A high-voltage, high electrochemical performance electrolyte for low-temperature lithium ion batteries, and a preparation method and application thereof

Abstract

The application provides a high-voltage and high electrochemical performance electrolyte for a low-temperature lithium ion battery, a preparation method and application thereof, and belongs to the technical field of low-temperature lithium ion batteries.The electrolyte comprises the following components: a lithium salt, a base solvent and a non-solvated cosolvent; the base solvent is one or a combination of two or more of linear siloxanes or nitriles; the non-solvated cosolvent is one or a combination of two or more of fluorinated silanes or stannanes; and the volume ratio of the base solvent and the non-solvated cosolvent is 5-9:1-5.The pseudo-coordination bond between Sn (Si) in the non-solvated cosolvent and O (N) in the base solvent can be used to effectively adjust the solvation structure of the electrolyte, so that high ion conductivity at low temperature is achieved; and the prepared electrolyte is applied to a lithium ion battery, and exhibits excellent high-voltage and long cycle stability and other electrochemical performances at low temperature, so that the electrolyte has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of low-temperature lithium-ion battery technology, specifically relating to a high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries, composed of layered metal oxide cathodes, graphite anodes, and ethylene carbonate-based electrolytes, have become an indispensable core energy storage technology in many applications, including portable devices and electric vehicles. However, when the temperature drops to 0... o Below the temperature (°C), electrolytes often experience two major problems: firstly, ionic conductivity decreases significantly, and secondly, the desolvation process of lithium ions becomes sluggish. Furthermore, the transport efficiency of lithium ions across the solid electrolyte interface (SEI) and their diffusion within the electrodes are severely hampered. These combined adverse factors ultimately lead to significant capacity decay and energy loss in lithium-ion batteries at low temperatures.

[0003] Currently, electrolyte design plays a crucial role in achieving high-performance low-temperature lithium-ion batteries. Among these strategies, optimizing the lithium-ion solvation structure in the electrolyte by modulating intermolecular interactions has been proven to significantly improve the electrochemical performance of lithium-ion batteries at low temperatures. Of the various intermolecular interaction modulation strategies, hydrogen bonding and dipole-dipole interactions have received widespread attention. Specifically, intermolecular interactions between solvated solvents can construct a "push-pull" mechanism in electrolyte design. For example, utilizing the hydrogen bonding between 2,2-difluoroethyl ester trifluoromethanesulfonic acid and fluoroethylene carbonate can weaken the interaction between lithium ions and highly polar molecules, thereby achieving a weak coordination effect between lithium ions and the solvent. Similarly, utilizing the interaction between the solvated solvent and the non-solvated co-solvent can form a "drag" electrolyte design strategy. Taking ethylene glycol dimethyl ether (DME) and fluorobenzene as an example, a significant dipole-dipole interaction can occur between them, which can weaken the lithium-ion co-coordination of lithium-ion molecules. + The strong binding strength between the electrolyte and DME not only accelerates the desolvation process but also effectively suppresses the phenomenon of solvent co-intercalation into graphite. However, the electrolytes designed using the two strategies mentioned above still have room for improvement in enhancing the electrochemical performance of low-temperature lithium-ion batteries.

[0004] Chinese patent document CN117293397A discloses an electrolyte for lithium-ion batteries with improved low-temperature performance and an ultra-fast charging lithium-ion battery. The electrolyte comprises a lithium salt, a solvent, and additives. The lithium salt comprises at least one of lithium hexafluorophosphate and lithium difluorosulfonylimide. The solvent is a combination of carbonate and carboxylic acid ester. The additives are selected from at least one of vinylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, ethylene ethylene carbonate, vinyl sulfate, vinylene sulfite, fluoroethylene sulfate, 4,5-difluoroethylene sulfate, 1,3-propanesulfonyl lactone, 1,3-propenesulfonyl lactone, 1,4-butanesulfonyl lactone, 1,4-butenesulfonyl lactone, methanedisulfonate, hexamethyldisilazane, tris(trimethylsilane)borate, triargyl phosphate, tris(trimethylsilane) phosphite, and tris(trimethylsilane) phosphate. The invention improves the 5C fast charging performance of the lithium-ion battery, but still suffers from poor low-temperature electrochemical performance, such as the need for higher voltage and poor capacity retention.

[0005] Therefore, developing novel electrolytes is key to improving the performance of low-temperature lithium-ion batteries. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries, its preparation method, and its applications. The electrolyte of this invention utilizes the addition of a small amount of a non-solventized co-solvent (fluorinated silane and / or tinane), combined with a specific base solvent, to achieve high performance using Sn in the non-solventized co-solvent. δ+ (Si) δ+ The positive charge of Sn and the empty 3d orbital δ+ (Si) δ+ ) and O δ- (N) δ- The slight orbital overlap between Sn and Sn makes Sn δ+ (Si) δ+ ) and O δ- (N) δ- Pseudo-coordinate bonds are formed between (specifically Sn) δ+ (Si) δ+ ) and O δ- (N) δ- The pseudo-coordinate bond of Sn is primarily due to the positive charge of Sn. δ+ (Si) δ+ ) and negatively charged O δ- (N) δ- The interaction between them, and then Sn δ+ (Si) δ+ ) and O δ- (N) δ- The orbits of Sn and Sn slightly overlap, so Sn... δ+(Si) δ+ ) and O δ- (N) δ- The interaction between two atoms (or ions) is called a pseudo-coordinate bond; compared to a traditional coordinate bond (where one atom (or ion) provides a shared pair of electrons while the other atom (or ion) provides an empty orbital to accept these electrons, resulting in significant orbital overlap between the two atoms), Sn... δ+ (Si) δ+ ) and O δ- (N) δ- The orbitals that form pseudo-coordinate bonds between lithium ions have less overlap and are weaker than traditional coordinate bonds. These pseudo-coordinate bonds can weaken the ion-dipole interaction between lithium ions and O or N, effectively regulating the solvation structure of the electrolyte and achieving high ionic conductivity of the electrolyte at low temperatures. The prepared electrolyte, when applied to lithium-ion batteries, exhibits excellent electrochemical performance such as high voltage and long cycle stability at low temperatures, showing promising application prospects.

[0007] The technical solution of the present invention is as follows:

[0008] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries, the electrolyte comprising the following components: a lithium salt, a base solvent, and a non-solventized co-solvent; the base solvent is one or a combination of two or more of carbonates, linear siloxanes, or nitriles; the non-solventized co-solvent is one or a combination of two or more of fluorinated silanes or tinanes; the volume ratio of the base solvent to the non-solventized co-solvent is 5-9:1-5.

[0009] According to a preferred embodiment of the present invention, the lithium salt is one or a combination of two or more of lithium hexafluorophosphate (LiPF6), lithium difluorooxalate borate (LiDFOB), or lithium bis(fluorosulfonyl)imide (LiFSI); the concentration of the lithium salt in the electrolyte is 0.8-1.5 mol·L⁻¹. -1 Preferably 1 mol·L -1 .

[0010] Preferably, the lithium salt is a combination of lithium hexafluorophosphate (LiPF6), lithium difluorooxalate borate (LiDFOB), lithium bisfluorosulfonyl imide (LiFSI), lithium difluorooxalate borate (LiDFOB) and lithium hexafluorophosphate (LiPF6), a combination of lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonyl imide (LiFSI), or a combination of lithium difluorooxalate borate (LiDFOB) and lithium bisfluorosulfonyl imide (LiFSI); wherein, in the combination of lithium difluorooxalate borate (LiDFOB) and lithium bisfluorosulfonyl imide (LiFSI), the molar ratio of lithium difluorooxalate borate (LiDFOB) to lithium bisfluorosulfonyl imide (LiFSI) is 1:0.5-5, more preferably 1:3-5, and most preferably 1:4.

[0011] According to a preferred embodiment of the present invention, the carbonate is one or a combination of two or more of methyl carbonate (DMC), diethyl carbonate (DEC), or propylene carbonate (PC).

[0012] According to a preferred embodiment of the present invention, the linear siloxane is one or a combination of two or more of methoxytrimethylsilane (TMSOME), ethoxytriethylsilane (TEEOS), or 1,3-dioxo-2-silanecyclopentane (DS).

[0013] According to a preferred embodiment of the present invention, the nitrile is one or a combination of two or more of acetonitrile (AN), phenylacetonitrile (BAN), or ethylenedionitrile (MNT).

[0014] According to the present invention, the base solvent is preferably a combination of diethyl carbonate (DEC), acetonitrile (AN) and ethoxytriethylsilane (TEEOS), a combination of diethyl carbonate (DEC) and acetonitrile (BAN), a combination of 1,3-dioxo-2-silanecyclopentane (DS) and acetonitrile (AN), a combination of acetonitrile (AN) and phenylacetonitrile (BAN), a combination of oxadionitrile (MNT) and acetonitrile (AN), ethoxytriethylsilane (TEEOS), oxadionitrile (MNT), phenylacetonitrile, or acetonitrile (AN); preferably, the base solvent is a combination of acetonitrile (AN) and ethoxytriethylsilane (TEEOS), wherein the volume ratio of acetonitrile (AN) to ethoxytriethylsilane (TEEOS) is 2-3:1, more preferably 2.5:1.

[0015] According to a preferred embodiment of the present invention, the fluorinated silane is one or a combination of two or more of trimethylfluorosilane (FTMS), (difluoromethyl)trimethylsilane (DFTMS), (trifluoromethyl)trimethylsilane (TFTMS), or (pentafluoroethyl)trimethylsilane (PFTMS).

[0016] According to a preferred embodiment of the present invention, the tinane is one or a combination of two or more of tetrabutyltin (TBT), dioctyltin dilaurate (DOTDL), or tributyltin hydride (TBTH).

[0017] According to a preferred embodiment of the present invention, the non-solventizing cosolvent is a combination of trimethylfluorosilane (FTMS), (trifluoromethyl)trimethylsilane (TFTMS) and tetrabutyltin (TBT), a combination of (trifluoromethyl)trimethylsilane (TFTMS) and trimethylfluorosilane (FTMS), a combination of tetrabutyltin (TBT) and (pentafluoroethyl)trimethylsilane (PFTMS), a combination of (pentafluoroethyl)trimethylsilane (PFTMS) and (difluoromethyl)trimethylsilane (DFTMS), a combination of trimethylfluorosilane (FTMS) and tetrabutyltin (TBT), or (trifluoromethyl)trimethylsilane. Combinations of (TFTMS) and tetrabutyltin (TBT), combinations of (pentafluoroethyl)trimethylsilane (PFTMS), (trifluoromethyl)trimethylsilane (TFTMS) and (difluoromethyl)trimethylsilane (DFTMS), combinations of (pentafluoroethyl)trimethylsilane (PFTMS), (trifluoromethyl)trimethylsilane (TFTMS) and tributyltin hydride (TBTH), dioctyltin dilaurate (DOTDL), tributyltin hydride (TBTH), (pentafluoroethyl)trimethylsilane (PFTMS), trimethylfluorosilane (FTMS) or (trifluoromethyl)trimethylsilane. Preferably, the non-solventizing cosolvent is a combination of trimethylfluorosilane (FTMS), (trifluoromethyl)trimethylsilane (TFTMS), and tetrabutyltin (TBT), wherein the volume ratio of trimethylfluorosilane (FTMS), (trifluoromethyl)trimethylsilane (TFTMS), and tetrabutyltin (TBT) is 1-2:1-2:1, and more preferably 1:1:1.

[0018] According to a preferred embodiment of the present invention, the volume ratio of the base solvent to the nonsolventized cosolvent is 7-9:1-3, more preferably 7-8:2-3, and even more preferably 7:3.

[0019] The above-mentioned method for preparing high-voltage, high-electrochemical-performance electrolytes for low-temperature lithium-ion batteries includes the following steps:

[0020] The lithium salt, base solvent, and non-solventized co-solvent are thoroughly mixed to obtain a high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries.

[0021] The above-mentioned high-voltage, high-electrochemical-performance electrolytes for low-temperature lithium-ion batteries are used in low-temperature lithium-ion batteries.

[0022] According to a preferred embodiment of the present invention, the positive electrode active material of the low-temperature lithium-ion battery is NCM811 (LiNi). 0.8 Co 0.1 Mn 0.1 The negative electrode active material is graphite.

[0023] According to the present invention, the electrolyte can be used in the preparation of low-temperature lithium-ion batteries according to existing technology; preferably, the application of the electrolyte in the preparation of low-temperature lithium-ion batteries includes the following steps:

[0024] (1) Preparation of positive electrode sheet

[0025] The positive electrode active material, superconducting carbon black, and polyvinylidene fluoride (PVDF) are fully dispersed in N-methylpyrrolidone to form a slurry, which is then coated on aluminum foil and dried to obtain a positive electrode sheet; the mass ratio of the positive electrode active material, superconducting carbon black, and polyvinylidene fluoride is 8:1:1.

[0026] (2) Preparation of negative electrode sheet

[0027] The negative electrode active material, superconducting carbon black, and polyacrylic acid (PAA) binder are fully dispersed in deionized water to form a slurry; then, the obtained slurry is coated onto copper foil and dried to obtain a negative electrode sheet; the mass ratio of the negative electrode active material, superconducting carbon black, and polyacrylic acid is 8:1:1.

[0028] (3) Battery preparation

[0029] The electrode plates are placed in the battery casing, with a separator placed between the positive and negative electrode plates. 50-80 μL of electrolyte is added, and then the battery is encapsulated to obtain a low-temperature lithium-ion battery.

[0030] The technical features and beneficial effects of this invention are as follows:

[0031] 1. The electrolyte of this invention contains a specific proportion and type of base solvent, which can increase the solubility of lithium salts, reduce the migration resistance of lithium ions, and ensure battery performance. This invention adds a specific proportion and type of non-solventizing co-solvent, utilizing the weak orbital overlap between the positively charged Sn(Si) and the empty 3d orbitals of Sn(Si) in the non-solventizing co-solvent and the negatively charged O(N) in the base solvent. This allows Sn(Si) to form pseudo-coordinate bonds with the negatively charged O(N) in the base solvent. The pseudo-coordinate bonds between Sn(Si) and O(N) can effectively weaken the lithium salt's solubility. + The coordination with the base solvent increases the number of solvated anions, enabling rapid desolvation at low temperatures and high ionic conductivity.

[0032] 2. The electrolyte of this invention achieves excellent electrochemical performance of graphite||NCM811 batteries at low temperatures while ensuring high-voltage stability (4.5V). At -20℃ o Under C conditions, the graphite||NCM811 coin cell was charged and discharged at a rate of 0.2C. After 150 cycles, it still maintained a stable capacity of 184 mAhg. -1 High capacity, achieving a capacity retention rate of 95.2%. At -40...o It can be stably maintained at 153 mAhg after 100 cycles at C. -1 It has high capacity and achieves a capacity retention rate of 92.3%.

[0033] 3. The electrolyte of this invention is applied to a 4.7 Ah pouch cell at -20°C. o After 100 cycles under C conditions, the capacity remains above 4.0 Ah, with a capacity retention rate of 95%, providing a promising electrolyte for commercial low-temperature lithium-ion battery applications.

[0034] 4. The specific types and proportions of base solvents in this invention, combined with specific types and proportions of non-solventizing co-solvents, work together to achieve the excellent effects of the electrolyte of this invention. If the types and proportions of the base solvents and the non-solventizing co-solvents are unsuitable, it will result in Sn... δ+ (Si) δ+ ) and O δ- (N) δ- The strength of pseudo-coordination bonds formed between the electrolytes will vary, which will reduce the performance of the electrolyte. Attached Figure Description

[0035] Figure 1 The diagram shows the ionic conductivity of the electrolyte prepared in Example 1.

[0036] Figure 2 The graphite||NCM811 button cell based on the electrolyte prepared in Example 1 was tested at -20°C. o The loop performance of C.

[0037] Figure 3 The graphite||NCM811 button cell based on the electrolyte prepared in Example 1 was tested at -20°C. o Capacity-voltage curves for C-cycle performance.

[0038] Figure 4 The graphite||NCM811 button cell based on the electrolyte prepared in Example 1 was tested at -40°C. o C loop performance.

[0039] Figure 5 A 4.7 Ah graphite||NCM811 pouch cell based on the electrolyte prepared in Example 1 was tested at -20°C. o C loop performance. Detailed Implementation

[0040] The present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments.

[0041] This embodiment is implemented based on the technical solution of the present invention, and provides detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiment. Furthermore, unless otherwise specified, the experimental methods described in the following embodiments are conventional methods; and unless otherwise specified, the reagents, materials, and equipment are all commercially available.

[0042] Example 1

[0043] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries comprises the following components: acetonitrile (AN), ethoxytriethylsilane (TEEOS), trimethylfluorosilane (FTMS), (trifluoromethyl)trimethylsilane (TFTMS), tetrabutyltin (TBT), lithium difluorooxalate borate (LiDFOB), and lithium bisfluorosulfonylimide (LiFSI); wherein the volume ratio of acetonitrile (AN), ethoxytriethylsilane (TEEOS), trimethylfluorosilane (FTMS), (trifluoromethyl)trimethylsilane (TFTMS), and tetrabutyltin (TBT) is 5:2:1:1:1; the concentration of lithium difluorooxalate borate (LiDFOB) in the electrolyte is 0.2 mol / L, and the concentration of lithium bisfluorosulfonylimide (LiFSI) is 0.8 mol / L.

[0044] The preparation method of the above-mentioned high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries includes the following steps:

[0045] In an argon-filled glove box, acetonitrile (AN), ethoxytriethylsilane (TEEOS), trimethylfluorosilane (FTMS), (trifluoromethyl)trimethylsilane (TFTMS), and tetrabutyltin (TBT) are thoroughly mixed. Then, lithium difluorooxalate borate (LiDFOB) and lithium difluorosulfonyl imide (LiFSI) are added and stirred until completely dissolved to obtain the electrolyte.

[0046] The electrolyte obtained above is used to prepare a low-temperature lithium-ion battery (coin cell), including the following steps:

[0047] (1) Preparation of positive electrode sheet

[0048] The positive electrode active material (NCM811), superconducting carbon black, and polyvinylidene fluoride (PVDF) dissolved in N-methylpyrrolidone were mixed evenly to form a slurry, which was then coated on an aluminum foil with a thickness of 20 μm and dried to obtain a positive electrode sheet; the mass ratio of the positive electrode active material, superconducting carbon black, and polyvinylidene fluoride was 8:1:1.

[0049] (2) Preparation of negative electrode sheet

[0050] The negative electrode active material (graphite), superconducting carbon black, and polyacrylic acid (PAA) binder are mixed evenly in deionized water solvent to form a slurry; then, the obtained slurry is coated onto copper foil and dried to obtain a negative electrode sheet; the mass ratio of the negative electrode active material, superconducting carbon black, and polyacrylic acid is 8:1:1.

[0051] (3) Battery preparation

[0052] The electrode plates are placed in the battery casing, with a 2325 separator placed between the positive and negative electrode plates. 50-80 μL of electrolyte is added, and then the battery is packaged to obtain a lithium-ion battery.

[0053] (4) Battery testing

[0054] After the battery was left to stand for 24 hours, it was activated by two charge-discharge cycles at 0.1C at room temperature, with the voltage range being 2.5V-4.5V, followed by activation at -20°C. o Cycle the battery at a charge / discharge rate of 0.2C under C conditions, record the discharge voltage and capacity, and calculate the discharge specific capacity.

[0055] The electrolyte prepared in this embodiment exhibits high ionic conductivity ( Figure 1 ).

[0056] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o C and charged to a high voltage of 4.5V, then subjected to charge-discharge cycles at a rate of 0.2C. Figure 2 As shown, it can still maintain a stable 170.6 mAh g after 150 cycles. -1 It achieves high capacity and maintains a high capacity retention rate of 95.2%. The charge / discharge curves are as follows: Figure 3 As shown, the capacity hardly decreased after 150 cycles and remained stable under high voltage; this indicates that the electrolyte of this invention has great stability when applied to low-temperature lithium-ion batteries under high voltage.

[0057] The lithium-ion battery (coin cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures of -40°C. o Under C and at a high voltage of 4.5V (activation method as above), perform charge-discharge cycles at a rate of 0.2C. Figure 4 As shown, it can stably maintain 140.1 mAhg after 100 cycles. -1 The electrolyte exhibits a high capacity retention rate of 92.3%, demonstrating excellent electrochemical stability in lithium-ion batteries at ultra-low temperatures.

[0058] The electrolyte prepared in this embodiment is used to assemble a 4.7 Ah lithium-ion pouch battery. The specific method is as follows: NCM811 is used as the positive electrode active material, graphite is used as the negative electrode active material, and the separator is a PE-based film composite ceramic layer. The assembly process is as follows: first, the positive electrode (NCM811) electrode sheet and the negative electrode (graphite) electrode sheet are prepared, using the same method as above; and then the PE separator is ceramic coated (after Al2O3 sol coating, in an air atmosphere, 850). o Sintering (C) for 1.5 hours, slitting and drying; then, Z-shaped alternating stacking (diaphragm-positive electrode-diaphragm-negative electrode) is achieved through a folding machine. After hot pressing and fixing, the positive electrode aluminum tabs are ultrasonically welded to the aluminum busbar, and the negative electrode copper tabs are ultrasonically welded to the nickel strip. Next, the folded assembly is placed into the groove of the punched aluminum-plastic film, and after top and side sealing, electrolyte is injected into the glove box. After pre-sealing, it is subjected to 55... o The film was formed by static incubation at C and activation at 0.1C. Subsequently, it was heated to -20°C. o After 100 cycles under condition C, the capacity remains above 3.7 Ah, with a capacity retention rate of 95%. Figure 5 This provides a promising electrolyte for the commercial application of low-temperature lithium-ion batteries.

[0059] Example 2

[0060] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries comprises the following components: diethyl carbonate (DEC), acetonitrile (AN), (trifluoromethyl)trimethylsilane (TFTMS), and lithium difluorooxalate borate (LiDFOB); wherein the volume ratio of diethyl carbonate (DEC), acetonitrile (AN), and (pentafluoroethyl)trimethylsilane (PFTMS) is 7:2:1; and the concentration of lithium difluorooxalate borate (LiDFOB) in the electrolyte is 1 mol / L.

[0061] The preparation method of the above-mentioned high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries includes the following steps:

[0062] In an argon-filled glove box, diethyl carbonate (DEC), acetonitrile (AN), and (trifluoromethyl)trimethylsilane (PFTMS) are thoroughly mixed and then lithium difluorooxalate borate (LiDFOB) is added and stirred until completely dissolved to obtain the electrolyte.

[0063] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0064] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o Under high voltage of 4.5V and charge-discharge cycled at a rate of 0.2C, it can still stably maintain 168mAh g after 150 cycles. -1It has a high capacity and exhibits a capacity retention rate of 93.5%.

[0065] The lithium-ion battery (coin cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures of -40°C. o Under C and at a high voltage of 4.5V (activation method as above), after charge-discharge cycle at a rate of 0.2C for 100 cycles, it can stably maintain 136.5 mAhg. -1 It has the capacity and achieves a high capacity retention rate of 91.6%.

[0066] Example 3

[0067] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries comprises the following components: diethyl carbonate (DEC), (pentafluoroethyl)trimethylsilane (PFTMS), and lithium difluorooxalate borate (LiDFOB); wherein the volume ratio of diethyl carbonate (DEC) to (pentafluoroethyl)trimethylsilane (PFTMS) is 9:1; and the concentration of lithium difluorooxalate borate (LiDFOB) in the electrolyte is 1 mol / L.

[0068] The preparation method of the above-mentioned high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries includes the following steps:

[0069] In an argon-filled glove box, diethyl carbonate (DEC) and (pentafluoroethyl)trimethylsilane (PFTMS) are thoroughly mixed, and then lithium difluorooxalate borate (LiDFOB) is added and stirred until completely dissolved to obtain the electrolyte.

[0070] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0071] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o At a high voltage of 4.5V and a charge-discharge rate of 0.2C, after 150 cycles, it still maintains a stable performance of 160.8 mAh g⁻¹. -1 It has a high capacity and exhibits a capacity retention rate of 85.4%.

[0072] The lithium-ion battery (coin cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures of -40°C. o Under C and at a high voltage of 4.5V (activation method as above), after 100 charge-discharge cycles at a rate of 0.2C, it can stably maintain 132.3 mAhg. -1 It has the capacity and achieves a high capacity retention rate of 84.3%.

[0073] Example 4

[0074] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries comprises the following components: 1,3-dioxo-2-silanecyclopentane (DS), acetonitrile (AN), trimethylfluorosilane (FTMS), lithium difluorooxalate borate (LiDFOB), and lithium hexafluorophosphate (LiPF6); wherein the volume ratio of 1,3-dioxo-2-silanecyclopentane (DS), acetonitrile (AN), and trimethylfluorosilane (FTMS) is 8:1:1; the concentration of lithium difluorooxalate borate (LiDFOB) in the electrolyte is 0.8 mol / L, and the concentration of lithium hexafluorophosphate (LiPF6) is 0.2 mol / L.

[0075] The preparation method of the above-mentioned high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries includes the following steps:

[0076] In an argon-filled glove box, 1,3-dioxo-2-silane (DS), acetonitrile (AN), and trimethylfluorosilane (FTMS) are thoroughly mixed, and then lithium difluorooxalate borate (LiDFOB) and lithium hexafluorophosphate (LiPF6) are added and stirred until completely dissolved to obtain the electrolyte.

[0077] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0078] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o At a high voltage of 4.5V and a charge-discharge rate of 0.2C, after 150 cycles, it still maintains a stable performance of 150.3 mAh g⁻¹. -1 It has high capacity and exhibits a capacity retention rate of 88.6%.

[0079] Example 5

[0080] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries comprises the following components: phenylacetonitrile (BAN), acetonitrile (AN), tetrabutyltin (TBT), (pentafluoroethyl)trimethylsilane (PFTMS), and lithium difluorooxalate borate (LiDFOB); wherein the volume ratio of phenylacetonitrile (BAN), acetonitrile (AN), tetrabutyltin (TBT), and (pentafluoroethyl)trimethylsilane (PFTMS) is 6:1:2:1; and the concentration of lithium difluorooxalate borate (LiDFOB) in the electrolyte is 1 mol / L.

[0081] The preparation method of the above-mentioned high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries includes the following steps:

[0082] In an argon-filled glove box, phenylacetonitrile (BAN), acetonitrile (AN), tetrabutyltin (TBT), and (pentafluoroethyl)trimethylsilane (PFTMS) are thoroughly mixed and then lithium difluorooxalate borate (LiDFOB) is added and stirred until completely dissolved to obtain the electrolyte.

[0083] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0084] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o At a high voltage of 4.5V and a charge-discharge rate of 0.2C, after 150 charge-discharge cycles, it still maintains a stable performance of 140.5 mAh g⁻¹. -1 It has a high capacity and exhibits a capacity retention rate of 91.5%.

[0085] Example 6

[0086] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries comprises the following components: oxalonitrile (MNT), acetonitrile (AN), tributyltin hydride (TBTH), lithium difluorooxalate borate (LiDFOB), and lithium bisfluorosulfonylimide (LiFSI); wherein the volume ratio of oxalonitrile (MNT), acetonitrile (AN), and tributyltin hydride (TBTH) is 6:3:1; the concentration of lithium difluorooxalate borate (LiDFOB) in the electrolyte is 0.6 mol / L, and the concentration of lithium bisfluorosulfonylimide (LiFSI) is 0.4 mol / L.

[0087] The preparation method of the above-mentioned high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries includes the following steps:

[0088] In an argon-filled glove box, ethylene nitrile (MNT), acetonitrile (AN), and tributyltin hydride (TBTH) are thoroughly mixed, and then lithium difluorooxalatoborate (LiDFOB) and lithium difluorosulfonylimide (LiFSI) are added and stirred until completely dissolved to obtain the electrolyte.

[0089] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0090] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o At a high voltage of 4.5V and a charge-discharge rate of 0.2C, after 150 cycles, it still maintains a stable performance of 100.3 mAh g⁻¹. -1 It has a high capacity and exhibits a capacity retention rate of 84.3%.

[0091] Example 7

[0092] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries comprises the following components: phenylacetonitrile (BAN), dioctyltin dilaurate (DOTDL), lithium difluorooxalate borate (LiDFOB), lithium hexafluorophosphate (LiPF6), and lithium bisfluorosulfonylimide (LiFSI); wherein the volume ratio of phenylacetonitrile (BAN) to dioctyltin dilaurate (DOTDL) is 9:1; the concentration of lithium difluorooxalate borate (LiDFOB) in the electrolyte is 0.5 mol / L, the concentration of lithium hexafluorophosphate (LiPF6) is 0.4 mol / L, and the concentration of lithium bisfluorosulfonylimide (LiFSI) is 0.1 mol / L.

[0093] The preparation method of the above-mentioned high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries includes the following steps:

[0094] In an argon-filled glove box, phenylacetonitrile (BAN) and dioctyltin dilaurate (DOTDL) are thoroughly mixed, and then lithium difluorooxalate borate (LiDFOB), lithium hexafluorophosphate (LiPF6), and lithium difluorosulfonylimide (LiFSI) are added and stirred until completely dissolved to obtain the electrolyte.

[0095] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0096] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o At a high voltage of 4.5V and a charge-discharge rate of 0.2C, after 150 cycles, it still maintains a stable performance of 120.3 mAh g⁻¹. -1 It has high capacity and achieves a capacity retention rate of 73.6%.

[0097] Example 8

[0098] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries comprises the following components: acetonitrile (AN), (pentafluoroethyl)trimethylsilane (PFTMS), (trifluoromethyl)trimethylsilane (TFTMS), tributyltin hydride (TBTH), and lithium hexafluorophosphate (LiPF6); wherein the volume ratio of acetonitrile (AN), (pentafluoroethyl)trimethylsilane (PFTMS), (trifluoromethyl)trimethylsilane (TFTMS), and tributyltin hydride (TBTH) is 7:1:1:1; and the concentration of lithium hexafluorophosphate (LiPF6) in the electrolyte is 1 mol / L.

[0099] The preparation method of the above-mentioned high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries includes the following steps:

[0100] In an argon-filled glove box, acetonitrile (AN), (pentafluoroethyl)trimethylsilane (PFTMS), (trifluoromethyl)trimethylsilane (TFTMS), and tributyltin hydride (TBTH) are thoroughly mixed and then lithium hexafluorophosphate (LiPF6) is added. The mixture is stirred until it is completely dissolved to obtain the electrolyte.

[0101] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0102] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o At a high voltage of 4.5V and a charge-discharge rate of 0.2C, after 150 cycles, it still maintains a stable performance of 165.2 mAh g⁻¹. -1 It has high capacity and achieves a capacity retention rate of 83.9%.

[0103] Example 9

[0104] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries comprises the following components: oxonium (MNT), (pentafluoroethyl)trimethylsilane (PFTMS), (difluoromethyl)trimethylsilane (DFTMS), and lithium hexafluorophosphate (LiPF6); wherein the volume ratio of oxonium (MNT), (pentafluoroethyl)trimethylsilane (PFTMS), and (difluoromethyl)trimethylsilane (DFTMS) is 8:1:1; and the concentration of lithium hexafluorophosphate (LiPF6) in the electrolyte is 1 mol / L.

[0105] The preparation method of the above-mentioned high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries includes the following steps:

[0106] In an argon-filled glove box, ethylene nitrile (MNT), (pentafluoroethyl)trimethylsilane (PFTMS), and (difluoromethyl)trimethylsilane (DFTMS) are thoroughly mixed and then lithium hexafluorophosphate (LiPF6) is added. The mixture is stirred until it is completely dissolved to obtain the electrolyte.

[0107] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0108] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. oWhen charged to a high voltage of 4.5V and cycled at a rate of 0.2C for 150 cycles, it still maintains a stable performance of 166.5 mAh g. -1 It has high capacity and achieves a capacity retention rate of 92.7%.

[0109] Example 10

[0110] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries comprises the following components: acetonitrile (AN), (pentafluoroethyl)trimethylsilane (PFTMS), (trifluoromethyl)trimethylsilane (TFTMS), (difluoromethyl)trimethylsilane (DFTMS), and lithium hexafluorophosphate (LiPF6); wherein the volume ratio of acetonitrile (AN), (pentafluoroethyl)trimethylsilane (PFTMS), (trifluoromethyl)trimethylsilane (TFTMS), and (difluoromethyl)trimethylsilane (DFTMS) is 7:1.5:1:0.5; and the concentration of lithium hexafluorophosphate (LiPF6) in the electrolyte is 1 mol / L.

[0111] The preparation method of the above-mentioned high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries includes the following steps:

[0112] In an argon-filled glove box, acetonitrile (AN), (pentafluoroethyl)trimethylsilane (PFTMS), (trifluoromethyl)trimethylsilane (TFTMS), and (difluoromethyl)trimethylsilane (DFTMS) are thoroughly mixed and then lithium hexafluorophosphate (LiPF6) is added. The mixture is stirred until it is completely dissolved to obtain the electrolyte.

[0113] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0114] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o At a high voltage of 4.5V and a charge-discharge rate of 0.2C, after 150 charge-discharge cycles, it still maintains a stable 169mAh capacity. -1 It has high capacity and maintains a capacity retention rate of 94.1%.

[0115] Example 11

[0116] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries is described in Example 1, except that lithium difluorooxalate borate (LiDFOB) is used as the lithium salt, and the concentration of LiDFOB in the electrolyte is 1 mol / L; the composition of other raw materials is the same as in Example 1.

[0117] The preparation method of the high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries described above is the same as that in Example 1, except that it is the same as above.

[0118] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0119] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o At a high voltage of 4.5V and a charge-discharge rate of 0.2C, after 150 charge-discharge cycles, it still maintains a stable 165mAh capacity. -1 It has high capacity and maintains a capacity retention rate of 90.3%.

[0120] Example 12

[0121] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries is described in Example 1, except that lithium bis(fluorosulfonyl)imide (LiFSI) is used as the lithium salt, and the concentration of lithium bis(fluorosulfonyl)imide (LiFSI) in the electrolyte is 1 mol / L; the composition of other raw materials is the same as in Example 1.

[0122] The preparation method of the high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries described above is the same as that in Example 1, except that it is the same as above.

[0123] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0124] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o At a high voltage of 4.5V and a charge-discharge rate of 0.2C, after 150 charge-discharge cycles, it still maintains a stable 167mAh capacity. -1 It has high capacity and maintains an 89.6% capacity retention rate.

[0125] Example 13

[0126] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries, as described in Example 1, except that the base solvent is acetonitrile (AN); the volume ratio of acetonitrile (AN), trimethylfluorosilane (FTMS), (trifluoromethyl)trimethylsilane (TFTMS), and tetrabutyltin (TBT) is 7:1:1:1; the composition of other raw materials is the same as in Example 1.

[0127] The preparation method of the high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries described above is the same as that in Example 1, except that it is the same as above.

[0128] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0129] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o At a high voltage of 4.5V and a charge-discharge rate of 0.2C, after 150 cycles, it still maintains a stable performance of 163 mAh g⁻¹. -1 It has high capacity and maintains a capacity retention rate of 93.7%.

[0130] Example 14

[0131] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries, as described in Example 1, except that the base solvent is ethoxytriethylsilane (TEEOS); the volume ratio of ethoxytriethylsilane (TEEOS), trimethylfluorosilane (FTMS), (trifluoromethyl)trimethylsilane (TFTMS), and tetrabutyltin (TBT) is 7:1:1:1; the composition of other raw materials is the same as in Example 1.

[0132] The preparation method of the high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries described above is the same as that in Example 1, except that it is the same as above.

[0133] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0134] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o At a high voltage of 4.5V and a charge-discharge rate of 0.2C, after 150 charge-discharge cycles, it still maintains a stable performance of 161.8 mAh g / L. -1 It has high capacity and maintains an 85.6% capacity retention rate.

[0135] Example 15

[0136] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries, as described in Example 1, except that the non-solvent co-solvent is trimethylfluorosilane (FTMS); the volume ratio of acetonitrile (AN), ethoxytriethylsilane (TEEOS), and trimethylfluorosilane (FTMS) is 5:2:3; the composition of other raw materials is the same as in Example 1.

[0137] The preparation method of the high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries described above is the same as that in Example 1, except that it is the same as above.

[0138] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0139] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o At a high voltage of 4.5V and a charge-discharge rate of 0.2C, after 150 charge-discharge cycles, it still maintains a stable performance of 142.1 mAh g / L. -1 It has high capacity and maintains a capacity retention rate of 70.4%.

[0140] Example 16

[0141] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries, as described in Example 1, except that the non-solvent co-solvent is trimethylfluorosilane (FTMS) and (trifluoromethyl)trimethylsilane (TFTMS); the volume ratio of acetonitrile (AN), ethoxytriethylsilane (TEEOS), trimethylfluorosilane (FTMS), and (trifluoromethyl)trimethylsilane (TFTMS) is 5:2:1.5:1.5; the composition of other raw materials is the same as in Example 1.

[0142] The preparation method of the high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries described above is the same as that in Example 1, except that it is the same as above.

[0143] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0144] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o At a high voltage of 4.5V and a charge-discharge rate of 0.2C, after 150 cycles, it still maintains a stable performance of 156 mAh g⁻¹. -1 It has high capacity and maintains an 82.5% capacity retention rate.

[0145] Example 17

[0146] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries, as described in Example 1, except that the non-solvent co-solvent is trimethylfluorosilane (FTMS) and tetrabutyltin (TBT); the volume ratio of acetonitrile (AN), ethoxytriethylsilane (TEEOS), trimethylfluorosilane (FTMS), and tetrabutyltin (TBT) is 5:2:1.5:1.5; the composition of other raw materials is the same as in Example 1.

[0147] The preparation method of the high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries described above is the same as that in Example 1, except that it is the same as above.

[0148] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0149] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o At a high voltage of 4.5V and a charge-discharge rate of 0.2C, after 150 cycles, it still maintains a stable performance of 162 mAh g⁻¹. -1 It has high capacity and maintains an 86.1% capacity retention rate.

[0150] Example 18

[0151] A high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries is described in Example 1, except that the non-solvent co-solvent is (trifluoromethyl)trimethylsilane (TFTMS) and tetrabutyltin (TBT); the volume ratio of acetonitrile (AN), ethoxytriethylsilane (TEEOS), (trifluoromethyl)trimethylsilane (TFTMS), and tetrabutyltin (TBT) is 5:2:1.5:1.5; the composition of other raw materials is the same as in Example 1.

[0152] The preparation method of the high-voltage, high-electrochemical-performance electrolyte for low-temperature lithium-ion batteries described above is the same as that in Example 1, except that it is the same as above.

[0153] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0154] The lithium-ion battery (button cell) assembled with the electrolyte prepared in this embodiment can withstand temperatures up to -20°C. o At a high voltage of 4.5V and a charge-discharge rate of 0.2C, after 150 charge-discharge cycles, it still maintains a stable performance of 160.1 mAh g / L. -1 It has high capacity and maintains an 85% capacity retention rate.

[0155] Comparative Example 1

[0156] An electrolyte for a low-temperature lithium-ion battery comprises: ethylene carbonate (EC), diethyl carbonate (DEC), and lithium hexafluorophosphate (LiPF6); wherein the volume ratio of ethylene carbonate (EC) to diethyl carbonate (DEC) is 1:1; and the concentration of lithium hexafluorophosphate (LiPF6) in the electrolyte is 1 mol / L.

[0157] The preparation method of the electrolyte for the aforementioned low-temperature lithium-ion battery includes the following steps:

[0158] In an argon-filled glove box, ethylene carbonate (EC) and diethyl carbonate (DEC) are thoroughly mixed, and then lithium hexafluorophosphate (LiPF6) is added and stirred until completely dissolved to obtain the electrolyte.

[0159] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0160] The lithium-ion battery (coin cell) assembled with the electrolyte prepared in this comparative example, at -20°C... o Under C and charged to 4.5 V, it was charged and discharged at a rate of 0.2 C for 150 cycles, maintaining a capacity of 42 mAh g. -1 The capacity retention rate was 36.4%; the cycle performance was poor.

[0161] Comparative Example 2

[0162] An electrolyte for a low-temperature lithium-ion battery comprises: ethylene carbonate (EC), ethyl methyl carbonate (EMC), and lithium hexafluorophosphate (LiPF6); wherein the volume ratio of ethylene carbonate (EC) to ethyl methyl carbonate (EMC) is 3:7; and the concentration of lithium hexafluorophosphate (LiPF6) in the electrolyte is 1 mol / L.

[0163] The preparation method of the electrolyte for the aforementioned low-temperature lithium-ion battery includes the following steps:

[0164] In an argon-filled glove box, ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are thoroughly mixed, and then lithium hexafluorophosphate (LiPF6) is added and stirred until completely dissolved to obtain the electrolyte.

[0165] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0166] The lithium-ion battery (coin cell) assembled with the electrolyte prepared in this comparative example, at -20°C... o Under C and at a voltage of 4.5 V, after charge-discharge cycling at a rate of 0.2 C for 150 cycles, it exhibits an 80mAh capacity. -1 The capacity retention rate was 43.3%; the cycle performance was poor.

[0167] Comparative Example 3

[0168] An electrolyte for a low-temperature lithium-ion battery comprises: propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and lithium hexafluorophosphate (LiPF6); wherein the volume ratio of propylene carbonate (PC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) is 1:1:1; and the concentration of lithium hexafluorophosphate (LiPF6) in the electrolyte is 1 mol / L.

[0169] The preparation method of the electrolyte for the aforementioned low-temperature lithium-ion battery includes the following steps:

[0170] In an argon-filled glove box, propylene carbonate (PC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are thoroughly mixed and then lithium hexafluorophosphate (LiPF6) is added. The mixture is stirred until it is completely dissolved to obtain the electrolyte.

[0171] The electrolyte obtained above was used to prepare a low-temperature lithium-ion battery (button cell), and the steps were as described in Example 1.

[0172] The lithium-ion battery (coin cell) assembled with the electrolyte prepared in this comparative example, at -20°C... o Under C and charged to 4.5 V, and subjected to charge-discharge cycles at a rate of 0.2 C, after 150 cycles, it exhibits a capacity of 100 mAh g. -1 The capacity retention rate was 48.5%; the cycle performance was poor.

[0173] The following table compares some of the electrical performance data of the electrolytes prepared in the embodiments and comparative examples of the present invention.

[0174] Table 1 Comparison of Partial Electrical Performance Data (-20) o C)

[0175]

[0176] As can be clearly seen from the data in the table above, the electrolyte of this invention can not only achieve a high charging cutoff voltage of 4.5V, but also achieve -20V. o High capacity retention at low temperatures. The electrolyte-matched lithium-ion battery obtained in this invention exhibits high capacity, good cycle stability, and high capacity retention at low temperatures.

Claims

1. An electrolyte for a lithium ion battery, characterized by, The electrolyte comprises the following components: lithium salt, base solvent and non-solvent co-solvent; the base solvent is one or a combination of two or more of linear siloxane or nitrile; the non-solvent co-solvent is a combination of fluorinated silane and stannane; the volume ratio of the base solvent and non-solvent co-solvent is 5-9:1-5; The stannane is one or a combination of two or more of tetrabutyltin, dioctyltin dilaurate or tributyltin hydride.

2. The electrolyte for a lithium ion battery according to claim 1, wherein The lithium salt is one or a combination of two or more of lithium hexafluorophosphate, lithium difluoro(oxalato)borate or lithium bis(fluorosulfonyl)imide; the concentration of the lithium salt in the electrolyte is 0.8-1.5 mol·L -1 .

3. The electrolyte for a lithium ion battery according to claim 1, wherein The lithium salt is lithium hexafluorophosphate, lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide, a combination of lithium difluoro(oxalato)borate and lithium hexafluorophosphate, a combination of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, or a combination of lithium difluoro(oxalato)borate and lithium bis(fluorosulfonyl)imide; in the combination of lithium difluoro(oxalato)borate and lithium bis(fluorosulfonyl)imide, the molar ratio of lithium difluoro(oxalato)borate and lithium bis(fluorosulfonyl)imide is 1:0.5-5.

4. The electrolyte for a lithium ion battery according to claim 1, wherein One or more of the following conditions is included: i. The linear siloxane is one or a combination of two or more of methoxytrimethylsilane, ethoxytriethylsilane or 1,3-dioxo-2-silacyclopentane; ii. The nitrile is one or a combination of two or more of acetonitrile, benzonitrile or ethanedinitrile.

5. The electrolyte for a lithium ion battery according to claim 1, wherein The base solvent is a combination of acetonitrile and ethoxytriethylsilane, a combination of 1,3-dioxo-2-silacyclopentane and acetonitrile, a combination of acetonitrile and benzonitrile, a combination of ethanedinitrile and acetonitrile, ethoxytriethylsilane, ethanedinitrile, benzonitrile or acetonitrile.

6. The electrolyte for a lithium ion battery according to claim 1, wherein The fluorinated silane is one or a combination of two or more of trimethylfluorosilane, (difluoromethyl)trimethylsilane, (trifluoromethyl)trimethylsilane or (pentafluoroethyl)trimethylsilane.

7. The electrolyte for a lithium ion battery according to claim 1, wherein The non-solvent co-solvent is a combination of trimethylfluorosilane, (trifluoromethyl)trimethylsilane and tetrabutyltin, a combination of tetrabutyltin and (pentafluoroethyl)trimethylsilane, a combination of trimethylfluorosilane and tetrabutyltin, a combination of (trifluoromethyl)trimethylsilane and tetrabutyltin, or a combination of (pentafluoroethyl)trimethylsilane, (trifluoromethyl)trimethylsilane and tributyltin hydride.

8. The electrolyte for a lithium ion battery according to claim 1, wherein The volume ratio of the base solvent and non-solvent co-solvent is 7-9:1-3.

9. The process for the preparation of an electrolyte for lithium-ion batteries according to any one of claims 1 to 8, characterized in that, The step of mixing the lithium salt, base solvent and non-solvent co-solvent sufficiently and uniformly to obtain the electrolyte for lithium ion battery is included.

10. Use of the electrolyte for lithium ion battery according to any one of claims 1-8 in a lithium ion battery.

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