CN115954547A - Electrolyte, electrochemical device and electronic device - Google Patents
Electrolyte, electrochemical device and electronic device Download PDFInfo
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- CN115954547A CN115954547A CN202310238462.6A CN202310238462A CN115954547A CN 115954547 A CN115954547 A CN 115954547A CN 202310238462 A CN202310238462 A CN 202310238462A CN 115954547 A CN115954547 A CN 115954547A
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Abstract
An electrolyte, an electrochemical device and an electronic device are provided, the electrolyte including a compound represented by formula (I)
Description
Technical Field
The present disclosure relates to the field of electrochemical technologies, and more particularly, to an electrolyte, an electrochemical device, and an electronic device.
Background
Electrochemical devices, such as lithium ion batteries, have the advantages of high energy storage density, high open circuit voltage, low self-discharge rate, long cycle life, good safety, etc., and have been widely used as power sources in electronic products such as cameras, mobile phones, unmanned aerial vehicles, notebook computers, smart watches, etc.
With the wide application of lithium ion batteries in various electronic products, users have also raised higher and higher requirements for the performance of electrochemical devices, particularly high-temperature storage performance and cycle performance. The electrolyte is an important component of the lithium ion battery, and therefore, developing a suitable electrolyte to improve the high-temperature storage performance and the cycle performance of the lithium ion battery becomes a technical problem to be solved urgently.
Disclosure of Invention
An object of the present application is to provide an electrolyte, an electrochemical device, and an electronic device to improve high-temperature storage performance and cycle performance of the electrochemical device. The specific technical scheme is as follows:
in a first aspect, the present application provides an electrolyte comprising a compound of formula (I):
In some embodiments of the present application, the compound of formula (I) is present in an amount of 0.1% to 3% by mass of A, based on the mass of the electrolyte. By controlling the mass percentage of the compound represented by the formula (I) within the above range, the cyano group in the compound represented by the formula (I) is easily complexed with the positive electrode active material and adsorbed on the surface of the positive electrode, and thus the elution of metal elements, such as transition metal elements, in the positive electrode active material can be suppressed; meanwhile, the compound of the formula (I) can assist in forming a film on the anode to obtain a stable anode electrolyte interface (CEI) film, so that the continuous decomposition of the electrolyte is inhibited, the heat generation is reduced, and the high-temperature storage performance, the cycle performance and the safety performance of the electrochemical device are improved.
In some embodiments of the present application, the compound of formula (I) comprises at least one of the following compounds:
when the electrolyte including the compound of formula (I) in the above range is applied to an electrochemical device, the cyano group in the compound of formula (I) is more likely to form a complex with the positive electrode active material and adsorb on the surface of the positive electrode, and thus elution of a metal element, for example, elution of a transition metal element, in the positive electrode active material can be further suppressed; meanwhile, the compound of the formula (I) can assist in forming a film at the positive electrode to obtain a more stable CEI film, so that the continuous decomposition of the electrolyte is further inhibited, and the high-temperature storage performance, the cycle performance and the safety performance of the electrochemical device are improved.
In some embodiments of the present application, the electrolyte further comprises a compound of formula (II):
In some embodiments of the present application, the compound of formula (II) comprises at least one of 1,3-propane sultone, 1,4-butane sultone, methylene methanedisulfonate, 1,3-propane disulfonic anhydride, vinyl sulfate, vinyl 4-methylsulfate, 2,4-butane sultone, 2-methyl-1,3-propane sultone, propenyl-1,3-sultone, or propenyl sulfate. The electrolyte containing the compound of formula (II) in the above range is applied to an electrochemical device, which is beneficial to further inhibiting the reaction of the electrolyte at the positive and negative electrodes and further enhancing the stability of a CEI film and an SEI film, thereby further improving the high-temperature storage performance and the cycle performance of the electrochemical device.
In some embodiments of the present application, the electrolyte further comprises a compound of formula (iii):
In some embodiments of the present application, the compound of formula (iii) comprises at least one of the following compounds:
the electrolyte containing the compound of formula (III) in the above range is applied to an electrochemical device, and is beneficial to further enhancing the film forming stability and flexibility of an SEI film, so that the side reaction between the electrolyte and a negative electrode active material is further reduced, and the cycle performance of the electrochemical device is further improved.
In some embodiments of the present application, the electrolyte further comprises a polynitrile compound including at least one of:
In some embodiments herein, the electrolyte solution satisfies at least one of: (1) The electrolyte also comprises a boron-containing lithium salt, wherein the boron-containing lithium salt comprises at least one of lithium tetrafluoroborate, lithium dioxalate borate or lithium difluorooxalate borate, and based on the mass of the electrolyte, the mass percentage of the boron-containing lithium salt is E, the E is more than or equal to 0.01% and less than or equal to 1%, and the E/A is more than or equal to 0.01 and less than or equal to 5; (2) The electrolyte also comprises a phosphorus-containing lithium salt, wherein the phosphorus-containing lithium salt comprises at least one of lithium difluorophosphate, lithium difluorobis (oxalato) phosphate and lithium tetrafluoro (oxalato) phosphate, and based on the mass of the electrolyte, the mass percentage of the phosphorus-containing lithium salt is F, and F is more than or equal to 0.01% and less than or equal to 1%. By selecting the above-mentioned boron-containing lithium salt and controlling E and E/A within the above-mentioned ranges, and/or selecting the above-mentioned phosphorus-containing lithium salt and controlling F within the above-mentioned ranges, it is advantageous for the compound of formula (I) to form a synergistic effect with the boron-containing lithium salt and/or the phosphorus-containing lithium salt, resulting in an electrochemical device having good cycle performance and safety performance.
In some embodiments of the present application, the electrolyte further comprises a carbonate ester comprising at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl ethyl carbonate, dipropyl carbonate, butylene carbonate, or bis (2,2,2-trifluoroethyl) carbonate, the carbonate ester being present in an amount of G in a mass percent of 40% to 75%, based on the mass of the electrolyte; the electrolyte also comprises a carboxylic ester, wherein the carboxylic ester comprises at least one of methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, acetic acid-2,2-difluoroethyl ester, valerolactone, butyrolactone, 2-fluoroacetic acid ethyl ester, 2,2-difluoroacetic acid ethyl ester, trifluoroacetic acid ethyl ester, 2,2,3,3,3-pentafluoropropionic acid ethyl ester, 2,2,3,3,4,4,4-heptafluorobutyric acid methyl ester, 4,4,4-trifluoro-3- (trifluoromethyl) butyric acid methyl ester, 2,2,3,3,4,4,5,5,5-nonafluoropentanoic acid ethyl ester, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanoic acid methyl ester or 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanoic acid ethyl ester, and the mass percentage of the carboxylic ester is H, and H is not less than 15% and not more than 50% based on the mass of the electrolyte; the electrolyte also comprises a lithium salt, wherein the lithium salt comprises at least one of lithium hexafluorophosphate, lithium bistrifluoromethanesulfonylimide, lithium bis (fluorosulfonyl) imide, lithium hexafluorocaesate, lithium perchlorate or lithium trifluoromethanesulfonate, and based on the mass of the electrolyte, the mass percentage content of the lithium salt is I, and I is more than or equal to 8% and less than or equal to 15%. The carbonate, the carboxylate and the lithium salt are selected, the mass percentage of the carbonate, the carboxylate and the lithium salt is controlled within the range, and the compound shown in the formula (I) is added, so that the stability of the CEI film is improved, the CEI film is not easy to decompose in the charge-discharge cycle process, the oxygen release of the positive active material is reduced, the oxidative decomposition gas generation of the electrolyte at high temperature is improved, and the high-temperature storage performance, the cycle performance and the safety performance of the electrochemical device are improved.
In some embodiments of the present application, the electrolyte further comprises a carbonate ester comprising at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl ethyl carbonate, dipropyl carbonate, butylene carbonate, or bis (2,2,2-trifluoroethyl) carbonate, the carbonate ester being present in an amount of G in a mass percent of 25% to 75%, based on the mass of the electrolyte; the electrolyte also comprises a carboxylic ester, wherein the carboxylic ester comprises at least one of methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, acetic acid-2,2-difluoroethyl ester, valerolactone, butyrolactone, 2-fluoroacetic acid ethyl ester, 2,2-difluoroacetic acid ethyl ester, trifluoroacetic acid ethyl ester, 2,2,3,3,3-pentafluoropropionic acid ethyl ester, 2,2,3,3,4,4,4-heptafluorobutyric acid methyl ester, 4,4,4-trifluoro-3- (trifluoromethyl) butyric acid methyl ester, 2,2,3,3,4,4,5,5,5-nonafluoropentanoic acid ethyl ester, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanoic acid methyl ester or 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanoic acid ethyl ester, and the mass percentage of the carboxylic ester is H, and H is not less than 15% and not more than 60% based on the mass of the electrolyte; the electrolyte further comprises a lithium salt, wherein the lithium salt comprises at least one of lithium hexafluorophosphate, lithium bistrifluoromethanesulfonylimide, lithium bis (fluorosulfonyl) imide, lithium hexafluorocaesate, lithium perchlorate or lithium trifluoromethanesulfonate, and the mass percentage content of the lithium salt is I, and I is more than or equal to 8% and less than or equal to 15% based on the mass of the electrolyte. By selecting the carbonate, the carboxylate and the lithium salt, controlling the mass percentage of the carbonate, the carboxylate and the lithium salt within the range, and adding at least one of the compound shown in the formula (II), the compound shown in the formula (III), the polynitrile compound, the boron-containing lithium salt or the phosphorus-containing lithium salt on the basis of adding the compound shown in the formula (I), the low-temperature discharge performance of the obtained electrochemical device can be improved, and the high-temperature storage performance, the cycle performance or the safety performance of the electrochemical device can be further improved on the basis of having good high-temperature storage performance, cycle performance and safety performance.
In a second aspect, the present application provides an electrochemical device comprising the electrolyte provided in the first aspect, which has good high-temperature storage performance and cycle performance.
In a third aspect, an electronic device is provided that includes an electrochemical device provided in the second aspect of the present application. The electrochemical device provided by the application has good high-temperature storage performance and cycle performance. Therefore, the electronic device has good high-temperature storage performance and cycle performance.
The application has the beneficial effects that:
an electrolyte, an electrochemical device, and an electronic device are provided, the electrolyte including a compound represented by formula (I). The cyano group in the compound represented by the formula (I) is easily complexed with the positive electrode active material and adsorbed on the surface of the positive electrode, and can inhibit the elution of metal elements, such as transition metal elements, in the positive electrode active material; meanwhile, the compound shown in the formula (I) can assist in forming a film at the positive electrode to obtain a stable CEI film, so that the continuous decomposition of the electrolyte is inhibited, and the high-temperature storage performance, the cycle performance and the safety performance of the electrochemical device are improved.
Of course, not all advantages described above need to be achieved at the same time in the practice of any one product or method of the present application.
Detailed Description
The technical solutions in the embodiments of the present application will be described clearly and completely below, and it should be understood that the described embodiments are only a part of the embodiments of the present application, and not all embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application are within the scope of protection of the present application.
In the present application, the present application is explained by taking a lithium ion battery as an example of an electrochemical device, but the electrochemical device of the present application is not limited to a lithium ion battery.
An object of the present application is to provide an electrolyte, an electrochemical device, and an electronic device to improve high-temperature storage performance and cycle performance of the electrochemical device. The specific technical scheme is as follows:
in a first aspect, the present application provides an electrolyte comprising a compound of formula (I):
The inventors have studied and found that, by selecting the compound of formula (I), the cyano group in the compound of formula (I) is easily complexed with the positive electrode active material and adsorbed on the surface of the positive electrode, and the elution of the metal element, for example, the transition metal element in the positive electrode active material can be suppressed; meanwhile, the compound of the formula (I) can assist in forming a film on the anode to obtain a stable anode electrolyte interface (CEI) film, so that the continuous decomposition of electrolyte is inhibited, the heat generation is reduced, and the high-temperature storage performance, the cycle performance and the safety performance of the electrochemical device are improved. In this application, the positive electrode refers to the positive electrode piece, and the negative electrode refers to the negative electrode piece.
In some embodiments of the present application, the compound of formula (I) is present in an amount of 0.1% to 3% by mass, based on the mass of the electrolyte. For example, a may be 0.1%, 0.5%, 1%, 2%, 3%, or any two of these ranges. By controlling a within the range of the present application, the cyano group in the compound of formula (I) readily forms a complex with the positive electrode active material and adsorbs on the surface of the positive electrode, and elution of a metal element, such as a transition metal element, in the positive electrode active material can be suppressed; meanwhile, the compound of the formula (I) can assist in forming a film on the anode to obtain a stable anode electrolyte interface (CEI) film, so that the continuous decomposition of the electrolyte is inhibited, the heat generation is reduced, and the high-temperature storage performance, the cycle performance and the safety performance of the electrochemical device are improved.
In some embodiments of the present application, the compound of formula (I) comprises at least one of the following compounds:
without being limited to any theory, when the electrolyte including the compound of formula (I) in the above range is applied to an electrochemical device, the cyano group in the compound of formula (I) is more likely to form a complex with the positive electrode active material and is adsorbed on the surface of the positive electrode, and the elution of the metal element in the positive electrode active material can be further inhibited; meanwhile, the compound of the formula (I) can assist in forming a film at the positive electrode to obtain a more stable CEI film, so that the continuous decomposition of the electrolyte is further inhibited, and the high-temperature storage performance, the cycle performance and the safety performance of the electrochemical device are improved.
In some embodiments of the present application, the electrolyte further comprises a compound of formula (II):
In some embodiments of the present application, the compound of formula (II) comprises at least one of 1,3-propane sultone, 1,4-butane sultone, methylene methanedisulfonate, 1,3-propane disulfonic anhydride, vinyl sulfate, vinyl 4-methylsulfate, 2,4-butane sultone, 2-methyl-1,3-propane sultone, propenyl-1,3-sultone, or propenyl sulfate. Without being limited to any theory, the application of the electrolyte including the compound of formula (II) within the above range to an electrochemical device is advantageous to further inhibit the reaction of the electrolyte at the positive and negative electrodes, and also to further enhance the stability of the CEI film and the SEI film, thereby further improving the high-temperature storage performance and cycle performance of the electrochemical device.
In some embodiments of the present application, the electrolyte further comprises a compound represented by formula (iii):
In some embodiments of the present application, the compound of formula (iii) comprises at least one of the following compounds:
the electrolyte containing the compound of formula (III) in the above range is applied to an electrochemical device, which is beneficial to further enhancing the film forming stability and flexibility of an SEI film, thereby further reducing the side reaction between the electrolyte and a negative electrode active material, and further improving the cycle performance of the electrochemical device.
In some embodiments of the present application, the electrolyte further comprises a polynitrile compound including at least one of:
In some embodiments of the present application, the electrolyte further comprises a boron-containing lithium salt comprising at least one of lithium tetrafluoroborate, lithium dioxalate borate or lithium difluorooxalate borate, wherein the mass percentage of the boron-containing lithium salt is E, E is 0.01% to 1%, and E/A is 0.01 to 5, based on the mass of the electrolyte. For example, E can be 0.01%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, or any two of these ranges, and E/a can be 0.01, 1, 2,3, 4,5, or any two of these ranges. By selecting the lithium salt containing boron and controlling the mass percentage content of the lithium salt containing boron and the ratio of E/A within the range, the compound of the formula (I) and the lithium salt containing boron can form a synergistic effect to obtain a more stable CEI film, so that the continuous decomposition of the electrolyte is inhibited, the heat generation is reduced, and the cycle performance and the safety performance of the electrochemical device are improved.
In some embodiments of the present application, the electrolyte further comprises a phosphorus-containing lithium salt, wherein the phosphorus-containing lithium salt comprises at least one of lithium difluorophosphate, lithium difluorobis (oxalato) phosphate and lithium tetrafluorooxalato phosphate, and the mass percentage of the phosphorus-containing lithium salt is F, and the F is between 0.01% and 1%, based on the mass of the electrolyte. For example, F can be 0.01%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, or a range of any two of these values. By selecting the lithium salt containing phosphorus and controlling the mass percentage content of the lithium salt containing phosphorus within the range, the metal elements and oxygen atoms in the positive active material are stabilized, and the compound of the formula (I) and the lithium salt containing phosphorus form a synergistic effect to obtain a stable CEI film, so that the continuous decomposition of the electrolyte is inhibited, the heat generation is reduced, and the high-temperature storage performance and the safety performance of the electrochemical device are improved.
In some embodiments of the present application, the electrolyte further comprises a boron-containing lithium salt comprising at least one of lithium tetrafluoroborate, lithium dioxalate borate, or lithium difluorooxalate borate, and a phosphorus-containing lithium salt comprising at least one of lithium difluorophosphate, lithium difluorobis-oxalate phosphate, lithium tetrafluorooxalate phosphate. Based on the mass of the electrolyte, the mass percentage content of the boron-containing lithium salt is E, the mass percentage content of the phosphorus-containing lithium salt is F, E is more than or equal to 0.01% and less than or equal to 1%, E/A is more than or equal to 0.01% and less than or equal to 5,0.01% and less than or equal to 1%. By selecting the lithium salt containing boron and the lithium salt containing phosphorus and controlling E, E/A and F in the range, the compound shown in the formula (I) and the lithium salt containing boron and the lithium salt containing phosphorus can form a synergistic effect to obtain a stable CEI film, so that the continuous decomposition of an electrolyte is inhibited, the heat generation is reduced, and the cycle performance and the safety performance of an electrochemical device are improved.
In some embodiments of the present application, the electrolyte further comprises a carbonate ester comprising Ethylene Carbonate (EC), propylene Carbonate (PC), dimethyl carbonate, diethyl carbonate (DEC), ethyl methyl carbonate, propyl methyl carbonate, ethyl carbonateAt least one of propyl carbonate, dipropyl carbonate, butylene carbonate or di (2,2,2-trifluoroethyl) carbonate, wherein the mass percentage of the carbonate is G, based on the mass of the electrolyte, and the mass percentage of the carbonate is more than or equal to 40% and less than or equal to 75%, for example, G can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or the range formed by any two numerical values; the electrolyte further comprises a carboxylic acid ester comprising at least one of methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl Propionate (EP), propyl Propionate (PP), butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, 2,2-difluoroethyl acetate, valerolactone, butyrolactone, ethyl 2-fluoroacetate, 2,2-difluoroethyl acetate, ethyl trifluoroacetate, 2,2,3,3,3-ethyl pentafluoropropionate, 2,2,3,3,4,4,4-methyl heptafluorobutyrate, 4,4,4-trifluoro-3- (trifluoromethyl) methyl butyrate, 2,2,3,3,4,4,5,5,5-ethyl nonafluoropentanoate, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-methyl heptadecafluorononanoate, or 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-ethyl heptadecafluorononanoate, the mass percentage content of the carboxylic ester is H,15 percent to 50 percent of H, for example, H can be 15 percent, 20 percent, 25 percent, 30 percent, 35 percent, 40 percent, 45 percent, 50 percent or a range formed by any two numerical values; the electrolyte also includes a lithium salt including lithium hexafluorophosphate (LiPF) 6 ) At least one of lithium bistrifluoromethanesulfonylimide, lithium bis (fluorosulfonyl) imide, lithium hexafluorocaesate, lithium perchlorate or lithium trifluoromethanesulfonate, wherein the lithium salt is present in an amount of I in a range of 8% to 15% by mass, for example, I may be 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% by mass or in a range of any two of these values, based on the mass of the electrolyte. By selecting the carbonate and controlling the mass percentage of the carbonate within the above range, the stability of the CEI film is improved, thereby improving the high-temperature storage performance and the cycle performance of the electrochemical device. By selecting the carbonate, the carboxylate and the lithium salt, controlling the mass percentage of the carbonate, the carboxylate and the lithium salt within the range, and simultaneously adding the compound of the formula (I), the stability of the CEI film is favorably improved so that the CEI film is not easy to decompose in the charge-discharge cycle process, and the oxygen release of the positive active material is reduced so as to improve the oxidation of the electrolyte at high temperatureThe gas is decomposed, so that the high-temperature storage performance, the cycle performance and the safety performance of the electrochemical device are improved.
In some embodiments of the present application, the electrolyte further comprises a carbonate ester, the carbonate ester comprises at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl ethyl carbonate, dipropyl carbonate, butylene carbonate, or bis (2,2,2-trifluoroethyl) carbonate, and the mass percentage of the carbonate ester is G, wherein G is 25% or more and 75% or less, for example, G can be 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or a range consisting of any two values; the electrolyte further comprises a carboxylic acid ester comprising at least one of methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, acetic acid-2,2-difluoroethyl ester, valerolactone, butyrolactone, ethyl 2-fluoroacetate, 2,2-difluoroethyl acetate, ethyl trifluoroacetate, 2,2,3,3,3-ethyl pentafluoropropionate, 2,2,3,3,4,4,4-methyl heptafluorobutyrate, 4,4,4-trifluoro-3- (trifluoromethyl) methyl butyrate, 2,2,3,3,4,4,5,5,5-ethyl nonafluoropentanoate, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-methyl heptadecafluorononanoate, or 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-ethyl heptadecafluorononanoate, the mass percent of carboxylic acid ester being H,15% or more and less than 60%, e.g. H may be 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, or any one or two of these compositional values; the electrolyte also comprises lithium salt, the lithium salt comprises at least one of lithium hexafluorophosphate, lithium bistrifluoromethanesulfonylimide, lithium bis (fluorosulfonyl) imide, lithium hexafluorocaesate, lithium perchlorate or lithium trifluoromethanesulfonate, and the mass percentage of the lithium salt is I, wherein I is more than or equal to 8% and less than or equal to 15%, for example, I can be 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% or a range formed by any two numerical values. By selecting the carbonate and controlling the mass percentage of the carbonate within the above range, the stability of the CEI film is further improved, thereby further improving the high-temperature storage performance and the cycle performance of the electrochemical device. By selecting the carboxylic ester and controlling the mass percentage of the carboxylic ester within the range, the stability of the CEI film is further improved, the CEI film is not easy to decompose in the charge-discharge cycle process, and the oxygen release of the positive active material is reduced, so that the oxidative decomposition gas generation of the electrolyte at high temperature is further improved, and the high-temperature storage performance and the cycle performance of the electrochemical device are further improved. By selecting the lithium salt and controlling the mass percentage content of the lithium salt within the above range, the stability of the CEI film is further improved, and the high-temperature storage performance and the cycle performance of the electrochemical device are further improved. By selecting the carbonate, the carboxylate and the lithium salt, controlling the mass percentage of the carbonate, the carboxylate and the lithium salt within the range, and adding at least one of the compound shown in the formula (II), the compound shown in the formula (III), the polynitrile compound, the boron-containing lithium salt or the phosphorus-containing lithium salt on the basis of adding the compound shown in the formula (I), the low-temperature discharge performance of the obtained electrochemical device can be improved, and the high-temperature storage performance, the cycle performance or the safety performance can be further improved on the basis of the good high-temperature storage performance, the cycle performance and the safety performance of the obtained electrochemical device.
In some embodiments of the present application, the electrolyte comprises a compound of formula (I), a carbonate ester, a carboxylate ester, a lithium salt, wherein the mass percentage G of the carbonate ester is 40% to 75%, the mass percentage H of the carboxylate ester is 15% to 50%, and the mass percentage of the lithium salt is the aforementioned mass percentage, based on the mass of the electrolyte. By controlling the mass percentage of the carbonate and the carboxylate within the above range, the compound of formula (I) can inhibit the dissolution of metal elements in the positive active material, and can also assist in film formation at the positive electrode to obtain a stable CEI film, thereby inhibiting the continuous decomposition of the electrolyte, reducing heat generation, and further improving the high-temperature storage performance, cycle performance, and safety performance of the electrochemical device.
In some embodiments of the present application, the electrolyte comprises a compound of formula (I), a polynitrile compound, a carbonate ester, a carboxylate ester, a lithium salt, wherein the mass percentage G of the carbonate ester is 25% to 75%, the mass percentage H of the carboxylate ester is 15% to 60%, and the mass percentages of the polynitrile compound and the lithium salt are the aforementioned mass percentages, based on the mass of the electrolyte. By controlling the mass percentage of the carbonate and the carboxylate within the range, the formation of the synergistic effect between the compound of the formula (I) and the polynitrile compound is facilitated, and a more stable CEI film is obtained, so that the continuous decomposition of the electrolyte is inhibited, the heat generation is reduced, the high-temperature storage performance, the cycle performance and the safety performance of the electrochemical device are further improved, and the electrochemical device has good low-temperature discharge performance.
In some embodiments of the present application, the electrolyte comprises a compound of formula (I), a compound of formula (II), a carbonate, a carboxylate, a lithium salt, the carbonate is present in an amount of 25 to 75% by mass, the carboxylate is present in an amount of 15 to 60% by mass, and the compound of formula (II) and the lithium salt are present in the aforementioned amounts, based on the mass of the electrolyte. By controlling the mass percentage of the carbonate and the carboxylate within the above range, the formation of a synergistic effect between the compound of formula (I) and the compound of formula (II) is facilitated, and a more stable CEI film and an SEI film are obtained, so that the continuous decomposition of an electrolyte is inhibited, the heat generation is reduced, and the high-temperature storage performance, the cycle performance and the safety performance of the electrochemical device are further improved.
In some embodiments herein, the electrolyte comprises a compound of formula (I), a carbonate, a carboxylate, a lithium salt, and a phosphorus-containing lithium salt. Based on the mass of the electrolyte, the mass percentage content G of the carbonic ester is 25-75%, the mass percentage content H of the carboxylic ester is 15-60%, and the mass percentage contents of the lithium salt and the phosphorus-containing lithium salt are the mass percentage contents. By controlling the mass percentage of the carbonate and the carboxylate within the above range, the formation of a synergistic effect between the compound of formula (I) and the lithium salt containing phosphorus is facilitated, and a more stable CEI film is obtained, so that the continuous decomposition of the electrolyte is inhibited, the heat generation is reduced, and the electrochemical device with good high-temperature storage performance, cycle performance and safety performance is obtained.
In some embodiments herein, the electrolyte includes a compound of formula (I), a compound of formula (II), a carbonate, a carboxylate, a lithium salt, and a phosphorus-containing lithium salt. Based on the mass of the electrolyte, the mass percent G of the carbonic ester is 25-75%, the mass percent H of the carboxylic ester is 15-60%, and the mass percent of the compound of the formula (II), the lithium salt and the phosphorus-containing lithium salt is the aforementioned mass percent. By controlling the mass percentage of the carbonate and the carboxylate within the above range, the formation of a synergistic effect among the compound of formula (I), the compound of formula (II) and the lithium phosphate-containing salt is facilitated, and a more stable CEI film can be obtained, so that the continuous decomposition of the electrolyte is inhibited, the heat generation is reduced, and the electrochemical device with good high-temperature storage performance, cycle performance and safety performance is facilitated to be obtained.
In some embodiments herein, the electrolyte comprises a compound of formula (I), a carbonate, a carboxylate, and a lithium salt, and a compound of formula (iii) and/or a boron-containing lithium salt. Based on the mass of the electrolyte, the mass percentage content G of the carbonic ester is 25-75%, the mass percentage content H of the carboxylic ester is 15-60%, and the mass percentages of the lithium salt, the boron-containing lithium salt and the compound shown in the formula (III) are the mass percentages. The electrolyte comprises carbonate, carboxylate and lithium salt in the above range, the electrolyte also comprises a compound of formula (III) and/or a lithium salt containing boron, and the content of the components is controlled to be in the above range, so that the compound of formula (I) and the compound of formula (III) and/or the lithium salt containing boron are favorably cooperated, a stable CEI film can be obtained, the stability and flexibility of the SEI film can be enhanced, the continuous decomposition of the electrolyte is inhibited, the heat generation is reduced, and the cycle performance and the safety performance of an electrochemical device are favorably improved.
In some embodiments of the present application, the electrolyte further includes an ether solvent including, but not limited to, at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dibutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, or bis (2,2,2-trifluoroethyl) ether. The content of the ether solvent is not particularly limited in the present application as long as the object of the present invention can be achieved. For example, the ether solvent is contained in an amount of 10 to 50% by mass based on the mass of the electrolyte.
In a second aspect, the present application provides an electrochemical device comprising the electrolyte provided in the first aspect of the present application, thereby providing the electrochemical device with good high-temperature storage performance and cycle performance.
The electrochemical device of the present application further comprises an electrode assembly comprising a positive electrode tab, a negative electrode tab, and a separator.
The application has no particular limitation on the positive electrode piece as long as the purpose of the application can be achieved. For example, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector. The positive electrode current collector is not particularly limited as long as the object of the present invention can be achieved. For example, the positive electrode collector may include an aluminum foil or an aluminum alloy foil, etc. The positive electrode material layer of the present application includes a positive electrode active material. The kind of the positive electrode active material is not particularly limited as long as the object of the present application can be achieved. For example, the positive active material may include LiCo 1-y M y O 2 、LiNi 1-y M y O 2 、LiMn 2-y M y O 4 、LiNi x Co y Mn z M 1-x-y-z O 2 And the like, M comprises at least one of Fe, co, ni, mn, mg, cu, zn, al, sn, B, ga, cr, sr, V, ti and the like, y is more than or equal to 0 and less than or equal to 1,0 and less than or equal to x is more than or equal to 1,0 and less than or equal to z is more than or equal to 1, and x + y + z is less than or equal to 1. For example, the positive electrode active material may also include lithium cobaltate (LiCoO) 2 ) Lithium manganate (LiMn) 2 O 4 ) Lithium nickelate (LiNiO) 2 ) Lithium iron phosphate (LiFePO) 4 ) And lithium manganese iron phosphate, the positive electrode active material may be doped and/or coated. In the present application, the thickness of the positive electrode current collector and the positive electrode material layer is not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the positive electrode current collector is 1 μm to 200 μm. The thickness of the single-sided positive electrode material layer is 10 μm to 500 μm. In the present application, the positive electrode material layer may be provided on one surface in the thickness direction of the positive electrode current collector, and may also be provided on both surfaces in the thickness direction of the positive electrode current collector. The "surface" herein may be the entire region of the positive electrode current collector or a partial region of the positive electrode current collector, and the present application is not particularly limited as long as the surface can be formed byThe purpose of the application is achieved. The positive electrode material layer of the present application may further include a conductive agent and a binder.
The application has no particular limitation on the negative electrode sheet as long as the purpose of the application can be achieved. For example, the negative electrode tab includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The present application is not particularly limited as long as the object of the present application can be achieved. For example, the negative electrode current collector may include, but is not limited to, a copper foil, an aluminum foil, a nickel foil, a carbon-based current collector, or the like. The anode material layer of the present application includes an anode active material. The present application does not particularly limit the kind of the anode active material as long as the object of the present application can be achieved. For example, the negative active material may include, but is not limited to, at least one of lithium metal, natural graphite, artificial graphite, or a silicon-based material including at least one of silicon, a silicon oxy compound, a silicon carbon compound, or a silicon alloy. In the present application, the thickness of the anode current collector and the anode material layer is not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the negative electrode current collector is 1 μm to 200 μm, and the thickness of the single-sided negative electrode material layer is 10 μm to 500 μm. In the present application, the negative electrode material layer may be provided on one surface in the thickness direction of the negative electrode current collector, and may also be provided on both surfaces in the thickness direction of the negative electrode current collector. The "surface" herein may be the entire region of the negative electrode current collector or a partial region of the negative electrode current collector, and the present application is not particularly limited as long as the object of the present application can be achieved. The negative electrode material layer of the present application may further include a conductive agent and a binder.
The above-mentioned conductive agent and binder are not particularly limited as long as the object of the present application can be achieved. For example, the conductive agent may include at least one of conductive carbon black, acetylene black, ketjen black, flake graphite, graphene, carbon nanotubes, carbon nanowires, or carbon fibers. The binder may include at least one of polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, styrene-acrylate copolymer, styrene-butadiene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethylcellulose (CMC-Na), polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyaniline, polyimide, polyamideimide, polysiloxane, epoxy resin, polyester resin, polyurethane resin, polyfluorene, or the like.
In some embodiments of the present application, the mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode material layer may be (70 to 98): (0.5 to 15): 1 to 15. In some embodiments of the present application, the mass ratio of the negative electrode active material, the conductive agent, and the binder in the negative electrode material layer may be (80 to 99): (0.5 to 10).
The separator is not particularly limited as long as the object of the present application can be achieved. For example, the separator may include at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, aramid, or the like, and the polyethylene and the polypropylene may prevent a short circuit and may also improve the stability of the electrochemical device by a shutdown effect. For example, the polyethylene may comprise at least one of high density polyethylene, low density polyethylene, or ultra high molecular weight polyethylene. The surface of the isolating membrane can comprise a porous layer, the porous layer is arranged on at least one surface of the isolating membrane, the porous layer can comprise at least one of inorganic particles or a binder, and the porous layer can improve the heat resistance, the oxidation resistance and the electrolyte wetting performance of the isolating membrane and enhance the adhesion between the isolating membrane and a pole piece. For example, the inorganic particles may include alumina (Al) 2 O 3 ) Silicon oxide (SiO) 2 ) Magnesium oxide (MgO), titanium oxide (TiO) 2 ) Hafnium oxide (HfO) 2 ) Tin oxide (SnO) 2 ) Cerium oxide (CeO) 2 ) Nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO) 2 ) Yttrium oxide (Y) 2 O 3 ) At least one of silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium sulfate, and the like. For example, the binder of the porous layer mayThe adhesive comprises at least one of polyvinylidene fluoride, copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethylcellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene and the like. In some embodiments of the present application, the pore size of the separation membrane may be 0.01 μm to 1 μm.
The electrochemical device of the present application is not particularly limited, and may include any device in which electrochemical reactions occur. In one embodiment of the present application, an electrochemical device may include, but is not limited to: a lithium ion secondary battery (lithium ion battery), a lithium metal secondary battery, a lithium polymer secondary battery, a lithium ion polymer secondary battery, or the like.
The preparation process of the electrochemical device is well known to those skilled in the art, and the present application is not particularly limited, and for example, may include, but is not limited to, the following steps: stacking the positive pole piece, the isolating membrane and the negative pole piece in sequence, winding, folding and the like according to needs to obtain an electrode assembly with a winding structure, putting the electrode assembly into a packaging bag, injecting electrolyte into the packaging bag and sealing the packaging bag to obtain the electrochemical device; or, stacking the positive pole piece, the isolating membrane and the negative pole piece in sequence, fixing four corners of the whole lamination structure by using an adhesive tape to obtain an electrode assembly of the lamination structure, placing the electrode assembly into a packaging bag, injecting electrolyte into the packaging bag and sealing the packaging bag to obtain the electrochemical device. In addition, an overcurrent prevention element, a guide plate, or the like may be placed in the packaging bag as necessary to prevent a pressure rise or overcharge/discharge inside the electrochemical device. The application has no limitation to the packaging bag, and the person skilled in the art can select the packaging bag according to actual needs as long as the purpose of the application can be achieved. For example, a plastic-aluminum film package can be used.
In a third aspect, an electronic device is provided that includes an electrochemical device provided in the second aspect of the present application. The electrochemical device provided by the application has good high-temperature storage performance and cycle performance. Therefore, the electronic device has good high-temperature storage performance and cycle performance.
The electronic device of the present application is not particularly limited, and may be any electronic device known in the art. In some embodiments, the electronic device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile machine, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a handheld cleaner, a portable CD player, a mini-disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power source, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a large household battery or lithium ion capacitor, and the like.
Examples
Hereinafter, embodiments of the present application will be described in more detail with reference to examples and comparative examples. Various tests and evaluations were carried out according to the following methods. Unless otherwise specified, "part" and "%" are based on mass.
Test method and apparatus
25 ℃ cycle performance test:
charging the lithium ion battery at a constant current of 0.7 ℃ to a voltage of 4.5V, then charging at a constant voltage of 4.5V to a current of 0.05C, then discharging at a constant current of 0.7C to a voltage of 3.0V, which is a charge-discharge cycle, and then repeating the charge-discharge cycle to 800 cycles according to the flow of 0.7C charging and 1C discharging. And taking the cycle discharge capacity of the 3 rd cycle as a standard, and taking the capacity retention rate as an index for evaluating the cycle performance of the lithium ion battery.
The cycle capacity retention ratio = discharge capacity at 800 th cycle/discharge capacity at 3 rd cycle × 100%.
And (3) testing the high-temperature storage performance:
charging the lithium ion battery at 25 ℃ with a constant current of 0.5 ℃ to a voltage of 4.55V, then charging with a constant voltage of 4.55V to a current of 0.05C, testing and recording the thickness of the lithium ion battery with a micrometer and recording the thickness as d 0 . Will testAnd (4) transferring the lithium ion battery to a constant temperature box of 60 ℃ for storage for 20 days, and after 20 days, testing and recording the thickness of the lithium ion battery by using a micrometer and recording the thickness as d.
Storage thickness expansion ratio = (d-d) 0 )/d 0 ×100％。
Testing the performance of the hot box:
charging the lithium ion battery at 25 ℃ with a constant current of 0.5 ℃ until the voltage is 4.55V, then charging at a constant voltage of 4.55V until the current is 0.02C, placing the fully charged lithium ion battery in a high-low temperature box, raising the temperature to 200 +/-2 ℃ at a temperature raising speed of 2 ℃/min, timing from the beginning of temperature raising, and recording the failure time of a hot box (the failure is the ignition or explosion of the lithium ion battery).
And (3) testing low-temperature discharge performance:
at 25 ℃, the lithium ion battery is charged with a constant current of 0.5 ℃ until the voltage is 4.5V, and then charged with a constant voltage of 4.5V until the current is 0.025C. Discharging at 25 deg.C with constant current of 0.2C to voltage of 3.0V, recording discharge capacity and recording as C 0 . Then charging the lithium ion battery at a constant current of 0.5C to a voltage of 4.5V and then at a constant voltage of 4.5V to a current of 0.025C at 25 ℃. Discharging at-20 deg.C with constant current of 0.2C to voltage of 3.0V, recording discharge capacity and recording as C 1 。
Low temperature discharge capacity retention = C 1 /C 0 ×100%。
Examples 1 to 1
< preparation of Positive electrode sheet >
The positive electrode active material lithium cobaltate LiCoO 2 The conductive agent, conductive carbon black and a binder, namely polyvinylidene fluoride (PVDF), are mixed according to the mass ratio of 97.9 to 1.2, N-methylpyrrolidone (NMP) is added, and the mixture is stirred under the action of a vacuum stirrer until the system becomes uniform and transparent, so that anode slurry is obtained, wherein the solid content of the anode slurry is 70wt%. And uniformly coating the positive electrode slurry on one surface of a positive electrode current collector aluminum foil with the thickness of 13 mu m, and drying the aluminum foil at 120 ℃ for 1h to obtain a positive electrode piece with the thickness of a positive electrode material layer of 60 mu m. And repeating the steps on the other surface of the aluminum foil to obtain the positive pole piece with the positive pole material layer coated on the two sides. Then cold pressing and cuttingAnd (3) slicing and cutting, and drying for 1h at 120 ℃ under vacuum to obtain the positive pole piece with the specification of 74mm multiplied by 851 mm.
< preparation of negative electrode sheet >
Mixing artificial graphite, styrene Butadiene Rubber (SBR) serving as a binder and sodium carboxymethyl cellulose (CMC-Na) serving as a thickening agent according to a mass ratio of 97.4. And uniformly coating the negative electrode slurry on one surface of a negative electrode current collector copper foil with the thickness of 10 mu m, and drying the copper foil at 120 ℃ to obtain a negative electrode pole piece with the thickness of a negative electrode material layer of 50 mu m. And repeating the steps on the other surface of the copper foil to obtain the negative electrode with the negative electrode material layer coated on the two surfaces. And then carrying out cold pressing, cutting into pieces and slitting, and drying for 1h at 120 ℃ under a vacuum condition to obtain the negative pole piece with the specification of 76mm multiplied by 867 mm.
< preparation of electrolyte solution >
In an argon atmosphere glove box with a water content of less than 10ppm, ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate were mixed in a mass ratio of 1 6 And a compound of formula (I) formula (I-9) to obtain an electrolyte. Wherein the mass percent of the lithium salt is 12.5 percent, the mass percent of the compound of the formula (I) is 0.1 percent, and the balance is the basic solvent.
< preparation of separator >
Aluminum oxide (Al) 2 O 3 ) Adding the ceramic into NMP, blending to obtain ceramic layer slurry with the solid content of 30wt%, uniformly stirring, uniformly coating the ceramic layer slurry on one surface of a polyethylene base material with the thickness of 5 mu m, and drying to obtain the isolating membrane with the single surface coated with the ceramic layer. Then, PVDF is added into NMP and stirred evenly to prepare binder slurry with the solid content of 30wt%, and then 2.5mg/1540.25mm is coated on the surface of the ceramic layer 2 The PVDF is dried for 4 hours at 85 ℃ to obtain an adhesive layer, and then the other surface of the polyethylene base material is coated with 2.5mg/1540.25mm 2 Obtaining an adhesive layer, drying at 85 ℃ for 4 hours to obtain the isolating membrane. The porosity of the separator was 39%.
< preparation of lithium ion Battery >
And sequentially stacking the prepared positive pole piece, the isolating film and the negative pole piece in sequence, enabling one surface of the isolating film with the ceramic layer and the adhesive layer to face the positive pole piece, and enabling the other surface (namely one surface with the adhesive layer) to face the negative pole piece, enabling the isolating film to be positioned between the positive pole piece and the negative pole piece to play an isolating role, and winding to obtain the electrode assembly. And after welding the tabs, putting the electrode assembly into an aluminum plastic film outer package, placing the aluminum plastic film outer package in a vacuum oven at 80 ℃ for drying for 12h to remove moisture, injecting the prepared electrolyte, packaging, and performing the working procedures of formation, degassing, edge cutting and the like to obtain the lithium ion battery.
Examples 1-2 to examples 1-13
The procedure of example 1-1 was repeated, except that the kind and mass% of the compound of formula (I) in < preparation of electrolyte solution > were changed according to Table 1, the mass% of the base solvent was changed, and the mass% of the lithium salt was not changed.
Example 2-1 to example 2-11
The examples were conducted in the same manner as in examples 1 to 4 except that in < preparation of electrolyte > the polynitrile compound was further added as shown in Table 2, and the type and mass% of the compound of formula (I), the type and mass% of the polynitrile compound, and the mass% of the base solvent were changed as shown in Table 2, and the mass% of the lithium salt was not changed.
Example 3-1 to example 3-7
Examples 1 to 4 were repeated except that the compound of formula (II) was added as shown in Table 3 in < preparation of electrolyte solution > and the kind and the content by mass of the compound of formula (II) were adjusted as shown in Table 3, the content by mass of the base solvent was changed, and the content by mass of the lithium salt was not changed.
Examples 3 to 8 to 3 to 11
The examples were conducted in the same manner as in examples 1 to 4 except that in < preparation of electrolyte > a phosphorus-containing lithium salt was further added as shown in Table 3, and the mass percentage of lithium difluorophosphate was adjusted as shown in Table 3, the mass percentage of the base solvent was changed, and the mass percentage of the lithium salt was not changed.
Examples 3 to 12
The examples were conducted in the same manner as in examples 1 to 4 except that in < preparation of electrolyte > the compound of formula (II) and the phosphorus-containing lithium salt were further added as shown in Table 3, and the mass% of the compound of formula (II) and the mass% of lithium difluorophosphate were adjusted as shown in Table 3, and the mass% of the base solvent was changed without changing the mass% of the lithium salt.
Example 4-1 to example 4-12
The examples were conducted in the same manner as in examples 1 to 4 except that in < preparation of electrolyte > the compound of the formula (III) and/or the lithium bis (oxalato) borate containing a boron lithium salt were further added as shown in Table 4, and the kind and the mass% of the compound of the formula (I), the kind and the mass% of the compound of the formula (III), and the mass% of the lithium bis (oxalato) borate containing a boron lithium salt were adjusted as shown in Table 4, and the mass% of the base solvent was changed while the mass% of the lithium salt was kept constant.
Comparative examples 1 to 1
The procedure of example 1-1 was repeated, except that the compound of formula (I) was not added in < preparation of electrolyte solution >, the mass% of the base solvent was changed, and the mass% of the lithium salt was not changed.
Comparative example 2-1
The procedure of example 2-1 was repeated, except that in < preparation of electrolyte > the compound of formula (I) was not added, the polynitrile compound of formula (IV-8) was added, the mass% of the base solvent was changed, and the mass% of the lithium salt was not changed, as shown in Table 2.
The production parameters and performance parameters of each example and comparative example are shown in tables 1 to 4.
TABLE 1
Note: in table 1, "/" indicates that there is no corresponding manufacturing parameter, material or performance parameter, "greater than 50" indicates that the test is stopped if the storage thickness expansion rate exceeds 50%, and "-" indicates that the lithium ion battery prepared from the electrolyte cannot be cycled up to 800 cycles, so that the lithium ion battery does not have the parameter of "cycle capacity retention rate".
As can be seen from examples 1-1 to 1-13 and comparative examples 1-1, the application of the electrolyte comprising the compound of formula (I) to a lithium ion battery can improve the high temperature storage performance, the cycle performance and the safety performance of the lithium ion battery.
It can be seen from examples 1-1 to 1-13 that the mass percentage A of the compound of formula (I) generally affects the high temperature storage and cycling performance of the lithium ion battery. When A is more than or equal to 0.1% and less than or equal to 3%, the lithium ion battery has low storage thickness expansion rate, high capacity retention rate and long hot box failure time. Therefore, the lithium ion battery has good high-temperature storage performance, cycle stability and safety performance by regulating and controlling A within the range of the application.
TABLE 2
Note: the "/" in table 2 indicates the absence of the corresponding manufacturing, material or performance parameter.
It can be seen from examples 1-4, 2-1 to 2-11 that the electrolyte, in the case of containing the compound of formula (I), allows the lithium ion battery to have good high-temperature storage performance, cycle performance and low-temperature discharge performance by introducing the polynitrile compound.
The type and content of the polynitrile compound, the content of the compound shown in the formula (I) and the ratio D/A of the two contents generally influence the high-temperature storage performance and the cycle performance of the lithium ion battery. It can be seen from examples 2-1 to 2-11 that when the above parameters are within the ranges of the present application, the lithium ion battery has a low storage thickness expansion rate, a high cycle capacity retention rate, and a high low-temperature discharge capacity retention rate, indicating that the lithium ion battery has excellent high-temperature storage performance, cycle performance, and low-temperature discharge performance.
As can be seen from examples 1-4, examples 2-2, and comparative examples 2-1, examples 1-4 contained only the compound of formula (I), comparative examples 2-1 contained only the polynitrile compound, and examples 2-2 contained both the compound of formula (I) and the polynitrile compound, whereas the lithium ion battery of examples 2-2 had better high-temperature storage and cycle properties, and also had good low-temperature discharge properties. Thus, it was demonstrated that, when the electrolyte contains both the compound of formula (I) and the polynitrile compound, the lithium ion battery has excellent high-temperature storage properties, cycle properties and low-temperature discharge properties.
TABLE 3
Note: the "/" in table 3 indicates that no corresponding manufacturing, material or performance parameters are present.
As can be seen from examples 3-1 to 3-7 and examples 1-4, in the case of an electrolyte containing a compound of formula (I), the high-temperature storage performance and cycle performance of a lithium ion battery can be improved by further adding a compound of formula (II) to the electrolyte.
The type and content of the compound of formula (II) generally affect the high-temperature storage performance and the cycle performance of the lithium ion battery, and it can be seen from examples 3-1 to 3-7 that when the above parameters are within the range of the present application, the storage thickness expansion rate of the lithium ion battery is low, and the cycle capacity retention rate is high, indicating that the lithium ion battery has excellent high-temperature storage performance and cycle performance.
It can be seen from examples 3-8 to 3-11 and 1-4 that the electrolyte contains the compound of formula (I), and the high-temperature storage performance and cycle performance of the lithium ion battery can be improved by further adding a phosphorus-containing lithium salt to the electrolyte.
As can be seen from examples 3 to 12, in the case of the electrolyte containing the compound of formula (I), by further adding the compound of formula (II) and a phosphorus-containing lithium salt to the electrolyte, the lithium ion battery has better high-temperature storage performance and cycle performance through the synergistic effect of the above substances.
TABLE 4
Note: the "/" in table 4 indicates the absence of the corresponding manufacturing, material or performance parameters.
As can be seen from examples 4-1 to 4-6 and examples 1-4, in the case of the electrolyte containing the compound of formula (I), the cycle performance of the lithium ion battery is remarkably improved by further adding the compound of formula (III) to the electrolyte.
As can be seen from examples 4-7 to 4-11 and examples 1-4, the electrolyte containing the compound of formula (I) is advantageous for further improving the cycle performance of the lithium ion battery by further adding a boron-containing lithium salt to the electrolyte.
As can be seen from examples 4 to 12, the lithium ion battery has better cycle performance by the synergistic effect of the compound of formula (iii) and the boron-containing lithium salt further added to the electrolyte in the case where the electrolyte contains the compound of formula (I).
The ratio of E/A also generally affects the high temperature storage and cycling performance of the lithium ion battery, and as can be seen from examples 4-7 through examples 4-12, the lithium ion battery has good cycling performance when the E/A is within the range of the present application.
It should be noted that, in this document, the term "comprises/comprising" or any other variation thereof is intended to cover a non-exclusive inclusion, so that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but also other elements not expressly listed or inherent to such process, method, article, or apparatus.
All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments.
The above description is only for the preferred embodiment of the present application, and is not intended to limit the scope of the present application. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application are included in the protection scope of the present application.
Claims (13)
1. An electrolyte, comprising a compound of formula (I):
x is selected from
Or->
；
A 11 、A 12 And A 13 Each independently selected from
；A 11 、A 12 And A 13 At least one of which is selected from>
；R 11 、R 12 、R 13 And R 14 Each independently selected from hydrogen, halogen atoms, C unsubstituted or substituted by Ra 1 To C 5 Alkyl, unsubstituted or Ra-substituted C 2 To C 6 Alkenyl of (3), C unsubstituted or substituted by Ra 2 To C 6 Alkynyl of (2), C unsubstituted or substituted by Ra 6 To C 10 Aryl of (a);
R 15 、R 16 and R 17 Each independently selected from C unsubstituted or substituted by Ra 1 To C 6 An alkylene group of (a); ra in each group is independently selected from halogen atoms.
2. The electrolyte according to claim 1, wherein the compound represented by the formula (I) is contained in an amount of 0.1% to 3% by mass based on the mass of the electrolyte.
3. The electrolyte of claim 1, wherein the compound of formula (I) comprises at least one of the following compounds:
4. the electrolyte of claim 1, further comprising a compound of formula (II):
based on the mass of the electrolyte, the mass percentage content of the compound shown in the formula (II) is B, and B is more than or equal to 0.01% and less than or equal to 8%.
5. The electrolyte of claim 4, wherein the compound of formula (II) comprises at least one of 1,3-propane sultone, 1,4-butane sultone, methylene methanedisulfonate, 1,3-propane disulfonic anhydride, vinyl sulfate, 4-methyl vinyl sulfate, 2,4-butane sultone, 2-methyl-1,3-propane sultone, propenyl-1,3-sultone, or allyl sulfate.
6. The electrolyte of claim 1, further comprising a compound of formula (iii):
based on the mass of the electrolyte, the mass percentage content of the compound shown in the formula (III) is C, and C is more than or equal to 0.01% and less than or equal to 15%.
7. The electrolyte of claim 6, wherein the compound of formula (III) comprises at least one of the following compounds:
8. the electrolyte of claim 2, further comprising a polynitrile compound comprising at least one of:
9. The electrolyte of claim 2, wherein the electrolyte meets at least one of:
(1) The electrolyte also comprises a boron-containing lithium salt, wherein the boron-containing lithium salt comprises at least one of lithium tetrafluoroborate, lithium dioxalate borate or lithium difluorooxalate borate, and based on the mass of the electrolyte, the mass percentage of the boron-containing lithium salt is E, the E is more than or equal to 0.01% and less than or equal to 1%, and the E/A is more than or equal to 0.01 and less than or equal to 5;
(2) The electrolyte also comprises a phosphorus-containing lithium salt, wherein the phosphorus-containing lithium salt comprises at least one of lithium difluorophosphate, lithium difluorobis (oxalato) phosphate and lithium tetrafluoro (oxalato) phosphate, and based on the mass of the electrolyte, the mass percentage of the phosphorus-containing lithium salt is F, and F is more than or equal to 0.01% and less than or equal to 1%.
10. The electrolyte of any one of claims 1 to 3,
the electrolyte also comprises carbonic ester, wherein the carbonic ester comprises at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl ethyl carbonate, dipropyl carbonate, butylene carbonate or bis (2,2,2-trifluoroethyl) carbonic ester, and the mass percentage of the carbonic ester is G, and G is more than or equal to 40% and less than or equal to 75% based on the mass of the electrolyte;
the electrolyte also comprises a carboxylic ester, wherein the carboxylic ester comprises at least one of methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, acetic acid-2,2-difluoroethyl ester, valerolactone, butyrolactone, 2-fluoroacetic acid ethyl ester, 2,2-difluoroacetic acid ethyl ester, trifluoroacetic acid ethyl ester, 2,2,3,3,3-pentafluoropropionic acid ethyl ester, 2,2,3,3,4,4,4-heptafluorobutyric acid methyl ester, 4,4,4-trifluoro-3- (trifluoromethyl) butyric acid methyl ester, 2,2,3,3,4,4,5,5,5-nonafluoropentanoic acid ethyl ester, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanoic acid methyl ester or 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanoic acid ethyl ester, and the mass percentage of the carboxylic ester is H, and H is not less than 15% and not more than 50% based on the mass of the electrolyte;
the electrolyte further comprises a lithium salt, wherein the lithium salt comprises at least one of lithium hexafluorophosphate, lithium bistrifluoromethanesulfonylimide, lithium bis (fluorosulfonyl) imide, lithium hexafluorocaesate, lithium perchlorate or lithium trifluoromethanesulfonate, and the mass percentage content of the lithium salt is I, and I is more than or equal to 8% and less than or equal to 15% based on the mass of the electrolyte.
11. The electrolyte of any one of claims 4 to 9,
the electrolyte also comprises carbonic ester, wherein the carbonic ester comprises at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl ethyl carbonate, dipropyl carbonate, butylene carbonate or bis (2,2,2-trifluoroethyl) carbonic ester, and the mass percentage of the carbonic ester is G, and G is more than or equal to 25% and less than or equal to 75% based on the mass of the electrolyte;
the electrolyte also comprises a carboxylic ester, wherein the carboxylic ester comprises at least one of methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, acetic acid-2,2-difluoroethyl ester, valerolactone, butyrolactone, 2-fluoroacetic acid ethyl ester, 2,2-difluoroacetic acid ethyl ester, trifluoroacetic acid ethyl ester, 2,2,3,3,3-pentafluoropropionic acid ethyl ester, 2,2,3,3,4,4,4-heptafluorobutyric acid methyl ester, 4,4,4-trifluoro-3- (trifluoromethyl) butyric acid methyl ester, 2,2,3,3,4,4,5,5,5-nonafluoropentanoic acid ethyl ester, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanoic acid methyl ester or 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanoic acid ethyl ester, and the mass percentage of the carboxylic ester is H, and H is not less than 15% and not more than 60% based on the mass of the electrolyte;
the electrolyte also comprises a lithium salt, wherein the lithium salt comprises at least one of lithium hexafluorophosphate, lithium bistrifluoromethanesulfonylimide, lithium bis (fluorosulfonyl) imide, lithium hexafluorocaesate, lithium perchlorate or lithium trifluoromethanesulfonate, and based on the mass of the electrolyte, the mass percentage content of the lithium salt is I, and I is more than or equal to 8% and less than or equal to 15%.
12. An electrochemical device comprising the electrolyte of any one of claims 1 to 11.
13. An electronic device, characterized in that the electronic device comprises the electrochemical device according to claim 12.
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| US20090136779A1 (en) * | 2007-11-26 | 2009-05-28 | Chien-Hong Cheng | Conjugated compounds containing hydroindoloacridine structural elements, and their use |
| CN107394258A (en) * | 2017-06-19 | 2017-11-24 | 华南师范大学 | A kind of high-voltage lithium-ion battery electrolyte and high-voltage lithium ion batteries |
| CN113140796A (en) * | 2021-04-20 | 2021-07-20 | 东莞市杉杉电池材料有限公司 | Lithium ion battery electrolyte and lithium ion battery containing same |
| CN114094102A (en) * | 2021-11-03 | 2022-02-25 | 珠海冠宇电池股份有限公司 | Secondary battery |
| CN115398695A (en) * | 2021-12-31 | 2022-11-25 | 东莞新能源科技有限公司 | Electrolyte solution, electrochemical device comprising the same, and electronic device |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20090136779A1 (en) * | 2007-11-26 | 2009-05-28 | Chien-Hong Cheng | Conjugated compounds containing hydroindoloacridine structural elements, and their use |
| CN107394258A (en) * | 2017-06-19 | 2017-11-24 | 华南师范大学 | A kind of high-voltage lithium-ion battery electrolyte and high-voltage lithium ion batteries |
| CN113140796A (en) * | 2021-04-20 | 2021-07-20 | 东莞市杉杉电池材料有限公司 | Lithium ion battery electrolyte and lithium ion battery containing same |
| CN114094102A (en) * | 2021-11-03 | 2022-02-25 | 珠海冠宇电池股份有限公司 | Secondary battery |
| CN115398695A (en) * | 2021-12-31 | 2022-11-25 | 东莞新能源科技有限公司 | Electrolyte solution, electrochemical device comprising the same, and electronic device |
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