Electrolyte, electrochemical device thereof, and electronic device thereof

Abstract

To provide: an electrolyte which enables the improvement in film formation on the surface of a negative electrode to optimize an internal resistance, allows an electrochemical device to exhibit a satisfactory cycle performance at a high temperature and a room temperature, and to exhibit a satisfactory capacity performance at a high temperature and thus, achieves a low internal resistance; and an electrochemical device and an electronic device, both arranged by use thereof.SOLUTION: An electrolyte comprises vinylene carbonate and a carboxylate-based compound. To a mass of the electrolyte, the vinylene carbonate is A% by mass, and the carboxylate-based compound is B% by mass. The electrolyte satisfies the following requirements: the value of A / B is in a range of 0.1-10, and the value of A+B falls in a range of 1.1-6.SELECTED DRAWING: None

Description

[Background technology]

[0001] The present invention relates to the technical field of electrolytes, and in particular to an electrolyte, an electrochemical device using the electrolyte, and an electronic device using the electrolyte.

[0002] Lithium-ion batteries exhibit the important advantages of high voltage and large capacity, with long cycle life and excellent safety performance, and therefore have broad application prospects in portable electronic devices, electric vehicles, space technology and defense industries.

[0003] The electrolyte is the "blood" of a lithium battery, one of the four main materials in a lithium battery, and the carrier of ion transport within the battery. The electrolyte conducts lithium ions between the positive and negative electrodes, and has an important effect on the energy density, specific capacity, operating temperature range, cycle life, and safety performance of a lithium battery.

[0004] The performance of a lithium-ion battery, especially a high-voltage lithium-ion battery, is mainly determined by the composition and properties of its positive electrode active material and electrolyte. In order to develop a suitable high-performance electrolyte, suitable electrolyte additives are often added to the electrolyte. Commonly used electrolyte additives include boron-containing additives, organic phosphorus-based additives, carbonate-based additives, carboxylate-based additives, sulfur-containing additives, ionic liquid additives, etc.

[0005] Currently, when vinylene carbonate (VC), a common negative electrode film forming additive, is used alone, it is difficult to consider both high temperature and room temperature cycle performance and low resistance of the battery. Although the use of a carboxylate-based additive alone can increase the impedance of the battery, the stability of the negative electrode is poor, which limits the application of carboxylate-based compounds. Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the deficiencies of the related art, the present invention aims to provide an electrolyte, an electrochemical device thereof, and an electronic device thereof, through which the electrolyte provided by the present invention can improve the film formation on the surface of the negative electrode, optimize the internal resistance, enhance the cycle performance at high temperature and room temperature in the electrochemical device, and achieve low internal resistance. [Means for solving the problem]

[0007] One of the objectives of the present invention is to provide an electrolyte, and the following technical solutions are adopted in the present invention:

[0008] The electrolyte contains vinylene carbonate and a carboxylate compound.

[0009] Based on the mass of the electrolyte, the mass percentage of vinylene carbonate is A%, the mass percentage of the carboxylate compound is B%, and the electrolyte satisfies the following: the value of A / B is in the range of 0.1 to 10; and the value of A / B is in the range of 1.1 to 6.

[0010] In the electrolyte provided by the present invention, vinylene carbonate and a carboxylate compound are used in combination to cause a copolymerization reaction between the two. In the carboxylate compound, a carboxylate carbonyl group that can bond well with lithium ions and provide lithium ion migration sites is introduced into the negative electrode solid electrolyte film formed mainly by vinylene carbonate. By adjusting the content ratio of the two, the film formation on the surface of the negative electrode is improved and the internal resistance is optimized, so that the lithium battery exhibits good cycle performance at high temperature and room temperature, good capacity performance at high temperature, and achieves low internal resistance.

[0011] In the present invention, A and B satisfy the value A in the range of 0.1 to 5. For example, the value range of A is 0.1, 0.2, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5, etc. If A is too small, the amount of film-forming additive is too small, and the protective effect cannot be achieved; if A is too large, the polymerization reaction may be too strong, and the impedance of the battery may increase sharply. The value of B ranges from 0.1 to 5, for example, the value range of B is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5, etc. When the amount of the carboxylate compound is too small, such as less than 0.1%, the film formation effect is not obvious, and when an excessive amount of the carboxylate compound is used, such as more than 5%, the impedance may also increase sharply. A / B is 0.1 to 10, for example, A / B is 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10. A+B is 1.1 to 6, for example, A+B is 1.1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, or 6. When A / B is too small, the carboxylic acid content is relatively excessive, which consumes the carboxylic acid at the negative electrode and causes a side reaction. When A / B is too large, the content of the carboxylate may be relatively too small, and the effect of reducing impedance together with vinylene carbonate may not be obvious.If A+B is too small, the film formation effect may be insignificant, and if A+B is too large, the impedance of the battery may become too large.

[0012] Preferably, the value of A / B is in the range of 0.7-3, and the value of A+B is in the range of 1.1-4.

[0013] The carboxylate compound is a compound represented by formula (1): [ka] wherein R1, R3, and R4 are each hydrogen, substituted or unsubstituted C 1-12 R2 is independently selected from substituted or unsubstituted hydrocarbon groups, 1-12 and, if substituted, the substituents are halogen atoms, wherein C 1-12 The hydrocarbon group refers to a hydrocarbon group containing 1 to 12 carbon atoms.

[0014] The compound represented by formula (1) is dimethyl fumarate. [ka] , Methyl methacrylate [ka] , Dimethyl Maleate [ka] , 1,1,1,3,3,3-Hexafluoroisopropyl methacrylate [ka] , and vinyl methacrylate [ka] The mixture may be any one or more of the following. Exemplary, but non-limiting, combinations of mixtures include a mixture of dimethyl fumarate and methyl methacrylate, a mixture of dimethyl fumarate and dimethyl maleate, a mixture of dimethyl fumarate and 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, a mixture of dimethyl fumarate and vinyl methacrylate, a mixture of dimethyl fumarate, methyl methacrylate and dimethyl maleate, a mixture of dimethyl fumarate, methyl methacrylate and 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, a mixture of dimethyl fumarate, methyl methacrylate and vinyl methacrylate, a mixture of methyl methacrylate, dimethyl maleate and 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, a mixture of methyl methacrylate, dimethyl maleate and vinyl methacrylate, a mixture of methyl methacrylate, dimethyl maleate and 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, a mixture of methyl methacrylate, dimethyl maleate and vinyl methacrylate, and a mixture of methyl methacrylate, dimethyl maleate and vinyl methacrylate. mixtures of dimethyl fumarate, methyl methacrylate, dimethyl maleate, 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, and vinyl methacrylate; mixtures of dimethyl fumarate, methyl methacrylate, dimethyl maleate, and 1,1,1,3,3,3-hexafluoroisopropyl methacrylate; mixtures of dimethyl fumarate, methyl methacrylate, dimethyl maleate, and vinyl methacrylate; mixtures of methyl methacrylate, dimethyl maleate, 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, and vinyl methacrylate; and mixtures of dimethyl fumarate, methyl methacrylate, dimethyl maleate, 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, and vinyl methacrylate.

[0015] The electrolyte also includes ethylene carbonate (EC), where the weight percent of ethylene carbonate is C%, based on the weight of the electrolyte, and the electrolyte meets a value of C in the range of 15-60, such as 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60. If C is too small, the conductivity of the electrolyte may decrease, affecting the impedance of the battery. If C is too large, the electrolyte may be too soluble for the components of the solid electrolyte membrane, which may cause unstable membrane formation and affect performance. The value of C / (A+B) is in the range of 5-20, such as 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20. If C / (A+B) is too small, the solvent may be too poor for the membrane-forming additive, which may increase the impedance of the battery. If C / (A+B) is too large, the solvent may be too much relative to the film-forming additive, and film formation may become unstable.

[0016] The value of C / (A+B) is preferably in the range of 8.3 to 15.

[0017] Another object of the present invention is to provide an electrochemical device comprising a positive electrode, a negative electrode, a separator, and the above-mentioned electrolyte.

[0018] The electrochemical device provided by the present invention includes any device in which an electrochemical reaction occurs, and specific examples thereof include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0019] In some embodiments, the electrochemical device provided by the present invention is an electrochemical device that includes a positive electrode having a positive electrode active material capable of absorbing and releasing metal ions, and a negative electrode having a negative electrode active material capable of absorbing and releasing metal ions.

[0020] The positive electrode contains a positive electrode active material, and the positive electrode active material is selected from one or a mixture of two or more of lithium iron phosphate, lithium nickel transition metal composite oxide, and lithium nickel manganese composite oxide having a spinel structure.

[0021] The general formula of the lithium nickel transition metal composite oxide is Li 1+a Ni x Co y Mn z M b O 2-e X e wherein in the general formula, -0.2 < a < 0.2, 0.3 ≤ x ≤ 0.95, 0.05 ≤ y ≤ 0.3, 0.03 ≤ z ≤ 0.4, 0 ≤ b ≤ 0.05, 0 ≤ e ≤ 0.1, M is selected from one or a combination of two or more of Al, Ti, Zr, Nb, Sr, Sc, Sb, Y, Ba, Co, and Mn, and X is selected from F and / or Cl. It should be noted that the general chemical formula of the lithium nickel transition metal composite oxide is the chemical formula when the state of charge (SOC) of the battery is 0%.

[0022] The negative electrode contains a negative electrode active material and a current collector, and the negative electrode active material contains graphite or a silicon-carbon negative electrode active material.

[0023] The silicon-carbon negative electrode active material is selected from any one or a mixture of two or more of silicon, silicon oxide compound, and silicon-based alloy.

[0024] The negative electrode further contains a carbon material, and the carbon material is selected from any one or a mixture of two or more of acetylene black, conductive carbon black, carbon fiber, carbon nanotube, and ketjen black.

[0025] The chlorine content in the separator is 20 ppm or less. The chlorine content in the separator is preferably 7 ppm to 20 ppm, such as 3 ppm, 5 ppm, 7 ppm, 8 ppm, 9 ppm, 10 ppm, 11 ppm, 12 ppm, 13 ppm, 14 ppm, 15 ppm, 16 ppm, 17 ppm, 18 ppm, 19 ppm, or 20 ppm. If the chlorine content in the separator is too low, the effect of chlorine on the battery may be reduced, but it is limited by current separator technology and it is difficult to further reduce the chlorine content. If the chlorine content in the separator exceeds 20 ppm, the polymerization reaction of SVC and additives may stop, which may adversely affect battery performance.

[0026] Another object of the present invention is to provide an electronic device including the above-mentioned electrochemical device.

[0027] Examples of electronic devices include, but are not limited to, notebook computers, pen-based computers, mobile computers, e-book readers, mobile phones, portable fax machines, portable copiers, portable printers, stereo headphones, video cassette recorders, LCD televisions, portable vacuum cleaners, portable CD players, mini-discs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting equipment, toys, game consoles, watches, electronic tools, flashlights, cameras, large household batteries, or lithium-ion batteries. Effect of the Invention

[0028] Compared with the related art, the beneficial effects of the present invention are as follows:

[0029] The electrolyte provided by the present invention uses vinylene carbonate and a carboxylate compound in combination to adjust the content, thereby improving the film formation on the surface of the negative electrode and optimizing the internal resistance, so that the electrochemical device exhibits good cycle performance at high temperature and room temperature, good capacity performance at high temperature, and achieves low internal resistance.

[0030] In order to make the above easier to understand, several embodiments are described in detail below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The technical solutions of the present invention are further illustrated below through specific embodiments.

[0032] Unless otherwise specified, the various raw materials of the present invention can be purchased commercially or prepared according to conventional methods in the art.

[0033] The electrolyte provided by the present invention contains vinylene carbonate and a carboxylate compound.

[0034] Based on the mass of the electrolyte, the mass percentage of vinylene carbonate is A%, the mass percentage of the carboxylate compound is B%, and the electrolyte satisfies a value of A in the range of 0.1-5, a value of B in the range of 0.1-5, a value of A / B in the range of 0.1-10, and a value of A+B in the range of 1.1-6.

[0035] In the present invention, the electrochemical device is a lithium ion battery, which may be a primary or secondary lithium battery, and includes a positive electrode, a negative electrode, a separator located between the positive and negative electrodes, and an electrolyte.

[0036] A method for making a secondary lithium battery of the present invention is provided below.

[0037] (1) Preparation of LFP (LiFePO4) positive electrode

[0038] The positive electrode active material (LiFePO4), polyvinylidene fluoride (as binder), and Super P (as conductive agent) were mixed in a weight ratio of 97:2:1, N-methylpyrrolidone (NMP) was added, and the mixture was stirred in a vacuum mixer until the system was uniform and transparent to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on an aluminum foil. The aluminum foil was dried at room temperature and then transferred to an oven for drying, and then cold pressed and cut out to obtain a positive electrode (electrode piece).

[0039] (2) Preparation of graphite anode

[0040] Artificial graphite (as negative electrode active material), Super P (as conductive agent), sodium carboxymethyl cellulose (CMC-Na; thickener), and styrene butadiene rubber (SBR; as binder) were mixed in a mass ratio of 96:1:1:2. Deionized water was added to obtain a negative electrode slurry in the operation of a vacuum mixer. The negative electrode slurry was uniformly coated on a negative electrode current collector copper foil. The copper foil was dried at room temperature, then transferred to an oven for drying, and then cold pressed and cut out to obtain a negative electrode (electrode piece).

[0041] (3) Preparation of electrolyte

[0042] To form an organic solvent, battery grade ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed according to the ratio in an argon atmosphere glove box with a water content of less than 10 ppm. Other components were added quantitatively according to the electrolyte composition listed in the table provided in the following paragraphs and mixed uniformly to obtain an electrolyte solution. The content of each component in the table is the weight percentage calculated based on the total weight of the electrolyte solution, and the DTD is ethylene sulfate.

[0043] (4) Preparation of the separator membrane

[0044] A polypropylene membrane was used as the separator membrane.

[0045] (5) Preparation of secondary batteries

[0046] A 12 μm thick polypropylene thin film (PP) was used as the separator film. The positive electrode, separator film, and negative electrode prepared above were stacked in order so that the separator film was placed between the positive electrode and the negative electrode for separation, covered with an aluminum laminate film, transferred to a vacuum oven for drying at 120° C., and 3.0 g / Ah of the electrolyte prepared above was injected, and then sealed to form the electrolyte. Finally, a soft-pack battery (i.e., a lithium-ion battery) with a capacity of 1 Ah was obtained.

[0047] In the present invention, the obtained lithium ion battery has a negative electrode gram capacity of 350 mAh / g, a liquid injection coefficient of 3 g / Ah, a battery capacity of 1 Ah, a negative electrode mass of 3 g, and an electrolyte mass of 3 g.

[0048] The conditions for the formation of the electrolyte in the lithium ion battery in the present invention are provided below.

[0049] The steps of forming the electrolyte in the lithium-ion battery are given below: After injection, the electrolyte is kept under high temperature pressure of 0.1 MPa, charged at 0.02 C for 17 minutes at 45 ° C in a static state, then left for 5 minutes and charged at 0.02 C to 0.3 Ah. Then, the airbag is cut and vacuum sealed, and the electrolyte is left at room temperature for 48 hours to complete the formation of the electrolyte.

[0050] In the examples provided by the present invention, the following five compounds were used as the compound represented by formula (1): Compound 1 is methyl methacrylate, Compound 2 is dimethyl fumarate, Compound 3 is dimethyl maleate, Compound 4 is 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, and Compound 5 is vinyl methacrylate.

[0051] The secondary battery provided by the present invention can be tested through the following method.

[0052] (1) Secondary battery cycle test

[0053] The batteries were cycled at a current of 1 C within a specific potential interval in an oven at a specific temperature (room temperature 25°C or high temperature 45°C), and the discharge capacity of each cycle was recorded. The test was terminated when the battery capacity reached 80% of the capacity of the first cycle.

[0054] (2) Secondary battery direct current resistance (DCR) test

[0055] At a certain temperature, when the battery is discharged to 50% SOC (state of charge, reflecting the remaining capacity of the battery) at a current of 1C, the current is increased to 4C and maintained for 30 seconds. The difference between the updated stable voltage and the original platform voltage is detected, and the ratio of its value to the 3C current is the DC resistance of the battery. The first DCR test result performed after the battery is fully charged is the initial DCR of the battery.

[0056] (3) High-temperature capacity retention test for secondary batteries

[0057] After being fully charged, the secondary battery was placed in a 60° C. incubator, taken out after 30 days, cooled to room temperature, and then discharged at 0.33 C to a cut-off voltage to compare its capacity as a percentage of the initial discharge capacity.

[0058] Here, the charge / discharge cutoff voltages are as follows: LFP-graphite, 2.5V-3.65V;

[0059] (4) The chlorine content in the separator was tested by the following method.

[0060] The separator was combusted in an automatic sample combustion device (AQF-100, manufactured by Mitsubishi Chemical Analytech), then absorbed in an absorption solution (a mixed solution of Na2CO3 and NaHCO3), and the absorption solution was injected into an ion chromatography device (manufactured by Dionex, ICS1500, column (separation column: AS12A, guard column: AG12A), suppressor ASRS300) to measure the total chlorine content.

[0061] Table 1-1 shows the electrolyte compositions of Examples 1 to 10, Comparative Examples 1, 2, and 3 in the present invention. Lithium ion batteries were produced by the above-mentioned production method and their performance was tested. The test results are shown in Table 1-2.

[0062] [Table 1-1]

[0063] [Table 1-2]

[0064] From the data in Table 1-2, it can be seen that the value range of A+B determines the total amount of additives for forming a film on the negative electrode. That is, the larger the value, the higher the impedance, and the smaller the value, the poorer the film formation effect. Vinylene carbonate and carboxylate are used simultaneously to reduce impedance. The content of vinylene carbonate determines the film quality but increases the impedance, and the content of carboxylate determines the effect of reducing impedance, but adding excessive carboxylate has the opposite effect. Therefore, by controlling A / B and A+B to be in the appropriate range, the synergistic effect of these improves the performance and strength of the film formed on the negative electrode, increases lithium ion conductivity, and reduces impedance.

[0065] The electrolyte components of Examples 11 to 14 of the present invention are shown in Table 2-1. Lithium ion batteries were produced by the above-mentioned production method and their performance was tested. The test results are shown in Table 2-2.

[0066] [Table 2-1]

[0067] [Table 2-2]

[0068] As can be seen from Table 2, in the preferred ranges of A+B and A / B, when the value of A+B is in the range of 1.1 to 4 and the value of A / B is in the range of 0.7 to 3, it has been found that a balance between negative electrode film formation and a decrease in battery impedance can be effectively achieved.

[0069] Table 3-1 shows the electrolyte compositions of Examples 15 to 17 and Comparative Example 4. Lithium ion batteries were produced by the above-mentioned production method and their performance was tested. The test results are shown in Table 3-2.

[0070] [Table 3-1]

[0071] [Table 3-2]

[0072] In the determined optimal total amount and ratio of the negative electrode film-forming additive, the ratio of EC to the total amount and ratio is limited, and from the data in Table 3-2, if the ratio is too high, the film formation on the surface of the negative electrode may become unstable, which may impair the battery performance, but if the ratio is too low, the dissociation of lithium ions may be insufficient, the conductivity of the electrolyte may decrease, and the battery impedance may increase.

[0073] The difference in the electrolyte composition between Examples 18 to 21 and Example 8 is the type of compound represented by formula (1). Compound 1 was used in Example 8, Compound 2 was used in Example 18, Compound 3 was used in Example 19, Compound 4 was used in Example 20, and Compound 5 was used in Example 21. The other components were the same as those in Example 8.

[0074] The lithium ion battery was fabricated by the above-mentioned method and its performance was tested. The test results are shown in Table 4.

[0075] [Table 4]

[0076] The data in Table 4 show that in Examples 8 and 18-21, different types of compounds represented by formula (1) can be used to enhance the cycling performance of the battery at high temperature and room temperature, improve the high temperature capacity performance, and reduce the resistance.

[0077] The difference between Examples 22 and 23 compared to Example 8 is that the separator of Example 8 has a chlorine content of 7 ppm, whereas the separators of Examples 22 and 23 have a chlorine content of 10 ppm and 20 ppm, respectively.

[0078] [Table 5]

[0079] As can be seen from the data in Table 5, by controlling the chlorine content of the separator between 7 and 20 ppm, it was found that the higher the chlorine content, the more serious the loss of the film-forming reaction of ethylene carbonate, vinylene carbonate, and carboxylate-based compounds becomes. Furthermore, by controlling the chlorine content of the separator between 7 and 10 ppm, the performance can be effectively improved. Therefore, by controlling the synergistic effect of the contents of chlorine, ethylene carbonate, vinylene carbonate, and carboxylate-based compounds in the separator, the battery performance can be improved.

[0080] In the present invention, the processing equipment and processing flow of the present invention are shown in detail in the above embodiment. However, the present invention is not limited to the detailed processing equipment and processing flow described above. That is, this does not mean that the present invention cannot be implemented without relying on the detailed processing equipment and processing flow described above. Those skilled in the art should understand that the improvement of the present invention, the equivalent replacement of each raw material of the present invention, the addition of auxiliary components, the selection of a specific method, etc. are all within the protection scope and disclosure scope of the present invention.

[0081] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above-mentioned embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and all of these simple modifications belong to the protection scope of the present invention.

[0082] In addition, it should be noted that each specific technical feature described in the above specific implementation methods can be combined in any appropriate manner under non-conflicting circumstances, and in order to avoid unnecessary repetition, various possible combinations are not described in the present invention.

[0083] In addition, the various embodiments of the present invention can be arbitrarily combined, and as long as they are not contrary to the spirit of the present invention, they should also be considered as contents disclosed in the present invention. [Industrial Applicability]

[0084] The electrolyte, electrochemical device, and electronic device of the present invention can be applied to a primary battery, a secondary battery, a fuel cell, a solar cell, or a capacitor.

Claims

1. An electrolyte solution containing vinylene carbonate and a carboxylate compound, The carboxylate compound is any one or a mixture of two or more of methyl methacrylate, 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, and vinyl methacrylate; Based on the weight of the electrolyte, the weight percentage of the vinylene carbonate is A% and the weight percentage of the carboxylate-based compound is B%; The electrolyte satisfies the following: A / B is in the range of 0.1 to 10; and A+B is in the range of 1.1 to 6. Electrolyte.

2. The value of A / B is in the range of 0.7 to 3, and the value of A+B is in the range of 1.1 to 4. The electrolyte solution according to claim 1.

3. Further comprising ethylene carbonate, the weight percent of the ethylene carbonate is C%, based on the weight of the electrolyte; The electrolyte satisfies the value of C / (A+B) in the range of 5 to 20. The electrolyte solution according to claim 1 or 2.

4. The value of C / (A+B) is in the range of 8.3 to 15; The electrolyte according to claim 3.

5. A positive electrode, a negative electrode, a separator, and the electrolyte solution according to claim 1. Including, Electrochemical devices.

6. the positive electrode comprises a positive electrode active material, The positive electrode active material is selected from one or a mixture of two or more of lithium iron phosphate, lithium nickel transition metal composite oxide, and lithium nickel manganese composite oxide having a spinel structure. The electrochemical device according to claim 5 .

7. the negative electrode includes a negative electrode active material and a current collector, the negative electrode active material comprises graphite or silicon-carbon negative electrode active material, The chlorine content of the separator is 20 ppm or less.

7. The electrochemical device according to claim 5 or 6.

8. The chlorine content in the separator is 7 ppm to 20 ppm. The electrochemical device of claim 7.

9. The electrochemical device according to claim 5 , Electronic devices.

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