Secondary battery, solid-state electrolyte, and electric device

Abstract

A secondary battery, a solid-state electrolyte, and an electric device. The secondary battery comprises a positive electrode sheet, a solid-state electrolyte, and a negative electrode sheet. The solid-state electrolyte comprises a first polymer matrix, a first lithium salt, and a first additive. The first additive comprises a first oligomer, wherein the structural unit of the first oligomer comprises a first heteroatom, the first heteroatom comprising one or more of O, N and S. The degree of polymerization n of the first oligomer is: 5≤n≤60. The solid-state electrolyte in the secondary battery has a relatively high ionic conductivity.

Description

Secondary batteries, solid electrolytes and electrical devices

[0001] Related applications

[0002] This application claims priority to Chinese patent application filed on November 15, 2024, with application number 2024116428874 and entitled "Secondary Battery, Solid Electrolyte and Electrical Device", the entire contents of which are incorporated herein by reference. Technical Field

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

[0004] In recent years, the application range of rechargeable batteries has become increasingly wide, and they are now widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, and electric vehicles. Due to the significant development of rechargeable batteries, higher requirements have been placed on their energy density, cycle performance, and safety performance.

[0005] Compared to liquid batteries using liquid electrolytes, solid-state batteries using solid electrolytes typically offer higher energy density and safety. Among solid electrolytes, polymer-based solid polymer electrolytes have attracted widespread attention due to their high flexibility, excellent processability, and good interfacial contact properties. However, the low ionic conductivity of solid polymer electrolytes is one of the main factors limiting their application. Summary of the Invention

[0006] To achieve the above objectives, this application provides a secondary battery, a solid electrolyte, and an electrical device, wherein the solid electrolyte in the secondary battery has a high ionic conductivity.

[0007] A first aspect of this application provides a secondary battery, including a positive electrode, a solid electrolyte, and a negative electrode. The solid electrolyte comprises a first polymer matrix, a first lithium salt, and a first additive. The first additive comprises a first oligomer, the structural unit of which contains a first heteroatom, the first heteroatom comprising one or more of O, N, and S, and the degree of polymerization n of the first oligomer is 5 ≤ ​​n ≤ 60.

[0008] The aforementioned secondary battery, by adding oligomers to the solid electrolyte, wherein the structural units of the oligomers contain one or more heteroatoms selected from O, N, and S, and by reasonably controlling the degree of polymerization n of the oligomers to be 5 ≤ n ≤ 60, can effectively improve the ionic conductivity of the solid electrolyte in the secondary battery.

[0009] In some implementations, 10 ≤ n ≤ 40.

[0010] In some embodiments, the first oligomer includes one or more of polyethers, polysulfides, polyamines, polyesters, and polyamides. Using a suitable type of first oligomer, with its more extended chain segments and appropriate mobility, can improve the ionic conductivity and high-temperature capacity of the solid electrolyte.

[0011] In some embodiments, the first oligomer comprises one or more compounds with the following structures:

[0012] Among them, R1, R2, R3, R4, R5, and R6 each independently include a C1-C20 alkylene group or a C6-C20 arylene group;

[0013] R 11 R 22 Each independently includes H, C1-C20 alkyl or C6-C20 aryl;

[0014] 10≤n1≤40, 10≤n2≤40, 10≤n3≤40, 10≤n4≤40, 10≤n5≤40, 10≤n6≤40.

[0015] In some embodiments, the number-average molecular weight of the first oligomer is 200–3000. Properly controlling the number-average molecular weight of the first oligomer can improve ionic conductivity and high-temperature capacity.

[0016] In some embodiments, the weight of the first oligomer is 0.2 to 2 parts per part by weight of the first polymer matrix. Properly controlling the weight of the first oligomer can improve the ionic conductivity and high-temperature capacity of the polymer matrix.

[0017] In some embodiments, the first lithium salt has one or both of the following features:

[0018] (1) Based on 1 part by weight of the first polymer matrix, the first lithium salt is 0.1 to 0.8 parts by weight;

[0019] (2) The first lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium perchlorate, and lithium nitrate.

[0020] In some embodiments, the first polymer matrix has one or both of the following features:

[0021] (1) The first polymer matrix includes one or more of polyvinylidene fluoride and its copolymers;

[0022] (2) The number average molecular weight of the first polymer matrix is ​​100,000 to 8 million.

[0023] This is more conducive to improving the mechanical properties of solid electrolytes.

[0024] In some embodiments, the positive electrode includes a positive active layer comprising a positive active material, a second polymer matrix, a second lithium salt, and a second additive. The second additive includes a second oligomer, the structural unit of which contains a second heteroatom, which includes one or more of O, N, and S. The degree of polymerization n of the second oligomer is... 01 For: 5≤n 01 ≤60.

[0025] A second aspect of this application provides a solid electrolyte comprising a first polymer matrix, a first lithium salt, and a first additive; the first additive comprises a first oligomer, wherein the structural unit of the first oligomer contains a first heteroatom, the first heteroatom comprising one or more of O, N, and S, and the degree of polymerization n of the first oligomer is 5 ≤ ​​n ≤ 60.

[0026] In some embodiments, the solid electrolyte is the solid electrolyte in the secondary battery described in the first aspect.

[0027] A third aspect of this application provides an electrical device comprising at least one of the secondary battery described in the first aspect and the solid electrolyte described in the second aspect. Attached Figure Description

[0028] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0029] Figure 1 is a schematic diagram of a secondary battery according to an embodiment of this application.

[0030] Figure 2 is an exploded view of the secondary battery according to one embodiment of this application shown in Figure 1.

[0031] Figure 3 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of this application.

[0032] Figure 4 shows the relationship between the ionic conductivity of the solid electrolyte membranes prepared in Comparative Example 1 and Example 1 and the change over time.

[0033] Explanation of reference numerals in the attached drawings: 1. Secondary battery; 11. Casing; 12. Electrode assembly; 13. Cover plate; 2. Electrical device. Detailed Implementation

[0034] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0036] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. Ranges defined in this way can include or exclude endpoints. Any endpoint can be included or excluded independently, and they can be combined arbitrarily; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is expected that ranges of 60–110 and 80–120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are also listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0037] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0038] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0039] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0040] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0041] In this application, unless otherwise specified, A (e.g., B) means that B is a non-limiting example of A, and it is understood that A is not limited to B.

[0042] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0043] Traditional methods aim to improve the ionic conductivity of solid polymer electrolytes by introducing small-molecule plasticizers, such as ethylene carbonate (EC), propylene carbonate (PC), and diethylene glycol dimethyl ether (DME). However, this method has limited effectiveness in improving ionic conductivity in practical applications. Research suggests this may be because small-molecule plasticizers are difficult to stably exist in solid polymer electrolytes. By the time battery manufacturing is complete, most of the small-molecule plasticizers in the solid polymer electrolyte have volatilized, leaving only a small amount that cannot effectively improve ionic conductivity. Furthermore, as time progresses, the continued volatilization of small-molecule plasticizers further diminishes their effect on improving ionic conductivity.

[0044] Based on this, one embodiment of this application provides a secondary battery, including a positive electrode, a solid electrolyte, and a negative electrode. The solid electrolyte includes a first polymer matrix, a first lithium salt, and a first additive. The first additive includes a first oligomer, and the structural unit of the first oligomer contains a first heteroatom. The first heteroatom includes one or more of O, N, and S. The degree of polymerization n of the first oligomer is 5 ≤ ​​n ≤ 60.

[0045] The aforementioned secondary battery incorporates oligomers into the solid electrolyte. These oligomers contain one or more heteroatoms selected from O, N, and S in their structural units. The presence of these heteroatoms gives the oligomer chains a certain degree of mobility, thereby enhancing the lithium conductivity of the polymer matrix. Furthermore, the degree of polymerization (n) of the oligomer needs to be reasonably controlled to 5 ≤ n ≤ 60. If the degree of polymerization is too low, the oligomer will still easily volatilize during battery processing, making it difficult to effectively and continuously enhance the lithium conductivity of the polymer matrix; if the degree of polymerization is too high, the mobility of the chain segments will significantly decrease, making it difficult to enhance the lithium conductivity of the polymer matrix. Thus, this application, by using the specific oligomers described above, can effectively improve the ionic conductivity of the solid electrolyte in the secondary battery, while also increasing the high-temperature capacity of the secondary battery.

[0046] In addition, by adding oligomers to solid electrolytes, the mobility of their chain segments can be controlled to a certain extent compared to smaller molecule plasticizers. While providing enhanced lithium conductivity to the polymer matrix, this has little impact on the mechanical properties of the solid electrolyte.

[0047] In some embodiments, the oligomer does not contain reactive groups, such as carbon-carbon double bonds. Such oligomers are less likely to cross-link with each other to form a network structure, giving their chain segments a degree of mobility and allowing them to enhance the lithium conductivity of the polymer matrix.

[0048] In some embodiments, the solid electrolyte is a solid electrolyte membrane.

[0049] Specifically, the degree of polymerization n of the first oligomer includes, but is not limited to, 5, 8, 9, 10, 13, 15, 17, 20, 23, 25, 27, 30, 35, 40, 45, 48, 50, 55, 60, or any two of the foregoing. Further, 10 ≤ n ≤ 40. This can further improve the ionic conductivity of the solid electrolyte.

[0050] In some embodiments, the first oligomer comprises one or more of polyethers, polysulfides, polyamines, polyesters, and polyamides. Using a suitable type of first oligomer, with more extended chain segments and appropriate mobility, can improve the ionic conductivity and high-temperature capacity of the solid electrolyte. Further, the first oligomer comprises one or more of polyethers, polysulfides, and polyesters.

[0051] In some embodiments, the first oligomer comprises one or more compounds with the following structures:

[0052] Among them, R1, R2, R3, R4, R5, and R6 each independently include a C1-C20 alkylene group or a C6-C20 arylene group;

[0053] R 11 R 22 Each independently includes H, C1-C20 alkyl or C6-C20 aryl;

[0054] 5≤n1≤60, 5≤n2≤60, 5≤n3≤60, 5≤n4≤60, 5≤n5≤60, 5≤n6≤60.

[0055] Furthermore, 10≤n1≤40, 10≤n2≤40, 10≤n3≤40, 10≤n4≤40, 10≤n5≤40, and 10≤n6≤20.

[0056] In some embodiments, the number-average molecular weight of the first oligomer is 200 to 3000. Reasonably controlling the number-average molecular weight of the first oligomer can improve ionic conductivity and high-temperature capacity. Specifically, the number-average molecular weight of the first oligomer includes, but is not limited to: 200, 300, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 2000, 3000, or any range between the foregoing. Further, the number-average molecular weight of the first oligomer is 500 to 2000.

[0057] In some embodiments, the first oligomer includes one or more of diethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, polycaprolactone, polyethylene glycol, and polyethyleneimine.

[0058] In some embodiments, the weight of the first oligomer is 0.2 to 2 parts per part by weight of the first polymer matrix. Specifically, the weight of the first oligomer includes, but is not limited to, 0.2, 0.6, 0.8, 0.85, 0.9, 0.95, 1.1, 1.2, 1.3, 1.4, 1.5, 2 parts, or any combination thereof. Reasonably controlling the weight of the first oligomer can improve the ionic conductivity and high-temperature capacity of the polymer matrix. Further, the weight of the first oligomer is 0.6 to 1.5 parts per part by weight of the first polymer matrix.

[0059] In some embodiments, the first lithium salt comprises 0.1 to 0.8 parts by weight, based on 1 part by weight of the first polymer matrix. Specifically, the weight of the first lithium salt includes, but is not limited to, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 parts, or any range between the foregoing. Reasonably controlling the weight of the lithium salt allows for better compatibility with the first oligomer, improving the lithium-ion transport performance in the polymer matrix and enhancing the ionic conductivity of the polymer matrix.

[0060] In some embodiments, the first lithium salt comprises one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate, and lithium nitrate.

[0061] In some embodiments, the first polymer matrix comprises one or more of polyvinylidene fluoride (PVDF) and its copolymers. Using a specific polymer matrix, on the one hand, forms a microphase-separated structure between the polymer and the oligomer and the lithium salt, which is beneficial for obtaining higher mechanical properties; on the other hand, it reduces the formation of lithium bonds with lithium ions, maintaining the polymer configuration within the system, which is also beneficial for obtaining better mechanical properties. This further improves the mechanical properties of the solid electrolyte.

[0062] In some embodiments, the first polymer matrix includes one or more of PVDF, poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)), poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)), and poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)).

[0063] In some embodiments, the number-average molecular weight of the first polymer matrix is ​​≥100,000. This is more beneficial for improving the mechanical properties of the solid electrolyte. Further, the number-average molecular weight of the first polymer matrix is ​​between 100,000 and 8,000,000. Specifically, the number-average molecular weight of the polymer matrix includes, but is not limited to: 100,000, 130,000, 150,000, 200,000, 300,000, 500,000, 1,000,000, 1,500,000, 2,000,000, 2,500,000, 3,000,000, 3,500,000, 4,000,000, 4,500,000, 5,000,000, 5,500,000, 6,000,000, 6,500,000, 7,000,000, 7,500,000, 8,000,000, or any range between the foregoing. Even further, the number-average molecular weight of the first polymer matrix is ​​between 100,000 and 300,000.

[0064] In some embodiments, the positive electrode includes a positive active layer comprising a positive active material, a second polymer matrix, a second lithium salt, and a second additive. The second additive includes a second oligomer, the structural unit of which contains a second heteroatom, which includes one or more of O, N, and S. The degree of polymerization n of the second oligomer is... 01 For: 5≤n 01 ≤60.

[0065] Understandably, the polymer matrix, lithium salt, and additive schemes in solid-state electrolytes are also applicable to the positive electrode active layer of the positive electrode sheet to achieve better overall ionic conductivity in the secondary battery. The schemes and advantages of the second polymer matrix, second lithium salt, and second additive are similar to those of the first polymer matrix, first lithium salt, and first additive, and will not be elaborated further here. Furthermore, in application, the second polymer matrix can be the same as or different from the first polymer matrix, the second lithium salt can be the same as or different from the first lithium salt, and the second additive can be the same as or different from the first additive.

[0066] In some embodiments, the negative electrode comprises a lithium metal sheet.

[0067] In other embodiments, the negative electrode sheet includes a negative electrode active layer, which comprises a negative electrode active material, a third polymer matrix, a third lithium salt, and a third additive. The third additive includes a third oligomer, the structural unit of which contains a third heteroatom, which includes one or more of O, N, and S. The degree of polymerization n of the third oligomer is... 02 For: 5≤n 02 ≤60.

[0068] Understandably, in non-lithium metal sheet solutions for the negative electrode, the polymer matrix, lithium salt, and additive scheme in the solid electrolyte are also applicable to the negative electrode active layer to achieve better overall ionic conductivity in the secondary battery. The scheme and advantages of the third polymer matrix, third lithium salt, and third additive are similar to those of the first polymer matrix, first lithium salt, and first additive, and will not be elaborated further here. Furthermore, in application, the third polymer matrix can be the same as or different from the first polymer matrix, the third lithium salt can be the same as or different from the first lithium salt, and the third additive can be the same as or different from the first additive.

[0069] In some embodiments, the secondary battery includes a solid-state battery.

[0070] In other embodiments of this application, a solid electrolyte is also provided, comprising a first polymer matrix, a first lithium salt, and a first additive; the first additive comprises a first oligomer, the structural unit of the first oligomer containing a first heteroatom, the first heteroatom comprising one or more of O, N, and S, and the degree of polymerization n of the first oligomer is: 5≤n≤60.

[0071] In some embodiments, the solid electrolyte is the solid electrolyte in the secondary battery as described above.

[0072] Without limitation, the method for preparing the solid electrolyte includes: mixing the first polymer matrix, the first lithium salt, the first additive, and the solvent to prepare an electrolyte slurry; and casting and drying the electrolyte slurry to form a film.

[0073] Without limitation, the solvent may be one or both of tetrahydrofuran (THF) and N-methylpyrrolidone (NMP).

[0074] Other embodiments of this application also provide an electrical device, including at least one of the secondary battery and the solid electrolyte as described above.

[0075] The secondary battery and power-consuming device of this application will be described below with appropriate reference to the accompanying drawings.

[0076] Typically, a secondary battery consists of a positive electrode, a negative electrode, and a solid electrolyte. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The solid electrolyte acts as a conductor of ions between the positive and negative electrodes.

[0077] The positive electrode includes a positive current collector and a positive active layer disposed on at least one surface of the positive current collector, the positive active layer comprising a positive active material.

[0078] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0079] 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 substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on the polymer material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymer material substrate in the positive electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0080] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As a non-limiting example, the positive electrode active material may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, one or more of lithium cobalt oxides (such as LiCoO2), lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium manganese iron phosphate and carbon composites. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.8 Co 0.15 Al 0.05 O2.

[0081] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0082] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive electrode active material, conductive agent, and other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto at least one surface of the positive electrode current collector, and obtaining the positive electrode sheet after drying, cold pressing, and other processes. The solvent can be selected from, but is not limited to, any of the solvents described in the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface or both 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 adjusted to 5000 mPa·s to 25000 mPa·s. When coating the positive electrode slurry, the coating unit areal density (dry weight, minus solvent) can be 15 mg / cm³. 2 ~35mg / cm 2 The compaction density of the positive electrode sheet can be 3.0 g / cm³. 3 ~3.6g / cm 3 3.3g / cm³ is an option. 3 ~3.5g / cm 3 .

[0083] The negative electrode sheet can be a lithium metal sheet, or it can include a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, wherein the negative active material layer includes a negative active material.

[0084] As a non-limiting example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0085] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on the polymeric material substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the negative electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0086] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As a non-limiting example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0087] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0089] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (a non-limiting example of a solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto at least one surface of the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing, and other processes. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector. The solid content (mass percentage) of the negative electrode slurry can be 40wt% to 60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 mPa·s to 10000 mPa·s. When coating the negative electrode slurry, the coating unit areal density on a dry weight basis (excluding solvent) can be 75 g / m². 2 )~220g / m 2 The compacted density of the negative electrode sheet can be 1.0 g / cm³. 3 ~1.8g / cm 3 .

[0090] Solid electrolyte membranes have the function of conducting ions between positive and negative electrode plates, and the specific technical solutions are as described above.

[0091] In some embodiments, the secondary battery may further include a separator. The separator is disposed between the positive and negative electrodes, primarily serving to prevent short circuits between the positive and negative electrodes while allowing ions to pass through. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0092] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0093] In some embodiments, the thickness of the isolation membrane is 6 micrometers (μm) to 40 μm, and optionally 12 μm to 20 μm.

[0094] In some embodiments, the positive electrode, negative electrode, solid electrolyte membrane, and separator membrane can be fabricated into electrode assemblies using a winding process or a stacking process.

[0095] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly described above.

[0096] In some embodiments, the outer packaging of the secondary battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft pack, such as a pouch-type soft pack. The material of the soft pack can be plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0097] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0098] In this application, unless otherwise specified, "cell battery" refers to the basic unit capable of converting chemical energy into electrical energy, and generally includes at least a positive electrode, a negative electrode, and a solid electrolyte membrane. During the charging and discharging process, active ions move back and forth between the positive and negative electrode plates, inserting and extracting. The solid electrolyte membrane acts as a conductor for active ions between the positive and negative electrode plates.

[0099] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 shows a square-structured secondary battery 1 as an example.

[0100] In some embodiments, referring to FIG2, the outer packaging may include a housing 11 and a cover plate 13. The housing 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be placed over the opening to close the receiving cavity. Positive electrode sheets, negative electrode sheets, a solid electrolyte membrane, and a separator membrane may be formed into electrode assemblies 12 via a winding process or a stacking process. The electrode assemblies 12 are encapsulated within the receiving cavity. The secondary battery 1 may contain one or more electrode assemblies 12, which can be selected by those skilled in the art according to actual needs.

[0101] Secondary batteries can be battery modules or battery packs.

[0102] A battery module includes at least one battery cell. The number of battery cells in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0103] In a battery module, multiple battery cells can be arranged sequentially along the length of the module. Of course, they can also be arranged in any other manner. Furthermore, these battery cells can be secured using fasteners.

[0104] Optionally, the battery module may also include a housing with a receiving space in which multiple battery cells are housed.

[0105] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select an appropriate number according to the application and capacity of the battery pack.

[0106] The battery pack may include a battery box and multiple battery modules disposed within the battery box. The battery box includes an upper body and a lower body, with the upper body covering the lower body to form a closed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0107] In addition, this application also provides an electrical device, which includes the secondary battery provided in this application. The secondary battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to.

[0108] As an electrical device, a rechargeable battery can be selected based on its usage requirements.

[0109] Figure 3 shows an example of an electrical device 2. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0110] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0111] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0112] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0113] Example 1

[0114] 1) Preparation of positive electrode sheet

[0115] Lithium iron phosphate (LFP), solid electrolyte (1 part P(VDF-HFP) (number average molecular weight 130,000), 1.1 parts polyethylene glycol dimethyl ether (number average molecular weight 500, n=10) and 0.4 parts LiTFSI), and conductive carbon were dissolved, dispersed and stirred evenly in NMP at a mass percentage of 70%:25%:5%. The mixture was then coated onto aluminum foil, dried, and cold-pressed to obtain the positive electrode sheet.

[0116] 2) Preparation of negative electrode sheet

[0117] Lithium-coated copper foil is used, with a copper foil thickness of 13μm and a lithium metal layer thickness of 50μm.

[0118] 3) Solid electrolyte membrane

[0119] One part of P(VDF-HFP) (number average molecular weight 130,000), 1.1 parts of polyethylene glycol dimethyl ether (number average molecular weight 500, n=10), and 0.4 parts of LiTFSI were dissolved in THF by stirring. The solution was then cast onto a tetrafluoroethylene plate and dried in a drying room (dew point temperature -30℃, room temperature drying) for 24 hours to prepare the polymer electrolyte.

[0120] 5) Battery manufacturing

[0121] The positive electrode, solid electrolyte membrane, and negative electrode are stacked in sequence, with the solid electrolyte membrane positioned between the positive and negative electrodes, and then hot-pressed to obtain the finished solid-state battery.

[0122] The preparation methods of solid-state batteries in Examples 2-4 are similar to those in Example 1, with the main difference being that the degree of polymerization n of polyethylene glycol dimethyl ether used is different.

[0123] The preparation methods of solid-state batteries in Examples 5-7 are similar to those in Example 1, with the main difference being that different types of oligomers are used, and Example 5 uses a combination of two polymer matrices.

[0124] The preparation methods of the solid-state batteries in Examples 8 and 9 are similar to those in Example 1, with the main difference being the use of different weight parts of oligomers or lithium salts.

[0125] The preparation method of the solid-state battery in Comparative Example 1 is similar to that in Example 1, the main difference being that diethylene glycol dimethyl ether is used in place of polyethylene glycol dimethyl ether in equal parts by weight.

[0126] The preparation method of the solid-state battery in Comparative Example 2 is similar to that in Example 1, the main difference being that the degree of polymerization n of the polyethylene glycol dimethyl ether used is different.

[0127] The various embodiments and comparative examples are shown in Table 1 below.

[0128] Table 1 Note: The number-average molecular weight of P(VDF-TrFE-CFE) in Example 5 is 130,000.

[0129] Test example:

[0130] (1) Ionic conductivity test:

[0131] A solid electrolyte membrane was assembled into a stainless steel / solid electrolyte membrane / stainless steel symmetric blocked cell for electrochemical impedance spectroscopy (EIS) testing. The scan frequency was 1–10^6 Hz, the amplitude was 10 mV, the intersection of the imaginary and real parts was taken as the bulk resistance R, L was the thickness of the composite electrolyte membrane, and S was the electrode area. The ionic conductivity of the electrolyte membrane was calculated as follows:

[0132] σ = L / SR.

[0133] (2) Solid-state battery performance testing:

[0134] Battery performance was tested using a charge / discharge tester (LFP: 2.5-3.9V). Capacity tests were performed on solid-state lithium metal battery cells at 60°C after charging and discharging at 0.1C (4mA). Specifically, the solid-state lithium metal battery cells were charged at a constant current rate of 0.1C to 3.9V, followed by constant voltage charging until the current decayed to 0.05C.

[0135] The test results are shown in Table 2 below:

[0136] Table 2

[0137] As can be seen from the comparison between the examples and the comparative examples, the examples can effectively improve the ionic conductivity, high-temperature capacity and mechanical properties of the solid electrolyte in the secondary battery by using oligomers with appropriate degrees of polymerization.

[0138] As can be seen from Examples 1 to 4, reasonable control of the number-average molecular weight and degree of polymerization n of oligomers can further improve ionic conductivity and high-temperature capacity.

[0139] As can be seen from Examples 1, 5 to 7, different types of oligomer or polymer matrices can achieve high ionic conductivity and high-temperature capacity, with polyester and polyether showing better results.

[0140] As can be seen from Examples 1, 8-9, high ionic conductivity and high-temperature capacity can be obtained by using different weight parts of oligomers or lithium salts.

[0141] Furthermore, the relationship between the ionic conductivity of the solid electrolyte membranes prepared in Comparative Example 1 (using diethylene glycol dimethyl ether as an oligomer) and Example 1 (using polyethylene glycol dimethyl ether as an oligomer) and time was further investigated. The results are shown in Figure 4. It can be seen that, due to the high volatility of diethylene glycol dimethyl ether, the solid electrolyte membrane of Comparative Example 1 exhibits extremely low conductivity (only 1.8 x 10⁻¹⁰) immediately after drying in the drying chamber. -3 The concentration of mS / cm decreased to as low as the drying time continued to increase, even dropping to 10. -4 mS / cm; while the solid electrolyte membrane of Example 1 maintains a high ionic conductivity, consistently above 10 mS / cm; -2 The mS / cm conductivity remains at least one order of magnitude higher than the comparative example even after drying for 120 hours. Therefore, in practical applications, the solid electrolyte membrane provided in this application can maintain good ionic conductivity compared to the comparative example.

[0142] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0143] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A secondary battery, comprising a positive electrode, a solid electrolyte, and a negative electrode, wherein the solid electrolyte comprises a first polymer matrix, a first lithium salt, and a first additive; the first additive comprises a first oligomer, wherein the structural unit of the first oligomer contains a first heteroatom, the first heteroatom comprising one or more of O, N, and S, and the degree of polymerization n of the first oligomer is: 5≤n≤60.

2. The secondary battery according to claim 1, wherein 10≤n≤40。 3. The secondary battery according to claim 1 or 2, wherein The first oligomer includes one or more of polyether, polysulfide, polyamine, polyester and polyamide.

4. The secondary battery according to any one of claims 1 to 3, wherein The first oligomer includes one or more of the compounds having the structure shown below: Among them, R1, R2, R3, R4, R5, and R6 each independently include a C1-C20 alkylene group or a C6-C20 arylene group; R 11 , R 22 each independently comprises H, C1-C20 alkyl or C6-C20 aryl; 10≤n1≤40, 10≤n2≤40, 10≤n3≤40, 10≤n4≤40, 10≤n5≤40, 10≤n6≤40.

5. The secondary battery according to any one of claims 1 to 4, wherein The number average molecular weight of the first oligomer is 200 to 3000.

6. The secondary battery according to any one of claims 1 to 5, wherein Based on 1 part by weight of the first polymer matrix, the first oligomer is 0.2 to 2 parts by weight.

7. The secondary battery according to any one of claims 1 to 6, wherein The first lithium salt has one or two of the following characteristics: (1) Based on 1 part by weight of the first polymer matrix, the first lithium salt is 0.1 to 0.8 parts by weight; (2) The first lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium perchlorate, and lithium nitrate.

8. The secondary battery according to any one of claims 1 to 7, wherein The first polymer matrix has one or both of the following features: (1) The first polymer matrix includes one or more of polyvinylidene fluoride and its copolymers; (2) The number average molecular weight of the first polymer matrix is ​​100,000 to 8 million.

9. The secondary battery according to any one of claims 1 to 8, wherein The positive electrode tab includes a positive electrode active layer, the positive electrode active layer includes a positive electrode active material, a second polymer matrix, a second lithium salt, and a second additive, the second additive includes a second oligomer, a second heteroatom is included in a structural unit of the second oligomer, the second heteroatom includes one or more of O, N, and S, a polymerization degree n of the second oligomer 01 is: 5 ≤ n 01 ≤ 60.

10. A solid electrolyte comprising a first polymer matrix, a first lithium salt, and a first additive; the first additive comprising a first oligomer, wherein the structural unit of the first oligomer contains a first heteroatom, the first heteroatom comprising one or more of O, N, and S, and the degree of polymerization n of the first oligomer is 5 ≤ ​​n ≤ 60.

11. The solid-state electrolyte of claim 10, wherein, The solid electrolyte is the solid electrolyte described in any one of claims 2 to 8 for the secondary battery.

12. An electrical device comprising at least one of the secondary battery according to any one of claims 1 to 9 and the solid electrolyte according to any one of claims 10 to 11.

Images