Electrolyte solution, lithium-ion battery, and electronic product
By using an electrolyte that combines low-concentration ether solvents with lithium salts in lithium-ion batteries, the problems of freezing and solvent co-intercalation in lithium-ion batteries at low temperatures were solved, achieving improved stability and high-voltage performance in low-temperature environments.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- NATIONAL INSTITUTE OF GUANGDONG ADVANCED ENERGY STORAGE CO LTD
- Filing Date
- 2024-12-26
- Publication Date
- 2026-07-02
Smart Images
Figure CN2024142618_02072026_PF_FP_ABST
Abstract
Description
Electrolytes, lithium-ion batteries, and electronic products Technical Field
[0001] This application relates to the field of lithium-ion batteries, and in particular to an electrolyte, a lithium-ion battery, and electronic products. Background Technology
[0002] Since the commercialization of lithium-ion batteries (LIBs), they have been widely used in small smart wearable devices, mobile electronic devices, electric vehicles, and grid energy storage. Currently, traditional carbonate-based electrolytes are mainly prepared by dissolving lithium hexafluorophosphate (LiPF6) in a mixed solution of ethylene carbonate (EC) and chain carbonates (such as ethyl methyl carbonate / EMC, dimethyl carbonate / DMC, diethyl carbonate / DEC, etc.). However, due to the extremely high freezing point of EC (36.4℃) and its high proportion (25-50%) in commercial electrolytes (such as 1.0M LiPF6-EC-DMC), these commercial electrolytes freeze at temperatures below -20℃. This causes LIBs to struggle at low temperatures, resulting in a sharp decline in performance and safety issues such as lithium dendrite growth. This severely hinders the use and promotion of 3C electronic devices and new energy vehicles in cold regions (such as northern my country where winter temperatures are often below freezing). Secondly, LIBs are also used in military equipment, polar exploration, and space applications, where they operate in more complex and extreme environments. For example, military equipment faces operating temperatures as low as -40°C, while polar exploration and space applications face even lower temperatures.
[0003] Traditional low-concentration (~1 mol / L) ether-based electrolytes (such as ethylene glycol dimethyl ether / DME) have extremely low freezing points and high ionic conductivity, making them suitable for low-temperature electrolytes. However, traditional low-concentration ether-based electrolytes suffer from problems such as solvent co-intercalation into graphite and poor oxidative stability, hindering their development in low-temperature lithium-ion batteries. Some research has addressed these problems by formulating locally high-concentration ether-based electrolytes. These locally high-concentration electrolytes are prepared by adding a diluent to a high-concentration electrolyte. However, high-concentration electrolytes exhibit high viscosity, low ionic conductivity, and poor wettability with the separator and electrodes, resulting in poor low-temperature battery performance. Summary of the Invention
[0004] Therefore, it is necessary to provide an electrolyte, lithium-ion battery, and electronic product that reduces co-intercalation behavior and has good stability at low temperatures.
[0005] This application provides an electrolyte, including an electrolyte salt and an ether solvent;
[0006] The concentration of the electrolyte salt is 0.1 mol / L to 5 mol / L, and the ether solvent includes one or more of the following: dimethoxymethane, diethoxymethane, 1,2-diethoxyethane, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, diethyl ether, cyclopentyl methyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.
[0007] In one embodiment, the ether solvent includes a first solvent or a second solvent and a third solvent in a volume ratio of (1-2):1, wherein the first solvent and the second solvent each independently include one or more of diethoxymethane, 1,2-diethoxyethane and dimethoxymethane, and the third solvent includes one or more of 1,3-dioxolane, 1,4-dioxane and 1,3-dioxane.
[0008] In one embodiment, the electrolyte salt includes a lithium salt.
[0009] In one embodiment, the lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, lithium tetrafluoroborate, lithium difluoroborate, lithium perchlorate, lithium hexafluoroarsenate, and lithium trifluoromethanesulfonate.
[0010] In one embodiment, the concentration of the lithium salt in the electrolyte is 0.1 mol / L to 5 mol / L.
[0011] Furthermore, this application also provides a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and the electrolyte described above, wherein the separator is disposed between the positive electrode and the negative electrode, and the positive electrode, the negative electrode, and the separator are immersed in the electrolyte.
[0012] In one embodiment, the positive electrode includes a positive current collector and a positive active layer formed on at least one side surface of the positive current collector, the positive active layer being made of a positive active material, the positive active material being one or more of lithium nickel cobalt manganese oxide ternary material, lithium nickel manganese oxide, and lithium cobalt oxide.
[0013] In one embodiment, the loading of the positive electrode active material on the positive electrode is 1.5 mg / cm³. 2 ~3.0mg / cm 2 .
[0014] In one embodiment, the negative electrode includes either a graphite electrode or a lithium metal electrode.
[0015] Furthermore, this application provides an electronic product whose power supply device is the aforementioned lithium-ion battery.
[0016] The electrolyte provided in this application, through reasonable screening of ether solvents, selects ether solvents with weak lithium salt dissolution ability, so that the electrolyte forms contact ion pairs and aggregated ion pairs at low concentrations, thereby introducing anion-derived interfacial chemistry. The resulting electrolyte reduces co-intercalation behavior and has good stability at low temperatures, making it suitable for low-temperature environments. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.
[0018] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings. In the following description, the same reference numerals denote the same parts.
[0019] Figure 1 shows the cycle performance of Li|| graphite batteries using the electrolyte of Example 1 and the electrolyte of Comparative Example 1 at 25°C and 0.5C rate.
[0020] Figure 2 shows the cycle performance of Li|| graphite batteries at 25℃ and 0.5C rate using electrolytes from Example 1, Example 2, and Example 3, respectively.
[0021] Figure 3 shows the rate performance of Li|| graphite batteries at 25°C using the electrolyte of Example 1 and the electrolyte of Comparative Example 2, respectively.
[0022] Figure 4a shows the specific capacity of Li|| graphite batteries using the electrolyte of Example 1 and the electrolyte of Comparative Example 2 at different temperatures and 0.1C rates. Figure 4b shows the low-temperature cycling performance of Li|| graphite batteries using the electrolyte of Example 1 and the electrolyte of Comparative Example 2 at -20℃ and 0.2C rates.
[0023] Figure 5 shows the cycle performance of graphite||NCM811 batteries at 25℃ and 0.5C rate, using electrolytes from Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively.
[0024] Figure 6 shows the cycle performance of the graphite||NCM811 battery using the electrolyte of Example 1 at -20℃ and 0.1C rate. Detailed Implementation
[0025] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.
[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
[0027] As used herein, the term "and / or" encompasses any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" includes three parallel options: A, B, and "a combination of A and B".
[0028] In this document, unless otherwise stated, "one or more" means any one of the listed items or any combination of the listed items. Similarly, "one or more" and other instances of "one or more" are to be understood in the same way unless otherwise stated.
[0029] In this document, terms such as "further," "even further," "especially," "for example," "as," "example," and "exemplary" are used for descriptive purposes to indicate a connection in the coverage of different technical solutions presented earlier and later. However, they should not be construed as limitations on the preceding technical solution or on the scope of protection of this document. Unless otherwise specified, A (as in B) indicates that B is a non-limiting example of A, and it can be understood that A is not limited to B.
[0030] In this document, "optionally," "optionally," and "optional" mean that something is optional, that is, it is selected from either "present" or "absent." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent. In this application, descriptions such as "optionally contains" and "optionally includes" indicate "contains or does not contain." "Optional component X" indicates whether component X exists or does not exist, or whether component X is contained or not.
[0031] In this document, the terms "first aspect," "second aspect," "third aspect," and "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," and "fourth" serve only as a non-exhaustive enumeration and should be understood as not constituting a closed limitation on quantity.
[0032] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.
[0033] In this document, when referring to numerical intervals (i.e., numerical ranges), unless otherwise specified, the distribution of selectable values within a numerical interval is considered continuous, and includes the two endpoints (i.e., the minimum and maximum values) of the numerical interval, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all subranges included therein. The "numerical value" in this numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, and other numerical interval types.
[0034] In this document, the term "room temperature" or "normal temperature" generally refers to 4°C to 35°C, for example, 20°C ± 5°C. In some embodiments of this document, "room temperature" or "normal temperature" refers to 10°C to 30°C. In some embodiments of this document, "room temperature" or "normal temperature" refers to 20°C to 30°C.
[0035] In this document, for methods involving multiple steps, unless otherwise explicitly stated herein, there is no strict order constraint on the execution of these steps; they may be executed in any order other than those described. Moreover, any step may include multiple sub-steps or multiple stages, which are not necessarily completed at the same time, but may be executed at different times, and their execution order is not necessarily sequential, but may be executed in turn, alternately, or simultaneously with other steps or parts of the sub-steps or stages of other steps.
[0036] This application provides an electrolyte comprising an electrolyte salt and an ether solvent; wherein the concentration of the electrolyte salt is 0.1 mol / L to 5 mol / L, and the ether solvent comprises one or more of the following: dimethoxymethane, diethoxymethane, 1,2-diethoxyethane, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, diethyl ether, cyclopentyl methyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.
[0037] In a specific example, the ether solvent includes a first solvent or a second solvent and a third solvent in a volume ratio of (1-2):1, wherein the first solvent and the second solvent each independently include one or more of diethoxymethane, 1,2-diethoxyethane and dimethoxymethane, and the third solvent includes one or more of 1,3-dioxolane, 1,4-dioxane and 1,3-dioxane.
[0038] Furthermore, the ether solvent can be one of diethoxymethane, 1,2-diethoxyethane, and dimethoxymethane. The ether solvent can also be a second solvent and a third solvent with a volume ratio of, but not limited to, 1:1, 1.5:1, or 2:1.
[0039] In one specific example, the electrolyte salt includes lithium salt.
[0040] In one specific example, the lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, lithium tetrafluoroborate, lithium difluoroborate, lithium perchlorate, lithium hexafluoroarsenate, and lithium trifluoromethanesulfonate.
[0041] In a specific example, the concentration of lithium salt in the electrolyte is 0.1 mol / L to 5 mol / L. Further, the concentration of lithium salt in the electrolyte may be, but is not limited to, 0.1 mol / L, 0.5 mol / L, 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, or 5 mol / L.
[0042] The electrolyte provided in this application, through reasonable screening of ether solvents, selects ether solvents with weak lithium salt dissolution ability, so that the electrolyte forms contact ion pairs and aggregated ion pairs at low concentrations, thereby introducing anion-derived interfacial chemistry. The resulting electrolyte reduces co-intercalation behavior and has good stability at low temperatures, making it suitable for low-temperature environments.
[0043] Furthermore, this application also provides a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and the above-mentioned electrolyte, wherein the separator is disposed between the positive electrode and the negative electrode, and the positive electrode, the negative electrode, and the separator are immersed in the electrolyte.
[0044] In one specific example, the positive electrode includes a positive current collector and a positive active layer formed on at least one side surface of the positive current collector. The material of the positive active layer includes a positive active material, which includes one or more of lithium nickel cobalt manganese oxide ternary materials, lithium nickel manganese oxide, and lithium cobalt oxide.
[0045] Furthermore, the composition of the positive electrode active layer includes a positive electrode active material in a mass ratio of (75-90):(5-12):(3-15), a first binder, and a first conductive agent. Specifically, the first binder may be, but is not limited to, polyvinylidene fluoride, and the first conductive agent may be, but is not limited to, acetylene black.
[0046] In a specific example, the loading of the positive electrode active material on the positive electrode is 1.5 mg / cm³. 2 ~3.0mg / cm 2 .
[0047] Specifically, the loading of the positive electrode active material on the positive electrode can be, but is not limited to, 1.5 mg / cm³. -2 2mg / cm 2 2.5 mg / cm 2 Or 3mg / cm 2 .
[0048] Furthermore, the positive current collector can be, but is not limited to, aluminum foil or copper foil.
[0049] In one specific example, the negative electrode includes either a graphite electrode or a lithium metal electrode.
[0050] Understandably, the negative electrode can use only lithium metal as the negative electrode, or it can be a graphite electrode. Specifically, the graphite electrode includes a negative electrode current collector and a negative electrode active layer formed on at least one side surface of the negative electrode current collector. The material of the negative electrode active layer includes a negative electrode active material, which includes graphite. The loading of the negative electrode active material on the negative electrode is 0.5 mg / cm³. 2 ~2.0mg / cm 2 .
[0051] Specifically, the loading of the negative electrode active material on the negative electrode can be, but is not limited to, 0.5 mg / cm³. 2 1mg / cm 2 1.5 mg / cm 2 Or 2mg / cm 2 .
[0052] Furthermore, the composition of the negative electrode active layer includes a negative electrode active material, a second binder, and a second conductive agent in a mass ratio of (85-90):(5-12):(3-8). Specifically, the second binder may be, but is not limited to, polyvinylidene fluoride, and the second conductive agent may be, but is not limited to, acetylene black.
[0053] Furthermore, this application provides an electronic product whose power supply device is the aforementioned lithium-ion battery.
[0054] The present application will be further described in detail below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application. For experimental methods in the following embodiments where specific conditions are not specified, please refer to the guidelines given in this application, or follow experimental manuals or conventional conditions in the art, or follow the conditions recommended by the manufacturer, or refer to experimental methods known in the art.
[0055] In the specific embodiments described below, the measurement parameters of the raw material components may have slight deviations within the weighing accuracy range unless otherwise specified. Temperature and time parameters are subject to acceptable deviations due to instrument testing accuracy or operational precision. "Ambient temperature" refers to 25°C; "atmospheric pressure" refers to 100 kPa or 101 kPa.
[0056] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0057] Example 1
[0058] This embodiment provides a formulation for a low-temperature, high-voltage resistant lithium-ion battery electrolyte, as detailed below:
[0059] Step 1) In a glove box at 25°C with water and oxygen content below 0.01 ppm, mix diethoxymethane and 1,3-dioxolane at a volume ratio of 1:1 to obtain a homogeneous mixture of diethoxymethane and 1,3-dioxolane (1:1).
[0060] Step 2) Add lithium bisfluorosulfonylimide to the above uniform mixture of diethoxymethane:1,3-dioxolane (1:1) and stir until it is fully dissolved and mixed evenly to obtain a 1 mol / L lithium bisfluorosulfonylimide / diethoxymethane:1,3-dioxolane (1:1) electrolyte.
[0061] Example 2
[0062] This embodiment provides a formulation for a low-temperature, high-voltage resistant lithium-ion battery electrolyte, as detailed below:
[0063] Step 1) In a glove box at 25°C with water and oxygen content below 0.01 ppm, mix diethoxymethane and 1,3-dioxolane at a volume ratio of 1:1 to obtain a homogeneous mixture of diethoxymethane and 1,3-dioxolane (1:1).
[0064] Step 2) Add lithium bisfluorosulfonylimide to the above uniform mixture of diethoxymethane:1,3-dioxolane (1:1) and stir until it is fully dissolved and mixed evenly to obtain a 2 mol / L lithium bisfluorosulfonylimide / diethoxymethane:1,3-dioxolane (1:1) electrolyte.
[0065] Example 3
[0066] This embodiment provides a formulation for a low-temperature, high-voltage resistant lithium-ion battery electrolyte, as detailed below:
[0067] Step 1) In a glove box at 25°C with water and oxygen content below 0.01 ppm, mix diethoxymethane and 1,3-dioxolane at a volume ratio of 1:1 to obtain a homogeneous mixture of diethoxymethane and 1,3-dioxolane (1:1).
[0068] Step 2) Add lithium bisfluorosulfonylimide to the above uniform mixture of diethoxymethane:1,3-dioxolane (1:1) and stir until it is fully dissolved and mixed evenly to obtain a 0.5 mol / L lithium bisfluorosulfonylimide / diethoxymethane:1,3-dioxolane (1:1) electrolyte.
[0069] Example 4
[0070] This embodiment provides a formulation for a low-temperature, high-voltage resistant lithium-ion battery electrolyte, as detailed below:
[0071] Step 1) In a glove box at 25°C with water and oxygen content below 0.01 ppm, dimethoxymethane and 1,3-dioxolane are mixed evenly at a volume ratio of 1:1 to obtain a uniform mixture of dimethoxymethane and 1,3-dioxolane (1:1).
[0072] Step 2) Add lithium bisfluorosulfonylimide to the above uniform mixture of dimethoxymethane:1,3-dioxolane (1:1) and stir until it is fully dissolved and mixed evenly to obtain a 1 mol / L lithium bisfluorosulfonylimide / dimethoxymethane:1,3-dioxolane (1:1) electrolyte.
[0073] Example 5
[0074] This embodiment provides a formulation for a low-temperature, high-voltage resistant lithium-ion battery electrolyte, as detailed below:
[0075] Step 1) In a glove box at 25°C with water and oxygen content below 0.01 ppm, dimethoxymethane and 1,4-dioxane are mixed evenly at a volume ratio of 2:1 to obtain a uniform mixture of dimethoxymethane and 1,4-dioxane (2:1).
[0076] Step 2) Add lithium difluorosulfonylimide to the above uniform mixture of dimethoxymethane:1,4-dioxane (2:1) and stir until it is fully dissolved and mixed evenly to obtain a 1 mol / L lithium difluorosulfonylimide / dimethoxymethane:1,4-dioxane (2:1) electrolyte.
[0077] Example 6
[0078] This embodiment provides a formulation for a low-temperature, high-voltage resistant lithium-ion battery electrolyte, as detailed below:
[0079] Step 1) In a glove box at 25°C with water and oxygen content below 0.01 ppm, 1,2-diethoxyethane and 1,3-dioxolane are mixed evenly at a volume ratio of 1:1 to obtain a uniform mixture of 1,2-diethoxyethane and 1,3-dioxolane (1:1).
[0080] Step 2) Add lithium bisfluorosulfonylimide to the above uniform mixture of 1,2-diethoxyethane:1,3-dioxolane (1:1) and stir until it is fully dissolved and mixed evenly to obtain a 1 mol / L lithium bisfluorosulfonylimide / 1,2-diethoxyethane:1,3-dioxolane (1:1) electrolyte.
[0081] Comparative Example 1
[0082] Step 1) In a glove box at 25°C with water and oxygen content below 0.01 ppm, ethylene glycol dimethyl ether and 1,3-dioxolane are mixed evenly at a volume ratio of 1:1 to obtain a uniform mixture of ethylene glycol dimethyl ether and 1,3-dioxolane (1:1).
[0083] Step 2) Add lithium bis(fluorosulfonyl)imide to the above uniform mixture of ethylene glycol dimethyl ether: 1,3-dioxolane (1:1) and stir until it is fully dissolved and mixed evenly to obtain a 1 mol / L lithium bis(fluorosulfonyl)imide / ethylene glycol dimethyl ether: 1,3-dioxolane (1:1) electrolyte.
[0084] Comparative Example 2
[0085] A common commercial electrolyte for lithium-ion batteries, 1 mol / L LiPF6 in EC:DMC (1:1), was selected. Lithium hexafluorophosphate was dissolved in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) with a volume ratio of 1:1 to prepare an electrolyte with a concentration of 1 mol / L.
[0086] Comparative Example 3
[0087] Step 1) In a glove box at 25°C with water and oxygen content below 0.01 ppm, ethylene carbonate and ethylene glycol dimethyl ether are mixed evenly at a volume ratio of 1:1 to obtain a uniform mixture of ethylene carbonate and ethylene glycol dimethyl ether (1:1).
[0088] Step 2) Add lithium bis(fluorosulfonyl imide) to the above uniform mixture of ethylene carbonate and ethylene glycol dimethyl ether (1:1) and stir until it is fully dissolved and mixed evenly to obtain a 1 mol / L lithium bis(fluorosulfonyl imide) / ethylene carbonate: ethylene glycol dimethyl ether (1:1) electrolyte.
[0089] The electrolytes prepared in the examples and comparative examples were used to assemble Li||graphite batteries and graphite||NCM811 batteries, and their electrochemical performance was tested.
[0090] Preparation method of graphite electrode: Graphite, polyvinylidene fluoride (PVDF) binder, and acetylene black were mixed in a ratio of 87:8:5 and dispersed in N-methylpyrrolidone (NMP) solution to obtain a uniform slurry. The slurry was then coated onto copper foil using a 50 μm doctor blade. The electrode was first dried in a 60℃ forced-air oven for 6 hours to remove most of the NMP solvent, and then vacuum dried overnight in a 120℃ vacuum drying oven. The electrode was then pressed into tablets with a diameter of 12 mm and an active material loading of 1.4 mg / cm³. 2 Store the round pieces in the glove box.
[0091] Preparation method of lithium nickel cobalt manganese oxide 811 (NCM811) electrode: NCM811, polyvinylidene fluoride (PVDF) binder, and acetylene black were mixed in a ratio of 80:8:12 and dispersed in N-methylpyrrolidone (NMP) solution to obtain a uniform slurry. The slurry was then coated onto aluminum foil using a 100 μm doctor blade. The electrode was first dried in a 60℃ forced-air oven for 6 hours to remove most of the NMP solvent, and then vacuum dried overnight in a 120℃ vacuum drying oven. The electrode was then pressed into tablets with a diameter of 12 mm and an active material loading of 3.0 mg / cm³. 2 The round pieces were placed in the glove box for storage.
[0092] Assembly method of Li|| graphite battery: At 25℃ in a glove box, using lithium metal as the negative electrode, the prepared graphite electrode as the positive electrode, PP2500 as the separator, and the comparative electrolyte and the electrolyte system prepared in this application as the electrolyte, a Li|| graphite battery was assembled. After the assembled battery was allowed to stand at room temperature for 10 hours, a charge-discharge test was performed.
[0093] Assembly method of graphite||NCM811 battery: At 25℃ in a glove box, using the prepared graphite electrode as the negative electrode, the prepared NCM811 electrode as the positive electrode, PP2500 as the separator, and the comparative electrolyte and the electrolyte system prepared in this application as the electrolyte, the graphite||NCM811 battery was assembled. After the assembled battery was allowed to stand at room temperature for 10 hours, a charge-discharge test was performed.
[0094] Test results
[0095] The cycling performance of Li|| graphite batteries using the electrolyte of Example 1 and Comparative Example 1 was tested at 25°C and 0.5C rate, and the results are shown in Figure 1. As can be seen from Figure 1, due to the co-intercalation behavior of ethylene glycol dimethyl ether (DME), the battery using the electrolyte of Comparative Example 1 exhibits only a very low specific capacity, while the battery using the electrolyte of Example 1 can cycle stably for 300 cycles, with a specific capacity of 350 mAh g⁻¹ at 0.5C rate. -1 The capacity retention rate was 93.3%, and the average coulombic efficiency was 99.9%. This fully demonstrates that the weakly solvated electrolyte provided in this application can effectively solve the bottleneck problem of conventional chain ether solvents co-intercalating into graphite, enabling the battery to cycle stably and normally.
[0096] The cycling performance of Li|| graphite batteries using the electrolytes of Example 1, Example 2, and Example 3 was tested at 25°C and 0.5C rate, and the results are shown in Figure 2. Figure 2 shows that the fully ether-based weakly solvated electrolytes at different concentrations also enabled stable cycling of the graphite anode. This further demonstrates that the electrolyte design strategy of this application can effectively solve the bottleneck problem of ether solvent co-intercalation in graphite, broadening the application range of ether-based electrolytes.
[0097] At 25°C, the rate performance of Li|| graphite batteries using the electrolyte of Example 1 and the electrolyte of Comparative Example 2 was tested, and the results are shown in Figure 3 and Table 1. As can be seen from the data in Figure 3 and Table 1, the battery using the electrolyte of Example 1 has better rate performance compared to the electrolyte of Comparative Example 2, which proves that this electrolyte system has rapid charge and discharge capabilities.
[0098] The specific capacity of Li|| graphite batteries using different electrolytes was tested at different temperatures (25℃, 0℃, -10℃, -20℃, and -30℃) and a 0.1C rate. The results are shown in Figure 4a and Table 2. As can be seen from Figure 4a and Table 2, within the tested temperature range, the specific capacity of the battery using the electrolyte of Example 1 is significantly higher than that of the battery using the electrolyte of Comparative Example 2. The battery using the electrolyte of Example 1 exhibits high specific capacity and capacity retention at the tested temperatures, indicating that this electrolyte has extremely high potential for low-temperature applications. The low-temperature cycling performance of Li|| graphite batteries using different electrolytes was tested at -20℃ and a 0.2C rate. The results are shown in Figure 4b. As can be seen from Figure 4b, the electrolyte of Example 1 enables the battery to cycle stably at -20℃ and results in a higher specific capacity, indicating that the electrolyte system designed in this application can provide the battery with excellent low-temperature long-cycle performance.
[0099] The cycle performance of graphite||NCM811 batteries using different electrolytes was tested at 25℃ and 0.5C rate. The results are shown in Figure 5 and Table 3. As shown in Figure 5, due to the severe graphite co-intercalation behavior of the electrolyte in Comparative Example 1, the full cell assembled using it has an extremely low specific capacity. Meanwhile, due to the poor oxidation stability of the electrolyte in Comparative Example 2, the coulombic efficiency of the full cell assembled using it showed a precipitous decline after 250 cycles, with a capacity retention of 46.9% and an average coulombic efficiency of 98.1% after 300 cycles. The battery using the electrolyte in Comparative Example 3 experienced rapid capacity decay and poor cycle performance. In contrast, the battery using the electrolyte in Example 1 had a capacity retention of 74.5% and an average coulombic efficiency of 99.5% after 300 cycles. Furthermore, as shown in Table 3, the batteries using the electrolytes in Examples 1-6 exhibited higher cycle stability at high voltages compared to Comparative Example 2. As is well known, conventional ether-based electrolytes are difficult to match with high-voltage ternary cathode materials due to their poor oxidation stability. This application uses weakly solvated ether solvents to enable all-ether electrolytes to be matched with high-voltage ternary cathode materials, which helps to improve battery energy density.
[0100] The cycle performance of the graphite||NCM811 battery from Example 1 was tested at -20℃ and 0.1C rate, and the results are shown in Figure 6. As can be seen from the figure, the battery using the electrolyte designed in this application can cycle stably at -20℃ and has a high efficiency of 144.8 mAh g⁻¹. -1 The specific capacity is 99.6%, the capacity retention is 99.6%, and the average coulombic efficiency is 99.0%. This indicates that the all-ether weakly solvated electrolyte designed in this application can be used in low-temperature LIBs and can be matched with high-voltage cathode materials, effectively improving the battery energy density and broadening the temperature application range of lithium-ion batteries.
[0101] Table 1 shows the rate performance of Li|| graphite batteries using different electrolytes at 25℃.
[0102]
[0103] Table 2. Performance of Li||graphite batteries using different electrolytes at different temperatures and 0.1C rates.
[0104]
[0105] Table 3 shows the performance of graphite||NCM811 batteries using different electrolytes at 25℃ and 0.5C rate.
[0106]
[0107] This application provides a weakly solvated electrolyte using all-ether solvents. This electrolyte achieves the formation of anion-rich solvated structures at low concentrations, resulting in anion-derived SEI films rich in inorganic components on the graphite surface. It also effectively solves the co-intercalation problem of ether solvents in graphite electrodes, enabling Li|| graphite batteries to exhibit excellent long-cycle and rate performance at both room temperature and low temperatures. Furthermore, this electrolyte can be matched with high-voltage ternary cathode materials, allowing graphite|| NCM811 batteries to exhibit excellent long-cycle stability under both room temperature and low-temperature conditions. This provides an effective solution for matching all-ether electrolytes with high-voltage ternary materials, effectively improving the low-temperature and high-voltage performance of lithium-ion batteries.
[0108] The above embodiments merely illustrate several implementation methods of this application to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.
Claims
An electrolyte, characterized in that Including electrolyte salts and ether solvents; The concentration of the electrolyte salt is 0.1 mol / L to 5 mol / L, and the ether solvent includes one or more of the following: dimethoxymethane, diethoxymethane, 1,2-diethoxyethane, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, diethyl ether, cyclopentyl methyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. The electrolyte of claim 1, wherein The ether solvent includes a first solvent or a second solvent and a third solvent in a volume ratio of (1-2):1, wherein the first solvent and the second solvent each independently include one or more of diethoxymethane, 1,2-diethoxyethane and dimethoxymethane, and the third solvent includes one or more of 1,3-dioxolane, 1,4-dioxane and 1,3-dioxane. The electrolyte as claimed in claim 1 or 2, characterized in that The electrolyte salt includes lithium salt. The electrolyte of claim 3, wherein The lithium salt includes one or more of the following: lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, lithium tetrafluoroborate, lithium difluoroborate, lithium perchlorate, lithium hexafluoroarsenate, and lithium trifluoromethanesulfonate. The electrolyte of claim 3, wherein The concentration of the lithium salt in the electrolyte is 0.1 mol / L to 5 mol / L. A lithium-ion battery, characterized in that It includes a positive electrode, a negative electrode, a separator, and an electrolyte as described in any one of claims 1 to 5, wherein the separator is disposed between the positive electrode and the negative electrode, and the positive electrode, the negative electrode, and the separator are immersed in the electrolyte. The lithium ion battery of claim 6, wherein The positive electrode includes a positive current collector and a positive active layer formed on at least one side surface of the positive current collector. The material of the positive active layer includes a positive active material, which includes one or more of lithium nickel cobalt manganese oxide ternary materials, lithium nickel manganese oxide, and lithium cobalt oxide. The lithium-ion battery of claim 7, wherein The positive electrode active material has a loading on the positive electrode of 1.5 mg / cm 2 ~ 3.0 mg / cm 2 . The lithium-ion battery according to any one of claims 6 to 8, characterized in that The negative electrode includes either a graphite electrode or a lithium metal electrode. An electronic product, characterized in that, Its power supply device is the lithium-ion battery as described in any one of claims 6 to 9.