Preparation method and application of mercaptan 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide lithium-tripropylene phosphite organic coating material

Abstract

The application relates to a preparation method and application of a mercaptan 3-chloropropyl sulfone (trifluoromethylsulfonyl) imide lithium-tripropylene phosphate organic coating material, and relates to a preparation method and application of an organic coating material. The application is aimed at solving the high reactivity of SC-NCM, combining the influence of coating material types and coating layer forms on the performance of the positive electrode material, and proposing a new organic coating material: mercaptan 3-chloropropyl sulfone (trifluoromethylsulfonyl) imide lithium-tripropylene phosphate (SH-LiCPSI-TLP). Since the Young's modulus of the organic material is generally lower than that of the inorganic material, a simple wet coating method can be used to form a uniform coating layer on the surface of the positive electrode material. It is found through electrochemical tests that, after being coated with SH-LiCPSI-TLP, the capacity diving phenomenon of SC-NCM811 can be effectively inhibited, and even after 600 cycles at a 1C rate, the capacity retention rate is still 52.78%.

Description

Technical Field

[0001] The invention relates to a preparation method and application of an organic coating material. Background Art

[0002] High nickel ternary cathode material Ni-rich NCM (Ni-rich LiNi x Co y Mn 1-x-y O2, x>0.6) is considered an ideal cathode for high-energy-density lithium-ion batteries due to its high specific capacity and excellent rate performance. However, as nickel content increases, high-nickel ternary cathode materials, while achieving higher specific capacity, also face challenges such as microcracks and increased side reactions. These issues have become key obstacles hindering the large-scale commercial application of high-nickel ternary cathode materials.

[0003] During the cycling process of polycrystalline high-nickel ternary materials (PC-NCM), the anisotropic stress accumulation between the primary particles leads to intergranular cracks in the secondary particles, which is the main reason for the rapid attenuation of its capacity. The single-crystal high-nickel ternary positive electrode material (SC-NCM) is composed only of primary particles. Compared with PC-NCM, it can fundamentally solve the problem of intergranular cracks caused by stress accumulation between grains during the cycling process. Compared with intergranular cracks, intragranular cracks are smaller in size, so their impact on high-nickel ternary positive electrode materials is significantly reduced. However, the impact of intragranular cracks cannot be ignored.

[0004] The generation of intracrystalline cracks mainly comes from two aspects: First, the high temperature during the production process causes defects such as dislocations to appear inside the Ni-rich NCM structure. As the cycle progresses, these defects become the starting point of intracrystalline cracks; second, the interface side reaction causes irreversible phase changes on the crystal surface, accompanied by the accumulation of stress, which eventually leads to the generation of intracrystalline cracks. At present, the synthesis process of SC-NCM relies on a high-temperature synthesis environment, so reducing the degree of interface side reactions has become an effective measure to reduce intracrystalline cracks. In addition, Ni in Ni-rich NCM 4+ The content is high, due to Ni 4+ Due to the high reactivity of Ni-rich NCM, the degree of side reactions between the Ni-rich NCM and the electrolyte also increases significantly. Therefore, for SC-NCM, reducing the degree of side reactions between the cathode material and the electrolyte can effectively reduce the formation of intergranular cracks and the impact of side reactions on the cathode material, which is also the prerequisite for the ultimate industrialization of SC-NCM.

[0005] Surface coating is a modification strategy that can effectively hinder the reaction between cathode materials and electrolytes. Its principle is to construct a protective layer between the cathode material and the electrolyte, thereby preventing direct contact between the cathode material and the electrolyte. For Ni-rich NCM, surface coating can effectively reduce the negative effects of high reactivity and significantly improve its interfacial stability and electrochemical stability. Therefore, research on surface coating modification of Ni-rich NCM has attracted significant attention from researchers and some related companies.

[0006] The type of coating material affects its effect on the positive electrode material. Coating materials with a stable chemical state can protect the positive electrode for a long time; lithium-containing compounds (organic / inorganic) can usually improve the rate performance of the positive electrode material. In addition, the morphology of the coating material on the positive electrode surface also has a certain impact on its performance. Generally, a coating layer with uniform coating and moderate thickness is considered to be an ideal coating layer morphology. However, in the coating process of existing inorganic materials, high temperature is required to provide thermodynamic power, but high temperature has an impact on the structural stability of the positive electrode material; in addition, when the coating material with slow lithium ion kinetics is coated on the surface of SC-NCM811, it will affect the rate performance of SC-NCM811, and the coating state of the coating layer also affects the performance of the positive electrode material after the overall coating. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention provides a preparation method and application of a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material.

[0008] The organic coating material prepared by the present invention can reduce the complexity of the coating process, lower costs, and ensure the uniformity of the coating layer and the feasibility of its large-scale production. Combining with lithium salts can effectively increase the lithium ion dynamics of the organic coating material, providing protection for the positive electrode material while increasing its rate performance.

[0009] Since phosphite has a relatively stable structure, choosing it as a coating material can increase the thermal stability and high-voltage resistance of the electrode material after coating.

[0010] A method for preparing a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material is specifically completed by the following steps:

[0011] 1. Preparation of thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium:

[0012] ①, sodium hydrosulfide and lithium 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide were added to anhydrous methanol at room temperature, and then heated under reflux for a period of time under nitrogen protection. After the reaction was completed, impurities were removed by filtration, and the filtrate was rotary evaporated to obtain reaction product I;

[0013] ②, adding acetonitrile to the reaction product I, stirring evenly and filtering again, and rotary evaporating the filtrate to obtain the reaction product II; drying the reaction product II in an oven to obtain lithium thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide;

[0014] 2. Preparation of thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite:

[0015] ①, adding lithium thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide, tripropylene phosphite and azobisisobutyronitrile to anhydrous tetrahydrofuran at room temperature, and then heating under reflux for a period of time under nitrogen protection. After the reaction is completed, the filtrate is rotary evaporated to obtain reaction product III;

[0016] ②. Add the reaction product III to dichloromethane, stir evenly, filter again, and rotary evaporate the filtrate to obtain the reaction product IV; place the reaction product IV in an oven to dry to obtain a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material.

[0017] A thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material is used for coating anode materials of lithium-ion batteries.

[0018] Principles and advantages of the present invention:

[0019] The application aims to solve the high reactivity of SC-NCM, combines the influence of the types of coating materials and the morphology of the coating layer on the performance of the positive electrode material, and proposes a new organic coating material: mercaptan 3-chloropropyl sulfonamide (trifluoromethylsulfonyl) imide lithium-tripropylene phosphate (SH-LiCPSI-TLP). Since the Young's modulus of organic materials is generally lower than that of inorganic materials, a simple wet coating can form a uniform coating layer on the surface of the positive electrode material. Through electrochemical testing, it is found that the SH-LiCPSI-TLP coating can effectively inhibit the capacity drop of SC-NCM811, and even after 600 cycles at 1C rate, the capacity retention rate is 52.78%, while the capacity retention rate of uncoated SC-NCM811 is only 19.74% after 600 cycles. Under high temperature / high pressure conditions, the cycle performance is still better than that of uncoated SC-NCM811. In addition, due to the presence of lithium salt in SH-LiCPSI-TLP, the coated SC-NCM811 shows high discharge capacity and excellent rate performance: at 5C rate, the coated SC-NCM811 still has a discharge specific capacity of 107.18 mAh g -1 BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The substance structure formula and the nuclear magnetic hydrogen spectrum diagram, Figure 1 In the formula, a is the synthesis reaction equation of SH-LiCPSI-TLP, b is the nuclear magnetic hydrogen spectrum diagram of LiCPSI and SH-LiCPSI, and c is the nuclear magnetic hydrogen spectrum diagram of TLP and SH-LiCPSI-TLP.

[0021] Figure 2 The XRD comparison diagram of SC-NCM811 powder before and after coating;

[0022] Figure 3 The scanning electron microscope diagram, wherein a is the scanning electron microscope diagram of Pristine SC-NCM811, and b is the scanning electron microscope diagram of M-TLP@SC-NCM811;

[0023] Figure 4 The scanning electron microscope diagram and the EDS mapping image of M-TLP@SC-NCM811, wherein a is the scanning electron microscope diagram, b is Ni, c is Co, d is P, e is S, f is F, and g is N;

[0024] Figure 5 The first cycle to the fifth cycle cyclic voltammetry curves of Pristine SC-NCM811 and M-TLP@SC-NCM811, wherein a is Pristine SC-NCM811, and b is M-TLP@SC-NCM811.​

[0025] Figure 6 This is a comparison of the cycling performance of M-TLP@SC-NCM811||Li and Pristine SC-NCM811||Li. In the figure, a is the room temperature standard voltage cycling performance, b is the high temperature standard voltage cycling performance, and c is the room temperature high voltage cycling performance;

[0026] Figure 7 This is a comparison of the rate performance and lithium ion diffusion rate of M-TLP@SC-NCM811||Li and Pristine SC-NCM811||Li. In the figure, a is the discharge capacity of M-TLP@SC-NCM811||Li and Pristine SC-NCM811||Li at different rates, and b is the 3C-5C high-rate cycling performance of M-TLP@SC-NCM811||Li and Pristine SC-NCM811||Li. DETAILED DESCRIPTION

[0027] Specific embodiment 1: This embodiment is a method for preparing a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material, which is specifically completed by the following steps:

[0028] 1. Preparation of thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium:

[0029] ①, sodium hydrosulfide and lithium 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide were added to anhydrous methanol at room temperature, and then heated under reflux for a period of time under nitrogen protection. After the reaction was completed, impurities were removed by filtration, and the filtrate was rotary evaporated to obtain reaction product I;

[0030] ②, adding acetonitrile to the reaction product I, stirring evenly and filtering again, and rotary evaporating the filtrate to obtain the reaction product II; drying the reaction product II in an oven to obtain lithium thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide;

[0031] 2. Preparation of thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite:

[0032] ①, adding lithium thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide, tripropylene phosphite and azobisisobutyronitrile to anhydrous tetrahydrofuran at room temperature, and then heating under reflux for a period of time under nitrogen protection. After the reaction is completed, the filtrate is rotary evaporated to obtain reaction product III;

[0033] ②. Add the reaction product III to dichloromethane, stir evenly, filter again, and rotary evaporate the filtrate to obtain the reaction product IV; place the reaction product IV in an oven to dry to obtain a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material.

[0034] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that: the preparation method of lithium 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide described in step 1① is specifically completed by the following steps: 200mmol LiOH·H2O is dissolved in 20mL C2H3N solution, and then 100mmol C3H6Cl2O2S and 100mmol CH2F3NO2S are added in an ice-water bath, stirred for 48h, and then filtered. The filtrate is concentrated at 50°C using a rotary evaporator to obtain a reaction product; the reaction product is dissolved in 20mL dichloromethane, filtered again, and the filtrate is dried at 50°C using a rotary evaporator to obtain lithium 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide. The other steps are the same as those in specific embodiment 1.

[0035] Specific embodiment 3: This embodiment differs from specific embodiments 1 or 2 in that: the molar ratio of sodium hydrosulfide to lithium 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide in step 1 (1) is 2:1; the volume ratio of sodium hydrosulfide to anhydrous methanol in step 1 (1) is (15 mmol to 25 mmol): (15 mL to 30 mL); the heating reflux temperature in step 1 (1) is 65°C, and the heating reflux time is 20 h to 28 h; the rotary evaporation temperature in step 1 (1) is 50°C to 55°C. The other steps are the same as those in specific embodiments 1 or 2.

[0036] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the volume ratio of reaction product I to acetonitrile in step 1 (2) is 1 mL:(20 mL to 60 mL); the rotary evaporation temperature in step 1 (2) is 50°C to 55°C; the drying temperature in step 1 (2) is 70°C to 90°C, and the drying time is 10 to 14 hours. Other steps are the same as specific embodiments 1 to 3.

[0037] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that: the molar ratio of thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium, tripropylene phosphite, and azobisisobutyronitrile described in step 2 ① is (3 mmol to 4 mmol): (0.5 mmol to 1.5 mmol): (2.5 mmol to 3.5 mmol); the volume ratio of thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium to anhydrous tetrahydrofuran described in step 2 ① is (3 mmol to 4 mmol): (15 mL to 30 mL); the heating reflux temperature described in step 2 ① is 65° C., and the heating reflux time is 10 h to 14 h; the rotary evaporation temperature described in step 2 ① is 50° C. to 55° C. The other steps are the same as specific embodiments 1 to 4.

[0038] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that the rotary evaporation temperature in step 2 (2) is 50°C; the drying temperature in step 2 (2) is 70°C to 90°C, and the drying time is 10 to 14 hours. The other steps are the same as specific embodiments 1 to 5.

[0039] Specific embodiment seven: This embodiment is a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material used for coating lithium ion battery positive electrode materials.

[0040] Specific embodiment eight: This embodiment differs from specific embodiments one to seven in that a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material is used to coat the positive electrode material of a lithium ion battery, which is specifically completed by the following steps:

[0041] 1. Thoroughly stir the thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material and N-methylpyrrolidone in a glove box to obtain a SH-LiCPSI-TLP / NMP mixed solution;

[0042] The mass fraction of the thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material in the SH-LiCPSI-TLP / NMP mixed solution in step 1 is 15% to 25%;

[0043] Second, the SH-LiCPSI-TLP / NMP mixed solution, SC-NCM811 powder, and N-methylpyrrolidone were mixed, and the mixture was heated and stirred for a period of time. After the reaction was completed, the N-methylpyrrolidone was completely volatilized to obtain a lithium-ion battery positive electrode material coated with thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium tripropylene phosphite. The other steps were the same as those in Specific Embodiments 1 to 7.

[0044] Specific embodiment 9: The difference between this embodiment and specific embodiments 1 to 8 is that the mass volume ratio of the SH-LiCPSI-TLP / NMP mixed solution, SC-NCM811 powder and N-methylpyrrolidone described in step 2 is (15mg~25mg):(1g~3g):(5mL~10mL); the temperature of the heating and stirring in step 2 is 50℃~70℃, and the stirring speed is 350rmin -1 ~500rmin -1 The stirring time is 10 hours to 12 hours. The other steps are the same as those in the first to eighth embodiments.

[0045] Specific embodiment ten: This embodiment differs from specific embodiments one to nine in that: a method for preparing a positive electrode sheet of a lithium-ion battery using a lithium-ion battery positive electrode material coated with thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite is specifically completed in the following steps:

[0046] 1. The lithium-ion battery positive electrode material coated with thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite, conductive carbon black and binder were mixed in a mass ratio of 8:1:1, and then N-methylpyrrolidone was added. The mixture was stirred at room temperature for 10 h to 12 h to obtain a positive electrode slurry.

[0047] The mass ratio of the total mass of the lithium ion battery positive electrode material coated with thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite, conductive carbon black and binder to N-methylpyrrolidone in step 1 is 1:1; the binder in step 1 is polyvinylidene fluoride;

[0048] Second, the positive electrode slurry was evenly coated onto aluminum foil using an automatic tape casting machine. The aluminum foil was then dried in a vacuum oven at 80°C for 20 to 24 hours. The foil was then cut into 12 mm diameter discs using a sheet cutter and roll-pressed at 5 MPa. Finally, the positive electrode sheets were vacuum-dried at 80°C for 10 to 12 hours to obtain the positive electrode sheets for the lithium-ion battery. The sheets were then transferred to a glove box for storage until further use. The remaining steps were the same as those in Specific Embodiments 1 to 9.

[0049] The following examples are used to verify the beneficial effects of the present invention:

[0050] Example 1: A method for preparing a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material, specifically completed by the following steps:

[0051] 1. Preparation of thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium:

[0052] ①. At room temperature, add 20 mmol of sodium hydrosulfide and 10 mmol of lithium 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide (LiCPSI) to 20 mL of anhydrous methanol. Then, under nitrogen protection, heat to 65°C and reflux at 65°C for 24 hours. After the reaction is complete, filter to remove impurities and rotary evaporate the filtrate at 50°C for 0.5 hours. The product is a transparent oil, which is reaction product I.

[0053] The preparation method of lithium 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide described in step 1① is specifically completed according to the following steps: dissolving 200mmol LiOH·H2O in 20mL C2H3N solution, and then adding 100mmol C3H6Cl2O2S and 100mmol CH2F3NO2S in an ice-water bath, stirring for 48h, and then filtering, and concentrating the filtrate with a rotary evaporator at 50°C to obtain a reaction product; dissolving the reaction product in 20mL dichloromethane, filtering again, and drying the filtrate with a rotary evaporator at 50°C to obtain lithium 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide;

[0054] ②, add 50 mL of acetonitrile to the reaction product I, stir evenly and filter again, and rotary evaporate the filtrate at 50°C to obtain the reaction product II; place the reaction product II in an oven at a temperature of 80°C for 12 hours to obtain lithium thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide (SH-LiCPSI);

[0055] 2. Preparation of thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite:

[0056] ① At room temperature, 3.5 mmol of lithium thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide (SH-LiCPSI), 1 mmol of tripropylene phosphite (TLP), and 3 mmol of azobisisobutyronitrile were added to 20 mL of anhydrous tetrahydrofuran, and then heated to 65°C under nitrogen protection. The mixture was heated under reflux at 65°C for 12 h. After the reaction was completed, the filtrate was rotary evaporated at 50°C for 0.5 h to obtain reaction product III;

[0057] ②. Add the reaction product III to 50 mL of dichloromethane, stir evenly and filter again. The filtrate is rotary evaporated at 50°C for 0.5 h to obtain the reaction product IV. The reaction product IV is placed in an oven at 80°C and dried for 12 h to obtain thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material (SH-LiCPSI-TLP).

[0058] Example 2: A lithium ion battery positive electrode material is coated with a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material prepared in Example 1, specifically by the following steps:

[0059] First, thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material (SH-LiCPSI-TLP) and N-methylpyrrolidone (NMP) were fully stirred in a glove box (H2O <0.1ppm; O2 <0.1ppm) to obtain a SH-LiCPSI-TLP / NMP mixed solution;

[0060] The mass fraction of the thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material in the SH-LiCPSI-TLP / NMP mixed solution described in step 1 is 20%;

[0061] 2. Mix 20 mg of SH-LiCPSI-TLP / NMP mixed solution, 2 g of SC-NCM811 powder and 7 mL of N-methylpyrrolidone (NMP), then heat to 60 ° C and stir at 60 ° C and 350 rmin. -1 The reaction was stirred for 12 h under the conditions of 40 ° C., and the N-methylpyrrolidone was completely volatilized to obtain a lithium ion battery cathode material (M-TLP@SC-NCM811) coated with thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite.

[0062] The SC-NCM811 powder described in Example 2 was purchased from Hefei Kejing Material Technology Co., Ltd., model: M2-S single crystal 811 lithium nickel cobalt manganese oxide.

[0063] The synthesis path of SH-LiCPSI-TLP is divided into two steps. The first step is the thiolation reaction of LiCPSI, and the second step is the thiol-ene reaction of SH-LiCPSI and TLP. The reaction process is as follows Figure 1 As shown in a.

[0064] H NMR spectroscopy ( 1 H-NMR) is an important characterization technique used to study molecular structure, configuration, conformation and molecular dynamics. 1 The structures of LiCPSI, SH-LiCPSI, TLP and SH-LiCPSI-TLP were analyzed by H-NMR in dimethyl sulfoxide (DMSO). Figure 1As shown in Figures b and c, in addition to the internal reference peak, three groups of peaks are observed, with the area integration ratio of these three groups being 2:2:2, consistent with the expected molecular structure. Thiolation modifies the functional groups at the end of the LiCPSI carbon chain, altering the chemical environment of the hydrogen atoms on the carbon chain. Consequently, the chemical shifts of all three peaks in the SH-LiCPSI spectrum change. The area integration results and chemical position shifts are consistent with the molecular structure, indicating successful thiolation of LiCPSI.

[0065] Figure 1 c is TLP and SH-LiCPSI-TLP 1 Comparison of H-NMR spectra. In the spectrum of TLP, three groups of peaks were observed in addition to the internal reference peak. The integrated area ratio between these three groups of peaks was 2:1:2, consistent with the expected molecular structure. In the spectrum of SH-LiCPSI-TLP, six groups of peaks were observed in addition to the internal reference peak. The integrated area ratio between these six groups of peaks was 2, and the peak area ratios were consistent with the structure. This indicates that the thiol-ene reaction between SH-LiCPSI and TLP was successful.

[0066] X-ray diffraction (XRD) is a method to characterize the crystal structure and its changing rules. XRD was used to characterize the SC-NCM811 powder before and after coating. Figure 2 As shown. Comparing the angles of the diffraction peaks of SC-NCM811 before and after coating with those of the standard crystal card (ICSD#01-070-4314), it can be seen that there are no impurity peaks in the diffraction patterns before and after coating, indicating that the coating has not changed the crystal structure of SC-NCM811. The separation degree between the two pairs of peaks (006) and (012) and (108) and (110) has not changed significantly, so the crystallinity of M-TLP@SC-NCM811 has not decreased due to the coating of SH-LiCPSI-TLP; in addition, the peak intensities of the (003) peak and the (104) peak have not changed significantly before and after coating, which shows that the degree of cation mixing in M-TLP@SC-NCM811 has not changed significantly.

[0067] In order to determine the changes in the single crystal surface before and after coating, scanning electron microscopy (SEM) tests were performed on the single crystal particles before and after coating. Figure 3 (a) is an SEM image of a single Pristine SC-NCM811 particle. The single crystal particle has a polyhedral structure, a smooth surface, and distinct corners. Only a few protrusions are present on the surface, presumably from a broken single crystal particle. Figure 3Figure b shows an SEM image of a single M-TLP@SC-NCM811 particle. After coating with SH-LiCPSI-TLP, the single crystal particle retains its basic polyhedral structure, but its surface is roughened with moss-like protrusions, and the coating material is clearly visible at the corners. This preliminarily indicates that SH-LiCPSI-TLP has been successfully coated on the surface of SC-NCM811.

[0068] Through SEM images, we can only observe the presence of SH-LiCPSI-TLP coating material on the surface of SC-NCM811, but we cannot determine whether SH-LiCPSI-TLP is evenly coated on the surface of SC-NCM811. Therefore, energy dispersive X-ray spectroscopy (EDS mapping) is used to characterize the distribution of elements in M-TLP@SC-NCM811. Figure 4 The D-G plot shows that the distribution of P, S, F, and N elements is almost identical to the SEM image of M-TLP@SC-NCM811. This confirms that SH-LiCPSI-TLP has been uniformly coated on the SC-NCM811 crystal surface.

[0069] Application Example 1: A method for assembling M-TLP@SC-NCM811||Li is specifically completed by the following steps:

[0070] First, the lithium-ion battery cathode material (M-TLP@SC-NCM811) coated with thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite, conductive carbon black (Super-P) and binder (polyvinylidene fluoride, PVDF) were mixed at a mass ratio of 8:1:1, and then N-methylpyrrolidone (NMP) was added. The mixture was stirred at room temperature for 12 hours to obtain a cathode slurry.

[0071] The mass ratio of the total mass of the lithium ion battery positive electrode material coated with thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide-tripropylene phosphite, the conductive carbon black and the binder to N-methylpyrrolidone is 1:1;

[0072] Second, the positive electrode slurry was evenly coated on the aluminum foil using an automatic casting machine, and the aluminum foil was placed in a vacuum oven at 80°C and dried for 24 hours. Then, a sheet cutter was used to cut the discs into 12 mm diameter discs, and the discs were roll-pressed at a pressure of 5 MPa for 10 seconds. Finally, the discs were vacuum-dried at 80°C for 12 hours to obtain the positive electrode sheets of the lithium-ion battery. The discs were then transferred to a glove box for storage.

[0073] 3. Assembled in a glove box (H2O <0.1ppm, O2 <0.1ppm), the battery composition is (from the negative electrode battery shell to the positive electrode battery shell): negative electrode battery shell, stainless steel spring, stainless steel gasket, lithium sheet (thickness 0.4mm, diameter 14mm), PP separator (Clude), lithium-ion battery positive electrode sheet (diameter 12mm, total load of approximately 5mg), positive electrode battery shell; the electrolyte composition is 1MLiPF6 in ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) (1:1:1 by volume) with 5wt.% fluoroethylene carbonate (FEC), the total addition amount is 100μL, and it is added to the lithium sheet and separator in two equal amounts; the battery shell is purchased from Clude, model 2032.

[0074] Comparative Application Example 1: This example differs from Application Example 1 in that the lithium-ion battery cathode material (M-TLP@SC-NCM811) coated with thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium tripropylene phosphite is replaced with pristine SC-NCM811. Other steps and parameters are the same as those in Application Example 1.

[0075] The reversibility of the electrochemical reaction of M-TLP@SC-NCM811 was determined by cyclic voltammetry (CV). Cyclic voltammetry was performed on the batteries assembled in Application Example 1 and Comparative Application Example 1. Figure 5 As shown; Figure 5 Cyclic voltammograms from the first to the fifth cycle of PristineSC-NCM811 and M-TLP@SC-NCM811. (a) is PristineSC-NCM811, and (b) is M-TLP@SC-NCM811.

[0076] Comparing the degree of overlap between the two CV curves shows that there is no significant difference in the reversibility of pristine SC-NCM811 and M-TLP@SC-NCM811. Since SH-LiCPSI-TLP and SC-NCM811 have essential differences in structure, lithium ion kinetics and other properties, the introduction of the SH-LiCPSI-TLP coating layer will inevitably lead to an increase in the polarization voltage of M-TLP@SC-NCM811. Comparing the magnitude of the redox peak voltage in the CV curve, it can be found that the polarization voltage of M-TLP@SC-NCM811 increases less, so it can be inferred that SH-LiCPSI-TLP has a good lithium ion transfer rate. This conclusion will be confirmed in subsequent rate performance tests.

[0077] The modification principle of surface coating modification on Ni-rich NCM is mainly to avoid direct contact of the positive material with the electrolyte, thereby reducing the interface side reaction, prolonging the service life of Ni-rich NCM and improving its electrochemical performance. In order to broaden the use scenarios of Ni-rich NCM, the coating material is required to not only play a modification role under normal conditions, but also have a certain modification effect in some harsh environments (high temperature, high pressure, etc.). Therefore, in order to verify the improvement of SH-LiCPSI-TLP on the cycle performance of SC-NCM811 under multiple environments, the present application designs cycle performance tests under three conditions, which are: room temperature standard voltage (25℃, 3.0V-4.3V), high temperature standard voltage (40℃, 3.0V-4.3V), room temperature high voltage (25℃, 3.0V-4.5V); the cycle performance is as follows Figure 6 .

[0078] Figure 6 In the middle a, M-TLP@SC-NCM811||Li shows a higher initial specific capacity (M-TLP@SC-NCM811||Li: 169.45 mAh g -1 , Pristine SC-NCM811||Li: 165.99 mAh g -1 ). In terms of capacity retention rate, the capacity of Pristine SC-NCM811||Li rapidly decays after 350 cycles, while M-TLP@SC-NCM811 still has a higher capacity retention rate (100 cycles: M-TLP@SC-NCM811 85.24%, Pristine SC-NCM811||Li 82.33%; 300 cycles: M-TLP@SC-NCM811 67.91%, Pristine SC-NCM811||Li 66.13%; 600 cycles: M-TLP@SC-NCM811 52.78%, Pristine SC-NCM811||Li 19.74%).

[0079] Figure 6 In the middle b, after 500 cycles at 40℃, 1C, the capacity retention rate of M-TLP@SC-NCM811||Li is 56.42%, while the capacity retention rate of Pristine SC-NCM811||Li is 49.26%. Therefore, it can be inferred that SH-LiCPSI-TLP has higher thermal stability, so that it can still provide sufficient protection for SC-NCM811 in a high temperature environment. Figure 6Under the condition of medium c and high pressure, the capacity retention rate of M-TLP@SC-NCM811||Li was still 28.17% after 900 cycles of long cycle. Compared with Pristine SC-NCM811||Li (24.55%), the capacity retention rate was increased by 3.62%.

[0080] In summary, SH-LiCPSI-TLP significantly improved the cycle performance of SC-NCM811 at room temperature and standard voltage. Even under the condition of high temperature / high pressure, SH-LiCPSI-TLP still played a certain modification role.

[0081] Since there is lithium salt in SH-LiCPSI-TLP, as a coating material, it has a certain improvement effect on the rate performance of SC-NCM811 in theory. Therefore, in order to verify the improvement of SH-LiCPSI-TLP coating on the rate performance of SC-NCM811, the present application carried out rate test and constant current intermittent titration test (GITT), as shown in Figure 7 .

[0082] Figure 7 Under the condition of medium c and high pressure, the capacity retention rate of M-TLP@SC-NCM811||Li was still 28.17% after 900 cycles of long cycle. Compared with Pristine SC-NCM811||Li (24.55%), the capacity retention rate was increased by 3.62%. -1 -1 -1 In addition, it is worth noting that at 0.3C rate before cycling, there is no obvious difference in capacity between Pristine SC-NCM811||Li and M-TLP@SC-NCM811||Li. But after high-rate cycling, the capacity of Pristine SC-NCM811||Li is significantly lower than that of M-TLP@SC-NCM811||Li at the same rate (0.3C). It can be inferred that SH-LiCPSI-TLP not only improves the rate performance of SC-NCM811, but also continuously protects SC-NCM811 under high current density.

[0083] Therefore, the present application designs a cycle performance test under high rate. Figure 7 ​​(B) At a 3C charge / discharge rate, M-TLP@SC-NCM811||Li maintains high capacity retention and specific discharge capacity (50 cycles: M-TLP@SC-NCM811||Li 88.9%, pristine SC-NCM811||Li 82.28%). Even at a 5C rate, although M-TLP@SC-NCM811||Li exhibits faster capacity decay, its capacity remains higher than that of pristine SC-NCM811||Li. This increased capacity is likely due to the SH-LiCPSI-TLP coating layer increasing lithium ion dynamics in the electrode.

Claims

1. A method for preparing a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material, characterized in that The preparation method is specifically completed according to the following steps:

1. Preparation of thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium: ①, sodium hydrosulfide and lithium 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide were added to anhydrous methanol at room temperature, and then heated under reflux for a period of time under nitrogen protection. After the reaction was completed, impurities were removed by filtration, and the filtrate was rotary evaporated to obtain reaction product I; ②, adding acetonitrile to the reaction product I, stirring evenly and filtering again, and rotary evaporating the filtrate to obtain the reaction product II; drying the reaction product II in an oven to obtain lithium thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide; 2. Preparation of thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite: ①, adding lithium thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide, tripropylene phosphite and azobisisobutyronitrile to anhydrous tetrahydrofuran at room temperature, and then heating under reflux for a period of time under nitrogen protection. After the reaction is completed, the filtrate is rotary evaporated to obtain reaction product III; ②. Add the reaction product III to dichloromethane, stir evenly, filter again, and rotary evaporate the filtrate to obtain the reaction product IV; place the reaction product IV in an oven to dry to obtain a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material.

2. The method for preparing a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material according to claim 1, characterized in that The preparation method of lithium 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide described in step 1① is specifically completed according to the following steps: dissolving 200mmol LiOH·H2O in 20mL C2H3N solution, and then adding 100mmol C3H6Cl2O2S and 100mmol CH2F3NO2S in an ice-water bath, stirring for 48h, and then filtering, and concentrating the filtrate with a rotary evaporator at 50°C to obtain a reaction product; dissolving the reaction product in 20mL of dichloromethane, filtering again, and drying the filtrate with a rotary evaporator at 50°C to obtain lithium 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide.

3. The method for preparing a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material according to claim 1, characterized in that The molar ratio of sodium hydrosulfide to lithium 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide described in step 1① is 2:1; the volume ratio of the amount of sodium hydrosulfide described in step 1① to anhydrous methanol is (15mmol~25mmol):(15mL~30mL); the heating reflux temperature described in step 1① is 65°C, and the heating reflux time is 20h~28h; the temperature of the rotary evaporation described in step 1① is 50°C~55°C.

4. The method for preparing a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material according to claim 1, characterized in that The volume ratio of the reaction product I described in step 1 ② to acetonitrile is 1 mL: (20 mL to 60 mL); the temperature of the rotary evaporation described in step 1 ② is 50° C. to 55° C.; the temperature of the drying described in step 1 ② is 70° C. to 90° C., and the drying time is 10 h to 14 h.

5. The method for preparing a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material according to claim 1, characterized in that The molar ratio of the thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium, tripropylene phosphite and azobisisobutyronitrile described in step 2 ① is (3mmol to 4mmol): (0.5mmol to 1.5mmol): (2.5mmol to 3.5mmol); the volume ratio of the amount of the thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium to anhydrous tetrahydrofuran is (3mmol to 4mmol): (15mL to 30mL); the heating reflux temperature described in step 2 ① is 65°C, and the heating reflux time is 10h to 14h; the temperature of the rotary evaporation described in step 2 ① is 50°C to 55°C.

6. The method for preparing a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material according to claim 1, characterized in that The temperature of the rotary evaporation in step 2② is 50°C; the temperature of the drying in step 2② is 70°C to 90°C, and the drying time is 10h to 14h.

7. Use of a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material prepared by the preparation method according to claim 1, characterized in that A thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material is used for coating anode materials of lithium-ion batteries.

8. The use of a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material according to claim 7, characterized in that A thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material is used to coat a positive electrode material for a lithium-ion battery, and is specifically completed by the following steps:

1. Thoroughly stir the thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material and N-methylpyrrolidone in a glove box to obtain a SH-LiCPSI-TLP / NMP mixed solution; The mass fraction of the thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material in the SH-LiCPSI-TLP / NMP mixed solution in step 1 is 15% to 25%; 2. Mix the SH-LiCPSI-TLP / NMP mixed solution, SC-NCM811 powder and N-methylpyrrolidone, then heat and stir for a period of time. After the reaction is completed, the N-methylpyrrolidone is completely volatilized to obtain a lithium-ion battery positive electrode material coated with thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite.

9. The use of a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material according to claim 8, characterized in that The mass volume ratio of the SH-LiCPSI-TLP / NMP mixed solution, SC-NCM811 powder and N-methylpyrrolidone described in step 2 is (15 mg to 25 mg): (1 g to 3 g): (5 mL to 10 mL); the temperature of the heating and stirring in step 2 is 50°C to 70°C, and the stirring speed is 350 rmin -1 ~500rmin -1 The stirring time is 10h to 12h.

10. The use of a thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite organic coating material according to claim 8, characterized in that The method for preparing a lithium-ion battery positive electrode sheet using a lithium-ion battery positive electrode material coated with thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite is specifically completed by the following steps:

1. The lithium-ion battery positive electrode material coated with thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite, conductive carbon black and binder were mixed in a mass ratio of 8:1:1, and then N-methylpyrrolidone was added. The mixture was stirred at room temperature for 10 h to 12 h to obtain a positive electrode slurry. The mass ratio of the total mass of the lithium ion battery positive electrode material coated with thiolated 3-chloropropanesulfonyl (trifluoromethanesulfonyl) imide lithium-tripropylene phosphite, conductive carbon black and binder to N-methylpyrrolidone in step 1 is 1:1; the binder in step 1 is polyvinylidene fluoride; 2. Use an automatic casting machine to evenly coat the positive electrode slurry on the aluminum foil, and place the aluminum foil in a vacuum oven at 80°C to dry for 20h to 24h. Then use a cutting machine to cut it into discs with a diameter of 12mm, and roll it under a pressure of 5MPa. Finally, vacuum dry it at 80°C for 10h to 12h to obtain the positive electrode sheet of the lithium-ion battery, and transfer it to a glove box for storage.

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