CN115911554A - Electrolyte, battery and electric equipment - Google Patents
Electrolyte, battery and electric equipment Download PDFInfo
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- CN115911554A CN115911554A CN202211445410.8A CN202211445410A CN115911554A CN 115911554 A CN115911554 A CN 115911554A CN 202211445410 A CN202211445410 A CN 202211445410A CN 115911554 A CN115911554 A CN 115911554A
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Abstract
The invention discloses an electrolyte, a battery and electric equipment, wherein the electrolyte comprises: diboronate additives, solvents and electrolyte salts; the diboronate additive is selected from at least one of compounds with a structure shown in a formula I:
wherein R is selected from C 1 ～C 6 Of (a) an alkylene group of O, C 2 ～C 7 Alkenylene of (A), C 2 ～C 5 Alkynylene of (2), C 4 ～C 20 Arylene of (a) O-R 3 -O, substituted C 4 ～C 20 Arylene of (a), substituted C 2 ～C 7 Any of the alkenylene groups of (a); r 1 And R 2 Each independently selected from C 1 ～C 6 Alkylene of (a), substituted C 1 ～C 6 Alkylene of (C) 6 ～C 10 Any of the arylene groups of (a); r is 3 Is selected from C 1 ～C 6 An alkylene group of (a). The diboronate additive improves the electrochemical window and thermodynamic stability of the electrolyte and also improves the storage performance of the battery at high temperature.
Description
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to an electrolyte, a battery and electric equipment.
Background
Since the 21 st century, lithium ion batteries have been widely used in the fields of consumer electronics, industrial energy storage, and new energy automobiles due to their advantages of high energy density, no memory effect, and the like. To meet the increasing demand of people, higher requirements are put on the energy density and the safety of the battery. Improving the energy density and safety of batteries is really the most valuable innovation direction for the successful application of lithium batteries. However, in order to increase the energy density, it would be the most straightforward direction to increase the operating voltage of the battery.
A large amount of research data show that the interfacial reaction of the electrode material and the electrolyte is a main factor causing the decomposition of the electrolyte and limiting the increase of the voltage of the battery cell. Therefore, in order to develop a high-pressure stable and thermodynamically stable electrolyte system, various electrolyte additives are widely used, and this method has also proved to be the most effective method for improving the stability of the electrolyte.
At present, most of commercialized electrolyte adopts a carbonate solvent system, and when the voltage is greater than 4.3V, the electrolyte is decomposed, so that the battery fails. Meanwhile, there is a great risk in the safety of the battery, for example, the electrode material is damaged, which leads to thermal runaway of the battery, and in order to avoid this phenomenon, a thermodynamically stable interface protection film needs to be formed between the electrode material and the electrolyte interface.
In the prior art, a single functional effect is realized only through a certain special structure of the electrolyte, and the existing electrolyte additive has the characteristics of low reactivity, low solubility, various additive types and the like. On one hand, the cost of the electrolyte is increased, and on the other hand, the conductivity of the electrolyte is reduced due to the addition of the inactive components, so that the performance of the battery is reduced.
Therefore, the development of an electrolyte additive with multiple functionalities is considered to be the most significant research direction for improving the liquid lithium battery.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, the invention aims to provide an electrolyte, a battery and electric equipment. The diboronate additive improves the electrochemical window and the thermodynamic stability of the electrolyte, and finally obviously improves the cycle performance and the high-temperature performance of the battery. Meanwhile, the diborate additive also has better high-pressure stability and high-temperature stability, thereby improving the storage performance of the battery at high temperature.
In one aspect of the invention, an electrolyte is provided. According to an embodiment of the invention, the electrolyte comprises:
diboronate additives, solvents and electrolyte salts;
the diboronate additive is selected from at least one of compounds with a structure shown in a formula I:
wherein R is selected from C 1 ～C 6 Of (a) an alkylene group of O, C 2 ～C 7 Alkenylene of (A), C 2 ～C 5 Alkynylene of (2), C 4 ～C 20 Arylene of (a) O-R 3 -O, substituted C 4 ～C 20 Arylene of (a), substituted C 2 ～C 7 Any of the alkenylene groups of (a);
R 1 and R 2 Each independently selected from C 1 ～C 6 Alkylene of (a), substituted C 1 ～C 6 Alkylene of (C) 6 ～C 10 Any of the arylene groups of (a);
R 3 is selected from C 1 ～C 6 An alkylene group of (a).
In addition, the electrolyte according to the above embodiment of the present invention may further have the following additional technical features:
in some embodiments of the invention, the substituted C 1 ～C 6 The substituents in the alkylene group of (a) are selected from halogen, amino, C 6 ～C 20 Any one of the aryl groups of (a); and/or, said C 4 ～C 20 The arylene group of (a) is selected from any one of a thienylene group, an anthracenylene group, a pyridinylene group, a phenylene group and a derivative group thereof; and/or, the saidSubstituted C 4 ～C 20 The substituents in the arylene group of (A) are selected from cyano, C 1 ～C 6 Any of alkyl groups and halogens of (1); and/or, said substituted C 2 ～C 7 The substituents in the alkenylene group of (a) are selected from C 1 ～C 6 The alkyl group of (1).
In some embodiments of the invention, R 1 And R 2 Are all ethylene groups; or, R 1 And R 2 Are all substituted ethylene groups; or, R 1 And R 2 Are both propylene groups; or, R 1 And R 2 Are all substituted propylene groups.
In some embodiments of the invention, in the compound of formula I, R 1 And R 2 Are all substituted ethylene groups, and the formula of formula I is:
wherein R is 11 、R 12 、R 13 、R 14 、R 21 、R 22 、R 23 And R 24 Each independently selected from F atom, C 1 ～C 6 Alkyl or F-substituted C 1 ～C 6 Alkyl group of (1).
In some embodiments of the invention, in the compound of formula I, R 1 And R 2 Are all substituted propylene groups, and the formula of formula I is:
wherein R' 11 、R' 12 、R' 13 、R' 21 、R' 22 、R' 23 、R" 11 、R" 12 、R" 21 And R " 22 Each independently selected from F atom, C 1 ～C 6 Alkyl or F-substituted C 1 ～C 6 The alkyl group of (1).
In some embodiments of the invention, the diboronate-based additive is selected from at least one of the following structural compounds:
in some embodiments of the invention, the diboronate-based additive is present in an amount of 0.1 to 3% by mass, based on the total mass of the electrolyte.
In some embodiments of the present invention, the electrolyte salt is present in an amount of 10% to 20% by mass, based on the total mass of the electrolyte.
In some embodiments of the invention, the electrolyte salt is an electrolyte lithium salt selected from at least one of lithium hexafluorophosphate, lithium bis (oxalato) borate, lithium tetrafluoroborate and lithium bis (fluorosulfonimide).
In some embodiments of the present invention, the solvent is selected from at least one of a carbonate-based solvent and a carboxylate-based solvent.
In some embodiments of the invention, the electrolyte further comprises an auxiliary film-forming additive, the auxiliary film-forming additive being present in an amount of 0.2% to 10% by mass, based on the total mass of the electrolyte.
In some embodiments of the invention, the auxiliary film-forming additive is selected from at least one of vinylene carbonate, 1,3-propane sultone, lithium difluorophosphate, tris (trimethylsilyl) phosphite, and vinyl sulfate.
In a second aspect of the invention, a battery is provided. According to an embodiment of the present invention, the battery has the above-described electrolyte. Therefore, the cycle performance and the high-temperature performance of the battery are improved, and the storage performance of the battery at high temperature is also improved; meanwhile, the gas generation of the battery in a high-temperature environment is reduced, the increase of the internal resistance of the battery is inhibited, and the electrochemical performance of the battery is improved.
In a third aspect of the present invention, an electrical device is presented. According to an embodiment of the present invention, the electric device has the battery as described above. Therefore, the electric equipment loaded with the battery has excellent cruising ability, and further meets the use requirements of consumers.
Description of terms:
in this application, C 1 ～C 6 、C 2 ～C 7 And the like refer to the number of carbon atoms involved. The carbon atom of the "substituted alkylene group" is defined to mean the number of carbon atoms contained in the alkylene group itself, not the number of carbon atoms after substitution. Such as C 1 ～C 12 The substituted alkyl group of (1) means an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen atom is substituted with a substituent.
In the present application, an "alkylene group" is a group formed by losing any two hydrogen atoms on the molecule of an alkane compound. The alkane compound comprises straight-chain alkane, branched-chain alkane, cycloalkane and cycloalkane with branched chain.
In the present application, "arylene" is a group formed by losing two hydrogen atoms on an aromatic ring on an aromatic compound molecule; e.g. formed by benzene losing two hydrogen atoms in ortho-position on the benzene ring
And (4) a base.
In the present application, an "alkenylene group" is a group formed by the loss of any two hydrogen atoms from the molecule of an olefin compound. The olefin compound includes linear olefin, branched olefin, cyclic olefin, and cyclic olefin with branched chain.
In the present application, an "alkynylene group" is a group formed by losing any two hydrogen atoms on the molecule of an alkyne compound. The alkyne compound includes a straight-chain alkyne, a branched-chain alkyne, a cycloalkyne, and a cycloalkyne with a branch.
In this application, "cyano" is NC-.
In the present application, the thienylene group has the formula
The structural formula of the anthrylene group is->
The structure of the pyridinylene group is->
Has the beneficial effects that:
according to the electrolyte provided by the embodiment of the invention, compared with a solvent, the diboronate additive in the electrolyte also has higher highest occupied orbital energy and lower lowest unoccupied orbital energy, so that when the diboronate additive is subjected to an electrochemical reaction in the electrolyte, the diboronate additive can be decomposed and reduced preferentially, and films are formed on a positive electrode and a negative electrode respectively (an SEI film is formed on the negative electrode and a CEI film is formed on the positive electrode), so that side reactions between positive and negative electrode materials and the electrolyte are inhibited, the electrochemical window and the thermodynamic stability of the electrolyte are improved, and finally the cycle performance and the high-temperature performance of a battery are improved remarkably. In addition, the diboronate additive also has better high-pressure stability and high-temperature stability, thereby improving the storage performance of the battery at high temperature; meanwhile, the gas generation of the battery in a high-temperature environment is reduced, the increase of the internal resistance of the battery is inhibited, and the electrochemical performance of the battery is improved.
Detailed Description
Reference will now be made in detail to the embodiments of the present invention, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The following described embodiments are exemplary and are intended to be illustrative of the invention and are not to be construed as limiting the invention.
In one aspect of the invention, an electrolyte is provided. According to an embodiment of the invention, the electrolyte comprises: diboronate additives, solvents and electrolyte salts; the diboronate additive is selected from at least one of compounds with a structure shown in a formula I:
wherein R is selected from C 1 ～C 6 Of (a) an alkylene group of O, C 2 ～C 7 Alkenylene of (2), C 2 ～C 5 Alkynylene of (2), C 4 ～C 20 Arylene of (a) O-R 3 -O, substituted C 4 ～C 20 Arylene of (a), substituted C 2 ～C 7 Any of the alkenylene groups of (a); r 1 And R 2 Each independently selected from C 1 ～C 6 Alkylene of (a), substituted C 1 ～C 6 Alkylene of (C) 6 ～C 10 Any of the arylene groups of (a); r is 3 Is selected from C 1 ～C 6 An alkylene group of (a).
Compared with a solvent, the diboronate additive in the electrolyte also has higher highest occupied orbital energy HOMO and lower lowest unoccupied orbital energy LUMO, so when the diboronate additive is subjected to electrochemical reaction in the electrolyte, on one hand, the HOMO of the diboronate additive is higher than the HOMO of solvent molecules, and is oxidized in preference to the solvent, a stable CEI film is formed on the positive electrode, the continuous side reaction of a positive electrode material and the electrolyte is reduced, the integrity of an electrode structure is ensured, and meanwhile, the decomposition of the electrolyte solvent is inhibited; on the other hand, the LUMO of the diboronate additive is lower than that of solvent molecules, so that the solvent reduction is prioritized, a more compact SEI film is formed on the negative electrode, and the decomposition of the electrolyte solvent is inhibited. Therefore, the diboronate additive improves the electrochemical window and the thermodynamic stability of the electrolyte, and finally obviously improves the cycle performance and the high-temperature performance of the battery. Meanwhile, the diboronate additive also has better high-pressure stability and high-temperature stability, thereby improving the storage performance of the battery at high temperature. In addition, the gas generation of the battery in a high-temperature environment is reduced, the increase of the internal resistance of the battery is inhibited, and the electrochemical performance of the lithium ion battery is further improved.
It should be noted that, the conventional additive can only inhibit the side reaction between the positive electrode material and the electrolyte or between the negative electrode material and the electrolyte, and cannot achieve the effect of inhibiting the side reaction between the positive electrode material and the electrolyte. The diboronate additive can achieve the effect of simultaneously inhibiting side reactions between the anode and cathode materials and the electrolyte, and reduces the types of the additives in the electrolyte, thereby avoiding the problem of reducing the conductivity of the electrolyte caused by excessive additives in the electrolyte.
Specifically, the diborate additive is obtained by structurally modifying borate through functional groups, and the introduction of functional groups R improves the thermal stability and the dissolving capacity of the borate; meanwhile, through functional modification of a molecular structure, higher HOMO and lower LUMO are realized, so that interface protective films can be generated on both the positive electrode and the negative electrode. For example, the introduction of fluorine-containing benzene ring improves the film forming capability of the positive electrode; the introduction of the thiophene structure improves the inorganic salt component containing S in the SEI film of the negative electrode, thereby improving the storage performance of the battery in a high-temperature environment; the introduction of the alkene or alkyne increases the probability of containing the polymer in the interface protective film component, thereby inhibiting the negative effects caused by the electrode swelling.
In addition, when the electrolyte additive provided by the invention is applied to a lithium ion battery, a B-R bond on one side can be broken to form B-R-Li, if R is alkyl, alkyl lithium can be formed, and the alkyl lithium is the main component of the organic lithium salt of SEI, so that the proportion of the organic lithium salt is increased, and the Li content is further increased + The transmission capability of the lithium ion battery reduces the interface impedance, inhibits the increase of the internal resistance of the battery, and further improves the electrochemical performance of the lithium ion battery.
According to a specific embodiment of the present invention, in the compound of formula I, the substituted C 1 ～C 6 The substituents in the alkylene group of (a) are selected from halogen, amino, C 6 ～C 20 At least one of aryl groups of (a); and/or, said C 4 ～C 20 The arylene group of (a) is selected from any one of a thienylene group, an anthracenylene group, a pyridinylene group, a phenylene group and a derivative group thereof; and/or, said substituted C 4 ～C 20 The substituents in the arylene group of (A) are selected from cyano, C 1 ～C 6 At least one of alkyl and halogen of (a); and/or, said substituted C 2 ～C 7 The substituents in the alkenylene group of (a) are selected from C 1 ～C 6 Alkyl group of (1).
According to still another aspect of the present inventionIn a particular embodiment, in said compound of formula I, R 1 And R 2 The structure of the left side and the structure of the right side of the R group respectively form five-membered rings, therefore, the diborate additive with the structure increases the structure of alkyl, and the component of alkyl lithium is added in the film forming process of an SEI film, and the component of the alkyl lithium is the main source of organic lithium salt of the SEI film, thereby improving the ionic conductivity of an interface, reducing the interface impedance, inhibiting the increase of the internal resistance of the battery, and further improving the electrochemical performance of the lithium ion battery.
According to yet another embodiment of the invention, in said compound of formula I, R 1 And R 2 The structure of the left side and the right side of the R group respectively form a six-membered ring, so that the chain of alkyl lithium formed by the fracture of the B-R bond of the diboronate additive with the structure is longer, the proportion of organic matter components in an SEI film is increased, the formation of a telescopic interface protective film is further facilitated, and the expansion of the volume of the electrode can be inhibited.
According to yet another embodiment of the invention, in said compound of formula I, R 1 And R 2 Are all substituted ethylene groups, and the formula of formula I is:
wherein R is 11 、R 12 、R 13 、R 14 、R 21 、R 22 、R 23 And R 24 Each independently selected from F atom, C 1 ～C 6 Alkyl or F-substituted C 1 ～C 6 The alkyl group of (1). Particularly, the F atom substituted diborate additive with the structure can play a role in improving the oxidation stability of the electrolyte in the electrolyte, so that the high-voltage stability of the battery is improved; on the other hand, F atoms favor the formation of LiF component, which is a key component of the SEI film.
According to a further embodiment of the inventionExamples in said compounds of formula I, R 1 And R 2 Are each a substituted propylene group, and the formula of formula I is:
wherein R' 11 、R' 12 、R' 13 、R' 21 、R' 22 、R' 23 、R" 11 、R" 12 、R" 21 And R " 22 Each independently selected from F atom, C 1 ～C 6 Alkyl or F-substituted C 1 ～C 6 Alkyl group of (1). Similarly, the F atom substituted diborate additive with the structure can play a role in improving the oxidation stability of the electrolyte in the electrolyte, so that the high-voltage stability of the battery is improved; on the other hand, F atoms contribute to the formation of LiF component, which is a key component of the SEI film.
Preferably, the diboronate additive is selected from at least one of the following structural compounds:
specifically, A 3 、A 9 And A 10 Unsaturated bonds are introduced, and the probability of containing polymers in the interface protective film component is improved by introducing alkenes or alkynes, so that negative effects caused by electrode expansion are inhibited. A. The 5 The thienyl group is introduced, so that the proportion of S-containing inorganic salt components in the SEI film of the negative electrode is improved, and the storage performance of the battery in a high-temperature environment is improved. A. The 3 And A 7 The phenylene and the derivative group thereof are introduced, so that the film forming capability of the positive electrode is improved. A. The 1 And A 6 In which alkylene groups are introduced, favouring alkyllithiumThereby contributing to improvement of ion conductivity, reduction of interface resistance, and the like. A. The 8 The fluorine-containing pyridylene is introduced, so that the high-voltage stability of the battery is improved.
In addition, the diboronate additive has multiple functional groups, so the use amount of the diboronate additive in the electrolyte is obviously reduced, and more excellent electrochemical performance is realized. According to another embodiment of the invention, the mass content of the diborate additive can be 0.1-3% based on the total mass of the electrolyte, so that the content of the diborate additive is limited within the range, the purpose of improving the electrochemical window and thermodynamic stability of the electrolyte can be achieved, and the cost waste and the reduction of the battery performance caused by overhigh content can be avoided. The inventors have found that if the amount of diboronate additive in the electrolyte is too low, the effect of improving the electrochemical window and thermodynamic stability of the electrolyte is not achieved; if the content of the diboronate-based additive in the electrolyte is too high, the cost is increased on one hand, and the content of the solvent and the lithium salt is relatively reduced on the other hand, so that the performance of the battery is negatively influenced.
According to another embodiment of the present invention, the electrolyte salt may be present in an amount of 10% to 20% by mass based on the total mass of the electrolyte, and thus, the content of the electrolyte salt in the electrolyte is limited to the above range, which can ensure that the electrolyte has good ionic conductivity and is beneficial to the exertion of the electrical properties of the battery.
In the embodiment of the present invention, the specific kind of the electrolyte salt is determined depending on whether the electrolyte is applied to a lithium ion battery, a sodium ion battery, or other kinds of ion batteries. For example, if the above electrolytic solution is applied to a lithium ion battery, the above electrolyte salt is an electrolyte lithium salt. As some specific examples, the electrolyte lithium salt is selected from lithium hexafluorophosphate (LiPF) 6 ) Lithium bis (oxalato) borate (LiODFB) and lithium tetrafluoroborate (LiBF) 4 ) And lithium bis-fluorosulfonamide (LiFSI), said kind of electrolyte lithium salt has better ionic conductivity, further beneficial to the exertion of battery electric property。
In the embodiment of the present invention, the specific kind of the solvent is also not particularly limited, and at least one of a carbonate-based solvent and a carboxylate-based solvent is preferable. Specifically, the carbonate-based solvent includes at least one of Ethylene Carbonate (EC), ethyl Methyl Carbonate (EMC), and fluoroethylene carbonate (FEC). The carboxylic ester solvent comprises at least one of propyl propionate, methyl propionate, ethyl acetate and propyl formate. As some specific examples, the solvent includes Ethylene Carbonate (EC), ethyl Methyl Carbonate (EMC), propyl Propionate (PP), and fluoroethylene carbonate (FEC), and the mass ratio of the ethylene carbonate, the ethyl methyl carbonate, the propyl propionate, and the fluoroethylene carbonate is (2-7): (1-5): (3-7): (5-8), preferably, the mass ratio of the ethylene carbonate, the fluoroethylene carbonate, the ethyl methyl carbonate and the propyl propionate is 6:2:5:7.
according to another embodiment of the invention, the electrolyte may further include an auxiliary film-forming additive, where the auxiliary film-forming additive is used to assist the diboronate additive to form a more stable CEI film on the positive electrode and a more dense SEI film on the negative electrode. Specifically, based on the total mass of the electrolyte, the mass content of the auxiliary film-forming additive can be 0.2-10%, so that the auxiliary film-forming additive can fully assist the diboronate additive to form a more stable CEI film on the positive electrode and a more compact SEI film on the negative electrode, side reactions between the auxiliary film-forming additive and other components of the electrolyte caused by excessive content of the auxiliary film-forming additive are avoided, and the waste of the auxiliary film-forming additive is avoided.
In the embodiments of the present invention, the specific kind of the above-described auxiliary film-forming additive is also not particularly limited, and as some specific examples, the auxiliary film-forming additive is selected from at least one of Vinylene Carbonate (VC), 1,3-Propane Sultone (PS), lithium difluorophosphate (LiDFP), tris (trimethylsilyl) phosphite (TMSP), and vinyl sulfate (DTD), the effect of auxiliary film formation by the above-described kind of auxiliary film-forming additive is more excellent.
In a second aspect of the invention, a battery is provided. According to an embodiment of the present invention, the battery has the above-described electrolyte. Therefore, the cycle performance and the high-temperature performance of the battery are improved, and the storage performance of the battery at high temperature is also improved; meanwhile, the gas generation of the battery in a high-temperature environment is reduced, the increase of the internal resistance of the battery is inhibited, and the electrochemical performance of the battery is improved.
Specifically, the battery may be a conventional liquid battery (e.g., lithium ion battery, sodium ion battery), a lithium metal battery, a semi-solid battery, or the like.
In a third aspect of the present invention, an electrical device is presented. According to an embodiment of the present invention, the electric device has the battery as described above. Therefore, the electric equipment loaded with the battery has excellent cruising ability, and further meets the use requirements of consumers.
Specifically, the electric device may include, but is not limited to, a vehicle, a ship, an aircraft, or the like. The vehicle can be a fuel automobile, a gas automobile or a new energy automobile. The new energy automobile can be a pure electric automobile, a hybrid electric automobile or a range-extended automobile and the like.
The following detailed description of the embodiments of the present invention is provided for the purpose of illustration only and should not be construed as limiting the invention. In addition, all reagents used in the following examples are commercially available or can be synthesized according to methods herein or known, and are readily available to those skilled in the art for reaction conditions not listed, if not explicitly stated.
Example 1
The embodiment provides a preparation method of a lithium ion battery, which comprises the following steps:
preparing electrolyte: in a drying room with a dew point lower than-50 ℃, EC, FEC, EMC and PP are mixed according to the weight ratio of 6:2:5:7, and mixing and shaking up to obtain the mixed solvent. Then, 13wt% of lithium hexafluorophosphate (LiPF) based on the total weight of the electrolyte was slowly added to the mixed solvent 6 ) And assistThe types and amounts of the film-forming auxiliary additives and the auxiliary film-forming additives are shown in Table 1. Finally, 0.3wt% of compound A with the structure shown in formula I based on the total weight of the electrolyte is added 6 . And uniformly stirring to obtain the lithium ion battery electrolyte.
Preparing a positive plate: according to the weight ratio of lithium cobaltate: super-P (conductive agent): PVDF: CNTs =96.5:1.3:2.0: weighing the raw materials according to the mass ratio of 0.2, uniformly stirring the raw materials, adding NMP to adjust the viscosity to 4200cp and the solid content to 64.1% to obtain stable lithium cobaltate slurry, coating the stable lithium cobaltate slurry on two sides of an aluminum foil with the thickness of 12 microns, and drying, rolling and die-cutting the stable lithium cobaltate slurry to obtain a single positive plate.
Preparing a negative plate: mixing artificial graphite (particle diameter D50: less than 15 microns), a conductive agent Super-P, a binder Styrene Butadiene Rubber (SBR), and a thickener sodium carboxymethylcellulose (CMC-Na) according to a weight ratio of 95.5:1.5:2:1, adding deionized water, uniformly stirring, controlling the viscosity to be 3200cp and the solid content to be 42.0 percent to obtain cathode slurry, coating the cathode slurry on a Cu foil with the thickness of 16 microns, drying, cold pressing and die cutting to obtain the cathode sheet.
A diaphragm: a 9+2 micron ceramic composite PE diaphragm was used.
Preparing a soft package battery: and (3) sequentially laminating the prepared positive plate, the diaphragm and the negative plate, placing the diaphragm between the positive plate and the negative plate to ensure that the positive plate and the negative plate are completely separated by the diaphragm, and winding to obtain the dry battery core. And (3) placing the dry battery core in an aluminum-plastic film outer package, injecting the prepared electrolyte into the dried battery, standing, forming and grading, wherein the liquid retention capacity of the electrolyte is 2.75-3.0g/Ah. Thus, the preparation of the lithium ion soft package battery (the full battery material is a high-pressure lithium cobaltate/artificial graphite battery system) is completed.
TABLE 1
Example 2
The preparation method of this example is the same as that of example 1, except for the kinds and amounts of the components of the electrolyte, and the kinds and amounts of the components of the electrolyte of this example are shown in table 1, and the other contents are the same as those of example 1.
Example 3
The preparation method of this example is the same as that of example 1, except for the kinds and amounts of the components of the electrolyte, which are shown in table 1, and the other contents are the same as those of example 1.
Example 4
The preparation method of this example is the same as that of example 1, except for the kinds and amounts of the components of the electrolyte, which are shown in table 1, and the other contents are the same as those of example 1.
Example 5
The preparation method of this example is the same as that of example 1, except for the kinds and amounts of the components of the electrolyte, which are shown in table 1, and the other contents are the same as those of example 1.
Example 6
The preparation method of this example is the same as that of example 1, except for the kinds and amounts of the components of the electrolyte, which are shown in table 1, and the other contents are the same as those of example 1.
Example 7
The preparation method of this example is the same as that of example 1, except for the kinds and amounts of the components of the electrolyte, and the kinds and amounts of the components of the electrolyte of this example are shown in table 1, and the other contents are the same as those of example 1.
Example 8
The preparation method of this example is the same as that of example 1, except for the kinds and amounts of the components of the electrolyte, which are shown in table 1, and the other contents are the same as those of example 1.
Example 9
The preparation method of this example is the same as that of example 1, except for the kinds and amounts of the components of the electrolyte, which are shown in table 1, and the other contents are the same as those of example 1.
Example 10
The preparation method of this example is the same as that of example 1, except for the kinds and amounts of the components of the electrolyte, which are shown in table 1, and the other contents are the same as those of example 1.
Comparative example 1
The comparative example was prepared in the same manner as in example 1 except for the kinds and amounts of the components of the electrolyte, and the kinds and amounts of the components of the electrolyte of this example are shown in table 1, and the other contents are the same as in example 1.
Comparative example 2
The comparative example was prepared in the same manner as in example 1 except for the kinds and amounts of the components of the electrolytic solution, and the kinds and amounts of the components of the electrolytic solution of this example are shown in table 1, and the other contents were the same as in example 1.
Comparative example 3
The comparative example was prepared in the same manner as in example 1 except for the kinds and amounts of the components of the electrolyte, and the kinds and amounts of the components of the electrolyte of this example are shown in table 1, and the other contents are the same as in example 1.
And (3) performance testing:
the lithium ion pouch batteries prepared in examples 1 to 10 and comparative examples 1 to 3 were respectively tested for cycle stability at high temperature (45 deg.c) and high pressure (3.0 to 4.48V).
Specifically, the battery is aged at 45 ℃ for 6 hours after being subjected to a formation process, and then subjected to capacity grading. And carrying out a cycle stability test after the capacity grading is finished. The testing department is as follows: first, constant current and constant voltage charging of 0.3C current to 4.48V, then 0.5C discharging to 3.0V, and then 0.5C current calibration of actual capacity. Wherein the normal temperature cycle condition of the battery is 25 ℃, the high temperature cycle condition of the battery is 45 ℃, the current is 0.5 ℃, and the calibrated capacity is converted into the current. The circulation part adopts a step charging mode, firstly, the constant current charging at 0.5C is carried out to 4.4V, the constant current charging at 0.2C is carried out to 4.48V, the cut-off current is 0.05C, and the circulation test is carried out for 500 times continuously.
Then, a high-temperature shelf experiment at 55 ℃ is carried out, and the test method comprises the following steps: the lithium ion soft package batteries prepared in examples 1 to 10 and comparative examples 1 to 3 were fully charged with the same current, and the capacity thereof was recorded as (Q) 0 ) The voltage range is (3.0-4.48V); standing at high temperature for 5 days, cooling in oven at 25 deg.C for 2-3h after 5 days, recovering battery capacity, and discharging to 3.0V at the same current to obtain capacity Q 7 (hold) and then charge-discharge cycle was performed again to record the discharge capacity as Q 7 (recovery).
The capacity retention rate of the battery is cycled for 300 times at 45 ℃, and the recovery retention rate after the battery is placed for 7 days at high temperature is calculated as follows:
battery capacity retention rate = (Q) after 300 cycles at 45 = 300 /Q 0 )*100％；
Capacity retention ratio = Q after 7 days of high temperature storage at 55 ℃ 7 (Retention)/Q 0 *100％；
Capacity retention = Q after 7 days of high temperature storage at 55 DEG C 7 (Retention)/Q 0 *100％。
The results of the above performance tests are shown in table 2.
TABLE 2
As can be seen from table 2, the high-temperature cycle performance and the capacity retention rate after high-temperature shelf life of the batteries of examples 1 to 10 (with the diboronate additive added) were significantly improved as compared to those of comparative examples 1 to 3.
As can also be seen from table 2, the increase rate of the internal resistance after the batteries of examples 1 to 10 were stored at a high temperature of 55 c for 7 days was significantly reduced, as compared to comparative examples 1 to 3.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (13)
1. An electrolyte, comprising:
diboronate additives, solvents and electrolyte salts;
the diboronate additive is selected from at least one of compounds with a structure shown in a formula I:
wherein R is selected from C 1 ～C 6 Of (a) an alkylene group of O, C 2 ～C 7 Alkenylene of (A), C 2 ～C 5 Alkynylene of (2), C 4 ～C 20 Arylene of (a) O-R 3 -O, substituted C 4 ～C 20 Arylene of (a), substituted C 2 ～C 7 Any of the alkenylene groups of (a);
R 1 and R 2 Each independently selected from C 1 ～C 6 Alkylene of (a), substituted C 1 ～C 6 Alkylene of (C) 6 ～C 10 Any of the arylene groups of (a);
R 3 is selected from C 1 ～C 6 An alkylene group of (a).
2. The electrolyte of claim 1,
said substituted C 1 ～C 6 The substituents in the alkylene group of (a) are selected from halogen, amino, C 6 ～C 20 Any one of the aryl groups of (a);
and/or, said C 4 ～C 20 The arylene group of (a) is selected from any one of a thienylene group, an anthracenylene group, a pyridinylene group, a phenylene group and a derivative group thereof;
and/or, said substituted C 4 ～C 20 The substituents in the arylene group of (A) are selected from cyano, C 1 ～C 6 Any of alkyl groups and halogens of (1);
and/or said substituted C 2 ～C 7 The substituents in the alkenylene group of (a) are selected from C 1 ～C 6 Alkyl group of (1).
3. The electrolyte of claim 1,
R 1 and R 2 Are all ethylene groups;
or, R 1 And R 2 Are all substituted ethylene groups;
or, R 1 And R 2 Are both propylene groups;
or, R 1 And R 2 Are all substituted propylene groups.
4. The electrolyte of claim 3, wherein in the compound of formula I, R is 1 And R 2 Are all substituted ethylene groups, and the formula of formula I is:
wherein R is 11 、R 12 、R 13 、R 14 、R 21 、R 22 、R 23 And R 24 Each independently selected from F atom, C 1 ～C 6 Alkyl or F-substituted C 1 ～C 6 Alkyl group of (1).
5. The electrolyte of claim 3, wherein in the compound of formula I, R is 1 And R 2 Are all substituted propylene groups, and the formula of formula I is:
wherein R' 11 、R' 12 、R' 13 、R' 21 、R' 22 、R' 23 、R" 11 、R" 12 、R" 21 And R " 22 Each independently selected from F atom, C 1 ～C 6 Alkyl or F-substituted C 1 ～C 6 Alkyl group of (1).
6. The electrolyte of claim 1, wherein the diboronate-based additive is selected from at least one of the following structural compounds:
7. the electrolyte of any one of claims 1-6, wherein the diboronate-based additive is present in an amount of 0.1-3% by mass, based on the total mass of the electrolyte.
8. The electrolyte of claim 7, wherein the electrolyte salt is present in an amount of 10-20% by mass, based on the total mass of the electrolyte.
9. The electrolyte of any one of claims 1-6, wherein the electrolyte salt is an electrolyte lithium salt selected from at least one of lithium hexafluorophosphate, lithium bis (oxalato) borate, lithium tetrafluoroborate, and lithium bis (fluorosulfonato) imide;
optionally, the solvent is selected from at least one of a carbonate-based solvent and a carboxylate-based solvent.
10. The electrolyte according to claim 8, further comprising an auxiliary film-forming additive in an amount of 0.2-10% by mass, based on the total mass of the electrolyte.
11. The electrolyte of claim 10, wherein the auxiliary film-forming additive is selected from at least one of vinylene carbonate, 1,3-propane sultone, lithium difluorophosphate, tris (trimethylsilyl) phosphite, and vinyl sulfate.
12. A battery having an electrolyte as claimed in any one of claims 1 to 11.
13. An electrical consumer, characterized in that the electrical consumer has a battery according to claim 12.
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