Lithium ion battery electrolyte based on ferroferric oxide magnetorheological fluid as well as preparation method and application of lithium ion battery electrolyte

Abstract

The invention relates to a lithium ion battery electrolyte based on ferroferric oxide magnetorheological fluid as well as a preparation method and application of the lithium ion battery electrolyte. According to the electrolyte, the nano-scale ferroferric oxide particles are introduced, and the characteristics that the nano-scale ferroferric oxide particles quickly respond and change the rheological state under the action of a magnetic field are utilized, so that the electrolyte can be quickly cured under the condition of collision or impact, and the electrolyte with solid mechanical characteristics is formed. The cured electrolyte can effectively resist external impact, buffer collision energy and prevent the internal structure damage and internal short circuit phenomenon of the battery. Compared with a traditional electrolyte, the electrolyte shows remarkable stability and impact resistance under the collision condition, meanwhile, good electrochemical performance is kept, and the electrolyte has wide application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a lithium-ion battery electrolyte based on magnetorheological fluid of iron tetroxide, a preparation method thereof, and an application thereof. Background Art

[0002] Due to advantages such as high energy density, long cycle life, and low self-discharge rate, lithium-ion batteries are widely used in fields such as portable electronic devices, electric vehicles, and energy storage systems. However, when lithium-ion batteries are subjected to external impacts or collisions, internal structural damage is likely to occur, resulting in electrolyte leakage, internal short circuit, and even thermal runaway, leading to serious safety problems. Traditional lithium-ion battery electrolytes are mainly composed of organic solvents and lithium salts. Although they exhibit good electrochemical performance under normal usage conditions, under mechanical impact or collision conditions, their fluidity may cause internal short circuits in the battery, increasing safety risks.

[0003] To improve the safety of lithium-ion batteries, researchers have proposed various improvement schemes, including using solid electrolytes, adding flame retardants, and optimizing battery structure design. However, these methods often sacrifice the electrochemical performance of the battery or increase the manufacturing cost while improving safety.

[0004] Therefore, developing an electrolyte that can not only maintain good electrochemical performance but also provide effective protection under impact conditions has become an important research direction in the field of lithium-ion batteries.

[0005] Chinese Patent CN119381569A discloses a highly stable lithium-ion battery electrolyte, and the raw materials include LiPF6, ethylene carbonate, dimethyl carbonate, and additives. Although this scheme attempts to improve the stability of the electrolyte through complex chemical reactions, its preparation process is complex, the reaction conditions are harsh, the raw material cost is high, the environmental friendliness is poor, and it may affect the electrochemical performance of the electrolyte. Summary of the Invention

[0006] The purpose of the present invention is to provide a lithium-ion battery electrolyte based on magnetorheological fluid of iron tetroxide, a preparation method thereof, and an application thereof. By introducing nanoscale iron tetroxide particles into the traditional electrolyte, the present invention utilizes their fast response characteristics under the action of a magnetic field, and can rapidly solidify under collision or impact conditions to form an electrolyte with solid mechanical properties. The electrolyte based on magnetorheological fluid of iron tetroxide in the present invention not only has a simple preparation process, but also can provide effective anti-impact protection under impact conditions, and has higher practicality and application prospects.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A lithium-ion battery electrolyte based on magnetorheological fluid of magnetite, the lithium-ion battery electrolyte comprising the following components:

[0009]

[0010] Among them, the magnetite is spherical particles with a diameter of 20 to 200 nanometers. As a key component, the magnetite can quickly respond and change its rheological state under the action of a magnetic field.

[0011] Further, the highly fluorinated solvent is selected from any one or a combination of ethylene carbonate (EC), propylene carbonate, diethyl carbonate, dimethyl carbonate (DMC), or ethyl methyl carbonate (EMC).

[0012] Still further, the highly fluorinated solvent consists of the following components:

[0013] Ethylene carbonate 15 - 25 vol%,

[0014] Dimethyl carbonate 25 - 40 vol%,

[0015] Ethyl methyl carbonate 35 - 50 vol%.

[0016] Further, the lithium salt is lithium hexafluorophosphate (LiPF6).

[0017] Further, the composite additive includes a film-forming additive and a flame retardant additive.

[0018] Still further, the film-forming additive is selected from vinylene carbonate, ethylene sulfite, tris(trimethylsilyl) phosphate, or ethylene sulfate.

[0019] Still further, the flame retardant additive is fluorinated ethylene carbonate.

[0020] As a preferred technical solution, the addition amounts of both the film-forming additive and the flame retardant additive are 1 - 2 vol%.

[0021] The present invention also provides a preparation method for a lithium-ion battery electrolyte based on magnetorheological fluid of magnetite, and the specific steps are as follows:

[0022] S1. Mix a variety of highly fluorinated solvents uniformly in a glove box with an inert gas environment to obtain a mixed solvent;

[0023] S2. Dissolve lithium hexafluorophosphate in the mixed solvent obtained in step S1, and stir until completely dissolved to obtain a mixed solution A;

[0024] S3. Add a composite additive to the mixed solution A obtained in step S2 to enhance its electrochemical performance, and stir evenly to obtain a mixed solution B;

[0025] S4. In a glove box with an inert gas environment, disperse the iron tetroxide particles in the mixed liquid B obtained in step S2, and stir to obtain a lithium-ion battery electrolyte based on iron tetroxide magnetorheological fluid.

[0026] Further, in step S4, the stirring time is 1 - 2 hours.

[0027] Further, in step S4, in a glove box with an inert gas environment, disperse the iron tetroxide particles in the mixed liquid B obtained in step S2, and filter with a filter membrane to obtain a lithium-ion battery electrolyte based on iron tetroxide magnetorheological fluid.

[0028] In the above further step, the pore size of the filter membrane is 0.2 microns.

[0029] In addition, the present invention also provides an application of a lithium-ion battery electrolyte based on iron tetroxide magnetorheological fluid in the preparation of lithium-ion batteries.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] The present invention provides a lithium-ion battery electrolyte based on iron tetroxide magnetorheological fluid. By introducing nano-scale iron tetroxide particles and utilizing their characteristics of rapidly responding and changing the rheological state under the action of a magnetic field, this electrolyte can quickly solidify under collision or impact conditions to form an electrolyte with solid mechanical properties. This solidified electrolyte can effectively resist external impacts, buffer the collision energy, and prevent the destruction of the internal structure of the battery and the phenomenon of internal short circuit. Compared with traditional electrolytes, the electrolyte of the present invention exhibits remarkable stability and impact resistance under collision conditions, while maintaining good electrochemical performance, and has broad application prospects. Description of the Drawings

[0032] Figure 1 The rate performance graph of the batteries prepared with the electrolytes of Examples 1 - 2 and Comparative Example 1 at 30°C in a normal temperature environment;

[0033] Figure 2 The charge and discharge cycle performance graph of the batteries prepared with the electrolytes of Examples 1 - 2 and Comparative Example 1 at 30°C in a normal temperature environment;

[0034] Figure 3 The mechanical response graph of the batteries prepared with the electrolytes of Examples 1 - 2 and Comparative Example 1 during the impact process. Detailed Embodiments

[0035] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation procedures are given, but the protection scope of the present invention is not limited to the following embodiments.

[0036] The following will describe in detail some embodiments of the present invention with reference to the accompanying drawings. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0037] Embodiment 1

[0038] This embodiment provides a preparation method of a lithium-ion battery electrolyte based on iron tetroxide magnetorheological fluid, and the specific steps are as follows:

[0039] S1. In a glove box with an inert gas environment, mix ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate evenly according to a volume ratio of 17.5:40:27.5 to obtain a mixed solvent;

[0040] S2. Dissolve lithium hexafluorophosphate in the mixed solvent obtained in step S1, and stir until completely dissolved to obtain a mixed solution A, and lithium hexafluorophosphate accounts for 12.5% of the total mass of the mixed solution A;

[0041] S3. Add 1.5% of vinylene carbonate and 1.5% of fluoroethylene carbonate based on the total mass of the mixed solution A to the mixed solution A obtained in step S2, and stir evenly to obtain a mixed solution B;

[0042] S4. In a glove box with an inert gas environment, disperse iron tetroxide particles accounting for 20 vol% of the total volume of the lithium-ion battery electrolyte in the mixed solution B obtained in step S2, continue to stir for 1-2 hours, and filter with a 0.2-micron pore size filter membrane to obtain a lithium-ion battery electrolyte based on iron tetroxide magnetorheological fluid.

[0043] Embodiment 2

[0044] This embodiment provides a preparation method of a lithium-ion battery electrolyte based on iron tetroxide magnetorheological fluid, and the specific steps are as follows:

[0045] S1. In a glove box with an inert gas environment, mix ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate evenly according to a volume ratio of 17.5:40:27.5 to obtain a mixed solvent;

[0046] S2. Dissolve lithium hexafluorophosphate in the mixed solvent obtained in step S1, and stir until completely dissolved to obtain a mixed solution A, and lithium hexafluorophosphate accounts for 12.5% of the total mass of the mixed solution A;

[0047] S3. Add vinylene carbonate accounting for 1.5% of the total mass of the mixed solution A and fluoroethylene carbonate accounting for 1.5% to the mixed solution A obtained in step S2, and stir evenly to obtain a mixed solution B.

[0048] S4. In a glove box with an inert gas environment, disperse iron oxide particles accounting for 40 vol% of the total volume of the lithium-ion battery electrolyte in the mixed solution B obtained in step S2, continue to stir for 1 - 2 hours, and filter through a 0.2-micron pore size filter membrane to obtain a lithium-ion battery electrolyte based on iron oxide magnetorheological fluid.

[0049] Comparative Example 1

[0050] This comparative example provides a method for preparing a lithium-ion battery electrolyte, and the specific steps are as follows:

[0051] S1. In a glove box with an inert gas environment, mix ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate evenly according to a volume ratio of 17.5:40:27.5 to obtain a mixed solvent.

[0052] S2. Dissolve lithium hexafluorophosphate in the mixed solvent obtained in step S1, and stir until completely dissolved to obtain a mixed solution A, where lithium hexafluorophosphate accounts for 12.5% of the total mass of the mixed solution A.

[0053] S3. Add vinylene carbonate accounting for 2% of the total mass of the mixed solution A to the mixed solution A obtained in step S2 to obtain a lithium-ion battery electrolyte.

[0054] Performance Test

[0055] Prepare lithium-ion battery electrolytes according to the steps of Example 1, Example 2, and Comparative Example 1 respectively. At room temperature, stack the positive electrode sheet, separator, corresponding electrolyte, and negative electrode sheet in sequence to assemble a lithium-ion battery.

[0056] Perform the following tests on the batteries prepared in Examples 1 - 2 and Comparative Example 1:

[0057] (1) Let the assembled battery stand, and perform a cycle test at different charge-discharge rates (0.1C, 0.2C, 0.5C, 1.0C). Record the comparable capacity (mAh / g) corresponding to different cycle numbers, and analyze the capacity retention ability of the battery at different rates.

[0058] (2) Let the battery stand for 24 h, and perform 100 charge-discharge cycles at a cut-off voltage of 2.5V and 3.8V and a rate of 0.5C. Record the capacity retention rate of the battery after 100 cycles.

[0059] (3) Perform a ball drop impact test on the assembled battery. The initial voltage of the battery is 3.3V, and record the change data of the impact time and impact force in real time. Synchronously monitor the change of the open circuit voltage of the battery during the impact process, and analyze the voltage stability and safety of the battery during impact.

[0060] The results of the above tests are shown in Table 1.

[0061] Table 1 Test results of Examples 1-2 and Comparative Example 1

[0062] Test Items Example 1 Example 2 Comparative Example 1 Rate Cycling Performance (0.1C) 130.9 mAh / g 115.4 mAh / g 136.5 mAh / g Rate Cycling Performance (0.2C) 108.1 mAh / g 98.1 mAh / g 110.9 mAh / g Rate Cycling Performance (0.5C) 70.0 mAh / g 60.8 mAh / g 72.9 mAh / g Rate Cycling Performance (1C) 66.8 mAh / g 58.6 mAh / g 70.1 mAh / g Rate Cycling Performance (0.1C) 121.9 mAh / g 115.7 mAh / g 130.9 mAh / g Capacity Retention Rate 99.3％ 99.3％ 99.8％ Coulombic Efficiency 100％ 100％ 100％ Peak Impact Force 4.7 kN 2.9 kN 5.1 kN Lowest Open Circuit Voltage during Impact 0.33V 3.29V 0V

[0063] The test results are as Figures 1 - 3 shown in Table 1. The lithium-ion battery with magnetorheological fluid of iron oxide provided by the present invention has excellent impact resistance. In terms of rate cycling performance, the specific capacity of Example 2 can reach 130.9 mAh / g at a rate of 0.1C. Although the initial capacity of Comparative Example 1 is low (136.5 mAh / g) at 0.1C, the capacity decay of Examples 1 and 2 is better controlled at multiple rates (such as 0.5C and 1C), reflecting the optimization of the electrolyte for the rate adaptability of the battery. In terms of capacity retention rate, both Examples 1 and 2 reach 99.3%, which is close to 99.8% of Comparative Example 1, indicating good cycle stability; the coulombic efficiency of all three is 100%, and the charge transfer efficiency is excellent. In terms of the peak impact force, Example 2 is the lowest (2.9 kN), and the impact resistance performance is more prominent; in terms of the impact open circuit voltage, the lowest value of Example 2 reaches 3.29V, far superior to Example 1 (0.33V) and Comparative Example 1 (0V), indicating that Example 2 has more advantages in voltage stability under impact. In summary, the electrolyte prepared in the examples shows excellent performance in key properties such as rate cycling and impact resistance, and some indicators exceed those of the comparative example, verifying the superiority of its comprehensive performance.

[0064] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. Obviously, those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A lithium-ion battery electrolyte based on ferroferric oxide magnetorheological fluid, characterized in that: The lithium ion battery electrolyte comprises the following components: Highly fluorinated solvent 48~68vol% Lithium salt 6~12vol% Ferroferric oxide 10~30vol% Composite additives 2~10vol% Wherein, the ferrosoferric oxide is spherical particles with a diameter of 20 to 200 nanometers.

2. The lithium-ion battery electrolyte based on ferroferric oxide magnetorheological fluid according to claim 1, characterized in that: The highly fluorinated solvent is selected from any one or more combinations of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate or ethyl methyl carbonate.

3. The lithium-ion battery electrolyte based on ferroferric oxide magnetorheological fluid according to claim 2, characterized in that: The highly fluorinated solvent consists of the following components: Ethylene carbonate 15-25 vol%, Dimethyl carbonate 25~40vol% Ethyl methyl carbonate 35-50 vol%.

4. The lithium-ion battery electrolyte based on ferroferric oxide magnetorheological fluid according to claim 1, characterized in that: The lithium salt is lithium hexafluorophosphate.

5. The lithium-ion battery electrolyte based on ferroferric oxide magnetorheological fluid according to claim 1, characterized in that: The composite additive comprises a film-forming additive and a flame retardant additive.

6. The lithium-ion battery electrolyte based on ferroferric oxide magnetorheological fluid according to claim 5, characterized in that: The film-forming additive is selected from vinylene carbonate, vinyl sulfite, tris(trimethylsilyl)phosphate or vinyl sulfate; The flame retardant additive is fluoroethylene carbonate.

7. A method for preparing a lithium-ion battery electrolyte based on a magnetorheological fluid of ferroferric oxide as claimed in any one of claims 1 to 6, characterized in that: The specific steps are as follows: S1. Mixing a plurality of highly fluorinated solvents uniformly in a glove box with an inert gas environment to obtain a mixed solvent; S2, dissolving lithium hexafluorophosphate in the mixed solvent obtained in step S1, and stirring until completely dissolved to obtain a mixed solution A; S3, adding a composite additive to the mixed solution A obtained in step S2 to enhance its electrochemical performance, and stirring to obtain a mixed solution B; S4. In a glove box with an inert gas environment, disperse the ferroferric oxide particles in the mixed solution B obtained in step S2, and stir to obtain a lithium-ion battery electrolyte based on ferroferric oxide magnetorheological fluid.

8. The lithium-ion battery electrolyte based on ferroferric oxide magnetorheological fluid according to claim 7, characterized in that: In step S4, the stirring time is 1-2 hours.

9. The lithium-ion battery electrolyte based on ferroferric oxide magnetorheological fluid according to claim 7, characterized in that: In step S4, in a glove box with an inert gas environment, ferroferric oxide particles are dispersed in the mixed solution B obtained in step S2, and filtered using a filter membrane to obtain a lithium-ion battery electrolyte based on ferroferric oxide magnetorheological fluid.

10. Use of a lithium ion battery electrolyte based on the magnetorheological fluid of ferroferric oxide as claimed in any one of claims 1 to 6 in the preparation of a lithium ion battery.

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