Carbonate-based electrolyte containing lithium nitrate, preparation method of carbonate-based electrolyte, lithium metal battery and lithium ion battery

Abstract

The invention discloses a carbonic ester-based electrolyte containing lithium nitrate, a preparation method of the carbonic ester-based electrolyte, a lithium metal battery and a lithium ion battery, and relates to the technical field of batteries. The electrolyte comprises a carbonic ester solvent, a lithium salt, a LiNO3 additive and a non-polar anion receptor additive, the content of the non-polar anion acceptor additive is 1 vol%-10 vol%. The preparation method comprises the following steps: adding the lithium salt into the carbonic ester solvent, uniformly mixing, and adding the LiNO3 additive and the non-polar anion acceptor additive, thereby obtaining the lithium ion battery positive electrode material. The invention also provides a lithium metal battery and a lithium ion battery comprising the electrolyte. The non-polar anion acceptor additive is added to promote LiNO3 to be dissolved in the carbonic ester electrolyte, so that the solvation structure of the electrolyte is regulated and controlled, and the electrolyte enters a solvation sheath layer and is preferentially decomposed at a negative electrode interface to form SEI rich in Li3N; and dendritic crystals generated by non-uniform deposition of the lithium metal negative electrode in the lithium metal battery in the circulation process are inhibited.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a carbonate-based electrolyte containing lithium nitrate, a preparation method thereof, a lithium metal battery, and a lithium ion battery. Background Art

[0002] With the rapid progress of society, people's demand for high-performance energy storage systems is increasing. After more than 30 years of development, lithium-ion batteries have made great progress. Lithium-ion batteries with graphite as the negative electrode can achieve long-term and stable cycles. However, the solid electrolyte interface (SEI) containing LiF derived from commercial carbonate-based electrolytes has the disadvantage of low ionic conductivity, which greatly limits the migration of lithium ions in the graphite negative electrode SEI, thereby affecting the overall low-temperature and fast-charging performance of the battery. On the other hand, lithium-ion batteries with graphite as the negative electrode are close to their theoretical energy density (300Whkg -1 The use of lithium metal, silicon-carbon alloys, silicon oxide, and elemental silicon as negative electrodes with high theoretical specific capacity has been widely studied in recent years. However, the fragile SEI derived from conventional commercial carbonate-based electrolytes is difficult to prevent the growth of dendrites in the lithium metal negative electrode and the expansion of the silicon-based negative electrode, resulting in a sharp decline in battery cycling stability.

[0003] As an effective additive, lithium nitrate (LiNO3) derived SEI containing Li3N not only has high ionic conductivity (5.02×10 -1 S cm -1 ), which can enable lithium ions to migrate quickly in SEI, thereby improving the low-temperature and fast-charging performance of the negative electrode; and has a high Young's modulus (48GPa), which can effectively inhibit the precipitation of lithium on the graphite surface, the growth of dendrites on the lithium metal surface, and the expansion of the silicon-based negative electrode. In addition, LiNO3 also has unique commercial advantages such as simple production process and low cost. However, LiNO3 has extremely low solubility in conventional carbonate-based electrolytes (800ppm, 0.01mol L -1 ), which has become the main limitation for the application of LiNO3.

[0004] In recent years, a series of strategies have been developed to improve the solubility of LiNO3 in conventional commercial carbonate-based electrolytes, such as introducing highly polar solvents, that is, solvents with high solubility for LiNO3, into carbonate-based electrolytes to promote dissolution. However, highly polar solvents often react chemically with lithium metal and co-intercalate with negative electrodes such as graphite, which limits the further application of this strategy. On the other hand, high-valent salts with strong Lewis acid sites are introduced into carbonate electrolytes. High-valent cations preferentially coordinate with nitrates to promote dissolution. However, high-valent cations are often easily preferentially reduced on the negative electrode surface, resulting in unstable SEI on the negative electrode surface, which seriously affects the battery cycle stability. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art and to provide a carbonate-based electrolyte containing lithium nitrate and a preparation method thereof, as well as a lithium metal battery and a lithium ion battery.

[0006] The technical solutions of the present invention are as follows:

[0007] A first aspect of the present invention provides a carbonate-based electrolyte containing lithium nitrate, the electrolyte comprising the following components: a carbonate solvent, a lithium salt, a LiNO3 additive, and a non-polar anion receptor additive;

[0008] The content of the non-polar anion receptor additive in the electrolyte is 1 vol%-10 vol%.

[0009] In a preferred embodiment of the present invention, the non-polar anion receptor additive includes at least one of benzene, fluorobenzene, o-difluorobenzene, m-difluorobenzene, p-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,2,5-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, nitrobenzene, trifluorotoluene, biphenyl and benzonitrile.

[0010] In a preferred embodiment of the present invention, the concentration of the LiNO3 additive in the electrolyte is 0.01 mol / L to 0.1 mol / L.

[0011] In a preferred embodiment of the present invention, the carbonate solvent comprises at least one of ethylene carbonate, fluoroethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

[0012] In a preferred embodiment of the present invention, the carbonate solvent is a mixed solution of ethylene carbonate, ethyl methyl carbonate and fluoroethylene carbonate, and the molar ratio of ethylene carbonate, ethyl methyl carbonate and fluoroethylene carbonate in the mixed solution is 2-4:6-8:0.5-1.5.

[0013] In a preferred embodiment of the present invention, the lithium salt is selected from at least one of LiPF6, LiBF4, LiTFSI, LiFSI and LiDFOB, and the concentration of the lithium salt in the electrolyte is 0.1 mol / L to 8 mol / L.

[0014] A second aspect of the present invention provides a method for preparing a carbonate-based electrolyte containing lithium nitrate, comprising the following steps:

[0015] adding lithium salt to a carbonate solvent and mixing uniformly to obtain a solution;

[0016] Adding LiNO3 additive and non-polar anion receptor additive to the solution to obtain an electrolyte.

[0017] A third aspect of the present invention provides a lithium metal battery comprising the electrolyte.

[0018] A fourth aspect of the present invention provides a lithium-ion battery comprising the electrolyte.

[0019] In a preferred embodiment of the present invention, the negative electrode of the lithium-ion battery is one of graphite, silicon-carbon alloy, silicon oxide and elemental silicon, and the positive electrode of the lithium-ion battery is one of lithium iron phosphate, lithium titanate, lithium cobalt oxide, polyacrylonitrile sulfide and nickel-cobalt-manganese ternary material.

[0020] The present invention has at least one of the following beneficial effects:

[0021] 1. The present invention introduces a class of dissolution-promoting non-polar anion receptor additives into traditional commercial carbonate-based electrolytes to promote the dissolution of LiNO3 in carbonate-based electrolytes. This in turn regulates the electrolyte solvation structure, allowing it to enter the solvation sheath and preferentially decompose at the negative electrode interface to form a Li3N-rich SEI. This inhibits dendrite formation due to uneven deposition of lithium metal anodes in lithium metal batteries during cycling, improves the SEI stability of graphite and silicon-based anodes, and inhibits side reactions between the anode and the electrolyte. Experiments have shown that the present invention can increase the solubility of LiNO3 in the electrolyte by 6 times by adding only a trace amount (approximately 1 vol% of the electrolyte). Furthermore, the non-polar anion receptor additives in the present invention are chemically stable with lithium metal, do not affect the intrinsic solvation structure of the electrolyte, and have no significant effect on the physical properties of the electrolyte.

[0022] 2. The carbonate electrolyte based on the dissolution of LiNO3 in the present invention shows good compatibility with various negative electrodes, greatly improving the low-temperature and fast-charging performance of graphite, the cycle stability of silicon-based and silicon-carbon negative electrodes, and the coulombic efficiency of lithium metal negative electrodes, which plays a constructive role in achieving high-power, high-energy density and long-term stable lithium-ion batteries and lithium metal batteries.

[0023] 3. The non-polar anion receptors introduced in the present invention are all conventional industrial raw materials with a wide range of sources and low prices. They will not increase the cost of the electrolyte, can be used on a large scale, and have extremely high commercial value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a digital photo of LiNO3 in RE electrolyte and HFB electrolyte in Example 1 of the present invention;

[0025] Figure 2 is the lithium nitrate content in different electrolytes in Example 1 of the present invention;

[0026] Figure 3 This is a digital photograph of lithium metal immersed in HFB solution in Example 1 of the present invention;

[0027] Figure 4 1 is a time-voltage curve of deposition and stripping of the lithium metal negative electrode in different electrolytes in Example 1 of the present invention;

[0028] Figure 5 1 is the cycle-specific capacity curve of the graphite negative electrode in Example 1 of the present invention in different electrolytes;

[0029] Figure 6 1 is the cycle-specific capacity curve of the silicon-carbon negative electrode in different electrolytes in Example 1 of the present invention;

[0030] Figure 7 1 is the cycle-specific capacity curve of the NCM811 positive electrode in different electrolytes in Example 1 of the present invention;

[0031] Figure 8 is the XPS N 1s spectrum of lithium metal after cycling in different electrolytes in Example 1 of the present invention;

[0032] Figure 9 This is a digital photo of LiNO3 after the RE electrolyte is added to the TFB electrolyte in Example 2 of the present invention;

[0033] Figure 10 The coulombic efficiency test of the lithium-copper half-cell assembled with the electrolyte in Example 2 of the present invention;

[0034] Figure 11 This is a digital photo of LiNO3 after RE electrolyte was added to BTF electrolyte in Example 3 of the present invention;

[0035] Figure 12 The coulombic efficiency test of the lithium-copper half-cell assembled with the electrolyte in Example 3 of the present invention;

[0036] Figure 13This is the coulombic efficiency test of the lithium-copper half-cell assembled with the electrolyte in Example 4 of the present invention;

[0037] Figure 14 This is the coulombic efficiency test of the lithium-copper half-cell assembled with the electrolyte in Example 5 of the present invention. DETAILED DESCRIPTION

[0038] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0039] One embodiment of the present invention provides a carbonate-based electrolyte containing lithium nitrate,

[0040] The electrolyte comprises the following components: a carbonate solvent, a lithium salt, a LiNO3 additive, and a non-polar anion receptor additive;

[0041] The content of the non-polar anion receptor additive in the electrolyte is 1 vol%-10 vol%.

[0042] The present invention adds a dissolution-promoting non-polar anion receptor additive to a conventional commercial carbonate-based electrolyte. The non-polar anion receptor additive is primarily used to promote the dissolution of LiNO3 in the carbonate electrolyte, thereby regulating the electrolyte solvation structure, causing it to enter the solvation sheath and preferentially decompose at the negative electrode interface to form a Li3N-rich SEI. This inhibits dendrite formation due to uneven deposition of lithium metal anodes in lithium metal batteries during cycling, improves the SEI stability of graphite and silicon-based anodes, and inhibits side reactions between the anode and the electrolyte. Furthermore, the non-polar anion receptor additive of the present invention does not react with lithium metal, does not affect the intrinsic solvation structure of the electrolyte, and has no significant effect on the physical properties of the electrolyte.

[0043] In some embodiments, the content of the non-polar anion receptor additive in the electrolyte is 1 vol%-8 vol%, preferably 1 vol%-5 vol%, more preferably 1 vol%-3 vol%, and specifically 1 vol%, 1.5 vol%, 2 vol%, 2.5 vol%, and 3 vol%. The present invention increases the solubility of LiNO3 in the electrolyte by 6 times by adding only a trace amount of the non-polar anion receptor additive.

[0044] In some embodiments, the non-polar anion receptor additive includes at least one of benzene, fluorobenzene, o-difluorobenzene, m-difluorobenzene, p-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,2,5-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, nitrobenzene, trifluorotoluene, biphenyl, and benzonitrile. Preferably, the anion receptor is hexafluorobenzene (HFB).

[0045] In some embodiments, the concentration of the LiNO3 additive in the electrolyte is 0.01 mol / L to 0.1 mol / L; preferably, the concentration of the LiNO3 additive is 0.01 mol / L to 0.08 mol / L; more preferably, the concentration of the LiNO3 additive is 0.06 mol / L.

[0046] In some embodiments, the carbonate solvent comprises at least one of ethylene carbonate, fluoroethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. Preferably, the carbonate solvent is a mixed solution of ethylene carbonate, ethyl methyl carbonate and fluoroethylene carbonate, and the molar ratio of ethylene carbonate, ethyl methyl carbonate and fluoroethylene carbonate is 2-4:6-8:0.5-1.5; more preferably, the molar ratio of ethylene carbonate, ethyl methyl carbonate and fluoroethylene carbonate is 2.5-3.5:6.5-7.5:1; specifically, the molar ratio of ethylene carbonate, ethyl methyl carbonate and fluoroethylene carbonate is 3:7:1, 2:7:1, 4:7:1, 3:6:1, 3:8:1, etc.

[0047] In some embodiments, the lithium salt is selected from any one or more of LiPF6, LiBF4, LiTFSI, LiFSI or LiDFOB. Preferably, the lithium salt is LiPF6.

[0048] In some embodiments, the concentration of the lithium salt in the electrolyte is 0.1 mol / L to 8 mol / L. Preferably, the concentration of the lithium salt in the electrolyte is 0.1 mol / L to 5 mol / L. More preferably, the concentration of the lithium salt in the electrolyte is 1 mol / L.

[0049] Another embodiment of the present invention provides a method for preparing a carbonate-based electrolyte containing lithium nitrate, comprising the following steps:

[0050] adding lithium salt to a carbonate solvent and mixing uniformly to obtain a solution;

[0051] Adding LiNO3 additive and non-polar anion receptor additive to the solution to obtain an electrolyte.

[0052] The preparation method of the electrolyte of the present invention is simple. After adding a non-polar anion receptor additive to the electrolyte, the dissolution of LiNO3 is greatly improved, thereby regulating the electrolyte solvation structure so that it enters the solvation sheath and preferentially decomposes at the negative electrode interface to form a Li3N-rich SEI, thereby suppressing the dendrites generated by the uneven deposition of the lithium metal negative electrode in the lithium metal battery during the cycle process, improving the SEI stability of the graphite negative electrode and the silicon-based negative electrode, and being able to suppress side reactions between the negative electrode and the electrolyte.

[0053] Yet another embodiment of the present invention provides a lithium metal battery comprising the above electrolyte.

[0054] The use of the above-mentioned electrolyte can inhibit the dendrites generated by uneven deposition of the lithium metal negative electrode in the lithium metal battery during the cycle process, improve the cycle stability of the lithium metal battery, and help achieve high power, high energy density and long-term stability.

[0055] In some embodiments, the negative electrode of the lithium metal battery is metallic lithium.

[0056] In some embodiments, the positive electrode of the lithium metal battery is lithium iron phosphate, lithium titanate, lithium cobaltate, polyacrylonitrile sulfide, and nickel cobalt manganese ternary material (LiNi 0.33 Co 0.33 Mn 0.33 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.9 Co 0.05 Mn 0.05 O2).

[0057] In some embodiments, the separator of the lithium metal battery is a glass fiber separator, a polytetrafluoroethylene separator, a polypropylene separator, a polyethylene separator, or a cellulose separator.

[0058] Yet another embodiment of the present invention provides a lithium-ion battery comprising the above-mentioned electrolyte.

[0059] The above-mentioned electrolyte can show good compatibility with the negative electrode of lithium-ion batteries, improve the SEI stability of graphite negative electrodes and silicon-based negative electrodes, and can inhibit the side reactions between the negative electrode and the electrolyte, greatly improving the low-temperature and fast-charging performance of graphite, the cycle stability of silicon-based and silicon-carbon negative electrodes, and the coulombic efficiency of lithium metal negative electrodes, thereby improving the cycle stability of lithium-ion batteries and helping to achieve high power, high energy density and long-term stability.

[0060] In some embodiments, the negative electrode of the lithium-ion battery is one of graphite, silicon-carbon alloy, silicon monoxide, and elemental silicon.

[0061] In some embodiments, the positive electrode of the lithium-ion battery is lithium iron phosphate, lithium titanate, lithium cobalt oxide, polyacrylonitrile sulfide, and nickel-cobalt-manganese ternary material (LiNi 0.33 Co 0.33 Mn 0.33 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.9 Co 0.05 Mn 0.05 O2).

[0062] The present invention is further described in detail below with reference to specific examples, but the present invention is not limited to the following specific examples.

[0063] Example 1

[0064] A method for preparing a carbonate-based electrolyte containing lithium nitrate comprises the following steps:

[0065] Lithium hexafluorophosphate, ethylene carbonate, ethyl methyl carbonate and fluoroethylene carbonate were respectively prepared into a uniform electrolyte solution in a molar ratio of 1:3:7:1 to obtain RE electrolyte; then a corresponding amount of lithium nitrate was added at a molar ratio of lithium nitrate to lithium hexafluorophosphate of 0.06:1, and stirred at 45°C for 6 hours, but the lithium nitrate could not be completely dissolved; then the corresponding hexafluorobenzene was added at a molar ratio of hexafluorobenzene to fluoroethylene carbonate of 0.1:1, and stirred at 45°C for 6 hours, until the lithium nitrate was completely dissolved to obtain HFB-LiNO3 electrolyte.

[0066] Figure 1 This is a digital photo of LiNO3 in RE electrolyte and HFB electrolyte in Example 1 of the present invention. Figure 1It can be seen that lithium nitrate cannot be completely dissolved in RE electrolyte, but after adding HFB to RE electrolyte, lithium nitrate is completely dissolved, indicating that HFB helps to improve the solubility of lithium nitrate.

[0067] The above RE electrolyte and HFB-LiNO3 electrolyte were analyzed by a fully automatic discontinuous chemical analyzer to analyze the nitrate content in the electrolyte to obtain the solubility of LiNO3 in the corresponding electrolyte. Figure 2 As shown in Figure 3, it was found that the amount of lithium nitrate dissolved in the carbonate electrolyte increased by 6 times after adding a trace amount of hexafluorobenzene.

[0068] In order to verify whether hexafluorobenzene can dissolve lithium metal, the following experiment was also conducted in this embodiment: lithium metal was added to the hexafluorobenzene solution. After 24 hours, no significant changes occurred between the lithium metal and the hexafluorobenzene solution. Figure 3 As shown, this indicates that the hexafluorobenzene in this embodiment does not react with lithium metal.

[0069] In order to verify the electrochemical performance of the above RE electrolyte and HFB-LiNO3 electrolyte, RE electrolyte and HFB-LiNO3 electrolyte were assembled into batteries respectively as follows:

[0070] (1) The above RE electrolyte and HFB-LiNO3 electrolyte were used to assemble lithium copper half-cells with lithium sheet, copper sheet and polypropylene separator respectively. -2 The coulombic efficiency test was carried out at a current density of Figure 4 As shown in Figure 3, the coulombic efficiency of the lithium-copper half-cell assembled using HFB-LiNO3 electrolyte can reach 99.14%, while the coulombic efficiency of the lithium-copper half-cell assembled in RE electrolyte is only 97.63%.

[0071] (2) The above RE electrolyte and HFB-LiNO3 electrolyte were used to assemble graphite half-cells with lithium sheets, graphite negative electrode sheets, and polypropylene separators, respectively. -1 ) current density, the charge and discharge cycle test was carried out, and the results were as follows Figure 5 As shown in Figure 3, the performance of the graphite half-cell assembled using HFB-LiNO3 electrolyte is significantly better than that using RE electrolyte.

[0072] (3) The above RE electrolyte and HFB-LiNO3 electrolyte were used to assemble silicon-carbon half-cells with lithium sheets, silicon-carbon negative electrode sheets, and polypropylene separators, respectively. -1 ) current density, the charge and discharge cycle test was carried out, and the results were as follows Figure 6 As shown in Figure 3, the performance of the silicon-carbon negative electrode half-cell assembled using HFB-LiNO3 electrolyte is significantly better than that using RE electrolyte.

[0073] (4) The above RE electrolyte and HFB-LiNO3 electrolyte were used to assemble NCM811 half-cells with lithium sheets, NCM811 positive electrode sheets, and polypropylene separators, respectively. -1 ) current density, the charge and discharge cycle test was carried out, and the results were as follows Figure 7 As shown in Figure 3, the performance of the silicon-carbon negative electrode half-cell assembled using HFB-LiNO3 electrolyte is significantly better than that using RE electrolyte.

[0074] Figure 8 The following are XPS N 1s spectra of the lithium metal anode in Example 1 of the present invention after cycling in RE electrolyte and HFB-LiNO3 electrolyte, respectively. It can be clearly observed that the lithium metal surface circulating in RE electrolyte has no N-containing components, while the lithium metal surface after cycling in HFB-LiNO3 electrolyte is rich in Li3N. This indicates that the non-polar anion receptor additive in this example enters the solvation sheath and preferentially decomposes at the anode interface to form a Li3N-rich SEI.

[0075] Example 2

[0076] A method for preparing a carbonate-based electrolyte containing lithium nitrate comprises the following steps:

[0077] Lithium hexafluorophosphate, ethylene carbonate, ethyl methyl carbonate and fluoroethylene carbonate were respectively prepared into a uniform electrolyte in a molar ratio of 1:3:7:1 to obtain RE electrolyte; then a corresponding amount of lithium nitrate was added at a molar ratio of lithium nitrate to lithium hexafluorophosphate of 0.08:1, and the corresponding TFB was added at a molar ratio of 1,2,4,5-tetrafluorobenzene (TFB) to fluoroethylene carbonate of 0.1:1 to obtain TFB-LiNO3 electrolyte.

[0078] Figure 9 This is a digital photo of LiNO3 after RE electrolyte was added to TFB electrolyte in Example 2 of the present invention. Figure 8 It can be seen that after adding TFB to the RE electrolyte, lithium nitrate is completely dissolved, indicating that 1,2,4,5-tetrafluorobenzene helps to improve the solubility of lithium nitrate.

[0079] In order to verify the electrochemical performance of the above RE electrolyte and TFB-LiNO3 electrolyte, the RE electrolyte and TFB-LiNO3 electrolyte were assembled into batteries respectively. The method is as follows: the above RE electrolyte and TFB-LiNO3 electrolyte were used to assemble lithium-copper half-cells together with lithium sheet, copper sheet and polypropylene separator respectively. -2 The coulombic efficiency test was carried out at a current density of Figure 10As shown in Figure 3, the coulombic efficiency of the lithium-copper half-cell assembled using TFB-LiNO3 electrolyte can reach 99.02%, while the coulombic efficiency of the lithium-copper half-cell assembled in RE electrolyte is only 97.63%.

[0080] Example 3

[0081] A method for preparing a carbonate-based electrolyte containing lithium nitrate comprises the following steps:

[0082] Lithium hexafluorophosphate, ethylene carbonate, ethyl methyl carbonate and fluoroethylene carbonate were respectively prepared into a uniform electrolyte in a molar ratio of 1:3:7:1 to obtain RE electrolyte; then a corresponding amount of lithium nitrate was added at a molar ratio of lithium nitrate to lithium hexafluorophosphate of 0.06:1, and the corresponding trifluorotoluene (BTF) was added at a molar ratio of BTF to fluoroethylene carbonate of 0.2:1 to obtain BTF-LiNO3 electrolyte.

[0083] Figure 11 This is a digital photo of LiNO3 after RE electrolyte was added to BTF electrolyte in Example 3 of the present invention. Figure 11 It can be seen that after adding BTF to the RE electrolyte, lithium nitrate is completely dissolved, indicating that trifluorotoluene helps to improve the solubility of lithium nitrate.

[0084] In order to verify the electrochemical performance of the above RE electrolyte and BTF-LiNO3 electrolyte, the RE electrolyte and BTF-LiNO3 electrolyte were assembled into batteries respectively. The method is as follows: the above RE electrolyte and TFB-LiNO3 electrolyte were used to assemble lithium-copper half-cells with lithium sheet, copper sheet and polypropylene separator respectively. -2 The coulombic efficiency test was carried out at a current density of Figure 12 As shown in Figure 3, the coulombic efficiency of the lithium-copper half-cell assembled using BTF-LiNO3 electrolyte can reach 98.96%, while the coulombic efficiency of the lithium-copper half-cell assembled in RE electrolyte is only 97.63%.

[0085] Example 4

[0086] Lithium hexafluorophosphate, ethylene carbonate, ethyl methyl carbonate and fluoroethylene carbonate are respectively prepared into a uniform electrolyte in a molar ratio of 1:3:7:1 to obtain RE electrolyte; then a corresponding amount of lithium nitrate is added in a molar ratio of lithium nitrate to lithium hexafluorophosphate of 0.1:1, and corresponding hexafluorobenzene is added in a molar ratio of hexafluorobenzene to fluoroethylene carbonate of 0.8:1 to obtain HFB-LiNO3 electrolyte.

[0087] In order to verify the electrochemical performance of the above RE electrolyte and HFB-LiNO3 electrolyte, the RE electrolyte and HFB-LiNO3 electrolyte were assembled into batteries respectively. The method is as follows: the above RE electrolyte and HFB-LiNO3 electrolyte were used to assemble lithium-copper half-cells together with lithium sheet, copper sheet and polypropylene separator respectively. -2 The coulombic efficiency test was carried out at a current density of Figure 13 As shown in Figure 3, the coulombic efficiency of the lithium-copper half-cell assembled using HFB-LiNO3 electrolyte can reach 99.08%, while the coulombic efficiency of the lithium-copper half-cell assembled in RE electrolyte is only 97.63%.

[0088] Example 5

[0089] Lithium hexafluorophosphate, ethyl methyl carbonate and fluoroethylene carbonate were respectively prepared into a uniform electrolyte in a molar ratio of 1:7:1 to obtain RE electrolyte; then, corresponding amounts of lithium nitrate and hexafluorobenzene were added in a molar ratio of lithium nitrate to lithium hexafluorophosphate of 0.06:1, and corresponding hexafluorobenzene was added in a molar ratio of hexafluorobenzene to fluoroethylene carbonate of 0.1:1 to obtain HFB-LiNO3 electrolyte.

[0090] In order to verify the electrochemical performance of the above RE electrolyte and HFB-LiNO3 electrolyte, the RE electrolyte and HFB-LiNO3 electrolyte were assembled into batteries respectively. The method is as follows: the above RE electrolyte and HFB-LiNO3 electrolyte were used to assemble lithium-copper half-cells together with lithium sheet, copper sheet and polypropylene separator respectively. -2 The coulombic efficiency test was carried out at a current density of Figure 14 As shown in Figure 3, the coulombic efficiency of the lithium-copper half-cell assembled using HFB-LiNO3 electrolyte can reach 99.11%, while the coulombic efficiency of the lithium-copper half-cell assembled in RE electrolyte is only 97.63%.

[0091] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A carbonate-based electrolyte containing lithium nitrate, characterized in that: The electrolyte The invention comprises the following components: a carbonate solvent, a lithium salt, a LiNO3 additive and a non-polar anion receptor additive; The content of the non-polar anion receptor additive in the electrolyte is 1 vol%-10 vol%.

2. The electrolyte according to claim 1, characterized in that The non-polar anion receptor additive includes at least one of benzene, fluorobenzene, o-difluorobenzene, m-difluorobenzene, p-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,2,5-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, nitrobenzene, trifluorotoluene, biphenyl and benzonitrile.

3. The electrolyte according to claim 1, characterized in that The concentration of the LiNO3 additive in the electrolyte is 0.01 mol / L to 0.1 mol / L.

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

5. The electrolyte according to claim 4, characterized in that The carbonate solvent is a mixed solution of ethylene carbonate, ethyl methyl carbonate and fluoroethylene carbonate, and the molar ratio of ethylene carbonate, ethyl methyl carbonate and fluoroethylene carbonate in the mixed solution is 2-4:6-8:0.5-1.

5.

6. The electrolyte according to claim 1, characterized in that The lithium salt is selected from at least one of LiPF6, LiBF4, LiTFSI, LiFSI and LiDFOB, and the concentration of the lithium salt in the electrolyte is 0.1 mol / L to 8 mol / L.

7. The method for preparing the electrolyte according to any one of claims 1 to 6, characterized in that: The following steps are involved: adding lithium salt to a carbonate solvent and mixing uniformly to obtain a solution; Adding LiNO3 additive and non-polar anion receptor additive to the solution to obtain an electrolyte.

8. A lithium metal battery, characterized in that: The electrolyte comprises the electrolyte according to any one of claims 1 to 6.

9. A lithium-ion battery, characterized in that: The electrolyte comprises the electrolyte according to any one of claims 1 to 6.

10. The lithium-ion battery according to claim 9, characterized in that The negative electrode of the lithium ion battery is one of graphite, silicon-carbon alloy, silicon oxide and elemental silicon, and the positive electrode of the lithium ion battery is one of lithium iron phosphate, lithium titanate, lithium cobaltate, polyacrylonitrile sulfide and nickel-cobalt-manganese ternary material.

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