Secondary battery and apparatus

Abstract

A secondary battery and an apparatus. The secondary battery comprises a positive electrode sheet, a negative electrode sheet and an electrolyte, wherein the electrolyte comprises a silane compound containing at least one carbon-carbon double bond and a nitrogen-containing compound, the negative electrode sheet comprises a negative electrode active material layer and a solid electrolyte interfacial film located on a surface of the negative electrode active material layer, and the solid electrolyte interfacial film comprises lithium nitride and a substance containing a silicon-carbon bond; and, an X-ray photoelectron spectrometer is used for testing, the peak area of the nitrogen element in the lithium nitride is X, and the peak area of the silicon element in the substance containing a silicon-carbon bond is Y, where 1<X / Y<6.

Description

Secondary batteries and devices

[0001] This application claims priority to Chinese patent application No. 202310718601.5, filed on June 16, 2023, with the invention name “Secondary Battery and Device”. The entire contents of the above Chinese patent application are incorporated into this application by reference. Technical Field

[0002] The present application relates to the field of energy storage technology, and in particular, to a secondary battery and a device. Background Art

[0003] Lithium-ion batteries, with their numerous advantages, have rapidly taken over the 3C fields such as mobile phones and laptops, and have even become a key component of various electric vehicles. However, due to the limitations of the theoretical specific capacity of positive and negative electrode materials, the energy density of existing commercial lithium-ion batteries is difficult to exceed 300Wh kg -1 , which limits its application in pure electric vehicles, aerospace, and 5G. Therefore, it is urgent to develop the next generation of high-energy-density battery systems and high-capacity electrode materials to meet the development needs of future society. The theoretical specific capacity of silicon is as high as 4200mAh g -1 (Li 4.4 Si), which is more than 10 times that of graphite, and silicon has a moderate electrode potential (~0.3V vs Li / Li + ) and extremely abundant reserves in the Earth's crust, it is considered one of the most promising anode materials. However, during cycling, silicon undergoes significant volume changes, which accelerates mechanical fracture and loss of electrical contact in the silicon electrode, forming "dead silicon." Furthermore, the electrolyte commonly used in industry forms a loose and porous negative electrode interface passivation film (SEI) on the silicon surface, which is unable to prevent the electrolyte's continued decomposition. These factors can lead to low coulombic efficiency, rapid capacity decay, and a short cycle life.

[0004] Summary of the Invention

[0005] In order to solve the above problems, the purpose of this application is to provide a secondary battery, which improves the cycle performance, kinetic performance and storage performance of the secondary battery by controlling the content of lithium nitride and substances containing silicon-carbon bonds in the solid electrolyte interface film (SEI film) formed on the surface of the negative electrode active material layer, and can have high safety performance, cycle performance and rate performance even at high temperatures.

[0006] The first aspect of the present application provides a secondary battery, which includes a positive electrode plate, a negative electrode plate and an electrolyte, wherein the electrolyte of the secondary battery includes a silane compound containing at least one carbon-carbon double bond and a nitrogen-containing compound; the negative electrode plate includes a negative electrode active material layer and a solid electrolyte interface film located on the surface of the negative electrode active material layer, the solid electrolyte interface film includes lithium nitride and a substance containing a silicon-carbon bond, and an X-ray photoelectron spectrometer is used for testing. The peak area of ​​the nitrogen element in the lithium nitride at the position of 398.7eV is X, and the peak area of ​​the silicon element in the substance containing a silicon-carbon bond at the position of 100.5eV is Y, wherein 1 <X / Y<6。

[0007] A second aspect of the present application provides a device, comprising the secondary battery according to the first aspect.

[0008] The beneficial effects of this application are:

[0009] The secondary battery of the present application, by controlling the content of lithium nitride and the substance containing silicon-carbon bond in the solid electrolyte interface film (SEI film) formed on the surface of the negative electrode active material layer, the interface film is more dense and stable, which can extend the cycle life and high temperature stability of the battery. This is mainly because the lithium nitride and the substance containing silicon-carbon bond in SEI have a good synergistic effect, which can effectively suppress the negative effects such as low coulombic efficiency and fast consumption of electrolyte caused by the continuous occurrence of side reactions due to contact between the electrolyte and the negative electrode material, and continuously repair the interface film broken during the cycle, and ultimately improve the cycle performance of the battery. In addition, the SEI film in the secondary battery of the present application can accelerate the transmission and movement of lithium ions at the battery negative electrode interface, thereby ensuring the kinetic performance of the battery, and therefore can significantly improve the initial impedance and rate performance of the silicon-based negative electrode battery system. At the same time, the reduction resistance of the electrolyte at high voltage can also be increased, thereby reducing the decomposition of the electrolyte on the negative electrode side, and ultimately extending the battery life.

[0010] BRIEF DESCRIPTION OF THE DRAWINGS

[0011] To make the above-mentioned objects, features and advantages of the present application easier to understand, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. In the following description, many specific details are set forth to fully understand the present application, but the present application can also be implemented in other ways different from those described herein, and therefore the present application is not limited to the specific embodiments disclosed below.

[0012] Figure 1 schematically shows the XPS spectra of the negative electrode SEI film from Example 2, with the left image showing N1s and the right image showing Si2p. The peak at 398.7 eV in N1s, with an area of ​​3831.8, is attributable to lithium nitride (Li3N). The peak at 100.5 eV in Si2p, with an area of ​​2197.1, is attributable to compounds containing silicon-carbon bonds. The atomic percentages of nitrogen and silicon in the interfacial film are calculated as the ratio of their peak areas: 3913.8 / 2197.1 = 1.74.

[0013] FIG2 schematically shows the XPS spectrum of the SEI film at the negative electrode interface of Example 6.

[0014] FIG3 schematically shows the XPS spectrum of the SEI film at the negative electrode interface of Example 12. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions 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 are 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 solutions and embodiments provided in the present application fall within the scope of protection of the present application.

[0016] Unless otherwise specified, the terms used in this application have the commonly understood meanings commonly 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).

[0017] 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 comprise a single component or multiple components. Item B may comprise a single component or multiple components. Item C may comprise a single component or multiple components.

[0018] Primary and secondary batteries

[0019] The secondary battery of the present application includes a positive electrode sheet, a negative electrode sheet, and an electrolyte. Among them, the electrolyte includes a silane compound containing at least one carbon-carbon double bond and a nitrogen-containing compound. The negative electrode sheet includes a negative electrode active material layer and a solid electrolyte interface film (SEI) on the surface of the negative electrode active material layer. When tested by an X-ray photoelectron spectrometer (XPS), the peak area of nitrogen element in lithium nitride at the position of 398.7 eV is X, and the peak area of silicon element in the substance containing a silicon-carbon bond at the position of 100.5 eV is Y, where 1 < X / Y < 6.

[0020] In some embodiments of the present application, the substance containing a silicon-carbon bond refers to a silicon-containing polymer generated in the interface film after the silane compound containing at least one carbon-carbon double bond is reduced on the negative electrode side.

[0021] In some embodiments of the present application, X / Y is 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, 6 or any range composed of these values. In some embodiments of the present application, 1 < X / Y < 3.5. By adjusting the composition of the electrolyte additive and the reduction film-forming conditions of the electrolyte on the negative electrode side surface (such as: the content of the conductive agent in the negative electrode sheet, the electrolyte injection coefficient, the formation temperature, the porosity of the negative electrode sheet), the appropriate value range of X / Y in the interface film on the electrode surface can be found, thereby greatly improving the electrochemical performance and high-temperature safety performance of the battery.

[0022] The electrolyte used in the lithium battery of the present application is any of the following electrolytes of the present application. In addition, the electrolyte used in the lithium battery of the present application may also contain other electrolytes within the scope not departing from the gist of the present application.

[0023] In some embodiments of the present application, the general formula of the silane compound containing at least one carbon-carbon double bond is shown in Formula 1:

[0024] Among them, R1, R2, and R3 are independently selected from a hydrogen atom, a fluorine atom, a C1-C6 alkyl group, a C2-C6 alkenyl group, a benzene ring, a fluorinated C1-C6 alkyl group, a fluorinated C2-C6 alkenyl group, or a fluorinated benzene ring. R4 does not exist or R4 is selected from a C1-C6 alkylene group, a C2-C6 alkenylene group, a fluorinated C1-C6 alkylene group, or a fluorinated C2-C6 alkenylene group. The sum of the number of C atoms in R1, R2, R3, and R4 is less than or equal to 6; R5, R6, and R7 are independently selected from a C1-C6 alkyl group, a C1-C6 alkoxy group, a C2-C6 alkenyl group, a C2-C6 alkynyl group, a C1-C6 ester group, or a fluorinated C1-C6 alkyl group.

[0025] In some embodiments of the present application, R1, R2, and R3 are independently selected from hydrogen atom, C1-C4 alkyl, and C1-C4 alkenyl, R4 does not exist or R4 is selected from C1-C4 alkylene and C1-C4 alkenylene, and the sum of the number of C atoms in R1, R2, R3, and R4 is less than or equal to 4; R5, R6, and R7 are independently selected from C1-C4 alkyl and C1-C4 alkenyl.

[0026] In some embodiments of the present application, the silane compound containing at least one carbon-carbon double bond includes at least one of tetravinylsilane, trivinylethylsilane, divinyldiethylsilane, trivinylethoxysilane, vinyltriethylsilane, trivinylethynylsilane, tetrapropylenesilane, trivinylpropylsilane, tripropylenepropylsilane, dipropylenedipropylsilane, and divinyldipropylsilane.

[0027] In some embodiments of the present application, the silane compound includes at least one of tetravinylsilane, trivinylethylsilane, divinyldiethylsilane, and vinyltriethylsilane.

[0028] In some embodiments of the present application, based on the total mass of the electrolyte, the mass content of the silane compound containing at least one carbon-carbon double bond is in the range of 0.5% to 5%. In some embodiments of the present application, based on the total mass of the electrolyte, the mass content of the silane compound containing at least one carbon-carbon double bond is 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5% or any range consisting of these values. In some embodiments of the present application, based on the total mass of the electrolyte, the mass content of the silane compound containing at least one carbon-carbon double bond is in the range of 1% to 4%.

[0029] In some embodiments of the present application, the nitrogen-containing compound includes at least one of lithium bis(fluorosulfonyl)imide, lithium (trifluoromethylsulfonyl)(perfluorobutylsulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonic acid)imide, lithium 4,5-dicyano-2-(trifluoromethyl)imidazole, lithium nitrate, succinonitrile, adiponitrile, glutaronitrile, hexanetrinitrile, ethoxypentafluorocyclotriphosphazene, trifluoroethoxypentafluorocyclotriphosphazene, nitromethane, nitroethane, methyl nitrate, nitrobenzene, azobisisobutyronitrile, and lithium azide. In some embodiments of the present application, the nitrogen-containing compound includes at least one of lithium bis(fluorosulfonyl)imide, succinonitrile, and trifluoroethoxypentafluorocyclotriphosphazene.

[0030] In some embodiments of the present application, the mass content of the nitrogen-containing compound is 0.05% to 10% based on the total mass of the electrolyte. In some embodiments, the mass content of the nitrogen-containing compound is 0.1%, 0.3%, 0.6%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9% or any value therebetween based on the total mass of the electrolyte. In some embodiments of the present application, the mass content of the nitrogen-containing compound is 0.1% to 5% based on the total mass of the electrolyte.

[0031] In some embodiments of the present application, the electrolyte further comprises other additives, and the other additives include at least one of a cyclic carbonate containing a carbon-carbon double bond, a silyl-containing phosphate, a silyl-containing borate, a fluorocarbon, and a sulfonate. In some embodiments of the present application, the other additives are selected from at least one of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), tris(trimethylsilyl) phosphate (TMSP), tris(trimethylsilyl) borate (TMSB), fluoroethylene carbonate (FEC), methylene dimethyl sulfonate (MMDS), and 1,3-propane sultone (PS). In some embodiments of the present application, the other additives are selected from at least one of tris(trimethylsilyl) phosphate (TMSP), vinylene carbonate (VC), fluoroethylene carbonate (FEC), and methylene dimethyl sulfonate (MMDS).

[0032] In some embodiments of the present application, based on the total mass of the electrolyte, the mass content of the other additives is 0.05%-10%. In some embodiments, based on the total mass of the electrolyte, the mass content of the other additives is 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9% or any value therebetween. In some embodiments of the present application, based on the total mass of the electrolyte, the mass content of the other additives is 0.1%-5%. In some embodiments of the present application, based on the total mass of the electrolyte, the mass content of the other additives is 0.5%.

[0033] The lithium salt used in the electrolyte of the present application is selected from one or more of inorganic lithium salts and organic lithium salts.

[0034] In some embodiments of the present application, the lithium salt is selected from at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium trifluorosulfonyl (LiTf), lithium bis(fluorosulfonyl)imide (LiFSI), lithium (trifluoromethylsulfonyl) (perfluorobutylsulfonyl) imide (LiFNFSI), lithium bis(trifluoromethylsulfonyl) imide (LiTFSI), lithium bis(pentafluoroethylsulfonic acid) imide (LiBETI), lithium bis(oxalatoborate) (LiBOB), lithium bis(fluoromalonate) borate (LiBFMB), lithium 4,5-dicyano-2-(trifluoromethyl)imidazolium (LiTDI), and lithium difluorooxalatoborate (LiDFOB); in some embodiments of the present application, the lithium salt is selected from lithium hexafluorophosphate (LiPF6) and / or lithium bis(fluorosulfonyl) imide (LiFSI).

[0035] In some embodiments of the present application, the concentration of the lithium salt in the electrolyte is 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3 mol / L, or any range consisting of these values.

[0036] In some embodiments of the present application, the solvent includes, but is not limited to, linear carbonates, cyclic carbonates, cyclic carboxylates, and linear carboxylates.

[0037] In some embodiments of the present application, the cyclic carbonate includes, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate. In some embodiments, the cyclic carbonate has 3-6 carbon atoms.

[0038] In some embodiments of the present application, the chain carbonates include, but are not limited to, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate (DEC), methyl n-propyl carbonate, ethyl n-propyl carbonate, di-n-propyl carbonate and the like; and as fluorine-substituted chain carbonates, for example, bis(fluoromethyl) carbonate, bis(difluoromethyl) carbonate, bis(trifluoromethyl) carbonate, bis(2-fluoroethyl) carbonate, bis(2,2-difluoroethyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 2-fluoroethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate and 2,2,2-trifluoroethyl methyl carbonate.

[0039] In some embodiments of the present application, the cyclic carboxylic acid ester includes, but is not limited to, γ-butyrolactone and γ-valerolactone. In some embodiments, some hydrogen atoms of the cyclic carboxylic acid ester may be substituted with fluorine.

[0040] In some embodiments of the present application, chain carboxylates include, but are not limited to, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate and ethyl pivalate. In some embodiments, some hydrogen atoms of chain carboxylates may be substituted by fluorine. In some embodiments, fluorine-substituted chain carboxylates include, but are not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate and 2,2,2-trifluoroethyl trifluoroacetate.

[0041] In some embodiments of the present application, the mass content of the solvent is 50%-90% based on the total mass of the electrolyte. In some embodiments of the present application, the mass content of the solvent is 60%-80% based on the total mass of the electrolyte.

[0042] In some embodiments of the present application, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer, wherein the negative electrode current collector includes: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or any combination thereof. In some embodiments of the present application, the negative electrode active material layer includes a negative electrode active material, wherein the negative electrode active material includes a silicon-based material, or a mixture of a silicon-based material and at least one material selected from a carbon-based material, a tin-based material, a phosphorus-based material, and metallic lithium.

[0043] In some embodiments of the present application, the silicon-based material includes at least one of silicon, a silicon alloy, a silicon oxide, and a silicon carbon compound. In some embodiments of the present application, the carbon-based material includes at least one of graphite, soft carbon, hard carbon, carbon nanotubes, and graphene. In some embodiments of the present application, the tin-based material includes at least one of tin, tin oxide, and a tin alloy. In some embodiments of the present application, the phosphorus-based material includes phosphorus and / or a phosphorus complex.

[0044] In some embodiments of the present application, based on the mass of the negative electrode active material, the mass content g% of the silicon-based material satisfies: 10≤g≤100. In some embodiments of the present application, g is 11, 13, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or any value therebetween.

[0045] In some embodiments of the present application, the negative electrode active material layer further includes a binder and a conductive agent. In some embodiments of the present application, the binder includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon.

[0046] In some embodiments of the present application, the conductive agent includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, 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, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0047] In some embodiments of the present application, the conductive agent is acetylene black. In some embodiments, the mass content of the conductive agent is 1.5%-4% based on the mass of the negative electrode active material layer. In some embodiments, the mass content of the conductive agent is 1.5%, 1.7%, 2.0%, 2.3%, 2.5%, 2.7%, 2.9%, 3.0%, 3.3%, 3.5%, 3.7%, 3.9%, 4.0%, or any value therebetween. In some embodiments, the mass content of the conductive agent is 1.6%-3.3%. In some embodiments, the mass content of the conductive agent is 1.6%, 2.0%, 3.3%.

[0048] In some embodiments of the present application, the porosity of the negative electrode sheet is 20%-40%. In some embodiments, T is 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40% or any value therebetween. In some embodiments, the porosity of the negative electrode sheet is 20%-35%. In some embodiments, the porosity of the negative electrode sheet is 27.5%, 29.2%, or 31.0%. In the present application, the porosity of the negative electrode sheet can be adjusted according to the characteristics of the selected active material by conventional technical means in the art, such as controlling the rolling pressure, rolling temperature, and rolling speed of the electrode sheet.

[0049] In some embodiments of the present application, the positive electrode includes a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector.

[0050] In some embodiments of the present application, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer substrate.

[0051] In some embodiments of the present application, the positive electrode active material includes at least one of a nickel-cobalt ternary material and a phosphate-based material.

[0052] In some embodiments of the present application, the nickel-cobalt ternary material includes LiNi m Co n A (1-m-n) At least one of the O2 materials, A is selected from at least one of manganese, aluminum, magnesium, chromium, calcium, zirconium, molybdenum, silver, or niobium, 0.5≤m≤1, 0≤n≤0.5, and m+n≤1. In some embodiments of the present application, m is 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or a range consisting of any two of these values. In some embodiments of the present application, n is 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, or a range consisting of any two of these values.

[0053] In some embodiments of the present application, the nickel-cobalt ternary material includes at least one of NCA, NCM111, NCM523, NCM622, NCM811, Ni90, Ni92 or Ni95.

[0054] In some embodiments of the present application, the phosphate-based material includes LiMn k B (1-k) PO4, wherein 0≤k≤1, and the B element is selected from at least one of iron, cobalt, magnesium, calcium, zinc, chromium or lead. In some embodiments of the present application, k is 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 or a range consisting of any two of these values. In some embodiments of the present application, the phosphate-based material includes lithium iron phosphate, LiMn 0.6 Fe 0.4 PO4 or LiMn 0.8 Fe 0.2 At least one of PO4.

[0055] In some embodiments of the present application, the positive electrode active material includes at least one of lithium nickel oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium nickel manganese cobalt magnesium oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium iron phosphate and lithium manganese iron phosphate.

[0056] In some embodiments of the present application, the positive electrode active material is Li[Ni 1-x-y Co x 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).

[0057] In some embodiments of the present application, the positive electrode active material layer further includes a binder and optionally 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, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (ester) styrene-butadiene rubber, epoxy resin or nylon, etc.

[0058] 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, 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, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0059] The material and shape of the separator used in the embodiments of the present application are not particularly limited and can be any technology disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic substance formed of a material that is stable to the electrolyte of the present application.

[0060] For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, membrane, or composite membrane having a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, and polyethylene terephthalate. Specifically, polypropylene porous membrane, polyethylene porous membrane, polypropylene nonwoven fabric, polyethylene nonwoven fabric, or polypropylene-polyethylene-polypropylene porous composite membrane may be used.

[0061] A surface treatment layer is provided 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.

[0062] The inorganic layer includes inorganic particles and a binder, wherein the inorganic particles are selected from 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 is selected from at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxide, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0063] The polymer layer contains a polymer, and the material of the polymer is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxy, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0064] In some embodiments of the present application, the separator is a polyethylene (PE) separator coated with ceramic layers on both sides, wherein the PE layer thickness 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.

[0065] In some embodiments of the present application, the preparation method of the secondary battery includes providing an electrode assembly, injecting electrolyte, packaging, and forming electrolyte. In some embodiments of the present application, the electrolyte injection coefficient of the secondary battery is 1.5g Ah. -1 -2.5g Ah - 1 In some embodiments of the present application, the electrolyte filling coefficient of the secondary battery is 1.5g Ah -1 , 1.6g Ah -1 , 1.7g Ah -1 、1.8g Ah -1 、1.9g Ah -1 , 2.0g Ah -1 , 2.1g Ah -1 , 2.2g Ah -1 , 2.3g Ah -1 , 2.4g Ah -1 , 2.5 g Ah -1 Or any value therebetween. In some embodiments of the present application, the electrolyte filling coefficient of the secondary battery is 1.8g Ah -1 、1.9g Ah -1 .

[0066] In some embodiments of the present application, the temperature of the formation is 30°C-50°C. In some embodiments of the present application, the temperature of the formation is 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C or any value therebetween. In some embodiments of the present application, the temperature of the formation is 40°C to 50°C. In some embodiments of the present application, the temperature of the formation is 40°C or 45°C.

[0067] In some embodiments of the present application, the formation includes: charging to 4.2V at a current of 0.05C and standing for 60 minutes at a temperature of 40°C-50°C, for example, 45°C, and a pressure of 150kgf-250kgf, for example, 210kgf, followed by charging to 4.2V at 0.1C, and then discharging to 3.0V at 0.2C.

[0068] In some embodiments of the present application, the secondary battery may include an outer packaging, which may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging 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.

[0069] In some embodiments of the present application, the shape of the secondary battery is not particularly limited, and it can be cylindrical, square, or any other shape.

[0070] In some embodiments of the present application, a battery module is provided. The battery module includes the aforementioned secondary battery. The battery module of the present application utilizes the aforementioned secondary battery and therefore possesses at least the same advantages as the aforementioned secondary battery. The battery module of the present application may include multiple secondary batteries, the specific number of which can be adjusted based on the application and capacity of the battery module.

[0071] In some embodiments of the present application, the present application further provides a battery pack comprising the above-mentioned battery module. The number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0072] 2. Device

[0073] The present application also provides a device comprising at least one of the above-mentioned secondary battery, battery module or battery pack.

[0074] In some embodiments of the present application, the device includes, but is not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, power storage systems, etc. To meet the device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module may be used.

[0075] In other embodiments, the device may be a mobile phone, a tablet computer, a laptop computer, etc. The device is usually required to be lightweight and thin, and may use a secondary battery as a power source.

[0076] 3. Test Method

[0077] 1. Determination of electrode porosity

[0078] Porosity is measured using a mercury intrusion porosimeter. Specifically, the dried electrode sample is cut into thin strips of a certain size. A micrometer is used to measure the apparent volume of the electrode coating: apparent volume = sample coating thickness * sample length * sample width. The electrode is then vacuum-degassed, rolled, and placed in a sample cell. The sample volume must be 40-70% of the effective volume of the sample tube to ensure measurement accuracy. A mercury intrusion porosimeter is then used to measure the sample's pore volume (i.e., the volume of mercury intruded into the sample). Porosity = pore volume / apparent volume.

[0079] 2. Cycle capacity retention test

[0080] At 25°C, the lithium-ion battery was charged to 4.25 V at 1C constant current and constant voltage, and then discharged to 2.5 V at 1C constant current. After 1000 charge and discharge cycles, the capacity retention after the 1000th cycle at 25°C was calculated according to the following formula: discharge capacity after the 1000th cycle / discharge capacity after the first cycle × 100%.

[0081] At 25°C, the lithium-ion battery was charged to 4.25V at 2C constant current and constant voltage, and then discharged to 2.5V at 2C constant current. After 300 charge and discharge cycles, the capacity retention after the 300th cycle at 25°C was calculated according to the following formula: discharge capacity after the 500th cycle / discharge capacity after the first cycle × 100%.

[0082] At 45°C, the lithium-ion battery was charged to 4.25V at 1C constant current and constant voltage, and then discharged to 2.5V at 1C constant current. After 500 charge and discharge cycles, the capacity retention after the 5400th cycle at 45°C was calculated according to the following formula: discharge capacity after the 400th cycle / discharge capacity in the first cycle × 100%.

[0083] Thickness change rate at 3.45℃ storage

[0084] The battery was discharged at 0.5C to 3.0V at 25°C, then charged at 0.5C to 4.45V. Constant voltage charging at 4.45V was continued to 0.05C. The thickness of the battery at this point was measured using a PPG soft-pack battery thickness gauge, and recorded as "a". The battery was placed in an oven at 45°C and stored at a constant voltage of 4.45V for 21 days. The thickness after 21 days was recorded as "b". The thickness expansion ratio was calculated as: (b) / a × 100%.

[0085] 4.XPS test

[0086] The lithium-ion battery was discharged at a current of 0.1C to 2.5V. The battery was then disassembled in an argon-filled glove box to obtain the electrode sheets. The resulting electrode sheets were cut into 8mm x 8mm test specimens and cleaned by soaking them in a low-boiling-point dimethyl carbonate (DMC) solvent for half an hour. After complete drying, they were attached to the XPS sample stage with the surface of the positive electrode active material layer facing away from the current collector facing upward. Measurements were performed without exposure to the atmosphere. The specific test conditions and steps are as follows:

[0087] Single crystal spectrum AlKα rays were used. As for the X-ray points, an elliptical form of 1000×1750μm with an output of 10KV and 22mA was used. The data when the sputtering etching time was 0 seconds was selected. For neutral carbon C1s, 284.8eV was used as the standard. As for data processing, a 3-point smoothing operation was used for fitting and peak separation. Then, the peak area was measured through background subtraction and peak synthesis operations. Finally, the atomic % of each component was calculated.

[0088] In the following examples and comparative examples, all reagents, materials and instruments used are commercially available unless otherwise specified.

[0089] Examples and Comparative Examples

[0090] Example 1

[0091] The steps of preparing the positive electrode sheet, the negative electrode sheet, the electrolyte, the separator and the battery are described as follows. 0.9 Co 0.05 Mn 0.05 O2; the negative electrode active material is artificial graphite and silicon oxide (SiO X , 0.5≤x≤1.5) composite material (silicon oxide / graphite = 14 / 86), and the coating surface density is determined according to the battery size, capacity design and positive and negative electrode material capacity.

[0092] Positive electrode sheet preparation steps: positive electrode active material LiNi 0.9 Co 0.05 Mn 0.05O2, conductive agent carbon nanotube / acetylene black, binder polyvinylidene fluoride PVDF, according to the mass ratio of LiNi 0.9 Co 0.05 Mn 0.05 O2: CNT / Super-P: PVDF = 95: 2.0 / 1.0: 2 was fully homogenized in an N-methylpyrrolidone (NMP) solvent system, coated on a 12 μm thick aluminum-coated current collector, dried, and roller-pressed to obtain a positive electrode sheet.

[0093] Preparation steps of the negative electrode sheet: the negative electrode active material silicon-graphite composite, conductive agent acetylene black, binder styrene-butadiene rubber SBR, thickener sodium carboxymethyl cellulose CMCNa, and polyacrylic acid PAA are fully homogenized in deionized water in a mass ratio of 96:2:1.5:1:0.5, and then coated on the surface of an 8um thick copper current collector. After drying, rolling, and striping, the negative electrode sheet is obtained.

[0094] The diaphragm adopts PP / PE / PP three-layer composite diaphragm.

[0095] Electrolyte preparation steps: In a glove box filled with argon (H2O <0.1ppm, O2 <0.1ppm), lithium salt LiPF6 and solvent EC / DEC / EMC = 25 / 20 / 55 are mixed in a certain proportion to form a 1M solution, and finally the silane compound additive listed in Table 1 is added and stirred to obtain the lithium ion battery electrolyte of Example 1.

[0096] Preparation steps of lithium-ion battery: stack the prepared positive electrode sheet, separator and negative electrode sheet in order, make the separator in the middle of the positive and negative electrode sheets, and wind them to get the bare battery cell; place the bare battery cell in an aluminum-plastic film outer packaging, inject the prepared lithium-ion power battery electrolyte into the fully dried silicon-artificial graphite / LiNi 0.9 Co 0.05 Mn 0.05 In the O2 battery, the battery is placed at 45°C for 48 hours, formed in a high-temperature fixture (the formation conditions are: temperature 45°C, pressure 210kgf, charging to 4.2V at 0.05C current and standing for 60 minutes, then charging to 4.2V at 0.1C and then discharging to 3.0V at 0.2C, and this is repeated twice) and secondary sealing, and then conventional capacity division is carried out.

[0097] Example 2-20

[0098] Examples 2 to 20 are achieved on the basis of Example 1 by adjusting the type and content of additives in the electrolyte, the content of the negative electrode conductive agent, the electrolyte injection coefficient, the formation temperature, and the porosity of the negative electrode. Specific adjustment measures and detailed data are shown in Table 1.

[0099] Comparative Examples 1-14

[0100] Comparative Examples 1 to 14 are achieved on the basis of Example 1 by adjusting the type and content of additives in the electrolyte, the content of the negative electrode conductive agent, the electrolyte injection coefficient, the formation temperature, and the porosity of the negative electrode. Specific adjustment measures and detailed data are shown in Table 1.

[0101] The structural formulas of the four silane compounds containing at least one carbon-carbon double bond (Formula I-1, Formula I-2, Formula I-3, Formula I-4) in Table 1 are as follows:

[0102] Table 1

[0103] Silicon-artificial graphite / LiNi prepared by the electrolytes obtained in Examples 1-20 and Comparative Examples 1-18 0.9 Co 0.05 Mn 0.05 The O2 battery was subjected to X-ray photoelectron spectroscopy XPS test and lithium-ion battery performance test, and the test results are shown in Table 2.

[0104] Table 2

[0105] 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 certain 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 such modifications and changes also fall within the scope of protection of the present application.

Claims

1. A secondary battery, comprising a positive electrode sheet, a negative electrode sheet and an electrolyte, characterized in that: The electrolyte includes a silane compound containing at least one carbon-carbon double bond and a nitrogen-containing compound; The negative electrode plate includes a negative electrode active material layer and a solid electrolyte interface film located on the surface of the negative electrode active material layer. The solid electrolyte interface film includes lithium nitride and a substance containing a silicon-carbon bond. Using an X-ray photoelectron spectrometer to test, the peak area of ​​nitrogen in lithium nitride at a position of 398.7 eV is X, and the peak area of ​​silicon in the substance containing a silicon-carbon bond at a position of 100.5 eV is Y, wherein 1 <X / Y<6。 2. The secondary battery according to claim 1, characterized in that: 1 <X / Y<3.5。 3. The secondary battery according to claim 1 or 2, characterized in that: The general formula of the silane compound is shown in Formula 1: Wherein, R1, R2, and R3 are independently selected from a hydrogen atom, a fluorine atom, a C1-C6 alkyl group, a C2-C6 alkenyl group, a benzene ring, a fluorinated C1-C6 alkyl group, a fluorinated C2-C6 alkenyl group, or a fluorinated benzene ring; R4 does not exist or R4 is selected from a C1-C6 alkylene group, a C2-C6 alkenylene group, a fluorinated C1-C6 alkylene group, or a fluorinated C2-C6 alkenylene group; the sum of the number of C atoms in R1, R2, R3, and R4 is less than or equal to 6; R5, R6, and R7 are independently selected from a C1-C6 alkyl group, a C1-C6 alkoxy group, a C2-C6 alkenyl group, a C2-C6 alkynyl group, a C1-C6 ester group, or a fluorinated C1-C6 alkyl group.

4. The secondary battery according to claim 1 or 2, characterized in that: The mass content of the silane compound is 0.5% to 5% based on the total mass of the electrolyte.

5. The secondary battery according to claim 3, characterized in that: The silane compound includes at least one of tetravinylsilane, trivinylethylsilane, divinyldiethylsilane, and vinyltriethylsilane.

6. The secondary battery according to claim 4, characterized in that: The mass content of the silane compound is 1% to 4% based on the total mass of the electrolyte.

7. The secondary battery according to claim 1 or 2, characterized in that: The nitrogen-containing compound includes at least one of lithium bis(fluorosulfonyl)imide, lithium (trifluoromethylsulfonyl)(perfluorobutylsulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonic acid)imide, lithium 4,5-dicyano-2-(trifluoromethyl)imidazole, lithium nitrate, succinonitrile, adiponitrile, glutaronitrile, hexanetrinitrile, ethoxypentafluorocyclotriphosphazene, trifluoroethoxypentafluorocyclotriphosphazene, nitromethane, nitroethane, methyl nitrate, nitrobenzene, azobisisobutyronitrile, and lithium azide.

8. The secondary battery according to claim 1 or 2, characterized in that: The mass content of the nitrogen-containing compound is 0.05% to 10% based on the total mass of the electrolyte.

9. The secondary battery according to claim 7, characterized in that: The nitrogen-containing compound includes at least one of lithium bis(fluorosulfonyl)imide, succinonitrile, and trifluoroethoxypentafluorocyclotriphosphazene.

10. The secondary battery according to claim 8, characterized in that: The mass content of the nitrogen-containing compound is 0.1% to 5% based on the total mass of the electrolyte.

11. The secondary battery according to claim 1 or 2, characterized in that: The porosity of the negative electrode plate is 20%-40%.

12. The secondary battery according to claim 1 or 2, characterized in that: The mass content of the conductive agent of the negative electrode plate is 1.5%-4%.

13. The secondary battery according to claim 1 or 2, characterized in that: The electrolyte filling coefficient of the secondary battery is 1.5g Ah -1 -2.5g Ah -1 .

14. The secondary battery according to claim 1 or 2, characterized in that: The formation temperature of the secondary battery is 30°C-50°C.

15. The secondary battery according to claim 1 or 2, characterized in that: The electrolyte contains other additives, and the other additives include at least one of vinylene carbonate, vinylethylene carbonate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, and cyclic sulfonate.

16. The secondary battery according to claim 1 or 2, characterized in that: Based on the total mass of the electrolyte, the mass content of the other additives is 0.1%-5%.

17. The secondary battery according to claim 1 or 2, characterized in that: The electrolyte solvent is a carbonate solvent.

18. The secondary battery according to claim 1 or 2, characterized in that: The negative electrode active material layer includes a negative electrode active material, which includes a mixture of a silicon-based material and a carbon-based material, wherein the silicon-based material includes at least one of silicon, a silicon alloy, a silicon oxide compound and a silicon carbon compound, and the carbon-based material includes at least one of graphite, soft carbon, hard carbon, carbon nanotubes and graphene. Based on the mass of the negative electrode active material, the mass content g% of the silicon-based material satisfies: 10≤g≤100.

19. The secondary battery according to claim 1 or 2, characterized in that: The positive electrode comprises a positive electrode active material layer, wherein the positive electrode active material layer comprises an active material selected from lithium nickel transition metal oxides, wherein the chemical formula of the lithium nickel transition metal oxide is LiNi m Co n A (1-m-n) As shown in O2 material, A is selected from at least one of manganese, aluminum, magnesium, chromium, calcium, zirconium, molybdenum, silver or niobium, 0.5≤m≤1, 0≤n≤0.5, m+n≤1.

20. A device, characterized in that: The device comprises the secondary battery according to any one of claims 1-19.

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