Electrolyte additive, electrolyte, secondary battery, and electric device

Abstract

The invention discloses an electrolyte additive, an electrolyte, a secondary battery and an electric device, and relates to the technical field of batteries. The structural formula of the electrolyte additive comprises at least one nitrogen atom with lone pair electrons. Lone pair electrons on nitrogen atoms have relatively strong electron donating capability and are easy to react with electron-deficient R < + > to generate----N < + >-R, so that the probability that the R < + > is reduced at a negative electrode and the damage to an SEI membrane are reduced, the consumption of active lithium at the negative electrode is reduced, and the first efficiency and the cycle performance of the battery are further improved.

Description

Electrolyte additive, electrolyte, secondary battery and electrical device Technical Field

[0001] The present application relates to the field of battery technology, and in particular to an electrolyte additive, an electrolyte, a secondary battery, and an electrical device. Background Art

[0002] Lithium-ion batteries, due to their high operating potential, long lifespan, and environmental friendliness, have become the most popular energy storage system. They are now widely used in pure electric vehicles, hybrid electric vehicles, smart grids, and other fields. However, current lithium-ion batteries struggle to meet the increasing demand for battery life. To overcome the "range anxiety" associated with electric vehicles, the development of lithium-ion batteries with higher energy density is urgently needed.

[0003] During the first charge of a battery, the formation of a solid electrolyte interlayer (SEI) on the negative electrode surface consumes a large amount of lithium source, converting lithium into inactive lithium-containing compounds such as lithium carbonate, lithium fluoride, and alkyl lithium, resulting in a loss of recyclable lithium and a reduction in the battery's initial coulombic efficiency and capacity. In a battery system using a graphite negative electrode, the first charge consumes approximately 10% of the lithium source, and the initial coulombic efficiency is approximately 90%. When using high-specific-capacity negative electrode materials such as alloys (silicon, tin, aluminum), oxides (silicon oxide, tin oxide, titanium oxide), and amorphous carbon negative electrodes, the consumption of lithium source is further exacerbated.

[0004] To further improve the energy density of lithium-ion batteries, pre-replenishing lithium to the positive or negative electrodes is an effective method. During the initial charging process of the positive electrode, an excess lithium source is provided by the lithium replenishment additive to compensate for the lithium consumption caused by the formation of the SEI film at the positive and negative electrodes, thereby increasing the energy density of the lithium-ion battery and improving the battery's first-cycle coulombic efficiency and cycle performance. However, the positive electrode lithium replenisher undergoes an irreversible phase change during the initial charging process, generating oxygen free radicals. The oxygen free radicals further oxidize the electrolyte to produce harmful products such as water. The water further causes the electrolyte to decompose and generate R+ (such as H+). The R+ will further destroy the SEI or reduce it at the negative electrode, consuming the active lithium at the negative electrode, thereby deteriorating the battery's initial efficiency and cycle performance.

[0005] Summary of the Invention

[0006] This application is made in view of the above-mentioned problems, and its purpose is to provide an electrolyte additive to improve the initial efficiency and cycle performance of the battery.

[0007] In order to achieve the above-mentioned objectives, embodiments of the present application provide an electrolyte additive, an electrolyte, a secondary battery, and an electrical device.

[0008] In a first aspect, an embodiment of the present application provides an electrolyte additive, wherein the structural formula of the electrolyte additive includes at least one nitrogen atom having a lone pair of electrons.

[0009] Therefore, in the technical solution of the embodiment of the present application, the structural formula of the electrolyte additive includes at least one nitrogen atom with a lone pair of electrons. The lone pair of electrons on the nitrogen atom makes the nitrogen atom electron-rich, and it is easy to react with the electron-deficient R+ to generate ----N+-R, thereby reducing the probability of R+ being reduced at the negative electrode, consuming the active lithium of the negative electrode, and destroying the SEI film, thereby improving the battery's initial efficiency and battery cycle performance.

[0010] In any embodiment, the electrolyte additive includes at least one of the compound represented by structural formula (I), the compound represented by structural formula (II), the compound represented by structural formula (III), the compound represented by structural formula (IV), and the compound represented by structural formula (V):

[0011] Wherein, in structural formula (I), Y1 and Y2 are each independently selected from C atoms and N atoms, and R2, R3 and R4 are each independently selected from H atoms, alkyl groups of 1 to 6 carbon atoms, allyl groups, propargyl groups, halogen atoms, hydroxyl groups, primary amines with 6 or less carbon atoms, secondary amines with 6 or less carbon atoms, tertiary amines with 6 or less carbon atoms, and alkoxy groups with 6 or less carbon atoms;

[0012] In structural formula (II), W1 is selected from a C atom, a N atom, an O atom, and an S atom, W2 is selected from a C atom and a N atom, and R5, R6, R7, and R8 are each independently selected from an H atom, an alkyl group having 1 to 6 carbon atoms, an allyl group, a propargyl group, a halogen atom, a hydroxyl group, a primary amine having 6 or less carbon atoms, a secondary amine having 6 or less carbon atoms, a tertiary amine having 6 or less carbon atoms, and an alkoxy group having 6 or less carbon atoms;

[0013] In structural formula (III), A1, A2, A3, A4 and A5 are each independently selected from C atoms and N atoms, and R9 is selected from H atoms, alkyl groups of 1 to 6 carbon atoms, allyl groups, propargyl groups, halogen atoms, hydroxyl groups, primary amines with 6 or less carbon atoms, secondary amines with 6 or less carbon atoms, tertiary amines with 6 or less carbon atoms, and alkoxy groups with 6 or less carbon atoms;

[0014] In structural formula (IV), X1, X2 and X3 are each independently selected from C atoms and N atoms, a and b are each independently selected from constants ranging from 0 to 3, and R1 is selected from an H atom, an alkyl group having 1 to 6 carbon atoms, an allyl group, a propargyl group, a halogen atom, a hydroxyl group, a primary amine having 6 or less carbon atoms, a secondary amine having 6 or less carbon atoms, a tertiary amine having 6 or less carbon atoms, and an alkoxy group having 6 or less carbon atoms;

[0015] In the structural formula (V), V1, V2 and V3 are each independently selected from C atoms and N atoms, d is selected from a constant of 0 to 3, R 11 、R 12 、R 13 and R 14 Each is independently selected from an H atom, an alkyl group with 1 to 6 carbon atoms, an allyl group, a propargyl group, a halogen atom, a hydroxyl group, a primary amine with 6 carbon atoms or less, a secondary amine with 6 carbon atoms or less, a tertiary amine with 6 carbon atoms or less, and an alkoxy group with 6 carbon atoms or less.

[0016] Experiments have shown that using at least one of the compounds shown in the above structural formula as an electrolyte additive can easily react with electron-deficient R+, thereby improving the battery's initial efficiency and battery cycle performance.

[0017] In any embodiment, in structural formula (I), at least one of Y1 and Y2 is a N atom, and further, both Y1 and Y2 are N atoms. In this way, as many nitrogen atoms as possible can react with R+, which can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0018] In any embodiment, in structural formula (II), at least one of W1 and W2 is a N atom; further, W1 and W2 are both N atoms, so that as many nitrogen atoms as possible can react with R+, which can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0019] In any embodiment, in structural formula (III), at least one of A1, A2, A3, A4 and A5 is a N atom; further, A1, A2, A3, A4 and A5 are all N atoms, and A1, A2, A3, A4 and A5 are all N atoms. In this way, as many nitrogen atoms as possible can react with R+, which can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0020] In any embodiment, in structural formula (IV), at least one of X1, X2 and X3 is a N atom; further, X1, X2 and X3 are all N atoms, so that as many nitrogen atoms as possible can react with R+, which can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0021] In any embodiment, in structural formula (V), at least one of V1, V2 and V3 is a N atom; further, V1, V2 and V3 are all N atoms, so that as many nitrogen atoms as possible can react with R+, which can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0022] In any embodiment, the compound represented by structural formula (I) is selected from at least one of the following compounds:

[0023] Experiments show that electrolyte additives using at least one of the above-mentioned compounds can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0024] In any embodiment, the compound represented by structural formula (II) is selected from at least one of the following compounds:

[0025] Experiments show that electrolyte additives using at least one of the above-mentioned compounds can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0026] In any embodiment, the compound represented by structural formula (III) is selected from at least one of the following compounds:

[0027] Experiments show that electrolyte additives using at least one of the above-mentioned compounds can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0028] In any embodiment, the compound represented by structural formula (IV) is selected from at least one of the following compounds:

[0029] Experiments show that electrolyte additives using at least one of the above-mentioned compounds can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0030] In any embodiment, the compound represented by structural formula (V) is selected from at least one of the following compounds:

[0031] Experiments show that electrolyte additives using at least one of the above-mentioned compounds can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0032] Secondly, the embodiments of the present application provide an electrolyte comprising the electrolyte additive described in the above embodiments. The electrolyte additive is added to the electrolyte. The structural formula of the electrolyte additive in the above embodiments includes at least one nitrogen atom with a lone pair of electrons. The lone pair of electrons on the nitrogen atom makes the nitrogen atom electron-rich, which easily reacts with the electron-deficient R+ to generate ----N+-R, reducing the probability of R+ being reduced at the negative electrode, consuming the active lithium at the negative electrode, and destroying the SEI film, thereby improving the battery's initial efficiency and battery cycle performance.

[0033] In any embodiment, the electrolyte additive has a mass fraction W2 of 0.005% ≤ W2 ≤ 20%. Furthermore, 0.1% ≤ W2 ≤ 10%; and even more preferably, 1% ≤ W2 ≤ 5%. Experiments have shown that this mass fraction ensures that the electrolyte additive fully consumes R+ in the electrolyte without excessive consumption, thereby improving the battery's initial efficiency and cycle performance.

[0034] In a third aspect, embodiments of the present application provide a secondary battery comprising the electrolyte additive described in the above embodiments. The electrolyte additive is added to the electrolyte of the secondary battery. The structural formula of the electrolyte additive in the above embodiments includes at least one nitrogen atom with a lone pair of electrons. The lone pair of electrons on the nitrogen atom makes the nitrogen atom electron-rich, easily reacting with the electron-deficient R+ to generate ----N+-R, thereby reducing the reduction of R+ at the negative electrode or destroying the SEI film, consuming the active lithium at the negative electrode, and thereby improving the battery's initial efficiency and battery cycle performance.

[0035] In any embodiment, the secondary battery further comprises a positive electrode plate, the positive electrode plate comprises a positive electrode lithium supplement, and the positive electrode lithium supplement comprises Li6CoO4, Li5FeO4, Li3VO4, Li2MoO3, Li2RuO3, Li2MnO3, Li2MnO2, Li2NiO2, Li2CuO2 and Li2Cu x Ni 1-x M y At least one of O2, with 0<x<1, 0≤y<0.1, and M includes at least one of Zn, Sn, Mg, Fe, and Mn. The above-mentioned positive electrode lithium supplement, on the one hand, provides an excess lithium source to compensate for the lithium consumption caused by the formation of the SEI film at the positive and negative electrodes, thereby increasing the energy density of the lithium-ion battery and improving the battery's first cycle coulombic efficiency and cycle performance; on the other hand, it reduces the probability of R+ generated in the electrolyte being reduced at the negative electrode, consuming the active lithium at the negative electrode and destroying the SEI film, thereby improving the battery's first cycle efficiency and cycle performance.

[0036] In any embodiment, the positive electrode plate also includes a current collector. In the positive electrode plate, the mass of the positive electrode lithium replenisher is a, the mass of the current collector is b, and the mass of the positive electrode plate is c. W1=a / (cb), 0.1%≤W1≤10%. Experiments show that the above mass ratio of the positive electrode lithium replenisher can effectively improve the first efficiency and battery cycle performance of the battery.

[0037] In any embodiment, further, 1%≤W1≤8%; further, 1%≤W1≤5%. Within the above range, the first efficiency and cycle performance of the battery can be effectively improved.

[0038] In any embodiment, the positive electrode plate further includes a positive electrode active material, and the ratio of the Dv50 particle size of the positive electrode lithium supplement to the Dv50 particle size of the positive electrode active material is A, where 1≤A≤10. Studies have shown that the ratio A also affects the lithium ion conductivity of the positive electrode plate. As the ratio A decreases, the ion conductivity of the positive electrode plate improves, but the contact area between the positive electrode lithium supplement and the electrolyte increases, increasing side reactions and reducing the capacity of the lithium-ion battery. When the ratio A is within the above range, the battery exhibits good initial efficiency and cycle performance.

[0039] In any embodiment, further, 2≤A≤8, and the ratio A is within the above range, and the first efficiency and cycle performance of the battery are good.

[0040] In any embodiment, the secondary battery includes a positive electrode sheet, the specific surface area of ​​the positive electrode sheet is B, wherein B≤20m 2 / g, the specific surface area B of the positive electrode sheet is ≤ 20m 2 / g, reducing the contact area between the positive electrode lithium supplement and the electrolyte, slowing down the oxidation of the electrolyte at the positive electrode, and optimizing the first efficiency and cycle performance of the battery. 2 / g≤B≤10m 2 / g, the specific surface area of ​​the positive electrode is too small, which will cause the lithium-ion battery to be polarized too much, affecting the capacity of the lithium-ion battery. Within the above range, the battery's first efficiency and cycle performance are good.

[0041] In a fourth aspect, an embodiment of the present application provides an electrical device comprising the secondary battery of the above embodiment of the present application. DETAILED DESCRIPTION

[0042] Below, the embodiments of the adhesive, separator, electrode, electrode assembly, battery cell, battery and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0043] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0045] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0046] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0047] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0048] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0049] To further improve the energy density of lithium-ion batteries, pre-replenishing lithium to the positive or negative electrodes is an effective method. During the initial charging process of the positive electrode, an excess lithium source is provided by the lithium replenishment additive to compensate for the lithium consumption caused by the formation of the SEI film at the positive and negative electrodes, thereby increasing the energy density of the lithium-ion battery and improving the battery's first-cycle coulombic efficiency and cycle performance. However, the positive electrode lithium replenisher undergoes an irreversible phase change during the initial charging process, generating oxygen free radicals. The oxygen free radicals further oxidize the electrolyte to produce harmful products such as water. The water further causes the electrolyte to decompose and generate R+ (such as H+). The R+ will further destroy the SEI or reduce it at the negative electrode, consuming the active lithium at the negative electrode, thereby deteriorating the battery's initial efficiency and cycle performance.

[0050] Therefore, there are endless studies on improving the first effect and cycle performance of the above-mentioned battery cells. For example, porous materials are added to the positive electrode sheets, such as aluminosilicates, zeolites, activated carbon or molecular sieves as oxygen-absorbing additives, and the pores and active sites on the materials are used to adsorb gas molecules. However, this method is physical adsorption, the adsorption force is not strong, and the amount of oxygen adsorption cannot be quantitatively controlled. For another example, transition metal disulfide MS2 is coated on the surface of the positive electrode. MS2 is coated on the surface of the positive electrode as an active oxygen scavenger to eliminate the active oxygen formed during the cycle or storage process of the high-nickel ternary positive electrode material. However, the introduction of transition metal disulfide will cause the impedance of the positive electrode sheet to increase and the battery cycle performance to decrease. For another example, a molten metal element is coated on the surface of the positive electrode active material, and the reducing property of the metal element is used to reduce the oxygen generated by the positive electrode, showing an excellent slow deoxygenation effect, improving the safety performance of the battery, and ensuring good electrochemical performance. However, this method has harsh preparation process conditions and a low yield.

[0051] Unexpectedly, after conducting a large number of experiments, it was found that adding electrolyte additives to the electrolyte, whose structural formula includes at least one nitrogen atom with a lone pair of electrons, can improve the battery's initial efficiency and battery cycle performance. There is no need to add substances to the positive electrode plate, which simplifies the battery preparation process and improves the battery's initial efficiency and cycle performance.

[0052] Based on this, the present application provides an electrolyte additive, an electrolyte, a secondary battery and an electrical device.

[0053] In a first aspect, the present application proposes an electrolyte additive, wherein the structural formula of the electrolyte additive includes at least one nitrogen atom having a lone pair of electrons.

[0054] Therefore, in the technical solution of the embodiment of the present application, the structural formula of the electrolyte additive includes at least one nitrogen atom with a lone pair of electrons. The lone pair of electrons on the nitrogen atom makes the nitrogen atom electron-rich, and easily reacts with the electron-deficient R+ to generate ----N+-R, thereby reducing the probability of R+ being reduced at the negative electrode and destroying the SEI film, consuming the active lithium of the negative electrode, and thereby improving the battery's initial efficiency and battery cycle performance.

[0055] The present application does not limit the specific structural formula of the electrolyte additive. As long as the compound contains a nitrogen atom with a lone pair of electrons, it is within the scope of protection of the present application. In any embodiment, the electrolyte additive includes at least one of the compound represented by structural formula (I), the compound represented by structural formula (II), the compound represented by structural formula (III), the compound represented by structural formula (IV) and the compound represented by structural formula (V):

[0056] Wherein, in structural formula (I), Y1 and Y2 are each independently selected from C atoms and N atoms, and R2, R3 and R4 are each independently selected from H atoms, alkyl groups of 1 to 6 carbon atoms, allyl groups, propargyl groups, halogen atoms, hydroxyl groups, primary amines with 6 or less carbon atoms, secondary amines with 6 or less carbon atoms, tertiary amines with 6 or less carbon atoms, and alkoxy groups with 6 or less carbon atoms;

[0057] In structural formula (II), W1 is selected from a C atom, a N atom, an O atom, and an S atom, W2 is selected from a C atom and a N atom, and R5, R6, R7, and R8 are each independently selected from an H atom, an alkyl group having 1 to 6 carbon atoms, an allyl group, a propargyl group, a halogen atom, a hydroxyl group, a primary amine having 6 or less carbon atoms, a secondary amine having 6 or less carbon atoms, a tertiary amine having 6 or less carbon atoms, and an alkoxy group having 6 or less carbon atoms;

[0058] In structural formula (III), A1, A2, A3, A4 and A5 are each independently selected from C atoms and N atoms, and R9 is selected from H atoms, alkyl groups of 1 to 6 carbon atoms, allyl groups, propargyl groups, halogen atoms, hydroxyl groups, primary amines with 6 or less carbon atoms, secondary amines with 6 or less carbon atoms, tertiary amines with 6 or less carbon atoms, and alkoxy groups with 6 or less carbon atoms;

[0059] In structural formula (IV), X1, X2 and X3 are each independently selected from C atoms and N atoms, a and b are each independently selected from constants ranging from 0 to 3, and R1 is selected from an H atom, an alkyl group having 1 to 6 carbon atoms, an allyl group, a propargyl group, a halogen atom, a hydroxyl group, a primary amine having 6 or less carbon atoms, a secondary amine having 6 or less carbon atoms, a tertiary amine having 6 or less carbon atoms, and an alkoxy group having 6 or less carbon atoms;

[0060] In the structural formula (V), V1, V2 and V3 are each independently selected from C atoms and N atoms, d is selected from a constant of 0 to 3, R 11 、R 12 、R 13 and R 14 Each is independently selected from an H atom, an alkyl group with 1 to 6 carbon atoms, an allyl group, a propargyl group, a halogen atom, a hydroxyl group, a primary amine with 6 carbon atoms or less, a secondary amine with 6 carbon atoms or less, a tertiary amine with 6 carbon atoms or less, and an alkoxy group with 6 carbon atoms or less.

[0061] The structures of formulas (I), (II), and (III) are conjugated, resulting in a higher electron cloud density on the N, which makes it easier for the N to donate electrons and react with the electron-deficient R+. In formulas (IV) and (V), the N element is directly connected to the electron-donating alkyl or alkenyl group, which also increases the electron cloud density on the N, making it easier to react with the electron-deficient R+.

[0062] Experiments have shown that using at least one of the compounds shown in the above structural formula as an electrolyte additive can easily react with electron-deficient R+, thereby improving the battery's initial efficiency and battery cycle performance.

[0063] It is understood that the compounds represented by the above-mentioned structural formula (I), the compounds represented by the structural formula (II), the compounds represented by the structural formula (III), the compounds represented by the structural formula (IV) and the compounds represented by the structural formula (V) in this application can be purchased or prepared by conventional preparation methods in the art, and this application does not impose any restrictions on this.

[0064] In any embodiment, in structural formula (I), at least one of Y1 and Y2 is a N atom, and further, both Y1 and Y2 are N atoms. In this way, as many nitrogen atoms as possible can react with R+, which can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0065] In any embodiment, in structural formula (II), at least one of W1 and W2 is a N atom; further, W1 and W2 are both N atoms, so that as many nitrogen atoms as possible can react with R+, which can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0066] In any embodiment, in structural formula (III), at least one of A1, A2, A3, A4 and A5 is a N atom; further, A1, A2, A3, A4 and A5 are all N atoms, and A1, A2, A3, A4 and A5 are all N atoms. In this way, as many nitrogen atoms as possible can react with R+, which can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0067] In any embodiment, in structural formula (IV), at least one of X1, X2 and X3 is a N atom; further, X1, X2 and X3 are all N atoms, so that as many nitrogen atoms as possible can react with R+, which can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0068] In any embodiment, in structural formula (V), at least one of V1, V2 and V3 is a N atom; further, V1, V2 and V3 are all N atoms, so that as many nitrogen atoms as possible can react with R+, which can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0069] In any embodiment, the compound represented by structural formula (I) is selected from at least one of the following compounds:

[0070] The above compounds are numbered in sequence as Compound 1-1, Compound 1-2, Compound 1-3, Compound 1-4, Compound 1-5, Compound 1-6, Compound 1-7, Compound 1-8, Compound 1-9, Compound 1-10, Compound 1-11 and Compound 1-12.

[0071] Experiments show that electrolyte additives using at least one of the above-mentioned compounds can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0072] In any embodiment, the compound represented by structural formula (II) is selected from at least one of the following compounds:

[0073] The above compounds are numbered in sequence as Compound 2-1, Compound 2-2, Compound 2-3, Compound 2-4, Compound 2-5, Compound 2-6, Compound 2-7, Compound 2-8 and Compound 2-9.

[0074] Experiments show that electrolyte additives using at least one of the above-mentioned compounds can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0075] In any embodiment, the compound represented by structural formula (III) is selected from at least one of the following compounds:

[0076] The above compounds are numbered in sequence as Compound 3-1, Compound 3-2, Compound 3-3, Compound 3-4, Compound 3-5, Compound 3-6, Compound 3-7, Compound 3-8, Compound 3-9 and Compound 3-10.

[0077] Experiments show that electrolyte additives using at least one of the above-mentioned compounds can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0078] In any embodiment, the compound represented by structural formula (IV) is selected from at least one of the following compounds:

[0079] The above compounds are numbered in sequence as Compound 4-1, Compound 4-2, Compound 4-3, Compound 4-4, Compound 4-5 and Compound 4-6.

[0080] Experiments show that electrolyte additives using at least one of the above-mentioned compounds can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0081] In any embodiment, the compound represented by structural formula (V) is selected from at least one of the following compounds:

[0082] The above compounds are numbered in sequence as Compound 5-1, Compound 5-2, Compound 5-3, Compound 5-4, Compound 5-5, Compound 5-6, Compound 5-7 and Compound 5-8.

[0083] Experiments show that electrolyte additives using at least one of the above-mentioned compounds can easily consume R+ in the electrolyte and improve the battery's initial efficiency and battery cycle performance.

[0084] Secondly, the embodiments of the present application provide an electrolyte comprising the electrolyte additive described in the above embodiments. The above electrolyte additive is added to the electrolyte. The structural formula of the electrolyte additive in the above embodiments includes at least one nitrogen atom with a lone pair of electrons. The lone pair of electrons on the nitrogen atom makes the nitrogen atom electron-rich and easily reacts with the electron-deficient R+ to generate ----N+-R, thereby reducing the probability of R+ being reduced at the negative electrode and damaging the SEI film, reducing the loss of active lithium at the negative electrode, and thereby improving the battery's initial efficiency and battery cycle performance.

[0085] In any embodiment, in the electrolyte, the mass proportion of the electrolyte additive is W2, 0.005% ≤ W2 ≤ 20%. For example, it can be 0.005%, 0.01%, 0.05%, 0.1%, 1%, 3%, 5%, 8%, 10%, 15%, 17%, 20%, etc. Further, 0.1% ≤ W2 ≤ 10%, for example, it can be 0.1%, 1%, 2%, 4%, 5%, 6%, 7%, 9%, 10%, etc.; further, 1% ≤ W2 ≤ 5%, for example, it can be 1%, 2%, 3%, 4%, 5%, etc. Experiments show that the above mass proportion of the electrolyte additive can enable the electrolyte additive to fully consume R+ in the electrolyte without excessive, thereby improving the battery's first efficiency and battery cycle performance.

[0086] Thirdly, embodiments of the present application provide a secondary battery comprising the electrolyte additive described in the above embodiments. The electrolyte additive is added to the electrolyte of the secondary battery. The structural formula of the electrolyte additive in the above embodiments includes at least one nitrogen atom with a lone pair of electrons. The lone pair of electrons on the nitrogen atom makes the nitrogen atom electron-rich, easily reacting with the electron-deficient R+ to generate ----N+-R, reducing the probability of R+ being reduced at the negative electrode, consuming the active lithium at the negative electrode, and destroying the SEI film, thereby improving the battery's initial efficiency and battery cycle performance.

[0087] In any embodiment, the secondary battery further comprises a positive electrode plate, the positive electrode plate comprises a positive electrode lithium supplement, and the positive electrode lithium supplement comprises Li6CoO4, Li5FeO4, Li3VO4, Li2MoO3, Li2RuO3, Li2MnO3, Li2MnO2, Li2NiO2, Li2CuO2 and Li2Cu x Ni 1-x M y At least one of O2, with 0<x<1, 0≤y<0.1, and M includes at least one of Zn, Sn, Mg, Fe, and Mn. The use of the above-mentioned positive electrode lithium supplement, on the one hand, provides an excess lithium source to compensate for the lithium consumption caused by the formation of the SEI film at the positive and negative electrodes, thereby increasing the energy density of the lithium-ion battery and improving the battery's first cycle coulombic efficiency and cycle performance; on the other hand, it reduces the probability of R+ being reduced at the negative electrode and destroying the SEI film, reducing the loss of active lithium at the negative electrode, thereby improving the battery's first cycle efficiency and battery cycle performance.

[0088] In any embodiment, the positive electrode plate also includes a current collector. In the positive electrode plate, the mass of the positive electrode lithium replenisher is a, the mass of the current collector is b, and the mass of the positive electrode plate is c, W1=a / (cb), 0.1%≤W1≤10%, for example, it can be 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc. Experiments show that the above mass proportion of the positive electrode lithium replenisher can effectively improve the first efficiency and battery cycle performance of the battery.

[0089] In any embodiment, further, 1%≤W1≤8%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, etc.; further, 1%≤W1≤5%, for example, it can be 1%, 2%, 3%, 4%, 5%, etc. Within the above range, the first efficiency and cycle performance of the battery can be effectively improved.

[0090] In any embodiment, the positive electrode plate further includes a positive electrode active material, and the ratio of the Dv50 particle size of the positive electrode lithium supplement to the Dv50 particle size of the positive electrode active material is A, where 1≤A≤10. For example, A can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. Studies have shown that the ratio A also affects the lithium ion conductivity of the positive electrode plate. As the ratio A decreases, the ion conductivity of the positive electrode plate increases, but the contact area between the positive electrode lithium supplement and the electrolyte increases, which increases side reactions and reduces the capacity of the lithium-ion battery. When the ratio A is within the above range, the battery has good initial efficiency and cycle performance.

[0091] It is understood that Dv50 is a well-known term in the art, meaning that 50% of the powder particles are larger than or smaller than this particle size. This can be measured using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK, in accordance with GB / T 19077-2016 Particle Size Distribution - Laser Diffraction Method.

[0092] In any embodiment, further, 2≤A≤8, for example, A can be 1, 2, 3, 4, 5, 6, 7, 8, etc., and the ratio A is within the above range, and the first efficiency and cycle performance of the battery are good.

[0093] In any embodiment, the secondary battery includes a positive electrode sheet, the specific surface area of ​​the positive electrode sheet is B, wherein B≤20m 2 / g, the specific surface area B of the positive electrode sheet is ≤ 20m 2 / g, reducing the contact area between the positive electrode lithium supplement and the electrolyte, slowing down the oxidation of the electrolyte at the positive electrode, and optimizing the first efficiency and cycle performance of the battery. 2 / g≤B≤10m 2 / g, for example, B can be 2m 2 / g、3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g、10m 2 / g, etc. If the specific surface area of ​​the positive electrode is too small, the polarization of the lithium-ion battery will be too large, affecting the capacity of the lithium-ion battery. Within the above range, the battery's first efficiency and cycle performance are good.

[0094] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0095] The preparation of secondary batteries can be carried out by methods commonly used in the art. For example, the positive electrode sheet, the negative electrode sheet and the isolation membrane can be made into an electrode assembly through a winding process or a lamination process, and then the electrolyte is injected into the electrode assembly and sealed to produce a secondary battery.

[0096] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector.

[0097] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0098] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0099] In some embodiments, the positive electrode active material is selected from materials capable of extracting and inserting lithium ions. Specifically, the positive electrode active material can be selected from one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and compounds obtained by adding other transition metals or non-transition metals to the above compounds. The positive electrode plate may also include a conductive agent and a binder, wherein the type and content of the conductive agent and binder are not specifically limited and can be selected according to actual needs.

[0100] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0101] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0102] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0103] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0104] In some embodiments, the solvent may include an organic solvent. The type of organic solvent is not particularly limited and can be selected according to actual needs. Specifically, the organic solvent may also include one or more of other types of linear carbonates, cyclic carbonates, and carboxylates. Wherein, the types of linear carbonates, cyclic carbonates, and carboxylates are not specifically limited and can be selected according to actual needs. Preferably, the organic solvent may also include one or more of diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl propionate, and tetrahydrofuran.

[0105] In some embodiments, the electrolyte may further include other additives, wherein the additives are selected from at least one of cyclic carbonate compounds containing unsaturated bonds, halogen-substituted cyclic carbonate compounds, sulfate compounds, sulfite compounds, sultone compounds, disulfonic acid compounds, nitrile compounds, aromatic compounds, isocyanate compounds, phosphazene compounds, cyclic acid anhydride compounds, phosphite compounds, phosphate compounds, borate compounds, and carboxylate compounds.

[0106] The secondary battery also includes a lithium salt. The type of the lithium salt is not particularly limited and can be selected according to actual needs. Specifically, the lithium salt can be selected from LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2), LiPF6, LiBF4, LiBOB, LiAsF6, Li(FSO2)2N, LiCF3SO3 and LiClO4, wherein x and y are natural numbers. The concentration range of the lithium salt is 0.5M to 2.5M, preferably 0.8M to 2M.

[0107] In some embodiments, the type of negative electrode active material in a secondary battery is not specifically limited, and preferably can be selected from one or more of graphite, soft carbon, hard carbon, mesocarbon microbeads, carbon fibers, carbon nanotubes, elemental silicon, silicon oxides, silicon-carbon composites, and lithium titanate. The negative electrode plate may further include a conductive agent and a binder, wherein the type and amount of the conductive agent and binder are not specifically limited and can be selected based on actual needs. The type of the negative electrode current collector is also not specifically limited and can be selected based on actual needs.

[0108] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0109] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0110] At least one of the secondary batteries in the above embodiments can be assembled into a battery module and a battery pack. The number of battery cells contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0111] In a battery module, multiple secondary batteries can be arranged in sequence along the length of the battery module. Of course, they can also be arranged in any other manner. Furthermore, the multiple secondary battery cells can be fixed by fasteners.

[0112] In any of the embodiments, the battery module may further include a housing having an accommodation space in which the plurality of secondary battery cells are accommodated.

[0113] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0114] In a fourth aspect, an embodiment of the present application provides an electrical device, comprising the secondary battery of the above embodiment of the present application.

[0115] The secondary batteries, battery packs, and battery modules can all be used as power sources or energy storage units for electrical devices. These devices may include, but are not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, and energy storage systems.

[0116] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0117] The technical solutions of the present invention are further described in detail below in conjunction with specific embodiments and drawings. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0118] The relevant parameters of the negative electrode active materials of Examples 1 to 61 and Comparative Example 1 are shown in Table 1 below.

[0119] Table 1 Parameters of Examples 1 to 61 and Comparative Example 1

[0120] Lithium-ion batteries were prepared from Examples 1 to 61 and Comparative Example 1 according to the following method, wherein no positive electrode lithium supplement and electrolyte additive were added in Comparative Example 1:

[0121] (1) Preparation of positive electrode sheet

[0122] The positive electrode active material lithium iron phosphate, the positive electrode lithium supplement agent, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black are dissolved in the solvent N-methylpyrrolidone (NMP) in a mass ratio of (97-W1):W1:2:1, and are fully stirred and mixed to obtain a positive electrode slurry; the positive electrode slurry is then evenly coated on the positive electrode collector, and then dried, cold pressed, and cut to obtain a positive electrode sheet.

[0123] (2) Preparation of negative electrode sheet

[0124] The active material artificial graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are dissolved in the solvent deionized water in a mass ratio of 95:2:2:1 and uniformly mixed with the solvent deionized water to prepare a negative electrode slurry; the negative electrode slurry is then evenly coated on the negative electrode current collector copper foil, and after drying, a negative electrode film is obtained, which is then cold pressed and cut into negative electrode sheets.

[0125] (3) Preparation of electrolyte

[0126] In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), 1 mol / L LiPF6 was dissolved in an organic solvent (EC / DMC / EMC = 1 / 1 / 1), and the electrolyte additives shown in Table 1 were added and stirred evenly to obtain the corresponding electrolyte.

[0127] (4) Preparation of isolation film: Conventional polypropylene film was used as the isolation film.

[0128] (5) Preparation of lithium-ion batteries

[0129] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation, and then wound to obtain an electrode assembly; the electrode assembly is placed in a battery casing, dried, and then injected with electrolyte, and then undergoes formation, static and other processes to produce a lithium-ion battery.

[0130] The lithium-ion batteries of Examples 1 to 61 and Comparative Example 1 were subjected to the following operations and tests:

[0131] 1. Lithium-ion battery capacity test

[0132] At 25°C, charge the lithium-ion battery at a constant current of 0.33C to 3.65V, then charge it at a constant voltage of 3.65V until the current is less than 0.05C. Then discharge the lithium-ion battery at a constant current of 0.33C to 2.5V, and record its actual capacity as C0 (mAh). The gram capacity of the lithium-ion battery is C0 / W3 (mAh / g), where W3 is the mass (g) of the positive electrode active material and the positive electrode lithium supplement.

[0133] 2. Lithium-ion battery 45°C cycle performance test

[0134] At 45°C, charge the lithium-ion battery at a constant current of 1C to a voltage of 3.65V, then charge it at a constant voltage of 3.65V to a current of ≤0.05C, and then discharge it at a constant current of 1C to a voltage of 2.5V. This is one charge and discharge process, and the discharge capacity at this time is recorded as the discharge capacity of the battery's first cycle. Repeat the charge and discharge cycles in this way, and calculate the number of cycles corresponding to the battery's capacity retention rate of 80%.

[0135] The capacity retention rate (%) of the battery after N cycles at 45° C. = (discharge capacity of the battery at the Nth cycle / discharge capacity of the battery at the first cycle)×100%.

[0136] The results of the above two tests are shown in Table 2.

[0137] Table 2 Performance measurement of lithium ion batteries of Examples 1 to 61 and Comparative Example 1

[0138] As can be seen from Table 2, it can be seen from the results of Examples 1 to 46 and Comparative Example 1 that Example 1 does not add lithium supplements and electrolyte additives, and by introducing a positive electrode lithium supplement (Li2Cu 0.6 Ni 0.4 O2) can effectively compensate for the lithium consumption caused by the SEI film formed at the positive and negative electrodes, thereby improving the specific capacity of lithium-ion batteries. However, during the delithiation process, the positive electrode lithium supplement generates oxidized electrolyte, producing R+. This R+ is further reduced at the negative electrode, consuming excessive lithium and deteriorating cycle performance. The introduction of an R+ scavenger allows the nitrogen on the scavenger to further react with R+, consuming the R+ in the electrolyte and preventing further R+ reduction at the negative electrode or damage to the SEI film, which would consume excessive lithium and deteriorate cycle performance.

[0139] It can be seen from the results of Examples 52 to 57 that when the mass proportion of the R+ capture additive in the electrolyte is within the above-mentioned preferred range, it can not only improve the cycle performance of the battery cell but also not deteriorate the battery's specific capacity, thereby improving the battery's initial efficiency and cycle performance.

[0140] It can be seen from the results of Examples 58 to 61 that by introducing an appropriate amount of other positive electrode lithium supplements, such as Li2CuO2, Li2NiO2, Li5FeO4, Li6CoO4, etc., into the lithium-ion battery, and at the same time using an appropriate amount of R+ capture additives, the battery's initial efficiency and cycle performance can also be effectively improved.

[0141] In summary, the structural formula of the electrolyte additive proposed in this application includes at least one nitrogen atom with a lone pair of electrons. The lone pair of electrons on the nitrogen atom makes the nitrogen atom electron-rich, and it is easy to react with the electron-deficient R+ to generate ----N+-R, reducing the probability of R+ being reduced at the negative electrode and destroying the SEI film, consuming the active lithium of the negative electrode, and thus improving the battery's initial efficiency and battery cycle performance.

[0142] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of the present invention.

Claims

1. An electrolyte additive, characterized in that: The structural formula of the electrolyte additive includes at least one nitrogen atom having a lone pair of electrons.

2. The electrolyte additive according to claim 1, characterized in that The electrolyte additive includes at least one of the compound represented by structural formula (I), the compound represented by structural formula (II), the compound represented by structural formula (III), the compound represented by structural formula (IV) and the compound represented by structural formula (V): Wherein, in the structural formula (I), Y1 and Y2 are each independently selected from C atoms and N atoms, and R2, R3 and R4 are each independently selected from H atoms, alkyl groups of 1 to 6 carbon atoms, allyl groups, propargyl groups, halogen atoms, hydroxyl groups, primary amines having 6 or less carbon atoms, secondary amines having 6 or less carbon atoms, tertiary amines having 6 or less carbon atoms, and alkoxy groups having 6 or less carbon atoms; In the structural formula (II), W1 is selected from C atoms, N atoms, O atoms and S atoms, W2 is selected from C atoms and N atoms, R5, R6, R7 and R8 are each independently selected from H atoms, alkyl groups of 1 to 6 carbon atoms, allyl groups, propargyl groups, halogen atoms, hydroxyl groups, primary amines having 6 or less carbon atoms, secondary amines having 6 or less carbon atoms, tertiary amines having 6 or less carbon atoms and alkoxy groups having 6 or less carbon atoms; In the structural formula (III), A1, A2, A3, A4 and A5 are each independently selected from C atoms and N atoms, and R9 is selected from H atoms, alkyl groups having 1 to 6 carbon atoms, allyl groups, propargyl groups, halogen atoms, hydroxyl groups, primary amines having 6 or less carbon atoms, secondary amines having 6 or less carbon atoms, tertiary amines having 6 or less carbon atoms, and alkoxy groups having 6 or less carbon atoms; In the structural formula (IV), X1, X2 and X3 are each independently selected from C atoms and N atoms, a and b are each independently selected from constants of 0 to 3, and R1 is selected from H atoms, alkyl groups of 1 to 6 carbon atoms, allyl groups, propargyl groups, halogen atoms, hydroxyl groups, primary amines having 6 or less carbon atoms, secondary amines having 6 or less carbon atoms, tertiary amines having 6 or less carbon atoms, and alkoxy groups having 6 or less carbon atoms; In the structural formula (V), V1, V2 and V3 are each independently selected from C atoms and N atoms, d is selected from a constant of 0 to 3, and R 11 , R 12 , R 13 and R 14 Each is independently selected from an H atom, an alkyl group with 1 to 6 carbon atoms, an allyl group, a propargyl group, a halogen atom, a hydroxyl group, a primary amine with 6 carbon atoms or less, a secondary amine with 6 carbon atoms or less, a tertiary amine with 6 carbon atoms or less, and an alkoxy group with 6 carbon atoms or less.

3. The electrolyte additive according to claim 2, characterized in that In the structural formula (I), at least one of Y1 and Y2 is a nitrogen atom; and / or, In the structural formula (II), at least one of W1 and W2 is a N atom; and / or, In the structural formula (III), at least one of A1, A2, A3, A4 and A5 is a N atom; and / or, In the structural formula (IV), at least one of X1, X2 and X3 is a N atom; and / or, In the structural formula (V), at least one of V1, V2 and V3 is a N atom.

4. The electrolyte additive according to claim 2, characterized in that In the structural formula (I), Y1 and Y2 are both N atoms; and / or, In the structural formula (II), W1 and W2 are both N atoms; and / or, In the structural formula (III), A1, A2, A3, A4 and A5 are all N atoms; and / or, In the structural formula (IV), X1, X2 and X3 are all N atoms; and / or, In the structural formula (V), V1, V2 and V3 are all N atoms.

5. The electrolyte additive according to any one of claims 2 to 4, characterized in that: The compound represented by structural formula (I) is selected from at least one of the following compounds: and / or, The compound represented by structural formula (II) is selected from at least one of the following compounds: and / or, The compound represented by structural formula (III) is selected from at least one of the following compounds: and / or, The compound represented by structural formula (IV) is selected from at least one of the following compounds: and / or, The compound represented by structural formula (V) is selected from at least one of the following compounds:

6. An electrolyte, characterized in that: The electrolyte additive comprises the electrolyte additive as claimed in any one of claims 1 to 5.

7. The electrolyte according to claim 6, characterized in that In the electrolyte, the mass proportion of the electrolyte additive is W2, 0.005%≤W2≤20%.

8. The electrolyte according to claim 6, characterized in that 0.005%≤W2≤10%; preferably, 1%≤W2≤5%.

9. A secondary battery, characterized in that: The electrolyte additive comprises the electrolyte additive as claimed in any one of claims 1 to 5.

10. The secondary battery according to claim 9, characterized in that The secondary battery also includes a positive electrode plate, the positive electrode plate includes a positive electrode lithium supplement, and the positive electrode lithium supplement includes Li6CoO4, Li5FeO4, Li3VO4, Li2MoO3, Li2RuO3, Li2MnO3, Li2MnO2, Li2NiO2, Li2CuO2 and Li2Cu x Ni 1-x M y At least one of O2, 0<x<1, 0≤y<0.1, M includes at least one of Zn, Sn, Mg, Fe and Mn.

11. The secondary battery according to claim 10, characterized in that: The positive electrode plate also includes a current collector. In the positive electrode plate, the mass of the positive lithium supplement is a, the mass of the current collector is b, the mass of the positive electrode plate is c, W1=a / (cb), 0.1%≤W1≤10%.

12. The secondary battery according to claim 11, wherein: 1%≤W1≤8%; preferably, 1%≤W1≤5%.

13. The secondary battery according to any one of claims 10 to 12, characterized in that: The positive electrode plate also includes a positive electrode active material, and the ratio of the Dv50 particle size of the positive electrode lithium supplement to the Dv50 particle size of the positive electrode active material is A, 1≤A≤10.

14. The secondary battery according to claim 13, characterized in that: 2≤A≤8。 15. The secondary battery according to any one of claims 9 to 14, characterized in that: The secondary battery comprises a positive electrode sheet, the specific surface area of ​​the positive electrode sheet is B, wherein B≤20m 2 / g.

16. The secondary battery according to claim 15, characterized in that: 0.5m 2 / g≤B≤10m 2 / g。 17. An electrical device, characterized in that: Comprising the secondary battery as claimed in any one of claims 9 to 16.