CN114530632A - Lithium ion battery electrolyte and lithium ion battery - Google Patents

Abstract

The application discloses lithium ion battery electrolyte and a lithium ion battery. The electrolyte of the lithium ion battery comprises an organic solvent, a film forming agent and a lithium salt, wherein the organic solvent comprises a carboxylic ester compound; the film forming agent comprises a cyclic carbonate compound or/and a sulfonate compound; the molar concentration of the lithium salt is 2-4 mol/L. The lithium ion battery electrolyte containing the carboxylic ester organic solvent, the cyclic carbonate compound or/and the sulfonate film-forming agent and the high-concentration lithium salt has high ionic conductivity and a stable electrode interface structure, is simple in preparation process, has low requirements on equipment, and plays an important role in prolonging the cycle life and improving the capacity retention rate of the lithium ion battery in a low-temperature environment.

Description

A lithium ion battery electrolyte and lithium ion battery

technical field

The application belongs to the technical field of lithium ion batteries, and in particular relates to a lithium ion battery electrolyte and a lithium ion battery.

Background technique

Lithium-ion batteries are widely used in military equipment, electronic equipment, power tools and other fields due to their high energy density, long cycle life, large specific capacity, and no memory effect. In recent years, lithium-ion batteries have also been regarded as the most promising energy storage and conversion devices in electric vehicles. However, with the expansion of the application field of lithium-ion batteries and the continuous improvement of battery performance requirements, researchers have found that the low temperature environment will greatly limit the application performance of lithium-ion batteries.

Among them, the main reasons why low temperature affects the performance of lithium-ion batteries include: (1) the viscosity of the electrolyte increases, and even part of the electrolyte solidifies, resulting in a decrease in ionic conductivity; (2) the impedance of the solid electrolyte interface (SEI) and the effect of charge transfer. The impedance increases; (3) the solid-phase diffusivity of lithium ions is weakened. In addition to the weakening of the solid-phase diffusion ability of the above-mentioned lithium ions, the other two main reasons are closely related to the electrolyte. Therefore, the development of new electrolytes is important for achieving both long cycle life and stable capacity retention of lithium-ion batteries at low temperatures. significant.

SUMMARY OF THE INVENTION

The present application provides an electrolyte for a lithium ion battery and a lithium ion battery, aiming at solving the problems of short cycle life and low capacity retention rate of the lithium ion battery in a low temperature environment.

One aspect of the present application provides a lithium-ion battery electrolyte, comprising an organic solvent, a film-forming agent and a lithium salt, wherein,

The organic solvent includes carboxylate compounds; the film-forming agent includes cyclic carbonate compounds or/and sulfonate compounds; and the molar concentration of the lithium salt is 2-4 mol/L.

In an optional embodiment of one aspect of the present application, the above-mentioned carboxylate compounds include methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, and propyl propionate and one or more of methyl butyrate.

In an optional embodiment of one aspect of the present application, based on the total volume of the electrolyte solution, the volume ratio of the organic solvent is 70-90%.

In an optional embodiment of one aspect of the present application, the above-mentioned cyclic carbonate compounds include one or more of fluoroethylene carbonate, ethylene ethylene carbonate, and vinylene carbonate.

In an optional embodiment of one aspect of the present application, the above-mentioned sulfonate compound includes at least one of methanesulfonic acid-2-propyn-1-ol and 1,3-propane sultone.

In an optional embodiment of an aspect of the present application, based on the total volume of the electrolyte solution, the volume ratio of the film-forming agent is 10-30%.

In an optional embodiment of an aspect of the present application, the above-mentioned lithium salt includes one or more of lithium hexafluorophosphate, lithium bisoxalateborate, lithium bistrifluoromethanesulfonimide, and lithium bisfluorosulfonimide.

In an optional embodiment of an aspect of the present application, the molar concentration of the above-mentioned lithium salt is 2-3 mol/L.

Another aspect of the present application provides a lithium-ion battery, including the above-mentioned lithium-ion battery electrolyte.

Compared with the prior art, the present application at least has the following beneficial effects:

(1) The lithium ion battery electrolyte provided by the present application has good ionic conductivity at low temperature.

On the one hand, the lithium ion battery electrolyte of the present application uses a carboxylate compound as an organic solvent, which can significantly reduce the melting point and viscosity of the electrolyte system and improve the ionic conductivity of the electrolyte system at low temperatures. On the other hand, lithium salts can promote the solvation of Li ⁺ , increase the carrier concentration in the electrolyte, and then improve the conductivity of the electrolyte.

(2) The lithium ion battery electrolyte provided by the present application is beneficial to maintain the stability of the interface structure of the electrode electrolyte.

In this application, the cyclic carbonate or/and sulfonate film-forming agents and high-concentration lithium salts can be reduced and decomposed together, wherein the insoluble reduction products will gradually deposit on the surface of the electrode material, so that the electrode surface forms a firm and relatively strong The thin solid-state electrolyte interface film not only ensures the stable electrode structure during the cycle, but also shortens the transport distance of lithium ions in the interface film, laying a good foundation for further improving the cycle life of the battery.

(3) The preparation method of the lithium ion battery electrolyte provided by the present application is simple, has low requirements for equipment, is well compatible with existing processes, and has great potential for large-scale application.

(4) The lithium ion battery provided by the present application has good cycle life and capacity retention rate in a low temperature environment.

According to the examples of the present application, it can be seen that the lithium-ion battery composed of the above-mentioned lithium-ion battery electrolyte can achieve a stable cycle of more than 240 cycles at a charge-discharge current of 0.2C under a working environment of -20°C, and the discharge capacity retention rate is still close to 100%, the average coulomb is over 99.91%. The lithium-ion battery electrolyte is an electrolyte with great research value and practical application potential.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present application more clearly, the following briefly introduces the drawings required in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained according to the drawings without any creative effort.

1 is an electrochemical performance diagram of a button-type lithium ion battery provided in Example 1 of the present application;

FIG. 2 is an electrochemical performance diagram of a soft-pack lithium-ion battery provided in Example 1 of the present application.

Detailed ways

In order to make the application purpose, technical solutions and beneficial technical effects of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the embodiments described in this specification are only for explaining the present application, but not for limiting the present application.

For the sake of brevity, only some numerical ranges are expressly disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with any other lower limit to form an unspecified range, and likewise any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, every point or single value between the endpoints of a range is included within the range, even if not expressly recited. Thus, each point or single value may serve as its own lower or upper limit in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.

In the description herein, it should be noted that, unless otherwise specified, “above” and “below” are inclusive of the numerals, and the meaning of “multiple” in “one or more” means two or more.

The above summary of this application is not intended to describe each disclosed embodiment or every implementation in this application. The following description illustrates exemplary embodiments in more detail. In various places throughout this application, guidance is provided through a series of examples, which examples can be used in various combinations. In various instances, the enumeration is merely a representative group and should not be construed as exhaustive.

At present, the viscosity of the electrolyte increases at low temperature, and the ionic conductivity decreases; the impedance of the SEI film and the impedance of charge transfer are large; the above reasons lead to the low operating efficiency of the existing lithium-ion battery electrolyte at low temperature, which seriously affects the battery. It is difficult to meet the requirements of the existing technology for the use of lithium-ion batteries.

Based on this, the inventors have conducted a lot of research, aiming to provide a lithium-ion battery electrolyte with low viscosity, high ionic conductivity, and low SEI film and charge transfer resistance in a low-temperature environment, so as to give the electrolyte containing the electrolyte. Lithium-ion batteries have good cycle life and capacity retention in low temperature environments.

Lithium-ion battery electrolyte

An embodiment of the first aspect of the present application provides an electrolyte for a lithium ion battery, including an organic solvent, a film-forming agent, and a lithium salt, wherein the organic solvent includes a carboxylate compound; the film-forming agent includes a cyclic carbonate compound or / and sulfonate compounds; the molar concentration of lithium salt is 2-4 mol/L.

According to the lithium-ion battery electrolyte of the embodiments of the present application, through the selection of organic solvents and film-forming agents and the regulation of lithium salt concentration, the components in the electrolyte are made to act together, thereby endowing the lithium-ion battery electrolyte with both High conductivity and low impedance performance.

According to the embodiments of the present application, with respect to the electrolyte containing ethylene carbonate, propylene carbonate, etc., using the carboxylate compound as the organic solvent can significantly reduce the melting point and viscosity of the electrolyte system, thereby ensuring that the electrolyte is The system has high ionic conductivity at low temperature, which lays a good foundation for the efficient and stable operation of lithium-ion batteries.

However, the carboxylate compounds in the examples of the present application have poor film-forming properties, which may cause co-insertion of the solvent into the negative electrode material, resulting in peeling of the negative electrode material. Therefore, in the examples of the present application, the formation of the SEI film at the anode/electrolyte interface is promoted by introducing a film-forming agent with high reactivity of cyclic carbonates or/and sulfonate compounds. During the charging process of the lithium-ion battery, the film-forming agent is reductively decomposed to generate products such as polyethylene carbonate, _LiF , _Li2CO3 , etc., which adhere to the surface of the negative electrode material to form a thin SEI film. The film has low impedance, and can prevent the co-insertion of solvent molecules, weaken the damage to the negative electrode material caused by solvent co-insertion, and reduce the loss of active lithium, thereby ensuring the good operation of lithium-ion batteries at low temperatures.

Furthermore, in some non-aqueous electrolytes, when the lithium salt concentration exceeds a certain threshold, the physical and chemical properties of the bulk phase and interface will undergo dramatic changes, resulting in performance changes that are different from those of dilute solutions. Compared with the conventional lithium salt electrolyte, the high-concentration lithium salt electrolyte can form a dense and tough solid electrolyte film on the surface of the negative electrode, which can reduce the side reaction between the electrode material and the electrolyte, thereby improving the safety of the battery. performance. At the same time, the solvation number of Li ⁺ in the high-concentration lithium salt electrolyte will decrease, resulting in a decrease in the stability of solvated Li ⁺ and a decrease in desolvation energy, so solvent co-insertion can be effectively suppressed. In addition, the high-concentration lithium salt electrolyte can also passivate the aluminum foil, maintain good contact between the positive electrode material and the current collector, and improve the cycle life of the lithium-ion battery.

According to the embodiments of the present application, under the combined action of organic solvents of carboxylate compounds, cyclic carbonates or/and sulfonate film-forming agents and high-concentration lithium salts, not only can the ionicity of the electrolyte be improved Conductivity, reduce SEI film and charge transfer resistance, and can enhance the stability of electrode cycling, so that the battery has a good cycle life.

In some embodiments, the carboxylate compound includes one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, and methyl butyrate one or more.

According to the embodiments of the present application, the above-mentioned carboxylate compounds are in a liquid state at room temperature, wherein methyl formate, ethyl formate, methyl acetate, and ethyl acetate not only have lower melting points but also lower viscosity, and propylene Methyl acid, ethyl propionate, propyl propionate and methyl butyrate have lower melting points, and the use of carboxylate compounds as organic solvents can ensure that the electrolyte has higher ionic conductivity at low temperatures.

In some embodiments, based on the total volume of the electrolyte, the volume ratio of the organic solvent is 70-90%.

Preferably, the volume ratio of the organic solvent is 75-90%.

More preferably, the volume ratio of the organic solvent is 80-90%.

According to the embodiments of the present application, due to the difference in structure between carboxylate compounds and conventional carbonates, their electrochemical stability is poor, and redox reactions are likely to occur during battery cycling, making it difficult to ensure battery cycle life. Therefore, as a The solvent should be added to the electrolyte in an appropriate amount. The volume ratio of the above-mentioned carboxylate organic solvent can not only reduce the melting point and viscosity of the electrolyte, improve the ionic conductivity of the electrolyte, but also work together with the added film-forming agent and lithium salt to improve the battery cycle. stability.

If the volume ratio of the carboxylate compound is less than 70%, the volume of the film-forming agent will increase accordingly, which is not conducive to the reduction of the overall viscosity of the electrolyte and the improvement of the ionic conductivity, nor to the high concentration of lithium salts. of dissolution.

In some embodiments, the cyclic carbonate compounds include one or more of fluoroethylene carbonate, ethylene ethylene carbonate, and vinylene carbonate.

In some embodiments, the sulfonate compound includes at least one of methanesulfonic acid-2-propyn-1-ol and 1,3-propane sultone.

According to the embodiments of the present application, cyclic carbonate compounds refer to carbonate compounds containing atoms in a cyclic arrangement in the molecule, and have a high dielectric constant; sulfonate compounds are a class of compounds with the general formula R ₁ Compounds of SO ₂ OR ₂ . Cyclic carbonate compounds and sulfonate compounds have high reactivity and can participate in the formation of SEI film by retroactive reduction reaction on the surface of the negative electrode of the battery, thereby improving the composition and structure of the SEI film and improving the mechanical properties of the SEI film , prevent the reduction reaction of the electrolyte on the surface of the negative electrode and the deposition of transition metals, stabilize the structure of the negative electrode material, and effectively inhibit the increase of the internal resistance of the battery during the cycle.

Further, the sulfonic acid ester compound can also effectively inhibit the oxidation reaction in the system and play the role of protecting the positive electrode. Adding the above-mentioned film-forming agent to the electrolyte can significantly improve the battery discharge platform and improve the battery cycle performance and low-temperature discharge performance.

In some embodiments, the film-forming agent accounts for 10-30% by volume based on the total volume of the electrolyte.

Preferably, the volume ratio of the film-forming agent is 10-25%.

Further preferably, the volume ratio of the film-forming agent is 10-20%.

According to the embodiments of the present application, if the amount of film-forming agent added in the electrolyte is too large, the SEI film will be too thick and the impedance will be too large, thereby deteriorating the performance of the battery; too little film-forming agent is not conducive to the formation of the SEI film. When the volume ratio of the film-forming agent in this application is 10-30%, the SEI film formed at the interface of the negative electrolyte is both strong and thin, which not only ensures the stability of the electrode cycle but also shortens the amount of lithium ions in the SEI film. Transmission distance.

In some embodiments, the lithium salt includes one or more of lithium hexafluorophosphate, lithium bisoxalateborate, lithium bistrifluoromethanesulfonimide, and lithium bisfluorosulfonimide.

Preferably, the lithium salt is lithium hexafluorophosphate or a mixture of lithium hexafluorophosphate and other lithium salts.

According to the embodiments of the present application, by adding the above-mentioned lithium salts with different compositions and ratios, the synergistic effect between various lithium salts can be exerted, the composition ratio of the SEI film can be improved, so that it is beneficial to the conduction of Li ⁺ , and the electrolyte has good properties. Low temperature performance, thereby improving the rate performance, cycle performance, safety performance and anti-overcharge ability of lithium-ion batteries. In addition, the addition of lithium salt can also promote the solvation of Li ⁺ , thereby increasing the carrier concentration in the electrolyte and improving the conductivity of the electrolyte.

In some embodiments, the molar concentration of the lithium salt is 2-3 mol/L.

The above-mentioned concentration of lithium salt is easily dissolved in the electrolyte, and can also promote the formation of a dense and strong SEI film on the surface of the negative electrode, inhibit the co-insertion of the solvent, and achieve the effect of improving the cycle life of the lithium-ion battery.

According to the embodiments of the present application, the stability of the electrolyte can be further improved by adjusting the types and contents of the organic solvent, the film-forming agent and the lithium salt so that they can play a synergistic effect. In addition, the preparation method of the lithium-ion battery electrolyte is simple, which can be well compatible with the existing technology, and the prepared lithium-ion battery electrolyte has good performance in low temperature environment, and has great potential for large-scale application.

Lithium Ion Battery

Another embodiment of the present application provides a lithium-ion battery, including the above-mentioned lithium-ion battery electrolyte.

According to an embodiment of the present invention, the positive electrode used in the lithium ion battery may be nickel cobalt lithium manganate or nickel cobalt lithium aluminate; the negative electrode used in the lithium ion battery may be graphite.

According to the lithium ion battery of the embodiments of the present application, since it contains the lithium ion battery electrolyte in any embodiment of the first aspect, it has good cycle life and capacity retention rate in a low temperature environment. The lithium-ion batteries of the embodiments of the present application can be applied to energy storage power systems such as hydraulic power, fire power, wind power, and solar power plants in low temperature environments, as well as power tools, military equipment, aerospace, and other fields.

Example

The following examples describe the disclosure of the present application in more detail, and these examples are provided for illustrative purposes only, as various modifications and changes within the scope of the disclosure of the present application will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are on a weight basis, and all reagents used in the examples are either commercially available or synthesized according to conventional methods, and can be directly Used without further processing, and the instruments used in the examples are commercially available.

Example 1

The preparation method of the lithium ion battery electrolyte provided in this embodiment: take a solution of ethyl acetate: fluoroethylene carbonate=90:10 (volume ratio), and mix evenly to obtain an electrolyte solvent; add a certain mass to the electrolyte solvent The concentration of lithium hexafluorophosphate in the electrolyte is 3.0mol L ^-1 , and the lithium ion battery electrolyte is obtained after fully dissolving.

The lithium-ion battery electrolyte in the above embodiment is assembled with the nickel-cobalt lithium manganate positive electrode and the graphite negative electrode to form a button-type lithium-ion battery.

The lithium ion battery electrolyte in the above embodiment is assembled with the nickel cobalt lithium aluminate positive electrode and the graphite negative electrode to form a soft pack lithium ion battery.

Example 2

The preparation method of the lithium-ion battery electrolyte provided in this embodiment: take a solution of methyl formate: ethyl acetate: fluoroethylene carbonate = 40:40:20 (volume ratio), and mix evenly to obtain an electrolyte solvent; A mixed lithium salt of lithium hexafluorophosphate and lithium bisoxalate borate (mass ratio of 9:1) is added to the liquid solvent, so that the concentration in the electrolyte is 3.0 mol L ^-1 , and the lithium ion battery electrolyte is obtained after fully dissolving.

The lithium-ion battery electrolyte in the above embodiment is assembled with the nickel-cobalt lithium manganate positive electrode and the graphite negative electrode to form a soft-pack lithium-ion battery.

Example 3

The preparation method of the lithium-ion battery electrolyte provided in this embodiment: take a solution of methyl formate: methyl acetate: fluoroethylene carbonate: vinylene carbonate = 40:50:8:2 (volume ratio), and mix them evenly Obtaining electrolyte solvent; adding lithium hexafluorophosphate: lithium bistrifluoromethanesulfonimide=1:1 (mass ratio) mixed lithium salt to electrolyte solvent, so that its concentration in electrolyte is 2.0mol L ^-1 , After fully dissolving, a lithium-ion battery electrolyte is obtained.

The lithium-ion battery electrolyte in the above embodiment is assembled with the nickel-cobalt lithium manganate positive electrode and the graphite negative electrode to form a soft-pack lithium-ion battery.

Example 4

The preparation method of the lithium-ion battery electrolyte provided in this embodiment: take methyl acetate: methyl propionate: fluoroethylene carbonate: 1,3-propane sultone=60:30:7:3 (volume ratio ) solution, mix well to obtain electrolyte solvent; In electrolyte solvent, add lithium hexafluorophosphate: the mixed lithium salt of lithium bisfluorosulfonimide=1:1 (mass ratio), so that its concentration in electrolyte is 3.0mol L ^-1 , the lithium ion battery electrolyte is obtained after fully dissolving.

The lithium-ion battery electrolyte in the above embodiment is assembled with the nickel-cobalt lithium manganate positive electrode and the graphite negative electrode to form a soft-pack lithium-ion battery.

Example 5

The preparation method of the lithium ion battery electrolyte provided in this embodiment: take methyl butyrate: methyl propionate: fluoroethylene carbonate: 1,3-propane sultone=50:40:8:2 (volume ratio) solution, mix well to obtain an electrolyte solvent; add lithium hexafluorophosphate: lithium bisfluorosulfonimide=1:1 (mass ratio) mixed lithium salt in the electrolyte solvent, so that its concentration in the electrolyte is 4.0 mol L ^-1 , and fully dissolved to obtain a lithium-ion battery electrolyte.

The lithium-ion battery electrolyte in the above embodiment is assembled with the nickel-cobalt lithium manganate positive electrode and the graphite negative electrode to form a soft-pack lithium-ion battery.

Example 6

The preparation method of the lithium ion battery electrolyte provided in this embodiment: take a solution of ethyl acetate: methyl propionate: fluoroethylene carbonate: vinylene carbonate=70:20:8:2 (volume ratio), mix The electrolyte solvent is uniformly obtained; the mixed lithium salt of lithium hexafluorophosphate:lithium bisfluorosulfonimide=1:1 (mass ratio) is added to the electrolyte solvent, so that the concentration in the electrolyte is 3.0mol L ^-1 , sufficient After dissolving, a lithium-ion battery electrolyte is obtained.

The lithium ion battery electrolyte in the above embodiment is assembled with the nickel cobalt lithium aluminate positive electrode and the graphite negative electrode to form a soft pack lithium ion battery.

Example 7

The preparation method of the lithium ion battery electrolyte provided in this embodiment: take a solution of ethyl acetate: fluoroethylene carbonate=90:10 (volume ratio), and mix evenly to obtain an electrolyte solvent; add a certain mass to the electrolyte solvent The concentration of lithium hexafluorophosphate in the electrolyte is 3.0mol L ^-1 , and the lithium ion battery electrolyte is obtained after fully dissolving.

The lithium ion battery electrolyte in the above embodiment is assembled with the nickel cobalt lithium aluminate positive electrode and the graphite negative electrode to form a soft pack lithium ion battery.

Example 8

The preparation method of the lithium ion battery electrolyte provided in this embodiment: take ethyl acetate: methyl propionate: fluoroethylene carbonate: 1,3-propane sultone=50:40:7:3 (volume ratio ) solution, mix well to obtain electrolyte solvent; Add lithium hexafluorophosphate in electrolyte solvent: the mixed lithium salt of lithium bistrifluoromethanesulfonimide, make its concentration in electrolyte be 2.0mol L ^-1 , fully dissolve Then the lithium ion battery electrolyte is obtained.

The lithium ion battery electrolyte in the above embodiment is assembled with the nickel cobalt lithium aluminate positive electrode and the graphite negative electrode to form a soft pack lithium ion battery.

test section

The lithium ion batteries in the above Examples 1 to 8 were tested at a certain temperature and rate, and the test results of the capacity retention rate of the lithium ion batteries are shown in Table 1 below. Specifically, the battery was first formed at room temperature at 25°C, that is, the battery was charged and discharged at a constant current for 3 cycles at 0.1°C. After the formation was completed, the battery was charged and discharged at a constant current of 0.2C or 0.5C at low temperature, and the first cycle discharge capacity at low temperature was recorded. After cycling for X cycles according to the above method, the discharge capacity of the X-th cycle at low temperature was recorded.

In this test, the capacity retention rate (%) of the lithium ion battery after X cycles = the discharge capacity of the Xth cycle/the discharge capacity of the first cycle x 100%.

Table 1: Performance test results of Examples 1 to 8

According to the above performance test results, the lithium ion batteries containing the electrolytes of Examples 1 to 8 have a good capacity retention rate. To sum up, when the carboxylate compound is used as the organic solvent in the electrolyte, the good ionic conductivity of the electrolyte system at low temperature can be ensured; by adding an ester film-forming agent and a high concentration of lithium salt, the surface of the negative electrode can be improved. The formation of a strong and thin solid-state electrolyte interface film reduces the resistance of the SEI film and charge transfer, resulting in a high capacity retention rate of Li-ion batteries after multiple cycles in a low-temperature environment.

The above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of various equivalents within the technical scope disclosed in the present application. Modifications or substitutions shall be covered by the protection scope of this application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims (9)

1. a lithium ion battery electrolyte, comprising organic solvent, film-forming agent and lithium salt, is characterized in that, The organic solvent includes carboxylate compounds; The film-forming agent includes cyclic carbonate compounds or/and sulfonate compounds; The molar concentration of the lithium salt is 2-4 mol/L. 2. The lithium-ion battery electrolyte according to claim 1, wherein the carboxylate compound comprises methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, propionic acid One or more of ethyl ester, propyl propionate and methyl butyrate. 3 . The lithium-ion battery electrolyte according to claim 1 , wherein, based on the total volume of the electrolyte, the volume ratio of the organic solvent is 70-90%. 4 . 4. The lithium ion battery electrolyte according to claim 1, wherein the cyclic carbonate compound comprises one or more of fluoroethylene carbonate, ethylene ethylene carbonate, and vinylene carbonate kind. 5 . The lithium ion battery electrolyte according to claim 1 , wherein the sulfonate compound comprises methanesulfonic acid-2-propyn-1-ol and 1,3-propane sultone. 6 . at least one. 6 . The lithium-ion battery electrolyte according to claim 1 , wherein, based on the total volume of the electrolyte, the volume ratio of the film-forming agent is 10-30%. 7 . 7. The lithium-ion battery electrolyte according to claim 1, wherein the lithium salt comprises lithium hexafluorophosphate, lithium bisoxalatoborate, lithium bistrifluoromethanesulfonimide and lithium bisfluorosulfonimide. one or more. 8. The lithium-ion battery electrolyte according to claim 1, wherein the molar concentration of the lithium salt is 2-3 mol/L. 9 . A lithium ion battery, characterized in that it comprises the lithium ion battery electrolyte according to any one of claims 1 to 8 . 10 .

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