Carbonic ester electrolyte and preparation method and application thereof

Abstract

The invention discloses a carbonic ester electrolyte as well as a preparation method and application thereof. The carbonic ester electrolyte comprises electrolyte lithium salt, a carbonic ester organic solvent and an acetonitrile solvent containing nitrate. According to the invention, acetonitrile is selected to assist the dissolution of nitrate, so that the solubility of nitrate in the carbonic ester electrolyte is improved, the cycle life and energy density of the lithium ion battery at normal temperature are improved, and the scheme is easy to realize industrialization.

Description

Technical Field

[0001] The invention belongs to the technical field of electrolytes, and in particular relates to a carbonate electrolyte and a preparation method thereof, and also relates to the application of the carbonate electrolyte in the preparation of lithium ion batteries. Background Art

[0002] Lithium-ion batteries have become the main energy storage technology for modern portable electronics, electric vehicles and renewable energy storage systems. Due to their high energy density, long life and no memory effect, lithium-ion batteries have become an ideal energy solution for smartphones, laptops, tablets and other portable electronic devices. With the development of new energy, the application of lithium-ion batteries in electric vehicles (EVs), electric bicycles and other electric vehicles has expanded rapidly, thus putting forward higher requirements for the energy density of lithium-ion batteries.

[0003] Lithium metal has an ultra-high theoretical specific capacity (3860mAh / g), the lowest redox potential (-3.04V vs standard hydrogen electrode), and a low mass density (0.53g / cm 3 ), is considered to be a promising next-generation lithium battery negative electrode material. However, at present, lithium negative electrode metal uses lithium deposition / stripping to complete the charge and discharge cycle in the cycle. The lithium negative electrode is prone to side reactions with the electrolyte, consuming the electrolyte and resulting in low lithium deposition / stripping efficiency, affecting the battery's cycle stability. The use of lithium nitrate (LiNO3) additives can effectively inhibit the growth of lithium dendrites on the surface of the lithium metal negative electrode and reduce the roughness of the lithium negative electrode metal surface. However, this additive is difficult to dissolve in carbonate electrolytes, but can be dissolved in ether electrolytes. However, the higher highest occupied molecular orbital energy level (HOMO) of ether electrolytes makes its inherent antioxidant property insufficient. When the battery voltage exceeds 4.0V, severe oxidative decomposition will occur, making it difficult to form a stable and reliable electrode / electrolyte interface, resulting in serious irreversible capacity loss and poor electrochemical stability. Therefore, it cannot be effectively applied to positive electrode material systems with higher voltages.

[0004] A Chinese patent application with publication number CN113131000A discloses a carbonate electrolyte, which adds crown ethers and their derivatives of a specific structure as cosolvents of nitrates in the electrolyte, so that they react with cations in the nitrates to produce more nitrates in the electrolyte, improve the dissolution of nitrates, and make nitrates applicable to carbonate electrolytes. However, crown ethers are expensive and difficult to manufacture, which will increase the cost of such electrolytes and is not conducive to industrial application; and the addition of crown ethers to the electrolyte will increase the viscosity of the electrolyte, which is not conducive to improving the ion transmission rate. Summary of the invention

[0005] In view of this, the primary purpose of the present invention is to provide a carbonate electrolyte to increase the solubility of nitrate in the carbonate electrolyte, thereby increasing the cycle life of lithium-ion batteries, especially lithium metal batteries, and improving safety performance.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention firstly provides a carbonate electrolyte, which comprises an electrolyte lithium salt, a carbonate organic solvent and an acetonitrile solvent containing nitrate.

[0008] In a further embodiment, the electrolyte lithium salt is at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

[0009] In a further embodiment, the concentration of the electrolyte lithium salt is 1 mol / L to 3 mol / L, taking the carbonate electrolyte as a measurement basis.

[0010] In a further embodiment, the carbonate organic solvent is at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, fluoroethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0011] In a further embodiment, the nitrate is one or a mixture of two or more of sodium nitrate, lithium nitrate, magnesium nitrate, rubidium nitrate, cesium nitrate, potassium nitrate, calcium nitrate, strontium nitrate and barium nitrate.

[0012] In a further embodiment, in the acetonitrile solvent containing nitrate, the mass ratio of nitrate to acetonitrile is (40-70):(30-60).

[0013] In a further embodiment, the carbonate electrolyte is used as a measurement basis, and the added mass percentage of the nitrate-containing acetonitrile solvent is 0.5% to 2%.

[0014] In a further embodiment, the carbonate electrolyte further contains additives.

[0015] In a further embodiment, the additive is at least one of lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorophosphate, vinylene carbonate, and 1,3-propane sultone.

[0016] In a further embodiment, the carbonate electrolyte is used as a measurement basis, and the additive is added in an amount of 0.5% to 1.5% by mass.

[0017] The present invention further provides a method for preparing the carbonate electrolyte as described above, which is carried out under the condition of isolating water and oxygen, comprising the following steps:

[0018] A carbonate electrolyte base liquid containing an electrolyte lithium salt is prepared;

[0019] The nitrate and acetonitrile are mixed according to a ratio, and stirred evenly to obtain an acetonitrile solvent containing the nitrate;

[0020] Add the acetonitrile solvent containing nitrate into the carbonate electrolyte base liquid and stir evenly.

[0021] The present invention further provides the use of the carbonate electrolyte as described above or the carbonate electrolyte prepared by the method for preparing the carbonate electrolyte as described above in the preparation of a lithium ion battery.

[0022] The present invention further provides a lithium ion battery, which contains the carbonate electrolyte as described above or a carbonate electrolyte prepared by the method for preparing the carbonate electrolyte as described above.

[0023] In a further embodiment, the lithium ion battery is a lithium metal battery.

[0024] Beneficial effects of the present invention:

[0025] The carbonate electrolyte uses acetonitrile to assist in the dissolution of nitrates, which not only improves the solubility of nitrates in the carbonate electrolyte, but also reduces the viscosity of the carbonate electrolyte, increases the conductivity of the electrolyte, and improves the ion transfer rate, so that the lithium-ion battery has a better cycle life at room temperature and a higher energy density, and is particularly suitable for lithium metal batteries, so that the electrolyte containing nitrates can also be used for high-energy-density lithium metal negative electrode batteries. In addition, the acetonitrile used in the present invention is cheap and easy to obtain, which can reduce the cost of the carbonate electrolyte containing nitrates and is easy to realize industrialization. DETAILED DESCRIPTION

[0026] Embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0028] A first aspect of the present invention provides a carbonate electrolyte, which includes an electrolyte lithium salt, a carbonate organic solvent and an acetonitrile solvent containing nitrate.

[0029] The present invention adopts acetonitrile to assist nitrate in dissolving in carbonate electrolyte, which not only significantly improves the solubility of nitrate in carbonate electrolyte, but also reduces the viscosity of high-concentration electrolyte, improves the ion conductivity of electrolyte, and further improves the ion transmission rate, thereby being able to significantly improve the cycle life and rate performance of lithium-ion battery while effectively inhibiting lithium dendrites. In addition, the acetonitrile used is cheap and easy to obtain, which can significantly reduce the cost of such electrolyte, making it easier to realize industrial application.

[0030] In the present invention, in the acetonitrile solvent containing nitrate, the nitrate can be a nitrate additive conventionally added to the electrolyte in the art, and specific examples include at least one of sodium nitrate, lithium nitrate, magnesium nitrate, rubidium nitrate, cesium nitrate, potassium nitrate, calcium nitrate, strontium nitrate, and barium nitrate, but are not limited thereto.

[0031] In the present invention, nitrate and acetonitrile can be mixed in any proportion as long as the mixed nitrate can be completely dissolved in acetonitrile. Preferably, the mass ratio of nitrate to acetonitrile is (40-70):(30-60), for example, it can be any ratio of 40:60, 45:55, 50:50, 55:45, 60:40, 65:35, 70:30. Preferably, the mass ratio of nitrate to acetonitrile is 50:50.

[0032] In the present invention, the preparation method of the acetonitrile solvent containing nitrate is as follows: under the condition of isolating water and oxygen and protecting with inert gas, nitrate powder and acetonitrile solvent are mixed in proportion, and stirred evenly at room temperature to obtain the acetonitrile solvent containing nitrate.

[0033] In the present invention, the electrolyte lithium salt is a lithium salt conventionally used in lithium-ion battery electrolytes in the art, and specific examples include at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), but are not limited thereto.

[0034] In the present invention, the carbonate organic solvent is a type of solvent conventionally used in the electrolyte in the art, and specific examples include but are not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), dimethyl carbonate (DMC) or ethyl methyl carbonate (EMC).

[0035] It is understood that, with carbonate electrolyte as the measurement basis, the concentration of the electrolyte lithium salt can be designed based on the conventional concentration in the art. For example, in some specific implementation cases of the present invention, the concentration of the electrolyte lithium salt is 1 mol / L to 3 mol / L. The amount of the nitrate-containing acetonitrile solvent added can be determined by an experimental method well known in the art. In some preferred implementation cases of the present invention, the mass percentage of the nitrate-containing acetonitrile solvent is 0.5% to 2%. Within the above preferred ratio, the effect of the electrolyte can be better.

[0036] In some other specific implementation cases of the present invention, some functional additives can be added to the carbonate electrolyte as needed to further improve the performance of the carbonate electrolyte. The specific types of additives can be selected from conventional types in the art as needed, such as lithium bis(oxalatoborate) (LiBOB), lithium difluorooxalatoborate (LiDFOB), lithium difluorophosphate (LiDFP), vinylene carbonate (VC), 1,3-propane sultone (PS) at least one, but not limited thereto. The specific amount of addition can be selected based on the amount known in the art. In some specific implementation cases of the present invention, the mass percentage of the additive added is 0.5% to 1.5% based on the carbonate electrolyte as the measurement basis.

[0037] The second aspect of the present invention provides a method for preparing the carbonate electrolyte as described above, which is carried out under the condition of isolating water and oxygen, comprising the following steps:

[0038] A carbonate electrolyte base solution containing an electrolyte lithium salt is prepared. Specifically, the electrolyte lithium salt and additives (if any) are dissolved in a carbonate organic solvent;

[0039] The nitrate and acetonitrile are mixed according to a ratio, and stirred evenly to obtain an acetonitrile solvent containing the nitrate;

[0040] Add the acetonitrile solvent containing nitrate into the carbonate electrolyte base liquid and stir evenly.

[0041] The water and oxygen isolation conditions described in this article are achieved using a glove box commonly used in the art. The inert gas refers to nitrogen or a rare gas (such as helium or argon, etc.), which will not be described in detail here.

[0042] The present invention further provides the use of the carbonate electrolyte as described above or the carbonate electrolyte prepared by the method for preparing the carbonate electrolyte as described above in the preparation of a lithium ion battery.

[0043] The present invention further provides a lithium ion battery, comprising the carbonate electrolyte as described above or a carbonate electrolyte prepared by the method for preparing the carbonate electrolyte as described above. In some typical implementation cases of the present invention, the lithium ion battery is a lithium metal battery.

[0044] It is understandable that the lithium-ion battery described herein also includes key materials such as a positive electrode, a negative electrode and a separator, all of which can be conventional types in the art and will not be described in detail here.

[0045] The lithium-ion battery described in this article has the same advantages, strengths or progress as the carbonate electrolyte described above, which will not be elaborated here.

[0046] The present invention is described below by means of specific examples. It should be noted that the following specific examples are only for illustrative purposes and do not limit the scope of the present invention in any way. In addition, unless otherwise specified, methods without specific conditions or steps are conventional methods, and the reagents and materials used can be obtained from commercial channels.

[0047] Example 1

[0048] This embodiment provides a carbonate electrolyte, and the specific steps for preparing the electrolyte are as follows:

[0049] In an argon-protected glove box, lithium nitrate powder was added to acetonitrile solvent at a mass ratio of 1:1, and stirred continuously at room temperature to obtain an acetonitrile solution containing dissolved lithium nitrate.

[0050] The PC:EC:EMC:FEC solvents are uniformly mixed in a mass ratio of 30:10:50:10 to obtain a mixed organic solvent; then electrolyte salts LiPF6 and LiTFSI, additives LiDFOB, VC and PS are added thereto and fully dissolved to obtain an electrolyte base liquid;

[0051] An acetonitrile solution containing lithium nitrate is added to the electrolyte base liquid, and the mixture is stirred evenly at room temperature to fully dissolve all components to prepare a carbonate electrolyte.

[0052] In the electrolyte of this embodiment, the carbonate electrolyte is used as the reference for measurement, and the contents of each component are: LiPF6 (1 mol / L), LiTFSI (1 mol / L); LiDFOB (0.5 wt%), VC (1 wt%), PS (1 wt%); acetonitrile solution of lithium nitrate (0.5 wt%, lithium nitrate: acetonitrile = 1:1); PC:EC:EMC:FEC = 30:10:50:10.

[0053] Example 2

[0054] A carbonate electrolyte is provided in this embodiment, and its preparation method is the same as that in Example 1. Taking the carbonate electrolyte as the reference, the composition and content of the components of the electrolyte in this embodiment are: LiPF6 (1 mol / L), LiTFSI (2 mol / L); LiDFOB (0.5 wt%), VC (1 wt%), PS (1 wt%); acetonitrile solution containing lithium nitrate (0.5 wt%, lithium nitrate: acetonitrile = 1:1); PC:EC:EMC:FEC = 30:10:50:10.

[0055] Example 3

[0056] A carbonate electrolyte is provided in this embodiment, and its preparation method is the same as that in Example 1. Taking the carbonate electrolyte as the reference, the composition and content of the components of the electrolyte in this embodiment are: LiPF6 (1 mol / L), LiTFSI (1 mol / L); LiDFOB (0.5 wt%), VC (1 wt%), PS (1 wt%); acetonitrile solution containing lithium nitrate (1 wt%, lithium nitrate: acetonitrile = 1:1); PC:EC:EMC:FEC = 30:10:50:10.

[0057] Example 4

[0058] A carbonate electrolyte is provided in this embodiment, and its preparation method is the same as that in Example 1. Taking the carbonate electrolyte as the reference, the composition and content of the components of the electrolyte in this embodiment are: LiPF6 (1 mol / L), LiTFSI (2 mol / L); LiDFOB (0.5 wt%), VC (1 wt%), PS (1 wt%); acetonitrile solution containing lithium nitrate (1 wt%, lithium nitrate: acetonitrile = 1:1); PC:EC:EMC:FEC = 30:10:50:10.

[0059] Example 5

[0060] A carbonate electrolyte is provided in this embodiment, and its preparation method is the same as that in Example 1. Taking the carbonate electrolyte as the reference, the composition and content of the components of the electrolyte in this embodiment are: LiPF6 (1 mol / L), LiTFSI (2 mol / L); LiDFOB (0.5 wt%), VC (1 wt%), PS (1 wt%); acetonitrile solution containing lithium nitrate (2 wt%, lithium nitrate: acetonitrile = 1:1); PC:EC:EMC:FEC = 30:10:50:10.

[0061] Example 6

[0062] A carbonate electrolyte is provided in this embodiment, and its preparation method is the same as that in Example 1. Taking the carbonate electrolyte as the reference, the composition and content of the components of the electrolyte in this embodiment are: LiPF6 (1 mol / L), LiTFSI (1 mol / L); LiDFOB (0.5 wt%), VC (1 wt%), PS (1 wt%); acetonitrile solution containing lithium nitrate (2 wt%, lithium nitrate: acetonitrile = 1:1); PC:EC:DMC:FEC = 30:10:50:10.

[0063] Example 7

[0064] A carbonate electrolyte is provided in this embodiment, and its preparation method is the same as that in Example 1. Taking the carbonate electrolyte as the reference, the composition and content of the components of the electrolyte in this embodiment are: LiPF6 (1 mol / L), LiTFSI (1 mol / L); LiDFOB (0.5 wt%), VC (1 wt%), PS (1 wt%); acetonitrile solution containing lithium nitrate (2 wt%, lithium nitrate: acetonitrile = 1:1); PC:EC:DEC:FEC = 30:10:50:10.

[0065] Example 8

[0066] This embodiment provides a carbonate electrolyte and its preparation, and its composition and preparation adopt the same implementation method as that of Example 3, except that lithium nitrate is replaced by an equal mass of rubidium nitrate.

[0067] Example 9

[0068] This embodiment provides a carbonate electrolyte and its preparation, and its composition and preparation adopt the same implementation method as that of Example 3, with the only difference being that lithium nitrate is replaced by potassium nitrate of equal mass.

[0069] Example 10

[0070] This embodiment provides a carbonate electrolyte and its preparation, and its composition and preparation adopt the same implementation method as that of Example 3, with the only difference being that lithium nitrate is replaced by an equal mass of sodium nitrate.

[0071] Embodiment 11

[0072] This embodiment provides a carbonate electrolyte and its preparation, and its composition and preparation adopt the same implementation method as that of Example 3, with the only difference being that lithium nitrate is replaced by an equal mass of magnesium nitrate.

[0073] Example 12

[0074] This embodiment provides a carbonate electrolyte and its preparation, and its composition and preparation adopt the same implementation method as that of Example 3, with the only difference being that the mass ratio of lithium nitrate to acetonitrile is 4:6.

[0075] Embodiment 13

[0076] This embodiment provides a carbonate electrolyte and its preparation, and its composition and preparation adopt the same implementation method as that of Example 3, with the only difference being that the mass ratio of lithium nitrate to acetonitrile is 7:3.

[0077] Comparative Example 1

[0078] This comparative example provides a carbonate electrolyte and its preparation, and its composition and preparation adopt the same implementation method as Example 3, except that: the acetonitrile solution containing lithium nitrate is not added.

[0079] Taking carbonate electrolyte as the reference, the composition and content of each component of the electrolyte in this comparative example are: LiPF6 (1 mol / L), LiTFSI (1 mol / L); LiDFOB (0.5 wt%), VC (1 wt%), PS (1 wt%); PC:EC:EMC:FEC=30:10:50:10.

[0080] Comparative Example 2

[0081] This comparative example provides a carbonate electrolyte and its preparation, and its composition and preparation adopt the same implementation method as Example 3, with the only difference being that 0.5 wt % of lithium nitrate is directly added to the electrolyte base liquid without adding acetonitrile.

[0082] Taking the carbonate electrolyte as the reference, the composition and content of the electrolyte components in this comparative example are: LiPF6 (1 mol / L), LiTFSI (1 mol / L); LiDFOB (0.5 wt%), VC (1 wt%), PS (1 wt%); lithium nitrate (0.5 wt%); PC:EC:EMC:FEC=30:10:50:10.

[0083] Comparative Example 3

[0084] This comparative example provides a carbonate electrolyte and its preparation, and its composition and preparation adopt the same implementation method as Example 3, with the only difference being that 0.5wt% lithium nitrate powder and 0.5wt% acetonitrile solvent are directly added to the electrolyte base liquid, rather than first preparing an acetonitrile solution containing lithium nitrate.

[0085] Taking the carbonate electrolyte as the reference, the composition and content of each component of the electrolyte in this comparative example are: LiPF6 (1 mol / L), LiTFSI (1 mol / L); LiDFOB (0.5 wt%), VC (1 wt%), PS (1 wt%); lithium nitrate (0.5 wt%); acetonitrile (0.5 wt%); PC:EC:EMC:FEC=30:10:50:10.

[0086] Comparative Example 4

[0087] This comparative example provides a carbonate electrolyte and its preparation, and its composition and preparation adopt the same implementation as that of comparative example 3, except that acetonitrile is replaced by an equal mass of crown ether 18-crown-6.

[0088] Taking the carbonate electrolyte as the reference, the composition and content of the electrolyte components in this comparative example are: LiPF6 (1 mol / L), LiTFSI (1 mol / L); LiDFOB (0.5 wt%), VC (1 wt%), PS (1 wt%); lithium nitrate (0.5 wt%); 18-crown-6 (0.5 wt%); PC:EC:EMC:FEC=30:10:50:10.

[0089] Performance Testing

[0090] (1) Electrochemical performance test:

[0091] The carbonate electrolyte prepared in the examples and comparative examples was used to assemble a 811||Li button battery, wherein the positive electrode was prepared by using LiNi 0.8 Co 0.1 Mn 0.1 O2 is the active material, carbon black conductive agent (SP), multi-walled carbon nanotubes (MWCNT) are conductive agents, PVDF is a binder, N-methyl-2-pyrrolidone (NMP) is a dispersant, and LiNi 0.8 Co 0.1 Mn 0.1 The slurry was prepared with a mass ratio of O2:MWCNT:SP:PVDF=90:4:2:4, and the slurry was coated on a 12μm aluminum foil to make a positive electrode sheet with a coating surface density of 20mg / cm 2 ; Preparation of negative electrode: A 0.5 mm thick pure lithium sheet was used as the negative electrode; a polypropylene microporous membrane with ceramics (2+12+2 μm) on both sides was used as a separator; the electrolyte was the carbonate electrolyte in the embodiment and the comparative example respectively.

[0092] The electrochemical performance test was carried out at room temperature of 25°C. The batteries were placed in a constant temperature box at a constant temperature of 25°C. The charge and discharge voltage range of the 811||Li button battery was 2.7 to 4.2V, and the cycle test was carried out at a rate of 0.5C. The test results are shown in Table 1.

[0093] Table 1 Electrochemical performance test results of 811||Li button battery

[0094]

[0095]

[0096] It can be seen from the test results in Table 1 that the carbonate electrolyte in the present invention significantly improves the capacity retention rate and life of the lithium metal negative electrode. This is mainly due to the fact that the solution in the present invention can ensure the solubility of nitrate in the carbonate electrolyte. At the same time, the solution in the present invention can effectively inhibit the growth of lithium dendrites in the later stage.

[0097] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0098] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A carbonate electrolyte, characterized in that: The invention comprises an electrolyte lithium salt, a carbonate organic solvent and an acetonitrile solvent containing a nitrate.

2. The carbonate electrolyte according to claim 1, characterized in that The electrolyte lithium salt is at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide; Preferably, based on the carbonate electrolyte as a measurement basis, the concentration of the electrolyte lithium salt is 1 mol / L to 3 mol / L.

3. The carbonate electrolyte according to claim 1, characterized in that The carbonate organic solvent is at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, fluoroethylene carbonate, dimethyl carbonate and ethyl methyl carbonate.

4. The carbonate electrolyte according to claim 1, characterized in that The nitrate is one or a mixture of two or more of sodium nitrate, lithium nitrate, magnesium nitrate, rubidium nitrate, cesium nitrate, potassium nitrate, calcium nitrate, strontium nitrate and barium nitrate.

5. The carbonate electrolyte according to claim 1, characterized in that In the acetonitrile solvent containing nitrate, the mass ratio of nitrate to acetonitrile is (40-70): (30-60).

6. The carbonate electrolyte according to claim 1, characterized in that Taking the carbonate electrolyte as a measurement basis, the added mass percentage of the acetonitrile solvent containing nitrate is 0.5% to 2%.

7. The carbonate electrolyte according to claim 1, characterized in that The carbonate electrolyte further contains an additive; Preferably, the additive is at least one of lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorophosphate, vinylene carbonate, and 1,3-propane sultone; Preferably, based on the carbonate electrolyte as a measurement basis, the mass percentage of the additive added is 0.5% to 1.5%.

8. A method for preparing the carbonate electrolyte according to any one of claims 1 to 7, characterized in that: Under the condition of isolating water and oxygen, the process comprises the following steps: A carbonate electrolyte base liquid containing an electrolyte lithium salt is prepared; The nitrate and acetonitrile are mixed according to a ratio, and stirred evenly to obtain an acetonitrile solvent containing the nitrate; Add the acetonitrile solvent containing nitrate into the carbonate electrolyte base liquid and stir evenly.

9. Use of the carbonate electrolyte according to any one of claims 1 to 7 or the carbonate electrolyte prepared by the method for preparing the carbonate electrolyte according to claim 8 in preparing a lithium ion battery.

10. A lithium ion battery, characterized in that: A carbonate electrolyte comprising the carbonate electrolyte according to any one of claims 1 to 7 or a carbonate electrolyte prepared by the method for preparing a carbonate electrolyte according to claim 8; Preferably, the lithium ion battery is a lithium metal battery.

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