Electrolyte solution, secondary battery and electric device

Abstract

An electrolyte solution, a secondary battery and an electric device. The electrolyte solution comprises a cyclosiloxane compound represented by formula (1), wherein R1 and R2 are respectively independently selected from any one of H, a halogen, an aryl having 6-10 ring-forming atoms, an alkyl having 1-10 carbon atoms, a halogen-substituted alkyl having 1-10 carbon atoms, an aryl having 6-10 ring-forming atoms, and formula (2), and R1 and R2 are not H at the same time; R3 is selected from any one of an alkylene having 1-5 carbon atoms and a halogen-substituted alkylene having 1-5 carbon atoms; R4 and R5 are respectively independently selected from any one of H, an alkoxy having 1-10 carbon atoms and a halogen-substituted alkoxy having 1-10 carbon atoms, and R1 and R2 are not H at the same time; and "*" represents a connection site, formula (3) represents that atoms at two ends thereof are connected to form a ring, and n is any integer of 3 5.

Description

Electrolyte, secondary battery and electrical device

[0001] Cross-references

[0002] This application claims priority to Chinese Patent Application No. 202311413641.5, filed on October 30, 2023, entitled “Electrolyte, Secondary Battery and Electrical Device,” which is incorporated herein by reference in its entirety. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to an electrolyte, a secondary battery, and an electrical device. Background Art

[0004] Secondary batteries such as lithium batteries are becoming increasingly widely used due to their clean and renewable characteristics. They have a large specific energy density and a long cycle life, and have been widely used in many fields such as consumer electronics, electric vehicles, and energy storage.

[0005] As the application range of secondary batteries expands, the requirements for their electrochemical window are becoming increasingly stringent. Broadening the electrochemical window is crucial for adapting to various application scenarios, and safety performance is becoming increasingly important. However, traditional secondary batteries are prone to byproduct reactions such as oxidation and decomposition during the charge and discharge process, resulting in an excessively narrow electrochemical window, which restricts the expansion of secondary battery applications. They are also prone to thermal runaway, which can lead to battery failure at best and even safety accidents at worst.

[0006] Therefore, the electrochemical window and safety performance of traditional secondary batteries need to be further improved.

[0007] Summary of the Invention

[0008] According to various embodiments of the present application, the present application provides an electrolyte, a secondary battery, and an electrical device, aiming to broaden the electrochemical window of the secondary battery while improving its safety performance.

[0009] This application is achieved through the following technical solutions.

[0010] In a first aspect of the present application, an electrolyte is provided, wherein the components of the electrolyte include a cyclic silicon oxide compound represented by formula (1):

[0011] wherein each R1 and each R2 are independently selected from H, halogen, substituted or unsubstituted aryl having 6 to 10 ring atoms, alkyl having 1 to 10 carbon atoms, alkyl having 1 to 10 carbon atoms substituted by halogen, and Any one of the above, and at least one R1 or at least one R2 in the multiple repeating units of the cyclic silicon-oxygen compound is selected from substituted or unsubstituted aromatic groups with 6 to 10 ring atoms or

[0012] R3 is selected from any one of an alkylene group having 1 to 5 carbon atoms and an alkylene group having 1 to 5 carbon atoms substituted by halogen; R4 and R5 are each independently selected from any one of H, an alkoxy group having 1 to 10 carbon atoms and an alkoxy group having 1 to 10 carbon atoms substituted by halogen, and R4 and R5 are not both H;

[0013] “*” represents the connection site, It represents the atoms at both ends connected to form a ring, and n is an integer from 3 to 5.

[0014] The components of the above-mentioned electrolyte contain cyclic silicon oxide compounds with specific structures. The cyclic silicon oxide compounds shown in formula (1) contain a cyclic silicon oxide main structure and a specific hydrocarbon group connected to the main structure. On the one hand, the cyclic silicon oxide main structure has high thermal stability and chemical stability, and the cyclic silicon oxide main structure can undergo a ring-opening reaction when the temperature rises, and target the passivation of by-products such as LiCx in real time, effectively inhibit their exothermic side reactions with the electrolyte, and target the repair of the SEI film. When the ring-opening reaction proceeds to a certain extent, it can polymerize to form a gel-like substance, which adheres to the diaphragm to play a supporting role and inhibit the shrinkage of the isolation membrane; on the other hand, the specific hydrocarbon group connected to the main structure further improves the chemical stability of the cyclic silicon oxide compound. The organic combination of various specific structures can increase the critical point of thermal runaway while widening the electrochemical window of the electrolyte. When used in the preparation of secondary batteries, it can increase the thermal runaway trigger temperature of the secondary battery, delay the occurrence of thermal runaway, and widen the electrochemical window.

[0015] Aromatic groups have higher chemical stability, and halogens or phosphorus-containing groups of the above-mentioned specific structures can release halogen radicals or phosphorus radicals after being heated, which can effectively quench hydrogen radicals or hydroxyl radicals generated during the use of secondary batteries, further increase the battery thermal runaway trigger temperature, and delay the occurrence of thermal runaway.

[0016] In some embodiments, the halogen includes at least one of F and Br.

[0017] F and Br have strong electronegativity, especially F, which is more electronegative, which is conducive to the reduction of the graphite negative electrode and the formation of a dense LiF-rich inorganic SEI film, which is beneficial to increasing the decomposition temperature of the SEI film and delaying the occurrence of battery thermal runaway.

[0018] The aromatic group or the above-mentioned specific phosphorus-containing group not only has a good flame retardant effect, but also participates in the formation of the cathode CEI layer, can better protect the cathode interface, slow down the dissolution of transition metals, reduce side reactions, and improve battery performance.

[0019] In some embodiments, R4 and R5 are independently selected from any one of an alkoxy group having 1 to 5 carbon atoms and an alkoxy group having 1 to 5 carbon atoms substituted by halogen.

[0020] In some embodiments, the cyclic silicon-oxygen compound comprises at least one of the following formulas (1b) and (1d):

[0021] In some embodiments, in the electrolyte, the mass proportion of the cyclic silicon oxide compound is 0.1% to 10%.

[0022] In some embodiments, in the electrolyte, the mass proportion of the cyclic silicon oxide compound is 3% to 6%.

[0023] Further regulate the content of cyclic silicon oxide compounds to give full play to the synergistic effect.

[0024] In some embodiments, the electrolyte further comprises an electrolyte salt and an organic solvent.

[0025] In some embodiments, the electrolyte salt satisfies at least one of the following conditions (1) to (2):

[0026] (1) In the electrolyte solution, the concentration of the electrolyte salt is 0.8 mol / L to 1.2 mol / L;

[0027] (2) The electrolyte salt includes at least one of LiPF6, LiBF4, LiAsF6, LiBOB, LiDFOB, LiN(CF3SO2)2 and lithium bis(fluorosulfonyl imide).

[0028] According to a second aspect of the present application, a secondary battery is provided, wherein the secondary battery includes the electrolyte according to the first aspect.

[0029] According to a third aspect of the present application, an electric device is provided, wherein the electric device comprises the secondary battery according to the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive work. In the drawings:

[0031] FIG1 is a schematic diagram of an embodiment of a battery cell;

[0032] Figure 2 is an exploded view of Figure 1;

[0033] FIG3 is a schematic diagram of an embodiment of a battery pack;

[0034] FIG4 is an exploded view of FIG3 ;

[0035] FIG. 5 is a schematic diagram of an embodiment of an electric device using a battery as a power source.

[0036] Description of reference numerals:

[0037] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery cell; 41. Shell; 42. Electrode assembly; 43. Cover; 5. Electrical device. DETAILED DESCRIPTION

[0038] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0040] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0041] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0042] In this application, the term "alkyl" refers to a group formed when an alkane loses one hydrogen, including straight-chain alkyl and branched alkyl, for example, methane loses one hydrogen to form a methyl; similarly, the term "alkylene" refers to a group formed when an alkane loses two hydrogens, for example, methane loses two hydrogens to form a methylene.

[0043] In the present application, the number of carbon atoms in the "alkyl group having 1 to 10 carbon atoms" can be 1 to 10, including 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Non-limiting examples include methane, ethyl, and n-propyl.

[0044] The term "straight-chain alkyl group and branched-chain alkyl group" refers to a group formed by losing one hydrogen atom from an alkane in which the carbon atoms are all connected by carbon-carbon single bonds and do not form a ring, and the remaining valence bonds are all bonded to hydrogen.

[0045] In the present application, the halogen group includes chlorine, fluorine, bromine, and iodine.

[0046] In this application, "aryl" refers to a hydrocarbon group containing at least one aromatic ring, including non-fused-ring aromatic groups and fused-ring aromatic groups. A fused-ring aromatic group is a group formed by linking two or more aromatic rings through two common adjacent ring atoms, i.e., a fused ring.

[0047] Aromatic ring refers to a cyclic hydrocarbon compound with aromatic properties: that is, a hydrocarbon compound with a cyclic closed-ring conjugated system.

[0048] In this application, the term "ring atoms" refers to the number of atoms bonded to form a ring. When a ring is substituted with a substituent, the atoms contained in the substituent are not included in the ring atoms. The term "ring atoms" used below applies unless otherwise specified. For example, a benzene ring has 6 ring atoms, and a naphthalene ring has 10 ring atoms.

[0049] In one embodiment of the present application, an electrolyte is provided, wherein the components of the electrolyte include a cyclic silicon oxide compound represented by formula (1):

[0050] wherein each R1 and each R2 are independently selected from H, halogen, substituted or unsubstituted aryl having 6 to 10 ring atoms, alkyl having 1 to 10 carbon atoms, alkyl having 1 to 10 carbon atoms substituted by halogen, and Any one of the above, and at least one R1 or at least one R2 in the multiple repeating units of the cyclic silicon-oxygen compound is selected from substituted or unsubstituted aromatic groups with 6 to 10 ring atoms or

[0051] R3 is selected from any one of an alkylene group having 1 to 5 carbon atoms and an alkylene group having 1 to 5 carbon atoms substituted by halogen; R4 and R5 are each independently selected from any one of H, an alkoxy group having 1 to 10 carbon atoms and an alkoxy group having 1 to 10 carbon atoms substituted by halogen, and R4 and R5 are not both H;

[0052] “*” represents the connection site, It represents the atoms at both ends connected to form a ring, and n is an integer from 3 to 5.

[0053] The components of the above-mentioned electrolyte contain cyclic silicon oxide compounds with specific structures. The cyclic silicon oxide compounds shown in formula (1) contain a cyclic silicon oxide main structure and a specific hydrocarbon group connected to the main structure. On the one hand, the cyclic silicon oxide main structure has high thermal stability and chemical stability, and the cyclic silicon oxide main structure can undergo a ring-opening reaction when the temperature rises, and target the passivation of by-products such as LiCx in real time, effectively inhibit their exothermic side reactions with the electrolyte, and target the repair of the SEI film. When the ring-opening reaction proceeds to a certain extent, it can polymerize to form a gel-like substance, which adheres to the diaphragm to play a supporting role and inhibit the shrinkage of the isolation membrane; on the other hand, the specific hydrocarbon group connected to the main structure further improves the chemical stability of the cyclic silicon oxide compound. The organic combination of various specific structures can increase the critical point of thermal runaway while widening the electrochemical window of the electrolyte. When used in the preparation of secondary batteries, it can increase the thermal runaway trigger temperature of the secondary battery, delay the occurrence of thermal runaway, and widen the electrochemical window.

[0054] Understandable: The atoms at both ends of the "[]" are connected to form a ring, that is, the two atoms at both ends of the group represented by "[]": an oxygen atom and a silicon atom are connected; in other words, the cyclic silicon-oxygen compound includes at least one of the following formulas (1-1) to (1-3):

[0055] In some embodiments, the substituted or unsubstituted aryl group having 6 to 10 ring atoms includes at least one of an unsubstituted aryl group having 6 to 10 ring atoms, an aryl group having 6 to 10 ring atoms substituted by a C1 to C5 alkyl group, and an aryl group having 6 to 10 ring atoms substituted by a halogen.

[0056] In some embodiments, the halogen includes at least one of F and Br.

[0057] F and Br have strong electronegativity, especially F, which is more electronegative, which is conducive to the reduction of the graphite negative electrode and the formation of a dense LiF-rich inorganic SEI film, which is beneficial to increasing the decomposition temperature of the SEI film and delaying the occurrence of battery thermal runaway.

[0058] Saturated hydrocarbon groups or aromatic groups have higher chemical stability, and halogens or phosphorus-containing groups of the above-mentioned specific structures can release halogen radicals or phosphorus radicals after being heated, which can effectively quench hydrogen radicals or hydroxyl radicals generated during the use of secondary batteries, further increase the battery thermal runaway trigger temperature, and delay the occurrence of thermal runaway.

[0059] In some embodiments, each R1 and each R2 are independently selected from H, halogen, substituted or unsubstituted aryl with 6 to 8 ring atoms, alkyl with 1 to 5 carbon atoms, alkyl with 1 to 5 carbon atoms substituted by halogen, and Any one of .

[0060] In some embodiments, each R1 and each R2 are independently selected from H, halogen, substituted or unsubstituted aryl with 6 to 8 ring atoms, straight-chain alkyl with 1 to 5 carbon atoms, straight-chain alkyl with 1 to 5 carbon atoms substituted by halogen, and Any one of .

[0061] In some embodiments, each R1 and each R2 are independently selected from H, halogen, phenyl, phenyl substituted by halogen, straight-chain alkyl with 1 to 3 carbon atoms, straight-chain alkyl with 1 to 3 carbon atoms substituted by halogen, and Any one of .

[0062] In some embodiments, each R1 and each R2 are independently selected from H, halogen, phenyl, phenyl substituted by halogen, methyl, ethyl, n-propyl, isopropyl, methyl substituted by halogen, ethyl substituted by halogen, n-propyl substituted by halogen, isopropyl substituted by halogen, and Any one of .

[0063] In some embodiments, at least one R1 or at least one R2 in the multiple repeating units of the cyclic silicon-oxygen compound is selected from substituted or unsubstituted aromatic groups with 6 to 10 ring atoms and Any one of .

[0064] In some embodiments, at least one R1 or at least one R2 in the multiple repeating units of the cyclic silicon-oxygen compound is selected from substituted or unsubstituted aromatic groups with 6 to 8 ring atoms and Any one of .

[0065] In some embodiments, in the multiple repeating units of the cyclic silicon-oxygen compound, at least one R1 or at least one R2 is selected from a linear alkyl group having 1 to 5 carbon atoms or a linear alkyl group having 1 to 5 carbon atoms substituted by a halogen; at least another R1 or at least another R2 is selected from a substituted or unsubstituted aryl group having 6 to 10 ring atoms and Any one of .

[0066] In some embodiments, in the multiple repeating units of the cyclic silicon-oxygen compound, at least one R1 or at least one R2 is selected from methyl, ethyl, n-propyl, isopropyl, methyl substituted by halogen, ethyl substituted by halogen, n-propyl substituted by halogen or isopropyl substituted by halogen; at least another R1 or at least another R2 is selected from phenyl, phenyl substituted by halogen and Any one of .

[0067] In some embodiments, R4 and R5 are independently selected from any one of an alkoxy group having 1 to 5 carbon atoms and an alkoxy group having 1 to 5 carbon atoms substituted by halogen.

[0068] It should be noted that, if multiple R4 or multiple R5 appear in the same molecule, each R4 may be the same or different, and each R5 may also be the same or different.

[0069] In some embodiments, "alkoxy" is generally represented by "rO-", where r is an alkyl group having 1 to 5 carbon atoms or an alkyl group having 1 to 5 carbon atoms substituted by halogen.

[0070] In some embodiments, r is a chain alkyl group having 1 to 5 carbon atoms or a straight-chain alkyl group having 1 to 5 carbon atoms substituted by halogen.

[0071] In some embodiments, R4 and R5 are independently selected from any one of an alkoxy group having 1 to 3 carbon atoms and an alkoxy group having 1 to 3 carbon atoms substituted by halogen.

[0072] In other words, r is an alkyl group having 1 to 3 carbon atoms or an alkyl group having 1 to 3 carbon atoms substituted with a halogen.

[0073] In some embodiments, r is a linear alkyl group having 1 to 3 carbon atoms or a linear alkyl group having 1 to 3 carbon atoms substituted by halogen.

[0074] In some embodiments, r is any one of methyl, ethyl, n-propyl, isopropyl, methyl substituted by halogen, ethyl substituted by halogen, n-propyl substituted by halogen, and isopropyl substituted by halogen.

[0075] In some embodiments, the cyclic silicon oxide compound comprises at least one of the following formulas (1a) to (1f):

[0076] The cyclic silicon oxide compounds represented by formula (1) in the present application are all compounds with known structures in the art or compounds that can be obtained according to the existing technical records. For example, formula (1a) is 3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane, CAS No.: 2374-14-3; formula (1e) is 2,4,6,8-tetramethyl-2,4,6,8-tetra(3,3,3-trifluoropropyl)cyclotetrasiloxane, CAS No.: 429-67-4; formula (1b), formula (1c), formula (1d) and formula (1f) can all be obtained by searching the chemical reagent website or in literature or patents, and will not be repeated here.

[0077] In some embodiments, the mass proportion of the cyclic silicon oxide compound in the electrolyte is 0.1% to 10%.

[0078] In some embodiments, in the electrolyte, the mass proportion of the cyclic silicon oxide compound is 3% to 6%.

[0079] Further regulate the content of cyclic silicon oxide compounds to give full play to the synergistic effect.

[0080] In the above “0.1% to 10%”, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: “0.1%, 0.2%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10%; or a range consisting of any two values, for example: 0.1% to 10%, 0.1% to 8%, 0.1% to 9%; %, 0.1%~7%, 0.1%~6%, 0.1%~5%, 0.1%~4%, 0.1%~3%, 0.1%~2%, 0.1%~1%, 1%~10%, 1%~8%, 1%~9%, 1%~7%, 1%~6%, 1%~5%, 1%~4%, 1%~3%, 1%~2%, 2%~10%, 2%~8%, 2%~9%, 2%~7%, 2%~6%, 2%~5%, 2%~4%, 2%~3%, 3%~10%, 3%~8%, 3%~9%, 3%~7%, 3%~6%, 3%~5.

[0081] In some embodiments, the electrolyte solution further comprises an electrolyte salt and an organic solvent.

[0082] In some embodiments, the concentration of the electrolyte salt is 0.8 moL / L to 1.2 moL / L.

[0083] The electrolyte salt may be selected from electrolyte salts commonly used in the art, such as lithium ion electrolyte salts.

[0084] As an example, lithium ion electrolyte salts include, but are not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP), lithium bis(trifluoromethylsulfonyl)imide (LiN(CF3SO2)2) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0085] In some embodiments, the electrolyte salt includes at least one of LiPF6, LiBF4, LiAsF6, LiBOB, LiDFOB, LiN(CF3SO2)2, and lithium bis(fluorosulfonyl imide).

[0086] In some embodiments, the organic solvent includes at least one of a carbonate solvent, a carboxylic acid solvent, an ether solvent, a nitrile solvent, and a phosphazene solvent.

[0087] In some embodiments, the ether solvent includes a fluorinated ether solvent.

[0088] In some embodiments, the organic solvent can be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).

[0089] In some embodiments, the organic solvent includes at least one of a carbonate solvent, a carboxylic acid solvent, and a fluorinated ether solvent.

[0090] In some embodiments, the organic solvent includes carbonate solvents, carboxylic acid solvents, and fluorinated ether solvents.

[0091] In some embodiments, the mass ratio of the carbonate solvent, the carboxylic acid solvent and the fluorinated ether solvent is (1-3):(2-8):(1-3).

[0092] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0093] According to one embodiment of the present application, a secondary battery is provided. The secondary battery includes the electrolyte according to the first aspect.

[0094] In some embodiments, the secondary battery further includes a positive electrode sheet, a negative electrode sheet, and a separator.

[0095] In the present application, the positive electrode sheet, the negative electrode sheet and the separator may adopt the system commonly used in the art, and the positive electrode sheet, the negative electrode sheet and the separator are illustrated below.

[0096] Positive electrode sheet: The positive electrode sheet includes a current collector and a positive electrode active layer loaded on the surface of the current collector.

[0097] The components of the positive electrode active layer include a positive electrode active material. The positive electrode active material can be selected from commonly used positive electrode active materials in the art, including but not limited to: positive electrode active materials for lithium ion batteries, positive electrode active materials for sodium ion batteries, and positive electrode active materials for potassium ion batteries.

[0098] The positive electrode active material of a lithium ion battery, the positive electrode active material of a sodium ion battery, and the positive electrode active material of a potassium ion battery are hereinafter referred to as lithium ion active material, sodium ion active material, and potassium ion active material, respectively.

[0099] Further, as an example, the lithium ion active material may include at least one of the following materials: lithium phosphates containing olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries can also be used. These positive electrode active materials can be used alone or in combination of two or more. Examples of lithium transition metal oxides may include but are not limited to lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3O2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.80 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of lithium phosphates containing olivine structure may include but are not limited to at least one of lithium iron phosphate (such as LiFePO4, referred to as LFP), lithium manganese phosphate (such as LiMnPO4), and lithium manganese iron phosphate. In any embodiment of the present application, the molecular formula of the lithium ion active material is: LiFe x Mn (1-x) PO4, x is any number from 0 to 1.

[0100] It can be understood that when x is 0, LiFe x Mn (1-x) PO4 is LiMnPO4 lithium manganese phosphate. When x is 1, LiFe x Mn (1-x) PO4 is LiFePO4 lithium iron phosphate (LFP).

[0101] It should be noted that the lithium content in the positive electrode material exemplified above refers to its content when it is not in use. During the use of the battery, it will be repeatedly used as a battery, and the Li in the positive electrode active material will change during the charge and discharge process. That is, the molar subscript of Li in the positive electrode active material in the battery product will not always remain at 1, but will change; further, the range of change can be (0 to 1.2).

[0102] For example, LiFe x Mn (1-x) PO4 can be further expressed as Li y Fe x Mn (1-x) PO4, y is 0~1.1.

[0103] For example, for the ternary material Li y (Ni a Co b Mn c ) 1-d M d O 2-x A x, y is 0.2~1.2, a+b+c=1, 0≤d≤1, 0≤x<2; M is one or more of Zr, Sr, B, Ti, Mg, Sn and Al, and A is one or more of S, N, F, Cl, Br and I.

[0104] The battery is accompanied by Li intercalation and deintercalation and consumption during the charge and discharge process. The molar content of Li varies when the battery is discharged to different states. The above definition of y includes the molar content of Li under different charge and discharge states of the battery. Furthermore, the battery voltage is usually between 2-5V.

[0105] In any embodiment of the present application, in the positive electrode active layer, the mass proportion of the positive electrode active material is 70% to 99.8%.

[0106] In any embodiment of the present application, the components of the positive electrode active layer further include a conductive agent and a binder.

[0107] Taking the electrode sheet as the positive electrode as an example, the conductive agent can be any commonly used conductive agent in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black, and graphene. Specifically, it can be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber (VGCF), carbon nanotubes (CNTs), graphene, and composite conductive agents thereof.

[0108] The binder of the binder can be polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, hydrogenated nitrile rubber, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS) and at least one of fluorine-containing acrylate resin.

[0109] Optionally, in the positive electrode active layer, the conductive agent accounts for 1% to 20% by mass.

[0110] Optionally, in the positive electrode active layer, the binder accounts for 1% to 10% by mass.

[0111] In some embodiments, the thickness of the positive electrode active layer is 30 μm to 200 μm.

[0112] In any embodiment of the present application, the current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material on a polymer substrate.

[0113] In some embodiments, the metal material is selected from any one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

[0114] In some embodiments, the polymer material substrate includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0115] In any embodiment of the present application, a positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing a positive electrode sheet in a solvent to form a positive electrode slurry; applying the positive electrode slurry to a current collector, and performing drying, cold pressing, and other processes to obtain a positive electrode sheet. The positive electrode slurry has a solid content of 40 wt% to 80 wt%, and a viscosity at room temperature adjusted to 5000 mPa·s to 25000 mPa·s. The positive electrode slurry is applied to the surface of the positive electrode current collector, dried, and then cold-pressed on a cold rolling mill to form a positive electrode sheet.

[0116] Further, the solvent includes N-methylpyrrolidone.

[0117] In some embodiments, the surface density of the positive electrode active layer contained in the positive electrode sheet is 0.02 g / cm 2 ~0.08g / cm 2 .

[0118] Area density = mass of positive electrode active layer / area of ​​positive electrode sheet.

[0119] Negative electrode: The negative electrode may be any of the negative electrode systems commonly used in the art for secondary batteries. Examples of the negative electrode include lithium-ion secondary batteries and lithium metal secondary batteries, but are not limited to the following types.

[0120] In some embodiments, the secondary battery is a lithium metal secondary battery, and the negative electrode sheet can be a negative electrode sheet that can be used for a lithium metal battery and is well known in the art.

[0121] In some embodiments, the negative electrode sheet directly adopts a lithium-containing metal sheet.

[0122] In another embodiment, the negative electrode sheet includes a lithium-containing metal layer and a conductive layer stacked together.

[0123] Furthermore, the lithium-containing metal in the lithium-containing metal sheet and the lithium-containing metal layer can be lithium metal, or an alloy formed by lithium metal and other metal or non-metal elements.

[0124] Further, the other metals include at least one of tin (Sn), zinc (Zn), aluminum (Al), magnesium (Mg), silver (Ag), gold (Au), gallium (Ga), indium (In) and platinum (Pt); the non-metallic elements include at least one of boron (B), carbon (C) and silicon (Si).

[0125] In some embodiments, the conductive layer may be copper foil.

[0126] In any embodiment of the present application, the negative electrode sheet can be prepared by directly pressing a lithium-containing metal sheet to obtain the negative electrode sheet, or by stacking and pressing the lithium-containing metal layer and the conductive layer to obtain the negative electrode sheet.

[0127] In some embodiments, the secondary battery is a lithium-ion secondary battery, and the negative electrode sheet can be a negative electrode sheet that can be used for a lithium-ion secondary battery and is well known in the art.

[0128] In some embodiments, the negative electrode sheet includes a current collector and a negative electrode active layer supported on a surface of the current collector.

[0129] The components of the negative electrode active layer include a negative electrode active material.

[0130] The negative electrode active material may be any commonly used negative electrode active material in this application.

[0131] In any embodiment of the present application, the above-mentioned negative electrode active material includes at least one of mesocarbon microbeads, graphite, glassy carbon, carbon nanotubes, carbon-carbon composite materials, carbon fibers, hard carbon, soft carbon, silicon-based materials, tin-based materials, magnesium-based materials and iron-based materials.

[0132] Optionally, specific examples of the above-mentioned negative electrode active materials include, but are not limited to: at least one of mesophase carbon microbeads, natural graphite, artificial graphite, graphene, glassy carbon, carbon nanotubes, carbon fibers, hard carbon, soft carbon, iron oxide, tin oxide, silicon oxide, magnesium oxide, silicon-carbon composites, lithium metal and lithium metal alloys.

[0133] In any embodiment of the present application, the mass proportion of the negative electrode active material in the negative electrode active layer is 70% to 100%.

[0134] In any embodiment of the present application, the components of the negative electrode active layer further include a negative electrode conductive agent and a negative electrode binder.

[0135] In any embodiment of the present application, the negative electrode conductive agent may be a conductive material commonly used in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black, and graphene. Specifically, the negative electrode conductive agent may be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber VGCF, carbon nanotubes CNTs, graphene, and composite conductive agents thereof.

[0136] The weight ratio of the negative electrode conductive agent in the negative electrode active layer is 0 to 20 wt % based on the total weight of the negative electrode active layer.

[0137] The negative electrode binder can be a binder commonly used in the art, and can be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0138] The weight ratio of the negative electrode binder in the negative electrode active layer is 0 to 30 wt % based on the total weight of the negative electrode active layer.

[0139] In any embodiment of the present application, the negative electrode active layer may further optionally include other additives, such as a thickener, such as sodium carboxymethyl cellulose (CMC-Na), etc. Based on the total weight of the negative electrode active layer, the weight ratio of the other additives in the negative electrode active layer is 0 to 15 wt%.

[0140] In any embodiment of the present application, the current collector in the negative electrode sheet may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil.

[0141] The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material on a polymer substrate.

[0142] In some embodiments, the metal material is selected from any one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

[0143] In some embodiments, the polymer material substrate includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0144] In any embodiment of the present application, the negative electrode sheet can be prepared by the following method: the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0145] In some embodiments, the solvent includes but is not limited to water.

[0146] In some embodiments, the solid content of the negative electrode slurry is 30 wt % to 70 wt %, and the viscosity at 25° C. is adjusted to 2000 mPa·s to 10000 mPa·s.

[0147] In some embodiments, the surface density of the negative active layer contained in the negative electrode sheet is 0.005 g / cm 2 ~0.05g / cm 2 .

[0148] Separator: The separator is placed between the positive electrode and the negative electrode.

[0149] The present application has no particular limitation on the type of isolation membrane, and any known isolation membrane with a porous structure having good chemical stability and mechanical stability can be selected.

[0150] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0151] Optionally, the isolation film can be a single-layer film or a multi-layer composite film. Further, when the isolation film is a multi-layer composite film, the materials of each layer can be the same or different.

[0152] In some embodiments, the thickness of the isolation film is 2 μm to 15 μm; optionally, the thickness of the isolation film is 2 μm to 13 μm.

[0153] The secondary battery of the present application may be in a cylindrical, square, or any other shape. For example, FIG1 shows a battery cell 4 of a secondary battery with a square structure as an example.

[0154] In some embodiments, referring to FIG2 , the housing may include a shell 41 and a cover 43. Shell 41 may include a bottom plate and side plates connected to the bottom plate, with the bottom plate and side plates enclosing a receiving cavity. Shell 41 may have an opening communicating with the receiving cavity, and cover 43 may be positioned over the opening to seal the receiving cavity.

[0155] The positive electrode sheet, negative electrode sheet, and separator can be wound or laminated to form an electrode assembly 42. The electrode assembly 42 is enclosed in a housing. Electrolyte is infiltrated into the electrode assembly 42. The number of electrode assemblies 42 included in a battery cell 4 can be one or more, and can be adjusted based on demand.

[0156] The secondary battery includes one or more battery cells 4 .

[0157] A secondary battery can be a battery module or a battery pack. A battery module or battery pack includes at least one battery cell. A battery module can contain one or more battery cells, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0158] Figures 3 and 4 illustrate an exemplary battery pack 1. Battery pack 1 includes a battery case and one or more battery cells 4 disposed within the battery case. The battery case comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for the battery cells 4.

[0159] The plurality of battery cells 4 can be arranged in the battery box in any manner.

[0160] The present application also provides an electrical device, which includes the above-mentioned secondary battery.

[0161] Furthermore, in the above-mentioned electrical device, the secondary battery may exist in the form of a battery cell, or may be further assembled into a battery pack.

[0162] The above-mentioned battery or the battery pack assembled therefrom can be used as a power source for an electrical device, or as an energy storage unit for an electrical device.

[0163] The above-mentioned electrical devices may be, but are not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc.

[0164] Mobile devices include but are not limited to: mobile phones, laptops, etc. Electric vehicles include but are not limited to: pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.

[0165] Figure 5 shows an example of an electric device 5. The electric device 5 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the electric device 5's requirements for high power and high energy density of a secondary battery, a battery pack may be used.

[0166] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a battery cell as a power source.

[0167] The present application will be described below in conjunction with specific embodiments, but the present application is not limited to the following embodiments. It should be understood that the attached claims summarize the scope of the present application. Under the guidance of the concept of the present application, those skilled in the art should realize that certain changes made to the various embodiments of the present application will be covered by the spirit and scope of the claims of the present application.

[0168] The following are specific examples.

[0169] Example 1

[0170] S1. Preparation of lithium-ion batteries

[0171] (1) Preparation of electrolyte: In an argon-filled glove box (water content <10 ppm, oxygen content <1 ppm), the electrolyte salt LiPF6 is added to an organic solvent, wherein the organic solvent is a mixture of ethylene carbonate and dimethyl carbonate, and the mass content of ethylene carbonate is 20 wt% based on the total mass of the organic solvent. After the lithium salt is completely dissolved, the cyclic silicon oxide compound (1b) is added. After stirring, an electrolyte solution having an electrolyte salt concentration of 1.0 mol / L and a cyclic silicon oxide compound mass percentage of 5% is obtained.

[0172] Among them, the mass proportion of the cyclic silicon oxide compound in the electrolyte is recorded as M1, please see Table 1 for details.

[0173] The components and their proportions in the electrolyte can be analyzed using analytical methods commonly used in the art, and non-limiting examples include: quantitative analysis and detection of organic components by gas chromatography to confirm the structure and content of each component in the electrolyte.

[0174] (2) Preparation of negative electrode sheet

[0175] The negative electrode active material natural graphite, conductive carbon black SP, thickener CMC and binder SBR were prepared in a mass ratio of 96:1:1:2 and dispersed in a solvent deionized water and mixed evenly to obtain a negative electrode slurry; the negative electrode slurry was evenly coated on the negative electrode current collector copper foil; the negative electrode active layer was formed after drying and cold pressing, and the negative electrode sheet was obtained after stripping and cutting. The surface density of the negative electrode sheet was 46.67 mg / cm 2 .

[0176] (3) Preparation of positive electrode

[0177] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1O2, conductive carbon black SP and binder PVDF were prepared in a mass ratio of 96:2:2 and dispersed in the solvent NMP (N-methylpyrrolidone) and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on the positive electrode current collector aluminum foil, dried and cold pressed to form a positive electrode active layer, and then cut into strips and sheets to obtain a positive electrode sheet. The surface density of the positive electrode sheet was 73.3 mg / cm 2 .

[0178] (4) Isolation film: Polypropylene film (PP) is used.

[0179] (5) Assembly of lithium-ion batteries: The prepared positive electrode sheet, PP separator, and negative electrode sheet are stacked in order, with the separator placed between the positive electrode and the negative electrode, and wound to obtain a bare cell. After welding the tabs, the cells are placed in an outer package. The prepared electrolyte is injected into the dried cells, and the cells are allowed to stand and undergo formation to obtain a lithium-ion battery.

[0180] S2. Performance test of lithium-ion battery:

[0181] (1) Hot box test:

[0182] The battery cells are first fully charged with 1 / 3C, and temperature sensing wires are arranged on the large surface of the battery cells to monitor the temperature changes of the battery cells during the test. Voltage sensing wires are arranged on the battery poles to monitor the voltage changes of the battery cells during the test. Temperature sensing wires are arranged in the oven to monitor the temperature changes inside the oven. The temperature is raised to 55°C and maintained for 2 hours; the temperature is raised at a rate of 5°C / min, and the temperature is maintained for 30 minutes each time the temperature rises by 5°C, until the battery cells thermally run away or reach 200°C. The thermal runaway temperature is recorded and recorded as T1. If it reaches 200°C, it is kept warm for 3 hours. The experiment is stopped when either of the two conditions occurs.

[0183] Weigh the battery cells before and after the experiment, and calculate the mass loss according to the following formula to assist in evaluating the battery cell hot box performance.

[0184] Mass loss = (m1-m2) / m1×100%, where m1 and m2 are the mass of the battery cell before and after the experiment, respectively.

[0185] (2) Electrochemical window test

[0186] Linear sweep voltammetry (LSV) testing was performed using a CHI660E electrochemical analyzer. The LSV voltammetry curve was obtained by scanning the lithium ion battery prepared above. Specifically, the LSV voltammetry curve was obtained by scanning from the open circuit voltage to 6 V at a scan rate of 0.2 mV / s. The upper limit of the electrochemical window was obtained by analyzing the LSV voltammetry curve, which was denoted as H. The higher the upper limit of the electrochemical window, the higher the stability of the electrolyte and the wider the scope of application.

[0187] Please see Table 1 for specific results.

[0188] Examples 2 to 6

[0189] Examples 2 to 6 are basically the same as Example 1, with the only difference being that in step (1) the preparation of the electrolyte, the type of the cyclic silicon oxide compound is different from that in Example 1.

[0190] The other step conditions are the same as those in Example 1. The test results are shown in Table 1.

[0191] Example 7

[0192] Example 7 is basically the same as Example 1, except that: in the preparation of the electrolyte in step (1), the organic solvent is a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), and based on the total mass of the organic solvent, the mass proportions of ethylene carbonate (EC), dimethyl carbonate (DMC) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) are 20%, 60% and 20%, respectively.

[0193] The other step conditions are the same as those in Example 1. The test results are shown in Table 1.

[0194] Examples 8 to 11

[0195] Examples 8 to 11 are basically the same as Example 7, with the only difference being that in step (1) the preparation of the electrolyte, the type of the cyclic silicon oxide compound is different from that in Example 7.

[0196] The other step conditions are the same as those in Example 7. The test results are shown in Table 1.

[0197] Example 12

[0198] Example 12 is basically the same as Example 7, except that: in step (1) of preparing the electrolyte, the electrolyte salt is a mixed salt of LiPF6 and LiFSI in a mass ratio of 1:1, and the mass proportion of the cyclic silicon oxide compound is 1%.

[0199] The other step conditions are the same as those in Example 7. The test results are shown in Table 1.

[0200] Examples 13 to 16

[0201] Examples 13 to 16 are basically the same as Example 12, with the only difference being that in step (1) the preparation of the electrolyte, the type of the cyclic silicon oxide compound is different from that in Example 7.

[0202] The other step conditions are the same as those in Example 12. The test results are shown in Table 1.

[0203] Example 17

[0204] Example 17 is basically the same as Example 12, except that in step (1) of preparing the electrolyte, the mass proportion of the cyclic silicon oxide compound is 5%.

[0205] The other step conditions are the same as those in Example 12. The test results are shown in Table 1.

[0206] Examples 18 to 21

[0207] Examples 18 to 21 are basically the same as Example 17, with the only difference being that in step (1) the preparation of the electrolyte, the type of cyclic silicon oxide compound is different from that in Example 17.

[0208] The other step conditions are the same as those in Example 17. The test results are shown in Table 1.

[0209] Example 22

[0210] Example 22 is basically the same as Example 12, except that in step (1) of preparing the electrolyte, the mass proportion of the cyclic silicon oxide compound is 8%.

[0211] The other step conditions are the same as those in Example 12. The test results are shown in Table 1.

[0212] Examples 23 to 26

[0213] Examples 23 to 26 are basically the same as Example 22, with the only difference being that in step (1) the preparation of the electrolyte, the type of cyclic silicon oxide compound is different from that in Example 22.

[0214] The other step conditions are the same as those in Example 22. The test results are shown in Table 1.

[0215] Examples 27-28

[0216] Examples 27 to 28 are basically the same as Example 12, with the only difference being that in step (1) the preparation of the electrolyte, the mass proportion of the cyclic silicon oxide compound in Example 27 is 0.5%, and the mass proportion of the cyclic silicon oxide compound in Example 27 is 10%.

[0217] The other step conditions are the same as those in Example 12. The test results are shown in Table 1.

[0218] Comparative Example 1

[0219] Comparative Example 1 is substantially the same as Example 1, except that no cyclic silicon oxide compound is added in the preparation of the electrolyte in step (1).

[0220] The other step conditions are the same as those in Example 1. The test results are shown in Table 1.

[0221] Comparative Example 2

[0222] Comparative Example 2 is basically the same as Example 1, except that: in the preparation of the electrolyte in step (1), no cyclic silicon oxide compound is added, and the organic solvent is a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE). Based on the total mass of the organic solvent, the mass proportions of ethylene carbonate (EC), dimethyl carbonate (DMC) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) are 20%, 60% and 20%, respectively.

[0223] The other step conditions are the same as those in Example 1. The test results are shown in Table 1.

[0224] Comparative Example 3

[0225] Comparative Example 3 is basically the same as Comparative Example 2, except that in step (1) of preparing the electrolyte, the electrolyte salt is a mixed salt of LiPF6 and LiFSI in a mass ratio of 1:1.

[0226] The other step conditions are the same as those in Comparative Example 2. The test results are shown in Table 1.

[0227] Comparative Example 4

[0228] Comparative Example 4 is substantially the same as Example 1, except that in step (1) of preparing the electrolyte, the cyclic silicon oxide compound is of formula (2a).

[0229] The other step conditions are the same as those in Example 1. The test results are shown in Table 1.

[0230] The structures of the cyclic silicon-oxygen compounds used in the examples and comparative examples are shown below:

[0231] The main parameters and test results of each embodiment and comparative example are shown in Table 1.

[0232] Table 1

[0233] Wherein, “ / ” represents that the substance or parameter does not exist.

[0234] By analyzing the data in Table 1, comparing the test results of Examples 1 to 28 with those of Comparative Examples 1 to 4, and further comparing and analyzing Examples 1 to 6, it can be seen that the electrolyte of the present application can increase the critical point of thermal runaway while widening the electrochemical window. When used in the preparation of secondary batteries, it can increase the thermal runaway trigger temperature of the secondary battery, delay the occurrence of thermal runaway, and widen the electrochemical window.

[0235] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0236] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art could make several modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the patent in this application shall be based on the appended claims, and the specification and drawings may be used to interpret the claims.

Claims

1. An electrolyte, wherein The components of the electrolyte include a cyclic silicon-oxygen compound represented by formula (1): wherein each R1 and each R2 are independently selected from H, halogen, substituted or unsubstituted aryl having 6 to 10 ring atoms, alkyl having 1 to 10 carbon atoms, alkyl having 1 to 10 carbon atoms substituted by halogen, and any one of the following, and at least one R1 or at least one R2 in the multiple repeating units of the cyclic silicon-oxygen compound is selected from a substituted or unsubstituted aromatic group having 6 to 10 ring atoms or R3 is selected from any one of an alkylene group having 1 to 5 carbon atoms and an alkylene group having 1 to 5 carbon atoms substituted by halogen; R4 and R5 are independently selected from any one of H, an alkoxy group having 1 to 10 carbon atoms and an alkoxy group having 1 to 10 carbon atoms substituted by halogen, and R4 and R5 are not H at the same time; "*" represents the connection site, It represents that the atoms at both ends are connected to form a ring, and n is any integer from 3 to 5.

2. The electrolyte according to claim 1, wherein The halogen includes at least one of F and Br.

3. The electrolyte according to any one of claims 1 to 2, wherein R4 and R5 are each independently selected from an alkoxy group having 1 to 5 carbon atoms and an alkoxy group having 1 to 5 carbon atoms substituted with halogen.

4. The electrolyte according to any one of claims 1 to 3, wherein R4 and R5 are each independently selected from an alkoxy group having 1 to 3 carbon atoms and an alkoxy group having 1 to 3 carbon atoms substituted with halogen.

5. The electrolyte according to any one of claims 1 to 4, wherein The cyclic silicon-oxygen compound comprises at least one of the following formulas (1b) and (1d):

6. The electrolyte according to any one of claims 1 to 5, wherein In the electrolyte, the mass proportion of the cyclic silicon oxide compound is 0.1% to 10%.

7. The electrolyte according to any one of claims 1 to 6, wherein In the electrolyte, the mass proportion of the cyclic silicon oxide compound is 3% to 6%.

8. The electrolyte according to any one of claims 1 to 7, wherein The components of the electrolyte solution further include an electrolyte salt and an organic solvent.

9. The electrolyte according to claim 8, wherein The electrolyte salt satisfies at least one of the following conditions (1) to (2): (1) In the electrolyte, the concentration of the electrolyte salt is 0.8 mol / L to 1.2 mol / L; (2) The electrolyte salt includes at least one of LiPF6, LiBF4, LiAsF6, LiBOB, LiDFOB, LiN(CF3SO2)2 and lithium bis(fluorosulfonyl imide).

10. The electrolyte according to any one of claims 8 to 9, wherein The organic solvent includes at least one of a carbonate solvent, a carboxylic acid solvent, an ether solvent, a nitrile solvent and a phosphazene solvent.

11. The electrolyte according to any one of claims 8 to 10, wherein The organic solvent includes carbonate solvents, carboxylic acid solvents and fluorine-containing ether solvents.

12. The electrolyte according to claim 11, wherein The mass ratio of the carbonate solvent, the carboxylic acid solvent and the fluorinated ether solvent is (1-3):(2-8):(1-3).

13. A secondary battery, wherein: The secondary battery comprises the electrolyte according to any one of claims 1 to 12.

14. An electrical device, wherein: The electric device comprises the secondary battery as claimed in claim 13.

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