Secondary battery and electric device comprising same

Abstract

The invention provides a secondary battery which comprises at least two electrode plates, at least one electrode plate comprises an electrolyte in the electrode plate, and the electrolyte in the electrode plate comprises a gel-state electrolyte in the electrode plate and an electrolyte solution in the electrode plate. And the ratio RW of the mass of the electrolyte salt in the gel-state electrolyte in the pole piece to the mass of the electrolyte salt in the electrolyte in the pole piece is more than 1 and less than 9.

Description

Secondary battery and electrical device containing same Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to secondary batteries and electrical devices containing the same. Background Art

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] With the accelerated pace of life and the development of various electronic products such as smart phones, tablets, smart wearables, power tools and electric vehicles, comprehensive indicators such as the cycle performance and battery rate of secondary batteries are receiving more and more attention.

[0004] Based on this, research on improving the comprehensive performance of secondary batteries is of great value.

[0005] Summary of the Invention

[0006] In view of the above problems, the present application provides a secondary battery and an electrical device containing the same. The secondary battery comprises a pore of at least one electrode plate containing a properly matched gel electrolyte and liquid electrolyte, which can significantly improve the battery's rate and cycle performance, thereby facilitating the production of a secondary battery with superior overall performance.

[0007] In a first aspect, the present application provides a secondary battery comprising at least two electrode plates, any one of the electrode plates comprising an active material layer disposed on at least one side of the electrode plate; the active material layer on at least one side of at least one of the electrode plates comprising active particles and an intra-plate electrolyte located in pores between the active particles; the intra-plate electrolyte comprising an intra-plate gel electrolyte and an intra-plate electrolyte; the intra-plate gel electrolyte and the intra-plate electrolyte each independently comprising an electrolyte salt, and the ratio R of the mass of the electrolyte salt in the intra-plate gel electrolyte to the mass of the electrolyte salt in the intra-plate electrolyte W Satisfy 1 <R W <9.

[0008] By arranging a gel / liquid composite electrolyte in the pores of at least one electrode plate in a secondary battery, the electrolyte in the plate includes both a gel electrolyte and a liquid electrolyte. On the one hand, the ion path between the active particles in the electrode plate can be enhanced, and the liquid electrolyte can be squeezed out due to the expansion and contraction of the plate during charging and discharging can be reduced or avoided. On the other hand, the gel electrolyte is wrapped around the surface of the active material to reduce the direct contact between the active material and the liquid electrolyte, thereby reducing the electrolyte consumption rate during the cycle and improving the battery life, so that the secondary battery can obtain better battery rate and cycle performance. The step is to reasonably adjust the distribution mode of the electrolyte salt in the gel and liquid electrolyte in the gel / liquid composite electrolyte in the electrode plate to form a gel / liquid composite electrolyte in the plate with a special composite mode, so that the mass of the electrolyte salt in the gel electrolyte is higher than the mass of the electrolyte salt in the electrolyte solution, that is, the electrolyte salt in the pores of the electrode plate is more distributed in the gel electrolyte. At this time, it can better compensate for the consumption and shortage of electrolyte salt near the active material caused by the extension of the cycle time, inhibit the deterioration of the battery cycle performance, significantly extend the cycle life of the secondary battery, and is conducive to providing better battery rate performance in a longer cycle period.

[0009] In some embodiments, 1.2≤R W ≤8.5; optionally, 1.5≤R W ≤8.5.

[0010] By regulating the distribution of electrolyte salts in the gel / liquid composite electrolyte within the electrode plate, the electrolyte salts can be more appropriately distributed between the gel and liquid states, thereby improving the cycle life of the secondary battery and the battery rate performance during long cycles.

[0011] In some embodiments, the active material layer on at least one side of at least one of the electrode plates is a multi-layer structure, and the electrolyte in the plate is distributed in at least a portion of the pores in the outer active layer of the multi-layer structure;

[0012] Among them, in the multi-layer structure of the active material layer, the outer active layer is farthest away from the center of the pole piece along the thickness direction of the pole piece.

[0013] A multilayer structure can be set in the active material layer of at least one electrode plate, and the gel / liquid composite electrolyte in the plate of the aforementioned special gel / liquid composite method is distributed at least in the outer active layer, so that the electrolyte in the plate provides a better adsorption and polymerization effect, and has a better infiltration rate for the active particles, which is beneficial to improving the kinetic performance and can also better exert the aforementioned effect of improving the battery rate and cycle performance.

[0014] In some embodiments, in the electrode sheet having a multi-layer structure, the porosity of the outer active layer is higher than the porosity of the inner active layer; wherein the inner active layer is located inside the active material layer.

[0015] When the active material layer of the electrode plate has a multi-layer structure, on the basis of the outer active layer (or upper active layer) being provided with the aforementioned gel / liquid composite electrolyte in the plate with a special gel / liquid combination, the porosity of the outer active layer can be further made higher than that of the inner active layer. At this time, on the one hand, the outer active layer can be given higher dynamics and the charging window can be improved. On the other hand, the surface of the active material layer can be more easily infiltrated by the liquid phase component of the electrolyte.

[0016] In some embodiments, at least one of the electrode plates is a negative electrode plate, the active material layer of the negative electrode plate is a negative electrode active material layer, and the negative electrode active material layer is located on at least one side of the negative electrode plate.

[0017] For negative electrode plates, which are prone to volume expansion during battery cycling, the pores in the discharged state are larger than those in the charged state. If the pores are not effectively filled with electrolyte, bridges are prone to breakage, which deteriorates the electrical contact between the negative electrode active particles and the distance for active ion transport, and also leads to a decrease in rate discharge capability. The aforementioned special composite gel / liquid composite electrolyte can be placed at least within the negative electrode active material layer of the negative electrode plate, solidifying a portion of the electrolyte in the pores of the negative electrode active material layer. This reduces or prevents the extrusion of electrolyte between the active particles, significantly suppressing the deterioration of battery performance.

[0018] In some embodiments, the negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material comprises a silicon-based material;

[0019] Optionally, the mass proportion of the silicon-based material in the negative electrode active material is recorded as silicon content, and the silicon content is ≥3%.

[0020] Further optionally, the silicon content is 3% to 40%.

[0021] When the negative electrode plate contains silicon-based materials, it is beneficial to take into account the high specific energy strategy of the battery, but the expansion problem is also exacerbated. At this time, the expansion and contraction during the charging and discharging process will be more obvious. The gel / liquid composite electrolyte of the above-mentioned special composite method is set at least in the negative electrode plate, which can more significantly inhibit the deterioration of battery performance.

[0022] In some embodiments, the negative electrode active material layer has the aforementioned multi-layer structure, wherein the porosity of the outer active layer is 20% to 50%; further optionally 30% to 50%; further optionally 30% to 45%.

[0023] When the active material layer of the negative electrode sheet has any of the aforementioned multilayer structures, the porosity of the active layer on the outer side of the negative electrode can be further regulated, which is more conducive to improving the kinetics and charging window, and is also conducive to making the surface of the negative electrode active material layer more easily wetted by the liquid phase components of the electrolyte.

[0024] In some embodiments, the negative electrode active material layer on either side is independently 2.4≤R W / b1≤45, where b1 is the porosity of the negative electrode active material layer on either side;

[0025] Optionally, 3.75≤R W / b1≤36;

[0026] Further optionally, 7.5≤R W / b1≤18.

[0027] In some embodiments, the porosity b1 of the negative electrode active material layer on either side is independently 20% to 50%;

[0028] Optionally, the porosity b1 of the negative electrode active material layer on either side is independently 25% to 45%;

[0029] Further optionally, the porosity b1 of the negative electrode active material layer on either side is independently 25% to 40%.

[0030] For any of the aforementioned negative electrode sheets having the gel / liquid composite electrolyte of the present application, the electrolyte salt mass ratio R in the gel / liquid electrolyte on either side of the negative electrode sheet can be adjusted. W With the negative electrode porosity b1, through R W / b1 regulation makes the distribution of electrolyte salt in the negative electrode sheet and the porosity of the electrode sheet more optimized. On the one hand, the regulation of the porosity b1 of the negative electrode sheet is used to optimize the infiltration of the electrolyte into the interior. On the other hand, the R W The regulation can optimize the cycle life of secondary batteries and improve the battery rate performance during long cycles, thereby comprehensively improving the cycle performance, rate performance and kinetic performance of secondary batteries.

[0031] In some embodiments, at least one of the electrode plates is a positive electrode plate, the active material layer of the positive electrode plate is a positive electrode active material layer, and the positive electrode active material layer is located on at least one side of the positive electrode plate.

[0032] The positive electrode plate can adopt the gel / liquid composite electrolyte design of the aforementioned special composite method, thereby reducing or avoiding the extrusion of the electrolyte between particles, inhibiting the deterioration of battery performance, extending the cycle life of the secondary battery, and facilitating the provision of better battery rate performance over a long cycle period.

[0033] In some embodiments, the positive electrode active material layer has the aforementioned multi-layer structure, wherein the porosity of the outer active layer is 10% to 40%; further optionally 15% to 40%; further optionally 20% to 35%.

[0034] When the active material layer of the positive electrode sheet has any of the aforementioned multilayer structures, the porosity of the active layer on the outer side of the positive electrode can be further regulated, which is more conducive to improving the kinetics and charging window, and is also conducive to making the surface of the positive electrode active material layer more easily wetted by the liquid phase components of the electrolyte.

[0035] In some embodiments, the positive electrode active material layer on either side independently has 3.75≤R W / b2≤90, wherein b2 is the porosity of the positive electrode active material layer on either side;

[0036] Optionally, 3.75≤R W / b2≤60;

[0037] Further optionally, 4.2≤R W / b2≤25.

[0038] In some embodiments, the porosity b2 of the positive electrode active material layer on either side is independently 10% to 40%;

[0039] Optionally, the porosity b2 of the positive electrode active material layer on either side is independently 10% to 35%;

[0040] Further optionally, the porosity b2 of the positive electrode active material layer on either side is independently 15% to 35%.

[0041] For any of the aforementioned positive electrode sheets having the gel / liquid composite electrolyte of the present application, the electrolyte salt mass ratio R in the gel / liquid electrolyte on either side of the positive electrode sheet can be adjusted. W With the positive electrode porosity b2, through R W / b2 regulation makes the distribution method of electrolyte salt in the positive electrode sheet and the porosity of the electrode sheet more optimized. On the one hand, the regulation of the porosity b2 of the positive electrode sheet is used to optimize the infiltration of the electrolyte into the interior. On the other hand, the R W The regulation can optimize the cycle life of secondary batteries and improve the battery rate performance during long cycles, thereby comprehensively improving the cycle performance, rate performance and kinetic performance of secondary batteries.

[0042] In some embodiments, the secondary battery includes a positive electrode sheet, a negative electrode sheet, and a separator, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet;

[0043] The positive electrode sheet and the negative electrode sheet meet one or both of the following characteristics:

[0044] The negative electrode sheet is as defined above;

[0045] The positive electrode plate is as defined above.

[0046] One or both of the positive electrode sheet and the negative electrode sheet in the secondary battery can have the aforementioned gel / liquid composite electrolyte design within the electrode sheet, thereby exerting the aforementioned advantages or achieving synergistic efficiency of the positive and negative electrode sheets.

[0047] In some embodiments, the positive electrode sheet includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a lithium ion material;

[0048] Optionally, the secondary battery is a lithium-ion secondary battery.

[0049] In some embodiments, the electrolyte salt in the electrode sheet includes an electrolyte lithium salt;

[0050] Optionally, the electrolyte lithium salt is distributed in at least one or both of the gel electrolyte in the electrode sheet and the electrolyte in the electrode sheet in the same electrode sheet;

[0051] Optionally, the electrolyte lithium salt is distributed at least in the pores of the positive electrode active material layer;

[0052] Optionally, the negative electrode plate includes a negative electrode active material layer, and the electrolyte lithium salt is distributed at least in the pores of the negative electrode active material layer.

[0053] The special design of the gel / liquid composite electrolyte in the aforementioned electrode can be applicable to lithium-ion secondary batteries. Furthermore, the electrolyte salt in the electrode can include an electrolyte lithium salt that is more compatible with the active lithium ions, thereby promoting the efficient transmission of active lithium ions, which is beneficial for the secondary battery to have better comprehensive performance in terms of power density, cycle life, etc.

[0054] In a second aspect, the present application provides an electrical device comprising the secondary battery described in the first aspect of the present application.

[0055] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to better describe and illustrate the embodiments or examples of the applications disclosed herein, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered to limit the scope of the disclosed applications, the embodiments or examples currently described, and any of the best modes currently understood for these applications. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0057] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0058] FIG2 is an exploded view of the secondary battery of one embodiment of the present application shown in FIG1 ;

[0059] FIG3 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.

[0060] Explanation of reference numerals: 5, secondary battery; 51, housing; 52, electrode assembly; 53, cover plate; 6, power-consuming device. DETAILED DESCRIPTION

[0061] Below, some embodiments of the secondary battery and the electrical device containing the same of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0062] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are also listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is merely an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to listing the parameter as, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and so on. For example, when a parameter is expressed as an integer selected from "2-10", this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0063] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. Mentioning "embodiment" in this article means that the specific features, structures or characteristics described in conjunction with the embodiment can be included in at least one embodiment or embodiment of the present application. The appearance of this phrase in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The "embodiment" mentioned in this article has a similar understanding.

[0064] Unless otherwise specified, all steps of the present 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 may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0065] Unless otherwise specified, the terms "include," "contain," and "comprise" used in this application are open-ended or closed-ended. For example, "include" and "comprise" can mean that other elements or temporal features not listed are also included, or that only the listed elements or temporal features are included. Elements include materials or components, structures, elements, and instruments; non-limiting examples of temporal features include actions, conditions for the occurrence of actions, timing, and states.

[0066] 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." Furthermore, 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).

[0067] In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0068] In this application, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more relevant listed items, and also include any and all combinations of the relevant listed items, wherein the arbitrary and all combinations include any two relevant listed items, any more relevant listed items, or a combination of all relevant listed items. For example, "A and / or B" means a group consisting of A, B, and "a combination of A and B." Among them, "including A and / or B" can mean "including A, including B, and including A and B", and can also mean "including A, including B, or including A and B", which can be appropriately understood according to the sentence in which it is located.

[0069] In this application, references to "plurality," "multiple," and the like, unless otherwise specified, refer to a quantity greater than or equal to two. For example, "one or more" refers to one or greater than or equal to two. It is understood that references to "any number" of items refer to any suitable combination of multiple items, i.e., any combination of "any number" of items that is consistent with the present application and that allows for the implementation of the present application.

[0070] The terms "combination thereof", "any combination thereof", "any combination thereof" and the like used in this application include all suitable combinations of any two or more of the listed items.

[0071] In this application, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc. shall be based on the technical solution that can implement this application.

[0072] In this application, the terms "preferred," "better," "more preferred," and "suitable" are used solely to describe preferred implementations or examples and should not limit the scope of protection of this application. If multiple "preferred" terms appear in a technical solution, each "preferred" term is independent unless otherwise specified and there are no contradictions or mutual constraints.

[0073] In this application, the terms "optionally," "optional," and "optional" mean optional or dispensable, i.e., they refer to either option being selected from two parallel options: "with" or "without." If a technical solution contains multiple "optional" clauses, each "optional" clause is independent unless otherwise specified and there are no contradictions or constraints.

[0074] In this application, "further", "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be understood as limiting the scope of protection of this application.

[0075] In this application, the terms "first," "second," "third," "fourth," etc. in "the first aspect," "the second aspect," "the third aspect," "the fourth aspect," etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or quantity, nor should they be understood as implicitly indicating the importance or quantity of the indicated technical features. Furthermore, "first," "second," "third," "fourth," etc. serve only as non-exhaustive enumeration and description, and should be understood not to constitute a closed-ended limitation on quantity.

[0076] In this application, the term "room temperature" generally refers to 4°C to 35°C, and may refer to 20°C ± 5°C. In some embodiments of this application, room temperature refers to 20°C to 30°C, for example, 25°C.

[0077] In this application, when referring to a data range, if the unit is only after the right endpoint, it means that the units of the left and right endpoints are the same. For example, 3~5h or 3-5h both mean that the units of the left endpoint "3" and the right endpoint "5" are both hours.

[0078] The masses of the relevant components mentioned in the examples of this application may not only refer to the content of each component, but also represent the proportional relationship between the masses of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Furthermore, the masses described in the examples of this application may be mass units known in the chemical industry, such as μg, mg, g, and kg.

[0079] During the battery's charge and discharge, the negative and positive electrodes will expand and contract due to the changes in the embedding and deintercalation of active ions. In the charge state, the negative electrode expands and the positive electrode contracts. In the discharge state, the volume of the expanded negative electrode shrinks while the volume of the contracted positive electrode increases. There are pores between the active particles of the electrode electrode, and the pores of the electrode electrode in the expanded state are larger than those in the contracted state. During the battery's charge and discharge process, the pores of the active particles in the electrode electrode of a traditional secondary battery are filled with electrolyte. The expansion and contraction of the electrode can easily cause the liquid electrolyte in the electrode pores to be squeezed out, and may also cause the conductive path between the active particles in the electrode electrode to be unstable. In addition, direct contact between the electrolyte and the active particles can easily lead to electrolyte consumption. This results in less than ideal charge and discharge rate performance and battery cycle life of traditional secondary batteries.

[0080] Based on this, in the first aspect, the present application provides a secondary battery comprising at least two electrode plates, wherein at least one electrode plate comprises an electrolyte in the plate, the electrolyte in the plate comprises a gel electrolyte in the plate and an electrolyte solution in the plate, and the ratio of the mass of the electrolyte salt in the gel electrolyte in the plate to the mass of the electrolyte salt in the electrolyte solution in the plate is R W Satisfy 1 <R W <9.

[0081] In the present application, unless otherwise specified, a secondary battery includes a positive electrode sheet and a negative electrode sheet, and therefore includes at least two electrode sheets.

[0082] In the present application, any electrode plate includes an active material layer, and the active material layer is disposed on at least one side of the electrode plate, that is, the active material layer in the electrode plate can be disposed on one or both sides of the electrode plate. When the active material layer is disposed on both sides of the electrode plate: a current collector can be disposed between the active material layers on both sides; the composition of the active material layers on both sides can be the same or different; the thickness of the active material layers on both sides can also be the same or different; the number of structural layers of the active material layers on both sides can be the same or different; when both sides have the same number of structural layers, the multilayer structures on both sides can be the same or different in terms of parameters such as composition and thickness.

[0083] In this application, unless otherwise specified, "active material layer" includes at least one of the positive active material layer of the positive electrode sheet and the negative active material layer of the negative electrode sheet, and depending on the specific circumstances, it may refer to the positive active material layer or the negative active material layer. It is understood that the positive active material layer contains positive active material, and the negative active material layer contains negative active material. It is understood that when the active material layer has a multilayer structure, in this case, the active material layer includes multiple active layers, each of which independently contains the corresponding active material.

[0084] In this application, unless otherwise specified, the electrode plate can be a positive electrode plate or a negative electrode plate. The "active material" in the electrode plate refers to a substance that can reversibly embed and release active ions; since the active material is usually in granular form, it is also called "active particles". Unless otherwise specified, "negative active material" refers to a substance used for negative electrode plates that can reversibly embed and release active ions, also known as negative active material or negative active particles; "positive active material" refers to a substance used for positive electrode plates that can reversibly release and embed active ions, also known as positive active material or positive active particles. When the secondary battery is charged, the active ions are released from the positive electrode and embedded in the negative electrode through the electrolyte; when the secondary battery is discharged, the active ions are released from the negative electrode and embedded in the positive electrode. There is no special limitation on the active ions.

[0085] In the present application, the active ions may include at least one of lithium ions, sodium ions, and potassium ions, and further, the active ions may be lithium ions, sodium ions, or a combination thereof. When the active ions are mainly lithium ions (such as a molar ratio of more than 80%), it corresponds to a lithium ion secondary battery. When the active ions are mainly sodium ions (such as a molar ratio of more than 80%), it corresponds to a sodium ion secondary battery.

[0086] In this application, "active material" and "active substance" have the same meaning and can be used interchangeably. Active materials are generally granular and can also be called "active particles"; "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.

[0087] In the present application, unless otherwise specified, the secondary battery includes an electrolyte, and at least a portion of the electrolyte is disposed inside at least one electrode plate and is located in the pores between the active particles in the electrode plate in which it is located. The electrolyte can separate ions under the action of voltage and has the function of conducting active ions. The electrolyte inside at least one electrode plate is a mixture of a gel electrolyte and a liquid electrolyte; further, the form of the electrolyte distributed inside the remaining electrode plates is not particularly limited and can be liquid, gel or fully solid. In the present application, unless otherwise specified, the electrolyte distributed inside the electrode plate is referred to as an "electrolyte inside the plate", and in the present application, the electrolyte comprising a mixture of a gel electrolyte and a liquid electrolyte is referred to as a "gel / liquid composite electrolyte", and the gel / liquid composite electrolyte located inside the electrode plate is also referred to as a "gel / liquid composite electrolyte inside the plate".

[0088] In this application, a "gel electrolyte" is a semi-solid electrolyte having the following characteristics: it comprises a gel skeleton, a gelling solvent located within the gel skeleton region, and an electrolyte salt dissolved in the gelling solvent. The gel skeleton is a cross-linked polymer with a three-dimensional network structure; the gelling solvent is bounded within the mesh of the gel skeleton and cannot flow freely, resulting in the electrolyte in the gel skeleton region being a gel-like semi-solid. The electrolyte solvent in the gel electrolyte is dissolved within the gelling solvent and cannot migrate freely throughout the gel electrolyte, but can move over short distances within the confined space of the gel skeleton mesh. In addition, the gelling solvent has a certain degree of continuous distribution within the gel skeleton, allowing the gel electrolyte to still conduct active ions. In addition, the chain segments between adjacent crosslinks in the gel skeleton still have a certain degree of flexibility, giving the network structure not only a certain degree of support but also a certain degree of elasticity. However, the chain segments between these crosslinks are confined between the corresponding nodes of the mesh and cannot diffuse freely in the solvent like free molecules. Therefore, in terms of physical form, the gel electrolyte combines the solidity of the gel skeleton with the confined mobile phase of the gelling solvent, which is significantly different from traditional electrolytes that are free-flowing and have no fixed shape.

[0089] In the present application, "liquid electrolyte" is a liquid electrolyte, which includes an electrolyte salt and a solvent. The solvent is free-flowing, and the electrolyte salt dissolved in the solvent is free-migrating. The liquid electrolyte as a whole is free-flowing and has no fixed shape.

[0090] In a gel electrolyte, the electrolyte is in a colloidal state, which binds the electrolyte salts therein within the gel electrolyte, resulting in a low migration ability; whereas in a liquid electrolyte, the electrolyte is in a liquid state, and the electrolyte salts therein can be free in the liquid electrolyte, resulting in a strong migration ability. In the electrode plates of the present application, the cross-migration of the electrolyte salts in the gel electrolyte and the liquid electrolyte is small or non-existent, and can be basically ignored. The aforementioned cross-migration includes the electrolyte salts in the gel electrolyte being de-lithiated and migrating to the liquid electrolyte to form a free state, and also includes the electrolyte salts in the liquid electrolyte migrating into the gel electrolyte and being bound.

[0091] In this application, unless otherwise specified, "cross-linked polymer" has the commonly known meaning in the field of polymer technology. It has a three-dimensional network structure and can swell to a certain extent in the corresponding solvent, but will not dissolve. The degree of swelling depends on the degree of cross-linking of the cross-linked polymer.

[0092] In the secondary battery provided in the first aspect of the present application, at least one electrode plate has a reasonably matched gel electrolyte and liquid electrolyte, the problem of electrolyte extrusion due to electrode plate expansion is significantly suppressed, and the function of the liquid electrolyte in conducting active ions is retained, which can significantly improve the battery rate and cycle performance, and is conducive to obtaining a secondary battery with superior comprehensive performance.

[0093] In some embodiments, a secondary battery is provided, comprising at least two electrode plates, any one of the electrode plates comprising an active material layer disposed on at least one side of the electrode plate; the active material layer on at least one side of at least one of the electrode plates comprises active particles and an intra-plate electrolyte located in the pores between the active particles; the intra-plate electrolyte comprises an intra-plate gel electrolyte and an intra-plate electrolyte; the intra-plate gel electrolyte and the intra-plate electrolyte each independently contain an electrolyte salt, and the ratio R of the mass of the electrolyte salt in the intra-plate gel electrolyte to the mass of the electrolyte salt in the intra-plate electrolyte is W Satisfy 1 <R W <9.

[0094] In this application, unless otherwise specified, 1 <R W The gel / liquid composite electrolyte in the electrode of <9 is called the "gel / liquid composite electrolyte of this application".

[0095] By simultaneously arranging a gel electrolyte and a liquid electrolyte in the pores of the electrode plates in the secondary battery, on the one hand, the ion path between the active particles in the electrode plates can be enhanced, and the expansion and contraction of the plates during the charge and discharge process, which causes the liquid electrolyte to be squeezed out, can be reduced or avoided. On the other hand, by wrapping the surface of the active material with the gel electrolyte, the direct contact between the active material and the liquid electrolyte can be reduced, thereby reducing the electrolyte consumption rate during the cycle process and improving the battery life, so that the secondary battery can obtain better battery rate and cycle performance; further, the distribution of electrolyte salts in the gel electrolyte and the liquid electrolyte in the electrode plates is reasonably adjusted so that the mass of the electrolyte salt in the gel electrolyte is higher than that in the electrolyte, that is, the electrolyte salt in the pores of the electrode plates is more distributed in the gel electrolyte. At this time, the consumption and shortage of electrolyte salt near the active material caused by the extension of the cycle time can be better compensated, the deterioration of the battery cycle performance can be suppressed, the cycle life of the secondary battery can be significantly extended, and it is conducive to providing better battery rate performance over a longer cycle period.

[0096] In the context of this application, parameters such as mass, volume, and element distribution in the gel electrolyte within the electrode plate can be tested and analyzed using focused electron beam (FIB) technology, scanning electron microscopy (SEM), and elemental analysis techniques. For example, these parameters can be obtained by combining cryo-focused electron beam (FIB) continuous sectioning, cross-sectional SEM morphology observation, energy dispersive spectroscopy (EDS) elemental spectrum analysis, and three-dimensional reconstruction analysis software. For example, a cryo-focused ion beam (FIB) is used to finely section the sample (down to a nanometer-scale slice) to separate the first and second gel electrolyte samples. Furthermore, a scanning electron microscope (SEM) can be used to analyze the morphology, structure, and element distribution of each cross-section under FIB continuous sectioning. Combined with three-dimensional structure reconstruction software, the three-dimensional structure of the sample can be reconstructed to estimate the mass and / or volume of the sample to be tested. By disassembling the battery, we can obtain samples of the active material layer of the electrode plate, and further analyze the electrolyte in the plate by the following method: using the nano-spatial dynamic resolution and layer-by-layer cutting technology of FIB-SEM, we can reconstruct the three-dimensional structure of the sample, and use EDS element spectrum analysis to obtain the distribution and proportion of each element. Finally, through software quantitative analysis, we can obtain the pore distribution, volume distribution and mass distribution of each component. Combined with the total mass, total volume, total thickness and other parameter values ​​of the sample, we can also obtain the values ​​of parameters such as porosity, pore size, mass, volume, thickness, etc. The following parameters in the context can all be tested and analyzed by the aforementioned combined technology: the mass and volume of the active material layer of the electrode plate, the porosity b of the electrode plate (the porosity b of the electrode plate corresponds to the porosity of the corresponding active material layer, which can be the porosity b1 of the negative active material layer and the porosity b2 of the positive active material layer), the mass, volume, physical form (gel and / or liquid) and electrolyte salt distribution of the electrolyte in the electrode plate, the mass of the electrolyte salt in the gel electrolyte in the electrode plate, the mass of the electrolyte salt in the liquid electrolyte in the electrode plate, and the ratio R of the mass of the electrolyte salt in the gel electrolyte in the electrode plate to the mass of the electrolyte salt in the electrolyte solution in the electrode plate. W , the ratio R of the mass of the electrolyte salt in the gel electrolyte in the electrode sheet within the pores of the negative electrode active material layer to the mass of the electrolyte salt in the electrolyte solution in the electrode sheet within the pores of the negative electrode active material layer W1 The ratio of the mass of the electrolyte salt in the gel electrolyte in the electrode sheet within the pores of the positive electrode active material layer to the mass of the electrolyte salt in the electrolyte solution in the electrode sheet within the pores of the positive electrode active material layer is R W2 , the mass, volume, thickness and porosity of each layer of the active material layer having a multi-layer structure. As a non-limiting example, the test and analysis of the above parameters can be performed using FEI Scios 2HiVac equipment.

[0097] In this application, the terms "first" and "second" in "first gel electrolyte" and "second gel electrolyte" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features.

[0098] In an electrode plate, the ratio of the mass of the electrolyte salt in the gel electrolyte in the plate to the mass of the electrolyte salt in the electrolyte solution in the plate is recorded as R W In this case, the electrolyte in the electrode plate includes a gel / liquid composite electrolyte. In this application, unless otherwise specified, 1 <R W <9.

[0099] In some embodiments, wherein 1.2≤R W ≤8.5; optionally, 1.5≤R W ≤8.5. R W It can also be any of the following values, can be greater than or equal to any of the following values, can be greater than or equal to any of the following values ​​and less than 9, can be greater than 1 and less than or equal to any of the following values, and can also be selected from the interval consisting of any two of the following values: 1.05, 1.1, 1.2, 1.25, 1.3, 1.4, 1.5, 1.6, 1.8, 2, 2.5, 3, 3.5, 3.9, 4.0, 4.1, 4.5, 5, 5.5, 6, 6.3, 6.5, 7, 7.5, 8, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, etc. As a non-limiting example, R W It can also be selected from any of the following ranges: 1 <R W ≤8.9, 1 <R W ≤8.5, 1 <R W ≤8.0, 1.2 <R W ≤8.9, 1.2 <R W ≤8.5, 1.2 <R W ≤8.0, 1.5 <R W ≤8.9, 1.5 <R W ≤8.5, 1.5 <R W ≤8.0, 1.2≤R W ≤8.9, 1.2≤R W ≤8.5, 1.2≤R W ≤8.0, 1.5≤R W ≤8.9, 1.5≤R W ≤8.5, 1.5≤R W ≤8.0, 4.0≤R W ≤8.9, 4.0≤R W ≤8.5, 4.0≤R W ≤8.0, etc.

[0100] In an electrode plate having a gel / liquid composite electrolyte, the electrolyte salt in the gel / liquid composite electrolyte in the electrode plate can be regulated to have a more appropriate distribution between the gel state and the liquid state, thereby helping to better improve the cycle life of the secondary battery and the battery rate performance during long cycles.

[0101] The electrode plate including the aforementioned gel / liquid composite electrolyte may be only a positive electrode plate or only a negative electrode plate, or may be a combination of a positive electrode plate and a negative electrode plate.

[0102] Compared to placing the intra-electrode gel / liquid composite electrolyte only in the positive electrode, placing the intra-electrode gel / liquid composite electrolyte in at least the negative electrode provides a better overall improvement in battery rate and cycle performance. Placing the intra-electrode gel / liquid composite electrolyte in both the positive and negative electrode sheets creates a synergistic effect, surpassing placement in either the positive or negative electrode sheets alone.

[0103] In some embodiments, the active material layer on at least one side of at least one of the electrode plates is a multi-layer structure, and the electrolyte in the plate is distributed in at least a portion of the pores in the outer active layer of the multi-layer structure (the electrolyte in the plate here includes the aforementioned gel electrolyte in the plate and the electrolyte in the plate);

[0104] Among them, in the multi-layer structure of the active material layer, the outer active layer is farthest away from the center of the pole piece along the thickness direction of the pole piece.

[0105] For any electrode plate in a secondary battery, the active material layer on either side can independently be a single-layer structure or a multi-layer structure. When the active material layer is a single-layer structure, the material composition along the thickness direction can be basically the same or can have continuous changes. In this case, the various parts of the single-layer structure can be formed simultaneously in the same process. When the active material layer is a multi-layer structure, there are obvious discontinuous changes in the material composition along the thickness direction. For example, there can be an observable interlayer interface. In this case, different structural layers can be formed separately through different process steps. The interlayer interface of the multilayer structure can be observed by known cross-sectional analysis methods, such as scanning electron microscopy (SEM) observation.

[0106] When a certain active material layer has a multi-layer structure, the thickness, porosity and composition of each active layer in the active material layer may be independently the same or different.

[0107] In this application, unless otherwise specified, the "outer active layer" refers to the structural layer in the active material layer of the electrode sheet that is farthest from the thickness center. When a current collector is present in the electrode sheet, it generally refers to the structural layer in the active material layer that is farthest from the current collector. Unless otherwise specified, the "inner active layer" refers to the remaining portion of the active material layer other than the outer active layer. It can be directly laminated to the current collector or another structural layer containing no active material can be interposed between the inner active layer and the current collector. The inner active layer can include one or more active layers.

[0108] In the present application, when the electrode plate includes a current collector, the position of the current collector in the thickness direction of the plate can be regarded as the "plate center" position of the electrode plate in the thickness direction of the plate. When the active material layer of the electrode plate is provided on one or both sides of the current collector, "farthest from the plate center" refers to the farthest from the current collector. In this case, "the outer active layer is located on at least one side of the surface of the active material layer farthest from the plate center along the thickness direction of the plate" means that the outer active layer is located on at least one side of the surface of the active material layer farthest from the current collector along the thickness direction of the plate.

[0109] A multilayer structure can be set in the active material layer of at least one electrode plate, and the gel / liquid composite electrolyte in the plate of the aforementioned special gel / liquid composite method is distributed at least in the outer active layer (the inner active layer may or may not contain a gel / liquid composite electrolyte), so that the electrolyte in the plate provides a better adsorption and polymerization effect, and has a better infiltration rate for the active particles, which is beneficial to improving the kinetic properties and can also better exert the aforementioned effect of improving the battery rate and cycle performance.

[0110] When an electrode plate has a multi-layer structure, disposing the gel / liquid composite electrolyte at least in the outer active layer is more effective in improving the overall effect of battery rate and cycle performance than disposing the gel / liquid composite electrolyte only in the inner active layer.

[0111] Only the positive electrode active material layer may have a multilayer structure. Only the negative electrode active material layer may have a multilayer structure. Both the positive electrode active material layer and the negative electrode active material layer may have a multilayer structure.

[0112] The negative electrode sheet can independently have a multi-layer structure. In this case, the negative electrode active material layer includes multiple negative electrode active layers, each of which independently contains negative electrode active material. The outer active layer of the negative electrode active material layer can be referred to as the negative electrode outer active layer, and the inner active layer of the negative electrode sheet can be referred to as the negative electrode inner active layer.

[0113] The positive electrode sheet can also independently have a multi-layer structure. In this case, the positive electrode active material layer includes multiple positive electrode active layers, each of which independently contains positive electrode active material. The outer active layer of the positive electrode active material layer can be referred to as the positive electrode outer active layer, and the inner active layer of the positive electrode sheet can be referred to as the positive electrode inner active layer.

[0114] In some embodiments, the negative electrode active material layer is a multi-layer structure, and the gel / liquid composite electrolyte is distributed at least on the outer active layer of the negative electrode.

[0115] In some embodiments, the positive electrode active material layer is a multi-layer structure, and the gel / liquid composite electrolyte is distributed at least on the outer active layer of the positive electrode.

[0116] In some embodiments, the gel / liquid composite electrolyte is distributed only in the outer active layer of the negative electrode, but not in the inner active layer of the negative electrode, nor in the positive electrode sheet. In other embodiments, the gel / liquid composite electrolyte is distributed only in the outer active layer of the positive electrode, but not in the inner active layer of the positive electrode, nor in the negative electrode sheet. In other embodiments, the gel / liquid composite electrolyte is distributed in both the outer active layer of the negative electrode and the outer active layer of the positive electrode.

[0117] In some embodiments, in the electrode sheet having a multi-layer structure, the porosity of the outer active layer is higher than the porosity of the inner active layer; wherein the inner active layer is located inside the active material layer.

[0118] In some embodiments, the negative electrode active material layer is a multi-layer structure, and the porosity of the negative electrode outer active layer is higher than the porosity of the negative electrode inner active layer.

[0119] In some embodiments, the positive electrode active material layer is a multi-layer structure, and the porosity of the positive electrode outer active layer is higher than the porosity of the positive electrode inner active layer.

[0120] In some embodiments, the negative electrode active material layer and the positive electrode active material layer are both multilayer structures, the porosity of the negative electrode outer active layer is higher than the porosity of the negative electrode inner active layer, and the porosity of the positive electrode outer active layer is higher than the porosity of the positive electrode inner active layer.

[0121] When the active material layer of the electrode plate has a multi-layer structure, on the basis of the aforementioned gel / liquid composite electrolyte in the plate with a special gel / liquid combination, the porosity of the outer active layer can be further made higher than that of the inner active layer. At this time, on the one hand, the outer active layer can be given higher dynamics and the charging window can be improved. On the other hand, the surface of the active material layer can be more easily infiltrated by the liquid phase component of the electrolyte.

[0122] In this application, the porosity of an electrode plate, unless otherwise specified, refers to the porosity of the active material layer in the electrode plate, which refers to the percentage of the sum of the pore volumes between the material particles in the active material layer relative to the apparent total volume of the active material layer without considering the electrolyte in the plate. When the electrolyte in the plate is included, the volume occupied by the electrolyte in the plate is regarded as part of the pore volume in the active material layer.

[0123] During the battery's charge and discharge states, the negative and positive electrode sheets will expand and contract due to the changes in the embedding and deintercalation of active ions. The expansion and contraction of the negative electrode sheet has a greater impact on battery performance. The negative electrode sheet expands during the charging state and shrinks during the discharging state. There are pores between the negative active particles in the negative electrode sheet. The expansion and contraction of the negative electrode sheet can easily cause the liquid electrolyte in the pores of the negative electrode sheet to be squeezed out, and may also cause the ion path between the active particles in the negative electrode sheet to be unstable. In addition, direct contact between the electrolyte and the active particles can easily lead to electrolyte consumption. This results in the charge and discharge rate performance and battery cycle life of traditional secondary batteries being less than ideal.

[0124] In some embodiments, at least one of the electrode plates is a negative electrode plate, and the active material layer of the negative electrode plate is a negative electrode active material layer, and the negative electrode active material layer is located on at least one side of the negative electrode plate. In this case, the negative electrode plate includes the aforementioned gel / liquid composite electrolyte. The negative electrode active material layer can be located on one or both sides of the negative electrode plate.

[0125] For negative electrode plates, which are prone to volume expansion during battery cycling, the pores in the discharged state are larger than those in the charged state. If the pores are not effectively filled with electrolyte, bridges are prone to breakage, which deteriorates the electrical contact between the negative electrode active particles and the distance for active ion transport, and also leads to a decrease in rate discharge capability. The aforementioned special composite gel / liquid composite electrolyte can be placed at least within the negative electrode active material layer of the negative electrode plate, solidifying a portion of the electrolyte in the pores of the negative electrode active material layer. This reduces or prevents the extrusion of electrolyte between the active particles, significantly suppressing the deterioration of battery performance.

[0126] In some embodiments, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a silicon-based material.

[0127] The mass proportion of the silicon-based material in the negative electrode active material is recorded as the silicon content. In some embodiments, the silicon content is ≥3%. In some embodiments, the silicon content is ≤40%. In some embodiments, the silicon content is 3% to 40% (the two endpoint values ​​may be independently included or excluded). The silicon content can also be any of the following mass percentages, and can also be selected from the interval consisting of any two of the following mass percentages: 3%, 4%, 5%, 6%, 8%, 10%, 12%, 15%, 16%, 18%, 20%, 25%, 30%, 35%, 40%, etc.

[0128] In some embodiments, the silicon-based material may include one or more of elemental silicon, silicon-oxygen compounds, silicon-carbon compounds, silicon-nitrogen compounds, and silicon alloys.

[0129] Silicon-based materials, such as silicon, have a capacity approximately 10 times greater than that of graphite, enabling higher energy density. Their low cost and high specific capacity make them a highly sought-after negative electrode material. While the inclusion of silicon-based materials in the negative electrode plate facilitates the battery's high specific energy strategy, this also leads to significant expansion and contraction during charge and discharge. The aforementioned special composite gel / liquid composite electrolyte within the plate can significantly suppress battery performance degradation.

[0130] While silicon-based materials are beneficial in achieving a high specific energy density, they also exacerbate the problem of expansion. In this case, expansion and contraction during charge and discharge become more pronounced. Placing the aforementioned special composite gel / liquid electrolyte within at least the negative electrode significantly suppresses battery performance degradation. Furthermore, by controlling the silicon content within a more appropriate range, the battery's high specific energy density and excellent performance can be better balanced.

[0131] In some embodiments, the negative electrode active material layer has the aforementioned multilayer structure (which can be any suitable multilayer structure), wherein the porosity of the outer active layer (i.e., the negative electrode outer active layer) is 20% to 50%; further optionally 30% to 50%; and further optionally 30% to 45%. The porosity of the outer active layer can also be any of the following percentages, or can be independently selected from a range consisting of two of the following percentages: 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.

[0132] When the negative electrode active material layer has any of the aforementioned multilayer structures, the porosity of the negative electrode outer active layer can be further regulated, which is more conducive to improving the kinetics and charging window, and is also conducive to making the surface of the negative electrode active material layer more easily wetted by the liquid phase components of the electrolyte.

[0133] In some embodiments, the R of the negative electrode active material layer on either side is W Can also be denoted as R W1 , then the negative electrode active material layer on either side independently, 2.4≤R W / b1≤45, wherein b1 is the porosity of the negative electrode active material layer on either side. W / b1 can also be any of the following values, or an interval consisting of any two of the following values: 2.4, 2.5, 3, 3.5, 3.75, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 11, 12, 12.5, 13, 14, 15, 16, 18, 20, 25, 30, 35, 36, 37.5, 38, 40, 45, etc. Without limitation, either side independently, R W / b1 can be selected from any of the following ranges: 3.75≤R W / b1≤36,7.5≤R W / b1≤18, etc.

[0134] In some embodiments, the porosity b1 of the negative electrode active material layer on either side can independently be 20% to 50%, or can be any of the following percentages, or can be selected from an interval consisting of two of the following percentages: 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc. The porosity b1 of the negative electrode active material layer on either side can also be selected from any of the following ranges: 25% to 45%, 25% to 40%, etc.

[0135] In this application, reference to "either side" means at least one side unless otherwise specified; when the described object is located on both sides, "either side" can be one side or both sides. When both sides meet the described characteristics, the characteristics of the two sides can be the same or different.

[0136] For any of the aforementioned negative electrode sheets having the gel / liquid composite electrolyte of the present application, the electrolyte salt mass ratio R in the gel / liquid electrolyte on either side of the negative electrode sheet can be adjusted. W (Alternatively denoted as R W1 ) and the negative electrode porosity (b1), through R W / b1 regulation optimizes the distribution of electrolyte lithium salt in the negative electrode and the porosity of the electrode. On the one hand, the regulation of the porosity b1 of the negative electrode is used to optimize the infiltration of the electrolyte into the interior. On the other hand, the R W The regulation can optimize the cycle life of secondary batteries and improve the battery rate performance during long cycles, thereby comprehensively improving the cycle performance, rate performance and kinetic performance of secondary batteries.

[0137] In some embodiments, at least one of the electrode plates is a positive electrode plate, and the active material layer of the positive electrode plate is a positive electrode active material layer, and the positive electrode active material layer is located on at least one side of the positive electrode plate. In this case, the positive electrode plate includes the aforementioned gel / liquid composite electrolyte. The positive electrode active material layer can be located on one or both sides of the positive electrode plate.

[0138] The positive electrode plate can adopt the gel / liquid composite electrolyte design of the aforementioned special composite method, thereby reducing or avoiding the extrusion of the electrolyte between particles, inhibiting the deterioration of battery performance, extending the cycle life of the secondary battery, and facilitating the provision of better battery rate performance over a long cycle period.

[0139] In some embodiments, the positive electrode active material layer has the aforementioned multilayer structure (which can be any suitable multilayer structure mentioned above), wherein the porosity of the outer active layer (i.e., the positive electrode outer active layer) is 10% to 40%; further optionally 15% to 40%; further optionally 20% to 35%.

[0140] When the active material layer of the positive electrode sheet has the aforementioned multilayer structure, the porosity of the active layer on the outer side of the positive electrode can be further regulated, which is more conducive to improving the kinetics and charging window, and is also conducive to making the surface of the positive electrode active material layer more easily wetted by the liquid phase components of the electrolyte.

[0141] In some embodiments, the R of the positive electrode active material layer on either side is W Can also be denoted as R W2 , then independently on either side, 3.75≤R W / b2≤90, wherein b2 is the porosity of the positive electrode active material layer. W / b2 can also be any of the following values, or an interval consisting of any two of the following values: 3.75, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 11, 12, 12.5, 13, 14, 15, 16, 18, 20, 25, 30, 35, 36, 37.5, 38, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, etc. Without limitation, either side independently, R W / b2 can be selected from any of the following ranges: 3.75≤R W / b2≤60,4.2≤R W / b2≤25, etc.

[0142] In some embodiments, the porosity b2 of the positive electrode active material layer on either side is independently 10% to 40%, or may be any of the following percentages, or may be selected from an interval consisting of two of the following percentages: 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc. The porosity b2 of the positive electrode active material layer on either side may also be selected from any of the following ranges: 10% to 35%, 15% to 35%, etc.

[0143] For any of the aforementioned positive electrode sheets having the gel / liquid composite electrolyte of the present application, the electrolyte salt mass ratio R in the gel / liquid electrolyte can be adjusted. W (Alternatively denoted as R W2 ) and the positive electrode porosity (b2), through R W / b2 regulation optimizes the distribution of electrolyte salt in the positive electrode and the porosity of the electrode. On the one hand, the regulation of the b2 porosity of the positive electrode is used to optimize the infiltration of the electrolyte into the interior. On the other hand, the R W The regulation can optimize the cycle life of secondary batteries and improve the battery rate performance during long cycles, thereby comprehensively improving the cycle performance, rate performance and kinetic performance of secondary batteries.

[0144] In some embodiments, the secondary battery includes a positive electrode sheet, a negative electrode sheet, and a separator, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet;

[0145] The positive electrode sheet and the negative electrode sheet meet one or both of the following characteristics:

[0146] The negative electrode sheet is as defined above;

[0147] The positive electrode plate is as defined above.

[0148] One or both of the positive electrode sheet and the negative electrode sheet in the secondary battery can have the aforementioned gel / liquid composite electrolyte design within the electrode sheet, thereby exerting the aforementioned advantages or achieving synergistic efficiency of the positive and negative electrode sheets.

[0149] In some embodiments, the positive electrode sheet includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a lithium ion material.

[0150] In some embodiments, the secondary battery is a lithium-ion secondary battery.

[0151] In some embodiments, the electrolyte salt in the electrode sheet includes an electrolyte lithium salt.

[0152] In some embodiments, the electrolyte lithium salt is distributed in at least one or both of the gel electrolyte and the electrolyte in the electrode in the same electrode.

[0153] In some embodiments, the electrolyte lithium salt is distributed at least in the pores of the positive electrode active material layer.

[0154] In some embodiments, the negative electrode sheet includes a negative electrode active material layer, and the electrolyte lithium salt is distributed at least in the pores of the negative electrode active material layer.

[0155] The special design of the gel / liquid composite electrolyte in the aforementioned electrode can be applicable to lithium-ion secondary batteries. Furthermore, the electrolyte salt in the electrode can include an electrolyte lithium salt that is more compatible with the active lithium ions, thereby promoting the efficient transmission of active lithium ions, which is beneficial for the secondary battery to have better comprehensive performance in terms of power density, cycle life, etc.

[0156] In one embodiment of the present application, the secondary battery includes a positive electrode sheet, a negative electrode sheet, and an electrolyte. During the battery's charge and discharge processes, active ions are intercalated and released back and forth between the positive and negative electrode sheets. The electrolyte conducts the active ions between the positive and negative electrode sheets.

[0157] In one embodiment of the present application, the secondary battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are intercalated and released between the positive and negative electrode sheets. The electrolyte conducts active ions between the positive and negative electrode sheets. The separator is disposed between the positive and negative electrode sheets, primarily preventing a short circuit between the positive and negative electrodes while allowing the active ions to pass through.

[0158] The types of active ions can be as described above.

[0159] electrolytes

[0160] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode, and can transmit active ions.

[0161] The electrolyte in the secondary battery provided herein includes at least the aforementioned intra-electrode electrolyte, which is distributed in the active material layer on at least one side of at least one electrode plate. The aforementioned gel / liquid composite electrolyte is provided in the active material layer on at least one side of at least one electrode plate.

[0162] The electrolyte in the secondary battery provided in this application includes at least the following physical states: gel and liquid. In this application, the gel electrolyte is referred to as a gel electrolyte, and the liquid electrolyte is referred to as a liquid electrolyte or electrolyte. At least a portion of the gel electrolyte is located within the active material layer of the electrode plate, and the gel electrolyte located in the electrode plate is referred to as an intra-plate gel electrolyte. At least a portion of the electrolyte is located within the active material layer of the electrode plate, and the electrolyte located in the electrode plate is referred to as an intra-plate electrolyte.

[0163] At least a portion of the electrolyte in the electrode sheet of the secondary battery provided in the present application includes a gel electrolyte in the electrode sheet and an electrolyte solution in the electrode sheet.

[0164] The gel skeleton in the condensed electrolyte can be formed by a polymerization reaction of a cross-linkable monomer, wherein a corresponding initiator and / or a cross-linking agent can be added during the polymerization reaction.

[0165] The gelation reaction of the cross-linkable monomer is generally a polymerization reaction, and the cross-linkable monomer here is a polymerizing monomer. Monomers that participate in the formation of the gel skeleton through polymerization reaction can be collectively referred to as polymerizing monomers. Polymerizing monomers include at least cross-linkable monomers, but are not limited to this. For example, polymerizing monomers can also include chain-extending monomers. Chain-extending monomers can provide linear segments between the cross-linking points of the gel skeleton. Chain-extending monomers can be pre-buried in the active material layer of the electrode pole piece (positive pole piece, negative pole piece or a combination of the two), or can be introduced in other ways, such as by injection and infiltration of the electrolyte.

[0166] An initiator and / or crosslinker can be introduced when injecting the electrolyte into the housing. After sufficient infiltration, the electrolyte fills the pores of the active material layer in the electrode plate and undergoes an in-situ gelation reaction with the pre-embedded crosslinkable monomer. The polymerized monomer undergoes an in-situ gelation reaction to form a gel skeleton. A portion of the electrolyte immersed in the electrode plate pre-embedded with the crosslinkable monomer is converted into a gel electrolyte within the plate, while the unconverted portion serves as the electrolyte within the plate. This results in a gel / liquid composite electrolyte within the plate that includes both the gel electrolyte and the electrolyte within the plate. By controlling the amount of pre-embedded crosslinkable monomer, the mass ratio of the gel electrolyte to the electrolyte within the plate can be adjusted. The type and amount of the initiator and / or crosslinker can be appropriately selected based on the type and amount of the pre-embedded crosslinkable monomer. The electrode assembly, consisting of the positive electrode plate, negative electrode plate, and separator, can be placed into the housing, and then the electrolyte can be injected into the housing. This is described below.

[0167] In the present application, the cross-linkable monomer includes a functional group pair that can undergo a cross-linking reaction. Non-limiting examples of functional group pairs that can undergo a cross-linking reaction include multiple carbon-carbon double bonds, and further examples include monomers containing at least 2 carbon-carbon double bonds; such as a cross-linking monomer combination, and further examples include a cross-linking monomer combination including two monomers, one monomer including at least 2 reactive groups F1, and the other monomer including at least 3 reactive groups F2, and F1 and F2 can be coupled to form a covalent bond. Non-limiting examples of carbon-carbon double bonds include CH2=CH-CH2-, CH2=C(CH3)-CH2-, etc. The hydrogen atoms on the carbon-carbon double bonds can be replaced by suitable substituents, as long as they do not affect the cross-linking polymerization reaction. Non-limiting examples of cross-linking monomer combinations include a combination of a polyol or polyamine with a polyisocyanate, which can undergo a coupling reaction between -OH or an amino group (such as -NH2 or >NH) and -NCO to form a polyurethane or polyurea; and a combination of a polyacid and a polyamine, which can undergo a coupling reaction between -COOH and -NH2 or >NH to form a polymer containing an amide bond (-CO-NH- or -CO-N<), etc.

[0168] The types of polymerizable monomers may include, but are not limited to, one or more of carbonate monomers, sulfone monomers, isocyanate monomers, amide monomers, nitrile monomers, fluorinated monomers, ether compound monomers, ether segment-containing oligomers, and siloxanes.

[0169] When performing the crosslinking reaction of the crosslinkable monomer, the system may or may not contain an initiator, depending on the needs of the crosslinking reaction. When an initiator is added, the initiator may include, but is not limited to, one or more of azo initiators (such as azobisisobutyronitrile (AIBN)), peroxide initiators, anionic and cationic initiators, organometallic compound initiators, amine catalyst initiators, and organophosphorus initiators. The type and amount of the initiator can be appropriately selected and controlled based on the type and amount of the crosslinkable monomer. For example, the mass ratio of the initiator to the crosslinkable monomer can be 1% to 5%, but is not limited to this.

[0170] In some embodiments, the cross-linkable monomer contains at least two carbon-carbon double bonds.

[0171] In the present application, unless otherwise specified, a "carbon-carbon double bond" refers to a C=C structure capable of undergoing an addition reaction to form a -CC- structure.

[0172] In some embodiments, the cross-linkable monomer contains at least two carbon-carbon double bonds, which can provide cross-linking points for the gel skeleton through polymerization.

[0173] In the present application, unless otherwise specified, a "carbon-carbon double bond" refers to a C=C structure capable of undergoing an addition reaction to form a -CC- structure.

[0174] Without limitation, the crosslinkable monomer may include one or more of ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,4-butanediol diacrylate, glycerol dimethacrylate, 1,2-propylene glycol dimethyl acrylate, 1,3-butanediol dimethacrylate, dipropylene glycol diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, glycerol trimethacrylate, pentaerythritol tetramethacrylate, cyclohexanetriol trimethacrylate, divinylbenzene, ethylene glycol diallyl ether, polyethylene glycol diallyl ether, and pentaerythritol triallyl ether, and may also include one or more halogenated compounds of the foregoing compounds. The number of halogen atoms substituted in the halogenated compound may be one or more. In one embodiment, all hydrogen atoms on the carbon-carbon double bond are replaced by halogen atoms, such as fluorine atoms. The polyethylene glycol dimethacrylate may include one or more of diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate, but is not limited thereto. The polyethylene glycol portion of the polyethylene glycol diallyl ether may be 2, 3, or 4 ethylene glycol units, but is not limited thereto. The aforementioned carboxylate molecule may be methyl, ethyl, propyl, or butyl, but is not limited thereto, and as a non-limiting example, may be diethylene glycol methyl dimethacrylate or diethylene glycol ethyl dimethacrylate.

[0175] Without limitation, the chain-extending monomer may be an unsaturated monoolefin molecule, including but not limited to one or more of vinylidene fluoride, hexafluoropropylene, methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, n-butyl methacrylate, butyl acrylate, n-octyl methacrylate, n-octyl acrylate, allyl methacrylate, styrene, α-methylstyrene, acrylonitrile, acrylic acid, methacrylic acid, butyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, etc., and may also be a halogenated compound (such as a fluorinated compound) of the aforementioned suitable compound.

[0176] In the present application, the electrolyte in the secondary battery, in addition to being at least partially distributed within the electrode plate, can also be distributed outside the electrode plate, for example, at least a portion of the relative space between the positive electrode plate and the negative electrode plate. The electrolyte distributed outside the electrode plate can be referred to as an "extra-electrolyte", and its composition is not particularly limited, and can be liquid, gel or all-solid. In some embodiments, the extra-electrolyte includes at least a liquid electrolyte, and can further mainly include a liquid electrolyte (e.g., more than 80wt%), or can be essentially a liquid electrolyte (e.g., close to 100wt%).

[0177] In this application, wt% represents weight percentage.

[0178] In some embodiments, the electrolyte outside the electrode is a liquid electrolyte.

[0179] In some embodiments, the electrolyte in the secondary battery of the present application is a non-aqueous electrolyte, which includes an electrolyte salt and a solvent.

[0180] In some embodiments, the electrolyte inside the electrode and the electrolyte outside the electrode each independently include an electrolyte salt and a solvent. The definition of the electrolyte salt can be found below. The definition of the solvent can also be found below. The types of electrolyte salts in the electrolyte inside the electrode and the electrolyte outside the electrode can be the same or different. The types of solvents in the electrolyte inside the electrode and the electrolyte outside the electrode can be the same or different. The electrolyte salts in the gel electrolyte inside the electrode and the electrolyte solution inside the electrode can be the same or different. The solvents in the gel electrolyte inside the electrode and the electrolyte solution inside the electrode can be the same or different.

[0181] In some embodiments, the gel electrolyte in the electrode piece and the electrolyte in the electrolyte solution in the electrode piece have the same composition.

[0182] In some embodiments, the gel electrolyte in the electrode piece and the solvent composition in the electrolyte solution in the electrode piece are the same.

[0183] In some embodiments, the electrolyte salt includes an electrolyte lithium salt. In this case, the secondary battery may be a lithium ion secondary battery.

[0184] Without limitation, 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 (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0185] In some embodiments, the electrolyte salt includes an electrolyte sodium salt. In this case, the secondary battery may be a sodium ion secondary battery.

[0186] Without limitation, the electrolyte sodium salt may include one or more of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium tetrafluoroborate, sodium difluorophosphate, sodium perchlorate, and sodium chloride.

[0187] In some embodiments, the solvent in the electrolyte is a non-aqueous solvent, and further may be an organic solvent, and further may include but is not limited to one or more of a carboxylate solvent, a carbonate solvent, and a sulfone solvent. The carboxylate solvent may be a carboxylate or a halogenated carboxylate thereof, and further may be C 2-4 C of alkyl carboxylic acid 1-3 Alkyl ester or its halide. Halide of carboxylic acid ester is also called halocarboxylic acid ester. 1-4 Examples of alkyl carboxylic acids include acetic acid, propionic acid, and butyric acid. 1-3 Examples of alkyl esters include methyl ester, ethyl ester, and propyl ester. Carbonate solvents can be carbonates or their halides. Carbonate halides are also called halogenated carbonates. The halogen substituents in halogenated carboxylates and halogenated carbonates can be fluorine, and the number of halogen substituents can range from 1 to perhalogenated. Taking fluorinated as an example, the number of fluorine atoms in fluorinated carboxylates and fluorinated carbonates can range from 1 to perfluorinated.

[0188] Without limitation, the solvent in the electrolysis may include but is not limited to fluoroethylene carbonate, ethylene carbonate (or ethylene carbonate, ), propylene carbonate (or propylene carbonate, ), one or more of ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. In some embodiments, the solvent in the electrolyte of the secondary battery includes fluoroethylene carbonate. In some embodiments, the solvent in the electrolyte of the secondary battery is fluoroethylene carbonate.

[0189] In some embodiments, the solvent in the electrolyte can be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0190] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0191] In some embodiments, the electrolyte within the electrode and the electrolyte outside the electrode may independently include or exclude additives. The types of additives in the electrolyte within the electrode and the electrolyte outside the electrode may be the same or different. The gel electrolyte within the electrode and the electrolyte solution within the electrode may independently include additives. The additives in the gel electrolyte within the electrode and the electrolyte solution within the electrode may be the same or different. In some embodiments, the additive composition of the gel electrolyte within the electrode and the electrolyte solution within the electrode is the same.

[0192] In some embodiments, the additives in the electrolyte of the secondary battery may include, but are not limited to, vinylene carbonate (VC, ), vinyl ethylene carbonate (VEC, ), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), methylene methanedisulfonate (MMDS), 1-propylene-1,3-sultone (PST), ethylene sulfite (ES), propylene sulfite (PS), diethylene sulfate (DTD), succinonitrile (SN), adiponitrile (AND), sulfonate cyclic quaternary ammonium salt, tris(trimethylsilyl) phosphate (TMSP), tris(trimethylsilyl) borate (TMSB) and anisole.

[0193] Negative electrode

[0194] The negative electrode plate in the secondary battery provided in the present application includes a negative electrode active material layer, and the negative electrode active material layer includes a negative electrode active substance.

[0195] The negative electrode active material may include negative electrode active materials for batteries that are well known in the art. As non-limiting examples, other negative electrode active materials may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional 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.

[0196] As mentioned above, in some embodiments, the negative electrode active material includes a silicon-based material. Further, the silicon-based material may include one or more of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.

[0197] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material layer, and the negative electrode active material layer includes a negative electrode active material. The negative electrode active material can be as defined above.

[0198] As a non-limiting example, the negative electrode current collector has two surfaces opposite to each other in its 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.

[0199] 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 material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the negative electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0200] In some embodiments, the negative electrode active material layer may further include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acids (PAAs), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). An example of a PAA-based binder is polyacrylic acid (PAA).

[0201] In some embodiments, the binder in the negative electrode film layer or the negative electrode active material layer includes one or more of PAA and SBR.

[0202] In some embodiments, the negative electrode film layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0203] In some embodiments, the negative electrode active material layer may further include other auxiliary agents, such as a thickener, etc. Non-limiting examples of thickeners may include sodium carboxymethyl cellulose (CMC-Na), etc.

[0204] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the negative electrode current collector, and after drying, compacting (compacting can be performed by cold pressing), etc., the negative electrode sheet can be obtained. 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 two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 30wt% to 70wt%. The viscosity of the negative electrode slurry at room temperature can be 2000mPa·s to 10000mPa·s. When coating the negative electrode slurry, the unit surface density of the coating can be 35g / m2 on a dry weight basis. 2 ~150g / m 2 The compaction density of the negative electrode can be 1.0g / cm 3 ~2.0g / cm 3 .

[0205] The slurry used to prepare the negative electrode plate may or may not include the aforementioned cross-linkable monomer. When the aforementioned gel / liquid composite electrolyte is required to be provided in the negative electrode plate, a cross-linkable monomer can be added to the negative electrode slurry to form a gel skeleton for the gel electrolyte within the plate. After coating, drying, and cold pressing, the cross-linkable monomer is pre-embedded in the negative electrode plate. During the subsequent electrolyte injection process, an electrolyte containing an initiator and / or a cross-linking agent can be introduced to form a gel skeleton through an in-situ gelation reaction. A portion of the electrolyte immersed in the electrode plate pre-embedded with the cross-linkable monomer is converted into the gel electrolyte within the plate, while the unconverted portion serves as the electrolyte within the plate, thereby obtaining an intra-plate gel / liquid composite electrolyte comprising both the gel electrolyte within the plate and the electrolyte within the plate. By controlling the pre-embedded amount of cross-linkable monomer, the mass ratio of the gel electrolyte within the plate to the electrolyte within the plate can be adjusted. When the gel skeleton of the gel electrolyte in the negative electrode plate involves a chain-extending monomer, the chain-extending monomer can be introduced with the negative electrode slurry or injected when the electrolyte is subsequently injected.

[0206] Positive electrode

[0207] In the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material layer. Further, the positive electrode active material layer includes a positive electrode active substance.

[0208] As a non-limiting example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0209] 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 polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material on a polymer material substrate; the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy; non-limiting examples of polymer material substrates include substrates made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), and the like.

[0210] In some embodiments of the present application, the positive electrode active material includes a lithium ion material; further, the secondary battery is a lithium ion secondary battery.

[0211] In some embodiments of the present application, the secondary battery is a lithium-ion secondary battery. Lithium-ion secondary batteries utilize the intercalation and deintercalation of lithium ions in electrodes and their transport in electrolytes to achieve charge and discharge. Generally speaking, the active ions in lithium-ion secondary batteries are lithium ions, but this is not limited to this.

[0212] The positive electrode active material may be a positive electrode active material for batteries that is well known in the art. As a non-limiting example, the positive electrode active material or lithium ion material may include one or more of the following materials or substances: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials or substances, and other traditional materials or substances 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. Among them, non-limiting examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Non-limiting examples of lithium cobalt oxide include LiCoO2; non-limiting examples of lithium nickel oxide include LiNiO2; non-limiting examples of lithium manganese oxide include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxide include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide include LiNi 0.85 Co 0.15 Al 0.05 O2. Non-limiting examples of olivine-structured lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon. Non-limiting examples of lithium iron phosphate include LiFePO4 (also referred to as LFP); non-limiting examples of lithium manganese phosphate include LiMnPO4.

[0213] In some embodiments, the positive electrode active material or lithium ion material may include but is not limited to one or more of the following materials: 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, and a material composed of any of the foregoing substances and doping elements; further, the doping elements in any one of the positive electrode active materials independently include one or more of transition metal elements and non-transition metal elements.

[0214] In some embodiments of the present application, the positive electrode active material includes a sodium ion material; further, the secondary battery is a sodium ion secondary battery.

[0215] In some embodiments, the sodium ion material includes one or more of sodium transition metal oxides, polyanion compounds, and Prussian blue compounds. Flexible selection of suitable positive electrode active materials allows for greater selectivity and wider applicability of sodium ion batteries.

[0216] In some embodiments, the positive electrode active material may include, but is not limited to, one or more of sodium transition metal oxides, polyanion compounds, and Prussian blue compounds. However, the present application is not limited to the aforementioned materials or substances, and other known materials or substances that can be used as positive electrode active materials for sodium ion batteries may also be used.

[0217] In some embodiments, the transition metal in the sodium transition metal oxide may be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Non-limiting examples of sodium transition metal oxides may be Na x ZO2, wherein Z can be one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, 0 <x≤1。

[0218] In some embodiments, the sodium transition metal oxide may be Na 1-x Cu h Fe k Mn l M 1 m O 2-y , where 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. <x≤0.33,0<h≤0.24,0≤k≤0.32,0<l≤0.68,0≤m<0.1,h+k+l+m=1,0≤y<0.2。

[0219] In some embodiments, the sodium transition metal oxide may be Na 0.67 Mn 0.7 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, <q≤0.1。

[0220] In some embodiments, the sodium transition metal oxide may 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。

[0221] In some embodiments, the polyanion compound may be a compound having sodium ions, transition metal ions and tetrahedral (YO4) 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- valence.

[0222] In some embodiments, the polyanion compound can also be a compound having sodium ions, transition metal ions, tetrahedral (YO4 )n- A class of compounds containing anion units and halogen 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- valence state; the halogen can be one or more of F, Cl and Br.

[0223] In some embodiments, the polyanion compound can also be a compound having sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. Y can be one or more of P, S and Si, and n represents (YO4) n- 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+ valence state; the halogen can be one or more of F, Cl and Br.

[0224] In some embodiments, the polyanion compound may be NaFePO4, Na3V2(PO4)3, NaM'PO4F, and Na3(VO y )2(PO4)2F 3- 2 y (0≤y≤1) or more; wherein, M' in NaM'PO4F may be one or more of V, Fe, Mn and Ni.

[0225] In some embodiments, the Prussian blue compound may be a compound having sodium ions, transition metal ions and cyanide ions (CN — The transition metal may be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Non-limiting examples of Prussian blue compounds may be 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。

[0226] In some embodiments, the positive electrode active material layer may further optionally include a binder. As non-limiting examples, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0227] In some embodiments, the positive electrode active material layer may further include a conductive agent. As non-limiting examples, 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.

[0228] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on at least one side of the positive electrode current collector, and after drying, compacting (compaction can be performed by cold pressing) and other processes, the positive electrode sheet can be obtained. The type of solvent can be selected from but not limited to any one of the aforementioned 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 two surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40wt% to 80wt%. The viscosity of the positive electrode slurry at room temperature can be 5000mPa·s to 25000mPa·s. When applying the positive electrode slurry, the unit area density of the coating can be 130g / m2 on a dry weight basis. 2 ~400g / m 2 The compaction density of the positive electrode sheet can be 3.0 to 3.6 g / cm 3 , can be selected as 3.3~3.5g / cm 3 .

[0229] The slurry used to prepare the positive electrode plate may or may not include the aforementioned cross-linkable monomer. When it is necessary to set the aforementioned gel / liquid composite electrolyte in the positive electrode plate, a cross-linkable monomer can be added to the positive electrode slurry to form a gel skeleton of the gel electrolyte in the plate. After the coating, drying, and cold pressing processes, the cross-linkable monomer is pre-embedded in the positive electrode plate. During the subsequent injection of the electrolyte, an electrolyte containing an initiator and / or a cross-linking agent can be introduced to form a gel skeleton through an in-situ gelation reaction. A portion of the electrolyte immersed in the electrode plate pre-embedded with the cross-linkable monomer is converted into a gel electrolyte in the plate, and the unconverted portion serves as the electrolyte in the plate, thereby obtaining a gel / liquid composite electrolyte in the plate that includes both the gel electrolyte in the plate and the electrolyte in the plate. By controlling the pre-embedded amount of the cross-linkable monomer, the mass ratio of the gel electrolyte in the plate to the electrolyte in the plate can be adjusted. When the gel skeleton of the gel electrolyte in the positive electrode sheet involves a chain-extending monomer, the chain-extending monomer can be introduced with the positive electrode slurry or injected when the electrolyte is subsequently injected.

[0230] Isolation film

[0231] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0232] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven 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.

[0233] Electrode assembly, electrochemical energy storage device, secondary battery

[0234] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0235] In some embodiments, the electrochemical energy storage device may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0236] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0237] In some embodiments, the outer packaging of the secondary battery can be a hard 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 shell, such as a pouch-type soft shell. The material of the soft shell can be plastic. Further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0238] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape. For example, FIG1 shows a secondary battery 5 with a square structure as an example.

[0239] In some embodiments, referring to FIG. 2 , the outer packaging may include a housing 51 and a cover plate 53 . The housing 51 may include a bottom plate and side plates connected to the bottom plate, with the bottom plate and side plates enclosing a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be positioned over the opening to seal the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated within the receiving cavity. A liquid electrolyte is injected into the receiving cavity encapsulating the electrode assembly 52, causing a gelation reaction of the cross-linkable monomers pre-embedded within the electrode sheet, converting part of the liquid electrolyte within the electrode sheet into a gel electrolyte, thereby obtaining the aforementioned gel / liquid composite electrolyte within the electrode sheet. The secondary battery 5 may contain one or more electrode assemblies 52, and those skilled in the art can select the number based on actual needs. When the gel skeleton of the gel electrolyte within the electrode sheet includes a chain-extending monomer, the chain-extending monomer can be introduced with the corresponding slurry or injected later during the electrolyte injection.

[0240] In some embodiments, the secondary battery provided in the first aspect of the present application can be prepared by a method comprising the following steps:

[0241] Assembling a positive electrode sheet, a negative electrode sheet, and a separator into an electrode assembly, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet; wherein the active material layer of at least one of the positive electrode sheet and the negative electrode sheet comprises a polymerized monomer, wherein the polymerized monomer comprises at least a cross-linkable monomer; and the polymerized monomer may or may not comprise a chain-extending monomer;

[0242] Installing the electrode assembly into the housing;

[0243] Injecting an electrolyte base liquid into the housing containing the electrode assembly to fully infiltrate the positive electrode sheet and the negative electrode sheet, performing an in-situ gelation reaction, causing the polymerized monomers to form a gel skeleton in the corresponding active material layer, and causing a portion of the electrolyte base liquid in the active material layer to form an intra-electrode gel electrolyte including the gel skeleton, and the remaining portion of the electrolyte base liquid in the active material layer to serve as the intra-electrode electrolyte, thereby forming a gel / liquid composite electrolyte in the active material layer; wherein the electrolyte base liquid includes an electrolyte salt, a solvent, and an initiator for initiating a polymerization reaction of the polymerized monomers, and may or may not include additives;

[0244] After the gelation reaction is completed, chemical formation is carried out to obtain the secondary battery of the first aspect of the present application; the secondary battery includes at least two electrode plates, any one of the electrode plates includes an active material layer arranged on at least one side of the electrode plate; the active material layer on at least one side of at least one of the electrode plates includes active particles and an electrolyte in the plate located in the pores between the active particles; the electrolyte in the plate includes a gel electrolyte in the plate and an electrolyte solution in the plate; the gel electrolyte in the plate and the electrolyte solution in the plate each independently contain an electrolyte salt, and the ratio of the mass of the electrolyte salt in the gel electrolyte in the plate to the mass of the electrolyte salt in the electrolyte solution in the plate is R W Satisfy 1 <R W <9.

[0245] The terms or phrases such as positive electrode sheet, negative electrode sheet, separator, electrode assembly, polymerized monomer, cross-linkable monomer, and chain-extending monomer involved in the above-mentioned preparation methods can be referred to in the context of this application. For example, the preparation method of a positive electrode sheet pre-embedded with polymerized monomer and the preparation method of a negative electrode sheet pre-embedded with polymerized monomer are provided.

[0246] The gelation reaction may also be referred to as a cross-linking and curing reaction, and may be carried out under heating conditions. The heating temperature may be 50 to 80° C., such as 50° C., 60° C., 70° C., 80° C., and the like.

[0247] In a second aspect, the present application provides an electrical device comprising the secondary battery described in the first aspect of the present application.

[0248] The secondary battery can be used as a power source or energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, and energy storage systems. Examples of mobile devices include, but are not limited to, mobile phones and laptops; and examples of electric vehicles include, but are not limited to, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, and electric trucks.

[0249] As the electrical device, a secondary battery can be selected according to its usage requirements.

[0250] FIG3 shows an example of an electric device 6. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the electric device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module may be used.

[0251] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0252] Below, some embodiments of the present application are described. The embodiment described below is exemplary, is only used to explain the present application, and cannot be construed as limiting the present application. In the embodiment, if no technology or conditions are indicated, it is carried out according to the description above, or according to the technology or conditions described in the document in this area or according to the product specification. Reagents used or instruments that are not indicated by the manufacturer are conventional products that can be obtained commercially, or can be synthesized in a conventional manner by commercially available products.

[0253] In the following embodiments, unless otherwise specified, "room temperature" refers to 20°C to 30°C, and further, may be 25°C.

[0254] The term "compacted density" as used in this application has a well-known meaning in the art and is one of the reference indicators of material energy density. In this application, unless otherwise specified, the compacted density of an electrode plate refers to the ratio of the mass of the active material layer to its volume. The compacted density of a positive electrode plate refers to the ratio of the mass of the positive electrode active material layer to its volume, and the compacted density of a negative electrode plate refers to the ratio of the mass of the negative electrode active material layer to its volume. This can be obtained by testing using conventional methods in the art.

[0255] In the following examples, AIBN is azobisisobutyronitrile, which is an initiator for initiating the polymerization reaction and achieving gelation. Diethylene glycol dimethacrylate is diethylene glycol ethyl dimethacrylate.

[0256] Example 1. Gel / liquid composite electrolyte is provided in the negative electrode

[0257] (1) Negative electrode, pre-embedded polymer monomer

[0258] The negative electrode active material (artificial graphite and silicon oxide SiO x A mixture of 20% by mass of silicon oxide), conductive agent acetylene black, binder styrene butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na) and polymer monomer (diethylene glycol dimethacrylate) are added to deionized water in a mass ratio of 93.8%: 2%: 1%: 2%: 1.2% and mixed evenly to form a negative electrode slurry with a solid content of about 48%; the prepared negative electrode slurry is evenly coated on the double-sided surface of the negative electrode current collector copper foil, dried at 80°C and cold pressed, and the appropriate cold pressing pressure is controlled according to the preset porosity to obtain a negative electrode sheet pre-embedded with a polymer monomer. The compaction density of the negative electrode sheet is 1.7g / cm 3 .

[0259] In this example, the mass proportion of the polymerized monomer in the non-solvent component of the negative electrode slurry is 1.2%.

[0260] (2) Positive electrode

[0261] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (i.e. NCM811), conductive agent acetylene black and polyvinylidene fluoride (PVDF) are mixed evenly in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 97%:1%:2% to obtain a positive electrode slurry with a solid content of about 65%. The positive electrode slurry is coated on both sides of an aluminum foil, dried at 100°C, and cold pressed to obtain a positive electrode sheet. The compacted density of the positive electrode sheet is 3.5g / cm 3 , the porosity of the positive electrode sheet is about 15%.

[0262] (3) Isolation film

[0263] The isolation film adopts PE isolation film.

[0264] (4) Liquid electrolyte

[0265] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed evenly in a volume ratio of 1:1:1, lithium hexafluorophosphate (LiPF6) is added to fully dissolve it, and azobisisobutyronitrile (initiator) is added to obtain a liquid electrolyte, wherein the concentration of LiPF6 is 1 mol / L and the mass ratio of the initiator to the pre-embedded polymer monomer is 3%.

[0266] (5) Assembly and preparation of secondary batteries

[0267] Place the separator between the positive electrode sheet and the negative electrode sheet and stack them in order, so that the separator is between the positive and negative electrode sheets to play a role of isolation, and wind them in a conventional manner to obtain an electrode assembly, and place the electrode assembly in a battery case;

[0268] After drying, the above-mentioned liquid electrolyte is injected into the shell at an injection coefficient of 1.6g / Ah, fully infiltrated, and allowed to stand at 70°C for 12 hours to allow the polymerized monomers embedded in the electrode plates to fully cross-link and solidify, forming a gel electrolyte in the pores of the corresponding electrode plates;

[0269] After cooling, the secondary battery having a gel / liquid composite electrolyte in the negative electrode plate is obtained through processes such as formation and standing.

[0270] The filling coefficient has a conventional meaning in this field, and its calculation formula is: the filling volume divided by the preset capacity, and the unit is g / Ah.

[0271] Examples 2-9 adopt a method that is basically the same as that of Example 1, with the following differences: the amount of polymerization monomer added to the negative electrode slurry is changed, as shown in Table 1. The pressure in the cold pressing process of the negative electrode plate can also be appropriately adjusted according to Table 1 to obtain the target porosity, and the porosity value is allowed to fluctuate within ±2%.

[0272] Example 10 uses a method substantially identical to that of Example 1, with the following differences: the negative electrode active material layer has a double-layer structure. The negative electrode slurry of step (1) is applied twice. The first application of the negative electrode slurry does not contain polymerized monomer (the lower active layer formed is not pre-embedded with polymerized monomer). The polymerized monomer is pre-embedded only in the upper active layer (i.e., the outer active layer of the negative electrode) during the second application. The total mass of polymerized monomer remains unchanged during the second application. The thickness and porosity of the upper and lower active layers are substantially the same.

[0273] Example 11 employed a method substantially identical to that of Example 1, with the following differences: the negative electrode active material layer had a double-layer structure. The negative electrode slurry of step (1) was applied twice. The polymerized monomer was pre-embedded only in the upper active layer (i.e., the outer active layer of the negative electrode) during the first application. The negative electrode slurry applied in the second application contained no polymerized monomer (the lower active layer formed was not pre-embedded with polymerized monomer), and the concentration of polymerized monomer remained unchanged during the first application. The thickness and porosity of the upper and lower active layers were substantially the same.

[0274] Example 13: Gel / liquid composite electrolyte is provided in the positive electrode

[0275] A method substantially the same as that of Example 1 is adopted, except that the polymerized monomer is pre-embedded in the positive electrode slurry, while the polymerized monomer is not pre-embedded in the negative electrode slurry.

[0276] (1) Negative electrode

[0277] The negative electrode active material (artificial graphite and silicon oxide SiO x A mixture of 20% by mass of silicon oxide, acetylene black as a conductive agent, styrene butadiene rubber (SBR) as a binder, and sodium carboxymethyl cellulose (CMC-Na) as a thickener were added to deionized water in a mass ratio of 94:2:1:2 and mixed evenly to form a negative electrode slurry with a solid content of about 46%. The prepared negative electrode slurry was evenly coated on both sides of the negative electrode current collector copper foil, dried at 80°C, and then cold pressed to obtain a negative electrode sheet. The compacted density of the negative electrode sheet is about 1.7g / cm 3 The porosity of the negative electrode sheet is about 40%.

[0278] (2) Positive electrode, pre-embedded polymer monomer

[0279] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (i.e. NCM811), conductive agent acetylene black, polyvinylidene fluoride (PVDF) and polymerization monomer (a mixture of vinylidene fluoride, hexafluoropropylene and ethylene glycol diallyl ether, with a mass ratio of 1:1:1) are mixed evenly in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 95.7%:1%:2%:1.3% to obtain a positive electrode slurry with a solid content of about 65%. The positive electrode slurry is coated on both sides of the aluminum foil, dried at 100°C and then cold pressed. The appropriate cold pressing pressure is controlled according to the preset porosity to obtain a positive electrode sheet pre-embedded with polymerization monomer. The compaction density of the positive electrode sheet is 3.5g / cm 3 .

[0280] In this example, the mass proportion of the polymerized monomer in the non-solvent component of the positive electrode slurry is 1.3%.

[0281] (3) Isolation film

[0282] The same isolation film as in Example 1 was used.

[0283] (4) Liquid electrolyte

[0284] The same liquid electrolyte as in Example 1 was used.

[0285] (5) Assembly and preparation of secondary batteries

[0286] The same process as in Example 1 was used to prepare a secondary battery having a gel / liquid composite electrolyte in the positive electrode sheet.

[0287] Examples 13-17 adopt a method basically the same as that of Example 12, with the following differences: the amount of polymerization monomer added to the positive electrode slurry is changed, as shown in Table 1. The pressure in the cold pressing process of the positive electrode plate is appropriately adjusted according to Table 1 to obtain the target porosity, and the porosity value is allowed to fluctuate within ±2%.

[0288] Example 18. Both the positive electrode and the negative electrode are provided with a gel / liquid composite electrolyte

[0289] (1) Negative electrode

[0290] The same method as in Example 3 was used to obtain a negative electrode sheet pre-embedded with polymerized monomers.

[0291] (2) Positive electrode

[0292] The same method as in Example 14 was used to obtain a positive electrode sheet pre-embedded with polymerized monomers.

[0293] (3) Isolation film

[0294] The same isolation film as in Example 3 was used.

[0295] (4) Liquid electrolyte

[0296] The same liquid electrolyte as in Example 3 was used.

[0297] (5) Assembly and preparation of secondary batteries

[0298] The same process as in Example 3 was used to prepare a secondary battery having a gel / liquid composite electrolyte in both the positive electrode sheet and the negative electrode sheet.

[0299] Comparative Example 1: No gel / liquid composite electrolyte is provided in the positive electrode sheet and the negative electrode sheet.

[0300] The preparation method is basically the same as that in Example 1, except that no polymerizable monomer is added to the negative electrode slurry, and the remaining operating steps and parameters are the same as those in Example 1.

[0301] In addition, the difference between this example and Example 13 is that no polymerizable monomer is added to the positive electrode slurry.

[0302] Please refer to Table 1.

[0303] Comparative Example 2: The proportion of gel electrolyte in the pores of the negative electrode is too high

[0304] The preparation method is basically the same as that in Example 1, except that the content of the polymerized monomer in the negative electrode slurry is increased. Please refer to Table 1. The remaining operating steps and parameters are the same as those in Example 1.

[0305] Comparative Example 3: The proportion of gel electrolyte in the pores of the positive electrode is too high

[0306] The preparation method is basically the same as that of Example 13, except that the content of the polymerized monomer in the positive electrode slurry is increased. Please refer to Table 1. The remaining operating steps and parameters are the same as those of Example 1.

[0307] Comparative Example 4. Polymerization monomer introduced with liquid electrolyte

[0308] The negative electrode sheet was prepared by the method of Example 3, the positive electrode sheet was prepared by the method of Example 14, and the isolation membrane was prepared by the method of Example 3.

[0309] The composition of the liquid electrolyte is as follows: ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed uniformly in a volume ratio of 1:1:1, lithium hexafluorophosphate (LiPF6) is added to fully dissolve it, and a polymerization monomer (diethylene glycol dimethacrylate) and an initiator AIBN are added and mixed uniformly to obtain a liquid electrolyte containing a polymerization monomer, wherein the concentration of LiPF6 is 1 mol / L. The concentration of the polymerization monomer is converted in combination with the injection coefficient so that the total amount of polymerization monomer in the prepared secondary battery is basically consistent with the amount of polymerization monomer pre-embedded in the negative electrode plate of the secondary battery in Example 1.

[0310] Place the separator between the positive electrode sheet and the negative electrode sheet and stack them in order, so that the separator is between the positive and negative electrode sheets to play a role of isolation, and wind them in a conventional manner to obtain an electrode assembly, and place the electrode assembly in a battery case;

[0311] After drying, the liquid electrolyte containing the polymerized monomer is injected into the housing at the same injection coefficient as in Example 1. After injection, the liquid electrolyte is cross-linked and cured as soon as possible using the same cross-linking and curing conditions as in Example 1, so that the gel electrolyte is basically distributed outside the electrode sheet.

[0312] After cooling, the secondary battery is subjected to processes such as formation and standing to obtain a secondary battery having a gel / liquid composite electrolyte in addition to an electrode plate.

[0313] Material structure and composition test methods

[0314] Through focused electron beam (FIB) technology, scanning electron microscope (SEM) testing and analysis, combined with focused electron beam (FIB) continuous sectioning, energy dispersive spectroscopy (EDS) elemental spectrum and three-dimensional reconstruction analysis software, the following were obtained: including the pore size of the active material layer, the porosity b of the active material layer (the porosity b1 of the negative active material layer, the porosity b2 of the positive active material layer) and the layer thickness, the pore size, porosity and layer thickness of the inner active layer and the outer active layer in the multi-layer structure of the active material layer, the mass and volume of the gel electrolyte, the mass and volume of the liquid electrolyte, the mass of the electrolyte salt in the gel electrolyte and the liquid electrolyte, and the ratio R of the mass of the electrolyte salt in the gel electrolyte in the electrode plate to the mass of the electrolyte salt in the electrolyte solution. W , the ratio of the mass of the electrolyte salt in the gel electrolyte in the pores of the negative electrode active material layer to the mass of the electrolyte salt in the electrolyte in the pores of the negative electrode active material layer R W1, the ratio of the mass of the electrolyte salt in the gel electrolyte in the pores of the positive electrode active material layer to the mass of the electrolyte salt in the electrolyte in the pores of the positive electrode active material layer R W2 .

[0315] The above parameters were tested and analyzed using a FEI Scios 2HiVac instrument. The specific method employed was as follows: Utilizing the nanometer spatial dynamic resolution and layer-by-layer cutting technology of a FIB-SEM, the three-dimensional structure of the sample was reconstructed. EDS elemental spectrum analysis was then used to determine the distribution and proportion of each element. Finally, software-based quantitative analysis revealed the pore distribution, volume distribution, and mass distribution of each component. Combined with the sample's total mass, volume, and thickness, the values ​​of pore size, porosity, mass, volume, and thickness were also determined.

[0316] To test the above parameters, the following method is used to prepare the active material layer sample of the electrode plate: discharge the secondary battery to the nominal lower limit voltage, then disassemble the battery cell to obtain the positive electrode plate or the negative electrode plate, and then extract the positive electrode active material layer or the negative electrode active material layer sample to be tested.

[0317] The nominal lower limit voltage can be obtained by conventional testing methods or defined by the manufacturer.

[0318] Test methods for performance indicators

[0319] 1. Battery rate

[0320] At room temperature (25°C), the secondary battery under test was charged at a 1 / 3C rate to the upper voltage limit. It was then discharged at 0.33C and 2C to the lower voltage limit, respectively. The discharge capacity at the 0.33C rate was used as the nominal capacity reference group. The capacity retention rate of the secondary battery at a 2C rate was calculated, as shown in Table 1, "Discharge Capacity Retention at 2C Rate." The discharge capacity retention rate reflects the rate performance of the secondary battery. A larger value indicates better rate performance.

[0321] Using the same method, multiple substantially identical secondary batteries to be tested are prepared. The upper charge voltage and lower discharge voltage can be obtained by conventional methods in the art or according to manufacturer's definition. For example, in Example 1, the upper charge voltage is 4.25V and the lower discharge voltage is 2.8V.

[0322] 3. Energy density

[0323] At room temperature, charge the secondary battery under test at a 1 / 3C rate to the upper voltage limit, then discharge it at a 1 / 3C rate to the lower voltage limit. The energy during the discharge is calculated. The mass energy density (Wh / kg) of a secondary battery is calculated as: energy during discharge divided by the mass of the secondary battery.

[0324] 4. Cycle performance

[0325] At room temperature (25°C), the secondary battery under test was charged at a rate of 1 / 3C to the upper limit voltage, then charged at a constant voltage to 0.05C. After standing for 10 minutes, the battery was discharged at a rate of 1 / 3C to the lower limit voltage and allowed to stand for 10 minutes. This charge and discharge process was repeated. The ratio of the discharge capacity of each cycle to the discharge capacity of the first cycle was recorded. The number of cycles recorded when the capacity decayed to 80% was used as a parameter for evaluating the cycling performance, as shown in Table 1, "Number of Cycles to 80% Capacity Decay at 25°C." A larger value indicates a longer cycle life.

[0326] Test results and analysis

[0327] Structural and compositional analysis revealed that the negative electrode active material layers of the secondary batteries prepared in Examples 1-11 contained a gel / liquid composite electrolyte. The positive electrode active material layers of the secondary batteries prepared in Examples 12-17 contained a gel / liquid composite electrolyte. The secondary battery prepared in Example 18 contained a gel / liquid composite electrolyte in both the negative and positive electrode active material layers. The electrolyte salt ratios in the corresponding gel and liquid electrolytes can be found in Table 1.

[0328] Examples 1 to 18 have both excellent rate performance and cycle performance. The cycle performance and rate performance of Example 18 are both very excellent.

[0329] Comparative Example 1 does not contain a gel / liquid composite electrolyte in either the positive or negative electrode sheets. The cycle performance of Comparative Example 1 is significantly worse than that of Examples 1-11 and 18, and also worsens to a certain extent compared to Examples 12-17.

[0330] The proportion of gel electrolyte in the pores of the negative electrode plate of Comparative Example 2 is too high; compared with Examples 1-11 and 18, not only the cycle performance of Comparative Example 2 deteriorates, but the deterioration of some examples is very serious, and the rate performance also deteriorates seriously.

[0331] The proportion of gel electrolyte in the pores of the positive electrode plate of Comparative Example 3 is too high; compared with Examples 12-17, Comparative Example 3 not only deteriorates in cycle performance, but also in rate performance.

[0332] Although gel electrolyte exists in Comparative Example 4, it is mainly distributed outside the electrode plates; compared with Examples 1-18, the rate performance of Comparative Example 4 also deteriorates to a certain extent; compared with Examples 1-11 and 18, the cycle performance of Comparative Example 4 deteriorates significantly; compared with Examples 13-17, the cycle performance of Comparative Example 4 also deteriorates to a certain extent.

[0333] Table 1.

[0334] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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.

[0335] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and within the scope of the technical solution of the present application, embodiments that have substantially the same structure as the technical idea and exert the same effect are all included in the technical scope of the present application. The above-mentioned embodiments only express several embodiments of the present application, and their descriptions are relatively detailed, but they cannot be understood as limiting the scope of the patent. In addition, without departing from the scope of the subject matter of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of constructing by combining some of the constituent elements in the embodiments are also included in the scope of the present application. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several modifications and improvements can be made, which all fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be based on the attached claims, and the description and drawings may be used to explain the content of the claims.

Claims

1. A secondary battery, comprising at least two electrode plates, any one of the electrode plates comprising an active material layer disposed on at least one side of the electrode plates; the active material layer on at least one side of at least one of the electrode plates comprising active particles and an intra-electrolyte located in the pores between the active particles; the intra-electrolyte comprising an intra-electrolyte gel electrolyte and an intra-electrolyte solution; the intra-electrolyte gel electrolyte and the intra-electrolyte solution each independently comprising an electrolyte salt, and the ratio of the mass of the electrolyte salt in the intra-electrolyte gel electrolyte to the mass of the electrolyte salt in the intra-electrolyte solution is R W Satisfy 1 <R W <9.

2. The secondary battery according to claim 1, wherein 1.2≤R W ≤8.5； Optionally, 1.5 ≤ R W ≤8.

5.

3. The secondary battery according to claim 1 or 2, wherein: The active material layer on at least one side of at least one of the electrode plates is a multi-layer structure, and the electrolyte in the electrode plate is distributed in at least a portion of the pores in the outer active layer of the multi-layer structure; Among them, in the multilayer structure of the active material layer, the outer active layer is farthest from the center of the pole piece along the thickness direction of the pole piece.

4. The secondary battery according to claim 3, wherein In the electrode sheet having a multi-layer structure, the porosity of the outer active layer is higher than the porosity of the inner active layer; wherein the inner active layer is located inside the active material layer.

5. The secondary battery according to any one of claims 1 to 4, wherein At least one of the electrode plates is a negative electrode plate, the active material layer of the negative electrode plate is a negative electrode active material layer, and the negative electrode active material layer is located on at least one side of the negative electrode plate.

6. The secondary battery according to claim 5, wherein The negative electrode active material layer contains a negative electrode active material, and the negative electrode active material includes a silicon-based material; Optionally, the mass proportion of the silicon-based material in the negative electrode active material is recorded as silicon content, and the silicon content is ≥3%; Further optionally, the silicon content is 3% to 40%.

7. The secondary battery according to claim 5 or 6, wherein: The negative electrode active material layer has a multilayer structure as claimed in claim 3 or 4, wherein the porosity of the outer active layer is 20% to 50%; further optionally 30% to 50%; further optionally 30% to 45%.

8. The secondary battery according to any one of claims 5 to 7, wherein The negative electrode active material layer on either side independently has 2.4≤R W / b1≤45, wherein b1 is the porosity of the negative electrode active material layer on either side; Optionally, 3.75≤R W / b1≤36; Further optionally, 7.5≤R W / b1≤18.

9. The secondary battery according to any one of claims 5 to 8, wherein The porosity b1 of the negative electrode active material layer on either side is independently 20% to 50%; Optionally, the porosity b1 of the negative electrode active material layer on either side is independently 25% to 45%; Further optionally, the porosity b1 of the negative electrode active material layer on either side is independently 25% to 40%.

10. The secondary battery according to any one of claims 1 to 9, wherein At least one of the electrode plates is a positive electrode plate, the active material layer of the positive electrode plate is a positive electrode active material layer, and the positive electrode active material layer is located on at least one side of the positive electrode plate.

11. The secondary battery according to claim 10, wherein The positive electrode active material layer has a multilayer structure as claimed in claim 3 or 4, wherein the porosity of the outer active layer is 10% to 40%; further optionally 15% to 40%; further optionally 20% to 35%.

12. The secondary battery according to claim 10 or 11, wherein The positive electrode active material layer on either side independently has 3.75≤R W / b2≤90, wherein b2 is the porosity of the positive electrode active material layer on either side; Optionally, 3.75≤R W / b2≤60; Further optionally, 4.2≤R W / b2≤25.

13. The secondary battery according to any one of claims 11 to 12, wherein The porosity b2 of the positive electrode active material layer on either side is independently 10% to 40%; Optionally, the porosity b2 of the positive electrode active material layer on either side is independently 10% to 35%; Further optionally, the porosity b2 of the positive electrode active material layer on either side is independently 15% to 35%.

14. The secondary battery according to any one of claims 1 to 13, wherein The secondary battery comprises a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is arranged between the positive electrode sheet and the negative electrode sheet; The positive electrode sheet and the negative electrode sheet meet one or two of the following characteristics: The negative electrode sheet is as defined in any one of claims 5 to 9; The positive electrode sheet is as defined in any one of claims 10 to 13.

15. The secondary battery according to claim 14, wherein The positive electrode sheet includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active substance, and the positive electrode active substance includes a lithium ion material; Optionally, the secondary battery is a lithium-ion secondary battery.

16. The secondary battery according to claim 15, wherein The electrolyte salt in the electrode sheet includes electrolyte lithium salt; Optionally, the electrolyte lithium salt is distributed in at least one or both of the gel electrolyte in the electrode sheet and the electrolyte in the electrode sheet in the same electrode sheet; Optionally, the electrolyte lithium salt is distributed at least in the pores of the positive electrode active material layer; Optionally, the negative electrode plate includes a negative electrode active material layer, and the electrolyte lithium salt is distributed at least in the pores of the negative electrode active material layer.

17. An electrical device comprising the secondary battery according to any one of claims 1 to 16.

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