Pole piece, secondary battery, and electric device

Abstract

The present application provides a pole piece, a secondary battery, and an electrical device. The pole piece includes an active material layer, the active material layer contains a first binder and a second binder, the first binder includes an alkali metal polymer salt, and the average molecular weight M of the alkali metal polymer salt satisfies: 400,000 < M ≤ 3,000,000. The binding strength of the second binder is greater than that of the first binder. The weight percentage of the alkali metal polymer salt in the active material layer is A, and the weight percentage of the second binder in the active material layer is B. A and B satisfy: 0 < A + B ≤ 5%. The pole piece provided by the present application can improve the cycle performance and fast charging performance of the secondary battery.

Description

[0001] Related applications

[0002] This application is a divisional application of Chinese patent application No. CN2023116335108, filed on December 1, 2023, entitled "Electrode, Secondary Battery and Electrical Device", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, and in particular to an electrode, a secondary battery, and an electrical device. Background Technology

[0004] The statements herein are provided only as background information in connection with this application and do not necessarily constitute prior art.

[0005] In recent years, with the increasingly widespread application of secondary batteries, represented by lithium-ion batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. Due to the significant development of secondary batteries, higher requirements have been placed on their energy density, cycle performance, and safety performance. Summary of the Invention

[0006] Based on this, this application provides an electrode, a secondary battery, and an electrical device. By improving the electrode, the cycle performance and fast charging performance of the secondary battery can be enhanced.

[0007] To achieve the above objectives, a first aspect of this application provides an electrode sheet comprising an active material layer, the active material layer including a first binder and a second binder, the first binder comprising an alkali metal polymer salt, the second binder having a greater bonding strength than the first binder, the alkali metal polymer salt having a weight percentage A in the active material layer, and the second binder having a weight percentage B in the active material layer, wherein A and B satisfy the following condition: 0 <A+B≤5%。

[0008] The active material layer of the electrode includes a first binder and a second binder. The first binder comprises an alkali metal polymer salt. The alkali metal polymer salt in the first binder promotes the increase of alkali metal ions (i.e., active ions) in the active material layer, thereby improving cycle performance. Furthermore, since the second binder has a greater bonding strength than the first binder, by using the first and second binders in combination and ensuring their weight ratio meets the aforementioned range, the relatively higher bonding strength of the second binder can effectively enhance the bonding strength of the first binder. This improves the adhesion of the electrode and keeps it at a relatively high level, reducing the problem of electrode demolding during use, improving the stability of the electrode, and ultimately improving the cycle stability of the battery.

[0009] In addition, alkali metal polymer salts can also dissociate alkali metal ions (such as lithium ions), which can increase the content of alkali metal ions in the active material layer and enable the transport of alkali metal ions along the molecular chain of the first binder. At the same time, by using the first binder in combination with the second binder, the dissociated alkali metal ions can be further transported along the molecular chain of the second binder. This can effectively shorten the time for alkali metal ions to be transported to the current collector, reduce polarization accumulation, and thus improve the transport efficiency of alkali metal ions, thereby improving the fast charging capability of the battery.

[0010] In some embodiments of this application, A and B satisfy the following condition: 0.3 ≤ B / A ≤ 8.5.

[0011] In the active material layer of the electrode, the weight ratio B / A of alkali metal polymer salt to the second binder is within the above range, which is beneficial to improving the adhesion of the electrode and thus improving its stability; it is also beneficial to reduce the influence of polyacrylate on the uniformity of slurry particle dispersion in the active material layer and improve the cycle performance of the electrode.

[0012] In some embodiments of this application, the active material layer further comprises a dispersant.

[0013] In some embodiments of this application, the dispersant has a weight percentage of C,0 in the active material layer. <C≤1.5%。

[0014] The active material layer contains a dispersant, and the weight ratio of the dispersant is controlled to meet the above-mentioned range, which is beneficial to improve the dispersion uniformity of slurry particles in the active material layer of the electrode and to keep the dispersion uniformity at a relatively high level, thereby improving the cycle performance of the electrode.

[0015] In some embodiments of this application, A, B, and C satisfy the following condition: 0 <A+B+C≤6%。

[0016] When the weight ratios of the alkali metal polymer salt, the second binder, and the dispersant meet the above ranges, while improving the adhesion of the electrode and the uniformity of the dispersion of the slurry particles in the active material layer of the electrode, it can also reduce the occupation of the active materials contained in the active material layer by the various additives described above, and improve the capacity of the active materials and the electrode.

[0017] In some embodiments of the present application, the average molecular weight M of the alkali metal polymer salt satisfies: 3000 < M ≤ 100,000, and 1.2 ≤ B / A ≤ 8.5.

[0018] When the average molecular weight of the alkali metal polymer salt is in the range of 3000 < M ≤ 100,000, its own adhesion is relatively low; in the positive electrode active material layer, when the alkali metal polymer salt is used as a binder in combination with the second binder, and the weight ratio thereof and the weight ratio of the second binder satisfy 1.2 ≤ B / A ≤ 8.5, the adhesion of the electrode can be effectively improved, the problem of demoulding during the use of the electrode can be reduced, and the stability of the electrode can be improved.

[0019] In some embodiments of the present application, C satisfies: 0.2 < C ≤ 1%.

[0020] When the average molecular weight of the alkali metal polymer salt is in the range of 3000 < M ≤ 100,000, due to its relatively short chain length and the electrostatic repulsion between the carboxyl groups in its molecular structure, the dispersion uniformity between the slurry particles in the active material layer can be at a relatively moderate level. In this case, by controlling the weight ratio of the dispersant to satisfy 0.2 < C ≤ 1%, on the one hand, the dispersion uniformity between the slurry particles can be further improved to reach a relatively higher level, thereby further improving the cycle performance of the electrode. On the other hand, the dosage of the dispersant can be minimized to minimize its occupation of the active materials in the active material layer, thereby improving the capacity of the active materials and the electrode. In addition, some dispersants are insulating materials, and when the addition amount is relatively large, it will affect the conductivity of the electrode; when the weight ratio of the dispersant satisfies 0.2 < C ≤ 1%, the influence on the conductivity of the electrode can also be minimized, and the conductivity of the electrode can be improved.

[0021] In some embodiments of the present application, the average molecular weight M of the alkali metal polymer salt satisfies: 100,000 < M ≤ 400,000, and 0.8 ≤ B / A ≤ 8.1.

[0022] When the average molecular weight of the alkali metal polymer salt is between 100,000 and 400,000, its own adhesion is moderate; in the positive electrode active material layer, the alkali metal polymer salt is used as a binder in combination with a second binder, and the weight ratio of it to the weight ratio of the second binder satisfies 0.8 ≤ B / A ≤ 8.1, which can further improve the adhesion of the electrode sheet, make the slurry particles in the active material layer contact well with the current collector, and further enhance the adhesion between the slurry particles, reduce the shedding of the slurry particles during the charge and discharge cycle of the electrode sheet, so as to further improve the kinetic performance and stability of the electrode sheet.

[0023] In some embodiments of the present application, C satisfies: 0.4 < C ≤ 1.2%.

[0024] When the average molecular weight of the alkali metal polymer salt is between 100,000 and 400,000, the length of its chain is moderate at this time. During the process of preparing it into a slurry and using it for the electrode sheet, there will be a certain degree of agglomeration between the slurry particles, which will reduce the dispersion uniformity between the slurry particles to a certain extent. In this case, by controlling the weight ratio of the dispersant to satisfy 0.4 < C ≤ 1.2%, it can improve the dispersion uniformity between the slurry particles to a certain extent, thereby improving the cycle performance of the electrode sheet to a certain extent; and can minimize the dosage of the dispersant and minimize its occupation of the active material in the active material layer to improve the capacity of the active material and the electrode sheet.

[0025] In some embodiments of the present application, the average molecular weight M of the alkali metal polymer salt satisfies: 400,000 < M ≤ 3,000,000, and 0.3 ≤ B / A ≤ 6.6.

[0026] When the average molecular weight of the alkali metal polymer salt is 400,000 < M ≤ 3,000,000, it already has a certain degree of adhesion by itself. In the active material layer, when it is used in combination with a second binder, the weight ratio of it to the weight of the second binder satisfies 0.3 ≤ B / A ≤ 6.6, which can make the adhesion of the electrode sheet reach a relatively higher level, make the slurry particles in the active material layer contact better with the current collector, and further enhance the adhesion between the slurry particles, reduce the shedding of the slurry particles during the charge and discharge cycle of the electrode sheet, so as to further improve the kinetic performance and stability of the electrode sheet.

[0027] In some embodiments of the present application, C satisfies: 0.7 < C ≤ 1.5%.

[0028] When the average molecular weight of the alkali metal polymer salt is from 400,000 to 3,000,000, although the high-molecular-weight alkali metal polymer salt has relatively high adhesion, due to its relatively long chain length, during the process of preparing it into a slurry and using it for the electrode sheet, the slurry particles will become agglomerated and larger due to the bridging effect between the molecular chains of the alkali metal polymer salt, thereby easily reducing the dispersion uniformity between the slurry particles and affecting the cycle performance of the battery. In this case, by controlling the weight percentage of the dispersant to satisfy 0.7 < C ≤ 1.5%, the dispersion uniformity between the slurry particles can be effectively improved, thereby improving the cycle performance of the electrode sheet; and the dosage of the dispersant can be minimized as much as possible, and the occupation of the active material in the active material layer by it can be minimized as much as possible to improve the capacity of the active material and the electrode sheet.

[0029] The mass percentage content of the alkali metal element contained in the first binder is m, and 3% ≤ m ≤ 8.9%.

[0030] Controlling the mass percentage of the alkali metal element in the first binder within the above range can promote the transmission of the dissociated alkali metal ions on the molecular chains of the first binder and the second binder, shorten the time for the alkali metal ions to be transmitted to the current collector, and reduce the polarization accumulation, thereby improving the kinetic performance of the secondary battery. In some embodiments of the present application, the alkali metal polymer salt includes alkali metal polyacrylate;

[0031] Optionally, the alkali metal polyacrylate includes one or more of lithium polyacrylate, sodium polyacrylate, and potassium polyacrylate.

[0032] In some embodiments of the present application, the second binder includes one or more of styrene-butadiene rubber and its modified compounds, polyacrylic acid, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, polyvinylidene fluoride, and polytetrafluoroethylene.

[0033] In some embodiments of the present application, the dispersant includes one or more of polyethylene glycol, hydroxypropyl methyl cellulose, polyvinylpyrrolidone, sodium dodecylsulfonate, carboxymethyl starch, polyvinylbenzyltrimethylammonium salt, polyethyleneglycol octylphenyl ether, polystyrenesulfonic acid, polypropylene maleic acid, methylene dimethylnaphthalene disulfonate, polyethyleneimine, N-methylpyrrolidone, carboxymethyl cellulose, and carboxymethyl cellulose salt. Optionally, the carboxymethyl cellulose salt includes sodium carboxymethyl cellulose and / or potassium carboxymethyl cellulose.

[0034] In some embodiments of the present application, the active material layer further contains an active material, and the active material includes one of a positive electrode active material and a negative electrode active material.

[0035] The second aspect of the present application further provides a secondary battery, including the electrode sheet of the first aspect of the present application.

[0036] A third aspect of this application provides an electrical device, including a secondary battery as described in the second aspect of this application.

[0037] The electrical device of this application includes the secondary battery provided in this application, and therefore has at least the same advantages as the secondary battery.

[0038] 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

[0039] To better describe and illustrate the embodiments or examples provided in this application, 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 currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0040] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0041] Figure 2 for Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0042] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0043] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0044] Figure 5 for Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0045] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0046] Explanation of reference numerals in the attached figures:

[0047] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate; 6 Electrical device. Detailed Implementation

[0048] Hereinafter, some embodiments of the electrode, secondary battery, and power-consuming device of this application are described in detail with appropriate reference to the accompanying drawings. However, some unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0049] The "range" disclosed in this application can be defined in the form of 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; any endpoint can be independently included or excluded, and they can be combined arbitrarily, meaning 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 ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also 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" and "5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when describing a parameter as an integer ≥ 2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 for that parameter. For instance, when describing a parameter as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0050] 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.

[0051] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0052] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0053] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can 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.

[0054] In this application, open-ended technical features or solutions described using terms such as "containing," "comprising," or "including" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A' includes a1', a2', and a3'. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both the feature or solution that "A' consists of a1', a2', and a3'" and the feature or solution that "A' includes not only a1', a2', and a3', but also other members." In this application, unless otherwise specified, A' (e.g., B') indicates that B' is a non-limiting example of A', and it can be understood that A' is not limited to B'.

[0055] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0056] Electrodes are a crucial component of batteries, and binders in the electrodes reduce the probability of expansion. Currently, commonly used binders in electrodes exhibit poor adhesion between particles and between particles and current collectors, leading to potential demolding issues and poor stability during use. Furthermore, current electrodes and batteries also suffer from poor fast-charging performance.

[0057] To address the aforementioned technical issues, this application provides an electrode sheet that, by adjusting the weight ratio of alkali metal polymer salt and binder contained in the active material layer, not only improves the adhesion of the electrode sheet but also enhances the fast-charging performance of the electrode sheet and the battery.

[0058] In a first aspect, this application provides an electrode sheet comprising an active material layer, the active material layer including a first binder and a second binder, the first binder comprising an alkali metal polymer salt, the second binder having a greater bonding strength than the first binder, the alkali metal polymer salt having a weight percentage A in the active material layer, and the second binder having a weight percentage B in the active material layer, wherein A and B satisfy the following condition: 0 <A+B≤5%。

[0059] It is understood that the "bonding strength" mentioned in this application refers to the stress required to cause the interface between the adhesive and the bonded object or its vicinity to fail under the action of external force.

[0060] It is understood that the aforementioned electrode may include a positive electrode or a negative electrode. When the electrode is a positive electrode or a negative electrode, the corresponding active material layer is a positive active material layer or a negative active material layer.

[0061] The active material layer of the electrode includes a first binder and a second binder. The first binder comprises an alkali metal polymer salt. The alkali metal polymer salt in the first binder promotes the increase of alkali metal ions (i.e., active ions) in the active material layer, thereby improving the battery's cycle performance. Furthermore, since the second binder has a greater bonding strength than the first binder, by using the first and second binders in combination and ensuring their weight ratio meets the aforementioned range, the relatively higher bonding strength of the second binder can effectively enhance the bonding strength of the first binder. This improves the electrode's adhesion force and keeps it at a relatively high level, reducing the problem of electrode demolding during use, improving the electrode's stability, and ultimately enhancing the battery's cycle stability.

[0062] In addition, alkali metal ions (such as lithium ions) can also be dissociated from the alkali metal polymer salt, which can increase the content of alkali metal ions in the active material layer and enable the transmission of alkali metal ions on the molecular chains of the first binder. At the same time, by using the first binder in combination with the second binder, the dissociated alkali metal ions can be further transmitted on the molecular chains of the second binder, effectively shortening the time for the alkali metal ions to be transmitted to the current collector, reducing polarization accumulation, and thus improving the transmission efficiency of the alkali metal ions and the fast charging ability of the battery.

[0063] In some embodiments, the active material layer further comprises a dispersant.

[0064] In some embodiments, the weight percentage of the dispersant in the active material layer is C, where 0 < C ≤ 1.5%. For example, C can be 0.1%, 0.3%, 0.7%, 0.9%, 1.1%, 1.3%, 1.5% or within the range composed of any of the above values.

[0065] In the active material layer, controlling the weight percentage of the dispersant to meet the above range is beneficial to improving the dispersion uniformity of the slurry particles in the active material layer of the electrode sheet and keeping the dispersion uniformity at a relatively high level, thus being beneficial to improving the cycling performance of the electrode sheet.

[0066] In some embodiments, the following relationship is satisfied between A and B: 0.3 ≤ B / A ≤ 8.5. For example, B / A can be 0.3, 0.5, 0.7, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5 or within the range composed of any of the above values.

[0067] In the active material layer of the electrode sheet, when the weight ratio B / A of the alkali metal polymer salt to the second binder is within the above range, it is beneficial to improve the adhesion of the electrode sheet, thereby enhancing the stability of the electrode sheet; and it is also beneficial to reduce the influence of the alkali metal polymer salt on the dispersion uniformity of the slurry particles in the active material layer and improve the cycling performance of the electrode sheet.

[0068] In some embodiments, the following relationship is satisfied among A, B, and C: 0 < A + B + C ≤ 6%. For example, A + B + C can be 0.1%, 0.3%, 0.7%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6% or within the range composed of any of the above values.

[0069] When the weight ratios of alkali metal polymer salt, second binder, and dispersant meet the above ranges, while improving the adhesion of the electrode and the uniformity of slurry particle dispersion in the electrode active material layer, it can also reduce the occupation of the active material contained in the active material layer by the above-mentioned additives, thereby increasing the capacity of the active material and the electrode.

[0070] In some embodiments, A, B, and C may satisfy one of the following relationships: A + B + C = 6%, 0 <A+B≤5%,0<C≤1.5%;A+B+C=5%,0<A+B≤5%,0<C≤1.5%;0<A+B+C≤6%,A+B=5%,0<C≤1.5%;0<A+B+C≤6%,A+B=4%,0<C≤1.5%;0<A+B+C≤6%,0<A+B≤5%,C=1.5%;0<A+B+C≤6%,0<A+B≤5%,C=1%。

[0071] When the weight ratios of alkali metal polymer salt, second binder, and dispersant simultaneously meet the above-mentioned ranges, it is beneficial to simultaneously improve the stability, cycle performance, and capacity of the electrode; moreover, while improving performance, the manufacturing cost of the electrode can be controlled at a relatively low level.

[0072] In some embodiments, the average molecular weight M of the alkali metal polymer salt satisfies: 3000≤M≤100,000, and 1.2≤B / A≤8.5.

[0073] In some implementations, 0.2 <C≤1%。

[0074] It should be noted that the average molecular weight M of the alkali metal polymer salt in this application refers to the number-average molecular weight of the alkali metal polymer salt.

[0075] In some embodiments, the average molecular weight M of the alkali metal polymer salt can be 3,000, 5,000, 7,000, 9,000, 10,000, 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, 80,000, 90,000, 100,000, or within any of the above values.

[0076] In some embodiments, B / A can be 1.2, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5 or within any of the above values.

[0077] In some embodiments, C can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or a range of any of the above values.

[0078] When the average molecular weight of the alkali metal polymer salt is between 3000 and 100,000, its own adhesion is relatively low. In the positive electrode active material layer, the alkali metal polymer salt is used as the first binder in combination with the second binder, and the weight ratio of it to the weight ratio of the second binder satisfies 1.2 ≤ B / A ≤ 8.5, which can effectively improve the adhesion of the electrode sheet, reduce the problem of demolding during the use of the electrode sheet, and improve the stability of the electrode sheet.

[0079] At the same time, when the average molecular weight of the alkali metal polymer salt is between 3000 and 100,000, due to its relatively short chain length and the electrostatic repulsion between the carboxyl groups in its molecular structure, the dispersion uniformity between the slurry particles in the active material layer can be at a relatively moderate level. In this case, by controlling the weight ratio of the dispersant to satisfy 0.2 ≤ C ≤ 1%, on the one hand, the dispersion uniformity between the slurry particles can be further improved to reach a relatively higher level, thereby further improving the cycle performance of the electrode sheet. On the other hand, the amount of the dispersant can be minimized to minimize its occupation of the active material in the active material layer, thereby improving the capacity of the active material and the electrode sheet. In addition, some dispersants are insulating materials, and when the addition amount is relatively large, it will affect the conductivity of the electrode sheet; when the weight ratio of the dispersant satisfies 0.2 < C ≤ 1%, its influence on the conductivity of the electrode sheet can also be minimized, and the conductivity of the electrode sheet can be improved.

[0080] In some embodiments, the average molecular weight M of the alkali metal polymer salt satisfies: 100,000 < M ≤ 400,000, and 0.8 ≤ B / A ≤ 8.1.

[0081] In some embodiments, 0.4 ≤ C ≤ 1.2%.

[0082] In some embodiments, the average molecular weight M of the alkali metal polymer salt can be 100,000, 200,000, 300,000, 400,000 or within the range composed of any of the above values.

[0083] In some embodiments, B / A can be 0.8, 1, 1.3, 1.5, 1.7, 2, 2.3, 2.5, 2.7, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.1 or within the range composed of any of the above values.

[0084] In some embodiments, C can be 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.1, 1.2 or within the range composed of any of the above values.

[0085] When the average molecular weight of the alkali metal polymer salt is between 100,000 and 400,000, its own adhesion is moderate. In the positive electrode active material layer, the alkali metal polymer salt is used as the first binder in combination with the second binder, and the weight ratio of it to the weight ratio of the second binder satisfies 0.8 ≤ B / A ≤ 8.1, which can further improve the adhesion of the electrode sheet, make the slurry particles in the active material layer contact well with the current collector, and further enhance the adhesion between the slurry particles, reduce the shedding of the slurry particles during the cyclic charge and discharge of the electrode sheet, so as to further improve the kinetic performance and stability of the electrode sheet.

[0086] At the same time, when the average molecular weight of the alkali metal polymer salt is between 100,000 and 400,000, the length of its chain is moderate at this time. During the process of preparing it into a slurry and using it for the electrode sheet, there will be a certain degree of agglomeration between the slurry particles, which will reduce the dispersion uniformity between the slurry particles to a certain extent. In this case, by controlling the weight ratio of the dispersant to satisfy 0.4 < C ≤ 1.2%, it can not only improve the dispersion uniformity between the slurry particles to a certain extent, thereby improving the cyclic performance of the electrode sheet to a certain extent; but also minimize the dosage of the dispersant, minimize its occupation of the active material in the active material layer, so as to improve the capacity of the active material and the electrode sheet. At the same time, it can also minimize the influence of the dispersant on the conductivity of the electrode sheet and improve the conductivity of the electrode sheet.

[0087] In some embodiments, the average molecular weight M of the alkali metal polymer salt satisfies: 400,000 < M ≤ 3,000,000, and 0.3 ≤ B / A ≤ 6.6.

[0088] In some embodiments, 0.7 < C ≤ 1.5%.

[0089] In some embodiments, the average molecular weight M of the alkali metal polymer salt can be 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, 1,000,000, 1,500,000, 2,000,000, 2,500,000, 3,000,000 or within the range composed of any of the above values.

[0090] In some embodiments, B / A can be 0.3, 0.5, 0.8, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.6 or within the range composed of any of the above values.

[0091] In some embodiments, C can be 0.7, 0.8, 0.9, 1.1, 1.2, 1.3, 1.4, 1.5 or within the range composed of any of the above values.

[0092] When the average molecular weight of the alkali metal polymer salt is 400,000 to 3,000,000, it already has certain adhesiveness by itself. In the active material layer, when it is used as the first binder in combination with the second binder, making the weight ratio of it to the weight of the second binder satisfy 0.3 ≤ B / A ≤ 6.6 can make the adhesion force of the electrode sheet reach a relatively higher level, make the contact between the slurry particles in the active material layer and the current collector better, and further improve the adhesion between the slurry particles, reduce the shedding of the slurry particles during the charge-discharge cycle of the electrode sheet, so as to further improve the kinetic performance and stability of the electrode sheet. In addition, since the cost of the alkali metal polymer salt is relatively high when its average molecular weight is relatively high, controlling B / A within the above range is also beneficial to reducing the preparation cost of the battery.

[0093] At the same time, when the average molecular weight of the alkali metal polymer salt is 400,000 to 3,000,000, although the high molecular weight alkali metal polymer salt has relatively high adhesiveness, due to its relatively long chain length, during the process of preparing it into a slurry and using it for the electrode sheet, the slurry particles will become agglomerated and larger due to the bridging effect between the molecular chains of the alkali metal polymer salt, which is likely to reduce the dispersion uniformity between the slurry particles and affect the cycle performance of the battery. In this case, controlling the weight ratio of the dispersant to satisfy 0.7 < C ≤ 1.5% can not only effectively improve the dispersion uniformity between the slurry particles, thus improving the cycle performance of the electrode sheet; but also minimize the dosage of the dispersant, minimize its occupation of the active material in the active material layer, so as to improve the capacity of the active material and the electrode sheet.

[0094] The average molecular weight of the alkali metal polymer salt has the meaning well-known in the art and can be tested by methods known in the art. For example, it can be tested by a gel permeation chromatograph (GPC, model LC-20ADXR) referring to the standard GB / T21863-2008 "Gel Permeation Chromatography (GPC) Using Tetrahydrofuran as Eluent".

[0095] In some embodiments, the mass percentage content of the alkali metal element contained in the first binder is m, and 3% ≤ m ≤ 8.9%. For example, m can be 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 8.9% or within the range composed of any of the above values.

[0096] Alkali metal polymer salts can dissociate alkali metal ions. By making the mass percentage of alkali metal elements in the first binder 3%~8.9%, the content of alkali metal ions in the active material layer can be increased, and the transport of alkali metal ions on the molecular chains of the first and second binders can be further promoted. This further shortens the time for alkali metal ions to be transported to the current collector, reduces polarization accumulation, and thus improves the transport efficiency of alkali metal ions, thereby further improving the fast charging capability of the battery.

[0097] In some embodiments, the comprising includes an alkali metal polyacrylate.

[0098] In some embodiments, the alkali metal polyacrylate includes one or more of lithium polyacrylate (PAALi), sodium polyacrylate (PAANa), and potassium polyacrylate (PAAK).

[0099] In some embodiments, the type of the second adhesive is not limited and can be selected according to actual needs. For example, the second adhesive may include one or more of styrene-butadiene rubber and its modified compounds, polyacrylic acid, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, polyvinylidene fluoride, and polytetrafluoroethylene.

[0100] It can be understood that when the electrode is a positive electrode, the active material layer is a positive active material layer. In this case, the second binder in the positive active material layer may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0101] It can be understood that when the electrode is a negative electrode, the active material layer is a negative active material layer. In this case, the second binder in the negative active material layer may include one or more of styrene-butadiene rubber (SBR) and its modified compounds, polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0102] In some embodiments, the type of dispersant is not limited and can be selected according to actual needs. For example, the dispersant may include one or more of polyethylene glycol, hydroxypropyl methylcellulose, polyvinylpyrrolidone, sodium dodecyl sulfonate, carboxymethyl starch, polyvinylbenzenemethyltrimethylammonium salt, polyethylene glycol octylphenyl ether, polystyrene sulfonic acid, polypropylene maleic acid, sodium methylene dimethyl dinaphthalene sulfonate, polyethyleneimine, N-methylpyrrolidone, carboxymethyl cellulose, and carboxymethyl cellulose salts.

[0103] In some embodiments, the carboxymethyl cellulose salt may include sodium carboxymethyl cellulose and / or potassium carboxymethyl cellulose.

[0104] In some embodiments, the active material layer further comprises an active material, which includes one of a positive electrode active material and a negative electrode active material.

[0105] Secondly, this application provides a secondary battery, including the electrode sheet described in the first aspect of this application.

[0106] It is understood that in a secondary battery, the electrode described in the first aspect of this application may be only a positive electrode, or only a negative electrode, or may be both a positive electrode and a negative electrode.

[0107] In some implementations, the secondary battery may include one or more of lithium-ion batteries, sodium-ion batteries, and potassium-ion batteries.

[0108] In addition, the secondary battery and power-consuming device of this application will be described below with appropriate reference to the accompanying drawings.

[0109] 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 between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0110] Positive electrode sheet

[0111] The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer including a positive active material.

[0112] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0113] In some embodiments, the positive electrode 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 polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on a polymeric material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the positive electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0114] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As a non-limiting example, the positive electrode active material may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, one or more of lithium cobalt oxides (such as LiCoO2), lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium manganese iron phosphate and carbon composites. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 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 Mn0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.85 Co 0.15 Al 0.05 O2.

[0115] Given that the Li content in cathode materials can change, how should the subscript for Li be defined in the general formula?

[0116] For ternary materials:

[0117] Li x (Ni a Co b Mn c ) 1-d M d O 2-y A y x is between 0.2 and 1.2;

[0118] Li x A a (Ni a Co b Mn c ) 1-d M d O 2-y A y x+a is 0.2-1.2.

[0119] For lithium manganese iron phosphate materials:

[0120] Li a Mn 1-y B y P 1-z C z O 4-n D n a is 0-1.1;

[0121] Li a A x Mn 1-y B y P 1-z C z O 4-n D n , a+x is 0-1.1.

[0122] The above limitation on x includes the molar content of Li under different charge and discharge states of the battery (typically the battery voltage is between 2-5V).

[0123] Understandably, lithium (Li) is intercalated and deintercalated during the charging and discharging process of a battery, and the Li content in the positive electrode varies depending on the state of discharge. Unless otherwise specified, the Li content in the examples of positive electrode materials listed in this application refers to the initial state of the material. When a positive electrode material is applied to a positive electrode in a battery system, the Li content in the positive electrode material typically changes after charge-discharge cycles. The Li content can be measured using molar content, but is not limited to this. Regarding "Li content refers to the initial state of the material," the initial state of the material refers to its state before being added to the positive electrode slurry. It is understood that new materials obtained by appropriately modifying the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for the positive electrode material; non-limiting examples include coating modification.

[0124] In the examples of cathode materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause changes in the molar content of oxygen, and the actual O content will fluctuate. The O content can be measured in molar content, but is not limited to this.

[0125] In some embodiments, the positive electrode active material may also include at least one of the following materials: sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0126] As an optional technical solution in this application, the transition metal in the sodium transition metal oxide may include one or more of 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 MO2, where M can include one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 < x ≤ 1.

[0127] As an optional technical solution in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds with anionic units. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be one or more of P, S, and Si; n represents (YO4). n- The price state.

[0128] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (YO4) ions. n-A class of compounds consisting of anionic units and halide anions. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may 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.

[0129] Polyanionic compounds can also be sodium-containing tetrahedral (YO4) compounds. 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 include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and m represents (ZO). y ) m+ The valence state; halogens can be one or more of F, Cl and Br.

[0130] Polyanionic compounds can include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F and Na3(VO y )2(PO4)2F 3-2y One or more of (0≤y≤1). Among them, M' in NaM'PO4F can include one or more of V, Fe, Mn and Ni.

[0131] Prussian blue compounds can contain sodium ions, transition metal ions, and cyanide ions (CN). - A class of compounds containing Prussian blue. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. A non-limiting example of Prussian blue compounds is Na. a Me b Me' c (CN)6, wherein Me and Me' can each be one or more of Ni, Cu, Fe, Mn, Co and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0132] In some embodiments, the positive electrode active material layer may optionally include a conventional binder. As a non-limiting example, the conventional 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.

[0133] In some embodiments, the positive electrode active material layer 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.

[0134] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto at least one surface of the positive electrode current collector, and obtaining the positive electrode sheet after drying, cold pressing, and other processes. The solvent can be selected from, but is not limited to, any of the solvents described in the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40wt%~80wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000~25000 mPa·s. When coating the positive electrode slurry, the coating areal density (dry weight, minus solvent) can be 15~35 mg / cm². 2 The compaction density of the positive electrode sheet can be 3.0~3.6 g / cm³. 3 The concentration can be selected as 3.3~3.5g / cm³. 3 .

[0135] Negative electrode sheet

[0136] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, wherein the negative active material layer includes a negative active material.

[0137] 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 active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0138] 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 polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on the polymeric material substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the negative electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0139] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As a non-limiting example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0140] In some embodiments, the negative electrode active material layer may optionally include a conventional binder. Conventional binders may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0141] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. 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.

[0142] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0143] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (a non-limiting example of a solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto at least one surface of a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing, and other processes. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt%~60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000~10000 mPa·s. When coating the negative electrode slurry, the coating unit areal density (dry weight, deducting solvent) can be 75~220 g / m². 2 The compaction density of the negative electrode sheet can be 1.0 g / cm³. 3 ~1.8g / cm 3 .

[0144] electrolytes

[0145] Electrolytes function to conduct ions between the positive and negative electrode plates. This application does not impose any particular restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or completely solid.

[0146] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0147] In some embodiments, the electrolyte 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 (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0148] In some embodiments, the solvent may include ethylene carbonate (EC, ), propylene carbonate (PC, ), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butene carbonate ( One or more of the following: fluoroethylene carbonate (FEC), 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.

[0149] 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.

[0150] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), etc.

[0151] Separating membrane

[0152] 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.

[0153] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may 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 may be the same or different, without particular limitation.

[0154] In some embodiments, the thickness of the isolation membrane is 6~40μm, optionally 12~20μm.

[0155] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding process or a stacking process.

[0156] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0157] In some embodiments, the outer packaging of the secondary battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft pack, such as a pouch-type soft pack. The material of the soft pack can be plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0158] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0159] In this application, unless otherwise specified, "cell battery" refers to the basic unit capable of converting chemical energy into electrical energy, and generally includes at least a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process of the battery, active ions move back and forth between the positive and negative electrode plates, inserting and extracting. The electrolyte acts as a conductor for the active ions between the positive and negative electrode plates.

[0160] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 The example shown is a square-structured battery cell 5.

[0161] In some of these embodiments, reference is made 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. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to actual needs.

[0162] The secondary battery can be either battery module 4 or battery pack 1.

[0163] A battery module includes at least one battery cell. The number of battery cells in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0164] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0165] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0166] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select an appropriate number according to the application and capacity of the battery pack.

[0167] Figure 4 and Figure 5This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0168] In addition, this application also provides an electrical device, which includes the secondary battery provided in this application. The secondary battery can be used as the power source of the electrical device or as the energy storage unit of 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. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, 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.

[0169] As an electrical device, a rechargeable battery can be selected based on its usage requirements.

[0170] Figure 6 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. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0171] 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.

[0172] Example

[0173] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where the technology or conditions are not specified in the embodiments, they are performed 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 all conventional products that can be obtained commercially.

[0174] Example 1-1

[0175] (1) Preparation of negative electrode sheet

[0176] With a solid content of 53%, graphite (anode active material), carboxymethyl cellulose (CMC), conductive carbon (SP), binder (SBR), and lithium polyacrylate (PAALi) were mixed at high speed in deionized water at a weight ratio of 96:1:0.5:2:0.5 to obtain a cathode slurry. The weight of the obtained cathode slurry was controlled at 0.209 g / 1540.25 mm. 2 The paste is uniformly coated on both sides of a 10μm thick copper foil. After the paste on the copper foil is fully dried in an environment of 50~140℃, it is cold-pressed with a compaction of 1.7g / cc to obtain a negative electrode sheet with a thickness of 0.1694mm, which is then cut into 97mm wide pieces for later use.

[0177] (2) Preparation of positive electrode sheet

[0178] With a solid content of 62%, lithium iron phosphate (LFP) positive electrode active material, PVDF binder, and conductive carbon (SP) were dispersed in NMP solvent at a weight ratio of 97:2:1 and mixed evenly to obtain a positive electrode slurry. The weight of the obtained positive electrode slurry was controlled at 0.45 g / 1540.25 mm. 2 The paste is uniformly coated on both sides of a 15μm thick aluminum foil. After the paste on the aluminum foil is fully dried in an environment of 50~140℃, it is cold-pressed with a compaction of 2.6g / cc to obtain a positive electrode sheet with a thickness of 0.2384mm, which is then cut into 100mm wide pieces for later use.

[0179] (3) Separating membrane

[0180] A 7μm thick polypropylene separator membrane was selected.

[0181] (4) Preparation of electrolyte

[0182] The organic solvent was a mixture containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and propylene carbonate (PC), with a volume ratio of EC, EMC, and PC of 1:1:1. Thoroughly dried lithium salt LiPF6 was dissolved in the organic solvent and mixed thoroughly in an argon-atmosphere glove box with a water content of <10 ppm to obtain the electrolyte. The concentration of the lithium salt was 1 mol / L.

[0183] (5) Battery manufacturing

[0184] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. After being wound into a square bare cell, it is placed in an aluminum-plastic film, baked at 80°C to remove water, and then 10g of the corresponding non-aqueous electrolyte is injected and sealed. After processes such as standing, hot and cold pressing, formation, clamping, and capacity testing, the finished battery is obtained.

[0185] Examples 1-2 to 1-17, Examples 2-1 to 2-15, Examples 3-1 to 3-14, Comparative Examples 1-1 to 1-4, Comparative Examples 2-1 to 2-4, and Comparative Examples 3-1 to 3-4

[0186] The preparation of the electrode and the battery is similar to that in Example 1-1, except that the relevant parameters in the preparation process are adjusted, as detailed in Tables 1-6 below. Here, "~" indicates that M is near the corresponding value; for example, "~4000" means that M is near 4000, i.e., M is approximately 4000.

[0187] Table 1

[0188]

[0189] Table 2

[0190]

[0191] Table 3

[0192]

[0193] Table 4

[0194]

[0195] Table 5

[0196]

[0197] Table 6

[0198]

[0199] In addition, the batteries obtained in the above embodiments and comparative examples were subjected to cycle performance tests, and the test results are shown in Tables 7 to 9 below.

[0200] Test section

[0201] (1) Method for testing the mass percentage of alkali metal elements

[0202] A certain mass M of alkali metal polyacrylate sample is taken, and the mass m1 of the alkali metal element is determined by inductively coupled plasma atomic emission spectrometry (ICP). The average mass percentage of the alkali metal element in the alkali metal polyacrylate is then calculated as m1 / M × 100%. The sample is prepared as follows: 0.2 g of sample is weighed into a beaker, 10 mL of concentrated HNO3 solution is added, and the sample is placed on a 180℃ heating plate for digestion for 30 min. After digestion, the sample is cooled to room temperature, and the digested solution is transferred to a 50 mL volumetric flask and diluted to volume. Testing is performed according to USEPA-6010D-2018. A standard test solution is prepared; this solution is the multi-element ICP analysis standard solution from the National Nonferrous Metals Testing Center, with curve concentration points of 0, 0.2, 0.5, 1.0, and 2.0 mg / L. A standard solution calibration curve is first established using the instrument, with the sample mass and volume entered. The digested solution is then tested. Solutions exceeding the curve range need to be diluted before testing. Finally, the presence of elements is identified by the characteristic spectra of atomic emission (qualitative analysis), and the content of elements is determined based on the intensity of the spectral lines (quantitative analysis).

[0203] (2) Cyclic performance test

[0204] At 25℃, the battery is charged at a constant current of 1 / 3C to a voltage of 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C. After resting for 5 minutes, the battery is discharged at a constant current of 1C to a voltage of 2.0V. This constitutes one charging cycle, and the discharge capacity of this cycle is the discharge capacity of the first cycle. After performing the cycle charging test in the above manner, the cycle ends when the discharge capacity decays to 80% of the initial value. The total number of cycles is recorded to obtain the battery's cycle performance (cycle life).

[0205] (3) Fast charging performance test

[0206] Using Cu wire as the three electrodes, the battery is charged at a 5C rate until the anode potential drops to 0mV. Then, it switches to a lower charging rate, charging sequentially at 4C, 3C, 2C, and 1C to obtain the cell's maximum charging capacity map. Starting from 0% SOC, the battery is charged in stages at its maximum capacity map until the cell's cutoff voltage reaches 3.8V. The time required to charge from 20% SOC to 80% SOC is recorded as the battery's fast charging time.

[0207] Table 7

[0208]

[0209] Table 8

[0210]

[0211] Table 9

[0212]

[0213] In Tables 7-9 above, comparing Examples 1-1-1-17 with Comparative Examples 1-1-1-4, Examples 2-1-2-15 with Comparative Examples 2-1-2-4, and Examples 3-1-3-14 with Comparative Examples 3-1-3-4, it can be seen that the cycle life of the examples is higher than that of the corresponding comparative examples. This indicates that by adjusting the ratio of the first binder and the second binder in the active material layer, this application can improve the cycle performance and fast charging performance of the battery.

[0214] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0215] 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. 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, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. An electrode sheet, characterized in that, It includes an active material layer, and the active material layer contains a first binder and a second binder. The first binder includes an alkali metal polymer salt, and the average molecular weight M of the alkali metal polymer salt satisfies: 400,000 < M ≤ 3,000,000. The binding strength of the second binder is greater than that of the first binder. The weight percentage of the alkali metal polymer salt in the active material layer is A, and the weight percentage of the second binder in the active material layer is B. The relationship between A and B satisfies: 0 < A + B ≤ 5%, 0.3 ≤ B / A ≤ 6.

6. The active material layer further contains a dispersant, and the weight percentage of the dispersant in the active material layer is C, and C satisfies: 0.7 ≤ C ≤ 1.5%.

2. The electrode sheet according to claim 1, characterized in that, The relationship among A, B, and C satisfies: 0 < A + B + C ≤ 6%.

3. The electrode sheet according to claim 1 or 2, characterized in that, The mass percentage content of the alkali metal element contained in the first binder is m, and 3% ≤ m ≤ 8.9%.

4. The electrode sheet according to any one of claims 1-3, characterized in that, The alkali metal polymer salt includes alkali metal polyacrylate.

5. The electrode sheet according to claim 4, characterized in that, The alkali metal polyacrylate includes one or more of lithium polyacrylate, sodium polyacrylate, and potassium polyacrylate.

6. The electrode sheet according to any one of claims 1-5, characterized in that, The second binder includes one or more of styrene-butadiene rubber and its modified compounds, polyacrylic acid, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, polyvinylidene fluoride, and polytetrafluoroethylene.

7. The electrode sheet according to any one of claims 1-6, characterized in that, The dispersant includes one or more of polyethylene glycol, hydroxypropyl methyl cellulose, polyvinylpyrrolidone, sodium dodecyl sulfonate, carboxymethyl starch, polyethylene benzyl trimethyl ammonium salt, polyethylene glycol octyl phenyl ether, polystyrene sulfonic acid, polypropylene maleic acid, sodium methylene bisnaphthalene sulfonate, polyethyleneimine, N-methylpyrrolidone, carboxymethyl cellulose, and carboxymethyl cellulose salt.

8. The electrode sheet according to any one of claims 1-7, characterized in that, The active material layer further contains an active material, and the active material includes one of a positive electrode active material and a negative electrode active material.

9. A secondary battery, characterized in that, It includes the electrode sheet according to any one of claims 1-8.

10. An electrical device, characterized in that, It includes the secondary battery according to claim 9.

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