Electrolyte additive, electrolyte, battery and electric device

Abstract

The present disclosure provides an electrolyte additive, an electrolyte, a battery, and an electric device. The electrolyte additive, which is for use in batteries having silicon-based negative electrodes, comprises a first additive and a first lithium salt, wherein the first additive comprises tetravinylsilane and tris(vinyldimethylsilyl) phosphate, and the first lithium salt comprises lithium tetrafluoro oxalato phosphate.

Description

Electrolyte additive, electrolyte, battery, electrical device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 1, 2023, with application number 202311637451.1 and application name “Electrolyte Additive, Electrolyte, Battery, Electrical Device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present disclosure relates to the field of electrolytes, and in particular, to electrolyte additives, electrolytes, batteries, and electrical devices. Background Art

[0003] As people pay more attention to the depletion of non-renewable energy and environmental pollution, renewable clean energy has developed rapidly. Lithium-ion batteries are widely used in consumer electronics, energy storage, and power batteries due to their advantages such as high specific energy, long cycle life, and low self-discharge. Typically, a battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The electrolyte of a lithium-ion battery is composed of a solvent, an electrolyte lithium salt, and an electrolyte additive. The addition of electrolyte additives can effectively improve the battery's cycle performance and high-temperature storage performance. However, current electrolyte additives still have some problems in actual application.

[0004] It should be noted that the above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art.

[0005] Application Contents

[0006] In a first aspect of the present application, an electrolyte additive for a silicon-based negative electrode battery is provided, comprising a first additive and a first lithium salt, wherein the first additive comprises tetravinylsilane and tris(vinyldimethylsilyl)phosphate, and the first lithium salt comprises lithium tetrafluorooxalophosphate. Thus, an electrolyte containing the electrolyte additive can improve the cycle performance and high-temperature performance of the battery.

[0007] In some embodiments, the mass fraction of tetravinylsilane in the electrolyte additive is a, the mass fraction of lithium tetrafluorooxalophosphate in the electrolyte additive is b, and a / b is 0.05-20. Thus, the cycle performance of a battery containing the electrolyte additive can be improved.

[0008] In some embodiments, the mass fraction of lithium tetrafluorooxalophosphate in the electrolyte additive is b, the mass fraction of tris(vinyldimethylsilyl)phosphate in the electrolyte additive is c, and b / c is 0.05-20. Thus, the high-temperature storage performance of a battery containing the electrolyte additive can be improved.

[0009] In some embodiments, the electrolyte further comprises a second additive, wherein the second additive comprises at least one of a high-temperature additive, a negative electrode film-forming additive, a lithium salt additive, and a water and acid removal additive. This can improve the rate capability, high-temperature performance, and cycle life of a battery containing the electrolyte additive.

[0010] In some embodiments, the second additive satisfies at least one of the following conditions: the high-temperature additive includes at least one of 1,3-propane sultone, 1,3-propylene sultone, ethylene sulfate, and vinyl sulfite; the negative electrode film-forming additive includes at least one of vinylene carbonate, fluoroethylene carbonate, and vinyl ethylene carbonate; the lithium salt additive includes at least one of lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorobis(oxalatophosphate), lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, and lithium difluorophosphate; the water and acid removal additive includes at least one of tris(trimethylsilyl)borate and tris(trimethylsilyl)phosphate. Thus, the rate performance, high-temperature performance, and cycle life of the battery containing the electrolyte additive can be further improved.

[0011] In a second aspect of the present application, the present application provides an electrolyte solution comprising the aforementioned electrolyte solution additive. Thus, the electrolyte solution has all the features and advantages of the aforementioned electrolyte solution additive, which will not be described in detail here.

[0012] In some embodiments, the electrolyte further comprises: a solvent and an electrolyte lithium salt, wherein the electrolyte lithium salt comprises at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. Thus, the ionic conductivity and long-term stability of the electrolyte can be improved.

[0013] In some embodiments, the mass fraction of the electrolyte lithium salt in the electrolyte is 12%-18%, thereby further improving the ionic conductivity of the electrolyte.

[0014] In some embodiments, the mass fraction of tetravinylsilane in the electrolyte is 0.1%-2%, thereby improving the cycle performance of the battery containing the electrolyte.

[0015] In some embodiments, the mass fraction of lithium tetrafluorooxalophosphate in the electrolyte is 0.1%-2%, thereby improving the cycle performance of the battery containing the electrolyte.

[0016] In some embodiments, the mass fraction of tris(vinyldimethylsilyl)phosphate in the electrolyte is 0.1%-2%, thereby improving the high-temperature storage performance of the battery containing the electrolyte.

[0017] In some embodiments, the mass fraction of the second additive in the electrolyte is 0.5%-3%, thereby improving the rate performance, high temperature performance, and cycle life of a battery containing the electrolyte.

[0018] In a third aspect of the present application, a battery is provided, comprising the aforementioned electrolyte additive or the aforementioned electrolyte. Thus, the battery has all the features and advantages of the aforementioned electrolyte additive and electrolyte, which will not be further elaborated here.

[0019] In some embodiments, the battery further includes a negative electrode plate, the negative electrode plate including a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode plate, the negative electrode active material layer including a negative electrode active material, wherein the mass fraction of silicon in the negative electrode active material is 3% to 50%. Thus, the energy density of the battery can be increased.

[0020] In a fourth aspect of the present application, the present application provides an electrical device comprising the aforementioned battery. Thus, the electrical device has all the features and advantages of the aforementioned battery, which will not be described in detail here. DETAILED DESCRIPTION

[0021] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application; 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 embodiments of this application).

[0022] The terms "include" and "have" in the description and claims of this application and any variations thereof are open expressions, that is, including the contents specified in this application but not excluding other contents.

[0023] In the description of this application, regardless of whether the word "about" or "approximately" is used, all numbers disclosed herein are approximate values. The value of each number may vary by less than 10% or by a reasonable difference considered by a person skilled in the art, such as 1%, 2%, 3%, 4% or 5%.

[0024] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly specifying the quantity of the technical features indicated. "First feature" and "second feature" may include one or more of the features.

[0025] In the description of this application, "A and / or B" may include the case of A alone, the case of B alone, or any of the cases of A and B, where A and B are only used for example, and may be any technical feature connected by "and / or" in this application.

[0026] Electrolyte additives only account for a small portion of the electrolyte in lithium-ion batteries. The right amount of additives can form a solid electrolyte interface (SEI) on the surface of the negative electrode active material and a cathode electrolyte interface (CEI) on the surface of the positive electrode active material. The SEI and CEI films form on the surfaces of the negative and positive electrode active materials, respectively, effectively mitigating the side effects of direct contact between the active materials and the electrolyte.

[0027] The electrolyte additive tetravinylsilane has a high HOMO energy level. After the battery capacity is divided, it can form an organic polymer film with Si-C as the main component on the interface of the positive electrode active material in preference to the solvent in the electrolyte, reducing the direct contact between the positive electrode active material and the electrolyte, thereby effectively reducing the decomposition and gas production of other components in the electrolyte at the positive electrode interface under high voltage, as well as the acidic corrosion and structural collapse of the positive electrode active material, thereby effectively improving the cycle performance of lithium-ion batteries. At the same time, tetravinylsilane will also participate in the formation of SEI, but the SEI film layer formed by tetravinylsilane is thick and uneven in thickness, which will increase the internal resistance of the battery and affect the rate performance of the battery. Furthermore, when silicon-based materials are used as negative electrode active materials, the SEI film formed by tetravinylsilane has poor structural uniformity, which causes lithium atoms to enter the silicon crystal to generate Li 15 Si4, which in turn prevents some lithium ions from participating in the battery's charge and discharge cycle again, causing the battery to lose capacity and cannot be recovered.

[0028] The SEI film formation potential of lithium tetrafluorooxalate phosphate is earlier than that of tetravinylsilane, that is, lithium tetrafluorooxalate phosphate will form a film earlier than tetravinylsilane. Therefore, lithium tetrafluorooxalate phosphate can preferentially form an inorganic film rich in phosphate and LiF with high thickness uniformity on the surface of the negative electrode active material, hindering lithium atoms from entering the interior of the silicon crystal, thereby inhibiting the Li in the silicon material. 15 The formation of Si4 allows the battery's capacity to be maintained during the charge-discharge cycle, improving the battery's cycle performance. After the lithium tetrafluorooxalophosphate SEI film forms, tetravinylsilane forms an organic polymer film composed mainly of Si-C on the outside of the inorganic film rich in phosphate and LiF, thereby jointly reducing the negative electrode impedance.

[0029] Furthermore, the free fluoride ions in lithium tetrafluorooxalophosphate combine with the free hydrogen ions in the electrolyte to form hydrofluoric acid, which increases the overall acidity of the electrolyte. During long-term high-temperature storage (for example, when the outdoor temperature is close to 40°C, the internal battery temperature of an electric vehicle can reach 70°C when it is stationary in the open air), hydrofluoric acid will attack the positive and negative active materials and produce serious side reactions, causing the battery voltage to drop and the capacity retention rate to be significantly reduced.

[0030] The Si-O bonds and Si-C=C bonds in tris(vinyldimethylsilyl) phosphate (CAS No.: 113419-25-3) will break after combining with hydrofluoric acid in the electrolyte, thereby reducing the acidity. At the same time, tris(vinyldimethylsilyl) phosphate also contributes to the formation of CEI and SEI films. The addition of tris(vinyldimethylsilyl) phosphate can effectively alleviate the adverse effect of increased electrolyte acidity caused by lithium tetrafluorooxalophosphate, improve the high-temperature resistance of the electrolyte, and thus improve the high-temperature performance of the battery.

[0031] In the first aspect of the present application, the present application proposes an electrolyte additive for a silicon-based negative electrode battery, comprising a first additive and a first lithium salt, wherein the first additive comprises tetravinylsilane and tris(vinyldimethylsilyl)phosphate, and the first lithium salt comprises lithium tetrafluorooxalate phosphate. In the present application, by combining tetravinylsilane, tris(vinyldimethylsilyl)phosphate and lithium tetrafluorooxalate phosphate, it is helpful to form a SEI film and a CEI film with low interfacial impedance, thereby improving the cycle performance of the battery containing the additive combination, and significantly improving the high-temperature storage performance of the battery using the silicon-based negative electrode, thereby broadening the battery usage scenarios.

[0032] In some embodiments, the mass fraction of the tetravinylsilane in the electrolyte additive is a, the mass fraction of the lithium tetrafluorooxalophosphate in the electrolyte additive is b, and a / b is 0.05-20.

[0033] As an example, a / b can be 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5 or 20.

[0034] The reasonable ratio of tetravinylsilane and lithium tetrafluorooxalophosphate helps to form uniform and strong CEI film and SEI film for battery systems using silicon-based negative electrodes.

[0035] Compared with other lithium salt additives, lithium tetrafluorooxalate phosphate has a lower film-forming potential, is not easily decomposed to produce gas, and has better chemical stability.

[0036] In some embodiments, the mass fraction of lithium tetrafluorooxalophosphate in the electrolyte additive is b, the mass fraction of tris(vinyldimethylsilyl)phosphate in the electrolyte additive is c, and b / c is 0.05-20. Thus, the high-temperature storage performance of a battery containing the electrolyte additive can be improved.

[0037] As an example, b / c can be 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5 or 20.

[0038] Compared to other additives containing Si—O bonds and Si—C═C bonds, tris(vinyldimethylsilyl)phosphate has better chemical stability, ionic conductivity, and higher compatibility.

[0039] In some embodiments, the method further includes: a second additive, wherein the second additive includes at least one of a high-temperature additive, a negative electrode film-forming additive, a lithium salt additive, and a water- and acid-removing additive.

[0040] The addition of the second additive can improve the rate performance, high temperature cycle performance, and cycle life of the battery containing the electrolyte additive.

[0041] In some embodiments, the high temperature additive includes at least one of 1,3-propane sultone (PS), 1,3-propylene sultone (PST), diethylene sulfate (DTD), and ethylene sulfite (ES).

[0042] The high temperature resistance of the electrolyte can be improved by adding high temperature additives.

[0043] In some embodiments, the negative electrode film-forming additive includes at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and vinyl ethylene carbonate (VEC).

[0044] The addition of negative electrode film-forming additives can improve SEI film formation and enhance the uniformity of SEI film formation.

[0045] In some embodiments, the lithium salt additive includes at least one of lithium bis(oxalatoborate) (LiBOB), lithium difluorooxalatoborate (LiODFB), lithium difluorobis(oxalatophosphate) (LiODFP), lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, and lithium difluorophosphate (LiPO2F2).

[0046] The addition of lithium salt additives can increase the solubility of lithium salt in the electrolyte, improve the stability of the electrolyte under high temperature conditions, increase the ionic conductivity of the electrolyte, reduce the hydrolysis of the electrolyte under aqueous conditions, and inhibit the oxidation of the electrolyte.

[0047] In some embodiments, the water and acid scavenging additive includes at least one of tris(trimethylsilyl)borate (TMSB) and tris(trimethylsilyl)phosphate (TMSP).

[0048] By adding dehydration and deacidification additives, they can react with water and acidic substances, such as hydrofluoric acid, in the electrolyte, reducing the impact of water and / or acidic substances on the stability of the electrolyte, and can also participate in the formation of SEI and CEI films after dehydration and deacidification.

[0049] In a second aspect of the present application, the present application provides an electrolyte solution comprising the aforementioned electrolyte solution additive. Thus, the electrolyte solution has all the features and advantages of the aforementioned electrolyte solution additive, which will not be described in detail here.

[0050] In some embodiments, the method further comprises: a solvent and an electrolyte lithium salt, wherein the electrolyte lithium salt comprises at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

[0051] The solvent is the main component of the electrolyte, and the solvent should have a high solubility of the lithium salt so that the electrolyte has a high ionic conductivity.

[0052] When the electrolyte lithium salt is dissolved in the electrolyte solvent, lithium ions can be released. The lithium ions and the electrolyte form a solvation structure, which is conducive to the rapid migration of lithium ions.

[0053] In some embodiments, the mass fraction of the electrolyte lithium salt in the electrolyte is 12%-18%.

[0054] As an example, the mass fraction of the electrolyte lithium salt in the electrolyte can be 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5% or 18%.

[0055] When the mass fraction of the electrolyte lithium salt in the electrolyte is within the above range, the electrolyte lithium salt can be fully dissolved in the electrolyte solvent, and the electrolyte has higher ion conductivity and lower manufacturing cost.

[0056] In some embodiments, the solvent may include at least one of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethyl propionate, propyl propionate, methyl acetate, ethyl acetate, propyl acetate, and methyl propionate.

[0057] The solvent in the electrolyte is an important carrier for ion transport. When the electrolyte lithium salt is dissolved in the solvent, the electrolyte has a higher electronic conductivity. Then, by selecting the above solvent, the cycle life and charge and discharge rate of the battery can be improved.

[0058] In some embodiments, the mass fraction of the solvent in the electrolyte is 50%-80%.

[0059] As an example, the mass fraction of the solvent in the electrolyte may be 55%, 57%, 60%, 63%, 65%, 67%, 70%, 73%, 75%, 77% or 80%.

[0060] In some embodiments, the mass fraction of tetravinylsilane in the electrolyte is 0.1%-2%.

[0061] As an example, the mass fraction of tetravinylsilane in the electrolyte can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2.0%.

[0062] When the mass fraction of tetravinylsilane in the electrolyte is 0.1%-2%, the tetravinylsilane content is moderate, the CEI film is formed more fully and has a moderate thickness, and less tetravinylsilane remains after the CEI film is consumed, which can reduce the side reaction decomposition and gas production of tetravinylsilane.

[0063] In some embodiments, the mass fraction of lithium tetrafluorooxalophosphate in the electrolyte is 0.1%-2%.

[0064] As an example, the mass fraction of lithium tetrafluorooxalophosphate in the electrolyte can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2.0%.

[0065] When the mass fraction of lithium tetrafluorooxalate phosphate in the electrolyte is 0.1%-2%, lithium tetrafluorooxalate phosphate can form a uniform SEI film earlier than tetravinylsilane, inhibiting the direct film formation of tetravinylsilane on the surface of the negative electrode active material and improving the thickness uniformity of the SEI film.

[0066] In some embodiments, the mass fraction of tris(vinyldimethylsilyl)phosphate in the electrolyte is 0.1%-2%, thereby improving the high-temperature storage performance of the battery containing the electrolyte.

[0067] As an example, the mass fraction of tri(vinyldimethylsilyl)phosphate in the electrolyte can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2.0%.

[0068] When the mass fraction of tri(vinyldimethylsilyl)phosphate in the electrolyte is 0.1%-2%, tri(vinyldimethylsilyl)phosphate can effectively consume acidic substances in the electrolyte, such as hydrofluoric acid, thereby reducing the side reactions of the positive and negative active materials with the acidic substances under high temperature conditions, thereby improving the cycle performance and high-temperature performance of the battery.

[0069] In some embodiments, the mass fraction of the second additive in the electrolyte is 0.5%-3%.

[0070] As an example, the mass fraction of the second additive in the electrolyte can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9% or 3.0%.

[0071] As an example, when the second additive includes a high-temperature additive, the mass fraction of the high-temperature additive in the electrolyte is 0-2%.

[0072] As an example, when the second additive includes a negative electrode film-forming additive, the mass fraction of the negative electrode film-forming additive in the electrolyte is 0.5%-3%.

[0073] As an example, when the second additive includes a lithium salt additive, the mass fraction of the lithium salt additive in the electrolyte is 0-1%.

[0074] As an example, when the second additive includes a water-removing and acid-removing additive, the mass fraction of the water-removing and acid-removing additive in the electrolyte is 0-1%.

[0075] In a third aspect of the present application, a battery is provided, comprising the aforementioned electrolyte additive or the aforementioned electrolyte. Thus, the battery has all the features and advantages of the aforementioned electrolyte additive and electrolyte, which will not be further elaborated here.

[0076] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0077] In some embodiments, the present invention further includes a negative electrode plate, wherein the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode plate, wherein the negative electrode active material layer includes a negative electrode active material, and the mass fraction of silicon element in the negative electrode active material is 3%-50%.

[0078] The energy density of a battery can be effectively increased by increasing the specific capacity of the negative electrode active material. The current specific capacity of graphite-based materials has reached its theoretical upper limit (372mAh / g), while the highest theoretical specific capacity of silicon-based negative electrode materials can reach 4200mAh / g. Silicon-based negative electrode active materials have great application prospects. Silicon-based negative electrode materials experience significant volume changes during the charge and discharge process of the battery. During repeated charge and discharge cycles, due to the large changes in their own volume expansion and contraction, the SEI film on the surface of the silicon-based negative electrode will repeatedly rupture and form, continuously consuming the electrolyte and resulting in poor battery cycle performance.

[0079] In the present application, by optimizing the composition of the electrolyte additive, a SEI film with high structural stability can be formed on the surface of the silicon-based negative electrode active material. Even if the silicon-based negative electrode active material undergoes a large volume change during the charge and discharge cycle, it can still effectively adhere to the surface of the negative electrode active material, effectively reducing the repeated rupture of the SEI film and the resulting electrolyte consumption, thereby improving the cycle performance of the battery.

[0080] In some embodiments, the battery includes a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode plate, the positive electrode active material layer includes a positive electrode active material, and the mass fraction of nickel element in the positive electrode active material is greater than or equal to 40%.

[0081] When the mass fraction of nickel element in the positive electrode active material is within the aforementioned range, the cost of the positive electrode active material is low and the gram capacity is significantly improved.

[0082] In some embodiments, the positive electrode active material satisfies the general formula Li a Ni b Co c M1 d M2 e O f R g , where 1 ≤ a ≤ 1.2, 0.6 < b < 1, 0 < c < 1, 0 < d < 1, 0 ≤ e ≤ 0.2, b + c + d + e = 1, 1 ≤ f ≤ 2, 0 ≤ g ≤ 1, f + g = 2; M1 includes Mn and / or Al, M2 includes at least one of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb, and R includes at least one of N, F, S, Cl.

[0083] In some embodiments, the positive electrode active material may include LiNi 0.7 Co 0.1 Mn 0.2 O2 (NCM712), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.9 Co 0.05 Mn<000…21>O2, or at least one of them. Thus, the specific capacity of the positive electrode active material can be further increased, and the cost of the positive electrode active material can be reduced.

[0084] During the charge and discharge process of the battery, the insertion and extraction and consumption of Li will occur. When the battery discharges to different states, the Li content of the positive electrode active material is also different. In the listing of the positive electrode active material in this application, the molar content of Li is the initial state of the material. When the positive electrode active material is applied to the battery and undergoes cyclic charge and discharge, the molar content of Li will change.

[0085] In the listing of the positive electrode active material in this application, the molar content of O is only the theoretical state value. During the cyclic charge and discharge process of the battery, the lattice oxygen release of the positive electrode active material will cause the molar content of oxygen to change.

[0086] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0087] In some embodiments, the positive electrode active material layer may further optionally include a binder. For example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0088] In some embodiments, the positive electrode active material layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0089] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material. The negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, mesocarbon microbeads, silicon-based materials, tin-based materials, and lithium titanate.

[0090] In some embodiments, the negative electrode active material layer may further include a binder, a conductive agent, and other additives. For example, the binder may include at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS); the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, single-walled carbon nanotubes, graphene, and carbon nanofibers; and the additive may include a thickener, such as sodium carboxymethyl cellulose (CMC-Na).

[0091] The present application does not specifically limit the type of separator; any porous separator with good chemical and mechanical stability may be used. For example, the separator may be made of at least one of fiberglass, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film.

[0092] The battery of the present application may include a battery cell form, a battery module form, and a battery pack form.

[0093] In some embodiments, battery cells may be assembled into a battery module. The number of battery cells contained in a battery module may be one or more. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0094] In some embodiments, the battery modules can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more. The specific number can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0095] In a fourth aspect of the present application, the present application provides an electrical device comprising the aforementioned battery. Thus, the electrical device has all the features and advantages of the aforementioned battery, which will not be described in detail here.

[0096] Battery cells, battery modules, and battery packs can be used as power sources or energy storage units for electrical devices. Electrical devices may include, but are not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, and energy storage systems.

[0097] As an electrical device, a battery, battery module or battery pack can be selected according to its usage requirements.

[0098] As an embodiment, the electric device may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the electric device's requirements for high power and high energy density of the battery, a battery pack or a battery module may be used.

[0099] As another embodiment, the device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be light and thin, and may use a battery cell as a power source.

[0100] The present invention will be described below by way of specific examples. It should be noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Where specific techniques or conditions are not specified in the examples, they are determined according to the techniques or conditions described in the literature in this area or according to the product specifications. Reagents or instruments not specified by manufacturer are all commercially available conventional products.

[0101] Example 1

[0102] Positive electrode preparation:

[0103] The positive electrode active material NCM811, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black are mixed in a weight ratio of 96.5:2:1.5, and N-methylpyrrolidone (NMP) is added. The mixture is stirred under the action of a vacuum mixer until the mixed system becomes a positive electrode slurry with uniform fluidity; the positive electrode slurry is evenly coated on both surfaces of the aluminum foil; the aluminum foil coated with the positive electrode slurry is dried in an oven at 120°C for 8 hours, and finally rolled and cut to obtain positive electrode sheets.

[0104] Negative electrode preparation:

[0105] The negative electrode active materials artificial graphite, silicon oxide, sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP) and single-walled carbon nanotubes (SWCNTs) were mixed in a mass ratio of 79.5:15:2.5:1.5:1:0.5, deionized water was added, and a negative electrode slurry was obtained under the action of a vacuum mixer; the negative electrode slurry was evenly coated on both surfaces of the copper foil; the copper foil coated with the negative electrode slurry was dried at room temperature, and then transferred to an 80°C oven for drying for 10 hours, and finally cold pressed and cut to obtain the negative electrode sheet.

[0106] Preparation of electrolyte:

[0107] In an argon-filled glove box (moisture <10ppm, oxygen <1ppm), the solvents EC:EMC:DEC were mixed in a mass ratio of 3:5:2. A fully dried electrolyte lithium salt, LiPF6, with a mass fraction of 14.5%, and electrolyte additives were quickly added to the mixed solvent. The electrolyte additives included a first additive and a first lithium salt. The first additive was tetravinylsilane and tris(vinyldimethylsilyl)phosphate (CAS No.: 113419-25-3), and the first lithium salt was lithium tetrafluorooxalophosphate. The substance types and mass fractions of the additives in the electrolyte are shown in Table 1. After thorough mixing, the electrolyte was stirred to obtain an electrolyte.

[0108] Preparation of isolation membrane:

[0109] A polyethylene isolation film with a thickness of 8 μm was selected.

[0110] Preparation of lithium-ion batteries:

[0111] The positive electrode sheet, separator, and negative electrode sheet prepared above are wound to obtain a bare cell without liquid injection; the bare cell is placed in an outer package, and the prepared electrolyte is injected into the dried bare cell. After vacuum packaging, standing, formation, shaping, sorting and other processes, a lithium-ion battery is obtained.

[0112] The lithium ion batteries in Examples 2-36 and Comparative Examples 1-7 were all prepared according to the above preparation method. The differences are shown in Table 1, where:

[0113] The difference between Example 2-6 and Example 1 is the amount of lithium tetrafluorooxalate phosphate used;

[0114] The difference between Examples 7-11 and Example 3 is the amount of tetravinylsilane used;

[0115] The difference between Example 12 and Example 2 is the amount of tetravinylsilane used;

[0116] The difference between Examples 13-17 and Example 3 is the amount of tris(vinyldimethylsilyl)phosphate used;

[0117] The difference between Example 18 and Example 2 is the amount of tris(vinyldimethylsilyl)phosphate used;

[0118] The difference between Example 19 and Example 5 is the amount of tris(vinyldimethylsilyl)phosphate used;

[0119] The difference between Examples 20-28 and Example 3 lies in the substance and amount of the second additive;

[0120] The difference between Examples 29-31 and Example 1 is that different negative electrode active materials are used. Specifically, Examples 29, 30, and 31 use natural graphite, hard carbon, and lithium titanate, respectively, to replace the artificial graphite in Example 1.

[0121] The difference between Examples 32-33 and Example 1 is that different positive electrode active materials are used. Specifically, Examples 32 and 33 use LiNi 0.7 Co 0.1 Mn 0.2 O2、LiNi 0.9 Co 0.05 Mn 0.05 O2 replaces NCM811 in Example 1.

[0122] The difference between Examples 34-36 and Example 1 is that different negative electrode sheets are used. Specifically,

[0123] In Example 34, the negative electrode active materials artificial graphite, silicon oxide, sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP) and single-walled carbon nanotubes (SWCNTs) were mixed in a mass ratio of 91.5:3:2.5:1.5:1:0.5, deionized water was added, and the negative electrode slurry was obtained under the action of a vacuum mixer.

[0124] In Example 35, the negative electrode active materials artificial graphite, silicon oxide, sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP) and single-walled carbon nanotubes (SWCNTs) were mixed in a mass ratio of 74.5:20:2.5:1.5:1:0.5, deionized water was added, and the negative electrode slurry was obtained under the action of a vacuum mixer.

[0125] In Example 36, the negative electrode active materials artificial graphite, silicon oxide, sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP) and single-walled carbon nanotubes (SWCNTs) were mixed in a mass ratio of 64.5:30:2.5:1.5:1:0.5, deionized water was added, and the negative electrode slurry was obtained under the action of a vacuum mixer.

[0126] The differences between Comparative Examples 1-7 and Example 3 are: the first additive and the first lithium salt were not added in Comparative Example 1; lithium tetrafluorooxalate phosphate and tris(vinyldimethylsilyl) phosphate were not added in Comparative Example 2; tetravinylsilane and tris(vinyldimethylsilyl) phosphate were not added in Comparative Example 3; tetravinylsilane and lithium tetrafluorooxalate phosphate were not added in Comparative Example 4; tris(vinyldimethylsilyl) phosphate was not added in Comparative Example 5; lithium tetrafluorooxalate phosphate was not added in Comparative Example 6; and tetravinylsilane was not added in Comparative Example 7.

[0127] Table 1

[0128] The electrochemical performance of the lithium-ion batteries obtained in the above comparative examples and embodiments was tested. The test results are shown in Table 2:

[0129] (1) 60℃ storage test: The obtained battery was placed in a 25℃ environment, and the battery was discharged at a constant current of 1C to a cutoff voltage of 2.75V, which was recorded as the initial capacity Q1. It was left for 5 minutes, and then charged at a constant current and constant voltage of 1C to an upper limit voltage of 4.2V, with a cutoff current of 0.05C. The initial voltage of the battery was measured to be V1. The lithium-ion battery was placed in a 60℃ high temperature box for 30 days, taken out and left at room temperature for 4 hours. When the temperature of the battery body dropped to room temperature, the battery voltage V2 was measured, and then the battery was discharged at a constant current of 1C to a cutoff voltage of 2.75V, which was recorded as the capacity Q2. It was left for 5 minutes, and then charged at a constant current and constant voltage of 1C to an upper limit voltage of 4.2V, with a cutoff current of 0.05C, which was recorded as the capacity Q3. The calculation formula used is: voltage drop = V1-V2; capacity retention rate = Q2 / Q1×100%.

[0130] (2) -20℃ EIS test: The battery was charged at 1C constant current and constant voltage to an upper limit voltage of 4.2V and a cutoff current of 0.05C. The fully charged battery was placed at -20℃ for 10 hours for EIS test. The potential value was set to open circuit voltage, the amplitude of the sinusoidal voltage was 1-10mV, and the scanning frequency was 0.1Hz-1000000Hz. The data after the test was fitted and analyzed using Z-view software. The measured SEI film impedance R SEI .

[0131] (3) 45°C cycle test: Place the battery in a (45±2)°C environment and let it rest for 3 hours. Then charge it at a constant current and constant voltage of 1C to an upper limit voltage of 4.2V, with a cutoff current of 0.05C. After the battery is fully charged, let it rest for 5 minutes, then discharge it at a constant current of 1C to a cutoff voltage of 2.75V. The highest discharge capacity of the first three cycles is recorded as the initial capacity Q3. When the cycle reaches 300 cycles, record the final discharge capacity Q4 of the battery. Calculation formula: Capacity retention (%) = Q4 / Q3 × 100%.

[0132] Table 2

[0133] As can be seen from Table 2, the electrolytes in Examples 1-36 all use a combination of electrolyte additives including tetravinylsilane, tris(vinyldimethylsilyl) phosphate, and lithium tetrafluorooxalophosphate. The SEI film impedance on the surface of the negative electrode active material is small, the internal resistance of the battery is small, and the decomposition and gas production of the electrolyte can be effectively suppressed. The battery's cycle performance and high-temperature storage performance are both excellent. In the electrolyte of Comparative Example 1, the first additive and the first lithium salt in the present application are not added, the SEI film impedance of the battery is large, and the cycle performance and high-temperature storage performance are poor; in the electrolyte of Comparative Example 2, only tetravinylsilane is added. Since the SEI film formed by tetravinylsilane on the surface of the negative electrode active material has poor uniformity, the SEI film impedance of the negative electrode active material is still large; in the electrolyte of Comparative Example 3, only lithium tetrafluorooxalophosphate is added, which helps to reduce the SEI film impedance on the surface of the negative electrode active material, but the improvement in the battery cycle performance is small; in the electrolyte of Comparative Example 4, only tris (vinyldimethylsilyl) phosphate is added, which helps to improve the high-temperature storage performance of the battery, but the improvement in the battery cycle performance and the SEI film impedance on the surface of the negative electrode active material is weak; Tetravinylsilane and lithium tetrafluorooxalate phosphate were added to the electrolyte of Example 5, and the SEI film impedance was low. The decomposition and gas production of the electrolyte could be effectively suppressed, and the cycle performance of the battery was good, but the high-temperature storage performance of the battery was poor. Tetravinylsilane and tris(vinyldimethylsilyl) phosphate were added to the electrolyte of Comparative Example 6, and the cycle performance of the battery was better. However, since lithium tetrafluorooxalate phosphate with a film formation potential earlier than that of tetravinylsilane was not added, the SEI film impedance on the surface of the negative electrode active material was large, and the internal resistance of the battery was large. Lithium tetrafluorooxalate phosphate and tris(vinyldimethylsilyl) phosphate were added to the electrolyte of Comparative Example 7, which helped to improve the high-temperature storage performance and SEI film impedance of the battery. However, since the decomposition and gas production of the electrolyte could not be effectively suppressed, the cycle performance of the battery was poor.

[0134] It should be noted that the above embodiments are only examples, and the present application is not limited to the above embodiments. Within the scope of the technical solution of the present application, embodiments having substantially the same composition as the technical idea and exerting the same effect are all included in the technical scope of the present application. Without departing from the scope of the subject matter of the present application, various modifications that can be thought of by those skilled in the art are applied to the embodiments, or some or all of the technical features thereof are replaced by equivalents, and these modifications or replacements do not deviate from the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and description of the present application.

[0135] In addition, as long as there is no conflict between the embodiments, the various technical features mentioned in each embodiment can be combined in any manner. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. An electrolyte additive for a silicon-based negative electrode battery, wherein: The invention comprises a first additive and a first lithium salt, wherein the first additive comprises tetravinylsilane and tris(vinyldimethylsilyl)phosphate, and the first lithium salt comprises lithium tetrafluorooxalate phosphate.

2. The electrolyte additive according to claim 1, wherein The mass fraction of the tetravinylsilane in the electrolyte additive is a, the mass fraction of the lithium tetrafluorooxalate phosphate in the electrolyte additive is b, and a / b is 0.05-20.

3. The electrolyte additive according to claim 1 or 2, wherein The mass fraction of the lithium tetrafluorooxalate phosphate in the electrolyte additive is b, the mass fraction of the tris(vinyldimethylsilyl)phosphate in the electrolyte additive is c, and b / c is 0.05-20.

4. The electrolyte additive according to any one of claims 1 to 3, wherein: Further including: The second additive includes at least one of a high temperature additive, a negative electrode film-forming additive, a lithium salt additive, and a water and acid removal additive.

5. The electrolyte additive according to claim 4, wherein The second additive satisfies at least one of the following conditions: The high temperature additive includes at least one of 1,3-propane sultone, 1,3-propylene sultone, ethylene sulfate, and vinyl sulfite; The negative electrode film-forming additive includes at least one of vinylene carbonate, fluoroethylene carbonate, and vinyl ethylene carbonate; The lithium salt additive includes at least one of lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorobis(oxalatophosphate), lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, and lithium difluorophosphate; The water-removing and acid-removing additive includes at least one of tris(trimethylsilyl)borate and tris(trimethylsilyl)phosphate.

6. An electrolyte, wherein The electrolyte additive comprises the electrolyte additive according to any one of claims 1 to 5.

7. The electrolyte according to claim 6, wherein Further including: A solvent and an electrolyte lithium salt, wherein the electrolyte lithium salt comprises at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

8. The electrolyte according to claim 7, wherein The mass fraction of the electrolyte lithium salt in the electrolyte is 12%-18%.

9. The electrolyte according to any one of claims 6 to 8, wherein: The mass fraction of tetravinylsilane in the electrolyte is 0.1%-2%.

10. The electrolyte according to any one of claims 6 to 9, wherein: The mass fraction of lithium tetrafluorooxalate phosphate in the electrolyte is 0.1%-2%.

11. The electrolyte according to any one of claims 6 to 10, wherein: The mass fraction of tri(vinyldimethylsilyl)phosphate in the electrolyte is 0.1%-2%.

12. The electrolyte according to any one of claims 6 to 11, wherein: The mass fraction of the second additive in the electrolyte is 0.5%-3%.

13. A battery, wherein: The electrolyte additive comprises any one of claims 1 to 5, or the electrolyte comprises any one of claims 6 to 12.

14. The battery according to claim 13, wherein It further comprises a negative electrode plate, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode plate, wherein the negative electrode active material layer comprises a negative electrode active material, and the mass fraction of silicon in the negative electrode active material is 3%-50%.

15. An electrical device, wherein: A battery comprising any one of claims 13 or 14.

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