Non-aqueous electrolyte, lithium ion battery and electric device

Abstract

According to the non-aqueous electrolyte, trialkylfluorosilane is combined with carboxylic ester and cyclic sulfate for use, so that the normal-temperature and low-temperature input and output characteristics of a lithium ion battery can be remarkably improved, the self-discharge rate of the battery can be remarkably reduced, DCR increase in the storage process is reduced, and the service life of the battery is prolonged; the battery has high input and output characteristics, low self-discharge rate and long service life, and the comprehensive performance of the battery is improved.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a non-aqueous electrolyte, a lithium-ion battery and an electrical device. Background Art

[0002] Lithium-ion batteries are now widely used in pure electric vehicles, hybrid electric vehicles, smart grids and other fields. With the rapid development of lithium-ion battery technology, people have higher and higher requirements for battery performance. As an important component of lithium-ion batteries, electrolytes have attracted much attention, but conventional electrolytes have poor performance and cannot take into account the high input-output characteristics, low self-discharge rate and long life of batteries.

[0003] Therefore, there is an urgent need to develop an electrolyte that can take into account the high input-output characteristics, low self-discharge rate and long life of the battery, so as to improve the overall performance of the battery. Summary of the invention

[0004] In view of the problems existing in the background technology, the present application provides a non-aqueous electrolyte, which can take into account the high input-output characteristics, low self-discharge rate and long life of the battery, and improve the comprehensive performance of the battery.

[0005] The non-aqueous electrolyte provided in the first aspect of the present application includes: carboxylic acid ester, cyclic sulfate ester and trialkyl fluorosilane.

[0006] The non-aqueous electrolyte of the present application includes a carboxylate solvent, a first additive cyclic sulfate and a second additive trialkyl fluorosilane. Adding a carboxylate solvent to the electrolyte can improve the input and output characteristics of the battery at room temperature and low temperature, but the electrochemical stability of the carboxylate solvent itself is relatively poor, which will deteriorate the self-discharge and life characteristics of the battery. Cyclic sulfate is added to the electrolyte, and a SEI film with good passivation effect is formed at the negative electrode during formation, which can improve the self-discharge and life deterioration problems caused by carboxylate, but in turn will cause the interface impedance to increase and deteriorate the input and output characteristics of the battery. In order to solve this contradiction, the present application further adds trialkyl fluorosilane to the electrolyte, and a SEI film with low interface impedance can be formed at the negative electrode during formation, which can improve the problem of increased interface impedance caused by the use of cyclic sulfate. In addition, trialkyl fluorosilane can reduce the side reactions of the battery during storage, reduce the increase of the interface impedance of the battery during storage, improve the DCR growth during storage, and enable the battery to maintain high input and output characteristics during life, thereby extending the battery life. Therefore, the present application, by using trialkyl fluorosilane in combination with carboxylic acid ester and cyclic sulfate ester, can not only significantly improve the room temperature and low temperature input and output characteristics of lithium-ion batteries, but also significantly reduce the self-discharge rate of the battery, reduce the DCR growth during the battery storage process, and increase the battery life, so that the battery has high input and output characteristics, low self-discharge rate and long life, thereby improving the overall performance of the battery.

[0007] In some embodiments, according to the first aspect, a first example of the first aspect is provided, and the trialkylfluorosilane includes tri-C1-C6 alkylfluorosilane.

[0008] The addition of trialkyl fluorosilane makes it possible for the battery to have high input-output characteristics, low self-discharge rate and long life. By optimizing the type of trialkyl fluorosilane, it is beneficial to further improve the input-output characteristics of lithium-ion batteries at room temperature and low temperature, reduce the self-discharge rate of the battery, reduce the DCR growth during the battery storage process, and increase the battery life.

[0009] In some embodiments, according to the first aspect, a second example of the first aspect is provided, the tri-C1-C6 alkyl fluorosilane includes one or more of trimethyl fluorosilane and triethyl fluorosilane. Preferably, the tri-C1-C6 alkyl fluorosilane includes trimethyl fluorosilane.

[0010] By optimizing the types of trialkylfluorosilane, it is beneficial to further improve the room temperature and low temperature input and output characteristics of lithium-ion batteries, reduce the battery's self-discharge rate and increase battery life.

[0011] In some embodiments, according to the first aspect, a third example of the first aspect is provided, the mass content of the carboxylic acid ester in the non-aqueous electrolyte is A%, 5≤A≤80. The mass content of the cyclic sulfate in the non-aqueous electrolyte is B%, 0.0001≤B≤2. The mass content of the trialkyl fluorosilane in the non-aqueous electrolyte is C%, 0.001≤C≤1.

[0012] In the non-aqueous electrolyte, the content of trialkyl fluorosilane is related to the content of carboxylate and cyclic sulfate. The addition of an appropriate amount of trialkyl fluorosilane can improve the problem of deterioration of input-output characteristics caused by cyclic sulfate. The present application further improves the room temperature and low temperature input-output characteristics of the lithium-ion battery by optimizing the content of carboxylate, cyclic sulfate and trialkyl fluorosilane within the above range, reduces the self-discharge rate of the battery and increases the battery life.

[0013] In some embodiments, according to the first aspect, a fourth example of the first aspect is proposed, 20≤A≤60; and / or 0.01≤B≤1.5; and / or 0.1≤C≤0.5.

[0014] By optimizing the content of carboxylate, cyclic sulfate and trialkyl fluorosilane, it is beneficial to further improve the room temperature and low temperature input and output characteristics of lithium-ion batteries, reduce the self-discharge rate of the battery and increase the battery life.

[0015] In some embodiments, according to the first aspect, a fifth example of the first aspect is proposed, the carboxylic acid ester includes a chain carboxylic acid ester. Preferably, the chain carboxylic acid ester includes one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate.

[0016] Chain carboxylates can significantly improve the input-output characteristics of batteries at room temperature and low temperature. Although cyclic carboxylates have a high dielectric constant, they have a large viscosity and poor input-output characteristics of batteries at low temperatures.

[0017] In some embodiments, according to the first aspect, a sixth example of the first aspect is provided, wherein the cyclic sulfate comprises a compound shown in Formula I,

[0018]

[0019] In Formula I,

[0020] R1 is one of the groups shown in formula a, formula b or formula c below;

[0021] R2 is a hydrogen atom, or one of the groups shown in formula a, formula b or formula c below;

[0022] Alternatively, R1 and R2 are connected to form a structure shown in formula d,

[0023]

[0024] In formula c, R3 represents a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group or a group represented by formula b;

[0025] In formula a to formula d, Indicates the bonding position.

[0026] By optimizing the types of cyclic sulfates, it is beneficial to further improve the input-output, self-discharge and life characteristics of lithium-ion batteries.

[0027] In some embodiments, according to the first aspect, a seventh example of the first aspect is provided, wherein the cyclic sulfate ester includes one or more of the following compounds:

[0028]

[0029] When one or more of the three cyclic sulfates are used in combination with carboxylates and trialkylfluorosilanes, it is more conducive to improving the input-output, self-discharge and life characteristics of lithium-ion batteries.

[0030] In some embodiments, according to the first aspect, an eighth example of the first aspect is provided, wherein the cyclic sulfate comprises a compound shown in Formula II,

[0031]

[0032] In Formula II, R a , R b , R c , R d are each independently H or F; preferably, R a , R c One of them is H and the other is F; and R b , R d At least one of them is H.

[0033] By optimizing the types of cyclic sulfates, it is beneficial to further improve the input-output, self-discharge and life characteristics of lithium-ion batteries.

[0034] In some embodiments, according to the first aspect, a ninth example of the first aspect is provided, wherein the cyclic sulfate comprises

[0035] By optimizing the types of cyclic sulfates, it is beneficial to further improve the input-output, self-discharge and life characteristics of lithium-ion batteries.

[0036] A second aspect of the present application provides a lithium-ion battery, comprising the non-aqueous electrolyte of the first aspect of the present application.

[0037] Due to the use of the non-aqueous electrolyte of the first aspect of the present application, the lithium-ion battery of the second aspect of the present application can have high input-output, low self-discharge rate and long life.

[0038] In some embodiments, according to the second aspect, a first example of the second aspect is provided, wherein the liquid retention coefficient of the lithium-ion battery is ng / Ah, 2≤n≤10.

[0039] The liquid retention coefficient refers to the amount of electrolyte retained per unit capacity of the battery cell, and the unit is g / Ah. The liquid retention coefficient is the ratio of the mass of the electrolyte injected into the battery cell to the battery cell capacity, which determines the absolute amount of electrolyte present in the battery cell, and thus affects the content of carboxylic acid esters, cyclic sulfates and trialkylfluorosilanes in the battery cell. When the battery cell capacity is constant, a high liquid retention coefficient means a high amount of electrolyte injected into the battery cell, and correspondingly, the absolute content of the above three components will also be high, and the content of the above three components will further affect the battery performance. Therefore, controlling the liquid retention coefficient of lithium-ion batteries within a reasonable range is conducive to improving the comprehensive performance of lithium-ion batteries, taking into account the high input and output, low self-discharge rate and long life of the battery.

[0040] In some embodiments, according to the second aspect, a second example of the second aspect is provided, where 3≤n≤7.

[0041] By optimizing the liquid retention coefficient of lithium-ion batteries, it is beneficial to further improve the comprehensive performance of lithium-ion batteries and better balance high input and output, low self-discharge rate and long life.

[0042] In some embodiments, according to the second aspect, a third example of the second aspect is proposed, the mass content of the carboxylate, the cyclic sulfate and the trialkyl fluorosilane in the non-aqueous electrolyte and the liquid retention coefficient simultaneously satisfy the following relationship:

[0043]

[0044] 0.0033≤(B+C)*n≤30.

[0045] The addition of carboxylates, cyclic sulfates and trialkylfluorosilanes each has certain beneficial functions on the performance of non-aqueous electrolytes, but also has adverse effects. By controlling the content of the three components and the liquid retention coefficient to satisfy a certain relationship, the adverse effects can be minimized to the greatest extent, promoting the improvement of the comprehensive performance of lithium-ion batteries, and better balancing high input and output, low self-discharge rate and long life.

[0046] A third aspect of the present application provides an electrical device, comprising the lithium-ion battery of the second aspect of the present application.

[0047] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. DETAILED DESCRIPTION

[0048] The exemplary embodiments of the present disclosure will be described in more detail below. However, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to enable the scope of the present disclosure to be fully communicated to those skilled in the art.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application. The terms "including" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusions.

[0050] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range, and any upper limit can be combined with any other upper limit to form an unambiguous range. In addition, although not explicitly stated, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unambiguous range.

[0051] In the description of this article, it should be noted that, unless otherwise specified, "above" and "below" are inclusive of the number itself, and the "multiple" in "one or more" means more than two (including two).

[0052] In the description of the embodiments of the present application, the term "and / or" is merely a term used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent three situations: A exists, A and B exist at the same time, and B exists.

[0053] The above-mentioned summary of the invention of the present application is not intended to describe each disclosed embodiment or each implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided by a series of examples, which can be used in various combinations. In each example, enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0054] Lithium-ion batteries are now widely used in pure electric vehicles, hybrid electric vehicles, smart grids and other fields. With the rapid development of lithium-ion battery technology, people have higher and higher requirements for battery performance. As an important component of lithium-ion batteries, electrolytes have attracted much attention, but traditional electrolytes have poor performance and cannot take into account the high input and output, low self-discharge rate and long life of the battery. Therefore, it is urgent to develop an electrolyte that can take into account the high input and output characteristics, low self-discharge rate and long life of the battery.

[0055] Research has found that adding carboxylic acid ester solvents to the electrolyte can improve the input and output characteristics of the battery at room temperature and low temperature, but the electrochemical stability of the carboxylic acid ester solvent itself is relatively poor, which will deteriorate the self-discharge and life characteristics of the battery. Adding cyclic sulfate to the electrolyte will form a SEI film with good passivation effect at the negative electrode during formation, which can improve the self-discharge and life deterioration problems caused by carboxylic acid esters, but in turn will increase the interface impedance and deteriorate the input and output characteristics of the battery. Due to the existence of this contradiction, the battery cannot take into account high input and output characteristics, low self-discharge rate and long life.

[0056] After in-depth research, it was found that adding trialkylfluorosilane to the electrolyte containing carboxylic acid esters and cyclic sulfate esters can form a SEI film with low interfacial impedance at the negative electrode during formation, which can improve the problem of increased interfacial impedance caused by the use of cyclic sulfate esters, thereby alleviating the conflict caused by the addition of cyclic sulfate esters and carboxylates.

[0057] Therefore, the present application, by using trialkyl fluorosilane in combination with carboxylic acid ester and cyclic sulfate ester, can not only significantly improve the room temperature and low temperature input and output characteristics of lithium-ion batteries, but also significantly reduce the self-discharge rate of the battery, reduce the DCR growth during storage, and increase the battery life, so that the battery has high input and output characteristics, low self-discharge rate and long life, thereby improving the overall performance of the battery.

[0058] Specifically, the first aspect of the present application provides a non-aqueous electrolyte, which includes: carboxylic acid ester, cyclic sulfate ester and trialkyl fluorosilane.

[0059] In some embodiments, the trialkylfluorosilane includes tri-C1-C6 alkylfluorosilane.

[0060] The addition of trialkyl fluorosilane makes it possible for the battery to have high input-output characteristics, low self-discharge rate and long life. By optimizing the type of trialkyl fluorosilane, it is beneficial to further improve the room temperature and low temperature input-output characteristics of lithium-ion batteries, reduce the battery's self-discharge rate and increase battery life.

[0061] In some embodiments, the tri-C1-C6 alkyl fluorosilane includes one or more of trimethyl fluorosilane and triethyl fluorosilane. Preferably, the tri-C1-C6 alkyl fluorosilane includes trimethyl fluorosilane.

[0062] By optimizing the types of trialkylfluorosilane, it is beneficial to further improve the room temperature and low temperature input and output characteristics of lithium-ion batteries, reduce the battery's self-discharge rate and increase battery life.

[0063] In some embodiments, the mass content of carboxylic acid ester in the non-aqueous electrolyte is A%, 5≤A≤80. The mass content of cyclic sulfate in the non-aqueous electrolyte is B%, 0.0001≤B≤2. The mass content of trialkyl fluorosilane in the non-aqueous electrolyte is C%, 0.001≤C≤1.

[0064] In the non-aqueous electrolyte, the content of trialkyl fluorosilane is related to the content of carboxylate and cyclic sulfate. The addition of an appropriate amount of trialkyl fluorosilane can improve the problem of deterioration of input-output characteristics caused by cyclic sulfate. The present application further improves the room temperature and low temperature input-output characteristics of the lithium-ion battery by optimizing the content of carboxylate, cyclic sulfate and trialkyl fluorosilane within the above range, reduces the self-discharge rate of the battery and increases the battery life.

[0065] In some specific embodiments, A can be 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80.

[0066] In some embodiments, B can be 0.0001, 0.001, 0.01, 0.1, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.

[0067] In some specific embodiments, C can be 0.001, 0.01, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or 1.

[0068] In some embodiments, 20≤A≤60; and / or 0.01≤B≤1.5; and / or 0.1≤C≤0.5.

[0069] By optimizing the content of carboxylate, cyclic sulfate and trialkyl fluorosilane, it is beneficial to further improve the room temperature and low temperature input and output characteristics of lithium-ion batteries, reduce the self-discharge rate of the battery and increase the battery life.

[0070] In some embodiments, the carboxylic acid ester comprises a linear carboxylic acid ester.

[0071] Chain carboxylates can significantly improve the input-output characteristics of batteries at room temperature and low temperature. Although cyclic carboxylates have a high dielectric constant, they have a large viscosity and poor input-output characteristics of batteries at low temperatures.

[0072] Preferably, the chain carboxylic acid ester includes one or more of ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate.

[0073] In some embodiments, the cyclic sulfate comprises a compound of Formula I,

[0074]

[0075] In Formula I,

[0076] R1 is one of the groups shown in formula a, formula b or formula c below;

[0077] R2 is a hydrogen atom, or one of the groups shown in formula a, formula b or formula c below;

[0078] Alternatively, R1 and R2 are connected to form a structure shown in formula d,

[0079]

[0080] In formula c, R3 represents a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group or a group represented by formula b;

[0081] In formula a to formula d, Indicates the bonding position.

[0082] By optimizing the types of cyclic sulfates, it is beneficial to further improve the input-output, self-discharge and life characteristics of lithium-ion batteries.

[0083] In some embodiments, the cyclic sulfate comprises one or more of the following compounds:

[0084]

[0085] When one or more of the three cyclic sulfates are used in combination with carboxylates and trialkylfluorosilanes, it is more conducive to improving the input-output, self-discharge and life characteristics of lithium-ion batteries.

[0086] In some embodiments, the cyclic sulfate comprises a compound of Formula II,

[0087]

[0088] In Formula II, R a , R b , R c , R d are each independently H or F; preferably, R a , R c One of them is H and the other is F; and R b , R d At least one of them is H.

[0089] By optimizing the types of cyclic sulfates, it is beneficial to further improve the input-output, self-discharge and life characteristics of lithium-ion batteries.

[0090] In some embodiments, the cyclic sulfate comprises

[0091] When the above-mentioned spirocyclic sulfate is used in combination with carboxylic acid ester and trialkyl fluorosilane, it is more conducive to improving the input-output, self-discharge and life characteristics of the lithium-ion battery.

[0092] In some specific embodiments, the cyclic sulfate includes one or more of the compounds shown in Formula I and the compounds shown in Formula II.

[0093] In some embodiments, the cyclic sulfate comprises one or more of the following compounds:

[0094]

[0095] In some embodiments, the non-aqueous electrolyte further includes an electrolyte. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.

[0096] Alternatively, the electrolyte may be a lithium salt. The lithium salt may include one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium bis(difluorophosphino)imide.

[0097] In some embodiments, the non-aqueous electrolyte may also include other organic solvents, such as one or more of cyclic carbonates and chain carbonates. Cyclic carbonates may include one or more of ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, etc. Chain carbonates may include one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate, dipropyl carbonate, methyl butyl carbonate, ethyl butyl carbonate, dibutyl carbonate, methyl pentyl carbonate, ethyl pentyl carbonate, dipentyl carbonate, methyl heptyl carbonate, ethyl heptyl carbonate, diheptyl carbonate, methyl hexyl carbonate, ethyl hexyl carbonate, dihexyl carbonate, methyl octyl carbonate, ethyl octyl carbonate, dioctyl carbonate, etc.

[0098] In addition to the first additive and the second additive, the non-aqueous electrolyte may also include one or more of the following compounds: vinylene carbonate, vinyl ethylene carbonate, acetylene ethylene carbonate, fluorocarbonate, cyclic sulfonate, acetylene ethylene sulfate, (trimethylsilane) phosphate, (trimethylsilane) borate, monofluorophosphate, difluorophosphate, difluorooxalato borate, difluorobisoxalato phosphate, tetrafluorooxalato phosphate and hexamethylene diisocyanate. When one or more of the above additives are further added to the non-aqueous electrolyte, the cycle performance, storage performance and DCR growth during the life of the battery can be further improved.

[0099] The method for determining the content of the first additive cyclic sulfate and the second additive trialkyl fluorosilane in the non-aqueous electrolyte is not particularly limited. The content of the first additive can be determined using methods such as gas chromatography and liquid nuclear magnetic resonance. The content of the second additive can be determined using a gas chromatography method.

[0100] A second aspect of the present application provides a lithium-ion battery, comprising the non-aqueous electrolyte of the first aspect of the present application.

[0101] Due to the use of the non-aqueous electrolyte of the first aspect of the present application, the lithium-ion battery of the second aspect of the present application can have high input-output characteristics, low self-discharge rate and long life.

[0102] In some embodiments, the lithium-ion battery has a liquid retention coefficient of ng / Ah, 2≤n≤10.

[0103] The liquid retention coefficient refers to the amount of electrolyte retained per unit capacity of the battery cell, and the unit is g / Ah. The liquid retention coefficient is the ratio of the mass of the electrolyte injected into the battery cell to the battery cell capacity, which determines the absolute amount of electrolyte present in the battery cell, and thus affects the content of carboxylic acid esters, cyclic sulfates and trialkylfluorosilanes in the battery cell. When the battery cell capacity is constant, a high liquid retention coefficient means a high amount of electrolyte injected into the battery cell, and correspondingly, the absolute content of the above three components will also be high, and the content of the above three components will further affect the battery performance. Therefore, controlling the liquid retention coefficient of lithium-ion batteries within a reasonable range is conducive to improving the comprehensive performance of lithium-ion batteries, taking into account the high input-output characteristics, low self-discharge rate and long life of the battery.

[0104] In some specific embodiments, n can be 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10.

[0105] In some embodiments, 3≤n≤7.

[0106] By optimizing the liquid retention coefficient of lithium-ion batteries, it is beneficial to further improve the comprehensive performance of lithium-ion batteries and better balance high input-output characteristics, low self-discharge rate and long life.

[0107] In some specific embodiments, the mass content of the carboxylate in the non-aqueous electrolyte is A%, 5≤A≤80; the mass content of the cyclic sulfate in the non-aqueous electrolyte is B%, 0.0001≤B≤2; the mass content of the trialkylfluorosilane in the non-aqueous electrolyte is C%, 0.001≤C≤1; the liquid retention coefficient of the lithium-ion battery is ng / Ah, 2≤n≤10.

[0108] In some embodiments, the mass content of carboxylic acid ester, cyclic sulfate ester and trialkyl fluorosilane in the non-aqueous electrolyte and the liquid retention coefficient satisfy the following relationship:

[0109]

[0110] 0.0033≤(B+C)*n≤30.

[0111] The addition of carboxylates, cyclic sulfates and trialkylfluorosilanes each has certain beneficial functions on the performance of non-aqueous electrolytes, but also has adverse effects. By controlling the content of the three components and the liquid retention coefficient to satisfy a certain relationship, the adverse effects can be minimized to the greatest extent, promoting the improvement of the comprehensive performance of lithium-ion batteries, and better balancing high input-output characteristics, low self-discharge rate and long life.

[0112] In some specific embodiments, It may be 0.0025, 0.025, 0.25, 2.5, 25, 250, 500, 1000, 5000, 10000, 50000, 100000, 200000 or 300000.

[0113] In some specific embodiments, (B+C)*n can be 0.0033, 0.033, 0.33, 3.3, 5, 10, 15, 20, 25, or 30.

[0114] A third aspect of the present application provides an electrical device, comprising the lithium-ion battery of the second aspect of the present application.

[0115] Explanation of terms

[0116] In the present application, the term "halogen atom" refers to a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0117] In the present application, the term "C1-C6 alkyl" refers to a straight-chain or branched alkyl group having 1 to 6 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, and the like.

[0118] In the present application, the term "C1-C6 haloalkyl" refers to a straight or branched haloalkyl group having 1 to 6 carbon atoms, such as monofluoromethyl, difluoromethyl, trifluoromethyl, 2,2,2-trifluoroethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluoropentyl, perfluorohexyl, perfluoroisopropyl, perfluoroisobutyl, chloromethyl, chloroethyl, chloropropyl, bromomethyl, bromoethyl, bromopropyl, iodomethyl, iodoethyl, iodopropyl, and the like.

[0119] In the present application, "C1-C6 alkoxy" refers to a straight chain or branched alkoxy group having 1 to 6 carbon atoms, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, hexyloxy, etc.

[0120] The present application is further described below in conjunction with the examples. The following examples describe the disclosure of the present application in more detail, and these examples are merely illustrative, because it is obvious to those skilled in the art that various modifications and variations are made within the scope of the disclosure of the present application. Unless otherwise stated, all reagents used in the examples are commercially available or synthesized according to conventional methods, and the instruments used in the examples are commercially available.

[0121] Example 1

[0122] (1) Preparation of positive electrode sheet

[0123] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (lithium nickel cobalt manganese), binder polyvinylidene fluoride, and conductive agent acetylene black are mixed in a weight ratio of 98:1:1 and dispersed in a solvent N-methylpyrrolidone (NMP) and stirred in a stirring tank to form a positive electrode slurry. The above slurry is then coated on the current collector aluminum foil, and after drying, it is cold pressed, trimmed, cut into pieces, and striped to prepare a positive electrode sheet.

[0124] (2) Preparation of negative electrode sheet

[0125] The negative electrode active material graphite, conductive carbon black, thickener sodium carboxymethyl cellulose (CMC), and binder styrene butadiene rubber (SBR) are mixed in a weight ratio of 96:2:1:1 and dispersed in a solvent deionized water, and stirred in a stirring tank to obtain a negative electrode slurry; then the above-mentioned negative electrode slurry is coated on the collector copper foil, and after drying, cold pressing, trimming, cutting, striping, etc. are performed to prepare a negative electrode sheet.

[0126] (3) Preparation of electrolyte

[0127] The electrolytes were prepared according to the following method:

[0128] In an argon-filled glove box with a water content of <1 ppm, ethylene carbonate, diethyl carbonate, ethyl acetate (i.e., carboxylate solvent), (i.e. the first additive cyclic sulfate) and trimethylfluorosilane (i.e. the second additive trialkylfluorosilane) are mixed, and then lithium hexafluorophosphate (LiPF6) is added and stirred evenly to obtain an electrolyte, in which the mass content (%) of each component is shown in Table 1 below.

[0129] Table 1

[0130]

[0131] (4) Preparation of lithium-ion batteries

[0132] The positive electrode sheet, polypropylene separator (Hunan Zhongli New Material Technology Co., Ltd., SBA), and negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then wound to obtain a bare battery cell; the bare battery cell is placed in an outer package, and the prepared electrolyte is injected into the dried battery, and then vacuum packaging, standing, forming, shaping and other processes are performed to obtain a lithium-ion battery. It has been determined that the liquid retention coefficient of the lithium-ion battery is 5. The liquid retention coefficient of the lithium-ion battery is determined as follows:

[0133] Liquid retention coefficient = electrolyte retention / lithium-ion battery capacity.

[0134] Electrolyte retention test: First, weigh the lithium-ion battery for the first time, and the weight is recorded as m0. Then disassemble the lithium-ion battery, pour out the electrolyte, and soak the disassembled battery shell or aluminum-plastic film, top cover, isolation film, positive electrode sheet, negative electrode sheet, tabs and other components in acetonitrile solution for a certain period of time. Then take out the shell or aluminum-plastic film, top cover, isolation film, positive electrode sheet, negative electrode sheet, tabs, dry them, weigh them and record them as m1. The electrolyte retention is m0-m1.

[0135] Lithium-ion battery capacity test: When testing the capacity of a lithium-ion battery, define the design capacity or nominal capacity (in Ah) of the battery as the current value at a 1C rate. Then, at 25°C, charge the lithium-ion battery to 4.25V at a constant current of 0.5C, then charge it at a constant voltage of 4.25V until the current is less than 0.05C, keep it in a fully charged state of 4.25V for 10 minutes, then discharge it to 2.8V at a constant current of 0.5C, and record the discharge capacity of the lithium-ion battery at this time as the capacity of the lithium-ion battery.

[0136] After calculation, is 15, (B+C)*n is 6.5.

[0137] Example 2

[0138] A lithium-ion battery was prepared according to the method of Example 1, except that the type of the second additive trialkylfluorosilane was different, as shown in Table 2 below.

[0139] Table 2

[0140] serial number Trialkyl fluorosilane Example 1 Trimethylsilyl fluoride Example 2 Triethylfluorosilane

[0141] Embodiment 3-8

[0142] A lithium ion battery was prepared according to the method of Example 1, except that the mass content (%) of trimethylsilyl fluoride in the non-aqueous electrolyte was different from that in Example 1, as shown in Table 3 below.

[0143] Table 3

[0144]

[0145] “ / ” means not calculated.

[0146] Examples 9-14

[0147] A lithium ion battery was prepared according to the method of Example 1, except that the mass content (%) of ethyl acetate in the non-aqueous electrolyte was different from that in Example 1, as shown in Table 4 below.

[0148] Table 4

[0149]

[0150]

[0151] “ / ” means not calculated.

[0152] Examples 15-20

[0153] A lithium ion battery was prepared according to the method of Example 1, except that the cyclic sulfate The mass content (%) in the non-aqueous electrolyte is different from that in Example 1, as shown in Table 5 below.

[0154] Table 5

[0155]

[0156] “ / ” means not calculated.

[0157] Examples 21-22

[0158] A lithium ion battery was prepared according to the method of Example 1, except that the type of carboxylate solvent was different, as shown in Table 6 below.

[0159] Table 6

[0160] serial number Carboxylate Solvents Example 1 Ethyl acetate Embodiment 21 Methyl acetate Embodiment 22 Propyl acetate

[0161] Embodiment 23-25

[0162] A lithium-ion battery was prepared according to the method of Example 1, except that the type of the first additive cyclic sulfate was different, as shown in Table 7 below.

[0163] Table 6

[0164]

[0165] Examples 26-31

[0166] A lithium ion battery was prepared according to the method of Example 1, except that the porosity and thickness of the isolation membrane used were adjusted so that the liquid retention coefficient of the lithium ion battery was different from that of Example 1, as shown in Table 7 below.

[0167] Table 7

[0168] serial number Liquid retention coefficient n Example 1 5 Embodiment 26 3 Embodiment 27 7 Embodiment 28 2 Embodiment 29 10 Embodiment 30 1 Embodiment 31 15

[0169] Embodiment 32

[0170] A lithium-ion battery was prepared according to the method of Example 1, except that the porosity and thickness of the separator used and the ethyl acetate, and the mass content of trimethylfluorosilane, so that The sum (B+C)*n is different from that in Example 1, as shown in Table 8 below.

[0171] Table 8

[0172]

[0173]

[0174] Comparative Example 1

[0175] A lithium ion battery was prepared according to the method of Example 1, except that the second additive trialkylfluorosilane was not used.

[0176] Comparative Example 2

[0177] A lithium ion battery was prepared according to the method of Example 1, except that trimethylfluorosilane was replaced by triethoxyfluorosilane.

[0178] Comparative Example 3

[0179] A lithium ion battery was prepared according to the method of Example 1, except that ethyl acetate was not used.

[0180] Comparative Example 4

[0181] A lithium ion battery was prepared according to the method of Example 1, except that no cyclic sulfate was used.

[0182] Battery performance test

[0183] 1. Normal temperature DCR input and output test

[0184] 25℃ 4C constant current charge (CC) 30s DCR test: At 25℃, charge the lithium-ion battery to 4.25V at 0.5C constant current, then charge it at 4.25V constant voltage until the current is less than 0.05C, keep it in a 4.25V fully charged state for 10 minutes, and then discharge it to 2.8V at 0.5C constant current. Record the discharge capacity of the battery at this time as D0. The battery is then discharged at a constant current of 0.5C, with the discharge capacity as the cutoff condition, and the discharge capacity is stopped when it is 1 / 2D0. At this time, the battery is in a 50% SOC state. After standing for 10 minutes, it is charged at 4C for 30 seconds. The voltage of the last point when the battery is in a 50% SOC state and standing for 10 minutes is recorded as V1, in V; the voltage of the last point when the battery is charged at 4C for 30 seconds is recorded as V2, in V; the current value of 4C charging is recorded as M, in A; then the DCR of 25℃ 4C charging for 30 seconds = (V2-V1) / M, in ohms (Ω).

[0185] 25℃4C constant current discharge (DC) 30s DCR test: At 25℃, the lithium-ion battery is charged to 4.25V at 0.5C constant current, and then charged to a current lower than 0.05C at 4.25V constant voltage, so that it is in a 4.25V fully charged state and stands for 10min, and then the battery is discharged at 0.5C constant current, with the discharge capacity as the cut-off condition, and stops when the discharge capacity is 1 / 2D0. At this time, the battery is in a 50% SOC state. After standing for 10min, it is discharged at 4C for 30s. The voltage of the last point where the battery is in a 50% SOC state and stands for 10min is recorded as V3, in V; the voltage of the last point of 4C discharge for 30s is recorded as V4, in V; the current value of 4C discharge is recorded as N, in A; then the DCR of 25℃4C discharge for 30s = (V3-V4) / N, in ohms (Ω).

[0186] The results are shown in Table 9 below.

[0187] 2. Low temperature DCR input and output test

[0188] -25℃ 0.36C DC 10s DCR test: At 25℃, the lithium-ion battery is charged to 4.25V at a constant current of 0.5C, and then charged at a constant voltage of 4.25V until the current is less than 0.05C, so that it is in a fully charged state of 4.25V and stands for 10 minutes. Then the battery is discharged at a constant current of 0.5C, with the discharge capacity as the cutoff condition, and stops when the discharge capacity is 1 / 2D0, at which time the battery is in a 50% SOC state. The battery is then placed in a -25°C high and low temperature box and left to stand for 3 hours. When the battery temperature reaches -25°C, it is left to stand for another 10 minutes. It is then discharged at 0.36C for 10 seconds. The voltage at the last point when the battery is at 50% SOC and left to stand for 10 minutes is recorded as V5 in V. The voltage at the last point of 0.36C discharge for 10 seconds is recorded as V6 in V. The current value of 0.36C discharge is recorded as P in A. Then the DCR of -25°C 0.36C discharge for 10 seconds = (V5-V6) / P, in ohms (Ω).

[0189] The results are shown in Table 9 below.

[0190] 3. Self-discharge rate test

[0191] First, at 25°C, charge the lithium-ion battery at a constant current of 0.5C to 4.25V, then charge at a constant voltage of 4.25V until the current is less than 0.05C, let it stand for 10 minutes in a fully charged state at 4.25V, then discharge at a constant current of 0.5C to 2.8V, then charge at a constant current of 0.5C to 3.85V, then charge at a constant voltage of 3.85V until the current drops to 0.05C, then let it stand for 10 minutes to test the open circuit voltage of the battery, recorded as V7, in V, then place the battery in an oven at 25°C for 48 hours, and then test the open circuit voltage of the battery again, recorded as V8, in V, then the self-discharge rate of the battery = (V7-V8)*1000 / 48.

[0192] The results are shown in Table 9 below.

[0193] 4. Cycle performance test

[0194] At 25°C, the lithium-ion battery is charged to 4.25V at a constant current of 1C, then charged at a constant voltage of 4.25V until the current drops to 0.05C, and then discharged to 2.8V at a constant current of 1C. This is a charge and discharge cycle process. The discharge capacity this time is the discharge capacity of the first cycle of the lithium-ion battery. The lithium-ion battery is subjected to 1000 cycle charge and discharge tests in the above manner. The capacity retention rate of the nth cycle during the battery cycle process = the discharge capacity of the nth cycle / the discharge capacity of the first cycle.

[0195] The results are shown in Table 9 below.

[0196] 5. Storage performance test

[0197] First, at 25°C, charge the lithium-ion battery to 4.25V at a constant current of 0.5C, then charge it at a constant voltage of 4.25V until the current is less than 0.05C, and let it stand for 10 minutes at a full charge state of 4.25V, and then discharge it to 2.8V at a constant current of 0.5C, and record the discharge capacity of the battery at this time as D1. Then discharge the battery at a constant current of 0.5C, cut off at the discharge capacity, and stop when the discharge capacity is 1 / 2D1. At this time, the battery is in a 50% SOC state. After standing for 10 minutes, discharge it at 4C for 30s, and then calculate the DCR before storage in the same way as above.

[0198] Next, at 25°C, the battery is charged to a full charge state (100% SOC) under the same conditions as above, and then the fully charged lithium-ion battery is placed in a 60°C oven for storage. After a certain period of storage, the battery is taken out and charged to a full charge state of 4.25V at 25°C under the same conditions as above, and the discharge capacity of the battery at this time is recorded as Dn. Then the battery is discharged at a constant current of 0.5C, and the discharge capacity is cut off, and the discharge capacity is stopped when it is 1 / 2Dn. At this time, the battery is in a 50% SOC state. After standing for 10 minutes, it is discharged at 4C for 30 seconds, and then the DCR after storage is calculated by the same method as above.

[0199] The capacity retention rate of the battery after the battery is stored at 60℃ and 100% SOC for a certain period of time is

[0200] =Dn / D0

[0201] After the battery is stored at 60°C and 100% SOC for a certain period of time, the DCR growth rate of the battery = DCR after storage / DCR before storage-1.

[0202] The results are shown in Table 9 below.

[0203] Table 9

[0204]

[0205]

[0206] By comparing the embodiments and comparative examples, it can be seen that the present application can significantly improve the room temperature and low temperature input and output characteristics of the lithium-ion battery by using trialkyl fluorosilane in combination with carboxylic acid ester and cyclic sulfate ester, and can also significantly reduce the self-discharge rate of the battery, reduce the DCR growth during storage, and increase the battery life, so that the battery has high input and output characteristics, low self-discharge rate and long life, thereby improving the overall performance of the battery.

[0207] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A non-aqueous electrolyte, characterized in that: include: Carboxylates, cyclic sulfates and trialkylfluorosilanes.

2. The non-aqueous electrolyte according to claim 1, characterized in that The trialkyl fluorosilane includes tri-C1-C6 alkyl fluorosilane.

3. The non-aqueous electrolyte according to claim 2, characterized in that The tri-C1-C6 alkyl fluorosilane includes one or more of trimethyl fluorosilane and triethyl fluorosilane; preferably, the tri-C1-C6 alkyl fluorosilane includes trimethyl fluorosilane.

4. The non-aqueous electrolyte according to any one of claims 1 to 3, characterized in that The mass content of the carboxylate in the non-aqueous electrolyte is A%, 5≤A≤80; the mass content of the cyclic sulfate in the non-aqueous electrolyte is B%, 0.0001≤B≤2; the mass content of the trialkyl fluorosilane in the non-aqueous electrolyte is C%, 0.001≤C≤1.

5. The non-aqueous electrolyte according to claim 4, characterized in that 20≤A≤60; and / or 0.01≤B≤1.5; and / or 0.1≤C≤0.

5.

6. The non-aqueous electrolyte according to any one of claims 1 to 5, characterized in that The carboxylic acid ester includes chain carboxylic acid ester; preferably, the chain carboxylic acid ester includes one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate.

7. The non-aqueous electrolyte according to any one of claims 1 to 6, characterized in that: The cyclic sulfate includes a compound shown in Formula I, In Formula I, R1 is one of the groups shown in formula a, formula b or formula c below; R2 is a hydrogen atom, or one of the groups shown in formula a, formula b or formula c below; Alternatively, R1 and R2 are connected to form a structure shown in formula d, In formula c, R3 represents a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group or a group represented by formula b; In formula a to formula d, Indicates the bonding position.

8. The non-aqueous electrolyte according to claim 7, characterized in that The cyclic sulfates include one or more of the following compounds:

9. The non-aqueous electrolyte according to any one of claims 1 to 8, characterized in that The cyclic sulfate includes a compound shown in Formula II, In Formula II, R a , R b , R c , R d are each independently H or F; preferably, R a , R c One of them is H and the other is F; and R b , R d At least one of them is H.

10. The non-aqueous electrolyte according to claim 9, characterized in that The cyclic sulfate includes 11. A lithium ion battery, characterized in that: The invention comprises the non-aqueous electrolyte according to any one of claims 1 to 10.

12. The lithium ion battery according to claim 11, characterized in that: The liquid retention coefficient of the lithium ion battery is ng / Ah, 2≤n≤10.

13. The lithium ion battery according to claim 12, characterized in that: 3≤n≤7。 14. The lithium ion battery according to claim 12, characterized in that: The values ​​of the mass contents of the carboxylate, the cyclic sulfate and the trialkyl fluorosilane in the non-aqueous electrolyte and the value of the liquid retention coefficient simultaneously satisfy the following relationship: 0.0033≤(B+C)*n≤30.

15. An electrical device, characterized in that: A lithium ion battery comprising the lithium ion battery according to any one of claims 11 to 14.

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