Fast charging electrolyte and lithium ion battery containing same

Abstract

The invention discloses a fast charging electrolyte and a lithium ion battery containing the same. The fast charging electrolyte comprises an additive and a non-aqueous solvent, the additives comprise a lithium-containing additive, tris (pentafluorophenyl) borane and a film-forming additive, the mass percentage of the additives is 0.5-5% based on the total mass of the fast charging electrolyte, and the mass ratio of the lithium-containing additive to the tris (pentafluorophenyl) borane is 1: 0.5-1: 5; the non-aqueous solvent comprises a first solvent component, a second solvent component and a third solvent component, the volume ratio of the first solvent component to the second solvent component is 1: 1-1: 2, and the third solvent component contains fluorine. The fast-charging electrolyte can effectively optimize ion transmission of lithium ions at an interface in the high-rate charging process of the battery and maintain dynamic balance of the interface, and the charging rate of the lithium ion battery is improved.

Description

Technical Field

[0001] This application belongs to the field of battery energy storage technology, and particularly relates to a fast-charging electrolyte and a lithium-ion battery containing the same. Background Technology

[0002] Currently, fast charging of lithium-ion batteries faces three major challenges: First, there is a hysteresis problem in the anode dynamics. The layered structure of graphite allows lithium ions to be inserted only from the ends. During high-current charging, ion accumulation and lithium plating are likely to occur, which not only reduces coulombic efficiency but also induces the risk of battery thermal runaway. Second, there is a contradiction between mass transfer path and energy density. Although thick electrode design can improve energy density, it will extend the solid-phase diffusion path of lithium ions to the micrometer level, resulting in intensified concentration polarization and a surge in capacity decay at the end of charging. Third, interface stability is prone to collapse. Traditional carbonate-based electrolytes will continue to decompose during high-potential fast charging, causing the SEI film to repeatedly break and repair, continuously consuming the active lithium source. Summary of the Invention

[0003] This application provides a fast-charging electrolyte and a lithium-ion battery containing the same. The fast-charging electrolyte can effectively optimize the ion transport of lithium ions at the interface and maintain the dynamic balance of the interface during the high-rate charging process of the battery, thereby improving the charging rate of the lithium-ion battery.

[0004] In a first aspect, embodiments of this application provide a fast-charging electrolyte, comprising: additives and a non-aqueous solvent; the additives include a lithium-containing additive, tris(pentafluorophenyl)borane, and a film-forming additive, wherein the mass percentage of the additives is 0.5% to 5% based on the total mass of the fast-charging electrolyte, and the mass ratio of the lithium-containing additive to tris(pentafluorophenyl)borane is 1:0.5 to 1:5; the non-aqueous solvent comprises a first solvent component, a second solvent component, and a third solvent component, wherein the volume ratio of the first solvent component and the second solvent component is 1:1 to 1:2, and the third solvent component contains fluorine.

[0005] According to the embodiments of this application, the fast-charging electrolyte of this application satisfies the following conditions: the mass percentage content of the additive is 0.5% to 5%, the mass ratio of lithium-containing additive to tris(pentafluorophenyl)borane is 1:0.5 to 1:5, the volume ratio of the first solvent component to the second solvent component is 1:1 to 1:2, and the third solvent component contains fluorine. When the components in the electrolyte work synergistically, a dynamic dissolution-deposition electrode / electrolyte interface can be established, effectively optimizing the ion transport of lithium ions at the interface and maintaining the dynamic balance of the interface during the high-rate charging process of lithium-ion batteries, thereby improving the charging rate of lithium-ion batteries.

[0006] In some possible implementations, the third solvent component comprises fluoroethylene carbonate, and the mass percentage of the third solvent component is 10% to 30% based on the total mass of the non-aqueous solvent.

[0007] In the above possible embodiments, when the third solvent component includes fluoroethylene carbonate, and its mass percentage is 10% to 30% based on the total mass of the non-aqueous solvent, the synergistic effect among the electrolyte components can be further enhanced. This promotes the dissociation and migration of lithium ions in the electrolyte, providing a more favorable environment for the rapid transport of lithium ions at the electrode / electrolyte interface. Simultaneously, the fluorine characteristics of fluoroethylene carbonate allow it to participate in the film-forming reaction on the electrode surface, working in conjunction with lithium-containing additives, tris(pentafluorophenyl)borane, and film-forming additives to form a more stable, denser, and ionicly conductive solid electrolyte interphase (SEI) film. This effectively inhibits excessive decomposition of the electrolyte on the electrode surface, reduces the occurrence of side reactions, and better adapts to volume changes in the electrode material during high-rate charging, maintaining the integrity and stability of the interface.

[0008] In some possible implementations, the mass ratio of tris(pentafluorophenyl)borane to film-forming additives is 1:1 to 1:3.

[0009] In the above possible implementations, when the mass ratio of tris(pentafluorophenyl)borane to film-forming additives is 1:1 to 1:3, the dynamic dissolution-deposition interface balance can be further optimized. During high-rate charging, when lithium ions rapidly migrate to the electrode surface, the high-quality SEI film formed by tris(pentafluorophenyl)borane and film-forming additives reduces concentration polarization and kinetic hindrance at the interface. This allows lithium ions to quickly cross the interface and enter the electrode to complete deposition, while maintaining the dynamic stability of the film layer during minor deposition / dissolution at the interface, thus preventing the aggravation of side reactions caused by film layer damage. Therefore, the effect of fast-charging electrolytes in improving the charging rate of lithium-ion batteries is further enhanced, especially under high-rate conditions, better improving the cycle stability and charging efficiency of lithium-ion batteries.

[0010] In some possible implementations, the fast-charging electrolyte may further include a lithium salt, wherein the molar concentration of the lithium salt in the fast-charging electrolyte is 1 mol / L to 5 mol / L. Optionally, the lithium salt may include lithium bis(fluorosulfonyl)imide and / or lithium hexafluorophosphate.

[0011] In some possible implementations, the lithium salt comprises lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate, wherein the mass ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate is 1:1 to 1:3.

[0012] In the above possible implementations, when the mass ratio of lithium difluorosulfonylimide to lithium hexafluorophosphate is 1:1 to 1:3, the mixed lithium salt system, together with lithium-containing additives and tris(pentafluorophenyl)borane, further optimizes the solvation structure of lithium ions. The FSI- in LiFSI has a moderate binding capacity with lithium ions and can work with fluoroethylene carbonate to regulate the desolvation process of lithium ions, making lithium ion transport smoother at the electrode / electrolyte interface. Simultaneously, the fluorine-containing species generated from the decomposition of LiFSI can participate in the formation of the SEI film, working in conjunction with the film-forming additives to enhance the density and stability of the film, effectively suppressing excessive decomposition of the electrolyte during high-rate charging.

[0013] Furthermore, this mixed lithium salt system exhibits a good synergistic effect with the fluorinated third solvent component. The fluorinated solvent has good solubility for both LiFSI and LiPF6, ensuring uniform dispersion of the mixed lithium salt in the electrolyte and maintaining high ionic conductivity. At ratios of 1:1 to 1:3, the system formed by the mixed lithium salt and non-aqueous solvent possesses suitable viscosity and dielectric constant, providing a smooth channel for lithium-ion migration while reducing concentration polarization. This plays a positive role in the dynamic dissolution-deposition electrode / electrolyte interface balance, further improving the charging rate and cycle stability of lithium-ion batteries.

[0014] In some possible implementations, the lithium-containing additive includes lithium difluorophosphate.

[0015] In the above possible embodiments, lithium difluorophosphate can form a boron-fluorine composite SEI film with tris(pentafluorophenyl)borane, which can further improve the chemical stability of the SEI film, effectively resist electrolyte erosion, and reduce the dissolution or decomposition of the SEI film. Simultaneously, the boron-fluorine composite SEI film has a dense and uniform structure, which can act as a physical barrier to reduce direct contact between the electrolyte and the electrode, inhibit the continuous decomposition of the electrolyte during charge and discharge, and reduce the battery capacity decay rate.

[0016] In some possible implementations, the film-forming additive includes 1,3-propanesulfonyl lactone.

[0017] In some possible implementations, the first solvent component includes dimethyl carbonate; and / or, the second solvent component includes ethyl methyl carbonate and / or diethyl carbonate, optionally, the second solvent component is ethyl methyl carbonate.

[0018] In the above possible implementation, when the first component is dimethyl carbonate and the second component is ethyl methyl carbonate, a mixed solvent base with low viscosity and high ionic conductivity can be formed. The lower viscosity can reduce the resistance during lithium ion migration, allowing ions to quickly pass through the electrolyte to reach the electrode interface during high-rate charging. Meanwhile, a suitable dielectric constant can ensure that the lithium salt is fully dissociated, providing sufficient charge carriers for ion transport. The synergistic effect of the two can further improve the lithium ion transport efficiency.

[0019] Secondly, embodiments of this application provide a lithium-ion battery, which includes a positive electrode, a negative electrode, a separator, and a fast-charging electrolyte as described in the first aspect. This lithium-ion battery exhibits excellent fast-charging performance.

[0020] In the above possible implementations, when the lithium-ion battery satisfies any of the above conditions, the negative electrode active material layer and the fast-charging electrolyte work together to further enhance the stability of the SEI film, so that the SEI film can withstand the stress generated by repeated lithium-ion insertion / extraction during high-rate charging.

[0021] In some possible implementations, the lithium-ion battery satisfies at least one of the following: (1) after 500 cycles at 25°C, a charging rate of 4.0C, and a discharging rate of 1.0C, the capacity retention rate of the lithium-ion battery is greater than or equal to 65%; optionally, after 3000 cycles at 25°C, a charging rate of 4.0C, and a discharging rate of 1.0C, the capacity retention rate of the lithium-ion battery is greater than or equal to 70%; (2) after 500 cycles at 25°C, a charging rate of 4.0C, and a discharging rate of 1.0C, the coulombic efficiency of the lithium-ion battery is greater than or equal to 99.5%; optionally, after 3000 cycles at 25°C, a charging rate of 4.0C, and a discharging rate of 1.0C, the coulombic efficiency of the lithium-ion battery is greater than or equal to 99.9%. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a graph showing the high-rate, long-cycle performance of a lithium-ion battery in Example 1 of this application.

[0024] Figure 2 This is a graph showing the high-rate, long-cycle performance of a lithium-ion battery in Example 2 of this application.

[0025] Figure 3This is a graph showing the high-rate, long-cycle performance of the lithium-ion battery in Example 3 of this application.

[0026] Figure 4 This is a graph showing the high-rate, long-cycle performance of the lithium-ion battery in Example 4 of this application.

[0027] Figure 5 This is a graph showing the high-rate, long-cycle performance of a lithium-ion battery in Example 5 of this application.

[0028] Figure 6 This is a graph showing the high-rate, long-cycle performance of a lithium-ion battery in Comparative Example 1 of this application.

[0029] Figure 7 This is a graph showing the high-rate, long-cycle performance of the lithium-ion battery in Comparative Example 2 of this application.

[0030] Figure 8 This is a graph showing the high-rate, long-cycle performance of the lithium-ion battery in Comparative Example 3 of this application. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] The embodiments of this application will be described in detail below. These embodiments should not be construed as limiting the scope of this application.

[0033] As used in this application, the terms “comprising,” “containing,” and “including” are used in their open, non-restrictive sense.

[0034] Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format in this document. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only the numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0035] In the detailed description and claims, a list of items connected by the terms "one or more of," "one or more of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A or B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, or C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0036] With the rapid increase in electric vehicle penetration to over 25% of global car sales, and the rigid demand for high-power-density batteries from emerging fields such as drones and power tools, ultra-fast charging technology (XFC) for lithium-ion batteries, aiming for a charging rate of 6C or higher, has become a core driving force for industrial upgrading. The increasing demands from the consumer market for fast charging of lithium-ion batteries in various application scenarios are forcing battery material systems to break through traditional limitations.

[0037] However, current technology faces a triple coupling bottleneck: First, negative electrode kinetics are sluggish. The layered structure of graphite means that lithium ions can only be inserted from the ends. During high-current charging, ion accumulation leads to lithium plating, which not only reduces coulombic efficiency but also induces the risk of thermal runaway. Second, there is a contradiction between mass transfer pathways and energy density. While thick electrode designs improve energy density, they extend the lithium ion solid-phase diffusion path to the micrometer level, exacerbating concentration polarization and causing a surge in capacity decay at the end of charging. Third, interface stability collapses. Traditional carbonate-based electrolytes continuously decompose during high-potential fast charging, and the SEI film repeatedly ruptures and repairs, consuming the active lithium source. Optimizing existing electrolyte formulations is an effective measure to achieve stable high-rate discharge while ensuring high compatibility with current battery manufacturing processes.

[0038] To address the aforementioned technical problems, this application provides a fast-charging electrolyte and a lithium-ion battery containing the same. This fast-charging electrolyte can effectively optimize the ion transport of lithium ions at the interface and maintain the dynamic balance of the interface during high-rate charging of the battery, thereby improving the charging rate of the lithium-ion battery.

[0039] The embodiments of this application will be described in detail below.

[0040] Fast charging electrolyte

[0041] This application provides a fast-charging electrolyte, comprising: additives and a non-aqueous solvent; the additives include a lithium-containing additive, tris(pentafluorophenyl)borane, and a film-forming additive, wherein the mass percentage of the additives is 0.5% to 5% based on the total mass of the fast-charging electrolyte, and the mass ratio of the lithium-containing additive to tris(pentafluorophenyl)borane (TPFPB) is 1:0.5 to 1:5; the non-aqueous solvent comprises a first solvent component, a second solvent component, and a third solvent component, wherein the volume ratio of the first solvent component to the second solvent component is 1:1 to 1:2, and the third solvent component contains fluorine.

[0042] For example, based on the total mass of the fast-charging electrolyte, the mass percentage of the additive can be 0.5%, 1%, 2%, 3%, 4%, 5%, or within any two of the above values; the mass ratio of the lithium-containing additive to tris(pentafluorophenyl)borane can be 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, or within any two of the above values; the volume ratio of the first solvent component to the second solvent component can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, or within any two of the above values.

[0043] According to the embodiments of this application, the fast-charging electrolyte of this application satisfies the following conditions: the mass percentage content of the additive is 0.5% to 5%, the mass ratio of lithium-containing additive to tris(pentafluorophenyl)borane is 1:0.5 to 1:5, the volume ratio of the first solvent component to the second solvent component is 1:1 to 1:2, and the third solvent component contains fluorine. When the components in the electrolyte work synergistically, a dynamic dissolution-deposition electrode / electrolyte interface can be established, effectively optimizing the ion transport of lithium ions at the interface and maintaining the dynamic balance of the interface during the high-rate charging process of lithium-ion batteries, thereby improving the charging rate of lithium-ion batteries.

[0044] In some embodiments, the third solvent component comprises fluoroethylene carbonate (FEC), and the mass percentage of the third solvent component is 10% to 30% based on the total mass of the non-aqueous solvent. For example, the mass percentage of the third solvent component may be 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or within any two of the above values.

[0045] In the above embodiments, when the third solvent component includes fluoroethylene carbonate, and its mass percentage is 10%–30% based on the total mass of the non-aqueous solvent, the synergistic effect among the electrolyte components can be further enhanced. This promotes the dissociation and migration of lithium ions in the electrolyte, providing a more favorable environment for the rapid transport of lithium ions at the electrode / electrolyte interface. Simultaneously, the fluorine characteristics of fluoroethylene carbonate allow it to participate in the film-forming reaction on the electrode surface, working in conjunction with lithium-containing additives, tris(pentafluorophenyl)borane, and film-forming additives to form a more stable, denser, and ionicly conductive solid electrolyte interphase (SEI) film. This effectively inhibits excessive decomposition of the electrolyte on the electrode surface, reduces the occurrence of side reactions, and better adapts to volume changes in the electrode material during high-rate charging, maintaining the integrity and stability of the interface.

[0046] In some embodiments, the mass ratio of tris(pentafluorophenyl)borane to film-forming additive is 1:1 to 1:3, for example, it can be 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.5, 1:2.8, 1:3, or within any two of the above values.

[0047] In the above embodiments, when the mass ratio of tris(pentafluorophenyl)borane to film-forming additives is 1:1 to 1:3, the dynamic dissolution-deposition interface balance can be further optimized. During high-rate charging, when lithium ions rapidly migrate to the electrode surface, the high-quality SEI film formed by tris(pentafluorophenyl)borane and the film-forming additives reduces concentration polarization and kinetic hindrance at the interface. This allows lithium ions to quickly cross the interface and enter the electrode to complete deposition, while maintaining the dynamic stability of the film layer even when minor dissolution occurs at the interface, thus preventing the aggravation of side reactions caused by film layer damage. Therefore, the effect of fast-charging electrolytes in improving the charging rate of lithium-ion batteries is further enhanced, especially under high-rate conditions, better improving the cycle stability and charging efficiency of lithium-ion batteries.

[0048] In some embodiments, the fast-charging electrolyte may further include a lithium salt, wherein the molar concentration of the lithium salt in the fast-charging electrolyte is 1 mol / L to 5 mol / L. For example, the molar concentration of the lithium salt in the fast-charging electrolyte may be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, or within any two of the above values. Optionally, the lithium salt may include lithium bis(fluorosulfonyl)imide (LiFSI) and / or lithium hexafluorophosphate (LiPF6).

[0049] In some embodiments, the lithium salt includes lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate, wherein the mass ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate is 1:1 to 1:3. For example, the mass ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate can be 1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.5, 1:2.8, 1:3, or within any two of the above values.

[0050] In the above embodiments, when the mass ratio of lithium difluorosulfonylimide to lithium hexafluorophosphate is 1:1 to 1:3, the mixed lithium salt system, together with lithium-containing additives and tris(pentafluorophenyl)borane, further optimizes the solvation structure of lithium ions. The FSI- in LiFSI has a moderate binding capacity with lithium ions and can work with fluoroethylene carbonate to regulate the desolvation process of lithium ions, making lithium ion transport smoother at the electrode / electrolyte interface. Simultaneously, the fluorine-containing species generated from the decomposition of LiFSI can participate in the formation of the SEI film, working in conjunction with the film-forming additives to enhance the density and stability of the film, effectively suppressing excessive decomposition of the electrolyte during high-rate charging.

[0051] Furthermore, this mixed lithium salt system exhibits a good synergistic effect with the fluorinated third solvent component. The fluorinated solvent has good solubility for both LiFSI and LiPF6, ensuring uniform dispersion of the mixed lithium salt in the electrolyte and maintaining high ionic conductivity. At ratios of 1:1 to 1:3, the system formed by the mixed lithium salt and non-aqueous solvent possesses suitable viscosity and dielectric constant, providing a smooth channel for lithium-ion migration while reducing concentration polarization. This plays a positive role in the dynamic dissolution-deposition electrode / electrolyte interface balance, further improving the charging rate and cycle stability of lithium-ion batteries.

[0052] In some embodiments, the lithium-containing additive is lithium difluorophosphate (LiPO2F2).

[0053] In the above embodiments, lithium difluorophosphate can form a boron-fluorine composite SEI film with tris(pentafluorophenyl)borane, which can further improve the chemical stability of the SEI film, effectively resist electrolyte erosion, and reduce the dissolution or decomposition of the SEI film. Simultaneously, the boron-fluorine composite SEI film has a dense and uniform structure, which can act as a physical barrier to reduce direct contact between the electrolyte and the electrode, inhibit the continuous decomposition of the electrolyte during charge and discharge, and reduce the battery capacity decay rate.

[0054] In some embodiments, the film-forming additive is 1,3-propanesulfonyl lactone (1,3-PS).

[0055] In some embodiments, the first solvent component includes dimethyl carbonate (DMC).

[0056] In some embodiments, the second solvent component includes ethyl methyl carbonate (EMC) and / or diethyl carbonate (DEC).

[0057] In some embodiments, the first solvent component is dimethyl carbonate and the second solvent component is diethyl carbonate.

[0058] In the above embodiments, when the first component is dimethyl carbonate and the second component is ethyl methyl carbonate, a mixed solvent base with low viscosity and high ionic conductivity can be formed. The lower viscosity can reduce the resistance during lithium ion migration, allowing ions to quickly pass through the electrolyte to reach the electrode interface during high-rate charging. Meanwhile, a suitable dielectric constant can ensure that the lithium salt is fully dissociated, providing sufficient charge carriers for ion transport. The synergistic effect of the two can further improve the lithium ion transport efficiency.

[0059] Lithium-ion batteries

[0060] This application provides a lithium-ion battery, which includes a positive electrode, a negative electrode, a separator, and a fast-charging electrolyte.

[0061] In some embodiments, the lithium-ion battery satisfies at least one of the following: (1) after 500 cycles at 25°C, a charging rate of 4.0C, and a discharging rate of 1.0C, the capacity retention rate of the lithium-ion battery is greater than or equal to 65%, for example, it can be 65%, 70%, 75%, 80%, 85%, 90%, or within any two of the above values; (2) after 500 cycles at 25°C, a charging rate of 4.0C, and a discharging rate of 1.0C, the coulombic efficiency of the lithium-ion battery is greater than or equal to 99.5%.

[0062] In some embodiments, (1) after 3000 cycles at 25°C, a charging rate of 4.0C, and a discharging rate of 1.0C, the capacity retention rate of the lithium-ion battery is greater than or equal to 70%, for example, it can be 70%, 75%, 80%, 85%, 90%, or within any two of the above values; (2) after 3000 cycles at 25°C, a charging rate of 4.0C, and a discharging rate of 1.0C, the coulombic efficiency of the lithium-ion battery is greater than or equal to 99.9%.

[0063] Performance testing

[0064] In an environment of 25±2℃, the battery cell was left to rest for 30 minutes. The electrode assembly was then charged at a constant current of 4C to the full charge voltage (the battery's maximum design voltage is 4.3V). Next, it was charged at the maximum voltage using a constant voltage until the current reached 0.02C. Finally, it was discharged at a constant current of 0.5C until the final voltage reached 3.0V. The capacity retention rate of the first cycle was recorded. The above conditions and steps were then repeated for 100 to 3000 charge-discharge cycles, and the capacity retention rate and coulombic efficiency of the lithium-ion battery after each cycle were recorded.

[0065] Example

[0066] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0067] In the embodiments and comparative examples of this application, lithium-ion batteries were prepared using the following methods, and the performance of the lithium-ion batteries was tested.

[0068] Example 1

[0069] Methods for preparing lithium-ion batteries

[0070] The dry cell used in this embodiment is a dry cell from Cubic New Energy, model number 575166-1Ah3.0~4.2V-S233110F.

[0071] Preparation of fast charging electrolyte

[0072] In an argon-filled glove box (H2O ≤ 0.1 ppm, O2 ≤ 0.1 ppm), 0.9114 g of lithium hexafluorophosphate and 1.122 g of lithium difluorosulfonyl imide were weighed and placed in glass bottles. 1 mL of fluoroethylene carbonate, 4 mL of dimethyl carbonate, and 5 mL of methyl ethyl carbonate were added, and the mixture was shaken and stirred until the lithium salts were completely dissolved. Then, 130 mg of lithium difluorophosphate, 130 mg of 1,3-propanesulfonyl lactone, and 130 mg of tris(pentafluorophenyl)borane were added and mixed thoroughly to obtain a fast-charging electrolyte. The molar concentrations of LiPF6 and LiFSI in the fast-charging electrolyte were both 0.6 M, the volume ratio of FEC:DMC:EMC was 1:4:5, and the mass concentrations of TPFPB, 1,3-PS, and LiPO2F2 were all 1 wt%.

[0073] Assembly of lithium-ion batteries

[0074] The fast-charging electrolyte was injected into the dry cell under an argon protective atmosphere and then packaged to obtain a pouch battery.

[0075] The capacity retention and coulombic efficiency of lithium-ion batteries were tested at high rates, cycling from 500 to 3000 cycles. The results are as follows: Figure 1 As shown, after 500 cycles, the capacity retention rate of the lithium-ion battery is 91.2%; after 2000 cycles, the capacity retention rate is 82.8%; and after 3000 cycles, the capacity retention rate is 79.2%, with a coulombic efficiency of 99.9%.

[0076] Example 2

[0077] The only difference between Example 2 and Example 1 is that ethyl methyl carbonate (EMC) in the fast-charging electrolyte is replaced with diethyl carbonate (DEC). The capacity retention and coulombic efficiency of the lithium-ion battery were tested at high rates for 500 to 2000 cycles. The results are as follows: Figure 2 As shown, after 500 cycles, the capacity retention rate of the lithium-ion battery is 75.8%, and after 2000 cycles, the capacity retention rate is 65.3%, with a coulombic efficiency of 99.5%.

[0078] Example 3

[0079] The only difference between Example 3 and Example 1 is that the mass concentrations of TFPB, 1,3-PS, and LiPO2F2 in the fast-charging electrolyte are 1 wt%, 2 wt%, and 0.5 wt%, respectively. The capacity retention and coulombic efficiency of the lithium-ion battery were tested after 500 cycles at high rate. The results are as follows: Figure 3 As shown, after 500 cycles, the capacity retention rate of this lithium-ion battery is 66.5%, and the coulombic efficiency is 99.7%.

[0080] Example 4

[0081] The only difference between Example 4 and Example 1 is that the mass concentrations of TFPB, 1,3-PS, and LiPO2F2 in the fast-charging electrolyte are 1 wt%, 3 wt%, and 0.2 wt%, respectively. The capacity retention and coulombic efficiency of the lithium-ion battery were tested after 500 cycles at high rate. The results are as follows: Figure 4 As shown, after 500 cycles, the capacity retention rate of this lithium-ion battery is 67.3%, and the coulombic efficiency is 99.6%.

[0082] Example 5

[0083] The only difference between Example 5 and Example 1 is that the mass concentrations of TFPB, 1,3-PS, and LiPO2F2 in the fast-charging electrolyte are 0.5 wt%, 1 wt%, and 1 wt%, respectively. The capacity retention and coulombic efficiency of the lithium-ion battery were tested after 500 cycles at high rate. The results are as follows: Figure 5 As shown, after 500 cycles, the capacity retention rate of this lithium-ion battery is 76.1%, and the coulombic efficiency is 99.8%.

[0084] Comparative Example 1

[0085] The only difference between Comparative Example 1 and Example 1 is that 1,3-PS was replaced with vinylene carbonate (VC). The capacity retention and coulombic efficiency of the lithium-ion battery were tested after 500 cycles at high rate, and the results are as follows: Figure 6 As shown, after 160 cycles, the capacity retention of this lithium-ion battery is 65.1%, and the coulombic efficiency is 94.4%.

[0086] Comparative Example 2

[0087] The only difference between Comparative Example 2 and Example 1 is that FEC was replaced with ethylene carbonate (EC), and the solvent was EC:DMC:EMC = 1:4:5. The capacity retention and coulombic efficiency of the lithium-ion battery were tested after 500 cycles at high rate. The results are as follows: Figure 7 As shown, after 150 cycles, the capacity retention rate of this lithium-ion battery is 68.2%, and the coulombic efficiency is 97.5%.

[0088] In Comparative Examples 1 and 2, the lithium-ion batteries, due to changes in film-forming additives and solvent components, resulted in an SEI film that was transformed from being rich in S and F to an organic carbon-containing film. This led to changes in the mechanical properties of the SEI film and the Li-ion battery. + The transport performance deteriorates, continuously consuming active materials, leading to a decline in cycle performance. After 150 or 160 cycles, it can no longer be recycled.

[0089] Comparative Example 3

[0090] The only difference between Comparative Example 3 and Example 1 is that the solvent is EC:DEC = 3:7. The capacity retention and coulombic efficiency of the lithium-ion battery were tested after 500 cycles at high rate. The results are as follows: Figure 8 As shown, after 70 cycles, the capacity retention of this lithium-ion battery was 69.6%, and the coulombic efficiency was 93.6%. Comparative Example 3, by changing the solvent composition, reduced the solubility of the BF compound in the SEI, failing to achieve dynamic deposition and dissolution of the SEI, leading to a further decrease in SEI stability. The battery could not be cycled further after 70 cycles.

[0091] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A fast-charging electrolyte, characterized in that, include: Additives and non-aqueous solvents; The additives include lithium-containing additives, tris(pentafluorophenyl)borane, and film-forming additives. Based on the total mass of the fast-charging electrolyte, the mass percentage of the additives is 0.5% to 5%, and the mass ratio of the lithium-containing additives to the tris(pentafluorophenyl)borane is 1:0.5 to 1:

5. The non-aqueous solvent includes a first solvent component, a second solvent component, and a third solvent component. The volume ratio of the first solvent component to the second solvent component is 1:1 to 1:2, and the third solvent component contains fluorine.

2. The fast-charging electrolyte according to claim 1, characterized in that, The third solvent component includes fluoroethylene carbonate, and the mass percentage of the third solvent component is 10% to 30% based on the total mass of the non-aqueous solvent.

3. The fast-charging electrolyte according to claim 1, characterized in that, The mass ratio of the tris(pentafluorophenyl)borane to the film-forming additive is 1:1 to 1:

3.

4. The fast-charging electrolyte according to claim 1, characterized in that, The fast-charging electrolyte further includes a lithium salt, wherein the molar concentration of the lithium salt in the fast-charging electrolyte is 1 mol / L to 5 mol / L. Optionally, the lithium salt includes lithium bis(fluorosulfonyl)imide and / or lithium hexafluorophosphate.

5. The fast-charging electrolyte according to claim 4, characterized in that, The lithium salt includes lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate, wherein the mass ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate is 1:1 to 1:

3.

6. The fast-charging electrolyte according to any one of claims 1 to 5, characterized in that, The lithium-containing additive includes lithium difluorophosphate.

7. The fast-charging electrolyte according to any one of claims 1 to 5, characterized in that, The film-forming additive includes 1,3-propanesulfonyl lactone.

8. The fast-charging electrolyte according to any one of claims 1 to 5, characterized in that, The first solvent component is dimethyl carbonate; and / or, the second solvent component includes ethyl methyl carbonate and / or diethyl carbonate.

9. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode, a negative electrode, a separator, and the fast-charging electrolyte as described in any one of claims 1 to 8.

10. The lithium-ion battery according to claim 9, characterized in that, The lithium-ion battery satisfies at least one of the following: (1) Under the conditions of 25°C, 4.0C charging rate and 1.0C discharging rate, after 500 cycles, the capacity retention rate of the lithium-ion battery is greater than or equal to 65%. Optionally, under the conditions of 25°C, 4.0C charging rate and 1.0C discharging rate, after 3000 cycles, the capacity retention rate of the lithium-ion battery is greater than or equal to 70%. (2) Under the conditions of 25°C, 4.0C charging rate, and 1.0C discharging rate, after 500 cycles, the coulombic efficiency of the lithium-ion battery is greater than or equal to 99.5%. Optionally, under the conditions of 25°C, 4.0C charging rate, and 1.0C discharging rate, after 3000 cycles, the coulombic efficiency of the lithium-ion battery is greater than or equal to 99.9%.

Images