Non-aqueous electrolytes, secondary batteries, battery modules, battery packs, and electrical devices

Abstract

The present invention provides a non-aqueous electrolyte, a secondary battery, a battery module, a battery pack, and an electric device. The non-aqueous electrolyte comprises an orthocarbonate, a chain carbonate, a cyclic carbonate, and a lithium salt, wherein, based on mass content, the content of the orthocarbonate is 10% to 80%, and at least one of the chain carbonate and the cyclic carbonate is a fluoride. The central carbon atom of the orthocarbonate is connected to an alkyl or haloalkyl chain linked to four oxygen atoms and serves to absorb lone electron pairs of oxygen atoms, thereby increasing steric hindrance around the oxygen atoms, weakening the binding energy with lithium ions, and promoting the formation of an SEI film in which anionic decomposition is dominant. The highly inorganic SEI film component formed by anionic decomposition promotes the conversion of metal lithium deposition from a dendritic state to a bulk state, slows down the occurrence of corrosion reactions, and further improves the safety and cycle life of the metal lithium secondary battery, and the fluorinated chain carbonate or cyclic carbonate further promotes the safety and cycleability of the metal lithium battery.

Description

Technology Field

[0001] The present invention relates to the field of battery technology, and in particular to a non-aqueous electrolyte, a secondary battery, a battery module, a battery pack, and an electric device. Background Technology

[0002] Electrification of transportation is the mainstream trend under the broad backdrop of carbon neutrality. However, the insufficient energy density of power batteries and the resulting “range anxiety” are stimulating the development of secondary battery systems with higher energy density. Here, the lithium anode of a metal lithium secondary battery has a very low electrode potential (-3.04V vs. SHE) and a very high specific capacity (3860 mAh / g), making it the most suitable choice for secondary batteries to increase the energy density of current power batteries.

[0003] However, metallic lithium is a highly reactive metal that causes continuous side reactions with the electrolyte, forming a non-uniform solid electrolyte interface (SEI) and inducing the growth of dendritic lithium to form “dead lithium” that loses significant electrochemical activity during cycling, resulting in rapid capacity reduction and serious safety risks.

[0004] The present invention provides a non-aqueous electrolyte, a secondary battery, a battery module, a battery pack, and an electric device for improving the cyclability of a metal lithium secondary battery.

[0005] A first embodiment of the present invention provides a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises an orthocarbonate, a chain carbonate, a cyclic carbonate, and a lithium salt, and based on mass content, the content of the orthocarbonate is 10% to 80%, and at least one of the chain carbonate and the cyclic carbonate is a fluoride.

[0006] In the non-aqueous electrolyte of the present invention, the central carbon atom of the orthocarbonate is connected to four oxygen atoms, and each oxygen atom is also connected to an alkyl or haloalkyl chain. The alkyl or haloalkyl chain acts to absorb lone electron pairs of the oxygen atom and increases the steric hindrance around the oxygen atom, thereby weakening the binding energy with lithium ions. Consequently, the anionic participation of the lithium salt within the lithium ion solvation sheath is significantly increased, and the formation of an SEI film dominated by anionic decomposition is promoted. The highly inorganic SEI film component formed by anionic decomposition promotes the conversion of the metallic lithium deposition from a dendritic state to a bulk state, inhibits the formation of dead lithium, reduces the specific surface area of ​​the metallic lithium deposition, slows down the occurrence of corrosion reactions, and further improves the cycle life and safety of the metallic lithium secondary battery. The chain-type carbonate primarily serves to lower the viscosity of the electrolyte and improve infiltration and ion conductivity. Fluorinated chain-type carbonates or fluorinated ring-type carbonates decompose on the surface of a metallic lithium anode to form inorganic components such as lithium fluoride, which are advantageous for the deposition of metallic lithium, thereby rapidly forming a passivation layer, which further promotes the safety and cyclability of the metallic lithium battery. In addition, a non-aqueous electrolyte using orthocarbonate as one of the main solvents can react with metallic lithium at 80°C to form a protective layer that effectively passivates the surface of the metallic lithium, thereby disconnecting the complete battery and preventing the additional occurrence of side reactions, and further helping to improve the thermal stability of the metallic lithium secondary battery.

[0007] In any embodiment of the first aspect, the mass content of orthocarbonate in the non-aqueous electrolyte is 15 to 50%, optionally 20 to 30%. By controlling the mass of orthocarbonate within the above range, not only is the SEI film component effectively promoted to mainly form an SEI film in which anionic decomposition is dominant, but the problem of excessive viscosity of the electrolyte due to its use is also prevented.

[0008] In any embodiment of the first aspect, the mass ratio of the orthocarbonate to the lithium salt is 1:3 to 3:1, optionally 1:1.5 to 1.5:1. Thus, the orthocarbonate is utilized more sufficiently to form as many SEI films as possible in which anionic decomposition is dominant.

[0009] In any embodiment of the first aspect, the mass content of the chain carbonate is 1% to 80%, optionally 4% to 40%, and more optionally 20% to 30%. The chain carbonate within the above usage range is used to further improve the lithium ion transfer effect by reducing the viscosity caused by the addition of orthocarbonate.

[0010] In any embodiment of the first aspect, the mass content of the cyclic carbonate is 1 to 80%, optionally 4% to 40%, and more optionally 20% to 30%. The cyclic carbonate within the above usage range is used to further improve the lithium ion transfer effect by reducing the viscosity caused by the addition of orthocarbonate.

[0011] In any embodiment of the first aspect, the mass content of the lithium salt is 10% to 70%, optionally 15% to 40%, and more optionally 20% to 30%. By using the lithium salt, an SEI film component with a more suitable thickness and superior structure and performance is formed on the metal lithium surface to further improve cycleability.

[0012] In any embodiment of the first aspect, one of the chain carbonate and the cyclic carbonate is a fluoride. Thus, the simultaneous use of two types of fluorocarbonates can prevent greater difficulty in electrolyte infiltration, thereby preventing it from affecting the long-term stable cycle of the secondary battery. Optionally, the cyclic carbonate is a fluorinated cyclic carbonate, and the fluorinated cyclic carbonate decomposes at the negative electrode interface to produce lithium fluoride, which is advantageous for the metallic lithium cycle.

[0013] In any embodiment of the first aspect, the orthocarbonate is selected from one or more of the group consisting of a compound having a structure represented by Formula I, a compound having a structure represented by Formula II, or a compound having a structure represented by Formula III, and

[0014] Formula I,

[0015] Formula II,

[0016] Equation III,

[0017] In the above formula, R1 to R4, R6 and R7 each independently represent either a C1-C10 alkyl or a C1-C10 haloalkyl, and R5, R8 and R9 each independently represent either a C1-C10 alkylene or a C1-C10 haloalkylene.

[0018] Optionally, the orthocarbonate is selected from one or more compounds having a structure represented by Formula I, and R1 to R4 each independently represent either a C1-C10 alkyl or a C1-C10 haloalkyl; further optionally, the orthocarbonate is tetramethyl orthocarbonate, tetraethyl orthocarbonate, tetrapropyl orthocarbonate, tetrabutyl orthocarbonate, tetrapentyl orthocarbonate, tetrahexyl orthocarbonate, tetraheptyl orthocarbonate, tetraoctyl orthocarbonate, tetranonyl orthocarbonate, tetradecyl orthocarbonate, tetramethyl fluoro orthocarbonate, tetraethyl fluoro orthocarbonate, tetrapropyl fluoro orthocarbonate, tetrabutyl fluoro orthocarbonate, tetrapentyl fluoro orthocarbonate, tetrahexyl fluoro orthocarbonate, tetraheptyl fluoro orthocarbonate, tetraheptyl fluoro orthocarbonate, tetramethyl fluoro orthocarbonate, tetraethyl fluoro orthocarbonate, tetrapropyl fluoro orthocarbonate, tetrabutyl fluoro orthocarbonate, tetrapentyl fluoro orthocarbonate, tetrahexyl fluoro orthocarbonate, tetraheptyl fluoro orthocarbonate. It is selected from one or more of the group consisting of tetraoctyl fluoroorthocarbonate, tetranonyl fluoroorthocarbonate, and tetradecyl fluoroorthocarbonate. The orthocarbonate may be selected from the specific substances listed above, and the smaller the molecular weight of the orthocarbonate, the lower the viscosity and the better the solubility for lithium salts.

[0019] In any embodiment of the first aspect, the chain-type carbonate is selected from one or more compounds having a structure represented by Formula IV, and

[0020] Formula IV

[0021] In the above formula, R10 and R11 each independently represent any one of a halogen group, a C1-C5 alkyl, or a C1-C5 haloalkyl, and optionally, the chain carbonate is dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, dipentyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl butyl carbonate, methyl pentyl carbonate, ethyl propyl carbonate, ethyl butyl carbonate, ethyl pentyl carbonate, propyl butyl carbonate, propyl pentyl carbonate, butyl pentyl carbonate, dimethyl fluorocarbonate, diethyl fluorocarbonate, dipropyl fluorocarbonate, dibutyl fluorocarbonate, dipentyl fluorocarbonate, ethyl methyl fluorocarbonate, methyl propyl fluorocarbonate, methyl butyl fluorocarbonate, methyl pentyl fluorocarbonate, ethyl propyl fluorocarbonate It is selected from one or more of the group consisting of carbonates, ethyl butyl fluorocarbonates, ethyl pentyl fluorocarbonates, propyl butyl fluorocarbonates, propyl pentyl fluorocarbonates, and butyl pentyl fluorocarbonates. Since the viscosity of each of the above chain-type carbonates is lower than that of cyclic carbonates, particularly low molecular weight chain-type carbonates, the viscosity of the electrolyte can be reduced more effectively, and the infiltration and ionic conductivity of the electrolyte can be improved.

[0022] In any embodiment of the first aspect, the cyclic carbonate is selected from one or more compounds having a structure represented by the formula V, and

[0023] Formula V,

[0024] In the above formula, R12 to R15 each independently represent any one of a halogen group, a C1-C3 alkyl, or a C1-C3 haloalkyl, and optionally, the cyclic carbonate is selected from one or more of the group consisting of ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, propylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, and trifluoropropylene carbonate. Here, the fluorinated cyclic carbonate is more advantageous for decomposing at the cathode interface to produce inorganic components such as lithium fluoride, which is advantageous for the metallic lithium cycle, thereby better improving the cycle capability of the battery.

[0025] In any embodiment of the first aspect, the lithium salt is selected from one or more of the group consisting of lithium bisfluorosulfonylimide (LiFSI), lithium bisfluoromethylsulfonylimide (LiTFSI), lithium bispentafluoroethylsulfonylimide (LiBETI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium difluorooxalate borate (LiBOB), and lithium difluorophosphate (LiDFOB). Each of the lithium salts has its own advantages, and among them, fluorine-containing lithium sulfonylimide has a high thermal decomposition temperature and is less sensitive to water, which can further improve the safety performance of the battery.

[0026] In some embodiments of the first aspect, the orthocarbonate is tetramethyl orthocarbonate or tetraethyl orthocarbonate, the chain carbonate is any one of dimethyl carbonate, diethyl carbonate, dimethyl fluorocarbonate and diethyl fluorocarbonate, the cyclic carbonate is selected from any one of fluoroethylene carbonate, fluoropropylene carbonate and difluoropropylene carbonate, and the lithium salt is lithium bisfluorosulfonylimide or lithium bisfluoromethylsulfonylimide. More optionally, the orthocarbonate is tetramethyl orthocarbonate, the chain carbonate is dimethyl carbonate, the cyclic carbonate is fluoroethylene carbonate, and the lithium salt is selected from lithium bisfluorosulfonylimide or lithium bisfluoromethylsulfonylimide. The combination method of each of the above materials can further cooperate with each other on the basis of fully exhibiting their respective effects to improve the cyclability and safety of metal lithium secondary batteries.

[0027] A second aspect of the present invention provides a secondary battery comprising a positive plate, a negative plate, an electrolyte, and a separator, wherein the electrolyte is any one of the above-mentioned non-aqueous electrolytes and the negative plate comprises metallic lithium. The non-aqueous electrolyte of the present invention has low corrosiveness to the negative plate, thereby improving the safety and cycleability of the secondary battery equipped with it.

[0028] In any embodiment of the second aspect, the cathode plate comprises a current collector and a cathode active layer, and the cathode active layer is metallic lithium or a lithium alloy, optionally, the lithium alloy comprises any one of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, foil, boron, carbon and silicon and metallic lithium.

[0029] A third aspect of the present invention provides a battery module comprising a secondary battery, wherein the secondary battery is a secondary battery of any one of the second aspects.

[0030] A fourth aspect of the present invention provides a battery pack comprising a battery module, wherein the battery module is a battery module of any one of the third aspects.

[0031] A fifth aspect of the present invention provides an electric device comprising a secondary battery, a battery module, or a battery pack, wherein the secondary battery is a secondary battery of any one of the second aspects, the battery module is a battery module of any one of the third aspects, and the battery pack is a battery pack of any one of the fourth aspects.

[0032] Through the composition of the non-aqueous electrolyte of the present invention, the secondary battery, battery module, battery pack, and electric device of the present invention all possess high safety and cycleability. Brief explanation of the drawing

[0033] To more clearly explain the technical solution means of the embodiments of the present invention, the attached drawings to be used in the embodiments of the present invention are briefly introduced below. The attached drawings described below are merely some embodiments of the present invention, and it is obvious to those skilled in the art that other drawings can be obtained based on the attached drawings without creative labor. FIG. 1 is a schematic diagram of a secondary battery according to one embodiment of the present invention. FIG. 2 is an exploded view of a secondary battery according to one embodiment of the present invention illustrated in FIG. 1. FIG. 3 is a schematic diagram of a battery module according to one embodiment of the present invention. FIG. 4 is a schematic diagram of a battery pack according to one embodiment of the present invention. FIG. 5 is an exploded view of a battery pack according to one embodiment of the present invention shown in FIG. 4. FIG. 6 is a schematic diagram of an electric device in which a secondary battery is used as a power source according to one embodiment of the present invention. Figure 7 illustrates the charge-discharge cycle test results of the Li-Li button battery of Example 1 of the present invention at different current densities. Figure 8 shows the impedance test results of the Li-Li button battery of Example 1 at room temperature. Figure 9 shows the impedance test results after placing the Li-Li button battery of Example 1 in an 80°C environment for 3 hours. FIG. 10 illustrates the cycle voltage curve of the liquid metal lithium secondary battery of Example 1, wherein the ambient temperature of the cell cycle is set to 25°C and the charge-discharge cycle is performed using a multiplier of 0.5 C (i.e., 70 mA). The charge-discharge cutoff voltages are set to 3.65 V and 2.80 V, respectively. Specific details for implementing the invention

[0034] Hereinafter, embodiments of the present invention will be described in further detail in conjunction with the attached drawings and examples. The detailed description of the embodiments below and the attached drawings are used to illustratively explain the principles of the present invention and do not limit the scope of the present invention. That is, the present invention is not limited to the described embodiments.

[0035] Hereinafter, embodiments of the negative plate, secondary battery, battery module, battery pack, and electrical device of the present invention are described in detail and disclosed with appropriate reference to the attached drawings. However, in some cases, unnecessary detailed descriptions are omitted. For example, detailed descriptions of known matters and redundant descriptions of structures that are actually identical may be omitted. This is intended to prevent unnecessary duplication of the following descriptions and to enable those skilled in the art to easily understand them. Furthermore, the attached drawings and the following description are provided to enable those skilled in the art to fully understand the present invention and are not intended to limit the subject matter described in the claims.

[0036] The “range” disclosed in the present invention is defined in the form of a lower limit and an upper limit, and a given range is defined by the selection of one lower limit and one upper limit, and the selected lower limit and upper limit define the boundaries of a specific range. A range defined in this manner may or may not include endpoint values ​​and may be arbitrarily combined. That is, any lower limit and any upper limit may be combined to form a single range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it should be understood that ranges of 60–110 and 80–120 are also considered. Furthermore, if minimum range values ​​1 and 2 are listed and maximum range values ​​3, 4, and 5 are listed, all ranges of 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5 are expected. In the present invention, unless otherwise specified, a numeric range “a–b” represents an abbreviated expression of a combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range “0 to 5” means that all real numbers between “0 to 5” are listed in this specification, and “0 to 5” is merely an abbreviated expression for combinations of these numerical values. Additionally, if a specific parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is an integer, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0037] Unless otherwise specified, all embodiments and optional embodiments of the present invention may be combined with one another to form a new technical solution.

[0038] Unless otherwise specified, all technical features and optional technical features of the present invention can be combined with one another to form a new technical solution.

[0039] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, and are preferably performed sequentially. For example, the method comprises steps (a) and (b), which indicates that the method may comprise steps (a) and (b) performed sequentially and steps (b) and (a) performed sequentially. For example, the mentioned method may further comprise step (c), which indicates that step (c) may be added to the method in any order, for example, the method may comprise steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0040] Unless otherwise specified, "comprehensive" and "included" as used in the present invention may mean open and closed forms. For example, "comprehensive" and "included" may further encompass or include other unlisted components, or indicate that they encompass or include only the listed components.

[0041] Unless otherwise specified, the term "or" in the present invention is inclusive. For example, the phrase "A or B" indicates "A, B, or both A and B." More specifically, any one of the conditions satisfies both conditions "A or B": A is true (or exists) and B is false (or absent); A is false (or absent) and B is true (or exists); or A and B are both true (or exist).

[0042] The inventors noted that the design and optimization of the electrolyte can significantly improve the cycleability and safety of the metallic lithium anode, which is a key factor in the realization of metallic lithium secondary batteries. Recently, various electrolyte design ideas have been proposed, including high-concentration electrolytes, localized high-concentration electrolytes, electrolytes mixed with various lithium salts, and perfluoroelectrolytes. These design methods change the growth of metallic lithium from a dendritic to a bulk structure, thereby significantly reducing the risk of short circuits caused by separator penetration. Simultaneously, they reduce the specific surface area of ​​the metallic lithium deposition to slow down corrosion reactions and improve the cycleability of the metallic lithium anode. However, these design paths still present problems such as high costs and insufficient cycleability. Therefore, further optimization of the electrolyte composition is a top priority for improving the cycleability and safety of metallic lithium secondary batteries and for realizing commercialization.

[0043] A first aspect of the present invention provides a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises an orthocarbonate, a chain carbonate, a cyclic carbonate, and a lithium salt, and based on mass content, the content of the orthocarbonate is 10% to 80%, and at least one of the chain carbonate and the cyclic carbonate is a fluoride.

[0044] In the non-aqueous electrolyte of the present invention, the central carbon atom of the orthocarbonate is connected to four oxygen atoms, and each oxygen atom is also connected to an alkyl or haloalkyl chain. The alkyl or haloalkyl chain acts to attract lone electron pairs of the oxygen atoms and increases the steric hindrance around the oxygen atoms, thereby weakening the binding energy with lithium ions. This significantly increases the anionic participation of the lithium salt within the lithium ion solvation sheath and promotes the formation of an SEI film dominated by anionic decomposition. The highly inorganic SEI film component formed by anionic decomposition promotes the conversion of the metal lithium deposition from a dendritic state to a bulk state, suppresses the formation of dead lithium, reduces the specific surface area of ​​the metal lithium deposition, slows down the occurrence of corrosion reactions, and further improves the cycle life and safety of the metal lithium secondary battery. The chain-type carbonate primarily serves to lower the viscosity of the electrolyte and improve infiltration and ion conductivity, thereby increasing the mobility of lithium ions not bound to the orthocarbonate and optimizing the formation efficiency of the formed SEI film. Fluorinated cyclic carbonates or fluorinated chain carbonates decompose on the surface of the metallic lithium anode to form inorganic components such as lithium fluoride, which are favorable for the deposition of metallic lithium, thereby rapidly forming a passivation layer and further promoting the safety and cyclability of the metallic lithium battery.

[0045] In the present invention, the orthocarbonate content is in the range of 10% to 80%, and it can be considered as one of the main solvents of the non-aqueous electrolyte rather than an additive. Therefore, the concentration of the non-aqueous electrolyte can be appropriately adjusted, further reducing the solvation energy, and ensuring the lithium ion transfer effect and high cycle efficiency of the secondary battery. In addition, the non-aqueous electrolyte using orthocarbonate as one of the main solvents reacts with metallic lithium at 80°C to form a protective layer that can effectively passivate the surface of the metallic lithium, thereby disconnecting the complete battery and blocking the additional occurrence of side reactions, which helps improve the thermal stability of the metallic lithium secondary battery.

[0046] When using orthocarbonate as one of the main solvents of a non-aqueous electrolyte, since the viscosity of orthocarbonate is higher than that of the other two types of carbonates, in order to prevent the concentration of the non-aqueous electrolyte from becoming too high due to excessive usage and affecting the lithium ion transfer effect, in some embodiments of the first aspect, the mass content of orthocarbonate in the non-aqueous electrolyte is 15 to 50%, optionally 20 to 30%. By controlling the mass of orthocarbonate within the above range, not only is it advantageous to improve the solvation environment of lithium ions through the orthocarbonate, but also reduces solvation energy, increases the proportion of anions participating in solvation, and effectively promotes the SEI film component to mainly form an SEI film in which anion decomposition is dominant; and also prevents the problem of excessive viscosity of the electrolyte caused by its use, thereby ensuring high-efficiency transfer of lithium ions and high cycle efficiency of the secondary battery.

[0047] As described above, the use of orthocarbonate changes the formation of the SEI film. In order to adjust the bonding form of lithium ions in the lithium salt by utilizing orthocarbonate sufficiently, in some embodiments of the first aspect, the mass ratio of the orthocarbonate to the lithium salt is 1:3 to 3:1, optionally 1:1.5 to 1.5:1. Thus, the orthocarbonate is utilized more sufficiently to form as many SEI films as possible in which anion decomposition is dominant.

[0048] In some embodiments of the first aspect, the mass content of the chain carbonate is 1% to 80%, optionally 4% to 40%, and more optionally 20% to 30%. The chain carbonate within the above usage range is used to further improve the lithium ion transfer effect by reducing the viscosity caused by the addition of orthocarbonate.

[0049] In some embodiments of the first aspect, the mass content of the cyclic carbonate is 1 to 80%, optionally 4% to 40%, and more optionally 20% to 30%. The cyclic carbonate within the above usage range is used to further improve the lithium ion transfer effect by reducing the viscosity caused by the addition of orthocarbonate.

[0050] In some embodiments of the first aspect, one of the chain carbonate and the cyclic carbonate is a fluoride, and the simultaneous use of two types of fluorocarbonates can prevent greater difficulty in infiltrating the electrolyte, thereby preventing it from affecting the long-term stable cycle of the secondary battery. Optionally, the cyclic carbonate is a fluorinated cyclic carbonate, and the fluorinated cyclic carbonate decomposes at the negative electrode interface to produce lithium fluoride, which is advantageous for the metallic lithium cycle.

[0051] In some embodiments of the first aspect, the mass content of the lithium salt is 10% to 70%, optionally 15% to 40%, and more optionally 20% to 30%. The lithium salt of the above content forms an SEI film component with a thickness more suitable and superior structure and performance on the metal lithium surface, thereby further improving cycle performance.

[0052] The orthocarbonate used in the present invention may be selected from commonly used orthocarbonate-based materials, and in some embodiments of the first aspect, the orthocarbonate is selected from one or more of the group consisting of a compound having a structure represented by Formula I, a compound having a structure represented by Formula II, or a compound having a structure represented by Formula III.

[0053] Formula I,

[0054] Formula II,

[0055] Equation III,

[0056] In the above formula, R1 to R4, R6 and R7 each independently represent either a C1-C10 alkyl or a C1-C10 haloalkyl, and R5, R8 and R9 each independently represent either a C1-C10 alkylene or a C1-C10 haloalkylene.

[0057] Optionally, the orthocarbonate is selected from one or more compounds having a structure represented by Formula I, and R1 to R4 each independently represent either a C1-C10 alkyl or a C1-C10 haloalkyl; further optionally, the orthocarbonate is tetramethyl orthocarbonate, tetraethyl orthocarbonate, tetrapropyl orthocarbonate, tetrabutyl orthocarbonate, tetrapentyl orthocarbonate, tetrahexyl orthocarbonate, tetraheptyl orthocarbonate, tetraoctyl orthocarbonate, tetranonyl orthocarbonate, tetradecyl orthocarbonate, tetramethyl fluoro orthocarbonate, tetraethyl fluoro orthocarbonate, tetrapropyl fluoro orthocarbonate, tetrabutyl fluoro orthocarbonate, tetrapentyl fluoro orthocarbonate, tetrahexyl fluoro orthocarbonate, tetraheptyl fluoro orthocarbonate, tetraheptyl fluoro orthocarbonate, tetramethyl fluoro orthocarbonate, tetraethyl fluoro orthocarbonate, tetrapropyl fluoro orthocarbonate, tetrabutyl fluoro orthocarbonate, tetrapentyl fluoro orthocarbonate, tetrahexyl fluoro orthocarbonate, tetraheptyl fluoro orthocarbonate. It is selected from one or more of the group consisting of tetraoctyl fluoroorthocarbonate, tetranonyl fluoroorthocarbonate, and tetradecyl fluoroorthocarbonate. The orthocarbonate may be selected from the specific substances listed above, and the smaller the molecular weight of the orthocarbonate, the lower the viscosity and the better the solubility for lithium salts.

[0058] A chain carbonate is a type of solvent commonly used in non-aqueous electrolytes, and a person skilled in the art may select from existing chain carbonates, and in some embodiments of the first aspect, the chain carbonate is selected from one or more compounds having a structure represented by Formula IV, and

[0059] Formula IV

[0060] In the above formula, R10 and R11 each independently represent any one of a halogen group, a C1-C5 alkyl, or a C1-C5 haloalkyl, wherein the halo may be fluoro, chloro, or bromo, and optionally fluoro. Optionally, chain carbonates are dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, dipentyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl butyl carbonate, methyl pentyl carbonate, ethyl propyl carbonate, ethyl butyl carbonate, ethyl pentyl carbonate, propyl butyl carbonate, propyl pentyl carbonate, butyl pentyl carbonate, dimethyl fluorocarbonate, diethyl fluorocarbonate, dipropyl fluorocarbonate, dibutyl fluorocarbonate, dipentyl fluorocarbonate, ethyl methyl fluorocarbonate, methyl propyl fluorocarbonate, methyl butyl fluorocarbonate, methyl pentyl fluorocarbonate, ethyl propyl fluorocarbonate, ethyl butyl fluorocarbonate, ethyl pentyl fluorocarbonate, propyl butyl fluorocarbonate, propyl pentyl fluorocarbonate, and It is selected from one or more of the group consisting of butyl pentyl fluorocarbonates. Since the viscosity of each chain carbonate is lower than that of cyclic carbonates, particularly low molecular weight chain carbonates, it can more effectively reduce the viscosity of the electrolyte and improve the infiltration and ionic conductivity of the electrolyte.

[0061] A cyclic carbonate is a type of solvent commonly used in non-aqueous electrolytes, and a person skilled in the art may select from existing cyclic carbonates, and in some embodiments of the first aspect, the cyclic carbonate is selected from one or more compounds having a structure represented by Formula V, and

[0062] Formula V,

[0063] In the above formula, R12 to R15 each independently represent any one of a halogen group, a C1-C3 alkyl, or a C1-C3 haloalkyl. The halo may be fluoro, chloro, or bromo, and optionally fluoro. Optionally, the cyclic carbonate is selected from one or more of the group consisting of ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, propylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, and trifluoropropylene carbonate. Among these, the fluorinated cyclic carbonate is more advantageous for decomposing at the cathode interface to produce inorganic components such as lithium fluoride, which is advantageous for the metallic lithium cycle, and better improves the cycle capability of the battery.

[0064] The lithium salt of the present invention may be selected from lithium salts commonly used in electrolytes, and in some embodiments of the first aspect, the lithium salt is selected from one or more of the group consisting of lithium bisfluorosulfonylimide (LiFSI), lithium bisfluoromethylsulfonylimide (LiTFSI), lithium bispentafluoroethylsulfonylimide (LiBETI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium difluorooxalate borate (LiBOB), and lithium difluorophosphate (LiDFOB). Each of the lithium salts has its own advantages, and among them, fluorine-containing lithium sulfonylimide has a high thermal decomposition temperature and is less sensitive to water, which can further improve the safety performance of the battery to some extent; In particular, lithium bisfluorosulfonylimide can form a better SEI film component on the surface of metallic lithium.

[0065] In order to fully exert the cooperative action of the orthocarbonate, chain carbonate, and cyclic carbonate, in some embodiments of the first aspect, the orthocarbonate is tetramethyl orthocarbonate or tetraethyl orthocarbonate, the chain carbonate is any one of dimethyl carbonate, diethyl carbonate, dimethyl fluorocarbonate, and diethyl fluorocarbonate, the cyclic carbonate is selected from any one of fluoroethylene carbonate, fluoropropylene carbonate, and difluoropropylene carbonate, and the lithium salt is lithium bisfluorosulfonylimide or lithium bisfluoromethylsulfonylimide. More optionally, the orthocarbonate is tetramethyl orthocarbonate, the chain carbonate is dimethyl carbonate, the cyclic carbonate is fluoroethylene carbonate, and the lithium salt is selected from lithium bisfluorosulfonylimide or lithium bisfluoromethylsulfonylimide. The combination method of each of the above materials can further cooperate with each other on the basis of fully exhibiting their respective effects to improve the cyclability and safety of metal lithium secondary batteries.

[0066] [Rechargeable Battery]

[0067] A secondary battery, also known as a rechargeable battery or accumulator, refers to a battery that can be used continuously by reactivating the active material through a method of charging electricity after it has been discharged.

[0068] Generally, a secondary battery comprises a positive plate, a negative plate, a separator, and an electrolyte. During the charging and discharging process of the battery, active ions (e.g., lithium ions) repeatedly undergo intercalation and deintercalation between the positive and negative plates. The separator is installed between the positive and negative plates and primarily serves to prevent short circuits between them while allowing active ions to pass through. The electrolyte serves to transfer active ions between the positive and negative plates.

[0069] A second aspect of the present invention provides a secondary battery comprising a positive plate, a negative plate, an electrolyte, and a separator, wherein the electrolyte is any one of the above non-aqueous electrolytes and the negative plate comprises metallic lithium. The non-aqueous electrolyte of the present invention has low corrosiveness to the negative plate, thereby improving the safety and cycleability of the secondary battery equipped with it.

[0070] [Cathode]

[0071] The cathode plate includes a cathode current collector and a cathode active layer installed on at least one surface of the cathode current collector.

[0072] As an example, the cathode current collector has two opposing surfaces in the direction of its own thickness, and the cathode film layer is installed on either or both of the two opposing surfaces of the cathode current collector.

[0073] In any embodiment of the second aspect, the cathode plate comprises a current collector and a cathode active layer, and the cathode active layer is metallic lithium or a lithium alloy, optionally, the lithium alloy comprises any one of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, foil, boron, carbon and silicon and metallic lithium.

[0074] [Polar Plate]

[0075] The positive plate generally comprises a positive current collector and a positive film layer installed on at least one surface of the positive current collector, and the positive film layer comprises a positive active material.

[0076] As an example, the positive current collector has two opposing surfaces in the direction of its own thickness, and the positive film layer is installed on either or both of the two opposing surfaces of the positive current collector.

[0077] In some embodiments, the positive current collector may use a metal foil or a composite current collector. For example, the metal foil may be aluminum foil. The composite current collector may include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate layer. The composite current collector may be formed on a polymer material substrate (e.g., a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.) by a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.).

[0078] In some embodiments, the positive electrode active material may be a positive electrode active material for a battery known in the art. As an example, the positive electrode active material may include at least one of a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide and a modified compound thereof, elemental sulfur, and a gas electrode including oxygen gas, carbon dioxide, nitrogen gas, etc. However, the present invention 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. Such positive electrode active materials may be used alone or in combination of two or more types. Here, examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM 333 It may also be abbreviated as), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM 523 It may also be abbreviated as), LiNi O. 5 Co0.25 Mn 0.25 O2 (NCM 211 It may also be abbreviated as ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM 622 It may also be abbreviated as ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM 811 It may also be abbreviated as), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 It includes, but is not limited to, at least one of O2) and modified compounds thereof. Examples of lithium-containing phosphates of an olivine structure include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which may be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron-manganese phosphate, and a composite material of lithium iron-manganese phosphate and carbon.

[0079] In some embodiments, the anode film layer may optionally further include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0080] In some embodiments, the anode film layer may optionally further include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0081] In some embodiments, the positive plate may be manufactured by a method of forming a positive plate slurry by dispersing components for manufacturing the positive plate, such as a positive active material, a conductive agent, a binder, and any other components, in a solvent (e.g., N-methylpyrrolidone), coating the positive plate slurry onto a positive current collector, and then obtaining the positive plate through processes such as drying and cold pressing.

[0082] [Separator]

[0083] In some embodiments, the secondary battery further comprises a separator. The present invention has no particular limitation on the type of separator, and a known porous separator with excellent chemical stability and mechanical stability may be selected.

[0084] In some embodiments, the material of the separator may be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, but is not particularly limited thereto. If the separator is a multilayer composite film, the material of each layer may be the same or different, but is not particularly limited thereto.

[0085] In some embodiments, the positive plate, the negative plate, and the separator can be manufactured into an electrode assembly through a winding process or a lamination process.

[0086] In some embodiments, the secondary battery may include an external packaging. The external packaging is for packaging the electrode assembly and the electrolyte.

[0087] In some embodiments, the external packaging of the secondary battery may be a rigid case, such as a rigid plastic case, an aluminum case, a steel case, etc. The external packaging of the lithium-ion battery may be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, polybutylene succinate, etc.

[0088] The present invention does not specifically limit the shape of the secondary battery, and it may be cylindrical, rectangular, or any other shape. For example, FIG. 1 illustrates an exemplary rectangular secondary battery (5).

[0089] In some embodiments, referring to FIG. 2, the outer packaging may include a case (51) and a cover plate (53). Here, the case (51) may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate surround to form a receiving cavity. The case (51) has an opening communicating with the receiving cavity, and the cover plate (53) may be installed over the opening to seal the receiving cavity. The positive plate, the negative plate, and the separator may be formed into an electrode assembly (52) through a winding process or a lamination process. The electrode assembly (52) is packaged within the receiving cavity. An electrolyte is infiltrated into the electrode assembly (52). The number of electrode assemblies (52) included in the secondary battery (5) may be one or more, which can be selected by a person skilled in the art according to specific needs.

[0090] In some embodiments, the secondary battery may be assembled into a battery module, and the number of ion cells included in the battery module may be one or more, which can be selected by a person skilled in the art according to the application and capacity of the battery module.

[0091] FIG. 3 illustrates an exemplary battery module (4). Referring to FIG. 3, in the battery module (4), a plurality of secondary batteries (5) may be arranged sequentially along the length direction of the battery module (4). Of course, they may also be arranged in any other arbitrary manner. Additionally, the plurality of secondary batteries (5) may be secured through fasteners.

[0092] Optionally, the battery module (4) may further include a case having a receiving space, and a plurality of secondary batteries (5) are received in the receiving space.

[0093] In some embodiments, the battery module may also be assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, which can be selected by a person skilled in the art according to the application and capacity of the battery pack.

[0094] FIGS. 4 and 5 illustrate an exemplary battery pack (1). Referring to FIGS. 4 and 5, the battery pack (1) may include a battery box and a plurality of battery modules (4) installed in the battery box. The battery box includes an upper box body (2) and a lower box body (3), and the upper box body (2) may be installed over the lower box body (3) and may form a sealed space for accommodating the battery modules (4). The plurality of battery modules (4) may be arranged in the battery box in any manner.

[0095] In addition, the present invention also provides an electric device. The electric device comprises one or more of a secondary battery, a battery module, or a battery pack provided in the present invention. The secondary battery, the battery module, or the battery pack may be used as a power source for the device or as an energy storage unit for the electric device. The electric device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0096] The above electrical device may select a secondary battery, a battery module, or a battery pack depending on the usage needs.

[0097] FIG. 6 illustrates an exemplary electric device. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To satisfy the electric device's requirements for high power and high energy density of a secondary battery, a battery pack or a battery module may be used.

[0098] [Example]

[0099] The embodiments of the present invention are described below. The embodiments described below are illustrative and intended only to interpret the present invention; they should not be understood as limiting the present invention. Where specific technical or conditional descriptions are not specified in the embodiments, they shall be performed in accordance with technical or conditional descriptions or product specifications found in the literature of the art. Unless the manufacturer is specified, all reagents and equipment used are commercially available products.

[0100] Example 1.

[0101] Preparation of orthocarbonate-based liquid metal lithium secondary battery electrolyte

[0102] 1.23 g of tetraethyl orthocarbonate, 1.25 g of LiFSI lithium salt, 1.24 g of dimethyl carbonate (DMC), and 1.24 g of fluoroethylene carbonate (FEC) were weighed and mixed at room temperature, and stirred sufficiently until a clear and transparent solution was formed to obtain an electrolyte that can be used in a metal lithium secondary battery cycle.

[0103] Electrochemical performance test

[0104] A button battery was constructed using 50 μm copper-clad metallic lithium foil as the cathode and anode, and a polyethylene porous film as the separator. The prepared electrolyte was injected to completely infiltrate the separator and electrode surfaces. Charge-discharge cycle tests were performed on the symmetrical battery assembled using a Solartron electrochemical workstation at various current densities ranging from low to high, and the results are shown in Fig. 7. In the figure, the current densities used to test the symmetrical battery were 4 mA / cm², respectively. 2 , 6 mA / cm 2 , 8 mA / cm 2 , 10 mA / cm 2 , 20 mA / cm 2 and the surface capacity density is 2 mAh / cm² 2 It is a cycle, and three cycles were performed at each current density. From the figure, the electrolyte is 10 mA / cm² 2 Maintains a stable cycle at a high current density of 20 mA / cm² 2 It can be observed that although the overpotential is unstable at ultra-high current densities, the cycle is still maintained, which means that the combination of orthocarbonate, chain carbonate, and cyclic carbonate produces a cooperative effect that simultaneously achieves ion conductivity and stable deposition and exfoliation of metallic lithium.

[0105] For the Li-Li button cell of the above composition, an impedance test was performed at room temperature using a Solartron electrochemical workstation, with the test frequency range set to 1 MHz to 1 Hz and the AC voltage amplitude set to 5 mV to obtain the electrochemical impedance curve of the button cell. The results of the impedance test at room temperature are shown in Fig. 8. From the figure, it can be seen that the volume and interfacial impedance of the cell are very small, which further proves that the electrolyte can perform high-current cycles. After placing the button cell in an 80°C environment for 3 hours, the impedance was tested again as shown in Fig. 9. At this time, it was found that the interfacial resistance increased significantly and the cell was completely disconnected. As a result of disassembling the battery and performing a gas generation test, it was found that no obvious gas components were formed and the surface of the metallic lithium appeared grayish-black. This means that at that temperature, the reaction between the electrolyte and the metallic lithium rapidly passivates the surface, prevents battery overcurrent, and suppresses the additional occurrence of side reactions, thereby improving the thermal stability of the battery.

[0106] Manufacturing and testing of liquid metal lithium secondary batteries

[0107] Cathode Preparation: Lithium iron phosphate (LiFePO4) as the cathode active material, acetylene black as the conductive agent, and PVDF as the binder were mixed in a mass ratio of 98:1:1, NMP as the solvent was added, and the mixture was stirred until the system exhibited a uniform shape to obtain a cathode slurry; the cathode slurry was uniformly coated onto both sides of the aluminum foil of the cathode current collector, dried at room temperature, transferred to an oven for continued drying, and then cut into a 40 mm x 50 mm rectangle to be used as a cathode plate, wherein the capacitance of the cathode surface is 3.5 mAh / cm² 2 It was.

[0108] Separator: A polyethylene porous film was selected and used.

[0109] Cathode fabrication: A 50 μm lithium foil was coated onto a 12 μm copper foil using a rolling method, and then cut into a 41 mm x 51 mm rectangle to be prepared as a cathode plate.

[0110] Battery Assembly: One cut positive electrode and two cut negative electrodes are matched, and the positive and negative electrodes are separated using the separator in between. The mixture is then wrapped in an aluminum-plastic film bag to form a laminated battery cell. 0.3 g of the electrolyte prepared above is injected, and the aluminum-plastic film bag is vacuum heat-pressed and packaged. After leaving the mixture for at least 12 hours, an impedance test is performed on the laminated cell at room temperature. The internal resistance of the battery is reflected as the value obtained by intercepting the real part of the resistance to the right of the semicircle in the electrochemical impedance spectrum. After the impedance test is completed, a cycle test can be performed. The rated capacity of the laminated battery manufactured by this method is 140 mAh.

[0111] Cell cycle: The ambient temperature for the cell cycle was set to 25°C, and a charge-discharge cycle was performed at a rate of 0.5°C (i.e., 70 mA). The charge-discharge cutoff voltages were set to 3.65 V and 2.80 V, respectively.

[0112] The cycle voltage of the above battery is shown in FIG. 10. From the figure, it can be seen that the charge / discharge capacity of the battery cycle curve tends to stabilize after 10 cycles, can discharge the rated capacity, and has a 100% cycle Coulomb efficiency. The number of cycles was recorded when the cycle retention rate decreased to 80%.

[0113] Gas generation test of liquid lithium metal secondary battery

[0114] The laminate cell manufactured above is connected to a differential electrochemical mass spectrometer (DEMS), and the test method can detect gas generation conditions in situ during the cell cycle. One cycle was performed on the laminate cell at a magnification of 0.5C, and the amount of gas generated by the cell during the cycle was recorded and compared.

[0115] Safety test of liquid lithium metal secondary battery hot box

[0116] Cathode Preparation: Lithium nickel manganese cobaltate (NMC) as the cathode active material, acetylene black as the conductive agent, and PVDF as the binder were mixed in a mass ratio of 98:1:1, NMP as the solvent was added, and the mixture was stirred until the system exhibited a uniform shape to obtain a cathode slurry; the cathode slurry was uniformly coated onto both sides of the aluminum foil of the cathode current collector, dried at room temperature, transferred to an oven for continued drying, and then cut into a 40 mm x 50 mm rectangle to be used as a cathode plate, wherein the capacitance of the cathode surface is 3.5 mAh / cm² 2 It was.

[0117] Separator: A polyethylene porous film was selected and used.

[0118] Cathode fabrication: A 50 μm lithium foil was coated onto a 12 μm copper foil using a rolling method, and then cut into a 41 mm x 51 mm rectangle to be prepared as a cathode plate.

[0119] Ten cut positives and twenty cut negatives prepared above were taken and matched, and the positive and negatives were separated using the separator in the middle and wrapped in an aluminum-plastic film bag to form a pouch battery cell. 3g of the prepared electrolyte was injected, and the aluminum-plastic film tape was vacuum-sealed. The rated capacity of the pouch battery prepared by this method was 1.4 Ah. After leaving it for at least 12 hours, the cell was fully charged (4.3V) at a rate of 0.5C. The fully charged pouch battery was placed in a hot box and heated for 30 minutes at 5℃ increments starting from 30℃ until thermal runaway of the cell occurred, and the above temperature is the thermal runaway temperature of the cell.

[0120] The manufacturing and testing methods of Examples 2 to 34 and Comparative Examples 1 to 8 are similar to those of Example 1, and details are provided in Table 1.

[0121] number Orthocarbonate lithium salt chain-type carbonate Ring-shaped carbonate Cycle count Battery internal resistance (Ω) Battery gas production amount (mL) substance Mass (g) substance Mass (g) substance Mass (g) substance Mass (g) Example 1 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 153 5.1 0.1275 Example 2 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 Methyl trifluoroethyl carbonate 1.24 Ethylene carbonate 1.24 148 5.4 0.1305 Example 3 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 dimethyl carbonate 0.62 Fluoroethylene carbonate 0.62 128 6.8 0.1233 Example 4 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 Methyl trifluoroethyl carbonate 0.62 Ethylene carbonate 0.62 123 7.1 0.1296 Example 5 Tetramethyl orthocarbonate 1.23 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 136 4.6 0.1306 Example 6 Tetrapropyl orthocarbonate 1.23 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 131 7.6 0.1177 Example 7 Tetraethyl orthocarbonate 1.23 LiPF6 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 141 5.8 0.1396 Example 8 Tetraethyl orthocarbonate 0.41 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 102 5.0 0.1408 Example 9 Tetraethyl orthocarbonate 14.92 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 82 10.4 0.0967 Example 10 Tetraethyl orthocarbonate 0.93 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 148 4.9 0.1228 Example 11 Tetraethyl orthocarbonate 1.60 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 150 5.3 0.1201 Example 12 Tetraethyl orthocarbonate 1.23 LiFSI 0.41 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 104 9.8 0.1530 Example 13 Tetraethyl orthocarbonate 1.23 LiFSI 8.66 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 90 8.6 0.0872 Example 14 Tetraethyl orthocarbonate 1.23 LiFSI 0.93 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 144 5.8 0.1373 Example 15 Tetraethyl orthocarbonate 1.23 LiFSI 1.59 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 147 5.2 0.1259 Example 16 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 dimethyl carbonate 0.04 Fluoroethylene carbonate 1.24 101 14.7 0.1593 Example 17 Tetraethyl orthocarbonate 1.23 LiFSI 0.41 dimethyl carbonate 8.2 Fluoroethylene carbonate 0.41 87 9.5 0.1021 Example 18 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 dimethyl carbonate 0.93 Fluoroethylene carbonate 1.24 141 5.2 0.1295 Example 19 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 dimethyl carbonate 1.59 Fluoroethylene carbonate 1.24 148 4.8 0.1194 Example 20 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 0.04 81 4.4 0.0926 Example 21 Tetraethyl orthocarbonate 1.23 LiFSI 0.41 dimethyl carbonate 0.41 Fluoroethylene carbonate 8.2 85 7.1 0.1582 Example 22 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 0.93 145 5.0 0.1202 Example 23 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.59 142 5.5 0.1281 Example 24 Tetraethyl orthocarbonate 0.66 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 136 4.9 0.1289 Example 25 Tetraethyl orthocarbonate 1.87 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 144 5.6 0.1146 Example 26 Tetraethyl orthocarbonate 1.65 LiFSI 3.3 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 120 5.5 0.1121 Example 27 Tetraethyl orthocarbonate 1.03 LiFSI 0.62 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 133 5.4 0.1356 Example 28 Tetramethyl fluoro orthocarbonate 1.23 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 107 8.9 0.0489 Example 29 2,2-dimethoxy-1,3-dioxane 1.23 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 138 7.2 0.1250 Example 30 Tetraethyl orthocarbonate 1.23 LiTFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 137 5.1 0.1293 Example 31 Tetraethyl orthocarbonate 1.23 LiDFOB 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 115 7.8 0.2165 Example 32 Tetrabutyl orthocarbonate 1.23 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 119 8.4 0.1066 Example 33 Tetraethyl orthocarbonate 1.23 LiFSI 0.75 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 131 5.9 0.1285 Example 34 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 Methyl trifluoroethyl carbonate 1.24 Fluoroethylene carbonate 1.24 118 9.9 0.1682 Example 35 Tetraethyl orthocarbonate 3.73 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 118 6.8 0.1192 Example 36 Tetraethyl orthocarbonate 1.23 LiFSI 2.47 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 130 5.6 0.1226 Example 37 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 dimethyl carbonate 2.48 Fluoroethylene carbonate 1.24 129 4.4 0.1282 Example 38 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 2.48 127 5.9 0.1295 Comparative Example 1 Tetraethyl orthocarbonate 20.89 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 65 12.2 0.0951 Comparative Example 2 Tetraethyl orthocarbonate 0.32 LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 77 5.2 0.1499 Comparative Example 3 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 dimethyl carbonate 2.48 - - 17 4.7 0.0972 Comparative Example 4 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 Ethyl methyl carbonate 2.48 - - 19 4.8 0.0926 Comparative Example 5 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 - - Fluoroethylene carbonate 2.48 21 9.6 0.1603 Comparative Example 6 - - LiFSI 1.25 dimethyl carbonate 1.24 Fluoroethylene carbonate 1.24 37 5.0 0.1233 Comparative Example 7 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 Methyl trifluoroethyl carbonate 2.48 - - 31 10.1 0.1582 Comparative Example 8 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 - - Ethylene carbonate 2.48 19 5.2 0.0827 Comparative Example 9 - - LiFSI 1.25 Methyl trifluoroethyl carbonate 1.24 Ethylene carbonate 1.24 41 5.5 0.1293 Comparative Example 10 Tetraethyl orthocarbonate 1.23 LiFSI 1.25 dimethyl carbonate 1.24 Ethylene carbonate 1.24 20 4.9 0.1028

[0122] Through a comparison of the data from Examples 1, 5 to 6, and 28 to 29, it can be found that tetraethyl orthocarbonate shows the most evident improvement in the cycle life of metal lithium batteries compared to tetramethyl orthocarbonate, tetrapropyl orthocarbonate, tetramethyl fluoroorthocarbonate, and 2,2-dimethoxy-1,3-dioxane.

[0123] Through a comparison of Examples 1, 8 to 11 and Comparative Example 6, it was found that when the amount of orthocarbonate added is 30% or less, the internal resistance of the battery does not increase significantly, and not only does the amount of gas generated in the initial cycle not increase significantly, but on the contrary, gas generation is suppressed to some extent. However, when the amount of orthocarbonate added is too high, it affects the cycle life of the metal lithium battery. This is because the orthocarbonate content is too high, causing the internal resistance of the battery to be too high, and the consumption rate of the lithium salt during the cycle increases, thereby shortening the cycle life compared to the cycle life with a content of 80% or less.

[0124] Through a comparison of Example 1 and Examples 12 to 15, it can be found that cycle life is reduced if the concentration of the lithium salt is too low or too high. This is because the higher the concentration of the lithium salt, the higher the degree of participation of anions involved in the solvation of lithium ions, which is favorable for the formation of an SEI film for anion decomposition and thus improves cycle life; however, if the concentration of the lithium salt is too high, the efficiency of the SEI film decreases, which affects the improvement of cycle life.

[0125] Through a comparison of Example 1 and Comparative Examples 3 to 9, it was found that a deficiency of any one of the orthocarbonate, chain carbonate, or cyclic carbonate has a fatal effect on battery cycle life. This is because the orthocarbonate promotes weak solvation and a solvation structure with high anion participation, the chain carbonate lowers the viscosity of the electrolyte to improve infiltration and ion conductivity, and the fluorinated cyclic carbonate plays a role in the decomposition and formation of components that are more favorable for the metallic lithium cycle. None of the three components must be omitted.

[0126] Through a comparison of Example 1, Example 34 and Comparative Example 10, it can be found that one of the chain carbonate and cyclic carbonate solvents must be a fluorocarbonate and the other must be a fluorocarbonate. This is because fluorine-containing components, such as lithium fluoride produced by the decomposition of fluorocarbonates, can promote good cycling of metallic lithium, and if both solvents are fluorocarbonates, it becomes more difficult for the electrolyte to penetrate, thereby hindering the long-term stable cycling of the battery.

[0127] The thermal runaway temperature of Example 1 is 150°C, and the thermal runaway temperature of Comparative Example 6 is 140°C. Through a comparison between Example 1 and Comparative Example 6, it can be found that the safety of a metal lithium secondary battery hot box using a ternary cathode material can be improved after adding orthocarbonate. This is because orthocarbonate molecules react with the metal lithium surface at high temperatures to rapidly passivate the surface, thereby suppressing the additional occurrence of exothermic reactions.

[0128] In addition, in all embodiments, the amount of gas generated by the metal lithium battery is less than 0.2 mL, and within the said range of gas generation, the cycle life and safety of the battery are not negatively affected.

[0129] Although the present invention has been described with reference to preferred embodiments, various improvements may be made without departing from the scope of the invention, and some components may be replaced with equivalents. In particular, as long as there is no structural conflict, each technical feature mentioned in each embodiment may be combined in any manner. The present invention is not limited to the specific embodiments disclosed herein but includes all technical solutions within the scope of the claims. Explanation of the symbols

[0130] 1: Battery pack; 2: Upper box body; 3: Lower box body; 4: Battery module; 5: Secondary battery; 51: Case; 52: Electrode assembly; 53: Top cover assembly. In the attached drawings, the drawings were not drawn to the actual scale.

Claims

Claim 1 A secondary battery comprising a positive electrode plate, a negative electrode plate, an electrolyte, and a separator, wherein the electrolyte is a non-aqueous electrolyte, the negative electrode plate comprises a current collector and a negative electrode active layer, the negative electrode active layer is metallic lithium or a lithium alloy, the non-aqueous electrolyte comprises an orthocarbonate, a chain carbonate, a cyclic carbonate, and a lithium salt, wherein, based on mass content, the content of the orthocarbonate is 10% to 80%, at least one of the chain carbonate and the cyclic carbonate is a fluoride, and the orthocarbonate is selected from one or more of the group consisting of a compound having a structure represented by Formula I, a compound having a structure represented by Formula II, or a compound having a structure represented by Formula III. Formula I, Formula II, Formula III, wherein R1 to R4, R6 and R7 each independently represent either a C1-C10 alkyl or a C1-C10 haloalkyl, and R5, R8 and R9 each independently represent either a C1-C10 alkylene or a C1-C10 haloalkylene, a secondary battery. Claim 2 A secondary battery according to claim 1, wherein the mass content of the orthocarbonate in the non-aqueous electrolyte is 15 to 50%. Claim 3 A secondary battery according to claim 1 or 2, wherein the mass ratio of the orthocarbonate to the lithium salt is 1:3 to 3:

1. Claim 4 A secondary battery according to claim 1 or 2, wherein the mass content of the chain-type carbonate is 1% to 80%; and / or the mass content of the cyclic carbonate is 1% to 80%; and / or the mass content of the lithium salt is 10% to 70%. Claim 5 A secondary battery according to claim 1 or 2, wherein one of the chain-type carbonate and the cyclic carbonate is a fluoride. Claim 6 A secondary battery according to claim 1 or 2, wherein the orthocarbonate is selected from one or more of the group consisting of tetramethyl orthocarbonate, tetraethyl orthocarbonate, tetrapropyl orthocarbonate, tetrabutyl orthocarbonate, tetrapentyl orthocarbonate, tetrahexyl orthocarbonate, tetraheptyl orthocarbonate, tetraoctyl orthocarbonate, tetranonyl orthocarbonate, tetradecyl orthocarbonate, tetramethyl fluoroorthocarbonate, tetraethyl fluoroorthocarbonate, tetrapropyl fluoroorthocarbonate, tetrabutyl fluoroorthocarbonate, tetrapentyl fluoroorthocarbonate, tetrahexyl fluoroorthocarbonate, tetraheptyl fluoroorthocarbonate, tetraoctyl fluoroorthocarbonate, tetranonyl fluoroorthocarbonate, and tetradecyl fluoroorthocarbonate. Claim 7 In claim 1 or 2, the chain-type carbonate is selected from one or more of compounds having a structure represented by Formula IV, and Formula IV In the above formula, R10 and R11 each independently represent any one of a halogen group, a C1-C5 alkyl, or a C1-C5 haloalkyl secondary battery. Claim 8 In claim 1 or 2, the cyclic carbonate is selected from one or more of compounds having a structure represented by formula V, and Formula V, wherein R12 to R15 each independently represent any one of a halogen group, a C1-C3 alkyl, or a C1-C3 haloalkyl secondary battery. Claim 9 A secondary battery according to claim 1 or 2, wherein the lithium salt is selected from one or more of the group consisting of lithium bisfluorosulfonylimide, lithium bisfluoromethylsulfonylimide, lithium bispentafluoroethylsulfonylimide, lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium difluorooxalate borate, and lithium difluorophosphate. Claim 10 A secondary battery according to claim 1 or 2, wherein the orthocarbonate is tetramethyl orthocarbonate or tetraethyl orthocarbonate, the chain carbonate is any one of dimethyl carbonate, diethyl carbonate, dimethyl fluorocarbonate and diethyl fluorocarbonate, the cyclic carbonate is selected from any one of fluoroethylene carbonate, fluoropropylene carbonate and difluoropropylene carbonate, and the lithium salt is lithium bisfluorosulfonylimide or lithium bisfluoromethylsulfonylimide. Claim 11 A battery module comprising a secondary battery, wherein the secondary battery is a secondary battery according to claim 1. Claim 12 A battery pack comprising a battery module, wherein the battery module is a battery module according to claim 11. Claim 13 An electric device comprising a secondary battery, a battery module, or a battery pack, wherein the secondary battery is selected from a secondary battery according to claim 1 or 2, and the battery module is a battery module according to claim 11 or the battery pack is a battery pack according to claim 12. Claim 14 delete Claim 15 delete

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