A non-aqueous electrolyte, a lithium ion battery, a battery module, a battery pack, and a power utilization device

Abstract

This invention provides a non-aqueous electrolyte, a lithium-ion battery, a battery module, a battery pack, and an electrical device. The non-aqueous electrolyte comprises a lithium salt, an organic solvent, and electrolyte additives. The electrolyte additives include 1,3-propanesulfonate lactone, fluoroethylene carbonate, vinylene carbonate, lithium tetrafluoroborate, and compounds represented by Formula I. Formula I. The non-aqueous electrolyte of this invention is applied to lithium-ion batteries to improve their cycle life.

Description

A non-aqueous electrolyte, lithium-ion battery, battery module, battery pack, and electrical device. Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a non-aqueous electrolyte, lithium-ion battery, battery module, battery pack, and electrical device. Background Technology

[0002] High-capacity anode materials are a key breakthrough for improving the energy density of lithium-ion batteries. Compared with graphite anodes, silicon-carbon anodes have significant advantages in both compaction density and specific capacity. Graphite anode materials are currently approaching their theoretical capacity limit and it is difficult to improve them significantly. Their theoretical energy density of 372 mAh / g is also far lower than that of silicon anode materials, which have a theoretical energy density of up to 4200 mAh / g. Meanwhile, silicon anode materials have suitable discharge potential and relatively abundant reserves in nature, making them the most likely anode material to replace graphite.

[0003] However, the commercial application of elemental silicon in lithium-ion batteries faces numerous challenges. Firstly, the lithium-ion insertion / extraction process generates internal stress within the silicon material, leading to volume expansion and structural damage. This can result in issues such as active particle breakage, electrode pulverization, and active material detachment. Secondly, changes in silicon volume cause the solid electrolyte interphase (SEI) film to rupture. Newly exposed silicon produces a new SEI film, continuously consuming lithium ions in the electrolyte and reducing the initial coulombic efficiency. Finally, during cycling, volume changes in the electrode material cause repeated growth and rupture of the SEI film at the silicon anode interface, rapid lithium source depletion, and other issues, all contributing to rapid capacity decay and significantly impacting cycle stability.

[0004] To develop suitable high-performance electrolytes, appropriate electrolyte additives are often added. CN115020809A discloses the combined use of fluoroethylene carbonate with sulfonates and carboxylic acid esters. However, this system has poor compatibility with high-voltage lithium cobalt oxide cathodes. The amount of sulfonates and carboxylic acid esters used is often high, leading to high internal resistance in the battery, affecting capacity utilization, and deteriorating cycle performance. Electrolytes with stable interfaces to the cathode and suitable for high-temperature conditions can inhibit electrolyte oxidation. CN115020812A proposes a phosphate ester compound additive with a side chain containing a trialkoxysilane. The silane in this compound can act as a stabilizer, adsorbing free protons, reducing the content of water and HF in the electrolyte, thereby improving electrolyte stability, improving the high-temperature performance of lithium-ion secondary batteries, and reducing gas generation during storage. However, when substances containing the above structure react with HF, they trap and coordinate F atoms to form fluorosilanes. These fluorosilanes have low boiling points and are easily vaporized, and also have low solubility in the electrolyte. This exacerbates gas generation during high-temperature storage and cycling, thus affecting the battery's electrochemical performance. To address the shortcomings of existing technologies, this invention aims to provide an additive, an electrolyte containing this additive, and a lithium battery. The electrolyte of this invention can form a stable interface on both the positive and negative electrode surfaces, suppressing electrolyte consumption. It also has dehydration and deacidification functions, reducing interfacial side reactions and improving the cycle life of the lithium battery. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a non-aqueous electrolyte, a lithium-ion battery, a battery module, a battery pack, and an electrical device. The non-aqueous electrolyte of this invention is applied to lithium-ion batteries to improve the cycle life of lithium-ion batteries.

[0006] To achieve the above and other related objectives, a first aspect of the present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, and an electrolyte additive, wherein the electrolyte additive comprises 1,3-propanesulfonate lactone, fluoroethylene carbonate, vinylene carbonate, lithium tetrafluoroborate, and a compound represented by Formula I:

[0007] Formula I.

[0008] A second aspect of the present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte of the first aspect of the present invention.

[0009] A third aspect of the present invention provides a battery module comprising the lithium-ion battery described in the second aspect of the present invention.

[0010] A fourth aspect of the present invention provides a battery pack including the battery module described in the third aspect of the present invention.

[0011] A fifth aspect of the present invention provides an electrical device comprising the lithium-ion battery described in the second aspect of the present invention, wherein the lithium-ion battery serves as a power source for the electrical device, and the electrical device includes mobile devices, electric vehicles, power tools, electric trains, satellites, ships, and energy storage systems.

[0012] By adopting the aforementioned technical solution, the beneficial effects of the present invention are:

[0013] This invention uses the compound shown in Formula I (a chain-like unsaturated amide siloxane compound) as an electrolyte additive, which can preferentially react and form a film on the positive and negative electrode surfaces, forming an interfacial film containing LiN3, small molecule amide compounds, etc. on the electrode surface. The compound shown in Formula I can effectively improve the Li... + It enhances the transport capacity of the interfacial membrane, reduces impedance, improves interfacial stability, reduces interfacial side reactions, and improves cycle life and stability.

[0014] The compound shown in Formula I (a chain-like unsaturated amide siloxane compound) inhibits the decomposition of LiBF4 into a film and preferentially reacts at the interface with other electrolyte additives to form a high-conductivity decomposition product. It then forms a stable SEI with other subsequent electrolyte additives. After film formation, it inhibits the excessive decomposition of FEC, reduces interfacial impedance, reduces polarization, and improves the cycle stability of the battery. Attached Figure Description

[0015] Figure 1 shows the 1C cycle performance test of the lithium cobalt oxide / silicon-carbon batteries prepared with the electrolytes in Examples 1, 5, Comparative Example 1 and Comparative Example 5 at 45°C.

[0016] Figure 2 shows the 1C cycle performance test at 45°C of the high-nickel / silicon-carbon batteries prepared with the electrolytes in Examples 4, 6, Comparative Examples 4 and 6.

[0017] Figure 3 shows the formation dQ / dV curves of lithium cobalt oxide / silicon-carbon batteries prepared with the electrolytes in Examples 1, 5, Comparative Examples 1 and 5 at 45°C.

[0018] Figure 4 shows the formation dQ / dV curves of the high-nickel / silicon-carbon batteries prepared with the electrolytes in Examples 4, 6, Comparative Examples 4 and 6 at 25°C.

[0019] Figure 5 shows a comparison of the CV test results of the SiC / Pt / Li three-electrode batteries prepared with the electrolytes in Example 2 and Comparative Example 2.

[0020] Figure 6 shows the XPS test results of the SiC anode after 100 cycles at 1C at 45°C for the lithium cobalt oxide / silicon-carbon battery prepared with the electrolyte in Example 1.

[0021] Figure 7 shows the XPS test results of the SiC anode after 100 cycles at 1C at 45°C using the electrolyte in Comparative Example 1.

[0022] Figure 8 shows a comparison of CV tests of LCO / Pt / Li three-electrode batteries prepared with the electrolytes in Example 3 and Comparative Example 3.

[0023] Figure 9 shows the XPS test results of the LCO cathode after 100 cycles at 1C at 45°C for the lithium cobalt oxide / silicon-carbon battery prepared with the electrolyte in Example 1.

[0024] Figure 10 shows the XPS test results of the LCO cathode after 100 cycles at 45°C using the electrolyte in Comparative Example 1, which was prepared with the electrolyte in Comparative Example 1. Detailed Implementation

[0025] The following details the implementation methods of the non-aqueous electrolyte, lithium-ion battery, battery module, battery pack, and electrical device provided by the present invention.

[0026] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is also expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0027] [Non-aqueous electrolyte]

[0028] This invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, and an electrolyte additive. The electrolyte additive comprises 1,3-propanesulfonate lactone, fluoroethylene carbonate, vinylene carbonate, lithium tetrafluoroborate, and a compound represented by Formula I.

[0029] Formula I.

[0030] The compound represented by Formula I of this invention, containing trimethylsilyl groups and amide groups, can significantly improve film-forming performance under low addition conditions. It can form a stable interfacial film on the surfaces of the positive and negative electrodes, suppress electrolyte consumption, and simultaneously remove water and acid, reduce interfacial side reactions, and improve the cycle life of lithium-ion batteries. Specifically, the compound represented by Formula I is N-[3-(trimethoxysilyl)propyl]-2-acrylamide (CAS: 57577-96-5).

[0031] In the non-aqueous electrolyte provided by this invention, the 1,3-propanesulfonate lactone has a mass percentage of 0.1% to 3%. In some embodiments, the mass percentage of the 1,3-propanesulfonate lactone in the non-aqueous electrolyte can be, for example, 0.1% to 1%, 1% to 2%, or 2% to 3%. Preferably, the mass percentage of the 1,3-propanesulfonate lactone in the non-aqueous electrolyte is 1% to 2%. Within the above range, the advantages are improved high-temperature cycle life of the battery and suppression of battery gas generation; outside the range, the disadvantages are hindered ion transport and decreased high-temperature stability.

[0032] In the non-aqueous electrolyte provided by this invention, the fluoroethylene carbonate ester accounts for 0.1% to 5% of the total mass. In some embodiments, the fluoroethylene carbonate ester accounts for 0.1% to 2% or 2% to 5% of the total mass in the non-aqueous electrolyte. Preferably, the fluoroethylene carbonate ester accounts for 2% to 5% of the total mass in the non-aqueous electrolyte. Within the above range, the advantages are enhanced SEI density and improved battery high-temperature performance and cycle performance. Outside the range, the disadvantage is that excessive addition leads to severe gas generation, affecting battery life.

[0033] In the non-aqueous electrolyte provided by this invention, the mass percentage of vinylene carbonate in the non-aqueous electrolyte is 0.1% to 3%. In some embodiments, the mass percentage of vinylene carbonate in the non-aqueous electrolyte can be, for example, 0.1% to 1%, 1% to 2%, or 2% to 3%. Preferably, the mass percentage of vinylene carbonate in the non-aqueous electrolyte is 1% to 2%. Within the above range, the advantages are enhanced SEI density, suppression of electrolyte decomposition, and improved battery cycle performance. Outside the range, the disadvantages are that excessive amounts can lead to uneven SEI formation, excessive battery internal resistance, and thus affect battery efficiency and cycle life.

[0034] In the non-aqueous electrolyte provided by this invention, the lithium tetrafluoroborate accounts for 0.1% to 3% of the total mass. In some embodiments, the mass percentage of lithium tetrafluoroborate in the non-aqueous electrolyte can be, for example, 0.1% to 0.5%, 0.5% to 3%, 0.1% to 1%, or 1% to 3%. Preferably, the mass percentage of lithium tetrafluoroborate in the non-aqueous electrolyte is 0.1% to 0.5%. Within the above range, the advantages are that the solvent coordination structure can be adjusted to construct a stable inorganic-rich SEI. Outside the range, the disadvantage is that excessive amounts can lead to uneven SEI formation, excessive internal resistance of the battery, and thus affect battery efficiency and cycle life.

[0035] In the non-aqueous electrolyte provided by this invention, the compound represented by Formula I accounts for 0.1% to 3% of the total mass. In some embodiments, the chain-like unsaturated amide siloxane compound represented by Formula I may account for 0.1% to 1%, 1% to 3%, 0.1% to 0.5%, 0.5% to 2%, 2% to 3% of the total mass in the non-aqueous electrolyte, etc. Optionally, the compound represented by Formula I accounts for 1% to 3% of the total mass in the non-aqueous electrolyte. Within the above range, the advantages are improved by increasing Li... + The ability to transmit signals in the interface film reduces impedance, while out-of-range defects reduce interface stability, thus affecting battery life.

[0036] The non-aqueous electrolyte provided by this invention further includes 1,3,6-hexanetrionitrile as an electrolyte additive, wherein the mass percentage of the 1,3,6-hexanetrionitrile in the non-aqueous electrolyte is 0% to 2%. In some embodiments, the mass percentage of the 1,3,6-hexanetrionitrile in the non-aqueous electrolyte is 0% to 0.1%, 0.1% to 2%, 0.1% to 1%, 1% to 2%, 0.1% to 0.5%, 0.5% to 1%, 1% to 1.5%, or 1.5% to 2%. Within the above ranges, the advantage is improved high-voltage performance of the battery; outside the ranges, the disadvantage is disruption of the solvation structure of the electrolyte and increased internal resistance.

[0037] In the non-aqueous electrolyte provided by the present invention, the lithium salt is selected from at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium hexafluorosilicate (LiSiF6), lithium aluminum chloride (LiAlCl4), lithium bis(oxalateborate) (LiBOB), lithium chloride (LiCl), lithium bromide (LiBr), lithium iodide (LiI), lithium trifluoromethanesulfonate (LiOTF), and lithium bis(trifluoromethanesulfonate)imide (LiTFSI).

[0038] In the non-aqueous electrolyte provided by this invention, the concentration of the lithium salt in the non-aqueous electrolyte is 0.5 mol / L to 2 mol / L. In some embodiments, the content of the lithium salt in the non-aqueous electrolyte can also be 0.5 mol / L to 1 mol / L, 1 mol / L to 1.5 mol / L, 1.5 mol / L to 2 mol / L, etc. Within the above range, high lithium-ion conductivity and stable lithium-ion transport can be guaranteed. If the proportion of the lithium salt is too high (the content in the non-aqueous electrolyte is higher than 2 mol / L), it will lead to incomplete lithium salt dissociation, excessive electrolyte viscosity, which will hinder lithium-ion transport and reduce rate performance and low-temperature performance. If the proportion of the lithium salt is too low (the content in the non-aqueous electrolyte is lower than 0.5 mol / L), it will lead to reduced electrolyte ion transport efficiency and poor electrochemical stability.

[0039] In the non-aqueous electrolyte provided by this invention, the organic solvent is selected from cyclic carbonates, chain carbonates, and chain carboxylic esters. In some embodiments, the organic solvent is selected from one or more combinations of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, ethyl propionate, propyl propionate, and methyl butyrate.

[0040] In the non-aqueous electrolyte provided by this invention, the organic solvent accounts for 68% to 75% of the total mass. In some embodiments, the organic solvent may also account for 68% to 70%, 70% to 72%, or 72% to 75% of the total mass. Within these ranges, lithium salts and additives can be dissolved relatively well. If the proportion of the organic solvent is too high (more than 75% of the total mass in the non-aqueous electrolyte), the electrolyte will have poor electrochemical stability. If the proportion of the organic solvent is too low (less than 68% of the total mass in the non-aqueous electrolyte), the lithium salt will not dissociate completely, resulting in excessively high electrolyte viscosity.

[0041] Lithium-ion batteries

[0042] A second aspect of the present invention provides a lithium-ion battery, the lithium-ion battery further comprising a positive electrode, a negative electrode, a separator, and a lithium-ion battery electrolyte, wherein the lithium-ion battery electrolyte is selected from the lithium-ion battery electrolyte of the first aspect of the present invention.

[0043] The positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as a metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The positive electrode active material layer includes a positive electrode active material selected from one or more combinations of lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium manganese iron phosphate, lithium nickel cobalt aluminum oxide, and lithium iron phosphate. The positive electrode active material layer may also include a conductive agent and a binder. Those skilled in the art can select conductive agents and binders suitable for lithium-ion batteries. The conductive agent may include, for example, at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The adhesive may include, for example, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0044] In some embodiments, the positive electrode can be prepared by dispersing the above-mentioned components for preparing the positive electrode, such as the positive electrode material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode after drying, cold pressing and other processes.

[0045] The negative electrode 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. The negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The negative electrode active material layer includes a negative electrode active material selected from one or more combinations of silicon carbide, natural graphite, artificial graphite, lithium titanate, amorphous carbon, and lithium metal. The negative electrode active material layer may also include a plasticizer, a conductive agent, and a binder. The negative electrode active material may be selected from silicon carbide. Those skilled in the art may select plasticizers, conductive agents, and binders suitable for lithium-ion batteries. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The adhesive may be selected from 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), carboxymethyl chitosan (CMCS), and sodium carboxymethyl cellulose (CMC-Na).

[0046] In some embodiments, the negative electrode can be prepared by dispersing the components used to prepare the negative electrode, such as the negative electrode material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode after drying, cold pressing and other processes.

[0047] The separator membrane comprises a composite mainly composed of one or more of polyethylene, polypropylene, polyimide, aramid, ceramic and PVDF.

[0048] The lithium-ion battery is assembled into a button cell, a steel-cased cylindrical cell, an aluminum-cased cylindrical cell, a steel-cased square cell, an aluminum-cased square cell, or a pouch cell.

[0049] The lithium-ion battery provided in the second aspect of this invention can be prepared using methods known in the art. For example, a positive electrode, a separator, and a negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes, and then the layers are stacked to obtain a bare cell; the bare cell is placed in an outer packaging shell, dried, and then injected with lithium-ion battery electrolyte, and after vacuum sealing, settling, formation, and shaping processes, a lithium-ion battery is obtained.

[0050] Battery Module

[0051] A third aspect of the present invention provides a battery module comprising any one or more lithium-ion batteries described in the second aspect of the present invention. The number of lithium-ion batteries in the battery module can be adjusted according to the application and capacity of the battery module.

[0052] Battery Pack

[0053] A fourth aspect of the present invention provides a battery pack comprising any one or more battery modules described in the third aspect of the present invention. That is, the battery pack comprises any one or more lithium-ion batteries described in the second aspect of the present invention.

[0054] The number of battery modules in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0055] Electrical appliances

[0056] A fifth aspect of the present invention provides an electrical device comprising any one or more lithium-ion batteries described in the second aspect of the present invention. The lithium-ion batteries can be used as a power source for the electrical device. Preferably, the electrical device may be, but is 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 and satellites, energy storage systems, etc.

[0057] The beneficial effects of the present invention will be further illustrated below with reference to the embodiments.

[0058] To make the inventive objectives, technical solutions, and beneficial effects of this invention clearer, the invention is further described in detail below with reference to embodiments. However, it should be understood that the embodiments of this invention are merely for illustrative purposes and not for limiting the invention, and the embodiments are not limited to those given in the specification. Unless otherwise specified, specific experimental or operational conditions in the embodiments were prepared under conventional conditions or according to the conditions recommended by the material supplier.

[0059] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0060] In the following embodiments, unless otherwise specified, all the raw materials of the present invention are commercially available or prepared according to conventional methods in the art.

[0061] Example 1

[0062] Preparation of lithium-ion batteries:

[0063] Electrolyte was prepared in a dry room (dew point below -40℃). Diethyl carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), and propyl propionate (PrPr) were mixed in a volume ratio of 10:4:3:3 as an organic solvent, and a total of 100 mL was prepared. LiPF6 with a lithium salt molar concentration of 1.1 mol / L was added to this solvent. Then, 1 wt% of the compound shown in Formula I, 1 wt% of 1,3,6-hexanetrionitrile (HTCN), 1 wt% of 1,3-propanesulfonate lactone (PS), 2 wt% of vinylene carbonate, 5 wt% of fluoroethylene carbonate (FEC), and 0.5 wt% of lithium tetrafluoroborate (LiBF4) were added to the electrolyte. The mixture was stirred until completely dissolved to obtain the lithium-ion battery electrolyte of Example 1. The prepared electrolyte was injected into an LCO / SiC soft-pack battery. After standing, formation, and capacity testing, lithium-ion battery 1 was obtained.

[0064] Example 2

[0065] Preparation of lithium-ion batteries:

[0066] Prepare an electrolyte solution in a dry room (dry room dew point below -40℃). Mix diethyl carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and propyl propionate (PrPr) in a volume ratio of 10:4:3:3 as an organic solvent, and prepare a total of 100 mL. LiPF6 with a lithium salt molar concentration of 1.1 mol / L was added to the solvent. Then, 3 wt% of the total mass of the solvent and lithium salt (the compound shown in Formula I), 1 wt% 1,3,6-hexanetrionitrile (HTCN), 1 wt% 1,3-propanesulfonate lactone (PS), 2 wt% vinylene carbonate, 2 wt% fluoroethylene carbonate (FEC), and 0.5 wt% lithium tetrafluoroborate (LiBF4) were added to the electrolyte. The mixture was stirred until completely dissolved to obtain the lithium-ion battery electrolyte of Example 2. The prepared electrolyte was injected into a three-electrode device with silicon carbon as the working electrode, a lithium sheet as the counter electrode, and a platinum sheet as the reference electrode to obtain the three-electrode battery 1.

[0067] Example 3

[0068] Preparation of lithium-ion batteries:

[0069] An electrolyte was prepared in a dry room (dew point below -40°C). Diethyl carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 5:3:2 as an organic solvent, and a total of 100 mL was prepared. LiPF6 with a lithium salt molar concentration of 1.1 mol / L was added to this solvent. Then, 1 wt% of the compound shown in Formula I, 1 wt% of 1,3-propanesulfonyl lactone (PS), 2 wt% of vinylene carbonate (VC), 2 wt% of fluoroethylene carbonate (FEC), and 0.1 wt% of lithium tetrafluoroborate (LiBF4) were added to the electrolyte, and the mixture was stirred until completely dissolved to obtain the lithium-ion battery electrolyte of Example 3. The prepared electrolyte was injected into a three-electrode device with lithium cobalt oxide as the working electrode, a lithium sheet as the counter electrode, and a platinum sheet as the reference electrode to obtain three-electrode battery 2.

[0070] Example 4

[0071] Preparation of lithium-ion batteries:

[0072] Electrolyte was prepared in a dry room (dew point below -40℃). Diethyl carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 3:2:5 as an organic solvent, and a total of 100 mL was prepared. LiPF6 with a lithium salt molar concentration of 1.1 mol / L was added to this solvent. Then, 1 wt% of the total mass of the solvent and lithium salt of the compound shown in Formula I, 1 wt% of 1,3,6-hexanetrionitrile (HTCN), 1 wt% of 1,3-propanesulfonate lactone (PS), 2 wt% of vinylene carbonate (VC), 5 wt% of fluoroethylene carbonate (FEC), and 0.1 wt% of lithium tetrafluoroborate (LiBF4) were added to the above electrolyte. The mixture was stirred until completely dissolved to obtain the lithium-ion battery electrolyte of Example 4. The prepared electrolyte was injected into an NCM811 / SiC soft-pack battery. After standing, formation, and capacity testing, lithium-ion battery 2 was obtained.

[0073] Example 5

[0074] Preparation of lithium-ion batteries:

[0075] Electrolyte was prepared in a dry room (dew point below -40℃). Diethyl carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 5:3:2 as an organic solvent, and a total of 100 mL was prepared. LiPF6 with a lithium salt molar concentration of 1.1 mol / L was added to this solvent. Then, 1 wt% of the compound shown in Formula I, 2 wt% of 1,3-propanesulfonyl lactone (PS), 1 wt% of vinylene carbonate (VC), 5 wt% of fluoroethylene carbonate (FEC), and 0.5 wt% of lithium tetrafluoroborate (LiBF4) were added to the electrolyte. The mixture was stirred until completely dissolved to obtain the lithium-ion battery electrolyte of Example 5. The prepared electrolyte was injected into an LCO / SiC soft-pack battery. After standing, formation, and capacity testing, lithium-ion battery 3 was obtained.

[0076] Example 6

[0077] Preparation of lithium-ion batteries:

[0078] Electrolyte was prepared in a dry room (dew point below -40℃). Diethyl carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 5:3:2 as an organic solvent, and a total of 100 mL was prepared. LiFSI with a lithium salt molar concentration of 1.1 mol / L was added to this solvent. Then, 1 wt% of the compound shown in Formula I, 2 wt% of 1,3-propanesulfonyl lactone (PS), 1 wt% of vinylene carbonate (VC), 5 wt% of fluoroethylene carbonate (FEC), and 0.5 wt% of lithium tetrafluoroborate (LiBF4) were added to the electrolyte. The mixture was stirred until completely dissolved to obtain the lithium-ion battery electrolyte of Example 6. The prepared electrolyte was injected into an NCM811 / SiC soft-pack battery. After standing, formation, and capacity testing, lithium-ion battery 4 was obtained.

[0079] Comparative Example 1

[0080] Preparation of lithium-ion batteries:

[0081] Electrolyte was prepared in a dry room (dew point below -40℃). Diethyl carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and propyl propionate (PrPr) were mixed in a volume ratio of 10:4:3:3 as an organic solvent, totaling 100 mL. LiPF6 with a lithium salt molar concentration of 1.1 mol / L was added to this solvent. Then, 1 wt% 1,3,6-hexanetrionitrile (HTCN), 1 wt% 1,3-propanesulfonate lactone (PS), 2 wt% vinylene carbonate (VC), 5 wt% fluoroethylene carbonate (FEC), and 0.5 wt% lithium tetrafluoroborate (LiBF4) were added to the electrolyte, and the mixture was stirred until completely dissolved to obtain the lithium-ion battery electrolyte of Comparative Example 1. The prepared electrolyte was injected into an LCO / SiC soft-pack battery. After standing, formation, and capacity testing, lithium-ion battery 5 was obtained.

[0082] Comparative Example 2

[0083] Preparation of lithium-ion batteries:

[0084] Prepare an electrolyte solution in a dry room (dry room dew point below -40℃). Mix diethyl carbonate (EC), propylene carbonate (PC), diester carbonate (DMC), and propyl propionate (PrPr) in a volume ratio of 10:4:3:3 as an organic solvent, and prepare a total of 100 mL. LiPF6 with a lithium salt molar concentration of 1.1 mol / L was added to the solvent. Then, 1 wt% 1,3,6-hexanetrionitrile (HTCN), 1 wt% 1,3-propanesulfonate lactone (PS), 2 wt% vinylene carbonate (VC), 2 wt% fluoroethylene carbonate (FEC), and 0.5 wt% lithium tetrafluoroborate (LiBF4) were added to the electrolyte, and the mixture was stirred until completely dissolved to obtain the lithium-ion battery electrolyte of Comparative Example 2. The prepared electrolyte was injected into a three-electrode device with silicon carbon as the working electrode, lithium foil as the counter electrode, and platinum foil as the reference electrode to obtain three-electrode battery 3. The acid value of the electrolyte was measured before and after testing.

[0085] Comparative Example 3

[0086] Preparation of lithium-ion batteries:

[0087] Electrolyte was prepared in a dry room (dew point below -40℃). Diethyl carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 5:3:2 as an organic solvent, and a total of 100 mL was prepared. LiPF6 with a lithium salt molar concentration of 1.1 mol / L was added to this solvent. Then, 1 wt% of 1,3-propanesulfonyl lactone (PS), 2 wt% of vinylene carbonate (VC), 2 wt% of fluoroethylene carbonate (FEC), and 0.1 wt% of lithium tetrafluoroborate (LiBF4) were added to the electrolyte, and the mixture was stirred until completely dissolved to obtain the lithium-ion battery electrolyte of Comparative Example 3. The prepared electrolyte was injected into a three-electrode device with lithium cobalt oxide as the working electrode, a lithium sheet as the counter electrode, and a platinum sheet as the reference electrode to obtain the three-electrode battery 4.

[0088] Comparative Example 4

[0089] Preparation of lithium-ion batteries:

[0090] Electrolyte was prepared in a dry room (dew point below -40℃). Diethyl carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 3:2:5 as an organic solvent, and a total of 100 mL was prepared. LiPF6 with a lithium salt molar concentration of 1.1 mol / L was added to this solvent. Then, 1 wt% 1,3,6-hexanetrionitrile (HTCN), 1 wt% 1,3-propanesulfonate lactone (PS), 2 wt% vinylene carbonate (VC), 5 wt% fluoroethylene carbonate (FEC), and 0.1 wt% lithium tetrafluoroborate (LiBF4) were added to the electrolyte, and the mixture was stirred until completely dissolved to obtain the lithium-ion battery electrolyte of Comparative Example 4. The prepared electrolyte was injected into an NCM811 / SiC soft-pack battery. After standing, formation, and capacity testing, lithium-ion battery 6 was obtained.

[0091] Comparative Example 5

[0092] Preparation of lithium-ion batteries:

[0093] Electrolyte was prepared in a dry room (dew point below -40℃). Diethyl carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 5:3:2 as an organic solvent, and a total of 100 mL was prepared. LiPF6 with a lithium salt molar concentration of 1.1 mol / L was added to this solvent and stirred until completely dissolved to obtain the lithium-ion battery electrolyte of Comparative Example 5. The prepared electrolyte was injected into an LCO / SiC soft-pack battery. After standing, formation, and capacity testing, lithium-ion battery 7 was obtained.

[0094] Comparative Example 6

[0095] Preparation of lithium-ion batteries:

[0096] Electrolyte was prepared in a dry room (dew point below -40℃). Diethyl carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 5:3:2 as an organic solvent, and a total of 100 mL was prepared. LiFSI with a lithium salt molar concentration of 1.1 mol / L was added to this solvent. Then, 2 wt% of 1,3-propanesulfonyl lactone (PS), 1 wt% of vinylene carbonate (VC), 5 wt% of fluoroethylene carbonate (FEC), and 0.5 wt% of lithium tetrafluoroborate (LiBF4) were added to the electrolyte, and the mixture was stirred until completely dissolved to obtain the lithium-ion battery electrolyte of Comparative Example 6. The prepared electrolyte was injected into an NCM811 / SiC soft-pack battery. After standing, formation, and capacity testing, lithium-ion battery 8 was obtained.

[0097] Table 1 Electrolyte Formulation

[0098]

[0099] Performance testing

[0100] The lithium secondary batteries prepared above were subjected to the following performance tests:

[0101] High-temperature cycle performance test: At 45℃, the formed battery is charged to the cutoff voltage using 1C constant current and constant voltage, and then discharged at 3V using constant current. This charge-discharge cycle test is performed, and the discharge capacity of the first cycle and the discharge capacity of the last cycle are recorded.

[0102] Calculate the capacity retention during high-temperature cycling using the following formula:

[0103] Capacity retention rate = (Last discharge capacity / First discharge capacity) × 100%.

[0104] Figure 1 shows the 1C cycle performance test results of the lithium cobalt oxide / silicon-carbon batteries prepared with the electrolytes in Examples 1, 5, Comparative Example 1, and Comparative Example 5 at 45°C. It can be seen that the retention rates after 600 cycles at 45°C for Examples 1, 5, and Comparative Example 1 are 69.4%, 67.9%, and 57.1%, respectively. Comparative Example 5, without additives, exhibits very poor cycle stability. A comparison between Comparative Example 1 and Example 1 shows that the addition of Compound I can improve the high-temperature cycle stability of the battery. This indicates that the siloxane group in Compound I can effectively improve acid and water removal, suppress side reactions, and enhance battery cycle stability.

[0105] Figure 2 shows the 1C cycle performance test results of the high-nickel / silicon-carbon batteries prepared with the electrolytes in Examples 4, 6, 4, and 6 at 45°C. It can be seen that the retention rates after 600 cycles at 45°C for Examples 4, 6, 4, and 6 are 76.2%, 73.9%, 68.3%, and 54.3%, respectively. The addition of compound I can effectively improve the cycle stability of the battery.

[0106] Figure 3 shows the dQ / dV curves of the lithium cobalt oxide / silicon-carbon batteries prepared with the electrolytes in Examples 1, 5, Comparative Examples 1 and 5 at 25°C. It can be seen that after adding the compound shown in Formula I, the reaction intensity of LiBF4 at 1.7V decreases, and the compound shown in Formula I shows a reaction peak at around 2.0V. The battery in Comparative Example 5 does not form a film before 2.5V, but the reaction is intense after 2.5V. This indicates that the compound shown in Formula I can inhibit the decomposition reaction of LiBF4 and preferentially form a film at the interface compared to other additives. After film formation, it suppresses the reaction intensity of the FEC reaction peak at around 2.75V and reduces the interfacial impedance.

[0107] As can be seen from the dQ / dV curves of the high-nickel / silicon-carbon batteries prepared with the electrolytes in Examples 4, 6, 4, and 6 in Figure 4, the reaction intensity of the sulfide additives decreases at around 2.2V and the electrode reaction increases at around 3.5V after the addition of the compound shown in Formula I. This indicates that the compound shown in Formula I can inhibit the decomposition of the sulfide additives, effectively reduce the interfacial impedance, improve battery efficiency, and extend battery life.

[0108] Figure 5 shows the CV test comparison of the SiC / Pt / Li three-electrode batteries prepared with the electrolytes in Example 2 and Comparative Example 2. It can be seen that in Example 2, the battery after adding the compound shown in Formula I showed the reaction peak of the compound shown in Formula I at around 0.5V. Compared with Comparative Example 2, the polarization of Example 2 is smaller than that of Comparative Example 2. The SiC electrode impedance of the battery decreased after adding the compound shown in Formula I.

[0109] From Figure 6, after 100 cycles at 45°C and 1C, the XPS test results (N spectrum, O spectrum, Si spectrum, F spectrum) of the SiC negative electrode of the lithium cobalt oxide / silicon-carbon battery prepared with the electrolyte in Example 1 show that the compound represented by Formula I is effectively deposited on the negative electrode surface, and 1,3-propanesulfonate lactone is also reduced at the negative electrode to form a stable SEI.

[0110] From the XPS spectra (N, O, and F spectra) of the SiC anode after 100 cycles at 45°C using the electrolyte in Comparative Example 1 (Figure 7), it can be seen that a small number of positive electrode crystal signal peaks (O) appear at the anode. 2- The positive electrode active material dissolves and adheres to the negative electrode interface, which greatly affects the battery performance. Furthermore, the SEI fails to completely cover the negative electrode active material, thus failing to provide effective protection for the battery and significantly impacting its performance.

[0111] As can be seen from the CV test comparison of the LCO / Pt / Li three-electrode batteries prepared with the electrolytes in Example 3 and Comparative Example 3, the polarization of the battery after adding the compound shown in Formula I in Example 3 tends to decrease, and the impedance decreases. Compared with Comparative Example 3, the polarization of Example 3 is less than that of Comparative Example 3, and the impedance of the LCO electrode of the battery decreases after adding the compound shown in Formula I.

[0112] From Figure 9, the XPS spectra (N, O, Si, and F spectra) of the LCO cathode after 100 cycles at 45°C using the electrolyte in Example 1 for the lithium cobalt oxide / silicon-carbon battery can be seen that: the compound represented by Formula I can promote the binding with electrolyte components (such as LiBF4, HF, etc.) to form a more stable CEI film, which helps to suppress side reactions and improve structural stability at high temperatures; at the same time, the formed Si-O-Li bond structure further optimizes the lithium-ion reaction pathway and reduces the dissolution of the cathode active material. Meanwhile, the unsaturated end-group bonds enhance the compactness of the CEI, thereby improving the cycle stability of the battery.

[0113] From the XPS test images (N spectrum, O spectrum, F spectrum) of the LCO cathode after 100 cycles at 1C at 45℃ of the lithium cobalt oxide / silicon-carbon battery prepared with the electrolyte in Comparative Example 1 in Figure 10, it can be seen that: CEI does not uniformly cover the cathode active material, and the electrode is at risk of active material dissolution and capacity loss, which fails to provide effective protection for the battery and greatly affects the battery performance.

[0114] In summary, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0115] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A non-aqueous electrolyte, characterized in that, The non-aqueous electrolyte comprises lithium salt, organic solvent, and electrolyte additives. The electrolyte additives include 1,3-propanesulfonate lactone, fluoroethylene carbonate, vinylene carbonate, lithium tetrafluoroborate, and compounds represented by Formula I. The fluoroethylene carbonate comprises 0.1% to 5% of the non-aqueous electrolyte by mass, and the lithium tetrafluoroborate comprises 0.1% to 0.5% of the non-aqueous electrolyte by mass. The electrolyte additives also include 1,3,6-hexanetrionitrile, which comprises 0% to 2% of the non-aqueous electrolyte by mass. Formula I.

2. The non-aqueous electrolyte according to claim 1, characterized in that, It also includes any one or more of the following conditions: A1) the mass percentage of the 1,3-propanesulfonate lactone in the non-aqueous electrolyte is 0.1% to 3%; A2) the mass percentage of the vinylene carbonate in the non-aqueous electrolyte is 0.1% to 3%; A3) the mass percentage of the compound represented by Formula I in the non-aqueous electrolyte is 0.1% to 3%.

3. The non-aqueous electrolyte according to claim 2, characterized in that, It also includes any one or more of the following conditions: A11) In feature A1), the 1,3-propanesulfonate lactone has a mass percentage of 1% to 2% in the non-aqueous electrolyte; A21) In feature A2), the vinylene carbonate has a mass percentage of 1% to 2% in the non-aqueous electrolyte; A31) In feature A3), the compound represented by formula I has a mass percentage of 1% to 3% in the non-aqueous electrolyte.

4. The non-aqueous electrolyte according to claim 1, characterized in that, The fluoroethylene carbonate accounts for 2% to 5% of the mass of the non-aqueous electrolyte.

5. The non-aqueous electrolyte according to claim 1, characterized in that, It also includes any one or more of the following conditions: B1) The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorosilicate, lithium aluminum chloride, lithium bis(oxalate-borate), lithium chloride, lithium bromide, lithium iodide, lithium trifluoromethanesulfonate, and lithium bis(trifluoromethanesulfonate)imide; B2) The content of the lithium salt in the non-aqueous electrolyte is 0.5 to 2 mol / L; B3) The organic solvent includes cyclic carbonates, chain carbonates, and chain carboxylic acid esters; B4) The mass percentage of the organic solvent in the non-aqueous electrolyte is 68% to 75%.

6. The non-aqueous electrolyte according to claim 5, characterized in that, In feature B3), the organic solvent is selected from one or more combinations of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, ethyl propionate, propyl propionate, and methyl butyrate.

7. A lithium-ion battery, characterized in that, The invention comprises a positive electrode, a negative electrode, a separator membrane spaced between the positive and negative electrodes, and a non-aqueous electrolyte, characterized in that the non-aqueous electrolyte is the non-aqueous electrolyte according to any one of claims 1 to 6.

8. The lithium-ion battery according to claim 7, characterized in that, It also includes any one or more of the following conditions: C1) The negative electrode includes a negative electrode active material, which is selected from one or more combinations of silicon carbon, natural graphite, artificial graphite, lithium titanate, amorphous carbon and lithium metal; C2) The positive electrode includes a positive electrode active material, which is selected from one or more combinations of lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium manganese iron phosphate, lithium nickel cobalt aluminum oxide and lithium iron phosphate; C3) The separator includes a composite mainly composed of one or more of polyethylene, polypropylene, polyimide, aramid, ceramic and PVDF; C4) The lithium-ion battery is assembled as a button cell battery, a steel-cased cylindrical battery, an aluminum-cased cylindrical battery, a steel-cased prismatic battery, an aluminum-cased prismatic battery or a pouch battery.

9. A battery module, characterized in that, Including the lithium-ion battery according to claim 7 or 8.

10. A battery pack, characterized in that, Includes the battery module according to claim 9.

11. An electrical appliance, characterized in that, Includes the lithium-ion battery according to claim 7 or 8, wherein the lithium-ion battery is used as a power source for the device, and the device includes mobile devices, electric vehicles, power tools, electric trains, satellites, ships, and energy storage systems.

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