Electrolyte, secondary battery containing electrolyte and device

Abstract

The invention provides an electrolyte, the electrolyte comprises a non-aqueous organic solvent, a lithium salt and a silane-based diluent, and the silane-based diluent comprises at least one of a silane compound containing a silicon-carbon bond and a derivative thereof, a silane compound containing a silicon-oxygen bond and a derivative thereof, and a silane compound containing a silicon-nitrogen bond and a derivative thereof. The silane-based diluent promotes decomposition of lithium salt to form fluorine-containing SEI, so that formation of lithium dendrites is inhibited, and compared with traditional low-concentration electrolyte and high-concentration electrolyte, the local high-concentration electrolyte diluted by silane can prolong the cycle life of a lithium battery.

Description

Technical Field

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

[0002] Lithium batteries are widely used in smartphones, unmanned aerial vehicles and hybrid electric vehicles. However, with the advancement of technology, traditional lithium-ion batteries can no longer meet the demand. Metallic lithium has the advantages of low potential (-3.04V vs standard hydrogen electrode) and high specific capacity (3860mAh / g), and is a very excellent negative electrode material. However, the problem of lithium dendrites exists in the process of charging the metallic lithium negative electrode. Lithium dendrites will cause two problems. First, after the lithium dendrites grow to a certain extent, they will break and become dead lithium, causing the battery capacity to decay. Second, the lithium dendrites will continue to grow and eventually pierce the diaphragm, causing a short circuit between the positive and negative electrodes and causing thermal runaway.

[0003] Currently, most low-polarity solvents such as fluoroethers or alkanes are used in electrolytes. Fluorinated ether solvents are prone to cause damage to the environment, and alkane solvents are not resistant to high pressure and cannot be used in ternary systems. Therefore, it is very important to develop a diluent system that can inhibit the growth of lithium dendrites, withstand high pressure, and is green and pollution-free. Summary of the invention

[0004] In order to solve the above problems, the object of the present invention is to provide an electrolyte, which includes a non-aqueous organic solvent, a lithium salt and a silane-based diluent, wherein the silane-based diluent includes at least one of a silane compound containing a silicon-carbon bond and its derivatives, a silane compound containing a silicon-oxygen bond and its derivatives, and a silane compound containing a silicon-nitrogen bond and its derivatives, and the content of the silane-based diluent is 10 vol% to 90 vol% based on the total volume of the electrolyte.

[0005] With the electrolyte of the present invention, the silane-based diluent is used to promote film formation and modulate the local solvation effect, and forms a fluorine-containing SEI by promoting the decomposition of lithium salts, thereby inhibiting the formation of lithium dendrites. Compared with traditional low-concentration electrolytes and high-concentration electrolytes, the local high-concentration electrolyte with the addition of a silane-based diluent can extend the cycle life of the lithium battery.

[0006] In some embodiments of the present application, the silane compound containing a silicon-carbon bond and its derivatives include at least one of the compounds shown in Formula 1,

[0007]

[0008] In Formula 1, R1 is selected from fluorinated C1-C6 alkyl, phenyl, C2-C6 alkenyl, and R2, R3, and R4 are each independently selected from C1-C6 alkyl, C2-C6 alkenyl.

[0009] In some embodiments of the present application, the silane compounds containing silicon-carbon bonds and their derivatives include at least one of (heptafluoropropyl)trimethylsilane, (trifluoromethyl)trimethylsilane, triethyl(trifluoromethyl)silane, (difluoromethyl)trimethylsilane, (chlorodifluoromethyl)trimethylsilane, trimethyl(pentafluoroethyl)silane, (pentafluoroethyl)trimethylsilane, trimethyl(tridecafluorohexyl)silane, trimethylphenylsilane and tetravinylsilane.

[0010] In some embodiments of the present application, the silane compound containing a silicon-oxygen bond and its derivatives include at least one of the compounds shown in Formula 2 and Formula 3.

[0011]

[0012] In Formula 2 to Formula 3, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 Each independently selected from C1-C6 alkyl;

[0013] In some embodiments of the present application, the silane compound containing silicon-oxygen bonds and its derivatives include at least one of trimethylmethoxysilane, trimethylethoxysilane, trimethylpropoxysilane, isopropoxytrimethylsilane, tert-butoxytrimethylsilane, hexamethyldisiloxane and tetramethyldivinyldisiloxane.

[0014] In some embodiments of the present application, the silane compound containing a silicon-nitrogen bond and its derivatives include at least one of the compounds shown in Formula 4, Formula 5, and Formula 6.

[0015]

[0016] In formula 4 to formula 6, R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 , R 23 , R 24 , R 25 , R 26 , R 27 , R 28 , R 29 , R 30 , R 31 , R 32 Each is independently selected from C1-C6 alkyl.

[0017] In some embodiments of the present application, the silane compound containing a silicon-nitrogen bond and its derivatives include at least one of heptamethyldisilazane, N,N-dimethyltrimethylsilane and bis(dimethylamino)dimethylsilane.

[0018] In some embodiments of the present application, based on the total volume of the electrolyte, the content of the silane-based diluent is 20 vol% to 90 vol%.

[0019] Another object of the present invention is to provide a secondary battery, wherein the secondary battery comprises the electrolyte according to the present invention.

[0020] Another object of the present invention is to provide a device comprising the secondary battery according to the present invention.

[0021] Beneficial effects:

[0022] With the help of the electrolyte of the present invention, the silane diluent is used to promote film formation and modulate the local solvation. Since the silane-based diluent contains silicon-carbon bonds, silicon-nitrogen bonds, and silicon-oxygen bonds, they are more stable than ordinary carbon-oxygen bonds and have stronger resistance to reduction on the surface of lithium metal; at the same time, due to the presence of silicon atoms, the ability of the silane-based diluent to dissolve lithium salts decreases, which allows the silane-based diluent to be used as an inert component in the electrolyte to dilute the lithium ion solvation structure, thereby promoting the decomposition of lithium salts (such as LiFSI) and forming a fluorine-containing lithium salt-derived SEI layer, thereby inhibiting the formation of lithium dendrites and extending the cycle life of lithium batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to make the above-mentioned purpose, features and advantages of the present invention easier to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein, so the present invention is not limited to the specific embodiments disclosed below.

[0024] Figure 1 The electrochemical performance of the half-cells prepared by the electrolytes of Example 1 and Comparative Example 1 is schematically shown;

[0025] Figure 2 The electrochemical performance of half-cells prepared using the electrolytes of Example 2 and Comparative Example 2 is schematically shown. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The relevant embodiments described herein are illustrative and used to provide a basic understanding of the present application. The embodiments of the present application should not be interpreted as limiting the present application. All other embodiments obtained by those skilled in the art based on the technical scheme provided by the present application and the embodiments given belong to the scope of protection of the present application.

[0027] Unless otherwise specified, the terms used in this application have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0028] A list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A or B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, or C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0029] 1. Electrolyte

[0030] The electrolyte of the present application includes a non-aqueous organic solvent, a lithium salt and a silane-based diluent.

[0031] The silane-based diluent includes at least one of a silane compound containing a silicon-carbon bond and its derivatives, a silane compound containing a silicon-oxygen bond and its derivatives, and a silane compound containing a silicon-nitrogen bond and its derivatives. Based on the total volume of the electrolyte, the content of the silane-based diluent is 10 vol% to 90 vol%. In some embodiments of the present application, based on the total volume of the electrolyte, the content of the silane-based diluent is 10 vol%, 15 vol%, 20 vol%, 25 vol%, 30 vol%, 35 vol%, 40 vol%, 45 vol%, 50 vol%, 55 vol%, 60 vol%, 65 vol%, 70 vol%, 75 vol%, 80 vol%, 85 vol%, 90 vol%, or any range consisting of these values ​​or any range consisting of these values. Too little silane-based diluent is not enough to form a locally high-concentration lithium ion solvation structure, and the degree of modification of the interface SEI is insufficient; too high a content of silane-based diluent will affect the dissolution of lithium salts in the solvent, so that it cannot form a uniform and stable solution system.

[0032] In some embodiments of the present application, the silane compound containing a silicon-carbon bond and its derivatives include at least one of the compounds shown in Formula 1,

[0033]

[0034] In Formula 1, R1 is selected from fluorinated C1-C6 alkyl, phenyl, C2-C6 alkenyl, and R2, R3, and R4 are each independently selected from C1-C6 alkyl, C2-C6 alkenyl.

[0035] In some embodiments of the present application, the silane compound containing a silicon-carbon bond and its derivatives include at least one of the compounds shown in Formula 1,

[0036]

[0037] In Formula 1, R1 is selected from a fluorinated C1-C6 alkyl group and a C2-C6 alkenyl group, and R2, R3, and R4 are each independently selected from a C1-C6 alkyl group and a C2-C6 alkenyl group.

[0038] In some embodiments of the present application, the silane compound containing a silicon-carbon bond and its derivatives include at least one of the compounds shown in Formula 1,

[0039]

[0040] In Formula 1, R1 is selected from fluorinated C1-C3 alkyl and C2-C4 alkenyl, and R2, R3, and R4 are each independently selected from C1-C3 alkyl and C2-C4 alkenyl.

[0041] In some embodiments of the present application, the silane compounds containing silicon-carbon bonds and their derivatives include at least one of (heptafluoropropyl)trimethylsilane, (trifluoromethyl)trimethylsilane, triethyl(trifluoromethyl)silane, (difluoromethyl)trimethylsilane, (chlorodifluoromethyl)trimethylsilane, trimethyl(pentafluoroethyl)silane, (pentafluoroethyl)trimethylsilane, trimethyl(tridecafluorohexyl)silane, trimethylphenylsilane and tetravinylsilane.

[0042] In some embodiments of the present application, the silane compounds containing silicon-carbon bonds and their derivatives include at least one of (heptafluoropropyl)trimethylsilane, (trifluoromethyl)trimethylsilane, triethyl(trifluoromethyl)silane, (difluoromethyl)trimethylsilane, (chlorodifluoromethyl)trimethylsilane, trimethyl(pentafluoroethyl)silane, (pentafluoroethyl)trimethylsilane and trimethyl(tridecafluorohexyl)silane.

[0043] In some embodiments of the present application, the silane compound containing a silicon-carbon bond and its derivatives include (heptafluoropropyl)trimethylsilane.

[0044] In some embodiments of the present application, the silane compound containing a silicon-oxygen bond and its derivatives include at least one of the compounds shown in Formula 2 and Formula 3.

[0045]

[0046] In Formula 2 to Formula 3, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 Each independently selected from C1-C6 alkyl;

[0047] In some embodiments of the present application, the silane compound containing silicon-oxygen bonds and its derivatives include at least one of trimethylmethoxysilane, trimethylethoxysilane, trimethylpropoxysilane, isopropoxytrimethylsilane, tert-butoxytrimethylsilane, hexamethyldisiloxane and tetramethyldivinyldisiloxane.

[0048] In some embodiments of the present application, the silane compound containing a silicon-oxygen bond and its derivatives include at least one of trimethylethoxysilane, trimethylpropoxysilane, isopropoxytrimethylsilane and tetramethyldivinyldisiloxane.

[0049] In some embodiments of the present application, the silane compound containing silicon-oxygen bonds and its derivatives include at least one of hexamethyldisiloxane, trimethylmethoxysilane, and tert-butoxytrimethylsilane.

[0050] In some embodiments of the present application, the silane compound containing a silicon-nitrogen bond and its derivatives include at least one of the compounds shown in Formula 4, Formula 5, and Formula 6.

[0051]

[0052] In formula 4 to formula 6, R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 , R 23 , R 24 , R 25 , R 26 , R 27 , R 28 , R 29 , R 30 , R 31 , R 32 Each is independently selected from C1-C6 alkyl.

[0053] In some embodiments of the present application, the silane compound containing a silicon-nitrogen bond and its derivatives include at least one of heptamethyldisilazane, N,N-dimethyltrimethylsilane and bis(dimethylamino)dimethylsilane.

[0054] In some embodiments of the present application, the silane compound containing a silicon-nitrogen bond and its derivatives include at least one of N,N-dimethyltrimethylsilane and bis(dimethylamino)dimethylsilane.

[0055] In some embodiments of the present application, the silane compound containing a silicon-nitrogen bond and its derivatives include heptamethyldisilazane.

[0056] Silane-based diluents have high bond energy and electrochemical stability, and are a promising solvent for lithium metal-based electrolytes. Since the silicon-carbon bonds (Si-C) (347Kj / mol), silicon-nitrogen bonds (Si-N) (360Kj / mol), and silicon-oxygen bonds (Si-O) (443Kj / mol) contained in silane-based diluents are more stable than ordinary carbon-oxygen bonds (CO) (326Kj / mol), their anti-reduction ability on the surface of lithium metal is greatly enhanced. At the same time, due to the presence of silicon atoms, the ability of silane-based diluents to dissolve lithium salts decreases, which allows silane-based diluents to be used as inert components in electrolytes to dilute lithium ion solvation structures, thereby promoting the decomposition of lithium salts (such as LiFSI) and forming a fluorine-containing lithium salt-derived SEI layer.

[0057] Furthermore, when the volume fraction of the silane diluent is greater than 10% and less than 20% of the total volume of the electrolyte, the solid electrolyte interface on the electrode surface is formed by the interaction of lithium salt anions and non-aqueous organic solvent molecules, and its protective effect is better than the SEI formed by ordinary electrolytes. When the volume fraction of the silane diluent is higher than 20%, the content of non-aqueous organic solvent in the electrolyte decreases, and a large amount of lithium salt anions enter the first layer of lithium ion solvation sheath, forming a local high-concentration solvation structure, which promotes the decomposition of anions on the surface of lithium metal, thereby forming a passivation layer interface rich in lithium fluoride, and its protective effect is more significantly improved; when the volume fraction of the silane diluent is too high, the diluent will affect the dissolution of lithium salt in the solvent, making it unable to form a uniform and stable solution system.

[0058] In some embodiments of the present application, based on the total volume of the electrolyte, the content of the silane-based diluent is in the range of 20 vol% to 90 vol%. In some embodiments of the present application, based on the total volume of the electrolyte, the content of the silane-based diluent is 20 vol%, 25 vol%, 30 vol%, 35 vol%, 40 vol%, 45 vol%, 50 vol%, 55 vol%, 60 vol%, 65 vol%, 70 vol%, 75 vol%, 80 vol%, 85 vol%, 90 vol%, or any range consisting of these values ​​or any range consisting of these values.

[0059] In some embodiments of the present application, the electrolyte includes a non-aqueous organic solvent. The non-aqueous organic solvent used in the electrolyte of the present application may be any organic solvent known in the prior art that can be used as a solvent for the electrolyte.

[0060] In some embodiments of the present application, the non-aqueous organic solvent includes, but is not limited to, cyclic carbonates, chain carbonates, cyclic carboxylates, chain carboxylates, cyclic ethers, chain ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents and aromatic fluorine-containing solvents.

[0061] In some embodiments of the present application, the non-aqueous organic solvent includes at least one of carbonate, ether, phosphate, nitrile, sulfone, amide and siloxane organic reagents.

[0062] The siloxane organic reagent as a non-aqueous organic solvent contains at least 2 oxygen atoms, on this basis it can dissolve lithium salts, while the number of oxygen atoms in the siloxane compounds and their derivatives as diluents is less than or equal to 1. Therefore, the number of oxygen atoms in the siloxane compounds can be used as a basis for distinguishing whether they are non-aqueous organic solvents or silane-based diluents.

[0063] In some embodiments of the present application, the non-aqueous organic solvent used in the electrolyte of the present application is diphenyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, methyl ethyl carbonate, methyl acetate, methyl propionate, ethyl acetate, ethyl propionate, propyl acetate, propyl propionate, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, butylene carbonate, ethylene glycol dimethyl ether, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, dimethyl methylphosphonate, acetonitrile, cyclopentane sulfone, methyl ethyl sulfone, dimethylformamide, dimethylacetamide, dimethyldimethoxysilane, methyltriethoxysilane, tetraethyl orthosilicate, dimethyldiethoxysilane and methyltrimethoxysilane. At least one of silane.

[0064] In some embodiments of the present application, the non-aqueous organic solvent used in the electrolyte of the present application is ethylene carbonate, methyl ethyl carbonate, ethylene glycol dimethyl ether and a combination thereof.

[0065] In some embodiments of the present application, based on the total volume of the electrolyte, the content of the non-aqueous organic solvent is 10 vol% to 95 vol%. In some embodiments of the present application, based on the total volume of the electrolyte, the content of the non-aqueous organic solvent is 5 vol%, 10 vol%, 15 vol%, 20 vol%, 25 vol%, 30 vol%, 35 vol%, 40 vol%, 45 vol%, 50 vol%, 55 vol%, 60 vol%, 65 vol%, 70 vol%, 75 vol%, 80 vol%, 85 vol%, 90 vol%, 95 vol%, or any range consisting of these values ​​or any range consisting of these values. When the content of the non-aqueous organic solvent is too high, the solvent will replace the anion to enter the lithium ion solvation structure, resulting in the inability to form enough anion and cation aggregates, thereby affecting the composition and structure of the formed solid electrolyte interface film; when the content of the non-aqueous organic solvent is too low, there is not enough solvent to dissolve the lithium salt, resulting in the electrolyte being unable to form a uniform and stable solvent system.

[0066] In some embodiments of the present application, the electrolyte includes a lithium salt, and the lithium salt used in the electrolyte of the present application includes at least one of an inorganic lithium salt and an organic lithium salt. In some embodiments of the present application, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium tetrafluoroborate (LiBF4) and lithium trifluoromethanesulfonate (LiSO3CF3). Further preferably, the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI). In some embodiments of the present application, the molar concentration of the lithium salt in the electrolyte is 0.5mol / L to 2.5mol / L. In some embodiments of the present application, the concentration of the lithium salt in the electrolyte is 0.5mol / L, 0.8mol / L, 1.0mol / L, 1.3mol / L, 1.5mol / L, 1.8mol / L, 2.0mol / L, 2.3mol / L, 2.5mol / L or any range consisting of these values. When the concentration of the lithium salt is too high, the overall viscosity of the electrolyte increases, resulting in decreased conductivity and battery performance; when the salt concentration is too low, the electrolyte conductivity is too low, resulting in the battery cycle not being able to proceed normally.

[0067] In some embodiments of the present application, based on the total mass of the electrolyte, the content of the lithium salt is 5 wt % to 28 wt %.

[0068] In some embodiments of the present application, based on the total mass of the electrolyte, the ratio of the silane-based diluent, the non-aqueous organic solvent, and the lithium salt is (3.75-82.5): (7.5-86.3): (7-37.4). In some embodiments of the present application, based on the total mass of the electrolyte, the ratio of the silane-based diluent, the non-aqueous organic solvent, and the lithium salt is (12.5-73.3): (12.5-73.7): (12.5-28.0).

[0069] The diluent accounts for a larger proportion of the total volume of the electrolyte and is mainly used to regulate the local solvation structure around lithium ions in the electrolyte; the additive accounts for a smaller proportion of the total volume of the electrolyte and is mainly used for positive and negative electrode film formation.

[0070] In some embodiments of the present application, the electrolyte further comprises an additive, and the additive comprises at least one of a cyclic carbonate containing a carbon-carbon double bond, a silyl-containing phosphate, a silyl-containing borate, a nitrile compound, a propanesulfonic acid pyridinium salt, a fluorocarbon, and a sulfonate. In some embodiments of the present application, the additive comprises at least one of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), tris(trimethylsilane) phosphate (TMSP), tris(trimethylsilane) borate (TMSB), succinonitrile (SN), adiponitrile (ADN), glutaronitrile (GLN), hexane trinitrile (HTN), fluoroethylene carbonate (FEC), and 1,3-propane sultone (PS). In some embodiments of the present application, the additive comprises at least one of tris(trimethylsilane) phosphate (TMSP), fluoroethylene carbonate (FEC), and 1,3-propane sultone (PS).

[0071] In some embodiments of the present application, based on the total mass of the electrolyte, the mass content of the additive is 0.05%-10%. In some embodiments, based on the total mass of the electrolyte, the mass content of the additive is 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10% or any value therebetween. In some embodiments of the present application, based on the total mass of the electrolyte, the mass content of the additive is 0.1%-5%.

[0072] 2. Secondary battery

[0073] The secondary battery according to the present invention includes a lithium metal battery, a lithium ion battery, a sodium ion battery, a lithium metal polymer battery or a lithium ion polymer battery. In some embodiments of the present application, the secondary battery of the present application includes a positive electrode sheet, a negative electrode sheet, a separator and / or a solid electrolyte, an electrolyte.

[0074] The secondary battery according to the present invention can be used in the device according to the present invention, including but not limited to, laptop computers, input computers, mobile computers, electronic book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD televisions, portable cleaners, portable CD players, mini CDs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium ion capacitors, etc.

[0075] The electrolyte used in the secondary battery of the present application is any of the above-mentioned electrolytes of the present application. In addition, the electrolyte used in the secondary battery of the present application may also include other electrolytes within the scope not departing from the gist of the present application.

[0076] The materials, compositions and manufacturing methods of the negative electrode plates that can be used in the embodiments of the present application include any technology disclosed in the prior art. In some embodiments of the present application, the negative electrode plates involved in the present disclosure include a negative electrode current collector and a negative electrode material layer, the negative electrode material layer is arranged on the surface of the negative electrode current collector, and the negative electrode material layer includes a negative electrode active material. The specific types of negative electrode active materials are not subject to specific restrictions and can be selected according to needs. In some embodiments of the present application, the negative electrode active material includes at least one of silicon-based materials, carbon-based materials, tin-based materials, phosphorus-based materials, lithium metal or lithium alloys. The silicon-based material includes at least one of silicon, silicon alloys, silicon oxide compounds and silicon carbon compounds. The carbon-based material includes at least one of graphite, soft carbon, hard carbon, carbon nanotubes and graphene. The tin-based material includes at least one of tin, tin oxide and tin alloy. The phosphorus-based material includes phosphorus and / or phosphorus complexes.

[0077] In some embodiments of the present application, the negative electrode material layer further comprises a binder, and based on the total mass of the negative electrode material layer, the mass percentage of the binder is 0.3%-5%. The binder improves the bonding between the negative electrode active material particles and the bonding between the negative electrode active material and the current collector.

[0078] In some embodiments of the present application, non-limiting examples of the binder include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0079] In some embodiments of the present application, the negative electrode material layer may further include a conductive agent, and the mass percentage of the conductive agent is 0.3%-3% based on the total mass of the negative electrode material layer. The conductive agent may include any conductive material as long as it does not cause chemical changes. Non-limiting examples of conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., such as copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives) and mixtures thereof.

[0080] In some embodiments of the present application, the negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0081] In some embodiments of the present application, the negative electrode plate is lithium metal or lithium alloy.

[0082] In some embodiments of the present application, the lithium alloy includes lithium and a metal / metalloid that can be alloyed with lithium. For example, the metal / metalloid that can be alloyed with lithium is Si, Sn, Al, Ge, Pb, Bi, Sb, Si-Y alloy (wherein Y is an alkali metal, an alkaline earth metal, an element of Group 13-16, a transition metal, a rare earth element, or a combination thereof, except Si), or Sn-Y alloy (wherein Y is an alkali metal, an alkaline earth metal, an element of Group 13-16, a transition metal, a rare earth element, or a combination thereof, except Sn). Y can be Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po or a combination thereof.

[0083] The materials, compositions and manufacturing methods of the positive electrode sheets that can be used in the embodiments of the present application include any technology disclosed in the prior art.

[0084] In some embodiments of the present application, the positive electrode plate includes a current collector and a positive electrode active material layer located on the current collector. In some embodiments of the present application, the positive electrode active material includes, but is not limited to: lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese (NCM) ternary material, lithium nickel cobalt aluminum (NCA) ternary material, lithium iron phosphate (LiFePO4), lithium iron manganese phosphate (LiMn x Fe 1- x PO4) or lithium manganate (LiMn2O4).

[0085] In some embodiments of the present application, the positive electrode active material is Li[Ni 1-x-y Co x M y ]O2(M=Mn, Al, etc., such as lithium nickel cobalt manganese oxide Li[Ni 1-x-y Co x Mn y ]O2, 1-xy ≥ 0.5, lithium nickel cobalt aluminum oxide Li[Ni 1-x-y Co x Al y ]O2, 1-xy≥0.5).

[0086] In some embodiments of the present application, the positive electrode active material layer also includes a binder and optionally includes a conductive material. The binder improves the bonding between the positive electrode active material particles and also improves the bonding between the positive electrode active material and the current collector. In some embodiments of the present application, the binder includes: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (ester) styrene-butadiene rubber, epoxy resin or nylon, etc.

[0087] In some embodiments of the present application, the conductive material includes, but is not limited to: carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments of the present application, the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments of the present application, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments of the present application, the conductive polymer is a polyphenylene derivative.

[0088] The material and shape of the separator used in the embodiments of the present invention are not particularly limited, and can be any technology disclosed in the prior art. In some embodiments of the present application, the separator includes a polymer or inorganic substance formed of a material that is stable to the electrolyte of the present invention.

[0089] For example, the diaphragm may include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, a film or a composite film having a porous structure, and the material of the substrate layer includes at least one of polyethylene, polypropylene and polyethylene terephthalate. Specifically, polypropylene porous film, polyethylene porous film, polypropylene nonwoven fabric, polyethylene nonwoven fabric or polypropylene-polyethylene-polypropylene porous composite film can be selected.

[0090] A surface treatment layer is disposed on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic layer.

[0091] The inorganic layer includes inorganic particles and a binder, wherein the inorganic particles include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate. The binder includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxy, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.

[0092] The polymer layer includes a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxide, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0093] In some embodiments of the present application, the separator is a polyethylene (PE) separator coated with ceramic layers on both sides, wherein the thickness of the PE layer is in the range of 5 to 20 μm, and the coating thickness of each ceramic layer is in the range of 0 to 5 μm.

[0094] The material and shape of the solid electrolyte used in the embodiments of the present invention are not particularly limited, and can be any technology disclosed in the prior art. In some embodiments of the present application, the solid electrolyte includes but is not limited to a polymer solid electrolyte and an inorganic solid electrolyte.

[0095] In some embodiments of the present disclosure, the secondary battery involved in the present disclosure may include an outer package, which may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0096] In some embodiments of the present application, the present application further provides a device including the above-mentioned secondary battery, the device including but not limited to electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, power storage systems, etc. In order to meet the requirements of the device for high power and high energy density of the secondary battery, a battery pack or a battery module can be used.

[0097] In some embodiments of the present application, the device may be a mobile phone, a tablet computer, a laptop computer, etc. The device is usually required to be light and thin, and a secondary battery may be used as a power source.

[0098] In the following examples and comparative examples, the reagents, materials and instruments used are all commercially available unless otherwise specified.

[0099] 3. Electrochemical performance test

[0100] Coulomb efficiency test: Li / Cu batteries were used for testing. They were assembled in the order of negative electrode shell, spring, gasket, lithium sheet, diaphragm, copper sheet, and positive electrode shell. 30 to 60 microliters of electrolyte were added to each battery to wet the diaphragm, and finally the battery was packaged.

[0101] First, the battery was charged at 0.1 mA / cm2 in the 0-2 V voltage range. 2The pre-charge and discharge were performed at a current density of 1 mA / cm 2 The current density was 1 mA / cm 2 Lithium stripping was performed at a current density of 100 Å until the voltage was higher than 1 V, and the coulombic efficiency was calculated under the reverse polarity condition.

[0102] First coulomb efficiency = first cycle charging capacity / first cycle discharging capacity (current density is 1mA / cm 2 )

[0103] The 50th cycle coulombic efficiency = the 50th cycle charge capacity / the 50th cycle discharge capacity (current density is 1mA / cm 2 )

[0104] When the battery coulombic efficiency falls below 80% for the first time and fails to return to above 80% in the subsequent five cycles, the battery is considered to have failed.

[0105] Example 1

[0106] 187 mg of LiFSI was dissolved in 0.2 ml of ethylene glycol dimethyl ether, and then 0.8 ml of (heptafluoropropyl)trimethylsilane was added for dilution, and the mixture was stirred to obtain an electrolyte solution.

[0107] Example 2

[0108] 187 mg of LiFSI was dissolved in 0.2 ml of ethylene glycol dimethyl ether, and then 0.8 ml of hexamethyldisiloxane was added for dilution, and the electrolyte was obtained after stirring.

[0109] Example 3

[0110] 187 mg of LiFSI was dissolved in 0.39 ml of ethylene carbonate and 0.39 ml of methyl ethyl carbonate, and then 0.22 ml of trimethylmethoxysilane was added for dilution, and the mixture was stirred to obtain an electrolyte solution.

[0111] Example 4

[0112] 100 mg of LiFSI was dissolved in 0.05 ml of ethylene carbonate and 0.05 ml of methyl ethyl carbonate, and then 0.9 ml of tert-butoxytrimethylsilane was added for dilution, and the mixture was stirred to obtain an electrolyte solution.

[0113] Example 5

[0114] 374 mg of LiFSI was dissolved in 0.2 ml of ethylene carbonate and 0.2 ml of methyl ethyl carbonate, and then 0.6 ml of heptamethyldisilazane was added for dilution, and the electrolyte was obtained after stirring.

[0115] Comparative Example 1

[0116] 187 mg of LiFSI was dissolved in 1 ml of ethylene glycol dimethyl ether and stirred to obtain an electrolyte solution.

[0117] Comparative Example 2

[0118] 187 mg of LiFSI was dissolved in 0.2 ml of ethylene glycol dimethyl ether and stirred to obtain an electrolyte solution.

[0119] Comparative Example 3

[0120] 187 mg of LiFSI was dissolved in 0.01 ml of ethylene carbonate and 0.01 ml of methyl ethyl carbonate, and 0.98 ml of trimethylmethoxysilane was added and stirred to obtain a heterogeneous liquid in which the lithium salt was not dissolved.

[0121] Comparative Example 4

[0122] 47 mg of LiFSI was dissolved in 0.05 ml of ethylene carbonate and 0.05 ml of methyl ethyl carbonate, and then 0.9 ml of tert-butoxytrimethylsilane was added for dilution, and the mixture was stirred to obtain an electrolyte solution.

[0123] Table 1

[0124]

[0125]

[0126] The Li / Cu batteries manufactured using the electrolytes obtained from Examples 1-6 and Comparative Examples 1-4 were subjected to coulombic efficiency tests and cycle stability tests. The test results are shown in Table 2.

[0127] Table 2

[0128]

[0129]

[0130] It can be seen that Comparative Example 1 is a traditional low-concentration electrolyte (1M LiFSI) without adding a silane-based diluent, and Comparative Example 2 is a high-concentration electrolyte (lithium salt>3.33M) without adding a silane-based diluent. Compared with Comparative Examples 1 and 2, the local high-concentration electrolyte system diluted with silane groups in Examples 1-6 shows stable cycle coulomb efficiency and long life, which can effectively improve the cycle life of secondary batteries, especially Examples 1-5. Comparing Example 3 with Comparative Example 3, it is shown that too much silane diluent will lead to insufficient solubility of lithium salts and thus fail to form a homogeneous solution, affecting the normal cycle of the battery. Comparing Example 4 with Comparative Example 4, it is shown that insufficient lithium salt concentration will also affect the long cycle life of the battery.

[0131] Although some exemplary embodiments of the present application have been illustrated and described, the present application is not limited to the disclosed embodiments. On the contrary, those skilled in the art will recognize that some modifications and changes may be made to the described embodiments without departing from the spirit and scope of the present application as described in the appended claims, and these modifications and changes also fall within the scope of protection of the present invention.

Claims

1. An electrolyte, characterized in that: The electrolyte includes a non-aqueous organic solvent, a lithium salt and a silane-based diluent, wherein the silane-based diluent includes at least one of a silane compound containing a silicon-carbon bond and its derivatives, a silane compound containing a silicon-oxygen bond and its derivatives, and a silane compound containing a silicon-nitrogen bond and its derivatives, and the content of the silane-based diluent is 10 vol% to 90 vol% based on the total volume of the electrolyte.

2. The electrolyte according to claim 1, characterized in that The silane-based diluent satisfies at least one of the following conditions (i) to (iii): (i) the silane compound containing a silicon-carbon bond and its derivatives include at least one of the compounds represented by Formula 1, In Formula 1, R1 is selected from fluorinated C1-C6 alkyl, phenyl, C2-C6 alkenyl, and R2, R3, and R4 are each independently selected from C1-C6 alkyl, C2-C6 alkenyl; (ii) the silane compound containing a silicon-oxygen bond and its derivatives include at least one of the compounds represented by Formula 2 and Formula 3, In Formula 2 to Formula 3, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 Each independently selected from C1-C6 alkyl; (iii) the silane compound containing a silicon-nitrogen bond and its derivatives include at least one of the compounds represented by Formula 4, Formula 5 and Formula 6, In formula 4 to formula 6, R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 , R 23 , R 24 , R 25 , R 26 , R 27 , R 28 , R 29 , R 30 , R 31 , R 32 Each is independently selected from C1-C6 alkyl.

3. The electrolyte according to claim 2, characterized in that The silane-based diluent satisfies at least one of the following conditions (iv) to (vi): (iv) the silane compound containing a silicon-carbon bond and its derivatives include at least one of (heptafluoropropyl)trimethylsilane, (trifluoromethyl)trimethylsilane, triethyl(trifluoromethyl)silane, (difluoromethyl)trimethylsilane, (chlorodifluoromethyl)trimethylsilane, trimethyl(pentafluoroethyl)silane, trimethyl(tridecafluorohexyl)silane, trimethylphenylsilane and tetravinylsilane; (v) the silane compound containing a silicon-oxygen bond and its derivatives include at least one of trimethylmethoxysilane, trimethylethoxysilane, trimethylpropoxysilane, isopropoxytrimethylsilane, tert-butoxytrimethylsilane, hexamethyldisiloxane and tetramethyldivinyldisiloxane; (vi) The silane compound containing a silicon-nitrogen bond and its derivatives include at least one of heptamethyldisilazane, N,N-dimethyltrimethylsilylamine and bis(dimethylamino)dimethylsilane.

4. The electrolyte according to claim 1, characterized in that The content of the silane-based diluent is 20 vol % to 90 vol % based on the total volume of the electrolyte.

5. The electrolyte according to claim 1, characterized in that Based on the total mass of the electrolyte, the ratio of the silane-based diluent, the non-aqueous organic solvent and the lithium salt is (3.75-82.5): (7.5-86.3): (7-37.4).

6. The electrolyte according to claim 1, characterized in that The non-aqueous organic solvent comprises at least one of carbonate, ether, phosphate, nitrile, sulfone, amide and siloxane organic reagents; and / or The lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium tetrafluoroborate and lithium trifluoromethanesulfonate.

7. The electrolyte according to claim 6, characterized in that The non-aqueous organic solvent comprises at least one of diphenyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, methyl ethyl carbonate, methyl acetate, methyl propionate, ethyl acetate, ethyl propionate, propyl acetate, propyl propionate, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, butylene carbonate, ethylene glycol dimethyl ether, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetradiethylene glycol dimethyl ether, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, dimethyl methylphosphonate, acetonitrile, cyclopentane, methyl ethyl sulfone, dimethylformamide, dimethylacetamide, dimethyldimethoxysilane, methyltriethoxysilane, tetraethyl orthosilicate, dimethyldiethoxysilane and methyltrimethoxysilane; and / or Based on the total volume of the electrolyte, the content of the non-aqueous organic solvent is 10 vol% to 95 vol%; and / or The molar concentration of the lithium salt in the electrolyte is 0.5 mol / L to 2.5 mol / L.

8. A secondary battery, characterized in that: The secondary battery includes the electrolytic solution according to any one of claims 1 to 7.

9. The secondary battery according to claim 8, characterized in that: The secondary battery is a lithium ion battery or a lithium metal battery.

10. A device, characterized in that: The device comprises the secondary battery according to claim 8 or 9.

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