Electrolyte additive, electrolyte, and battery

Abstract

The application relates to the technical field of batteries, in particular to an electrolyte additive, an electrolyte and a battery. An electrolyte additive comprises a silicon-containing inorganic material and an organic silicon surfactant; the organic silicon surfactant comprises a hydrophilic group and a hydrophobic group. An electrolyte comprises an electrolyte salt, an organic solvent and an additive; wherein the additive comprises the electrolyte additive. The electrolyte additive can react with a lithium metal negative electrode to form a stable SEI film on the surface of the lithium metal, inhibit the occurrence of a side reaction between the electrolyte and the lithium metal, promote the uniform deposition of lithium ions, inhibit the generation of lithium dendrites and improve the cycle life of the lithium metal battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to an electrolyte additive, an electrolyte, and a battery. Background Technology

[0002] In the battery field, with the application of high-nickel materials and silicon-carbon composite materials in recent years, the energy density of lithium-ion batteries (LIBs) has reached over 300 Wh / kg, approaching the limit of 350 Wh / kg for conventional lithium-ion batteries, leaving little room for further improvement. If lithium-ion batteries are to achieve an energy density of over 400 Wh / kg, new material systems need to be developed. Among these, metallic lithium has a high theoretical capacity (3860 mAh / g) and the lowest electrode potential (-3.04 V vs. H / H). + ) and low density (0.534 g / cm³) 3 It is an ideal anode material for next-generation high-energy-density batteries.

[0003] In lithium metal batteries (LMBs), the behavior of lithium ions differs from that of lithium ion insertion / extraction in LIBs. During charging in LMBs, lithium ions gain electrons from an external circuit, and the resulting metallic lithium is deposited as particles on the negative electrode. In LMBs, without improvements to the battery system, lithium ions are prone to… + Uneven deposition of lithium ions can lead to the formation of lithium dendrites, which can cause electrical short circuits and thermal runaway in severe cases. In addition, uneven current density during high-current conditions can exacerbate the uneven deposition of lithium ions.

[0004] In related technologies, commonly used methods for suppressing lithium dendrites mainly include: preparing a three-dimensional framework, interface modification engineering, and optimizing electrolyte composition. These methods can alleviate the growth problem of lithium dendrites to some extent, but each has its limitations. For example, in the method of preparing a three-dimensional framework, the addition of the three-dimensional framework significantly reduces the energy density of the anode material; in the interface modification engineering method, it is difficult to simultaneously achieve the desired flexibility, mechanical strength, ionic conductivity, and lithiophilicity of the interface modification layer, and the preparation process is complex and uniformity is difficult to guarantee. Compared with the methods of preparing a three-dimensional framework and interface modification engineering, the method of optimizing electrolyte formulation is relatively simple and easier to industrialize. However, existing methods for suppressing lithium dendrites by optimizing electrolyte formulation still have problems such as complex operation or difficulty in controlling uniformity, which need further improvement. Summary of the Invention

[0005] In view of this, the present invention aims to at least partially solve one of the technical problems in the related art. To this end, the present invention provides an electrolyte additive, an electrolyte, and a battery, which can form a stable SEI film, promote uniform deposition of lithium ions, and thus help alleviate the problem of lithium dendrite growth.

[0006] To solve the above-mentioned technical problems, this application is implemented as follows:

[0007] According to one aspect of this application, an embodiment of this application provides an electrolyte additive, which includes a silicon-containing inorganic material and an organosilicon surfactant;

[0008] The organosilicon surfactant includes hydrophilic and hydrophobic groups.

[0009] In addition, the electrolyte additive according to this application may also have the following additional technical features:

[0010] In some of these embodiments, the particle size of the silicon-containing inorganic material is in the nanometer range.

[0011] In some embodiments, the particle size range of the silicon-containing inorganic material is 5 nm to 50 nm.

[0012] In some of these embodiments, the silicon-containing inorganic material includes at least one of nano glass powder, nano silicon dioxide, nano silicon suboxide, nano elemental silicon, or nano silicon carbide.

[0013] In some embodiments, the hydrophilic group is a group containing a CO bond, and the hydrophobic group is a group containing a silicon-oxygen bond.

[0014] In some embodiments, the organosilicon surfactant includes at least one of tetraethoxysilane, tetramethoxysilane, trimethoxy(3,3,3-trifluoropropyl)silane, methacryloxypropyltrimethoxysilane, dimethylmethoxy(3,3,3-trifluoropropyl)silane, phenylsilane, methoxytriphenylsilane, ethoxytriphenylsilane, dimethoxytetraphenyldisiloxane, diethoxytetraphenyldisiloxane, or methoxyethoxytetraphenyldisiloxane.

[0015] In some of these embodiments, the mass ratio of the silicon-containing inorganic material to the organosilicon surfactant is (1-10):(1-30).

[0016] According to another aspect of this application, embodiments of this application provide an electrolyte comprising an electrolyte salt, an organic solvent, and additives;

[0017] The additives include the electrolyte additives as described above.

[0018] In some embodiments, the content of the electrolyte additive is 0.02% to 4% of the total mass of the electrolyte.

[0019] In some embodiments, the content of the silicon-containing inorganic material is 0.01% to 2% of the total mass of the electrolyte.

[0020] In some embodiments, the content of the organosilicon surfactant is 0.01% to 2% of the total mass of the electrolyte.

[0021] In some embodiments, the electrolyte salt comprises an organic lithium salt and / or an inorganic lithium salt.

[0022] In some embodiments, the organic solvent includes ester organic solvents and / or ether organic solvents.

[0023] In some embodiments, the electrolyte salt includes at least one of LiPF6, LiFSI, LiTFSI, LiClO4, LiAsF6, LiBF4, LiPO2F2, LiDFOB, or LiBOB.

[0024] In some embodiments, the concentration of the electrolyte salt is 1 to 3 mol / L.

[0025] In some embodiments, the organic solvent includes at least one of ethylene glycol dimethyl ether, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, or methyl propyl carbonate.

[0026] In some embodiments, the organic solvent includes at least one of propylene carbonate and ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, or methyl propyl carbonate.

[0027] According to another aspect of this application, an embodiment of this application provides a battery that includes the aforementioned electrolyte additive, or includes the aforementioned electrolyte.

[0028] Implementing the technical solution of the present invention has at least the following beneficial effects:

[0029] In this embodiment, the provided electrolyte additive includes silicon-containing inorganic materials and organosilicon surfactants; wherein the organosilicon surfactants include hydrophilic and hydrophobic groups; the electrolyte additive can be used in electrolytes, and the electrolyte containing the electrolyte additive can be used in batteries, preferably in lithium metal batteries. Therefore, by using an electrolyte additive containing both silicon-containing inorganic materials and organosilicon surfactants, the hydrophilic and hydrophobic groups contained in the organosilicon surfactants can reduce the surface tension of the silicon-containing inorganic materials in the electrolyte, thus dispersing them and improving their stability in the electrolyte. Simultaneously, the silicon functional groups in the organosilicon surfactants can react with lithium hydroxide (LiOH) on the lithium metal surface, promoting the formation of a stable SEI film; moreover, the silicon-containing inorganic materials can also react with lithium metal to form a silicate-containing SEI film on the lithium metal surface, thereby promoting uniform lithium ion deposition, suppressing lithium dendrite formation, alleviating the lithium dendrite problem in existing lithium metal batteries, and improving the battery's cycle performance.

[0030] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0031] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0032] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0033] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0034] As mentioned in the background section, during the use of lithium metal batteries, uneven deposition of lithium ions on the negative electrode can lead to the growth of lithium dendrites. The presence of lithium dendrites can degrade battery performance, causing safety hazards or affecting cycle life. Optimizing the electrolyte formulation can suppress lithium dendrite formation to some extent, and this method is relatively simpler and easier to industrialize. Furthermore, electrolytes typically contain fluoride salts. Because water cannot be completely removed during electrolyte and battery manufacturing processes, hydrofluoric acid is easily generated in fluoride-containing electrolytes. Hydrofluoric acid readily reacts with the positive and negative electrode materials, affecting battery electrical performance.

[0035] In view of this, the technical solution of this application provides an electrolyte additive that can be used in an electrolyte, which can be used in a battery, such as a lithium metal battery. The technical solution of this application uses a silicon-containing inorganic material that can react with hydrofluoric acid in the electrolyte as the electrolyte additive, and simultaneously adds an organosilicon surfactant to promote the dispersion stability of the silicon-containing inorganic material in the electrolyte. The silicon-containing inorganic material and the organosilicon surfactant can react with the lithium metal anode to form a stable SEI film on the lithium metal surface, inhibiting the occurrence of side reactions between the electrolyte and lithium metal, stabilizing lithium ion transport, inhibiting lithium dendrite growth, and facilitating uniform lithium deposition, thereby improving the cycle life and safety performance of the lithium metal battery. A detailed description of the technical solution is provided below.

[0036] In some embodiments, this application provides an electrolyte additive comprising a silicon-containing inorganic material and an organosilicon surfactant; wherein the organosilicon surfactant comprises hydrophilic groups and hydrophobic groups.

[0037] In the embodiments of this application, the provided electrolyte additive can be used in electrolytes, and the electrolyte containing the electrolyte additive can be used in batteries, preferably in lithium metal batteries. That is, this application provides an electrolyte for use in lithium metal batteries, which contains the electrolyte additive of this invention.

[0038] In this article, the term "electrolyte" refers to the carrier for ion transport in a lithium battery.

[0039] In this article, the term "additive or electrolyte additive" refers to a component present in small amounts in the electrolyte, which can be a gas, liquid, or solid. Conceptually, the main difference between electrolyte additives, organic solvents, and lithium salts (or electrolyte salts) lies in their concentration in the electrolyte.

[0040] In this article, the term "silicon-containing inorganic materials" refers to inorganic silicon materials, that is, inorganic materials containing silicon.

[0041] In this article, the term "organosilicon surfactant" refers to organosilicon materials, that is, a class of surfactants containing one or more organosilicon groups. Organosilicon surfactants can be classified into four main categories according to the chemical properties of the hydrophilic groups in their chemical structure: anionic, cationic, nonionic, and amphoteric.

[0042] The organosilicon surfactants in this application contain both hydrophilic groups and hydrophobic groups.

[0043] Experiments show that the composition of silicon-containing inorganic materials and organosilicon surfactants used in this application as an electrolyte additive has several advantages. First, the silicon-containing inorganic materials can react with hydrofluoric acid in the electrolyte, thereby reducing the side reactions of hydrofluoric acid on the positive and negative electrode materials. Second, the silicon-containing inorganic materials (such as silicon dioxide) can react with lithium metal to form a silicate-containing SEI film on the lithium metal surface. The silicate can act as an ion conductor to promote the transport of lithium ions, promote the uniform deposition of lithium ions, suppress the formation of lithium dendrites, and improve the cycle performance and safety performance of lithium metal batteries. On the other hand, organosilicon surfactants contain both hydrophilic and hydrophobic groups, which can reduce the surface tension of silicon-containing inorganic materials in the electrolyte, thus playing a dispersing role and improving the stability of silicon-containing inorganic materials in the electrolyte. At the same time, the silicon functional groups in organosilicon surfactants can react with LiOH on the lithium metal surface to form Li-O-Si chemical bonds. Its organic functional groups are reactive and compatible with the organic components in the lithium metal SEI film, thereby forming a stable SEI film, which is conducive to promoting the uniform deposition of lithium ions, alleviating the lithium dendrite problem in existing lithium metal batteries, and improving the cycle performance and safety performance of the battery.

[0044] It should be understood that most related technologies reduce the hydrofluoric acid content in the electrolyte by controlling the solvent and lithium salt content. This method can control the hydrofluoric acid content in the electrolyte to a certain extent. However, during battery manufacturing, moisture from the environment and various materials and components used in battery assembly inevitably introduces some moisture. If the control at each stage is not strict, it can easily lead to the generation of excessive hydrofluoric acid in the electrolyte, which can easily cause side reactions with battery materials and affect battery performance. Therefore, adding substances that can react with hydrofluoric acid to the electrolyte can effectively suppress the hydrofluoric acid content. On the other hand, the high reactivity of the lithium metal anode in lithium metal batteries makes it prone to spontaneous reactions with the electrolyte, generating an unstable SEI film. This, in turn, affects the uneven deposition of lithium during subsequent charging and discharging, leading to the continuous growth of lithium dendrites and affecting the cycle life of the battery. Currently, an artificial SEI film is usually applied to the lithium metal surface to promote uniform lithium deposition, but this method is complex to operate and the uniformity is difficult to control. The method of this invention utilizes components dispersed in the electrolyte, namely electrolyte additives dispersed in the electrolyte, to react with lithium during the charging process, forming a highly ionicly conductive SEI film on the lithium metal surface, promoting uniform lithium deposition and effectively alleviating the lithium dendrite problem in existing lithium metal batteries.

[0045] In some embodiments, the particle size of the silicon-containing inorganic material is at the nanometer level. That is, in the embodiments of this application, the silicon-containing inorganic material is preferably an inorganic nano-silicon material, which is a nano-sized silicon particle.

[0046] Inorganic nano-silicon materials are used in the electrolyte additives, which are characterized by high purity, small particle size, and uniform distribution. Furthermore, they also feature a large surface area, high surface activity, and low bulk density.

[0047] In some embodiments, the particle size range of the silicon-containing inorganic material is 5 nm to 50 nm. As an example, the particle size of the silicon-containing inorganic material can be 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, or any combination of the above values.

[0048] By controlling the particle size of silicon-containing inorganic materials within the above range, they are not only easy to prepare and production costs can be reduced, but also have small particle size and uniform distribution. Applying inorganic nano-silicon materials within this particle size range to electrolytes can achieve better results, such as being more easily and uniformly dispersed in electrolytes.

[0049] In some embodiments, the silicon-containing inorganic material includes, but is not limited to, at least one of nano glass powder, nano silica, nano silicon suboxide, nano silicon element, or nano silicon carbide.

[0050] Preferably, the silicon-containing inorganic material is selected from any one or a mixture of at least two of nano glass powder, nano silica, nano silicon suboxide, or nano silicon element in any proportion.

[0051] By selecting the aforementioned nano-inorganic silicon materials, not only can they react with hydrofluoric acid in the electrolyte, reducing the side reactions of hydrofluoric acid on the positive and negative electrode materials, but the silicon dioxide and other nano-inorganic silicon materials can also react with lithium metal to form a silicate-containing SEI film on the lithium metal surface. The silicate can act as an ion conductor to promote the transport of lithium ions, promote the uniform deposition of lithium ions, and inhibit the formation of lithium dendrites, thereby improving the cycle performance and safety performance of the battery.

[0052] In some embodiments, the hydrophilic group is a group containing a CO bond, and the hydrophobic group is a group containing a silicon-oxygen bond. For example, the hydrophilic group may include a CO bond and the organic hydrocarbon connected thereto, and the hydrophobic group may include a silicon-oxygen bond and the organic hydrocarbon connected thereto.

[0053] It should be noted that this application does not limit the specific type of organic hydrocarbons linked to CO bonds or silicon-oxygen bonds, and the specific type can be selected according to the actual situation.

[0054] In this application, the selected silicone surfactant should contain a highly polar portion that can bind to silicon-containing inorganic materials and a low polar portion that can bind to solvents in the electrolyte.

[0055] In some embodiments, the organosilicon surfactant includes, but is not limited to, any one or a combination of at least two of the following: tetraethoxysilane, tetramethoxysilane, trimethoxy(3,3,3-trifluoropropyl)silane, methacryloyloxypropyltrimethoxysilane, dimethylmethoxy(3,3,3-trifluoropropyl)silane, phenylsilane, methoxytriphenylsilane, ethoxytriphenylsilane, dimethoxytetraphenyldisiloxane, diethoxytetraphenyldisiloxane, or methoxyethoxytetraphenyldisiloxane. For the sake of brevity, all combinations within the above range will not be listed individually.

[0056] Therefore, by selecting several organosilicon surfactants such as tetraethoxysilane and tetramethoxysilane, which contain both highly polar portions that can combine with silicon-containing inorganic materials and low polar portions that can combine with solvents in the electrolyte, the stability of the electrolyte system can be improved. They can also react with LiOH on the lithium metal surface to form Li-O-Si chemical bonds. Their organic functional groups are reactive and compatible with the organic components in the lithium metal SEI film, thus forming a stable SEI film.

[0057] In this application, the mass ratio of silicon-containing inorganic materials and organosilicon surfactants can affect the uniformity or stability of the electrolyte system, or the film formation effect at the electrode interface, the impedance of the electrode interface, etc., and ultimately affect the cycle performance or safety performance of the battery.

[0058] In some embodiments, the mass ratio of silicon-containing inorganic material to organosilicon surfactant is (1-10):(1-30). As examples, the mass ratio of silicon-containing inorganic material to organosilicon surfactant can be 1:2, 1:4, 1:10, 1:30, 5:2, 5:1, 10:1, 8:1, etc.

[0059] By maintaining the mass ratio of silicon-containing inorganic materials to organosilicon surfactants within the aforementioned range, it is possible to ensure that the silicon-containing inorganic materials are uniformly and stably distributed in the electrolyte, forming a homogeneous phase. This is beneficial for improving the uniformity and stability of the electrolyte system, and also helps to reduce the amount of electrolyte additives used, thus avoiding the deterioration of electrolyte conductivity. Furthermore, it can form a dense, stable, and uniform interfacial film at the electrode interface, effectively suppressing side reactions.

[0060] Therefore, this invention employs an electrolyte additive comprising silicon-containing inorganic materials and organosilicon surfactants. The organosilicon surfactants, with their combined hydrophilic and hydrophobic groups, reduce the surface tension of the silicon-containing inorganic materials in the electrolyte, thus dispersing them and improving their stability. Simultaneously, the silicon functional groups in the organosilicon surfactants react with lithium hydroxide (LiOH) on the lithium metal surface, promoting the formation of a stable SEI film. Furthermore, the silicon-containing inorganic materials also react with lithium metal to form a silicate-containing SEI film on the lithium metal surface, thereby promoting uniform lithium ion deposition, suppressing lithium dendrite formation, alleviating the lithium dendrite problem in existing lithium metal batteries, improving battery cycle performance, and enhancing battery safety.

[0061] In some embodiments, this application provides an electrolyte comprising an electrolyte salt, an organic solvent, and additives; wherein the additives include the electrolyte additives described above.

[0062] It should be understood that the electrolyte includes the aforementioned electrolyte additives. Therefore, all the features and advantages described above regarding the “electrolyte additives” also apply to the “electrolyte”, and will not be repeated here.

[0063] By controlling the mass content of electrolyte additives within a suitable range, such as controlling the mass content of silicon-containing inorganic materials and organosilicon surfactants within a suitable range, the electrolyte can enable the battery to have both excellent rate performance and good cycle performance and safety performance.

[0064] In some embodiments, the content of the electrolyte additive is 0.02% to 4% of the total mass of the electrolyte, and more particularly, it can be 0.05% to 3%. For example, including but not limited to, 0.02%, 0.04%, 0.08%, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 3%, 4%, including any values ​​therein and all ranges and subranges.

[0065] In some embodiments, the content of silicon-containing inorganic material is 0.01% to 2% of the total mass of the electrolyte, and more particularly, it can be 0.05% to 1.5%. For example, including but not limited to, 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, including any values ​​therein and all ranges and subranges.

[0066] In some embodiments, the content of the silicone surfactant is 0.01% to 2% of the total mass of the electrolyte, and more particularly, it can be 0.05% to 1.5%. For example, including but not limited to, 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, including any values ​​therein and all ranges and subranges.

[0067] By controlling the mass content of silicon-containing inorganic materials and organosilicon surfactants in the electrolyte within the above-mentioned range, it is beneficial to improve the uniformity or stability of the electrolyte system, and also helps to reduce the amount of electrolyte additives used, thus avoiding the deterioration of electrolyte conductivity. A dense, stable, and uniform interfacial film can be formed at the electrode interface, effectively suppressing side reactions and alleviating the formation of lithium dendrites. This enables batteries containing this electrolyte to have both excellent rate performance and good cycle performance and safety performance.

[0068] There are no specific limitations on the electrolyte lithium salt used in this application; it can be appropriately selected according to actual needs, as long as it can achieve the technical solution of this application. In some embodiments, the electrolyte salt includes organic lithium salts and / or inorganic lithium salts. That is, in the embodiments of this application, the electrolyte lithium salt can be selected from one or more of organic lithium salts and inorganic lithium salts.

[0069] For example, in some embodiments, the electrolyte salt includes, but is not limited to, any one or a combination of at least two of LiPF6 (lithium hexafluorophosphate), LiTFSI (lithium bis(trifluorosulfonyl)imide), LiFSI (lithium bis(fluorosulfonyl)imide), LiClO4, LiAsF6, LiBF4, LiPO2F2, LiDFOB, or LiBOB. For the sake of brevity, all combinations within the above range will not be listed individually.

[0070] In some embodiments, the concentration of the electrolyte salt is 1 to 3 mol / L, preferably 1 to 2 mol / L. For example, including but not limited to 0.5 mol / L, 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, including any values ​​therein and all ranges and subranges.

[0071] There are no specific limitations on the types of organic solvents used in this application; they can be appropriately selected according to actual needs, as long as they can achieve the technical solution of this application. As an example, in the embodiments of this application, the organic solvent can be selected from at least one of carbonates, carboxylic acid esters, sulfates, phosphates, amides, nitriles, or ethers. For example, including but not limited to, the organic solvent can be selected from ester organic solvents, ether organic solvents, or a mixture of ester organic solvents and ether organic solvents.

[0072] By way of example, in some embodiments, the organic solvent includes, but is not limited to, one or more of ethylene glycol dimethyl ether, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, or methyl propyl carbonate.

[0073] In other embodiments, the organic solvent includes, but is not limited to, one or more of propylene carbonate and ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, or methyl propyl carbonate.

[0074] In addition, in other embodiments, the organic solvent may be selected from one or more of the following known in the art: acetonitrile, sulfolane, dimethyl sulfoxide, ethylene sulfite, propylene sulfite, triethyl phosphate, methyl ethyl phosphate, fluorinated cyclic organic esters, sulfur-containing cyclic organic esters, etc.

[0075] The organic solvent may be a mixture of two or more of the aforementioned organic solvents. Their proportions are not particularly limited and can be appropriately selected according to actual needs, as long as the technical solution of this application can be achieved. For example, in the embodiments of this application, when the organic solvent contains two different organic solvents, they can be mixed and used in volume ratios of 1:1, 2:8, 3:7, 4:6, 8:2, 7:3, 6:4, etc.

[0076] There is no specific limitation on the content of the aforementioned organic solvent in the electrolyte; it can be appropriately selected according to actual needs, as long as the technical solution of this application can be achieved. For example, in the embodiments of this application, the content of the organic solvent in the electrolyte can be 50wt% to 90wt%, and more specifically, 70wt% to 80wt%. Examples include, but are not limited to, 50%, 55%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, etc., including any values ​​and all ranges and subranges thereof.

[0077] In addition, as an improvement to the electrolyte of this application, other functional additives known in the art that can be used to improve the performance of lithium batteries may be added to the electrolyte, such as flame retardant additives, overcharge prevention additives, conductive additives, and other functional additives, which will not be described in detail here.

[0078] Optionally, the electrolyte of this application can be prepared using methods known in the art. As an example, the preparation of the electrolyte includes the following steps: first, a basic electrolyte is prepared, which includes an organic solvent and an electrolyte salt (such as a lithium salt); then, nanoscale silicon-containing inorganic materials and organosilicon surfactants are added to the above-mentioned basic electrolyte, and the silicon-containing inorganic materials are uniformly dispersed in the electrolyte by ultrasonication to obtain a homogeneous suspension.

[0079] In some embodiments, this application provides a battery that includes the aforementioned electrolyte additive or the aforementioned electrolyte.

[0080] Preferably, the battery is a lithium metal battery.

[0081] The battery provided in this application, such as a lithium metal battery, includes a positive electrode, a separator, a negative electrode, and an electrolyte in any embodiment.

[0082] Optionally, the aforementioned negative electrode sheet can be a negative electrode sheet containing metallic lithium, such as a metallic lithium sheet, a copper-lithium sheet, or a negative electrode sheet obtained by combining metallic lithium with other functional layer phases.

[0083] Optionally, the aforementioned positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and comprising a positive electrode active material. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0084] There are no specific limitations on the type of positive current collector used in the positive electrode sheet of this application. It can be appropriately selected according to actual needs, as long as it can achieve the technical solution of this application. As an example, the positive current collector can be selected from several of the following: aluminum, nickel, titanium, stainless steel, carbon, aluminum sheet coated with nickel or titanium, and stainless steel sheet coated with nickel or titanium.

[0085] There are no specific limitations on the type of positive electrode active material used in the positive electrode sheet of this application. It can be appropriately selected according to actual needs, as long as it can achieve the technical solution of this application. As an example, the positive electrode active material can be selected from one or more of lithium-containing layered metal oxides, lithium-free metal oxides, spinel-structured lithium metal oxides, lithium metal phosphates, lithium metal fluoride sulfates, and lithium metal vanadates. Exemplarily, the positive electrode active material includes, but is not limited to, lithium cobalt oxide (LCO), nickel-cobalt-manganese ternary materials (NMC), lithium nickel-cobalt-aluminum oxide (NCA), lithium manganese oxide (LiMn2O4), and lithium iron phosphate (LFP).

[0086] Optionally, the positive electrode film layer may also include a conductive agent and a binder. This application does not limit the specific types of conductive agents and binders; types or components known in the art that can be used in positive electrode sheets of batteries may be selected.

[0087] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0088] I. Battery Preparation

[0089] Example 1

[0090] (1) Preparation of electrolyte

[0091] A basic electrolyte is provided, wherein the organic solvents in the basic electrolyte are ethylene carbonate (EC) and dimethyl carbonate (DMC), and the electrolyte salt is lithium hexafluorophosphate (LiPF6);

[0092] To a basic electrolyte of LiPF6 (concentration 1 mol / L) containing EC and DMC (volume ratio of EC and DMC 1:1), 0.05% and 0.2% by mass of nano-silica (average particle size 10 nm) and tetraethoxysilane were added, and the mixture was magnetically stirred at 500 r / min for 10 h. After uniform mixing, the electrolyte was obtained.

[0093] (2) Preparation of positive electrode sheet

[0094] The positive electrode active material NCM613, conductive carbon black (Super P) and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 96:2:2 and dispersed in N-methylpyrrolidone (NMP) solvent. The mixture was stirred evenly to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on the positive electrode current collector aluminum foil and dried at 80°C for 12 hours to form a positive electrode active material layer. The material was then pressed and cut into 3cm×4cm sheets to serve as positive electrode sheets.

[0095] (3) Preparation of negative electrode sheet

[0096] The 50μm copper-lithium strip was cut into 3.4cm×4.4cm pieces using a cutting machine to serve as the negative electrode.

[0097] (4) Separating membrane

[0098] A 4cm×5cm Celgard2023 membrane (polypropylene-polyethylene-polypropylene three-layer membrane) was used as the separator.

[0099] (5) Battery manufacturing

[0100] After welding the tabs of the positive and negative electrode sheets from Example 1 using an ultrasonic welding machine, the positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrode sheets to isolate them. The cells are then placed in an outer aluminum-plastic film, and the electrolyte prepared above is injected into the dried cell. After vacuum sealing, settling, and formation processes, a battery (lithium metal battery) is obtained.

[0101] In Examples 2 to 9, the amount of electrolyte additives in the electrolyte was adjusted (the amount of silicon-containing inorganic materials was mainly adjusted in Examples 2 to 5, and the amount of organosilicon surfactants was mainly adjusted in Examples 6 to 9). Other parameters remained basically the same as in Example 1. Specific parameters are shown in Table 1.

[0102] In Examples 10 to 13, the types of each component in the electrolyte additive were adjusted (Examples 10 and 11 mainly adjusted the types of silicon-containing inorganic materials, and Examples 12 and 13 mainly adjusted the types of organosilicon surfactants). Other parameters remained basically the same as in Example 1. Specific parameters are shown in Table 1.

[0103] In Example 14, the types of electrolyte salts and organic solvents in the base electrolyte were adjusted, while other parameters remained basically the same as in Example 1. Specific parameters are shown in Table 1.

[0104] In Comparative Examples 1 to 3, the composition of the electrolyte was adjusted so that the electrolyte contained no electrolyte additives or only one of silicon-containing inorganic materials and organosilicon surfactants. Other parameters were kept basically consistent with those in Example 1. Specific parameters are shown in Table 1.

[0105] In Comparative Examples 4 to 6, the composition of the electrolyte was adjusted so that the electrolyte contained no electrolyte additives or only one of silicon-containing inorganic materials and organosilicon surfactants. Other parameters were kept basically consistent with those in Example 14. Specific parameters are shown in Table 1.

[0106] Table 1

[0107]

[0108]

[0109] Note: In Table 1, " / " indicates that it has not been added.

[0110] II. Testing Methods

[0111] (1) Hydrofluoric acid content test: The current signal of hydrofluoric acid in the electrolyte is measured using an electrochemical tester to obtain the hydrofluoric acid (HF) content.

[0112] (2) Conductivity (25℃) test: The conductivity of the lithium-ion battery electrolyte was determined by the alternating impedance method (EIS) using a conductivity meter; by applying small alternating current signals of different frequencies, the characteristics of the electrochemical reaction in the lithium battery system were measured, thereby obtaining the electrolyte conductivity.

[0113] (3) Cyclic performance (capacity retention rate after 100 cycles) test: At 25℃, charge to 4.3V with a constant current at a current density of 0.2C, and record the charging capacity at this point as the initial charging capacity; then discharge to 3.0V with a constant current at a current density of 0.5C, and record the discharging capacity at this point as the initial discharging capacity. Repeat the above charge-discharge cycle for 100 cycles, and record the discharging capacity on the 100th cycle; the capacity retention rate after 100 cycles can be calculated by the following formula:

[0114] Capacity retention rate of the 100th cycle = Discharge capacity of the 100th cycle / Initial discharge capacity * 100%.

[0115] (4) Rate performance (capacity retention rate at different discharge rates at 25℃) test: At 25℃, charge at a rate of 0.2C to 4.3V, then discharge at a rate of 0.2C to 3.0V, cycle for 5 times to obtain a stable capacity, and record the discharge capacity at this time as the 0.2C discharge capacity; then charge at a rate of 0.2C to 4.3V, and continue to discharge at a high rate of XC (X=0.5, 1, 2, 3) to 3.0V, cycle for 5 times to obtain a stable capacity, and record the discharge capacity at this time as the XC (X=0.5, 1, 2, 3) discharge capacity retention rate = XC (X=0.5, 1, 2, 3) discharge capacity / 0.2C discharge capacity * 100%.

[0116] The results of the hydrofluoric acid content test and conductivity test are shown in Table 2 below.

[0117] The results of the above cycle performance test and rate performance test are shown in Table 3 below.

[0118] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0119] Table 2

[0120] Group Hydrofluoric acid content (mg / kg) <![CDATA[Conductivity at 25°C (g / cm 3 )]]> Example 1 37.5 15.7 Example 2 34.2 15.4 Example 3 26.5 14.5 Example 4 26.1 13.2 Example 5 25.8 12.9 Example 6 38.6 15.9 Example 7 37.9 15.5 Example 8 37.3 15.2 Example 9 37.5 14.9 Example 10 38.2 15.6 Example 11 38.2 15.8 Example 12 36.2 15.4 Example 13 36.7 15.5 Example 14 37.1 14.5 Comparative Example 1 73.6 16.7 Comparative Example 2 42.5 15.4 Comparative Example 3 70.8 14.9 Comparative Example 4 50.3 15.2 Comparative Example 5 32.1 14.9 Comparative Example 6 48.4 14.8

[0121] Table 3

[0122]

[0123]

[0124] As can be seen from the data in Tables 2 and 3 above, in general, compared with Comparative Examples 1 to 6, the batteries using the electrolytes of Examples 1 to 14 of the present invention can reduce the hydrofluoric acid (HF) content and improve the conductivity to a certain extent due to the addition of the electrolyte additives provided in this application to the electrolyte, and can also improve the rate performance and cycle performance of the battery.

[0125] Furthermore, the data in Table 2 also show that the HF content decreases with increasing electrolyte additive dosage, indicating that the added nano-silica can react with the hydrofluoric acid powder in the electrolyte, reducing its HF content. Additionally, the conductivity decreases with increasing nano-silica content. This indicates that electrolyte additives composed of silicon-containing inorganic materials and organosilicon surfactants increase the viscosity of the electrolyte, leading to a decrease in conductivity. The more additives, the higher the viscosity and the lower the conductivity. The addition of silicon-containing inorganic materials reduces the HF content in the electrolyte, but this is also affected by the amount of organosilicon surfactant added. Organosilicon surfactants can improve the dispersibility of inorganic silicon materials in the electrolyte, thus improving electrolyte stability. A silicon-containing inorganic material to organosilicon surfactant ratio of 5:2 provides good dispersibility. Therefore, the more silicon-containing inorganic materials added, and the more appropriate the amount of organosilicon surfactant, the lower the HF content in the electrolyte.

[0126] Table 3 data also shows that organosilicon surfactants spontaneously form a stable SEI film on the lithium metal surface, improving the stability of lithium metal during cycling. When the content of silicon-containing inorganic materials is 0.5% and the mass ratio of silicon-containing inorganic materials to organosilicon surfactants is 5:2, the resulting battery exhibits the best rate and cycle performance. In contrast, the electrolyte without additives in the comparative example shows the worst rate and cycle performance. This indicates that an appropriate amount of nano-silica can reduce the hydrofluoric acid content in the battery, promote uniform lithium deposition, and improve its rate and cycle performance. However, adding too much nano-silica will reduce the electrolyte conductivity, decrease ion migration rate, and increase battery polarization, thus negatively impacting the battery's rate and cycle performance. Furthermore, the decrease in rate and cycle performance of the electrolyte without organosilicon surfactants in the comparative example is because organosilicon surfactants can improve the stability of the electrolyte and simultaneously enhance the stability and conductivity of the SEI.

[0127] Furthermore, by adjusting the content of silicon-containing inorganic materials and organosilicon surfactants, the HF content and conductivity in the electrolyte can be changed, affecting the kinetic and cycle performance of the battery, thereby improving the battery's rate capability and cycle performance.

[0128] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0129] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0130] It should be noted that the terms "and / or" or " / " used herein are merely descriptions of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The singular forms "a," "described," and "the" used in the embodiments of the invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0131] In the detailed description and claims, 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, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte, characterized in that, The electrolyte includes electrolyte salts, organic solvents, and additives; The additives include silicon-containing inorganic materials and organosilicon surfactants; the organosilicon surfactants include hydrophilic groups and hydrophobic groups. The organosilicon surfactant includes tetraethoxysilane; The silicon-containing inorganic material includes nano-silicon dioxide; The mass ratio of the silicon-containing inorganic material to the organosilicon surfactant is 5:2 or 5:

1. The content of the silicon-containing inorganic material is 0.5% to 1% of the total mass of the electrolyte.

2. The electrolyte according to claim 1, characterized in that, The particle size range of the silicon-containing inorganic material is 5 nm to 50 nm.

3. The electrolyte according to claim 1, characterized in that, The content of the electrolyte additive is 0.02% to 4% of the total mass of the electrolyte.

4. The electrolyte according to claim 1, characterized in that, The electrolyte salt includes organic lithium salts and / or inorganic lithium salts; and / or, The organic solvents include ester organic solvents and / or ether organic solvents.

5. The electrolyte according to claim 1, characterized in that, The electrolyte salt includes at least one of LiPF6, LiFSI, LiTFSI, LiClO4, LiAsF6, LiBF4, LiPO2F2, LiDFOB, or LiBOB; And / or, the concentration of the electrolyte salt is 1 to 3 mol / L.

6. The electrolyte according to claim 1, characterized in that, The organic solvent includes at least one of ethylene glycol dimethyl ether, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, or methyl propyl carbonate.

7. A battery, characterized in that, The battery comprises the electrolyte according to any one of claims 1 to 6.

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