Electrolyte additive composition, electrolyte and lithium ion secondary battery comprising same, and use thereof

Abstract

The invention provides an electrolyte additive composition, an electrolyte containing the electrolyte additive composition, a lithium ion secondary battery containing the electrolyte additive composition and application of the electrolyte additive composition. The electrolyte additive composition includes a compound represented by the following formula (1) and a cyano-substituted C4-10 aromatic compound or heteroaromatic compound, in which R1 and R2 may be the same or different and are each independently selected from unsubstituted or F-substituted C1-6 alkyl groups. According to the electrolyte additive composition, the electrolyte containing the electrolyte additive composition, the lithium ion secondary battery and the application of the electrolyte additive composition, the internal resistance of the lithium ion secondary battery is reduced, and the technical effects of improving the capacity retention rate of the lithium ion secondary battery after circulation and the electrical property at high temperature are achieved. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the field of lithium ion secondary batteries, and in particular to an electrolyte additive composition, an electrolyte and a lithium ion secondary battery containing the electrolyte additive composition, and uses thereof. Background Art

[0002] In recent years, with the continuous updating of electronic technology, people's demand for battery devices used to support the energy supply of electronic devices has been increasing. Nowadays, batteries that can store more electricity and output high power are needed. Traditional lead-acid batteries and nickel-metal hydride batteries can no longer meet the needs of new electronic products such as mobile devices such as smartphones and fixed equipment such as power storage systems. Therefore, lithium batteries have attracted widespread attention. In the process of developing lithium batteries, their capacity and performance have been effectively improved. Lithium-ion batteries have the advantages of high energy density, high operating voltage, long cycle life, and low environmental pollution. They have become a new type of green high-energy chemical power source with great development potential in the world today. The electrolyte is an important component of lithium-ion batteries and has an important influence on many battery properties such as voltage, energy density, power, life, temperature range and safety performance.

[0003] Lithium-ion secondary batteries have been a hot topic in the field of new energy in recent years. They have the advantages of high energy density, low self-discharge rate, and low environmental pollution. At present, lithium-ion secondary batteries have been applied to the fields of mobile terminal electronic products and hybrid electric vehicles. With the continuous advancement of science and technology, the requirements for the performance of lithium-ion batteries are getting higher and higher. The development of high energy density, widening the temperature range of battery use, and improving battery safety performance have posed severe challenges to the majority of lithium-ion secondary battery researchers. Usually, during the first charge and discharge process of lithium-ion batteries, the electrode material and the electrolyte react at the solid-liquid interface, the electrolyte is reduced and decomposed, and a passivation layer covering the surface of the electrode material is formed. This passivation layer is an interface layer that is an insulator for electrons, but an excellent conductor for lithium ions. Lithium ions can be freely embedded and de-embedded through the passivation layer. The film formed by the passivation layer covering the electrode contains various inorganic components such as Li2CO3, LiF, Li2O, LiOH, and various organic components such as RO-CO2Li, ROLi, (ROCO2Li)2.

[0004] In order to solve the problem that the electrolyte reacts with the electrode material and adversely affects the performance of the lithium-ion secondary battery, an electrolyte additive is usually added so that a passivation layer is formed on the surface of the electrode material during the first charge and discharge cycle of the battery, thereby protecting the battery material from corrosion by the electrolyte. The main mechanism of action of the additives used in the prior art is that the additives react directly on the electrode surface, and the reaction products adhere to the electrode surface to form a relatively stable SEI or CEI passivation layer to increase the battery life. However, the electrolyte additives used in the prior art cannot effectively protect the electrode, so that the battery exhibits poor high temperature resistance and capacity retention. Therefore, in order to solve the problems mentioned above, it is still necessary to develop an electrolyte additive that can effectively form an electrode protective film and ensure the electrical properties of lithium-ion secondary batteries. Summary of the invention

[0005] The main purpose of the present invention is to provide an electrolyte additive composition, an electrolyte and a lithium ion secondary battery containing the same, and uses thereof, so as to solve the problem that the battery in the prior art exhibits poor high temperature resistance and capacity retention rate at high temperatures.

[0006] In order to achieve the above object, according to one aspect of the present invention, there is provided an electrolyte additive composition comprising a compound represented by the following formula (1) and a cyano-substituted C 4-10 Aromatic or heteroaromatic compounds:

[0007]

[0008] Wherein, R1 and R2 may be the same or different and are each independently selected from unsubstituted or F-substituted C 1-6 alkyl.

[0009] Furthermore, in the electrolyte additive composition, R1 and R2 are each independently selected from unsubstituted or F-substituted C 1-3 alkyl.

[0010] Furthermore, in the electrolyte additive composition, the cyano-substituted C 4-10 The aromatic compound or heteroaromatic compound is further substituted with a substituent selected from the group consisting of:

[0011] Unsubstituted or F-substituted C 1-6 alkyl, Wherein R3 is selected from C 1-6 alkyl.

[0012] Furthermore, in the above electrolyte additive composition, C 4-10The aromatic or heteroaromatic compound is selected from benzene, naphthalene, furan, thiophene, pyrrole, pyrazole, imidazole, oxazole, thiazole, pyridine, benzofuran, benzothiophene, indole, benzimidazole, benzoxazole, benzothiazole and quinoline.

[0013] Furthermore, in the above electrolyte additive composition, the compound of formula (1) is selected from any one of the following:

[0014]

[0015] Furthermore, in the electrolyte additive composition, the cyano-substituted C 4-10 The aromatic compound or heteroaromatic compound is any of the following

[0016]

[0017] Furthermore, in the electrolyte additive composition, the compound of formula (1) and the cyano-substituted C 4-10 The molar ratio between the aromatic compounds or heteroaromatic compounds is in the range of 1:2 to 7:2.

[0018] According to another aspect of the present invention, there is provided an electrolyte comprising an organic solvent, a lithium salt and the electrolyte additive composition according to any one of claims 1 to 7.

[0019] Furthermore, in the above-mentioned electrolyte, based on 100 parts by weight of the total weight of the organic solvent and the lithium salt, the amount of the compound represented by formula (1) is in the range of 0.1 parts by weight to 10 parts by weight; preferably, the amount of the compound represented by formula (1) is in the range of 0.1 parts by weight to 2.0 parts by weight; more preferably, the amount of the compound represented by formula (1) is in the range of 0.2 parts by weight to 1.0 parts by weight.

[0020] Furthermore, in the above electrolyte, based on 100 parts by weight of the total weight of the organic solvent and the lithium salt, the cyano-substituted C 4-10 The amount of the aromatic compound or heteroaromatic compound is in the range of 0.1 parts by weight to 10 parts by weight; preferably, the cyano-substituted C 4-10 The amount of the aromatic compound or heteroaromatic compound is in the range of 0.1 parts by weight to 2.0 parts by weight; more preferably, the cyano-substituted C 4-10 The amount of the aromatic compound or heteroaromatic compound is in the range of 0.2 to 1.0 parts by weight.

[0021] Furthermore, in the above-mentioned electrolyte, the lithium salt is selected from the group consisting of LiPF6, LiBF4, LiAsF6, LiCF3SO3, LiN(SO2F)2, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, or any combination thereof.

[0022] Furthermore, in the above electrolyte, the organic solvent is selected from the group consisting of propylene carbonate, butylene carbonate, fluoroethylene carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate or any combination thereof.

[0023] According to another aspect of the present invention, a lithium-ion secondary battery is provided, characterized in that it comprises: a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte described above in the present invention.

[0024] According to another aspect of the present invention, there is provided use of the electrolyte additive composition of the present invention for preparing an electrolyte for a lithium ion secondary battery and / or a lithium ion secondary battery.

[0025] The electrolyte additive composition, the electrolyte and lithium ion secondary battery containing the same and their uses of the present invention achieve the technical effects of reducing the internal resistance of the lithium ion secondary battery, improving the capacity retention rate after cycling and the electrical performance of the lithium ion secondary battery at high temperature. DETAILED DESCRIPTION

[0026] It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments. The following embodiments are merely exemplary and do not constitute a limitation on the scope of protection of the present invention.

[0027] In the present invention, "aromatic compound" refers to aromatic hydrocarbon compounds containing a specific number of carbon atoms, such as benzene, naphthalene, anthracene or phenanthrene. The prefix "hetero" means that the compound or group includes at least one ring member that is a heteroatom (e.g., 1, 2 or 3 heteroatoms), wherein each heteroatom is independently N, O or S.

[0028] As described in the background art, the electrolyte additives in the prior art cannot effectively form an interface film on the electrode surface and enable the lithium-ion secondary battery to exhibit excellent high temperature resistance and capacity retention. In view of the problems in the prior art, a typical embodiment of the present invention provides an electrolyte additive composition. The electrolyte additive composition comprises a compound represented by the following formula (1) and a cyano-substituted C 4-10 Aromatic or heteroaromatic compounds:

[0029]

[0030] In the above formula (1), R1 and R2 may be the same or different and are each independently selected from unsubstituted or F-substituted C 1-6 alkyl.

[0031] The inventors of the present invention surprisingly found after a large number of experiments that adding the compound represented by formula (1) and a cyano-substituted C 4-10 In the case of aromatic compounds or heteroaromatic compounds, after the first charge and discharge, the above two substances can react on the surface of the negative electrode and the positive electrode to form a heteropolycyclic structure. During the first charge and discharge cycle, the surface of the negative electrode is in an electron-deficient state, thus showing local strong alkalinity. The compound represented by formula (1) of the present invention and the cyano-substituted C 4-10 Aromatic compounds or heteroaromatic compounds can react on the surface of the negative electrode and shrink to form heteropolycyclic compounds (such as but not limited to pyrrolopyrrole). The heteropolycyclic compound formed has a planar structure, so that it can be attached to the surface of the negative electrode, thereby generating an interface film (SEI film) coated on the surface of the negative electrode. In other embodiments, after the heteropolycyclic compound is formed, the heteropolycyclic compound can further undergo a polymerization reaction to form a dimer, trimer or polymer, thereby generating a dense interface film (SEI film) coated on the surface of the negative electrode. In addition, since the polycyclic conjugated structure has a smaller HOMO-LUMO energy gap, the molecule can also react at the positive electrode after formation, thereby generating an interface film (CEI film) coated on the surface of the negative electrode. The formed interface film can effectively and completely coat the positive and negative electrodes, thereby avoiding direct contact between the positive and negative electrode materials and the electrolyte, and inhibiting the decomposition and degradation of the positive and negative electrode materials. In addition, the formed interface film has a primary structure such as pyrrolopyrrole (without dimerization or polymerization), so the multiple heteroatom sites in its structure can increase the conductivity of the interface film, thereby reducing the internal resistance of the lithium ion secondary battery formed thereby.

[0032] In some embodiments, the compound of formula (1) of the present invention is:

[0033]

[0034] wherein R1 and R2 may be the same or different and are each independently selected from unsubstituted or F-substituted C 1-3 alkyl.

[0035] In some preferred embodiments, the compound of formula (1) of the present invention can be selected from any one of the following:

[0036]

[0037] In some embodiments of the present invention, the cyano-substituted C 4-10 The aromatic or heteroaromatic compound may be substituted by additional substituents. These additional substituents are selected from the group consisting of:

[0038] Unsubstituted or F-substituted C 1-6 alkyl, Wherein R3 is selected from C 1-6 In some specific embodiments, the C 1-6 Alkyl is F substituted C 1-3 Alkyl, preferably CF3, C2F5, C3F7.

[0039] In addition, in a preferred embodiment, the cyano-substituted C 4-10 The skeleton (main chain) of the aromatic compound or heteroaromatic compound is selected from benzene, naphthalene, furan, thiophene, pyrrole, pyrazole, imidazole, oxazole, thiazole, pyridine, benzofuran, benzothiophene, indole, benzimidazole, benzoxazole, benzothiazole and quinoline. 4-10 The skeleton (main chain) of the aromatic compound or heteroaromatic compound is benzene, thiophene, or pyridine.

[0040] In a further embodiment of the present application, the compound of formula (1) and a cyano-substituted C 4-10 The molar ratio between the aromatic compound or heteroaromatic compound is in the range of 1:2 to 7:2. In a preferred embodiment, the compound of formula (1) and the cyano-substituted C 4-10 The molar ratio between the aromatic compound or the heteroaromatic compound is in the range of 2:2 to 4:2. 4-10 When the molar ratio of the aromatic compound or the heteroaromatic compound is less than 1:2, the amount of the compound of formula (1) is too small, and thus the planar structure having multiple heterocycles cannot be effectively formed. 4-10 When the molar ratio of aromatic compounds or heteroaromatic compounds is greater than 7:2, the cyano-substituted C 4-10 If the amount of the aromatic compound or heteroaromatic compound is too large, a polymer having a complex non-planar structure may be formed, and after being coated on the surface of the positive electrode and the negative electrode, the resistance of the lithium-ion battery is unfavorably increased.

[0041] In different embodiments of the present invention, the compound of formula (1) and a cyano-substituted C 4-10 The molar ratio between the aromatic or heteroaromatic compounds can be in the range of 1:2 to 7:2, 2:2 to 7:2, 3:2 to 7:2, 4:2 to 7:2, 5:2 to 7:2, 6:2 to 7:2, 1:2 to 6:2, 1:2 to 5:2, 1:2 to 4:2, or 1:2 to 3:2.

[0042] In another typical embodiment of the present invention, an electrolyte is provided, comprising an organic solvent, a lithium salt and the electrolyte additive composition described above in the present invention. Due to the inclusion of the electrolyte additive of the present invention, the electrolyte of the present invention can form a heteropolycyclic compound having a planar structure on the surface of the positive electrode and the negative electrode during the first cycle of the battery. Thus, it can be attached to the surface of the positive electrode and the negative electrode, thereby generating an interface film coated on the surface of the positive electrode and the negative electrode. When the electrolyte of the present invention is used, the conductivity of the interface film can be effectively increased, the internal resistance of the lithium-ion secondary battery formed thereby can be reduced, and the cycle maintenance rate can be increased.

[0043] In some embodiments of the present invention, in the electrolyte of the present invention, based on 100 parts by weight of the total weight of the organic solvent and the lithium salt, the amount of the compound represented by formula (1) is in the range of 0.1 parts by weight to 10 parts by weight; preferably, the amount of the compound represented by formula (1) is in the range of 0.1 parts by weight to 2.0 parts by weight; more preferably, the amount of the compound represented by formula (1) is in the range of 0.2 parts by weight to 1.0 parts by weight. In different embodiments of the present invention, according to the lithium salt, the organic solvent and the cyano-substituted C 4-10 Different combinations of aromatic compounds or heteroaromatic compounds, based on 100 parts by weight of the total weight of the organic solvent and the lithium salt, the amount of the compound represented by formula (1) present in the electrolyte can be in the following ranges: in the range of 0.1 parts by weight to 10 parts by weight, in the range of 0.2 parts by weight to 10 parts by weight, in the range of 0.3 parts by weight to 10 parts by weight, in the range of 0.4 parts by weight to 10 parts by weight, in the range of 0.5 parts by weight to 10 parts by weight, in the range of 0.6 parts by weight to 10 parts by weight, in the range of 0.7 parts by weight to 10 parts by weight, in the range of 0.8 parts by weight to 10 parts by weight, in the range of 0.9 parts by weight to 10 parts by weight, in the range of 1 part by weight to 10 parts by weight, in the range of 2 parts by weight to 10 parts by weight, in the range of 3 parts by weight to 10 parts by weight, in the range of 4 parts by weight to 10 parts by weight, in the range of 5 parts by weight to 10 parts by weight. The amount of the present invention is preferably in the range of 0.1 to 10 parts by weight, in the range of 0.1 to 9 parts by weight, in the range of 0.1 to 8 parts by weight, in the range of 0.1 to 7 parts by weight, in the range of 0.1 to 6 parts by weight, in the range of 0.1 to 5 parts by weight, in the range of 0.1 to 4 parts by weight, in the range of 0.1 to 3 parts by weight, in the range of 0.1 to 2 parts by weight, in the range of 0.1 to 1 part by weight, in the range of 0.2 to 1 part by weight, in the range of 0.3 to 1 part by weight, in the range of 0.4 to 1 part by weight, in the range of 0.5 to 1 part by weight, in the range of 0.6 to 1 part by weight, in the range of 0.7 to 1 part by weight, in the range of 0.8 to 1 part by weight, or in the range of 0.9 to 1 part by weight.

[0044] In some embodiments of the present invention, based on 100 parts by weight of the total weight of the organic solvent and the lithium salt, the cyano-substituted C 4-10 The amount of the aromatic compound or heteroaromatic compound is in the range of 0.1 parts by weight to 10 parts by weight; preferably, the cyano-substituted C 4-10 The amount of the aromatic compound or heteroaromatic compound is in the range of 0.1 parts by weight to 2.0 parts by weight; more preferably, the cyano-substituted C 4-10 The amount of the aromatic compound or heteroaromatic compound is in the range of 0.2 parts by weight to 1.0 parts by weight. In different embodiments of the present invention, according to different combinations of the lithium salt, the organic solvent and the compound represented by formula (1), based on 100 parts by weight of the total weight of the organic solvent and the lithium salt, the cyano-substituted C 4-10 The amount of the aromatic compound or heteroaromatic compound may be in the range of 0.1 to 10 parts by weight, in the range of 0.2 to 10 parts by weight, in the range of 0.3 to 10 parts by weight, in the range of 0.4 to 10 parts by weight, in the range of 0.5 to 10 parts by weight, in the range of 0.6 to 10 parts by weight, in the range of 0.7 to 10 parts by weight, in the range of 0.8 to 10 parts by weight, in the range of 0.9 to 10 parts by weight, in the range of 1 to 10 parts by weight, in the range of 2 to 10 parts by weight, in the range of 3 to 10 parts by weight, in the range of 4 to 10 parts by weight, in the range of 5 to 10 parts by weight, in the range of 0.1 to 9 parts by weight. The range of 0.1 to 8 parts by weight, the range of 0.1 to 7 parts by weight, the range of 0.1 to 6 parts by weight, the range of 0.1 to 5 parts by weight, the range of 0.1 to 4 parts by weight, the range of 0.1 to 3 parts by weight, the range of 0.1 to 2 parts by weight, the range of 0.1 to 1 part by weight, the range of 0.2 to 1 part by weight, the range of 0.3 to 1 part by weight, the range of 0.4 to 1 part by weight, the range of 0.5 to 1 part by weight, the range of 0.6 to 1 part by weight, the range of 0.7 to 1 part by weight, the range of 0.8 to 1 part by weight, or the range of 0.9 to 1 part by weight.

[0045] The present invention has no special restrictions on the lithium salt components contained in the electrolyte, and those known in the prior art that can be used for lithium battery electrolytes can be adopted. Examples of lithium salts include, but are not limited to: LiCl, LiBr, LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2F)2, LiN(SO2CF3)2, LiC(SO2CF3)3, LiAlCl4 and / or LiSiF6, and any combination thereof.

[0046] In the present invention, the organic solvent of the non-aqueous electrolyte can be any non-aqueous solvent used for non-aqueous electrolyte solutions to date. Examples include, but are not limited to: linear or cyclic carbonates, such as ethylene carbonate, propylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, fluoroethylene carbonate; ethers, such as 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether; sulfones, such as cyclopentane sulfone, methylcyclopentane sulfone; nitriles, such as acetonitrile, propionitrile, acrylonitrile; esters, such as acetate, propionate, butyrate, etc. These non-aqueous solvents can be used alone or in combination. In some embodiments of the present invention, preferred electrolyte comprises ethylene carbonate, propylene carbonate, butylene carbonate, fluorocarbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, ethylene carbonate and / or dimethyl carbonate and their combination in any. In a preferred embodiment, use at least one carbonate as the organic solvent of electrolyte of the present invention. In other preferred embodiments, above-mentioned nonaqueous solvent can be used in any combination to form the electrolyte solution that meets specific requirements.

[0047] In another typical embodiment of the present invention, a lithium ion secondary battery is provided, which includes: a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte described above. Since the lithium ion secondary battery of the present invention uses the electrolyte described above, it has reduced internal resistance and increased cycle retention rate.

[0048] The positive electrode sheet of the present invention includes a positive electrode collector and a positive electrode active material layer containing a positive electrode active material. The positive electrode active material layer is formed on both surfaces of the positive electrode collector. Metal foils such as aluminum foil, nickel foil, and stainless steel foil can be used as the positive electrode collector.

[0049] The positive electrode active material layer contains one or two or more of positive electrode materials capable of absorbing and releasing lithium ions as positive electrode active materials, and may contain additional materials such as a positive electrode binder and / or a positive electrode conductor as necessary.

[0050] Preferably, the positive electrode material is a lithium-containing compound. Examples of such lithium-containing compounds include lithium-transition metal composite oxides, lithium-transition metal phosphate compounds, and the like. Lithium-transition metal composite oxides are oxides containing Li and one or more transition metal elements as constituent elements, and lithium-transition metal phosphate compounds are phosphate compounds containing Li and one or more transition metal elements as constituent elements. Among them, the transition metal element is preferably any one or two or more of Co, Ni, Mn, Fe, etc.

[0051] Examples of lithium-transition metal composite oxides include, for example, LiCoO2, LiNiO2, etc. Examples of lithium-transition metal phosphate compounds include, for example, LiFePO4, LiFe 1-u Mn u PO4 (0 < u < 1), etc.

[0052] In some embodiments of the present application, the positive electrode material may be a ternary positive electrode material, such as lithium nickel cobalt aluminate (NCA) or lithium nickel cobalt manganate (NCM). Specific examples may be NCA, LixNiyCozAl1-y-zO2 (1 ≤ x ≤ 1.2, 0.5 ≤ y ≤ 1, and 0 ≤ z ≤ 0.5). NCM, LiNixCoyMnzO2 (x + y + z = 1, 0 < x < 1, 0 < y < 1, 0 < z < 1). Specific examples of the positive electrode material may include, but are not limited to, the following materials: LiNiO2, LiCoO2, LiCo 0.98 Al 0.01 Mg 0.01 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.33 Co 0.33 Mn 0.33 O2, Li 1.2 Mn 0.52 Co 0.175 Ni 0.1 O2 and Li 1.15 (Mn 0.65 Ni 0.22 Co 0.13 )O2, LiFePO4, LiMnPO4, LiFe 0.5 Mn 0.5 PO4 and LiFe 0.3 Mn 0.7 PO4.

[0053] In addition, the positive electrode material may be, for example, any one or two or more of an oxide, a disulfide, a chalcogenide, a conductive polymer, etc. Examples of oxides include, for example, titanium oxide, vanadium oxide, manganese dioxide, etc. Examples of disulfides include, for example, titanium disulfide, molybdenum sulfide, etc. Examples of chalcogenides include, for example, niobium selenide, etc. Examples of conductive polymers include, for example, sulfur, polyaniline, polythiophene, etc. However, the positive electrode material may be a material different from those above.

[0054] Examples of positive electrode conductors include carbon materials such as graphite, carbon black, acetylene black and Ketjenblack. These can be used alone, or two or more of them can be mixed and used. It should be noted that the positive electrode conductor can be a metal material, a conductive polymer or the like, as long as it has conductivity.

[0055] Examples of positive electrode binders include, for example, synthetic rubber and polymer materials, where the synthetic rubber may be, for example, styrene-butadiene rubber, fluororubber and ethylene-propylene-diene, and the polymer material may be, for example, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, lithium polyacrylate, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM and polyimide. These may be used alone, or two or more thereof may be mixed and used.

[0056] The negative electrode sheet of the present invention includes a negative electrode collector and a negative electrode active material layer containing a negative electrode active material. The negative electrode active material layer is formed on both surfaces of the negative electrode collector. Metal foils such as copper (Cu) foil, nickel foil, and stainless steel foil can be used as the negative electrode collector.

[0057] The negative electrode active material layer contains a material capable of absorbing and releasing lithium ions as a negative electrode active material, and may contain other materials such as a negative electrode binder and / or a negative electrode conductor if necessary. The details of the negative electrode binder and the negative electrode conductor are, for example, the same as those of the positive electrode binder and the positive electrode conductor.

[0058] The active material of the negative electrode is selected from any one or more combinations of lithium metal, lithium alloy, carbon material, silicon or tin and oxides thereof.

[0059] Because carbon material has low potential when absorbing lithium ions, high energy density can be obtained, and battery capacity can be increased. In addition, carbon material also serves as a conductive agent. Such carbon material is, for example, natural graphite, artificial graphite, a material obtained by coating them with amorphous carbon or the like. It should be noted that the shape of the carbon material is fibrous, spherical, granular, flaky or similar. Silicon-based materials include nano-silicon, silicon alloys, SiOw and graphite composite silicon-carbon composite materials, preferably, SiOw is silicon oxide, silicon oxide or other silicon-based materials.

[0060] In addition, the negative electrode material may be, for example, one or more of graphitizable carbon, difficult graphitizable carbon, metal oxides, polymer compounds, etc. Examples of metal oxides include, for example, iron oxide, ruthenium oxide, molybdenum oxide, etc. Examples of polymer compounds include, for example, polyacetylene, polyaniline, polypyrrole, etc. However, the negative electrode material may be another material different from those described above.

[0061] The separator of the present invention is used to separate the positive electrode sheet and the negative electrode sheet in the battery, and to allow ions to pass through while preventing the current short circuit caused by the contact between the two electrode sheets. The separator is, for example, a porous film formed of a synthetic resin, ceramic or the like, and can be a laminated film in which two or more porous films are laminated. Examples of synthetic resins include, for example, polytetrafluoroethylene, polypropylene, polyethylene, cellulose, etc.

[0062] In an embodiment of the present invention, when charging, for example, lithium ions are released from the positive electrode and absorbed in the cathode by the non-aqueous electrolyte impregnated in the separator. When discharging, for example, lithium ions are released from the negative electrode and absorbed in the positive electrode by the non-aqueous electrolyte impregnated in the separator.

[0063] In another typical embodiment of the present invention, the use of the electrolyte additive of the present application for preparing a lithium ion secondary battery is provided. After the electrolyte additive composition of the present application is added to the lithium ion secondary battery, the electrolyte additive composition will react during the first charge and discharge cycle, and the reaction product will be coated on the surface of the positive electrode and the negative electrode, thereby reducing the internal resistance of the battery and increasing the cycle retention rate.

[0064] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0065] Nickel cobalt aluminum oxide lithium battery embodiment

[0066] Preparation of electrolyte

[0067] Example 1

[0068] Preparation of negative electrode

[0069] Under vacuum and completely dry conditions, at a temperature of 20°C, 97.0 g of graphite powder, 2.0 g of styrene-butadiene rubber, and 1.0 g of carboxymethyl cellulose were weighed and added to water and stirred evenly to obtain a negative electrode active material slurry. The negative electrode active material slurry was coated on a copper foil to obtain a negative electrode collector, the negative electrode collector was dried, and a negative electrode sheet was formed by a stamping process.

[0070] Preparation of positive electrode

[0071] Under vacuum and completely dry conditions, at a temperature of 20°C, 92.0 g of positive electrode active material lithium nickel cobalt aluminum oxide, 5.0 g of conductive carbon black and 3.0 g of polyvinylidene fluoride were mixed to obtain a positive electrode mixture, and the obtained positive electrode mixture was dispersed in N-methylpyrrolidone to obtain a positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was coated on an aluminum foil to obtain a positive electrode collector, the positive electrode collector was dried, and a positive electrode sheet was formed using a stamping process.

[0072] Preparation of electrolyte

[0073] 20.0 g of ethylene carbonate, 62.0 g of dimethyl carbonate and 18.0 g of lithium hexafluorophosphate were mixed to prepare a basic electrolyte. 0.5 g of compound 1 of the following formula and 0.5 g of compound 2 of the following formula were added to the basic electrolyte to obtain an electrolyte for a battery, wherein compound 1 is:

[0074] Compound 2 is:

[0075] Battery Assembly

[0076] Assemble CR2016 button cells in a dry laboratory. Use the positive electrode sheet obtained in the above steps as the positive electrode, and the negative electrode sheet as the negative electrode. Assemble the positive electrode, negative electrode, separator and battery shell of the button cell and inject electrolyte. Assemble the positive electrode, negative electrode, separator and battery shell of the button cell. After the battery is assembled, let it stand for about 24 hours to age, thereby obtaining a nickel cobalt manganese oxide lithium button cell.

[0077] Example 2-14

[0078] The button cells of Examples 2-14 were prepared in the same manner as in Example 1, and the differences are shown in the following table:

[0079] Table 1

[0080]

[0081] Among them, the compound 3-7 used in Example 2-14 is as follows:

[0082] Compound 3: Compound 4: Compound 5: Compound 6: Compound 7:

[0083] Comparative Example 1

[0084] The button cell of Comparative Example 1 was prepared in the same manner as in Example 1, except that no electrolyte additive was added after the basic electrolyte was prepared.

[0085] Battery performance test

[0086] Determination of capacity retention

[0087] The capacity retention rate of the lithium-ion secondary batteries produced by the various embodiments and comparative examples described above was determined as follows. First, the battery was charged at room temperature, at a charging voltage of 4.25V, a charging current of 0.5mA, and a charging time of 10 hours, and then discharged at a discharge current of 0.5mA and a terminal voltage of 2.0V, and the initial discharge capacity was measured. Next, repeated charging and discharging were performed at an ambient temperature of 60°C, a charging voltage of 4.25V, a charging current of 5mA, and a charging time of 1 hour, and at a discharge current of 25mA and a terminal voltage of 2.5V. The discharge capacity of the first cycle and the discharge capacity of the 100th cycle were measured. Next, the capacity retention rate (%) after 100 cycles was calculated using the discharge capacity of the first cycle and the discharge capacity of the 100th cycle based on the following formula.

[0088] Capacity retention rate after 100 cycles [%] = (discharge capacity at 100th cycle / discharge capacity at 1st cycle) × 100% Impedance measurement

[0089] The lithium-ion secondary battery was kept at room temperature, charged once at 0.5C, and then the initial impedance value of the battery was determined. 100 charge-discharge cycles were performed at 60°C, and the final impedance value of the battery was measured after the end. The impedance growth of the battery was calculated by the following formula.

[0090] Impedance growth rate = final impedance value / initial impedance value

[0091] The experimental results are shown in Table 2 below.

[0092] Table 2

[0093]

[0094] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0095] It can be seen from the contents of Table 2 above that when the electrolyte additive composition of the present invention is used, the post-cycle impedance of the lithium-ion secondary battery is significantly reduced compared with Comparative Example 1 (electrolyte additive is not applicable). When the above battery performance tests were conducted at a high temperature of 60°C, the electrolyte additive composition of the present invention enables the lithium-ion secondary battery to exhibit excellent electrical properties at high temperatures. Compared with Comparative Example 1, Examples 1-3 of the present invention exhibit the best impedance reduction, and the impedance increase rate is reduced from 283% to 60%. Compared with Comparative Example 1, Examples 1-4, 7 and 11 of the present invention exhibit the best post-cycle capacity retention rate.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An electrolyte additive composition, characterized in that: It comprises a compound represented by the following formula (1) and a cyano-substituted C 4-10 Aromatic or heteroaromatic compounds: Wherein, R1 and R2 may be the same or different and are each independently selected from unsubstituted or F-substituted C 1-6 alkyl.

2. The electrolyte additive composition according to claim 1, characterized in that: R1 and R2 are each independently selected from unsubstituted or F-substituted C 1-3 alkyl.

3. The electrolyte additive composition according to claim 1, characterized in that: The cyano-substituted C 4-10 The aromatic compound or heteroaromatic compound is further substituted with a substituent selected from the group consisting of: Unsubstituted or F-substituted C 1-6 alkyl, Wherein R3 is selected from C 1-6 alkyl.

4. The electrolyte additive composition according to claim 1, characterized in that: The C 4-10 The aromatic or heteroaromatic compound is selected from benzene, naphthalene, furan, thiophene, pyrrole, pyrazole, imidazole, oxazole, thiazole, pyridine, benzofuran, benzothiophene, indole, benzimidazole, benzoxazole, benzothiazole and quinoline.

5. The electrolyte additive composition according to claim 1, characterized in that: The compound represented by formula (1) is selected from any one of the following:

6. The electrolyte additive composition according to claim 1, characterized in that: The cyano-substituted C 4-10 The aromatic compound or heteroaromatic compound is any of the following:

7. The electrolyte additive composition according to claim 1, characterized in that: The compound represented by formula (1) and the cyano-substituted C 4-10 The molar ratio between the aromatic compounds or heteroaromatic compounds is in the range of 1:2 to 7:

2.

8. An electrolyte comprising an organic solvent, a lithium salt and the electrolyte additive composition according to any one of claims 1 to 7.

9. The electrolyte according to claim 8, characterized in that Based on 100 parts by weight of the total weight of the organic solvent and the lithium salt, the amount of the compound represented by formula (1) is in the range of 0.1 parts by weight to 10 parts by weight; preferably, the amount of the compound represented by formula (1) is in the range of 0.1 parts by weight to 2.0 parts by weight; more preferably, the amount of the compound represented by formula (1) is in the range of 0.2 parts by weight to 1.0 parts by weight.

10. The electrolyte according to claim 8, characterized in that Based on 100 parts by weight of the total weight of the organic solvent and the lithium salt, the cyano-substituted C 4-10 The amount of the aromatic compound or heteroaromatic compound is in the range of 0.1 parts by weight to 10 parts by weight; preferably, the cyano-substituted C 4-10 The amount of the aromatic compound or heteroaromatic compound is in the range of 0.1 parts by weight to 2.0 parts by weight; more preferably, the cyano-substituted C 4-10 The amount of the aromatic compound or heteroaromatic compound is in the range of 0.2 to 1.0 parts by weight.

11. The electrolyte according to claim 8, characterized in that The lithium salt is selected from the group consisting of LiPF6, LiBF4, LiAsF6, LiCF3SO3, LiN(SO2F)2, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, or any combination thereof.

12. The electrolyte according to claim 8, characterized in that The organic solvent is selected from the group consisting of propylene carbonate, butylene carbonate, fluoroethylene carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate or any combination thereof.

13. A lithium ion secondary battery, characterized in that: include: Positive electrode, Negative electrode, Diaphragm, and The electrolyte according to any one of claims 8 to 12. 14 . Use of the electrolyte additive composition according to claim 1 for preparing an electrolyte for a lithium ion secondary battery and / or a lithium ion secondary battery.

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