Non-aqueous electrolyte, lithium ion battery and electric equipment

Abstract

The invention belongs to the technical field of new energy materials, and particularly relates to a non-aqueous electrolyte, a lithium ion battery and electric equipment. The additive with a specific structure and functional groups is introduced into the electrolyte, and the functional effects of passivating the surfaces of the positive electrode and the negative electrode, inhibiting the dissolution of transition metal ions and removing water and inhibiting acid can be realized through the common and synergistic effects of the functional groups of the additive, so that the high-temperature / high-pressure performance of the high-specific-energy lithium battery can be effectively improved; capacity attenuation is slowed down, and gas production and impedance increase are inhibited.

Description

Technical Field

[0001] The present application belongs to the technical field of new energy materials, and specifically relates to a non-aqueous electrolyte, a lithium-ion battery and an electrical device. Background Art

[0002] As the demand for energy density in the power lithium battery market continues to rise, lithium batteries urgently need to complete innovation and upgrades at the material level. High-energy-density lithium batteries have become the current research hotspot and are also the general trend of future lithium battery development. The development of high-energy-density lithium batteries at the material level mainly includes two directions. One is to broaden the voltage range of the material, especially to increase the upper voltage limit, which can effectively improve the specific capacity and voltage platform of the positive electrode material; the other is to upgrade the positive and negative electrode materials, and improve their specific capacity by optimizing the active components, structure and morphology of the electrode materials. For example, compared with the current mainstream medium-nickel ternary positive electrode with graphite negative electrode system, high-nickel ternary / lithium-rich manganese-based positive electrode materials with silicon oxygen / silicon carbon / lithium metal negative electrode systems have the advantage of significantly improving specific energy, but some practical problems in the high-energy-density system limit its actual development, mainly including the intensified dissolution of transition metal ions in the positive electrode under high pressure / high temperature (caused by the combined action of the Jan-Taylor effect and HF produced by the hydrolysis of commercial LiPF6 electrolyte), which leads to the destruction of the positive electrode structure, the oxidation and decomposition of the electrolyte under high pressure, the deposition of transition metal ions at the negative electrode, and the significant volume change of the negative electrode, which leads to the continuous destruction and reorganization of SEI, which makes the capacity decay of the high-energy-density system under high temperature / high pressure aggravated, accompanied by serious gas production and impedance growth. Summary of the invention

[0003] Therefore, the technical problem to be solved by the present application is to overcome the defects of the high specific energy system of lithium batteries in the prior art, such as the aggravated capacity attenuation under high temperature / high pressure, accompanied by serious gas production and impedance growth, so as to provide a non-aqueous electrolyte, lithium-ion battery and electrical equipment.

[0004] In order to solve the existing problems of the above-mentioned high energy density lithium battery, the present application introduces an additive containing a specific structure and functional groups into the electrolyte design. Through the joint and synergistic effect of the functional groups of the additive, the functional effects of passivating the positive and negative electrode surfaces, inhibiting the dissolution of transition metal ions, and removing water and inhibiting acid can be achieved, thereby effectively improving the high temperature / high pressure performance of the high energy density lithium battery.

[0005] To this end, this application provides the following technical solutions:

[0006] According to one aspect of the present application, a non-aqueous electrolyte is provided, comprising a lithium salt, an organic solvent and an additive, wherein the additive comprises a compound having a structure specifically shown in the following formula (I):

[0007]

[0008] Wherein, R1-R6 are independently selected from any one or combination of hydrogen, halogen, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 alkenyl, C1-C8 alkynyl, substituted or unsubstituted aromatic group, heterocycle containing at least one hetero element of S, N, O, silane group, siloxane group, siloxane group, carbonyl group, and at least one of R1-R5 includes alkynyl group.

[0009] In some optional embodiments, R1-R6 are independently selected from any one or combination of hydrogen, C1-C8 alkyl, C1-C8 alkynyl, C6-C9 substituted or unsubstituted aromatic, C3-C7 S-containing heterocycle, C1-C8 silyl, C1-C8 siloxane, C1-C8 siloxyamine, and C1-C8 carbonyl; wherein the substituents in the substituted aromatic group include halogen, any one or combination of C1-C4 alkyl.

[0010] In some optional embodiments, the additive includes a compound having any of the following structures:

[0011]

[0012]

[0013] In some optional embodiments, based on the total mass of the non-aqueous electrolyte, the content of the compound represented by formula (I) is 0.1%-2%.

[0014] In some optional embodiments, the molar concentration of the lithium salt is 0.7-1.5 mol / L;

[0015] And / or, the lithium salt includes at least one of LiPF6, LiClO4, LiBF4, LiAsF6, LiBOB, LiODFB, LiFSI, LiTFSI, and LiTDI.

[0016] In some optional embodiments, the non-aqueous electrolyte further includes other functional additives, and the other functional additives include positive and negative electrode film-forming additives;

[0017] And / or, based on the total mass of the non-aqueous electrolyte, the addition amount of the other functional additives is 0.5%-10%.

[0018] In some optional embodiments, the positive and negative electrode film-forming additives include at least one of an additive containing S or a double bond or F or B or P or CN or a lithium salt additive.

[0019] In some optional embodiments, the organic solvent includes at least one of a carbonate solvent or a carboxylate solvent.

[0020] According to another aspect of the present application, a lithium-ion battery is provided, comprising the above-mentioned non-aqueous electrolyte.

[0021] According to another aspect of the present application, there is provided an electrical device comprising the above-mentioned lithium-ion battery.

[0022] The technical solution of this application has the following advantages:

[0023] The non-aqueous electrolyte provided in the present application can achieve the functional effects of passivating the positive and negative electrode surfaces, inhibiting the dissolution of transition metal ions, and removing water and inhibiting acid by introducing an additive with a specific structure and functional groups into the electrolyte. This can effectively improve the high temperature / high pressure performance of high specific energy lithium batteries, slow down capacity decay, and inhibit gas production and impedance growth through the joint and synergistic effects of the functional groups of the additive. Specifically, the additive contains unsaturated acetylenic groups, which have the functions of forming films at both positive and negative electrodes and removing HF. The electron-withdrawing acetylenic groups are conjugated with benzene rings to reduce the electron cloud density on the benzene rings, thereby reducing the risk of the benzene rings losing electrons under high pressure and polymerizing to generate high-impedance polymers, thereby improving the high-voltage stability of the interface film. At the same time, the strong electron-withdrawing phenylacetylenic groups and silicon oxygen connected to N make it easier for the N central atom to obtain electron reduction at the negative electrode to form a Li3N-rich SEI, thereby improving the ion-conducting ability of the SEI. The N containing lone pairs of electrons can not only complex transition metal ions, but also provide electrons to adjacent silicon oxygen, thereby making it easier for the oxygen in silicon oxygen to combine with water or hydrogen protons or ions in HF, thereby further enhancing the water removal and acid suppression ability of silicon oxygen. The flexible Si-O and rigid The polar benzene ring makes the film have the characteristics of both rigidity and flexibility. The excellent mechanical stability can effectively match the volume expansion / contraction of the electrode material during the charge and discharge process, and alleviate the interface film damage caused by volume change. At the same time, the polar N / O can promote the rapid transmission of lithium ions in the interface film, so that the film has excellent ion conductivity. Under the synergistic effect of the above various functional groups, the additive can preferentially decompose on the surface of the positive and negative electrodes to form SEI and CEI interface films with excellent ion conductivity and high stability, which can effectively passivate the surface of the positive and negative electrodes, and at the same time have the functions of enhanced water removal, acid suppression and inhibition of transition metal ion dissolution. Under the comprehensive effect, the lithium battery using the optimized electrolyte containing the additive shows significantly improved high temperature / high pressure performance.

[0024] The non-aqueous electrolyte provided in the present application, by further limiting the structure of the compound represented by formula (I), increases the content of polar Si, O, and N groups or introduces benzene rings or heterocyclic groups while retaining the characteristic functional groups, thereby further improving the film-forming flexibility and firmness, ion conductivity, and film-forming properties.

[0025] The non-aqueous electrolyte provided in the present application, by limiting the content of the compound represented by formula (I), can ensure that the compound represented by formula (I) can fully participate in the formation of stable SEI and CEI interface films, while not forming a film that is too thick or too thin, thereby limiting the lithium ion transfer kinetics or insufficient film formation.

[0026] The non-aqueous electrolyte provided in the present application limits the lithium salt concentration, thereby ensuring that the electrolyte has appropriate ionic conductivity and lithium ion transference number.

[0027] The non-aqueous electrolyte provided in the present application limits the types and amounts of other additives, which has the effect of further optimizing the film structure and composition of the positive and negative electrodes and improving the film stability and uniformity.

[0028] The non-aqueous electrolyte provided in the present application limits the type of organic solvent, which can ensure that the solvent used has a suitable viscosity and dielectric constant, so that the lithium salt can be fully dissociated to ensure the high lithium ion conductivity of the electrolyte.

[0029] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. DETAILED DESCRIPTION

[0030] The following examples are provided for a better understanding of the present application, but are not limited to the best implementation mode described, and do not limit the content and protection scope of the present application. Any product identical or similar to the present application obtained by anyone under the inspiration of the present application or by combining the features of the present application with other prior arts shall fall within the protection scope of the present application.

[0031] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0032] In order to overcome the defects of the high specific energy system of lithium batteries in the prior art, such as the aggravated capacity attenuation under high temperature / high pressure, accompanied by serious gas production and impedance growth, the present application provides the following technical solutions:

[0033] According to one aspect of the present application, a non-aqueous electrolyte is provided, comprising a lithium salt, an organic solvent and an additive, wherein the additive comprises a compound having a structure specifically shown in the following formula (I):

[0034]

[0035] Wherein, R1-R6 are independently selected from any one or combination of hydrogen, halogen, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 alkenyl, C1-C8 alkynyl, substituted or unsubstituted aromatic group, heterocycle containing at least one hetero element of S, N, O, silane group, siloxane group, siloxane group, carbonyl group, and at least one of R1-R5 includes alkynyl group. As an example, the halogen includes at least one of F, Cl, and Br; the C1-C8 alkyl includes at least one of methyl, ethyl, trimethylalkyl, and triethylalkyl; the C1-C8 alkenyl includes at least one of vinyl, propenyl, and trimethylalkenyl; the C1-C8 alkynyl includes at least one of ethynyl, trimethylethynyl, and trimethylsilylethynyl; the substituted or unsubstituted aromatic group includes at least one of phenyl and halogen-substituted phenyl (fluorophenyl); the heterocycle containing at least one heteroelement among S, N, and O includes at least one of thienyl, furyl, and pyrrolyl; the silyl group may be a trimethylsilyl group; the silazane group may be a trimethylsiloxyamine group, the siloxane group may be a trimethylsiloxyalkyl group, the carbonyl group may be a trimethylethylcarbonyl group, and the like.

[0036] The present application introduces an additive with a specific structure and functional group into the electrolyte. Through the common and synergistic effects between the functional groups of the additive, the functional effects of passivating the positive and negative electrode surfaces, inhibiting the dissolution of transition metal ions, and removing water and inhibiting acid can be achieved, thereby effectively improving the high temperature / high pressure performance of high specific energy lithium batteries, slowing down capacity decay, and inhibiting gas production and impedance growth. Specifically, the additive contains an unsaturated acetylenic group, which has the functions of forming films at both positive and negative electrodes and removing HF. The electron-withdrawing acetylenic group is conjugated with the benzene ring to reduce the electron cloud density on the benzene ring, reducing the risk of high-impedance polymers generated by the high-voltage loss of electrons of the benzene ring, and improving the high-voltage stability of the interface film; at the same time, the strong electron-withdrawing phenylacetylenic group and silicon oxygen connected to N make it easier for the N central atom to obtain electron reduction at the negative electrode, forming a Li3N-rich SEI, and improving the ion-conducting ability of the SEI; N containing lone pairs of electrons can not only complex transition metal ions, but also provide electrons to adjacent silicon oxygen, making it easier for the oxygen in silicon oxygen to combine with hydrogen protons or ions in water or HF, further enhancing the ability of silicon oxygen to remove water and inhibit acid; flexible Si-O and rigid The polar benzene ring makes the film have the characteristics of both rigidity and flexibility. The excellent mechanical stability can effectively match the volume expansion / contraction of the electrode material during the charge and discharge process, and alleviate the interface film damage caused by volume change. At the same time, the polar N / O can promote the rapid transmission of lithium ions in the interface film, so that the film has excellent ion conductivity. Under the synergistic effect of the above various functional groups, the additive can preferentially decompose on the surface of the positive and negative electrodes to form SEI and CEI interface films with excellent ion conductivity and high stability, which can effectively passivate the surface of the positive and negative electrodes, and at the same time have the functions of enhanced water removal, acid suppression and inhibition of transition metal ion dissolution. Under the comprehensive effect, the lithium battery using the optimized electrolyte containing the additive shows significantly improved high temperature / high pressure performance.

[0037] In some optional embodiments, R1-R6 are independently selected from any one or combination of hydrogen, C1-C8 alkyl, C1-C8 alkynyl, C6-C9 substituted or unsubstituted aromatic, C3-C7 S-containing heterocycle, C1-C8 silyl, C1-C8 siloxane, C1-C8 siloxyamine, and C1-C8 carbonyl; wherein the substituents in the substituted aromatic group include halogen, any one or combination of C1-C4 alkyl.

[0038] In some optional embodiments, the additive includes a compound having any of the following structures:

[0039]

[0040]

[0041] The non-aqueous electrolyte provided in the present application, by limiting the structure of the compound represented by formula (I), increases the content of polar Si, O, and N groups or introduces benzene rings or heterocyclic groups while retaining the characteristic functional groups, thereby further improving the film-forming flexibility and firmness, ion conductivity, and film-forming properties.

[0042] In some optional embodiments, the content of the compound shown in formula (I) is 0.1%-2% based on the total mass of the non-aqueous electrolyte. As an example, the content of the compound shown in formula (I) is 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1.0%, 1.2%, 1.4%, 1.5%, 1.7%, 1.8%, 2.0%, or within the range of any of the above values. The present application limits the content of the compound shown in formula (I) to ensure that the compound can fully participate in the formation of a stable SEI and CEI interface film, and the film will not be too thick or too thin, which will limit the lithium ion transfer kinetics or insufficient film formation.

[0043] In some optional embodiments, the molar concentration of the lithium salt is 0.7-1.5 mol / L; as an example, the molar concentration of the lithium salt is 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, or within the range of any of the above values. By limiting the concentration of the lithium salt, the present application can ensure that the electrolyte has appropriate ionic conductivity and lithium ion migration number.

[0044] And / or, the lithium salt includes at least one of LiPF6, LiClO4, LiBF4, LiAsF6, LiBOB, LiODFB, LiFSI, LiTFSI, and LiTDI.

[0045] In some optional embodiments, the non-aqueous electrolyte further includes other functional additives, and the other functional additives include positive and negative electrode film-forming additives;

[0046] And / or, based on the total mass of the non-aqueous electrolyte, the amount of the other functional additives added is 0.5%-10%. As an example, the amount of the other functional additives added is 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or within the range of any of the above values.

[0047] The non-aqueous electrolyte provided in the present application limits the types and amounts of other additives, and the conventional functional additives involved have the effect of further optimizing the film structure and composition of the positive and negative electrodes and improving the film stability and uniformity.

[0048] In some optional embodiments, the positive and negative electrode film-forming additives include at least one of additives containing S or double bonds or F or B or P or CN or lithium salt additives.

[0049] In the embodiments of the present application, the specific type of the above-mentioned S-containing additive is not particularly limited. As an example, the S-containing additive includes but is not limited to at least one of 1,3-propane sultone (PS), propenyl-1,3-sultone (PST), dithiodisulfate (DTD), and methylene disulfonate (MMDS).

[0050] In the embodiments of the present application, the specific type of the above-mentioned double bond-containing additive is not particularly limited. As an example, the double bond-containing additive includes but is not limited to at least one of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and triallyl phosphate (TAP).

[0051] In the embodiments of the present application, the specific type of the above-mentioned F-containing additive is not particularly limited. As an example, the F-containing additive includes but is not limited to at least one of fluoroethylene carbonate (FEC) and tris(2,2,2-trifluoroethyl)phosphite (TTFP).

[0052] In the embodiments of the present application, the specific type of the above-mentioned B-containing additive is not particularly limited. As an example, the B-containing additive includes but is not limited to at least one of lithium dioxalatoborate (LiBOB), lithium difluorooxalatoborate (LiODFB), tris(trimethylsilyl)borate (TMSB), and 4-fluorophenylboronic acid pinacol ester.

[0053] In the embodiments of the present application, the specific type of the above-mentioned P-containing additive is not particularly limited. As an example, the P-containing additive includes but is not limited to at least one of tris(trimethylsilyl)phosphate (TMSP), tris(trimethylsilyl)phosphite (TMSPi), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalate)phosphate (LiODFP), tris(2,2,2-trifluoroethyl)phosphate (TFEP), and tris(2,2,2-trifluoroethyl)phosphite (TTFP).

[0054] In the embodiments of the present application, the specific type of the above-mentioned CN-containing ester additive is not particularly limited. As an example, the CN-containing additive includes but is not limited to at least one of hexane trinitrile (HTCN), succinonitrile (SN), adiponitrile (ADN), 1,2-bis(cyanoethoxy)ethane (DENE), and tricyanoethoxypropane (TCP).

[0055] In the embodiments of the present application, the specific types of the above-mentioned lithium salt additives are not particularly limited. As an example, the lithium salt additives include but are not limited to at least one of lithium bis(oxalatoborate) (LiBOB), lithium difluorobis(oxalatoborate) (LiODFB), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatophosphate (LiODFP), lithium bis(sulfonyl)imide (LiFSI), and lithium nitrate (LiNO3).

[0056] In some optional embodiments, the organic solvent includes at least one of a carbonate solvent or a carboxylate solvent. As an example, the carbonate solvent includes but is not limited to at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and various fluorinated cyclic and linear carbonates; the carboxylate solvent includes but is not limited to at least one of methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, and various fluorinated cyclic and linear carboxylates.

[0057] According to another aspect of the present application, a lithium ion battery is provided, comprising the above-mentioned non-aqueous electrolyte. The lithium ion battery exhibits significantly improved high temperature / high pressure performance due to the use of the above-mentioned non-aqueous electrolyte.

[0058] In the present application, the lithium-ion battery includes, in addition to the above-mentioned non-aqueous electrolyte, a positive electrode sheet, a negative electrode sheet and a separator, etc. These components and preparation methods are conventional in the field and are not specifically limited here.

[0059] According to another aspect of the present application, there is provided an electric device, comprising the above-mentioned lithium-ion battery. The advantages of the electric device and the above-mentioned lithium-ion battery over the prior art are the same, which will not be described in detail here.

[0060] In the present application, the lithium-ion battery can be used as a power source for the electrical equipment, or as an energy storage unit for the electrical equipment. The electrical equipment can be, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0061] The present application is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present application in any way.

[0062] In the following examples and comparative examples, "%" represents the mass percentage.

[0063] Example 1

[0064] The present embodiment provides a non-aqueous electrolyte, which is specifically composed, by mass percentage, of 0.1% of the compound represented by formula (I-1), 2% of DTD, 1% of PS, 1 mol / L of LiPF6, and an organic solvent composed of ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a volume ratio of 30:50:20.

[0065] Example 2

[0066] This embodiment provides a non-aqueous electrolyte, which is different from the embodiment 1 only in that it includes 1% of the compound represented by formula (I-1).

[0067] Example 3

[0068] This embodiment provides a non-aqueous electrolyte, which is different from the embodiment 1 only in that it includes 2% of the compound represented by formula (I-1).

[0069] Example 4

[0070] This embodiment provides a non-aqueous electrolyte, which is different from the embodiment 1 only in that it includes 0.05% of the compound represented by formula (I-1).

[0071] Example 5

[0072] This embodiment provides a non-aqueous electrolyte, which is different from the embodiment 1 only in that it includes 2.2% of the compound represented by formula (I-1).

[0073] Example 6

[0074] This embodiment provides a non-aqueous electrolyte, which is different from the embodiment 2 only in that it includes 1% of the compound represented by formula (I-2).

[0075] Example 7

[0076] This embodiment provides a non-aqueous electrolyte, which is different from the embodiment 2 only in that it includes 1% of the compound represented by formula (I-3).

[0077] Example 8

[0078] This embodiment provides a non-aqueous electrolyte, which is different from the embodiment 2 only in that it includes 1% of the compound represented by formula (I-4).

[0079] Example 9

[0080] This embodiment provides a non-aqueous electrolyte, which is different from Embodiment 2 only in that it includes 1% of the compound represented by formula (I-5).

[0081] Example 10

[0082] This embodiment provides a non-aqueous electrolyte, which is different from Embodiment 2 only in that it includes 1% of the compound represented by formula (I-6).

[0083] Embodiment 11

[0084] This embodiment provides a non-aqueous electrolyte, which is different from Embodiment 2 only in that it includes 0.5% of the compound represented by Formula (I-1) and 0.5% of the compound represented by Formula (I-3).

[0085] Example 12

[0086] This embodiment provides a non-aqueous electrolyte, which is different from Embodiment 2 only in that it includes 0.5% of the compound represented by Formula (I-1) and 0.5% of the compound represented by Formula (I-5).

[0087] Embodiment 13

[0088] This embodiment provides a non-aqueous electrolyte, which is different from Embodiment 2 only in that the lithium salt concentration is 1.5 mol / L.

[0089] Embodiment 14

[0090] This embodiment provides a non-aqueous electrolyte, which is different from Embodiment 2 only in that the lithium salt concentration is 0.7 mol / L.

[0091] Embodiment 15

[0092] This embodiment provides a non-aqueous electrolyte, which is different from the embodiment 2 only in that the organic solvent is composed of ethylene carbonate (EC): ethyl methyl carbonate (EMC): ethyl propionate (EP) in a volume ratio of 30:50:20.

[0093] Example 16

[0094] This embodiment provides a non-aqueous electrolyte, which is different from the embodiment 2 only in that it does not contain DTD and PS, and the composition of other additives is 2% VC and 1% FEC.

[0095] Comparative Example 1

[0096] This comparative example provides a non-aqueous electrolyte, which differs from Example 1 only in that it does not contain the compound represented by formula (I).

[0097] Comparative Example 2

[0098] This comparative example provides a non-aqueous electrolyte, which is different from Example 1 only in that the compound represented by formula (I-1) does not contain an alkynyl group, and the alkynyl group is replaced by H.

[0099] Comparative Example 3

[0100] This comparative example provides a non-aqueous electrolyte, which differs from Example 1 only in that an equal amount of phenylacetylene is used to replace the compound represented by formula (I-1).

[0101] Test Case

[0102] The non-aqueous electrolytes provided in the embodiments and comparative examples were prepared into batteries, and various performance tests were performed. The battery assembly steps are as follows:

[0103] 1) Preparation of positive electrode

[0104] The positive electrode active materials (LiNi 0.8 Co 0.1 Mn 0.1 O2), conductive agent carbon black and binder polyvinylidene fluoride (PVDF) are dispersed in solvent N-methyl-2-pyrrolidone (NMP), stirred under vacuum to obtain positive electrode slurry (solid content in positive electrode slurry is 56%), and the positive electrode slurry is evenly coated on both sides of the current collector aluminum foil, dried in an oven at 120°C for 8 hours, cold pressed, and then trimmed, cut and stripped to make positive electrode sheets (double-sided surface density is 400g / m 2 ).

[0105] 2) Preparation of negative electrode sheet

[0106] The negative electrode active material graphite, the conductive agent carbon black, the binder styrene butadiene rubber and the thickener sodium carboxymethyl cellulose (CMC) were mixed in a mass ratio of 95:1.5:1.5:3, dispersed in deionized water, and the negative electrode slurry (solid content in the negative electrode slurry was 55%) was obtained under vacuum stirring. The negative electrode slurry was evenly coated on both sides of the current collector copper foil, dried, rolled and vacuum dried, and then cold pressed, trimmed, cut and stripped to make a negative electrode sheet (double-sided surface density of 160g / m 2 ).

[0107] 3) Preparation of electrolyte

[0108] In a glove box with qualified water and oxygen content, the organic solvent of the electrolyte is first mixed evenly, and then the relevant additives and lithium salt are quantitatively added in sequence according to the electrolyte formula in each embodiment and comparative example, and stirred evenly.

[0109] 4) Isolation film

[0110] The diaphragm is a PE-coated ceramic diaphragm purchased from Xingyuan Materials with a thickness of 20 μm.

[0111] 5) Lithium-ion battery preparation

[0112] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is in the middle of the positive and negative electrode sheets to isolate the positive and negative electrodes, and the bare cell is wound, and the tabs are welded. The bare cell is placed in the outer package, and the prepared electrolyte is injected into the dried cell (design capacity 3.5Ah). After packaging, it is placed at 25℃ / 60℃ for 24h / 6h to allow the electrolyte to fully penetrate. Then, a small rate (0.05C / 0.2C) charge formation is performed at 45℃, and after 3 cycles of 0.33C charge and discharge, the cell is tested for various performances.

[0113] Perform performance testing as follows:

[0114] (1) High temperature cycle: At 45°C, the battery was cycled and charged to 4.25V at 1C constant current, then charged at constant voltage until the current reached 0.05C. After standing for half an hour, it was discharged at 1C constant current to obtain the initial capacity of the first cycle of the battery and recorded as C1. Thereafter, the first cycle of charging and discharging was repeated in the CCCV / DC mode. The capacity after the 400th cycle of discharge was recorded as C400. The capacity retention rate after 400 cycles of high temperature cycling (%) = C400 / C1×100%. Before and after the high temperature cycling of the battery cell, the DC internal resistance DCR value of the battery cell at 50% SOC was tested and recorded by the following current pulse method.

[0115] (2) DCR test: At 25°C, charge the cell before or after high temperature cycling at a constant current of 0.5C to 4.25V, charge at a constant voltage to a current of 0.05C, leave it for 1h, then discharge it at 0.5C for 1h (50% SOC), leave it for another 1h, and record the voltage V1 at the end; then discharge it at 2C for 10s, and record the voltage V2 at the end. The DCR of the cell before or after cycling = (V1-V2) / (I 1C -I 0.1C ), the unit is mΩ, and the DCR growth rate after cycling is (DCR 循环后 -DCR 循环前 ) / DCR 循环前 ×100%.

[0116] (3) Cyclic gas production test: At 25°C, the battery volume is tested by the drainage method before or after high-temperature cycling. The specific operation is as follows: Place a container filled with deionized water on an electronic scale, use a fixing clip to fix the pole ear on the upper end of the soft-pack battery, immerse the soft-pack battery completely in the liquid, and record the weight change displayed on the electronic scale. The volume of the soft-pack battery can be calculated by measuring the change in the volume of deionized water after the soft-pack battery is immersed in deionized water. The specific calculation formula is: V = (m1-m2) / ρ, where m1 is the weight of the soft-pack battery after it is completely immersed in deionized water, m2 is the weight of the soft-pack battery when it is not immersed in deionized water, and ρ is the density of deionized water (1g / L). The volume V before the cycle was measured respectively. 循环前 and the volume after the cycle V 循环后 , the cycle gas production is calculated by the following formula: (V 循环后 -V 循环前 ) / V 循环前 ×100%.

[0117] (4) High-temperature storage: The divided cells are charged to 100% SOC at 0.33C, and their capacity is recorded as C0. The fully charged batteries are then stored in a 60°C oven for 7 days. The cell capacity after storage is recorded as C1. The capacity retention rate (%) after 7 days of storage at 60°C = (C1-C0) / C0×100%.

[0118] The specific test results are shown in the table below:

[0119] Table 1

[0120]

[0121] It can be seen from the data in the above table that the embodiments can achieve both high-temperature cycle and high-temperature storage performance compared to the comparative examples, indicating that the compound additive with the structure shown in formula (I) can effectively improve the high-temperature cycle and high-temperature storage performance of lithium-ion batteries and inhibit the growth of cycle DCR and cycle gas production, and its mass proportion is preferably 0.1-2%.

[0122] Compared with Example 1, the comprehensive performance of Comparative Examples 2 and 3 is worse, which is attributed to the fact that when the selected additive structure contains only siloxane amine groups but no alkynyl groups, its reaction activity will be reduced, the film formation will not be sufficiently dense, and the film formation stability will deteriorate; when the selected additive structure contains only alkynyl groups but no siloxane amine groups, an interface film dominated by organic matter will be formed, resulting in a large film formation impedance and poor thermal stability; that is, only when the specified additive structure contains both alkynyl and siloxane functional groups, the synergistic effect of the two can form a dense, high ionic conductivity stable interface film, thereby improving the high temperature stability of the lithium battery.

[0123] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A non-aqueous electrolyte, characterized in that: It includes a lithium salt, an organic solvent and an additive, wherein the additive includes a compound having a structure shown in the following formula (I): Wherein, R1-R6 are independently selected from any one or combination of hydrogen, halogen, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 alkenyl, C1-C8 alkynyl, substituted or unsubstituted aromatic group, heterocycle containing at least one hetero element of S, N, O, silane group, siloxane group, siloxane group, carbonyl group, and at least one of R1-R5 includes alkynyl group.

2. The non-aqueous electrolyte according to claim 1, characterized in that R1-R6 are independently selected from any one or combination of hydrogen, C1-C8 alkyl, C1-C8 alkynyl, C6-C9 substituted or unsubstituted aromatic, C3-C7 S-containing heterocycle, C1-C8 silyl, C1-C8 siloxane, C1-C8 siloxyamine, C1-C8 carbonyl; wherein the substituents in the substituted aromatic group include halogen, any one or combination of C1-C4 alkyl.

3. The non-aqueous electrolyte according to claim 2, characterized in that The additive includes a compound having any of the following structures:

4. The non-aqueous electrolyte according to any one of claims 1 to 3, characterized in that: Based on the total mass of the non-aqueous electrolyte, the content of the compound represented by formula (I) is 0.1%-2%.

5. The non-aqueous electrolyte according to any one of claims 1 to 3, characterized in that: The molar concentration of the lithium salt is 0.7-1.5 mol / L; And / or, the lithium salt includes at least one of LiPF6, LiClO4, LiBF4, LiAsF6, LiBOB, LiODFB, LiFSI, LiTFSI, and LiTDI.

6. The non-aqueous electrolyte according to any one of claims 1 to 3, characterized in that The non-aqueous electrolyte also includes other functional additives, and the other functional additives include positive and negative electrode film-forming additives; And / or, based on the total mass of the non-aqueous electrolyte, the addition amount of the other functional additives is 0.5%-10%.

7. The non-aqueous electrolyte according to claim 6, characterized in that The positive and negative electrode film-forming additives include at least one of additives containing S or double bonds or F or B or P or CN or lithium salt additives.

8. The non-aqueous electrolyte according to any one of claims 1 to 3, characterized in that: The organic solvent includes at least one of a carbonate solvent or a carboxylate solvent.

9. A lithium ion battery, characterized in that: The non-aqueous electrolyte comprises the non-aqueous electrolyte according to any one of claims 1 to 8.

10. An electrical device, characterized in that: Includes the lithium ion battery as claimed in claim 9.

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