Lithium metal secondary battery and electric device

Abstract

The application relates to a lithium metal secondary battery and a power utilization device. The lithium metal secondary battery comprises a positive electrode sheet, a negative electrode sheet and an electrolyte, a separation film is arranged between the positive electrode sheet and the negative electrode sheet; the negative electrode sheet comprises a negative electrode active layer, the negative electrode active layer comprises lithium metal; the electrolyte comprises an electrolyte salt; the electrolyte salt comprises a first lithium salt and a second lithium salt, the first lithium salt is lithium bisfluorosulfonylimide, and the second lithium salt is one or both of lithium difluorophosphate and lithium difluorophosphate; wherein the molar percentage of the first lithium salt in the electrolyte salt is 50% to 95%, and the molar percentage of the second lithium salt in the electrolyte salt is 5% to 50%. The intensity of thermal runaway of the lithium metal secondary battery is significantly reduced, and the reliability during thermal runaway is significantly improved.

Description

Technical Field

[0001] This application relates to the field of lithium metal secondary battery technology, and further to lithium metal secondary batteries and electrical devices. Background Technology

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

[0003] With the development of various electronic products such as smartphones, tablets, smart wearables, power tools, and electric vehicles, high-energy-density rechargeable batteries are becoming increasingly popular. The high energy density of lithium metal anodes makes them one of the theoretically most ideal anode active materials. However, the reliability of lithium metal rechargeable batteries using lithium metal anodes is a key factor restricting their industrial-scale application. For example, during thermal runaway, high-temperature, high-speed molten metal flows are generated inside the battery, resulting in violent reactions that could lead to serious safety accidents. Therefore, it is necessary to improve the reliability of lithium metal rechargeable batteries, reduce the severity of thermal runaway, and avoid serious accidents such as fires and explosions. Summary of the Invention

[0004] According to various embodiments and examples of this application, this application provides a lithium metal secondary battery and an electrical device. The thermal runaway intensity (the severity of thermal runaway) of this lithium metal secondary battery is significantly reduced, and its reliability during thermal runaway is significantly improved.

[0005] According to some embodiments of the first aspect of this application, a lithium metal secondary battery is provided, which includes a positive electrode, a negative electrode and an electrolyte, wherein a separator is disposed between the positive electrode and the negative electrode; the negative electrode includes a negative active layer, and the negative active layer includes lithium metal.

[0006] The electrolyte comprises an electrolyte salt; the electrolyte salt comprises a first lithium salt and a second lithium salt, wherein the first lithium salt is lithium bis(fluorosulfonyl)imide, and the second lithium salt is one or both of lithium difluorooxalateborate and lithium di(oxalateborate); wherein the first lithium salt has a molar percentage of 50% to 95% in the electrolyte salt, and the second lithium salt has a molar percentage of 5% to 50% in the electrolyte salt.

[0007] The aforementioned lithium metal secondary battery incorporates a first lithium salt (lithium bisfluorosulfonylimide (LiFSI)) and a second lithium salt (lithium difluorooxalate borate (LiDFOB) and / or lithium dioxalate borate (LiBOB)) in the electrolyte salt of the electrolyte solution. By using the second lithium salt in combination with the first lithium salt, it is beneficial to reduce the heat generation and heat generation rate between the electrolyte salt and the lithium metal anode during thermal runaway. Furthermore, the carbon dioxide released during the thermal decomposition of the second lithium salt is beneficial for fire extinguishing. The introduction of the second lithium salt can suppress the problem that the thermal decomposition of LiFSI may release sulfur-containing substances, which could exacerbate the thermal runaway reaction. By further controlling the content of the first and second lithium salts in the electrolyte salt within the aforementioned ranges, the severity of thermal runaway of the lithium metal secondary battery can be significantly reduced (thermal runaway intensity), which is beneficial to avoiding serious consequences such as fire and explosion, and significantly improving the reliability of the LiFSI-containing lithium metal secondary battery during thermal runaway.

[0008] In some embodiments, the first lithium salt has a molar percentage of 50% to 80% in the electrolyte salt, and the second lithium salt has a molar percentage of 20% to 50% in the electrolyte salt.

[0009] By controlling the molar percentages of the first lithium salt (LiFSI) and the second lithium salt (LiDFOB and / or LiBOB) in the electrolyte salt within the aforementioned ranges, it is more beneficial to significantly reduce the intensity of thermal runaway in lithium metal secondary batteries and improve the reliability of lithium metal secondary batteries containing LiFSI during thermal runaway.

[0010] In addition, by controlling the content of LiFSI and the second lithium salt within a suitable range, the negative electrode film-forming effect of LiFSI can be better utilized, the stability of the negative electrode solid electrolyte interphase (SEI) film can be improved, the formation of lithium dendrites on the negative electrode can be reduced, the interfacial side reactions between the negative electrode and the electrolyte can be suppressed, and the lithium metal secondary battery can also have good cycle performance.

[0011] By controlling the content of LiFSI and the second lithium salt within a suitable range, the negative electrode film-forming effect of LiFSI can be better utilized, the formation of lithium dendrites on the negative electrode can be reduced, the interfacial side reactions between the negative electrode and the electrolyte can be suppressed, and the voltage drop during storage can be suppressed or delayed, so that the lithium metal secondary battery also has good storage performance.

[0012] In some embodiments, the molar ratio of the second lithium salt to the first lithium salt in the electrolyte is 0.05 to 1, and optionally 0.25 to 1.

[0013] The molar ratio of the second lithium salt (LiDFOB and / or LiBOB) to the first lithium salt (LiFSI) in the electrolyte (which can be denoted as R) is used to determine the ratio of the second lithium salt (LiDFOB and / or LiBOB) to the first lithium salt (LiFSI). II / IWithin the aforementioned range, on the one hand, by utilizing a relatively high content of LiFSI and a relatively low content of the second lithium salt, based on the better anode film-forming characteristics of LiFSI, it is more conducive to forming a uniform and stable anode solid electrolyte interphase (SEI) film, reducing the formation of lithium dendrites on the anode, suppressing the interfacial side reactions between the anode and the electrolyte, and enabling the lithium metal secondary battery to have better cycle performance; on the other hand, by introducing the aforementioned content of the second lithium salt, it can significantly reduce the heat generation and heat generation rate of the electrolyte salt during thermal runaway, reduce the release of sulfur-containing substances caused by the first lithium salt, and also form carbon dioxide which is beneficial for fire extinguishing; thus, LiFSI and the second lithium salt can better synergistically enhance each other, significantly improving the severity of thermal runaway while also taking into account good cycle performance.

[0014] By comparing the molar ratio of the second lithium salt to the first lithium salt in the electrolyte (R... II / I By controlling the voltage within the aforementioned range, the voltage drop during storage can be effectively suppressed or delayed, significantly improving the severity of thermal runaway while also maintaining good storage performance.

[0015] In some embodiments, the electrolyte satisfies one or more of the following characteristics:

[0016] (a1) The molar volume concentration of the first lithium salt in the electrolyte is 1 mol / L to 7 mol / L, and can be selected as 1 mol / L to 5 mol / L;

[0017] (a2) The molar volume concentration of the second lithium salt in the electrolyte is 0.5 mol / L to 4 mol / L, and can be selected as 1 mol / L to 3 mol / L;

[0018] (a3) The sum of the molar volume concentrations of the first lithium salt and the second lithium salt in the electrolyte is 2 mol / L to 8 mol / L, and can be selected as 2 mol / L to 6 mol / L;

[0019] (a4) The molar volume concentration of the electrolyte salt in the electrolyte is 2 mol / L to 8 mol / L, and can be selected as 2 mol / L to 6 mol / L.

[0020] By controlling the molar volume concentration (C) of the first lithium salt in the electrolyte I ), the molar volume concentration of the second lithium salt in the electrolyte (C II The sum of the molar volume concentrations of the first and second lithium salts in the electrolyte (C) I+II ) and the molar volume concentration of electrolyte salts in the electrolyte (C A Controlling one or more parameters within the aforementioned range is beneficial for better reducing the intensity of thermal runaway in lithium metal secondary batteries. In addition, it can also better balance cycle performance and / or storage performance.

[0021] By controlling the molar volume concentration (C) of the first lithium salt in the electrolyte I Within the aforementioned range, it is beneficial to better balance cyclic performance and / or storage performance.

[0022] By controlling the molar volume concentration (C) of the second lithium salt in the electrolyte. II Within the aforementioned range, it is beneficial to better reduce the intensity of thermal runaway in lithium metal secondary batteries.

[0023] In some embodiments, the second lithium salt comprises lithium difluorooxalate borate; the molar percentage of lithium difluorooxalate borate in the second lithium salt is 50% to 100%, optionally 80% to 100%.

[0024] By controlling the molar percentage (R) of lithium difluorooxalatoborate in the second lithium salt 21 Within the aforementioned range, it is beneficial to better reduce the intensity of thermal runaway in lithium metal secondary batteries.

[0025] In some embodiments, the sum of the molar ratios of the first lithium salt and the second lithium salt in the electrolyte salt is 80% to 100%, optionally 90% to 100%.

[0026] By controlling the sum of the molar percentages of the first lithium salt (LiFSI) and the second lithium salt (LiDFOB and / or LiBOB) in the electrolyte salt (R... I+II Within the aforementioned range, it is beneficial to better leverage the synergistic effect of the first and second lithium salts, and to significantly reduce the intensity of thermal runaway in lithium metal secondary batteries; in addition, it can also better balance cycle performance and / or storage performance.

[0027] In some embodiments, the lithium-containing metal includes one or more of elemental lithium and lithium alloys.

[0028] In some embodiments, the mass percentage or molar percentage of lithium in the lithium-containing metal is 95% to 100%.

[0029] When the lithium-containing metal in the negative electrode active layer is elemental lithium, the thermal runaway intensity of lithium metal secondary batteries can be significantly reduced by using the aforementioned electrolyte; in addition, cycle performance and / or storage performance can be well balanced.

[0030] In some embodiments, the electrolyte includes a non-aqueous solvent, which includes one or more of aliphatic ether solvents, fluorinated aliphatic ether solvents, and benzene-containing solvents.

[0031] In some embodiments, the electrolyte satisfies one or more of the following characteristics:

[0032] (d1) The electrolyte comprises a fatty ether solvent; the fatty ether solvent contains 2 to 14 carbon atoms; the fatty ether solvent contains one or more oxygen atoms; the fatty ether solvent has a chain structure;

[0033] (d2) The electrolyte comprises a fluorinated aliphatic ether solvent; the number of carbon atoms in the fluorinated aliphatic ether solvent is 3 to 14; the hydrogen atoms in the fluorinated aliphatic ether solvent are partially or completely fluorinated; the number of fluorine atoms in the fluorinated aliphatic ether solvent is one or more; the number of oxygen atoms in the fluorinated aliphatic ether solvent is one or more; the fluorinated aliphatic ether solvent has a chain structure;

[0034] (d3) The electrolyte comprises a benzene-containing solvent; the benzene-containing solvent comprises one or more of benzene, substituted benzene, anisole, and substituted anisole; wherein the benzene ring in the substituted benzene is substituted by one or more substituents Q1; each of the substituents Q1 is independently a fluorine atom, C 1-3 Chain alkyl or fluorinated C 1-3 Chain-like alkyl group; the phenyl and methyl groups in the substituted anisole are each independently substituted by one or more substituents Q2; each of the substituents Q2 is independently a fluorine atom, C 1-3 Chain alkyl or fluorinated C 1-3 Chain alkyl groups; in a benzene-containing solvent, any one of the fluorinated C groups 1-3 The number of fluorine atoms in the chain alkyl group is independently one or more;

[0035] (d4) In the electrolyte, the total mass percentage of the fatty ether solvent, the fluorinated fatty ether solvent and the benzene-containing solvent in the non-aqueous solvent is 80% to 100%.

[0036] By controlling one or more of the non-aqueous solvents in the electrolyte, including aliphatic ether solvents, fluorinated aliphatic ether solvents, and benzene-containing solvents, the solvent can be made to have better oxidation resistance.

[0037] Improving the oxidation resistance of the solvent can enhance the reliability of lithium metal secondary batteries during thermal runaway.

[0038] Improving the solvent's oxidation resistance also helps reduce side reactions between the solvent and the positive electrode.

[0039] Replacing the solvent with fluorine can improve its thermal stability and help reduce the intensity of thermal runaway in lithium metal secondary batteries.

[0040] Introducing benzene-containing solvents can help improve the solvent's oxidation resistance.

[0041] According to some embodiments of the second aspect of this application, an electrical device is provided, which includes the lithium metal secondary battery described in the first aspect of this application.

[0042] Details of one or more embodiments or examples of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0043] To better describe and illustrate the embodiments, examples, or models 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, examples, or models, or the best mode of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. It should also be noted that the drawings are drawn in a simplified form and are only intended to facilitate and clarify the illustration of this application. The various dimensions of each part shown in the drawings are arbitrarily shown and may be precise or not drawn to scale. For example, the dimensions of parts are appropriately exaggerated in some places in the drawings to make the illustration clearer. Unless otherwise specified, the parts in the drawings are not drawn to scale. This application does not limit every dimension of every part.

[0044] In the attached diagram:

[0045] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0046] Figure 2 for Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0047] Figure 3 This is a schematic diagram of a battery device according to one embodiment of this application.

[0048] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0049] Figure 5 for Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0050] Figure 6 This is a schematic diagram of an electrical device using a lithium metal secondary battery as a power source, according to one embodiment of this application.

[0051] Explanation of reference numerals in the attached figures:

[0052] 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery assembly; 5. Individual battery cell; 51. Battery housing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device. Detailed Implementation

[0053] The following describes in detail some embodiments and examples of the lithium metal secondary battery and power-consuming device of this application with appropriate reference to the accompanying drawings. However, some unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0054] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints. Any endpoint can be included or excluded independently and 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 ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when describing a parameter as an integer ≥ 2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 for that parameter. For instance, when describing a parameter as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0055] In this application, the term "numerical value" includes the number itself and its reasonable approximations. The definition of "numerical value" can apply to discrete numerical points or to the endpoints of a numerical range. Unless otherwise specified, the term "approximation" covers a numerical interval based on a reasonable range of fluctuations of the number itself. This reasonable range of fluctuations can vary depending on the type and magnitude of the number. This reasonable range of fluctuations can be reasonably determined based on the accuracy of the testing or measurement method. Therefore, when referring to a numerical value or a numerical range, unless otherwise specified, it should be understood that the numerical value includes its reasonable approximation, and the numerical range includes reasonable approximations at both endpoints. Those skilled in the art will understand that acceptable fluctuation ranges of the relevant approximations can be included within the definition of the numerical value or the numerical range. In this application, unless otherwise specified, "N1" can be reasonably understood as "about N1," and "N1~N2" can be reasonably understood as "about N1 to about N2," where N1 and N2 are two unequal numerical values. For example, in some cases, it is reasonable to include approximate values ​​within an approximate range into the range defined by that range, due to one or more factors such as reasonable deviations allowed in the art and the precision of instrument control; for example, "temperature of 20℃ to 30℃" can be understood as "approximately 20℃ to approximately 30℃"; furthermore, taking "20℃" as the endpoint and its approximation as ±1℃, approximate values ​​such as 19℃ and 19.5℃ within the approximation range corresponding to "approximately 20℃" should also be included in the range indicated by 20℃ to 30℃. As a non-limiting example, a percentage content of "10%" can be reasonably understood as "approximately 10%". As another non-limiting example, a percentage content of "80% to 100%" can be reasonably understood as "approximately 80% to 100%".

[0056] In this application, unless otherwise specified, "about" means within a reasonable range above and below the stated number, and the range of fluctuation may vary depending on the type and value of the stated number. For example, a range of ±10%, ±5%, ±2%, ±1%, etc., may be allowed. For example, taking "about 20°C" and its approximation as ±1°C, approximate values ​​such as 19°C, 19.5°C, etc., within the approximation range indicated by "about 20°C" should also be included in the range indicated by "about 20°C".

[0057] In this application, the terms "multiple," "various," "multiple items," "several," etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more (greater than or equal to) two. It can be understood that when "any number of" items are involved, it refers to any suitable combination of multiple items, that is, a combination of "any number of" items in a manner that does not conflict and enables the implementation of this application.

[0058] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0059] 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.

[0060] Those skilled in the art will understand that, unless otherwise specified, the order in which the steps are written in the various embodiments or methods of this application 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, but are preferably performed sequentially. For example, "method M includes steps (a) and (b)" means that method M may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. As another example, "method M may also include step (c)" means that step (c) can be added to method M in any order. For example, method M 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.

[0061] In this application, open-ended technical features or solutions described using terms such as "containing," "including," or "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may also include other members or exclude additional members unless otherwise specified. This can be considered as providing both features or solutions where "A consists of a1, a2, and a3" or "A is selected from a1, a2, and a3," and features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0062] 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.

[0063] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it is selected from either "with" or "without." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent. Unless otherwise specified, the descriptions such as "optionally include" and "optionally contain" in this application, taking "optionally include" as an example, mean "may include or not include."

[0064] In this application, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0065] The terms “combinations of,” “any combination of,” and “any combination of” used in this article include all suitable combinations of any two or more of the listed items.

[0066] In this document, the term "suitable" as used in "suitable combination", "suitable method", "any suitable method", etc., refers to the technical solution that enables the implementation of this application.

[0067] In this document, terms such as "preferred," "better," "more suitable," "ideal," "good," and "superior" are merely descriptions of more effective implementation methods or embodiments, and should be understood not to limit the scope of protection of this application. If multiple "preferred" terms appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "preferred" term shall be independent.

[0068] In this application, terms such as "further," "even more," "especially," "for example," "as," "example," and "exemplary" are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0069] In this application, the terms "first aspect," "second aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first aspect," "second aspect," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0070] In this application, unless otherwise expressly specified and limited, the terms "connected," "linked," etc., in device or mechanical structures should be interpreted broadly, for example, as a fixed connection, a detachable connection, or an integral part. Those skilled in the art can understand the meaning of the above terms in this application according to the context. In molecular structures, unless otherwise specified, "connected" means linked by chemical bonds.

[0071] In this application, unless otherwise expressly specified and limited, in a device structure or mechanical structure, the first feature being "on" or "under" a second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. In this application, unless otherwise expressly specified and limited, the first feature being "on" or "under" a second feature can indicate a horizontal positional relationship, or it can simply indicate the existence of an attachment relationship without specifying a horizontal positional relationship.

[0072] In this application, the term "room temperature" generally refers to 4℃ to 35℃, and may refer to 20℃ ± 5℃. In some embodiments of this application, room temperature refers to 20℃ to 30℃.

[0073] In this application, if the unit for a data range is only followed by the right endpoint, it indicates that the units for the left and right endpoints are the same. For example, 3~5h or 3-5h both mean that the unit for the left endpoint "3" and the right endpoint "5" is h (hours), and both have the same meaning as 3h~5h. Furthermore, similar descriptions of other parameters such as temperature and size are interpreted in the same way.

[0074] In this application, "greater than or equal to", "greater than or equal to", and "≥" have the same meaning and can be used interchangeably; "less than or equal to", "less than or equal to", and "≤" have the same meaning and can be used interchangeably; "greater than" can be equivalently represented as ">", and "less than" can be equivalently represented as "<". In this application, unless otherwise specified, "greater than or equal to" and "≥" can be considered as providing two additional solutions: "greater than" and "equal to". In this application, unless otherwise specified, "less than or equal to" and "≤" can be considered as providing two additional solutions: "less than" and "equal to".

[0075] In this application, the exemplary descriptions such as "in some implementations (or embodiments)" and "in one implementation (or embodiment)" may cover, but are not limited to, the following meanings: these solutions can be combined with other solutions in a suitable manner to form new technical solutions.

[0076] Unless otherwise stated, the improvements described in this application are not intended to be limited to any theoretical constraints.

[0077] In this application, unless otherwise specified, the number of carbon atoms in a compound or group may be described using the subscript "C". For example, "C 1-3 "" indicates that it has 1 to 3 carbon atoms, "C 1-3 Each time it appears, it can be independently classified as C1, C2, or C3. For example, "C..." 1-3 "alkyl" indicates an alkyl group having 1 to 3 carbon atoms, "C 1-3 Each time the word "alkyl" appears, it can independently be a C1 alkyl, C2 alkyl, or C3 alkyl. For example, "fluorinated C..." 1-3 "Alkyl" refers to a fluorinated derivative formed by replacing an alkyl group having 1 to 3 carbon atoms with one or more fluorine atoms. 1-3 Each time the word "alkyl" appears, it can be independently fluorinated C1 alkyl, fluorinated C2 alkyl, or fluorinated C3 alkyl.

[0078] Lithium metal anodes possess the advantage of high energy density, making them a crucial research direction for high-energy-density batteries. However, lithium metal anodes also present several challenges, including lithium dendrite formation leading to short circuits and severe thermal runaway reactions (due to high-temperature, high-speed liquid metal flow). Introducing lithium bisfluorosulfonylimide (LiFSI), which exhibits higher thermal stability than lithium hexafluorophosphate, into the electrolyte using lithium metal anodes can promote the formation of a stable, high-quality solid electrolyte interphase (SEI) film, thus reducing lithium dendrite formation. However, the high heat generation and rate of heat generation between LiFSI and the lithium metal anode result in poor reliability during thermal runaway.

[0079] The reliability of lithium metal secondary batteries using lithium metal anodes is one of the key factors restricting their industrial-scale application. For example, during thermal runaway, high-temperature, high-speed molten metal flows are generated inside the battery, resulting in a violent reaction that could lead to serious safety accidents. Therefore, it is necessary to improve the reliability of lithium metal secondary batteries and control the severity of thermal runaway to a lower level to avoid serious accidents such as fires and explosions.

[0080] According to various embodiments and examples of this application, this application provides a lithium metal secondary battery and an electrical device. This lithium metal secondary battery has significantly improved reliability during thermal runaway, and the intensity of thermal runaway (the severity of thermal runaway) is significantly reduced.

[0081] In this application, unless otherwise specified, a "lithium metal secondary battery" includes a negative electrode sheet, which includes a negative electrode active layer, and the negative electrode active layer includes lithium metal. For example, the negative electrode active layer may be lithium metal.

[0082] In some embodiments, a lithium metal secondary battery is provided, which includes an electrolyte; the electrolyte includes a first lithium salt and a second lithium salt, wherein the first lithium salt is lithium bis(fluorosulfonyl)imide and the second lithium salt is one or both of lithium difluorooxalateborate and lithium dioxalateborate.

[0083] In some embodiments, a lithium metal secondary battery is provided, comprising a negative electrode and an electrolyte; the negative electrode includes a negative active layer comprising lithium metal; the electrolyte includes a first lithium salt and a second lithium salt, wherein the first lithium salt is lithium bis(fluorosulfonyl)imide and the second lithium salt is one or both of lithium difluorooxalateborate and lithium dioxalateborate.

[0084] In this application, LiFSI refers to lithium bis(fluorosulfonyl)imide, LiDFOB refers to lithium difluorooxalate borate, and LiBOB refers to lithium dioxalate borate. In this application, LiFSI, LiDFOB, and LiBOB can all function as electrolyte salts.

[0085] In the electrolyte of lithium metal secondary batteries, by simultaneously setting a first lithium salt (LiFSI) and a second lithium salt (LiDFOB and / or LiBOB) in the electrolyte salt, the use of the second lithium salt in combination with the first lithium salt helps to reduce the heat generation and heat generation rate between the electrolyte salt and the lithium metal anode during thermal runaway. Furthermore, the carbon dioxide released during the thermal decomposition of the second lithium salt is beneficial for fire extinguishing. The introduction of the second lithium salt can suppress the problem that the thermal decomposition of LiFSI may release sulfur-containing substances, which could exacerbate the thermal runaway reaction. This electrolyte can reduce the severity of thermal runaway in lithium metal secondary batteries (thermal runaway intensity), which helps to avoid serious consequences such as fire and explosion, and can significantly improve the reliability of lithium metal secondary batteries containing LiFSI during thermal runaway.

[0086] As is understandable, a typical lithium metal secondary battery consists of a positive electrode, a negative electrode, and an electrolyte, with a separator between the positive and negative electrodes. During charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0087] In some embodiments, a lithium metal secondary battery is provided, comprising a positive electrode, a negative electrode, and an electrolyte, wherein a separator is disposed between the positive and negative electrode; the negative electrode includes a negative active layer comprising lithium metal; the electrolyte includes an electrolyte salt, which includes a first lithium salt and a second lithium salt, wherein the first lithium salt is lithium bis(fluorosulfonyl)imide, and the second lithium salt is one or both of lithium difluorooxalateborate and lithium dioxalateborate.

[0088] In some embodiments, the first lithium salt has a molar percentage of 50% to 95% in the electrolyte salt, and the second lithium salt has a molar percentage of 5% to 50% in the electrolyte salt.

[0089] In this application, the terms "electrode sheet" and "electrode plate" have the same meaning and can be used interchangeably. An electrode sheet can be a positive electrode sheet or a negative electrode sheet, and the "active material" or "active substance" in the electrode sheet has the ability to reversibly insert and extract active ions.

[0090] The positive electrode sheet includes a positive electrode active layer. This active layer contains positive electrode active material. The term "positive electrode active layer" can also be written as "positive electrode active material layer." The term "positive electrode active material" refers to the material used in the positive electrode sheet that can reversibly extract and insert active ions.

[0091] In this application, unless otherwise specified, "positive electrode sheet" includes a positive current collector. A "positive current collector" refers to a structure responsible for collecting and conducting electrons at the positive electrode. In the positive electrode sheet, the positive active layer is located on at least one side of the positive current collector, and may be located on one or both sides of the positive current collector.

[0092] In this application, unless otherwise specified, "separation membrane" and "diaphragm" have the same meaning and can be used interchangeably.

[0093] According to some embodiments of the first aspect of this application, a lithium metal secondary battery is provided, comprising an electrolyte; the electrolyte includes a first lithium salt and a second lithium salt, wherein the first lithium salt is lithium bis(fluorosulfonyl)imide, and the second lithium salt is one or both of lithium difluorooxalate borate and lithium dioxalate borate. The thermal runaway intensity (the severity of thermal runaway) of this lithium metal secondary battery is significantly reduced, and its reliability during thermal runaway is significantly improved.

[0094] In some embodiments, a lithium metal secondary battery is provided, comprising a positive electrode, a negative electrode, and an electrolyte, wherein a separator is disposed between the positive and negative electrode; the negative electrode includes a negative active layer comprising lithium metal; the electrolyte includes an electrolyte salt; the electrolyte salt includes a first lithium salt and a second lithium salt, wherein the first lithium salt is lithium bis(fluorosulfonyl)imide, and the second lithium salt is one or both of lithium difluorooxalateborate and lithium dioxalateborate;

[0095] In some embodiments, the first lithium salt has a molar percentage of 50% to 80% in the electrolyte salt, and the second lithium salt has a molar percentage of 20% to 50% in the electrolyte salt.

[0096] In this application, unless otherwise specified, the term "lithium-containing metal" can refer to a material substantially composed of lithium (Li) metal, a lithium alloy, or a mixture of elemental lithium and lithium alloys. The phrase "substantially composed of lithium metal" indicates that the weight percentage of metallic lithium is very high. The weight percentage described by "substantially" here can be, for example, greater than or equal to 80%, greater than or equal to 85%, greater than or equal to 90%, greater than or equal to 95%, greater than or equal to 96%, greater than or equal to 97%, greater than or equal to 98%, greater than or equal to 99%, equal to 100%, etc.

[0097] In this application, unless otherwise specified, the terms "lithium metal" or "lithium metal" refer to lithium in its metallic state.

[0098] In this application, the term "lithium" as used independently, unless otherwise specified, refers to lithium in its metallic state. For example, "lithium" in the context of lithium-containing metals.

[0099] In this application, "lithium element" is composed of the element lithium.

[0100] In this application, unless otherwise specified, the term "lithium alloy" refers to an alloy containing lithium. In addition to lithium, a lithium alloy may also contain one or more other types of metals. All reported lithium alloys used as negative electrode active materials in lithium metal batteries fall within the scope of this application. For example, a lithium alloy may be an alloy of lithium with one or more metals selected from silver, magnesium, aluminum, gold, zinc, tin, copper, nickel, and titanium. Non-limiting examples of lithium alloys include lithium-magnesium alloys and lithium-aluminum alloys. In other embodiments, the non-lithium metal in the lithium alloy includes one or both of aluminum and copper.

[0101] In this application, unless otherwise specified, "first lithium salt" is lithium bis(fluorosulfonyl)imide (LiFSI), and "second lithium salt" is one or both of lithium difluorooxalate borate (LiDFOB) and lithium dioxalate borate (LiBOB). The first lithium salt (LiFSI) exhibits good anode film-forming properties, forming a stable solid electrolyte interphase (SEI) film at the anode, which helps reduce lithium dendrites and suppress electrolyte side reactions. However, during thermal runaway in lithium metal secondary batteries, LiFSI generates a large amount of heat and a high rate of heat generation with the lithium metal anode. Furthermore, the release of sulfur-containing gases (such as sulfur dioxide) can further exacerbate the thermal runaway reaction. The second lithium salt has higher thermal stability than the first lithium salt; for example, the second lithium salt does not flash at 400°C, while under the same conditions, LiFSI will flash at 400°C. The heat generation and rate of heat generation between the second lithium salt and the lithium metal anode are significantly lower than those of the first lithium salt, as shown by differential scanning calorimetry (DSC) analysis results at the interface between the electrolyte containing the test electrolyte salt and the lithium metal anode. For example, in DSC analysis, the heat generation of LiFSI electrolyte (6 mol / L) with the lithium metal electrode is 6880 J / mAh, with a maximum heat generation rate of 1720 J / mAh / min, while the heat generation of LiDFOB electrolyte (6 mol / L) with the lithium metal electrode is 2819 J / mAh, with a maximum heat generation rate of 269 J / mAh / min. Furthermore, the second lithium salt contains oxalate anions, and the carbon dioxide released during thermal runaway helps extinguish fires and reduces the severity of thermal runaway. In this application, the terms "first lithium salt," "second lithium salt," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features.

[0102] In this application, unless otherwise specified, the heat generation at the interface between the electrolyte containing the electrolyte salt to be tested (referred to as "electrolyte to be tested") and the lithium metal anode can be measured using a differential scanning calorimeter (DSC). Unless otherwise specified, pure lithium sheets are used as the lithium metal anode, and the electrolyte can be composed of a "DME+TTE+FB mixed solvent" and the electrolyte salt to be tested. The amount of electrolyte relative to the lithium sheet can be basically the same as in Example 1; the concentration of the electrolyte salt to be tested in the electrolyte can be 6 mol / L to 8 mol / L, and 6 mol / L can be used unless otherwise specified; a Mettler-Toledo DSC-3 differential scanning calorimeter can be used, with a temperature range from room temperature (e.g., 25°C) to 800°C, a heating rate of 20°C / min, and an argon atmosphere. "DME+TTE+FB mixed solvent" refers to a solvent composed of DME, TTE, and FB. When performing heat generation analysis, the mass ratio of DME, TTE, and FB can be 1:2:1. The unit of heat generation can be joules per milliampere-hour (J / mAh).

[0103] In this application, unless otherwise specified, DME is ethylene glycol dimethyl ether; TTE is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (CHF2CF2OCH2CF2CHF2); FB is fluorobenzene (Ph-F), wherein Ph is phenyl.

[0104] The aforementioned lithium metal secondary battery incorporates a first lithium salt (LiFSI) and a second lithium salt (LiDFOB and / or LiBOB) in the electrolyte salt of the electrolyte solution. By using the second lithium salt in combination with the first lithium salt, it is beneficial to reduce the heat generation and heat generation rate between the electrolyte salt and the lithium metal anode during thermal runaway. Furthermore, the carbon dioxide released during the thermal decomposition of the second lithium salt is beneficial for fire extinguishing. The introduction of the second lithium salt can suppress the problem that the thermal decomposition of LiFSI may release sulfur-containing substances, which could exacerbate the thermal runaway reaction. By further controlling the content of the first and second lithium salts in the electrolyte salt within the aforementioned ranges, the severity of thermal runaway in the lithium metal secondary battery can be significantly reduced (thermal runaway intensity), which helps to avoid serious consequences such as fire and explosion, and significantly improves the reliability of the LiFSI-containing lithium metal secondary battery during thermal runaway.

[0105] The types and concentrations of electrolyte salts in the electrolyte can be tested with reference to relevant standards such as GB / T 34672-2017 General Rules for Determination of Chemical Reagents by Ion Chromatography and GB / T 6040-2019 General Rules for Infrared Spectroscopic Analysis. The types and contents of solvents in the electrolyte can be tested with reference to relevant standards such as GB / T 9722-2023 General Rules for Chemical Reagents by Gas Chromatography.

[0106] Those skilled in the art can also identify the components of the electrolyte in a lithium metal secondary battery using one or more of the following detection methods, including but not limited to: 1H NMR (1H NMR) spectroscopy. 1 Methods such as ¹H NMR, high-performance liquid chromatography (HPLC), matrix-assisted laser desorption / ionization mass spectrometry (MADI-TOF), Fourier transform infrared spectroscopy (FT-IR), and ultraviolet spectroscopy are available. The sample preparation and testing methods for these methods are known to those skilled in the art, and the test parameters can be appropriately adjusted according to the structure of the material or substance and the characteristics of the sample. As a non-limiting example, FT-IR, ultraviolet spectroscopy, etc., can be used. 1 One or more of the following methods may be used to detect the types and contents of electrolyte components: ¹H NMR, mass spectrometry, MADI-TOF, etc., but not limited to these.

[0107] Non-limiting, the molar percentage of the first lithium salt in the electrolyte salt can be 50% to 95%, optionally 50% to 80%, or any of the following percentages or a range selected from any two of the following percentages: 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc.

[0108] Non-limitingly, the molar percentage of the second lithium salt in the electrolyte salt can be 5% to 50%, optionally 20% to 50%, or any of the following percentages or a range selected from any two of the following percentages: 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.

[0109] In some embodiments, the first lithium salt has a molar percentage of 50% to 80% in the electrolyte salt, and the second lithium salt has a molar percentage of 20% to 50% in the electrolyte salt.

[0110] By controlling the molar percentages of the first lithium salt (LiFSI) and the second lithium salt (LiDFOB and / or LiBOB) in the electrolyte salt within the aforementioned ranges, it is more beneficial to significantly reduce the intensity of thermal runaway in lithium metal secondary batteries and improve the reliability of lithium metal secondary batteries containing LiFSI during thermal runaway.

[0111] In addition, by controlling the content of LiFSI and the second lithium salt within a suitable range, the negative electrode film-forming effect of LiFSI can be better utilized, the stability of the negative electrode solid electrolyte interphase (SEI) film can be improved, the formation of lithium dendrites on the negative electrode can be reduced, the interfacial side reactions between the negative electrode and the electrolyte can be suppressed, and the lithium metal secondary battery can also have good cycle performance.

[0112] By controlling the content of LiFSI and the second lithium salt within a suitable range, the negative electrode film-forming effect of LiFSI can be better utilized, the formation of lithium dendrites on the negative electrode can be reduced, the interfacial side reactions between the negative electrode and the electrolyte can be suppressed, and the voltage drop during storage can be suppressed or delayed, so that the lithium metal secondary battery also has good storage performance.

[0113] In some embodiments, the molar ratio of the second lithium salt to the first lithium salt in the electrolyte is 0.05 to 1, optionally 0.25 to 1, or any of the following values ​​or a range selected from any two of the following values: 0.05, 0.06, 0.08, 0.1, 0.12, 0.14, 0.15, 0.16, 0.18, 0.2, 0.25, 0.26, 0.28, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.7, 0.75, 0.8, 0.9, 1, etc.

[0114] The molar ratio of the second lithium salt (LiDFOB and / or LiBOB) to the first lithium salt (LiFSI) in the electrolyte (which can be denoted as R) is used to determine the ratio of the second lithium salt (LiDFOB and / or LiBOB) to the first lithium salt (LiFSI). II / I Within the aforementioned range, on the one hand, by utilizing a relatively high content of LiFSI and a relatively low content of the second lithium salt, based on the better anode film-forming characteristics of LiFSI, it is more conducive to forming a uniform and stable anode solid electrolyte interphase (SEI) film, reducing the formation of lithium dendrites on the anode, suppressing the interfacial side reactions between the anode and the electrolyte, and enabling the lithium metal secondary battery to have better cycle performance; on the other hand, by introducing the aforementioned content of the second lithium salt, it can significantly reduce the heat generation and heat generation rate of the electrolyte salt during thermal runaway, reduce the release of sulfur-containing substances caused by the first lithium salt, and also form carbon dioxide which is beneficial for fire extinguishing; thus, LiFSI and the second lithium salt can better synergistically enhance each other, significantly improving the severity of thermal runaway while also taking into account good cycle performance.

[0115] By comparing the molar ratio of the second lithium salt to the first lithium salt in the electrolyte (R... II / I By controlling the voltage within the aforementioned range, the voltage drop during storage can be effectively suppressed or delayed, significantly improving the severity of thermal runaway while also ensuring good storage performance.

[0116] In some embodiments, the sum of the molar ratios of the first lithium salt and the second lithium salt in the electrolyte salt can be 80% to 100%, optionally 90% to 100%, or any of the following percentages or a range selected from any two of the following percentages: 80%, 82%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0117] By controlling the sum of the molar ratios of the first lithium salt (LiFSI) and the second lithium salt (LiDFOB and / or LiBOB) in the electrolyte salt within the aforementioned range, it is beneficial to better leverage the synergistic effect of the first and second lithium salts, thereby significantly improving reliability during thermal runaway while also ensuring good cyclic storage performance.

[0118] In some implementations, the electrolyte satisfies one or more of the following characteristics:

[0119] (a1) Molar volume concentration of the first lithium salt in the electrolyte (C) I The concentration can be 1 mol / L to 7 mol / L, can be selected from 1 mol / L to 6 mol / L, and can be further selected from 1 mol / L to 5 mol / L. It can also be any of the following concentrations or a range selected from any two of the following concentrations: 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, etc.

[0120] (a2) Molar volume concentration of the second lithium salt in the electrolyte (C) II The concentration can be 0.5 mol / L to 4 mol / L, can be selected from 1 mol / L to 4 mol / L, can be further selected from 1 mol / L to 3 mol / L, and can also be any of the following concentrations or a range selected from any two of the following concentrations: 0.5 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, etc.

[0121] (a3) The sum of the molar volume concentrations of the first and second lithium salts in the electrolyte (C) I+II The concentration can be 2 mol / L to 8 mol / L, or can be selected from 2 mol / L to 6 mol / L. It can also be any of the following concentrations or a range selected from any two of the following concentrations: 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L, 8 mol / L, etc.

[0122] (a4) Molar volume concentration of electrolyte salts in the electrolyte (C AThe concentration can be 2 mol / L to 8 mol / L, or 2 mol / L to 6 mol / L, or any of the following concentrations or a range consisting of any two of the following concentrations: 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L, 8 mol / L, etc.

[0123] By controlling the molar volume concentration (C) of the first lithium salt in the electrolyte I ), the molar volume concentration of the second lithium salt in the electrolyte (C II The sum of the molar volume concentrations of the first and second lithium salts in the electrolyte (C) I+II ) and the molar volume concentration of electrolyte salts in the electrolyte (C A Controlling one or more parameters within the aforementioned range is beneficial for better reducing the intensity of thermal runaway in lithium metal secondary batteries. In addition, it can also better balance cycle performance and / or storage performance.

[0124] By controlling the molar volume concentration (C) of the first lithium salt in the electrolyte I Within the aforementioned range, it is beneficial to better balance cyclic performance and / or storage performance.

[0125] By controlling the molar volume concentration (C) of the second lithium salt in the electrolyte. II Within the aforementioned range, it is beneficial to better reduce the intensity of thermal runaway in lithium metal secondary batteries.

[0126] In some embodiments, the second lithium salt comprises lithium difluorooxalate borate. Non-limitingly, the molar percentage (R) of lithium difluorooxalate borate in the second lithium salt is... 21 The percentage can be 50% to 100%, or optionally 80% to 100%, or any of the following percentages or a range consisting of any two of the following percentages: 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0127] By controlling the molar percentage (R) of lithium difluorooxalatoborate in the second lithium salt 21 Within the aforementioned range, it is beneficial to better reduce the intensity of thermal runaway in lithium metal secondary batteries.

[0128] In some embodiments, the sum of the molar ratios of the first lithium salt and the second lithium salt in the electrolyte salt is 80% to 100%, which can be selected as 90% to 100% or a range selected from any two of the following percentages: 80%, 82%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0129] By controlling the sum of the molar percentages of the first lithium salt (LiFSI) and the second lithium salt (LiDFOB and / or LiBOB) in the electrolyte salt (R... I+II Within the aforementioned range, it is beneficial to better leverage the synergistic effect of the first and second lithium salts, and to significantly reduce the intensity of thermal runaway in lithium metal secondary batteries; in addition, it can also better balance cycle performance and / or storage performance.

[0130] In some embodiments, the lithium-containing metal includes one or more of elemental lithium and lithium alloys.

[0131] Without limitation, the mass percentage or molar percentage of lithium in lithium-containing metals can be 95% to 100%, and can be selected from 90% to 100% or a range consisting of any two of the following percentages: 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0132] When the lithium-containing metal in the negative electrode active layer is elemental lithium, the thermal runaway intensity of lithium metal secondary batteries can be significantly reduced by using the aforementioned electrolyte; in addition, cycle performance and / or storage performance can be well balanced.

[0133] Unless otherwise specified, the electrolyte includes an electrolyte solvent. In some embodiments, the electrolyte solvent includes a non-aqueous solvent.

[0134] In some embodiments, the electrolyte includes a non-aqueous solvent, which includes one or more of aliphatic ether solvents, fluorinated aliphatic ether solvents, and benzene-containing solvents.

[0135] In some embodiments, the non-aqueous solvent of the electrolyte includes at least one of aliphatic ether solvents and fluorinated aliphatic ether solvents, and also includes a benzene-containing solvent.

[0136] In some embodiments, the non-aqueous solvent of the electrolyte includes fluorinated aliphatic ether solvents and benzene-containing solvents.

[0137] In some embodiments, the non-aqueous solvent of the electrolyte includes aliphatic ether solvents, fluorinated aliphatic ether solvents, and benzene-containing solvents.

[0138] It is understandable that "non-aqueous solvents" can be used as solvents in the electrolyte of lithium metal secondary batteries.

[0139] In some embodiments, the fatty ether solvent has a chain structure.

[0140] In some embodiments, the fatty ether solvent is a saturated fatty ether solvent, and may further be a chain structure.

[0141] In some embodiments, the fluorinated aliphatic ether solvent has a chain structure.

[0142] In some embodiments, the fluorinated aliphatic ether solvent is a fluorinated saturated aliphatic ether solvent, and may further be a chain structure.

[0143] In this application, unless otherwise specified, "aliphatic ether solvent" refers to an ether solvent that is not aromatic, and unless otherwise specified, it is an ether solvent formed by replacing one or more non-terminal carbon atoms in an aliphatic hydrocarbon with oxygen atoms.

[0144] In this application, unless otherwise stated, "aliphatic hydrocarbon" refers to hydrocarbons that are not aromatic, that is, hydrocarbons that do not contain aromatic rings.

[0145] In this application, unless otherwise specified, "benzene-containing solvent" refers to a non-aqueous solvent containing a benzene ring.

[0146] In this application, unless otherwise specified, "saturated aliphatic ether solvent" refers to an ether solvent composed of a saturated carbon chain and oxygen atoms. That is, a saturated aliphatic ether solvent can be an ether solvent formed by replacing one or more non-terminal carbon atoms in a saturated hydrocarbon with oxygen atoms.

[0147] In this application, unless otherwise stated, "fluorinated aliphatic ether solvent" refers to an ether solvent in which one or more hydrogen atoms are replaced by fluorine atoms.

[0148] In this application, unless otherwise stated, "fluorinated saturated fatty ether solvent" refers to an ether solvent in which one or more hydrogen atoms in a saturated fatty ether solvent are replaced by fluorine atoms.

[0149] In this application, unless otherwise specified, the "chain structure" does not contain a ring structure, and can be a straight chain structure without branches or a branched chain structure.

[0150] By controlling one or more of the non-aqueous solvents in the electrolyte, including aliphatic ether solvents, fluorinated aliphatic ether solvents, and benzene-containing solvents, the solvent can be made to have better oxidation resistance.

[0151] Improving the oxidation resistance of the solvent can enhance the reliability of lithium metal secondary batteries during thermal runaway.

[0152] Improving the solvent's oxidation resistance also helps reduce side reactions between the solvent and the positive electrode.

[0153] In some embodiments, the electrolyte salt in the electrolyte is an electrolyte salt that is soluble in aliphatic ether solvents at 25°C to 45°C. In some embodiments, the electrolyte salt includes an electrolyte lithium salt, and more particularly, it can be an electrolyte lithium salt.

[0154] It is understood that electrolyte salts that can dissolve in the electrolyte solvent of the lithium metal secondary battery provided in this application should be selected, and lithium electrolyte salts can be further selected. LiFSI, LiDFOB and LiBOB can all dissolve, while lithium salts such as lithium hexafluorophosphate (LiPF6) and lithium tetrafluoroborate cannot dissolve or have poor solubility.

[0155] Unless otherwise specified, the solubility of the electrolyte salt in the "DME+TTE+FB mixed solvent" at 25°C can be used to determine the solubility. Furthermore, the mass ratio of DME, TTE and FB can be 1:2:1.

[0156] The electrolyte salt may optionally include other types of electrolyte salts. Examples of other types of electrolyte salts include lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Non-limitingly, the molar percentage of LiTFSI in the electrolyte salt may be 0–20%, optionally 0–10%, and may also be any of the following percentages or a range selected from any two of the following percentages: 0, 1%, 2%, 4%, 5%, 6%, 8%, 10%, 12%, 15%, 16%, 18%, 20%, etc.

[0157] In some embodiments, the electrolyte salt further includes lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Non-limitingly, the molar percentage of LiTFSI in the electrolyte salt may be less than or equal to 20%, optionally less than or equal to 10%, and may also be less than or equal to any of the following percentages: 2%, 4%, 5%, 6%, 8%, 10%, 12%, 15%, 16%, 18%, 20%, etc.

[0158] The heat generation and heat generation rate of LiTFSI with lithium metal anodes are between those of first and second lithium salts. In differential scanning calorimetry (DSC) analysis, the heat generation of LiTFSI electrolyte (6 mol / L) with lithium metal electrode is 5514 J / mAh, and the maximum heat generation rate is 220 J / mAh / min.

[0159] In some implementations, the electrolyte satisfies one or more of the following characteristics:

[0160] (d1) The electrolyte includes a fatty ether solvent; non-limitingly, the number of carbon atoms in the fatty ether solvent can be 2 to 14; the number of oxygen atoms in the fatty ether solvent can be 1 or more, optionally 1 or 2; in some embodiments, the fatty ether solvent has a chain structure.

[0161] (d2) The electrolyte includes a fluorinated aliphatic ether solvent; non-limitingly, the number of carbon atoms in the fluorinated aliphatic ether solvent can be 2 to 14; the hydrogen atoms in the fluorinated aliphatic ether solvent can be partially or perfluorinated; the number of fluorine atoms in the fluorinated aliphatic ether solvent can be one or more; the number of oxygen atoms in the fluorinated aliphatic ether solvent can be one or more, optionally one or two; in some embodiments, the fluorinated aliphatic ether solvent has a chain structure;

[0162] (d3) The electrolyte includes a benzene-containing solvent; non-limitingly, the benzene-containing solvent may include one or more of benzene, substituted benzene, anisole, and substituted anisole; wherein the benzene ring in the substituted benzene may be replaced by one or more substituents Q1; any substituent Q1 may independently be a fluorine atom, C 1-3 Chain alkyl or fluorinated C 1-3 Chain alkyl; the phenyl and methyl groups in substituted anisoles can each be independently replaced by one or more substituents Q2; any substituent Q2 can independently be a fluorine atom, C 1-3 Chain alkyl or fluorinated C 1-3 Chain alkyl groups; in benzene-containing solvents, any fluorinated C 1-3 The number of fluorine atoms in the chain alkyl group can be one or more independently, and can be selected as 1 or 2;

[0163] (d4) In the electrolyte, the sum of the mass percentages of aliphatic ether solvent, fluorinated aliphatic ether solvent and benzene-containing solvent in the non-aqueous solvent can be 80% to 100%, and can be selected as 90% to 100% or a range consisting of any two of the following percentages: 80%, 82%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0164] Replacing the solvent with fluorine can improve its thermal stability and help reduce the intensity of thermal runaway in lithium metal secondary batteries.

[0165] Introducing benzene-containing solvents can help improve the solvent's oxidation resistance.

[0166] Non-limitingly, the number of carbon atoms in the aliphatic ether solvent can be 2 to 14, preferably 2 to 12, further preferably 2 to 10, and can also be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14, and can also be selected from any of the aforementioned integer ranges.

[0167] Without limitation, the number of oxygen atoms in the aliphatic ether solvent can be one or more, optionally one or two.

[0168] Non-limitingly, the number of carbon atoms in the fluorinated aliphatic ether solvent can be 3 to 14, optionally 4 to 12, further optionally 5 to 12 or 4 to 10, and can also be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14, and can also be selected from any of the aforementioned integer ranges.

[0169] In a non-limiting sense, hydrogen atoms in fluorinated aliphatic ether solvents can be partially or perfluorinated.

[0170] Non-limitingly, the number of fluorine atoms in the fluorinated aliphatic ether solvent can be one or more, selected from 1 to 14, further selected from 1 to 10, and can also be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14, and can also be selected from any of the aforementioned integer ranges.

[0171] Without limitation, the number of oxygen atoms in the fluoroalicylic ether solvent can be one or more, optionally one or two.

[0172] Without limitation, benzene-containing solvents may include one or more of benzene, substituted benzene, anisole, and substituted anisole.

[0173] In some embodiments, the benzene-containing solvent includes one or more of benzene, substituted benzene, and substituted anisole.

[0174] In some embodiments, the benzene-containing solvent includes one or more of substituted benzene and substituted anisole.

[0175] In some embodiments, the benzene in the substituted anisole is unsubstituted.

[0176] In some embodiments, the substituted anisole is a fluorinated C-type anisole. 1-7 Alkylphenyl ethers, with the structure Ph-OR E , where R E fluorinated C 1-7 Alkyl group, optionally fluorinated C 1-6 Alkyl, further optionally fluorinated C 1-3 Alkyl group. R E It can be partially fluorinated or perfluorinated. R E The number of fluorine atoms in the sample can be one or more, and can be selected from 1 to 15. It can also be any of the following values ​​or a range selected from any two of the following values: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15.

[0177] Non-limitingly, the number of fluorine atoms in the benzene-containing solvent can be 0 to 15, optionally 0 or 1 to 15, and can also be any of the following values ​​or a range selected from any two of the following values: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15.

[0178] In some embodiments, the benzene-containing solvent is fluorinated and may be referred to as "fluorinated benzene-containing solvent". Non-limitingly, the number of fluorine atoms in the benzene-containing solvent may be 1 to 15, and may also be any of the following values ​​or a range selected from any two of the following values: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15.

[0179] In some embodiments, the non-aqueous solvent in the electrolyte may include one or more of aliphatic ether solvents, fluorinated aliphatic ether solvents, and fluorinated benzene-containing solvents.

[0180] In some embodiments, the non-aqueous solvent in the electrolyte may include one or more of fluorinated aliphatic ether solvents and fluorinated benzene-containing solvents.

[0181] In a non-limiting sense, the benzene ring in the substituted benzene may be replaced by one or more substituents Q1; any substituent Q1 may independently be a fluorine atom, C 1-3 Chain alkyl or fluorinated C 1-3 Alkyl chain.

[0182] In a non-limiting manner, the phenyl and methyl groups in the substituted anisole can each be independently substituted by one or more substituents Q2; any substituent Q2 can independently be a fluorine atom, C 1-3 Chain alkyl or fluorinated C 1-3 Alkyl chain.

[0183] In a non-limiting manner, the methyl groups in the substituted anisole can each be independently replaced by one or more substituents Q2; any one substituent Q2 can independently be a fluorine atom, C 1-3 Chain alkyl or fluorinated C 1-3 Chain alkyl; in some embodiments, the phenyl group in the substituted anisole is unsubstituted.

[0184] Non-limiting, in a benzene-containing solvent, any fluorinated C 1-3 The number of fluorine atoms in the chain alkyl group can be one or more independently, and can be selected from 1 to 7, or can be 1, 2, 3, 4, 5, 6 or 7, or can be selected from any of the aforementioned integers.

[0185] In this application, unless otherwise specified, "alkyl" refers to a monovalent residue formed by the loss of a hydrogen atom from a saturated hydrocarbon. Phrases containing this term, such as "C", are also acceptable.1-7 "Alkyl" refers to an alkyl group containing 1 to 7 carbon atoms. Each time it appears, it can be independently C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl or C7 alkyl.

[0186] Unless otherwise stated in this application, "C" 1-3 The "chain alkyl" can be methyl, ethyl, or n-propyl, and may further be methyl.

[0187] Unless otherwise stated in this application, "fluorinated C" 1-3 "Chain alkyl" can be a fluorinated methyl, a fluorinated ethyl, or a fluorinated n-propyl.

[0188] In some embodiments, the fluorinated C in the benzene solvent 1-3 The chain alkyl group is selected from one or more of trifluoromethyl (-CF3), pentafluoroethyl (-CF2CF3), and heptafluoropropyl (-CF2CF2CF3).

[0189] In some embodiments, the aliphatic ether solvent may include the structure R A -O(CH2)2O-R B and R C -OR D One or more of the compounds, wherein R A R B R C and R D Each independently is C 1-6 Alkyl, optionally C 1-5 Alkyl groups, which may further be methyl, ethyl, n-propyl, n-butyl, or n-pentyl, and may also be C 1-5 The alkyl group may further be methyl, ethyl, or n-propyl. In some embodiments, the aliphatic ether solvent has 3 or more carbon atoms.

[0190] In some embodiments, the fatty ether solvent includes one or both of ethylene glycol dimethyl ether.

[0191] In some embodiments, the fatty ether solvent includes ethylene glycol dimethyl ether.

[0192] In some embodiments, the fluorinated aliphatic ether solvent may include the structure R U -O(CH2)2O-R V and R X -OR Y One or more of the compounds, wherein R U R V R X and R Y Each independently is C 1-6Alkyl or fluorinated C 1-6 Alkyl groups, which can each independently be C10. 1-5 Alkyl or fluorinated C 1-5 Alkyl groups, and furthermore, each can be independently C10. 1-3 Alkyl or fluorinated C 1-3 Alkyl; wherein, R U and R V At least one of them contains F, R X and R Y At least one of them contains F. R U R V R X and R Y When any of them contains a fluorine atom (e.g., fluorinated C), 1-6 Alkyl groups, further such as fluorinated C 1-5 Alkyl groups can each be partially or fully fluorinated. Without limitation, R... U R V R X and R Y When any of them contains fluorine atoms, the number of fluorine atoms can be one or more independently, and can be selected from 1 to 7, or 1, 2, 3, 4, 5, 6 or 7, or selected from any of the aforementioned integer ranges. In some embodiments, the number of carbon atoms in the fluorinated aliphatic ether solvent is greater than or equal to 3.

[0193] In some embodiments, the substituted benzene may be one or more of toluene, p-xylene, o-xylene, m-xylene, fluorobenzene (containing one F atom, C6H5-F, which can be denoted as FB), p-difluorobenzene, o-difluorobenzene, m-difluorobenzene, 1,3,5-trifluorobenzene, hexafluorobenzene, trifluoromethylbenzene (Ph-CF3), pentafluoroethylbenzene (Ph-CF2CF3), heptafluoropropylbenzene (Ph-CF2CF2CF3), 1,4-bis(trifluoromethyl)benzene (CF3-Ph-CF3), 1,4-bis(pentafluoroethyl)benzene (CF3CF2-Ph-CF2CF3), 1,4-bis(heptafluoropropyl)benzene (CF3CF2CF2-Ph-CF2CF2CF3), 1,2-bis(trifluoromethyl)benzene, and 1,3-bis(trifluoromethyl)benzene.

[0194] In some embodiments, the substituted benzene is fluorinated benzene, and the number of fluorine atoms can be 1, 2, 3, 4, 5 or 6.

[0195] In some embodiments, the substituted anisole can be a fluoroanisole, and more particularly, it can be a fluoromethylphenyl ether (Ph-O-CH2F), a phenyl difluoromethyl ether (CHF2-O-Ph), a phenyl trifluoromethyl ether (Ph-O-CF3), a pentafluoroethylphenyl ether (Ph-O-CF2CF3), a heptafluoropropylphenyl ether (Ph-O-CF2CF2CF3), a nonafluorobutylphenyl ether (Ph-O-CF2CF2CF2CF3), a 1,1-difluoroethylphenyl ether (Ph-O-CF2CH3), a 1,1-difluoropropylphenyl ether (Ph-O-CF2CH2CH3), a 1,1-difluorobutylphenyl ether (Ph-O-CF2CH2CH2CH3), or a (2-fluoropropyl-2-yl)phenyl ether. One or more of the following: ether (Ph-O-CF(CH3)2), (3-fluoropentyl-3-yl)phenyl ether (Ph-O-CF(CH2CH3)2), (4-fluoroheptyl-4-yl)phenyl ether (Ph-O-CF(CH2CH2CH3)2), (perfluoropropan-1-yl)phenyl ether (Ph-O-CF(CF3)2, ((perfluoropropan-2-yl)oxy)benzene), (perfluoropentyl-2-yl)phenyl ether (Ph-O-CF(CF2CF3)2, ((perfluoropentan-3-yl)oxy)benzene), (perfluoroheptyl-4-yl)phenyl ether (Ph-O-CF(CF2CF2CF3)2).

[0196] In some embodiments, the aliphatic ether solvent may include the structure R A -O(CH2)2O-R B and R C -OR D One or more of the compounds, wherein R A R B R C and R D Each independently is C 1-5 The alkyl group may be methyl, ethyl, n-propyl, n-butyl, or n-pentyl; optionally, the aliphatic ether solvent has 3 or more carbon atoms.

[0197] In some embodiments, the fluorinated aliphatic ether solvent includes one or more of the following: compound 1 with the structure shown in Formula I, compound 2 with the structure shown in Formula II, compound 3 with the structure shown in Formula III, compound 4 with the structure shown in Formula VI, compound 5 with the structure shown in Formula V, and compound 6 with the structure shown in Formula VI.

[0198]

[0199] Among them, Rf 11 、Rf 12、Rf 21 、Rf 31 、Rf 41 、Rf 42 、Rf 51 and Rf 61 Each independently is C 1-5 Fluorinated chain alkyl, wherein, C 1-5 The number of fluorine atoms in the fluorinated chain alkyl group is one or more, and it can be partially fluorinated or perfluorinated;

[0200] R 11 R 12 R 13 R 14 R 15 R 16 R 17 R 18 R 21 R 22 R 23 R 24 R 25 R 26 R 27 R 28 R 31 R 32 R 33 R 34 R 35 R 36 R 37 R 38 R 39 R 41 R 42 R 43 R 44 R 51 R 52 R 53 R 54 R 61 R 62 R 63 R 64 and R 65 Each can be H or F independently;

[0201] R 20 and R 50 Each independently is C 1-5 The chain alkyl group may be methyl, ethyl, n-propyl, n-butyl, or n-pentyl.

[0202] In some embodiments, the fluorinated aliphatic ether solvent includes one or more of compounds 1a, 2a, 3a, 4a, 5a, and 6a;

[0203] in,

[0204] The structure of compound 1a is shown in Formula I, R 11 R 12 R 13 R 14 R 15 R 16 R 17 and R 18 All are H;

[0205] The structure of compound 2a is shown in Formula II, R 21 R 22 R 23 R 24 R 25 R 26 R 27 and R 28 All are H;

[0206] The structure of compound 3a is shown in Formula II, R 31 R 32 R 33 R 34 R 35 R 36 R 37 R 38 and R 39 All are H;

[0207] The structure of compound 4a is shown in Formula I, R 41 R 42 R 43 and R 44 All are H;

[0208] The structure of compound 5a is shown in Formula I, R 51 R 52 R 53 and R 54 All are H;

[0209] The structure of compound 6a is shown in Formula I, R 61 R 62 R 63 R 64 and R 65 All are H.

[0210] In some embodiments, the fluorinated aliphatic ether solvent may include one or more of the following compounds: F(CH2)2O(CH2)2OCH3, CHF2CH2O(CH2)2OCH3, CF3CH2O(CH2)2OCH3, F(CH2)2O(CH2)2OCH2CH3, CHF2CH2O(CH2)2OCH2CH3, CF3CH2O(CH2)2OCH2CH3, F(CH2)2O(CH2)2O(CH2)2F, F2CHCH2O(CH2)2O(CH2)2F, CF3CH2O(CH2)2O(CH2)2F, F2CHCH2O(CH2)2OCH2CHF2, CF3CH2O(CH2)2OCH2CHF2, CF3CH2O(CH2)2OCH2CF3, F(CH2)2O(CH2)2O(CH2)2CH3, F2CHCH2O(CH2)2O(CH2)2CH3, CF3CH2O(CH2)2O(CH2)2CH3, CH3CH2O(CH2)2O(CH2)3F, CH3CH2O(CH2)2O(CH2)2CHF2, CH3CH2O(CH2)2O(CH2)2CF3, CH3CH2O(CH2)2OCH2CHF(CH3), CH3CH2O(CH2)2OCH2CF2CH3, F(CH2)2O(CH2)2OCH2CF2CH3, F(CH2)2O(CH2)2OCH2CHF(CH3), F(CH2)2OC(CH2)2O(CH2)3F, F(CH2)2O(CH2)2O(CH2)2CHF2, F(CH2)2O(CH2)2O(CH2)2CF3, CHF2CH2O(CH2)2O(CH2)2CF3, CHF2CH2O(CH2)2O(CH2)3F, CHF2CH2O(CH2)2OCH2CHF(CH3), CHF2CH2O(CH2)2OCH2CF2CH3, CF3CH2O(CH2)2OCH2CF2CH3, CF3CH2O(CH2)2OCH2CHF(CH3), CF3CH2O(CH2)2O(CH2)3F, CF3CH2O(CH2)2OCH2CH2CHF2, CF3CH2O(CH2)2O(CH2)2CF3, CH3CH2O(CH2)2OCH2CF2CF3, F(CH2)2O(CH2)2OCH2CF2CF3, CHF2CH2O(CH2)2OCH2CF2CF3, CF3CH2O(CH2)2OCH2CF2CF3, CF3CF2CH2O(CH2)2OCH2CF2CF3, CH3CF2CH2O(CH2)2OCH2CF2CH3,CHF2(CH2)2O(CH2)2O(CH2)2CHF2, CF3(CH2)2O(CH2)2O(CH2)2CF3, F(CH2)3O(CH2)2O(CH2)3F, FCH2CF2CH2O(CH2)2OCH2CF2CH2F, CHF2CF2CH2O(CH2)2OCH2CF2CHF2, CHF2(CH2)2O(CH2)2CF3, CH3CH2CF2CH2O(CH2)2OCH2CF2CH2CH3, CH3CH2CF2CH2O(CH2)2OCH2CF2CH3, CH3CF2CF2CH2O(CH2)2OCH2CF2CH3 H2CF2CH3, CH3CF2(CH2)2O(CH2)2OCH2CF2CH3, CF3(CH2)3O(CH2)2O(CH2)3CF3, CF3CH2CF2CH2O(CH2)2OCH2CF2CH2CF3, CH3CH2CF2CH2O(CH2)2OCH2CF2(CH2)2CH3, CH3CF2(CH2)3O(CH2)2O(CH2)3CF2CH3, CF3(CH2)4O(CH2)2O(CH2)3CF3, CH3CH2CF2(CH2)2O(CH2)2O(CH2)2CF2CH3, CH3(CH2)2CF2CH2O(C H2)2OCH2CF2(CH2)2CH3, CF3(CH2)4OCH2CH2O(CH2)4CF3, CH3CH2CF2(CH2)2O(CH2)2O(CH2)2CF2CH2CH3, F(CH2)3O(CH2)2OCH3, CHF2(CH2)2OCH3, CF3(CH2)2OCH3, CH3CHFCH2OCH3, CH3CF2CH2OCH3, CH3CH2CF2CH2OCH3, CH3CHF(CH2)2OCH3, CH3CF2(CH2)2OCH3, F(CH2)4OCH3, CHF2(C H2)3OCH3, CF3(CH2)3OCH3, CF3CF2CF2CH2OCH3, CF3CHFCHFCH2OCH3, CHF2CHFCHFCH2OCH3, FCH2CHFCHFCH2OCH3, CH3CHFCH2OCH2CH3, CH3CF2CH2OCH2CH3, CH3(CH2)2O(CH2)2F, CH3(CH2)2OCH2CHF2, CH3(CH2)2OCH2CF3, F(CH2)3OCH2CH3, CHF2(CH2)2OCH2CH3, CF3(CH2)2OCH2CH3, CH3CF2CH2O(CH2)2CH3CH3CHFCH2O(CH2)2CH3, F(CH2)3O(CH2)2CH3, CHF2(CH2)2O(CH2)2CH3, CF3(CH2)2O(CH2)2CH3, CH3CH2CF2CH2O(CH2)2CH3, CH3CF2(CH2)2O(CH2)2CH3, CF3(CH 2)3O(CH2)2CH3, CH3(CH2)3OCH2CF2CH3, CH3(CH2)3O(CH2)2CF3, CH3CH2CF2CH2O(CH2)3CH3, CH3CF2(CH2)2O(CH2)3CH3, CF3(CH2)3O(CH2)3CH3, CF3(CH2)3O(C H2)4CH3, CH3CF2(CH2)2O(CH2)4CH3, CH3CH2CF2CH2O(CH2)4CH3, CH3(CH2)3OCH2CF2(CH2)2CH3, CH3(CH2)3O(CH2)2CF2CH2CH3, CH3(CH2)3O(CH2)4CF3, CH3(CH 2) 3O(CH2)3CF2CH3, CH3(CH2)4O(CH2)3CF2CH3, CH3(CH2)4O(CH2)4CF3, CH3(CH2)4O(CH2)2CF2CH2CH3, CH3(CH2)4OCH2CF2(CH2)2CH3, CHF2CF2OCH2CF2CHF2, etc. ,

[0211] In some embodiments, the benzene-containing solvent includes one or more of compound 7 with the structure shown in formula VII and compound 8 with the structure shown in formula VIII;

[0212]

[0213] Among them, R 71 R 72 R 73 R 74 R 75 R 76 R 81 and R 82 Each is independently a H, fluorine, or C atom. 1-3 Chain alkyl or fluorinated C 1-3 Alkyl chain. C 1-3 The chain alkyl group can be methyl, ethyl, or n-propyl. Fluorinated C 1-3 The alkyl chain can be partially fluorinated or perfluorinated. Fluorinated C 1-3 The fluorine atom in the chain alkyl group can be one or more, and can be selected from 1 to 7, or can be 1, 2, 3, 4, 5, 6 or 7, or can be selected from any of the aforementioned integers.

[0214] In some embodiments, the benzene-containing solvent includes one or more of the following compounds: benzene, toluene, p-xylene, o-xylene, m-xylene, fluorobenzene (containing one F atom, C6H5-F), p-difluorobenzene, o-difluorobenzene, m-difluorobenzene, 1,3,5-trifluorobenzene, hexafluorobenzene, trifluoromethylbenzene (Ph-CF3), pentafluoroethylbenzene (Ph-CF2CF3), heptafluoropropylbenzene (Ph-CF2CF2CF3), and 1,4-bis(trifluoromethyl)benzene (CF3-Ph-CF3). ), 1,4-bis(pentafluoroethyl)benzene (CF3CF2-Ph-CF2CF3), 1,4-bis(heptafluoropropyl)benzene (CF3CF2CF2-Ph-CF2CF2CF3), 1,2-bis(trifluoromethyl)benzene, 1,3-bis(trifluoromethyl)benzene, anisole, fluoromethylphenyl ether (Ph-O-CH2F), phenyl difluoromethyl ether (CHF2-O-Ph), phenyl trifluoromethyl ether (Ph-O-CF3), pentafluoroethylphenyl ether (Ph-O-CF 2CF3), heptafluoropropylphenyl ether (Ph-O-CF2CF2CF3), nonafluorobutylphenyl ether (Ph-O-CF2CF2CF2CF3), 1,1-difluoroethylphenyl ether (Ph-O-CF2CH3), 1,1-difluoropropylphenyl ether (Ph-O-CF2CH2CH3), 1,1-difluorobutylphenyl ether (Ph-O-CF2CH2CH2CH3), (2-fluoropropyl-2-yl)phenyl ether (Ph-O-CF(CH3)2) (3-fluoropentyl-3-yl)phenyl ether (Ph-O-CF(CH2CH3)2), (4-fluoroheptyl-4-yl)phenyl ether (Ph-O-CF(CH2CH2CH3)2), (perfluoroprop-1-yl)phenyl ether (Ph-O-CF(CF3)2), (perfluoropentyl-2-yl)phenyl ether (Ph-O-CF(CF2CF3)2), (perfluoroheptyl-4-yl)phenyl ether (Ph-O-CF(CF2CF2CF3)2), etc.

[0215] In some embodiments, the benzene-containing solvent is fluorinated benzene, which may include one or more of fluorinated benzene and fluorinated anisole, and may further be fluorinated benzene.

[0216] In some embodiments, the non-aqueous solvent in the electrolyte includes aliphatic ether solvents, fluorinated aliphatic ether solvents, and fluorinated benzene-containing solvents, and may further include dimethyl glycol ether (DME), TTE, and fluorobenzene (FB), or a combination of DME, TTE, and FB. Exemplarily, the non-aqueous solvent in the electrolyte may be DME, TTE, and FB in a mass ratio of 1:2:1.

[0217] Non-limiting, the mass percentage of the aliphatic ether solvent (such as DME) in the non-aqueous solvent of the electrolyte can be 10% to 30%, for example, 10%, 15%, 20%, 25%, 30%, or any two of the aforementioned percentages. Non-limiting, the mass percentage of the fluorinated aliphatic ether solvent (such as TTE) in the non-aqueous solvent of the electrolyte can be 40% to 60%, for example, 40%, 45%, 40%, 55%, 60%, or any two of the aforementioned percentages. Non-limiting, the mass percentage of the fluorinated benzene-containing solvent (such as FB) in the non-aqueous solvent of the electrolyte can be 10% to 30%, for example, 10%, 15%, 20%, 25%, 30%, or any two of the aforementioned percentages.

[0218] The following is a description of the positive electrode sheet.

[0219] 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 including a positive active material.

[0220] Without limitation, the weight percentage of the positive electrode active material in the positive electrode active layer may be greater than or equal to 80 wt%, further greater than or equal to 90 wt%, and even further greater than or equal to 92 wt%.

[0221] As a non-limiting example, the positive current collector has two surfaces that are opposite to each other in its own thickness direction, and the positive active layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0222] 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. In the positive electrode current collector, 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. In the positive electrode current collector, the composite current collector may 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 at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. Non-limitingly, in the positive electrode current collector, the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0223] In some embodiments, the positive electrode active material may be a positive electrode active material known in the art for lithium metal secondary batteries.

[0224] Without limitation, the positive electrode active material may include one or more of lithium transition metal oxide positive electrode materials and lithium phosphate active materials.

[0225] In this application, unless otherwise specified, "lithium transition metal oxide cathode material" refers to a cathode active material containing lithium, transition metal elements, and oxygen. Therefore, lithium transition metal oxide cathode materials include non-lithium metal elements, and these non-lithium metal elements include transition metal elements. Non-limitingly, in lithium transition metal oxide cathode materials, the molar percentage of transition metal elements relative to non-lithium metal elements can be 90% to 100%, and can also be any of the following percentages or a range selected from any two of the following percentages: 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc. In this application, unless otherwise specified, "non-lithium metal element" refers to a metal element that is not lithium (Li).

[0226] In some embodiments, lithium transition metal oxide cathode materials have a layered crystal structure.

[0227] In this application, unless otherwise specified, "lithium phosphate-containing cathode material" refers to a class of cathode active materials containing lithium iron phosphate components, and more specifically, includes lithium, transition metal elements, and phosphate ions (PO4). 3- The positive electrode active material is lithium phosphate. Unless otherwise specified, "lithium phosphate positive electrode material" may be olivine structure.

[0228] As a non-limiting example, the positive electrode active material may include one or more of the following materials: lithium 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. Among them, 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 phosphates with an olivine structure may 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 manganese iron 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 / 3Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.80 Co 0.15 Al 0.05 O2. Examples of lithium iron phosphate include LiFePO4. Examples of lithium manganese phosphate include LiMnPO4.

[0229] Understandably, lithium (Li) is intercalated and deintercalated during the charging and discharging process of a battery, and the Li content in the positive electrode varies depending on the state of discharge. In the exemplary description of the positive electrode active material in this application, unless otherwise specified, the Li content can be the initial state of the material or a non-initial state after charge-discharge cycles. When the positive electrode active material is applied to the positive electrode in a battery system, the Li content in the positive electrode active material at the positive electrode will usually change after charge-discharge cycles. The Li content can be measured in atomic molar content, but is not limited to this. Regarding "Li content is the initial state of the material," the initial state of the material refers to the state before it is formed into the positive electrode active layer. It is understood that new materials or substances obtained by appropriately modifying the listed positive electrode active materials are also within the scope of positive electrode active materials. The aforementioned appropriate modification refers to an acceptable modification method for the positive electrode active material, and non-limiting examples include one or more of coating modification and doping modification.

[0230] In the exemplary description of the positive electrode active material in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause changes in the atomic molar content of oxygen, and the actual O content will fluctuate. The O content can be measured in atomic molar content, but is not limited to this.

[0231] In some embodiments, the positive electrode active layer optionally includes a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. Typically, the binder may constitute 0–10 wt% of the weight of the positive electrode active layer, more commonly 0–8 wt%, and even more commonly 1 wt%–5 wt%, based on the total weight of the positive electrode active layer.

[0232] In some embodiments, the positive electrode active layer optionally includes 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. Typically, the weight percentage of the conductive agent in the positive electrode active layer can be 0–10 wt%, more commonly 0–8 wt%, and even more commonly 0–5 wt%, based on the total weight of the positive electrode active layer.

[0233] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry. Further, the positive electrode slurry is coated onto at least one surface of the positive current collector, and after drying, cold pressing, and other processes, the positive electrode sheet is obtained. Cold pressing can be performed using a cold rolling mill. The solvent in the positive electrode slurry can be, but is not limited to, any of the solvents described in the foregoing embodiments, for example, it can include N-methylpyrrolidone (NMP), and more specifically, NMP. The surface of the positive current collector coated with the positive electrode slurry can be a single surface of the positive current collector or both surfaces of the positive current collector. The solid content of the positive electrode slurry can be 40 wt% to 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 mPa·s to 25000 mPa·s.

[0234] In some embodiments, the positive electrode active material includes a lithium composite metal oxide-based positive electrode material. Further, the mass percentage of the lithium composite metal oxide-based positive electrode material in the positive electrode active material can be greater than or equal to 50%, and more preferably 95% to 100%, but is not limited thereto. Exemplarily, when coating the positive electrode slurry, the coating areal density (based on the coating areal density of one side) on a dry weight basis (excluding solvent) can be (0.05 to 0.6) g / 1540.25 mm². 2 The optional value is (0.1~0.3)g / 1540.25mm. 2 For example, the compaction density of the positive electrode sheet can be 3.0 g / cm³. 3 ~4.2g / cm 33.3g / cm³ is an option. 3 ~3.8g / cm 3 .

[0235] In some embodiments, the positive electrode active material includes a lithium phosphate-based positive electrode material. Further, the mass percentage of the lithium phosphate-based positive electrode material in the positive electrode active material can be greater than or equal to 50%, and more specifically, can be 95% to 100%, but is not limited thereto. Exemplarily, when coating the positive electrode slurry, the coating areal density (based on dry weight, minus solvent) (based on the coating areal density of one side) can also be (0.1 to 0.5) g / 1540.25 mm². 2 However, this is not the only possibility. For example, the compaction density of the positive electrode sheet can be 2.0 g / cm³. 3 ~2.8g / cm 3 2.3g / cm³ is an option. 3 ~2.6g / cm 3 .

[0236] The term "compacted density" as used in this application has a meaning known in the art and is one of the reference indicators for the energy density of materials. In this application, unless otherwise specified, the compacted density of the positive electrode refers to the ratio of the mass of the positive electrode active layer to its volume, and the compacted density of the negative electrode refers to the ratio of the mass of the negative electrode active layer to its volume.

[0237] The following is a description of the negative electrode plate.

[0238] The negative electrode sheet includes a negative current collector and a negative active layer disposed on at least one surface of the negative current collector, the negative active layer including a negative active material.

[0239] Without limitation, the weight percentage of the negative electrode active material in the negative electrode active layer may be greater than or equal to 80 wt%, and may further be greater than or equal to 90 wt%.

[0240] As a non-limiting example, the negative electrode current collector has two surfaces that are opposite to each other in its own thickness direction, and the negative electrode active layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0241] 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. In the negative electrode current collector, 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. In the negative electrode current collector, the composite current collector may be formed by forming a metal material on the polymer 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-limitingly, in the negative electrode current collector, the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0242] The electrolyte is described below as an example.

[0243] The electrolyte serves to conduct ions between the positive and negative electrodes. The electrolyte is a non-aqueous electrolyte. It includes electrolyte salts and non-aqueous solvents.

[0244] The definitions of electrolyte salts and non-aqueous solvents can be found in the context of this application. Without limitation, other types of electrolyte salts may also be introduced into the electrolyte.

[0245] In some embodiments, the electrolyte salt includes an electrolyte lithium salt, and may further be an electrolyte lithium salt.

[0246] In some embodiments, the electrolyte may optionally include additives. For example, additives may include positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0247] The following is an exemplary description of the separator membrane.

[0248] In some embodiments, the lithium metal secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0249] 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.

[0250] In some embodiments, the thickness of the separator can be 6μm to 40μm, and optionally 6μm to 20μm.

[0251] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0252] In some embodiments, the lithium metal secondary battery may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0253] In some embodiments, the outer packaging of the lithium metal secondary battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the lithium metal secondary battery can also be a soft pack, such as a pouch. The soft pack can be made of plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0254] A lithium metal secondary battery includes at least one battery cell. A lithium metal secondary battery may include one or more battery cells.

[0255] In this application, unless otherwise specified, "cell battery" refers to the basic unit capable of converting chemical energy into electrical energy. Typically, a cell battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and extracting. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator is positioned between the positive and negative electrodes; its primary function is to prevent short circuits between the positive and negative electrodes while allowing ions to pass through.

[0256] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 The example shown is a square-structured battery cell 5.

[0257] In some of these implementations, reference is made to... Figure 2 The outer packaging may include a battery casing 51 and a cover plate 53. The battery casing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The battery casing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. Positive electrode sheets, negative electrode sheets, and a separator can be formed into electrode assemblies 52 through a winding process or a stacking process. The electrode assemblies 52 are encapsulated within the receiving cavity. The electrode assemblies 52 are immersed in an electrolyte. The number of electrode assemblies 52 contained in a single battery cell 5 can be one or more, which can be selected by those skilled in the art according to actual needs. In some embodiments, the electrolyte injection coefficient is greater than or equal to 1.6 g / Ah.

[0258] The lithium metal secondary battery can be a battery device 4 or a battery pack 1.

[0259] The battery device includes at least one battery cell. The number of battery cells in the battery device can be one or more, and those skilled in the art can select an appropriate number according to the application and capacity of the battery device.

[0260] Figure 3 This is battery device 4, used as an example. (See reference...) Figure 3 In the battery assembly 4, multiple battery cells 5 can be arranged sequentially along the length of the battery assembly 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0261] Optionally, the battery device 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0262] In some embodiments, the battery devices described above can also be assembled into a battery pack, and the number of battery devices 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.

[0263] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery devices 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery devices 4. The multiple battery devices 4 can be arranged in any manner within the battery box.

[0264] In another aspect of this application, a method for preparing a lithium metal secondary battery is provided.

[0265] In some embodiments, a method for preparing a lithium metal secondary battery is provided, comprising the following steps: placing an electrode assembly including a positive electrode, a separator, and a negative electrode in a battery casing; injecting an electrolyte into the battery casing; and allowing the electrolyte to wet the electrode assembly, thereby preparing a lithium metal secondary battery. In the electrode assembly, a separator is disposed between the positive and negative electrode.

[0266] According to some embodiments of the second aspect of this application, an electrical device is provided, which includes the lithium metal secondary battery described in the first aspect of this application.

[0267] Electrical devices that include the aforementioned lithium metal secondary batteries can have the advantages and benefits of the aforementioned lithium metal secondary batteries.

[0268] In some embodiments, the electrical device includes a lithium metal secondary battery according to any of the embodiments provided in this application.

[0269] Lithium metal secondary batteries can be used as a power source for electrical devices or as an energy storage unit for electrical devices. Electrical devices can include, but are not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Mobile devices can include, for example, mobile phones and laptops; electric vehicles can include, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, electric motorcycles, power tools, etc., but are not limited to these. This electrical device can also be applied in aerospace and other fields, and can also be applied to energy storage power systems such as hydroelectric, thermal, wind, and solar power plants.

[0270] As an electrical device, lithium metal rechargeable batteries can be selected according to its usage requirements.

[0271] Figure 6 Here is an example of an electrical device 6. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device for lithium metal secondary batteries, a battery device or battery pack can be used.

[0272] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use lithium metal rechargeable batteries as their power source.

[0273] The following describes some embodiments of this application. The described embodiments are only a part of the embodiments of this application, and not all of them. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application and 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.

[0274] Unless otherwise specified in the examples, the procedures described above, or those described in the literature in this field, or those described in the product instructions, shall be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products, or products that can be synthesized using conventional methods from commercially available products.

[0275] In the following examples, room temperature refers to 20°C to 30°C.

[0276] The following examples use lithium electrolyte salts as the electrolyte salt. An example uses a "DME+TTE+FB mixed solvent" as the non-aqueous solvent in the electrolyte.

[0277] I. Preparation of lithium metal secondary batteries

[0278] Example 1.

[0279] 1. Negative electrode sheet: Pure lithium sheet is used to provide the negative electrode active layer.

[0280] A 50μm thick lithium foil is rolled onto both sides of a 12μm thick copper foil and then cut into 41mm×51mm rectangles to serve as negative electrode sheets.

[0281] 2. Preparation of the positive electrode sheet

[0282] ternary cathode active material (NCM) 811 LiNi 0.8 Co 0.1 Mn 0.1 O2), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 98:1:1. N-methylpyrrolidone (NMP) solvent was added and the mixture was stirred until homogeneous to obtain a positive electrode slurry with a solid content of 66 wt%. The positive electrode slurry was uniformly coated onto both sides of the positive electrode current collector aluminum foil, air-dried at room temperature, and then transferred to an oven for further drying. It was then cut into 40 mm × 50 mm rectangles to serve as the positive electrode sheet, with a positive electrode surface capacity of 3.5 mAh / cm². 2 .

[0283] 3. Separating membrane.

[0284] Polyethylene porous membrane was selected as the separator.

[0285] 4. Preparation of electrolyte.

[0286] The solvent components are mixed evenly according to the required mass ratio to obtain a mixed solvent. A fully dried electrolyte lithium salt is added to the mixed solvent, and the electrolyte lithium salt is fully dissolved on a magnetic stirrer to prepare an electrolyte solution.

[0287] In this example, the mixed solvent consists of DME, TTE, and FB in a mass ratio of 1:2:1; wherein DME is ethylene glycol dimethyl ether, TTE is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and FB is fluorobenzene.

[0288] In this example, the electrolyte lithium salt composition in the electrolyte is: 2 mol / L LiFSI and 2 mol / L LiDFOB.

[0289] 5. Assembly of lithium metal secondary batteries.

[0290] A pre-cut positive electrode is matched with two pre-cut negative electrodes, with the aforementioned separator used to separate the positive and negative electrodes. The electrodes are then wrapped in an aluminum-plastic film bag to form a stacked dry cell. 0.3g of the previously prepared electrolyte is injected, and the aluminum-plastic film bag is vacuum-sealed using heat pressing. After standing at room temperature for at least 6 hours, cycle testing can begin. The prepared stacked battery has a rated capacity of 140mAh.

[0291] Examples 2-9 and Comparative Examples 1-6 were prepared using essentially the same method as in Example 1, except that the electrolyte composition was different and one or more parameters of the type of electrolyte salt and the molar volume concentration of each electrolyte salt in the electrolyte were changed; see Table 1 for reference.

[0292] Examples 2-3 change the type of electrolyte lithium salt. In Example 2, LiBOB is used instead of LiDFOB. In Example 3, LiDFOB and LiBOB in a molar ratio of 1:1 are used instead of LiDFOB. The total concentration of the second lithium salt in the electrolyte is the same as in Example 1.

[0293] Examples 4-8: The molar volume concentration of at least one of LiFSI and LiDFOB in the electrolyte was changed.

[0294] Compared to the examples, the electrolyte of Example 9 also contained 1 mol / L of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0295] Compared to Example 1, Comparative Example 1 omits the second lithium salt and replaces LiDFOB with an equimolar amount of LiFSI.

[0296] Compared to Example 1, Comparative Example 2 changed the molar volume concentration of LiDFOB in the electrolyte and adjusted the molar volume concentration of LiFSI accordingly to keep the total concentration of electrolyte salts constant.

[0297] Comparative Example 3 uses an equimolar amount of LiTFSI instead of LiDFOB compared to Example 1.

[0298] The electrolyte composition in each embodiment and comparative example can also be found in Table 1. Based on Table 1, the relevant parameters in Table 2 can be calculated.

[0299] Table 1.

[0300]

[0301] Table 2.

[0302]

[0303] II. Testing and Analysis Methods

[0304] (I) Interfacial heat generation test between electrolyte and lithium metal anode

[0305] Differential scanning calorimeter (Mettler-Toledo DSC-3): Temperature range from room temperature 25°C to 500°C, heating rate 20°C / min, argon atmosphere.

[0306] Test system: The electrolyte to be tested is in contact with pure lithium sheet, and the ratio of the amount of electrolyte to pure lithium sheet is basically the same as in Example 1; the heat generation and the maximum heat generation rate are recorded.

[0307] (II) Battery Performance

[0308] 1. Examination of the severity of thermal runaway

[0309] Lithium metal secondary batteries were prepared using the same method as those used in Examples 1-9 and Comparative Examples 1-3, except that the cell size was adjusted to create a large cell with a capacity of 10 Ah. Thermal runaway tests were then conducted using this large cell.

[0310] The battery cell was first fully charged to 1 / 3C. Temperature sensing wires were placed on the large surface of the battery cell to monitor the temperature change during the test. Voltage sensing wires were placed on the battery cell terminals to monitor the voltage change during the test. Temperature sensing wires were placed in the oven to monitor the temperature change inside the oven. The temperature was raised to 55℃ and held for 2 hours. The temperature was increased at a rate of 5℃ / min, and held for 30 minutes for every 5℃ increase, until the battery cell thermally ran away or reached 300℃. The thermal runaway temperature T and the valve release time t were recorded. If 300℃ was reached, the temperature was held for 1 hour. The experiment was stopped when either of the two conditions occurred.

[0311] Based on the severity of thermal runaway, thermal runaway intensity is divided into 5 levels from 0 to 4. The higher the level, the higher the thermal runaway intensity and the worse the reliability during thermal runaway. The lower the level, the lower the thermal runaway intensity and the better the reliability during thermal runaway.

[0312] in,

[0313] "Level 0" test: No thermal runaway occurs during the heating time or the thermal runaway is "mild"; No thermal runaway occurs when the test is stopped or the valve spraying time t>5s when thermal runaway occurs.

[0314] The thermal runaway behavior is "relatively mild" in "Level 1-2" thermal runaway, with a valve ejection time of 3 seconds during thermal runaway. <t≤5s;

[0315] The thermal runaway of "Level 3" is "relatively severe", and the valve ejection time during thermal runaway is 1s≤t≤3s;

[0316] The thermal runaway at "Level 4" is "violent," with a valve release time t < 1s.

[0317] 2. Cyclic performance

[0318] The lithium metal secondary batteries prepared using the various embodiments and comparative examples were subjected to cycle performance tests.

[0319] The test temperature was 25℃. Test procedure: 0.2C CC to 4.3V, 1C DC to 2.8V, cutoff at 80% SOH.

[0320] The detailed test steps are as follows: At a test temperature of 25℃, the battery under test is charged at a constant current of 0.2C to 4.3V, then charged at a constant voltage of 4.3V to the cutoff current of 0.05C, left to rest for 10 minutes, and then discharged at a constant current of 1C to 2.8V, left to rest for 5 minutes. This constitutes one charge-discharge cycle. The discharge capacity (C0) at this point is recorded. This charge-discharge cycle is repeated, and the discharge capacity C of the 1st cycle, 2nd cycle, ..., nth cycle is recorded. n The capacity retention rate P of the battery under test after n cycles is then determined. n =C n / C0×100%. Record the number of cycles when the capacity decays to 80% SOH. The test result can be recorded as "the number of cycles when the capacity decays to 80% SOH at 25℃".

[0321] (III) Test Results and Analysis

[0322] The interfacial heat generation between the electrolyte and the lithium metal anode used in Examples 1-9 is significantly improved compared to the LiFSI electrolyte system of Comparative Example 1, with at least one of the heat generation and the maximum heat generation rate significantly decreasing. For example, see Table 3.

[0323] The lithium metal secondary batteries prepared in Examples 1-9 exhibited significantly lower thermal runaway intensity compared to Comparative Example 1, and significantly improved reliability during thermal runaway. Furthermore, all lithium metal secondary batteries prepared in Examples 1-9 demonstrated good cycle performance. For example, the thermal runaway test results and cycle performance test results can be found in Table 4. Notably, the thermal runaway intensity of Example 1 was lower than that of Example 2.

[0324] Table 3.

[0325]

[0326] In Table 3, “Heat Generation” is the relative percentage of the heat generation test value of each embodiment to the heat generation test value of Comparative Example 1; “Maximum Heat Generation Rate” is the relative percentage of the maximum heat generation rate test value of each embodiment to the maximum heat generation rate test value of Comparative Example 1.

[0327] Table 4.

[0328]

[0329] The descriptions of the various implementation methods and embodiments above tend to emphasize the differences between them. Similarities or resemblances can be referenced interchangeably, and for the sake of brevity, they will not be repeated here. The technical features of the implementation methods and embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combinations of these technical features do not contradict each other, they should be considered within the scope of this specification.

[0330] It should be noted that this application is not limited to the above-described embodiments and examples. The above-described embodiments and examples are merely examples, and any embodiments and examples that have the same structure and achieve the same effect as the technical concept within the scope of this application are included in the technical scope of this application. The embodiments and examples described above only illustrate several embodiments and examples of this application, and although the descriptions are relatively detailed, they should not be construed as limiting the scope of the patent. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments or examples, and other ways of constructing embodiments or examples by combining some of the constituent elements of the embodiments or examples, are also included in the scope of this application without departing from the spirit of this application.

Claims

1. A lithium metal secondary battery, characterized in that, It includes a positive electrode, a negative electrode, and an electrolyte, with a separator disposed between the positive electrode and the negative electrode; the negative electrode includes a negative active layer, which includes lithium-containing metal. The electrolyte comprises an electrolyte salt and a non-aqueous solvent; the electrolyte salt comprises a first lithium salt and a second lithium salt, wherein the first lithium salt is lithium bis(fluorosulfonyl)imide, and the second lithium salt is one or both of lithium difluorooxalate borate and lithium dioxalate borate; wherein the molar percentage of the first lithium salt in the electrolyte salt is 50% to 80%, and the molar percentage of the second lithium salt in the electrolyte salt is 20% to 50%; the electrolyte salt in the electrolyte is an electrolyte salt that can dissolve in aliphatic ether solvents at 25°C to 45°C.

2. The lithium metal secondary battery according to claim 1, characterized in that, The first lithium salt has a molar percentage of 50% to 60% in the electrolyte salt, and the second lithium salt has a molar percentage of 40% to 50% in the electrolyte salt.

3. The lithium metal secondary battery according to claim 1, characterized in that, In the electrolyte, the molar ratio of the second lithium salt to the first lithium salt is 0.5 to 1.

4. The lithium metal secondary battery according to claim 1 or 2, characterized in that, In the electrolyte, the molar ratio of the second lithium salt to the first lithium salt is 0.8 to 1.

5. The lithium metal secondary battery according to any one of claims 1 to 4, characterized in that, The electrolyte satisfies one or more of the following characteristics: (a1) The molar volume concentration of the first lithium salt in the electrolyte is 1 mol / L to 6 mol / L; (a2) The molar volume concentration of the second lithium salt in the electrolyte is 0.5 mol / L to 4 mol / L; (a3) The sum of the molar volume concentrations of the first lithium salt and the second lithium salt in the electrolyte is 2 mol / L to 8 mol / L; (a4) The molar volume concentration of the electrolyte salt in the electrolyte is 2 mol / L to 8 mol / L; (a5) The electrolyte salts do not include lithium hexafluorophosphate and lithium tetrafluoroborate.

6. The lithium metal secondary battery according to claim 5, characterized in that, The electrolyte satisfies one or more of the following characteristics: (a1') The molar volume concentration of the first lithium salt in the electrolyte is 1.5 mol / L to 4.5 mol / L; (a2') The molar volume concentration of the second lithium salt in the electrolyte is 1.5 mol / L to 3 mol / L; (a3') The sum of the molar volume concentrations of the first lithium salt and the second lithium salt in the electrolyte is 3 mol / L to 6 mol / L; (a4') The molar volume concentration of the electrolyte salt in the electrolyte is 3 mol / L to 6 mol / L.

7. The lithium metal secondary battery according to any one of claims 1 to 6, characterized in that, The second lithium salt includes lithium difluorooxalate borate; the molar percentage of lithium difluorooxalate borate in the second lithium salt is 50% to 100%.

8. The lithium metal secondary battery according to claim 7, characterized in that, The molar percentage of lithium difluorooxalate borate in the second lithium salt is 80% to 100%.

9. The lithium metal secondary battery according to any one of claims 1 to 8, characterized in that, The sum of the molar percentages of the first lithium salt and the second lithium salt in the electrolyte salt is 80% to 100%.

10. The lithium metal secondary battery according to claim 9, characterized in that, The sum of the molar percentages of the first lithium salt and the second lithium salt in the electrolyte salt is 90% to 100%.

11. The lithium metal secondary battery according to any one of claims 1 to 10, characterized in that, The lithium-containing metal includes one or more of elemental lithium and lithium alloys.

12. The lithium metal secondary battery according to claim 11, characterized in that, The mass percentage or molar percentage of lithium in the lithium-containing metal is 95% to 100%.

13. The lithium metal secondary battery according to any one of claims 1 to 12, characterized in that, The non-aqueous solvent includes one or more of aliphatic ether solvents, fluorinated aliphatic ether solvents, and benzene-containing solvents.

14. The lithium metal secondary battery according to claim 13, characterized in that, The electrolyte satisfies one or more of the following characteristics: (d1) The electrolyte comprises a fatty ether solvent; the fatty ether solvent contains 2 to 14 carbon atoms; the fatty ether solvent contains one or more oxygen atoms; the fatty ether solvent has a chain structure; (d2) The electrolyte comprises a fluorinated aliphatic ether solvent; the number of carbon atoms in the fluorinated aliphatic ether solvent is 3 to 14; the hydrogen atoms in the fluorinated aliphatic ether solvent are partially or completely fluorinated; the number of fluorine atoms in the fluorinated aliphatic ether solvent is one or more; the number of oxygen atoms in the fluorinated aliphatic ether solvent is one or more; the fluorinated aliphatic ether solvent has a chain structure; (d3) The electrolyte comprises a benzene-containing solvent; the benzene-containing solvent comprises one or more of benzene, substituted benzene, anisole, and substituted anisole; wherein the benzene ring in the substituted benzene is substituted by one or more substituents Q1; each of the substituents Q1 is independently a fluorine atom, C 1-3 Chain alkyl or fluorinated C 1-3 Chain-like alkyl group; the phenyl and methyl groups in the substituted anisole are each independently substituted by one or more substituents Q2; each of the substituents Q2 is independently a fluorine atom, C 1-3 Chain alkyl or fluorinated C 1-3 Chain alkyl group; in a benzene-containing solvent, any one of the fluorinated C 1-3 The number of fluorine atoms in the chain alkyl group is independently one or more; (d4) In the electrolyte, the total mass percentage of the fatty ether solvent, the fluorinated fatty ether solvent and the benzene-containing solvent in the non-aqueous solvent is 80% to 100%.

15. An electrical appliance, characterized in that, Includes the lithium metal secondary battery as described in any one of claims 1 to 14.

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