Non-aqueous electrolyte, lithium ion battery, battery module, battery pack and electric device

Abstract

The invention provides a non-aqueous electrolyte, a lithium ion battery, a battery module, a battery pack and a power utilization device, the non-aqueous electrolyte comprises a lithium salt, an organic solvent and an electrolyte additive, and the electrolyte additive comprises 1, 3-propane sultone, fluoroethylene carbonate, vinylene carbonate, lithium tetrafluoroborate and a compound I shown in the formula I. The non-aqueous electrolyte is applied to the lithium ion battery, and the cycle life of the lithium ion battery is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a non-aqueous electrolyte, a lithium ion battery, a battery module, a battery pack and a power utilization device. BACKGROUND

[0002] High-capacity anode materials are an important breakthrough for improving the energy density of lithium ion batteries. Silicon-carbon anodes have obvious advantages in compaction density and specific capacity compared with graphite anodes. The theoretical energy density of graphite anodes has reached the upper limit and it is difficult to improve further. The theoretical energy density of silicon anodes is 4200 mAh / g, which is much higher than that of graphite anodes (372 mAh / g). In addition, silicon anodes have suitable discharge potentials and abundant reserves in nature, and are considered to be the most likely anode material to replace graphite.

[0003] However, there are many problems in the commercial application of elemental silicon in lithium ion batteries. On the one hand, lithium ions are intercalated and deintercalated in the silicon material, which generates internal stress and causes volume expansion and damage to the material structure. This may lead to problems such as active particle breakage, electrode pulverization and active material shedding. On the other hand, the solid electrolyte interface film (SEI) will be broken due to the change in the volume of silicon, and new silicon exposed on the surface will produce a new SEI film, which will continuously consume lithium ions in the electrolyte and reduce the first coulombic efficiency. Finally, during the cycling process, the repeated growth and rupture of the SEI film at the interface of the silicon anode, the rapid consumption of lithium sources and other problems collectively cause rapid capacity decay, which greatly affects the cycling stability.

[0004] In order to develop a suitable high-performance electrolyte, a suitable electrolyte additive is often added to the electrolyte, CN115020809A discloses the cooperation of fluoroethylene carbonate and sulfonate compounds, carboxylate compounds, but the system is not suitable for high-voltage lithium cobaltate positive electrode, the use amount of sulfonate compounds and carboxylate compounds is often high, which leads to high battery resistance, affects the capacity, and deteriorates the cycle performance. The electrolyte stable at high temperature and with stable positive electrode interface can inhibit the oxidation of the electrolyte, CN115020812A proposes a phosphonate compound additive with a side chain containing trialkoxy silane, the silane in the compound can be used as a stabilizer to adsorb free protons, reduce the content of water and HF in the electrolyte, thereby improving the stability of the electrolyte, improving the high-temperature performance of the lithium ion secondary battery, and reducing the gas production during storage. However, when the substance with the above structure reacts with HF, it captures and coordinates with F atoms to form fluorosilane, but the substance has a low boiling point and is easy to vaporize, and has a low solubility in the electrolyte, thereby aggravating the gas production problem of the battery during high-temperature storage and high-temperature cycle, and further affecting the electrochemical performance of the battery. In view of the shortcomings of the prior art, the purpose of the present application is to provide an additive, an electrolyte containing the additive and a lithium battery, the electrolyte of the present application can form a stable interface on the surface of the positive and negative electrodes, inhibit the consumption of the electrolyte, and has the functions of water and acid removal, reduces the interface side reaction, and improves the cycle life of the lithium battery. SUMMARY

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a non-aqueous electrolyte, a lithium ion battery, a battery module, a battery pack and a power utilization device, the non-aqueous electrolyte of the present application is applied to a lithium ion battery to improve the cycle life of the lithium ion battery.

[0006] To achieve the above-mentioned purposes and other related purposes, the first aspect of the present application provides a non-aqueous electrolyte, which comprises a lithium salt, an organic solvent and an electrolyte additive, the electrolyte additive comprises 1,3-propane sulfone, fluoroethylene carbonate, vinylene carbonate, lithium tetrafluoroborate and a compound represented by formula I: Formula I.

[0007] The second aspect of the present application provides a lithium ion battery, which comprises a positive electrode, a negative electrode, a separator arranged between the positive electrode and the negative electrode, and the non-aqueous electrolyte of the first aspect of the present application.

[0008] The third aspect of the present application provides a battery module, which comprises the lithium ion battery of the second aspect of the present application.

[0009] The fourth aspect of the present application provides a battery pack, which comprises the battery module of the third aspect of the present application.

[0010] A fifth aspect of the present application provides a power utilization device comprising the lithium ion battery of the second aspect of the present application, the lithium ion battery serving as a power source of the power utilization device, the power utilization device comprising a mobile device, an electric vehicle, an electric tool, an electric train, a satellite, a ship and an energy storage system.

[0011] By adopting the foregoing technical solutions, the present application has the following beneficial effects: The compound (chain unsaturated amide siloxane compound) shown in Formula I is used as an electrolyte additive, can be preferentially reacted into a film on the positive and negative electrode surfaces, forms an interface film containing LiN3, small molecule amide compounds and the like on the electrode surface, and can effectively improve the Li + The compound (chain unsaturated amide siloxane compound) shown in Formula I can inhibit the decomposition of LiBF4 into a film, and preferentially reacts with other electrolyte additives at the interface and forms a high-conductivity decomposition product, and together with the subsequent other electrolyte additives, forms a stable SEI, inhibits excessive decomposition of FEC after film formation, reduces the interface impedance, reduces the polarization, and improves the cycle stability of the battery.

[0012] The compound (chain unsaturated amide siloxane compound) shown in Formula I can inhibit the decomposition of LiBF4 into a film, and preferentially reacts with other electrolyte additives at the interface and forms a high-conductivity decomposition product, and together with the subsequent other electrolyte additives, forms a stable SEI, inhibits excessive decomposition of FEC after film formation, reduces the interface impedance, reduces the polarization, and improves the cycle stability of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 A 1C cycle performance test graph of a lithium cobaltate / silicon-carbon battery prepared by using the electrolyte in Example 1, Example 5, Comparative Example 1 and Comparative Example 5 at 45°C is shown; Figure 2 A 1C cycle performance test graph of a high-nickel / silicon-carbon battery prepared by using the electrolyte in Example 4, Example 6, Comparative Example 4 and Comparative Example 6 at 45°C is shown; Figure 3 A formation dQ / dV curve of a lithium cobaltate / silicon-carbon battery prepared by using the electrolyte in Example 1, Example 5, Comparative Example 1 and Comparative Example 5 at 45°C is shown; Figure 4 A formation dQ / dV curve of a high-nickel / silicon-carbon battery prepared by using the electrolyte in Example 4, Example 6, Comparative Example 4 and Comparative Example 6 at 25°C is shown; Figure 5 A CV test comparison graph of a SiC / Pt / Li three-electrode battery prepared by using the electrolyte in Example 2 and Comparative Example 2 is shown; Figure 6 A SiC negative electrode XPS test graph of a lithium cobaltate / silicon-carbon battery prepared by using the electrolyte in Example 1 at 45°C after 100 cycles is shown; Figure 7XPS test chart of SiC negative electrode after 1C cycle at 45℃ for 100 cycles of lithium cobalt oxide / silicon carbon battery prepared by electrolyte in Comparative Example 1; Figure 8 CV test comparison chart of LCO / Pt / Li three-electrode battery prepared by electrolyte in Example 3 and Comparative Example 3; Figure 9 XPS test chart of LCO positive electrode after 1C cycle at 45℃ for 100 cycles of lithium cobalt oxide / silicon carbon battery prepared by electrolyte in Example 1; Figure 10 XPS test chart of LCO positive electrode after 1C cycle at 45℃ for 100 cycles of lithium cobalt oxide / silicon carbon battery prepared by electrolyte in Comparative Example 1. DETAILED DESCRIPTION

[0014] Hereinafter, embodiments of the non-aqueous electrolyte, lithium ion battery, battery module, battery pack, and power consuming device provided by the present application will be described in detail.

[0015] The ranges disclosed herein are intended to be "open" ranges, i.e., the given range is defined by selecting a lower limit and a higher limit, and the selected lower limit and upper limit define the boundaries of the particular range. The ranges defined by this approach can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., 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 particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Further, 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 contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise indicated, a numerical range "a-b" means a shorthand way of describing each and every intervening real number between the upper and lower limits of that range, wherein a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shorthand way of describing those numerical combinations. Additionally, when a parameter is stated to be an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0016]

Non-aqueous electrolyte

[0017] The compound shown in formula I of the present application can significantly improve the film forming performance under the condition of low additive amount, form a stable interface film on the surface of the positive and negative electrodes, inhibit the consumption of electrolyte, and has the functions of removing water and acid, reduces the interface side reaction, and improves the cycle life of the lithium ion battery.

[0018] In the non-aqueous electrolyte provided by the present application, the mass ratio of the 1,3-propane sulfone lactone in the non-aqueous electrolyte is 0.1% to 3%. In some embodiments, the mass ratio of the 1,3-propane sulfone lactone in the non-aqueous electrolyte may, for example, be 0.1% to 1, 1% to 2%, or 2% to 3%. Preferably, the mass ratio of the 1,3-propane sulfone 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 inhibited gas production of the battery, and outside the range, the disadvantages are hindered ion transmission and decreased high-temperature stability.

[0019] In the non-aqueous electrolyte provided by the present application, the mass ratio of the fluorinated ethylene carbonate in the non-aqueous electrolyte is 0.1% to 5%. In some embodiments, the mass ratio of the fluorinated ethylene carbonate in the non-aqueous electrolyte may, for example, be 0.1% to 2% or 2% to 5%. Preferably, the mass ratio of the fluorinated ethylene carbonate in the non-aqueous electrolyte may, for example, be 2% to 5%. Within the above range, the advantages are enhanced SEI density, improved high-temperature performance and cycle performance of the battery, and outside the range, the disadvantages are serious gas production caused by excessive addition, and the battery life is affected.

[0020] In the non-aqueous electrolyte provided by the present application, the mass ratio of the vinylene carbonate in the non-aqueous electrolyte is 0.1% to 3%. In some embodiments, the mass ratio of the vinylene carbonate in the non-aqueous electrolyte may, for example, be 0.1% to 1, 1% to 2%, or 2% to 3%. Preferably, the mass ratio of the vinylene carbonate in the non-aqueous electrolyte is 1% to 2%. Within the above range, the advantages are enhanced SEI density, inhibited electrolyte decomposition, and improved cycle performance of the battery, and outside the range, the disadvantages are non-uniform SEI formed by excessive addition, excessive battery internal resistance, and thus affected battery efficiency and cycle life.

[0021] The mass percentage of the lithium tetrafluoroborate in the non-aqueous electrolyte is 0.1% to 3%. In some embodiments, the mass percentage of the lithium tetrafluoroborate in the non-aqueous electrolyte can be, for example, 0.1% to 0.5%, 0.5% to 3%, 0.1% to 1%, 1% to 3%. Preferably, the mass percentage of the lithium tetrafluoroborate in the non-aqueous electrolyte is 0.1% to 0.5%. Within the above range, the solvent coordination structure is adjusted, and a stable inorganic SEI is constructed. Outside the range, excessive amounts can cause the formed SEI to be uneven, and the internal resistance of the battery to be too large, thereby affecting the efficiency and cycle life of the battery.

[0022] The mass percentage of the compound represented by Formula I in the non-aqueous electrolyte is 0.1% to 3%. In some embodiments, the mass percentage of the chain unsaturated amide siloxane compound represented by Formula I in the non-aqueous electrolyte can be, for example, 0.1% to 1%, 1% to 3%, 0.1% to 0.5%, 0.5% to 2%, 2% to 3%, etc. Alternatively, the mass percentage of the compound represented by Formula I in the non-aqueous electrolyte is 1% to 3%. Within the above range, the Li + The transport capacity in the interface film is reduced, the impedance is reduced, and outside the range, the interface stability is reduced, thereby affecting the battery life.

[0023] The non-aqueous electrolyte provided by the application further comprises 1,3,6-hexane trinitrile, and the mass percentage of the 1,3,6-hexane trinitrile in the non-aqueous electrolyte is 0% to 2%. In some embodiments, the mass percentage of the 1,3,6-hexane trinitrile 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%, 1.5% to 2%. Within the above range, the battery high-voltage performance is improved, and outside the range, the solvent structure of the electrolyte is destroyed, and the internal resistance is increased.

[0024] The lithium salt in the non-aqueous electrolyte provided by the application is selected from at least one of lithium hexafluorophosphate (LiPF6), lithium bisfluorosulfonylimide (LiFSI), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium hexafluorosilicate (LiSiF6), lithium aluminum chloride (LiAlCl4), lithium bisoxalate borate (LiBOB), lithium chloride (LiCl), lithium bromide (LiBr), lithium iodide (LiI), lithium triflate (LiOTF), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).

[0025] 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 transmission can be ensured. If the proportion of the lithium salt is too high (the content in the non-aqueous electrolyte is higher than 2 mol / L), the lithium salt will not be completely dissociated, the electrolyte viscosity will be too large, which will hinder the transmission of lithium ions and reduce the rate capability 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), the ion transmission efficiency of the electrolyte will be reduced and the electrochemical stability will be poor.

[0026] The organic solvent in the non-aqueous electrolyte provided by the application is selected from cyclic carbonates, chain carbonates and chain carboxylic acid esters. In some embodiments, the organic solvent is selected from a combination of one or more 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.

[0027] The mass proportion of the organic solvent in the non-aqueous electrolyte provided by the application is 68% to 75%. In some embodiments, the mass proportion of the organic solvent in the non-aqueous electrolyte can also be 68% to 70%, 70% to 72%, 72% to 75%, etc. Within the above range, the lithium salt and the additive can be better dissolved. If the proportion of the organic solvent is too high (the mass proportion in the non-aqueous electrolyte is higher than 75%), the electrochemical stability of the electrolyte will be poor. If the proportion of the organic solvent is too low (the mass proportion in the non-aqueous electrolyte is lower than 68%), the lithium salt will not be completely dissociated and the electrolyte viscosity will be too large.

[0028]

Lithium ion battery

[0029] 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 can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can 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 a combination of one or more of lithium cobaltate, lithium manganate, lithium nickel manganate, lithium nickel cobalt manganate, lithium manganese iron phosphate, lithium nickel cobalt aluminum, and lithium iron phosphate. The positive electrode active material layer can further include a conductive agent and a binder. A person skilled in the art can select a conductive agent and a binder suitable for a lithium ion battery in the art. Among them, the conductive agent can include at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, for example. The binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic ester resin, for example.

[0030] In some embodiments, the positive electrode can be prepared by dispersing the components described above for preparing the positive electrode, such as the positive electrode material, the conductive agent, the binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector; and drying, cold-pressing, or the like to obtain the positive electrode.

[0031] 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 can be a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The negative electrode active material layer includes a negative electrode active material selected from a combination of one or more of silicon carbon, natural graphite, artificial graphite, lithium titanate, amorphous carbon, and lithium metal. The negative electrode active material layer can further include a plasticizer, a conductive agent, and a binder. The negative electrode active material can be selected from silicon carbon. A person skilled in the art can select a plasticizer, a conductive agent, and a binder suitable for a lithium ion battery in the art. Among them, the conductive agent can be selected from at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, for example. The binder can 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), and carboxymethyl chitosan (CMCS), carboxymethyl cellulose sodium (CMC-Na), for example.

[0032] In some embodiments, the negative electrode can be prepared by dispersing the above-mentioned components for preparing the negative electrode, such as the negative electrode material, the conductive agent, the binder and any other components, in a solvent (e.g. deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode is obtained.

[0033] The separator film comprises a composite mainly composed of one or more of polyethylene, polypropylene, polyimide, aramid, ceramic and PVDF.

[0034] The lithium ion battery is assembled into a button-type battery, a steel shell cylindrical battery, an aluminum shell cylindrical battery, a steel shell square battery, an aluminum shell square battery or a soft pack battery.

[0035] The lithium ion battery provided in the second aspect of the present application can be prepared by using the methods known in the art. For example, the positive electrode, the separator film and the negative electrode are stacked in order with the separator film between the positive electrode and the negative electrode to play a role of separation, and then the stack is obtained to obtain a bare cell; the bare cell is placed in an outer packaging shell, and after drying, a lithium ion battery electrolyte is injected, and after vacuum packaging, standing, formation, shaping and other processes, a lithium ion battery is obtained.

[0036]

Battery module

[0037]

Battery pack

[0038] The number of battery modules in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0039]

Electric device

[0040] The beneficial effects of the present application are further illustrated below in conjunction with embodiments.

[0041] In order to make the invention purposes, technical solutions and beneficial technical effects of the present application clearer, the present application will be described in further detail below in conjunction with the examples. However, it should be understood that the examples of the present application are only for the purpose of explaining the present application, and are not intended to limit the present application, and the examples of the present application are not limited to the examples given in the specification. The specific experimental conditions or operation conditions not mentioned in the examples are made according to the conventional conditions or the conditions recommended by the material suppliers.

[0042] In addition, it should be understood that the one or more method steps mentioned in the present application do not exclude that there can be other method steps before and after the combination steps or other method steps can be inserted between the explicitly mentioned steps, unless otherwise stated; it should also be understood that the combination connection relationship between the one or more devices / apparatuses mentioned in the present application does not exclude that there can be other devices / apparatuses before and after the combination devices / apparatuses or other devices / apparatuses can be inserted between the two explicitly mentioned devices / apparatuses, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the arrangement order of each method step or to limit the range of implementation of the present application, and the change or adjustment of the relative relationship, without substantial change of the technical content, is also regarded as the scope of implementation of the present application.

[0043] In the following examples, unless specifically stated, the various raw materials of the present application can be commercially available or prepared according to the conventional methods in the art.

[0044] Example 1 Preparation of lithium ion battery: In a dry room (the dew point of the dry room is lower than -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. To the solvent, LiPF6 with a molar concentration of 1.1 mol / L was added, and 1wt% of the compound represented by Formula I, 1wt% of 1,3,6-hexanetricarbonitrile (HTCN), 1wt% of 1,3-propane sulfone lactone (PS), 2wt% of vinylene carbonate, 5wt% of fluoroethylene carbonate (FEC), and 0.5wt% of lithium tetrafluoroborate (LiBF4) were added in the above electrolyte, and 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, and after processes such as standing, formation and capacity distribution, a lithium ion battery 1 was obtained.

[0045] Example 2 Preparation of lithium ion battery: The electrolyte was prepared in a dry room (dew point of the dry room was lower than -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, and a total of 100 mL was prepared. LiPF6 with a molar concentration of 1.1 mol / L was added to the solvent. The total mass of the compound represented by Formula I, 1,3,6-hexane trinitrile (HTCN), 1,3-propane sulfone lactone (PS), 2wt% vinylene carbonate, 2wt% fluoroethylene carbonate (FEC), and 0.5wt% lithium tetrafluoroborate (LiBF4) in the above electrolyte was 3wt%, 1wt%, 1wt%, 2wt%, 2wt%, and 0.5wt%, respectively. After stirring until completely dissolved, the lithium ion battery electrolyte of Example 2 was obtained. The prepared electrolyte was injected into a three-electrode device with silicon-carbon as the working electrode, lithium sheet as the counter electrode, and platinum sheet as the reference electrode, and a three-electrode battery 1 was obtained.

[0046] Example 3 Preparation of lithium ion battery: The electrolyte was prepared in a dry room (dew point of the dry room was lower than -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 molar concentration of 1.1 mol / L was added to the solvent. The total mass of the compound represented by Formula I, 1,3-propane sulfone lactone (PS), 2wt% vinylene carbonate (VC), 2wt% fluoroethylene carbonate (FEC), and 0.1wt% lithium tetrafluoroborate (LiBF4) in the above electrolyte was 1wt%, 1wt%, 2wt%, 2wt%, and 0.1wt%, respectively. After stirring until completely dissolved, the lithium ion battery electrolyte of Example 3 was obtained. The prepared electrolyte was injected into a three-electrode device with lithium cobalt oxide as the working electrode, lithium sheet as the counter electrode, and platinum sheet as the reference electrode, and a three-electrode battery 2 was obtained.

[0047] Example 4 Preparation of lithium ion battery: The electrolyte was configured in a dry room (the dew point of the dry room was lower than -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 configured. LiPF6 with a lithium salt molar concentration of 1.1 mol / L was added to the solvent, and 1wt% of the compound represented by Formula I, 2wt% of 1,3-propane sultone (PS), 1wt% of vinylene carbonate (VC), 5wt% of fluoroethylene carbonate (FEC), and 0.5wt% of lithium tetrafluoroborate (LiBF4) were added to the above electrolyte, and the total mass of the solvent and the lithium salt was 1wt%. Stirring was performed until complete dissolution to obtain the lithium ion battery electrolyte of Example 5. The prepared electrolyte was injected into an LCO / SiC soft package battery, and after processes such as standing, formation and capacity distribution, lithium ion battery 3 was obtained.

[0048] Example 5 Preparation of lithium ion battery: The electrolyte was configured in a dry room (the dew point of the dry room was lower than -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 configured. LiPF6 with a lithium salt molar concentration of 1.1 mol / L was added to the solvent, and 1wt% of the compound represented by Formula I, 2wt% of 1,3-propane sultone (PS), 1wt% of vinylene carbonate (VC), 5wt% of fluoroethylene carbonate (FEC), and 0.5wt% of lithium tetrafluoroborate (LiBF4) were added to the above electrolyte, and the total mass of the solvent and the lithium salt was 1wt%. Stirring was performed until complete dissolution to obtain the lithium ion battery electrolyte of Example 5. The prepared electrolyte was injected into an LCO / SiC soft package battery, and after processes such as standing, formation and capacity distribution, lithium ion battery 3 was obtained.

[0049] Example 6 Preparation of lithium ion battery: The electrolyte was configured in a dry room (the dew point of the dry room was lower than -40℃), diethyl carbonate (EC), propylene carbonate (PC) and dimethyl carbonate (DMC) were mixed as organic solvents in a volume ratio of 5:3:2, and a total volume of 100 mL was configured. LiFSI with a molar concentration of 1.1 mol / L was added to the solvent, and 1wt% of the compound represented by Formula I, 2wt% 1,3-propane sultone (PS), 1wt% vinylene carbonate (VC), 5wt% fluoroethylene carbonate (FEC), and 0.5wt% lithium tetrafluoroborate (LiBF4) were added to the above electrolyte, and 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 package battery, and after the processes of standing, formation and capacity distribution, a lithium ion battery 4 was obtained.

[0050] Comparative Example 1 Preparation of lithium ion battery: The electrolyte was configured in a dry room (the dew point of the dry room was lower than -40℃), diethyl carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC) and propyl propionate (PrPr) were mixed as organic solvents in a volume ratio of 10:4:3:3, and a total volume of 100 mL was configured. LiPF6 with a molar concentration of 1.1 mol / L was added to the solvent, and 1wt% 1,3,6-hexanetricarbonitrile (HTCN), 1wt% 1,3-propane sultone (PS), 2wt% vinylene carbonate (VC), 5wt% fluoroethylene carbonate (FEC), and 0.5wt% lithium tetrafluoroborate (LiBF4) were added to the above 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 package battery, and after the processes of standing, formation and capacity distribution, a lithium ion battery 5 was obtained.

[0051] Comparative Example 2 Preparation of lithium ion battery: The electrolyte was prepared in a dry room (dew point of the dry room was lower than -40°C). 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 volume of 100 mL was prepared. LiPF6 with a molar concentration of 1.1 mol / L was added to the solvent. 1wt% 1,3,6-hexane trinitrile (HTCN), 1wt% 1,3-propane sulfone lactone (PS), 2wt% vinylene carbonate (VC), 2wt% fluoroethylene carbonate (FEC), and 0.5wt% lithium tetrafluoroborate (LiBF4) were added to the above 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 sheet as the counter electrode, and platinum sheet as the reference electrode to obtain a three-electrode battery 3. The acid value of the electrolyte was tested before and after the test.

[0052] Comparative Example 3 Preparation of lithium ion battery: The electrolyte was prepared in a dry room (dew point of the dry room was lower than -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 volume of 100 mL was prepared. LiPF6 with a molar concentration of 1.1 mol / L was added to the solvent. 1wt% 1,3-propane sulfone lactone (PS), 2wt% vinylene carbonate (VC), 2wt% fluoroethylene carbonate (FEC), and 0.1wt% lithium tetrafluoroborate (LiBF4) were added to the above 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, lithium sheet as the counter electrode, and platinum sheet as the reference electrode to obtain a three-electrode battery 4.

[0053] Comparative Example 4 Preparation of lithium ion battery: The electrolyte was configured in a dry room (the dew point of the dry room was lower than -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 configured. LiPF6 with a lithium salt molar concentration of 1.1 mol / L was added to the solvent, and the total mass of the solvent and lithium salt was 1wt% 1,3,6-hexanetricarbonitrile (HTCN), 1wt% 1,3-propane sulfone lactone (PS), 2wt% vinylene carbonate (VC), 5wt% fluoroethylene carbonate (FEC), and 0.1wt% lithium tetrafluoroborate (LiBF4) was added to the above electrolyte, and stirred until completely dissolved to obtain the lithium ion battery electrolyte of Comparative Example 6. The prepared electrolyte was injected into the NCM811 / SiC soft package battery, and after the processes of standing, formation and capacity distribution, the lithium ion battery 8 was obtained.

[0054] Comparative Example 5 Preparation of lithium ion battery: The electrolyte was configured in a dry room (the dew point of the dry room was lower than -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 configured. LiPF6 with a lithium salt molar concentration of 1.1 mol / L was added to the solvent, and the total mass of the solvent and lithium salt was 1wt% 1,3,6-hexanetricarbonitrile (HTCN), 1wt% 1,3-propane sulfone lactone (PS), 2wt% vinylene carbonate (VC), 5wt% fluoroethylene carbonate (FEC), and 0.1wt% lithium tetrafluoroborate (LiBF4) was added to the above electrolyte, and stirred until completely dissolved to obtain the lithium ion battery electrolyte of Comparative Example 6. The prepared electrolyte was injected into the NCM811 / SiC soft package battery, and after the processes of standing, formation and capacity distribution, the lithium ion battery 8 was obtained.

[0055] Comparative Example 6 Preparation of lithium ion battery: The electrolyte was configured in a dry room (the dew point of the dry room was lower than -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 configured. LiPF6 with a lithium salt molar concentration of 1.1 mol / L was added to the solvent, and the total mass of the solvent and lithium salt was 1wt% 1,3,6-hexanetricarbonitrile (HTCN), 1wt% 1,3-propane sulfone lactone (PS), 2wt% vinylene carbonate (VC), 5wt% fluoroethylene carbonate (FEC), and 0.1wt% lithium tetrafluoroborate (LiBF4) was added to the above electrolyte, and stirred until completely dissolved to obtain the lithium ion battery electrolyte of Comparative Example 6. The prepared electrolyte was injected into the NCM811 / SiC soft package battery, and after the processes of standing, formation and capacity distribution, the lithium ion battery 8 was obtained.

[0056] Table 1 Electrolyte formulation

[0057] Performance test The lithium secondary battery prepared above was subjected to the following performance test: High-temperature cycle performance test: at 45°C, the battery after formation was charged to the cut-off voltage with 1C constant current and constant voltage, and then discharged to 3V with constant current, and the cycle test was carried out in this way, and the discharge capacity of the first time and the discharge capacity of the last time were recorded.

[0058] The capacity retention rate of high-temperature cycle was calculated according to the following formula: Capacity retention rate = discharge capacity of the last time / discharge capacity of the first time x 100%.

[0059] From Figure 1 The 45°C 1C cycle performance test chart of the lithium cobalt oxide / silicon carbon battery prepared by the electrolyte in Example 1, Example 5, Comparative Example 1 and Comparative Example 5 can be seen that the cycle retention rates of Example 1, Example 5, Comparative Example 1 at 45°C are 69.4%, 67.9% and 57.1% respectively, and the cycle stability of Comparative Example 5 without additive is very poor. It can be seen from the comparison between Comparative Example 1 and Example 1 that the addition of the compound of formula I can improve the high-temperature cycle stability of the battery. It is proved that the siloxane group in the compound of formula I can effectively remove acid and water, inhibit side reactions and improve the cycle stability of the battery.

[0060] From Figure 2 The 45°C 1C cycle performance test chart of the high-nickel / silicon carbon battery prepared by the electrolyte in Example 4, Example 6, Comparative Example 4 and Comparative Example 6 can be seen that the cycle retention rates of Example 4, Example 6, Comparative Example 4 and Comparative Example 6 at 45°C are 76.2%, 73.9%, 68.3% and 54.3% respectively. The addition of the compound of formula I can effectively improve the cycle stability of the battery.

[0061] From Figure 3 The 25°C formation dQ / dV curve of the lithium cobalt oxide / silicon carbon battery prepared by the electrolyte in Example 1, Example 5, Comparative Example 1 and Comparative Example 5 can be seen that after the addition of the compound of formula I, the reaction intensity of LiBF4 at 1.7V is reduced, the compound of formula I appears a reaction peak at about 2.0V, the battery of Comparative Example 5 does not form a film before 2.5V, and the reaction is violent after 2.5V. It is proved that the compound of formula I can inhibit the decomposition reaction of LiBF4 and preferentially form a film at the interface than other additives, and after the film is formed, the reaction intensity of the reaction peak of FEC at about 2.75V is reduced, and the interface impedance is reduced.

[0062] From Figure 4The 25℃ dQ / dV curves of the high nickel / silicon carbon batteries prepared by the electrolyte in Example 4, Example 6, Comparative Example 4 and Comparative Example 6 can be seen: after adding the compound represented by Formula I, the reaction intensity of the sulfur-based additive around 2.2V is reduced, and the electrode reaction around 3.5V is enhanced, indicating that the compound represented by Formula I can inhibit the decomposition of the sulfur-based additive, effectively reduce the interface impedance, and improve the battery efficiency and prolong the battery life.

[0063] From Figure 5 The CV test comparison chart of the SiC / Pt / Li three-electrode battery prepared by the electrolyte in Example 2 and Comparative Example 2 can be seen: the battery after adding the compound represented by Formula I in Example 2 has a reaction peak of the compound represented by Formula I around 0.5V, and compared with Comparative Example 2, it can be seen that the polarization of Example 2 is smaller than that of Comparative Example 2, and the SiC electrode impedance of the battery after adding the compound represented by Formula I is reduced.

[0064] From Figure 6 The SiC negative electrode XPS test chart (N spectrum, O spectrum, Si spectrum, F spectrum) of the lithium cobalt oxide / silicon carbon battery prepared by the electrolyte in Example 1 after 1C cycle for 100 cycles at 45℃ can be seen: the compound represented by Formula I is effectively deposited on the negative electrode surface, and 1,3-propane sultone is also reduced on the negative electrode to form a stable SEI.

[0065] From Figure 7 The SiC negative electrode XPS test chart (N spectrum, O spectrum, F spectrum) of the lithium cobalt oxide / silicon carbon battery prepared by the electrolyte in Comparative Example 1 after 1C cycle for 100 cycles at 45℃ can be seen: a small amount of positive electrode crystal signal peak (O 2- ) appears on the negative electrode, the positive active material is dissolved and attached to the negative electrode interface, which greatly affects the battery performance, and the SEI cannot completely cover the negative active material, which greatly affects the battery performance.

[0066] From Figure 8 The CV test comparison chart of the LCO / Pt / Li three-electrode battery prepared by the electrolyte in Example 3 and Comparative Example 3 can be seen: the polarization of the battery after adding the compound represented by Formula I in Example 3 tends to decrease, and the impedance is reduced; compared with Comparative Example 3, it can be seen that the polarization of Example 3 is smaller than that of Comparative Example 3, and the LCO electrode impedance of the battery after adding the compound represented by Formula I is reduced.

[0067] From Figure 9The LCO positive electrode XPS test graph (N spectrum, O spectrum, Si spectrum, F spectrum) of the lithium cobalt oxide / silicon carbon battery prepared by the electrolyte in Example 1 after 1C cycle at 45 DEG C for 100 cycles can be seen: the compound shown in formula I can promote the combination with the electrolyte components (such as LiBF4, HF, etc.), form a more stable CEI film, help to inhibit the side reaction and improve the structural stability at high temperature; at the same time, the Si-O-Li bond structure formed further optimizes the reaction path of lithium ions, reduces the dissolution of the positive active material. At the same time, the end group unsaturated bond enhances the compactness of the CEI, thereby improving the cycle stability of the battery.

[0068] From Figure 10 The LCO positive electrode XPS test graph (N spectrum, O spectrum, F spectrum) of the lithium cobalt oxide / silicon carbon battery prepared by the electrolyte in Comparative Example 1 after 1C cycle at 45 DEG C for 100 cycles can be seen: the CEI does not uniformly cover the positive active material, the electrode has the risk of active material dissolution and capacity loss, and the battery fails to form effective protection, greatly affecting the battery performance.

[0069] In summary, the present application effectively overcomes the shortcomings in the prior art and has high industrial utilization value.

[0070] The above is only a preferred embodiment of the present application, and is not any form and substantial limitation of the present application. It should be noted that for ordinary skilled persons in the art, some improvements and supplements can be made without departing from the method of the present application, and these improvements and supplements should be considered as the protection scope of the present application. For those skilled in the art, some minor changes, modifications and equivalent changes made by using the disclosed technical content without departing from the spirit and scope of the present application are equivalent embodiments of the present application; at the same time, any equivalent change, modification and evolution of the above-mentioned embodiments according to the essential technology of the present application are still within the scope of the technical solutions of the present application.

Claims

1. A nonaqueous electrolyte, characterized by comprising: The non-aqueous electrolyte comprises a lithium salt, an organic solvent, and an electrolyte additive, the electrolyte additive comprises 1,3-propane sulfone lactone, fluorinated ethylene carbonate, vinylene carbonate, lithium tetrafluoroborate, and a compound represented by Formula I: Formula I.

2. The nonaqueous electrolyte according to claim 1, characterized by Any one or more of the following conditions are also included: A1) The mass percentage of the 1,3-propane sulfone lactone in the non-aqueous electrolyte is 0.1% to 3%; A2) The mass percentage of the fluorinated ethylene carbonate in the non-aqueous electrolyte is 0.1% to 5%; A3) The mass percentage of the vinylene carbonate in the non-aqueous electrolyte is 0.1% to 3%; A4) The mass percentage of the lithium tetrafluoroborate in the non-aqueous electrolyte is 0.1% to 3%; A5) The mass percentage of the compound represented by Formula I in the non-aqueous electrolyte is 0.1% to 3%.

3. The nonaqueous electrolyte according to claim 2, characterized by Any one or more of the following conditions are also included: A11) In feature A1), the mass percentage of the 1,3-propane sulfone lactone in the non-aqueous electrolyte is 1% to 2%; A21) In feature A2), the mass percentage of the fluorinated ethylene carbonate in the non-aqueous electrolyte is 2% to 5%; A31) In feature A3), the mass percentage of the vinylene carbonate in the non-aqueous electrolyte is 1% to 2%; A41) In feature A4), the mass percentage of the lithium tetrafluoroborate in the non-aqueous electrolyte is 0.1% to 0.5%; A51) In feature A5), the mass percentage of the compound represented by Formula I in the non-aqueous electrolyte is 1% to 3%.

4. The nonaqueous electrolyte according to claim 1, characterized by The electrolyte additive also comprises 1,3,6-hexane trinitrile, and the mass percentage of the 1,3,6-hexane trinitrile in the non-aqueous electrolyte is 0% to 2%.

5. The nonaqueous electrolyte according to claim 1, wherein Any one or more of the following conditions are also included: B1) The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium bisfluorosulfonimide, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorosilicate, lithium aluminum chloride, lithium bisoxalate borate, lithium chloride, lithium bromide, lithium iodide, lithium triflate, and lithium bis(trifluoromethylsulfonate)imide; B2) The content of the lithium salt in the non-aqueous electrolyte is 0.5 to 2 mol / L; B3) The organic solvent comprises a cyclic carbonate, a chain carbonate, and a chain carboxylate; B4) The mass percentage of the organic solvent in the non-aqueous electrolyte is 68% to 75%.

6. The nonaqueous electrolyte according to claim 5, wherein In feature B3), the organic solvent is selected from a combination of one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, gamma-butyrolactone, methyl acetate, ethyl acetate, ethyl propionate, propyl propionate, and methyl butyrate.

7. A lithium-ion battery, characterized by The non-aqueous electrolyte is the non-aqueous electrolyte according to any one of claims 1 to 6.

8. The lithium-ion battery of claim 7, wherein, Any one or more of the following conditions are also included: C1) The negative electrode comprises a negative electrode active material, and the negative electrode active material is selected from a combination of one or more of silicon carbon, natural graphite, artificial graphite, lithium titanate, amorphous carbon, and lithium metal. C2) the positive electrode comprises a positive electrode active material selected from a combination of one or more of lithium cobaltate, lithium manganate, lithium nickel manganate, lithium nickel cobalt manganate, lithium manganese iron phosphate, lithium nickel cobalt aluminate, and lithium iron phosphate; C3) the separator film comprises a composite consisting of one or several of polyethylene, polypropylene, polyimide, aramid, ceramic, and PVDF as a main body; C4) the lithium ion battery is assembled as a coin cell, a steel can cylindrical cell, an aluminum can cylindrical cell, a steel can prismatic cell, an aluminum can prismatic cell, or a pouch cell.

9. A battery module, characterized by A lithium ion battery according to claim 7 or 8.

10. A battery pack, characterized by, A battery module according to claim 9.

11. An electrical device, characterized by A lithium ion battery according to claim 7 or 8 for use as a power source for the device, the power consuming device comprising a mobile device, an electric vehicle, an electric power tool, an electric train, a satellite, a ship, and an energy storage system.

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