative electrode active material layer of the negative electrode comprises a silicate composite salt; the chemical formula of the silicate composite salt is selected from YSi2Z. 1 Z 2 O8 and X 1 X 2 Si2Z 1 Z 2 At least one of O8, Y is selected from Group 2, and X is selected from... 1 and X 2 Each element is independently selected from the first primary race element, Z. 1 and Z 2 Each element is selected from the third primary race.

[0104] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing active ions to pass through.

[0105] Unless otherwise specified in this application, the electrolyte is in liquid form and is referred to as an electrolyte solution.

[0106] In some embodiments of this application, a secondary battery is provided, which includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the separator is located between the positive electrode and the negative electrode; the positive electrode includes a positive active material layer, and the negative electrode includes a negative active material layer;

[0107] At least one of the positive electrode active material layer and the negative electrode active material layer contains a silicate composite salt;

[0108] The chemical formula of the silicate complex salt is selected from YSi2Z. 1 Z 2 O8 and X 1 X 2 Si2Z 1 Z 2 At least one of O8;

[0109] in,

[0110] Y is selected from the second main group element;

[0111] X 1 and X 2 Each element is independently selected from the first primary race.

[0112] Z1 and Z 2 Each element is selected from the third primary race.

[0113] In this application, unless otherwise specified, a silicate can be a simple silicate containing a single metal element or a complex silicate containing two or more metal elements.

[0114] In this application, unless otherwise specified, "silicate mono-metal salt of the present application" refers to a salt containing YSi2Z 1 Z 2 O8 or X 1 X 2 Si2Z 1 Z 2 The chemical formula shown in O8 represents a special silicate complex salt, where Y is selected from Group II elements, and X... 1 and X 2 Each element is independently selected from the first primary race element, Z. 1 and Z 2 Each element is selected from Group III elements. In this application, "the chemical formula of the silicate complex salt is selected from YSi22". 1 Z 2 O8 and X 1 X v Si2Z 1 Z 2 "At least one of O8" indicates that the silicate complex salt is selected from the chemical formula YSi2Z. 1 Z 2 The substance shown in O8 and its chemical formula X 1 X 2 Si2Z 1 Z 2 At least one of the substances shown in O8. Any substance in the context of this application that conforms to this chemical formula is within the scope of "silicic acid complex salts of this application".

[0115] In this application, unless otherwise specified, the electrode sheet can be a positive electrode sheet or a negative electrode sheet. The "active material" in the electrode sheet refers to a material capable of reversibly inserting and extracting active ions. Unless otherwise specified, "negative electrode active material" refers to a material used in the negative electrode sheet capable of reversibly inserting and extracting active ions; "positive electrode active material" refers to a material used in the positive electrode sheet capable of reversibly extracting and inserting active ions. During charging of the secondary battery, active ions are extracted from the positive electrode and inserted into the negative electrode via the electrolyte; conversely, during discharging, active ions are extracted from the negative electrode and inserted into the positive electrode. The active ions are not particularly limited and can be lithium ions (corresponding to lithium-ion secondary batteries), sodium ions (corresponding to sodium-ion secondary batteries), potassium ions, etc. In this application, "active material" and "active substance" have the same meaning and can be used interchangeably; "positive electrode active substance" and "positive electrode active material" have the same meaning and can be used interchangeably; "negative electrode active substance" and "negative electrode active material" have the same meaning and can be used interchangeably.

[0116] In this application, unless otherwise specified, "active material layer" includes the positive active material layer of the positive electrode sheet and the negative active material layer of the negative electrode sheet. Depending on the specific circumstances, it may refer to either the positive active material layer or the negative active material layer.

[0117] In this application, unless otherwise specified, "electrode-electrolyte interface" includes the positive electrode-electrolyte interface (CEI) between the positive electrode and the electrolyte and the negative electrode-electrolyte interface (SEI) between the negative electrode and the electrolyte. Depending on the specific circumstances, it may refer to the CEI interface or the SEI interface.

[0118] In this application, unless otherwise specified, "electrolyte interface film" refers to a passivation layer formed at the solid-liquid interface between the electrode material and the electrolyte during a charge-discharge process, resulting from an oxidation or reduction reaction of the electrolyte at the electrode material interface. This passivation layer is an interface layer with the characteristics of a solid electrolyte; it is an electronic insulator but an excellent conductor of active ions (such as lithium ions or sodium ions), allowing active ions to freely insert and extract through this passivation layer. Specifically, the electrolyte interface film formed between the positive electrode and the electrolyte is called the positive electrode electrolyte interface film, which can be denoted as the CEI film; the electrolyte interface film formed between the negative electrode and the electrolyte is called the negative electrode electrolyte interface film, which can be denoted as the SEI film. Unless otherwise specified, the electrolyte interface film involved in this application includes both CEI and SEI films, and may also refer to either CEI or SEI films.

[0119] By employing a special silicate composite salt as an interface stabilizer in the electrode plates of a secondary battery, the wetting performance of the electrolyte can be improved, the electrode-electrolyte interface can be stabilized, cycle performance can be improved, and battery life can be extended. The silicate composite salt of this application contains specific short-period Group I to III main group elements. These short-period main group elements can participate in the formation of the electrolyte interface film. The silicate composite salt of this application can act as an interface stabilizer, improving the wetting performance of the electrolyte, stabilizing the electrode-electrolyte interface, improving the cycle performance and storage performance of the secondary battery, and extending the battery's lifespan. This silicate composite salt can stabilize both the positive electrode electrolyte interface (CEI) and the negative electrode electrolyte interface (SEI). In comparison, the interaction between Group IV to VII main group elements and oxygen is weaker, or they contain more lone pairs of electrons and are more prone to oxidation reactions; in addition, long-period transition metal elements have more empty orbitals, which can catalyze the redox reactions of the electrolyte.

[0120] The inventors of this application also discovered that the aforementioned silicate composite salt is difficult to dissolve in non-aqueous electrolytes (such as commercial carbonates). Furthermore, increasing the amount of silicate composite salt to create an electrolyte gel state inhibits the conduction of active ions (lithium ions or sodium ions), affecting battery capacity. Therefore, improving the electrode-electrolyte interface stability by adding this special silicate composite salt to the electrolyte is quite difficult. The inventors of this application also discovered that even with the addition of a large amount of this silicate composite salt to the electrolyte, due to the small amount of solution, it has almost no effect on improving the cell internal resistance, cycle capacity retention, and other performance characteristics of the secondary battery after assembly into a full battery. The inventors of this application unexpectedly discovered that when the aforementioned silicate composite salt is introduced into the active material of the positive or negative electrode, it can be uniformly dispersed on the particle surface, stabilizing the electrode-electrolyte interface.

[0121] In some embodiments of this application, the structural formula of the silicate complex salt is selected from at least one of Formula I and Formula II:

[0122]

[0123] The various silicate composite salts used in this application possess excellent three-dimensional spatial structures and exhibit superior physicochemical properties in one or more aspects, such as spreadability, viscosity increase, film-forming assistance, thickening, rheology, thixotropy, suspension, colloidal solubility, and emulsion stabilizing effects. Adding these special silicate composite salts to the active material layer of the electrode sheet helps improve the wetting performance of the electrolyte and stabilize the electrode-electrolyte interface. Furthermore, the silicate composite salts used in this application also possess a certain degree of alkalinity, which can remove acidic substances from the electrolyte and inhibit the damage to the interfacial structure caused by hydrofluoric acid (HF).

[0124] In some embodiments of this application, the secondary battery satisfies any one or more of the following characteristics:

[0125] Y is either Mg or Be;

[0126] X 1 and X 2 Each can be either Li or Na;

[0127] In the same molecule, X 1 and X 2 same;

[0128] Z 1 and Z 2 Each is independently Al or B; and

[0129] In the same molecule, Z 1 and Z 2 same.

[0130] In some implementations, Y is Mg or Be.

[0131] X 1 and X 2 They can be the same or different. In some implementations, X 1 and X 2 Each is independently Li or Na; further, in some embodiments therein, X in the same molecule 1 and X 2 same.

[0132] Z 1 and Z 2 They can be the same or different. In some implementations, Z 1 and Z 2 Each is independently Al or B; further, in some embodiments therein, Z in the same molecule 1 and Z 2 same.

[0133] In some embodiments of this application, the silicate complex salt may include one or more of magnesium aluminum silicate, magnesium boron silicate, beryllium aluminum silicate, beryllium boron silicate, lithium aluminum silicate, lithium boron silicate, sodium aluminum silicate, and sodium boron silicate.

[0134] In some embodiments, the silicate complex salt comprises magnesium aluminum silicate. As a non-limiting example of a silicate complex salt, magnesium aluminum silicate possesses a unique three-dimensional chain structure and a special needle-like and rod-shaped crystal structure, thus exhibiting special colloidal and adsorption properties. It also possesses excellent thickening, suspending, and colloidal solubility properties, and can form a "card-like" associated network structure in aqueous media. Magnesium aluminum silicate has a certain degree of spreadability, which can increase viscosity and assist in film formation, thereby improving the wetting performance of the electrolyte at the electrode interface. Magnesium aluminum silicate also has a certain degree of viscosity, allowing it to coat the interface of the positive or negative electrode active material like glue. It can also improve the stability of the decomposition products of electrolyte additives (such as carbonates or other additives) at the electrolyte interface, thus improving the wetting performance of the electrolyte and stabilizing the electrode-electrolyte interface. Magnesium aluminum silicate also has a certain degree of alkalinity, which can remove acidic substances in the electrolyte and inhibit the damage to the interface structure caused by HF, etc.

[0135] In some embodiments of this application, the positive electrode active material layer contains the silicate composite salt, while the negative electrode active material layer does not contain the silicate composite salt.

[0136] In some embodiments of this application, the negative electrode active material layer contains the silicate composite salt, while the positive electrode active material layer does not contain the silicate composite salt.

[0137] In some embodiments of this application, both the positive electrode active material layer and the negative electrode active material layer contain the silicate composite salt.

[0138] The silicate composite salt of this application can be added to both the positive electrode active material layer and the negative electrode active material layer to stabilize the SEI film. Both methods help reduce impedance degradation during cycling, improve interface stability, and enhance cycle capacity retention, thus improving the cycle stability and capacity performance of the battery cell. In some embodiments, the silicate composite salt of this application is introduced into both the positive and negative electrode sheets, resulting in excellent improvement in the cycle stability and capacity performance of the battery cell.

[0139] In this application, the electrode sheet includes a current collector and a film layer disposed on at least one surface of the current collector, the film layer including a corresponding active material layer containing a corresponding active substance.

[0140] In this application, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes a positive electrode active material layer, and further, the positive electrode active material layer includes a positive electrode active substance. The positive electrode film layer is composed of a positive electrode material.

[0141] In this application, the negative electrode sheet includes a positive current collector and a negative electrode film layer disposed on at least one surface of the negative current collector. The negative electrode film layer includes a negative electrode active material layer, and further, the negative electrode active material layer includes a negative electrode active substance. The negative electrode film layer is composed of a negative electrode material.

[0142] The positive and negative electrode materials may each independently include additives (which may include one or more of conductive agents and binders). There are no particular restrictions on the type and content of conductive agents and binders; they can be selected according to actual needs. Furthermore, there are no particular restrictions on the type and model of the separator and current collector; they can be selected according to actual needs.

[0143] In this application, the content of silicate complex salt in the electrode sheet can be determined using elemental analysis methods known in the art, such as inductively coupled plasma atomic emission spectrometry (ICP-AES). Conventional methods can be used to remove the additives from the electrode sheet, and then elemental analysis can be performed on the remaining solid particles.

[0144] Positive electrode sheet

[0145] In this application, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes a positive electrode active material layer, and further, the positive electrode active material layer includes a positive electrode active substance.

[0146] In some embodiments of this application, the positive electrode active material layer comprises a positive electrode active material and the silicate composite salt; in this case, the silicate composite salt of this application is introduced into the positive electrode sheet. Adding the silicate composite salt of this application to the positive electrode active material layer of the positive electrode sheet helps reduce impedance deterioration during cycling, improves the stability of the positive electrolyte interface (CEI), and improves the cycle capacity retention rate, thus playing a certain role in improving the cycle stability and capacity performance of the battery cell.

[0147] In some embodiments of this application, the content of silicate composite salt in the positive electrode active material layer or positive electrode sheet can be characterized by one or more parameters such as the mass percentage of silicate composite salt relative to the positive electrode active material, the ratio of the mass of silicate composite salt to the specific surface area of ​​the positive electrode active material, and the areal density of silicate composite salt in the positive electrode sheet.

[0148] In some embodiments, the mass percentage of the silicate composite salt relative to the positive electrode active material layer is selected from 0.001% to 2%; optionally, the mass percentage of the silicate composite salt relative to the positive electrode active material is selected from 0.01% to 2%; optionally, the mass percentage of the silicate composite salt relative to the positive electrode active material is selected from 0.1% to 2%. The mass percentage of the silicate composite salt relative to the positive electrode active material layer can also be selected from any one or any two of the following percentages: 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, etc.

[0149] In some embodiments, the mass ratio of the silicate composite salt to the specific surface area of ​​the positive electrode active material layer is selected from 0.01 mg / m². 2 ~100mg / m 2 Optionally, the ratio of the mass of the silicate composite salt to the specific surface area of ​​the positive electrode active material is selected from 0.1 mg / m². 2 ~30mg / m 2 In the positive electrode active material layer, the ratio of the mass of the silicate composite salt to the specific surface area of ​​the positive electrode active material can also be selected from any one of the following values ​​or a range of any two of the following values: 0.01 mg / m³ 2 0.05mg / m 2 0.1 mg / m 2 0.5mg / m 2 1mg / m 2 2mg / m 2 3mg / m 2 4mg / m 2 5mg / m 2 6mg / m 2 8mg / m 2 10mg / m 2 12mg / m 2 15mg / m 2 16mg / m 2 18mg / m 2 20mg / m 2 25mg / m 2 30mg / m 2 35mg / m 2 40mg / m 2 45mg / m 250mg / m 2 60mg / m 2 70mg / m 2 80mg / m 2 90mg / rn 2 100rng / m 2 wait.

[0150] In some embodiments, the areal density of the silicate composite salt in the positive electrode sheet is selected from 0.001 g / cm³. 2 ~0.5g / cm 2 Optionally, the areal density of the silicate composite salt in the positive electrode sheet is selected from 0.01 g / cm³. 2 ~0.1g / cm 2 The areal density of the silicate composite salt in the positive electrode sheet can also be selected from any one of the following values ​​or a range of two values: 0.001 g / cm³ 2 0.005g / cm 2 0.01g / cm 2 0.02g / cm 2 0.03g / cm 2 0.04g / cm 2 0.05g / cm 2 0.06g / cm 2 0.07g / cm 2 0.08g / cm 2 0.09g / cm 2 0.1g / cm 2 0.15g / cm 2 0.2g / cm 2 0.25g / cm 2 0.3g / cm 2 0.35g / cm 2 0.4g / cm 2 0.45g / cm 2 0.5g / cm 2 wait.

[0151] In some embodiments, the positive electrode includes a CEI film located on the surface of the positive active material layer away from the positive current collector, and the CEI film contains the silicate composite salt.

[0152] In the positive electrode active material layer, when the amount of silicate complex salt added is relatively small, the dispersion uniformity of silicate complex salt on the surface of the positive electrode material is reduced, which affects the full play of the CEI interface protection function. When the amount of silicate complex salt added is relatively high, excessive silicate complex salt may accumulate at the interface of the positive electrode material. In addition, the poor conductivity of silicate complex salt may generate a large interfacial internal resistance, which deteriorates the cell performance.

[0153] In some embodiments of this application, the secondary battery is a lithium-ion secondary battery or a sodium-ion secondary battery.

[0154] The basic principles and electrochemical reaction properties of lithium-ion and sodium-ion secondary batteries are similar. Both utilize the insertion and extraction of active ions at the electrodes and their transport in the electrolyte to achieve the charging and discharging process. Generally, the active ion in a lithium-ion secondary battery is lithium ions, and the active ion in a sodium-ion secondary battery is sodium ions, but this is not the only possibility. The silicate composite salt of this application can be used to optimize the performance of both lithium-ion and sodium-ion secondary batteries. In both battery systems, it can improve the wetting performance of the electrolyte, stabilize the electrode-electrolyte interface, improve the cycle performance and storage performance of the secondary battery, and extend its service life. Furthermore, the silicate composite salt of this application can stabilize the electrode-electrolyte interface and improve cell performance in various secondary batteries containing different types of positive electrode active materials.

[0155] The positive electrode active material can be selected from materials that can undergo volume changes during the extraction and insertion of active ions (such as lithium ions, sodium ions, or potassium ions) and that have a catalytic effect on the electrolyte at the active material interface.

[0156] In some embodiments of this application, the positive electrode active material includes lithium-ion materials; further, the secondary battery is a lithium-ion secondary battery.

[0157] In some embodiments, the lithium-ion material includes at least one of lithium phosphate and lithium transition metal oxide.

[0158] In some embodiments, the positive electrode active material may be a known battery positive electrode active material. As a non-limiting example, the positive electrode active material may include one or more of the following materials or substances: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials or substances, and other conventional materials or substances that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Non-limiting examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 One or more of the following: (O2) and its modified compounds. Non-limiting examples of lithium phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0159] In some embodiments, the positive electrode active material may include, but is not limited to, lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, sodium oxide and potassium oxide, as well as materials composed of any of the aforementioned substances and doping elements; further, the doping elements in any positive electrode active material independently include one or more of transition metal elements and non-transition metal elements.

[0160] In some embodiments of this application, the positive electrode active material includes sodium ion materials; further, the secondary battery is a sodium ion secondary battery.

[0161] In some embodiments, the sodium-ion material includes one or more of sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. This allows for flexible selection of suitable positive electrode active materials, thus providing sodium-ion batteries with greater selectivity and wider applicability.

[0162] In some embodiments, the positive electrode active material may include, but is not limited to, one or more of sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to the materials or substances listed above, and other known materials or substances that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0163] In some embodiments, the transition metal in the sodium transition metal oxide can be one or more selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. A non-limiting example of a sodium transition metal oxide is Na. x ZO2, where Z can be one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, 0 <x≤1。

[0164] In some embodiments, the sodium transition metal oxide can be Na. 1-x Cu h Fe k Mn1M 1 m O 2-y M 1 It can be one or more of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn, and Ba, 0 <x≤0.33,0<h≤0.24,0≤k≤0.32,0<1≤0.68,0≤m<0.1,h+k+1+m=1,0≤y<0.2。

[0165] In some embodiments, the sodium transition metal oxide can be Na. 0.67 Mn0.7 Ni q M 2 0.3-z O2, where M 2 It can be one or more of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn, and Ba, 0 <q≤0.1。

[0166] In some embodiments, the sodium transition metal oxide can be Na. a Li b Ni c Mn d Fe e O2, of which 0.67 <a≤1,0<b<0.2,0<c<0.3,0.67<d+e<0.8,b+c+d+e=1。

[0167] In some embodiments, the polyanionic compound can be a sodium ion, a transition metal ion, or a tetrahedral (YO4) compound. n- A class of compounds with anionic units. The transition metal here can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be one or more of P, S, and Si; n represents (YO4). n- The price state.

[0168] In some embodiments, the polyanionic compound may also have sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds containing anionic units and halide anions. The transition metal here can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be one or more of P, S, and Si; and n represents (YO4). n- The valence state; halogens can be one or more of F, Cl and Br.

[0169] In some embodiments, the polyanionic compound may also be a tetrahedral compound (YO4) containing sodium ions. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be one or more of P, S, and Si, and n represents (YO4). n- The valence state; Z represents a transition metal, which can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) m+ The valence state; halogens can be one or more of F, Cl and Br.

[0170] In some embodiments, the polyanionic compound may be NaFePO4, Na3V2(PO4)3, NaM'PO4F, and Na3(VO4)2(PO4)3. y )2(PO4)2F 3- 2 y One or more of (0≤y≤1); wherein, M' in NaM'PO4F can be one or more of V, Fe, Mn and Ni.

[0171] In some embodiments, Prussian blue compounds can be a class of compounds containing sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. A non-limiting example of a Prussian blue compound is Na. a Me b Me' c (CN)6, wherein Me and Me' can each independently be one or more of Ni, Cu, Fe, Mn, Co, and Zn, 0 <a≤2,0<b<1,0<c<1。

[0172] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0173] In some embodiments, the positive current collector can be, but is not limited to, a conductive carbon sheet, a metal foil, a carbon-coated metal foil, a porous metal plate, or a composite current collector. The conductive carbon material of the conductive carbon sheet can be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers. The metal material of the metal foil, carbon-coated metal foil, and porous metal plate can each be independently selected from one or more of copper, aluminum, nickel, and stainless steel. The composite current collector can be a composite current collector formed by combining a metal foil with a polymer base film.

[0174] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0175] In some embodiments, the positive electrode film layer may optionally include a binder. As a non-limiting example, this binder is used to firmly bond the positive electrode active material and, optionally, a conductive agent to the positive electrode current collector. This application does not particularly limit the type of binder, and it can be selected according to actual needs. As a non-limiting example, in some secondary batteries (such as lithium-ion batteries), the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. As a non-limiting example, in some secondary batteries (such as sodium-ion batteries), the binder may be one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC) and its salts (such as sodium salts), sodium alginate (SA), polymethacrylic acid (PMA), and carboxymethyl chitosan (CMCS).

[0176] In some embodiments, the positive electrode film may optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0177] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, silicate complex salt (which may or may not be added), conductive agent, binder and any other components in a solvent (e.g., N-methylpyrrolidone), to form a positive electrode slurry; coating the positive electrode slurry onto at least one surface of the positive electrode current collector (which may be on a single surface or two surfaces), and then drying, compacting (which may be done by cold pressing) to obtain the positive electrode sheet.

[0178] Negative electrode sheet

[0179] In this application, the negative electrode sheet includes a positive current collector and a negative electrode film layer disposed on at least one surface of the negative current collector. The negative electrode film layer includes a negative electrode active material layer, and further, the negative electrode active material layer includes a negative electrode active substance.

[0180] Currently, commonly used anode active materials often exhibit some stability issues in their SEI films. For example, graphite is one of the most widely used commercial anode active materials, but during charge and discharge, the insertion and extraction of active ions (such as lithium ions) causes a certain degree (e.g., about 10%) of volume expansion and contraction, which damages the layered structure of graphite. Simultaneously, due to factors such as co-intercalation of the electrolyte solvent, reduction of organic solvents, and gas generation under high current during cycling, graphite sheets are prone to peeling off. Furthermore, under high temperature and high SOC conditions, the interfacial instability of graphite anodes increases, easily leading to loss of active materials and damage to the SEI film, thus reducing cycle life. In addition, silicon-based anode materials exhibit particularly large volume expansion (e.g., exceeding 300%), easily causing interfacial film rupture and regeneration, resulting in significant irreversible capacity loss. Moreover, lithium-silicon alloys possess a certain degree of reactivity; the new Li-Si interface generated by material expansion and contraction easily leads to excessive consumption of electrolyte and active lithium, deteriorating cell performance. To address the above issues, conventional solutions include using film-forming additives to generate stable interfacial components or suppressing volume expansion and contraction from the perspective of the negative electrode material.

[0181] In some embodiments of this application, the negative electrode active material layer comprises a negative electrode active material and the silicate composite salt, in which case the silicate composite salt of this application is introduced into the negative electrode sheet. Adding the silicate composite salt of this application to the negative electrode active material layer also helps to reduce impedance deterioration during cycling, improve the stability of the negative electrode electrolyte interface (SEI), and improve the cycle capacity retention rate, thus playing a certain role in improving the cycle stability and capacity performance of the battery cell.

[0182] In some embodiments of this application, the content of silicate composite salt in the negative electrode active material layer or negative electrode sheet can be characterized by one or more parameters such as the mass percentage of silicate composite salt relative to the negative electrode active material, the ratio of the mass of silicate composite salt to the specific surface area of ​​the negative electrode active material, and the areal density of silicate composite salt in the negative electrode sheet.

[0183] In some embodiments, the mass percentage of the silicate composite salt relative to the negative electrode active material layer is selected from 0.005% to 5%; optionally, the mass percentage of the silicate composite salt relative to the negative electrode active material is selected from 0.02% to 3%; optionally, the mass percentage of the silicate composite salt relative to the negative electrode active material is selected from 0.1% to 3%. In the negative electrode active material layer, the mass percentage of the silicate composite salt relative to the negative electrode active material can also be selected from any one percentage or any two percentage ranges: 0.005%, 0.01%, 0.02%, 0.04%, 0.05%, 0.06%, 0.08%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0184] In some embodiments, the mass ratio of the silicate composite salt to the specific surface area of ​​the negative electrode active material layer is selected from 0.01 mg / m². 2 ~100mg / m 2 Optionally, the ratio of the mass of the silicate composite salt to the specific surface area of ​​the negative electrode active material is selected from 0.1 mg / m². 2 ~30mg / m 2 In the negative electrode active material layer, the ratio of the mass of the silicate composite salt to the specific surface area of ​​the negative electrode active material can also be selected from any one of the following values ​​or a range of any two of the following values: 0.01 mg / m³ 2 0.05mg / m 2 0.1 mg / m 2 0.5mg / m 2 1mg / m 2 2mg / m 2 3mg / m 2 4mg / m 2 5mg / m 2 6mg / m 2 8mg / m 2 10mg / m 2 12mg / m 2 15mg / m 2 16mg / m 2 18mg / m 2 20mg / m 2 25mg / m 2 30mg / m 2 35mg / m2 40mg / m 2 45mg / m 2 50mg / m 2 60mg / m 2 70mg / m 2 80mg / m 2 90mg / m 2 100mg / m 2 wait.

[0185] In some embodiments, the areal density of the silicate composite salt in the negative electrode sheet is selected from 0.0005 g / cm³. 2 ~0.5g / cm 2 Optionally, the areal density of the silicate composite salt in the negative electrode sheet is selected from 0.001 g / cm³. 2 ~0.3g / cm 2 The areal density of the silicate composite salt in the negative electrode sheet can also be selected from any one of the following values ​​or a range of two of the following values: 0.0005%, 0.001 g / cm³. 2 0.005g / cm 2 0.01g / cm 2 0.02g / cm 2 0.03g / cm 2 0.04g / cm 2 0.05g / cm 2 0.06g / cm 2 0.07g / cm 2 0.08g / cm 2 0.09g / cm 2 0.1g / cm 2 0.15g / cm 2 0.2g / cm 2 0.25g / cm 2 0.3g / cm 2 0.35g / cm 2 0.4g / cm 2 0.45g / cm 2 0.5g / cm 2 wait.

[0186] In some embodiments, the negative electrode includes an SEI film located on the surface of the negative electrode active material layer away from the negative electrode current collector, and the SEI film contains the silicate composite salt.

[0187] In the negative electrode active material layer, when the amount of silicate composite salt added is relatively small, the dispersion uniformity of silicate composite salt on the surface of the negative electrode material is reduced, which affects the full play of the interface protection function. When the amount of silicate composite salt added is relatively high, excessive silicate composite salt is easy to accumulate at the material interface. In addition, the poor conductivity of silicate composite salt can easily generate a large interfacial internal resistance, which deteriorates the cell performance.

[0188] The negative electrode active material can be selected from materials that exhibit volume changes during the extraction and insertion of active ions (such as lithium ions, sodium ions, or potassium ions) and materials whose active material interface has a catalytic effect on the electrolyte.

[0189] In some embodiments, the negative electrode active material may be a known battery negative electrode active material. As a non-limiting example, the negative electrode active material may include one or more of the following materials or substances: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials or substances, and other conventional materials or substances that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0190] In some embodiments of this application, the negative electrode active material layer comprises a negative electrode active substance, which comprises one or more of carbon-based materials, silicon-based materials, silicon-carbon composite materials, tin-based materials, and lithium titanate.

[0191] In some embodiments, the negative electrode active material may include, but is not limited to, graphite, soft carbon, hard carbon, mesophase carbon microspheres, carbon fibers, carbon nanotubes, elemental silicon, silicon oxides, silicon-carbon composites, lithium titanate, and materials composed of any of the aforementioned substances and doping elements; further, the negative electrode active material includes one or more transition metal elements and non-transition metal elements.

[0192] The silicate composite salt of this application can stabilize the electrode-electrolyte interface and improve cell performance in various secondary batteries containing different types of negative electrode active materials.

[0193] In some embodiments, the negative electrode active material comprises graphite, which may include one or more of synthetic graphite and natural graphite. In some embodiments, the D of the graphite particles... v 50 can be selected from 8 to 12 μm (e.g., 10 μm), and the specific surface area can be selected from 1.1 to 1.5 m². 2 / g (e.g., 1.3m) 2The tap density can be selected from 0 to 1.2 g / cm³. 3 (e.g., 1.1 g / cm) 3 In one embodiment, the graphite particle size D v 50 has a thickness of 10 μm and a specific surface area of ​​1.3 m². 2 / g, tap density is 1.1g / cm³ 3 .

[0194] Unless otherwise stated in this application, D v 50 refers to the particle size corresponding to a cumulative volumetric distribution percentage of 50% in the material. This parameter indicates that the particle size of 50% of the material's volumetric particles is less than or equal to D. v 50, and particles accounting for 50% of the material volume have a particle size greater than D. v 50. Those skilled in the art will understand D v The meaning of 50 can be determined using instruments and methods known in the field.

[0195] In this application, unless otherwise specified, the specific surface area of ​​particulate matter refers to the ratio of the surface area of ​​particulate matter to its weight, and can be determined using instruments and methods known in the art, such as nitrogen adsorption specific surface area analysis.

[0196] In this application, unless otherwise specified, "tap density" refers to the mass per unit volume of powder after tapping under specified conditions, and the unit can be g / cm³. 3 .

[0197] In some embodiments of this application, the secondary battery is a lithium-ion battery, and the negative electrode active material includes graphite, further comprising one or more of artificial graphite and natural graphite. In some embodiments, the mass percentage of graphite in the negative electrode active material is greater than 50%. In other embodiments, the mass percentage of graphite in the negative electrode active material is selected from 70% to 100%. In other embodiments, the mass percentage of graphite in the negative electrode active material is selected from 80% to 100%. In other embodiments, the mass percentage of graphite in the negative electrode active material is selected from 90% to 100%. In other embodiments, the mass percentage of graphite in the negative electrode active material is 100%. The mass percentage of graphite in the negative electrode active material can also be selected from any one percentage or any range of two percentages: 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, etc. Graphite can be selected from any suitable specification within the context of this application.

[0198] In some embodiments of this application, the secondary battery is a lithium-ion battery, and the negative electrode active material includes a silicon-carbon composite. In some embodiments, the silicon-carbon composite accounts for more than 50% of the mass of the negative electrode active material. In other embodiments, the mass percentage of the silicon-carbon composite in the negative electrode active material is selected from 70% to 100%. In other embodiments, the mass percentage of the silicon-carbon composite in the negative electrode active material is selected from 80% to 100%. In other embodiments, the mass percentage of the silicon-carbon composite in the negative electrode active material is selected from 90% to 100%. In other embodiments, the mass percentage of the silicon-carbon composite in the negative electrode active material is 100%. The mass percentage of the silicon-carbon composite in the negative electrode active material can also be selected from any one percentage or any two percentage ranges: 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, etc.

[0199] In some embodiments of this application, the battery is a sodium-ion battery, and the negative electrode active material includes hard carbon. In some embodiments, the mass percentage of hard carbon in the negative electrode active material is greater than 50%. In other embodiments, the mass percentage of hard carbon in the negative electrode active material is selected from 70% to 100%. In other embodiments, the mass percentage of hard carbon in the negative electrode active material is selected from 80% to 100%. In other embodiments, the mass percentage of hard carbon in the negative electrode active material is selected from 90% to 100%. In other embodiments, the mass percentage of hard carbon in the negative electrode active material is 100%. The mass percentage of hard carbon in the negative electrode active material can also be selected from any one percentage or any two percentage ranges: 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, etc.

[0200] The silicate composite salts described in this application can be used to improve the electrode-electrolyte interface stability, cycle capacity, and other performance characteristics of various secondary batteries. Applicable secondary batteries include, but are not limited to, existing lithium-ion secondary batteries. Some non-limiting examples include, as mentioned above, lithium-ion batteries with graphite as the negative electrode active material and lithium-ion batteries with silicon-carbon composites as the negative electrode active material.

[0201] In the active material layer of the electrode sheet, when the amount of silicate composite salt added is relatively small, the dispersion uniformity of silicate composite salt on the electrode material surface is reduced, affecting the full play of the interface protection function; while when the amount of silicate composite salt added is relatively high, excessive silicate composite salt is prone to accumulate at the electrode material interface. In addition, the poor conductivity of silicate composite salt can easily generate a large interfacial internal resistance, which deteriorates the cell performance.

[0202] As a non-limiting example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0203] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0204] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0205] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0206] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0207] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, silicate composite salt (which may or may not be added), conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto at least one surface of the negative electrode current collector (which may be on a single surface or two surfaces), and then drying, compacting (which may be done by cold pressing) to obtain the negative electrode sheet.

[0208] electrolytes

[0209] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application uses a liquid electrolyte, i.e., an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent. In a lithium-ion secondary battery, the electrolyte salt may include a lithium electrolyte salt. In a sodium-ion secondary battery, the electrolyte salt may include a sodium electrolyte salt.

[0210] In some embodiments, the electrolyte lithium salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiCF3SO3), lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0211] In some embodiments, the electrolyte lithium salt may include one or more of LiPF6, LiBF4, LiBOB, LiAsF6, LiFSI, LiCF3SO3, LiClO4, etc.

[0212] In some embodiments, the electrolyte sodium salt may include one or more of sodium hexafluorophosphate (NaPF6), sodium perchlorate (NaClO4), sodium tetrafluoroborate (NaBF4), sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium difluorophosphate, etc.

[0213] In some embodiments, the electrolyte sodium salt includes one or more of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, and sodium trifluoromethanesulfonate.

[0214] In some embodiments, the solvent in the electrolyte is an organic solvent. There are no particular limitations on the type of organic solvent in the electrolyte; the organic solvent may include one or more of linear carbonates, cyclic carbonates, carboxylic acid esters, and ethers. The types of linear carbonates, cyclic carbonates, carboxylic acid esters, and ethers are not specifically limited and can be selected according to actual needs. In some embodiments, the organic solvent may include one or more of diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethylene carbonate, propylene carbonate, butenyl carbonate, γ-butyrolactone, methyl formate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, tetrahydrofuran, dimethyl ether, diethyl ether, and ethylene glycol dimethyl ether.

[0215] In some embodiments, the organic solvent in the electrolyte may include one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0216] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0217] In some embodiments, the additives in the electrolyte may include one or more of the following: cyclic carbonate compounds containing unsaturated bonds, halogen-substituted cyclic carbonate compounds (halogens may include at least one of fluorine, chlorine, etc.), sulfate compounds, sulfite compounds, sulfonyl lactone compounds, disulfonic acid compounds, nitrile compounds, aromatic compounds, isocyanate compounds, phosphonitrile compounds, cyclic anhydride compounds, phosphite compounds, phosphate compounds, borate ester compounds, carboxylic acid ester compounds, etc.

[0218] Separating membrane

[0219] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected. For different battery systems, the different diameters of the active ions lead to different requirements for the separator structure. For example, sodium ions and lithium ions in sodium-ion batteries have different diameters, with sodium ions having a larger diameter.

[0220] In some embodiments, the material of the separator can be selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0221] Electrode assembly, secondary battery

[0222] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0223] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0224] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0225] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0226] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to actual needs.

[0227] In a second aspect, an electrical device is provided, which includes the secondary battery described in the first aspect of this application.

[0228] Using the secondary battery described in the first aspect of this application in an electrical device can improve cycle performance and extend service life by utilizing the interfacial stabilizing effect of the aforementioned special silicate composite salt.

[0229] The secondary battery described in the first aspect of this application can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Mobile devices may include, for example, mobile phones, laptops, etc.; electric vehicles may include, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0230] As for the aforementioned electrical device, a secondary battery can be selected according to its usage requirements.

[0231] Figure 3 Here is an example of an electrical device 6. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0232] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0233] Thirdly, the application of silicate composite salts in the preparation of secondary batteries is provided, wherein the silicate composite salts are as defined in the first aspect of this application.

[0234] In some embodiments of this application, the application includes at least one of preparing a positive electrode containing the silicate complex salt and preparing a negative electrode containing the silicate complex salt.

[0235] In some embodiments, the application includes the preparation of a positive electrode containing the silicate complex salt.

[0236] In some embodiments, the application includes the preparation of a negative electrode containing the silicate complex salt.

[0237] In some embodiments, the application includes preparing a positive electrode containing the silicate complex salt and a negative electrode containing the silicate complex salt.

[0238] The use of the aforementioned special silicate composite salt to prepare secondary batteries (including but not limited to the secondary batteries described in the first aspect of this application) can improve the wetting performance of the electrolyte, increase the stability of the electrode-electrolyte interface, improve the battery cycle capacity, and extend the battery life.

[0239] In some embodiments of this application, the preparation of the positive electrode sheet containing the silicate composite salt includes: coating a positive electrode slurry onto at least one surface of a positive electrode current collector, drying, and compacting (cold pressing may be used); wherein the positive electrode slurry includes a positive electrode active material, a silicate composite salt (which may be selected from any suitable silicate composite salt of this application), a conductive agent, a binder, and a solvent. The definitions of the positive electrode active material, conductive agent, binder, and solvent are as described in the first aspect.

[0240] In some embodiments, the mass percentage of the silicate complex salt relative to the positive electrode active material in the positive electrode slurry is selected from 0.001% to 2%; optionally, the mass percentage of the silicate complex salt relative to the positive electrode active material is selected from 0.01% to 2%; optionally, the mass percentage of the silicate complex salt relative to the positive electrode active material is selected from 0.1% to 2%. The mass percentage of the silicate complex salt relative to the positive electrode active material in the positive electrode slurry can also be selected from any one percentage or a numerical range consisting of any two of the following percentages: 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, etc.

[0241] In some embodiments, the mass ratio of the silicate complex salt to the specific surface area of ​​the positive electrode active material in the positive electrode slurry is selected from 0.01 mg / m². 2 ~100mg / m 2 Optionally, the ratio of the mass of the silicate composite salt to the specific surface area of ​​the positive electrode active material is selected from 0.1 mg / m². 2 ~30mg / m 2In the positive electrode slurry, the ratio of the mass of the silicate composite salt to the specific surface area of ​​the positive electrode active material can also be selected from any one of the following values ​​or a range of any two of the following values: 0.01 mg / m³ 2 0.05mg / m 2 0.1 mg / m 2 0.5mg / m 2 1mg / m 2 2mg / m 2 3mg / m 2 4mg / m 2 5mg / m 2 6mg / m 2 8mg / m 2 10mg / m 2 12mg / m 2 15mg / m 2 16mg / m 2 18mg / m 2 20mg / m 2 25mg / m 2 30mg / m 2 35mg / m 2 40mg / m 2 45mg / m 2 50mg / m 2 60mg / m 2 70mg / m 2 80mg / m 2 90mg / m 2 100mg / m 2 wait.

[0242] In some embodiments, the areal density of the silicate composite salt in the positive electrode sheet is selected from 0.001 g / cm³. 2 ~0.5g / cm 2 Optionally, the areal density of the silicate composite salt in the positive electrode sheet is selected from 0.01 g / cm³. 2 ~0.1g / cm 2 See also the first aspect of this application.

[0243] In some embodiments of this application, the preparation of the negative electrode sheet containing the silicate composite salt includes: coating a negative electrode slurry onto at least one surface of a negative electrode current collector, drying, and compacting; wherein the negative electrode slurry includes a negative electrode active material, a silicate composite salt (which may be selected from any suitable silicate composite salt of this application), a conductive agent, a binder, and a solvent. The definitions of the negative electrode active material, conductive agent, binder, and solvent are as described in the first aspect.

[0244] In some embodiments, the mass percentage of the silicate composite salt relative to the negative electrode active material in the negative electrode slurry is selected from 0.005% to 5%; optionally, the mass percentage of the silicate composite salt relative to the negative electrode active material is selected from 0.02% to 3%; optionally, the mass percentage of the silicate composite salt relative to the negative electrode active material is selected from 0.1% to 3%. In the negative electrode slurry, the mass percentage of the silicate composite salt relative to the negative electrode active material can also be selected from any one percentage or any two percentage ranges: 0.005%, 0.01%, 0.02%, 0.04%, 0.05%, 0.06%, 0.08%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0245] In some embodiments, the mass ratio of the silicate composite salt to the specific surface area of ​​the negative electrode active material in the negative electrode slurry is selected from 0.01 to 100 mg / m². 2 Optionally, the ratio of the mass of the silicate composite salt to the specific surface area of ​​the negative electrode active material is selected from 0.1 to 30 mg / m². 2 In the negative electrode slurry, the ratio of the mass of the silicate composite salt to the specific surface area of ​​the negative electrode active material can also be selected from any one of the following values ​​or a range of any two of the following values: 0.01 mg / m³ 2 0.05mg / m 2 0.1 mg / m 2 0.5mg / m 2 1mg / m 2 2mg / m 2 3mg / m 2 4mg / m 2 5mg / m 2 6mg / m 2 8mg / m 2 10mg / m 2 12mg / m 2 15mg / m 2 16mg / m 2 18mg / m 2 20mg / m 2 25mg / m 2 30mg / m 2 35mg / m 2 40mg / m 2 45mg / m 250mg / m 2 60mg / m 2 70mg / m 2 80mg / m 2 90mg / m 2 100mg / m 2 wait.

[0246] In some embodiments, the areal density of the silicate composite salt in the positive electrode sheet is selected from 0.001 to 0.5 g / cm³. 2 Optionally, the areal density of the silicate composite salt in the positive electrode sheet is selected from 0.01 to 0.1 g / cm³. 2 See also the first aspect of this application.

[0247] The various silicate composite salts used in this application possess excellent three-dimensional spatial structures and exhibit superior physicochemical properties in one or more aspects, such as spreadability, viscosity enhancement, film-forming assistance, thickening, rheology, thixotropy, suspension, colloidal solubility, and emulsion stabilizing effects. Adding these special silicate composite salts to the positive or negative electrode slurry can increase the system stability of the positive or negative electrode slurry, improve the uniformity of the film layer when coated on the positive or negative electrode current collector, and enhance the quality stability of the electrode and the secondary battery.

[0248] In some embodiments of this application, the secondary battery is as defined in the first aspect of this application. The secondary battery prepared by the third aspect of this application can be any suitable secondary battery of the first aspect of this application, and has the characteristic of long life.

[0249] In another aspect of this application, a positive electrode slurry is provided, comprising a positive electrode active material, a silicate complex salt, a conductive agent, a binder, and a solvent; wherein the silicate complex salt is as defined in the first aspect of this application. This positive electrode slurry can be prepared using the aforementioned method.

[0250] In another aspect of this application, a method for preparing a positive electrode sheet is provided, comprising the following steps: coating the aforementioned positive electrode slurry onto at least one surface of a positive electrode current collector, drying, and compacting (cold pressing may be used). The aforementioned preparation method may also be referenced.

[0251] In another aspect of this application, a negative electrode slurry is provided, comprising a negative electrode active material, a silicate complex salt, a conductive agent, a binder, and a solvent; wherein the silicate complex salt is as defined in the first aspect of this application. This negative electrode slurry can be prepared using the aforementioned methods.

[0252] In another aspect of this application, a method for preparing a negative electrode sheet is provided, comprising the following steps: coating the aforementioned negative electrode slurry onto at least one surface of a negative electrode current collector, drying, and compacting (cold pressing may be used). The aforementioned preparation method may also be referenced.

[0253] The following describes some 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 the technology or conditions are not specified in the embodiments, they are performed according to the description above, or according to the technology or conditions described in the literature in this field, or according to the product instructions. Reagents or instruments used (unless otherwise specified) are commercially available conventional products, or can be synthesized using commercially available products in a conventional manner.

[0254] In the following examples, unless otherwise specified, the graphite raw materials used for the negative electrode active material are all artificial graphite with a particle size D. v 50 has a thickness of 10 μm and a specific surface area of ​​1.3 m². 2 / g, tap density is 1.1g / cm³ 3 The silicon-containing materials used for the negative electrode active material were all purchased from BTR New Materials Group Co., Ltd., model S500.

[0255] In the following examples, unless otherwise specified, the amount of silicate additive in the positive electrode in Part 1.1 is a percentage of the mass relative to the positive electrode active material (such as lithium iron phosphate or NCM811), the amount of silicate additive in the negative electrode in Part 1.2 is a percentage of the mass relative to the negative electrode active material (such as artificial graphite or silicon-carbon composite material), and the amount of silicate additive in the electrolyte in Part 1.3 is a percentage of the mass relative to the electrolyte.

[0256] The “wt%” mentioned below refers to the mass percentage.

[0257] 1. Preparation Example

[0258] 1.1. Preparation of positive electrode sheet

[0259] LFP0 positive electrode sheet: The positive electrode active material lithium iron phosphate, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are dissolved in the solvent N-methylpyrrolidone (NMP) at a weight ratio of 90:5:5. After thorough stirring and mixing, a positive electrode slurry is obtained. Then, the positive electrode slurry is uniformly coated on one side of the positive electrode current collector, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0260] LFP1 positive electrode sheet: The positive electrode active material lithium iron phosphate, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are dissolved in the solvent N-methylpyrrolidone (NMP) at a weight ratio of 90:5:5. Then, 1% magnesium aluminum silicate is added and the mixture is stirred and mixed evenly to obtain the positive electrode slurry. The positive electrode slurry is then uniformly coated on the positive electrode current collector, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0261] LFP2 positive electrode sheet: The positive electrode active material lithium iron phosphate, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are dissolved in the solvent N-methylpyrrolidone (NMP) at a weight ratio of 90:5:5. Then, 1% lithium aluminum silicate is added and the mixture is stirred and mixed evenly to obtain the positive electrode slurry. The positive electrode slurry is then uniformly coated on the positive electrode current collector, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0262] NCM0 positive electrode plate: The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) at a weight ratio of 90:5:5. After thorough stirring and mixing, a positive electrode slurry is obtained. The positive electrode slurry is then uniformly coated onto the positive electrode current collector, and after drying, cold pressing, and slitting, a positive electrode sheet is obtained.

[0263] NCM1 positive electrode plate: The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) at a weight ratio of 90:5:5. Then, 0.01% lithium aluminum silicate is added and the mixture is stirred and mixed thoroughly to obtain a positive electrode slurry. The positive electrode slurry is then uniformly coated onto the positive electrode current collector, and after drying, cold pressing, and slitting, a positive electrode sheet is obtained.

[0264] NCM2 positive electrode plate: The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) at a weight ratio of 90:5:5. Then, 0.1% lithium aluminum silicate is added and the mixture is stirred and mixed thoroughly to obtain a positive electrode slurry. The positive electrode slurry is then uniformly coated onto the positive electrode current collector, and after drying, cold pressing, and slitting, a positive electrode sheet is obtained.

[0265] NCM3 positive electrode plate: The positive electrode active material LiNi 0.8Co 0.1 Mn 0.1 O2 (NCM811), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) at a weight ratio of 90:5:5. Then, 1% lithium aluminum silicate is added and the mixture is stirred and mixed thoroughly to obtain a positive electrode slurry. The positive electrode slurry is then uniformly coated onto the positive electrode current collector, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0266] NCM4 positive electrode sheet: The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) at a weight ratio of 90:5:5. Then, 3% lithium aluminum silicate is added and the mixture is stirred and mixed thoroughly to obtain a positive electrode slurry. The positive electrode slurry is then uniformly coated onto the positive electrode current collector, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0267] NCM5 positive electrode sheet: The positive electrode active material LiNi... 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) at a weight ratio of 90:5:5. Then, 5% lithium aluminum silicate is added and the mixture is stirred and mixed thoroughly to obtain a positive electrode slurry. The positive electrode slurry is then uniformly coated onto the positive electrode current collector, and after drying, cold pressing, and slitting, a positive electrode sheet is obtained.

[0268] 1.2. Preparation of negative electrode sheet

[0269] Gr0 negative electrode sheet: The active material is artificial graphite (particle size D). v 50 has a thickness of 10 μm and a specific surface area of ​​1.3 m². 2 / g, tap density is 1.1g / cm³ 3 The conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose are dissolved in deionized water at a weight ratio of 90:4:4:2 to prepare a negative electrode slurry. The negative electrode slurry is then uniformly coated on both sides of the negative electrode current collector copper foil once or multiple times. After drying, a negative electrode film is obtained, which is then cold-pressed and slit to obtain a negative electrode sheet.

[0270] Gr1 negative electrode sheet: The active material artificial graphite (the same graphite raw material as Gr0), conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose are dissolved in deionized water at a weight ratio of 90:4:4:2 and then mixed evenly with the solvent deionized water. 1% magnesium aluminum silicate is then added to prepare a negative electrode slurry. The negative electrode slurry is then evenly coated onto the negative electrode current collector copper foil once or multiple times, dried to obtain a negative electrode film, and then cold-pressed and slit to obtain the negative electrode sheet.

[0271] Gr2 negative electrode sheet: The active material artificial graphite (the same graphite raw material as Gr0), conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose are dissolved in deionized water at a weight ratio of 90:4:4:2 and then mixed evenly with deionized water. 1% beryllium aluminum silicate is then added to prepare a negative electrode slurry. The negative electrode slurry is then evenly coated onto the negative electrode current collector copper foil once or multiple times, dried to obtain a negative electrode film, and then cold-pressed and slit to obtain the negative electrode sheet.

[0272] Gr3 negative electrode sheet: The active material artificial graphite (the same graphite raw material as Gr0), conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose are dissolved in deionized water at a weight ratio of 90:4:4:2 and then mixed evenly with deionized water. 1% magnesium boron silicate is then added to prepare a negative electrode slurry. The negative electrode slurry is then evenly coated onto the negative electrode current collector copper foil once or multiple times, dried to obtain a negative electrode film, and then cold-pressed and slit to obtain the negative electrode sheet.

[0273] Gr4 negative electrode sheet: The active material artificial graphite (the same graphite raw material as Gr0), conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose are dissolved in deionized water at a weight ratio of 90:4:4:2 and then mixed evenly with deionized water. 1% sodium aluminum silicate is then added to prepare a negative electrode slurry. The negative electrode slurry is then evenly coated onto the negative electrode current collector copper foil once or multiple times, dried to obtain a negative electrode film, and then cold-pressed and slit to obtain the negative electrode sheet.

[0274] SiO negative electrode sheet: The active material silicon-carbon composite material (BTR New Material Group Co., Ltd. S500), conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose are dissolved in deionized water at a weight ratio of 90:4:4:2 and mixed evenly to prepare a negative electrode slurry; then the negative electrode slurry is uniformly coated onto the negative electrode current collector copper foil once or multiple times, dried to obtain a negative electrode film, and then cold-pressed and slit to obtain the negative electrode sheet.

[0275] Si1 negative electrode sheet: The active material silicon-carbon composite material (BTR New Material Group Co., Ltd. S500), conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose are dissolved in deionized water at a weight ratio of 90:4:4:2. Then, 1% magnesium aluminum silicate is added and mixed evenly to prepare a negative electrode slurry. The negative electrode slurry is then coated evenly on the negative electrode current collector copper foil once or multiple times. After drying, a negative electrode film is obtained. Then, the negative electrode sheet is obtained by cold pressing and slitting.

[0276] Si2 negative electrode sheet: The active material silicon-carbon composite material (BTR New Material Group Co., Ltd. S500), conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose are dissolved in deionized water at a weight ratio of 90:4:4:2. Then, 1% magnesium phosphate silicate is added and mixed evenly to prepare a negative electrode slurry. The negative electrode slurry is then coated evenly on the negative electrode current collector copper foil once or multiple times. After drying, a negative electrode film is obtained. The negative electrode sheet is then obtained by cold pressing and slitting.

[0277] Si3 negative electrode sheet: The active material silicon-carbon composite material (BTR New Material Group Co., Ltd. S500), conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose are dissolved in deionized water at a weight ratio of 90:4:4:2. Then, 1% manganese aluminum silicate is added and mixed evenly to prepare a negative electrode slurry. The negative electrode slurry is then coated evenly on the negative electrode current collector copper foil once or multiple times. After drying, a negative electrode film is obtained. The negative electrode sheet is then obtained by cold pressing and slitting.

[0278] Si4 negative electrode sheet: The active material silicon-carbon composite material (BTR New Material Group Co., Ltd. S500), conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose are dissolved in deionized water at a weight ratio of 90:4:4:2. Then, 1% aluminum silicate is added and mixed evenly to prepare a negative electrode slurry. The negative electrode slurry is then coated evenly on the negative electrode current collector copper foil once or multiple times. After drying, a negative electrode film is obtained, which is then cold-pressed and slit to obtain the negative electrode sheet.

[0279] 1.3. Preparation of Electrolyte

[0280] EL0 electrolyte: In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), organic solvents EC and EMC are mixed evenly at a volume ratio of 3 / 7. 12.5wt% of lithium LiPF6 salt is added and dissolved in the organic solvent. 1wt% of PS, 0.5wt% of DTD, 0.5wt% of VC, and 2wt% of FEC are added as additives. The mixture is stirred evenly to obtain the corresponding electrolyte.

[0281] EL1 Electrolyte: In an argon-atmospheric glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), organic solvents EC and EMC were mixed evenly at a volume ratio of 3 / 7. 12.5 wt% of lithium LiPF6 salt was dissolved in the organic solvent, and 1 wt% of PS, 0.5 wt% of DTD, 0.5 wt% of VC, and 2 wt% of FEC were added as additives. The mixture was stirred until homogeneous. Then, 1 wt% magnesium aluminum silicate was added to the electrolyte, stirred evenly, centrifuged, and the supernatant was collected to obtain the corresponding electrolyte. During the preparation process, a relatively small amount of magnesium aluminum silicate was observed to dissolve.

[0282] In this context, PS stands for 1,3-propanesulfonic acid lactone; DTD stands for vinyl sulfate; VC stands for vinylene carbonate; and FEC stands for fluorovinyl carbonate.

[0283] Table 1.

[0284]

[0285] 1.4. Separating membrane

[0286] The separator uses commercially available PP separator film.

[0287] 1.5. Assembly of Lithium-ion Batteries

[0288] According to Table 2, the corresponding positive electrode, separator, and corresponding negative electrode are stacked in sequence so that the separator is between the positive and negative electrodes to play a role in isolation. Then, the electrode assembly is wound to obtain the electrode assembly. The electrode assembly is placed in the battery casing, dried, and then injected with the corresponding electrolyte. After formation, settling and other processes, a lithium-ion battery is obtained, which is recorded as the initial state of the lithium-ion battery.

[0289] 2. Parameter and performance testing

[0290] 2.1. Cell internal resistance before and after cycling

[0291] The lithium-ion battery under test: a lithium-ion battery in its initial state, and a lithium-ion battery that has been cycled 1000 times at 45°C (see the cycling conditions in Part 2.2).

[0292] Test Method: At 25℃, the lithium-ion battery under test is charged at a constant current of 1C to 4.3V, then charged at a constant voltage of 4.3V until the current is less than 0.05C, and then discharged at 1C for 30 minutes, adjusting the cell charge to 50% SOC. Then, the positive and negative probes of the TH2523A AC internal resistance tester are connected to the positive and negative terminals of the battery, respectively. The internal resistance value of the battery is read using the internal resistance tester. The internal resistance value obtained when testing the lithium-ion battery in its initial state is recorded as the "initial cell internal resistance," and the internal resistance value obtained after testing the lithium-ion battery at 45℃ for 1000 cycles is recorded as the "cell internal resistance after 1000 cycles," in mΩ.

[0293] 2.2.45℃ 1000-cycle capacity retention

[0294] At 45°C, the lithium-ion battery is charged at a constant current of 1C to 4.3V, then charged at a constant voltage of 4.3V until the current is less than 0.05C, and then discharged at a constant current of 1C to 3.0V. This constitutes one charge-discharge cycle. This charging and discharging process is repeated, and the capacity retention rate of the lithium-ion battery after 800 cycles is calculated.

[0295] The capacity retention rate (%) of a lithium-ion battery after 1000 cycles at 45℃ = (discharge capacity of the 1000th cycle / discharge capacity of the first cycle) × 100%.

[0296] 2.3. Capacity retention rate after 300 days of storage at 60℃

[0297] At 25°C, the lithium-ion battery was charged at a constant current of 1C to a voltage of 4.3V, then charged at a constant voltage of 4.3V to a current of 0.05C. The battery was then discharged at a constant current of 1C to a voltage of 3.0V. This completes one charge-discharge cycle, during which the lithium capacity was tested. The fully charged lithium-ion battery was then placed in a 60°C constant temperature chamber to test its capacity after 300 days of storage.

[0298] The capacity retention rate (%) of a lithium-ion battery after 300 days of storage at 60°C = (discharge capacity after 300 days of storage / discharge capacity of the first cycle) × 100%.

[0299] 3. Test Results and Analysis

[0300] The test results for the electrode plates and secondary batteries can be found in Table 2. According to Table 2, in Examples 1-22, the silicate composite salt of this application was introduced into at least one of the positive and negative electrode plates. Compared with Comparative Examples 1-7, the stability of the electrode-electrolyte interface was significantly improved, and the cycle capacity retention rate and storage capacity retention rate were significantly improved. It can be seen that the introduction of silicate composite salt into the electrode plates has a good effect on improving the cycle stability and capacity performance of the battery cell.

[0301] In Comparative Example 1, conventional lithium iron phosphate cathode and graphite anode were used in the lithium-ion battery without introducing the silica composite salt additive of this application as an interface stabilizer. The impedance before and after cycling was relatively large, and the capacity retention rate deteriorated significantly during cycling.

[0302] In Comparative Example 2, conventional NCM cathodes and silicon-containing anodes were used in the lithium-ion battery without introducing the silicate composite salt additive of this application as an interface stabilizer. The impedance before and after cycling was large and severely deteriorated, and the capacity retention during cycling and storage was low.

[0303] In Comparative Examples 3-5, using other silicate additives instead of the silicate composite salt additive of this application in lithium-ion batteries did not improve the cell impedance, cycle life, or capacity retention during storage; in fact, it worsened the performance. In Examples 18-19, adding the silicate composite salt of this application to the positive electrode significantly improved the deterioration of cell performance caused by negative electrode additives (other types of silicate composite salts or single silicate salts: magnesium phosphate silicate, aluminum manganese silicate, aluminum silicate).

[0304] In Comparative Examples 6-7, the silicate composite salt additive of this application was not added to the positive and negative electrode plates of the lithium-ion battery. The silicate composite salt additive of this application was only added to the electrolyte. The improvement effect on the internal resistance before and after cycling, the capacity retention rate after 1000 cycles at 45°C, and the capacity retention rate after 300 days of storage at 60°C as shown in Table 2 was slight or non-existent.

[0305] Table 2.

[0306]

[0307] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0308] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. The above-described embodiments only illustrate several embodiments of this application, and their descriptions are relatively detailed, but they should not be construed as limiting the scope of the patent. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, are also included in the scope of this application without departing from the spirit of this application. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, the separator being located between the positive electrode sheet and the negative electrode sheet; the positive electrode sheet comprising a positive electrode active material layer, the negative electrode sheet comprising a negative electrode active material layer; at least one of the positive electrode active material layer and the negative electrode active material layer comprising a silicate complex salt; when the positive electrode active material layer comprises the silicate complex salt, the positive electrode active material layer comprises a positive electrode active substance and the silicate complex salt; when the negative electrode active material layer comprises the silicate complex salt, the negative electrode active material layer comprises a negative electrode active substance and the silicate complex salt, the negative electrode active substance comprising one or more of artificial graphite, natural graphite, soft carbon, hard carbon, and a silicon-based material selected from one or more of elemental silicon, a silicon oxide compound, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy; wherein Y is selected from a second main group element; a structural formula of the silicate complex salt is selected from at least one of Formula I and Formula II: Formula I Formula II; the secondary battery satisfying any one or any plurality of the following characteristics: the silicate complex salt comprises one or more of magnesium aluminum silicate, magnesium boron silicate, beryllium aluminum silicate, beryllium boron silicate, lithium aluminum silicate, lithium boron silicate, sodium aluminum silicate, and sodium boron silicate; the positive electrode active material layer comprises a positive electrode active substance and the silicate complex salt; the positive electrode active material layer satisfying one or more of the following characteristics: a mass percentage of the silicate complex salt with respect to the positive electrode active substance in the positive electrode active material layer is selected from 0.001% to 2%; a mass percentage of the silicate complex salt with respect to the positive electrode active substance in the positive electrode active material layer is selected from 0.01% to 2%; a mass percentage of the silicate complex salt with respect to the positive electrode active substance in the positive electrode active material layer is selected from 0.1% to 2%; the secondary battery is a lithium ion secondary battery or a sodium ion secondary battery; the positive electrode active substance comprises a lithium ion material; the lithium ion material comprises at least one of a lithium-containing phosphate and a lithium transition metal oxide; the negative electrode active material layer comprises a negative electrode active substance and the silicate complex salt; the negative electrode active material layer satisfying one or more of the following characteristics: a mass percentage of the silicate complex salt with respect to the negative electrode active substance in the negative electrode active material layer is selected from 0.005% to 5%; a mass percentage of the silicate complex salt with respect to the negative electrode active substance in the negative electrode active material layer is selected from 0.02% to 3%; a mass percentage of the silicate complex salt with respect to the negative electrode active substance in the negative electrode active material layer is selected from 0.1% to 3%; the secondary battery is a lithium ion battery, and the negative electrode active substance comprises graphite; a mass percentage of graphite in the negative electrode active substance is greater than 50%; a mass percentage of graphite in the negative electrode active substance is selected from 70% to 100%; a mass percentage of graphite in the negative electrode active substance is selected from 80% to 100%. ​ ​ ​ the chemical formula of the silicate complex salt is selected from the group consisting of YSi2Z 1 Z 2 O8and X 1 X 2 Si2Z 1 Z 2 O8at least one of ​ ​ X 1 and X 2 each independently is selected from the first main group elements; Z 1 and Z 2 each is selected from a third main group element.

2. The secondary battery according to claim 1, wherein ​ 。 3. The secondary battery according to claim 1 or 2, wherein ​ ​ X 1 and X 2 each independently Li or Na; In the same molecule, X 1 and X 2 are the same; Z 1 and Z 2 each independently Al or B; and In the same molecule, Z 1 and Z 2 are the same.

4. The secondary battery according to any one of claims 1 to 3, wherein ​ 5. The secondary battery according to any one of claims 1 to 4, wherein ​ ​ ​ In the positive electrode active material layer, the ratio of the mass of the silicate complex salt relative to the specific surface area of the positive electrode active material is selected from the range of 0.01 mg / m 2 100 mg / m 2 ; The silicon acid complex salt has an areal density in the positive electrode tab selected from the group consisting of 0.001 g / cm 2 0.5 g / cm 2 .

6. The secondary battery according to claim 5, wherein ​ ​ In the positive electrode active material layer, the ratio of the mass of the silicate complex salt relative to the specific surface area of the positive electrode active material is selected from the range of 0.1 mg / m 2 30 mg / m 2 ; The silicon acid complex salt has an areal density in the positive electrode tab selected from the group consisting of 0.01 g / cm 2 0.1 g / cm 2 .

7. The secondary battery according to claim 5 or 6, wherein ​ 8. The secondary battery according to any one of claims 1 to 7, wherein ​ 9. The secondary battery according to claim 8, wherein ​ 10. The secondary battery according to claim 9, wherein ​ 11. The secondary battery according to any one of claims 1 to 10, wherein ​ ​ ​ In the negative electrode active material layer, the ratio of the mass of the silicate complex salt relative to the specific surface area of the negative electrode active material is selected from the range of 0.01 mg / m 2 100 mg / m 2 ; The areal density of the silicate complex salt in the negative electrode tab is selected from the group consisting of 0.0005 g / cm 2 0.5 g / cm 2 .

12. The secondary battery according to claim 11, wherein ​ ​ In the negative electrode active material layer, the ratio of the mass of the silicate complex salt relative to the specific surface area of the negative electrode active material is selected from the range of 0.1 mg / m 2 30 mg / m 2 ; The surface density of the silicate complex salt in the negative electrode tab is selected from 0.001 g / cm 2 0.3 g / cm 2 .

13. The secondary battery according to claim 11 or 12, wherein ​ 14. The secondary battery according to any one of claims 1 to 13, wherein ​ 15. The secondary battery according to claim 14, wherein ​ 16. The secondary battery of claim 14, wherein, ​ 17. The secondary battery of claim 14, wherein, ​ 18. The secondary battery of claim 14, wherein, The mass percentage of graphite in the negative active material is selected from 90% to 100%.

19. The secondary battery of claim 14, wherein, The mass percentage of graphite in the negative active material is 100%.

20. The secondary battery according to any one of claims 1 to 13, wherein The secondary battery is a lithium ion battery, and the negative active material comprises a silicon-carbon composite.

21. The secondary battery of claim 20, wherein, The mass percentage of the silicon-carbon composite in the negative active material is greater than 50%.

22. The secondary battery of claim 20, wherein, The mass percentage of the silicon-carbon composite in the negative active material is selected from 70% to 100%.

23. The secondary battery of claim 20, wherein, The mass percentage of the silicon-carbon composite in the negative active material is selected from 80% to 100%.

24. The secondary battery of claim 20, wherein, The mass percentage of the silicon-carbon composite in the negative active material is selected from 90% to 100%.

25. The secondary battery of claim 20, wherein, The mass percentage of the silicon-carbon composite in the negative active material is 100%.

26. An electric device comprising the secondary battery of any one of claims 1-25.

27. Use of a complex silicate salt in the manufacture of a secondary battery, wherein, The silicate composite salt is as defined in any one of claims 1-4; The application comprises at least one of preparing a positive electrode sheet containing the silicate composite salt and preparing a negative electrode sheet containing the silicate composite salt; The positive electrode sheet comprises a positive active material layer, and the negative electrode sheet comprises a negative active material layer; at least one of the positive active material layer and the negative active material layer comprises the silicate composite salt; When the positive active material layer comprises the silicate composite salt, the positive active material layer comprises a positive active material and the silicate composite salt; When the negative active material layer comprises the silicate composite salt, the negative active material layer comprises a negative active material and the silicate composite salt, and the negative active material comprises one or more of artificial graphite, natural graphite, soft carbon, hard carbon, and a silicon-based material selected from one or more of elemental silicon, a silicon oxide compound, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy.

28. The use according to claim 27, wherein, The application comprises preparing a positive electrode sheet containing the silicate composite salt.

29. The use of claim 27, wherein, The application comprises preparing a negative electrode sheet containing the silicate composite salt.

30. The use of claim 27, wherein, The application comprises preparing a positive electrode sheet containing the silicate composite salt and preparing a negative electrode sheet containing the silicate composite salt.

31. The use according to any one of claims 27 to 30, wherein, The preparation of the positive electrode sheet containing the silicate composite salt comprises: coating a positive electrode slurry on at least one surface of a positive current collector, drying, and compacting; wherein the positive electrode slurry comprises a positive active material, the silicate composite salt, a conductive agent, a binder, and a solvent.

32. The use of claim 31, wherein, In the positive electrode slurry, the mass percentage of the silicate composite salt relative to the positive active material is selected from 0.001% to 2%.

33. The use of claim 31, wherein, In the positive electrode slurry, the mass percentage of the silicate composite salt relative to the positive active material is selected from 0.01% to 2%.

34. The use of claim 31, wherein, In the positive electrode slurry, the mass percentage of the silicate composite salt relative to the positive active material is selected from 0.1% to 2%.

35. The use according to any one of claims 31 to 34, wherein, In the positive electrode slurry, the ratio of the mass of the silicic acid complex salt relative to the specific surface area of the positive electrode active material is selected from the range of 0.01 mg / m 2 100 mg / m 2 .

36. The use of claim 35, wherein, In the positive electrode slurry, the ratio of the mass of the silicic acid complex salt relative to the specific surface area of the positive electrode active material is selected from the range of 0.1 mg / m 2 30 mg / m 2 .

37. The use according to any one of claims 31 to 36, wherein, The silicon acid complex salt has an areal density in the positive electrode tab selected from the group consisting of 0.001 g / cm 2 0.5 g / cm 2 .

38. The use of claim 37, wherein, The silicon acid complex salt has an areal density in the positive electrode tab selected from the group consisting of 0.01 g / cm 2 0.1 g / cm 2 .

39. The use according to any one of claims 27 to 38, wherein, The preparation of the negative electrode sheet containing the silicate composite salt comprises: coating a negative electrode slurry on at least one surface of a negative current collector, drying, and compacting; wherein the negative electrode slurry comprises a negative active material, the silicate composite salt, a conductive agent, a binder, and a solvent.

40. The use according to claim 39, wherein, In the negative electrode slurry, the mass percentage of the silicate composite salt relative to the negative active material is selected from 0.005% to 5%.

41. The use of claim 39, wherein, In the negative electrode slurry, the mass percentage of the silicate complex salt with respect to the negative electrode active material is selected from 0.02% to 3%.

42. The use of claim 39, wherein, In the negative electrode slurry, the mass percentage of the silicate complex salt with respect to the negative electrode active material is selected from 0.1% to 3%.

43. The use according to any one of claims 39 to 42, wherein, In the negative electrode slurry, the ratio of the mass of the silicic acid complex salt relative to the specific surface area of the negative electrode active material is selected from the range of 0.01 mg / m 2 100 mg / m 2 .

44. The use of claim 43, wherein, In the negative electrode slurry, the ratio of the mass of the silicic acid complex salt relative to the specific surface area of the negative electrode active material is selected from the range of 0.1 mg / m 2 30 mg / m 2 .

45. The use according to any one of claims 39 to 44, wherein, The silicon acid complex salt has an areal density in the positive electrode tab selected from the group consisting of 0.001 g / cm 2 0.5 g / cm 2 .

46. The use of claim 45, wherein, The silicon acid complex salt has an areal density in the positive electrode tab selected from the group consisting of 0.01 g / cm 2 0.1 g / cm 2 .

47. The use according to any one of claims 27 to 46, wherein, The secondary battery is as defined in any one of claims 1 to 25.

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