CN117577945A - Electrolyte and secondary battery - Google Patents

Electrolyte and secondary battery Download PDF

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Publication number
CN117577945A
CN117577945A CN202410062204.1A CN202410062204A CN117577945A CN 117577945 A CN117577945 A CN 117577945A CN 202410062204 A CN202410062204 A CN 202410062204A CN 117577945 A CN117577945 A CN 117577945A
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China
Prior art keywords
silicon
compound
electrolyte
crown ether
substituent
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CN202410062204.1A
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Chinese (zh)
Inventor
王禹淳
王瀚森
钟韡
张儒鹏
冯富祥
万攀
黄圣源
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to CN202410062204.1A priority Critical patent/CN117577945A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

An electrolyte and a secondary battery are disclosed. The electrolyte comprises an active ion salt, a solvent and at least one silicon hybridization crown ether; the silicon-hybrid crown ether is a crown ether in which at least 1 carbon atom on the ring is replaced by a silicon atom, wherein each carbon atom in the silicon-hybrid crown ether has a substituent R, and/or each silicon atom has a substituent R ', wherein the substituent R is selected from at least one of hydrogen, phenyl, phenoxy, C1-C6 haloalkyl, C1-C6 haloalkoxy, halophenyl, and halophenoxy, and the substituent R' is selected from at least one of hydrogen and C1-C6 alkyl, and wherein the substituent R that at least one carbon atom on the silicon-hybrid crown ether ring has is not hydrogen. The secondary battery using the electrolyte has improved cycle life.

Description

Electrolyte and secondary battery
Technical Field
The present application relates to the field of batteries, and in particular, to an electrolyte and a secondary battery.
Background
The secondary battery (rechargeable battery) is also called a rechargeable battery, and is a battery that can be continuously used by charging after discharging. In general, a secondary battery may include a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. Active ions in the electrolyte can pass through the isolating film to be embedded and separated back and forth between the positive electrode plate and the negative electrode plate, so that the secondary battery is charged and discharged.
In recent years, as the application range of secondary batteries has become wider, higher demands have been made on the cycle life of secondary batteries and the like. In the formation process of the secondary battery, a passivation layer, i.e., an SEI film, is generally formed on the surface of the negative electrode film layer. The ideal SEI film is compact and stable, can inhibit side reactions between electrode active substances and electrolyte, reduces consumption of the active substances and the electrolyte in the use process, and inhibits formation of lithium dendrites, thereby being beneficial to improving the cycle performance of the secondary battery. Therefore, forming an ideal SEI film is one direction of improvement of secondary batteries.
Disclosure of Invention
The present application has been made in view of the above problems, and an object thereof is to provide an electrolyte solution and a secondary battery including the same. The electrolyte contains the silicon hybridization crown ether, can participate in the formation of an SEI film, and improves the toughness of the SEI film, thereby improving the cycle performance of the secondary battery.
In order to achieve the above object, the present application provides an electrolyte comprising a reactive ion salt, a solvent and at least one silicon hybrid crown ether; the silicon-hybrid crown ether is a crown ether in which at least 1 carbon atom on the ring is replaced by a silicon atom, wherein each carbon atom in the silicon-hybrid crown ether has a substituent R, and/or each silicon atom has a substituent R ', wherein the substituent R is selected from at least one of hydrogen, phenyl, phenoxy, C1-C6 haloalkyl, C1-C6 haloalkoxy, halophenyl and halophenoxy, and the substituent R' is selected from at least one of hydrogen and C1-C6 alkyl, and wherein the substituent R that at least one carbon atom on the silicon-hybrid crown ether ring has is not hydrogen.
Silicon hybrid crown ethers contained in the electrolyte of the present application. The silicon hybridization crown ether and the active ions have enhanced coordination effect, and a polymer obtained by ring-opening polymerization reaction of the silicon hybridization crown ether on the surface of the negative electrode plate can be deposited in the SEI film, so that the toughness of the SEI film is improved. The stability of the silicon hybridization crown ether is improved.
The secondary battery using the electrolyte has improved cycle life, and in addition, the substituent R can further improve the cycle life of the secondary battery.
In some embodiments, the silicon hybrid crown ether is a 12 crown 4 ether to 24 crown 8 ether in which at least one pair of carbon atoms bonded to each other on the ring is replaced by a silicon atom.
In some embodiments, the silicon hybrid crown ether is a 12 crown 4 ether to 24 crown 8 ether in which one or two pairs of carbon atoms bonded to each other on the ring are replaced by silicon atoms. The ring space of the silicon hybridization crown ether is matched with the diameter of the active ion, so that the silicon hybridization crown ether has strong complexing capability with the active ion.
In some embodiments, the substituent R is selected from at least one of hydrogen, phenyl, phenoxy, C1-C4 thioalkoxy, C1-C4 haloalkoxy, halophenyl, and halophenoxy, and the substituent R' is selected from at least one of hydrogen and C1-C4 alkyl.
In some embodiments, the substituent R is selected from at least one of hydrogen, C1-C4 haloalkyl and C1-C4 haloalkoxy, wherein halogen is fluorine and/or chlorine, and the substituent R' is methyl and/or ethyl.
In some embodiments, the substituent R is selected from at least one of hydrogen, C1-C4 haloalkyl, wherein halogen is F, and the substituent R' is methyl.
In some embodiments, at least one non-alpha carbon atom of the silicon-hybrid crown ether is substituted with a substituent R comprising at least one fluorine atom, wherein the non-alpha carbon atom is a carbon atom on the ring of the silicon-hybrid crown ether that is not attached to an oxygen atom of a silicon-oxygen bond. When the substituent R of the fluorine atom replaces the non-alpha carbon atom, the substituent R of the fluorine atom has a larger distance from the oxygen atom in the space of the molecular structure, the oxygen atom can have more electronegativity, and the coordination effect of the silicon hybridization crown ether and the active ions is further enhanced.
In some embodiments, the silicon-hybridized crown ether is selected from compounds of the following general formula I-general formula XVI:
general formula I, (-)>General formula II,
General formula III>General formula IV,
General formula V, (-)>General formula VI,
Formula VII, (-)>General formula VIII,
General formula IX, & lt ]>A general formula X,
General formula XI, & lt + & gt>General formula XII,
Formula XIII, < >>Of the general formula XIV,
General formula XV, & lt + & gt>General formula XVI.
In some embodiments, the silicon-hybridized crown ether is selected from compounds represented by the following structural formula:
compound a,/->Compound b,/->A compound c,
Compound d, < >>A compound e,
Compound f, < >>A compound g,
Compound h,/-, and>a compound i,
Compound j, < >>Compound k,
Compound i,/->A compound m,
Compound n, < >>A compound o,
Compound p,/->A compound q,
Compound r,/->A compound s,
A compound t; silicon hybrid crown ethers selected from the above compounds, -CF 3 Attached to non-carbon atomsOn the son, the silicon hybridization crown ether has strong complexing ability with active ions.
In some embodiments, the silicon hybrid crown ether is added in an amount of 0.5wt% to 15wt% based on the total weight of the electrolyte. When the addition amount of the silicon hybrid crown ether is within the above range, ring-opening polymerization can occur at the anode surface in an appropriate amount at the formation stage and deposit into the SEI film. When the addition amount of the silicon hybrid crown ether is within the above range, the remaining silicon hybrid crown ether is not ring-opening polymerized at the anode but is complexed with the active ions in a sufficient amount to increase the migration number of the active ions, since the active substances in the anode can be prevented from continuing to react with the electrolyte after the SEI film is formed on the surface of the anode.
In some embodiments, the active ion salt is selected from a lithium salt or a sodium salt.
In some embodiments, the lithium salt is selected from at least one of lithium bis (fluorosulfonyl) imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis (trifluoromethanesulfonyl) imide, lithium trifluoromethanesulfonate, lithium difluorophosphate.
In some embodiments, the sodium salt is selected from at least one of sodium difluorosulfonimide, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium bis (trifluoromethylsulfonyl) imide, sodium trifluoromethylsulfonate, sodium difluorophosphate, sodium difluorooxalato borate, sodium tetrafluorooxalato phosphate.
In some embodiments, the concentration of the active ion salt in the electrolyte is 0.5mol/L to 4mol/L.
In some embodiments, the solvent includes at least one selected from the group consisting of an ester solvent, an ether solvent, a siloxane solvent, a phosphate solvent, a sulfone solvent, and a nitrile solvent; alternatively, the solvent includes at least one of ethylene carbonate, ethylmethyl carbonate, fluoroethylene carbonate, difluoroethylene carbonate, diethyl carbonate, methyltrifluoroethyl carbonate, dimethyl carbonate, dimethoxyethane, 1, 2-dimethoxypropane, 1, 3-dimethoxypropane, dimethoxybutane, diethoxyethane, 1, 2-diethoxypropane, 1, 3-diethoxypropane, tetrahydrofuran, 1, 3-epoxypentane, dimethoxydimethylsilane, methoxytrimethylsilane, trimethoxymethylsilane, tetramethoxysilane, methyl phosphate, methylene triphosphate, ethyl triphosphate, ethylene triphosphate, acetonitrile and dimethyl sulfoxide; further alternatively, the solvent comprises at least one of dimethoxyethane, 1, 2-dimethoxypropane, 1, 3-dimethoxypropane, dimethoxybutane, diethoxyethane, 1, 2-diethoxypropane, 1, 3-diethoxypropane, tetrahydrofuran, and 1, 3-pentaoxide; still further alternatively, the solvent comprises dimethoxyethane and/or diethoxyethane. The solvent selected from the above can improve ion conductivity of the electrolyte, and the solvating layer of the electrolyte can contain enough anions (fluoride ions), which is advantageous for increasing the content of inorganic substances such as LiF in the SEI film and for improving the cycle performance of the battery.
A second aspect of the present application provides a battery cell comprising a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte provided in the first aspect, the negative electrode sheet comprising a negative electrode material.
In some embodiments, the negative electrode material comprises metallic lithium and/or a lithium alloy.
A third aspect of the present application provides a secondary battery comprising the battery cell provided in the second aspect.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the application. Also, like reference numerals are used to designate like parts throughout the figures. In the drawings:
FIG. 1 is a schematic illustration of a battery cell according to an embodiment of the present application;
fig. 2 is an exploded view of a battery cell according to an embodiment of the present application shown in fig. 1;
FIG. 3 is a schematic view of a battery module according to an embodiment of the present application;
FIG. 4 is a schematic view of a battery pack according to an embodiment of the present application;
FIG. 5 is an exploded view of the battery pack of one embodiment of the present application shown in FIG. 4;
fig. 6 is a schematic view of an electric device in which the secondary battery according to an embodiment of the present application is used as a power source.
Reference numerals illustrate:
1, a battery pack; 2, upper box body; 3, lower box body; 4, a battery module; 5, a battery cell; 51 a housing; 52 electrode assembly; 53 top cap assembly.
Detailed Description
Hereinafter, embodiments of the electrolyte and the secondary battery of the present application are specifically disclosed with reference to the accompanying drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter described in the present application.
The "range" disclosed herein is defined in terms of lower and upper limits, with a given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.
All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, unless specifically stated otherwise. All technical features and optional technical features of the present application may be combined with each other to form new technical solutions, unless specified otherwise.
Unless specifically stated otherwise, terms used in the present application have well-known meanings commonly understood by those skilled in the art.
The values of the parameters mentioned in the examples of the present application may be determined by various test methods commonly used in the art, for example, according to the test methods given in the examples of the present application, unless otherwise specified.
In the embodiments of the present application, the term "active ion" refers to an ion capable of being inserted and extracted back and forth between the positive electrode and the negative electrode of the secondary battery, including, but not limited to: lithium ion, sodium ion.
A lithium metal battery is a typical secondary battery, and a current collector surface of a negative electrode thereof has a metal layer containing lithium metal. The metal lithium has extremely high theoretical specific capacity (3860 mAh/g) and lowest reduction potential (-3.04 Vvs. standard hydrogen electrode), so that the metal lithium battery has extremely high energy density. Accordingly, lithium metal batteries may be used as a battery for some flying devices (e.g., unmanned aerial vehicles).
In general, the surface of metallic lithium inevitably introduces defects (e.g., protrusions, depressions) that have high electric field strength, and in addition, the metal bond energy between Li atoms inside metallic lithium is low, so Li ions are more likely to deposit at the protrusions, forming lithium dendrites. The presence of lithium dendrites can reduce the cycling performance of the battery. Other secondary batteries, such as lithium ion batteries, also suffer from reduced battery cycle performance due to lithium dendrites.
Generally, in a formation process of a secondary battery, a negative electrode (e.g., metallic lithium, or carbon-based material) is reacted with an electrolyte to form a solid electrolyte interface (Solid Electrolyte Interface, SEI) film on the surface of the negative electrode. The ideal SEI film is compact, flat and flexible, and can block the further reaction between the anode active material and the electrolyte, thereby inhibiting the formation of lithium dendrite to a certain extent and prolonging the cycle life of the secondary battery.
For this reason, attempts have been made to add crown ethers to the electrolyte of secondary batteries, which can suppress the formation of lithium dendrites to some extent. The crown ether and the active ions (usually lithium ions) have stronger coordination effect, the volume of a complex structure formed by the crown ether and the active ions is larger, the steric hindrance is larger on the surface of the negative electrode, and the tip growth advantage of lithium dendrites at the high electric field intensity of the surface of the negative electrode can be weakened, so that the formation of the lithium dendrites is inhibited. In addition, the crown ether can induce the lithium ion to be deposited smoothly, which is favorable for forming a smooth SEI film. In addition, the crown ether can be matched with the active ions, so that the migration number and the solubility of the active ions can be improved, the conductivity of the electrolyte is improved, the cathode efficiency is improved, and the secondary battery has better cycle performance under a large multiplying power.
But the crown ether has higher molecular orbital energy level, weaker oxidation resistance and poor stability. It has been proposed to introduce groups with electron withdrawing capability, such as F atoms, into the crown ether molecule to reduce the molecular orbital energy level and improve the stability of crown ether. However, the coordination ability of the crown ether derivative with the active ions is reduced, and the regulation and control effect on the deposition of the active ions is weakened, which is unfavorable for forming an ideal SEI film. To compensate for this, it has been proposed to use a fluorine-containing lithium salt in the electrolyte, thereby increasing the content of LiF in the SEI film to improve the stability of the SEI film. However, the SEI film having a high inorganic content (e.g., liF) is not sufficiently tough, and the volume is easily changed during the charge and discharge of the battery, resulting in rupture of the SEI film. This not only results in further consumption of active materials and electrolytes of the battery to form a new SEI film, but also affects the cycle performance of the secondary battery.
Based on this, the first aspect of the present application provides an electrolyte. The electrolyte comprises: a reactive ion salt, a solvent, and at least one silicon hybrid crown ether. The silicon-hybrid crown ether is a crown ether in which at least 1 carbon atom on the ring is replaced by a silicon atom, wherein each carbon atom in the silicon-hybrid crown ether has a substituent R, and/or each silicon atom has a substituent R ', wherein the substituent R is selected from at least one of hydrogen, phenyl, phenoxy, C1-C6 haloalkyl, C1-C6 haloalkoxy, halophenyl and halophenoxy, and the substituent R' is selected from at least one of hydrogen and C1-C6 alkyl, and wherein the substituent R that at least one carbon atom on the silicon-hybrid crown ether ring has is not hydrogen.
Compared with crown ether, particularly compared with crown ether containing electron-withdrawing substituent, the silicon hybridization crown ether contained in the electrolyte disclosed by the embodiment of the application has enhanced coordination effect with active ions, can improve the migration number and solubility of the active ions, and improves the conductivity of the electrolyte, thereby being beneficial to the cycle performance under high multiplying power. The enhanced coordination can regulate and control the smooth deposition of active ions, and is beneficial to forming a smooth and compact SEI film.
The silicon hybrid crown ether related to the embodiment of the application is crown ether in which at least one carbon atom (C) on a ring is replaced by a silicon atom (Si). Si has weaker electronegativity than C, and the introduction of Si allows oxygen atoms (O) adjacent to Si to take on more electronegativity. Thus, the incorporation of Si can enhance the complexation of the silicon hybrid crown ether with the active ions.
In addition, unexpectedly, the cooperation of the silicon hybridization crown ether and the promotion of the active ions enables the electrode potential of the metal negative electrode to carry out negative shift, and the ring-opening reaction (reduction reaction) of the silicon-oxygen bond (Si-O) existing on the ring of the silicon hybridization crown ether is easier to occur on the negative electrode with enhanced electronegativity, so that when the potential reaches a certain threshold value in the formation process of the battery, the silicon hybridization crown ether molecules complexed with the active ions carry out ring-opening polymerization reaction on the surface of the negative electrode plate under the catalysis of Lewis acid (such as anions of active ion salts) to obtain the polymer. The polymer and lithium compound (such as LiF) are jointly deposited on the surface of the anode to form an SEI film, so that the toughness of the SEI film is improved, and the stability of the SEI film in the charge and discharge process of the secondary battery is further improved.
Furthermore, silicon hybrid crown ethers are also capable of forming a bulky complex structure with active ions, in particular lithium ions. The complexing structure has larger steric hindrance on the surface of the negative electrode plate, and can weaken the tip growth advantage of lithium dendrites at the high electric field intensity position on the surface of the negative electrode plate, thereby inhibiting the formation of dendrites (lithium dendrites and sodium dendrites).
The secondary battery using the electrolyte thus has an improved cycle life, and in addition, the substituent R can further improve the cycle life of the secondary battery.
In some embodiments, the silicon-hybridized crown ether is a 12-crown 4 ether to 24-crown 8 ether in which at least one carbon atom on the ring is replaced with a silicon atom (silicon hybridization). As an example, silicon hybrid crown ethers may include, but are not limited to: silicon-hybridized 12 crown 4 ether, silicon-hybridized 15 crown 5 ether, silicon-hybridized 18 crown 6 ether, silicon-hybridized 21 crown 7 ether, silicon-hybridized 24 crown 8 ether. The ring space and the active ion (such as Li) + Or Na (or) + ) And thus have a strong complexing ability with active ions.
In some embodiments, the silicon hybrid crown ether is a 12 crown 4 ether to 24 crown 8 ether in which at least one pair of carbon atoms bonded to each other on the ring are replaced with silicon atoms. At least one pair of carbon atoms bonded to each other on the silicon hybrid crown ether ring is replaced by silicon atoms, i.e. there is at least one (two) pair of silicon atoms bonded to each other on the silicon hybrid crown ether ring. At least two silicon atoms can greatly improve the coordination of the silicon hybridization crown ether and the active ions. The larger the number of silicon atoms, the stronger the coordination with the active ions, and the more silicon-containing polymer is advantageous for improving the toughness of the SEI film. The silicon hybridization crown ether is applied to the electrolyte, so that the migration number and the solubility of active ions in the electrolyte can be further improved, the conductivity of the electrolyte is improved, and the electrolyte is facilitated to form a smooth and compact SEI film. The cycle life of a secondary battery using the electrolyte is further improved.
According to specific embodiments, the silicon hybrid crown ether is 12 crown 4 ether-24 crown 8 ether with a pair of carbon atoms bonded with each other on the ring or two pairs of carbon atoms replaced by silicon atoms. Wherein, the silicon hybridization crown ether containing two pairs of silicon atoms bonded with each other has a further enhanced coordination function with the active ions, so that the cycle life of the secondary battery can be further improved.
In some embodiments, each carbon atom in the above-described silicon-hybridized crown ether has a substituent R, wherein the substituent R is selected from at least one of hydrogen, phenyl, phenoxy, C1-C6 haloalkyl, C1-C6 haloalkoxy, halophenyl, and halophenoxy, wherein the substituent R of at least one carbon atom on the silicon-hybridized crown ether ring is not hydrogen.
The term "alkyl" as referred to herein, unless otherwise indicated, wherein the carbon chain is linear or branched.
Illustratively, the C1-C6 alkyl groups are selected from: methyl, ethyl, propyl, butyl, pentyl, hexyl.
The halogen atom in the C1-C6 haloalkyl, C1-C6 haloalkoxy, halophenyl and halophenoxy may be selected from F, cl, br, especially F. Halogen-containing substituents can introduce electron withdrawing groups into the silicon-hybridized crown ether, increasing the oxidation resistance of the compound. Particularly contains fluorine substituent groups, which is more beneficial to the stability of molecules and can also increase the flame retardance of electrolyte. The number of halogen atoms in the substituents in the examples is not particularly limited. In some embodiments, the haloalkyl group may contain one halogen atom, such as a fluorine atom, or may contain multiple halogen atoms, such as 2, 3, etc.
In some embodiments, the substituent R is selected from at least one of hydrogen, phenyl, phenoxy, C1-C4 haloalkyl, C1-C4 haloalkoxy, halophenyl, and halophenoxy, and the substituent R' is selected from C1-C4 alkyl; optionally, the substituent R is selected from at least one of hydrogen, C1-C4 haloalkyl and C1-C4 haloalkoxy, wherein halogen is fluorine and/or chlorine, and the substituent R' is methyl and/or ethyl; further alternatively, the substituent R is selected from at least one of hydrogen, C1-C4 haloalkyl, wherein halogen is F, and the substituent R' is methyl. Particularly, the halogen of the haloalkyl is F, so that the LiF content in the SEI film can be improved, and the cycle performance of the battery can be improved.
In some embodiments, the substituent R contains 1 to 4 halogen atoms, particularly F atoms. According to a more specific embodiment, all substitutable sites of substituent R are substituted with halogen atoms, in particular fluorine atoms. The substituent containing at least one halogen atom can reduce the molecular orbital energy level and improve the stability of the silicon hybridization crown ether. In addition, fluorine atoms have certain flame retardant property, so that the safety performance of the silicon hybrid crown ether can be improved.
At least one substituent R of the halogen atom being a C1-C4 haloalkyl radical, as exemplified by-CH 2 F、-CH 2 CH 2 F、-CH 2 CH 2 CH 2 F、-CH 2 CH 2 CH 2 CH 2 F、-CH 2 Cl、-CH 2 CH 2 Cl、-CH 2 CH 2 CH 2 Cl、-CH 2 CH 2 CH 2 CH 2 Cl、-CHF2、-CF 3 、-CH 2 CHF 2 、-CH 2 CF 3 、-CH 2 CH 2 CHF 2 、-CH 2 CH 2 CF 3 Etc., but is not limited thereto. preferably-CF 3 、-CH 2 CF 3 Etc.
In some embodiments, at least one non-alpha carbon atom of the silicon hybrid crown ether is substituted with a substituent R comprising at least one fluorine atom. The non-alpha carbon atoms are carbon atoms on the silicon hybrid crown ether ring that are not attached to an oxygen atom in the siloxane bond. In this embodiment, the substituent R of the fluorine atom has a larger distance from the oxygen atom in the space of the molecular structure, and the oxygen atom has more electronegativity, so that the coordination between the silicon hybrid crown ether and the active ion is further enhanced, as compared with the embodiment in which the substituent R of the fluorine atom replaces the α carbon atom.
In some embodiments, each silicon atom in the silicon hybrid crown ether described above has a substituent R' selected from at least one of hydrogen and C1-C6 alkyl. C1-C6 alkyl as R' substituent is as exemplified above.
In some embodiments, the substituent R' is selected from at least one of hydrogen, C1-C4 alkyl. Specifically, the substituent R' is methyl or ethyl. More specifically, each silicon atom in the silicon hybrid crown ether is substituted with two C1-C4 alkyl groups, particularly methyl groups. And when the substituent R' is methyl or ethyl, excessive steric hindrance is not brought, and the coordination and migration of the silicon hybridization crown ether and the active particles are more facilitated.
In some embodiments, the silicon hybrid crown ether is selected from compounds represented by the following formulas I-XVI:
general formula I, (-)>General formula II,
General formula III>General formula IV,
General formula V, (-)>General formula VI,
Formula VII, (-)>General formula VIII,
General formula IX, & lt ]>General formula X, (-) ->
General formula XI, & lt + & gt>General formula XII,
Formula XIII, < >>Of the general formula XIV,
General formula XV, & lt + & gt>General formula XVI.
In the silicon hybrid crown ethers of the general formula I-XVI, the substituents R and R' are as defined in the previous embodiments.
In some embodiments, silicon hybrid crown ethers having a pair of-Si-groups on the ring are easier to prepare, relatively higher yields, lower costs, and easy to industrialize.
In some embodiments, the silicon hybrid crown ether ring has 4 or 6 oxygen atoms thereon. Such hybrid crown ethers have a good complexation with active ions, in particular lithium ions, and the ring space is adapted to the lithium ions.
In some embodiments, preferred are silicon hybrid crown ethers having two pairs of-Si-groups on the ring, which compounds interact more strongly with active ions than silicon hybrid crown ethers having one pair of-Si-groups on the ring, thereby facilitating even deposition of active ions in the SEI film and migration of active ions.
In some embodiments, preferred are silicon-hybrid crown ethers having fluoro substituents, particularly on carbon atoms other than alpha. The silicon hybridization crown ether has better stability and better complexation capability with active ions. In some embodiments, the silicon-hybridized crown ether is selected from compounds represented by the following structural formula:
compound a,/->Compound b,/->A compound c,
Compound d, < >>A compound e,
Compound f, < >>A compound g,
Compound h,/-, and>a compound i,
Compound j, < >>Compound k,
Compound i,/->Compound m,/->
Compound n, < >>A compound o,
Compound p,/->A compound q,
Compound r,/->A compound s,
Compound t.
In some embodiments, the silicon hybrid crown ether is selected from among compound c, compound d, compound g, compound i, compound j, compound k, compound m, compound n, compound o, among others. The stability, the coordination with lithium ions and the ring-opening deposition of the compound g are obviously improved compared with the corresponding non-silicon hybridized crown ether, and the compound g is easy to prepare and has better industrialization prospect. In addition, compounds c, d, i, j, k, m, n, o each have two pairs of-Si-groups and have-CF attached to a non-alpha carbon atom 3 The silicon hybridization crown ether has good stability and strong complexing capacity with active ions, and can provide high-rate cycle performance. In addition, the existence of two pairs of silicon atoms is more beneficial to ring-opening polymerization reaction, so that the toughness of the SEI film is improved, and the cycle performance of the secondary battery is further improved.
In some embodiments, the silicon hybrid crown ether is added in an amount of 0.5wt% to 15wt% based on the total weight of the electrolyte. Optionally 1-10 wt%, and the addition amount of the silicon hybridization crown ether is as follows: 0.5wt%, 0.8wt%, 1.0wt%, 1.2wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, 2wt%, 2.1wt%, 2.2wt%, 2.3wt%, 2.4wt%, 2.5wt%, 2.6wt%, 2.7wt%, 2.8wt%, 2.9wt%, 3wt%, 5wt%, 7wt%, 10wt%, 15wt%, or a value between any two values. When the addition amount of the silicon hybrid crown ether is within the above range, ring-opening polymerization can occur at the anode surface in an appropriate amount at the formation stage and deposit into the SEI film. When the addition amount of the silicon hybrid crown ether is within the above range, the remaining silicon hybrid crown ether is not ring-opening polymerized at the anode but is complexed with the active ions in a sufficient amount to increase the migration number of the active ions, since the active substances in the anode can be prevented from continuing to react with the electrolyte after the SEI film is formed on the surface of the anode.
The secondary battery is accompanied by the consumption of the silicon hybrid crown ether in the formation process. The addition amount of the silicon hybrid crown ether listed in the examples of the present application is the addition amount of the silicon hybrid crown ether in the electrolyte in the initial state. The electrolyte is used in a battery system, and after formation, the addition amount of the silicon hybridization crown ether in the electrolyte can be changed.
The silicon hybrid crown ethers described above can be prepared using conventional methods. For example, the preparation can be as follows: dissolving silicane substances and alcohol substances in an organic solvent such as Tetrahydrofuran (THF), heating under alkaline condition, and performing cyclization reaction to obtain the silicon hybridization crown ether. Wherein, the silane substances and the alcohol substances are determined by the structure of the silicon hybridization crown ether. As the silane-based material, there may be mentioned, but not limited to: 1, 2-dichloro-tetramethyl disilane, 1, 2-dihydroxy-tetramethyl disilane. Alcohols include, but are not limited to: 2-chloroethanol, triethylene glycol, ethylene glycol,Etc.
Illustratively, taking the preparation of compound c as an example, the preparation of compound c comprises steps 1 and 2.
Step 1: and (3) carrying out substitution reaction on the silane substance and hydrochloric acid (HCl) to obtain an intermediate product.
The reaction equation of step 1 is as follows:
Step 2: and (2) dissolving the intermediate product obtained in the step (1) and an alcohol substance in tetrahydrofuran, and reacting at the temperature of 15-18 ℃ in the environment of 150-180 ℃ and 40wt% of KOH to obtain a compound c.
The reaction equation of step 2 is as follows:
the above-described silicon hybrid crown ethers herein can be synthesized in a similar manner using the corresponding starting materials.
Active ion salt:
the active ion salts referred to in the embodiments of the present application are used to provide sufficient conductivity to the electrolyte and to provide active ions, wherein the active ions are lithium ions or sodium ions. The active ion salt is selected from lithium salt or sodium salt.
The embodiment of the present application is not particularly limited, and any salt that can provide lithium ions may be used as the lithium salt in the embodiment of the present application. The lithium salt is at least one selected from lithium difluorosulfimide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bistrifluoromethanesulfonimide, lithium trifluoromethanesulfonate, and lithium difluorophosphate. The lithium salt is selected in particular from lithium bis (fluorosulfonyl) imide and/or lithium bis (trifluoromethanesulfonyl) imide.
The active ion salt contains fluorine, and the fluorine in the active ion salt can be combined with active ions to generate LiF and NaF, and the LiF and the NaF are deposited in the SEI film, so that the content of LiF in the SEI film is improved. The contents of LiF and NaF in the SEI film are improved, which is beneficial to the improvement of the stability of the SEI film. In some embodiments, the sodium salt is selected from at least one of sodium bis (fluorosulfonyl) imide, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium bis (trifluoromethylsulfonyl) imide, sodium trifluoromethylsulfonate, sodium difluorophosphate, sodium difluorooxalato borate, sodium tetrafluorooxalato phosphate. The sodium salt is selected in particular from sodium bis (trifluoromethylsulfonyl) imide and/or sodium bis (trifluoromethylsulfonyl) imide.
The concentration of the active ion salt in the examples of the present application is not particularly limited. In some embodiments, the concentration of the active ion salt is from 0.5mol/L to 4mol/L. The concentration of the active ion salts (e.g., lithium salts) can be exemplified by: values of 0.5mol/L, 1mol/L, 1.0mol/L, 1.5mol/L, 2mol/L, 2.5mol/L, 3mol/L, 3.5mol/L, 4mol/L, etc., or ranges between any two values, are not limited thereto.
The secondary battery may have different molar contents of active ions when discharged to different states, due to the deintercalation and consumption of active ions during the charge and discharge of the battery. The active ion salt concentrations listed in the examples herein are those of the initial state electrolyte. The electrolyte is applied to a battery system, and the concentration of active ion salt of the electrolyte can be changed after charge and discharge cycles.
Solvent:
the kind of the solvent is not particularly limited in the examples of the present application. Illustratively, the solvent includes at least one of an ester solvent, an ether solvent, a siloxane-based solvent, a phosphate-based solvent, a sulfone-based solvent, and a nitrile-based solvent. The solvent can regulate the solvation structure of the electrolyte, and is favorable for maintaining excellent ionic conductivity of the electrolyte. As the solvent, there may be mentioned at least one of ethylene carbonate, ethylmethyl carbonate, fluoroethylene carbonate, difluoroethylene carbonate, diethyl carbonate, methyltrifluoroethyl carbonate, dimethyl carbonate, dimethoxyethane, 1, 2-dimethoxypropane, 1, 3-dimethoxypropane, dimethoxybutane, diethoxyethane, 1, 2-diethoxypropane, 1, 3-diethoxypropane, tetrahydrofuran, 1, 3-epoxypentane, dimethoxydimethylsilane, methoxytrimethylsilane, trimethoxymethylsilane, tetramethoxysilane, methyl phosphate, methylene triphosphate, ethyl triphosphate, ethylene triphosphate, acetonitrile and dimethyl sulfoxide.
In some embodiments, the solvent comprises or is selected from at least one of dimethoxyethane, 1, 2-dimethoxypropane, 1, 3-dimethoxypropane, dimethoxybutane, diethoxyethane, 1, 2-diethoxypropane, 1, 3-diethoxypropane, tetrahydrofuran, and 1, 3-pentaoxide. Specifically, the solvent comprises or is dimethoxyethane and/or diethoxyethane. The solvent selected from the above can improve ion conductivity of the electrolyte, and the solvating layer of the electrolyte can contain enough anions (fluoride ions), which is advantageous for increasing the content of inorganic substances such as LiF in the SEI film and for improving the cycle performance of the battery.
In one embodiment of the present application, a secondary battery is provided.
The term "secondary battery" referred to herein refers to a battery cell, a battery module, or a battery pack. The following description will be given separately.
Typically, the secondary battery cell includes a positive electrode tab, a negative electrode tab, a separator, and an electrolyte provided in embodiments of the present application. During the charge and discharge of the battery, active ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The isolating film is arranged between the positive pole piece and the negative pole piece, and mainly plays a role in preventing the positive pole piece and the negative pole piece from being short-circuited, and meanwhile ions can pass through the isolating film.
The electrolyte according to each of the above embodiments is suitable for secondary batteries such as lithium metal batteries, sodium metal batteries, lithium ion batteries, and sodium ion batteries, and is particularly suitable for lithium metal batteries.
Positive pole piece:
the positive pole piece comprises a positive current collector and a positive film layer arranged on at least one surface of the positive current collector.
As an example, the positive electrode current collector has two surfaces opposing in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two surfaces opposing the positive electrode current collector.
In some embodiments, the positive current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
In some embodiments, when the secondary battery is a lithium ion battery, the positive electrode active material may be a positive electrode active material for a lithium ion battery, which is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material may be used. These positive electrode active materials may 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 (e.g., liCoO) 2 ) Lithium nickel oxide (e.g. LiNiO) 2 ) Lithium manganese oxide (e.g. LiMnO 2 、LiMn 2 O 4 ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi) 1/3 Co 1/ 3 Mn 1/3 O 2 (also referred to as NCM) 333 ）、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also referred to as NCM) 523 ）、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also referred to as NCM) 211 ）、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also referred to as NCM) 622 ）、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM) 811 ) Lithium nickel cobalt aluminum oxide (e.g. LiNi 0.85 Co 0.1 Al 0.05 O 2 ) And at least one of its modified compounds and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO 4 (also abbreviated as LFP)), composite material of lithium iron phosphate and carbon, and manganese lithium phosphate (such as LiMnPO) 4 ) At least one of a composite material of lithium manganese phosphate and carbon, a lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbonA kind of module is assembled in the module and the module is assembled in the module.
In some embodiments, when the secondary battery is a sodium-ion battery, the positive electrode active material may employ a positive electrode active material for a sodium-ion battery, which is well known in the art. As an example, the positive electrode active material may include a sodium transition metal oxide, a polyanion-type compound, a prussian blue-type compound, and the like.
The battery is charged and discharged with the release and consumption of Li, and the molar contents of Li are different when the battery is discharged to different states. In the list of the positive electrode active materials in the application, the molar content of Li is in the initial state of the materials, namely the state before charging, and the molar content of Li can be changed after charge and discharge cycles when the positive electrode active materials are applied to a battery system. A similar situation exists for sodium ion batteries.
In the list of the positive electrode active materials in the application, the molar content of O is only a theoretical state value, the molar content of oxygen is changed due to lattice oxygen release, and the actual molar content of O can float.
In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluoroacrylate resin.
In some embodiments, the positive electrode film layer further optionally includes 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.
In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and (3) coating the positive electrode slurry on a positive electrode current collector, and obtaining a positive electrode plate after the procedures of drying, cold pressing and the like.
Negative pole piece:
according to some embodiments, the negative electrode tab has a negative electrode current collector and a metal layer comprising metallic lithium or metallic sodium deposited on at least one surface of the negative electrode current collector. Taking a negative electrode plate containing metallic lithium as an example, the metallic layer exists in the form of metallic lithium simple substance and/or alloy. Wherein the alloy is formed by metal lithium and other various metal or nonmetal elements. Other various metals include, but are not limited to: metallic tin (Sn), metallic zinc (Zn), metallic aluminum (Al), metallic magnesium (Mg), metallic silver (Ag), metallic gold (Au), metallic gallium (Ga), metallic indium (In), metallic foil (Pt), and the like. Nonmetallic elements include, but are not limited to: boron (B), carbon (C), silicon (Si).
According to some embodiments, for a lithium ion battery or a sodium ion battery, a negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.
As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode film layer is provided on either one or both of the two surfaces opposing the anode current collector.
In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
In some embodiments, the anode active material may employ an anode active material for a battery, which is well known in the art. As an example, the anode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material may be at least one selected from elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxide, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery anode active material may be used. These negative electrode active materials may be used alone or in combination of two or more.
In some embodiments, the negative electrode film layer further optionally includes a binder. The binder may be at least one selected from 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).
In some embodiments, the negative electrode film layer further optionally includes a conductive agent. The conductive agent is at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
In some embodiments, the negative electrode film layer may optionally further include other adjuvants, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.
In some embodiments, the negative electrode sheet may be prepared by: dispersing the above components for preparing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and obtaining a negative electrode plate after the procedures of drying, cold pressing and the like.
When the electrolyte disclosed by the embodiment of the application is adopted by the lithium ion battery disclosed by the embodiment, the electrolyte can play a role in inhibiting the growth of lithium dendrites, and the SEI film with enhanced toughness is formed to further block side reactions of the active material and the electrolyte, so that the lithium ion battery can keep higher energy density and has improved safety performance and cycle life.
Isolation film:
in some embodiments, a separator is also included in the battery cell. The type of the separator is not particularly limited, and any known porous separator having good chemical stability and mechanical stability may be used.
In some embodiments, the material of the isolating film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.
In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.
In some embodiments, the battery cell may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte described above.
In some embodiments, the exterior packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The outer package of the battery cell may also be a pouch, such as a pouch-type pouch. The material of the flexible bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
The shape of the battery cell is not particularly limited in this application, and may be cylindrical, square, or any other shape. For example, fig. 1 is a square-structured battery cell 5 as one example.
In some embodiments, referring to fig. 2, the overpack may include a housing 51 and a cap assembly 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 51 has an opening communicating with the accommodating chamber, and the top cover assembly 53 can be provided to cover the opening to close the accommodating chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is enclosed in the accommodating chamber. The electrolyte is impregnated in the electrode assembly 52. The number of the electrode assemblies 52 included in the battery cell 5 may be one or more, and those skilled in the art may select the number according to specific practical requirements.
In some embodiments, the battery cells may be assembled into a battery module, and the number of battery cells included in the battery module may be one or more, and the specific number may be selected by one skilled in the art according to the application and capacity of the battery module.
Fig. 3 is a battery module 4 as an example. Referring to fig. 3, in the battery module 4, a plurality of battery cells 5 may be sequentially arranged in the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of battery cells 5 may be further fixed by fasteners.
Alternatively, the battery module 4 may further include a housing having an accommodating space in which the plurality of battery cells 5 are accommodated.
In some embodiments, the above battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and a specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
Fig. 4 and 5 are battery packs 1 as an example. Referring to fig. 4 and 5, a battery case and a plurality of battery modules 4 disposed in the battery case may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.
In addition, the application also provides an electric device, which comprises the secondary battery provided by the application. The secondary battery may be used as a power source of the power consumption device, and may also be used as an energy storage unit of the power consumption device. The power utilization device may include mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric-only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.
As the electricity consumption device, a battery cell, a battery module, or a battery pack may be selected according to the use requirements thereof.
Fig. 6 is an electrical device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. In order to meet the high power and high energy density requirements of the secondary battery by the power consumption device, a battery pack or a battery module may be employed.
As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be light and thin, and a battery cell can be used as a power supply.
Examples:
hereinafter, embodiments of the present application are described. The embodiments described below are exemplary only for the purpose of illustrating the present application and are not to be construed as limiting the present application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
Preparation of silicon hybrid crown ether:
preparation 1 (preparation of compound g):
step 1 will18g of 2-chloro-1-trifluoromethylethanol (16 g) was added to a beaker and stirred at 160℃for 5 hours to give a first mixture. Filtering the first mixture, distilling under reduced pressure after evaporating the solvent, collecting distilled products at 70-75 ℃, and drying to obtain intermediate products (I) >）。
Step 2 the above intermediate 10g, 1, 2-dichloro-tetramethyl disilane 15g, 2-chloroethanol 15g were dissolved in 100ml of THF solvent, hydrochloric acid was added to adjust the pH of the solution to 10, and stirring was carried out for 6.5h to obtain a second mixture.
And (3) carrying out reduced pressure distillation on the second mixture under nitrogen, collecting distillation components at 88-90 ℃, and drying to obtain 21.6g of white solid compound.
Preparation examples 2 to 12:
the synthesis was carried out in analogy to preparation 1 using the corresponding starting materials. See in particular table 1 below:
in some embodiments, when the compound contains a pair of-Si-Si-groups, raw material 1 and raw material 2 shown in the following table are reacted at a temperature of 150-180 ℃ for 4-6 hours to prepare an intermediate product, and the intermediate product and raw material 3 are mixed and stirred in a THF solvent with a pH of 8-13 for 6-8 hours in step 2 to prepare the corresponding silicon hybridized crown ether. In some embodiments, where two pairs of-Si-Si-groups are included in the compound, the starting material 3 may be obtained by stirring for 2-5 hours at 0-10 ℃ using the corresponding starting material.
Table 1:
preparation examples 13 to 20:
mixing the raw materials 1 and 2 in the following table 2, adding other raw materials, and mixing and stirring in a THF solvent with pH of 8-13 for 6-8 hours to obtain the corresponding compound.
Table 2:
example 1:
preparation of electrolyte:
3.74g of a reactive ion salt (LiWSI) was dissolved in 10ml of Dimethoxyethane (DME), and the silicon-hybridized crown ether (compound g) was added thereto, and the mixture was sufficiently stirred so that the content of the silicon-hybridized crown ether was 2% by weight, to form a colorless transparent electrolyte.
Preparation of laminated battery:
1) Preparing a positive electrode plate:
the positive electrode active material nickel cobalt lithium manganate) Mixing acetylene black serving as a conductive agent and PVDF serving as a binder according to a mass ratio of 98:1:1, adding N-methylpyrrolidone (NMP) serving as a solvent, and stirring until the system is uniform to obtain positive electrode slurry (the solid content is 70%); the positive electrode slurry was mixed at about 25Uniformly coating the load on the aluminum foil of the positive current collector on both sides, airing at room temperature, transferring to an oven for continuous drying, and then cutting into the aluminum foilAnd (3) obtaining the positive pole piece.
2) Preparing a negative electrode plate:
coating 50 μm lithium foil on one surface of 12 μm copper foil by rolling, and cuttingIs used as a negative pole piece for standby.
3) Isolation film:
selecting polyethylene porous membrane, cutting intoIs a rectangle.
4) Preparation of laminated battery:
and stacking the prepared positive pole piece and the two negative pole pieces, separating by using a separation film, and wrapping the positive pole piece and the two negative pole pieces in an aluminum plastic film bag to form the laminated dry battery cell. And injecting 0.3g of the prepared electrolyte, and carrying out vacuum hot-pressing packaging on the aluminum-plastic film bag to obtain the laminated battery.
Examples 2 to 20:
the electrolytes and laminated batteries of examples 2 to 20 were prepared in a similar manner to the electrolyte and laminated battery preparation method of example 1, except that the silicon hybrid crown ether added to the electrolyte was used for the compounds b to t prepared in preparation examples 2 to 20, respectively.
Comparative example 1:
an electrolyte and a laminated battery of comparative example 1 were prepared in a similar manner to the electrolyte and laminated battery preparation method of example 1, except that no silicon-hybridized crown ether was added to the electrolyte.
Comparative example 2:
an electrolyte and a laminated battery of comparative example 2 were prepared in a similar manner to the electrolyte and laminated battery preparation method of example 1, except that compound g was replaced with 18 crown 6 ether in the electrolyte.
Comparative example 3:
an electrolyte and a laminated battery of comparative example 3 were prepared in a similar manner to the electrolyte and laminated battery preparation method of example 1, except that compound g was replaced with trifluoromethyl instead of 18 crown 6 ether in the electrolyte.
Cell performance test:
1. cycle life test at 1C discharge rate:
the laminated batteries fabricated in examples 1, 4, 7, 10, 12, 15, 19, 20 and comparative examples 1 to 3 were set to an ambient temperature of 25℃and charge and discharge cycles were performed using a rate of 0.2C (i.e., 28 mA) and 1C discharge (i.e., 140 mA). The cut-off voltage of charge and discharge is set to be 4.3V and 2.8V respectively, and the charging process adopts a constant current-constant voltage charging method, specifically, after the 0.2C constant current charging reaches the cut-off voltage of 4.3V, constant voltage charging of 4.3V is continued until the current decays to 0.1C (i.e. 14 mA). The number of turns when the discharge capacity decays to 80% of the first turn discharge capacity is recorded.
2. Cycle life test at 4C discharge rate:
the laminated batteries fabricated in examples 1, 4, 7, 10, 12, 15, 19, 20 and comparative examples 1 to 3 were set to an ambient temperature of 25℃and were charged at 0.2C (i.e., 28 mA) and discharged at a rate of 4C (i.e., 560 mA) for charge and discharge cycles. The cut-off voltage of charge and discharge is set to 4.3V and 2.8V respectively, and the charging process adopts a constant current-constant voltage charging method, specifically, after the 0.2C constant current charging reaches the cut-off voltage of 4.3V, constant voltage charging of 4.3V is continued until the current decays to 0.1C (i.e. 14 mA), and the number of cycles when the discharge capacity decays to 80% is recorded.
The results of the above test are shown in table 3 below.
TABLE 3 Table 3
As can be seen from the results in Table 3, laminated cells prepared with an electrolyte containing a silicon hybrid crown ether each had significantly improved cycle life at 1C and 4C discharge rates.
In contrast, the cycle life of the electrolyte of comparative example 1 was drastically reduced without adding a crown ether compound. The electrolyte of comparative example 2, to which a crown ether containing no silicon was added, was significantly lower than the examples of the electrolyte containing a silicon-hybridized crown ether, although the cycle performance was significantly improved as compared with comparative example 1 due to the insufficient stability of crown ether. To the electrolyte of comparative example 3 was added a non-silicon hybridized 18 crown 6 ether having a trifluoromethyl group. Examples 1, 4, 7, 10, 12 and 15, which contained compound g, f, j, l, o in the electrolyte (differing from the crown ether in comparative example 3 in that one or two pairs of-Si-groups were contained in the ring), significantly improved cycle life at normal and high rates as compared to comparative example 3. In addition, examples 19 and 20, in which the phenyl group-containing compound s or the phenoxy group-containing compound t was added to the electrolyte, also had significantly improved cycle life at normal magnification and at high magnification as compared with comparative example 3. Compared with other examples of the electrolyte containing the silicon hybridization crown ether with trifluoromethyl substituent, the stability of the silicon hybridization crown ether with non-fluoro substituent is relatively low, so the improvement range of the cycle life is slightly low.
The laminated batteries prepared in other examples also had significantly improved cycle life at normal rates and at high rates relative to comparative example 3.
Examples 21 to 23:
a laminated battery was produced in the same manner as in example 1, except that the content of the silicon hybrid crown ether in the electrolyte was changed as shown in table 4 below.
Performance evaluation was performed in the same manner as in example 1, and the test results are shown in table 4 below.
TABLE 4 Table 4
As can be seen from the results of Table 4, the content of the silicon-hybrid crown ether in the electrolyte is too low or too high, and the cycle life is reduced, preferably the content of the silicon-hybrid crown ether is 1.5wt% to 3wt%.
The present application is not limited to the above embodiment. The above embodiments are merely examples, and embodiments having substantially the same configuration and the same effects as those of the technical idea within the scope of the present application are included in the technical scope of the present application. Further, various modifications that can be made to the embodiments and other modes of combining some of the constituent elements in the embodiments, which are conceivable to those skilled in the art, are also included in the scope of the present application within the scope not departing from the gist of the present application.

Claims (16)

1. An electrolyte comprising a reactive ion salt, a solvent, and at least one silicon hybrid crown ether;
The silicon-hybridized crown ether is crown ether with at least 1 carbon atom on the ring replaced by silicon atom, wherein each carbon atom in the silicon-hybridized crown ether has substituent R, and/or each silicon atom has substituent R ', wherein the substituent R is selected from at least one of hydrogen, phenyl, phenoxy, C1-C6 halogenated alkyl, C1-C6 halogenated alkoxy, halogenated phenyl and halogenated phenoxy, the substituent R' is selected from at least one of hydrogen and C1-C6 alkyl,
wherein at least one carbon atom on the silicon hybrid crown ether ring has a substituent R that is not hydrogen.
2. The electrolyte of claim 1, wherein the silicon hybrid crown ether is 12 crown 4 ether to 24 crown 8 ether in which at least one pair of carbon atoms bonded to each other on a ring is replaced by a silicon atom.
3. The electrolyte of claim 2, wherein the silicon hybrid crown ether is 12 crown 4 ether to 24 crown 8 ether in which one or two pairs of carbon atoms bonded to each other on a ring are replaced by silicon atoms.
4. The electrolyte of claim 1 wherein the substituent R is selected from at least one of hydrogen, phenyl, phenoxy, C1-C4 haloalkyl, C1-C4 haloalkoxy, halophenyl, and halophenoxy, and wherein the substituent R' is selected from at least one of hydrogen and C1-C4 alkyl.
5. The electrolyte of claim 4 wherein the substituent R is selected from at least one of hydrogen, C1-C4 haloalkyl and C1-C4 haloalkoxy, wherein halogen is fluorine and/or chlorine, and wherein the substituent R' is methyl and/or ethyl.
6. The electrolyte of claim 5 wherein the substituent R is selected from at least one of hydrogen, C1-C4 haloalkyl wherein halogen is F and the substituent R' is methyl.
7. The electrolyte of claim 1 wherein at least one non-alpha carbon atom of the silicon-hybrid crown ether is substituted with a substituent R comprising at least one fluorine atom, wherein the non-alpha carbon atom is a carbon atom on the ring of the silicon-hybrid crown ether that is not attached to an oxygen atom of a siloxane bond.
8. The electrolyte of any one of claims 1 to 7 wherein the silicon hybrid crown ether is selected from the group consisting of compounds of the following general formulas I-XVI:
general formula I, (-)>General formula II,
General formula III>General formula IV,
General formula V, (-)>General formula VI,
Formula VII, (-)>General formula VIII,
General formula IX, & lt ]>A general formula X,
General formula XI, & lt + & gt>General formula XII,
Formula XIII, < >>Of the general formula XIV,
General formula XV, & lt + & gt>General formula XVI.
9. The electrolyte of claim 1 wherein the silicon hybrid crown ether is selected from the group consisting of compounds of the following structural formula:
compound a,/->Compound b,/->A compound c,
Compound d, < >>A compound e,
Compound f, < >>A compound g,
Compound h,/-, and>a compound i,
Compound j, < >>Compound k,
Compound i,/->A compound m,
Compound n, < >>A compound o,
Compound p,/->A compound q,
Compound r,/->A compound s,
Compound t.
10. The electrolyte according to any one of claims 1 to 7, wherein the silicon hybrid crown ether is added in an amount of 0.5wt% to 15wt%, based on the total weight of the electrolyte.
11. The electrolyte according to any one of claims 1 to 7, wherein the active ion salt is selected from lithium salts or sodium salts.
12. The electrolyte of claim 11, wherein the lithium salt is at least one selected from the group consisting of lithium bis (fluorosulfonyl) imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis (trifluoromethanesulfonyl) imide, lithium trifluoromethanesulfonate, and lithium difluorophosphate.
13. The electrolyte of any one of claims 1-7 wherein the concentration of the active ionic salt in the electrolyte is 0.5mol/L to 4mol/L.
14. A battery cell comprising a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte of any one of claims 1-13, wherein the negative electrode sheet comprises a negative electrode material.
15. The battery cell of claim 14, wherein the negative electrode material comprises metallic lithium and/or a lithium alloy.
16. A secondary battery comprising the battery cell according to claim 14 or 15.
CN202410062204.1A 2024-01-16 2024-01-16 Electrolyte and secondary battery Pending CN117577945A (en)

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