Lithium imine compounds, their preparation methods, and their applications in batteries

Abstract

This invention provides an imine lithium compound, its preparation method, and its application in batteries. The structural formula of the imine lithium compound is shown in Formula 1. The preparation method of the imine lithium compound includes the following steps: adding thioyl fluoride, ammonia, and an acid-binding agent to carry out an ammoniation reaction to obtain a first intermediate; adding phosphorus trichloride to the first intermediate to carry out a phosphating reaction to obtain a second intermediate; adding ethylene glycol to the second intermediate to carry out a substitution reaction to obtain a third intermediate; and adding a lithium compound to the third intermediate to carry out a lithiation reaction. The imine lithium compound of this invention, as a novel substance, contains fluorosulfonyl imide groups and cyclic phosphate groups, combining the advantages of cyclic phosphate esters, sulfonyl imide groups, and fluorine groups, and has good application prospects. It can be used in secondary batteries and can also be used as an intermediate in the processing of materials and pharmaceuticals.

Description

Technical Field

[0001] This invention relates to the field of materials synthesis technology, and more particularly to a compound for use in batteries, and even more particularly to lithium imine compounds and their preparation methods, the application of lithium imine compounds and their preparation methods in batteries, and their application in batteries. Background Technology

[0002] With the rapid development of pure electric vehicles and hybrid electric vehicles, people's requirements for the energy density, long cycle life, rate performance, and safety performance of lithium-ion batteries are constantly increasing. The cathode material of lithium-ion batteries has shifted from lithium iron phosphate and lithium manganese oxide systems to high-voltage ternary material systems.

[0003] Electrolyte is the lifeblood of lithium-ion batteries, playing a crucial role in transferring lithium ions between the positive and negative electrode materials and the separator. Furthermore, the electrolyte significantly influences the formation of the SEI and CEI at the interface between the positive and negative electrode materials, as well as the battery impedance. In traditional electrolyte systems, ternary materials undergo significant interfacial catalytic reactions under high voltage and high temperature conditions, leading to electrolyte decomposition and gas production, which compromises the lifespan and safety of lithium-ion batteries. Current research reports that adding additives that promote film formation at the ternary material interface (such as organic additives like VC, PS, DTD, and TMSP, and inorganic additives like LiPO2F2, LiFSI, LiTFSI, LiPF2(C2O4)2, and LiBOB) can effectively protect the positive electrode, improve the electrolyte's voltage withstand window, and extend the battery's cycle life.

[0004] However, researchers have also found that these additives can form CEI not only at the cathode material interface but also SEI at the graphite anode interface, leading to increased internal resistance and affecting the battery's rate capability and low-temperature performance. Therefore, developing an additive that can form a good protective film at the cathode and anode material interface while having low internal resistance remains a pressing challenge for the industry. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide an imine lithium compound, its preparation method, and its application in batteries. The preparation method is simple to operate, and the yield and purity of the target product are high. As a novel substance comprising fluorosulfonylimide groups and cyclic phosphate ester groups, the imine lithium compound has promising applications in materials processing, pharmaceuticals, and secondary batteries.

[0006] To achieve the above objectives, the first aspect of the present invention provides an imine lithium compound with the structural formula shown in Formula 1.

[0007]

[0008] The lithium imine compounds of this invention, as a novel substance, contain fluorinated sulfonyl imide groups and cyclic phosphate groups, combining the advantages of cyclic phosphate groups, sulfonyl imide groups, and fluorine groups. They have good application prospects and can be used in secondary batteries or as intermediates in the processing of materials and pharmaceuticals.

[0009] A second aspect of this invention provides a method for preparing lithium imine compounds, comprising the steps of:

[0010] (1) Ammoniation reaction

[0011] The first intermediate is obtained by adding sulfuryl fluoride, ammonia and an acid-binding agent to carry out an ammoniation reaction.

[0012] (2) Phosphating reaction

[0013] Phosphorus trichloride was added to the first intermediate to carry out a phosphating reaction to obtain the second intermediate;

[0014] (3) Substitution reaction

[0015] Ethylene glycol was added to the second intermediate to carry out a substitution reaction to obtain the third intermediate;

[0016] (4) Lithification reaction

[0017] A lithiation reaction is carried out by adding a lithium compound to the third intermediate.

[0018] The preparation method of the present invention is simple. An organolithium compound containing cyclic phosphate, sulfonylimide and fluorine groups can be obtained by sequentially passing an ammoniation reaction, a phosphating reaction, a substitution reaction and a lithiation reaction. The organolithium compound is easy to produce industrially and can be widely used.

[0019] As a technical solution of the present invention, an organic solvent is added to the raw materials of the amination reaction, the phosphating reaction and the lithiation reaction, and each of the organic solvents independently includes at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, 1,4-dioxane, toluene, acetonitrile, diethyl ether, tetrahydrofuran, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate and propylene carbonate.

[0020] As a technical solution of the present invention, the acid-binding agent includes at least one of triethylamine, pyridine and 1,8-diazabicycloundec-7-ene.

[0021] As one technical solution of the present invention, the molar ratio of the sulfuryl fluoride and the ammonia is 1:1 to 2, and the molar ratio of the sulfuryl fluoride and the acid-binding agent is 1 to 4:1.

[0022] As a technical solution of the present invention, the molar ratio of the first intermediate to the phosphorus trichloride is 0.01-1.00:0.01-1.00, the molar ratio of the second intermediate to the ethylene glycol is 1:1-10, and the molar ratio of the third intermediate to the lithium compound is 1:0.1-2.0.

[0023] As one technical solution of the present invention, the lithium compound includes lithium methoxide, lithium ethanol, lithium isopropoxide, or lithium tert-butoxide.

[0024] As one technical solution of the present invention, the temperature of the ammoniation reaction is -40 to 50°C, the time of the ammoniation reaction is 1 to 10 hours, the temperature of the phosphating reaction is 20 to 100°C, the time of the phosphating reaction is 5 to 25 hours, the temperature of the substitution reaction is 20 to 150°C, the time of the substitution reaction is 10 to 36 hours, the temperature of the lithiation reaction is -25 to 10°C, and the time of the lithiation reaction is 0.1 to 2.0 hours.

[0025] As one technical solution of the present invention, the ammoniation reaction, the phosphating reaction, the substitution reaction and the lithiation reaction are carried out in different reactors.

[0026] A third aspect of this invention provides the application of lithium imine compounds in secondary batteries. These lithium imine compounds not only form a good protective film at the interface between the positive and negative electrode materials, but also have low internal resistance, thus improving the electrochemical performance of the battery and showing promising application prospects. Detailed Implementation

[0027] The lithium imine compounds of this invention can be used as intermediates in the synthesis of materials or pharmaceuticals, and can also be used in secondary batteries. In particular, when used in secondary batteries such as lithium-ion batteries or sodium-ion batteries, the lithium imine compounds, as a novel film-forming compound, can not only form a good protective film at the interface of positive and negative electrode materials, but also have low internal resistance, thereby improving the electrochemical performance of secondary batteries, such as cycle performance at high rates.

[0028] The structural formula of the lithium imine compounds of the present invention is shown in Formula 1.

[0029]

[0030]

[0031] The method for preparing the lithium imine compounds of the present invention may include the following steps.

[0032] (1) Ammoniation reaction

[0033] The first intermediate is obtained by adding thioyl fluoride, ammonia and an acid-binding agent to carry out an ammoniation reaction.

[0034] (2) Phosphating reaction

[0035] Phosphorus trichloride was added to the first intermediate to carry out a phosphating reaction to obtain the second intermediate.

[0036] (3) Substitution reaction

[0037] Ethylene glycol was added to the second intermediate to carry out a substitution reaction to obtain the third intermediate.

[0038] (4) Lithification reaction

[0039] A lithiation reaction is carried out by adding a lithium compound to the third intermediate.

[0040] The acid-binding agent includes at least one of triethylamine, pyridine, and 1,8-diazabicycloundec-7-ene. This acid-binding agent absorbs the acid generated during the reaction, preventing it from affecting the reaction process. The lithium compound includes lithium methoxide, lithium ethoxide, lithium isopropoxide, or lithium tert-butoxide. The raw materials involved in the preparation method of the imine lithium compounds of this invention—thioyl fluoride, ammonia, acid-binding agent, phosphorus trichloride, ethylene glycol, and lithium compound—are all conventional substances, commercially available, and the reaction conditions are simple, thus facilitating industrial application.

[0041] The reaction formula for step (1) amination is shown below.

[0042]

[0043] An organic solvent may be added to the raw materials for the ammoniation reaction, and the organic solvent includes at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, 1,4-dioxane, toluene, acetonitrile, diethyl ether, tetrahydrofuran, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, and propylene carbonate. The molar ratio of thioyl fluoride to ammonia is 1:1 to 2. As an example, the molar ratio of thioyl fluoride to ammonia may be, but is not limited to, 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, and 1:2.0. Preferably, the molar ratio of thioyl fluoride to ammonia is 1:1.0. The molar ratio of sulfuryl fluoride to the acid-binding agent is 1 to 4:1. For example, the molar ratio of sulfuryl fluoride to the acid-binding agent can be, but is not limited to, 1:1, 2:1, 3:1, or 4:1. Preferably, the molar ratio of sulfuryl fluoride to the acid-binding agent is 1:1. The temperature of the ammoniation reaction is -40 to 50°C. For example, the temperature can be, but is not limited to, -40°C, -30°C, -20°C, -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, or 50°C. The time of the ammoniation reaction is 1 to 10 hours. For example, the time can be, but is not limited to, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours.

[0044] The reaction formula for step (2) phosphating is shown below.

[0045]

[0046] The phosphating reaction can be carried out in other reactors, and organic solvents can be added to the feedstock, including at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, 1,4-dioxane, toluene, acetonitrile, diethyl ether, tetrahydrofuran, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, and propylene carbonate. The molar ratio of the first intermediate to phosphorus trichloride is 0.01–1.00:0.01–1.00. As an example, the molar ratio may be, but is not limited to, 0.01:0.02, 0.01:0.10, 0.01:0.50, 0.01:1.00, 0.10:0.01, 0.10:0.05, 0.10:0.50, 0.10:1.00, 0.50:0.01, 0.50:0.10, 0.50:0.60, 0.50:1.00, 1.00:0.01, 1.00:0.15, 1.00:0.55, 1.00:1.00. Preferably, the molar ratio of the first intermediate to phosphorus trichloride is 1.00:1.00. The phosphating reaction temperature is 20–100°C. For example, the temperature can be, but is not limited to, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C. The phosphating reaction time is 5–25 hours. For example, the time can be, but is not limited to, 5 hours, 8 hours, 10 hours, 13 hours, 15 hours, 18 hours, 20 hours, 23 hours, or 25 hours.

[0047] The reaction equation for the substitution reaction in step (3) is shown below.

[0048]

[0049] The substitution reaction can be carried out in other reactors, and an organic solvent can be added to the feedstock. The organic solvent includes at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, 1,4-dioxane, toluene, acetonitrile, diethyl ether, tetrahydrofuran, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, and propylene carbonate. The molar ratio of the second intermediate to ethylene glycol is 1:1 to 10. Examples of molar ratios include, but are not limited to, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, and 1:10. Preferably, the molar ratio of the second intermediate to ethylene glycol is 1:5. The temperature for the substitution reaction is 20–150°C. For example, the temperature can be, but is not limited to, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, and 150°C. The reaction time is 10–36 hours. For example, the time can be, but is not limited to, 10 hours, 13 hours, 15 hours, 18 hours, 20 hours, 23 hours, 25 hours, 28 hours, 30 hours, 33 hours, and 36 hours.

[0050] The reaction formula for the lithiation reaction in step (4) is shown below. M is an alkane, specifically methyl, ethyl, isopropyl, or tert-butyl.

[0051]

[0052] The lithiation reaction can be carried out in other reactors, and an organic solvent can be added to the feedstock. The organic solvent includes at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, 1,4-dioxane, toluene, acetonitrile, diethyl ether, tetrahydrofuran, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, and propylene carbonate. The lithium compound includes lithium methoxide, lithium ethoxide, lithium isopropoxide, or lithium tert-butoxide. The molar ratio of the third intermediate to the lithium compound is 1:0.1 to 2.0. Examples of molar ratios include, but are not limited to, 1:0.1, 1:0.5, 1:0.7, 1:1.0, 1:1.2, 1:1.4, 1:1.6, 1:1.8, and 1:2.0. Preferably, the molar ratio of the third intermediate to the lithium compound is 1:1.0. The lithiation reaction temperature is -20 to 10°C. For example, the temperature may be, but is not limited to, -20°C, -15°C, -10°C, -5°C, -0°C, 5°C, and 10°C. The lithiation reaction time is 0.1 to 2.0 h. For example, the time may be, but is not limited to, 0.1 h, 0.3 h, 0.5 h, 0.8 h, 1.0 h, 1.3 h, 1.5 h, 1.8 h, and 2.0 h.

[0053] To better illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below with reference to specific embodiments. It should be noted that the methods described below are further explanations of this invention and should not be construed as limiting it.

[0054] Example 1

[0055] This embodiment describes the preparation of lithium imine compounds, and the preparation method includes the following steps.

[0056] (1) Ammoniation reaction

[0057] In a 1000ml high-pressure reactor, 500g of acetonitrile and 103g of triethylamine were added. The mixture was cooled to 0-5℃, and 102g of sulfuryl fluoride was introduced. 17g of ammonia gas was slowly added, and the reaction was maintained at -25-0℃ for 3.5h. The organic layer was concentrated and washed with dichloromethane and water. The concentrated organic layer yielded 75g of the first intermediate, with a yield of 75%. The structure of the first intermediate was characterized, and the mass spectrometry data were as follows: 19 F-NMR (CD3CN): 53.0 1F, indicating that the first intermediate was synthesized.

[0058] (2) Phosphating reaction

[0059] In a 1000 ml three-necked flask, 500 ml of tetrahydrofuran, 99 g of the first intermediate, and 137 g of phosphorus trichloride were added. The mixture was heated to 40–50 °C and reacted for 10 h. The organic layer was concentrated to obtain 105 g of the second intermediate, with a yield of 52%. The structure of the second intermediate was characterized, and the mass spectrometry data were as follows: 19 F-NMR (CD3CN): 53.51F, indicating that the second intermediate was synthesized.

[0060] (3) Substitution reaction

[0061] In a 1000 ml three-necked flask, 500 g of ethylene glycol and 100 g of the second intermediate were added. The mixture was heated to 90–120 °C and reacted for 24 h. The organic layer was concentrated to obtain 70 g of the third intermediate, with a yield of 74%. The structure of the third intermediate was characterized, and the mass spectrometry data are as follows: 19 F-NMR (CD3CN): 53.5 1F; H-NMR (CD3CN): 2.1 1H, 3.7 4H, indicating that a third intermediate was synthesized.

[0062] (4) Lithification reaction

[0063] In a 1000 ml three-necked flask, 500 g of acetonitrile and 95 g of the third intermediate were added. The mixture was cooled to 0–5 °C, and 19 g of lithium methoxide was slowly added. The reaction was maintained at 0–5 °C for 0.5 h. The organic layer was lowered and concentrated, and dichloromethane was added for crystallization to obtain 80 g of the product, with a yield of 82%. The product was structurally characterized, and the mass spectrometry data were as follows: 19 F-NMR (CD3CN): 53.5 1F; H-NMR (CD3CN): 3.74H, indicating that an imine lithium compound of formula one was synthesized.

[0064] Example 2

[0065] This example demonstrates the application of lithium amine compounds in secondary batteries.

[0066] 1.0g of the imine lithium compound prepared in Example 1 and 87.0g of non-aqueous organic solvent (ethylene carbonate EC, diethyl carbonate DEC, and methyl ethyl carbonate EMC in a mass ratio of 1:2:1) were mixed evenly, and then 12.0g of lithium hexafluorophosphate LiPF6 was added and mixed evenly to prepare non-aqueous electrolyte 1#.

[0067] 3.0g of the imine lithium compound prepared in Example 1 and 86.0g of non-aqueous organic solvent (ethylene carbonate EC, diethyl carbonate DEC, and methyl ethyl carbonate EMC in a mass ratio of 1:2:1) were mixed evenly, and then 11.0g of lithium hexafluorophosphate LiPF6 was added and mixed evenly to prepare non-aqueous electrolyte 2#.

[0068] 12.0g of lithium hexafluorophosphate (LiPF6) was added to 88.0g of non-aqueous organic solvent (ethylene carbonate EC, diethyl carbonate DEC, and methyl ethyl carbonate EMC in a mass ratio of 1:2:1) and mixed thoroughly to prepare non-aqueous electrolyte 1#.

[0069] Lithium cobalt oxide was used as the positive electrode material and lithium metal as the counter electrode. Non-aqueous electrolytes 1# to 3# were injected to assemble coin cells 1# to 3#. Under normal temperature (25℃) conditions, the coin cells were subjected to one 4.0C / 4.0C charge and discharge cycle (the battery discharge capacity was recorded as C0), with an upper limit voltage of 4.55V. Then, 300 cycles of 4.0C / 4.0C charge and discharge were performed, and the capacity retention rate was calculated.

[0070] Capacity retention rate = (Battery capacity after 300 cycles C1 / Initial battery capacity C0) * 100%

[0071] Table 1. Electrochemical performance test results for each example.

[0072]

[0073] As shown in Table 1, the high-rate cycle performance of coin cells 1-2# is better than that of coin cell 3#. This is because the electrolyte of coin cells 1-2# contains lithium imine compounds, which contain fluorinated sulfonyl imide groups and cyclic phosphate groups. It combines the advantages of cyclic phosphate groups, sulfonyl imide groups and fluorine groups, which can form a good protective film at the interface of positive and negative electrode materials. It also has low internal resistance, which can improve the cycle performance of the battery at high rates.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A lithium imine compound, characterized in that, The structural formula is shown in Equation 1. Formula 1.

2. The method for preparing lithium imine compounds according to claim 1, characterized in that, Including the following steps: (1) Ammoniation reaction The first intermediate is obtained by adding sulfuryl fluoride, ammonia and an acid-binding agent to carry out an ammoniation reaction. (2) Phosphating reaction Phosphorus trichloride was added to the first intermediate to carry out a phosphating reaction to obtain the second intermediate; (3) Substitution reaction Ethylene glycol was added to the second intermediate to carry out a substitution reaction to obtain the third intermediate; (4) Lithification reaction A lithiation reaction is carried out by adding a lithium compound to the third intermediate.

3. The method for preparing lithium imine compounds according to claim 2, characterized in that, Organic solvents are added to the raw materials for the ammoniation, phosphating, and lithiation reactions, and each organic solvent is independently selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, 1,4-dioxane, toluene, acetonitrile, diethyl ether, tetrahydrofuran, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, and propylene carbonate.

4. The method for preparing lithium imine compounds according to claim 2, characterized in that, The acid-binding agent is selected from at least one of triethylamine, pyridine, and 1,8-diazabicycloundec-7-ene.

5. The method for preparing lithium imine compounds according to claim 2, characterized in that, The molar ratio of the sulfuryl fluoride to the ammonia is 1:1 to 2, and the molar ratio of the sulfuryl fluoride to the acid-binding agent is 1:1 to 4.

6. The method for preparing lithium imine compounds according to claim 2, characterized in that, The molar ratio of the first intermediate to the phosphorus trichloride is 0.01~1.00: 0.01~1.00, the molar ratio of the second intermediate to the ethylene glycol is 1:1~10, and the molar ratio of the third intermediate to the lithium compound is 1:0.1~2.

0.

7. The method for preparing lithium imine compounds according to claim 2, characterized in that, The lithium compound is selected from lithium methoxide, lithium ethanol, lithium isopropoxide, or lithium tert-butoxide.

8. The method for preparing lithium imine compounds according to claim 2, characterized in that, The ammoniation reaction is carried out at a temperature of -40 to 50°C for 1 to 10 hours; the phosphating reaction is carried out at a temperature of 20 to 100°C for 5 to 25 hours; the substitution reaction is carried out at a temperature of 20 to 150°C for 10 to 36 hours; and the lithiation reaction is carried out at a temperature of -25 to 10°C for 0.1 to 2.0 hours.

9. The method for preparing lithium imine compounds according to claim 2, characterized in that, The ammoniation, phosphating, substitution, and lithiation reactions are carried out in separate reactors.

10. The application of the lithium imine compound according to claim 1 or the lithium imine compound prepared by the preparation method according to any one of claims 2 to 9 in a secondary battery.

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